Efficacy of vaccination and nisin Z treatments to eliminate intramammary Staphylococcus aureus infection in lactating cows.

This study evaluated the effect of a Staphylococcus aureus bacterin and nisin on bovine subclinical mastitis. A total of 75 Holstein subclinically mastitic cows were randomly allocated to three groups with 25 cows per group. In group I, an intramammary infusion of nisin Z at a dose of 2.50×106 IU was carried out once daily for three days, and an autogenous S. aureus bacterin was inoculated into the supramammary lymph node one week before and one week after nisin treatment. In group II, nisin was administered in the same way as in group I, but no bacterin was inoculated. Group III received no treatment and served as a control. Milk was aseptically sampled from the affected quarters before and 2, 4, and 6 weeks after treatment, for bacteriological examination and analyses of N-acetyl-ß-D-glucosaminidase (NAGase) activity, somatic cell count (SCC), and milk protein and fat contents. Results indicated that, compared to the nisin-treated group, nisin-bacterin treatment significantly reduced intramammary S. aureus infections, reduced the number of quarters with milk SCCs of more than 5×105 cells/ml, and increased the protein and fat contents of the milk. Therefore, nisin-bacterin therapy is suggested when subclinical mastitis occurs in lactating cows.

Ethylene is Involved in Brassinosteroids Induced Alternative Respiratory Pathway in Cucumber (Cucumis sativus L.) Seedlings Response to Abiotic Stress.

Effects of brassinosteroids (BRs) on cucumber (Cucumis sativus L.) abiotic stresses resistance to salt, polyethylene glycol (PEG), cold and the potential mechanisms were investigated in this work. Previous reports have indicated that BRs can induce ethylene production and enhance alternative oxidase (AOX) pathway. The mechanisms whether ethylene is involved as a signal molecule which connected BR with AOX in regulating stress tolerance are still unknown. Here, we found that pretreatment with 1 µM brassinolide (BL, the most active BRs) relieved stress-caused oxidative damage in cucumber seedlings and clearly enhanced the capacity of AOX and the ethylene biosynthesis. Furthermore, transcription level of ethylene signaling biosynthesis genes including ripening-related ACC synthase1 (C S ACS1), ripening-related ACC synthase2 (C S ACS2), ripening-related ACC synthase3 (C S ACS3), 1-aminocyclopropane-1-carboxylate oxidase1 (C S ACO1), 1-aminocyclopropane-1-carboxylate oxidase2 (C S ACO2), and C S AOX were increased after BL treatment. Importantly, the application of the salicylhydroxamic acid (SHAM, AOX inhibitor) and ethylene biosynthesis inhibitor aminooxyacetic acid (AOA) decreased plant resistance to environmental stress by blocking BRs-induced alternative respiration. Taken together, our results demonstrated that ethylene was involved in BRs-induced AOX activity which played important roles in abiotic stresses tolerance in cucumber seedlings.