The Effect of Ecological Factors on Spore Germination and the Viability of the Mycelial Fragments of Microscopic Fungi

Spore germination and the viability of the mycelial fragments of the microscopic fungi Alternaria alternata, Penicillium spinulosum, and Mucor hiemaliswere studied with respect to the action of certain ecological factors: sucrose concentration (0, 0.2, 2, 10, and 100 g/l), temperature (4, 20, 25, and 30°C), pH (3.5, 4.0, 5.0, 6.2, and 7.0), and cadmium concentration (0, 2, 10, and 100 mg/l). The spore germination and the viabilities of different mycelial fragments were found to reach their maxima at different values of the ecological factors studied. This finding suggests that the vegetative and asexual types of reproduction of microscopic fungi may have different ecological optima.     

Spatial Peculiarities in the Colonization of the Plant Rhizoplane by Microscopic Fungi

Spatial peculiarities in the colonization of the tomato, cucumber, and barley rhizoplanes by microscopic fungi were studied. The apical zone of roots was colonized with a limited number of Rstrategists (the order Mucorales, Fusariumsp., Aspergillus niger, and Mycelia sterilia). The fungal population of the root hairs and the basal zone of roots was 2- to 3-fold denser due to the prevalence of Kstrategists. Fusaria, Fusarium oxysporumin particular, colonized roots in earlier terms than the genera Trichoderma, Penicillium, Gliocladium, and others. The F. oxysporumpopulation was at a maximum in the rhizoplane zone nearest the root tip.     

The Distribution of Microscopic Fungi along Moscow Roads

The distribution of microscopic fungi in soils and surface air along some Moscow roads was studied from 1994 through 2000 at several distances (0, 5, 10, and 20 m) from the roads. Soil fungal complexes in roadside zones with different levels of pollution from automobile engines were found to differ in their composition, species structure, and biomorphology. Relatively far from the roads, the content of fungal mycelium diminished, while that of fungal spores increased. Close to the roads, fungal complexes in soil and surface air were dominated by dark melanin-containing fungi. The microscopic fungal complexes of soil and surface air along the roadsides were similar but differed in the relative abundance of some species.     

Interaction of Hydrogen Peroxide with Ribulose-1,5-bisphosphate Carboxylase/Oxygenase from Rice

The properties of rice-derived ribulose-1,5-bisphosphate carboxylase/oxygenase (rubisco) in different concentrations of hydrogen peroxide (H2O2) solutions have been studied. The results indicate that at low H2O2 concentrations (0.2-10 mM), the properties of rubisco (e.g., carboxylase activities, structure, and susceptibility to heat denaturation) change slightly. However, at higher H2O2 concentrations (10-200 mM), rubisco undergoes an unfolding process, including the loss of secondary and tertiary structure, forming extended hydrophobic interface, and leading to cross-links between large subunits. High concentrations of H2O2 can also result in an increase in susceptibility of rubisco to heat denaturation. Further pre-treatments with or without reductive reagents to rubisco show that the disulfide bonds in rubisco help to protect the enzyme from damage by H2O2 as well as other reactive oxygen species.     

Analysis of Hydrogen Peroxide in an Aqueous Extract of Cigarette Smoke and Effect of pH on the Yield

An analysis of hydrogen peroxide in an aqueous extract of cigarette smoke, which contains many redox-active compounds, requires a method with high selectivity. An aqueous extract of the particulate phase of cigarette smoke was analyzed by HPLC with an electrochemical detector (ECD). Samples were prepared by collecting the particulate phase of the cigarette smoke on a glass fiber filter and extracting it with a phosphate buffer. The obtained solution was purified by using a Waters Oasis MCX cation-exchange cartridge, and then analyzed by an HPLC-ECD system with a Shodex KS-801 mixed-mode resin column. Pre-injecting hydrogen peroxide at a high concentration into the HPLC instrument stabilized the analytical results. The recovery of hydrogen peroxide by using an extract of the particulate phase of the cigarette smoke was more than 80%. An increase in the amount of hydrogen peroxide was observed during extraction with the phosphate buffer at higher pH values. In contrast, extraction with phosphoric acid did not increase the amount of hydrogen peroxide during extraction.     

Peroxidation of Linoleic Acid Induced by Interaction with Haemoglobin and Hydrogen Peroxide

Peroxidation of linoleic acid was found lo be induced by interaction with haemoglobin and hydrogen peroxide. The peroxidation of linoleic acid induced by this interaction was inhibited by desferrioxamine. ethylenediaminetetraacetic acid or α-tocopherol. and poorly by catalase. However. it was accelerated by ascorbic acid.     

Screening for Ergot Alkaloid Producers among Microscopic Fungi by Means of the Polymerase Chain Reaction

The potential of the polymerase chain reaction for the detection of ergot alkaloid producers among microscopic fungi of the generaPenicilliumand Clavicepswas evaluated. Twenty-three strains of various species of fungi with a previously studied capacity for alkaloid production were used. The internal fragment of the gene encoding 4-dimethylallyltryptophan synthase, the enzyme catalyzing the first step in the biosynthesis of ergot alkaloids, was amplified using degenerate primers. This approach revealed an about 1.2-kb specific DNA fragment in micromycetes synthesizing ergot alkaloids with complete tetracyclic ergoline system. Microorganisms that produce alkaloids with modified C or D ergoline rings, as well as -cyclopiazonic acid, did not yield the PCR fragment of the expected size. This fragment was also not found in fungi incapable of ergot alkaloid production.     

The Beneficial Effect of Ginsenoside Rg1 on Schwann Cells Subjected to Hydrogen Peroxide Induced Oxidative Injury

Ginsenoside Rg1 (GRg1) has been considered to have therapeutic potential in promoting peripheral nerve regeneration and functional recovery after sciatic nerve injuries. However, the mechanism underlying the beneficial effect of GRg1 on peripheral nerve regeneration is currently unclear. The possible effect of GRg1 on Schwann cells (SCs), which were subjected to oxidative injury after nerve injury, might contribute to the beneficial effect of GRg1 on nerve regeneration. The present study was designed to investigate the potential beneficial effect of GRg1 on SCs exposed to oxidative injury. The oxidative injury to SCs was induced by hydrogen peroxide. The effect of GRg1 (50 μM) on SCs exposed to oxidative injury was measured by the levels of malondialdehyde (MDA), superoxide dismutase (SOD), glutathione (GSH) and catalase (CAT) in SCs. The cell number and cell viability of SCs were evaluated through fluorescence observation and MTT assay. The apoptosis of SCs induced by oxidative injury was evaluated by an apoptosis assay. The expression and secretion of nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) were evaluated using RT-PCR, Western blotting, and an ELISA method. We found that GRg1 significantly up-regulated the level of SOD, GSH and CAT, and decreased the level of MDA in SCs treated with hydrogen peroxide. In addition, GRg1 has been shown to be able to inhibit the proapoptotic effect of hydrogen peroxide, as well as inhibit the detrimental effect of hydrogen peroxide on cell number and cell viability. Furthermore, GRg1 also increased the mRNA levels, protein levels and secretion of NGF and BDNF in SCs after incubation of hydrogen peroxide. Further study showed that preincubation with H89 (a PKA inhibitor) significantly inhibited the effects induced by hydrogen peroxide, indicating that the PKA pathway might be involved in the antioxidant effect and neurotrophic factors (NTFs) promoting effect of GRg1. In addition, a short-term in vivo study was performed to confirm and validate the antioxidant effect and nerve regeneration-promoting effect of GRg1 in a sciatic crush injury model in rats. We found that GRg1 significantly increased SOD, CAT and GSH, decreased MDA, as well as promoted nerve regeneration after crush injury. In conclusion, the present study showed that GRg1 is capable of helping SCs recover from the oxidative insult induced by hydrogen peroxide, which might account, at least in part, for the beneficial effect of GRg1 on nerve regeneration.     

家蚕胚胎发育中过氧化氢的代谢(英文)

过氧化氢（Ｈ_２Ｏ_２）是生物体内主要的活性氧来源之一。在超氧化物歧化酶（ＳＯＤ）、过氧化氢酶（ＣＡＴ）等的催化作用下,Ｈ_２Ｏ_２。被降解,释放出活性氧。所以,生物个体发育过程中体内Ｈ_２Ｏ_２、ＳＯＤ和ＣＡＴ含量的变化反映着Ｈ_２Ｏ_２的代谢水平。另外,家蚕是蚕卵滞育昆虫,实验设计考虑到了滞育前后可能会有的差别。取产后１０分钟内的卵为供试材料。采用即时浸酸法解除卵滞育。采用比色法和氧电极法测定并比较家蚕胚胎滞育形成与解除过程中过氧化氢的代谢。结果表明：（１）受精初期（０～４ｈ）,Ｈ_２Ｏ_２含量在２．５ｈ时达到峰值（Ｆｉｇ．１）,相应地ＳＯＤ活性处于较高水平,而ＣＡＴ活性处于最低水平（Ｆｉｇ．２）;（２）胚胎发育过程中（即时浸酸解除滞育）,Ｈ_２Ｏ_２含量除１６８～２１６ｈ处于低水平外均显著高于滞育卵（Ｆｉｇ．３）,ＳＯＤ活性分别在７２ｈ、１６８ｈ,形成小大两峰,后期显著高于滞育卵（Ｆｉｇ．４）,而ＣＡＴ活性７２－１９２ｈ保持平稳,随后急剧上升,前期显著低于滞育卵,后期相反（Ｆｉｇ．５）;（３）滞育形成过程中Ｈ_２Ｏ_２水平变化平缓（Ｆｉｇ．６）,ＳＯＤ活性前期剧烈变动,但后期保持平稳（Ｆｉｇ．７）,ＣＡＴ活性逐步升     

The Use of Hydrogen Peroxide for Closing Disulfide Bridges in Peptides

The use of hydrogen peroxide for the formation of disulfide bridges was studied in 15 peptides of various lengths and structures. The oxidation of peptide thiols by hydrogen peroxide was shown to proceed under mild conditions without noticeable side reactions of Trp, Tyr, and Met residues. Yields of the corresponding cyclic disulfides were high and mostly exceeded those obtained with other oxidative agents, in particular, iodine. It was established that the use of hydrogen peroxide in organic medium also provided sufficiently high yields when large-scale syntheses of oxytocin and octreotide (up to 10 g) were carried out.     

衰老叶片和叶绿体中H_2O_2的累积与膜脂过氧化的关系

在自然衰老和ABA处理的叶片和叶绿体中活性氧H_2O_2均比对照明显增高。外加H_2O_2刺激水稻叶绿体膜脂过氧化作用。叶绿体的丙二醛含量随H_2O_2浓度、光照时间、光照强度及叶绿体完整性而变化。AsA、GSH、SOD、甘露醇和过氧化氢酶对外源H_2O_2引起的膜脂过氧化有缓解作用,Fe~(2+)有刺激作用。而H_2O_2对叶绿体过氧化损伤主要是转化为OH之故。     

Action of Cystine in the Cytotoxic Response of Escherichia Coli Cells Exposed to Hydrogen Peroxide

Cystine markedly enhanced the cytotoxic response of Escherichia coli cells to concentrations of hydrogen peroxide resulting in mode one killing, but displayed little effect in mode two killed cells. The effect of cystine was concentration-dependent over a range of 5-50 μM and did not further increase at higher levels. Cystine had similar effects in other bacterial systems.

In order to sensitize the cells to the oxidative injury, the amino acid must be present during exposure to the oxidant since no enhancement of the cytotoxic response can be observed in cystine pre-loaded cells. In addition, no further enhancement of cytotoxicity could be detected when cystine was added before and left during challenge with the oxidant. The enhancing effect of cystine on oxidative injury of E. coli cells appears to be directly mediated by the amino acid and in fact cysteic acid, the most likely oxidation product, had no effect on the killing of bacterial cells elicited by hydrogen peroxide. Other disulfide compounds such as oxidized glutathione, cystamine and dithionitrobenzoic acid only slightly increased the susceptibility of bacteria to the oxidant. The effect of the disulfides was not concentration-dependent over a range of 200-800 μM and was statistically significant only for cystamine.

Taken together, these results indicate that cystine markedly increases the cytotoxic response of bacteria to hydrogen peroxide and suggest that the amino acid might impair the cellular defence machinery against hydrogen peroxide. This effect may involve a thiol-disulfide exchange reaction at the cell membrane level.     

Reaction of Vanadyl with Hydrogen Peroxide. An ESR and Spin Trapping Study

Vanadyl reacts with hydrogen peroxide forming hydroxyl radicals in a Fenton-like reaction. The hydroxyl radicals were spin trapped and identified using 5.5-dimethyl-I-pyrroline-N-oxide (DMPO). The quantity of hydroxyl radicals spin trapped during the reaction between vanadyl and hydrogen peroxide are equal to half of the hydroxyl radicals spin trapped during the reaction between ferrous ions and hydrogen peroxide. Experiments in the presence of formate show that this hydroxyl radical scavenger effectively competes with DMPO preventing the formation of the DMPO-OH adduct. However. in experiments using ethanol as the hydroxyl radical scavenger it was not possible to completely prevent the formation of DMPO-OH. The formation of this additional DMPO-OH in the presence of ethanol does not depend on the concentration of dissolved oxygen, but does depend on the concentration of hydrogen peroxide added to the vanadyl solution. The results suggest that the additional DMPO-OH formed in the presence of ethanol originates from a vanadium (V) intermediate. This intermediate may oxidize DMPO leading to the formation of DMPO-0; which rapidly decomposes forming DMPO-OH.     

Effects of Peroxidase and Hydrogen Peroxide on the Dityrosine Formation and the Mixing Characteristics of Wheat-Flour Dough

The effects of adding hydrogen peroxide and peroxidase to wheat-flour dough on dityrosine formation and mixing characteristics were investigated. Dityrosine in wheat-flour dough was identified by HPLC with a fluorescence detector and by LC/MS/MS. Formation of dityrosine increased with the addition of hydrogen peroxide, and hydrogen peroxide plus peroxidase, to wheat-flour dough, while the addition of peroxidase had no effect on the amount of dityrosine formed. The mixing curve obtained by a doughgraph changed with the addition of hydrogen peroxide, and hydrogen peroxide plus peroxidase; the peak time was significantly delayed and the dough development time was extended. We found that dityrosine cross-links in wheat-flour dough increased with the addition of peroxidase plus hydrogen peroxide. It is thought that these cross-links can lead to polymerization of the proteins in wheat-flour dough.     

Reaction of Vanadyl with Hydrogen Peroxide. An ESR and Spin Trapping Study

Vanadyl reacts with hydrogen peroxide forming hydroxyl radicals in a Fenton-like reaction. The hydroxyl radicals were spin trapped and identified using 5.5-dimethyl-I-pyrroline-N-oxide (DMPO). The quantity of hydroxyl radicals spin trapped during the reaction between vanadyl and hydrogen peroxide are equal to half of the hydroxyl radicals spin trapped during the reaction between ferrous ions and hydrogen peroxide. Experiments in the presence of formate show that this hydroxyl radical scavenger effectively competes with DMPO preventing the formation of the DMPO-OH adduct. However. in experiments using ethanol as the hydroxyl radical scavenger it was not possible to completely prevent the formation of DMPO-OH. The formation of this additional DMPO-OH in the presence of ethanol does not depend on the concentration of dissolved oxygen, but does depend on the concentration of hydrogen peroxide added to the vanadyl solution. The results suggest that the additional DMPO-OH formed in the presence of ethanol originates from a vanadium (V) intermediate. This intermediate may oxidize DMPO leading to the formation of DMPO-0; which rapidly decomposes forming DMPO-OH.     

Hydrogen Peroxide and the Proliferation of Bhk-21 Cells

Intracellular levels of H2O2 in BHK-21 cells are not static but decline progressively with cell growth. Exposure of cells to inhibitors of catalase, or glutathione peroxidase, not only diminishes this decline but also depresses rates of cell proliferation, suggesting important growth regulatory roles for those antioxidant enzymes. Other agents which also diminish the growth-associated decline in intracellular levels of H₂O₂, such as the superoxide dismutase mimic, copper II—(3,5-diisopropylsalicylate)₂, or docosahexaenoic acid, also reduced cell proliferation. In contrast, proliferation can be stimulated by the addition of 1 μM exogenous H₂O₂ to the culture medium. Under these conditions, however, intracellular levels of H₂O₂ are unaffected, whereas there is a reduction in intracellular levels of glutathione. It is argued that critical balances between intracellular levels of both H₂O₂ and glutathione are of significance in relation both to growth stimulation and inhibition. In addition growth stimulatory concentrations of H₂O₂, whilst initially leading to increased intracellular levels of lipid peroxidation breakdown products, appear to “trigger” their metabolism, possibly through aldehyde dehydrogenase, whose activity is also stimulated by H₂O₂     

丛枝菌根真菌对植物生长影响的研究

菌根是自然界中一种极为普遍和重要的共生现象,其中分布最为广泛的菌根类型就是丛枝菌根,可以增强植物从土壤中获取水分的能力,改善植物根系对磷、镉等矿质元素及养分的吸收,从而促进植物的生长。本文综述了丛枝菌根真菌对植物生长影响的概况。有关丛枝菌根真菌对植物水分和矿质营养的利用,尤其是磷素营养的研究较为深入,而对植物光合特性的研究较少,这些研究工作为深入理解菌根真菌与植物的相互关系提供基础资料。     

H_2O_2参与离体蒜苔细胞内含物再分配的调控(英文)

植物生长发育过程中经常发生新老器官更替和细胞内含物的再分配、再利用。Lepold提出新生器官向衰老器官传递某种信息 ,动员后者细胞内含物向前者再分配。但是该信息的化学本质迄今仍不清楚。大蒜 (Alliumsativum)的离体蒜苔是研究细胞内含物再分配的良好材料。细胞内含物大量从苔茎向珠蒜中再分配 ,结果珠蒜显著膨大而苔茎衰老死亡。蔡可等发现赤霉素 (GA3)处理可有效抑制细胞内含物再分配。我们此前的研究发现GA3处理苔茎基部可显著改变珠蒜和苔茎H2 O2 代谢。本研究中我们分别用GA3和 3-氨基 - 1 ,2 ,4-三唑 (AT)H2 O2 清除酶catalase的专一性抑制剂处理珠蒜 ,结果发现GA3和AT均可有效抑制离体蒜苔细胞内含物再分配 (Fig .1 )。根据浓度不同 ,H2 O2 可以诱导细胞产生保护性反应或凋亡。细胞内含物再分配过程中 ,珠蒜H2 O2 浓度显著下降后保持于低水平 ,相反苔茎H2 O2 浓度极显著升高 1 0倍以上 ,而且细胞内含物转移早的苔茎下部H2 O2 峰值出现也早 (Fig .2 )。GA3或AT处理珠蒜 ,珠蒜H2 O2 浓度显著提高而苔茎H2 O2 浓度保持稳定的低水平或峰值显著推迟 (Fig .2 )。可见苔茎高浓度的H2 O2 诱导了苔茎细胞凋亡并把细胞内含物转移给珠蒜。已知约 2 %的呼吸耗氧生成H2 O2 。珠蒜呼吸速率显著高于苔茎 (王     

过氧化氢在水杨酸诱导的蚕豆气孔关闭中的作用

许多植物病原菌可通过气孔进入叶片组织,因此减小气孔开度有利于提高植物的抗性。我们通过表皮条分析和激光扫描共聚显微镜得到的证据表明在保卫细胞中过氧化氢可能是水杨酸信号的中间环节。SA可以浓度依赖的方式诱导气孔关闭（图1A）,H2O2也有类似的作用（图1B）。100μmol/L的水杨酸诱导的气孔关闭作用可明显地被20U/ml的过氧化氢酶或10μmol/L的Vc逆转,但CAT和Vc单独处理时诱导气孔开放的作用很微弱。单细胞中基于荧光探针DCFH的时间进程实验表明直接外加（图版I）或显微注射100μmol/L的SA均可诱导保卫细胞中H2O2产生,但以显微注射双蒸水作为对照时对DCFH荧光无影响（图版II）。这些结果暗示了植物被病原菌感染时可能通过产生H2O2导致气孔关闭而阻止病原菌继续通过气孔侵入。     

黄花夹竹桃内生真菌抗病原细菌的初步研究

从植物黄花夹竹桃 (Thevetiaperuviana)的根、茎、叶、果实中分离出内生真菌 10 1株。以鼠伤寒沙门氏菌 (Salmonellatyphimurium)、肺炎链球菌 (Streptococcuspneumoniae)、乙型溶血链球菌 (Streptococcushemolyticus)、金黄色葡萄球菌 (Staphyllococcusaureus) 4种人类病原菌为指示菌 ,对其进行抑菌活性筛选 ,结果有 17株内生真菌对 1株或 1株以上人类病原菌有抑菌活性 ,其中平板抑菌圈直径大于 2 0mm的菌株有9株。具有抗菌活性的内生真菌分别来自木霉属 (Trichoderma)、曲霉属 (Aspergillus)等 9个属。