In vitro antiplasmodial and antibacterial activities of Canthium multiflorum Schum and Thonn (Rubiacea) extracts.

Because of the resistance of pathogens to actually available drugs, there is a continuous need for new agents to cure several diseases such as malaria and microbial infections. In the establishment of new drugs, plant are often a source of new leads, indeed aqueous, acetone and methanol extracts of Canthium multiflorum were tested for antiplasmodial and antibacterial activities. The antiplasmodial activity was performed on fresh clinical strains of Plasmodium falciparum using light microscopy. The results revealed that the methanol extract was the most active with IC50 of 4.69 microg mL(-1). The NCCLS microdilution method performed on clinical and reference strains of pathogenic bacteria yielded MIC and MBC values ranging from 312 to 1250 and 625 to 2500 microg mL(-1), respectively. The qualitative analysis of the extract revealed the presence of several chemical groups such as alkaloids, terpens and tannins that might be responsible for the activity of the plant. The issue of this study showed that C. multiflorum is a plant that many attention should be paid to because of it pharmacological potentials.

Differential regulation of tyrosine hydroxylase and estradiol receptor expression in the rainbow trout brain.

In numerous fish species, dopamine has been found to strongly inhibit gonadotropin release. Among the enzymes that regulate dopamine turnover, tyrosine hydroxylase (TH), the rate-limiting anabolic enzyme, could be a target for endocrine feedback regulation. Since dopamine turnover is stimulated by estradiol in rainbow trout, we have investigated the effect of estradiol on TH and estradiol receptor expression. In situ hybridization was used to quantify mRNA levels in the brain of ovariectomized female rainbow trout implanted or not with estradiol pellets. We demonstrated that preoptic TH and estradiol receptor mRNA levels are greatly decreased by gonadectomy during vitellogenesis. For TH expression, this effect was reversed in part by estradiol supplementation. We have also confirmed the existence of an inhibitory gonadal feedback on FSH secretion, mediated by estradiol. The stimulating effect of estradiol on TH expression found in this study could be a pathway involved in gonadal feedback on gonadotropin release.

Differential regulation of the estrogen receptor mRNA by estradiol in the trout hypothalamus and pituitary.

In an attempt to understand the molecular mechanisms by which steroids can modulate brain functions in fish, we first localized the cells which produce estrogen receptor mRNA in the rainbow trout forebrain (Salbert et al., 1991). We now report how estradiol itself can alter the estrogen receptor mRNA content of these cells in a sterile strain of female rainbow trout. We also examined liver and pituitary levels of the estrogen receptor mRNA under the same estrogenic treatment. As revealed by slot blot and in situ hybridisations, a single injection (1.5 mg/kg) of estradiol can induce a strong increase (about five-fold) in the estrogen receptor mRNA levels in the liver, as well as a moderate increase (about two-fold) in two nuclei of the hypothalamus/preoptic area: the nucleus lateralis tuberis and the nucleus preopticus periventricularis. Conversely, no modifications of these levels were observed in the pars intermedia and the proximal pars distalis of the pituitary. Moreover, a comparison between estrogen receptor mRNA levels in the brain of sexually active female trout and in the brain of these sterile animals revealed that, in these latter, estrogen receptor mRNA levels are lower but can be increased by a single estradiol injection and reached the levels observed in mature females.