Acta physiologica et pharmacologica Bulgarica最新文献

The renal excretory function and plasma renin activity (PRA) were studied in conscious rats on a low sodium diet (25 mmol/kg) after atrial natriuretic peptide (ANP) infusion (100 ng/kg b.w./min) for 80 min through a catheter implanted in the right atrium. The half of the animals were with bilateral kidney denervation. The rats were housed every day from 8 a.m. to 2 p.m. in individual metabolic cages for urine collection and Na, Cl, osmolality and endogenous creatinine determination. At the last day of the experiments after the ANP infusion, blood was taken from the heart for electrolytes, endogenous creatinine and PRA. The effect of denervation was monitored by measuring of noradrenaline in kidney homogenate. The data indicated that even at low sodium diet ANP stimulates the diuresis and sodium excretion without changing the glomerular filtration rate (GFR). The kidney denervation combined with ANP infusion increased twice the diuresis and four times sodium excretion vs. the control animals. In the same time PRA was decreased by about 70%. We assume that the low sodium diet attenuates the effect of ANP in respect to the excretory function. This inhibitory effect is amplified by the renal sympathetic nerves. The decrease of PRA and possibly the increased activity of renal receptors after the denervation could explain the data obtained.

We studied the ultrastructural changes in the alveolar type II cells from the lung of immobilized male Wistar rats divided into 6 groups: control; immobilized for 1, 12, 24 and 30 hours; immobilized for 30 hours and readapted for 5 hours. We used the routine methods of fixation through perfusion and electron microscopy. The results indicated progressive structural changes in the alveolar type II cells, correlating with a prolonged time of akinesia. Characteristic was the swelling affecting first the mitochondria and then all other organelles and the plasmalemma. Hypertrophy and hyperplasia of the lamellar bodies were clearly seen. The relatively quick recovery suggested the accelerated mitosis of the alveolar type II cells.

The antiinflammatory effects of the anthocyane flavonoids in the natural juice from Aronia melanocarpa and of rutin-magnesium complex, the water-soluble derivative of rutin were studied in comparison with rutin. Two experimental models of inflammation were used. Inflammation of rat hind paw was induced either by 0.5% solution of histamine or by 0.01% solution of serotonin. The swelling of the rat paw was measured oncometrically by a pletismometer. The results showed that the anthocyane flavonoids from the natural juice of Aronia melanocarpa exerted more pronounced effects as compared to rutin in both models of inflammation. The rutin-magnesium complex did not exhibit any antiinflammatory activity against histamine-induced inflammation. Its effects against serotonin-induced inflammation were comparable to those of rutin.

The memory effects of agonists and antagonists of some serotonin (5-HT)-receptor subtypes were studied in experiments on rats using the method for passive avoidance with punishment reinforcement (step-down). The 5-HT1A-receptor agonist buspirone (1 mg/kg i.p.) elicited behavioural responses which suggested the lack of pronounced effect on learning and retention; the 5-HT1A-receptor antagonists NAN-190 (1 mg/kg i.p.) and pindolol (6 mg/kg i.p.) impaired retention tested 24 hours and 7 days after training as compared to controls. The 5-HT2-receptor antagonist ritanserin (1 mg/kg i.p.) impaired retention tested 24 hours and 7 days after training as compared to controls, while the 5-HT3-receptor antagonist ondansetron (0.1 mg/kg i.p.) improved it. The 5-HT1/5-HT2-receptor antagonist dotarizine (50 mg/kg orally), characterized by a calcium-antagonistic action, too, exerted some facilitating effect on learning. Most of the effects of the 5-HT-receptor agonists and antagonists were changed when the 5-HT concentration in the synaptic region was increased by the 5-HT-uptake inhibitor fluoxetine (20 mg/kg orally). The results suggest different participation of 5-HT1A-, 5-HT2- and 5-HT3-receptors in the mechanisms of memory process and its modulation by the serotonin level in the cerebral serotonergic synapses.

The cytotoxic activities of unloaded polybutylcyanoacrylate nanoparticles (PBCN), free vinblastine, vinblastine-loaded nanoparticles (by incorporation and adsorption processes) and a mixture of vinblastine-free and unloaded PBCN were compared in vitro on human erythroleukemic K-562 cells. Enhanced cytotoxicity was observed when vinblastine was either adsorbed on PBCN or mixed with them rather than free. When vinblastine was incorporated into polymer matrix of nanoparticles, a lag period and postponed cytotoxic effect on K-562 cells were observed.

This is a report on ventricular contractility and electrogenesis disorders in rabbits, following intravenous injection of E. coli endotoxin at a dose of 2 mg.kg-1. At the 30th min, the right ventricular contractility indices (dP/dtmax)/P and [(dP/dt)/P]max had lower values, whereas end diastolic pressure (EDP), right ventricular systolic pressure (RVSP) and P(dP/dtmax) showed higher values compared to the initial ones. Most of the left ventricular contractility indices tested showed significantly lower values at the 30th and 60th min of the registration. In the scalar orthogonal ECG leads, at the 5th min an increased Qz amplitude, and at the 60th min an increased Rz amplitude, a decreased Ry amplitude, and QRS complex widening and bradicardia, were registered. In the spatial magnitude curve an increased amplitude of the main vectors of ventricular depolarization was documented. The changes in electrogenesis are interpreted first and foremost by the presence of hemodynamic disorders. The inference is reached that both left and right ventricular dysfunction have been already formed during the initial stage of endotoxin shock.

The tissue distribution of polybutylcyanoacrylate nanoparticles (PBCN) with a diameter of 127 nm, loaded with 1-(2-chloroethyl)-3-(1-oxyl-2,2,6,6-tetramethylpiperidinyl)-1- nitrosourea (spin-labelled nitrosourea, SLCNU) is described. PBCN-suspensions were intraperitoneally (i.p.) injected into Lewis lung carcinoma bearing mice. The biodistribution of PBCN in the visceral organs, blood and tumor was studied by electron spin resonance (ESR) spectroscopy. A relatively low accumulation of nanoparticles in the liver and spleen was found. The accumulation was negligible in the i.m. implanted primary tumor. SLCNU-loaded nanoparticles were mainly found in the lungs, kidneys, and heart. The highest content of the particles studied was observed in the lungs of tumor bearing experimental animals damaged by metastases. These findings suggest that PBCN offer some opportunities in the targeting of SLCNU to lung metastases.

This is a study on the location of the ventricular depolarization center, carried out on fifteen healthy rabbits according to the method of Ritsema van Eck. It is established that the level of equivalent heart dipole coincides with the fourth or fifth intercostal space, but in some laboratory animals this level displays a lower positioning. The inference is reached that to secure correct application of Frank's lead system it is necessary to use a prompt and precision method for determination of the level in question in each individual case. Such a method has not been developed as yet. For the time being, the optimal solution of the problem could be accomplished through a lead system that is less sensitive to electrode positioning errors.

The diphenyl-methyl-piperazine derivatives with Ca(2+)-antagonistic effect dotarizine (DOT), Fl-6020 and flunarizine were investigated in experiments on rats. The substances tested were administered repeatedly at an oral dose of 50 mg/kg. Behavioral methods were used to study the exploratory activity when the animals were placed in an environment that was unfamiliar to them (the chamber of the Opto Varimex apparatus), the elevated plus-maze method for examining the effect on anxiety, and the method of recording changes in motor activity (using the Automex II apparatus). DOT was found to increase motor activity and to have an anxiolytic effect. Combination of DOT--a compound with Ca(2+)--and 5-HT2-receptor antagonistic action--and the 5-HT-receptor agonists and antagonists used (buspirone, NAN190, pindolol, ritanserin and ondansetron) resulted in such changes in the development of habituation and in anxiety, which suggest that the modulating effects of DOT depend but partly on its typical interaction with the 5-HT2 receptor. Apparently, the Ca(2+)-antagonistic action of DOT plays a definite role, changing its biological activity depending on the 5-HT receptor subtype at the level of which the interaction is taking place.

Unlabelled: All the studies were performed on chronically cannulated, conscious Brattleboro rats, housed in metabolic cages under standard conditions. The renal excretory indices: diuresis (V), sodium (UNa.V), potassium (UK.V), chloride (UCl.V) and osmotic (Uosm.V) excretion were measured under the following experimental protocol: (1) controls, (2) 2% volume expansion (AVE)-0.9% NaCl i.v. for 2 min, (3) Dopamine (DA) receptor antagonist Flupentixol (FLU) 0.5 mg.kg-1 i.v., and (4) AVE 10 min after i.v. application of FLU. All the indices studied, given as cumulative curves, showed a firm linearity with time during the whole experimental period (5 h) in groups 1 and 2 (p < 0.05), while such a relationship was not found significantly in groups 3 and 4. AVE quickly, strongly and significantly (p < 0.01) increased V and especially UNa.V, UCl.V and Uosm.V. Pretreatment with FLU potently suppressed the effect of AVE on the renal excretion. FLU alone decreased almost equally V and saliuresis.

In conclusion: the DA antagonist FLU blocks the diuretic and saliuretic response to AVE probably by affecting tubular processes.