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International Journal of Epidemiology Dec 1993This paper examines the ability of three indicators to detect changes in women's vitamin A status. Serum retinol concentration, milk vitamin A concentration, and milk... (Clinical Trial)
Clinical Trial Comparative Study Randomized Controlled Trial
This paper examines the ability of three indicators to detect changes in women's vitamin A status. Serum retinol concentration, milk vitamin A concentration, and milk vitamin A per gram milk fat were used to assess the vitamin A status of mildly deficient Indonesian women before and after supplementation in a randomized intervention trial. Choice of indicator made a fourfold difference in the sample size required to measure a statistically significant change in vitamin A status. Milk vitamin A per gram milk fat was the best indicator of response, milk vitamin A concentration was intermediate, and serum retinol concentration performed most poorly. Serum retinol concentration was equally responsive across the range of vitamin A status in this population. The milk indicators were more responsive among women of lower status than women of higher status. Milk vitamin A is an efficient indicator for monitoring the effects of vitamin A interventions in women.
Topics: Adult; Female; Humans; Lactation; Milk, Human; ROC Curve; Vitamin A
PubMed: 8144294
DOI: 10.1093/ije/22.6.1111 -
The American Journal of Clinical... Nov 1999The deuterated-retinol-dilution (DRD) technique provides a quantitative estimate of total body stores of vitamin A. However, it is not known whether the technique can... (Clinical Trial)
Clinical Trial Randomized Controlled Trial
BACKGROUND
The deuterated-retinol-dilution (DRD) technique provides a quantitative estimate of total body stores of vitamin A. However, it is not known whether the technique can detect changes in vitamin A pool size in response to different intakes of vitamin A.
OBJECTIVE
Our objective was to determine the responsiveness of the DRD technique to 3 different daily supplemental vitamin A intakes during a period of 2.5-4 mo.
DESIGN
Two oral doses of [(2)H(4)]retinyl acetate [52.4 micromol retinol equivalent (RE)] were administered on study days 1 and 91 to 26 men (18-32 y of age) who were consuming controlled, low-vitamin A diets, and receiving daily either 0, 5.2, or 10.5 micromol RE of unlabeled supplemental retinyl palmitate during a 75- or 129-d period. Plasma isotopic ratios of [(2)H(4)]retinol to retinol on day 115 were used to estimate final vitamin A body stores per Furr et al (Am J Clin Nutr 1989;49:713-6).
RESULTS
Final ( +/- SD) estimated vitamin A pool sizes were 0.048 +/- 0.031, 0.252 +/- 0.045, and 0.489 +/- 0.066 mmol in the treatment groups receiving 0, 5.2, and 10.5 micromol RE/d, respectively (P < 0.001). Estimated mean changes in vitamin A pool sizes were similar to those expected for the vitamin A-supplemented groups [estimated:expected (95% CI of change in pool size): 1.08 (0.8, 1.2) and 1.17 (1.0, 1.3)].
CONCLUSIONS
The DRD technique can detect changes in total body stores of vitamin A in response to different daily vitamin A supplements. However, abrupt changes in dietary vitamin A intake can affect estimates of total-body vitamin A stores.
Topics: Adolescent; Adult; Chromatography, High Pressure Liquid; Deuterium; Humans; Indicator Dilution Techniques; Male; Vitamin A
PubMed: 10539748
DOI: 10.1093/ajcn/70.5.874 -
Journal of Dairy Science Apr 1976The effect of intravenous injection of vitamin A alcohol and vitamin A ester on the vitamin A concentration of bovine milk was studied. Holstein cows received either an...
The effect of intravenous injection of vitamin A alcohol and vitamin A ester on the vitamin A concentration of bovine milk was studied. Holstein cows received either an intravenous injection of 1 million international units (IU) of vitamin A alcohol, 1 million international units of vitamin A palmitate, or served as controls. Blood serum and milk were sampled at intervals prior to and following injection. Mean concentrations of vitamin A in milk at time 0 were 59.0, 52.0, and 58.4 mug/100 ml for the control, alcohol, and palmitate treatments. Mean contrations of vitamin A in milk, expressed as mug/100 ml or mug/g fat of cows receiving vitamin A alcohol at +195, +451, and +678 min postinjection, were greater than concentrations for either control cows or cows receiving palmitate. Partition of milk Vitamin A at +195 min postinjection for cows injected with vitamin A alcohol showed 4.1% of the recovered vitamin A in the alcohol and 95.9% in the ester form. Injection of vitamin A palmitate had little effect on milk vitamin A concentration. Vitamin A in serum (mug/100 ml) at 195 min after vitamin A alcohol injection was higher (100.4) than for either control (84.0) or cows injected with vitamin A palmitate (89.0).
Topics: Animals; Biological Transport; Cattle; Female; Lactation; Lipid Metabolism; Mammary Glands, Animal; Milk; Pregnancy; Structure-Activity Relationship; Time Factors; Vitamin A
PubMed: 1262574
DOI: 10.3168/jds.S0022-0302(76)84248-8 -
The Annals of Pharmacotherapy Mar 1992
Clinical Trial Randomized Controlled Trial
Topics: Child, Preschool; Humans; Measles; Vitamin A
PubMed: 1554956
DOI: No ID Found -
Arizona Medicine Feb 1980
Topics: Humans; Neoplasms; Vitamin A
PubMed: 7369876
DOI: No ID Found -
Experimental Eye Research Jun 1987Vitamin A plays a central role in visual transduction and in maintaining the structural integrity of the retina. It is possible that age-related alterations in vitamin A...
Vitamin A plays a central role in visual transduction and in maintaining the structural integrity of the retina. It is possible that age-related alterations in vitamin A metabolism in the eye could contribute to the impairment of visual function that occurs during senescence. Therefore, investigations were conducted to determine whether the metabolism of this vitamin in the rat retina was altered during aging. Pigmented rats aged 12-, 22-, and 32 months were dark-adapted, and one eye from each animal was enucleated under dim red light. The neural retinas were separated from the retinal pigment epithelium (RPE)-choroid-scleral complexes, and the amounts and forms of vitamin A in both tissues were determined. The animals were then fully light-adapted, and the same measurements were performed on the tissues from the remaining eye of each rat. A number of age-related alterations in the vitamin A composition and content of the retina and RPE were observed. The most pronounced of these changes were significant increases in the ratios of retinyl palmitate to retinyl stearate with advancing age in both the neural retina and RPE. The total vitamin A ester contents of the RPEs increased during senescence in the dark-adapted state, but not in the light-adapted state. Retinyl ester levels in the neural retinas, on the other hand, did not differ significantly between 12- and 32-month-old animals in either the light-adapted or dark-adapted states. The amounts of all-trans retinol in the neural retinas decreased during aging, mainly in the dark-adapted state, whereas aging had no influence on RPE all-trans retinol content. The age-related alterations in metabolism of vitamin A that these observations reflect may be related to certain changes in visual function that occur during senescence.
Topics: Adaptation, Ocular; Aging; Animals; Diterpenes; Male; Pigment Epithelium of Eye; Rats; Rats, Inbred ACI; Retina; Retinyl Esters; Vitamin A
PubMed: 3653281
DOI: 10.1016/s0014-4835(87)80055-6 -
Cancer Chemotherapy and Pharmacology 1979The early and recent investigations in the field of retinoids and cancer are reviewed. The retinoids, including natural vitamin A compounds and their synthetic analogs,... (Clinical Trial)
Clinical Trial Review
The early and recent investigations in the field of retinoids and cancer are reviewed. The retinoids, including natural vitamin A compounds and their synthetic analogs, present a new class of substances exerting a prophylactic and a therapeutic effect both in certain experimental tumor models and in certain clinical conditions of preneoplastic and neoplastic lesions. Because of a particular physiological mechanism of action, the retinoids offer a new approach to the cancer problem, which is different from those of surgery, X-ray therapy, conventional chemotherapy, and immunotherapy.
Topics: Animals; Cell Division; Cell Transformation, Neoplastic; Clinical Trials as Topic; Humans; Neoplasms; Neoplasms, Experimental; Tretinoin; Vitamin A
PubMed: 394876
DOI: 10.1007/BF00254733 -
The Journal of Nutrition May 1979Rats were fed diets deficient [-A] or sufficient [+A] (3 mg retinol equivalents/kg) in vitamin A, and without [-RA] or with [+RA] (12 mg/kg) retinoic acid...
Rats were fed diets deficient [-A] or sufficient [+A] (3 mg retinol equivalents/kg) in vitamin A, and without [-RA] or with [+RA] (12 mg/kg) retinoic acid supplementation for up to 33 days. Rats with plasma vitamin A levels ranging from 7 to 62 micrograms/dl were studied at intervals during progressive depletion of liver stores of vitamin A (expt. 2) and when liver stores were nearly exhausted (less than 10 micrograms/g) or replete (up to 100 micrograms/g) with vitamin A (expt. 1). A dose of retinyl acetate in corn oil (20 micrograms retinol equivalents) was administered by intubation directly into the stomach. The relative dose response (RDR), expressed as a percentage and defined as the absolute magnitude of the rise in plasma vitamin A levels 5 hours after the dose of retinyl acetate, divided by the plasma level of vitamin A attained after 5 hours, was determined for each rat and correlated over a wide range of vitamin A plasma and liver levels. An RDR above 50% invariably was associated with low plasma levels (10 to 30 micrograms/dl) and low liver stores (less than 10 micrograms/g) of vitamin A, whereas an RDR of less than 40% was associated with plasma levels above 30 micrograms/dl and liver stores ranging from 3 to 100 micrograms/g.
Topics: Animals; Body Weight; Dose-Response Relationship, Drug; Liver; Male; Rats; Tretinoin; Vitamin A; Vitamin A Deficiency
PubMed: 438896
DOI: 10.1093/jn/109.5.778 -
Federation Proceedings 1969
Review
Topics: Animals; Asia, Southeastern; Eye; Humans; Nutritional Physiological Phenomena; Rats; Retinal Pigments; Vitamin A; Vitamin A Deficiency
PubMed: 4897769
DOI: No ID Found -
The Journal of Nutrition May 19883,4-Didehydroretinol (vitamin A2, DR, dehydroretinol), a naturally occurring analogue of retinol (vitamin A1, R), is active in vision, growth and cellular...
3,4-Didehydroretinol (vitamin A2, DR, dehydroretinol), a naturally occurring analogue of retinol (vitamin A1, R), is active in vision, growth and cellular differentiation but is converted to retinol in very small amounts, if at all. When vitamin A-depleted rats were given 500 micrograms of R acetate, a naturally occurring mixture of 480 micrograms DR ester and 20 micrograms R ester or 500 micrograms DR acetate orally in corn oil, serum levels of all administered retinoids peaked between 3.5 and 5 h and then declined. When an oral dose of 600 micrograms DR/kg body wt was administered to rats with various liver reserves of vitamin A, the serum ratio of DR to R at 3.5 h was inversely related to the liver reserves of vitamin A below approximately 2 micrograms/g liver. Because the administration of DR does not affect serum R values, a single blood sample taken at 3.5 h might provide information analogous to that obtained from two blood samples in the conventional relative dose-response method.
Topics: Animals; Chromatography, High Pressure Liquid; Female; Liver; Rats; Rats, Inbred Strains; Tretinoin; Vitamin A; Vitamin A Deficiency
PubMed: 3367238
DOI: 10.1093/jn/118.5.598