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Biomedical subjects

L A Johnson

Publications and source records attributed to L A Johnson.

At least 181 records · Page 10Linked to original sources
PubMed1977

Hypoxanthine-guanine phosphoribosyltransferase: a simple spectrophotometric assay.

A simple spectrophotometric assay is described based on the conversion of hypoxanthine to inosine monophosphate and precipitation of both the reaction product and protein with lanthanum phosphate. The extent of conversion is determined by the fall in absorbance of hypoxanthine at 249 nm. The assay is suitable for screening red cell lysates for hypoxanthine-guanine phosphoribosyltransferase deficiency.

Erythrocytes↗
PubMed1977

Hypoxanthine-guanine phosphoribosyltransferase activity in individual erythrocytes: autoradiographic studies in heterozygotes.

Heterozygotes for the Lesch-Nyhan syndrome have normal hypoxanthine-guanine phosphoribosyltransferase (HGPRT) activity in their erythrocyte lysates. However, HGPRT activity in lysates from heterozygotes for the partial HGPRT deficiency states is often between that seen in the affected hemizygote and the normal. An autoradiographic technique was developed which demonstrated the HGPRT activity in individual erythrocytes in vitro. This technique revealed that heterozygotes for the Lesch-Nyhan syndrome had erythrocytes that contained normal HGPRT activity but heterozygotes for the partial deficiency had two populations of erythrocytes, one with normal HGPRT activity and the other with the reduced HGPRT activity characteristic of the hemizygote. With these latter heterozygotes, the proportion of HGPRT-deficient erythrocytes agreed with that calculated on the basis of enzyme activity in erythrocyte lysates.

Autoradiography↗
PubMed1977

Adenine phosphoribosyltransferase: a simple spectrophotometric assay and the incidence of mutation in the normal population.

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.

Adenine Phosphoribosyltransferase↗
PubMed1977

Accidental hypothermia: peritoneal dialysis.

Accidental hypothermia may develop within a few minutes by immersion in cold water, in a matter of hours by exposure to cold weather, and in a matter of days in debilitatted victims by continuous exposure to milder cold stress. The prognosis in accidental hypothermia depends on the patient's premorbid condition, the depth and duration of the hypothermia and the degree of exhaustion and metabolic acidosis that result from physiologic attempts to compensate for the heat loss. For deep hypothermia (deep body temperature below 20 C [82.4F]), internal rewarming is strongly recommended as a means of supporting function in body core organs and minimizing the risk of "rewarming shock". For lesser degrees of hypothermia, recoverability depends more on the adequacy of supportive care than on the method of rewarming. The rapid and complete recovery experienced in the case presented is not surprising since the patient's premorbid condition was good, chilling had been rapid, metabolic exhaustion was mild, and internal rewarming was accomplished without delay, using heated peritoneal dialysis.

Acidosis↗
PubMed1976

Induction of chronic lethal Australia antigen hepatitis in mice.

Clinically, idiopathic uveitis may be associated with chronic active hepatitis B. In searching for a possible cause of the uveitis in 6 patients having concurrent chronic iridocyclitis and chronic active hepatitis with serum Australia antigen (AA), the aqueous humor from each patient was analyzed for AA, passed through 220-mmu filters and inoculated directly into the livers of mice. The animals were observed for spontaneous mortality for 12 months, at which time the remaining animals were sacrificed. The livers of all animals were examined for hepatitis and AA. Although the aqueous humor from only 1 patient was found to contain AA, all six aqueous specimens produced a lethal viral hepatitis-like disease with liver AA. The results suggest that the six positive aqueous specimens contained a viral infection agent, which may have been the core of the Dane particle, and that the mouse is suitable for the laboratory investigation of Type B hepatitis by the technique described.

Animals↗
PubMed1976

Urate kinetics in hypoxanthine-guanine phosphoribosyltransferase deficiency: their significance for the understanding of gout.

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.

Adolescent↗