Saló E, Baguñà J
J Embryol Exp Morphol. 1984 Oct;83:63-80.
Mitotic activity during regeneration in the planarian Dugesia (G) tigrina shows a biphasic pattern, with a first maximum at 4-12 h, a second and higher maximum at 2-4 days, and a relative minimum in between. The first peak is mainly due to pre-existing G2 cells entering mitosis shortly after cutting, whereas the second maximum is due to cells that divide after going through the S period from the onset of regeneration. From a spatial point of view, the highest mitotic values are found in stump (postblastema) regions near the wound (0-300 micron), though regions far from it also show increased mitotic values but always lower overall values. As regeneration continues the postblastema maximum shifts slightly to more proximal regions. In contrast, no mitosis has been found within the blastema, even though the number of blastema cells increases steadily during regeneration. The results suggest that blastema in planarians forms through an early accumulation of undifferentiated cells from the stump to the base of blastema. The results obtained demonstrate that blastema formation in planarians occurs through mechanisms somewhat different to those shown to occur in the classical epimorphic models of regeneration (Annelida, Insecta, Amphibia), and suggest that planarian regeneration could represent an intermediate stage between morphallactic and epimorphic modalities of regeneration.
真涡虫杜氏虎纹涡虫再生过程中的有丝分裂活动呈现出双相模式，在4 - 12小时出现第一个峰值，在2 - 4天出现第二个且更高的峰值，两者之间有一个相对低谷期。第一个峰值主要是由于切割后不久预先存在的G2期细胞进入有丝分裂，而第二个峰值是由于从再生开始后经历S期后进行分裂的细胞。从空间角度来看，有丝分裂值最高的区域位于伤口附近的残端（芽基后）区域（0 - 300微米），尽管远离伤口的区域也显示有丝分裂值增加，但总体值始终较低。随着再生的继续，芽基后的最大值会稍微向更靠近近端的区域移动。相比之下，在芽基内未发现有丝分裂，尽管在再生过程中芽基细胞数量稳步增加。结果表明，涡虫的芽基是通过未分化细胞从残端到芽基基部的早期积累形成的。获得的结果表明，涡虫的芽基形成机制与经典的再生模式（环节动物、昆虫、两栖动物）中所显示的机制有所不同，并表明涡虫再生可能代表形态再生和变形再生模式之间的中间阶段。
