Intrauterine injection of recombinant ovine interferon-tau extends the interestrous interval in sheep

The ability of recombinant ovine interferon-tau (roIFNtau) to extend the interestrous interval (IEI) in sheep was studied. Ewes were fitted with bilateral uterine catheters 7 or 8 days post estrus and were assigned to receive either 10 or 20 million antiviral (AV) units/day i.u. ( approximately 100 or 200 ug) of roIFNtau or ovine conceptus secretory proteins containing equivalent AV units of native oIFNtau (noIFNtau; 4 ewes/treatment). Four control ewes received ovine serum proteins (SP). Total protein injected was 6 mg per day, half at 0700 hours and half at 1730 hours. The treatments were administered from Day 11.5 (estrus=Day 0) to Day 16. Blood samples were collected by jugular vienipuncture daily from Day 11 until ewes returned to estrus. Concentrations of progesterone (P) in plasma were determined by RIA. Treatment with either noIFNtau or roIFNtau extended IEI beyond that of SP-treated ewes (19.1 vs 31.2+/-3.4 days P<0.03). Of the ewes receiving 100 mug/day of oIFNtau, 2 of 4 receiving noIFNtau (23.6+/-5.2 days) and 3 of 4 receiving roIFNtau (34.2+/-5.2 days) had an extended IEI. All ewes receiving 200 mug/day of noIFNtau or roIFNtau had an extended IEI (28.8 and 38.5+/-5.2 days. respectively). Ewes receiving roIFNtau had a longer IEI than those receiving noIFNtau (36.7 vs 26.2+/-3.4 days; P=0.07). Ewes with an extended IEI had functional corpora lutea, as assessed by P production. The results demonstrate that 10 or 20 million AV units ( approximately 100 or 200 ug) of roIFNtau extends the IEI and that the length of the IEI is longer for ewes receiving roIFNtau than noIFNtau following injection of equivalent AV units.     

Novel serum protein biomarkers indicative of growth hormone doping in healthy human subjects

The detection of recombinant human growth hormone (rhGH) is difficult due to its short half‐life; therefore, novel and robust biomarkers of rhGH abuse are needed. In this study, serum samples derived from subjects treated with rhGH in a randomized, double blind, placebo‐controlled crossover study were analyzed by 2‐DE coupled with MS. Eight healthy male subjects aged 23.2±0.6 years were injected with rhGH (2 mg/day) or saline for 7 days with serum samples drawn at days 0, 3, and 8. Protein intensities were quantified and analyzed for differences between rhGH and placebo treatments. Proteins that showed significant changes were identified and confirmed by Western blotting. These included specific isoforms of α‐1 antitrypsin and transthyretin that increased; and inter‐α‐trypsin inhibitor heavy chain H4, apolipoprotein A‐1, and hemoglobin β chain that decreased. These proteins represent novel biomarkers of short‐term rhGH exposure and may lead to a new method for detecting rhGH doping.     

Protective effects of green tea polyphenol against reactive oxygen species-induced oxidative stress in cultured rat calvarial osteoblast

The injurious effects of reactive oxygen species on osteoblasts and the potential protective role played by green tea polyphenols (GtPP) were investigated using primarily cultured rat calvarial osteoblasts. Oxidative stress was induced in cultured osteoblasts, either by adding 100 mmol/L H2O2 or by the action of 40 U/L xanthine oxidase (XO) in the presence of xanthine (250 micromol/L). After incubation, the cellular viability, function and morphology were evaluated. Both treatments produced a significant reduction in osteoblast viability, as assessed by a two-colored fluorescence staining method combined with flow cytometric analysis and MTT assay. A significant reduction in the alkaline phosphatase activity was observed after H2O2 addition, whereas XO did not have the same effect. On the microscopic observations, the morphological changes and intracellular ultrastructural damages were remarkably induced by both treatments. The H2O2-induced alterations were prevented by pre-incubating the osteoblasts with 200 microg/ml GtPP for 1 h. When the oxidative stress was induced by XO, the cellular viability and morphology was also maintained at the same polyphenol concentration. These results demonstrate that GtPP can act as a biological antioxidant in a cell culture experimental model and protect cells from oxidative stress-induced toxicity.     

Inactivation of mitochondrial adenosine triphosphatase from Trypanosoma cruzi by oxygen radicals

Incubation of Trypanosoma cruzi mitochondrial ATPase (Fo-F1) with the xanthine oxidase system (XO), Fenton's reagent (Fe2+ + H2O2) and the ascorbate-Cu system, caused gradual loss of enzyme activity, which increased as a function of incubation time and rate of oxygen radical generation. The essential role of OH. radicals for ATPase inactivation was supported by a) the enzyme protection afforded by superoxide dismutase, catalase and mannitol, when using the XO system; b) the similar effect of mannitol and benzoate with Fenton's reagent; c) the similar effect of catalase, EDTA and histidine with the ascorbate-Cu system; d) the increased rate of ATPase inactivation by 1) the XO system supplemented with chelated iron, and 2) the ascorbate-Cu system supplemented with H2O2. Comparison of oxygen radical generators for their action on membrane-bound (Fo-F1) and soluble F1 revealed that ascorbate-Cu was the most effective one, possibly because of its capability of producing OH. radicals that react preferentially with the enzyme at their formation site.     

High incidence of partial biotinidase deficiency cases in newborns of Greek origin

Biotinidase deficiency (BTD) is an inherited disorder with severe clinical manifestations if not treated early. 63,119 neonates were tested for BTD according to a 3-step protocol. Biotinidase activity was initially estimated through standard colorimetric method on dried blood spots, then the suspected samples were subjected to molecular analysis of the BT gene and determination of BT activity in serum through an HPLC method. 14 infants with partial BTD (incidence 1:4508) were detected. Nine of them were homozygotes (D444H/D444H), and 4 compound heterozygotes carrying D444H combined with Q456H, T532M, C186Y and R157H, respectively. All were asymptomatic and supplemented with 10 mg biotin. Although the number of screened neonates is rather small, it may be suggested that the incidence of the partial BTD infants is the highest ever reported. Detection of BTD should be added to the Greek national neonatal screening program.     

Antipyrine,paracetamol, and lignocaine elimination in chronic liver disease.

The plasma half lives of antipyrine, paracetamol, and lignocaine given by mouth were measured in 23 patients with stable chronic liver diseases of varying severity. Fifteen patients received all three drugs and 19 at least two. The half life of paracetamol was abnormally prolonged in nine out of 17 patients (mean 2-9 hours, normal 2-0 hours), of antipyrine in 10 out of 19 patients (mean 30-4 hours, normal 12-0 hours), and of lignocaine in 19 out of 21 patients (mean 6-6 hours, normal 1-4 hours). Prolongation of the half lives of all three drugs was significantly correlated with an increase of the vitamin-K1-corrected prothrombin time ratio and a reduction in serum albumin concentration. There was no correlation with serum bilirubin concentration or serum alanine aminotransferase activity. This suggests that impaired drug elimination was related to depressed hepatic protein synthesis. Considerable prolongation of the half life of one drug was invariably associated with delayed elimination of the others. The half life of lignocaine, however, was always the most prolonged and was a highly sensitive indicator of hepatic dysfunction. The pharmacokinetic characteristics of a drug as well as the severity of liver disease should be taken into account when considering drug dosage in patients with chronic liver disease.     

Effects of Selenium Source and Level on Growth Performance, Tissue Selenium Concentrations, Antioxidation, and Immune Functions of Heat-Stressed Broilers

An experiment is conducted to investigate the effects of selenium (Se) source and level on growth performance, tissue Se concentrations, antioxidation, and immune functions of heat-stressed broilers from 22 to 42?days of age. A total of 210 22-day-old Arbor Acres commercial male chicks were assigned by body weight to one of seven treatments with six replicates of five birds each in a completely randomized design involving a 3?×?2 factorial arrangement plus one Se-unsupplemented basal diet control (containing 0.027?mg of Se/kg). The three Se sources were sodium selenite (Na₂SeO₃), Se yeast, and AMMS Se (Se protein), and the two supplemental Se levels were 0.15 or 0.30?mg Se/kg. All birds were reared under heat-stressed condition (33?±?1?°C during 0900?C1700?hours and 27?±?1?°C during 1900?C0700?hours with a relative humidity of 60?C80?%). The results showed that heat-stressed chicks fed Se-supplemented diets had higher (P?<?0.10) average daily feed intake, Se concentrations in liver and breast muscle, liver glutathione peroxidase (GSH-Px) activity, serum antibody titers against H5N1(Re-4 strain), H5N1(Re-5 strain) and lower (P?<?0.01) mortality compared with the control. Chicks fed the diets supplemented with 0.30?mg/kg of Se had higher (P?<?0.05) Se concentrations in liver and breast muscle, liver GSH-Px activity, and serum antibody titer against H5N1 (Re-4 strain) than those fed the diets supplemented with 0.15?mg/kg of Se. Broilers fed the diets supplemented with Se yeast had higher (P?<?0.001) Se concentrations in liver and breast muscle than those fed the diets supplemented with Na₂SeO₃ or AMMS Se. However, broilers fed the diets supplemented with AMMS Se had higher (P?<?0.05) serum antibody titers against H5N1 (Re-4 strain) and H5N1 (Re-5 strain) than those fed the diets supplemented with Na₂SeO₃. These results indicated that Se yeast was more effective than Na₂SeO₃ or AMMS Se in increasing tissue Se retention; however, AMMS Se was more effective than Na₂SeO₃ or Se yeast in improving immune functions of heat-stressed broilers.     

Exposure to cigarette smoke increases apoptosis in the rat gastric mucosa through a reactive oxygen species-mediated and p53-independent pathway

Cigarette smoking is a major risk factor for gastric cancer and peptic ulcer. The aim of our study was to investigate the relationship between exposure to cigarette smoke and apoptosis in the rat gastric mucosa and the mechanism involved. Rats were exposed to different concentrations of cigarette smoke (0, 2, and 4%) once daily for a different number of 1 h periods (1, 3, 6, and 9 d). Apoptosis was identified by the terminal deoxy-transferase (TdT)-mediated dUTP-biotin nick end labeling (TUNEL) method and caspase-3 activity. The mucosal xanthine oxidase (XO) activity and p53 level were also measured. The results showed that exposure to cigarette smoke produced a time- and concentration-dependent increase in apoptosis in the rat gastric mucosa that was accompanied by an increase in XO activity. The increased apoptosis and XO activity could be detected after even a single exposure. In contrast, the level of p53 was elevated only in the later stage of cigarette smoke exposure. The apoptotic effect could be blocked by pretreatment with an XO inhibitor (allopurinol, 20 mg/kg intraperitoneally) or a hydroxyl free radical scavenger (DMSO, 0.2%, 1 ml/kg intravenously). However, neither of these treatments had any effect on the p53 level of the mucosa. In summary, we conclude that exposure to cigarette smoke can increase apoptosis in the rat gastric mucosa through a reactive oxygen species- (ROS) mediated and a p53-independent pathway.     

心理应激对小鼠脂肪组织黄嘌呤氧化酶表达、活性及相关指标的影响*

目的:探讨心理应激对小鼠脂肪组织黄嘌呤氧化酶表达、活性及相关指标的作用。方法:雄性无特定病原体(SPF)级20只昆明小鼠随机分2组(每组10只),即慢性束缚应激(Stress)组和正常对照(Control)组。Stress组小鼠每天在自制式束缚器中限制活动2 h,其余时间两组小鼠在相同环境中自由饮水摄食,实验持续14 d,取血和白色脂肪组织(WAT);观察脂肪组织病理学改变,检测WAT中黄嘌呤氧化酶(XO)和烟酰胺腺嘌呤二核苷酸磷酸氧化酶4(Nox-4)的蛋白水平,检测WAT组织中XO、Nox-4、超氧化物歧化酶(Mn SOD)、谷胱甘肽过氧化物酶(GSH-Px)、过氧化氢酶(CAT)、脂联素(ADPN)、单核细胞趋化蛋白1(MCP-1)、白介素6(IL-6)、肿瘤坏死因子α(TNF-α)、胰岛素受体底物1(IRS-1)、葡萄糖转运蛋白4(GLUT-4)、组织因子(TF)、纤溶酶原激活物抑制物1(PAI-1)的mRNA表达,检测血清和WAT组织中XO酶活性以及血清甘油三酯(TG)、总胆固醇(T-Cho)、游离脂肪酸(FFA)、尿酸(UA)的含量。结果:与control组比较,stress小鼠腹股沟WAT组织中XO免疫染色阳性着色细胞黄褐色沉淀深且丰富,WAT中出现大量的单核细胞、中性粒细胞、嗜酸性粒细胞及浆细胞浸润反应和炎症性的改变;血清XO浓度、WAT组织中XO mRNA水平和XO的酶活性显著升高(P＜0.01),血清游离脂肪酸(FFA)和尿酸(UA)的含量显著增高(P＜0.01),WAT组织中Nox-4蛋白、MCP-1、IL-6、TNF-α、TF、PAI-1mRNA的表达水平显著增高(P＜0.01),而Mn-SOD、GSH-Px、CAT、ADPN、IRS-1和GLUT-4的mRNA水平则显著降低(P＜0.01)。结论:心理应激可诱发脂肪XO过量表达及其活性增高,进而引起脂肪炎症、糖代谢及凝血酶原异常等反应。     

Molecular mechanism of an adverse drug–drug interaction of allopurinol and furosemide in gout treatment

Gout patients receiving a combination of allopurinol and furosemide require higher allopurinol doses to achieve the target serum urate (SU) of <6 mg/dl (Stamp et al., 2012) [1]. Our study aimed to identify the molecular basis for this observation. We used a fluorimetric assay to determine the impact of furosemide and oxypurinol (the active metabolite of allopurinol) on xanthine oxidase (XO) activity. Immunoblot analysis quantified expression of XO and AMP-kinase (AMPK) in drug-treated human liver (HepG2) and primary kidney (HRCE) cells. In silico analysis identified miR-448 as a potential XO-regulator, whose expression level in HepG2 cells was examined by qPCR.     

产腈水解酶基因工程菌的产酶诱导条件及培养基优化

本文通过对产酶诱导条件及发酵培养基进行优化,成功提高了产腈水解酶基因工程菌E. coli BL21(DE3)-pETNYNit的产酶水平。研究结果显示,最佳发酵培养基为：葡萄糖0.2%、甘油0.7%(v/v)、蛋白胨1.2%、酵母膏0.8%、NaCl 0.3%、(NH4)2SO40.3%、NH4Cl 0.13%、Na2 HPO4·12H2 O 1.04%、KH2 PO40.39%、MgSO4·7H2 O 0.03%,pH 7.2。最佳产酶诱导条件为：发酵4 h时加入0.5 mmol/L IPTG,然后在28℃、240 r/min下诱导腈水解酶基因表达14 h~16 h。采用优化方案,重组菌产酶水平可提升至0.9~1×105 U,与野生菌株的产酶水平相比,提高幅度超过50%。同时重组菌培养仅需24 h,培养周期缩短超过50 h。     

Altered polyamine metabolism in Chinese hamster cells growing in a defined medium

Chinese hamster cells (line CHO) maintained in McCoy's 5A medium (modified) supplemented with insulin (10 micrograms/ml), transferrin (5 micrograms/ml), and ferrous sulfate (1.1 microgram/ml) proliferate at rates similar to cultures growing in the McCoy's medium supplemented with 10% fetal bovine serum. Colony-forming ability is similar in cultures supplemented with either serum or the combination of growth factors. By 6 hours after replacement of serum with growth factors, ornithine decarboxylase (ODCase) activity increases, reaching a maximum value by 24 hours after serum replacement. This maximum is cell density dependent and can exceed a 30-fold increase over enzyme activity in cultures supplemented with serum. The increased enzyme activity is due to a decrease in the turnover rate of the enzyme, based on protein synthesis inhibition studies, and an accumulation of active enzyme molecules rather than an activation of existing molecules, since the catalytic activity of ODCase, determined using the radiolabeled form of alpha-difluoromethylornithine (an enzyme-activated, irreversible inhibitor of ODCase) in concert with supplements. Intracellular putrescine and spermidine levels are substantially decreased when cultures are maintained in medium supplemented with insulin, transferrin, and ferrous sulfate, rather than serum, which is the sole source of exogenous ornithine. Titration of cultures growing in the defined medium with ornithine leads to a decrease in ODCase activity and an increase in intracellular putrescine and spermidine levels. Putrescine- and spermidine-dependent S-adenosyl-L-methionine decarboxylase activities are similar in cultures maintained in either medium. These data demonstrate that some, but not all, aspects of polyamine biosynthesis are affected by the availability of ornithine, the first substrate in the pathway.     

A Thin‐Layer Liquid Culture Technique for the Growth of Helicobacter pylori

Background and Aims: Several attempts have been successful in liquid cultivation of Helicobaccter pylori. However, there is a need to improve the growth of H. pylori in liquid media in order to get affluent growth and a simple approach for examining bacterial properties. We introduce here a thin‐layer liquid culture technique for the growth of H. pylori. Methods: A thin‐layer liquid culture system was established by adding liquid media to a 90‐mm diameter Petri dish. Optimal conditions for bacterial growth were investigated and then viability, growth curve, and released proteins were examined. Results: Maximal growth of H. pylori was obtained by adding 3 mL of brucella broth supplemented with 10% horse to a Petri dish. H. pylori grew in both DMEM and RPMI‐1640 supplemented with 10% fetal bovine serum and 0.5% yeast extract. Serum‐free RPMI‐1640 supported the growth of H. pylori when supplemented with dimethyl‐β‐cyclodextrin (200 μg/mL) and 1% yeast extract. Under optimal growth, H. pylori grew exponentially for 28 hours, reaching a density of 3.4 OD₆₀₀ with a generation time of 3.3 hours. After 24 hours, cultures at a cell density of 1.0 OD₆₀₀ contained 1.3 ± 0.1 × 10⁹ CFU/mL. γ‐Glutamyl transpeptidase, nuclease, superoxide dismutase, and urease were not detected in culture supernatants at 24 hours in thin‐layer liquid culture, but were present at 48 hours, whereas alcohol dehydrogenase, alkylhydroperoxide reductase, catalase, and vacuolating cytotoxin were detected at 24 hours. Conclusions: Thin‐layer liquid culture technique is feasible, and can serve as a versatile liquid culture technique for investigating bacterial properties of H. pylori.     

维生素C和酸应激对中华鳖幼鳖血清补体C3和C4含量的影响

为研究维生素C对中华鳖(Pelodiscus sinensis)血清补体C3和C4的影响及其在酸应激条件下的变化,我们设置了6个实验组,饵料中维生素C的添加量依次为0、250、500、2500、5000和10000mg／kg,喂食4周后取其血清,用透射比浊法测定酸应激前后中华鳖血清补体C3和C4的含量。结果表明,维生素C添加量为250mg／kg时,血清补体C3的含量与对照组间没有明显不同;维生素C添加量为500、2500、5000和10000mg／kg的4组,血清补体C3的含量明显高于对照组和维生素C添加量为250mg／kg组;维生素C添加量为500mg／kg的一组,血清补体CA含量明显高于其它5组;维生素C添加量为250mg／kg组明显高于10000mg／kg组。酸应激后,补体C3的含量没有明显下降,将维生素C添加量为0、250和500mg／kg的三组并为一组处理,则应激后有明显下降。维生素C添加量为0、250和500mg／kg的3组,血清补体CA的含量在酸应激后明显下降,而维生素C添加量为2500、5000和10000mg／kg的3组,应激后血清补体C4没有明显变化。维生素C和酸应激对中华鳖血清补体C3和CA含量的影响没有交互作用。这说明,维生素C在一定剂量范围内,能提高中华鳖血清补体C3和CA的水平,酸应激能导致其含量降低,而高剂量的维生素C对其下降有颉颃作用[动物学报49(6)：769～774,2003]。     

Inactivation of xanthine oxidase by hydrogen peroxide involves site-directed hydroxyl radical formation.

The mechanism of xanthine oxidase (XO) inactivation by hydrogen peroxide (H2O2) and its biologic significance are unclear. We found that addition of increasing concentrations of H2O2 progressively decreased xanthine oxidase activity in the presence but not the absence of xanthine in vitro. Inactivation of XO by H2O2 was also enhanced by anaerobic reduction of XO by xanthine. Inactivation of XO by H2O2 was accompanied by production of hydroxyl radical (.OH), measured as formation of formaldehyde from dimethylsulfoxide (DMSO). In contrast, addition of H2O2 to deflavo XO did not produce .OH. Inactivation of XO by H2O2 was decreased by simultaneous addition of the .OH scavenger, DMSO. However, inactivation of XO by H2O2 and formation of .OH were not decreased following addition of the metal chelator. DETAPAC, and/or the O2 scavenger, superoxide dismutase. The results suggest that inactivation of XO by H2O2 occurs by production of .OH following direct reduction of H2O2 by XO at the flavin site.     

Iron regulates xanthine oxidase activity in the lung

The iron chelator deferoxamine has been reported to inhibit both xanthine oxidase (XO) and xanthine dehydrogenase activity, but the relationship of this effect to the availability of iron in the cellular and tissue environment remains unexplored. XO and total xanthine oxidoreductase activity in cultured V79 cells was increased with exposure to ferric ammonium sulfate and inhibited by deferoxamine. Lung XO and total xanthine oxidoreductase activities were reduced in rats fed an iron-depleted diet and increased in rats supplemented with iron, without change in the ratio of XO to total oxidoreductase. Intratracheal injection of an iron salt or silica-iron, but not aluminum salts or silica-zinc, significantly increased rat lung XO and total xanthine oxidoreductase activities, immunoreactive xanthine oxidoreductase, and the concentration of urate in bronchoalveolar fluid. These results suggest the possibility that the production of uric acid, a major chelator of iron in extracellular fluid, is directly influenced by iron-mediated regulation of the expression and/or activity of its enzymatic source, xanthine oxidase.     

Efficacy of a Metalloproteinase Inhibitor in Spinal Cord Injured Dogs

Matrix metalloproteinase-9 is elevated within the acutely injured murine spinal cord and blockade of this early proteolytic activity with GM6001, a broad-spectrum matrix metalloproteinase inhibitor, results in improved recovery after spinal cord injury. As matrix metalloproteinase-9 is likewise acutely elevated in dogs with naturally occurring spinal cord injuries, we evaluated efficacy of GM6001 solubilized in dimethyl sulfoxide in this second species. Safety and pharmacokinetic studies were conducted in naïve dogs. After confirming safety, subsequent pharmacokinetic analyses demonstrated that a 100 mg/kg subcutaneous dose of GM6001 resulted in plasma concentrations that peaked shortly after administration and were sustained for at least 4 days at levels that produced robust in vitro inhibition of matrix metalloproteinase-9. A randomized, blinded, placebo-controlled study was then conducted to assess efficacy of GM6001 given within 48 hours of spinal cord injury. Dogs were enrolled in 3 groups: GM6001 dissolved in dimethyl sulfoxide (n = 35), dimethyl sulfoxide (n = 37), or saline (n = 41). Matrix metalloproteinase activity was increased in the serum of injured dogs and GM6001 reduced this serum protease activity compared to the other two groups. To assess recovery, dogs were a priori stratified into a severely injured group and a mild-to-moderate injured group, using a Modified Frankel Scale. The Texas Spinal Cord Injury Score was then used to assess long-term motor/sensory function. In dogs with severe spinal cord injuries, those treated with saline had a mean motor score of 2 (95% CI 0–4.0) that was significantly (P<0.05; generalized linear model) less than the estimated mean motor score for dogs receiving dimethyl sulfoxide (mean, 5; 95% CI 2.0–8.0) or GM6001 (mean, 5; 95% CI 2.0–8.0). As there was no independent effect of GM6001, we attribute improved neurological outcomes to dimethyl sulfoxide, a pleotropic agent that may target diverse secondary pathogenic events that emerge in the acutely injured cord.     

Impact of single anaerobic exercise on delayed activation of endothelial xanthine oxidase in men and women

Objectives: The aim of the study was to evaluate the activity of xanthine oxidase (XO) in the blood of men and women during the first hour following a single anaerobic exercise (AN-EX), and after 24 hours of recovery, and to determine whether the changes in XO activity in the blood after AN-EX are dependent on anaerobic performance.

Methods: Ten men and ten women performed a single AN-EX. Blood was collected before and five times after completion of the AN-EX. The activity of XO was determined.

Results: In both groups, a significant (P?P?Discussion: In the first hour after the single AN-EX, XO activity in the blood of women and men did not change, but after 24 hours of recovery, it was significantly higher compared to baseline levels in both sexes. Single AN-EX causes a smaller increase in XO activity in people with higher anaerobic performance.     

Mechanism of the inhibition of milk xanthine oxidase activity by metal ions: a transient kinetic study

The nature and mechanism of the inhibition of the oxidoreductase activity of milk xanthine oxidase (XO) by Cu(2+), Hg(2+) and Ag(+) ions has been studied by steady state and stopped flow transient kinetic measurements. The results show that the nature of the inhibition is noncompetitive. The inhibition constants for Cu(2+) and Hg(2+) are in the micromolar and that for Ag(+) is in the nanomolar range. This suggests that the metal ions have strong affinity towards XO. pH dependence studies of the inhibition indicate that at least two ionisable groups of XO are involved in the binding of these metal ions. The effect of the interaction of the metal ions on the reductive and oxidative half reactions of XO has been investigated, and it is observed that the kinetic parameters of the reductive half reaction are not affected by these metal ions. However, the interaction of these metal ions with XO significantly affects the kinetic parameters of the oxidative half reaction. It is suggested that this may be the main cause for the inhibition of XO activity by the metal ions.     

Selenium Distribution in Camel Blood and Organs After Different Level of Dietary Selenium Supplementation

Eight young female camels shared in four groups of two 2 years received a basal diet enriched respectively with 0, 2, 4, and 8 mg selenium under sodium selenite form for 64 days. Feed intake was assessed daily; blood samples were taken on weekly basis. One camel from each group was killed at the end of the experiment. Se concentration in serum was increased significantly in the supplemented groups with an average of 176.3 ± 18.0 ng/mL in the control group, 382.7 ± 107.6 in the group receiving 2 mg Se, 519.8 ± 168.4 in the group receiving 4 mg Se, and 533.4 ± 158.6 in the group receiving 8 mg Se daily. For glutathione peroxidase (GSH-Px) activity, the control group (51.0 IU/g Hb) and the group receiving 2 mg (50.5 IU/g Hb) were significantly different than groups receiving 4 and 8 mg (respectively, 65.9 and 76.1 IU/g Hb). No significant variation occurred for vitamin E (mean, 0.56 ± 0.23 ng/mL). Significant correlation between serum Se and GSH-Px was reported. Kidney was the richest organ in selenium followed by lung, spleen, and liver, but the increase in supplemented groups was more marked in liver and kidney. The hair seemed to be the best indicator of selenium intake in camel.