Azo-Dye Carcinogenesis: Ribonucleotides and Ribonucleases

IN " precancerous liver " and hepatomas obtained from rats fed a hepatocarcinogen, there are so many biochemical abnormalities that it is difficult to decide which of them reflect fundamental steps in neoplasia (Reid, 1962a), although changes not crucial to neoplasia may nevertheless give guidance to pharmacologists (Potter, 1962). For the present purpose of elucidating the mechanism of hepatocarcinogenesis, certain questions can usefully be posed concerning each change observed in hepatoma nodules:-(1) is the change, as observed in the tissue mass examined, truly attributable to living hepatoma cells as distinct from dying cells or non-hepatoma cells in the sample? (2) is the change, as found in primary hepatomas induced by a particular agent, an irreducible property of all hepatomas? (3) is the change an early event, observable in the " precancerous " liver obtained by feeding the agent for a few weeks only, or a late event associated with the actual appearance of cancer cells? With precancerous liver further questions arise: (4) are there changes which are lacking, or converse in direction, in the hepatoma ultimately obtained? (5) is each observed change specific both in being attributabl

Electron acceleration and heating in collisionless magnetic reconnection

We discuss electron acceleration and heating during collisionless magnetic reconnection by using the results of implicit kinetic simulations of Harris current sheets. We consider and compare electron dynamics in plasmas with different \beta values and perform simulations up to the physical mass ratio. We analyze the typical trajectory of electrons passing through the reconnection region, we study the electron velocity, focusing on the out-of-plane velocity, and we discuss the electron heating along the in-plane and out-of-plane directions