Structural analysis of a bovine arginine tRNA(CCG) gene.

A bovine genomic clone containing a 17.4-kb DNA fragment was isolated and found to contain a solitary arginine tRNA gene with an anticodon of CCG that has a 100% identity to its cognate tRNA. This arginine tRNA gene, symbolized as TRR4, has a characteristic internal split promoter and a typical termination site for RNA polymerase III. The tRNA gene was transcribed in vitro by RNA polymerase III using a HeLa cell-free extract to yield a mature-sized tRNA product. The gene was mapped to bovine chromosome 19 using a panel of bovine-rodent somatic cell hybrid DNAs.

In vitro effects of soy phytoestrogens on rat L6 skeletal muscle cells.

Soy isoflavones display estrogenic activity in humans and animals, and thus are referred to as phytoestrogens. This study was performed to observe the effects of the soy isoflavones genistein, daidzein, and glycitein on cell cultures of rat skeletal muscles. [3H]Thymidine incorporation was used to determine cell proliferation, while protein synthesis and degradation were determined by tracking radiolabeled leucine. For the proliferation studies, insulin, estradiol, genistein, daidzein, or glycitein was supplemented at 0, 0.04, 0.08, 0.16, 0.31, 0.63, 1.25, 2.5, 5, 10, or 20 microM, respectively, or in combinations with final concentrations of 0, 0.1, 1, or 10 microM. Genistein reacted most similarly to estradiol, inhibiting proliferation at > or = 1 microM (P < .001). A combination of phytoestrogens resulted in significant inhibition of cell proliferation, but not to the extent observed with genistein alone. For the protein synthesis and degradation experiments, treatments of 0.1 microM dexamethasone or 1 microM concentrations of insulin, genistein, daidzein, or glycitein were used. Phytoestrogens did not inhibit or stimulate protein degradation or synthesis (P > .05). A one-tailed univariate analysis of variance revealed a trend (P < or = .1) in protein stimulation with genistein and glycitein treatments. These results suggest that the tyrosine kinase inhibiting activity of genistein may be affecting phosphorylation of the mitosis-promoting factor, preventing the advancement of the mitotic cell cycle. In addition, at higher total combined concentrations, daidzein and glycitein may be able to outcompete genistein for receptor sites. These results suggest that soy isoflavones in the diet may potentially modulate normal growth and development in humans and animals that ingest soy-based products.

Interactions in postweaning production of F1 cattle from Hereford, Limousin, or Piedmontese sires.

A 2-yr study was conducted to evaluate the interactions of castration, feeding length, and dietary CP on growth and carcass characteristics of male cattle (bulls and steers) that vary in expression of muscular hypertrophy. Crossbred cows were bred by AI to Hereford, Limousin, or Piedmontese bulls, which represented genotypes with normal, moderate, and hypermuscularity, respectively, but with similar mature weights. Male calves (131 in yr 1 and 120 in yr 2) were placed in pens with individual electronic feeding gates. Calves were fed growing diets until they reached 386 kg BW and then were individually switched to finishing diets for 90 or 132 d. Interactions were observed among sire breed, gender, and feeding length on carcass composition. Bulls were more efficient than steers in producing live weight gain. Length of finishing period accounted for a larger source of variation than gender for weight characteristics, whereas gender was the larger source of variation for carcass composition. Concentration or degradability of dietary CP influenced rate of gain from weaning to 386 kg. Interactions resulting from varying management on carcass characteristics among calves of different sire breeds indicate that unique strategies may be beneficial for the production of meat from these breeds.

Effects of training on maximum oxygen consumption of ponies.

OBJECTIVES: To establish maximum oxygen consumption VO2max) in ponies of different body weights, characterize the effects of training of short duration on VO2max, and compare these effects to those of similarly trained Thoroughbreds. ANIMALS: 5 small ponies, 4 mid-sized ponies, and 6 Thoroughbreds. PROCEDURE: All horses were trained for 4 weeks. Horses were trained every other day for 10 minutes on a 10% incline at a combination of speeds equated with 40, 60, 80, and 100% of VO2max. At the beginning and end of the training program, each horse performed a standard incremental exercise test in which VO2max was determined. Cardiac output (Q), stroke volume (SV), and arteriovenous oxygen content difference (C [a-v] O2) were measured in the 2 groups of ponies but not in the Thoroughbreds. RESULTS: Prior to training, mean VO2max for each group was 82.6 = 2.9, 97.4 +/- 13.2, and 130.6 +/- 10.4 ml/kg/min, respectively. Following training, mean VO2max increased to 92.3 +/- 6.0, 107.8 +/- 12.8, and 142.9 +/- 10.7 ml/kg/min. Improvement in VO2max was significant in all 3 groups. For the 2 groups of ponies, this improvement was mediated by an increase in Q; this variable was not measured in the Thoroughbreds. Body weight decreased significantly in the Thoroughbreds but not in the ponies. CONCLUSIONS AND CLINICAL RELEVANCE: Ponies have a lower VO2max than Thoroughbreds, and larger ponies have a greater VO2max than smaller ponies. Although mass-specific VO2max changed similarly in all groups, response to training may have differed between Thoroughbreds and ponies, because there were different effects on body weight.