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Biomedical subjects

F Vargas

Publications and source records attributed to F Vargas.

At least 181 records · Page 10Linked to original sources

Effects of selective and non-selective beta 1-blockade on renin secretion in the isolated rat kidney.

The participation of beta 1-adrenoceptor on renin secretion was studied in perfused rat kidney. Administration of propranolol, inhibited the renin release mediated by isoproterenol. Likewise, metoprolol and practolol, showed a similar potency to propranolol in inhibiting isoproterenol-induced renin secretion. These results suggest that the for isoproterenol-induced renin release in rats is a beta 1-type adrenoceptor.

Adrenergic beta-Antagonists↗

Colchicine in the treatment of cirrhosis of the liver.

There is preliminary evidence that colchicine, an inhibitor of collagen synthesis, may be beneficial in the treatment of cirrhosis of the liver. To evaluate the use of colchicine (1 mg per day, five days per week) in the treatment of hepatic cirrhosis, we performed a randomized, double-blind, placebo-controlled trial in which 100 patients were followed for up to 14 years. Forty-five patients had alcoholic cirrhosis, 41 had posthepatitic cirrhosis, and the remaining 14 had cirrhosis with various other causes. Histologic studies were available for 92 percent of patients. Seventy-three patients were in Child-Turcotte class A, 26 were in class B, and one was in class C. Fifty-four patients received colchicine, and 46 received placebo. The overall survival in the colchicine group was markedly better than in the placebo group (median survival, 11 and 3.5 years, respectively; P less than 0.001). The cumulative 5-year survival rates were 75 percent in the colchicine group and 34 percent in the placebo group; the corresponding 10-year survival rates were 56 percent and 20 percent. Among the 30 patients treated with colchicine who underwent repeated liver biopsies, histologic improvement was seen in 9; the liver appeared normal in 2, and 7 had minimal portal fibrosis. No histologic improvement was observed in the 14 members of the placebo group who had two or more biopsies. Few side effects were observed in either group.

Clinical Trials as Topic↗

Preparation and quantification of 3'-phosphoadenosine 5'-phospho[35S]sulfate with high specific activity.

The synthesis and quantitation of the sulfate donor 3'-phosphoadenosine 5'-phospho[35S]sulfate (PAP35S), prepared from inorganic [35S]sulfate and ATP, were studied. An enzymatic transfer method based upon the quantitative transfer of [35S]sulfate from PAP35S to 2-naphthol and 4-methylumbelliferone by the action of phenolsulfotransferase activity from rat brain cytosol was also developed. The 2-naphthyl[35S]sulfate or 35S-methylumbelliferone sulfate formed was isolated by polystyrene bead chromatography. This method allows the detection of between 0.1 pmol and 1 nmol/ml of PAP35S. PAP35S of high specific activity (75 Ci/mmol) was prepared by incubating ATP and carrier-free Na2 35SO4 with a 100,000g supernatant fraction from rat spleen. The product was purified by ion-exchange chromatography. The specific activity and purity of PAP35S were estimated by examining the ratios of Km values for PAP35S of the tyrosyl protein sulfotransferase present in microsomes from rat cerebral cortex. The advantage and applications of these methods for the detection of femtomole amounts, and the synthesis of large scale quantities of PAP35S with high specific activity are discussed.

Adenine Nucleotides↗

Studies on thyroid activity in deoxycorticosterone-salt and Goldblatt two-kidney, one-clip hypertensive rats.

In this paper we studied the role of thyroid gland function in two experimental hypertension models with different pathophysiological mechanisms: deoxycorticosterone-salt (DOCA-salt, volume dependent) and Goldblatt 2-kidney, 1-clip (2K1C, renin dependent). DOCA-salt hypertensive rats showed lower T3 and T4 serum levels by the third week of induced hypertension. Goldblatt 2K1C hypertensive rats, however, exhibited normal values for both hormones. Treatment with thyroxine accelerated the evolution of hypertension and did not affect the PRA of DOCA-salt rats. Radiothyroidectomy inhibited DOCA-salt and Goldblatt 2K1C hypertension, and prevented the suppression of PRA in DOCA-salt rats, without altering PRA or serum aldosterone in Goldblatt 2K1C rats. These results suggest that: a) a thyroid depressing factor is not activated in Goldblatt 2K1C rats; b) thyroidectomy interferes with the suppressor effect of mineralocorticoid on renin secretion; and c) normal thyroid activity is required for the hypertensive effect of the renin-angiotensin-aldosterone system in Goldblatt 2K1C rats.

Animals↗

The handling of NaCl load in rats during DOCA-salt and Goldblatt 2 kidney-1 clip hypertension development.

The handling of an intraperitoneal NaCl load (2% body weight, 0.9% NaCl) administered twice a week during DOCA-salt and Goldblatt 2K-1C hypertension development has been evaluated. An exaggerated natriuresis was observed in DS-hypertensive rats since blood pressure became higher with respect to normal (C), Doca (D) and uninephrectomized-salt (NS) rats that served as controls. However, this phenomenon was not observed in Goldblatt 2K-1C hypertensive rats (2K-1C) when compared to the response obtained in sham-operated (SO) rats. These results suggest that: 1) An increased blood pressure, per se, is not a determinating factor for exaggerated natriuresis. 2) Rise in blood pressure and exaggerated natriuresis may be related through a common mechanism in Doca-salt hypertension.

Animals↗

Apparent identity of cerebral tyrosylsulfotransferase activities using either a cholecystokinin derivative or an acidic amino acid polymer as substrate.

The tyrosylsulfotransferase activities of rat cerebral fractions transferring [35S]sulfate groups from 3'-phosphoadenosine 5'-[35S]phosphosulfate to either Boc-cholecystokinin-8 (in non-sulfated form) or the acidic amino acid polymer (Glu, Ala, Tyr)n (6:3:1) were compared. They appear similar regarding subcellular distribution (both being enriched in the microsomal fraction) and inhibition by an excess of the acidic amino acid polymer, NaCl or 2,6-dichloro 4-nitrophenol. These results obtained with artificial substrates suggest that identical (or closely similar) tyrosylsulfotransferases are responsible for sulfation of tyrosine residues of several secretory proteins from various tissues.

Amino Acids↗

Lactitol, a second-generation disaccharide for treatment of chronic portal-systemic encephalopathy. A double-blind, crossover, randomized clinical trial.

A double-blind crossover trial was performed to test the therapeutic usefulness and safety of lactitol, a beta-galactoside sorbitol, against lactose in 18 patients with chronic portal-systemic encephalopathy (PSE). The study included four periods: two for washout and two for lactitol and lactose administration. During washout periods, which lasted two weeks each, patients were stabilized with neomycin plus milk of magnesia. Lactitol and lactose were administered during four weeks each. Ten patients were randomly assigned to receive lactose (group A) and eight patients to receive lactitol (group B) first. PSE parameters, ie, mental state, number connection test performance, asterixis and blood ammonia levels were assessed fortnightly. Electroencephalographic tracings and stool pHs were evaluated at the end of each study period. After the first administration of lactose and lactitol, no statistically significant differences in PSE parameters were found. At the same stage, a significant stool acidification (P less than 0.05) was detected. It is concluded that lactitol seems to be safe and efficacious in treating patients with chronic PSE.

Clinical Trials as Topic↗

Formation and utilization of the active sulfate donor [35S]3'-phosphoadenosine 5'-phosphosulfate in brain slices: effects of depolarizing agents.

The accumulation and utilization of [35S]3'-phosphoadenosine 5'-phosphosulfate (PAPS) were studied in slices from rat cerebral cortex incubated in the presence of inorganic [35S]sulfate. [35S]PAPS levels were directly evaluated after either isolation by ion-exchange chromatography or quantitative enzymatic transfer of its active [35S]sulfate group to an acceptor phenol under the action of added phenolsulfotransferase activity. [35S]PAPS formation was also indirectly followed by incubating slices in the presence of beta-naphthol and measuring the levels of [35S]beta-naphthyl sulfate ([35S]beta-NS). Whereas [35S]PAPS levels rapidly reached a plateau, [35S]beta-NS formation proceeded linearly with time for at least 1 h, an observation indicating that the nucleotide was continuously synthesized and utilized for endogenous sulfation reactions. [35S]PAPS formation in slices was completely and rather potently blocked by 2,6-dichloro-4-nitrophenol (IC50 = 10 microM), an inhibitor of the PAPS-synthesizing enzyme system in a cytosolic preparation. [35S]PAPS accumulation and [35S]beta-NS formation were strongly reduced by depolarizing agents such as potassium or veratridine. At millimolar concentrations, various excitatory amino acids (glutamate, aspartate, cysteate, quisqualate, and homocysteate) also elicited similar effects, whereas kainate and N-methyl-D-aspartate were inactive. This suggests that PAPS synthesis is turned off when cerebral cells are strongly depolarized.

Adenine Nucleotides↗

Properties and localization of the sulfate-activating system in rat brain.

The formation of the sulfate donor [35S]3'-phosphoadenosine 5'-phosphosulfate (PAPS) from inorganic [35S]sulfate was studied using a novel assay. The assay was based on the quantitative transfer of radioactivity from [35S]PAPS to beta-naphthol under the action of phenolsulfotransferase activity from rat brain cytosol, with the [35S]beta-naphthyl sulfate formed being isolated by polystyrene bead chromatography. This simple assay was validated by comparison of results with those derived from direct assay of [35S]PAPS isolated by either TLC or ion exchange chromatography. [35S]PAPS formation by a high-speed supernatant of rat cerebral cortex occurred with an optimal pH of approximately 7.6, varied linearly with time and protein concentration, and depended on the presence of Mg2+-ATP. The latter could not be replaced by other nucleotides such as GTP, UTP, or CTP, which at 1-5 mM concentrations inhibited the reaction. Mg2+ could not be replaced by Mn2+, which at micromolar concentrations inhibited the reaction. The apparent Km values of Mg2+-ATP (at 0.1 mM [35S]sulfate) and inorganic sulfate (at 5 mM Mg2+-ATP) were 2.7 and 0.2 mM, respectively. These kinetics parameters corresponded to those reported for purified ATP sulfurylase (EC 2.7.7.4), the enzyme responsible for the first step of PAPS synthesis in liver. The product of its reaction, [35S]adenosine 5'-phosphosulfate (APS), could not be detected after incubations, an observation implying that the action of APS kinase was not rate limiting in cerebral extracts tested under the selected experimental conditions. [35S]PAPS formation was detectable in cytosolic fractions from various brain regions, which displayed only limited differences in synthesizing activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenine Nucleotides↗

[Water intake induced by isoprenaline in 2 models of experimental hypertension in rats].

The drinking response to systemic injection of isoprenaline has been used to study the decreased beta-adrenergic reactivity in hypothyroid rats. Using the same test, the beta-adrenergic responsiveness has been investigated in two models of experimental hypertension (DOCA-salt and Goldblatt two kidney one clip rats). Three weeks after induction of hypertension, control and hypertensive rats were injected subcutaneously isoprenaline (0.1 mg/kg) and the accumulative water intake at 1st, 2nd and 3rd hours was recorded. Isoprenaline induced a smaller drinking response in DOCA-salt hypertensive (DS) and DOCA-normotensive (D) rats than in normotensive (age control, normal uninefrectomized-salt and sham operated) or hypertensive Goldblatt two kidney one clip rats. Isoprenaline induced a 50% mortality in the mineral-corticoid treated D and DS rats. The present study suggests that the reduced beta-adrenergic response (water intake) and the rate of mortality observed in DOCA treated rats may be due to the absence of renin release after isoprenaline injection, as previously reported by us.

Animals↗

Inhibitors and dipeptide substrates for a microsomal tyrosylsulfotransferase from rat brain.

The sulfotransferase associated with a microsomal fraction from rat brain was previously shown to transfer sulfate groups from 3'-phosphoadenosine 5'-phosphosulfate (PAPS) to peptides derived from the cholecystokinin (CCK) molecule. Three tyrosine-containing dipeptide derivatives, i.e., Cbz-Glu-Tyr, Cbz-Gly-Tyr and Ac-Phe-Tyr are shown here to accept the [35S] sulfate group from [35S] PAPS under the action of this sulfotransferase. The sulfotransferase activity evaluated with either any of these dipeptide derivatives or CCK-8 as acceptors is similarly inhibited by a series of compounds, i.e., lipophilic polycyclic compounds like fluphenazine, tyrosine derivatives like Boc-O-benzyl-tyrosine and phenolsulfotransferase inhibitors like 4,4-di-isothiocyano 2',2'-disulfonic acid stilbene.

Animals↗

Peripheral veno-lymphatic communications.

Though there have been a number of articles on lympho-venous anastomoses, there have been no reports of the opposite situation, namely veno-lymphatic communication. A case of veno-lymphatic communication is presented, and possible explanations for this finding are described.

Aged↗

Characterization of a tyrosine sulfotransferase in rat brain using cholecystokinin derivatives as acceptors.

An apparently novel tyrosyl sulfotransferase activity was detected in a crude microsomal fraction from rat cerebral cortex by using 3'-phosphoadenosine 5'-phospho[35S]sulfate [( 35S]PAPS) as the sulfate donor and various cholecystokinin (CCK) fragments or derivatives as acceptors. Among the latter, the shortest substrate was tert-butoxycarbonylaspartyltyrosine (Boc-Asp-Tyr), but the reaction was optimized by increasing the length of the peptide sequence on the C-terminal side up to tert-butoxycarbonylcholecystokinin octapeptide (Boc-CCK-8) as well as by the presence of acidic amino acid residues at the N-terminal side. Peptides with an N-terminal Tyr residue (e.g., CCK-7 or enkephalins) were not sulfated. With Boc-CCK-8 the optimum pH was 5.8, and apparent KM values were 0.14 +/- 0.02 mM for the peptide (0.5 microM PAPS) and 0.12 +/- 0.01 microM for PAPS (0.25 mM Boc-CCK-8). In the presence of 0.2 mM MnCl2 the Vmax of the reaction was enhanced without change of apparent affinities of the two substrates. The possible role of this sulfotransferase activity in posttranslational modification of CCK and other secretory proteins is suggested.

Animals↗

Beneficial effect of vegetable protein diet supplemented with psyllium plantago in patients with hepatic encephalopathy and diabetes mellitus.

A controlled crossover study was performed in 8 diabetic patients with chronic portal-systemic encephalopathy. After a basal period the patients were treated during periods A and B. During period A, a meat protein diet (0.8 g/kg body wt, approximately 1800 kcal/day) was consumed and neomycin plus laxatives were given. During period B patients received vegetable protein (0.8 g/kg body wt, 1800 kcal/day). This diet was supplemented with psyllium fiber to reach 35 g of fiber per day. Four patients were randomly assigned to receive the treatments in the order A-B and the other 4 patients in the order B-A. At the end of the first experimental period, fasting glucose levels were 204 +/- 86 mg% in the meat protein diet group and 127 +/- 8 mg% in the vegetable protein diet group (p less than 0.014). The patients were receiving 2.5 +/- 0.2 g/day and 2.1 +/- 0.5 g/day of tolbutamide at the end of the meat protein diet and vegetable protein diet, respectively. In all cases, fasting glucose levels decreased at the end of the vegetable diet period regardless of the previous treatment. An improvement of greater than or equal to 25 mg% of fasting glucose levels was observed in 7 of the 8 patients after the vegetable protein diet and in no case after the meat protein diet (p less than 0.0078). The parameters of encephalopathy were comparable at the end of both the meat protein diet and the vegetable protein diet. A significant increase in the number of bowel movements was noticed after the vegetable diet plus fiber (p less than 0.01). We propose the use of vegetable diet plus fiber to facilitate the treatment of patients with both diabetes and hepatic encephalopathy.

Adult↗

Sulfation and desulfation of cerebral cholecystokinin.

An apparently novel sulfotransferase present in microsomal and vesicular fractions from rat brain is able to transfer [35S]sulfate groups from [35S]PAPS to CCK derivatives. Its optimum pH (approximately 6), its substrate specificity, and its subcellular localization are all consistent with its function as post-translational processing enzyme. However, its presence in tissues devoid of CCK argues against this idea, or could simply mean that it is involved in the processing of other peptides besides CCK. No evidence could be obtained for extensive desulfation of endogenous CCK-8 released by depolarization of brain slices.

Animals↗

Effects of changes in circulating volume and in arterial pressure on plasma renin activity in the intact rat.

The effects of changes in arterial pressure and in circulating volume on Plasma Renin Activity (PRA) in the intact rat were compared by two experimental procedures. Gradual volume depletion was induced by intraperitoneal injection of a hyperoncotic polyethyleneglycol solution (PEG) in absence of acute changes in Systolic Arterial Pressure (SAP). SAP was measured in the conscious state by the tail cuff technique. Plasma Protein Concentration (PPC) and Hematocrit (Hct) increases after PEG injection were compared as the index for measuring the Plasma Volume Reduction (PVR). PRA showed a significant (p less than 0.001) linear relationship with PPC, suggesting a direct dependence of renin secretion on volume depletion. Acute changes in the circulating volume were induced by controlled hemorrhages of 5.0, 10.0, 15.0 and 20.0 ml of blood/kg body weight. The increase in PRA showed a significant relationship with the changes in circulating volume, but it did not show any dependence on the changes in Mean Arterial Pressure (MAP). Our results suggest that, in the intact and conscious rat, renin secretion responds to the information from the cardiopulmonary volume receptors rather than to that from the high pressure receptors.

Animals↗