A monoclonal antibody L8 specific to fibronectin was shown to inhibit fibronectin incorporation into the fibroblast extracellular matrix. Antibody L8 could not interact with fibronectin complexed with gelatin. The results suggest the existence of a specific site on the fibronectin molecule playing a critical role in the assembly of the fibronectin extracellular matrix. This site is located near the collagen-binding domain.

Ca2+-activated K+ ionic currents in the membrane of cultured smooth muscle cells isolated from foetal and adult human aorta were studied using whole cell and single-channel patch-clamp techniques. Whole cell currents in adult smooth muscle cells were 3-8 times larger than in foetal cells of similar sizes. The elementary conductance and ionic selectivity of single Ca2+-activated K+ were identical for both types of cells. Channel openings occurred in burst, the duration of which was 3-5-fold longer in adult than in foetal cells. The voltage dependency of the channel activating mechanism and the dependency of the mean open time on the Ca2+ concentration on the inner side of the membrane were similar for both types of cells. These results suggest that the main reason for the increase in potassium conductance during development is an alteration in the open time of the Ca2+-activated K+ channels.

No abstract

Retinoic acid (RA, 10(-5) - 10(-7) M) is shown to enhance the proliferation of cultured rat aortic smooth muscle cells (SMC). This effect is not connected with a synergistic action of RA together with serum mitogens. Moreover, the expression of L1, a surface antigen specific for modulated SMC entering the cell cycle, is amplified by RA treatment.

No abstract