Vitamin A Levels Research Articles

Hypervitaminosis and safe levels of vitamin A for larval flounder Paralichthys olivaceus fed Artemia nauplii

An experiment was designed to identify signs of hypervitaminosis and establish a safe incorporation level of vitamin A (VA) in Artemia nauplii in terms of biological performances and uptake of the vitamin A by larval flounder. Ten-day-old larval flounder were chosen as the experimental fish and cultured for 40 days. Larvae were fed on Tien-tsin strain Artemia enriched in a 10-liter medium containing either 0, 20, 40, 60, and 80 mg or 100 mg VA palmitate (1 μg VA palmitate = 1 IU VA). The enriched Artemia were offered to the larvae till the end of metamorphosis; after that the fish were fed with an artificial diet containing 25 IU VA/g. The VA content of both Artemia and fish was elevated by increasing the VA content of the Artemia culture medium. Feeding Artemia enriched with more than 40 mg VA palmitate produced a negative effect on growth of fish as well as a high incidence of bone deformity. On the other hand, survival of fish was not affected by elevation of VA levels in Artemia, and almost all the fish showed normal body coloration. Thus, excess dietary levels of VA proved detrimental. The safe level of VA in Artemia nauplii was estimated to be less than 50 IU VA/ g on a dry weight basis (20 mg VA palmitate in a 10-liter medium).

Vitamin A status in preterm neonates with and without chronic lung disease

It has been proposed that there is an association between vitamin A (VA) deficiency and the development of chronic lung disease (CLD) in preterm infants. This study was designed to measure the VA status in preterm infants and to compare the results in the group of babies who developed CLD with the group who did not. Vitamin A status was assessed by measuring plasma VA, retinol binding protein (RBP) and the plasma VA:RBP molar ratio in 25 infants of less than 31 weeks gestation during the first 28 days of life. Eleven babies developed CLD and 14 did not. There was no significant difference in plasma VA levels between the CLD and non CLD groups during the first 28 days. The majority of infants had adequate VA status, with a subgroup being deficient.

Effect of Zinc Deficiency on Hepatic Enzymes Regulating Vitamin A Status

The elevation of hepatic vitamin A (VA) in zinc deficiency (ZD) is thought to be due, in part, to a reduced synthesis of plasma retinol-binding protein with a subsequent decrease in the release of retinol into the circulation. We hypothesized that the hepatic VA elevation may also be secondary to a change in the activity of enzymes that either regulate retinol degradation or affect the synthesis or hydrolysis of retinyl esters. To examine this question, 20 rats were divided into two groups and pair-fed for 3 wk. ZD rats received a ZD diet (zinc 2.3 mg/kg diet) and controls were fed a zinc-sufficient diet (zinc 50 mg/kg diet). The enzymes studied were retinyl ester hydrolase (REH) and microsomal acyl coenzyme A:retinol acyl transferase (ARAT), the principal enzymes regulating retinyl ester hydrolysis and synthesis. The activities of retinol (alcohol) dehydrogenase (ADH) and retinal oxidase (RO), enzymes regulating retinol degradation to polar metabolites, were also studied. ZD caused an increase in both total hepatic VA concentration and total hepatic VA content, but did not alter the ratio of retinol to retinyl esters. The specific activities of REH and ARAT were not affected by ZD. However, ZD caused a significant reduction in the activity of ADH, the enzyme that catalyzes the first step in retinol oxidation. In contrast, the activity of RO, the enzyme that regulates the irreversible oxidation of retinal to retinoic acid, was significantly increased in ZD rats. These findings indicate that the elevation in hepatic levels of VA in ZD rats may be, in part, secondary to decreased retinol degradation.

Implications of hypervitaminosis A on the calcium-phosphate metabolism and on blood lipids in hemodialysis.

Serum levels of vitamin A (VA) were measured in 71 hemodialysis (HD) patients and in 30 normal controls. 65 of the 71 patients were taking multivitamin preparations (MP) containing VA. The HD patients had significantly greater values: 7.81 +/- 2.86 mumol/l (224 +/- 82 micrograms/dl) versus 3.97 +/- 0.97 mumol/l (114 +/- 28 micrograms/dl; p less than 0.0005); those taking MP with large doses of VA showed the highest levels. Patients were divided as having normal (group I, n = 21) or elevated (group II, n = 50) serum levels of VA. Patients of group II had higher levels of serum calcium (Ca) and lower of serum phosphate (P) and PTH than those of group I. Four months after the withdrawal of oral VA, the serum levels of VA and Ca fell significantly in group II, while the serum P increased. On the contrary, in group I serum levels of VA, Ca and P remained unchanged. Serum triglycerides (TG) were significantly higher in group II but did not change after the withdrawal of VA. No differences between both groups of patients were observed for age, time on HD, residual diuresis, residual renal function, serum levels of cholesterol (CL) or anemia. A retrospective study of 18 hepatic biopsies of HD patients disclosed hyperplasia of Ito cells (VA-storaging cells) in 7 of them. These 7 biopsies belonged to patients who had taken large amounts of oral VA. Our data indicate that prolonged VA intake in HD patients is followed by an increase of serum CA, a decrease of serum P and PTH and a hepatic accumulation of VA.(ABSTRACT TRUNCATED AT 250 WORDS)

Distribution of vitamins A and E in blood and liver of rats depleted of vitamin A or vitamin E.

Young Sprague-Dawley male rats (n = 150) were fed a semipurified diet, either without vitamin A (VA), without vitamin E (VE) or supplemented with both vitamins A and E (control). At the end of weeks 0, 1, 3, 5, 6, 7, 8 and 9, groups of rats were anesthetized with methoxyflurane, and blood was collected by cardiac puncture until the rat was exsanguinated. The liver was excised. Whole blood (WB) from each rat was fractionated into plasma (PLA), leukocytes (LEU), platelets (PLT) and erythrocytes (RBC). Each blood component was extracted with heptane and livers were extracted with CHCl3/CH3OH (2:1, v/v). The extracts were analyzed for VA and VE by high performance liquid chromatography. The relationship among blood components in the loss of VA was PLT = LEU greater than WB greater than PLA. The relationship among blood components in the loss of VE was PLA greater than RBC greater than WB greater than LEU = PLT. VA and VE levels in other blood components decreased precipitously between weeks 0 and 4 in the animals placed on deficient diets. These results and correlation analyses between vitamin contents of blood components and of livers indicate inadequacies for the use of certain blood components as monitors of lipid-soluble vitamin status in the rat.

Restoration of mucociliary tracheal epithelium following deprivation of vitamin A. A quantitative morphologic study.

In order to learn more about the respective roles played by basal cells and mucous cells in the maintenance of tracheal mucociliary epithelium, cell kinetics and epithelial cell morphology were characterized over a 7-day period, during which dietary vitamin A was restored to previously deprived hamsters. Hamsters were reared from birth to 35 days of age on vitamin A-replete or deficient diets. Deprived hamsters were made replete by 5 mg vitamin A-acetate orally, plus a vitamin A-replete diet. Colchicine and 3HTdR were given 6 h before death. The numbers of basal cells, mucous cells, preciliated cells and ciliated cells, and mitotic rates (MR) and labeling indices (LI) of basal cells and mucous cells, were quantified in glycol methacrylate sections stained with PAS-lead hematoxylin. Vitamin A-deprivation decreased replication of basal cells and mucous cells in tracheal epithelium which showed minimal morphological change. The proportion of basal cells was increased and proportions of mucous, preciliated and ciliated cells were decreased. Following restoration of vitamin A to the diet, the basal cell MR remained below control level throughout the experimental period, but the mucous cell MR started to rise on day 2-replete, and on day 3-replete and thereafter the mucous cell MR was within the control range. Basal cell and mucous cell LI's showed similar trends. Preciliated cells were reduced or absent in vitamin A-deprived epithelium. Their number had risen by day 3-replete and thereafter they were generated within the control range. These cells matured into ciliated cells. By day 4-replete, the proportion of basal cells had decreased markedly and the proportions of mucous cells, and preciliated plus ciliated cells had increased, so that at this time cellular proportions were within or near control values. This trend continued so that by day 7-replete, a nearly normal mucociliary epithelium was restored. The results show that vitamin A-levels modulate replication rates of basal cells and mucous cells and indicate that mitotic division of mucous cells is a prerequisite for the genesis of preciliated cells and new mucous cells and for restoration of the mucociliary epithelium following deprivation of vitamin A in the diet.

The effect of heavy metals on vitamin A metabolism

Three kinds of divalent ions were injected subcutaneously to rats. Copper at the total dose of 6.2 mg/kg and zinc at the total dose of 12.6 mg/kg did not alter the plasma or liver vitamin A (VA) concentrations. The liver concentration of both had returned to control levels by 2 weeks after the final injection. Cadmium, at the total dose of 6.2 mg/kg, decreased significantly the plasma level of VA, although the liver VA content was not affected. This effect persisted till 2 weeks after the final injection.

Effects of Oral Contraceptives on Vitamin Metabolism

Literature on the effects of oral contraceptives (OCs) on vitamin metabolism is reviewed. OCs have been reported to markedly increase serum levels of Vitamin-A. OCs may induce a thiamine deficiency and lower levels of Vitamin-B2. Concentrations of ascorbic acid in platelets, white cells, plasma, and urine are decreased by OCs. Decreased plasma and red blood cell concentrations of folic acid have been reported in OC users, though it does not appear that absorption of folate polyglutamate is affected. OC users may develop megaloblastic anemia because of folic acid deficiency. OCs have been reported to markedly reduce serum levels of Vitamin-B12. Some OC users who excrete abnormal amounts of tryptophan metabolites have some degree of true Vitamin-B6 deficiency. Evidence of altered tryptophan metabolism and/or absolute Vitamin-B6 deficiency has been found in emotionally depressed women taking OCs. OCs, especially estrogens, produce tryptophan metabolism abnormalities in the great majority of users. An effect of OCs on alpha-tocopherol plasma concentrations has yet to be demonstrated in humans.

Effects of oral contraceptives on vitamin A metabolism in the human and the rat

This study reexamines the effects of oral contraceptives (OC) on Vitamin-A metabolism in humans. Data from a similar study using rats is reported. College girls aged 20 to 23 were given Ovral or Norlestrin. A group of 11 had never taken OCs; 7 had used OCs from 2 months to 2 years. Oral temperatures were recorded daily for 28 days beginning on Day 1 of menses. A dietary record was also made. For the animal tests 15 female Wistar rats were given Ovral as a saline suspension by stomach intubation. 5 rats were given daily doses proportional to that taken by the human participants. 5 controls received only the saline. Animals were given a commerical Vitamin-A free diet. Fasting venous blood samples were taken from the human subjects on 2 consecutive days at 5 intervals of 5 days during the menstrual cycles. Rat blood and liver specimens for tests were obtained at sacrifice after 18 hour fasts. The mean plasma Vitamin-A level of the human OC users was significantly higher than in non-users (p less than .01). In the samples chromatographed on alumina colums the plasma Vitamin-A in both groups was found to be mainly retinol. Wide variations in the individual plasma carotene levels were observed. During the 5 intervals studied the levels of carotenoids was relatively constant. However in the period between Day 1 and Day 5 there was a drop in plasma carotenoids in the control group but not in the OC group. Total Vitamin-A intake by each subject varied from day to day from 1000 to 16000 IU but was similar in the 2 groups. Total Vitamin-A in the diet and plasma Vitamin-A were not correlated however. Waking oral temperatures were significantly higher in the OC group only on Days 10-23 and on Day 1 (p less than .01). The higher basal temperatures of the OC subjects during midcycle were thought to be due to the progestogen. Plasma Vitamin-A levels and basal body temperatures did not show correlation. Hematocrit values were not altered. In the animal experiments food consumption and body weight gains were similar to controls. Higher plasma Vitamin-A levels did not occur in rats given OC drugs but liver Vitamin-A content was lower. Liver depletion rate of OC-treated rats was 3 times greater than controls. These results suggest a higher Vitamin-A requirement for rats given OC drugs. For humans such increased metabolic need for Vitamin-A is not clear.

PATTERN OF PROTEIN-CALORIE MALNUTRITION IN YOUNG CHILDREN ATTENDING AN OUTPATIENT CLINIC IN BAGHDAD

The classification of protein-calorie malnutrition suggested by the Wellcome Trust working-party has been applied to 200 randomly selected malnourished children under the age of five years and attending the outpatient clinic of the Children's Hospital in Baghdad. Of the children under 80% of the Boston standard, only 12% were kwashiorkor or marasmic-kwashiorkor; most of them were marasmic or underweight. Marasmus was common in the second year of life. Use of clinical judgment alone, without anthropometric measurements, resulted in about 30% of the malnourished children being misdiagnosed as normal. Simple anthropometric measurements such as the chest/head ratio and the mid-upper arm circumference were found to be reliable tests for detecting malnourished children, even if the age was not known. Hair and skin changes and hepatomegaly were not prominent clinical signs. Vitamin-deficiency syndromes were not found, except for 1 case of xerophthalmia. The biochemical features in normal children showed low serum-albumin, serum-iron, hæmoglobin, hæmatocrit, and vitamin-A levels. There was a preponderance of females over males in the malnourished group. A comparison with the McLaren scoring system suggests a remarkable similarity when the scores given to serum-albumin levels are adjusted.

Vitamin-A deficiency in turkeys

Abstract does not appear. First page follows. Losses from obscure causes on certain California turkey ranges, where green feed is limited during much of the growing season, suggested the need for studies on vitamin-A deficiency in turkeys. The experiments reported herein were outlined to determine the possible relation of A-avitaminosis4 to turkey mortality and to obtain information concerning the effect on turkeys of various vitamin-A levels. A-avitaminosis in chickens has been fully described by Beach(1), Emmett and Peacock?(3), Seifried(10), Elvehjem and Neu(4), and many other investigators, so that the pathological changes in chickens are well established. Chicks were included in one experiment as a control on the methods used and as a basis for comparing A-avitaminosis in the two species. Scott and Hughes(9), using yellow corn as the source of vitamin A, showed that turkeys required more vitamin A than did chickens. This paper is concerned chiefly with the disease phases of the problem. Because published data on the vitamin-A requirements of turkeys are limited, the results on the comparative value of dehydrated alfalfa-leaf meal for turkeys and chickens are also included. Certain vitamin-A liver storage data collected in connection with the experiments have already been published by Guilbert and Hinshaw.(6)