RESUMO
Toxoplasmosis is caused by the intracellular protozoan Toxoplasma gondii. It is anopportunistic zoonosis in warm-blooded animals and humans, with a worldwide distribution. Toxoplasma gondii dense granule protein 16 (TgGRA16) can modulate some functions in host cells and is considered a significant virulent factor of the parasite. The present study reports sequence variation in TgGRA16 gene among T. gondii strains from different hosts and geographical locations, and the construction of phylogenetic relationships of these T. gondii strains based on sequences of TgGRA16, and analysis of B cell epitopes in TgGRA16. Our results showed that all TgGRA16 gene sequences were 1518 bp and the C+G contents ranged from 52.17% to 52.59%. Sequence variation in the TgGRA16 gene was 0-1.51%. Phylogenetic analysis revealed that TgGRA16 gene sequence could not be used to differentiate the different T. gondii genotypes. Six B cell epitopes were predicted in TgGRA16. These results indicated that TgGRA16 gene is not an ideal marker for studying genetic relationships of T. gondii isolates, but may represent a good vaccine candidate against toxoplasmosis.
RESUMO
The physiological mechanisms involved in isoproterenol (ISO)-induced chronic heart failure (CHF) are not fully understood. In this study, we investigated local changes in cardiac aldosterone and its synthase in rats with ISO-induced CHF, and evaluated the effects of treatment with recombinant human brain natriuretic peptide (rhBNP). Sprague-Dawley rats were divided into 4 different groups. Fifty rats received subcutaneous ISO injections to induce CHF and the control group (n=10) received equal volumes of saline. After establishing the rat model, 9 CHF rats received no further treatment, rats in the low-dose group (n=8) received 22.5 μg/kg rhBNP and those in the high-dose group (n=8) received 45 μg/kg rhBNP daily for 1 month. Cardiac function was assessed by echocardiographic and hemodynamic analysis. Collagen volume fraction (CVF) was determined. Plasma and myocardial aldosterone concentrations were determined using radioimmunoassay. Myocardial aldosterone synthase (CYP11B2) was detected by quantitative real-time PCR. Cardiac function was significantly lower in the CHF group than in the control group (P<0.01), whereas CVF, plasma and myocardial aldosterone, and CYP11B2 transcription were significantly higher than in the control group (P<0.05). Low and high doses of rhBNP significantly improved hemodynamics (P<0.01) and cardiac function (P<0.05) and reduced CVF, plasma and myocardial aldosterone, and CYP11B2 transcription (P<0.05). There were no significant differences between the rhBNP dose groups (P>0.05). Elevated cardiac aldosterone and upregulation of aldosterone synthase expression were detected in rats with ISO-induced CHF. Administration of rhBNP improved hemodynamics and ventricular remodeling and reduced myocardial fibrosis, possibly by downregulating CYP11B2 transcription and reducing myocardial aldosterone synthesis.