Author for correspondence: Keith L. Williams. Tel: +61 2 805 8212. Fax: +61 2 805 8174. e-mail: keith.williams@mq.edu.au
† Present address: CSIRO Division of Mathematics and Statistics, Institute of Information Science and Engineering, Locked bag 17, Nth Ryde, NSW 2113 Australia.
A digital image analysis system for extracting motion information from time-varying digital light microscopy images is presented. This system is then used to map out the movement profile of the surface layer of cells in contact with the substratum through the extracellular matrix (ECM) of the migrating Dictyostelium discoideum slug. From digital high magnification light microscopy images, the morphology of moving cells within the tail region of a young migrating wild-type WS380B slug is described, and compared with the morphology of streaming D. discoideum cells. It is shown that: (i) when the migrating tip of the slug touches the agar substrate, cells in the anterior ventral surface layer of the tip region slow dramatically; (ii) overall cell movement in the ventral surface layer of the migrating D. discoideum slug is slower than the movement of the slug as a whole; and (iii) in less than 10% of cases a wave of movement (groups of cells synchronously slowing down and then accelerating forward) propagates down the slug axis at approx. 1·2 [μm s-1. The time interval between waves may be related to the time interval between tip-to-substratum contact that is periodically re-established during normal WS380B slug migration after each aerial projection of the tip.
BonnerJ.T.>
Evidence for the formation of cell aggregates by chemotaxis in the development of the slime mold Dictyostelium discoideum. J Exp Zool1947; 106:1–26
BreenE.J.,
EliottS.,
VardyP.H.,
WhiteA.,
WilliamsK.L.>
Length regulation in the Dictyostelium discoideum slug is a late event. J Exp Zool1992a; 262:299–306
BreenE.J.,
JossG.H.,
WilliamsK. L>
Locating objects of interest within biological images: the top hat box filter. J Comput Assisted Microsc1991; 3:97–101
BreenE.J.,
JossG.H.,
WilliamsK.L.>
Dynamic arrays for fast, efficient, data manipulation during image analysis: a new software tool for exploratory data analysis. Comput Methods Programs Biomed1992b; 37:85–92
BreenE.J.,
VardyP.H.,
WilliamsK.L.>
Movement of the multicellular slug stage of Dictyostelium discoideum: an analytical approach. Development1987; 101:313–321
Demi RandK.,
SussmanM.>
The morphogenetic sequence followed by migrating slugs of Dictyostelium discoideum during reentry into the fruiting mode. Differentiation1983; 24:88–96
HondaH.,
OgitaY.,
HiguchiS.,
KaniK.>
Cell movements in living mammalian tissue: long term observation of individual cells in wounded corneal endothelia of cats. J Morphol1982; 174:25–39
SchaapP.,
WangM.>
The possible involvement of oscillatory cAMP signalling in multicellular morphogenesis of the cellular slime molds. Dev Biol1984; 105:470–478
ShafferB.M.>
Cell movement within aggregates of the slime mould Dictyostelium discoideum revealed by surface markers. J Embryol Exp Morphol1965; 13:97–117
SiegertF.,
WeijerC.J.>
Analysis of optical density wave propagation and cell movement in the cellular slime mould Dictyostelium discoideum. Physica1991; D49:224–232
WilliamsK.L.,
VardyP.H.,
SegelL.A.>
Cell migrations during morphogenesis: some clues from the slug of Dictyostelium discoideum. BioEssays1986; 5:148–152