Subependymal Layer Research Articles

Expression of polysialylated neural cell adhesion molecule by proliferating cells in the subependymal layer of the adult rat, in its rostral extension and in the olfactory bulb

The highly sialylated isoform of the neural cell adhesion molecule is thought to be expressed predominantly in the developing nervous system, where it is implicated in a variety of dynamic events linked to neural morphogenesis. It has become increasingly evident, however, that this “embryonic” neural cell adhesion molecule isoform continues to be expressed in certain adult neuronal systems, and in particular, in those that can undergo structural plasticity. In the present study, we performed light microscopic immunocytochemistry with an antibody specific for polysialylated neural cell adhesion molecule and confirmed our earlier observations [Bonfanti L. et al. (1992) Neuroscience 49, 419–436] showing polysialylated neural cell adhesion molecule-immunoreactive cells in the subependymal layer of the lateral ventricle of the adult rat, a region where cell proliferation continues into the postnatal period. In addition, we used an antibody raised against the proliferating cell nuclear antigen and found that proliferating cells continue to be visible in this area, even in the adult. Double immunolabeling showed that many of these newly generated cells displayed high polysialylated neural cell adhesion molecule immunoreactivity. Cells from a portion of the subependymal layer migrate to the olfactory bulb and contribute to the continual replacement of its granule neurons [Luskin M.B. (1993) Neuron 11, 173–189]. We found polysialylated neural cell adhesion molecule-immunoreactive cells all along the pathway purported to be followed by the newly generated cells to their final destination and in neurons corresponding to granular and periglomerular cells in the olfactory bulb. Our present observations thus support the contention that polysialylation is a feature of neurons capable of dynamic change and may contribute to the molecular mechanisms permitting cell proliferation and migration not only during development but also in the adult.

N-CAM mutation inhibits tangential neuronal migration and is phenocopied by enzymatic removal of polysialic acid

The mutation of N-CAM in mice produces a phenotype dominated by an undersized olfactory bulb and accumulation of precursors in the subependymal layer. We demonstrate here that this defect can be duplicated by injection of an enzyme that specifically destroys the polysialic acid (PSA) moiety associated with N-CAM. Studies of BrdU-labeled and pyknotic cells suggest that this defect reflects a decrease in the rostral migration of olfactory precursors and not a change in the proliferation or rate of death of these cells. In addition to their ectopic location, these cells had fewer growth cone-like processes oriented along the migration route. In contrast to tangential movement, radial migration of granule cells in the olfactory bulb was not affected by loss of PSA. These results support the proposed role for PSA in cell translocation, discriminate between different mechanisms of cell migration, and provide insight as to the nature of the N-CAM mutant phenotype.

Odor deprivation leads to reduced neurogenesis and reduced neuronal survival in the olfactory bulb of the adult mouse

Neurogenesis persists in the olfactory bulbs of adult mice, with new cells being generated in the proliferative subependymal layer. Our previous work has shown that unilateral odor deprivation through naris closure leads to a net loss of granule neurons in the ipsilateral (odor-deprived) olfactory bulb, while not affecting the contralateral bulb. Here we used several experimental approaches to determine if this loss of neurons results from reduced neurogenesis, reduced neuronal survival, or both. First, bromodeoxyuridine immunohistochemistry was used to determine the number of S-phase cells in the subependymal layer eight weeks after naris closure. Proliferation was reduced within and just caudal to the odor-deprived bulb compared to the open-side (control) bulb. Second, counts of pyknotic nuclei four weeks after naris closure were used to document a higher rate of cell death on the deprived side. Third, 3H-thymidine autoradiography was used to assess differences in granule cell survival on the two sides. Granule cell precursors were labeled by a single injection of 3H-thymidine eight weeks after naris closure, and the number of surviving labeled granule cells assessed four and 16 weeks later. Granule cell survival was significantly reduced within the odor-deprived bulbs. These data indicate that the loss of granule cells which follows odor deprivation is caused, at least in part, by reduced neurogenesis and reduced survival of these adult-generated neurons.

Distribution of manganese-dependent superoxide dismutase in the human brain

The distribution of manganese-dependent Superoxide dismutase, an enzyme that transforms superoxide radicals into hydrogen peroxide, was studied in the human brain post mortem using a sheep polyclonal antiserum raised against the enzyme from liver mitochondria. One band, corresponding to a protein of 22,000 mol. wt was detected in the human brain by western blot analysis. At the light-microscopy level, a punctate immunostaining was observed in the neuropil and in some, but not all, glial and neuronal cell bodies. Electron-microscopy revealed that the staining was exclusively confined to the inner mitochondrial membrane. A heterogeneous distribution of manganese-dependent superoxide dismutase was observed in the human brain. In the forebrain, numerous immunostained neurons were detected in the striatum, thalamus, pallidal complex and the nucleus basalis of Meynert. In the cerebellum, only granular and Purkinje cells were immunostained. Various nuclei from the brainstem displayed superoxide dismutase immuno-reactivity, including the cranial nerve nuclei, the nucleus supratrochlearis, the red nucleus, the substantia nigra, the nucleus cuneiformis and subcuneiformis, the nucleus parabigeminal, the nucleus centralis superior, the nucleus supraspinalis, the nucleus of the medullae oblongata and the gigantocellularis nucleus. Large pyramidal neurons containing superoxide dismutase were detected in the CA subsectors, the hilus of the hippocampus and the cerebral cortex. Smaller immunostained neurons were also observed in layers I, IV and VI of all cortical regions studied. The distribution of immunostained glial cells was more limited, and restricted to the internal and external capsules, the hypothalamus, the red nucleus, the pyramidal white matter and surrounding areas, the cerebral cortex and the sub-ependymal layer, the alveus and the stratum oriens of the hippocampus. This heterogeneous but not ubiquitous distribution of cells expressing manganese-dependent superoxide dismutase suggests that not all cells in the human brain are protected to the same extent against the deleterious effects of Superoxide.

Age‐dependent changes in the glial cell nests of the canine rhinencephalic allocortex. A morphometric study

In the present study, the morphological features as well as the age-dependent changes of the glial cell nests (GCN) within the rhinencephalic allocortex of the dog are described. A combination of two stereological methods, i.e., Cavalieri's principle and the optical disector, was used to obtain unbiased estimates of the volumes of the whole brain, the allocortex, and the GCN. Furthermore, the numerical densities and total number of the two prevailing populations of undifferentiated cells within these nests were determined. Cells with medium-sized dark nuclei (CMD) and cells with large pale nuclei (CLP) were distinguished. The volume of the GCN in relation to the volume of the allocortex decreased with increasing age. The numerical density and the total number of all cells of the GCN and of the CMD were reduced with age, whereas the numerical density and number of the CLP increased with advancing age. Similar morphological features as well as age-dependent changes have already been described of the cell populations in the subependymal layer. Therefore, in analogy, we presume that the glial cells of the GCN have emigrated from the subependymal layer. The significance of these age-dependent changes remains as obscure as does the function of the GCN.

Blockade of NMDA receptors increases cell death and birth in the developing rat dentate gyrus

Excitatory input regulates cell birth and survival in many systems. The granule cell population of the rat dentate gyrus is formed primarily during the postnatal period. Excitatory afferents enter the dentate gyrus and begin to form synapses with granule cells during the first postnatal week, the time of maximal cell birth and death. In order to determine whether excitatory input plays a role in the regulation of cell birth and survival in the developing granule cell layers and their germinal regions, the subependymal layer and hilus, we treated rat pups with the N-methyl D-aspartate (NMDA) receptor antagonists MK-801, CGP 37849, or CGP 43487 during the first postnatal week and examined the numbers of 3H-thymidine-labeled cells, pyknotic cells, and healthy cells in these regions. In order to determine the cell type that was affected, sections from brains of MK-801-treated rats were processed for 3H-thymidine autoradiography combined with immunohistochemistry for the marker of radial glia, vimentin, and the marker of mature astrocytes, glial fibrillary acidic protein (GFAP). Within the dentate gyrus, NMDA receptor blockade resulted in the following changes: (1) the density of 3H-thymidine-labeled cells was increased, (2) the density of pyknotic cells was increased, (3) the density of 3H-thymidine-labeled pyknotic cells was increased, and (4) the density of healthy cells was decreased. The infrapyramidal blade/hilus showed changes throughout its extent, whereas the suprapyramidal blade showed changes only at the rostral level. No change in the numbers of 3H-thymidine-labeled vimentin-immunoreactive or GFAP-immunoreactive cells was observed in the dentate gyrus with MK-801 treatment, indicating that glia are not primarily affected by NMDA receptor blockade. Blockade of NMDA receptors resulted in gross morphologic changes in the dentate gyrus; in most cases, the infrapyramidal blade was indistinguishable from the hilus. Moreover, in several brains of animals treated with CGP 37849 or CGP 43487 on postnatal day (P)5, an abnormal aggregation of cells was observed ventral to the normal location of the infrapyramidal blade. This cellular cluster contained many pyknotic and 3H-thymidine-labeled cells and may represent cells that normally comprise the infrapyramidal blade. Dramatic changes to the subependymal layer were also seen following NMDA receptor blockade. The cross-sectional area of this region was significantly increased with MK-801, CGP 37849, or CGP 43487 treatment and contained a high density of 3H-thymidine-labeled cells and 3H-thymidine-labeled pyknotic cells.(ABSTRACT TRUNCATED AT 400 WORDS)

A new subdivision of the rat midbrain periaqueductal gray based on its myeloarchitecture

A new subdivision of the periaqueductal gray (PAG) based on its myelin content is described. Using a methacrylate-resin embedding technique for high resolution light microscopy, a myeloarchitectonic map of the normal rat PAG was made. Six main columns were distinguished. Column I is the central thin subependymal layer, in which myelinated axons are virtually absent. This layer is surrounded by column II with many rostrocaudally oriented fibers. Lateral and dorsolateral to column II lies column III, which contains rostrocaudally as well as tangentially oriented fibers. Column III is divided into a ventral and a dorsal part by column IV. This column is located in the dorsolateral part of the PAG and contains very few, mostly tangentially oriented fibers. Column V is located ventrally and contains a mixture of rostrocaudally and tangentially oriented fibers. Column VI is only present in the most caudal part of the PAG and contains mainly tangential fibers.

Neuropeptide Y in the carp torus semicircularis: an immunocytochemical study.

The presence of neuropeptide Y-like immunoreactivity in the torus semicircularis of the teleost fish Cyprinus carpio was studied using an indirect immunoperoxidase technique. In general, both the nuclei lateralis and centralis of the torus semicircularis showed a high density of immunoreactive fibers from rostral to caudal levels. In particular, in the nucleus lateralis a low density of immunoreactive fibers was only found in the subependymal layer, whereas this was high in the small cell, fibrillar and disperse cells layers. Similarly, the nucleus centralis showed a low density of immunoreactive fibers in the fibrillar cortex, and a high density in the cellular region. Moreover, a moderate density of fusiform or round-ovoid cell bodies containing neuropeptide Y-like immunoreactivity was found in the cellular region of the nucleus centralis. These neurons were located dorsally or near to the lateral lemniscus, and situated perpendicular, parallel or oblique to the surface, showing one or two long and relatively unbranching dendritic trunks. The localization of neuropeptide Y-like immunoreactivity in both nuclei--lateralis and centralis--of the carp torus semicircularis suggests that this peptide is involved in the control of visual, auditive, and lateral line mechanisms, as well as in the control of feeding.

Differential expression of insulin-like growth factor binding proteins (IGFBP) 4 and 5 mRNA in the rat brain after transient hypoxic-ischemic injury

Recent studies suggest a role for the insulin-like growth factor (IGF) system in the repair of damaged tissue following hypoxic-ischemic injury in the infant rat brain. We have used a unilateral model of hypoxic-ischemic injury to assess the possible involvement of two IGF binding proteins (IGFBPs), IGFBP-4 and IGFBP-5, in the post-asphyxial response. Ligation of the right carotid artery of 21-day-old rats was followed by either 15 min or 60 min exposure to 8% oxygen to produce moderate and severe damage respectively. Using in situ hybridization, the distribution of IGFBP-4 and IGFBP-5 mRNA was determined in brains collected over 10 days following the insult. In the control brains (no damage), both IGFBPs were expressed in distinct regions. IGFBP-4 mRNA was detected in limited areas of the hippocampus and in several cortical layers, while IGFBP-5 mRNA was found primarily in the thalamus. In response to hypoxic-ischemic injury, IGFBP-4 mRNA expression was reduced in regions of neuronal loss, suggesting a neuronal origin for IGFBP-4. The expression of IGFBP-5 mRNA was not altered by the 15 min insult, but was heavily induced from 3 days following the 60 min insult, particularly in the subependymal layer and adjacent white matter on the ligated hemisphere. This suggests that IGFBP-5 may be involved in recovery from severe hypoxic-ischemic injury and may be important in the regeneration of oligodendrocytes.

The cloning of a receptor-type protein tyrosine phosphatase expressed in the central nervous system

We have isolated cDNA clones and deduced the complete amino acid sequence of a large receptor-type protein tyrosine phosphatase containing 2307 amino acids. The human gene encoding this phosphatase, denoted RPTP beta (or PTP zeta), has been localized to chromosome 7q31-33. RPTP beta is composed of a large extracellular domain, a single transmembrane domain, and a cytoplasmic portion with two tandem catalytic domains. We have also cloned a variant of RPTP beta lacking 859 amino acids from the extracellular domain but with intact transmembrane and cytoplasmic domains. Interestingly, the amino-terminal region of the extracellular domain of RPTP beta contains a stretch of 266 amino acids with striking homology to the enzyme carbonic anhydrase. Immunoprecipitation experiments from a human neuroblastoma cell line indicate that the apparent molecular mass of the core and glycosylated forms of RPTP beta are approximately 250 and 300 kDa, respectively. Northern blot analysis shows that RPTP beta is strictly expressed in the central nervous system. In situ hybridization was used to further localize the expression to different regions of the adult brain including the Purkinje cell layer of the cerebellum, the dentate gyrus, and the subependymal layer of the anterior horn of the lateral ventricle. Hence, RPTP beta represents the first mammalian tyrosine phosphatase whose expression is restricted to the nervous system. The high level of expression of RPTP beta transcripts in the ventricular and subventricular zones of the embryonic mouse brain suggests the importance of this tyrosine phosphatase in the development of the central nervous system.

Developmentally regulated expression of pleiotrophin, a novel heparin binding growth factor, in the nervous system of the rat

Pleiotrophin (PTN) is a newly identified heparin-binding growth factor which is closely related to the retinoic acid-inducible MK protein. PTN is expressed at high levels in perinatal brain and promotes neurite outgrowth from embryonic brain neurons and mitogenesis in fibroblasts, suggesting that it may play an important role in the development of the nervous system. We have used in situ hybridization to examine PTN expression in the developing and adult rat nervous systems. During embryogenesis, PTN mRNA is primarily expressed by neuroglial progenitor cells in the subependymal layer of the central nervous system (CNS), whereas during the perinatal period high levels of PTN transcripts are found in neurons as well as glial elements (astrocytes and oligodendrocytes). In the adult brain, PTN expression is markedly decreased relative to early postnatal brain and, in contrast to the neuronal and glial expression observed in young animals, is confined to specific neuronal subpopulations (especially hippocampal CA1–3 regions, cerebral cortex laminae II–IV). PTN is also expressed in the developing spinal cord and eye. In the peripheral nervous system (PNS), PTN mRNA is present in ganglionic neurons during embryogenesis. In adult ganglia, however, PTN expression becomes localized to the satellite cells of the ganglia. The developmental pattern of PTN expression in the CNS and the ‘switch’ in expression from neurons to satellite cells in the PNS suggests that it has important functions not only in the developing nervous system, but also in the adult CNS and PNS and that the functions performed by this growth factor change during ontogeny. We have also found that levels of PTN mRNA are dramatically but transiently elevated in neurons of the hippocampus, piriform cortex and parietal cortex following a chemically induced seizure, indicating that neuronal PTN mRNA expression is increased by intense physiological stimuli and may play a role in the response to these stimuli.

Neurogenesis persists in the subependymal layer of the adult mouse brain

Neurogenesis of olfactory bulb granule cells is known to persist in adult rats where, in some strains, the bulbs grow throughout life. In mice, bulb growth ceases early in adulthood and here we ask if granule cell neurogenesis persists after the bulbs have stopped growing. By injecting adult mice with bromodeoxyuridine (BrdU) and allowing short and long survival times, we found that new cells form in the subependymal layer and that they migrate subsequently into the olfactory bulbs where they acquire the nuclear morphology of granule cells and express neuron-specific markers. Using [ 3H]thymidine, we found that most of these adult-generated granule neurons persist within the bulbs for at least 16 weeks. This shows the persistence of neurogenesis and neuronal migration in adult animals in which the olfactory bulbs have stopped growing.

Development of granule cells of the rat olfactory bulb: an autoradiographic and electron microscopic study.

The rate of migration of immature granule cells of the rat olfactory bulb and polarity of cell-organelles in the migrating granule cells were investigated by 3H-thymidine autoradiographic and electron microscopic methods. The time lag in migration between two points was determined by cross-correlation analysis of labeling indices of the two areas. Granule cells were estimated to take 6 days to migrate rostralwardly from the subependymal layer at the anterior wall of the lateral ventricle to the center of the bulb, and an additional 1 to 6 days to migrate radially from the subependymal layer to the granular layer of the bulb. These results showed that the rate of rostralward migration of granule cells was faster than that of their radial migration. Golgi-electron microscopic as well as routine electron microscopic studies on migrating granule cells revealed that centrioles and Golgi apparatus were located at the base of the leading process that possesses a growth cone at its tip.

Expression of connexins in the developing olfactory system of the mouse.

To gain insight into the function of gap junctions' connexin43, connexin32 and connexin26 in a neural structure that retains neuronal turnover capacities throughout adulthood, the expression of these molecules has been investigated in the developing and adult olfactory system by immunocytochemical and biochemical methods. Connexin43 was detectable from the olfactory placode stage. During early embryonic development, the levels of connexin43 expression remained low. An increase in the expression of this connexin occurred perinatally. Expression of connexin43 became very high during the postnatal stages and adulthood. Electron microscopy (EM) immunocytochemistry of the olfactory system showed connexin43 expression in non-neuronal cells. Strong regional differences in the expression of connexin43 in the olfactory epithelium were observed. No apparent relationship between connexin43 expression and turnover activity of olfactory neurons was detected. Western blots of olfactory tissues revealed the presence of three different isoforms of connexin43. Connexin32 was detected in the olfactory bulb at late postnatal stages including adulthood. Connexin32 was observed on some cells tentatively identified as oligodendrocytes. Connexin26 was localized onto leptomeninges. Some immunofluorescence was also obtained in the periglomerular region and in the subependymal layer of the bulb. Northern blot analysis revealed the presence of mRNA of connexin32 and connexin26 in the adult olfactory system. Our results substantiate the cell specific expression of these three types of connexins and they document the primary of connexin43 in olfactory tissues. Moreover, our findings indicate that although expression of connexin43 in the olfactory system is developmentally regulated, it is not directly associated with the neuronal cell turnover of the olfactory epithelium.

Immunohistochemical localization of gangliosides in ENU-induced rat glioma.

Biochemical studies have indicated that the structurally simple gangliosides, including GD3 and GM3, are major glycolipid components of glioma tissues. In order to clarify the localization of the gangliosides in ethylnitrosourea-induced rat glioma, an immunohistochemical study was performed using antibodies against GM1, GM3, and GD3. The results obtained in normal fetus, newborn, and adult rat brain, and also in human glioma, were compared. In fetal and newborn rat brain, GD3 was present mainly in the neuroepithelial cell surface of the matrix and subependymal layers of the ventricular wall, but GM3 and GM1 were not detected. In adult rat brain, GD3-positive cells were absent, or present in diminished number, and GM1 was found chiefly in the neuropil of the cerebral cortex. Most of the rat glioma cells were positive for GD3, but not for GM1. It was demonstrated that the ganglioside composition of glioma cells was similar to that of immature neuroectodermal cells in fetal and newborn rat brain. Furthermore, the number of GD3-positive oligodendroglioma cells increased with tumor growth. In anaplastic gliomas and gross oligodendrogliomas, most tumor cells expressed not only GD3 but also GM3. These results suggest that GD3 is a marker of proliferating neuroectodermal cells, and that activity of the key enzymes in ganglioside synthesis alters with tumor growth and anaplastic change.

II. Localization of Pi class glutathione‐S‐transferase in the forebrains of neonatal and young rats: Evidence for separation of astrocytic and oligodendrocytic lineages

The Yp isoform (Pi class) of glutathione-S-transferase has recently been localized in oligodendrocytes in the brains of mature rats. To examine at what postnatal age Pi first appears in oligodendrocytes or precursor cells, antibodies against Pi were used to immunostain tissue sections from the forebrains of neonatal rats and young rats up to 17 days of age. In the brains of neonates Pi immunofluorescence was observed in ovoid cells in the subependymal layer, and in ovoid cells and cells bearing short, thick processes in the corpus callosum and cingulum. These cells did not immunostain for vimentin. During the first postnatal week Pi-positive cells showed positive immunostaining for ganglioside GD3, which is characteristic of oligodendrocyte precursors, and process-bearing Pi-positive cells appeared in the cingulum and at the lateral borders of the corpus callosum in increasing numbers. During the second postnatal week the cytoplasm of Pi-positive cells became more compact, and the processes thinner, and the Pi-positive cells and their processes began to immunostain for 2',3'-cyclic nucleotide-3'-phosphohydrolase, which is characteristic of immature and mature oligodendrocytes and myelin sheaths. By age 17 days Pi was observed in relatively mature oligodendrocytes. The observations suggest that Pi occurs in oligodendrocyte precursors, immature oligodendrocytes, and mature oligodendrocytes in the postnatal through 17 day old rat forebrain. In the accompanying paper (Cammer and Zhang, '92)--if references are permitted in the Abstract a different glutathione-S-transferase isoform, Yb (Mu class), was localized in cells of the astrocyte lineage, beginning in the forebrains of neonatal rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunohistochemical localization of delta sleep-inducing peptide (DSIP) in the brain and pituitary of the cartilaginous fish Scyliorhinus canicula

The distribution of delta sleep-inducing peptide (DSIP) in the brain and pituitary of the cartilaginous fish Scyliorhinus canicula was investigated using the indirect immunofluorescence technique. Delta sleep-inducing peptide-like immunoreactive cell bodies were mainly observed in the nucleus lateralis tuberis of the hypothalamus. Immunolabeled perikarya were also distributed in the nucleus lobi lateralis hypothalami and in the dorso-lateral wall of the recessus posterioris. Most of these cells, located in the subependymal layers of the infundibulum and lateral lobes, had the typical aspect of cerebrospinal fluid-contacting elements. The DSIP-like immunoreactive fibers were localized in the basal telencephalon, within the regions of the nucleus interstitialis commissurae anterioris and the nucleus entopeduncularis. A dense network of DSIP-positive fibers was seen throughout the midcaudal hypothalamus, the lateral lobes, and the posterior lobe. In the pituitary, numerous DSIP-like immunoreactive cells were detected in the median lobe of the pars distalis. In particular, a high concentration of cells was seen in the dorsal wall of the median lobe, an area which is known to contain melanin-concentrating hormone (MCH)-producing cells. Comparison of the distribution of DSIP- and MCH-like immunoreactive cells revealed that the two neuropeptides are stored in the same cells of the median lobe of the pituitary. These findings provide the first evidence for the presence of a DSIP-related peptide in fish. The distribution of the immunoreactive material supports the view that DSIP may act as a neuromodulator and/or a hypophysiotropic factor. Moreover, the presence of DSIP-like immunoreactive cells in the pars distalis suggests that this peptide may exert autocrine or paracrine effect in the pituitary.

Distribution of neuropeptide Y-like immunoreactivity in the brain and hypophysis of the cloudy dogfish, Scyliorhinus torazame.

Using a specific antiserum raised against synthetic neuropeptide Y, we examined the localization of immunoreactivity in the brain and hypophysis of the cloudy dogfish, Scyliorhinus torazame, by the peroxidase-antiperoxidase method. Immunoreactive perikarya were demonstrated in the ganglion of the nervus terminalis, the dorsocaudal portions of the pallium dorsale, the basal telencephalon, and the nucleus lateralis tuberis and the nucleus lobi lateralis in the hypothalamus. Labeled perikarya were also found in the tegmentum mesencephali, the corpus cerebelli, and the medulla oblongata. Some of the immunoreactive neurons in the hypothalamus were of the CSF-contacting type. The bulk of the labeled fibers in the nervus terminalis ran toward the basal telencephalon, showing radial projections and ramifications. Large numbers of these fibers coursed into the nucleus septi caudoventralis and the nucleus interstitialis commissurae anterioris, where they became varicose and occasionally formed fine networks or invested immunonegative perikarya. In the diencephalon, immunoreactive fibers were observed throughout the hypothalamus, e.g., in the pars neurointermedia of the hypophysis, the subependymal layer of the lobus inferior hypothalami, and in the neuropil of the posterior (mammillary) recess organ. Labeled fibers were scattered throughout the rest of the brain stem and were also seen in the granular layer of the cerebellum. These results suggest that, in the dogfish brain, neuropeptide Y or a related substance is involved in a variety of physiological processes in the brain, including the neuroendocrine control of the hypophysis.

Postmitotic death is the fate of constitutively proliferating cells in the subependymal layer of the adult mouse brain

The early development of the mammalian forebrain involves the massive proliferation of the ventricular zone cells lining the lateral ventricles. A remnant of this highly proliferative region persists into adult life, where it is known as the subependymal layer. We examined the proliferation kinetics and fates of the mitotically active cells in the subependyma of the adult mouse. The medial edge, the lateral edge, and the dorsolateral corner of the subependymal layer of the rostral portion of the lateral ventricle each contained mitotically active cells, but the dorsolateral region had the highest percentage of bromodeoxyuridine (BrdU)-labeled cells per unit area. Repeated injections of BrdU over 14 hr revealed a proliferation curve for the dorsolateral population with a growth fraction of 33%, indicating that 33% of the cells in this subependymal region make up the proliferating population. The total cell cycle time in this population was approximately 12.7 hr, with an S-phase of 4.2 hr. To examine the fate of these proliferating cells, we injected low concentrations of a replication-deficient, recombinant retrovirus directly into the lateral ventricles of adult mice for uptake by mitotically active subependymal cells. Regardless of the survival time postinjection (10 hr, 1 d, 2 d, or 8 d), the number of retrovirally labeled cells per clone remained the same (1 or 2 cells/clone). This suggests that one of the progeny from each cell division dies. Moreover, the clones remained confined to the subependyma and labeled cells were not seen in the surrounding brain tissue. Thus, while 33% of the dorsolateral subependymal cells continue to proliferate in adult life, the fate of the postmitotic progeny is death.

Distribution of two forms of somatostatin and peptides belonging to the pancreatic polypeptide family in tissues of larval lampreys, Petromyzon marinus L.: An immunohistochemical study

Immunohistochemistry on tissues of larval lampreys, Petromyzon marinas L., was used to determine the distribution of invariant somatostatin-14 (SST-14) and lamprey somatostatin-34 (SST-34) in the brain while antisera against porcine peptide tyrosine tyrosine (PYY), human neuropeptide Y (NPY), anglerfish peptide YG (aPY), salmon glucagon-like peptide (GLP), SST-14, and SST-34 were used in studies of the pancreas and anterior intestine. In the brain, SST-14 is the major form of somatostatin. SST-14- and SST-34immunoreactive nerve fibers are distributed throughout the telencephalon, diencephalon, and mesencephalon. In the latter region SST-14 immunoreactivity is concentrated in nerve tracts in the nucleus interpeduncularis. Nerve cells within the olfactory bulbs are immunoreactive only to anti-SST-34. Cells immunostained with anti-SST-14 were localized within the ependymal and subependymal layers of the pars ventralis hypothalami and the subependymal layers of the pars dorsalis thalami. SST- 14-immunoreactive perikarya are also distributed within the tegmentum mesencephali. Nerve fibers and cells immunoreactive to anti-SST-34 are detected in the pars ventralis hypothalami but these cells do not colocalize SST-14. Pancreatic islets, distributed within the epithelium and in the submucosal connective tissue at the esophagal-intestinal junction, are only immunoreactive to anti-insulin. The antisera revealed three distinct cell types in the intestinal epithelium: type 1 colocalizes aPY, NPY, and PYY; type 2 colocalizes SST-14 and SST-34; and type 3 demonstrates immunoreactivity only to anti-SST-34. Immunoreactivity to anti-GLP is absent.