三种荒漠地衣共生菌藻的耐热性研究

作为沙漠生物地毯工程研究的组成部分,对荒漠地衣石果衣Endocarpon pusillum、节瘤微孢衣Acarospora nodulosa以及荒漠微孢衣A. schleicheri的共生菌藻进行了耐热性研究。结果表明,3种荒漠地衣的共生菌藻在湿润条件下对温度的最大忍受力仅为50℃,而在干燥条件下石果衣的共生菌藻的最大忍受力均为75℃,而其他两种地衣共生菌藻的最大忍受力均为80℃。3种荒漠地衣共生菌、藻分别对高温胁迫的耐受力,在干燥状态下均比在湿润状态下明显增高。     

Estimation of soluble β-glucan content of yeast cell wall by the sensitivity to Glucanex 200G treatment

The soluble β-glucan contents in the cell wall of yeasts were estimated by treating cells with Glucanex^® 200G that contained mainly β1,3-glucanase and some β1,6-glucanase. The sensitivity of cell walls of 11 yeasts to various concentrations of β-glucanase was compared. The yeasts that are resistant to β-glucanase treatment are expected to contain higher β-glucan content and those that are sensitive to the β-glucanase treatment are expected to contain lower β-glucan content. Two yeast strains were selected for further study by comparing the sensitivity of cell wall to β-glucanase; Candida bombicola and Candida albicans. Candida bombicola was more resistant and C. albicans was more sensitive to the Glucanex^® 200G treatment. The results of enzyme sensitivity tests were verified by quantification of soluble β-glucan content purified from the yeasts. Much larger amount of soluble β-glucan was obtained from the cell walls of C. bombicola (0.08 g g⁻¹ dried cell) than C. albicans (0.025 g g⁻¹ dried cell).     

Main sterols from the ophiuroids Ophiocoma echinata, Ophiocoma wendtii, Ophioplocus januarii and Ophionotus victoriae

Sterol compositions of the cold water ophiuroids Ophioplocus januarii and Ophionotus victoriae and of the tropical ophiuroids Ophiocoma echinata and Ophiocoma wendtii are reported. The four sterol mixtures contain Δ⁵ mono- and di-unsaturated common 3β-hydroxy-sterols. Ophioplocus januarii and O. victoriae contain 24-methylcholesta-5,24(28)-dien-3β-ol and 24ζ-ethylcholesta-5,24(28)-dien-3β-ol in higher abundance than in O. echinata. These sterols were not found in O. wendtii. An interesting finding is the presence of Δ^5,24(28)-24-n-propylidenecholesterol in 7.6% in Ophionotus victoriae.     

Structural characterization of a galactomannan from the cyanolichen Leptogium azureum

A galactomannan was isolated from the cyanolichen Leptogium azureum via successive alkaline extraction and precipitation with Fehling solution. The structure of the polysaccharide was investigated using NMR spectroscopy, methylation analysis, Smith degradation, and HPSEC-MALLS. As galactomannans from other lichens species, the polymer obtained presents a (1→6)-linked main chain of -mannopyranose, substituted preferentially at O-2 by -Manp or β-Galp non-reducing ends. As observed in previous investigations, the C-1 region of the ¹³C-NMR of these heteropolysaccharides are typical of some lichens species, and can be used as fingerprints in chemotaxonomy. However, in despite of the general structure in common, the substitution level of this structure and their content of mannose is higher than of the others galactomannans obtained of lichenized fungi contained the green alga of the genus Trebouxia.     

Beta-ketothiolase genes in Azotobacter vinelandii

Azotobacter vinelandii is proposed to contain a single β-ketothiolase activity participating in the formation of acetoacetyl-CoA, a precursor for poly-β-hydroxybutyrate (PHB) synthesis, and in β-oxidation (Manchak, J., Page, W.J., 1994. Control of polyhydroxyalkanoate synthesis in Azotobacter vinelandii strain UWD. Microbiology 140, 953–963). We designed a degenerate oligonucleotide from a highly conserved region among bacterial β-ketothiolases and used it to identify bktA, a gene with a deduced protein product with a high similarity to β-ketothiolases. Immediately downstream of bktA, we identified a gene called hbdH, which encodes a protein exhibiting similarity to β-hydroxyacyl-CoA and β-hydroxybutyryl-CoA dehydrogenases. Two regions with homology to bktA were also observed. One of these was cloned and allowed the identification of the phbA gene, encoding a second β-ketothiolase. Strains EV132, EV133, and GM1 carrying bktA, hbdH and phbA mutations, respectively, as well as strain EG1 carrying both bktA and phbA mutations, were constructed. The hbdH mutation had no effect on β-hydroxybutyryl-CoA dehydrogenase activity or on fatty acid assimilation. The bktA mutation had no effect on β-ketothiolase activity, PHB synthesis or fatty acid assimilation, whereas the phbA mutation significantly reduced β-ketothiolase activity and PHB accumulation, showing that this is the β-ketothiolase involved in PHB biosynthesis. Strain EG1 was found to grow under β-oxidation conditions and to possess β-ketothiolase activity. Taken together, these results demonstrate the presence of three genes coding for β-ketothiolases in A. vinelandii.     

Cytochrome P450(11β): Structure-function relationship of the enzyme and its involvement in blood pressure regulation

Cytochrome P450(11β) is deeply involved in the final steps of biosynthesis of mineralocorticoids. This paper deals with following issues about this enzyme. (1) The structure and function of the enzymes of various animal species are discussed. By making alignment of amino acid sequences of the enzymes, we identified peptide domains essential for the enzyme actions such as a putative steroid binding domain and a heme binding region. Estimates of molecular similarity among the P450(11β) family enzymes suggested that the enzymes having both 11β-hydroxylation activity and aldosterone (ALDO) synthetic activity of certain animals such as frog, cattle and pig are more similar to the ALDO synthases of the other animals, such as rat, mouse and human, than the 11β-hydroxylases of these animals. (2) The molecular nature of the P450(11β) family enzymes of genetically hypertensive rats as well as adrenal regeneration hypertension (ARH) rats is examined. (i) Mutation was found in the P450(11β) gene of Dahl's salt-resistant normotensive rat. Steroidogenic activity expressed by the mutated gene accounted well for abnormal plasma levels of steroid hormones in this rat. (ii) 11β-, 18- and 19-Hydroxylation activities of adrenal mitochondria prepared from spontaneously hypertensive rat (SHR), Wistar-Kyoto rat (WKY), and stroke-prone (SP)-SHR were not significantly different from each other. Levels of mRNA of ALDO synthase in adrenal glands of 50-week-old SHR was significantly lower than those of 10-week-old SHR, WKY and SHR-SP. (iii) No significant difference in 19-hydroxylation activity was found between adrenal mitochondria prepared from ARH rat and those from control rat. The level of message of ALDO synthase was lower in adrenal glands of ARH rat.     

The contribution of beta1 integrins to neuronal migration and differentiation depends on extracellular matrix molecules

The interaction of β1 integrin receptors and different extracellular matrix molecules during neuronal development was investigated by comparing both migration and morphological differentiation of D3 wild-type embryonic stem (ES) cell line-derived neural precursor cells with those of the β1 integrin knockout ES cell line G201. Analysing neurosphere explants on laminin and fibronectin as major β1 integrin ligands, the maximal spreading of outward migrating neuronal cells was determined. Compared with gelatine as a standard substrate, migration was found to be significantly increased for D3-derived neurospheres on fibronectin and laminin-1. These matrix effects were found to be even enhanced for G201 preparations. In addition, also the differentiation of wild-type and β1 integrin −/− neurones – as determined by MAP-2- and HNK-1-immunoreactive processes – was found to be increased on fibronectin and laminin when compared to gelatine standards. In the respective knockout preparations on these matrices, again perturbation effects were less pronounced than on gelatine. Our observations indicate that laminin and fibronectin are involved both in β1 integrin-dependent and -independent signalling mechanisms during neurogenesis. Upregulation of compensatory mechanisms such as β1 integrin-independent receptors for laminin and fibronectin might be responsible for the much less pronounced perturbations of G201 neural precursor migration and differentiation on these two substrates than on gelatine.     

阴天和晴天对黄河三角洲芦苇湿地净生态系统CO2交换的影响

云量以及大气气溶胶含量变化引起的阴天和晴天会对局地的微气候环境产生综合效应, 影响地面接收的太阳辐射强度, 同时引起环境因子的变化, 最终对净生态系统CO₂交换(NEE)产生影响。该文通过涡度相关系统以及微气象梯度观测系统, 对黄河三角洲芦苇(Phragmites australis)湿地NEE以及环境要素进行了观测。在自然条件下选择12对相邻阴天和晴天数据, 在生物要素(生物量、叶面积指数)、土壤水分以及养分特征保持不变的前提下, 揭示了阴天和晴天变化对湿地生态系统NEE的光响应和温度响应的影响。结果表明: 12对阴天和晴天生态系统NEE的日平均动态均呈“U”型曲线, 但阴天NEE的变幅较小。晴天条件下湿地生态系统NEE的日均值显著高于阴天(p < 0.01)。阴天和晴天湿地生态系统NEE与光合有效辐射(PAR)之间均呈直角双曲线关系, 但晴天条件下, 最大光合速率(A_max)显著大于阴天(p < 0.01), 同时白天生态系统呼吸(R_eco,daytime)也显著大于阴天(p < 0.01)。不论阴天还是晴天, R_eco,daytime与气温均呈显著的指数关系。晴天湿地生态系统呼吸的温度敏感系数Q₁₀ (5.5)远大于阴天(1.9)。阴天和晴天昼间PAR差值以及气温差值对NEE差值的协同影响达到63%。     

Functional expression of cDNAs for bovine 11 beta-hydroxylase-aldosterone synthases, P450(11 beta)-2 and -3 and their chimeras.

Two molecular species of bovine P450(11β), P450(11β)-2 and P450(11β)-3 have been identified, in which the amino acid differences were found at the 6th, 36th and 82nd positions from the NH₂-termini of the mature proteins. They catalyzed the 11β-, 18- and 19-hydroxylation and aldosterone formation from 11-deoxycorticosterone, and the rate of production of 18-hydroxycorticosterone and aldosterone by P450(11β)-3 was greater than that by P450(11β)-2 [Morohashi et al., J. Biochem. 107 (1990) 635–640].

In this study, chimeric clones were constructed whose 6th, 36th and 82nd amino acid residues were exchanged with each other. Two original clones and six chimeric clones were expressed in COS-7 cells, and their steroidogenic activities studied. The ratio of aldosterone or 18-hydroxycorticosterone production to corticosterone production by one clone was compared with that of the other. The ratios for the four clones having Gly36 [P450(11β)-3 type] were 0.08–0.22, whereas those for the clones having Ser36 [P450(11β)-2 type] were 0.03–0.05, suggesting that the Gly36 structure is important for aldosterone production.     

Further farnesyl-homogentisic acid derivatives from Otoba parvifolia

The seeds of Otoba parvifolia contain three novel compounds apparently derived from homogentisic acid, rel-(1′R,5′R)-2-(1′-farnesyl-5′-hydroxy-2′-oxocyclohex-3′-en-1′-yl)-acetic acid and its acetate as well as rel-(1′R,4′S,5′R)-2-(1′-farnesyl-4′,5′-dihydroxy-2′-oxocyclohexan-1′-yl)-acetic acid δ-lactone. The structure of an additional isolate, previously described as 2-(1′-farnesyl-2′-hydroxy-5′-oxocyclohex-3′-en-1′-yl)-acetic acid γ-lactone was revised to rel-(1′R,5′R)-2-(1′-farnesyl-5′-hydroxy-2′-oxocyclohex-3′-en-1′-yl)-acetic acid δ-lactone.     

Variation in δC values for the seagrass Thalassia testudinum and its relations to mangrove carbon

Carbon isotope ratios (¹³C/¹²C) were measured for the leaves of the seagrass Thalassia testudinum Banks ex König and carbonates of shells collected at the seagrass beds from seven sites along the coast of southern Florida, U.S.A. The δ¹³C values of seagrass leaves ranged from −7.3 to −16.3‰ among different study sites, with a significantly lower mean value for seagrass leaves from those sites near mangrove forests (−12.8 ± 1.1‰) than those far from mangrove forests (−8.3 ± 0.9‰; P < 0.05). Furthermore, seagrass leaves from a shallow water area had significantly lower δ¹³C values than those found in a deep water area (P < 0.01). There was no significant variation in δ¹³C values between young and mature leaves (P = 0.59) or between the tip and base of a leaf blade (P = 0.46). Carbonates of shells also showed a significantly lower mean δ¹³C value in the mangrove areas (−2.3 ± 0.6‰) than in the non-mangrove areas (0.6 ± 0.3‰; P <0.025). In addition, the δ¹³C values of seagrass leaves were significantly correlated with those of shell carbonates (δ¹³C seagrass leaf = −9.1 + 1.3δ¹³C shell carbonate (R² = 0.83, P < 0.01)). These results indicated that the input of carbon dioxide from the mineralization of mangrove detritus caused the variation in carbon isotope ratios of seagrass leaves among different sites in this study.     

An unusual juxtaposition of polysaccharide components of Collema leptosporum

The lichenised ascomycete, Collema leptosporum Malme, was extracted with aqueous methanol to give traces of mannitol and 3-O-β- -glucopyranosyl- -mannitol (2.7% yield). The residue was consecutively extracted with hot water to give a complex uronic acid-containing polysaccharide, and then with hot aqueous alkali which provided a mixture of polysaccharides. This was fractionated with Cetavlon to give a branched galactomannan, which had the lowest content of galactose yet reported for such a lichen polysaccharide. It has a main chain of (1→6)-linked -Manp units partly substituted at O-2,4 by non-reducing end-units of Manp and Galp, shown by NMR spectroscopy to have - and β-configurations, respectively. The other polysaccharide component was unexpectedly a branched (1→3), (1→6)-linked β-glucan, which is typical of a basidiomycete, whereas those of ascomycetes contain similar linkages but in linear glucans.     

Effects of β-glucanase supplementation of barley diets on growth performance of broilers

A trial was performed to examine the effects of levels of barley substitution and supplementation with β-glucanase in a corn-soybean diet on growth performance and intestinal characteristics of broiler chickens. The experiment involved five levels of barley substituted for corn (0, 125, 250, 500, and 1000 g/kg) and two levels of β-glucanase supplement (with 0.5 g/kg and without) in a factorial arrangement with two replicates. Four hundred day-old commercial strain Harber broiler chickens were randomly allocated into twenty groups of ten dietary treatments for a six-week feeding trial, growing (0-3 week) and finishing period (4-6 week). Unless supplemented with β-glucanase, broilers receiving the diet with more than 250 g/kg of the barley substitute gained slower during the growth period. Conversely, supplementing β-glucanase did not improve total weight gain (0-6 weeks) with a diet of 500 g/kg barley substitution. As the level of barley substitution increased, feed intake in the growing period decreased significantly and viscosity of the intestinal contents increased. However, such an increase did not significantly influence feed conversion (P > 0.05). Supplementation with β-glucanase on diet up to 250 g/kg of barley substitute not only enhanced body weight gains of growing broilers, but also improved the live-weight of six-week-old broilers (P < 0.05).     

Identification of tubulin isoforms in different tissues of Ascaris suum using anti-tubulin monoclonal antibodies.

Three monoclonal antibodies specific to - and β-tubulin were used to examine the expression of tubulin isofoms in the intestine, reproductive tract and body wall muscle of A. suum. The tubulins were found to be different in their isoelectric points, number of isoforms and peptide maps with Western blot analysis of one-dimensional polyacrylamide gel confirming the presence of -, β₁- and β₂- tubulin. Commercial cross-reactive anti- and anti-β MAbs 356 and 357 recognized tubulin from A. suum tissues as well as from pig brain, whereas anti-A. suum β-tubulin specific MAb P3D6 recognized tubulin from the A. suum tissues only. Two-dimensional gel analysis showed different isoform patterns in different A. suum tissues with anti-A. suum β-tubulin MAb P3D6 and cross-reactive β-tubulin MAb 357 recognizing 2–4 β- tubulin isoforms and anti--tubulin MAb 356 recognizing 1–6 -tubulin isoforms. Different peptide maps of tubulin were observed in the three tissues, when subjected to limited proteolysis followed by SDS-PAGE. The data indicate that different tubulins are found in different tissues of adult A. suum.     

Structural studies on hairy region of pectic polysaccharide from campion Silene vulgaris (Oberna behen)

Using enzymic digestion with pectinase, controlled Smith degradation and NMR-spectroscopy, some structural features of the hairy region of pectic polysaccharide termed silenan SV from the aerial part of campion Silene vulgaris (Moench) Garke (Oberna behen (L.) Ikonn) were elucidated.

Silenan was subjected to enzymic digestion with pectinase to furnish the polysaccharide fraction (SVP). The contained residues of -galacturonic acid (43%), arabinose, galactose and rhamnose as main constituents. The backbone of the hairy region of silenan was found to consist of -1,4-galactopyranosyl uronic acid and 2-O-glycosylated rhamnopyranose residues. The side chains contained linear regions of residues of -1,5-linked arabinofuranose and β-1,3-, β-1,4-linked galactopyranose. Silenan SV and its fragment SVP were subjected to Smith degradation to give fractions SVS and SVPS. These contain the residues of terminal and 2-substituted -arabinofuranose as well as residues of terminal, 3-, and 2,3-substituted β-galactopyranose. In addition, NMR-spectral data confirmed that the residues of -rhamnopyranose 2-O-glycosylated with the residues of -1,4-galactopyranosyl uronic acid of the backbone occurred in the core of SVPS and, therefore, in the backbone of silenan SV.

On the basis of data obtained, the hairy regions of silenan were suggested to contain mainly the linear chains of β-1,3-, β-1,4-galactopyranan and -1,5-arabinofuranan. The chains of -1,5-linked arabinofuranose, β-1,3- and β-1,4-linked galactopyranose were shown to be involved in the side chains of the hairy region having branching points at 2,3-substituted β-galactopyranose residues.     

A repressor element in the 5'-untranslated region of human Pax5 exon 1A

Five members of the RecQ helicase family, RECQL, WRN, BLM, RTS and RECQL5, have been found in human and three of them (WRN, BLM and RTS) were disclosed to be the genes responsible for Werner, Bloom and Rothmund–Thomson syndromes, respectively. RECQL5 (RecQ helicase protein-like 5) was isolated as the fifth member of the family in humans through a search of homologous expressed sequence tags. The gene is expressed with at least three alternative splicing products, , β and γ. Here, we isolated mouse RECQL5β and determined the DNA sequence of full-length cDNA as well as the genome organization and chromosome locus. The mouse RECQL5β gene consists of 2949 bp coding 982 amino acid residues. Comparison of amino acid sequence among human (Homo sapiens), mouse (Mus musculus), Drosophila melanogaster and Caenorhabditis elegans RECQL5β homologs revealed three portions of highly conserved regions in addition to the helicase domain. Nineteen exons are dispersed over 40 kbp in the genome and all of the acceptor and donor sites for the splicing of each exon conform to the GT/AG rule. The gene is localized to the mouse chromosome 11E2, which has a syntenic relation to human 17q25.2-q25.3 where human RECQL5β exists. Our genetic characterizations of the mouse RECQL5β gene will contribute to functional studies on the RECQL5β products.     

β-carrageenan: Isolation and characterization

β-Carrageenan, essentially devoid of ester sulfate, was isolated from the hot aqueous extracts of alkali-modified Eucheuma gelatinae, Eucheuma speciosa, and Endocladia muricatum by precipitating the more anionic moieties with a quaternary ammonium salt, isolating the fractions that did not precipitate, then treating these with an anion-exchange cellulose. The β-carrageenan was characterized by chemical analysis, optical rotation, and NMR. Gelling was found to be ion-independent, with T_g = 31–33°C and T_m = 63–70°C. Specific optical rotations of the isolated β-carrageenan samples were more positive than the κ-, λ-, and ι-carrageenans with which they were compared, while agarose, its stereoisomer, exhibited a negative specific rotation. Electrophoresis gels made from β-carrageenan were used to separate DNA fragments which exhibited faster migration than on an agarose gel of comparable concentration, indicating that β-carrageenan has a less restrictive pore structure.     

Effects of electronic structure on chiral induction in outer-sphere electron transfer reactions of complexes with the C3 symmetric ligand, 1,4,7-triazacyclononane-1,4,7-tris[2′(R)-2′-propionate](-3)

The ligand 1,4,7-triazacyclononane-1,4,7-tris[2′(R)-2′-propionate](-3)((R)-tacntp³⁻), binds stereospecifically to transition metal ions. The structures of the complexes [Cr((R)-tacntp)]·NaBr and [Fe((R)-tacntp)]·H₂O have been determined by X-ray crystallography. Both complexes have the Λ-configuration but the conformation of the chelate rings in Λ-[Cr((R)-tacntp)] is (λ,λ,λ) with a geometry close to octahedral while in Λ-[Fe((R)-tacntp)] it is (δ,δ,δ) and the geometry is closer to that of a trigonal prism. Chiral induction in the electron transfer reactions of Λ-[Co((R)-tacntp)], Λ-[Fe((R)-tacntp)] and Λ-[Mn((R)-tacntp)] with [Co((RR,SS)-chxn)₃]²⁺ has been investigated. All three reactions are outer-sphere and four isomeric [Co((RR,SS)-chxn)₃]³⁺ products are identified in each case. The oxidants Λ-[Fe((R)-tacntp)] and Λ-[Mn((R)-tacntp)] show very similar selectivities, quite different from those of Λ-[Co((R)-tacntp)]. Reasons for this behavior are discussed.     

Localization of 17beta-hydroxysteroid dehydrogenase in Mycobacterium sp. VKM Ac-1815D mutant strain

The localization of mycobacterial 17β-hydroxysteroid dehydrogenase (17β-OH SDH) was studied using cell fractionation and cytochemical investigation. Mycobacterium sp. Et1 mutant strain derived from Mycobacterium sp. VKM Ac-1815D and characterized by increased 17β-OH SDH activity was used as a model organism.

Subcellular distribution study showed both soluble and membrane-bound forms of mycobacterial 17β-hydroxysteroid dehydrogenase. The cytochemical method based on a copper ferrocyanide procedure followed by electron microscopic visualization was applied in order to investigate the intracellular localization of bacterial 17β-OH SDH in more detail. The enzyme was found to be located in the peripheral cytoplasmic zone adjoining the cytoplasmic membrane (CM). 17β-OH SDH was loosely membrane bound and easily released into the environment under the cell integrity failure.