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Biomedical subjects

R Valderrama

Publications and source records attributed to R Valderrama.

At least 37 records · Page 2Linked to original sources
PubMed1993

An improved Bradford protein assay for collagen proteins.

A modification of the protein determination method of Bradford adapted for collagen-rich samples is described. The use of Coomassie-based protein determination methods is limited by the great variation in colour yield obtained for different proteins. This is especially important in samples containing significant amounts of collagen where direct application of the methods of Lowry and Bradford results in underestimated values. Addition of small amounts of sodium dodecyl sulphate (SDS) (0.0035%) to the diluted solutions of Coomassie Brilliant Blue G used as dye reagent in the Bradford colorimetric assay caused a 4-fold increase in the colour response of three collagen proteins (Col I, III and IV) and a decrease in absorbance for various non-collagen proteins. The presence of SDS in the reagent did not result in a significant metachromatic shift of the collagen-dye complexes. This simple modification in the preparation of the reagent for the Bradford assay allows similar response curves to be obtained for collagen and non-collagen proteins, making the modified assay of potential use for protein determination in collagen-rich samples such as pancreatic extracts.

Collagen↗
PubMed1992

Imaging of human T-lymphotropic virus type I-associated chronic progressive myeloneuropathies.

We studied magnetic resonance imaging (MRI) of the head and cervical spine and CT of the head in 46 patients (14 men, 32 women) with chronic progressive myeloneuropathy. The findings were correlated with human T-lymphotropic virus type I (HTLV-I) serology, race, country of origin, and age. We found a female predominance of 2:1. Most patients were aged between 30 and 50 years, and most were Caribbean immigrants and black. There were 9 men and 17 women with blood antibody titers to HTLV-I and 7 men and 15 women with cerebrospinal fluid (CSF) titers. All patients with virus or antibodies in blood or CSF were Caribbean immigrants or black. T2-weighted cranial MRI showed scattered areas of high signal intensity in the cerebral white matter, usually in the periventricular and subcortical areas, but not in the posterior cranial fossa. Cranial CT revealed periventricular low density areas, ventricular enlargement, and atrophy MRI of the cervical spine showed atrophy of the cord. Myelography was normal in all 15 patients examined. No imaging differences were observed between the HTLV-I-positive and -negative patients. These findings, although consistent with demyelination, are not specific.

Adolescent↗
PubMed1992

Multicenter double-blind trial of gabexate mesylate (FOY) in unselected patients with acute pancreatitis.

A multicenter, randomized, double-blind trial was carried out to evaluate the efficacy of gabexate mesylate (FOY) in acute pancreatitis. One hundred unselected patients were randomly allocated into two groups: 51 were assigned to receive FOY (12 mg/kg/day as continuous intravenous infusion for a minimum of 4 days and a maximum of 12 days), and 49 were allocated to placebo. The groups were comparable in demographic, clinical and biochemical parameters, etiology of pancreatitis, and disease severity, which was generally mild. Gallstones were the main etiological factor. All patients received fluid and electrolyte replacement, analgesia and nasogastric suction for at least 48 h after admission. Experimental therapy was initiated no later than 12 h after the beginning of symptoms. The results showed no statistically significant differences between the two groups with respect to the evolution of clinical and biochemical parameters, analgesic requirements, development of complications, hospitalization time or mortality at completion of the trial. In conclusion, early treatment with FOY does not appear to have any demonstrable beneficial effects in acute pancreatitis.

Acute Disease↗
PubMed1991

Propranolol in prevention of recurrent bleeding from severe portal hypertensive gastropathy in cirrhosis.

The two main causes of gastrointestinal bleeding in cirrhosis are oesophageal varices and portal hypertensive gastropathy (PHG). Rebleeding from varices can be prevented by beta-blockers, but it is not clear whether these drugs effectively reduce rebleeding from PHG. 54 cirrhotic patients with acute or chronic bleeding from severe PHG took part in a randomised, controlled trial to investigate the efficacy of propranolol in prevention of rebleeding from PHG. 26 patients were randomised to receive propranolol daily at a dose that reduced the resting heart rate by 25% or to 55 bpm (20-160 mg twice daily), throughout mean follow-up of 21 (SD 11) months. 28 untreated controls were followed-up, with the same examinations, for 18 (13) months. The actuarial percentages of patients free of rebleeding from PHG were significantly higher in the propranolol-treated patients than in the untreated controls at 12 months (65% vs 38%; p less than 0.05) and at 30 months of follow-up (52% vs 7%; p less than 0.05). Propranolol-treated patients had fewer episodes of acute bleeding than controls (0.010 [0.004] vs 0.120 [0.040] per patient per month). Multivariate analysis showed that absence of propranolol treatment was the only predictive variable for rebleeding. Actuarial survival was slightly higher in the propranolol group than in the controls, but the difference was not significant. Thus, long-term propranolol treatment significantly reduces the frequency of rebleeding from severe PHG, and may improve the prognosis of cirrhotic patients with this disorder.

Actuarial Analysis↗
PubMed1991

Quantitative measurement of fibrosis in pancreatic tissue. Evaluation of a colorimetric method.

A colorimetric method has been used to quantify the collagen contained in 23 specimens of pancreatic tissue (11 controls and 12 chronic pancreatitis). The method takes advantage of the selective capacity of Sirius red to stain collagen protein and of rapid green to stain noncollagen protein. The results obtained by this method were compared with those of standard morphometry to determine tissue fibrosis. With the morphometric method, the values of the control group were 6.6 +/- 4.0% (fiber area/total area), and those of chronic pancreatitis 66.0 +/- 19.0% (difference 59.4, 95% confidence interval for difference: 47.2-71.6, P less than 0.001). The values obtained with the colorimetric method were 89.1 +/- 11.6 micrograms collagen/mg total protein in the control group, and 132.7 +/- 25.3 micrograms collagen/mg total protein in the chronic pancreatitis group (difference 43.6, 95% confidence interval for difference: 26.3-61.0, P less than 0.001). A highly significant correlation (r = 0.847; p less than 0.001) was observed between the amount of collagen measured colorimetrically and the degree of fibrosis determined morphometrically. These results demonstrate that the colorimetric method is a reproducible, simple, and rapid technique to quantitate fibrosis in histological preparations of pancreatic tissue.

Alcoholism↗
PubMed1991

Occult microlithiasis in 'idiopathic' acute pancreatitis: prevention of relapses by cholecystectomy or ursodeoxycholic acid therapy.

Gallstone pancreatitis is usually related to small stones, which may not be detected by conventional cholecystographic techniques. In the current study, it was hypothesized that some patients with acute pancreatitis of unknown cause could harbor occult microstones in the gallbladder. Therefore, evidence was sought prospectively of missed gallstones by biliary drainage and microscopic examination of centrifuged duodenal bile in 51 patients recovering from an attack of acute pancreatitis, including 24 patients with relapsing episodes. Clusters of cholesterol monohydrate crystals, calcium bilirubinate granules, and/or CaCO3 microspheroliths were found in 67% of the patients. Biliary drainage showed no abnormal findings in 12 patients convalescing from a bout of known alcoholic pancreatitis. Examination of gallbladder bile at cholecystectomy and/or serial ultrasonography of the gallbladder for up to 12 months showed that 73% of the patients with unexplained pancreatitis had biliary sludge or microlithiasis; the prior finding of biliary crystal/solid markers predicted their existence with both a sensitivity and a specificity of 86% and a predictive value of 94%. The probability of harboring occult gallstones was also associated with age (P = 0.004), prior recurrent pancreatitis (P = 0.024), and altered liver function tests results during an index episode (P = 0.003). In 13 patients with cholesterol monohydrate crystals in bile, ursodeoxycholic acid (10 mg.kg-1.day-1) eliminated gallbladder microlithiasis within 3-6 months, and subsequent maintenance treatment with a daily dose of 300 mg prevented both gallstone recurrence and further attacks of pancreatitis over a mean follow-up period of 44 months. Cholecystectomy also prevented gallstone-associated relapses in 17 of 18 patients followed up for a mean postoperative period of 36 months. This study provides firm evidence showing that in most patients with idiopathic acute pancreatitis, the disease is related to microscopic gallstones, as evidenced by the follow-up development of macroscopic stones or sludge and by the prevention of relapses with either cholecystectomy or a cholelitholytic bile acid. Occult gallstones should be strongly suspected when acute pancreatitis of unknown cause occurs in a relapsing manner and in aged patients and when it is associated with altered liver function test results. Biliary microscopy and/or follow-up ultrasonography of the gallbladder provide a simple means of uncovering them to institute appropriate therapy and prevent further attacks.

Acute Disease↗
PubMed1990

[Predictive factors of mortality in a series of 61 patients with severe acute pancreatitis].

The predictive value of eight clinical variables and 20 analytical variables on mortality was retrospectively analyzed in 61 patients with severe acute pancreatitis, fulfilling at least three Ranson criteria, admitted to the ICU between 1977 and 1987. The mean age of the series was 57 +/- 16.6 years. Twenty seven were males and 34 females. The mortality rate was 60%. Univariate analysis demonstrated that the variables with greater predictive value of mortality were: age, days of hospitalization, presence of associated diseases, plasma lactodehydrogenase, more than 10% hematocrit decrease during the first 48 hours, plasma ureic nitrogen on admission and a value greater than 1.8 mmol/l during the first 48 hours, calcemia, arterial oxygen pressure, plasma albumin, and prothrombin time. A logistic regression multivariate analysis disclosed that the variables with independent predictive value of mortality were: age, serum ureic nitrogen, calcemia, arterial oxygen pressure, plasma albumin, and hematocrit decrease after 48 hours. When the patients were grouped according to the presence of less than three, three, four or more than four of these risk factors (being, the average the cutting point) we obtained a good prognostic discriminative power since the mortality in those groups was 0, 30%, 60%, and 100%, respectively.

Acute Disease↗
PubMed1990

Otolaryngic manifestations of myiasis.

Although rare in North America and Europe, myiasis is seen occasionally in tropical and undeveloped countries. This disorder results from the penetration of a fly larva into a part of the human body, and it causes various symptoms in the host. The exposed areas of the skin are the ones predominantly affected and the eyes, ears, nose, and paranasal sinuses are less commonly affected. We review our experience with 12 patients with myiasis of the ears, nose, and paranasal sinuses.

Adult↗
PubMed1988

Idiotypic control of the immune response.

Anti-idiotypic antibodies are antibodies against the antigenic determinants (idiotypes) of an antibody's antigen-binding region. Anti-idiotypes can bind near (Ab2 gamma) or away (Ab2 alpha) from the antigen-combining site or can carry the internal image of the antigen (Ab2 beta). Idiotypes and anti-idiotypes have been described in T- and B-cell systems. They have been used in basic research to purify and characterize receptors and ligands against receptors, to treat tumors, to make vaccines and to diagnose and suppress the immune response. In experimental myasthenia gravis anti-idiotypes protect animals against the disease, block idiotype binding and share idiotypic specificities.

Animals↗
PubMed1988

Treatment of experimental myasthenia with autologous idiotypes linked to muramyl dipeptide.

In order to develop a new treatment of experimental autoimmune myasthenia gravis (EAMG), rabbits were injected with purified acetylcholine receptor (AChR) from Torpedo californica. Polyclonal affinity-purified anti-AChR antibodies (idiotypes, Ids) were coupled covalently to muramyl dipeptide and injected back into the same (i.e. autologous) rabbits from which the Ids were obtained. Treated animals developed anti-Ids that bound to the F(ab')2 fragments of the Ids as demonstrated by ELISA and that also blocked binding of Ids to AChR in a radioimmunoassay. Treated animals showed a protective effect compared to control animals when challenged with a second injection of AChR. Anti-AChR titres in surviving animals achieved a steady-state equilibrium. No apparent toxicity from the treatment was noted.

Acetylmuramyl-Alanyl-Isoglutamine↗
PubMed1987

Treatment of experimental autoimmune myasthenia gravis in rabbits with leupeptin, a protease inhibitor.

We injected 12 New Zealand white rabbits intraperitoneally with 15 mg/kg Leupeptin on alternative days for about 4 months. After 1 week of Leupeptin treatment, they were challenged with purified acetylcholine receptor (AChR) from Torpedo californica in Freund's complete adjuvant. All control animals died within 60 days. Six animals treated with Leupeptin did not develop EAMG in spite of repeated AChR injections. Three animals developed clinical signs of EAMG after 65 days. The clinical course was short in the one that survived and prolonged in the 2 that finally died. All animals (Leupeptin-treated and controls) had circulating anti-AChR antibodies. Among the survivors, titers were slightly lower and EMG repetitive stimulation tests were normal. Leupeptin (0.02-200 mM) did not prevent curaremimetic [3H]toxin binding to AChR in membranes or in solution, nor dissociate AChR-toxin-antibody complexes. Immune response to antigens other than receptor remained intact in Leupeptin-treated animals. Leupeptin was not toxic at the doses given. The mechanism of this protection is not well understood. Leupeptin seems to decelerate the turnover rate of AChR induced by anti-AChR antibodies and/or to decrease the complement-mediated immune attack against the muscle end-plate.

Animals↗
PubMed1984

Cerebral infarction and subdural hematoma. Advantage of nuclear magnetic resonance imaging in cerebral ischemia.

Visual hallucinations were the initial complaints in a patient with a posterior cerebral artery occlusions who fell and sustained bilateral subdural hematomas. In addition to poor vision, the patient experienced formed visual hallucinations of the epileptic type in the hemianopic field. The hemianopia was dense with macular sparing. CAT scans, which were done pre- and postoperatively, showed no abnormalities in the temporal and occipital lobes to explain the "epileptic visual hallucinations" and macular sparing. The NMR scan showed low-density changes in those areas. At the time that the NMR scan was done, most of the patient's deficits, including the hemianopia and hallucinations, had resolved.

Aged↗
PubMed1978

Binding of antibodies to acetylcholine receptors in Electrophorus and Torpedo electroplax membranes.

Antisera against purified acetylcholine receptors from the electric tissues of Torpedo californica and of Electrophorus electricus were raised in rabbits. The antisera contain antibodies which bind to both autologous and heterologous receptors in solution as shown by an immunoprecipitation assay. Antibodies in both types of antisera bind specifically to the postjunctional membrane on the innervated surface of the intact electroplax from Electrophorus electric tissue as demonstrated by an indirect immunohistochemical procedure using horseradish peroxidase conjugated to anti-rabbit IgG. Only anti-Electrophorus receptor antisera, however, cause inhibition of the receptor-mediated depolarization of the intact Electrophorus electroplax. The lack of inhibition by anti-Torpedo receptor antibodies, which do bind, suggests that the receptor does not undergo extensive movement during activity. The binding of anti-Torpedo antibodies to receptor-rich vesicles prepared by subcellular fractionation of Torpedo electric tissue was demonstrated by both direct and indirect immunohistochemical methods using ferritin conjugates. These vesicles can be conveniently collected and prepared for electron microscopy on Millipore filters, a procedure requiring only 25 micrograms of membrane protein per filter. In addition, it was possible to visualize the binding of anti-Torpedo receptor antibodies directly, without ferritin. These anti-Torpedo receptor antibodies, however, do not inhibit the binding of acetylcholine or of alpha-neurotoxin to receptor in Torpedo microsacs but do inhibit binding of alpha-neurotoxin to Torpedo receptor in Triton X-100 solution. It is likely that the principal antigenic determinants on receptor are at sites other than the acetylcholine-binding sites and that inhibition of receptor function, when it occurs, may be due to a stabilization by antibody binding of an inactive conformational state.

Acetylcholine↗
PubMedDate not supplied

Collagenolytic activity in human pancreatic tissue with different degrees of fibrosis.

The present study was designed to establish a valid method for expressing collagenolytic activity in pancreatic tissue with different degrees of fibrosis. Collagenolytic activity was measured in pancreatic tissue of control and alcoholic chronic pancreatitis (CP) patients and data were expressed as percent digestion/mg tissue or as percent digestion/mg protein obtaining different results. The values were 18.4 +/- 4.7% digestion/mg tissue in the control group, and 8.4 +/- 3.2% digestion/mg tissue in the chronic pancreatitis group (p < 0.001). When collagenolytic activity was expressed as percent digestion/mg protein, measured by the Bradford assay, the values of the control group were 190.2 +/- 69.0% digestion/mg protein, and those of chronic pancreatitis patients were 187.2 +/- 61.7% digestion/mg protein (p = ns). Protein determination in pancreatic tissue of control and CP patients was seen to be influenced by the method assayed. Protein content per mg of fresh tissue, measured by the methods of Lowry, Bradford, and Bradford-SDS, were similar and twofold higher in controls than in CP samples. However, the Kjeldahl assay showed that protein content per mg of dry tissue was the same in both groups. The high degree of fibrosis in the pancreas of CP patients (60.2 +/- 28.0%) with regard to controls (4.7 +/- 1.8%) (p < 0.001) and the low response of collagen proteins to the Lowry and Bradford assays could explain the differences observed in protein content of human samples.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMedDate not supplied

[Pharmacologic and enzymatic effects of snake venoms from Antioquia and Choco (Colombia)].

We compared several pharmacological and enzymatic effects induced by 11 snake venoms from seven species, six of them from different geographic areas of Antioquia and Choco, north-west of Colombia, South America (Bothrops atrox, B. nasutus, B. schlegelii, B. punctatus, Lachesis muta, Micrurus mipartitus), and Crotalus durissus terrificus venom, from specimens captured in other provinces of the country (Tolima, Huila, Meta and Atlantico). Differences were observed in edema-forming, hemorrhage, defibrination, indirect hemolysis, myonecrosis, proteolysis and lethal activity between venoms from different genera or species, as well as according to the geographic area of origin in B. atrox and B. nasutus snake venoms. Bothrops venoms, in particular B. atrox and L. muta, produced major local effects. All of the venoms, including M. mipartitus, had myotoxic effects. The most defibrinating venoms were B. atrox, L. muta, B. punctatus and C. d. terrificus. All of the venoms had indirect hemolytic activity; the venom of M. mipartitus being greatest. The most lethal venoms were those of C. d. terrificus and M. mipartitus. Within Bothrops species, the venom of B. schlegelii was the least active in terms of local and systemic pathologic effects.

Animals↗