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Biomedical subjects

A R Collins

Publications and source records attributed to A R Collins.

At least 19 recordsLinked to original sources
PubMed2003

Plasma vitamin C, cholesterol and homocysteine are associated with grey matter volume determined by MRI in non-demented old people.

We studied 82 non-demented old people and, using MRI, derived measures of grey and white matter and intracranial volumes. Controlling for sex and intracranial volume, we related grey and white matter volumes to plasma concentrations of vitamins C, B(12), folate, homocysteine, cholesterol, triglycerides, high density and low density (LDL) lipoproteins, and to red blood cell folate and glycated haemoglobin concentrations (HbA1(c)). We found that lower grey matter volume was associated with lower plasma vitamin C and higher homocysteine, cholesterol and LDL. Lower blood cell folate was also associated with lower grey matter volume but HbA1(c) was not. These data are consistent with the putative benefits of dietary vitamin C and folate intake and the role of cholesterol in age related neurodegeneration.

Aged↗
PubMed2003

Dietary supplement use in old age: associations with childhood IQ, current cognition and health.

AIMS: Dietary supplement (DS) use is actively promoted among old people but there is little evidence in favour of DS use or information about the demographic, health and cognitive characteristics of DS users. METHOD: We examined 176 healthy, old people without dementia all born in 1921 and living independently in the community. IQ scores aged about 11 years were available for all subjects. DS users were more often female, had a lower BMI and were taking fewer prescribed medications than non-users. RESULTS: Usual dietary intake, as measured by food frequency questionnaire, did not differ between DS users and DS non-users. DS users were seen to have higher Vitamin C (p<0.05), alpha-carotene (p<0.05) and lower gamma-tocopherol (p<0.001) and homocysteine (p<0.01). DS users did not differ from DS non-users in years of education, indices of occupational code, current socio-economic category or parameters of cardiovascular or respiratory functions. DS users had higher (p<0.05) childhood IQ scores but did not differ in current Mini-Mental State Examination (MMSE) score or performance on Raven's Progressive Matrices (RPM) either before or after adjustment for childhood IQ. CONCLUSIONS: DS users may enjoy somewhat better general health than non-users but the source of this difference is unknown. Possible health benefits of DS use merit further study.

Aged↗
PubMed2003

Nutritional supplementation with antioxidants decreases chromosomal damage in humans.

In order to investigate the effects of antioxidant supplementation on chromosome damage, a 3 month antioxidant supplementation trial was conducted on groups of 28 myocardial infarction survivors and 57 rural controls, all male. The supplement consisted of vitamin C (100 mg/day), vitamin E (100 mg/day), beta-carotene (6 mg/day) and selenium (50 microg/day). Dietary antioxidants in plasma were measured, as well as the ferric reducing ability of plasma (a measure of total plasma antioxidant status) and the concentration of malondialdehyde as an indicator of oxidative stress. Lymphocytes collected at the beginning and end of the supplementation period were stimulated to proliferate and metaphases accumulated for scoring of chromosome aberrations: per cent aberrant cells and chromatid and chromosome breaks. Supplementation with antioxidants was associated with a decrease in the percentage of cells with chromosome aberrations in the group of rural controls (0.63% before compared with 0.27% after supplementation; P = 0.03). The largest effect of supplementation was seen in smokers in this group (0.12% aberrant cells in supplemented compared with 0.81% in placebo group; P > 0.001). The results support the hypothesis that antioxidants decrease genetic damage.

Adult↗
PubMed2002

Effects of dietary antioxidants on DNA damage in lysed cells using a modified comet assay procedure.

A modified version of the comet assay was employed to investigate the effect in vitro of dietary antioxidants in the subcellular environment. Human lymphocytes were isolated, embedded in agarose gel, lysed in high ionic strength solution with Triton X-100, and then incubated for 30 min with antioxidants at different concentrations. Gels were washed, and the comet assay performed on cells stressed by 5 min incubation with 45 microM hydrogen peroxide and on unstressed cells in parallel. Results showed that alpha-tocopherol was protective against oxidant stress, whereas caffeic acid did not protect, and at high concentration (100 microM) caused increased DNA damage. Results for quercetin suggested a direct damaging effect, but this did not reach statistical significance. However, at low concentration (3.1 microM), quercetin appeared protective. Thus some dietary antioxidants that have been shown previously to have a protective effect in the 'standard', whole-cell, comet assay cause DNA damage in this lysed-cell version. The cell membrane may have an important role in limiting cellular access of these 'double-edged' antioxidants. Furthermore, the absolute concentration and the presence of complementary or synergistic intracellular antioxidants may delineate the type of action of a putative antioxidant. We suggest that, used in conjunction with the standard comet assay, this lysed-cell version is useful for assessing the effect of the cell membrane and intracellular systems on susceptibility of DNA to oxidative damage, and will help determine the mechanism of protection or damage by phytochemicals.

Antioxidants↗
PubMed2002

DNA damage and antioxidants; fluctuations through the year in a central European population group.

Dietary antioxidant levels in the blood depend on intake of fruits and vegetables and therefore might be expected to show seasonal variation. A group of healthy male subjects in Bratislava, Slovakia gave blood samples each month for 1 year. Vitamin C, alpha- and gamma-tocopherol and several carotenoids were measured in plasma, and concentrations of essential metals zinc, copper and selenium in serum. Oxidative DNA damage was assessed in lymphocytes using the comet assay. Seasonal variations in antioxidant levels did not follow a common pattern. beta-Cryptoxanthin was highest in the spring. Lycopene peaked in late summer. Lutein/zeaxanthin was higher in summer than in winter. The concentration of zinc in serum was higher in winter than in summer. DNA damage was lower in summer than in winter. Selenium as well as several antioxidants correlated negatively with indices of DNA damage, while zinc levels showed a positive correlation with DNA damage. These results provide some support for a link between consumption of antioxidants and protection against DNA oxidation.

Antioxidants↗
PubMed2002

Possible genotoxic activity of extracts of Bryonia alba roots on human lymphocytes and transformed cells.

Bryonia alba roots (BAR) are widely used as an adaptogenic and restorative drug with immunomodulatory and stress-protective properties that increase the non-specific resistance of an organism toward harmful stimuli. Potential genotoxic activity of aqueous and methanol extracts of BAR was studied on human normal (lymphocytes) and transformed (HeLa and Caco-2) cells using single cell gel electrophoresis (the comet assay). The results obtained did not show any evidence of genotoxic effects of BAR.

Cell Survival↗
PubMed2001

Anthocyanin-rich extract decreases indices of lipid peroxidation and DNA damage in vitamin E-depleted rats.

Anthocyanins are secondary plant metabolites responsible for the blue, purple, and red color of many plant tissues. The phenolic structure of anthocyanins conveys marked antioxidant activity in model systems via donation of electrons or hydrogen atoms from hydroxyl moieties to free radicals. Dietary intakes of anthocyanins may exceed 200 mg/day, however, little is known about their antioxidant potency in vivo. Consequently, the aim of this study was to establish whether anthocyanins could act as putative antioxidant micronutrients. Rats were maintained on vitamin E-deficient diets for 12 weeks in order to enhance susceptibility to oxidative damage and then repleted with rations containing a highly purified anthocyanin-rich extract at a concentration of 1 g/kg diet. The extract consisted of the 3-glucopyranoside forms of delphinidin, cyanidin, petunidin, peonidin, and malvidin. Consumption of the anthocyanin-repleted diet significantly improved (p <.01) plasma antioxidant capacity and decreased (p <.001) the vitamin E deficiency-enhanced hydroperoxides and 8-Oxo-deoxyguanosine concentrations in liver. These compounds are indices of lipid peroxidation and DNA damage, respectively. Dietary consumption of anthocyanin-rich foods may contribute to overall antioxidant status, particularly in areas of habitually low vitamin E intake.

8-Hydroxy-2'-Deoxyguanosine↗
PubMed2001

DNA-damaging potential and glutathione depletion of 2-cyclohexene-1-one in mammalian cells, compared to food relevant 2-alkenals.

2-Cyclohexene-1-one (CHX) occurs as a natural ingredient in some tropical fruits and has been detected as a contaminant in certain artificially sweetened soft drinks. To elucidate its cytotoxic/genotoxic effectiveness, CHX was tested in mammalian cell lines (V79 and Caco-2) and in primary human colon cells in comparison to structurally related 2-alkenals. Inhibition of cell growth (IC(50)) and cytotoxicity (LC(50)) were determined by protein staining with sulforhodamin B (SRB) and by trypan blue exclusion, respectively. DNA damage--both strand breaks and oxidised purines--was quantified by comet assay. Depletion of glutathione was measured in a kinetic assay, based on 5-thio-2-nitrobenzoate (TNB) formation. For CHX, a moderate cytotoxicity was observed after 1h incubation in V79 cells (LC(50): 4.75mM). The 2-alkenals ((E)-2-octenal (OCTE), (2E,4Z)-2,4-hexadienal (HEXDI), (E)-2-nonenal (NONE), (2E,6Z)-2,6-nonadienal (NONDI)) exhibited a distinctly higher cytotoxicity, except for (E)-2-hexenal (HEX) (LC(50): 3.67mM) and cinnamaldehyde (CA) (LC(50): 4.45mM). If the incubation time was prolonged to 24h, an IC(50) of 15microM was obtained for CHX which is well within the range obtained for the 2-alkenals (4 and 17microM). Concentration-dependent DNA damage was observed after 1h incubation with CHX. The respective DC(50) values (concentration inducing DNA damage in 50% of cells) were 272microM (V79) and 455microM (Caco-2). All 2-alkenals were more active under these conditions, except for CA. In primary human colon cells, CHX (800microM, 30min) exhibited a weak, but still significant DNA-damaging potential. Glutathione levels in V79 cells were effectively depleted (down to approximately 20%) by CHX concentrations not yet inducing DNA damage (c < or = 50microM). Incubation with CHX or 2-alkenals (50 and 100microM, 1h), followed by H2O2 treatment (5min, 25microM) resulted in increased levels of oxidised purines in the modified comet assay. CHX and HEX, additionally tested in primary human colon cells, depleted glutathione and increased the sensitivity towards oxidative stress.

Aldehydes↗
PubMed2001

Glutathione S-transferase polymorphisms influence the level of oxidative DNA damage and antioxidant protection in humans.

Glutathione S-transferase genotypes GSTT1, GSTM1, GSTP1 were characterised in 155 middle-aged men and compared with parameters of oxidative stress at the level of DNA and lipids, with antioxidant enzymes, and with plasma antioxidants in smokers and non-smokers. Smokers had on average significantly lower levels of Vitamin C, beta-carotene and beta-cryptoxanthin and higher amounts of oxidised purines and pyrimidines in lymphocyte DNA. The GSTM1 null genotype was associated with elevated glutathione as well as with higher Vitamin C concentration in plasma. Vitamin C was higher in GSTT1+ compared with GSTT1 null--as was glucose-6-phosphate dehydrogenase activity. The homozygous GSTP1 a/a genotype was associated with significantly higher levels of GST activity measured in lymphocytes, in comparison with the b/b genotype. Using multifactorial statistical analysis we found significant associations between smoking, GSTP1 genotype, plasma Vitamin C, and purine base damage in lymphocyte DNA. The difference in Vitamin C plasma levels between smokers and non-smokers was seen only with the GSTP1 b/b genotype. This group accounted also for most of the increase in purine oxidation in smokers. In contrast, the link between smoking and oxidised pyrimidines in DNA was seen only in the GSTT1 null group. It seems that polymorphisms in the phase II metabolising enzyme glutathione S-transferase may be important determinants of commonly measured biomarkers.

Analysis of Variance↗
PubMed2001

Troglitazone inhibits growth of MCF-7 breast carcinoma cells by targeting G1 cell cycle regulators.

Peroxisome proliferator activated receptor gamma (PPARgamma) is a member of the nuclear receptor superfamily. Ligand activation of PPARgamma has been shown to cause growth arrest in several human tumor cell types, but the underlying molecular mechanism has not been elucidated. We report here that the PPARgamma ligand troglitazone (TRO) inhibited MCF-7 cell proliferation by blocking events critical for G1 --> S progression. Flow cytometry demonstrated that TRO at 20 microM increased the percentage of cells in G1 from 51 to 69% after 24 h. Accumulation of cells in G1 was accompanied by an attenuation of Rb protein phosphorylation associated with decreased CDK4 and CDK2 activities. Inhibition of CDK activity by TRO correlates with decreased protein levels for several G1 regulators of Rb phosphorylation (cyclin D1, and CDKs 2, 4, and 6). Overexpression of cyclin D1 partially rescued MCF-7 cells from TRO-mediated G1 arrest. Targeting of G1 regulatory proteins, particularly cyclin D1, and the resulting induction of G1 arrest by TRO may provide a novel antiproliferative therapy for human breast cancer.

Annexin A5↗
PubMed2001

An efficient procedure for genotyping single nucleotide polymorphisms.

Analysis of single nucleotide polymorphisms (SNPs) has been and will be increasingly utilized in various genetic disciplines, particularly in studying genetic determinants of complex diseases. Such studies will be facilitated by rapid, simple, low cost and high throughput methodologies for SNP genotyping. One such method is reported here, named tetra-primer ARMS-PCR, which employs two primer pairs to amplify, respectively, the two different alleles of a SNP in a single PCR reaction. A computer program for designing primers was developed. Tetra-primer ARMS-PCR was combined with microplate array diagonal gel electrophoresis, gaining the advantage of high throughput for gel-based resolution of tetra-primer ARMS-PCR products. The technique was applied to analyse a number of SNPs and the results were completely consistent with those from an independent method, restriction fragment length polymorphism analysis.

DNA↗
PubMed2001

Carotenoids and genomic stability.

Epidemiological evidence abounds for a link between intake of carotenoids from fruit and vegetable foods and relatively low incidence of various cancers. However, intervention trials have shown, in some cases, a significant increase in occurrence of lung cancer in those volunteers taking supplements of beta-carotene. More information is clearly needed about the mechanism of action of carotenoids. Effects of carotenoids on cells in culture include inhibition of DNA synthesis and proliferation, changes in gene expression, decreased micronucleus frequency, and inhibition of transformation via synthesis of gap-junction proteins. Experiments with animal models are unsatisfactory because of the very poor uptake of carotenoids in rodents compared with man. In humans, oxidative damage to lymphocytes correlates negatively with plasma carotenoid concentrations, and the level of DNA damage is susceptible to reduction by carotenoid-rich foods. It seems clear that the carotenoids act as antioxidants in vivo, and yet this activity may not result in cancer prevention.

Antioxidants↗
PubMed2001

Maternal sex chromosome non-disjunction: evidence for X chromosome-specific risk factors.

Human trisomy is attributable to many different mechanisms and the relative importance of each mechanism is highly chromosome specific. The association between altered recombination and maternal non-disjunction is well documented: reductions in recombination have been reported for maternal meiosis I (MI) errors involving chromosomes 15, 16, 18 and 21 and increased recombination has been reported for meiosis II (MII) errors involving chromosome 21. We therefore investigated maternal X chromosome non-disjunction, to determine whether the effects of recombination are unique to the X chromosome or similar to any of the autosomes thus far studied. We genotyped 45 47,XXX females and 95 47,XXY males of maternal origin. Our results demonstrate that 49% arose during MI, 29% during MII and 16% were postzygotic events; a further 7% were meiotic but could not be assigned as either MI or MII because of recombination at the centromere. Among the MI cases, a majority (56%) had no detectable transitions and so absent recombination is an important factor for X chromosome non-disjunction. However, similar to trisomy 15 and unlike trisomy 21, we observed a significant increase in the mean maternal age of transitional MI errors compared with nullitransitional cases. In our studies of MII errors, recombination appeared normal and there was no obvious effect of maternal age, distinguishing our results from MII non-disjunction of chromosomes 18 or 21. Thus, surprisingly, the risk factors associated with both MI and MII non-disjunction appear to be different for virtually every chromosome that has been adequately studied.

Adult↗
PubMed2001

Oxidative DNA damage, antioxidants and DNA repair: applications of the comet assay.

Estimates of background levels of oxidative base damage in human white blood cells vary enormously, from 300 down to 0.4 molecules of 8-oxoguanine per 10(6) guanines. An EC-funded Concerted Action, the European Standards Committee on Oxidative DNA Damage, is currently attempting to resolve the discrepancy and to agree a realistic estimate of basal endogenous oxidation. Oxidation of lymphocyte DNA is a useful marker of oxidative stress, and this can be decreased by supplementation with pure antioxidants or with foods rich in antioxidants. The steady-state level of DNA oxidation is ultimately controlled by the process of DNA repair; the extent to which this varies between individuals has yet to be established.

Animals↗
PubMed2001

Inter-individual differences in repair of DNA base oxidation, measured in vitro with the comet assay.

There is a need for a reliable, robust and sensitive assay for DNA repair, suitable for use with human lymphocyte samples in molecular epidemiological investigations. The comet assay (single cell alkaline gel electrophoresis) has been modified to measure the ability of a simple subcellular extract of lymphocytes to carry out the initial step of repair, i.e. incision, on a DNA substrate carrying specific lesions--namely, oxidized bases introduced by visible light in the presence of photosensitizer. The cell extract is free of non-specific nuclease activity, incising DNA only if the DNA has been treated with photosensitizer and light. The activity varies between individuals, but consistency is seen between samples from each individual taken on occasions several months apart. The lack of activity of extract from Ogg1(-) mouse cells (deficient in the glycosylase that excises 8-oxoguanine) in this assay confirms that the activity measured is predominantly excision repair of oxidized bases. This new DNA repair assay is simple, rapid and requires only small quantities of lymphocyte extract (obtainable from 10 ml blood).

Animals↗
PubMed2001

Peroxisome proliferator-activated receptor-gamma ligands inhibit nuclear but not cytosolic extracellular signal-regulated kinase/mitogen-activated protein kinase-regulated steps in vascular smooth muscle cell migration.

Vascular smooth muscle cell (VSMC) migration involves adhesion, locomotion, and invasion regulated by various signaling molecules, among which the extracellular signal-regulated kinase (ERK)/mitogen-activated protein kinases (MAPK) play a critical role. We have shown that the peroxisome proliferator-activated receptor-gamma (PPAR-gamma) ligands troglitazone and rosiglitazone inhibit VSMC migration downstream of ERK MAPK. The purpose of the current study was to more specifically determine which step(s) in VSMC migration are targeted by inhibition of the ERK MAPK pathway or activation of PPAR-gamma. VSMC adhesion was not affected by the ERK MAPK pathway inhibitor PD98059 or PPAR-gamma ligands. Phosphorylation and activation of myosin light chain kinase (MLCK) play important roles in cell locomotion. Platelet-derived growth factor (PDGF)-induced MLCK phosphorylation (1.7-fold) was completely blocked by PD98059 at 30 microM (p < 0.05), but not by troglitazone or rosiglitazone. PDGF-directed migration (5.8-fold) was inhibited by PD98059 (-88% at 30 microM) and the MLCK inhibitor ML9 (0.1-1 microM, -84% at 1 microM) (all p < 0.05). The transcription factor Ets-1 mediates matrix metalloproteinase induction required for tissue invasion by VSMC. PDGF (20 ng/ml) stimulated an Ets-1 protein expression (14-fold at 60 min) in VSMC, which was inhibited by PD98059 (-72% at 30 microM), troglitazone (-69% at 20 microM), and rosiglitazone (-54% at 10 microM) (all p < 0.05). Immunohistochemistry of rat aortae 2 h after balloon injury showed a dramatic upregulation of Ets-1, which was markedly inhibited in animals that had received troglitazone treatment. In contrast, phosphorylated ERK MAPK was not affected by troglitazone. These data are consistent with PPAR-gamma ligands exerting their anti-migratory effects downstream of ERK MAPK activation by blocking nuclear events, such as Ets-1 expression, required for cell invasion in response to arterial injury.

Animals↗