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251.
The indigenous plasmid pIJ101 is the parent of many cloning vectors used in Streptomyces. One early pIJ101 derivative, pIJ702, has been particularly widely used. pIJ702 lacks sti:cop/korB and accumulates single-stranded DNA (ssDNA). The 1.2 kb BclI-BclI sti:cop/korB and 0.7 kb SpeI-BclI sti regions were isolated from pIJ101 and cloned into pIJ702 at the PstI site in both orientations. No ssDNA was detected in constructs containing sti present in its correct orientation with respect to the basic replicon, with or without cop/korB. Constructs which contained sti in the reverse orientation did accumulate ssDNA. Thus, sti is only active as the site for second-strand synthesis in its natural orientation. Furthermore, sti inserted in either orientation into the structurally unstable pIJ702-pUC8 shuttle vectors prevented them from rearranging in S. lividans. The sti function was defined to a 0.53 kb SpeI-SacII fragment and the probable site for second-strand initiation (ssi) was identified. 相似文献
252.
TP Roberts Z Vexler N Derugin ME Moseley J Kucharczyk 《Canadian Metallurgical Quarterly》1993,13(6):940-946
Magnetic susceptibility contrast-enhanced and diffusion-weighted echo planar magnetic resonance (MR) imaging was performed using a cat model of acute regional cerebral ischemia induced by partial stenosis of the right middle cerebral artery (MCA). The imaging data were correlated with triphenyltetrazolium chloride (TTC)-stained histopathologic coronal brain sections to determine the prognostic efficacy of high-speed MR imaging techniques in differentiating mild, moderate, and severe cerebral hypoperfusion. Brains of animals without cortical injury on TTC staining were found to have a reduction in peak contrast enhancement of 32 +/- 6% (mean +/- SD) below control values with no significant change in the apparent diffusion coefficient (ADC), determined from the diffusion-weighted MR images. In cases where moderate ischemic injury was observed in the TTC-stained sections, a 10-20% drop in the ADC was found over the 6-h study period, accompanied by a much wider variation in peak contrast enhancement. Finally, where TTC staining showed severe ischemic brain damage, a 40-50% drop in ADC and a reduction in peak contrast enhancement effect of > 95% were observed as early as 1 h following MCA stenosis. The significant correlation between imaging observations and histologically confirmed cerebral ischemia indicates that magnetic susceptibility contrast-enhanced echo planar MR imaging is sensitive to slight reductions in cerebral perfusion that fall below the threshold for reliably detectable ischemia-induced alterations in ADC. First-pass perfusion-sensitive imaging may thus be diagnostically useful in differentiating severely hypoperfused permanently injured tissue from the mildly hypoperfused ischemic penumbra. 相似文献
253.
TP de Rooy JW Oestmann LJ Schultze Kool H Vrooman F Buchmann 《Canadian Metallurgical Quarterly》1993,34(5):445-449
The combined use of AMBER (Advanced Multiple Beam Equalization Radiography) and a digital storage phosphor (SP) radiography system was evaluated for chest radiography in a pilot study with 4 patients. Four image modes with different dose levels were compared: the SP in combination with an AMBER equalized exposure (SP/AMBER) and 3 nonequalized exposures with dose levels corresponding to the respective calculated AMBER lung dose (SP/lung field dose), the calculated AMBER mediastinal dose (SP/mediastinal dose) and the calculated AMBER average dose (SP/average dose). All image modes were matched for Hurter and Driffield characteristics and subjectively rated according to visibility of details. The improved signal-to-noise (S/N) ratio of SP/AMBER resulted in a better visualization of structures in the mediastinum and the basal lung where SP/lung field dose scored lowest. For the central lung no quality differences were seen between techniques. The compressed dynamic range of the SP/AMBER images was more easily displayed on the hard-copy film. The combination of AMBER with SP radiography promises to overcome the dynamic range limitations of digital displays while, at moderate doses, giving better S/N and image quality than standard SP technique. 相似文献
254.
The terminal bowel is congenitally aganglionic in ls/ls mice. The condition has been associated with an overabundance of laminin and other matrix molecules. Aggregation ls/ls<==>C3H chimeric mice and interspecies mouse<==>quail chimeras were constructed to test the hypothesis that the aganglionosis arises because the ls/ls gut and not the neural crest is abnormal. Demonstration of beta-glucuronidase activity permitted genotypically ls/ls and C3H cells to be distinguished in the ls/ls<==>C3H chimeras. Aganglionosis did not occur in the ls/ls<==>C3H mice and ls/ls neurons were observed in the terminal bowel. Following bactransplantation of control segments of mouse gut into quail host embryos, mouse cells migrated to host targets normally colonized by cells from the neural crest; moreover, quail crest-derived cells entered the mouse gut. In contrast, cells did not migrate to these targets from presumptive aganglionic ls/ls bowel and quail crest-derived cells neither entered the ls/ls gut nor migrated through it. Laminin immunoreactivity was present in the backgrafts of murine colon and was far more abundant and widespread in those from ls/ls than in those from control animals. These data suggest that the presumptive aganglionic ls/ls bowel does not contain crest-derived cells because these cells, which are normal in ls/ls mice, do not enter it. This failure of colonization may be related to the premature formation of neurons outside the abnormal gut, a response that may be promoted by the excessive secretion of laminin by the ls/ls enteric mesenchyme. 相似文献
255.
Conner Mark; Godin Gaston; Norman Paul; Sheeran Paschal 《Canadian Metallurgical Quarterly》2011,30(3):300
Objective: To test the efficacy of interventions based on the question-behavior effect in promoting the adoption of disease prevention behaviors. Design: In Study 1, adults from the general public were randomly allocated to complete a questionnaire about health checks (question-behavior effect condition) or not (control) and later received an invitation to attend for screening. In Study 2, health care professionals were randomly allocated to complete a questionnaire about influenza vaccination or not and later had the opportunity to receive a vaccination. Main Outcome Measures: We objectively assessed health check attendance (Study 1) and influenza vaccination (Study 2). Results: In Study 1, intention-to-treat analyses indicated that health check attendance was significantly higher in the question-behavior effect condition (68.3%) compared with the control condition (53.5%). In Study 2, intention-to-treat analyses indicated that influenza vaccination was significantly higher among participants in the question-behavior effect condition (42.0%) compared with the control condition (36.3%), and this effect persisted after controlling for demographic variables. Explanatory analyses indicated that the effects in both studies were attributable to completing rather than merely receiving the questionnaire and were stronger for those with positive attitudes or intentions about the target behavior. Conclusion: The question-behavior effect represents a simple, cost-effective means to increase disease prevention behaviors among the general public and health professionals. Implications for promoting health behaviors are discussed. (PsycINFO Database Record (c) 2011 APA, all rights reserved) 相似文献
256.
At joint replacement operations local air suction is used to reduce the air pollution from organic solvents in the operation theatre during insertion of cement and prosthesis. In order to find out whether the local suction in an ultraclean-air operation theatre with laminar airflow influenced the number of colony forming units (cfu) of bacterial in vicinity of the wound, one m3 of air was sampled 20 cm and one metre from the wound before, during and after use of local suction during insertion of cement and prosthesis using a Sartorius membrane filter sampler. There was no significant difference between the groups in the numbers of cfu of bacteria found. It is concluded that use of local air suction over the operative area while cementing hip prosthesis does not affect the number of bacteria in the vicinity of the operation. 相似文献
257.
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259.
BJ Conlon M Walsh D McShane N Corcoran M Moriarty JB Healy I Fraser TP O''Dwyer 《Canadian Metallurgical Quarterly》1997,22(4):327-331
In a unilateral ureteral obstruction model, a progressive accumulation of hyaluronan (HA) was observed in the renal papilla during the first 11 days of obstruction, after which the amount of HA decreased until the last day of observation, i.e. day 22. The initial accumulation of HA in the obstructed kidney probably reflects the attempts of the kidney to maintain osmotic balance. Consequently, when filtration ceases, HA synthesis decreases and the concentration of HA falls. In the papilla of the contralateral kidney, that had not been exposed to any mechanical damage, the HA content was found to vary in a similar way to that in the obstructed kidney. The explanation for this could be that the mesenchymal cells within the papilla increase their production of HA in order to meet the requirements of increased function necessary to also shoulder the function of the damaged kidney. In short similar variations in the HA content of the renal papilla was observed in both healthy and obstructed kidneys in a unilateral ureteral obstruction model. 相似文献
260.
In occasional families in whom cases of classic Friedreich's ataxia (FRDA) coexist with affected cases with retained reflexes, linkage analysis has shown that both map to the FRDA locus on chromosome 9q13-21.1. A gene X25 has been identified within the critical region of the FRDA locus, and an intronic expanded GAA trinucleotide repeat has been found in most cases of FRDA. We report two further FRDA families in whom some patients with classic FRDA were areflexic whereas others had brisk reflexes. Molecular genetic analysis disclosed an abnormal trinucleotide repeat expansion within intron 1 of the FRDA gene in both phenotypes. 相似文献