Showing papers in "Acta physiologica latino americana in 1982"

Antistress and antifatigue properties of Panax ginseng: comparison with piracetam

Abstract: The antistress and antifatigue properties of a Chinese ginseng preparation were tested on Swiss albino mice, exposed to various experimental models of stress, and were compared with those of piracetam. Both ginseng and piracetam were administered chronically in drinking water for 16-18 days as well as acutely, by injection, 30-60 min prior to the experiments. Reactivity of the mice, loss in body weight, amount of faeces, length of endurance and incidence of mortality were graded and measured. Both piracetam and ginseng treatment provided good protection against electroshock stress when compared to the untreated mice; fighting scores, incidence of tonic convulsion and mortality were significantly less in the treated groups. In the heat stress experiments, both piracetam and ginseng provided significant protection to the treated mice against exposure to heat. In the fatigue stress of forced swim test, ginseng treatment provided effective adaptation to fatigue and increased endurance in both male and female mice; piracetam showed some antifatigue effects on the male mice only. In the locomotor activity tests, ginseng did not depress motility, while piracetam did so in the later part of the tests. These results are discussed in the light of the antistress properties of the drugs as reported in the literature.

Effect of estrogen and progesterone priming on the uptake and release of serotonin and noradrenaline from the ventromedial hypothalamus.

Abstract: Estradiol benzoate (EB) or EB plus progesterone (P) were administered to chronic ovariectomized rats in doses which are known to induce sexual receptivity. P was injected 48 hr after EB and the animals were decapitated 54 hr after E.B. The ventromedial hypothalamus (VMH) (excluding the arcuate-median eminence region) was dissected out and used to determine 3H-noradrenaline (3H-NA) and 3H-serotonin (3H-5-HT) uptake and release induced by high potassium concentration. Animals injected with oil were used as controls. VMH from EB (10 micrograms/kg) plus P (2 mg/kg) primed animals had higher release of 3H-NE than controls; uptake and release of 3H-5-HT was also augmented in these animals. EB (100 micrograms/kg) priming alone did not induce significant variations. The increase in 3H-NA release is interpreted as evidence of incremented activity in a 3H-NA system, facilitating sexual receptivity. The change in 3H-5-HT uptake and release is discussed in respect to the existence of an inhibitory serotonergic system modulating sexual behavior.

Modifications of the pituitary-thyroid axis induced by hypobaric hypoxia.

Abstract: The effects of simulated altitude induced by a decompression chamber upon the blood levels of thyrotropin (TSH), thyroxine (T4) and triiodothyronine (T3), measured by radioimmunoassay, were studied in male Wistar rats. When blood was extracted during the first 15 minutes after the rats were removed from the chamber and analysed, it was found that TSH levels decreased at 380 mmHg during 24 hours and sometimes at 440 mmHg during 24 hours, but this did not happen when the exposure lasted a week. Likewise, serum levels of T4 and T3 decreased at 440 mmHg during 24 hours, but they did not decrease using the same exposure during a week. When the blood was extracted 1 hour after the rats were removed from the chamber and analysed, TSH levels markedly increased at 380 mmHg and at 440 mmHg, during 1 day and during a week. Serum T4 and T3 levels were found to be normal. These results show that severe hypobaric hypoxia is needed in order to depress serum TSH levels. When the rats are removed from the decompression chamber, however, a rebound effect with marked increase in serum TSH levels can be seen before 1 hour elapses.

Ultrastructural changes in somatotropic cells induced by anemic or hypoxic hypoxia.

Abstract: Somatotropic cells from three months old male mice, made hypoxic by either bleeding or exposure to 0.5 atm. barometric pressure in a decompression chamber, showed important ultrastructural changes when compared with normoxic controls, during the 36 hours that follow initiation of hypoxia. These changes were found to be similar for both types of hypoxic animals. An equivalent number of dark cells, cells with a swollen rough endoplasmic reticulum (RER), extremely granulated and degranulated, were successively--and in this order--seen along the experiment. Most of the observed differences between experimental and control animals appears as a magnification of the normal circadian rhythms. The degranulation rate, which probably reflects growth hormone (GH) secretion rate, was found to be about three times greater in hypoxic than in control mice. These findings indicate that a decrease in the red cell mass or its consequence (hypoxia), induce important ultrastructural variations in somatotropic (STH) cells, which may or not be specific.

Exchange of palmitic acid from cytosolic proteins to microsomes, mitochondria and lipid vesicles.

Abstract: The presence of two fractions with affinity for 1-14C palmitic acid was demonstrated in the 105,000 x g supernatant of rat liver homogenate by Sephadex G-75 gel filtration. The lowest molecular weight fraction was identified as fatty acid binding protein as judged by its relative elution volume in Sephadex G-75, its binding characteristics to sulfobromophthalein and palmitic acid binding inhibition by flavaspidic acid. Discontinuous sucrose gradient was used to study palmitic acid exchange from these cytosolic fractions to microsomes and mitochondria. Both fractions from rat liver were more effective than albumin in the exchange of palmitic acid to particulate material. Palmitic acid was exchanged from fatty acid binding protein to liposomes. This and perhaps other cytosolic protein/s participate in cellular fatty acid transport.

Effect of starvation and refeeding on the blood and liver of domesticated rabbits

Abstract: A group of male rabbits was starved for 7 days. Their blood samples were collected, before and after the starvation period. Six rabbits were slaughtered for the recovery of livers, while the rest were refed for the next 7 days, at the end of which their blood samples were collected and livers taken out for various analyses. After 7 days of starvation, the total leukocytic count, haemoglobin, bilirubin, proteins and glucose contents, and activities of alkaline phosphatase and glutamate pyruvate transaminase of blood serum decreased significantly, while its lactate dehydrogenase activity and cholesterol, total lipids and urea contents showed a significant increase. In liver, except for the bilirubin and glucose contents, all the biochemical components--RNA, DNA and total proteins included--showed highly elevated values. Refeeding of the starved rabbits tended to normalize most within 7 days. Although RNA, DNA, total proteins, cholesterol and urea contents did not reach the normal level in liver during this period, they were definitely less than those of the starved condition. The hepatic transaminases activities and lipid content in starved + refed livers were considerably decreased during the refeeding period. The histological parameters were slow to recover.

Ecdysteroids: biochemical mechanism of 20-hydroxyecdysone inactivation in Triatoma infestans (Hemiptera, Reduviidae).

Abstract: When 3H-20-hydroxyecdysone was injected into Triatoma infestans during the fifth nymphal instar, it was converted to very polar metabolites (peak 1). The polar metabolites were glucuronoconjugates of 20-hydroxyecdysone. Acetylation of the conjugates followed by hydrolysis with glucuronidase gave a major labelled product: 20-hydroxyecdysone and minor peaks corresponding to a mixture of 20-hydroxyecdysone acetates. These results indicated that the 2,3,22,25-glucuronoconjugates of 20-hydroxyecdysone were the principal products in the inactivation process.

Influence of corticoids on the production of glomerulopressin by isolated rat liver.

Abstract: The isolated liver of rats treated with dexamethasone, hydrocortisone, and deoxycorticosterone acetate (DOCA) was perfused with Krebs-Ringer Bicarbonate (KRB). The liver of adrenalectomized rats was also perfused with KRB. The glomerulopressin activity of the ultrafiltrate of the liver perfusates was assayed in the tonic tension contraction (TTC) of isolated stomach fundus from rats. As glomerulopressin is known to be a glucuronide, it was inactivated with beta-glucuronidase to confirm that the effect on the stomach fundus was due to the glomerulopressin and not to an autacoid. It was observed that dexamethasone, hydrocortisone and DOCA inhibit glomerulopressin production, but adrenalectomy had no effect, therefore it can be deduced that the adrenals are not necessary for the production of glomerulopressin.

Characteristics of aldosterone binding in rat and human serum.

Abstract: Binding of cortisol and corticosterone by serum proteins is well established, but discrepancies exist regarding aldosterone. We have observed that approximately 1% of 3H-aldosterone incubated with rat serum was bound in a time-dependent process, although it was not competed by a large excess of non-radioactive aldosterone, assessed by Florisil separation or gel filtration on Sephadex G-50 columns. After electrophoresis on cellulose acetate of rat serum incubated with 3H-aldosterone, specific or non-specific binding to protein fractions was not obtained. Further, a 10 000-fold molar excess of aldosterone (10 microM) displaced only 34% of the bound 3H-aldosterone to rat serum, preventing the calculation of the IC50 value. Increasing concentrations of aldosterone (3-83 nM) did not displace 3H-corticosterone bound in rat serum to presumably corticosterone binding globulin (CBG). In contrast, inhibition of this binding by 3-83 nM corticosterone was concentration dependent, showing an IC50 value of 10(-8) M. In normal human serum, binding of 3H-aldosterone demonstrated competition by a 100 and 1 000-fold excess of aldosterone. Displacement curves of 3H corticosterone bound to human serum by 1.7-75 nM corticosterone or 0.05-8.8 microM aldosterone yielded IC50 values in the range of 10(-8) M for corticosterone and 10(-6) M for aldosterone. With horse serum, aldosterone's binding affinity was three orders of magnitude lower than that of corticosterone. These studies suggest that in the rat aldosterone was loosely and weakly bound to a high capacity binder, possibly albumin. In agreement with the work of others, in humans aldosterone may be bound to both CBG and albumin. The current data do not substantiate for the presence of specific aldosterone binding proteins in serum.

Sensitivity of enzymatic release due to ischemia in the isolated rat heart.

Abstract: The sensitivity of cardiac enzymes (GOT, a-HBDH, LDH, LDH-1, CPK and CPK-MB) was studied in the isolated rat heart subjected to 0 (non-ischemic), 20, 30 and 40 min of total global ischemia (0 ml/min) followed by reperfusion in which three consecutive perfusate samples were collected for enzymatic measurements. Cardiac function, estimated by peak tension (Tp), maximal rate of tension development (Tc) and relaxation (Tr) decreased to 0 with ischemia and recovered with reperfusion to 100% in the 20 min, 50% in the 30 min and 10% in the 40 min ischemic groups. In these three groups, enzymatic release, measured as the relative increment (RI) with respect to the control samples, gave significantly higher values than those of non-ischemic hearts (P less than 0.001). LDH-1 was the most sensitive enzyme (P less than 0.0005) for the detection of ischemia in these experimental conditions.

Effects of cyproterone and tamoxifen upon the hair waves in mice.

Abstract: The effects of cyproterone and of tamoxifen citrate upon the hair waves were studied in normal and castrated C57 mice. Cyproterone (1 mg/day) had no effect upon the hair waves in normal male mice and produced a slight inhibition of the diffuse growth induced by their castration. Tamoxifen citrate (1 mg/day) had no effect upon the hair waves in normal female mice and produced a marked inhibition (0.2 to 1 mg/day) upon the diffuse hair growth induced by their castration. The differences between the effects of castration and the effect of these drugs can be explained in the case of cyproterone by a slight agonistic androgenic effect and in the case of tamoxifen citrate by a marked agonistic estrogenic effect upon the hair follicles in mice.

Biochemistry of the developmental cycle of Triatoma infestans (Vinchuca). VI. Identification and lipid composition of hemolymph lipoproteins of adult males

Abstract: Three lipoproteins were separated from the haemolymph of adult males of Triatoma infestans fed on hen blood. The densities were similar to the high density lipoprotein (HDL) and to two very high density lipoproteins (VHDL) isolated from a pool of adult male and female insects fasted during twelve days. The relative distribution and composition of the three lipoproteins were studied. The fatty acids were mainly carried by the 1.3 and 1.2 diacylglycerols of high density lipoprotein. Triacylglycerols were minor components. Similarly to fasted insects, the main fatty acids were oleic and palmitic. Linoleic was also present. Very high density lipoproteins (VHDL-II) (d 1.25-1.26) were found in the haemolymph of male insects. The relative distribution of HDL and VHDL on fed and fasted insects was different.

Decrease in time to peak tension produced by calcium blockers and isoproterenol. Its dependence on extracellular calcium.

Abstract: The present experiments were designed to analyze the effect of verapamil, nifedipine and isoproterenol on myocardial contractility (+dT/dtmax) and time to peak tension (TTP) and its dependence on extracellular calcium concentration (Ca2+). The experiments were performed on cat papillary muscles from reserpinized cats. At (Ca2+) 1.34 mM the negative inotropic effect of cumulative doses of verapamil and nifedipine and the positive inotropic effect of isoproterenol occurred associated with a significant and dose-dependent decrease in TTP. The decrease in TTP produced by calcium blockers was completely reversed by the addition of calcium in a close parallelism with the recovery in myocardial contractility: At (Ca2+) 1.34 mM; verapamil 10(-6)M significantly decreased TTP from 299 +/- 14 msec to 250 +/- 11 msec. At (Ca2+) 15 mM values for TTP were 285 +/- 7 msec (control) and 291 +/- 5 msec (verapamil). Nifedipine 5 X 10(-7) M decreased TTP from 343 +/- 20 msec to 246 +/- 4 msec (Ca 1.34 mM). Values of TTP at calcium 15 mM were 296 +/- 6 msec (control) and 300 +/- 17 msec (nifedipine). On the contrary, the significant decrease in TTP produced by isoproterenol 10(-5)M at (Ca2+) 1.34 from 266 +/- 14 msec to 222 +/- 14 msec was still present at (Ca2+) 15 mM: 233 +/- 8 msec (control) and 220 +/- 8 msec (isoproterenol). The results suggest that the decrease in TTP produced by calcium blockers and isoproterenol is mediated by different mechanisms.