Prioritising control measures for occupationally related cancers should be evidence based. We est... more Prioritising control measures for occupationally related cancers should be evidence based. We estimated the current burden of cancer in Britain attributable to past occupational exposures for International Agency for Research on Cancer (IARC) group 1 (established) and 2A (probable) carcinogens. We calculated attributable fractions and numbers for cancer mortality and incidence using risk estimates from the literature and national data sources to estimate proportions exposed. 5.3% (8019) cancer deaths were attributable to occupation in 2005 (men, 8.2% (6362); women, 2.3% (1657)). Attributable incidence estimates are 13 679 (4.0%) cancer registrations (men, 10 063 (5.7%); women, 3616 (2.2%)). Occupational attributable fractions are over 2% for mesothelioma, sinonasal, lung, nasopharynx, breast, non-melanoma skin cancer, bladder, oesophagus, soft tissue sarcoma, larynx and stomach cancers. Asbestos, shift work, mineral oils, solar radiation, silica, diesel engine exhaust, coal tars and...
Advances in Mental Health and Intellectual Disabilities, 2011
... Rett Rubinstein-Taybi Smith Lemli-Opitz ... However, individuals with Downs... more ... Rett Rubinstein-Taybi Smith Lemli-Opitz ... However, individuals with Downsyndrome are more ''socially competent'' that individuals with other causes for their developmental disorders, and social skills improve with age (Patti and Tsiouris, 2006). ...
The aim of the current HBM-study is to further the understanding of the impact of inter- and intr... more The aim of the current HBM-study is to further the understanding of the impact of inter- and intra-individual variability in HBM surveys as it may have implications for the design and interpretation of the study outcomes. As spot samples only provide a snapshot in time of the concentrations of chemicals in an individual, it remains unclear to what extent intra-individual variability plays a role in the overall variability of population-wide HBM surveys. The current paper describes the results of an intensive biomonitoring study, in which all individual urine samples of 8 individuals were collected over a 6-day sampling period (a total of 352 unique samples). By analyzing different metals (As, Cd, Mn, Ni) in each individual sample, inter- and intra-individual variability for these four metals could be determined, and the relationships between exposure, internal dose, and sampling protocol assessed. Although the range of biomarker values for different metals was well within the normal range reported in large-scale population surveys, large intra-individual differences over a 6-day period could also be observed. Typically, measured biomarker values span at least an order of magnitude within an individual, and more if specific exposure episodes could be identified. Fish consumption for example caused a twenty- to thirty-fold increase in urinary As-levels over a period of 2-6h. Intra-class correlation coefficients (ICC) were typically low for uncorrected biomarker values (between 0.104 and 0.460 for the 4 metals), but improved when corrected for creatinine or specific gravity (SG). The results show that even though urine is a preferred matrix for HBM studies, there are certain methodological issues that need to be taken into account in the interpretation of urinary biomarker data, related to the intrinsic variability of the urination process itself, the relationship between exposure events and biomarker quantification, and the timing of sampling. When setting up HBM-projects, this expected relationship between individual exposure episode and urinary biomarker concentration needs to be taken into account.
In response to a Hazard Notice by the Medical Devices Agency of the UK in 2000 regarding the Tril... more In response to a Hazard Notice by the Medical Devices Agency of the UK in 2000 regarding the Trilucent breast implant (TBI), an expert panel was convened to implement a research program to determine whether genotoxic compounds were formed in the soybean oil filler (SOF) of TBIs and whether these could be released to produce local or systemic genotoxicity. The panel established a research program involving six laboratories. The program recruited 47 patients who had received TBIs (9 patients had received silicone implants previously). A reference group (REBI) of 34 patients who had exchanged either silicone (17 patients) implants (REBI-E) or patients (17) who were to receive primary implantation augmentation with silicone (REBI-PIA), and who were included as needed to increase either the pre- or post-explantation sample number. Of the 17 REBI-E patients, 5 had silicone implants and 12 had saline implants previously (prior to the last exchange). Investigation was undertaken before and after replacement surgery in the TBI patients and before and after replacement or augmentation surgery in the REBI patients. The pre- to post-operative sample interval was 8-12 weeks. Pre-operative samples were collected within 7 days prior to the operation. Information on a variety of demographic and behavioral features was collected. Biochemical and biological endpoints relating to genotoxic lipid peroxidation (LPO) products potentially formed in the SOF, and released locally or distributed systemically, were measured. The SOF of explanted TBIs was found to have substantial levels of LPO products, particularly malondialdehyde (MDA), and low levels of trans-4-hydroxy-2-nonenal (HNE) not found in unused implants. Mutagenicity of the SOF was related to the levels of MDA. Capsules that formed around TBIs were microscopically similar to those of reference implants, but MDA-DNA adducts were observed in capsular macrophages and fibroblasts of only TBI capsules. These cell types are not progenitors of breast carcinoma (BCa) and the location of the implants precludes LPO products reaching the mammary epithelial cells which are progenitors of BCa. Blood levels of LPO products were not increased in TBI patients compared to REBI patients and did not change with explantation. In TBI patients, white blood cells did not show evidence of increased levels of LPO-related aldehyde DNA adducts. In conclusion, based on a number of measured parameters, there was no evident effect that would contribute to breast or systemic cancer risk in the TBI patients, and the recommended treatment of TBI patients involving explantation was judged appropriate.
Page 1. INTRODUCTION During inflammation, many cell types release reactive oxygen species (ROS) v... more Page 1. INTRODUCTION During inflammation, many cell types release reactive oxygen species (ROS) via the respiratory burst.1 These ROS are potent oxidants of LDL and its major protein, apolipoprotein B. Whilst native LDL ...
Vascular monocyte retention in the subintima is pivotal to the development of cardiovascular dise... more Vascular monocyte retention in the subintima is pivotal to the development of cardiovascular disease and is facilitated by up-regulation of adhesion molecules on monocytes/endothelial cells during oxidative stress. Epidemiological studies have shown that cardiovascular disease risk is inversely proportional to plasma levels of the dietary micronutrients, vitamin C and vitamin E (alpha-tocopherol). We have tested the hypothesis that alpha-tocopherol supplementation may alter endothelial/monocyte function and interaction in subjects with normal ascorbate levels (> 50 microM), as ascorbate has been shown to regenerate tocopherol from its oxidised tocopheroxyl radical form in vitro. Healthy male subjects received alpha-tocopherol supplements (400 IU RRR-alpha-tocopherol/day for 6 weeks) in a placebo-controlled, double-blind intervention study. There were no significant differences in monocyte CD11b expression, monocyte adhesion to endothelial cells, plasma C-reactive protein or sICAM-1 concentrations post-supplementation. There was no evidence for nuclear translocation of NF-kappaB in isolated resting monocytes, nor any effect of alpha-tocopherol supplementation. However, post-supplementation, sVCAM-1 levels were decreased in all subjects and sE-selectin levels were increased in the vitamin C-replete group only; a weak positive correlation was observed between sE-selectin and alpha-tocopherol concentration. In conclusion, alpha-tocopherol supplementation had little effect on cardiovascular disease risk factors in healthy subjects and the effects of tocopherol were not consistently affected by plasma vitamin C concentration.
Ethylene thiourea (ETU) is a metabolite of ethylenebisdithiocarbamates (EBDCs); it is the best in... more Ethylene thiourea (ETU) is a metabolite of ethylenebisdithiocarbamates (EBDCs); it is the best indicator of exposure to these fungicides. Therefore, high-performance liquid chromatography with photodiode-array detection (HPLC-DAD) was optimized and validated for the determination of ETU in human urines. Urine samples were extracted by solid-phase extraction using Extrelut and analyzed using HPLC-DAD set at 231 nm. The analyses were carried out using a mobile phase of 0.01 M phosphate buffer (pH 4.5) on a C18 Uptisphere NEC-5-20, 250- x 4.6-mm x 5-microm column. The internal standard used was 4-pyridinecarboxylic acid hydrazide. The method was successfully validated in compliance with requirements set by the International Committee on Harmonization 1996. The lower limit of quantitation was at 1 microg/L, and the linearity was studied from 1 to 100 microg/L. There were 272 urine samples collected from farmers exposed to EBDCs in different regions in France analyzed in this study.
International Journal of Hygiene and Environmental Health, 2013
Human biomonitoring (HBM) is a widely accepted tool to aid assessment of chemical uptake in risk ... more Human biomonitoring (HBM) is a widely accepted tool to aid assessment of chemical uptake in risk assessment. However, our understanding of the biological relevance of the results of HBM can be restricted, due in some part to the limited information on background environmental exposures and biomarker concentrations in the general population. The study described here specifically addresses the question of what constitutes normal background levels in the UK population of a number of biomarkers (the chemical itself or one of its stable metabolites) for a variety of environmental chemicals that are frequently encountered because of their widespread use. The environmental chemicals selected for this study were benzene, chlorinated hydrocarbons, dithiocarbamates, cadmium, mercury, naphthalene, diethylhexyl phthalate, synthetic pyrethroids and xylene. Volunteers (n=436) were randomly sought by a postal survey based on the UK Electoral Register. Participants were asked to complete a questionnaire and provide a urine sample. The overall response rate was 7.5%, with volunteers being recruited from all areas of the UK including, England, Scotland, Wales and Northern Ireland. Study participants were adults and comprised 45% male and 55% females. We have conducted a simple, postal-based, cost-effective study and generated similar reference values to very large surveys such as NHANES. This demonstrates that large investigations may not be necessary to get a reasonable idea of environmental exposures, especially in initial 'screening-type' investigations to identify particular exposures of concern or to demonstrate that exposures are reassuring low and that no further survey data needs to be gathered.
Polyunsaturated fats have been linked to occurrences of sporadic colon cancer. One possible cause... more Polyunsaturated fats have been linked to occurrences of sporadic colon cancer. One possible cause may be degradation of polyunsaturated fats during cooking, resulting in multiple reactive carbonyl species (RCS) that can damage nuclear DNA and proteins, particularly in rapidly dividing colon crypt cells. This study describes a novel antiserum against RCS-modified DNA, with apparent order of reactivity to DNA modified with 4-hydroxy-trans-2-nonenal > glyoxal > acrolein > crotonaldehyde > malondialdehyde; some reactivity was also observed against conjugated Schiff base-type structures. Anti-(RCS-DNA) antiserum was successfully utilised to demonstrate formation of RCS-DNA in a human colon cell model, exposed to RCS insult derived from endogenous and exogenous lipid peroxidation sources. Further utilisation of the antiserum for immunohistochemical analysis confirmed RCS-modified DNA in crypt areas of 'normal' colon tissue. These results fully support a potential role for dietary lipid peroxidation products in the development of sporadic colon cancer.
The product of oxidative damage to DNA, 8-hydroxy-2'-deox... more The product of oxidative damage to DNA, 8-hydroxy-2'-deoxyguanosine (8-OHdG), when detected in urine, is considered to be a global, noninvasive biomarker of in vivo oxidative DNA damage. In this paper we describe a novel approach to confirm the presence of oligonucleotides containing 8-OHdG in human urine. Fractions of urine were prepared by gel-filtration chromatography, and the presence of oligonucleotides was confirmed by ELISA using a monoclonal anti-(single-stranded DNA) antibody. Pools of urine fractions were subsequently prepared according to ELISA reactivity, each containing oligonucleotides with a known range of base numbers. The level of 8-OHdG in each pool was subsequently determined using a commercial ELISA kit. Results confirmed that oligonucleotides containing 8-OHdG are present in urine and, most significantly, oligomers of <30-55 bases were found to be associated with 8-OHdG. This finding strongly supports the involvement of nucleotide excision repair (NER) in the removal of 8-OHdG from the cell. The novel approach adopted in this study was validated using cell culture supernatant obtained from an in vitro model comprising CCRF cells exposed to vitamin C; this model has previously been shown to stimulate removal of 8-OHdG from the cell by an NER-dependent process.
Biochemical and Biophysical Research Communications, 2000
We have investigated vitamin C supplementation effects on immunoglobulin oxidation (carbonyls) an... more We have investigated vitamin C supplementation effects on immunoglobulin oxidation (carbonyls) and total plasma protein sulfhydryls in healthy human volunteers. After receiving placebo, plasma ascorbate and oxidation markers were unchanged. Following 5 weeks supplementation with vitamin C (400 mg/day), plasma ascorbate increased but no significant effect on protein oxidation was observed. At 10 and 15 weeks supplementation, carbonyl levels were significantly reduced (P < 0.01) in subjects with low baseline ascorbate (29.51 +/- 5.3 microM) but not in those with normal baseline ascorbate (51.81 +/- 2.3 microM). To eliminate any effect from seasonal variation in dietary antioxidant intake, a second phase was undertaken. Subjects on vitamin C for 15 weeks were randomly assigned to receive either placebo or vitamin C. No difference in plasma sulfhydryl content was observed. Subjects withdrawn from supplementation showed an increase in immunoglobulin carbonyl content (P < 0.01). This demonstrates that dietary vitamin C supplementation can reduce certain types of oxidative protein damage in subjects with low basal antioxidant.
Prioritising control measures for occupationally related cancers should be evidence based. We est... more Prioritising control measures for occupationally related cancers should be evidence based. We estimated the current burden of cancer in Britain attributable to past occupational exposures for International Agency for Research on Cancer (IARC) group 1 (established) and 2A (probable) carcinogens. We calculated attributable fractions and numbers for cancer mortality and incidence using risk estimates from the literature and national data sources to estimate proportions exposed. 5.3% (8019) cancer deaths were attributable to occupation in 2005 (men, 8.2% (6362); women, 2.3% (1657)). Attributable incidence estimates are 13 679 (4.0%) cancer registrations (men, 10 063 (5.7%); women, 3616 (2.2%)). Occupational attributable fractions are over 2% for mesothelioma, sinonasal, lung, nasopharynx, breast, non-melanoma skin cancer, bladder, oesophagus, soft tissue sarcoma, larynx and stomach cancers. Asbestos, shift work, mineral oils, solar radiation, silica, diesel engine exhaust, coal tars and...
Advances in Mental Health and Intellectual Disabilities, 2011
... Rett Rubinstein-Taybi Smith Lemli-Opitz ... However, individuals with Downs... more ... Rett Rubinstein-Taybi Smith Lemli-Opitz ... However, individuals with Downsyndrome are more ''socially competent'' that individuals with other causes for their developmental disorders, and social skills improve with age (Patti and Tsiouris, 2006). ...
The aim of the current HBM-study is to further the understanding of the impact of inter- and intr... more The aim of the current HBM-study is to further the understanding of the impact of inter- and intra-individual variability in HBM surveys as it may have implications for the design and interpretation of the study outcomes. As spot samples only provide a snapshot in time of the concentrations of chemicals in an individual, it remains unclear to what extent intra-individual variability plays a role in the overall variability of population-wide HBM surveys. The current paper describes the results of an intensive biomonitoring study, in which all individual urine samples of 8 individuals were collected over a 6-day sampling period (a total of 352 unique samples). By analyzing different metals (As, Cd, Mn, Ni) in each individual sample, inter- and intra-individual variability for these four metals could be determined, and the relationships between exposure, internal dose, and sampling protocol assessed. Although the range of biomarker values for different metals was well within the normal range reported in large-scale population surveys, large intra-individual differences over a 6-day period could also be observed. Typically, measured biomarker values span at least an order of magnitude within an individual, and more if specific exposure episodes could be identified. Fish consumption for example caused a twenty- to thirty-fold increase in urinary As-levels over a period of 2-6h. Intra-class correlation coefficients (ICC) were typically low for uncorrected biomarker values (between 0.104 and 0.460 for the 4 metals), but improved when corrected for creatinine or specific gravity (SG). The results show that even though urine is a preferred matrix for HBM studies, there are certain methodological issues that need to be taken into account in the interpretation of urinary biomarker data, related to the intrinsic variability of the urination process itself, the relationship between exposure events and biomarker quantification, and the timing of sampling. When setting up HBM-projects, this expected relationship between individual exposure episode and urinary biomarker concentration needs to be taken into account.
In response to a Hazard Notice by the Medical Devices Agency of the UK in 2000 regarding the Tril... more In response to a Hazard Notice by the Medical Devices Agency of the UK in 2000 regarding the Trilucent breast implant (TBI), an expert panel was convened to implement a research program to determine whether genotoxic compounds were formed in the soybean oil filler (SOF) of TBIs and whether these could be released to produce local or systemic genotoxicity. The panel established a research program involving six laboratories. The program recruited 47 patients who had received TBIs (9 patients had received silicone implants previously). A reference group (REBI) of 34 patients who had exchanged either silicone (17 patients) implants (REBI-E) or patients (17) who were to receive primary implantation augmentation with silicone (REBI-PIA), and who were included as needed to increase either the pre- or post-explantation sample number. Of the 17 REBI-E patients, 5 had silicone implants and 12 had saline implants previously (prior to the last exchange). Investigation was undertaken before and after replacement surgery in the TBI patients and before and after replacement or augmentation surgery in the REBI patients. The pre- to post-operative sample interval was 8-12 weeks. Pre-operative samples were collected within 7 days prior to the operation. Information on a variety of demographic and behavioral features was collected. Biochemical and biological endpoints relating to genotoxic lipid peroxidation (LPO) products potentially formed in the SOF, and released locally or distributed systemically, were measured. The SOF of explanted TBIs was found to have substantial levels of LPO products, particularly malondialdehyde (MDA), and low levels of trans-4-hydroxy-2-nonenal (HNE) not found in unused implants. Mutagenicity of the SOF was related to the levels of MDA. Capsules that formed around TBIs were microscopically similar to those of reference implants, but MDA-DNA adducts were observed in capsular macrophages and fibroblasts of only TBI capsules. These cell types are not progenitors of breast carcinoma (BCa) and the location of the implants precludes LPO products reaching the mammary epithelial cells which are progenitors of BCa. Blood levels of LPO products were not increased in TBI patients compared to REBI patients and did not change with explantation. In TBI patients, white blood cells did not show evidence of increased levels of LPO-related aldehyde DNA adducts. In conclusion, based on a number of measured parameters, there was no evident effect that would contribute to breast or systemic cancer risk in the TBI patients, and the recommended treatment of TBI patients involving explantation was judged appropriate.
Page 1. INTRODUCTION During inflammation, many cell types release reactive oxygen species (ROS) v... more Page 1. INTRODUCTION During inflammation, many cell types release reactive oxygen species (ROS) via the respiratory burst.1 These ROS are potent oxidants of LDL and its major protein, apolipoprotein B. Whilst native LDL ...
Vascular monocyte retention in the subintima is pivotal to the development of cardiovascular dise... more Vascular monocyte retention in the subintima is pivotal to the development of cardiovascular disease and is facilitated by up-regulation of adhesion molecules on monocytes/endothelial cells during oxidative stress. Epidemiological studies have shown that cardiovascular disease risk is inversely proportional to plasma levels of the dietary micronutrients, vitamin C and vitamin E (alpha-tocopherol). We have tested the hypothesis that alpha-tocopherol supplementation may alter endothelial/monocyte function and interaction in subjects with normal ascorbate levels (> 50 microM), as ascorbate has been shown to regenerate tocopherol from its oxidised tocopheroxyl radical form in vitro. Healthy male subjects received alpha-tocopherol supplements (400 IU RRR-alpha-tocopherol/day for 6 weeks) in a placebo-controlled, double-blind intervention study. There were no significant differences in monocyte CD11b expression, monocyte adhesion to endothelial cells, plasma C-reactive protein or sICAM-1 concentrations post-supplementation. There was no evidence for nuclear translocation of NF-kappaB in isolated resting monocytes, nor any effect of alpha-tocopherol supplementation. However, post-supplementation, sVCAM-1 levels were decreased in all subjects and sE-selectin levels were increased in the vitamin C-replete group only; a weak positive correlation was observed between sE-selectin and alpha-tocopherol concentration. In conclusion, alpha-tocopherol supplementation had little effect on cardiovascular disease risk factors in healthy subjects and the effects of tocopherol were not consistently affected by plasma vitamin C concentration.
Ethylene thiourea (ETU) is a metabolite of ethylenebisdithiocarbamates (EBDCs); it is the best in... more Ethylene thiourea (ETU) is a metabolite of ethylenebisdithiocarbamates (EBDCs); it is the best indicator of exposure to these fungicides. Therefore, high-performance liquid chromatography with photodiode-array detection (HPLC-DAD) was optimized and validated for the determination of ETU in human urines. Urine samples were extracted by solid-phase extraction using Extrelut and analyzed using HPLC-DAD set at 231 nm. The analyses were carried out using a mobile phase of 0.01 M phosphate buffer (pH 4.5) on a C18 Uptisphere NEC-5-20, 250- x 4.6-mm x 5-microm column. The internal standard used was 4-pyridinecarboxylic acid hydrazide. The method was successfully validated in compliance with requirements set by the International Committee on Harmonization 1996. The lower limit of quantitation was at 1 microg/L, and the linearity was studied from 1 to 100 microg/L. There were 272 urine samples collected from farmers exposed to EBDCs in different regions in France analyzed in this study.
International Journal of Hygiene and Environmental Health, 2013
Human biomonitoring (HBM) is a widely accepted tool to aid assessment of chemical uptake in risk ... more Human biomonitoring (HBM) is a widely accepted tool to aid assessment of chemical uptake in risk assessment. However, our understanding of the biological relevance of the results of HBM can be restricted, due in some part to the limited information on background environmental exposures and biomarker concentrations in the general population. The study described here specifically addresses the question of what constitutes normal background levels in the UK population of a number of biomarkers (the chemical itself or one of its stable metabolites) for a variety of environmental chemicals that are frequently encountered because of their widespread use. The environmental chemicals selected for this study were benzene, chlorinated hydrocarbons, dithiocarbamates, cadmium, mercury, naphthalene, diethylhexyl phthalate, synthetic pyrethroids and xylene. Volunteers (n=436) were randomly sought by a postal survey based on the UK Electoral Register. Participants were asked to complete a questionnaire and provide a urine sample. The overall response rate was 7.5%, with volunteers being recruited from all areas of the UK including, England, Scotland, Wales and Northern Ireland. Study participants were adults and comprised 45% male and 55% females. We have conducted a simple, postal-based, cost-effective study and generated similar reference values to very large surveys such as NHANES. This demonstrates that large investigations may not be necessary to get a reasonable idea of environmental exposures, especially in initial 'screening-type' investigations to identify particular exposures of concern or to demonstrate that exposures are reassuring low and that no further survey data needs to be gathered.
Polyunsaturated fats have been linked to occurrences of sporadic colon cancer. One possible cause... more Polyunsaturated fats have been linked to occurrences of sporadic colon cancer. One possible cause may be degradation of polyunsaturated fats during cooking, resulting in multiple reactive carbonyl species (RCS) that can damage nuclear DNA and proteins, particularly in rapidly dividing colon crypt cells. This study describes a novel antiserum against RCS-modified DNA, with apparent order of reactivity to DNA modified with 4-hydroxy-trans-2-nonenal > glyoxal > acrolein > crotonaldehyde > malondialdehyde; some reactivity was also observed against conjugated Schiff base-type structures. Anti-(RCS-DNA) antiserum was successfully utilised to demonstrate formation of RCS-DNA in a human colon cell model, exposed to RCS insult derived from endogenous and exogenous lipid peroxidation sources. Further utilisation of the antiserum for immunohistochemical analysis confirmed RCS-modified DNA in crypt areas of 'normal' colon tissue. These results fully support a potential role for dietary lipid peroxidation products in the development of sporadic colon cancer.
The product of oxidative damage to DNA, 8-hydroxy-2'-deox... more The product of oxidative damage to DNA, 8-hydroxy-2'-deoxyguanosine (8-OHdG), when detected in urine, is considered to be a global, noninvasive biomarker of in vivo oxidative DNA damage. In this paper we describe a novel approach to confirm the presence of oligonucleotides containing 8-OHdG in human urine. Fractions of urine were prepared by gel-filtration chromatography, and the presence of oligonucleotides was confirmed by ELISA using a monoclonal anti-(single-stranded DNA) antibody. Pools of urine fractions were subsequently prepared according to ELISA reactivity, each containing oligonucleotides with a known range of base numbers. The level of 8-OHdG in each pool was subsequently determined using a commercial ELISA kit. Results confirmed that oligonucleotides containing 8-OHdG are present in urine and, most significantly, oligomers of <30-55 bases were found to be associated with 8-OHdG. This finding strongly supports the involvement of nucleotide excision repair (NER) in the removal of 8-OHdG from the cell. The novel approach adopted in this study was validated using cell culture supernatant obtained from an in vitro model comprising CCRF cells exposed to vitamin C; this model has previously been shown to stimulate removal of 8-OHdG from the cell by an NER-dependent process.
Biochemical and Biophysical Research Communications, 2000
We have investigated vitamin C supplementation effects on immunoglobulin oxidation (carbonyls) an... more We have investigated vitamin C supplementation effects on immunoglobulin oxidation (carbonyls) and total plasma protein sulfhydryls in healthy human volunteers. After receiving placebo, plasma ascorbate and oxidation markers were unchanged. Following 5 weeks supplementation with vitamin C (400 mg/day), plasma ascorbate increased but no significant effect on protein oxidation was observed. At 10 and 15 weeks supplementation, carbonyl levels were significantly reduced (P < 0.01) in subjects with low baseline ascorbate (29.51 +/- 5.3 microM) but not in those with normal baseline ascorbate (51.81 +/- 2.3 microM). To eliminate any effect from seasonal variation in dietary antioxidant intake, a second phase was undertaken. Subjects on vitamin C for 15 weeks were randomly assigned to receive either placebo or vitamin C. No difference in plasma sulfhydryl content was observed. Subjects withdrawn from supplementation showed an increase in immunoglobulin carbonyl content (P < 0.01). This demonstrates that dietary vitamin C supplementation can reduce certain types of oxidative protein damage in subjects with low basal antioxidant.
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Papers by Ruth Bevan