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Biomedical subjects

E Medina

Publications and source records attributed to E Medina.

At least 181 records · Page 10Linked to original sources
PubMed1982

Pharmacological properties of melochinine, an alkaloid producing Central American cattle paralysis.

A Central American cattle paralysis is produced by ingestion of the plant Melochia pyramidata L. (Sterculiaceae). Its main alkaloid "melochinine" has been shown to produce paralysis, bradypnea, bradycardia and hypotension in laboratory animals after p.o., i.p. and i.v. applications. Bradycardia and negative inotropia have been demonstrated in isolated guinea pig atria and paralysis in the isolated phrenic nerve diaphragma preparation as well as in the phrenic nerve in situ preparation with local application. Gas chromatographic measurements suggest a rapid disappearance of melochinine after intravenous application and showed the similarity of the biologically active melochinine concentrations in vivo and in vitro. No unchanged melochinine was found in the urines of mice by thin-layer chromatography. A slight inhibition of the mitochondrial respiration and of some cholinesterases and none of the ATPase was found. Melochinine does not reveal insecticidal activity as does its structural analogue piericidin A, a well known inhibitor of the mitochondrial respiratory chain. The action of the alkaloid may be explained by an unspecific interaction with membranes, partially responsible for a Ca2+-antagonistic effect found in the isolated guinea pig papillary muscle. The proposed non-specific action could be a possible reason for the fact that trials of a specific therapy failed in our experiments.

Action Potentials↗
PubMed1982

[Not Available].

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Chile↗
PubMed1981

Epidemiology of gastric cancer in Chile: I - Case-control study.

The results of a case-control study of stomach cancer carried out with the collaboration of 7 participating hospitals in Santiago, Chile are reported. Patients attending gastroscopy clinics were interviewed before or after gastroscopy. The diagnosis was unknown to either the patient or the interviewer at the time of interview. 360 stomach cancer cases were subsequently matched to non-cancer patients selected from the pool interviewed at the same time as the cases. Study findings show: 1) longer-term residence in high-risk areas in early life by cases than controls; 2) an association between stomach cancer and a prior occupation in agriculture. In a subgroup of 98 cases for whom histologic classification was available, the association with residence in early life in a high-risk area was seen only for cases with intestinal-type stomach cancer.

Adult↗
PubMed1978

Significance of leaf orientation for leaf temperature in an Amazonian sclerophyll vegetation.

The influence of leaf orientation on leaf temperature has been studied in an sclerophyll vegetation of the Amazon basin, which grows on white sandy soils of very low water retention capacity and variable depth of the water table. Leaf size of the species studied is mainly mesophyllous (sensu Raunkiaer). The high degree of leaf inclination in all species is very characteristic; 55% of the leaves present inclination angles (relative to the vertical) smaller than 45 degrees. Water potential is generally high, not being lower than -14 bars. Leaf resistance increases toward noon during the course of sunny days, indicating either water stress at leaf level or the influence of low relative humidity on stomata opening. Leaf temperature under sunny conditions reflects the influence of leaf orientation on the amount of radiation absorbed by the leaf. Temperature differences recorded range from 1.8--5.4 degrees C. The difference depends on leaf angle, leaf color and leaf diffusion resistance during the period of measurement. Analysis of the relationship between leaf angle and leaf temperature, using Gates leaf energy balance, shows that under the conditions prevailing at noon in sunny days, leaf angles smaller than 50 degrees are effective in reducing leaf temperature within a wide range of leaf resistances to water vapor transfer.

Ecology↗
PubMed1978

Prevalence of intrahepatic cholestasis of pregnancy in Chile.

The prevalence of intrahepatic cholestasis of pregnancy was studied immediately postpartum in 869 women from three distant Chilean cities differing in climate and food supply. Cholestatic jaundice of pregnancy was detected in 2.4% and pruritus gravidarum in 13.2%, without significant differences between the three cities. Every woman was then ethnically classified as predominantly Caucasoid, Araucanian Indian, or Aimara Indian. A significantly higher prevalence of cholestatic jaundice of pregnancy (5.5%) and pruritus gravidarum (22.1%) was found in Araucanians than in Caucasoids (2.5% and 12.6% respectively) or in the Aimaras (0 and 11.8% respectively). The prevalence of intrahepatic cholestasis of pregnancy in Araucanians increased directly with the degree of "ethnic purity." Recurrence of the disease in multiparous women was also greater in Araucanians (13.8%) than in Caucasoids (5.5%) or in the Aimaras (3.9%). We propose that an ethnic predisposition to develop intrahepatic cholestasis of pregnancy is present in Araucanian women and that the high prevalence of the disease in Chile is mainly influenced by ethnic admixture with this South American Indian (ethnic) group.

Adult↗