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41.
玉米粗缩病毒基因组第七组份的cDNA克隆及序列分析 总被引:5,自引:0,他引:5
从采自中国河北滦城感病的玉米材料中提取玉米粗缩病毒(MRDV)的双链RNA。根据已知MRDV的部分序列设计引物,反转录、PCR扩增,克隆并测序分析了MRDV的第七片段(S7)cDNA序列。结果表明,S7 cDNA序列全长为1936bp,与国外所测的MRDV S7的序列长度相等,而且S7包含的两个阅读框(ORF1和ORF2)位置无变化。它们的核苷酸和最大开放阅读框(ORF1)同源性分别为877%和91.6%,然而,MRDV S7的片段与水稻黑条矮缩病毒(RBSDV)S8片段的核苷酸和最大开放阅读框(ORF1)有更高的同源性,分别为95.5%和93.5%。 相似文献
42.
Bioethanol production from ammonia percolated wheat straw 总被引:2,自引:0,他引:2
Minhee Han Se-Kwon Moon Yule Kim Youngran Kim Bongwoo Chung Gi-Wook Choi 《Biotechnology and Bioprocess Engineering》2009,14(5):606-611
This study examined the effectiveness of ammonia percolation pretreatment of wheat straw for ethanol production. Ground wheat
straw at a 10% (w/v) loading was pretreated with a 15% (v/v) ammonia solution. The experiments were performed at treatment
temperature of 50∼170°C and residence time of 10∼150 min. The solids treated with the ammonia solution showed high lignin
degradation and sugar availability. The pretreated wheat straw was hydrolyzed by a cellulase complex (NS50013) and β-glucosidase
(NS50010) at 45°C. After saccharification, Saccharomyces cerevisiae was added for fermentation. The incubator was rotated at 120 rpm at 35°C. As a result of the pretreatment, the delignification
efficiency was > 70% (170°C, 30 min) and temperature was found to be a significant factor in the removal of lignin than the
reaction time. In addition, the saccharification results showed an enzymatic digestibility of > 90% when 40 FPU/g cellulose
was used. The ethanol concentration reached 24.15 g/L in 24 h. This paper reports a total process for bioethanol production
from agricultural biomass and an efficient pretreatment of lignocellulosic material. 相似文献
43.
44.
Distribution of histopathology and Ia positive cells in actively induced and passively transferred experimental autoimmune orchitis 总被引:4,自引:0,他引:4
K S Tung T D Yule C A Mahi-Brown M B Listrom 《Journal of immunology (Baltimore, Md. : 1950)》1987,138(3):752-759
Histopathology in testes from mice with actively induced experimental orchitis (EAO) (active EAO) and those from recipients of testis-sensitized lymphocytes (passive EAO) had different distributions. In passive EAO, maximum orchitis existed in the straight tubules, rete testis, and ductus efferentes, obstruction of which led to extreme dilatation of seminiferous tubules. Unusual intralymphatic granulomata also resulted in dilated testicular lymphatics. In active EAO, maximum orchitis affected seminiferous tubules under the testicular capsule, away from the rete testes. Vasitis was common and occurred in both active and passive EAO. In normal testes, IA+ F4/80+ cells were sparse but formed a cuff around the straight tubules. After immunization with testis in adjuvant or with adjuvant alone, the number, size, and staining intensity of IA+ cells increased dramatically beginning on day 5, 7 days before disease onset. Simultaneously, epithelial cells confined to the ductus efferentes became Ia+. Although recipients of sensitized lymphocytes also developed epithelial Ia in the ductus efferentes, they did not show changes in testicular interstitial Ia+ cells. Our findings indicate that testicular autoantigens are not completely sequestered, but are accessible to and can react with passively transferred immune lymphocytes in well-defined regions of the germ cell compartment. These regions coincided to a large extent with maximum expression of periductal or epithelial Ia. Changes in Ia+ cells in the testis, which are inducible by adjuvants and precede orchitis, may account in part for the different distribution of histopathology of active EAO. 相似文献
45.
46.
Dejong JM Liu Y Bollon AP Long RM Jennewein S Williams D Croteau RB 《Biotechnology and bioengineering》2006,93(2):212-224
Baccatin III, an intermediate of Taxol biosynthesis and a useful precursor for semisynthesis of the anti-cancer drug, is produced in yew (Taxus) species by a sequence of 15 enzymatic steps from primary metabolism. Ten genes encoding enzymes of this extended pathway have been described, thereby permitting a preliminary attempt to reconstruct early steps of taxane diterpenoid (taxoid) metabolism in Saccharomyces cerevisiae as a microbial production host. Eight of these taxoid biosynthetic genes were functionally expressed in yeast from episomal vectors containing one or more gene cassettes incorporating various epitope tags to permit protein surveillance and differentiation of those pathway enzymes of similar size. All eight recombinant proteins were readily detected by immunoblotting using specific monoclonal antibodies and each expressed protein was determined to be functional by in vitro enzyme assay, although activity levels differed considerably between enzyme types. Using three plasmids carrying different promoters and selection markers, genes encoding five sequential pathway steps leading from primary isoprenoid metabolism to the intermediate taxadien-5alpha- acetoxy-10beta-ol were installed in a single yeast host. Metabolite analysis showed that yeast isoprenoid precursors could be utilized in the reconstituted pathway because products accumulated from the first two engineered pathway steps (leading to the committed intermediate taxadiene); however, a pathway restriction was encountered at the first cytochrome P450 hydroxylation step. The means of overcoming this limitation are described in the context of further development of this novel approach for production of Taxol precursors and related taxoids in yeast. 相似文献
47.
Tropical peat swamp forests are important and endangered ecosystems, although little is known of their microbial diversity
and ecology. We used molecular and enzymatic techniques to examine patterns in prokaryotic community structure and overall
microbial activity at 0-, 10-, 20-, and 50-cm depths in sediments in a peat swamp forest in Malaysia. Denaturing gradient
gel electrophoresis profiles of amplified 16S ribosomal ribonucleic acid (rRNA) gene fragments showed that different depths
harbored different bacterial assemblages and that Archaea appeared to be limited to the deeper samples. Cloning and sequencing
of longer 16S rRNA gene fragments suggested reduced microbial diversity in the deeper samples compared to the surface. Bacterial
clone libraries were largely dominated by ribotypes affiliated with the Acidobacteria, which accounted for at least 27–54%
of the sequences obtained. All of the sequenced representatives from the archaeal clone libraries were Crenarchaeota. Activities
of microbial extracellular enzymes involved in carbon, nitrogen, and phosphorus cycling declined appreciably with depth, the
only exception being peroxidase. These results show that tropical peat swamp forests are unusual systems with microbial assemblages
dominated by members of the Acidobacteria and Crenarchaeota. Microbial communities show clear changes with depth, and most
microbial activity is likely confined to populations in the upper few centimeters, the site of new leaf litter fall, rather
than the deeper, older, peat layers. 相似文献
48.
Matthew J. Betzenhauser Larry E. Wagner II Hyung Seo Park David I. Yule 《The Journal of biological chemistry》2009,284(24):16156-16163
ATP is known to increase the activity of the type-1 inositol 1,4,5-trisphosphate receptor (InsP3R1). This effect is attributed to the binding of ATP to glycine rich Walker A-type motifs present in the regulatory domain of the receptor. Only two such motifs are present in neuronal S2+ splice variant of InsP3R1 and are designated the ATPA and ATPB sites. The ATPA site is unique to InsP3R1, and the ATPB site is conserved among all three InsP3R isoforms. Despite the fact that both the ATPA and ATPB sites are known to bind ATP, the relative contribution of these two sites to the enhancing effects of ATP on InsP3R1 function is not known. We report here a mutational analysis of the ATPA and ATPB sites and conclude neither of these sites is required for ATP modulation of InsP3R1. ATP augmented InsP3-induced Ca2+ release from permeabilized cells expressing wild type and ATP-binding site-deficient InsP3R1. Similarly, ATP increased the single channel open probability of the mutated InsP3R1 to the same extent as wild type. ATP likely exerts its effects on InsP3R1 channel function via a novel and as yet unidentified mechanism.Inositol 1,4,5-trisphosphate receptors (InsP3R)3 are a family of large, tetrameric, InsP3-gated cation channels. The three members of this family (InsP3R1, InsP3R2, and InsP3R3) are nearly ubiquitously expressed and are localized primarily to the endoplasmic reticulum (ER) membrane (1–3). Numerous hormones, neurotransmitters, and growth factors bind to receptors that stimulate phospholipase C-induced InsP3 production (4). InsP3 subsequently binds to the InsP3R and induces channel opening. This pathway represents a major mechanism for Ca2+ liberation from ER stores (5). All three InsP3R isoforms are dynamically regulated by cytosolic factors in addition to InsP3 (1). Ca2+ is perhaps the most important determinant of InsP3R activity besides InsP3 itself and is known to regulate InsP3R both positively and negatively (6). ATP, in concert with InsP3 and Ca2+, also regulates InsP3R as do numerous kinases, phosphatases, and protein-binding partners (7–10). This intricate network of regulation allows InsP3R activity to be finely tuned by the local cytosolic environment (9). As a result, InsP3-induced Ca2+ signals can exhibit a wide variety of spatial and temporal patterns, which likely allows Ca2+ to control many diverse cellular processes.Modulation of InsP3-induced Ca2+ release (IICR) by ATP and other nucleotides provides a direct link between intracellular Ca2+ signaling and the metabolic state of the cell. Metabolic fluctuations could, therefore, impact Ca2+ signaling in many cell types given that InsP3R are expressed in all cells (11, 12). Consistent with this, ATP has been shown to augment IICR in many diverse cell types including primary neurons (13), smooth muscle cells (14), and exocrine acinar cells (15) as well as in immortalized cell lines (16–18). The effects of ATP on InsP3R function do not require hydrolysis because non-hydrolyzable ATP analogues are as effective as ATP (7, 14). ATP is thought to bind to distinct regions in the central, coupling domain of the receptors and to facilitate channel opening (2, 19). ATP is not required for channel gating, but instead, increases InsP3R activity in an allosteric fashion by increasing the open probability of the channel in the presence of activating concentrations of InsP3 and Ca2+ (7, 8, 20).Despite a wealth of knowledge regarding the functional effects of ATP on InsP3R function, there is relatively little known about the molecular determinants of these actions. ATP is thought to exert effects on channel function by direct binding to glycine-rich regions containing the consensus sequence GXGXXG that are present in the receptors (2). These sequences were first proposed to be ATP-binding domains due to their similarity with Walker A motifs (21). The neuronal S2+ splice variant of InsP3R1 contains two such domains termed ATPA and ATPB. A third site, ATPC, is formed upon removal of the S2 splice site (2, 22). The ATPB site is conserved in InsP3R2 and InsP3R3, while the ATPA and ATPC sites are unique to InsP3R1. Our prior work examining the functional consequences of mutating these ATP-binding sites has yielded unexpected results. For example, mutating the ATPB site in InsP3R2 completely eliminated the enhancing effects of ATP on this isoform while mutating the analogous site in InsP3R3 failed to alter the effects of ATP (23). This indicated the presence of an additional locus for ATP modulation of InsP3R3. In addition, mutation of the ATPC in the S2− splice variant of InsP3R1 did not alter the ability of ATP to modulate Ca2+ release, but instead impaired the ability of protein kinase A to phosphorylate Ser-1755 of this isoform (22).The ATPA and ATPB sites in InsP3R1 were first identified as putative nucleotide-binding domains after the cloning of the full-length receptor (24). Early binding experiments with 8-azido-[α-32P]ATP established that ATP cross-linked with receptor purified from rat cerebellum at one site per receptor monomer (19). Later, more detailed, binding experiments on trypsinized recombinant rat InsP3R1 showed cross-linking of ATP to two distinct regions of the receptor that corresponded with the ATPA and ATPB sites (17). We and others (16, 22, 23) have also reported the binding of ATP analogues to purified GST fusions of small regions of InsP3R1 surrounding the ATPA and ATPB sites. It is widely accepted, in the context of the sequence similarity to Walker A motifs and biochemical data, that the ATPA and ATPB sites are the loci where ATP exerts its positive functional effects on InsP3R1 function (1–3, 16). Furthermore, the higher affinity of the ATPA site to ATP is thought to confer the higher sensitivity of InsP3R1 to ATP versus InsP3R3, which contains the ATPB site exclusively (25, 26). The purpose of this study, therefore, was to examine the contributions of the ATPA and ATPB sites to ATP modulation of the S2+ splice variant of InsP3R1. We compared the effects of ATP on InsP3R1 and on ATP-binding site mutated InsP3R1 using detailed functional analyses in permeabilized cells and in single channel recordings. Here we report that InsP3R1 is similar to InsP3R3 in that ATP modulates IICR even at maximal InsP3 concentrations and that neither the ATPA nor the ATPB site is required for this effect. 相似文献
49.
Bruno G. Madeira Mário M. Espírito-Santo Santos D’?ngelo Neto Yule R. F. Nunes G. Arturo Sánchez Azofeifa G. Wilson Fernandes Mauricio Quesada 《Plant Ecology》2009,201(1):291-304
We investigated changes in species composition and structure of tree and liana communities along a successional gradient in
a seasonally dry tropical forest. There was a progressive increase in tree richness and all tree structural traits from early
to late stages, as well as marked changes in tree species composition and dominance. This pattern is probably related to pasture
management practices such as ploughing, which remove tree roots and preclude regeneration by resprouting. On the other hand,
liana density decreased from intermediate to late stages, showing a negative correlation with tree density. The higher liana
abundance in intermediate stage is probably due to a balanced availability of support and light availability, since these
variables may show opposite trends during forest growth. Predicted succession models may represent extremes in a continuum
of possible successional pathways strongly influenced by land use history, climate, soil type, and by the outcomes of tree–liana
interactions. 相似文献
50.
David I. Yule 《The international journal of biochemistry & cell biology》2010,42(11):1757-1761
Pancreatic acinar cells are classical exocrine gland cells. The apical regions of clusters of coupled acinar cells collectively form a lumen which constitutes the blind end of a tube created by ductal cells – a structure reminiscent of a “bunch of grapes”. When activated by neural or hormonal secretagogues, pancreatic acinar cells are stimulated to secrete a variety of proteins. These proteins are predominately inactive digestive enzyme precursors called “zymogens”. Acinar cell secretion is absolutely dependent on secretagogue-induced increases in intracellular free Ca2+. The increase in [Ca2+]i has precise temporal and spatial characteristics as a result of the exquisite regulation of the proteins responsible for Ca2+ release, Ca2+ influx and Ca2+ clearance in the acinar cell. This brief review discusses recent studies in which transgenic animal models have been utilized to define in molecular detail the components of the Ca2+ signaling machinery which contribute to these characteristics. 相似文献