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G Davidson

Publications and source records attributed to G Davidson.

At least 19 recordsLinked to original sources
PubMed2005

Antro-pyloro-duodenal motor responses to gastric and duodenal nutrient in critically ill patients.

BACKGROUND: Gastric emptying is frequently delayed in critical illness which compromises the success of nasogastric nutrition. The underlying motor dysfunctions are poorly defined. AIMS: To characterise antro-pyloro-duodenal motility during fasting, and in response to gastric and duodenal nutrient, as well as to evaluate the relationship between gastric emptying and motility, in the critically ill. SUBJECTS: Fifteen mechanically ventilated patients from a mixed intensive care unit; 10 healthy volunteers. METHODS: Antro-pyloro-duodenal pressures were recorded during fasting, after intragastric administration (100 ml; 100 kcal), and during small intestinal infusion of liquid nutrient (6 hours; 1 kcal/min). Gastric emptying was measured using a (13)C octanoate breath test. RESULTS: In healthy subjects, neither gastric nor small intestinal nutrient affected antro-pyloro-duodenal pressures. In patients, duodenal nutrient infusion reduced antral activity compared with both fasting and healthy subjects (0.03 (0-2.47) waves/min v 0.14 (0-2.2) fasting (p = 0.016); and v 0.33 (0-2.57)/min in healthy subjects (p = 0.005)). Basal pyloric pressure and the frequency of phasic pyloric pressure waves were increased in patients during duodenal nutrient infusion (3.12 (1.06) mm Hg; 0.98 (0.13)/min) compared with healthy subjects (-0.44 (1.25) mm Hg; p<0.02 after 120 minutes; 0.29 (0.15)/min; p = 0.0002) and with fasting (-0.06 (1.05) mm Hg; p<0.03 after 160 minutes; 0.49 (0.13)/min; (p = 0.0001). Gastric emptying was delayed in patients (gastric emptying coefficient 2.99 (0.2) v 3.47 (0.1); p = 0.015) and inversely related to the number of pyloric pressure waves (r = -0.563, p = 0.029). CONCLUSIONS: Stimulation of pyloric and suppression of antral pressures by duodenal nutrient are enhanced in the critically ill and related to decreased gastric emptying.

Adult↗
PubMed2005

Laboratory evaluation of entomopathogenic fungi against larvae and adults of onion maggot (Diptera: Anthomyiidae).

Laboratory experiments were done to measure the susceptibility of larvae and adults of the onion maggot, Delia antiqua (Meigen) (Diptera: Muscidae: Anthomyiidae) to 27 isolates of entomopathogenic fungi from four genera [Beauveria Vuillemin, Lecanicillium (Petch) Zare & W. Gams, Metarhizium Sorokin, and Paecilomyces Bainier]. A novel bioassay was developed for D. antiqua larvae by using a diet based on mixed vegetable powder. When evaluated in a virulence screen, the fungal isolates caused less mortality of D. antiqua larvae than adults. Only three isolates caused > 50% mortality of larvae, whereas 12 isolates caused > 50% mortality of adults. Fungal species was a statistically significant factor affecting the mortality of larvae but not of adults. The fungal isolates causing the most mortality of larvae tended to belong to Metarhizium anisopliae (Metschnikoff) Sorokin. Two M. anisopliae isolates (389.93 and 392.93) were evaluated in dose-response bioassays. The median lethal concentrations of the isolates against larvae were 6.1 x 10(7) conidia ml(-1) for isolate 389.93 and 7.6 x 10(7) conidia ml(-1) for isolate 392.93. The emergence of adult flies from pupae was reduced at high concentrations of conidia (3.0 x 10(8) and 1.0 x 10(8) conidia ml(-1)). The median lethal concentrations of the isolates against adults were 1.7 x 10(7) and 4.0 x 10(7) conidia ml(-1), respectively. Some of the fungal isolates examined may have potential as biological control agents of larvae of D. antiqua and related species.

Animals↗
PubMed2005

Evaluation of entomopathogenic fungus Metarhizium anisopliae against soil-dwelling stages of cabbage maggot (Diptera: Anthomyiidae) in glasshouse and field experiments and effect of fungicides on fungal activity.

The effect of two isolates of the entomopathogenic fungus Metarhizium anisopliae (Metchnikoff) Sorokin (389.93 and 392.93) on root-feeding stages of cabbage root fly, Delia radicum (L.), was studied under glasshouse and field conditions. In glasshouse studies, the effect of drenching a suspension of conidia (concentration 1 x 10(8) m(-1), 40 ml per plant, applied on four occasions) onto the base of cabbage plants infested with D. radicum eggs was compared with mixing conidial suspension into compost modules (concentration 1 x 10(8) ml(-1), 25 ml per plant) used to raise seedlings. Drench application reduced the mean number of larvae and pupae recovered per plant by up to 90%, but the compost module treatment had no statistically significant effect. Both application methods reduced the emergence of adult flies from pupae by up to 92%. Most conidia applied as a drench application remained in the top 10-cm layer of compost. Applications of the fungicides iprodione and tebuconazole, which are used routinely on brassica crops, were compatible with using M. anisopliae 389.93 against D. radicum under glasshouse conditions, even though these fungicides were inhibitory to fungal growth on SDA medium. In a field experiment, drench applications of M. anisopliae 389.93 to the base of cauliflower plants at concentrations of 1 x 10(6) to 1 x 10(8) conidia ml(-1) did not control D. radicum populations, although up to 30% of larval cadavers recovered supported sporulating mycelium. Drench applications often exhibited considerable lateral movement on the soil surface before penetrating the ground, which may have reduced the amount of inoculum in contact with D. radicum larvae.

Animals↗
PubMed2003

Cefazolin does not accelerate gastric emptying in the critically ill.

OBJECTIVE: To evaluate the effect of intravenous cefazolin on gastric emptying measured by the C-13 octanoic acid breath test. DESIGN: Prospective, double-blind, cross-over, randomised, placebo-controlled trial. SETTING: Mixed multidisciplinary intensive care unit in a university hospital. PATIENTS: Fourteen critically ill, mechanically ventilated patients. INTERVENTIONS: After a 4-h fast patients received either 50 mg cefazolin or 20 ml saline over 20 min immediately prior to measurement of gastric emptying. The next day the study was repeated with the alternative therapy. MEASUREMENTS AND RESULTS: Breath samples were analysed for the concentration of (13)CO2 by mass spectrometer, and the gastric emptying coefficient (GEC) and half-emptying time (t(50)) were calculated. Results are mean (standard deviation). Data were analysed with the paired t-test (saline vs cefazolin). Two patients were excluded for technical problems. Twelve patients remained (six male/six female), aged 57 (+/-16) years, with an APACHE II score of 20 (+/-8). Both GEC and t(50) were unchanged after administration of cefazolin compared with placebo (t(50) cefazolin, 138 (+/-54) vs saline 122 (+/-46) min, P=0.32; GEC cefazolin 3.27 (+/-0.83) vs saline 3.55 (+/-0.6), P=0.24). Two patients had abnormal t(50) after saline and five after cefazolin. There was no order effect of the study day. CONCLUSION: In mechanically ventilated patients, cefazolin had no effect on gastric emptying. These data do not support the use of low-dose cefazolin as a pro-kinetic agent in critically ill patients.

Adult↗
PubMed2003

Study of temperature-growth interactions of entomopathogenic fungi with potential for control of Varroa destructor (Acari: Mesostigmata) using a nonlinear model of poikilotherm development.

AIMS: To investigate the thermal biology of entomopathogenic fungi being examined as potential microbial control agents of Varroa destructor, an ectoparasite of the European honey bee Apis mellifera. METHODS AND RESULTS: Colony extension rates were measured at three temperatures (20, 30 and 35 degrees C) for 41 isolates of entomopathogenic fungi. All of the isolates grew at 20 and 30 degrees C but only 11 isolates grew at 35 degrees C. Twenty-two isolates were then selected on the basis of appreciable growth at 30-35 degrees C (the temperature range found within honey bee colonies) and/or infectivity to V. destructor, and their colony extension rates were measured at 10 temperatures (12.5-35 degrees C). This data were then fitted to Schoolfield et al. [J Theor Biol (1981)88:719-731] re-formulation of the Sharpe and DeMichele [J Theor Biol (1977)64:649-670] model of poikilotherm development. Overall, this model accounted for 87.6-93.9% of the data variance. Eleven isolates exhibited growth above 35 degrees C. The optimum temperatures for extension rate ranged from 22.9 to 31.2 degrees C. Only three isolates exhibited temperature optima above 30 degrees C. The super-optimum temperatures (temperature above the optimum at which the colony extension rate was 10% of the maximum rate) ranged from 31.9 to 43.2 degrees C. CONCLUSIONS: The thermal requirements of the isolates examined against V. destructor are well matched to the temperatures in the broodless areas of honey bee colonies, and a proportion of isolates, should also be able to function within drone brood areas. SIGNIFICANCE AND IMPACT OF THE STUDY: Potential exists for the control of V. destructor with entomopathogenic fungi in honey bee colonies. The methods employed in this study could be utilized in the selection of isolates for microbial control prior to screening for infectivity and could help in predicting the activity of a fungal control agent of V. destructor under fluctuating temperature conditions.

Acari↗
PubMed2001

Isolation, characterization and gene sequence analysis of a membrane-associated 89 kDa Fe(III) reducing cytochrome c from Geobacter sulfurreducens.

Geobacter sulfurreducens is capable of anaerobic respiration with Fe(III) as a terminal electron acceptor via a membrane-bound Fe(III) reductase activity associated with a large molecular mass cytochrome c. This cytochrome was purified by detergent extraction of the membrane fraction, Q-Sepharose ion-exchange chromatography, preparative electrophoresis, and MonoQ ion-exchange chromatography. Spectrophotometric analysis of the purified cytochrome reveals a c-type haem, with no evidence of haem a, haem b or sirohaem. The cytochrome has an M(r) of 89000 as determined by denaturing PAGE, and has an isoelectric point of 5.2 as determined by analytical isoelectric focusing. Dithionite-reduced cytochrome can donate electrons to Fe(III)-nitrilotriacetic acid and synthetic ferrihydrite, thus demonstrating that the cytochrome has redox and thermodynamic properties required for reduction of Fe(III). Analysis using cyclic voltammetry confirmed that the reduced cytochrome can catalytically transfer electrons to ferrihydrite, further demonstrating its ability to be an electron transport mediator in anaerobic Fe(III) respiration. Sequence analysis of a cloned chromosomal DNA fragment revealed a 2307 bp open reading frame (ferA) encoding a 768 amino acid protein corresponding to the 89 kDa cytochrome. The deduced amino acid sequence (FerA) translated from the open reading frame contained 12 putative haem-binding motifs, as well as a hydrophobic N-terminal membrane anchor sequence, a lipid-attachment site and an ATP/GTP-binding site. FerA displayed 20% or less identity with amino acid sequences of other known cytochromes, although it does share some features with characterized polyhaem cytochromes c.

Amino Acid Sequence↗
PubMed2001

An XAS investigation of product and inhibitor complexes of Ni-containing GlxI from Escherichia coli: mechanistic implications.

Escherichia coli glyoxalase I (GlxI) is a metalloisomerase that is maximally activated by Ni(2+), unlike other known GlxI enzymes which are active with Zn(2+). The metal is coordinated by two aqua ligands, two histidines (5 and 74), and two glutamates (56 and 122). The mechanism of E. coli Ni-GlxI was investigated by analyzing Ni K-edge X-ray absorption spectroscopic (XAS) data obtained from the enzyme and complexes formed with the product, S-D-lactoylglutathione, and various inhibitors. The analysis of X-ray absorption near edge structure (XANES) was used to determine the coordination number and geometry of the Ni site in the various Ni-GlxI complexes. Metric details of the Ni site structure were obtained from the analysis of extended X-ray absorption fine structure (EXAFS). Interaction of S-D-lactoylglutathione (product) or octylglutathione with the enzyme did not change the structure of the Ni site. However, analysis of XAS data obtained from a complex formed with a peptide hydroxamate bound to Ni-GlxI is consistent with this inhibitor binding to the Ni center by displacement of both water molecules. XANES analysis of this complex is best fit with a five-coordinate metal and, given the fact that both histidine ligands are retained, suggests the loss of a glutamate ligand. The loss of a glutamate ligand would preserve the neutral charge on the Ni complex and is consistent with the lack of a significant shift in the Ni K-edge energy in this complex. These data are compared with data obtained from the E. coli Ni-GlxI selenomethionine-substituted enzyme. The replacement of three methionine residues in the native enzyme with selenomethionine does not affect the structure of the Ni site. However, addition of the peptide hydroxamate inhibitor leads to the formation of a complex whose structure as determined by XAS analysis is consistent with inhibitor binding via displacement of both water molecules but retention of both histidine and glutamate ligands. This leads to an anionic complex, which is consistent with an observed 1.7 eV decrease in the Ni K-edge energy. Plausible reaction mechanisms for Ni-GlxI are discussed in light of the structural information available.

Binding Sites↗
PubMed2001

Aids to quitting tobacco use: how important are they outside controlled trials?

BACKGROUND: Although there is good evidence that several pharmacotherapies and counseling can effectively facilitate smoking cessation, there is little information about the use or effectiveness of these or any other quit aids outside of controlled trials. METHODS: A mailed survey with phone follow-up documented the use of various quit aids among 3,122 health plan members who smoke. A multilevel statistical modeling technique controlled for potentially confounding variables. RESULTS: Nearly half (1,513) of these smokers reported a quit attempt during the preceding 6 months. Although 1,036 (33.2%) reported using some type of aid to quitting, primarily nicotine products or bupropion, 10-26% of these "users" did not report an actual quit attempt. Ninety percent of the medication users had a personal cost, averaging $53-$87. Fully 26.9% of those reporting a quit without any type of aid quit for at least 7 days. This rate equals that of users of all types of aids except for nicotine patches and bupropion, both of which had associated 7 or more day quit rates of about 46% (95% CI 39.3-52.2). CONCLUSIONS: Pharmacotherapeutic quit aids are being widely used, even in the absence of significant insurance coverage.

Bupropion↗
PubMed2001

Patient satisfaction and discussion of smoking cessation during clinical visits.

OBJECTIVE: To learn whether patients who smoke and who receive smoking cessation information during medical office visits were less likely to be satisfied with the smoking cessation help they received than patients who smoke but who did not receive such information. PATIENTS AND METHODS: A total of 3703 current cigarette smokers were identified by a mailing in November 1998 to 163,596 members of 2 Minnesota health plans, and 2714 (77.3%) responses to a 44-item questionnaire were available for analysis. Using hierarchical analysis to control confounding variables, we assessed the relationship between patient-reported smoking cessation support actions at the last physician visit and satisfaction "with the help received from your doctor about quitting smoking." RESULTS: Smokers were very satisfied (12.0%), satisfied (25.3%), neutral (48.6%), and dissatisfied or very dissatisfied (13.5%) with physician help. After controlling for other characteristics, the 1898 patients who reported that they had been asked about tobacco use or advised to quit during the latest visit had 10 percentage point greater satisfaction ratings and 5 percentage point less dissatisfaction than those not reporting such discussions (P<.001). Smokers reporting no interest in quitting at the time of the latest visit also demonstrated greater satisfaction in association with these actions. CONCLUSION: Smoking cessation interventions during physician visits were associated with increased patient satisfaction with their care among those who smoke. This information should reduce concerns of physicians or nurses about providing tobacco cessation assistance to patients during office visits.

Adult↗
PubMed2001

Delayed gastric emptying in ventilated critically ill patients: measurement by 13 C-octanoic acid breath test.

OBJECTIVE: To measure gastric emptying in ventilated critically ill patients with a new noninvasive breath test. DESIGN: Single-center, open study. SETTING: Combined medical and surgical intensive care unit of a university hospital. SUBJECTS: Thirty unselected mechanically ventilated critically ill patients receiving gastric feeding and 22 healthy volunteers. INTERVENTIONS: None. PATIENTS: After 4 hrs without feeding, intragastric infusion of 100 mL of a liquid meal (Ensure) labeled with 100 microL 13C-octanoic acid. End-expiratory breath samples were collected into evacuated tubes from the respirator circuit every 5 mins for the first hour, then every 15 mins for 3 hrs. End-expiratory breath samples were also collected from volunteers studied supine after an overnight fast following an identical infusion via a nasogastric tube. Breath 13CO2 was measured with an isotope ratio mass spectrometer. MEASUREMENTS AND MAIN RESULTS: Performance of the breath test posed no difficulty or interference with patient care. The CO2 level was >1% in 1297/1300 breath samples, indicating satisfactory end-expiratory timing. Data are median and interquartile range. Gastric emptying was slower in patients compared with volunteers: gastric emptying coefficient 2.93 (2.17-3.39) vs. 3.58 (3.18-3.79), p <.001 and gastric half emptying time, derived from the area under the 13CO2 curve, 155 min (130-220) vs. 133 min (120-145), p <.008. Fourteen of the 30 patients had a gastric emptying coefficient <95% of all volunteers and 11 had a gastric half emptying time longer than 95% of all volunteers. The Acute Physiology and Chronic Health Evaluation (APACHE II) score (median 22, range 13-43) either at admission or on the day of the study did not correlate with gastric emptying coefficient. CONCLUSION: Gastric emptying of a calorie-dense liquid meal is slow in 40% to 45% of unselected mechanically ventilated patients in a combined medical and surgical intensive care unit. The 13C-octanoic acid breath test is a novel and useful bedside technique to measure gastric emptying in these patients.

APACHE↗
PubMed2001

Relationship between straining, transient lower esophageal sphincter relaxation, and gastroesophageal reflux in children.

OBJECTIVE: Physical straining such as deep inspiration or coughing may induce gastroesophageal reflux (GER) by overcoming feeble lower esophageal sphincter (LES) pressure. The role of straining as a provocant of GER has not been analyzed systematically in children. It was our aim to examine the contribution of straining to the occurrence of GER with particular attention to its relationship to transient LES relaxations, which are a major mechanism of the occurrence of GER in pediatric patients. METHODS: Concurrent esophageal manometry and pH monitoring was performed for 4 h postprandially in six children with esophagitis (age 9 months to 12 yr). Analysis was performed on isolated single strain episodes, defined as an increased intragastric pressure > 10 mm Hg. When a drop of esophageal pH < 4.0 was noted within 15 sec after any part of a strain, this strain was defined as related to the reflux episode. RESULTS: The median value of basal LES pressure was 10 mm Hg (range 1-18). In all, 134 analyzable strains and 87 analyzable reflux episodes were recorded. Isolated strains were associated with 20 reflux episodes (23%). Reflux was observed more frequently with strains that occurred during transient LES relaxations (12/40) than straining when the LES was contracted (8/94) (p < 0.01). Sustained strain (35%) and inspiratory strain (25%) were the major patterns of straining related to reflux. CONCLUSION: Straining provoked reflux infrequently and simultaneous occurrence of straining and transient LES relaxation was important in determining the occurrence of strain-related reflux in pediatric patients with reflux esophagitis.

Child↗
PubMed2001

FGF signalling is required for differentiation-induced cytoskeletal reorganisation and formation of actin-based processes by podocytes.

To examine the potential role of fibroblast growth factor (FGF) signalling during cell differentiation, we used conditionally immortalised podocyte cells isolated from kidneys of Fgf2 mutant and wild-type mice. Wild-type mouse podocyte cells upregulate FGF2 expression when differentiating in culture, as do maturing podocytes in vivo. Differentiating wild-type mouse podocyte cells undergo an epithelial to mesenchymal-like transition, reorganise their actin cytoskeleton and extend actin-based cellular processes; all of these activities are similar to the activity of podocytes in vivo. Molecular analysis of Fgf2 mutant mouse podocyte cells reveals a general disruption of FGF signalling as expression of Fgf7 and Fgf10 are also downregulated. These FGF mutant mouse podocyte cells in culture fail to activate mesenchymal markers and their post-mitotic differentiation is blocked. Furthermore, mutant mouse podocyte cells in culture fail to reorganise their actin cytoskeleton and form actin-based cellular processes. These studies show that FGF signalling is required by cultured podocytes to undergo the epithelial to mesenchymal-like changes necessary for terminal differentiation. Together with other studies, these results point to a general role for FGF signalling in regulating cell differentiation and formation of actin-based cellular processes during morphogenesis.

Actins↗
PubMed2000

Development of a packed-column supercritical fluid chromatography/atmospheric pressure chemical-ionisation mass spectrometric technique for the analysis of atropine.

A packed-column supercritical fluid chromatography/atmospheric pressure chemical-ionisation mass spectrometry (pSFC-APCI/MS) method has been developed for the determination of atropine from Atropa belladonna L extracts. The technique does not require any kind of derivatisation prior to the analysis. The optimum conditions were studied by using the pure substance in methanol (MeOH). All samples were simply dissolved in MeOH and injected into the mobile phase. Detection was achieved by using mass spectrometry (MS) with atmospheric pressure chemical ionisation (APCI). Terbutaline was used as an internal standard for the determination of the analytical reproducibility. The supercritical carbon dioxide (scCO(2)) mobile phase was modified by 15% MeOH containing 0.5% trifluoroacetic acid (TFAA) and 0.5% diethylamine (DEA) additives. Concentrations of atropine were determined with a relative standard deviation of less than 1% by the pSFC-APCI/MS procedure for a sample containing atropine and terbutaline. The correlation coefficient was 0.997 and detection limit 700 pg. The absolute retention time was 9.87 min with a standard deviation of 5.2x10(-3) min and a relative standard deviation of 0.61% with respect to terbutaline.

Atropine↗
PubMed2000

SFC/FTIR, SFC/APCI-MS and MALDI-TOF-MS for the analysis of siloxane-ethylene oxide copolymers.

Polydimethylsiloxanes (PDMSs) modified by introducing ethylene oxide units with the aim of forming sufficiently water-soluble siloxane compounds were characterized using supercritical fluid chromatography (SFC) coupled with Fourier transform infrared (FTIR) spectroscopy and atmospheric pressure chemical ionization mass spectrometry (APCI-MS), and matrix-assisted laser desorption-ionization time-of-flight mass spectrometry (MALDI-TOF-MS). SFC has a domain in analyzing oligomers. Hyphenated techniques enable elucidation of the components. Remarkable is the resolution and short analysis time of MALDI-TOF-MS. SFC also allows quantification of the basic and reaction products.

Chromatography↗
PubMed2000

Structural examination of the nickel site in chromatium vinosum hydrogenase: redox state oscillations and structural changes accompanying reductive activation and CO binding.

An X-ray absorption spectroscopic study of structural changes occurring at the Ni site of Chromatium vinosum hydrogenase during reductive activation, CO binding, and photolysis is presented. Structural details of the Ni sites for the ready silent intermediate state, SI(r), and the carbon monoxide complex, SI-CO, are presented for the first time in any hydrogenase. Analysis of nickel K-edge energy shifts in redox-related samples reveals that reductive activation is accompanied by an oscillation in the electron density of the Ni site involving formally Ni(III) and Ni(II), where all the EPR-active states (forms A, B, and C) are formally Ni(III), and the EPR-silent states are formally Ni(II). Analysis of XANES shows that the Ni site undergoes changes in the coordination number and geometry that are consistent with five-coordinate Ni sites in forms A, B, and SI(u); distorted four-coordinate sites in SI(r) and R; and a six-coordinate Ni site in form C. EXAFS analysis reveals that the loss of a short Ni-O bond accounts for the change in coordination number from five to four that accompanies formation of SI(r). A shortening of the Ni-Fe distance from 2.85(5) A in form B to 2.60(5) A also occurs at the SI level and is thus associated with the loss of the bridging O-donor ligand in the active site. Multiple-scattering analysis of the EXAFS data for the SI-CO complex reveals the presence of Ni-CO ligation, where the CO is bound in a linear fashion appropriate for a terminal ligand. The putative role of form C in binding H(2) or H(-) was examined by comparing the XAS data from form C with that of its photoproduct, form L. The data rule out the suggestion that the increase in charge density on the NiFe active site that accompanies the photoprocess results in a two-electron reduction of the Ni site [Ni(III) --> Ni(I)] [Happe, R. P., Roseboom, W., and Albracht, S. P. J. (1999) Eur. J. Biochem. 259, 602-608]; only subtle structural differences between the Ni sites were observed.

Carbon Monoxide↗
PubMed2000

Exposure to airborne dust contaminated with pesticide in the Aral Sea region.

The Aral Sea region is one of the world's foremost ecological disaster zones and there is increasing local concern for the health of millions of people living in this region. We have found that dust deposition rates across eastern Turkmenistan are among the highest in the world and that the dust is contaminated with pesticide.

Air Pollutants↗