Maspin plays an important role in mammary gland development.

Maspin is a unique member of the serpin family, which functions as a class II tumor suppressor gene. Despite its known activity against tumor invasion and motility, little is known about maspin's functions in normal mammary gland development. In this paper, we show that maspin does not act as a tPA inhibitor in the mammary gland. However, targeted expression of maspin by the whey acidic protein gene promoter inhibits the development of lobular-alveolar structures during pregnancy and disrupts mammary gland differentiation. Apoptosis was increased in alveolar cells from transgenic mammary glands at midpregnancy. However, the rate of proliferation was increased in early lactating glands to compensate for the retarded development during pregnancy. These findings demonstrate that maspin plays an important role in mammary development and that its effect is stage dependent.     

Cell kinetic analysis of a murine macrophage cell line

For the present study, which was performed to find a reliable method suitable for determination of the cell kinetic parameters of a continuous cell line, use was made of the macrophage cell line J774.1. The doubling time of the cell population was approximately 27 h. The continuous labeling curve showed that all the cells divide and almost no quiescent cells occur. The cell-cycle time as determined from the curve of the labeled cells in mitosis, the course of the stathmokinetic index, and time-lapse videorecordings, was about 19 h. The discrepancy between the population doubling time and the cell-cycle time must be due to death and disintegration of cells during culture in vitro. The results indicate that the doubling time of a cell population is not a reliable parameter to determine the kinetics of a population of continuously proliferating cells and that determination of the course of the stathmokinetic index offers a rapid and simple method to establish the cell-cycle time reliably.