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Biomedical subjects

M Welch

Publications and source records attributed to M Welch.

At least 19 recordsLinked to original sources
PubMed2001

Further insights into the mechanism of function of the response regulator CheY from crystallographic studies of the CheY--CheA(124--257) complex.

New crystallographic structures of the response regulator CheY in association with CheA(124--257), its binding domain in the kinase CheA, have been determined. In all crystal forms, the molecular interactions at the heterodimer interface are identical. Soaking experiments have been performed on the crystals using acetyl phosphate as phosphodonor to CheY. No phosphoryl group attached to Asp57 of CheY is visible from the electron density, but the response regulator in the CheY-CheA(124--257) complex may have undergone a phosphorylation-dephosphorylation process. The distribution of water molecules and the geometry of the active site have changed and are now similar to those of isolated CheY. In a second soaking experiment, imido-diphosphate, an inhibitor of the phosphorylation reaction, was used. This compound binds in the vicinity of the active site, close to the N-terminal part of the first alpha-helix. Together, these results suggest that the binding of CheY to CheA(124--257) generates a geometry of the active site that favours phosphorylation and that imido-diphosphate interferes with phosphorylation by precluding structural changes in this region.

Amino Acid Sequence↗
PubMed2000

Capsaicin-stimulated release of substance P from cultured dorsal root ganglion neurons: involvement of two distinct mechanisms.

Capsaicin, the pungent component of "hot" chili peppers, selectively activates a distinct population of primary sensory neurons responsive to noxious stimuli. Many of these fibres express neuropeptides including the tachykinin, substance P. Using cultured dorsal root ganglion neurons, we found that capsaicin (10 microM) stimulated a 2-fold increase in release of substance P in the absence of extracellular Ca(2+). Elevated potassium (75 mM) was unable to induce release under these conditions. The introduction of Ca(2+) enhanced capsaicin-induced release and brought about a robust response to potassium. Preincubation of cells with botulinum neurotoxin A (100 nM) completely blocked potassium-induced release but the capsaicin response, in the absence of Ca(2+), was unaffected. However, toxin treatment dramatically reduced capsaicin-stimulated release in the presence of Ca(2+). It is concluded that capsaicin induces release of substance P from dorsal root ganglion neurons via two mechanisms, one requiring extracellular Ca(2+) and the intact synaptosomal-associated protein 25 kDa (SNAP-25), and the other independent of extracellular Ca(2+) and not involving SNAP-25.

Animals↗
PubMed2000

N-acyl homoserine lactone binding to the CarR receptor determines quorum-sensing specificity in Erwinia.

Quorum sensing via an N-acyl homoserine lactone (HSL) pheromone controls the biosynthesis of a carbapenem antibiotic in Erwinia carotovora. Transcription of the carbapenem biosynthetic genes is dependent on the LuxR-type activator protein, CarR. Equilibrium binding of a range of HSL molecules, which are thought to activate CarR to bind to its DNA target sequence, was examined using fluorescence quenching, DNA bandshift analysis, limited proteolysis and reporter gene assays. CarR bound the most physiologically relevant ligand, N-(3-oxohexanoyl)-L-homoserine lactone, with a stoichiometry of two molecules of ligand per dimer of protein and a dissociation constant of 1.8 microM, in good agreement with the concentration of HSL required to activate carbapenem production in vivo. In the presence of HSL, CarR formed a very high molecular weight complex with its target DNA, indicating that the ligand causes the protein to multimerize. Chemical cross-linking analysis supported this interpretation. Our data show that the ability of a given HSL to facilitate CarR binding to its target DNA sequence is directly proportional to the affinity of the HSL for the protein.

Bacterial Proteins↗
PubMed2000

Longitudinal growth in infants and young children treated with budesonide inhalation suspension for persistent asthma.

BACKGROUND: Results of recent growth studies suggest that inhaled glucocorticosteroids may affect growth in children. OBJECTIVE: Three 52-week, open-label extension studies (studies A, B, and C) were conducted to compare the effects of budesonide inhalation suspension (BIS) with conventional asthma therapy (CAT) on long-term safety, including intermediate-term growth, in 3 different pediatric asthma populations. METHODS: Pediatric asthma patients (ages 6 months to 8 years) from 3 multicenter, randomized, 12-week, double-blind, placebo-controlled studies were eligible to enroll in the 52-week, open-label extension studies. The extension studies were multicenter, randomized, open-label, active-controlled, parallel-group studies performed at 26 centers in the United States. Subjects in each extension study were randomized in a 2:1 ratio to receive either BIS or CAT. BIS was initially administered at a dose of 0.5 mg once (studies A and C) or twice daily (study B), with attempts made at each clinical visit to gradually reduce the dose to the minimum effective dose that maintains asthma control, as judged by the investigator. CAT consisted of any available therapy for asthma, including inhaled glucocorticosteroids in studies B and C only. Height SD scores, growth velocity, and skeletal age (only in studies B and C) were examined. RESULTS: In total, 670 subjects were randomized; 223 subjects received CAT and 447 received BIS. Mean ages at entry were 63.0 months and 60.9 months in CAT and BIS groups, respectively. Median total daily doses of BIS ranged from 0.5 to 1. 0 mg and the mean duration of treatment exposure was 304 +/- 119 days and 342 +/- 83 days in CAT and BIS groups, respectively. Changes in height SD scores differed significantly between the BIS and CAT groups in study A (-0.19, P =.003), and there was a small, statistically significant decrease in growth velocity (-0.8 cm/y, P =.002) in the BIS-treated group compared with the CAT group. No significant differences were observed between BIS and CAT groups in the changes in height SD scores or in growth velocities in studies B (+0.10 and +0.7 cm/y, respectively) and C (+0.12 and +0.8 cm/y, respectively). No differences in skeletal age were observed between BIS and CAT groups in studies B and C. CONCLUSION: There was a small, statistically significant decrease in growth velocity in the BIS-treated group compared with the CAT group in the study (study A) where inhaled glucocorticosteroid use was prohibited before entry and in the CAT group during the study. In the studies (B and C) where inhaled glucocorticosteroids were allowed in the CAT group, no differences were observed in height SD scores or growth velocity. The clinical relevance of these effects, including impact on final adult height, remain to be determined in prospectively planned studies that assess growth in children.

Administration, Inhalation↗
PubMed2000

Peptidyl transferase: ancient and exiguous.

The finding that the universal ribosomal peptidyl transferase is an RNA enzyme casts new light on its ancient origins, on the use of transition state analogues for ribozymes, and on the role of selection-amplification in studies of molecular evolution.

Base Sequence↗
PubMed2000

Listening for the sounds of silence: a nursing consideration of caring for the politically tortured.

In 1997 Amnesty International reported that 115 out of 251 countries surveyed practised torture on their citizens. Many of these victims have been forced to flee their country of origin and become refugees in the West, in countries such as Australia, Canada, the UK and the United States. However, torture itself remains an unspoken and covert problem. In addition to the obvious traumatic effects, it may induce shame and dread on the part of the victim. It may be too terrifying and too painful to talk about, and yet may affect every aspect of a person's life (Forrest 1996). All too commonly a victim of torture may pass unnoticed or unrecognised because health care providers do not know how, or may be unwilling to engage with the issue. This paper will examine the implications for nurses of caring for the tortured. It will explore the nature of torture itself, who might be the perpetrators and who might be the victims (always acknowledging that nurses and other health care staff are often both), how victims of torture may present for health care, and the possible subjective perceptions of a torture victim when faced with a Western health care process and understanding. Finally, it will argue for an increase in awareness and sensitivity on the part of all nurses in all health care settings to the needs and sensibilities of victims of torture, and suggest that caring for them is the distillation of everything good nursing practice should be.

Empathy↗
PubMed2000

First, build the foundations: practical considerations in general practitioner-mental health service liaison.

The co-working relationship between general practitioners and local mental health services lies at the heart of the success of recent changes in mental health care. These changes have seen large-scale deinstitutionalisation, a shift to primary and community care, and a government policy of prevention and partnerships. This article outlines a liaison project developed jointly by the South-East New South Wales Division of General Practice and the Southern Area Mental Health Service to address these issues. We describe the development of a protocol of basic standards which were practical, pragmatic and possible and, when fully established, would be the foundation of effective, efficient and efficacious shared care in mental health.

Australia↗
PubMed1999

Enzymatic syntheses of 6-(4H-selenolo[3,2-b]pyrrolyl)-L-alanine, 4-(6H-selenolo[2,3-b]pyrrolyl)-L-alanine, and 6-(4H-furo[3,2-b]pyrrolyl-L-alanine.

6-(4H-Selenolo[3,2-b]pyrrolyl)-L-alanine 1, 4-(6H-selenolo[2,3-b]pyrrolyl)-L-alanine 2, and 6-(4H-furo[3,2-b]pyrrolyl)-L-alanine 3 have been synthesized via reactions of selenolo[3,2-b]pyrrole, selenolo[2,3-b]pyrrole, and furo[3,2-b]pyrrole, respectively, with L-serine. The reactions are catalyzed by Salmonella typhimurium tryptophan synthase.

Alanine↗
PubMed1999

DNA shuffling of subgenomic sequences of subtilisin.

DNA family shuffling of 26 protease genes was used to create a library of chimeric proteases that was screened for four distinct enzymatic properties. Multiple clones were identified that were significantly improved over any of the parental enzymes for each individual property. Family shuffling, also known as molecular breeding, efficiently created all of the combinations of parental properties, producing a great diversity of property combinations in the progeny enzymes. Thus, molecular breeding, like classical breeding, is a powerful tool for recombining existing diversity to tailor biological systems for multiple functional parameters.

Enzyme Stability↗
PubMed1999

Vascular surgical society of great britain and ireland: randomized double-blind study of dopexamine versus placebo in aortic surgery

BACKGROUND: Mechanisms involved in the development of colon- ic ischaemia are not fully understood and there are conflicting reports regarding predisposing factors. The aim of this study was to evaluate the effect of dopexamine hydrochloride on the incidence of colonic ischaemia following aortic surgery and to correlate immunohistochemical markers of inflammatory activation in its pathogenesis. METHODS: Thirty patients, of mean age 65 (range 46-84) years, undergoing elective infrarenal aortic surgery were randomized to receive a perioperative infusion of either dopexamine 2 &mgr;g kg-1 min-1 (n = 12) or 0.9 per cent saline placebo (n = 18). All patients underwent colonoscopy and biopsy following induction of anaesthesia and at 1 week after operation. Sections were stained with haematoxylin and eosin, and for mast cell tryptase (MCT), myeloperoxidase (MPO) and both the inducible (iNOS) and endothelial (eNOS) isoforms of nitric oxide synthase. Sections were analysed blindly and independently by two histopathologists. Patient and operative data were collected and stored separately. RESULTS: Colonic ischaemia was noted in nine patients based on microscopic findings. Endoscopy alone had a sensitivity of 56 per cent. There was a significantly lower incidence of colonic ischaemia in patients receiving dopexamine compared with placebo (P < 0.05). One death resulted from colonic infarction in the placebo group 11 days after operation. There was increased MPO and MCT expression in patients with histological evidence of ischaemia (P < 0.05); iNOS staining within the vascular (P = 0.001) and lamina propria (P < 0.05) components of the mucosa was also significantly greater. No association was found with eNOS. CONCLUSION: Perioperative dopexamine infusion confers a degree of protection to colonic mucosa following aortic surgery, possibly through an anti-inflammatory effect.

Journal Article↗
PubMed1999

A psycho for every generation.

For almost 40 years, thanks to Alfred Hitchcock's seminal film, the word Psycho has conjured up some of the strongest and most enduring, not to say frightening and even misleading images of mental illness in contemporary western culture. It has become a byword for terrifying homicidal impulses, the unpredictability of a deranged mind, and has created, in Norman Bates, an archetype for the Other. However, we must now accept that time has passed. There is now another Psycho with which we have to deal, so close in shot selection and script as to pass for identical. Gus van Sant has produced a Psycho for the 1990s--or so we might consider. This paper will examine the way in which the two films, one produced in 1960 and the second in 1988, deal with the notions of mental illness, madness and the construction of the Other. It will pay particular attention to the central character of Norman Bates, how and why he is so terrifying to us, how his madness is explained and demonstrated and what a deconstructed analysis of that portrayal may signal. It will consider the notion that, just as we have come to accept that every generation may produce its own interpretation of roles from the classical stage repertoire, such as Hamlet, every generation can and will interpret Psycho to mirror its own concerns.

Attitude to Health↗
PubMed1999

Variations of the pursestring suture in skin cancer reconstruction.

BACKGROUND: The pursestring suture (PSS) utilizes a circumferentially placed intradermal suture to decrease the size of a defect. Its primary application in dermatologic surgery has been to allow placement of a smaller full-thickness skin graft and to enhance secondary intention wound healing. OBJECTIVE: To present our experience with 3 variations of the PSS. METHODS: The oval defects resulting after surgical excision of cutaneous malignancies were managed with 3 variations of the traditional pursestring technique. These variations included (1) complete closure of the PSS-reduced defect by the placement of traditional interrupted sutures; (2) PSS with the Burow's triangle graft; (3) use of a PSS only part way around an oval defect to avoid distortion of a nearby free margin. RESULTS: In the 7 years of performing these variations of the PSS technique, we have consistently achieved favorable results. CONCLUSION: We report 3 simple-to-use variations of the PSS technique that have been extremely useful in the management of cutaneous malignancies.

Facial Neoplasms↗
PubMed1999

Studies of human immunodeficiency virus type 1 mucosal viral shedding and transmission in Kenya.

If human immunodeficiency virus type 1 (HIV-1) vaccines are to be highly effective, it is essential to understand the virologic factors that contribute to HIV-1 transmission. It is likely that transmission is determined, in part, by the genotype or phenotype (or both) of infectious virus present in the index case, which in turn will influence the quantity of virus that may be exchanged during sexual contact. Transmission may also depend on the fitness of the virus for replication in the exposed individual, which may be influenced by whether a virus encounters a target cell that is susceptible to infection by that specific variant. Of interest, our data suggest that the complexity of the virus that is transmitted may be different in female and male sexual exposures.

Adult↗
PubMed1999

A controlled trial of chlorofluorocarbon-free triamcinolone acetonide inhalation aerosol in the treatment of adult patients with persistent asthma. Azmacort HFA Study Group.

STUDY OBJECTIVE: To compare the dose response, efficacy, and safety of inhaled triamcinolone acetonide (TAA) with a hydrofluoroalkane (HFA) propellant (75 microg/puff), TAA with a chlorofluorocarbon propellant (dichlorodifluoromethane [P-12]; 75 microg/puff), and placebo in adult patients with persistent asthma. DESIGN: Multicenter, randomized, double-blind, placebo-controlled, parallel-group study of 514 adult patients with persistent asthma. INTERVENTIONS AND MEASUREMENTS: Patients received 8 weeks of treatment with 150, 300, or 600 microg/d of TAA HFA, the same doses of TAA P-12, or placebo following a 5- to 21-day baseline period. Efficacy was assessed by spirometry, and by daily recordings of albuterol use, peak expiratory flow (PEF), asthma symptom ratings, and nighttime awakenings throughout the study. RESULTS: Linear trend analysis showed that both formulations of TAA at all doses produced statistically significant improvements compared with placebo in spirometry, asthma symptom scores, albuterol use, and PEF. Significant improvement was seen as early as 24 h for morning PEF and as early as 1 week for FEV(1) (TAA HFA, 600 microg/d; TAA P-12, 300 and 600 microg/d) and albuterol use (all doses of both formulations). The P-12 and HFA formulations had comparable efficacy. A dose response showing greater improvement with higher doses was evident for the majority of parameters for both formulations. The incidences of adverse events were similar across all treatment groups with no dose-related trends. CONCLUSION: HFA and P-12 formulations of TAA inhalation aerosol were therapeutically equivalent and showed comparable safety and dose-related efficacy in the treatment of patients with persistent asthma.

Administration, Inhalation↗
PubMed1999

A multiple-dosing, placebo-controlled study of budesonide inhalation suspension given once or twice daily for treatment of persistent asthma in young children and infants.

RATIONALE: Topical antiinflammatory medications such as inhaled corticosteroids are recommended for therapy of asthma, but no formulation suitable for administration to infants and young children is available in the United States. METHODS: This was a 12-week, multicenter, double-blind, randomized, parallel-group study comparing the efficacy and safety of four dosing regimens of bude-sonide inhalation suspension (BIS) or placebo in 480 asthmatic infants and children (64% boys), ages 6 months to 8 years, with moderate persistent asthma. Approximately 30% of children were previously on inhaled corticosteroids that were discontinued before the study. Active treatments were comprised of BIS 0.25 mg once daily (QD), 0.25 mg twice a day (BID), 0.5 mg BID, or 1.0 mg QD. Efficacy was assessed by twice daily recording at home of asthma symptom scores and use of rescue medication, and discontinuation from the study because of worsening asthma and/or a requirement for systemic steroids. Peak flow measurements were recorded twice daily on diary and spirometry was recorded at clinic visits for those children able to perform these tests. Safety was assessed by reported adverse events and by cortisol testing (adrenocorticotropic hormone stimulation) in a subset of patients. RESULTS: Patients enrolled had an average duration of asthma of 34 months; the mean asthma symptom score was approximately 1.3 (scale of 0-3). All dosing regimens with BIS produced statistically significant improvement in various clinical efficacy measures for asthma control compared with placebo. The lowest dose used, 0.25 mg QD, was efficacious but with fewer efficacy parameters than seen with the other doses administered. Separation between active treatment and placebo in daytime and nighttime symptom scores were observed by week 2 of treatment for all BIS treatment regimens. A significant increase in peak flow measurement was observed in most active treatment groups compared with placebo in the subset of children able to do pulmonary function testing. All treatment groups showed numerical improvement in forced expiratory volume in 1 second but only the 0.5-mg BID dose was significantly different from placebo. Adverse events for the entire group and response to adrenocorticotropic hormone in a subgroup of children who underwent cortisol testing before and at the end of the treatment period were no different in budesonide-treated patients in comparison to placebo. CONCLUSION: Results of this study demonstrate that BIS is effective and safe for infants and young children with moderate persistent asthma in a multiple dose range, and that QD dosing is an important option to be considered by the prescribing physician.

Administration, Inhalation↗
PubMed1999

Web-based teledermatology consult system: preliminary results from the first 100 cases.

The TRICARE Region 1 Teledermatology Consortium has developed a secure web-based "store and forward" consult system designed to allow medical treatment facilities throughout the region to submit dermatology consults. Realizing that there is very little objective data on teledermatology, we have begun to evaluate our system through the integration of questionnaires for patients, referring physicians, and consultants in addition to telephonic patient follow up. We report the preliminary data from the first 100 cases received in the first two months since partly deploying the web based teledermatology consult system in the Tricare Region I (Northeast United States). We primarily address system effectiveness (percentage of cases that required follow up to dermatology and/or primary care physicians, adequacy of evaluating pigmented lesions) diagnostic agreement, acceptance, effect on access to care, and educational value to the primary care physicians.

Attitude of Health Personnel↗
PubMed1998

Pretreatment with intralesional hyaluronidase prior to excision of dermatofibrosarcoma protuberans.

Dermatofibrosarcoma protuberans (DFSPs) are an uncommon malignancy that commonly recur, but rarely metastasize. The origin of DFSPs is controversial; however, they stain with the progenitor marker CD34. DFSPs usually show increased stromal mucin, mainly hyaluronic acid (HA). HA increases cellular proliferation, delays differentiation and increases cellular motion. We evaluated the pretreatment of DFSPs with intralesional injections of hyaluronidase (HD) prior to the surgical excision. Five of nine cases of DFSPs were pretreated with HD. In HD-pretreated cases the margins for excision of the residual tumor were reduced. HD pretreatment also decreased CD34 staining and increased polarizable collagen in the residual tumor.

Adult↗