Autoradiographic studies of rat astroglial cell proliferation in vitro with and without treatment with basic fibroblast growth factor

Abstract

Using specific autoradiographic methods, cell cycle parameters of untreated and basic fibroblast growth factor (bFGF)-treated astroglial cells from newborn rats grown in primary culture were directly measured. The mode of proliferation was also analysed. In untreated cultures, S phase duration (Ts = 6.9-13.1 h) and cell cycle time (Tc = 10-18 h) can be modified by about a factor of 2 depending on the culture conditions (serum-supplemented or defined medium, thyroid hormone concentration). However, growth fraction (GF = 0.15) and the ratio Ts/Tc remain stable. With increasing days in vitro (DIV) (DIV 7-DIV 20), Ts (7.8-10.6 h) and Tc (10-21 h) are prolonged and GF (0.14-0.06) decreases, probably due to cell maturation. In general, astroglial cells proliferate exponentially with a GF < 1, but stop proliferating about 30-36 h after the last feeding, probably caused by exhaustion of the medium. However, after refeeding they continue to proliferate. As opposed to in vivo, no transition of non-proliferating cells into the GF occurs. After addition of bFGF, GF increases (e.g. GF at DIV 7 = 0.43), but Ts and Tc are not influenced at DIV 7 and 12. At DIV 20, bFGF additionally shortens Ts and Tc, thereby producing values of Ts, Tc and GF like 'younger' cultures. However, the revitalizing effect on 'mature' cells is only transitory. In general, bFGF leads to a single re-entry of G0 cells into the GF. Thereafter, bFGF does not affect the mode of proliferation.

Cell cycle time of murine neopallial cells in vitro

“…For mice glial cells in vitro, Knapp (1992) gives the cell cycle time of 20.5 hr and combined pre-mitosis and mitosis time (G, and M phases, respectively) between 2 and 3 hr. The value of 8 hr for the S-phase time obtained here falls within the range 6.9-9.4 hr reported by Korr (1986Korr ( , 1992a. Regarding the cell cycle time, the dispersion is too large for meaningful comparison.…”

“…The S-phase time can be determined from equations (17) and (1 8), provided that the time of continuous labeling is shorter than T~,,,. Recalling that the interval of the pulse labeling is 2 hr, we can write between 3 and 5 hr (Korr, 1980;Korr et al, 1992a); considering that the discontinuity of the first derivative appears to occur at about 6 hr, we will assume T~~ = 5 hr and, consequently, T~~ = 3 hr. Taking further n,,(O) = 804, T~ = 8 hr and dtL = 0.25 hr we obtain no = 1,230.…”

An immortalized jimpy oligodendrocyte cell line: Defects in cell cycle and cAMP pathway

“…Two other jimpy lines tested, one carrying the wild-type promoter (149JP) and the other the synthetic promoter (JP2s), showed a similarly longer cell cycle than the normal immortalized cells. Even though the cells were immortalized, the cell cycle time for the normal (158N) cells remained within the average cycle time reported for glial cells in the brain (Korr et al, 1975) and for cultured astrocytes from rat (Korr et al, 1992) and chicken (Barakat et al, 1985).…”

MODEL OF THE DYNAMICS OF A BRANCHING SYSTEM OF THE GLIAL CELL LINEAGESIN VITRO

“…Moreover, it was assumed that the cell cycle time and other kinetic coefficients are constant. This assumption is justified by the observations of Korr et al [13,14], who noted that for astroglial cells in vitro the cell cycle time, the S-phase time and the labeled fraction are timeindependent up to day 12, provided the experimental conditions are constant and the cultures not overcrowded. Great care was exercised in the present experiments to ensure these requirements were fulfilled.…”