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L Barker

Publications and source records attributed to L Barker.

At least 37 records · Page 2Linked to original sources
PubMed2000

Predicting the success of a trial of labor with a simple scoring system.

OBJECTIVE: To determine the applicability of a simple scoring system, by Troyer and Parisi, in predicting the success of a trial of labor among parturients with prior cesarean delivery. STUDY DESIGN: Retrospectively, all patients who underwent a trial of labor over six consecutive years were reviewed. chi 2, Fisher's exact test and analysis of variance followed by the Turkey or Dunn test were used when appropriate. P < .05 was considered significant. RESULTS: There were 263 trials of labor, of which 63% (167) ended in vaginal delivery. While 21% had a score of 0, 40%, 28% and 11% had a score of 1, 2 and at least 3, respectively. The frequency of vaginal birth was significantly different between the four groups (P < .001): 98% for a score of 0, 69% for 1, 40% for 2 and 33% for 3-4. Occurrence of cesarean delivery for cephalopelvic disproportion (2%, 24%, 39%, 56%; P < .001) or for a nonreassuring fetal heart rate tracing (0%, 7%, 21%, 11%; P < .001) was significantly different between the four groups. CONCLUSION: In our population, we confirmed the inverse relationship between the Troyer-Parisi scoring system and a successful trial of labor.

Adult↗
PubMed1999

Identification of a pollen-specific sucrose transporter-like protein NtSUT3 from tobacco.

Pollen cells are symplasmically isolated during maturation and germination. Pollen therefore needs to take up nutrients via membrane carriers. Physiological measurements on pollen indicate sucrose transport in the pollen tube. A cDNA encoding a pollen-specific sucrose transporter-like protein NtSUT3 was isolated from a tobacco pollen cDNA library. NtSUT3 expression is detected only in pollen and is restricted to late pollen development, pollen germination and pollen tube growth. Altogether these data indicate that pollen is supplied not only with glucose, but also with sucrose through a specific sucrose transporter. The respective contribution of each transport pathway may change during pollen tube growth.

Amino Acid Sequence↗
PubMed1994

Pulmonary function in spinal muscular atrophy.

We present the first prospective study on pulmonary function in spinal muscular atrophy patients. Seventy-seven spinal muscular atrophy patients, ages 5 to 18 years, from three centers, were studied with regard to forced vital capacity, using height as a predictor. Patients were categorized into four motor function categories. The highest-functioning group had normal or near-normal values, and those who sat with support had the lowest values. Those with intermediate function had intermediate values. Forced vital capacity was studied longitudinally in 40 spinal muscular atrophy patients for 1.1 to 4.4 years. Eighty-eight percent of patients grew in height, but only 35% showed an increase in height-adjusted forced vital capacity percent. In those patients with the least function, 100% lost height-adjusted forced vital capacity over time. In those patients with the highest function, 57% lost height-adjusted forced vital capacity. In addition, the basic forced vital capacity, not correlated to height, decreased in 43% of cases. These pulmonary function alterations appear to be important determinants for function and survival in spinal muscular atrophy patients.

Adolescent↗
PubMed1993

The Australian Incident Monitoring Study. The pulse oximeter: applications and limitations--an analysis of 2000 incident reports.

The first 2000 incidents reported to the Australian Incident Monitoring Study were analysed with respect to the role of the pulse oximeter. Of these 184 (9%) were first detected by a pulse oximeter and there were a further 177 (9%) in which desaturation was recorded. Of the 1256 incidents which occurred in association with general anaesthesia 48% were "human detected" and 52% "monitor detected". The pulse oximeter was ranked first and detected 27% of these monitor detected incidents; this figure would have been over 40% if an oximeter had always been used and its more informative modulated pulse tone relied upon instead of that of the "bleep" of the ECG. The pulse oximeter is the "front-line" monitor for endobronchial intubation, the fourth most common incident in association with general anaesthesia (it detected 87% of the 76 cases in which it was in use). It also played an invaluable role as a "back-up" monitor in 40 life-threatening situations in which "front-line" monitors (e.g. oxygen analyser, low pressure alarm, capnograph) were either not in use, were being used incorrectly or failed. Other situations detected, in order of frequency of detection, were: circuit disconnection, circuit leak, desaturation (severe shunt), oesophageal intubation, aspiration and/or regurgitation, pulmonary oedema, endotracheal tube obstruction, severe hypotension, failure of oxygen delivery, hypoxic gas mixture, hypoventilation, anaphylaxis, air embolism, bronchospasm, malignant hyperthermia, and tension pneumothorax.(ABSTRACT TRUNCATED AT 250 WORDS)

Accidents↗
PubMed1993

The Australian Incident Monitoring Study. The oxygen analyser: applications and limitations--an analysis of 200 incident reports.

The first 2000 incidents reported to the Australian INcident Monitoring Study were analysed with respect to the role of the oxygen analyser; 27 (1%) were first detected by the oxygen analyser. All of these were amongst the 1256 incidents which occurred in association with general anaesthesia, of which 48% were "human detected" and 52% "monitor detected". The oxygen analyser was ranked 7th and detected 4% of these monitor detected incidents. This figure would have been much higher had the oxygen analyser been correctly used on more occasions. The oxygen analyser detected 10 ventilator-driving-gas leaks into the circuit, 6 hypoxic mixtures due to rotameter settings, 3 inappropriate nitrous oxide concentrations, 2 disconnections and 1 leak at the common gas outlet, and 2 partial and 1 total failure of ventilation. In a theoretical analysis of these 1256 incidents it was considered that the oxygen analyser, used on its own, would have detected 114 (9%), had they been allowed to evolve (3% before any potential for organ damage). In 4 incidents an oxygen analyser gave faulty readings, in 3 caused a leak and in one a total circuit obstruction; 5 incidents were not detected because the alarm had been disabled. Despite the advent of piped gas supplies, failure of gas delivery or delivery of a "wrong" gas mixture still occurs surprisingly frequently in current anaesthetic practice; hypoxic mixtures were supplied on 16 occasions, other "wrong" mixtures on 23 and the oxygen supply failed on 7 occasions.(ABSTRACT TRUNCATED AT 250 WORDS)

Accidents↗
PubMed1993

The Australian Incident Monitoring Study. Crisis management--validation of an algorithm by analysis of 2000 incident reports.

Anaesthetists are called upon to manage complex life-threatening crises at a moment's notice. As there is evidence that this may require cognitive tasking beyond the information-processing capacity of the human brain, it was decided to try and develop a generic crisis management algorithm analogous to the "Phase I" immediate response routine used by airline pilots. Such an algorithm, based on the mnemonic "COVER ABCD, A SWIFT CHECK", was developed and refined over 3 meetings, each attended by 60-100 anaesthetists and aviation psychologists. It was validated against 1301 relevant incidents among the first 2000 incidents reported to the Australian Incident Monitoring Study. It proved sufficiently robust and safe to recommend its general use as an initial response to any incident or crisis which occurs when a patient is breathing gas from an anesthetic machine. It requires a limited knowledge base and is easily learnt and rehearsed during the anaesthetist's working day. It will provide a functional diagnosis in over 99% of cases and will correct 62% of the problems in 40-60 seconds. In the remaining 37% it will allow the anaesthetist to proceed with a "sub-algorithm", confident in the knowledge that some important step has not been missed. In just over 30% of incidents this will be for a problem familiar to all anaesthetists (e.g. laryngospasm, bradycardia); in just over 6% it will be for a less common, more complex, but finite, set of problems (3% cardiac arrest, 1% air embolism, 1% anaphylaxis, 1% for the remaining desaturations); in less than 1% diagnosis and correction will require a more complex checklist (e.g. for malignant hyperthermia, pneumothorax). The next stage, the development of specific sub-algorithms and a structured team approach for ongoing problems, is in progress.

Algorithms↗
PubMed1993

Evaluation of safety procedures in anaesthesia and intensive care.

A study was conducted to determine the ability of junior anaesthetists to check the anaesthetic machine, demonstrate a knowledge of a multifunction monitor and a defibrillator, and know the hospital fire drill. The subjects were 38 junior anaesthetists working in a large multi-disciplinary teaching hospital. 45% were able to check the anaesthetic machine according to the guidelines of the Australian and New Zealand College of Anaesthetists, and 16% had a complete working knowledge of the monitor. All subjects could use the defibrillator but only 24% could adequately solve the problem of malfunction. Only one subject had a working knowledge of the fire drill; excluding knowledge of the fire drill only 3 subjects (8%) satisfactorily completed all aspects of the assessment. As a result of this study structured checking routines are being introduced into anaesthetic teaching and practice and a similar multi-center study of specialist anaesthetists is being planned.

Anesthesia↗
PubMed1992

Benefits of combined balloon pumping and percutaneous cardiopulmonary bypass.

Sixteen patients (2 women, 14 men) aged 29 to 72 years with continued cardiogenic shock during intraaortic balloon pumping (IABP) had additional treatment with percutaneous cardiopulmonary bypass (PBY). Cause of cardiogenic shock was myocardial infarction in 7 (3 survived), failed percutaneous transluminal coronary angioplasty requiring emergency coronary artery bypass grafting in 5, postoperative aortic valve replacement in 1, postoperative emergency coronary artery bypass grafting in 1, after cardiac transplantation in 1, and bridging to transplantation in 1. Mean blood pressure with PBY and IABP combined was 75 mm Hg versus 60 mm Hg with IABP off. Percutaneous cardiopulmonary bypass flows ranged from 0.8 to 2.1 L/min with a mean flow of 1.3 L/min. Time on IABP ranged from 24 hours to 1 week. Time on IABP to PBY ranged from 1 to 20 hours, and time on PBY ranged from 65 minutes to 20 hours. Ten of 16 (63%) were successfully weaned, and 3 died after weaning. Seven of 16 (44%) survive. Combined IABP with PBY appears to be a better therapy than either one individually. Staging the therapy as the balloon first in and last out appears to be a good methodology.

Adult↗
PubMed1992

Spinal muscular atrophy: new thoughts on the pathogenesis and classification schema.

We have established the first prospective, collaborative study of spinal muscular atrophy, the second most common neuromuscular disease of childhood. One hundred and forty-one patients have been evaluated on at least four occasions over a 3-year period. The patients have been grouped by age of onset, as well as by function at the time of initial evaluation. The muscle strength of 96 patients aged 5 years or older was evaluated at 6-month intervals using a fixed myometry system. The new observations made are: (1) The present classification schema is not valid; for example, 49 patients with onset of weakness before 6 months of age (type I or Werdnig-Hoffmann disease), whose life span is said to be only 2 to 4 years, participated in the study and are 4 months to 31 years of age. (2) Thirty-seven patients were evaluated over an 18-month period. None lost strength during this time but four lost function. Although the period of observation was short, the results suggest that the loss of function in patients with spinal muscular atrophy might be explained by a process other than cell death that allows patient strength to be maintained and simultaneously prevents the motor unit from achieving its normal adult potential.

Adolescent↗
PubMed1988

Vasoactive intestinal polypeptide alters GH3/B6 pituitary cell excitability.

The effects of the prolactin secretagogue vasoactive intestinal peptide (VIP) on the membrane excitability of clonal prolactin-secreting (GH3/B6) cells were studied using the whole-cell configuration of the patch recording technique. Submicromolar concentrations of VIP affected membrane excitability in more than half the cells tested, increasing the frequency of spontaneous Ca2+-dependent action potentials and prolonging individual action potentials, as well as changing their rheobase. Under voltage clamp, VIP induced changes in several voltage-sensitive conductances at both instantaneous and steady-state times. Some of these changes in membrane excitability may be related to VIP's stimulatory effects on prolactin secretion.

Action Potentials↗
PubMed1985

Mammalian chymotrypsin-like enzymes. Comparative reactivities of rat mast cell proteases, human and dog skin chymases, and human cathepsin G with peptide 4-nitroanilide substrates and with peptide chloromethyl ketone and sulfonyl fluoride inhibitors.

The extended substrate binding sites of several chymotrypsin-like serine proteases, including rat mast cell proteases I and II (RMCP I and II, respectively) and human and dog skin chymases, have been investigated by using peptide 4-nitroanilide substrates. In general, these enzymes preferred a P1 Phe residue and hydrophobic amino acid residues in P2 and P3. A P2 Pro residue was also found to be quite acceptable. The S4 subsites of these enzymes are less restrictive than the other subsites investigated. The substrate specificity of these enzymes was also investigated by using substrates which contain model desmosine residues and peptides with amino acid sequences of the physiologically important substrates angiotensin I and angiotensinogen and alpha 1-antichymotrypsin, the major plasma inhibitor for chymotrypsin-like enzymes. These substrates were less reactive than the most reactive tripeptide reported here, Suc-Val-Pro-Phe-NA. The thiobenzyl ester Suc-Val-Pro-Phe-SBzl was found to be an extremely reactive substrate for the enzymes tested and was 6-171-fold more reactive than the 4-nitroanilide substrate. The four chymotrypsin-like enzymes were inhibited by chymostatin and N-substituted saccharin derivatives which had KI values in the micromolar range. In addition, several potent peptide chloromethyl ketone and substituted benzenesulfonyl fluoride irreversible inhibitors for these enzymes were discovered. The most potent sulfonyl fluoride inhibitor for RMCP I, RMCP II, and human skin chymase, 2-(Z-NHCH2CONH)C6H4SO2F, had kobsd/[I] values of 2500, 270, and 1800 M-1 s-1, respectively. The substrates and inhibitors reported here should be extremely useful in elucidating the physiological roles of these proteases.

Amino Acid Chloromethyl Ketones↗
PubMedDate not supplied

Logistic regression when binary predictor variables are highly correlated.

Standard logistic regression can produce estimates having large mean square error when predictor variables are multicollinear. Ridge regression and principal components regression can reduce the impact of multicollinearity in ordinary least squares regression. Generalizations of these, applicable in the logistic regression framework, are alternatives to standard logistic regression. It is shown that estimates obtained via ridge and principal components logistic regression can have smaller mean square error than estimates obtained through standard logistic regression. Recommendations for choosing among standard, ridge and principal components logistic regression are developed. Published in 2001 by John Wiley & Sons, Ltd.

Computer Simulation↗