1. After a preliminary period on pelleted perennial ryegrass hay (0.28% sodium in dry matter) groups of sheep were fed on timothy hay (0.04% Na) with and without added sodium chloride or sodium bicarbonate.

2. When the sheep were fed on timothy hay, the Na content of urine and faeces fell and balances were negative. Na content of saliva fell markedly and potassium content increased.

3. Supplementary N a prevented these changes.

4. The low levels of dietary Na appeared to have no effect on the well-being of the sheep.

1. Body-weight changes and nitrogen balance were studied, together with the concentration of various nitrogenous muscle components, in adult cocks before and after a 6-day period on a N-free diet and again after a 16-day repletion period on diets supplying various amounts and types of dietary N.

2. In the first experiment a comparison was made during the repletion period between a fish-protein supplement and a supplement of glycine + glutamic acid added to an essential amino acid mixture.

3. During the depletion period the muscle concentration of RNA, DNA and of two transaminase enzymes decreased significantly; during the repletion period these components increased again significantly, and usually to levels greater than the pre-depletion concentration. There were no differences in these responses obtained during repletion with the two N supplements, although the cocks given the glycine–glutamic acid supplement differed from those receiving fish protein in being in Negative N balance and in losing body-weight during the repletion period.

4. In the second experiment one group of depleted cocks was given an essential amino acid mixture alone as the dietary N source and a second group this mixture supplemented by aspartic acid.

5. A decrease in RNA and in the transaminase enzymes during depletion was followed by a significant increase during repletion, but the increase was greater for the group receiving the aspartic acid than for that receiving only the essential amino acid mixture.

6. It was concluded that adding non-essential amino acids to a maintenance mixture of essential amino acids will permit greater repletion in mature cocks.

7. The fluctuations in concentration of RNA and of certain enzymes with dietary protein supply may well be controlling factor in the regulation of N losses and accretions during protein deficiency and sufficiency.

5. The relative constancy of muscle DNA in contrast to the fluctuations in other nitrogenous muscle constituents provides additional support for the concept of protein reserves.

1. The apparent digestibilities for chicks, operated on so as to allow separate collection of urine and faeces, of the nitrogen in a heat-damaged cod flour (C35) and of a control, freezedried cod muscle (C23) were 77 and 90% respectively.

2. The differences are similar to those found for rats in earlier work and considerably smaller than the differences found in nutritional value of the materials as sources of either lysine or methionine for chicks.

3. Chicks killed 3 h after a test meal containing C23 showed little more N in their small intestine than did those on a N-free diet; other chicks receiving C35 showed much more N remaining in the gut.

4. It is hypothesized that significant quantities of heat-damaged protein may remain undigested in the small intestine, but may then be de-aminated by fermentation in the caecum so that values for the digestibility of N and of individual amino acids may be misleadingly high.

5. This hypothesis is supported by the finding that in caecectomized chicks the apparent digestibility of the N of C35 was only 68%, whereas the digestibility of C23 remained the same as in intact chicks.

1. Samples of whale, meat, fish, groundnut and soya-bean meals and skim-milk powders were assayed microbiologically with Tetrahymena pyriformis W and Streptococcus zymogenes for available methionine and available lysine.

2. Detailed collaborative studies on the assay of available methionine with Strep. zymogenes were conducted on the effects of dry- or wet-grinding the test meals, the use of crude or purified papain for predigesting the ground meals and the use of optical density or titratable acidity as criteria of bacterial growth response.

3. Wide differences were observed in the available methionine and available lysine contents of a variety of meals in the preliminary studies, with a promising measure of interlaboratory agreement in the assay of available methionine with Strep. zymogenes.

4. As a result of detailed collaborative studies a provisional method is proposed for the assay of available methione with Strep. zymogenes, adopting dry-grinding and predigestion with an agreed level of papain in the preparation of the meals. No general recommendation could be offered on the comparative merits of optical density and titratable acidity as criteria of bacterial growth response.

1. Eleven groups of male rabbits (eight to eleven per group) were given ad lib. a diet consisting of 61 parts of a low-fat basal ration to which were added: for groups 1–3, 20 parts maize oil; for groups 4–7, 20 parts butterfat; and for groups 8–11, 0.47 parts maize oil and 43.1 parts wheat starch. Different types of roughage were added to the 61 parts of basal ration as follows: for groups 1, 4 and 8, 19 parts ground wheat straw; for groups 2, 5 and 9, 19 parts Solkafioc; for groups 3, 6 and 10, 19 parts of shredded cellophane; and for groups 7 and 11, 14 parts shredded cellophane and 5 parts peat.

2. After the rabbits had been given the experimental diets for a period of 40 weeks, the plasma cholesterol levels were determined. The animals were then killed and the degree of atheromatous degeneration was determined after the aortas had been stained with Sudan IV.

3. Elevated levels of plasma cholesterol and extensive atheromatous degeneration were observed in the rabbits given the diets containing 20% butterfat (groups 4–7) and in those given the diets containing 48% starch (groups 8–11). Lower levels of plasma cholesterol and only slight atheromatous degeneration were observed in the rabbits given the diets containing 20% maize oil (groups 1–3).

4. The levels of plasma cholesterol and the degree of aortic atherosis were influenced very markedly by the nature of the dietary roughage. Plasma cholesterol levels and degrees of aortic atherosis tended to be higher when cellophane was the roughage component than when wheat straw was the roughage component of the diet. The replacement of part of the cellophane of the diet by peat reduced the level of plasma cholesterol and the degree of aortic atherosis.

5. The possible mechanisms by which the nature of the dietary roughage influences plasma cholesterol levels are discussed.

1. The interrelationships between dietary calcium, fluorine and vitamin D were studied in young rats.

2. Rats maintained on a low-Ca diet gained less weight and had less ash in their bones. Their femurs incorporated more radioactive Ca than those of rats kept on a control diet. Supplementation of the diet with F slightly decreased growth and the content of bone ash without any effect on the content of Ca and phosphorus in the bone ash. The F supplement decreased uptake of radioactive Ca by bone. Addition of vitamin D to a low-Ca diet improved growth and, when added alone, increased uptake of radioactive Ca by bone without affecting the content in femurs of ash, Ca or P. Addition of F to a low-Ca diet supplemented with vitamin D diminished the uptake of radioactive Ca.

3. Decrease of bone ash in rats fed the low-Ca diet was accompanied by an increase in bone nitrogen. The bones of the unsupplemented rats contained less citric acid per unit of dry, fat-free mass. Addition of F decreased citric acid, whereas addition of vitamin D increased it.

4. The results are discussed and it is concluded that vitamin D added to a low-Ca diet does not exert a calcifying effect on bone, but rather increases Ca turnover. F, on the other hand, reduces the exchangeability of bone mineral.

1. Vitamin E-deficient rats were found to be more susceptible than vitamin E-supplemented controls to the toxic effects of hyperbaric oxygen (60 lb/in.2 for 20 min). This agrees with the findings of other workers.

2. Hyperbaric O2 treatment did not increase the metabolic destruction of a small amount (46.65 μg) of [14C-5-Me]D-α-tocopherol given to adult vitamin E-deficient rats 24 h previously. The O2 treatment also did not affect the soluble sulphydryl compounds and ascorbic acid of rat liver, nor the percentag haemolysis in vivo of rat blood.

3. Hyperbaric O2 treatment did not increase the true lipid peroxide content of rat brain, compared to control rats treated with hyperbaric air, which has no toxic effects. Increases in ‘lipid peroxidation’ reported by previous workers are considered to have been due to the use of inadequate controls (untreated rats) and of in vitro techniques that are open to criticism.

4. The toxic effects of hyperbaric O2 in the vitamin E-deficient rat cannot be attributed to peroxidation in vivo.

5. Vitamin E was not found to protect rats against the effects of reduced O2 tension (anoxic anoxia). This finding contrasts with some reports by earlier workers. Reduced O2 tension had no effect on the metabolism of radioactive tocopherol, on blood haemolysis in vivo, or on the soluble sulphydryl compounds and ascorbic acid of liver.

1. The total polyunsaturated fatty acid (PUFA) content of tissues of vitamin E-deficient rats and chicks has been measured by the lipoxidase method.

2. Vitamin E deficiency did not depress total PUFA in rat liver, kidney, heart, spleen, brain, adrenal and adipose tissue during experimental periods up to 13 months.

3. Liver PUFA was not depressed by deficiency of vitamin E and selenium in rats at 9 weeks or 8 months of age.

4. Rats given a muscular dystrophy-producing diet (containing oxidized cod-liver oil) showed a severe depletion of PUFA in muscle, but not in kidney or adipose tissue.

5. Exudative diathesis induced in chicks by a deficiency of vitamin E and Se did not depress liver PUFA.

6. It is considered that in vitamin E deficiency there is no general decrease in PUFA due to peroxidative loss. Changes of a more specific nature occur, as found by other workers.

1. Skinfold thickness and body density were measured on 105 young adult men and women and 86 adolescent boys and girls.

2. The correlation coefficients between the skinfold thicknesses, either single or multiple, and density were in the region of −0.80.

3. Regression equations were calculated to predict body fat from skinfolds with an error of about ±3.5%.

4. A table gives the percentage of the body-weight as fat from the measurement of skin-fold thickness.

1. The concentration of copper in the liver of six African children suffering from marasmus has been compared with the values found for six children from the same area suffering from other diseases.

2. No significant difference was found in the concentration of Cu in the livers of children with marasmus compared with the values for the controls when the results were expressed either on a dry whole tissue basis or on a dry fat-free basis.

3. A highly significant difference was found in the concentration of Cu in the livers of children with marasmus when these values were compared, on a dry fat-free basis, with those found in an earlier study for children with kwashiorkor. The concentration of Cu in the livers of children with marasmus was twice that in the children with kwashiorkor.

1. One hundred and ten weanling rats were distributed between five dietary groups in randomized blocks. Each block was constructed from within a litter and each member of the block received a different diet.

2. The main features of the diets were: group I (twenty-six rats) 72% sucrose, group 2 (sixteen rats) 72% uncooked maize starch, group 3 (sixteen rats) 72% roll-dried maize starch, group 4 (twenty-six rats) 36% sucrose and 36% uncooked starch, group 5 (twenty-six rats) 36% sucrose and 36% roll-dried starch.

3. The animals were killed after 20 days on the diets and assessed for dental caries. The rats of group 1 (sucrose) had significantly more caries than all other groups, the rats of group 2 (uncooked starch) had significantly less caries than any of the other groups. Roll-dried starch (group 3) produced significantly more caries than uncooked starch (group 2). The mixture of uncooked starch and sucrose (group 4) was significantly more cariogenic than the mixture of roll-dried starch and sucrose (group 5).

1. Two experiments are described in which the effects of dietary fat on the synthesis of milk fat in the dairy cow have been investigated. In the first experiment a change-over design was used with two cows to study the effect of removing a mixed-oil supplement to a basal diet low in fat on the concentration and composition of plasma lipids and on the yield and composition of milk fat.

2. Reducing the dietary fat intake from about 430 to 170 g/day caused falls in the concentrations in plasma of phospholipid and of free and esterified cholesterol and, in one cow, also of triglyceride. The changes in composition and concentration of the fatty acids in the plasma triglyceride fraction also reflected changes in dietary intake of fatty acids. No effect of dietary fat intake on the total synthesis of milk fat was observed, but the composition of the milk fat reflected that of the dietary fat, and the yields of lauric, myristic, stearic and oleic acids were decreased in association with a decreased dietary intake of these acids.

3. In the second experiment the effect of supplementing a basal diet low in fat with either coconut, red palm or groundnut oil on the composition and yield of milk fat was studied in four cows using a 4 x 4 Latin square design balanced with respect to residual effects.

4. With each oil, increasing the dietary fat intake from about 100 to 400 g/day significantly increased the total yield of milk fat. Also, coconut and red palm oils significantly increased the fat content of milk, and groundnut oil the yield of milk.

5. With the exception of linoleic and palmitic acids, the increased dietary intake of the major fatty acids characteristic of the various oil supplements led to increased yields of these acids in the milk.

1. Groups of turkeys were given, to 10 weeks of age: diets E, basal, containing 2.3% mainly cereal lipid; A, basal plus 2.5% beef fat; B, basal plus 2.5% anchovy oil; C, as B, plus 0.02% ethoxyquin; D, basal plus 5% anchovy oil. Lipids from breast and leg muscle of all five groups were fractionated by thin-layer chromatography into five ‘neutral’ and six phospholipid fractions and the fatty-acid composition of each was determined by gas–liquid chromatography.

2. Individual lipid fractions differed widely in fatty-acid composition and in the degree to which they could be influenced by dietary fat supplements. Small but usually consistent differences were observed between corresponding fractions from breast and leg. Sphingomyelin (SP) and lysophosphatidylcholine contained largely saturated acids (76–80%); the other phospholipids were 44–48% and the ‘neutral’ lipids 38–50% saturated. Phosphatidylserine (PS), phosphatidylinositol(PI) and, in less degree, phosphatidylethanolamine (PE) were rich in stearic acid, though palmitic was much more abundant in the diets and in the other muscle lipids. SP contained no acid more unsaturatedthan linoleic (1–2%). PE and PI were richest in arachidonic and PE and PI in other polyene acids.

3. The effects of beef fat on the muscle lipids were small and mainly on the ‘neutral’ fractions.

4. The polyunsaturated fatty acids of the fish oil extensively displaced linoleic (and oleic) acids from all fractions (except SP); arachidonic acid was displaced from PE but not from PI.

5. The degree to which the fish-oil polyunsaturated acids of the three series entered the muscle lipids varied with the acid and with the fraction. Docosahexaenoic acid (22:6) reached a concentration of 20–25% in PE, nearly five times as great as its concentration in the dietary lipid.

6. Hydrolysis with phospholipase A showed that most of the unsaturated fatty acids were present in the 2-position of PC and PE, but the positional specificity was not complete, particularly for the less highly unsaturated acids.

7. The antioxidant ethoxyquin had no effect on the fatty-acid composition of any of the muscle lipid fractions.

1. Cages are described for housing copper-deficient rats.

2. The cages are of simple design and constructed of glass and Perspex. Urine and faeces can be readily obtained without exposing the animals to contamination with copper.

1. The compositions of the lipids in the atheromatous lesions of rabbits have been studied in an experiment in which two groups of rabbits (twelve/group) were given different atherogenic diets for a period of 38 weeks. One group of rabbits was given a diet in which 35% of the total calories was derived from butterfat and the other group was given a diet in which 48% of the total calories was derived from starch.

2. At the end of the feeding period the rabbits were killed and the atheromatous plaques were dissected out from the aortic intima of each rabbit. The lipid compositions of the aortic lesions were determined and the results compared with the compositions of the plasma lipids.

3. In the lipids of the aortic lesions in the rabbits given the high-butterfat diet, the proportions of cholesterol and cholesterol esters were higher and the proportion of triglycerides was lower than in the lipids of the aortic lesions in the rabbits given the high-starch diet. Irrespective of dietary treatment, free cholesterol constituted a higher proportion of the lesion lipids than it did of the plasma lipids.

4. In the rabbits on either dietary treatment, the lesion cholesterol esters contained higher concentrations of oleic acid and lower concentrations of linoleic acid than did the plasma cholesterol esters. In the lesion phospholipids there were higher concentrations of palmitic, palmitoleic, stearic and oleic acids and lower concentrations of linoleic and arachidonic acids than in the plasma phospholipids.

5. In both groups of rabbits the phospholipids of the aortic lesions contained higher proportions of cephalin and sphingomyelin and lower proportions of lecithin than did the plasma phospholipids.

6. The results of this investigation are discussed in relation to the possible origins of the lipids in the aortic lesions of the experimental rabbits.

1. Skinfold thicknesses at seven sites were measured during and after pregnancy in eighty- four women; in forty-eight of these, total body water was measured concurrently.

2. Early in pregnancy (10 weeks) the skinfold measurements were highly correlated with each other and with maternal weight, ratio of observed weight to standard weight-for-height,‘dry’ (water-free) weight, and with calculated estimates of body fat.

3. At nearly all sites, skinfold thicknesses increased up to about 30 weeks of pregnancy. Increases were greater at ‘central’ and least at ‘peripheral’ sites, and were not proportional to the initial skinfold thickness.

4. From 30 to 38 weeks of pregnancy, the patterns were variable: the mid-thigh skinfold continued to increase and at the other sites there was little change or a decrease.

5. All sites decreased by a surprisingly large amount between 38 weeks of pregnancy and the end of the first post-partum week. The evidence suggests that this change, which was not related to the presence or absence of oedema, occurred about the time of parturition.

6. From the end of the first post-partum week to 6–8 weeks post partum, the changes were again variable.

7. The increase of skinfolds during pregnancy was greater in underweight than in overweight women, and in primiparae than in multiparae. The pattern of change was not affected in any consistent manner by oedema.

8. The changes in skinfold thicknesses during pregnancy, especially up to about 30 weeks, showed patterns similar to those of total body-weight and ‘dry’ body-weight. A formula is given by means of which ‘dry’ weight can be predicted from five skinfolds, height and duration of gestation.

I. The carotene and vitamin A levels of liver, pancreas and body fat were determined in seventeen Ghanaians coming from areas where carotene-rich foods were freely available.

2. The liver was confirmed as the main storehouse of vitamin A, and vitamin A values for it were exceptionally high. Values for the other tissues were not higher than average.

3. In the study the carotene and vitamin A concentrations in the liver were higher in the females than in the males.

4. Under the conditions of high intake of carotene-rich foods, carotene was found to be distributed more evenly in various tissues than vitamin A.

1. The effects of iron overloading and unsaturation of dietary lipid on the metabolism of α-tocopherol in the rat were studies.

2. Young adult male vitamin E-deficient rats were given 1000 i.u. of vitamin A and 100 μg of [14C-5-Me]D-α-tocopherol and then given diets containing 5% methyl oleate or 5% cod-liver oil fatty-acid methyl esters. Rats from each group were given intramuscular injections of iron-dextran (50 mg Fe/kg rat) at 48 h intervals for 15 days, and compared with controls given dextran. After this time, liver, kidney and the remainder of the carcass were analysed for [14C]α-tocopherol, and liver and kidney were also analysed for vitamin A.

3. There was no evidence that Fe overloading caused any increase in the destruction of either tocopherol or vitamin A in vivo, whether or not the diet contained polyunsaturated fatty acids. Indeed, treatment with Fe significantly decreased the metabolism of the radioactive tocopherol dose in all three tissues studied.

4. These experiments show that the stress effect of Fe in the vitamin E-deficient animal is unrelated to an increase in oxidative reactions. They provide further evidence that ‘lipid peroxidation’ is not causally concerned in ‘anti-vitamin E’ stress conditions and that α-tocopherol does not function, in vivo, as an antioxidant.