Iron, folate and vitamin B12 nutrition and anaemia in black preschool children in the northern Transvaal.

The prevalence of anaemia and deficiencies of iron, folate and vitamin B12 were investigated in 140 rural black preschool children aged 3-5 years living in five different villages in the Letaba area, near Tzaneen. Anaemia was highly prevalent, 39.2% of the children having haemoglobin levels below 11.1 g/dl. Approximately 10% were considered to be iron-deficient. On the basis of subnormal red cell folate values, 1 in 4 children was folate-deficient, suggesting the need for intervention at the community level such as enrichment of the staple foodstuff, maize meal, with folic acid.

Dissociation of methionine synthetase (EC 2.1.1.13) activity and impairment of DNA synthesis in fruit bats (Rousettus aegyptiacus) with nitrous oxide-induced vitamin B12 deficiency.

1. The effect of methylcobalamin inactivation by the anaesthetic gas nitrous oxide on the activity of the cobalamin-dependent methionine synthetase (5-methyltetrahydrofolate homocysteine methyltransferase; EC 2.1.1.13) reaction, and on DNA synthesis, in the fruit bat Rousettus aegyptiacus, was examined. 2. Methionine synthetase activity in the liver of bats exposed to N2O-oxygen (50:50, v/v) for 90 min/d averaged 32% of that of controls after 4 d of exposure and only 5% after 12-14 weeks of exposure. 3. DNA synthesis in the bone marrow, as reflected by the deoxyuridine suppression test, was unaffected by 4 d of exposure to N2O and only minimally affected after 5-10 weeks of exposure. 4. These results suggest that DNA synthesis in the fruit bat is unusually resistant to inhibition of methionine synthetase and imply the existence of a non-methylated circulating folate pool in this species.

Ferritin in breast milk of black urban and rural mothers.

Ferritin levels in serum and milk were investigated in series of 15 urban and 18 rural black mothers. No mother was anaemic. Mean serum ferritin levels in the urban and rural groups were 57 +/- 55 ug/l and 25 +/- 28 ug/l (mean +/- SD). Corresponding milk ferritin concentrations were 21 +/- 22 ug/l and 29 +/- 30 ug/l respectively. The significance of ferritin in human milk is discussed.

Plasma amino acids and tissue methionine levels in fruit bats (Rousettus aegyptiacus) with nitrous oxide-induced vitamin B12 deficiency.

The effect of methylcobalamin inactivation by the gas nitrous oxide on plasma amino acid and tissue methionine levels in fruit bats (Rousettus aegyptiacus) was examined. Animals exposed to N2O-oxygen (1:1, v/v) for 90 min daily received a fruit diet with or without methionine or betaine supplements. Exposure and diets were continued for up to 17 weeks or until neurological impairment and muscular weakness was established. All the groups exposed to N2O had significantly lower liver, brain and plasma methionine concentrations except the methionine-supplemented animals which showed significantly raised levels. Plasma homocysteine, which was absent in controls, was present in all the N2O-exposed groups. Betaine supplementation resulted in reduced accumulation of homocysteine in plasma. However, plasma and liver methionine levels were only slightly increased compared with animals on the basal diet, and brain methionine levels were the lowest of all the groups studied. These results support the hypothesis that reduced methionine synthesis is an important contributor to the development of neurological impairment in this species and suggest that dietary supplementation with the methionine precursor betaine cannot replace the loss of vitamin B12-dependent methionine synthesis.

Transition from a hunter-gatherer to a settled lifestyle in the !Kung San: effect on iron, folate, and vitamin B12 nutrition.

In 1969 a group of hunter-gatherer San were studied (Am J Clin Nutr 1971;24:229-42). Their state of hematological nutrition was excellent with a negligible incidence of iron, folate, or vitamin B12 deficiency. A genetically and linguistically similar San community who have been settled for the past 15 yr were the subjects of the present study. Anemia, due in the main to iron and/or folate deficiency, has become more common. Alcoholism has become rife in both sexes and all age groups. Our findings show that a settled lifestyle has resulted in a significant deterioration in the San's hematological nutrition.

Absorption of biliary cobalamin in baboons following total gastrectomy.

Absorption of radiolabeled cobalamin in baboons was assessed by whole body counting. Retention of biliary cobalamin and an aqueous solution of cyanocobalamin was measured in normal baboons and in baboons after total gastrectomy by using 57Co-labeled biliary cobalamin and 58C0-cyanocobalamin, with and without baboon gastric juice containing intrinsic factor. Radiolabeled biliary cobalamin was obtained by intravenous injection of 57Co-cyanocobalamin in baboons and collection of bile through a cannula placed in the common bile duct. Cobalamin absorption was not completely abolished by gastrectomy and biliary cobalamin was better retained than cyanocobalamin; intrinsic factor enhanced absorption of both forms. After gastrectomy there was steady depletion of liver and serum cobalamin levels, which ceased after a new equilibrium was reached between a progressively diminishing cobalamin loss and the impaired but significant residual level of absorption. These studies in the nonhuman primate provide further information concerning the enterohepatic circulation of cobalamin and suggest that the form of cobalamin in bile may be more readily absorbed than is cyanocobalamin or that bile itself may have an enhancing effect on cobalamin absorption. The data also suggest that physiologically significant amounts of cobalamin may be absorbed in the absence of a gastric source of intrinsic factor.

Enterohepatic circulation of cobalamin in the nonhuman primate.

Biliary excretion of cobalamin was studied in baboons after intravenous injection of 57Co-radiolabeled cyanocobalamin. Radioactivity appeared in bile after 20 min, and up to 4.4% of the dose was recovered in 6 h. It was estimated that 4 microgram cobalamin traverses the baboon biliary tract each day. These studies in the nonhuman primate confirm that there is considerable biliary excretion of cobalamin and that enterohepatic circulation of the vitamin is important for maintenance of normal cobalamin balance.

Pancreatic polypeptide (PP) responses to oral and intravenous glucose in man.

Serum human pancreatic polypeptide (hPP) responses to 50 gm. of oral glucose and a 25 gm. intravenous bolus of glucose were measured in 10 healthy human volunteers. Oral glucose caused a 50% rise, whereas I.V. glucose caused a 35% fall in hPP concentration. There was no relationship between the absolute glucose concentration or the change in glucose level and the PP concentration. It is suggested that oral and I.V. glucose affect PP by indirect mechanisms and that PP may be involved in carbohydrate metabolism in man.

Vitamin B12 metabolism in the fruit bat (Rousettus aegyptiacus). The induction of vitamin B12 deficiency and its effect on folate levels.

1. Vitamin B12 metabolism was studied in bats of the species Rousettus aegyptiacus, which live on an all-fruit diet in the wild. 2. There was a wide range in values for the serum vitamin B12 concentration of newly captured bats, but bats captured in the early spring had significantly higher mean serum vitamin B12 levels than bats captured in the early autumn. 3. There was an exponential decrease in serum vitamin B12 concentration with time in captivity for bats fed on a vitamin B12-deficient, all-fruit diet; the biological half-life was 80 d in serum, 109 d in liver and 164 d in kidney. 4. The main storage organ for vitamin B12 in the bats was the liver, mean content 1067 ng vitamin B12. After 50 d, injected [57Co]cyanocobalamin had equilibrated with body vitamin B12 stores, and 17% of the retained radioactivity was present in the liver. From these results it was calculated that the total body vitamin B12 content of the bat was c. 6500 ng. 5. The biological half-life of injected [57Co]cyanocobalamin was 70--88 d and the calculated daily requirement was 50--60 ng (0-2 mug/kg body-weight per d). 6. As serum vitamin B12 levels decreased, serum folate levels increased. The erythrocyte folate concentration increased significantly after 130 d on the all-fruit diet and then decreased to the initial values after 190 d. 7. Vitamin B12 metabolism in the fruit bat is similar in many respects to that of man, but on a 'weight-for-weight' basis the bat has a 5- to 15-fold greater requirement for this vitamin. 8. Vitamin B12 deficiency may be induced fairly rapidly in fruit bats fed on an all-fruit diet.

Tissue vitamin B-12 assay by a radioisotope dilution technique.

A method is described for the measurement of vitamin B-12 (B-12) in solid tissues by radioisotope dilution (RID) assay. The method is a modivication using double extraction of a serum B-12 RID assay which uses chicken serum as the B-12 binder. The method was developed and tested using human and bat liver specimens. Double extraction was shown to be more efficient than single extraction, and resulted in complete release of endogenous liver [57Co] B-12 administered to bats. Results using the RID assay in 16 humans and 17 bat liver specimens were compared with those obtained using the Lactobacillus leichmannii microbiological assay. Correlation was good, but the RID assay gave higher results using the microbiological assay appear to be due to inadequate extraction of B-12 from tissues.