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Biomedical subjects

R Rodríguez

Publications and source records attributed to R Rodríguez.

At least 253 records · Page 14Linked to original sources
PubMed1987

Relaxant action of androgens, progestins and corticosteroids on the isolated ileum of the guinea pig.

The action of three different kinds of progesterone related compounds was tested on the spontaneous contractility of the isolated guinea pig ileum. The results showed that this tissue was very sensitive to the action of androgens, progestins and corticosteroids. Relaxation was observed as dose-dependent; however, effective doses 50 were different, being related to the chemical structure of the compound. 5 beta-progestins were the most potent steroids followed by 5-reduced androgens (5 alpha or 5 beta). 4-en compounds such as testosterone, progesterone, 17 alpha-OH-progesterone, and corticosteroids were the lower in potency. 5 alpha-pregnanedione and pregnanediols were practically ineffective. The high sensitiveness of the ileum smooth muscle makes this organ a target for steroids. Thus, steroidal influence on the intestine might be related with contractility changes in some physiological circumstances, e.g., pregnancy.

Adrenal Cortex Hormones↗
PubMed1986

Kindling-like phenomenon in the isolated ileum of the guinea-pig.

Repeated bursts of low voltage electrical stimulation of the isolated ileum of the guinea-pig gradually leads to the development and progressive intensification of the tissue basal activity, culminating in spontaneous, sudden strong contractions of the preparation, which persist for several hours after the stimulation has been discontinued. The magnitude of these alterations are determined by the parameters of the stimulation, mainly by the number of electrical stimulations, the frequency of stimulation, and the interstimulus interval. Maximal alterations are obtained with periods of stimulation of 20 Hz for 10 sec, pulses of 3.0 msec, repeated every 20 min for 15 times. Phenytoin, flunitrazepam, diazepam, phenobarbital and carbamazepine effectively inhibited the fully developed phenomenon in the tissues. The effect described in this report may be related to kindling in the brain.

Animals↗
PubMed1986

Influence of hormones on DNA synthesis of breast tumors in culture.

Tissue culture techniques have been developed for studying the influence of hormones on human breast tissues. The present study demonstrated that estrogen induced a highly significant increase in 3H-thymidine incorporation into DNA and labelling index of ductal epithelium of fibrocystic disease; there was no effect of progesterone, either alone or in combination with ovine prolactin, on benign lesions. Estrogen stimulated certain malignant tumors derived from postmenopausal women. These studies also showed that there was an inhibitory effect of 3H-thymidine incorporation into DNA by the effect of progesterone on malignant lesions. When menopausal status was considered, it was found that DNA synthesis was significantly higher in the presence of insulin and hydrocortisone in malignant tumors derived from premenopausal women than from postmenopausal women, or than in benign lesions. Thus, the present findings may provide evidence that specific activity may be an important measurement for breast tumor DNA synthesis in response to ovarian hormones or other substances.

Adenoma↗
PubMed1984

Comparative study on the secondary structure of lysozymes from different sources.

The secondary structure of 16 type c lysozymes, 2 type g lysozymes, phage T4 lysozyme and bovine alpha-lactalbumin have been estimated according to the method of Chou and Fasman (1978). The prediction has been done on the partial sequence of lysozymes from three insects and tortoise egg-white lysozyme. From these studies, patterns of common secondary structure domains on lysozymes have been developed. These patterns have been compared attending to the active site and the antigenic loop of the hen enzyme of which three-dimensional structure is known. The three-dimensional structures of phage T4 and hen egg-white lysozymes have common alpha-carbon backbone domains being that also observed by these predictions. Immunological results are also discussed in terms of secondary structure homologies.

Amino Acids↗
PubMed1983

Ethanol and receptor function.

The effects of ethanol in vitro (21 and 42 mM) and in vitro (10 and 30 days of exposure) on the dose:effect curves for noradrenaline and acetylcholine in isolated auricles and uterus of rats, respectively, have been studied. Likewise, the acetylcholine-atropine interaction was studied in rat uterus under the above-mentioned conditions. Analysis of theoretical curves as well as pD2 and pA2 calculations revealed that ethanol causes changes in the tissue responses to the agents assayed which in turn may be an expression of modification in the receptor function.

Acetylcholine↗
PubMed1983

Early effects of medium change in cultured cells: evidences for the existence of negative modulators of cell proliferation.

Serum deprivation of cells in culture leads usually to an arrest of DNA synthesis and cell proliferation but the transfer of cultured cells from serum-containing to serum-free medium results in a transient stimulation of the incorporation of radioactive thymidine to macromolecules. This stimulation effect produced by medium change can be separated into two different phenomena: a stimulation of thymidine incorporation induced by transfer of cells from conditioned serum-containing medium to fresh serum-containing medium and an additional stimulation induced by transfer of cells from serum-containing medium to serum-free medium. Experimental results indicate that the first effect is probably due to the removal of inhibitors released by the cells even in exponentially growing cultures, and that the second effect is probably due to the removal of inhibitory molecules coexisting in serum with stimulatory factors.

Animals↗