Acta physiologica Academiae Scientiarum Hungaricae最新文献

The escape of radioiodinated serum albumin (RISA) from the circulation and lymphatic albumin transport was investigated in anaesthetized rabbits. The fraction of RISA escaping each hour from the circulation was 0.0932 +/- 0.0075, lymphatic albumin transport in the thoracic duct was 0.0389 +/- 0.0026 in the hepatic lymph trunk 0.0115 +/- 0.016, in the intestinal trunk 0.0122 +/- 0.0037 and in the renal lymphatics 0.0185 +/- 0.0021. About 78% of the lymph and 91% of albumin transported by the thoracic duct originated from the abdominal and renal lymphatics. The ratio of albumin escape from the circulation versus lymphatic return was 2.36. From the first slopes of the lymphatic RISA activity curves the albumin escape rates were calculated and found to be 1.89 in the liver, 2.32 in the kidney, 0.69 in the intestine and 0.20 g h-1 kg-1 tissue weight in the leg (skin). The lymph vessels returned 17% of the escaped albumin, from the liver about 12% from the intestines and almost all from the kidneys. A very strong correlation (r = 0.996) was found between lymph to plasma albumin concentration ratios and the first slopes of the RISA equilibration curves, proving that protein concentration in the lymph is determined by the rate of protein escape from the capillaries and that the rates obtained from the first slopes of the RISA cpm/g albumin in lymph per RISA cpm/g albumin in plasma equilibration curves are a measure of capillary permeability to protein.

Three fractions were isolated from the venom of Dendroaspis angusticeps by column chromatography on CM-Sephadex C-25. All the three fractions were shown to possess acetylcholinesterase inhibiting activity. The toxicity of the fractions as tested on mice were variable. Although the toxic signs were identical, fraction DaVI was highly lethal (LD50 1.9 microgram/g) whereas fractions DaIV and T39 were less lethal, the LD50 being 3.6 micrograms/g and 4.1 micrograms/g respectively. The three fractions significantly inhibited true acetylcholinesterase to the extent of 91-95%.

The authors studied the effect of drugs with different mechanisms of action on the prevention of stress ulcer production in the rat. Stress ulcer was induced by a method developed by the authors: intact, starved rats were swum in water at 23 degrees C for 5 hours. Atropine (0.1-0.5 and 1.0 mg/kg i.m.), cimetidine (1.0-5.0 and 25 mg/kg i.p.), prostacyclin (PGI2) (5.0-25.0 and 100 micrograms/kg i.p.) and phentolamine (0.35-1.75-3.5 and 7.0 mg/kg i.m.) were shown to decrease the production of stress ulcers significantly, in a dose-dependent fashion. Propranolol (0.35-1.75-3.5 and 7.0 mg/kg i.m.) did not influence the production of stress ulcers. The finding that drugs with different actions could considerably reduce or prevent the production of stress ulcer appears to indicate the complexity of the neural, hormonal and biochemical processes involved in the pathogenesis. On the basis of the present results the authors suggest the use of a preventive therapeutic regimen in clinical practice with an appropriate combination of drugs.

To determine whether renal prostaglandins participate in the regulation of renal blood flow, sodium and water excretion during "stress situation", renal function was investigated in two groups of anaesthetized dogs, subjected to minor and to more severe surgical stress under control conditions, and following the administration of 4 mg/kg indomethacin i.v. In the control studies, the renal haemodynamic parameters (CPAH, Cinulin), urine output and sodium excretion were not different in those animals in which the surgical traumatization was more severe from data obtained in similarly anaesthetized dogs. Extracellular volume expansion induced with i.v. infusion of Ringer solution enhanced sodium and water excretion in both groups, however, the increase of sodium excretion was less in the dogs subjected to more severe stress. During indomethacin infusion glomerular filtration did not change in either groups; CPAH decreased by 20-25% in the anaesthetized animals and 35-40% in dogs in which the surgical stress was more severe. In this group the total renal blood flow was reduced by 40% simultaneously with the haemodynamic changes; sodium and water excretion fell in both groups. After indomethacin infusion the diuretic response of the kidneys to extracellular volume expansion was markedly reduced in the anaesthetized dogs, the diuretic and natriuretic effects being almost completely inhibited in the animals subjected to more severe stress. These data suggest that in the anaesthetized dog endogenous prostaglandins may serve to maintain renal blood flow but not the glomerular filtration rate. Inhibition of prostaglandin synthesis during more severe stress results in increased renal vascular resistance and reduced renal blood flow. Accordingly, the data provide evidence that renal prostaglandins counteract in the kidney the vasoconstrictor mechanisms activated during more severe surgical traumatization. The data do not support the direct physiological role of prostaglandins in regulating tubular function.

In open chest dogs under sodium pentobarbital anaesthesia the interaction of mechanical constriction on a large coronary branch and autoregulatory capacity of the relevant small resistance vessels was analyzed. Coronary blood flow (CBF) was measured with an electromagnetic flowmeter. Step-by-step mechanical constriction gradually abolished adenosine-induced coronary vasodilation, whereas the resting level of mean CBF remained unaltered. At this point verapamil (0.2 mg/kg i.v.), a vasodilator with a strong potency of blocking adenosine action, eventually decreased CBF and increased coronary resistance. Similar results were obtained with these drugs injected directly into a bypass established between the carotid and left common coronary arteries. The results suggest that (i) adenosine affects the same coronary segments which accomplish compensatory autoregulation (ii); with critical stenosis verapamil augments indirectly coronary resistance by inhibiting an "intrinsic" adenosine effect (iii); the functional state of stenosed coronaries can be assessed with the aid of these pharmacologic tests.

The effects on renal function of isoproterenol and vasopressin were compared in conscious hydrated dogs. In response to isoproterenol infusion (12 micrograms/kg/h) urine flow, sodium and potassium excretion, free water clearance dropped markedly whereas glomerular filtration rate, blood flow, and the distribution of cortical blood flow remained practically unaffected. Vasopressin infusion (2 mU/kg/h) produced an antidiuresis comparable to that after isoproterenol infusion, but sodium and potassium excretion was considerably enhanced. Since isoproterenol and vasopressin are known to exert opposing effects on ion excretion, it is suggested that the increased secretion of vasopressin cannot play an exclusive role in the development of changes of renal function induced by isoproterenol.

Solvents were tested for their influence on motivational state, as well as for their sedative effects, after intraperitoneal administration. The following tests were used: open field (exploratory activity, locomotion), activity wheel (running activity), tube test and tilted plane (muscle weakness, incoordination). The agents proved to be similar in causing muscle weakness and ataxia already at low dose levels. Benzene was the most potent in this respect. The three solvents, however, contrasted strongly in influencing motor activity. While benzene and especially toluene exerted CNS stimulation, no such effect could be detected following m-xylene treatment. On the basis of human experiences with these substances it may be suggested that the screening procedure applied in rats might be useful for predicting acute adverse effects in man.

A number of changes in peptide components could be demonstrated in sera of patients with end stage malignant diseases. Total and free alfa amino-N content of such sera was shown to be significantly higher than those in sera of patients with no sign of malignancy. In addition, a significant increase was found in one of the serum fraction obtained by Sephadex G-25 chromatography. This increase was shown to be due to an increase in the amount of one of the isotachophoretically separated serum components of anionic character as well as to the appearance in sera of tumour bearing patients of two additional isotachophoretic components never detected in non tumour bearing patients. Based on their chromatographic behavior as well as on observations made in earlier experiments, the peptide nature of the two isotachophoretic serum components seemingly characteristic of sera of tumour bearing patients is highly probable.

In the present study the dose-related effects of linear and cyclic somatostatin were compared on the self-stimulation rate of rats. Twenty micrograms of linear somatostatin administered intracerebroventricularly (icv.) markedly decreased the self-stimulation rate, while 5 micrograms and 10 micrograms was ineffective. Cyclic somatostatin in a dose of 1 microgram caused a transitory but not significant increase in the self-stimulation rate, which later returned to the control level. Five micrograms and 10 micrograms of the peptide decreased the self-stimulation rate. These results indicate that the cyclic somatostatin is more effective in inhibiting the self-stimulation rate than the linear one.

The effects of peripherally administered cholecystokinin octapeptide sulphate ester and its unsulphated form on the active avoidance behaviour of rats were studied. The acquisition of avoidance behaviour was impaired, while extinction was facilitated, following cholecystokinin octapeptide sulphate ester or unsulphated cholecystokinin octapeptide treatment. These peptides had no action on open-field activity. It is concluded that peripherally administered cholecystokinin octapeptide influences acquisition and extinction of active avoidance behaviour and this effect is unrelated to general motor activity of the animals.