PubMed Health⌕ Search

Biomedical subjects

S Ramos

Publications and source records attributed to S Ramos.

At least 91 records · Page 5Linked to original sources
PubMed1990

Radiolysis of aqueous solutions of acetic acid in the presence of Na-montmorillonite.

The gamma-irradiation of 0.8 mol dm-3 aqueous, oxygen-free acetic acid solutions was investigated in the presence or absence of Na-montmorillonite. H2, CH4, CO, CO2, and several polycarboxylic acids were formed in all systems. The primary characteristics observed in the latter system were: (1) Higher yield of the decomposition of acetic acid; (2) Lower yield of the formation of polycarboxylic acids; (3) No effect on the formation of methane; (4) Higher yield of the formation of carbon dioxide; and (5) The reduction of Fe3+ in the octahedral sites of Na-montmorillonite. A possible reaction scheme was proposed to account for the observed changes. The results are important in understanding heterogeneous processes in radiation catalysis and might be significant to prebiotic chemistry.

Acetates↗
PubMed1989

The mechanism of intracellular acidification induced by glucose in Saccharomyces cerevisiae.

Addition of glucose or fructose to cells of Saccharomyces cerevisiae adapted to grow in the absence of glucose induced an acidification of the intracellular medium. This acidification appeared to be due to the phosphorylation of the sugar since: (i) glucose analogues which are not efficiently phosphorylated did not induce internal acidification; (ii) glucose addition did not cause internal acidification in a mutant deficient in all the three sugar-phosphorylating enzymes; (iii) fructose did not affect the intracellular pH in a double mutant having only glucokinase activity; (iv) glucose was as effective as fructose in inducing the internal pH drop in a mutant deficient in phosphoglucose isomerase activity; and (v) in strains deficient in two of the three sugar-phosphorylating activities, there was a good correlation between the specific glucose- or fructose-phosphorylating activity of cell extracts and the sugar-induced internal acidification. In addition, in whole cells any of the three yeast sugar kinases were capable of mediating the internal acidification described. Glucose-induced internal acidification was observed even when yeast cells were suspended in growth medium and in cells suspended in buffer containing K+, which supports the possible signalling function of the glucose-induced internal acidification. Evaluation of internal pH by following fluorescence changes of fluorescein-loaded cells indicated that the change in intracellular pH occurred immediately after addition of sugar. The apparent Km for glucose in this process was 2 mM. Changes in both the internal and external pH were determined and it was found that the internal acidification induced by glucose was followed by a partial alkalinization coincident with the initiation of H+ efflux. This reversal of acidification could be due to the activity of the H+-ATPase, since it was inhibited by diethylstilboestrol. Coincidence between internal alkalinization and the H+ efflux was also observed after addition of ethanol.

Carbohydrates↗
PubMed1989

A double-blind clinical trial with a lotion containing 5% benzoyl peroxide and 2% miconazole in patients with acne vulgaris.

The therapeutic efficacy of a lotion containing 5% benzoyl peroxide and 2% miconazole was compared with 5% benzoyl peroxide alone, in a double-blind, randomized, parallel study. Thirty patients with comedonal or inflammatory acne vulgaris were enrolled. The medications were applied once daily during the first week, and then twice daily for the rest of the trial (45 days). In patients with comedonal acne there was no difference in the effect of the two therapies. In patients with inflammatory acne the percentage reduction of the number of lesions on Day 30 was significantly higher in the benzoyl peroxide plus miconazole group (66%) compared to benzoyl peroxide alone (37%). At Day 45 there was a trend favouring the combined therapy but the difference was not significant. There were no significant differences in the adverse reactions reported by the two groups of patients (erythema, itching or moderate exfoliation).

Acne Vulgaris↗
PubMed1987

External K+ affects the internal acidification caused by the addition of glucose to yeast cells.

In glucose-grown cells of Saccharomyces cerevisiae, collected during the stationary phase of growth, the addition of K+ to the external medium reversed glucose-induced internal acidification in 2 min. However, in ethanol-grown cells external K+ did not reverse the effect of glucose even after 20 min. The presence or absence of external K+ did not alter the modification of trehalase and fructose-1,6-bisphosphatase induced by glucose. It is concluded that transient acidification may be sufficient to cause the associated transient increase in cAMP.

Benzoates↗
PubMed1987

[Sebaceous trichofolliculoma].

A case of sebaceous trichofolliculoma on the nose of a 42 year old man, present at the birth, is reported. The histology was typical, with a cavity formed by the skin of the nose having numerous well developed sebaceous glands along with vellus and terminal hairs.

Adult↗
PubMed1987

[Biochemical complications of experimental vesico-sigmoidostomy].

Three experimental models of vesico-sigmoidostomy are studied (model-1, end to side V-S plus urethral ligation, model-2, end to end V-S, in "Y of Rous" plus urethral ligation and model-3, vesico-sigmoidoplasty), with aim of reproducing chemical imbalance observed in human subjects with ureterosigmoidostomy. Authors have evaluated clinical biochemical (serum acido-base balance, Cl, Na+, K+, BUN, creatinine, ammonia and albumin), and histologic variables in the first, third and fifth month after operation in 225 rats. Animal of model-1 presented more frequently than model-2 and model-3, alterations (hyperchloraemic acidosis, uraemia, hyperammonemia and hypoalbumin) as well as affectation of upper urinary system for acute or chronic pyelonephritis.

Animals↗
PubMed1986

Trehalase activation in yeasts is mediated by an internal acidification.

It has been reported that the addition of glucose, uncouplers and nystatin to yeast cells grown in a sugarfree medium causes trehalase activation; it has been postulated that this activation might be mediated by the depolarization of the plasma membrane. In this article the values of membrane potential and pH gradient across the plasma membrane of Saccharomyces cerevisiae have been determined under the same conditions as those in which trehalase is activated. Membrane potential was evaluated from the distribution of triphenylmethylphosphonium, the pH gradient from the distribution of benzoic acid across the plasma membrane. When the effect of several agents on the two components of the electrochemical proton gradient across the plasma membrane of ethanol-grown yeast cells were studied, under trehalase activation conditions, the following observations were made. (a) The addition of glucose activated trehalase and caused internal acidification of the cells, but had practically no effect on the membrane potential. (b) The addition of 200 mM KCl depolarized the cell membrane but did not affect the internal pH, nor trehalase activity. (c) Although carbonyl cyanide m-chlorophenylhydrazone depolarized the cells at external pH 6.0 and 7.0, it only activated trehalase at an external pH 6.0, leading to the acidification of the internal medium at this pH. (d) Nystatin caused an increase in the triphenylmethylphosphonium accumulation at external pH 6.0 and 7.0, but only activated trehalase at external pH 6.0, causing acidification of the cell interior at this pH. (e) Activation of trehalase was also observed when the internal acidification was caused by addition of a weak acid such as acetate. It is concluded that trehalase activation is mediated by an intracellular acidification and is independent of the membrane potential.

Culture Media↗
PubMed1986

Chromosomal anomalies in children treated for cancer.

Cytogenetic studies were carried out in peripheral blood lymphocytes of 31 children with cancer (12 retinoblastomas, 9 non-Hodgkin's lymphomas, 7 neuroblastomas and 3 Wilms' tumors) with the purpose of investigating the prevalence and persistence of chromosomal aberrations before onset of antineoplastic treatment and at different intervals thereafter. The number of treated patients with chromosomal anomalies was significantly higher (p less than 0.01) and so was the percent of cells with aberrations, as compared to untreated patients or healthy controls. The most frequent aberrations were of chromatid type. One patient had a number five trisomy in the third posttreatment study and another presented abnormal aneuploid cells in the third and fourth posttreatment studies. Congenital chromosomal anomalies were not observed, nor anomalies described for some of these tumors. There was no regularity in the effected chromosomes. We conclude that the observed chromosomal aberrations were due to treatment. We consider a prolonged and stringent cytogenetic follow up of such patients necessary to detect the induced aberrations.

Child↗
PubMed1985

Persistence of DNA lesions and the cytological cancellation of sister chromatid exchanges.

The ability of UV light, mitomycin C and ionizing radiation to induce the formation of sister chromatid exchanges (SCEs) at the same locus in successive cell generations was investigated in human lymphocytes. Cells were exposed to the DNA damaging agents after they had completed their first round of DNA replication, and SCEs were examined at the third division in chromosomes that had been differentially stained three ways. Although some of these treatments induced long-lived lesions that increased the frequency of SCEs in successive cell generations, none of the lesions led to the formation of consecutive SCEs at the same locus in successive cell generations. This observation seriously challenges the hypothesis that SCE cancellation results as a consequence of persistence of the lesions induced by these agents.

Antibiotics, Antineoplastic↗
PubMed1983

[Enzymatic changes in cancer].

Several enzymes were estimated in different tumors. Ceruloplasmin, lactate dehydrogenase (LDH), and phosphohexose isomerase (PHI) showed a direct correlation with tumor growth and remission. The ratio LDH/PHI was low in solid tumors and high in lymphomas, suggesting a different metabolism.

Ceruloplasmin↗
PubMed1981

Effect of yeast killer toxin on sensitive cells of Saccharomyces cerevisiae.

Killer toxin from Saccharomyces cerevisiae inhibited the pumping of protons into the medium by metabolically active sensitive cells. Such inhibition coincided with that of the uptake of potassium ions which are thought to be accumulated by yeast cells in order to neutralize the membrane potential created because of the extrusion of protons. The consumption of glucose, however, was identical in killer-treated and untreated cells. These alterations can be explained by the ability of the toxin to reduce the chemical proton gradient across the plasma membrane as measured by the accumulation of the weak permeable [14C]propionic acid. With this method, an internal pH of 6.42 was calculated from normal cells (the external pH was 4.6) while that of toxin-treated cells was decreased as a function of time. The proton concentration gradient was reduced from 66- to 17-fold. It is shown that the toxin-induced alteration of the proton gradient is due to an enhanced proton permeability of the yeast plasma membrane upon binding of the toxin. It is suggested that killer toxin acts as a macromolecular proton conductor similar in some respects to the known proton conductors 2,4-dinitrophenol and carbonyl cyanide m-chlorophenylhydrazone, since all the described effects are also observed with these substances.

Biological Transport↗