1. Sprague–Dawley rats were injected for 16 d with long-acting insulin, and energy balance was calculated using the comparative carcass technique. Two experiments were carried out with females (starting weights 150 and 90 g respectively), and one with males (starting weight 150 g). In a fourth experiment, cytochrome c oxidasc (EC 1.9.3.1) activity was measured as an indicator of the capacity for substrate oxidation.

2. Insulin increased weight gain by up to 57% (P < 0.01 for all studies). Metabolizable energy intake (kJ/d) was also consistently higher in the treated groups, by up to 34% (P < 0.01 for all studies). The excess weight gained by the insulin-treated rats was predominantly due to fat deposition.

3. Energy expenditure, calculated as the difference between metabolizable intake and carcass energy gain. was expressed on a whole-body basis, or relative to either metabolic body size (kg body-weight0.75) or fat-free mass. Insulin consistently raised energy expenditure, regardless of the method of expression, but this change reached statistical significance in only two of the nine comparisons.

4. Cytochrome c oxidase activity was not affected by insulin treatment in either interscapular brown adipose tissue or gastrocnemius muscle. In liver, total enzyme activity (U/tissue) was increased from 2928 (se 162) in the controls to 3940 (se 294) in the treated group (P < 0.02), but specific activity (U/mg protein) was unchanged.

5. It is concluded that, despite causing substantial hyperphagia, insulin treatment only slightly increases energy expenditure in rats. The costs of increased tissue deposition may account for this change.

1. Sprague–Dawley rats were given corticosterone for 4 to 14 d either by subcutaneous injection (50 mg/kg body-weight per d) or as a higher dose in the diet (1 g/kg diet). Energy balance was calculated using the comparative carcass technique.

2. Corticosterone significantly suppressed growth rate by at least 50% (P < 0·001 in all experiments). The reduction in growth was more marked in males than in females.

3. Hormone treatment significantly reduced metabolizable intake (kJ/d) in males but not in females. Expressed relative to either metabolic body size (kg body-weight0·75) or fat-free mass, metabolizable intake tended to be increased in the treated groups.

4. Energy expenditure, calculated as the difference between metabolizable intake and gain and expressed as kJ/d, did not differ between treated and control rats. Relative to either metabolic body size or fat-free mass, expenditure was consistently increased in treated rats. This change was statistically significant in five of the eight comparisons.

5. The corticosterone-treated rat is characterized by high energy intake and expenditure relative to its body size and growth rate. Alterations in the relative sizes of different lean tissues may contribute to these changes.

1. Eighteen pigs were offered diets containing 130, 170 or 210 g protein/kg with three barrows and three gilts per diet from 20 to 60 kg live weight. Oxygen consumption, Na1, K1-ATPase (EC 3·6·1· 3)-dependent and -independent respiration and protein synthesis were measured in vitro in intercostal and sartorius muscle preparations from these pigs.

2. Increasing dietary protein concentration increased (P < 0·01) daily gain and dissectible muscle in carcass.

3. O2 consumption and Na+, K+-ATPase-dependent respiration of the intercostal and sartorius muscles increased linearly (P < 0·01) with increase in dietary protein concentration. The requirement for the support of the transport of Na+ and K+ across the cell membrane in these muscles, on average, accounted for 22–25% of the O2 consumption.

4. Synthesis rate (mg/g per d) of protein in the sartorius muscle increased (P < 0·05) from 3·05 to 5·07 and increased (P < 0·1) from 2·57 to 4.06 in the intercostal muscle as dietary protein increased from 130 to 210 g/kg diet.

5. Regression of Na+, K+-ATPase-dependent respiration against protein synthesis in each of intercostal and sartorius muscles showed a linear relation, an attestation of a close link between productive processes and auxiliary energy expenditure.

1. The effect of different doses of ouabain, an inhibitor of the sodium pump, or saline (9 g sodium chloride/1; the vehicle) on the metabolic rate of guinea-pigs weighing 500 g was measured by indirect calorimetry for 120 min.

2. Ouabain (0·02–0·07 nmol/g body-weight) decreased the oxygen consumption in a dose-related manner. When higher doses of ouabain (0·10 nmol/g body-weight or greater) were injected the animals were observed to shiver. Ouabain (0.07 nmol/g body-weight) reduced Na+, K+-ATPase (EC 3. 6. 1. 3) activity of liver, kidney and skeletal muscle by 18·0 (se 6·6), 21.5 (se 6·0) and 21·9 (se 6·8)% respectively. An Eadie-Hofstee plot of percentage decrease in O2 consumption v. percentage inhibition ÷ dose of ouabain showed that maximal inhibition of O2 consumption was 39·4 %.

3. It is concluded that Na pump activity contributed to about 40 % of the resting O2 consumption.

1. The effects of riboflavin deficiency on growth, whole-body oxygen consumption, cytochrome c oxidase (EC 1.9.3.1) activity and GDP-binding capacity of brown adipose tissue were measured in three groups of rats: sucking pups, weanling rats, and dams. Control groups were weight-matched, pair-fed or fed ad lib.

2. Riboflavin deficiency reduced growth rate and increased the activation coefficient of erythrocyte glutathione reductase (NAD(P)H) (EC 1.6.4.2), as predicted. In sucking pups it also reduced whole-body O2 consumption per unit body-weight, especially after noradrenaline stimulation. In weanling rats, however, it increased O2 consumption both before and after noradrenaline stimulation.

3. Cytochrome c oxidase (EC 1.9.9.1) activity of brown adipose tissue was not consistently affected by riboflavin deficiency. Binding of [3H]GDP to the mitochondria was increased in the deficient weanling rats.

4. Weanling rats therefore, seemed better able to withstand the effects of severe depletion. Their reduced growth and increased non-shivering thermogenesis helped to counteract the unfavourable ratio of riboflavin: other tissuebuilding materials. The relevance for thermoregulation in riboflavin-deficient children is discussed.

1. Analbuminaemic and Sprague-Dawley (control) rats were fed on low- (60 g/kg) protein and control (200 g protein/kg) diets ad lib. from weaning. Males and females were studied separately. Body-weight and plasma protein concentrations were determined at 10 d intervals from 25 to 75 d of age. Electrophoresis of plasma proteins was performed in samples from day 75. Extracellular fluid volume was measured at 10 d intervals from day 45 onwards. Colloid osmotic pressure was measured in plasma and interstitial fluid (wick technique) at the start and end of the trial.

2. Body-weight increased much less on the low-protein diet than on the normal diet in both strains and sexes. The growth retardation was slightly more pronounced in the male analbuminaemic rats than in the male Sprague-Dawley controls.

3. Plasma protein concentration increased during normal growth in all groups, particularly in the female analbuminaemic rats. This increase was reduced by the 60 g protein/kg diet in all groups, with the exception of the male analbuminaemic rats.

4. Differences in plasma colloid osmotic pressure were similar to those seen in plasma protein concentration. Interstitial colloid osmotic pressure was higher in the control rats than in the analbuminaemic ones. The interstitial colloid osmotic pressure increased during growth in the control but not in the analbuminaemic rats. The difference in interstitial colloid osmotic pressure between the strains was maintained during low-protein intake, but at a lower level than during normal protein intake.

5. Subtracting interstitial from plasma colloid osmotic pressure, resulted in a rather similar transcapillary oncotic gradient in the various groups at 75 d, both on the control protein diet (11–14 mmHg), and on the lowprotein diet (9–11 mmHg).

6. All protein fractions were reduced to a similar extent by the low-protein diet in the control rats, whereas in the analbuminaemic rats protein fractions produced in the liver were more severely depressed.

7. Extracellular fluid volume as a percentage of body-weight was similar in all groups, and decreased with increasing age.

8. In conclusion, the analbuminaemic rats were able to maintain the transcapillary oncotic gradient on both diets by reducing the interstitial colloid osmotic pressure. Oedema was not observed.

9. Despite the absence of albumin, the protein-malnourished analbuminaemic rat is no more susceptible to hypoproteinaemia and oedema than its normal counterpart.

1. Procedures are described to prepare nutritionally adequate rat milk-substitutes by modifying commercially available processed cow's milk, rich in carbohydrate and low in protein and fat compared with rat's milk.

2. Premilk formulas, prepared as intermediates in the preparation of rat milk-substitutes, are rich in protein but low in their concentration of fat, carbohydrate, and minerals when compared with rat's milk.

3. Premilks were supplemented with lactose, vitamins, minerals, fat as oil mixtures, certain amino acids and other constituents to yield rat milk-substitutes which resemble the known composition of rat's milk in their properties and composition.

4. Detailed analyses of the milk-substitutes show them to be comparable to rat's milk in energy content, pH, osmolarity, the concentration of the macronutrients, fat, protein and carbohydrate, and the major minerals.

5. Rat pups were artificially reared from postnatal day 4 or 5 until days 16–18 by fitting them with gastric cannulas through which the milk-substitutes could be infused automatically.

6. The nutritional impact of the milk-substitutes was assessed by a comparison of growth and mctabolic characteristics for artificially reared rats with age-matched sucking rats reared by their mother.

7. Indices which were taken to be appropriate included (a) body-weight gain; (b) the concentration in blood of protein, amino acids, ketone bodies, carnitine, glucose, galactose, lactate, insulin, and the electrolytes calcium, sodium, potassium and chloride; (c) the turnover of glucose and 3-hydroxybutyrate; (d) the concentration in brain of protein, cholesterol, cerebroside sulphate and the activities of the enzymes pyruvate dehydrogenase (EC 1.2.4.1), 3-oxo-acid-CoA transferase (EC 2.8.3.5) and acetoacetyl-CoA ligase (EC 6.2.1.16).

8. The studies suggest that milk-substitutes approximating to rat's milk in composition promote acceptable metabolism in the artificially reared rat pup.

1. Wistar rats were fed for three successive generations on a semi-purified diet, in which the fat was provided by butter, sunflower oil, rapeseed oil or hydrogenated vegetable fat, differing in the content of cis, cis-18:2 and trans-18:1 fatty acids. Effects of these fats on the composition of adipose tissue and reproductive performance were studied. Fatty acids were analysed using high-performance liquid chromatography.

2. The fatty acid pattern of adipose tissue was closely related to dietary fat composition and, established in the first generation, did not change significantly in successive generations of rats.

3. Hydrogenated fat adversely affected litter size, sperm morphology and regularity of oestrous cycle, and prolonged the period of gestation in experimental animals. Differences observed between the generations were not significant.

4. Hydrogenated fat decreased the level of serum testosterone in males, but the differences observed in levels of serum progesterone in females were not apparently related to the dietary trans-fatty acids.

1. Male rats at 1 (young) and 9 months (adult) of age were fed on purified diets, supplemented with or without cholesterol, containing 200 g protein/kg (casein (CAS), whey protein (WHY) or soya-bean protein (SOY)) for 4 weeks.

2. SOY exerted a hypocholesterolaemic effect in young rats regardless of dietary cholesterol, whereas in adult rats it was observed only when a cholesterol-enriched diet was given. WHY was also hypocholesterolaemic in rats of both ages given cholesterol. SOY tended to reduce the liver cholesterol both in young and adult rats.

3. The liver hydroxymethylglutaryl-CoA reductase (NADPH) (EC 1.1.1.34) activity tended to be lower in the vegetable-protein groups than in the animal-protein groups in young rats, but the age-related reduction was observed only in the latter groups.

4. There was no significant age-related difference in the activity of liver cholesterol 7α-monooxygenase (EC 1.14.13.17) in response to diets. However, when cholesterol was given, activity tended to decrease with age. Rats given SOY excreted more faecal steroids than those given casein, particularly adult rats.

5. The fatty acid profile of phosphatidylcholine and the Δ6-desaturase activity of liver microsomes indicated the reduced desaturation of linoleate in the SOY and WHY groups compared with the CAS groups.

6. The results thus showed a complex interaction of protein type, cholesterol and age on cholesterol homeostasis.

1. Bile acids were analysed in the bile and lumen samples of rats which received a cholesterol-free or cholesterol-enriched (5 g/kg) diet free from fibre, or containing cellulose or citrus pectin at the level of 100 g/kg.

2. Dietary pectin but not cellulose increased biliary bile acid concentration and excretion. Dietary cholesterol did not affect biliary bile acids quantitatively.

3. Biliary bile acids were almost exclusively conjugated with glycine or taurine in the various experimental situations. The predominant portion of bile acids in rats fed on the cholesterol-free diet was conjugated with taurine when the diet was either free from fibre or contained cellulose; the ratio of bile acids conjugated with glycine: those conjugated with taurine (G:T) was less than 0·2. In contrast, with pectin as a fibre source, the conjugation with glycine increased enormously (G:T increased to approximately 4). Cholesterol enrichment of the diet also increased the glycine conjugation in all groups of rats. Even in this situation, the G:T was highest in rats fed on pectin.

4. Pectin, but not cellulose, increased the bile acid content of the small intestine and caecum, both in rats fed on the cholesterol-free and cholesterol-enriched diets. Cholesterol feeding doubled the bile acid content of the caecum in rats fed on a fibre-free diet or a cellulose diet, but not in those fed on pectin. No such effect of cholesterol was observed in the small intestine, except for the ileal bile acid content in rats fed on cellulose.

5. A considerable portion of the bile acids in the small intestine was deconjugated. The extent of the deconjugation was higher in the ileum than in the jejunum. As in the bile, G:T in rats fed on pectin (3·5·5) were higher than those in the other groups (0·05–1·05) in various situations. Also, cholesterol feeding considerably increased the ratio in all groups of rats.

6. The observed dietary alteration of the partition of bile acids between glycine and taurine may be of physiological significance in regulating bile acid and lipid metabolism in rats.

1. Mn and Cu intake and retention in twenty full-term infants and six preterm infants were studied on the basis of 72 h balances. The age of the infants was 2–16 weeks and the gestational age of the preterm infants (triplets) 34 and 36 weeks. Three nutrition schemes were pursued: breast-fed, formula-fed with unsupplemented adapted formula and formula-fed with trace element supplementation.

2. The mean Mn concentration of all breast-milk samples (n 2339) was 6·2 μg/1. The two formulas had similar Mn concentrations (77 and 99 μg/1) but had different Fe, Cu (121 and 619 μg/1), Zn and I contents. The mean Cu concentration in mother's milk was 833 μg/1.

3. The following mean daily Mn intakes and retentions (μg/kg) respectively were measured: breast-fed fullterm 1·06 (sd 0·43) and 0·43 (sd 0·65), formula-fed full-term 14·2 (sd 3·1) and 2·8 (sd 4·8), formula-fed preterm 15·0 (sd 2·2) and 0·06 (sd 5·87). The results for Cu were 114·5 (sd 22·3) and 88·0 (sd 46·5) μg/kg in breast-fed, 19–8 (sd 4·2) and 4·6 (-11·5–9·6) in the unsupplemented formula-fed and 106·4 (sd 18·9) and 55·5 (sd 20·3) in the supplemented formula full-term infant group. No significant influence of the trace element contents of the formulas on the relative retention of Mn or Cu was found.

4. Young preterm infants, and to some degree young full-term infants, often had negative Mn balances caused by a high faccal excretion. The formulas with a Mn concentration below 100 μg/l gave a sufficient supply of Mn. Preterm infants fed on the unsupplemented formula had a marginal Cu supply and their first balances were negative (-3·8 (sd 1·8) μg/kg).

5. In accordance with the estimated safe and adequate daily dietary intakes (recommended dietary allowances), formula-fed infants receive much more Mn than breast-fed infants and their absolute retention is higher.

6. Cu from breast-milk had a significantly better biological availability than that from cow's milk formula. If retentions similar to those in breast-fed infants are intended, we conclude, therefore, that cow's milk formula should be fortified with Cu up to a level of at least 600 μg/l.

1. In vivo 59Fe absorption from intrinsically labelled Fe-containing fractions of liver and blood were measured in rats by intragastric dosing. All rats were fed on a low-Fe diet for 3 d before dosing in order to standardize the Fe status of the intestinal mucosal cells.

2. An increase in digestion time from 2 to 12 h increased 59Fe absorption (P < 0.01) from all fractions except ferritin.

3. Fe-deficient rats when compared with essentially Fe-replete rats showed decreased gastric retention for all fractions, but increased 59Fe absorption over 2 h only from ferritin. Ferritin showed several unusual absorption characteristics.

4. Dietary tungsten supplementation of Fe-deficient rats reduced the ferroxidase activity of intestinal mucosal xanthine oxidase. In addition, gastric retention and 59Fe absorption (P < 0.05) from all fractions were increased.

1. The effects of four diets on water intake, rumen fluid outflow-rate, rumen pH and mineral metabolism were studied in wether sheep. The diets were barley and hay, flaked maize and hay, dried grass and frozen grass.

2. Experimental periods were of 12 d duration, and plasma magnesium concentrations were lower at the end of treatment periods when the grass diets were given and were significantly different (P < 0.05) at 11.00 and 20.45 hours. Also, the concentration was significantly lower with the dried-grass diet than with the frozen-grass diet (P < 0.05).

3. The concentration of Mg in rumen fluid centrifuged at 30000 g (ultracentrifuged) varied with the diet. Maximum concentrations (tmax) were reached 4 h later on the grass diets than on the hay and concentrate diets. In the latter case tmax coincided with that for calcium, potassium, chloride and ammonia. At this time sodium and phosphate were at a minimum. The concentration of Mg in ultracentrifuged rumen fluid was negatively correlated (r −0.89) with pH, which was significantly higher (P < 0.01) at all times on the grass diets. This relation was also reflected in the apparent availability of Mg.

4. Total water intake on the frozen grass was about twice that on the barley and hay diet. The outflow rate of liquid from the rumen was higher on the frozen grass than on the other three diets.

5. The proportion of absorbed Mg excreted in urine was significantly influenced by diet.

1. In the first trial, hourly blood samples were drawn during the light period (06·30–20·30 hours) from thirtyfour dairy heifers in two groups of different ages.

2. Concentrations of serum folates were 8·2 (se 0·1) ng/ml at the age of 18·2 (se 0·6) d and 14·8 (se 0·2) ng/ml at 120·7 (se 2·9) d (P ≤ 0·001).

3. In the second trial, forty heifers were randomly assigned to a factorial experiment where age (2 weeks v. 4 months) and quantity of pteroylmonoglutamic acid injected intramuscularly (2·5, 5·0, 10·0 and 20·0 mg) were the two factors studied. Blood samples were taken immediately before injection and on days 1,2,3,4,7 and 10 after the injection.

4. Serum folates reached a maximum on day 1 after the injection of pteroylmonoglutamic acid. The response to the injection was different for the two age groups (P ≤ 0·0002); concentration of serum folates for 2-week-old heifers markedly increased, while in 4-month-old heifers the effect of a supplement of pteroylmonoglutamic acid was less marked.

5. These results might indicate a need for pteroylmonoglutamic acid in young animals during the development of rumen function.

1. Studies were carried out on the distribution of ascorbic acid in human fetal tissues with the progress of gestation.

2. Fetuses and stillborn babies varying in gestational age from 12 to 38 weeks were obtained from various Baroda hospitals. Ascorbic acid levels were determined in selected tissues: brain, adrenal, liver, kidney, lung, heart and placenta.

3. Ascorbic acid concentration in the brain was higher than that in the adrenal at all gestational ages, suggesting the importance of this vitamin in brain development. The concentrations of this vitamin in liver, kidney, lung and placenta were comparable, but that in the heart tended to be lower. In all the tissues, there was a fall in ascorbic acid during late gestation. However, the levels in tissues of stillborn babies were higher than those reported for adults.

1. Two experiments were conducted to determine whether or not high dietary levels of vitamin E affect the development of atherosclerotic lesions in aortas of cholesterol-fed (5 g/kg diet) rabbits that were mechanically deendothelialized by balloon catheterization.

2. In the first experiment, the aortas of rabbits fed 2000 mg vitamin E/kg diet (i.e. 50-fold their nutritional requirement) for 8 weeks showed no gross morphological differences, either within or outside experimentally damaged areas, from those of rabbits fed the nutritionally adequate control level (40 mg/kg) of the vitamin.

3. In the second experiment, rabbits fed 10000 mg vitamin E/kg diet (i.e. 250-fold requirement) for 14–15 weeks showed significantly greater endothelial loss and plaque formation at aortic sites outside of the mechanically damaged area than did controls. Plasma cholesterol levels were very high (9000–14000 mg/1) and were not affected by dietary vitamin E level until 10–12 weeks when they were reduced moderately (18%).

4. It is concluded that very high levels of vitamin E can potentiate spontaneous atherosclerotic lesions, and it is suggested that this effect may depend on high cholesterol status.

1. In vitro, pyridoxal phosphate extracts steroid-hormone receptors from tight nuclear binding (Cidlowski & Thanassi, 1981); in vitamin B6-deficient rats there is increased and prolonged nuclear accumulation of oestradiol in the uterus and testosterone in the prostate, associated with enhanced biological responsiveness of these target tissues to steroid hormone action (Symes et al. 1984; Bowden et al. 1986).

2. Slices of uterus from vitamin B6-deficient rats accumulated more [3H]oestradiol than did tissue from repleted animals. Acute repletion with vitamin B6 (0.5–1 h before killing) further increased the uptake of the steroid.

3. Isolated hepatocytes from vitamin B6-deficient rats accumulated more [3H]dexamethasone than did cells from repleted animals. Pre-incubation of the hepatocytes with pyridoxal phosphate resulted in a further increase in the uptake of the steroid.

4. The results suggest that in addition to the putative role of pyridoxal phosphate in releasing steroid-hormone-receptor complexes from tight nuclear binding (Cidlowski & Thanassi, 1981), vitamin B6 deficiency may also increase the concentration of steroid-hormone receptors or enzymes and other steroid-binding proteins in target tissues.