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Biomedical subjects

A Duncan

Publications and source records attributed to A Duncan.

At least 19 recordsLinked to original sources
PubMed2001

Serum hyaluronic acid in patients with veno-occlusive disease following bone marrow transplantation.

The development of hepatic veno-occlusive disease following bone marrow transplantation is associated with high-dose combination cytoreductive therapy. Experimental models have suggested that drug-induced injury to hepatic sinusoidal endothelial cells is involved in the pathogenesis of this syndrome. Hyaluronic acid is a polysaccharide that is metabolized, almost exclusively, by hepatic sinusoidal endothelial cells. The aim of the present study was to evaluate serum hyaluronic acid as a marker for endothelial cell injury in patients with veno-occlusive disease following bone marrow transplantation. Hyaluronic acid was measured in sera from patients with and without veno-occlusive disease using an enzyme-linked protein binding assay. Mean peak serum hyaluronic acid levels were significantly greater in patients who had a diagnosis of VOD compared to those transplant patients who did not, 1173.4 +/- 982.9 vs 444.9 +/- 735.6 ng/ml (P = 0.01). Serial serum samples obtained from a separate cohort of patients also demonstrated that serum hyaluronic acid levels were higher in patients with moderate or severe veno-occlusive disease compared to those with none or mild disease at days 7, 17 and 25 following transplantation (greatest difference at day 25: 366 +/- 327 vs 126 +/- 151, P = 0.01). Serum hyaluronic acid levels are increased in veno-occlusive disease and increase over time in patients with severe disease. Further studies are required to determine if elevated serum hyaluronic acid levels are due to decreased clearance by injured hepatic sinusoidal endothelial cells or increased production from early hepatic fibrogenesis associated with the acute liver injury.

Adult↗
PubMed2001

Surreptitious abuse of magnesium laxatives as a cause of chronic diarrhoea.

Surreptitious laxative abuse is increasingly considered as a possible cause of unexplained chronic diarrhoea. Laboratory services for detection of colonic stimulant laxatives are widely available; however, laboratory facilities for identifying patients with magnesium-induced diarrhoea are not commonly provided, making diagnosis difficult. We describe three patients who surreptitiously abused magnesium laxatives, and whose diagnoses were delayed, leading in each case to extensive investigations and lengthy in-patient stays. In all three cases, the diagnosis was eventually made by the simple measurement of magnesium in a random faecal sample. We would like to increase the awareness of surreptitious magnesium laxative abuse as a cause of chronic diarrhoea so that costly and unnecessary investigations may be minimized.

Adult↗
PubMed2000

Stretch reflex distinguished from pre-programmed muscle activations following landing impacts in man.

1. Electromyographic activity and joint rotation were measured whilst human subjects jumped down to land on a solid surface 0.45 m below them and then to a false collapsible surface at the same level. The collapsible surface did not produce ankle joint rotation. Objective evidence from post-take-off EMG onset latencies showed that the subjects were surprised by the false surface. 2. Following landing on the solid surface, the gastrocnemius and soleus muscles showed peak responses at latencies of 53 and 56 ms, respectively, and the antagonist m. tibialis anterior showed an early peak response with a latency of 26 ms. These responses occurred following landing on the solid surface but not following passage through the false surface. 3. The rectus femoris and biceps femoris muscles showed no clear reflex activity with this fall distance but pre-programmed activity was clearly present following impact. 4. It is concluded that the post-landing activity in m. soleus and m. gastrocnemius is a short-latency spinal reflex triggered by ankle joint rotation.

Adult↗
PubMed2000

Adenocarcinoma in situ of the uterine cervix: an experience with 100 cases.

OBJECTIVE: The aim of this study was to ascertain whether cold knife conization alone for cervical adenocarcinoma in situ is safe. METHODS: One hundred consecutive patients with a histologically proven adenocarcinoma in situ (AIS) of the cervix were studied from 1970 to 1992. RESULTS: Ninety-two women presented with abnormal smears, and of these 56% contained abnormal glandular cells. Sixty-seven (74%) of 90 women who underwent colposcopy had an abnormal examination, but a glandular abnormality was suspected in only 19 (28%). In all, 80 cold knife conizations were performed. In 7, no abnormality was found following punch biopsy. The margins were free of disease in 55 (75%). The most commonly involved margin in the remainder was the apical. Conization was followed by hysterectomy in 20 women: in 8 of these the cone margins were free and residual disease was found in 2 of the extirpated uteri: as these were extramural cases, inadequate sampling could not be excluded. Of the 12 women where hysterectomy followed conization with diseased margins, 9 had residual disease in the hysterectomy specimen. The definitive therapy was cold knife conization in 56 patients, hysterectomy in 38, and electrocoagulation diathermy in 6. Follow-up of the 53 patients treated by conization alone ranging from 1 to 16 years, with a mean of 8 years (3 have been lost to follow-up) revealed no recurrence of AIS or adenocarcinoma to date. CONCLUSION: It is concluded that cold knife conization is a safe therapeutic modality, provided that the cone biopsy has been adequately sampled and the margins are free.

Adenocarcinoma↗
PubMed2000

Partitioning of a polymer chain between two confining cavities: the role of electrostatic interactions

A recently developed lattice field theory approach to the statistical mechanics of charged polymers in electrolyte solutions [S. Tsonchev, R. D. Coalson, and A. Duncan, Phys. Rev. E 60, 4257, (1999)] is generalized to the case where ground-state dominance in the polymer's Green's function does not apply. The full mean-field equations for the system are derived and are shown to possess a unique solution. The approach is applied to the problem of a charged Gaussian polymer chain confined to move within the region defined by two fused spheres. The failure of the notion of ground-state dominance under certain conditions even in the limit of large monomer number is demonstrated.

Journal Article↗
PubMed1999

Homocysteine levels in healthy New Zealanders and those with vascular disease.

AIMS: Levels of plasma homocysteine (tHcy) have been shown to vary between populations. The aim of the present study was to determine tHcy levels in a New Zealand population to facilitate interpretation of international reference ranges. METHODS: Fasting tHcy levels were determined in 431 volunteer men and women, aged between 17 and 83 years, from the greater Otago region. Subjects with self-reported incidences of vascular disease (n=138) were compared with healthy control subjects (n=293). RESULTS: Mean (SD) fasting tHcy level of the entire population was 8.3(3.5) micromol/L and men had significantly higher levels than women (9.0(3.4) and 7.8(3.5) micromol/L, respectively, p<0.05). Levels increased significantly with increasing age (0.5 micromol/L for every ten years). There was a small but non-significant difference in tHcy levels between subjects with and without vascular disease (difference after excluding two outliers and adjusting for age and gender; 0.63, 95% CI, -0.03,1.29). tHcy levels were not significantly correlated with lipid or lipoprotein levels. CONCLUSION: Levels of tHcy in a group of volunteers from the greater Otago region were similar to those reported in other populations at high risk of cardiovascular disease. Reference ranges derived from these populations would appear to be applicable for New Zealanders. tHcy measurements should be made when assessing individuals at high risk of vascular disease and intervention strategies considered.

Adolescent↗
PubMed1999

Scleromyxedema: a complete response to prednisone.

Scleromyxedema is a disorder characterized by a typical rash due to the accumulation of mucin in the dermis. It is always associated with a monoclonal protein in the serum and can have a wide variety of systemic manifestations. We describe a 40-year-old woman who had scleromyxedema associated with a monoclonal G lambda protein. Severe systemic symptoms included fatigue, esophageal dysmotility, and myopathy. Symptoms resolved completely with oral prednisone therapy, and she remained in clinical remission 24 months after use of prednisone was discontinued. Scleromyxedema is commonly treated with alkylating agents, which have been associated with pronounced morbidity and mortality. We suggest that oral corticosteroid therapy may be a reasonable initial choice for treating this disease and that alkylating agents be reserved for corticosteroid-refractory disease.

Adult↗
PubMed1999

Cells expressing the NG2 antigen contact nodes of Ranvier in adult CNS white matter.

The NG2 antibody, which recognises an integral membrane chondroitin sulphate, labels a significant population of cells in adult CNS white matter tracts of the rat optic nerve and anterior medullary velum (AMV). Adult NG2+ cells are highly complex with multiple branching processes and we show by EM immunocytochemistry that they extend perinodal processes, which contact nodes of Ranvier. NG2+ cells do not react to conventional immunohistochemical markers for adult glia and so we reservedly term them NG2P cells. In vitro, NG2 labels oligodendrocyte-type-2 astrocyte (O-2A) progenitors that can give rise to oligodendrocytes or type-2 astrocytes, depending on the culture medium. Thus, it is possible that NG2P cells may be derived from the same stem cells as oligodendrocytes. Interestingly, NG2+ cells identified previously in adult CNS displayed phenotypic characteristics of O-2Aadult progenitors and it is possible that, like them, NG2P cells might retain the capacity of generating oligodendrocytes in the adult CNS. This may be an important role of NG2P cells in demyelinating diseases such as multiple sclerosis. It is significant therefore that the perinodal processes of NG2P cells contact the only sites of exposed axolemma in myelinated axons, so that NG2P cells are ideally situated to detect and respond to changes in axonal function during demyelination. A further implication of our finding is that NG2P cells may perform functions at nodes of Ranvier previously attributed to perinodal astrocytes, including the clustering and maintenance of sodium channels in the axon membrane at nodes, during development and following demyelination.

Animals↗
PubMed1999

Effects of variations in live weight gain on bone growth and composition and on markers of bone turnover in lambs.

Growing lambs were fed the same diet at intakes supporting mean live weight gains of 0.1, 0.2 and 0.3 kg day-1, representing slow, intermediate and fast growth groups, respectively. The effects on bone growth and composition, and on blood and urinary bone marker concentrations or excretion rates were monitored. Compared with the slow-growing lambs, the higher intake group grew twice as fast, had higher rates of bone growth (indicated by external metatarsal length), and larger and heavier bones at slaughter. Bones from fast-growing animals had higher collagen and deoxypyridinoline concentrations, and lower Ca:collagen, Ca :P and pyridinoline : deoxypyridinoline ratios, indicating a less mature bone compared with the slow-growing lambs. Bone growth rate had no effect on plasma osteocalcin, bone-specific alkaline phosphatase or growth hormone concentrations, nor on the urinary excretion of pyridinoline and deoxypyridinoline. The results for plasma markers may be explained by an increase in blood volume linked with increased body weight.

Alkaline Phosphatase↗
PubMed1998

Axon-glial relations during regeneration of axons in the adult rat anterior medullary velum.

The anterior medullary velum (AMV) of adult Wistar rats was lesioned in the midsagittal plane, transecting all decussating axons including those of the central projection of the IVth nerve. At selected times up to 200 days after transection, the degenerative and regenerative responses of axons and glia were analyzed using transmission and scanning electron microscopy and immunohistochemistry. In particular, both the capacity of oligodendrocytes to remyelinate regenerated fibers and the stability of the CNS/PNS junctional zone of the IVth nerve rootlet were documented. Transected central AMV axons exhibited four patterns of fiber regeneration in which fibers grew: rostrocaudally in the reactive paralesion neuropil (Group 1); randomly within the AMV (Group 2); into the ipsilateral IVth nerve rootlet, after turning at the lesion edge and growing recurrently through the old degenerated contralateral central trochlear nerve trajectory (Group 3); and ectopically through paralesion tears in the ependyma onto the surface of the IVth ventricle (Group 4). Group 1-3 axons regenerated unperturbed through degenerating central myelin, reactive astrocytes, oligodendrocytes, microglia, and large accumulations of hematogenous macrophages. Only Group 3 axons survived long term in significant numbers, and all became myelinated by oligodendrocytes, ultimately establishing thin sheaths with relatively normal nodal gaps and intersegmental myelin sheath lengths. Schwann cells at the CNS/PNS junction of the IVth nerve rootlet did not invade the CNS, but astrocyte processes grew across the junction into the PNS portion of the IVth nerve. The basal lamina of the junctional glia limitans remained stable throughout the experimental period.

Animals↗
PubMed1998

A diet rich in walnuts favourably influences plasma fatty acid profile in moderately hyperlipidaemic subjects.

OBJECTIVE: To compare two low fat diets one rich in walnuts on parameters of lipid metabolism in a group of hyperlipidaemic subjects. DESIGN: A randomised cross over study. SETTING: Department of Human Nutrition, University of Otago, Dunedin, New Zealand SUBJECTS: Twenty one men with mean (s.d.) levels of total and LDL cholesterol of 6.58 (0.60) and 4.63 (0.58) respectively. INTERVENTIONS: For two periods of four weeks subjects were asked to consume two low fat diets (fat 30% total energy), one containing, on average, 78 g/d walnuts. Walnuts obtained through Lincoln University and the Walnut Growers Group (South Canterbury). RESULTS: Participants reported a higher total fat intake on the walnut diet (38% compared with 30% on the low fat diet P < 0.01) The most consistent change in fatty acid profile of triacylglycerol, phospholipid and cholesterol ester on the walnut diet was a significant (P < 0.01) increase in linoleic acid. Triacylglycerol linolenate also increased significantly (P < 0.01). Total and LDL cholesterol were lower on both experimental diets than at baseline, 0.25 mmol/l and 0.36 mmol/l respectively on the walnut diet and 0.13 mmol/l and 0.20 mmol/l respectively on the low fat diet. High density lipoprotein cholesterol was higher on both the walnut and low fat diets when compared to baseline (0.15 mmol/l and 0.12 mmol/l, respectively). When comparing the walnut and low fat diets only apo B was significantly lower (P < 0.05) on the walnut diet. CONCLUSIONS: Despite an unintended increase in the total fat intake on the walnut diet, fatty acid profile of the major lipid fractions showed changes which might be expected to reduce risk of cardiovascular disease. The reduction of apolipoprotein B suggests a reduction in lipoprotein mediated risk, the relatively low myristic acid content of both diets perhaps explaining the absence of more extensive differences in lipoprotein levels on the two diets.

Adult↗