Cyclophosphamide effect on ultrastructural myocardial changes in rats on low-magnesium diet.

Intraperitoneal cyclophosphamide administration to a total dose of 225 mg/kg body weight during six weeks produced in rat myocardial fibres evident focal degenerative changes in all organelles, and, fairly frequently, significant damage even up to necrosis. The experiment showed that in rats on low-magnesium diet cyclophosphamide produced more intense and more extensive changes than in rats receiving only cyclophosphamide. The extent of the lesions produced with low and high doses of cyclophosphamide was compared and it was observed that the lesions increased with an enlargement of doses of the drug.

Ultrastructural studies of the myocardium of rats on low-magnesium diet treated with cyclophosphamide.

Cyclophosphamide administration in 20 mg/kg doses intraperitoneally at intervals of 6 days for 6 weeks produced the appearance of slight focal changes in myocardial fibres from the third week on, with dilatation of T-tubules and smooth endoplasmic reticulum channels with electron-dense deposits in them, with the appearance of numerous fat droplets in myocardial fibres, slight mitochondrial changes, with swelling and the appearance of giant or bizarre shaped mitochondria with electron-dense granules and lamellae in them, with numerous lysosomes and some increase in the number of autophagosomes, focal widening of intercalated discs, lysis of myofilaments and myofibrils, cytoplasm swelling, focal necrosis of some myocardial fibres in the 6th week of the experiment, marked swelling of vascular endothelial cells, and a very great rise in the number of collagen fibres. Simultaneous administration of low-magnesium diet and cyclophosphamide caused a greater intensity and an earlier appearance from the 2nd week on, of the disseminated degenerative and necrotic changes in myocardial fibres.

Ultrastructural examinations of rat myocardium on low-magnesium diet during administration of methotrexate.

Methotrexate administration intraperitoneally in doses of 1 mg/kg body weight twice weekly for six weeks produced in the myocardial fibres of these animals slight focal lesions from the third week of the experiment on with the appearance of isolated giant mitochondria of bizarre shapes with electron-dense membranes containing granules, or groups of mitochondria with swollen matrix and disintegration or, partial breakdown of mitochondrial cristae, numerous lysosomes and less numerous autophagosomes, considerable lysis of myofibrils and myofilaments, widening of the tubules of the sarcoplasmic reticulum and T-tubules, presence of few fat droplets, widening of intercalated discs, rarely cytoplasm swelling. From the fifth week on foci of cardiomyocyte fibrosis, in some places swelling of vascular endothelial cells, and a very considerable rise in the number of collagen cells in extracellular spaces. Simultaneous low-magnesium diet and methotrexate caused earlier, from the second week on, and greater intensity of focal necrotic and degenerative changes of cardiomyocytes.

Stress-induced injury of pig myocardium is accompanied by increased lipid peroxidation and depletion of mitochondrial ATP.

The aim of the study was to investigate the mechanisms of myocardial lesions induced by stress in conscious, intact pigs. The animals were subjected to 24 h immobilization, controls were kept in normal conditions. The pigs were killed by electric shock and exsanguination. Lipid peroxidation products: malondialdehyde (MDA), conjugated dienes (CDB), fluorescent end products (RF) and adenine nucleotides (ATP, ADP) were measured in the left ventricular myocardium which was also subjected to histoenzymatic and electron microscopic examination. In stressed animals as opposed to the control group, alterations in ultrastructure and diminution of mitochondrial ATP have been found, together with augmented formation of MDA and CDB reflecting increased free radical generation. These changes may be the component of stress-induced myocardial injury.

Histological and histochemical examinations of the myocardium of rats kept on low-magnesium diet and treated with cyclophosphamide.

Cyclophosphamide administered intraperitoneally in 20 mg/kg doses at intervals of six days for six weeks caused focal morphological and histochemical lesions of low intensity in rat myocardium. From the third week of the experiment focal eosinophilia and fuchsinophilia of the cytoplasm of a part and later on, of the whole cytoplasm of myocardial fibres, contraction nodes, undulant shape of the fibres, rupture of intercalated discs, very rarely in the sixth week small focal infiltrations composed of mononuclear cells at the site of damaged and disintegrated myocardial fibres, small amount of glycogen, focal increase of acid phosphatase activity and low-grade loss of alkaline phosphatase and magnesium and calcium-dependent ATPases in the sixth week, and unchanged activity of succinic dehydrogenase. Simultaneous use of cyclophosphamide and low-magnesium diet increased the intensity of degenerative changes, which appeared from the second week on, and necrotic changes appearing from the third week on, with more pronounced disturbances in the activity of all studied enzymes, including succinic dehydrogenase, in the sixth week.

Histological and histochemical examinations of myocardium of rats kept on low-magnesium diet and receiving methotrexate.

Methotrexate administration in 1 mg/kg doses intraperitoneally twice weekly for six weeks caused in rat myocardium the following focal, not very intense, histological and histochemical changes from the third week of the experiment on: focal increasing eosinophilia and fuchsinophilia of myocyte cytoplasm, undulating shape of myocardial fibres, contraction nodes, in the sixth week small necrotic foci with associated infiltrations composed of mononuclear cells, presence of p.a.S. positive substance resistant to diastase digestion in foci of damaged cardiomyocytes, focal rise of acid phosphatase, local loss of calcium and magnesium dependent ATPases in the sixth week, and unchanged succinic dehydrogenase activity. Simultaneous administration of low-magnesium diet and methotrexate caused more frequent (from the second week on) the appearance of more intense degenerative changes, and from the third week on the appearance of necrotic changes of cardiomyocytes, local increase of acid phosphatase activity from the second week on, falling activity of calcium and magnesium dependent ATPases from the fifth week on, and losses of succinic dehydrogenase activity in the sixth week of the experiment.

Effect of nisoldipine on stress-induced myocardial damage in the conscious pig.

1. The effect of the calcium channel blocker nisoldipine on the myocardial content of lipid peroxidation products (malondialdehyde (MDA), conjugated double bonds (CDB), fluorescent end-products (RF) and mitochondrial adenine nucleotides) was investigated in conscious pigs (n = 14) subjected to 24 h of immobilization stress. Histoenzymatic and electron microscopic studies of the myocardium were also performed. Nisoldipine was given orally in a twice daily dose of 20 mg for 2 days before and on the day of the experiment. Results were compared with those obtained in immobilized untreated pigs (n = 10) and in non-stressed treated controls (n = 8). 2. Pretreatment with nisoldipine significantly attenuated stress-induced increase in myocardial contents of CDB and RF and prevented decline of mitochondrial adenine nucleotides. Stress-induced myocardial histoenzymatic changes (decrease of succinic dehydrogenase, ATPase, acid phosphatase activity) and ultrastructural alterations (mitochondrial damage, lysis of myofibrils, dilatation of sarcoplasmic reticulum and endothelial swelling) were also diminished. 3. It is concluded that treatment with a Ca2(+)-antagonist is beneficial to the heart exposed to environmental stress.

[Selected organopathies caused by experimental magnesium deficiency]. / Wybrane organopatie wywolane doswiadczalnym niedoborem magnezu.

A role of enzyme mediated metabolic processes is discussed. Unfavourable effect of magnesium deficiency on the functioning of various organs may lead to extensive and irreversible morphological changes of focal character. Basing on the results of several experiments and own experience, the author discusses an effect of low-magnesium diet on histological, histochemical, and microscopic lesions to the myocardium, skeletal musculature, liver, and pancreas. Magnesium deficiency predisposes to myocardial necrosis which simulates electrolyte-steroid-cardiomyopathy by necrosis (ESCN). Low-magnesium diet decreases resistance of the animals to various types of stress such as: cooling, immobilization, and noise. Insignificant degree of the lesions to skeletal musculature produced by magnesium deficiency and no progress in these lesions during the experiment may depend upon relatively stable magnesium reserve in the muscles. Low-magnesium diet increases the number of so-called Ito cells in the liver. It is probable that these cells together with hepatocytes contribute to the formation of collagen fibres. Magnesium deficiency may lead to the abnormal digestion of nutrients in the pancreas, interfering with exocytosis of zymogen granules. Supplementation of the diet with magnesium may prevent various organopathies.

[Dynamics of lesions to the myocardium in experimental hyper- cholesterolemia]. / Dynamika zmian miesnia sercowego w hipercholesterolemii doswiadczalnej.

Dynamics of changes in the myocardium of rabbits subjected to food hypercholesterolemia lasting from 6 to 16 weeks was investigated. An intensification of coronary atheromatosis was proportional to the duration of the high-cholesterol diet. There were observed focal and growing in time damages of cardiomyocytes. They were sharply outlined in atherosclerotically changed coronary arteries. The following morphological and histochemical changes have been observed: increased acidophilia and fuchsinophilia in the single and grouped muscle fibres, foci of infiltrations by mononuclear cells, contraction bands, and outlines of myocardial fibres, separation of myofibrils, granular disintegration of cardiomyocytes, healed infarcts, depletion and excessive accumulation of glycogen in muscle fibres, presence of neutral fats, cholesterol and its esters in atheromatous plaques of coronary arteries, presence of neutral fats in some cardiomyocytes: focal acid phosphates, loss of activity of Mg- and Ca-dependent ATPases and SDH: oedema of mitochondria with disorganization of cristae, disorganisation of fibres and lysis of myofilaments, margination of chromatin in cardiomyocyte nuclei, increased number of lysosomes, intensified symptoms of egzocytosis, widening of channels of sarcoplasmatic reticulum, oedema of endothelium of capillary vessels and increased number of the collagenous fibres in the interstitial space. The results of histological, histochemical and microscopic-electron investigations correlated with each other. It may be considered that the observed damages of cardiomyocytes precede myocardial infarction and result from progressive and increasing ischemia, hypoxia and accumulation of fat substances and cholesterol and its esters in intima of coronary arterioles as well as in cardiomyocytes.