1. Seven pigs of 30 kg initial live weight were fitted with re-entrant cannulas in the terminal ileum. Each was fed, in succession, four purified diets having cellulose and sodium levels (g/kg) of 30 and 2.7, 30 and 0.9, 90 and 2.7 or 90 and 0.9, respectively. Collections of digesta (24 h) and 3 or 4 d collections of faeces were made.

2. There was a greater throughput of ileal digesta with the high-cellulose diets than with the low-cellulose diets, mainly due to increased water content, and there was a concomitant reduction in the net absorption of Na from the small intestine. The immediate response to reduced Na intake was increased secretion of Na into the gut lumen anterior to the terminal ileum; this was more pronounced with the high-cellulose diet. Na concentrations in ileal digesta were very similar for all four diets.

3. The apparent absorptions of calcium, phosphorus, magnesium, potassium and zinc were reduced by the high-cellulose diets. In each instance this was due to reduced absorption posterior to the terminal ileum.

1. A prospective randomized study of two dietary regimens has been started in newly-diagnosed diabetics to determine their effect on circulating metabolites and on diabetic complications.

2. During the first year of treatment the fasting plasma glucose concentrations on both the low-carbohydrate diet and the high-carbohydrate, modified-fat (MF) diet showed a similar decrease.

3. Plasma cholesterol showed a sustained decrease only in patients recommended a MF diet. Transient changes in plasma triglyceride concentrations occurred in patients on both dietary regimens.

4. Increased plasma cholesterol levels are associated with atheromatous disease which is common in diabetics in Europe and North America. A MF diet may therefore have an advantage in that it lowers the plasma cholesterol as well as being effective in lowering the plasma glucose.

1. The effect of caffeine (2.5 g/kg diet) on lipid metabolism was examined in rats fed on a stock (low-cholesterol) diet or on a cholesterol plus cholic acid-supplemented (high-cholesterol) semi-synthetic diet.

2. When caffeine was included in the stock diet fed to rats for 7 d, there was a moderate but significant increase in the concentration of serum cholesterol compared to the levels observed in the control rats. This change can be accounted for by the increase that was observed in the rate of cholesterogenesis in the liver.

3. After 25 d of caffeine in the stock diet, hepatic cholesterogenesis was still increased but the concentration of serum cholesterol was now the same as in the control rats. During the experimental period there was a progressive increase in the faecal excretion of neutral sterols in the rats receiving caffeine.

4. When caffeine was added to a cholesterol plus cholic acid-supplemented diet, there was a marked increase in the concentration of serum cholesterol but hepatic cholesterogenesis was now reduced.

5. Caffeine in the high-cholesterol diet appeared to delay, but probably did not reduce, the absorption of an oral dose of radio-labelled cholesterol. This conclusion was confirmed using rats which had not previously received either caffeine or cholesterol in the diet.

6. When the effect of caffeine in the high-cholesterol diet was investigated during a 24 h period, an exacerbation of the hypercholesterolaemia was seen only at certain times.

7. After a 4-month period of feeding rats on the caffeine-supplemented high-cholesterol diet, histological examination did not detect any damage to the heart and aorta.

8. The metabolic regulations involved in the effects of caffeine in the two diets are discussed and the relevance of the present results to observations made with human subjects is considered.

1. Blood pyruvate carboxylase (pyruvate-CO2 ligase (ADP-forming); EC 6.4.1.1; PC) activities in young chickens and turkeys given low-biotin diets supplemented with biotin at graded levels were studied in three experiments.

2. In both species PC activity was related positively to the supplemental biotin level. The relationship was sigmoid and maximum activity was attained with supplemental levels above those required to give maximal growth response.

3. Enzyme activity decreased between 2 and 4 weeks of age but remained almost constant thereafter.

4. Activity in chicks was not affected by alterations in the fat or protein content of the diet.

5. Changing poults from high to low and from low to high supplemental biotin levels resulted in reversals in the levels of enzyme activity.

6. It is concluded that blood PC activity is a promising new criterion for assessing the biotin status of young chickens and turkeys.

1. Plant foods, especially green leafy vegetables, are the cheapest and richest source of calcium in developing countries and are recommended in balanced diets. Hence it was worth while obtaining further information about the availability of Ca from these commonly-consumed green leaves.

2. The green leafy vegetable belonging to Amaranthus spp. was taken as a suitable experimental model because it is not only commonly-consumed, but is also rich in Ca and oxalates. In the first experiment, each of the eight adult male subjects was given a basal diet containing negligible Ca, a milk diet and an ‘Amaranthus’ diet, both containing the same amount of Ca. These diets were given on 3 consecutive days and the urinary Ca excreted in a 6 h period after the test diet was considered an approximate index of Ca absorbed in that period. The second experiment was designed to study the influence of Amaranthus spp. on the availability of milk Ca. Each of the ten adult male subjects were given a basal diet, a milk diet and a diet containing the same amount of milk with Amaranthus spp. added to it. Urinary Ca excreted in a period of 6 h was estimated.

3. While availability of Ca from milk was good, that from Amaranthus leaves was low. The ingestion of Amaranthus leaves together with milk adversely affected the absorption of milk Ca.

4. In view of these findings, recommendation of green leaves as a regular source of Ca to the vulnerable section of the Indian Community should be considered with caution. Since green leaves are a main source of other nutrients, especially β-carotene, their consumption cannot be discouraged and hence leaves low in oxalates should be recommended.

1. Male Wistar rats were given isoenergetic, semi-synthetic diets deficient in thiamin, riboflavin, pyrid-oxine or all the B-vitamins.

2. In rats given these deficient diets the ‘sleeping time’ induced with pentobarbital (PB) and the ‘paralysis time’ with zoxazolamine (Zz) were prolonged.

3. The tolerance effect against both drugs was nearly independent of the levels of B-vitamins in the diets.

4. In preparations from vitamin-B deficient animals the activities of the following hepatic microsomal enzymes were reduced: the aliphatic hydroxylase of PB, the aromatic hydroxylases of aniline (EC 1.14.14.1) and of Zz, the N-demethylase of aminopyrine, the UDP glucuronyltransferase (EC 2.4.1.17) of p-nitrophenol. The reactions most influenced were those of ‘type-1’ substrates, particularly those involving the hydroxylases.

5. The effects observed were caused mainly by deficiency of riboflavin and to a lesser extent of thiamin or pyridoxine.

1. A calorimeter for the continuous measurement of heat production and heat loss in the human subject, for at least 24 h, is described. The calorimeter operated on the heat-sink principle for direct calorimetry and an open-circuit system for indirect calorimetry.

2. Sensible heat loss was measured using a water-cooled heat exchanger, and the temperature of water entering the heat exchanger was controlled to maintain a mean temperature gradient of zero across the chamber walls.

3. Evaporative heat loss was determined from ingoing and outgoing wet-and-dry bulb temperatures and air flow-rates.

4. Problems associated with the calculation of evaporative heat loss and the estimation of the volume of incoming air in open-circuit systems are considered.

5. The calibration, limits of accuracy, sources of error and experiments with subjects are discussed.

1. Deficiency of zinc inhibits growth and also increases the activity of alkaline ribonuclease in certain tissues of the rat (Prasad & Oberleas, 1973). Zn could influence ribonuclease activity by direct effects on the enzyme or its natural inhibitor, or non-specifically as occurs when growth rate is affected by various other factors. These possibilities were studied.

2. Alkaline ribonuclease was shown to be inhibited by Zn in vitro, but the concentrations of Zn required were so high that the enzyme was probably not directly affected by changes in tissue Zn concentration caused by dietary deficiency.

3. At lower concentrations, Zn added in vitro increased the activity of alkaline ribonuclease in tissue homogenates probably by inactivating the inhibitor of the enzyme.

4. Age, weight and particularly food restriction caused tissue-specific alterations of ribonuclease and ribonuclease inhibitor concentrations in liver, kidney, oesophagus, testis and thymus.

5. The ribonuclease activities in liver, kidney and testis of Zn-deficient rats were unaltered in comparison with those of pair-fed rats. In thymus, which decreased in weight in the Zn-deficient animals, there was a concomitant increase in ribonuclease activity, but in oesophagus, the deficiency reduced the activity of ribonuclease.

6. The effects of Zn deficiency upon alkaline ribonuclease and its inhibitor are probably secondary consequences of reductions in food intake or growth.

1. Leucocyte ascorbic acid concentrations have been measured in 1147 females during early pregnancy and in smaller numbers of women before conception, throughout pregnancy and at 6 months post partum.

2. The leucocyte concentration in the 1st trimester was found to be affected by season, social class and smoking. Selecting individuals by extremes of social class, season and smoking produced two small populations with almost separate ascorbic acid distributions and mean concentrations of 21.7 and 45.1 μg/108 leucocytes.

3. Early pregnancy had little effect on leucocyte ascorbic acid concentrations but values decreased in the second trimester. However, this was associated with a leucocytosis so that the total leucocyte ascorbic acid content of blood was unchanged.

4. Low ascorbic acid concentrations during the 1st trimester were not associated with subsequent spontaneous abortions, still-births or neonatal deaths, but there was an increased frequency of low values in women who gave birth to infants smaller than 3250 g.

5. The adequacy of ascorbic acid reserves in early pregnancy is discussed.

1. Serum ferritin concentrations were measured in 378 Zulu children aged 1–4 years living in Nqutu, KwaZulu and in 342 children of mixed race (Cape coloureds) aged between 1 and 16 years living near Johannesburg.

2. The pattern of serum ferritin concentrations encountered in the children at different ages tended to parallel the changes in iron stores which are known to occur during development.

3. Serum ferritin concentrations showed a significant direct correlation with age, haemoglobin, serum Fe and percentage saturation of transferrin values.

4. Anaemia was most prevalent in the younger children. Of the rural and urban children aged 13–24 months 60 and 53% respectively were anaemic while only 11% of those over 24 months had haemoglobin concentrations that were below normal.

5. The prevalence of anaemia among children who had serum ferritin values below 12 μg/l was only slightly higher than that for the groups as a whole (38.8 % v. 24.3%), while the prevalence in those with values of 12 μg/l or more was only slightly less (18.2%). However, when a ferritin concentration of less than 12μg/l was associated with a percentage saturation of transferrin of less than 16%, the prevalence of anaemia was 70.0%, and only 10.2% of children in whom both values were within the normal range were anaemic.

6. Since 67% of children had either a normal serum ferritin and a normal percentage saturation of transferrin or both values below the normal range, the two measurements taken together provided a useful means of separating the children who had significant Fe deficiency from those whose Fe stores were sufficient to make the appearance of anaemia unlikely.

1. Pelleted diets containing concentrates and 0, 200, 400 or 600 g chopped straw/kg were fed ad lib. for 5 h daily to four cows. Concentrations of various energy-yielding metabolites were measured in samples of rumen fluid and jugular blood taken before feeding and at intervals after food was offered.

2. After feeding, the pH of rumen fluid decreased rapidly and the total concentration of volatile fatty acids (VFA) increased; the changes were greatest in the diet containing no roughage. The changes were essentially complete by 135 min at approximately the time feeding stopped. Rumen lactate concentrations were always low and increased significantly only in cows given no roughage.

3. There were highly significant relationships between the peak rumen acetate concentration after a meal and the apparent digestibility of the dry matter of that meal, and the amount of material in the rumen at the end of a meal. The latter relationship resulted in there being no difference between treatments in the total amount of acetate present in the rumen after feeding.

4. In the blood, concentrations of acetate, propionate, β-hydroxybutyrate (BHB) and lactate all increased after feeding. The increase was prolonged and maximum values were rarely reached before 4–5 h. The highest concentrations of acetate and BHB were found in cows given 200 g roughage/kg and were twice as great as those in cows given no roughage; lower concentrations were found in cows given 400 or 600 g roughage/kg. This information, together with the rumen concentrations of acetate and butyrate, was interpreted as indicating an inhibition of VFA absorption from the rumen of cows given no roughage.

5. Plasma glucose concentrations decreased rapidly for 4 h after feeding, the decrease being greatest in cows given 200 g roughage/kg. Non-esterified fatty acid concentrations also decreased after feeding 200 and 0 g roughage/kg rations, but concentrations were not high at any time.

6. It is concluded that chemical changes in the rumen correspond to feeding behaviour much more closely than changes in blood and therefore any chemostatic regulation of food intake probably occurs at the former site, with acetate playing a major role. Monitoring energy balance at tissue level is likely to be mediated hormonally, with insulin an important factor.

1. The amount of selenium in nationally representative samples of prepared and cooked groups of foods, and in a variety of raw individual foods, was determined fluorimetrically.

2. The average British diet was calculated to provide approximately 60 μg Se/d, of which half was derived from cereals and cereal products and another 40% from meat and fish. Milk, table fats, fruit and vegetables provided little or no Se.

3. Individual foods which were particularly rich in Se (>0.2 mg/kg) included ‘bread-making’ and wholemeal flours, kidney, fatty fish, brazil nuts (Bertholletia excelsa) and several other varieties of nut. In contrast, breast milk and other foods for babies (except some cereal products) contained little Se.

4. The total intake, and the amounts of Se in major foods, were lower than in most other studies. This is probably the result of the comparatively low levels of this element in British soil.

1. Urinary and faecal excretion of single oral doses of 1 mg selenium or 0.1 mg Se as selenomethionine (Semet-Se) in solution were studied in two women. Most of the Se was absorbed and little was eliminated in the urine (0.05–0.22 dose).

2. The results have been compared with those from an earlier study (Thomson, 1974) on the same two women after similarly sized doses of sodium selenite (selenite-Se) in solution. Although selenite-Se was almost as well absorbed as Semet-Se more was excreted in the urine (0.41–0.85 dose).

3. Repeated dosing with 1 mg selenite-Se on five consecutive days in one of the women indicated that 1.1 mg had been retained.

4. Twenty patients with muscular complaints from Tapanui (South Otago, New Zealand), a low-Se soil area, ingested 0.5 mg selenite-Se daily for 20 d. Blood Se increased rapidly to almost twice the initial concentration but reached a plateau well below most values reported for residents outside New Zealand. No difference in blood Se concentration was found between those who did or did not report improvement.

5. Spasmodic medication with selenite-Se by some residents near Lincoln (Christchurch, New Zealand) for periods of up to 10 years or more had increased the blood Se somewhat.

1. Chicks, 3-d-old, of a heavy breed (HB) and a light breed (LB) were overfed for 18 d. The activities of acetyl-CoA carboxylase (EC 6.4.1.2; CBX), fatty acid synthetase (FAS), ATP citrate lyase (EC 4.1.3.8; CCE), NADP-malate dehydrogenase (decarboxylating) (EC 1.1.1.40; ME), 6-glucose-6-phosphate dehydrogenase (EC 1.1.1.49; G6PDH) and phosphogluconate dehydrogenase (EC 1.1.1.44; 6PGDH) were determined in abdominal adipose tissue (AT) and liver samples of overfed and ad lib.-fed chicks. Size and fat content of liver and adipose tissue were also determined in order to evaluate the extent of obesity.

2. On ad lib.-feeding HB chicks consumed more food, gained more weight and deposited more fat than the corresponding LB chicks. Their lipogenic enzymes were more active than in the LB chicks in both adipose tissue and liver. The increase in food consumption (%) that could be achieved by overfeeding was three times greater in the LB chicks than in the HB chicks.

3. Overfeeding increased the weight and fat content of liver and AT in both breeds. The specific activities of CBX, FAS, CCE and ME in liver and AT increased in the LB chicks only and the total activities of liver and AT enzymes increased much more in the LB chicks than in the HB chicks in which the increase was derived mainly from tissue enlargement.

4. The activity of the pentose cycle dehydrogenases was very low in liver, but in AT about one third of the NADPH generating capacity could be accounted for by these dehydrogenases.

5. The results show that lipogenic enzymes of chicks respond to an increased substrate flux. It is suggested that the enlarged liver, the higher participation of AT in lipogenesis and the uninterrupted supply of cropstored excess food enable the chick to accommodate the increased amounts of substrate with only moderate enzymic adaptation.

1. The body compositions of obob and lean (ob+ and + +) mice at 10, 12, 17 and 28 d of age were investigated using a ‘cold stress’ test to identify the two groups.

2. At each of these ages the obob mice were found to contain significantly more fat than the lean. At 10 d 20 % more fat was present and by 17 d the increase was 72 %. The obob mice at 28 d contained nearly three times as much fat as the lean.

3. Carcass energy was significantly higher in obob mice at all ages investigated.

4. Other changes in body composition found in the 28 d obob mice, i.e. a reduction in total carcass nitrogen and water content, were already established in the 17-d-old mice but differences at 10 and 12 d were not apparent.

5. The livers of obob mice were significantly heavier than those from lean control mice at 28 d but no differences were detected at the earlier ages.

6. The results are discussed with reference to the early origin of obesity in obob mice.

1. The effects were examined of two approximately isoenergetic diets differing widely in saturated fat content on the levels of serum cholesterol and triglycerides of nomads and non-nomads in eastern Niger. Each person was also examined for clinical and electrocardiographic evidence of heart disease.

2. No significant differences could be found between serum cholesterol and triglyceride levels of 297 Anagamba nomad men consuming 73 % energy as fat and 303 Kanouri sedentary men consuming 9 % energy as fat.

3. Rheumatic heart disease was common in nomads and four possible cases of ischaemic heart disease were found in sedentary men only.

1. The daily intake of selenium by three subjects was supplemented with 100 μg Se as selenomethionine (Semet-Se) or sodium selenite (selenite-Se)/d for 10–11 weeks, or with 65 μg Se as in mackerel (Scomber japonicus) (fish-Se)/d for 4 weeks.

2. Urinary and faecal excretion of Se was measured and also Se concentration in whole blood, plasma and erythrocytes. Measurements on blood were made at intervals after supplementation had ceased.

3. Selenite-Se was not as well absorbed (0.46 of the intake) during the first 4 weeks as Semet-Se (0.75 of the intake) and fish Se (0.66 of the intake).

4. Blood Se increased steadily with Semet-Se, from 0.08 to 0.18 μg Se/ml, but more slowly with selenite-Se, reaching a plateau in 7–8 weeks at 0.11 μg Se/ml. Plasma Se increased more rapidly with Semet-Se than with selenite-Se, so that initially with Semet-Se plasma Se was greater than erythrocyte Se.

5. Daily urinary excretion increased with all forms of supplement, with initially a greater proportion of absorbed selenite-Se being excreted than Semet-Se or fish-Se. A close relationship was found between plasma Se and 24 h urinary excretion. The findings suggested that there was a rapid initial excretion of presumably unbound Se then a slower excretion of residual unbound, loosely bound or bound Se.

6. Total retentions of 3.5 mg selenite-Se and 4.5 mg Semet-Se were large when compared with an estimate of body content of 6 mg Se, derived in another paper (Stewart, Griffiths, Thomson & Robinson, 1978). Retentions of Semet-Se and fish-Se appeared to be reflected in blood Se, whereas for selenite-Se, blood Se reflected retention for only a short period after which Se appeared to be retained without altering the blood Se. This suggested that Semet-Se and selenite-Se were metabolized differently.

7. A double blind-dosing trial with 100 μg Semet-Se was carried out for 12 weeks on twenty-four patients with muscular complaints in Tapanui, a low-Se-soil area. Blood Se increased in the experimental group (from 0.067 to 0.143 μg Se/ml); clinical findings were not conclusive and will be presented elsewhere.

8. Blood Se was measured in New Zealand residents before travelling to Europe or to North America. On return their blood Se was increased, and depending upon the period of time spent outside New Zealand some values reached concentrations found in visitors and new settlers to New Zealand.

9. The results from these studies and the earlier studies of single and multiple dosing have been used to look at the various criteria in use for assessing Se status of subjects. It is suggested that plasma Se be used in preference to 24 h urinary excretion, and in addition to whole blood Se and glutathione peroxidase (EC 1.11.1.9) activity.

Fat-free body mass is an important component of body composition which is of particular interest to nutritionists and related workers. Fat-free mass has been determined from the simple measurement of skinfold thickness and it has been demonstrated that there is a close correlation with total body nitrogen even though the test subjects had a wide range of nutritional status.

1. Three sheep, each fitted with a ruminal cannula and duodenal re-entrant cannulas were given three isonitrogenous, isoenergetic diets in a Latin-Square design. Each diet contained (/kg) approximately 400 g N as white fish meal, soya-bean meal or urea and approximately 600 g dry matter (dm) was barley grain. The diets were fed continuously and supplied about 28 g N/d.

2. Total duodenal digesta was collected manually for 72 h and the proportions of microbial N in that digesta were simultaneously estimated for all sheep using RNA, radioactive sulphur (35S), diaminopimelic acid (DAPA) and aminoethylphosphonic acid (AEPA) as markers.

3. Three of the estimation methods showed that the variable source of dietary N had the greatest (RNA P < 0.05, 35S P < 0.005, DAPA P < 0.1) effect on the proportions of microbial N in duodenal digesta, though differences between sheep accounted for some variation.

4. These methods also ranked the diets in the order: urea > soya-bean meal > fish meal with respect to the proportions of digesta N that were microbial in origin; the respective mean values for these diets with the different markers were: RNA 0.98, 0.70, 0.56; 35S 0.92, 0.64, 0.54; DAPA 0.80, 0.47, 0.42.

5. AEPA was found to be present in substantial quantities not only in isolated rumen protozoa, but also in dietary and bacterial material; an observation that invalidated its further use as a protozoal marker.

6. Calculations using values obtained from the 35S procedure showed that the proportions of dietary N degraded within the rumen were 0.38, 0.43 and 0.89 for the white fish meal, soya-bean meal and barley respectively.

7. The marker methods are compared and their advantages and disadvantages (real and apparent) are discussed. It is concluded that where microbial N estimates of a more general and comparative nature are required, the use of RNA as a marker is probably adequate. Where information for more exacting purposes is required, the use of 35S appears to be more appropriate.

1. New Zealand White (NZW) rabbits were given, between 4 and 8 weeks of age, a range of diets, based on oats and fish meal, containing from 104 to 255 g crude protein (nitrogen × 6.25; CP)/kg to establish the level of CP below which growth was retarded.

2. In three experiments each diet was fed to four animals and food intake, growth and N balance were measured over 4 weeks. Body analysis was also carried out after two of the experiments.

3. The rates of food intake and growth of animals increased with dietary CP concentration until a CP concentration of approximately 150 g/kg diet had been reached. Beyond this there was little further improvement. N balance studies showed that once this dietary concentration of CP had been reached, there was a reduced rate of N retention.

4. Good agreement was found between N retention measured by balance methods and by body analysis: body composition showed a tendency towards an increase in fat and a decrease in N as the dietary protein concentration was reduced.

5. Microbial protein produced in the caecum and eaten during coprophagy, was found to supplement the dietary protein by approximately 2 g CP/d, or by only 0.1 of a normal dietary intake of CP.

6. In the second part of the study NZW rabbits were offered, between 5 and 8 weeks of age, diets based on oats containing 150 g CP/kg. The protein supplied by oats was supplemented with maize gluten, gelatin, groundnut meal, casein, soya-bean meal or fish meal.

7. Rabbits offered diets containing casein, soya-bean meal and fish meal gained 40–50 g/d similar, to animals given a well-balanced control diet, while those given diets containing maize gluten, gelatin or groundnut meal gained approximately 30 g/d. This indicated that amino acid balance in dietary protein was important to the growing rabbit.

8. In later experiments, diets based on cereals and groundnut meal supplemented with varying amounts of lysine and methionine were offered during a 3-week post-weaning period in order to assess requirements for those limiting amino acids.

9. The addition of both lysine and methionine improved growth rates. The minimum requirements for normal growth were found to be 6.2 g methionine+cystine and 9.4 g lysine/kg diet.