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Biomedical subjects

J Barbosa

Publications and source records attributed to J Barbosa.

At least 73 records · Page 4Linked to original sources
PubMed1997

Effect of protein kinase C activation on the release of [3H]acetylcholine in the presence of vesamicol.

The present work tested whether pharmacological activation of protein kinase C (PKC) influences the release of [3H]acetylcholine ([3H]ACh) synthesized in the presence of vesamicol, an inhibitor of the vesicular acetylcholine transporter (VAChT). Newly synthesized [3H]ACh was released from hippocampal slices by field stimulation (15 Hz) in the absence of vesamicol, but as expected [3H]ACh synthesized during exposure to vesamicol was not released significantly by stimulation. Treatment of slices with the PKC activator phorbol myristate acetate (PMA) decreased the inhibitory effect of vesamicol on [3H]ACh release. The effect of PMA was dose-dependent, was sensitive to calphostin C, a PKC-selective inhibitor, and could not be mimicked by alpha-PMA, an inactive phorbol ester. PMA did not alter the release of [3H]ACh in the absence of vesamicol, suggesting that the site of PKC action could be related to the VAChT. In agreement with this observation, immunoprecipitation of VAChT from 32P-labeled synaptosomes showed that phosphorylation occurs and that incorporation of 32P in the VAChT protein increases in the presence of PMA. We suggest that PKC alters the output of [3H]ACh formed in the presence of vesamicol and also provide circumstantial evidence for a role of phosphorylation of VAChT in this process.

Acetylcholine↗
PubMed1997

Production and characterization of a novel monoclonal antibody against phosphorylated T cell receptor zeta chain.

One of the earliest events following T cell receptor (TCR) triggering is the activation of the protein kinase Lck and induction of tyrosine phosphorylation of zeta, the major signal transduction subunit of the T cell receptor complex. Here we report the generation and characterization of a monoclonal antibody specific for human phosphozeta. The antibody was produced by immunizing mice with a truncated recombinant form of human zeta together with the Lck enzyme. The C415.9A antibody recognizes recombinant as well as cellular phosphozeta but is unreactive with unphosphorylated zeta or other tyrosine phosphorylated proteins. Using this antibody, we have demonstrated aberrant TCR-zeta tyrosine phosphorylation in Jurkat T cell transduction mutants. Therefore, this antibody can be used to elucidate T cell signal transduction mechanisms by analyzing and monitoring tyrosine phosphorylation of zeta in vitro and in vivo directly. Furthermore, this antibody could find application in the analysis of abnormal T cell signaling in autoimmune disease, cancer, and immunodeficiency disorders.

Amino Acid Sequence↗
PubMed1997

Variation of acidity constants of peptides in acetonitrile-water mixtures with solvent composition: effect of preferential solvation.

The dissociation constant values of a series of peptides in 5.54, 10, 16.30, 25.03 and 50% (w/w) acetonitrile-water mixed solvents at 298.15 K were determined according to the criteria endorsed by IUPAC. A pronounced change in the acid-base pK values of carboxylic, phenol and thiol groups was observed as the solvent was enriched in acetonitrile. By contrast, pK values of protonated amino-terminal groups were influenced slightly as the solvent was enriched in acetonitrile, although continually increasing pK values were observed. The variation of the pK values obtained, over the whole composition ranged studies, was explained by taking into account the preferential solvation of electrolytes in acetonitrile-water mixtures. To obtain pK values in all possible binary solvent acetonitrile-water mixtures, relationships between pK values and different bulk properties were examined and the Linear Solvation Energy Relationships methodology was applied. The pKa values were then correlated with the Kamlet-Taft, phi, alpha and beta solvatochromic parameters of acetonitrile-water mixtures. The equations obtained allowed calculation of the pK values of peptides in acetonitrile-water mixtures up to 50% (w/w) and thus permitted the acid-base behavior of these substances in the widely used acetonitrile-water media to be known.

Acetonitriles↗
PubMed1997

Acid-base behavior of quinolones in aqueous acetonitrile mixtures.

Quinolones are a family of antibacterial agents that are used extensively in both human and veterinary clinics. Their antibacterial activity is pH-dependent, and therefore an examination of protonation equilibria in quinolone solutions is essential. pK-Values of nine quinolone antibacterials in acetonitrile-water mixtures containing 0, 10, 30, 40, 50 and 70%(w/w) acetonitrile were determined according to the rules and procedures endorsed by IUPAC. In order to obtain quinolone pK-values in any acetonitrile-water mixture up to 70%(w/w) acetonitrile, relationships between pK-values and different bulk properties (such as dielectric constant) and some microscopic parameters (such as solvatochromic parameters alpha, beta and pi*) were established. These relationships and the application of the preferential solvation theory of electrolytes in acetonitrile-water mixtures permit the interpretation of acid-base behaviour of these important antimicrobials in the widely used acetonitrile-water media.

Acetonitriles↗
PubMed1997

Determination of dissociation constants of loop diuretics in acetonitrile-water mixtures.

The dissociation pK values of the representative loop diuretics furosemide, bumetanide and ethacrynic acid in 10, 30, 40, 50 and 70% (w/w) acetonitrile-water mixtures at 298.15 K were determined, according to the rules and procedures endorsed by IUPAC. The variation in pK values over the whole composition range studied can be explained by tacking into account the preferential solvation of ionizable substances in acetonitrile-water mixtures. With a view to determining the pK values of the loop diuretics studied in any of the binary solvent acetonitrile-water mixtures, correlations of pK values and different bulk properties of the solvent were examined, and the linear solvation energy relationships method, LSER, has been applied. The pK values were then correlated with the pi*, alpha and beta solvatochromic parameters of acetonitrile-water mixtures. The resulting equations allowed us to calculate pK values for the loop diuretics in any acetonitrile-water mixture up to 70% (w/w) acetonitrile.

Acetonitriles↗
PubMed1997

[Cardiac changes in children with AIDS].

PURPOSE: To describe the cardiac findings in children with AIDS, the follow-up with treatment and the correlation between clinical and pathological features. METHODS: We studied prospectively 25 children with clinical-laboratorial diagnosis of AIDS, ages between 3 months and 11 years, even those without cardiac symptoms. We classified the signs of AIDS following that of CDC-Atlanta 1994. Eight children died and it was done necropsy in six with macro and microscopic examinations. RESULTS: Fifteen cases had already complications of AIDS and were classified as C2 and C3, 5 as B2, 3 B1 and 2 as A1. Beside the symptoms related to the disease and infections we found signs of congestive heart failure III and IV (NYHA) in 5 children, pericardial effusion in 5, (one of them had cardiac tamponade). In the electrocardiogram (EKG), 8 children had repolarization abnormalities. In 1st echocardiogram (ECHO) we found some features of dilated myocardiopathy in 8 (6 were asymptomatic) 5 of those had pericardial effusion, one child had huge amount of pericardial liquid and also increased measures of intraventricular septum and posterior wall of left ventricle by ECHO and confirmed by necropsy examination. All cases of diagnosis of myocardiopathy received treatment with captopril and 4 also received furosemide and digoxina. Even under oral treatment three of them had deterioration of heart failure but after combined anti-retroviral drugs they showed better cardiac functions. From the six necropsied cases, two had increased heart weight without myocarditis, one had toxoplasma pancarditis and other one had fibrocalcic vasculopathy. CONCLUSION: We found several assymptomatic cases already with decreased ventricular function. Some worsened of heart failure even under apropriate treatment and showed better cardiac index after combined anti-retroviral drugs.

Acquired Immunodeficiency Syndrome↗
PubMed1996

Solvatochromic parameter values and pH in acetonitrile-water mixtures. Optimization of mobile phase for the separation of peptides by high-performance liquid chromatography.

The proportion of the organic modifier and the pH of the mobile phase were optimized in order to separate a series of low-molecular-mass peptides by HPLC. The composition of the mobile phase was optimized by establishing relationships between retention parameters and Reichardt's ENT scale of solvent polarity, and between retention and the Kamlet-Taft multiparameter solvent scale of the eluent, using linear solvation energy relationships (LSER). The pH of the mobile phase was also successfully optimized by establishing relationships between the retention and the pH measured in the aqueous-organic mixture used as eluent.

Acetonitriles↗
PubMed1996

Direct determination of anabolic steroids in human urine by on-line solid-phase extraction/liquid chromatography/mass spectrometry.

A fully automated method is presented for the determination of anabolic steroids in human urine. On line solid-phase extraction with automatic cartridge exchange is used for sample clean-up followed by an high-performance liquid chromatographic isocratic separation. A narrow-bore 5 microns reversed-phase column (250 x 2.1 mm i.d.) at a flow rate of 0.2 ml min-1 is connected to a particle beam interface linked to a single-quadrupole mass spectrometer. No derivatization is needed and normal electron impact mass spectra are obtained for a series of up to 28 steroids and metabolites. Urine samples collected following the ingestion of therapeutic doses of some of the steroids were analysed and the detection and confirmation of excreted compounds accomplished. A dramatic reduction in human intervention and overall analysis time was achieved compared with other common approaches.

Anabolic Agents↗
PubMed1996

Nd-YAG laser as a palliative treatment for malignant dysphagia.

Two hundred and twenty-four patients with histologically-confirmed carcinoma of the oesophagus received palliative Nd-YAG laser therapy for malignant dysphagia between January 1986 and December 1994. The results are appraised in terms of the degree of relief obtained, its relation to the macroscopic type and the size of the tumour, peri-operative complications, duration of hospitalization and survival after treatment. Recannulation of the oesophageal lumen was obtained in 98.2% of the patients, after which 93.7% were able to ingest at least semi-solids. Although the lumen was permeable for a 9.8 mm endoscope, the remainder could only ingest liquids. The only complication was a perforation is six cases (2.7%). After treatment, 14.8% survived more than 1 year and 3.4% more than 2 years. After discussing the role of lasers in the palliative treatment of malignant dysphagia, the authors conclude that it can be considered effective in that it relieves the dysphagia and improves the patients' quality of life.

Adult↗
PubMed1995

Endoscopic ultrasonography in the study of extramucosal swellings in the upper digestive tract.

The authors performed an echoendoscopic examination of 91 patients who, at a previous endoscopy, had presented extramucosal swellings in the upper digestive tract. On this occasion, the images were suggestive of a leiomyoma in 73 cases, a schwannoma in 3, an ectopic pancreas in 1, and a cyst of the gastric wall in 1. There was an extrinsic compression of the tract by an adjacent organ in three cases and by an adenopathy in two others. In six patients the authors were unable to make an echographic identification of the swellings noted upon endoscopy as they noted no echographic alteration. The echoendoscopic examination was considered normal. Given that most of these patients did not undergo surgery, the authors were only able to obtain a histological examination of surgically removed tissue in 11. The diagnosis was confirmed in eight cases. In one patient in which it proved impossible to pass the endoscope through the stenotic area, the histological examination did not confirm the echography: In two others, classified as leiomyomas, the histology showed leiomyosarcomas.

Digestive System Neoplasms↗
PubMed1995

Assignment of reference pH-values to primary standard buffer solutions for standardization of potentiometric sensors in acetonitrile-water mixtures.

Standard pH-values pH(PS) for seven primary standard buffer solutions in 0, 10, 30, 40, 50, 70 and 100% (w/w) acetonitrile-water mixed solvents at 298.15 K were determined according to the criteria recently endorsed by IUPAC. The preferential solvation of the ions in acetonitrile-water mixtures was studied in order to clarify the acid-base behaviour of the solutes in such mixtures. The influence of variation in the solvent composition on pH(PS) values was considered with a view to obtaining correlations that can be used to determine the pH(PS) values in any acetonitrile-water mixture up to 70% (w/w) acetonitrile. The pH(PS) values were then correlated with the weight and volume percentages and molar fraction of acetonitrile and with the Kamlet-Taft, pi(*), alpha and beta solvatochromic parameters of the acetonitrile-water mixtures. The equations obtained permit the standardization of potentiometric sensors in these mixtures.

Journal Article↗
PubMed1994

Sphenoid sinus involvement in neuroblastoma.

PURPOSE: Malignancy of the sphenoid sinus, especially metastatic involvement, is an extremely rare event at any age and is usually associated with a poor prognosis. We present a case of a 5-year-old boy who underwent allogenic bone marrow transplantation for stage IV neuroblastoma. PATIENTS AND METHODS: Three years later, he presented with an isolated lesion, histologically proven to be neuroblastoma, in the sphenoid sinus. RESULTS: Partial excision of the tumor, followed by chemotherapy and radiotherapy, achieved a remission for 3 years.

Child, Preschool↗
PubMed1994

Endoscopic Nd-YAG laser surgery in the treatment of villous adenomas of the rectum.

In the majority of cases, conventional techniques for the treatment of villous tumors of the rectum are, if they are to be effective, too aggressive for this usually benign pathology. Our experience with the outpatient laser treatment of 31 patients leads us to conclude that this is a safe and effective technique, which should be attempted before a colectomy or abdominoperineal amputation is indicated.

Adenoma, Villous↗
PubMed1993

Homozygous parent affected sib pair method for detecting disease predisposing variants: application to insulin dependent diabetes mellitus.

For complex genetic diseases involving incomplete penetrance, genetic heterogeneity, and multiple disease genes, it is often difficult to determine the molecular variant(s) responsible for the disease pathogenesis. Linkage and association studies may help identify genetic regions and molecular variants suspected of being directly responsible for disease predisposition or protection, but, especially for complex diseases, they are less useful for determining when a predisposing molecular variant has been identified. In this paper, we expand upon the simple concept that if a genetic factor predisposing to disease has been fully identified, then a parent homozygous for this factor should transmit either of his/her copies at random to any affected children. Closely linked markers are used to determine identity by descent values in affected sib pairs from a parent homozygous for a putative disease predisposing factor. The expected deviation of haplotype sharing from 50%, when not all haplotypes carrying this factor are in fact equally predisposing, has been algebraically determined for a single locus general disease model. Equations to determine expected sharing for multiple disease alleles or multiple disease locus models have been formulated. The recessive case is in practice limiting and therefore can be used to estimate the maximum proportion of putative susceptibility haplotypes which are in fact predisposing to disease when the mode of inheritance of a disease is unknown. This method has been applied to 27 DR3/DR3 parents and 50 DR4/DR4 parents who have at least 2 children affected with insulin dependent diabetes mellitus (IDDM). The transmission of both DR3 and DR4 haplotypes is statistically different from 50% (P < 0.05 and P < 0.001, respectively). An upper estimate for the proportion of DR3 haplotypes associated with a high IDDM susceptibility is 49%, and for DR4 haplotypes 38%. Our results show that the joint presence of non-Asp at DQ beta position 57 and Arg at DQ alpha position 52, which has been proposed as a strong IDDM predisposing factor, is insufficient to explain the HLA component of IDDM predisposition.

Adult↗
PubMed1993

Adenocarcinoma of the rectum in a 15 year old.

A 15 year old with Duke's C2 adenocarcinoma of the rectum was treated with a sphincter-saving surgical resection and adjuvant chemotherapy and radiation. The patient is alive and has been disease-free for over 5 years. Adenocarcinoma of the colon is a virulent disease in children and has a poor prognosis. The reasons for this are explored, and a literature review is included.

Adenocarcinoma↗
PubMed1993

[Anatomical classification of anterior encephaloceles].

The authors present an anatomical classification of the anterior encephaloceles. The importance of a topographic knowledge of such anomalies in their diagnosis and treatment is emphasized in order to avoid complications during the investigation of a cranio-facial protrusion.

Encephalocele↗
PubMed1991

Shared genetic susceptibility of type 1 (insulin-dependent) and type 2 (non-insulin-dependent) diabetes mellitus: contributions of HLA and haptoglobin.

Epidemiologic data suggest that having a parent with Type 2 (non-insulin-dependent) diabetes mellitus increases the risk for Type 1 (insulin-dependent) diabetes in siblings of a Type 1 diabetes proband. This increase in risk is consistent with a shared genetic susceptibility between Type 1 diabetes and Type 2 diabetes. We contrast genetic risk factors in three sets of families, consisting of (1) a single Type 1 diabetic child (proband) and non-diabetic parents, (2) multiple Type 1 diabetic siblings and non-diabetic parents, and (3) at least one Type 1 diabetic child and at least one Type 2 diabetic parent. Previous studies have demonstrated that HLA region genes, which elevate the risk in Type 1 diabetes, have no significant effect with respect to the risk for developing Type 2 diabetes. An earlier report cited a contribution by the haptoglobin locus to genetic susceptibility for Type 2 diabetes. We provide evidence that a high risk HLA antigen (HLA-DR3) is decreased to a greater extent in Type 1 patients with a Type 2 parent than in Type 1 patients in which the parents are not diabetic. The role of HLA-DR4 is maintained in these families, with an unexpectedly significant increased rate of transmission of the HLA-DR4 allele from Type 2 parent to Type 1 offspring. The role of haptoglobin in these families does not appear to be important, either with respect to association with diabetes or with respect to linkage with a secondary susceptibility locus. These results indicate that families with a Type 2 parent and Type 1 child, heavily determined by HLA-DR4 linked factors, may represent a homogeneous subset of diabetes susceptibility.

Adult↗