Effect of nitrate, ammonium and phosphate on the growth and microcystin production of Korean Microcystis species

Aim: This study aimed to investigate the effects of nitrogen (NO3-N, NH3-N) and phosphorus (PO4-P) on the growth and microcystin production of two bloom-forming Microcystis species (toxic M. aeruginosa MAHC160824 and non-toxic M. viridis MVHC160824).Methodology: The two Microcystis species were isolated from the lower reaches of the Nakdong river, South Korea. In the culture experiments, the average nutrient concentrations (NH3-N, NO3-N and PO4-P) at which Microcystis appeared (> 15°C) was used as control medium. Different concentrations of NH3-N, NO3-N and PO4-P were then employed in nutrient testing (control, vs. 4 times and 16 times higher than the control). Microcystin levels were measured using a UPLC™ (LC MS/MS) system. Results: Both toxic and non-toxic Microcystis strains exhibited a maximum cell density at 30°C and a maximum growth rate at 25-30°C. In the nutrient addition assays, the maximum growth of two Microcystis species were found at nutrient concentrations 4 to 16 times higher than the control (NH3-N: 0.468 mg l-1, PO4-P: 0.100 mg l-1, NO3-N: 32.5 mg l-1). The highest microcystin production levels were found under optimal growth conditions. The microcystin levels of toxic M. aeruginosa MAHC160824 were below the detection limit despite a higher number of cells (> 300,000 cells ml-1) at the same nutrients concentrations as those found in raw water from the Nakdong river. Interpretation: Higher production of microcystin occurs when there is an increase in NH3-N and PO4-P within a restricted range in toxic species M. aeruginosa MAHC160824, else the production is low

Hepatic inducible nitric oxide synthase expression increases upon exposure to hypergravity

Stimulation by a number of conditions, including infection, cytokines, mechanical injury, and hypoxia, can upregulate inducible nitric oxide synthase (iNOS) in hepatocytes. We observed that exposure to hypergravity significantly upregulated the transcription of the hepatic iNOS gene. The aim of this study was to confirm our preliminary data, and to further investigate the distribution of the iNOS protein in the livers of mice exposed to hypergravity. ICR mice were exposed to +3 Gz for 1 h. We investigated the time course of change in the iNOS expression. Hepatic iNOS mRNA expression progressively increased in centrifuged mice from 0 to 12 h, and then decreased rapidly by 18 h. iNOS mRNA levels in the livers of centrifuged mice was significantly higher at 3, 6, and 12 h than in uncentrifuged control mice. The pattern of iNOS protein expression paralleled that of the mRNA expression. At 0 and 1 h, weak cytoplasmic iNOS immunoreactivity was found in some hepatocytes surrounding terminal hepatic venules. It was noted that at 6 h there was an increase in the number of perivenular hepatocytes with moderate to strong cytoplasmic immunoreactivity. The number of iNOS-positive hepatocytes was maximally increased at 12 h. The majority of positively stained cells showed a strong intensity of iNOS expression. The expression levels of iNOS mRNA and protein were significantly increased in the livers of mice exposed to hypergravity. These results suggest that exposure to hypergravity significantly upregulates iNOS at both transcriptional and translational levels.

Efeitos do D-600 (metoxi-verapamil) na mortalidade e tamanho do infarto apos oclusao coronariana em ratos. / Effects of D-600 (metoxy-verapamil) on the mortality and infarction size after coronary occlusion in rats

A finalidade deste estudo foi avaliar os efeitos de metoxi-verapamil (D-600) na mortalidade e no tamanho final do infarto, em ratos com oclusao coronariana. Inicialmente, o tronco comum da coronaria esquerda foi ocluido em 212 ratos. Os animais foram randomizados em um grupo controle e um grupo tratado com D-600. A mortalidade apos os primeiros 15 minutos da oclusao do tronco comum da arteria coronaria esquerda era 40% menor no grupo tratado que no grupo controle (p < 0,01). A diferenca de mortalidade entre os dois grupos manteve-se 48 horas apos a oclusao. Os ratos que sobreviveram 48 horas apos-oclusao coronaria tiveram seus infartos medidos por planimetria e os resultados foram: 38,2% no grupo controle e 37,6% no grupo tratado. Estes resultados permitem-nos concluir que D-600 diminui a mortalidade apos oclusao coronariana em ratos, provavelmente por acao antiarritmica