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At least 973 records · Page 54Linked to original sources
PubMed1984

[Effect of different acclimatization temperatures on the ultrastructure of neuronal synapses of perch (Tilapia mariae; Cichlidae, Teleostei)].

The ultrastructure of synapses in the stratum fibrosum marginale (SM) of the optic tectum of cichlid fishes (Tilapia mariae) was investigated following acclimation to extreme environmental temperatures (experimental temperatures 16 degrees C and 32 degrees C; preference temperature: 26 degrees C). Four different types of synapses can be differentiated, from which 90% of all synapses belong to axodendritic spine synapses. The general ultrastructural appearance is more distinct in case of cold -adapted fishes, which in particular is due to a more pronounced staining of the polysaccharide-surface coat of the membranes. Analyzing quantitatively the axo-dendritic spine synapses (600 of each collective) significant differences were found for the length of the synaptic contact zone (16 degrees C: 0,391 micron; 32 degrees C: 0,369 micron) and for the thickness of postsynaptic densities (16 degrees C 42,6 nm; 32 degrees C: 52,7 nm). The number of mitochondria per presynapse was rised for cold-adapted animals to a value of 0,29 as compared to 0,18 mitochondria/presynapse for warm-adapted animals. The vesicle density per micron 2 of synaptic area, however, remained unchanged (approximately equal to 89 vesicles/micron 2). The morphological synaptic plasticity thus demonstrated in the optic tectum of chichlid teleosts, is correlated with behavioural changes and with alterations in the biochemical composition of synaptic membranes.

Acclimatization↗
PubMed1983

[Effect of catecholamines and propranolol on the acute acclimatization to high altitude in man].

The venous concentrations of epinephrine and norepinephrine and changes in ventilation, respiratory gases, circulation and ECG were determined in 20 young healthy male medical students during standardized stepwise ascent to 6000 m in a low pressure chamber, once without (control) and once with beta-receptor blockade (propranolol). The results show that the plasma concentration of norepinephrine increased significantly as a result of hypoxic hypoxia. The moderate increase in epinephrine was, besides the minor but significant hypoxic influence, mainly due to psychic tension. Since beta-receptor blockade does not prevent the respiratory and circulatory adjustment, beta-adrenergic stimulation is not thought to be necessary at altitude. Propranolol, on the contrary, lowers the hypoxia-induced increase in cardiac output and diminishes the ECG changes, in particular the S-T depression, significantly. By antagonizing the effects of epinephrine and by its central effects, propranolol improves subjective tolerance to altitude, and, on the other hand, by economizing the cardiac work load, the objective ability to withstand oxygen want.

Acclimatization↗
PubMedDate not supplied

[Polyamine contents in the brain and liver of rats during acclimatization to the cold].

The content of polyamines, spermidine and spermine in the brain and liver was studied in rats during acclimation to cold for 45 days. In the brain the amount of spermidine after one and three days does not change, on the 7th and 15th day it decreases and by the end of acclimation returns to the control value. The content of spermine lowers by 29% by the third day of acclimation and on the 7th day returns to the initial level and does not change up to it end. In the liver the amount of spermidine rises significantly on the third day of acclimation, returns to the control level on the 7th day and then its amount falls. The content of spermine is increased in all period of acclimation and only by the 45th day it returns to its initial level.

Acclimatization↗