No abstract

A rapid and precise procedure for serum alkaline phosphatase employs phenolphthalein monophosphate as the substrate. This compound is readily hydrolyzed and directly provides a chromogen for colorimetric determination. The color produced is linear with respect to both enzyme concentration and incubation time and is stable. Reagent and serum blanks are negligible. Various factors which affect alkaline phosphatase activity have been evaluated. The importance of the proper selection of buffer species, concentration, and pH is emphasized.

A kinetic colorimetric assay procedure is described for measuring lactate dehydrogenase activity, in which the reduction of NAD is coupled to the reduction of a tetrazolium salt, 2-p-iodophenyl-3-p-nitrophenyl-5-phenyl tetrazolium chloride (INT), with phenazine methosulfate serving as an intermediate electron carrier. The molar absorptivity of the formazan of INT was found to be 19.3 x 103 at 503 nm, which provides a threefold increase in sensitivity over the ultraviolet (340 nm) kinetic assay. The results correlate well with those obtained by 340-nm kinetic methods and the procedure does not require an ultraviolet spectrophotometer. The method is simple, rapid, and does not rely on secondary enzyme standards. It requires only two reagents, which are stable.

No abstract

A disposable bleeding time device that provides two simultaneous standardized incisions is described. The mean bleeding time of 47 normal adults was 4.1 min with a 95% range of 2.2--7.0 min. The standard deviation of duplicate bleeding times was 0.7 min, and the day-to-day standard deviation for individuals was 0.9 min. In a double-blind crossover study of 20 normal adults, the mean bleeding time increased from 3.7 to 6.2 min after ingestion of 1 g aspirin. The device is extremely simple to use and is essentially painless. Physical trauma is minimal.