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Biomedical subjects

A B Scheibel

Publications and source records attributed to A B Scheibel.

At least 55 records · Page 3Linked to original sources

Dementia in the elderly: the silent epidemic.

The graying of America will be accompanied by an epidemic of major proportions--dementia or intellectual impairment--that will have an impact on all aspects of the helath care system, particularly on the institutional component of the long-term care system. Health professionals; federal, state, and local health planners; families; and others must recognize that many ameliorable or curable physical and emotional diseases in the elderly are associated with intellectual impairment that may be difficult to distinguish from irreversible brain disease of the Alzheimer type. We present information on the cause, physiopathologic mechanism, clinical presentation, appropriate laboratory studies, and anticipated outcomes in the various forms of intellectual impairment found in the elderly. Important new developments will occur in the next decade that will address the cause, pathogenesis, further refinement of laboratory investigation, and specific therapeutic intervention in dementia.

Aged↗

Structural correlates of seizure behavior in the mongolian gerbil.

Hippocampi of seizure-sensitive and seizure-resistant Mongolian gerbils were examined in search of structural correlates of seizure behavior. In animals with well-established seizure histories, differences were found in both presynaptic and postsynaptic structures. Seizing animals had less dense dendritic spines, a greater proportion of mossy tuft area devoted to presynaptic vesicles, and a smaller proportion devoted to spines. The possible relationship of these findings to epilepsy is discussed.

Animals↗

Scanning electron microscopy of the central nervous system. I. The cerebellum.

The fine structure of the cerebellar cortex has been studied by means of scanning electron microscopy (SEM). The neuropil is revealed by careful tearing of aldehyde-fixed tissue specimens which are prepared by means of dehydration, critical point freeze-drying, and sputter-coating with gold-palladium. Specimens are subsequently viewed at magnifications of up to X 16,000 with capabilities for extension up to about X 40,000. The technique provides remarkable three-dimensional views of neuropil including cell bodies and dendrites, details of presynaptic and postsynaptic morphology, axonal structure, neuroglia, and the microvasculature. It seems particularly powerful in demonstrating relationships between neuropil elements such as the terminal synaptic array on neuron somata and the arrangements of structures on membrane surfaces.

Animals↗

Development of the brain stem reticular core: an assessment of dendritic state and configuration in the perinatal rat.

The brain stems of normal newborn, 11- and 20-day-old rats were examined using Golgi techniques in the light and electron microscope. Patterns of dendritic branching and growth of brain stem reticular core neurons were analyzed by projection drawing and quantitative methods. The number of protospines and dendritic varicosities was counted on proximal and distal dendritic segments. The amount of DNA and protein in the brain stem was determined using colorimetric methods. During the course of early development, the sparsely branched reticular core dendrites extend rapidly into the neuropil. The dendritic branching of these neurons increases slightly but the number of primary dendrites remains constant. Protospine development follows a regular progression increasing in number to 11 days, then declining to 20 days as protospines are resorbed onto the dendritic surface. Dendritic varicosities often contain additional vesicles as a source of dendritic membrane and subsequent preterminal dendritic growth. The gradual decline of dendritic varicosities, first proximally then distally, indicates a shift of growth toward the distal extreme of the dendrite.

Aging↗

The hippocampus: organizational patterns in health and senescence.

The human hippocampal-dentate complex and the adjacent entorhinal cortex undergo a sequence of histological changes during the process of aging and senescence. Such alterations show a loose correlation with the age of the individual, and a more precise fit with the degree of clinical and psychosocial deterioration demonstrated prior to the individual's death. The structural changes are more or less idiosyncratic to the specific area involved but, in general, include loss of dendrite spines. distortion and swelling of the cell-body dendrite complex, and progressive destruction of the dendrite domain. Since one-third to two-thirds of the complement of archicortical neurons may be involved, a very significant fraction of synaptic connections are lost, and with them, much of the computational power of these areas. Psychophysiological studies strongly suggest a relationship between the human hippocampus-entorhinal complex with memory formation and/or retrieval. Animal studies indicate a possible role for the hippocampus as a cognitive mapping system which generates working models of the environment. The utility of such models might lie in part in facilitating selection of context-dependent behavior in a changing spatio-temporal setting. Progressive alteration of hippocampal function with aging and senescence could thus contribute significantly to patterns of increasing confusion and disorientation so common in the senile individual.

Aged↗

Dendritic bundles: survey of anatomical experiments and physiological theories.

Dendritic bundles have been found throughout the mammalian brain. Unquestionably, these bundles must serve one or more important, fundamental roles in the brain's functioning. However, no physiological experiments to determine their function have been performed on these well-established anatomical units. We survey the numerous anatomical reports of bundling. In addition, we discuss several physiological possibilities for the functional significance of bundles.

Animals↗