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Biomedical subjects

M F Lopes

Publications and source records attributed to M F Lopes.

23 records · Page 2Linked to original sources
PubMed1995

Apoptosis as a cause of T-cell unresponsiveness in experimental Chagas' disease.

A murine model of Chagas' disease induced by metacyclic forms of T. cruzi was used to evaluate T-cell function during infection. T-cell unresponsiveness to TcR;CD3 stimulation in vitro and lymphocyte activation in vivo occurred simultaneously. These paradoxical findings are discussed in the light of recent evidence that mature activated T cells become susceptible to TcR-mediated apoptosis. Activation-induced death in T cells from T. cruzi-infected mice has recently been demonstrated in this model. Evidence that TcR-induced death of activated T cells could be a cause for T-cell unresponsiveness in vitro and in vivo, as well as the possible molecular mechanisms involved, are discussed.

Animals↗
PubMed1994

Trypanosoma cruzi-induced immunosuppression: blockade of costimulatory T-cell responses in infected hosts due to defective T-cell receptor-CD3 functioning.

A model of experimental Trypanosoma cruzi murine infection with chemically induced metacyclic forms (opossum clone Dm28c) showed a marked state of T-cell unresponsiveness during acute phase, but lacked evidence of suppressor cell activity. Spleen cells from infected mice were suppressed in vitro in responses to T-cell activators concanavalin A, anti-Thy1 monoclonal antibody (MAb), and anti-CD3 MAb compared with spleen cells from control littermates. Activation with accessory cell-independent stimulus provided by immobilized anti-CD3 was defective in splenic CD4-positive T cells from infected mice, but not in such cells from control mice. No evidence of splenic suppressor cell activity was found in cell-mixing experiments using nylon-passed T cells from control and infected donors. Kinetic experiments showed that there was a discrete stage in infection when T cells were already suppressed in response to anti-CD3 but still responded to anti-CD69 MAb. In these T cells, immobilized anti-CD3 failed to enhance simultaneous CD69 responses, although anti-CD3 enhanced CD69 responses in control T cells from uninfected donors. These results demonstrate an intrinsic defect in T-cell receptor-mediated T-cell activation, which could be a mechanism generating T-cell suppression during infection by T. cruzi.

Animals↗
PubMedDate not supplied

[Transoperative anatomopathologic examinations: quality control].

Frozen sections (FS) are usually performed in a General Hospital and are very useful for the surgical procedure orientation. PURPOSE--To verify the accuracy of the FS performed at the Hospital de Clínicas de Porto Alegre (HCPA), RS, Brazil. METHOD--2,152 FS were carried out between March 1986-September 1991, in a prospective study. RESULTS--3.7% of the conventional pathologic examinations (58,127), performed in the same period, correspond to the FS examined. When the FS diagnosis differed from the definitive one (in paraffin) it was classified as False Positive (0.4%), False Negative (1.8%) or inconclusive (2.8%). The organs more frequently examined were lymph nodes (19.3%), ovary (17.21%), breast (16.6%) and thyroid gland (12.4%). We observed accuracy indices in 95% of the FS examined, and in 97.8% when excluding the inconclusive ones. CONCLUSION--The accuracy indices of FS performed in HCPA were similar to the ones found in the literature, which vary from 90.4% to 98.5%.

Diagnosis, Differential↗
PubMedDate not supplied

[Pneumoperitoneum in bladder rupture].

Pneumoperitoneum is rarely seen with bladder rupture. In blunt abdominal trauma this sign is strongly suggestive of gastric or bowel perforation. In our child, suspicion of bladder trauma was evoked by car belt marks in the hypogastrium and by gross hematuria. Preoperative diagnosis was not confirmed because immediate surgical exploration was required based on the presence of free air in the abdominal roentgenograph.

Accidents, Traffic↗