Physiologia Bohemoslovaca最新文献

Although the role of prostaglandins (PG) in the mechanism of dilatation of the ductus arteriosus (DA) has received considerable attention, no data on their possible interaction with the pressure-induced myogenic reaction are available. There is also a lack of information on PG production by the foetal blood vessels of the guinea-pig, in which the DA closes rapidly. Use of the RIA method showed relatively low PG production by isolated foetal guinea pig blood vessels, as represented by the main products, PGI1 and PGE2. When computed in pmol per mg wet weight, the production of 6-keto-PGF1 alpha (an equivalent of PGI2) was statistically significantly higher in the foetal DA (4.06 +/- 1.13) than in the foetal aorta (2.04 +/- 0.33). The isolated DA reacts to a sudden increase in perfusion pressure by marked constriction, which in some cases leads to functional closure of the DA. In 10(-7) to 10(-5) mol.l-1 concentration, PGE2 reversibly inhibits pressure-induced myogenic constriction, while under the same conditions the contractility of the DA in response to oxygen is unaffected. In concentrations of 10(-6)-10(-5) mol.l-1, indomethacin, a blocker of PG biosynthesis, also induces pressure constriction and it raises the basal flow resistance of isolated DA preparations. The results indicate that PGs play a modulator role in the pressure myogenic response of the DA of guinea-pig and rabbit foetuses.

The authors studied 1-14C-palmitate metabolism in rat muscle, renal cortex and liver incubated with synthetic hippurate in vitro (1 mmol/l). a) Hippurate did not affect 1-14C-palmitate uptake and utilization in the muscle (hemidiaphragm). b) In the renal cortex it stimulated only the incorporation into total lipids and from the individual lipid fractions into mono- and diglycerides and free fatty acids (FFA). c) In the liver it stimulated the uptake, oxidation to 14CO2 and incorporation into total lipids and, out of the individual lipid fractions, into phospholipids, triacylglycerols and free fatty acids. d) Hippurate already had a significant effect in the concentration of 0.5 mmol/l, i.e. during the development of the disturbance and not just as a supplementary factor in advanced renal insufficiency. It is concluded that, by interfering with fatty acid metabolism, the hippurate present in the serum of patients with renal insufficiency plays an active role in the development of dyslipoproteinaemia in such patients.

Successful and unsuccessful reaching attempts in rats were analysed with the aim of resolving the question of the programming of reaching movement. The course of movement was monitored continuously by a method based on the law of magnetic induction. The study of reaching showed that the forelimb extension had the same time course characteristics in both cases of reaching attempts and displayed features of preprogrammed ballistic movement. The course of the consecutive phases (grasping, forelimb flexion) showed differences between successful and unsuccessful attempts and also between individual successful attempts. The variability of the course of grasping and forelimb flexion indicates that a peripheral feedback participates in regulation of its performance and that the information on grasping the pellet is decisive for the subsequent performance of reaching. Reaching as a whole cannot be considered as a preprogrammed ballistic movement, but some of its components correspond to this pattern.

1. The influence of chronic forelimb immobilization enforcing movement in upright position on blood pressure was studied in monkeys. 2. In the course of 6 months all animals subjected to immobilization became hypertensive due to a parallel increase of systolic and diastolic pressure by about 30%. The hypertension was demonstrable both in awake and anaesthetized animals and persisted even after restitution of a normal movement regime. 3. In the chronic stage (after 15 months), the plasma renin concentration was decreased by 55%, indicating that the renin-angiotensin system activation does not participate in the maintenance of the hypertensive state. The plasma volume was diminished by 18%, while the interstitial fluid volume did not differ significantly from control values. 4. It is concluded that chronic forelimb immobilization in monkeys induces a low-renin hypertension, associated with changes in extracellular fluid compartments resembling the pattern found in the hypovolaemic type of essential hypertension.

Adult SHR aged 19-21 weeks, subjected to osmotic diuresis, responded to an intravenous 1.8% saline loading (15 ml/kg b.w.) with greater sodium excretion than age-matched WKY. Young (6-7 weeks old) SHR and WKY also responded to saline loading with an increased sodium excretion but there were no differences in the relative changes of sodium excretion between young WKY and SHR. In adult WKY, saline loading induced a faster erythrocyte 22Na uptake as compared with adult SHR or young WKY. This suggests that volume and/or sodium loading increased sodium turnover of red cells only in adult WKY. The sodium transport differences found in erythrocytes of adult SHR and WKY could be caused by some membrane differences or could be due to different hormonal and nonhormonal response(s) to saline loading. If similar alterations would also occur in other tissues, they might be important for the sodium excretion pattern.

1. The levels of reduced glutathione (GSH) in the liver and brain of newborn rats were independent of the birth mechanism (Cesarean section or natural birth). A significant increase of GSH content could be demonstrated 3 h after birth in the liver only. 2. The influence of reversible hypoxia (9 vol. % O2 in the respired air for one hour) on GSH and oxidized glutathione (GSSG) levels and the content of thiobarbituric acid (TBA) reagible products were investigated in the liver and brain of newborn rats in dependence on the duration of reoxygenation. Only small changes were observed in the liver indicating a relative resistance of this organ to hypoxic stress and reoxygenation. Distinct effects were found in the brain, indicating that the glutathione status is altered by increased lipid peroxidation.

The anticonvulsant action of a new antiepileptic drug ORG 6370 (Organon International B.V.) was studied in 217 male albino rats aged 7, 12, 18, 25 and 90 days. Epileptic phenomena induced by a subcutaneous injection of a 100 mg/kg dose of metrazol (isolated myoclonic jerk, minimal metrazol seizures and major, generalized tonic-clonic metrazol seizures) were used as a model. ORG 6370 did not influence myoclonic jerks or minimal metrazol seizures in those age groups where they were regularly elicited. In 12-day-old rats pretreatment with ORG 6370 led to the appearance of minimal metrazol seizures, a phenomenon rarely seen under control conditions. Major seizures were suppressed only in adult rats with a 20 mg/kg dose; on the other hand, ORG 6370 exhibited a selective action against the tonic phase of major seizures at all stages of development. The profile of action of ORG 6370 is almost the same as that of phenytoin.

The effects of acute hypoxic hypoxia elicited by N2 inhalation on the driving and timing components of the breathing pattern were studied in 18 adult anaesthetized cats. Two phases could be distinguished in the ventilatory response to acute hypoxia. During the first phase, mean inspiratory flow (VT/TI) increased exponentially up to 240% of the initial value. During the second phase, VT/TI gradually decreased, reaching the control values in the last preapnoeic breaths during the first exposure and remained higher than normal with earlier respiratory arrest in three repeated N2 inhalations. No significant changes could be observed in the timing component of breathing pattern (TI/TT) in the course of the first hypoxic exposure, and the changes in TI/TT did not exceed 7% in repeated attacks. This suggests that the shortening of both inspiratory and expiratory durations increased the breathing frequency up to 130% of its resting value. Moreover, tachypnoea was preserved until respiratory arrest. Accordingly, it is concluded that the decrease in ventilation with the appearance of apnoea during the second phase of N2 inhalation in anaesthetized cats is not due to a failure of respiratory timing, but to a depression of the driving mechanisms which are responsible for this phenomenon.

Golden hamsters with alimentary hyperlipoproteinaemia (fed on a diet in which 44% of the energy was accounted for by fats, 52 mg cholesterol (CH)/100 g) were given apple pulp (10% of the diet) for six months. From the end of the first month up to the end of the experiment, elevation of serum CH, triacylglycerol (TG) and phospholipid (PL) levels and CH and TG accumulation in the liver were effectively inhibited. At the close of the experiment, hyperlipoproteinaemia was characterized by an increase in the amount of very low density lipoproteins (VLDL), which carried 60-80% of all circulating lipids, accounted for over 70% of the total lipoprotein pool and transported almost 60% of the serum CH (high density lipoproteins--HDL--only 16%). The apple diet markedly reduced (by 50-80%) the amount of all lipids in the lipoproteins within density limits of 1,006-1,063 kg/m3 and lowered the total lipid concentration in these density classes and in the lipoprotein pool as a whole (by 50%). The proportion of the individual lipoprotein classes in the lipoprotein pool was not significantly affected. The apple diet did not affect either the chemical composition of HDL or their participation in the lipoprotein pool, but raised the proportion of serum CH transported in this lipoprotein class. Neither the lipoprotein lipase activity of the adipose tissue nor lecithin:cholesterol acyltransferase activity were influenced by the apple diet.