The symmetrical dimer structure of tryptophanyl-tRNA synthetase is similar to that of tyrosyl-tRNA synthetase whose binding behavior and structural details have been elucidated in detail. The ...structure of both subunits after forming the intermediate tryptophanyl-AMP has important implications for the binding of the cognate tRNATrp. Single tryptophan mutants of Bacillus stearothermophilus tryptophanyl-tRNA synthetase have been constructed and expressed and used to probe structural changes in different domains of the enzyme in both subunits. Substrate titrations using the Trp analogues 4-fluorotryptophan and 7-azatryptophan in the presence of ATP to form the corresponding aminoacyl-adenylate reveal significant structural changes occurring throughout the active subunit in regions not confined to the active site. Changes in environment around the specific Trp residues were monitored using UV absorbance and steady-state fluorescence measurements. When titrated with 4-fluorotryptophan, both Trp 91 and Trp 290 fluorescence is quenched (49 and 22%, respectively) when one subunit has formed Trp-AMP. The fluorescence of Trp 48 is enhanced 19%. No further change in signal was observed after a 1:1 dimer/l-4FW-AMP complex ratio had been established. Using an anion-exchange filter binding assay with radiolabeled l-Trp as a substrate, binding to only one subunit was observed under nonsaturating conditions. This agrees with the results of the assay using 7-azatryptohan as a substrate. The observed changes extend to the unfilled subunit where a similar structure is believed to form after one subunit has formed tryptophan-AMP. Movement in the regions of the enzyme containing Trp 290 and Trp 91 suggests a mechanism for cross-subunit communication involving the helical backbone and dimer interface containing these two residues.
Anterior cervical plate (ACP) failure is rarely addressed in the literature. In this retrospective, observational, longitudinal, cohort study, the objectives were to (1) identify incidences of in ...vivo biomechanical failure in commercially available, US Food and Drug Administration-approved ACP systems, (2) describe modes of failure, (3) suggest structural explanations for system failure, and (4) discuss complications and treatment of patients with failed ACP systems. Investigators retrospectively identified patients who underwent anterior cervical procedures followed by use of ACP as a fusion adjunct and showed evidence of ACP failure on plain radiographs. Components of the ACP system that led to failure were identified and examined. A total of 240 patients received ACP supplementation of anterior cervical fusion constructs during the 9.5-y study period. Evidence of ACP failure was noted in 7 patients (3.3%), and an eighth patient was referred for evaluation after ACP failure. Screw-plate interface failure occurred in all 8 cases. The biomechanical method by which the bone screw head was secured into the vertebral body, or against the ACP, the use of hybrid systems, the surgical technique selected, and host factors were used to determine the rate of failure. Concern for esophageal or other tissue injury often necessitated ACP removal. Screw-plate interface failure, which was found to be the most common mode of biomechanical ACP failure, may occur in hybrid constructs and in systems that do not create a rigid interface between the screw head and the ACP. Surgical technique and patient host factors may also influence the rate of biomechanical construct failure.
Bladder exstrophy is a complex anomaly involving the urinary, genital, and intestinal tracts and the musculoskeletal system. The diagnosis is made typically at the newborn examination or on fetal ...ultrasonography that is performed by an experienced observer. Management of bladder exstrophy presents several challenges, beginning with initial repair using the more conventional staged approach or the recently re-popularized complete primary repair technique. Major goals in the management of bladder exstrophy are preservation of normal kidney function, close observation for development of adequate bladder function including urinary continence, and provision of acceptable cosmesis and function of the external genitalia. This article provides a brief overview of bladder exstrophy and a detailed description of modern management.
The provision of computer support for collaborative work is a central concern for Information Systems (IS) research and practice. In this paper we present the details of an information flow study ...undertaken in the household division of a large European design and manufacturing company (Delta). The goal of the study was to elicit user requirements for a computer system to facilitate the collaborative work of new product design teams. These requirements form the basis for the design and development of a Web-based LIRE (Living Repository) prototype system, the functionalities, features, and rationale of which are discussed. We also present the results of the evaluation of LIRE by the users at Delta and our observations on enhancing the sophistication and usefulness of this class of system. A production version based on the prototype but using commercially available software is currently in use by the New Product Development group at Delta. PUBLICATION ABSTRACT
The Reply Verbalis, Joseph G., MD; Goldsmith, Steven R., MD; Greenberg, Arthur, MD ...
The American journal of medicine,
2014, Letnik:
127, Številka:
7
Journal Article
Preface
This classification summarizes the suprageneric taxonomy of the Bivalvia for the upcoming revision of the Bivalvia volumes of the Treatise on Invertebrate Paleontology, Part N.
Objective: The purpose of this study is to report the results of a novel procedure for femoral-distal bypass grafting using a composite graft with an adjunctive remote popliteal fistula distal to the ...prosthetic portion of the graft. This reconstruction was developed for use in limb salvage in the absence of satisfactory autogenous vein.
Method: Data were collected prospectively on all patients undergoing this procedure from January 1, 1993 to December 31, 1999. Graft patency was determined from follow-up duplex scanning. Patient survival was determined by clinic follow-up.
Results: A total of 43 procedures were performed in 38 patients. In 34 patients, 72 previous arterial operations had been previously performed on the ipsilateral limbs. There were 20 men and 18 women with a mean age of 72 years. The indication for surgery was limb salvage in all, with rest pain in 30, and tissue loss in 13. The outflow artery was the below-knee popliteal artery in 10 and a tibial artery in the remainder. Operative mortality was 6.8%. Mean follow up was 26.9 months. The primary patency was 54% at 12 months. Six reconstructions were revised for a primary assisted patency of 60% at 16 months. Secondary patency was 69% at 16 months. Patient survival was 62% at 2 years and 26% at 5 years.
Conclusions: The technique of composite grafting with remote popliteal arteriovenous fistula may be a useful alternative in infragenicular bypass when a satisfactory autogenous vein is not available. (J Vasc Surg 2002;36:330-5.)
Objectives. Cryptorchidism is associated with infertility, even in those patients with unilateral undescended testes. The mechanism for this infertility is not understood. We demonstrated recently ...that in mice, a stable nuclear matrix, a structural component of the nucleus that organizes DNA, is necessary for proper embryogenesis. We tested the hypothesis that spermatozoa from cryptorchid patients had unstable nuclear matrices.
Methods. Semen samples from 7 patients with a history of undescended testes and decreased fertility were tested for sperm nuclear matrix stability using our halo assay.
Results. All 7 patients were found to have unstable nuclear matrices, as compared with controls.
Conclusions. This preliminary study suggests that one factor in the decreased fertility of cryptorchid patients may be unstable sperm nuclear matrices.
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