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Biomedical subjects

R J Leeming

Publications and source records attributed to R J Leeming.

At least 37 records · Page 2Linked to original sources
PubMed1988

Preliminary identification of a low molecular weight serological mediator in chronic idiopathic urticaria.

Sixteen patients with chronic idiopathic urticaria were skin tested with their own serum, IO with autologous plasma and five with serum that had been heated to 56 degrees C to inactivate complement. Eight showed a weal and flare response to whole serum, four to plasma and five to heat-treated serum. All serum-positive patients showed the same response to their own plasma and to heated serum, indicating that the mediator concerned is not generated by clotting and is not dependent on a functioning complement pathway. Three control subjects were negative to autologous serum, plasma and heated serum. Local tachyphylaxis was demonstrated in five serum-positive patients on reinjection of the same site with autologous serum on 3 consecutive days. This raises the possibility that the serological mediator may be acting by mast cell degranulation or directly on receptors in blood vessels and that repeated injections could induce a change in the number of receptors. Passage of whole autologous serum from four serum-positive patients through ultrafiltration membranes showed that fractions with a molecular weight of less than 30,000 daltons were still able to produce a positive skin test response, but those less than 1000 daltons were not. All serum fractions from two serum-negative patients and three normal controls were negative. Whole autologous serum from five serum-positive patients and two control subjects were separated by column chromatography. On skin testing with pooled fractions, the greatest response was produced by fractions of 10,000-15,000 daltons in the serum-positive patients, but there was no response in the controls.

Adolescent↗
PubMed1986

Biopterin and neurotransmitter amine metabolism in children with acute lymphoblastic leukemia receiving methotrexate therapy.

To test the hypothesis that some of the neurologic sequelae of treatment for acute lymphoblastic leukemia (ALL) might be related to abnormalities in biopterin metabolism associated with methotrexate (MTX) therapy, total biopterin levels in cerebrospinal fluid (CSF) and plasma, and homovanillic acid (HVA) and 5-hydroxyindoleacetic acid (5HIAA) were measured in a cross-sectional study of 80 children with ALL. For comparison, biopterins were also measured in a group of children of similar age undergoing investigation for neurologic disease. In children with ALL studied before therapy, no significant difference was found between the means of plasma biopterin or CSF biopterin concentrations and the means in the control group. In children receiving MTX, plasma biopterin values were higher in the group given maintenance therapy than in children observed before treatment. CSF levels were significantly increased only in those patients who had completed 2 years of maintenance therapy. CSF concentrations of HVA and 5HIAA in patients with ALL who had received no treatment (median values 52 and 18 ng/ml, respectively) showed a wide scatter and were inversely related to age. In patients receiving MTX, concentrations of these metabolites were higher than in the untreated group, again reaching a peak in patients just completing 2 years of treatment (median HVA 110 ng/ml, 5HIAA 34 ng/ml). These results provide no support for the idea that neurotransmitter amine deficiency occurs in children with ALL receiving MTX, and indicate, rather, that amine and biopterin synthesis increases in such patients.

Adolescent↗
PubMed1986

Neurological aspects of biopterin metabolism.

Plasma total biopterin concentration was measured by bioassay in 59 infants with hyperphenylalaninaemia and in 50 children with developmental regression and or movement disorder with normal plasma phenylalanine concentrations. In infants with raised phenylalanine concentrations plasma biopterin concentrations were significantly raised in proportion to the phenylalanine values. Five patients had plasma biopterin concentrations at the extremes of the range, and of these two had defective biopterin metabolism. One with low plasma biopterin concentration apparently had a partial defect of biopterin synthesis but died before investigations were complete. One with high plasma biopterin concentration, even when phenylalanine concentrations had fallen to the normal range, had dihydropteridine reductase deficiency. In this patient concentrations of homovanillic acid and 5-hydroxyindolacetic acid in the cerebrospinal fluid (CSF) were severely reduced. In children without hyperphenylalaninaemia plasma biopterin concentrations were normal. Twenty two patients were subjected to lumbar puncture, of whom six with developmental regression without movement disorder had normal CSF biopterin concentrations, and 11 with movement disorder other than torsion dystonia had significantly lower CSF biopterin concentrations. Five patients with torsion dystonia had normal biopterin concentrations.

Adolescent↗
PubMed1986

Subacute combined degeneration of the cord, dementia and parkinsonism due to an inborn error of folate metabolism.

A 2-year-old girl with 5,10-methylenetetrahydrofolate reductase deficiency developed subacute combined degeneration of the cord and a leuco-encephalopathy which was confirmed at necropsy. Total folate concentrations in serum, red cells and CSF were markedly reduced whereas vitamin B12 concentrations were normal. In addition the patient had Parkinsonism and reduced concentrations of homovanillic acid, 5-hydroxyindoleacetic acid and total biopterins in cerebrospinal fluid. Folic acid administration was accompanied by fits and acute deterioration in the movement disorder. At necropsy the basal ganglia showed no detectable abnormality.

5,10-Methylenetetrahydrofolate Reductase (FADH2)↗
PubMed1984

Blood spots on Guthrie cards can be used for inherited tetrahydrobiopterin deficiency screening in hyperphenylalaninaemic infants.

We describe a method of screening for dihydropteridine reductase deficiency and dihydrobiopterin synthesis deficiency--the two inherited defects that cause tetrahydrobiopterin deficiency--using blood spots on Guthrie cards. Dihydropteridine reductase deficiency may be identified positively, and a biopterin value of less than 6.0 micrograms/l in the presence of hyperphenylalaninaemia indicates further investigation for dihydrobiopterin synthesis deficiency.

Adolescent↗
PubMed1983

Dihydrobiopterin biosynthesis deficiency.

For the last 2 years, a program has been developed to screen all hyperphenylalaninemic babies for tetrahydrobiopterin deficiency, by measurement of pterins in urine. High neopterin and low biopterin levels were found in the urine of a 1-month-old girl. Further investigations confirmed an impaired conversion of neopterin to biopterin. No neurological signs were noted, but, in regard to the laboratory data, neurotransmitter replacement therapy was instituted at 2.5 months of age. The most remarkable feature was a rapid increase in the dietetic phenylalanine tolerance, despite the proof that the child was not able to clear a challenging dose of phenylalanine and the record of unchanged pathologically low excretion of biopterin during a 2 month period.

Biopterins↗