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Biomedical subjects

I Ziegler

Publications and source records attributed to I Ziegler.

67 records · Page 4Linked to original sources
PubMed1982

Blood levels of a pteridine-binding alpha 1-acid glycoprotein in cancer patients.

A variant of alpha 1-acid glycoprotein was found previously in blood of malignant cases. It had been characterized as a pteridine-binding alpha 1-acid glycoprotein (P-AGPM). P-AGPM as well as the corresponding fraction of control origin were selectively enriched in the supernatant (Fraction b), obtained after digitonin extraction and subsequent alcohol and trichloroacetic acid fractionation of whole blood. In Fraction b, alpha 1-acid glycoprotein from control subjects + P-AGPM comprised 90 to 95% of total protein; it was quantitated by colorimetric determination of the protein-bound tyrosine and calibrated with the isolated compound. During a screening of malignant and nonmalignant cases, P-AGPM proved to be an acute-phase reactant to some extent. Marked increases during extended cancer and especially during leukemias corroborated the view that P-AGPM may be identical with abnormal orosomucoid. Longitudinal sections during leukemias suggested that the biopterin of leukemic cells may be metabolically related to the pteridine moiety of P-AGPM. Biopterin determinations by means of Crithidia assay in the blood of 136 cases of solid tumors showed that, due to its high rate of renal clearance, blood biopterin is not a reliable and persistent marker for proliferative activity, unless it is contained in the immature blood cells themselves, as is the case during leukemias.

Biopterins↗
PubMed1977

In vivo metabolism of deutero-L-phenylalanine and deutero-L-tyrosine in normal and in various tumor-bearing rats.

The hydroxylation rate and rate of tyrosine catabolism are measured by injection of ring-deuterated L-phenylalanine and ring-deuterated L-tyrosine and subsequent deuterium determination in the water fraction of the blood. The hydroxylation rate was confirmed as the rate-limiting step. Whereas tyrosine catabolism yields normal Michaelis-Menten kinetics, homotropic activation is demonstrated for the hydroxylation step. In all tumor rats under study, the rates of phenylalanine hydroxylation and tyrosine catabolism are decreased. The delta-values to control increase with tumor age. In tumor rats, the hydroxylation step remains the rate-limiting one. Kinetic data indicate that the decrease in hydroxylation is due to a decreased turnover rate of the enzyme, whereas the increase in tyrosine catabolism is caused by the branching off of tyrosine or an intermediate on the route to D2O formation. The results are discussed with respect to altered levels of tetrahydrobiopterin, phenylalanine and tyrosine found during parallel investigations.

Animals↗
PubMed1977

On the levels of phenylalanine, tyrosine and tetrahydrobiopterin in the blood of tumor-bearing organisms.

The levels of free phenylalanine and free tyrosine (and m-tyrosine) as well as of protein-bound tyrosine were determined by means of automated aminoacid analysis and by reaction with 1-nitrosonaphthol(2). Their absolute values as well as their percentages relative to total aminoacids of the blood were markedly increased in all tumor patients tested, as well as in experimental tumor rats. Although tetrahydrobiopterin could scarcely be detected by fluorometric methods in the blood of control persons, it is accumulated blood of all tumor patients tested. The major part was found in the erythrocyte fraction. The results are discussed with respect to decreased phenylalanine hydroxylation rate and to depressed tyrosine catabolism recently found by means of in vivo experiments in tumor-bearing rats.

Animals↗
PubMedDate not supplied

The enhancement of CO2 fixation in isolated chloroplasts by low sulfite concentrations and by ascorbate.

The enhancement of CO2 fixation in isolated, intact spinach chloroplasts by ascorbate or by low sulfite concentrations (less than 1 mM) is strongly reduced or even abolished by the addition of superoxide dismutase (SOD). By the use of 35SO3(2-) it is demonstrated that the rate of sulfate formation is much lower than the sulfite induced increase in CO2 fixation. This indicates that the superoxide radical is the chain initiating event; and, in parallel to ascorbate (Elstner and Kramer, 1973), the HSO3 radical, acting as a Hill reagent for photosystem I, is reduced to sulfite in turn. The ingibitory action of sulfite at concentrations greater than 1 mM is not relieved by SOD, since this effect is mainly based on a competitive inhibition of ribulosediphosphate carboxylase. SOD itself stimulates the CO2 fixation, if the reaction is started after 3 min of pre-illumination. This effect is discussed with respect to factors linked with the isolation procedure.

Ascorbic Acid↗