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Biomedical subjects

A C Barros

Publications and source records attributed to A C Barros.

12 recordsLinked to original sources
PubMed1999

Mice devoid of all known thyroid hormone receptors are viable but exhibit disorders of the pituitary-thyroid axis, growth, and bone maturation.

Thyroid hormone (T3) has widespread functions in development and homeostasis, although the receptor pathways by which this diversity arises are unclear. Deletion of the T3 receptors TRalpha1 or TRbeta individually reveals only a small proportion of the phenotypes that arise in hypothyroidism, implying that additional pathways must exist. Here, we demonstrate that mice lacking both TRalpha1 and TRbeta (TRalpha1(-/-)beta-/-) display a novel array of phenotypes not found in single receptor-deficient mice, including an extremely hyperactive pituitary-thyroid axis, poor female fertility and retarded growth and bone maturation. These results establish that major T3 actions are mediated by common pathways in which TRalpha1 and TRbeta cooperate with or substitute for each other. Thus, varying the balance of use of TRalpha1 and TRbeta individually or in combination facilitates control of an extended spectrum of T3 actions. There was no evidence for any previously unidentified T3 receptors in TRalpha1(-/-)beta-/- mouse tissues. Compared to the debilitating symptoms of severe hypothyroidism, the milder overall phenotype of TRalpha1(-/-)beta-/- mice, lacking all known T3 receptors, indicates divergent consequences for hormone versus receptor deficiency. These distinctions suggest that T3-independent actions of T3 receptors, demonstrated previously in vitro, may be a significant function in vivo.

Age Factors↗
PubMed1998

Absence of thyroid hormone receptor beta-retinoid X receptor interactions in auditory function and in the pituitary-thyroid axis.

THYROID hormone receptor beta-deficient (TRbeta-/-) mice have defective auditory-evoked brain stem responses (ABR). Since in vitro, TRbeta binds to DNA as homodimers or as heterodimers with retinoid X receptors (RXRs), we investigated whether the TRbeta-/- phenotype may reflect loss of RXR-TRbeta heterodimer or TRbeta homodimer function. Normal ABR thresholds were recorded in RXRbeta-/-, RXRgamma-/-, RXRalpha-/+ and RXR compound mutant mice. When RXR mutations were introduced onto TRbeta-/+ or TRbeta-/- backgrounds, thresholds were dictated solely by TRbeta and not RXR genotype. TRbeta-/-mice also over-produce thyroid hormones and thyroid stimulating hormone; however, levels of these hormones were unaltered by RXR mutations. This suggests that, contrary to in vitro models, RXRs may be dispensable and that TRbeta may function in vivo by an RXR-independent mechanism in the auditory system and pituitary-thyroid axis.

Acoustic Stimulation↗
PubMed1994

Local effects induced by venoms from five species of genus Micrurus sp. (coral snakes).

Venoms from five species of Micrurus (coral snakes) from Brazil (Amazonas State) were tested for the following effects: edematogenic, myotoxic, coagulant, hemorrhagic and phospholipase A2 (PLA2) detection. None of the venoms tested presented coagulant activity. The presence of PLA2 was detected by ELISA in the venoms of M. spixii, M. averyi and M. lemniscatus. The myotoxicity was estimated by the increase in the serum creatine kinase level and by histological analysis. All venoms, except that from M. surinamensis, induced intense edematogenic and myotoxic effects. The venom of M. averyi showed hemorrhagic activity which was confirmed by histopathological analysis. This is the first evidence of such an effect by coral snake venom.

Animals↗
PubMed1994

Experience with CA 15.3 as a tumor marker in breast cancer.

CA 15.3, a new tumor marker, is a glycoprotein antigen produced in greater amounts by breast tumor cells. It can be quantitatively detected, circulating in human serum or plasma, using an immunoradiometric assay with monoclonal antibodies. In order to evaluate the usefulness of the method and to determine the cut-off for metastatic disease, the CA 15.3 levels were determined in 78 patients (5 patients with breast fibroadenoma and 73 patients with breast cancer). The conclusions of the study are that the CA 15.3 is a useful parameter in the management of patients in different stages of the disease: levels above 36 U/ml are suggestive of metastasis, and above 86 U/ml are indicative of them. On the other hand, CA 15.3 does not seem to be helpful in the pre-operative differential diagnosis of breast lumps.

Antigens, Tumor-Associated, Carbohydrate↗
PubMed1993

Breast cancer control programme in developing countries.

Breast cancer is a very important health problem in developing countries, where its incidence has increased in the last decades. Mortality rates due to breast cancer have also increased, and the main reason for this is late diagnosis. The authors demonstrate that organizing programmes for early breast cancer detection is possible by making use of simple resources. A set of tiered interventions is proposed, stratified in levels of complexity: Level 1--Identification of abnormal breast by health professionals; Level 2--Medical assistance to women whose breast is considered abnormal, in order to diagnose and treat benign diseases and recognize suspect cases of cancer; Level 3--Management of the women with suspected or diagnosed breast cancer by a multidisciplinary team. Therefore, a proposal for wide action for breast cancer control in developing countries is presented.

Breast Neoplasms↗
PubMedDate not supplied

[The management of acute pancreatitis in pregnancy--the coadjuvant role of parenteral feeding].

Acute pancreatitis in pregnancy is not a frequent condition: only a few hundred cases have been published in the literature. Its diagnosis can be misguided by clinical manifestations of the pregnancy itself, and by the delay in ordering the required diagnostic tests. These facts may contribute to the serious prognosis of this disease, which in the past had a mortality of up to 20%. The treatment recommended is conservative. A surgical intervention in the event of biliary lithiasis is best to be postponed till after delivery. Parenteral alimentation can be helpful because of its effects in the promotion of pancreatic rest with simultaneous improvement of the nutritional conditions of the mother and the fetus.

Acute Disease↗