Biomedical subjects
A Butler
Publications and source records attributed to A Butler.
Photochemical cycling of iron in the surface ocean mediated by microbial iron(III)-binding ligands.
Iron is a limiting nutrient for primary production in large areas of the oceans. Dissolved iron(III) in the upper oceans occurs almost entirely in the form of complexes with strong organic ligands presumed to be of biological origin. Although the importance of organic ligands to aquatic iron cycling is becoming clear, the mechanism by which they are involved in this process remains uncertain. Here we report observations of photochemical reactions involving Fe(III) bound to siderophores--high-affinity iron(III) ligands produced by bacteria to facilitate iron acquisition. We show that photolysis of Fe(III)-siderophore complexes leads to the formation of lower-affinity Fe(III) ligands and the reduction of Fe(III), increasing the availability of siderophore-bound iron for uptake by planktonic assemblages. These photochemical reactions are mediated by the alpha-hydroxy acid moiety, a group which has generally been found to be present in the marine siderophores that have been characterized. We suggest that Fe(III)-binding ligands can enhance the photolytic production of reactive iron species in the euphotic zone and so influence iron availability in aquatic systems.
On the regiospecificity of vanadium bromoperoxidase.
Vanadium haloperoxidase enzymes catalyze the oxidation of halide ions by hydrogen peroxide, producing an oxidized intermediate, which can halogenate an organic substrate or react with a second equivalent of hydrogen peroxide to produce dioxygen. Haloperoxidases are thought to be involved in the biogenesis of halogenated natural products isolated from marine organisms, including indoles and terpenes, of which many are selectively oxidized or halogenated. Little has been shown concerning the ability of the marine haloperoxidases to catalyze regioselective reactions. Here we report the regiospecific bromoperoxidative oxidation of 1,3-di-tert-butylindole by V-BrPO from the marine algae Ascophyllum nodosum and Corallina officinalis. Both enzymes catalyze the regiospecific oxidation of 1,3-di-tert-butylindole in a reaction requiring both H(2)O(2) and Br(-) as substrates, but which produce the unbrominated 1,3-di-tert-butyl-2-indolinone product exclusively, in near quantitative yield (i.e. one H(2)O(2) consumed per product). By contrast, reactions with the controlled addition of aqueous bromine solution (HOBr = Br(2) = Br(3)(-)) produce three monobromo and one dibromo-2-indolinone products, all of which differ from the V-BrPO-catalyzed product. Further, reactivities of 1,3-di-tert-butyl-2-indolinone with both aqueous bromine and V-BrPO differ significantly and shed light onto the possible nature of the oxidizing intermediate. This is the first example of a regiospecific bromination by a vanadium haloperoxidase and further extends their usefulness as catalysts.
Evolution tunes the excitability of individual neurons.
The relationship between the genome and the evolution of the nervous system may differ between an animal like C. elegans with 302 neurons, and mammals with tens of billions of neurons. Here we report that a class of nonconserved potassium channels highly expanded in C. elegans may play a special role in the evolution of its nervous system. The C. elegans genome contains an extended gene family of potassium channels whose members fall into two evolutionary divergent classes. One class constitutes an ancient conserved "set" of K+ channels with orthologues in both humans and Drosophila and a second larger class made up of rapidly evolving genes unique to C. elegans. Chief among this second class are novel potassium channels having four transmembrane domains per subunit that function as regulated leak conductances to modulate cell electrical excitability. This inventory of novel potassium channels is far larger in C. elegans than in humans or Drosophila. We found that, unlike conserved channel genes, the majority of these genes are expressed in very few cells. We also identified DNA enhancer elements associated with these genes that direct gene expression to individual neurons. We conclude that C. elegans may maintain an exceptionally large inventory of these channels (as well as ligand-gated channels) as an adaptive mechanism to "fine tune" individual neurons, making the most of its limited circuitry.
What is the role of circulating IGF-I?
Postnatal growth and development are coordinated by genetic and environmental influences and numerous growth factors. The growth hormone-insulin-like growth factor-I (GH-IGF-I) axis plays an essential role in these processes. Although the GH-IGF-I axis is a closely coordinated system, both GH and IGF-I have independent actions, many of which have become apparent more recently following the characterization of clinical syndromes and the development of mouse models. Genetic manipulation of mice has enabled investigators to re-examine many of the established hypotheses regarding the GH-IGF-I axis. Results gleaned from a mouse model created by tissue-specific gene deletion of liver IGF-I has enabled investigators to re-evaluate the original 'somatomedin hypothesis'.
The tylosin-biosynthetic genes of Streptomyces fradiae.
The tylosin-biosynthetic (tyl) gene cluster occupies about 1% of the genome of Streptomycesfradiae and includes at least 43 open reading frames. In addition to structural genes required for tylosin production, the tyl cluster contains three resistance determinants and several regulatory genes. Tylosin production is evidently controlled by pathway-specific and pleiotropic regulators with the likely involvement of y-butyrolactone signalling factors. Accumulation of the polyketide aglycone is controlled by glycosylated macrolides and optimal performance of the complex polyketide synthase enzyme requires the activity of an editing thioesterase.
Botulinum toxin for people with dystonia treated by an outreach nurse practitioner: a comparative study between a home and a clinic treatment service.
OBJECTIVE: To study whether a trained outreach nurse practitioner could provide a service that is as good as, or better than, that provided at a hospital outpatient clinic for people who had been diagnosed with dystonia and required treatment with botulinum toxin. DESIGN: Randomized trial. SETTING: An outpatient department of a regional neurorehabilitation center and patients' homes in northern England. PATIENTS: Eighty-nine patients with a clinical diagnosis of spasmodic torticollis, blepharospasm, or hemifacial spasm who had ongoing treatment of dystonia with botulinum injections. INTERVENTIONS: Individuals were randomly allocated either to receive ongoing botulinum injections at home by the nurse practitioner or to continue attending the hospital outpatient clinic and be injected by medical staff. MAIN OUTCOME MEASURES: The following measures were recorded at each visit: demographic descriptors, dosage of botulinum toxin, treatment interval, side-effect profile, external referrals, and a questionnaire to determine qualitative opinion. RESULTS: Efficacy and duration of the botulinum was similar in both groups. Botulinum dosage and side-effect profiles were similar in both groups except for significantly less dysphagia (p < .018) in the home group (7 vs 24 occasions). Subjective opinion by the patients indicated statistically significant preference for home injections. Economic analysis indicated that the overall cost of the treatment was less in the home injection group (total cost per visit $36.90 [ pound 23.36] vs $79.00 [ pound 50.01]), but this difference was not statistically significant. CONCLUSION: A trained outreach nurse practitioner provided a service that was as good as, and in certain aspects better than, that provided by a hospital outpatient clinic. The nurse practitioner provided a more flexible, much appreciated, safe, and cost-effective service for this client group. Wider use of outreach nurse practitioners for dystonia should be encouraged.
Concept, development, administration, and analysis of a certifying examination in echocardiography for physicians.
In 1993, the American Society of Echocardiography appointed a committee to develop an objective examination in echocardiography. In 1995, a pilot of this examination was administered, with operational examinations offered each year from 1996 to 1999. This report describes the development of the examination, including its underlying philosophy, the test itself, and the scoring process, and includes results from the first 4 examinations. To date, 1266 physicians have taken the examination, and roughly 60% of those have passed. The number of echocardiograms performed or interpreted each week had the largest effect on examination scores; the effects of both the amount of training and the practice discipline were small but significant. The evolution of the original committee and new directions for the testing organization are also discussed.
Apolipoprotein E genotype differentially influences the proinflammatory and anti-inflammatory response to cardiopulmonary bypass.
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The somatomedin hypothesis: 2001.
Since the original somatomedin hypothesis was conceived, a number of important discoveries have allowed investigators to modify the concept. Originally somatic growth was thought to be controlled by pituitary GH and mediated by circulating insulin-like growth factor-I (IGF-I, somatomedin C) expressed exclusively by the liver. With the discovery that IGF-I is produced by most, if not all, tissues, the role of autocrine/paracrine IGF-I vs. the circulating form has been hotly debated. Recent experiments using transgenic and gene-deletion technologies have attempted to answer these questions. In the liverspecific igf-1 gene-deleted mouse model, postnatal growth and development are normal despite the marked reduction in circulating IGF-I and IGF-binding protein levels; free IGF-I levels are normal. Thus, the normal postnatal growth and development in these animals may be due to normal free IGF-I levels (from as yet unidentified sources), although the role of autocrine/paracrine IGF-I has yet to be determined.
Self-assembling amphiphilic siderophores from marine bacteria.
Most aerobic bacteria secrete siderophores to facilitate iron acquisition. Two families of siderophores were isolated from strains belonging to two different genera of marine bacteria. The aquachelins, from Halomonas aquamarina strain DS40M3, and the marinobactins, from Marinobacter sp. strains DS40M6 and DS40M8, each contain a unique peptidic head group that coordinates iron(III) and an appendage of one of a series of fatty acid moieties. These siderophores have low critical micelle concentrations (CMCs). In the absence of iron, the marinobactins are present as micelles at concentrations exceeding their CMC; upon addition of iron(III), the micelles undergo a spontaneous phase change to form vesicles. These observations suggest that unique iron acquisition mechanisms may have evolved in marine bacteria.
Nasally inhaled dornase alfa in the postoperative management of chronic sinusitis due to cystic fibrosis.
OBJECTIVE: To determine the benefit of nasally inhaled dornase alfa in cystic fibrosis (CF) sinusitis. DESIGN: Retrospective chart review comparing postsurgical course, radiographic studies, and pulmonary function test results in patients who were treated with nasally inhaled dornase alfa with those in patients who were not treated with dornase alfa. PATIENTS: Twenty consecutive patients with CF who underwent functional endoscopic sinus surgery from 1993 to 1997 were included in the study. Treatment with nasally inhaled dornase alfa was initiated in 5 of the 20 patients after they underwent functional endoscopic sinus surgery. SETTING: Tertiary care academic center. RESULTS: The dornase alfa-treated patients had less mucosal edema and no polyps at serial endoscopy over 3 years compared with the non-dornase alfa-treated patients. The patients who received nasally inhaled dornase alfa also underwent fewer revision functional endoscopic sinus surgical procedures (1.6 vs 3.2), even though there was essentially no change in pulmonary function test results in these patients. CONCLUSIONS: Sinusitis continues to be a major cause of morbidity in patients with CF. Symptomatic patients frequently require multiple drug regimens, including long-term systemic antibiotic therapy, topical and systemic steroid therapy, and antibiotic nasal irrigations. This preliminary study indicates the potential impact of nasally inhaled dornase alfa in controlling postoperative symptoms in CF sinusitis.
Zotepine in the prevention of recurrence: a randomised, double-blind, placebo-controlled study for chronic schizophrenia.
RATIONALE: Zotepine is an antipsychotic drug with proven efficacy for treatment of acute episodes of schizophrenia. Antipsychotic drugs also require to be effective in prevention of recurrence. OBJECTIVE: This trial was designed to compare the effects of zotepine and placebo in the prevention of recurrence of acute episodes in a population of patients with chronic schizophrenia. METHODS: The study was a double-blind, parallel group, 26-week comparison of zotepine (300 mg daily, with fall back to 150 mg if necessary) versus placebo in 121 patients with chronic schizophrenia and a history of recurrence in the previous 18 months. The primary outcome measure was the time to recurrence. Other evaluations included the brief psychiatric rating scale (BPRS), the scale for the assessment of negative symptoms (SANS), the clinical global impression (CGI) severity and improvement scales, and the Simpson and Angus scale for extrapyramidal symptoms (EPS). RESULTS: Fewer zotepine patients experienced recurrence over 26 weeks than placebo patients (4 versus 21, respectively). The estimated 26-week risk of recurrence was six times lower for zotepine than placebo (8.7% versus 52.8%; hazard ratio 0.16, 95% CI 0.053, 0.484; P<0.001). Scores on the BPRS and CGI supported the efficacy of zotepine. There was no difference between the treatments with respect to EPS. CONCLUSIONS: Zotepine is effective in preventing recurrence in patients with chronic schizophrenia. The level of EPS was not different between zotepine and placebo.
Caspase-3 protease activation during the process of genistein-induced apoptosis in TM4 testicular cells.
The role of caspase-3 (CPP32) protease in the molecular pathways of genistein-induced cell death in TM4 cells was investigated. Fluorescence microscopy with Hoechst-33258-PI nuclear stain was used to distinguish between apoptosis and necrosis pathways of cell death. The viability of the test cells was assessed with both the trypan blue exclusion and MTT tetrazolium (3-[4,5-dimethyl-thiazol-2-yl]-2,5-diphenyltetralzolium bromide, 2.5 mg/mL) assays. Caspase-3 enzymatic activity was determined using CasPASE Apoptosis Assay Kit. The overall results from all the data demonstrated that: i) genistein exerts dose- and time-dependent effects on TM4 testis cells; ii) apoptosis is induced by lower concentrations of genistein and necrosis induced by higher concentrations of genistein; iii) genistein induced activation caspase-3 enzymatic activity; iv) genistein-induction of apoptosis and necrosis was significantly inhibited by the caspase-3 inhibitor, z-DEV-FMK; v) sodium azide induced necrosis without activation of CPP32 enzymatic activity, and induction of apoptosis; and vi) genistein-induced apoptosis was associated with activation of CPP32 enzymatic activity in the cells. The overall results indicate a strong evidence of caspase-3 (CPP332) mediation in the molecular pathways of genistein-induced apoptosis in testicular cells. Apoptosis is the physiologically programmed cell death in which intrinsic mechanisms participate in the death of the cell, in contrast to necrosis, which induces inflammatory response in the affected cell. The fact that the chemopreventive role of several cancer drugs is due to induction of apoptosis augments the biotherapeutic potential of genistein for the treatment of malignant diseases including prostate and testicular cancers. It is therefore inevitable that identification of the apoptotic pathways and the points at which regulation occurs could be instrumental in the design of genistein biotherapy for such diseases.
TRPgamma, a drosophila TRP-related subunit, forms a regulated cation channel with TRPL.
TRP and TRPL are two light-sensitive cation channel subunits required for the Drosophila photoresponse; however, our understanding of the identities, subunit composition, and function of the light-responsive channels is incomplete. To explain the residual photoresponse that remains in the trp mutant, a third TRP-related subunit has previously been proposed to function with TRPL. Here, we identify such a subunit, TRPgamma. We show that TRPgamma is highly enriched in photoreceptor cells and preferentially heteromultimerizes with TRPL in vitro and in vivo. The N-terminal domain of TRPgamma dominantly suppressed the TRPL-dependent photoresponse, indicating that TRPgamma-TRPL heteromultimers contribute to the photoresponse. While TRPL and TRPgamma homomultimers are constitutively active, we demonstrate that TRPL-TRPgamma heteromultimers form a regulated phospholipase C- (PLC-) stimulated channel.
SLO-2, a K+ channel with an unusual Cl- dependence.
The gating of different potassium channels depends on many diverse factors. We now report a unique example of a K+ channel with a Cl - dependence. The slo-2 gene was cloned from Caenorhabditis elegans and is widely expressed in both neurons and muscles; it was highly abundant, as suggested by its high representation in the C. elegans EST database. SLO-2, like its paralogue, SLO-1, was also dependent on Ca 2+. We show by site-directed mutagenesis that its requirements for both Cl- and Ca2+ are synergistic and associated with the same functional domain. SLO-2's dependence on Cl - implies that intracellular Cl- homeostasis may be important in regulating cellular excitability through this unusual K+ channel.
A placebo-controlled comparison of zotepine versus chlorpromazine in patients with acute exacerbation of schizophrenia.
OBJECTIVE: The aim of this study was to evaluate the efficacy of zotepine in the treatment of acute episodes of schizophrenia. METHOD: Patients with acute exacerbation of schizophrenia (DSM-III-R criteria; n = 158) were allocated on a random, double-blind basis to receive zotepine (150 or 300 mg/day), chlorpromazine (300 or 600 mg/day) or placebo for 8 weeks. Symptoms were assessed on the BPRS, SANS and CGI scales at baseline and weeks 1, 2, 4, 6 and 8 and patients were assessed at these times for adverse effects. Analysis was by analysis of variance on the intent-to-treat population, with last observation carried forward. RESULTS: Mean BPRS scores improved statistically significantly more with zotepine than chlorpromazine (point estimate of difference -12.4, 95% CI -18.3 to -6.5) or placebo (point estimate of difference -12.7, 95% CI -18.6 to -6.8). Zotepine produced significantly fewer extrapyramidal symptoms (EPS) than chlorpromazine. CONCLUSION: Zotepine is an effective antipsychotic with low propensity for EPS.
Self-care skills in young children with myelomeningoceles.
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