1. To study the potential of the constant-infusion technique for measuring rates of protein synthesis in New Zealand White rabbits, animals were infused for up to 6 h with radioactively-labelled tyrosine.

2. Labelled tyrosine from plasma and tissues was isolated from labelled metabolites by ion-exchange chromatography.

3. Analysis of serial blood and muscle biopsy samples removed under anaesthesia showed that the specific radioactivity (SR) of the free tyrosine pools reached an approximately constant value within 2 h.

4. Certain commercial preparations of L-[side-chain 2,3-3H]tyrosine were contaminated with 300 mg radioactive D-tyrosine/g. The D-isomer appeared to enter the muscle intracellular pool.

5. In constant-infusion experiments L-[3H]tyrosine could replace the uniformly-14C-labelled L-isomer for the determination of rates of protein synthesis in muscle. L-[side-chain 2,3-3H]tyrosine may not be suitable for use as a precursor for measuring rates of liver protein synthesis.

6. Evidence is presented that the precursor of liver protein synthesis may not be well defined by the SR for free tyrosine of the homogenate.

7. The technique was used to measure the rates of protein synthesis in adult rabbits. The rates of protein synthesis in liver and muscle were measured and from measurements of tyrosine flux the mean rate of whole-body protein synthesis was calculated as 13.8 g/kg per d.

1. [75Se]selenite or [75Selenomethionine was injected into the coelomic cavity of fish. After 2 d or 14 d the muscle portion of the fish was removed and homogenized. The long-term fate in rats of an oral dose of each labelled homogenate was compared with that of an oral dose of [75Se]selenite or [75Se]selenomethionine mixed with unlabelled fish homogenate.

2. Urinary and faecal radioactivity were measured during the 1st week and whole-body radioactivity was determined for 10 weeks. Rats were killed at weekly intervals for 4 weeks for analysis of tissue distribution of 75Se.

3. Intestinal absorption of 75Se given as labelled fish homogenate was less complete than that of 75Se mixed with unlabelled homogenate, and the absorption of 75Se from the 14d-labelled fish homogenate derived from [75Se]selenite was less complete than that of 75Se from the other labelled homogenates.

4. Urinary excretion of absorbed 75Se in the first 7 d was in the range 5-8 % absorbed dose and was slightly greater in the rats given 75Se as selenite or derived from selenite than in those given 75Se as selenomethionine or derived from selenomethionine. Endogenous faecal excretion of absorbed Se was similar in all groups, as also were tissue distribution of retained 75Se and long-term whole-body turnover rate.

5. The results of these studies are compared with those of earlier studies of the metabolism in rats of [75Selenomethionine, [75Se]selenite, [75Sejselenocystine and 75Se incorporated in vivo into rabbit kidney. There were differences in the initial utilization of 75Se from these various sources but after the 1st week 75Se from all sources appeared to be metabolized similarly, suggesting that for rats dietary Se of all forms is ultimately incorporated into the same metabolic pool.

1. The concentrations of serum protein albumin, prealbumin and transferrin were determined in twentyeight cases of protein-energy malnutrition (PEM) with infection, together with the levels of serum proteinase inhibitors (PI), α1-antitrypsin (AT), α1-antichymotrypsin (Ach), α2-macroglobulin (α2M) and inter-α-trypsin inhibitor (IαI).

2. Albumin, prealbumin and transferrin concentrations, as well as the levels of PI, IαI and α2M were found to be lower in cases of PEM associated with infection than the corresponding values for a group of healthy Thai preschool children and a group of newborn Thai children, but despite starvation AT and Ach values generally were increased.

3. The results provide support for the hypothesis that PI, especially AT and Ach might limit the synthesis of albumin, prealbumin and transferrin in PEM associated with infection, via the inhibition of the mobilization of body's own protein.

1. Six groups of rats were given diets containing protein at three levels (SO, 100 and 200 g/kg), with and without nicotinic acid. After 4 weeks on these diets some key enzymes of the tryptophan and nicotinic acid-NAD pathway, liver nicotinamide nucleotide concentration, and urinary metabolites of tryptophan and nicotinic acid were studied.

2. Liver nicotinamide nucleotide levels were lower in rats given the diet with 50 g protein/kg as compared to those in rats given diets with 100 and 200 g protein/kg. The addition of nicotinic acid to the diet resulted in a significant increase in the levels of nicotinamide nucleotides only in rats given 50 g protein/kg diet but not in those given either 100 or 200 g protein/kg diet.

3. Liver tryptophan oxygenase (EC 1.13.1.12) activity increased with increasing dietary protein level. Nicotinic acid in the diet had no effect on its activity.

4. Quinolinate phosphoribosyltransferase (EC 2.4.2.a) activity in liver was inversely related to dietary protein level, and nicotinic acid in the diet had no effect on its activity.

5. Liver nicotinate phosphoribosyltransferase (EC 2.4.2.11) activity and kidney picolinate carboxylase (EC 4.1.1.45) activity were not altered either by dietary protein level or nicotinic acid in the diet.

6. The addition of nicotinic acid to the diet resulted in increased excretion of W-methylnicotinamide at all dietary protein levels.

7. The inverse relationship between protein level in the diet and liver quinolinate phosphoribosyltransferase activity, the rate-limiting enzyme of the tryptophan-NAD pathway suggests that the efficiency of conversion of tryptophan to NAD is related to protein level in the diet, the efficiency decreasing with an increase in the level of dietary protein.

1. As most of the studies on the regulation of renal 25-hydroxycholecalciferol-1-hydroxylase (25-HCC-1-hydroxylase) activity have been done in marginally-vitamin D-defieient animals and as it is known that vitamin D administration suppresses the specific activity of the 25-HCC-1-hydroxylase, it was decided to study the effect of dietary calcium on the activity of 25-HCC-1-hydroxylase and on Ca absorption in vitamin Dreplete chicks.

2. Chicks, 10 d old, were given diets differing in their Ca contents (65 nmol cholecalciferol/kg diet) for 10 d and the activity of 25-HCC-1-hydroxylase in kidney homogenates, Ca absorption from the duodenum, Cabinding protein (CaBP) activity in the duodenal mucosa and plasma Ca and phosphate concentrations were all determined.

3. The CaBP activity and the efficiency of Ca absorption both decreased with increasing dietary intake of Ca. Ca absorption and CaBP activity were significantly correlated (r 0.995, P < 0.01).

4. The activity of 25-HCC-1-hydroxylase decreased as the dietary level of Ca increased and was significantly correlated with Ca absorption (r0.900, P < 005). The plasma Ca concentration and the activity of 25-HCC-1-hydroxylase were inversely related (r-0.940, P < 0.01).

5. It is concluded that in the vitamin D-replete chick the efficiency of duodenal Ca absorption is regulated by the renal 25-HCC-1-hydroxylase activity via production of 1,25-dihydroxycholecalciferol and CaBP synthesis.

1. A total of 179 duplicate diets were collected by twenty-three women consuming their habitual diet. Twelve of the subjects were living in a residential hall for students, the others were living in their own homes or in flats. Collection periods varied from 3 to 21 d.

2. Average daily intakes were: manganese 2.7 mg; copper 1.5 mg for diets not containing liver, 7.6 mg for fifteen diets containing liver; zinc 10.0 mg; cadmium 21 μg for diets not containing liver, 27μg for fifteen diets containing liver.

3. The intakes were compared with values for adults from other countries and with current recommended dietary allowances or estimated minimum requirements. Mn intakes were typical for non-vegetarian Western diets. Cu and Zn intakes may have been marginally low. The intakes of Cd were low.

4. Daily intakes of protein (71 g), fat (83 g), carbohydrate (224 g) and energy (8.1 MJ) from 129 of the diets were similar to recent values obtained for New Zealand women.

5. Subjects living in the residential hall had higher intakes of all nutrients than subjects living in their own homes or flats.

1. There was little difference in digestive (voluntary food intake, dry matter digestibility and nitrogen balance) and blood measurements (venous concentrations of corticosteroids, serum aspartate aminotransferase (EC 2.6.1.1), protein-bound iodine, urea and glucose) of intact sheep (eight animals) and of sheep prepared with rumen cannulas (sixteen animals) and subsequently with either simple 'T-shaped' (eight animals) or re-entrant cannulas (eight animals) at the duodenum and ileum, when fed ad lib. a chopped, medium-quality-hay ration.

2. Wool growth rates of the intact sheep were similar to those in sheep with rumen cannulas and with rumen cannulas plus simple 'T-shaped' cannulas, but higher (P < 0-01) than those with rumen cannulas plus re-entrant cannulas.

3. When the sheep were subsequently given a restricted intake (800 g/d) of dried grass, retention times of solid- and liquid-phase digesta markers in the rumen and caecum were similar in all sheep.

4. The use of the different preparations in digestive physiology studies is discussed.

1. Male weanling rats were maintained at a constant body-weight by feeding them reduced amounts of the normal diet for various periods up to 4 weeks. Control male rats were allowed free access to the normal diet and some were killed at the beginning of the experiment and others at the same ages as the experimental rats.

2. After killing by cervical dislocation the rats had their liver, quadriceps muscles and spleen removed. The tissues were weighed and the activities of the enzymes ornithine decarboxylase (ODC; EC 4.1.1.17) and 5-adenosylmethionine decarboxylase (SAMD; EC 4.1.1.50) assayed in each tissue. In the liver the content of the polyamines (spermidine and spermine) and putrescine was also measured.

3. The liver and quadriceps muscles showed an over-all maintenance of weight during undernutrition, but the spleen lost weight during the first 7 d of undernutrition and then remained constant. The weight of the liver increased by approximately 50 % following the daily maintenance feed, but returned to its prefeeding value by 24 h after feeding.

4. During the first 7 d of undernutrition ODC activity decreased in all three tissues, and remained fairly constant thereafter. In the liver there were marked increases in the activity of ODC during the first 4 h after the daily feed, but the activity then decreased to prefeeding values. SAMD activity tended to remain normal in the liver, decreased initially and then returned to normal in the quadriceps muscles, and remained normal initially and then decreased in the spleen. Hepatic SAMD activity showed no consistent response to the daily feed, but quadriceps SAMD activity increased significantly between 1 and 8 h after feeding.

5. Hepatic putrescine content remained constant during undernutrition whilst spermine increased slightly and was then maintained above normal for liver size. Hepatic spermidine content decreased initially and then remained constant. Putrescine increased slightly in response to the daily feed and spermidine increased considerably. Spermine content was unaffected by the daily feed.

6. It is suggested that the response of polyamine synthesis in the various tissues is primarily dependent upon the way in which nutrients are made available to the tissues. The maintenance of spermine content in the liver at the expense of spermidine may be related to differential changes in the nucleic acids.

1. A study has been made of the copper- and zinc-binding proteins in the livers from sheep foetuses of 80-142 d gestational age.

2. Metallothionein was found to constitute the major Zn-binding component in the cytosol at all times and to be identical to Zn-thionein from adult sheep liver.

3. Zn also occurred in two fractions, not normally found in sheep liver, with approximate molecular weights of 28000 and 47000. The relative proportions of these were age-dependent.

4. Between 15 and 35 % of the hepatic Cu, corresponding to most of the Cu in the cytosol, also occurred in the metallothionein-containing fraction.

1. A cereal-based diet containing 16 mg copper/kg was fed ad lib. to a group of laying hens for 35 d. Five other groups were given this control diet to which was added 120, 240, 480, 960 and 1920 mg Cu/kg (as copper sulphate).

2. Records were kept of daily food intake, water intake and egg production.

3. After 35 d the hens were slaughtered and blood haemoglobin, packed cell volume, Cu and aspartate aminotransferase (EC2.6.1.1) levels assayed. Liver, oviduct, kidney and breast muscle Cu and iron concentrations were measured.

4. Food and water intakes were depressed by the two highest levels of dietary Cu and water intake was increased by the diet with 240 mg added Cu/kg. Both food and water intake showed a quadratic relationship with the level of added dietary Cu.

5. Body-weight loss was increased by the addition of Cu and showed a significant linear relationship with the concentration of added Cu in the diet. Liver and oviduct weights were depressed at the two highest levels of Cu addition.

6. Liver and oviduct Cu and Fe concentrations were significantly increased by high dietary Cu and mean total liver and kidney Cu and Fe showed an increase although for the liver this was not statistically significant.

1. The extracellular phosphate pool in incubations of rumen fluid or washed cell suspensions of mixed rumen bacteria (WCS) was labelled with 32P. From the constant extracellular phosphate pool specific activity and the amount of radioactivity incorporated during incubation, the amount of P incorporated in the microbial fraction was calculated. From the value for nitrogen: P determined in microbial matter, the amount of N incorporated was calculated as a measure of microbial growth.

2. Incorporation of soluble non-protein-N in incubations devoid of substrate protein was 50 and 80 % of the values obtained using the isotope method for rumen fluid and WCS respectively. It is suggested that results obtained using the former method reflect 'net growth' of micro-organisms which is the result of simultaneous growth and degradation. The isotope method measures 'total growth', as isotope incorporation is not affected by degradation of non-growing cells.

3. Incorporation of 32P in P-containing microbial components (mainly nucleic acids) was compared with net synthesis of these components in incubations of WCS. The results showed different specific rates of synthesis and degradation for all components studied. It is concluded that the composition of microbial matter changed during growth.

4. When N incorporation, calculated from results obtained using the isotope method in incubations with rumen fluid, was compared with the amount of carbohydrate substrate fermented and the type of fermentation, values between 18.3 and 44.6 g N incorporated/kg of organic matter fermented were obtained. Low values were associated with large proportions of the substrate being fermented to lactate and the use of glucose instead of disaccharides as substrate. Part of the variation could also be attributed to differences in incubation period, reflected in different proportions of polysaccharide formed.

5. The use of isotopes for determination of rumen microbial growth in vitro is critically discussed.

1. Investigations have been carried out in experimentally-malnourished rats in an attempt to explain the reasons for the development of the two main forms of protein-energy malnutrition in children, kwashiorkor and marasmus.

2. Isoenergetic diets with values for protein: energy (P:E) of 0.21 (control diet; C) 0.032 (low-protein diet; LP) and 0.005 (very-low-protein diet; VLP) were fed to groups of twenty-six rats either ad lib. or in restricted amounts from 5 weeks of age. Rats were killed at the start of the experiment and 1, 2 and 3 or 4 weeks later. Estimations were made of plasma albumin, insulin, corticosterone and amino acid concentrations and of the total protein content of the gastrocnemius muscles and liver.

3. Rats given diet LP ad lib. gained weight slowly and by week 1 plasma albumin concentration was slightly reduced. Rats given diet VLP ad lib. gradually lost weight and plasma albumin concentrations decreased continuously.

4. In contrast the major effect of dietary restriction during the first 2 weeks of the experiment was to maintain plasma albumin concentrations at normal values, irrespective of the diet given.

5. At later stages, however, when the ‘restricted’ animals had become very severely wasted, albumin concentrations decreased rapidly to values approaching those found in rats given diet VLP ad lib.

6. When diets LP and VLP were given ad lib. body protein was proportionally distributed in favour of muscle rather than liver. For ‘restricted’ rats the reverse was true, at least up to the time when plasma albumin concentration began to decrease.

7. Plasma corticosterone concentrations increased and insulin concentrations decreased when diets LP and VLP were fed in both an ad lib. and a ‘restricted’ regimen but the effects were significantly greater in the latter situation.

8. Ad lib. feeding of diets LP and VLP produced a distorted plasma amino acid pattern resembling that of kwashiorkor, but although dietary restriction resulted in a decrease in total amino acid concentration, the plasma concentration ratio, non-essential amino acids:essential amino acids was virtually unaffected.

9. It was concluded that whilst the lower the protein concentration in the diet the greater is the extent of hypoalbuminaemia which develops, dietary restriction with an increase in plasma glucocorticoid concentration and body-wasting can initially delay the development of the hypoalbuminaemia. However, in the final stages of wasting which ensue, low plasma albumin concentrations can appear because of a failure of the mechanisms which had earlier been able to preserve them at normal levels. It is possible that these two separate and distinct routes to hypoalbuminaemia observed in this study may have parallels in human situations in developing countries.

1. Replicate groups of rainbow trout (Salmo gairdneri) were given one of five experimental diets (diets 1-5) for 16 weeks. The diets contained different amounts of calcium, phosphorus and magnesium and were prepared so that there were three levels of Ca (g/kg): 14 (diet 1), 26 (diets 2 and 3) and 40 (diets 4 and 5), Ca:P being approximately 1:1 in all diets. Diets 1, 2 and 4 had basal Mg levels (not more than 0.063 g/kg) whereas diets 3 and 5 contained supplementary Mg (1.0 g/kg).

2. Weight gains of the trout given diets containing supplementary Mg were twice those of trout given diets with basal levels of Mg. At both dietary Mg concentrations weight gain was unaffected by the dietary Ca level.

3. Serum Mg levels were significantly reduced in those trout given diets without supplementary Mg. The serum Ca level in those trout given the lowest concentration of Ca in their diet (14 g/kg, diet 1) was significantly greater than in those given higher amounts of Ca in their diets. Serum P levels were not significantly different with any of the experimental diets.

4. The renal Ca concentration was increased in trout given diet 3 (26 g Ca/kg; basal Mg levels). No further increase in renal Ca concentration occurred in trout given diet 5 (40 g Ca/kg; basal Mg levels). With diets containing supplementary Mg renal Ca levels were increased at a dietary Ca level of 40 g/kg but not at a dietary Ca level of 26 g/kg. Renal Mg and P concentrations were not significantly different between any of the dietary treatments.

5. Renal calculi were demonstrated by light and electron microscopy in tubules of those trout given diets 3 and 5 (basal Mg; 26 and 40 g Ca/kg respectively). Electron-probe micro-analysis showed that these calculi contained or comprised tricalcium phosphate.

6. The skeletal muscle of Mg-deficient trout contained significantly more sodium than that of normal trout. It is suggested that this is indicative of an increase in extracellular fluid in the muscle of Mg-deficient trout.

1. Essential fatty acid-deficient rats were fed γ-linolenic acid (18:3ω6) at 2 % dietary energy and α-linolenic acid (18:3ω3) at 0, 1.6, 2.8 and 4.0 % of the dietary energy.

2. 18:3ω3 at 1.6% apparently inhibits the synthesis of the C20 and C22 ω6 long-chain polyunsaturated fatty acids (ω6 LC-PUFA) metabolized from 18:3ω6.

3. However, increasing the dietary levels of 18:3ω3 from 1.6 to 4.0% has no further influence.

4. The results suggest that dietary 18:3ω6 is an efficient precursor for the ω6 LC-PUFA synthesis even in the presence of 18:3ω3.

1. The effects of protein-energy malnutrition on brain free amino acids of acidic and neutral groups were investigated in experimental rats.

2. Severe energy restriction did not modify the free amino acid composition of the brain while protein deficiency affected certain amino acids of the brain in opposite directions. Significant decreases in the levels of aspartic acid, threonine and tyrosine were observed in the protein-deficient rats.

3. These changes in brain amino acids appear to be specific to protein deficiency and not affected by energy deficiency.

1. Discrepancies between the results obtained from experiments on pigs with re-entrant duodenal cannulas have been investigated with reference to diet, cannula site and collection procedure.

2. The results obtained from a sealed automatic collection system were different from those obtained from an open manual method and it was concluded that the maintenance of gut intra-luminal pressure in the automatic system was the causative factor.

1. Fractional flux rates of Nτ-methylhistidine (3-methylhistidine; Me-His) of skin and gastrointestine were measured by administering [methyl-3H]methionine to rats.

2. The results showed that the contribution of these tissues to urinary excretion of Me-His was at least 16.6 %. This means that when fractional catabolic rates of myosin and actin were estimated from urinary excretion of Me-His, the part of Me-His derived from skin and gastrointestine should not be neglected.

1. Suckling lambs maintained for 4 weeks on a milk-substitute diet containing 407 g Toprina yeast/kg dry matter of diet exhibited poor growth, low appetite and extensive renal damage.

2. The batch of yeast used contained 2065 mg zinc/kg.

3. The kidneys of lambs offered a milk diet supplemented with the same Zn content as the yeast-fed diet (32.1 mg Zn/1000 kJ) were similarly affected.