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PubMed1990

[Anti-arrhythmic effects and electrophysiological properties of Ophiopogon total saponins].

The arrhythmias induced by chloroform-epinephine, BaCl2, and aconitine were prevented and antagonized by Ophiopogon total saponins (OTS) which were extracted from the root of Ophiopogon japonicus (Thunb) Ker-Gawl. The incidence of ventricular arrhythmia produced by ligation of the left anterior descending coronary artery was effectively decreased without any changes in the hemodynamic indices of dogs. The electrophysiological effects of OTS in vivo and in vitro were studied by means of contact electrode and intracellular microelectrode techniques. The results showed that OTS shortened APD10, APD50, APD90; decreased APA and Vmax of both monophasic and transmembrane action potentials. OTS also increased the ERP/APD ratio and prevented or abolished the arrhythmikinesis provoked by ouabain and aconitine. The anti-arrhythmic properties of OTS lead us to draw an inference that the anti-arrhythmic mechanism may be related to the blocking of sodium and calcium channels.

Aconitine↗
PubMed1990

[The anti-arrhythmia activity of isoteolin (IST)].

The antiarrhythmic activity of IST was studied on some experimental models of cardiac arrhythmia--caused by adrenaline in rats, caused by barium in non-narcotized rabbits, caused by strophanthin in guinea pigs, caused by aconitine and calcium in rats. Rhythmic disturbances were recorded by a 12-channel polyphysiograph "Galileo" or a single-channel electrocardiograph "Cardiomat". The obtained results showed that IST manifested antiarrhythmic activity in respect to adrenaline, barium and strophanthin arrhythmias without affecting substantially aconitine and calcium arrhythmias. It is thought that antiarrhythmic activity of IST, found in the indicated experimental models of cardiac arrhythmias, is most probably connected with a lowering of the peripheral sympathetic activity, realized by a central way.

Aconitine↗
PubMedDate not supplied

Propagated constriction in mouse pial arterioles: possible role of endothelium in transmitting the propagated response.

Two lines of evidence are presented demonstrating propagated constriction in mouse pial arterioles. First, a 2 second microapplication from a 6 micron pipette tip of approximately 12 nanoliters of BaCl2 or uridine triphosphate produced constrictions which spread to points 300 microns or more upstream from the point of application. Second, constrictions were elicited between 2 points of endothelial injury, each made with a focused laser beam 18 microns wide. A helium-neon laser was used in the presence of intravascular Evans blue. The constrictions were produced when a very brief exposure at a downstream site was followed by a more prolonged exposure at an upstream site 300 to 1100 microns from the downstream injury. In approximately half the cases the upstream damage elicited a local platelet aggregate. Therefore, vasoconstrictors released by aggregating platelets may have played a role in initiating constriction. Constriction was limited to the segment between the two endothelial injuries. The necessity for 2 injuries, rather than one, suggests that local losses of endothelium derived vasodilators also played a role in initiating constriction and/or permitting its propagation. Abrupt cessation of constriction at the sites of endothelial damage suggests that endothelium plays a role in propagation of constriction. Propagated constriction may play a role in amplifying the spasmotic effects of local subarachnoid hemorrhage or in the spread of constriction beyond local areas of reduced metabolic demand.

Animals↗
PubMed1986

Pharmacological characterization of rat jejunal contractility after chronic ablation of the myenteric plexus.

The authors have pharmacologically characterized longitudinal muscle contractility of the isolated rat jejunum chronically devoid of myenteric neurons. The myenteric plexus of a 3- to 4-cm segment of rat jejunum was ablated by serosal application of the cationic surfactant benzalkonium chloride (BAC). Fifteen days after treatment, both BAC-treated and untreated control jejunal segments were removed from each animal for pharmacological studies. BAC-treated tissues did not respond to the ganglionic stimulants nicotine, 1,1-dimethyl-4-phenylpiperazinium iodide and McN-A-343 or to the acetylcholinesterase inhibitor physostigmine. Short-pulse duration transmural electrical stimulation (0.1 msec) caused a frequency-dependent, tetrodotoxin-sensitive contraction in control but not BAC-treated tissues. Long-pulse duration transmural electrical stimulation (5.0 msec) contracted both control and BAC-treated jejunum. These contractions were partially reduced but not completely blocked by tetrodotoxin. To assess smooth muscle function, the mechanical responses to the muscarinic receptor agonist carbachol were examined. Carbachol contracted both control and BAC-treated tissues with maximal responses and ED50 values that were not significantly different. In addition, the maximal tension development produced by 10(-2) M barium chloride in similar lengths of control and BAC-treated jejunal segments was not significantly different. These studies demonstrate that chronic ablation of the myenteric plexus by serosal application of BAC essentially eliminates neuronally mediated responses without a concomitant alteration in longitudinal muscle contractility. Because nerve-mediated longitudinal muscle responses are lost despite the presence of an intact submucosal plexus in the BAC-treated jejunum, our data suggest that the motor neurons innervating the rat jejunal longitudinal muscle are located in the myenteric plexus.

(4-(m-Chlorophenylcarbamoyloxy)-2-butynyl)trimethy↗
PubMed1987

Effect of K+ and K+ channel blockers on pancreatic HCO3-transport.

The present study investigated whether there is a K+ conductive pathway on the basolateral membrane of pancreatic duct cells. Small inter- and intralobular ducts were isolated from rat pancreas and perfused in vitro. Duct cells were impaled and the potential across the basolateral membrane (PDbl) was measured. The resting potential was -61 +/- 1 mV. Ouabain (3 mmol/l) depolarized PDbl by 11 mV. Increase in the bath K+ concentration from 5 to 20 mmol/l depolarized PDbl by 15-16 mV. The effect of K+ channel blockers was tested. Ba2+ (1 mmol/l) added to the bath depolarized PDbl by 23-26 mV, whereas TEA+ (50 mmol/l) depolarized PDbl only by 7-8 mV. Dibutyryl cyclic AMP (0.5 mmol/l) depolarized PDbl by 20-30 mV. The results show that on the basolateral membrane of pancreatic duct cells there is a (Na+ + K+)-ATPase and a K+ conductive pathway sensitive to Ba2+.

Animals↗
PubMed1987

[Development of electrical activity of hypothalamic cells in culture].

The development of the electrical activity of hypothalamic cells was studied using intracellular and patch clamp recording technics on cultured hypothalamic neurones from 14 days mouse embryos. After 24 h of incubation, 15% of recorded cells were spontaneously active. During the first five days of culture this ratio increased exponentially to reach 95% at day 5. Between the 5th and the 9th day the spontaneous activity progressively decreased although the majority of cells remained excitable. Spontaneous activity reappeared after the 9th day and was underlain by a synaptic potential activity. During the first five days of culture, only a TTX sensitive inward current was observed in all cell tested. A calcium inward current appeared after the first week of incubation. It was recorded on 40% of cells at day 11th and in 80% of cells tested after a month of incubation. Our results show that electrical activity of cultured hypothalamic neurones develop in three stages. A first stage characterized by a spontaneous electrical activity without post synaptic potential, an intermediate stage during which a Calcium inward current appeared corresponding to synaptic contact development and a third stage during which post synaptic potential activity was observed, corresponding to synaptic contact maturation.

Animals↗
PubMed1989

In vitro method for measurement of free radical effects: effect of PMS (phenazine methosulphate) on red blood cell membrane.

The aim of this study was to elaborate a simple in vitro model for rapid and quantitative measurement of free radical effects. Free radical generating characteristics of PMS were measured in the case of red blood cell (RBC) membrane. The mechanism of free radical action was investigated in MgCl2, CaCl2, BaCl2 and in Verapamil HCl medium. The most important result of the investigations is as follows: Membrane damage of RBC provoked by the mechanism of free radical generation of PMS is proportional to the intracellular K+-efflux and to the extracellular Na+-influx. The PMS dependent K+-efflux in a NaCl containing medium in the presence of CaCl2 increases significantly, while it remains unchanged in MgCl2 medium. The PMS dependent K+-efflux and Na+-influx were considerably decreased by Verapamil HCl in NaCl containing solution. We have come to the conclusion that new, non-selective pores are formed in the membrane. The measure of the damage increases in the presence of Ca2+ions and decreases in the medium containing Verapamil HCl.

Barium↗
PubMed1989

[Antiarrhythmic effects of Cordyceps sinensis (Berk.) Sacc].

The administration of 65% alcohol extracts of Cordyceps sinensis can counteract the arrhythmias induced by aconitine or BaCl2 in rats, and increase the tolerant dose of ouabain to produce the arrhythmias in guinea pigs. The drug can reduce the heart rate of anesthetic rats, decreasing the contractility of isolated papillary muscle or atria in guinea pigs, but showing no effect on the automatic rhythmicity and the functional refractory period of the atria.

Aconitine↗
PubMedDate not supplied

Altered responsiveness of coronary arteries in hyperthyroid rats.

The effect of thyroid hormones on vascular responses to various agents was examined in the coronary vascular bed perfused by the Langendorff's method at a fixed flow rate with Krebs-Henseleit solution in isolated rat hearts. In this study, ventricular fibrillation was induced by electrical stimulation to avoid secondary influences derived from alteration of ventricular contractility by agents. Vasodilator responses of coronary arteries to isoproterenol and methacholine were significantly enhanced in hyperthyroid preparations compared with those observed in euthyroid ones, though vasodilator responses to histamine and adenosine were not affected by hyperthyroidism. Vasoconstrictor response to 5-hydroxytryptamine (5-HT) was significantly potentiated by hyperthyroidism though that to balium chloride was not affected. So, these alterations in vascular responses by hyperthyroidism are assumed not to be nonspecific but to be mediator-specific events. As vasoconstriction in coronary arteries lowers oxygen supply to myocardium, enhanced vasoconstrictivity of coronary arteries to 5-HT by hyperthyroidism may be responsible for an exacerbation of heart disease in the case of patients having agglutinative thrombus, which should be a source of 5-HT, in their coronary arteries.

Adenosine↗
PubMed1987

[The spasmolytic activity of propiverine and some of its structural analogs].

The spasmolytic activity of propiverine and its corresponding methyl ether analogue was investigated in the isolated ileum and urinary bladder of the rat. It could be demonstrated that the antispasmodic properties of propiverine were, in contrast to its methyl ether analogue, not only based on a blockade of muscarinic receptors but were also a consequence of nonspecific papaverine-like effects. Investigations with three putative metabolites showed that the alcohol derivative O-desalkylpropiverine was about two orders of magnitude more potent than propiverine itself in blocking spasmogenic effects of the agonist arecaidine propargyl ester. In contrast no spasmolytic effect could be observed after application of the corresponding carboxylic acids (benzilic acid propyl ether; benzilic acid 2-hydroxypropyl-ether.

Adrenergic alpha-Antagonists↗
PubMed1986

Effect of Salmonella typhimurium porins on the cardiovascular and renal apparatus.

The cardiovascular effects of porins were evaluated using porins isolated from Salmonella typhimurium SH5014. In dogs porins depress arterial systemic pressure, vasomotor reactivity of norepinephrine and peripheral vagal stimulation. They are capable of modifying the sinocarotidal baroreceptor reactivity. In mice porins increase the cardiotoxic effects of isoprenaline, thyroxine, emetine and of p-nitrophenol. In rats porins increase the arrhythmogenic and lethal effects of BaCl2 and also give rise to renal lesions, probably at the tubular level.

Animals↗
PubMed1988

The effect of BaCl2 on intestinal sugar transport in the rat in vitro.

The effect of BaCl2 on galactose transport across isolated rat small intestine has been investigated. The addition of 5 mM BaCl2 or theophylline (3 mM) to the bathing solutions increased cell water free sugar accumulation and decreased mucosal to serosal sugar fluxes. However the effects of BaCl2 were smaller than those induced by theophylline. Removal of Ca2+ from the bathing solutions did not modify the response to BaCl2, though the response to theophylline was partially reduced. In the presence of 0.1 mM trifluoperazine, both theophylline and BaCl2 were without effect on sugar transport. These findings are discussed in terms of an effect of Ba2+ on intestinal smooth muscle tone.

Animals↗
PubMed1988

PET camera performance design evaluation for BGO and BaF2 scintillators (non-time-of-flight).

Bismuth germanate (BGO) and barium fluoride (BaF2) scintillators are presently used in positron emission tomegraphy (PET) cameras. This study evaluates the important PET performance parameters of image resolution, true sensitivity, scatter background, accidental background, and realistic maximum radioactivity in the field of view for both BGO and BaF2 in an identical non-time-of-flight, whole-body camera configuration. These performance parameters are evaluated for three phantoms simulating (a) the head, (b) whole-body cross-section and (c) heart/kidney. This study finds that the high stopping power of BGO yields higher sensitivity, higher resolution, less vignetting, better immunity from scattered gamma, and lower accident/true ratio at any dose level. The faster BaF2 timing acceptance window is traded off by its vulnerability to noncoincidental scatter-gamma which increases accidental coincidences. The BGO is found to be a better choice for non-time-of-flight systems especially with large objects which produce a lot of noncoincidental scatter-gammas. This study also found that the practical diminishing return maximum activity within the field-of-view is approximately 20-25 mCi for existing conventional cameras.

Barium↗