A new assay for intracellular measurement of inosine monophosphate dehydrogenase activity: a guide for better selection of patients for enzyme-targeted chemotherapy.

Abstract

We developed a new cytochemical assay for identification of cells containing inosine monophosphate dehydrogenase (IMPDH) and measurement of tumor cell sensitivity to the escalating doselschedule of the IMPDH pattern-targeting drugs. The assay is based on cytochemical principles for development of DH activity markers inside morphologically classified cells, image analysis for measuring the amount of this marker, and computer assistance for data management. The assay was optimized on a human leukemia cell line (K562-NS) and reference values for enzyme activity were established. Assay specificity was determined with different substrates and enzyme inhibitors. Sensitivity depends on the measuring instrument (image analyzing system), and the precision of the biological model used for assessment of refer-

Glucose-6-phosphate dehydrogenase activity in spinach as measured by image analysis: A new approach for plant enzyme histochemistry

“…For many years, scanning and integrating microdensitometers have been widely considered to be the best instruments for such in situ studies. However, automated instruments using video methods have also been employed successfully during the past few years in quantitative enzyme histochemistry and cytochemistry in animal tissue sections (Hildebrand & Schleicher, 1986;Blanco et al, 1988;Lawrence et al, 1989;Van Noorden, 1989;Laborde et al, 1990;Van Noorden & Butcher, 1991;Markovic et al, 1994). Despite the important development of image analysis systems and the various advantages they show over microdensitometers, they do not seem to have been used for quantification of enzyme reactions in plant tissue sections.…”