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Biomedical subjects

R Johnston

Publications and source records attributed to R Johnston.

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

Short Report: Engraftment of T-cell-depleted allogeneic haematopoietic stem cells using a reduced intensity conditioning regimen.

Graft-versus-host disease (GVHD) remains a significant complication in patients undergoing allogeneic stem cell transplantation (SCT) using a reduced intensity conditioning regimen. Although T-cell depletion (TCD) reduces the risk of GVHD after a myeloablative conditioning regimen, it is associated with an increased risk of graft failure. We have therefore examined whether TCD compromises engraftment using a fludarabine-based conditioning regimen. Fifteen patients have been transplanted using such a regimen of whom 13 underwent ex vivo TCD. All but one patient demonstrated durable engraftment and no patient receiving a TCD product developed severe GVHD. Thus, TCD may play a role in GvHD prophylaxis using such regimens.

Adult↗
PubMed1999

Evaluation of an intervention to reduce sun exposure in children: design and baseline results.

The Kidskin Study is a 5-year intervention study (1995-1999) involving 1,776 5- and 6-year-old children attending 33 primary schools in Perth, Western Australia. The aim of the study is to design, implement, and evaluate an intervention to reduce sun exposure in young children. There are three study groups: a control group, a "moderate intervention" group, and a "high intervention" group. The control schools receive the standard Western Australian health education curriculum, while the moderate and high intervention schools receive a specially designed curricular intervention. In addition, children in the high intervention group receive program materials over the summer holidays, when exposure is likely to be highest, and are offered sun-protective swimwear at low cost. The main outcome measure is the number of nevi on the back. Other outcomes include nevi on the chest (boys only), face, and arms, levels of suntanning, degree of freckling, and sun-related behaviors. At baseline, the three groups were similar with respect to nevi and freckling after adjustment for observer and month of observation. Sun exposure was slightly higher in the high intervention group. The groups were also similar with respect to most potential confounders, although they differed with respect to Southern European ethnicity and parental education.

Back↗
PubMed1999

Direct measurement of sun protection in primary schools.

BACKGROUND: "Kidskin" is an intervention study involving children at 33 primary schools in Perth, Western Australia. This study includes measurement of changes in implementation of schools' sun protection policies. This paper reports on measurement of observable aspects of sun protection. METHODS: Hat use was assessed from videos of children in the playground. Shade use was measured using UVR-sensitive polysulfone badges worn by a random sample of children. Shade provision was measured from aerial photographs of the schools. Principals were surveyed about school policies and practices. RESULTS: Eighty-seven percent of children wore a hat during lunch time at school, although only 14% wore the most protective styles of hats. The mean proportion of ambient UVR exposure received by Year 1 children was 15.5%; children spent less time in the sun on sunnier days. On average, 14.5% of the playground was shaded; this was not associated with children's sun exposure. Correlations between these results and the principals' estimates were poor. CONCLUSIONS: Children should be encouraged to wear more protective styles of hats and to avoid sun exposure, even on less sunny days during spring and summer. Principals' estimates of shade provision and children's sun protection behavior at school are of little value.

Analysis of Variance↗
PubMed1999

A double-blind, multicentre study to assess the tolerability and efficacy of paroxetine compared with amitriptyline in the treatment of depressed patients in Australian general practice.

OBJECTIVE: This study compared the tolerability and efficacy of paroxetine and amitriptyline in the treatment of depression in general practice. METHODS: In this double-blind, multicentre study conducted in the general practice, patients with depression (Montgomery Asberg Depression Rating Scale [MADRS] score > or = 20) who were regarded as requiring antidepressant therapy were randomly assigned to receive paroxetine (20 mg, n = 184) or amitriptyline (50-100 mg, n = 191) once daily for 9 weeks. RESULTS: More patients completed treatment with paroxetine than with amitriptyline (71.1% vs 56.1%, p = 0.009). Depression rating scores (MADRS and Clinical Global Impression [CGI]) were improved with both agents, but at week 9, paroxetine achieved more favourable scores compared with amitriptyline on MADRS (p=0.019), CGI severity of depression (p=0.044), and CGI efficacy index (p = 0.038). CONCLUSIONS: Depressed patients treated in general practice respond more quickly and are more likely to complete the treatment regimen with paroxetine than with amitriptyline.

Adult↗
PubMed1999

The use of observational methods for monitoring sun-protection activities in schools.

Evaluation of health promotion interventions aimed at behavioural or environmental change involves assessing change that occurs as a result of the program. Direct observational methods can be used for this purpose and this paper describes three such methods that we pilot tested for use in a 5-year intervention study aimed at reducing sun exposure in primary school children. (1) Monitoring 'No hat, no play' policies. This method involved video taping children in selected school play areas during lunch time and analysing the content of the videos to assess the proportion of children wearing various types of hats. (2) Assessing shade provision in the playground. This method involved taking aerial photographs of each school and using them to estimate the proportion of shade in play areas available to children at lunchtime. (3) Shade use. This involved children wearing polysulphone film badges to measure the amount of UV-B exposure they received during one lunch period, relative to the total possible dose registered on index badges. Each method was implemented successfully, and we demonstrated that the video and aerial photography methods produced highly reproducible results and that all three methods were feasible. These three methods will be used in our intervention study to assess longitudinal change in schools' sun-protection policy and practice.

Child↗
PubMed1999

The relationships among pulmonary function, aerobic fitness, and cognitive functioning in older COPD patients.

STUDY OBJECTIVES: To study the predictive relationships among age, pulmonary function, aerobic fitness, and cognition in people with COPD. DESIGN: Observational study conducted during baseline testing with COPD patients who volunteered to participate in an exercise intervention. PARTICIPANTS: Older adults (age, 56 to 80 years) with COPD. MEASUREMENTS AND RESULTS: Age, depression, education level, aerobic fitness, blood oxygen saturation levels, and pulmonary function were assessed. Participants were randomly assigned to take cognitive tests of (1) fluid intelligence, (2) processing speed and working memory span, or (3) processing speed and inhibition. After controlling for education and depression (F(2,57) = 7.43; r(2) = 0. 21), performance on the 6-min walk (F(1,56) = 15.27; r(2) = 0.17) and age (F(1,55) = 7.52; r(2) = 0.08) were significant predictors of fluid intelligence. On the speed-of-processing task, performance on the 6-min walk (F(1,30) = 8.17; r(2) = 0.20), maximum voluntary ventilation (F(1,29) = 5.81; r(2) = 0.16), and age (F(1,28) = 5.26; r(2) = 0.10) were significant predictors. FVC was a significant predictor (F(1,25) = 6.37; r(2) = 0.18) of working memory span. The ability to inhibit a response was not significantly predicted by any of the variables assessed. CONCLUSIONS: In an older COPD sample, age, aerobic fitness, and pulmonary function are predictive of cognitive performance on various tasks. In particular, age and aerobic fitness are predictive of speed of processing, which is a cognitive variable that may itself underlie performance on a majority of cognitive tasks.

Adult↗
PubMed1998

Targeted lung expression of interleukin-11 enhances murine tolerance of 100% oxygen and diminishes hyperoxia-induced DNA fragmentation.

Acute lung injury is a frequent and treatment-limiting consequence of therapy with hyperoxic gas mixtures. To determine if IL-11 is protective in oxygen toxicity, we compared the effects of 100% O2 on transgenic mice that overexpress IL-11 in the lung and transgene (-) controls. IL-11 markedly enhanced survival in 100% O2 with 100% of transgene (-) animals dying within 72-96 h and > 90% of transgene (+) animals surviving for more than 10 d. This protection was associated with markedly diminished alveolar-capillary protein leak, endothelial and epithelial membrane injury, lipid peroxidation, and pulmonary neutrophil recruitment. Significant differences in copper zinc superoxide dismutase and catalase activities were not noted and the levels of total, reduced and oxidized glutathione were similar in transgene (+) and (-) animals. Glutathione reductase, glutathione peroxidase, and manganese superoxide dismutase activities were slightly higher in transgene (+) as versus (-) mice after 100% O2 exposure, and IL-11 diminished hyperoxia-induced expression of IL-1 and TNF. Hyperoxia also caused cell death with DNA fragmentation in the lungs of transgene (-) animals and IL-11 markedly diminished this cell death response. These studies demonstrate that IL-11 markedly diminishes hyperoxic lung injury. They also demonstrate this protection is associated with small changes in lung antioxidants, diminished hyperoxia-induced IL-1 and TNF production, and markedly suppressed hyperoxia-induced DNA fragmentation.

Animals↗
PubMed1998

High-throughput genetic analysis using microfabricated 96-sample capillary array electrophoresis microplates.

Capillary array electrophoresis (CAE) microplates that can analyze 96 samples in less than 8 min have been produced by bonding 10-cm-diameter micromachined glass wafers to form a glass sandwich structure. The microplate has 96 sample wells and 48 separation channels with an injection unit that permits the serial analysis of two different samples on each capillary. An elastomer sheet with an 8 by 12 array of holes is placed on top of the glass sandwich structure to define the sample wells. Samples are addressed with an electrode array that makes up the third layer of the assembly. Detection of all lanes with high temporal resolution was achieved by using a laser-excited confocal fluorescence scanner. To demonstrate the functionality of these microplates, electrophoretic separation and fluorescence detection of a restriction fragment marker for the diagnosis of hereditary hemochromatosis were performed. CAE microplates will facilitate all types of high-throughput genetic analysis because their high assay speed provides a throughput that is 50 to 100 times greater than that of conventional slab gels.

Capillary Action↗
PubMed1998

Air insufflation technique of enteral tube insertion: a randomized, controlled trial.

OBJECTIVE: To test air insufflation as an adjunct to placement of enteral feeding tubes. DESIGN: Prospective, randomized study. SETTING: Intensive care unit in a tertiary hospital. SUBJECTS: Sixty-four consecutive patients requiring enteral nutrition, in whom a decision to insert a nasoenteral feeding tube was made. INTERVENTIONS: A 12-Fr feeding tube was inserted to the level of the fundus of the stomach. A 60-mL syringe was used to pump 500 mL of air into the stomach. The tube was then advanced. An abdominal flat plate was obtained within 2 hrs of completion of the procedure and the tube position noted. If the tube was not in the duodenum, the patient was placed on a promotility agent and a repeat radiograph was performed the next day. The technique varied from our control technique only by the instillation of air. MEASUREMENTS AND MAIN RESULTS: Using the study technique, 21 of 32 tubes were successfully placed, as seen on the initial radiograph, in our study patients compared with only 12 of 34 tubes in our control patients (p< .02). In addition, the success rate at 24 hrs was 25 of 32 vs. 16 of 34 (p< .02). Only 3 of 21 tubes placed in the antrum, body, or fundus of the stomach advanced to the duodenum the following day, compared with 5 of 12 tubes initially placed in the pylorus (p< .075). No complications were noted. CONCLUSION: Instilling air into the stomach may facilitate the ability to get the feeding tube to the level of the pylorus, at which point it is more likely to advance into the duodenum and beyond.

Critical Illness↗
PubMed1998

Is it 'worthwhile' to continue treating patients with a prolonged stay (>14 days) in the ICU? An economic evaluation.

OBJECTIVE: To compare the cost and consequences of a policy of continuing to care for patients with a prolonged stay in the ICU with a proposed policy of withdrawing support. DESIGN: Economic evaluation using data derived from a prospective cohort study. SETTING: Adult medical/surgical ICU in a tertiary care hospital. PATIENTS: Consecutive patients admitted to the ICU. INTERVENTION: None. MAIN OUTCOME MEASURES: We performed a cost-accounting analysis on each patient in the ICU and followed up patients until 12 months after admission to ICU and assessed components of quality of life in survivors. RESULTS: During the study period, 690 patients were admitted to the ICU. Only 61 (9%) patients remained in the ICU for > 14 days. For this group, the mean length of stay in the ICU was 24.5 (+/-11.7) days and duration in hospital was 57.9 (+/-56.9) days. At 12 months, 27 (44%) were alive. Overall, the mean quality of life score at 12 months did not differ between patients with a short or prolonged stay in the ICU. The average ICU cost per day per patient was $1,565 (Canadian) resulting in a total cost for the whole cohort of Can $1,917,382. Over the same time period, 58 patients had life support withdrawn. On average, patients survived another day in the ICU, 2 more days in hospital, and all patients ultimately died. When treatment was discontinued, the costs of treating this cohort was Can $156,465. The incremental cost-effectiveness ratio is Can $65,219 per life saved or Can $4,350 per life-year saved. CONCLUSIONS: A considerable proportion of patients with a prolonged length of stay in the ICU survive their critical illness. Furthermore, their long-term quality of life seems reasonable. Our data suggest that continuing treatment for patients with a prolonged ICU stay may represent an efficient use of hospital resources and should be considered in the context of local budgets.

Adult↗
PubMed1997

Laser safety analysis of a retinal scanning display system.

The Virtual Retinal Display (VRD) is a visual display that scans modulated laser light on to the retina of the viewer's eye to create an image. Maximum permissible exposures (MPE) have been calculated for the VRD in both normal viewing and possible failure modes. The MPE power levels are compared to the measured power that enters the eye while viewing images with the VRD. The power levels indicate that the VRD is safe in both normal operating mode and in failure modes.

Data Display↗
PubMed1997

Building a virtual reality temporal bone dissection simulator.

The temporal bone is one of seven bones that comprise the human skull, and has an intimate relationship with many vital structures. Anatomically, its three-dimensional relationships make it one of the most challenging areas for surgeons to understand and master. In addition, the temporal bone contains minute structures that are among the most sophisticated and delicate in the human body. These structures include the cochlea and vestibular organs, which are responsible for hearing and balance; the middle ear, including the ossicles, which conduct acoustic energy to the cochlea; and the facial nerve, which is responsible for controlling the muscles of facial expression, and contributes to the sensation of taste. Additionally, the temporal bone forms a major portion of the skull base, and has intimate relationships to vital structures including the carotid artery, jugular vein, cerebral cortex, brainstem, and cranial nerves. Surgical procedures performed on the temporal bone include: procedures to eradicate chronic and acute infections; procedures to remove malignant and benign tumors within the temporal bone, from the skull base, or from the posterior cranial fossa; procedures to restore the hearing mechanism; procedures to eliminate balance disorders; and procedures to correct congenital anomalies. For surgeons-in-training, and even surgeons-in-practice, mastery of the anatomy of the temporal bone and the many complex approaches necessary to treat patients takes years of focused endeavor. This is typically accomplished through the dissection of human cadaver temporal bones, which are scarce, and require a dedicated laboratory facility. Efforts are currently underway to develop a realistic simulator for temporal bone procedures. Users immersed in the simulator will interact with a three-dimensional temporal bone, derived from patient-specific data, using a haptic interface to simulate traditional surgical procedures. Feedback from experts in otologic surgery will be built into the system for additional instruction. This presentation will include an overview of the application being developed, a report of its current state of development, and plans for the future.

Computer Simulation↗
PubMed1996

Virtual reality surgical simulation and otolaryngology.

Large-scale flight simulation was pioneered in the 1940s to help meet the training requirements and demand for pilots in World War II. Flight simulators have been effective for training, evaluating, and certifying military and commercial pilots. Accurate scenarios have been developed that allow pilots in training to gain experience without the risk and expense of learning while in flight. The research in aviation simulation suggests a transfer effectiveness ratio of 0.48. This means that 1 hour in the simulator saves a half hour in the air. Because of the successful use of flight simulation as a training technique, computer-based simulators are now used in a variety of domains.

Computer Simulation↗
PubMed1996

Vitamin D receptor genotype is not associated with bone mineral density in three ethnic/regional groups.

We report a cross-sectional study of 48 men, 56 premenopausal women, and 80 postmenopausal women who were of three ethnic/regional backgrounds: southern European (Greek, Italian), eastern European (Jewish, Polish, Hungarian), and western European (French, British). We determined bone mineral density (BMD) at four skeletal sites and assessed the vitamin D receptor (VDR) genotype by the Bsml restriction site polymorphism. Age and body mass index had significant effects on BMD by multiple regression analysis. In addition, ethnic/regional group had a significant effect on spinal BMD in premenopausal females (P = 0.014) and in males (P = 0.039). However, VDR genotype had no significant effect on BMD in any of the three study groups.

Bone Density↗
PubMed1996

Optimal positioning for cervical immobilization.

STUDY OBJECTIVE: We hypothesized that optimal positioning of the head and neck to protect the spinal cord during cervical spine immobilization can be determined with reference to external landmarks. In this study we sought to determine the optimal position for cervical spine immobilization using magnetic resonance imaging (MRI) and to define this optimal position in a clinically reproducible fashion. METHODS: Our subjects were 19 healthy adult volunteers (11 women, 8 men). In each, we positioned the head to produce various degrees of neck flexion and extension. This positioning was followed by quantitative MRI of the cervical spine. RESULTS: The mean ratio of spinal canal and spinal cord cross-sectional areas was smallest at C6 but exceeded 2.0 at all levels from C2 to T1 (P < .05). At the C5 and C6 levels, the maximal area ratio was most consistently obtained with slight flexion (cervical-thoracic angle of 14 degrees) (P < .05). For a patient lying flat on a backboard, this corresponds to raising the occiput 2 cm. More extreme flexion or extension produced variable results. CONCLUSION: In healthy adults, a slight degree of flexion equivalent to 2 cm of occiput elevation produces a favorable increase in spinal canal/spinal cord ration at levels C5 and C6, a region of frequent unstable spine injuries.

Adult↗