PubMed Health⌕ Search

Biomedical subjects

M A Santos

Publications and source records attributed to M A Santos.

At least 19 recordsLinked to original sources
PubMed1995

The Saccharomyces cerevisiae RIB4 gene codes for 6,7-dimethyl-8-ribityllumazine synthase involved in riboflavin biosynthesis. Molecular characterization of the gene and purification of the encoded protein.

6,7-Dimethyl-8-ribityllumazine, the immediate biosynthetic precursor of riboflavin, is synthesized by condensation of 5-amino-6-ribitylamino-2,4(1H,3H)-pyrimidinedione with 3,4-dihydroxy-2-butanone 4-phosphate. The gene coding for 6,7-dimethyl-8-ribityllumazine synthase in Saccharomyces cerevisiae (RIB4) has been cloned by functional complementation of a mutant accumulating 5-amino-6-ribitylamino-2,4(1H,3H)-pyrimidinedione, which can grow on riboflavin- or diacetyl- but not on 3,4-dihydroxy-2-butanone-supplemented media. Gene disruption of the chromosomal copy of RIB4 led to riboflavin auxotrophy and loss of enzyme activity. Nucleotide sequencing revealed a 169-base pair open reading frame encoding a 18.6-kDa protein. Hybridization analysis indicated that RIB4 is a single copy gene located on the left arm of chromosome XV. Overexpression of the RIB4 coding sequence in yeast cells under the control of the strong TEF1 promoter allowed ready purification of 6,7-dimethyl-8-ribityllumazine synthase to apparent homogeneity by a simple procedure. Initial structural characterization of 6,7-dimethyl-8-ribityllumazine synthase by gel filtration chromatography and both nondenaturing pore limit and SDS-polyacrylamide gel electrophoresis showed that the enzyme forms a pentamer of identical 16.8-kDa subunits. The derived amino acid sequence of RIB4 shows extensive homology to the sequences of the beta subunits of riboflavin synthase from Bacillus subtilis and other prokaryotes.

Amino Acid Sequence↗
PubMed1995

Hydrogen bonding in a non-steroidal anti-inflammatory drug--Naproxen.

Photophysical properties of a non-steroidal anti-inflammatory drug, Naproxen (6-methoxy alpha-methyl-2-naphthalene acetic acid sodium salt), were investigated in solvents of different polarity, hydrogen donor ability and also in cyclodextrins. The results indicate that in all cases the emitting state is the 1L(b) singlet. In alcoholic solvents, an intermolecular hydrogen bond is responsible for the observed photophysical behaviour of the probe whereas in non-protic solvents (polar and weakly polar) an intramolecular hydrogen bond type is postulated to rationalize the data found. In water, the non-radiative rate constant has a value similar to those found in aqueous solutions of alpha- and beta-cyclodextrins where the probe form complexes. The behaviour in water is explained by a water-structure enforced hydrophobic effect. The spectroscopic results are interpreted on the basis of a multiple-parameter model that considers specific solute-solvent interactions. These were also observed in the ground state and detected by Fourier transform infrared spectroscopy. Molecular mechanics (MM) and molecular orbital (AM1) calculations also support the existence of two conformations (rotamers) in Naproxen with non-equivalent intramolecular hydrogen bond-like formation.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1992

A kindred with multiple endocrine neoplasia type 2A associated with pruritic skin lesions.

BACKGROUND: A kindred affected by multiple endocrine neoplasia type 2A (MEN 2A), associated with symmetric, bilateral, scapular pruritic skin lesions (PSL), is reported. METHODS: There were 21 members, including the propositus, in four generations. Screening of 10 family members showed a palpable thyroid tumor in 1 and positive results for a pentagastrin test in 7 others. Two of these patients had surgically confirmed pheochromocytoma. Two others had a biochemical diagnosis of pheochromocytoma but did not have surgery. RESULTS: Medullary thyroid carcinoma was confirmed in five patients and nodular C-cell hyperplasia in another. In five affected adults, PSL were observed in the interscapular region, crossing the midline in some. These lesions were characterized by hyperkeratosis and hyperpigmentation. In all the patients, the pruritus had been present long before the clinical or biochemical diagnosis. Skin biopsies were performed in two of these patients. No amyloid deposits were found (Congo red stain and electron microscopic examination were used). Two children (14 and 6 years old) in the fourth generation complained of scapular pruritus, although skin lesions were not apparent. CONCLUSIONS: Localized PSL must be sought when screening for MEN 2A.

Adolescent↗
PubMed1992

Identification of a gene in Bacillus subtilis bacteriophage SPP1 determining the amount of packaged DNA.

The virulent Bacillus subtilis bacteriophage SPP1 encapsidates its DNA by a headful mechanism. Analyzing phage missense mutants, which package less DNA than SPP1 wild-type but show no other affected properties, we have identified a gene whose product is involved in the sizing of phage DNA during maturation. Characterization of this gene and its product provides an experimental access to the poorly understood mechanism of DNA sizing in packaging. The gene (gene 6 or siz) was cloned and sequenced. An open reading frame (ORF) coding for a 57.3 kDa polypeptide was identified. All the single nucleotide substitutions present in different siz mutants affect the net charge of that protein. The gene was further characterized by assignment of several nonsense mutations (sus) to the ORF. Phages carrying the latter type of mutations could be complemented in trans when gene 6 is provided by a plasmid.

Amino Acid Sequence↗
PubMed1992

Characterization of big, big prolactin in patients with hyperprolactinaemia.

OBJECTIVE: The present study was designed to characterize the clinical findings of patients with macroprolactinaemia (sustained hyperprolactinaemia where the predominant form of prolactin is of large molecular size) and to further assess the bioactivity and structure of big, big prolactin (BB-PRL). DESIGN: The patients with macroprolactinaemia were identified by the domperidone test and by gel filtration of their serum samples. The bioactivity of sera and fractions containing BB-PRL was evaluated and the fractions analysed by affinity chromatography and electrophoresis. PATIENTS: Eleven patients with hyperprolactinaemia in whom BB-PRL was the predominant form (group 1) were studied. Sera were also examined from eight patients with prolactinomas (group 2). Thirty-one first-degree relatives from patients in group 1 were screened for macroprolactinaemia. MEASUREMENTS: Prolactin in the sera and fractions was measured by radioimmunoassay (RIA), immunoradiometric assay (IRMA) and Nb2 cell bioassay (Nb2 BA). The distribution of BB-PRL was also investigated after protein A Sepharose chromatography, immunoprecipitation, SDS-PAGE and Western blotting. RESULTS: (1) Seven out of 11 patients in group 1 had galactorrhoea, menstrual disturbances or both; (2) the ratio Nb2 BA/RIA in whole serum was similar to the ratio found in group 2 patients; (3) the ratios Nb2 BA/RIA and Nb2 BA/IRMA in the BB-PRL fractions obtained after gel filtration were significantly lower than in whole serum (P < 0.003); (4) in group 1 patients, RIA estimates of PRL did not correlate either with Nb2 BA or with IRMA, while Nb2 BA and IRMA were correlated. In group 2 patients, RIA and Nb2 BA were correlated (r = 0.881; P = 0.02); (5) 24-86% of BB-PRL reacted as immunoglobulin-bound PRL as demonstrated by protein A Sepharose and by SDS-PAGE; (6) a high percentage of BB-PRL (54, 49 and 43%), was found in three of the serum samples obtained from 31 first-degree relatives of patients in group 1. CONCLUSIONS: Macroprolactinaemia must be suspected not only in patients with asymptomatic hyperprolactinaemia but also in women with galactorrhoea and/or menstrual disturbances who have normal responses to PRL stimulating tests. Our results also suggest that the absence of symptoms in these women is not explained by a lower bioactivity of BB-PRL. Instead, we postulate that due to the high molecular weight, BB-PRL does not easily cross the capillary walls. During gel chromatography either a change in the structure of BB-PRL and/or a removal of substances which potentiate the bioactivity of PRL occurs, explaining the lower bioactivity of fractions containing BB-PRL in comparison with the serum. In this study we demonstrated that at least half (range 24-86%) of BB-PRL behaves as an immunoglobulin-bound PRL. Finally, we found that macroprolactinaemia was not genetically transmitted to first-degree relatives in the majority of the cases studied.

Adult↗
PubMed1992

Effects of longitudinal laparotomy on respiratory system, lung, and chest wall mechanics.

In six sedated, anesthetized, paralyzed, and mechanically ventilated guinea pigs, total respiratory system (RT,rs), lung, and chest wall resistances and respiratory system (Est,rs), lung, and chest wall (Est,w) elastances were determined before and after longitudinal laparotomy. Furthermore the resistances were also split into their initial and difference components, with the former reflecting the Newtonian resistances and the latter representing the viscoelastic/inhomogeneous pressure dissipations in the system. For such purpose the end-inflation occlusion during constant inspiratory flow method was used. During laparotomy, a statistically significant increase in respiratory system difference resistance (from 0.086 to 0.101 cmH2O.ml-1.s) significantly augmented RT,rs (from 0.157 to 0.167 cmH2O.ml-1.s). The former was entirely secondary to a significant increase in chest wall difference resistance (0.019 to 0.034 cmH2O.ml-1.s), which naturally raised chest wall total resistance (from 0.030 to 0.047 cmH2O.ml-1.s). Est,rs and Est,w also increased (14.7 and 13.1%, respectively) after abdominal incision. It can be concluded that the midline xiphipubic laparotomy accompanied by the bilateral ventrodorsal infracostal incision increases RT,rs as a consequence of augmented chest wall difference resistance and Est,rs as a result of higher Est,w.

Airway Resistance↗
PubMed1992

Respiratory system mechanics in patients treated with isotonic or hypertonic NaCl solutions.

Twenty-one patients who underwent elective surgery for coronary artery bypass were studied right after chest wall closure. They were anesthetized, paralyzed, and artificially ventilated with a constant-flow ventilator. Airflow, changes in lung volume, and tracheal pressure were measured. Respiratory system resistance (Rrs,max) was partitioned into its homogeneous (Rrs,min) and uneven (Rrs,u) components. Respiratory system elastance (Ers) was also measured. The subjects were randomly divided into two groups injected with test solutions just after chest wall closure: eleven patients received isotonic saline (0.9% NaCl solution), whereas the remaining ten were injected with hypertonic saline (7.5% NaCl solution). In all patients, mechanical parameters were measured at six different times: just before infusion, at 5 and 10 min (end of infusion); and at 15, 20, and 25 min after beginning of injection. No statistically significant differences were observed in respiratory system mechanical parameters between groups or between different times within each group. Our data suggest that hypertonic saline infusion does not result in significant changes in respiratory system mechanics in patients submitted to coronary artery bypass.

Adult↗
PubMed1991

Small bowel bacterial overgrowth in strongyloidiasis.

Small bowel bacterial growth was studied in patients with strongyloidiasis, and the results were compared to controls. We concluded that in strongyloidiasis there is small bowel bacterial overgrowth, and so it should be considered in the pathogenesis of some of the gastrointestinal manifestations and complications of strongyloidiasis.

Adolescent↗
PubMed1990

The surface free energy of Leishmania mexicana amazonensis.

Surface charge of Leishmania mexicana amazonensis was investigated by direct zeta-potential determination and ultrastructural cytochemistry, and its surface tension was studied by measurements of the advancing contact angle formed by the parasite monolayers with drops of liquids of different polarities. Both virulent and avirulent promastigotes exhibited negatively charged surfaces with a zeta-potential of about -15 mV. Treatment of these cells with trypsin, alkaline phosphatase, or phospholipase C rendered their surfaces less negatively charged, whereas neuraminidase did not alter the parasite negativeness. Cytochemically, we could observe a reduction in the cationized ferritin binding after the parasite treatment with each of the former enzymes, but not with neuraminidase. The surface free energy of parasites was calculated by taken to account the London dispersion, the Keeson dipole-dipole, and the Debye dipole-induced forces, as well as the surface polarity of the parasites and their zeta-potentials, by considering their adhesion to polystyrene surfaces. The delta G values of -6.4 and -18.1 mJ.m-2 were obtained for avirulent and virulent promstigotes, respectively.

Alkaline Phosphatase↗
PubMed1990

Influence of inorganic lead on the biochemical blood composition of the eel, Anguilla anguilla L.

Yellow eels (Anguilla anguilla L.) with an average weight of 50 g were caught in September in the Aveiro Lagoon on the Portuguese West Coast and kept in aerated aquaria for 1 week before the experiment started. The eels were exposed to an inorganic lead concentration of 300 micrograms Pb/liter for 30 days. Differential white blood cell count showed an increase in the number of lymphocytes in exposed fish. Blood hemoglobin and number of red blood cells per cubic millimeter showed no differences between the control and the exposed fish. Biochemical analyses of blood composition, such as plasma glucose, total plasma protein, total plasma cholesterol, and sodium and potassium plasma, showed no differences between treated and control animals. Plasma lactate levels increased in treated animals compared with those in controls.

Animals↗
PubMed1990

Metabolic effects of kraft mill effluents on the eel Anguilla anguilla L.

Yellow eels (Anguilla anguilla L.) with an average weight of 60 g were used in this experiment. The fish were caught in June/July at the Aveiro Lagoon on the Portuguese West Coast, transported to the Department of Biology, Aveiro University, and kept in aerated aquaria for 1 week before the experiment started. The eels were then exposed for 1 and 3 weeks to 75 and 50% of the kraft pulp mill effluent. The eels exposed to the kraft pulp mill effluent developed an increase in red blood cell number per cubic millimeter and several biochemical changes, such as an increase in plasma lactate and sodium and a decrease in plasma pyruvate and potassium. Histological examination of the experimental eels exposed to the 50% kraft pulp mill effluent revealed deep alteration of the tissue structure, such as disruption of the skin and edematous hypertrophy of covering epithelial cells in secondary gill lamellae. The kidney had damage of the renal tubules. The liver developed necrosis supported by a significant decrease in GOT and GPT activity. The spleen had an increase in blood content as well as in pigment centers. Previous results indicated the kraft pulp mill effluent causes tissue damage and consequent metabolic changes in the eel Anguilla anguilla L.

Alanine Transaminase↗
PubMed1990

Erythema multiforme associated with autoreactivity to 17 alpha-hydroxyprogesterone.

We report a case of a 23-year-old woman who was afflicted with disseminated skin erythema multiforme-like eruptions that started at the menarche, relapsed at the premenstrual periods, dramatically spread during two pregnancies and cleared after abortion; the skin lesions responded dramatically to thalidomide treatment. A high-affinity binding factor to 17 alpha-hydroxyprogesterone (17-OHP) was found in the serum of this patient. Her lymphocytes did not proliferate in vitro after exposure to exogenous 17-OHP but showed significant chromatin activation. There was a decreased expression of HLA antigens at the surface of the patient's blood lymphocytes. This is a unique well-documented case of erythema multiforme most possibly due to autoreactivity to 17-OHP; the precise mechanism(s) of this autoreactivity has not been established.

17-alpha-Hydroxyprogesterone↗
PubMed1989

The effect of short-wavelength ultraviolet light on antigens, lectin receptors and the ultrastructure of Crithidia fasciculata.

Crithidia fasciculata is an important trypanosomatid parasite commonly affecting insects and is used extensively as a model for the study of the biochemistry, ultrastructure and organization of the kDNA network of trypanosomatids. The present study describes the evolution of UV-induced morphological changes detectable by transmission electron microscopy in Crithidia fasciculata. Although only rare and minor changes in kinetoplast DNA were demonstrable 7 h after UV irradiation, alterations of this organelle were present in almost all flagellates observed 24 h and 48 h after irradiation. Other cell structures were apparently undamaged. Ultrastructural changes in kDNA did not correspond to changes in antigenicity of protein bands in western blotting against serum from Chagas' disease patients or in the presence of 3 different lectin receptors on the surface of the parasite.

Animals↗
PubMed1989

[Syphilitic aneurysm communicating with an aortic sinus of Valsalva. A case report].

The authors present the case of a 27-year old woman with an aneurysm, possibly originating from an ectopic coronary sprout and communicating with the right anterior sinus of Valsalva. Secondary syphilitic lesions were observed. By virtue of its great size and localization, this aneurysm produced obstruction of the outlet of the right ventricle and dislocation of the left coronary artery. The authors conclude that this aneurysm was a congenital anomaly because of its great volume, configuration, the way it opened in the aortic right anterior sinus of Valsalva, the normal aortic wall and valve, and normal sinuses of Valsalva, observed at surgery. The follow-up was uneventful.

Adult↗
PubMed1988

Mapping of the rib5 gene in Saccharomyces cerevisiae using UV light as an enhancer of rad52-mediated chromosome loss.

Rib5 mutants of S. cerevisiae are blocked at the end of the riboflavin biosynthetic pathway. Using UV light to increase rad52-mediated chromosome loss, we have assigned the rib5 mutation to chromosome II. Tetrad analysis of crosses between rib5 and other markers on chromosome II shows that the RIB5 gene is located on the right arm of this chromosome, closely linked to HIS7.

Chromosome Mapping↗