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Biomedical subjects

R Brito

Publications and source records attributed to R Brito.

At least 19 recordsLinked to original sources
PubMed2003

Cytogenetic analysis of spontaneously activated noninseminated oocytes and parthenogenetically activated failed fertilized human oocytes--implications for the use of primate parthenotes for stem cell production.

PURPOSE: [corrected] Spontaneous parthenogenetically activated noninseminated oocytes and failed fertilized oocytes after ART activated by puromycin were studied to assess cleavage ability and the cytogenetic constitution of the resulting embryos. METHODS: Failed fertilized oocytes were exposed to puromycin, and whenever activation occurred, they were further cultured until arrest of development. FISH was used to assess the ploidy of spontaneous (group A) and induced parthenotes (group B). RESULTS: The mean number of oocytes exposed to puromycin and the percentage and type of activation were identical in IVF and ICSI patients. The more frequent types of activation were one or two pronuclei and one polar body suggesting that retention of the second polar body is a common event after parthenogenetic activation. CONCLUSIONS: Retention of the second polar body and chromosome malsegregation were observed after parthenogenetic activation, either spontaneous or induced by puromycin. This means that using parthenogenetic embryos for stem cell research will require great care and attention.

Cytogenetic Analysis↗
PubMed2003

The study of tuberculosis-attributed deaths as a tool for disease control planning in Rio de Janeiro, Brazil.

SETTING: Two tuberculosis (TB) reference hospitals and three general hospitals in Rio de Janeiro (RJ). OBJECTIVE: To analyze TB-attributed deaths as a tool for evaluating the TB control program in RJ. DESIGN: Retrospective study based on 302 medical records selected from the 1998 death database. RESULTS: Of 1146 registered adult (>14 years) TB-attributed deaths in RJ, 328 occurred in five hospitals, and 302 records were analyzed. Median age was 47.5 (17-89) years; 237 (78.5%) were male. Median time elapsed from onset of symptoms until diagnosis was 60 (7-730) days; median hospitalization was 60 (0-517) days. Acid-fast bacilli sputum smears were performed in 200 (69%) of 290 cases of pulmonary disease. Among 32 (36%) smear-negative patients, culture was done in only one. The recommended regimen (RHZ) was used in 175 (58%). Among 125 re-treatment patients, 55 (44%) were on RHZ instead of RHZE. Notification to health authorities was recorded in 131 (43.4%) cases. CONCLUSION: In RJ, young people die from TB. Major issues identified in the public health system were poor detection and notification and a high default rate, perpetuating the spread of TB. Treating professionals do not follow guidelines, and political commitment is needed to ensure TB control in the state and in the country.

Adolescent↗
PubMed2002

Driven inelastic Maxwell models with high energy tails.

The solutions of the homogeneous nonlinear Boltzmann equation for inelastic Maxwell models, when driven by different types of thermostats, show, in general, overpopulated high energy tails of the form approximately exp(-ac), with power law tails and Gaussian tails as border line cases. The results are compared with those for inelastic hard spheres, and a comprehensive picture of the long time behavior in freely cooling and driven inelastic systems is presented.

Journal Article↗
PubMed2002

Analysis of human spermatozoa by fluorescence in situ hybridization with preservation of the head morphology is possible by avoiding a decondensation treatment.

PURPOSE: Development of a hybridization technique for spermatozoa allowing the preservation of the head morphology. METHODS: FISH analysis of fixed semen samples from oligoasthenoteratozoospermia (OAT) patients with a normal somatic karyotype attending the Cytogenetics and the IVF Laboratories of a University hospital for semen analysis. In situ hybridization with centromeric probes for chromosomes X, Y, and 18 and locus specific probe for chromosome 21. RESULTS: More than 95% of the sperm heads showed clear hybridization signals and a conserved morphology including the visualization of the tail. Few cells with splitted signals were not considered. CONCLUSIONS: This is the first description of a simple and fast hybridization protocol for spermatozoa without a decondensation step, allowing preservation of the morphology of the sperm head that is particularly useful to correlate abnormal spermatozoa with specific chromosome aneuploidies. With this technique we were able to avoid troubles in interpretation of FISH spots that does not depend on the quality of nuclear decondensation, as it is the case in the previously described methods. Our goal was to demonstrate the efficiency of the method without loosing sperm head morphology. Further studies are needed to correlate the aneuploidy rates for specific chromosomes with sperm morphology.

Aneuploidy↗
PubMed2000

Growth, metabolic rate, and digestive enzyme activity in the white shrimp Litopenaeus setiferus early postlarvae fed different diets.

Growth rate, soluble-protein content, oxygen consumption, ammonia excretion, and digestive-enzyme activity were studied in Litopenaeus setiferus early postlarvae under four feeding regimens that included combinations of freshly hatched Artemia nauplii, microparticulate commercial diet, and algae. Growth and of postlarvae fed a mixed diet were significantly higher. Artificial diet used alone caused the lowest growth, lowest soluble-protein content, higher ammonia excretion, lowest O:N ratio, and higher proteolytic and amylase activities. The artificial diet stimulated proteolytic activity and ammonia excretion of postlarvae, apparently in response to some deficiency in protein composition of the diet. Based on results in growth, soluble-protein content, enzymatic activity, and metabolic substrate, we determined that partial substitution of Artemia nauplii by artificial diet, with or without addition of algae when rearing early postlarval stages, will benefit the growth and nutritional state of L. setiferus postlarvae.

Journal Article↗
PubMed1999

Oral fluoropoyrimidines.

Protracted intravenous infusions of fluorouracil (5-FU) in the treatment of colorectal cancer have been associated with a reduction in toxicity and enhanced clinical activity compared with bolus 5-FU schedules. However, these protracted infusions require portable infusion pumps and central venous lines, which are associated with complications of venous thrombosis, infection, and line slippage. An effective oral 5-FU formulation could provide a more convenient protracted treatment method with fewer complications. Because of its inconsistent and erratic absorption, the use of oral 5-FU was abandoned decades ago. The inconsistent absorption of oral 5-FU may be attributed to varying levels of dihydropyrimidine dehydrogenase (DPD) in the gastrointestinal tract. Two methods have been used to circumvent 5-FU's metabolism by DPD in the gastrointestinal tract. First, DPD may be inactivated, allowing for reliable, consistent absorption of 5-FU. Second, 5-FU prodrugs can be administered, being absorbed as intact molecules via the gastrointestinal tract and subsequently converted to 5-FU. The oral fluoropyrimidines discussed here are capable of providing prolonged 5-FU exposure with a reduced incidence of toxicity.

Animals↗
PubMed1998

The oral fluorouracil prodrugs.

Discussed herein are selected oral fluorinated pyrimidines that are converted to 5-fluorouracil (5-FU) in vivo to exert antitumor activity. These agents include capecitabine (Xeloda), tegafur-uracil (UFT) plus leucovorin (Orzel), and S-1 (BMS247616). These agents offer the convenience of an orally administered therapy with potentially fewer toxic effects than conventional bolus regimens of 5-FU plus leucovorin. These oral agents provide prolonged 5-FU exposure at lower peak concentrations than observed with bolus intravenous administration of 5-FU and may confer pharmacoeconomic advantages by reducing administration costs and toxicity-related hospitalizations. These regimens also have the potential for improved therapeutic activity by achieving higher 5-FU concentrations in the tumor or by biochemically modulating 5-FU. Phase III trials in patients with advanced colorectal carcinomas are comparing the antitumor activity of these agents with that of intravenous 5-FU plus leucovorin.

Administration, Oral↗
PubMed1979

Neurofibrillary changes in the cerebral cortex of a patient with subacute sclerosing panencephalitis (SSPE).

Biopsy fragments from the frontal cortex of one patient with SSPE were studied with ultrastructural methods. Special attention was given to the presence of neurofibrillary tangles observed in all cortical layers. These tangles were composed either of filaments with a diameter of 10 -- 12 nm or of paired helical filaments 22 -- 24 nm at their widest and periodically reduced to 10 nm about every 80 nm. These tangles were observed in all cortical layers, while those formed by single filaments were only visualized in layer 3. The simultaneous appearance of both types of tangles in the same patient suggests that they may be chemically related, which is in keeping with recent chemical data concerning the nature of the neurofilament protein subunit.

Adolescent↗