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Biomedical subjects

A B Scheibel

Publications and source records attributed to A B Scheibel.

At least 37 records · Page 2Linked to original sources
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↗
PubMed1986

Structural substrates of epilepsy.

Although interest in possible structural substrates of epilepsy has been high since anatomical abnormalities in autopsy material were first noted, a clear pathognomic picture has yet to emerge for subtypes other than temporal lobe epilepsy. While identification of anatomical features unique to the diseased brain does not ensure that a cure will be found (viz. Alzheimer's disease), such knowledge can certainly guide researchers who must search out both the necessary and sufficient etiologic agent. Such investigation is hampered by the difficulty of separating cause from effect in clinical material, where the patient may have a history of drug use or of poorly controlled seizures. For instance, the cell-density depletion noted in temporal-lobe epileptics could follow from, or be a cause of, seizures. An experimental approach to isolating the structural substrates of epilepsy requires establishing several "levels" of epilepsy of varying duration, and observing the evolution of anatomical change. Such manipulation is, of course, possible only when an animal model is used, and it is for this reason, among others, that researchers have developed several of these. In general, there are two types of animal model: one where an exogenous agent (for example, a neurotoxin) or treatment (kindling) is applied, and another that relies on a strain of animal bred to exhibit seizures. Anatomical findings in this latter case have been reported infrequently, although the approach, which is not confounded by central nervous system (CNS) damage, seems promising as a model for certain types of epilepsy. Rodents have been among the best-researched genetic preparations, and several such reports appear in this volume. We have investigated one such strain, the Mongolian gerbil, which has been bred in UCLA's animal colony to exhibit seizures (the SS strain). Another strain (SR) has been bred to be seizure-free. Our initial study compared adult SS and SR animals with respect to two morphometric parameters in hippocampal region CA3. We found that the SS adult gerbil had fewer dendritic spines than its nonseizuring counterpart. Dendritic spines are considered the locus of excitatory synapses, and their density has been correlated with a variety of functional states in other paradigms. Our next set of questions concerned the development of these strain differences, and we accordingly set up four different age groups, bracketing the age at which seizures first appear in the gerbil. Again, spine-density differences appeared between SS and SR animals, but in the opposite direction from the adult case.(ABSTRACT TRUNCATED AT 400 WORDS)

Aging↗
PubMed1985

On the brain of a scientist: Albert Einstein.

Neuron:glial ratios were determined in specific regions of Albert Einstein's cerebral cortex to compare with samples from 11 human male cortices. Cell counts were made on either 6- or 20-micron sections from areas 9 and 39 from each hemisphere. All sections were stained with the Klüver-Barrera stain to differentiate neurons from glia, both astrocytes and oligodendrocytes. Cell counts were made under oil immersion from the crown of the gyrus to the white matter by following a red line drawn on the coverslip. The average number of neurons and glial cells was determined per microscopic field. The results of the analysis suggest that in left area 39, the neuronal: glial ratio for the Einstein brain is significantly smaller than the mean for the control population (t = 2.62, df 9, p less than 0.05, two-tailed). Einstein's brain did not differ significantly in the neuronal:glial ratio from the controls in any of the other three areas studied.

Aged↗
PubMed1985

Dendritic organization of the anterior speech area.

Golgi studies revealed significant differences in dendritic patterns between neurons of the left and right opercular regions of the frontal lobe (Broca's speech area on the dominant side) and between cells of the left and right precentral areas (the orofacial motor zones) just behind. Although total dendritic length of the basilar dendritic array seemed characteristic of an area independent of side, a larger proportion of the length on the left (dominant) side was made up of higher order (4, 5, 6) dendrite branches, and lower order (1, 2, 3) segments predominated on the right. The pattern was partially reversed in non-right-handed patients. These findings can be interpreted as indicating an early preponderance of dendrite growth in the non-speech-gifted hemisphere followed by enhanced dendrite growth in the dominant hemisphere coincident with the beginning of conceptualization and speech function.

Aged↗
PubMed1985

On the apparent nonadhesive nature of axospinous dendritic synapses.

Synaptosome preparations are rich in synaptic sacs with adherent fragments of postsynaptic membrane and it has been hypothesized that pre- and postsynaptic membranes are strongly adherent across the synaptic cleft. Scanning electron microscopy of tissue specimens subject to preliminary tearing reveals synaptic terminals on neuronal cell bodies and dendrites as well as pits in the plasma membrane from which other terminals have been avulsed. However, neither synaptic terminals nor membrane pits were seen on dendrite spines in our material. These observations support the notion of adhesion between pre- and postsynaptic membranes but suggest an absence of such adhesiveness between the elements of the axospinous synapse, fitting well with recent conceptions about spine lability and the rapid making and breaking of axospinous synapses.

Adhesiveness↗
PubMed1985

Falls, motor dysfunction, and correlative neurohistologic changes in the elderly.

The development of structural and functional deficits in the aging nervous system may constitute one important source of falls in the elderly. Present information is suggestive and is still based primarily upon tissue specimens from chronically ill and hospitalized patients. Within these limits, examples of structural changes are presented, and the possible functional consequences are examined. Although discrete patterns of motor weakness may follow such dysfunctions, overall problems in the timing and sequencing of motor action programs may be equally important in leading to falls and injury in the elderly.

Accidents↗
PubMed1984

Scanning electron microscopy of the central nervous system. II. The hippocampus.

This study has presented cells, fibers and non-neuronal elements as seen in 3 dimensions using the SEM. Our discussion on possible artifacts which can occur with this method is offered in the hope that others will develop better techniques of dissection and specimen preparation. With the picture of normal tissue in mind, the investigator can undertake studies to determine the effects of various interventions on the structures of interest. Such treatments could include deafferentation or the use of macromolecular probes bound to cell surfaces. We anticipate that improvements in tissue preparation techniques by ourselves and others will open the way to intensive investigation of the nervous system using this powerful tool.

Animals↗
PubMed1984

A neurohistological correlate of schizophrenia.

We report an apparently consistent alteration of pyramidal cell orientation in ten chronic schizophrenic patients compared with eight nonschizophrenic controls from a Veterans Administration Medical Center. A blind study based upon measurement of over 13,000 cells indicates highly significant differences between the two groups, particularly in anterior and middle hippocampal regions. Cell disarray is most pronounced at the CA 1-prosubiculum and CA 1/CA 2 interfaces. Smaller degrees of deviation, noted in the controls, together with more extreme deviation reported in a previous qualitative study of chronic schizophrenics from a state hospital, could be interpreted as suggesting a histopathological continuum ranging from the clinically nonpsychotic individual, through borderline states to the intractable long-term psychotic.

Adult↗