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Biomedical subjects

E Molina

Publications and source records attributed to E Molina.

At least 127 records · Page 7Linked to original sources
PubMed1981

Histamine H-2 receptor stimulation and inhibition of pepsin secretion in the dog.

Although low doses of histamine (less than 150 nM/kg.hr) stimulate pepsin secretion, higher doses inhibit pepsin secretion in a dose-dependent manner. To better histamine stimulation of pepsin, histamine was used at doses at the lower end of the dose-response scale in five dogs with gastric fistula. Five doses of histamine below the ED50 for acid, viz, 9, 22.5, 67.5, 90 and 112 nM/kg.hr in 45-min steps, provided values for pepsin secretion from which Ed50 = 11.4 nmol/kg.hr (i.e., about 1/12 the ED50 for acid) and calculated maximum 22,600 peptic U/30 min were calculated. To document the inhibition, pepsin secretion was first stimulated by an infusion of bethanechol (0.4 mumol/kg.hr). A super-added injection of the histamine H-2 agonist 4-methylhistamine (0.4 or 0.8 mumol/kg) produced strong additional acid stimulation and immediate 40% suppression of pepsin secretion. The ratio pepsin/acid was reduced to one-third of control for the 90 min after 4-methylhistamine. The most specific H-2 agonist impromidine had the same effects, whereas pentagastrin (1.95 nmol/kg) inhibited both acid and pepsin secretion stimulated by bethanechol. The specificity of H-2 effect of impromidine was confirmed by simultaneous tachycardia and hypotension; pentagastrin did not produce cardiovascular effects. These studies confirm the unique effect of histamine on the peptic cell of the dog in which both stimulation and inhibition are H-2 receptor-mediated effects.

Animals↗
PubMed1981

Atropine suppresses gastrin release by food intact and vagotomized dogs.

We have demonstrated that at doses lower than those used by others in dogs, atropine consistently inhibited food-stimulated gastrin release irrespective of vagal innervation of the stomach. Gastrin release induced by food placed directly into the stomach was studied in four gastric fistula dogs with intact vagi and in three other similar dogs with fundic vagotomy. The studies were repeated in dogs after conversion to truncal vagotomy. Fasting serum gastrin was lower in the intact dogs (33 +/- 1.7 pg/ml) than after fundic vagotomy (61 +/- 13 pg/ml) or truncal vagotomy (97 +/- 20 pg/ml). The same relationship held for absolute postprandial values. However, the integrated gastrin response to food over 2 h was similar in the three groups of dogs (intact 14 +/- 4.6, fundic vagotomy 10.3 +/- 4.3, truncal vagotomy 17.4 +/- 2.4 ng.min/ml). Regardless of the state of gastric vagal innervation atropine 20 microgram/kg . h reduced gastrin releases due to food by 66-76% (p less than 0.05) in all three groups. In small doubling doses (1-16 microgram/kg), atropine given i.v. at 15-min intervals, dose-responsively inhibited food-stimulated gastrin release in the four dogs with intact vagi. Assuming that the atropine effect was cumulative, kinetic analysis of the dose-response data gave a calculated maximum inhibition of 91% and an ID50 of 5.1 microgram/kg or 7.2 X 10-9 mol/kg. Findings of this study indicate a previously undescribed muscarinic cholinergic pathway leading to gastrin release by food.

Animals↗
PubMed1980

Gastric and cardiac H-2 receptor effects of dimaprit and N'(Me),5(Me)histamine in conscious dogs.

Two new H-2 agonists 5,N'-dimethyl histamine (DMH), an imidazole analog, and dimaprit, a non-imidazole compound, and histamine (H), a mixed H-1, H-2 agonist, were given to four conscious gastric fistula dogs. Gastric acid was stimulated dose responsively. Dimaprit stimulated a 20% greater maximum output of acid, and more pepsin than the other agents, but inhibited pepsin secretion as doses of greater than 0.63 mumol/kg-h. Heart rate was increased dose responsively by all drugs to approximately 200 beats/min with ED50 of 0.17:0.42:0.80 mumol/kg-h (H:DMH:dimaprit). Normalized dose responses showed that histamine was equipotent on acid and heart rate (ED50 0.15 vs. 0.14 respectively) while DMH (ED50 0.21 vs. 0.40) and dimaprit (ED50 0.27 vs. 0.85) stimulated heart rate less effectively than acid. Histamine was more effective at reducing blood pressure, with approximate ED50 of 0.28:0.60:0.96 for H, DMH and dimaprit respectively. The results indicate considerable heterogeneity of histamine responses for different actions mediated by the H-2 receptors, as well as differences for any one action between H-2 agonists.

Animals↗
PubMed1980

Use of impromidine to define specific histamine H-2 effects on gastric secretion, heart rate and blood pressure in conscious dogs.

Histamine H-2 receptor-mediated effects of the very selective H-2 agonist (H-1:H-2 < 1:1000) impromidine on gastric acid, chloride and pepsin secretion and on heart rate (HR) and systolic blood pressure were compared to those of histamine in five conscious gastric fistula dogs. In each dog, impromidine in a step-dose response (0.46 to 46 nmol/kg.hr) in 45-min steps was given without and with a background infusion of cimetidine (2 mumol/kg.hr). Histamine acid phosphate was given in a seven step-dose response (18 to 1350 nmol/kg. hr). Impromidine produced the same maximum stimulation of gastric HCI output, increase of HR and fall in systolic blood pressure as histamine. Impromidine was some 38 times more potent than histamine in stimulation of acid (ED50 3.8 vs. 145 nmol/kg.hr) and 30 times more potent in raising HR (ED50 5.6 vs. 172 nmol/kg.hr). Cimetidine competitively inhibited the effects of impromidine with similar pA2 values for each effect (acid, 5.99; chloride, 6.03; change in HR, 6.03; and change in systolic blood pressure, 6.32). The effects of impromidine on pepsin secretion were qualitatively and quantitatively similar to those of histamine and other H-2 agonists with weak stimulation at low doses and progressive inhibition with increasing doses of impromidine. Coupling the results with the known high specificity of impromidine, gastric acid secretion, chronotropism and hypotension all seem to be purely H-2-mediated effects of histamine in the intact conscious dog.

Animals↗
PubMed1979

Histamine receptors in the guinea pig ileum.

Histamine and some related compounds acting selectively on H2-or H1 receptors were tested for their ability to contract the guinea pig ileum, in the usual whole ileum preparation and in the longitudinal muscle preparation. The concentrations elicited by histamine in both kinds of preparations were not potentiated by cimetidine or metiamide and were not inhibited by administration of H2 receptor selective agonists in doses which were subthreshold for contracting the guinea pig ileum; higher doses of the H2 agonists could actually potentiate the effect of histamine. The results obtained suggest that H2 receptors with relaxing effect do not occur in the guinea pig ileum or at least that they are not involved in the contraction of the longitudinal muscle layers. The possibility that a sub-type of H2 receptors with properties different from those of the "classical" H2 receptors so far known, exists in the guinea pig ileum, cannot be excluded.

Animals↗
PubMed1979

Use of the central venous pressure catheter to obtain blood cultures.

The results of aerobic and anaerobic blood cultures obtained from a peripheral venopuncture and from the central venous pressure catheter were compared in critically ill patients admitted to the ICU to determine if pain and anxiety from multiple venopunctures could be alleviated while the physician's task is facilitated. The results were identical in 93.5% of the 92 comparisons. The discrepancies were evaluated and it was concluded that the method was easy, quick, and reliable. We recommend it as a suitable alternative to venopuncture.

Bacteriological Techniques↗
PubMed1979

Action of histamine receptor agonists and antagonists on the rat uterus.

1 Histamine and a series of compounds acting selectively on H1- and H2-receptors were tested on the isolated oestrous uterus of the rat. 2 Histamine had a dose-dependent inhibitory effect on the contractions elicited by acetylcholine. This action was unaffected by H1-blockers but was competitively inhibited by H2-blockers. The H1-selective agonist, 2-(2-aminoethyl)thiazole was ineffective at doses 100 times greater than those of histamine. Conversely, all the H2-agonists showed activity in the order of potency: N'-methylhistamine greater than histamine greater than N'-N'-dimethylhistamine greater than 5-methylhistamine greater than 5-methyl-N'-methylhistamine. Among the non-imidazole compounds, dimaprit had an activity identical to that of histamine, but all the dimaprit-like compounds showed negligible activity. 3 The data obtained suggest that in the rat uterus, (a) the activation of H2-receptors is responsible for the inhibitory effect of histamine and its analogues; (b) the integrity of the histamine molecule seems to be less crucial than that of the dimaprit molecule for the maintenance of the H2-activity, since changes in its structure modify but do not abolish the biological activity as they do in the case of dimaprit; (c) the order of activity of the various H2-receptor agonists is different from that observed in other tissues.

Animals↗
PubMed1979

"In vitro" duodenal muscle in the pharmacological study on natural compounds.

In vitro duodenal muscle was found to be a useful tool in the study of natural compounds. In the field of polypeptides rat duodenum was found to be of definite importance to differentiate the bradykinins (which induce relaxation) from the tachykinins (which evoke contractions). Human duodenum both "in vitro" and "in vivo" is relaxed by peptides of the gastrin and cholecystokinin family (like caerulein), whereas it is contracted by bombesin. Dog and cat duodenum is contracted by all the different types of peptides though in various degrees. Guinea pig duodenum is contracted by many peptides and also by histamine and related substances. In this case another differentiation seems to be possible as contraction induced by stimulation of H1 receptors concerns essentially the longitudinal muscle layer whereas stimulation of H2 receptors seems to inhibit the longitudinal contraction because of a contraction of the circular muscle or because of true relaxation of the longitudinal muscle. All the above considerations suggest that a comparative study performed on duodenal muscle of different animals might give useful information in the screening of new natural active compounds of synthetic analogues.

Animals↗
PubMed1978

Effects of ovariectomy and estradiol injection on nuclear structures of endometrial epithelial cells.

The changes of the rate of RNA synthesis produced by castration and estradiol injection on the surface endometrial cells of the rat are profited to study the variations in the number and size of nuclear ribonucleoprotein structures and in the disposition of chromatin. Two-dimensional measurements on sections contrasted with preferential procedures were employed to estimate the fraction of nuclear volume occupied by each element. Young adult rats in estrus are used as controls. 3 weeks after ovariectomy, the area fraction occupied by the nucleolus is reduced almost to a third of the control value, while the number of perichromatin granules per unit area of nucleus has significantly increased. A single injection of 20 microgram of estradiol produces a rapid decrease of the number of perichromatin granules to a fourth of the value of castrate animals, in 15-30 min, followed by a slow increase. Nucleolar area fraction begins to increase 2 h after estrogen administration and at 24 h it is higher than in controls. It is concluded that the changes of the nucleolar volume are due to the effects of estradiol on the synthesis of nucleolar RNA, while the variations of perichromatin granules are produced by the combination of the effect on extranucleolar RNA synthesis and on its processing and/or transporting to the cytoplasm. Both effects are independent and undergo different temporal courses.

Animals↗
PubMed1978

[Action of some gastric antisecretory drugs on histamine H2-receptors (author's transl)].

A series of compounds endowed with gastric antisecretory activity were examined for their possible effects on histamine H2 receptors in different experimental conditions. The data obtained suggest that, apart from cimetidine, all the other compounds are devoid of antagonistic properties on H2 receptors. The inhibitory effect observed in some of the examined preparations is probably connected with unspecific actions.

Animals↗
PubMed1978

[Effect of 2-(5-methyl-4-imidazolyl)-1-methylethylamine on histamine receptors].

Compound 2-(5-methyl-4-imidazolyl)-1-methylethylamine was tested on different preparations for its histamine-like activity. It was found to markedly affect H2 receptors and at the same time to be practically devoid of any activity on H1 receptors. This high selectivity of action indicates that this compound may represent a useful tool for characterizing the distribution of H2 and H1 receptor sites.

Airway Resistance↗
PubMed1977

Action of some natural polypeptides on the longitudinal muscle of the guinea pig ileum.

The structure--activity relationship of some natural tachykinins was investigated in the longitudinal muscle of the guinea pig ileum. The order of potency was eledoisin greater than uperolein greater than substance P greater than phyllomedusin greater than physalaemin. This ratio of activity is different from that observed in other experimental conditions, and in different in vivo or in vitro preparations; it is suggested that the N-terminal part of the molecule of the tachykinins plays a role in determining the degree of potency of these compounds.

Animals↗
PubMed1977

[Biological properties of 1,2-benzisothiazole compounds. Spasmolytic effect of N-(cyclohexylaminoethyl)-1,2-benzisothiazole-3-carboxyamides benzene-substituted on segments of human myometrium in virto].

A report is given on the spasmolytic effect of two benzisothiazolcarboxyamides (compound A and compound B). These drugs were able to inhibit the stimulant action of histamine on human isolated myometrium. The potency of the two compounds exceeded by ten times that of ritodrine (a beta adrenergic stimulant), the efficacy was slightly higher (20-30%) than that of papaverine. This pharmacological effect is discussed on the light of the spectrum of activites of the benzisothiazolcarboxyamidic compounds.

Female↗