Table 1.

Characteristics of cultured fibroblasts.

Cell Line	Early Passage			Late Passage
	Passage no.	Doubling time (d)	beta-gal % pos.	Passage no.	Doubling time (d)	beta-gal % pos.
DS1	13	2	<1	23	5.5	63.4
DS2	7	1	<1	12	19.5	37.2
DS3	4	2.5	<1	11	9	41.0
DS4	10	1.5	<1	14	8	47.5
DS5	3	5	nd	nd	nd	nd
C1	12	2	<1	24	12	55.5
C2	9	1.5	6.7	15	21	63.3
C3	5	1.5	<1	11	9.5	46.2
C4	10	2.5	<1	14	4.5	34.0
C5	3	2	n.d.	n.d.	n.d.	n.d.
C6	3	5	n.d.	n.d.	n.d.	n.d.