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Biomedical subjects

H A Simmonds

Publications and source records attributed to H A Simmonds.

At least 199 records · Page 11Linked to original sources
PubMed1982

An X-linked syndrome characterised by hyperuricaemia, deafness, and neurodevelopmental abnormalities.

Purine overproduction, with normal levels of the purine salvage enzymes, has been found in a 3-year-old boy and his mother. Both have high-frequency hearing loss from infancy. The child is hypotonic and shows locomotor delay. Two male siblings with similar neurodevelopmental problems died in early childhood. Biochemical studies suggest a combined syndrome associated with a superactive PP-ribose-P synthetase which in its severest form may produce neurodevelopmental complications, as well as uric-acid overproduction. Severe depletion of erythrocyte nicotinamide adenine dinucleotide and guanosine triphosphate appears to be associated with the neurological abnormalities and may be useful in diagnosis.

Adenine Phosphoribosyltransferase↗
PubMed1982

GTP depletion and other erythrocyte abnormalities in inherited PNP deficiency.

GTP levels were low and NAD+ levels high in purine nucleoside phosphorylase (PNP) deficient erythrocytes, in addition to the raised deoxy-GTP (dGTP) levels previously noted by others. dGTP was also identified in the PNP deficient child's lymphocytes. A further novel finding was the conversion of hypoxanthine to inosine by the PNP deficient red cells, as compared to inosine monophosphate (IMP) in controls. This has been attributed to IMP formation with subsequent breakdown, and raises interesting questions regarding the controls which normally maintain erythrocyte nucleotide pools. These findings may also explain the gross purine overproduction seen in this defect; they may likewise be related to the associated immunodeficiency, anaemia, and other clinical manifestations. The results may also have important implications for the development and clinical use of PNP inhibitors.

Adenosine Deaminase↗
PubMed1982

Reciprocal relationship between erythrocyte ATP and deoxy-ATP levels in inherited ADA deficiency.

A reciprocal relationship between erythrocyte ATP and deoxy-ATP levels has been noted in an immunodeficient child with adenosine deaminase (ADA) deficiency during therapy with red cell transfusions. The sum of red cell ATP plus deoxy-ATP equalled the normal complement of ATP prior to any form of therapy. dATP, dADP and dAMP levels were found in the same ratio (10:1:0.1) as the adenine nucleotides ATP, ADP and AMP. Red cell ATP levels were low, not high or normal as found by others in ADA deficiency, but no deoxyadenosine nucleotides could be found in peripheral blood mononuclear cells. Erythrocyte ATP depletion has recently been identified as a serious consequence of anti-leukaemic therapy with ADA inhibitors; it may thus be an important but hitherto unrecognised contributing factor in the clinical expression of inherited ADA deficiency.

Adenosine↗
PubMed1982

Human adenine phosphoribosyltransferase. Immunochemical quantitation and protein blot analysis of mutant forms of the enzyme.

We have studied the catalytic, immunochemical, and electrophoretic properties of adenine phosphoribosyltransferase in hemolysates from 30 patients with a deficiency of this enzyme in six unrelated families. We have found that: 1) the level of adenine phosphoribosyltransferase enzyme activity and immunoreactive protein in the four homozygous deficient patients was less than 1% of control values; 2) adenine phosphoribosyltransferase enzyme activity was uniformly decreased to approximately 25% of normal in all 26 heterozygotes studied while the level of adenine phosphoribosyltransferase immunoreactive protein was consistent within each kindred but ranged in value from 22% to 112% of control; and 3) protein blot analysis revealed a single isoelectric form of the adenine phosphoribosyltransferase subunit in hemolysate from normal controls and from every heterozygote except for patient M.R. who exhibited both a normal and a more acidic adenine phosphoribosyltransferase subunit species. These studies provide the first evidence for the existence of a variety of different mutations in the structural gene for adenine phosphoribosyltransferase in patients exhibiting a deficiency of enzyme activity. We further conclude from our data that: 1) the variant enzymes are more labile in vivo and/or catalytically nonfunctional, and 2) heterozygotes express only 25% of normal enzyme activity because the normal and variant enzyme subunits form a hybrid dimer which is either more labile or less catalytically active than the normal adenine phosphoribosyltransferase dimer.

Adenine Phosphoribosyltransferase↗
PubMed1982

Renal failure due to 2,8-dihydroxyadenine urolithiasis.

A four-year-old girl presented in renal failure due to dihydroxyadenine urolithiasis. Prior to this she had been fed a high purine macrobiotic diet, rich in pulses and grain. She was comatose, anuric, requiring peritoneal dialysis, and bilateral radiolucent renal calculi were revealed by ultrasonography and retrograde pyelography. 2,8-dihydroxyadenine stones were found at pyelolithotomy, renal biopsy revealed interstitial birefringent crystals, and a complete lack of adenine phosphoribosyl transferase (APRT) was found subsequently in erythrocyte lysates. APRT levels were initially falsely raised due to a blood transfusion on admission. The mother was shown to have heterozygote levels. The child was treated successfully with allopurinol, and a reduction in dietary purine but with only partial return of renal function.

Adenine↗
PubMed1982

Formation and degradation of deoxyadenosine nucleotides in inherited adenosine deaminase deficiency.

dATP, dADP, and dAMP equalled or exceeded the depleted levels of ATP, ADP, and AMP in erythrocytes from two children with adenosine deaminase (ADA; EC 3.5.4.4) deficiency. dATP and dADP were identified in the mononuclear cells of only one child. The levels of deoxyadenosine compounds fell dramatically after enzyme replacement therapy and were no longer detectable in the urine or in mononuclear cells. Erythrocyte adenosine nucleotide levels showed a corresponding increase. Intact erythrocytes prior to treatment contained adenine, presumed to be from deoxyadenosine degraded during extraction. Adenosine at high concentrations in vitro increased both dATP and ATP levels and decreased intracellular deoxyadenosine levels. There was no significant deamination of either [8-14C]adenosine or deoxyadenosine by intact ADA-deficient erythrocytes. About 90% of adenosine was metabolized to ATP at substrate concentrations from 10-100 microM, compared to 40-60% of deoxyadenosine metabolized to dATP. These studies suggest that (i) high intracellular deoxyadenosine levels may be necessary in vivo to sustain the raised dATP levels in ADA deficiency. (ii) When ADA is inhibited or absent, deoxyadenosine is removed rapidly from the circulation by the human erythrocyte utilizing an adenosine transport system linked to both ADA and adenosine kinase (EC 2.7.1.20).

Adenosine↗
PubMed1982

Allopurinol treatment and its effect on renal function in gout: a controlled study.

Fifty-nine patients with primary gout were treated with either a combination of colchicine and allopurinol or colchicine alone. Assessments of renal function over 2 years revealed a statistically significant fall of glomerular filtration rate an urine concentrating ability in those receiving only colchicine. The renal function of patients given allopurinol did not change. Treatment with allopurinol resulted ina significant reduction of ammonium excretion, a phenomenon which could not be readily explained. Urate clearance also declined during allopurinol treatment, and the impaired urate clearance associated with gout became more evident. The most important observation was that allopurinol retarded an apparent decline of renal function. Presumably this was achieved through its hypouricaemic effect and implies that the hyperuricaemia of gouty patients is deleterious to the kidneys.

Adult↗
PubMed1981

Pyrimidine and purine metabolites in ornithine carbamoyl transferase deficiency.

Detailed biochemical studies have been carried out in a female heterozygote for ornithine carbamoyl-transferase (OCT) deficiency. Increased levels of the pyrimidines, orotic acid, uridine and uracil, were observed in plasma as well as urine by utilizing an adaptation of high performance liquid chromatography (HPLC). Urinary clearances of these compounds were high, that of orotic acid indicating net secretion. Urinary uric acid clearance was also elevated, a finding attributed to the uricosuric effect of the orotic acid excreted concomitantly. The results in this child and her family are typical of OCT deficiency. They confirm considerable genetic heterogeneity in the biochemical as well as clinical expression in this defect.

Child↗
PubMed1981

Familial gout and renal failure.

Clinical gout and renal failure was seen in a 9-year-old girl. The family tree showed that 9 out of 11 young females in three generations suffered from hyperuricaemia and normal (n = 1), or impaired (n = 8), renal function. One set of twins occurred in each generation and there is only one living male subject. In members with renal failure there was no improvement in renal function after treatment of hyperuricaemia, and in 2 sisters oral contraceptives appeared to precipitate hypertension. This clinical picture may be more common than is generally realised because of failure to compare blood uric acid values with suitable age- and sex-matched controls. The evidence from this family suggests that hyperuricaemia preceded the development of renal failure.

Adult↗