Effect of Calcium and Zinc on the Activity and Thermostability of Superoxide Dismutase

The effect of calcium and zinc ions on superoxide dismutase (SOD) from four plant species (Taxus baccata, Pinus sylvestris, Medicago rigidula, and Zea mays) was followed at three temperatures: optimal (20 °C), increased (50 °C), and high, inhibiting temperature (70 – 80 °C). At 20 and 50 °C in vitro added calcium increases SOD activity, but the degree was different for the plants investigated. The effect of zinc ions at the same temperatures varied in the investigated plants from activation to inhibition. An inhibiting effect of high temperature on SOD activity was diminished in the presence of calcium or zinc ions. It was shown that calcium and zinc ions can increase activity and thermostabilize different SOD isoforms.     

Kinetics and mechanism of tolerance induction on acclimation ofVillorita cyprinoides (Hanley) to copper and zinc

The typical euryhaline clamVillorita cyprinoides (Hanley) was acclimated to copper and zinc at salinity 13 × 10⁻³ and < 1 × 10⁻³ (fresh water). Acclimation enhanced the lethal tolerance, as denoted by dose-survival curves, which was more pronounced after zinc acclimation. In fresh water copper acclimation sensitized the organisms. The copper accumulation trend was significantly changed consequent to metal acclimation, especially after zinc acclimation, indicating some tissue metal regulatory effect. Acclimation to copper equiped the organism to survive for longer periods with increased body burden of copper, while zinc acclimation supressed the uptake of the more toxic ion copper. The earlier report of increased uptake of zinc by this organism during combined exposure with copper is corelated in the present context. The role of metallothionein like protein in providing protection against metal toxicity, the environmental implication of acclimation phenomena are indicated     

In vitro antifungal efficacy of ciclopirox olamine alone and associated with zinc pyrithione compared to ketoconazole against Malassezia globosa and Malassezia restricta reference strains

The aim of this study was to determine the in vitro fungicidal and growth inhibitory activity of ciclopirox olamine alone (1% and 1.5%) or in association with 1% zinc pyrithione compared to 2% ketoconazole, against Malassezia species particularly involved in the pathogenesis of seborrheic dermatitis. Experiments were performed on Malassezia globosa IP 2387.96 and M. restricta IP 2392.96 strains. Growth inhibitory activity of the active compounds in solution was evaluated by measuring minimal inhibitory concentrations using a broth micro-method and their fungicidal activity by a filtration method after contact times between solutions and yeasts ranging from 3–5 to 30 min. Concerning the determination of minimal inhibitory concentration of ciclopirox olamine/zinc pyrithione, it revealed the marked synergistic inhibitory effect of the association, leading to a higher efficacy compared to ketoconazole. As to the fungicidal activity of ciclopirox olamine, it significantly increased with the contact time. After 15–30 min of contact between 1.5% ciclopirox olamine and Malassezia strains, a 2-log reduction of Malassezia counts was observed. The 1.5% ciclopirox olamine/1% zinc pyrithione association was characterized by a steady fungicidal efficacy whereas the 2% ketoconazole solution did not express any fungicidal effect. In conclusion, this study demonstrates the in vitro inhibitory and fungicidal efficacy of the ciclopirox olamine/zinc pyrithione association against Malassezia species and underscores its potential interest in the treatment of seborrheic dermatitis.     

Heterologous expression of bacterial and human multidrug resistance proteins protect Escherichia coli against mercury and zinc contamination

In order to determine the role of multidrug resistance proteins in mercury and zinc resistance, human MDR1, Lactococcus lactis lmrA, and Oenococcus oeni omrA genes were expressed in an Escherichia coli tolC mutant which is hypersensitive to metals. The three transporters conferred an increased mercury and zinc resistance to E. coli as compared to the control bacteria. This improved resistance correlated with a decreased zinc and mercury bioaccumulation. Indeed, quantification of intracellular metal concentrations by atomic absorption spectrometry (AAS) showed a 2.1-, 3-, and 5.1-fold decrease in zinc in cells expressing hMDR1, omrA, and lmrA, respectively, and a 2.7-, 7.5-, and 7.7-fold decrease in mercury in cells expressing omrA, lmrA, and hMDR1, respectively, as compared to the control bacteria. This means that hMDR1, LmrA, and OmrA proteins which are specialised in xenobiotic scavenging, their main known function, are nevertheless able to confer some resistance against metals. Our results show that the tolC mutated strain is well adapted to the study of MDR transporter activity and could be used to screen substrates and competitive hMDR1 inhibitors.     

Body zinc distribution profile during N-methyl-N-nitrosourea-induced mammary tumorigenesis in rats at various levels of dietary zinc intake

Zinc distribution is apparently altered in breast cancer patients. It is unclear if this apparent zinc redistribution is a consequence of altered zinc nutrition or tissue-specific response to breast cancer. Our objectives were to assess effects of N-methyl-N-nitrosourea-treatment and N-methyl-N-nitrosourea-induced mammary tumorigenesis on body zinc-distribution profile in rats and to assess effects of dietary zinc intake on the body zinc-distribution profile during N-methyl-N-nitrosourea treatment and N-methyl-N-nitrosourea-induced mammary tumorigenesis in rats. Female Sprague-Dawley rats were assigned to zinc-deficient (3 mg/kg diet) or zinc-adequate (31 mg/kg diet) ad libitum or pair-fed group. Rats were sham treated or N-methyl-N-nitrosourea treated (50 mg/kg body weight; Experiment 1 or 40 mg/kg body weight; Experiment 2) (n=6). In both experiments, the zinc concentration was significantly higher (6–19 times) in mammary tumor than in mammary gland. Tissue zinc concentration was essentially unaffected by N-methyl-N-nitrosourea treatment and tumor bearing, but was reduced by zinc deficiency in the bone, kidney, and liver. Overall, higher mammary tumor zinc concentration and absence of zinc redistribution during N-methyl-N-nitrosourea treatment and N-methyl-N-nitrosourea-induced mammary tumorigenesis, regardless of zinc intakes, indicates zinc accumulation in mammary tumors. Because zinc is essential for growth and cancer is characterized by uncontrolled growth, this zinc accumulation suggests an involvement of zinc in N-methyl-N-nitrosourea-induced rat mammary tumorigenesis.     

铜绿假单胞菌锌离子摄取系统的研究进展

锌作为一种结构、催化和信号的成分,在许多生理过程中起着关键的作用.它也是病原微生物生长所必需的,不但参与病原微生物代谢和各种毒力因子的调控,而且是病原微生物在宿主中感染和定殖所必需的.铜绿假单胞菌侵染宿主发挥毒力时,宿主会采取营养免疫的策略来限制体内环境中游离的锌离子浓度而抑制该病原菌的感染和定殖.反过来,铜绿假单胞菌...     

Effect of zinc supply on growth of three species of Eucalyptus seedlings and wheat

Summary Effects of zinc supply on shoot and root dry weight, root length, zinc concentrations and carbonic anhydrase activity were measured in 52 day old seedlings ofEucalyptus maculata, E. marginata, E. patens and wheat grown in a zinc deficient soil in the glasshouse.Symptoms of zinc deficiency in the eucalyptus and wheat appeared within 20 to 35 days. Eucalypt seedlings had short internodes and small necrotic leaves, reduced dry weight of shoots and roots, root length and zinc concentrations in young leaves; the measurable level of leaf carbonic anhydrase activity decreased to zero. Similar responses also occurred in wheat.The level of zinc fertilizer required for normal growth of Eucalyptus seedlings is therefore likely to be similar to that used for wheat and other agricultural crops.     

Rat osseous plate alkaline phosphatase: mechanism of action of manganese ions

Polidocanol-solubilized osseous plate alkaline phosphatase was modulated by manganese ions in a similar way as by zinc ions. For concentrations up to 1.0 nm, the enzyme was stimulated by manganese ions, showing site-site interactions (n = 2.2). However, larger concentrations (> 0.1 m) were inhibitory. Manganese ions could play the role of zinc ions stimulating the enzyme synergistically in the presence of magnesium ions (K _d = 7.2 m; V = 1005.5 U mg^–1). Manganese ions could also play the role of magnesium ions, stimulating the enzyme synergistically in the presence of zinc ions (K _d = 2.2 m; V = 1036.7 U mg^–1). However, manganese ions could not substitute for zinc and magnesium at the same time since ion assymetry is necessary for full activity of the enzyme. A steady-state kinetic model for the modulation of enzyme activity by manganese ions is proposed.     

Responsivenes of total content changes of magnesium and zinc status in patients infected with Giardia intestinalis

The aim of the study was to investigate the changes of total content of the essential elements of zinc and magnesium levels in patients infected with Giardia intestinalis. Zinc and magnesium concentrations were measured in 64 patients who were positive for the intestinal parasite G. intestinalis. Scores were obtained for the positives and their 60 age- and sex-matched G. intestinalis-negative healthy controls. The mean concentration of magnesium in blood was significantly lower in G. intestinalis-positive patients than in their controls both in females (p<0.05) and males (p<0.05). The average zinc concentration in G. intestinalis-positive female patients was 0.76±0.3 mg/L and it was 0.60±0.2 mg/L in controls (p>0.05). The mean values of the zinc in blood were 0.73±0.2 mg/L in G. intestinalis-positive male patients and 0.82±0.1 mg/L in controls (p>0.05). No correlation could be demonstrated between age and mean values of zinc and magnesium in both G. intestinalis-positive females/males and controls (p>0.05). No significant correlation could be found between blood zinc and magnesium levels in G. intestinalis-positive female/male patients and controls (p>0.05). Magnesium levels were found to be clearly decreased, whereas no change was observed in zinc level in the patients infected with G. intestinalis compared to controls.     

Zinc ions as cytochrome <Emphasis Type="Italic">c</Emphasis> oxidase inhibitors: two sites of action

Zinc ions are shown to be an efficient inhibitor of mitochondrial cytochrome c oxidase activity, both in the solubilized and the liposome reconstituted enzyme. The effect of zinc is biphasic. First there occurs rapid interaction of zinc with the enzyme at a site exposed to the aqueous phase corresponding to the mitochondrial matrix. This interaction is fully reversed by EDTA and results in a partial inhibition of the enzyme activity (50–90%,depending on preparation) with an effective K _i of 10 µM. The rapid effect of zinc is observed with the solubilized enzyme, it vanishes upon incorporation of cytochrome oxidase in liposomes,and it re-appears when proteoliposomes are supplied with alamethicin that makes the membrane permeable to low molecular weight substances. Zinc presumably blocks the entrance of the D-protonic channel opening into the inner aqueous phase. Second, zinc interacts slowly (tens of minutes, hours) with a site of cytochrome oxidase accessible from the outer aqueous phase bringing about complete inhibition of the enzymatic activity. The slow phase is characterized by high affinity of the inhibitor for the enzyme:full inhibition can be achieved upon incubation of the solubilized oxidase for 24 h with zinc concentration as low as 2 µM. The rate of zinc inhibitory action in the slow phase is proportional to Zn²⁺ concentration. The slow interaction of zinc with the outer surface of liposome-reconstituted cytochrome oxidase is observed only with the enzyme turning over or in the presence of weak reductants, whereas incubation of zinc with the fully oxidized proteoliposomes does not induce the inhibition. It is shown that zinc ions added to cytochrome oxidase proteoliposomes from the outside inhibit specifically the slow electrogenic phase of proton transfer, coupled to a transition of cytochrome oxidase from the oxo-ferryl to the oxidized state (the F O step corresponding to transfer of the 4th electron in the catalytic cycle).Translated from Biokhimiya, Vol. 70, No. 2, 2005, pp. 160–170.Original Russian Text Copyright © 2005 by Kuznetsova, Azarkina, Vygodina, Siletsky, Konstantinov.This revised version was published online in April 2005 with corrections to the post codes.     

Digestive strategies in the South American subterranean rodent Ctenomys talarum

Ctenomys talarum is a subterranean herbivorous rodent which due to its particular life style is frequently exposed to variations in surface environmental conditions (i.e. food quality and availability, temperature). Thus, unlike other subterranean rodents, C. talarum has to buffer both the surface and burrow challenging environmental conditions. We studied the occurrence of digestive strategies at different levels of C. talarum living in their natural habitat. We determined the dimensions of different parts of the gastrointestinal tract and organs along as the activity of key digestive enzymes (disaccharidase, N-aminopeptidase) in different parts of the gut in individuals seasonally caught. The results show that C. talarum exhibits characteristics in the gut at the biochemical level (high disaccharidase activities in small intestine, high N-aminopeptidase activity in the caecum and large intestine, and a seasonal differential modulation of N-aminopeptidase activity in small and large intestines), which could represent adaptive strategies to face seasonal variations in key environmental factors.     

嗜水气单胞菌zntR调控的生理功能及其机制研究

【目的】ZntR是一种金属调控蛋白,可催化锌外排基因的转录激活,防止细胞内二价Zn离子过量,但其对细菌生理功能的影响目前尚不清楚。【方法】本研究构建了嗜水气单胞菌ATCC7966(Aeromonas hydrophila,A.h)的zntR缺失株及补救株,对菌株的生物被膜形成能力、溶血活性、运动能力和响应金属离子胁迫等生理表型进行评估。【结果】敲除zntR基因的菌株对锌和铬离子胁迫敏感、对钴离子胁迫耐受,并且生物被膜形成能力下降、运动能力增强,这些表型在其补救菌株中均能得到恢复。进一步利用DIA定量蛋白质组学技术比较野生株和zntR缺失株的蛋白表达差异,发现ZntR还可能参与双组分系统、细菌的趋化性等代谢通路的调控。【结论】该研究结果可为今后深入探讨zntR转录因子参与细菌生理功能的调控机制提供理论依据。     

Hypoglycemic activity of inorganic constitutents in Eugenia jambolana seed on streptozotocin-induced diabetes in rats

Medicinal herbs used in indigenous medicines for the management of diabetes mellitus contain both organic and inorganic constituents. Some of these inorganic trace elements possess antidiabetic properties, which accounts for the activity of medicinal herbs. The aim of this study was to analyze the inorganic trace elements present in Eugenia jambolana seeds and to evaluate the hypoglycemic activity of the inorganic part of E. jambolana seeds on streptozotocin-induced diabetes. The seeds of E. jambolana seeds were reduced to ash and the inorganic elements present were assayed. The hypoglycemic efficacy of the inorganic part was tested by the glucose tolerance test on streptozotocin-induced diabetes. Elements such as zinc, chromium, vanadium, potassium, and sodium, possessing hypoglycemic activity, were present in the seed. The E. jambolana seed ashtreated diabetic rats exhibited normoglycemia and better glucose tolerance. The conclusion that the inorganic constituents might play a important role in the antidiabetic nature E. jambolana seeds was reached.     

原绿球藻对环境胁迫的生理和分子响应机制

原绿球藻(Prochlorococcus)作为海洋丰度最高的浮游植物,对海洋生态系统的物质循环和能量流动起着重要的驱动作用。原绿球藻生长和光合作用活性容易受到环境胁迫的影响,进而影响整个海洋生态系统的稳定性。因此,研究原绿球藻应对环境胁迫的响应机制具有重要的生态意义。原绿球藻主要通过分化出不同的生态型来适应不同光照和营养盐的海洋环境,但仍然会很难快速适应各种突如其来的海洋环境变化。本文从原绿球藻应对环境胁迫的角度,探讨了其生理和分子响应机制的最新研究进展,包括光系统I循环电子传递在光照变化时发挥的重要作用,通过RNA快速响应而调控基因表达应对环境胁迫,以及在辅助异养细菌的保护下应对活性氧的胁迫等。本文也展望了原绿球藻对环境胁迫响应的生理和分子机制的未来研究方向,旨在为原绿球藻抗逆机制的深入研究提供参考。     

Effect of environmental alcohol on in Vivo properties of Drosophila alcohol dehydrogenase

The effects of environmental 2-propanol on the in vivo properties of Drosophila alcohol dehydrogenase (E.C. 1.1.1.1.) are presented. Exposed flies were found to exhibit a significant decrease in ADH specific activity with a concomitant increase in the enzyme's relative in vivo stability and concentration. The possible adaptive significance of the observed responses is discussed.This work was supported by NSF grant #DEB 7815466 to J.M. Journal Paper No. J-9979 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa. Project No. 2272.     

Serum zinc and magnesium levels in patients with blastocystosis

The aim of the study was to investigate the total content of the essential elements of zinc and magnesium levels in patients infected with Blastocystis hominis. Zinc and magnesium concentrations were measured in 52 patients who were positive for the intestinal parasite Blastocystis hominis. Scores were obtained for the positives and their age- and sex-matched 60 Blastocystis hominis-negative healthy controls. For comparison of two groups of continuous variables, the independent samples t-test was used. The mean concentration of magnesium in blood was significantly lower in Blastocystis hominis-positive patients than in their controls both in females (p<0.05) and males (p<0.05). The average zinc concentration in Blastocystis hominis-positive female patients was 0.61±0.2 mg/L and 0.60±0.2 mg/L in controls (p>0.05). The mean values of the zinc in blood were 0.62±0.2 mg/L in Blastocystis hominis-positive male patients and 0.82±0.1 in controls (p>0.05). No correlation could be demonstrated between age and mean values of zinc and magnesium in Blastocystis-positive females/males and controls (p>0.05). No significant correlation could be found between blood zinc and magnesium levels in Blastocystis-positive female/male patients and controls (p>0.05). Magnesium levels were found to be clearly decreased, whereas no change was observed in zinc levels in the patients with Blastocystis compared to controls.     

Teniasis

The aim of this study was to investigate the changes of level of the essential elements of copper, magnesium, and zinc status in cases of teniasis in children. Copper, magnesium, and zinc levels were measured in 40 children who were positive for intestinal parasite of Taenia saginata. Scores were obtained for the positives and their 30 age- and sex-matched T. saginata-negative healthy children. The mean concentration of copper, magnesium, and zinc in blood showed no statistically difference in T. saginata-positive children than in their controls both in females (p>0.05) and males (p>0.05). However, a clear numerically decrease was observed especially in magnesium and zinc levels compared to the controls both in females and males. The average magnesium concentration in T. saginata-positive female children and male children were 20±1.9 and 22±2.2 mg/L and it was 27±2.1 and 27±2.3 mg/L in controls, respectively. The mean values of the zinc in blood were 0.76±0.5 and 0.72±0.4 mg/L in T. saginata-positive female children and male children and 0.85±0.3 and 0.81±0.5 mg/L in female and male controls, respectively. No correlation could be demonstrated between age and mean values of copper, magnesium, and zinc in T. saginata-positive females and males and controls (p>0.05). No significant correlation could be found between blood copper, magnesium and zinc levels in T. saginata-positive female and male children and controls (p>0.05). Although there was no statistical correlation observed in copper, magnesium, and zinc levels between patients and controls, there seem to be, especially in magnesium and zinc levels, a decrease, whereas no change was seen in the zinc level in children infected with T. saginata compared to controls.     

EXAFS investigation of the active site of iron superoxide dismutase of Escherichia coli and Propionibacterium shermanii

The local structure of the iron site in ferric superoxide dismutase from P. shermanii was analyzed by X-ray absorption spectroscopy. The metal-ligand cluster of the enzyme is found to be similar to the crystallographically investigated ferric superoxide dismutase from E. coli. At pH 6.4 the enzyme is five-fold coordinated with three histidines, an aspartate and a water molecule. The average bond lengths between the metal and the histidines are about 2.10 Å, between metal and aspartate they are about 1.86 Å and between metal and water 1.96 Å. With an increase in pH a change in the coordination number from five to six is observed both in pre-edge peak and EXAFS spectra analysis. However, the bond lengths of the ligands do not change dramatically, they are conserved for the aspartate and increase slightly to 2.13 Å for the average metal - histidine distance at pH 9.3. The observation of the increase in coordination number is correlated with a decrease in enzymatic activity which occurs in the high pH range. The zinc EXAFS spectra of P. shermanii superoxide dismutase have shown that zinc can be incorporated in the active center instead of the iron.