Cut-off levels for serum retinol levels of 20 micrograms/dl for marginal and 10 micrograms/dl for definite deficiency have been advocated and extensively used in population studies. However, the blood serum levels of retinol of the newborn are known to be very low and although the age dependency of the retinol binding protein has been described, the normal levels of serum retinol at different a...

Although the anticarcinogenic and antiproliferative effects of vitamin A (retinol) have been extensively studied in vitro, there are few data regarding the response of human tumor cells to this agent in vivo. We have studied the effects of retinol on the human breast carcinoma cell line, MDA-MB-231. Initial in vitro studies on monolayer cultures demonstrated a retinol-induced growth inhibition ...

Newly absorbed chylomicron remnant retinyl ester is endocytosed by parenchymal liver cells, and retinol is subsequently transferred to perisinusoidal stellate cells in liver. In the present study we have used several approaches to elucidate the mechanism for the paracrine transfer of retinol between liver parenchymal and stellate cells. In one series of experiments, chylomicrons labeled with [3...

An endoplasmic reticulum fraction from pig liver enriched in transitional endoplasmic reticulum vesicles capable of forming 50-60 nm buds in the presence of ATP and retinol was assayed for retinol-responsive oxidation of NADH and cleavage of a dithiodipyridine (DTDP) protein disulfide-thiol interchange substrate. Maxima for the two activities alternated giving rise to a 24 min period. The NADH ...

Adipose tissue is an important storage depot for retinol, but there are no data regarding retinol mobilization from adipose stores. To address this, dibutyryl cAMP was provided to murine BFC-1beta adipocytes and its effects on retinol efflux assessed. High performance liquid chromatography analysis of retinol and retinyl esters in adipocytes and media indicated that cAMP stimulated, in a time- ...

To explore the nature of retinyl ester synthesis by liver microsomes, membranes prepared from rat or cat liver were incubated under various conditions with [3H] retinol dispersed in dimethyl sulfoxide. When [3H]retinol, buffer, and microsomes were incubated together (basal conditions), some [3H]retinol esterification was consistently observed. However, the rate of esterification could be increa...

OBJECTIVE To investigate the vitamin A status of pregnant mothers, lactating mothers, preterm and term infants who were being fed exclusively on breast milk. DESIGN Systematic/cross sectional. SETTING Vitamin A research laboratory, animal science research laboratory, University of Zimbabwe, and Harare Central Hospital. SUBJECTS 105 pregnant mothers attending the antenatal clinic at Harare...

BACKGROUND Vitamin A deficiency is an important dietary deficiency in the world. Thus, the ne¬cessity of screening for deficient populations is obvious. This paper introduces a fast, cheap and relatively reliable method called "dried blood spot" (DBS) method in screening the deficient populations. The validity of this method for retinol measurement was investigated. METHOD The "precision" and...

Perfusion feeding in rats induced a decrease in circulating retinol despite an adequate supply of vitamin A. We studied the effect of total parenteral nutrition (TPN) on the retinol specific carrier in rat, analyzing holo-RBP (bound to retinol) and apo-RBP (without retinol) in serum and in liver. Vitamin A-sufficient (A+) and -deficient (A-) rats were characterized in terms of vitamin A and RBP...

Although the anticarcinogenic and antiproliferative effects of vitamin A (retinol) have been extensively studied in vitro, there are few data regarding the response of human tumor cells to this agent in vivo. We have studied the effects of retinol on the human breast carcinoma cell line, MDA-MB-231. Initial in vitro studies on monolayer cultures demonstrated a retinol-induced growth inhibition ...