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S M Martins

Publications and source records attributed to S M Martins.

5 recordsLinked to original sources
PubMed2000

Inhibition of the ecto-ATPdiphosphohydrolase of Schistosoma mansoni by thapsigargin.

ATPdiphosphohydrolases (ATPDases) are ubiquitous enzymes capable of hydrolyzing nucleoside di- and triphosphates. Although a number of possible physiological roles have been proposed for ATPDases, detailed studies on structure-function relationships have generally been hampered by the lack of specific inhibitors of these enzymes. We have previously characterized a Ca2+-activated ATPDase on the external surface of the tegument of Schistosoma mansoni, the etiologic agent of human schistosomiasis. In the present work, we have examined the effects of thapsigargin, a sesquiterpene lactone known as a high affinity inhibitor of sarco-endoplasmic reticulum calcium transport (SERCA) ATPase, on ATPDase activity. Whereas other lactones tested had little or no inhibitory action, thapsigargin inhibited ATP hydrolysis by the ATPDase (K(i) approximately 20 microM). Interestingly, hydrolysis of ADP was not inhibited by thapsigargin. The lack of inhibition of ATPase activity by orthovanadate, a specific inhibitor of P-type ATPases, and the inhibition of the Mg2+-stimulated ATP hydrolysis by thapsigargin ruled out the possibility that the observed inhibition of the ATPDase by thapsigargin could be due to the presence of contaminating SERCA ATPases in our preparation. Kinetic analysis indicated that a single active site in the ATPDase is responsible for hydrolysis of both ATP and ADP. Thapsigargin caused changes in both Vmax and Km for ATP, indicating a mixed type of inhibition. Inhibition by thapsigargin was little or not affected by changes in free Ca2+ or Mg2+ concentrations. These results suggest that interaction of thapsigargin with the S. mansoni ATPDase prevents binding of ATP or its hydrolysis at the active site, while ADP can still undergo catalysis.

Adenosine Diphosphate↗
PubMed1994

Interleukin-1B: a clinically relevant urinary marker.

Urinary cytokines as markers for the intravesical inflammatory response have become an active area of research. Interleukin-1b, a well studied and early produced cytokine in the immune recognition cascade, was evaluated. After extensive analysis of 56 control and study group urine samples, a simplified and reliable protocol for the preparation of urine before cytokine analysis was devised. The application of an available serum interleukin-1b enzyme-linked immunosorbent assay kit for urinary interleukin-1b analysis was then tested. Finally, a reference value for interleukin-1b in normal human urine was established and urinary interleukin-1b was measured in various bladder diseases. The normal and interstitial cystitis groups showed no interleukin-1b elevation. Significant elevation of urinary interleukin-1b was found in patients with bacterial cystitis compared to the interstitial cystitis and control groups (p < 0.001). Of the patients with bladder tumors 58% showed elevation of urinary interleukin-1b (p < 0.001). Urinary interleukin-1b may be used as a marker to distinguish between bacterial and interstitial cystitis. The absence of urinary interleukin-1b in interstitial cystitis argues against an immunological or autoimmune etiology of the disorder. This study represents an important methodological approach to cytokine subtyping of bladder diseases.

Adolescent↗
PubMed1993

[Blood pressure variability and left ventricular hypertrophy in arterial hypertension].

PURPOSE: To evaluate the left ventricular hypertrophy correlation with blood pressure variability during day and night time as well as throughout the 24h period. METHODS: Fifteen patients with mild to moderate essential hypertension underwent to bi-dimensional echocardiographic study and to 24h ambulatory blood pressure monitorization. Left ventricular mass was calculated according to previous validated formulas. The standard deviation of the mean blood pressures during day-time, night-time and 24h period was taken as blood pressure variability indices. The mean age of the group was 42 years old; 9 patients were male and all were white. RESULTS: This study showed that only the systolic and diastolic blood pressure variability during the 24h period correlated significantly with left ventricular mass, (r = 0.53 and p < 0.05; r = 0.58 and p < 0.05 respectively). There was no significant correlation of the day-time and night-time pressures variability with left ventricular mass. CONCLUSION: The systolic and diastolic blood pressure variability during the 24h period may be one of the many determinants of left ventricular hypertrophy in patients with mild to moderate hypertension.

Adolescent↗
PubMed1991

[Multiple causes of death in diabetics in the municipality of Recife, 1987].

In 1987, diabetes mellitus was mentioned in 492 death certificates of the population of the city of Recife, Brazil, 202 of them for males and 290 for females. Diabetes mellitus was the underlying cause of death according to 80 certificates for men and 290 for women, as a result of which premature death occurred in 16.2% of men and 11.1% of women. Multiple cause of death analysis showed that cardiovascular diseases were the most frequent underlying cause of death in individuals over 50 years of age and acute complications of diabetes mellitus in individuals under 50. Cerebrovascular diseases were the most frequent in the cardiovascular group, particularly in females. Arterial hypertension was the most frequent associated cause of death appearing in death certificates mentioning diabetes mellitus (not as the underlying cause of death), also more often in females. The acute complications of diabetes mellitus (keto-acidosis and coma) and peripheral circulatory disorders peculiar to this disease caused 23% and 30% of the deaths, respectively, in cases where diabetes mellitus was the underlying cause. Infectious and parasitic diseases were the most frequent associated causes of death according to those certificates which gave diabetes mellitus as the underlying cause.

Brazil↗