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Biomedical subjects

J Laszlo

Publications and source records attributed to J Laszlo.

At least 109 records · Page 6Linked to original sources
PubMed1975

Inhibition of rat liver DNA polymerase by nitrosoureas and isocyanates.

The effects of 1,3-bis(2-chloroethyl)-1-nitrosourea, 1-(2-chloroethyl)-3-cyclohexl-1-nitrosourea, and 1-(2-chloroethyl)-3-(trans-4-methylcyclohexyl)-1-nitrosourea on two nonmitochondrial DNA polymerases (I and II) purified from rat liver and hepatoma were examined. The activity of DNA polymerase I was not altered by treatment with any of the nitrosoureas or the corresponding isocyanates, 2-chloroethyl isocyanate and cyclohexyl isocyanate. Incubation of DNA polymerase II with the nitrosoureas (1 mM) inhibited its enzymatic activity 30 to 45%. DNA polymerase II was inhibited 75 and 90% by 1.mM 2-chloroethyl isocyanate and cyclohexyl isocyanate, respectively. The nitrosoureas appear to exert their inhabitory action on the enzyme (DNA polymerase II) rather than on the DNA template. Pretreatment of the enzyme increased the degree of inhibition by 1 mM nitrosourea (50 to 60% inhibition) or 2-chloroethul isocyanate (greater than 90% inhibition), whereas pretreatment of the DNA template did not enhance the inhibitory effect. The three nitrosoureas are equally effective as inhibitors of DNA polymerase II. 2-Chloroethyl isocyanate and cyclohexyl isocyanate are better inhibitors than are the nitrosoureas. Since further decomposition products of the isocyanates, 2-chloroethylamine and cyclohexylamine, do not inhibit DNA polymerase II, we conclude that the isocyanates, which are decomposition products of the nitrosoureas, are the active inhibitors of the enzyme.

Animals↗
PubMed1973

Granule assembly in precursors of human leukemia granulocytes.

In human leukemic myeloblasts, the granule enzymes beta-glucuronidase, myeloperoxidase and acid phosphatase were associated with light particles of varying densities that were separable from each other by means of zonal density gradient centrifugation. In more mature granulocytic cells of chronic myelogenous leukemia the three enzymes merged within a single group of denser particles; such particles were absent in myeloblasts. Myeloblast particles had two to three times higher activity of beta-glucuronidase and acid phosphatase, but only one-tenth of the myeloperoxidase activity. Some of the cationic proteins and lysozyme were not found in leukemic myeloblasts but were present in particles of chronic myelogenous leukemia; alkaline phosphatase was absent from both types of leukemic cells.

Acid Phosphatase↗
PubMed1970

DNA polymerase activities associated with smooth membranes and ribosomes from rat liver and hepatoma cytoplasm.

Deoxyribonucleic acid polymerase activity that prefers denatured DNA primer concentrates with the smooth membranes during sucrose gradient centrifugation of rat liver and hepatoma cytoplasmic extracts. The activity in this fraction is eightfold higher in hepatoma tissue. Deoxyribonucleic acid polymerase activity that prefers native DNA primer concentrates with the free ribosome fraction from both tissues.

Ammonium Chloride↗