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PubMed1990

Premitotic DNA synthesis in the brain of the adult frog (Rana esculenta L.): an autoradiographic 3H-thymidine study.

Replicative synthesis of DNA in the brain of the adult frog was studied by light microscope autoradiography. Animals collected during the active period (May-June) and in hibernation (January) were used. In active frogs, 3H-thymidine labelling occurred mainly in the ependymal cells which line the ventricles. The mean labelling index (LI%) was higher in the ependyma of the lateral and fourth ventricles than in the ependyma of the lateral diencephalon and tectal parts of the mesencephalon. In the recessus infundibularis and preopticus the number of labelled cells (LCs) was several times greater than in the lateral parts of the third ventricle. LCs were seen subependymally only occasionally. The incidence of LCs in the parenchyma of the brain was much lower in most regions than in the ventricular ependyma; LCs were mainly small and, from their nuclear morphology, they were glial cells. The LI% reached the highest value in the septum hippocampi and in the nucleus entopeduncularis. In these locations, LCs were larger and closer in size to the nerve cells of these regions. From comparison with data obtained earlier in the brain of mammals, it is evident that the distribution of proliferating cells in the olfactory and limbic system is phylogenetically conservative. The occurrence of pyknotic cells in the same areas which contain LCs, suggests that cell division reflects in part the process of cell renewal observed in mammals. However, proliferating cells could also be linked to the continuous growth observed in non-mammalian vertebrates. In hibernating frogs, LCs and pyknoses were not seen or were found occasionally, which further indicates the functional significance of both processes.

Animals↗
PubMed1991

Parasympathetic postganglionic cells in the glossopharyngeal nerve trunk and their relationship to unmyelinated nerve fibers in the fungiform papillae of the frog.

The glossopharyngeal nerve of the frog is made up of afferent nerve fibers and efferent, parasympathetic and sympathetic nerve fibers. The precise origin and course of the parasympathetic efferent nerve fibers in the fungiform papillae of the frog's tongue were investigated. We found the ganglionic cells in the lingual branch of the frog glossopharyngeal nerve. The surface of the ganglionic cell bodies was partly covered by synaptic endings that impinged upon it. Synaptic endings contained clear synaptic vesicles and large dense-cored vesicles. After cutting of the glossopharyngeal nerve proximal to the jugular ganglion, synaptic endings were found to show definite signs of degeneration. These findings led us to the conclusion that the ganglionic cells in the lingual branch of the glossopharyngeal nerve are the parasympathetic postganglionic cells. After cutting of the glossopharyngeal nerve distal to the jugular ganglion, some unmyelinated nerve fibers in the fungiform papillae and postganglionic cells in the lingual branch remained intact. These results strongly suggest that the origin of some of the unmyelinated nerve fibers is the parasympathetic postganglionic cell in the lingual branch.

Animals↗
PubMed1990

Exposure of frog hearts to CW or amplitude-modulated VHF fields: selective efflux of calcium ions at 16 Hz.

Isolated frog hearts were exposed for 30-min periods in a Crawford cell to a 240-MHz electromagnetic field, either continuous-wave or sinusoidally modulated at 0.5 or 16 Hz. Radiolabeled with calcium (45Ca), the hearts were observed for movement of Ca2+ at calculated SARs of 0.15, 0.24, 0.30, 0.36, 1.50, or 3.00 mW/kg. Neither CW radiation nor radiation at 0.5 Hz, which is close to the beating frequency of the frog's heart, affected movement of calcium ions. When the VHF field was modulated at 16 Hz, a field-intensity-dependent change in the efflux of calcium ions was observed. Relative to control values, ionic effluxes increased by about 18% at 0.3 mW/kg (P less than .01) and by 21% at 0.15 mW/kg (P less than .05), but movement of ions did not change significantly at other rates of energy deposition. These data indicate that the intact myocardium of the frog, akin to brain tissue of neonatal chicken, exhibits movement of calcium ions in response to a weak VHF field that is modulated at 16 Hz.

Animals↗
PubMed2002

Isolation, characterization, and distribution of a novel neuropeptide, Rana RFamide (R-RFa), in the brain of the European green frog Rana esculenta.

A novel neuropeptide of the RFamide peptide family was isolated in pure form from a frog (Rana esculenta) brain extract by using reversed-phase high performance liquid chromatography in combination with a radioimmunoassay for mammalian neuropeptide FF (NPFF). The primary structure of the peptide was established as Ser-Leu-Lys- Pro-Ala-Ala-Asn-Leu-Pro-Leu- Arg-Phe-NH(2). The sequence of this neuropeptide, designated Rana RFamide (R-RFa), exhibits substantial similarities with those of avian LPLRFamide, gonadotropin-inhibitory hormone, and human RFRP-1. The distribution of R-RFa was investigated in the frog central nervous system by using an antiserum directed against bovine NPFF. In the brain, immunoreactive cell bodies were primarily located in the hypothalamus, i.e., the anterior preoptic area, the suprachiasmatic nucleus, and the dorsal and ventral hypothalamic nuclei. The most abundant population of R-RFa-containing neurons was found in the periependymal region of the suprachiasmatic nucleus. R-RFa- containing fibers were widely distributed throughout the brain from the olfactory bulb to the brainstem, and were particularly abundant in the external layer of the median eminence. In the spinal cord, scattered immunoreactive neurons were found in the gray matter. R-RFa-positive processes were found in all regions of the spinal cord, but they were more abundant in the dorsal horn. This study provides the first characterization of a member of the RFamide peptide family in amphibians. The occurrence of this novel neuropeptide in the hypothalamus and median eminence and in the dorsal region of the spinal cord suggests that, in frog, R-RFa may exert neuroendocrine activities and/or may be involved in the transmission of nociceptive stimuli.

Amino Acid Sequence↗
PubMed2002

Immunohistochemical localization and biochemical characterization of ghrelin in the brain and stomach of the frog Rana esculenta.

Ghrelin is a 28-amino acid n-octanoylated peptide recently isolated from the rat stomach as an endogenous ligand of the growth hormone secretagogue receptor. So far, the occurrence of ghrelin has not been investigated in submammalian vertebrates. In the present work, we have studied the anatomic distribution and biochemical characterization of ghrelin-like immunoreactivity in the brain and stomach of the frog Rana esculenta by using two distinct antisera directed against rat ghrelin. In the brain, sparse ghrelin-positive cells were detected in three nuclei of the diencephalon, namely the suprachiasmatic nucleus and the posterior tuberculum in the hypothalamus, and the posterodorsal aspect of the lateral nucleus in the thalamus. A few ghrelin-immunoreactive neurons were also found in the mesencephalon, i.e., in the pretoral gray and the anterodorsal tegmental nucleus. Ghrelin-containing fibers were widely distributed in the frog brain. In particular, diffuse networks of immunoreactive processes were observed in various regions of the telencephalon, including the medial pallium, the striatum, the nucleus of the diagonal band of Broca, the nucleus accumbens, and the amygdala. In the diencephalon, the magnocellular nucleus, the suprachiasmatic nucleus, the posterior tuberculum, and the ventrolateral and lateral thalamic nuclei were moderately to densely innervated with ghrelin-containing fibers. A moderate density of positive fibers was also found in different areas of the mesencephalon such as the nucleus of the medial longitudinal fasciculus, the pretoral gray, and the tegmentum. In the stomach, a few brightly immunofluorescent cells were detected in the mucosa. The distribution pattern and morphologic characteristics of ghrelin-containing cells in the stomach suggest that they correspond to endocrine cells. Reversed-phase high performance liquid chromatography analysis of frog brain and stomach extracts, combined with RIA detection, revealed that ghrelin-immunoreactive material eluted as a single peak with a retention time slightly shorter than that of synthetic rat ghrelin. The present data provide the first evidence that a ghrelin-related peptide is present in submammalian vertebrates. The occurrence of ghrelin-containing cells in the hypothalamus and the stomach mucosa suggests that, in amphibians, ghrelin may exert both neuroendocrine and endocrine activities.

Animals↗
PubMed2003

Molecular characterization of the cDNA and localization of the mRNA encoding the prohormone convertase PC5-A in the European green frog.

The structure and distribution of PC5-A, a prohormone convertase that is thought to be involved in post-translational processing of peptide hormone and neuropeptide precursors, have not been investigated in submammalian vertebrates. In the present study, we characterized the cDNA encoding PC5-A in the European green frog Rana esculenta. The frog PC5-A cDNA encodes a 913-amino acid protein that encompasses a 28-amino acid signal peptide, the Asp/His/Ser catalytic triad found in all serine proteinases of the subtilisin family, and two potential N-linked glycosylation sites located in a C-terminal cysteine-rich domain. Reverse transcriptase polymerase chain reaction amplification showed that PC5-A mRNA is expressed in various organs including the brain, spinal cord, pituitary, lung, liver, intestine, and testis, but not in the stomach and pancreas. The distribution of PC5-A mRNA in the frog brain was studied by in situ hybridization histochemistry. Intense expression was observed in the mitral cellular layer of the olfactory bulb, the nucleus of the diagonal band of Broca, the anterior preoptic area, and the suprachiasmatic and ventral hypothalamic nuclei. The expression pattern of PC5-A mRNA in the central nervous system of anuran amphibians was consistent with the implication of this prohormone convertase in the processing of various neuropeptide precursors.

Amino Acid Sequence↗
PubMed2003

Normal chiasmatic routing of uncrossed projections from the ventrotemporal retina in albino Xenopus frogs.

Albino mammals lacking melanin in the embryonic retinal pigment epithelium (RPE) have abnormal retinal decussation patterns at the optic chiasm: their uncrossed projections are smaller and arise from fewer, more peripheral temporal retinal ganglion cells than in con-specific wild-types. To determine whether these abnormalities generalize to nonmammalian mutants, we used anterograde and retrograde labeling methods to compare the distribution of retinal projections to the thalamus in adult normal and albino Xenopus frogs. In both pigmentation phenotypes, crossed retinal terminations covered approximately 80% of the neuropil of Bellonci (nB) and corpus geniculatum thalamicum (cgt) and uncrossed inputs occupied, respectively, approximately 75% and 25% of these two main visual centers. In the wild-type frogs and in the albinos, ganglion cells giving rise to the crossed projections were distributed throughout the retina, whereas ipsilaterally projecting cells were confined to a specific ventrotemporal retinal division. This region comprised approximately 40% of the total retinal area, was bordered by a well-defined line of decussation, and contained an average of approximately 3,000 ipsilaterally projecting ganglion cells of equivalent soma sizes in the two pigmentation phenotypes. In summary, we found no evidence of chiasmatic misrouting in the uncrossed retinothalamic projections of albino Xenopus, even though these pathways are substantial in normal frogs and share features in common with mammalian retinogeniculate projections. Our findings suggest that congenital RPE melanin deficiency results in major defects in the development of the retina and its central projections only in mammals.

Albinism, Ocular↗
PubMed2001

Distribution and ultrastructure of tachykinin-like immunoreactivity in the frog (Rana esculenta) spinal cord, notably, the dorsal horn.

Tachykinins are involved in pain transmission at the spinal level. In frog, at least four tachykinins [TK] have been isolated from the brain, but their organization in the dorsal horn of the spinal cord is still poorly known. We have reexamined TK distribution by immunocytochemistry using an antibody recognizing the sequence common to all tachykinins in the spinal cord and dorsal root ganglia of the green frog Rana esculenta. A dense tachykinin-like immunoreactivity (TK-LI) was observed in the dorsolateral fasciculus or Lissauer's tract running ventromedial to the entry of the dorsal root and in numerous small and medium-sized dorsal root ganglion cells showing a primary afferent origin for part of TK-LI of the dorsal horn. The observation of numerous cell bodies in the dorsal horn, in addition, suggested a local or propriospinal origin. One group of cells was localized at the entrance of the Lissauer's tract TK-LI fibers into the dorsal horn, and another group was localized in the upper dorsal horn, a region with a low density of TK-LI fibers. It was suggested that the latter group may correspond to neurokinin B. Electron microscopic examination of the Lissauer's tract showed numerous immunoreactive axons, some located at the center of glomerular-like arrangements, suggesting that the information brought by these fibers may be transmitted and most probably modulated before their entry in the dorsal horn. In conclusion, the functional organization of tachykinins in the frog spinal cord seems to be similar to that of mammals, albeit with a different morphological organization.

Animals↗
PubMed2004

Immunohistochemical localization of cocaine- and amphetamine-regulated transcript peptide in the central nervous system of the frog Rana esculenta.

The distribution of cocaine- and amphetamine-regulated transcript peptide (CARTp)- like immunoreactivity was studied only in the rat central nervous system (CNS). In mammals, CART peptides occur among others in brain areas that control feeding behavior. We mapped CARTp-immunoreactive structures in the CNS of the frog Rana esculenta and assumed that differences may exist in the CARTp-containing neuronal populations between the frog, which does not feed in winter, and the rat. In the forebrain, immunoreactive cells and fibers were found in the olfactory bulb, nucleus accumbens, amygdala, medial pallium, septum, striatum, the preoptic nuclei, ventromedial nucleus, central thalamic nucleus, and the hypothalamus. The optic pathway was free of immunoreactivity. The neurohypophysis showed intense immunostaining. In the mesencephalon, many cells were stained in the Edinger-Westphal nucleus, and a few in the optic tectum, where fibers were stained in all plexiform layers. In the retina, some cells in the inner nuclear layer contained CARTp. In the rhombencephalon, cells were stained in the raphe nuclei, central gray, nucleus of the solitary tract, and the vicinity of motor nuclei. Neurons of the motor cranial nerves were densely innervated by CARTp-positive fibers originating from the spinal cord. In the spinal cord, preganglionic cells were stained, and motoneurons were surrounded by immunoreactive varicose axon terminals. Major differences were found between the frog and the rat brains in the distribution of CARTp in the visual system, olfactory bulb, preoptic area, and the motor nuclei. Some of these differences may be related to feeding behavior of these animals.

Animals↗
PubMed2006

Distribution of hyaluronan in the central nervous system of the frog.

The qualitative and quantitative distribution pattern of hyaluronan (HA), a component of the extracellular matrix (ECM), was studied in the frog central nervous system by using a highly specific HA probe and digital image analysis. HA reaction was observed in both the white and the gray matter, showing a very intense staining around the perikarya and dendrites in the perineuronal net (PN). In the telencephalon, strong reaction was found in different parts of the olfactory system, in the pallium, and in the amygdala. In the diencephalon, intensive staining was found in the nucleus of Bellonci, the dorsal habenula, the lateral and central thalamic nuclei, and the subependymal zone of the third ventricle. In the mesencephalon, layers of optic tectum displayed different intensities, with the strongest reaction in layers B, D, F, 3, and 5. Other structures of the mesencephalon showed regional differences. The PN was especially intensively stained around the perikarya of the toral nuclei, the oculomotor and trochlear nuclei, and the basal optic nucleus. In the rhombencephalon, the granular layer of cerebellum, the vestibulocochlear nuclei, the superior olive, the spinal tract of the trigeminal nerve, and parts of the reticular formation showed the most intense reaction in the PN. In the spinal cord, considerable HA staining was found in the white matter and around the perikarya of motoneurons. The present study is the first description of the HA-positive areas of frog brain and spinal cord demonstrating the heterogeneity of HA distribution in the frog central nervous system.

Animals↗
PubMed1981

The aberrant retino-retinal projection during optic nerve regeneration in the frog. II. Anterograde labeling with horseradish peroxidase.

Previous experiments have shown that a substantial number of regenerating optic axons in adult frogs (Rana pipiens) are misrouted into the opposite optic nerve and retina during early stages of regeneration. This projection is maximal at 5 and 6 weeks after optic nerve crush. To further characterize this anomalous projection, small quantities of horseradish peroxidase (HRP) were injected into the right eye or right optic nerve 5 or 6 weeks after right optic nerve crush. Twenty-four hours later the animals were killed and regenerating axons anterogradely filled with HRP were reacted with the tetramethyl-benzidine method or a diaminobenzidine-CoCl2 method. Serial reconstruction tracing the course of individual axons through the optic chiasm showed that few of the axons projecting into the opposite optic nerve were collaterals of axons projecting centrally. Instead, the majority of labeled axons misdirected into the opposite nerve or contributing to an expanded projection into the ipsilateral optic tract turned out of the chiasm without branching. Many of the labeled regenerating axons had unusual trajectories within the chiasm, making abrupt turns or changing their direction of growth. Most of the axons misrouted into the opposite nerve came from portions of the chiasm nearest to the nerve of other eye. In three of eight frogs with an intact optic nerve, a small number of HRP-labeled axons were found in the left nerve after right nerve injection, but there was no indication that these axons reached the left eye. The results from this investigation suggest that the most parsimonious explanation for the chiasmal misrouting of regenerating frog optic axons is that axons are mechanically deflected into inappropriate pathways.

Animals↗
PubMed1983

Hyperplasia in the spinal sensory system of the frog. II. Central and peripheral connectivity patterns.

Central and peripheral connectivity patterns of hyperplastic dorsal root ganglia (DRGs) in Rana pipiens are examined in order to determine the relative roles of peripheral and central contacts in the production of DRG hyperplasias. The hyperplasias are produced in the intact hindlimb DRGs after the removal in tadpoles and young postmetamorphic frogs of neighboring DRGs (Davis and Constantine-Paton, '83). The peripheral target zones of the hyperplastic DRGs, determined by physiological recordings of sensory receptive fields, are found to undergo a significant degree of expansion relative to controls. Peripheral expansion is most pronounced in caudalmost DRG 10, and this effect occurs in experimental animals operated during larval and postmetamorphic stages. Further, anatomical labelling of peripheral sensory fibers coursing to the hindlimb reveals that the hyperplastic DRG 10 actually contains additional fibers projecting to the denervated regions. The central projection of the hyperplastic DRG 10 does not show corresponding increases in longitudinal arborization after the application of horseradish peroxidase to the appropriate dorsal roots. These observations are made on some of the same experimental animals in which peripheral fields are shown to have vastly expanded. We conclude that the peripheral processes of the hyperplastic DRGs are less rigidly specified than the central terminations, and that it is the periphery which plays the primary role in controlling the cell numbers increases. A second aim of this investigation is to identify whether sexually dimorphic connectivity patterns in normal frogs explain the production of DRG 10 hyperplasias exclusively in male experimental animals (Davis and Constantine-Paton, '83). We apply the same techniques used in our connectivity studies of hyperplastic DRGs to the investigation of connectivity patterns of DRG 10s in normal males and females. No sex-dependent differences in peripheral and central connectivity are found. Thus, since normal male and female frogs possess an equivalent amount of target space for DRG 10, the unique production of hyperplasias in male experimental animals cannot be explained solely on the basis of connectivity. We speculate on what other factors may be involved.

Animals↗
PubMed1984

Organization within the cranial IX-X complex in ranid frogs: a horseradish peroxidase transport study.

Cranial nerves IX and X in frogs have been described as originating from a nuclear group referred to as the IX-X complex. We studied the central nervous system components of this complex in Rana pipiens and R. catesbiana by labeling peripheral branches of cranial nerves IX and X and identifying the central nervous system contributions of these branches. Various peripheral nerves (IX and the cardiac, gastric, pulmonary, and laryngeal branches of X) were identified and soaked in horseradish peroxidase (HRP). One to 2 weeks later, the frogs were killed and processed for HRP by the tetramethylbenzidine method. Glossopharyngeal efferents originated from a small ventrolateral cell group found at the level of IX root exit. Vagal efferents formed a single column of cells in a ventrolateral position from the level of the brainstem exist of the vagus nerve (approximately 2,000 micrometers above the obex) to 200 micrometers below the obex (values given are for an 80-g frog). This cell group was separate from and just caudal to efferent cells of the glossopharyngeal nerve. Within the vagal portion of the column, cells projecting through the gastric branch were found throughout the rostral-caudal extent of the nucleus. "Cardiac" cells tended to be more rostral than "pulmonary" cells, and both groups of cells were located in the middle of the nucleus. "Laryngeal" cells were located more caudally in the nucleus. This peripheral representation within the vagal nucleus corresponds more closely to the organization found in the mammalian nucleus ambiguus, rather than to the apparent lack of organization found in the mammalian dorsal motor nucleus. Afferents of IX and X entered slightly rostral to the ventral roots of their respective nerves and descended in two tracts. The majority entered the tractus solitarius and descended in a medial position to cervical spinal cord. A portion of the afferents from the vagus nerve crossed the midline in the lower myelencephalon just dorsal to the central canal and ascended a short distance on the contralateral side. Within the solitary tract, vagal afferents were located in a ventrolateral position as they descended to below the obex. Glossopharyngeal afferents filled the remainder of the tract. A smaller portion of afferents from both IX and X did not enter the solitary tract but descended in the spinal tract of V and the dorsolateral funiculus of the spinal cord (Lissauer's tract) to thoracic levels. Afferents of IX also formed a rostral bundle which extended in the solitary tract to the caudal metencephalon.

Animals↗
PubMed1986

A quantitative analysis of frog optic nerve regeneration: is retrograde ganglion cell death or collateral axonal loss related to selective reinnervation?

The present study was designed to assess whether axon collateral formation and loss or retrograde cell death contribute to selective reinnervation during optic nerve regeneration in the frog, Rana pipiens. The right optic nerve was crushed in 18 frogs, and samples were taken near the optic disc (retinal segment) and near the optic chiasm (brain segment). These samples were studied quantitatively with the electron microscope at various postoperative survival times (1, 2, 3, 4, 6, 12 weeks, 6 months, 1 year; N = 2). The number and size of axons in each segment were estimated from a series of electron micrographs taken at intervals across the transverse extent of each nerve and compared with normal nerves (N = 4). Results show that there are 5.3 +/- 1.8 X 10(5) (S.D.) unmyelinated and 2.3 +/- .5 X 10(4) myelinated axons in the normal nerve. One week post-crush (p.c.) there is a 27% decrease in the number of axons in the retinal segment (4.1 +/- 1.4 X 10(5)), indicating early retrograde axonal loss. As expected, there is a greater loss of axons at this time in the brain segment (3.0 +/- 1.3 X 10(5)). Between 2 and 6 weeks p.c. the number of axons increases in the retinal segment to over twice the normal number of axons increases in the retinal segment to over twice the normal number (12.3 +/- 3.8 X 10(5)) and to over four times this number in the brain segment (20.0 +/- 3.0 X 10(5)), showing collateral axon formation results from this injury. A large loss in the number of axons occurs in both nerve segments between 6 and 12 weeks p.c. (4.3 +/- 1.5 X 10(5)) and an additional loss at 20 weeks p.c. (2.2 +/- .98 X 10(5)). Subsequently, the number remains constant, approximately 40% of normal. Visual recovery was seen in the two frogs tested one year after optic nerve crush that were used for optic axon counts. Autoradiography in these same animals showed the optic nerve projections normally seen after regeneration. Besides axonal loss, our results also indicate that the size of both myelinated and unmyelinated axons is significantly above normal at chronic postoperative periods. This increase in axonal size is interpreted to be related to the increased territory each remaining optic axon must fill to restore the optic projections.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1987

Effect of tetraploidy on dendritic branching in neurons and glial cells of the frog, Xenopus laevis.

Morphological aspects of four different groups of Golgi impregnated brain cells from a tetraploid strain of Xenopus laevis frogs were compared to analogous cells in comparably sized diploid frogs. The cells examined included neurons from the telencephalon, caudal hypothalamus, and optic tectum, and radial glial cells from the optic tectum. The brains of tetraploid frogs appeared grossly normal and were the same size and contained similar cell types as diploid brains. As observed in previous studies on polyploid amphibia, somal diameters increased significantly in tetraploid cells for each of the four groups of cells examined. Also, the total length of the dendritic arbors in tetraploid brain cells increased significantly by factors ranging from 1.4 to 2.4 times the total length of the analogous processes in diploid cells. Tetraploid neurons in the telencephalon and hypothalamus increased their arbor lengths predominantly by increasing the number of dendritic branches, while maintaining the average distance between branch points in the dendritic segments. In contrast, the tetraploid large pear-shaped neurons in the optic tectum had significantly longer terminal dendritic segments than the analogous diploid neurons, although these tetraploid neurons maintained their average number of dendritic segments per cell. Tetraploid tectal radial glial cells appeared to increase both their number of branches and the lengths of their terminal segments. Thus, the mode by which tetraploid brain cells achieved longer dendritic arbors varied from cell type to cell type. These results suggest a hypothetical basis for possible effects of genomic size on vertebrate brain structure and evolution at the cellular level.

Animals↗
PubMed1988

Identities, antigenic determinants, and topographic distributions of neurofilament proteins in the nervous systems of adult frogs and tadpoles of Xenopus laevis.

Three proteins with nominal molecular weights of 73 kDa (XNF-L), 175 kDa (XNF-M), and 205 kDa (XNF-H) were identified as putative neurofilament proteins in the nervous system of the frog, Xenopus laevis. These conclusions were based on four criteria: (1) these proteins were enriched in cytoskeletal preparations; (2) they reacted with a monoclonal antibody (anti-IFA) that cross-reacts with an epitope found in all intermediate filament proteins; (3) they cross-reacted with monoclonal antibodies directed against specific mammalian neurofilaments; and (4) antibodies that reacted with these proteins on Western blots specifically stained neurons in immunohistochemical analyses. The neurofilament proteins in Xenopus were antigenically similar, but not identical to mammalian neurofilament proteins. The principal difference was that four antibodies that reacted on Western blots with rat NF-H reacted with XNF-M in Xenopus. However, similarly to mammals, antibodies against phosphorylated XNF-M specifically labeled axons, whereas an antibody that reacted only with dephosphorylated epitopes on XNF-M specifically labeled neuronal cell bodies in immunohistochemistry. Three other antibodies that reacted equally well with untreated or alkaline-phosphatase-treated XNF-M or XNF-H proteins also showed axonally restricted staining in the adult Xenopus nervous system. An XNF-L (XC5D10) antibody was produced which stained axons and cell bodies equivalently throughout the adult Xenopus nervous system. By 3 days of development (stage 42; Xenopus tadpoles), antibodies to all three molecular weight forms of the frog neurofilament proteins detected specific neurons in the brainstem and spinal cord; and antibodies to phosphorylated and dephosphorylated epitopes on XNF-M could discriminate between axons and cell bodies in the rhombencephalon. The immunoreactivities of four antibodies directed at XNF-L, -M, or -H, which were unaffected by alkaline phosphatase treatment, differed significantly in their immunohistochemical staining patterns in adult vs. premetamorphic frogs.

Aging↗
PubMed1990

Tectal connectivity in the frog Rana pipiens: tectotegmental projections and a general analysis of topographic organization.

Recent studies of visually elicited orienting in the frog Rana pipiens suggest that tectofugal signals important in this behavior relay in the midbrain tegmentum before descending to the spinal cord. They also suggest that the high degree of topographic organization displayed by the retinotectal projection may be less characteristic of other tectal afferent and efferent pathways. To explore these possibilities, we have studied patterns of retrograde and anterograde labelling following multiple and single injections of horseradish peroxidase into the tectum. We have found that the midbrain tegmentum is a major terminal zone for tectal efferent projections. Our material also provided a description of the boundaries of other structures which project to and receive input from the tectum. With this background, we studied topographic organization by analyzing for each structure the distribution of labelling following multiple injections, and comparing it with the label distribution following single injections at tectal loci with known visual field input. Multiple injections produced patchy anterograde and retrograde labelling in the nucleus isthmi, with the number of patches corresponding to the number of tectal sites injected. Single injections produced labelling in restricted regions of the nucleus isthmi, the location of which varied systematically with the location of the tectal injection site. In all other structures studied, labelling was more evenly distributed following multiple injections. In none of these structures could we detect systematic variations in the location of labelling associated with variations in the location of single tectal injection sites, and the labelling following single injections was frequently coextensive with that following multiple injections. We also found no evidence that there exist structures which project to or receive input from particular tectal regions and not others. We conclude that there exist adequate neuroanatomical substrates for a tectotegmentospinal pathway believed to be important for visually elicited orienting in the frog. We also conclude that a high degree of topographic organization is more the exception than the rule in considering tectal connections generally in the frog. Topographic organization was readily apparent in connections related to the nucleus isthmi but not in connections related to any other nonretinal structure.

Animals↗
PubMed1992

Immunohistochemical distribution and biological activity of pituitary adenylate cyclase-activating polypeptide (PACAP) in the central nervous system of the frog Rana ridibunda.

The primary structure of frog pituitary adenylate cyclase-activating polypeptide (PACAP) has recently been determined and the results show that the sequence of PACAP has been highly conserved during evolution. In particular, the structure of the 1-27 fragment of PACAP is identical in frog and mammals. Using an antiserum raised against PACAP27, we have investigated the distribution of PACAP-containing neurons in the central nervous system of the frog Rana ridibunda by the immunofluorescence technique. The main populations of immunoreactive perikarya were located in the medial and ventral diencephalon, i.e., the preoptic nucleus, the ventral and dorsal infundibular nuclei, the nucleus posterocentralis thalami, and the ventral and ventrolateral areas of the thalamus. In the telencephalon, sparse cell bodies were found in the nucleus accumbens septi, the amygdala, the pallial commissure, and the bed nucleus of the pallial commissure. In the hindbrain, the torus semicircularis, the nucleus profundus and the nucleus anteroventralis tegmenti of the mesencephalon also contained populations of PACAP-immunoreactive perikarya. Beaded nerve fibers were observed throughout the brain. Occasionally they formed bundles, e.g., from the ventral infundibulum to the external vascular layer of the median eminence, from the central thalamus to the optic tectum, and rostrocaudally, from the nucleus accumbens septi to the nucleus entopeduncularis. Other areas, such as the interpeduncular nucleus, the nucleus isthmi and the roots of cranial nerves V and VIII in the medulla oblongata, were also densely innervated. The adenylate cyclase-stimulating activity of PACAP was tested by using a static incubation technique for hypothalamic slices.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗