[Effect of geomagnetic activity on the rhythm of resistance of rats to hypoxia]. / Vliianie geomagnitnoi aktivnosti na ritmy ustoichivosti krys k gipoksii.

The resistance of male Wistar rats to acute hypoxia was estimated from the lifetime at an "altitude" of 11.5 km above sea level from 13 to 21 p.m. and in different seasons of a year. Identical types of rhythms (circaseptan, circasemiseptan, infradian, circadian, and ultradian) of geomagnetic activity and lifetime were revealed. It was found that the periods of basal rhythms either coincide or are multiple. It was shown that the rhythms of geomagnetic activity (including nonbasal rhythms) affect lifetime rhythms (especially ultradian rhythms). As the periods of the rhythms decrease, the number of rhythms for both parameters increase (ultradian rhythms are most numerous), and relative differences in the values of periods (they are minimal for ultradian rhythms) and the amplitudes of rhythms decrease.

[Changes in the sympathetic-adrenal system during stress in rats with high and low resistance to acute hypoxia]. / Izmeneniia simpato-adrenalovoi sistemy pri stresse u krys s vysokoi i nizkoi ustoichivost'iu k ostroi gipoksii.

Quantitative luminescent microscopy was used to examine the sympathetic system of cardiac ventricles (SSCV) and the adrenal medulla (AM) of adult Wistar male rats high-resistant (HRH) and low-resistant (LRH) to acute hypoxia and exposed norepinephrine (NE) stress. The relative area of fluorescence adrenergic terminals (RAFAT) of the ventricles and AM catecholamine levels (CL) were shown to be equal in control HRH and LRH rats. The LRH rats displayed a two-phase SSCV response in the first 6 hours of NE stress. Their RAFAT rose an hour later and their RAFAT in the basal zone of the left ventricle insignificantly exceeded that of HRH rats, RAFAT in the latter being unchanged by that time. At hour 6, the heart RAFAT decreased as compared to 1-hour and control levels in LRH and HRH rats and became equal in the two groups. The AM CL in LRH and HRH rats remained unaltered within the whole period of the examination. Despite the profound differences in the resistance of HRH and LRH rats to hypoxia, the responsiveness of their sympathoadrenal system (SAS) to stress is rather homogeneous. With stress, the sympathetic link of SAS is more labile than the adrenal one.