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Biomedical subjects

I Lazăr

Publications and source records attributed to I Lazăr.

9 recordsLinked to original sources
PubMed1981

Plasma renin activity in hyperthermic rats.

Heating rats exposed 30' to a 40 degrees C environmental temperature increases plasma renin activity (PRA). Propranolol as such decreased PRA, but heating propranolol-treated rats induced also an increased PRA. Hexamethonium increases PRA, that increases additionally when rats are heated. It may be concluded that increased PRA by heating is produced by other ways as catecholamine response and stimulation of beta-receptors, despite the important sympatho-adrenergic reaction that occurred in this circumstance [6], [13], probably by a decreased glomerular filtration rate and consequently that of Na in macula densa. Hyperthermia produced also an important plasma aldosterone increased concentration.

Aldosterone↗
PubMedDate not supplied

Effects of a seven-day hypokinesia on the digestive tract of nonpregnant and pregnant rats.

Hypokinesia (HK) produced by a 7-day contention of pregnant rats in small cages is followed by a discrete decrease of PAS reaction for glycoproteins in the submandibular and sublingual glands, in the mucosa of the stomach, duodenum, small intestine and colon, and also by a small but evident increase of that for leucineaminopeptidase and acid phosphatase in the duodenum and in the intestine. The moderation of these reactions may be explained by the small interval of contention, and not by pregnancy, because the changes are similar in male rats after the same interval. After a longer interval, these reactions change in the same manner but they are more evident, as results from our previous studies. They are not connected with a corticosterone hypersecretion (the principal glucocorticoid in rat) because adrenalectomy does not influence them as results from our previous research. HK increases the 4 and 5 isoenzymes of lactic dehydrogenase (LDH) in the stomach. In the small intestine appeared only the LDH 4 and 5 isoenzymes, HK increases LDH5 isoenzyme. Adrenalectomy increases all LDH isoenzymes of gastric mucosa, and in the small intestine all five fractions appeared, but with a slight activity of LDH 1 and 2. This relation between adrenal hormones and these isoenzymes must be further studied, especially after HK. After a 7-day HK, nonpregnant female rats present an augmented total gastric acid output (TAO), as previously found by us in males. After adrenalectomy this acid hypersecretion disappeared. Even smaller values for TAO were found. Pregnancy considerably increased TAO which may be due, as we have already found, to a blood pH decrease. After HK this hypersecretion decreased remaining nevertheless great. Progeni born of rats submitted to HK have, after 30 days of life, an augmented TAO. Parts of this research were carried out in order to reproduce by HK, at ground level, the 5-day orbital flight conditions of the soviet Cosmos 1514 biosatellite containing pregnant rats in which we studied some identical parameters.

Acid-Base Equilibrium↗
PubMedDate not supplied

Blood coagulation and fibrinolysis in rats after hypokinesia and hyperthermia.

Coagulation and fibrinolysis were studied in rats exposed to hypokinesia (HK) obtained by including rats (for 1, 2 and 3 weeks) in small cages designed to limit their movements, permitting only spontaneous feeding (a method widely used for mimicking space flight conditions). The number of thrombocytes, the Quick time, the Howell time and the euglobulinlysis time (ELT) decreased after 1 and 2 weeks of HK; however, after 3 weeks, the parameters of coagulation approached normal control levels, while ELT was still significantly under the control values. An increased blood level of corticosterone in animals subjected to HK suggested that changes observed in the blood coagulation could be linked with it. After exposing rats to heat, similar changes were noticed, i.e. thrombocytopenia and an increase in the speed of coagulation and fibrinolysis. When hyperthermia was induced in hypokinetic animals (after 1 and 2 weeks of HK), the association of exposure to HLK and heat was not followed by a cumulative response.

Animals↗
PubMedDate not supplied

The influence of magnetic fields on some humoral parameters and on resistance to hyperthermia in rats.

The influence of magnetic fields of moderate intensities (50 and 120 Oe) was studied in rats after single or repeated exposures with or without a rise in environmental temperature. The following parameters were investigated: the number of erythrocytes and leucocytes, the percentage of different varieties of leucocytes, serum Na+ and K+, plasma corticosterone, ascorbic acid in adrenals, blood catecholamines, plasma fibrinolytic activity, plasma antidiuretic hormone. The resistance to hyperthermia was tested after single exposures to magnetic fields and the survival time was measured. The only significant change recorded in the number of blood cells was a leucopenia after single exposures to 50 Oe for 4 hrs. The parameters indicating the activity of the adrenal cortex were not altered significantly. A moderate rise in blood noradrenaline suggested a possible mild stimulation of the adrenergic system. The plasma fibrinolytic activity was significantly stimulated after single exposures, but no change in fibrinolysis could be recorded after repeated exposures to magnetic fields. Changes observed in plasma ADH were not conclusive. The resistance of animals to hyperthermia - as a general test of reactivity - showed minimal changes in the survival time, loss of weight, and rectal temperature in animals exposed to hyperthermia (40 degrees C) under the influence of the magnetic fields.

Animals↗