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Biomedical subjects

R E Turner

Publications and source records attributed to R E Turner.

At least 19 recordsLinked to original sources
PubMed2002

Hohlraum-driven high-convergence implosion experiments with multiple beam cones on the omega laser facility.

High-convergence implosion experiments have been performed on the Omega laser facility [T.R. Boehly, Opt. Commun. 133, 495 (1997)]] using cylindrical gold hohlraums with 40 drive beams arranged into multiple cones. These experiments make use of improved hohlraum radiation symmetry conditions [T.J. Murphy, Phys. Rev. Lett. 81, 108 (1998)]] to demonstrate near predicted primary (2.45 MeV) neutron production from single-shell implosions with measured deuterium fuel convergence ratios exceeding 20 at an ignition-relevant hohlraum case-to-capsule ratio approximately 3.

Journal Article↗
PubMed2001

Social identity in adolescence.

Social identity theory (SIT) was used to investigate the effects of social categorization on adolescents' intergroup behaviour. One hundred and forty-nine male adolescents aged 14-15 years made comparisons between an ingroup and an outgroup along a series of dimensions. Participants displayed consistent ingroup-favouring behaviour in their ratings: the ingroup was associated to a greater extent than the outgroup with positively valued dimensions, and to a lesser extent with negatively valued dimensions. Those participants who demonstrated the most discrimination reported highest levels of ingroup identification. The utility of applying predictions from SIT to the study of adolescence is discussed.

Adolescent↗
PubMed2001

A model for an Ascaris muscle cell.

Muscle cells in the nematode Ascaris suum undergo bouts of oscillation in the behaving worm, these being correlated with progressing waves of contraction along the body of the worm. The bouts have three time scales: a rough period of 7-20 s, 10-20 short bursts of spikes within a bout, and three to eight spikes per burst. This paper has two aims: showing that there is consistency between measurements of individual currents and measurements on whole muscle cells, and creating a building block to eventually explain the locomotion in this 'simple' system. A realistic model for a single Ascaris suum muscle cell is developed using existing data from experiments which have established the types of ionic currents in the muscle cell and many of their kinetic properties. Numerical simulations are carried out. The model cell reproduces the two shorter time scales present. It has some robustness with regard to parameter changes, but also allows for the different numbers of spikes per burst seen in recordings from muscle cells. The third time scale, the length of a bout, may originate from some system effect, a combination of neural and stretch effects and possibly a secondary effect of the calcium-activated chloride channel.

Animals↗
PubMed2000

Computer-based simulations enhance clinical experience of dietetics interns.

OBJECTIVE: To determine the impact of computer-based simulations on the performance of dietetics interns in initial clinical rotations. DESIGN: Interns used either a simulation program (Care Planning Simulation System CPSS[) or a computer-based tutorial (Nutrition Care Planning Tutorial NCPT[) during their orientation. Performance of these interns on nutrition care skills was evaluated during their initial clinical rotations. SUBJECTS/SETTING: Participants were 108 dietetics interns from 8 different programs. Each internship had at least 8 interns, and none of the internships awarded a graduate degree. INTERVENTION: Subjects in the experimental group completed nutrition assessment and care planning activities for 3 simulated patients. Subjects in the control group completed a tutorial on assessment and care planning. MAIN OUTCOME MEASURES: Likert scale ratings of 31 behaviors were recorded by clinical preceptors. Behavior statements were grouped into 8 categories and average ratings for each category were determined. STATISTICAL ANALYSIS: Repeated-measures analysis of variance and linear regression were used to compare performance ratings between groups. RESULTS: There were no differences in overall evaluations of the simulation and tutorial groups for the 8-week period. Interns who started clinical rotations immediately after orientation (CPSS-I and NCPT-I groups) were rated lower in all categories than those who began their clinical rotations later (CPSS-D and NCPT-D groups). Maturation and acquisition of general skills likely influenced ratings of interns with delayed clinical rotations. For most categories of behavior the rate of improvement in rating scores was greatest for interns who used CPSS. APPLICATIONS: Computer-based simulations are a promising supplement to current techniques in didactic instruction and may be useful in both didactic and practice settings. Computer-based simulations can provide more varied practice experiences to didactic students and interns in preparation for more skilled entry-level positions in dietetics.

Adult↗
PubMed1999

Identification and characterization of novel variant major surface glycoprotein gene families in rat Pneumocystis carinii.

The major surface glycoprotein (MSG) is an abundant, immunodominant protein on the surface of the opportunistic pathogen Pneumocystis carinii. The current study identified two novel variant MSG (vMSG) gene families in rat P. carinii that are closely related to but distinct from MSG. These gene families encode proteins of approximately 90 kDa (v1MSG) and approximately 115 kDa (v2MSG). Compared with MSG, v1MSG is characterized by a deletion near the carboxyl terminus. The predicted v1MSG and v2MSG proteins are highly homologous to MSG at the carboxyl, but not the amino, terminus. Like MSG, they are cysteine-rich. Approximately 10% of the apparent molecular weight is due to N-linked glycosylation. Southern blotting studies demonstrated that, like MSG, v1MSG and v2MSG are the products of multicopy gene families. However, unlike MSG, each vMSG gene encodes a signal peptide, suggesting that the regulation of vMSG is different from that of MSG.

5' Untranslated Regions↗
PubMed1998

Fluctuating silicate:nitrate ratios and coastal plankton food webs.

Marine diatoms require dissolved silicate to form an external shell, and their growth becomes Si-limited when the atomic ratio of silicate to dissolved inorganic nitrogen (Si:DIN) approaches 1:1, also known as the "Redfield ratio." Fundamental changes in the diatom-to-zooplankton-to-higher trophic level food web should occur when this ratio falls below 1:1 and the proportion of diatoms in the phytoplankton community is reduced. We quantitatively substantiate these predictions by using a variety of data from the Mississippi River continental shelf, a system in which the Si:DIN loading ratio has declined from around 3:1 to 1:1 during this century because of land-use practices in the watershed. We suggest that, on this shelf, when the Si:DIN ratio in the river decreases to less than 1:1, then (i) copepod abundance changes from >75% to <30% of the total mesozooplankton, (ii) zooplankton fecal pellets become a minor component of the in situ primary production consumed, and (iii) bottom-water oxygen consumption rates become less dependent on relatively fast-sinking (diatom-rich) organic matter packaged mostly as zooplankton fecal pellets. This coastal ecosystem appears to be a pelagic food web dynamically poised to be either a food web composed of diatoms and copepods or one with potentially disruptive harmful algal blooms. The system is directed between these two ecosystem states by Mississippi River water quality, which is determined by land-use practices far inland.

Animals↗
PubMed1998

Characterization of major surface glycoprotein genes of human Pneumocystis carinii and high-level expression of a conserved region.

To facilitate studies of Pneumocystis carinii infection in humans, we undertook to better characterize and to express the major surface glycoprotein (MSG) of human P. carinii, an important protein in host-pathogen interactions. Seven MSG genes were cloned from a single isolate by PCR or genomic library screening and were sequenced. The predicted proteins, like rat MSGs, were closely related but unique variants, with a high level of conservation among cysteine residues. A conserved immunodominant region (of approximately 100 amino acids) near the carboxy terminus was expressed at high levels in Escherichia coli and used in Western blot studies. All 49 of the serum samples, which were taken from healthy controls as well as from patients with and without P. carinii pneumonia, were reactive with this peptide by Western blotting, supporting the hypothesis that most adult humans have been infected with P. carinii at some point. This recombinant MSG fragment, which is the first human P. carinii antigen available in large quantities, may be a useful reagent for investigating the epidemiology of P. carinii infection in humans.

AIDS-Related Opportunistic Infections↗
PubMed1997

Esophageal pressure measurements in cardiopulmonary exercise testing.

STUDY OBJECTIVES: We sought to determine the adaptability and effectiveness of a new esophageal balloon technique to measure changes in esophageal pressure (Pes) as a reflection of pleural pressure with progressive incremental exercise testing in normal subjects. DESIGN: An 8F (0.9 cm) esophageal balloon catheter (Smart Cath; Allied Health Products; Riverside, Calif), a CP-100 pulmonary monitor (BiCore Monitoring Systems PC-100; Irvine, Calif), and a flow transducer (Var flex; Allied Health Products; Riverside, Calif) were connected to a breathing valve (model 2700; Hans-Rudolph Inc; Kansas City, Mo). This apparatus was then used to measure Pes during a graded cardiopulmonary exercise test (CPX) to symptom limitation. SETTING: University-affiliated Veterans Affairs Hospital. PARTICIPANTS: Eight nonsmoking volunteers with normal results of pulmonary function tests. INTERVENTIONS: Plots of deltaPes against pressure time product (PTP), minute ventilation (VE), and oxygen consumption (VO2) were obtained. Pes at baseline, anaerobic threshold (AT), and maximum oxygen consumption (VO2max) were obtained by comparing the Pes measurements from the computer printout to the corresponding breath-by-breath measurements on the CPX. MEASUREMENTS AND RESULTS: The flow transducer (Varflex) connection added only 20 mL of dead space to the standard mouthpiece apparatus. The mean maximum work performance was 203+/-32 W. The mean VO2max was 29+/-9 mL/kg/min. The Pes at AT was 16+/-3 cm H2O. The Pes at maximal exercise was 42+/-16 cm H2O. CONCLUSION: The small esophageal balloon was well tolerated by all subjects. Plots of deltaPes vs PTP, VE, and VO2 demonstrated a linear correlation. This apparatus could be added to the standard CPX to assess the contribution of the diaphragm and respiratory muscles in patients with dyspnea.

Adult↗
PubMed1996

Noninvasive positive pressure ventilation via face mask. First-line intervention in patients with acute hypercapnic and hypoxemic respiratory failure.

OBJECTIVES: We have previously reported our experience with noninvasive positive pressure ventilation (NPPV) via face mask in a small group of selected patients with acute respiratory failure (ARF). NPPV was frequently effective (70% success rate) in correcting gas exchange abnormalities and in avoiding endotracheal intubation (ETI); NPPV also had a low rate of complications. We have evaluated the clinical application of NPPV as first-line intervention in patients with hypercapnic and short-term hypoxemic ARF. A dedicated respiratory therapist conducted an educational program with physicians-in-training rotating through the medical ICUs of a university medical center and supervised implementation of a simplified management protocol. Over 24 months, 164 patients with heterogeneous forms of ARF received NPPV. We report on the effectiveness of NPPV in correcting gas exchange abnormalities, in avoiding ETI, and associated complications, in different conditions precipitating ARF. PATIENT POPULATION: One hundred fifty-eight patients completed the study. Forty-one had hypoxemic ARF, 52 had hypercapnic ARF, 22 had hypercapnic acute respiratory insufficiency (ARI), 17 had other forms of ARF, and 26 with advanced illness had ARF and refused intubation. Twenty-five percent of the patients developed ARF after extubation. INTERVENTION: Mechanical ventilation was delivered via a face mask. Initial ventilatory settings were continuous positive airway pressure (CPAP) mode, 5 cm H2O, with pressure support ventilation of 10 to 20 cm H2O titrated to achieve a respiratory rate less than 25 breaths/min and an exhaled tidal volume of 7 mL/kg or more. Ventilator settings were adjusted following arterial blood gases (ABG) results. RESULTS: The mean duration of NPPV was 25 +/- 24 h. When the 26 patients with advanced illness are excluded, NPPV was effective in improving or correcting gas exchange abnormalities in 105 patients (80%) and avoiding ETI in 86 (65%). Failure to improve ABG values was the reason for ETI in 20 of 46 (43%). The overall average predicted and actual mortality were 32% and 16%, respectively. Survival was 93% in non-intubated patients and 79% in intubated patients. NPPV was effective in lessening dyspnea throughout treatment in all but seven patients. Complications developed in 24 patients (16%). In patients with hypercapnic ARF, nonresponders had a higher PaCO2 at entrance (91.5 +/- 4.2 vs 80 +/- 1.5; p < 0.01). In patients with hypercapnic ARF and ARI, arterial blood gases response (pH and PaCO2) within 2 h of NPPV predicted success (p < 0.0001). None of the entrance parameters predicted need for ETI. CONCLUSIONS: We conclude that application of NPPV in clinical practice is an effective and safe alternative to ETI in many hemodynamically stable patients with hypercapnic ARF and in those with hypoxemic ARF in whom the clinical condition can be readily reversed in 48 to 72 h. An educational and supervision program is essential to successfully implement this form of therapy.

Acute Disease↗
PubMed1996

Noninvasive positive pressure ventilation in status asthmaticus.

OBJECTIVE: In asthmatic patients with acute respiratory failure (ARF), placing an endotracheal tube is associated with a high rate of complications and results in increased airway resistance. In acute asthma, mask-continuous positive airway pressure (CPAP) decreases airway resistance and the work of breathing (WOB), but does not improve gas exchange. In COPD with ARF, adding intermittent positive pressure ventilation to mask-CPAP results in an additional improvement in WOB and is highly effective in correcting gas exchange abnormalities. In our medical ICU, noninvasive positive pressure ventilation (NPPV) is used as first-line interventional therapy in eligible patients with hypercapnic ARF. We report our experience with NPPV in 17 episodes of asthma and ARF over a 3-year period. METHODS: A face mask was secured with head straps, avoiding a tight fit, and connected to a ventilator (PB-7200). Initial ventilatory settings included CPAP at 4 +/- 2 cm H2O to offset intrinsic positive end-expiratory pressure and pressure support ventilation (PSV) at 14 +/- 5 cm H2O aiming at a respiratory rate less than 25 breaths/min and an exhaled tidal volume of 7 mL/kg or more. PSV was then adjusted following arterial blood gas results. RESULTS: Mean age was 35.4 +/- 11.3 years; 10 patients were female. The mean (+/- SE) for different physiologic values are reported at initiation, less than 2 h, 2 to 6 h, and 12 to 24 h into NPPV. pH was 7.25 +/- 0.01, 7.32 +/- 0.02 (p = 0.0012), 7.36 +/- 0.02 (p < 0.0001), and 7.38 +/- 0.02; PaCO2 was 65 +/- 2, 52 +/- 3(p = 0.002), 45 +/- 3(p < 0.0001), and 45 +/- 4; PaO2 fraction of inspired oxygen was 315 +/- 41, 403 +/- 47, 367 +/- 47, and 472 +/- 67 (p = 0.06); and respiratory rate was: 29.1 +/- 1, 22 +/- 1 (p < 0.0001), 20 +/- 1, and 17 +/- 1. NPPV was well tolerated, and only two patients required sedation. Initial delivered minute ventilation was 16 +/- 4 L/min. The mean (+/- SD) peak inspiratory pressure to ventilate in the NPPV-treated patients was 18 +/- 5 cm H2O and always less than 25 cm H2O. There was no complication or problem with expectorating of secretions. Oral intake (liquid diet) was preserved. Two patients required intubation (35 min and 89 h into NPPV) for worsening PaCO2. Duration of NPPV was 16 +/- 21 h. All patients survived. Length of hospital stay was 5 +/- 4 days. CONCLUSIONS: In asthmatic patients with ARF, NPPV via a face mask appears highly effective in correcting gas exchange abnormalities using a low inspiratory pressure (< 25 cm H2O). A randomized study is in progress to assess fully the role of NPPV in status asthmaticus.

Adult↗
PubMed1995

Characterization of a specific interaction between Escherichia coli thymidylate synthase and Escherichia coli thymidylate synthase mRNA.

Previous studies have shown that human TS mRNA translation is controlled by a negative autoregulatory mechanism. In this study, an RNA electrophoretic gel mobility shift assay confirmed a direct interaction between Escherichia coli (E.coli) TS protein and its own E.coli TS mRNA. Two cis-acting sequences in the E.coli TS mRNA protein-coding region were identified, with one site corresponding to nucleotides 207-460 and the second site corresponding to nucleotides 461-807. Each of these mRNA sequences bind TS with a relative affinity similar to that of the full-length E.coli TS mRNA sequence (IC50 = 1 nM). A third binding site was identified, corresponding to nucleotides 808-1015, although its relative affinity for TS (IC50 = 5.1 nM) was lower than that of the other two cis-acting elements. E.coli TS proteins with mutations in amino acids located within the nucleotide-binding region retained the ability to bind RNA while proteins with mutations at either the nucleotide active site cysteine (C146S) or at amino acids located within the folate-binding region were unable to bind TS mRNA. These studies suggest that the regions on E.coli TS defined by the folate-binding site and/or critical cysteine sulfhydryl groups may represent important RNA binding domains. Further evidence is presented which demonstrates that the direct interaction with TS results in in vitro repression of E.coli TS mRNA translation.

Base Sequence↗
PubMed1995

A case-control study of hantavirus pulmonary syndrome during an outbreak in the southwestern United States.

In May 1993, an outbreak of hantavirus pulmonary syndrome (HPS) occurred in the southwestern United States. A case-control study determined risk factors for HPS. Seventeen case-patients were compared with 3 groups of controls: members of case-patient households (household controls), members of neighboring households (near controls), and members of randomly selected households > or = 24 km away (far controls). Investigators trapped more small rodents at case households than at near (P = .03) or far control households (P = .02). After the number of small rodents was controlled for, case-patients were more likely than household controls to hand plow (odds ratio [OR], 12.3; 95% confidence interval [CI], 1.1-143.0) or to clean feed storage areas (OR, 33.4; 95% CI, 1.7-666.0). Case-patients were more likely than near controls to plant (OR, 6.2; 95% CI, 1.1-34.0) and more likely than far controls to clean animal sheds (OR, 11.9; 95% CI, 1.4-103.0). Peridomestic cleaning, agricultural activities, and an increased number of small rodents at the household were associated with HPS.

Adolescent↗
PubMed1994

Separation and purification of recombinant proteins from Escherichia coli with aqueous two-phase systems.

The partition of the protein thaumatin in the presence of Escherichia coli contaminant proteins has been studied. Extraction of thaumatin was followed by back-extraction of the product into a new phosphate phase and also back extraction combined with recycle of the top polyethylene glycol (PEG) phase. When partitioned in the absence or presence of insoluble cell debris (whole cell homogenate) little effect on the partitioning of thaumatin or the soluble E. coli protein was observed. A back extraction step that allowed for dilution of the NaCl was successful in extracting thaumatin back into a heavy phosphate phase. The PEG top phase was recycled to the first extraction stage. The stability ratio (tie-line length) had an effect on the average partition coefficient (Kapp) of E. coli soluble proteins in PEG-phosphate systems but in PEG sulphate systems Kapp was independent of this ratio. An increase in NaCl resulted in an increase in Kapp but this was always below 1. A mathematical model that describes the continuous steady-state operation of extraction and back extraction has been developed; it is based on steady state mass balances of the main components and phase equilibrium data and was successfully used to simulate the extraction and back extraction processes.

Bacterial Proteins↗
PubMed1994

An evaluation of patient-controlled analgesia in adults undergoing cardiac surgery.

OBJECTIVE: To evaluate the effectiveness of patient-controlled analgesia (PCA) in postoperative cardiac surgery patients. DESIGN: Prospective evaluation. SAMPLE: Ten patients who had undergone coronary artery vein grafting. SETTING: A cardiac intensive care unit in a private clinic in London, UK. MEASUREMENTS: Pain scores, level of sedation and amount of analgesia and sedation required were recorded, together with each patient's perception of PCA. RESULTS: Patients had very little recall of their time in the ICU and none was aware of pain during this period. Patients liked managing their own pain. CONCLUSION: PCA is an effective means of controlling postoperative pain in cardiac surgery patients.

Aged↗
PubMed1990

The clinical presentation of command hallucinations in a forensic population.

In a forensic population, patients with command hallucinations (N = 25) were compared to two groups of psychotic patients: those with noncommand hallucinations (N = 24) and those without hallucinations (N = 16). The three groups did not differ in overall impairment as measured by the Global Assessment Scale and the Social Behavior Rating Schedule. However, the group with command hallucinations differed in the content of their hallucinations (more aggression, dependency, and self-punishment themes), and nearly one-half did not report or denied their command hallucinations to the assessment team. Many patients (N = 11, 44%) reported that they frequently responded to hallucinatory commands with unquestioning obedience.

Adult↗