We conclude that PF4 upregulates MMP-1 expression in HGFs in a p44/42 MAPK-dependent manner. These findings point to a previously unidentified role for platelets in the pathogenesis of periodontal diseases.
Serum from Bl x C3H mice carrying syngeneic, progressively growing, highly immunogenic 3-methylcholanthrene-induced tumors when admixed with the specific tumor and inoculated into immunologically crippled syngeneic recipients, stimulated growth as compared with serum from control normal mice. It appears that this acceleration of tumor growth is an immune effect since it is not present when a non-immunogenic (spontaneous tissue culture) tumor is used; and the active factor can be absorbed from the serum by the specific tumor but not by an immunologically unrelated tumor. Normal serum per se also stimulated tumor growth, but to a smaller extent.
A human teratoma cell line (Tera-2) was grown in serum-free medium, and the population multiplication was stimulated by the addition of somatomedins/insulin-like growth factors (IGFs). Both IGF-I and IGF-II gave maximal stimulation when added daily at 10 ng ml-1. The IGFs did not substantially change the labelling index of the cells, and the IGFs appeared to exert their effect on population multiplication by increasing cell survival. Membranes isolated from Tera-2 cells displayed both type 1 and type 2 IGF receptors.
The quantity of c-myc mRNA was measured during the retinoic-acid-induced differentiation of the pluripotent human teratoma cell line, Tera-2 cl. 13. As the cells were exposed to retinoic acid for longer periods of time the duration of the cell cycle progressively increased (measured by the rate of S phase entry) until the cells were effectively quiescent and expressed characteristic differentiation markers. Under these circumstances steady-state levels of c-myc expression increased by up to 1.6-fold with respect to rapidly growing undifferentiated cells. Southern blot analysis of the c-myc genes in Tera-2 indicated no major rearrangement or amplification in the cell line.
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