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Biomedical subjects

E Borda

Publications and source records attributed to E Borda.

At least 109 records · Page 6Linked to original sources
PubMed1982

In vitro effect of acetylcholine and bethanechol on the contractions of the human detrusor muscle. Influence of prostaglandins.

The effects of acetylcholine and bethanechol on the basal resting tone of the isolated detrusor muscle were explored. It was observed that the tone was augmented by both agents. On the other hand, in the presence of prostaglandin (PG)-inhibitors the dose-response curve of acetylcholine shifts to the right. PGF 2 alpha (10(-10)M) but not PGE2 (10(-10)M) completely blocked the inhibitory effect of PG-inhibitors upon the inotropic effect of acetylcholine, without modifying the influence of bethanechol. After inhibitors of PG-synthesis, eserine abolished the inhibitory action of acetylcholine but did not change the influence of bethanechol. Our results suggest that endogenous PGs facilitate the action of acetylcholine through an increase in the concentration of the cholinergic neurotransmitter probably via an inhibition of the acetylcholinesterase activity.

Acetylcholine↗
PubMed1982

Selective stimulation of PGE1-synthesis by soterenol in the isolated rat vas deferens is mediated by alpha adrenoreceptors.

The effects of soterenol on prostaglandin (PG) release by the isolated rat vas deferens were studied. Soterenol increased the amount of PGE1 released into the medium without affecting that of PGE2 or PGF2 alpha. The effect of soterenol was inhibited by phentolamine but not by butoxamine. It is concluded that soterenol elicits the release of PGE1 by the isolated rat vas deferens via stimulation of alpha adrenoreceptors.

Animals↗
PubMed1981

Chagasic sera alter the effects of ouabain on isolated rat atria. Participation of adrenergic mechanisms.

The effects of chagasic sera, containing an antibody (EVI antibody) which reacts with the plasma membrane of working myocardial cells, on "toxic" and "non-toxic" actions of ouabain upon isolated self beating or paced rat atria suspended in different media, were explored. Although ouabain produced a dose-dependent positive inotropic influence on atria suspended in Krebs-Ringer-bicarbonate (KRB) and in KRB plus normal human serum (KRB + NHS) it did not elicit any significant positive inotropic effect on atria beating in KRB plus EVI positive human chagasic serum (EVI(+)S). Additionally, EVI(+)S dose-response curves of classical signs of digitalis cardiac toxicity shifted to the left. The threshold concentration of ouabain required to elicit the onset of "toxic" effects was higher in control preparations (kept in KRB or KRB + NHS) than in EVI(+)S exposed preparations. (-)-Propranolol attenuated the overall toxic action of ouabain in EVI(+)S and facilitated its positive inotropic influence. In control media, the beta-adrenoceptor blocker failed to modify either the "non-toxic" or the "toxic" effect of ouabain. On the other hand, with control atria, subthreshold exogenous norepinephrine inhibited the positive inotropism of ouabain. The data suggest that an adrenergic mechanism is involved in the action of ouabain on cardiac tissue immersed in an EVI(+)S-containing solution. The foregoing results may explain the severe "toxic" effects observed with cardioactive glycosides when they are used in patients with Chagas' heart disease, even at low doses.

Animals↗
PubMed1981

Inhibitory effects of some catecholamines on contractions of uterine strips isolated from estrous and spayed rats. Influence of endogenous and exogenous prostaglandins on the action of methoxamine.

Cumulative dose-response curves were produced for the effect of different adrenergic agonists on the contractions of uterine strips from natural estrous and ovariectomized rats. Isoproterenol, norepinephrine and phenylephrine inhibited uterine spontaneous contractions, whilst methoxamine stimulated them. The inhibitory influences were blocked by propranolol and the excitatory effect of methoxamine was abolished by phentolamine. However, the sensitivity of the rat uterus to beta- and alpha-adrenergic agonists varied depending on the hormonal state i.e. strips from rats in natural estrus were more sensitive to inhibitory effect of beta-agonist than were those from ovariectomized animals. On the contrary, the apparent potency and the efficacy of an alpha-agonist (methoxamine) was higher in ovariectomized uterine strips than in those from estrous rats. Indomethacin, at a concentration known to inhibit the endogenous synthesis of prostaglandins, depressed the spontaneous activity of strips from spayed rats and prevented the response to methoxamine, whereas in strips from natural estrous rats, the drug was unable to modify either the spontaneous contractions or the stimulating action of methoxamine. In addition in the presence of threshold doses of PGE1, PGE2 and F2 alpha the dose-response curve to methoxamine shifted to the left for uterus from ovariectomized animals. The results suggest that uterine strips from estrous rats have more affinity to the effect of beta-adrenergic agonists, whereas those from spayed animals were more sensitive to the effect of an alpha-adrenergic agent. Also the effectiveness of an alpha-adrenergic agonist, methoxamine, appears to be related to unaltered tissue prostaglandins.

Animals↗
PubMed1981

Prostacyclin (PGI2) and U-46619 stimulate coronary arteries from diabetic dogs and their action is influenced by inhibitors of prostaglandin biosynthesis.

Isolated coronary arteries from diabetic dogs presented different contractile response to U-46619 to prostacyclin (PGI2) and to arachidonic acid (AA) than those of normal dogs. The stimulatory effect of the synthetic endoperoxide analogue U-46619, was significantly higher in the diabetic condition than in preparations from normal animals. On the other hand, while PGI2 evoked a dose-dependent relaxation of normal coronary arteries, diabetic vessels were not relaxed by low concentration of PGI2 whereas higher ones produced a distinct constrictor effect. Additionally, inhibitors of prostaglandins and thromboxane (TX) biosynthesis such as corticosterone, indomethacin, acetylsalicylic acid, imidazole and L-8027, abolished the stimulatory effect of PGI2 in coronary arteries from diabetic dogs. AA relaxed coronaries from normal dogs and constricted those from diabetic animals, this action being inhibited by imidazole and L-8027. The present results suggest that: a) coronary vessels from diabetic dogs are more reactive to an endoperoxide analogue than normal preparations and b) PGI2 and AA probably contract diabetic coronary arteries via the participation of a TX like material. It is then plausible that this effect could be tentatively ascribed to the production of a prostaglandin constricting substance including also the probable generation of a TXA2-like agonist.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed1980

The effect of calcium and calcium antagonists on the electrically-evoked contractile activity of isolated rat ovaries.

The effects of different calcium concentrations and calcium antagonists on the mechanical activity evoked by electrical field stimulation of isolated rat ovaries, were explored. It was observed that the force of contraction augmented and the electrical threshold diminished as the (Ca2+)0 increased. On the other hand, in the presence of calcium antagonists (Verapamil, D-600 and MnCl2) as well as in calcium-free media, the force of contraction decreased and the electrical threshold augmented. TTX, high (K+)0, propranolol and phentolamine failed to modify the responses of rat ovaries to the electrical field stimulation. The results suggest an important participation of calcium ions in the mechanisms of ovarian excitation-contraction coupling. The fast channels and intraovarian nerve endings, do not appear to be relevant for the electrically-evoked contractions of isolated rat ovaries.

Animals↗
PubMed1979

Adrenoceptors involved in the contractile activity of islated pregnant rat uterus.

Cumulative log dose-response curves of soterenol, isoproterenol, phenylephrine and norepinephrine on isolated pregnant rat uterus at different days of gestation, were investigated. Soterenol produced a sustained inhibition of spontaneous motility during the whole pregnancy and this effect was blocked by butoxamine. The affinity of myometrium for the beta 2-adrenoceptor agonist was parallel to the concentration of progesterone in plasma during pregnancy. Isoproterenol, norepinephrine and phenylephrine caused dual, alpha- and beta-mediated responses, their relative dominance varied with the concentration and the days of pregnancy, alpha-Adrenoceptor effects of the amines coincided with increased plasma concentrations of estrogens, whereas beta ones were in parallel with the increment of plasma progesterone. It is concluded that: (a) there exist in the pregnant rat uterus beta 2-receptor-mediated responses influenced by the length of gestation; and (b) the concentration-pregnancy-dependent biphasic actions of isoproterenol, norepinephrine or phenylephrine suggest that their variable hormone-modulated ability interacts with both alpha- and beta-adrenoceptive uterine sites.

Animals↗
PubMed1976

Spontaneous and prostaglandin- or oxytocin-induced motility of rat ovaries isolated during different stages of the estrous cycle: effects of norepinephrine.

Ovaries isolated from rats in different stages of the sex cycle were explored for spontaneous or drug-induced contractile activity. The number of spontaneously active ovaries as well as the magnitude of the isometrically developed tension and frequency of contractions were greater during the periovulatory interval (late proestrus and estrus) than during early proestrus or metestrus. Furthermore, during estrus or late proestrus the left ovaries exhibited a mechanical activity significantly greater than that of the right ovaries. The oxytocin-triggered motility was clearly more marked immediately prior to ovulation (late proestrus) and greater in left ovaries than in right ovaries. In contrast, the contractions induced by prostaglandin F2alpha were similar during early proestrus and late proestrus. Ovarian contractile reactivity to norepinephrine indicated the presence in the tissue of alpha- and beta-adrenergic receptors. During early proestrus this agent stimulated the motility of left and right ovaries, whereas close to the ovulatory interval (late proestrus) it depressed the contractions of left ovaries. This last influence was blocked by propranolol. The existence of a close relationship between ovarian contractile activity and ovulation is reinforced by the present results in the rat. A tentative participation of oxytocin is also suggested. In addition, the influences of other possible regulatory agents of ovarian contraction, such as catecholamines and prostaglandins, are presented and discussed.

Animals↗
PubMed1976

Pharmacologic influences on human ovarian contractions.

Spontaneous motility in whole ovarian follicles, as well as in strips from the stroma and capsule of ovaries isolated from premenopausal and menopausal women, was explored. The pharmacologic contractile reactivity of these ovarian structures to different smooth muscle-stimulating agents, ie, prostaglandins E1, E2, F2alpha; norepinephrine; 5-hydroxytriptamine; acetylcholine, phenylephrine; and phentolamine, was also studied. Strips from the capsule and stroma of isolated ovaries showed spontaneous motility in both menopausal and nonmenopausal preparations. The addition of phenylephrine, norepinephrine, acetylcholine, 5-HT, or PGF2alpha induced a sustained tonic contractile tension, whereas PGE1 elicited the opposite influence. Stromal strips from nonmenopausal women showed more reaction to norepinephrine than those from menopausal ones. Ovarian follicles did not exhibit spontaneous motility but responded to added norepinephrine. This influence was blocked by phentolamine, indicating the eventual participation of alpha-adrenergic receptors. Acetylcholine, PGF2alpha and, to a smaller extent, PGE2, also increased follicular resting tension. On the contrary, PGE1 was clearly inhibitory both upon the spontaneous basal tone and the PGF2alpha-induced sustained contractions.

Acetylcholine↗
PubMed1975

Motility of the rat oviductal tract isolated in different stages of the sex cycle. Effects of catecholamines.

Physiological and pharmacological characteristics of the spontaneous motility of rat oviductal tracts (the coiled oviduct plus its mesosalpinx), isolated in proestrus, estrus or metestrus, are described. The initial contractile tension (recorded following isolation) was comparable in the three stages of the cycle, but its decrement with time was greater in metestrus than in proestrus; the opposite being observed regarding the rate of contractions. Norepinephrine and phenylephrine depress motility in proestrus and metestrus, but not in estrus. The inhibition of motility during proestrus, produced by added norepinephrine, phenylephrine or isoproterenol was not modified by phenotolamine but was abolished by propranolol. During estrus, norepinephrine and phenylephrine inhibited tubal contractions of preparations incubated with phentolamine, whereas it produced a distinct stimulation in the presence of propranolol. It is concluded that: (a) the rat mesosalpinx might play some role in the motility of the whole isolated oviductal tract; (b) there are variations in the decrement with time of contractile tension and frequency of contractions in different stages of the sex cycle; (c) the effects of catecholamines upon the rat oviductal tract also varies within the cycle, probably due to influences imposed by sex hormones.

Animals↗
PubMed1974

Introduction to library services for allied health personnel.

Experience with a non-credit course, given by the staff of the University of Western Ontario Health Sciences Library, within the framework of the University's Summer School and Extension Program, to allied health personnel is presented. The purpose of this course was to acquaint allied health personnel with the library and its services and how to use the services to the best advantage.

Allied Health Personnel↗