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Biomedical subjects

A A Jackson

Publications and source records attributed to A A Jackson.

At least 163 records · Page 9Linked to original sources
PubMed1985

Plasma concentrations of N-acetylneuraminic acid in severe malnutrition.

In rat studies, circulating concentrations of N-acetylneuraminic acid (NANA) have been shown to be an indicator of NANA concentrations in the brain and functional brain activity, in relation to nutritional state and stimulation. Abnormal behaviour can be improved with exogenous NANA. In the present study, the plasma NANA concentration has been measured in children with severe malnutrition and compared with that in controls. NANA was measured colorimetrically in the plasma of twenty-three severely malnourished children (mean age 11.43 (SD 6.05) months) before and after recovery, and in thirty-four controls (mean age 14.28 (SD 7.32)months). In thirteen of the malnourished children, NANA was measured after infections had been treated with a course of antibiotics. Mean plasma NANA concentration was significantly higher in protein-energy malnutrition (PEM) (2.89 (SD 0.58) mumol/ml; n 23) compared with controls (2.13 (SD 0.37) mumol/ml; n 34, P less than 0.001). The levels remained high in PEM after infections had been treated (2.87 (SD 0.43) mumol/ml, n 13) but returned to control levels at recovery from PEM (2.14 (SD 0.24) mumol/ml). In contrast to the findings in rats, in malnourished children plasma NANA concentrations were not reduced and did not relate directly to nutritional state or, by inference, brain function. These findings do not provide any support for the use of exogenous NANA supplements to improve brain function in humans.

Child, Preschool↗
PubMed1985

Thiamin status in normal and malnourished children in Jamaica.

Thiamin status has been measured using the erythrocyte transketolase (EC 2.2.1.1) assay in twenty-eight normal children and in twenty-five severely-malnourished children throughout the course of recovery. Subclinical thiamin deficiency was found in 7% of the normal children and 36% of the malnourished children on admission. There was no significant association between thiamin status and oedema, stunting or wasting, history of breast-feeding, pattern of weaning, age or sex. Five malnourished children, who died, all had a normal thiamin status on admission; however, two developed biochemical evidence of thiamin deficiency preterminally.

Erythrocytes↗
PubMed1985

Whole-body protein turnover in Jamaican women during normal pregnancy.

A cross-sectional study was carried out among 18 Jamaican pregnant women divided into three groups of 6 subjects according to the stage of pregnancy: group B, 12 weeks, group C, 24 weeks and group D, 33 weeks. A group (group A) of 6 non-pregnant women was selected as control. The rate of whole-body protein turnover was measured by continuous oral administration of 15N-glycine and the resting metabolic rate by the open-circuit method. All subjects had a normal pregnancy outcome. The composition of the diet on the day of the study was comparable between the four groups (approximately 80 g protein and 9.45 MJ energy) and not significantly different from the composition of the diet during the 2 d prior to the experiment. The rates of protein synthesis and breakdown were higher in groups B and C compared to group A and lower in group D where they reached values slightly higher than in group A. Estimated from urea enrichment, these rates did not vary significantly among the groups, while estimated from ammonia enrichment the difference was significant (P less than 0.05) and there was a negative correlation between the gestational age and the rate of synthesis (r = -0.63) and breakdown (r = -0.69). Nitrogen retention was comparable between the three groups of pregnant women and significantly higher than in the group A. The resting metabolic rate was similar between the groups of pregnant women. These results suggest that the rates of protein turnover observed during gestation reflect more the changes that occur in maternal than those in fetal tissues. The values for protein synthesis and nitrogen retention indicate that the amount of protein deposited during pregnancy is greater than that expected on the basis of body composition analysis. It is also suggested that as pregnancy proceeds whole-body protein turnover represents a smaller part of the resting metabolic rate.

Adult↗
PubMed1985

Free and total triiodothyronine and thyroxine in malnourished Jamaican infants. The effect of diet on plasma levels of thyroid hormones, insulin and glucose during recovery.

Plasma concentrations of free triiodothyronine (FT3), total triiodothyronine (TT3) and total thyroxine (TT4) were reduced to 63.0, 37.7, 61.7 per cent of controls respectively in protein-energy malnutrition (PEM), while free thyroxine (FT4) was elevated by 23 per cent. There was a gradual increase of both TT4 and TT3 during recovery. The ratio of free to bound hormones was high in malnutrition and declined with recovery, indicating a deficiency of thyroid-hormone binding in malnutrition. The observation of a significant reduction (P less than 0.05) in T3/T4 ratios, which occurred in malnutrition and was induced during recovery after 3 d on a low energy maintenance diet, suggested depressed conversion of T4 to T3 due to energy restriction. Energy restriction also significantly (P less than 0.001) depressed plasma insulin concentrations in the presence of nearly constant plasma glucose levels.

Blood Glucose↗
PubMed1984

The non-invasive measurement of urea kinetics in normal man by a constant infusion of 15N15N-urea.

A two-pool model is described for the non-invasive measurement of urea kinetics in man. The isotope, 15N15N-urea, was given until an isotopic steady state was reached in urine and the time taken to achieve this is defined. During an isotopic steady state, a comparison was made of the effect of giving the isotope orally, intravenously and intragastrically; no differences were found between the different routes. Measurements of enrichment were made on excretion products in urine. In six normal adults with a protein intake of 200 mg N/kg/d, the urea production rate was 139 +/- 15 mg N/kg/d, 70 per cent of which was excreted in urine. Of the 34 mg N/kg/d produced by hydrolysis of urea in the gastrointestinal tract, 41 per cent was resynthesized to urea, and about 48 per cent was available for other synthetic processes.

Adult↗
PubMed1983

Whole-body protein turnover and nitrogen balance in young children at intakes of protein and energy in the region of maintenance.

Nitrogen balance and whole-body protein turnover were measured in children aged about one year taking diets which provided 1.7 or 0.7 g milk protein/kg/d at three levels of metabolizable energy, 80, 90 and 100 kcal/kg/d. All the children were in positive nitrogen balance at all levels of energy intake on 1.7 g protein/kg/d. Nitrogen equilibrium was maintained on 0.7 g protein/kg/d when the energy intake exceeded 90 kcal/kg/d, but on 80 kcal/kg/d nitrogen balance was negative. Whole-body protein turnover was measured from the enrichment in urinary ammonia following a continuous infusion of 15N-glycine. The variation between individuals on the same diet was significantly greater than the variation within individuals at different levels of energy intake. For the group as a whole protein synthesis on 1.7 g protein/kg/d was 0.74, 0.75 and 0.87 g N/kg/d on 100, 90 and 80 kcal/kg/d respectively; whereas on 0.7 g protein/kg/d it was 0.37, 0.38 and 0.40 g N/kg/d. These results show that over this range of intakes protein synthesis decreased as dietary protein fell, but tended to increase as energy intake fell.

Ammonia↗
PubMed1982

Glutamine production rate and its contribution to urinary ammonia in normal man.

1. Glutamine [15N]amide was infused at a steady rate of 33.34 mumol/h into seven male adult volunteers who were in the fed state and normal acid-base status. 2. Plasma glutamine amide N enrichment and urinary ammonia N enrichment rose to a constant rate within 3 h. 3. The glutamine production rate was 51.8 +/- 7.9 mmol/h. 4. The total ammonia excretion rate was 0.87 mmol/h. Of this excreted ammonia 62.6 +/- 9% was derived from the amide N atom of glutamine. 5. The excreted glutamine amide N (0.53 mmol/h) was only 1% of the glutamine production. If half the ammonia formed by the kidney is excreted in urine and half liberated into the renal vein in subjects with normal acid-base status [E. E. Owen & R. R. Robinson (1963) Journal of Clinical Investigation, 42, 263-276], then the kidney accounts for only 2% of glutamine disposal. 6. Whole body protein turnover, measured from the urinary [15N]ammonia enrichment, was 30.3 +/- 7.7 g of N/day (2.8 g of protein day-1 kg-1).

Adult↗
PubMed1982

Hepatic function in rats with dietary-induced fatty liver, as measured by the uptake of indocyanine green.

1. The hepatic uptake of indocyanine green (ICG) has been measured in rats receiving a 50 g protein/kg diet for 6, 12 or 20 d or a choline-deficient diet for 2 or 6 d. 2. There was no effect on ICG uptake on the choline-deficient diet, although all the rats developed an intense fatty infiltration of the liver by 6 d. 3. The rats on the 50 g protein/kg diet showed impaired uptake of ICG at 6, 12 and 20 d, which appeared to be related to the extent of fatty infiltration. 4. It is concluded that ICG uptake is predominantly a function of the periportal zone of the liver lobule, and therefore likely to be sensitive to insults that exert their predominant effect in this zone.

Animals↗
PubMed1981

Nitrogen metabolism in preterm infants fed human donor breast milk: the possible essentiality of glycine.

Nitrogen metabolism was studied in three preterm infants (mean gestation 32 wk) by the method of consecutive metabolic balance. The absorption and retention of nitrogen from breast milk was measured, and protein turnover, synthesis, and breakdown were calculated from isotopic plateau of urinary urea and ammonia using an intermittent oral administration of 15N-glycine. Weight gain and nitrogen retention were compared with the weight gain and nitrogen accumulated for a foetus of equivalent gestational age in utero. The average composition of the milk was 289 +/- 19 KJ dl-1 and 1.44 +/- 24 g protein dl-1. The intake of energy was 572 +/- 61 KJ kg-1 day -1 and of nitrogen 447 +/- 99 mg kg-1 day-1. Stool output of nitrogen was 100 +/- 32 mg kg-1 day-1 giving an absorption of 348 +/- 78 mg kg-1 day-1, as urinary excretion was 91 +/- 17 mg kg-1 day-1 retained nitrogen was 256 +/- 71 mg kg-1 day-1, or 56% of intake. The specific weight gain was 15.6 +/- 2.6 g kg-1 day-1 and 53% of this comprised lean tissue (range 34 to 89%). In all but one study the postnatal retention of nitrogen fell far short of calculated in utero accumulation. The results of protein turnover were surprising. In six of the eight studies urinary urea failed to become enriched at all. Protein turnover calculated from the ammonia plateau was 1.94 +/- 0.54 g nitrogen kg-1 day-1, synthesis 10.9 +/- 3.4 g protein kg-1 day-1 and breakdown 9.3 +/- 3.4 g protein kg-1 day-1. It is concluded that the amino acid composition of breast milk may be inappropriate for supporting rates of lean tissue deposition equivalent to in utero accumulation.

Body Weight↗
PubMed1980

Albumin and nutritional oedema.

The nature of the association between plasma albumin and nutritional oedema has been examined by observing the changes in albumin during loss of oedema in patients on a restricted diet. Since there was no difference in the concentration of plasma albumin before and after loss of oedema, the association is not causal. These results provide no support for the assertion that nutritional oedema should be treated with a high-protein diet or an albumin infusion.

Dietary Proteins↗
PubMed1980

[15N]Glycine metabolism in normal man: the metabolic alpha-amino-nitrogen pool.

1. [15N]Glycine was infused into fed, fasted or acidotic humans. 2. In all metabolic states there was considerable transfer of labelled nitrogen to urea and ammonia, but alanine and glutamate did not become enriched. 3. The findings show that free exchange of nitrogen between all amino acids does not take place. Glycine, serine, threonine, lysine and histidine cannot be considered part of the alpha-amino-nitrogen pool as classically conceived, although they form up to one-half of that pool.

Acidosis↗