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Biomedical subjects

M Harris

Publications and source records attributed to M Harris.

At least 109 records · Page 6Linked to original sources

Ossification of the ligamentum flavum as a cause of myelopathy in North America: report of three cases.

Myelopathy caused by ossification of the ligamentum flavum is a rare condition in North America. The authors describe three patients whose myelopathy was attributed to posterior cord compression warranting laminectomy to decompress the cervical spine (in one patient) and the thoracic spine (in two patients). The spinal computed tomographic scan (especially after myelography) can be instrumental in guiding the management of this condition.

Aged↗

Implementing and maintaining school-based mental health services in a large, urban school district.

The Dallas (Texas) Public Schools established the first school-based health center in the United States in 1969. In 1993 a partnership between two school principals, a school mental health professional, and the medical director of the county mental health center was the impetus for the first comprehensive school-based mental health center in Texas. In 1995 the programs joined together as Youth and Family Centers (YFCs) to provide physical health, mental health, and other support services to students and their families. The 10 strategically located school-based centers are directed by licensed mental health professionals employed by the district who lead a multidisciplinary team of physical health and mental health providers. Students served by the YFCs have fewer discipline problems, course failures, and school absences.

Adolescent↗

Assessing body composition and changes in body composition. Another look at dual-energy X-ray absorptiometry.

Dual-energy X-ray absorptiometry (DXA) is selected with increasing frequency as a method for both assessing body composition and measuring the changes in body composition. Issues have been raised about hydration, software version, hardware (fan beam vs. pencil beam), and the subject population in relation to the validity of DXA-derived estimates of body composition. This paper reviews validation studies of DXA to assess the impact of recent developments in its technology. Studies by Prior et al., Kohrt et al., Salamone et al., Going et al., and Pietrobelli et al. demonstrate the effectiveness of DXA estimates of changes in body composition. By contrast, Clasey et al., Nelson et al., and Friedl et al. found limitations in DXA estimates of body composition and its changes. These contradictory conclusions were explored for threats to internal validity in each research study. From this analysis, two validation guidelines are recommended for use when evaluating estimates of body composition. When multicomponent models are used, it is essential that estimates of body water as a fraction of fat-free mass fall in the expected range (71 to 75%) and have a relatively small standard deviation (2 to 3%). For measuring changes in body composition, DXA estimates of total body mass must accurately reflect both baseline and posttreatment scale body weight estimates. Failure to meet these guidelines threatens the internal validity of the study and raises the likelihood of methodological discrepancies. Applying these criteria to DXA studies of body composition under review accounts for much of the contradictory conclusions among investigations.

Absorptiometry, Photon↗

The use and perceived value of diabetes clinical management guidelines in general practice.

OBJECTIVE: To assess attitudes to and use of NSW Health Department (NSWHD) guidelines for the clinical management of diabetes mellitus by divisions of general practice, general practitioners, patients and allied health professionals. METHOD: A mail cross sectional survey of divisions of general practice and a series of focus groups of GPs, patients and allied health professionals, on extent of use and perceived usefulness of the NSWHD guidelines. RESULTS: Forty divisions had or recently concluded a diabetes shared care project. Thirteen out of the 31 diabetes projects with guidelines reported using the NSWHD guidelines. Nineteen divisions were aware of the NSWHD guidelines. While the general response to the guidelines in both the survey and the focus groups was positive, there were suggestions for modifications. Many respondents were not aware of the guidelines. CONCLUSION: Optimal use of the guidelines in general practice requires improved dissemination and an implementation strategy based not only on GP education but also systems to reduce barriers to implementation and to support better quality of GP care.

Attitude of Health Personnel↗

Diabetes information management systems. General practitioner and population reach.

AIM: To assess the extent to which Australian divisions of general practice are facilitating structured management of diabetes. METHOD: The study was conducted over a 12 month period (1998/1999) and involved two postal surveys of Australia's 123 divisions. RESULTS: In both surveys 53% of divisions were implementing a diabetes program, the main components being continuing education of general practitioners (GPs), establishment of information systems, use of guidelines and shared care. In the 30 divisions operating a program for more than 12 months there was a significant increase in the proportion of GPs registering patients (p = 0.03) and the population who were registered with diabetes (p < 0.001). In 43% of divisions, GP reach was greater than 50%. Population reach of more than 50% was achieved by only 17% of divisions. The larger the division, the lower the GP participation rate (p = 0.001) and the lower the population reach (p < 0.001). CONCLUSION: Strategies to facilitate adequate reach of programs in divisions with large populations warrant consideration. This may include the formation of subgroups and support for practices and divisions to implement structured evidence based care systems for the management of chronic diseases in general practice.

Adult↗

Effect of low dose daily aspirin on serum urate levels and urinary excretion in patients receiving probenecid for gouty arthritis.

OBJECTIVE: To determine if low dose daily enteric coated aspirin significantly affects the therapeutic actions of probenecid with respect to serum urate levels or urinary urate excretion. METHODS: Patients with gouty arthritis taking a stable dose of probenecid for at least 3 months were enrolled in a prospective crossover study. Twenty-four hour urinary and serum uric acid levels were measured after 14 days in patients crossed over to receive probenecid alone; probenecid and aspirin 325 mg taken concomitantly; and probenecid followed by aspirin 325 mg at 6 hours. RESULTS: Eleven patients completed the crossover study. The addition of aspirin to a stable dose of probenecid had no significant effect upon serum urate levels or 24 h urinary urate excretion (p > 0.05, paired t test). CONCLUSION: Low dose daily enteric coated aspirin does not significantly interfere with the uricosuric effects of probenecid in patients with gouty arthritis.

Aged↗

Integration between GPs and hospitals: lessons from a division-hospital program.

The aim of the study reported here was to evaluate current initiatives in GP-hospital integration and highlight areas where further research, development and evaluation are required. Seven pre-existing GP-hospital programs were selected and given supplementary funding to allow for more effective evaluation. These local evaluations were then incorporated into a national program on GP-hospital collaboration. We found that the seven projects made substantial progress towards their goals, and in the process highlighted important aspects of successful collaboration. The collective evaluation of DHIP identified expected benefits of collaboration for patients (improved access to services, reduced anxiety, and fewer post discharge complications), for GPs (increased involvement in acute care and in hospital decision making), and for service organisations (stronger working relationships, increased capacity, and greater efficiency). Barriers to service integration were also identified, including the different cultures of Divisions and hospitals, their lack of internal coherence and the Commonwealth-state divide. The evaluation showed that much has been achieved in building the relationships and the capacity needed for GP-hospital collaboration, and that effective models exist. The current challenge is to extend successful models across health areas and make effective collaboration part of the normal system of care. Substantial progress towards integrated care relies on a shift from a focus on systems within general practice or hospital environments to a patient centred approach. This will require general practice, hospitals, community services and consumer organisations to form long term partnerships and move beyond their currently disjointed view of acute and community care. The development of practical indicators for integrated care will support the process and facilitate shared learning across Commonwealth and state divides.

Australia↗

Identification of a novel fusion gene involving hTAFII68 and CHN from a t(9;17)(q22;q11.2) translocation in an extraskeletal myxoid chondrosarcoma.

A proportion of extraskeletal myxoid chondrosarcomas (EMC) have been shown to have a characteristic translocation t(9;22)(q22;q12) involving the EWS gene at 22q12 and the CHN orphan nuclear receptor gene at 9q22. This translocation appears to be largely specific for EMC, but has not been detected in all such tumours. We report here a case of EMC with a t(9;17)(q22;q11.2) as the sole chromosome abnormality. We have determined that the translocation results in the fusion of the entire coding region of CHN to the N-terminal transactivation domain of RBP56/hTAFII68. This is the first report of a translocation involving RBP56/hTAFII 68, a protein with sequence homology to both EWS and TLS/FUS. The involvement of RBP56/hTAFII68 may explain some unusual features of the tumour.

Amino Acid Sequence↗

Identification of the Nef-associated kinase as p21-activated kinase 2.

The Nef protein of primate immunodeficiency viruses plays an important role in the pathogenesis of acquired immunodeficiency syndrome (AIDS) [1] [2]. The interaction of Nef with the Nef-associated kinase (NAK) is one of the most conserved properties of different human and simian immunodeficiency virus (HIV and SIV) Nef alleles. The role of NAK association is currently not known but it has been implicated in enhanced viral infectivity in cell culture and in disease progression in SIV-infected macaques [3]. Previous studies have indicated that NAK shares many features with the p21-activated kinases (PAKs) [3], but the molecular identity of NAK has remained unknown. We have generated specific antisera against PAKs 1-3, and expressed these kinases individually as epitope-tagged proteins. By using these reagents in experiments involving partial proteolytic mapping, and exploiting the unique ability of PAK2 to serve as a caspase substrate, we have positively identified NAK as PAK2. Interestingly, although ectopic PAK2 overexpression efficiently replaced endogenous PAK2 from the complex with Nef, the total Nef-associated PAK2 activity was not increased, indicating the abundance of another cellular factor(s) as the limiting factor in Nef-PAK2 complex formation. Identification of NAK as PAK2 should now facilitate elucidation of its role as a mediator of the pathogenic effects of Nef.

Animals↗

Biomechanics of increased exposure to lumbar injury caused by cyclic loading: Part 1. Loss of reflexive muscular stabilization.

STUDY DESIGN: The recording of electromyographic responses from the in vivo lumbar multifidus of the cat, obtained while cyclic loading was applied as in occupational bending/lifting motion over time. OBJECTIVES: To determine whether the effectiveness of stabilizing reflexive muscular activity diminishes during prolonged cyclic activity; the recovery of lost muscle activity by a 10-minute rest; and whether such diminished muscular activity is caused by fatigue, neurologic habituation, or desensitization of mechanoreceptors in spinal viscoelastic tissues resulting from its laxity. SUMMARY OF BACKGROUND DATA: The literature repeatedly confirms observation that cyclic occupational functions expose workers to a 10-fold increase in episodes of low back injury and pain. The biomechanical evidence indicates that creep in the viscoelastic tissues of the spine causes increased laxity in the intervertebral joints. The impact of cyclic activity on the function of the muscles, which are the major stabilizing structures of the spine, is not known. METHODS: Electromyography was performed from the L1 to L7 in vivo multifidus muscles of the cat, while cyclic passive loading of 0.25 Hz was applied to L4-L5. Cyclic loading was applied for 50 minutes, followed by 10 minutes rest and a second 50-minute cyclic loading session. A third 50-minute cyclic loading period also was applied after the preload was reset to 0.5 N to offset the effect of laxity. RESULTS: Reflexive muscular activity was recorded from the multifidus muscles of all lumbar levels at the initiation of the first 50 minutes of cyclic loading. Activity recorded on electromyography quickly diminished with each cycle during the first 8 minutes of loading to 15% of its initial value. A slower decrease in muscular activity was evident throughout the remaining period, settling at 5% to 10% of its initial level by the end of 50 minutes. A 10-minute rest provided a 20% to 25% recovery of the electromyographic activity, but that was lost within the first minute of cycling. Offsetting the laxity in the spine resulted in full restoration of the electromyographic activity at all lumbar levels. CONCLUSIONS: The creep induced in the viscoelastic tissues of the spine as a result of cyclic loading desensitizes the mechanoreceptors within, which is manifest in dramatically diminished muscular activity, allowing full exposure to instability and injury, even before fatigue of the musculature sets in.

Animals↗

Biomechanics of increased exposure to lumbar injury caused by cyclic loading. Part 2. Recovery of reflexive muscular stability with rest.

STUDY DESIGN: Electromyographic responses from the lumbar multifidus muscle of the cat were recorded in vivo during 50 minutes of cyclic loading followed by 2 hours of rest. OBJECTIVE: To determine the rate of recovery of reflexive muscular stabilizing activity resulting from rest after viscoelastic laxity induced by 50 minutes of cyclic loading. SUMMARY OF BACKGROUND DATA: Muscular forces from agonists and antagonists were repeatedly shown to be the most significant stabilizing structures of the lumbar spine. Reflexive muscular coactivation force from the multifidus muscle elicited by mechanoreceptors in the spinal viscoelastic structures were, however, shown to diminish drastically with the onset of laxity in the viscoelastic structures. Data describing the rate of recovery of reflexive muscular coactivation forces resulting from rest after cyclic loading were not found. METHODS: Cyclic loading of the lumbar spine at 0.25 Hz was applied to L4-L5 for 50 minutes while electromyograms from the multifidus muscles of L1-L2 to L6-L7 were recorded. A rest period of up to 2 hours was given, during which electromyographic responses and load were measured every 10 minutes to sample recovery of laxity and reflexive muscular activity. RESULTS: Load and electromyographic response demonstrated an exponential decrease during the 50 minutes of cyclic loading. The first 10 minutes of rest allowed a significant recovery in laxity and muscle activity, with additional slow recovery over the next 20 to 30 minutes. The electromyographic response and load were increasing at an extremely slow rate thereafter. Overall, 2 hours of rest yielded only a 20% to 30% recovery in electromyographic response. Full recovery was never observed. A biexponential model was developed to predict loss and recovery of reflexive muscular activity and viscoelastic tension with laxity. CONCLUSIONS: Laxity in the viscoelastic structures of the lumbar spine desensitizes the mechanoreceptors within and causes loss of reflexive stabilizing forces from the multifidus muscles. The first 10 minutes of rest after cyclic loading results in fast partial recovery of muscular activity. However, full recovery is not possible even with rest periods twice as long as the loading period, placing the spine at an increased risk of instability, injury, and pain.

Animals↗