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Biomedical subjects

A B Scheibel

Publications and source records attributed to A B Scheibel.

At least 19 recordsLinked to original sources
PubMed1992

Fiber composition of the human corpus callosum.

The densities of fibers of different sizes were calculated in ten regions of the corpus callosum of twenty human brains (ten females, ten males). Light microscopic examination revealed a consistent pattern of regional differentiation of fiber types in the corpus callosum. Thin fibers are most dense in the anterior corpus callosum (genu), and decrease in density posteriorly towards the posterior midbody, where they reach a minimum. Towards the posterior corpus callosum (splenium), the density of thin fibers increases again, but in the posterior pole of the callosum the density decreases locally. Large-diameter fibers show a pattern complementary to that of thin fibers, having a peak of density in the posterior midbody and a local increase of density in the posterior pole of the corpus callosum. Across subjects, the overall density of callosal fibers had no significant correlation with callosal area and an increased callosal area indicated an increased total number of fibers crossing through. Considering different fiber sizes, this was only true for small diameter fibers, whose large majority is believed to interconnect association cortex. No sex differences in fiber composition of the corpus callosum were found.

Adult↗
PubMed1992

Individual differences in brain asymmetries and fiber composition in the human corpus callosum.

There have been several recent reports concerning individual differences in the gross morphometry of the human corpus callosum. However, no studies exist on individual differences in the fiber composition of the corpus callosum. Here we report for the first time the relation of fiber composition in specific callosal segments (as seen in light microscopy) to anatomical asymmetries in language-gifted cortex, as a function of sex. We found a significant negative correlation between Sylvian fissure asymmetries and the total numbers of fibers in the isthmus of males, and in the anterior splenium of females. In addition, a population of relatively large fibers (between 1 micron and 3 microns in diameter) in the isthmus showed a strong negative correlation with perisylvian asymmetries only in males. These findings suggest a sex-dependent, pathway-specific decrease in interhemispheric connectivity with increasing lateralization.

Adult↗
PubMed1992

Immunohistochemical analysis of the basal forebrain in Alzheimer's disease.

An immunohistochemical analysis utilizing antibodies to glial fibrillary acid protein (GFAP), microglia, beta-amyloid, amyloid P-component, neurofibrillary tangles (NFT), and microtubule associated protein-tau (MAP-tau) was performed on the cholinergic basal forebrain in Alzheimer's disease (AD). This severely compromised system, which includes the nucleus basalis of Meynert, is largely responsible for the massive loss of cortical and subcortical cholinergic innervation in the diseased state. Our study juxtaposes the basal forebrain immunohistopathology to the hippocampus, amygdala, and entorhinal cortex in AD. Key findings include a progressive degeneration of these cholinergic neurons characterized by the formation of immunoreactively atypical NFT, the loss of intraneuronal lipofuscin, a lack of senile plaque and beta-amyloid deposition within the basal forebrain, and end-stage gliosis without residual extracellular NFT. These structural and compositional differences suggest a unique pathogenesis of the basal forebrain separate from other cortical regions in AD.

Acetylcholinesterase↗
PubMed1992

Morphometry of the Sylvian fissure and the corpus callosum, with emphasis on sex differences.

The relationship between anatomical asymmetries in the perisylvian region and the sizes of different regions of the corpus callosum was investigated post-mortem in 40 brains of right-handed hospital admissions (20 males, 20 females) with no cortical involvement. There were no sex differences either in anatomical asymmetries or in regional size of the callosum. There was a negative correlation between the absolute value of Sylvian fissure (planum temporale) asymmetries and the size of the isthmus in males but not in females. Further, there was a significant negative correlation between the size of the Sylvian fissure (or planum temporale) and the size of the callosal mid-body in males but not in females. There was no correlation between the asymmetry of the planum temporale magnitude of left-right and total size of the planum (left+right). These findings constrain theories about the ontogenesis of hemispheric specialization through changes in callosal connectivity and about sex differences in interhemispheric organization.

Adult↗
PubMed1991

Hippocampal pyramidal cell disarray in schizophrenia as a bilateral phenomenon.

In a continuing quantitative study of hippocampal cell orientation in schizophrenic subjects and nonschizophrenic control subjects, a pattern of right hemispheric cell disorganization in schizophrenic subjects, as robust as that previously described in the left hemisphere, was shown. The study was based on tissue from 11 schizophrenic and seven approximately age-matched control subjects from a Veterans Administration Medical Center. Using a new measuring technique that proved complementary and superior to the method formerly used, we determined the axes of orientation for approximately 10,800 neurons. A significant difference in cell disorganization was found between schizophrenic and control subjects. From separate analyses of the interface zones among the various hippocampal cell sectors, this difference was found to be significant at the interfaces between cornu ammonis zones 1 and 2 and zones 2 and 3. Analysis of the pattern of disorganization numbers suggests a bimodal distribution in which the cell orientation values of one group of schizophrenic subjects overlap those of the nonschizophrenic control group, while the cell orientation values of a second group significantly exceed those of the control population. Although some recent studies have suggested that schizophrenia may be related exclusively to the left hemisphere, the results of this study indicate that schizophrenia-related structural changes involve the right hemisphere as well. Thus, schizophrenia may be a bilateral rather than unilateral disorder.

Adult↗
PubMed1991

Are complex partial seizures a sequela of temporal lobe dysgenesis?

1. Complex partial seizures are closely associated with a group of discrete neuropathological entities which include focal lesions (such as hamartomas and heterotopias) and small vascular lesions, all of which are generally considered to have been present at birth. 2. The pathological change most frequently found in patients with temporal lobe epilepsy is mesiotemporal sclerosis. Although this pathological alteration in subicular and hippocampal structures has been attributed to any one of a number of perinatal or postnatal insults, we suggest that it also may represent a sequela of disturbed neuroembryogenesis. 3. We suggest that many, perhaps most, cases of temporal lobe epilepsy may resemble other major disorders of cognition and behavior (such as schizophrenia) in representing the sequelae of temporal lobe dysgenesis.

Animals↗
PubMed1989

Immunodetection of the amyloid P component in Alzheimer's disease.

Amyloid P component (AP), a plasma constituent normally not found in brain parenchyma, has been immunohistochemically determined in brains from patients with Alzheimer's disease (AD). Tissue came from 11 clinically diagnosed and neuropathologically verified AD patients and from 6 normal aged controls. Positive labeling for AP was observed in amyloidotic blood vessels, senile plaques (SP) and neurofibrillary tangles (NFT). The immunoreactivity was specific for these AD-associated lesions and clearly revealed their morphological appearance. Affected blood vessels appeared to be mainly of the arteriolar type and were labeled abluminally in short segments. SP constituents such as amyloid fibrils, amyloid core and degenerative axonal and dendritic processes were positive for AP antiserum; the morphology and distribution of immunoreactive SP corresponded to previous descriptions. Labeling of NFT revealed the morphology of paired helical and straight filaments. In all cerebral areas studied, tangle-bearing neurons were immunoreactive to AP antiserum, suggesting that AP is involved in early cellular development of NFT. Given the large molecular weight of AP (about 220,000), these results point to a potential impairment of the blood-brain barrier in AD. Since AP is always present in systemic amyloidosis, its detection in cerebral amyloidosis associated with AD may suggest mechanisms common to the two disorders.

Aged↗
PubMed1989

The postnatal development of the motor speech area: a preliminary study.

This preliminary study follows the maturation of motor speech areas and their adjacent orofacial motor zones in the right and left hemispheres of the human infant from 3 months to 72 months of age. Quantitative studies of basilar dendrite patterns of layer 5 cortical pyramids are reported in 17 age-graded subjects. The sequence of developmental changes is characterized by early (3 month) prominence of orofacial motor zones over motor speech areas and of the right hemisphere over the left as expressed in total basilar dendritic length and the length of proximal order dendritic segments. The complex series of changes which follow appear to involve increase in number and marked increase in length of the developing distal order segments and possible shortening of the proximal segments. During a variable sequence of apparent growth spurts and resorptions, dendrite arborizations of the motor speech areas overtake and exceed those of orofacial musculature and the total length of dendrite systems on the left finally exceeds those on the right, although even in the most mature group, (42-72 months), distal segment length in the right motor speech area still exceeds that of the left. The early structural primacy of right-sided dendrite systems and the progressive shift to left-sided primacy is considered in the light of the presence of a long phylogenetic and ontogenetic history of gross anatomical asymmetry favoring the left side. The possibility that developmental patterns of the cortical macroenvironment and microenvironment may be dissociated with the microenvironment depending heavily on epigenetic factors receives support from recent data suggesting the existence of a time window or critical period during which primary language proficiency must be attained if normal lateralization of language function is to occur.

Child↗
PubMed1989

A reexamination of aluminum in Alzheimer's disease: analysis by energy dispersive X-ray microprobe and flameless atomic absorption spectrophotometry.

We have attempted to verify the presence of increased aluminum (Al) levels in Alzheimer's disease (AD) brains by energy dispersive X-ray microanalysis (EDX) and flameless atomic absorption spectrophotometry (AAS). Tissue from seven AD brains, mounted on carbon polymerized coverslips, were stained with Congo-red or treated immunohistochemically to allow optical localization of AD-associated lesions during EDX. Despite a demonstrated sensitivity of 20-25 ppm, we were unable to detect Al in either plaque cores or neurons containing neurofibrillary tangles. For AAS, wet weight samples (ranging from 48-144 mg) from six of the seven AD brains and four controls were selected from regions similar to those studied under EDX, i.e., Brodmann areas 9, 11, 28, 46, 47, and the hippocampus. The tissue surrounding each sample site was sectioned and stained for thioflavin S. Both controls and AD samples revealed similar levels of Al ranging from undetectable to 1.80 ng/mg wet wt. (mean AD: 0.28 +/- 0.39 (SD), control: 0.54 +/- 0.58 (SD], independent of degree of histopathology or age of the case. We conclude that the combined strengths of these two techniques on similar tissue specimens demonstrate that abnormal Al levels are not required to produce the histologic findings of AD and that this element may not accumulate in the aging brain. It is unlikely, therefore, that Al is essential in the etiology of pathogenesis of plaques and tangles in AD. Al's role as a primary or secondarily associated event, when present, needs further delineation.

Aged↗
PubMed1989

Alzheimer's disease as a capillary dementia.

In addition to the well known structural stigmata which accompany the senile dementia of Alzheimer, attention is called to the presence of a group of robust changes which affect the fine vessels (capillaries, capillary arterioles and capillary venules), particularly of the cerebral cortex. These alterations include irregular pouches and excrescences on the vessels (a "lumpy-bumby" appearance), general thickening of the basement membrane, loss of the fine perivascular neuronal plexus which seems to invest each vessel, no matter how small, and the appearance of pits or lacunae in the vessel walls of about one half of the Alzheimer patients studied. None of these changes have been seen in a group of approximately age-matched, non-demented controls. Much of this perivascular neural plexus originates within a few specific subcortical fields, especially the locus ceruleus and the nucleus basalis of Meynert and basal forebrain area. These also happen to be included among those brain areas which experience the most marked neuronal atrophy or loss in Alzheimer's disease. Since there is some evidence suggesting that surgically induced vascular denervation in myocardium produces dramatic changes in vascular wall structure we wonder whether neuronal pathology developing initially in these subcortical areas may not play a significant role in the development of the characteristic neuropathology in Alzheimer's disease. These speculations emphasize the possible importance of a failing blood brain barrier in the development of the disease.

Alzheimer Disease↗
PubMed1987

Alterations of the cerebral capillary bed in the senile dementia of Alzheimer.

Brain tissue specimens from 15 patients dying with neuropathologically confirmed clinical diagnoses of senile dementia, Alzheimer type, and 10 approximately age and sex matched elderly patients without signs of senile change, were compared using a group of neurohistological techniques including scanning electron microscopy. In addition to previously described changes in structure of neurons and neuropil, dramatic changes were noted in the capillary bed. Normal cerebral vessels are characterized by smooth contours, the presence of occasional pericytes, and a plexus of pericapillary nerve fibers bearing many varicosities which have been shown to be strongly positive for norepinephrine, acetylcholine, dopamine and several other putative neurotransmitters or neuromodulators. In our series of Alzheimer patients the cerebral vessels were highly irregular in appearance, covered with rounded or conical extrusions (lumps and bumps), and totally lacking in the perivascular plexus of nerve fibers. In about three quarters of the cases studied the vessel walls were perforated by multiple openings of varying sizes, most of which appeared to run through the complete thickness of the thickened basement membrane but did not perforate the endothelial lining of the capillary lumen. The origin and pathogenesis of these changes is still unknown although some of the materials infiltrating the vascular walls appear to contain amyloid. On the basis of presently available evidence, it is suggested that widespread microvascular pathology may be caused by loss of the perivascular neural plexus (denervating microangiopathy) and that this may result in breakdown of the blood brain barrier.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1987

Schizophrenia and the hippocampus: the embryological hypothesis extended.

Recent studies suggest that consistent structural changes exist in the hippocampi of schizophrenic patients. These alterations are characterized by a significant degree of disorientation of the hippocampal pyramidal cells when compared with age-matched nonschizophrenic controls. The degree of neuronal disorientation seems to correlate positively with the severity of the clinical picture. A hypothesis on the pathogenesis of this process, suggested in an earlier article, is extended here. Putative maternal infection with one of several neuraminidase-bearing viruses, especially during the second trimester of pregnancy, may severely affect the migration of primitive neurons into the primordial hippocampus. The "neuraminidase effect," expressed through alteration of the normal sequential patterns of N-CAM (neuronal-cell adhesion molecule) maturation, may result in the cellular disarray we have noted. This alteration may prove useful as a cell marker for schizophrenia, even though its actual relation to clinical symptomatology has still to be evaluated. Genetic factors also are believed to be involved, perhaps in the form of certain patterns of reduced immunocompetence, which might render the mother more susceptible to viral infection.

Adult↗
PubMed1987

Denervation microangiopathy in senile dementia, Alzheimer type.

Structural analysis of the capillary plexus in the brains of 5 patients with clinical and neuropathological diagnosis of Senile Dementia, Alzheimer Type, revealed a group of striking physical alterations compared with tissue specimens from 5 age-matched controls. Capillary walls were thickened with irregular lumpy, nodulated contours which appeared due, in part, to infiltration of the vascular wall with rounded cell-like bodies. In some cases, these resembled the perikarya of pericytes or monocytes, or their protoplasmic extensions, which were often filled with lipids. In each case, there was no trace of the perivascular neural plexus which regularly invests the microvasculature of the brain parenchyma. The loss of this neural plexus, believed to originate largely from locus ceruleus and the basal forebrain, may be related to the changes in capillary wall structure, and these, in turn, may lead to profound alterations in blood-brain barrier function. We suggest that this subcortically induced denervation microangiopathy may serve as a pathogenic factor in the development of SDAT.

Aged↗
PubMed1986

Biological substrates of schizophrenia.

Schizophrenia is increasingly believed to represent a group of organic disorders which primarily, although not exclusively, affect the central nervous system. Our purpose is to review a representative sample of twentieth-century literature which speaks to the biological substrates of the syndrome. Subjects reviewed include genetic and environmental contributions to the onset of illness, early and recent findings of gross structural anomalies, and apparent histopathological alterations in cerebral cortex, cerebellar vermis, limbic system, and brain stem, as well as problems of cerebral asymmetry. Data from a diverse group of electrophysiological studies reveal several promising correlates of these areas of investigation. Despite the inconsistent nature of the findings to date, several themes have begun to emerge, including patterns of hypofrontal/hyperparietal regional cerebral flow and glucose utilization, left hemispheric dysfunction, and deficits of interhemispheric information processing. The interpretation and significance of these emerging patterns remains unclear and must await more profound insights into the nature of normal and abnormal cerebral function.

Adoption↗
PubMed1986

Lower Purkinje cell counts in the cerebella of four autistic subjects: initial findings of the UCLA-NSAC Autopsy Research Report.

As part of an autopsy research project, the brains of four autistic subjects were examined and compared with those of three comparison subjects without CNS pathology and one with phenytoin toxicity. The cerebellum was selected for initial investigation because pathognomonic symptoms and neurophysiological measures suggest that pathology may exist in the cerebellar-vestibular axis in certain patients. Total Purkinje cell counts were significantly lower in the cerebellar hemisphere and vermis of each autistic subject than in the comparison subjects.

Adolescent↗