Search PubMed⌕ Search

Biomedical subjects

J Ruiz

Publications and source records attributed to J Ruiz.

At least 343 records · Page 19Linked to original sources
PubMed1988

The effect of methimazole on bile flow and bile acid secretion in the rat.

The effect of methimazole on bile flow and composition was studied in male Wistar rats. Administration of methimazole as a single bolus (175-700 mumol/kg body wt) or infusion over three hours (1 mumol/100 g body wt/min) significantly increased bile flow and the biliary output of bile acids and inorganic electrolytes. Choleresis was a transient phenomenon and at the end of the experiments bile flow had returned to control values, although bile acid output was significantly lowered. When the amounts of bile acids arriving into the liver were increased by taurocholate infusion or decreased by cholestyramine pretreatment, a transitory enhancement was also found in bile flow and bile acid output, but the amounts of bile acid secreted and the choleretic effect induced were different according to the bile acid secretory rate found before methimazole administration. The bile acid content in the liver of taurocholate-infused rats was reduced during methimazole-induced choleresis. Our data indicate that the higher bile flow in methimazole-treated rats is related to an enhanced biliary secretion of bile acids probably due to a transitory stimulating effect on the transport into bile of the intrahepatocytary bile acid pool. The choleretic effect is not apparently shared by other thiocarbamide compounds.

Animals↗
PubMed1988

Surfactant-induced release of liposomal contents. A survey of methods and results.

A systematic approach to the phenomenon of surfactant-dependent release of liposomal contents has been attempted. A variety of methods have been comparatively studied. The influence of the size of the entrapped molecule, nature of the surfactant, composition of bilayers and sonication of liposomes have been considered separately. In order to compare different results, a parameter has been defined, R50, as the phospholipid/surfactant mole ratio producing 50% release of the entrapped solute. This parameter appears to be, to a large extent, independent of time and liposome concentration. Surfactant-induced release of liposomal contents does not occur as a result of breakdown of phospholipid bilayers, but is rather a different phenomenon, occurring at detergent concentrations substantially lower (2-5 times) than solubilization. The required amount of surfactant appears to increase with the size of the entrapped solute. R50 depends clearly on the nature of the soluble amphiphile, but there is no obvious relationship with its critical micellar concentration. Liberation of vesicle content also depends on bilayer composition: phospholipids have various effects on the stability of the membrane, while the hydrophobic peptide, gramicidin A, appears to have little influence. Cholesterol is interesting, since at equimolar proportions with phosphatidylcholine, it decreases the stability of bilayer towards Triton X-100, while increasing it in the presence of cholate. Sonication also exerts an influence on the surfactant-dependent release of vesicle contents; it appears to decrease the bilayer stability, so that lower detergent concentrations are required to liberate the entrapped solutes. Finally, it should be noted that, although the decrease in self-quenching of 6-carboxyfluorescein is a convenient method for the study of solute liberation, glucose release, as detected by enzymatic methods, may be more reliable for accurate measurements.

Fluoresceins↗
PubMed1988

Rapid sample preparation for determination of iron in tissue by closed-vessel digestion and microwave energy.

We developed a rapid acid-digestion method for preparing tissue samples for iron determination. Specimens were digested in nitric acid and hydrogen peroxide under high temperature and pressure in closed Teflon vessels, with microwave energy. Analysis for iron in 25- to 250-mg portions of digested bovine liver powder (National Bureau of Standards Certified Reference Material no. 1577a) showed excellent linearity ([predicted] = 1.007[actual] - 0.166 micrograms per sample) and analytical recovery (98%). Precision (CV) was 5.4% when iron content was 10 micrograms per sample. Assaying split samples of mouse tissues, we found a close correlation between iron concentrations obtained with closed vs open vessels ([closed] = 0.878[open] + 68 micrograms/g, r = 0.994, range 400-4600 micrograms/g dry weight). In contrast to time-consuming conventional procedures for tissue dissolution, closed-vessel digestion with microwave energy dramatically shortens time for tissue preparation, minimizes use of caustic acid, reduces risk of sample loss or contamination, and yields accurate and reproducible results.

Animals↗
PubMed1987

Description of a case of rhinosporidiosis in Spain.

Rhinosporidiosis is reviewed, and the first autochthonous case in Spain is presented (site: in the nasal cavity of a 19-year-old male from a rural background). Diagnosis was established morphologically after eliminating the possibilities of Cryptococcus neoformans, Coccidioides immitis, and Chrysosporium crescens. Clinico-pathological features are described. Preparations were stained with hematoxylin-eosin, PAS, and methenamine silver, and studied for fluorescence. Certain aspects of the epidemiology and diagnosis are commented upon.

Adult↗
PubMed1987

Predicting pulmonary embolism in postoperative patients with deep venous thrombosis of lower limbs.

Ventilation-perfusion lung scans were done in 70 patients admitted because of an iliofemoral deep vein thrombosis (DVT), and diagnosed by venography. Eighteen items of clinical and laboratory information were measured to predict the presence of lung scan abnormalities consistent with asymptomatic pulmonary embolism. Eighteen patients had perfusion defects in the lung scan that were classified as "high probability of pulmonary embolism", while the lung scan was normal in 32 patients. Patients with an idiopathic DVT were at high risk of pulmonary embolism, but those with a postoperative DVT had a low embolic risk. In patients with a postoperative DVT two factors predicted pulmonary embolism: those patients who developed symptomatic DVT after an operation but had a normal lung scan showed higher platelet counts than their preoperative levels. Conversely, it they developed a pulmonary embolism their platelet count dropped from their preoperative levels.

Adult↗
PubMed1987

A randomized study comparing platinum, doxorubicin, and VP-16 with platinum, 4'-epidoxorubicin, and VP-16 in patients with non-small-cell lung cancer.

Forty-four previously untreated patients with advanced non-small-cell lung cancer were treated in a randomized trial comparing platinum (60 mg/m2), doxorubicin (40 mg/m2), and VP-16 (150 mg/m2) (PAV) with platinum (60 mg/m2), 4'-epidoxorubicin (50 mg/m2), and VP-16 (150 mg/m2) (PEV). The overall response rate was 10%. Major response rates were quite similar for the 21 patients treated with PAV (5%) and the 23 patients treated with PEV (18%) (p = 0.2). Of the 23 patients with assigned to PEV, two (9%) achieved complete responses for a median duration of 20 weeks and 44+ weeks. There was no significant difference (p = 0.75) in the median survival among patients treated with PAV (24 weeks) and those treated with PEV (20 weeks). Toxicity was generally mild and tolerable. The lack of response found in both arms of treatment caused the study to be terminated early. Some benefit could be appreciated in patients with limited disease and good Karnofsky performance status.

Adenocarcinoma↗
PubMed1986

A dose-response study of forskolin, stimulatory hormone, and guanosine triphosphate analog on adenylate cyclase from several sources.

We have described relationships involving forskolin stimulation of adenylate cyclase (AC) from a variety of sources and the potentiation of forskolin effects by stimulatory hormones (glucagon, ACTH, and epinephrine) and beta, gamma-imidoguanosine 5'-triphosphate (Gpp(NH)p). The effects on AC were examined using membrane preparations of rabbit adipocytes, rat adipocytes, rat erythrocytes, and rat liver. Also examined was the AC of liver membranes of rat pretreated with pertussis toxin as well as that solubilized from rat liver membranes. Maximal forskolin stimulation of AC in all preparations studied revealed a consistent 10-fold increase in AC activity. The EC50 for forskolin was 10 microM for rat liver, 15 microM for rabbit and rat adipocytes and 17 microM for rat erythrocyte AC stimulation. In all cases the AC activity attained by forskolin stimulation was further enhanced by stimulatory hormones in a dose-dependent manner. Furthermore, a combination of all three activators (forskolin, stimulatory hormone, and Gpp(NH)p) resulted in an even greater overall stimulation to levels ranging from 25- to 30-fold over unstimulated activity levels. In the presence of saturating levels of each stimulatory hormone and Gpp(NH)p, the EC50 for forskolin diminished markedly to the range of 0.5 to 4.0 microM. In the absence of any apparent tissue specificity for forskolin stimulation, the general pattern of these results further implicates the catalytic site of the AC complex as the site of forskolin activation. Furthermore, activation of additional components of the complex by Gpp(NH)p and tissue specific hormones may further influence the AC activity and thereby potentiate the stimulation by forskolin.

Adenylyl Cyclases↗
PubMed1986

Conditional inhibition of forskolin-activated adenylate cyclase by guanosine diphosphate and its analog.

Forskolin-activated adenylate cyclases (AC) in intact membranes, solubilized with Lubrol or eluted following adsorption on a forskolin-Sepharose column, were examined for inhibition by GDP and GDP beta S. AC in intact membranes of rat or rabbit adipocytes was activated by 100 microM forskolin and further potentiated by 10 microM Gpp(NH)p in combination with either 230 microM epinephrine or 50 mU X ml-1 ACTH. GDP (0-1 mM) or GDP beta S (0-500 microM) inhibited activation in a dose-dependent manner to a level similar to or slightly below that produced by 100 microM forskolin alone. Forskolin at 100 microM stimulated solubilized AC of rabbit adipocytes and rat liver membranes for 10 +/- 4 to 160 +/- 10 and from 26 +/- 2 to 274 +/- 21 pmol(mg X min)-1, respectively, in the absence of GDP beta S; forskolin-activated activity decreased from 160 +/- 10 to 157 +/- 6 and from 274 +/- 21 to 238 +/- 14 pmol(mg X min)-1 in the presence of 500 microM GDP beta S. Forskolin-activated solubilized enzyme was further potentiated by 10 microM Gpp(NH)p from 160 +/- 10 to 289 +/- 52 and from 274 +/- 21 to 702 +/- 50 pmol(mg X min)-1. GDP beta S at 500 microM inhibited 93 and 103% of the Gpp(NH)p-potentiated activity. AC of rat adipocytes eluted from forskolin-Sepharose affinity column with 500 mM NaCl and 100 microM forskolin was not significantly activated by Gpp(NH)p nor inhibited by GDP beta S. However, it was activated by forskolin. The lack of inhibition of unmodified forskolin-activated activity by GDP or GDP beta S in contrast to the inhibition of Gpp(NH)p-activated enzyme or Gpp(NH)p-potentiated forskolin-activated enzyme may be a general phenomenon descriptive of the action of forskolin on AC. Furthermore, inhibition of forskolin-activated AC by GDP and its analog may be a useful index in analyzing the degree of guanine nucleotide potentiation of this enzyme.

Adenylyl Cyclases↗
PubMed1986

In vivo measurement of electrical parameters with alumina-covered stainless steel electrodes.

An experimental method has been developed for in vivo measurement of electrical parameters. It is thus possible to evaluate not only the instantaneous corrosion rate of implants but also their susceptibility to pitting corrosion. It has also been shown that when the method is applied to stainless steel/ceramic electrodes, these remain in the passive condition. If an eventual breakdown of the passivating film occurs, it will quickly regenerate itself.

Aluminum Oxide↗