The object of the present study was to determine the effect of thyroxine (T4) treatment of sheep on protein synthesis and associated energy costs in skeletal muscle and hepatocytes. Protein synthesis, and ouabain-sensitive and cycloheximide-sensitive respiration in isolated intercostal muscle and hepatocytes were determined in sheep after 5 weeks of daily injections of either saline or T4. Plasma T4 and total triiodothyronine (T3) concentrations were doubled and free T3 concentrations were quadrupled by T4 injections. The fractional rates of protein synthesis increased in isolated external intercostal muscle and hepatocytes from hyperthyroid sheep. Fractional rates of protein synthesis in isolated external intercostal muscle and hepatocytes were linearly correlated with plasma free T3 concentrations. Total oxygen consumption of muscle and hepatocytes was unaffected by T4 injections. Ouabain-sensitive respiration increased in hepatocytes and muscle of T4-treated animals. Cycloheximide-sensitive respiration was elevated in hepatocytes from hyperthyroid sheep. Cycloheximide-sensitive respiration in muscle was unaffected by T4 treatment. The present experiment demonstrates that T4 increases protein synthesis in ruminants. The energy expenditure in support of Na+, K+-ATPase and protein synthesis in skeletal muscle and hepatocytes may account for 34–60% of total cellular energy expenditure.

Calcium absorption was measured in ten male volunteers from skimmed milk, Ca-enriched skimmed milk or watercress (Nasturtium officinale) soup. The foods were labelled extrinsically with 30 mg 44Ca. Shortly after consuming the labelled meal, each subject was given an intravenous injection of 3 mg 42ca. Fractional absorption from the oral dose was determined from plasma and urine samples collected 24–72 h later, using fast atom bombardment mass spectrometry to measure isotope ratios. The values for urine and plasma were in good agreement. Mean percentage absorption was 45.5 (SEM 1.9)% from the skimmed milk, 35.7 (SEM 4.7) % from the Ca-enriched milk and 27.4 (SEM 1.9) % from the watercress soup. The effect of consuming 568 ml (1 pint) Ca-enriched milk each day for 4 weeks on the efficiency of absorption of Ca was studied. Although there was no statistically significant difference between Ca absorption before and after the supplementation period, the results were considered to be somewhat inconclusive due to the small number of subjects and wide individual variation in Ca absorption.

The hypothesis that factors such as dietary fibre and phytate in wheat bran limit the availability of Zn was tested in growing rats fed on low-Zn diets with different wheat crispbreads as the major source of Zn. Six groups of six weanling male rats each were fed on 5 parts semi-synthetic Zn-deficient diet and 1 part wheat-endosperm crispbread for 1 week. At the beginning of the second week, the crispbread in the diet of five groups was exchanged for crispbread made using one of the following wheat flours: (1) whole grain, (2) bran-enriched whole grain, (3) endosperm with Zn added to the whole-grain level, (4) endosperm with Zn added to the bran-enriched level, (5) whole grain with Zn added to the bran-enriched level. These diets were given ad lib. together with deionized water for 2.5 weeks. The relative absorption of Zn was lowest from the three non-supplemented diets (75–82%). All the added Zn was absorbed. As appetite, body-weight increase, Zn absorption, Zn retention and the Zn concentrations in serum and bone differed only slightly among groups fed on diets with similar Zn concentrations, it is concluded that factors such as dietary fibre or phytate in wheat bran limit the availability of Zn in wheat crispbreads very little when all the Zn is needed for growth and development in rats.

The initial distribution and absorption of biotin in chickens was studied in vivo from either changes in the composition of intestinal contents or analysis of blood draining the gut. The progressive decline in biotin concentration and flow along the small intestine demonstrated absorption throughout this organ. Quantitatively the duodenum was the most significant site of biotin absorption when crystalline biotin was included in the diet and when dietary ingredients contained highly available biotin. In contrast, when diets of low biotin availability were given the distal segments of the small intestine contributed a relatively greater amount to biotin absorption. During passage of digesta from the ileum to the caecum there was a tenfold increase in biotin concentration. About half the amount was of ileal origin with the remainder presumably resulting from microbial synthesis. About 20% of caecal biotin was in a ‘free’ form but the degree of absorption from the caeca was not determined. The amount of biotin disappearing from the gut of birds given maize-based diets was similar to the quantity appearing in portal blood. Biotin absorption was not detected from wheat-based diets using arteriovenous differences.

Administration of oral glutathione (GSH) increases hepatic GSH levels in fasted rats, in mice treated with GSH depletors such as diethyl maleate and in mice treated with high doses of paracetamol. An increase in hepatic GSH levels after administration of oral GSH does not occur in animals treated with buthionine sulphoximine, an inhibitor of GSH synthesis. Administration of oral GSH leads to an increase in the concentration of l-cysteine, a precursor of GSH, in portal blood plasma. Oral administration of l-methionine produced a significant decrease of hepatic ATP in fasted rats, but not in fed rats. Administration of N−acetylcysteine or GSH did not affect the hepatic ATP levels. The results show that the oral intake of GSH is a safe and efficient form of administration of its constituent amino acids in cases when GSH synthesis is required to replete hepatic GSH levels.

The total lipid fatty acid composition of mature breast milk has been analysed in a group of twenty-five mothers of children with atopic eczema, and compared with breast milk from twenty-two controls. Total lipids were extracted into chloroform–methanol (2:1, v/v) and the methyl esters prepared by alkali-catalysed trans-esterification were separated by gas–liquid chromatography and identified by comparison with standard fatty acid methyl esters. Results show that mothers of children with atopic eczema have a significantly greater proportion of linoleic acid, and a smaller proportion of dihomo-γ-linolenic acid in their total breast milk lipid than the controls. Proportions of total derived fatty acids were similar between groups and there were no differences in the principal saturated and monounsaturated fats. It was concluded that mothers of children with atopic eczema have an abnormal breast-milk fatty acid composition. This supports previous evidence of a defect of conversion of linoleic acid into its long-chain polyunsaturated metabolites in the condition.

Alterations in sodium or potassium intake, or both, affect the distribution and excretion of magnesium in man and animals. Experiments were performed on rats to investigate the effect of varying Na, K or Na+K intakes on Na, K and Mg excretion and plasma and tissue concentrations. In Expt 1, increasing the Na intake in a linear fashion produced a significant (P < 0.05) quadratic response in urinary Mg excretion, with a decrease followed by an increase as Na intake rose. No effect was observed on faecal excretion of Mg. Plasma and tissues were sampled at the end of an 18 d collection period; concentrations of aldosterone in plasma and Mg, Na and K in plasma and tissue were determined. Increasing Na intake in a linear fashion produced a significant (P < 0.05) quadratic effect on Mg concentration in heart and muscle, i.e. a decrease followed by an increase as Na intake rose; Na intake did not affect liver or bone Mg concentrations. There were no significant effects of Na intake on plasma Mg, Na or aldosterone but plasma K fell significantly (P < 0.01) as Na intake increased. In Expt 2, constant amounts of four diets supplying adequate or high levels of Na and adequate or high levels of K but a constant intake of Mg were given to rats. The rats fed on the adequate-Na diet had a significantly (P < 0.05) higher urinary Mg excretion than those fed on the high-Na diet; Na intake did not affect faecal Mg excretion.

Female C57BL mice heterozygous for the brindled gene were mated to normal males and fed on a purified diet low in copper throughout gestation and lactation with (+ Cu) or without (−Cu) Cu-supplemented drinking water. Male offspring of two genotypes (control, + /y and brindled, Mobr/y) were compared when 10–12 d old. Brindled mice from dams on the – Cu treatment were smaller and had lower packed cell volumes than brindled mice from dams on the + Cu treatment. The −Cu brindled mice were smaller than their littermate brothers (+/y) but had equivalent biochemical features consistent with severe Cu deficiency. Compared with control mice from dams on the +Cu treatment, caeruloplasmin (EC 1.16.3.1) activity was lower in offspring of all three other groups including Mobr/y mice who were not anaemic. Iron levels were similar in organs and bone marrow from all four groups of offspring. When dietary Cu is limiting in brindled mice a more severe Cu deficiency ensues. Thus, appropriate Cu nutriture is important to the management of Menkes' disease in humans, a genetic analogue of the brindled mouse.

Adipose tissue levels of linoleic acid were determined from biopsies of subcutaneous abdominal fat of normal healthy controls (n 40) and from two patient groups with endoscopically evaluated non-ulcer dyspepsia (n 40) or peptic ulcer disease (n 38). The level (g/100 g) of adipose tissue linoleic acid in the normal healthy controls (15·0 (sd 4·1)) was significantly (P < 0·05) greater than that in patients with non-ulcer dyspepsia (12·8 (sd 3·5)) and in patients with peptic ulcer disease (11·7 (sd 2·7)). A dietary history revealed a lower intake of linoleic acid and a significantly (P < 0·05) lower intake of dietary fibre (g/d) for both the non-ulcer dyspepsia (15·9 (sd 6·2)) and peptic ulcer disease (15·2 (sd 7·8)) patients compared with normal healthy controls (20·2 (sd 11·2)). Adipose tissue linoleic acid tended to increase with indices of increasing socioeconomic status, although the differences between patient and controls were not confounded by socioeconomic status. Patients with dyspepsia reported more foods causing symptoms (onion, fried foods, alcohol, citrus fruits and spices) and more foods giving relief (milk, bread) compared with control orthopaedic patients.

The effect of dietary zinc deficiency on γ-glutamyl hydrolase (EC 3.4.22.12) activity and on pteroylpolyglutamate absorption was investigated in rats. Enzyme activity was determined in pancreas and gut lumen washings. Pteroylpolyglutamate absorption was studied by determining the rise in plasma folate levels following pteroylpolyglutamate ingestion. Two experiments were performed; in each purified diets were given to three groups of immature male Wistar rats for approximately 2 weeks. One group was given a Zn-deficient diet ad lib. (ZD), the second was pair-fed daily with this group on a Zn-adequate diet (PF) and the third was given the Zn-adequate diet ad lib. (AL). In Expt 1, significantly reduced pancreatic γ-glutamyl hydrolase activity was observed in ZD rats. In Expt 2, pteroylpolyglutamate was administered on day 14 and in the 3 h period following pteroylpolyglutamate ingestion, lumen γ-glutamyl hydrolase activity and plasma folate levels were significantly lower in ZD rats. Pancreas is reported as the source of lumen γ-glutamyl hydrolase in rats. The results presented indicate that the pancreatic enzyme is Zn-sensitive. It was concluded that, as a result, γ-glutamyl hydrolase activity was reduced in the lumen of ZD rats. Consequently the hydrolysis and subsequent absorption of pteroylpolyglutamate was impaired in ZD rats, as indicated by the smaller rise in plasma folate levels that occurred following pteroylpolyglutamate ingestion. Results of this study concur with previous observations in human beings and rats that Zn deficiency has an adverse effect on folate metabolism.

Zinc, sodium, potassium, copper and iron concentrations were analysed in serum and tissues of guinea-pigs fed on a diet containing 1.25 mg Zn/kg diet over a period of 60 d. The response of the Zn-deficient (ZnD) animals to Zn supplementation (100 mg Zn/kg diet) was also studied for 15 d. Serum studies in the ZnD group revealed significant decreases in the concentrations of Zn and Na from 24 d, and increases in the concentrations of Fe and K from 36 and 48 d onwards respectively; an increase in Cu was seen on day 60 only. Zn deficiency caused significant reductions in Na, K and Zn and increases in Cu and Fe contents of liver and kidney. In testis, significant decreases were noted only in Zn, K and Fe contents. Zn supplementation of the previously ZnD group resulted in marked improvements in serum and tissue mineral levels. However, hepatic Cu and Fe and renal K did not appear to respond appreciably.

In the present study the effect of combined iron, calcium and folic acid supplementation of the diet on 65Zn retention and zinc status was studied in the pregnant rat. Female Wistar rats were fed on a low-(8 μg/g) or high- (60 μg/g) Zn diet for 14 d and then mated overnight. After mating, half the rats were fed on the low- or high-Zn diet as before, whilst the other half were fed on similar diets supplemented with Fe, Ca and folic acid. The level of supplementation was chosen to reflect proportionately the possible increase in daily intakes of these nutrients by pregnant women. Rats which did not mate successfully were used as non-pregnant controls. On day 18 of pregnancy, each animal was given a meal of the appropriate diet labelled extrinsically with 65Zn, and on day 20 rats were killed. Carcass 65zn retention was lower in pregnant and non-pregnant rats fed on the supplemented diets compared with those fed on the unsupplemented diets. Rats which consumed the supplemented diets throughout pregnancy had reduced plasma Zn concentrations but femur and fetal Zn concentrations were unaffected. Maternal femur Ca and fetal Fe concentrations were lower in the high-Zn groups compared with rats fed on low-Zn diets. It was concluded that the risk of inducing fetal Zn depletion as a consequence of Fe, Ca and folic acid supplementation during pregnancy appeared to be slight. However, significant differences in 65Zn retention and maternal plasma Zn concentration in the supplemented groups, and reduced maternal bone Ca deposition and fetal Fe accretion in the high-Zn groups, indicated that it would seem wise to adopt a cautious approach to routine supplementation with individual minerals during pregnancy.

The aim of the present work was to determine the effect of giving increasing doses of supplements of β-carotene on serum retinoic acid levels in rabbits. Four groups of 7-week-old female rabbits were fed for 9 weeks on a pelleted diet containing 1.72 mg vitamin A as retinyl acetate/kg and including control gelatin beadlets devoid of β-carotene or 1, 2 or 4 mg β-carotene/kg body-weight per d. Serum was collected at 3, 6 and 9 weeks after the beginning of the experiment and the concentration of all-trans retinoic acid was determined by a gradient reverse-phase high-performance liquid chromatography system following a double-phase extraction. The average concentration of retinoic acid in serum of the combined control and 1 mg β-carotene/kg groups was 3.80, 3.06 and 2.40 nM at 3, 6 and 9 weeks respectively. The concentrations of retinoic acid in serum of the combined 2 and 4 mg β-carotene/kg groups were 4.80 nM (P < 0.05), 3.76 nM (not significant) and 4.90 nM (P < 0.005) at 3, 6 and 9 weeks respectively. A SAS (SAS Institute Inc., 1985) general linear model repeated-measures analysis of variance revealed that the effects of treatment (P <0.01), time (P < 0.05) and treatment x time interaction (P < 0.05) were statistically significant. It is concluded that giving β-carotene is associated with higher concentrations of all-trans retinoic acid in the serum of rabbits than in those receiving no β-carotene.

The effect of iron intake on 59Fe absorption throughout pregnancy, and on maternal and fetal Fe status towards the end of pregnancy, was investigated in rats. The influence of pregnancy and dietary Fe on duodenal morphology was also studied. Female rats were fed on a diet containing 17 or 100 mg Fe/kg for 2 weeks before and throughout pregnancy. 59Fe absorption was measured on days 1 or 2, 8 or 9 and 17 or 18 of pregnancy, and maternal and fetal Fe status was determined on days 18 or 19. Pregnancy resulted in a fall in haemoglobin (Hb) concentration. Compared with non-pregnant counterparts, total liver Fe was reduced in the low-Fe group, but not in the high-Fe group, indicating that the fall in Hb in the high-Fe rats was not associated with an Fe-deficient state. 59Fe absorption in rats fed on both diets increased throughout pregnancy, demonstrating that Fe supplementation of the diet, to a level that prevented the development of Fe-deficiency, failed to suppress an increase in absorption. Fetal weight appeared to be an important determinant of the efficiency of Fe absorption in late pregnancy. Poor maternal Fe status was accompanied by a reduction in fetal Fe concentration but results also suggested that fetuses were partly protected from maternal Fe-deficiency. Pregnancy resulted in increased duodenal circumference and villus dimensions, whilst high dietary Fe reduced duodenal growth in both pregnant and non-pregnant animals. The relevance of this finding is discussed. It was concluded that, in rats, pregnancy per se causes an enhancement in Fe absorption and that the degree of enhancement is in part related to fetal mass.

Male Wistar rats (188 g) were fed on a semi-synthetic (SS) diet (38 mg iron/kg) ad lib. for 7 d and then meal-fed for 1 d. After a 21 h fast each rat was given one meal (10 g) of high-Fe SS (500 mg Fe/kg; high-Fe group) or control (38 mg Fe/kg; control group) diet. After 16 h 2 ml of an 59Fe-labelled ferrous sulphate solution (18 kBq 59Fe; 120 μg Fe) was administrated by gavage and equal numbers of rats from each group were killed 6 or 24 h after dosing. Mucosal uptake of 59Fe from the gut lumen and transfer of 59Fe from mucosa into the carcass were measured. Total Fe content of the duodenum was also determined. Mucosal 59Fe uptake and transfer were markedly lower in the high-Fe group compared with the control group. The Fe content of the duodenum, the major region of Fe absorption, was significantly greater in the high-Fe group than in the controls. A larger amount of Fe may thus have been released into the lumen of the high-Fe rats, via mucosal cell turnover, resulting in a greater lumen dilution of the 59Fe dose in this group compared with the controls. Calculations are presented which demonstrate that such an effect could not possibly account for the observed difference in mucosal 59Fe uptake between groups. Differences in rates of ‘cold’ Fe and 59Fe loss from the duodenal mucosa during the 6–24 h interval suggested that, at the time of dosing, Fe retained in the mucosa from the previous meal had been incorporated into a non-exchangeable pool and as such would not dilute radioactive Fe entering the mucosa. It was concluded that whole-body 59Fe retention from a labelled source, given orally after an overnight fast, provided an accurate estimate of Fe absorption.

Responses of several folate-metabolizing pathways to dietary folic acid were studied in 2-week-old chicks. Oxidation of a histidine load to carbon dioxide was impaired in folate-deficient chicks. There was a curvilinear relation between oxidation and dietary folate, and maximum oxidation occurred with 2 mg supplemental folic acid/kg. Hepatic activities of glutamic acid formiminotransferase (EC 2.1.2.5) and glycine N-methyltransferase (EC 2.1.1.20) were not affected significantly (P > 0.05) by dietary folic acid. The activity of dihydrofolate reductase (EC 1.5.1.3) in erythrocytes was elevated in folate-deficient chicks. These studies show that the activities of two folate-dependent pathways can be used as biochemical criteria of folate status in chicks.

The present study was aimed at determining the influence of nutrients supplied by a milk diet (glucose, amino acids, triglycerides) on hepatic somatomedin C (IGF1) production in vivo in four 30-d-old milk-fed calves fitted with chronically indwelling catheters in hepatic (HV), portal (PV) and mesenteric veins and in the hepatic artery (HA), and with electromagnetic flow-meters on HA and PV. Fasting for 16 h induced a decrease (P < 0.01) in hepatic IGF1 production (nmol/kg body-weight (BW) for 6 h) (1.1 (SE 0.2) ν. 6.6 (SE 0.7) in control animals). Infusion of glucose (1.8 g/kg BW for 4 h) or a mixture of amino acids (Azonutril; R. Bellon, Neuilly sur Seine; 62.5 mg nitrogen/kg BW for 3 h) in a mesenteric vein led to no significant effect on hepatic IGF1 production for 6 h (1.2 (SE 0.3) and 0.7 (SE 0.3) nmol/kg BW respectively) compared with fasted calves. Infusion of chylomicrons purified from milk-fed calves (10.5 mg/h per kg BW, i.e. 0.16 mg triglycerides/kg BW per min) enhanced significantly (P < 0.01) the hepatic production of IGF1 (mean value for 6 h: 5.3 (SE 0.8) nmol/kg BW). Infusion of Intralipid (7 mg triglycerides/kg BW per min) induced a slight but significant hepatic IGF1 production which amounted to 3.5 (SE 0.4) nmol/kg BW (P < 0.01 compared with chylomicron treatment) and it began only 5 h after starting the infusion. Neither triglyceride nor chylomicron infusion significantly modified hepatic blood flow. Thus, these results demonstrate for the first time the role of lipids in the regulation of hepatic IGF1 production in vivo.

Eight lambs were fed on a cobalt-deficient whole-barley diet supplemented with urea, vitamins and minerals. Four control lambs were fed on the same diet which had been further supplemented with Co. Plasma vitamin B12 levels in the Co-depleted group declined rapidly, falling below the normal range within 5 weeks. Differences between the live weights of the animals in the two groups approached statistical significance by week 14. However, methylmalonic acid (MMA) rose above normal levels in the Co-depleted group within 7 weeks. This suggested that an elevated plasma concentration of MMA is a comparatively early indicator of functional vitamin B12 deficiency. It is recommended that 10 μmol/l be the upper level of normality for plasma MMA concentration in barley-fed animals, in contrast with the level of 5 μmol/l for grass-fed animals. Changes in the plasma concentrations of MMA and ethylmalonic acid associated with feeding the barley-based diet per se did not significantly affect the validity of the gas-liquid chromatographic assay for MMA.

The calcium, magnesium and phosphorus status of a group of elderly inpatients was studied by use of duplicate meal analysis over a 5 d period and biochemical indices in twenty-one patients, and metabolic balance (5 d) in six of these. Mean daily Ca intake was lower than that of apparently healthy elderly subjects in metabolic equilibrium, although commensurate with present UK recommendations. Metabolic balance was negative for Ca. Mean daily Mg intake was approximately half the US recommendation, and half the intake at which metabolic balance has been observed in healthy elderly people. The five patients studied were in metabolic balance for Mg. Mean daily P intake was close to the UK recommendation, but negative metabolic balance was observed. The disparity between official recommendations for Ca intake, factors contributing to suboptimal Ca status, and measures that may improve Ca status in this group are discussed.

Vitamin A deficiency results in decreased immune responses; the objective of the present study was to investigate the involvement of T lymphocytes in the depression of immune responses resulting from vitamin A depletion. This objective was achieved by evaluating antigen-specific T lymphocyte proliferative responses in vitro as vitamin A depletion developed. The evaluation was performed in both rat and chick to examine the generality of immune effects due to vitamin A depletion. Our findings show that vitamin A depletion led to severe impairment of T lymphocyte activity in both animal models, and that this was directly related to the vitamin A status in both species. Immune response impairment was found to precede other manifestations of vitamin A deficiency, and was rapidly corrected by feeding retinyl acetate boluses. This implied a possible regulatory, rather than constitutive, role of vitamin A in immune responsiveness.