Senile dementia: a threshold phenomenon of normal aging? A contribution to the functional reserve hypothesis of the brain.

Neurochemical investigations with normal aging brains show that in the first 70 years of life no major changes of the glycolytic pathway can be observed. Only in the following decades does a significant decrease of brain metabolic turnover occur. Changes in nerve cell size, one of the most relevant parameters in evaluating a diffuse nerve cell atrophy, appear in the brain cortex not earlier than between 85 and 94 years of age; a 21% nerve cell shrinkage is the mean.

Stereological changes in the capillary network and nerve cells of the aging human brain.

Stereologic parameters of the capillaries and nerve cells of the brain cortex and putamen were investigated. Thirty-eight brains from subjects aged between 19 and 94 years were examined. All cases were free of metabolic, neurologic and psychiatric diseases.

Comparative studies of neuronal perikaryon size and shape in the aging cerebral cortex.

The stereological investigation comprised three groups of people aged 19 to 44, 65 to 74 and 85 to 94. Perikaryal area and circumference of cortical neurons in the superior part of the cerebral precentral gyrus were determined. Opening classes of single neurons were measured with the Leitz texture analyzer to calculate size and shape.

Postmortem changes in stereological parameters of cerebral neurons.

The form and size of neurons in the cat cerebral cortex were stereologically investigated intravitally, and 30 sec., 5 hours, and 22 hours postmortem. For comparison, the human cerebral cortex of a 60 year old male subject was deep frozen 16 hours postmortem, and fixed in formalin.

[Quantitative-morphological changes of capillaries and neurons in the aging human putamen (author's transl)].

Stereological investigations (Classimat) of the capillary net of 4 age-groups, ranging between 19 and 94 years, revealed significant increase of capillary volume and total length, and decreased intercapillary distances in the aging putamen. Neuronal size and shape measurements (Texture-Analyzer-System) of the same brain region showed significant changes between the young (19-44 y.) and oldest (85-94 y.

The aging human cerebral cortex: a stereological characterization of changes in the capillary net.

Capillaries in the cerebral cortex of six age groups, ranging between 19 and 94 years (= 34 human brains) were stereologically investigated. Capillary parameters such as diameter, volume fraction, specific surface area, mean intercapillary distances and total length per unit cortex volume in patients older than 75 years were similar to those in young ones, 19 to 44 years old. Aged subjects between 64 and 74 years revealed increased capillary diameter, volume and total length per unit cortex volume, as well as decreased specific surface area.

[Stereological investigation in the cerebral cortex of aging subjects (author's transl)].

Involving cortical regions, capillaries of the human cerebrum of two 19 and 27 years old men, a 69 years old woman and a 72 years old man were stereologically investigated by optical-electronic image-analysis. The cortical capillary net work was demonstrated by the alkaline phosphatase activity. Each cortex region comprised a determination of the stereological parameters diameter, projected area, specific surface area, capillary distances in linear direction of TV-lines and total length per unit cortex volume.

Quantitative studies in the cerebral cortex of aging humans.

The capillary network of the human cerebral cortex was morphometrically investigated in a young, aged and aged hypertonic group. In the aging cortex, augmented values of capillary diameter and volume are accompanied by smaller distances between capillaries and an extended length per unit cortex volume. An increased capillary diameter of the aged hypertonic group is probably due to a high blood pressure.

Postmortem changes in stereological parameters of cerebral capillaries.

The present study investigated the influence of different postmortem times on stereological parameters of capillaries in the cerebral cortex. For the human investigation different brain regions of two 77 and 79 year-old subjects were examined. The animal experiment, carried out on 10 male cats, allowed a comparison between intravitam deep-frozen cerebral cortex and tissue obtained after decapitation.