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Biomedical subjects

F Rivera

Publications and source records attributed to F Rivera.

At least 163 records · Page 9Linked to original sources
PubMed1990

[Lymphocyte beta 2-adrenergic receptors in pheochromocytoma].

To assess the effect of chronic exposure to high circulating catecholamine concentrations on the beta 2-adrenergic receptors, the density and affinity of lymphocyte beta 2-adrenergic receptors were measured in 5 patients with pheochromocytoma (2 males and 3 females, with a mean age of 39 +/- 12 years). In 4 patients the studies were repeated 15 days after tumor removal. Before surgery, all patients had high plasma catecholamine concentration. The density of beta 2-adrenergic receptors was reduced, although their affinity was within the reference range. There was an inverse correlation between plasma epinephrine concentration and beta 2-adrenergic receptor density (r = -0.959, p = 0.01). After surgical resection, plasma catecholamine concentrations and receptor density became normal. The dissociation constant decreased in the four patients. In conclusion, in the presence of chronically high levels of circulating catecholamines the density of lymphocyte beta 2-adrenergic receptors is reduced. However, it becomes normal when plasma catecholamine concentration returns to the reference values, the dynamic character of this regulation being thus shown. The measurement of these receptors in the lymphocyte could be useful for the diagnosis and follow up of patients with pheochromocytoma.

Adrenal Gland Neoplasms↗
PubMed1990

Effects of intravenous amino acid infusion and dietary proteins on kidney function in cirrhosis.

Acute intravenous amino acid infusion or a high-protein diet increases renal plasma flow and the glomerular filtration rate in healthy subjects. Conversely, a low-protein diet reduces renal plasma flow and glomerular filtration rate. The aim of this study was to investigate the effect of intravenous amino acid infusion and dietary proteins on kidney function in cirrhosis. Protocol 1: renal plasma flow and glomerular filtration rate were measured before and during intravenous administration of a 10% amino acid solution (0.043 ml/kg/min) to eight compensated cirrhotic patients (group 1), nine nonazotemic cirrhotic patients with ascites (group 2) and seven cirrhotic patients with ascites and functional renal failure (group 3). Amino acid administration induced a significant increase in renal plasma flow and glomerular filtration rate in all groups studied. Renal plasma flow and glomerular filtration rate increased by 16% and 14%, respectively, in group 1; 31% and 22% in group 2 and 25% and 21% in group 3. Protocol 2: Renal plasma flow and glomerular filtration rate were measured in nine cirrhotic patients with ascites after 11 days on a low-protein diet (0.5 gm/kg body weight/day) and also after the patients followed for 11 days a moderately high-protein diet (1.5 gm/kg body weight/day). The moderately high-protein diet was associated with a significant increase in renal plasma flow (12%) and glomerular filtration rate (13%) compared with values obtained while the patients followed the low-protein diet. Plasma glucagon levels increased markedly during the intravenous administration of amino acid and the intake of the moderately high-protein diet.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acids↗
PubMed1990

Hemodynamic effects of glucagon in portal hypertension.

It has been suggested that glucagon contributes to the pathogenesis of portal hypertension by increasing portal blood flow. This study examined this issue by assessing the hemodynamic effects of a pharmacological dose of glucagon (1 mg, intravenously) in patients with cirrhosis and portal hypertension (n = 10) and in subjects without significant liver disease (controls = n = 5). Patients with cirrhosis had much higher glucagon levels than control subjects (875 +/- 167 vs. 186 +/- 25 pg/ml, p less than 0.01) and showed blunted hemodynamic responses after glucagon administration. This occurred despite greater circulating glucagon levels, probably because of a significant prolongation of the plasma half-life of exogenously administered glucagon (4.9 +/- 0.4 vs. 2.7 +/- 0.1 min, p less than 0.1). Control subjects had marked increases in heart rate (+ 19% +/- 4%, p less than 0.01), cardiac index (+ 16% +/- 4%, p = 0.01) and arterial pressure (+ 10% +/- 3%, p less than 0.05), but corresponding changes in patients with cirrhosis (+ 7% +/- 1%, + 6% +/- 1%, and + 6% +/- 2%, respectively) were significantly less pronounced (p = 0.05), and there was a negative correlation between basal glucagon levels and the response of heart rate to glucagon injection (r = -0.804, p less than 0.001). Resistance to the systemic effects of glucagon in cirrhosis may thus be caused by a down-regulation of vascular glucagon receptors. In addition, glucagon administration caused a significant increase in portal pressure (from 18.1 +/- 1.1 to 19.0 +/- 1.2 mm Hg, p less than 0.01), as well as in azygos blood flow (from 0.54 +/- 0.03 to 0.64 +/- 0.04 L/min, + 19% +/- 4%, p less than 0.02), reflecting increased portocollateral blood flow. These findings are consistent with the hypothesis that glucagon is one of the factors contributing to the splanchnic vasodilatation and increased portal pressure of cirrhosis.

Azygos Vein↗
PubMed1990

Natriuretic hormone activity in the urine of cirrhotic patients.

The ability of urine extracts to inhibit sodium and potassium-activated ATPase, cross-react with antidigoxin antibodies and induce natriuresis in rats was investigated in 10 healthy subjects, 10 cirrhotic patients without ascites (compensated cirrhotics), 27 nonazotemic cirrhotic patients with ascites and 10 cirrhotic patients with ascites and functional renal failure to assess whether reduced activity of natriuretic hormone contributes to sodium retention in cirrhosis. No significant differences were seen between healthy subjects and compensated cirrhotic patients in any of these parameters (sodium and potassium-activated ATPase inhibition = 178.5 +/- 19.8 vs. 247.4 +/- 48.7 nmol equivalent of ouabain/day; digoxinlike activity = 43.9 +/- 6.1 vs. 48.0 +/- 5.6 ng equivalent of digoxin/day; natriuretic activity = 0.36 +/- 0.15 vs. 0.63 +/- 0.27 mumol/min). Cirrhotic patients with ascites with and without functional renal failure showed significantly higher values of sodium and potassium-activated ATPase inhibition (708.1 +/- 94.0 and 529.2 +/- 53.9 nmol equivalent of ouabain/day, respectively), digoxinlike activity (136.9 +/- 7.2 and 116.3 +/- 7.9 ng equivalent of digoxin/day) and natriuretic activity (1.78 +/- 0.48 and 1.93 +/- 0.37 mumol/min) than healthy subjects and compensated cirrhotic patients. We saw no significant differences between these two groups of cirrhotic patients with ascites with respect to these parameters. In the cirrhotic patients studied, sodium and potassium-activated ATPase inhibition and antidigoxin antibodies directly correlated with the degree of impairment of hepatic and renal function, plasma renin activity and plasma levels of aldosterone and norepinephrine.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Effects of thromboxane synthesis inhibitor triflusal on renal hemodynamics in microalbuminuric diabetic patients.

Triflusal (2-acetoxy-4-trifluormethylbenzoic acid) is a platelet-antiaggregant drug that selectively inhibits thromboxane synthesis with little effect on prostacyclin production. In this study, we evaluated the effect of 5-day administration of 900 mg/day triflusal on glomerular filtration rate (GFR), renal plasma flow (RPF), urinary albumin excretion (UAE), thromboxane B2 (TXB2), 6-ketoprostaglandin F1 alpha (PGF1 alpha), and PGE2 in nine normotensive insulin-dependent diabetic patients with UAE between 30 and 103 micrograms/min. Plasma TXB2 and plasma renin activity (PRA) were also determined. After administration of triflusal, we observed a reduction in microalbuminuria (59 +/- 25 vs. 33 +/- 22 micrograms/min, P less than 0.01), an increase in RPF (648 +/- 119 vs. 722 +/- 134 ml.min-1 x 1.73 m-2, P less than 0.01), and a reduction in filtration fraction (0.24 +/- 0.04 vs. 0.20 +/- 0.03, P less than 0.01). Triflusal produced a significant reduction in both plasma TXB2 (130 +/- 39 vs. 52 +/- 32 pg/ml, P less than 0.02) and urine TXB2 (523 +/- 249 vs. 312 +/- 11 pg/min, P less than 0.02), without changes in PRA and UAE of 6-keto-PGF1 alpha and PGE2. Metabolic control and arterial blood pressure did not change during the study. These results suggest that platelet-antiaggregant therapy can reduce microalbuminuria in diabetic patients. This effect could be mediated by a reduction in the transglomerular hydraulic pressure through a vasodilation of efferent arterioles secondary to renal thromboxane synthesis inhibition.

6-Ketoprostaglandin F1 alpha↗
PubMed1990

Urinary excretion of endogenous digitalis-like natriuretic substances in healthy subjects. Effect of sodium load.

In the current study digoxin-like immunoreactivity (DLIA), Na-K-ATPase inhibition and natriuretic activity of urinary extracts from 10 healthy volunteers following a low and a high-sodium intake, respectively, were measured. Detectable urinary DLIA (46.1 +/- 5.6 ng eq digoxin/day), Na-K-ATPase inhibition (182.9 +/- 22.7 nmol eq oub/day) and natriuretic activity (UNaV: 0.38 +/- 0.11 microEq/min) were observed during the low-sodium diet period in all subjects. High-sodium diet was associated with a significant increase in DLIA (87.9 +/- 9.2 ng eq digoxin/day, p less than 0.001) which parallelled changes in Na-K-ATPase inhibition (359.8 +/- 51.9 nmol eq oub/day, p less than 0.005) and natriuretic activity (UNaV: 1.33 +/- 0.3 microEq/min, p less than 0.025). These results support the contention that DLIA is related to NH.

Adult↗
PubMed1990

[Prolactin receptors and breast cancer].

A study has been carried out on 116 mammary neoplasias in which the prolactin receptors together with other clinical and hormonal parameters have been determined. A 46.3% frequency of PRLR+ has been obtained as well as a statistically significant correlation between these and blood estradiol (p less than 0.05). PRLR- have greater survival and PRLR may act as a growth factor.

Breast Neoplasms↗
PubMed1990

Factors influencing the development of metabolic bone disease in primary biliary cirrhosis.

The prevalence, type, and factors that may influence the development of bone disease in primary biliary cirrhosis, have been investigated in 20 consecutive patients, who, in addition to liver function tests and mineral and vitamin D metabolism studies, were submitted to a transiliac bone biopsy after tetracycline double-labeling for quantitative histomorphometric examination. Intestinal calcium absorption was also assessed in 16 patients. Seven patients (35%) had reduced bone volume and were considered osteoporotic. Three also had bone mineralization impairment, but did not have criteria for osteomalacia. Bone formation was depressed in 15 patients, and bone resorption was low or normal in 19 cases. Eroded surfaces were reduced in all osteoporotic patients. Duration of primary biliary cirrhosis was significantly longer in patients with osteoporosis (6.3 +/- 0.6 yr) than in those without osteoporosis (2.6 +/- 0.6, p = 0.004). Moreover, osteoporosis was more prevalent in postmenopausal women, and in those who had intestinal calcium malabsorption, which was present in 80% of osteoporotic patients but in only 18% of nonosteoporotic patients (p = 0.03). Osteoporosis and mineralization bone impairment were unrelated to the severity of cholestasis. 25-Hydroxyvitamin D was significantly lower in those patients with intestinal calcium malabsorption. The results of this study indicate that osteodystrophy in primary biliary cirrhosis is characterized mainly by "low-turnover" osteoporosis, which is related to the duration of the liver disease, postmenopausal condition, and calcium malabsorption.

Adult↗
PubMed1989

Effects of atrial natriuretic peptide on urinary kallikrein excretion and renal function in rats.

We investigated whether the renal kallikrein-kinin system is involved in the renal effects of atrial natriuretic peptide (ANP) by measuring the glomerular filtration rate (GFR), urine volume (UV) and urinary excretion of sodium (UNaV) and kallikrein (UkkV) in 4 groups of 10 anesthetized rats before and during (two 10 min periods) the i.v. infusion of Ringer solution (control group) or different doses of ANP (0.25, 0.5 and 1 microgram, respectively). The administration of ANP was associated with a marked and significant increase in UV, UNaV, UkkV and GFR. The diuretic and natriuretic responses to ANP were dose-related, while the changes in GFR and UkkV were short-lived and not related to the dose of ANP. There was no relationship between UV or UNaV and UkkV after ANP administration. In contrast, UkkV correlated closely with GFR (r = 0.675, P less than 0.001). These data do not support the hypothesis that the kallikrein-kinin system contributes to the diuretic and natriuretic effects of ANP, but it might be involved in the renal hemodynamic action of this peptide.

Animals↗
PubMed1989

[Diagnosis by DNA analysis in familial isolated growth hormone deficiency type I-A].

We show the autoradiograms of DNA from one child affected of familial isolated growth hormone deficiency type I-A. Restriction endonuclease analysis of DNA isolated from leukocytes was done using 32P-labeled human GH cDNA clone as a probe. DNA analysis using the restriction endonuclease Bam HI revealed that the 3.8 kb restriction fragment, which contain the normal hGH-N gene, was absent. Since these deletions preclude production of any GH-N protein, affected individuals tend to be immunologically intolerant to exogenous GH. The child was homozygote and after treatment with exogenous GH developed a high titre of antibodies to GH and growth arrest. This is the first case of this genetic disorder studied in Spain.

Autoradiography↗
PubMed1989

Mucinous metaplasia to neoplastic lesions in endometrial samples with cytohistologic correlation.

Seven cases of endometrial mucinous metaplasia and five of well-differentiated mucinous adenocarcinoma of the endometrium were studied. Cytologic specimens were obtained by Isaacs endometrial sampler, avoiding endocervical contamination. The histologic diagnosis between the intermediate type of mucinous metaplasia and the well-differentiated mucinous adenocarcinoma posed no problems. DNA analyses of the histologic samples showed a euploid pattern in benign and intermediate types of metaplasia, while well-differentiated mucinous adenocarcinoma showed a hyperdiploid pattern. The cytologic diagnosis of benign mucinous metaplasia should be suggested in the presence of abundant mucinous cells in endometrial samples in the absence of nuclear abnormalities.

Adenocarcinoma, Mucinous↗
PubMed1989

Blockade of the hydroosmotic effect of vasopressin normalizes water excretion in cirrhotic rats.

Water retention in cirrhosis has classically been considered to be due to a low distal fluid delivery secondary to increased proximal sodium reabsorption. However, recent studies showing high plasma vasopressin levels in patients and rats with cirrhosis, ascites, and dilutional hyponatremia suggest that a nonosmotic vasopressin hypersecretion could be an alternative mechanism. To investigate the role of vasopressin in water retention in cirrhosis, the renal ability to excrete a water load (50 ml/kg body wt), as estimated by the minimum urinary osmolality and the percentage of the water load excreted during 3 h, was assessed in 10 control rats and in 20 cirrhotic rats with ascites and impaired water excretion and high urinary excretion of vasopressin. Twenty-four hours later, the same procedure was repeated in cirrhotic rats 20 min after the subcutaneous injection (30 micrograms/kg body wt) of d(CH2)5Tyr(Et) VAVP, an antagonist of the hydroosmotic effects of vasopressin (10 rats), or the vehicle (10 rats). Treatment with the vasopressin antagonist normalized water excretion in 9 of the 10 rats. No significant changes in renal water metabolism were observed in the group of rats given the vehicle. These results indicate that vasopressin hypersecretion is the predominant mechanism of the impairment in water excretion in rats with experimental cirrhosis and ascites.

Animals↗
PubMed1989

Role of altered systemic hemodynamics in the blunted renal response to atrial natriuretic peptide in rats with cirrhosis and ascites.

The natriuretic effect of pharmacological doses of atrial natriuretic peptide (ANP) is markedly reduced in cirrhosis with ascites. The current study, which includes two protocols, was carried out to investigate whether this phenomenon is related to the altered systemic hemodynamics present in cirrhosis. In protocol A, the administration of ANP (2.5 micrograms.kg-1 as a bolus followed by a constant infusion of 0.1 microgram.kg-1.min-1) to 10 rats with carbon tetrachloride-induced cirrhosis and ascites produced a significantly lower increase in diuresis (13.4 +/- 1.3 microliters/min) and natriuresis (2.3 +/- 0.3 mu Equiv/min) than in 10 control rats (56.3 +/- 1.4 microliters/min and 8.7 +/- 0.5 mu Equiv/min, respectively), indicating a renal resistance to the effect of ANP in this experimental model of cirrhosis. The reduction of arterial pressure induced by ANP was similar in both groups. However, since baseline mean arterial pressure was significantly lower in cirrhotic rats, the degree of hypotension during ANP infusion was also greater in this group of animals (82 +/- 3 vs. 109 +/- 2 mmHg). The aim of protocol B was to assess whether normalization of arterial pressure in cirrhotic rats increases the renal response to ANP. This protocol includes two groups of 10 rats with cirrhosis and ascites infused with a glucose solution containing norepinephrine (CT-NE rats) or angiotensin II (CT-AII rats) at doses to normalize arterial pressure and an additional control group of 10 cirrhotic rats with ascites receiving only glucose solution (CT rats). Angiotensin II, but not norepinephrine or glucose solution administration, was associated with a significant increase in urine volume and sodium excretion. During ANP infusion, CT rats showed a blunted diuretic and natriuretic response. In contrast, the ANP-induced increase in urine volume and sodium excretion observed in CT-NE (53.6 +/- 10.4 microliters/min and 9.3 +/- 2.2 mu Equiv/min) and CT-AII rats (98.3 +/- 11.6 microliters/min and 15.5 +/- 2.9 mu Equiv/m), was similar or even greater than that showed by the healthy rats of protocol A. The degree of hypotension during ANP administration was also similar (CT-NE, 104 +/- 2; CT-AII, 108 +/- 5 mmHg). These results suggest that the blunted response to pharmacological doses of ANP in cirrhosis with ascites is related to altered systemic hemodynamics of cirrhosis, which further deteriorates during the infusion of the peptide.

Angiotensin II↗
PubMed1989

Pathogenic amoebae in natural thermal waters of three resorts of Hidalgo, Mexico.

In a search for free-living amoebae, seven water samples from three thermal water bathing resorts in Tecozautla, Hidalgo, were analyzed during December 1984. The samples were concentrated by filtration and centrifugation, and inoculated later on monoxenic and axenic media. The identification of the isolates was performed by morphology and isoelectric focusing of isoenzymes and total proteins. Thirty-three strains of free-living amoebae belonging to the genera Naegleria, Acanthamoeba, and Willaertia were isolated. Twenty of these strains belonged to the Naegleria genus, 16 of them were classified as Naegleria spp., and 2 were classified as Naegleria lovaniensis. Noteworthy was the finding of two pathogenic strains of the species Naegleria australiensis. N. australiensis and N. lovaniensis may be considered good indicator organisms, since they live in the same environmental conditions as N. fowleri, the agent of primary amoebic encephalitis (PAM). On the other hand, amoebae other than Naegleria were isolated and identified as Acathamoeba castellanii (two strains), and Acanthamoeba lugdunensis (one strain), which proved to be pathogenic when tested in mice. Nine more pathogenic strains of the genus Acanthamoeba spp. were isolated together with one strain of Willaertia magna, a thermophilic nonpathogenic amoeba. The chlorination and periodical surveillance of water resorts like the one studied is recommended, in order to prevent the appearance of more cases of PAM or other human diseases associated with pathogenic Acanthamoeba spp.

Amoeba↗
PubMed1989

Lymphocyte beta 2-adrenergic receptors in essential hypertension: studies in basal conditions and after dynamic exercise.

In order to study the density and response to dynamic exercise of lymphocyte beta 2-adrenoceptors in essential hypertension, 30 moderate essential hypertensives (12 men: 18 women, mean age 50.3 +/- 9.2 years) and 14 normotensive controls (8 men: 7 women, mean age 47 +/- 15 years) were studied. Beta 2-adrenoceptors density in basal conditions was higher in essential hypertensives than in controls (1950 +/- 625 vs 1278 +/- 356 binding sites per cell [bs/c], respectively, p less than 0.01) (mean +/- SD). After dynamic exercise beta 2-adrenoceptors density increased both in controls (to 1491 +/- 342 bs/c, p less than 0.01) and in hypertensives (to 2632 +/- 715 bs/c, p less than 0.001). However, the percentage of increase after the exercise was significantly higher in hypertensives than in controls (40.5 +/- 6.1 vs 20.2 +/- 6.5%, p less than 0.05). In summary, the higher density in basal conditions, as well as the exaggerated increase in the number of beta 2-adrenoceptors after dynamic exercise observed in essential hypertension, suggest an impaired regulation of these receptors in essential hypertension.

Adult↗
PubMed1988

Prevention of post-transfusion non-A, non-B hepatitis by non-specific immunoglobulin in heart surgery patients.

To evaluate the effectiveness of immune serum globulin (ISG) in preventing non-A, non-B hepatitis, 291 heart surgery patients who received blood from voluntary donors were randomly assigned to receive either ISG or no additional protection. ISG was given intramuscularly before and 1 week after transfusion. 98 controls and 100 in the ISG group completed the study. Post-transfusion non-A, non-B hepatitis developed in 11 (11.2%) controls but in only 3 (3.0%) of the ISG group (p = 0.0203). 8 (72.7%) of control group with hepatitis had symptoms, and in 5 (45.4%) the disease became chronic. The disease was self-limiting in all 3 ISG patients affected, and only 1 of them had symptoms. Among those with non-A, non-B hepatitis aminotransferase levels were higher in the controls than in the ISG patients. Incubation periods longer than 8 weeks correlated with a tendency for the disease to become chronic. ISG recipients had shorter as well as more homogeneous incubation periods. ISG could be a safe, low-cost means for preventing post-transfusion non-A, non-B hepatitis which does not call for the discarding of donated blood.

Adolescent↗