1. Thirty-six male rats of initial age 27 d were fed on diets based on barley grain for 3 weeks. Crude protein (nitrogen × 6.25) was fixed at 120.0 g/kg dry matter (dm) and cystine at 2.0 g/kg dm in all diets. The basal diet contained 3.5 g methionine plus cystine/kg dm with l-methionine added in increments of 0.5 g/kg dm up to a final level of 7.0 g methionine plus cystine/kg dm. A ‘positive control’ diet of barley plus 193.7 g soya-bean meal/kg dm contained 6.0 g methionine plus cystine/kg dm.

2. Weight gain, food conversion efficiency (FCE), urinary urea-N excretion, carcass composition and activities of liver cystathionine synthase (EC 4.2.1.22) and N5-methyltetrahydrofolate-homocysteine-methyltransferase (EC 2.1.1.13) were determined.

3. Weight gain, FCE and urinary urea-N excretion indicated that levels of 3.5 and 4.0 g methionine plus cystine/kg dm were inadequate for optimal growth of the rats. These variables indicated 4.7 g/kg dm to be the requirement for methionine plus cystine. Carcass composition results gave no clear indication of optimal requirements for methionine plus cystine.

4. Cystathionine synthase and N5-methyltetrahydrofolate-homocysteine-methyltransferase activities (/mg protein per 60 min) were constant at 24.32 μmol and 0.64 μmol respectively, when methionine plus cystine level was between 3.5 and 5.0 g/kg dm. Cystathionine synthase was then inhibited at the 6.0 g/kg dm level to a minimum activity of 16.12 μmol/mg protein per 60 min, whereas activity of the re-methylation enzyme increased to a maximum level of 2.92 μmol/mg protein per 60 min at the 6.0 g/kg dm level of methionine plus cystine. At the levels of methionine plus cystine above 6.0 g/kg dm cystathionine synthase activity increased while the activity of N5-methyltetrahydrofolate-homocysteine-methyltransferase decreased.

1. Nitrogen retention was determined by classical N balance techniques in fourteen rapidly growing low-birth-weight infants receiving 3 g protein/kg body-weight and during their 3rd week of life. This was compared with plasma free alkaline ribonuclease (EC 3.1.4.22; RNase) activity and other biochemical measurements of protein nutrition.

2. Plasma RNase showed a significant positive correlation with N retention and a corresponding negative correlation with urine urea-N. These results were unexpected and suggest a different relationship between RNase and N retention in infants compared with that found by other workers in children and adults.

3. The most likely explanation of this apparent anomaly is that in all instances high activities of plasma RNase are associated with a need to conserve N. In the infants studied this may indicate some measure of ‘protein economy’ and they could therefore benefit from a higher protein intake.

1. Quantitative selenium metabolism has been studied in normal young New Zealand women by measuring total Se intake and urinary and faecal Se output, and by using values for absorption, excretion and turnover of 75Se determined after administration of [75Se]selenomethionine or [75Se]selenite.

2. In a period of 14 d when a normal ad lib. diet was being consumed, mean dietary Se for four women was 24.2 μg/d, mean urinary Se was 13.1 μg/d and mean faecal Se was 10.8 μg/d; mean Se balance during this time was +0.3 μg/d.

3. Intestinal absorption of food Se was 0.76−0.83 of intake (mean 0.79).

4. Whole-body Se was calculated in three different ways; (a) using the specific activity of urinary Se and retained whole-body 75Se; (b) using plasma Se and the occupancy of 75Se in whole-body and plasma; (c) using absorbed food Se and the occupancy of absorbed 75Se in whole-body.

5. Whole-body Se calculated from measurements obtained following the administration of [75Se]seleno-methionine was 4.7−10.0 mg (mean 6.9) using method (a), 4.1−7.2 mg (mean 5.2) using method (b) and 4.3−8.9 mg (mean 6.2) using method (c).

6. Whole-body Se calculated from results obtained after giving [75Se]selenite was 2.7−3.4 mg (mean 2.9) using method (a), 2.3−5.0 mg (mean 3.5) using method (b) and 2.1−3.0 mg (mean 2.6) using method (c).

7. The results of this study indicate that the minimum dietary requirement of Se for the maintenance of normal human health is probably not more than 20 μg/d.

1. The fractional synthetic rates of tissue proteins were studied in growing pigs using the constant-infusion technique of tracer-labelled amino acids ([14C]leucine and [14C]lysine) and the mathetmatical model for calculation, employed in rats by Garlick, Millward & James (1973).

2. During a 6 h infusion, samples were taken from blood and muscle and at the end of the infusion from liver, muscle, pancreas, heart, duodenum, jejunum, ileum, colon, and skin. The specific radioactivity of free and protein-bound leucine and lysine was estimated.

3. A quasi-steady-state in the specific radioactivity of free plasma leucine and lysine was reached within approximately 2 h, the rate-constants being 35 and 48/d respectively.

4. The specific radioactivity of free leucine and lysine in plasma was used to calculate the flux of these amino acids. It was found to be higher than the daily intake.

5. The average fractional rate of protein synthesis in muscle and heart was 8.1 %/d, in small and large intestine the values were 50 and 33 %/d respectively and in liver and pancreas more than 100 %/d.

6. The calculation of protein synthetic rate in pig tissue using the constant-infusion method of labelled amino acids seems to be a suitable tool for study of this species.

1. Adult female rats given a diet containing 200 g casein/kg showed an increase in heat production which reached a maximum in 10–20 min after completion of food intake.

2. Replacement of casein in the diet by enzymic hydrolysates of casein of different extents of hydrolysis (pepsin for 1 or 3 h and pancreatin for 6, 12 or 24 h) resulted in a decrease in metabolic rate (stimulation) in the rat, reaching a maximum of 61.8% of the control value (non-hydrolysed casein).

3. The specific dynamic action of casein and casein hydrolysate was inversely proportional to the amount of amino-nitrogen released.

4. On the basis of the experimental findings it may be concluded that the synthesis and secretion of digestive enzymes were the main causes of the increase in metabolic rate after protein ingestion.

1. When lead is administered in drinking-water iron-deficient rats retain more Pb than Fe-replete rats (Six & Goyer, 1972; Klauder & Petering, 1975). In the present study the relationship between the absorption of Pb and Fe was investigated.

2. Adult male rats were transferred to a milk-based diet fed with or without supplementary Fe (180 mg Fe/kg as ferrous sulphate). After 7–9 d the absorption of duodenally-administered 203Pb and 59Fe was measured as uptake of radioactivity from the gastrointestinal tract after 90 min. 59Fe absorption was increased in rats given the unsupplemented diet for 7 d and was further increased in rats kept on the diet for up to 7 weeks. 203Pb absorption was not consistently increased by either short- or long-term Fe deprivation.

3. Much of the 203Pb in homogenates of the upper small intestine was bound to soluble protein of which up to 85% was dialysable. In contrast little 59Fe was dialysable. Only a small proportion of the soluble musosal Pb was associated with ferritin during gel-filtration chromatography although 203Pb precipitated together with carrier rat-liver ferritin with an antibody to rat-liver ferritin.

4. There appeared to be no direct relationship between the transfer of Fe and Pb across the small intestine of the adult rat.

1. Food intake studies were carried out on three groups of captive primates (anthropoid apes (Pongidae), lemurs (Lemuridae) and marmosets (Callitrichidae).

2. Determination and analysis of the nutrient intakes were carried out by calculations based on food tables. The results from all groups were compared.

3. Marmosets were found to have higher intakes of energy and many other nutrients than the apes and lemurs.

4. The results suggest that there is a tendency towards over use of dietary supplements and foods of higher nutrient density for captive primates.

1. Diets containing graded levels of pyridoxine hydrochloride (to supply 0.26–30 mg pyridoxine/kg) were given to seven duplicate groups of turbot (Scophthalmus maximus) for 12 weeks and their growth rate was measured during this period.

2. Good growth was obtained on all treatments except those groups given less than 1.0 mg pyridoxine/kg diet. These fish grew normally until weeks 8–10 but thereafter their weight gain was significantly less than that for other treatments.

3. Measurements of aspartate aminotransferase (EC 2.6.1.1) in muscle and liver and of alanine aminotransferase (EC 2.6.1.2) in liver of the turbot showed that the activities of these enzymes increased with increasing dietary pyridoxine intake up to a level of 2.5 mg pyridoxine/kg. The activities of these enzymes were not further enhanced by additional dietary pyridoxine.

4. Percentage stimulation of these enzymes by pre-incubation of extracts with pyridoxal phosphate was minimal with those groups of turbot given 2.5 mg pyridoxine/kg diet or more.

5. It is concluded that the dietary requirement of turbot for vitamin B6 can be safely met with a diet containing between 1.0 and 2.5 mg pyridoxine/kg.

6. An eighth group of turbot given the pyridoxine antagonist 4-deoxypyridoxine hydrochloride (20 mg/kg) showed retarded growth after 2 weeks, together with a high mortality rate.

1. Steers with rumen and simple duodenal cannulas were allowed to graze pasture or were given diets of dried grass or flaked maize with or without hay. For an experiment a solution or suspension of magnesium chloride, polyethylene glycol (molecular weight 4000) and either 144Ce (as cerous chloride) or chromic oxide was added to the rumen with a morning feed. Conditions in the rumen were sometimes modified by adding sodium chloride or hydrochloric acid.

2. Changes in magnesium: marker in samples of strained rumen contents with time interval after adding the dose were due partly to changes in Mg distribution between different phases. Results indicated, but not unequivocably, that negligible amounts of Mg were absorbed in the first few hours.

3. Relative recoveries of Mg and markers at the duodenum indicated that proportions of Mg intake absorbed (net) varied from approximately zero for pasture to 0.2–0.5 for flaked maize. Significant correlations between absorption efficiency and sodium: potassium in rumen contents (positive) and rumen pH (negative) were observed.

4. Steers with simple duodenal and re-entrant ileal cannulas were given a diet of flaked maize and hay supplemented with different amounts of magnesium oxide. Little net change in Mg relative to an unabsorbed marker was found between these sites even for a diet containing an Mg supplement of 8 g/kg dry matter.

1. Groups of chicks were given a low-residue diet with or without supplements of dietary fibre in the form of wheat bran, wheat straw or bagasse. Growth and food conversion efficiency (g weight gained/g food eaten; FCE) during the first 4 weeks of life were measured.

2. In every one of seven experiments supplementation of the diet with 100 g wheat bran/kg resulted in improved growth, and in three experiments FCE was also increased.

3. Supplementation with coarsely-milled wheat straw to provide an amount of unavailable carbohydrate equivalent to that in the bran diet resulted in poorer growth; finely-milled wheat straw had little effect on growth.

4. The growth-promoting effect of bran was destroyed by sterilization with heat or gamma-radiation.

5. In some experiments weights, lengths and volumes of small intestines were measured. Differences in intestinal dimensions between birds given the diet with and without fibre were not consistent, nor were they correlated with growth rate or FCE.

6. Histometric observations on small intestines from a few birds indicated that those given coarse wheat straw had longer villi and thicker muscularis layers, and the caecal tonsils had a greater area of lymphoid tissue and more follicles.

1. Fistulated sheep given a concentrate diet were used to study the behaviour of solute ([51Cr]EDTA) and particle ([103Ru]phenanthroline) markers in the stomach under conditions of continuous feeding.

2. An injection of a mixed dose of [51Cr]EDTA and [103Ru]phenanthroline was given into the rumen and the time course of marker concentrations in the rumen and the abomasum was recorded. The curves were analysed on the assumption that the stomach of the sheep could be represented as two mixing compartments (reticulo-rumen and abomasum) and a time delay (omasum). This model provided a very good description of the data.

3. [103Ru]phenanthroline associated with small particles was retained in the rumen much longer than [51Cr]EDTA. Although exchange of [103Ru]phenanthroline occurred between large and small particle fractions, the results suggested that small particles may have been retained somewhat longer in the rumen than solutes. However, it was clear from the results that the mean retention times for particulate matter in the rumen could not be simply obtained using adsorbable markers.

4. Cyclical fluctuations in the concentration of [51Cr]EDTA in the rumen indicated that there were daily variations in net water flux in the rumen.

5. The presence of protozoa was associated with much shorter retention times of both solutes and particles in the rumen. Protozoa were also associated with reduced rumen volumes.

1. Physical performance capacity was assessed before and after injection of cyanocobalamin and a placebo for thirty-one Burmese male subjects whose age ranged from 18.7 to 20.8 years.

2. The subjects chosen were free from anaemia and were paired on a ‘weight-age’ basis and divided into two groups.

3. One group received an injection of 1 mg cyanocobalamin and the other was given a placebo injection three times weekly for 6 weeks. This was done on a ‘double-blind’ basis.

4. There was no significant difference between the two groups in any of the criteria measured, before and after administration of either 1 mg cyanocobalamin or placebo injection. So also there was no significant increase in any of the measurements in the subjects after receiving cyanocobalamin injections compared with those receiving the placebo.

1. Total skinfold thicknesses (sum of seven sites) were measured in fifty-seven pregnant women with low energy and protein intake, at weeks 24, 30 and 35 of gestation.

2. Women were classified in two groups (overweight and low weight), according to their weight-for-height at week 24 of gestation.

3. Half of the women did not increase, or even reduced the amount of subcutaneous fat during the observation period. The lowest mean value of total skinfold thickness was found in the low-weight women who showed a reduction of the subcutaneous fat.

4. This finding shows that a significant proportion of malnourished women do not follow the average pattern of subcutaneous fat accumulation seen in healthy pregnant women without food intake restriction, during the second half of pregnancy.

1. The concentration of 2-aminoethylphosphonic acid (AEP) in 96 h cultures of Tetrahymena pyriformis W was studied in order to apply it as an indicator in the assay of the relative nutritive value (RNV; protozoa population with test protein: protozoa population with whole-egg powder) of protein. Foodstuffs and food mixtures of different protein contents and qualities were used as test samples.

2. RNV values based on AEP determination (RNVAEP) were compared with corresponding values calculated from protozoa counts (RNVpc), as well as with biological value (bv) and net protein utilization (npu) of the same proteins assayed on rats.

3. Both for foodstuffs and food mixtures highly significant correlations were found between RNVAEP and RNVpc, RNVAEP and both bv and npu, and RNVpc, and both bv and npu.

4. AEP content in the protozoal suspension was preferred to cell count as a measure of growth response, since it took into account large differences in cell dimensions that were observed between cultures grown with different test proteins.

1. Naturally-occurring and synthetic analogues of phenylalanine, tyrosine, histidine, arginine, proline, tryptophan and the sulphur amino acids have been tested in rat reticulocytes and in the Reuber H35 hepatoma for effects on protein synthesis and protein degradation and on the heat lability of phosphoenolpyruvate carboxykinase (EC 4.1.1.32) in the hepatoma cells. The experiments were designed to test whether the analogues could be incorporated into mammalian proteins and whether the resultant proteins would be degraded at an accelerated rate.

2. Several analogues, including thiazolylalanine, triazolalanine and selenocystine both stimulated protein synthesis and produced labile protein in reticulocytes. Other analogues, such as dihydroxyphenylalanine, thioproline and pipecolic acid accelerated protein breakdown but probably indirectly via an inhibition of protein synthesis. Azetidine-2-carboxylic acid had the largest effect on protein breakdown in reticulocytes.

3. Labile protein was produced in hepatoma cells incubated in the presence of azetidine-2-carboxylic acid, canavanine, indospicine, triazolalanine, 2-, 3- and 4-fluorophenylalanine. These same analogues, together with 3, 4-dehydroproline, β-2-thienylalanine, dihydroxyphenylalanine, histidinol, 5- and 6-fluorotryptophan, selenocystine and selenomethionine produced heat-labile phosphoenolpyruvate carboxykinase. Enzyme induced in the presence of selenomethionine or indospicine showed the largest increases in heat lability, and for these analogues equimolar concentrations of methionine and arginine respectively were needed to nullify the enzyme abnormality.

4. The toxicity of the same naturally-occurring analogues has been discussed in terms of their ability to be incorporated into cell proteins.

1. Two groups of four 18-month-old ewes fitted with a rumen cannula and re-entrant cannulas in the proximal duodenum were fed on one of two diets based on varying proportions of dried-grass meal, ground straw and barley.

2. The apparent availability, retention and amount of the mineral reaching the proximal duodenum were measured for calcium, phosphorus, magnesium, copper and zinc. Significant differences were found between diets for Ca only. Net absorption of Mg occurred before the proximal duodenum and also, lower down the alimentary tract. Marked increases were observed in the amount of Cu, Zn and P reaching the proximal duodenum relative to that ingested.

1. Twelve gastric-cannulated litter-mate pigs were used to study secretion and proteolytic activity in the stomach of suckling and early-weaned pigs in relation to age and food intake.

2. Results demonstrate that from the first observation at day 8, piglets were able to secrete acid. pH and acid concentration did not change during the first 4 weeks of life.

3. Proteolytic activity was low during the first 2–3 weeks of life and rapidly increased thereafter.

4. Two phenomena differentiated suckling pigs from pigs given dry cow's milk: (1) a low buffering capacity the gastric contents, beginning 1 h after feeding the dry cow's-milk formula, results in a low total acid concentration in the weaned pigs and (2) the increase in proteolytic activity in relation to the age is much more pronounced in the artificially-reared pigs.

5. These two phenomena are discussed and related to the formation of a hard casein clot in the stomach of the cow's-milk-fed pigs, which has a long retention time and stimulates gastrin release.

1. Skinfold thickness, body circumferences and body density were measured in samples of 308 and ninety-five adult men ranging in age from 18 to 61 years.

2. Using the sample of 308 men, multiple regression equations were calculated to estimate body density using either the quadratic or log form of the sum of skinfolds, in combination with age, waist and forearm circumference.

3. The multiple correlations for the equations exceeded 0.90 with standard errors of approximately ±0.0073 g/ml.

4. The regression equations were cross validated on the second sample of ninety-five men. The correlations between predicted and laboratory-determined body density exceeded 0.90 with standard errors of approximately 0.0077 g/ml.

5. The regression equations were shown to be valid for adult men varying in age and fatness.

1. Rabbits hand-reared on a diet based on cow's milk frequently experience convulsive and sometimes fatal reactions to their feed. These have been thought to be caused by immunological hypersensitivity to cow's milk.

2. This explanation has been re-examined and found to be untenable.

1. The effect of protein intake on calcium metabolism has been studied in the pregnant ewe.

2. Results suggest that decreased Ca retention in protein-deficient animals was a result of a decreased rate of Ca absorption and not a decreased rate of bone accretion as suggested by other workers.