Preface

Azaarenes in Recent lake sediments

“…Aza heterocyclic hydrocarbons (azaarenes) are potentially hazardous environmental contaminants because of their carcinogenic and mutagenic character (1,2). As trace components, azaarenes have been detected in cigarette smoke (3), automobile exhaust (4), industrial stack effluents (5), and urban suspended particulate matter (6)(7)(8).…”

The composition of β-lactamase I and β-lactamase II from Bacillus cereus 569/H

“…The failure to find muramic acid in this fragment suggests that the latter is not derived from the murein of the cell wall. It has been reported by Arcos (1968) that exo-,Blactamase produced by B. cereus 569/H can be separated by agar-gel electrophoresis into several active components and that some of the components are glycoproteins. The relative thermostability of fl-lactamase II is a property that it shares with a number of glycoproteins and carbohydrate-protein complexes (Keller & Block, 1960;Putnam, 1965).…”

Systematic Carcinogen Testing Through the Decision Point Approach

“…Of principal importance is the fact that predictions as to whether or not a given chemical might be carcinogenic can be made with fair success within certain classes of chemicals (29,(47)(48)(49)(50)(51). This is particularly true in the case of chemicals of a type that includes known carcinogens.…”

“…If substantial human exposure is likely, careful consideration should be given to the necessity for additional testing. The chemical structure and the properties 'of the material provide direct obvious guidance on the proper relevant course of action (47)(48)(49)(50)(51). Organic chemi cals with structures suggesting possible sites of activation may reveal their carcinogenicity in limited in vivo bioassays.…”

“…The carcinogenicity of a limited number of chemicals and crude products can be revealed readily upon continuous application to the skin of mice, producing papillomas or car cinomas, or upon subcutaneous injection, yielding sarcomas (48). Also, activity as initiating agents can be rapidly determined by the concurrent or sequential application of a promoter, such as one of the phorbol esters.…”