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The structure and metabolic properties of tissue preparations from Schistocerca gregaria (Desert Locust)
... G. E. Pearse, personal communication). Bellamy (1958), obtained a very small uptake of oxygen on incubating homogenates of Schistocerca fat body with a-ketoglutarate and succinate and he suggested that a-ketoglutarate oxidase and succinic dehydrogenase were present but were labile on homogenizing. ...
... These tissues were incubated in locust saline with trace amounts of glycine-1^ (G) and leucine-14 C (G) and the radioactivity of the carbon dioxide produced was measured and expressed in terms of the dry weight of the tissue. Bellamy (1958) has shown that Schistocerca fat body and flight muscle have similar rates of respiration when incubated in 0-25 M sucrose. The results are given in Table 3. Table 3. Production o/ 14 CO 2 by whole fat body and flight muscle from glycine-ll C (G) and leucine-ll C (G) during incubation in saline for 4 hr. ...
... It is well known that these amino acids can become labelled with acetate via the tricarboxylic acid cycle and the result shows that in insects, as in other organisms, the intermediates of the tricarboxylic acid cycle can provide the carbon skeletons of the non-essential amino acids. It is surprising that no radioactivity was found in glutamine as Bellamy (1958) found glutamine to be twice as abundant as glutamate in Sckistocerca fat body. ...
The successive accumulation and depletion of reserves in the fat body of insects shows that it is an important storage organ, but it seems possible that it is also an organ of intermediary metabolism, degrading some substances and elaborating others for use by other tissues. A study was made in vitro of the incorporation of certain metabolites, glycine, leucine, acetate and glucose, labelled with carbon-14, into the fat body of the desert locust, Schistocerca gregaria Forskal. This showed something of the degradation and synthesis occurring in locust fat body and also suggested that the tricarboxylic acid cycle functioned normally, contrary to an earlier report (Hearfield & Kilby, 1958). The results obtained from these studies on the incorporation of labelled metabolites and on the respiration of locust fat body are presented here.
... Xanthommatin, the best-known and most-widespread ommochrome, is yellow in its oxidized state (oxo-pyrido[3,2-a]phenoxazinone; absorption at 440 nm) but red when reduced to dihydroxanthommatin (oxo-pyrido[3,2-a]hydroxyphenoxazine; absorption at 480 nm) (Figon & Casas, 2019). This unusual color-changing molecular property mediates important biological functions (Linzen, 1974), such as nuptial colorations in dragonflies , light filtering in insect eyes (Langer, 1975), as well as electron transfers in a marine worm (Horowitz & Baumberger, 1941;Linzen, 1959) and various insects (Bellamy, 1958;Linzen & Bückmann, 1961;Harano & Chino, 1971). Besides, the bathochromic reduction of xanthommatin has shown biomimetic potential to craft colorchanging electrochromic devices (Kumar et al., 2018). ...
L’évolution de la capacité à changer de couleur chez les animaux est un sujet majeur. Son étude requiert une compréhension intégrée de l’importance biologique des couleurs. Dans ces travaux, j’explore la relation structure–fonction, en termes de changement de couleur, des pigments appelés ommochromes et de leurs organites. J’utilise pour cela la chimie analytique, la modélisation quantique et l’imagerie multimodale à l’échelle subcellulaire. Cette approche interdisciplinaire révèle que les bases photochimiques et intracellulaires des ommochromes déterminent, à la fois, leurs capacités à changer de couleur et leur réactivité chimique. Mes résultats renforcent l’idée que les changements de couleur des ommochromes sont une propriété multi-échelle qui a des effets sur des fonctions biologiques au-delà de la coloration, comme l’homéostasie redox et métallique.
... Xanthommatin, the best-known and most-widespread ommochrome, is yellow in its oxidized state (oxo-pyrido [3,2-a]phenoxazinone; absorption at 440 nm) but red when reduced to dihydroxanthommatin (oxo-pyrido [3,2-a] hydroxyphenoxazine; absorption at 480 nm) [3]. This unusual color-changing molecular property mediates important biological functions [4], such as nuptial colorations in dragonflies [5], light filtering in insect eyes [6], as well as electron transfers in a marine worm [7,8] and various insects [9][10][11]. Besides, the bathochromic reduction of xanthommatin has shown biomimetic potential to craft color-changing electrochromic devices [12]. ...
In the colorful world of pigments and dyes, the chemical reduction of chromophores usually leads to bleaching because of π-conjugation interruption. Yet, the natural phenoxazinone-based ommochrome pigment called xanthommatin displays a bathochromic (i.e. red) shift upon two-electron reduction to its corresponding phenoxazine, whose electronic origins are not completely disclosed. In this study, we investigated, at quantum chemical level, a series of phenoxazinone/phenoxazine pairs that was previously explored by UV-Vis spectroscopy (Schäfer and Geyer, 1972), and which displays different hypsochromic and bathochromic shifts upon reduction. Density Functional Theory (DFT) and Time Dependent DFT (TDDFT) have been applied to compute their optical properties in order to find a rational explanation of the observed photophysical behavior. Based on our results, we propose that the electro-accepting power of auxochromes and their conjugation facilitate intramolecular charge-transfers across the phenoxazine bridge by lowering unoccupied molecular orbitals via electronic and geometric couplings, leading ultimately to bathochromy. Our findings therefore suggest new potential ways to adjust the color-changing ability of phenoxazinones in technological contexts. Overall, this model extends our mechanistic understanding of the many biological functions of ommochromes in invertebrates, from tunable color changes to antiradical behaviors.
... Xanthommatin, the best-known and most-widespread ommochrome, is yellow in its oxidized state (oxo-pyrido [3,2-a]phenoxazinone; absorption at 440 nm) but red when reduced to dihydroxanthommatin (oxo-pyrido [3,2-a]hydroxyphenoxazine; absorption at 480 nm) [3]. This unusual color-changing molecular property mediates important biological functions [4], such as nuptial colorations in dragonflies [5], light filtering in insect eyes [6], as well as electron transfers in a marine worm [7,8] and various insects [9][10][11]. Besides, the bathochromic reduction of xanthommatin has shown biomimetic potential to craft colorchanging electrochromic devices [12]. ...
In the colorful world of pigments and dyes, the chemical reduction of chromophores usually leads to bleaching because of π-conjugation interruption. Yet, the natural phenoxazinone-based ommochrome pigment called xanthommatin displays a bathochromic (i.e. red) shift upon two-electron reduction to its corresponding phenoxazine, whose electronic origins are not completely disclosed. In this study, we investigated, at quantum chemical level, a series of phenoxazinone/phenoxazine pairs that was previously explored by UV-Vis spectroscopy (Schäfer and Geyer, 1972), and which displays different hypsochromic and bathochromic shifts upon reduction. Density Functional Theory (DFT) and Time-Dependent DFT (TDDFT) have been applied to compute their optical properties in order to find a rational explanation of the observed photophysical behavior. Based on our results, we propose that the electro-accepting power of auxochromes and their conjugation facilitate intramolecular charge-transfers across the phenoxazine bridge by lowering unoccupied molecular orbitals via electronic and geometric couplings, leading ultimately to bathochromy. Our findings therefore suggest new potential ways to adjust the color-changing ability of phenoxazinones in technological contexts. Overall, this model extends our mechanistic understanding of the many biological functions of ommochromes in invertebrates, from tunable color changes to antiradical behaviors.
... In several of the species examined, there is a tendency for the general level of black pigmentation to increase at a lower temperature (Husain & Ahmad, 1936;Duck, 1944;Okay, 1954). It has been suggested that both melanin and ommochrome pigments are responsible for the black colour (Uvarov, 1966;Fuzeau-Braesch, 1985;Pener, 1991), and that ommochrome production in locusts tends to be suppressed at higher temperature (Bellamy, 1958). However, little is known about the endocrine control of body colour at different temperatures. ...
[His7]-corazonin is a neuropeptide that induces dark coloration in locusts. This study examined the effect of temperature on body colour in the migratory locust, Locusta migratoria. L. Injection of a low dose (1 pmol) of [His7]-corazonin caused albino nymphs to develop dark coloration at 25–34 °C, but little darkening occurred at 38 and 42 °C. However, injection of a high dose (10 pmol) induced darkening even at these high temperatures. Transfer of nymphs injected with 1 pmol of [His7]-corazonin from 30 to 42 °C, and vice versa, indicated that temperature influenced darkening at any time after injection. Measurements of the luminance of the pronotum were made using commercially available computer software to follow continuous changes in darkening of the body. The body colour of nymphs injected with [His7]-corazonin was reddish-brown at 25 °C, blackish at 30 and 34 °C, and greyish or whitish at 38 and 42 °C. High temperature also suppressed darkening in a normal (pigmented) strain. Most nymphs transferred from 30 to 42 °C during the first three stadia developed a light colour in the fifth stadium without the striking black patterns that are typically manifested in gregarious nymphs at lower temperatures. Such individuals developed black patterns in the fifth stadium when injected with [His7]-corazonin at a mid stage of the previous stadium. These results indicate that high temperature may induce light body coloration by suppressing the release of [His7]-corazonin in normal locusts.
Bei der Erforschung der chemischen Eigenschaften von morphologischen Strukturen ergeben sich zwei Fragestellungen: 1. Die chemische Zusammensetzung morphologischer Substrate, und 2. die morphologische Lokalisation von chemischen Substanzen. Man kann diese Probleme mit zwei grundsätzlich verschiedenen Methoden angehen.
To fulfil its function as a chemical transmitter, acetylcholine (ACh) must be held ready in the tissue so that it can be liberated on demand, and following its release be replaced rapidly enough for transmission to occur repetitively in response to successive nerve impulses. The question of how the ester is replaced at the release points of the synapse in available form is one which as yet can be answered only in the most general way. In tissue such as the superior cervical ganglion of mammals the amount of ACh liberated by a single volley of impulses is only a fraction of the total amount present, and one might suppose that replacement occurs from the existing store of ester; but experiment has shown that even at stimulation rates of 20 per sec the release of ACh may continue for an hour or more while the tissue stores remain normal or are increased (see Brown and Feldberg 1936 b, Mac
Intosh 1959). It is evident then that resynthesis alone can account for the replacement of the ester at the synaptic release points. Evidently the situation is more complicated, however, since there are other experiments to show that when synthesis of ACh in the ganglion is prevented some release still occurs, and as much as 90% of the tissue store may be mobilized by stimulation of the preganglionic nerve continued for an hour or longer (Mac
Intosh
l.c.). It must be assumed therefore that both re-synthesis and translocation of ester are involved in its replacement at the release points at least over periods as long as this, although it can not be excluded that the immediate means of replacement is normally by re-synthesis. The probability of a close spatial relation between release and re-synthesis is strengthened by the evidence that whether resting or active the tissue store of ACh always remains nearly constant.
This chapter assembles data, which contribute to a physiological understanding of this pathway in insects, to appraise the role of ommochromes in insect life, and the relation of tryptophan metabolism to insect development. Tryptophan is an outstanding amino acid. It has the highest molecular weight of all amino acids occurring in proteins, and comprises, in its indolyl moiety, a system capable of donating electrons and; therefore, liable to form complexes with a range of other molecules. Molecular interactions have been observed between tryptophan and nucleic acids, and a variety of other molecules of biological importance. Organisms have taken advantage of the potentialities of this molecule and have transformed it into a wide range of biologically active compounds. In these, either the indole ring or its benzene nucleus are retained, the latter also being recast into the pyridine ring. In insects, a major product of tryptophan degradation is a group of 10 to 15 pigments, the ommochromes. Being brownish-yellow, bright red or dark violet-purple, these pigments produce the deep tinge of insect eyes and contribute to the brilliant coloration of many species.
The insect fat body may be a site of intermediary metabolism as distinct from its more passive role of serving as a depot for the storage of fats, protein, and carbohydrate reserves. A recurrent suggestion is that the fat body may be analogous to the mammalian liver. In the different stages such as the immature forms, prepupa, diapausing, and developing pupae and the adult form, the biochemical processes taking place in the fat body may vary according to the specific point in the insect's development. The fat body has two well-defined functions—storage and intermediary metabolism. Various types of metabolic activity are operative in the fat body. Enzyme systems are present for the synthesis to reserve materials from small molecules brought by the blood and a good deal of interconversion is possible. The composition of insect blood can vary between much wider limits than are permissible in mammals, but homeostatic regulation is effected by tissues like the fat body. An analogy that has repeatedly been drawn between the fat body and the mammalian liver is thus not without foundation, but the analogy must clearly not be pressed too far, as much work still remains to be done on the biochemistry of the fat body.
In insects, evidence concerning the regulation of physiological function by hormones is well established. The term “neurosecretion” can be defined as the production of physiologically active substances within neurons, which may act either locally on neighboring neurons or on effector cells or be carried in the blood to acton more distant sites. This chapter describes what is known about the acetylcholine system in insects and the possible occurrence of other pharmacologically active substances, the identity and physiological function of which are even less certain. By an examination of the distribution of elements of the cholinergic system in insects, it is likely that acetylcholine (Ach) has function in the nervous system but not in synaptic transmission at neuromuscular junctions. In the nervous system, there is a correlation between nervous activity and ACh when acetylcholine E (AChE) is inhibited. The evidence for transmitter properties of ACh in autonomic ganglia of vertebrates is based on four indications: (1) ACh is released following stimulation of preganglionic fibers, (2) ACh is effective in low concentrations, (3) stimulation of the postganglionic fibers (antidromic stimulation) does not release Ach, and (4) atropine and curare that abolish the action of ACh do not prevent its release.
The flight of an insect involves very rapid oxidation of respiratory fuels by the flight muscle (see reviews by Sacktor 1965, 1970 and Chapter 1). High, overall levels of metabolism of working flight muscle have been calculated (Weis-Fogh, 1952) and flight is known to be accompanied by a substantial increase in oxygen uptake (Davis and Fraenkel, 1940; Krogh and Weis-Fogh, 1951). Clearly in order to maintain very high rates of respiration, the flight muscles must be well supplied with both oxygen and the appropriate fuels. The rapid increase in respiration that occurs at the onset of flight, and the decrease in respiration rate that occurs at the end of flight, necessitates the existence of systems to control the rate of flight muscle metabolism and the supply of oxygen and substrates for respiration. The previous article has discussed the oxidation of substrates by flight muscles and the control of such processes. This review is concerned with the supply of respiratory fuels to the flight muscles and the control of such supply.
The sections in this article are:1The Size, Structure and Function of the Adipose Organ2The Function of Adipose Tissue3Changing Concepts of Adiposity4Adiposity in Man
The crossing experiment and the selection experiment were carried out at 25℃ and 67% r.h. to define genetic mechanisms of the colour variation in larvae of Ephestia kuhniella. The populations sampled from the Wild-type stock showed the wide range of continuous colour variation from white to deep pink in the 5th inster lavae. The results of the crossing experiment between white larval strain and red larval strain selected from the Wild-type stock suggested the larval colour variation was a quantitative character inherited under the form of autosomal polygene. The analysis of variance component indicated additive genetic variance was the largest component and dominance effect was absent or balanced. The estimated heritability was 0.87. It was inferred two pairs of alleles were concerned in this character. The results of the two-way selection experiment showed the realized heritability for the selection for red colour was larger than that for the selection for white colour and the pooled realized heritability was 0.51.
Oiniiiocliromes, estracted from tlic eyes and tlic tegument of pigrncnted and albino locusts, Schislocerca gregaria, were scparatcd by paper cliromatograpliy and idcntificd according to BUTENANDTSC, SCHIEDT, BIEKERT and KORMANN(N19 543). Xanthommatin and 2 ominidins were found both in pigmented and in albino locusts eyes; in albinos thc ommocliromes mcrc in an about 50% lower quantity. Xantliommatin and two ommocliromes werc identified in tegument; tlic first substance was present both in pigmented and in R loner amount in albino locusts, wliercas ommoeliromes werc found only in pigmented insects. The teymental omrnochromcs show quantitativc variations during growth and sexual maturation: They disappear in mature yellow males.
The release of adipokinetic hormone at the paralytic stage of poisoning is probably a result of the excitant effects of insecticides on the central nervous system. When poisoned with organophosphorus compounds, the synaptic buildup of acetylcholine acts as a transmitter for the release of hormone. Muscarinic and nicotinic antagonists prevent organophosphate-induced release of this hormone.
Ommochromes are well known for their redox-behaviour in vitro, the oxidized from being yellow or brown, the reduced one being red. Whether this change does occur in vivo and whether it may have a respiratory function is investigated here.Larvae of Cerura vinula contain in epidermal cells of certain areas, especially the ‘saddle patch’, the ommochrome xanthommatine. This pigment may be withdrawn from the cells or reformed; it thus remains subject to pigment metabolism.In most of the larval instars the xanthommatine is hidden by the melanin of the cuticle. The distribution of pigments suggests that the ability to incorporate melanin into the cuticle is restricted to cells containing ommochrome. The melanin is shed with the cuticle at every ecdysis.Both the brown and the red form of xanthommatine may be present simultaneously in different parts of the skin. Before the pigment is withdrawn entirely from some part of the skin, its brown form is always converted to the red one. This occurs in the ‘saddle patch’ sooner or later during pupal development, the exact timing depending on temperature conditions. It may also be evoked during every larval instar by raising the temperature to 35°C, and it then takes about 24 hr. During this reddening, which is a local response, the ommochrome content decreases by about one-third. If afterwards the larvae are transferred to 20°C, the ommochrome becomes brown again very slowly within several days, and its amount increases, by 20% to 60%. Usually the brown colour manifests itself clearly only after the next ecdysis.If the larvae suffer from total lack of oxygen, the brown ommochrome containing parts of the skin will also become red within 24 hr, but without significant change of ommochrome content. Plugging some of the tracheal spiracles causes the ommochrome to redden only in the part of the body thus asphyxiated.Cyanide or carbon monoxide does not evoke this colour change. On the other hand, reddening caused by high temperature cannot be inhibited by these poisons, nor by pure oxygen.The experiments show that redox behaviour of ommochrome in vivo is an effect of certain metabolic situations. During lack of oxygen the xanthommatine is reduced to red dihydro-xanthommatine, thus serving as a hydrogen-acceptor. But since both oxidation and reduction in vivo are very slow, they seem very unlikely to have any significance for the respiratory metabolism of the whole animal. However, they may sustain the metabolism of those epidermal cells, which themselves contain ommochrome, during short periods of local lack of oxygen assumed to occur in insect epidermis.
Calculated on the basis of intracellular and haemolymph water, free amino acids in the southern armyworm, Prodenia eridania, are about equally distributed between larval fat body and haemolymph but their concentration is lower in the gut. Free glutamine and glutamate titres are about the same in the fat body, whereas in the gut and the haemolymph glutamine predominates. During adult development the levels of total ninhydrin-positive substances and the large extra increment thereof obtained by acid hydrolysis (‘peptides’) first drop abruptly, then increase to about the original values, and subsequently decrease gradually by ca. 40 per cent. A sharp decrease in free glutamine and glutamic acid also occurs early in adult development. The magnitude of the subsequent rise and fall in glutamine and glutamate levels is relatively greater than for the total amino acid ‘pool’.
1.1. Free amino acids of the haemolymph of the second, third, fourth, fifth and sixth instar larvae of Spodoptera littoralis Boisduval, were determined quantitatively by two-dimensional paper chromatography.2.2. Nineteen amino acids were detected in the haemolymph of all instars.3.3. Glutamine, threonine and lysine occurred in high concentrations and represent the largest part of free amino acids in all instars, while glutamic acid and citrulline were found in smaller quantities.4.4. Glutamine and tyrosine showed a continuous decrease but histidine, citrulline and γ-aminobutyric acid increased steadily as development proceeded.5.5. Other amino acids showed quantitative variations.
1.Hormone content (pressor activity) was estimated in the posterior pituitary of the cod. An average of 160 mU pressor activity per gland was found2.Subcellular particles containing the pressor hormone (arginine vasotocin) were isolated from homogenates of cod pituitaries. These particles were identified as the elementary granules (800–2000 Å). 3.The hypothalamo-hypophysial system of three species of teleost fishes (Gadus morrhua, Cottus bubalis, Salmo irideus) was examined with the electron microscope:aThe fine structure of the neurohypophysis, its relations with the adenohypophysial elements and with blood vessels was shown, and methods of hormone release from the neurohypophysis were discussed.bThe ultrastructure of the large neurosecretory cells of the preoptic nucleus in the three teleost fishes was investigated. The central zone of the cytoplasm of these cells contained numerous Golgi complexes and secretory inclusions mainly of two orders of size: elementary granules (800–2200 Å) and large secretory granules (5000–15000 Å).cA great variation of form and electron-density was observed in the large secretory granules.dA spatial association between the neurosecretory inclusions and the Golgi complex was shown and its functional implications were discussed.4Mechanisms and site of formation of the elementary granules and their contents were tentatively suggested.
Recording weight-specific total body metabolism of the mouse at two ambient temperatures (22.5°, 35° C) and plotting the resulting data on a double logarithmic grid revealed a cyclic allometry with a positive constant between 1.3 and 5 g body weight (cycle I) and a negative constant between 5 (or 7) and 23 g (cycle II). Similar cycles concerning the weight-allometry of the mass of several organs (brain, heart, liver, skin) and the tissue respiration of brain, liver, intestine and kidneys are statistically significant. If the summated tissue respiration is determined over the entire body size range — by summing up tissue respiration for several individual body weights and calculating the regression lines — two cycles are, again, observable; their slopes cannot be distinguished statistically from those of the cycles of total body O2-uptake at 35° C. Its intensity, however, is considerably lower than that of the directly measured total body metabolism. If certain corrections are applied (inclusion of skin respiration and extrapolation of respiration in vitro to t0 the intensity of summated tissue respiration as well as its slope coincide well with the BMR obtained from literature.
Summary
Psophus stridulus L. andOedipoda coerulescens L. were fed or injected with solutions of Na
2
35
SO4 and35S-l-cystine. The radioactive radiation pattern of the wings was found to depend on the time of application. Differences in radiation intensity were found to correspond to the red, blue and dark areas.
The absorption spectra of the skin of the hibernating brown Hestina larvae were measured directly with the aid of the ‘multipurpose-spectrophotometer’ in the intact, reduced, and oxidized states, respectively. The skin, washed with acetone to remove carotenoids and other fatty materials, turned red on reduction with 5% sodium hydrosulphite solution, and then light brown on oxidation with 1% hydrogen peroxide solution. The colour-change reaction can be repeated as many times as one wishes. From the results it is recognized that a brown pigment, xanthommatine, not only exists as xanthommatine-protein complex (xanthommatinoprotein) in the epidermis of the hibernating larva of Hestina japonica but also that it is probably capable of a redox reaction in the epidermis.ZusammenfassungDie Absorptionsspektren der Haut von der überwinternden braunen Hestina-Raupe wurde in intaktem, reduziertem und oxidiertem Zustand direkt durch das ‘Multipurpose-Spectrophotometer’ gemessen. Nach der Entfettung mit Azeton wurde die Haut durch die Reduktion mit 5-proz. Natriumdithionit gerötet und dann durch die Oxidation mit 1-proz. Hydrogenperoxid zum hellen Braun umgefärbt. Man kann die Umfärbung der Haut durch die Redoxreaktion mehrmals wiederholen. Es ist dadurch gezeigt dass der braune Farbstoff, Xanthommatin, in Form einer Verbindung mit einem Eiweiss, als Xanthommatinoprotein, in der Epidermis der überwinternden Raupen von Hestina japonica vorliegt und noch das Redoxverhalten zeigt.
1.An dem Regenwurm Lumbricus terrestris L. wurden der O2-Verbrauch des lebenden Tieres, der Anteil der einzelnen Organe am Gesamtgewicht und die Atmung der isolierten Organe in vitro bestimmt.2.Die Atmung des intakten Tieres betrug bei 25° im Mittel 119µlO2/g Frischgewicht · h.3.In vier Medien unterschiedlicher Zusammensetzung zeigten weder Hautmuskelschlauch noch Mitteldarm signifikante Unterschiede des O2-Verbrauchs.4.Die summierte Gewebsatmung betrug 116% der Atmung des lebenden Tieres.5.Die mittlere Atmungsgröße aller stoffwechselaktiven Gewebe betrug bei 250 0,200 µ O2/mg Frischgewicht · h. Signifikant höheren O2-Verbrauch wiesen Nervensystem (0,327) und Mitteldarm (0,380) auf.6.Von den beiden Geweben des Mitteldarms zeigte das Chloragog den niedrigeren O2-Verbrauch (0,240); die Atmung des Darmepithels konnte nicht gemessen werden, ist aber zweifellos größer als 0,380.7.Die hohe Atmungsintensität der Mitteldarmgewebe spricht dafür, daß diesen außer den Funktionen der Verdauung, Resorption und Speicherung noch weitere Stoffwechselaufgaben zukommen.
Phospholipase C (α toxin of Clostridium perfringens) has been found to cause, at relative high concentrations, the lysis of fat cells isolated from rat epididymal adipose tissue.
Lysis of the fat cells resulted in the loss of insulin response in proportion to the amount of cells broken. It is suggested
that the effects of insulin on glucose metabolism by the fat cell are dependent on the presence of an intact cell membrane.
The level of flexokinase activity in the fat cell was not affected by insulin or phospholipase C; sufficient hexokinase was
present to account for all the glucose phosphorylated by fat cells in response to insulin.
Evidence is presented that glucose is transported in the fat cell by a carrier-mediated, stereospecific process. Insulin and
treatment of fat cells with phospholipase C under conditions that did not cause lysis, stimulated the transport of glucose.
Anabolic processes, such as fatty acid synthesis from glucose and amino acid incorporation into protein, were also stimulated
by insulin and phospholipase C. The action of phospholipase C on glucose transport and amino acid utilization was a function
of enzyme concentration, suggesting that the amount of cellular phospholipid hydrolyzed by the enzyme determined the amount
of solute entering the cell. Phospholipids appear, therefore, to be linked to transport processes.
The common effects of insulin and phospholipase C on the fat cell suggests that the same parameter in the cell is affected
by these substances. It is hypothesized that insulin and phospholipase C act on the plasma membrane to alter the configuration
of its lipoproteins from a laminated to a micellar or globular form. The latter configuration of the membrane lipoproteins
might have interstices that permit the carrier-mediated passage of solutes into the cell.
A method of obtaining locust eggs which could be expected to be deficient in carotene is described. It involved rearing a parental generation on an artificial diet which, because of certain pigmentation abnormalities it induced, was probably itself deficient in carotene.
Using crowded hatchlings of Locusta migratoria (L.) from eggs thus modified, it was shown that they were sensitive to dietary carotene, whereas hatchlings from normal eggs were indifferent. The absence of carotene was marked by inferior growth, lessened activity and most notably by an extremely different coloration in both hoppers and adults. Without carotene, melanisation was absent or greatly reduced and in many cases the integument developed a greenish-blue colour. With carotene, heavy melanisation occurred in the hoppers, and the colour of the adults was characteristically gregarious.
It was concluded that in normal eggs the amount of carotene present is usually sufficient to mask the expression of a dietary deficiency during nymphal growth, but that with normal eggs having low amounts of carotene, a dietary deficiency might become apparent as it did with modified eggs.
It is suggested that the blue colour of modified Locusta hoppers reared without carotene is due to mesobiliverdin, a prochromogen of insectoverdin, the green pigment of the solitaria phase of locusts. Insectoverdin itself could not be formed because it contains carotenoids, and these were absent from the diet. The effect of extreme deprivation of carotene is therefore to induce solitaroid tendencies, notably in regard to colour (suppression of melanin and production of mesobiliverdin) but also in regard to activity.
Crowded hoppers of Schistocerca gregaria (Forsk.) reared on synthetic diets lacking carotene usually had turquoise-blue blood by the fifth instar. It was shown, by the electrophoresis of yellow, green and blue bloods in parallel, that the blue chromoprotein of blue blood is the same as the blue chromoprotein of green blood. Its prosthetic pigment must therefore be mesobiliverdin.
The abnormalities of coloration which arise in crowded Locusta and Schistocerca when deprived of carotene are normal in the solitary phase. Moreover, they resemble those abnormalities of coloration consequent upon the implantation of additional corpora allata into gregarious hoppers. The implications of this are discussed in relation to the validity of phase criteria, and an attempt is made to relate these findings to hypotheses on the humoral regulation of phase.
Abstract— The ocellar pigment of Spirocodon saltatrix extractable with phosphate buffer and acidified methanol was considered to be a substance closely related to or identical with xanthommatin, from its behaviour on paper and thin-layer chromatography and from the position of the absorption maxima in the ultra-violet and visible ranges of the spectrum in various solvents. The infra-red spectrum also supported this view. The pigment extracted with cetyltrimethylammonium bromide was gel-filtered through a column of Sephadex G 100. The pigment was eluted fairly quickly and the elution pattern was narrow, indicating that the eluted pigment is large as well as homogeneous in its molecular size. The gel-filtered pigments from medusan ocelli and fly ommatidia underwent an almost indentical photoreduction under anaerobic conditions.
The sections in this article are:
The sections in this article are:
1.1. Xanthommatin synthesis was realized in vitro with homogenates and cell fractions of the eyes and integument but not with the fat body or Malpighian tubes of Schistocerca gregaria.2.2. The above enzymatic activity, which leads to xanthommatin, was localized in the mitochondria-like fraction of the epidermal cells and seemed to be mainly bound to the membranes.3.3. The synthesis is not coupled to the dopa-tyrosinase system, since it was only slightly inhibited by phenylthiourea, and the partially purified enzyme(s) did not show any tyrosinase activity.4.4. In the albino insect the xanthommatin synthesis is reduced to a tenth.
Experiments were carried out on normally pigmented and albino locusts to measure their social behaviour. Albino nymphs and adults grouped less than normal locusts. This is unlikely to be due to their providing each other with insufficient stimulus to grouping, as in mixed-animal tests, albino locusts showed no increase in grouping and normal locusts showed no fall in grouping.
Mitochondria were prepared from the fat body and thoracic muscles of Locusta migratoria and Schistocerca gregaria. The respiration of the mitochondria in a sodium succinate substrate was measured, and the effects of adding various substances on the oxygen consumption of the mitochondria recorded. The addition of 2 : 4-dinitrophenol (DNP) in physiological quantities resulted in a decrease in oxygen consumption when compared with a control on mitochondria prepared from adult Locusta migratoria. It increased the oxygen consumption of mitochondria from the fifth instar of Schistocerca gregaria.The addition of the corpora allata to mitochondria prepared from adult Locusta migratoria caused an increase in oxygen consumption whilst their addition to those prepared from fifth instar Schistocerca gregaria decreased oxygen consumption. When both DNP and corpora allata were present together the oxygen consumption was stimulated in both Locusta and Schistocerca. The amount of stimulation was slightly greater than when either was present alone. The effect of the addition of the corpora cardiacum to preparations of adult mitochondria was to depress their oxygen consumption. One of the sites of the action of the corpora allata hormone is shown to be the mitochondrion. The possibility that the known action of DNP might provide a further clue to the site of action of the C.A. hormone is discussed.
The sections in this article are:
The sections in this article are:
1. The ATPase activity of insect mitochondria has been investigated. A comparison was made to determine the distribution and nature of such activity in other isolated fractions of the house fly, Musca domestica L.
2. The ATPase in insect mitochondria is specific in that orthophosphate can be cleaved only from ATP. The Michaelis-Menten constant K8 = 2.78 x 10–3 M and Vmax. = 76 micrograms P min.–1 mg.–1 dry weight.
3. Mg++ and Mn++ activate this enzymatic reaction in mitochondria, but Ca++ does not. The extent of activation is 60 per cent with the optimal concentration 6 x 10–4 M. Experiments with combinations of Mg++ and Mn++ show that either ion can replace the other and that the effects are additive, depending solely on the final concentration of the combination. Concentrations of Mg, Mn, or Ca ions higher than 6 x 10–3 M inhibit the enzyme.
4. Fluoride does not inhibit the ATPase of insect mitochondria, whereas azide and chloromercuribenzoate do. The per cent inhibition depends on the concentration of inhibitor.
5. Finely dispersed mitochondrial particles have much greater ATPase activity than intact mitochondria. The possible relationship of this observation to latent ATPase is considered.
6. A magnesium-activated adenylate kinase is present in these mitochondria. The liberated orthophosphate, derived from ADP, is the result of the activity of adenylate kinase followed by the specific ATPase.
7. ATP can be dephosphorylated by enzymes found in the muscle fibrils, and in a "soluble" fraction, as well as in mitochondria. The fibrillar ATPase is Ca++-activated. The "soluble" fraction, however, like the mitochondria, is Mg++-activated. The "soluble" ATP dephosphorylation mechanism is distinguished from the mitochondrial ATPase in that it is inhibited by fluoride.
8. The "soluble" fraction also contains a magnesium-activated inorganic pyrophosphatase. Fluoride completely inhibits this enzymatic reaction.
9. The possible mechanism of ATP dephosphorylation in the "soluble" fraction is discussed.
Changes in the morphology of rat liver mitochondria brought about by different methods of isolation and the concomitant changes in ATP-ase activity were studied. The morphology was investigated with the electron microscope. It was found that the ATP-ase activity of the isolated mitochondria cannot be readily correlated with the morphology of the mitochondria. The ATP-ase found in these preparations was latent, resembling the enzyme described in mitochondria prepared in 0.25 M sucrose. In confirmation of earlier results the use of 0.88 M sucrose yielded preparations with a higher initial ATP-ase than did other methods. Preparation in 0.25 M sucrose resulted in round, swollen mitochondria of which 30 to 40 per cent appeared to have lost a substantial part of the mitochondrial matrix. Preparations in 0.44 to 0.88 M sucrose contained mainly rod-shaped mitochondria plus a small amount of another type of swollen mitochondria. The matrix of mitochondria isolated in 0.88 M sucrose was highly condensed. By the use of 0.44 M sucrose adjusted to pH 6.2 with citric acid, it was possible to isolate, for the first time, mitochondria closely resembling those in situ and containing latent ATP-ase.
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