Conditional expression of harpinPsscauses yeast cell death that shares features of cell death pathway with harpinPss-mediated plant hypersensitive response (HR)

Conditional expression of harpin_Psscauses yeast cell death that shares features of cell death pathway with harpin_Pss-mediated plant hypersensitive response (HR).Pseudomonas syringae pv.syringae 61 hrp Z gene encodes harpin_Pss, a 34.7 kD extracellular protein that elicits a hypersensitive response (HR) in plants. Conditional expression of either full-length or truncated hrp Z sequences under the GAL1 promoter caused cell death in Saccharomyces cerevisiae Y187. Plating of pYEUT- hrp Z transformants on a medium containing galactose resulted in complete inhibition of colony formation, whereas their growth on a glucose-based medium was unaffected. Western blot analysis confirmed the expression of harpin_Pssin yeast cells transformed with pYEUT- hrp Z and grown in galactose-containing medium. A time-dependent decline in the percentage of trypan blue-excluding cells in cultures of pYEUT- hrp Z transformants was observed when cultured on galactose-containing medium. Similarly, the number of viable cells reduced to about 50% within 6 h. There were similarities in the harpin_Pss-mediated cell death in plants and yeast cell death (YCD). Galactose-induced cell death in pYEUT-hrp Z transformants of S. cerevisiae Y187 was suppressed by a protein kinase inhibitor K252a (10 μ M). The viability of pYEUT- hrp Z transformants was prolonged in the presence of 100 U ml⁻¹catalase suggesting a role for the oxidative burst in YCD that was further supported by the flow cytometric patterns of propidium iodide uptake by yeast cells. Overall, it appears that yeast provides a useful model system to understand the molecular mechanism of harpin_Pss-mediated cell death.     

Effects of Staphylococcus aureus mastitis on bovine mammary gland plasma cell populations and immunoglobin concentrations in milk

Bovine mammary tissue and milk samples were examined to determine effects of chronic Staphylococcus aureus mastitis on the humoral immune response. Parenchymal and teat end tissues from lactating bovine mammary glands were stained immunohistochemically to determine distribution of immunoglobulin (Ig) G1-, IgG2-, IgA-, and IgM-producing plasma cells. Numbers of all Ig-producing plasma cells tended to be higher in tissues from S. aureus infected quarters compared with controls, but most differences were not statistically different. Numbers of IgG1-producing plasma cells at the Furstenberg's rosette area of infected quarters were significantly (P less than 0.05) higher than uninfected quarters. There were no significant differences in concentrations of Ig isotypes in milk from S. aureus infected and uninfected quarters. Data suggest that the antigenic effect of chronic S. aureus infection on the humoral immune response of the bovine mammary gland is minimal. Persistency of S. aureus infection may result, in part, from suboptimal stimulation or immunosuppression of the mammary immune system.     

Efficiency of amino acid utilization in the growing pig at suboptimal levels of intake: branched-chain amino acids, histidine and phenylalanine + tyrosine

Five balance experiments on growing pigs were carried out to study the marginal efficiency of utilization of isoleucine, leucine, valine, histidine and phenylalanine + tyrosine and to estimate their requirements for maintenance. Purified diets based on casein and crystalline amino acids as the sole source of N contained graded levels of each amino acid, corresponding to protein accretion rates of 0, 33, 66, 99 and 132 g/day, respectively. All other essential amino acids were given in a 30% excess. N retention increased linearly (p < 0.01) as the dietary concentration of the limiting amino acid increased. Based on linear regression equations relating amino acid deposition in body protein to amino acid intake, marginal efficiencies of ileal digestible amino acid utilization were calculated to be isoleucine - 0.81, leucine - 0.81, valine - 0.82, histidine - 1.17 and phenylalanine + tyrosine - 0.67. Extrapolating the regression equations to zero N retention, the daily requirements of amino acids for N equilibrium were estimated to be (mg/kg0.75) isoleucine - 18, leucine - 33, valine - 23, histidine - 14 and phenylalanine + tyrosine - 43.     

Efficacy of extended pirlimycin therapy for treatment of experimentally induced Streptococcus uberis intramammary infections in lactating dairy cattle

Streptococcus uberis is an important cause of mastitis in dairy cows throughout the world, particularly during the dry period, around the time of calving, and during early lactation. Strategies for controlling S. uberis mastitis have not received adequate research attention and are therefore poorly defined and inadequate. Objectives of the present study were to evaluate the efficacy of extended therapy regimens with pirlimycin for treatment of experimentally induced S. uberis intramammary infections in lactating dairy cows during early lactation and to evaluate the usefulness of the S. uberis experimental infection model for evaluating antimicrobial efficacy in dairy cows. The efficacy of extended pirlimycin intramammary therapy regimens was investigated in 103 mammary glands of 68 dairy cows that became infected following experimental challenge with S. uberis during early lactation. Cows infected with S. uberis in one or both experimentally challenged mammary glands were randomly allocated to three groups, representing three different treatment regimens with pirlimycin, including 2-day (n = 21 cows, 31 mammary quarters), 5-day (n = 21 cows, 32 quarters), and 8-day (n = 26 cows, 40 quarters). For all groups, pirlimycin was administered at a rate of 50 mg of pirlimycin hydrochloride via intramammary infusion. A cure was defined as an experimentally infected mammary gland that was treated with pirlimycin and was bacteriologically negative for the presence of S. uberis at 7, 14, 21, and 28 days after treatment. Experimental S. uberis intramammary infections were eliminated in 58.1% of the infected quarters treated with the pirlimycin 2-day regimen, 68.8% for the 5-day regimen, and 80.0% for the 8-day regimen. Significant differences (P <.05) in efficacy were observed between the 2-day and 8-day treatment regimens. The number of somatic cells in milk decreased significantly following therapy in quarters for which treatment was successful in eliminating S. uberis. However, there was no evidence to suggest that extended therapy with pirlimycin resulted in a greater reduction in somatic cell counts in milk than the 2-day treatment. The S. uberis experimental infection model was a rapid and effective means of evaluating antimicrobial efficacy during early lactation at a time when mammary glands are highly susceptible to S. uberis intramammary infection.