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1.
2.
The bias due to incomplete matching 总被引:8,自引:0,他引:8
Observational studies comparing groups of treated and control units are often used to estimate the effects caused by treatments. Matching is a method for sampling a large reservoir of potential controls to produce a control group of modest size that is ostensibly similar to the treated group. In practice, there is a trade-off between the desires to find matches for all treated units and to obtain matched treated-control pairs that are extremely similar to each other. We derive expressions for the bias in the average matched pair difference due to the failure to match all treated units--incomplete matching, and the failure to obtain exact matches--inexact matching. A practical example shows that the bias due to incomplete matching can be severe, and moreover, can be avoided entirely by using an appropriate multivariate nearest available matching algorithm, which, in the example, leaves only a small residual bias due to inexact matching. 相似文献
3.
Chlamydomonas alpha-tubulin is posttranslationally modified by acetylation on the epsilon-amino group of a lysine 总被引:25,自引:0,他引:25
Previous work has shown that the principal alpha-tubulin within Chlamydomonas reinhardtii flagellar axonemes differs from the major alpha-tubulin in the cell body. These two variants of alpha-tubulin are related to one another since posttranslational modification of the cell body form converts it to the axonemal form. When flagella are induced to assemble in the absence of de novo protein synthesis, tritiated acetate can be used to posttranslationally label alpha-tubulin in vivo, and under these conditions, no other flagellar polypeptides exhibit detectable labeling [L'Hernault, S. W., & Rosenbaum, J. L. (1983) J. Cell Biol. 97, 258-263]. In the present report, this labeling method has been used to provide material for chemical analysis of the tritiated moiety that is posttranslationally added to flagellar alpha-tubulin. This radioactivity was volatile after acid hydrolysis, suggesting that the posttranslational modification is the addition of neither an amino acid nor carbohydrate. Treatment of posttranslationally 3H-labeled alpha-tubulin with hydrazine yields radioactive acetylhydrazine, indicating that the moiety involved in posttranslational modification is an acetyl group. Analysis of complete proteolytic digests by thin-layer chromatography has revealed that this acetyl group is located on the epsilon-amino group of a flagellar alpha-tubulin lysine residue. 相似文献
4.
Discriminant analysis was used to explore multivariate associations with ABO blood types in a biracial sample of 898 Bogalusa youths. Dependent variables included blood pressure (systolic and diastolic), serum lipid and lipoprotein levels (total cholesterol, alpha-, beta-, and pre-beta-lipoprotein cholesterol, and triglycerides), and anthropometric variables (height, weight, right arm length, triceps skinfold thickness, and a computed ponderal index). Analyses performed within race showed that several variables including beta-lipoprotein cholesterol, systolic blood pressure, and the ponderal index were sufficient to discriminate between individuals possessing the B antigen (B and AB) and those not possessing the B antigen (A and O) in the White subsample. However, height in itself can account for the detected difference, B individuals being taller than non-B individuals by a mean value of 2.4 cm. A concordant, but not significant effect was found in the Black subsample. Further tests support the conclusion that the strongest association is between ABO blood type and height. 相似文献
5.
The effect of endotoxin and endotoxin tolerance on inflammation induced by mycobacterial adjuvant 总被引:1,自引:0,他引:1
Peptidoglycan, the substance in mycobacteria thought to be responsible for inducing adjuvant arthritis, and endotoxin (lipopolysaccharide or LPS) share many inflammatory properties. Since repeated administration of LPS produces tolerance, i.e., resistance to the toxic and inflammatory effects of LPS, we tested whether LPS and/or LPS tolerance might influence inflammation due to mycobacterial adjuvant. Male Sprague-Dawley rats were injected with Escherichia coli LPS or saline intraperitoneally and then challenged with 100 micrograms killed Mycobacteria butyricum (adjuvant) in the footpad. A single dose of 100 micrograms LPS three or 24 hours before adjuvant markedly, but transiently, reduced the local footpad swelling that begins within hours of the adjuvant injection and histologically resembles a sterile abscess. Animals that received multiple doses of LPS and were therefore tolerant or animals that received LPS 72 hours before adjuvant demonstrated adjuvant-induced footpad swelling nearly equal to controls. The anti-inflammatory effect of LPS was transient since footpad swelling in all groups was nearly comparable six days after the adjuvant injection and LPS failed to inhibit consistently the arthritis that develops two or more weeks after adjuvant injection. These studies establish that LPS can markedly inhibit the prodrome of adjuvant arthritis (footpad swelling due to M. butyricum), that inhibition of this prodrome does not prevent the subsequent development of arthritis, and that LPS tolerance diminishes this anti-inflammatory effect of LPS. 相似文献
6.
E W Jabs C A Coss S J Hayflick T E Whitmore R M Pauli S J Kirkpatrick D A Meyers R Goldberg D W Day K N Rosenbaum 《Genomics》1991,11(1):188-192
Treacher Collins syndrome is an autosomal dominant condition of bilateral craniofacial abnormalities of structures derived from the first and second branchial arches. A patient with severe manifestations of Treacher Collins syndrome and a de novo chromosomal deletion in region 4p15.32----p14 was identified. Anonymous DNA sequences of loci D4S18, D4S19, D4S20, D4S22, and D4S23 were mapped to the deleted region. DNA probes previously mapped to loci on chromosome 4p (D4S10, D4S15, D4S16, D4S26, D4S35, D4S95, D4S144, RAF1P1, QDPR, and HOX7) were not deleted in this patient. Linkage analysis between the D4S18, D4S23, and QDPR loci and Treacher Collins syndrome in eight families excluded the Treacher Collins syndrome locus from the region of the deletion. 相似文献
7.
Over the past decade, microbial electrochemical technologies, originally developed from an interesting physiological phenomenon, have evolved from a rush of initiatives for sustainable bioelectricity generation to a multitude of specialized applications in very different areas. Genetic engineering of microbial biocatalysts for target bioelectrochemical applications like biosensing or bioremediation, as well as the discovery of entirely new bioelectrochemical processes such as microbial electrosynthesis of commodity chemicals, open up completely new possibilities. Where stands this technology today? And what are the general and specific challenges it faces not only scientifically but also for transition into commercial applications? This review intends to summarize the recent advances and provides a perspective on future developments. 相似文献
8.
Romano Ngui Noor Amira Abdul Halim Yamuna Rajoo Yvonne AL Lim Stephen Ambu Komalaveni Rajoo Tey Siew Chang Lu Chan Woon Rohela Mahmud 《The Korean journal of parasitology》2016,54(5):673-678
Epidemiological study on strongyloidiasis in humans is currently lacking in Malaysia. Thus, a cross-sectional study was carried out to determine the prevalence of Strongyloides stercoralis infection among the inhabitants of longhouse indigenous communities in Sarawak. A single stool and blood sample were collected from each participant and subjected to microscopy, serological and molecular techniques. Five species of intestinal parasites were identified by stool microscopy. None of the stool samples were positive for S. stercoralis. However, 11% of 236 serum samples were seropositive for strongyloidiasis. Further confirmation using molecular technique on stool samples of the seropositive individuals successfully amplified 5 samples, suggesting current active infections. The prevalence was significantly higher in adult males and tended to increase with age. S. stercoralis should no longer be neglected in any intestinal parasitic survey. Combination of more than 1 diagnostic technique is necessary to increase the likelihood of estimating the ‘true’ prevalence of S. stercoralis. 相似文献
9.
Paced QRS morphology predicts incident left ventricular systolic dysfunction and atrial fibrillation
Martin van Zyl Chance M. Witt Subir Bhatia Majd Khasawneh Prakriti Gaba Charles J. Lenz Andrew N. Rosenbaum Htin Aung David O. Hodge Christopher J. McLeod Samuel J. Asirvatham 《Indian pacing and electrophysiology journal》2019,19(2):40-46
Background
The prognostic significance of paced QRS complex morphology on surface ECG remains unclear. This study aimed to assess long-term outcomes associated with variations in the paced QRS complex.Methods
Adult patients who underwent dual-chamber pacemaker implantation with 20% or more ventricular pacing and a 12-lead ECG showing a paced complex were included. The paced QRS was analyzed in leads I and aVL. Long-term clinical and echocardiographic outcomes were compared at 5 years.Results
The study included 844 patients (43.1% female; age 75.0?±?12.1). Patients with a longer paced QRS (pQRS) duration in lead I had a lower rate of atrial fibrillation (HR 0.80; p?=?0.03) and higher rate of systolic dysfunction (HR 1.17; p?<?0.001). Total pacing complex (TPC) duration was linked to higher rates of ICD implantation (HR 1.18; p?=?0.04) and systolic dysfunction (HR 1.22, p?<?0.001). Longer paced intrinsicoid deflection (pID) was associated with less atrial fibrillation (HR 0.75; p?=?0.01), more systolic dysfunction (HR 1.17; p?<?0.001), ICD implantation (HR 1.23; p?=?0.04), and CRT upgrade (HR 1.23; p?=?0.03). Exceeding thresholds for TPC, pQRS, and pID of 170, 146, and 112?ms in lead I, respectively, was associated with a substantial increase in systolic dysfunction over 5 years (p?<?0.001).Conclusions
Longer durations of all tested parameters in lead I were associated with increased rates of left ventricular systolic dysfunction. ICD implantation and CRT upgrade were also linked to increased TPC and pID durations. Paradoxically, patients with longer pID and pQRS had less incident atrial fibrillation. 相似文献10.
Katrin Bierhals Anna C Sondersorg Chiann-Tso Lin Claudia Rosenbaum Herbert Waldmann Frank Wehner 《Cellular physiology and biochemistry》2007,20(5):397-404
We were interested whether PKC alpha, delta, epsilon or zeta is the isoform actually employed in the activation of hypertonicity-induced cation channels (HICCs) in primary cultures of rat hepatocytes. Quantitative SDS-page and Western-blot experiments revealed that PKC alpha, delta and epsilon were stimulated by Indolactam V (as a DAG substitute for activation of c and nPKCs) but that only PKC delta and epsilon did respond to hypertonic stress. Furthermore, chelation of intracellular Ca(++) by BAPTA-AM did not alter HICC activation in cable-analysis experiments whereas Indolactam V as well as V8 (an Indolactam derivative specific for PKC delta and epsilon) activated HICC currents under isotonic conditions. Finally, by use of Rottlerin (as an inhibitor exhibiting a slight preference for PKC delta over epsilon) PKC epsilon could be identified as the most likely isoform responsible for the activation of the HICC. 相似文献