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L M Costa

Publications and source records attributed to L M Costa.

6 recordsLinked to original sources
PubMed2000

Voltage-clamp: a useful approach to study in vitro duodenal iron transport in the mouse.

The mechanism(s) controlling iron absorption remain(s) uncertain despite the progress in the identification of genes selectively expressed in the duodenum. The availability of experimental models of iron absorption is critical to the clarification of such mechanism(s). In the present study, a simple method for studying in vitro iron absorption in mouse duodenum is described. Short circuit current, open circuit potentials and epithelial conductances were measured in mouse duodenal segments. Also, unidirectional 55Fe fluxes at different pH conditions were measured in mice with varying iron status. The findings reinforce evidence for an adaptive response of the iron absorptive process according to the body iron status. Significant differences are demonstrated between iron fluxes measured in normal and parenterally iron loaded mice and at acidic compared to neutral pH environment. Also, a significant difference was observed between transepithelial potential measured in duodenum from iron-loaded compared to untreated mice. Advances in the understanding of the mechanism(s) of iron absorption can be brought by the application of voltage-clamp techniques to the electrophysiologic study of iron overload mouse models.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1998

Iron compounds after erythrophagocytosis: chemical characterization and immunomodulatory effects.

In humans, the lymphomyeloid system has a fundamental role on iron metabolism promoting its recycling due to a continuous removal of effete red blood cells. Additionally, one of the most intriguing aspects of metalloporphyrins in biology is their effect on the immune system. However, the process of erythrocyte catabolism is still poorly understood and needs further research. In the present study, we attempt to investigate the nature and the possible physiologic role of Fe compounds released after erythrophagocytosis during the removal of red blood cells. Monocyte erythrophagocytosis in vitro experiments were done to characterize chemically the Fe compounds present inside the cells and in the culture supernatants. We tested the probable immunomodulatory functions of erythrophagocytosis products over lymphocyte cultures activated in vitro with T mitogens (alpha-CD3). Data obtained from atomic absorption spectroscopy confirmed the presence of Fe in the culture supernatants of monocyte cultures after erythrophagocytosis. Also, high-spin haem complexes derived from erythrocyte catabolism were detected by electron paramagnetic electronic resonance. Finally, in vitro activated lymphocyte proliferation experiments indicate the co-mitogenic properties of monocyte culture supernatants after red blood cells phagocytosis. Thus, the results of the present work provide evidence that culture monocyte supernatants after in vitro erythrophagocytosis contain Fe (III) high-spin haem complexes and show lymphocyte proliferation co-stimulatory properties.

Adjuvants, Immunologic↗
PubMedDate not supplied

[Clinical significance, epidemiology and microbiology of coagulase-negative staphylococcal nosocomial bacteremia at a teaching hospital].

Coagulase-negative staphylococci (CNS) are an important cause of nosocomial bacteremia and they are frequently considered as contaminants of blood-cultures. From October 1990 to September 1992, 300 positive blood-cultures for CNS at the Hospital São Paulo were studied and 141 CNS bacteremias were characterized as nosocomial bacteremias. Clinical and microbiological criteria were defined to differentiate between true CNS bacteremia and contaminated cultures. Only 20.6% of the CNS nosocomial bacteremia were considered as true bacteremia. Most of the CNS true nosocomial bacteremia were detected among newborns admitted to the neonatal intensive care unit; the presence of intravascular catheter and parenteral nutrition were significant findings. We did not detect significant difference between true nosocomial bacteremia and contaminated cultures regarding to resistance to oxacillin and SLIME production. The clinical criteria and the positivity of the blood-cultures up to 48 hours after incubation, utilized in our definitions, were useful parameters to characterize the CNS true nosocomial bacteremia.

Adolescent↗