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Biomedical subjects

C L Santos

Publications and source records attributed to C L Santos.

At least 37 records · Page 2Linked to original sources
PubMed1999

Thyrotropin receptor mutations in hyperfunctioning thyroid adenomas from Brazil.

Constitutively activating mutations in the thyrotropin (TSH) receptor have been identified as a major molecular cause of hyperfunctioning thyroid adenomas. A smaller subset of these benign tumors is caused by constitutive activation of the adenylyl cyclase cascade by somatic mutations in the Gsalpha gene. In this study, we analyzed hyperfunctioning thyroid adenomas from seven Brazilian patients for TSH receptor and G(s)alpha gene mutations. Solitary autonomous thyroid adenomas were identified by ultrasound and scintigraphy, and DNA was extracted from adenomatous and periadenomatous tissue. Exons 9 and 10 of the TSH receptor gene, and exons 8 and 9 of the G(s)alpha gene, were amplified by polymerase chain reaction (PCR) and subjected to direct sequence analysis. Six of seven adenomas harbored heterozygous mutations known to confer constitutive activity to the TSH receptor. In one case, aspartate 619 was substituted by glycine (D619G). In four adenomas, alanine 623 was replaced by valine (A623V). Both residues are located in the third intracellular loop. In one instance, aspartate 633 located in the sixth transmembrane domain was replaced by tyrosine (D633Y). In this patient, one allele also contained a change of aspartate 727 to glutamate (D727E). This substitution is thought to be a polymorphic variant of the wild-type but it has also been associated with toxic multinodular goiters. Functional comparison of D727 with E727 did not reveal differences in basal or TSH-stimulated cyclic adenosine monophosphate (cAMP)-dependent luciferase activity in transiently transfected cells. These results demonstrate a high prevalence of activating TSH receptor mutations in toxic adenomas in this small series from Brazil (approximately 86%). These findings are in agreement with reports from other countries with a marginal iodine intake but contrast with studies from regions with a high iodine intake where these mutations appear to be less prevalent.

Adenoma↗
PubMed1999

Phenocopies for deafness and goiter development in a large inbred Brazilian kindred with Pendred's syndrome associated with a novel mutation in the PDS gene.

Pendred's syndrome is an autosomal recessive disease characterized by goiter, impaired iodide organification, and congenital sensorineural deafness. The gene mutated in Pendred's syndrome, PDS (Pendred's syndrome gene), was cloned very recently and encodes the putative sulfate transporter pendrin. Pendred's syndrome may account for up to 10% of the cases with hereditary hearing loss, and pendrin mutations have also been found in a kindred with non-syndromic deafness. In this study, 41 individuals from a large, highly inbred pedigree from Northeastern Brazil were examined for features of Pendred's syndrome. Linkage studies and sequence analysis of the coding region of the PDS gene were performed with DNA from 36 individuals. The index patient, with the classical triad of deafness, positive perchlorate test, and goiter, was found to be homozygous for a deletion of thymidine 279 in exon 3, resulting in a frameshift and a premature stop codon at amino acid 96. This alteration resulted in truncation of the protein in the first transmembrane domain. Two other patients with deafness were found to be homozygous for this mutation; 19 were heterozygous and 14 were homozygous for the wild type allele. Surprisingly, 6 deaf individuals in this kindred were not homozygous for the PDS gene mutation; 3 were heterozygous and 3 were homozygous for the wild type allele, suggesting a probable distinct genetic cause for their deafness. All 3 homozygous individuals for the PDS mutation had goiters. However, goiters were also found in 10 heterozygous individuals and in 6 individuals without the PDS mutation and are most likely caused by iodine deficiency. In conclusion, we identified a novel mutation in the PDS gene causing Pendred's syndrome. The comparison of phenotype and genotype reveals, however, that phenocopies generated by distinct environmental and/or genetic causes are present in this kindred and that the diagnosis of Pendred's syndrome may be difficult without molecular analysis.

Adult↗
PubMed1998

Metastatic thyroid carcinoma arising from congenital goiter due to mutation in the thyroperoxidase gene.

A very large cervical tumor that extended to the upper mediastinum was seen in a newborn after an uneventful pregnancy. The computed axial tomography scan confirmed the presence of a solid mass with precise limits and scattered foci of calcifications situated in the anterolateral region of the neck. The infant underwent thyroidectomy on the seventh day after birth. Pathological examination revealed a follicular carcinoma of the thyroid and probable dyshormonogenetic hyperplastic goiter. At 5 months of age, whole body scans indicated the presence of lung and bone metastases, which were treated with therapeutic doses of radioiodine. Genomic DNA was obtained from the newborn, her parents, her paternal aunt, and her paternal grandparents. Denaturing gradient gel electrophoresis analysis of PCR fragments corresponding to exon 14 of the thyroid peroxidase (TPO) gene indicated the presence of a mutant TPO allele present in the propositus, her father, and her paternal grandmother. Sequencing of the TPO gene demonstrated a mutation resulting from an insertion of a single extra cytosine in a stretch of seven cytosines at positions 2505-2511. The insertion caused a frame shift and a stop signal in exon 16. This sequence would translate into a structurally modified and probably inactive TPO protein. We conclude that the aggressive thyroid metastatic carcinoma arose from a dyshormonogenetic goiter caused by a defective TPO protein.

Bone Neoplasms↗
PubMed1997

Anomalous patterns of nitroimidazole binding adjacent to necrosis in human glioma xenografts: possible role of decreased oxygen consumption.

In contrast to reports of extensive hypoxia in human gliomas in situ measured by pO2 histography, non-invasive methods of assessing glioma oxygenation, including nitroimidazole binding, have yielded surprisingly contradictory results. In order to investigate the relationship of necrosis, hypoxia, nitroreductase activity and cellular respiration in human gliomas, subcutaneous models using the human glioma cell lines M059K, M006 and M010b were developed in the murine SCID host. Intracranial growth of the M006 line was achieved in nude rats. The nitroreductive capacity of glioma cell lines was assessed and found to be similar to transplanted tumours previously reported in the literature. This suggests that if substantial numbers of viable hypoxic cells were present in situ in gliomas, then nitroimidazole-binding techniques should be capable of identifying them. Inter-tumour variability in the amount of necrosis was seen. M006 xenografts growing in subcutaneous and intracranial sites revealed extensive necrotic regions histologically, some of which were surrounded by cells labelled heavily for [3H]misonidazole, while other areas were lightly labelled. Similar binding patterns were seen for subcutaneous M059K tumours, while subcutaneous M010b tumours display necroses of which almost all were surrounded by heavily labelled cells. The oxygen consumption rates of tumour cell lines grown in vivo, in which venous pO2 concentrations are of the order of 2-5%, were two to sevenfold less than those of the same lines grown as monolayers in vitro under oxygen concentrations of 18%. We postulate that glioma cell lines behave as 'oxygen conformers', in that their rate of oxygen consumption appears to vary with the availability of oxygen. Together with the misonidazole-binding data, the results in this glioma tumour model are consistent with coordinate inhibition or down-regulation of respiration under moderate hypoxia.

Animals↗
PubMed1994

Regulation of vitronectin receptor expression by retinoic acid on human melanoma cells.

The integrin family of adhesion receptors is likely to be important for tumor cell invasion and dissemination. We have studied the effects of the differentiating agents retinoic acid on integrin expression by the human melanoma cell line MeWo. Our results show that this agent inhibits cellular proliferation, increases melanin content and induces morphological changes in MeWo cells. Functionally, these alterations are associated with an enhanced adhesion to matrix protein vitronectin and higher levels of expression of vitronectin receptor on the cell surface. This is accompanied by increased levels of alpha v integrin mRNA. Although the mechanism by which retinoic acid regulates the expression of vitronectin receptor in MeWo cells needs further examination, this system may represent a good model for understanding the role of this receptor in melanoma progression, as well the molecular basis for retinoic acid therapy in these tumors.

Blotting, Northern↗
PubMed1994

Adhesion to laminin is down-regulated upon retinoic acid-induced F9 cell differentiation: a role for alpha 6/beta 1 integrin.

F9 mouse teratocarcinoma cells have a high capacity to adhere to laminin and we identified alpha 6/beta 1 integrin as the principal laminin-binding protein present in these cells. F9 cells differentiated into parietal endoderm when monolayer cultures were treated with retinoic acid and dibutyryl cyclic AMP. In this process a decreased adherence to laminin was observed due to a lower expression of alpha 6/beta 1 integrin on the cell surface.

Animals↗
PubMed1993

[Atrial septostomy at the intensive care unit under echocardiographic monitoring. Initial experience of the Heart Institute of Pernambuco].

The present article describes the initial experience of the Instituto do Coração de Pernambuco, at the neonatal intensive care unit, with the performance of Rashkind atrioseptostomy under two-dimensional echocardiographic control, through percutaneous venous approach (right femoral vein catheterization), under local anaesthesia, in three cases, two neonates with transposition of the great arteries and one with tricuspid atresia. In two children the procedure was successful both technically and haemodynamically. In the third child, aged 36 days, the atrial septum was thickened not allowing for satisfactory withdraw. In none of the three cases significant complications were observed during the procedure. Despite of the small number of patients, our experience showed that this new approach to the performance of Rashkind atrioseptostomy is feasible without major complications to the neonate and with advantages over the conventional technique.

Cardiac Catheterization↗
PubMed1992

[Tricuspid valve endocarditis in children].

Four children, three males, with ages 5, 1, 16 and 6 years, presented with isolated tricuspid valve endocarditis. Two of them were submitted to surgical treatment. Sepsis, cardiac murmur and heart failure were present in all of them. Three presented pulmonary embolism. Echocardiography demonstrated vegetation in the tricuspid valve in all cases. Two patients, one of them submitted to surgery, died. Tricuspid valve endocarditis in children with sepsis, heart failure and pulmonary embolism is a severe condition and early surgical treatment may diminished the high mortality.

Adolescent↗
PubMed1991

Nucleotide sequence of a variant protein A of Staphylococcus aureus suggests molecular heterogeneity among strains.

Protein A is a cell wall linked protein of Staphylococcus aureus that binds mammalian IgG. Although protein A displays high size heterogeneity among strains, cloning and sequencing of its gene from two strains had not shown a large difference in size. Here we report a third protein A gene sequence that shows a size variation relative to these two, due to deletions on both one IgG binding domain and a cell wall binding domain (region X). By analysis of the three sequences we were able to delineate a hypothetic model for region X domain evolution and discussed the origin of genetic variability within and without strains.

Amino Acid Sequence↗
PubMed1991

Differences in human laminin B2 sequences.

A cDNA clone encoding the B2 chain of laminin has been isolated from a human endothelial lambda gt11 cDNA library. The nucleotide and deduced amino acid sequences of the clone were determined and showed one amino acid substitution (Ser1519 instead of Asn) when compared to lung laminin B2 chain and one silent nucleotide change (G4200 instead of A) in relation to the human placenta laminin B2 chain. Other differences in the 3'-untranslated region were also found.

Amino Acid Sequence↗
PubMed1987

A direct method for cDNA cloning employing translation-released mRNA.

1. A new cloning procedure is described for cDNA synthesis from mRNA released by in vitro translation of polysomes in a cell-free amino acid incorporating system. The usefulness of the method lies in the feasibility of employing nanogram amounts of mRNA. 2. Complementary DNA is synthesized directly in the translation mixture simply by adjusting the concentration of some components and removing ribosomes by boiling and centrifugation. 3. As an example, we report here the construction and characterization of a cDNA clone corresponding to chick alpha(I)procollagen starting from a collagen-synthesizing polysome fraction obtained from chick embryos.

Amino Acyl-tRNA Synthetases↗
PubMed1983

In vitro synthesis of Trypanosoma cruzi antigenic polypeptides.

A ribosomal fraction of Trypanosoma cruzi was isolated with detergent lysis and differential ultracentrifugation. This ribosomal fraction directed in vitro protein synthesis, in a heterologous incorporation system (rat liver pH 5 fraction), leading to values up to 10 times higher than endogenous control. The ideal concentrations of Mg2+, K+, and ribosomal proteins and the time of incubation of the incorporation mixtures were 6 mM, 21 mM, 60 microliters, and 45 min, respectively. The product thus obtained was analyzed by fluorography after polyacrylamide-sodium dodecyl sulfate gel electrophoresis and showed the presence of many protein bands, but few bands were present in the immunoprecipitate obtained with serum from Chagas' disease patients. This product was able to react with anti-T. cruzi antibodies when submitted to an immunoenzymatic assay.

Animals↗
PubMed1975

New syndromes of mental retardation.

During a survey of a selected group of residents of an institution for the mentally retarded, four previously undescribed syndromes were found. They were characterized as follows: cerebral maldevelopment, dwarfism and cataracts (autosomal recessive inheritance); cerebral maldevelopment, dwarfism and facial osteoproliferation (autosomal recessive inheritance); cerebral maldevelopment and colobomata (autosomal recessive inheritance); and cerebral maldevelopment and acrocephaly (X-linked recessive inheritance).

Abnormalities, Multiple↗
PubMedDate not supplied

First isolation of dengue 3 in Brazil from an imported case.

The authors report the isolation of dengue 3 virus for the first time in Brazil. The patient, resident in Limeira-SP, traveled to Nicaragua on May 16th, 1998, where he stayed for two months. Starting on August 14 th he had fever, headache, myalgia, arthralgia, retro-orbital pain and diarrhea. He returned to Brazil on August 16th and was hospitalized in the next day. The patient had full recovery and was discharged on August 20th. The virus was isolated in C6/36 cell culture inoculated with serum collected on the 6th day after the onset of the symptoms. The serotype 3 was identified by indirect immunofluorescence assays performed with type-specific monoclonal antibodies. This serotype was further confirmed by polymerase chain reaction analysis. The introduction of a new dengue serotype in a susceptible population is a real threat for the occurrence of severe forms of the disease. The isolation and identification of dengue virus are important in order to monitoring the serotypes circulating in Brazil and to take the measures necessary to prevent and control an epidemic.

Brazil↗