In vitro serum glycogenolytic activity in rats during hypothermia induced with 2-deoxy-D-glucose

During hypothermia induced by intraperitoneal administration of 2-deoxy-D-glucose (600 mg/kg of body weight) the serum levels of glucose and FFA rise and the hepatic glycogen content falls in relation to rats in control group. The glycogenolytic activity of the serum in vitro determined against liver slices is also higher in the group of rats receiving 2-DG. The obtained results point to an activation of the glycogenolysis process and glycolysis in the organism of rats after administration of hypothermia-inducing doses of 2-DG.     

Aminotransferase activity in the brain of rats of various ages during hypothermia

Studies have been made on the activity of aspartate and alanine aminotransferase in the brain of 1, 4, 12-14, 16, 22 days, 1, 1 1/2, 3 months and 2 years old rats under hypothermic conditions (20-19 degrees C). It was shown that hypothermia decreases both total and specific activities of the enzymes in the developing brain. Alanine aminotransferase activity in brain homogenates determined at 37 and 20-19 degrees C, exhibits more significant changes than of aspartate aminotransferase.     

Effect of enhanced geomagnetic activity on hypothermia and mortality in rats

The hypothesis was investigated that variability in the severity of limbic seizure-induced hypothermia in rats was affected by ambient geomagnetic activity. Data were obtained in support of this hypothesis. The depth of the hypothermia was significantly (P < 0.001) reduced if the ambient geomagnetic activity exceeded 35 nT to 40 nT. Mortality during the subsequent 5 days was increased when the geomagnetic activity was > 20 nT. The magnitude of the effect was comparable to the difference between exposure to light or to darkness during the 20 h after the induction of limbic seizures.     

Effect of different albumin media on the lipid-mobilizing action of sympathicotropic substances in vitro.

The authors studied the effect of adrenotropic substances on lipolysis in rat epididymal adipose tissue in albumin medium in vitro. On using albumins of different origin (human, bovine), the pD2 values for catecholamines differed by more than one order, in correlation to the type of albumin used. The isopropylnorsynephrine pD2 values did not differ. The addition of ascorbic acid (100 microng/ml) raised the catecholamine pD2 values and completely equalized the pD2 values found in both media. The pD2 values for the synephrine derivative did not alter. The propranolol pA2 values were not negatively affected by the addition of ascorbic acid. Ascorbic acid also produced a mild increase in the maximum lipid-mobilizing values obtained with any of the given substances in either medium. It was concluded in the discussion that catecholamines are oxidized at different rates in different albumin media and that this oxidation can be inhibited by adding ascorbic acid. Ascorbic acid likewise mildly stimulates the maximum lipid-mobilizing effect. The authors recommend the addition of ascorbic acid to albumin medium as a regular component for the study of adrenergic lipid mobilization.     

Effect of splenic humoral factors on the cholinesterase activity of liver tissue and blood serum in experimental toxic hepatitis in rats

Activity of cholinesterase in the liver of rats with experimental toxic hepatitis decreases, while in the serum it remains unchanged. Introduction of splenin, a spleen preparation, normalizes indices of the cholinesterase activity, extract of muscles possessing no such property. Boiling-heated spleen preparation looses its activity. Activity of the studied enzyme remains unchanged both after splenectomy and splenin introduction to intact animals.     

Effects of insulin and beta-adrenergic blockade on certain indicators of carbohydrate metabolism in the blood and tissues of rats during short-lasting hypothermia

Administration of insulin 1 i.u./100 g of body weight to hypothermic rats causes a fall of glucose and lactate levels in the serum and a rise in myocardial glycogen level in relation to the group of control rats kept at room temperature and to the group of rats subjected only to hypothermia. Beta-adrenergic blockade (propranolol 0.6-1 mg/kg) caused no changes in the levels of carbohydrate metabolites in the serum of hypothermic rats but raised the myocardial glycogen level by 42% in relation to the animals subjected only to hypothermia. Simultaneous administration of both these agents during hypothermia produces a fall of the serum levels of glucose and pyruvate with a rise in the level of lactate, and raises the glycogen level in the myocardium (by about 161%) and in the skeletal muscle (by 54%) in relation to the rats subjected to hypothermia alone. Insulin and/or propranolol fail to prevent glycogen reserve exhaustion in the liver of hypothermic rats which could be due to activation of non-blocked alpha-adrenergic receptors or to the action of yet another glycogenolytic agent, e.g. glucagon, during hypothermia.     

Demonstration of potent, gonadotropin-like biological activity in the serum of rats during midpregnancy

The gonadotropin-like activity (GnLa) of serum from pregnant rats was measured using the rat interstitial cell testosterone (RICT) bioassay. Serum GnLA was elevated on day 9 of pregnancy, peaked at 7.2 μg rat LH-RPl equivalents/ml on day 11 and declined to undetectable levels by day 15. Serum LH, measured by homologous RIA, was consistently low (<20 ng/ml) during pregnancy, except near term.Rat placental lactogen (rPL), which was measured in the same serum samples by rat radioreceptor assay (RRA), reached maximal concentrations on days 12 and 13 of pregnancy.These data suggest the presence in pregnancy serum of a potent-gonadotropin-like hormone, different from pituitary LH, whose origin is unknown. Furthermore, there are discrepancies between the times of appearance of this GnLA and rPL.     

Development of deep hypothermia in rats with limited motor activity

Changes of the main organism functions (breathing frequency, heart rate and shivering) were investigated under hypothermia in two groups of rats. Animals of the first group were fixed rigidly on the special platform with fixing of head and limbs, and those of the second one--the rats, were placed in a punched cylindrical chamber, inside which they could move freely forward and back. In 2.5-3.0 hours after anaesthesia the rats were placed in a refrigerator (-5 degrees C) until they stop breathing. Cessation of breathing of the first group rats occurred in 1.7 +/- 0.3 hours from the beginning of cooling at body temperature 17.3 +/- 0.6 degrees C and the brain temperature 15.7 +/- 0.5 degrees C. In the second group, a prolonged activation of the frequency of breathing, heart rate and intensity of electrical activity of muscles during 2.5-3.0 hours, was observed. Only in 4.5-5.0 hours, the breathing stopped at rectal temperature 12.3 +/- 1.1 degrees C and the brain temperature 12.9 +/- 0.9 degrees C. In these animals, the time of survival in the cold environment increased considerably and the temperature thresholds of the termination of breathing were lowered. Thus, the activation in the thermo-regulative muscle tone and in shivering muscles provides the most effective resistance against cooling of rats, reducing a surface of heat, dissipation and keeping the temperature of internal areas of body.     

Plasma catecholamines in rats during rewarming from induced hypothermia

The present study sought to quantitate the levels of plasma catecholamines [norepinephrine (NE), epinephrine (E), and dopamine (DA)] during induction and rewarming from hypothermia. Male rats (317 +/- 8 g) were made hypothermic by exposure to 0.9% halothane at -10 to -15 degrees C while blood pressure (carotid artery), heart rate, and colonic temperature (Tc) were monitored. Anesthesia was discontinued when Tc reached 28 degrees C. Tc continued to fall but was held at 20-20.5 degrees C for 30 min. Rewarming was then initiated by raising ambient temperature to 22 degrees C. Arterial blood samples were taken 1) before cooling, 2) just before rewarming, 3) when Tc reached 22 degrees C during rewarming, and 4) when Tc reached 27 degrees C during rewarming. Plasma was assayed radioenzymatically for catecholamines using both phenylethanolamine-N-methyltransferase and catechol-O-methyltransferase procedures, and hypothermic induction resulted in significant increases in NE, E, and DA above control levels (P less than 0.01). With rewarming to Tc = 22 degrees C, all catecholamines increased above the level observed during hypothermia (P less than 0.01), and NE and DA increased still further (P less than 0.01) when Tc reached 27 degrees C. The levels of plasma catecholamines observed during hypothermia and during the rewarming phase indicate a role of the sympathoadrenal medullary system in the metabolic adjustments associated with hypothermia and recovery. During rewarming, the levels of E and NE attained exceed those at which both substances may be expected to act as circulating hormones.     

Effect of various agents on ovarian plasminogen activator activity during ovulation in pregnant mare's serum gonadotropin-primed immature rats

The plasminogen activator/plasmin synthetic substrate S-2251 was used to measure the effect of indomethacin, cycloheximide, colchicine, dexamethasone, tranexamic acid, and aprotinin on the elevation of ovarian plasminogen activator (PA) that normally occurs during ovulation in the rat. Young Wistar rats were weaned on the morning of Day 21, given 4.0 IU of pregnant mare's serum gonadotropin (PMSG) s.c. at 0800 h on Day 22, and given 10.0 IU of human chorionic gonadotropin (hCG) on Day 24. These animals normally began ovulating between 0000 and 0200 h on Day 25. The induced ovulation rate was 11.5 +/- 2.2 ova/rat, based on the number of ova in the oviducts of control animals at 0900 h on Day 25. In the controls, PA activity in extracts of homogenized ovaries increased 3-fold from 0.125 +/- 0.010 OD units just before the administration of hCG to 0.371 +/- 0.021 at 12 h after hCG, i.e., near the time of ovulation. Indomethacin, in doses of 0.1-1.0 mg/rat, inhibited ovulation but did not inhibit the normal increase in PA activity, whereas indomethacin at the high dose of 10.0 mg/rat inhibited both ovulation and PA activity. Cycloheximide, at a dose of 0.1 mg/rat, was given at 12 h before hCG, immediately after hCG, and at 9 h after hCG. This agent inhibited ovulation most effectively when given at 12 h before hCG, yet it inhibited PA activity most effectively when given immediately after or at 9 h after hCG. Colchicine, at a dose of 0.1 mg/rat, inhibited ovulation, but not PA activity, when it was given 1 h before hCG.(ABSTRACT TRUNCATED AT 250 WORDS)