The hows and whys of aerobic H2 metabolism

The bacterial [NiFe]-hydrogenases have been classified as either 'standard' or 'O2-tolerant' based on their ability to function in the presence of O2. Typically, these enzymes contain four redox-active metal centers: a Ni-Fe-CO-2CN- active site and three electron-transferring Fe-S clusters. Recent research suggests that, rather than differences at the catalytic active site, it is a novel Fe-S cluster electron transfer (ET) relay that controls how [NiFe]-hydrogenases recover from O2 attack. In light of recent structural data and mutagenic studies this article reviews the molecular mechanism of O2-tolerance in [NiFe]-hydrogenases and discusses the biosynthesis of the unique Fe-S relay.     

The dynamics and prognostic potential of DNA methylation changes at stem cell gene loci in women's cancer

Aberrant DNA methylation is an important cancer hallmark, yet the dynamics of DNA methylation changes in human carcinogenesis remain largely unexplored. Moreover, the role of DNA methylation for prediction of clinical outcome is still uncertain and confined to specific cancers. Here we perform the most comprehensive study of DNA methylation changes throughout human carcinogenesis, analysing 27,578 CpGs in each of 1,475 samples, ranging from normal cells in advance of non-invasive neoplastic transformation to non-invasive and invasive cancers and metastatic tissue. We demonstrate that hypermethylation at stem cell PolyComb Group Target genes (PCGTs) occurs in cytologically normal cells three years in advance of the first morphological neoplastic changes, while hypomethylation occurs preferentially at CpGs which are heavily Methylated in Embryonic Stem Cells (MESCs) and increases significantly with cancer invasion in both the epithelial and stromal tumour compartments. In contrast to PCGT hypermethylation, MESC hypomethylation progresses significantly from primary to metastatic cancer and defines a poor prognostic signature in four different gynaecological cancers. Finally, we associate expression of TET enzymes, which are involved in active DNA demethylation, to MESC hypomethylation in cancer. These findings have major implications for cancer and embryonic stem cell biology and establish the importance of systemic DNA hypomethylation for predicting prognosis in a wide range of different cancers.     

Characterization of the porcine KIT ligand gene: expression analysis, genomic structure, polymorphism detection and association with coat colour traits

Kit ligand (KITLG) is the ligand for the type III receptor tyrosine kinase KIT. Studies of the KIT/KITLG pathway in a number of mammalian species have shown that it is important for the development of stem cell populations in haematopoietic tissues, germ cells in reproductive organs and the embryonic migrating melanoblasts that give rise to melanocytes. Consequently, mutations in the pathway may result in a range of defects including anaemia, sterility and de-pigmentation. The cDNA sequence of the porcine KITLG gene has been reported previously, and is an attractive candidate locus for moderating coat colour in pigs. In this paper we report the gene structure and physical mapping of the porcine gene. We also report the identification of polymorphisms in the gene, one of which was used to confirm linkage to chromosome 5. Preliminary RNA expression studies using a panel of tissues have shown that in addition to the known variant lacking exon 6, there is alternative splicing of exon 4. However, little evidence was found for the KITLG gene being linked to variation in colour in a Meishan x Large White cross.     

<Emphasis Type="Italic">Escherichia coli tat</Emphasis> mutant strains are able to transport maltose in the absence of an active <Emphasis Type="Italic">malE</Emphasis> gene

The twin-arginine transport (Tat) system is a prokaryotic protein transport system. Escherichia coli mutants in this pathway show a defect in cell separation during cell division, resulting in destabilization and permeability of the outer membrane. Maltose uptake is catalysed by a membrane-bound transporter of the ATP binding cassette (ABC) superfamily, where MalE is the essential periplasmic binding protein component. Here, we report that tat mutants are unexpectedly able to transport maltose in the absence of malE. This observation is specific to the MalE component since co-inactivation of malF, which encodes one of the channel components of the transporter, completely abolishes maltose transport even when the Tat system is inactivated. Genetic repair of the outer membrane leaky phenotype of the tat mutant strain re-established the absolute requirement for MalE in maltose uptake. In addition, we demonstrate that phenotypic repair of the outer membrane defect of the tat strain can also be achieved chemically by the inclusion of high concentrations of calcium or magnesium in the growth medium.     

Ecology of cavernicolous ciliates from the anchihaline lagoons of Mallorca

On the island of Mallorca, anchihaline lagoons, meromictic in character, are common in the flooded coastal karst. These subterranean lagoons, containing important populations of crustacea, maintain a connection, albeit tenuous, to the sea. Thus, the first truly quantitative study of marine ciliates inhabiting anchihaline lagoons was undertaken between April 1996 and April 1997. Physical and chemical measurements were taken in-situ, together with water samples for faunal analysis in each of four stratified lakes. These lagoons typically displayed a temperature inversion, an increase in conductivity and a decrease in dissolved oxygen concentration with depth. Ciliates were present in all lagoons studied, with a total of nine species recorded. All were assigned to known taxa. Spatial distribution of the trophic cells was noteworthy with populations clearly stratified within the water column, most being found at the waters surface, sometimes in association with rafts of floating calcite crystals, or in the sediment. Only on one occasion were ciliates recorded in mid-water. Abundance was very low, typically <1 ciliate cm^–3. The floating calcite crystals may form a delimitable biotope for ciliate populations. The role of the cyst in maintaining populations of ciliates in these cave waters is discussed.     

质膜NAD(P)H氧化酶参予金瓜炭疽(Colletotrichum lagerarium)细胞壁激发子诱导人参细胞产生激发反应(英文)

在人参(Panax ginseng C.A.Meyer)悬浮细胞质膜上测出了NAD(P)H氧化酶活性。这类NAD(P)H氧化酶活性可以被金瓜炭疽细胞壁激发子(Cle)诱导。Cle处理还能诱导人参悬浮细胞的氧进发、促进人参悬浮细胞的皂苷合成、提高苯丙氨酸解氨酶(PAL)的活力、以及诱导查尔式酮酶(CHS)的累积和细胞壁上抗性相关蛋白基因脯氨酸富裕蛋白基因hrgp(Hydroxyprolin-rich glycoproleins)的表达。当用哺乳动物白细胞质膜NADPH氧化酶的特异性抑制剂二亚苯基碘(Diphenylene iodonium,DPI)与奎吖因(quinacrine)预处理人参悬浮细胞30 min 后,Cle诱导的H2O2释放与Cle激活的质膜NAD(P)H氧化酶活性被抑制,同时Cle诱导的PAL活性及CHS的积累下降,皂苷合成与hrgp的表达被抑制。由此推测:人参细胞质膜NAD(P)H氧化酶与哺乳动物白细胞质膜NADPH氧化酶有很大的相似性。在Cle激发人参悬浮细胞产生氧进发的过程中,NAD(P)H氧化酶活性被诱导从而导致H2O2的产生,H2O2作为第二信使,激活苯丙氨酸途径,诱发人参皂苷的合成及hrgp防御基因的表达。这一过程中还涉及到Ca2+内流,胞内Ca2+浓度的升高,蛋白磷酸化与去磷酸化。人参细胞质膜NAD(P)H氧化酶在人参细胞对Cle的反应过程中起一种介导作用。因此可能存在由Cle刺激,NAD(P)H氧化酶被诱导,H2O2释放,到人     

A Human Health Risk Assessment of Pharmaceuticals in the Aquatic Environment

Analyses were conducted on four pharmaceutical compounds, representing different therapeutic classes, to evaluate the presence and potential adverse human health effects of trace levels of these substances in aqueous environmental media. Acetylsalicylic acid, clofibrate, cyclophosphamide, and indomethacin have been detected in aqueous environmental media including sewage treatment plant effluent, surface water, drinking water, and groundwater. An extensive literature search and chemical-specific risk assessments were performed to assess the potential human health significance of each compound's individual presence in environmental media. Safe water quality limits were estimated for each pharmaceutical by following the USEPA Methodology for Deriving Ambient Water Quality Criteria for the Protection of Human Health and were compared to the concentrations found in the environment. The calculation of the provisional ambient water quality criteria involved estimation of human exposure to contaminated water, including intake via bioaccumulation in fish, and calculation of cancer risk and non-cancer hazard indices. Parameters detailing the toxicological and pharmacological nature, exposure assessment, and environmental fate and transport of each pharmaceutical were also considered. The overall conclusion was that based on available data, no appreciable risk to humans exists, as the detected concentrations of each of these pharmaceutical compounds found in aqueous media were far below the derived safe limits