Effects of supplemental lysine and methionine with zilpaterol hydrochloride on feedlot performance, carcass merit, and skeletal muscle fiber characteristics in finishing feedlot cattle.

Feeding zilpaterol hydrochloride (ZH) with ruminally protected AA was evaluated in a small-pen feeding trial. Crossbred steers ( = 180; initial BW = 366 kg) were blocked by weight and then randomly assigned to treatments (45 pens; 9 pens/treatment). Treatment groups consisted of no ZH and no AA (Cont-), ZH and no AA (Cont+), ZH and a ruminally protected lysine supplement (Lys), ZH and a ruminally protected methionine supplement (Met), and ZH and ruminally protected lysine and methionine (Lys+Met). Zilpaterol hydrochloride (8.3 mg/kg DM) was fed for the last 20 d of the finishing period with a 3-d withdrawal period. Lysine and Met were top dressed daily for the 134-d feeding trial to provide 12 or 4 g·hd·d, respectively, to the small intestine. Carcass characteristics, striploins, and prerigor muscle samples were collected following harvest at a commercial facility. Steaks from each steer were aged for 7, 14, 21, and 28 d, and Warner-Bratzler shear force (WBSF) was determined as an indicator of tenderness. Prerigor muscle samples were used for immunohistological analysis. Cattle treated with Met and Lys+Met had increased final BW ( < 0.3) and ADG ( < 0.05) compared to Cont- and Cont+. Supplementation of Lys, Met, and Lys+Met improved G:F ( < 0.05) compared to Cont- during the ZH feeding period (d 111 to 134) as well as the entire feeding period ( < 0.05). Zilpaterol hydrochloride increased carcass ADG ( < 0.05) when compared to non-ZH-fed steers. Methionine and Lys+Met treatments had heavier HCW ( < 0.02) than that of Cont-. Yield grade was decreased ( < 0.04) for Cont+ steers compared to steers treated with Lys, Lys+Met, and Cont-. Tenderness was reduced ( < 0.05) with ZH regardless of AA supplementation. Lysine, Met, Lys+Met, and Cont+ had less tender steaks ( < 0.05) throughout all aging groups compared to Cont-. Steaks from Lys-treated steers were less tender ( < 0.05) than those of Cont+ during the 7- and 14-d aging periods. Nuclei density was the greatest with Cont- cattle compared to all other treatments suggesting a dilution effect of the nuclei in the larger muscle fibers with ZH feeding. Supplementation of Met in conjunction with ZH feeding increased ADG and HCW although this may lead to decreased tenderness even after aging for 28 d. These findings indicated that steers fed ZH may require additional AA absorbed from the small intestine to maximize performance.

Optimization of in situ cellular ELISA performed on influenza A virus-infected monolayers for screening of antiviral agents.

Viral susceptibility testing has been traditionally performed by the plaque reduction assay (PRA) which is laborious, time consuming, relatively expensive, and requires subjective input by the reader. An in situ cellular enzyme-linked immunosorbent assay (ELISA) has been developed with the potential to overcome many of the limitations of PRA and has been applied to a variety of viruses. This study establishes the specific conditions necessary for susceptibility testing of influenza A virus to antiviral agents such as amount of inoculum size, duration of incubation, fixative type, and cell number; factors which are critical to the performance of the in situ cellular ELISA. In situ cellular ELISA was found to correlate strongly with the plaque assay (PA) (R2 = 0.997, P < 0.002). Both assays were applied to test the susceptibility of influenza A virus to a new antiviral emulsion agent and yielded comparable data. The optimized in situ cellular ELISA can serve as a reliable assay for the rapid screening of large numbers of antiviral agents.

Substantial carbon recycling from linoleate into products of de novo lipogenesis occurs in rat liver even under conditions of extreme dietary linoleate deficiency.

A significant portion of the beta-oxidized carbon skeleton of some polyunsaturated fatty acids can be recycled into de novo lipogenesis, i.e., cholesterol, saturates and monounsaturates. The recycling of carbon from linoleate was quantified in liver lipids of severely linoleate-deficient rats to determine whether it is more likely to be a function of redundancy or could be obligatory. After 13 wk on a control (2 energy % linoleate) or severely linoleate-deficient (<0. 05 energy % linoleate) diet, 7 muCi [1-14C]linoleate was given by gavage and the rats were killed 48 h later. A second linoleate-deficient group received an oral bolus of 256 mg linoleate as a supplement with the radiotracer. In comparison to the controls, 14C recovery in liver total lipids of the linoleate deficient group was increased about 5-fold with increased dpm/g in linoleate (13.7-fold higher), arachidonate (2.7-fold higher) and products of de novo lipogenesis (3.5-fold higher). In livers of control rats, 14C distribution was: 41% arachidonate, 29% linoleate, 22% sterols, 3% oleate, 3% palmitate, and 2% stearate. In livers of linoleate-deficient rats, 14C distribution was: 63% linoleate, 19% arachidonate, 11% sterols, 4% oleate, 3% palmitate, and <1% stearate. Thus, in controls, equivalent amounts of 14C were in products of de novo lipogenesis as in linoleate (29-30%), and in livers of linoleate-deficient rats, a similar proportion of 14C was in products of de novo lipogenesis as was converted to arachidonate (18-19%). We conclude that carbon recycling into de novo lipogenesis accounts for a significant, obligatory component of linoleate metabolism even during extreme linoleate deficiency.

Itraconazole resistance in Aspergillus fumigatus.

Invasive aspergillosis is an increasingly frequent opportunistic infection in immunocompromised patients. Only two agents, amphotericin B and itraconazole, are licensed for therapy. Itraconazole acts through inhibition of a P-450 enzyme undertaking sterol 14alpha demethylation. In vitro resistance in Aspergillus fumigatus to itraconazole correlated with in vivo outcome has not been previously described. For three isolates (AF72, AF90, and AF91) of A. fumigatus from two patients with invasive aspergillosis itraconazole MICs were elevated. A neutropenic murine model was used to establish the validity of the MICs. The isolates were typed by random amplification of polymorphic DNA. Analysis of sterols, inhibition of cell-free sterol biosynthesis from [14C] mevalonate, quantitation of P-450 content, and [3H]itraconazole concentration in mycelial pellets were used to determine the mechanisms of resistance. The MICs for the three resistant isolates were >16 microg/ml. In vitro resistance was confirmed in vivo for all three isolates. Molecular typing showed the isolates from the two patients to be genetically distinct. Compared to the susceptible isolate from patient 1, AF72 had a reduced ergosterol content, greater quantities of sterol intermediates, a similar susceptibility to itraconazole in cell-free ergosterol biosynthesis, and a reduced intracellular [3H]itraconazole concentration. In contrast, AF91 and AF92 had slightly higher ergosterol and lower intermediate sterol concentrations, fivefold increased resistance in cell-free systems to the effect of itraconazole on sterol 14alpha demethylation, and intracellular [3H] itraconazole concentrations found in susceptible isolates. Resistance to itraconazole in A. fumigatus is detectable in vitro and is present in wild-type isolates, and at least two mechanisms of resistance are responsible.

Pure linoleate deficiency in the rat: influence on growth, accumulation of n-6 polyunsaturates, and [1-14C]linoleate oxidation.

Essential fatty acid deficiency has been widely studied but the extent to which its effects are attributable specifically to deficiency of linoleate as opposed to deficiency of all unsaturated fatty acids is unknown. Our objective was to evaluate the effect of pure linoleate deficiency on growth as well as changes in the metabolism and oxidation of n-6 polyunsaturates. The diets contained 20 energy % fat blended from 3 energy % pure oleate, 2 energy % linoleate (0.01 energy % in the linoleate-deficient group), 0.3 energy % pure alpha-linolenate, and the balance as palmitate and stearate from fully hydrogenated soybean oil. Thirty-five-day-old rats consumed the two diets for 84 days, after which the linoleate-deficient rats weighed 15% less than the controls (P < 0.05), had mild scaling on the paws, and visible hair loss (in a few rats). Compared with the controls, the ratio of eicosatrienoate to arachidonate after 84 days was elevated in liver (170-fold) and serum (520-fold) phospholipids of the linoleate-deficient group. In total, linoleate-deficient rats consumed 122 mg of linoleate and had a net whole body loss of 479 mg n-6 polyunsaturates compared with an intake of 24,130 mg and a net whole body gain of 7206 mg n-6 polyunsaturates in the control group. Linoleate-deficient rats oxidized 1% of an oral bolus of [1-14C]linoleate over 8 h compared with 34% in the control rats (P < 0.05). We conclude that pure linoleate deficiency has marked effects on accumulation of n-6 polyunsaturates but induces milder gross symptoms, particularly growth retardation, than classical essential fatty acid deficiency. alpha-Linolenate and possibly oleate may have a sparing effect on linoleate oxidation from body stores during linoleate deficiency.

Rubella epidemiology in South East England.

Analyses of data collected in a large survey (sample size greater than 3000) of rubella antibody in South East England, finely stratified according to age, reveal age-dependent changes in the pattern of virus transmission. The rate or force of infection changes from low in the young children to high in the 5- to 15-year-olds and back to low again in the adult age classes (there is a 50% reduction between the 5- to 15-year-olds and the 20+-year-olds). Raised levels of immunity are recorded in the teenage and young adult female segments of the population as a consequence of the UK rubella immunization programme. Mean antibody concentrations show a decline with age and are, on average, lower in vaccinated females when compared with unvaccinated males of the same age. The interpretation of horizontal cross-sectional serological data and future research needs are discussed.

Fluorescent staining of acetylcholine receptors in vertebrate skeletal muscle.

1. alpha-Bungarotoxin was labelled with fluorescent dyes and used as a stain for visualizing the distribution of acetylcholine receptors in vertebrate skeletal muscle fibres.2. Dye-toxin conjugates had the same pharmacological properties as native toxin, but their potencies were lower.3. Fluorescent staining was examined in teased muscle fibres. The stain was found to be confined to the neuromuscular junction and associated with the subsynaptic membrane.4. Staining intensity was reduced by curare and even more so by carbachol, but not by atropine or neostigmine. Pre-treatment of muscles with unlabelled alpha-bungarotoxin entirely prevented staining.5. The staining at amphibian neuromuscular junctions was characterized by a pattern of intense transverse bands occurring at intervals of approximately 0.5-1 mum, with fluorescence of lower intensity between them. Fluorescent staining was not detected on adjacent, extrasynaptic, muscle membrane. In side views the staining appeared as a fine line with small protuberances occurring at the same intervals as the intense bands seen face-on. These results indicate that acetylcholine receptors are associated with the entire subsynaptic membrane, including the membrane of the junctional folds and that their density changes abruptly at the border between synaptic and extrasynaptic muscle membrane.