Response of C2C12 mouse and turkey skeletal muscle cells to the beta-adrenergic agonist ractopamine

The effects of ractopamine (RAC) and ractopamine stereoisomers (RR, RS, SR, and SS) on cyclic AMP (cAMP) production, total protein, and DNA concentrations in mouse skeletal muscle cells (C2C12) were evaluated. The RAC (10 microM) caused an approximately 30% increase in cell number, protein, and DNA concentrations in myoblasts after 48 h; no differences were found in myotubes. The RAC-stimulated increase of these variables in myoblasts was blocked by the presence of equimolar concentrations of propranolol. At a later passage, myoblasts failed to exhibit an increase in cell number, protein, or DNA upon exposure to RAC. Both myoblasts and myotubes increased cAMP production in response to 10 microM RAC. The RAC isomers ranked RR > SR > RS approximately SS in ability to stimulate cAMP production, with essentially no response to SS. The SR produced about 50% of the RR response. Coincubation of propranolol (10 microM) and RAC (10 microM) prevented RAC-stimulated cAMP production in myotubes but not in myoblasts (approximately 35% of cAMP produced by RAC alone). Turkey satellite cells (derived from biceps femoris of 12-wk-old toms) produced essentially no increased cAMP when exposed to 10 microM RAC stereoisomers. Stability of RAC was evaluated under laboratory storage and culture conditions. The RAC was stable for more than 4 mo when stored in deuterated DMSO (>98% purity) at room temperature or in aqueous solutions at -80 degrees C, as determined from sequential nuclear magnetic resonance studies. Radiolabeled RAC was incubated for 72 h in the presence of serum-containing medium, with or without C2C12 cells. Ninety-eight percent of the parent compound found in the medium at time zero was present in the medium as parent at the end of 72 h. The cellular cAMP response to RAC through beta-adrenergic receptors seems to be stereospecific. If the state of myoblasts and myotubes in vitro reflects the in vivo state, then the ractopamine effect in vivo on cellular processes (including cell division and protein and DNA accumulation) may be independent of beta-adrenergic receptors in muscle.     

Effect of dietary glycine and benzoate level on benzoate metabolism in mink (Mustela vision), blue fox (Alopex lagopus), and raccoon dog (Nyctereutes procyonoides)

Three 2 x 4 factorial experiments were carried out from August to September with 30 juvenile male mink, 24 raccoon dogs, and 24 blue foxes to investigate the effect of dietary glycine supply (low or high) on the efficiency of these species to excrete hippuric acid with incremental benzoate intake (0, 1, 2, or 4 mmol/kg BW). For mink, two additional treatments with 1 or 2 mmol/kg BW of ethyl benzoate were included. A basal low-glycine diet was formulated to meet the minimum protein requirements of fur animals (30% of ME). This diet was supplemented with 0 or 3 g/kg of glycine, or with 0, 1.0, 2.07, or 4.15 g/kg of sodium benzoate for mink and blue foxes, and with 0 or 4.5 g/kg of glycine and 0, 1.58, 3.17, or 6.34 g/kg of sodium benzoate for raccoon dogs, respectively. Two additional diets with .76 or 1.53 g/kg of ethyl benzoate were made for mink. Fecal and urinary benzoic and hippuric acid excretion were measured for 3 d. The 24-h recovery of [14C]benzoic acid injected intraperitoneally was measured from urine, the liver, and the kidneys. All animals appeared healthy and no clinical signs of benzoate overdose were observed. Dietary benzoate level did not affect ADFI or ADG in any species. Glycine supplementation lowered ADFI in mink. The majority of ingested benzoates were absorbed from the gut (over 95%), except in blue foxes, which excreted 6 to 15% of ingested benzoates in feces with incremental increases in benzoate intake. Urinary free benzoic acid excretion accounted for 10% of the ingested benzoates in blue foxes but less than 5% in mink and raccoon dogs. When benzoate intake was 1 mmol/kg BW, mink, blue foxes, and raccoon dogs excreted 71, 77, and 34% of ingested benzoates as hippuric acid in urine, respectively. With higher benzoate intakes, urinary hippuric acid excretion decreased quadratically with mink to 20%, and linearly with blue foxes and raccoon dogs to 45 and 16%, respectively. The hippuric acid pathway appears to be the principal route of benzoate elimination in the mink and blue fox, whereas, in the raccoon dog, other pathways appear to be more important. In mink, the elimination of ethyl benzoate did not differ from that of sodium benzoate. Because glycine conjugation is the primary route of benzoate elimination, it is recommended that benzoate content in fur animal feeds should not exceed 1 g/kg feed on an as-fed basis.     

Evaluation of numbers of microscopic and macroscopic follicles in cattle selected for twinning

We hypothesized that the number of microscopic follicles present in the ovaries of cattle selected for twin births (Twinner) would be greater than in the ovaries of contemporary Controls. Ovaries were collected from seven Control and seven Twinner cows at slaughter. The number of Small (1 to 3.9 mm), Medium (4 to 7.9), and Large (> 8 mm) surface follicles was counted and one ovary was fixed for histological evaluation. Fifty to sixty consecutive 6-microm slices were taken from a piece of cortical tissue, approximately 1 cm x 1 cm in area, located between the surface follicles. Microscopic follicles were classified as primordial (oocyte surrounded by a single layer of squamous pregranulosa cells), primary (oocyte surrounded by a single layer of one or more cuboidal granulosa cells), secondary (oocyte surrounded by two or more layers of granulosa cells), or tertiary (oocyte surrounded by multiple layers of granulosa cells with initiation of antrum formation to < or = 1 mm in diameter). The total number of follicles was counted in 200 fields (2 mm x 2 mm) per ovary. A field containing no follicles was classified as empty. There were significantly more secondary follicles in Twinner compared with Control ovaries (12.9 vs 6.3; P < .05). Twinners also tended to have more small surface follicles (35.4 vs 49.0; P < 0.1). We conclude that ovaries of Control and Twinner cows do not differ in the number of primordial follicles or in the number of follicles activated into the growing pool; however, Twinner cows are able to maintain more growing follicles at the secondary and subsequent stages of development.     

Forage systems for production of stocker steers in the upper south

The southern states produce large numbers of beef calves that are generally weaned and sold in autumn. Keeping calves in this region beyond weaning to graze high-quality forages through a stocker cattle phase could improve profitability. Autumn-weaned Angus crossbred steers were allocated by breeding and weight to four forage systems that began in mid-November and continued through mid-October as follows: System 1, tall fescue (Festuca arundinacea Schreb.) and Kentucky bluegrass (Poa pratensis L.)-white clover (Trifolium repens L.); System 2, tall fescue, caucasian bluestem (Bothriochloa caucasica [Trin.] C. E. Hubbard) and tall fescue-red clover (Trifolium pratense L.); System 3, orchardgrass-alfalfa and bluegrass-white clover; and System 4, rye (Secale cereale L.), soybeans (Glycine max)-foxtail millet (Setaria italica), and bluegrass-white clover. All steers were supplemented with hay or silage previously cut from their respective systems when forage for grazing was limited. System 2 which used stockpiled tall fescue for winter grazing and caucasian bluestem for summer forage plus fescuered clover for hay and grazing in a three-paddock system, resulted in greater (P < .01) gain per hectare and per steer, more grazing days, and reduced stored forage requirements and produced more surplus feed than the other systems tested. Gains per hectare for Systems 1 through 4 were 454, 554, 472, and 487 kg (SE = 18), respectively. Harvested forage from Systems 1, 2, and 3 met needs for stored forages but System 4 required additional "purchased" hay. Stored forage was fed for 61, 38, 112, or 104 d for Systems 1 through 4, respectively. Within the physio-climatic region of this experiment, a simple three-paddock system based on cool- and warm-season perennial forages could improve beef production per unit of land area while reducing inputs of labor and equipment.     

Differential expression of surface membrane antigens on bovine monocytes activated with recombinant cytokines and during Trypanosoma congolense infection

The expression of surface membrane antigens on peripheral blood monocytes (PBM) of cattle of the Boran and N'Dama breeds activated with recombinant cytokines (TNF-alpha and IFN-gamma) and during experimental infection with Trypanosoma congolense was investigated using monoclonal antibodies (MoAbs) and fluorescein-activated cell sorter (FACS). The surface antigens investigated were C3bi receptor, major histocompartibility (MHC) II complex (Ia antigen) and two monocyte/macrophage (Mphi) differentiation antigens. The study revealed that both cytokines caused the enhancement of the expression of all the PBM surface antigens studied. rBolFN-gammaat low concentrations was more efficient in causing the activation of PBM. While the PBM of Boran cattle were more significantly activated to express the C3bi receptor vis-à-vis the Ia antigen than N'Dama cattle, the reverse was the case with the PBM of N'Dama cattle which expressed more Ia antigens than Boran PBM. Similar results were observed during T. congolense infection in the two breeds of cattle. The significantly higher expression of C3bi receptor and correspondingly lower Ia antigen expression by the PBM of Boran cattle, both during trypanosomosis and in vitro may be responsible for the higher rate of erythrocyte phagocytosis, hence the development of more severe anaemia by Boran cattle during trypanosomosis than N'Dama. In addition, the expression of significantly higher numbers of Ia antigen by N'Dama Mphi, hence are more able to process, present and initiate better trypanosome antigen-specific immune response than Boran cattle during infection. These two attributes are known genetic characteristics of trypanotolerance in cattle.     

Gene expression in the forebrain of dexamethasone-treated pigs: effects on stress neuropeptides in the hypothalamus and hippocampus and glutamate receptor subunits in the hippocampus

Gene expression studies advance our understanding of the effects of stress and glucocorticoids on brain function and give a new direction to animal welfare research. In this context, the presence of messenger RNA s (m RNA s) for corticotrophin releasing hormone (CRH) and vasopressin (VP) in the porcine hypothalamus has recently been documented. This study investigated the expression of CRH, VP and ionotropic glutamate receptor (iGluR) subunit m RNA s in the brains of pigs treated with the synthetic glucocorticoid dexamethasone (Dex; 5 mg kg(-1)i.v.). In the hypothalamus, VP, but not CRH, m RNA was reduced 3 hours after Dex. In the hippocampus, expression of m RNA s for some iGluR subunits appeared to be differentially regulated 6 hours after Dex. In addition, CRH message was detected in the hippocampus and significantly upregulated in the CA1 region 3 hours after Dex. The relevance of these findings to stress neurobiology of the growing pig is discussed.