Biomedical subjects

N Wiernsperger

Publications and source records attributed to N Wiernsperger.

75 records · Page 5Linked to original sources

PubMedDate not supplied

Incomplete transient ischemia: a non-destructive evaluation of in vivo cerebral metabolism and hemodynamics in rat brain.

Differential near infrared spectrophotometry was used to monitor sequential in vivo alterations in cerebral hemoglobin saturation, blood volume, and cytochrome c oxidase reduction/oxidation responses during and after a period of incomplete transient ischemia (acute, reversible common carotid artery occlusion). In this study the rat brain was monitored non-invasively in the intact skull by transillumination. The data show that an increase in cerebral deoxygenation of hemoglobin, which occurs simultaneously with a decrease in blood volume subsequent to carotid ligation, acts as a compensatory mechanism to assist in maintaining aerobic energy metabolism. The observations also demonstrate that in this species the effects of bilateral carotid occlusion on the cerebrovascular parameters are not necessarily irrevocable. The intramitochondrial metabolic alterations, as evaluated by cytochrome c oxidase redox transitions, are reversible as long as the systemic arterial blood pressure does not fall below a value of approximately 40 mm Hg. These data suggest that possibility of being able to use a critical reduction level of cytochrome c oxidase as an early indication of ischemia-induced cerebral metabolic dysfunction prior to major changes in high energy stores.

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PubMedDate not supplied

Calcium antagonist PY 108-068: demonstration of its efficacy in various types of experimental brain ischemia.

The protective properties of PY 108-068 against ischemic disturbances in the brain were investigated in vitro and in vivo. The calcium antagonistic effects were demonstrated on isolated, calcium-loaded arterial rings of feline cerebral arteries. Determination of brain tissue oxygenation with pO2 microelectrodes showed that PY 108-068 improved oxygen supply in the cortex of cats subjected to epicerebral arterial occlusion. In a model of cerebral vasospasm induced by autologous blood superfusion, PY 108-068 reversed the spastic state of cortical microvessels. In a chronic stroke model (microsphere embolization in rats) PY 108-068 led to a significant reduction in mortality and in the severity of neurological symptoms, whereby the peroral efficacy of the drug could be demonstrated. The efficacy of PY 108-068 in a variety of ischemic insults makes this drug a promising aid in the treatment of cerebrovascular accidents.

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PubMedDate not supplied

Metabolic and drug distribution studies do not support direct inhibitory effects of metformin on intestinal glucose absorption.

In an attempt to clarify the question of an involvement of the inhibition of intestinal glucose absorption in the mechanism of action of Metformin, we used several experimental approaches: 1 glucose/lactate measurement in rat portal blood in vivo and 2 in the venous effluent of an isolated perfused rat intestinal segment; 3 metabolism of freshly isolated enterocytes in vitro and tissue distribution of 3H-labeled Metformin was investigated both in vivo and in vitro. Metformin applied intraluminally had no significant effect on portal glycaemia after a glucose load, but lactate increased, whereas in vivo only a high Metformin dosage reduced portal glucose appearance significantly. Although high Metformin concentrations were found in gut biopsies, precise histological analysis in the isolated intestine revealed that it was absent from enterocytes; however the drug accumulated in villous lacteals. Intrarterially applied Metformin decreased glucose absorption in the isolated perfused ileo-jejunal segment. These data suggested that vascular Metformin boosted intestinal anaerobic glucose metabolism. Biochemical measurements performed on freshly isolated enterocytes showed that even high Metformin levels did not interfere with cell respiration or with Na+/K+ ATPase activity. Thus, our data agree with other recent reports, suggesting that even at nontherapeutic concentrations Metformin has no relevant inhibitory effect on intestinal glucose absorption. The data are discussed in the frame of previous divergent observations. The results suggest however that Metformin of vascular origin stimulates glucose consumption by the intestine, which then increases lactate output from the gut.

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