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排序方式: 共有255条查询结果,搜索用时 31 毫秒
61.
62.
During late stages of spermatogenesis in mammals, most histones bound to DNA are replaced by protamines (PRM), which results in formation of supercondensed and genetically inert sperm chromatin. At fertilization, mature spermatozoon penetrates oocyte and chromatin is remodeled "back" from nucleoprotamine to nucleohistone state. While being crucial for activation of male genome and ultimately for initiation of embryonic development, this process is poorly studied, especially in humans. Data on model animals concerning PRM to histones exchange post fertilization are few and contradictory. As direct experimentation with human embryos is impossible due to ethical, legal and technical reasons, we evaluate the timing and mode of PRM removal in a heterologous ICSI system using hamster ova injected with human sperm. Localization of human PRM 1 and 2 in hybrid zygotes was established using immunofluorescence. We observed a marked zygote to zygote variability in male pronuclei size for any time point post ICSI and demonstrated that PRM removal correlates with the developing pronuclei area rather than time after injection. Overall, the disappearance of protamines from sperm is rather rapid and most likely completed within 1 hr. We propose that the critical characteristic influencing PRM removal after heterologous fertilization is the intrinsic heterogeneity of the human sperm population. The same yet unexplored variance may be one of the reasons for canceled, delayed or aberrant early embryonic development during natural or artificial fertilization in humans. 相似文献
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Allen JP Atekwana EA Atekwana EA Duris JW Werkema DD Rossbach S 《Applied and environmental microbiology》2007,73(9):2860-2870
The interdependence between geoelectrical signatures at underground petroleum plumes and the structures of subsurface microbial communities was investigated. For sediments contaminated with light non-aqueous-phase liquids, anomalous high conductivity values have been observed. Vertical changes in the geoelectrical properties of the sediments were concomitant with significant changes in the microbial community structures as determined by the construction and evaluation of 16S rRNA gene libraries. DNA sequencing of clones from four 16S rRNA gene libraries from different depths of a contaminated field site and two libraries from an uncontaminated background site revealed spatial heterogeneity in the microbial community structures. Correspondence analysis showed that the presence of distinct microbial populations, including the various hydrocarbon-degrading, syntrophic, sulfate-reducing, and dissimilatory-iron-reducing populations, was a contributing factor to the elevated geoelectrical measurements. Thus, through their growth and metabolic activities, microbial populations that have adapted to the use of petroleum as a carbon source can strongly influence their geophysical surroundings. Since changes in the geophysical properties of contaminated sediments parallel changes in the microbial community compositions, it is suggested that geoelectrical measurements can be a cost-efficient tool to guide microbiological sampling for microbial ecology studies during the monitoring of natural or engineered bioremediation processes. 相似文献
66.
Rodina EV Vorobyeva NN Kurilova SA Belenikin MS Fedorova NV Nazarova TI 《Biochemistry. Biokhimii?a》2007,72(1):93-99
The interaction of Escherichia coli inorganic pyrophosphatase (E-PPase) with effector ATP has been studied. The E-PPase has been chemically modified with the
dialdehyde derivative of ATP. It has been established that in the experiment only one molecule of effector ATP is bound to
each subunit of the hexameric enzyme. Tryptic digestion of the adenylated protein followed by isolation of a modified peptide
by HPLC and its mass-spectrometric identification has showed that it is an amino group of Lys146 that undergoes modification.
Molecular docking of ATP to E-PPase indicates that the binding site for effector ATP is located in a cluster of positively
charged amino acid residues proposed earlier on the basis of site-directed mutagenesis to participate in binding of effector
pyrophosphate. Molecular docking also reveals several other amino acid residues probably involved in the interaction with
effectors.
Published in Russian in Biokhimiya, 2007, Vol. 72, No. 1, pp. 110–117. 相似文献
67.
Rodina EV Vorobyeva NN Kurilova SA Sitnik TS Nazarova TI 《Biochemistry. Biokhimii?a》2007,72(1):100-108
It has been shown that PPi, methylenediphosphonate, and ATP act as effectors of Escherichia coli inorganic pyrophosphatase (E-PPase), and that they compete for binding at the allosteric regulatory site. On the basis of
chemical modification and computer modeling of a structure of the enzyme-ATP complex, a number of amino acid residues presumably
involved in binding effectors has been revealed. Mutant variants Lys112Gln, Lys112Gln/Lys148Gln, and Lys112Gln/Lys115Ala of
E-PPase have been obtained, as well as a modified variant of wild type E-PPase (Adwt PPase) with a derivative of ATP chemically attached to the amino group of Lys146. Kinetic properties of these variants
have been investigated and compared to the earlier described variants Lys115Ala, Arg43Gln, and Lys148Gln. Analysis of the
data confirms the proposed location of an effector binding site in a cluster of positively charged amino acid residues including
the side chains of Arg43, Lys146 (subunit A), Lys112, and Lys115 (subunit B). Lys112 is supposed to play a key role in forming
contacts with the phosphate groups of the three studied effectors.
Published in Russian in Biokhimiya, 2007, Vol. 72, No. 1, pp. 118–127. 相似文献
68.
Petra Videnska Md. Masudur Rahman Marcela Faldynova Vladimir Babak Marta Elsheimer Matulova Estella Prukner-Radovcic Ivan Krizek Sonja Smole-Mozina Jasna Kovac Ama Szmolka Bela Nagy Karel Sedlar Darina Cejkova Ivan Rychlik 《PloS one》2014,9(10)
Poultry meat is the most common protein source of animal origin for humans. However, intensive breeding of animals in confined spaces has led to poultry colonisation by microbiota with a zoonotic potential or encoding antibiotic resistances. In this study we were therefore interested in the prevalence of selected antibiotic resistance genes and microbiota composition in feces of egg laying hens and broilers originating from 4 different Central European countries determined by real-time PCR and 16S rRNA gene pyrosequencing, respectively. strA gene was present in 1 out of 10,000 bacteria. The prevalence of sul1, sul2 and tet(B) in poultry microbiota was approx. 6 times lower than that of the strA gene. tet(A) and cat were the least prevalent being present in around 3 out of 10,000,000 bacteria forming fecal microbiome. The core chicken fecal microbiota was formed by 26 different families. Rather unexpectedly, representatives of Desulfovibrionaceae and Campylobacteraceae, both capable of hydrogen utilisation in complex microbial communities, belonged among core microbiota families. Understanding the roles of individual population members in the total metabolism of the complex community may allow for interventions which might result in the replacement of Campylobacteraceae with Desulfovibrionaceae and a reduction of Campylobacter colonisation in broilers, carcasses, and consequently poultry meat products. 相似文献
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Little PJ Getachew R Rezaei HB Sanchez-Guerrero E Khachigian LM Wang H Liao S Zheng W Ballinger ML Osman N 《Archives of biochemistry and biophysics》2012,525(1):25-31
The signaling pathways that regulate the synthesis and structure of proteoglycans secreted by vascular smooth muscle cells are potential therapeutic targets for preventing lipid deposition in the early stage of atherosclerosis. PDGF stimulates both core protein expression and elongation of glycosaminoglycan (GAG) chains on proteoglycans. In this study we investigated the effects of the tyrosine kinase inhibitor genistein on PDGF mediated receptor phosphorylation and proteoglycan synthesis in human vascular smooth muscle cells. We demonstrate that genistein does not block phosphorylation of the activation site of the PDGF receptor at Tyr(857) and two other downstream sites Tyr(751) and Tyr(1021). Genistein blocked PDGF-mediated proteoglycan core protein synthesis however it had no effect on GAG chain elongation. These results differ markedly to two other tyrosine kinase inhibitors, imatinib and Ki11502, that block PDGF receptor phosphorylation and PDGF mediated GAG elongation. We conclude that the action of genistein on core protein synthesis does not involve the PDGF receptor and that PDGF mediates GAG elongation via the PDGF receptor. 相似文献