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81.
The authors have investigated the electrical activity of corpus cavernous, first according to Wagner and Gerstenberg’ method, then, since one year, according to Stief method, in the basal state and following intracavernosal injection of vasoactive agents, or following various stimulation tests. They have found again the electrical activity described by these authors, but have been confronted with the difficulty in quantifying the data. Specially single potential analysis seems to them little reliable and reproducible for an objective interpretation. At this stage of their experience, they test two simpler criteria interpretation: the richness of the electrical activity, and the reactivity of the recording to various stimulations. Their preminary results suggest a correlation between those criteria and the state of the autonomic nervous system of the penis. 相似文献
82.
Complete sequences of the rRNA genes of Drosophila melanogaster 总被引:19,自引:0,他引:19
In this, the first of three papers, we present the sequence of the
ribosomal RNA (rRNA) genes of Drosophila melanogaster. The gene regions of
D. melanogaster rDNA encode four individual rRNAs: 18S (1,995 nt), 5.8S
(123 nt), 2S (30 nt), and 28S (3,945 nt). The ribosomal DNA (rDNA) repeat
of D. melanogaster is AT rich (65.9% overall), with the spacers being
particularly AT rich. Analysis of DNA simplicity reveals that, in contrast
to the intergenic spacer (IGS) and the external transcribed spacer (ETS),
most of the rRNA gene regions have been refractory to the action of
slippage-like events, with the exception of the 28S rRNA gene expansion
segments. It would seem that the 28S rRNA can accommodate the products of
slippage-like events without loss of activity. In the following two papers
we analyze the effects of sequence divergence on the evolution of (1) the
28S gene "expansion segments" and (2) the 28S and 18S rRNA secondary
structures among eukaryotic species, respectively. Our detailed analyses
reveal, in addition to unequal crossing-over, (1) the involvement of
slippage and biased mutation in the evolution of the rDNA multigene family
and (2) the molecular coevolution of both expansion segments and the
nucleotides involved with compensatory changes required to maintain
secondary structures of RNA.
相似文献
83.
The structure of tyrosine aminotransferase. Evidence for domains involved in catalysis and enzyme turnover 总被引:2,自引:0,他引:2
J L Hargrove H A Scoble W R Mathews B R Baumstark K Biemann 《The Journal of biological chemistry》1989,264(1):45-53
The primary structure of tyrosine aminotransferase, as deduced from the nucleotide sequence of complementary DNA, was confirmed by fast atom bombardment mass spectrometry of tryptic peptides derived from the purified protein. Limited digestion of the native enzyme with trypsin released an acetylated, amino-terminal peptide; the new amino terminus in the modified enzyme was Val65. Endogenous proteases generated a chromatographically separable form of tyrosine aminotransferase that began at Lys35. Neither trypsin nor the other proteases altered the catalytic activity of tyrosine aminotransferase. Reduction of the holoenzyme with sodium borohydride yielded a major tryptic peptide containing phosphopyridoxamine bound to lysine 280, which probably functions in transamination. The carboxyl terminus of tyrosine aminotransferase contains features that typify proteins with short half-lives; it includes two negatively charged, hydrophilic segments that are enriched for glutamyl residues and are similar to a PEST region in ornithine decarboxylase (Rogers, S., Wells, R., and Rechsteiner, M. (1986) Science 234, 364-368). Tyrosine aminotransferase belongs to a superfamily of enzymes which includes aspartate aminotransferase and can be aligned so that many invariant, functional residues coincide. Like the isoenzymes of aspartate aminotransferase, tyrosine aminotransferase may contain two domains, with a central, catalytic core, and a small domain made up of both amino- and carboxyl-terminal components. We speculate that the exposed small domain may confer the unusually rapid degradative rate that characterizes this enzyme. 相似文献
84.
85.
86.
Physiological functions of mineral macronutrients 总被引:6,自引:0,他引:6
Frans JM Maathuis 《Current opinion in plant biology》2009,12(3):250-258
87.
Andrew RJ Mitchell Philip Roberts Jonas Eichhöfer Jonathan Timperley Oliver JM Ormerod 《Cardiovascular ultrasound》2004,2(1):1-4
Percutaneous coronary intervention can be associated with distal embolization of thrombotic material causing myocardial necrosis and infarction. We discuss the role of intravascular imaging to guide the use of a distal protection device by describing the outcome of a young woman presenting with non-ST elevation myocardial infarction. Coronary angiography demonstrated an isolated minor stenosis in the proximal left anterior descending coronary artery with slight haziness beyond the lesion. Intravascular ultrasound confirmed an extensive thrombus overlying a bulky atherosclerotic plaque. A distal filter wire was therefore successfully used to reduce the risk of distal embolization. The use of intravascular ultrasound in patients presenting with acute coronary syndrome may reveal large thrombi that are difficult to image using conventional angiographic techniques. Intravascular ultrasound can therefore be used as a tool to select lesions requiring distal protection. 相似文献
88.
89.
Juan Hou Anita M Charters Sam C Lee Yongjun Zhao Mona K Wu Steven JM Jones Marco A Marra Pamela A Hoodless 《BMC developmental biology》2007,7(1):92
Background
The embryonic definitive endoderm (DE) gives rise to organs of the gastrointestinal and respiratory tract including the liver, pancreas and epithelia of the lung and colon. Understanding how DE progenitor cells generate these tissues is critical to understanding the cause of visceral organ disorders and cancers, and will ultimately lead to novel therapies including tissue and organ regeneration. However, investigation into the molecular mechanisms of DE differentiation has been hindered by the lack of early DE-specific markers. 相似文献90.
Accurate prediction of protein secondary structure and solvent accessibility by consensus combiners of sequence and structure information 总被引:1,自引:0,他引:1
Gianluca Pollastri Alberto JM Martin Catherine Mooney Alessandro Vullo 《BMC bioinformatics》2007,8(1):201