1. Metabolic balance studies (5 d) for Se were conducted in twenty-four apparently healthy elderly people (age 69·6–85·4 years), and twenty housebound subjects (age 69·9–85·1 years) with chronic disease. During the study the subjects lived in their own homes, ate self-selected diets and continued their normal daily activities.

2. Geometric mean daily dietary intakes of the two groups were significantly different (P < 0·01), being 819 (range 310–1631) nmol for the healthy and 475 (range 233–1136) nmol for the housebound elderly.

3. Daily intake of Se significantly correlated with balance in both groups. Solution of the regression equations gave theoretical daily requirements of 447 nmol for the healthy and 419 nmol for the housebound subjects. The healthy elderly were in positive balance of 148 nmol/d for Se and the housebound were in equilibrium with an overall mean retention of 43 nmol/d.

4. Mean levels of Se in blood fractions for the healthy and housebound subjects were significantly different, being 1·65 and 1·40 μmol/l whole blood, 1·45 and 1·21 μmol/l plasma and 5·72 and 5·30 nmol/g haemoglobin in erythrocytes respectively. There was no difference in the whole-blood glutathione peroxidase (EC 1.11.1.9) activities between the two groups.

5. There were clear differences in Se status between the two groups of elderly people. The cause of the positive balance in the healthy subjects remains unexplained.

1. Duplicate diet analysis for energy, protein, zinc and copper with estimates of biochemical status for Zn and Cu were undertaken in twenty-one elderly long-stay inpatients (mean age 82 (range 63–89) years) consuming their customary hospital diet and in a stable medical condition. Fourteen patients had a long-standing and significant healing problem, either a leg ulcer or pressure sore.

2. Mean daily intakes of energy (5·2 MJ), protein (45 g), Zn (85 μmol) and Cu (14 μmol) were low in comparison with both official recommendations and levels of intake at which metabolic equilibrium was observed in healthy elderly people studied by the same methods (Bunker et al. 1984a).

3. Mean leucocyte Zn (9 pmol/106 cells) and Cu (7·5 pmol/106cells) were low in comparison with results from healthy elderly people (Bunker et al. 1984a), implying suboptimal status for these elements. Those patients with healing problems tended to have the lower values within the range.

4. Recommendations are made with respect to improving nutritional status in this disadvantaged group of people.

1. Zinc metabolism has been studied in a group of undernourished, slum-dwelling, lactating women in Manaus, Brazil, by means of modified metabolic balance techniques and the stable isotope 67Zn.

2. The subjects were found to be consuming a diet which provided an average of 34% of the recommended dietary allowance for lactating women, but six of the seven appeared to achieve Zn balance. In five of the subjects use of 67Zn in a stable isotope dilution manner demonstrated that they were absorbing a high proportion of the dietary Zn (proportional absorption ranged from 0·59 to 0·84), suggesting an adaptation to the chronically low intake.

3. Two subjects had marginally low plasma Zn concentrations, although hair, urine and milk Zn contents were all within accepted normal values.

4. Preliminary findings on the rate of plasma Zn turnover and the size of the exchangeable body Zn pool obtained using 67Zn suggest that these subjects may have a reduction in both.

1. Radio-iron absorption measurements were performed in healthy volunteer subjects to assess the availability of fortification Fe added to various bread products.

2. When ferrous sulphate was used as a fortifier, Fe absorption from a traditional Egyptian flat bread (Baladi) averaged only 16% of that observed with European bread. This difference was attributed to the high extraction flour used to prepare Baladi bread.

3. The inhibiting effect of Baladi bread was largely eliminated by adding EDTA to the flour before baking.

1. The effect of partial replacement of meat protein with three different soya-bean-protein products on bile acid and cholesterol excretion was studied in seven ileostomy subjects. Four different test diets containing 60 g meat, rice and bread protein, or a replacement of 250 g protein/kg total dietary protein by soya-bean protein from soya-bean flour, soya-bean concentrate or soya-bean isolate, were randomly assigned to the subjects in 2-d periods.

2. Ileostomy contents were collected at 2-h intervals during the day and in one portion during the night, and immediately deep-frozen to avoid bacteriological degradation. Bile acids and cholesterol were quantified by gas-liquid chromatography.

3. No difference in daily excretion of bile acids and cholesterol was noted between test diets. Ileostomy sterol concentrations were lower when soya-bean products were fed.

4. Incorporation of moderate amounts of soya-bean products in solid diets does not seem to affect short-term sterol balance in man.

1. The effect of addition of guar gum (5 and 10 g/l) to a radiolabelled, homogenized, baked-bean test meal on the distribution of that meal in the gastrointestinal tract was investigated in groups of male rats killed at 25, 50, 100, 200, 300 and 400 min after gavage.

2. Addition of 5 and 10 g guar gum/l significantly increased the proportion of the meal remaining in the stomach at 25 and 50 min after gavage (P <0·01).

3. The heads of the control meal and meals containing guar gum reached the distal small intestine within 25 min after gavage but radioactivity was not observed in the caecum until 100 min after administration of each of the meals. Addition of guar gum (5 and 10 g/l) delayed caecal filling even though the head of each meal reached the caecum at the same time after gavage.

4. The geometric centres of guar-gum-containing meals were proximal to that of the control meal at all times after gavage.

5. The observed delay in the passage of a guar-gum-containing meal through the stomach and small intestine is probably due to the viscous nature of the meal resisting the propulsive and mixing effects of the gastrointestinal contractions, thereby reducing access of the glucose to the absorptive epithelium. This could contribute to the observed reductions in postprandial glycaemia seen in previous studies after incorporating guar gum into a meal.

1. In order to examine the interaction of dietary fat and carbohydrate in the regulation of lipid metabolism, we have studied hepatic and extrahepatic lipogenesis, and adipose tissue lipoprotein lipase (EC 3.1.1.34) in rats fed on one of the following diets: a fructose-based diet containing 0 (F0) or 150 g maize oil (F15)/kg, or a glucose based diet containing 0 (G0) or 150 g maize oil (G15)/kg.

2. The rats were meal-fed on the diets for 2 weeks after which the activities of a number of hepatic ‘lipogenic’ enzymes were measured and the activity of epididymal-fat-pad lipoprotein lipase. The activities of the lipogenic enzymes were: F0 > G0 > G15 > F15. Lipoprotein lipase activity was F0 = G0 = F15 = G15. The percentage of total body fatty acid synthesis which occurred in the liver was F0 > G0 > F15 > G15.

3. We conclude that fructose-induced hypertriglyceridaemia is primarily a result of the increased hepatic synthesis rather than decreased adipose-tissue lipoprotein lipase activity.

1. Weanling Wistar rats were pair fed for 10 weeks on a purified diet containing either normal or suboptimal quantities of magnesium (960 or 80 mg/kg respectively).

2. At week 2, hypomagnesaemia was accompanied by hypertriglyceridaemia, an increase in plasma cholesterol and a decrease in high-density-lipoprotein-cholesterol in animals fed on the Mg-deficient diet. At week 10, the increase in triglycerides observed in Mg-deficient animals was less marked while the increase in total cholesterol was more important.

3. During the whole experimental period, Mg-deficient animals never showed hypertension. At week 2, mean arterial blood pressure was significantly lower in Mg-deficient rats than in their respective controls, while heart rate was significantly increased. However, hypotension accompanied by tachycardia was a transitory phenomenon which appeared only in the early phase of deficiency.

4. Vascular reactivity was studied in vagotomized anaesthetized rats after ganglionic blockade with pentolinium and atropine sulphate. The reactivity to noradrenaline was significantly higher in Mg-deficient rats compared with pair-fed controls after 2 weeks on the experimental diet.

1. The objective of the present study was to determine the effects of two levels of folic acid and two levels of zinc in the diets of rats during pregnancy and lactation. It addressed, among other things, the question of whether an inhibitory effect of folic (pteroylmonoglutamic) acid on Zn absorption might result in a secondary Zn deficiency in either the dams or the pups.

2. A purified diet was given to four groups of female DNL (Norwegian) Hooded rats, before and during pregnancy and during lactation. It contained the four possible combinations of: no added folic acid or 100 μg added pteroylmonoglutamic acid/g, and 6·6 or 20·2 μg Zn/g. Pups and dams were killed on day 20 of gestation or on day 20 postpartum. Measurements of body-weights, food intakes, blood folate and tissue Zn levels were performed.

3. The group with low Zn and low folate intake had a satisfactory reproductive outcome, and there were only minor effects of the supplements on body-weights.

4. Additional folate greatly increased blood (erythrocyte and plasma) folate levels, but did not compromise tissue Zn concentrations. Zn supplementation also enhanced blood folate levels, for reasons which are not yet clear.

5. There was a moderate enhancing effect of the Zn supplement on Zn levels in the livers and kidneys of pregnant dams, and the kidneys of lactating dams.

6. If the conclusions can be extrapolated to humans, then the results provide some reassurance that a high folate intake from prenatal supplementation need not necessarily cause Zn depletion, and hence functional Zn deficiency in pregnant women and their offspring.

1. It has been suggested that deconjugation of food folates with pig kidney, compared with chicken pancreas, may increase measureable folate by approximately 50% (Phillips & Wright, 1983). Therefore deconjugation with conjugases from these two enzyme sources was optimized and compared. Folate was measured microbiologically with Lactobacillus casei (ATCC 7469) as the test organism at pH 5·6.

2. Treatment for 6 h with 200 mg pig kidney/200 mg sample was compared with the conventional assay employing overnight incubation with 20 mg chicken pancreas/5 g sample. Comparison of the deconjugation systems showed chicken pancreas to be superior for peas (Pisum sativum) and beans (Phaseolus vulgaris), while there was no difference for potatoes.

3. γ-Glutamyl hydrolase (conjugase; EC 3. 4.22. 12) treatment for 2 and 20 h with pig kidney and chicken pancreas was optimized for raw potatoes and green frozen peas. Treatments with pig kidney were conducted at pH 4·6, which is optimal, and at pH 5·2. There was no significant difference between 2 and 20 h treatments at pH 5·2. Treatments with chicken pancreas were conducted at pH 6·1. Treatment for 2 h was preferred as it resulted in significantly higher measureable folate activity in peas and potatoes, and because overnight treatment can be influenced by microbial production of folate.

4. With optimal treatment conditions the source of enzymes did not significantly influence measureable folate activity. Chicken pancreas is the traditional source of conjugase in Scandinavia and was preferred for deconjugation.

5. Chicken pancreas, 20 and 60 mg, was used for deconjugation of sixteen different food samples, each containing approximately 200 ng folate. Chicken pancreas at 60 mg/sample gave significantly higher results. Further addition of enzyme did not increase the folate values.

6. A combined amylase treatment using heat-resistant α-amylase (EC 3.2.1.1) during extraction to ensure the gelatinization of the sample, and glucan 1,4-α-glucosidase (amyloglucosidase; EC 3.2.1.3), along with the incubation with chicken pancreas to complete the digestion, was shown to give a small but significant increase in folate values of starch-containing samples.

7. Folate results using the recommended procedure are given for raw potatoes, wheat bran, rolled oats, wheat flour and dark rye bread.

8. Chicken pancreas was shown to contain equally high amounts of amylases as did the α-amylase and amyloglucosidase sources. This finding may explain the relatively small benefit of a specific amylase addition.

1. Young male rats were fed on diets containing 3·4, 36 or 411 mg zinc/kg for 10 weeks in order to determine whether effects of Zn deficiency on plasma and liver essential fatty acid composition could be distinguished from those of reduced protein and energy intake.

2. Fatty acid analysis revealed that a Zn intake of 3·4 mg/kg (plasma Zn 0·80 v. 1·97 mmol/l in controls fed on 36 mg Zn/kg) resulted in a significant increase in the linoleic acid: arachidonic acid ratio in both plasma and liver phospholipids in comparison with rats fed on 36 or 411 mg Zn/kg.

3. Zn supplementation (411 mg/kg) decreased the linoleic acid: arachidonic acid ratio in plasma phosphatidylserine compared with that of the controls.

4. The previously reported increase in arachidonic acid (mol %) in liver triacylglycerol of Zn-deficient rats was shown to be a function of a reduced liver triacylglycerol pool size; quantitatively, triacylglycerol content of arachidonic acid in the liver was not significantly affected by Zn intake.

1. Incubation of isolated rat hepatocytes with nicotinamide or nicotinic acid showed that while both vitamers were taken up from the incubation medium, neither was utilized to any significant extent as a precursor of the nicotinamide nucleotide coenzymes, NAD and NADP, and neither was capable of preventing the loss of nucleotides that occurs on incubating the cells.

2. Incubation of hepatocytes with tryptophan showed that de novo synthesis from tryptophan permitted replacement of the nucleotides lost during incubation; at high concentrations of tryptophan there was an increase above the initial intracellular concentration of NAD(P). Incubation of hepatocytes with tryptophan also resulted in the formation and release from the cells of a considerable amount of niacin, as well as the two principal metabolities of NAD(P), N1-methyl nicotinamide and methyl pyridone carboxamide.

3. It is suggested that, in the liver, preformed niacin is not utilized for nucleotide synthesis, and indeed the function of the liver appears to be synthesis of niacin from tryptophan, and its release for use by extrahepatic tissues that lack the pathway for de novo synthesis of nicotinamide nucleotides from tryptophan.

1. The effects of intravenous trithiomolybdate administration on the fate of 64Cu and on stable Cu metabolism were examined in sheep held in metabolism cages and fed on a low-Cu diet supplying 2·95 mg Cu/animal per d.

2. In Expt 1 the injection of trithiomolybdate, 30 mg molybdenum/sheep per d for 5 d, greatly increased plasma Cu levels and more than doubled the faecal Cu excretion. Urinary Cu excretion was unaffected. The disappearance from plasma of 64Cu injected during the trithiomolybdate administration was slowed although faecal 64Cu excretion was increased more than threefold.

3. In Expt 2 trithiomolybdate, 10 and 30 mg Mo/sheep per d for 3 d, was administered 22 h after the injection of 64Cu. Radioactivity reappeared immediately in plasma and faecal 64Cu excretion was increased.

4. In both experiments the 64Cu and the increased stable Cu in plasma were associated with albumin.

5. The experiments explain the effectiveness of thiomolybdates as ‘decoppering’ agents and provide a model for some of the systemic effects seen in ruminants exposed to increased dietary Mo. The experiments support the view that the thiomolybdates, by causing the appearance of new ligands, alter the distribution of Cu in tissues and cause an overall depletion.

1. The nature of the digestion-inhibiting substance in Kikuyu grass (Pennisetum clandestinum, Hochst), containing high levels of nitrate, was investigated using in vitro digestibility techniques.

2. Nitrite, which accumulated during the reduction of nitrate to ammonia, seemed to be the primary factor reducing digestibility. Nitrate and ammonia did not affect digestion in vitro.

3. Nitrite caused a reduction in the cellulolytic, xylanolytic and total microbial population, with a concomitant reduction in cellulase and xylanase activity of the digesta.

4. The mode of action of nitrite on rumen microbial growth was investigated.

5. The possibility that the growth of cellulolytic rumen microbes was depressed by a reduction in concentration of essential branched-chain volatile fatty acids by nitrite was discounted.

6. Although nitrite caused a marked increase in the redox potential, due to its oxidizing properties, the more-positive redox potential did not reduce the digestibility of the grass.

7. The growth of three of the four major cellulolytic bacteria commonly found in the rumen was severely depressed by nitrite, while some rumen bacteria were relatively insensitive to nitrite.

8. Growth inhibition seemed to depend primarily on the extent to which these microbes derive their energy from electron-transport-mediated processes.

9. It was suggested that, due to the sensitivity of some rumen bacteria to nitrite, digestibility and therefore animal performance could be affected long before clinical symptoms of nitrite toxicity become apparent.

1. Wistar rats were fed on a control semi-synthetic diet throughout pregnancy, or a control diet in the first 2 weeks and a marginal-zinc diet in the 3rd week of pregnancy. On day 20, after an overnight fast, half the animals in each group were given glucose by gavage and the 0–30 min rise in blood glucose measured in tail blood. After 60 min blood was taken by cardiac puncture for glucose and insulin assay. Maternal pancreases were removed and the Zn contents measured. Fetuses from each litter were combined for wet/dry weights, protein and DNA determinations.

2. Plasma insulin concentration was higher, and glucose concentration and pancreatic Zn content lower, in pregnant v. non-pregnant animals of similar age, fed on the same diet. Pancreatic Zn content was lowest in the marginal-Zn group of pregnant rats. Fetuses from mothers fed on the marginal-Zn diet during the last week of pregnancy were slightly heavier than controls and had a significantly higher protein: DNA ratio. The 0–30 min rise in blood glucose was significantly greater in the marginal-Zn animals.

3. In a second experiment, pregnant rats were given similar diets to those used in the first study, but the marginal-Zn diet was given for a shorter period (days 15–19 of pregnancy). On day 19 the rats were meal-fed and on day 20, after an overnight fast, an oral glucose dose was administered. Tail-blood was taken at timed intervals up to 60 min post-dosing for glucose assay. Both maternal and fetal blood glucose and insulin concentration was measured 70 min post-dosing.

4. Values for maternal and fetal blood glucose and plasma insulin, measured 70 min after the administration of a glucose dose, were similar in the two groups, but the initial rise in blood glucose concentration was again significantly higher in pregnant rats given the marginal-Zn diet towards term.

5. It is suggested that the change in growth and composition, observed in fetuses from rats given a marginal-Zn diet in later pregnancy, is associated with altered maternal carbohydrate metabolism.

1. In vitro leucine catabolism in adipose tissue, skeletal muscle, kidney and liver homogenates was studied in sheep.

2. In Expt 1, Suffolk × Targhee ram lambs were slaughtered at 1, 28, 56, 84, 112, 140, 168, 196, 224 and 365 d of age. In Expt 2, 5-month-old crossbred wethers were fed on 80, 120 or 180 g crude protein (nitrogen × 6·25) /kg diets for 4 weeks or fed on 120 g crude protein/kg for 4 weeks and then fasted for 48 or 96 h before slaughter. Leucine catabolism was assayed in tissue homogenates for Expts 1 and 2.

3. Leucine deamination (per unit protein) was highest in skeletal muscle at day 1 and then declined; liver exhibited an activity pattern akin to muscle while kidney activity tended to rise over the duration of the study. Adipose tissue in vitro leucine deamination was higher at all ages studied and 9- to 50-fold higher than all other tissues at 365 d. Leucine decarboxylation (per unit protein) was highest at day 1 in muscle and declined to low levels (P < 0·01) after 28 d; liver and kidney decarboxylation activities were higher than muscle at all ages with kidney showing the highest activity. Whilst adipose had high initial activity it declined significantly (P < 0·01) by day 28 and remained low.

4. Dietary protein intake had no effect on leucine deamination in any tissue. Leucine decarboxylation tended to increase with protein intake for all tissues except kidney. Length of fast (96 h) resulted in a variable decline in leucine deamination; leucine decarboxylation was significantly lower in kidney, liver and adipose tissue after a 96 h fast.

5. When these in vitro enzyme activity results are related to questions concerning the role of skeletal muscle in leucine catabolism in sheep, the present findings indicate that in grown sheep, skeletal muscle has a small to moderate role in total body leucine deamination but plays a very minor role in leucine decarboxylation. Adipose tissue appears to be a major site of leucine deamination in grown sheep. These results are not in agreement with the idea that during fasting leucine becomes an important energy substrate and is oxidized in skeletal muscle as has been shown in rodents.

1. Studies of gastric function were made in preruminant calves fitted with a single abomasal cannula, re-entrant cannulas in the duodenum close to the pylorus and recording electrodes on the pyloric antrum and proximal duodenum.

2. Simultaneous measurements were made of gastric emptying of a saline (9 g sodium chloride/1) meal, myoelectric activity of antral muscle and plasma concentration of somatostatin in jugular blood whilst infusing the duodenum with different solutions. The duodenal infusates were isotonic sodium bicarbonate (300 mosmol/kg), hyperosmolar solutions of NaCl (1000 mosmol/kg), sodium carbonate (500 mosmol/kg), sucrose (1000 mosmol/kg), 41 g emulsified butterfat/kg or 60 mM-hydrochloric acid.

3. Infusing the duodenum with isotonic NaHCO3 stimulated intense myoelectric activity of the antral smooth muscle and rapid emptying of the test meal. In contrast, infusions of 60 mM-HCl reduced antral motility and inhibited gastric emptying of digesta. This inhibitory response to HCl infusion was related to a significant (P < 0·05) increase of somatostatin in peripheral venous blood.

4. The Na2CO3 infusate, like HC1, inhibited gastric motor activity and digesta emptying, but the concentration of circulating somatostatin was only slightly elevated above pre-infusion levels.

5. Compared with the effects of infusing HCl, infusions of emulsified butterfat or hyperosmolar NaCl and sucrose induced a greater intensity of antral motor activity and faster outflow of gastric effluent, although not to the same extent as with isotonic NaHCO3. However, as with isotonic NaHCO3, these infusates did not evoke the release of somatostatin.

6. The results support the concept of duodenal receptors which, in response to a variety of stimuli in gastric chyme, modulate stomach emptying of digesta through actions on contractile processes of antral smooth muscle. Activation of such receptors by fat or osmotic stimuli, both ionic and non-ionic, do not appear to involve the release of somatostatin. However, the hormone appears to have an entero-gastrone role in mediating the inhibitory action of HCI on gastric motor function.