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Biomedical subjects

D Dittmar

Publications and source records attributed to D Dittmar.

6 recordsLinked to original sources
PubMed1979

Immunoglobulin G- and M-specific enzyme-linked immunosorbent assay for detection of dengue antibodies.

An enzyme-linked immunosorbent assay for the detection of antibodies to dengue virus is described. This method correlates well with a hemagglutination inhibition technique. The enzyme-linked immunosorbent assay can also be specific for human immunoglobulin M antibodies when a mu-chain-specific antiglobulin-enzyme conjugate and fractionated serum are employed. By using this technique, dengue immunoglobulin M antibodies were demonstrated in an infant suspected of having a recent dengue infection.

Antibodies, Viral↗
PubMed1979

Enzyme-linked immunosorbent choriomammotropin assay.

We have devloped an enzyme-linked immunosorbent assay for determining choriomammotropin (human placental lactogen) in serum. Unlabeled hormone competes with choriomammotropin-beta-galactosidase conjugate for antibody bound to polystyrene tubes. The entire assay can be performed in 2.5 h with good precision. The coefficient of variation for one sample with a mean concentration of 5.6 mg/L, assayed 10 times on the same day, was 5.7%. The coefficient of variation for nine samples (3.5 to 9.0 mg/L) assayed on five different days was 7.9%. Forty-eight clinical samples were assayed (y) and compared with results obtained by radial immunodiffusion (x). The resulting regression equation was: y = 1.05x + 0.78; r = 0.91.

Enzyme-Linked Immunosorbent Assay↗
PubMed1977

Phosphoribosylpyrophosphate synthesis in cultured human cells.

Phosphoribosylpyrophosphate (PRPP) concentrations and PRPP synthetase activity were studied in cultured human fibroblasts with control and mutant hypoxanthine-guanine phosphoribosylpyrophosphate (HPRT) activity. The PRPP concentrations increased 20- to 50-fold and PRPP synthetase activity 3-fold in cells from patients with the Lesch-Nyham syndrome when aminopterin, an inhibitor of de novo purine synthesis, was added to the medium. Concentrations of PRPP and PRPP synthetase activity did not increase in control cells in medium containing aminopterin unless hypoxanthine was removed from the medium. Exposure of cells to cycloheximide, a protein synthesis inhibitor, prevented the induction of PRPP synthetase and the formation of high PRPP concentrations. Cells from a patient with a mutant HPRT with a high Michaelis constant for PRPP increased PRPP levels and PRPP synthetase activity to a new steady state when they were grown in medium containing aminopterin. Inhibitors of de novo purine synthesis, the presence of hypoxanthine in the medium, and mutant HPRT activity affect the regulation of PRPP levels and PRPP synthetase activity.

Aminopterin↗
PubMed1976

Purine dysfunction in cells from patients with adenosine deaminase deficiency.

Conversion of adenosine to inosine is decreased in adenosine deaminase (ADA)-deficient fibroblasts at all concentrations of adenosine tested. Adenosine is not differentially toxic to ADA-deficient fibroblasts except at very high (5 X 10(-4) -1 X 10(-3) M) adenosine levels. Conversion of [14C] adenosine to GTP is not decreased in ADA-deficient cells compared with control cell strains. Adenosine conversion to ATP is the same as that in mutant cells except at high nonphysiologic concentrations, at which it is slightly decreased in ADA-deficient fibroblasts. This effect is probably not related to the biochemical pathology of ADA-deficient lymphocytes in vivo. Uridine, a pyrimidine compound, "rescues" control cells from the effects of adenosine toxicity, as previously reported, but it has no protective effect on ADA-deficient fibroblasts. This suggests that uridine will have no therapeutic role in the treatment of the ADA-deficient form of severe combined immunodeficiency (SCID) disease.

Adenosine↗