Long-chain polyunsaturated fatty acids protect the heart against ischemia/reperfusion-induced injury via a MAPK dependent pathway

The mechanisms by which long-chain dietary polyunsaturated fatty acids (PUFAs) protect against cardiovascular disease are largely unknown. The present study determines the effects of eicosapentaenoic acid (EPA) and arachidonic acid (ARA) on the response of neonatal rat cardiomyocytes to simulated ischaemia (SI) and reperfusion (R). Myocytes isolated from 1-2 day old Wistar rat hearts were cultured with or without EPA or ARA and exposed to 1 h SI followed by 30 minutes reperfusion. Apoptosis was evaluated by caspase-3 activation, poly-(ADP-ribose) polymerase (PARP) cleavage and nuclear condensation. EPA (20microM) and ARA (20microM) significantly inhibited caspase-3 activation and PARP-cleavage and reduced the apoptotic index during reperfusion. Both fatty acids significantly increased ERK phosphorylation and decreased p38 phosphorylation during reperfusion. The mechanism of action of ARA on the MAPKs was further investigated with okadaic acid (to inhibit serine-threonine phosphatases) and orthovanadate (to inhibit tyrosine phosphatases). Vanadate, but not okadaic acid, significantly reduced ARA-induced inhibition of p38 phosphorylation, suggesting the involvement a tyrosine phosphatase during SI/R. Mitogen-activated protein kinase phosphatase-1 (MKP-1), a dual-specificity phosphatase, was targeted and a significant induction of MKP-1 by ARA and EPA was observed. It was demonstrated for the first time that EPA and ARA protect neonatal cardiac myocytes from ischaemia/reperfusion-induced apoptosis through activation of ERK as well as induction of a dual-specific phosphatase, causing dephosphorylation of the pro-apoptotic kinase, p38. The cardioprotective effects of EPA and ARA could also be demonstrated on the functional recovery of isolated perfused hearts subjected to global ischemia.

Characteristics and efficiency of fast-growing feedlot steers fed different dietary energy concentrations

Most prediction equations of feedlot performance cover average daily gains (ADG) below 1.5 kg/d. The question is whether these equations would be accurate for higher ADG. Medium-to-large-framed weanling and yearling steer calves were fed individually using a transponder-electronic gate system in three feedlot trials and fed in groups in two trials. Average daily gain ranged from .9 to 2.1 kg. Steers were implanted, fed to the same degree of finish, and slaughtered to obtain dressing percentage and cold carcass weight. Initial carcass weights were estimated from initial slaughter groups. Dietary ME concentration (i.e., 10.5, 11.5, 12.0, and 12.5 MJ ME/kg of DM, where 1 Mcal = 4.184 MJ), initial weight, dry matter intake (DMI), and days fed could explain 57% of the variation in ADG. The partial contribution of DMI to the total variation was only 5.2%, confirming the low correlation between DMI and ADG in feedlot trials. The correlation between metabolizable energy intake (MEI) and MEI/ADG also was low, but 80% of the variation in MEI/ADG was accounted for by the variation in ADG. Intake patterns, regardless of dietary energy concentration, indicate that ADG increased with DMI only when ADG was below 1.5 kg/d. Therefore, current prediction equations apparently overpredict ME requirements for fast-growing feedlot steers. Optimal performance occurred at a ME concentration of 12.0 MJ/kg of DM rather than 12.5 MJ/kg of DM. Dressing percentage and carcass gain increased as dietary energy concentration and ADG increased, and current prediction equations should predict that of fast-growing feedlot steers equally well.

Retention time of digesta in the rumen: its repeatability and relationship with wool production of Merino rams

The purpose of this experiment was to determine whether differences in retention time (RT) of digesta in the rumen are associated with individual differences in wool growth rate between Merino rams. Fifty-eight rams were offered a pelleted diet at ad libitum and restricted levels. Digesta RT in the rumen was estimated from fecal excretion plots using 51Cr-mordanted feed as a marker. Wool growth rate during feeding for ad libitum intake was linearly correlated to DMI (r = .37; P < .01) and RT (r = -.32; P < .01). Multiple logistic regression analysis, used to overcome multicollinearity, showed that RT per se exerted a greater effect (P < .07) than DMI (P < .34) on wool growth rate at ad libitum feed intake. When data were blocked by wool growth rate keeping mean BW constant over all groups, high wool producers had shorter (P < .01) RT than low wool producers. Using the probability values of the multiple logistic regression analysis (CATMOD), the probability of obtaining a low wool growth rate with long RT was estimated to be .73, whereas that of obtaining a low wool growth rate with short RT approximated zero, in the ad libitum period. During the restricted feeding period, the probability of obtaining a low wool growth rate with long RT was estimated to be .46, whereas that of obtaining a low wool growth rate with short RT was estimated to be .17. Repeatability, the upper limit of heritability, was .45 (P < .01) and .6 (P < .01), using regression correlation and Spearman rank correlation coefficients, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood metabolite and regulatory hormone concentrations and response to metabolic challenges during the infusion of mimosine and 2,3-dihydroxypyridine in alpine goats

Sixteen Alpine wethers (average BW 35 +/- 2 kg) were used to evaluate the effect of continuous 48-h intravenous infusions of saline (CON), mimosine (MIM; 200 mg.kg.75.d-1), 2-hydroxy-3(1H)-pyridine (2,3-DHP; 200 mg.kg.75.d-1, or MIM+2,3-DHP (100 mg of MIM plus 100 mg of 2,3-DHP-kg.75.d-1) on hepatic function and selected blood metabolite and circulating hormone concentrations. Neither MIM nor 2,3-DHP affected plasma ammonia N, glucose, cortisol, or insulin concentrations over time (P > .10). Jugular plasma total protein concentration was greater in the MIM group (P < .07). Plasma triiodothyronine (P < .01) and thyroxine (P < .08) concentrations were higher in the goats receiving the MIM, 2,3-DHP, and MIM+2,3-DHP infusions than in the goats receiving the CON infusion. Plasma urea N concentration was decreased by MIM (P < .10) and MIM+2,3-DHP (P < .03) compared with the CON infusion. A Propionate Load Test was conducted at 24 to 28 h into the infusion to assess the toxins' effects on the liver's ability to increase circulating glucose concentrations in the presence of elevated propionate levels. The results indicated that neither 2,3-DHP nor MIM reduced the liver's ability to respond to a bolus dose of propionate (P > .10). Following a Urea Load Test, circulating ammonia N and glucose concentrations in the MIM, 2,3-DHP, and MIM+2,3-DHP treatments had lower peak values than that in the CON treatment (P < .01).(ABSTRACT TRUNCATED AT 250 WORDS)