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Z Turek

Publications and source records attributed to Z Turek.

At least 37 records · Page 2Linked to original sources
PubMed1990

Mast cells in the rat heart during normal growth and in cardiac hypertrophy.

Mast cells in rat hearts were studied quantitatively during normal postnatal growth and in two types of cardiac hypertrophy. Normally, cardiac mast cell density in 11-12-day-old animals is very low, but increases markedly in the following 2-3 weeks to its highest values, with a subsequent decline toward adult values. At the peak of mast cell density, the percentage of mast cells in close proximity to capillaries is also highest. In adult animals, mast cell counts are significantly higher in the right ventricle than in the left. This relation is preserved even when the right ventricle is hypertrophic, as in rats born at simulated high altitude. Chronic hypertension and swimming have little effect on the mast cell density in rat hearts. Conspicuous changes in the mast cell density at the time of capillary proliferation seem to indicate a special role played by these cells in the formation of new vessels.

Altitude↗
PubMed1989

Microelectrode studies of facilitated O2 transport across hemoglobin and myoglobin layers.

Experimentally measured PO2 profiles across layers of hemoglobin and myoglobin solutions were compared with profiles predicted from facilitated transport theory assuming chemical equilibrium. Measurements across myoglobin layers were in excellent agreement with theory, but measurements across hemoglobin layers departed from theory at low PO2. This departure was greatest for salt-free hemoglobin solution, which may be caused by an electrical potential formed by a pH gradient in the layer as oxyhemoglobin is deoxygenated.

Animals↗
PubMed1988

Differing patterns of capillary distribution in fish and mammalian skeletal muscle.

The heterogeneity of capillary supply to muscles of different metabolic capacity and fibre size was assessed in slow and fast muscles from a fish and a mammal. The area surrounding each capillary delineated by equidistant boundaries from adjacent vessels, the capillary domain, was derived from morphometric analysis of histological sections. This 2-D integration of intercapillary distances may reveal heterogeneity of supply that is hidden by a global approach, especially when compared with the more usual 0- and 1-D indices of capillarisation. Mean radii of the equivalent Kroghian tissue cylinders (R) and heterogeneity of their lognormal distribution, represented by the logarithmic standard deviation (LogSD), were calculated. In eel slow muscle there was a 35-fold greater capillary density (CD) than fast muscle (698 vs 20 mm-2) although heterogeneity of capillary spacing was similar (LogSD congruent to 0.06). The difference in CD between slow and fast muscles of rat was less pronounced, but there was significantly lower heterogeneity in the aerobic tissue (LogSD = 0.08 vs 0.10) corresponding to a range in domain area of around 350-2300 microns 2 and 400-2900 microns 2, respectively. The overall capillary to fibre ratio (C:F) is inappropriate for sparse networks where many fibres lack direct capillary contact. The cumulative fraction of individual domains overlapping a muscle fibre (local capillary to fibre ratio, LCFR) plotted against fibre area showed the best correlation of any index in all tissue and was strongest in both fish muscles (r = 0.9), indicating a functionally homologous spatial distribution of capillaries with respect to muscle fibres in tissue of widely differing oxidative capacity. These data suggest that maximal oxygen supply to, or metabolite removal from, muscle fibres is not restricted to contiguous capillaries but also involves those remote from the fibre surface.

Animals↗
PubMed1988

Hypoxic ventilatory response of rats born at simulated altitude.

Steady-state ventilatory response to isocapnic hypoxia was measured in awake rats: a) resident at sea level (Control); b) born at sea level and acclimatized to a simulated altitude of 3500 m (Newcomers); c) born and raised for two generations at a simulated altitude of 3500 m (HA-II Generation). Arterial PO2, PCO2, and pH were measured at the same time as ventilation. Resting ventilation (mean +/- SE) on room air in Control, Newcomers, and HA-II Generation was 707 +/- 25, 811 +/- 28 and 878 +/- 21 ml.min-1.kg-1, respectively. The ratios of ventilations measured at PaO2 55 and 100 Torr were 1.61 for Control, 1.52 for Newcomers, and 1.60 for HA-II Generation and were not significantly different from one another. The ventilatory response to 5% CO2 in air was also similar in all three groups. After four days at sea level, ventilatory responses of HA-II Generation to normoxia or isocapnic hypoxia were the same as those of sea level control. We conclude that the HA-II Generation groups had ventilatory responses to hypoxia that did not differ from those of Newcomers acclimatized to the same altitude. Unlike man, rats that were born and raised at altitude for two generations did not show any "blunting" of the ventilatory response to hypoxia.

Altitude↗
PubMed1987

Morphometric analysis of sparse capillary networks.

Two methods were used to assess the heterogeneity of capillary supply to muscles of widely differing metabolic capacity and fibre size. Using the method of capillary domains (DOM; Hoofd et al., 1985) and the closest-individual method (CI; Kayar et al., 1981) radii of Kroghian cylinders (R) can be calculated, and the heterogeneity of their lognormal distribution represented by the logarithmic standard deviation (Log SD). Both methods yield similar values for mean R in a tissue. DOM is more direct and quicker than CI, and may be particularly useful in the analysis of capillary oxygen supply during functional hypertrophy and in muscle regeneration where a broad distribution of fibre areas may be found. Despite a 500-fold range of capillary density, to a minimum of 20 capillaries mm-2, heterogeneity of capillary supply was similar in all muscles, indicating a functionally homologous spatial distribution. The relationship between number of fibres overlapped by a capillary domain, and domain area has zero correlation in most tissues but shows a negative trend in fish fast muscle, reflecting hyperplastic and hypertrophic growth. Capillary/fibre ratio is inappropriate for sparse networks whereas the cumulative fraction of domains vs fibre area shows a strong correlation, suggesting that maximal oxygen supply to muscle fibres is not restricted to contiguous capillaries, but also involves those remote from the fibre surface.

Animals↗
PubMed1987

Improved myocardial capillarisation in spontaneously hypertensive rats treated with nifedipine.

The effect of long term administration of nifedipine on myocardial capillarity was studied in spontaneously hypertensive rats. Nifedipine was given for 20 weeks, mixed into commercial rat chow (0.3 g per 1 kg). Untreated spontaneously hypertensive rats had higher arterial blood pressure and developed cardiomegaly when compared with Wistar-Kyoto rats used as controls. Nifedipine administration in spontaneously hypertensive rats lowered the arterial blood pressure and reduced cardiac weight; however, both values remained far above those for controls. Myocardial capillarity was determined using the recently introduced method of capillary domains. Hearts from untreated spontaneously hypertensive rats were characterised by greater and more variable intercapillary spacing than those from controls. The treatment of spontaneously hypertensive rats with nifedipine resulted in normalisation of morphometric indices characterising capillary spacing, probably as a result of stimulation of capillary growth as indicated by a significant decrease in myocyte to capillary ratio. Thus, despite persistent hypertension and cardiomegaly the treatment of spontaneously hypertensive rats with nifedipine restored mean intercapillary distance and index of heterogeneity of capillary spacing to normal values.

Animals↗
PubMed1987

Failure of swimming exercise to improve capillarization in cardiac hypertrophy of renal hypertensive rats.

Female Sprague-Dawley rats were made hypertensive by the two kidney/one clip Goldblatt procedure, while control animals were sham-operated. One week later, half of the animals were subjected to a moderate swimming exercise and the other half remained sedentary. Thus, four experimental groups, each consisting of 14 rats, were formed: control animals that were exercised or kept sedentary and corresponding renal hypertensive animals either exercised or sedentary. In hypertensive rats, a significantly increased left ventricular weight and reduced coronary reserve were found. Cardiac hypertrophy in hypertensive rats was characterized by a lower number of capillaries on a tissue cross-section, larger heterogeneity of the capillary net, and a less uniform orientation of capillaries in space. Total length of capillaries in the hypertrophic hearts increased significantly, but less than the increase in cardiac weight, resulting in reduced capillary length density. Chronic swimming for 2 hr/day for a period of 6 weeks, subsequent to a 4-week acclimation period, did not significantly influence any of the investigated indexes of capillaries from hypertrophic hearts. In the normotensive rats, chronic swimming resulted only in a moderate increase in total capillary length associated with a small increase in the left ventricular weight of similar degree. Thus, chronic exercise in normotensive rats induced a moderate increase in total capillary length per left ventricle, while it did not alleviate impaired capillarization of hypertrophic hearts from hypertensive rats.

Animals↗
PubMed1986

Merits and pitfalls in morphological assessment of cardiac growth.

The basic principles of quantitative morphological analysis of myocardial tissue are presented. Particular attention is paid to the effects of stimulated cardiac growth on the relationship between cell size and various indices of myocardial capillary supply in pressure-overloaded rat hearts. The importance of adequate sampling and of the number of measurements is stressed with respect to reliable estimation of the mean values but even more for assessment of variability of the measured data. When estimating myocardial capillary supply by average values of capillary density and/or of areas supplied by a single capillary, this crucial information is missing. Therefore the merits of more advanced techniques allowing for the estimation of variability of capillary spacing are critically examined and the significance of their application to myocardial tissue is outlined (method of concentric circles and method of triangular nets). Finally, the importance of variability of capillary spacing on oxygen supply is demonstrated. The variability of capillary spacing alone may affect oxygen supply independently of the average values of intercapillary distance.

Animals↗