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Biomedical subjects

W M Azevedo

Publications and source records attributed to W M Azevedo.

11 recordsLinked to original sources
PubMed2006

Defect analysis in natural quartz from Brazilian sites for ionising radiation dosimetry.

The impurity-related point defects and the dosimetry properties of quartz irradiated with gamma- and X-rays doses were investigated for natural crystals taken from different geologies. The specimens were initially irradiated with gamma particles from (137)Cs to determine the sensitivity and repeatability of thermoluminescence (TL) emission at approximately 503 K. The dose response was investigated in the range 1-20 mGy. The energy dependence was considered in the range 16-65 keV with X rays and with gamma rays from 137Cs and 60Co. It was found that quartz material from two geologies exhibit a linear relationship between TL intensities and absorbed doses with high angular coefficients. Its sensitivities are higher than that found for LiF TLD-100 dosemeters irradiated in the same conditions. The results were discussed in relation to pre-existing impurity contents and the formation of Al-hole centres.

Brazil↗
PubMed2003

T-lymphocyte function from peripheral blood stem-cell donors is inhibited by activated granulocytes.

BACKGROUND: PBSC transplant provides 10 times more T cells than BMT However, the incidence and severity of acute GvHD is similar among recipients of both types of transplants. Studies in mouse models suggest that the similar clinical outcome in BMT and PBSCT is due to differences in the lymphokine profiles. METHODS: PBMC, PBMC from G-CSF mobilized donors (G-PBMC)and BM mononuclear cells (BM-MC) were analyzed by flow cytometry and ELISA to detect gamma-IFN and IL-4 production. Hematoxylin and eosin staining was used to identify morphology and annexin/propidium-iodide was used for apoptosis assays. RESULTS: We show decreased production of gamma-interferon (85%) and IL-4 (60%) in G-PBMC when compared with either PBMC or BM-MCT cells on ex vivo assays. Surprisingly, 85% of fresh G-PBMC is composed of low-density granulocytes (LDG), which undergo apoptosis after 48 h in culture. At this same time, gamma-IFN production from G-PBMC T cell was reverted. In vitro, G-CSF converts granulocytes into LDGs, able to inhibit T-cell function by H2O2 production, and not through immune-deviation towards a Th2-type phenotype. DISCUSSION: We show that the estimated numbers of Th1 and Th2 cells infused in BMT and PBSCT do not differ significantly. These findings are discussed with reference to the relatively low incidence of acute GvHD in PBSCT shown in the literature. We suggest that these results might depend on the high number of granulocytes and progenitors infused. The potential use of granulocytes as immunosupressive short-term therapy is now being investigated by our group using a mouse experimental model.

Annexin A5↗
PubMed2002

Polysiloxane/PVA-glutaraldehyde hybrid composite as solid phase for immunodetections by ELISA.

We developed an efficient method to prepare a hybrid inorganic-organic composite based on polyvinyl alcohol (PVA) and polysiloxane using the sol-gel disc technique. Antigen obtained from Yersinia pestis was covalently immobilized onto these discs with glutaraldehyde and used as solid phase in ELISA for antibody detection in serum of rabbits experimentally immunized with plague. Using 1.25 microg antigen per disc, a peroxidase conjugate dilution of 1:4,000 and a serum dilution of 1:200 were adequate for the establishment of the procedure. These values are similar to those used for PVA-glutaraldehyde discs, plasticized filter paper discs and the polyaniline-Dacron composite discs. This procedure is comparable to that which utilizes the adsorption of the antigen to conventional PVC plates, with the amount of antigen being one fourth that employed in conventional PVC plates (5 microg/well). In addition to the performance of the polysiloxane/PVA-glutaraldehyde disc as a matrix for immunodetection, its easy synthesis and low cost are additional advantages for commercial application.

Animals↗
PubMed2001

Polyaniline-dacron composite as solid phase in enzyme linked immunosorbent assay for Yersinia pestis antibody detection.

Polyaniline (PANI) was chemically synthesized on a dacron disk surface and an antigen (F1 fraction) obtained from Yersinia pestis was covalently fixed onto this composite via glutaraldehyde. The enzyme linked immunosorbent assay (ELISA) or rapid ELISA procedure detected immunoglobulin G (IgG) anti-F1 fraction in human serum employing this derivative. The appropriate conditions for carrying out the test were established as an antigen concentration of 2 microg/PANI-dacron disk, peroxidase labeled goat anti-human IgG conjugate diluted 4000 times, and a serum dilution of 1:100. The PANI-dacron disks showed greater antigen retention than conventional poly(vinyl chloride) plates and less antibody unspecific adsorption.

Aniline Compounds↗
PubMed1998

A randomised, prospective comparison of allogeneic bone marrow and peripheral blood progenitor cell transplantation in the treatment of haematological malignancies.

We present the results of a prospective, randomised study comparing PBPC and BM focusing on engraftment, acute and chronic GVHD and survival. Forty patients with haematological malignancies received HLA-identical sibling BM (group A) or PBPC (group B). Evaluable patients were 19 (A) and 18 (B). Median age was 35 (17-56) in A and 29.5 (9-51) in B. Conditioning was mainly Bu-Cy2; GVHD prophylaxis was CSA-MTX. PBPC were harvested after 5 days of G-CSF 10 microg/kg/day. Median days for an ANC >0.5 x 10(9)/l was 18 (13-30) in A and 16 (11-25) in B (P = 0.10). Platelets >20 x 10(9)/l occurred at +17 (10-40) in A and +12 (9-36) in B (P = 0.01). The probability of > or =2 grade a-GVHD was 19% (A) and 27% (B) (P = 0.53). The probability of all grade c-GVHD was 70% with BM. In spite of the small number of patients in group B (PBPC), our data suggest the great majority of them will have c-GVHD (P = 0.08); extensive disease was present in 50 and 100%, respectively (P = 0.05). The estimates of overall survival for A and B at 1000 days are 51 and 47%, respectively (P = 0.67); DFS at 1000 days are 52 and 58%, respectively (P = 0.50). PBPC resulted in faster platelet engraftment. The incidence of acute and chronic GVHD was similar in both groups, but the severity of c-GVHD was higher with PBPC. No differences in survival and DFS have been observed to date.

Adolescent↗
PubMed1996

Immobilization of xanthine oxidase on a polyaniline silicone support.

A polyaniline silicone support to immobilize xanthine oxidase is proposed as a reactor coil to monitor the action of xanthine oxidase on hypoxanthine, xanthine and 6-mercaptopurine. A purified xanthine oxidase immobilized on this support lost 80% of the initial activity after 12 min of use. Co-immobilization of superoxide dismutase and catalase increased the stability of immobilized xanthine oxidase so that the derivative maintained 79% of its initial activity after 4.6 h of continuous use in which 1.5 mumol purine bases were converted by the immobilized enzyme system. There is no evidence of either polyaniline or protein leaching from the coil during 3 h of continuous use. When solutions (10 ml) of hypoxanthine, xanthine and 6-mercaptopurine were circulated individually through the xanthine oxidase-superoxide dismutase-catalase-polyaniline coil (1 mm internal diameter and 3 m in length, 3 ml internal volume) activities of 8.12, 11.17 and 1.09 nmol min-1 coil-1, respectively, were obtained. The advantages of the reactor configuration and the redox properties of the polymer, particularly with respect to immobilized oxidoreductases, make this methodology attractive for similar enzyme systems. This immobilized enzyme system using polyaniline-silicone as support converted 6-mercaptopurine to 6-thiouric acid with equal efficiency as resins based on polyacrylamide and polyamide 11.

Enzymes, Immobilized↗
PubMed1995

Allogeneic transplantation with blood stem cells mobilized by rhG-CSF for hematological malignancies.

Allogeneic blood stem cell (BSC) transplantation has been performed experimentally in some patients with success. Wider application of this therapeutic modality has been hampered ultimately by many factors, mainly the concern that infusion of large numbers of donor T cells could result in an increased incidence and severity of graft-versus-host disease (GVHD). We report the short-term results of 17 allogeneic BSC transplants in patients with hematologic malignancies. When compared to standard BMT results, BSC transplants showed the advantages of faster engraftment, shorter hospital stay and fewer antibiotic needs. The incidence and severity of GVHD, as well as the general BMT-associated morbidity, was comparable between the two groups. BSC collection by apheresis was well tolerated and associated with less morbidity for donors, probably reducing the cost of the treatment. The collection of BSC was a single apheresis procedure and yielded adequate numbers of stem cells to ensure engraftment. Although this was not a prospective randomized study, the data obtained are encouraging and warrant more prospective and controlled studies.

Acute Disease↗
PubMed1992

Glucose biosensor using glucose oxidase immobilized in polyaniline.

A biosensor for glucose utilizing kinetics of glucose oxidase (EC 1.1.3.4.) was developed. The enzyme was immobilized on polyaniline by covalent bonding, using glutaraldehyde as a bifunctional agent. The system showed a linear response up to 2.2 mM of glucose with a response time of 2.5-4.0 min. In addition, the immobilized enzyme had a higher activity between pH 6.5 and 7.5. The system retained 50% of its activity after 30 d of daily use. The optical absorption spectra of the polyaniline/glucose oxidase electrode after glucose had been added to the buffer solution showed that the absorption band around 800 nm had changed considerably when glucose was allowed to react with the electrode. This optical variation makes polyaniline a very promising polymer for use as a support in optical sensor for clinical application.

Aniline Compounds↗
PubMedDate not supplied

Polyvinyl alcohol-glutaraldehyde as solid-phase in ELISA for schistosomiasis.

Soluble adult Schistosoma mansoni antigen preparation (SWAP) was covalently fixed onto polyvinyl alcohol-glutaraldehyde discs and an enzyme linked-immunosorbent assay (ELISA) was set up. The best conditions for the assay were established and it was found that small amount of antigen such as 1.5 micrograms was required. A comparison between this procedure and the conventional ELISA was proceeded. A reliable method of antigen immobilization was achieved and the low prices of the employed reagents are economically attractive.

Animals↗
PubMedDate not supplied

Cellulose acetate as solid phase in ELISA for plague.

Antigen from Yersinia pestis was adsorbed on cellulose acetate discs (0.5 cm of diameter) which were obtained from dialysis membrane by using a paper punch. ELISA for human plague diagnosis was carried out employing this matrix and was capable to detect amount of 1.3 microg of antigen, 3,200 times diluted positive serum using human anti-IgG conjugate diluted 1:4,000. No relevant antigen lixiviation from the cellulose acetate was observed even after washing the discs 15 times. The discs were impregnated by the coloured products from the ELISA development allowing its use in dot-ELISA. Furthermore, cellulose acetate showed a better performance than the conventional PVC plates.

Antigens, Bacterial↗