The commentary is based on our results of biological aging research with the following findings: a loss of neurons cannot be found, the size of neurons and the number of synapses decrease with age, the various regions of brain react quite differently. Altogether, these results speak for "use it or lose it." However, the genetically determined decreased brain function during aging can only be inhibited, not permanently preserved.

Aged↗

PubMedDate not supplied

[Morphometric studies of biological changes in synapses of the human caudate nucleus].

In the adult the caudate nucleus decreases with increasing age. Light microscopic measurements result in smaller sized neurons and a reduced neuropil in the aged. Comparable to a sintering, nerve cells move nearer, and in consequence, their density increases. The total number of nerve cells, however, does not change remarkably. Using electronmicroscopic methods the aging of synapses was morphometrically examined: Blocks of the caudate nucleus were cut out of formalin-fixed brains from 43 males who had died between the 22nd and 102nd year of age without any neurological symptoms. The blocks were contrasted with EPTA (ethanolic phosphotungstic acid) and embedded in araldite. Though the whole tissue was autolytic, presynaptic and postsynaptic densities were well-preserved and clearly visible. Their numbers and sizes were measured with semiautomatic procedures. The regression analysis shows a significant decrease of the density of synapses with increasing age. The aging of the human caudate nucleus is characterized by a decrease of its volume, by a reduction of the size of neuronal perikarya, and a diminution of the number of synapses per neuron. But the total number of nerve cells remains nearly constant.

Adult↗

PubMedDate not supplied

[Enzyme activity in the hemolysate after post-traumatic splenectomy].

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Adult↗

PubMedDate not supplied

Vascular changes in the cerebral cortex in HIV-1 infection: I. A morphometric investigation by light and electron microscopy.

The microvasculature of the cerebral cortex in AIDS brains was investigated by means of stereology at the light and electron microscopic levels. Stereologic parameters for microvessels were determined in formalin-fixed autopsy tissue of 24 AIDS patients and of 35 age- and sex-matched controls. At the light microscopic level these encompassed the measurement of the diameter, volume fraction, surface area density, and length density; at the electron microscopic level profile area, perimeter, diameter of capillaries, endothelial cells, pericytes, and basal lamina as well as the mean thickness of the basal lamina were measured. In AIDS brains a significant increase in the diameter of cortical vessels was noted. The surface area density (Sv) and volume fraction (Vv) of microvessels were likewise significantly increased in AIDS brains. No changes were noted for the length density (Lv) which also indicates that no changes in the number of vessels occur in HIV-1 infection. Ultrastructural thinning of the basal lamina was a consistent finding. Vacuoles occurred in the basal lamina of capillaries and increased in number and size in AIDS brains. Using morphometric methods, significant changes of cortical vessels are detectable at the light and electron microscopic level. These changes most probably represent the morphological substrate of an altered blood-brain-barrier in AIDS brains and may account for the reported hypoperfusion demonstrated in SPECT analyses.

Acquired Immunodeficiency Syndrome↗