The toxic effects on cardiac myocytes of tyledoside F, a cumulative neurotoxic cardiac glycoside isolated from Tylecodon grandiflorus

To investigate the cardiac cellular effects of tyledoside F, a cumulative neurotoxic bufadienolide and ouabain, a non-cumulative cardenolide, the whole-cell clamp method was used to measure the Na-K pump current after the Na-K pump had been activated by high intracellular Na2+. The toxic effects of tyledoside F and ouabain on cardiac myocytes were also investigated by observing the effect of the Ca2+ overload on the variability of myocytes during a period of 75 min. From the results it is clear that there are similarities in the direct effects of tyledoside F and ouabain on the Na-K pump. It was found that ouabain inhibited the Na-K pump current more than that of tyledoside F. With regard to Ca2+ overload, there are differences in their mode of production of Ca2+ overload because cinnarizine protects the myocytes against ouabain-induced Ca2+ overload but not against tyledoside-induced Ca2+ overload. This study shows that with the whole-cell clamp technique tyledoside F inhibited the Na-K pump in a manner similar to inhibition of the pump by ouabain. Viability studies with myocytes indicated that tyledoside F also has other effects which are different from these of ouabain.     

Voorlopige verslag oor die reaksie van dorre karooveld op beweiding gedurende spesifieke jaargetye: Boesmangrasveld

Uittreksel

Die plantegroeiveranderinge in 32 persele van boesmangrasveld wat vir vier jaar volgens bepaalde jaargetye bewei is, is volgens die wydgepasiëerdepuntmetode bepaal. Daar is bevind dat die effek van beweiding gedurende die somermaande November, Desember en Januarie was om die starabedekking van beide Stipagrostis ciliata en S. obtusa te onderdruk. Die effek van beweiding gedurende die winter, Mei, Junie en Julie daarenteen was om die bedekking van S. ciliata te vermeerder.     

The first isolations of Campylobacter mucosalis from pigs in South Africa

The first isolations of Campylobacter mucosalis in South Africa are described. Isolations were made from a 6-week-old weaner pig with necrotic enteritis and from 2 gingival swabs of suckling piglets from herds with histories of porcine intestinal adenomatosis. The isolates were serologically identified as being serotype A strains.     

The demonstration of the K-antigen of Campylobacter fetus venerealis using a microtitre agglutination test

Using specific antisera prepared against heat-treated and untreated cells in a microtitre system, 7 strains of Campylobacter fetus venerealis were examined for the presence of K-antigen. The technique was effective for distinguishing between strains and it was found that 4 out of 7 isolates contained microcapsules, therefore being potentially suitable for vaccine production.     

An accurate, sensitive and reproducible method for the colorimetric estimation of free fatty acids in plasma

A sensitive and reproducible method permitting the estimation of 0,030-3,000 mM free fatty acids (FFA) in plasma with a standard error of 0,006 5 was developed. The method is based on the extraction of phosphate-buffered plasma with a chloroform-heptane-methanol mixture, formation of the cobalt complex and on the subsequent determination of the metal with 1-nitroso-2-naphthol. The method was used to obtain normal values (mean 0,547 mM range 0,147-1,197 mM) for Merino wethers fed lucerne hay.     

Socioecological Determinants of Drought Impacts and Coping Strategies for Ranching Operations in the Great Plains

In Great Plains rangelands, drought is a recurring disturbance. Ranchers in this region expect to encounter drought but may not be adequately prepared for it. Efforts to encourage drought preparedness would benefit from a better understanding of the conditions under which managers make decisions to minimize the impacts of drought. We tested the direct and moderating roles of the drought hazard and the social-ecological context on drought impacts and response. This study was conducted with ranchers in western and central South Dakota and Nebraska following the drought that began in 2012. We surveyed ranchers regarding the effects of the drought and their responses and used multimodel analysis to explore the relationships among measures of drought preparedness, drought response, and drought impacts. Drought severity was the primary predictor of all impacts, but specific types of impacts were varied depending on the operation’s enterprise mix, resources, and management. The socioecological characteristics of the ranch system predicted drought response actions taken, by either providing the necessary resources and capacity to take action or creating sensitivity in the system that required action to be taken. We conclude with recommendations for learning from current drought experiences in order to better adapt to future drought events.