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Biomedical subjects

J D Thomson

Publications and source records attributed to J D Thomson.

At least 19 recordsLinked to original sources
PubMed2006

Within-host dynamics of an intestinal pathogen of bumble bees.

The success of a pathogen depends not only on its transmission to new hosts, but also on its ability to colonize and persist within its current host. Studies of within-host dynamics have focused on only a few diseases of humans, whereas little is known about the factors that influence pathogen populations as they develop inside non-human hosts. Here, we investigate pathogen dynamics occurring within bumble bees (Bombus impatiens) infected by the gut trypanosome Crithidia bombi. Infection by C. bombi showed several features characteristic of vertebrate diseases, including a rapid initial increase in infection intensity, marked oscillations in parasitaemia, and the stimulation of a systemic immune response in infected bees. Within-host dynamics generated substantial variation in the infectiousness and flower-visiting behaviour of bumble bees. Changes in bee foraging that arise from infection may influence the probability of C. bombi transmission between bees at flowers.

Animals↗
PubMed2004

'Anti-bee' and 'pro-bird' changes during the evolution of hummingbird pollination in Penstemon flowers.

Floral phenotypes may be as much the result of selection for avoidance of some animal visitors as selection for improving the interaction with better pollinators. When specializing on hummingbird-pollination, Penstemon flowers may have evolved to improve the morphological fit between bird and flower, or to exclude less-efficient bees, or both. We hypothesized how such selection might work on four floral characters that affect the mechanics of pollen transfer: anther/stigma exsertion, presence of a lower corolla lip, width of the corolla tube, and angle of flower inclination. We surgically modified bee-pollinated P. strictus flowers changing one trait at a time to make them resemble hummingbird-pollinated P. barbatus flowers, and measured pollen transfer by bumblebees and hummingbirds. Results suggest that, apart from 'pro-bird' adaptations, specific 'anti-bee' adaptations have been important in shaping hummingbird-flowers. Moreover, some trait changes may have been selected for only if changing in concert with other traits.

Adaptation, Biological↗
PubMed2001

Mitral regurgitation after anthracycline treatment for childhood malignancy.

OBJECTIVE: To investigate the new onset of mitral regurgitation in patients with otherwise normal echocardiograms after anthracycline treatment and to assess its relation to other selected indicators of myocardial damage. DESIGN: Prospective echocardiographic and electrocardiographic study. SETTING: Tertiary paediatric cardiac referral centre. PATIENTS: 305 patients, aged 2-33 years (median 14 years), treated with cumulative anthracycline doses of between 150-450 mg/m(2) (median 180 mg/m(2)) for childhood malignancy. MAIN OUTCOME MEASURES: Colour flow Doppler detection of mitral regurgitation and its relation to changes in echocardiographic indices of left ventricular function (systolic and diastolic dimensions, fractional shortening) and to changes in the 12 lead ECG; and the prevalence of mitral regurgitation in the anthracycline treated patients in comparison with previously studied normal volunteers of similar age. RESULTS: 34 patients (11.6%) developed ultrasound detectable mitral regurgitation, which was not apparent clinically, during or after anthracycline treatment, compared with only 1.8% of a normal population of similar age (p < 0.0001). Nine of the 34 also developed non-specific T wave abnormalities. All 34 patients had normal systolic function at the time of initial detection of mitral regurgitation, but four later developed impaired left ventricular function (5, 11, 20, and 27 months after the first detection of mitral regurgitation). CONCLUSIONS: Mitral regurgitation occurs much more often in patients treated with anthracyclines than in the normal population. Echocardiographic detection of new mitral regurgitation with or without ECG abnormalities may be an early predictor of anthracycline cardiomyopathy.

Adolescent↗
PubMed2001

Scoliosis in cerebral palsy: an overview and recent results.

The natural history of scoliosis in cerebral palsy as well as the treatments that include observation, bracing, and surgery are reviewed. If surgery is indicated, a careful preoperative evaluation is essential, focusing especially on the patient's nutritional, gastrointestinal, neurologic, and orthopedic systems. Intraoperative and perioperative issues such as blood loss control are reviewed. The Luque-Galveston method of instrumentation for scoliosis secondary to cerebral palsy is our preferred method of treatment. Our recent results compare favorably with the literature with fewer complications.

Blood Loss, Surgical↗
PubMed2000

Effectiveness of the boston brace in treatment of large curves in adolescent idiopathic scoliosis.

STUDY DESIGN: This is a retrospective study of 50 patients with adolescent idiopathic scoliosis with curves measuring 35 degrees to 45 degrees who were treated with a Boston brace. OBJECTIVES: The purpose of this study was to determine whether the Boston brace could effectively halt long-term progression in skeletally immature adolescents with idiopathic scoliosis who had a curve between 35 degrees and 45 degrees. SUMMARY OF BACKGROUND DATA: The Boston brace has been shown to be effective in preventing curve progression in adolescent idiopathic scoliosis, but its efficacy in large curves has not been fully studied. METHODS: Fifty adolescents were treated with a Boston brace for idiopathic scoliosis curves of 35-45 degrees (mean, 38.55 degrees ). All were judged to be skeletally immature based on menarcheal status (mean, 2.6 months before menarche), Risser sign (mean, 0.90; range, 0-2), and chronologic age (mean, 13 +/- 1 years). Patients were recalled for long-term follow-up at a mean of 9.7 years (range, 6.23-13.22 years) after brace discontinuation. Three well-matched patient subsets were then identified based on compliance. Group 1 (n = 24) consisted of patients who were compliant with the brace program and wore the brace 18 or more hours per day, Group 2 (n = 14) contained patients who wore the brace 12-18 hours per day, and Group 3 (n = 12) contained patients who wore the brace 0-12 hours per day. RESULTS: There was a significant difference in the amount of initial correction seen in the brace between the groups: 49%, 45%, and 33% curve correction in the brace for Groups 1, 2, and 3, respectively (P < 0.05). At long-term follow-up there was a statistically significant difference between Groups 1, 2, and 3 in the percentage of patients in whom the curve had progressed to more than 45 degrees (P < 0.001), who had more than 5 degrees of curve progression (P < 0. 05), or who had undergone posterior spinal fusion (P < 0.001). CONCLUSIONS: These long-term data confirm that the Boston brace when used 18 or more hours per day is effective in preventing progression of large curves at a mean of 9.8 years after bracing is discontinued.

Adolescent↗
PubMed2000

Cardiac catheter guided surgical closure of an apical ventricular septal defect.

Surgical closure of muscular ventricular septal defects can be difficult. We report a technique in which a preoperatively placed cardiac catheter allowed accurate localization of a residual apical muscular defect at operation. The approach not only allowed improved visualization of the defect from the right side of the heart, but also helped to minimize the size of the left ventriculotomy required for satisfactory closure.

Blood Vessel Prosthesis↗
PubMed2000

Left sided valvar regurgitation in normal children and adolescents.

OBJECTIVE: To determine the prevalence and characteristics of left sided valvar regurgitation in normal children and adolescents. DESIGN: Prospective observational study. SETTING: Tertiary paediatric referral centre. PATIENTS: 329 volunteers (194 male, 135 female, age range 3-18 years). MAIN OUTCOME MEASURES: Detection of regurgitation with colour flow mapping after valve closure. Measurement of jet area, maximal velocity, and duration. RESULTS: Mitral regurgitation was present in six subjects (1.82%, 95% confidence interval (CI) 0.38% to 3.3%) and was not seen before 7 years of age. The jets ranged from 1.1 to 1.9 cm(2) (mean 1.4 cm(2)) in area and were confined to the proximal half of the left atrium. All of the detectable jets were pansystolic and five of six arose from the posteriomedial aspect of the mitral valve. Aortic regurgitation was seen in one girl aged 11 years (0.3%, 95% CI 0% to 0.9%). The signal was pandiastolic and 0.44 cm(2) in area. CONCLUSIONS: True mitral regurgitation occurring after rather than during mitral valve closure was detected in < 2% of subjects. These data support previous work in adult patients suggesting that trivial degrees of mitral regurgitation may be related to the process of aging. Aortic regurgitation is very rare in normal children and adolescents and should not be considered as a normal finding.

Adolescent↗
PubMed1999

Cyanosis due to diastolic right-to-left shunting across a ventricular septal defect in a patient with repaired tetralogy of Fallot and pulmonary atresia.

Cyanosis as a result of right-to-left shunting across a ventricular septal defect is commonly encountered in patients with congenital heart disease when systolic pressure in the right ventricle exceeds that in the left ventricle. Reported is the case of a child who remained cyanosed after surgical correction of pulmonary atresia despite right ventricular systolic pressure being lower than left ventricular pressure. Colour-flow Doppler showed a residual ventricular septal defect, with right-to-left shunting in diastole alone.

Child↗
PubMed1999

Childhood leukemia presenting with back pain and vertebral compression fractures.

Vertebral body collapse and back pain are an unusual presentation for childhood leukemia. This report is intended to promote greater awareness that acute lymphocytic leukemia can cause significant back pain in children without other systemic symptoms. We describe four cases in which patients with acute lymphocytic leukemia presented with back pain and vertebral compression fractures. All of the patients were initially misdiagnosed. No patient had neurologic compromise, despite extensive vertebral body collapse. The back pain was relieved after chemotherapy.

Back Pain↗
PubMed1998

Results and morbidity in a consecutive series of patients undergoing spinal fusion for neuromuscular scoliosis.

STUDY DESIGN: A retrospective clinical and radiographic review. OBJECTIVES: To provide current data on the results and complications of patients who have undergone spinal fusion for neuromuscular scoliosis at a center with physicians experienced in these types of cases. SUMMARY OF BACKGROUND DATA: The reported complication rate in the management of neuromuscular scoliosis ranges from 44% to 62% in the recent literature. This literature is that of 1991 or earlier reflecting operative techniques of the mid-1980s, and it has been used to argue against the efficacy of neuromuscular spinal fusions. METHODS: A retrospective chart and radiographic review of 50 consecutive spinal fusions for neuromuscular scoliosis was performed at Connecticut Children's Medical Center between January 1990 and January 1994. The three most common diagnoses were spastic quadriplegic cerebral palsy (20 patients), myelomeningocele (13 patients), and muscle disease (8 patients). There were 38 posterior spinal fusions including two kyphectomies and 12 anteroposterior spinal fusions. The Luque-Galveston technique was used in 39 of 50 patients. The average age at surgery was 13 years and 6 months, with an average follow-up of 40 months (minimum, 24 months). RESULTS: Before surgery, the mean major scoliosis measured 72 degrees, with mean best bend or traction view of 35 degrees. At most recent follow-up, the mean scoliosis magnitude was 25 degrees (mean correction, 65%). There were 17 minor complications in 14 patients and three major complications (deep wound infections) in three myelomeningocele patients. Rod breakage was noted in two patients, one of whom had an asymptomatic pseudarthrosis. There were no neurologic complications or deaths, and none of the complications affected the final results. CONCLUSIONS: The data in the current study support the authors' belief that with current surgical techniques and perioperative management in an experienced center, the results for patients undergoing spinal fusion for neuromuscular scoliosis have been improved, and major complications have been minimized.

Adolescent↗
PubMed1993

Coronal-plane transcondylar fracture of the humerus in a child.

A coronal plane fracture of the distal humerus in a child is an uncommon fracture, with the most familiar example being a capitellar fracture. An unusual coronal fracture of the entire distal humeral articular surface (capitellum and trochlea) occurred in a three-year-old boy. This fracture pattern has been described in adults but is believed to be previously unreported in children. This Salter-Harris Type IV fracture was initially misdiagnosed as a lateral humeral condyle fracture. Three years after treatment with open reduction and pin fixation, the distal humerus shows no evidence of growth disturbance.

Bone Wires↗
PubMed1993

Injuries and deaths from collecting war souvenirs in Operation Desert Storm.

Data were collected on 22 patients who sustained injuries or death from collecting war souvenirs during Operation Desert Storm from December 1990 to May 1991. Nine of 16 patients injured and 3 of 6 patients killed were non-combat arms personnel. Non-combat personnel closely followed combat units, and subsequently were exposed to unexploded ordnance. Combat and non-combat personnel should be warned that innocent-appearing material on or near a battlefield may be an explosive device. They should be instructed concerning the types of ordnance used, as well as the dangers of unexploded ordnance.

Blast Injuries↗
PubMed1991

Anterior and posterior spinal fusion. Staged versus same-day surgery.

Seventy-five patients who underwent combined anterior and posterior spinal fusion were compared to evaluate the results and safety of staged vs. continuous anterior and posterior spinal fusion. Thirty-five patients underwent two-stage anterior and posterior spinal fusion. The first stage consisted of anterior release; the second stage, which took place 7-10 days later, consisted of posterior spinal fusion and instrumentation. Forty patients underwent continuous anterior and posterior spinal fusion. This procedure consisted of anterior release followed by immediate posterior spinal fusion and instrumentation. The results show that 1) a continuous procedure is faster than the staged procedure; 2) there is less blood loss; 3) fewer days are spent in the hospital; and 4) better correction of the spinal deformity is achieved. Also, the complications were less frequent and less severe with the continuous procedure. It was concluded that the continuous procedure is safe and efficacious and has several advantages over the staged procedure.

Adult↗
PubMed1989

Analysis of lumbar lordosis in posterior spine fusions for idiopathic scoliosis.

Previous reports are inconclusive regarding changes in the lumbar region after Harrington rod distraction and posterior spinal fusion for idiopathic scoliosis. The purpose of this study was to evaluate the effects of spinal fusion on the lumbar region, particularly the overall lumbar lordosis, the lumbar lordosis in and below the fused segment, the sacro-horizontal angle, and the sagittal plane alignment of the spine. Sixty-six patients under 21 years of age with idiopathic scoliosis who had spine fusion extending to the lumbar vertebrae using only Harrington distraction instrumentation were evaluated. The total lordosis, sacro-horizontal angle, and sagittal plane alignment remained relatively constant. The lordosis within the fusion decreased, and lordosis caudal to the fusion, including the last fused vertebra, increased as the lower hook placement site moved caudally.

Adolescent↗