OXYGEN FREE RADICAL IN HUMAN OSTEOARTHRITIS

The xanthine oxidase catalysed release of superoxide free radicals (O2-) from endogenous hypoxanthine was determined in homogenates of synovium obtained from three groups of patients, those undergoing primary or revision total hip replacement (THR) for osteoarthritis and those undergoing arthroscopy of the knee for semilunar disc injuries. The concentrations of hypoxanthine in homogenates obtained during THR were found to be significantly higher than those in the group with semilunar disc injuries. The results suggest that there is a greater predisposition to free radical release and tissue damage in osteoarthritis.     

Comparative mapping of X chromosomes in vole species of the genus Microtus

Comparative mapping of X-linked genes has progressed rapidly since Ohno's prediction that genes on the X chromosome should be conserved as a syntenic group in all mammals. Although several conserved blocks of homology between human and mouse have been discovered, rearrangements within the X chromosome have also been characterized. More recently, some exceptions to Ohno's law have been reported. We have used fluorescence in situ hybridization (FISH) to map five genes, Gla, G6pd, Hprt, Pgk1 and Xist, to two of the largest conserved segments of X material in five members of the genus Microtus (grey vole) and show that vole X chromosomes demonstrate greater homology to human than to mouse. Cytogenetic analysis indicates a relatively high frequency of rearrangement during vole evolution, although certain blocks of homology appear to be highly conserved in all species studied to date. On this basis we were able to predict the probable location of the rat X inactivation centre (Xic) based solely on high-resolution G-banding. Our prediction was then confirmed by mapping the rat Xist gene by FISH. The possible significance of conserving long-range chromosome structure in the vicinity of the Xic is discussed with respect to the mechanism of X inactivation.     

Dietary flavonoids protect human colonocyte DNA from oxidative attack in vitro

Summary Background & Aims: Epidemiological studies suggest that antioxidant polyphenols in the human diet may protect against diseases such as cancer. In this study we investigated the cytoprotective potential of the flavonoids, quercetin, myricetin, kaempferol and rutin against oxidative DNA damage in human colonocytes in vitro. Methods: Caco-2 cells, which display specialised enterocyte/colonocyte cell functions, were used as an in vitro model for human colonocytes. Hydrogen peroxide was employed as the oxidant. DNA damage (strand breakage, oxidised purines and oxidised pyrimidines) was determined using the alkaline single cell gel electrophoresis or comet assay. Cell growth and viability were measured. Results: Hydrogen peroxide caused a dose-dependent increase in DNA strand breakage in human colonocytes, presumably via oxygen free radical generation. Quercetin and myricetin protected Caco-2 cells against oxidative attack. In addition, quercetin decreased hydrogen peroxide-mediated inhibition of growth. Neither rutin nor kaempferol was effective. However, quercetin, while inhibiting DNA strand breakage, did not alter the levels of oxidised bases following peroxide treatment. The antifungal agent ketoconazole, prevented quercetin cytoprotection in Caco-2 cells, indicating that P450-mediated metabolism may alter the efficacy of the flavonoids against oxidative DNA damage. Conclusion: Flavonoids, particularly quercetin, the most abundant flavonoid in the human diet, are likely to be important in defending human colonocytes from oxidative attack. Received: 7 October 1998, Accepted: 5 November 1998     

Optimal education techniques for basic surgical trainees: lessons from education theory

"Calmanisation" of surgical training and the introduction of the "New Deal" on doctor's hours has led to a reduction in "in service" training and a proliferation of training courses. Little research has been done into the optimum design of these courses. Education theory has shown that individuals have optimal learning styles and that these styles tend to be generalised across professional groups. It was decided, therefore, to investigate the optimal learning styles of basic surgical trainees. A learning style inventory was used to assess the preferred learning style of 52 basic surgical trainees. The predominant learning styles (86.5%) were convergent (n = 31) or accommodative (n = 14) whilst only 5 (9.6%) assimilative and 2 (3.9%) divergent styles were detected. Convergent and accommodative learners rely principally on hands on experience and problem solving as their optimal learning technique. Given the shorter hours and duration of Basic Surgical Training, in service practical training and surgical courses should be structured accordingly.     

Dietary intakes of polyunsaturated fatty acids and indices of oxidative stress in human volunteers.

OBJECTIVE: To assess whether nutritionally-relevant changes in polyunsaturated fatty acid (PUFA) intake alter indices of oxidative stress in human volunteers DESIGN: A split plot/change over dietary study where half the volunteers consumed a diet containing 5% PUFA (low PUFA) as food energy for 4 weeks and after a 6 week washout period consumed a 15% PUFA (high PUFA) diet for another 4 weeks. The second group of volunteers completed this protocol in reverse. Total fat, carbohydrate, protein and vitamin E contents of the diets were constant. SUBJECTS: 10 healthy, non-smoking, male volunteers aged 32.6 +/- 1.7 y RESULTS: There was a significant increase in whole blood oxidised glutathione (P < 0.05), an index of oxidative stress, after consumption of the high PUFA diet. Moreover, urinary thiobarbituric acid reactive substances (TBARS), an index of lipid peroxidation, significantly increased (P = 0.038) following consumption of the high PUFA diet and decreased (P = 0.031) after consuming the low PUFA diet. However, there was no change in non specific plasma indices of lipid peroxidation, conjugated dienes and TBARS, nor in red cell antioxidant enzymes glutathione peroxidase, glutathione reductase, and catalase. However, superoxide dismutase significantly decreased (13%, P=0.018) after consumption of the low PUFA diet. Total cholesterol increased by 13% (P=0.014) after consumption of the low PUFA diet. CONCLUSIONS: This study indicates that although increasing dietary levels of PUFA may favourably alter cholesterol profiles, the same dietary changes may adversely affect some indices of lipid peroxidation. Care should be taken when providing dietary advice on PUFA intake and an adequate intake of antioxidants to match any increased PUFA may be important for preventing oxidative stress.     

Effect of folic Acid supplementation on the folate status of buccal mucosa and lymphocytes.

Folate deficiency may be associated with an increased risk of cancer at certain sites. There is a need to measure folate status and putative biomarkers of cancer risk in the same target tissue, or in surrogate tissues. A study was carried out to develop a method for the rapid measurement of folate in human buccal mucosa and lymphocytes and to evaluate the responsiveness of this measurement in both tissues to folic acid supplementation in healthy subjects, relative to conventional markers of folate status. Three hundred and twenty-three adults, ages between 20 and 60 years, were screened for RBC folate concentrations. Sixty-five subjects with red cell folate between 200 and 650 nmol/L participated in a randomized, double blind, placebo-controlled, folic acid (1.2 mg) intervention trial, lasting 12 weeks. As anticipated, a significant baseline correlation (r = 0.36, P < 0.01) was observed between red cell folate and plasma 5-methyltetrahydrofolate (5-MeTHF). Lymphocyte total folate was significantly associated with plasma 5-MeTHF (r = 0.28, P < 0.05) and plasma total homocysteine concentration (r = -0.34, P < 0.05). Buccal mucosa total folate showed no correlation with either red cell folate or 5-MeTHF, but was significantly associated with lymphocyte total folate (r = 0.35, P < 0.01). Supplementation elicited a significant increase in lymphocyte total folate (P < 0.01), and this was strongly associated with the increase in RBC total folate (P < 0.01) and plasma 5-MeTHF (P < 0.01). Buccal mucosa total folate was not influenced by folate supplementation. Methods have been developed for the rapid measurement of lymphocyte and buccal mucosal total folate. Lymphocyte folate is sensitive to folate intake and is reflected by plasma 5-MeTHF.     

Associations between two common variants C677T and A1298C in the methylenetetrahydrofolate reductase gene and measures of folate metabolism and DNA stability (strand breaks, misincorporated uracil, and DNA methylation status) in human lymphocytes in vivo.

OBJECTIVE: Homozygosity for variants of the methylenetetrahydrofolate reductase (MTHFR) gene is associated with decreased risk for colorectal cancer. We have investigated the relationships between two variants of the MTHFR gene (C677T and A1298C) and blood folate, homocysteine, and genomic stability (strand breakage, misincorporated uracil, and global cytosine methylation in lymphocytes) in a study of 199 subjects. RESULTS: The frequencies of homozygosity for the C677T and A1298C variants of the MTHFR gene were 12.6% and 14.6%, respectively. Plasma homocysteine, folate, vitamin B12, 5-methyltetrahydrofolate, and RBC folate were determined in the C677T genotypes. Plasma folate was significantly lower (P < 0.001) in the homozygous variants (6.7 +/- 0.6 ng/mL) compared with wild-types (8.8 +/- 0.4 ng/mL) and heterozygotes (9.1 +/- 0.5 ng/mL). Homocysteine was significantly higher (P < 0.05) in homozygous variants (13.2 +/- 1.1 micromol/L) compared with homozygous subjects (10.9 +/- 0.4 micromol/L). Homozygous variants had significantly lower (P < 0.05) RBC folate (84.7 +/- 6.3 ng/mL) compared with wild-types (112.2 +/- 5.2 ng/mL) and heterozygous individuals (125.1 +/- 6.6 ng/mL). No significant difference in RBC folate was observed between wild-types and heterozygotes. The A1298C variant did not influence plasma homocysteine, folate, 5-methyltetrahydrofolate, vitamin B12, or RBC folate. Lymphocyte DNA stability biomarkers (strand breaks, misincorporated uracil, and global DNA methylation) were similar for all MTHFR C677T or A1298C variants. CONCLUSION: Data from this study do not support the hypothesis that polymorphisms in the MTHFR gene increase DNA stability by sequestering 5,10-methylenetetrahydrofolate for thymidine synthesis and reducing uracil misincorporation into DNA.