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Biomedical subjects

M Hjelm

Publications and source records attributed to M Hjelm.

At least 55 records · Page 3Linked to original sources
PubMed1987

Effect of partial ornithine carbamoyltransferase deficiency on urea synthesis and related biochemical events.

The biochemical response to an intravenous alanine load of 0.25 g/kg was studied in nine adult female relatives of children with ornithine carbamoyltransferase deficiency. Six were classified as affected by partial deficiency and three as unaffected. The plasma ammonium concentration showed no change after the alanine load in the unaffected group, but marked increases occurred in all but one of the affected groups. The maximum rate of urea synthesis after the alanine load was decreased by 37% (P = 0.02) and delayed by 43% (P = 0.02) in the affected group. In the affected group a low rate of urea synthesis was associated with high urinary orotate excretion, high maximum plasma ammonium concentration and delay in the time taken to reach the maximum rate of urea synthesis (Kendall concordance W = 0.55, P less than 0.05). The effects of a higher dose of alanine and of oral protein were compared. The alanine load of 0.25 g of alanine/kg body weight was shown to provide an adequate stimulus to urea synthesis with a more rapid return of ammonium concentration to the pre-load level than with the protein load. The implication of these results in determining the distribution of flux control of urea synthesis, the discrepancy between them and predicted results and the necessary modifications to quantitative simulations are discussed.

Alanine↗
PubMed1987

Recommendation for collection of skin puncture blood from children, with special reference to production of reference values.

Reliable reference values need to be collected under standardized conditions. In order to enable comparison of values observed on patients with reference values, it is also desirable to use the same standardized conditions on patients. The present recommendation was produced as a joint effort of representatives of the clinical chemists and paediatricians of Scandinavia and describes the following details. Preparation of the child before specimen collection (food intake, time of day, physical activity, posture, environment), preparation of skin puncture site (warming, disinfection, ointment), instruments for blood collection (lancet, blood collection vessel), site of puncture (plantar surface of foot, finger, ear lobe), collection of emerging blood and handling and storage of the specimen.

Adolescent↗
PubMed1987

Haemoglobin A/F ratio in neonates at 7 days correlated with birth weight and estimated gestational age.

Haemoglobin (Hb) A and Hb F has been determined in neonates of Afro-Caribbean and North European origin with gestational ages varying from 32 to 42 weeks. There was no difference in the distribution of Hb A/F ratios between the two groups. Only weak correlations could be established between the Hb A/F ratio and the estimated gestational age or birth weight. This would indicate that there is a considerable interindividual variation in the timing of the switching of haemoglobin synthesis from Hb F to Hb A and erythrocyte production from liver to bone marrow and of oxygen affinity of fetal blood. Thus, intra-uterine adjustments of the oxygen release capacity of haemoglobin would have to rest on biochemical mechanisms during the third trimester.

Birth Weight↗
PubMed1987

Transient hyperphosphatasemia of infancy and early childhood: clinical and biochemical features of 21 cases and literature review.

Clinical and biochemical features of transient hyperphosphatasemia of infancy and early childhood are reviewed in 21 patients we have studied and in a further 93 cases reported in the literature. The diagnosis is suggested by the finding of an increased activity of alkaline phosphatase (EC 3.1.3.1) in plasma, typically more than fivefold the adult upper reference limit, in a child under five years of age, without evidence of liver or bone disease. The condition is confirmed by the presence of a characteristic pattern of alkaline phosphatase isoenzymes and by the normalization of the enzyme's activity in plasma within approximately three months. The etiology of the condition and possible mechanisms of the enzyme increase are discussed.

Age Factors↗
PubMed1986

Packing materials suitable for rapid, analytical, low-pressure chromatography of haemoglobins on midget columns.

Rapid, quantitative, chromatographic separations of mixtures of human haemoglobins have been performed on short (5-20 mm) columns of packing material. The desirable characteristics of suitable column packing materials are illustrated and discussed. Simple, inexpensive, manually operated equipment can be used for the analysis, since the specifically designed midget columns generate little back pressure (10-30 lb/in2) when eluted at constant flow rates up to 2 mL/min. Cation exchange chromatography on bonded silicas has been used for the detection of pathological haemoglobinopathies. Separations similar to the HPLC procedures are possible with the correct selection of buffer composition. It also compares favourably with the methods in common clinical use employing electrophoresis on cellulose acetate. Both ion-exchange and affinity methods for the estimation of glycated haemoglobins have been developed and are compared.

Chromatography, Ion Exchange↗
PubMed1986

Validation of a method for measuring the short-term rate of urea synthesis after an amino acid load.

The response of the plasma concentration of urea to the oral and intravenous administration of alanine was studied in healthy adult humans. The instantaneous rate of urea synthesis was calculated by using a model-dependent procedure. The errors in this procedure were calculated and it was shown that analytical precision and sampling frequency, and the estimates of the distribution volume and elimination fluxes, were adequate to determine the synthesis parameters. A direct test of the compartmental model was made by the intravenous injection of exogenous urea. The one-compartment model with first-order elimination gave a good fit to the experimental results at times greater than 8 min after the injection. Both oral and intravenous loads of alanine had dose-dependent effects on the rate of urea synthesis. There was no evidence of a limit to the maximum possible rate of urea synthesis in these experiments and the values obtained were similar to published results for different stimuli and methods of measurement. The rate of synthesis increased more rapidly after intravenous loads and subjective side-effects were less severe. The intravenous administration of alanine appears to be a suitable stimulus for urea synthesis.

Administration, Oral↗
PubMed1986

Sweat sodium related to amount of sweat after sweat test in children with and without cystic fibrosis.

The sweat concentration of sodium was found to be inversely correlated with the amount of sweat obtained after a sweat test according to the method of Gibson & Cook in children without and with cystic fibrosis. Reference intervals for sweat sodium overlapped for the two groups but two-dimensional reference distributions for the amount of sweat (range 20-440 mg) correlated with its sodium content were completely separated. The establishment of similar distributions in centres carrying out sweat tests could serve to assess the performance of this investigation at local level.

Adolescent↗
PubMed1986

Deletion of the steroid 21-hydroxylase and complement C4 genes in congenital adrenal hyperplasia.

DNA was analysed from 20 patients with congenital adrenal hyperplasia due to cytochrome P-450 steroid 21-hydroxylase deficiency. Using probes recognising sequences in both the 21-hydroxylase gene and the adjacent fourth component of complement (C4), one patient was found to have a homozygous deletion of DNA which encompassed the C4B and 21-hydroxylase B genes. Evidence is presented for this deletion arising by recombination between homologous regions of 21-hydroxylase A and B. Seven patients appeared to be heterozygous for the same deletion, but no detectable alteration in the 21-hydroxylase gene could be demonstrated in others.

Adrenal Hyperplasia, Congenital↗
PubMed1985

Determination of the rate of urea synthesis from serial measurements of plasma urea concentration after an alanine load: theoretical and methodological aspects.

A method is described by which the rate of synthesis of urea can be calculated from the change of plasma concentration of urea after an alanine load. The results can be expressed in terms of f, the maximum increase in the rate of urea synthesis, and t, the time at which urea synthesis reaches its maximum. These parameters are calculated by an algebraic curve-fitting technique which is suitable for a desk computer. The method removes the need for isotopic analysis and urine collections. The effect of various errors and experimental conditions on the calculated synthesis parameters is investigated.

Alanine↗