Gilbert's jaundice. Current clinico-nosographical, physiopathological and therapeutic aspects. Note II. The phenomenon of enzyme induction at the level of the liver

After a brief survey of the various modifications that may be encountered by drugs through the work of systems that detoxify the liver cell, attention is given to the problem of enzymic induction. The latter is the result of derepression of a gene that codes for a given enzyme; at the molecular level, derepression takes place when the substrate, by changing the tertiary structure of the repressor, brings about its detachment from DNA: in this way, RNA-polymerase is made capable of synthesising the corresponding mRNA. The inducing activity of phenobarbitone, a drug employed classically in the management of Gilbertian forms, must be substantially attributed to an increase in the synthesis of microsomial proteins, as shown by studies with labelled amino acids.     

Growth rates of normal and abnormal human mammary epithelia in cell culture

The in vitro growth rates of different classifications of human mammary epithelium were compared. Samples included 4 established breast cell lines and excised tissue or breast fluid cells originating WOMEN FOR 40 DIFFERENT AND comprising 3 classifications: normal, nonmalignant atypical, and malignant. Growth was quantitated in situ and expressed as population-doubling time. Principal findings were: (a) malignant cells divided at a slower mean rate than normal cells; (b) population-doubling time values of malignant cells were more heterogenous than those of normal cells; (c) cultures from nonmalignant atypias showed population-doubling time means and standard deviations between those of normal and malignant cells; and (d) long-term mammary tumor cell lines divided more slowly than did normal cells. Discussion includes implications of data for the preneoplastic state and cell culture of mammary epithelium.