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排序方式: 共有797条查询结果,搜索用时 15 毫秒
101.
P Rajagopal EB Waygood J Reizer MH Saier RE Klevit 《Canadian Metallurgical Quarterly》1997,6(12):2624-2627
Chemical shift mapping is becoming a popular method for studying protein-protein interactions in solution. The technique is used to identify putative sites of interaction on a protein surface by detecting chemical shift perturbations in simple (1H, 15N)-HSQC NMR spectra of a uniformly labeled protein as a function of added (unlabeled) target protein. The high concentrations required for these experiments raise questions concerning the possibility for non-specific interactions being detected, thereby compromising the information obtained. We demonstrate here that the simple chemical shift mapping approach faithfully reproduces the known functional specificities among pairs of closely related proteins from the phosphoenolpyruvate:sugar phosphotransferase systems of Escherichia coli and Bacillus subtilis. 相似文献
102.
LM Rodriguez JL Smeets C Timmermans D Blommaert JM van Dantzig EB de Muinck HJ Wellens 《Canadian Metallurgical Quarterly》1997,8(7):803-806
INTRODUCTION: Incessant monomorphic ventricular tachycardia (VT) with a right bundle branch block morphology and a northwest axis is a rare arrhythmic complication in a patient with hypertrophic cardiomyopathy and apical left ventricular aneurysm. METHODS AND RESULTS: The origin of this VT was localized using the following criteria: the presence of entrainment without fusion, equal intervals from the stimulus to the beginning of the QRS complex and from the electrogram to the QRS complex during VT, and the first postpacing interval identical to the tachycardia cycle length. Radiofrequency energy applied to the septoapical part of the apical left ventricular aneurysm terminated the tachycardia within 2 seconds. CONCLUSION: Using criteria to guide radiofrequency (RF) ablation of VT in patients with coronary artery disease, an incessant monomorphic VT in a patient with hypertrophic cardiomyopathy was successfully ablated. 相似文献
103.
The effect of (+)-5-oxo-D-prolinepiperidinamide monohydrate (NS-105), a novel cognition enhancer, on adenylate cyclase activity was investigated in cultured neurons of the mouse cerebral cortex. NS-105 (10(-7) and 10(-6) M) inhibited forskolin-stimulated cyclic AMP formation, an action that was dependent on pertussis toxin-sensitive G proteins. Conversely, in pertussis toxin-pretreated neurons, NS-105 (10(-7)-10(-5) M) significantly enhanced the forskolin-stimulated cyclic AMP formation, and this action was completely reversed by cholera toxin. A metabotropic glutamate receptor agonist (1S, 3R)-1-aminocyclopentane-1,3-dicarboxylic acid (1S, 3R-ACPD) produced similar bi-directional actions on the cyclic AMP formation. Both of these inhibitory and facilitatory actions of NS-105 and 1S, 3R-ACPD were blocked by L(+)-2-amino-3-phosphopropinoic acid (L-AP3). NS-105 (10(-6) M) and 1S, 3R-ACPD (10(-4) M) significantly enhanced isoproterenol- and adenosine-stimulated cyclic AMP formation. The enhancement of such Gs-coupled receptor agonists-stimulated cyclic AMP formation was also produced by quisqualate but not by L(+)-2-amino-4-phosphonobutanoate (L-AP4). The phosphoinositides hydrolysis was enhanced by 1S, 3R-ACPD (10(-4) M) but not by NS-105 (10(-6) M), however, 1S, 3R-ACPD-induced increase in phosphoinositides turnover was attenuated by NS-105. These findings suggest that NS-105 stimulates metabotropic glutamate receptor subclasses that are coupled both negatively and positively to adenylate cyclase, but it acts as an antagonist at the receptor subclasses that are linked to phosphoinositides hydrolysis. 相似文献
104.
Peripheral chemoreceptors are commonly thought to respond to hypoxia by releasing neurotransmitters from the type 1 cells of the carotid body; these molecules then bind to post-synaptic receptors on the carotid sinus nerve. The tachykinin substance P (SP) may act as an important neurotransmitter/neuromodulator in hypoxic chemotransmission in peripheral arterial chemoreceptors. In order to elucidate the role of SP in modulating hypoxic chemotransmission, we have used quantitative in situ hybridization histochemistry, to determine the effect of hypoxia on SP gene induction, and the localization of neurokinin 1 (NK-1) receptor mRNA in the carotid body and petrosal ganglia complex in rats at 21 days post-natal age. For comparison, we also determined: (1) the effect of hypoxia on tyrosine hydroxylase (TH) gene induction and (2) the localization of the mRNA encoding the D2-dopamine receptor. SP mRNA was not detected in the rat carotid body during normoxia and its expression was not induced after a 1 h of exposure to hypoxia (10% O2/90% N2), a stimulus that was sufficient to cause a significant increase (P < 0.01) in TH mRNA levels in the carotid body. Both SP and TH mRNAs were abundantly expressed in multiple cells in the petrosal and the jugular ganglia. However, these mRNAs were not co-localized and SP and TH mRNA levels were not affected by hypoxia in these ganglia. Although D2-dopamine receptor mRNA was abundantly expressed in the rat carotid body, we found no evidence of NK-1 receptor mRNA in the carotid body. In contrast, both NK-1 receptor mRNA and D2-dopamine receptor mRNA were present in petrosal ganglion cells. In the rat, SP does not appear to modulate hypoxic chemotransmission by being made in and released from type 1 cells in the carotid body, and neither does SP modulate the activity of type 1 cells by binding to NK-1 receptors on these cells. 相似文献
105.
EA Cummings EB Sochett MG Dekker ML Lawson D Daneman 《Canadian Metallurgical Quarterly》1998,47(8):1341-1346
In children and adolescents with type 1 diabetes, we have reported an association between duration of puberty and the prevalence of nephromegaly and microalbuminuria (MA), which are early markers of diabetic nephropathy. Growth hormone (GH), IGF-I, testosterone, and prorenin are potential mediators of this effect. This study examined the relationship of these hormonal factors to kidney volume (KV) and MA in 155 subjects (78 males, age 13.2 +/- 3.5 years [mean +/- SD]) with similar diabetes duration (6.83 +/- 1.6 years) but varying pubertal experience (0-10 years). KV (by ultrasound), plasma IGF-I, testosterone, prorenin, and NaLi countertransport, and urinary albumin, urinary GH, and urinary IGF-I from three 24-h collections were measured. Multiple regression analysis showed that BSA (P < 0.0001) and urinary IGF-I (P = 0.001) were significantly associated with KV. MA subjects (albumin excretion rate 15-200 microg/min) had higher urinary IGF-I (P = 0.005) and urinary GH (P = 0.05) compared with normoalbuminuric subjects. Only 9% of the variance in urinary IGF-I could be attributed to plasma IGF-I (r = 0.30, P < 0.0001). Testosterone and prorenin were not associated with MA, but they were associated with KV in univariate analyses. The strong association of urinary IGF-I with KV, a marker for glomerular hypertrophy, and of both urinary IGF-I and urinary GH with MA suggests a role for these growth factors in the development of human diabetic nephropathy. Together, these data support animal studies that have shown that renal GH and IGF-I may contribute significantly to the pathogenesis of early diabetic nephropathy. 相似文献
106.
A 62 element MRI-compatible linear phased array was designed and constructed to investigate the feasibility of using transrectal ultrasound for the thermal therapeutic treatment of prostate cancer and benign prostatic hyperplasia. An aperiodic design technique developed in a previous study was used in the design of this array, which resulted in reduced grating lobe levels by using an optimized random distribution of unequally sized elements. The element sizes used in this array were selected to be favorable for both grating lobe levels as determined by array aperiodicity and array efficiency as determined by width to thickness ratios. The heating capabilities and MRI compatibility of the array were tested with in vivo rabbit thigh muscle heating experiments using MRI temperature monitoring. The array produced therapeutic temperature elevations in vivo at depths of 3-6 cm and axial locations up to 3 cm off the central axis and increased the size of the heated volume with electronic scanning of a single focus. The ability of this array to be used for ultrasound surgery was demonstrated by creating necrosed tissue lesions in vivo using short high-power sonications. The ability of the array to be used for hyperthermia was demonstrated by inducing therapeutic temperature elevations for longer exposures. Based on the acoustic and heating performance of this array, it has the potential to be clinically useful for delivering thermal therapies to the prostate and other target volumes close to body cavities. 相似文献
107.
WH Aldoori EL Giovannucci HR Rockett L Sampson EB Rimm WC Willett 《Canadian Metallurgical Quarterly》1998,128(4):714-719
To examine prospectively dietary fiber calculated from food composition values based on analytic techniques and specific dietary fiber types in relation to risk of diverticular disease, we analyzed data from a prospective cohort of 43,881 U.S. male health professionals 40-75 y of age at base line; subjects were free of diagnosed diverticular disease, colon or rectal polyps, ulcerative colitis and cancer. The insoluble component of fiber was inversely associated with risk of diverticular disease relative risk (RR) = 0. 63, 95% confidence interval (CI), 0.44-0.91, P for trend = 0.02, and this association was particularly strong for cellulose (RR = 0.52, 95% CI, 0.36-0.75, P for trend = 0.002). The association between diverticular disease and total dietary fiber intake calculated from the AOACstandards method was not appreciably different from results using the Southgate or Englyst method [for AOAC method, RR = 0.60, 95% CI, 0.41-0.87; for Southgate method, RR = 0.61, 95% CI, 0.42-0. 88; for Englyst method, RR = 0.60, 95% CI, 0.42-0.87, for the highest quintiles]. Our findings provide evidence for the hypothesis that a diet high in dietary fiber decreases the risk of diverticular disease, and this result was not sensitive to the use of different analytic techniques to define dietary fiber. Our findings suggest that the insoluble component of fiber was significantly associated with a decreased risk of diverticular disease, and this inverse association was particularly strong for cellulose. 相似文献
108.
SF Keevil B Barbiroli JC Brooks EB Cady R Canese P Carlier DJ Collins P Gilligan G Gobbi J Hennig H Kügel MO Leach D Metzler V Mlynárik E Moser MC Newbold GS Payne P Ring JN Roberts IJ Rowland T Thiel I Tkác S Topp HJ Wittsack F Podo 《Canadian Metallurgical Quarterly》1998,16(9):1093-1106
We have performed a multicentre trial to assess the performance of three techniques for absolute quantification of cerebral metabolites using in vivo proton nuclear magnetic resonance (NMR). The techniques included were 1) an internal water standard method, 2) an external standard method based on phantom replacement, and 3) a more sophisticated method incorporating elements of both the internal and external standard approaches, together with compartmental analysis of brain water. Only the internal water standard technique could be readily implemented at all participating sites and gave acceptable precision and interlaboratory reproducibility. This method was insensitive to many of the experimental factors affecting the performance of the alternative techniques, including effects related to loading, standing waves and B1 inhomogeneities; and practical issues of phantom positioning, user expertise and examination duration. However, the internal water standard method assumes a value for the concentration of NMR-visible water within the spectroscopic volume of interest. In general, it is necessary to modify this assumed concentration on the basis of the grey matter, white matter and cerebrospinal fluid (CSF) content of the volume, and the NMR-visible water content of the grey and white matter fractions. Combining data from 11 sites, the concentrations of the principal NMR-visible metabolites in the brains of healthy subjects (age range 20-35 years) determined using the internal water standard method were (mean+/-SD): [NAA]=10.0+/-3.4 mM (n=53), [tCho]=1.9+/-1.0 mM (n=51), [Cr + PCr]=6.5+/-3.7 mM (n=51). Evidence of system instability and other sources of error at some participating sites reinforces the need for rigorous quality assurance in quantitative spectroscopy. 相似文献
109.
BL Chang LV Rubenstein EB Keeler LN Miura KL Kahn 《Canadian Metallurgical Quarterly》1996,5(4):298-303
PURPOSE: This study examined the validity of medical-record-based nursing assessment and monitoring of signs and symptoms (nursing surveillance) in predicting patients who were admitted to ICUs and those admitted to non-ICUs. The association of this assessment and monitoring with differences in an intermediate patient outcome, instability at discharge, was also explored. Patients admitted to either setting with a diagnosis of acute myocardial infarction, cerebrovascular accident, congestive heart failure, or pneumonia, were included in the study. METHOD: A secondary analysis was carried out using a subset of data originally collected for a quality-of-care study. Data from the medical records of 11,246 patients (52% female, 48% male) with a mean age of 76.4 years were used in the present study. RESULTS: ICU patients (n = 3969) were found to have a longer length of stay and to be sicker on admission than non-ICU patients (n = 7277). Overall, patients in the ICU received significantly higher nursing assessment and monitoring of signs and symptoms scores than non-ICU patients. Nursing assessment and monitoring of signs and symptoms scores were lower for patients discharged with greater instability for three of the four diseases (cerebrovascular accidents, congestive heart failure, and pneumonia). 相似文献
110.
Standard accounts of pure alexia have favoured the view that this acquired disorder of reading arises from damage to a left posterior occipital cortex mechanism dedicated to the processing of alphanumeric symbols. We challenge these accounts in two experiments and demonstrate that patients with this reading deficit are also impaired at object identification. In the first experiment, we show that a single subject, EL, who shows all the hallmark features of pure alexia, is impaired at picture identification across a large set of stimuli. As the visual complexity of pictures increases, so EL's reaction time to identify the stimuli increases disproportionately relative to the control subjects. In the second experiment, we confirm these findings with a larger group of five pure alexic patients using a selected subset of high- and low-visual complexity pictures. These findings suggest that the deficit giving rise to pure alexia is not restricted to orthographic symbols per se but, rather, is a consequence of damage to a more general-purpose visual processing mechanism. 相似文献