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Biomedical subjects

F Rivera

Publications and source records attributed to F Rivera.

At least 181 records · Page 10Linked to original sources
PubMed1988

The effect of hypoglycemic sulfonylureas on human red blood cell transglutaminase activity.

We have examined the effect of glipizide, a hypoglycemic sulfonylurea, upon transglutaminase activity in human red blood cells. In a first series of experiments the in vitro effect of the drug was assessed. The results obtained showed that glipizide inhibits transglutaminase activity in human red blood cells. In a second approach, glipizide was administered orally to six type 2 diabetic patients during 3 months, in order to evaluate the long-term effect upon transglutaminase activity. Again, glipizide induced a significant decrease in the enzyme activity in blood red cells (P less than 0.01). We suggest that treatment of type 2 diabetes mellitus with hypoglycemic sulfonylureas could improve insulin effects by inhibiting cellular transglutaminase activity.

Calcium↗
PubMed1988

Prognostic value of arterial pressure, endogenous vasoactive systems, and renal function in cirrhotic patients admitted to the hospital for the treatment of ascites.

To identify prognostic factors in cirrhotic patients admitted to the hospital for the treatment of an episode of ascites, a survival analysis was performed in a series of 139 patients hospitalized in our Unit between 1980 and 1985. Mean follow-up was 12.8 +/- 14.2 mo (mean +/- SD). A total of 38 variables based on history, physical examination, hepatic biochemical tests, renal function tests, and endogenous vasoactive systems were analyzed for prognostic value. Eighteen of these variables had prognostic value in the univariate analysis. A multivariate analysis (Cox's regression method) disclosed that 7 of these 18 variables had independent prognostic value. Of these independent predictors of survival, mean arterial pressure and plasma norepinephrine concentration were the variables that best predicted prognosis. Two other variables that independently correlated with survival were urinary sodium excretion and glomerular filtration rate. The remaining three independent predictors of survival were nutritional status, hepatomegaly, and serum albumin concentration. Therefore, these findings indicate that, in patients with cirrhosis and ascites, parameters estimating systemic hemodynamics and renal function are better predictors of survival than those routinely used to estimate hepatic function.

Adult↗
PubMed1988

Hyperglucagonism and glucagon resistance in cirrhosis. Paradoxical effect of propranolol on plasma glucagon levels.

Propranolol, a non-selective beta-blocker, is known to decrease glucagon release in normal subjects. The present study was aimed at investigating the effects of propranolol on the hyperglucagonism commonly observed in patients with cirrhosis. Eight cirrhotic patients and 6 matched healthy controls were studied. The plasma concentrations of glucagon, insulin, c-peptide and glucose were measured in basal conditions and after stimulating glucagon secretion by an i.v. infusion of arginine (0.4 g/kg/30 min). The study was repeated 24 h later after inducing beta-blockade by the i.v. infusion of propranolol (10 mg). In baseline conditions, patients with cirrhosis, despite normal levels of insulin and glucose, had a marked hyperglucagonism (654 +/- 303 pg/ml vs. 269 +/- 90 in controls, P less than 0.01). Prior to propranolol, arginine infusion caused greater glucagon release in cirrhotics (71 +/- 31 ng.h.ml-1) than in controls (33 +/- 17 ng.h.ml-1, P less than 0.02), but despite a similar insulin secretion (assessed from c-peptide), blood glucose did not increase. After propranolol, glucagon secretion decreased as expected in controls (29 +/- 12 ng.h.ml-1, P less than 0.05) but experienced a paradoxical increase in cirrhotics (113 +/- 64 ng.h.ml-1, P less than 0.05). Again, despite the marked increase in glucagon release, there was no increase in glucose production, providing further evidence of the glucagon resistance that accompanies hyperglucagonism in cirrhosis. Our results suggest that hyperglucagonism with glucagon resistance might be the initial disturbance in carbohydrate metabolism in patients with cirrhosis. Contrary to what could be expected, propranolol does not correct but further accentuates this disturbance.

Adult↗
PubMed1988

Longitudinal study of renal prostaglandin excretion in cirrhotic rats: relationship with the renin-aldosterone system.

1. A cross-sectional study (protocol A) was performed in 19 rats with cirrhosis, induced by carbon tetrachloride (CCl4), and ascites and in 10 control animals to assess renal prostaglandin (PG) excretion in experimental cirrhosis. In an additional group of animals, including nine rats chronically exposed to CCl4 (CCl4 rats) and six control rats, a longitudinal study (protocol B) was performed to investigate the temporal relationship between changes in renal PG excretion, the renin--aldosterone system and renal function. 2. Urinary PG excretion was assessed by specific radioimmunoassay of PGE2, PGF2 alpha, 6-keto-PGF1 alpha and thromboxane (TX) B2 after extraction with octadecyl silica cartridges and h.p.l.c. purification. Recoveries for each prostanoid (61 +/- 8% for PGE2, 64 +/- 12% for PGF2 alpha, 65 +/- 11% for 6-keto-PGF1 alpha and 66 +/- 17% for TXB2) were determined in every sample by adding tritiated standards, and the final values were corrected according to the individual recoveries. 3. Cirrhotic rats with ascites in protocol A showed a significantly higher plasma renin and aldosterone concentrations and urinary excretion of 6-keto-PGF1 alpha and TXB2 than did control animals. Urinary excretion of PGE2 and PGF2 alpha, however, was significantly reduced in cirrhotic animals as compared with controls. 4. In CCl4 rats included in protocol B, there was a close chronological relationship between the activation of the renin-aldosterone system, as estimated by urinary aldosterone excretion, the onset of sodium retention and the increase in urinary excretion of 6-keto-PGF1 alpha and TXB2. The urinary excretion of PGE2 and PGF2 alpha in CCl4 rats was reduced throughout the study.(ABSTRACT TRUNCATED AT 250 WORDS)

6-Ketoprostaglandin F1 alpha↗
PubMed1988

Effects of somatostatin on splanchnic hemodynamics and plasma glucagon in portal hypertensive rats.

The effects of somatostatin infusion on splanchnic and systemic hemodynamics and plasma glucagon levels were investigated in rats with portal hypertension. Forty-four male Sprague-Dawley rats were studied. Portal hypertension was induced in 26 rats by partial portal vein ligation (PVL). These rats were divided in two experimental groups to receive blindly 1) somatostatin (PVL-SMT, n = 13) at a dose of 25 micrograms/kg body wt during 30 min preceded by a bolus injection of 15 micrograms/kg body wt or 2) placebo (saline) (PVL-P, n = 13) infused at the same rate as in the previous group. The remaining 18 rats were used as normal controls and received somatostatin (n = 9) or saline infusion (n = 9). Regional blood flows and cardiac output were measured using radioactive microspheres. Arterial and portal pressures were also measured. In portal hypertensive rats somatostatin infusion produced significant reductions in the increased portal venous inflow, reductions in portal pressure, and significantly increased portal venous resistance. Reduction of portal venous inflow was due to splanchnic vasoconstriction, evidenced by increased splanchnic arteriolar resistance. No significant differences were observed in systemic hemodynamic parameters between PVL-SMT and PVL-P rats. Plasma glucagon levels were significantly reduced by somatostatin to levels similar to those observed in sham-operated rats. In sham-operated rats, somatostatin also caused significant reduction in portal venous inflow and plasma glucagon concentration, although these changes were of lesser magnitude than in portal hypertensive rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Presence of insulin autoantibodies at clinical diagnosis of diabetes mellitus type I predicts loss of beta cell function.

Recently the spontaneous development of insulin autoantibodies (IAA) has been detected in patients at diagnosis of Type I diabetes mellitus before the beginning of insulin treatment. The present study was undertaken to investigate if the presence of IAA at clinical onset of IDDM may act as a new marker of the beta cell function. The results obtained showed that IAA were present in 44% of newly diagnosed diabetic patients before therapy. Patients without IAA displayed a higher C-peptide secretion than those with IAA, at six months (12.11 +/- 5.08 versus 5.88 +/- 3.25 ng/ml/10 min.)(X +/- SD) and at twelve months (10.45 +/- 3.05 versus 4.90 +/- 5.25 ng/ml/10 min)(X +/- SD) of the follow up period. HbA1 levels, and insulin requirements were similar in both groups (IAA+ and IAA-). We conclude that the presence of insulin autoantibodies at clinical diagnosis, before initiating insulin treatment, may well predict the loss of the beta cell function.

Adolescent↗
PubMed1988

Effect of atrial natriuretic peptide on arterial pressure and renal function in cirrhotic rats with ascites.

Glomerular filtration rate, urine volume, sodium excretion and mean arterial pressure were measured in 10 rats with Cl4C induced cirrhosis presenting sodium retention and ascites, and in 10 control rats before and during the iv administration of the 28 aminoacid rat alpha-Atrial Natriuretic Peptide (alpha-ANP) (a bolus of 1 microgram followed by a constant infusion of 33 ng/min). alpha-ANP induced a similar increase in glomerular filtration rate and filtered sodium load in both groups of rats. In contrast, the increase in urine volume and sodium excretion produced by alpha-ANP was significantly lower in cirrhotic rats (from 13.8 +/- 1.9 to 37.9 +/- 9.1 microliters/min., and from 0.5 +/- 0.1 to 3.3 +/- 1.0 microEq/min) than in control animals (from 14.6 +/- 1.3 to 102.5 +/- 17.7 microliters/min., p less than 0.005; and from 1.0 +/- 0.3 to 14.1 +/- 3.2 microEq/min., p less than 0.001). The results indicate that in rats with experimental cirrhosis and ascites there are blunted diuretic and natriuretic responses to alpha-ANP, probably as a consequence of the exaggerated tubular sodium reabsorption present in these animals.

Animals↗
PubMed1988

Effect of spironolactone on the renin-aldosterone system in rats.

PRA, PRC and the plasma concentration of aldosterone (Aldo) were measured in rats (Sp-rats) receiving a daily sc injection of Spironolactone, (Sp, 20 mg in olive oil) and in control rats (C-rats) receiving olive oil only. Animals were studied one day after starting treatment, 5 days on treatment or after 5 weeks on the study. PRA, PRC and Aldo were significantly increased in Sp-rats as compared to C-rats throughout all the study. In additional Sp-rats and C-rats, the urine volume, serum Na+ and K+ concentration, Na+ and K+ intake and the urinary excretion of Na+, K+ and aldosterone-18-glucuronide (UAldV) were serially measured during 5 weeks. The total radioactivity plasma clearance after an i.v. bolus injection of 3H-aldosterone was subsequently measured in (5 Sp-rats and 5 C-rats). No significant differences in serum Na+ and K+ concentration and in Na+ and K+ balance were observed between Sp-rats and C-rats. UAldV was significantly higher in Sp-rats than in C-rats during all the study. After 5 weeks on treatment the total radioactivity plasma clearance was significantly higher in Sp-rats than in C-rats. These results indicate that Sp, at high dosage, stimulates renin release and aldosterone secretion by a mechanism unrelated to alterations in Na+ and K+ balance.

Aldosterone↗
PubMed1987

Temporal relationship between the impairment of free water excretion and antidiuretic hormone hypersecretion in rats with experimental cirrhosis.

To investigate the temporal relationship between the impairment of water excretion, sodium retention, and antidiuretic hormone hypersecretion in cirrhosis, free water excretion (estimated by the minimum urinary osmolality) and urinary antidiuretic hormone excretion (which correlates with the plasma levels of this hormone) were measured weekly after an oral water load in 18 rats with carbon tetrachloride-induced cirrhosis and in 20 control animals. The onset of ascites (as an index of sodium retention) in cirrhotic rats was estimated by sequential paracentesis. Thirteen cirrhotic animals developed an impairment of water excretion 2-5 wk after the onset of ascites. The urinary excretion of antidiuretic hormone in these animals, which was normal before the impairment of water excretion, increased markedly within the week in which this abnormality was first detected and remained high thereafter. The remaining 5 cirrhotic rats did not experience an impairment of free water excretion in spite of developing ascites. The urinary excretion of antidiuretic hormone in these animals was similar to that of control rats during the entire study. In all urine samples obtained from cirrhotic rats, there was a highly significant direct linear correlation between the urinary excretion of antidiuretic hormone and the minimum urinary osmolality. Our results show the following: in rats with carbon tetrachloride-induced cirrhosis, sodium retention preceded the impairment of water excretion; and in these animals, the defect in water metabolism correlated chronologically and quantitatively with antidiuretic hormone hypersecretion. These findings are consistent with the concept that antidiuretic hormone is a major determinant of the impaired water metabolism in cirrhosis.

Animals↗
PubMed1987

Amoebae isolated from the atmosphere of Mexico City and environs.

A protozoological analysis was performed from June to August, 1982 to isolate small free-living amoebae from the atmosphere by using an air vacuum sampler and several filters. Monoxenic medium (nonnutritive agar plus Escherichia coli) and axenic medium (De Jonckheere, 1977) were used to culture the isolates. The species isolated included Naegleria sp. Alexeieff emend. Calkins, Acanthamoeba polyphaga Puschkarew, Vahlkampfia jugosa Page, Acanthamoeba astronyxis Ray and Hayes, Acanthamoeba castellanii Douglas, Acanthamoeba culbertsoni Singh y Das, Vahlkampfia ustiana Page, Saccamoeba stagnicola Page, Hyalodiscus sp. Hertwig and Lesser, Platyamoeba placida Page, Rugipes sp. Schaeffer, Vannella platypodia Gläser, Vahlkampfia russelli Singh, Vahlkampfia ovis Schmidt, and Leptomyxa flabellata Goodey. Among the species isolated Naegleria sp., A. polyphaga, A. culbertsoni, and A. castellanii include strains, known to be pathogenic in humans.

Amoeba↗
PubMed1987

Inhibition of testicular testosterone biosynthesis following experimental varicocele in rats.

In an attempt to determine whether defective testicular testosterone (T) biosynthesis may be associated with a varicocele, an experimental study was performed in adult rats whereby a unilateral left varicocele was surgically created. At 2, 4, 8, and 12 wk following the creation of the varicocele, intratesticular T as well as the activities of three (17 alpha-hydroxylase, 17,20-desmolase, and 17 beta-hydroxysteroid dehydrogenase) of the five enzymes in the delta 4 pathway of testicular T biosynthesis were measured. Intratesticular T (ng/g testis +/- SEM) in the left testis decreased significantly from 121 +/- 21 in the control group to 59 +/- 8 in the two-wk varicocele group (p less than 0.01), and remained significantly suppressed throughout the experimental period. The T concentrations in the right testis paralleled those in the left in both the control and varicocele animals. At 2 wk following the creation of the varicocele, the activity (nmol/min/testis +/- SEM) of the 17,20-desmolase enzyme decreased significantly, from 115 +/- 8 in the left testis of control rats to 87 +/- 6 in the left testis of the varicocele animals (p less than 0.025), and remained low throughout the 12 weeks of the study. The activity of the 17 alpha-hydroxylase enzyme was significantly decreased at the 8th and 12th weeks of the study, while the 17 beta-hydroxysteroid dehydrogenase activity did not show any significant change during the study period. The enzyme activities in the right testis paralleled those in the left testis.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗