Search PubMed⌕ Search

Biomedical subjects

M Santos

Publications and source records attributed to M Santos.

At least 55 records · Page 3Linked to original sources
PubMed2001

Characterization of the gdhA gene from the phytopathogen Botrytis cinerea.

A 3.48-kb DNA region containing the gdhA gene, which codifies the NADP-dependent glutamate dehydrogenase enzyme from Botrytis cinerea, has been cloned and characterized. A fragment of 2351 nucleotides was sequenced and found to contain an ORF of 1350 bp that encodes a protein of 450 amino acids. The gene, containing two introns that showed polymorphic size between them, was located by pulsed-field gel electrophoresis in chromosome X in seven strains, which were isolated from several hosts and had different levels of pathogenesis. The protein was similar to the gdhA of various other organisms, with nine highly conserved motifs that included the known active site sequence. The cloned gene was proven to be functional since it complemented two different Aspergillus nidulans gdhA mutants, restoring high levels of NADP-dependent glutamate dehydrogenase activity to the transformants. gdhA was transcribed as a monocistronic transcript of 1.7 kb starting at an A or a T, located 40 or 47 bp, respectively, upstream from the initial ATG codon of the ORF. Transcription levels of the gdhA gene were high during the rapid growth phase. Very high expression levels of the gdhA gene were observed in media with asparagine as the nitrogen source, whereas glutamic acid repressed transcription of the gdhA gene. Similarly high levels of gdhA gene transcription were observed in media with acetate as the carbon source, while glycerol strongly repressed gdhA gene transcription. These results indicate that expression of the gdhA gene is subject to strong nitrogen and carbon regulation at the transcriptional level.

Amino Acid Sequence↗
PubMed2001

Immunogold localization of a transglutaminase related to grana development in different maize cell types.

A comparative study of the subcellular localization of a plant transglutaminase (TGase; EC 2.3.2.13) in various in vivo and in vitro maize cell types was carried out with a polyclonal antibody raised against a 58 kDa TGase purified from Helianthus tuberosus leaves. Immunocytochemical staining, followed by electron microscopy, showed that this enzyme was markedly present in the grana-appressed thylakoids of mature chloroplasts of the light-exposed cells. Moreover, during embryogenic callus chloroplast differentiation, the abundance of TGase in the grana-appressed thylakoids depended on the degree of grana development and was greater than in mature leaf chloroplasts. In addition to the 58 kDa form, two other forms of the protein (of 77 and 34 kDa) were obtained by Western blot. The 77 kDa form might correspond to the inactive form and was immunodetected in dense vesicles observed in dark-grown embryogenic callus cells. In adult leaves, the enzyme was also markedly present in the grana-appressed thylakoids of the mesophyll cell chloroplasts, though very scarce and dispersed in the bundle-sheath cell chloroplasts (which do not contain grana). The concordance of these localizations with those described for the light-harvesting antenna proteins of the photosystem II suggests that it is possible that this TGase has a functional role in photosynthesis, perhaps modulating the photosynthetic efficiency and the absorption of excess light by means of polyamine conjugation to the antenna proteins.

Immunoblotting↗
PubMed2001

Accessory spleen torsion: US, CT and MR findings.

Torsion of an accessory spleen is a very unusual entity that can appear with abdominal pain associated with the presence of an avascular mass. We report the case of a 13-year-old boy with torsion and infarction of an accessory spleen presenting as a painful abdominal mass in which imaging examination with US, CT and MR showed a large avascular mass in the upper left abdomen.

Abdominal Pain↗
PubMed2001

Exposure of workers in mineral processing industries in Brazil.

The mining, milling and processing of uranium and thorium bearing minerals may result in radiation doses to workers. A preliminary survey pilot program, that included six mines in Brazil (two coal mines, one niobium mine, one nickel mine, one gold mine and one phosphate mine), was launched in order to determine the need to control the radioactive exposure of the mine-workers. Our survey consisted of the collection and analysis of urine samples, complemented by feces and air samples. The concentrations of uranium, thorium and polonium were measured in these samples and compared to background data from family members of the workers living in the same dwelling and from residents from the general population of Rio de Janeiro. The results from the coal mines indicated that the inhalation of radon progeny may be a source of occupational exposure. The workers from the nickel, gold and phosphate mines that were visited do not require a program to control internal radiological doses. The niobium mine results showed that in some areas of the industry exposure to thorium and uranium might occur.

Brazil↗
PubMed2001

[Environmental mycobacterial diseases in patients with and without HIV infection: epidemiology and clinical course].

The objective of the present study was to ascertain the clinical features, risk factors, microbiologic spectrum and course of disease after treatment of infections by environmental mycobacteria (EM) in patients with and without HIV infection in our community. Eighty-eight patients with diseases caused by EM diagnosed between 1989 and 1997 were studied; 46 (52.7%) were HIV-positive. Mycobacterium kansasii was the most prevalent pathogen (54%) overall, followed by M. avium complex (40%). However, M. avium complex was most prevalent among HIV-positive patients (61%) and M. kansasii was most prevalent among HIV-negative patients (76%). Localized lung infections were most common among HIV-negative patients, whereas 74% of HIV-positive patients had disseminated disease. Among HIV-negative patients, chronic obstructive pulmonary disease and corticosteroid use were common associations. Pulmonary disease was subacute and non-specific in both patient groups, whereas abdominal pain was the first symptom of most patients with disseminated disease. On the chest films of 76% of the HIV-negative patients, we observed cavitation and infiltrates; 60% of HIV-negative patients had normal x-rays. No differences in antibiotic sensitivity were observed between strains from HIV-positive and HIV-negative patients. The prognosis was good in the HIV-negative group with combined therapy with 2 to 4 first-line antituberculous drugs, whereas response was poor in HIV-positive patients in spite of prolonged treatment with 3 to 5 drugs. Nevertheless, thanks to the highly effective anti-retroviral treatment of recent years, we seem to be observing improved response to therapy with less aggressive forms of EM disease.

Adult↗
PubMed2001

Identification and sequence characterization of a novel HLA-A11 serological variant (HLA-A*1108).

In this report we describe the identification of a novel HLA-A*11 allele, HLA-A*1108, found in two individuals of a Spanish family. This new allele was detected during routine HLA typing by an atypical serological reactivity pattern and by inconclusive patterns obtained in DNA-based typing methods. The nucleotide sequence of exons 2 and 3 of HLA-A*1108 was identical to HLA-A*11011 except for two nucleotide substitutions at codons 152 (GCG-->GAG) and 156 (CAG-->CGG). These mutations change the non-charged amino acid alanine, at codon 152, to negative glutamic acid, and also non-charged glutamine, at codon 156, to positive arginine, which may explain its anomalous serological reactivity.

Alleles↗
PubMed2001

Identification of a new HLA-DRB1*04 allele, DRB1*0437.

In this report we describe the identification of a novel DRB1*04 allele, DRB1*0437, found in a Spanish individual. The routine HLA typing, in the context of bone marrow transplantation, by polymerase chain reaction-sequence-based typing (PCR-SBT) made possible the identification of this new allele. This allele is identical to DRB1*0402 except for a single nucleotide substitution at position 286 (A-->C), changing the encoded Isoleucine to a Leucine. The DRB1*0437 allele conserves the same two acidic residues at codons 70 and 71 that confer to DRB1*0402 its association to some autoimmune diseases.

Alleles↗
PubMed2001

Identification of a novel HLA-DQB1*06 allele, DQB1*0618.

We report here the identification of a novel DQB1*06 allele, DQB1*0618, found in a bone marrow donor. The new allele was detected during routine DNA-based HLA typing by an ambiguous pattern of probe hybridization, obtained by polymerase chain reaction using sequence-specific oligonucleotides (PCR-SSO). Molecular cloning and sequencing confirmed that the new allele is identical to DQB1*0609 at exon 2 except for 3 nucleotide substitutions at positions 353, 356 and 367, also found in other alleles. These nucleotide changes may explain its anomalous reactivity.

Alleles↗
PubMed2001

Optical aggregometry versus the PFA-100: experimental studies in pigs treated with propofol.

An experimental study of platelet aggregation was performed in 22 male Landrace x Large-White crossbred pigs treated with propofol at different doses, to compare the results of optical aggregometry with those of the PFA-100 (Dade Int., Miami, FL, USA), a new platelet function analyzer. Platelet aggregation was analyzed in basal blood samples by both methods, after which the pigs were divided into three groups: G1, anaesthetic induction with propofol (2 mg/kg intravenously (i.v.)); G2, anaesthetic induction with propofol (2 mg/kg i.v.), followed by a second dose of 1.5 mg/kg; and G3, anaesthetic induction with propofol (2 mg/kg i.v.), followed by 1 h of continuous i.v. infusion at 13 mg/kg/h. Four minutes after propofol injection, blood samples were again taken from each group and studied by both methods. In groups G2 and G3, both methods showed reduced platelet aggregation, while in group G1 neither evidenced an anti-aggregating effect of propofol. Under our experimental conditions: (1) the propofol effect on platelet aggregation depends on the plasma concentration; (2) the results obtained with the two methods are comparable; (3) PFA-100 may provide an alternative to optical aggregometry for detecting the effects of anaesthetic agents ex vivo.

Adenosine Diphosphate↗
PubMed2001

Sequence and chromosomal context effects on variegated expression of keratin 5/lacZ constructs in stratified epithelia of transgenic mice.

The expression of transgene loci in mammals often occurs in a heterocellular fashion resulting in variegated patterns of expression. We have examined the effect of chromosomal integration site, copy number, and transcriptionally activating sequences on the variegation of a keratin 5-lacZ (K5Z) construct in the stratified epithelia of transgenic mice. lacZ expression in these mice is always mosaic, and the beta-gal activity per cell is usually higher in the lines with a higher proportion of expressing cells. Similar constructs, in which cDNAs were exchanged by lacZ sequences, showed no variegation. Also, when a strongly active, nonvariegating construct was coinjected with K5Z, most transgenic lines showed an almost homogeneous lacZ expression. The comparison of transgene arrays of different copies inserted at the same locus (obtained by using a lox/Cre system) showed that the reduction of copy number does not lead to an increase in the proportion of cells that express the transgene. Finally, in most of the variegating or nonexpressing lines the transgenes were located both at intermediate positions and at peritelomeric regions in the long chromosome arms. These findings suggest that the probability and efficiency of expression of K5Z genes depend on both long range chromosomal influences and on sequences in the transgene array.

Animals↗
PubMed2001

Characterization of GFAP expression and cell proliferation in the rat median eminence following hypophysectomy.

To analyze whether the reorganization of the rat median eminence after hypophysectomy might be related to changes in glial fibrillary acidic protein (GFAP)- and cellular proliferation, the distribution of cells immunoreactive for GFAP and the proliferation rate of such cells were analyzed at 20, 40 and 60 days posthypophysectomy. For this study, four rostro-caudal regions of the median eminence were differentiated: the retrochiasmatic, preinfundibular, infundibular and postinfundibular regions. In each of these regions, three layers were studied: the ependymal, the internal and the external. At 20 and 40 days after hypophysectomy, significant increases in cellular proliferation affecting all three layers studied in the preinfundibular and infundibular regions were found. At the same time points, increases in GFAP expression were also observed. However, after 60 days, GFAP and proliferative cellular nuclear antigen (PCNA) expression decreased. Although variations of PCNA and GFAP levels were evident, no colocalisation of PCNA and GFAP was found in the cells of the median eminence in untreated or hypophysectomized rats when sections were analyzed by double immunohistochemical staining. Our results suggest that reorganization of median eminence involves alterations (or modulation) of GFAP-immunoreactive cells together with a proliferation of cells that are not GFAP-immunoreactive. This study also demonstrates that this reorganization is completed within the first two months after hypophysectomy.

Animals↗
PubMed2000

First asymmetric hetero Diels-Alder reaction of 1-sulfinyl dienes with nitroso derivatives. A new entry to the synthesis of optically pure 1,4-imino-L-ribitol derivatives.

Hetero Diels-Alder (HDA) cycloaddition of chiral 1-p-tolylsulfinyl-1,3-pentadiene with benzyl nitrosoformate, under mild conditions, yields 2H-1,2-oxazine 3 with complete regioselectivity and pi-facial diastereoselectivity. Sequential osmylation and protection of the resulting glycol gives the oxazine 5 which is directly transformed into enantiomerically pure 1,4,5-trideoxy-1,4-imino-L-ribitol 8 by reduction under Pd/C.

Cyclization↗
PubMed2000

Effect of propranolol on the factors promoting bacterial translocation in cirrhotic rats with ascites.

Bacterial translocation appears to be an important mechanism in the pathogenesis of spontaneous infections in cirrhosis. Cirrhotic patients are commonly treated with beta-adrenoceptor blockers, but the impact of this treatment in the factors promoting bacterial translocation has not been investigated. This study was aimed at investigating in cirrhotic rats with ascites the effect of propranolol on intestinal bacterial load, transit, and permeability of the bowel and on the rate of bacterial translocation. Bacterial translocation to mesenteric lymph nodes and intestinal bacterial overgrowth, permeability (urinary excretion of (99m)Tc-diethylenetriaminepentaacetic acid [(99m)Tc-DTPA]), and transit (geometric center ratio of (51)Cr) were assessed in 29 rats with carbon tetrachloride (CCl(4)) cirrhosis and 20 controls. These variables were then measured in 12 placebo- and in 13 propranolol-treated ascitic cirrhotic rats. Bacterial translocation was present in 48% of the cirrhotic rats and in none of the controls. Cirrhotic rats with intestinal bacterial overgrowth had a significantly higher rate of translocation and slower intestinal transit than those without it. Among the 15 rats with overgrowth and a (99m)Tc-DTPA excretion greater than 10%, 15 had translocation and 2 had bacterial peritonitis. Only 1 of the 14 rats with either intestinal overgrowth or a (99m)Tc-DTPA excretion greater than 10% presented translocation. Compared with the placebo group, propranolol-treated animals had significantly lower portal pressure, faster intestinal transit, and lower rates of bacterial overgrowth and translocation. In ascitic cirrhotic rats, bacterial translocation results from intestinal overgrowth and severe damage to gut permeability. In this setting, intestinal overgrowth is associated with intestinal hypomotility. Propranolol accelerates the intestinal transit, decreasing the rates of bacterial overgrowth and translocation.

Animals↗
PubMed2000

Clinical and molecular studies in three Portuguese mtDNA T8993G families.

The T8993G mutation in the mitochondrial DNA adenosine triphosphatase 6 gene represents an important cause of maternally inherited Leigh's syndrome. Reported are the clinical findings and mutational loads in three Portuguese T8993G pedigrees. Polymerase chain reaction-restriction fragment length polymorphism analyses demonstrated the T8993G mutation in a high percentage of tissues from all patients (97% +/- 2.3%), but it was less abundant in the blood from 14 maternal relatives. The disease progressed severely in the probands but did not have the fatal course reported by others. To test whether this prolonged course was related to the presence of a specific, disease-associated haplogroup the origin of the mutational event in Portugal was traced. Haplotype investigation revealed an independent occurrence of the mutation in the three probands. These analyses represent the first molecular characterization of Portuguese patients with Leigh's syndrome.

Adenosine Triphosphatases↗