In rats exposed to a simulated high altitude of 3500 m or 6000 m for 6--7 weeks, myocardial necrosis was produced by ligation of the left coronary artery close to its origin, by ligation of the descending branch of the left coronary artery (true infarcts), or by administration of a large dose of isoprenaline. The same was done in control sea-level animals. The extent of the necrosis 24 hours after its induction was estimated from the activity of creatine phosphokinase in the tissue of the left ventricle and, in rats continuously exposed to 6000 m, also by measuring the surface of necrosis marked histochemically with phosphorylase activity in histological slides. In rats continuously exposed to 3500 m the extent of the isoprenaline-induced necrosis was smaller than in the controls, but there was no difference in true infarction. In rats intermittently exposed to 6000 m, no difference in the extent of any type of experimental necrosis was found when compared with sea-level rats. In rats continuously exposed to 6000 m, the extent of all types of experimental necrosis was smaller than in control animals. In histological sections of hearts with true infarctions it was possible to distinguish between the intact tissue, a zone of total necrosis and a zone of partial necrosis. Whether the main trunk or the descending branch of the left coronary artery was ligated, the extent of the zone of total necrosis in rats continuously exposed to 6000 m was smaller, the zone of partial necrosis was larger only in rats with a ligature of the trunk, and the extent of intact myocardium was not different when compared with control sea-level animals with the same type of myocardial infarction.

Acclimatization↗

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Cell size and capillary supply of the hypertensive rat heart: quantitative study.

Cardiac mass, cell size and capillary supply were studied in the hearts of spontaneously hypertensive rats (SHR) and compared to genetically similar non-hypertensive Wistar-Kyoto (WKY) of three adult ages: 5, 15 and 23 months. The left ventricular weight of SHR was not significantly greater than that of WKY at 5 months, but was by 15 months and became even more so by 23 months. This increase could be attributed to hypertrophy of the individual cardiac muscle cells and therefore, the estimated total number of myocytes per left ventricle was essentially the same in all experimental groups. Various indices of the myocardial capillary supply were also investigated. Cardiac hypertrophy in older hypertensive rats was characterized by greater and more variable intercapillary spacing, which may have importance in myocardial oxygen supply.

Age Factors↗

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[Role of alcoholism in the development of upper gastrointestinal tumors].

A preliminary report on the results of studies on the relationship between alcohol abuse and upper gastrointestinal tumours is presented. Alcohol abuse was measured with the aid of a questionnaire. GGTP and mean MCV were determined. Within the 1st September, 1986--30th September, 1987, 75 patients with the cancer of the upper gastrointestinal tract and 107 patients with benign lesions to this area were examined. Alcohol abuse was found in 33% of patients with the cancer and 19% of patients with benign lesions to the upper gastrointestinal tract. This difference is statistically significant (p greater than 0.05). The results of GGTP and MCV values were statistically insignificant in both groups. The authors have found more marked correlation of alcohol abuse with the cancer of the upper gastrointestinal tract in relation to the oral cavity and pharynx than the stomach. Further studies including larger groups of patients are recommended.

Adult↗

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A new look into the microscope: proliferation and regression of myocardial capillaries.

The key to understanding the mechanics of capillary proliferation probably lies in comprehension of the normal capillary growth during the early postnatal period when most of the terminal vessels in mammalian hearts are being formed. Similarly, stimulated cardiac growth is accompanied mainly, but not exclusively, by capillary proliferation if it takes place in the young, growing organism. The opposite situation, decreased capillarization of the heart, is commonly found in several experimental and clinical situations. The cause of lower capillary density is more often due to the growth of capillaries which is slower than the rate of growth of the remaining tissue, rather than to a disappearance of the existing capillaries. This brief review is followed by the discussion of how to evaluate the myocardial capillary supply based on the theoretical analysis of the effect of alterations in capillary surface density on myocardial PO2. The final part deals with confusing teminology in the field, with the following terms discussed in depth: diffusion distance, maximal diffusion distance and hexagonal array.

Animals↗

PubMedDate not supplied

Myocardial capillaries and tissue oxygenation.

The classical tissue model of August Krogh remains the cornerstone in the modeling of tissue PO2. However, heterogeneities of O2 determinants can profoundly affect the calculated oxygen fields. One of them is the heterogeneity in capillary spacing. At the present time there are two methods available for the estimation of capillary spacing: the method of capillary domains and the closest-individual method. The former estimates the distribution of the surface areas surrounding each capillary while the latter derives the distribution of distances of tissue points to the nearest capillary. Both can be transformed into the distribution of the radii of tissue cylinders according to the model of Krogh. Their distribution is approximately lognormal and is characterized by the mean (or median) value and the logarithmic standard deviation (log SD), which serves as the heterogeneity index. When applied to the same photomicrographs, both methods give similar values of the mean but the domain method yields a smaller log SD than does the closest-individual method. Subsequently, the calculated tissue PO2 histograms are also more uniform with the domain method. This difference is caused by the asymmetry of the domains. The shape of the domains is not circular and the capillary is not situated in the center as suggested by the model of Krogh. The method of capillary domains, however, is more direct and less time-consuming and thus more suitable for routine work. Nevertheless, the goal of future research is to develop a method that would characterize not only the distribution of the surface area of the domains but also their asymmetry.

Animals↗

PubMedDate not supplied

Acclimation to simulated high altitude and acute cardiac necrosis.

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Acclimatization↗