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Biomedical subjects

R Meli

Publications and source records attributed to R Meli.

At least 19 recordsLinked to original sources
PubMed1997

Prolactin modulation of nitric oxide and TNF-alpha production by peripheral neutrophils in rats.

It has been demonstrated that prolactin (PRL) is a potent immunomodulator that exerts stimulatory effects on physiological responses of immune cells. In the present research we have investigated whether PRL may influence nitric oxide (NO) and/or tumor necrosis factor-alpha (TNF-alpha) production in neutrophils obtained from inflammatory exudate of carrageenin-induced experimental pleurisy in the rat. In this acute model of inflammation the role of endogenous NO was evaluated using an inhibitor of NO-synthase, NG-nitro-L-arginine methyl ester (L-NAME). A treatment of animals with L-NAME (10 mg/kg s.c.) induced a reduction of volume and cell number of pleural exudate and a decrease of nitrite production (measured by the Griees reaction) by polymorphonuclear cells after 24 h of incubation, while D-NAME, the inactive isomer, was without effect. Neutrophils from ovine prolactin (oPRL) treated rats (5 mg/kg for 5 times s.c.) or from rats with a hyperprolactinaemia induced by pituitary gland graft produced higher amounts of NO both after 24 and 48 h of incubation. On the contrary, a clear reduction in the production of NO was found in neutrophils from rats treated with bromocriptine (BRC) (2 mg/kg s.c.), a dopamine D2-receptor agonist. TNF-alpha production (measured by MTT/cytotoxic assay) by neutrophils was markedly increased in PRL-treated or pituitary-grafted rats in comparison to controls, whereas BRC treatment reduced TNF-alpha production.

Animals↗
PubMed1996

The effect of age and sex on the expression of prolactin binding activity in the chicken bursa of Fabricius.

The binding of 125I-labeled prolactin (PRL) to membranes from the bursa of Fabricius of male and female chicks of different ages (15-30-45 and 60 days) was studied. In male chicks the binding was very low in 15 day-old animals and slightly increased in more aged animals. In female chicks the binding was more evident in young animals and decreased in 60 day-old animals. The binding showed a hormonal specificity and Scatchard analysis of the binding revealed the presence of binding sites with low capacity and high affinity. The presence of PRL receptors in the bursa of the chick, a structure that confers immunological competence to birds, gives further support to the involvement of the hormone in the immune processes.

Aging↗
PubMed1996

Recombinant human prolactin induces protection against Salmonella typhimurium infection in the mouse: role of nitric oxide.

In the present study, we demonstrated that repeated treatment with recombinant human prolactin (rhPRL) protected mice against Salmonella typhimurium infection. The protective activity was statistically significant, dose-dependent and present only when rhPRL treatments were performed before the infection. This activity was probably related to the observed increases in phagocytosis and intracellular killing of peritoneal macrophages induced by the hormonal treatment. The number of peripheral leukocytes was not modified, excluding a mobilization of cells from other compartments. A decrease in the mortality rate after challenge was also observed in mice treated with the monoclonal antibody anti-PRL receptor U5, confirming that the protective activity was associated with receptor activation. Our studies also suggest that nitric oxide (NO) production was involved in the protective effect of rhPRL since pre-treatment of the animals with L-NAME, an inhibitor of NO-synthase, was able to completely revert the protective activity, whereas D-NAME, the inactive D-isomer, was without effect.

Animals↗
PubMed1996

The effects of volcanoes on health: preparedness in Mexico.

The article reviews the most important aspects of volcanic eruptions and presents a summary of the harmful materials they emit. The main health effects can be classified as either physical (trauma, respiratory diseases, etc.) or psychological (depression, anxiety, nightmares, neurosis, etc.). Popocatépetl, the most famous active volcano in Mexico, lies on the borders of the States of Mexico, Puebla and Morelos. In 1993, seismic activity intensified, as did as the emission of fumaroles, followed in December 1994 by moderate tremors and strong emissions of gases and ash. In 1996, a number of seismic events led to an unexpected explosion. A daily emission of 8,000 to 15,000 tonnes of sulfur dioxide has been measured. Popocatépetl is located in a densely populated region of Mexico. A complex network to monitor the volcano using sophisticated equipment has been set up, including visual surveillance, seismic, geochemical and geodesic monitoring. An early warning system (SINAPROC/CENAPRED) has been developed to keep the population permanently informed. The warning system uses colour codes: green for normal, yellow for alert, and red for warning and evacuation. An emergency plan has been prepared, including evacuation and preparation for medical centres and hospitals in the region, as well as intense public information campaigns.

Air Pollutants↗
PubMed1995

Regulation of prolactin receptor mRNA expression in peripheral lymphocytes in rats in response to changes in serum concentrations of prolactin.

In the present study we have evaluated the absolute number of the two forms of prolactin (PRL) receptor mRNA in rat peripheral blood lymphocytes and the modulation of receptor mRNA induced by changes in serum levels of endogenous PRL or by administration of ovine PRL. Lymphocytes expressed low levels of both forms of PRL receptor transcripts. Repeated treatments with ovine PRL significantly reduced levels of mRNA encoding the long form PRL receptor, whereas expression was markedly increased by repeated doses of bromocriptine. In contrast, the mRNA level of short form PRL receptor was unchanged by both treatments. The expression of long form transcripts was also markedly decreased in lymphocytes from pituitary-grafted rats. Therefore it appears that in rat peripheral lymphocytes PRL has a negative effect on the expression of its own receptor.

Animals↗
PubMed1995

Effect of prolactin, rIFN-gamma or rTNF-alpha in murine toxoplasmosis.

Mice lethally infected with T. gondii and treated with prolactin (PRL), recombinant interferon gamma (rIFN-gamma) or recombinant tumour necrosis factor (rTNF-alpha) were protected against death, as compared to untreated controls. The protective effect of PRL (0.5-2 mg/kg/twice daily for 12 days) was dose dependent and statistically significant (P < 0.001). The survival was 50% or 40% in mice that received doses of 1 x 10(4) U of rIFN-gamma or 4 x 10(4) U of rTNF-alpha at -2, 0, +2 days before and after infection (P < 0.0001). An increase of time to death, up to 60 days after challenge, and of survival rate (50% up to 70%) were observed in animals treated with PRL in combination with either rTNF-alpha or rIFN-gamma, compared to those that received treatments with the same therapeutic agents alone; however the differences were not statistically significant. In addition, a slight synergistic effect on brain cyst formation, with lower number of Toxoplasma cysts, was observed in mice treated with PRL plus TNF-alpha (P < 0.01), compared with animals that received rTNF-alpha alone (P < 0.05). These data suggest that PRL can regulate in vivo endogenous TNF-alpha production in the cytokine cascade. We conclude that prolactin may play an important role in modulating the host's immune defence against T. gondii opportunistic infection.

Adult↗
PubMed1993

Prolactin protection against lethal effects of Salmonella typhimurium.

The immunoregulatory role of prolactin (PRL) has been well established. In order to clarify if the hormone is also able to stimulate a protective activity against pathogens-induced infections we have studied the modifications of the infective capacity of Salmonella typhimurium induced in mice by repeated treatments with ovine PRL. A significant dose-dependent reduction in the mortality rate was observed in comparison to controls. This activity is probably related to the observed increases in phagocytosis and intracellular killing of the peritoneal macrophages and chemotaxis of the peritoneal granulocytes induced by the hormonal treatment. On the contrary, the number of leukocytes in blood was not modified by PRL treatment excluding a mobilization of cells from other districts. Our findings confirm the existence of a linkage between the neuroendocrine and immune systems suggesting a possible role for PRL in the regulation of non-specific immune response.

Animals↗
PubMed1993

Further evidence for the involvement of prolactin in the inflammatory response.

The pro-inflammatory activity of prolactin (PRL) was clearly demonstrated in our previous research on rat paw oedema. In the present study we report our results on the activity of PRL on other animal models of acute and chronic inflammation. Repeated administration of ovine PRL provoked a significant increase in the inflammatory parameters in experimental carrageenan pleurisy (leukocytes number and prostaglandin E2 concentration in the exudate). A pro-inflammatory effect was also present after a hyperprolactinaemia induced by pituitary gland graft. Moreover, the inflammatory response to polyester sponge implantation was significantly potentiated by oPRL, whereas the hormone was completely inactive on cotton pellet granuloma test. A possible involvement of prostaglandins in the pro-inflammatory activity of PRL is suggested.

Analysis of Variance↗
PubMed1993

Synthesis and muscarinic receptor binding profiles of antagonist benzotriazole derivatives.

A series of benzotriazole derivatives were synthesized and tested in order to determine their activities for muscarinic receptor subtypes (M1, M2 and M3). Binding affinities were measured as KI values by competition against [3H]-N-methylscopolamine in rat cortex, atria and ileum. Pharmacological in vitro tests were performed on isolated tissue preparations (rabbit vas deferens, guinea pig atria and ileum); the compounds showed antimuscarinic activity. The synthesized ligands were characterized by moderate activity; however, some of them displayed interesting selectivity profiles (M2/M1 and M2/M3); particularly, the selectivity exhibited by the benzotriazole derivative 14b was quite similar to that observed for AF-DX 116, a typical M2 specific antagonist.

Animals↗
PubMed1992

Effects of prolactin on rat paw oedema induced by different irritants.

Evidence suggests that prolactin (PRL) may have a role in immune function, but no data exist on the possible interference between PRL and inflammatory processes, in spite of the known correlation between inflammatory and immune reactions. In the present study the activity of prolactin on rat paw oedema was investigated. Repeated administrations of ovine PRL or a hyperprolactinaemia induced by pituitary gland graft provoked an evident increase of the inflammatory response induced by carrageenan. This effect was also present when adrenalectomised animals were used. Indomethacin completely suppressed the pro-inflammatory effect of ovine PRL; bromocriptine reduced the paw oedema, but when both bromocriptine and PRL were administered the two opposite effects seem to annual each other. Also phospholipase A2-induced paw oedema was potentiated by PRL pretreatment and inhibited by bromocriptine, whereas in dextran or serotonin-induced paw oedema both PRL and bromocriptine were ineffective. A possible involvement of prostaglandins and/or of phospholipase A2 in the pro-oedemigenic activity of PRL is suggested.

Adrenalectomy↗
PubMed1988

Inhibitory effects of fungi on aggregation of rabbit platelets and rat polymorphonuclear leucocytes in vitro.

Fungi of six families, encompassing 28 species, have been screened for their inhibitory effects on adenosine-5'-diphosphate (ADP), acetyl-glyceryl-phosphorylcholine (PAF) or collagen-induced rabbit platelet aggregation. Some fungi have also been studied for their ability to inhibit neutrophil aggregation induced by calcium ionophore A 23187. The results suggest that fungi may be a potential source of inhibitors of platelet and neutrophil aggregation.

Adenosine Diphosphate↗
PubMed1988

Senna still causes laxation in rats maintained on a diet deficient in essential fatty acids.

The laxative effect of senna has been investigated in normal and essential fatty acid deficient (EFAD) rats. Oral administration of senna pod extract (7-5-90 mg kg-1) produced a dose-dependent increase in the number of soft faeces excreted by normal rats. Senna 30 mg kg-1 also reversed net absorption of water and increased the prostaglandin (PG) production in the colonic lumen of normal rats by about four times. Oral administration of senna pod extract to rats, maintained on a fat-free diet for 30-90 days, produced diarrhoea and reversed net absorption of water as in normal rats. However, a fat-free diet reduced the PG production drastically in the colonic lumen both in senna-free rats and in senna-treated rats. In EFAD rats carrageenan oedema, but not dextran oedema, was also drastically reduced. Since PG mediation is not present in EFAD rats we conclude that the PG are not essential for laxation induced by senna and that water secretion and PG production in the rat intestinal lumen are unrelated.

Animals↗
PubMed1988

Evidence against a dependence of the senna effect on prostaglandin formation.

The laxation induced by senna is not modified in rats either maintained on a diet deficient in essential fatty acids (EFAD) or exposed to cold (6 degrees C) or with yeast-induced fever. In light of our findings it appears conceivable that non-PG-mediated mechanism(s) play a relevant role in laxation induced by senna.

Animals↗
PubMed1984

Distinct inhibition of membrane-bound and lysosomal phospholipase A2 by glucocorticoid-induced proteins.

Anti-inflammatory steroids induce the release in vivo of antiphospholipase proteins (APP) into the peritoneal cavities of rats. APP were partially purified by ion- exchange chromatography. The main anti-phospholipase activity was recovered in two zones of the elution gradient named APP I and APP II; their molecular weight (mol. wt) was determined with molecular sieve chromatography. Two phospholipase A2 (PLA2) activities were identified from rat peritoneal leucocytes, one with a pH optimum at 4.5 (a lysosomal enzyme) and one with pH optimum at 8.5 (a membrane-bound enzyme); the selective secretion of the former was observed when leucocytes were stimulated by phagocytosis. The effect of APP on both enzyme activities was studied on enzyme preparations from resting leucocytes. APP were also added to leucocytes incubated with or without phagocytozable material. After incubation, PLA2 activities were determined both inside the cells and in the culture medium. APP I revealed a mol. wt of 200 k with a small fragment of 15 k and inhibited membrane-bound PLA2; APP II revealed a mol. wt of 40 k and inhibited lysosomal PLA2.

Animals↗