Structure and function of S-adenosylhomocysteine hydrolase

In mammals, S-adenosylhomocysteine hydrolase (AdoHcyase) is the only known enzyme to catalyze the breakdown of S-adenosylhomocysteine (AdoHcy) to homocysteine and adenosine. AdoHcy is the product of all adenosylmethionine (AdoMet)-dependent biological transmethylations. These reactions have a wide range of products, and are common in all facets of biometabolism. As a product inhibitor, elevated levels of AdoHcy suppress AdoMet-dependent transmethylations. Thus, AdoHcyase is a regulator of biological transmethylation in general. The three-dimensional structure of AdoHcyase complexed with reduced nicotinamide adenine dinucleotide phosphate (NADH) and the inhibitor (1′R, 2′S, 3′R)-9-(2′,3′-dihyroxycyclopenten-1-yl)adenine (DHCeA) was solved by a combination of the crystallographic direct methods program, SnB, to determine the selenium atom substructure and by treating the multiwavelength anomalous diffraction data as a special case of multiple isomorphous replacement. The enzyme architecture resembles that observed for NAD-dependent dehydrogenases, with the catalytic domain and the cofactor binding domain each containing a modified Rossmann fold. The two domains form a deep active site cleft containing the cofactor and bound inhibitor molecule. A comparison of the inhibitor complex of the human enzyme and the structure of the rat enzyme, solved without inhibitor, suggests that a 17° rigid body movement of the catalytic domain occurs upon inhibitor/substrate binding.     

Land,livestock, and livelihoods: Changing dynamics of gender,caste, and ethnicity in a Nepalese Village

Over the past 10 years, Ghusel VDC, Lalitpur District has moved from primarily subsistence agriculture into the wider cash economy aided by the Small Farmers' Development Program (SFDP), which provides credit to farmers mainly for the purchase of buffalo for milk production, and by the National Dairy Corporation, which supports local dairy cooperatives. Analysis reveals that buffalo-keeping and milk sales are increasing the well-being of many households, while at the same time creating new inequalities in gender roles and responsibilities, greater inequities between Brahmin and Tamang residents in Ghusel, and placing pressures on the ecosystem for increased supplies of fodder and fuelwood. Evidence suggests that there is critical, need for attention to the social, and particularly gender-based, implications of maintaining livestock for milk sales and to the ecological underpinnings of this livelihood system.     

Highly flexible O,O′,N ligands and their Fe, Ni, Cu and Zn complexes

Three new chiral ligands bearing an O,O′,N donor set (O_methoxyO_hydroxyN_pyridine) were synthesised and coordinated to Fe^III, Fe^II, Ni^II, Cu^II and Zn^II to yield complexes with the general formula [M(OON)Cl_x]_y. While the pyridine N and the hydroxy O atoms coordinate strongly to all applied metal ions, the methoxy donor seems not to be involved in coordination, although some evidence for a weak interaction between O_Me and the Zn^II were found in NMR spectra. In the bidentate O′,N coordination mode the new ligands exhibit several coordination geometries as analysed in the solid compounds by XRD, EXAFS and EPR and in solution by UV-Vis absorption, cyclic voltammetry, EXAFS, EPR or NMR spectroscopy.     

Influence of Fluoride on Rat Kidney Antioxidant System: Effects of Methionine and Vitamin E

The aim of the study has been to determine and compare the influence upon the kidney antioxidative system, exercised by administration of vitamin E, and vitamin E in combination with methionine, under conditions of oxidative stress induced by sodium fluoride. The experiment was carried out on Wistar FL rats (adult males) that, for 35 days, were administered water, NaF, NaF with vitamin E, or vitamin E with methionine (doses: 10 mg NaF/kg of body mass/24 h, 3 mg vitamin E per 10 μl per rat for 24 h, 2 mg methionine per rat for 24 h). The influence of administered sodium fluoride and antioxidants upon the antioxidative system in kidney was examined by analyzing the concentration of malondialdehyde (MDA) and the activity of the most important antioxidative enzymes (SOD, total and both its isoenzymes, GPX, GST, GR, and CAT). The studies carried out confirmed the disadvantageous effect of the administered dose of NaF upon the antixodiative system in rats (increase in the concentration MDA, decrease activity of all antioxidative enzymes). The administration of vitamin E increased the activity of studied enzymes with the exception of glutathione reductase GR; it also reduced the procesess of lipid peroxidation. It has been found that combined doses of vitamin E and methionine were most effective in inhibiting lipid peroxidation processes. The results confirmed the antioxidative properties of methionine.     

邻苯二甲酸二丁酯对翡翠贻贝抗氧化酶及脂质过氧化水平的影响

实验室条件下,研究了不同浓度邻苯二甲酸二丁酯(DBP)长期胁迫(15 d)对翡翠贻贝内脏团和外套膜抗氧化酶(超氧化物歧化酶SOD、过氧化氢酶CAT)及脂质过氧化(LPO)水平(以MDA含量表示)的影响,以及受胁迫翡翠贻贝在清洁海水中恢复阶段上述生化指标的变化特征.结果表明:胁迫阶段,0.5和2.5 mg.L-1DBP下翡翠贻贝内脏团SOD活性表现为先抑制后逐渐恢复,12.5和62.5 mg.L-1下则持续受到显著抑制;不同浓度组CAT活性均明显被抑制.LPO水平明显升高.外套膜中,2.5 mg.L-1下SOD活性受到持续诱导,其他浓度组则先被抑制,后随曝露时间延长逐渐被诱导;各浓度组CAT的变化波动较大,没有明显规律;而LPO水平明显升高.净化恢复阶段,12.5和62.5 mg.L-1DBP胁迫下的内脏团SOD和CAT活性恢复较慢,其LPO水平随时间延长逐渐恢复至对照组水平;外套膜中SOD活性呈持续升高趋势,CAT活性和LPO水平则随时间延长恢复到对照组水平.     

In vitro studies of the rabbit immune system. IV. Differential mitogen responses of isolated T and B cells.

The mitogenic responses of separated rabbit lymphocyte populations functionally analogous to mouse T and B cells have been tested in vitro. Purified T cells were prepared by passage over nylon wool (NW) and purified B cells prepared by treatment with antithymocyte serum and complement (ATS + C). ATS + C kills 70% of peripheral blood lymphocytes (PBL's) and 50% of the spleen cells while passage over NW yields 40% of the applied PBL's and 5–23% of the applied spleen cells. NW-purified T cells from the spleen or PBL's respond fully to concanavalin A (Con A) but have a reduced response to phytohemaglutinin (PHA) and little or no response to goat anti-rabbit immunoglobulin (anti-Ig). PBL's that survive ATS + C (B cells) are stimulated by anti-Ig but not by Con A or PHA. B cells purified from spleen do not respond to Con A or PHA but will respond to anti-Ig under appropriate conditions. A full spleen B-cell response to anti-Ig required removal of Ig produced by the cultures that blocked anti-Ig stimulation. It is concluded that, for rabbit lymphocytes, Con A and PHA are primarily T-cell mitogens and that anti-Ig is primarily a B-cell mitogen. However, the mitogen response of unfractionated PBL or spleen cell populations indicates an overlap in reactivity. This could be due to cells sharing T and B properties, alteration of cell populations by the fractionation procedures used, or recruitment of one population in the presence of a mitogenic response of the other population.     

Tuning of electronic properties of one-dimensional cyano-bridged Cu-Ni, Cu-Pd, and Cu-Pt bimetallic assemblies by stereochemistry of ligands

Preparations, XPS and electronic spectroscopy, and magnetism of seven new one-dimensional cyano-bridged coordination polymers, chiral [Cu(RR-chxn)₂][Pd(CN)₄] · 2H₂O (1), [Cu(trans-chxn)₂][M(CN)₄] · 2H₂O (2, 4, and 6 for M = Pd, Ni, and Pt), and [Cu(cis-chxn)₂][M(CN)₄] · 2H₂O (3, 5, and 7 for M = Pd, Ni, and Pt) (RR-chxn = cyclohexane-(1R,2R)-diamine, trans-chxn = racemic trans-cyclohexane-(1,2)-diamine, and cis-chxn = racemic cis-cyclohexane-(1,2)-diamine) have been reported in view of tuning of their electronic properties by stereochemistry of chxn ligands and metal-substitution. Comparison of Cu 2p_1/2 and 2p_3/2 peaks of XPS and broad d-d bands around 18 000 cm⁻¹ of electronic spectra are described systematically for 1-7. Variable-temperature magnetic measurement shows that complexes 1-7 indicate weak antiferromagnetic interactions via cyano-bridges. Because of semi-coordination coupled with pseudo Jahn-Teller elongation and electrostatic interaction for 1, the axial Cu-N coordination bond distances of 2.330(7) and 3.092(8) Å are considerably longer than those of equatorial ones in the range from 2.016(6) to 2.030(6) Å. The former bond distances of 1 are intermediate values among the related Ni (2.324(6) and 3.120(8) Å) and Pt (2.34(1) and 3.09(1) Å) complexes.     

Gamma-glutamylcysteine protects ergothioneine-deficient Mycobacterium tuberculosis mutants against oxidative and nitrosative stress

Mycobacterium tuberculosis (M.tb.), the causative agent of tuberculosis (TB), cannot synthesize GSH, but synthesizes two major low molecular weight thiols namely mycothiol (MSH) and ergothioneine (ERG). Gamma-glutamylcysteine (GGC), an intermediate in GSH synthesis, has been implicated in the protection of lactic acid bacteria from oxidative stress in the absence of GSH. In mycobacteria, GGC is an intermediate in ERG biosynthesis, and its formation is catalysed by EgtA (GshA). GGC is subsequently used by EgtB in the formation of hercynine-sulphoxide-GGC. In this study, M.tb. mutants harbouring unmarked, in-frame deletions in each of the fives genes involved in ERG biosynthesis (egtA, egtB, egtC, egtD and egtE) or a marked deletion of the mshA gene (required for MSH biosynthesis) were generated. Liquid chromatography tandem mass spectrometry analyses (LC-MS) revealed that the production of GGC was elevated in the MSH-deficient and the ERG-deficient mutants. The ERG-deficient ΔegtB mutant which accumulated GGC was more resistant to oxidative and nitrosative stress than the ERG-deficient, GGC-deficient ΔegtA mutant. This implicates GGC in the detoxification of reactive oxygen and nitrogen species in M.tb.     

Intracoronary and systemic release of the atrial natriuretic factor and cyclic-guanosine monophosphate during coronary angioplasty

Summary This study was undertaken to investigate intracoronary production and systemic release of the atrial natriuretic factor (ANF) and cyclic-guanosine monophosphate (c-GMP) during coronary angioplasty (PTCA). three coronary blood samples were collected, through a balloon catheter, from the area distal to the lesion: before balloon inflation, at maximum inflation and 5 min later. Four additional venous samples were collected: before PTCA, and 5 min, 2 h and 24 h after the procedure. Local intracoronary c-GMP production increased from the baseline level of 7.5±0.9 pmol/ml to 11.1±1.3 pmol/ml at maximum balloon inflation (p<0.01) and decreased 5 min later to 9.5 ±1.0 pmol/ml (p=NS). In contrast, intracoronary ANF production failed to show any significant change at any time during the procedure. Peripheral venous ANF levels increased from 79.1±11.1 pmol/ml to 99.9±16.6 pmol/ml 5 min after balloon inflation (p<0.05) and gradually decreased 2 h (91.9±13.6 pmol/ml) and 24 h (85.6±10.4 pmol/ml) after the procedure. Similarly, peripheral venous c-GMP levels increased from 11.3±1.7 pmol/ml before PTCA to 14.9±1.9 pmol/ml 5 min after balloon inflation (p<0.05), and then gradually decreased 2 h (10.8±1.4 pmol/ml) and 24 h (8.2±1.4 pmol/ml) after the procedure (p<0.01 and <0.0001 compared to the peak value, respectively). In conclusion, acute vessel occlusion and distension during balloon inflation stimulates intracoronary c-GMP production without affecting ANF release.     

Malondialdehyde,carbonyl proteins and albumin-disulphide as useful oxidative markers in mild cognitive impairment and Alzheimer's disease

The question arises as to whether oxidative stress has a primary role in neurodegeneration or is a secondary end-stage epiphenomenon. The aim of the present study was to determine oxidative stress parameters like malondialdehyde (MDA), carbonyl proteins (CP) and Albumin-disulphide (Alb-SSR) and relate these parameters to the immune parameter neopterin, folic acid and vitamin B12 as vitamins and homocysteine in patients with neuro-degenerative diseases (NDD), namely mild cognitive impairment (MCI) and Alzheimer's disease (AD) compared to an aged matched control group. MDA, CP and Alb-SSR were significantly increased in the NDD group compared to controls, but not vitamin B12, folic acid and neopterin. Significant correlations were found between CP and Alb-SSR, CP and MDA and between MDA and Alb-SSR including patients with NDD and the control group. These results support the hypothesis that oxidative damage to lipids and proteins is an important early event in the pathogenesis of neurodegenerative diseases.     

Selective inhibition of human acetylcholinesterase by xanthine derivatives: In vitro inhibition and molecular modeling investigations

The commonly used beverage and psychostimulant caffeine is known to inhibit human acetylcholinesterase enzyme. This pharmacological activity of caffeine is partly responsible for its cognition enhancing properties. However, the exact mechanisms of its binding to human cholinesterases (acetyl and butyrylcholinesterase; hAChE and hBuChE) are not well known. In this study, we investigated the cholinesterase inhibition by the xanthine derivatives caffeine, pentoxifylline, and propentofylline. Among them, propentofylline was the most potent AChE inhibitor (hAChE IC₅₀ = 6.40 μM). The hAChE inhibitory potency was of the order: caffeine (hAChE IC₅₀ = 7.25 μM) < pentoxifylline (hAChE IC₅₀ = 6.60 μM) ? propentofylline (hAChE IC₅₀ = 6.40 μM). These compounds were less potent relative to the reference agent donepezil (hAChE IC₅₀ = 0.04 μM). Moreover, they all exhibited selective inhibition of hAChE with no inhibition of hBuChE (IC₅₀ > 50 μM) relative to the reference agent donepezil (hBuChE IC₅₀ = 13.60 μM). Molecular modeling investigations indicate that caffeine binds primarily in the catalytic site (Ser203, Glu334 and His447) region of hAChE whereas pentoxifylline and propentofylline are able to bind to both the catalytic site and peripheral anionic site due to their increased bulk/size, thereby exhibiting superior AChE inhibition relative to caffeine. In contrast, their lack of hBuChE inhibition is due to a larger binding site and lack of key aromatic amino acids. In summary, our study has important implications in the development of novel caffeine derivatives as selective AChE inhibitors with potential application as cognitive enhancers and to treat various forms of dementia.     

Chromium accumulation, translocation and chemical speciation in vegetable crops

Trivalent chromium (Cr³⁺) is essential for animal and human health, whereas hexavalent Cr (CrO₄ ²⁻) is a potent carcinogen and extremely toxic to animals and humans. Thus, the accumulated Cr in food plants may represent potential health hazards to animals and humans if the element is accumulated in the hexavalent form or in high concentrations. This study was conducted to determine the extent to which various vegetable crops absorb and accumulate Cr³⁺ and CrO₄ ²⁻ into roots and shoots and to ascertain the different chemical forms of Cr in these tissues. Two greenhouse hydroponic experiments were performed using a recirculating-nutrient culture technique that allowed all plants to be equally supplied with Cr at all times. In the first experiment, 1 mg L⁻¹ Cr was supplied to 11 vegetable plant species as Cr³⁺ or CrO₄ ²⁻, and the accumulation of Cr in roots and shoots was compared. The crops tested included cabbage (Brassica oleracea L. var. capitata L.), cauliflower (Brassica oleracea L. var. botrytis L.), celery (Apium graveolens L. var. dulce (Mill.) Pers.), chive (Allium schoenoprasum L.), collard (Brassica oleracea L. var. acephala DC.), garden pea (Pisum sativum L.), kale (Brassica oleracea L. var. acephala DC.), lettuce (Lactuca sativa L.), onion (Allium cepa L.), spinach (Spinacia oleracea L.), and strawberry (Fragaria ×  ananassaDuch.). In the second experiment, X-ray absorption spectroscopy (XAS) analysis on Cr in plant tissues was performed in roots and shoots of various vegetable plants treated with CrO₄ ²⁻ at either 2 mg Cr L⁻¹ for 7 d or 10 mg Cr L⁻¹ for 2, 4 or 7 d. The crops used in this experiment included beet (Beta vulgaris L. var. crassa (Alef.) J. Helm), broccoli (Brassica oleracea L. var. Italica Plenck), cantaloupe (Cucumis melo L. gp. Cantalupensis), cucumber (Cucumis sativus L.), lettuce, radish (Raphanus sativus L.), spinach, tomato (Lycopersicon lycopersicum (L.) Karsten), and turnip (Brassica rapa L. var. rapifera Bailey). The XAS speciation analysis indicates that CrO₄ ²⁻ is converted in the root to Cr³⁺ by all plants tested. Translocation of both Cr forms from roots to shoots was extremely limited and accumulation of Cr by roots was 100-fold higher than that by shoots, regardless of the Cr species supplied. Highest Cr concentrations were detected in members of the Brassicaceae family such as cauliflower, kale, and cabbage. Based on our observations and previous findings by other researchers, a hypothesis for the differential accumulation and identical translocation patterns of the two Cr ions is proposed. Received: 27 February 1998 / Accepted: 2 April 1998     

Accumulation of Storage Materials,Precocious Germination and Development of Desiccation Tolerance During Seed Maturation in Mustard (Sinapis alba L.)

Under defined environmental conditions (20°C, continuous light of 15 klx) development of mustard seeds from artificial pollination to maturity takes about 60 d. After surpassing the period of embryo cell division and histodifferentiation (12–14d after pollination = dap), the seed enters into a maturation period. The time courses of various physiological, biochemical, and structural changes of embryo and testa during seed maturation were analyzed in detail (dry and fresh mass changes, osmotic and water potential changes, respiration, DNA amplification by endomitosis, total ribosome and polysome formation, storage protein synthesis and accumulation, storage lipid accumulation). In addition to the final storage products protein and lipid, embryo and testa accumulate transiently large amounts of starch within the chloroplasts during early maturation. Concomitantly with the subsequent total breakdown of the starch, the plastids lose most of their internal structure and chlorophyll and shrink into proplastids, typical for the mature seed. At about 30 dap the seeds shift from a desiccation-sensitive to a desiccation-tolerant state and are able then to germinate rapidly upon drying and reimbibition. If isolated from the immature fruit and sown directly on water, the seeds demonstrate precocious germination from about 13 dap onwards. Young seeds (isolated ≦ 38 dap) germinate only after surpassing a lag-phase of several days (after-ripening) during which the embryo continues to accumulate storage protein and lipid at the expense of the surrounding seed tissues. We conclude from these results that the maturing seed represents a rather closed developmental system which is able to continue its development up to successful germination without any specific regulatory influence from the mother plant. Immature seeds are able to germinate without a preceding dehydration treatment, which means that partial or full desiccation does not serve as an environmental signal for reprogramming seed development from maturation to germination. Instead, it is argued that the water relations of the seed are a critical element in the control of maturation and germination: during maturation on the mother plant the embryo is subject to a considerable turgor pressure (of the order of 12 bar) accompanied by a low water potential (of the order of ?12 bar). This turgor permits maturation growth but is subcritical for germination growth. However, upon imbibition in water, the low water potential provides a driving force for a burst of water uptake overcoming the critical turgor threshold and thereby inducing germination.     

The nature of Radiocyathidsand their relationship to Receptaculitids and Archaeocyathids

The morphological analysis of the structural plan of the Radiocyathids skeleton implies a closer relationship to Receptaculitids than to Archaeocyathids. As a working hypothesis, they may possibly form a link between part or all of these two groups and use as a test for the validity of the new kingdom Archaeata proposed by I. T. Zhuravleva & E. I. Miagkova.     

大豆蛋白复合酶解产物在促微生物生长和发酵中的初步应用研究

为探讨大豆蛋白复合酶解产物在促微生物生长和发酵中的可行性,利用2709碱性蛋白酶和中性纤维素酶复合酶解大豆蛋白,酶解产物经干燥、粉碎后添加到培养基中,通过接种微生物观察其生长状况和发酵情况表征效果。研究发现,大豆蛋白复合酶解产物可以促进微生物生长和发酵产酶,试验结论为微生物培养提供了新的代谢资源。     

X-ray induction of dominant lethals in late spermatids and mature spermatozoa of Drosophila melanogaster: the role of oxygenation

The role of oxygenation in determining the sensitivity to the induction of dominant lethals was examined in late spermatids and mature spermatozoa of Drosophila melanogaster. 0–2-h-old or 7-day-old Oregon-K males were irradiated with different X-ray exposures in nitrogen, air or in oxygen and the frequencies of dominant lethals induced in these stages were studied. The results obtained confirm and extend Sobels' earlier observations and the interpretation derived therefrom namely, that under normal conditions in air, mature spermatozoa are characterised by a higher degree of oxygenation than late spermatids and this difference is sufficient to explain the differential response of these stages. Similar Oxygen-Enhancement-Ratios(OERs) (of about 2) were obtained for both the cell stages. The present data also revealed that late spermatids are significantly less sensitive than mature spermatozoa to the X-ray-induction of dominant lethals in a nitrogen atmosphere. A plausible mechanism is suggested to explain this observation.     

Comparison of the inhibitory potential towards carbonic anhydrase,acetylcholinesterase and butyrylcholinesterase of chalcone and chalcone epoxide

Chalcones and chalcone epoxides are important synthetic intermediates in organic and medicinal chemistry. Chalcones possess a broad spectrum of biological activities; however, 1,3‐diphenyl‐2‐propenone or chalcone has not been given the attention it deserve as its substituted derivatives. In this study, the inhibition effects of chalcone and its epoxidated derivative chalcone epoxide against human carbonic anhydrase isozymes I and II (hCA I and hCA II), acetylcholinesterase (AChE), and butyrylcholinesterase (BuChE) were evaluated. The results obtained showed that both compounds exhibited potent inhibitory activity, with IC₅₀ values less than 10 µM. IC ₅₀ values in the submicromolar (hCA I and hCA II) to low micromolar range (AChE and BuChE) were observed for both compounds. The mechanism of inhibition and the inhibitory constants ( K _i values) for each compound were also determined. Furthermore, chalcone epoxide was docked within the active sites of hCA I, hCA II, AChE, and BuChE to explore its binding mode with the enzymes.