Leo Peichl

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• PhD, Adjunct Professor
• Professor Emeritus at Goethe University Frankfurt

Mammalian cryptochrome 1 (CRY1) is a central player in the circadian transcription‐translation feedback loop, crucial for maintaining a roughly 24‐h rhythm. CRY1 was suggested to also function as a blue‐light photoreceptor in humans and has been found to be expressed at the mRNA level in various cell types of the inner retina. However, attempts to...

The nocturnal aardvark Orycteropus afer is the only extant species in the mammalian order Tubulidentata. Previous studies have claimed that it has an all-rod retina. In the retina of one aardvark, we found rod densities ranging from 124,000/mm² in peripheral retina to 214,000/mm² in central retina; the retina of another aardvark had 163,000 – 245,0...

African mole-rats (Bathyergidae, Rodentia) are subterranean rodents that live in extensive dark underground tunnel systems and rarely emerge aboveground. They can discriminate between light and dark but show no overt visually driven behaviours except for light-avoidance responses. Their eyes and central visual system are strongly reduced but not de...

The nocturnal aardvark Orycteropus afer is the only extant species in the mammalian order Tubulidentata. Previous studies have claimed that it has an all-rod retina. In the retina of one aardvark, we found rod densities ranging from 124,000/mm² in peripheral retina to 214,000/mm² in central retina; the retina of another aardvark had 182,000 – 245,0...

Mammalian cryptochrome 1 (CRY1) is a central player in the circadian transcription-translation feedback loop, crucial for maintaining a roughly 24-hour rhythm. CRY1 was suggested to also function as blue-light photoreceptor in humans and has been found to be expressed at the mRNA level in various cell types of the inner retina. However, attempts to...

The retina of the fat dormouse Glis glis was studied histologically. Opsin immunolabeling identified an unusually dense population of rod photoreceptors (ca. 600,000–780,000/mm²) and a low-density population of L cone photoreceptors containing the longwave-sensitive (LWS) cone opsin, with a shallow maximum of ca. 3,300/mm² in temporal retina and ca...

The physiological aging process of the retina is accompanied by various and sometimes extensive changes: Macular degeneration, retinopathies and glaucoma are the most common findings in the elderly and can potentially lead to irreversible visual disablements up to blindness. To study the aging process and to identify possible therapeutic targets to...

The diverse family Canidae has spread across many continents and contains species with different habitats and feeding behaviors. The family includes the domestic dog (Canis familiaris), and the majority of studies into canid ocular anatomy, physiology and clinical medicine have been performed in this species. In this chapter, normal ocular and reti...

Molecular genetic data have recently been incorporated in attempts to reconstruct the ecology of the ancestral snake, though this has been limited by a paucity of data for one of the two main extant snake taxa, the highly fossorial Scolecophidia. Here we present and analyse vision genes from the first eye transcriptomic and genome-wide data for Sco...

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

We examined lens and brille transmittance, photoreceptors, visual pigments, and visual opsin gene sequences of viperid snakes with and without infrared-sensing pit organs. Ocular media transmittance was high in both groups. Contrary to previous reports, both small and large single cones occur in pit vipers. Non-pit vipers differ from pit vipers in...

We examined lens and brille transmittance, photoreceptors, visual pigments, and visual opsin gene sequences of viperid snakes with and without infrared-sensing pit organs. Ocular media transmittance was high in both groups. Contrary to previous reports, both small and large single cones occur in pit vipers. Non-pit vipers differ from pit vipers in...

The avian magnetic inclination compass is based on radical pair processes, with cryptochrome (Cry) assumed to form the crucial radical pairs; it requires short-wavelength light from UV to green. Under high-intensity narrow-band lights and when yellow light is added, the magnetic compass is disrupted: migratory birds no longer prefer their migratory...

The retinal rod pathway, featuring dedicated rod bipolar cells (RBCs) and AII amacrine cells, has been intensely studied in placental mammals. Here, we analyzed the rod pathway in a nocturnal marsupial, the South American opossum Monodelphis domestica to elucidate whether marsupials have a similar rod pathway. The retina was dominated by rods with...

The red fox (Vulpes vulpes) is the carnivore with the widest distribution in the world. Not much is known about the visual system of these ecologically highly adaptable animals that predominantly are forest‐dwellers. The closely related Arctic fox (Vulpes lagopus) lives in more open tundra habitats. In search for corresponding adaptations, we exami...

Elephants are precocial mammals that are relatively mature as newborns and mobile shortly after birth. To determine whether the retina of newborn elephants is capable of supporting the mobility of elephant calves, we compared the retinal structures of 2 newborn elephants (1 African and 1 Asian) and 2 adult animals of both species by immunohistochem...

The lemurs of Madagascar (Primates: Lemuriformes) are a monophyletic group that has lived in isolation from other primates for about 50 million years. Lemurs have diversified into species with diverse daily activity patterns and correspondingly different visual adaptations. We assessed the arrangements of retinal cone and rod photoreceptors in six...

Thyroid hormone is a crucial regulator of gene expression in the developing and adult retina. Here we sought to map sites of thyroid hormone signaling at the cellular level using the transgenic FINDT3 reporter mouse model in which neurons express β-galactosidase (β-gal) under the control of a hybrid Gal4-TRα receptor when triiodothyronine (T3) and...

Cryptochromes, blue-light absorbing proteins involved in the circadian clock, have been proposed to be the receptor molecules of the avian magnetic compass. In birds, several cryptochromes occur: Cryptochrome 2, Cryptochrome 4 and two splice products of Cryptochrome 1, Cry1a and Cry1b. With an antibody not distinguishing between the two splice prod...

Additional Figures and Text. (PDF)

Cryptochromes are a ubiquitous group of blue-light absorbing flavoproteins that in the mammalian retina have an important role in the circadian clock. In birds, cryptochrome 1a (Cry1a), localized in the UV/violet-sensitive S1 cone photoreceptors, is proposed to be the retinal receptor molecule of the light-dependent magnetic compass. The retinal lo...

We studied the retinal cone bipolar cells of Carollia perspicillata, a microchiropteran bat of the phyllostomid family. Microchiroptera are strongly nocturnal, with small eyes and rod-dominated retinae. However, they also possess a significant cone population (2-4%) comprising two spectral types and hence the basis for daylight and color vision. We...

Cryptochrome 1a, located in the UV/violet-sensitive cones in the avian retina, is discussed as receptor molecule for the magnetic compass of birds. Our previous immunohistochemical studies of chicken retinae with an antiserum that labelled only activated cryptochrome 1a had shown activation of cryptochrome 1a under 373 nm UV, 424 nm blue, 502 nm tu...

BackgroundMethyl-CpG binding protein 2 (MECP2) is a protein that specifically binds methylated DNA, thus regulating transcription and chromatin organization. Mutations in the gene have been identified as the principal cause of Rett syndrome, a severe neurological disorder. Although the role of MECP2 has been extensively studied in nervous tissues,...

Diurnality, associated with enhanced visual acuity and color vision, is typical of most modern Primates. However, it remains a matter of debate when and how many times primates re-acquired diurnality or returned to nocturnality. We analyzed the features specific to nocturnal and diurnal vision that were recently found in the nuclei of mammalian rod...

A quantitative analysis of photoreceptor properties was performed in the retina of the nocturnal deer mouse, Peromyscus maniculatus, using pigmented (wildtype) and albino animals. The aim was to establish whether the deer mouse is a more suitable model species than the house mouse for photoreceptor studies, and whether oculocutaneous albinism affec...

The radical pair model proposes that the avian magnetic compass is based on radical pair processes in the eye, with cryptochrome, a flavoprotein, suggested as receptor molecule. Cryptochrome 1a (Cry1a) is localized at the discs of the outer segments of the UV/violet cones of European robins and chickens. Here, we show the activation characteristics...

S cones expressing the short wavelength-sensitive type 1 (SWS1) class of visual pigment generally form only a minority type of cone photoreceptor within the vertebrate duplex retina. Hence, their primary role is in color vision, not in high acuity vision. In mammals, S cones may be present as a constant fraction of the cones across the retina, may...

A nocturnal activity pattern is central to almost all hypotheses on the adaptive origins of primates. This enduring view has been challenged in recent years on the basis of variation in the opsin genes of nocturnal primates. A correspondence between the opsin genes and activity patterns of species in Euarchonta—the superordinal group that includes...

Eukaryotic cells have a layer of heterochromatin at the nuclear periphery. To investigate mechanisms regulating chromatin distribution, we analyzed heterochromatin organization in different tissues and species, including mice with mutations in the lamin B receptor (Lbr) and lamin A (Lmna) genes that encode nuclear envelope (NE) proteins. We identif...

We studied the retinal rod pathway of Carollia perspicillata and Glossophaga soricina, frugivorous microbats of the phyllostomid family. Protein kinase Cα (PKCα) immunolabeling revealed abundant rod bipolar cells (RBCs) with axon terminals in the innermost sublamina of the inner plexiform layer (IPL), which is typical for mammals. Extraordinarily,...

In a recent paper, we described the localization of cryptochrome 1a in the retina of domestic chickens, Gallus gallus, and European robins, Erithacus rubecula: Cryptochrome 1a was found exclusively along the membranes of the disks in the outer segments of the ultraviolet/violet single cones. Cryptochrome has been suggested to act as receptor molecu...

Electron-microscopic image of the inner segment of a Cry1a-immunoreactive cone in the chicken retina. (PDF)

Controls for the immuno-labelling (PDF)

The Radical-Pair-Model postulates that the reception of magnetic compass directions in birds is based on spin-chemical reactions in specialized photopigments in the eye, with cryptochromes discussed as candidate molecules. But so far, the exact subcellular characterization of these molecules in the retina remained unknown. We here describe the loca...

Mammalian retinas display an astonishing diversity in the spatial arrangement of their spectral cone photoreceptors, probably in adaptation to different visual environments. Opsin expression patterns like the dorsoventral gradients of short-wave-sensitive (S) and middle- to long-wave-sensitive (M) cone opsin found in many species are established ea...

Many disabling human retinal disorders involve the central retina, particularly the macula. However, the commonly used rodent models in research, mouse and rat, do not possess a macula. The purpose of this study was to identify small laboratory rodents with a significant central region as potential new models for macular research. Gerbillus perpall...

Traditionally, vision was thought to be useless for animals living in dark underground habitats, but recent studies in a range of subterranean rodent species have shown a large diversity of eye features, from small subcutaneous eyes to normal-sized functional eyes. We analyzed the retinal photoreceptors in the subterranean hystricomorph rodents Cte...

We studied the retinal photoreceptors in the mouse opossum Thylamys elegans, a nocturnal South American marsupial. A variety of photoreceptor properties and color vision capabilities have been documented in Australian marsupials, and we were interested to establish what similarities and differences this American marsupial showed. Thylamys opsin gen...

The effects of postnatal hypothyroidism on retinal development and spatial patterning of cone opsin expression were studied in Pax8-deficient mice. Pax8(-/-) mice are incapable of synthesizing thyroxine and serve as a model for congenital hypothyroidism. Pax8(-/-), Pax8(+/-), and Pax8(+/+) littermates were studied. Serum thyroid hormone levels, bod...

Retinal topography in juvenile harbor seals (Phoca vitulina) was analyzed in retinal wholemounts stained with cresyl violet. A region of highest ganglion cell density, i.e., an area centralis, was identified in the temporal retina at a mean distance of 7.7 mm from the papilla (mean peak ganglion cell density 3,952 cells/mm(2)). With an estimated po...

Mammalian retinae have rod photoreceptors for night vision and cone photoreceptors for daylight and colour vision. For colour discrimination, most mammals possess two cone populations with two visual pigments (opsins) that have absorption maxima at short wavelengths (blue or ultraviolet light) and long wavelengths (green or red light). Microchiropt...

Die Augen nachtaktiver Säugetiere enthalten besonders viele der für das Nachtsehen zuständigen, hochempfindlichen Stäbchen-Fotorezeptoren. Damit können sie Licht wahrnehmen, dessen Intensität millionenfach unter der des Tageslichts liegt. Neue Untersuchungen zeigen, dass sich der nächtliche Lebensstil und die damit verbundenen visuellen Herausforde...

We show that the nuclear architecture of rod photoreceptor cells differs fundamentally in nocturnal and diurnal mammals. The rods of diurnal retinas possess the conventional architecture found in nearly all eukaryotic cells, with most heterochromatin situated at the nuclear periphery and euchromatin residing toward the nuclear interior. The rods of...

The presence, density distribution, and mosaic regularity of cone types were studied in the retina of the diurnal agouti, Dasyprocta aguti. Longwave-sensitive (L-) and shortwave-sensitive (S-) cones were detected by antibodies against the respective cone opsins. L- and S-cones were found to represent around 90 and 10% of the cone population, respec...

While cells are mostly transparent they are phase objects that differ in shape and refractive index. Any image that is projected through layers of cells will normally be distorted by refraction, reflection, and scattering. Strangely, the retina of the vertebrate eye is inverted with respect to its optical function and light must pass through severa...

DefinitionSomething that exists but is not spatiotemporally located, e.g. universals (whiteness, horseness), numbers or states of affairs.Possible WorldProperty

In the retina the segregation of different aspects of visual information starts at the first synapse in signal transfer from the photoreceptors to the second-order neurons, via the neurotransmitter glutamate. We examined the distribution of the four AMPA glutamate receptor subunits GluR1–GluR4 at the photoreceptor synapses in mouse and rat retinae...

We have studied the visual system of subterranean mole-rats of the rodent family Bathyergidae, for which light and vision seem of little importance. The eye diameter varies between 3.5mm in Bathyergus suillus and 1.3mm in Heterocephalus glaber. The small superficial eyes have features typical of sighted animals (clear optics, well-developed pupil a...

This chapter discusses the anatomy and physiology of the retina in aquatic tetrapods. It focuses on the input and output stages of retinal processing: the photoreceptors and the ganglion cells. It describes the characteristics of rod and cone visual pigments, photoreceptor sensitivity, and the importance of temporal summation of photoreceptor signa...

We have examined the presence, the distribution, and the opsin identity of photoreceptor types in the retina of the European mole, Talpa europaea, a subterranean insectivore with regressed morphology of the visual system. Cones and rods were identified using opsin antisera, and their topographies determined from flat-mounted retinas. The retina (to...

In der Netzhaut der meisten Säugetiere gibt es zwei Typen von Lichtsinneszellen: die Zapfen für das Tageslicht- und Farbensehen sowie die empfindlicheren Stäbchen für das Nachtsehen. Bisher nahm man an, dass die nachtaktiven Fledermäuse jedoch nur Stäbchen besitzen. Aktuelle Forschungsergebnisse belegen nun, dass die Netzhaut der ebenfalls nachtakt...

Older studies have claimed that bats including the Megachiroptera (fruit bats or flying foxes) have pure-rod retinas and possess no cone photoreceptors. We have determined the presence and the population densities of spectral cone types in six megachiropteran species belonging to four genera: Pteropus rufus, P. niger, P. rodricensis, Rousettus mada...

The visual system of subterranean mammals is assumed to be regressed and rudimentary in response to their lightless ecotope. Among rodents this has been exemplified by detailed studies of the blind mole-rat Spalax ehrenbergi (see Nevo 1999, this volume). However, recent studies involving a larger spectrum of subterranean mammalian species have 'une...

All mammalian retinae contain rod photoreceptors for low-light vision and cone photoreceptors for daylight and color vision. Most nonprimate mammals have dichromatic color vision based on two cone types with spectrally different visual pigments: a short-wavelength-sensitive (S-)cone and a long-wavelength-sensitive (L-)cone. Superimposed on this bas...

Subterranean mammals are generally considered to have reduced eyes and apparent blindness as a convergent adaptation to their lightless microhabitat. However, there are substantial interspecific differences. We have studied the prospect of vision in the Chilean subterranean rodent cururo (Spalacopus cyanus, Octodontidae) by analyzing the optical pr...

Abstract We studied the retinal projections, the distribution of cytochrome oxidase activity and the cyto- and myeloarchitecture of the subcortical visual system in the subterranean Ansell's mole-rat Cryptomys anselli. The optic nerve contained 1500 myelinated and a similar number of unmyelinated fibres. The retina projected to all the visual struc...

We have determined the presence of spectral cone types, and the population densities of cones and rods, in subterranean mole-rats of the rodent family Bathyergidae, for which light and vision seems of little importance. Most mammals have two spectral cone types, a majority of middle- to long-wave-sensitive (L-) cones, and a minority of short-wave-s...

Aquatic mammals had to adapt to visual environments that are very diVerent from those encountered by terrestrial mammals. Herein, we review the current knowledge on the colour-vision capabilities of aquatic mammals and discuss the puzzles that emerge from those studies. The common pattern in terrestrial mammals is dichromatic colour vision based on...

To determine the eye's spectral sensitivity in three species of the genus Octodon (order Rodentia; infraorder Caviomorpha), O. degus, O. bridgesi, and O. lunatus, as well as the spectral properties of the animals' fur and urine and of objects in their habitat. The genus is endemic in Chile and contains species with different habitats and circadian...

Biological images often contain branching structures, especially those obtained from neural tissue. Neurons are known to fall into several types, but distinguishing these types is a continuing problem. Automatic classification of neuron type relies upon suitable measurements or features. Recently fractal dimension has been suggested as a useful fea...

Aquatic mammals had to adapt to visual environments that are very diVerent from those encountered by terrestrial mammals. Herein, we review the current knowledge on the colour-vision capabilities of aquatic mammals and discuss the puzzles that emerge from those studies. The common pattern in terrestrial mammals is dichromatic colour vision based on...

We examined the distribution of the AMPA glutamate receptor subunits GluR1 to GluR4, of the kainate receptor subunits GluR6/7 and KA2, and of the glutamate receptor subunits delta1/2, during postnatal development of the rat retina by immunocytochemistry and light microscopy using receptor subunit specific antisera. The various ionotropic glutamate...

Most terrestrial mammals have colour vision based on two spectrally different visual pigments located in two types of retinal cone photoreceptors, i.e. they are cone dichromats with long-to-middle-wave-sensitive (commonly green) L-cones and short-wave-sensitive (commonly blue) S-cones. With visual pigment-specific antibodies, we here demonstrate an...

In the retina the segregation of different aspects of visual information starts at the first synapse in signal transfer from the photoreceptors to the second-order neurons, via the neurotransmitter glutamate. We examined the distribution of the four AMPA glutamate receptor subunits GluR1-GluR4 at the photoreceptor synapses in mouse and rat retinae...

The retinae of insectivores have been rarely studied, and their photoreceptor arrangements and expression patterns of visual pigments are largely unknown. We have determined the presence and distribution of cones in three species of shrews (common shrew Sorex araneus, greater white-toothed shrew Crocidura russula, dark forest shrew Crocidura poensi...

In the mammalian retina, extensive processing of spatiotemporal and chromatic information occurs. One key principle in signal transfer through the retina is parallel processing. Two of these parallel pathways are the ON- and OFF-channels transmitting light and dark signals. This dual system is created in the outer plexiform layer, the first relay s...

Mammalian horizontal cells have generally been assumed to be spectrally non-selective in their cone contacts until recently, when specific contacts have been found for some species. The rabbit retina is frequently studied as a representative of dichromatic mammalian retinae. These are the reasons for elucidating the connections of the two types of...

Most non-primate mammals have two types of cone: short-wavelength sensitive (S) and middle-to-long-wavelength sensitive (M/L) cones. In two species of African giant rats, Cricetomys gambianus and C. emini, and in two species of earless seals, Phoca hispida and P. vitulina, the retinal cone types and cone distributions were assessed with antibodies...

Calcium-binding proteins are abundantly expressed in many neurons of mammalian retinae. Their physiological roles are, however, largely unknown. This is particularly true for calcium-modulating proteins ("calcium buffers") such as calbindin D28k. Here, we have studied retinae of wildtype (+/+) and calbindin-null mutant (-/-) mice by using immunocyt...

In all mammalian retinae studied to date, starburst cholinergic amacrine cells are a consistently occurring cell type. Here, we show that the cone-dominated retina of the tree shrew also has starburst cells with the characteristic radially symmetric branching pattern known from other species. Dendritic field sizes increase from 150 microm in the ce...

Near the end of his life Ramón y Cajal (1933) summarized aspects of his view of the retina and, under the section heading “The paradox of vertebrate retinal horizontal cells” admitted defeat in understanding their role in visual processing. By then, horizontal cells had been identified and studied anatomically for more than six decades; today, six...

Katzen sehen im Dunkeln, Hunde sind farbenblind, Maulwürfe sind völlig blind. Stimmen diese volkstümlichen Aussagen? Unterschiede im Sehvermögen haben Laien und vergleichende Zoologen seit langem gleichermaßen fasziniert; sie haben den Stoff für unzählige Einzelarbeiten und einige umfangreiche Werke geliefert (siehe etwa [1, 2, 8–10]). Vieles in äl...

Den gemeinsamen Nobelpreis erhielten Golgi und Cajal „in Anerkennung ihrer Arbeiten über die Struktur des Nervensystems”. Die Namen dieser beiden Wissenschaftler haben in der Biologie heute noch Klang. Der Spanier Santiago Ramón y Cajal (1852–1934) führte bahnbrechende Untersuchungen an praktisch allen Teilen des Nervensystems durch, und die meiste...

The morphology of horizontal cells in ox, sheep, and pig retinae as observed after Lucifer Yellow injections are described and compared with the descriptions of Golgi-stained cells by Ramón y Cajal (1893). Horizontal cells in the retinae of less domesticated species, wild pig, fallow and sika deer, mouflon, and aurochs were also examined. All these...

The morphology of horizontal cells chiefly of the horse, but also of asses, mules, and a zebra, has been examined by Lucifer yellow injections into lightly fixed retinae and by immunocytochemistry. In common with other mammals, equids have a B-type horizontal cell, i.e., a cell with dendrites synapsing with cones and possessing a single axon synaps...

Somatostatin-like immunoreactive cells in the tree shrew retina were studied with the monoclonal antibody S8 against the neuropeptide somatostatin 14. As in some other mammals, immunoreactive somata are exclusively found in the ganglion cell layer. Immunoreactive processes form a sparse main plexus in the inner plexiform layer near the border of th...

Classical neurofibrillar staining methods and immunocytochemistry with antibodies to the light, medium and heavy chain subunits of the neurofilament triplet have been used for in situ and in vitro investigation of the organization of neurofilaments in A- and B-type horizontal cells of the adult rabbit retina. Surprisingly, their expression and orga...