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1.
DC Reynolds CE Leak KK Bajaj CE Stutz RL Jones KR Evans PW Yu WM Theis 《Canadian Metallurgical Quarterly》1989,40(9):6210-6217
2.
Surface expression of the T cell antigen receptor (TCR) in mature T cells requires the association of a variable heterodimer (alpha.beta or gamma.delta) with six invariant CD3 polypeptides (gamma, delta, epsilon-epsilon, zeta-zeta, or zeta-eta). We described here that deletion of the cytoplasmic tail polypeptide sequence (Lys-Lys-Lys-Asn-Ser) of TCR beta-chain (beta CT) results in expression of the truncated beta-chain on the surface of a mature T cell hybridoma line, in the absence of TCR-alpha, as a glycophosphatidylinositol (GPI)-anchored monomeric polypeptide. The GPI-anchored TCR-beta CT is not associated with CD3-epsilon and is incapable of conventional signal transduction. Association with TCR-alpha prevents beta CT from GPI-linkage formation. The alpha beta CT heterodimer binds the CD3 polypeptides, and the resultant TCR alpha beta CT/CD3 complex is capable of signal transduction. Our data show that a signal sequence for GPI-linkage formation is present in TCR-beta, and this alternative membrane anchoring mechanism can be utilized by beta-chain polypeptide lacking the CT sequence. We conclude therefore that in the absence of TCR-alpha expression, the beta-chain CT sequence plays an essential function in hindering GPI-linkage formation, thereby preventing escape of incompletely assembled TCR beta-chain to the cell surface of mature T cells. 相似文献
3.
The surB gene was identified as a gene product required for Escherichia coli cells to exit stationary phase at 37 degrees C under aerobic conditions. surB was shown to be the same as cydC, whose product is required for the proper assembly and activity of cytochrome d oxidase. Cytochrome d oxidase, encoded by the cydAB operon, is one of two alternate terminal cytochrome oxidases that function during aerobic electron transport in E. coli. Mutations inactivating the cydAB operon also cause a temperature-sensitive defect in exiting stationary phase, but the phenotype is not as severe as it is for surB mutants. In this study, we examined the phenotypes of surB1 delta(cydAB) double mutants and the ability of overexpression of cytochrome o oxidase to suppress the temperature-sensitive stationary-phase-exit defect of surB1 and delta(cydAB) mutants and analyzed spontaneous suppressors of surB1. Our results indicate that the severe temperature-sensitive defect in exiting stationary phase of surB1 mutants is due both to the absence of terminal cytochrome oxidase activity and to the presence of a defective cytochrome d oxidase. Membrane vesicles prepared from wild-type, surB1, and delta(cydAB) strains produced superoxide radicals at the same rate in vitro. Therefore, the aerobic growth defects of the surB1 and delta(cydAB) strains are not due to enhanced superoxide production resulting from the block in aerobic electron transport. 相似文献
4.
5.
KR Porter PL Summers D Dubois B Puri W Nelson E Henchal JJ Oprandy CG Hayes 《Canadian Metallurgical Quarterly》1993,48(3):440-446
A polymerase chain reaction (PCR) assay was developed to rapidly detect and identify West Nile (WN) virus. The RNA from seven isolates of WN virus from six countries and four other flaviviruses (Kunjin, Japanese encephalitis, St. Louis encephalitis, and yellow fever viruses) was reverse-transcribed (RT) and amplified by PCR. The nucleotide sequences of the amplified products were determined by a rapid, automated DNA sequencing method. The WN virus RT/PCR assay detected the target gene segment of sequencing method. The WN virus RT/PCR assay detected the target gene segment of isolates from both the African-Middle Eastern group and the Indian group with a sensitivity of approximately 0.05 pg of viral RNA. Kunjin virus was the only other flavivirus tested that produced a band of the appropriate size. Five of seven WN virus isolates showed 92-98% homology in the nucleotide sequence of their PCR products. The sequence of one isolate was virtually identical to the published sequence of the Nigerian isolate (99.5% homology). No correlation was established between the degree of nucleotide homology, geographic location, time of isolation, or source of the isolates. 相似文献
6.
TM Munger DL Packer SC Hammill BJ Feldman KR Bailey DJ Ballard DR Holmes BJ Gersh 《Canadian Metallurgical Quarterly》1993,87(3):866-873
BACKGROUND: Virtually all natural history studies of Wolff-Parkinson-White (WPW) syndrome have been case series and, as such, have been constrained by referral biases, skewed age and sex distributions, or brief follow-up periods. The purpose of our study was to examine the natural history, the development of arrhythmias, and the incidence of sudden death in an entire cohort of pediatric and adult WPW patients from a community-based local population. METHODS AND RESULTS: We identified 113 residents of Olmsted County, Minnesota, during the period 1953-1989 using the centralized records-linkage system provided by the Mayo Clinic and the Rochester Epidemiology Program Project. Medical records and ECGs were reviewed to confirm the diagnosis and to establish pathway location by ECG criteria. Follow-up, via record review and telephone interview, was complete in 95% of subjects through 1990. The incidence of newly diagnosed cases was approximately four per 100,000 per year. Preexcitation was not present on the initial ECG of 22% of the cohort. Approximately 50% of the population was asymptomatic at diagnosis, with 30% subsequently having symptoms related to arrhythmia at follow-up. Two sudden cardiac deaths (SCD) occurred over 1,338 patient-years of follow-up, yielding an overall SCD rate of 0.0015 (95% confidence interval, 0.0002-0.0054) per patient-year. No SCD occurred in patients asymptomatic at diagnosis. CONCLUSIONS: The incidence of sudden death in a local community-based population is low and suggests that electrophysiological testing should not be performed routinely in asymptomatic patients with WPW syndrome. Nevertheless, young, asymptomatic patients, particularly those < 40 years old, should return for medical follow-up should symptoms develop. 相似文献
7.
We evaluate sexual behaviour change among homosexual men enrolled in the cohorts in four AIDS Community Demonstration Projects. Behaviour change is classified following the stages of behaviour change model and described using a Markov model. Predictors of behaviour change are identified and evaluated using logit models for correlated data. Sexual behaviour change within the cohort could be modelled as a first-order Markov process. In addition, predictors suggested by models of health behaviour were correlated with particular patterns of sexual behaviour change. Our evaluation revealed a variety of patterns of sexual behaviour change in the cohorts and suggests multi-faceted interventions for promotion of behaviour change. 相似文献
8.
One hundred and seven consecutive patients presenting with significant peptic ulcer haemorrhage were randomised to endoscopic injection with 3-10 ml of 1:100,000 adrenaline (55 patients, group 1) or to a combination of adrenaline and 5% ethanolamine (52 patients, group 2). All had major stigmata of haemorrhage and endoscopic injection was undertaken by a single endoscopist. The groups were well matched with regard to risk factors. Rebleeding occurred in eight of the group 1 patients and seven in the group 2 patients; surgical operation rates, median blood transfusion requirements, and hospital stay were similar in both groups. The efficacy of either form of injection was similar whether patients presented with active bleeding or a non-bleeding visible vessel. No complications occurred. In patients presenting with significant peptic ulcer bleeding, the addition of a sclerosant confers no advantage over injection with adrenaline alone. 相似文献
9.
The removal of most ceramic brackets is accomplished by specially designed pliers that apply some form of tensile or shear force to the tooth surface. While the shear and tensile bond strengths for ceramic brackets in vitro have been reported, a simulation of the actual force application when using sharp-edged debonding pliers to debond a bracket has not. The purpose of this study is to determine the effectiveness and the force levels generated by the use of both the wide and the narrow blades in the debonding of ceramic brackets. The present findings indicate that the narrow blades effectively debonded ceramic brackets with a significantly lower mean debonding force (120 kg/cm2) than the wider blades (150 kg/cm2). The surface area of the blade in contact with the bracket-adhesive interface is less for the narrow blade (2.0 mm) than for the wide blade (3.2 mm). This relatively smaller contact area is sufficient to debond a bracket at a significantly lower debonding force. 相似文献
10.
KR Kaderlik GJ Mulder RJ Turesky NP Lang CH Teitel MP Chiarelli FF Kadlubar 《Canadian Metallurgical Quarterly》1994,15(8):1695-1701
The food-borne carcinogenic and mutagenic heterocyclic aromatic amines undergo bioactivation to the corresponding N-hydroxy (OH)-arylamines and the subsequent N-glucuronidation of these metabolites is regarded as an important detoxification reaction. In this study, the rates of glucuronidation for the N-OH derivatives of 2-amino-3-methylimidazo[4,5-f]-quinoline (IQ), 2-amino-1-methyl-6-phenylimidazo[4,5-b]-pyridine (PhIP), 2-amino-6-methyl-dipyrido[1,2-a:3',2'-d]imidazole (Glu-P-1) and 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) by liver microsomal glucuronosyltransferase were compared to that of the proximate human urinary bladder carcinogen, N-OH-aminobiphenyl (N-OH-ABP) and the proximate rat colon carcinogen N-OH-3,2'-dimethyl-4-amino-biphenyl (N-OH-DMABP). Human liver microsomes catalyzed the uridine 5'-diphosphoglucuronic acid (UDPGA)-dependent glucuroidation of N-OH-IQ, N-OH-PhIP, N-OH-Glu-P-1 and N-OH-MeIQx at rates of 59%, 42%, 35% and 27%, respectively, of that measured for N-OH-ABP (11.5 nmol/min/mg). Rat liver microsomes also catalyzed the UDPGA-dependent glucuronidation of N-OH-PhIP, N-OH-Glu-P-1 and N-OH-IQ at rates of 30%, 20% and 10%, respectively of that measured for N-OH-DMABP (11.2 nmol/min/mg); activity towards N-OH-MeIQx was not detected. Two glucuronide(s) of N-OH-PhIP, designated I and II, were separated by HPLC. Conjugate II was found to be chromatographically and spectrally identical with a previously reported major biliary metabolite of PhIP in the rat, while conjugate I was identical with a major urinary metabolite of PhIP in the dog. Hepatic microsomes from rat, dog and human were found to catalyze the formation of both conjugates. The rat preferentially formed conjugate II (I to II ratio of 1:15), while the dog and human formed higher relative amounts of conjugate I (I to II ratio of 2.5:1.0 and 1.3:1.0 respectively). Fast atom bombardment mass spectrometry of conjugates I and II gave the corresponding molecular ions and showed nearly identical primary spectra. However, collision-induced spectra were distinct and were consistent with the identity of conjugates I and II as structural isomers. Moreover, the UV spectrum of conjugate I exhibited a lambda max at 317 nm and was essentially identical to that of N-OH-PhIP, while conjugate II was markedly different with a lambda max of 331 nm. Both conjugates were stable in 0.1 N HCl and were resistant to hydrolysis by rat, dog and human liver microsomal beta-glucuronidases.(ABSTRACT TRUNCATED AT 400 WORDS) 相似文献