Glucose activation of adenylate cyclase in Saccharomyces cerevisiae mutants lacking glucose-phosphorylating enzymes

The "in vitro" activation by glucose of the RAS-adenylate cyclase system in membranes from a strain of Saccharomyces cerevisiae lacking any functional glucose kinase activity presents similar features to those of the wild type. However, this triple mutant appears to be unable to produce the glucose-induced increase of cAMP levels "in vivo". The results obtained in vitro indicate that the signal transduction mechanism is active in the mutant cells and suggest that the absence of intracellular acidification in vivo might be responsible for the lack of response to glucose.

[Cardiovascular syphilis. Report of 2 cases]

We present two cases of cardiovascular syphilis being one of them a curious case of chronic pericardial effusion associated with cardiovascular complications of lues. In this article we will make as well a review of cardiovascular syphilis.

Activation of adenylate cyclase in cdc25 mutants of Saccharomyces cerevisiae

The activation of adenylate cyclase by guanine nucleotides and 6-deoxyglucose was studied in membrane preparations from S. cerevisiae mutants lacking the CDC25 gene product. Adenylate cyclase from cdc25 ts membranes was activated by GTP and GppNHp in membranes from cells collected after glucose was exhausted from the medium. The activation was also observed in membranes from repressed cells at 2.5 mM Mg2+. It is also shown that 6-deoxyglucose can activate adenylate cyclase in the absence of CDC25 gene product. The relative amount of membrane-bound adenylate cyclase was drastically reduced in cdc25 ts membranes when subjected to the restrictive temperature, while no significant change was observed in the wild type. These data suggest that Cdc25 might not be required in certain conditions for the guanine nucleotide exchange reaction in Ras and that it might be implicated in anchoring the Ras/adenylate cyclase system to the plasma membrane.

Pathogen-specific risk factors and protective factors for acute diarrheal disease in urban Brazilian infants

To evaluate potential risk factors and protective factors for acute diarrheal disease in urban infants, 500 infants < or = 12 months old with diarrhea and 500 age-matched control subjects coming to a São Paulo emergency room were studied. On multivariate analysis, these apparently sporadic community-acquired cases of diarrhea were significantly associated with hospitalization in the month before onset (odds ratio [OR], 3.4), day care center exposure (OR, 2.0), prior diarrhea in another household member (OR, 4.4), and low family income (OR, 1.8). Breast-feeding infants < 6 months old (OR, 0.3) and boiling household drinking water (OR, 0.4) were protective. Enteropathogenic Escherichia coli (EPEC; OR, 12.0) and Salmonella (OR, 7/0, discordant pairs) infections were associated with prior hospitalization, rotavirus infections were associated with day care (OR, 6/0), and breast-feeding was protective against EPEC infections (OR, 0.1). These results suggest that certain preventive strategies can prevent a substantial proportion of cases of diarrheal disease in Brazilian infants.

A prospective randomized double blind study of perioperative antibiotic use in the grafting of ulcers of the lower extremity

We conducted a prospective, randomized, double blind study of the use of a perioperative antibiotic in the skin grafting of arterial and venous ulcers of the lower extremity. Ninety-four patients were randomized and 90 were available for analysis. There was no statistically significant difference in graft "take" or incidence of recipient site infection in the antibiotic versus the no antibiotic group.

[Pulmonary stenosis in adults. Report of a clinical case]

The authors report a case of valvular pulmonary stenosis in a 60 years old patient, admitted to hospital with heart failure and angor pectoris. Four years previously a VVI pacemaker had been implanted for complete heart block. At the time of the admission he had two pacemakers leads in the right ventricle; one of them was retained and functionless since the changing of the generator which occurred 1 year before. The usual complications of endocardial pacemakers are discussed, as well as the natural course and surgery indications for valvular pulmonary stenosis in adults.

In vitro activation of the Saccharomyces cerevisiae Ras/adenylate cyclase system by glucose and some of its analogues

Using crude membrane preparations of Saccharomyces cerevisiae, we have demonstrated that glucose and glucose analogues which are not efficiently phosphorylated activate the guanine nucleotide-dependent adenylate cyclase in vitro. The activation appears to be mediated by the Ras proteins. Moreover, data are presented indicating that glucose and its analogues activate adenylate cyclase by stimulating the exchange of guanine nucleotides at its regulatory component. Thus, it has been possible to show the action of a physiological effector on the nucleotide exchange reaction in a member of the ras superfamily.

[Structural changes in pulmonary vessels and coronary arteries in hypoplastic left heart syndrome]

In order to correlate gross morphological features with pulmonary and coronary vasculature changes in hypoplastic left heart syndrome (HLHS) 15 heart-lung necropsy specimens from neonates were analysed. Histology of left atrium wall, lung vessels with pulmonary arteriolar disease morphometric grading, study of intra and extra pulmonary wall veins and coronary arteries were recorded. Classic HLHS was observed in 11, and DORV with mitral atresia in 4, the foramen ovale (FO) being the only left atrium outflow tract in all. All specimens had increased % of thickness and muscular extension of arterioles and increased wall thickness of pulmonary veins, but severer arteriolar and venous changes with left atrium fibrosis were noticed in 8 specimens with either closed FO (3 cases) or mean FO diameter (d) of 5 mm when compared with specimens with mean FOd of 9 mm. Coronary arteries histology disclosed in 4 of 8 specimens with opened but hypoplastic mitral valve, intima proliferative changes with lumen narrowing, not observed in 7 specimens with mitral valve atresia. We concluded that in HLHS closed or restrictive FO and permeable mitral valve may predispose neonates to respiratory complications, right ventricle abnormal function and arrhythmias, specially after cardiac surgery.

Medullary carcinoma of thyroid: a re-evaluation of the cytological criteria of diagnosis

We have reviewed the fine needle aspiration cytology appearances of a series of 31 consecutive and histologically confirmed medullary carcinomas of the thyroid. Despite the absence of a totally specific diagnostic feature, this retrospective re-evaluation indicates that a preoperative diagnosis of medullary carcinoma of the thyroid is possible in almost every case. The features occurring most commonly include a dispersed cell pattern in which round or spindle shaped cells with eccentric speckled nuclei were seen showing slight pleomorphism with inconspicuous nucleoli. In a third of cases fine red granularity was present in the cytoplasm in slides stained with Giemsa and by the Papanicolaou technique.

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).

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.

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.

[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.

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.

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.