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Results for “selective vulnerability”

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PubMed1998

Somatic mosaicism of the CAG repeat expansion in spinocerebellar ataxia type 3/Machado-Joseph disease.

An expanded and unstable CAG repeat in the coding region of the MJD1 gene is the mutation responsible for spinocerebellar ataxia 3/Machado-Joseph disease. In order to determine whether there was a higher degree of instability in affected regions, the size of the expanded CAG repeat was analyzed in different regions of the central nervous system, in two unrelated SCA3/MJD patients. The degree of somatic mosaicism was quantified and compared to that in a SCA1 patient. Instability of the expanded CAG repeat was observed in peripheral tissues as well as in CNS of the three patients, but there was no correlation between the degree of mosaicism and the selective vulnerability of CNS structures. As in the other diseases caused by expanded CAG repeats, a lower degree of mosaicism was found in the cerebellar cortex of both SCA1 and SCA3/MJD patients, probably reflecting specific properties of this structure. In SCA3/MJD, the degree of mosaicism seemed to correlate with age at death rather than with the size of the expanded CAG repeat. Finally, somatic instability was more pronounced in SCA1 than in SCA3/MJD patients.

Adult↗

PubMed1992

Aluminium accumulation, beta-amyloid deposition and neurofibrillary changes in the central nervous system.

Deposition of beta-amyloid and the formation of neurofibrillary tangles (NFTs) are central to the aetiopathogenesis of Alzheimer's disease (AD). The possible effects of aluminium on these processes have been investigated in patients with renal failure who are exposed chronically to high blood levels of aluminium. Focal accumulation of aluminium was observed in neurons with high densities of transferrin receptors, indicating transferrin-mediated uptake, in regions such as cortex and hippocampus which are selectively vulnerable in AD. Increased staining for the beta-amyloid precursor protein (APP) in cortical pyramidal neurons was evident in the majority of renal patients and immature senile plaques were present in 30% of cases, suggesting that aluminium may induce or accelerate beta-amyloid deposition. The absence of neurofibrillary changes in this group of renal patients indicates that aluminium does not directly cause the formation of NFTs. The brain aluminium content was not raised in neuropathologically assessed cases of AD and we have been unable to confirm claims of defective transferrin binding in this disorder. If aluminium contributes to the development of sporadic AD, it must do so indirectly, perhaps via effects on the synthesis or metabolism of APP, or by contributing generally to the age-related attrition of neurons and thus reducing the threshold for deficits produced by more specific disease-related processes.

Aluminum↗

PubMed2005

Role of Folbp1 in the regional regulation of apoptosis and cell proliferation in the developing neural tube and craniofacies.

Folic acid is essential for many cellular reactions, including synthesis of nucleotides and regulation of cell cycle. Folic acid-binding protein one (Folbp1), a membrane-bounded protein, is the primary mediator of folic acid transport. Mice deficient in Folbp1 gene die in utero with multiple malformations, including severe exencephaly and craniofacial defects. Fusion of the neural tube and craniofacies require precisely regulated interactions of apoptosis, cell proliferation, and differentiation. To understand the role of Folbp1 in regulating the fusions of these primordia, levels of dead and proliferating precursor cells from Folbp1 embryos were quantified before the fusion processes. Massive apoptosis was detected in the Folbp1-/- defective tissues, with Bax and activated caspase-3 distributed evenly across the apico-basal axis of the lateral neural plate. 5-Bromodeoxyuridine (BrdU) and PCNA labeling assays revealed a reduced cell proliferation as well. However, telomerase activity was unaltered, arguing against telomere shortening and consequently, chromosomal instability, as the cause of the apoptosis. Notably, Islet-1 and 2H3 immunohistochemistry demonstrated the presence of differentiating neuronal cells, albeit in decreased numbers. Interestingly, Folbp1-/- embryos also elaborated novel neural structures that sprouted orthogonally from the embryonic neuraxis. Assays on the defective craniofacies exhibited similar phenomena, suggesting the neural crest precursor population that gives rise to both these structures is selectively vulnerable to Folbp1 inactivation. The results demonstrate a prominent role of Folbp1 in the regional regulation of apoptosis and cell proliferation that underlies the aberrant neural tube and craniofacial defects.

Animals↗

PubMed2003

Pathogenesis of clinical signs in recessive ataxia with saccadic intrusions.

We describe a family of Slovenian descent with progressive ataxia, corticospinal signs, axonal sensorimotor neuropathy, and disruption of visual fixation by saccadic intrusions. Chromosome mapping indicated a mutation on 1p36, and this recessive disorder has been designated spinocerebellar ataxia with saccadic intrusions. Affected patients showed overshooting horizontal saccades, macrosaccadic oscillations, and increased velocity of larger saccades; other eye movements were normal. Slowed conduction in axons that are selectively vulnerable to the molecular defect could explain both the sensorimotor neuropathy and the saccadic disorder, which would be caused by delayed feedback control because of slow conduction in cerebellar parallel fibers.

Adult↗

PubMed2004

Metabolic and neuropsychological phenotype in women heterozygous for ornithine transcarbamylase deficiency.

We compared neurocognitive indices with clinical status, mutation analysis, and urea synthetic capacity in 19 women heterozygous for ornithine transcarbamylase deficiency. Although as a group, these women had average IQ scores, they displayed a specific neuropsychological phenotype with significant strengths in verbal intelligence, verbal learning, verbal memory, and reading, and significant weaknesses in fine motor dexterity/speed and nonsignificant weaknesses in nonverbal intelligence, visual memory, attention/executive skills, and math. This suggests selective vulnerability of white matter and better preservation of gray matter. When the group was divided into symptomatic and asymptomatic subgroups, based on either clinical history or residual urea synthetic capacity, the asymptomatic subgroup outperformed the symptomatic subgroup on all tested domains of neuropsychological functioning. Furthermore, the amount of residual urea synthetic capacity was predictive of several end point cognitive measures. There was no correlation between neonatal versus late-onset mutation or between normal or abnormal allopurinol challenge and neuropsychological outcome. In sum, we identified a specific metabolic and neurocognitive phenotype in women heterozygous for ornithine transcarbamylase deficiency. The findings support the importance of maintaining meticulous metabolic control in children with urea cycle disorders, because even mildly symptomatic subjects demonstrate cognitive deficits.

Adult↗

PubMed2004

Ataxin-7 aggregation and ubiquitination in infantile SCA7 with 180 CAG repeats.

Extremely long (>150) CAG repeats are often used to create models of polyglutamine diseases yet are very rare in humans where they manifest as pediatric multisystem syndromes of little specificity. Here, we describe an infant with 180 CAG repeats in the spinocerebellar ataxia type 7 gene and focus on systemic ataxin-7 aggregation. This was found in many organs, including the cardiovascular system. In the brain, the hippocampus emerged as a principal site of ataxin-7 aggregation without cell loss. We note differential ubiquitination of aggregates and discuss how this may relate to selective vulnerability.

Ataxin-7↗

PubMed2005

Model-guided microarray implicates the retromer complex in Alzheimer's disease.

Although, in principle, gene expression profiling is well suited to isolate pathogenic molecules associated with Alzheimer's disease (AD), techniques such as microarray present unique analytic challenges when applied to disorders of the brain. Here, we addressed these challenges by first constructing a spatiotemporal model, predicting a priori how a molecule underlying AD should behave anatomically and over time. Then, guided by the model, we generated gene expression profiles of the entorhinal cortex and the dentate gyrus, harvested from the brains of AD cases and controls covering a broad age span. Among many expression differences, the retromer trafficking molecule VPS35 best conformed to the spatiotemporal model of AD. Western blotting confirmed the abnormality, establishing that VPS35 levels are reduced in brain regions selectively vulnerable to AD. VPS35 is the core molecule of the retromer trafficking complex and further analysis revealed that VPS26, another member of the complex, is also downregulated in AD. Cell culture studies, using small interfering RNAs or expression vectors, showed that VPS35 regulates Abeta peptide levels, establishing the relevance of the retromer complex to AD. Reviewing our findings in the context of recent studies suggests how downregulation of the retromer complex in AD can regulate local levels of Abeta peptide.

Adult↗

PubMed1985

Amyotrophic lateral sclerosis: Part 2. Etiopathogenesis.

The pathogenesis of the motor neuronal degeneration in amyotrophic lateral sclerosis (ALS) is unclear, though several possible etiological factors are currently being investigated. A unifying hypothesis will have to explain the diverse geographical occurrence, clinical features, and selective vulnerability and relative resistance of different neuronal populations in the disease. It is possible that different biochemical defects underlie this diversity, or alternatively that the many factors incriminated in the etiology may act upon an underlying genetic-biochemical abnormality to trigger premature neuronal death. Viruses, metals, endogenous toxins, immune dysfunction, endocrine abnormalities, impaired DNA repair, altered axonal transport, and trauma have all been etiologically linked with ALS, but convincing research evidence of a causative role for any of these factors is yet to be demonstrated.

Aged↗

PubMed1985

Regional glucose utilization and blood flow following graded forebrain ischemia in the rat: correlation with neuropathology.

Regional patterns of cerebral glucose utilization (rCMRglc) and blood flow (rCBF) were examined in the early recovery period following transient forebrain ischemia in order to correlate early postischemic physiological events with regionally selective patterns of ischemic neuropathology. Wistar rats were subjected to 30 or 60 minutes of graded forebrain ischemia by a method combining unilateral occlusion of the common carotid artery with moderate elevation of intracranial pressure and mild hypotension; this procedure results in a high-grade ischemic deficit affecting chiefly the lateral neocortex, striatum, and hippocampus ipsilateral to the carotid occlusion. Simultaneous measurements of rCMRglc and rCBF made in regional tissue samples after 2 and 4 hours of postischemic recirculation using a double-tracer radioisotopic strategy revealed a disproportionately high level of glucose metabolism relative to blood flow in the early postischemic striatum, owing to the resumption of nearly normal rCMRglc in the face of depressed flow. In contrast, the neocortex, which had been equally ischemic, showed parallel depressions of both metabolism and blood flow during early recovery. Light microscopy at 4 and 8 hours after recovery revealed the striatum to be the predominant locus of ischemic neuronal alterations, whereas neocortical lesions were much less prominent in extent and severity at this time. The resumption of normal levels of metabolism in the setting of a disproportionate depression of rCBF in the early postischemic period may accentuate the process of neuronal injury initiated by ischemia and may contribute to the genesis of neuronal necrosis in "selectively vulnerable" areas of the forebrain.

Animals↗

PubMed1986

Neuropeptide Y immunoreactivity is reduced in cerebral cortex in Alzheimer's disease.

Neuropeptide Y is a 36-amino acid peptide that is found in high concentrations in cerebral cortex and is contained in cortical neurons. We measured concentrations of this peptide in postmortem tissue from patients with Alzheimer's disease and controls using a sensitive and specific radioimmunoassay. High-performance liquid chromatography showed that more than 95% of immunoreactivity co-migrated with synthetic standards in both Alzheimer's disease and control frontal cortex. Significant reductions in neuropeptide Y-like immunoreactivity were found in eleven cortical regions, the hippocampus, and the locus ceruleus. The regions particularly affected included the temporal lobe, frontal lobe, and occipital cortex. As neuropeptide Y is co-localized with somatostatin in a considerable proportion of cortical neurons, the loss of immunoreactivity may in part reflect degeneration of these neurons. Further study of the selective vulnerability of these neurons in Alzheimer's disease cortex may provide clues to the nature of the underlying disease process.

Aged↗

PubMed1986

A postmortem study of amino acid neurotransmitters in Alzheimer's disease.

Concentrations of putative neurotransmitter amino acids were measured in postmortem brains from 10 patients with Alzheimer's disease and 10 controls. Glutamate, aspartate, taurine, gamma-aminobutyric acid (GABA), and alanine levels were examined in 9 cortical regions, hippocampus, thalamus, and basal ganglia using high-performance liquid chromatography with electrochemical detection. There were no significant alterations in aspartate, taurine, or alanine levels in any of the regions examined. Widespread significant reductions in cortical GABA concentrations were observed in the Alzheimer's brains, with the largest decreases in the temporal lobe. Overall values for glutamate concentrations in temporal and frontal cortices showed a significant 12% reduction in Alzheimer's brains, but the only individual cortical region showing a significant reduction in glutamate was the inferior temporal gyrus. These results suggest that gamma-aminobutyric acidergic neurons in Alzheimer's cerebral cortex may be selectively vulnerable to the disease process.

Aged↗

PubMed1987

Cholinergic-dependent cognitive deficits in Parkinson's disease.

In a double-blind cross-over study, the effects of a subthreshold dose of scopolamine (0.25 mg) on memory were compared in 32 control subjects and 32 parkinsonian patients who were without any sign of intellectual and mnemic impairment. Although the scores of the controls in the memory test battery showed no deterioration after the administration of scopolamine, the same dose resulted in significantly reduced memory performance in parkinsonian patients in two tests which involved the recognition of meaningless drawings. The selective vulnerability of parkinsonian subjects without cognitive impairment to a subthreshold dose of scopolamine suggests the existence of an underlying alteration of central cholinergic transmission. The neuropsychological findings in our study agree with postmortem biochemical data, which showed decreased cortical choline acetyltransferase activity in all parkinsonian patients, suggesting the existence of neuronal compensation in parkinsonian patients who are without cognitive impairment.

Acetylcholine↗

PubMed1987

Acute ischemia causes axonal stasis, swelling, attenuation, and secondary demyelination.

Microsphere embolization of rat sciatic nerve capillaries results in a central fascicular ischemic core. Twenty-four hours after microembolization, the pathological alterations along the length of 55 myelinated fibers were reconstructed by computer imaging of 2,000 serial semi-thin epoxy sections of a tissue block that extended from just above and into an ischemic core. From proximal to distal, the typical sequence of pathological alterations was: normal----swollen dark axons + thin myelin or demyelination----attenuated axons----axon cytolysis (46 fibers) or normal axons (9 fibers). Because organelle accumulation and axonal swelling were the earliest and most proximal pathological lesions, we infer that regional hypoxia causes axonal stasis as a primary event. Demyelination was found in fibers showing swollen dark and attenuated axons. These findings suggest that axons are selectively vulnerable to acute ischemia and that, depending on severity, the fibers either undergo axonal degeneration or transitory structural alterations without axonal degeneration, the latter consisting of axonal changes and secondary demyelination.

Animals↗

PubMed1990

The effect of mild hyperthermia and hypothermia on brain damage following 5, 10, and 15 minutes of forebrain ischemia.

The present study examines the effects of mild hypothermia and hyperthermia on the density and distribution of ischemic brain damage, and compares these effects to those induced by variations in the duration of ischemia. Body temperatures were maintained at 35 degrees C, 37 degrees C, and 39 degrees C, before, during, and after ischemia, and brain temperatures were held at similar values with a technique that in preliminary experiments proved to avoid intracerebral temperature gradients or overheating of surface structures. In all animals, brain damage was assessed by histopathological analysis of perfusion-fixed brains after six to seven days of recovery. Our results confirm previous findings showing that a decrease in temperature of only 2 degrees C significantly reduces damage to several selectively vulnerable neuronal populations. The results also showed that an increase in temperature of 2 degrees C significantly enhances brain damage. In general, a rise in temperature had effects similar to an increased duration of the ischemia. In some areas, such as the CA1-subiculum sectors of the hippocampus, temperature and ischemic duration altered damage in a gradual manner, but in others, such as the caudoputamen, there was a steplike change from virtually no to virtually complete damage. In some areas, the effects of hypothermia and hyperthermia appeared symmetrical around the normal temperature of 37 degrees C. Hyperthermia had some seemingly "specific" effects, however, notably the tendency to induce pannecrosis ("infarction") in the neocortex and caudoputamen, and to cause damage to the substantia nigra pars reticulata. The results underscore the potentially devastating effects of fever in patients with cerebrovascular disease.

Animals↗

PubMed1993

The pathogenesis of superficial siderosis of the central nervous system.

In advanced cases of superficial siderosis of the human central nervous system, the clinical triad of hearing loss, cerebellar ataxia, and myelopathy permits the diagnosis at the bedside, and magnetic resonance imaging readily confirms the hemosiderin deposits in brainstem, cerebellum, and spinal cord. To study the pathogenesis of this condition and explain the selective vulnerability of the cerebellum, experimental siderosis was induced in rabbits by the repeated intracisternal injection of autologous red blood cells. The earliest cellular response in the cerebellar molecular layer was hyperplasia and hypertrophy of microglia as displayed by immunocytochemistry for ferritin. Microglia also contained iron, but ferritin biosynthesis appeared to proceed without commensurate iron accumulation. This early apoferritin response probably occurred due to the presence of heme, rather than iron, in the cerebrospinal fluid and subpial tissue. Ferritin biosynthesis is accelerated when the ferritin repressor protein is dissociated from ferritin messenger ribonucleic acid. A specific antiserum localized ferritin repressor protein predominantly to astrocytes including Bergmann glia. It is proposed that abundance and proximity of ferritin repressor protein--immunoreactive Bergmann glia and ferritin-containing microglia in the cerebellar molecular layer permit prompt cellular interaction in the conversion of heme to ferritin and ultimately hemosiderin.

Animals↗

PubMed1998

Cognitive, neuroimaging, and pathological studies in a patient with Pick's disease.

We conducted cognitive, imaging, and neuropathological studies on a patient with Pick's disease. The patient was impaired at interpreting sentences with complex grammatical constructions, differing significantly from control subjects and patients with Alzheimer's disease (AD). Evaluation of regional brain functioning at rest, with positron emission tomography, revealed reduced left frontal activity compared with control subjects and AD patients. Autopsy demonstrated the classic pathology of Pick's disease, including massive neuron loss and gliosis in the frontal and cingulate cortex as well as numerous tau-positive hippocampal Pick bodies. The abnormal tau proteins were phosphorylated at the same amino acid residues as AD paired helical filament tau (PHFtau), but they exhibited a unique migration profile on western blot. Our observations support the hypothesis that a distinct variety of hyperphosphorylated tau in Pick's disease compromises the long-term viability of selectively vulnerable populations of neurons in frontal cortices that contribute to sentence processing.

Aged↗

PubMed1998

Frontotemporal dementia: neuropil spheroids and presynaptic terminal degeneration.

We compared the neuropathological changes of 6 patients with clinically diagnosed lobar dementia. In the 4 patients with histopathology consistent with frontotemporal dementia (FTD), moderate neuronal loss contrasted with marked cortical and subcortical gliosis. We found silver-positive, carbohydrate-rich, spheroidal enlargements of presynaptic terminals within the neuropil of specific central nervous system regions. The spheroids were immunopositive for the cytoskeletal proteins tau, the high molecular weight neurofilament subunit (NF-H), and beta-tubulin. No abnormal tau phosphorylation and only rare ubiquitin immunoreactivity were detected in these structures. Carbohydrate modifications, including advanced glycation end products within the spheroid matrix, were confirmed by lectin binding, and by anti-pentosidine immunoreactivity, an indicator of oxidative stress. Ultrastructurally, the spheroids consisted of unmyelinated, membrane-enclosed structures filled with randomly arrayed pairs of filaments, approximately 8 to 10 nm in diameter, that were sparsely labeled with antibodies to unmodified tau (T14) and NF-H. Despite clinical overlap, the central nervous systems of our FTD patients are distinguishable from those of other patients with other lobar dementias, including Pick's disease and corticobasal degeneration, by the absence of abnormally phosphorylated neuronal or glial tau inclusions. The neuropil spheroids are dystrophic changes of certain selectively vulnerable presynaptic terminals, suggesting a retrograde degenerative process in FTD.

Adult↗

PubMed1998

Enhanced oxygen radical production in a transgenic mouse model of familial amyotrophic lateral sclerosis.

Mutations of the SOD1 gene encoding copper/zinc superoxide dismutase (CuZnSOD) cause an inherited form of amyotrophic lateral sclerosis. When expressed in transgenic mice, the same SOD1 mutations cause progressive loss of spinal motor neurons with consequent paralysis and death. In vitro biochemical studies indicate that SOD1 mutations enhance free radical generation by the mutant enzyme. We investigated those findings in vivo by using a novel, brain-permeable spin trap, azulenyl nitrone. Reaction of azulenyl nitrone with a free radical forms a nitroxide adduct that then fragments to yield the corresponding azulenyl aldehyde. Transgenic mice expressing mutant SOD1-G93A show enhanced free radical content in spinal cord but not brain. This correlates with tissue-specific differences in the level of transgene expression. In spinal cord, the increase in free radical content is in direct proportion to the age-dependent increase in mutant human CuZnSOD expression. This increase precedes motor neuron degeneration. The higher level of human CuZnSOD expression seen in spinal cord compared with brain, and consequent difference in free radical generation, provides a basis for understanding the selective vulnerability of the spinal cord in this disease model.

Aging↗