Effects of alternating 45-min light-dark cycles on sleep in the rat.

We studied the effect of alternating 45-min light-dark (L-D) cycles on sleep in rats. Introduction of short L-D cycles did not abolish the normal circadian rhythm of sleep-wake activity. The amount of non-REM sleep was however increased in the L and decreased in the D 45-min periods. REM was promoted in the D and inhibited in the L 45-min periods. The influence of L-D or D-L transitions depended on the sleep wake activity immediately before the transition.

Quantitative alterations of intramuscular connective tissue in calf muscles of the rat during combined hypoxia and hypokinesia.

The investigations were designed to study the long-term effect of hypoxia, hypokinesia and of combined hypokinesia and hypoxia on the skeletal muscle in the rat. In the muscles of the hypoxic and hypokinetic animals serious degenerative changes were found and the fibre-type ratio was altered. In the hypoxic animals moderate fibrosis was revealed. In the hypokinetic, and hypokinetic + hypoxic animals the amount of connective tissue was 5 to 10-fold greater in the calf muscles as compared to the control.

Oxygen regimen in the human peripheral tissue during space flights.

A survey of the results of the experiment "Oxygen," carried out within the scope of the INTER-KOSMOS program in members of the permanent crews and of international visiting expeditions to the Soviet orbital station Salyut-6, is given. During the 7-day space flights of the international visiting expeditions a significant decrease in pO2ic by 3.28 kPa was observed. Local oxygen utilization reduced significantly by 0.44 kPa. During hyperventilation testing after return to earth a statistically significant decrease in the peak value by 1.39 kPa was noted. In the long-term crews of the orbital station Salyut-6 the highest decrease in pO2ic of 3.8 kPa and the absolutely lowest value of 3.4 -/+ 0.5 kPa during space flight were observed. The decrease in local oxygen utilization during the flight of 0.8 kPa/min was greater than that of the visiting crews. The results indicate the importance of investigating the dynamics of the oxygen regimen for medical control of the crew members both during the space flight and during the readaptation phase after return to earth.

Capsaicin pretreatment reduces the gastric acid secretion elicited by histamine but does not affect the responses to carbachol and pentagastrin.

Gastric acid secretion was studied following stimulation with a subcutaneous injection of histamine (0.1, 0.5 or 5 mg/kg), carbachol (4, 40 or 160 micrograms/kg) or pentagastrin (25 or 250 micrograms/kg) in conscious rats pretreated with either capsaicin or the vehicle. The secretory response to histamine (0.5 or 5 mg/kg) was greatly reduced in the capsaicin-treated rats, while the slight effect of 0.1 mg/kg histamine and the increase of secretion in response to carbachol and pentagastrin were not affected. The basal secretion was also normal in the capsaicin-treated rats. It is suggested that unlike the effects of carbachol and pentagastrin, the increase of acid secretion elicited by histamine involves a capsaicin-sensitive mechanism. Since capsaicin is a specific neurotoxin for the peptide-containing primary sensory neurons, the present results may indicate that the neurons contribute essentially to the effect of histamine on gastric acid secretion.

Modern method and instrument for measuring psychic performance.

This paper shows that cortical processing of information quantity can be given in bits, while speed of information processing can be given in bit/sec; therefore the information processing ability can be denoted in algebraical expression. Changes of emotional tension can be objectified by galvanic skin reflex and pulse reaction. This method and device is suitable to measure psychic state of space station personnel and to predict psychic activity.

Non-opiate analgesia following stressful acoustic stimulation.

The change in the nociceptive reactions of rats was characterized after stressful acoustic (115 dB) stimulation. Acoustic loading for five minutes resulted in considerable analgesia in the hot-plate test, whereas a significant analgesic response was not observed in the tail-flick test. The analgesic reaction after acoustic stimulation was resistant to naloxone pretreatment and was also found in morphine-tolerant rats, but the acute thermoregulatory and analgesic effects of morphine were greatly potentiated by simultaneous acoustic loading. Substance P or cholecystokinin treatment likewise failed to prevent the analgesic effect of auditory stimulation. No tolerance developed to the analgesic effect on repeated stressing. Diltiazem, a slow calcium channel blocker, facilitated the analgesia. The data suggest a stress-induced analgesia with obviously non-opiate properties, although an indirect involvement of opiate effects could not be excluded.

Histochemical and biochemical alterations in skeletal muscles of rats during combined chronic hypoxia and hypokinesia.

This investigation was designed to study the long term effect of combined hypokinesia and hypoxia on the skeletal muscle. In the muscles of the hypoxic and hypokinetic animals, serious degenerative changes were found and the fibre type ratio was alterated. The malate dehydrogenase activity was decreased, and both LDH and MDH isoenzymes pattern were alterated.

The blood-brain barrier in hypoxia: ultrastructural aspects and adenylate cyclase activity of brain capillaries.

The ultrastructure of brain microvessels, their permeability to serum albumin, the activities of some endothelial enzymes and the effect of histamine were investigated in rats after a prolonged hypobaric-hypoxic treatment. After prolonged hypoxia, the permeation of serum albumin into endothelial cells increased together with the number of pinocytotic vesicles of the endothelium. Intracarotid histamine stimulated this process even further, and its effect was mediated by H2-histamine receptors. After hypoxia the specific activity of capillary alkaline phosphatase and gamma-glutamyl transpeptidase remained unchanged, while that of adenylate cyclase was greatly increased. Histamine did not modify the structure of tight junctions of isolated capillaries of normoxic animals. Both hypoxia- and histamine-induced modification of the brain microvessels were accompanied by an increase of pinocytosis, which may be stimulated by the activation of capillary adenylate cyclase.

Histamine-stimulated prostaglandin synthesis in rat brain microvessels.

The histamine-sensitivity of prostacyclin and prostaglandin synthesis was investigated in isolated brain microvessels prepared from normal and hypoxic exercised rats. 10(-4) M histamine stimulated the in vitro synthesis of all components of arachidonate cascade. The chronic hypoxic exercise also resulted in an enhanced production of each fraction. Hypoxia and histamine showed an additive effect in the synthesis of PGE2 only. The possible molecular mechanism induced by hypoxia and histamine is discussed.

Prostacyclin and prostaglandin synthesis in rat brain microvessels: characteristic changes in hypoxaemia.

The effects of hypoxaemia on the synthesis of prostacyclin and prostaglandins in the cerebral microvessels and on the ultrastructure of brain cortex capillaries were investigated in three groups of rats. Series I: rat embryos were kept in hypoxic-hypobaric condition for 42 hours. It resulted in the enhancement of synthesis of PG2alfa and PGE2 even two months after birth. The fine structure of the capillary endothelium remained without any pathological change. Series II: adult male rats were on hypoxic-hypobaric environment for 42 hours. There was a slight increase in the synthesis of PGE2 and PGD2 while the ultrastructure of brain capillaries was found to be normal. Series III: the hypoxic-hypobaric condition lasted for 240 hours in adult male rats. This long term hypoxaemia affected greatly the prostaglandin synthesis of brain cortex capillaries and resulted in changes in the fine structure of brain microvessels as well. The possible molecular mechanism activated by hypoxaemia in brain capillaries is discussed.

The role of adrenergic receptors in the regulation of gastric motility in the rat.

Gastric motility was investigated under the effect of adrenergic receptor agonist and antagonist substances in albino rats of both sexes and weighing 150 to 180 g. Gastric evacuation was studied, after introducing 2 ml/100 g of Novobarium suspension in the stomach, by radioscopy and radiography. Epinephrine (Tonogen) was found to inhibit gastric motility, this inhibition being effective even after pylorotomy. The dominantly alpha adrenergic agonist phenylephrine (Sympathomim) had not any effect; the alpha blocker phenoxybenzamine (Dibenzyline) slightly depressed gastric evaluation. A marked inhibitory influence was noted with stimulating the beta receptors by isoproterenol (Prophylon), while propranolol (Inderal) slightly accelerated gastric evacuation by blocking beta receptors. A pretreatment by phenoxybenzamine of the animals did not affect epinephrine influence whereas a pretreatment by propranolol completely abolished the inhibitory effect of epinephrine on gastric motility. These results suggest the presence of a slight beta receptor tone in gastric motility at rest, and indicate further that epinephrine exerts its inhibitory effect on gastric motility via adrenergic beta receptors.