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Biomedical subjects

D E Wood

Publications and source records attributed to D E Wood.

At least 19 recordsLinked to original sources
PubMed1995

Efficacy of a 6-week prophylactic ganciclovir regimen and the role of serial cytomegalovirus antibody testing in lung transplant recipients.

CMV is a frequently occurring pathogen in recipients of solid organ transplants, and those receiving lung transplants seem to be affected more frequently and more severely. Because the duration of prophylactic ganciclovir may influence the incidence of CMV disease in solid organ transplant recipients, we evaluated the efficacy of a 6-week prophylactic regimen in lung transplant recipients. We also evaluated the ability of a fourfold rise in CMV antibody titer to predict the development of CMV disease. Twenty-one consecutive lung transplant recipients were enrolled: 15 were CMV antibody-positive at the time of transplantation, and six were CMV antibody-negative and received a lung transplant from CMV-positive donors. Mean +/- SD follow-up was 430 +/- 157 days (range 178-730 days, median 449 days). The 6-week ganciclovir regimen prevented neither CMV infection (which occurred in 17/21 patients, 81%) nor CMV disease (seen in 8/21 patients, 38%). A fourfold rise in CMV antibody titer only preceded the onset of CMV disease in 3/13 instances (23%). We conclude that a 6-week regimen of ganciclovir prophylaxis does not prevent CMV infection or disease in lung transplant recipients and that a rise in serially obtained CMV antibody titers rarely precedes the development of CMV disease.

Antibodies, Viral↗
PubMed1995

Coordination and neuromuscular control of rhythmic behaviors in the blue crab, Callinectes sapidus.

The stereotypical courtship display (CD) behavior of the male blue crab, Callinectes sapidus, includes an unusual component: the rhythmic waving of the swimming appendages above the carapace. This behavior occurs in a unique context but it resembles two other rhythmic behaviors performed using the swimming legs: sideways swimming and backward swimming. As a first step to understanding the mechanisms that allow the expression of apparently different rhythmic motor patterns, we have examined these behaviors using slow motion video analysis and electromyography of the basal muscles of the swimming legs in freely behaving crabs. The results show that these behaviors are distinguished by four parameters: the frequency of leg waving, the phase relationship between the legs, the presence of a stationary pause in basal muscle activity combined with rotation of the distal leg during CD, and an extended range of motion of these legs during CD and backward swimming, relative to sideways swimming. EMG analysis revealed that during sideways swimming, the sequence of muscular activity between the two legs was different. In contrast, during CD and backward swimming the sequence of activity for these legs is identical.

Animals↗
PubMed1995

Modulation of behavior by biogenic amines and peptides in the blue crab, Callinectes sapidus.

Using the blue crab Callinectes sapidus as a model system, we have investigated the effects of potential neuromodulators on freely behaving animals. Of interest is the modulatory effect of a number of drugs on three rhythmic behaviors of the blue crab: courtship display (CD) of the male crab, sideways swimming and backward swimming. The drugs tested were proctolin, dopamine, octopamine, serotonin, and norepinephrine. Injection of each drug elicited a unique posture or combination of limb movements. These experiments showed two results pertinent to CD behavior: A posture identical to the CD posture was displayed after dopamine injection; and rhythmic leg waving similar to CD was evoked by proctolin. An unusual combination of flexion and extension of all limbs and movements of some limbs occurred after serotonin injection. Injection of octopamine led to a posture antagonistic to CD posture. The effects of these drugs were concentration- and time-dependent. Injection of dopamine, octopamine, or serotonin produced effects that were seasonally-dependent, and the influence of proctolin proved to be dependent on developmental stage. Quantitative analysis of leg waving movements after proctolin injection allowed for comparison of these movements to naturally-occurring behavior.

Aging↗
PubMed1995

Neuromodulation of rhythmic motor patterns in the blue crab Callinectes sapidus by amines and the peptide proctolin.

The blue crab Callinectes sapidus, provides an opportunity to study neuromodulation of three variations of rhythmic behavior produced by the same appendages. These behaviors are sideways swimming, backward swimming and courtship display (CD). Each behavior has a different context, and despite similarities among them, each is quantifiably distinguishable. CD behavior occurs in males, is stimulated naturally by pheromone, and elements of the behavior are evoked by proctolin and dopamine. Sideways and backward swimming do not share these characteristics. Bath-applied proctolin, combined with either electrical or pheromonal stimulation, was used to search for interneurons influencing motor outflows from the fifth legs. Interneurons were found which, when stimulated electrically, initiated rhythmic behavior. At least one of these neurons responded to pheromonal stimulation. Application of proctolin combined with stimulation of descending 'trigger' cells resulted in changes from a backward swimming motor pattern toward a CD pattern. Dopamine applied with proctolin lowered the concentration threshold for proctolin-evoked changes in motor outflows. Octopamine co-applied with proctolin extinguished the proctolin effect unless dopamine was co-applied. Combinations of modulators appear to play critical roles in shaping patterns of rhythmic motor activity of the fifth legs.

Animals↗
PubMed1995

Comparative analysis of power-line interference between two- or three-electrode biopotential amplifiers.

Differential input amplifiers are commonly used in the measurement of biopotential signals. This is because of their ability to reject common-mode signals, for example power-line interference. Rejection is further enhanced by referencing the subject to the instrumentation system. One such referencing technique uses a third subject electrode connected either to circuit common or to ground. However, these techniques are rarely explained or quantified in the literature. Four recording configurations are examined, isolated and non-isolated amplifiers with two and with three electrodes, and existing models are extended. From a brief assessment of power-line interference sources, it is concluded that only displacement currents induced into the leads and the body need be considered. The effect of these on the four configurations is analysed using SPICE. Results show that interference from displacement currents induced into the leads and into the body is dependent upon the recording configuration used and is significantly lower in three-electrode than in two-electrode amplifiers. Isolation also reduces levels of interference. It is concluded that the choice of referencing may affect interference levels on the biopotential signal significantly. Experimental and further analytical work is planned to confirm this.

Amplifiers, Electronic↗
PubMed1995

Dynamic pharyngoscopy in predicting outcome of uvulopalatopharyngoplasty for moderate and severe obstructive sleep apnea.

STUDY OBJECTIVE: We sought to determine whether preoperative fiberoptic pharyngoscopy (FOP) with Müller's maneuver (dynamic FOP) could be used to establish a subgroup of obstructive sleep apnea (OSA) patients with better outcome after uvulopalatopharyngoplasty (UPPP). DESIGN: Retrospective review of an observational cohort. SETTING: Tertiary care referral center. PATIENTS: Twenty-nine patients who underwent UPPP and nasopharyngeal surgery by one surgeon. INTERVENTION: The patients were divided into two groups based on the findings of preoperative dynamic FOP: group 1 (11 patients) had collapse of the velopharynx and the base of the tongue-epiglottis-hypopharynx (TEH) complex and group 2 (18 patients) had velopharyngeal collapse only. MEASUREMENTS AND RESULTS: Surgical success was defined using a conventional definition (> 50% reduction in the apnea-plus-hypopnea index [OAHI]), and a criterion for cure (> 90% reduction in OAHI and postoperative OAHI < 15). Both groups had a significant improvement in their OAHI. The success rate was significantly higher in patients with velopharyngeal collapse only compared with patients with additional collapse of the TEH complex (78 vs 36% with the conventional definition, and 50 vs 9% using the definition for cure, respectively). Predictive value of dynamic FOP in predicting cure failure when collapse of the TEH complex was present was 91%. CONCLUSIONS: Dynamic FOP may help establish a subgroup of OSA patients with greater likelihood of successful UPPP. The high negative predictive value of dynamic FOP when a criterion for cure is used suggests that this maneuver could best be used to exclude patients with TEH complex collapse from UPPP.

Adult↗
PubMed1995

The cost-effectiveness of lung transplantation. A pilot study. University of Washington Medical Center Lung Transplant Study Group.

OBJECTIVE: Lung transplantation is one of the fastest-growing solid organ transplant procedures in the world, yet its cost-effectiveness is unknown. We compared the costs and outcomes of the first 25 patients who received lung transplants at the University of Washington with 24 patients currently on the lung transplant waiting list. DESIGN: Inpatient and outpatient charges were obtained from the hospital billing service and home health agencies. Quality-adjusted life year scores (QALYs) were computed from the following: (1) utility scores obtained through standard gamble interviews, and (2) published survival data from an international lung transplant registry and from studies of patients on lung transplant waiting lists. RESULTS: Transplantation charges averaged $164,989 (median, $152,071). Average monthly charges posttransplant were $11,917 in year 1 and $4,525 thereafter, vs $3,395 for waiting-list patients. Posttransplant utility scores were significantly higher than waiting-list scores (0.80 vs 0.68; p < 0.001). Life expectancy was not greater for lung transplant vs waiting-list patients (5.89 vs 5.32 years; p > 0.05), although quality-adjusted life expectancy did improve significantly. After converting charges to costs, the incremental cost per QALY gained for posttransplant compared with waiting-list patients was $176,817. CONCLUSIONS: Lung transplantation is very expensive, although it can substantially improve quality of life. Two-thirds of care costs are incurred after transplantation. The principal barriers to cost-effectiveness at present are the high cost of postrecovery care and marginal gains in life expectancy compared with conservative care.

Adult↗
PubMed1994

Proficiency testing in parasitology. An educational tool to improve laboratory performance.

In 1977, the Laboratory Proficiency Testing Program began testing laboratories that examine samples for gastrointestinal parasites and operated with little change in the subsequent 17 years. Four surveys, each containing four samples, are distributed each year to every currently licensed medical laboratory in Ontario. Participation is mandatory. Survey results indicate a remarkable improvement in laboratory performance during this period. Improvement is believed to result from a combination of the voluntary withdrawal from testing by laboratories with poor performance and the improved performance of the others. The extensive educational services devised and carried out by the Parasitology Committee is believed to have been a significant factor leading to this improvement.

Data Collection↗
PubMed1992

Proficiency testing of platelet counting in Ontario.

Proficiency testing results provide data for interlaboratory comparisons. The Laboratory Proficiency Testing Program of Ontario, Canada, has tested platelet counting for a decade and other hematology parameters for 15 years. Despite the fact that all testing programs are compromised by the type of testing material used, for platelet count testing, conclusions are possible. The data indicate that most laboratories in Ontario have greater difficulty performing reproducible platelet counting as compared with other components of hematologic cytometry. A major contributor to this shortfall is the method used by the laboratory. It was not a surprise that manual counting had a high coefficient of variation. Unexpectedly, the semiautomated methods used in the mid-1980s also displayed a high coefficient of variation.

Humans↗
PubMed1992

Testing for creatine kinase and creatine kinase-2 in Ontario: reference ranges and assay types.

In 1991, 246 and 136 Ontario laboratories performed total creatine kinase (CK; EC 2.7.3.2) and creatine kinase-2 (CK-2) assays, respectively. A questionnaire mailed to these laboratories requested information about the types of assay used, the origin of their reference ranges, and the source of their instruments and reagents. All laboratories used current test formulations for CK, although seven laboratories did not assay at 37 degrees C. For CK, 69% of all laboratories reported different upper reference limits for men and women (5th-95th percentiles: 160-250 and 115-215 U/L, respectively); 31% reported similar ranges for both sexes. Fifty-six percent derived their own ranges; the remainder used either kit inserts or literature references, and nearly 60% of this latter group claimed to have validated these suggested ranges before use. For 6% of all laboratories, their pediatric ranges were similar to their adult ranges. For CK-2, only 32% used their own reference range; the remainder used kit inserts or literature references, but only 49% of this group validated these ranges before use. Reference limits (5th-95th percentiles) for CK-2 were as follows: activity 6-24 U/L; fraction of CK, 0.022-0.06; and, for mass assays, 5-10 micrograms/L and relative index 0.015-0.04.

Creatine Kinase↗
PubMed1991

The lower trapezius flap. Vascular anatomy and surgical technique.

The lower trapezius flap was first described in 1980 based on the transverse cervical artery. The older anatomical literature, however, describes the dorsal scapular artery as a major contributor of blood supply to the skin overlying the lower trapezius fibers. To clarify this, 30 dissections of this vascular region were performed. In 15 of 30 dissections, the dorsal scapular artery was dominant and the distal transverse cervical artery arose from the dorsal scapular. In nine of 30 dissections, the transverse cervical artery was dominant and the distal dorsal scapular artery arose from the transverse cervical. In six of 30 dissections, both proximal arteries were of equal caliber with no distal communication. We describe a surgical technique that makes use of the lower trapezius flap with inclusion of the dorsal scapular artery; this technique greatly extends the usefulness of the lower trapezius flap, while decreasing the morbidity caused by division of the upper portion of the trapezius muscle during flap harvest.

Arteries↗
PubMed1991

Results of a province-wide quality assurance program assessing the accuracy of cholesterol, triglycerides, and high-density lipoprotein cholesterol measurements and calculated low-density lipoprotein cholesterol in Ontario, using fresh human serum.

To evaluate laboratory performance, eight to 13 samples of fresh human serum from volunteers were sent to 250 laboratories in the Canadian province of Ontario licensed to perform lipid analysis. Fresh human specimens were used because of potential matrix effects with processed materials. We show that on all survey samples, 71% (range, 63% to 82%) of participating laboratories are within +/- 5% of the target cholesterol value and that 93% are within +/- 10%. The goal of the National Cholesterol Education Program for 1992 is total error of no more than +/- 9% for 95% of results. The unblanked triglycerides results show that on all samples 40% (14% to 59%) of participants are within +/- 5% and 68% (range, 31% to 86%) are within +/- 10% of the target value. For triglycerides results from 0.9 to 2.0 mmol/L, 80% or more are within +/- 0.2 mmol/L. Between 2.0 and 3.0 mmol/L, 90% are within +/- 0.3 mmol/L of the target values. For high-density lipoprotein cholesterol, for all samples 35% (range, 24% to 50%) of laboratories are within +/- 5% and 68% (range, 55% to 88%) are within +/- 10%. A range of 80% to 95% of participants are within +/- 0.2 mmol/L of the target values. For calculated low-density lipoprotein cholesterol, 51% and 62% of the laboratories surveyed are within +/- 5%, with 83% and 89% within +/- 10% of the target values. We conclude that the laboratory measurement of lipids is approaching the degree of accuracy and precision required for clinical purposes, and that the use of fresh human serum samples is a viable approach to their proficiency testing.

Blood Chemical Analysis↗
PubMed1991

Late complications of tracheotomy.

Complications of tracheotomy are largely preventable. Although some authors cite these complications as indications for prolonged endotracheal intubation to avoid tracheotomy, others believe that the laryngotracheal complications of prolonged endotracheal intubation warrant early tracheotomy. Obviously, unnecessary tracheotomies should not be performed, and the controversy regarding the timing of conversion of endotracheal intubation to tracheotomy is handled in an earlier article in this issue. We feel, however, that a properly performed tracheotomy has a low incidence of complications that are more easily managed than are the complex laryngotracheal complications of prolonged endotracheal intubation. Significant post-tracheotomy tracheal stenosis occurs in 8% of patients and is secondary to an overly large tracheotomy stoma or damage at the tracheostomy tube cuff site. Stoma stenosis can be minimized by not making an overly large tracheal stoma and by prevention of undue leverage on the tracheostomy tube. Cuff stenosis can be minimized by the use of the high-volume low-pressure cuffs with careful prevention of overdistention of the cuff. Bronchoscopic dilatation, laser resection, and Silastic T-tube placement provide control of the airway until definitive surgical resection and reconstruction can be performed safely. Tracheoesophageal fistula is an uncommon but life-threatening complication that can be prevented by avoiding overdistention of the tracheostomy tube cuff and by avoiding the concomitant use of a stiff nasogastric tube. These patients are best managed conservatively until they are able to be weaned from a ventilator. A single-stage repair of both the esophagus and the trachea should then be done. Tracheoinnominate artery fistula can be avoided by correct placement of the tracheostomy stoma through the second and third tracheal rings rather than lower in the trachea and by avoidance of overinflation of tracheostomy tube cuffs.

Brachiocephalic Trunk↗
PubMed1990

Decompression of the brain stem and superior cervical spine for congenital/acquired craniovertebral invagination: an interdisciplinary approach.

A transoropharyngeal/transpalatal approach to the clivus and anterior cervical spine in association with a midline labiomandibular glossotomy has proved successful in the treatment of craniovertebral instability. Nine cases at this institution between 1978 and 1986 were retrospectively reviewed. A head-and-neck surgeon, along with a neurosurgeon and/or orthopedic surgeon collaborated on these procedures. The indications, methods, operative techniques, results and postoperative complications are presented.

Adolescent↗
PubMed1990

Proficiency testing for creatine kinase isoenzyme CK-2 (CK-MB) in Ontario.

Three surveys of the measurement and interpretation of creatine kinase (CK; EC 2.7.3.2) isoenzyme 2 (CK-MB) were conducted in Ontario, Canada, in 1989. Of the clinical laboratories participating, 66% used immunological methods and 24% used electrophoretic methods. Although reference ranges and interpretative routines varied widely, 95% of the laboratories reported correct interpretations for 10 of the 15 vials tested. The only major problems occurred with samples with very low total CK activity. Within-survey duplicate results compared well, and 89% of the laboratories had consistent between-survey results, even for specimens with low total CK activity. Errors were proportional to the frequency of use of the different analytical methods. The lyophilized testing material gave higher results with methods for measuring the mass of CK-2, suggesting that the material contained inactive but immunologically intact CK-2. The surveys indicate that laboratories should review their protocols for measuring CK-2 when only a single sample from the patient is available.

Creatine Kinase↗
PubMed1989

Reliability of white blood cell counting.

The Laboratory Proficiency Testing Program has successfully operated mandatory proficiency testing for 13 years in Ontario, Canada, using committees of volunteer peers. This is an alternative to gubernatorial proficiency testing. Using white blood cell (WBC) count determinations as a focus, we present our results. Ninety-six percent of participants attained WBC count results within +/- 10% of an all-methods mean and 77% attained results within +/- 5%. Ninety-six percent displayed satisfactory precision. Details of the program, ie, testing material, computer analysis, reference results, and scope of committee action, are discussed. In 1975, clinical expectations for WBC count determinations greatly exceeded most laboratories' capabilities. By 1987, participants were able to produce reliable, clinically useful WBC count results. The paramount reason for this improvement is the transition from manual to automated counting methods resulting from the stimulus of proficiency testing and the concomitant education.

Electronics, Medical↗