No abstract

Eleven Landrace pigs (six boars and five gilts, 50 kg) representing lines selected for three generations for maximum weight at 200 d of age were compared to eight pigs (four boars and four gilts, 50 kg) representing contemporary randomly selected Landrace controls to determine the effect of selection for growth on the metabolic clearance rate (MCR) and plasma concentrations of porcine growth hormone (GH). To estimate MCR of GH, the disappearance of a bolus of porcine GH was monitored over 120 min following its i.v. injection. Blood samples also were collected every 15 min over a 6-h period before injecting GH to determine baseline and overall mean GH concentrations, mean peak amplitude and number of GH secretory episodes. Boars exhibited greater overall mean GH concentrations (4.80 vs 3.11 ng/ml; P less than .05) and had greater maximum GH concentrations associated with secretory episodes (16.11 vs 10.80 ng/ml; P less than .05) than did gilts. There were no differences between boars and pigs exhibited greater baseline GH concentrations (2.04 vs 1.25 ng/ml; P less than .01) than did those from the unselected Landrace line. Selected and control pigs exhibited similar (P greater than .15) overall mean concentrations of GH, frequency of secretory episodes, amplitude of GH peaks and MCR. These data demonstrate that pigs selected for heavier weight at 200 d of age had greater basal plasma GH concentrations than did unselected control pigs.

The aquaculture of macroalgae for human consumption and other high-end applications is experiencing unprecedented development in European countries, with the brown algae Saccharina latissima being the flag species. However, environmental conditions in open sea culture sites are often unique, which may impact the biochemical composition of cultured macroalgae. The present study compared the elemental compositions (CHNS), fatty acid profiles, and lipidomes of S. latissima originating from three distinct locations (France, Norway, and the United Kingdom). Significant differences were found in the elemental composition, with Norwegian samples displaying twice the lipid content of the others, and significantly less protein (2.6%, while French and UK samples contained 6.3% and 9.1%, respectively). The fatty acid profiles also differed considerably, with UK samples displaying a lower content of n-3 fatty acids (21.6%), resulting in a higher n-6/n-3 ratio. Regarding the lipidomic profile, samples from France were enriched in lyso lipids, while those from Norway displayed a particular signature of phosphatidylglycerol, phosphatidylinositol, and phosphatidylcholine. Samples from the UK featured higher levels of phosphatidylethanolamine and, in general, a lower content of galactolipids. These differences highlight the influence of site-specific environmental conditions in the shaping of macroalgae biochemical phenotypes and nutritional value. It is also important to highlight that differences recorded in the lipidome of S. latissima make it possible to pinpoint specific lipid species that are likely to represent origin biomarkers. This finding is relevant for future applications in the field of geographic origin traceability and food control.

The effects of bovine skeletal muscle m-calpain and calpastatin on the degradation of casein and isolated bovine myofibrils were characterized under various pH values (7.0, 6.2, 5.7) and ionic strengths (32 to 400 mM KCl) at 25 degrees C. Caseinolytic assays indicated that m-calpain activity increased with increasing pH (P < .01) but decreased with increasing ionic strength (P < .01). Regardless of the presence of m-calpain, SDS-PAGE of myofibrils showed increased solubilization of myofibrillar proteins as pH and ionic strength increased. However, only in the presence of m-calpain were changes normally observed during postmortem storage reproduced. Protein release attributed to m-calpain activity increased with pH, but the effects of elevated ionic strength on the ability of m-calpain to hydrolyze myofibrillar proteins were not evident from SDS-PAGE, except for the decreased troponin-T degradation by m-calpain at the higher ionic strengths. A pH x ionic strength interaction was observed for calpastatin activity determined by caseinolytic assays (P < .01). No changes in m-calpain inhibition were detected at pH 7.0 and 6.2 at different ionic strengths. However, at pH 5.7 the ability of calpastatin to inhibit m-calpain decreased with increasing ionic strength. No changes in m-calpain inhibition could be detected with SDS-PAGE. Based on these results, it can be concluded that although m-calpain and calpastatin activities decrease with increasing ionic strength, their activities in the presence of myofibrils were not affected by ionic strengths typically found in postmortem muscle.

An indirect antibody ELISA was developed for rapid and sensitive quantification of skeletal muscle calpastatin. Polyclonal antibodies were raised in rabbits against recombinant calpastatin, corresponding to domains 2, 3, and 4 of bovine skeletal muscle calpastatin. Western blot analysis revealed that these antibodies specifically recognize an immunoreactive calpastatin protein of approximately 130 kDa in prerigor skeletal muscle extracts. The intensity of the immunoreactive bands corresponds qualitatively with assayable calpastatin activity. For ELISA development, optimum dilutions of sample, primary anti-calpastatin antibody, and peroxidase-conjugated secondary antibody were determined by titration. A dilution optimum for coating of Immulon 4 (Dynatech) plates was observed when heated muscle extracts were diluted to 2 to 4 micrograms of protein/mL and incubated for 2 h at 37 degrees C. Optimum primary (30 micrograms IgG/mL) and secondary (Sigma A-6154; 1:1000 dilution) antibody incubations were for 1 h at 37 degrees C. Tetramethylbenzidine was used as substrate and A450 of the stopped reaction product was recorded in an automated plate reader. Calpastatin ELISA results were linearly related to calpastatin activity (calpain inhibitory activity) of heated longissimus muscle homogenates from prerigor lamb (r2 = .89; n = 40) and beef aged for 24 or 48 h (r2 = .90; n = 47). Intra-assay CV was < 5% (n = 8) and inter-assay CV was < 6% (n = 5). This assay offers advantages of speed, simplicity, and sensitivity over conventional methodology for calpastatin quantification.