Impact of oxidative stress on ascorbate biosynthesis in Chlamydomonas via regulation of the VTC2 gene encoding a GDP-L-galactose phosphorylase

The L-galactose (Smirnoff-Wheeler) pathway represents the major route to L-ascorbic acid (vitamin C) biosynthesis in higher plants. Arabidopsis thaliana VTC2 and its paralogue VTC5 function as GDP-L-galactose phosphorylases converting GDP-L-galactose to L-galactose-1-P, thus catalyzing the first committed step in the biosynthesis of L-ascorbate. Here we report that the L-galactose pathway of ascorbate biosynthesis described in higher plants is conserved in green algae. The Chlamydomonas reinhardtii genome encodes all the enzymes required for vitamin C biosynthesis via the L-galactose pathway. We have characterized recombinant C. reinhardtii VTC2 as an active GDP-L-galactose phosphorylase. C. reinhardtii cells exposed to oxidative stress show increased VTC2 mRNA and L-ascorbate levels. Genes encoding enzymatic components of the ascorbate-glutathione system (e.g. ascorbate peroxidase, manganese superoxide dismutase, and dehydroascorbate reductase) are also up-regulated in response to increased oxidative stress. These results indicate that C. reinhardtii VTC2, like its plant homologs, is a highly regulated enzyme in ascorbate biosynthesis in green algae and that, together with the ascorbate recycling system, the L-galactose pathway represents the major route for providing protective levels of ascorbate in oxidatively stressed algal cells.     

Identification of the Binding Site of Methylglyoxal on Glutathione Peroxidase: Methylglyoxal Inhibits Glutathione Peroxidase Activity via Binding to Glutathione Binding Sites Arg 184 and 185

Methylglyoxal (MG), a physiological &#102 -dicarbonyl compound is derived from glycolytic intermediates and produced during the Maillard reaction. The Maillard reaction, a non-enzymatic reaction of ketones and aldehydes with amino group of proteins, contributes to the aging of proteins and to complications associated with diabetes. In our previous studies (Che, et al. (1997) "Selective induction of heparin-binding epidermal growth factor-like growth factor by MG and 3-deoxyglucosone in rat aortic smooth muscle cells. The involvement of reactive oxygen species formation and a possible implication for atherogenesis in diabetes". J. Biol. Chem., 272 , 18453-18459), we reported that MG elevates intracellular peroxide levels, but the mechanisms for this remain unclear. Here, we report that MG inactivates bovine glutathione peroxidase (GPx), a major antioxidant enzyme, in a dose- and time-dependent manner. The use of BIAM labeling, it was showed that the selenocysteine residue in the active site was intact when GPx was incubated with MG. MALDI-TOF-MS (matrix-assisted laser desorption/ionization time-of-flight mass spectrometry) and protein sequencing examined the possibility that MG modifies arginine residues in GPx. The results show that Arg 184 and Arg 185, located in the glutathione binding site of GPx was irreversively modified by treatment with MG. Reactive dicarbonyl compounds such as 3-deoxyglucosone, glyoxal and phenylglyoxal also inactivated GPx, although the rates for this inactivation varied widely. These data suggest that dicarbonyl compounds are able to directly inactivate GPx, resulting in an increase in intracellular peroxides which are responsible for oxidative cellular damage.     

Molecular cloning and characterization of the glutathione reductase gene from Stipa purpurea

Reactive oxygen species (ROS) are a key factor in abiotic stresses; excess ROS is harmful to plants. Glutathione reductase (GR) plays an important role in scavenging ROS in plants. Here, a GR gene, named SpGR, was cloned from Stipa purpurea and characterized. The full-length open reading frame was 1497 bp, encoding 498 amino acids. Subcellular localization analysis indicated that SpGR was localized to both the plasma membrane and nucleus. The expression of SpGR was induced by cold, salt, and drought stresses. Functional analysis indicated that ectopic expression of SpGR in Arabidopsis thaliana resulted in greater tolerance to salt stress than that of wild-type plants, but no difference under cold or drought treatments. The results of GR activity and GSSG and GSH content analyses suggested that, under salt stress, transgenic plants produced more GR to reduce GSSG to GSH for scavenging ROS than wild-type plants. Therefore, SpGR may be a candidate gene for plants to resist abiotic stress.     

海藻糖生产菌株筛选过程中产物鉴定的研究

在海藻糖生产菌的筛选过程中,微生物胞内酶转化淀粉生成的产物复杂,将产物逐一纯化是非常烦琐的,但又必须确证产物中是否含有海藻糖。本文将薄层层析、高效液相电喷雾电离质谱联用及核磁共振等分析手段综合应用于海藻糖生产菌株的筛选,在酶反应产物不必被纯化的前提下,准确、快捷地鉴定了酶反应产物中的未知糖组分,最终证明食尼古丁节杆菌（Arthrobacter nicotinovorus）D97利用淀粉或麦芽寡糖的酶反应产物中含有海藻糖。该方法在筛选海藻糖及其它功能性葡二糖生产菌株时较为严密。     

Synthesis and Pharmacological Study of Rho-Kinase Inhibitors: Pharmacomodulations on the Lead Compound Fasudil

With a view to specifying structure–activity relationships we have synthesised a new series of analogues of the Rho-kinase inhibitor 1-(5-isoquinolinesulfonyl)-homopiperazine (Fasudil). The structural modifications concerned the isoquinolinyl heterocycle and the sulfonyl group which are the two main features of this lead compound. These analogues were evaluated on the actin cytoskeleton and on the enzymatic activity of Rho-kinase. Most of the chemical modifications result in a loss of activity showing that interactions of Fasudil with the catalytic domain of Rho-kinase seem to be particularly definite and sensitive to structural variations. The presence of an isoquinolinyl nitrogen and a basic amino group separated by a spacer bearing a sulfonamide function are of utmost importance. Only the tetrahydroisoquinoline analogue 3 shows the same activity as Fasudil. Moreover, this compound is unable to inhibit PKC biological activity contrary to Fasudil. The loss of the aromatic property could increase the selectivity level in favour of compound 3.     

Protective action of vitamins on the spermatogenesis in lead-treated Swiss mice

The protective action of vitamins C and E against lead acetate-induced reduced sperm count and sperm abnormalities in Swiss mice has been studied. Intraperitoneal injection of lead acetate (10mg/kg body weight) in the present study stimulates lipid peroxidation in the testicular tissue, indicated by a significant increase in malondialdehyde content in the experimental mice group. This is associated with an increased generation of noxious reactive oxygen species (ROS). Significantly reduced sperm count associated with increased sperm abnormality percentage in the lead-injected mice group compared to controls substantially proves the ongoing damaging effects of lead-induced ROS on developing germ cells. However, intraperitoneal administration of vitamin C (Vit C) at a concentration equivalent to the human therapeutic dose (10 mg/kg body weight) was able to minimize significantly the testicular malondialdehyde content with a concomitant increase in sperm count and significant decrease in the percentage of abnormal sperm population. Vitamin E (Vit E) (100 mg/kg body weight) treatment of a batch of lead-injected mice had a similar effect as Vit C but with a comparatively lower efficacy. On the other hand, coadministration of both vitamins (Vit C + Vit E) at the above mentioned doses to lead-treated mice led to the most significant decline in malondialdehyde content along with elevated sperm count and reduction in the percentage of abnormal sperm population. The protective action and the synergistic action of both vitamins (C and E) against lead-induced genotoxicity are discussed.     

不同来源肝细胞在体外降脂药物评价中药效反应的对比

目的:通过对比不同来源的人肝癌细胞系HepG2和原代大鼠肝细胞在体外降脂药物评价中药效反应,指导两种肝细胞在体外降脂药物评价中的实际应用。方法:用游离脂肪酸(油酸/棕榈酸,2:1)诱导HepG2细胞、原代大鼠肝细胞脂肪变性,并用100μmol·L-1苯扎贝特干预,检测细胞内甘油三酯(TG)、总胆固醇(TC)、活性氧(ROS)含量,细胞内脂滴数目、并检测细胞上清液中丙二醛(MDA)含量和超氧化物歧化酶(SOD)活性。结果:FFA刺激使HepG2细胞和原代大鼠肝细胞脂质沉积(TG、脂滴)和氧化应激(ROS、MDA、SOD)水平上升。苯扎贝特对HepG2细胞1 mmol·L-1FFA造模组和原代大鼠肝细胞0.5 mmol·L-1FFA造模组脂质沉积和氧化应激水平改善显著;而HepG2细胞0.5 mmol·L-1FFA造模组和原代大鼠肝细胞1 mmol·L-1FFA造模组脂质沉积和氧化应激水平在苯扎贝特干预后变化不明显。结论:在相同FFA造模浓度,原代大鼠肝细胞病理特征变化更为明显;苯扎贝特对两种肝细胞在脂质沉积和氧化应激水平的作用也不完全相同。因而HepG2细胞和原代大鼠肝细胞在体外降脂药物评价中药效反应是不完全相同的。     

Study of the thiol/disulfide redox systems of the anaerobe Desulfovibrio vulgaris points out pyruvate:ferredoxin oxidoreductase as a new target for thioredoxin 1

Sulfate reducers have developed a multifaceted adaptative strategy to survive against oxidative stresses. Along with this oxidative stress response, we recently characterized an elegant reversible disulfide bond-dependent protective mechanism in the pyruvate:ferredoxin oxidoreductase (PFOR) of various Desulfovibrio species. Here, we searched for thiol redox systems involved in this mechanism. Using thiol fluorescent labeling, we show that glutathione is not the major thiol/disulfide balance-controlling compound in four different Desulfovibrio species and that no other plentiful low molecular weight thiol can be detected. Enzymatic analyses of two thioredoxins (Trxs) and three thioredoxin reductases allow us to propose the existence of two independent Trx systems in Desulfovibrio vulgaris Hildenborough (DvH). The TR1/Trx1 system corresponds to the typical bacterial Trx system. We measured a TR1 apparent K(m) value for Trx1 of 8.9 μM. Moreover, our results showed that activity of TR1 was NADPH-dependent. The second system named TR3/Trx3 corresponds to an unconventional Trx system as TR3 used preferentially NADH (K(m) for NADPH, 743 μM; K(m) for NADH, 5.6 μM), and Trx3 was unable to reduce insulin. The K(m) value of TR3 for Trx3 was 1.12 μM. In vitro experiments demonstrated that the TR1/Trx1 system was the only one able to reactivate the oxygen-protected form of Desulfovibrio africanus PFOR. Moreover, ex vivo pulldown assays using the mutant Trx1(C33S) as bait allowed us to capture PFOR from the DvH extract. Altogether, these data demonstrate that PFOR is a new target for Trx1, which is probably involved in the protective switch mechanism of the enzyme.     

Identification of a Novel Selenium-containing Compound,Selenoneine, as the Predominant Chemical Form of Organic Selenium in the Blood of Bluefin Tuna

A novel selenium-containing compound having a selenium atom in the imidazole ring, 2-selenyl-N_α,N_α,N_α-trimethyl-l-histidine, 3-(2-hydroseleno-1H-imidazol-5-yl)-2-(trimethylammonio)propanoate, was identified from the blood and other tissues of the bluefin tuna, Thunnus orientalis. The selenium-containing compound was purified from the tuna blood in several chromatographic steps. High resolution mass spectrometry and nuclear magnetic resonance spectroscopy showed that the exact mass of the [M+H]⁺ ion of the compound was 533.0562 and the molecular formula was C₁₈H₂₉N₆O₄Se₂. Its gross structure was assigned as the oxidized dimeric form of an ergothioneine selenium analog in which the sulfur of ergothioneine is replaced by selenium. Therefore, we named this novel selenium-containing compound “selenoneine.” By speciation analysis of organic selenium compounds using liquid chromatography inductively coupled plasma mass spectrometry, selenoneine was found widely distributed in various tissues of the tuna, with the highest concentration in blood; mackerel blood contained similar levels. Selenoneine was measurable at 2–4 orders of magnitude lower concentration in a limited set of tissues from squid, tilapia, pig, and chicken. Quantitatively, selenoneine is the predominant form of organic selenium in tuna tissues.     

Semichronic inhibition of glutathione reductase promotes oxidative damage to proteins and induces both transcription and translation of tyrosine hydroxylase in the nigrostriatal system

We have evaluated the effect of N,N-bis (2-chloroethyl)-N-nitrosourea (BCNU), an inhibitor of glutathione reductase (GR), on the oxidative status along with the integrity of the nigrostriatal dopaminergic system of the rat. The oxidative status was studied by the quantification of carbonyl groups coupled to protein homogenates. Moreover, the specific oxidations in glial fibrillary acidic protein (GFAP) and neurofilament-200 (NF-200) were also measured. The results show that oxidative damage in proteins in the nigrostriatal system is confined to the striatum. Specific carbonyl groups coupled to native NF-200 and GFAP were also increased. These changes were accompanied by reactive astrocytosis in striatum but not in substantia nigra. In substantia nigra, decreased levels of dopamine (DA) and 3,4-dihydroxyphenylacetic acid (DOPAC) were observed following BCNU treatment. In contrast, DA levels were increased in the striatum along with an overall decrease in the ratios of DA metabolites to DA. We also studied the mRNA levels for tyrosine hydroxylase (TH) and the dopamine transporter (DAT) by in situ hybridization. TH mRNA but not DAT mRNA was significantly induced in substantia nigra following BCNU treatment, which was consistent with significant elevations in TH enzyme amount and activity and unchanged DA uptake in striatum. All these results support the DA free radical hypothesis and the key role of the striatal glutathione system in protecting the striatal system against oxidative stress.     

The influence of vitamin C supplementation on the oxidative status of rat interscapular brown adipose tissue

The interscapular brown adipose tissue (IBAT) thermogenesis is accompanied with oxidative stress. In spite of the ability of rats to synthesize vitamin C, we tested the possibility that its additional intake may improve the tissue antioxidative protection. Thus, we studied the IBAT oxidative status in rats supplemented by two doses of ascorbic acid over a 4-week period of time.

Our results confirmed that the additional intake of ascorbate improves the tissue antioxidative defense. Probably acting through enhanced insulin release, vitamin C also exerted some metabolic effects, which emphasize its role in the regulation of IBAT functions under normal physiological conditions.     

Regulation of cathelicidin antimicrobial peptide expression by an endoplasmic reticulum (ER) stress signaling, vitamin D receptor-independent pathway

Vitamin D receptor (VDR)-dependent mechanisms regulate human cathelicidin antimicrobial peptide (CAMP)/LL-37 in various cell types, but CAMP expression also increases after external perturbations (such as infection, injuries, UV irradiation, and permeability barrier disruption) in parallel with induction of endoplasmic reticulum (ER) stress. We demonstrate that CAMP mRNA and protein expression increase in epithelial cells (human primary keratinocytes, HaCaT keratinocytes, and HeLa cells), but not in myeloid (U937 and HL-60) cells, following ER stress generated by two mechanistically different, pharmacological stressors, thapsigargin or tunicamycin. The mechanism for increased CAMP following exposure to ER stress involves NF-κB activation leading to CCAAT/enhancer-binding protein α (C/EBPα) activation via MAP kinase-mediated phosphorylation. Furthermore, both increased CAMP secretion and its proteolytic processing to LL-37 are required for antimicrobial activities occur following ER stress. In addition, topical thapsigargin also increases production of the murine homologue of CAMP in mouse epidermis. Finally and paradoxically, ER stress instead suppresses the 1,25(OH)(2) vitamin D(3)-induced activation of VDR, but blockade of VDR activity does not alter ER stress-induced CAMP up-regulation. Hence, ER stress increases CAMP expression via NF-κB-C/EBPα activation, independent of VDR, illuminating a novel VDR-independent role for ER stress in stimulating innate immunity.     

Assessment of a glutathione S-transferase and related proteins in the gill and digestive gland of Mytilus edulis (L.), as potential organic pollution biomarkers

The response of the glutathione S-transferase (GST, EC 2.5.1.18) and related proteins of Mytilus edulis to environmental pollution load was assessed. Mussels were reciprocally transplanted between an industrial estuary (Douglas), a rural estuary (Youghal) and a m arine site (Bantry). In addition, m ussels were sam pled along a pollution gradient in an estuary receiving leather tannery effluent (Colligan). These latter m ussels were previously shown to be subject to oxidative stress resulting from the discharges. GST specific activity of cytosolic extracts from the gill and digestive gland tissues was determ ined for all anim als. Specific activity was shown to vary significantly in anim als from different sites, with highest specific activity always observed in sam ples (local and transplanted) taken from the industrial site. By com parison, the m ussels exposed to tannery discharges displayed no significant alteration in GST specific activity. Total intracellular glutathione (GSH) was also determ ined for sam ples taken from the Douglas and Youghal estuaries but no correlation with pollution load was observed. Using FPLC analysis, we observed no specific effect on the relative levels of the GST and the individual GST related proteins in gill or digestive gland sam ples from local or reciprocally transplanted anim als from Douglas or Youghal. The increase in GST specific activity observed in samples from the industrial estuary are indicative of a possible, specific inductive agent at this site. The results from the tannery site, by com parison, indicate that general oxidative stress does not result in elevated G ST specific activity in M. edulis.     

Studies on the glutathione S-transferase proteome of adult Drosophila melanogaster: responsiveness to chemical challenge

GSTs from adult Drosophila melanogaster have been partially purified using three different affinity chromatography media and separated by 2-DE. Nine GSTs have been identified by MALDI-TOF MS. In the absence of special treatments, eight GSTs could be positively identified. These were DmGSTs D1 (the dominant Delta isoform which was present in five protein zones of differing pI) and D3 (and possibly also D5); the Epsilon-class GSTs E3, 6, 7 and 9 and a previously uncharacterised, probable member of the class, CG16936. The Sigma-class DmGSTS1 was prominent. DmGSTD2 was detected only after pretreatment of the flies with Phenobarbital (PhB). Treatment with Paraquat (PQ) led to an increase in the total GST activity, as measured with the substrates 1-chloro-2,4-dinitrobenzene (CDNB) and 3,4-dichloro-nitrobenzene (DCNB) and an increase in the relative amounts of the D1, D3, E6 and E7 isoforms. PhB treatment led to increases in the relative amounts of the D1, D2, E3, E6, E7 and E9 isoforms detected with a possible depression in the relative amount of GSTS1. CG16936 was unaffected by either pretreatment.     

Influence of vitamin C and vitamin E on redox signaling: Implications for exercise adaptations

The exogenous antioxidants vitamin C (ascorbate) and vitamin E (α-tocopherol) often blunt favorable cell signaling responses to exercise, suggesting that redox signaling contributes to exercise adaptations. Current theories posit that this antioxidant paradigm interferes with redox signaling by attenuating exercise-induced reactive oxygen species (ROS) and reactive nitrogen species (RNS) generation. The well-documented in vitro antioxidant actions of ascorbate and α-tocopherol and characterization of the type and source of the ROS/RNS produced during exercise theoretically enable identification of redox-dependent mechanisms responsible for the blunting of favorable cell signaling responses to exercise. This review aimed to apply this reasoning to determine how the aforementioned antioxidants might attenuate exercise-induced ROS/RNS production. The principal outcomes of this analysis are (1) neither antioxidant is likely to attenuate nitric oxide signaling either directly (reaction with nitric oxide) or indirectly (reaction with derivatives, e.g., peroxynitrite); (2) neither antioxidant reacts appreciably with hydrogen peroxide, a key effector of redox signaling; (3) ascorbate but not α-tocopherol has the capacity to attenuate exercise-induced superoxide generation; and (4) alternate mechanisms, namely pro-oxidant side reactions and/or reduction of bioactive oxidized macromolecule adducts, are unlikely to interfere with exercise-induced redox signaling. Out of all the possibilities considered, ascorbate-mediated suppression of superoxide generation with attendant implications for hydrogen peroxide signaling is arguably the most cogent explanation for blunting of favorable cell signaling responses to exercise. However, this mechanism is dependent on ascorbate accumulating at sites rich in NADPH oxidases, principal contributors to contraction-mediated superoxide generation, and outcompeting nitric oxide and superoxide dismutase isoforms. The major conclusions of this review are: (1) direct evidence for interference of ascorbate and α-tocopherol with exercise-induced ROS/RNS production is lacking; (2) theoretical analysis reveals that both antioxidants are unlikely to have a major impact on exercise-induced redox signaling; and (3) it is worth considering alternate redox-independent mechanisms.     

Influence of novel naphthalimide-based organoselenium on genotoxicity induced by an alkylating agent: the role of reactive oxygen species and selenoenzymes

Abstract

Objective

The protection conferred by a series of synthetic organoselenium compounds against genotoxicity and oxidative stress induced by a reference mutagen cyclophosphamide (CP) was assessed.

Method

Genotoxicity was induced in mice by CP treatment (25 mg/kg b.w.) for 10 consecutive days. Organoselenium compounds (3 mg/kg b.w.) were administered orally in a concomitant and pretreatment schedule. DNA damage in peripheral blood lymphocytes and frequency of chromosomal aberration in the bone marrow cells were measured. Liver tissues were collected for analysis of the activity of antioxidant and detoxifying enzymes, lipid peroxidation (LPO) level, glutathione content, and histopathology.

Results

Exposure to CP not only led to a significant increase in the percent of chromosomal aberration and DNA damage, but also enhanced generation of hepatic reactive oxygen species (ROS) and LPO level. The organoselenium compounds demonstrated marked functional protection against CP-induced genotoxicity. DNA damage and chromosomal aberration along with ROS generation were attenuated in the organoselenium-treated mice compared with the CP-treated control mice. CP caused marked depression in the activities of the selenoenzymes (glutathione peroxidase (GPx) and thioredoxin reductase (TRxR)) and other detoxifying and antioxidant enzymes, while treatment with organoselenium compounds restored all these activities towards normal.

Discussion

The protective effect of these compounds may be primarily associated with the improvement of the activity of antioxidant and detoxifying enzymes (including the selenoenzymes, GPx, and TRxR) that are known to protect the DNA and other cellular components from oxidative damage.     

Evaluation of the effect of oxygen exposure on human liver microsomal metabolism of mitomycin C in the presence of glutathione using liquid chromatography-quadrupole time of flight mass spectrometry

This article describes a metabolite profiling method for evaluating the effect of oxygen exposure on human liver microsomal metabolism of mitomycin C (MC) in the presence of glutathione (GSH) and NADPH under hypoxic (100% helium), limitedly and fully aerobic, and hyperoxic (100% oxygen) conditions. MC and its metabolite(s) were characterized and the relative percentages of these components were estimated at different incubation times using liquid chromatography and quadrupole time-of-flight mass spectrometry. The MC metabolite profiles were confirmed using purified human cytochrome P450 reductase, acidic activation, and UV-Vis detection at 550 nm. In hypoxia, MC was exclusively metabolized into 2,7-diaminomitosene-10-glutathione-S-conjugate (2,7-DAM-10-SG) within 30 min, whereas approximately 5% of this conjugate, 16% of 2,7-diaminomitosene (2,7-DAM), and 77% of MC were observed under a fully aerobic condition at 90 min. Under limitedly aerobic conditions, the relative percentages of the two metabolites in incubations varied greatly depending on the volume ratio of air to liquid. In hyperoxia, 2% of 2,7-DAM-10-SG, 9% of 2,7-DAM, and 86% of MC were obtained at 90 min. The results indicate that oxygen strongly inhibits the in vitro metabolism of MC. These data suggest that GSH may serve a dual function in facilitating the formation of a leucoaziridinomitosene followed by electron rearrangement giving intermediate metabolite 2,7-DAM, and then trapping this intermediate giving rise to 2,7-DAM-10-SG. These findings provide direct evidence for understanding the fate of oxygen-sensitive metabolic deactivation of MC by GSH.     

Hematological and biochemical investigations on the effect of vitamin E and C on Oreochromis niloticus exposed to zinc oxide nanoparticles

This study was carried out to determine the LC₅₀ of zinc oxide nanoparticles (ZnONPs) on Oreochromis niloticus and to investigate the effect of vitamin E and C on hematological and biochemical alterations induced by two sublethal concentrations (1 and 2 mg/L) of ZnONPs. One hundred and eighty fish were used for studying the lethal concentrations of ZnONPs. For sublethal study two hundred and twenty-five males of O. niloticus were equally divided into five groups, control, the second and the third were treated with 1 and 2 mg/L ZnONPs respectively. The fourth and fifth were exposed to the same concentrations of ZnONPs plus vitamins E and C. The results revealed that the 96 h LC₅₀ of ZnONPs was 3.1 ± 0.4 mg/L. The sublethal study revealed the presence of normocytic normochromic anemia in groups (2, 3 and 5) along the experiment period. The 4th group showed normocytic normochromic anemia at the 7th day and microcytic hypochromic anemia at the 15th day. Leukocytosis, heterophilia, lymphopenia and monocytopenia were recorded at the 7th day in all treated groups compared with the normal control. At the 15th day heteropenia, lymphopenia and monocytopenia were reported in all treated groups. A significant increase in the serum levels of alkaline phosphatase, aminotransferases, urea, creatinine and erythrocytic nuclear and morphological abnormalities along the experimental periods in all treated groups compared with the normal control. Serum total protein and albumin levels were significantly decreased at the same period in the same groups. Addition of vitamin E and C to the diet (groups 4 and 5) significantly improved all measured parameters compared with groups (2 and 3) which treated with ZnONPs only.     

Glucose-6-phosphate dehydrogenase activity and NADPH/NADP+ ratio in liver and pancreas are dependent on the severity of hyperglycemia in rat

Hyperglycemia is associated with metabolic disturbances affecting cell redox potential, particularly the NADPH/NADP+ ratio and reduced glutathione levels. Under oxidative stress, the NADPH supply for reduced glutathione regeneration is dependent on glucose-6-phosphate dehydrogenase. We assessed the effect of different hyperglycemic conditions on enzymatic activities involved in glutathione regeneration (glucose-6-phosphate dehydrogenase and glutathione reductase), NADP(H) and reduced glutathione concentrations in order to analyze the relative role of these enzymes in the control of glutathione restoration. Male Sprague-Dawley rats with mild, moderate and severe hyperglycemia were obtained using different regimens of streptozotocin and nicotinamide. Fifteen days after treatment, rats were killed and enzymatic activities, NADP(H) and reduced glutathione were measured in liver and pancreas. Severe hyperglycemia was associated with decreased body weight, plasma insulin, glucose-6-phosphate dehydrogenase activity, NADPH/NADP+ ratio and glutathione levels in the liver and pancreas, and enhanced NADP+ and glutathione reductase activity in the liver. Moderate hyperglycemia caused similar changes, although body weight and liver NADP+ concentration were not affected and pancreatic glutathione reductase activity decreased. Mild hyperglycemia was associated with a reduction in pancreatic glucose-6-phosphate dehydrogenase activity. Glucose-6-phosphate dehydrogenase, NADPH/NADP+ ratio and glutathione level, vary inversely in relation to blood glucose concentrations, whereas liver glutathione reductase was enhanced during severe hyperglycemia. We conclude that glucose-6-phosphate dehydrogenase and NADPH/NADP+ were highly sensitive to low levels of hyperglycemia. NADPH/NADP+ is regulated by glucose-6-phosphate dehydrogenase in the liver and pancreas, whereas levels of reduced glutathione are mainly dependent on the NADPH supply.     

L—山梨糖脱氢酶的纯化及性质的研究

从５Ｌ罐发酵Ｌ－山梨糖的Ｇｌｕｃｏｎｉｂａｃｔｅｒ ｏｘｙｄａｎｓ ＳＣＢ３２９和Ｂａｃｉｌｌｕｓ ｔｈｕｒｉｎｇｉｅｎｓｉｓ ＳＣＢ９３３混合菌株中差速离心收集ＳＣＢ３２９菌体,破碎,离心获得无细胞抽提液,硫酸铵分级沉淀蛋白后依次经ＤＥＡＥ Ｃｅｌｌｕｌｏｓｅ ５２和Ｑ Ｓｅｐｈａｒｏｓｅ ＦＦ柱层析分得到了Ｌ－册梨糖脱氢酶（ＳＤＨ）,它能将Ｌ－册梨糖脱氢氧化为Ｌ－册梨酮,ＳＤＳ－ＰＡＧＥ电泳测