bluuebunny/crossref_metadata_2025_split huggingface dataset:
Variation in the decision to terminate pregnancy in the setting of fetal aneuploidy
Authors: Shaffer Brian L. , Caughey Aaron B. , Norton Mary E. 
Published: May 2006

AbstractObjectiveTo investigate the rate of pregnancy termination for various fetal aneuploidies, and to evaluate predictors of this choice.MethodsA retrospective cohort study identified all patients with any of seven common fetal aneuploidies (trisomies 21, 18, and 13; 45,X, 47,XXX, 47,XXY, and 47,XYY) at a referral prenatal diagnosis unit from 1983 to 2003. We abstracted type of aneuploidy, time and type of diagnostic procedure, maternal age, and ethnicity as predictors of the decision to terminate. Statistical comparisons were made using the chi‐square test. Potential confounding variables were controlled for using multivariate logistic regression.ResultsOverall, there were 833 patients who had fetuses with aneuploidy. In our study population, the overall rate of termination was 81%: 86% in cases of autosomal trisomy and 60% in cases of sex chromosome aneuploidy (SCA) (p < 0.001). Rates were lowest in cases with the least severe prognosis, 47,XYY (57%) and 47,XXX (40%) compared with 45,X (65%) and 47,XXY (70%) (p = 0.05). Patients with SCA detected by chorionic villus sampling (CVS) had a higher termination rate than those who had undergone amniocentesis (77% vs 55%, p = 0.015). Increased maternal age was associated with higher termination rates in autosomal trisomy (88% vs 76% p < 0.001) and a trend toward decreased rates in those with SCA (55% vs 71%, p = 0.06). Hispanic women were less likely to terminate pregnancy (69%, p = 0.01) than those from other racial/ethnic groups.ConclusionType and severity of aneuploidy, type of diagnostic procedure, maternal age, and ethnicity contribute to patients' decision‐making in the setting of fetal aneuploidy. Copyright © 2006 John Wiley & Sons, Ltd.
Nonuniversal transport behavior in heterogeneous high‐density polyethylene/graphite nanosheet composites
Authors: Lu Wei , Lin Hongfei , Chen Guohua 
Published: May 2006

AbstractThe direct‐current resistivity of high‐density polyethylene/graphite nanosheet composites above the percolation threshold has been measured and fitted to a power law, which gives a conductivity critical exponent (0.10 ± 0.01) and a percolation threshold (2.97 ± 0.03). These fitted parameters are in disagreement with universal theoretical predictions, and plausible explanations of the observed discrepancies are given. The sample‐to‐sample fluctuations in the relative resistivity seem to obey a power law. This fluctuation behavior, if interpreted in terms of correlation‐length fluctuations, yields a correlation‐length critical exponent, 0.52 ± 0.06, that is consistent with the mean‐field value of 1/2. Interpretations of these experimental results imply that nonuniversal transport behavior in disordered composites is caused by composites being in a nonuniversal scaling regime. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1846–1852, 2006
Error distribution derived NOE distance restraints
Authors: Nilges Michael , Habeck Michael , O'Donoghue Seán I. , Rieping Wolfgang 
Published: May 2006

AbstractErrors and imprecisions in distance restraints derived from NOESY peak volumes are usually accounted for by generous lower and upper bounds on the distances. In this paper, we propose a new form of distance restraints, replacing the subjective bounds by a potential function obtained from the error distribution of the distances. We derived the shape of the potential from molecular dynamics calculations and by comparison of NMR data with X‐ray crystal structures. We used complete cross‐validation to derive the optimal weight for the data in the calculation. In a model system with synthetic restraints, the accuracy of the structures improved significantly compared to calculations with the usual form of restraints. For experimental data sets, the structures systematically approach the X‐ray crystal structures of the same protein. Also standard quality indicators improve compared to standard calculations. The results did not depend critically on the exact shape of the potential. The new approach is less subjective and uses fewer assumptions in the interpretation of NOESY peak volumes as distance restraints than the usual approach. Figures of merit for the structures, such as the RMS difference from the average structure or the RMS difference from the data, are therefore less biased and more meaningful measures of structure quality than with the usual form of restraints. Proteins 2006. © 2006 Wiley‐Liss, Inc.
Ab initio computational modeling of loops in G‐protein‐coupled receptors: Lessons from the crystal structure of rhodopsin
Authors: Mehler Ernest L. , Hassan Sergio A. , Kortagere Sandhya , Weinstein Harel 
Published: May 2006

AbstractWith the help of the crystal structure of rhodopsin an ab initio method has been developed to calculate the three‐dimensional structure of the loops that connect the transmembrane helices (TMHs). The goal of this procedure is to calculate the loop structures in other G‐protein coupled receptors (GPCRs) for which only model coordinates of the TMHs are available. To mimic this situation a construct of rhodopsin was used that only includes the experimental coordinates of the TMHs while the rest of the structure, including the terminal domains, has been removed. To calculate the structure of the loops a method was designed based on Monte Carlo (MC) simulations which use a temperature annealing protocol, and a scaled collective variables (SCV) technique with proper structural constraints. Because only part of the protein is used in the calculations the usual approach of modeling loops, which consists of finding a single, lowest energy conformation of the system, is abandoned because such a single structure may not be a representative member of the native ensemble. Instead, the method was designed to generate structural ensembles from which the single lowest free energy ensemble is identified as representative of the native folding of the loop. To find the native ensemble a successive series of SCV‐MC simulations are carried out to allow the loops to undergo structural changes in a controlled manner. To increase the chances of finding the native funnel for the loop, some of the SCV‐MC simulations are carried out at elevated temperatures. The native ensemble can be identified by an MC search starting from any conformation already in the native funnel. The hypothesis is that native structures are trapped in the conformational space because of the high‐energy barriers that surround the native funnel. The existence of such ensembles is demonstrated by generating multiple copies of the loops from their crystal structures in rhodopsin and carrying out an extended SCV‐MC search. For the extracellular loops e1 and e3, and the intracellular loop i1 that were used in this work, the procedure resulted in dense clusters of structures with Cα‐RMSD ∼0.5 Å. To test the predictive power of the method the crystal structure of each loop was replaced by its extended conformations. For e1 and i1 the procedure identifies native clusters with Cα‐RMSD ∼0.5 Å and good structural overlap of the side chains; for e3, two clusters were found with Cα‐RMSD ∼1.1 Å each, but with poor overlap of the side chains. Further searching led to a single cluster with lower Cα‐RMSD but higher energy than the two previous clusters. This discrepancy was found to be due to the missing elements in the constructs available from experiment for use in the calculations. Because this problem will likely appear whenever parts of the structural information are missing, possible solutions are discussed. Proteins 2006. © 2006 Wiley‐Liss, Inc.
Short Thyromental Distance: A Predictor of Difficult Intubation or an Indicator for Small Blade Selection?
Authors: Tripathi Mukesh , Pandey Mamta 
Published: May 2006

Background
Short thyromental distance (TMD; < 5 cm) has been correlated with difficult direct laryngoscopic intubation in adult patients. The authors hypothesized that a smaller Macintosh curved blade (No. 2 MCB) would improve the predicted difficult laryngoscopy in short-TMD patients over that with a standard Macintosh curved blade (No. 3 MCB).

Methods
In a preliminary study of 11 consenting adults (7 females and 4 males), American Society of Anesthesiologists physical status I and TMD < or = 5 cm, lateral neck radiographs were recorded during laryngoscopy with a No. 2 and No. 3 MCB in sequential fashion. In a prospective clinical study, laryngoscopy and tracheal intubation were evaluated in 83 adult patients with TMD < or = 5 cm by randomly assigning them to two groups for the blade used at first intubation. Those who failed intubation with the first blade were switched to the alternate blade. In total 100 laryngoscopies and intubations were performed: the No. 2 MCB (n = 50) and the No. 3 MCB (n = 50).

Results
Lateral neck radiographs recorded at the best laryngeal view revealed that the tip of the No. 2 MCB was proximal to the hyoid body with the No. 2 MCB and distal to it with the No. 3 MCB. The intubation distance (C5 to blade tip) on neck radiographs with the No. 2 MCB was significantly greater than it was with the No. 3 MCB for similar anterior jaw displacement. In the clinical study, the laryngoscopic grade with the No. 2 blade was considered easy (median, 2B), better than the grade with the No. 3 MCB (median, 3). When the No. 2 MCB was used, external laryngeal pressure improved the laryngoscopic grade (1, full glottic view) in 46% of patients. In contrast, when the No. 3 MCB was used, pressure improved the grade in only 10% of the patients. Intubation time with the No. 2 MCB was significantly (P < 0.05) less than it was in patients with No. 3 MCB. Overall, 14 patients who failed intubation with the No. 3 MCB were switched to the No. 2 MCB, and intubation was successful with an easy laryngoscopic grade. Three patients who failed intubation with the No. 2 MCB were switched to the No. 3 MCB.

Conclusions
The predicted difficult laryngoscopy and intubation with the use of the adult No. 3 MCB in standard adult patients with a TMD < or = 5 cm is significantly easier with use of the smaller No. 2 MCB.
A Comparison of the Effect of High- and Low-dose Fentanyl on the Incidence of Postoperative Cognitive Dysfunction after Coronary Artery Bypass Surgery in the Elderly
Authors: Silbert Brendan S. , Scott David A. , Evered Lisbeth A. , Lewis Matthew S. , Kalpokas Mario , Maruff Paul , Myles Paul S. , Jamrozik Konrad 
Published: May 2006

Background
Postoperative cognitive dysfunction (POCD) after coronary artery bypass graft surgery is a common complication for which, despite many clinical investigations, no definitive etiology has been found. The current use of both high- and low-dose fentanyl as anesthetic techniques allowed us to investigate the effect of fentanyl on the incidence of POCD.

Methods
Three hundred fifty patients scheduled to undergo elective coronary artery bypass graft surgery were randomized to receive either high-dose fentanyl (50 microg/kg) or low-dose fentanyl (10 mug/kg) as the basis of the anesthetic. All patients underwent neuropsychological testing before surgery and at 1 week, 3 months, and 12 months after surgery.

Results
One hundred sixty-eight patients in the low-dose group and 158 patients in the high-dose group were included in the final analysis. Neuropsychological testing was performed on 88%, 93%, and 92% of patients at 1 week, 3 months, and 12 months, respectively. There was no difference between group mean scores at any of the three testing times. Analysis of individual patients by the 20% rule did not detect any differences between groups. The one SD rule, which has fewer false-positive results, detected significantly more patients with POCD in the low-dose group than in the high-dose group at 1 week (23.6% vs. 13.7%; P = 0.03) but not at the other testing times. Patients with POCD spent an average of 1.2 days longer in the hospital than those without POCD (P = 0.021).

Conclusions
High-dose fentanyl is not associated with a difference in the incidence of POCD at 3 or 12 months after surgery. Low-dose fentanyl leads to shorter postoperative ventilation times and may be associated with a greater incidence of POCD 1 week after surgery. Early POCD is associated with an increased duration of stay in the hospital.
Malignant Hyperthermia in Japan
Authors: Ibarra M Carlos A. , Wu Shiwen , Murayama Kumiko , Minami Narihiro , Ichihara Yasuko , Kikuchi Hirosato , Noguchi Satoru , Hayashi Yukiko K. , Ochiai Ryoichi , Nishino Ichizo 
Published: May 2006

Background
Malignant hyperthermia (MH) is a disorder of calcium homeostasis in skeletal muscle triggered by volatile anesthetics or succinylcholine in susceptible persons. More than 100 mutations in the ryanodine receptor type 1 gene (RYR1) have been associated with MH susceptibility, central core disease, or both. RYR1 mutations may account for up to 70% of MH-susceptible cases. The authors aimed to determine the frequency and distribution of RYR1 mutations in the Japanese MH-susceptible population.

Methods
The authors selected 58 unrelated Japanese diagnosed as MH-susceptible for having an enhanced Ca-induced Ca release rate from the sarcoplasmic reticulum on chemically skinned muscle fibers. They sequenced the entire RYR1 coding region from genomic DNA. Muscle pathology was also characterized.

Results
Seven previously reported and 26 unknown RYR1 potentially pathogenic sequence variations were identified in 33 patients (56.9%). Of these patients, 48% had cores on muscle biopsy. The mutation detection rate was higher in patients with clear enhancement of Ca-induced Ca release rate (72.4%), whereas all patients with central core disease had RYR1 mutations. Six patients harbored potentially causative compound heterozygous sequence variations.

Conclusions
Distribution and frequency of RYR1 mutations differed markedly from those of the North American and European MH-susceptible population. Comprehensive screening of the RYR1 gene is recommended for molecular investigations in MH-susceptible individuals, because many mutations are located outside the "hot spots." Based on the observed occurrence of compound heterozygous state, the prevalence of a possibly predisposing phenotype in the Japanese population might be as high as 1 in 2,000 people.
Differences between Midazolam and Propofol Sedation on Upper Airway Collapsibility Using Dynamic Negative Airway Pressure
Authors: Norton J Russell , Ward Denham S. , Karan Suzanne , Voter William A. , Palmer Linda , Varlese Anna , Rackovsky Ori , Bailey Peter 
Published: May 2006

Background
Upper airway obstruction (UAO) during sedation can often cause clinically significant adverse events. Direct comparison of different drugs' propensities for UAO may improve selection of appropriate sedating agents. The authors used the application of negative airway pressure to determine the pressure that causes UAO in healthy subjects sedated with midazolam or propofol infusions.

Methods
Twenty subjects (12 male and 8 female) completed the study. After achieving equivalent levels of sedation, the subjects' ventilation, end-tidal gases, respiratory inductance plethysmographic signals, and Bispectral Index values were monitored for 5 min. Negative airway pressure was then applied via a facemask in steps of 3 cm H(2)O from -3 to -18 cm H(2)O. UAO was assessed by cessation of inspiratory airflow and asynchrony between abdomen and chest respiratory inductance plethysmographic signals.

Results
Equivalent levels of sedation were achieved with both drugs with average (+/- SD) Bispectral Index levels of 75 +/- 5. Resting ventilation was mildly reduced without any changes in end-tidal pressure of carbon dioxide. There was no difference between the drugs in the negative pressure resulting in UAO. Five female subjects and one male subject with midazolam and four female subjects and one male subject with propofol did not show any UAO even at -18 cm H(2)O. Compared with males, female subjects required more negative pressures to cause UAO with midazolam (P = 0.02) but not with propofol (P = 0.1).

Conclusions
At the mild to moderate level of sedation studied, midazolam and propofol sedation resulted in the same propensity for UAO. In this homogeneous group of healthy subjects, there was a considerable range of negative pressures required to cause UAO. The specific factors responsible for the maintenance of the upper airway during sedation remain to be elucidated.
Interaction of Propofol and Sevoflurane on Loss of Consciousness and Movement to Skin Incision during General Anesthesia
Authors: Harris Robert S. , Lazar Olga , Johansen Jay W. , Sebel Peter S. 
Published: May 2006

Background
Loss of consciousness (LOC) and immobility to surgical incision seem to be mediated at different levels of the central nervous system. Pharmacologic studies of hypnotic agents have previously focused on combinations of either volatile or intravenous anesthetics. This study examined the combination of inhaled sevoflurane and intravenous propofol at these two clinically relevant anesthetic end points.

Methods
Thirty-six elective surgical patients were initially enrolled. Conditions approximating steady state were obtained for sevoflurane and target-controlled propofol infusions. Patients were sequentially evaluated for LOC (loud voice plus mild prodding) and immobility to surgical incision. The study was designed using the Dixon up-down method.

Results
The observed propofol effect target with 50% response plus sevoflurane (0.46% end-tidal concentration) was 1.2 microg/ml (95% confidence interval, 1.1-1.3 microg/ml). It was not significantly different from that predicted (1.5 microg/ml; 95% confidence interval, 1.2-1.7 microg/ml) by simple additivity. The effective plasma concentration of propofol that suppressed movement to skin incision in 50% of patients was 5.4 microg/ml (95% confidence interval, 4.8-6.0 microg/ml) plus sevoflurane (0.86%) and was not significantly different from that predicted by additivity (5.4 microg/ml; 95% confidence interval, 4.8-5.9 microg/ml). Both analyses had adequate power (90%) to detect a significant change (+/-19 to 25%) from predicted value. Repeated-measures analysis of variance identified a Bispectral Index value of 70 as the break point between those who responded at LOC or did not.

Conclusions
Propofol and sevoflurane interact in a simple additive manner to produce LOC and immobility to surgical incision, suggesting a common mechanism or a single site of action. These clinical observations are consistent with a single site of interaction at the gamma-aminobutyric acid type A receptor.
Preparation and Anesthetic Properties of Propofol Microemulsions in Rats
Authors: Morey Timothy E. , Modell Jerome H. , Shekhawat Dushyant , Grand Todd , Shah Dinesh O. , Gravenstein Nikolaus , McGorray Susan P. , Dennis Donn M. 
Published: May 2006

Background
The lipophilicity of propofol has required dispersion in a soybean macroemulsion. The authors hypothesized that the anesthetic properties of propofol are preserved when reformulated as a transparent microemulsion rather than as a turbid macroemulsion and that the dose-response relation can be selectively modified by altering the microemulsion's surfactant type and concentration.

Methods
Microemulsions of propofol were formulated using purified poloxamer 188 (3%, 5%, 7%), and sodium salt of fatty acids (C(8), C(10), C(12)) in saline and characterized using ternary/binary diagrams, particle sizing, and stability upon dilution. Rats received propofol (10 mg . kg(-1) . min(-1)) as either a microemulsion or a conventional macroemulsion to determine these end points: induction (dose; stunned; loss of lash reflex, righting reflex, withdrawal to toe pinch) and recovery (recovery of lash, righting, withdrawal reflexes). After a 14-day recovery period, rats were crossed over into the opposite experimental limb.

Results
Forty-eight microemulsions (diameter, 11.9-47.7 nm) were formulated. Longer carbon chain length led to a marked increase in the volume of diluent necessary to break these microemulsions. All rats experienced anesthetic induction with successful recovery, although significantly greater doses of propofol were required to induce anesthesia with microemulsions irrespective of surfactant concentration or type than with macroemulsions. The sodium salt of C10 fatty acid microemulsion required the greatest dose and longest time for anesthetic induction.

Conclusion
Propofol microemulsions cause induction in rats similar to that from macroemulsions. The surfactant concentration and type markedly affect the spontaneous destabilization and anesthetic properties of microemulsions, a phenomenon suggesting a mechanism whereby dose-response relation can be selectively modified.
Blood Warming during Hemofiltration Can Improve Hemodynamics and Outcome in Ovine Septic Shock
Authors: Rogiers Peter , Sun Qinghua , Dimopoulos George , Tu Zizhi , Pauwels Dirk , Manhaeghe Cindy , Su Fuhong , Vincent Jean-Louis 
Published: May 2006

Background
This study was designed to evaluate the effects of blood warming during hemofiltration on global and regional hemodynamics, plasma lactate, and 24-h survival during septic shock.

Methods
Twenty anesthetized and mechanically ventilated sheep underwent induction of peritonitis and, 4 h later, were treated by hemofiltration with (n = 10) or without (n = 10) blood warming.

Results
In the group without blood warming, body temperature decreased after starting hemofiltration and remained below baseline. In the other animals, body temperature stabilized at baseline level during hemofiltration and increased to a maximum of 40.8 degrees C thereafter. The group without warming experienced a decrease in blood pressure (from 90 mmHg to 38 mmHg) and cardiac output (from 4.0 l/min to 2.3 l/min). Metabolic acidosis and the increase in lactate were less marked when temperature was maintained. None of the animals without warming but all of the animals with warming survived to 16 h.

Conclusions
Differences in temperature during hemofiltration resulted in striking differences in hemodynamics, metabolic acidosis, and survival rate in this clinically relevant experimental model of septic shock.