Insulin binding to bovine mammary membranes: comparison of microsomes versus smooth membranes

The study was undertaken to determine if membrane preparations of bovine mammary tissue bound insulin. If binding occurred, it was also the intent to compare binding kinetics between microsomes and smooth membranes. Insulin binding to bovine mammary membranes attained equilibrium, was saturable and was specific for insulin. Additional studies showed binding to be pH sensitive and maximal at 10 mM calcium. Binding affinity of insulin to microsomes and smooth membranes was similar, with the exception that smooth membranes bound 1.8 times more insulin per unit of membrane protein than microsomes. Two different methods were used to generate data for kinetic analysis of the insulin-receptor interaction in microsomes. Competitive binding assays (.6 ng [125I]insulin plus 0 to 100 ng insulin) indicated the presence of two binding sites with dissociation constants (Kd) of .32 and 15.8 nM. Direct titration of microsomes with [125I]insulin (.02 to 10 ng/ml) revealed two binding sites with Kd of .017 and .31 nM. The affinity of the second binding site measured by the competitive binding assay method (Kd of 15.8 nM) is low and therefore may not be of physiological importance for insulin action. Insulin appears to bind to two high-affinity receptor sites in bovine mammary microsomes with Kds of .017 nM and .32 nM. These findings show that bovine mammary tissue contains receptors for insulin. In addition, isolation of smooth membranes from microsomes enriches the number of insulin receptors per unit of membrane protein without altering their binding characteristics.     

Stimulation of swine growth by porcine growth hormone

Highly purified porcine growth hormone (pGH; USDA-B1) was administered by im injection (22 micrograms X kg body weight-1 X d-1) to rapidly growing Yorkshire barrows for 30 d. Growth hormone significantly increased growth rate (10%), feed efficiency (4%), cartilage growth and muscle mass. However, pGH did not affect carcass adipose tissue mass. Intramuscular lipid content of the longissimus was increased 50% by pGH administration. Plasma pGH concentration was elevated (7- to 11-fold) for 3 to 5 h post-injection. Chronic administration of pGH depressed pituitary GH content and concentration approximately 45%. No GH antibodies were detected in the plasma of GH-treated swine. Plasma somatomedin-C concentration was increased 55% by GH treatment 3 h post-injection. Plasma glucose and insulin concentrations were both significantly increased in GH-treated swine, suggesting that the animals had developed a state of insulin resistance. Plasma-free fatty acid concentration tended to be higher in GH-treated animals. Treatment of swine with pGH significantly decreased plasma blood urea nitrogen. Assessment of animal health during the trial and postmortem indicated that pGH administration did not have any adverse effects. In summary, treatment of young, rapidly growing swine with pGH stimulated growth performance without affecting animal health or inducing the production of GH antibodies.     

Retracted: Effect of Post‐Thaw Storage Time on Motility and Fertility of Cryopreserved Beluga Sturgeon (Huso huso) Sperm

The aim of this study was to test the influence of post ‐ thaw storage time on the duration of sperm motility, percentage of motile sperm, and fertilization and hatching rates of fresh sperm and sperm stored for 0, 30 and 60 min at 4°C post‐thawing. After being frozen in liquid nitrogen and then thawed, the percentage of motile sperm and duration of motility were not affected by 30 min of storage at 4°C, whereas a significant decline in these parameters was observed after 60 min of storage. Similarly, fertilization and hatching rates were significantly affected within 60 min of storage at 4°C, and the fertility of frozen‐thawed sperm was significantly lower than that of fresh sperm. We conclude that cryopreserved sperm of beluga sturgeon could be stored for 30 min without the loss of sperm quality. This described procedure for beluga sturgeon cryopreservation is reliable and efficient and therefore can be recommended for hatchery practice after scaling up this technique.     

Rhodococcus equi-associated osteomyelitis in foals

Two cases of Rhodococcus equl infection in foals are described, in which osteomyelitis was a feature. Because rhodococcal infection is usually low grade and chronic, and because the signs of early metaphysitis can be subtle, any articular or periarticular swelling in a foal from a farm with a history of rhodococcosis should be strongly suspected to be associated with R equl until proven otherwise.     

Finite element modeling of ROPS in static testing and rear overturns

Even with the technological advances of the last several decades, agricultural production remains one of the most hazardous occupations in the United States. Death due to tractor rollover is a prime contributor to this hazard. Standards for rollover protective structures (ROPS) performance and certification have been developed by groups such as the Society of Automotive Engineers (SAE) and the American Society of Agricultural Engineers (ASAE) to combat these problems. The current ROPS certification standard, SAE J2194, requires either a dynamic or static testing sequence or both. Although some ROPS manufacturers perform both the dynamic and static phases of SAE J2194 testing, it is possible for a ROPS to be certified for field operation using static testing alone. This research compared ROPS deformation response from a simulated SAE J2194 static loading sequence to ROPS deformation response as a result of a simulated rearward tractor rollover. Finite element analysis techniques for plastic deformation were used to simulate both the static and dynamic rear rollover scenarios. Stress results from the rear rollover model were compared to results from simulated static testing per SAE J2194. Maximum stress values from simulated rear rollovers exceeded maximum stress values recorded during simulated static testing for half of the elements comprising the uprights. In the worst case, the static model underpredicts dynamic model results by approximately 7%. In the best case, the static model overpredicts dynamic model results by approximately 32%. These results suggest the need for additional experimental work to characterize ROPS stress levels during staged overturns and during testing according to the SAE standard.     

Characterization of somatotropin binding sites in pig skeletal muscle.

The present study was conducted to determine whether somatotropin (ST) binding sites are present in crude membrane preparations containing sarcolemma of pig skeletal muscle. Initial characterization experiments indicated that binding of bovine ST (bST) was time- and temperature-dependent and that binding was reversible. At 23 degrees C, binding was maximized between 36 and 48 h, whereas at 4 degrees C binding had not reached a maximum by 96 h. Somatotropin binding was stable between pH 5.5 and 8.5 and increased linearly between 100 and 600 micrograms of membrane protein. Addition of unlabeled bST decreased specific binding of [125I]bST in a dose-dependent manner (ED50: 1 to 1.6 ng/mL). The binding sites for bST were specific because porcine prolactin poorly inhibited bST binding. Scatchard analysis revealed the presence of a single class of binding sites (Ka: 9 to 15 x 10(9)M-1; Bmax: 5 to 6 fmol/mg of protein). In summary, the present report is the first to demonstrate that specific ST receptors are present in pig skeletal muscle. The role that ST plays in directly stimulating muscle growth and(or) muscle synthesis of insulin-like growth factor I (IGF-I) in pST-treated pigs as opposed to changes that occur as the result of an increase in plasma IGF-I concentration remains to be resolved.