Women's dietary intakes in the context of household food insecurity.
(9/3171)
A study of food insecurity and nutritional adequacy was conducted with a sample of 153 women in families receiving emergency food assistance in Toronto, Canada. Contemporaneous data on dietary intake and household food security over the past 30 d were available for 145 of the women. Analyses of these data revealed that women who reported hunger in their households during the past 30 d also reported systematically lower intakes of energy and a number of nutrients. The effect of household-level hunger on intake persisted even when other economic, socio-cultural, and behavioral influences on reported dietary intake were considered. Estimated prevalences of inadequacy in excess of 15% were noted for Vitamin A, folate, iron, and magnesium in this sample, suggesting that the low levels of intake associated with severe household food insecurity are in a range that could put women at risk of nutrient deficiencies. (+info)
Preferential release of 11-cis-retinol from retinal pigment epithelial cells in the presence of cellular retinaldehyde-binding protein.
(10/3171)
In photoreceptor cells of the retina, photoisomerization of 11-cis-retinal to all-trans-retinal triggers phototransduction. Regeneration of 11-cis-retinal proceeds via a complex set of reactions in photoreceptors and in adjacent retinal pigment epithelial cells where all-trans-retinol is isomerized to 11-cis-retinol. Our results show that isomerization in vitro only occurs in the presence of apo-cellular retinaldehyde-binding protein. This retinoid-binding protein may drive the reaction by mass action, overcoming the thermodynamically unfavorable isomerization. Furthermore, this 11-cis-retinol/11-cis-retinal-specific binding protein potently stimulates hydrolysis of endogenous 11-cis-retinyl esters but has no effect on hydrolysis of all-trans-retinyl esters. Apo-cellular retinaldehyde-binding protein probably exerts its effect by trapping the 11-cis-retinol product. When retinoid-depleted retinal pigment epithelial microsomes were preincubated with different amounts of all-trans-retinol to form all-trans-retinyl esters and then [3H]all-trans-retinol was added, as predicted, the specific radioactivity of [3H]all-trans-retinyl esters increased during subsequent reaction. However, the specific radioactivity of newly formed 11-cis-retinol stayed constant during the course of the reaction, and it was largely unaffected by expansion of the all-trans-retinyl ester pool during the preincubation. The absence of dilution establishes that most of the ester pool does not participate in isomerization, which in turn suggests that a retinoid intermediate other than all-trans-retinyl ester is on the isomerization reaction pathway. (+info)
Chemical synthesis of all-trans-beta-retinoyl phosphat.
(11/3171)
all-trans-beta-Retinoic acid is phosphorylated to retinoyl phosphate by bis(triethylamine) phosphate with yields of 10-15%. The product is soluble in methanol and is eluted from DEAE-cellulose acetate at a concentration of 0.1M-ammonium acetate in 99% (v/v) methanol. Its phosphate/retinoic acid molar ratio is 1. Retinoyl phosphate has an absorption maximum at 360nm in methanol, whereas retinoic acid has a maximum at 350 nm. The compound is hydrolysed at pH2 and pH13 for 20 min at 37 degrees C, but is relatively stable under the same conditions at pH4, 6, 8 and 10. Retinoyl phosphate (RF 0.1) can be separated from retinyl phosphate (RF 0.2) by chromatography on thin layers of silica gel in chloroform/methanol/water (60:25:4, by vol.). (+info)
Dietary carotenoids and vitamins A, C, and E and risk of breast cancer.
(12/3171)
BACKGROUND: Data on intake of specific carotenoids and breast cancer risk are limited. Furthermore, studies of vitamins A, C, and E in relation to breast cancer risk are inconclusive. We have conducted a large, prospective study to evaluate long-term intakes of these nutrients and breast cancer risk. METHODS: We examined, by use of multivariate analysis, associations between intakes of specific carotenoids, vitamins A, C, and E , consumption of fruits and vegetables, and breast cancer risk in a cohort of 83234 women (aged 33-60 years in 1980) who were participating in the Nurses' Health Study. Through 1994, we identified 2697 incident cases of invasive breast cancer (784 premenopausal and 1913 postmenopausal). RESULTS: Intakes of beta-carotene from food and supplements, lutein/zeaxanthin, and vitamin A from foods were weakly inversely associated with breast cancer risk in premenopausal women. Strong inverse associations were found for increasing quintiles of alpha-carotene, beta-carotene, lutein/zeaxanthin, total vitamin C from foods, and total vitamin A among premenopausal women with a positive family history of breast cancer. An inverse association was also found for increasing quintiles of beta-carotene among premenopausal women who consumed 15 g or more of alcohol per day. Premenopausal women who consumed five or more servings per day of fruits and vegetables had modestly lower risk of breast cancer than those who had less than two servings per day (relative risk [RR] = 0.77; 95% confidence interval [CI] = 0.58-1.02); this association was stronger among premenopausal women who had a positive family history of breast cancer (RR = 0.29; 95% CI = 0.13-0.62) or those who consumed 15 g or more of alcohol per day (RR = 0.53; 95% CI = 0.27-1.04). CONCLUSIONS: Consumption of fruits and vegetables high in specific carotenoids and vitamins may reduce premenopausal breast cancer risk. (+info)
Differential mechanisms of retinoid transfer from cellular retinol binding proteins types I and II to phospholipid membranes.
(13/3171)
Cellular retinol-binding proteins types I and II (CRBP-I and CRBP-II) are known to differentially facilitate retinoid metabolism by several membrane-associated enzymes. The mechanism of ligand transfer to phospholipid small unilamellar vesicles was compared in order to determine whether differences in ligand trafficking properties could underlie these functional differences. Unidirectional transfer of retinol from the CRBPs to membranes was monitored by following the increase in intrinsic protein fluorescence that occurs upon ligand dissociation. The results showed that ligand transfer of retinol from CRBP-I was >5-fold faster than transfer from CRBP-II. For both proteins, transfer of the other naturally occurring retinoid, retinaldehyde, was 4-5-fold faster than transfer of retinol. Rates of ligand transfer from CRBP-I to small unilamellar vesicles increased with increasing concentration of acceptor membrane and with the incorporation of the anionic lipids cardiolipin or phosphatidylserine into membranes. In contrast, transfer from CRBP-II was unaffected by either membrane concentration or composition. Preincubation of anionic vesicles with CRBP-I was able to prevent cytochrome c, a peripheral membrane protein, from binding, whereas CRBP-II was ineffective. In addition, monolayer exclusion experiments demonstrated differences in the rate and magnitude of the CRBP interactions with phospholipid membranes. These results suggest that the mechanisms of ligand transfer from CRBP-I and CRBP-II to membranes are markedly different as follows: transfer from CRBP-I may involve and require effective collisional interactions with membranes, whereas a diffusional process primarily mediates transfer from CRBP-II. These differences may help account for their distinct functional roles in the modulation of intracellular retinoid metabolism. (+info)
Vitamin dificiencies and neural tube defects.
(14/3171)
Serum folate, red cell folate, white blood cell vitamin C, riboflavin saturation index, and serum vitamin A were determined during the first trimester of pregnancy in over 900 cases. For each of these there was a social classes I + II showed the highest levels which differed significantly from other classes, except for serum folate. In 6 mothers who gave birth to infants with neural tube defects, first trimester serum folate, red cell folate, white blood cell vitamin C, and riboflavin values were lower than in controls. In spite of small numbers the differences were significant for red cell folate (P less than 0-001) and white blood cell vitamin C (P less than 0-05). These findings are compatible with the hypothesis that nutritional deficiencies are significant in the causation of congenital defects of the neural tube in man. (+info)
Using cost-effectiveness analysis to evaluate targeting strategies: the case of vitamin A supplementation.
(15/3171)
Given the demonstrated efficacy of vitamin A supplements in reducing childhood mortality, health officials now have to decide whether it would be efficient to target the supplements to high risk children. Decisions about targeting are complex because they depend on a number of factors; the degree of clustering of preventable deaths, the cost of the intervention, the side-effects of the intervention, the cost of identifying the high risk group, and the accuracy of the 'diagnosis' of risk. A cost-effectiveness analysis was used in the Philippines to examine whether vitamin A supplements should be given universally to all children 6-59 months, targeted broadly to children suffering from mild, moderate, or severe malnutrition, or targeted narrowly to pre-schoolers with moderate and severe malnutrition. The first year average cost of the universal approach was US$67.21 per death averted compared to $144.12 and $257.20 for the broad and narrow targeting approaches respectively. When subjected to sensitivity analysis the conclusion about the most cost-effective strategy was robust to changes in underlying assumptions such as the efficacy of supplements, clustering of deaths, and toxicity. Targeting vitamin A supplements to high risk children is not an efficient use of resources. Based on the results of this cost-effectiveness analysis and a consideration of alternate strategies, it is apparent that vitamin A, like immunization, should be provided to all pre-schoolers in the developing world. Issues about targeting public health interventions can usefully be addressed by cost-effectiveness analysis. (+info)
Biochemical studies of isolated hamster tracheal epithelium.
(16/3171)
The epithelial lining of respiratory air passageways is a primary target tissue for toxicity and carcinogenesis in man and in animal models of human disease. The importance of this target tissue was the basis for development of methods to study its biochemistry, and with this information to distinguish the unique properties of this tissue from properties common to all cell types. Biochemical methods employed labeling of macromolecules in isolated hamster treacheas during brief (less than 4 hr) incubation in vitro. Studies of RNA metabolism in isolated tracheas demonstrated a pattern of maturation of ribosomal RNA like that shown for other cell types. Alterations in RNA metabolism were observed in isolated tracheas obtained from vitamin A-deficient hamsters and hamsters previously treated by intratracheal administration of benzo[a]pyrene (BP) plus ferric oxide (Fe2O3) in vivo. Studies with toyocamycin, actinomycin D, and alpha-amanitin, all inhibitors of RNA metabolism, were performed to characterize the class of RNA molecules with a decreased proportion of labeling in tracheas from vitamin A deficient hamsters. In another series of experiments, BP was shown to bind to DNA in epithelial cells of isolated tracheas. The quantity of BP binding was increased by prior intratracheal treatment of hamsters with BP plus Fe2O3 in vivo, this induced binding was inhibited by addition of 7,8-benzoflavone to the incubation medium. Increased BP binding was also observed in isolated tracheas from hamsters believed to be in states of increased susceptibility to respiratory carcinogenesis in vivo. The results show that biochemical studies are feasible with this tissue. Furthermore, a number of questions of importance with regard to this target epithelium are best studied directly in its constituent cells. (+info)