Sexual dimorphism of circulating somatotropin, insulin-like growth factor I and II, insulin-like growth factor binding proteins, and insulin: relationships to growth rate and carcass characteristics in growing lambs

The effects of sex and age on patterns of circulating somatotropin (ST) concentration and plasma IGF-I, IGF-II, insulin, and IGF binding protein-3 (IGFBP-3) were studied in ram, wether, and ewe lambs (n = 7 or 8) sampled at mean ages of 81 (I1) and 158 d (I2). Between 81 and 158 d of age, rams grew more rapidly than wethers (P < .01), and wethers grew more rapidly than ewes (P < .01). The sex differences in growth were reflected in empty body weight at slaughter: rams > wethers > ewes (P < .05). Mean plasma ST concentrations, ST pulse amplitude, and integrated plasma ST concentrations were greater (P < .05) in rams than in ewes at I1 and I2. Characteristics of the ST plasma profile in wethers were generally intermediate between those of rams and ewes. The interpulse interval was greater in ewes than in wethers at I2. The IGF-I and IGFBP-3 concentrations were greater in rams than in ewes at both sampling times. Plasma IGF-II was greater in ewes than in rams at I2. Mean plasma ST was approximately two thirds less at I2 than at I1 regardless of sex. Mean plasma ST and IGF-I at both ages were positively correlated with growth. Mean plasma ST at I2 was negatively correlated with fatness at slaughter. Sex and age significantly affected patterns of circulating ST and concentrations of IGF-I and IGFBP-3 in prepubertal growing lambs, under conditions for which growth rates and composition were also sexually dimorphic.     

Analysis of laser source nonlinearity due to longitudinal mode-hopping

The nonlinearity of a frequency-ramped single-mode laser source to be used in optical heterodyne interferometry has been investigated. The analysis is based on mode-hopping due to variation in injection current, temperature and mismatch reflections.     

Abrasion phenomena in twill tencel fabric

The abrasion characteristics of Tencel fabrics were evaluated by Martindale abrasion and laundering, and the breakdown mechanism of fibers was surveyed by scanning electron microscopy. The fabric was subjected to pad‐dry‐cure treatment with two different types of modified dimethyloldihydroxyethylene urea resins (Reaktant DH and Reaktant FC). Although the degree of dry abrasion varied with different resins, the damage exhibited by individual fibers differed little from untreated to resin‐treated; the major mechanism of abrasion was through friction, and the mechanism of fiber failure was multiple splitting and transverse cracking. In untreated Tencel, the characteristic feature of wet abrasion was massive fibrillation, and in crosslinked fabrics, the wet abrasion mechanism was through fiber slippage and slicing action, although in the Reaktant FC‐treated fabric, the wet abrasion mechanism was more through slicing than through fiber splitting. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1391–1398, 2006     

A procedure for measuring peptides in rumen fluid and evidence that peptide uptake can be a rate-limiting step in ruminal protein degradation

A relatively simple and sensitive procedure was developed to measure the concentration of peptides in rumen fluid. Feed particles and microorganisms were removed by centrifugation, and the supernatant was treated with perchloric acid (5% final concentration). Perchloric acid precipitated macromolecules that included protein, RNA, and DNA. Perchlorate was subsequently removed by precipitation with an excess of potassium carbonate. Ammonia was removed by boiling the alkaline sample. Supernatant samples were then analyzed for ninhydrin reactive material before and after HCl hydrolysis. Because ninhydrin reaction was 3 to 7.5 times greater after HCl hydrolysis, peptides rather than amino acids were the primary source of nonprotein, nonammonia nitrogen. Rumen fluid from a cow fed timothy hay and concentrate supplement (16% crude protein) contained more than 1200 mg peptides/L (192 mg N/L), 1 h after feeding, and this value declined the prefeeding value of 400 mg/L (64 mg N/L) by 8 h after feeding. Comparison of ninhydrin reactivity with and without HCl hydrolysis indicated that peptides present before feeding contained more peptide bonds than the peptides soon after feeding. High pressure liquid chromatography revealed a variety of peaks soon after feeding and fewer dominant peaks 8 h later. The data suggest that peptide uptake into rumen microorganisms can be a rate-limiting step in ruminal protein degradation.