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71.
Fate of elemental sulfur in an intertidal sediment 总被引:2,自引:0,他引:2
Abstract: Sediment from a tidal flat at Wedderwarden, near the mouth of the Weser estuary, northern Germany, was amended with elemental sulfur, and concentrations of metabolic end products were monitored. The production of both sulfate and sulfide was consistent with disproportionation as the most important fate of the added elemental sulfur. A population of bacteria conducting active elemental sulfur disproportionation was also enriched from the sediment. In the enrichments, containing both elemental sulfur and Fe oxides as a sulfide 'scrub', sulfide and sulfate were produced in a ratio of , somewhat lower than the predicted ratio of . The mismatch between predicted and observed production ratios is explained by the channelling of electrons into autotrophic or mixotrophic CO2 fixation rather than sulfide formation. The production of organic carbon, in the correct amount to explain the observed sulfide to sulfate production ratio, was verified by organic carbon analysis. Finally, rates of sulfate reduction were identical in the elemental sulfur amended sediment, and in control sediment with no added sulfur. Hence, the heterotrophic bacterial community was completely unaffected by an active metabolism conducting elemental sulfur disproportionation. 相似文献
72.
Ejaculates from 3 young boars were collected on 4 occasions as a series of separate 15-ml fractions. The contribution of different fractions of these ejaculates to observed variability in the quality of the semen when used for IVF was then determined. On the basis of sperm concentration, 3 fractions representing the first peak concentration (Fraction 1), the lowest sperm concentration after Fraction 1 (Fraction 2), and the second peak concentration (Fraction 3) were selected for analysis in vitro. Oocyte-cumulus-granulosa cell complexes were obtained by dissection from slaughterhouse ovaries. In vitro matured oocytes were randomly assigned for fertilization by the 3 semen samples from each boar. Sperm concentration was the same in all the samples during prefertilization incubation, while the final concentration for fertilization was 5 x 10(5) sperm/ml. Data were analysed using ANOVA for a split-plot design. In the presence of fraction effects, Student-Newman-Keuls (SNK) test was used for multiple comparison of treatment means. Oocyte penetration rates differed among fractions (P = 0.001) and varied from 69 to 100% (mean 95.7%) for Fraction 1, from 0 to 100% (mean 53.3%) for Fraction 2, and from 50to 100% (mean 89.9%) for Fraction 3. There were also differences in male pronuclear formation rate (P = 0.028; mean 27.6, 9.3 and 16.4% for Fractions 1, 2 and 3, respectively); in the rate of polyspermy (P = 0.0001; mean 92.3, 31.9 and 76.3% for Fractions 1, 2 and 3, respectively); and in the number of penetrated spermatozoa per oocyte P = 0.002; mean 5.58, 1.94 and 4.07 for Fractions 1, 2, and 3, respectively). The first peak concentration of semen (Fraction 1) showed superiority in fertilizing ability and less variability in penetration rate from replicate to replicate compared with the other 2 fractions. By multiple comparison, Boar 1 showed higher rates of penetration (P < 0.05), male pronuclear formation (P < 0.05) and polyspermy (P < 0.05) than the other 2 boars. There was no fraction-by-boar interaction. The IVM-IVF system adopted proved to be a promising method for boar semen evaluation. 相似文献
73.
74.
兔出血症病毒主要结构多肽的氨基酸分析 总被引:1,自引:0,他引:1
兔出血症病毒主要结构多肽的氨基酸分析王恒安,杜念兴,徐为燕(南京农业大学,南京210095)关键词兔出血症病毒,结构多肽,氨基酸分析有关兔出血症病毒(RHDV)结构多肽的报道很多,有认为只有1条,有报道4条的,也有报道多达6条的。但其主要结构多肽为分... 相似文献
75.
酸水解蚕蛹制备复合氨基酸的研究 总被引:7,自引:0,他引:7
采用硫酸水解法,以蚕蛹制取复合氨基酸产品,得到氨基酸态氮分别为9.05%和13.45%的食用复合氨基粉和精制复合氨基酸粉。食用复合氨基酸粉含有18种氨基酸,其中必需氨基酸含量为39.2%。食用复合氨基酸粉的制备方法经工厂小批量生产证实,其工艺简单易行,适合于中小企业采用,该产品的质量优良,生产成本低廉,具有市场竞争力。 相似文献
76.
黑节草从传粉到受精约需130d,精子在花粉管中形成,胚囊发育属蓼型胚囊,因反足细胞较早退化,故受精前胚囊多只由卵器和中央细胞组成。精卵核融合时,精核染色质进入卵核后凝集成颗粒状,并在原位与卵核的染色质融合,雌、雄性核仁一直维持至合子的第一次分裂期前。双受精作用正常,属于有丝分裂前配子融合类型,初生胚乳核发生2-3次分裂后逐渐退化消失,胚的发育局限于球形胚阶段。 相似文献
77.
利用人粒细胞集落刺激因子(hG-CSF)cDNA3′端非翻译区(3′-UTR)中存在的DraⅠ酶切位点,通过部分酶切与完全酶切,删除3′-UTR不同长度,构建了四种hG-CSFcDNA瞬时重组表达质粒。转染COS-7细胞后,生物活性测定结果提示,hG-CSFcDNA3′-UTR对其表达起负调控作用,其关键性序列位于紧接终止密码子TGA下游的65bp范围内,3′-UTR对hG-CSFcDNA表达的影响与转录水平的差别有一定关系。 相似文献
78.
Missense mutations define a restricted segment in the C-terminal domain of phytochrome A critical to its regulatory activity. 总被引:13,自引:4,他引:9 下载免费PDF全文
The phytochrome family of photoreceptors has dual molecular functions: photosensory, involving light signal perception, and regulatory, involving signal transfer to downstream transduction components. To define residues necessary specifically for the regulatory activity of phytochrome A (phyA), we undertook a genetic screen to identify Arabidopsis mutants producing wild-type levels of biologically defective but photochemically active and dimeric phyA molecules. Of eight such mutants identified, six contain missense mutations (including three in the same residue, glycine 727) clustered within a restricted segment in the C-terminal domain of the polypeptide. Quantitative photobiological analysis revealed retention of varying degrees of partial activity among the different alleles--a result consistent with the extent of conservation at the position mutated. Together with additional data, these results indicate that the photoreceptor subdomain identified here is critical to the regulatory activity of both phyA and phyB. 相似文献
79.
80.
Red cell Lewis antigens are carried by glycosphingolipids passively absorbed from plasma. Plasma was collected from a spectrum of individuals with normal and unusual Lewis/secretor phenotypes in order to investigate the glycolipid basis for the unusual phenotypes. Samples were obtained from: a Le(a+b–) ABH nonsecretor who secreted Lewis substances; a Le(a+b–) partial secretor; Le(a+b+) partial secretors; Le(a+b+) secretors; and a full range of normal Lewis/secretor phenotypes as controls. The Le(a+b+) samples represented Polynesian, Asian and Réunion Island ethnic backgrounds. Nonacid glycolipids were prepared, separated by thin-layer chromatography, and then immunostained with potent monoclonal antibodies of known specificity. Despite different serological profiles of the Le(a+b–) and Le(a+b+) Polynesian samples, their plasma glycolipid expressions were very similar, with both Lea and Leb co-expressed. The copresence of Lea and Leb in Le(a+b+) samples is in marked contrast to Caucasians with normal Lewis phenotypes, who have predominantly either Lea or Leb. These results suggest that there is a range of the secretor transferases in different individuals, possibly due to different penetrance or to several weak variants. We also show that Lewis epitopes on longer and/or more complex core chains appear to be predominant in the Polynesian Le(a+b+) samples. The formation of these extended glycolipids is compatible with the concept that in the presence of reduced secretor fucosyltransferase activity, increased elongation of the precursor chain occurs, which supports the postulate that fucosylation of the precursor prevents or at least markedly reduces chain elongation.Abbreviations CBA
chromatogram binding assay
- TLC
thin-layer chromatography 相似文献