Showing papers on "Ascorbic acid published in 1997"

Osteogenic differentiation of purified, culture‐expanded human mesenchymal stem cells in vitro

Abstract: Human bone marrow contains a population of cells capable of differentiating along multiple mesenchymal cell lineages. Recently, techniques for the purification and culture-expansion of these human marrow-derived Mesenchymal Stem Cells (MSCs) have been developed. The goals of the current study were to establish a reproducible system for the in vitro osteogenic differentiation of human MSCs, and to characterize the effect of changes in the microenvironment upon the process. MSCs derived from 2nd or 3rd passage were cultured for 16 days in various base media containing 1 to 1000 nM dexamethasone (Dex), 0.01 to 4 mM L-ascorbic acid-2-phosphate (AsAP) or 0.25 mM ascorbic acid, and 1 to 10 mM beta-glycerophosphate (beta GP). Optimal osteogenic differentiation, as determined by osteoblastic morphology, expression of alkaline phosphatase (APase), reactivity with anti-osteogenic cell surface monoclonal antibodies, modulation of osteocalcin mRNA production, and the formation of a mineralized extracellular matrix containing hydroxyapatite was achieved with DMEM base medium plus 100 nM Dex, 0.05 mM AsAP, and 10 mM beta GP. The formation of a continuously interconnected network of APase-positive cells and mineralized matrix supports the characterization of this progenitor population as homogeneous. While higher initial seeding densities did not affect cell number of APase activity, significantly more mineral was deposited in these cultures, suggesting that events which occur early in the differentiation process are linked to end-stage phenotypic expression. Furthermore, cultures allowed to concentrate their soluble products in the media produced more mineralized matrix, thereby implying a role for autocrine or paracrine factors synthesized by human MSCs undergoing osteoblastic lineage progression. This culture system is responsive to subtle manipulations including the basal nutrient medium, dose of physiologic supplements, cell seeding density, and volume of tissue culture medium. Cultured human MSCs provide a useful model for evaluating the multiple factors responsible for the step-wise progression of cells from undifferentiated precursors to secretory osteoblasts, and eventually terminally differentiated osteocytes.

The pharmacology of the antioxidant lipoic acid

Abstract: 1. Lipoic acid is an example of an existing drug whose therapeutic effect has been related to its antioxidant activity. 2. Antioxidant activity is a relative concept: it depends on the kind of oxidative stress and the kind of oxidizable substrate (e.g., DNA, lipid, protein). 3. In vitro, the final antioxidant activity of lipoic acid is determined by its concentration and by its antioxidant properties. Four antioxidant properties of lipoic acid have been studied: its metal chelating capacity, its ability to scavenge reactive oxygen species (ROS), its ability to regenerate endogenous antioxidants and its ability to repair oxidative damage. 4. Dihydrolipoic acid (DHLA), formed by reduction of lipoic acid, has more antioxidant properties than does lipoic acid. Both DHLA and lipoic acid have metal-chelating capacity and scavenge ROS, whereas only DHLA is able to regenerate endogenous antioxidants and to repair oxidative damage. 5. As a metal chelator, lipoic acid was shown to provide antioxidant activity by chelating Fe2+ and Cu2+; DHLA can do so by chelating Cd2+. 6. As scavengers of ROS, lipoic acid and DHLA display antioxidant activity in most experiments, whereas, in particular cases, pro-oxidant activity has been observed. However, lipoic acid can act as an antioxidant against the pro-oxidant activity produced by DHLA. 7. DHLA has the capacity to regenerate the endogenous antioxidants vitamin E, vitamin C and glutathione. 8. DHLA can provide peptide methionine sulfoxide reductase with reducing equivalents. This enhances the repair of oxidatively damaged proteins such as alpha-1 antiprotease. 9. Through the lipoamide dehydrogenase-dependent reduction of lipoic acid, the cell can draw on its NADH pool for antioxidant activity additionally to its NADPH pool, which is usually consumed during oxidative stress. 10. Within drug-related antioxidant pharmacology, lipoic acid is a model compound that enhances understanding of the mode of action of antioxidants in drug therapy.

Dietary Flavonoids and the Risk of Lung Cancer and Other Malignant Neoplasms

Abstract: Flavonoids are effective antioxidants and, in theory, may provide protection against cancer, although direct human evidence of this is scarce. The relation between the intake of antioxidant flavonoids and subsequent risk of cancer was studied among 9,959 Finnish men and women aged 15-99 years and initially cancer free. Food consumption was estimated by the dietary history method, covering the total habitual diet during the previous year. During a follow-up in 1967-1991, 997 cancer cases and 151 lung cancer cases were diagnosed. An inverse association was observed between the intake of flavonoids and incidence of all sites of cancer combined. The sex- and age-adjusted relative risk of all sites of cancer combined between the highest and lowest quartiles of flavonoid intake was 0.80 (95% confidence interval 0.67-0.96). This association was mainly a result of lung cancer, which presented a corresponding relative risk of 0.54 (95% confidence interval 0.34-0.87). The association between flavonoid intake and lung cancer incidence was not due to the intake of antioxidant vitamins or other potential confounding factors, as adjustment for factors such as smoking and intakes of energy, vitamin E, vitamin C, and beta-carotene did not materially alter the results. The association was strongest in persons under 50 years of age and in nonsmokers with relative risks of 0.33 (95% confidence interval 0.15-0.77) and 0.13 (95% confidence interval 0.03-0.58), respectively. Of the major dietary flavonoid sources, the consumption of apples showed an inverse association with lung cancer incidence, with a relative risk of 0.42 (95% confidence interval 0.23-0.76) after adjustment for the intake of other fruits and vegetables. The results are in line with the hypothesis that flavonoid intake in some circumstances may be involved in the cancer process, resulting in lowered risks.

Single‐Colony Derived Strains of Human Marrow Stromal Fibroblasts Form Bone After Transplantation In Vivo

Abstract: Populations of marrow stromal fibroblasts (MSFs) can differentiate into functional osteoblasts and form bone in vivo. It is not known, however, what proportion of MSF precursor cells, colony forming units-fibroblast (CFU-Fs), have osteogenic potential. In the present study, analysis of bone formation in vivo by single-colony derived strains of human marrow stromal fibroblasts (HMSFs) has been performed for the first time. Each strain originated from an individual CFU-F and underwent four passages in vitro prior to subcutaneous implantation into immunodeficient mice within vehicles containing hydroxyapatite-tricalcium phosphate ceramic. Multicolony derived HMSF strains were also transplanted to serve as positive controls. After 8 weeks, abundant bone formation was found in the transplants of all multicolony derived HMSF strains, whereas 20 out of 34 (58.8%) single-colony derived strains from four donors formed bone. Immunostaining with antibody directed against human osteonectin and in situ hybridization for human-specific alu sequences demonstrated that cells forming new bone were of human origin and were vital for at least 45 weeks post-transplantation. Both the incidence of bone-forming colonies and the extent of bone formation by single-colony derived HMSF strains were increased by cultivation with dexamethasone and ascorbic acid phosphate. Other factors, including type of transplantation vehicle, morphology, size, and structure of the original HMSF colonies showed no obvious correlation with the incidence or extent of bone formation. Hematopoietic tissue within the newly formed bone was developed in the transplants exhibiting exuberant bone formation. These results provide evidence that individual human CFU-Fs have osteogenic potential and yet differ from each other with respect to their osteogenic capacity.

Factors Influencing the Antioxidant Activity Determined by the ABTS•+ Radical Cation Assay

Abstract: (1997). Factors Influencing the Antioxidant Activity Determined by the ABTS•+ Radical Cation Assay. Free Radical Research: Vol. 26, No. 3, pp. 195-199.

Validation of dietary assessment methods in the UK arm of EPIC using weighed records, and 24-hour urinary nitrogen and potassium and serum vitamin C and carotenoids as biomarkers.

Abstract: Background In the UK EPIC validation studies, the accuracy of several methods was assessed by comparison with to-day weighed records and the biomarkers, 24-hour urine nitrogen (N) and potassium (K), plasma carotenoids and plasma vitamin C. Methods Comparisons between methods were made on 156 women, studied over 1 year at 3-monthly intervals at home. On each of four occasions, volunteers completed 4 days of weighed records and provided two 24-hour urine collections and a fasting blood sample. Results In comparison with the 16 days of weighed records, a food frequency questionnaire (FFQ) yielded higher values mainly due to greater reported consumption of milk and of vegetables. A 24-hour recall was as good as the FFQ in placing individuals in the distribution of habitual diet from weighed records. Results obtained from a 7-day estimated record were closest to those obtained from the weighed record. Correlations between 24-hour urine excretion and dietary N intake from weighed records were high (0.78-0.87) as were those with estimated food diaries (0.60-0.70). Correlations between urine N and the FFQ and 24-hour recall were lower (0.10 to 0.27), but improved by energy adjustment using residuals for N and K which are correlated with total energy intake. Comparisons between dietary estimates and urinary K and serum carotenoids and vitamin C showed broadly similar results. Limited biomarker information amongst 200 UK EPIC participants supported the findings of the validation study. Conclusions UK EPIC uses three methods (the 7-day diary, an improved FFQ, and the 24-hour recall) to assess diet. 93% of first food diaries are returned completed by participants. Repeated diaries are the main dietary assessment method for nested case-control analyses.

Fibroblast growth factor-2 supports ex vivo expansion and maintenance of osteogenic precursors from human bone marrow.

Abstract: We have investigated the effects of different growth factors on the proliferation and osteogenic potential of primary cultures of human bone marrow stromal cells (BMSC). Fibroblast growth factor (FGF)-2 was the most effective in promoting growth of these cells in vitro. The size of colonies formed in clonal conditions was approximately 2.5 times larger in presence of FGF-2. Also the morphology of BMSC was affected: cells cultured in 10% FCS alone became flattened, whereas FGF-2 expanded cells maintained a fibroblast-like elongated phenotype. Levels of alkaline phosphatase activity in BMSC expanded with FGF-2 were significantly lower (56%) than control and, after stimulation with ascorbic acid, bGlycerophosphate and dexamethasone, FGF-2 expanded BMSC deposited approximately 3-fold more mineralized matrix than control cells. We have assessed osteogenicity of BMSC on hydroxyapatite porous scaffolds (bioceramics) by an ectopic bone formation assay. FGF-2 expanded BMSC yielded a higher bone formation (.20-fold) than control cells. We conclude that FGF-2, promoting BMSC proliferation, maintains cells in a more immature state allowing in vitro expansion of human osteo-progenitors which, associated with bioceramics, can differentiate in vivo and form bone tissue. (Endocrinology 138: 4456 ‐ 4462, 1997)

Human nutrition in the developing world

Abstract: In this publication, Professor Michael Latham draws upon his far-reaching experience in the field of international nutrition to provide a rich source of information about nutrition science, public health, food science and public policy. The text summarizes key points in human nutrition and provides information about protein, fats, carbohydrates, minerals and vitamins. Special emphasis is given to the nutritional needs of infants, children, mothers and the elderly. Basic information about foods commonly found in the diets of Africans, Asians and Latin Americans is given. The book focuses on the nutritional and health consequences of inadequate food consumption. Each major nutritional disorder is described and factors contributing to malnutrition such as low food production, food insecurity, poor health status and social and cultural factors are reviewed.[This is a reprint of the 1997 edition.]

Advanced glycation end product-induced activation of NF-kappaB is suppressed by alpha-lipoic acid in cultured endothelial cells.

Abstract: Depletion of cellular antioxidant defense mechanisms and the generation of oxygen free radicals by advanced glycation end products (AGEs) have been proposed to play a major role in the pathogenesis of diabetic vascular complications. Here we demonstrate that incubation of cultured bovine aortic endothelial cells (BAECs) with AGE albumin (500 nmol/l) resulted in the impairment of reduced glutathione (GSH) and ascorbic acid levels. As a consequence, increased cellular oxidative stress led to the activation of the transcription factor NF-kappaB and thus promoted the upregulation of various NF-kappaB-controlled genes, including endothelial tissue factor. Supplementation of the cellular antioxidative defense with the natural occurring antioxidant alpha-lipoic acid before AGE albumin induction completely prevented the AGE albumin-dependent depletion of reduced glutathione and ascorbic acid. Electrophoretic mobility shift assays (EMSAs) revealed that AGE albumin-mediated NF-kappaB activation was also reduced in a time- and dose-dependent manner as long as alpha-lipoic acid was added at least 30 min before AGE albumin stimulation. Inhibition was not due to physical interactions with protein DNA binding, since alpha-lipoic acid, directly included into the binding reaction, did not prevent binding activity of recombinant NF-kappaB. Western blots further demonstrated that alpha-lipoic acid inhibited the release and translocation of NF-kappaB from the cytoplasm into the nucleus. As a consequence, alpha-lipoic acid reduced AGE albumin-induced NF-kappaB mediated transcription and expression of endothelial genes relevant in diabetes, such as tissue factor and endothelin-1. Thus, supplementation of cellular antioxidative defense mechanisms by extracellularly administered alpha-lipoic acid reduces AGE albumin-induced endothelial dysfunction in vitro.

The Dutch EPIC food frequency questionnaire. II. Relative validity and reproducibility for nutrients.

Abstract: Background A self-administered semi-quantitative food frequency questionnaire (FFQ) was developed for the Dutch cohort of the European Prospective Investigation into Cancer and Nutrition (EPIC). Methods The reproducibility and relative validity of nutrient intake as assessed by this questionnaire were investigated in a population of 121 men and women. To assess the relative validity, 12 monthly 24-hour recalls served as reference method, together with four determinations of 24-hour urinary nitrogen excretion, predicted basal metabolic rate, and serum beta-carotene and alpha-tocopherol levels. Results Protein and among women, energy intake were underestimated by the questionnaire compared to urinary nitrogen excretion and the basal metabolic rate, respectively. The underestimation for protein decreased with increasing protein intake. Pearson correlation coefficients between nutrient intakes assessed by repeated questionnaires ranged from 0.70 to 0.94 among men and from 0.59 to 0.94 among women. Correlation coefficients between nutrient intakes assessed by the questionnaire and 24-hour recalls ranged from 0.26 to 0.83 for men and from 0.35 to 0.90 for women, with medians of 0.59 and 0.58, respectively. Correlation coefficients between 0.2 and 0.5 were observed for beta-carotene and vitamin C for men and for beta-carotene and vitamin E for women. Associations with serum beta-carotene (r = -0.16 for men; 0.13 for women) and alpha-tocopherol (0.23 and 0.15, respectively) were much poorer than those obtained with 24-hour recalls. Correlations between protein intake and 24-hour urinary nitrogen excretion were 0.47 and 0.53, respectively. Conclusions The FFQ seems adequate for ranking subjects according to intake of energy, macronutrients, dietary fibre and retinol, but it does not yield such good results for beta-carotene, vitamin C for men, vitamin E for women.

Boron deficiency-induced impairments of cellular functions in plants

Abstract: The essentiality of B for growth and development of plants is well-known, but the primary functions of B still remain unknown Evidence in the literature supports the idea that the major functions of B in growth and development of plants are based on its ability to form complexes with the compounds having cis-diol configurations In this regard, the formation of B complexes with the constituents of cell walls and plasma membranes as well as with the phenolic compounds seems to be a decisive step affecting the physiological functions of B Boron seems to be of crucial importance for the maintenance of structural integrity of plasma membranes This function of B is mainly related to stabilisation of cell membranes by B association with membrane constituents Possibly, B may also protect plasma membranes against peroxidative damage by toxic O2 species In B-deficient plants, plasma membranes are highly leaky and lose their functional integrity Under B-deficient conditions, substantial changes in ion fluxes and proton pumping activity of the plasma membranes were noted Impairments in phenol metabolism and increases in levels of phenolics and polyphenoloxidase activity are typical indications of B deficiency, particularly in B deficiency-sensitive plant species, such as Helianthus annuus (sunflower) Enhanced oxidation of phenols is responsible for generation of reactive quinones which subsequently produce extremely toxic O2 species, thus resulting in the increased risk of a peroxidative damage to vital cell components such as membrane lipids and proteins In B-deficient tissues, enhancement in levels of toxic O2 species may also occur as a result of impairments in photosynthesis and antioxidative defence systems Recent evidence shows that the levels of ascorbic acid, non-protein SH-compounds (mainly glutathione) and glutathione reductase, the major defence systems of cells against toxic O2 species, are reduced in response to B deficiency There is also increasing evidence that, in the heterocyst cells of cyanobacteria, B is involved in protection of nitrogenase activity against O2 damage

Vitamin C Improves Endothelium-Dependent Vasodilation in Forearm Resistance Vessels of Humans With Hypercholesterolemia

Abstract: Background Endothelium-dependent vasodilation is impaired in humans with hypercholesterolemia. Oxidative degradation of endothelium-derived nitric oxide plays a major role in endothelial dysfunction in animal models of hypercholesterolemia. To assess whether this mechanism is relevant to humans, we studied the effect of vitamin C, an antioxidant, on vasodilator function in forearm resistance vessels of patients with hypercholesterolemia. Methods and Results We studied 11 hypercholesterolemic and 12 healthy control subjects. Forearm blood flow was determined by venous occlusion plethysmography. Endothelium-dependent vasodilation was assessed by intra-arterial infusion of methacholine (0.3 to 10 μg/min). Endothelium-independent vasodilation was measured by intra-arterial infusion of nitroprusside (0.3 to 10 μg/min) and verapamil (10 to 300 μg/min). Forearm blood flow dose-response curves were determined for each drug before and during coadministration of vitamin C (24 mg/min). In hypercholesterolemic subjec...

The xanthophyll cycle, its regulation and components

Abstract: During the last few years much interest has been focused on the photoprotective role of zeaxanthin. In excessive light zeaxanthin is rapidly formed in the xanthophyll cycle from violaxanthin, via the intermediate antheraxanthin, a reaction reversed in the dark. The role of zeaxanthin and the xanthophyll cycle in photoprotection, is based on fluorescence quenching measurements, and in many studies a good correlation to the amount of zeaxanthin (and antheraxanthin) has been found. Other suggested roles for the xanthophylls involve, protection against oxidative stress of lipids, participation in the blue light response, modulation of the membrane fluidity and regulation of abscisic acid synthesis. The enzyme violaxanthin de-epoxidase has recently been purified from spinach and lettuce as a 43-kDa protein. It was found as 1 molecule per 20-100 electron-transport chains. The gene has been cloned and sequenced from Lactuca sativa, Nicotiana tabacum and Arabidopsis thaliana. The transit peptide was characteristic of nuclear-encoded and lumen-localized proteins. The activity of violaxanthin de-epoxidase is controlled by the lumen pH. Thus, below pH 6.6 the enzyme binds to the thylakoid membrane. In addition ascorbate becomes protonated to ascorbic acid (pKa= 4.2) the true substrate (Km= 0.1 mM) for the violaxanthin de-epoxidase. We present arguments for an ascorbate transporter in the thylakoid membrane. The enzyme zeaxanthin epoxidase requires FAD as a cofactor and appears to use ferredoxin rather than NADPH as a reductant. The zeaxanthin epoxidase has not been isolated but the gene has been sequenced and a functional protein of 72.5 kDa has been expressed. The xanthophyll cycle pigments are almost evenly distributed in the thylakoid membrane and at least part of the pigments appears to be free in the lipid matrix where we conclude that the conversion by violaxanthin de-epoxidase occurs.

The Relation Between Antioxidants and Memory Performance in the Old and Very Old

Abstract: OBJECTIVES: Aging processes, and among them brain aging, are thought to be associated with free radical action. It is hypothesized that plasma antioxidant vitamin levels correlate with cognitive performance in healthy older subjects. DESIGN: Longitudinal and cross-sectional comparisons. SETTING: The city of Basle, considered representative of the older urban population in Switzerland. PARTICIPANTS: A total of 442 subjects aged 65 to 94 years (mean: 75 years; 312 male, 132 female) was selected from a random sample. MEASUREMENTS: In 1993, participants were tested for memory, and plasma vitamin levels were measured for the three antioxidants α-tocopherol, ascorbic acid, and β-caro-tene. These vitamin parameters, measured previously in 1971 in the same sample, were integrated in our analyses. In addition, plasma cholesterol, ferritin, and systolic blood pressure were taken into account. Memory variables were priming, working-memory, free recall, recognition and the WAIS-R vocabulary test (semantic memory). RESULTS: Correlations showed significant stability of the plasma antioxidants over the time lag of 22 years (a-tocopherol: r = .47, P ≥ .001; β-carotene: r = .43, P < .001; ascorbic acid: r = .22, P < .001). Free recall, recognition, and vocabulary (but not priming and working-memory) correlated significantly with ascorbic acid and β-carotene in the cross-sectional 1993 data as well as in the longitudinal 1971–1993 analysis. These two antioxidants remained significant predictors, especially of semantic memory, after controlling for possible confounding variables like age, education, and gender using multiple regression analyses and ANOVAs. CONCLUSION: Among people aged 65 and older, higher ascorbic acid and β-carotene plasma level are associated with better memory performance. These results indicate the important role played by antioxidants in brain aging and may have implications for prevention of progressive cognitive impairments.

Association of Soy and Fiber Consumption with the Risk of Endometrial Cancer

Abstract: The authors conducted a case-control study among the multi-ethnic population of Hawaii to examine the role of dietary soy, fiber, and related foods and nutrients on the risk of endometrial cancer. Endometrial cancer cases (n = 332) diagnosed between 1985 and 1993 were identified from the five main ethnic groups in the state (Japanese, Caucasian, Native Hawaiian, Filipino, and Chinese) through the rapid-reporting system of the Hawaii Tumor Registry. Population controls (n = 511) were selected randomly from lists of female Oahu residents and matched to cases on age (+/-2.5 years) and ethnicity. All subjects were interviewed using a diet history questionnaire that included over 250 food items. Non-dietary risk factors for endometrial cancer included nulliparity, never using oral contraceptives, fertility drug use, use of unopposed estrogens, a history of diabetes mellitus or hypertension, and a high Quetelet's index (kg/cm2). Energy intake from fat, but not from other sources, was positively associated with the risk of endometrial cancer. The authors also found a positive, monotonic relation of fat intake with the odds ratios for endometrial cancer after adjustment for energy intake. The consumption of fiber, but not starch, was inversely related to risk after adjustment for energy intake and other confounders. Similar inverse gradients in the odds ratios were obtained for crude fiber, non-starch polysaccharide, and dietary fiber. Sources of fiber, including cereal and vegetable and fruit fiber, were associated with a 29-46% reduction in risk for women in the highest quartiles of consumption. Vitamin A and possibly vitamin C, but not vitamin E, were also inversely associated with endometrial cancer, although trends were not strong. High consumption of soy products and other legumes was associated with a decreased risk of endometrial cancer (p for trend = 0.01; odds ratio = 0.46, 95% confidence interval 0.26-0.83) for the highest compared with the lowest quartile of soy intake. Similar reductions in risk were found for increased consumption of other sources of phytoestrogens such as whole grains, vegetables, fruits, and seaweeds. Ethnic-specific analyses were generally consistent with these results. The observed dietary associations appeared to be largely independent of other risk factors, although the effects of soy and legumes on risk were limited to women who were never pregnant or who had never used unopposed estrogens. These data suggest that plant-based diets low in calories from fat, high in fiber, and rich in legumes (especially soybeans), whole grain foods, vegetables, and fruits reduce the risk of endometrial cancer. These dietary associations may explain in part the reduced rates of uterine cancer in Asian countries compared with those in the United States.

Vitamin C crosses the blood-brain barrier in the oxidized form through the glucose transporters.

Abstract: Vitamin C concentrations in the brain exceed those in blood by 10-fold. In both tissues, the vitamin is present primarily in the reduced form, ascorbic acid. We identified the chemical form of vitamin C that readily crosses the blood-brain barrier, and the mechanism of this process. Ascorbic acid was not able to cross the blood-brain barrier in our studies. In contrast, the oxidized form of vitamin C, dehydroascorbic acid (oxidized ascorbic acid), readily entered the brain and was retained in the brain tissue in the form of ascorbic acid. Transport of dehydroascorbic acid into the brain was inhibited by d-glucose, but not by l-glucose. The facilitative glucose transporter, GLUT1, is expressed on endothelial cells at the blood-brain barrier, and is responsible for glucose entry into the brain. This study provides evidence showing that GLUT1 also transports dehydroascorbic acid into the brain. The findings define the transport of dehydroascorbic acid by GLUT1 as a mechanism by which the brain acquires vitamin C, and point to the oxidation of ascorbic acid as a potentially important regulatory step in accumulation of the vitamin by the brain. These results have implications for increasing antioxidant potential in the central nervous system.

Cell proliferation and hair tip growth in the Arabidopsis root are under mechanistically different forms of redox control

Abstract: We provide evidence that the tripeptide thiol glutathione (GSH) participates in the regulation of cell division in the apical meristem of Arabidopsis roots. Exogenous application of micromolar concentrations of GSH raised the number of meristematic cells undergoing mitosis, while depletion of GSH had the opposite effect. A role for endogenous GSH in the control of cell proliferation is also provided by mapping of GSH levels in the root meristem using the GSH-specific dye monochlorobimane and confocal laser scanning microscopy. High levels of GSH were associated with the epidermal and cortical initials and markedly lower levels in the quiescent center. The mechanisms controlling cell division could also be triggered by other reducing agents: ascorbic acid and dithiothreitol. Our data also reveal significant plasticity in the relationship between the trichoblast cell length and the hair it subtends in response to alterations in intracellular redox homeostasis. While mechanisms that control trichoblast elongation are influenced by nonspecific redox couples, root hair tip growth has a more specific requirement for sulfhydryl groups. The responses we describe here may represent the extremes of redox control of root plasticity and would allow the root to maintain exploration of the soil under adverse conditions with minimal cell divisions and root hair production or capitalize on a favorable environment by production of numerous long hairs. Redox sensing of the environment and subsequent redox-dependent modulation of growth and development may be crucial components in the strategies plants have evolved for survival in a fluctuating environment.

Reproducibility and relative validity of an extensive semi-quantitative food frequency questionnaire using dietary records and biochemical markers among Greek schoolteachers.

Abstract: Background We evaluated the reproducibility and relative validity of a 190-item semi-quantitative food frequency questionnaire (FFQ) to be used in a large prospective study in the Athens area of Greece. Methods In all, 42 men and 38 women, aged 25-67 years, completed two self-administered semi-quantitative FFQ spaced approximately 1 year apart. Within this 1-year interval, participants visited the study centre monthly and completed an interviewer-administered 24-hour diet recall questionnaire. We also collected two venous blood and three 24-hour urine samples from participants at randomly selected periods during the year between the two administrations of the dietary questionnaire. Results Mean values for intake of most nutrients assessed by the two FFQ were in good agreement while those assessed by the two different dietary methods were reasonably similar for most nutrients. Intraclass correlation coefficients for energy-adjusted nutrient intakes assessed by questionnaires one year apart averaged 0.57 (range 0.24-0.75) and were not substantially different between genders. Correlation coefficients between the energy-adjusted nutrients measured by repeated 24-hour recalls and the semi-quantitative FFQ ranged from 0.25 for beta-carotene and polyunsaturated fats to > 0.50 for saturated fats, cis-linoleic acid, calcium and phosphorus (average: 0.46 for men and 0.39 for women). Reliability and relative validity were very high for alcohol intake. Dietary intakes from the FFQ were significantly correlated to plasma levels of vitamin C, but not beta-carotene or cholesterol. Dietary protein intake assessed by both FFQ was correlated (0.36, 0.30) with average urinary nitrogen excretion levels from three 24-hour urine samples. Conclusions These data indicate that the semi-quantitative FFQ is reproducible and provides a reasonably reliable measure of intake. Significant correlations between diet and an independent biochemical marker further corroborate the relative validity of our questionnaire in this Greek population.

Vitamin C Improves Endothelial Dysfunction of Epicardial Coronary Arteries in Hypertensive Patients

Abstract: Background There is evidence for increased formation of free radicals in patients with hypertension, raising the possibility that NO is inactivated by free radicals, which impairs coronary endothelial function Therefore, we tested the hypothesis that the antioxidant vitamin C could improve abnormal endothelial function of coronary arteries in patients with hypertension Methods and Results In 22 hypertensive patients without relevant coronary artery stenoses, endothelium-dependent vascular responses of the left anterior descending coronary artery (LAD) to acetylcholine (001, 01, and 10 μmol/L) were determined before and immediately after intravenous infusion of 3 g vitamin C (17 patients) or placebo (5 patients) In a subgroup of 10 patients, papaverine-induced flow-dependent vasodilation (FDD) was measured before and after vitamin C (5 patients) or placebo (5 patients) infusion Segmental responses of the coronary artery luminal area were analyzed with quantitative coronary angiography Before vitami