Evaluation of structuro-functional heterogeneity of isolated mitochondria from the normal and the ischemic myocardium

The structural and functional heterogeneity of mitochondria isolated from intact and ischemic (after 60 min exposure at 37 degrees C) rabbit myocardium was evaluated. In the presence of cytochrome c. a relatively high (260 +/- 26 ng at O/min . mg of protein) rate of rotenone-sensitive NADH oxidation was observed, which was increased in ischemia. Cytochrome c stimulated the increase of NADH oxidation in mitochondria of normal and ischemic myocardium by the factors of 3.5 and 3.4, respectively. Succinate oxidation in the presence of bromthymol blue in normal and ischemic myocardium mitochondria was activated by cytochrome c 3.3- and 2.9-fold, respectively. The percentage of mitochondria with both structurally damaged membranes was 15% and 25% in normal and ischemic myocardium preparations, respectively. In the absence of ADP, cytochrome c contributed to the increase of the succinate oxidase activity in ischemic mitochondria; that in the 3rd state was inhibited in ischemia and normalized by cytochrome c. A principle was proposed for estimating the percentage of mitochondria with damaged outer membranes, the indices being equal to 34% in control and to 56% in ischemic myocardium. Evidence was obtained suggesting that this mitochondrial fraction was characterized by lowered coupling and absence of rotenone-sensitive NADH: oxidase activity. The percentage of intact mitochondria, in which succinate oxidation is inhibited by bromthymol blue and does not need exogenous cytochrome c, is 51% in control and 19% in ischemic myocardium mitochondria.     

Characteristics of the protective action of ethacizin on the ischemic myocardium

A study was made of the effect of ethacizine, a new antiarrhythmic phenothiazint derivative, on the size of experimental myocardial infarction in rabbits 7 days after ligation of the coronary artery. Ethmozine was used as reference. Ethacizine diminished the extent of necrosis by 22.8% (P less than 0.05) when injected intravenously in divided doses beginning from the 30th minute of 2-hour ligation, the total dose being 1.5 mg/kg. The six-day cycle of ethacizine treatment instituted 24 h after coronary artery ligation (daily dose 1.2 mg/kg) provoked a more considerable reduction of the myocardial infarction size (by 44.9%). The effect of ethmozine was less pronounced though statistically significant. Ethacizine increased ATP content in both the ischemic and "intact" myocardium and minimized the impairment of membrane permeability in the occlusion zone 3 h after ligation when injected according to the first above-described scheme. It is assumed that these effects may contribute to the drug protective action on the ischemic myocardium.     

Alterations in fatty acid oxidation in ischemic and reperfused myocardium

Summary The focus of this review centered on describing the effects of excess fatty acids on myocardial recovery during reperfusion following ischemic stress. Effects on mechanical function were modest in our studies and are likely to remain difficult/impossible to measure due to the independent phenomenon of stunning which obfuscates and no doubt dominates the influences of other mechanical determinants. Mitochondria appear capable of again using long-chain fatty acids as a preferred substrate and in the presence of restored oxygen delivery can produce normal levels of CO₂. These changes in oxidative metabolism are not mirrored by equal recoveries in mitochondrial energetics. Because of inefficiencies in electron transport and oxidative phosphorylation together with moderate uncoupling of electron transport from oxidative phosphorylation, ATP resynthesis is blunted. This explains in part the absolute decrease in contents of exchangeable nucleotides noted both in cytosol and mitochondria. Further impairments in recovery reside in the inability of the mitochondria to exchange adenine nucleotides into cytosol through the adenine nucleotide translocase antiport. These findings contribute to our understanding of mechanical stunning and may be of value in designing future strategies to optimize the handling of substrates during myocardial reperfusion.Visiting scientist from the Shang Hai Second Medical University, Peoples Republic of China.     

The state of lipid peroxidation and enzymes of calcium transport system in sarcoplasmic reticulum of ischemic myocardium

In 30 experiments on mongrel dog hearts it was shown that 30 min of total ischemia (37 degrees C) followed by accumulation of MDA in the SR membranes and decrease of their Ca2+-uptake, but had no effect on activity Ca2+-ATPase. After 60-120 min ischemia marked a decrease of Ca2+-uptake and activity Ca2+-ATPase took place, MDA content remained at the increased level. The results show that lipid peroxidation take part in the increase of the permeability of SR membranes for Ca2+ and inhibiting of Ca2+-ATPase.     

The role of the cortex in indentation experiments of animal cells

We present a model useful for interpretation of indentation experiments on animal cells. We use finite element modeling for a thorough representation of the complex structure of an animal cell. In our model, the crucial constituent is the cell cortex—a rigid layer of cytoplasmic proteins present on the inner side of the cell membrane. It plays a vital role in the mechanical interactions between cells. The cell cortex is modeled by a three-dimensional solid to reflect its bending stiffness. This approach allows us to interpret the results of the indentation measurements and extract the mechanical properties of the individual elements of the cell structure. During the simulations, we scan a broad range of parameters such as cortex thickness and Young’s modulus, cytoplasm Young’s modulus, and indenter radius, which define cell properties and experimental conditions. Finally, we propose a simple closed-form formula that approximates the simulated results with satisfactory accuracy. Our formula is as easy to use as Hertz's function to extract cell properties from the measurement, yet it considers the cell’s inner structure, including cell cortex, cytoplasm, and nucleus.

     

The ultrastructure of the pituitary gland under chronic stimulation of the ACTH-cells in human pathology and animal experiments.

Chronic stimulation of the ACTH-cells in rats was undertaken by adrenalectomy, chemical adrenostasis, by application of a CRF-analog and by non-specific means. The ultrastructural findings of the ACTH-cells were compared to those of the human pituitary gland in Cushing's disease. The pituitaries of 12 patients with the hypothalamic-hypophyseal form of Cushing's syndrome were studied by electron microscopy. A good correlation of the experimental observations to those in human pathology could be seen in the first steps of reaction. There was an enlargement of the ACTH-cells with well developed organelles and there was a simple hyperplasia. The following forms of reaction, nodular hyperplasia and adenomas, were only observed in the human pituitary glands. Chronic suppression by steroids leads to a diminution of the single ACTH-cell and their organelles and a reduction. The appearance of Crooke's cells is specific for the human pituitary and is not reproduced in animal experiments.     

On the use of response models in mixture experiments

Summary Methods for assessing mixtures and their dynamic interaction over time are proposed, based on response functions relating biomass yield of each species to the densities of the component species. This approach allows a number of different facets of mixtures to be studied in a common framework. Two examples are given. Substitution rates between species and perceived densities for individuals in mixture are defined. These measure the impact of their environment on individuals. The relative resource total (RRT), is suggested as an index of whether species are capturing the same resource amount in mixture as in pure stand. Two indices of the comparative performance of species over time are proposed. The two examples, one with cattle and sheep and the other a plant mixture diallel with 6 genotypes illustrate the use of the methods. In the animal example the maximum yield mixture was calculated, the species perceptions of each other assessed and it is shown that mixing increased the resource capture by up to 17%. In general, the smaller species performed relatively better in mixture over the experimental period. In the plant example, individual plant size varied considerably over genotypes and this was reflected in their perceptions of each other, but not in their pure stand or mixed crop yield potential. Most genotype pairs showed antagonistic behaviour, whether measured by crop yield potential or by the index of resource capture. These conclusions are contrasted with those from an analysis of the data using substitutive methods.