Conversion of beta sitosterol to cholesterol blocked in an insect by hypocholesterolemic agents

Two vertebrate hypocholesterolemic agents (triparanol and 22,25-diazacholesterol) block the conversion of beta-sitosterol to cholesterol in the larva of the tobacco hornworm, Manduca sexta (Johannson). A primary site of inhibitory action is the terminal step in this conversion-the reduction of desmosterol (24-dehydrocholesterol) to cholesterol. This is also the site at which these compounds inhibit de novo cholesterol biosynthesis in higher animals. Both agents severely inhibit growth and maturation of the tobacco hornworm.     

Watershed vs in-lake alkalinity generation: A comparison of rates using input-output studies

As a means of assessing the relative contributions of watershed (terrestrial) and in-lake processes to overall lake/watershed alkalinity budgets, alkalinity production rates for watersheds and low alkalinity lakes were compiled from the literature and compared. Based on net alkalinity production data, derived using wet or bulk deposition data, mean and median alkalinity production for 20 watersheds in North America and Europe were 89 and 69 meq m^?2 yr^?1 (range 20 to 235 meq m^?2 yr^?1). For a subset of 10 watersheds with dry deposition data, terrestrial alkalinity production neutralized an additional 35 meq m^?2 yr^?1 of acidic deposition. For 11 lakes, mean and median in-lake alkalinity generation were 99 and 88 meq m^?2 yr^?1 (range 22 to 240 meq m^?2 yr^?1). Analysis of data indicates that for the low alkalinity systems described here, areal alkalinity production rates for watersheds and lakes are approximately equal. This relationship suggests that watershed area to lake area ratio can be used as a convenient estimator of the relative importance of watershed and in-lake sources of alkalinity for drainage lake systems. For precipitation-dominated seepage lakes and other systems where hydrology limits soil-water contact, hydrologic flow paths and residence times can be of overriding importance in determining alkalinity sources. For regions dominated by drainage lakes with high watershed area to lake area ratios (such as the Northeastern U.S.), however, alkalinity budgets are dominated by watershed processes. Omission of in-lake alkalinity consideration for most lakes in such regions would have little impact on computed alkalinity budgets or on predicted response to changes in acidic deposition loadings.     

Parasites of free-ranging small canids and felids in the Bolivian Chaco.

Parasite surveys of free-ranging wildlife provide important information for monitoring population health. Between March 2001 and March 2003, we sampled 10 ocelots (Leopardus pardalis), eight Geoffroy's cats (Oncifelis geoffroyi), a jaguarundi (Herpailurus yaguarondi), five pampas foxes (Pseudalopex gymnocercus), and three crab-eating foxes (Cerdocyon thous) at three sites in the Bolivian Chaco. The objective of the study was to survey the parasite fauna of these carnivores and compare prevalence of parasites among the sites. The parasite community of these carnivores was diverse, with representatives from eight genera of nematodes, two families of cestodes, two protozoan species, and six arthropod species. Fecal parasites identified from 12 of the 13 felids and five of the six canids examined included Aelurostrongylus abstrusus, Ancylostoma tubaeforme, Uncinaria sp., Crenosoma sp., Toxocara cati, Spirurida, Capillaria aerophila, Spirometra sp., Taeniidae, and Cystoisospora sp. Four tick species, Amblyomma parvum, A. tigrinum, A. ovale, and A. cajennense, and two flea species, Pulex irritans and Delostichus phyllotis, were identified. Two crab-eating foxes had serologic evidence of heartworm disease (HWD). Antibodies against Toxoplasma gondii were found in 15 of 26 animals. Although HWD was found only in canids inside the national park, parasite prevalence did not appear to differ among sites, and no evidence was found of parasite spillover from domestic to wild carnivores.     

Effect of yohimbine hydrochloride on serum prolactin concentration in the rat: possible antagonist for fescue toxicosis

Yohimbine hydrochloride is an indole alkaloid which blocks alpha 2-adrenergic and dopamine receptors and stimulates serotonergic receptors. Yohimbine was selected for testing as a possible antagonist in fescue toxicosis. Reduced body weight gains in cattle with chronic fescue toxicosis may be due to ergot alkaloids produced by fungi which infect the fescue grass. Ergot alkaloids stimulate dopamine receptors, antagonize serotonin, and lower serum prolactin concentrations. It was hypothesized that yohimbine may reverse or counteract the effects of the toxic fescue. Investigation was made of the treatment effects of multiple doses of yohimbine given in rats by intraperitoneal and oral routes. Given intraperitoneally once a day for 8 days, yohimbine hydrochloride increased serum prolactin concentrations. When given orally in feed for 7 days, the drug decreased the serum prolactin concentration. The effects of yohimbine on prolactin concentrations were dependent on the dosages and routes of administration. The inability of yohimbine, when given orally, to increase serum prolactin levels decreased its potential usefulness for prolonged treatment of fescue toxicosis.     

A practical longitudinal model for evaluating growth in Gelbvieh cattle

Genetic evaluation of growth in Gelbvieh beef cattle was examined by multiple-trait (MTM) and random regression (RRM) analysis. The data set comprised 541,108 animals with 1,120,086 records. Approximately 15% of the animals in the data set had at least one record measured outside of the accepted MTM age ranges for weaning weight (Wwt) and yearling weight (Ywt). Fourteen percent of Wwt records and 19% of Ywt records were measured outside the accepted ranges for MTM analysis, and thus were excluded from MTM evaluations. Two RRM evaluations were performed using cubic Legendre polynomials (RRML) and linear splines (RRMS) with three knots at 1, 205, and 365 d of age. Data Set 1 (d1) utilized all available records, whereas Data Set 2 (d2) included only records measured within MTM ranges (1 d, 160 to 250 d, and 320 to 410 d). The RRML models did not reach convergence until diagonalization was imposed. After diagonalization, it was found that all longitudinal models required fewer iterations to converge than the MTM. Correlations between the MTM, RRML-d2, and RRMS-d2 evaluations were >or=0.99 for all three traits, indicating that these models were equivalent when predicting breeding values from data within the MTM age ranges. Correlations between MTM, RRML-d1, and RRMS-d1 were >0.99 for Bwt and >0.95 for Wwt and Ywt. The lower correlations for Wwt and Ywt indicate that the added information does affect breeding value prediction. The RRM has the capability to incorporate records measured at all ages into genetic evaluations at a computing cost similar to the MTM.