1. Phospholipid content of brains of 3- or 8-week-old undernourished rats was 7–9 % less than that for the corresponding control animals and this deficit could not be made up by rehabilitation. Phosphatidyl ethanolamine and plasmalogen were the components most affected in brains of undernourished rats.

2. Incorporation of 32P into phospholipids by brain homogenates was 28% higher in 3-week-old undernourished rats. It is suggested that enhanced phospholipid metabolism in undernourished animals may be related to behavioural alterations noted previously (Sobotka, Cook & Brodie, 1974).

3. Ganglioside concentrations in 3- and 8-week-old undernourished animals were 14% and 11.5% less respectively than those of the control animals and this difference could be made up by rehabilitation. [14C]Glucosamine incorporation in vivo into brain gangliosides was not affected by undernutrition.

1. The heat losses and energy balances of thirty-eight individually housed pigs (initial body-weights 21–38 kg) were measured continuously for periods of 14 d when they were maintained at environmental temperatures of 10, 15, 20, 25 or 30°. At each temperature four levels of feeding were given approximating to once, twice and three times the maintenance energy intake and the ad lib. level. The minimal maintenance energy requirement (M) was calculated to be 440 kJ metabolizable energy (me)/kg0.75 per d at 25°.

2. me intake at the ad lib. level decreased from 1965 kJ/kg0.75 per d at 10° to 1202 at 30°.

3. Heat loss calculated from multiple regression analysis decreased to minimum levels between 20 and 25° 30° was within the hyperthermic zone at each plane of nutrition.

4. The partition of heat loss into its sensible and evaporative components showed that evaporation increased from 25% at 10° to 78% at 30°.

5. Critical temperature was dependent upon food intake and decreased from 23.1° at M to 20.7° at 2M, 18.0° at 3M and 16.7° at 4M.

6. The extra food required to meet extra thermoregulatory heat production per 1° below the effective critical temperature was 0.65 g/kg body-weight per d.

1. Measurements of energy and nitrogen balances were made on thirty-eight individually housed pigs (initial body-weights 21–38 kg) at environmental temperatures of 10, 15, 20, 25 and 30° with four levels of feeding at each temperature. Values for energy retention (ER), protein (P) and fat (F) deposition and body weight gain (δW) were calculated at each temperature at metabolizable energy (me) intakes equivalent to once (M; 440 kJ/kg0.75 per d), twice (2M), three (3M) and four (4M) times the thermoneutral maintenance energy requirement.

2. ER at each plane of nutrition increased with temperature to maximal values between approximately 20 and 25° ER was negative at four of the five environmental temperatures at M.

3. P increased significantly with increase in me intake but was dependent on environmental temperatures only at intakes of M and 2M. The increase in P per unit increment in me intake decreased from 0.16 at 10° to 0.12 at 30°. The net efficiency of protein utilization also decreased with increase in environmental temperature from 0.54 at 10° to 0.39 at 30°.

4. F increased significantly with increase in me intake, but was more temperature-dependent than P, increasing to maximum values estimated to be between 20 and 25° at each level of intake; F at 30° was less than that at 25°. The increase in F per unit increment in me intake decreased from 0.63 at 10° to 0.51 at 30°.

5. The optimum temperature for ΔW was dependent upon me intake, varying from above 30° at M to less than 20° at 4M. The reduction in ΔW per 1° at 15° was also dependent upon the level of intake decreasing from 1.63 g/kg0.75 per d at M to -0.09 at 4M.

6. For a 35 kg pig the reduction in P, as a result of a 1° decrease in temperature at 15° at an intake corresponding to 2.5M, was equivalent to a 4 g/d reduction in food intake; the corresponding equivalent for F was 28 g/d.

1. From the relation between metabolizable energy (me) intake and heat loss (H), energy retention (ER), protein (P) and fat (F) deposition the energy costs of maintenance (MEm) and the partial efficiencies of energy retention (k) and protein (kp) and fat (kf) retention were determined in growing pigs at environmental temperatures of 10, 15, 20, 25 or 30°.

2. k decreased with increase in environmental temperature from 0.79 at 10° to 0.63 at 30° with 0.67 at the thermally-neutral temperature of 25°. Each 0.04 decrease in k was associated with a 100 kJ/kg0.75 per d decrease in mem Analysis, within several ranges of environmental temperature, suggested a curvilinear relation between ER and me intake indicating a decrease in k with increase in level of feeding, particularly at thermally-neutral temperatures.

3. Both kp and kf were similar at each environmental temperature and decreased from 0.78 at 10° to 0.63 at 30°. These values are discussed in relation to those predicted from experimentation and it is suggested that the wide range of predicted estimates of kp could be attributed to differences in the rate of protein turnover.

1. Serum albumin levels have been estimated in healthy adult Nigerians. The average level of albumin was 41.4 g/l and there was no sex difference, but the findings differed from that of a previous survey in Ibadan. The importance of serum albumin measurement in relation to the socio-economic and dietary habits of the population has been reviewed.

2. It is concluded that socio-economic, dietary and cultural changes associated with Western education could be responsible for the increased level of serum albumin in this healthy population.

3. It is suggested that similar surveys should be done by locally-practising chemical pathologists.

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. 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. 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. 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. 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. 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. 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.

1. Rabbit caecal segments in situ were used to measure absorption rates of volatile fatty acids (VFA) and inorganic ions from a saline solution comparable in composition to normal caecal fluid.

2. Results confirm the importance of VFA absorption from caecal material found by other workers.

3. Like the mammalian colon, the rabbit caecum conserved large amounts of sodium, chloride and water. Bicarbonate was also absorbed.

4. VFA replacement studies showed that net water absorption was reduced, net electrolyte absorption was hardly influenced.

5. Na replacement completely inhibited net water absorption and decreased net VFA and Cl absorption, HCO3 was heavily secreted.

6. These findings indicate that VFA absorption in the rabbit caecum is partly dependent on Na absorption and that in the absence of Na an anion-exchange mechanism occurs.

1. In vitamin B12 deficiency the activity of tetrahydropteroylglutamate methyltransferase (EC 2.1.1.13) is depressed and the synthesis of methionine is reduced. Because the methyl group of methionine is largely utilized for the methylation of phosphatidylethanolamine, we investigated the effects of vitamin B12 deficiency on phosphatidylcholine synthesis.

2. The incorporation of injected [14Clformaldehyde into liver phosphatidylcholine was reduced by approximately 50% in vitamin B12-deficient rats. Also the corresponding incorporation of 5-[14C]methyl-tetrahydrofolic acid tended to decrease. The findings are consistent with a lower conversion of these precursors to methionine.

3. The effect of the deficient methyl-group supply on phosphatidylcholine synthesis was also investigated by the injection of [14C]ethanolamine. The amount (%) of lipid-14C recovered in phosphatidylcholine was significantly reduced in vitamin B12 deficiency.

4. Chemical analysis of liver phospholipids showed that the vitamin B12-deficient rats had a higher proportion of phosphatidylethanolamine and a lower proportion of phosphatidylcholine, indicating that the impaired synthesis of phosphatidylcholine by methylation leads to changes in membrane phospholipid composition.

1. Twenty-four Sprague-Dawley female rats were randomly assigned to three groups (groups A, B, C). Group A was given a folic acid-free diet and groups B and C received 0.0018 g folic acid/kg diet. Rats in group C were also given a supplement of 1 mg folic acid/d by intraperitoneal injection.

2. After 14 d of feeding the rats were mated. The diets were continued throughout gestation. On day 21, of gestation the dams were killed and their livers and products of conception assayed for RNA, DNA, protein and tetrahydrofolate dehydrogenase (5,6,7,8-tetrahydrofolate dehydrogenase; EC1.5.1.3) activity.

3. The foetuses, placentas and livers from supplemented rats (group C) were significantly larger than those from groups A and B and had a higher content of RNA, DNA and protein. Those tissues from group A dams were smaller than those from the other groups and had a correspondingly reduced nucleic acid and protein content.

4. The activity of tetrahydrofolate dehydrogenase, the first and rate-limiting enzyme in the metabolism of folate, was increased in the folate supplemented rats (group C) and reduced in the rats given a folic acid-free diet (group A). These changes in enzyme activity could explain the differences in nucleic acid biosynthesis and growth shown by the different groups.

1. Rats given diets containing freshly-irradiated wheat showed significantly lower mean antibody titres to four different antigens, decreased numbers of antibody-forming cells in the spleen and rosette-forming lymphocytes as compared to rats given either unirradiated wheat or irradiated wheat stored for a period of 12 weeks.

2. The immune response in rats given 90 g protein/kg diet was essentially similar to that seen in animals given 180 g protein/kg diet.

1. Guinea-pigs were growth-retarded in early life by feeding their mothers a restricted quantity of food during the second half of pregnancy. After birth, all animals were fed ad lib. Body-weights were recorded weekly and behavioural tests were made on adult males. The animals were then killed and their brains dissected into forebrain, cerebellum and brain stem. These regions were weighed and DNA-phorphorus content measured.

2. At 14 weeks each male was paired with another male for 10 min on four consecutive days and their social behaviour scored. Tests 1 and 2 were on like-treatment pairs and tests 3 and 4 on unlike-treatment pairs. At 25 weeks the same animals were subjected to six graded series of brief, unavoidable shocks and their responses recorded. After 3 d, thresholds of aversion to electric shock were measured by recording the period of time spent on the ‘safe’ side of a rectangular box at five shock levels.

3. Undernourished guinea-pigs were significantly lighter than controls at birth but not at adulthood. Regional brain weights and DNA-P content of previously-undernourished guinea-pigs were significantly lower than those of controls, with the greatest deficit in brain stem.

4. Pairs of previously-undernourished guinea-pigs began to interact more quickly and threatened and nosed each other more often than pairs of controls. In mixed pairs previously-undernourished animals chased controls more than their control partners chased them. There were no differences between groups in responsiveness to unavoidable shock or in aversion thresholds.

1. The effects of bucket- v. teat-feeding and warm- v. cold-milk feeding on the flow of duodenal digesta and the concurrent pancreatic secretion were studied in two experiments in preruminant Ayrshire calves (28–43 d of age), fitted with duodenal re-entrant and pancreatic sac cannulas.

2. As measured by the time interval taken for total recovery of the polyethylene glycol fed in the milk, the whey fluids had a more rapid passage through the abomasum when the calves were given warm milk by teat rather than by bucket (Expts 1 and 2). The duodenal digesta contained less sodium ions and more ‘Cl-Na+’ when the calves were fed by teat even though the volumes of milk drunk and duodenal flow were similar. It was concluded that more abomasal acid was secreted when calves were fed by teat.

3. When the calves were fed by teat rather than by bucket, the protein-nitrogen : N (PN : N) in the duodenal digesta was lower, especially during the first 6 h after feeding and there was a tendency for more pancreatic proteases to be secreted.

4. In Expt 1, when the calves were given warm milk the total flow of N and lipid in the duodenal digesta was 22 and 19% greater than that ingested. This was considered to be due to the coagulum from the penultimate meal plus the experimental meal passing more readily through the duodenum when sampling and to endogenous secretion of N and lipid.

5. When four Ayrshire calves were bucket-fed cold, rather than warm milk there was a reduced secretion of abomasal and pancreatic fluids and abomasal acid. There were no differences in the time interval required for the whey fluids to leave the abomasum or the PN : N value.

6. There was a positive correlation between the total duodenal flow of non-whey fluids and the pancreatic secretion regardless of the method of feeding.

7. The completeness of digestion and susceptibility of calves to diarrhoea when fed by teat and bucket is discussed.