Somatostatin mediates nitric oxide production by activating sst(2) receptors in the rat retina.

Somatostatin and its receptors (ssts) are found in the retina. Recent evidence suggested the involvement of sst(2A) and sst(2B) receptors in the regulation of nitric oxide (NO) (). In this study, we investigated further the localization of sst(1), sst(3)-sst(5), and the possible involvement of all subtypes, present in the rat retina, in the regulation of NO production. Polyclonal antibodies raised against sst(1), sst(3-5) were applied to 10-14 micro m cryostat sections of rat retinas fixed in paraformaldehyde. NADPH-diaphorase reactivity was assessed histochemically. The levels of NO in rat retinal explants were assessed by the production of its stable metabolites NO(2)(-) and NO(3)(-). sst(1) immunofluorescence was detected mainly in the retinal pigment epithelium, blood vessels of the inner retina, where it was colocalized with NADPH-diaphorase, and in processes of the inner plexiform layer (IPL). sst(4) immunohistochemistry was found in ganglion cell bodies, where it was colocalized with NADPH-diaphorase, processes of the IPL and ganglion cell layer, and optic nerve fibers. sst(3) or sst(5) immunostain was not detected. Somatostatin increased NO production and this effect was mimicked only by the sst(2) specific analog L-779976. The sst(2) antagonist CYN-154806 blocked the L-779976 increase of NO production. These results present conclusive evidence that somatostatin's role in the retina involves the regulation of NO by an sst(2) mechanism.

L-carnitine modifies the humoral immune response in mice after in vitro or in vivo treatment.

Although the role of L-carnitine (L-Cn) as a cofactor in the oxidation of long-chain fatty acids has been well established, this agent has also been recognized to have an important role in the regulation of carbohydrate metabolism, and consequently, the maintenance of cell membrane structure and cell viability. L-Cn has been reported to reduce the apoptotic levels of CD4+ and CD8+ cells. It has also been demonstrated to interfere with cells of the monocytic lineage by regulating their ability to produce growth factors that ultimately affect both T and B lymphocytic subsets. Therefore, in this study, we examined whether this agent affects the antigenic response of immune cells and determined the relative numbers of immune cells in the murine spleen after in vitro and in vivo treatment. The results showed that L-Cn reduces the relative numbers of CD8+, CD4+ and Ly5+ cells. This observation was consistent in all systems studied including (a) in vitro inoculation of antigen (DNP-HSA) and L-Cn, (b) in vitro priming of spleen cells treated with L-Cn in vivo, and (c) in vivo immunization and L-Cn administration. In all cases, the reduction of T lymphocytes correlated with the decreased production of interleukin-2. L-Cn, however, did not affect the production of specific antibody, which indicates that the observed reduction of Ly5-positive cells is due to cell differentiation of B cells to plasma cells.

Cytogenetic effects of occupational exposure in the peripheral blood lymphocytes of pesticide sprayers.

The potential clastogenic effect of pesticides was investigated in 56 (29 indoor and 27 outdoor) agricultural workers exposed to complex chemical mixtures. Exposed and referent subjects were selected from the same geographical area located in Ionia, province of Thessaloniki, Greece. Chromosome aberrations (CA) and sister chromatid exchanges (SCE), were studied in peripheral lymphocytes. Comparison between workers and control group revealed that the individuals exposed to pesticides showed substantial clastogenic effects (CA = 2.66% compared to 0.53%, P < 0.001), in their lymphocytes without indication of increases in their basal frequency of SCE. Moreover, the condition of exposure has been found to influence the CA frequency. It was observed that individuals working exclusively in greenhouses (confined spaces) showed higher CA levels than subjects working in open fields (3.37 versus 1.88, P < 0.01). No significant difference in their expression of CA between smokers and non-smokers was found. The present chromosome study included workers living in the close vicinity of a large industrial zone near Thessaloniki. The percentage of CA in these indoor sprayers was higher compared to our previous study carried out in a different area of Thessaloniki, free of industrial plants (3.37% compared to 2.14%, P < 0.02).

Recurrence of acute leukemia in donor cells after bone marrow transplantation: documentation by in situ DNA hybridization.

Donor cell leukemia after BMT has been documented in a small number of cases mainly by cytogenetic studies. We describe a case of leukemia relapse in a 16-year-old girl 1 year after BMT from her histocompatible brother. Relapse in donor cells was initially suspected on the basis of cytogenetic analysis and confirmed by DNA in situ hybridization in blast cells using a Y chromosome-specific probe.

Frequencies of chromosomal aberrations in pesticide sprayers working in plastic green houses.

The frequency of chromosome aberrations was studied in peripheral blood lymphocytes of 29 workers occupationally exposed to a mixture of pesticides and in 14 age- and sex-matched healthy controls. There was a significant increase in chromosome aberrations in sprayers when compared to unexposed persons (2.39% compared to 0.54%). No positive correlation between the frequency of chromosome aberrations and the duration of exposure was observed. No significant difference between smokers and non-smokers was found.