HGPRT-positive and HGPRT-negative erythrocytes in heterozygotes for HGPRT deficiency.
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Biomedical subjects
Publications and source records attributed to R B Gordon.
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The significance of partial deficiency of erythrocyte adenine phosphoribosyltransferase (APRT), reported in a number of subjects with gout, has been investigated by studying its incidence in 700 normal blood donors. Three clearly deficient subjects were found, an incidence not significantly different from that in patients with abnormalities of urate metabolism. A new assay method for APRT is described in which an erythrocyte lysate is incubated with adenine and phosphoribosylpyrophosphate (PRPP) for a given time; both hemoglobin and adenine nucleotide (AMP) are then precipitated with lanthanum phosphate; the change in absorbance of adenine at 260 nm reflects the extent of its conversion to AMP by APRT.
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Urate production (miscible urate pool and turnover, daily production, glycine incorporation into urate) and urate excretion (24 hour urinary urate excretion on a purine free diet, renal clearances of urate and creatinine, per cent renal excretion of labelled urate, extra-renal elimination of urate) were measured in members of five families who demonstrated varying degrees of deficiency of the X-linked condition hypoxanthine-guanine phosphoribosyltransferase (HGPRT) deficiency. The hemizygous males, all of whom eventually developed symptoms, showed consistent overproduction of urate with a renal excretion of urate that varied from moderately to considerably increased. The nine heterozygotes, of whom seven were asymptomatic, also showed abnormalities of urate production, although all but two had normal serum urate concentrations. The one heterozygote who had developed gouty arthritis had the lowest renal excretory capacity for urate, whereas the one heterozygote who had developed an episode of renal colic had the highest urate clearance. In the heterozygotes with normal serum urate concentrations, the increase urate production was balanced by the renal excretion of urate. This demonstrates the importance of the relation between urate. This demonstrates the importance of the relation-between urate production and urate excretion in determining the clinical expression of abnormal urate metabolism.
A deficiency of adenine phosphoribosyltransferase (APRT) enzyme activity to approximately 40% of normal has been found in erythrocytes from a young woman aged 24 years, who had suffered from recurrent gouty arthritis since 11 years of age. She also demonstrated considerable, although asymptomatic, renal impairment with a creatinine clearance of one-third normal. Her father had suffered from gouty arthritis but had a normal APRT activity; he was obese, had a high purine intake and was a regular beer drinker. The patient's mother was asymptomatic with a normal serum urate concentration, but demonstrated a similar reduction in APRT activity to that of her daughter. Eleven other asymptomatic members of the family also demonstrated a similar reduction in APRT activity in erythrocyte lysates. The pattern of inheritance was consistent with autosomal transmission. Concentrations of phosphoribosylpyrophospate (PRPP) in erythrocytes were within normal limits both in the subjects with deficient, and in those with normal, APRT activity. Partial purification of APRT enzyme from erythrocytes of the index case did not reveal any difference from the normal enzyme as far as Michaelis constants, heat stability, or mobility in polyacrylamide gel was concerned. No primary abnormality of lipoprotein metabolism was demonstrated either in the propositus or in other members of her family. Study of urate metabolism in the propositus indicated that, although urate production was within the normal range in absolute terms, there was increased incorporation of glycine into produced urate, usually taken as one index of de novo urate production. Impaired renal excretion of urate was also shown. Although detailed study of urate metabolism has not been undertaken in other family members with APRT deficiency, no conclusive relationship has yet been demonstrated between APRT deficiency and disordered urate metabolism.
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This report presents two cases of abdominal aortic dissecting hematoma without involvement of the thoracic aorta. Computed tomography can reliably diagnose or exclude aortic dissection by demonstrating the specific findings of an intimal flap and displacement of intimal calcification into the aortic lumen.