Biomedical Engineering Reference
In-Depth Information
a
b
400
300
399.95
250
399.9
200
Beginning of
interactions with
substrate
399.85
150
399.8
100
Tethering
cells travel at v < 0.5 v h
and experience no durable
arrests
399.75
50
0
399.7
0
0
0.5
1
1.5
2
2.5
3
3.5
4
10
0
2
4
6
8
Time (sec)
Time (sec)
c
d
140
120
100
80
120
Beginning of interactions with substrate
100
Beginning of interaction with substrate
80
60
Firm adhesion:
cells bind to substrate
and remain motionless
60
Rolling:
cells travel at v < 0.5 v h
and experience durable arrests
40
40
20
0
20
0
0
4
6
8
10
2
0
2
4
6
8
10
Time (sec)
Time (sec)
Fig. 7 ( a ) Time evolution of bond density in Dembo adhesion model. ( b ), ( c )and( d )show
representative trajectory of lymphocyte tethering at a mean velocity v equal to one half of the
hydrodinamic velocity v h . The parameters are the following: D 0:001 nm, k on D 84 s 1 ,
k of f D 1 s 1 ( b ). Representative trajectory of rolling motion of lymphocyte, with a mean velocity
v <0:5 v h , that experience durable arrests ( c ). Representative trajectory of lymphocyte for firm
adhesion. The parameters are the following:
D 0:001 nm, k on D 84 s 1 , k off
D 20 s 1
( d )
The physicochemical properties that give rise to the various dynamic states of cell
adhesion are mainly the rates of reaction. From different values of rates constants,
in particular of the dissociation rates [ 4 ] (see caption of Fig. 7 ), different motion
state diagrams emerge [ 18 ]: tethering , in which lymphocytes move at a translational
velocity v <0:5 v h (where v h is the hydrodinamical velocity of the blood flow) but
exhibit no durable arrest is shown in Fig. 7 b; rolling for which cells travel at v <
0:5 v h , but experience durable arrests, is shown in Fig. 7 c. Finally in firm adhesion ,
shown in Fig. 7 d, cells bind to the endothelium and remain motionless.
References
1. BioSpi Project home page: http://www.wisdom.weizmann.ac.il/ biopsi/ , 2002
2. Bell GI (1978) Models for the specific adhesion of cells to cells. Science 200:618-627
3. Bell GI, Dembo M, Bongrand P (1984) Cell adhesion. Competition between non-specific
repulsion and specific bonding. Biophys J 45:1051-1064
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