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Biomedical subjects

M Marzilli

Publications and source records attributed to M Marzilli.

113 records · Page 7Linked to original sources
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Different respiratory activities of mitochondria isolated from the subendocardium and subepicardium of the canine heart.

Mitochondria were prepared from the subendocardial and subepicardial layers of the canine left ventricle. The oxidation rates of palmitate, palmitoyl carnitine and pyruvate of the mitochondria obtained from the two cardiac layers were measured. The cytochrome content and the specific activities of different beta oxidation and Krebs cycle enzymes were also measured in the two mitochondrial populations. Mitochondria isolated from the ENDO layer showed significantly higher oxidation rates than mitochondria from the EPI layer for all the three substrates. No statistically significant differences in cytochrome c+c1 and a+a3 content were found in mitochondria isolated from the two regions. No significant transmural differences were found in fatty acyl CoA, L-3-hydroxy fatty acyl CoA, succinic and malic dehydrogenase specific activities, whilst isocitric dehydrogenase (NADP) specific activity was significantly higher in mitochondria isolated from the inner layer. In conclusion, the mitochondria isolated from the inner left ventricular layer of the canine heart show a higher oxidative capacity than subepicardial mitochondria. This difference could partly be explained by the higher specific activity of isocitric dehydrogenase in this layer. These properties of subendocardial mitochondria could represent a metabolic support for the greater contractile performance of this layer.

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Doxorubicin affects both the number and the morphology of specific atrial granules in dog heart.

A morphometric study was performed in dog atria to assess the effects of both single and repeated doses of doxorubicin on specific granules containing the natriuretic factor. Male beagle dogs were divided into 4 groups and treated i.v. as follows: groups A and B were controls and received isotonic saline; group C was given doxorubicin 2.4 mg/kg in a single injection; group D received doxorubicin 1.2 mg/kg once a week for 3 consecutive weeks. Samples of left atrium were taken 8 hours (groups A and C) or 28 days (groups B and D) after the last dose, and examined by the electron microscope. Compared with controls, the atrial tissue of group C dogs showed a significant increase in the number of specific granules; by contrast, the granularity was found to decrease significantly in the atria from group D dogs. These observations indicate a significant biphasic effect of doxorubicin on specific atrial granules of dog heart. The increase in granule density might be due to a block of the secretory process which is dependent on the metabolic energy supply. The reduction in cardiomyocyte granularity may be ascribed to the impairment of nucleic acid and protein synthesis induced by doxorubicin. Such alterations may play a significant role in doxorubicin-induced cardiovascular toxicity.

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Ultraminiature strain gauge transducer for assessing regional intramyocardial pressure.

A probe consisting of an ultraminiature strain gauge mounted on a 1.6-mm diam stainless-steel hypodermic needle for the measurement of intramyocardial pressure is described. Measurements were made of regional intramyocardial pressure throughout the cardiac cycle in 18 dogs. Simultaneous measurements were made in the left ventricular free wall at the subendocardial and subepicardial level. Advantages of the probe are: (a) an ability to localize pressure measurements at various depths within the myocardial wall; (b) minimal trauma and distortion of the myocardial tissue at the site of measurement because of the small volume occupied by the sensor; and (c) the high frequency response and insignificant time delay of the transducer. The method allows a simultaneous comparative assessment of intramyocardial pressure with other hemodynamic events.

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