Philosophical Transactions of The Royal Society B Biological Sciences

Published by The Royal Society

Online ISSN: 1471-2970


Print ISSN: 0962-8436


Life at low water activity
  • Literature Review

September 2004


317 Reads

Two major types of environment provide habitats for the most xerophilic organisms known: foods preserved by some form of dehydration or enhanced sugar levels, and hypersaline sites where water availability is limited by a high concentration of salts (usually NaCl). These environments are essentially microbial habitats, with high-sugar foods being dominated by xerophilic (sometimes called osmophilic) filamentous fungi and yeasts, some of which are capable of growth at a water activity (a(w)) of 0.61, the lowest a(w) value for growth recorded to date. By contrast, high-salt environments are almost exclusively populated by prokaryotes, notably the haloarchaea, capable of growing in saturated NaCl (a(w) 0.75). Different strategies are employed for combating the osmotic stress imposed by high levels of solutes in the environment. Eukaryotes and most prokaryotes synthesize or accumulate organic so-called 'compatible solutes' (osmolytes) that have counterbalancing osmotic potential. A restricted range of bacteria and the haloarchaea counterbalance osmotic stress imposed by NaCl by accumulating equivalent amounts of KCl. Haloarchaea become entrapped and survive for long periods inside halite (NaCl) crystals. They are also found in ancient subterranean halite (NaCl) deposits, leading to speculation about survival over geological time periods.

Surface-Associated Growth
  • Article
  • Full-text available

July 1982


240 Reads






In natural ecosystems, microbial activity is often associated with the presence of a surface, particularly in low-nutrient environments. The chemostat allows the study of such low-nutrient environments together with the precise control of other growth parameters. By using this system, enrichment cultures with inocula from two different river sources have been made. A more diverse community attached itself to surfaces placed in the chemostat when the cultures were carbon-limited than when the limiting nutrient was nitrogen. Further studies on a pseudomonad isolated from the carbon-limited enrichment cultures have shown that surface-associated organisms grow at approximately twice the rate of the same organism in the free surrounding medium. A hypothesis to explain this phenomenon based on the chemiosmotic theory is discussed.

Figure 6. Evaluation of biochemical and metabolomic parameters in P. pavonaceae cells growing exponentially on MMY medium containing either 30 mM D-glucose or citrate (i.e. glycolytic and gluconeogenic metabolic regimes) under control conditions (nil) and in the presence of 0.5 mM 1,3-dichloroprop-1-ene (1,3-DCP). (a) In vitro quantification of the specific (Sp) D-glucose-6-P dehydrogenase activity. Note that the superoxide-generating naphtoquinone menadione was added at 0.15 mM to some cultures to impose oxidative stress conditions. (b) Determination of the intracellular D-glucose-6-P concentration. Appropriate aliquots of clarified cellfree extracts were boiled and centrifuged, and supernatants were spectrophotometrically analysed for D-glucose-6-P as detailed in §2. Each bar represents the mean value of the corresponding parameter + s.d. of duplicate measurements from at least three independent experiments. In both cases, the asterisk marks denote significant differences in the corresponding parameter at either the 95% level (single asterisk) or the 99% level (double asterisks) when compared with the control culture (without additives), as evaluated with ANOVA. 
Why are chlorinated pollutants so difficult to degrade aerobically? Redox stress limits 1,3-dichloprop-1-ene metabolism by Pseudomonas pavonaceae

April 2013


331 Reads

Chlorinated pollutants are hardly biodegradable under oxic conditions, but they can often be metabolized by anaerobic bacteria through organohalide respiration reactions. In an attempt to identify bottlenecks limiting aerobic catabolism of 1,3-dichloroprop-1-ene (1,3-DCP; a widely used organohalide) in Pseudomonas pavonaceae, the possible physiological restrictions for this process were surveyed. Flow cytometry and a bioluminescence reporter of metabolic state revealed that cells treated with 1,3-DCP experienced an intense stress that could be traced to the endogenous production of reactive oxygen species (ROS) during the metabolism of the compound. Cells exposed to 1,3-DCP also manifested increased levels of d-glucose-6-P 1-dehydrogenase activity (G6PDH, an enzyme key to the synthesis of reduced NADPH), observed under both glycolytic and gluconeogenic growth regimes. The increase in G6PDH activity, as well as cellular hydroperoxide levels, correlated with the generation of ROS. Additionally, the high G6PDH activity was paralleled by the accumulation of d-glucose-6-P, suggesting a metabolic flux shift that favours the production of NADPH. Thus, G6PDH and its cognate substrate seem to play an important role in P. pavonaceae under redox stress caused by 1,3-DCP, probably by increasing the rate of NADPH turnover. The data suggest that oxidative stress associated with the biodegradation of 1,3-DCP reflects a significant barrier for the evolution of aerobic pathways for chlorinated compounds, thereby allowing for the emergence of anaerobic counterparts.

Logothetis NK. The neural basis of the blood-oxygen-level-dependent functional magnetic resonance imaging signal. Philos Trans R Soc Lond B Biol Sci 357: 1003-1037

September 2002


166 Reads

Magnetic resonance imaging (MRI) has rapidly become an important tool in clinical medicine and biological research. Its functional variant (functional magnetic resonance imaging; fMRI) is currently the most widely used method for brain mapping and studying the neural basis of human cognition. While the method is widespread, there is insufficient knowledge of the physiological basis of the fMRI signal to interpret the data confidently with respect to neural activity. This paper reviews the basic principles of MRI and fMRI, and subsequently discusses in some detail the relationship between the blood-oxygen-level-dependent (BOLD) fMRI signal and the neural activity elicited during sensory stimulation. To examine this relationship, we conducted the first simultaneous intracortical recordings of neural signals and BOLD responses. Depending on the temporal characteristics of the stimulus, a moderate to strong correlation was found between the neural activity measured with microelectrodes and the BOLD signal averaged over a small area around the microelectrode tips. However, the BOLD signal had significantly higher variability than the neural activity, indicating that human fMRI combined with traditional statistical methods underestimates the reliability of the neuronal activity. To understand the relative contribution of several types of neuronal signals to the haemodynamic response, we compared local field potentials (LFPs), single- and multi-unit activity (MUA) with high spatio-temporal fMRI responses recorded simultaneously in monkey visual cortex. At recording sites characterized by transient responses, only the LFP signal was significantly correlated with the haemodynamic response. Furthermore, the LFPs had the largest magnitude signal and linear systems analysis showed that the LFPs were better than the MUAs at predicting the fMRI responses. These findings, together with an analysis of the neural signals, indicate that the BOLD signal primarily measures the input and processing of neuronal information within a region and not the output signal transmitted to other brain regions.

Table 3 . Richness and percentage complementarity of spider faunas along an elevational gradient in Bolivia (Coddington et al. 1991; J. A. Coddington L. H. Young, unpublished data) (Sequential sites are separated by about 110 km Matrix entries: percentage complementarity (number of species in common).) 
Colwell RK, Coddington JA.. Estimating terrestrial biodiversity through extrapolation. Philos Trans R Soc London B-Biol Sci 345: 101-118

August 1994


5,277 Reads

Both the magnitude and the urgency of the task of assessing global biodiversity require that we make the most of what we know through the use of estimation and extrapolation. Likewise, future biodiversity inventories need to be designed around the use of effective sampling and estimation procedures, especially for 'hyperdiverse' groups of terrestrial organisms, such as arthropods, nematodes, fungi, and microorganisms. The challenge of estimating patterns of species richness from samples can be separated into (i) the problem of estimating local species richness, and (ii) the problem of estimating the distinctness, or complementarity, of species assemblages. These concepts apply on a wide range of spatial, temporal, and functional scales. Local richness can be estimated by extrapolating species accumulation curves, fitting parametric distributions of relative abundance, or using non-parametric techniques based on the distribution of individuals among species or of species among samples. We present several of these methods and examine their effectiveness for an example data set. We present a simple measure of complementarity, with some biogeographic examples, and outline the difficult problem of estimating complementarity from samples. Finally, we discuss the importance of using 'reference' sites (or sub-sites) to assess the true richness and composition of species assemblages, to measure ecologically significant ratios between unrelated taxa, to measure taxon/sub-taxon (hierarchical) ratios, and to 'calibrate' standardized sampling methods. This information can then be applied to the rapid, approximate assessment of species richness and faunal or floral composition at 'comparative' sites.

Riera J, Aubert E, Iwata K, Kawashima R, Wan X, Ozaki TFusing EEG and fMRI based on a bottom-up model: inferring activation and effective connectivity in neural masses. Philos Trans R Soc London B Biol Sci 360:1025-1041

May 2005


208 Reads

The elucidation of the complex machinery used by the human brain to segregate and integrate information while performing high cognitive functions is a subject of imminent future consequences. The most significant contributions to date in this field, known as cognitive neuroscience, have been achieved by using innovative neuroimaging techniques, such as electroencephalogram (EEG) and functional magnetic resonance imaging (fMRI), which measure variations in both the time and the space of some interpretable physical magnitudes. Extraordinary maps of cerebral activation involving function-restricted brain areas, as well as graphs of the functional connectivity between them, have been obtained from EEG and fMRI data by solving some spatio-temporal inverse problems, which constitutes a top-down approach. However, in many cases, a natural bridge between these maps/graphs and the causal physiological processes is lacking, leading to some misunderstandings in their interpretation. Recent advances in the comprehension of the underlying physiological mechanisms associated with different cerebral scales have provided researchers with an excellent scenario to develop sophisticated biophysical models that permit an integration of these neuroimage modalities, which must share a common aetiology. This paper proposes a bottom-up approach, involving physiological parameters in a specific mesoscopic dynamic equations system. Further observation equations encapsulating the relationship between the mesostates and the EEG/fMRI data are obtained on the basis of the physical foundations of these techniques. A methodology for the estimation of parameters from fused EEG/fMRI data is also presented. In this context, the concepts of activation and effective connectivity are carefully revised. This new approach permits us to examine and discuss some future prospects for the integration of multimodal neuroimages.

Figure 1. Expanded polyglutamine protein causes degeneration of the Drosophila eye. ( a ) Eye of a normal £y, showing highly ordered precise neurocrystalline lattice, and red pigmentation. ( b ) Eye of a £y expressing the control protein, MJDtr-Q27. The eye morphology is identical to that of a normal £y. Fly of genotype w ; gmr-GAL4 / UAS-MJDtr- Q27 . ( c ) Eye of a £y expressing the expanded polyglutamine protein, MJDtr-Q78. The eye shows severe degeneration compared to the normal eye. Externally, pigmentation is lost (seen here as a light coloured eye), internally (see Warrick et al . 1998) the eye shows complete loss of the photoreceptor neurons. ( d ) Developing eye disc of a larva expressing the MJDtr-Q27 protein. The protein is being expressed from the start of di¡erentiation at the furrow (arrow), and shows a di¡use cytoplasmic expression pattern. Larva of genotype w ; gmr-GAL4 / UAS-MJDtr-Q27 . ( e ) Developing eye disc of a larva expressing the MJDtr-Q78 protein. The protein is being expressed from the start of di¡erentiation at the furrow (arrow). The protein shows eventual concentration into brightly £uorescing nuclear inclusions. Older cells are to the left. Larva of genotype w ; gmr-GAL4 / UAS-MJDtr-Q78 . 
Bonini, N. M. A genetic model for human polyglutamine-repeat disease in Drosophila melanogaster. Philos. Trans. R. Soc. Lond. B. 354, 1057-1060

July 1999


90 Reads

To apply genetics to the problem of human polyglutamine-repeat disease, we recreated polyglutamine-repeat disease in Drosophila melanogaster. To do this, we expressed forms of the human gene encoding spinocerebellar ataxia type 3, also called Machado-Joseph disease (SCA-3/MJD). This gene is responsible for the most common form of human ataxia worldwide. Expression of a normal form of the MJD protein with 27 polyglutamines (MJDtr-Q27) had no phenotype. However, expression of a form of the protein with an expanded run of 78 glutamines (MJDtr-Q78) caused late onset progressive degeneration. In addition, the MJDtr-Q78 formed abnormal protein aggregates, or nuclear inclusions (NIs), whereas the control protein was cytoplasmic. These data indicate that the mechanisms of human polyglutamine-repeat disease are conserved to Drosophila. We are currently using this model to address potential mechanisms by which the mutant disease protein causes neural degeneration, as well as to define genes that can prevent polyglutamine-induced degeneration. By applying the power of Drosophila genetics to the problem of human polyglutamine-induced neural degeneration, we hope to identify ways to prevent and treat these diseases in humans.

Figure 1. Multiplicative gene action for a quantitative trait exhibiting inbreeding depression results in an expected loglinear decline (a) with increasing genome homozygosity (F). Epistasis can cause a curvilinear response, either concave up (diminishing epistasis, d) or concave down (reinforcing epistasis, r).
Figure 2. The North Carolina 3 breeding design. Inbred lines are crossed to form genetically uniform F 1 hybrids. F 1 hybrids are selfed to form segregating F 2 progeny. F 2 sires are used in backcrosses to the parental inbred lines.  
Figure 3. Graphical representation (after Fu & Ritland 1994a) of expected segregation ratios (the frequency of the marker heterozygote) and the less common homozygote ( p11) based on seven different models of allele interaction: overdominance (o), fully recessive (r), partly recessive (pr), additive (a), part dominance (pd), dominance (d) and underdominance (u). This model assumes unknown linkage between the marker and viability locus. Note the areas of overlap between the different types of allele interaction.  
Carr DE, Dudash MR. Recent approaches into the genetic basis of inbreeding depression in plants. Philos Trans R Soc Lond B Biol Sci 358: 1071-1084
Predictions for the evolution of mating systems and genetic load vary, depending on the genetic basis of inbreeding depression (dominance versus overdominance, epistasis and the relative frequencies of genes of large and small effect). A distinction between the dominance and overdominance hypotheses is that deleterious recessive mutations should be purged in inbreeding populations. Comparative studies of populations differing in their level of inbreeding and experimental approaches that allow selection among inbred lines support this prediction. More direct biometric approaches provide strong support for the importance of partly recessive deleterious alleles. Investigators using molecular markers to study quantitative trait loci (QTL) often find support for overdominance, though pseudo-overdominance (deleterious alleles linked in repulsion) may bias this perception. QTL and biometric studies of inbred lines often find evidence for epistasis, which may also contribute to the perception of overdominance, though this may be because of the divergent lines initially crossed in QTL studies. Studies of marker segregation distortion commonly uncover genes of major effect on viability, but these have only minor contributions to inbreeding depression. Although considerable progress has been made in understanding the genetic basis of inbreeding depression, we feel that all three aspects merit more study in natural plant populations.

Grant, T. R. & Temple-Smith, P. D. Field biology of the platypus (Ornithorhynchus anatinus): historical and current perspectives. Phil. Trans. R. Soc. Lond. B 353, 1081-1091
The field biology of the platypus, Ornithorhynchus anatinus, was first studied by a number of expatriate biologists who visited the Australian colonies to collect specimens in the 1800s. Their work was followed in the early to mid-1900s by a group of resident natural historians and later by an increasing number of academic biologists. All of these workers contributed significantly to the current understanding of the field biology of this unique Australian species. The platypus occupies much the same general distribution as it did prior to European occupation of Australia, except for its loss from the state of South Australia. However, local changes and fragmentation of distribution due to human modification of its habitat are documented. The species currently inhabits eastern Australia from around Cooktown in the north to Tasmania in the south. Although not found in the west-flowing rivers of northern Queensland, it inhabits the upper reaches of rivers flowing to the west and north of the dividing ranges in the south of the state and in New South Wales and Victoria. Its current and historical abundance, however, is less well known and it has probably declined in numbers, although still being considered as common over most of its current range. The species was extensively hunted for its fur until around this turn of this century. The platypus is mostly nocturnal in its foraging activities, being predominantly an opportunistic carnivore of benthic invertebrates. The species is homeothermic, maintaining its low body temperature (32 degrees C), even while foraging for hours in water below 5 degrees C. Its major habitat requirements include both riverine and riparian features which maintain a supply of benthic prey species and consolidated banks into which resting and nesting burrows can be excavated. The species exhibits a single breeding season, with mating occurring in late winter or spring and young first emerging into the water after 3-4 months of nurture by the lactating females in the nesting burrows. Natural history observations, mark and recapture studies and preliminary investigations of population genetics indicate the possibility of resident and transient members of populations and suggest a polygynous mating system. Recent field studies have largely confirmed and extended the work of the early biologists and natural historians.

Brown MW, Bashir ZI. Evidence concerning how neurons of the perirhinal cortex may effect familiarity discrimination. Philos Trans R Soc Lond Ser B 357: 1083-1095

September 2002


45 Reads

Many studies indicate that recognition memory involves at least two separable processes, familiarity discrimination and recollection. Aspects of what is known of potential neuronal substrates of familiarity discrimination are reviewed. Lesion studies have established that familiarity discrimination for individual visual stimuli is effected by a system centred on the perirhinal cortex of the temporal lobe. The fundamental change that encodes prior occurrence of such stimuli appears to be a reduction in the response of neurons in anterior inferior temporal (including perirhinal) cortex when a stimulus is repeated. The neuronal responses rapidly signal the presence of a novel stimulus, and are evidence of long-lasting learning after a single exposure. Computational modelling indicates that a neuronal network based on such a change in responsiveness is potentially highly efficient in information theoretic terms. Processes that occur in long-term depression within the perirhinal cortex provide candidate synaptic plastic mechanisms for that underlying the change, but such linkage remains to be experimentally established.

Table 1 . Concordant laterality of epithalamic and heart asymmetries in zebrafish and medaka. 
Figure 1. (a) Zebrafish and (b) medaka share an overall pattern of molecular and morphological epithalamic asymmetry. ((i),(ii)) Asymmetric expression of components of the nodal signalling pathway in the presumptive epithalamus. mRNA expression of orthologue genes was detected by whole-mount in situ hybridization (arrows) at (i) normalized STU 35 (Dr-lefty1, Ol-lefty) and (ii) 43 (Dr-pitx2c, Ol-pitx2c) (table 2). The lateral flexure of the third ventricle is indicated by arrowheads. (iii) Left-sided positioning and efferent projection of the parapineal organ. Expression of GFP was detected in medaka Tg( fRx2::GFP ) and zebrafish Tg(FoxD3::GFP ) and pseudo-coloured in blue and green to label pineal and parapineal organs, respectively. The red arrowhead points to the terminal dandelion seed-head-shaped domain of parapineal efferent connectivity. (iv) Asymmetric organization of neuropil in the habenulae. Arrows indicate the regions of neuropil, which exhibit dissimilar growth between the left and right habenulae, as detected by immunostaining against acetylated a-tubulin. The red arrowhead points to a neuropil domain that is detected exclusively in the left habenula of medaka. (v) Asymmetric organization of neuronal cell bodies in the habenulae. Asterisks indicate equivalent regions of the left and right habenulae. The red arrowhead points to a domain devoid of fluorescent Nissl staining that is detected exclusively in the left habenula of medaka. ((vi),(vii)) Dorsoventral segregation of left-right habenular efferents in the IPN. Left and right habenular projections were labelled with DiD (red) and DiO (green), respectively. Images correspond to ((i)-(vi)) dorsal and (vii) lateral views with anterior and dorsal to the top, respectively. Stages of development correspond to 120 HPF (zebrafish, at 268C) and Iwamatsu's stage 39 (medaka), unless otherwise stated. ((iii)-(vii)) Three-dimensional projections from confocal z-stacks. L, left; R, right; Lh, left habenula; Rh, right habenula; hc, habenular commissure; Lfr, left fasciculus retroflexus; Rfr, right fasciculus retroflexus; dIPN, dorsal domain of the IPN; vIPN, ventral domain of the IPN. Scale bars, ((i)-(v)) 20 mm, ((vi),(vii)) 30 mm. 
Figure 3. Comparison of sequence, relative timing and duration of developmental events during the establishment of epithalamic asymmetry in zebrafish and medaka. The diagrams show the temporal occurrence of key steps of asymmetric brain morphogenesis in zebrafish and medaka, expressed in (a) absolute and (b) normalized times. To provide a contextual view, the timing of main embryonic events is also included. The colour codes shown at the bottom of the figure indicate different developmental events (lines) and periods ( boxes or bars) analysed in the temporal plots of (a,b). For clarity, equivalent events in medaka and zebrafish are joined. Diagrams of developmental stages were obtained from the literature (Kimmel et al. 1995; Iwamatsu 2004). Schematic of epithalamic asymmetry events (bottom right) correspond, from top to bottom, to: a frontal view of the epithalamus depicting left-sided asymmetric nodal expression, a dorsal view of the pineal complex showing the initiation of left-sided parapineal axonal projection and a dorsal view of the IPN (white circle) revealing habenular efferent connectivity reaching dorsal and ventral regions of the IPN. The scale was maintained in (a,b) to emphasize the effect of time normalization. Zebrafish and medaka show a conserved sequence of developmental events of epithalamic asymmetry although they exhibit distinct relative timing ( heterochrony). 
Figure 4. Developmental models of heterotopic parapineal efferent connectivity. (a) Zebrafish: asymmetries of the parapineal organ and habenulae interact in three consecutive steps during development. (i) Initial left-right biases in the presumptive habenular region guide parapineal migration to the left side. (ii) Subsequent left-sided positioning of the parapineal organ is involved in the induction/propagation of a distinct spatial pattern of habenular differentiation. (iii) Finally, the topology of subdomains arising after habenular differentiation determines the position of habenular neurons receiving parapineal efferent connectivity. (b) Medaka (model 1): heterotopic parapineal efferent connectivity arises from a different topological organization of habenular subdomains. In this model, spatial differences in the location of the parapineal organ at the time of habenular differentiation and/or underlying differences in habenular (i) pre-patterning lead to (ii) distinct topological programmes of habenular subdomain differentiation and (iii) subsequent positioning of parapineal target cells. (c) Medaka (model 2): heterotopic parapineal efferent connectivity arises from different selection of parapineal target cells within the habenulae. In this model, parapineal migration and habenular differentiation are equivalent in both species. However, parapineal projections reach different target neurons in the habenula of both species owing to the differences in axon guidance cues. (i) Shaded green regions depict molecular left-right biases within the presumptive habenulae. The movement of the parapineal organ from the midline to the left side (arrows) is represented as partially overlapping drawings of parapineal outlines. (ii) White and red regions illustrate putative subdomains of the habenulae. Arrows illustrate the direction of the inductive properties of the parapineal organ. (iii) The topological pattern of parapineal efferent connectivity (black) and the location of parapineal target cells within the habenula (colours) are shown (see also figure 2). Colours represent equivalent cellular identities. All diagrams correspond to dorsal views, with anterior to the top. For clarity, only the left habenula is illustrated, and the right habenula is depicted with dotted lines. L, left; R, right; Lh, left habenula; Rh, right habenula; hc, habenular commissure. 
11-P010 Zebrafish and medaka: Model organisms for a comparative developmental approach of brain asymmetry

December 2008


187 Reads

Comparison between related species is a successful approach to uncover conserved and divergent principles of development. Here, we studied the pattern of epithalamic asymmetry in zebrafish (Danio rerio) and medaka (Oryzias latipes), two related teleost species with 115-200 Myr of independent evolution. We found that these species share a strikingly conserved overall pattern of asymmetry in the parapineal-habenular-interpeduncular system. Nodal signalling exhibits comparable spatial and temporal asymmetric expressions in the presumptive epithalamus preceding the development of morphological asymmetries. Neuroanatomical asymmetries consist of left-sided asymmetric positioning and connectivity of the parapineal organ, enlargement of neuropil in the left habenula compared with the right habenula and segregation of left-right habenular efferents along the dorsoventral axis of the interpeduncular nucleus. Despite the overall conservation of asymmetry, we observed heterotopic changes in the topology of parapineal efferent connectivity, heterochronic shifts in the timing of developmental events underlying the establishment of asymmetry and divergent degrees of canalization of embryo laterality. We offer new tools for developmental time comparison among species and propose, for each of these transformations, novel hypotheses of ontogenic mechanisms that explain interspecies variations that can be tested experimentally. Together, these findings highlight the usefulness of zebrafish and medaka as comparative models to study the developmental mechanisms of epithalamic asymmetry in vertebrates.

Postscript relating to new allegations made by Edward Hooper at The Royal Society Discussion Meeting on 11 September 2000

July 2001


96 Reads

At The Royal Society Discussion Meeting, Origins of HIV and the AIDS epidemic, which this issue records, Edward Hooper added two new 'smoking guns' to the accusations published previously in The river. These were proposed as conclusive evidence for the hypothesis that simian immunodeficiency virus-contaminated CHAT polio vaccine caused the HIV-1 group M epidemic. We have investigated the facts in relation to these 'smoking guns'.

Van Dijk PJ. Ecological and evolutionary opportunities of apomixis: insights from Taraxacum and Chondrilla. Philos Trans Roy Soc London Ser B-Biol Sci 358: 1113-1120

July 2003


212 Reads

The ecological and evolutionary opportunities of apomixis in the short and the long term are considered, based on two closely related apomictic genera: Taraxacum (dandelion) and Chondrilla (skeleton weed). In both genera apomicts have a wider geographical distribution than sexuals, illustrating the short–term ecological success of apomixis. Allozymes and DNA markers indicate that apomictic populations are highly polyclonal. In Taraxacum , clonal diversity can be generated by rare hybridization between sexuals and apomicts, the latter acting as pollen donors. Less extensive clonal diversity is generated by mutations within clonal lineages. Clonal diversity may be maintained by frequency–dependent selection, caused by biological interactions (e.g. competitors and pathogens). Some clones are geographically widespread and probably represent phenotypically plastic ‘general–purpose genotypes’. The long–term evolutionary success of apomictic clones may be limited by lack of adaptive potential and the accumulation of deleterious mutations. Although apomictic clones may be considered as ‘evolutionary dead ends’, the genes controlling apomixis can escape from degeneration and extinction via pollen in crosses between sexuals and apomicts. In this way, apomixis genes are transferred to a new genetic background, potentially adaptive and cleansed from linked deleterious mutations. Consequently, apomixis genes can be much older than the clones they are currently contained in. The close phylogenetic relationship between Taraxacum and Chondrilla and the similarity of their apomixis mechanisms suggest that apomixis in these two genera could be of common ancestry.

Inchausti P, Ginzburg L. Maternal effects mechanism of population cycling: a formidable competitor to the traditional predator-prey view. Philos Trans R Soc Lond B Biol Sci 364: 1117-1124
In the language of mathematics, one needs minimally two interacting variables (two dimensions) to describe repeatable periodic behaviour, and in the language of density dependence, one needs delayed, not immediate, density dependence to produce cyclicity. Neither language specifies the causal mechanism. There are two major potential mechanisms: exogenous mechanisms involving species interactions as in predator-prey or host-parasite, and endogenous mechanisms such as maternal effects where population growth results from the cross-generational transmission of individual quality. The species interactions view stemming from a major observation of Elton and a simultaneous independent theory by Lotka and Volterra is currently dominant. Most ecologists, when faced with cyclic phenomena, automatically look for an interacting species one step below or above in a food chain in order to find an explanation. Maternal effects hypothesis, verbally suggested in the 1950s, had only found its theoretical implementation in the 1990 s. In a relatively short time, the degree of acceptance of this view grew to the level of a 'minority opinion' as evidenced by the widely used textbook of Begon et al. This short review attempts to describe the arguments for and against this internal two-dimensional approach.

Table 2 . Proportions of antagonistic QTLs for various categories of organisms and traits in crosses involving wild species and tests for significant deviations from neutrality. 
ANOVA of the effects of kingdom, population type, cross type, mating system and trait type on the total number of QTLs per trait. 
Logistic analysis of whether or not each trait had at least one antagonistic QTL as a function of kingdom, popu- lation type, cross type, mating system, trait type and the total number of QTLs per trait. 
Rieseberg LH, Widmer A, Arntz AM, Burke JM. The genetic architecture necessary for transgressive segregation is common in both natural and domesticated populations. Philos Trans R Soc Lond B 358: 1141-1147

July 2003


146 Reads

Segregating hybrids often exhibit phenotypes that are extreme or novel relative to the parental lines. This phenomenon is referred to as transgressive segregation, and it provides a mechanism by which hybridization might contribute to adaptive evolution. Genetic studies indicate that transgressive segregation typically results from recombination between parental taxa that possess quantitative trait loci (QTLs) with antagonistic effects (i.e. QTLs with effects that are in the opposite direction to parental differences for those traits). To assess whether this genetic architecture is common, we tabulated the direction of allelic effects for 3252 QTLs from 749 traits and 96 studies. Most traits (63.6%) had at least one antagonistic QTL, indicating that the genetic substrate for transgressive segregation is common. Plants had significantly more antagonistic QTLs than animals, which agrees with previous reports that transgressive segregation is more common in plants than in animals. Likewise, antagonistic QTLs were more frequent in intra- than in interspecific crosses and in morphological than in physiological traits. These results indicate that transgressive segregation provides a general mechanism for the production of extreme phenotypes at both above and below the species level and testify to the possible creative part of hybridization in adaptive evolution and speciation.

Figure 3. A schematic illustration of the cytoarchitectonic division of (a) the hand and (b) the foot somatosensory cortices. The shadowed areas indicate areas where currents can generate MEG signals outside the head.
Forss, N.: Magnetoencephalography in the study of human somatosensory cortical processing. Philos. Trans. R. Soc. Lond. B 354, 1145-1154
Magnetoencephalography (MEG) is a totally non-invasive research method which provides information about cortical dynamics on a millisecond time-scale. Whole-scalp magnetic field patterns following stimulation of different peripheral nerves indicate activation of an extensive cortical network. At the SI cortex, the responses reflect mainly the activity of area 3b, with clearly somatotopical representations of different body parts. The SII cortex is activated bilaterally and it also receives, besides tactile input, nociceptive afference. Somatically evoked MEG signals may also be detected from the posterior parietal cortex, central mesial cortex and the frontal lobe. The serial versus parallel processing in the cortical somatosensory network is still under debate.

Comai L, Madlung A, Josefsson C, Tyagi A. Do the different parental 'heteromes' cause genomic shock in newly formed allopolyploids? Philos Trans R Soc Lond B Biol Sci 358: 1149-1155

July 2003


62 Reads

Allopolyploidy, the joining of two parental genomes in a polyploid organism with diploid meiosis, is an important mechanism of reticulate evolution. While many successful long-established allopolyploids are known, those formed recently undergo an instability phase whose basis is now being characterized. We describe observations made with the Arabidopsis system that include phenotypic instability, gene silencing and activation, and methylation changes. We present a model based on the epigenetic destabilization of genomic repeats, which in the parents are heterochromatinized and suppressed. We hypothesize that loss of epigenetic suppression of these sequences, here defined as the heterome, results in genomic instability including silencing of single-copy genes.

Magistretti PJ, Pellerin LCellular mechanisms of brain energy metabolism and their relevance to functional brain imaging. Phil Trans R Soc Lond B Biol Sci 354:1155-1163
Despite striking advances in functional brain imaging, the cellular and molecular mechanisms that underlie the signals detected by these techniques are still largely unknown. The basic physiological principle of functional imaging is represented by the tight coupling existing between neuronal activity and the associated local increase in both blood flow and energy metabolism. Positron emission tomography (PET) signals detect blood flow, oxygen consumption and glucose use associated with neuronal activity; the degree of blood oxygenation is currently thought to contribute to the signal detected with functional magnetic resonance imaging, while magnetic resonance spectroscopy (MRS) identifies the spatio-temporal pattern of the activity-dependent appearance of certain metabolic intermediates such as glucose or lactate. Recent studies, including those of neurotransmitter-regulated metabolic fluxes in purified preparations and analyses of the cellular localization of enzymes and transporters involved in energy metabolism, as well as in vivo microdialysis and MRS approaches have identified the neurotransmitter glutamate and astrocytes, a specific type of glial cell, as pivotal elements in the coupling of synaptic activity with energy metabolism. Astrocytes are ideally positioned to sense increases in synaptic activity and to couple them with energy metabolism. Indeed they possess specialized processes that cover the surface of intraparenchymal capillaries, suggesting that astrocytes may be a likely site of prevalent glucose uptake. Other astrocyte processes are wrapped around synaptic contacts which possess receptors and reuptake sites for neurotransmitters. Glutamate stimulates glucose uptake into astrocytes. This effect is mediated by specific glutamate transporters present on these cells. The activity of these transporters, which is tightly coupled to the synaptic release of glutamate and operates the clearance of glutamate from the extracellular space, is driven by the electrochemical gradient of Na+. This Na(+)-dependent uptake of glutamate into astrocytes triggers a cascade of molecular events involving the Na+/K(+)-ATPase leading to the glycolytic processing of glucose and the release of lactate by astrocytes. The stoichiometry of this process is such that for one glutamate molecule taken up with three Na+ ions, one glucose molecule enters an astrocyte, two ATP molecules are produced through aerobic glycolysis and two lactate molecules are released. Within the astrocyte, one ATP molecule fuels one 'turn of the pump' while the other provides the energy needed to convert glutamate to glutamine by glutamine synthase. Evidence has been accumulated from structural as well as functional studies indicating that, under aerobic conditions, lactate may be the preferred energy substrate of activated neurons. Indeed, in the presence of oxygen, lactate is converted to pyruvate, which can be processed through the tricarboxylic acid cycle and the associated oxidative phosphorylation, to yield 17 ATP molecules per lactate molecule. These data suggest that during activation the brain may transiently resort to aerobic glycolysis occurring in astrocytes, followed by the oxidation of lactate by neurons. The proposed model provides a direct mechanism to couple synaptic activity with glucose use and is consistent with the notion that the signals detected during physiological activation with 18F-deoxyglucose (DG)-PET may reflect predominantly uptake of the tracer into astrocytes. This conclusion does not question the validity of the 2-DG-based techniques, rather it provides a cellular and molecular basis for these functional brain imaging techniques.

Figure 1. Individual male fertilities {l k } of individuals in a population of Chamaelirium luteum estimated by ML paternity analysis. 
Table 2 . Nonlinear regression coefficients estimated for each plot -year combination using the model lnl ik = gd ik 1 af ik . 
Figure 2. Expected relative male reproductive success {l k } according to a negative exponential model of pollen dispersal (equation (2.2)) with different values for the distance effect parameter g. 
Figure 3. Observed counts of transgenic progeny over the hexagonal grid for each plot-year combination: (a) plot 1, 1999; (b) plot 2, 1999; (c) plot 1, 2000; (d ) plot 2, 2000. 
Figure 4. Predicted counts of transgenic progeny over the hexagonal grid (see table 2 for nonlinear regression coefficients) for each plot-year combination: (a) plot 1, 1999; (b) plot 2, 1999; (c) plot 1, 2000; (d ) plot 2, 2000. 
Meagher TR, Belanger FC, Day PR. Using empirical data to model transgene dispersal. Philos Trans R Soc London B 358: 1157-1162

July 2003


83 Reads

One element of the current public debate about genetically modified crops is that gene flow from transgenic cultivars into surrounding weed populations will lead to more problematic weeds, particularly for traits such as herbicide resistance. Evolutionary biologists can inform this debate by providing accurate estimates of gene flow potential and subsequent ecological performance of resulting hybrids. We develop a model for gene flow incorporating exponential distance and directional effects to be applied to windpollinated species. This model is applied to previously published data on gene flow in experimental plots of Agrostis stolonifera L. (creeping bentgrass), which assessed gene flow from transgenic plants resistant to the herbicide glufosinate to surrounding non-transgenic plants. Our results show that although pollen dispersal can be limited in some sites, it may be extensive in others, depending on local conditions such as exposure to wind. Thus, hybridization under field conditions is likely to occur. Given the nature of the herbicide resistance trait, we regard this trait as unlikely to persist in the absence of herbicide, and suggest that the ecological consequences of such gene flow are likely to be minimal.

Ellstrand NC. Current knowledge of gene flow in plants: implications for transgene flow. Philos Trans R Soc Lond B 358: 1163-1170

July 2003


81 Reads

Plant evolutionary biologists' view of gene flow and hybridization has undergone a revolution. Twenty-five years ago, both were considered rare and largely inconsequential. Now gene flow and hybridization are known to be idiosyncratic, varying with the specific populations involved. Gene flow typically occurs at evolutionarily significant rates and at significant distances. Spontaneous hybridization occasionally has important applied consequences, such as stimulating the evolution of more aggressive invasives and increasing the extinction risk for rare species. The same problems have occurred for spontaneous hybridization between crops and their wild relatives. These new data have implications for transgenic crops: (i) for most crops, gene flow can act to introduce engineered genes into wild populations; (ii) depending on the specific engineered gene(s) and populations involved, gene flow may have the same negative impacts as those observed for traditionally improved crops; (iii) gene flow's idiosyncratic nature may frustrate management and monitoring attempts; and (iv) intercrop transgene flow, although rarely discussed, is equally worthy of study.

Rothman DL, Sibson NR, Hyder F, Shen J, Behar KL, Shulman RGIn vivo nuclear magnetic resonance spectroscopy studies of the relationship between the glutamate-glutamine neurotransmitter cycle and functional neuroenergetics. Philos Trans R Soc Lond B Biol Sci 354:1165-1177
In this article we review recent studies, primarily from our laboratory, using 13C NMR (nuclear magnetic resonance) to non-invasively measure the rate of the glutamate-glutamine neurotransmitter cycle in the cortex of rats and humans. In the glutamate-glutamine cycle, glutamate released from nerve terminals is taken up by surrounding glial cells and returned to the nerve terminals as glutamine. 13C NMR studies have shown that the rate of the glutamate-glutamine cycle is extremely high in both the rat and human cortex, and that it increases with brain activity in an approximately 1:1 molar ratio with oxidative glucose metabolism. The measured ratio, in combination with proposals based on isolated cell studies by P. J. Magistretti and co-workers, has led to the development of a model in which the majority of brain glucose oxidation is mechanistically coupled to the glutamate-glutamine cycle. This model provides the first testable mechanistic relationship between cortical glucose metabolism and a specific neuronal activity. We review here the experimental evidence for this model as well as implications for blood oxygenation level dependent magnetic resonance imaging and positron emission tomography functional imaging studies of brain function.

Figure 4. Trends in central tendency and variability of incubation periods at varying dose. (a) Box-whisker plot of incubation period as a function of relative dose (di¡erence from ID 50 ). Relative dose is a logarithmic measure so a one unit increase represents a tenfold rise in the concentration of infectious material in the inoculum. As dose increases, median incubation period decreases in a linear fashion. (b) Detailed distribution of incubation periods at relative doses 4, 2 and 0. (c) Box-whisker plot of the di¡erence of each mouse's incubation period from the average for its group (i.e. all infected mice at that dose in that experiment). Mice in groups where only one animal was infected are excluded. This treatment of the data removes betweenexperiment variability and is therefore a better method for investigating trends in the variability of incubation period with dose. Between the ID 50 and four logs above, each tenfold increase in dose leads to a seven-day reduction in the interquartile range for the incubation period. (d ) Detail of the distributions of di¡erence from mean incubation period at relative doses 4, 2 and 0. These curves show that it would be reasonable to assume a normal distribution of the incubation period within an experimental group. (e) Box-whisker plot of incubation periods as a function of relative dose for the 16 experiments that used ME7 in C57 mice. ( f ) Box-whisker plot of incubation periods as a function of relative dose for the 22 experiments that used 22A in VM mice. 
Scrapie infections initiated at varying doses: An analysis of 117 titration experiments

September 2000


125 Reads

An analysis of 117 titration experiments in the murine scrapie model is presented. The experiments encompass 30 years' work and a wide range of experimental conditions. To check that the experimental designs were reasonably consistent over time, comparisons were made of size, duration, source of inoculum, etc., in each experiment. These comparisons revealed no systematic trends that would render invalid comparisons across experiments. For 114 of the experiments it was possible to calculate the dose at which half of the challenged animals were infected (the ID50). These 114 experiments were then combined on the basis of relative dose (i.e. tenfold dilution relative to the ID50). This created a data set in which over 4000 animals were challenged with doses of scrapie ranging from four orders of magnitude below to five orders of magnitude above the ID50. Analysis of this data reveals that mean incubation periods rise linearly with logarithmic decreases in dose. A one unit increase in relative dose (i.e. a tenfold increase in actual dose) will, on average, decrease the incubation period by 25 days. At ID50 the average incubation period in this data set is 300 days. Within a single dose, in a single experimental model, incubation periods have a distribution close to normal. Variability in incubation period also rises linearly as dose decreases. There is no age or sex effect upon the probability of infection, but female mice have incubation periods that are, on average, nine days shorter than their male counterparts and young mice have incubation periods that are longer by seven days. Although many of these patterns are apparent in the results of single titration curves, they can be more rigorously investigated by considering the outcome for thousands of mice.

Imaging the serotonin 1A receptor using [11C]WAY100635 in healthy controls and major depression
As a neurotransmitter, serotonin (5-HT) is widely used throughout the brain and known to play a role in many processes including emotion and brain development. Of the 15 subtypes of 5-HT receptors, the 1A receptor (5-HT(1A)) has been implicated in depression and suicide. Using the [carbonyl-(11)C]WAY100635 ([(11)C]WAY) ligand and positron emission tomography, we have studied the 5-HT(1A) receptor, first in a group of healthy controls, then in two separate groups of subjects with major depressive disorder (MDD) (antidepressant exposed and not recently medicated), and, lastly, in a group of subjects remitted from MDD. All MDD subjects were medication-free at the time of scan. We found higher 5-HT(1A) binding potential (BP(F)) in MDD subjects not recently exposed to an antidepressant compared with controls and recently medicated MDD subjects; and higher BP(F) in subjects with the C(-1019)G promoter polymorphism. We replicated these findings in a novel cohort and reconciled our discrepant findings with other groups using alternate quantification techniques. We also reported higher BP(F) in subjects remitted from a major depressive episode than in controls. From this work, we proposed a temporal model in which 5-HT(1A) BP(F) may be a trait abnormality of MDD. To further explore the genetic components of MDD and utility of 5-HT(1A) imaging as a potential tool for biomarker or treatment response prediction, these findings should be replicated in a larger cohort using the [(11)C]CUMI-101 agonist tracer.

Figure 1. Epifluorescence image of the surface of a rock from an intertidal pool on the South Devon coast.The sample was taken in December 2004 and was stained with SYBR Green I and viewed with a Bio-Rad 1024 confocal laser microscope. The bacteria are stained green and the red fluorescence is due to the autofluorescence of chloroplasts within microalgae. 
Figure 2. The relationship between the density of bacteria (Vibrio anguillarum) in a biofilm and the number of zoospores that attach to the biofilm. The response of the wild-type (C), which produces three AHL molecules (C6-HSL, 3-hydroxyHSL and 3-oxo-C10-HSL) is compared with a vanIM mutant (,) that produces no AHLs.
Figure 3. Attraction of zoospores to biofilm surface roughness. ( a ) Transmission image of zoospores settled on a filamentous actinobacteria biofilm (scale bar, 25 m m). Zoospore settlement on biofilms of ( b ) a filamentous actinobacteria is compared with ( c ) an AHL-producing strain. Treating the biofilms with UV (1 h) or antibiotics (5 units ml K 1 penicillin, 30 min) caused no significant 
Figure 4. Exposure to 3-oxo-C12-HSL induces a calcium influx in Ulva zoospores. (a) False colour image of an Ulva zoospore loaded with the fluorescent calcium indicator dye, calcium orange AM, and viewed by confocal laser microscopy. Calcium influx was determined by the manganese quench technique. Ulva zoospores were exposed to 175 mmol l K1 3-oxo-C12-HSL after prior incubation in seawater containing 100 mmol l K1 MnCl 2 for 5 min. Fluorescence was imaged following excitation at 568 nm, using a Bio-Rad 1024 confocal laser microscope. Only zoospores that had not undergone settlement and retained flagella throughout the time-course were measured. (b) Mean cellular fluorescence in Ulva zoospores expressed as a percentage of initial fluorescence on addition of 3-oxo-C12-HSL (nZ9, control nZ5). Scale bar is 5 mm.
Joint I, Tait K, Wheeler G.. Cross-kingdom signalling: exploitation of bacterial quorum sensing molecules by the green seaweed Ulva. Philos Trans Roy Soc B 362: 1223-1233
The green seaweed Ulva has been shown to detect signal molecules produced by bacteria. Biofilms that release N-acylhomoserine lactones (AHLs) attract zoospores--the motile reproductive stages of Ulva. The evidence for AHL involvement is based on several independent lines of evidence, including the observation that zoospores are attracted to wild-type bacteria that produce AHLs but are not attracted to mutants that do not produce signal molecules. Synthetic AHL also attracts zoospores and the attraction is lost in the presence of autoinducer inactivation (AiiA) protein. The mechanism of attraction is not chemotactic but involves chemokinesis. When zoospores detect AHLs, the swimming rate is reduced and this results in accumulation of cells at the source of the AHL. It has been demonstrated that the detection of AHLs results in calcium influx into the zoospore. This is the first example of a calcium signalling event in a eukaryote in response to bacterial quorum sensing molecules. The role of AHLs in the ecology of Ulva is discussed. It is probable that AHLs act as cues for the settlement of zoospores, rather than being directly involved as a signalling mechanism.

Mackay TFC. Mutations and quantitative genetic variation: lessons from Drosophila. Philos Trans R Soc B 365: 1229-1239
A central issue in evolutionary quantitative genetics is to understand how genetic variation for quantitative traits is maintained in natural populations. Estimates of genetic variation and of genetic correlations and pleiotropy among multiple traits, inbreeding depression, mutation rates for fitness and quantitative traits and of the strength and nature of selection are all required to evaluate theoretical models of the maintenance of genetic variation. Studies in Drosophila melanogaster have shown that a substantial fraction of segregating variation for fitness-related traits in Drosophila is due to rare deleterious alleles maintained by mutation-selection balance, with a smaller but significant fraction attributable to intermediate frequency alleles maintained by alleles with antagonistic pleiotropic effects, and late-age-specific effects. However, the nature of segregating variation for traits under stabilizing selection is less clear and requires more detailed knowledge of the loci, mutation rates, allelic effects and frequencies of molecular polymorphisms affecting variation in suites of pleiotropically connected traits. Recent studies in D. melanogaster have revealed unexpectedly complex genetic architectures of many quantitative traits, with large numbers of pleiotropic genes and alleles with sex-, environment- and genetic background-specific effects. Future genome wide association analyses of many quantitative traits on a common panel of fully sequenced Drosophila strains will provide much needed empirical data on the molecular genetic basis of quantitative traits.

Crow JF. On epistasis: why it is unimportant in polygenic directional selection. Philos Trans R Soc B 365: 1241-1244
There is a difference in viewpoint of developmental and evo-devo geneticists versus breeders and students of quantitative evolution. The former are interested in understanding the developmental process; the emphasis is on identifying genes and studying their action and interaction. Typically, the genes have individually large effects and usually show substantial dominance and epistasis. The latter group are interested in quantitative phenotypes rather than individual genes. Quantitative traits are typically determined by many genes, usually with little dominance or epistasis. Furthermore, epistatic variance has minimum effect, since the selected population soon arrives at a state in which the rate of change is given by the additive variance or covariance. Thus, the breeder's custom of ignoring epistasis usually gives a more accurate prediction than if epistatic variance were included in the formulae.

Asarian L, Geary N. Modulation of appetite by gonadal steroid hormones. Philos Trans R Soc Lond B Biol Sci 361: 1251-1263
Several sex differences in eating, their control by gonadal steroid hormones and their peripheral and central mediating mechanisms are reviewed. Adult female rats and mice as well as women eat less during the peri-ovulatory phase of the ovarian cycle (estrus in rats and mice) than other phases, an effect under the control of cyclic changes in estradiol secretion. Women also appear to eat more sweets during the luteal phase of the cycle than other phases, possibly due to simultaneous increases in estradiol and progesterone. In rats and mice, gonadectomy reveals further sex differences: orchiectomy decreases food intake by decreasing meal frequency and ovariectomy increases food intake by increasing meal size. These changes are reversed by testosterone and estradiol treatment, respectively. A variety of peripheral feedback controls of eating, including ghrelin, cholecystokinin (CCK), glucagon, hepatic fatty acid oxidation, insulin and leptin, has been shown to be estradiol-sensitive under at least some conditions and may mediate the estrogenic inhibition of eating. Of these, most progress has been made in the case of CCK. Neurons expressing estrogen receptor-alpha in the nucleus tractus solitarius of the brainstem appear to increase their sensitivity to CCK-induced vagal afferent input so as to lead to an increase in the satiating potency of CCK, and consequently decreased food intake, during the peri-ovulatory period in rats. Central serotonergic mechanisms also appear to be part of the effect of estradiol on eating. The physiological roles of other peripheral feedback controls of eating and their central mediators remain to be established.

Acoustic communication and the evolution of hearing in fishes. Phil. Trans. R. Soc. Lond. B. 355: 1285-1288

September 2000


40 Reads

Fishes have evolved a diversity of sound-generating organs and acoustic signals of various temporal and spectral content. Additionally, representatives of many teleost families such as otophysines, anabantoids, mormyrids and holocentrids possess accessory structures that enhance hearing abilities by acoustically coupling air-filled cavities to the inner ear. Contrary to the accessory hearing structures such as Weberian ossicles in otophysines and suprabranchial chambers in anabantoids, sonic organs do not occur in all members of these taxa. Comparison of audiograms among nine representatives of seven otophysan families from four orders revealed major differences in auditory sensitivity, especially at higher frequencies (> 1 kHz) where thresholds differed by up to 50 dB. These differences showed no apparent correspondence to the ability to produce sounds (vocal versus non-vocal species) or to the spectral content of species-specific sounds. In anabantoids, the lowest auditory thresholds were found in the blue gourami Trichogaster trichopterus, a species not thought to be vocal. Dominant frequencies of sounds corresponded with optimal hearing bandwidth in two out of three vocalizing species. Based on these results, it is concluded that the selective pressures involved in the evolution of accessory hearing structures and in the design of vocal signals were other than those serving to optimize acoustic communication.

Neovitamin B12 (cyano-13-epicobalamin)

March 1976


6 Reads

Beta-Epimerization in the corrinoid system has recently emerged as a complicating factor in the latter stages of the total synthesis of vitamin B12 (Eschenmoser 1971; Woodward 1973). It has also found some application in biosynthetic studies on the origin of the methyl groups in ring C (Scott, Townsend & Cushley 1973; Scott, this Discussion p. 303). This paper sets out to review briefly the beta-epimerization of corrinoid polyamides, with particular reference to our work on the neo-series which provided the first established example of this phenomenon.

Davis M, Walker DL, Lee Y. Amygdala and bed nucleus of the stria terminalis: differtial roles in fear and anxiety measured with the acoustic startle reflex. Philos Trans R Soc Lond B Biol Sci 352(1362): 1675-1687

December 1997


31 Reads

Neural stimuli associated with traumatic events can readily become conditioned so as to reinstate the memory of the original trauma. These conditioned fear responses can last a lifetime and may be especially resistant to extinction. A large amount of data from many different laboratories indicate that the amygdala plays a crucial role in conditioned fear. The amygdala receives information from all sensory modalities and projects to a variety of hypothalamic and brainstem target areas known to be critically involved in specific signs that are used to define fear and anxiety. Electrical stimulation of the amygdala elicits a pattern of behaviours that mimic natural or conditioned states of fear. Lesions of the amygdala block innate or conditioned fear and local infusion of drugs into the amygdala have anxiolytic effects in several behavioural tests. Excitatory amino acid receptors in the amygdala are critical for the acquisition, expression and extinction of conditioned fear.

Bestor T. Imprinting errors and developmental asymmetry. Philos Trans R Soc Lond B Biol Sci 358: 1411-1415

September 2003


33 Reads

There are, in the broadest sense, two mechanisms by which gene expression can be extinguished in vertebrates. The first of these is based on mass action effects of positive and negative regulatory factors and is termed activation and repression; the second is independent of positive regulatory factors but is based on the history of the affected gene and is termed silencing. It can be said, again in the broadest sense, that imprinted genes, genes subject to X inactivation, and transposon promoters are subject to silencing, while the promoters of tissue-specific genes in non-expressing tissues are controlled by activation and repression. The escape of imprinted genes from silencing through unknown mechanisms can cause developmental abnormalities and can predispose to the formation of embryonal tumours. One developmental disorder caused by loss of imprinting of genes on chromosome 11p15.5 is Beckwith-Wiedemann syndrome (BWS). This syndrome has long been known to be inexplicably common in monozygotic twins; the twins are nearly always discordant for BWS, and nearly all twins are female. A loss of imprinting model based on stochastic errors in the nucleocytoplasmic trafficking of the DNA methyltransferase DNMT1, or a paternally expressed function that opposes maintenance methylation of maternally repressed growth-enhancing genes, is proposed to explain the perplexing genetics of BWS in monozygotic twins.

Andersen, R. A. Multimodal integration for the representation of space in the posterior parietal cortex. Phil. Trans. R. Soc. Lond. B 352, 1421-1428

November 1997


34 Reads

The posterior parietal cortex has long been considered an 'association' area that combines information from different sensory modalities to form a cognitive representation of space. However, until recently little has been known about the neural mechanisms responsible for this important cognitive process. Recent experiments from the author's laboratory indicate that visual, somatosensory, auditory and vestibular signals are combined in areas LIP and 7a of the posterior parietal cortex. The integration of these signals can represent the locations of stimuli with respect to the observer and within the environment. Area MSTd combines visual motion signals, similar to those generated during an observer's movement through the environment, with eye-movement and vestibular signals. This integration appears to play a role in specifying the path on which the observer is moving. All three cortical areas combine different modalities into common spatial frames by using a gain-field mechanism. The spatial representations in areas LIP and 7a appear to be important for specifying the locations of targets for actions such as eye movements or reaching; the spatial representation within area MSTd appears to be important for navigation and the perceptual stability of motion signals.

Does the perception of moving eyes trigger reflexive visual orienting in autism? Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences, 358(1430), 325-334

March 2003


173 Reads

Does movement of the eyes in one or another direction function as an automatic attentional cue to a location of interest? Two experiments explored the directional movement of the eyes in a full face for speed of detection of an aftercoming location target in young people with autism and in control participants. Our aim was to investigate whether a low-level perceptual impairment underlies the delay in gaze following characteristic of autism. The participants' task was to detect a target appearing on the left or right of the screen either 100 ms or 800 ms after a face cue appeared with eyes averting to the left or right. Despite instructions to ignore eye-movement in the face cue, people with autism and control adolescents were quicker to detect targets that had been preceded by an eye movement cue congruent with target location compared with targets preceded by an incongruent eye movement cue. The attention shifts are thought to be reflexive because the cue was to be ignored, and because the effect was found even when cue-target duration was short (100 ms). Because (experiment two) the effect persisted even when the face was inverted, it would seem that the direction of movement of eyes can provide a powerful (involuntary) cue to a location.

Petrides M. Specialized systems for the processing of mnemonic information within the primate frontal cortex. Phil Trans R Soc Lond B Biol Sci 351: 1455-1461; discussion 1461-1452

November 1996


52 Reads

The lateral frontal cortex is involved in various aspects of executive processing within short- and long-term memory. It is argued that the different parts of the lateral frontal cortex make distinct contributions to memory that differ in terms of the level of executive processing that is carried out in interaction with posterior cortical systems. According to this hypothesis, the mid-dorsolateral frontal cortex (areas 46 and 9) is a specialized system for the monitoring and manipulation of information within working memory, whereas the mid-ventrolateral frontal cortex (areas 47/12 and 45) is involved in the active retrieval of information from the posterior cortical association areas. Data are presented which support this two-level hypothesis that posits two distinct levels of interaction of the lateral frontal cortex with posterior cortical association areas. Functional activation studies with normal human subjects have demonstrated specific activity within the mid-dorsolateral region of the frontal cortex during the performance of tasks requiring monitoring of self-generated and externally generated sequences of responses. In the monkey, lesions restricted to this region of the frontal cortex yield a severe impairment in performance of the above tasks, this impairment appearing against a background of normal performance on several basic mnemonic tasks. By contrast, a more severe impairment follows damage to the mid-ventrolateral frontal region and functional activation studies have demonstrated specific changes in activity in this region in relation to the active retrieval of information from memory.

Figure 1. Schematic overview of model for genomic medicine based on integration of gene expression profiles with clinical and other data. Based in part on Nevins et al. (2003). 
Figure 2. Integrated translational process for genomic medicine. 
Genomic medicine: genetic variation and its impact on the future of health care. Philos Trans R Soc Lond B Biol Sci 360(1460): 1543-1550
Advances in genome technology and other fruits of the Human Genome Project are playing a growing role in the delivery of health care. With the development of new technologies and opportunities for large-scale analysis of the genome, transcriptome, proteome and metabolome, the genome sciences are poised to have a profound impact on clinical medicine. Cancer prognostics will be among the first major test cases for a genomic medicine paradigm, given that all cancer is caused by genomic instability, and microarrays allow assessment of patients' entire expressed genomes. Analysis of breast cancer patients' expression patterns can already be highly correlated with recurrence risks. By integrating clinical data with gene expression profiles, imaging, metabolomic profiles and proteomic data, the prospect for developing truly individualized care becomes ever more real. Notwithstanding these promises, daunting challenges remain for genomic medicine. Success will require planning robust prospective trials, analysing health care economic and outcome data, assuaging insurance and privacy concerns, developing health delivery models that are commercially viable and scaling up to meet the needs of the whole population.

Figure 1. Dissociation between between components of spatial learning by using an NMDA receptor antagonist. (a) Experiment 1. Escape latency (s AE 1 s.e.m.) across training by the experimentally naive aCSF-(open symbols) and AP5-treated (¢lled symbols) groups. Note blockade of learning by the AP5-treated group. (b) Experiment 1. Percentage time ( AE 1 s.e.m.) spent in the training quadrant during TT1 (before training), TT2 (halfway through) and TT3 (after training). Note absence of searching in the training quadrant by the AP5-treated group. (c) Experiment 2. In animals given spatial pretraining in a watermaze in a separate room, AP5 has no signi¢cant e¡ect on the percentage of time spent searching in the training quadrant during the second task. (d) Experiment 4. In animals given random search pretraining in a separate room, AP5 impairs learning of the platform location during the second task. The de¢cit is not as substantial as in experimentally naive animals (Experiment 1). Based on Bannerman et al. (1995).
Figure 2. Blocking in the spatial domain. ( a ) The experimental design consisted of successive phases. For the experimental group (shown), the animals were ¢rst trained (phase 0) to ¢nd food (F+) in relation to two identical white towers. In phase 1, a landmark (grey pagoda symbol) was then added to disambiguate the situation and the animals trained until search was focused at F+ rather than F À ; in phase 2, a second landmark was then added (stack of golf balls) and additional training given for several days; ¢nally, a test was conducted with this added landmark (and the two identical landmarks). For the control group (not shown), the landmark used in phase 1 was visually distinctive and in a di¡erent geometric location. ( b ) Searching of the added landmarks during trial 1 of phase 2 (time spent (in seconds) in circle of radius 20 cm around each landmark Æ 1 s.e.m.). The control group explores both added landmarks (L1+L2/2); the experimental group directs search to the novel landmark added on that trial. ( c ) Searching during the transfer test with the landmark added at the start of phase 2 for the experimental group (preference ratio À T F+ /(T F+ T F 7 ) Æ 1 s.e.m.). The control group shows a bias 
Morris, R. G. M. & Frey, U. Hippocampal synaptic plasticity: role in spatial learning or the automatic recording of attended experience? Phil. Trans. R. Soc. Lond. B Biol. Sci. 352, 1489-1503
Allocentric spatial learning can sometimes occur in one trial. The incorporation of information into a spatial representation may, therefore, obey a one-trial correlational learning rule rather than a multi-trial error-correcting rule. It has been suggested that physiological implementation of such a rule could be mediated by N-methyl-D-aspartate (NMDA) receptor-dependent long-term potentiation (LTP) in the hippocampus, as its induction obeys a correlational type of synaptic learning rule. Support for this idea came originally from the finding that intracerebral infusion of the NMDA antagonist AP5 impairs spatial learning, but studies summarized in the first part of this paper have called it into question. First, rats previously given experience of spatial learning in a watermaze can learn a new spatial reference memory task at a normal rate despite an appreciable NMDA receptor blockade. Second, the classical phenomenon of 'blocking' occurs in spatial learning. The latter finding implies that spatial learning can also be sensitive to an animal's expectations about reward and so depend on more than the detection of simple spatial correlations. In this paper a new hypothesis is proposed about the function of hippocampal LTP. This hypothesis retains the idea that LTP subserves rapid one-trial memory, but abandons the notion that it serves any specific role in the geometric aspects of spatial learning. It is suggested that LTP participates in the automatic recording of attended experience': a subsystem of episodic memory in which events are temporarily remembered in association with the contexts in which they occur. An automatic correlational form of synaptic plasticity is ideally suited to the online registration of context event associations. In support, it is reported that the ability of rats to remember the most recent place they have visited in a familiar environment is exquisitely sensitive to AP5 in a delay-dependent manner. Moreover, new studies of the lasting persistence of NMDA-dependent LTP, known to require protein synthesis, point to intracellular mechanisms that enable transient synaptic changes to be stabilized if they occur in close temporal proximity to important events. This new property of hippocampal LTP is a desirable characteristic of an event memory system.

Genetics and the causes of evolution: 150 years of progress since Darwin

August 2010


393 Reads

The publication of The Origin of Species in 1859 represents an unsurpassed landmark in the history of biology. Charles Darwin had been thinking about evolution since 1836, and accumulating evidence both that it had occurred and that it was caused primarily (but not exclusively, as he was always

SCF ubiquitin protein ligases and phosphorylation-dependent proteolysis. Philos Trans R Soc Lond B Biol Sci 354: 1533-1550

October 1999


21 Reads

Many key activators and inhibitors of cell division are targeted for degradation by a recently described family of E3 ubiquitin protein ligases termed Skp1-Cdc53-F-box protein (SCF) complexes. SCF complexes physically link substrate proteins to the E2 ubiquitin-conjugating enzyme Cdc34, which catalyses substrate ubiquitination, leading to subsequent degradation by the 26S proteasome. SCF complexes contain a variable subunit called an F-box protein that confers substrate specificity on an invariant core complex composed of the subunits Cdc34, Skp1 and Cdc53. Here, we review the substrates and pathways regulated by the yeast F-box proteins Cdc4, Grr1 and Met30. The concepts of SCF ubiquitin ligase function are illustrated by analysis of the degradation pathway for the G1 cyclin Cln2. Through mass spectrometric analysis of Cdc53 associated proteins, we have identified three novel F-box proteins that appear to participate in SCF-like complexes. As many F-box proteins can be found in sequence databases, it appears that a host of cellular pathways will be regulated by SCF-dependent proteolysis.

Shhh! silencing by microRNA-155
Small RNAs mediate a diverse pot-pourri of post-transcriptional silencing mechanisms, ranging from 'classical' RNA interference (RNAi), to gene repression by microRNAs (miRNAs), to maintenance of genomic stability by repeat-associated small RNAs. Here, we review recent findings on the function of miR-155, particularly its roles in mammalian innate and adaptive immunity, viral infection and oncogenesis.

Plana V.. Mechanisms and tempo of evolution in the African Guineo-Congolian rainforest. Philos Trans R Soc B Biol Sci 359: 1585-1594

November 2004


119 Reads

This paper reviews how and when African rainforest diversity arose, presenting evidence from both plant and animal studies. Preliminary investigations show that these African forests are an assemblage of species of varying age. Phylogenetic evidence, from both African rainforest angiosperms and vertebrates, suggest a Tertiary origin for the major lineages in some of these groups. In groups where savannah species are well represented and rainforest species are a minority, the latter appear to be relics of a Mid-Tertiary rainforest. By contrast, species that are primarily adapted to rainforest have arisen in the past 10 Myr with the main morphological innovations dating from the Late Miocene, and Quaternary speciation dominating in large, morphologically homogeneous groups. The small number of species-level phylogenies for African rainforest plants hinders a more incisive and detailed study into the historical assembly of these continental forests.

Kraft P, Hunter D. Integrating epidemiology and genetic association: the challenge of gene-environment interaction. Philos Trans R Soc Lond B Biol Sci 360: 1609-1616
Recent advances in human genomics have made it possible to better understand the genetic basis of disease. In addition, genetic association studies can also elucidate the mechanisms by which "non-genetic" exogenous and endogenous exposures influence the risk of disease. This is true both of studies that assess the marginal effect of a single gene and studies that look at the joint effect of genes and environmental exposures. For example, gene variants that are known to alter enzyme function or level can serve as surrogates for long-term biomarker levels that are impractical or impossible to measure on many subjects. Evidence that genetic variants modify the effect of an established risk factor may help specify the risk factor's biologically active components. We illustrate these ideas with several examples and discuss design and analysis challenges, particularly for studies of gene-environment interaction. We argue that to increase the power to detect interaction effects and limit the number of false positive results, large sample sizes will be needed, which are currently only available through planned collaborative efforts. Such collaborations also ensure a common approach to measuring variation at a genetic locus, avoiding a problem that has led to difficulties when comparing results from genetic association studies.

Maynard, D. M. & Dando, M. R. The structure of the stomatogastric neuromuscular system in Callinectes sapidus, Homarus americanus, and Panulirus argus (decapoda crustacea). Philos. Trans. R. Soc. Lond. B Biol. Sci. 268, 161-220

September 1974


34 Reads

The stomatogastric nervous system of the reptantian Decapoda Crustacea, particularly the small isolated stomatogastric ganglion containing the 25-30 motor neurons that control the muscles of the gastric mill and the pyloric filter of the stomach, is an important preparation for research in comparative neurophysiology. Unfortunately there are no comprehensive descriptions of the neuromuscular system of the stomach in these animals. Therefore, since the stomatogastric motor neurons are identified by reference to the muscles they innervate, it has been difficult to identify neurons within or between species. The most important features for classifying the muscles of the decapod stomach are the ossicles to which the muscles attach. In the latter part of the last century Mocquard demonstrated that the stomach ossicles of the decapods could be compared in different groups despite the large variations from group to group. A summary of Mocquard’s (1883) classification scheme, with some modifications, is given. The scheme recognizes 33 ossicles in seven categories (cardiac gastric mill, I—VII; lateral supporting cardiac ossicles, VIII-XV ; ossicles of the cardio-pyloric valve, XVI-XVIII; supporting ossicles of the dorsal pyloric stomach, XIX -XXI; supporting ossicles of the ventral pylorus and ampullae, XXII-XXVII; supra-ampullary ossicles, XXVIII-XXX ; supporting ossicles of the lateral pylorus, XXXI-XXXIII). Where necessary, comments are then made on the ossicles of the three divergent species studied, the blue crab, Callinectes sapidus (Brachyura); the lobster, Homarus americanus (Macrura) and the spiny lobster Panulirus argus (Palinura). Most of the thirty-three ossicles are found in each of the species, but there are some major differences between species. Callinectes , for example, has the most complex ossicle system and Panulirus the most reduced.

Figure 3. (a) Standard BG model with additional simulated cortical noradrenaline (NA) effects. The locus coeruleus (LC) fires phasically upon sufficient activation of premotor units and reciprocally modulates the gain of these units via simulated NA. (b) Normalized distributions for model reaction times (number of processing cycles before the BG facilitates a response). The LC phasic mode is associated with a narrow distribution of reaction times, peaking at 50 cycles. In the tonic mode (LC units tonically 50% activated), noisy activation of both competing responses leads to a bimodal distribution and overall more RT variability, potentially explaining the variability seen in ADHD. In the 'supra-tonic' mode, LC activity was tonically set to maximal firing rates, leading to faster RTs. (c) Per cent accuracy in the same simple choice discrimination simulated to generate RT distributions in panel (b). High accuracy is seen in the phasic LC mode, as premotor responsiveness is boosted only in the presence of a task-relevant stimulus-response association. The tonic and supra-tonic modes lead to activation of alternative noisy responses, which can get inappropriately executed if not dynamically modulated by the LC. 
Frank M, Scheres A, Sherman SUnderstanding decision-making deficits in neurological conditions: insights from models of natural action selection. Philos Trans R Soc London B Biol Sci 362:1641-1654

April 2007


125 Reads

Models of natural action selection implicate fronto-striatal circuits in both motor and cognitive 'actions'. Dysfunction of these circuits leads to decision-making deficits in various populations. We review how computational models provide insights into the mechanistic basis for these deficits in Parkinson's patients and those with ventromedial frontal damage. We then consider implications of the models for understanding behaviour and cognition in attention-deficit/hyperactivity disorder (ADHD). Incorporation of cortical noradrenaline function into the model improves action selection in noisy environments and accounts for response variability in ADHD. We close with more general clinical implications.

Table 2 . Comparison of bootstrap values for the following clades: Margaritiferidae, Unionidae, Anondontinae, Ambleminae, Lampsilini, and Pleurobemini using different analyses. (EW = equal weighting, TV2 x TS = transitions weighted twice transversions, ST0.8/LPS 1.0 = stems weighted 20 % less than loops; NJ= neighbour joining (p) absolute genetic distance, (K) Kimura's (1980) two-parameter method; TE = 'Total evidence' (16S rRNA + anatomical data set).) 
Molecular Systematics and Evolution of Reproductive Traits of North American Freshwater Unionacean Mussels (Mollusca: Bivalvia) as Inferred from 16S rRNA Gene Sequences

December 1996


197 Reads

North American freshwater unionacean bivalves are a diverse group of nearly 300 species. Unionaceans exhibit an array of conchological, anatomical, life history, and reproductive characteristics that have figured prominently in proposed classification schemes. Recently, two very different classifications of North American unionaceans have been proposed. Depending on the classification system utilized, a very different evolutionary trajectory of anatomical and reproductive features is obtained. The lack of a robust, well corroborated phylogeny of North American unionacean bivalves hinders the progress of evolutionary and ecological studies involving these species. Here we present a mitochondrial DNA (mtDNA) based phylogeny for North American unionacean mussels and compare it to previously proposed classifications. In addition, we present a 'total evidence' phylogeny which incorporates both the mtDNA sequence data and available morphological data. The molecular and total evidence phylogenies agree largely with the conclusions of a previous study based largely on immunoelectrophoretic data. North American unionaceans can be divided into two families: the Unionidae, which is comprised of most of the species and the Margaritiferidae. Within the Uniondae are two subfamilies, the Anodontinae and Ambleminae. The resultant phylogeny was used to examine the evolution of several key anatomical features including the number of gills (demibranchs) used by females to brood developing embryos, incubation length (bradytictic vs tachytictic), larval (glochidial) tooth structures, and shell texture. Both molecular and total evidence phylogenies indicate several of the aforementioned characters evolved independently or were subsequently lost or gained in several lineages.

The Intrinsic, Association and Commissural Connections of Area 17 of the Visual Cortex
An experimental neurohistological study has been made of the intrinsic connections of the cortex of area 17 of the monkey, of the commissural connections of the visual cortex of the cat and monkey and of the association fibres passing into area 17 of the cat. In light microscopic studies the axonal degeneration method of Nauta has been used, and the site and mode of termination of the degenerating fibres has also been determined with the electron microscope...

Figure 1. Sir Hans Sloane. Portrait by Godfrey Kneller, 1716. Copyright & 
Figure 2. Lady Mary Wortley Montagu in Turkish costume. Copyright & National Portrait Gallery, London. 
Figure 4. Table in Benjamin Waterhouse’s 1809 tract on protection against smallpox in Milton, MA [42]. 
The prevention and eradication of smallpox: A commentary on Sloane (1755) ‘An account of inoculation’

April 2015


1,306 Reads

Sir Hans Sloane's account of inoculation as a means to protect against smallpox followed several earlier articles published in Philosophical Transactions on this procedure. Inoculation (also called 'variolation') involved the introduction of small amounts of infectious material from smallpox vesicles into the skin of healthy subjects, with the goal of inducing mild symptoms that would result in protection against the more severe naturally acquired disease. It began to be practised in England in 1721 thanks to the efforts of Lady Mary Wortley Montagu who influenced Sloane to promote its use, including the inoculation of the royal family's children. When Edward Jenner's inoculation with the cow pox ('vaccination') followed 75 years later as a safer yet equally effective procedure, the scene was set for the eventual control of smallpox epidemics culminating in the worldwide eradication of smallpox in 1977, officially proclaimed by WHO in 1980. Here, we discuss the significance of variolation and vaccination with respect to scientific, public health and ethical controversies concerning these 'weapons of mass protection'. This commentary was written to celebrate the 350th anniversary of the journal Philosophical Transactions of the Royal Society.

The Diet of Sperm Whales (Physeter macrocephalus Linnaeus 1758) off the Azores

February 1993


1,303 Reads

Stomach contents from 17 sperm whales, 15 males and two females, caught during commercial activities in 1981-1984 in the Azores region were identified and measured. A total of 28,738 cephalopods and 16 fish were represented in the collections. In addition, there were tunicates in two whales and man-made products in three whales. None of the stomachs were empty. Flesh was present in 94.1% and indigestible fragments alone, including mandibles (beaks) of cephalopods, were present in 5.9% of the stomachs. Twelve species of cephalopod were represented by flesh and 40 species were represented by lower beaks. The cephalopod families contributing food to the whales in this region are, in order of their contribution by estimated mass, the Octopoteuthidae (39.8%), the Histioteuthidae (32.7%), the Architeuthidae (12.1%), the Lepidoteuthidae (4.5%), the Ommastrephidae (3.4%), the Pholidoteuthidae (2.1%), the Cycloteuthidae (1.9%), the Cranchiidae (1.7%) and eight other families each contributing less than 1% by mass. Presence of Gonatus beaks in the stomachs show which whales have migrated southwards to the Azores just prior to capture and the presence of a large Megalocranchia species possibly shows which whales have migrated from higher latitudes off Iceland. However, the presence of Teuthowenia maculata shows which whales came north from the West coast of Africa, just prior to capture. The modal mass of cephalopods consumed is 400-450 g which represents 0.00001 of the whales' body mass. 77.5% of the species eaten have luminous organs and 82% of the species are neutrally buoyant. It seems likely that the sperm whale is obtaining 77% of its food by swimming through luminous shoals of slow-swimming, neutrally bouyant squids and only about 23% by chasing faster swimming, larger cephalopods. Cephalopods not previously recorded from the North Atlantic are Onychoteuthis boreali-japonicus, and Histioteuthis bonnellii corpuscula. Histioteuthis ?miranda may have been collected by the whales much further south than the Azores. Species not recorded previously in the diet of sperm whales in the North Atlantic are Ommastrephes bartrami, Gonatus steenstrupi, Histioteuthis ?miranda, H. bonnellii corpuscula, H. meleagroteuthis, Discoteuthis laciniosa, Mastigoteuthis species, Chiroteuthis species, ?Helicocranchia, Liocranchia reinhardti, and ?Liguriella.

From plant extract to molecular panacea: A commentary on Stone (1763) ‘An account of the success of the bark of the willow in the cure of the agues’
The application of aspirin-like drugs in modern medicine is very broad, encompassing the treatment of inflammation, pain and a variety of cardiovascular conditions. Although anecdotal accounts of willow bark extract as an anti-inflammatory drug have occurred since written records began (for example by Hippocrates), the first convincing demonstration of a potent anti-pyretic effect of willow bark containing salicylates was made by the English cleric Edward Stone in the late eighteenth century. Here, we discuss the route to optimizing and understanding the mechanism of action of anti-inflammatory drugs that have their origins in Stone's seminal study, 'An account of the success of the bark of the willow in the cure of agues'. This commentary was written to celebrate the 350th anniversary of the journal Philosophical Transactions of the Royal Society.

W??chtersh??user G.. From volcanic origins of chemoautotrophic life to Bacteria, Archaea and Eukarya. Philos Trans R Soc Lond B Biol Sci 361: 1787-1806

September 2006


116 Reads

The theory of a chemoautotrophic origin of life in a volcanic iron-sulphur world postulates a pioneer organism at sites of reducing volcanic exhalations. The pioneer organism is characterized by a composite structure with an inorganic substructure and an organic superstructure. Within the surfaces of the inorganic substructure iron, cobalt, nickel and other transition metal centres with sulphido, carbonyl and other ligands were catalytically active and promoted the growth of the organic superstructure through carbon fixation, driven by the reducing potential of the volcanic exhalations. This pioneer metabolism was reproductive by an autocatalytic feedback mechanism. Some organic products served as ligands for activating catalytic metal centres whence they arose. The unitary structure-function relationship of the pioneer organism later gave rise to two major strands of evolution: cellularization and emergence of the genetic machinery. This early phase of evolution ended with segregation of the domains Bacteria, Archaea and Eukarya from a rapidly evolving population of pre-cells. Thus, life started with an initial, direct, deterministic chemical mechanism of evolution giving rise to a later, indirect, stochastic, genetic mechanism of evolution and the upward evolution of life by increase of complexity is grounded ultimately in the synthetic redox chemistry of the pioneer organism.