Biomedical subjects

J Repérant

Publications and source records attributed to J Repérant.

At least 55 records · Page 3Linked to original sources

PubMed1997

The retinopetal visual system in the chameleon (Chameleo chameleon).

Intraocular injections of rhodamine and horseradish peroxidase in chameleon, labelled retrogradely neurons in the ventromedial tegmental region of the mesencephalon and the ventrolateral thalamus of the diencephalon. In both areas, staining was observed contralaterally to the injected eye. Labelling was occasionally observed in some rhombencephalic motor nuclei. These results indicate that chameleons, unlike other reptilian species, have two retinopetal nuclei.

Animals↗

PubMed1996

Distribution of serotonin-immunoreactivity in the brain of the pigeon (Columba livia).

The distribution of serotonin (5-HT)-containing perikarya, fibers and terminals in the brain of the pigeon (Columba livia) was investigated, using immunohistochemical and immunofluorescence methods combined with retrograde axonal transport. Twenty-one different groups of 5-HT immunoreactive (IR) cells were identified, 2 of which were localized at the hypothalamic level (periventricular organ, infundibular recess) and 19 at the tegmental-mesencephalic and rhombencephalic levels. Ten of the cell groups were situated within the region of the midline from the isthmic to the posterior rhombencephalic level and constituted the raphe system (nucleus annularis, decussatio brachium conjunctivum, area ventralis, external border of the nucleus interpeduncularis, zona peri-nervus oculomotorius, zona perifasciculus longitudinalis medialis, zona inter-flm, nucleus linearis caudalis, nucleus raphe superior pars ventralis, nucleus raphe inferior). The 9 other cell populations belonged to the lateral group and extended from the posterior mesencephalic tegmentum to the caudal rhombencephalon [formatio reticularis mesencephali, nucleus ventrolateralis tegmenti, ectopic area (Ec) of the nucleus isthmo-opticus (NIO), nucleus subceruleus, nucleus ceruleus, nucleus reticularis pontis caudalis, nucleus vestibularis medialis, nucleus reticularis parvocellularis and nucleus reticularis magnocellularis]. Combining the retrograde axonal transport of rhodamine beta-isothiocyanate (RITC) after intraocular injection and immunohistofluorescence (fluoresceine isothiocyanate: FITC/5-HT) showed the centrifugal neurons (NIO, Ec) to be immunonegative. Serotonin-IR fibers and terminals were found to be very broadly distributed within the brain and were particularly prominent in several structures of the telencephalon (archistriatum pars dorsalis, nucleus taeniae, area parahippocampalis, septum), diencephalon (nuclei preopticus medianus, magnocellularis, nucleus geniculatus lateralis pars ventralis, nucleus triangularis, nucleus pretectalis), mesencephalon-rhombencephalon (superficial layers of the optic tectum, nucleus ectomamillaris, nucleus isthmo-opticus and in most of the cranial nerve nuclei). Comparing the present results with those of previous studies in birds suggests some major serotonin-containing pathways in the avian brain and clarifies the possible origin of the serotonin innervation of some parts of the brain. Moreover, comparing our results in birds with those obtained in other vertebrate species shows that the organization of the serotoninergic system in many regions of the avian brain is much like that found in reptiles and mammals.

Animals↗

PubMed1996

Retinal and non-retinal inputs upon retinopetal RMA neurons in the lamprey: a light and electron microscopic study combining HRP axonal tracing and GABA immunocytochemistry.

A light and electron microscopic study, combining HRP axonal tracing or degeneration and GABA immunocytochemistry, was performed in the lamprey Lampetra fluviatilis in order to analyze retinal and non-retinal inputs upon the retinopetal neurons localized in the reticular mesencephalic area (RMA). The iontophoretic deposit of HRP onto the central stump of the cut optic nerve produced a dense anterograde labeling in the retino-recipient strata marginale and cellular externum of the optic tectum as well as the retrograde labeling of retinopetal neurons in the mesencephalic tegmentum. The large ascending proximal dendrites of the retinopetal neurons constituted a distinct bundle coursing first dorso-laterally in the dorsal mesencephalic tegmentum, and then dorso-medially in the strata fibrosum centrale and cellulare et fibrosum internum of the optic tectum before their distal portions penetrated the retino-recipient tectal layers. The distribution of GABA immunoreactivity was also investigated in the tectal layers and dorsal mesencephalic tegmentum with both pre- and post-embedding methods. The retinal terminals, identified either following HRP iontophoresis in the optic nerve or in early phases of degeneration after short-term survivals following retinal lesion, contained rounded-shaped synaptic vesicles and were always GABA immunonegative. They established asymmetrical synaptic contacts on the distal dendrites of RMA neurons and represented 11.4% of all terminals contacting such neurons (15% of these neurons were GABA immunopositive). The dense extra-retinal input upon the retinopetal RMA neurons was composed of five types of axon terminal profiles, either GABA-immunopositive or -immunonegative. Considering the different cytochemical types of axon terminals contacting RMA neurons, as well as the characteristics of the retinal targets of these neurons, we suggest that, globally, the effects of RMA neurons upon the retina are mainly inhibitory.

Afferent Pathways↗

PubMed1996

Retinopetal projections in lampreys.

In the lamprey Lampetra fluviatilis the centrifugal visual system is well developed. Centrifugal fibers arise from cells of two tegmentomesencephalic nuclei-reticular mesencephalic area and nucleus M5 of Schober-as demonstrated by axonal tracing techniques and antidromic neuronal recordings after optic nerve stimulation. Amacrine and ganglion cells in the retina are targets of centrifugal innervation, as shown by electrophysiology and axonal tracing. Following postembedding immunogold labeling, 40% of centrifugal axon terminals in the retina express immunoreactivity to gamma-aminobutyric acid (GABA). About 65% of neurons in M5 and 15% of those in the reticular mesencephalic area have been observed to be immunoreactive for GABA. Combined horseradish peroxidase (HRP) labeling and double immunogold staining were used to investigate the central organization of the retinal feed-back loop. Some terminals of optic nerve fibers from the retina made direct synaptic contacts on dendrites of centrifugal cells of the reticular mesencephalic area and nucleus M5. Terminals of non-retinal origin, immunoreactive for GABA and glutamate, also made synapses on centrifugal neurons. Monosynaptic feed-back loops may be complemented by interneurons as well as by excitatory and inhibitory inputs of non-visual origin.

Animals↗

PubMed1996

Topography of the NADPH-diaphorase system in the chameleon brain.

The NADPH-diaphorase histochemical technique, which reflects the activity of nitric oxide synthase was used in order to map the corresponding chameleon brain structures. In the forebrain, stained neurons were found particularly in the dorsal ventricular ridge and the ventral telencephalon, but no stained somata were observed in the cortical areas nor in the septum. In the midbrain, few NADPH-stained structures were seen. The stained cells were confined in the nucleus dorsomedialis, the nucleus geniculatus lateralis dorsalis, and the ventromedial hypothalamus. More caudally, some stained neurons were observed in the nucleus opticus mediodorsalis hypothalami posterior. In the brainstem, NADPH-stained cells were located in the optic tectum, the torus semicircularis, the substantia nigra, the ventral tegmental area, and all motor nuclei of the cranial nerves. The present results showed some striking differences and similarities with birds and mammals. Moreover, the presence of NADPH-staining in most of retinofugal, retinopetal and oculomotor nuclei suggests that nitric oxide system plays a prominent role in the visual and oculomotor functions.

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PubMed1996

A quantitative study of the effects of microphthalmia on the organisation of the primary visual system of the mouse.

The retinal projections of C57BL/Orl mice homozygous for the mutation microphthalmic-white (Miwh) were investigated by autoradiographic and HRP tracing techniques, and compared to those of heterozygous and normal mice of the same inbred strain; the anatomy of the eyes and optic nerves of the three genotypes were also examined. The eye of homozygous mutant mice is considerably reduced in size; the optic nerve shows a decrease in the number of myelinated fibres which is partially compensated by an increase in the proportion of unmyelinated axons. All primary visual centres that are labelled in normal mice receive retinal projections in mutant mice, although these centres are reduced in size in mutants. The reduction is most evident for those centres forming the thalamic relays of the retino-telencephalic pathway, to a lesser extent for the retino-collicular pathway and least of all for the retino-hypothalamic projections. These findings are compared to those obtained in naturally microphthalmic rodent species, and also to the effects of another mutation at the mi locus, maintained on a different background.

Animals↗

PubMed1995

Fine structure of the dorsal lateral geniculate nucleus of the turtle, Emys orbicularis: a Golgi, combined HRP tracing and GABA immunocytochemical study.

The afferent and efferent cortical projections of the dorsal lateral geniculate nucleus (GLD) of adult specimens of the turtle Emys orbicularis were investigated after intraocular or intracortical injections of horseradish peroxidase (HRP), and the distribution of gamma aminobutyric acid (GABA) immunoreactivity in the nucleus was carried out by immunocytochemical techniques, both techniques being combined with light and electron microscopy. In addition, some specimens were prepared for double-labeling of HRP and GABA immunoreactivity, and additional samples impregnated by a rapid Golgi technique. On purely morphological grounds, four types of neurons can be distinguished by light microscopy: two types of large cells in the cell plate which project to the cortex, and two types of smaller cells in the neuropil and optic tract which do not. The small cells are consistently GABA-immunoreactive, while the former are, with extremely rare exceptions, immunonegative for GABA. The supposition that the small neurons of the neuropil are interneurons is supported by electron microscopic observations; these strongly GABA-immunoreactive cells have large plicated nuclei surrounded by a thin layer of cytoplasm poorly endowed with organelles. The dendrites of these cells may contain pleomorphic synaptic vesicles (DCSVs) and appear to be presynaptic to other dendritic profiles. These DCSVs are occasionally contacted by GABA-immunoreactive axon terminals, and more frequently by retinal terminals consistently immunonegative for GABA. The latter, frequently organized in glomeruli, also make synaptic contacts with immunonegative dendrites arising from corticopetal neurons of the cell plate. Two major categories of GABA-immunoreactive axon terminals can be distinguished, and we are led to the conclusion that one of these represents an intrinsic GABAergic innervation of the GLD, while the second is tentatively interpreted as an extrinsic source of GABA to the nucleus, possibly from ventral thalamic structures. The fine structure of the dorsal lateral geniculate nucleus of Emys orbicularis thus shows many similarities with that of mammals.

Afferent Pathways↗

PubMed1995

Distribution of GABA immunoreactivity in the retino-recipient layer of the viper optic tectum. A light and electron microscope quantitative study.

The distribution of GABA-immunoreactivity was investigated in the principal retino-recipient layer of the optic tectum in the snake Vipera aspis. This layer, the stratum griseum et fibrosum superficiale, contained an important proportion (approximately 50%) of small GABA-immunoreactive interneurons, characterized by a voluminous invaginated nucleus surrounded by a thin rim of cytoplasm poor in organelles and occasionally showing pleiomorphic synaptic vesicles, which could also be observed in some of the dendrites that contained synaptic vesicles. In the neuropile, the GABA-immunoreactive profiles containing synaptic vesicles could be subdivided into dendrites containing synaptic vesicles and axon terminals with pleiomorphic synaptic vesicles. The dendrites containing synaptic vesicles (23.4% of all profiles containing synaptic vesicles) were postsynaptic either to optic terminals (39.2%), GABA-immunoreactive axon terminals with pleiomorphic synaptic vesicles (48.2%) or to immunonegative (S1) boutons with round synaptic vesicles (12.6%). These dendrites were presynaptic to GABA-immunoreactive (18%) neurons or immunonegative (82%) neurons. The axon terminals with pleiomorphic synaptic vesicles, which represented 47.4% of all profiles, were predominantly (99%) GABA-immunoreactive and four types could be distinguished according to cytological criteria. These axon terminals made synaptic contacts for the most part (78%) with immunonegative profiles, and more rarely (22%) with immunoreactive neurons. These data are compared to those previously obtained in the homologous structure of other vertebrate species, birds and mammals in particular.

Animals↗

PubMed1995

Ipsilateral visual projections in non-eutherian species: random variation in the central nervous system?

The published descriptions of ipsilateral visual pathways in non-eutherian species are reviewed. Such pathways exist in members of all vertebrate classes; since they exist in agnathans, it is suggested that the presence of ipsilateral visual projections is the ancestral condition. None of the published attempts to explain the considerable interspecific variation of these pathways can be generalised to all vertebrate species: in particular, this variation is not generally related to the degree of overlap of the visual fields, to a particular mode of life, nor to taxonomic position within a given vertebrate category and cannot consistently be explained by variation at the albino locus. It is suggested that this variation is the result of purely random variation of unidentified elements of the genetic material or of epigenetic mechanisms and hence that ipsilateral visual projections are functionally neutral. This conclusion is supported by some extremely fragmentary behavioral data indicating that the information they provide is redundant.

Animals↗

PubMed1995

Interspecific variation in the chelonian primary visual system.

The primary visual system of 21 species of turtles, distributed among nine of the existing 12 families, were studied by autoradiography. In all species, contralateral visual projections exist to 15 targets: two hypothalamic structures (nucleus suprachiasmaticus and n. periventricularis), three major thalamic visual centres (nucleus ovalis, n. geniculatus lateralis ventralis and n. geniculatus lateralis dorsalis) and two minor thalamic targets (nucleus dorsolateralis anterior and n. ventrolateralis), five pretectal sites (nucleus geniculatus pretectalis, n. opticus pretectalis ventrolateralis, n. lentiformis mesencephali, n. posterodorsalis and n. griseus tectalis), two strata of the optic tectum (stratum opticum and s. fibrosum et griseum superficiale), and a single tegmental target (nucleus opticus tegmenti). In contrast to the stability of contralateral visual projections, their ipsilateral counterparts varied considerably between species, being limited to the hypothalamus in some species, and involving the majority of the primary visual centres in others. This variation is not readily explainable in terms of taxonomic position or of differences in mode of life.

Animals↗

PubMed1995

Colocalization of glutamate and glycine in giant fiber synapses of the lamprey spinal cord.

Using electron microscope immunocytochemistry in serial and semi-serial sections, glutamate and glycine immunoreactivity was analyzed in various synapses of the lamprey spinal cord. Immunoreactivity to glutamate was observed over the synaptic vesicle clusters in the giant reticulospinal axons and dorsal/dorsolateral column fibers, both of which established "en passant" asymmetrical contacts. Most of giant axons (70%) were also observed to express an immunoreactivity to glycine. Glutamate or glycine immunopositive axon terminals were present throughout the spinal cord regions. Glutamate positive boutons made asymmetrical contacts and contained rounded synaptic vesicles. Glycine reactive axon terminals with rounded synaptic vesicles established asymmetrical contacts and those with flattened synaptic vesicles established symmetrical contacts. The possibility that these two amino acids could be released from the same reticulospinal synapse in the lamprey, with a glycine modulatory effect on NMDA receptors, is suggested.

Animals↗

PubMed1995

Vasopressin- and oxytocin-like systems in the chameleon brain.

The distribution of vasopressin (VP)-like and oxytocin (OX)-like immunoreactivities was investigated in the chameleon brain with antisera specific for either peptide. VP-like and OX-like neurons are found only in two nuclei: in the supraoptic and in the paraventricular nuclei, whereas both peptidergic innervations are restricted to some ventral areas, especially to the hypothalamus. However, in these areas, OX-like innervation is less dense than the VP-like innervation. Even though, no sex differences were noted for the two systems, differences are present between the normal female and the preoviposit one concerning VP-like system. In the latter female, numerous VPergic-like cell bodies occurred in the ependymal layer, making likely direct contact with the cerebrospinal fluid (CSF) of the third ventricle. In addition, some VP-like nerve fibers seem to be in supraependymal position at the septal wall, probably also in contact with CSF.

Animals↗

PubMed1995

Anatomical evidence of a retino-thalamo-hippocampal pathway in the pigeon (Columba livia).

The aim of the present study was to demonstrate the existence of a retino-thalamo-hippocampal pathway in the pigeon and, more specifically, to identify its thalamic relay (n. superficialis parvocellularis: SPC). Fluorescence axonal tracing techniques were used combining the orthograde axonal transport of RITC after its intraocular injection and the retrograde axonal transport of various other fluorescent tracers (FB, FG, EB) injected into the hippocampal complex. Since the n.SPC has also been shown to project upon the visual Wulst, different fluorescent dyes were injected concomitantly into the latter and the hippocampus and the distribution of retrograde somatic labeling within the thalamus was compared. The injections into both telencephalic target structures resulted in a differential pattern of labeling bilaterally within the thalamic dorsolateral anterior (DLA) complex and the n.SPC. Moreover, the distributions of both cell types overlapped within the n.SPC, although no double-labeling of individual cell bodies indicative of collateralized axonal projections was observed. Direct retinal projections upon the n.SPC were also demonstrated and terminated within the same regions of the nucleus containing relay cells projecting to both the hippocampus and the Wulst. The organization of the retino-thalamo-hippocampal pathway in birds is similar to that which has been described in other vertebrate groups. A common feature is the presence of divergent projections from a dorsal thalamic retino-recipient relay nucleus upon both neopallial visual cortical areas and the hippocampus (archipallium).

Animals↗

PubMed1994

Visual system of the fossorial mole-lemmings, Ellobius talpinus and Ellobius lutescens.

Ocular regression in subterranean species has been shown to be associated with a number of alterations in the retina and in retinal pathways. In order to examine the consequences of eye reduction, the visual system was studied in two species of the murine genus, Ellobius, a specialized fossorial rodent. The axial length of the eye is only 2.2 mm in E. lutescens and 2.9 mm in E. talpinus. The mean soma size of ganglion cells in Nissl-stained flatmounts is approximately 10 microns in E. lutescens and 12 microns in E. talpinus. The soma size distribution in both species appears unimodal and falls within a range of 6-17 microns in diameter. The topographic distribution of ganglion cells shows a weak centroperipheral gradient, and an area centralis cannot be distinguished. The total number of neurons in the ganglion cell layer in Nissl-stained flat mounts is 12,000 in E. lutescens and 28,500 in E. talpinus and, following injection of retrograde tracers in the superior colliculus, is, respectively, 3,600 and 20,000. Based on the axial length and maximum ganglion cell density, the calculated retinal magnification factor (20-26 microns/degree) and spatial resolution (0.4-0.9 cycles/degree) of these minute eyes are extremely reduced. Retinofugal projections, demonstrated by autoradiography and horseradish peroxidase histochemistry, are similar to those in other rodents. The superior colliculus is well developed and receives a predominantly contralateral projection. Ganglion cells projecting to the contralateral colliculus are distributed over the entire retina, while cells that project ipsilaterally are restricted to the ventrotemporal region. The dorsal lateral geniculate nucleus has clearly defined binocular and monocular segments, including a partial segregation of regions receiving ipsilateral or contralateral retinal innervation. In addition, a localized region of label is observed medial to the geniculate nucleus. The retina also sends a bilateral projection to the suprachiasmatic nucleus; the intergeniculate leaflet; the pretectum; and the medial, lateral, and dorsal terminal nuclei of the accessory optic system. Sparse retinal projections were also seen in the bed nucleus of the stria terminalis, the anterior thalamus, and the inferior colliculus. A substantial retinal projection is observed in the basal telencephalon, including the cortical amygdaloid region, the diagonal band of Broca, the olfactory tubercle, and the piriform cortex. The results suggest that the morphological constraints of reduced eye size are reflected in the retina by a generally homogeneous organization but that central visual projections are not substantially modified as in some more specialized, strictly subterranean rodents.

Animals↗

PubMed1994

Immunohistochemical localization of calbindin-D28K and calretinin in the lamprey retina.

Calbindin-D28K and calretinin are homologous cytosolic calcium binding proteins localized in many retinal neurons from different species. In this report, location of cells immunoreactive to both proteins was investigated in the retina of the lamprey, Lampetra fluviatilis. This organism constitutes one of the older representative vertebrates and possesses a peculiar organization, probably unique: two-thirds of the ganglion cells are in the classical amacrine cell layer and the nerve fiber layer is located in the scleral part of the inner plexiform layer. Calbindin-like immunoreactivity was demonstrated in large bipolar cells and in cell bodies located in the inner retina. Although the distinction between labelled ganglion cells and labelled amacrine cells was rendered difficult, we hypothesized that the majority of calbindin-immunoreactive cells observed in the inner retina are ganglion cells, because of the high number of labelled fibers in the nerve fiber layer. Calretinin-like immunoreactivity was detected in both large and small bipolar cells, and also in cells located in the inner retina. Since few calretinin-immunoreactive fibers were observed in the nerve fiber layer, we assume that the latter category of cells are amacrine cells. Horizontal cells were both negative for calbindin and calretin-like immunoreactivities. Calbindin and calretinin, which are present in cones from many species, could not be detected in the photoreceptor layer favouring the rod-dominated lamprey retina. Although their distribution differs from those observed in most vertebrates, the present results indicate the good conservation of both calcium binding proteins in the retina during the vertebrate evolution.

Animals↗

PubMed1994

The distribution of GABA-immunoreactive neurons in the brain of the silver eel (Anguilla anguilla L.).

The distribution of GABA-immunoreactivity was studied in the brain of the silver eel (Anguilla anguilla) by means of antibodies directed against GABA. Immunoreactive neuronal somata were distributed throughout the brain. Positive perikarya were detected in the internal cellular layer of the olfactory bulb, and in all divisions of the telencephalon, the highest density being observed along the midline. Numerous GABA-reactive cell bodies were found in the diencephalon, particularly in the preoptic and tuberal regions of the hypothalamus, and the dorsolateral, dorsomedial and ventromedial thalamic nuclei. In the optic tectum, the majority of GABA-positive cell bodies were located in the periventricular layer. A number of immunolabeled cell bodies were observed in different tegmental structures, notably the torus semicircularis. In the cerebellum, the Purkinje cells were either very intensely or very weakly immunoreactive. In the rhombencephalon, reactive cell bodies were observed in the eminentia granularis, the valvula cerebellaris, the octavolateral nucleus, the lobus vagus and in the vagal and glossopharyngeal motor nuclei. Intensely immunoreactive axons and terminals were observed in the external granular layer and internal cellular layer of the olfactory bulb. In the telencephalon, the highest density of reactive fibres and boutons was found in the fields of the medial wall. Many immunolabeled fibres were seen in the medial and lateral forebrain bundles. In the diencephalon, intense labelling of fibres and terminals were observed in the nuclei situated close to the midline. In the optic tectum the highest density of reactive fibres was seen in the sfgs, the layer to which the retina projects massively. Finally, in the rhombencephalon the strongest labelling of neurites was observed in the nuclei of the raphé, the nucleus octavocellularis magnocellularis and the nuclei of the IXth and Xth cranial nerves. The GABAergic system of the eel, which is well developed, appears to be generally comparable to that described in tetrapod vertebrates.

Anguilla↗

PubMed1994

An experimental re-evaluation of the primary visual system of the European chameleon, Chamaeleo chameleon.

The retinofugal projections of the chameleon were investigated by means of autoradiography, horseradish peroxidase and fluorescent techniques after intraocular injection of tracers. An ipsilateral contingent of visual fibers and projections is absent. The retinal fibers decussate completely in alternating fascicles at the optic chiasma and course to terminate in two hypothalamic nuclei (nucleus suprachiasmaticus and nucleus opticus periventricularis hypothalami posterior), six thalamic nuclei (nucleus ovalis, nucleus geniculatus lateralis dorsalis partes lateralis and medialis, nucleus geniculatus lateralis ventralis, lateral part of nucleus dorsolateralis anterior, and nucleus ventrobasalis), four pretectal nuclei (nucleus griseus tectalis, nucleus lentiformis mesencephali, nucleus geniculatus pretectalis and nucleus posterodorsalis), the optic tectum (stratum griseum et fibrosum superficiale) and the tegmental nucleus opticus tegmenti. Our findings are, in general, compatible with previous descriptions of the primary visual system in other species of lizards. However, they indicate three features particular to chameleons: first, the total absence of an ipsilateral retinofugal projection; second, the existence of an additional hypothalamic visual center located in the posterior mediodorsal hypothalamus; and third, the large size of nucleus opticus tegmenti. These features are discussed in terms of the taxonomic position of chameleons with respect to other lizards.

Animals↗

PubMed1994

Immunoreactivity to glial fibrillary acid protein (GFAP) in the brain and spinal cord of the lamprey (Lampetra fluviatilis).

In contradiction to previous results, under certain conditions, it is possible to demonstrate GFAP immunoreactivity in the brain and spinal cord of a jawless vertebrate. The critical parameters appear to be (1) fixation with 4% paraformaldehyde at pH 7.4, (2) a very short period (2-6 hr) of postfixation, and (3) immunovisualization by the avidin/biotin/peroxidase technique rather than immunofluorescence or PAP techniques. Immunoreactivity appears throughout the brain and spinal cord, most frequently as fine prolongations normal to the pial surface, which can on occasion be traced to cell bodies near the ventricles or in the ependymal layer. The evolutionary implications of the presence of glial fibrillary acidic protein in a member of the Agnatha are discussed.

Animals↗