Adult Rat Cerebrum Research Articles

Possible role of selenium in ameliorating lead-induced neurotoxicity in the cerebrum of adult male rats: an experimental study

Chronic lead (Pb) poisoning is one of the greatest public health risks. The nervous system is the primary and most vulnerable target of Pb poisoning. Selenium (Se) has been shown to be a potential protection against heavy metal toxicity through anti-inflammatory and antioxidant properties. Therefore, the present study aimed to elucidate the possible protective role of Se in ameliorating the effects of Pb on rat cerebral structure by examining oxidative stress and markers of apoptosis. The rats were divided into 6 groups: control group, Se group, low Pb group, high Pb group, low Pb + Se group, high Pb + Se group. After the 4-week experiment period, cerebral samples were examined using biochemical and histological techniques. Pb ingestion especially when administered in high doses resulted in cerebral injury manifested by a significant increase in glial fibrillary acidic protein, malondialdehyde (MDA) marker of brain oxidation and DNA fragmentation. Moreover, Pb produced alteration of the normal cerebral structure and cellular degeneration with a significant reduction in the total number of neurons and thickness of the frontal cortex with separation of meninges from the cerebral surface. There was also a decrease in total antioxidant capacity. All these changes are greatly improved by adding Se especially in the low Pb + Se group. The cerebral structure showed a relatively normal histological appearance with normally attached pia and an improvement in neuronal structure. There was also a decrease in MDA and DNA fragmentation and an increase TAC. Selenium is suggested to reduce Pb-induced neurotoxicity due to its modulation of oxidative stress and apoptosis.

Histopathological, Immunohistochemical, And Molecular Alterations In Brain Tissue And Submandibular Salivary Gland Of Atrazine-Induced Toxicity In Male Rats.

Atrazine (ATZ) is herbicide that has been widely used for different crops. This extensive use has resulted in severe deleterious effects in different species. In this work, we investigated the potentially harmful effect of atrazine herbicide on the brain and submandibular salivary gland. Our investigation was carried out on 20 adult male albino rats that were equally divided into two groups. The first group received distilled water as control, while the second group received ATZ at 200mg/kg body weight/ day via stomach gavage for 30 successive days of the experiment; the oral LD50 for ATZ is 3090mg/kg. Our findings revealed the ability of ATZ to cause damage to the cerebrum, hippocampus, and submandibular salivary gland. This damage resulted from the induced oxidative stress, which was indicated by a significant elevation in malondialdehyde (MDA) concentration, DNA fragmentation, tumor necrotic factor-alpha (TNF-α) expression, with a significant decrease in reduced glutathione (GSH) level and reduction of B cell lymphoma 2 (BCL2), dopamine receptor D1 (Drd1), cAMP-responsive element-binding protein 1 (Creb1) genes expression after ATZ exposure. Moreover, degeneration of cells, cytoplasmic vacuolation, congestion of blood vessels, a strong immune reaction to caspase 3, and negligible immune expression of a glial fibrillary acidic protein (GFAP) were also noticed in the ATZ-treated group. We concluded that ATZ induces oxidative stress and has a toxic and apoptotic effects on the cerebrum, hippocampus, and salivary gland of adult male albino rats.

Penconazole alters redox status, cholinergic function, and membrane-bound ATPases in the cerebrum and cerebellum of adult rats

Pesticides exposure causes usually harmful effects to the environment and human health. The present study aimed to investigate the potential toxic effects of penconazole, a triazole fungicide, on the cerebrum and cerebellum of adult rats. Penconazole was administered intraperitoneally to male Wistar rats at a dose of 67 mg kg-1 body weight every 2 days during 9 days. Results showed that penconazole induced oxidative stress in rat cerebrum and cerebellum tissues. In fact, we have found a significant increase in malondialdehyde, hydrogen peroxide, and advanced oxidation protein product levels, as well as an alteration of the antioxidant status, enzymatic (superoxide dismutase and catalase) and nonenzymatic (glutathione), the cholinergic function, and membrane-bound ATPases (Na+/K+-ATPase and Mg2+-ATPase). Penconazole also provoked histological alterations marked by pyknotic and vacuolated neurons in the cerebrum and apoptosis and edema in the cerebellum Purkinje cells' layer. Therefore, the use of this neurotoxicant fungicide must be regularly monitored in the environment.

Histological effects of ethanolic leaf extract ofCodiaeum variegatumon the cerebrum of adult Wistar rats

Background: Medicinal plants such as Codiaeum variegatum are recognized therapeutic agents and sources of the drug. The effect of ethanolic extract of C. variegatum was investigated in this study. Materials and Methods: Sixteen adult Wistar rats of both sexes weighing between 120 and 180 g were used for the study. They were randomly assigned to four groups 1, 2, 3, and 4 of 4 rats (N = 4) per group. The control (group 1) received 0.1 ml of normal saline, while 2, 3, and 4 experimental groups received 200 mg/kg, 400 mg/kg and 600 mg/kg of the leaf extract respectively for 2 weeks. They were sacrificed on the 15th day of the experiment; cerebrum was harvested, processed, and stained using the hematoxylin and eosin histological technique. Results: Sections of the cerebrum of the experimental groups showed sparse cellular population, microglia infiltration, focal, and liquefactive necrosis when compared to the control group. Conclusion: Ethanolic leaf extract of C. variegatum elicits an adverse effect on the cerebrum of adult Wistar rats.

A histomorphologic analysis of pyrethroid pesticide on the cerebrum and cerebellum of adult albino rats

Introduction: Pyrethroids Pesticide formulations are complex mixtures and some studies have associated their usage to predisposition to some degenerative diseases. This study was therefore aimed at investigating the sub-acute and acute histomorphologic effects of orally administered mixture of Allethrin, Imiprothrin and Phenothrin (P. pesticide) on the cerebrum and cerebellum of adult Wistar rats. Materials and Methods: 80 adult Wistar rats of both sexes were divided into 5 groups of 15 rats each. Group I-III which was the treatment groups were further subdivided into 3 groups of 5 rats each while groups IV and V were normal and oil control respectively. The Pesticide was diluted with olive oil into 3 grades (75, 50 and 25% concentration) and orally administered to the rats of the treatment groups for 7, 21 and 40 days. The rats in group IV and V were given water and olive oil respectively for the duration of the treatment. At the end of the treatment, the rats were sacrificed by cervical dislocation. The brains were harvested and processed for histology using standard manual tissue processing techniques. Results/Discussion: The behaviors exhibited by the animals included itching, twitch contraction, dilation of pupils, erected furs, tail suspension and increased salivation. Histological examination of the brain tissues revealed mild to marked distortion of the cyto-architectural patterns with multifoci of necrosis, severe gliosis involving predominantly astrocytes and olingodendrocytes both in the cerebral and cerebellar tissues. Conclusion: In conclusion, this study showed that oral administration of P. pesticide resulted in several histomorphologic changes in the brain tissues in both dose and time dependent manner.

Expression and immunolocalization of Gpnmb, a glioma‐associated glycoprotein, in normal and inflamed central nervous systems of adult rats

Glycoprotein nonmetastatic melanoma B (Gpnmb) is a type I transmembrane protein implicated in cell differentiation, inflammation, tissue regeneration, and tumor progression. Gpnmb, which is highly expressed in glioblastoma cells, is a potential therapeutic target. However, little is known about its expression, cellular localization, and roles in non-tumorous neural tissues. In this study, we examined Gpnmb expression in the central nervous system of adult rats under both normal and inflammatory conditions. Reverse transcription-polymerase chain reaction analysis revealed that Gpnmb mRNA was expressed in the cerebrum, cerebellum, brain stem, and spinal cord of normal adult rats. Immunoperoxidase staining revealed that Gpnmb-immunoreactive cells were widely distributed in the parenchyma of all brain regions examined, with the cells being most prevalent in the hippocampal dentate gyrus, cerebellar cortex, spinal dorsal horn, choroid plexus, ependyma, periventricular regions, and in layers II and III of the cerebral cortex. Double immunofluorescence staining showed that these cells were co-stained most frequently with the microglia/macrophage marker OX42, and occasionally with the radial glia marker RC2 or the neuronal marker NeuN. Furthermore, an intraperitoneal injection of bacterial endotoxin lipopolysaccharide increased the number of Gpnmb and OX42 double-positive cells in the area postrema, which is one of the circumventricular organs, indicating infiltration of hematogenous macrophages. These results suggest that Gpnmb, which is expressed in microglia and macrophages in non-tumorous neural tissues, plays an important role in the regulation of immune/inflammatory responses.

S.04.01 Differential role of the GABA transporters in the regulation of extracellular concentrations of GABA in the rat hippocampus

In the adult cerebral cortex, GABA transporters (GATs) are expressed by both neurons and astrocytes. GAT-1 immunoreactivity is found in axon terminals of GABAergic neurons and astrocytes, while GAT-3 immunolabeling occurs only in the latter. The present study was designed to determine whether the expression of GAT-1 and GAT-3 in the adult rat cerebrum changes after needle lesion and colchicine infusion. Following a needle puncture or a saline injection, immunolabeling for GAT-1 and GAT-3 was slightly increased in an area around the needle track. Not only was the neuropil labeling for both GATs increased, but also a few neuronal somata were found to be immunoreactive for GAT-1. Colchicine injections induced a striking increase in immunolabeling for both GATs in the neuropil in an area adjacent to the needle path and surrounding it. A homologous region of the contralateral hemisphere also showed a moderate increase of immunoreactivity in the neuropil for both GATs. Furthermore, this contralateral site showed many neuronal somata immunolabeled for GAT-1. These changes were mainly detected during the first 5 days following intracortical lesions. These results indicate that (1) the upregulation of GAT-1 and GAT-3 in cortical interneurons and astrocytes is caused by both mechanical and chemical factors associated with the injections; (2) increased GAT-1 and GAT-3 expression contralateral to the site of colchicine injection is mediated by transcellular signaling across the corpus callosum; and (3) the lesion-induced GAT expression may play a protective role by helping to balance excitatory and inhibitory neuronal activities.

Differential effect of amyloid beta on the cytochrome P450 epoxygenase activity in rat brain

One of the prominent features of Alzheimer's disease is the excessive accumulation of the protein amyloid beta (Aβ) in certain areas of the brain leading to neurodegeneration. Aβ is cytotoxic and disrupts several cytoprotective pathways. Recent literature has demonstrated that certain cytochrome P450 (CYP) products are neuroprotective, including epoxide metabolites of arachidonic acid (AA), epoxyeicosatrienoic acids (EETs). The action of Aβ with respect to regionally produced EETs in the brain has yet to be defined. Epoxygenases metabolize AA into four regioisomers of EETs (14,15-, 11,12-, 8,9- and 5,6-EET). EETs are rapidly degraded into dihydroxyeicosatrienoic acids (DiHETEs) by soluble epoxide hydrolase (sEH). To determine the effect of Aβ on the epoxygenase activity in different regions of the brain, microsomes were prepared from the cerebrum and cerebellum of adult Sprague-Dawley rats and incubated with 1 and 10 μM Aβ for 30 min after which epoxygenase activity assay was performed. Mass spectrometry indicated that incubation with Aβ reduced 14,15-EET production by 30% as compared to vehicle in the cerebrum, but not in the cerebellum. When we separated the cerebrum into cortex and hippocampus, significant decrease in the production of total EETs and DiHETEs were seen in presence of Aβ (81% and 74%) in the cortex. Moreover, 11,12-EET production was decreased to ∼70% of vehicle in both cortex and hippocampus. Epoxygenase activity in the cultured astrocytes and neurons also showed reduction in total EET and DiHETE production (to 80% and ∼70% of vehicle respectively) in presence of Aβ. Altogether, our data suggest that Aβ reduces epoxygenase activity differentially in a region-specific and cell-specific manner. The reduction of cytoprotective EETs by Aβ in the cerebrum may make it more prone to degeneration than the cerebellum. Further understanding of these interactions will improve our ability to protect against the pathology of Alzheimer's disease.

Expression of the IgSF protein Kirre in the rat central nervous system

AimsImmunoglobulin superfamily (IgSF) proteins play a critical role in development of the nervous system. Here, a new member of IgSF gene family was cloned from rat brain, which was subsequently identified as rat homolog of Drosophila Kirre. This new molecule was named as rat Kirre (rKirre). We aimed to reveal the developmental expression of rKirre, both at mRNA and protein levels, in the central nervous system. The deduced amino acid sequence of rKirre showed a putative PDZ binding motif at the C-terminus, which provided a rationale for analyzing the co-localization of rKirre and post-synaptic density protein 95 (PSD-95) in cultured rat cortical neurons. Main methodscDNA library screening was used in the isolation of cDNA. Northern blotting and Western blotting were used to reveal the levels of rKirre expression. In situ hybridization and immuno-fluorescent staining were used to determine the localization of rKirre. Key findingsThe rKirre gene was found to be highly expressed in the cerebrum, hippocampus, cerebellum, brain stem and spinal cord of adult rats. In parallel, the protein level of rKirre was also increased in a developing cerebral cortex. In cultured rat cortical neurons, the amount of rKirre was significantly increased during neuronal differentiation. Immuno-cytofluorescent staining indicated that rKirre was present along the neurites of cortical neurons, and was co-localized with PSD-95. SignificanceThese results suggested that rKirre might play an essential role in neuronal differentiation and development in the central nervous system.

Methylphenidate treatment increases Na+, K+-ATPase activity in the cerebrum of young and adult rats

Methylphenidate is a central nervous system stimulant used for the treatment of attention-deficit hyperactivity disorder. Na(+), K(+)-ATPase is a membrane-bound enzyme necessary to maintain neuronal excitability. Considering that methylphenidate effects on central nervous system metabolism are poorly known and that Na(+), K(+)-ATPase is essential to normal brain function, the purpose of this study was to evaluate the effect of this drug on Na(+), K(+)-ATPase activity in the cerebrum of young and adult rats. For acute administration, a single injection of methylphenidate (1.0, 2.0, or 10.0 mg/Kg) or saline was given to rats on postnatal day 25 or postnatal day 60, in the young and adult groups, respectively. For chronic administration, methylphenidate (1.0, 2.0, or 10.0 mg/Kg) or saline injections were given to young rats starting at postnatal day 25 once daily for 28 days. In adult rats, the same regimen was performed starting at postnatal day 60. Our results showed that acute methylphenidate administration increased Na(+), K(+)-ATPase activity in hippocampus, prefrontal cortex, and striatum of young and adult rats. In young rats, chronic administration of methylphenidate also enhanced Na(+), K(+)-ATPase activity in hippocampus and prefrontal cortex, but not in striatum. When tested in adult rats, Na(+), K(+)-ATPase activity was increased in all cerebral structures studied. The present findings suggest that increased Na(+), K(+)-ATPase activity may be associated with neuronal excitability caused by methylphenidate.

Immunohistochemical demonstration of cytochrome oxidase in different parts of the central nervous system: a comparative experimental study.

Cytochrome oxidase, the terminal enzyme of the electron transport chain, is a marker of the functional activity of the cell. In this study; localization of cytochrome oxidase in cerebrum, cerebellum, hippocampus, substantia nigra and choroid plexus of adult rats was investigated using immunohistochemical methods. Neural bodies were immunoreactive while neuroglial cells and axonal areas did not show significant immunostaining. The cerebral cortical substantia grisea region was stained almost homogeneously with cytochrome oxidase. In the cerebellar cortex, immunolabelling was more intense in the granular layer than the molecular layer. There was significant immunostaining in Purkinje cells. White matter, both in cerebrum and cerebellum, did not show immunoreactivity for cytochrome oxidase. Neurones in the hippocampus showed variable immunostaining; some of them were negative while others revealed high immunoreactivity. The neurones in substantia nigra were heavily labelled. Immunostaining for cytochrome oxidase in plexus choroideus epithelial cells was also remarkable. The morphological findings demonstrate the regions which most require and produce energy and reflect the differences in cellular activity in these parts of the central nervous system.

Alteration of GABA transporter expression in the rat cerebral cortex following needle puncture and colchicine injection

In the adult cerebral cortex, GABA transporters (GATs) are expressed by both neurons and astrocytes. GAT-1 immunoreactivity is found in axon terminals of GABAergic neurons and astrocytes, while GAT-3 immunolabeling occurs only in the latter. The present study was designed to determine whether the expression of GAT-1 and GAT-3 in the adult rat cerebrum changes after needle lesion and colchicine infusion. Following a needle puncture or a saline injection, immunolabeling for GAT-1 and GAT-3 was slightly increased in an area around the needle track. Not only was the neuropil labeling for both GATs increased, but also a few neuronal somata were found to be immunoreactive for GAT-1. Colchicine injections induced a striking increase in immunolabeling for both GATs in the neuropil in an area adjacent to the needle path and surrounding it. A homologous region of the contralateral hemisphere also showed a moderate increase of immunoreactivity in the neuropil for both GATs. Furthermore, this contralateral site showed many neuronal somata immunolabeled for GAT-1. These changes were mainly detected during the first 5 days following intracortical lesions. These results indicate that (1) the upregulation of GAT-1 and GAT-3 in cortical interneurons and astrocytes is caused by both mechanical and chemical factors associated with the injections; (2) increased GAT-1 and GAT-3 expression contralateral to the site of colchicine injection is mediated by transcellular signaling across the corpus callosum; and (3) the lesion-induced GAT expression may play a protective role by helping to balance excitatory and inhibitory neuronal activities.

Simultaneous detection of glutamic acid decarboxylase and reelin mRNA in adult rat neurons using in situ hybridization and immunofluorescence

The combination of in situ hybridization and immunocytochemical technique is an important tool to detail the biochemical phenotype of individual neurons. In this work, we have developed a double fluorescence method to show the presence of reelin mRNA in GABAergic cells. This was achieved by demonstrating the colocalization of glutamic acid decarboxylase 67, the synthesizing enzyme for GABA, with the mRNA for reelin, a novel factor involved in brain development and possibly the maintenance of the synaptic organization of layered structures in adult brain. The results demonstrated that reelin is expressed primarily in GABAergic cells in the adult rat cerebrum, but not in the cerebellum. Themes: Development and regeneration Topics: Neurotrophic factors: expression and regulation

Ocular and regional cerebral blood flow in aging Fischer-344 rats.

Vascular remodeling and changes in vascular responsiveness occur in the rat cerebrum with old age. This includes reductions in cerebral arteriolar numerical density, cross-sectional area, distensibility, the relative proportion of distensible elements in the cerebral arteriolar wall, and reduced endothelium-dependent relaxation. The purpose of this study was to test the hypothesis that old age results in an increase in vascular resistance and, correspondingly, a decrease in blood flow to ocular, regional cerebral, and spinal tissue in the rat. Blood flow was measured in the eye, olfactory bulb, left and right cerebrum, pituitary gland, midbrain, pons, cerebellum, medulla, and spinal cord of juvenile (2-mo-old, n = 6), adult (6-mo-old, n = 7), and aged (24-mo-old, n = 7) male Fischer-344 rats. Arterial pressure and blood flow were used to calculate vascular resistance. Vascular resistance in the eye of aged rats (6.03 +/- 1.08 mmHg . ml-1 . min . 100 g) was higher than that in juvenile (3.83 +/- 0.38 mmHg . ml-1 . min . 100 g) and adult rats (3.12 +/- 0.24 mmHg . ml-1 . min . 100 g). Similarly, resistance in the pons of older rats (2.24 +/- 0.55 mmHg . ml-1 . min . 100 g) was greater than in juvenile (0.66 +/- 0.06 mmHg .ml-1 . min . 100 g) and adult rats (0.80 +/- 0.11 mmHg . ml-1 . min . 100 g). In contrast, vascular resistance in the pituitary gland was lower in the aged rats (juvenile, 3.09 +/- 0.22; adult, 2.79 +/- 0.42; aged, 1.73 +/- 0.32 mmHg . ml-1 . min . 100 g, respectively). Vascular resistance was not different in other cerebral tissues or in the spinal cord in the aged rats. These data suggest that regional cerebral and spinal blood flow and vascular resistance remain largely unchanged in conscious aged rats at rest but that elevations in ocular vascular resistance and, correspondingly, decreases in ocular perfusion with advanced age could have serious adverse effects on visual function.

Immunocytochemical characterisation of proteins secreted by retinal pigment epithelium in retinas of normal and Royal College of Surgeons dystrophic rats.

In a previous study, an antigen consisting of proteins secreted by retinal pigment epithelial (RPE) cells was injected into a sheep and the specificity of the resulting antiserum was shown by Western blotting and its effects on retinal development were determined in vitro and in vivo. In the present study, the distribution of these secreted proteins was determined by light microscopy immunocytochemistry in cultured neonatal rat RPE cells and retinas of normal and Royal College of Surgeons (RCS) dystrophic rats and cerebrum of normal adult rats. Immunolabelling for these RPE-secreted proteins was detected in cytoplasmic vesicles surrounding nuclei and within processes of cultured normal and transformed rat RPE. In retinas of late postnatal and adult rats, dense immunostaining was found in the cytoplasm of RPE cells and ganglion cell bodies. In addition to RPE and ganglion cells, scattered photoreceptors within the thin outer nuclear layer and small structures within the debris zone were also densely immunoreactive in retinas of 2-mo-old RCS dystrophic rats. The numbers of immunostained ganglion cells appeared to decrease in retinas of older RCS rats, although the immunoreactivity within the RPE appeared to increase in density. No other neuron within the retina, i.e. bipolar, amacrine or horizontal, was immunoreactive for RPE-secreted proteins. In the cerebral cortex of adult rats, immunoreactivity for RPE-secreted proteins was primarily detected within large perikarya of pyramidal neurons and smaller granule neurons. In conclusion, we report an immunocytochemical analysis of an antiserum raised against secreted proteins of rat RPE. This antiserum recognised proteins within secretory-like vesicles of cultured neonatal normal and transformed rat RPE and showed a specificity for RPE and ganglion cells in normal rat retinas, that appeared to be developmentally regulated, and neuron perikarya in adult rat cerebrum.

Occurrence of a N-terminal proteolytic fragment of neurocan, not a C-terminal half, in a perineuronal net in the adult rat cerebrum

Neurocan is a nervous tissue-unique chondroitin sulfate proteoglycan (CSPG) whose expression and proteolytic cleavage are developmentally regulated. In the adult rat brain, neurocan is completely cleaved into some proteoglycan fragments including the C-terminal half known as neurocan-C and a N-terminal fragment with a 130 kDa core glycoprotein (neurocan-130). We describe here the differential distribution of these two neurocan-derived CSPGs in the adult rat cerebrum and the occurrence of neurocan-130 as a new member of a perineuronal net-constituting molecule. At the light microscopic level, neurocan-130 exhibited pericellular localization around a subset of neurons in addition to diffuse distribution in the neuropil. In contrast, neurocan-C was distributed only diffusely in the neuropil. Double staining with anti-neurocan-130 and anti-synaptophysin antibodies suggested that neurocan-130 was localized in the vicinity of the synapses, but not at the synapses. Immunoelectron microscopy showed that neurocan-130 was mainly localized in the cytoplasm of glial cell processes, the so-called glial perineuronal net, encompassing the cell bodies of certain neurons. The presence of neurocan-130 in a limited number of glial cells may reflect some functional heterogeneity of the glia.

Somatodendritic localization of phosphorylated tau in neonatal and adult rat cerebral cortex.

We studied the distribution of phosphorylated tau (p-tau) in neonatal and adult rat cerebrum using monoclonal antibodies that recognize distinct tau epitopes in a phosphorylation-dependent manner. In neonatal cortex, p-tau was detected in the apical dendrites and somata of pyramidal neurons as well as in axons. In adults, p-tau was present predominantly in neuronal somata and dendrites and, to a lesser extent, in axons, whereas tau-1, that recognizes a dephosphorylated tau epitope, immunolabeled neuropil and axons, and not the neuronal somata and dendrites. These results suggest that tau phosphorylated at multiple sites is present in somatodendritic compartments of rat cortical neurons throughout life, and that phosphorylation may be one of the determinants for the compartmentalization of tau in the brain.

Characterization of a novel oligodendrocyte cell surface molecule.

Cell-type-specific reagents have proven useful in the analysis of central nervous system (CNS) development and function. Most markers of oligodendrocytes are components of myelin sheath, which in the CNS is the specific product of oligodendrocytes. We have isolated a novel monoclonal antibody termed 2B10 which was raised against embryonic rat spinal cord tissue. In adult rat cerebrum, cerebellum, and spinal cord, 2B10 immunoreactivity is predominantly localized in white matter. 2B10 immunoreactivity is absent from peripheral nerve, suggesting that in the nervous system the 2B10 antigen is restricted to the CNS. Dissociated cell culture studies indicate that 2B10 labels a cell surface molecule, and its cellular distribution is coincident with O1 and myelin basic protein-positive oligodendrocytes. By contrast, 2B10 does not label GFAP-positive astrocytes. These data suggest that in the CNS the 2B10 antigen is expressed specifically on oligodendrocytes. Biochemical analysis indicates that 2B10 recognizes a protein with an apparent molecular weight of approximately 79,000 in reducing sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Developmentally, 2B10 immunoreactivity is detectable in rat spinal cord at as early as embryonic day 14. The relative abundance of this molecule decreases during myelination, but is maintained at a sustained level throughout adulthood. The 2B10 antigen appears not to be a myelin-associated protein since it is not detected in purified myelin fractions. 2B10 immunoreactivity is not detectable in extracts of rat sciatic nerve, heart, kidney, muscle, and skin, but is detectable in extracts of spleen and thymus. These data suggest that the 2B10 antigen is a novel cell surface molecule that is expressed on oligodendrocyte lineage cells throughout development.

Role of the basement membrane in neurogenesis and repair of injury in the central nervous system.

Although remarkable progress has been made during the last two decades concerning the biosynthesis, expression and assembly of extracellular matrix (ECM) macromolecules in nonneural cells, we are still far from a complete understanding of the role and function of the ECM and the basement membrane (BM) in the central nervous system (CNS). With the aid of correlative light and electron microscopic, Golgi and immunohistochemical studies of the developing neural tube of both early human fetus and mouse, we have shown that the establishment of the pial-glial barrier (PGB) is one of the earliest histogenetic events in neurogenesis. This is accomplished by coordinated interaction among the processes of radial glia, various ECM components, and mesenchymal cells at the pial surface, with the formation of a BM that tightly abuts the glia limitans. The PGB and the BM appear to be critical to the migration and final positioning of neurons and to the differentiation of the laminar cortical pattern within the developing neopallium. This hypothesis is further supported by our study of the brain of a human newborn infant in whom multiple sites of disruption of the BM and PGB resulted in abnormal neuronal migration and massive ectopia of neurons within the subarachnoid space, with abnormal cortical lamination. Finally, studies of the experimental cryogenic injury to the neonatal rat cerebrum have shown that the final positioning of neurons within the developing cortical plate appears to depend largely on the reconstitution of the BM and PGB, which presumably provide crucial positional signals for migrating neurons. Also, one of the essential reparative features seen following cryogenic injury to the adult rat cerebrum is an orderly and dynamic interaction between various ECM components and neural cells, resulting in the formation of the BM.

Developmentally regulated expression of a brain specific species of chondroitin sulfate proteoglycan, neurocan, identified with a monoclonal antibody 1G2 in the rat cerebrum

The mammalian brain contains many species of proteoglycan. To identify each proteoglycan species, we have raised monoclonal antibodies against soluble chondroitin sulfate proteoglycans purified from 10-day-old rat brains. One monoclonal antibody, named monoclonal antibody 1G2, recognized two proteoglycan species with 220,000 and 150,000 mol. wt core glycoproteins (chondroitin sulfate proteoglycan-220 and chondroitin sulfate proteoglycan-150). Partial amino acid sequences of N-termini of their core proteins coincided with those of neurocan, a brain-unique chondroitin sulfate proteoglycan species, whose complete coding sequence was recently reported [Rauch et al.(1992) J. biol. Chem. 269, 19,536–19,547]. Western blots revealed that chondroitin sulfate proteoglycan-220 became detectable in the rat cerebrum on embryonic day 14, and that it disappeared from the brain around postnatal day 30. In contrast, a fairly large amount of chondroitin sulfate proteoglycan-150 remained in the mature brain. Immunohisto-chemical studies revealed that 1G2 antigen was first localized in the preplate zone, then both in the marginal zone and in the subplate of the rat cerebrum on embryonic day 16, prior to arrival of the first thalamic afferents at the cortex. On embryonic day 20, immunolabeling with monoclonal antibody 1G2 began to spread from the subplate into the developing cortical plate. On postnatal day 10, the neuropil of the cerebrum, except for the barrel field, was diffusely stained with the antibody, intensely in the hippocampus and superficial layers (I–III) of the cerebral cortex and weakly elsewhere. The barrel hollows were stained very weakly compared with the barrel walls at this stage. The immunoreactivity in the hippocampus and superficial cortical layers was weakened in the mature brain, so that no particular staining pattern, but weak and diffuse staining was observed in the adult rat cerebrum. The 1G2 antigen was immunohistochemically associated largely with glial fibrillary acidic protein-positive cells in primary cultures of the neonatal rat cerebrum. Both chondroitin sulfate proteoglycan-220 and chondroitin sulfate proteoglycan-150 were detected in the conditioned media not only of highly enriched cultures of fetal rat cortical neurons but also of pure cultures of mature astrocytes; more (12- to 20-fold) in the astrocyte conditioned media. Astrocytes, in addition to neurons, may be a cellular source of neurocan in brain at least under certain physiological conditions. The spaciotemporal expression pattern of 1G2 epitope-bearing proteoglycan, or neurocan, suggests that this proteoglycan species plays some roles at least in forming the elongation pathway for early cortical afferent fibers as well as the functional barrel structure in the somatosensory cortex.