Pyramidal Neurons In Cerebral Cortex Research Articles

Morphological Alteration and Reduction of MAP2-Immunoreactivity in Pyramidal Neurons of Cerebral Cortex in a Rat Model of Focal Cortical Compression

Subdural hematoma causes cortical damage including brain tissue disruption, often resulting in neuronal dysfunction and neurological impairment. The aim of the present study was to identify the relationship between cerebral compression and neuronal injury. In this report, we investigated time-dependent morphological alterations within layers II, III, and V pyramidal neurons in the cerebral cortex, using Golgi-Cox staining and immunohistochemistry for microtubule-associated protein 2 (MAP2) in a rat model of focal cortical compression. An acryl pole was used to experimentally induce chronic cerebral compression by continuous pressure on the cortical surface. Changes in cellular morphology were examined at five survival time periods: 12 h and 1, 2, 3, and 4 weeks. The Golgi-Cox method revealed time-dependent alterations in dendritic length of apical and basilar dendrites of pyramidal neurons. The number of dendritic branch segments and spines of basilar dendrites were decreased in cells in layers II, III, and V. Immunohistochemical staining for MAP2 revealed changes in the intracellular distribution of immunoreactive materials. A significant reduction in MAP2 immunostaining was found in nerve cell bodies and apical dendrites of ipsilateral cortical neurons. The number of MAP2-immunoreactive neurons was significantly decreased at 12 h compared with the contralateral cerebral cortex in the same animal. Dendritic changes in layers II, III, and V pyramidal neurons were accompanied by reductions in intracellular MAP2-immunoreactive materials. The present results suggest that cortical compression causes alteration of cellular morphology as a consequence of injury, and that these morphological changes may be related to reductions in MAP2-immunoreactive materials.

Deficiency of the mitochondrial transporter of aspartate/glutamate aralar/AGC1 causes hypomyelination and neuronal defects unrelated to myelin deficits in mouse brain

The aralar/AGC1 knockout (KO) mouse shows a drastic decrease in brain aspartate and N-acetylaspartate levels and global hypomyelination, which are attributed to the lack of neuron-produced NAA used by oligodendrocytes as precursor of myelin lipid synthesis. In addition, these mice have a gradual drop in brain glutamine synthesis. We show here that hypomyelination is more pronounced in gray than in white matter regions. We find a lack of neurofilament-labelled processes in hypomyelinated fiber tracks from cerebral cortex but not from those of the cerebellar granule cell layer, which correspond to Purkinje neurons. Therefore, the impaired development or degeneration of neuronal processes in cerebral cortex is independent of hypomyelination. An increase in O4-labelled, immature oligodendrocytes is observed in gray and white matter regions of the aralar KO brain, suggesting a block in maturation compatible with the lack of NAA supplied by neurons. However, no defects in oligodendrocyte maturation were observed in in-vitro-cultured mixed astroglial cultures. We conclude that the primary defect of pyramidal neurons in cerebral cortex is possibly associated with a progressive failure in glutamatergic neurotransmission and may be among the main causes of the pathology of aralar/AGC1 deficiency.

Transgenic Mice as a Model of Pre-Clinical Alzheimers Disease

At diagnosis, Alzheimer's disease (AD) brains are extensively burdened with plaques and tangles and display a degree of synaptic failure most likely beyond therapeutic treatment. It is therefore crucial to identify early pathological events in the progression of the disease. While it is not currently feasible to identify and study early, pre-clinical stages of AD, transgenic (Tg) models offer a valuable tool in this regard. Here we investigated cognitive, structural and biochemical CNS alterations occurring in our newly developed McGill-Thyl-APP Tg mice (over-expressing the human amyloid precursor protein with the Swedish and Indiana mutations) prior to extracellular plaque deposition. Pre-plaque, 3-month old Tg mice already displayed cognitive deficits concomitant with reorganization of cortical cholinergic pre-synaptic terminals. Conformational specific antibodies revealed the early appearance of intracellular amyloid β (Aβ)-oligomers and fibrillar oligomers in pyramidal neurons of cerebral cortex and hippocampus. At the same age, the cortical levels of insulin degrading enzyme -a well established Aβ-peptidase, were found to be significantly down-regulated. Our results suggest that, in the McGill-Thy1-APP Tg model, functional, structural and biochemical alterations are already present in the CNS at early, pre-plaque stages of the pathology. Accumulation of intraneuronal neurotoxic Aβ-oligomers (possibly caused by a failure in the clearance machinery) is likely to be the culprit of such early, pre-plaque pathology. Similar neuronal alterations might occur prior to clinical diagnosis in AD, during a yet undefined 'latent' stage. A better understanding of such pre-clinical AD might yield novel therapeutic targets and or diagnostic tools.

The Distribution of MAP-2 Phosphorylation in Cerebral Cortex of Long-Tailed Monkey Fetuses (Macaca fascicularis) in the Last Trimester of Gestation

Memories are storage in cholinoceptive cells, the cells which are enriched with microtubule-associated protein 2 (MAP-2) that localized in the neuronal dendrite and the cell bodies. Phosphorylation of MAP-2 may increase memory with reduce stability of dendrite by altered dendrite length and lead new side-branches of neuronal as a neuronal plasticity processes in cerebral cortex. The aim of this research is to study the distribution of MAP-2 phosphorylation neurons in cerebral cortex of long-tailed macaques in the third semester of gestational immunohistochemically using avidin biotin conjugated complex method. Neurons MAP-2 phosphorylation immunoreactive were located in dendrites and cell bodies, mostly in pyramidal neurons of cerebral cortex. Intensity of MAP-2 phosphorylation immunoreactivity in layer V were stronger than another layer and the neurons that very intensely stained were the pyramidal cells in frontal and parietal lobes, that was suggested that neurons in this areas more responsive to neuroplasticity. From the results we concluded that MAP-2 phosphorylation already distributed in the cerebral cortex of long-tailed macaque fetuses at the last trimester of gestation, mostly in the pyramidal cells of layer V that is suggested plays a role for preparation of memory formation. Keywords: fetus, long-tailed monkey, cerebral cortex, memory, MAP-2 phosphorylation

Expression of luteinizing hormone in rat brain

A recent report demonstrated that in human aging brain after menopause/andropause luteinizing hormone (LH) is localized in the cytoplasm of pyramidal neurons and hippocampus and a significant increase of LH is also detected in the cytoplasm of pyramidal neurons and neurofibrillary tangles of Alzheimer's disease brain compared to age-matched control brain. It was suggested that the decreased steroid hormone production and the resulting LH expression in the neurons vulnerable to Alzheimer's disease pathology may have some relevance to the development of Alzheimer's disease. lt is, however, unclear whether the presence of LH in neurons of human aging and Alzheimer's disease brain is due to intracellular LH expression or to LH uptake from extracellular sources since gonadotropins are known to cross the blood brain barrier. Moreover, there is no report by using the brain of an experimental animal that LH is expressed in such neurons as found in the human brain. In the present study, we found that LH immunoreactivity is localized in the pyramidal neurons of cerebral cortex and hippocampus of 12 and 18 months old rats but can not detect any immunoreactivity for LH in the young adult (3-5 months old) rats. To confirm that these LH immunoreactivity results from de novo synthesis in the brain but not the uptake from extracellular space，we performed RT-PCR and found that mRNA for LH is detected in several regions of brain including cerebral cortex and hippocampus. These findings suggest us that LH expression in old rat brain may play an important role in aging process of rat brain.

Molecular stress response in the CNS of mice after systemic exposure to interferon-α, ionizing radiation and ketamine

We previously showed that the expression of troponin T1 (Tnnt 1) was induced in the central nervous system (CNS) of adult mice 30 min after treatment with ketamine, a glutamate N-methyl- d-aspartic acid (NMDA) receptor antagonist. We hypothesized that Tnnt 1 expression may be an early molecular biomarker of stress response in the CNS of mice. To further evaluate this hypothesis, we investigated the regional expression of Tnnt 1 in the mouse brain using RNA in situ hybridization 4 h after systemic exposure to interferon-α (IFN-α) and gamma ionizing radiation, both of which have be associated with wide ranges of neuropsychiatric complications. Adult B6C3F1 male mice were treated with either human IFN-α (a single i.p. injection at 1 × 10 5 IU/kg) or whole body gamma-radiation (10 cGy or 2 Gy). Patterns of Tnnt 1 transcript expression were compared in various CNS regions after IFN-α, radiation and ketamine treatments (previous study). Tnnt 1 expression was consistently induced in pyramidal neurons of cerebral cortex and hippocampus after all treatment regimens including 10 cGy of ionizing radiation. Regional expression of Tnnt 1 was induced in Purkinje cells of cerebellum after ionizing radiation and ketamine treatment; but not after IFN-α treatment. None of the three treatments induced Tnnt 1 expression in glial cells. The patterns of Tnnt 1 expression in pyramidal neurons of cerebral cortex and hippocampus, which are both known to play important roles in cognitive function, memory and emotion, suggest that the expression of Tnnt 1 may be an early molecular biomarker of induced CNS stress.

Expression and traffic of cellular prolyl oligopeptidase are regulated during cerebellar granule cell differentiation, maturation, and aging

Prolyl oligopeptidase (POP) is an endopeptidase which cleaves short proline-containing neuropeptides, and it is involved in memory and learning. POP also has an intercellular function mediated through the inositol pathway, and has been involved in cell death. POP has been early considered as a housekeeping enzyme, but the recent research indicates that POP expression is regulated across tissues and intracellularly. In the brain, POP is exclusively expressed in neurons and most abundantly in pyramidal neurons of cerebral cortex, in the CA1 field neurons of hippocampus and in cerebellar Purkinje's cells. Intracellularly, POP is mainly present in the cytoplasm and some in intracellular membranes, like rough endoplasmic reticulum and Golgi apparatus. In this paper, we systematically studied the levels of expression of POP along the life of cerebellar granule cells (CGC) in culture and the distribution of POP within different intracellular compartments. We used the tight-binding inhibitor JTP-4819 covalently coupled with fluorescein (FJTP) as a tool to study the changes on expression and localization of POP protein. Our results indicate that POP activity levels are regulated during the life of the neurons. POP was found mainly in cytoplasm and neuronal projections, but at an early developmental phase significant amounts were found also in nuclei. Along the life of the neurons, POP activity fluctuated in 7-day cycles. In young neurons, the cytosolic POP activity was low but increased by maturation so that the activity peak coincided with full differentiation. Over aging, cytoplasmic POP was concentrated around nucleus, but the activity decreased with time. POP was also present in vesicles across the neuron. No major changes were seen in the nuclear or membrane bound POP over aging until activity disappeared upon neuronal death. This is the first time when POP was found in the nuclei of human neuronal cells.

Distinct expression and subcellular localization patterns of Na +/HCO 3− cotransporter (SLC 4A4) variants NBCe1-A and NBCe1-B in mouse brain

The electrogenic Na +/HCO 3 − cotransporter (NBCe1) has been identified as a key player for regulation of intracellular pH in several cell types. The present study was undertaken to determine expression and subcellular localization of the NH 2-terminal solute carrier (SLC) 4A4 variants NBCe1-A and NBCe1-B in mouse brain using variant-specific antibodies by immunohistochemistry and immunoelectron microscopy. In addition, distribution of NBCe1 variants and activity-dependent regulation was investigated in mouse embryonic day 17.5 (E17.5) hippocampal primary cultures in vitro. The results showed NBCe1-A and NBCe1-B transcript expression in the mouse olfactory bulb, cerebral cortex, hippocampus and cerebellum. NBCe1-A was predominantly expressed in Purkinje cells, granule cells of the dentate gyrus, non-pyramidal cell bodies in cerebral cortex, and in periglomerular and mitral cells in the olfactory bulb. Pyramidal neurons in cerebral cortex and apical cell dendrites in the hippocampus were stained for both NBCe1-A and NBCe1-B. Moreover, NBCe1-B was present in Bergmann glia. At the ultrastructural level, NBCe1-B was preferentially expressed in perivascular astroglial lamellae, whereas both NBCe1 NH 2-terminal variants were localized in pre- and postsynaptic compartments. Except for the olfactory bulb, NBCe1-A was always colocalized with calbindin. Treatment of E17.5 primary hippocampal cultures with KCl, showed dramatic downregulation of NBCe1-B mRNA and protein after 60 min, whereas NBCe1-A expression remained unchanged. These data demonstrate for the first time distinct cellular distribution of NBCe1 NH 2-terminal variants in mouse brain. NBCe1 may be involved in neuronal modulation, and pH regulation during neuronal activity.

Physiological Evidence That Pyramidal Neurons Lack Functional Water Channels

The physiological conditions that swell mammalian neurons are clinically important but contentious. Distinguishing the neuronal component of brain swelling requires viewing intact neuronal cell bodies, dendrites, and axons and measuring their changing volume in real time. Cultured or dissociated neuronal somata swell within minutes under acutely overhydrated conditions and shrink when strongly dehydrated. But paradoxically, most central nervous system (CNS) neurons do not express aquaporins, the membrane channels that conduct osmotically driven water. Using 2-photon laser scanning microscopy (2PLSM), we monitored neuronal volume under osmotic stress in real time. Specifically, the volume of pyramidal neurons in cerebral cortex and axon terminals comprising cerebellar mossy fibers was measured deep within live brain slices. The expected swelling or shrinking of the gray matter was confirmed by recording altered light transmittance and by indirectly measuring extracellular resistance over a wide osmotic range of -80 to +80 milliOsmoles (mOsm). Neurons expressing green fluorescent protein were then imaged with 2PLSM between -40 and +80 mOsm over 20 min. Surprisingly, pyramidal somata, dendrites, and spines steadfastly maintained their volume, as did the cerebellar axon terminals. This precluded a need for the neurons to acutely regulate volume, preserved their intrinsic electrophysiological stability, and confirmed that these CNS nerve cells lack functional aquaporins. Thus, whereas water easily permeates the aquaporin-rich endothelia and glia driving osmotic brain swelling, neurons tenatiously maintain their volume. However, these same neurons then swell dramatically upon oxygen/glucose deprivation or [K+]0 elevation, so prolonged depolarization (as during stroke or seizure) apparently swells neurons by opening nonaquaporin channels to water.

Synaptic localization of receptor-type protein tyrosine phosphatase ζ/β in the cerebral and hippocampal neurons of adult rats

Receptor-type protein tyrosine phosphatase (RPTP) ζ/β is a nervous tissue-specific chondroitin sulfate proteoglycan. In this study, we investigated the immunohistochemical localization of RPTPζ/β in adult rat cerebral cortex and hippocampus at light and electron microscopic levels. Double labeling immunofluorescence microscopy revealed that the immunoreactivity of RPTPζ/β was observed at MAP2-positive dendrites and PSD-95-positive spines of pyramidal neurons in the cerebral cortex and hippocampus. Electron microscopic observation demonstrated a strong immunoreactivity of RPTPζ/β at the postsynaptic membrane of dendritic spines and shafts, and its moderate immunoreactivity at the dendritic membrane. In cultured cortical neurons, the immunoreactivity of RPTPζ/β was observed at some of PSD-95-positive spines. These results demonstrate that RPTPζ/β is localized mainly at the postsynaptic membrane of pyramidal neurons in adult cerebral cortex and hippocampus.

Immunocytochemical demonstration of reduced glutathione in neurons of rat forebrain

Histochemical studies show reduced glutathione (GSH) in neuroglia, whereas immunocytochemistry of glutaraldehyde-fixed tissue reveals GSH also in neurons. Using an antibody suitable for formaldehyde-fixed tissue, we find GSH staining in the cytoplasm of neurons throughout the brain. Staining was prominent in large pyramidal neurons of cerebral cortex, in basal ganglia, and in reticular and ventrobasal thalamic nuclei.

Elevated GM2 ganglioside is associated with dendritic proliferation in normal developing neocortex

Mature pyramidal neurons of cerebral cortex in several neuronal storage disease elaborate dendrites. These dendrites appear specifically on pyramidal neurons containing elevated GM2 ganglioside and a variety of studies support the hypothesis that this ganglioside is responsible for inducing the new dendrite growth. To determine whether a similar association between GM2 ganglioside and dendrite growth occurs in normal neurons, we used an antibody to localize GM2 in developing cat neocortex. Our results show that GM2 ganglioside is elevated in normal cortical neurons during the period when dendritogenesis is occurring, but is greatly diminished in these cells after dendritic differentiation is complete. Elevations of GM2 occur in deep neurons earlier than in superficial ones, a sequence that corresponds closely to the inside-first, outside-last progression of cortical neuron differentiation. Ultrastructurally, GM2 immunoreactivity is found sequestered in vesicles with a distribution that coincides with sites of ganglioside synthesis and transport. The close association between elevated GM2 ganglioside and dendrite growth in cortical pyramidal neurons during normal development, coupled with a similar correlation between GM2 and ectopic dendritogenesis in neuronal storage disease, support the view that this specific ganglioside plays a pivotal role in regulating dendritogenesis.

GM2 ganglioside and pyramidal neuron dendritogenesis.

GM2 ganglioside, although scarce in normal adult brain, is the predominant ganglioside accumulating in several types of lysosomal disorders, most notably Tay-Sachs disease. Pyramidal neurons of cerebral cortex in Tay-Sachs, as well as many other types of neuronal storage disorders, are known to exhibit a phenomenon believed unique to storage disorders: growth of ectopic dendrites. Recent studies have shown that a common metabolic abnormality shared by storage diseases with ectopic dendrite growth is the abnormal accumulation of GM2 ganglioside. The correlation between increased levels of GM2 and the presence of ectopic dendrites has been found in both ganglioside and nonganglioside storage disorders, the latter including sphingomyelin-cholesterol lipidosis, mucopolysaccharidosis, and alpha-mannosidosis. Quantitative HPTLC analysis has shown that increases in GM2 occur in proportion to the incidence of ectopic dendrite growth, whereas other gangliosides, including GM1, lack similar increases. Immunocytochemical studies of all nonganglioside storage diseases which exhibit ectopic dendritogenesis have revealed heightened GM2 ganglioside-immunoreactivity in the cortical pyramidal cell population, whereas nerurons in normal adult brain exhibit little or no staining for this ganglioside. Further, studies examining disease development have consistently shown that accumulation of GM2 ganglioside precedes growth of ectopic dendrites, indicating that it is not simply occurring secondary to new membrane production. These findings have prompted an examination for a similar relationship between GM2 ganglioside and dendritogenesis in cortical neurons of normal developing brain. Results show that GM2 ganglioside-immunoreactivity is consistently elevated in immature neurons during the period when they are undergoing active dendritic initiation, but this staining diminishes dramatically as the dendritic trees of these cells mature. Collectively, these studies on diseased and normal brain offer compelling evidence that GM2 ganglioside plays a pivotal role in the regulation of dendritogenesis in cortical pyramidal neurons.

HIV envelope protein-induced neuronal damage and retardation of behavioral development in rat neonates

Cognitive and motor impairment are common symptoms among patients infected with the human immunodeficiency virus (HIV), including children who suffer neurological deficits and are frequently developmentally impaired. The HIV envelope protein, gp120, which has been shown to be toxic to neurons in culture, is shed in abundance by infected cells, and thus may play a significant role in the neuropathology of AIDS. To test this possible mechanism, neonatal rats were injected systematically with purified gp120 and the following consequences were observed: (1) radiolabeled gp120 and toxic fragments thereof were recovered in brain homogenates; (2) dystrophic changes were produced in pyramidal neurons of cerebral cortex; (3) retardation was evident in developmental milestones associated with complex motor behaviors. In parallel studies, co-treatment with peptide T, a gp120-derived peptide having a pentapeptide sequence homologous with vasoactive intestinal peptide, prevented or attenuated the morphological damage and behavioral delays associated with gp120 treatment. These studies suggest that gp120 and gp120-derived toxic fragments may contribute to the neurological and neuropsychiatric impairment related to HIV infection, and that peptide T appears to be effective in preventing gp120-associated neutoxicity in developing rodents.

Distribution of ectopic neurite growth and other geometrical distortions of CNS neurons in feline GM2 gangliosidosis

Golgi and combined Golgi-electron microscopic (EM) studies were carried out on cats in the terminal stages of GM2 ganglioside storage disease and the resulting data were compared with those from similar studies other neuronal storage diseases in cats, including GM1 gangliosidosis. The results support the view that only limited types of neurons affected by the lysosomal hydrolase deficiency and subsequent intracellular storage have the capacity to sprout new dendritic-like growth processes from their axon hillocks, and that these neurons are essentially the same in all of these diseases studied to date. Golgi studies of CNS tissues from GM2 gangliosidosis cats revealed ectopic neurite growth on pyramidal neurons of cerebral cortex and multipolar cells of amygdala and claustrum, whereas other types of neurons responded to the metabolic defect with aspiny meganeurite formation or somatic enlargement, or appeared normal in terms of soma-dendritic morphology. Combined Golgi-EM studies of cortical pyramidal neurons revealed that ectopic, axon hillock neurites commonly possessed asymmetrical synapses which were similar to those observed in other storage disorders.