Vernon L. Verhoef

Learn More
Purine analogues are potentially useful agents for selective chemotherapy of lymphoproliferative diseases. We compared the toxic effects of various arabinonucleosides against eight human T- and B-lymphoblastoid lines. The arabinosides of cytosine (ara-C), 2-fluoroadenine (F-ara-A), adenine (ara-A) and guanine (ara-G) all inhibited the growth of(More)
The relationship between nucleoside triphosphate pyrophosphohydrolast (NTPH) (EC 3.6.1.19) activity in erythrocyte lysates and accumulation of radioactive inosine triphosphate (ITP) in human erythrocytes incubated in vitro with [14C]hypoxanthine, was studied in 93 humans. When ITP accumulation, expressed as percentage of total radioactive nucleotides, was(More)
The selective toxicity of purine deoxynucleosides against lymphoid cells appears to be mediated by a preferential accumulation of the corresponding triphosphates in these cells. We report a study of the metabolism and toxicity of arabinonucleosides of guanine and cytosine toward human T- and B-lymphoblastoid-cell lines. Both compounds inhibited the growth(More)
The kinetics and regulation of nucleoside phosphorylation by highly purified human deoxycytidine kinase from leukemic lymphoblasts were studied. The phosphorylation of purine nucleosides by this enzyme showed sensitivity to the endogenous inhibitors dCTP and UDP three times greater than the phosphorylation of dCyd. Examination of nucleotide pools in human T(More)
Mammalian cells have enzymes that deaminate adenosine to inosine, which can readily be phosphorolysed to hypoxanthine. They do not, however, possess enzymes to form adenine by the cleavage of adenosine. For this reason, the release of adenine from adenosine by mammalian cell cultures has usually been interpreted as indicating the presence of mycoplasma, a(More)
The biochemical basis of cellular resistance to 9-beta-D-arabinofuranosyladenine (ara-A) and its natural purine derivative, deoxyadenosine, was investigated with two mutants of cultured human T-lymphoblastoid CCRF-CEM cells. One mutant that lacked deoxycytidine kinase activity, designated CEM/ara-C, retained about 10% of wild-type deoxyadenosine kinase and(More)
Several potentially bis(alkylating) bis(quinones) (3-5) and 1,4- and 1,3-bis(alkylating) monoquinones (6-13) belonging to general structure 2,2'-ethylenebis[5-[(leaving group)methyl]-1,4-benzoquinone] (3-5) and 2,5- and 2,6-bis[(leaving group)methyl]-1,4-benzoquinone water-soluble and -insoluble classes were prepared by oxidative demethylation of the(More)
Mycobacterial infection is a common complication of acquired immunodeficiency syndrome (AIDS) frequently requiring antimycobacterial medication. It was of interest to determine if one such agent, rifabutin, could be tolerated by AIDS patients in conjunction with 3'-azido-3'-deoxythymidine (AZT) therapy. We evaluated the in vitro myelotoxic effects of(More)
Measurements of rates of inosinate synthesis from radioactive hypoxanthine by human erythrocytes show a large degree of individual variation. Rates of inosinate synthesis also vary with the pH and phosphate concentration of the incubation medium. This may be due to changes in the rate of phosphoribosyl pyrophosphate synthesis, and the stimulatory effect of(More)