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Biomedical subjects

L C Cork

Publications and source records attributed to L C Cork.

At least 55 records · Page 3Linked to original sources
PubMed1990

Development of senile plaques. Relationships of neuronal abnormalities and amyloid deposits.

The evolution of senile plaques and the relationships among neuritic elements, extracellular deposits of the beta-amyloid protein (beta/A4), and vascular beta/A4 are poorly understood. Immunocytochemical methods were used to examine fixed-frozen prefrontal cortices of 14 rhesus monkeys (Macaca mulatta) (14 to 37 years of age) for the presence of abnormal fibers/neurites, alpha 1-antichymotrypsin (alpha-ACT), and beta/A4. Age-associated alterations included abnormal fibers/neurites, presence of beta/A4, and association of alpha-ACT with beta/A4 in plaques and blood vessels. Vascular amyloid was present only in the oldest monkeys. The topographic distribution of abnormal fibers/neurites was mapped with acetylcholinesterase (AChE) histochemistry, and deposits of amyloid were visualized with immunocytochemistry for beta/A4. beta/A4 often was associated with neurites, but many neurites lacked demonstrable beta/A4. Thus in aged monkeys, abnormal neurites may provide one type of focus for the accumulation of the amyloid precursor, which is subsequently abnormally processed to form beta/A4. Our data in rhesus monkeys suggest that fiber and neuritic abnormalities increase with age and that they may precede the majority of beta/A4 deposits; the initial stages of neurite formation and parenchymal amyloid deposits may be independent of the appearance of vascular amyloid; and these processes may be synergistic with advanced age.

Acetylcholinesterase↗
PubMed1990

Hereditary canine spinal muscular atrophy: canine motor neuron disease.

Motor neuron diseases, manifest as weakness and atrophy of skeletal muscles, occur in infancy, childhood, and adult life. Some forms of this disease are inherited. Motor neurons are selectively affected and exhibit cytoskeletal pathology, primarily enlargements of proximal axons by accumulations of transported neurofilaments. A motor neuron disease, hereditary canine spinal muscular atrophy, has been discovered in Brittany spaniels. The disease is inherited as an autosomal dominant characteristic and shows striking clinical and pathological features in common with human motor neuron disease. The availability of this excellent animal model of the human condition has allowed neurobiological investigations of the dynamics of structural and chemical pathologies of vulnerable neurons.

Animals↗
PubMed1990

Aging changes of the rhesus monkey optic nerve.

The authors counted axons in one optic nerve from each of 28 juvenile and aged rhesus monkeys using an automated image analysis system. All nerves were fixed immediately after death and treated identically. Animals ranged in age from 1 1/2 to 29 yr, which correlates with a human age range of 4 1/2-87 yr. Mean axonal number for all specimens was 1,117,859. Large variations in axonal numbers were found, even within a subgroup of ten animals aged 1 1/2-2 yr. Although young nerves had generally more fibers than those from old animals, this difference was not quite statistically significant, translating into a yearly loss of 4319 fibers (0.45% of the total). Age did not have any significant effect on mean axonal diameter.

Aging↗
PubMed1989

Alpha 1-antichymotrypsin is present together with the beta-protein in monkey brain amyloid deposits.

The recent finding that the serine protease inhibitor, alpha 1-antichymotrypsin, is tightly associated with the amyloid deposits in brains of normal aged individuals and patients with Alzheimer's disease [Abraham C. R., Selkoe D. J. and Potter H. (1988) Cell 52, 487-501], suggests a role for this inhibitor in the progressive deposition of brain amyloid in humans. We have used immunocytochemistry to detect alpha 1-antichymotrypsin in the amyloid that accumulates in brains of aged monkeys, a naturally occurring animal model of Alzheimer-like neuropathology. In monkeys of increasing age, the earliest alpha 1-antichymotrypsin immunoreactivity was found in cortical perivascular cells, before the appearance of either Thioflavin S-detectable amyloid deposits or beta-protein reactivity in the vessel walls. Subsequently, amyloid deposits appeared in small meningeal blood vessels and cortical neuritic plaques. The oldest monkeys also showed microvascular amyloid in the cortical gray matter. Amyloid was never seen in white matter. The amyloid deposits in meningeal vessels were always positive for both beta-protein and alpha 1-antichymotrypsin, whereas in the cortex, alpha 1-antichymotrypsin immunoreactivity seemed to appear somewhat later than that of beta-protein. These findings demonstrate that two of the brain amyloid components of human senescence and Alzheimer's disease--the beta-protein and the protease inhibitor alpha 1-antichymotrypsin--are also present in the amyloid deposits of normal aged monkey brain. The extended molecular parallels between normal brain aging and Alzheimer's disease suggest that similar biochemical mechanisms may underlie progressive amyloid deposition in both situations.

Aging↗
PubMed1989

Canine GM2 gangliosidosis: morphological and biochemical analysis.

Beta-hexosaminidase activity and the effects of ganglioside storage on neuronal function were examined in a German shorthair pointer (GSHP) with progressive neurodegenerative signs. Morphologic evidence of neuronal storage and massive accumulation of GM2 ganglioside were present. Beta-hexosaminidase activity in plasma, liver, kidney, and brain, assayed with use of unsulfated fluorogenic substrates, was normal. There was no pathologic accumulation or aberrant localization of phosphorylated neurofilaments in neurons. Activity of cortical neurotransmitter synthesizing enzymes, choline acetyltransferase, and glutamate decarboxylase was unaffected. Ligand binding to carrier sites for choline high affinity uptake identified with [3H]hemicholinium-3 was increased, whereas post-synaptic binding to muscarinic cholinergic ([3H]QNB) and gamma-aminobutyric acid receptors ([3H]muscimol) was reduced.

Animals↗
PubMed1989

Changes in neuronal size and neurotransmitter marker in hereditary canine spinal muscular atrophy.

Hereditary canine spinal muscular atrophy (HCSMA) is a dominantly inherited motor neuron disease that produces muscle weakness and atrophy. Immunocytochemical and computer-imaging morphometric methods were used to compare early changes that occurred in dogs with HCSMA (n = 4) versus controls (n = 2). The size and number of neurons in the ventral horn and the number of motor neurons expressing choline acetyltransferase were quantitated. The density of all ventral horn neurons per micrometer squared in dogs with HCSMA was greater than controls, and there were more small neurons than in controls. Immunocytochemical methods revealed more small cholinergic neurons and fewer large cholinergic neurons in HCSMA than in controls, suggesting growth arrest in HCSMA or a shift in size class from large cholinergic neurons to small ones. The density of cholinergic neurons per micrometer squared was not significantly different between the two groups. Analysis of predicted distributions of cholinergic and noncholinergic neurons revealed that HCSMA cholinergic neurons were smaller and that, in some size classes, fewer neurons expressed choline acetyltransferase. These observations indicate that in HCSMA the motor neuron fails to achieve normal size and/or undergoes atrophy.

Animals↗
PubMed1989

Changes in size of motor axons in hereditary canine spinal muscular atrophy.

Hereditary canine spinal muscular atrophy (HCSMA), a dominantly inherited disorder of motor neurons, has three phenotypes: accelerated, intermediate, and chronic. In the accelerated and intermediate phenotypes, axonal sizes in ventral roots were smaller than in controls. Reductions in axonal size occurred primarily in large axons, and the frequency of small-caliber axons was increased. In HCSMA, nerve fiber shape, i.e., circularity, was reduced, and the relative thickness of the myelin sheath as a function of axonal caliber was decreased. The density of fibers in motor nerves was increased, making it unlikely that a selective loss of large-caliber axons explained the increased frequency of small-caliber axons. These observations suggest that, in HCSMA, changes in axonal size in motor nerves are associated with both growth arrest and axonal atrophy.

Age Factors↗
PubMed1988

Role of C3 in humoral immunity. Defective antibody production in C3-deficient dogs.

Previous studies have shown that animals pharmacologically depleted of C3 have impaired antibody responses. However, such C depletion is neither complete nor sustained, and the C3 cleavage products generated by C3 depletion can both enhance and inhibit the immune response. To clarify the role of C3 in humoral immunity, the antibody response of dogs with genetically determined total deficiency of C3 (C3D) was examined. Serum IgG levels of the C3D animals were within the normal range, but were significantly lower than levels seen in normal controls or C3D heterozygotes. Specific antibody production was defective: the antibody titers of C3D dogs in response to primary intravenous immunization with two different T cell-dependent Ag (sheep E and bacteriophage phi X-174) were markedly reduced when compared to either normal controls or C3D heterozygotes. After secondary immunization with T-dependent Ag, the total antibody titers were normal, but the C3D dogs made proportionately more IgM and less IgG antibody than did either control group. After i.v. immunization with a T cell-independent Ag (DNP-Ficoll), the C3D dogs had reduced levels of IgM and IgG antibody after primary and secondary immunization. Neither i.m. immunization nor the use of a 20-fold increase in Ag dose i.v. could correct the defect seen in the antibody response of C3D dogs. The results herein demonstrate that C3 plays a critical role in the generation of a normal humoral immune response.

Agammaglobulinemia↗
PubMed1988

Multiple transmitter systems contribute neurites to individual senile plaques.

Senile plaques (SP), which consist largely of abnormal neuronal processes in proximity to deposits of amyloid, are a characteristic neuropathological feature of Alzheimer's disease. In lesser numbers, SP also occur in the brains of nondemented aged humans and nonhuman primates. To date, it is not known whether neurites in individual SP derive from neurons of one or several neurotransmitter systems. In aged monkeys, two strategies were used to test the hypothesis that individual SP can contain abnormal neurites arising from multiple neuronal systems. First, immunocytochemical methods were used to identify somatostatin-immunoreactive neurites in plaques, and these sections were subsequently stained with silver to visualize other neurites. Numerous plaques contained both somatostatin-positive and somatostatin-negative (i.e. argyrophilic only) neurites, suggesting that more than one transmitter system contributed neurites to each of these plaques. Second, two-color immunocytochemical techniques showed, in a small percentage of plaques, that cholinergic neurites coexist with neuropeptide Y (NPY)-containing neurites or catecholaminergic neurites. These results suggest that the formation of SP may result from events that involve abnormalities of neuronal processes arising from multiple transmitter systems.

Alzheimer Disease↗
PubMed1988

Neurofilamentous abnormalities in motor neurons in spontaneously occurring animal disorders.

Cytoskeletal proteins have a characteristic distribution within neurons when immunocytochemical techniques are used on conventional paraffin sections. For example, phosphorylated neurofilaments are located within axons but are not normally present in the majority of perikarya of the central nervous system. This pattern can be altered in disease, and neurofilaments that accumulate within perikarya can be phosphorylated inappropriately. To determine whether retained neurofilaments were phosphorylated inappropriately, we used immunocytochemical techniques to examine several diseases in animals in which neurofilaments accumulate within neuronal perikarya. Our investigations of diseases with disparate etiologies show that, whenever neurofilaments are retained within the neuronal perikarya, they are phosphorylated. These results suggest that phosphorylation of neurofilaments in an inappropriate location, i.e. perikarya, may be a nonspecific disease-related response of neurons that can be initiated by a variety of cellular injuries.

Animal Diseases↗
PubMed1988

Neurofibrillary tangles and senile plaques in aged bears.

In aged human beings and in individuals with age-associated degenerative disorders, particularly Alzheimer's disease (AD), neurons develop cytoskeletal abnormalities, including neurofibrillary tangles (NFT) and senile plaques (SP). Senile plaques occur in several nonhuman species; however, NFT, with ultrastructural or immunocytochemical similarities to those occurring in humans, have not been identified in other mammals. In this study of five aged bears (Ursus, 20-30 years of age), we identified cytoskeletal abnormalities similar to those occurring in humans. An aged Asiatic brown bear had NFT, composed of straight 10-16-nm filaments, that were immunoreactive with antibodies directed against: phosphorylated epitopes of neurofilaments (NF); tau; A68 (a protein enriched in AD); and an antigen associated with paired helical filaments (PHF). An aged polar bear had numerous SP; neurites of these plaques were immunoreactive with antibodies against phosphorylated epitopes of NF, but NFT were not identified. These results indicate that nonprimate species develop age-related cytoskeletal abnormalities similar to those occurring in humans. Investigations of the comparative pathology of aged mammals may be useful in elucidating the pathogeneses of these abnormalities.

Alzheimer Disease↗
PubMed1987

Conservation of brain amyloid proteins in aged mammals and humans with Alzheimer's disease.

The formation of clusters of altered axons and dendrites surrounding extracellular deposits of amyloid filaments (neuritic plaques) is a major feature of the human brain in both aging and Alzheimer's disease. A panel of antibodies against amyloid filaments and their constituent proteins from humans with Alzheimer's disease cross-reacted with neuritic plaque and cerebrovascular amyloid deposits in five other species of aged mammals, including monkey, orangutan, polar bear, and dog. Antibodies to a 28-amino acid peptide representing the partial protein sequence of the human amyloid filaments recognized the cortical and microvascular amyloid of all of the aged mammals examined. Plaque amyloid, plaque neurites, and neuronal cell bodies in the aged animals showed no reaction with antibodies to human paired helical filaments. Thus, with age, the amyloid proteins associated with progressive cortical degeneration in Alzheimer's disease are also deposited in the brains of other mammals. Aged primates can provide biochemically relevant models for principal features of Alzheimer's disease: cerebrovascular amyloidosis and neuritic plaque formation.

Aging↗
PubMed1987

Dysfunction and death of neurons in human degenerative neurological diseases and in animal models.

The human neurological disorders--amyotrophic lateral sclerosis (ALS), Parkinson's disease (PD), and Alzheimer's disease (AD)--share certain features: they occur in later stages of adult life; are slowly progressive; and involve specific groups of nerve cells. Different clinical syndromes result from dysfunction and death of these specific groups of neurons. In ALS, patients are weak due to disease of motor neurons in the spinal cord. The clinical features of PD, e.g. slow movements, tremor and rigidity, are attributed, in part, to degeneration of dopaminergic neurons of the substantia nigra. Impairments of cognition and memory in AD result from disease of neurons in a number of regions, including brainstem, basal forebrain, amygdala, hippocampus, and neocortex. In each of these diseases, affected neurons exhibit abnormalities of the neuronal cytoskeleton: in ALS, neurofilaments accumulate and distend proximal motor axons; in PD, nigral perikarya show Lewy bodies-intracytoplasmic inclusions containing neurofilament antigens; in AD, neurons develop neurofibrillary tangles, Hirano bodies, granulovacuolar degeneration and filament-filled neurites in plaques. Certain features of ALS, PD and AD are recapitulated in animal models, three of which are described in this review. Hereditary canine spinal muscular atrophy (HCSMA), a dominantly inherited motor neuron disease, shows many clinical and pathological features in common with ALS, including weakness, muscle atrophy, neurofilamentous swellings of proximal axons, impaired transport of neurofilament proteins, and degeneration of motor neurons. In primates, intoxication with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) produces a parkinsonian syndrome due to injury of nigral dopaminergic neurons and associated denervation of the striatum. Finally, aged macaques exhibit memory deficits, and their cerebral cortices show senile plaques and filament-filled neurites derived from a variety of transmitter-specific populations of nerve cells. In human diseases, the causes and mechanisms leading to dysfunction and death of nerve cells are unknown. Investigators have begun using a variety of techniques derived from neurobiology to study animal models in an effort to clarify the mechanisms, evolutions, and consequences of structural-chemical abnormalities occurring in different neuronal systems implicated in human disease. Understanding such processes in these models should provide important new insights into the pathogeneses of similar processes occurring in ALS, PD and AD.

Animals↗
PubMed1987

Establishment of central nervous system infection by canine distemper virus: breach of the blood-brain barrier and facilitation by antiviral antibody.

Morphologic, immunologic and virologic data implicating antiviral antibody in promoting entry of canine distemper virus (CDV) into brain and reticuloendothelial tissues are reviewed. Infection of central nervous system (CNS) endothelium precedes invasion of virus-positive and -negative leukocytes into Virchow-Robin spaces and central nervous system (CNS) parenchyma by 1-3 days. Platelets are implicated in initiation of endothelial infection in that: CDV-infected dogs are thrombocytopenic; platelets from CDV-infected dogs contain IgG-virus complexes on their plasma membranes; platelet microthrombi were observed adjacent to foci of endothelial infection, and; CDV-susceptible ferrets rendered thrombocytopenic by antiplatelet antibody exhibit delayed viral entry into CNS tissues. Renal glomerular-bound IgG, IgM and occasionally CDV antigen were demonstrated in CDV-infected dogs by immunocytochemical techniques. Distemper-infected dogs with inherited C3 deficiency exhibited enhanced renal glomerular disease associated chiefly with deposition of IgM in mesengial regions vs. their homozygous normal CDV-infected littermates. Direct infusion of virus-positive leukocytes, plasma and platelets into the CNS capillary bed via the right carotid artery should establish the primacy of each in the initiation of CNS vascular endothelial infection by CDV.

Animals↗
PubMed1987

Animal models of degenerative neurological disease.

Amyotrophic lateral sclerosis (ALS), Parkinson's disease (PD), and Alzheimer's disease (AD) are human neurological disorders which occur in middle and late life. These three diseases share certain features: they are slowly progressive; transmitter-specific groups of neurons are selectively affected by disease processes; and affected nerve cells exhibit cytoskeletal pathology. The causes and mechanisms of cell injury are unknown, and there are no treatments which directly affect the disease process. Dysfunction and death of these specific cell groups account for different clinical syndromes. In ALS, patients become paralyzed, at-risk cholinergic motor neurons in the spinal cord develop neurofilamentous swellings of proximal axons, and distal axons atrophy. In PD, affected individuals show slowed movements, tremor, and rigidity. These clinical findings are attributed to regeneration of dopaminergic neurons of the substantia nigra, a cell group showing abnormal accumulations of neurofilament antigens in the form of Lewy bodies. In AD, patients develop dementia (a syndrome of cognitive and memory impairment), and cholinergic neurons of the basal forebrain and certain other populations of nerve cells develop abnormalities of the cytoskeleton. These include perikaryal neurofibrillary tangles and enlarged distal axons which appear as neurites in senile plaques. Certain features of ALS, PD, and AD are recapitulated in three animal models described in this review. Hereditary Canine Spinal Muscular Atrophy (HCSMA), a dominantly inherited motor neuron disease, shows many clinical and pathological features in common with ALS. Affected dogs are clinically weak, have denervation atrophy of muscles, and develop neurofilamentous swellings of proximal axons, atrophy of distal axons, and degeneration of motor neurons. These abnormalities of axonal caliber are associated with impaired transport of the neurofilament triplet proteins and a maldistribution of phosphorylated neurofilaments. Intoxication of macaques with 1-methyl-4-]henyl-1,2,3,6,tetrahydropyridine (MPTP) produces a Parkinsonian syndrome due to selective injury of dopaminergic neurons in the substantia nigra and associated denervation of the striatum. Finally, aged rhesus monkeys (older than 23 years of age) show cognitive and memory deficits and exhibit senile plaques whose neurites are derived from cholinergic and other transmitter systems. Although these macaques do not have AD, they do provide a model for examining the relationships between age-associated cognitive deficits and pathological changes occurring in certain transmitter systems of primates.(ABSTRACT TRUNCATED AT 400 WORDS)

Aging↗
PubMed1986

Sequestration of tubulin in neurons in Alzheimer's disease.

In Alzheimer's disease (AD), a variety of populations of neurons exhibits cytoskeletal abnormalities, including neurofibrillary tangles (NFT) in perikarya, Hirano bodies in dendrites and filament-distended axons/terminals/dendrites (neurites) in senile plaques. Some nerve cells, particularly pyramidal neurons of the hippocampus, also develop Hirano bodies (paracrystalline arrays of actin) and granulovacuolar degeneration (GVD; granular inclusions in cytoplasmic vacuoles). Since abnormalities of cytoskeletal elements have been implicated in the formation of NFT, neurites and Hirano bodies, the present study was designed to determine whether GVD also may represent a type of cytoskeletal pathology. Sections of hippocampus from controls and from individuals with AD were stained by immunocytochemical methods using monoclonal and polyclonal antibodies directed against a variety of cytoskeletal antigens. Granules of GVD contained tubulin-like immunoreactivity and absorption with purified tubulin abolished staining. Other antigens were not demonstrated in granules when antibodies directed against other cytoskeletal antigens were used. The observation of sequestration of tubulin in granules is consistent with the concept that abnormalities of the neuronal cytoskeleton are an important part of the cellular pathology of AD.

Adult↗
PubMed1986

Structural correlates of physiological abnormalities in beta, beta'-iminodipropionitrile.

beta, beta'-Iminodipropionitrile (IDPN) produces neurofilamentous giant axonal swellings in proximal internodes of large myelinated axons. Secondary demyelinative changes result from the production of these axonal enlargements. Electrophysiological studies have demonstrated profound alterations in the electrical properties of motor neurons (MN) within the spinal cord. On the basis of intracellular recordings, it has been suggested that electrical contacts may exist between swollen axons and neighboring MN. In addition, the possibility remained that synaptic contacts develop on demyelinated axonal swellings. In the present study, we report the lack of either synapses on demyelinated axonal swellings or direct electrical contacts between neighboring MN. Axonal swellings are surrounded by attenuated processes of glial cells (probably fibrillary astrocytes), a finding discussed in terms of its possible role in the production of ephaptic transmission. There was considerable variation in the degree of axonal enlargements and in the extent of secondary (passive and active) demyelination. It is suggested that these morphological changes may represent structural correlates of some electrophysiological alterations observed in IDPN neuropathy.

Animals↗