Biomedical subjects

C W Cotman

Publications and source records attributed to C W Cotman.

At least 19 recordsLinked to original sources

PubMed1992

bFGF promotes the survival of entorhinal layer II neurons after perforant path axotomy.

Infusion of basic fibroblast growth factor (bFGF) prevents the loss of cholinergic neurons in the septum/diagonal band of broca following fimbria-fornix transection. However, an in vivo test of whether bFGF will also rescue injured non-cholinergic or cortical neurons has not been carried out. Previous studies have shown that the majority of layer II stellate neurons utilize an excitatory amino acid as their neurotransmitter. In order to determine if bFGF acts on non-cholinergic cortical neurons, a paradigm was developed to examine whether or not bFGF could spare layer II entorhinal stellate cells from axotomy induced death or atrophy. Axotomy of the medial entorhinal cortex fibers projecting to the dentate gyrus of the hippocampal formation via the perforant path lead to retrograde cell loss in entorhinal cortex. Fourteen or thirty days after a unilateral knife cut axotomy of the perforant path, layer II of medical entorhinal cortex showed a 28% decrease in large stellate neurons as well as many weakly stained, hollow cells compared to the non-lesioned side or naive controls. Layer IV neurons, however, which do not project via the perforant path, showed little detectable change in the number of cells ipsilateral to the knife-cut as compared to the contralateral side. Intraventricular infusion of bFGF over a period of 14 days reduced the 28% cell loss to less than 6%. Thus, bFGF is capable of preventing cortical neuronal loss and/or atrophy associated with retrograde degeneration of non-cholinergic neurons following axotomy.

Animals↗

PubMed1992

Programmed cell death: its possible contribution to neurotoxicity mediated by calcium channel antagonists.

Organic calcium channel antagonists attenuate ischemic or excitotoxic neuronal injury, probably by limiting Ca2+ influx through the voltage-gated calcium channels. However, the possibility that calcium channel antagonists may compromise neuronal survival with long-term exposure has not been systemically examined. In the present study, we report that cerebral cortical cultures exposed for 2 days to either nifedipine, verapamil, diltiazem, or flunarizine, undergo selective neuronal degradation in a concentration-dependent fashion. This degeneration could be attenuated by protein synthesis inhibitors cycloheximide and actinomycin-D. Cortical cultures incubated for 2 days in low calcium media also exhibit widespread neuronal damage, which is similarly blocked by cycloheximide. Although we cannot exclude other possibilities, these findings suggest that a decrease in intraneuronal calcium levels may trigger synthesis of proteins mediating neuronal cell death. Regardless of the exact toxic mechanisms involved, additional studies on neurotoxicity of calcium channel antagonists seem warranted since some of these compounds are currently being clinically used.

Animals↗

PubMed1992

Adrenal hormone effects on hippocampal excitatory amino acid binding.

The influence of short-term adrenalectomy or corticosterone treatment on the binding of glutamate receptor subtypes in the rat hippocampus was explored using the technique of in vitro autoradiography. Analysis of NMDA, kainate and AMPA binding in the hippocampus was conducted on the brains of control, adrenalectomized, and adrenalectomized animals given corticosterone treatment. In addition, serum corticosterone levels were determined by RIA. No striking effects of acute adrenalectomy on the distribution or density of any glutamate receptor subtype were observed in the hippocampus. Adrenalectomy had a small but significant effect on kainate binding in the stratum lucidum and stratum radiatum of CA3 in the first experiment, but no effect in follow-up experiments. Short-term treatment with stress levels of corticosterone had no effect on the binding of NMDA or kainate in any hippocampal subfield. However, a small effect of high doses of corticosterone (CORT) was observed on AMPA binding in one subregion. Although the hippocampus is a target for glucocorticoids and uses excitatory amino acids as a primary neurotransmitter, transient manipulation of adrenal hormone levels did not directly modulate excitatory amino acid receptor binding.

Adrenal Cortex Hormones↗

PubMed1992

Decreased levels of soluble amyloid beta-protein precursor in cerebrospinal fluid of live Alzheimer disease patients.

The amyloid beta-protein is deposited in senile plaques and the cerebrovasculature in Alzheimer disease (AD). Since it is derived from proteolytic processing of its parent protein, the amyloid beta-protein precursor (APP), we investigated whether levels of the secreted forms of APP are altered in cerebrospinal fluid (CSF) of AD patients. Quantitative immunoblotting studies with the anti-APP monoclonal antibody P2-1 revealed that probable AD patients had markedly lower CSF APP levels than did demented non-Alzheimer-type patients and healthy control subjects. Using antibody P2-1 in an enzyme-linked immunosorbent assay, we measured CSF levels of APP in a larger population consisting of 13 patients diagnosed with probable AD, 18 patients diagnosed with dementia (non-Alzheimer type), and 16 nondemented, healthy controls. Mean CSF levels of APP were approximately 3.5-fold lower in the live patients diagnosed with probable AD compared to the demented non-Alzheimer-type controls or the nondemented, healthy individuals. These findings suggest that abnormal metabolism of APP is reflected in the extracellular fluids of the central nervous system and that CSF levels of soluble APP provide a useful biochemical marker to assist in the clinical diagnosis of AD.

Alzheimer Disease↗

PubMed1992

Beta-amyloid stimulates glial cells in vitro to produce growth factors that accumulate in senile plaques in Alzheimer's disease.

The effects of a synthetic homolog of beta-amyloid (beta 1-42) on the secretion of interleukin-1 (IL-1) and basic fibroblast growth factor (bFGF) from cultures of microglia and astrocytes, cells that surround beta-amyloid-containing plaques in Alzheimer's disease, were examined. Our results show that beta-amyloid not only enhances glial cell secretion of these factors, it stimulates the proliferation and morphological transformation of microglia. Since IL-1 and bFGF are known to elevate the synthesis of the beta-amyloid precursor protein and other plaque components, it is suggested that in this way, cascades may arise that contribute to the process of plaque development.

Alzheimer Disease↗

PubMed1992

Voltage-gated currents expressed by rat microglia in culture.

Using the whole-cell patch-clamp technique, at least three types of voltage-gated currents expressed by cultured rat microglia were identified: an inward rectifier K+ current, a delayed rectifier K+ current (IK), and a Na+ current activated by depolarization. The inward rectifier conductance was activated by hyperpolarization to potentials more negative than -80 mV, depended on the external K+ concentration, and declined over time during whole cell recording, as the cell was internally dialyzed. The delayed rectifier current was activated by depolarization to potentials more positive than -40 mV and the rates of activation and deactivation showed a voltage-dependence similar to such currents seen in other preparations. An inward current possibly carried by Na+ was seen in a small percentage of cells. Recordings had been made from two morphological cell types, namely process-bearing ("ramified") and non-process-bearing ("ameboid"). Each of these currents was present in microglia of both morphological types. However, microglial morphology, which is thought to represent different states of activation, was significantly related to the types of combinations of currents expressed in a given cell.

Animals↗

PubMed1992

Alterations in [3H]kainate and N-methyl-D-aspartate-sensitive L-[3H]-glutamate binding in the rat hippocampal formation following fimbria-fornix lesions.

Following lesions of the fimbria-fornix, there is a time-dependent increase in interictal spikes and seizure susceptibility. This may result from sprouting of local excitatory and inhibitory circuits in response to the loss of subcortical and commissural innervation of the hippocampal formation. We used receptor autoradiography to examine the density of N-methyl-D-aspartate (NMDA)-sensitive L-[3H]glutamate and [3H]-kainate (KA) binding sites in the hippocampal formation at 5 days, 3 months, and 1 year following bilateral aspiration lesions of the fimbria-fornix. At 5 days post-lesion, the CA3 and CA1 strata radiatum and oriens displayed a decrease (20-42%, P less than 0.01) in NMDA-sensitive L-[3H]glutamate binding. The initial decrease was followed by a moderate recovery at later time points but was still evident at 1 year postlesion. This may reflect a lesion-induced turnover of synaptic complexes, down-regulation of postsynaptic receptors, or loss of presynaptic receptors. Five days following fimbria-fornix lesion there was also a decrease (13-15%, P less than 0.05) in [3H]KA binding in CA3 strata radiatum and pyramidale. However, at 3 months postlesion KA receptor density was elevated by 29-33% (P less than 0.01) in the outer molecular layer of the dentate gyrus with no significant change in binding to the inner molecular layer. By 1 year postlesion, the density of [3H]KA binding sites was not significantly different from that observed in control animals of the same age. The increase in KA receptor density in the outer molecular layer 3 months after fimbria-fornix lesion may reflect sprouting of the perforant path input or mossy fibers to this region and contribute to the increase in interictal spikes and seizures susceptibility.

Acetylcholinesterase↗

PubMed1992

Gliotoxic actions of excitatory amino acids.

Cultures of neonatal Type I astrocytes of the rat were exposed to a series of excitatory amino acid analogs to identify those compounds that were gliotoxic. In addition to L-alpha-aminoadipate, a previously identified gliotoxin, L-homocysteate, L-serine-O-sulfate, L-alpha-amino-4-phosphonobutyrate and L-alpha-amino-3-phosphono-propionate were also found to induce a sequence of degenerative events that led to the lysis of the astrocytes. Cellular injury was assessed by quantifying the activity of lactate dehydrogenase present in the surviving astrocytes. Prior to lysis, the cells went through a succession of distinctive morphological changes, the most prominent of which involved nuclear alterations. The nuclei appeared swollen, contained "pale" or "watery" nucleoplasm and exhibited a very prominent nuclear membrane and obvious nucleoli. These astrocytes appeared quite similar in appearance to the Alzheimer's Type II astrocytes, principally associated with the pathology of hepatic encephalopathy. The nuclear anomalies, which are thought to be indicative of cellular damage and compromised function, were also produced by the endogenous transmitters L-glutamate and L-aspartate, although with time, the affected astrocytes appeared to recover and return to normal morphology, without lyzing. These findings suggest that excessive levels of excitatory amino acids may induce cellular damage to astrocytes, as well as neurons. Once damaged, the resulting reductions in astrocyte function may further contribute to CNS losses and the overall pathology attributed to the excitatory amino acids.

Alzheimer Disease↗

PubMed1992

Lesions of the rat postsubiculum impair performance on spatial tasks.

Previous studies have identified a population of neurons in the postsubiculum that discharge as a function of the rat's head direction in the horizontal plane (Taube, Muller, & Ranck, 1990a). To assess the contribution of these cells in spatial learning, Long-Evans rats were tested in a variety of spatial and nonspatial tasks following bilateral electrolytic or neurotoxic lesions of the postsubiculum. Compared to unlesioned control animals, lesioned animals were impaired on two spatial tasks, a radial eight-arm maze task and a Morris water task, although the performance scores of both lesion groups improved over the course of behavioral testing. In contrast, lesioned animals were unimpaired on two nonspatial tasks, a cued version of the water maze task and a conditioned taste-aversion paradigm. In addition, lesioned animals showed transient hyperactivity in an open-field activity test. These results support the concept that neurons in the postsubiculum are part of a neural network involved in the processing of spatial information.

Animals↗

PubMed1992

N-methyl-D-aspartate receptor complex in the hippocampus of elderly, normal individuals and those with Alzheimer's disease.

The various ligand binding sites of the N-methyl-D-aspartate receptor complex in the hippocampal formation and parahippocampal gyrus of Alzheimer's disease patients and age-matched normal individuals were examined using quantitative autoradiography. The hippocampus and parahippocampal gyrus of the normal elderly brain exhibited virtually identical distributions of L-[3H]glutamate, [3H]5-methyl-10,11-dihydro-5H- dibenzo[a,d]cyclohepten-5,10-iminemaleate ([3H]MK-801), [3H][(+/-)2-carboxypiperazine-4-yl]propyl-1-phosphonic acid ([3H]CPP) and strychnine-insensitive [3H]glycine binding sites (r greater than 0.87) suggesting that binding occurred to different domains of the same receptor macromolecule. The binding of [3H]MK-801 to channel-associated phencyclidine sites appeared to be most severely impaired in Alzheimer's disease, especially at the anterior hippocampal level. When the data were averaged and the means for Alzheimer's disease and control group compared, a 34% decrease (P less than 0.01) in [3H]MK-801 binding was identified in the CA1 stratum pyramidale and a smaller decrease was found in the dentate gyrus molecular layer, parahippocampal gyrus and subiculum. The CA1 region exhibited a similar 35% reduction (P less than 0.05) in L-[3H]glutamate binding to N-methyl-D-aspartate-sensitive sites. This decrease most probably reflected a decline in receptor density. Binding of [3H]CPP to antagonist-preferring sites and [3H]glycine to glycine modulatory sites did not change significantly. However, a marked intersubject variability in N-methyl-D-aspartate receptor binding was observed in control and Alzheimer's disease groups. This variability was not related to age, sex or post mortem delay. Some Alzheimer's disease patients showed markedly reduced receptor binding levels, while others showed no changes or even increased binding. The loss of N-methyl-D-aspartate-sensitive sites did not correlate with a loss of neurons in the CA1 region (r = 0.286). Similarly, no correlation between the level of binding to N-methyl-D-aspartate-sensitive sites and the density of neuritic plaques and neurofibrillary tangles was found. Intersubject variability in N-methyl-D-aspartate receptor responses in the Alzheimer's disease group may partially explain conflicting reports in the literature on the N-methyl-D-aspartate receptor changes in Alzheimer's disease, and imply that caution should be exercised before making any generalizations about receptor changes in Alzheimer's disease based on mean values only. The analysis of the individual Alzheimer's disease cases may also be valuable in determining the mechanism(s) underlying the disease.

Aged↗

PubMed1992

Aggregation of the amyloid precursor protein within degenerating neurons and dystrophic neurites in Alzheimer's disease.

Using a monoclonal antibody raised against purified, native, human protease nexin-2/amyloid precursor protein, which recognizes an amino terminal epitope on the amyloid precursor protein and detects all major isoforms of amyloid precursor protein, we examined the localization of the amyloid precursor protein within Alzheimer's and aged control brains. Very light cytoplasmic neuronal amyloid precursor protein staining but no neuritic staining was visible in control brains. In the Alzheimer's brain, we detected numerous amyloid precursor protein-immunopositive neurons with moderate to strong staining in select regions. Many neurons also contained varying levels of discrete granular, intracellular accumulations of amyloid precursor protein, and a few pyramidal neurons in particular appeared completely filled with amyloid precursor protein granules. "Ghost"-like deposits of amyloid precursor protein granules arranged in pyramidal, plaque-like shapes were identified. We detected long, amyloid precursor protein-immunopositive neurites surrounding and entering plaques. Many contained swollen varicosities along their length or ended in bulbous tips. Amyloid precursor protein immunoreactivity in the Alzheimer's brain was primarily present as granular deposits (plaques). The amyloid precursor protein granules do not appear to co-localize within either astrocytes or microglia, as evidenced by double-labeling immunohistochemistry with anti-glial fibrillary acidic protein and anti-leukocyte common antigen antibodies or Rinucus cummunicus agglutin lectin. Amyloid precursor protein could occasionally be detected in blood vessels in Alzheimer's brains. The predominantly neuronal and neuritic localization of amyloid precursor protein immunoreactivity indicates a neuronal source for much of the amyloid precursor protein observed in Alzheimer's disease pathology, and suggests a time-course of plaque development beginning with neuronal amyloid precursor protein accumulation, then deposition into the extracellular space, subsequent processing by astrocytes or microglia, and resulting in beta-amyloid peptide accumulation in plaques.

Aged↗

PubMed1992

Transient lesion-induced increase of basic fibroblast growth factor and its receptor in layer VIb (subplate cells) of the adult rat cerebral cortex.

Basic fibroblast growth factor is a potent trophic factor with a wide spectrum of activity at various stages of neuronal development. In our studies on the effects of select lesions on the expression of growth factors, we observed that neurons of layer VIb of the rat cerebral cortex developed immunoreactivity for basic fibroblast growth factor and its receptor following injury. Recent evidence indicates that layer VIb of the rat cerebral cortex contains the subplate cell population, a group of neurons shown to participate in the development of the cerebral cortex. In this article, we examined the nature and time-course of the response to injury of the expression of basic fibroblast growth factor and its receptor in these cells. We used an anti-basic fibroblast growth factor monoclonal antibody that recognizes the active form of basic fibroblast growth factor, and a polyclonal antibody that recognizes the extracellular domain of the basic fibroblast growth factor receptor. The induction of basic fibroblast growth factor and its receptor in layer VIb cells occurred after entorhinal cortex lesion, fimbria-formix transection or aspiration of small segment of the frontoparietal cortex. The lesion-induced effect was transient, appearing by postlesion day 2 and having disappeared by postlesion day 7. These findings suggest that endogenous basic fibroblast growth factor may have a neuroprotective role on layer VIb neurons after trauma and/or may participate in cortical plasticity during adulthood.

Animals↗

PubMed1992

Hippocampal excitatory amino acid receptors in elderly, normal individuals and those with Alzheimer's disease: non-N-methyl-D-aspartate receptors.

Quantitative receptor autoradiography was used to examine the density and distribution of [3H]kainic acid and [3H]alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) binding sites in the hippocampal formation and parahippocampal gyrus obtained at autopsy from 10 Alzheimer's disease and eight normal control individuals. In control and Alzheimer's disease individuals, [3H]kainic acid saturation binding analysis in the outer molecular layer of the dentate gyrus fitted a single-site model. Added calcium ions did not alter the density of [3H]kainic acid binding in the human tissues. These results suggest that calcium-sensitive high-affinity kainic acid binding sites are not present in the human brain in contrast to kainic acid receptors in the rat brain. [3H]AMPA binding was also slightly different in the human brain as compared to the rat, being greatest in the inner third as compared to the outer two-thirds of the dentate gyrus molecular layer. In both control and Alzheimer's disease individuals, [3H]kainic acid and [3H]AMPA binding densities were similar at anterior and posterior levels of the hippocampal formation. In Alzheimer's disease patients, there was a significant increase in [3H]AMPA binding in the infragranular layer. In some, but not all Alzheimer's disease patients, there was an increase in [3H]kainic acid binding densities in the outer half of the dentate gyrus molecular layer. The same individuals which exhibited an increase in [3H]kainic acid binding in the outer molecular layer also displayed increased [3H]AMPA binding in the hilar region. Similar alterations in [3H]kainic acid binding have been observed in rats which had received fimbria-fornix lesions, a model of chronic epilepsy and in individuals with temporal lobe epilepsy. Advanced Alzheimer's disease patients are at risk of developing seizures. The results suggest that several factors including cortical and subcortical pathology and seizure activity may contribute to the alterations in [3H]kainic acid and [3H]AMPA binding observed in the hippocampal formation in Alzheimer's disease.

Aged↗

PubMed1992

Localization of heparan sulfate glycosaminoglycan and proteoglycan core protein in aged brain and Alzheimer's disease.

Two monoclonal antibodies, one which recognizes a glycosaminoglycan epitope present in heparan sulfate glycosaminoglycan and another which recognizes the core protein of a basement membrane heparan sulfate proteoglycan, were used to study the distribution and localization of these components in Alzheimer's disease and control brain. The cytoplasm of neurons, and occasional neurofibrillary tangles, senile plaques and astrocytes were immunopositive for the heparan sulfate glycosaminoglycan antibody in control brains. In Alzheimer's tissue, however, the number and intensity of these elements was more extensive than in control brains. In addition, within the Alzheimer's brains studied, the nuclei of select neurons and a small number of microglia were also immunopositive for heparan sulfate glycosaminoglycan in contrast to controls, where nuclei and neuroglia were immuno-negative. Some senile plaques in Alzheimer's tissue also contained strong heparan sulfate glycosaminoglycan-positive neurites which were not seen in controls. In Alzheimer's tissue, double labeling for heparan sulfate glycosaminoglycans and the beta-amyloid protein in adjacent sections revealed that, in general, heparan sulfate glycosaminoglycan- and beta-amyloid protein-immunopositive plaques were co-localized. Occasionally, however, beta-amyloid-positive plaques were seen without heparan sulfate glycosaminoglycan immunoreactivity and vice versa. Heparan sulfate glycosaminoglycan immunoreactivity and Tau immunoreactivity co-localized in many neurofibrillary tangles; however a small number of heparan sulfate glycosaminoglycan-positive neurofibrillary tangles did not co-localize with Tau-positive neurofibrillary tangles. In contrast, the heparan sulfate proteoglycan antibody immunostained only the walls of blood vessels and a few senile plaques in Alzheimer's brains and primarily blood vessels in control brains. Heparan sulfate glycosaminoglycan immunostaining was present within neurons, glia, neurofibrillary tangles and senile plaques in Alzheimer's tissue. These results suggest that heparan sulfate-like molecules play an important role in the pathogenesis of the characteristic lesions of Alzheimer's disease and could serve as a marker reflecting early pathological changes.

Aged↗

PubMed1992

Transplantation of fetal cholinergic neurons into the hippocampus attenuates the cognitive and neurochemical deficits induced by AF64A.

The present experiments examined whether transplanted fetal cholinergic neurons would attenuate the behavioral and neurochemical deficits induced by the cholinotoxin AF64A (ethylcholine aziridinium ion). Bilateral injections of AF64A (3 nmol) into the lateral ventricles produced significant learning and memory impairments together with decreases in hippocampal high-affinity choline uptake (HAChU). AF64A-treated rats were impaired on both a standard radial arm maze (RAM) task and a working memory version in which a one-hour delay was imposed between the fourth and fifth arm choices. Transplantation of embryonic day E-17 septal/diagonal band tissue into the hippocampus (HPC) promoted recovery of performance on the standard version of the RAM task. However, this recovery was not observed when the animals were tested on the more difficult delay version of the task. Neurochemical analysis indicated that AF64A produced a significant (31%) decrease in hippocampal HAChU that was attenuated (14%) by transplantation of fetal cholinergic neurons. Histological analysis revealed that the transplants survived and innervated the HPC. There was no apparent relationship between fiber ingrowth into the HPC and behavioral recovery. These data indicate that transplant-induced behavioral recovery may be related to and limited by the cognitive demands of the testing situation. Generalized increases in cholinergic activity, transplant-mediated release of trophic factors, or a combination of both may underlie the behavioral recovery observed in the present studies.

Analysis of Variance↗

PubMed1992

In vitro autoradiography of hippocampal excitatory amino acid binding in aged Fischer 344 rats: relationship to performance on the Morris water maze.

Young and aged Fischer 344 rats were tested on the place and cue versions of the Morris water maze task. Although all of the young animals reached criterion within the 8-day testing period, the aged animals could be divided into two groups on the basis of their performance to criterion: achievers and nonachievers. Upon completion of the water maze testing, the animals were sacrificed, and their brains were processed for in vitro autoradiography of hippocampal excitatory amino acid receptors. Significant differences were found between the young and old rats in the levels of N-methyl-D-aspartate, CPP, kainate, and AMPA binding in subregions of the hippocampus. Despite the age-related decline in hippocampal glutamate receptors, no relationship was observed between the density or distribution of excitatory amino acid receptors and performance on the water maze task in the aged rats.

Aging↗

PubMed1992

beta-Amyloid induces neuritic dystrophy in vitro: similarities with Alzheimer pathology.

beta-Amyloid protein, the major component of neuritic plaques found in Alzheimer's disease, has been implicated as a potential contributor to the disease's progressive neuropathology. We report that within a two day exposure to aggregates of synthetic beta-amyloid peptide, the neurites of cultured rat hippocampal neurons adopt a dystrophic appearance. Observed morphological changes in the neurites include beading, fragmentation, terminal swelling and tortuous growth patterns. The degenerative changes are similar to those observed in neurites associated with neuritic plaques, suggesting that beta-amyloid may induce the neuritic abnormalities of Alzheimer neuropathology.

Alzheimer Disease↗

PubMed1992

Elevated NMDA receptors in parkinsonian striatum.

Dopamine-glutamate interactions contribute to normal striatal function and have been implicated in neurotoxicity at nigrostriatal dopamine (DA) terminals. The present study examined the striata of idiopathic Parkinson's disease (PD) patients and age-matched controls for regional differences in the DA transporter and binding to N-methyl-D-aspartate (NMDA) receptors. [3H]Mazindol labeling of the DA transporter was reduced by 70-80% in the caudate and putamen of PD patients, with reductions being more extensive dorsally than ventrally. In contrast, L-[3H]glutamate binding to NDMA-sensitive receptors was 20-40% higher in PD cases than in controls. These findings raise the possibility that modifications occur within corticostriatal glutamate synapses of PD patients, possibly as a consequence of reduced nigrostriatal DA activity.

Aged↗