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Biomedical subjects

D Hamilton

Publications and source records attributed to D Hamilton.

At least 19 recordsLinked to original sources
PubMed2006

Dance training intensity at 11-14 years is associated with femoral torsion in classical ballet dancers.

OBJECTIVE: To examine in a cross sectional study the influence of femoral torsion (FT) and passive hip external rotation (PER) on turnout (TO). Starting age, years of classical ballet training, and current and past dance training intensity were assessed to determine their influence on FT, PER, and TO in pre-professional female dancers. METHODS: Sixty four dancers (mean (SD) age 18.16 (1.80) years) were recruited from four different dance training programmes. They completed a dance history questionnaire. FT was measured using a clinical method. PER was measured with the subjects prone, and TO was measured with the subjects standing. RESULTS: Mean TO was 136 degrees, mean unilateral PER was 49.4 degrees, and mean FT was 18.4 degrees. A positive correlation was observed between PER combined (PERC) and TO (r = 0.443, p < 0.001). A negative association was found between FT combined (FTC) and PERC (r = -0.402, p = 0.001). No association was found between starting age or years of classical ballet training and FTC, PERC, or TO. Dancers who trained for six hours a week or more during the 11-14 year age range had less FT than those who trained less (mean difference 6 degrees, 95% confidence interval 1.4 to 10.3). Students currently training for longer had higher levels of TO (p < 0.001) but comparable PERC and FTC. CONCLUSION: FT is significantly associated with PERC. Dancers who trained for six hours a week or more at 11-14 years of age had significantly less FT. FTC had a significant influence on PERC, but no influence on the execution of TO.

Adolescent↗
PubMed2005

Further examination of relationships between life events and psychiatric symptoms in adults with intellectual disability.

BACKGROUND: It has been proposed that people with intellectual disability (ID) might be similar to the general population in the way they respond to significant life events. Some preliminary findings have demonstrated that adults with ID who have experienced recent life events have an increased probability of having psychiatric problems. The aims of the present study were to determine whether previous findings can be replicated, and to examine the influence of additional diagnoses associated with ID on the strength of relationships between life event frequency and psychiatric problems. METHODS: Adults with ID (n = 624), living either in staffed community accommodation or in family or foster homes, were assessed on the Developmental Behaviour Checklist for Adults (DBC-A) and a 37-item life events checklist. Carers who knew the person well acted as proxy informants. RESULTS: People living in staffed accommodation experienced more life events than people living with natural or foster families. Life event frequency predicted DBC-A total score, five of six sub-scale scores, and caseness status, after significant demographic factors were taken into account. However, the strength of correlations between life event frequency and DBC-A total score varied among sub-groups identified by type of developmental disability and level of ID. CONCLUSIONS: Weak but significant associations between emotional and behavioural problems and life events experienced by adults with ID were demonstrated, but it was also shown that the strength of such associations varies among sub-groups of this heterogeneous population. Future research needs to take account of the circumstances surrounding the life changes, the period of time over which changes might have taken place, and the meaning that the person might attach to the changes. Research into the causal relationship between exposure to life events and the onset of psychiatric problems is also warranted.

Adolescent↗
PubMed2004

Achievement of insulin independence via pancreatic islet transplantation using a remote isolation center: a first-year review.

BACKGROUND: Owing to advances in both immunosuppressive protocols and pancreatic islet isolation techniques, insulin independence has recently been achieved in type 1 insulin-dependent diabetics (IDDM) via pancreatic islet transplantation (PIT). Although the dissemination of immunosuppressive protocols is relatively easy, transferring the knowledge and expertise required to isolate a large number of quality human islets for transplantation is a far greater challenge. Therefore, in an attempt to centralize the critical islet processing needed for islet transplantation and to avoid the development of another islet processing center, we have established a collaborative islet transplant program between two geographically distant transplant centers. PATIENTS AND METHODS: Eleven consecutive type 1 IDDM patients with a history of severe hypoglycemia and metabolic instability underwent PIT at the Methodist Hospital (TMH) in Houston, Texas, utilizing pancreatic islets isolated at the Diabetes Research Institute (DRI) at the University of Miami in Miami, Florida between January 1, 2002 and June 31, 2003. Forty-one pancreata have been procured in the Houston area and have subsequently been transported for isolation at the DRI following enzymatic ductal perfusion by the automated method (Ricordi chamber). Following purification the islets were immediately transported back to TMH in Houston and transplanted via percutaneous transhepatic portal infusion. Immunosuppression regimen consisted of sirolimus, tacrolimus, and daclizumab. RESULTS: Following harvesting, donor pancreata arrived at the DRI for initiation of the isolation process within 6.5 hours of cross-clamping (median time 5.4 hours; range 4.8 to 6.5 hours). The islets were immediately transported back to TMH for final sterility and viability tests and transplanted via percutaneous transhepatic portal vein infusion. The harvesting of 41 pancreata has yielded a number of pancreatic islets sufficient for transplantation (>5000 IEQ/kg recipient body weight) 26 times (63% of harvested pancreata). Thus far, three patients have received three PITs and eight patients have received two PITs. Six remain insulin independent. All have experienced a decrease in serum hemoglobin A(1c) levels, and both basal and stimulated C-peptide levels have increased. There have been no major complications related to the procedure or the immunosuppressive regimen used. CONCLUSIONS: Our series demonstrates that pancreatic islets isolated at a remote isolation center can successfully and safely be used for PIT and the achievement of insulin independence.

Adult↗
PubMed2004

Waterhouse-Friderichsen syndrome as a result of non-meningococcal infection.

Waterhouse-Friderichsen syndrome--massive adrenal haemorrhage in the setting of overwhelming clinical sepsis--is usually taken at necropsy to indicate meningococcal infection, and may be the only evidence of this pathogen. This report describes three fatal cases of the syndrome in which the causative organism proved to be a streptococcus. The organisms were detected during routine coroners' autopsies with histology and microbiological investigations. In two cases, the syndrome followed Streptococcus pneumoniae infection and in a third beta haemolytic streptococcus group A. Thus, adrenal haemorrhage alone cannot be taken to indicate meningococcal disease and other pathogens, particularly streptococcus, must be considered.

Adrenal Gland Diseases↗
PubMed2003

Follicular lymphoma with marginal zone differentiation: cytogenetic findings in support of a high-risk variant of follicular lymphoma.

AIMS: The pathogenesis and clinical significance of marginal zone differentiation in follicular lymphoma remains to be determined, although genetic alterations are likely to be important determinants of both. We therefore report the cytogenetic findings in three cases of follicular lymphoma with marginal zone differentiation studied by routine karyotyping and in-situ hybridization. METHODS AND RESULTS: The morphology and immunophenotype of each case was typical of follicular lymphoma displaying marginal zone differentiation. Karyotyping, performed on GTL-banded preparations of cell cultures derived from fresh lymph node tissue, revealed a complex karyotype in all three cases, including t(14;18)(q32;q21) and abnormalities associated with progression and/or transformation of follicular lymphoma. In addition, trisomy 3 was found in one case and translocations between the q27-29 region of chromosome 3 and chromosome 2 in the other two cases; the latter was identified only in subclones derived from less complex stem lines possessing t(14;18). In-situ hybridization, performed on sections cut from routinely processed paraffin-embedded tissue blocks, localized cells possessing these abnormalities of chromosome 3 to both the follicular and marginal zone components of two lymphomas studied in this way. CONCLUSIONS: Trisomy 3 and alterations involving the q27-29 region of chromosome 3 are implicated in the pathogenesis of de novo marginal zone lymphoma. Their presence in the current cases indicates that they may also be responsible for marginal zone differentiation in follicular lymphoma when cells harbouring these genetic alterations are exposed to the appropriate microenvironment. Our findings are consistent with follicular lymphoma with marginal zone differentiation as a high-risk variant of follicular lymphoma.

Aged↗
PubMed2001

Endoscopic surgery in weightlessness: the investigation of basic principles for surgery in space.

BACKGROUND: Performing a surgical procedure in weightlessness, also called 0-gravity (0-g), has been shown to be no more difficult than in a 1-g environment if the requirements for the restraint of the patient, operator, surgical hardware, are observed. The performance of laparoscopic and thorascopic procedures in weightlessness, if feasible, would offer several advantages over the performance of an open operation. Concerns about the feasibility of performing minimally invasive procedures in weightlessness have included impaired visualization from the absence of gravitational retraction of the bowel (laparoscopy) or thoracic organs (thoracoscopy) as well as obstruction and interference from floating debris such as blood, pus, and irrigation fluid. The purpose of this study was to determine the feasibility of performing laparoscopic and thorascopic procedures and the degree of impaired surgical endoscopic visualization in weightlessness. METHODS: From 1993 to 2000, laparoscopic and thorascopic procedures were performed on 10 anesthetized adult pigs weighing approximately 50 kg in the National Aeronautics and Space Administration (NASA) Microgravity Program using a modified KC-135 airplane. The parabolic simulation system for advanced life support was used in this project, and 20 to 40 parabolas were used for laparoscopic or thorascopic investigation, each containing approximately 30 s of 0-g alternating with 2-g pullouts. The animal model was restrained in the supine position on a floor-level Crew Medical Restraint System, and the abdominal cavity was insufflated with carbon dioxide. The intraabdominal and intrathoracic anatomy was visualized in the 1-g, 0-g, and 2-g periods of parabolic flight. Bleeding was created in the animals, and the behavior of the blood in the abdominal and thoracic cavities was observed. In the thoracic cavity, gas insufflation and mechanical retraction was used at times unilaterally to decrease pulmonary ventilation enough to increase the thoracic domain. RESULTS: Visualization was improved in laparoscopy, from tethering of the bowel by the elastic mesentery, and from the strong tendency for debris and blood to adhere to the abdominal wall because of surface tension forces. The lack of adequate thoracic domain made thorascopy more difficult. Fluid in the thoracic cavity did not impair visualization because the fluid at 0-g does not loculate posteriorly, but disperses along the thoracic wall and mediastinal reflections. CONCLUSIONS: Performing minimally invasive procedures instead of open surgical procedures in a weightless environment has theoretical advantages, especially in the ability to prevent cabin atmosphere contamination from surgical fluids (blood, pus, irrigation). Visualization will become more important and practical as the endoscopic hardware is miniaturized from its current form, as endoscopic technology becomes more advanced, and as more surgically capable medical crew officers are present in future long-duration space exploration missions.

Animals↗
PubMed2001

Strontium-89 treatment for prostate cancer bone metastases: does a prostate-specific antigen response predict for improved survival?

A review of 50 patients treated with strontium-89 for prostate cancer bone metastases from January 1993-1997 at the Wellington Cancer Centre was undertaken to determine if there was any correlation between changes in prostate-specific antigen (PSA) following treatment and subsequent survival. Thirty cases were evaluable for PSA response. Of these, 14 had a fall in PSA following strontium-89 treatment, and their mean survival was 641 days. The remaining 16 patients did not demonstrate a post-treatment fall in PSA and their mean survival was 275 days. A difference between these two groups in the time to development of new bone symptoms following treatment was also observed. No significant correlation between pretreatment PSA and PSA response was observed. In conclusion, a PSA response following strontium-89 treatment appears to predict for improved survival in patients with bone metastases from carcinoma of the prostate. Further prospective studies are indicated.

Aged↗
PubMed2001

Cyclin D1 and p16 alterations in advanced premalignant lesions of the upper aerodigestive tract: role in response to chemoprevention and cancer development.

PURPOSE: To better understand the role of G(1)-S transition regulator abnormalities in the pathogenesis of advanced premalignant lesions of the upper aerodigestive tract and the biological effects of chemoprevention, we studied biopsies obtained sequentially from participants in a prospective trial using 13-cis retinoic acid, IFN-alpha, and alpha-tocopherol for 12 months. EXPERIMENTAL DESIGN: Cyclin D1 and p16 expression were analyzed by immunohistochemistry, loss of heterozygosity by polymerase chain reacting amplification, and then electrophoretic separation of the products, methylation of the p16 promoter by methylation-specific polymerase chain reacting, and cyclin D1 gene amplification by fluorescence in situ hybridization. RESULTS: Baseline dysregulation of cyclin D1 expression was found in 50% (14 of 28) and was reversed in 6 of 14 cases, whereas p16 expression was lost in 46% (13 of 28) and regained in 2 of 13 cases. Loss of heterozygosity at 9p21 occurred in 68% and p16(INK4a) promoter methylation occurred in 75% of cases, with increasing frequency from mild to severe dysplasia. Cyclin D1 gene amplification was identified in two cases. Cyclin D1 protein dysregulation at last follow-up alone and in combination with p16 loss was associated with histological progression and cancer development (P < 0.01). CONCLUSIONS: Additional study of these alterations in a larger sample and exploration of the upstream signaling partners of these cell cycle regulators in vivo is warranted to identify cancer risk profiles that would be meaningful targets for chemopreventive intervention.

Adult↗
PubMed2000

Risk assessment of organoleptic postmortem inspection procedures for pigs.

A systematic quantification of foodborne hazards in abnormal and normal tissues of pig carcases was undertaken to provide a risk-based assessment of the effectiveness of traditional organoleptic meat inspection. A total of 36,059 pigs, representing all major pig-producing areas and systems in Australia, were inspected on a seasonal basis at three abattoirs over 12 months. The prevalence of grossly detectable abnormalities of possible food-borne disease significance was recorded. A subset of the grossly detectable abnormalities, together with tissues classified by inspection as normal (controls) were submitted for the detection of a broad range of food-borne hazards. The potential exposure of consumers to hazards in fresh pork was characterised as the number of carcases per 10,000 containing hazards in selected tissues. The results indicated that the level of exposure of consumers to microbiological hazards in fresh pork is unlikely to be reduced significantly by the detection and removal of gross abnormalities in the tissues examined. On the basis of carcase throughput, the rate of contamination of normal lymph nodes was commonly 100 times higher, and no hazards were isolated from two types of grossly abnormal nodes. While further processing, cooking and handling may alter the exposure characterisation, the study nevertheless identifies the proportional contribution of abnormal and normal tissues to risks to consumers and clearly identifies the need for consideration of 'visual only' inspection in the re-evaluation of traditional inspection procedures.

Abscess↗
PubMed2000

Clinical trials of controlled-release melatonin in children with sleep-wake cycle disorders.

This is the first study to examine effective doses of controlled-release (CR) melatonin in children with chronic sleep wake cycle disorders. All 42 subjects had severe neurodevelopmental difficulties. Initially, a randomized double-blinded cross-over design was used in 16 children, comparing the effectiveness of fast-release (FR) and CR melatonin. In the remainder of the patients, the CR melatonin was studied on a clinical basis. The effectiveness of treatment was assessed by sleep charts and clinical follow-up. Emphasis was placed on the judgement of the parents, who had guidance from the physicians. The average final CR melatonin dose in the 42 patients was 5.7 mg (2-12 mg). The studies showed that the FR melatonin was most effective when there was only delayed sleep onset, but CR formulations were more useful for sleep maintenance. Children appeared to require higher doses than adults.

Adolescent↗
PubMed2000

Biomechanical comparison of quadriceps tendon fixation with patellar tendon bone plug interference fixation in cruciate ligament reconstruction.

PURPOSE: The purpose of this study was to use current fixation techniques and compare the stiffness and ultimate tensile failure of the tendinous end of the quadriceps tendon (QT) with the bone plug end of the bone-patellar tendon-bone (BPTB) graft using current techniques of fixation. TYPE OF STUDY: Randomized trial of elderly cadaver knees. MATERIALS AND METHODS: Tibial and femoral biodegradable interference fixation and femoral EndoButton (Smith & Nephew, Acufex, Mansfield, MA) fixation in bone tunnels with the QT and the BPTB graft were compared by using 10 pairs of elderly cadavers and biomechanical testing. Two groups, fixation at time zero (simulating fixation in the operating room) and testing after 1, 000 loading cycles (simulating patient rehabilitation exercises), were used. RESULTS: At time zero fixation, stiffness of the soft tissue QT tibial tunnel interference fixation was 59% less stiff than the stiffness of the interference fixation of a BPTB plug in a femoral tunnel (P =.11). The EndoButton femoral fixation resulted in a decrease in stiffness at time zero compared with femoral tunnel interference fixation of the soft tissue QT (P =.03). All groups improved stiffness with cycling the construct to 1,000 cycles. CONCLUSIONS: Placement of the QT tendinous end of the graft in the femoral bone tunnel when using a interference fixation will approximate the stiffness of a bone plug in the tibial bone tunnel with interference fixation. The EndoButton fixation is not as stiff as either of the femoral interference fixation options. The addition of more than 20 loading cycles could remove laxity from the graft fixation-graft cruciate ligament complex and improve its stiffness.

Anterior Cruciate Ligament↗
PubMed2000

Making best use of available residue data for acute intake assessment.

Risk assessment for pesticide residues in food has previously concentrated on chronic intake, probably with the assumption that if the chronic intake is acceptable, acute intake will also be acceptable. Data generation is expensive so we should extract, where possible, information useful for acute intake estimation from supervised residue trials. Residues in individual units of fruit or vegetables are more variable than the residues in composite samples and the distribution in individual units is probably best approximated by a log-normal distribution, but further evidence is needed. Theory provides a method for calculating the variability of replicate composite samples and applying it to individual units. The expected residue in the 95th or 99th percentile single fruits may then be calculated. An example for folpet residues in apples showed that the 95th and 99th percentile apples would contain 1.8 x and 2.3 x the residue in the composite sample, respectively. For abamectin in apples the 95th and 99th percentile factors were 6.7 and 15, respectively. The 95th and 99th percentile factors for azinphos-methyl in apples, based on single apple analysis, were 1.7 and 2.1, respectively.

Data Interpretation, Statistical↗
PubMed2000

Total plasma clearance of 51Cr-EDTA: variation with age and sex in normal adults.

Although inulin clearance measured during constant infusion is still considered the reference method, single-injection of 51Cr-EDTA with subsequent plasma sampling has become the most popular technique for the routine assessment of glomerular filtration rate. Despite the fact that the technique has been in use for 30 years, there are only a few reports of normal values calculated directly from 51Cr-EDTA data and normal ranges have generally been produced by conversions of inulin data. The aim of this study was to measure the variation in total plasma clearance, calculated directly from 51Cr-EDTA measurements, in normal males and females, of Saudi Arabian origin, over a wide range. Altogether, 201 potential kidney donors aged 16-60 years were studied. No statistically significant association of total plasma clearance with age or sex could be demonstrated; however, predictive equations suggesting a small decline in total plasma clearance with age were developed. The figures presented suggest that the reduction in total plasma clearance of 51Cr-EDTA with age is relatively shallow up to the age of at least 60 years and that normal ranges produced by conversion of inulin data may overestimate the decline with age.

Adolescent↗
PubMed2000

Vancomycin pharmacokinetics and Bayesian estimation in pediatric patients.

The vancomycin pharmacokinetic profile was characterized in six pediatric patients and the potential of nonlinear mixed effects modeling and Bayesian forecasting for vancomycin monitoring was explored using NONMEM V (1.1). Based on steady state serial vancomycin concentrations, the estimates of mean t1/2, Vd, and Cl derived by the Sawchuk and Zaske method (1) were 3.52 hours, 0.57 L/kg, and 0.12 L/h per kg, respectively. NONMEM analysis demonstrated that a weight-adjusted two-compartment model described individual patients' data better than a comparable one-compartment model. The two-compartment estimates of mean t1/2alpha, t1/2beta, Vss, and Cl were 0.80 hour, 5.63 hours, 0.63 L/kg, and 0.11 L/h per kg, respectively. The relatively long mean t1/2alpha suggests that peak vancomycin concentrations measured earlier than 4 hours postdose do not reflect postdistributional serum concentrations. NONMEM population modeling revealed that a weight-adjusted two-compartment model provided a better fit than a comparable one-compartment model. The resulting population parameters and variances were fixed in NONMEM to obtain Bayesian predictions of individual vancomycin serum concentrations. Bayesian estimation with either a single midinterval or trough sample has the potential to provide accurate and precise predictions of vancomycin concentrations. This should be evaluated using a vancomycin population pharmacokinetic model based on a larger sample of pediatric patients.

Anti-Bacterial Agents↗
PubMed1999

Osteomyelitis: a review of currently used imaging techniques.

Conventional radiographs remain the initial imaging modality involved in the diagnosis of osteomyelitis. Bone scintigraphy and its specific agents did not only eliminate the problems of inherent low sensitivity of conventional radiographs, but also increased the specificity to higher degrees. Spiral CT, on the other hand, has solved several diagnostic problems, such as osteomyelitis of the sterno-clavicular junction and hidden areas in the pelvic bones. Magnetic resonance imaging with its multiplanar capability, greater anatomic details and excellent soft tissue bone marrow contrast resolution has a significant role in surgical planning and limb preservation. Ultrasound and US-guided aspiration has recently been involved in the diagnosis and management of osteomyelitis with several advantages particularly in children. Our goal in this review is to outline the ability of various imaging techniques by comparing their strengths and weaknesses in the diagnosis of osteomyelitis. Finally, we suggest various imaging algorithms for specific clinical scenarios. Spondylitis and septic arthritis are not discussed in this review.

Bone and Bones↗
PubMed1999

Melatonin treatment of non-epileptic myoclonus in children.

Oral melatonin (MLT) has been used by our Vancouver research group in the treatment of paediatric sleep disorders since 1991; slightly over 200 children, mainly with multiple disabilities, who frequently had seizures, have been treated. Three children with markedly delayed sleep onset due to recurring myoclonus were also referred for MLT treatment: two had non-epileptic, and one had epileptic and non-epileptic myoclonus. Low doses of oral MLT (3 to 5 mg) unexpectedly abolished their myoclonus and allowed them to sleep. There were no adverse effects. It appears that certain types of myoclonus, which might be resistant to conventional anticonvulsant medications, may respond to MLT but the mechanism of action is unclear. Further research on this novel treatment is urgently needed.

Anticonvulsants↗