Acta physiologica Polonica最新文献

Earlier studies from this department have demonstrated that neurones of the V-th nerve motor nucleus (NVmt) have oligosynaptic, inhibitory output to the inspiratory motoneurone themselves under the influence of a polysynaptic input from vagal afferents. To check the hypothesis that NVmt is a part of the pneumotaxic mechanism, we studied the effects of pharmacological microblockade of the NVmt on Breuer-Hering reflexes in halothane-anesthetized, paralyzed and artificially ventilated rabbits. Activities of NVmt neurones and phrenic nerve firing were recorded. Acid-base balance was controlled and histologic examinations were routinely performed. Expiratory activities were regulatory found in NVmt. Its blockade elicited a typical apneustic breathing. During the blockade the Breuer-Hering reflexes gave "paradoxical" effects: an increase in central respiratory frequency following inflation, inspiratory apneusis in response to deflation. We conclude that the NVmt is an important component of the pneumotaxic mechanism or even the anatomical substrate of the pneumotaxic "centre".

The study was carried out on perfused livers isolated from rats receiving ethanol (EtOH) as their only drinking fluid for the period of 4 weeks. Twelve, 24, 72 and 120 hours after EtOH withdrawal the livers were isolated and perfused with 100 ml of perfusion mixture with addition of EtOH (0.2% final concentration). After 12 hours of EtOH withdrawal acceleration of the EtOH elimination from perfusate was observed. It returned to the control level after 24 hours, but after 72 and 120 hours of abstinence the rate of EtOH elimination from perfusate was found to diminish. CCl4 injected to the rats in doses of 2 and 5 mmoles/kg once a week for the period of 4 or 8 weeks, resulted in decreased EtOH elimination from the perfusate. In the EtOH-drinking group previously treated with CCl4 we found that irrespective of the time of EtOH withdrawal, EtOH elimination did not differ from that in the respective CCl4 treated group, only 12 hours after its withdrawal EtOH elimination was decreased in livers injured with CCl4 in dose of 5 mmoles/kg.

2-deoxy-D-glucose (2-DG), the unmetabolizable analogue of glucose induces a series of metabolic, hormonal and behavioral responses, causing cellular glucoprivation. According to in vitro studies, 2-DG inhibits phosphofructokinase in cultured human cells. The present investigations deal with changes in the cytosolic glucose-6-phosphate dehydrogenase activity following in vivo 2-DG administration. A single dose of 2-DG (600 mg/kg) has no influence on the activity of glucose-6-phosphate dehydrogenase in the cytosol of liver, heart and skeletal muscle of the rat. The concomitant increase in serum glucose, lactate and FFA concentrations observed in the study indicates indirectly a stimulation of adrenergic system. After three days of successive administration of 2-DG to rats, dehydrogenase activity decreased in the liver by approx 57% and in the skeletal muscle by approx 82% in comparison with control animals. Moreover the in vivo effect of 2-DG was found to be fully reversible, probably when the total amount of the inhibitor was excreted.

The investigation was performed on 8 sheep with implanted catheters in the common bile duct and in the cystic duct. Sodium taurocholate and sodium dehydrocholate were infused into the jugular vein at the rate of 50 mumol/min for 20 min. Directly after the termination of the sodium taurocholate infusion, the volume of the secreted bile increased from 8.4-9 microliters.kg-1.min-1 to the highest mean value of 17.8 microliters.kg-1, min-1, with a simultaneous increase in the concentration of cholates from 1.71 mmol/l to 4.82 mmol/l and bilirubin from 271.1 mumol/l to 461.7 mumol/l. The concentration of cholesterol and phospholipids in the bile also increased, but did not reach statistically significant values. The infusion of sodium dehydrocholate caused an increase in the bile secretion to the highest mean value of 20.59 microliters.kg-1.min-1 with a simultaneous decrease in the concentration of bilirubin to 148.75 mumol/l, cholesterol to 233.0 micrograms/ml, phospholipids to 56.11 micrograms/ml and cholate to 1.0 mmol/l. The results show that biliary secretion of phospholipids, cholesterol and bilirubin is dependent on the secretion of sodium taurocholate rather than on dehydrocholic acid.

Changes in body temperature, oxygen uptake (VO2), heart rate (HR), sweating rate and plasma osmolarity were examined in 10 human subjects, performing four successive 30 min exercise-bouts of the same intensity (50% VO2 max) separated by 30 min rest periods. In spite of the rest intervals and replacement of body fluid loss there was a progressive increase in VO2. HR, rectal (Tre) and mean body (Tb) temperatures in consecutive exercise bouts. The thermoregulatory efficiency showed an increasing tendency, and a delay in the sweating response at the beginning of each exercise was shortened. It is concluded that a drift in metabolic and temperature responses to exercise, reported throughout a long-term continuous work, occurs also in the euhydrated subjects performing a prolonged intermittent exercise. It is not caused by an impaired thermoregulation during exercise but rather by insufficient restitution of metabolic processes during rest intervals.

Investigations have shown the presence of a cardiodepressant factor in the fluid incubating the posterior pituitary lobe "in situ", which decreased contraction frequency of the isolated heart auricle (Acta Physiol. Pol., 1984, 35: 460-468). The influence on the spontaneous contraction frequency of the isolated heart auricle of the following synthetic neuropeptides was determined: substance P, leu-enkephalin, met-enkephalin, angiotensin II, arg-vasopressin, oxytocin, delta sleep-inducing peptide and atrial natriuretic factor. It was found that the investigated neuropeptides had no effect on the contraction frequency of the isolated auricle of the heart right atrium of two-day-old rat in a concentration from 2.1 x 10(-7) to 1 x 10(-3) mol/l in the bathing medium and it was concluded that their biological properties differ from the cardiodepressant factor.

Neocortical and hippocampal EEG activity was recorded in 23 rats subjected to the bilateral electrolytic lesions of the diencephalic zona incerta (ZI). The aim was to find whether damage to ZI can replicate insomnia and disturbances in cortical EEG desynchronization and hippocampal theta rhythm found after lesions of the lateral hypothalamic (LH) area. No effect of the ZI lesions on waking-sleep cycle was found. The amplitude and frequency of cortical waves and hippocampal theta rhythm during waking were changed only in some rats. These changes were small, short-lasting and bidirectional (toward and increase or decrease in different subjects). Both the amplitude and frequency of paradoxical sleep theta were depressed in part of animals. Thus the marked EEG changes after LH lesions can not be attributed to simultaneous damage of the adjacent subthalamic region. However, the ZI seems to constitute a part of a larger system regulating cortical arousal and hippocampal theta rhythm.

During a 4-week period the rats received ethanol (EtOH), as their only drinking fluid, in a concentration ranging from 6% to 20%. In the period of 72 hours after EtOH withdrawal the rats received diazepam (DZP), imipramine (IMI) or caffeine (CAFF) i.p. twice a day in a 12-hours interval. In the experiments carried out on the livers isolated from these rats, we observed the diminution of the rate of EtOH elimination from the perfusate by the livers of DZP and IMI treated rats. CAFF did not change the rate of EtOH elimination.

The influence of pinealectomy and melatonin administration on the levels of total T3 and T4 plasma levels were determined by RIA method. The results of hormonal measurements were evaluated by means of Student's t-test, and the diurnal rhythm by cosinor method. It has been established that pinealectomy disturbs the T3 diurnal rhythm and caused marked changes in T4 levels during the 24 hours. Exogenous melatonin does not influence the thyroid function during the light phase. During the dark phase, however, its inhibitory effect is prevalent in pinealectomized rats, and the stimulating in sham operated rats.