Biology Reference
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(a)
(b)
(c)
Figure 17.2. Simultaneous monitoring of AFM signal and phase contrast micrograph
on AT 1 -transfected HEK-293 cells stimulated by AngII. (a) In a typical experiment,
an AFM cantilever is allowed to contact the apical region of an individual cell with
a force inferior to 250 pN. A baseline is recorded for several minutes before the
injection of 100 nM AngII (0 minute). The cell mechanical response is plotted as cell
membrane displacement (nm) as a function of time. (b) Phase contrast micrographs
recorded before (−2 minutes) and after AngII stimulation (2 and 10 minutes). The
AFM cantilever can be seen in left lower corner of the micrograph. The micrograph
at 2 minutes shows contraction whereas spreading is observed at 10 minutes. (c)
Magniied view of the cell marked with a white asterisk in (b) to demonstrate cell
body contraction using the doted contour of the cell prior to stimulation. The contour
at −2 minutes is projected on the images at 2 and 10 minutes. Scale bars are 20 μm (b)
and 5 μm (c). Reprinted with permission from Ref. 23.
height change measured with the AFM is most certainly due to intrinsic
differences between individual cells composing the global cell population.
Another important feature of the AT 1 receptor-dependent cellular response
is the considerable change in morphology observed after the initial
contractile response. Indeed, the phase contrast micrograph taken 10
minutes after AngII stimulation ( Fig. 17.2b,c ) clearly shows a signiicant
spreading of the cell body as reported previously for this cell model. 25
Interestingly, these structural changes can be detected as an increased
luctuation in the AFM signal when comparing the signal before (
5 to 0
 
 
 
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