Physiologia Bohemoslovaca最新文献

Sexual behaviour of adult male rats weaned prematurely--on day 15 after birth--and of males weaned at the optimal age--on day 28--was compared at two life periods: at the age of 90 days and when the males were one year old. Sexual behaviour was evaluated by means of three characteristics: a) sniffing behaviour, b) copulatory readiness, c) copulatory performance. The differences in sniffing behaviour between prematurely and normally weaned males were assessed in terms of their responsiveness to sccents of unrelated adult males or oestrous females and from the point of view of both housing conditions after weaning and the animals' sexual experience. No differences were found in copulatory readiness as well as in copulatory performance between the two groups of males tested in their interaction with a female exhibiting complete precopulatory pattern. The morphological examination revealed no differences in the weight of reproductive organs and in spermatozoa development. We conclude that the sexual behaviour as well as reproductive organs of male rats are very resistant to early separation of pups from the mother which contrasts with some earlier findings.

A simple blind study with small doses of naloxone (0.8-1.6 mg i.v.) was carried out in 11 patients with hypersomnia with sleep apnoea (HSA). The effect was studied by diurnal polysomnography. It was found that the administration of naloxone was followed by significant prolongation of wakefulness and by significant shortening of the total duration of the second stage of NREM sleep. The duration of the apnoeic episodes was also significantly shortened after naloxone, although their number did not alter. Increased activity of the endorphinergic system (which naloxone inhibits by receptor competition) evidently plays a role in the pathophysiology of HSA.

The effect of i.v. bolus administration of PGE2 and PGF2 alpha on carotid blood flow (Q) and mean arterial blood pressure (MAP) was recorded in 21 anaesthetized normotensive control (N) and 12 rats with 1K1C renovascular hypertension (RH). From the measured parameters the regional vascular impedance (PVI) and the change in blood volume were calculated. In normotensive animals both PGs elicited a dose-dependent initial fast increase of Q (threshold dose 0.4 ng/kg) and a decrease of MAP and PVI (threshold dose 0.4 micrograms/kg). Subsequently, Q decreased below the initial level. MAP and PVI remained depressed after E2 but increased after F2 alpha. The time course of the Q and MAP responses was analyzed in more detail at a standard dose 4 micrograms/kg. The average time to peak of the first phase was 12 s and of the second approximately 80 s. The initial levels of Q and MAP were reestablished within 3 to 4 minutes. The total volume of carotid blood flow obtained by planimetric integration was unaltered after F2 alpha but depressed after E2. In hypertensive animals both phases of the response to E2 were significantly retarded and the Q response was nearly abolished. On the other hand, the time course of the reaction to F2 alpha was unchanged but the magnitude of the second pressoric phase was reduced. Thus, the capacity of the carotid vascular bed to dilate remains the same in RH while the ability to constrict is limited. It is concluded that the response of MAP and Q to both PGs are relatively independent.(ABSTRACT TRUNCATED AT 250 WORDS)

It has repeatedly been found that haemodynamic changes during hypoproteinaemia in the chronic phase of the nephrotic syndrome are different from those during hypoproteinaemia in the acute phase. In our series of patients, a decrease in the filtration fraction and relative hyperperfusion of the kidneys were associated with the presence of the nephrotic syndrome. No significant changes in renal haemodynamics were observed in patients with chronic glomerulonephritis without the nephrotic syndrome or in a group of healthy volunteers. The question of whether relative hyperperfusion of the kidneys in a repeatedly relapsing nephrotic syndrome can lead to the development of focal segmental glomerulosclerosis needs to be elucidated.

The disintegration of erythrocytes by brilliant cresyl blue was studied in rabbits and cats during two hypoxic periods resulting in apnoea which was followed by artificial ventilation and recovery. The rate of erythrocyte disintegration was measured after 2 hours' incubation in isotonic NaCl or Krebs-Ringer solution plus brilliant cresyl blue (0.5 mmol.l-1). Significant increases of disintegration rates were found in rabbits during recovery in both incubation solutions. Erythrocytes in cats seemed to be more resistant to acute hypoxia, as their disintegration rate rose only in isotonic NaCl solution, and that only transiently. Brilliant cresyl blue--induced erythrocyte disintegration in cats did not differ from the control values during 10 min of spontaneous breathing after the first and the second period of hypoxia in the isotonic NaCl solution, but it was significantly lower in Krebs-Ringer solution. The possible factors influencing the erythrocyte disintegration rate in acute hypoxia are discussed.

During the dynamic phase of external cooling of euthermic golden hamsters in the initial period of metabolic response, peripheral body temperature is the decisive control variable determining the level of metabolic heat production. Under these conditions the rate as well as the magnitude of the peripheral body temperature change constitute the effectual input to the controller of body temperature. The apparent sensitivity with which the regulator drives the metabolic response to unit change of the peripheral temperature is in an inverse relation to the rate of peripheral temperature change. This parameter, despite its limited significance can serve as a working index characterising the thermoregulatory system in different groups of experimental animals of the same species providing that the actual conditions of the experiment are comporting.

Isolated heart atria from rats of different ages were incubated in a medium containing (14C)choline and the rates of the uptake of (14C)choline into the tissue and of its conversion to (14C)acetylcholine (ACh) were measured. The synthesis of (14C)ACh (expressed per 1 g of fresh weight) increased from birth until 30 days of age and diminished after 40 days of postnatal life. The rate of (14C)ACh synthesis was considerably diminished when Na+ was omitted from the incubation medium or when hemicholinium-3 was added to it; these effects of the absence of Na+ and of hemicholinium-3 were already manifest on the 1st day after birth, indicating that the sodium-dependent high-affinity uptake of choline is operative and takes part in the synthesis of ACh in the heart from the start of postnatal life (if not earlier). In newborn rats, 4% of the (14C)choline that had been taken up by the atria was converted to (14C)Ach; this proportion rose to 7-9% at the age of 20 and 30 days and in adulthood. The total uptake of (14C)choline expressed per whole atria kept increasing from birth till adulthood when related to the whole atria, but it diminished when related to 1 g of atrial weight.

Negative correlation was found between the activity of liver glucose-6-phosphatase (EC 3.1.3.9) and the increasing radiation dose 24 h after continuous irradiation of rats. A dose response of increased fructose-1,6-diphosphatase (EC 3.1.3.11) was not confirmed.

The authors studied the acidification capacity of the kidneys in 60 healthy subjects aged 18-70 years after a single load of NH4Cl in a dose of 0.1 g/kg. The acidification load was followed by a significant increase in NH4+ excretion in the first five hours afterwards in young individuals (18-30 years). In subjects aged over 50, changes in NH4+ excretion were nonsignificant under these conditions. Titratable acid excretion rose significantly after the given acidification load in subjects aged 18-60 years; in older subjects it no longer increased significantly. Changes in titratable acid excretion displayed a significant correlation to the renal excretion of phosphates. The findings indicate that the diminished capacity of older subjects to increase titratable acid excretion after an acute NH4Cl load is due to an insufficient decrease in the tubular resorption of phosphates. Renal capacity for adequate reduction of the urine pH after a NH4Cl load was unimpaired.

The duration of protective action of valproate (VPA, 400 mg/kg i.p.) against metrazol-induced seizures was studied in rats aged 7, 12, 18 and 90 days. Fifteen, protected. The results differed between the various age groups after longer intervals: The protection was longest in 18-day-old rats--seizures did not appear even six hours after VPA administration. On the contrary, all 7-day-old rat pups exhibited seizures two hours after VPA. Plasma levels of VPA were measured by means of gas chromatography in the same age groups after an identical dose of VPA. After a single injection of VPA a clear-cut two-peak curve of plasma level was found in all young groups, which may be due to an enterohepatic recirculation of VPA. The maximum plasma levels were lowest in 7-day-old rats, the three older groups exhibited similar values. Plasma half-life was longest in the youngest animals (9.24) and decreased with age; values for 18- and 901 day-old rats did not differ (2.57 and 3.05 h respectively). No clear-cut correlation was found between the antimetrazol action and its plasma levels.