Antioxidants in neoplastic cells: I. Changes in the antioxidative capacity of mouse neuroblastoma cells measured by a single-phase assay.

Cultured mouse neuroblastoma cells exhibit a striking increase in antioxidative capacity during the transition from logarithmically dividing cells to nondividing, neurite-bearing cells. Two physically separable phenomena are involved: (a) the membrane pellet of neurite-bearing cells is highly resistant to lipid peroxidation, and (b) the postmicrosomal supernatant of these cells inhibits peroxidation in rat liver mitochondria and other biological membranes. A precise, single-phase assay has been developed for assessing antioxidant levels in lipid extracts. By means of this assay, the increase in membrane resistance to lipid peroxidation has been correlated with a threefold increase in the antioxidant activity of the neuroblastoma neutral lipid fraction. This finding implies that generations of a neutral lipid antioxidant (or antioxidants) is involved in the profound increase in antioxidative capacity which occurs in differentiating neuroblastoma cells.

Substrate irradiation stimulation of the in vitro lactate-pyruvate interconversion reactions mediated by lactic dehydrogenase.

Experimental studies of the Comorosan effect are presented for the LDH-mediated interconversions of lactate and pyruvate. Consistent with the findings of the Comorosan group, the rate of the lactate/LDH reaction was found increased for crystalline lithium lactate irradiated with green light for times t comprising the manifold t = 15+30n sec, n = 0,1,2... However, no upper limit to the number of activating times was encountered although the Comorosan group has always obtained only six such activations. The pyruvate/LDH reaction rate was found enhanced for crystalline sodium pyruvate irradiated t = 5+30n sec. Sharpness of activations for 5-sec and 65-sec irradiated samples was investigated and found to occur only within approximately +/- 0.5 sec of 5.0 and 65.0 sec, slightly broader than the +/- 0.15-sec peak reported by Comorosan for the 5-sec signal. The data contribute to the credibility of the phenomenon but reveal sensitivity of some properties to individual laboratory or procedural factors. The first support is provided for the "discriminating function" component of Comorosan's metabolic control hypothesis.

The Comorosan effect: single- and double-blind studies on the urea/urease system.

Characteristic alterations of enzymatic reaction rates by irradiation of the crystalline substrates for fixed periods with an Hg vapor lamp were reported by Comorosan in 1969. Results of single- and double-blind studies reported here support the validity of the key features of this striking and potentially important phenomenon.