Biomedical subjects

H H Klein

Publications and source records attributed to H H Klein.

113 records · Page 7Linked to original sources

PubMedDate not supplied

Loss of canine myocardial nicotinamide adenine dinucleotides determines the transition from reversible to irreversible ischemic damage of myocardial cells.

We investigated if the loss of nicotinamide coenzymes in ischemic-infarcted myocardium may be responsible for the transition from reversibly ischemic to irreversibly infarcted cell damage. The LAD was occluded in 6 dogs for 4 h. Transmural needle biopsies were taken from he ischemic-infarcted region after 1/2, 1, 11/2, 2, and 4 h of ischemia and further divided into subepicardial and subendocardial halves. At each time interval the concentration of the nicotinamide coenzymes NAD, NADH, and NADPH were measured, and the degree of cellular injury was evaluated by electron microscopy. The glycohydrolase activity (EC 3.2.2.5), the enzyme which splits NAD, was determined in brain, myocardium, kidney, and skeletal muscle of 4 rats. Total NAD, the sum of NAD and NADH, started to decrease significantly in the ischemic subendocardium 1 h after onset of ischemia. Degradation of NADPH occurred later. Loss ot total NAD was about 60-70% when electron microscopy diagnosed irreversible cell injury. The glycohydrolase activity was the highest in brain followed by myocardium, kidney, and skeletal muscle, reflecting the different tolerances of these tissues towards ischemia. The key mechanism for ischemic injury seems to be the tissue acidosis which activates the glycohydrolase leading to a loss of the vital coenzymes.

Animals↗

PubMedDate not supplied

Temporal and spatial development of infarcts in porcine hearts.

We investigated the temporal and spatial development of infarcts in porcine hearts to evaluate the time-dependent beneficial effect of reperfusion on infarct size. The left anterior descending coronary artery (LAD) was occluded in 17 pigs for different periods of time followed by 4 hours of reperfusion. Transmural needle biopsies subdivided into subendocardial and subepicardial halves were taken from the ischemic apex after 60 min of ischemia to determine the tissue concentrations of ATP and NAD. The myocardium-at-risk was assessed with a fluorescent dye injected into the right atrium at the end of the experiments, just after the LAD had been reoccluded. The excised hearts were cut into slices parallel to the heart basis. The ischemic myocardium was measured by planimetry of the non-fluorescent areas whereas the infarcted tissue was determined with the NBT stain and related to the area-at-risk. Ischemic cell death started in the jeopardized left ventricular subendocardial septum after about 30 min of ischemia. The further progress involved the right subendocardial septum and the subendocardium of the left anterior free wall. Already after 75 min of ischemia most of the myocytes-at-risk were irreversibly injured. Infarctions reached their final extent after 90-120 min of ischemia. These results indicate that in hearts without a significant collateral blood flow reperfusion can only reduce infarct size if its initiated within 60-75 min of ischemia. Like in canine hearts infarctions progress from the ischemic subendocardium towards the outer layers.

Animals↗

PubMedDate not supplied

The effect of chronic ethanol consumption on enzyme activities of the energy-supplying metabolism and the alcohol-aldehyde oxidizing system in rat hearts.

We investigated in rat hearts if chronic alcohol consumption causes an enzymatic adaption of the energy-supplying metabolism and/or of the alcohol-aldehyde metabolizing system. 16 rats were pair-fed with a liquid diet for 10 weeks. Ethanol was added to this diet to amount for 35% of calories in eight rats and was isocalorically replaced by saccharose in the control group. Selected enzyme activities of the glycolysis, the glycogenolysis, the beta-oxidation of fatty acids, the citric acid cycle and the alcohol-aldehyde oxidizing system were determined in the supernatants of the homogenized hearts. The intracellular redox state was assessed by measurement of the myocardial nicotinamide coenzymes. Enzyme activities of the alcohol-aldehyde metabolizing system did not alter after chronic alcohol intake. As we found that the capacity to oxidize acetaldehyde was much higher than the ability to oxidize ethanol we must question the role of acetaldehyde in inducing alcoholic cardiomyopathy. Chronic ethanol treatment significantly increased the activity of glyceraldehyde-3-phosphate dehydrogenase and decreased the activity of glycogen phosphorylase. The impairment of the hydroxyacylCoA dehydrogenase was not significant. The other measured enzyme activities did not alter, nor the intracellular redox state. The enzymatic adaption indicates an impaired glycogenolysis, an increased glycolysis, and probably a diminished beta-oxidation of fatty acids. We expect that the measurement of the responding enzyme activities in human endomyocardial biopsies should be a good tool to further classify cardiomyopathies according to biochemical criteria.

Alcoholism↗

PubMedDate not supplied

Acute treatment with vitamin E does not protect the regionally ischemic, reperfused porcine heart.

Thirty pigs were randomly assigned to a blind treatment with vitamin E or placebo. Ten animals each received 0.5 g d-alpha tocopherol intravenously before ischemia (group 1) or before reperfusion (group 2). Ten control pigs were treated with a lipid emulsion as placebo. The left anterior descending coronary artery was distally ligated for 45 min followed by 3 days of reperfusion. Infarct size was determined as ratio of infarcted (tetrazolium stain) to ischemic myocardium (dye technique). Regional systolic shortening was assessed by sonomicrometry. Myocardial and plasma concentrations of vitamin E were determined by high-performance liquid chromatography. Global hemodynamic parameters and estimated left ventricular oxygen consumption did not differ among the three groups. Intravenous treatment with vitamin E raised the plasma levels of this vitamin from 1 +/- 0.3 mg/l (control group) to 21 +/- 6 mg/l before ischemia, to 4 +/- 2 mg/l before reperfusion and to 2 +/- 0.6 mg/l at the end of the experiments in group 1. In group 2, vitamin E plasma levels increased from 1 +/- 0.3 mg/l to 24 +/- 13 mg/l before reperfusion and to 2 +/- 0.6 mg/l after 3 days of reperfusion. At the end of the experiments, myocardial vitamin E concentrations amounted to 4.2 +/- 0.7 ng/mg fresh weight (control group), 9.7 +/- 2.1 ng/mg (group 1), and to 8.7 +/- 1.4 ng/mg (group 2). The increase in vitamin E plasma concentration was not associated with a cardioprotective effect. Infarct sizes of the three groups (group 1: 68 +/- 12%, group 2: 66 +/- 15%, control group: 69 +/- 8%) were almost identical.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMedDate not supplied

Direct peripheral effects of ghrelin include suppression of adiponectin expression.

The stomach-derived peptide, ghrelin, has recently been discovered as an important regulator of energy homeostasis. Central nervous system pathways involving stimulation of hypothalamic neuropeptides play a prominent role in mediating ghrelin's orexigenic effects. However, potential direct peripheral effects remain poorly understood. Using a brown adipocyte model, we tested ghrelin-mediated influences on adipose tissue. Chronic ghrelin stimulation of differentiating adipocytes did not affect the pattern or extent of fat accumulation. Furthermore, insulin-induced glucose uptake as a hallmark of adipocyte function was not altered by ghrelin pre-treatment. However, acute ghrelin treatment resulted in a significant time-dependent increase in p44/42 mitogen-activated protein kinase phosphorylation. There was no stimulation of phosphatidylinositol 3-kinase, JAK/STAT, or stress kinase signaling pathways. Furthermore, ghrelin did not significantly alter gene expression of the thermogenic uncoupling protein-1. By contrast, expression of the novel adipokine adiponectin, which has been implicated in the pathogenesis of insulin resistance and obesity, was strongly impaired. This inhibition occurred acutely, and was sustained for several hours. In summary, our data provide evidence for selective effects of ghrelin on adipocyte signaling and function and thus propose a role for adipose tissue as a novel mediator of ghrelin's effects on energy balance and glucose homeostasis.

Adipocytes↗