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Biomedical subjects

M S Johnson

Publications and source records attributed to M S Johnson.

At least 91 records · Page 5Linked to original sources
PubMed1999

Hemodialysis graft: use as access for upper and lower extremity arteriography and interventional procedures--initial experience.

Functioning hemodialysis grafts were used as access sites for peripheral vascular arteriography and interventional procedures. In 11 patients with end-stage renal disease and ischemia, upper extremity (n = 8) or lower extremity (n = 3) arteriography was performed successfully. Angioplasty and other interventional procedures were performed via the same route in two of the patients. No bleeding complications occurred, and all patients were ambulatory immediately after the procedure.

Angiography↗
PubMed1999

Tunneled jugular small-bore central catheters as an alternative to peripherally inserted central catheters for intermediate-term venous access in patients with hemodialysis and chronic renal insufficiency.

In 34 patients with chronic renal insufficiency or failure, 43 small-bore central catheters were placed via the internal or external jugular veins: right internal jugular vein, 28; left internal jugular vein, 14; right external jugular vein, one. Central venous access was achieved in all patients (mean catheter dwell time, 28 days; range, 3-99 days), with two minor complications (arterial puncture and catheter damage during suturing). Tunneled jugular small-bore central catheters are a vein-preserving alternative to peripherally inserted central catheters in this population.

Adolescent↗
PubMed1999

Scavenger receptor class B type I in the rat ovary: possible role in high density lipoprotein cholesterol uptake and in the recognition of apoptotic granulosa cells.

Scavenger receptor class B type I (SR-BI) mediates the selective uptake of high density lipoprotein cholesterol. SR-BI is expressed at high levels in the ovary, indicating that it plays a role in the delivery of cholesterol as substrate for steroid hormone production. However, SR-BI also binds anionic phospholipids with high affinity and could therefore be involved in the recognition of apoptotic cells. In this study we have characterized the expression of SR-BI in rat ovarian follicles undergoing atresia. Atretic follicles with cells undergoing apoptosis were identified by in situ DNA end labeling, and SR-BI expression was determined by in situ hybridization and immunohistochemistry. SR-BI was expressed in thecal cells at all stages of follicular development, including atretic follicles, and in corpus luteum. Isolated apoptotic granulosa cells (but not viable granulosa cells) bound annexin V, indicating that they display anionic phospholipids on the cell surface. Transfection of COS-7 cells with an expression vector carrying the rat SR-BI complementary DNA resulted in increased binding to apoptotic granulosa cells (46 +/- 2% of the SR-BI-expressing cells bound at least one granulosa cell compared with 24 +/- 3% for the mock-transfected cells; P < 0.0001), whereas the binding to viable granulosa cells was unchanged. Apoptotic granulosa cells also bound to isolated thecal shells. We conclude that thecal cells of both nonatretic and atretic follicles express SR-BI. The location of SR-BI expression in the ovary supports a role of this receptor in the uptake of high density lipoprotein cholesterol. In addition, our data suggest that SR-BI mediates the recognition of apoptotic granulosa cells by the surrounding thecal cells and that it therefore may play a role in the remodeling of atretic follicles to secondary interstitial cells.

Animals↗
PubMed1999

Physician use of diagnostic codes for child and adult abuse.

OBJECTIVE: To report on physician use of diagnostic codes for child and adult abuse according to national medical care utilization data. METHODS: Secondary data analysis was performed on the National Ambulatory Medical Care Survey (NAMCS) of office-based physician visits and the National Hospital Ambulatory Medical Care Survey (NHAMCS) of visits to hospital emergency and outpatient departments for 1993 to 1996. Both databases describe physician, patient, and visit characteristics, and variables include up to three diagnoses per visit. RESULTS: Only 93 diagnoses of child or adult abuse were coded for 351,359 patient visits during the four years. As we would expect, child abuse was diagnosed more often than adult abuse (67 v 26), and the majority of cases (n = 57) were visits to emergency departments. CONCLUSION: Diagnostic codes for abuse are not often used. Because these codes represent an important tool for reporting the prevalence and incidence of abuse, such documentation could lead to greater support for health care policies and resource allocation for victims of abuse. Lack of awareness about the diagnostic codes for abuse may be one explanation for underuse, but other barriers are also discussed.

Adult↗
PubMed1998

AMPA receptors and bacterial periplasmic amino acid-binding proteins share the ionic mechanism of ligand recognition.

In order to identify key structural determinants for ligand recognition, we subjected the ligand-binding domain of the alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA)-selective glutamate receptor GluR-D subunit to site-directed mutagenesis. Based on the analysis of the [3H]AMPA-binding properties of the mutated binding sites, we constructed a revised three-dimensional model of the ligand-binding site, different in many respects from previously published models. In particular, our results indicate that the residues Arg507 and Glu727 represent the structural and functional correlates of Arg77 and Asp161 in the homologous bacterial lysine/ornithine/arginine-binding protein and histidine-binding protein, and directly interact with the alpha-carboxyl and alpha-amino group of the bound ligand, respectively. In contrast, Glu424, implicated previously in ionic interactions with the alpha-amino group of the agonist, is unlikely to have such a role in ligand binding. Our results indicate that glutamate receptors share with the bacterial polar amino acid-binding proteins the fundamental mechanism of amino acid recognition.

Amino Acid Sequence↗
PubMed1998

Rewiring a receptor: negative output from positive input.

A point mutation or covalent modification in bacterial chemotaxis receptors causes bacteria to be repelled by attractants, and attracted to repellents. The variety of conditions causing inverse responses suggest that the signal transduction mechanism in receptors can be readily rewired to elicit inverse responses. A model is presented in which the orientation of a critical residue with respect to an active site determines whether the receptor produces normal or inverted signals. The model is consistent with observed responses and can be generalized to include receptors in other signal transduction systems.

Bacterial Proteins↗
PubMed1998

Surveillance for nonfatal work-related injuries in Alaska, 1991-1995.

Historically, Alaska has had an occupational fatality rate five times greater than that for the United States. This article reports recent surveillance results for hospitalized nonfatal work-related injuries in Alaska, using the population-based Alaska Trauma Registry (ATR) from 1991 through 1995. The fishing, construction, and logging industries led with the highest number of reported cases in the ATR. Workers in the logging, water transportation, and wood product manufacturing industries had the highest injury rates. Cause, severity, type, and body region of injury were examined for each target industry. For industries with the highest numbers and rates of injuries, in most cases, falls were identified as a common cause of injuries. A fractured bone was the most common type of injury, and the extremities were the most common body region affected. The ATR has proved to be a reliable tool for work-related injury surveillance and will be helpful in planning research priorities and targeting injury prevention efforts.

Accidental Falls↗
PubMed1998

Two "unrelated" families of ATP-dependent enzymes share extensive structural similarities about their cofactor binding sites.

Two proteins, D-alanine:D-alanine ligase and cAMP-dependent protein kinase, share a remarkable degree of structural convergence despite having different three-dimensional folds and different enzymatic functions. Here we report that as many as 103 residues from 10 segments form two identical super-secondary structures between which the cofactor ATP is bound. The cofactor, two bound metal cations, and several water molecules form a large network of electrostatic and hydrophobic interactions common to both enzymes, and these are mediated by the similar placement of equivalent amino acids within the common supersecondary structures.

Adenosine Triphosphate↗
PubMed1998

Enzyme-mononucleotide interactions: three different folds share common structural elements for ATP recognition.

Three ATP-dependent enzymes with different folds, cAMP-dependent protein kinase, D-Ala:D-Ala ligase and the alpha-subunit of the alpha2beta2 ribonucleotide reductase, have a similar organization of their ATP-binding sites. The most meaningful similarity was found over 23 structurally equivalent residues in each protein and includes three strands each from their beta-sheets, in addition to a connecting loop. The equivalent secondary structure elements in each of these enzymes donate four amino acids forming key hydrogen bonds responsible for the common orientation of the "AMP" moieties of their ATP-ligands. One lysine residue conserved throughout the three families binds the alpha-phosphate in each protein. The common fragments of structure also position some, but not all, of the equivalent residues involved in hydrophobic contacts with the adenine ring. These examples of convergent evolution reinforce the view that different proteins can fold in different ways to produce similar structures locally, and nature can take advantage of these features when structure and function demand it, as shown here for the common mode of ATP-binding by three unrelated proteins.

Adenine↗
PubMed1998

Effect of breathing on the detection of in vivo simulated pulmonary nodules by spiral CT.

OBJECTIVE: To determine the effect of breathing on the detection of small dense pulmonary nodules of threshold conspicuity by spiral computed tomography (SCT). MATERIALS AND METHODS: Forty pulmonary nodules of high density were created by endobronchial deployment of 2 and 4mm diameter beads in the peripheral airways of five anaesthetized dogs. SCT was performed during induced breath-hold and quiet breathing, using 5 mm collimation, pitch 2 and reconstruction of contiguous 5 mm slices. Scans were reviewed by six radiologists. Detection rates were measured as the number of nodules seen by at least one reader. The data was modelled using ordinal logistic regression for repeated measures, and the Wald Chi-square statistic used to test if there was a breath-hold vs. breathing effect on reader confidence level. RESULTS: There was no difference in detection rates for breath-hold vs. breathing SCT (28 vs. 25, respectively; P=0.48). This was also true when only the 2 mm nodules (n=24) were considered (12 vs. 11, respectively; P=0.77). Reader confidence level was significantly higher for breath-hold vs. breathing SCT (Wald Chi-square statistic with 6 degrees of freedom=19.0; P=0.0041). CONCLUSION: SCT can be performed during quiet breathing without a significant reduction the overall detection rate for small dense pulmonary nodules, though reader diagnostic confidence level is reduced.

Animals↗
PubMed1998

JOY: protein sequence-structure representation and analysis.

MOTIVATION: JOY is a program to annotate protein sequence alignments with three-dimensional (3D) structural features. It was developed to display 3D structural information in a sequence alignment and to help understand the conservation of amino acids in their specific local environments. RESULTS: : The JOY representation now constitutes an essential part of the two databases of protein structure alignments: HOMSTRAD (http://www-cryst.bioc.cam.ac.uk/homstrad ) and CAMPASS (http://www-cryst.bioc.cam.ac. uk/campass). It has also been successfully used for identifying distant evolutionary relationships. AVAILABILITY: The program can be obtained via anonymous ftp from torsa.bioc.cam.ac.uk from the directory /pub/joy/. The address for the JOY server is http://www-cryst.bioc.cam.ac.uk/cgi-bin/joy.cgi. CONTACT: kenji@cryst.bioc.cam.ac.uk

Amino Acid Sequence↗
PubMed1998

The core domain of retrotransposon integrase in Hordeum: predicted structure and evolution.

Propagation of long terminal repeat (LTR)-bearing retrotransposons and retroviruses requires integrase (IN, EC 2.7.7.-), encoded by the retroelements themselves, which mediates the insertion of cDNA copies back into the genome. An active retrotransposon family, BARE-1, comprises approximately 7% of the barley (Hordeum vulgare subsp. vulgare) genome. We have generated models for the secondary and tertiary structure of BARE-1 IN and demonstrate their similarity to structures for human immunodeficiency virus 1 and avian sarcoma virus INs. The IN core domains were compared for 80 clones from 28 Hordeum accessions representative of the diversity of the genus. Based on the structural model, variations in the predicted, aligned translations from these clones would have minimal structural and functional effects on the encoded enzymes. This indicates that Hordeum retrotransposon IN has been under purifying selection to maintain a structure typical of retroviral INs. These represent the first such analyses for plant INs.

Amino Acid Sequence↗
PubMed1998

Structural model of the catalytic domain of an enzyme with cell adhesion activity: human vascular adhesion protein-1 (HVAP-1) D4 domain is an amine oxidase.

Human vascular adhesion protein-1 (HVAP-1) is a multifunctional protein having at least two different cellular roles, functioning both as a lymphocyte-endothelial cell adhesion protein and as an enzyme with monoamine oxidase activity. HVAP-1 is a 180 kDa homodimeric glycoprotein consisting of a membrane-spanning domain and three predicted extracellular copper-containing amine oxidase domains. In HVAP-1 the extracellular domains are composed of a large domain D4, containing the active site and forming the interface of the dimer, while the smaller D2 and D3 domains surround the D4 dimer near the entrance to the active site. The structural model of the catalytic D4 domain of HVAP-1 reveals that all components necessary for enzymatic monoamine oxidase activity are indeed present within the HVAP-1 and pinpoints residues that may be key to substrate entry through a channel to the active site and residues likely to be involved in substrate specificity as well as structural features critical to dimer formation. Proper glycosylation is required for the cell adhesion function of HVAP-1 and the predicted location of the sugar units at the solvent-exposed surface suits this function well.

Amine Oxidase (Copper-Containing)↗
PubMed1998

Radiologic percutaneous gastrostomy: results in 56 patients with head and neck cancer.

OBJECTIVE: The establishment of a direct enteral feeding route is critical in the overall treatment of many patients with head and neck cancer. Use of radiologic percutaneous gastrostomy (RPG), the newest technique for gaining enteral access, has not been studied in such patients extensively. This study evaluated the indications, technique, success rate, and complications associated with RPG in patients with head and neck cancer. STUDY DESIGN: Retrospective. METHODS: A comprehensive chart review was undertaken of 56 patients with head and neck cancer treated at a tertiary care institution who had undergone successful or attempted RPG at some point during their treatment course. RESULTS: Most study patients had advanced oropharyngeal squamous cell carcinoma. The most frequent indications for RPG were dysphagia/aspiration following tumor resection (n = 26) and dysphagia following completion of single- or combined-modality therapy (n = 22). The success rate of attempted RPGs was 98.2%. The overall complication rate for RPG was 12.7% (10.9% minor and 1.8% major). CONCLUSIONS: RPG is a valuable tool for establishing enteral nutrition in patients with head and neck cancer. Advantages of RPG include high success rate despite obstructing lesions, low complication rate, time efficiency and scheduling ease compared with intraoperative percutaneous gastrostomy (PEG) by a second team, no reported tumor seeding of the tube site, and the fact that postoperative RPG allows for more accurate selection of patients who require a gastrostomy tube.

Adult↗
PubMed1998

Possible pulmonary embolus: evaluation with digital subtraction versus cut-film angiography--prospective study in 80 patients.

PURPOSE: To determine whether intraarterial digital subtraction angiography (DSA) is as accurate as cut-film (film hard-copy) angiography (CFA) in the evaluation of suspected pulmonary embolus. MATERIALS AND METHODS: Under a protocol approved by the institutional review board, CFA and DSA images were obtained in identical posteroanterior and oblique projections in one lung of each patient undergoing pulmonary angiography (n = 80). Diagnoses based on results of blinded review of each study (CFA vs DSA) by three separate reviewers (80 patients x three reviewers = 240 diagnoses for each modality) were compared with the diagnoses made by the physician who performed the procedure on the basis of CFA, DSA, and clinical data and with the consensus diagnoses obtained by means of group review of both studies together if necessary. The reviewers' confidence in their diagnoses was graded from 1 (certain) to 10 (uncertain). RESULTS: Pulmonary emboli were present in 13 (16%) of 80 patients. Two hundred thirty-six (98.3%) of 240 DSA diagnoses and 231 (96.3%) of 240 CFA diagnoses were correct. The sensitivity (correct identification of emboli by all three reviewers) of DSA was 92% and of CFA was 69% (P = .083). The specificities of the modalities were not statistically significantly different. The reviewers' confidence was significantly better in their DSA diagnoses than in their CFA diagnoses (P < .004). CONCLUSION: DSA allows more confident detection of pulmonary embolus than does CFA, with no loss in diagnostic accuracy.

Adult↗
PubMed1998

Tunneled hemodialysis catheters: use of a silver-coated catheter for prevention of infection--a randomized study.

PURPOSE: To determine whether silver-coated tunneled hemodialysis catheters reduce infection and to determine the frequency of central venous thrombosis and stenosis with percutaneous placement of right internal jugular vein dialysis catheters by interventional radiologists. MATERIALS AND METHODS: Ninety-one patients were randomly assigned to a treatment (silver-coated catheter; n = 47) or control (identical catheter without silver coating; n = 44) arm. Baseline venography was performed. Catheter tips were cultured and venography was repeated at catheter removal. RESULTS: Mean duration of catheter placement was 92 days. Infection occurred in 11 patients (five in the treatment group, six in the control group). Tip cultures in 15 patients (eight treatment, seven control) were positive without clinical infection. Infection and colonization rates were slightly but not significantly higher in the treatment group than in the control group. Silver-coated catheters in two (4%) patients were removed due to reaction to the coating. Completion venograms (n = 72) showed new minor abnormalities in four (6%) patients and major abnormalities (stenosis, thrombosis) in three (4%) patients. Permanent venous abnormalities occurred in two (3%) patients. CONCLUSION: Silver coating does not confer a benefit against clinical infection or colonization. Interventional radiologic placement of tunneled dialysis catheters yields a low frequency of permanent central venous thrombosis and stenosis.

Bacteria↗