Catabolism of cytoplasmic and intramitochondrial adenine nucleotides in C2C12 skeletal myotube under chemical hypoxia

Loss of adenosine-5'-triphosphate (ATP) and accumulation of inosine-5'-monophosphate (IMP) are the major purine metabolic changes in the skeletal muscle during hypoxia. This study addressed whether chemical metabolic inhibition reflects those changes in cultured skeletal myotube. For this aim, mouse-derived C2C12 myotubes were cultured in Hank's balanced saline solution containing 2 mM sodium cyanide (CN) and/or 1 mM iodoacetic acid (IAA) up to 180 min. Inhibition of oxidative phosphorylation by CN induced a minimal change in the intracellular adenine nucleotide levels during 180 min. Blockage of glycolysis with IAA caused an over 90% decrease in adenine nucleotides both in the cytoplasmic and intramitochondrial spaces, accompanied with allantoin release. Since 1 mM allopurinol entirely inhibited the allantoin generation, xanthine dehydrogenase/oxidase was found to play a key role in the purine catabolism in IAA-treated C2C12 myotubes. By the combined treatment with CN+IAA, ATP exhaustion and IMP accumulation was achieved with significant cell injury. These changes were comparable with those in skeletal muscles during hypoxia, indicating that our model with CN+IAA is well applicable to the investigation of hypoxia-induced myopathy.     

不同来源高钙日粮对青年蛋鸡血清和肾脏线粒体自由基代谢的影响

以海蓝褐蛋鸡为试验对象,通过检测蛋鸡血清和肾脏线粒体自由基代谢的变化,研究不同来源高钙日粮对青年蛋鸡血清和肾脏线粒体自由基代谢的影响。选40日龄海蓝褐蛋鸡120羽,随机分成3组,每组40羽,分别饲喂正常钙日粮（以磷酸氢钙形式含钙0.9%,对照组）、石粉高钙日粮（含钙3.78%,试验组1）、磷酸氢钙高钙日粮（含钙3.78%,试验组2）,试验期65d。于试验65d,每组随机选取蛋鸡12羽,观察其病理学变化,并分离血清和肾脏线粒体,检测自由基代谢变化。结果显示：试验期间,高钙日粮组均出现青年蛋鸡的异常死亡。试验65d时,与正常对照组相比,石粉高钙组和磷酸氢钙高钙组的左肾重、右肾重、两侧肾总重及肾/体质量比均升高显著或极显著（P〈0.05或P〈0.01）,并导致肾脏出现不同程度的病理学损伤;高钙日粮组可导致蛋鸡血清及肾线粒体MDA、NO含量及XOD活性升高（P〈0.05或P〈0.01）,T-AOC、GSH-PX及SOD活性下降（P〈0.05或P〈0.01）;高钙组组间比较,石粉高钙组表现更严重的组织损伤,血清T-AOC活性降低,与磷酸氢钙高钙组比较差异显著（P〈0.05）。结果提示：高钙日粮可导致青年蛋鸡生长发育的缓慢,肾脏肿大,血清及肾线粒体的自由基生成增多及抗氧化功能的下降。     

Effect of biologically active substances present in water extracts of white mustard and coriander on antioxidant status and lipid peroxidation of mouse C2C12 skeletal muscle cells

Coriander and white mustard, an annual plants originated in the Mediterranean region, have been cultivated and used as spices for a long time. Recent studies have shown that they may constitute a potential source of phenolic compounds. The aim of this study was to evaluate the content of polyphenols in coriander and white mustard water extracts and to investigate their antioxidant activity in C2C12 mouse skeletal muscle cells, which serve as a good model of cells with intensive metabolism. HPLC analysis showed that polyphenols were able to permeate from the water extracts of studied plants into the undifferentiated myoblasts as well as myocytes undergoing differentiation, increasing the concentration of reduced glutathione and upregulating glutathione reductase and peroxidase activity. White mustard and coriander extracts also decreased the levels of oxysterols and sum of tiobarbituric acid reactive substances (TBARS) in both: myoblasts and differentiating myocytes, demonstrating protective effect on cell membranes. The obtained results indicate that polyphenols synthesized by both herbs may have beneficial effects on muscle tissue.     

Effects of dietary protein levels and 2‐methylbutyrate on ruminal fermentation,nutrient degradability,bacterial populations and urinary purine derivatives in Simmental steers

The objective of this study was to evaluate the effects of dietary crude protein (CP ) levels and 2‐methylbutyrate (MB ) supplementation on ruminal fermentation, bacterial populations, microbial enzyme activity and urinary excretion of purine derivatives (PD ) in Simmental steers. Eight ruminally cannulated Simmental steers, averaging 18 months of age and 465 ± 8.6 kg of body weight (BW ), were used in a replicated 4 × 4 Latin square design by a 2 × 2 factorial arrangement. Low protein (98.5 g CP /kg dry matter [LP ] or high protein (128.7 g CP /kg dry matter [HP ]) diets were fed with MB supplementation (0 g [MB ?] or 16.8 g steer^?1 day^?1 [MB +]). Steers were fed a total mixed ration with dietary corn straw to concentrate ratio of 50:50 (dry matter [DM ] basis). The CP  × MB interaction was observed for ruminal total VFA , molar proportions of acetate and propionate, acetate to propionate ratio, ammonia‐N, effective degradability of neutral detergent fibre (NDF ) and CP , microbial enzyme activity, bacterial populations and total PD excretion (p  < .05). Ruminal pH decreased (p  < .05), but ruminal total VFA concentration increased (p  < .05) with increasing dietary CP level or MB supplementation. Acetate molar proportion increased (p  = .043) with MB supplementation, but was not affected by dietary CP level. Propionate molar proportion decreased (p  < .05) with increasing dietary CP level or MB supplementation. Consequently, acetate‐to‐propionate ratio increased (p  = .001) with MB supplementation, but was not affected by dietary CP level. Ruminal ammonia‐N content increased (p  = .034) with increasing dietary CP level, but decreased (p  = .012) with MB supplementation. The effective degradability of NDF and CP increased (p  < .05) with increasing dietary CP level or MB supplementation. Microbial enzyme activity, bacterial populations and total PD excretion also increased (p  < .05) with increasing dietary CP level or MB supplementation. The results indicated that ruminal fermentation, nutrient degradability, microbial enzyme activity, ruminal bacterial populations and microbial protein synthesis improved with increasing dietary CP level or MB supplementation in steers.     

Teratogenicity of edoferon kappa A, a molecule derived from salicylate, in cultured rat embryos: differences from salicylate and interaction with free oxygen radical scavenging enzymes

The effect of edoferon kappa A (E-KA), a non-specific immunomodulatory and anti-neoplastic chemical substance derived from the methyl form of salicylate (acetyl salicylic acid; ASA), on mammalian embryos was studied and compared to the effects of ASA. Rat embryos were cultured in vitro from 9.5 days of gestation for 48 h. E-KA (0.1-12.8 mg/ml) and ASA (0.1-0.6 mg/ml) were added to the whole rat serum. To investigate the interaction of these molecules with antioxidant agents, the lowest effective concentrations of E-KA (0.6 mg/ml) and ASA (0.3 mg/ml) for all parameters were added to the culture media in the presence of superoxide dismutase (SOD) (30 U/ml) or glutathione (0.5 mumol/ml). The growth and development of embryos was compared and each embryo was evaluated for the presence of any malformations. E-KA and ASA decreased growth and development in a concentration-responsive manner. There was also a concentration-related increase in overall dysmorphology (haematoma in the yolk sac and neural system, open neural tube, abnormal tail torsion and the absence of fore limb bud). There were no statistically significant differences between the control and embryos grown in the presence of 0.1-0.4 mg/ml E-KA, although the effects of ASA started at a concentration of 0.2 mg/ml. Embryos showed significant growth retardation in all scoring criteria and severe malformations when 0.5-3.2 mg/ml E-KA and 0.3-0.6 mg/ml ASA were added. When SOD was added, there was a significant decrease in the incidence of malformations and growth and developmental parameters were increased but this decrease never reached the control level. We concluded that E-KA has direct toxic effects on the developing embryo but at much higher concentrations than ASA, and the teratogenic effects of these molecules might be related to free oxygen radicals.     

不同钼水平对山羊红细胞膜自由基代谢及其酶活性的影响

本研究旨在观察不同钼水平对山羊红细胞膜自由基代谢及其酶活性的影响。选用27头健康山羊随机分成3组,选用七钼酸铵（[（NH4）6Mo7O24·4H2O]）作为本试验口服钼源,采用（NH4）6Mo7O24·4H2O水溶液对实验山羊每d1次的方式进行灌服。对照组灌服相应剂量蒸馏水,高钼组山羊按每公斤体质量15mg和45mg（以钼计）灌服（NH4）6Mo7O24·4H2O水溶液（15mg Mo·kg^-1·BW组（Ⅱ组）和45mgMo·kg^-1·BW组（Ⅲ组））。试验为期50d,并于第0、10、20、30、40、50天采血,测定红细胞膜中自由基含量和酶活性变化。结果显示,组内比较,Ⅱ组、Ⅲ组GSH—Px、T—AOC、CAT、GST、T—AOC、ATPase和AKP活性在试验前期（0～30d）差异不显著（P〉0．05）,试验后期（40～50d）与前期比较下降,差异显著（P〈0．05）;MDA含量、XOD和LDH活性在实验前期（0～30d）差异不显著（P〉0．05）,后期（40～50d）与前期（0～30d）比较升高,差异显著（P〈0．05）;组间比较,Ⅱ组、Ⅲ组GSH—Px、T—AOC、CAT、GST、T—AOC、ATPase和AKP活性在实验前期（0～30d）与对照组比较差异不显著（P〉0．05）,后期（40～50d）与对照组比较降低,差异显著（P〈0．05）;MDA含量、XOD和LDH活性前期（0-30d）与对照组比较差异不显著（P〉0．05）,后期（40～50d）升高,差异显著（P〈0．05）。由此可见,摄入过量的钼会导致山羊红细胞膜抗氧化功能降低、自由基含量升高和能量代谢障碍。     

微粒蒙脱石对猪组织铅水平、红细胞生成和肝脏ALA-D酶活性及铅诱导的脂质过氧化的影响

选60头体质量约33kg的“杜长大”杂交猪，随机分成2组，每组3个重复，一组饲以基础日粮＋10mg/kg铅＋0.5％微粒蒙脱石，另一组饲以基础日粮＋10mg／kg铅作为对照。研究结果表明：添加微粒蒙脱石组与对照组相比，明显降低了猪全血、脑、肝、肾、骨和毛等组织中铅含量：通过血细胞计数、血红素和血球容积测定表明，添加微粒蒙脱石组的红细胞生成显著增高，且肝脏中ALA—D酶活性显著提高。铅对肝脏的损伤作用明显。表现为丙二醛（MDA）含量显著升高（17．08％），过氧化氢酶（CAT）、超氧化物歧化酶（SOD）、谷胱甘肽过氧化物酶（GPx）含量分别降低85．73％、52．17％、47．56％，而在日粮中添加微粒蒙脱石可以显著改善铅诱导的上述损伤。结果提示，微粒蒙脱石对铅中毒有潜在的治疗作用。     

Growth factor and cytokine interactions in myogenesis. Part I. The effect of TNF-alpha and IFN-gamma on IGF-I-dependent differentiation in mouse C2C12 myogenic cells

The aim of this study was to examine the potential interactions of IGF-I with TNF-alpha and IFN-gamma with regard to regulation of the myogenesis and proliferative potential of mouse C2C12 myoblasts. The stimulation of myogenesis by IGF-I (30 nmol/l) was manifested by an enhanced myoblast fusion and expression of myosin heavy chain (MHC) during the first 3 days of differentiation. IGF-I-dependent fusion and MHC expression was reduced by TNF-alpha and IFN-gamma. Both cytokines prevented the stimulatory effect of IGF-I on MyoD expression with minor modification of the myogenin level. Both TNF-alpha and IFN-gamma activated the expression of cyclin A in myoblasts restimulated to proliferation; however, when used in combination with IGF-I these cytokines prevented the rise in cyclin A induced by growth factor. In conclusion: i) TNF-alpha and IFN-gamma reduce IGF-I-dependent myogenesis which was manifested by the reduction of myoblast fusion and MHC cellular levels, ii) Molecular mechanisms of inhibitory action of TNF-alpha and IFN-gamma on IGF-I-mediated differentiation involve a decrease in MyoD whereas myogenin level plays a minor role, iii) TNF-alpha and IFN-gamma increase the proliferative potential of myoblasts; however, they reduced the mitogenic effect of IGF-I, manifested by a decrease of IGF-I-stimulated cyclin A expression in myoblasts reinduced to proliferation. Interactions among IGF-I and proinflammatory cytokines are therefore important to establish a number of myoblasts and the onset of myogenesis during muscle regeneration.     

Changes in blood levels of zinc, copper, selenium, glutathione peroxidase, vitamin B12 and total and free thyroxine in sheep removed from pasture and held without food for 50 hours

Blood was collected from a group of ten sheep immediately after removal from pasture and thereafter at regular intervals for 50 hours whilst maintaining them without food but with adequate water. The samples were analysed for parameters normally examined as an aid to the diagnosis of zinc, copper, selenium, cobalt and iodine status. Serum vitamin B12 levels increased with time. Mean plasma zinc concentrations and mean serum concentrations of both T4 and fT4 followed significant parabolic trends. Maximum mean zinc levels (50 +/- 10% higher than initial values) were recorded after 30 hours. T4 and fT4 levels peaked at approximately 26 hours. Zinc levels at two hours were 20 +/- 5% lower than the initial values. Whole blood copper, selenium and glutathione peroxidase levels did not change significantly with time the largest differences were 11 +/- 6%, 5 +/- 4% and 10 +/- 8% respectively.     

日粮酪氨酸水平对9～12周龄泰和乌骨鸡生产性能及组织黑色素含量的影响

试验旨在研究日粮酪氨酸水平对9～12周龄泰和乌骨鸡生产性能、游离酪氨酸含量和组织黑色素含量的影响。选用56日龄泰和乌骨鸡270只,随机分成6组,每组设3个重复,每个重复15只鸡,饲养至12周龄。6个处理组日粮酪氨酸水平分别为0.45%、0.65%、0.85%、1.05%、1.25%和1.45%。结果表明:泰和乌骨鸡平均日增重、料重比随着日粮酪氨酸水平的提高先增加后降低,在1.05%水平时的平均日增重最大,料重比最低且与0.45%水平组差异极显著(P0.01)。此外,酪氨酸水平极显著(P0.01)影响平均日采食量。泰和乌骨鸡血清及组织中游离酪氨酸含量随日粮酪氨酸水平的提高先增加后降低。心脏、肌肉、皮肤组织中游离酪氨酸的含量在1.25%水平时达到最高,且与0.45%水平组差异极显著(P0.01);而血清和肝脏组织中游离酪氨酸的含量在0.85%水平时达到最高。组织中黑色素含量随着日粮酪氨酸水平的提高先增加后降低。肝脏、肌肉、皮肤中黑色素的含量在1.05%水平时达到最高且与0.45%水平组差异极显著(P0.01);而心脏组织中黑色素的含量在1.25%水平达到最高。在一定的酪氨酸水平范围内,提高日粮酪氨酸水平可提高泰和乌骨鸡血清及组织中游离酪氨酸含量、组织中黑色素的含量和生产性能。     

Effects of palm oil on lipid peroxidation,reduced glutathione,glutathione peroxidase,and vitamin A levels in the corpus uteri,cornu uteri and corpus luteum of young and adult female sheep

The aim of the current study was to determine whether a rumen protected palm oil based diet affect malondialdehyde (MDA), glutathione peroxidase (GSH-Px), reduced glutathione (rGSH) and vitamin A levels in the tissues of cornu uteri, corpus uteri and corpus luteum over the barley based isoenergetic and isonitrogenous diet, and whether the response is different between ewes and ewe-lambs. During the breeding season, half of Morkaraman ewes (2-4-year-old, n = 10) and ewe-lambs (7-8-months-old, n = 10) was offered a barley based diet and the other half was offered a protected palm oil based diet for 42 +/- 0.7 days. At the end of the experiment all animals were slaughtered and measurements carried out in the tissues collected. In all animals tested, cornu uteri had the highest MDA levels followed by corpus uteri and corpus luteum (P < 0.01) but no differences were between the tissues observed in GSH-Px and rGSH levels (P > 0.05). Vitamin A levels were, however, higher in corpus luteum than in cornu uteri and corpus uteri (P < 0.05). Corpus uteri MDA levels were not different (P > 0.05) but rGSH levels were higher for the palm oil fed groups (P < 0.05). GSH-Px and rGSH levels were higher for ewe-lambs than ewes (P < 0.05). In conclusion, it appears that MDA, rGSH, GSH-Px, and vitamin A work in a different fashion for corpus uteri, cornu uteri and corpus luteum, and for ewes and ewe-lambs. Dietary palm oil did not significantly affect the parameters studied except higher rGSH levels in corpus uteri. Levels of antioxidatively active substances, such as rGSH and GSH-Px were lower in ewes compared with those in ewe-lambs.     

Effects of milk thistle meal on performance,ileal bacterial enumeration,jejunal morphology and blood lipid peroxidation in laying hens fed diets with different levels of metabolizable energy

This study was conducted to evaluate the effects of different levels of milk thistle meal on performance, blood biochemical indices, ileal bacterial counts and intestinal histology in laying hens fed diets containing different levels of metabolizable energy. A total number of 200 Leghorn laying hens (Hy‐Line W‐36) were randomly assigned to eight experimental treatments with five cage replicates of five birds each. Dietary treatments consisted of four levels of milk thistle meal (0%, 15%, 30% and 60%) and two levels of AME_n (11.09 and 12.34 MJ/kg) fed over a period of 80 days. In vitro studies revealed that the total phenolic component of milk thistle meal was 470.64 mg gallic acid equivalent/g of the sample, and its antioxidant activity for inhibiting the 2‐2‐diphenyl‐1‐picrichydrazyl free radical and reducing ferric ions was about 21% higher than that of butylated hydroxyltoluene (p < .05). Diets containing high level of AME_n led to improved egg production (p < .05), egg weight (p < .05), egg mass (p < .01) and feed conversion ratio (p < .01). In addition, offering diets containing high energy significantly enhanced (p < .01) serum triglyceride and malondialdehyde (MDA) concentrations as well as jejunal villus height. Dietary supplementation of 3% milk thistle meal resulted in the best feed conversion ratio (p < .05), reduction of ileal Escherichia coli enumeration (p < .01) and an enhancement in the villus height‐to‐crypt depth ratio (p < .05). Furthermore, feeding incremental levels of this meal led to remarkable decrease in serum cholesterol, triglyceride and MDA (p < .01) concentrations while significant increase in blood high‐density lipoprotein content and goblet cell numbers (p < .05). The present findings indicate that milk thistle meal with high antioxidant and antibacterial properties in laying hen diets may improve health indices and productive performance.     

日粮酪氨酸水平对泰和乌骨鸡生产性能及组织黑色素含量的影响

选用28日龄泰和乌骨鸡135只,随机分成3组,每组设5个重复,每个重复10只鸡(公母各半),饲养至12周龄.在5～8周龄3个处理组日粮酪氨酸水平分别为0.424%、0.566%和0.708%,在9～12周龄3个处理组日粮色氨酸水平分别为0.402%、0.521%和0.640%.结果表明:(1)在5～8周龄,泰和乌骨鸡平均日增重随日粮酪氨酸水平的提高显著降低(P<0.05),但酪氨酸水平对料重比和平均日采食量无显著影响(P>0.05);泰和乌骨鸡胸肌黑色素含量随日粮酪氨酸水平的提高极显著增大(P<0.01),但腿肌和皮肤黑色素含量未受酪氨酸水平影响(P>0.05).(2)在9～12周龄,日粮酪氨酸水平对泰和乌骨鸡平均日增重、料重比和平均日采食量均无显著影响(P>0.05),但显著影响胸肌和腿肌黑色素含量(P<0.05),而对皮肤黑色素含量无显著影响(P>0.05).在3个处理组中,高酪氨酸水平组的胸肌和腿肌黑色素最高.在本试验的酪氨酸水平范围内,提高日粮酪氨酸水平可促进泰和乌骨鸡组织黑色素沉积而不影响生产性能.     

Effects of graded levels of Fusarium toxin-contaminated wheat and of a detoxifying agent in broiler diets on performance,nutrient digestibility and blood chemical parameters

1. A growth experiment was carried out with male broilers from d 1 to d 35 of age in order to evaluate the effects of the addition of a detoxifying agent (Mycofix Plus, Biomin GmbH, Herzogenburg, Austria) at different dietary proportions of wheat (0, 16.5, 33, 49.5 and 66%) contaminated with Fusarium mycotoxins (21.2 mg of deoxynivalenol and 406 microg of zearalenone, ZON, per kg of wheat) on growth performance, nutrient and zearalenone balance and clinical-chemical parameters. 2. An increase in dietary mycotoxin concentration resulted in a linearly related decrease in feed intake, a slight decrease in weight gain and an improvement in feed to gain ratio. 3. Apparent protein digestibility and net protein utilisation were higher in diets containing exclusively Fusarium toxin-contaminated wheat than control diets. 4. The proportions of beta-zearalenol, alpha-zearalenol and ZON of total ZON metabolites in excreta of broilers fed on the diets containing the Fusarium toxin-contaminated wheat were approximately 3, 21 and 76%. 5. Serum antibody titres to Newcastle disease virus decreased in a linear fashion with increasing mycotoxin concentration in the diets, whereas other clinical-chemical serum parameters (liver cell and muscle cell necrosis indicating enzymes, haemoglobin, haematocrit, magnesium, inorganic phosphate) were not influenced by increasing Fusarium toxin concentrations. 6. Supplementation of the diets with Mycofix Plus decreased performance in a manner independent of mycotoxin concentration. Moreover, some clinical-chemical serum parameters were significantly altered due to Mycofix Plus but also independently of the dietary mycotoxin concentration.     

Effects of exposure to a 50 Hz electric field on plasma levels of lactate, glucose, free Fatty acids, triglycerides and creatine phosphokinase activity in hind-limb ischemic rats

We previously reported that extremely low frequency electric fields (ELF-EFs) affect energy metabolism in stressed conditions. To further confirm this, the effect of exposure to ELF-EFs on the experimental ischemic rat was examined. The test was based on a comparison of rats treated with EF alone, ischemic surgery alone, the combination of EF with ischemic surgery, or no treatment (double sham). The EF condition used in this study was an alternating current of 50 Hz EF at 17 500 V/m intensity for 15 min per day. The exposure to EF in ischemic rats significantly decreased plasma levels of free fatty acids and triglycerides, compared to those of the no treatment or EF alone group. The plasma lactate levels of two ischemic groups peaked on experimental day-4 and gradually decreased until the end of the study. The changes in the lactate levels induced by ischemia did not show any difference between rats treated with ischemia alone or a combination of ischemia with an EF. Any changes in plasma levels of glucose and creatine phosphokinase activity were not influenced by EF treatment. These results indicate that the EF effect on glycolysis parameters, plasma lactate or glucose levels, does not appear in a highly stressed condition and that EF effects varied dependent on the condition of organism but ELF-EF used in this study have impact on lipid metabolism parameter in a hind-limb ischemic rat. However, further studies are needed to elucidate the association of ELF-EF with the lipid metabolism system.     

Effects of 2 different infusion rates of medetomidine on sedation score,cardiopulmonary parameters,and serum levels of medetomidine in healthy dogs

The effects of 2 different continuous rate infusions (CRIs) of medetomidine over an 8-hour period on sedation score, selected cardiopulmonary parameters, and serum levels of medetomidine were evaluated in 6 healthy, conscious dogs using a crossover study design. The treatment groups were: CONTROL = saline bolus followed by saline CRI; MED1 = 2 μg/kg body weight (BW) medetomidine loading dose followed by 1 μg/kg BW per hour CRI; and MED2 = 4 μg/kg BW medetomidine loading dose followed by 2 μg/kg BW per hour CRI. Sedation score (SS), heart rate (HR), respiratory rate (RR), temperature (TEMP), systolic arterial pressure (SAP), mean arterial pressure (MAP), and diastolic arterial pressure (DAP), arterial and mixed venous blood gas analyses, lactate, and plasma levels of medetomidine were evaluated at baseline, at various intervals during the infusion, and 2 h after terminating the infusion. Statistical analysis involved a repeated measures linear model. Both infusion rates of medetomidine-induced dose-dependent increases in SS and dose-dependent decreases in HR, SAP, MAP, and DAP were measured. Respiratory rate (RR), TEMP, central venous pH, central venous oxygen tension, and oxygen extraction ratio also decreased significantly in the MED2 group at certain time points. Arterial oxygen and carbon dioxide tensions were not significantly affected by either infusion rate. In healthy dogs, both infusion rates of medetomidine-induced clinically relevant sedative effects, accompanied by typical alpha₂ agonist-induced hemodynamic effects, which plateaued during the infusion and subsequently returned to baseline. While additional studies in unhealthy animals are required, the results presented here suggest that medetomidine infusions at the doses studied may be useful in canine patients requiring sedation for extended periods.     

The impairment of IGF-I-stimulated protein synthesis and activation of protein kinase B, p70(S6k), MAP kinase, and p90(rsk) in mouse C2C12 myogenic cells exposed to high glucose and high insulin

The aim of the present study was to examine the effect of high glucose alone and in combination with high insulin on IGF-I-stimulated protein synthesis and the activation of IGF-I signaling pathways in mouse C2C12 myogenic cells. Experiments were performed on mouse C2C12 myoblasts subjected to differentiation under normal glucose (5 mmol/I), high glucose alone (15 mmol/l), or in combination with high insulin (50 nmol/l). Six-day differentiation under high glucose alone or in combination with high insulin resulted in IGF-I resistance, which was manifested by the abolition of the stimulatory effect on protein synthesis. IGF-I caused the activation of protein kinase B (PKB) in control C2C12 myogenic cells. Pretreatment with high glucose did not affect PKB phosphorylation whereas in cells differentiated under high glucose and high insulin PKB activation by IGF-I was markedly decreased as compared with control (differentiation under normal glucose). Neither the p70(S6k) protein content nor the pattern of IGF-I-mediated kinase activation was affected by pretreatment with high glucose, however high glucose and high insulin in combination caused an impairment of the p70(S6k) phosphorylation, in relation to the control. An increase in p42(MAPK) phosphorylation occurred under normal glucose conditions after the stimulation with IGF-I. The MAP kinase was not phosphorylated in response to IGF-I in cells preincubated with high glucose alone or in combination with high insulin. The pattern of p90(rsk) activation by IGF-I was not modified by pretreatment with high glucose, however no activation of p90(rsk) was found in cells pretreated with high glucose and high insulin in combination. In conclusions: 1) high glucose abolishes the stimulatory action of IGF-I on protein synthesis and it does not affect the activation of PKB, p70(S6k), and p90(rsk) in mouse C2C12 myogenic cells, 2) high glucose with high insulin in combination also abolish the stimulatory effect of IGF-I, but this phenomenon is accompanied by attenuated PKB and p70(S6k) activation and the lack of activation of p90(rsk), 3) apart from PKB, p70(S6k) and p90(rsk), other kinases are probably involved in the regulation of IGF-I-mediated protein synthesis in myogenic cells.     

低钙性笼养蛋鸡骨质疏松症PTH、CT及E2的变化

将180只19周龄伊莎笼养蛋鸡随机分为对照（A）、低钙Ⅰ（B）、低钙Ⅱ（C）、低钙Ⅲ（D）4组，分别饲喂含量为3．55％、2．50％、2．05％、1．27％的日粮，定期用放射免疫分析法检测血清甲状旁腺素（PTH）、血清降钙素（CT）和血清雌二醇（E2）。结果显示，日粮钙含量越低的组，骨质疏松越明显，其PTH和CT上升越明显，而E2下降越明显。结论：低钙性骨质疏松症蛋的雌激素和钙调节激素发生了明显的变化。     

mTOR信号通路在镉诱导PC12细胞凋亡和Bcl-2、Bax蛋白表达中的作用

为研究雷帕霉素靶蛋白(mammalian target of rapamycin,mTOR)信号通路在镉诱导神经细胞凋亡和相关蛋白Bcl-2、Bax表达中的作用,用醋酸镉和/或雷帕霉素(rapamycin,Rap)染毒PC12细胞24h,流式细胞术检测细胞凋亡率,Hoechst33258荧光染色法检测细胞凋亡形态学变化,Western blot法检测Bcl-2和Bax蛋白表达水平。结果显示:与对照组相比,染毒组细胞凋亡和Bax蛋白表达水平升高,Bcl-2蛋白表达水平降低,Bcl-2/Bax极显著降低(P<0.01);与镉染毒组相比,镉与Rap联合作用组细胞凋亡和Bax蛋白表达水平降低,Bcl-2蛋白表达水平升高,Bcl-2/Bax显著升高(P<0.05)。结果表明:镉可能通过激活mTOR信号通路调节Bcl-2和Bax的表达,从而诱导神经细胞凋亡。