Biomedical subjects
D MacDonald
Publications and source records attributed to D MacDonald.
Implications of managed care for medical ethics. South Carolina Medical Association Medical Ethics Committee.
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Mutations which reduce levels of pyruvate dehydrogenase in Schizosaccharomyces pombe cause a requirement for arginine or glutamine.
Forty-four mutants of Schizosaccharomyces pombe were isolated which required supplementation with arginine or glutamine. These mutants appear to define three genes, provisionally named agg1, agg2 and agg3 (arginine, glutamine requiring). Mutants in all three genes were found to have reduced levels of pyruvate dehydrogenase compared to wild-type.
The use of the percentage change in Oswestry Disability Index score as an outcome measure in lumbar spinal surgery.
STUDY DESIGN: A retrospective analysis of the change in the Oswestry Low Back Pain Disability Questionnaire in a heterogeneous group of 144 operatively managed patients was undertaken to examine the change in disability index as an outcome measure. OBJECTIVES: To establish the percent change in disability index as an outcome measure able to identify risk factors for poor results in lumbar spinal surgery. METHODS: Epidemiologic, diagnostic, and surgical variables were examined as risk factors using step-wise multiple linear regression analysis at both follow-up times (6 months and 2 years), with percent change in disability index used as the outcome measure. RESULTS: At 6-months follow-up, previous surgery, female gender, workers' compensation, a lower initial disability index score, increasing age, and spinal fusion alone as an operative procedure were independently and significantly negatively correlated with outcome. Further analysis revealed that for patients with spinal canal stenosis, the magnitude of the initial disability index did not correlate with outcome, whereas patients with low back pain or a prolapsed intervertebral disc fared better if they had high initial disability scores. Data at 2-years follow-up were less adequate. However, previous surgery on the spine and low initial disability score were significant negative predictors of outcome at 6-month and 2-year follow-up. CONCLUSIONS: The findings indicate that the absolute value and change in these scores after surgery vary from patient to patient, but that their percentage change is likely to be the best marker of outcome when such subjective scoring systems are used.
Effects of isotretinoin on male reproductive system.
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Protocols for deriving Canadian water quality guidelines for the protection of agricultural water uses. Canadian Council of Ministers of the Environment.
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Association between calcium regulatory hormones and other factors and bone mineral density in elderly Chinese men and women.
BACKGROUND: The purpose of the study was to determine if bone mineral density (BMD) in elderly Chinese subjects was associated with indices of calcium metabolism (parathyroid hormone, vitamin D), osteocalcin, and other nonbiochemical factors. METHOD: 104 men (mean age 74 +/- 6 yrs) and 213 women (mean age 76 +/- 8 yrs) with no previous history of fractures were recruited from old age hostels and community centers. BMD was measured with dual energy X-ray absorptiometry. RESULTS: BMD in both sexes was associated with body mass index (BMI), arm circumference, and skinfold thicknesses. Additionally, in women there was a positive association with grip strength and load-bearing activities, a negative association with age in all sites except for the lumbar spine, and negative associations with indices of bone turnover (osteocalcin, urinary hydroxyproline/creatinine and calcium/creatinine ratios). After adjusting for BMI, women with hypertension or taking antihypertensive drugs had higher mean BMD at the lumbar spine. Multivariate analyses showed that only BMI predicted BMD in men, while age, BMI, and arm circumference were predictors of BMD in women. CONCLUSION: Indices of calcium metabolism were not correlated with BMD in this elderly Chinese population, suggesting that the age-related rise in parathyroid hormone and reduced intestinal absorption of calcium may not be important factors in determining BMD in elderly Chinese men and women.
Adhesion molecule expression and the inflammatory cell infiltrate in delayed pressure urticaria.
We have investigated the kinetics of the leucocyte infiltrate in delayed pressure urticaria (DPU) in relation to the in vivo expression of the cytokine-regulated cell surface adhesion molecules, E-selectin (endothelial adhesion molecule-1, ELAM-1), intercellular adhesion molecule-1 (ICAM-1), and vascular adhesion molecule-1 (VCAM-1). Immunohistochemical analysis was performed on biopsies taken from unchallenged skin, and at 0, 2, 6, 24, 48 and 120 h after weighted rods had been applied to 13 patients with DPU. There was moderate to marked upregulation of E-selectin at 6 and 24 h after application of pressure. At 24 h, more patients showed expression of VCAM-1 on perivascular cells than before pressure. Moderate expression of ICAM-1 was present in some biopsies from both unchallenged and pressure-challenged skin, but there was no clear trend. In DPU, there was a significant increase in the neutrophil count at 2 h after a pressure challenge, with further increases at 6 and 24 h. The median cell counts per high-power field of eosinophils and monocyte/macrophages increased significantly at 24 h after pressure. Biopsies from four normal controls subjected to an identical pressure challenge showed no detectable changes in adhesion molecule expression or in the cell infiltrate. The findings in four patients with chronic idiopathic urticaria not associated with DPU were qualitatively similar to (but intermediate in severity between) the findings in DPU weals at 6 and 24 h. These results suggest that vascular endothelial activation is an early response to pressure challenge in DPU, and is also present in chronic idiopathic urticaria.(ABSTRACT TRUNCATED AT 250 WORDS)
Spinal subdural haematoma in a parturient after attempted epidural anaesthesia.
We report a case of spinal subdural haematoma with neurological deficit in a 36-yr-old woman following Caesarean section for severe preeclampsia and placental abruption. She had been taking chronic trifluoperazine treatment for depression. Her activated partial thromboplastin time (aPTT) was 49 sec (normal = 26-36) but all other tests of coagulation were normal. Epidural anaesthesia was attempted but, despite a negative test dose, injection of local anaesthetic resulted in a generalized seizure and general anaesthesia was induced. Seventy-two hours after delivery, she was found to have bilateral leg weakness, urinary incontinence, absent rectal sphincter tone and asymmetrical leg reflexes. The diagnosis of spinal haematoma was confirmed by magnetic resonance imaging. She underwent emergency laminectomy and made a full neurological recovery.
Septic pelvic thrombophlebitis: an unusual treatable postpartum complication.
Septic pelvic thrombophlebitis is an uncommon but serious postpartum complication occurring in about 1 in 2,000 pregnancies, characterized by pain, antibiotic resistant fever and tachycardia. In about 50% of cases a pelvic mass is present which is usually right-sided (especially when the ovarian vein is involved). It is estimated to cause 18 maternal deaths per million pregnancies in the United States. Use of contrast enhanced CT scanning and a trial of heparin therapy increases the diagnostic certainty. It is particularly important because surgical management which may otherwise be suggested because of a spiking fever and a mass seems to be associated with a poorer prognosis than does conservative management.
Potassium intake and urinary calcium excretion in healthy subjects.
Potassium depletion increases and potassium supplementation decreases urinary calcium excretion. To determine whether these experimental observations have any significance in healthy free living subjects, we measured 24 h urinary calcium, sodium, potassium and serum parathyroid hormone (PTH) in 142 healthy young (aged 18-40 years) female Chinese subjects. Sodium excretion and potassium excretion were positively correlated with calcium excretion (r = 0.494, p < 0.0001 and r = 0.181, p = 0.031, respectively). However stepwise multiple regression analysis showed that only urinary sodium excretion contributed to the excretion of calcium. We conclude that in free living subjects potassium intake has little effect on calcium excretion.
Intriguing structure-activity relations underlie the potent inhibition of HIV protease by norstatine-based peptides.
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Serum intact parathyroid hormone levels in elderly Chinese females with hip fracture.
Serum intact parathyroid hormone (PTH), 25 hydroxyvitamin D(25OHD), 1,25 dihydroxyvitamin D (1,25(OH)2D), albumin, and ionized calcium were measured in 61 Chinese female patients with hip fracture and 61 control subjects. Hip fracture patients had low albumin, ionized calcium, and 250HD levels. Serum PTH and 1,25(OH)2D values were not different between the two groups. We conclude that although 250HD level in hip fracture patients is low, there is no evidence of secondary hyperparathyroidism, suggesting that the low 250HD levels may be a secondary phenomenon in response to the fracture.
Case report: fatal overdose with sustained-release verapamil.
Verapamil is generally a safe and effective drug in the treatment of many vascular disorders. During the past 10 years, a number of serious poisonings have been attributed to verapamil overdose. A relatively new problem is toxicity with the sustained-release form of verapamil. Complications of verapamil overdose can be understood as simply an extension of its pharmacologic activity. Consistently effective therapy remains elusive. Specific calcium channel blocker antidotes are under investigation, but supportive therapy remains the mainstay for serious verapamil overdose.
HLA-A11 in renal allograft recipients with skin cancer.
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Age-related changes in bone density, serum parathyroid hormone, calcium absorption and other indices of bone metabolism in Chinese women.
OBJECTIVE: To study the age-related changes in bone density, serum parathyroid hormone, calcium absorption and other indices of calcium metabolism in Chinese women who habitually have a low calcium intake. DESIGN: Cross-sectional study. SUBJECTS: One hundred and fifty-six healthy Chinese women aged 20-83 years. None were on any medication or vitamin supplements. Subjects over the age of 60 years were all living in a hostel; younger subjects were nurses or subjects attending a family clinic for minor illnesses. MEASUREMENTS: Fasting blood and urine samples were collected for biochemical measurements and calcium absorption was measured using 45Ca by the method of Marshall and Nordin. Bone density was measured by dual energy X-ray densitometry (Norland X R20 X-ray bone densitometer) at the left hip and lumbar spine. Serum parathyroid hormone was measured by a chemiluminometric assay. RESULTS: Plasma ionized calcium concentration, alkaline phosphatase, bicarbonate, plasma creatinine and serum B2 microglobulin were significantly higher in the elderly than in the young, whereas plasma phosphate and the anion gap were higher in the young. Urinary excretion of calcium, phosphate and hydroxyproline were all higher in older women. Plasma parathyroid hormone concentration was positively correlated with age even after taking into account the decline in renal function (as indicated by the rise in B2 microglobulin (r = 0.506, P less than 0.001). Serum concentrations of 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D were not lower in the older women. Fractional calcium absorption from an oral load of radiolabelled calcium was significantly lower in the older women and 37% of the older women were below the 2.5 percentile found in the younger women. Bone density measured by dual energy X-ray densitometry was also significantly lower in the elderly. CONCLUSION: In Chinese women there is an increase in PTH and a decrease in calcium absorption with age in spite of the presence of normal vitamin D metabolites.
Interrelationships between urinary sodium, calcium, hydroxyproline and serum PTH in healthy subjects.
The effect of sodium intake on the excretion of calcium, hydroxyproline (OHP) and serum parathyroid hormone (PTH) was examined. When seven healthy males increased their sodium intake by 200 mmol/day, excretion of calcium increased by 1.70 mmol/day and that of OHP by 27%. Serum PTH, however, did not increase significantly. In a cross-sectional study of 334 healthy female subjects there were strong positive correlations between fasting urinary sodium/creatinine (Na/Cr) and calcium/creatinine (Ca/Cr) ratios (r = 0.573) and between Na/Cr and urinary OHP/Cr ratios (r = 0.246). Serum PTH was negatively correlated with Na/Cr ratio (r = -0.161). We conclude that an increase in dietary sodium causes calciuria and an increase in hydroxyproline excretion. The results do not support the hypothesis that this is mediated by PTH.