PubMed Health⌕ Search

Biomedical subjects

P M Marques

Publications and source records attributed to P M Marques.

4 recordsLinked to original sources
PubMed2001

Antagonistic and synergistic effects of combined treatment with interleukin-2 and interleukin-4 on mixed retinal cell cultures.

Cytokines play a fundamental role during development of the nervous system. In this work we demonstrate the effect of IL-2 and IL-4 on [(3)H]choline uptake by retinal cells in vitro. Treatments with both interleukins induced a twofold increase on [(3)H]choline uptake. This effect was dose- and time-dependent and inhibited by specific antibodies as well as by inhibition either of protein kinase C or tyrosine kinase activity or of the cytoplasmatic calcium level increase. A synergistic effect was obtained with low concentration of IL-2 (5 U ml(-1)) and IL-4 (0.5 U ml(-1)). However, high concentrations of IL-2 (50 U ml(-1)) and IL-4 (5 U ml(-1)) elicited an antagonistic effect. Our data indicate an important role for interleukins during retinal development.

Animals↗
PubMed2000

Effect of spleen-cell-conditioned medium on [3H]-choline uptake by retinal cells in vitro is mediated by IL-2.

Cytokines are essential molecules throughout the development of the nervous system and also play an important role during the adult life span. In the present work, we analyzed in vitro the effect of spleen-cell-conditioned medium (SCM) on the survival and [3H]-choline uptake of neonatal rat retinal cells. SCM induced an increase in neuronal survival, glial cell proliferation and neurite outgrowth, as evaluated by biochemical and morphological criteria. These effects were time dependent; after 120 h, SCM induced a 6-fold increase in the total protein level. The effect of SCM was blocked both by the inhibition of protein tyrosine kinase activity (10 microM genistein) and by the inhibition of cell division (20 microM fluorodeoxyuridine). SCM also increased the uptake of [3H]-choline by retinal cells. The effect was time dependent. The maximum effect was obtained after 48 h and was maintained at a high level until 120 h. Treatment by 10 microM genistein and 15 microM bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA-AM) (an intracellular calcium chelator) completely blocked this effect. However, 20 microM fluorodeoxyuridine did not abolish it. Conditioned medium obtained from glial cells stimulated with SCM (S-GCM) induced an effect on [3H]-choline uptake earlier than that promoted by SCM. Anti-interleukin-2 (IL-2) antibodies blocked the effect of both SCM and S-GCM on [3H]-choline uptake after 48 and 72 h. IL-2 (50 U/ml) elicited the same effect as that observed when the cells were maintained in the presence of SCM. Taken together, our results suggest that IL-2 plays an important role in controlling the survival and differentiation of retinal cells in vitro.

Animals↗
PubMedDate not supplied

The need for investigating the optical transfer functions in several field orientations for nonisotropic radiographic systems.

In this paper, it is demonstrated that obtaining OTF's for only two directions, parallel and perpendicular to the x-ray tube axis, is insufficient to completely describe the performance of nonisotropic radiographic systems. By performing experiments with three radiological systems in which slit images were obtained for ten different directions, we confirmed that OTF's vary in a nonlinear fashion for directions that are intermediate to the parallel and perpendicular ones. Moreover, we have also identified for each system a range of field orientations--referred to as "Optimum Region"--where sharper images can be obtained. These experimental results can be accounted for by the transfer functions theory.

Biometry↗