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Biomedical subjects

A Schweizer

Publications and source records attributed to A Schweizer.

102 records · Page 6Linked to original sources
PubMed1980

Simple estimation of blood content in bone homogenates for the determination of the real amount of drugs in bone tissue.

The content of blood in bone homogenates can be determined quantitatively by estimation of the haemin in the homogenate and in a sample of peripheral blood taken at the same time. Haem is completely split from the haemoglobin molecule by reaction with hydrochloric acid-acetone and converted to haemin, which can be analyzed spectrophotometrically. The blood content can be calculated from the amount of haemin in the homogenate in relation to that of the peripheral blood. This method is useful to determine the real amount of drugs in bone tissue.

Aged↗
PubMed1980

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. The stereologic parameters of the cat experiment included neuronal surface Ai, perimeter LPi, and formfactor fi. In our experiment, the neurons showed swelling and metachromasia 30 sec. postmortem, which disappeared with progressive autolysis. Postmortem neuronal swelling was attributed to circulatory disturbances in the course of fatal cardiac arrest, whereas metachromasia of nucleoli and Nissl bodies appeared together with increased lysosomal acid phosphatase activity. "Dark neurons were only found in the human cerebral cortex fixed by immersion, and are thus recognized as artefact due to fixation. The intravital occurence of "dark" neurons could not be excluded, however. Size and form determinations of the neuronal perikaryon are expected to give additional information on pathologic changes during the aging process of the human brain, especially in senile dementia and organic brain syndrome.

Acid Phosphatase↗
PubMed1979

Dopaminergic agonists and their influence on the oxygenation and function activity of underperfused brain tissue.

The effect of two dopaminergic agonists (apomorphine and bromocriptine) on electrical activity and oxygen supply of the brain was investigated in cats submitted to hypovolemic oligemia (mean arterial blood pressure: 45 mmHg). While both drugs stimulated the brain by prolonging the oligemia-induced seizures in the caudate nucleus and in the cerebral cortex, only apomorphine improved the pO2 distribution in the cortical tissue after 120 min oligemia. Bromocriptine, in contrast, had a beneficial effect of shorter duration. These data show that under conditions of incomplete ischemia the brain can still be activated. Furthermore, these results provide additional support for the biochemically founded hypothesis of different dopamine receptors in the brain.

Animals↗
PubMed1977

Quantitative determination of drugs in biological materials by means of extractive alkylation and gas-liquid chromatography.

Analytical methods utilizing extractive alkylation followed by gas-liquid chromatography are described for the quantitative determination of (neo)sulfalepsine and its metabolites, chlorthalidone and chlorquinaldol. The applications described indicate that, for the use of this technique, careful optimization and the introduction of a suitable internal standard at the beginning of the analytical manipulations are essential.

Alkylation↗
PubMed1977

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. The parameters were diameter Di, volume fraction VVi, surface-to-volume ratio Si/Vi, mean minimal distance between capillary centers of gravity deltaAB, length per unit cortex volume LVi, and number of fragments per measuring field Ni, AT. Neither the cat experiment nor the human investigation yielded a noteworthy change of the capillary diameter in the postmortem cortical tissue. Nevertheless, a significantly enlarged mean minimal distance between capillaries in the cat cerebral cortex shortly after decapitation (30 sec) suggests the formation of edema which then regresses. Furthermore the experiment revealed that 22 hours after death there is a significantly (p less than 0.01) diminished volume fraction and length per unit cortex volume with an augmented surface-to-volume ratio. These changes are thought to be a consequence of water loss. In contrast to the animal experiment the human cerebral capillaries showed no changes in stereological parameters at two different postmortem times. These results encourage continuation of further stereological investigations on human brains obtained at autopsy and may contribute to the understanding of the aging process in the human cerebral cortex.

Aged↗
PubMedDate not supplied

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. It is demonstrated that the capillary diameter remains unchanged during aging in both brain cortex and putamen. However, in the putamen the total capillary length per unit volume and the capillary volume fractions increase (approximately 60%) progressively with age. Consequently the mean inter-capillary distances in the putamen decrease (approximately 15%). These age-induced changes in the putamen indicate shrinking of subcortical brain structures. In contrast to those of the putamen, the morphometric data of the capillaries in the cortex remain unchanged during the aging process. Stereologic investigations of nerve cells in the brain cortex and putamen revealed that only in brains over 85 years of age can a significant decrease in nerve cell size be demonstrated. A correlation of all the data by a correspondence analytical procedure showed that only the surface/volume ratio of the capillaries correlates with the nerve cell size. This observation suggests a functional interaction between the nerve cells and the capillaries. From the data presented it becomes apparent that the shrinkage of the gyri in the aging brain is not a change in the volume of the cortex, but a decrease in the volume of subcortical structures.

Adult↗