Chloramphenicol and the neonatal calf

Pharmacokinetic values and possible toxic effects of chloramphenicol on bone marrow and hematologic and serum chemical values were determined in newborn calves given the drug (IV) once a week or in repeated doses, 12 hours between doses. The rates of elimination for chloramphenicol and antipyrine also were compared. Chloramphenicol also was administered to older calves by IM and subcutaneous routes, with an apparent bioavailability of 50% to 60%. The elimination half-lives for both chloramphenicol and antipyrine were markedly increased in the newborn calf for at least the first 3 to 4 weeks of life. Despite the high and prolonged serum chloramphenicol concentrations in these calves, there was little or no indication of toxic effects. Bone marrow aspirates did not reveal any signs of intoxication such as cytoplasmic or nuclear vacuolation. Marrow cellularity was not recognizably different from the control group.     

Congenital white muscle disease in a Belgian blue calf

In this case report about white muscle disease (WMD) in a Belgian Blue herd, the disease is described both as an individual and as a herd problem. Aetiology, diagnosis, and therapy of WMD are discussed. WMD is a disease of animals with muscle damage due to the presence of free radicals. Unsaturated fatty acids in the cell membrane are transformed into a radical form in a chain reaction: a fatty acid next to the fatty acid radical can be transformed into another free radical. In healthy animal the chain reaction is stopped by anti-oxidants such as vitamin E and glutathione peroxidase. WMD can occur when more free radicals are produced than the available anti-oxidants can deal with. The disease occurs in calves, lambs, and foals.     

新生犊牛皱胃平滑肌细胞的原代培养——组织块培养法和胶原酶消化法的比较研究

通过组织块培养法和胶原酶消化法分离培养犊奶牛皱胃平滑肌细胞,采用免疫细胞化学方法和免疫荧光化学方法对其进行鉴定,并将鉴定结果、细胞生长曲线进行比较。结果,两种方法培养出的细胞生长曲线基本相同,细胞纯度免疫细胞化学鉴定结果为：组织块培养法为95％以上,胶原酶消化法为90％;免疫荧光鉴定结果为：组织块培养法为96％,酶消化法为89％。组织块培养法操作简单、经济,但耗时较长;胶原酶消化法快速、获得细胞较多,但价格昂贵,故在实际操作中可将两种方法联合应用。     

反相高效液相色谱测定家兔肌肉中氯霉素残留量的研究

建立了反相高效液相色谱分析法测定家兔肌肉中氯霉素残留量的实验方法,能快速、简便、灵敏地测定兔肉中的氯霉素残留。本方法最低检出浓度为10μg.kg-1,氯霉素浓度在0.01～10μg.ml-1范围内具有良好的线性关系,平均回收率为92.6%,RSD为1.85%～2.78%。本方法适于动物肌肉组织中氯霉素残留的监测。     

Injection and sampling methods for drug residue study in calf muscle

Eight calves, weighing 50-150 kg, were given intramuscularly 5 ml of ampicillin (ABPC) aqueous suspensions (200 mg potency/ml) in their right and left gluteal and femoral regions. All calves were sacrificed one hour later to confirm the location of injected drug. The drug was found in a muscle layer when injected with a needle 15 mm long to the following positions, 1. the midpoint between the central position of the gluteal region (CG) and the tuber coxae (M-CTc), 2. the midpoint between CG and the tuber ossis ischii (M-CTo), 3. the central position of M. semimembranaceus in the femoral region (CF). Seven calves, weighing 130-150 kg, were given intramuscularly 5 ml of ABPC suspensions at M-CTo and CF and sacrificed one hour (4 calves) and 3 days (3 calves) later. ABPC diffused along the long axis of the muscle fibers but not to the radial direction. ABPC was detected only in the injected muscle layer even after 3 days indicating that the drug did not diffuse to the neighboring muscles. In the injected muscle layer, concentration of ABPC was remarkably different from part to part. From these results, sampling of the injected muscle for the drug residue study was proposed as follows: 1. isolate about 100 g of muscle just under the stick point marked on the skin considering the direction of drug diffusion, and 2. isolate separately about 200 g of the surrounding muscle to confirm if the sampling is appropriate.     

Adrenergic regulation of vascular smooth muscle tone in calf digital artery

Radioligand binding studies and functional assays on isolated smooth muscle preparations were performed in order to obtain a biochemical and functional characterization of the beta-adrenoceptor (beta-AR) subtypes involved in regulation of the smooth muscle relaxation of the calf's common digital artery. The results indicate that the common digital artery possesses two beta-AR populations (40% beta(1) and 60% beta(2)) and the beta(2)-subtype appears to predominate as far as function is concerned. Only the beta(2)-AR agonists clenbuterol and fenoterol caused dose-related relaxant effects, antagonized by propranolol, when tested in preparations precontracted both with PGF(2alpha) (1.4 x 10(-5) m) and noradrenaline (1.2 x 10(-6) m). In noradrenaline precontracted preparations the beta(1)-AR selective agonists dobutamine and xamoterol caused vasodilation which was not antagonized by (+/-)propranolol. While the functional relaxant effects of dobutamine may be attributed to its potent competitive alpha-AR blocking activity, further investigations are required to explain the effect of xamoterol. The vasodilator effect of (+/-)isoproterenol was irregular. The recorded contractile effects, mainly at dosages greater than 10(-6) m, suggest the loss of drug selectivity for beta-AR and alpha-AR activation. Indirect evidence indicates that the alpha-adrenoceptor (alpha-AR) population in this tissue which produces a strong contraction is functionally dominant over the beta-AR, suggesting limited therapeutic benefit for beta-AR drugs to control blood flow disorders in the calf's distal limb.     

Assessment of alterations in triglyceride and glycogen concentrations in muscle tissue of Alaskan sled dogs during repetitive prolonged exercise

OBJECTIVE: To assess changes in muscle glycogen (MG) and triglyceride (MT) concentrations in aerobically conditioned sled dogs during prolonged exercise. ANIMALS: 54 Alaskan sled dogs fed a high-fat diet. PROCEDURES: 48 dogs ran 140-km distances on 4 consecutive days (cumulative distance, up to 560 km); 6 dogs remained as nonexercising control animals. Muscle biopsies were performed immediately after running 140, 420, or 560 km (6 dogs each) and subsequently after feeding and 7 hours of rest. Single muscle biopsies were performed during recovery at 28 hours in 7 dogs that completed 560 km and at 50 and 98 hours in 7 and 6 dogs that completed 510 km, respectively. Tissue samples were analyzed for MG and MT concentrations. RESULTS: In control dogs, mean +/- SD MG and MT concentrations were 375 +/- 37 mmol/kg of dry weight (kgDW) and 25.9 +/- 10.3 mmol/kgDW, respectively. Compared with control values, MG concentration was lower after dogs completed 140 and 420 km (137 +/- 36 mmol/kgDW and 203 +/- 30 mmol/kgDW, respectively); MT concentration was lower after dogs completed 140, 420, and 560 km (7.4 +/- 5.4 mmol/kgDW; 9.6 +/- 6.9 mmol/kgDW, and 6.3 +/- 4.9 mmol/kgDW, respectively). Depletion rates during the first run exceeded rates during the final run. Replenishment rates during recovery periods were not different, regardless of distance; only MG concentration at 50 hours was significantly greater than the control value. CONCLUSIONS AND CLINICAL RELEVANCE: Concentration of MG progressively increased in sled dogs undergoing prolonged exercise as a result of attenuated depletion.     

Chloramphenicol toxicosis in cats

Six cats were given chloramphenicol orally at the dose level of 120/mg/kg/day in 3 divided doses for 14 days and were then observed for another 3 weeks after treatment. Five other cats were used as untreated controls for the first 14 days and subsequently were given 60 mg of chloramphenicol/kg/day for 21 days. Clinical signs of toxicosis, which were more severe in cats given the higher dose level, included central nervous system depression, dehydration, reduced food intake, body weight loss, sporadic diarrhea, and vomiting. In cats given the higher dose level, chloramphenicol caused reversible marrow suppression, with marrow hypoplasia, maturation arrest of erythroid cells, and inhibition of mitotic activity, and caused vacuolation of lymphocytes and of early myeloid and erythroid cells. Significant changes were evident in bone marrow after treatment for 1 week and in peripheral blood at the end of the 2nd week. Hematologic changes included decreased numbers of neutrophils, lymphocytes, reticulocytes, and platelets. In cats given the lower dose level, changes in blood and bone marrow were similar but less severe.     

Intercellular signaling between adipose tissue and muscle tissue

Adipose and muscle tissues undergo regulated growth and differentiation processes that are modulated by a wide range of factors. The interactions between myogenic cells and adipocytes play a significant role in growth and development, including the rate and extent of myogenesis, muscle growth, adipogenesis, lipogenesis/lipolysis, and in the utilization of energy substrates. Important hormones and growth factors involved in the regulation of these processes include glucocorticoids, insulin-like growth factors, various cytokines, insulin, and leptin. Interactions among these axes have important implications in their influence on relative fat and lean deposition and the efficiency of energy utilization in growth and development. As research progresses to better clarify the interactions among adipose tissue depots and muscle of different fiber types, pathways will become better understood, ultimately leading to the optimized management of fat and lean growth in domestic livestock species. This review will focus on elements of intercellular signaling, using data from cell culture studies to illustrate specific examples of signaling pathways between cells.     

Determining the IgG concentrations in bovine colostrum and calf sera with a novel enzymatic assay

Background: Immune protection in newborn calves relies on a combination of the timing,volume and quality of colostrum consumed by the calf after birth.Poor quality colostrum with inadequate immunoglobulin concentration contributes to failed transfer of passive immunity in calves,leading to higher calf morbidity and mortality.Therefore,estimating colostrum quality and ensuring the transfer of passive immunity on farm is of critical importance.Currently,there are no on-farm tools that directly measure immunoglobulin content in colostrum or serum.The aim of this study was to apply a novel molecular assay,split trehalase immunoglobulin G assay(STIGA),to directly estimate immunoglobulin content in dairy and beef colostrum and calf sera,and to examine its potential to be developed as on-farm test.The STIGA is based on a split version of trehalase TreA,an enzyme that converts trehalose into glucose,enabling the use of a common glucometer for signal detection.In a first study,60 dairy and64 beef colostrum and 83 dairy and 84 beef calf sera samples were tested with STIGA,and the resulting glucose production was measured and compared with radial immunodiffusion,the standard method for measuring immunoglobulin concentrations.Results: Pearson correlation coefficients between the methods were determined and the sensitivity,specificity,and accuracy of the test were calculated for different colostrum quality and failed transfer of passive immunity cut-off points.The correlations of the STIGA measured by colorimetric enzymatic reaction compared to radial immunodiffusion for dairy and beef colostrum were 0.72 and 0.73,respectively,whereas the correlations for dairy and beef sera were 0.9 and 0.85,respectively.Next,STIGA was tested in a blinded study with fresh colostrum and serum samples where the correlation coefficient was 0.93 and 0.94,respectively.Furthermore,the performance of STIGA followed by glucometer readings resulted in correlations with radial immunodiffusion of 0.7 and 0.85 for dairy and beef colostrum and 0.94 and 0.83 for dairy and beef calf serum.Conclusions: A split TreA assay was validated for measurement of the immunoglobulin content of colostrum and calf sera using both a lab-based format and in a more user-friendly format compatible with on-farm testing.     

Pharmacokinetics and lung tissue concentrations of tulathromycin in swine

The absolute bioavailability and lung tissue distribution of the triamilide antimicrobial, tulathromycin, were investigated in swine. Fifty-six pigs received 2.5 mg/kg of tulathromycin 10% formulation by either intramuscular (i.m.) or intravenous (i.v.) route in two studies: study A (10 pigs, i.m. and 10 pigs, i.v.) and study B (36 pigs, i.m.). After i.m. administration the mean maximum plasma concentration (C(max)) was 616 ng/mL, which was reached by 0.25 h postinjection (t(max)). The mean apparent elimination half-life (t(1/2)) in plasma was 75.6 h. After i.v. injection plasma clearance (Cl) was 181 mL/kg.h, the volume of distribution at steady-state (V(ss)) was 13.2 L/kg and the elimination t(1/2) was 67.5 h. The systemic bioavailability following i.m. administration was >87% and the ratio of lung drug concentration for i.m. vs. i.v. injection was > or =0.96. Following i.m. administration, a mean tulathromycin concentration of 2840 ng/g was detected in lung tissue at 12 h postdosing. The mean lung C(max) of 3470 ng/g was reached by 24 h postdose (t(max)). Mean lung drug concentrations after 6 and 10 days were 1700 and 1240 ng/g, respectively. The AUC(inf) was 61.4 times greater for the lung than for plasma. The apparent elimination t(1/2) for tulathromycin in the lung was 142 h (6 days). Following i.m. administration to pigs at 2.5 mg/kg body weight, tulathromycin was rapidly absorbed and highly bioavailable. The high distribution to lung and slow elimination following a single dose of tulathromycin, are desirable pharmacokinetic attributes for an antimicrobial drug indicated for the treatment of respiratory disease in swine.