Application and direct measurements of forces on neurons in the 2-1000 microdyne range are achieved with high precision using calibrated glass needles. This methodology can be used to control and measure several aspects of axonal development, including axonal initiation, axonal tension, velocity of axonal elongation, and force vectors.
Cell manipulations and extension of neuronal axons can be accomplished with calibrated glass micro-fibers capable of measuring and applying forces in the 10-1000 μdyne range1,2. Force measurements are obtained through observation of the Hookean bending of the glass needles, which are calibrated by a direct and empirical method3. Equipment requirements and procedures for fabricating, calibrating, treating, and using the needles on cells are fully described. The force regimes previously used and different cell types to which these techniques have been applied demonstrate the flexibility of the methodology and are given as examples for future investigation4-6. The technical advantages are the continuous ‘visualization’ of the forces produced by the manipulations and the ability to directly intervene in a variety of cellular events. These include direct stimulation and regulation of axonal growth and retraction7; as well as detachment and mechanical measurements on any type of cultured cell8.
Techniques to apply and measure cellular forces have a long history9. Our method was originally motivated by the work of Dennis Bray, who used glass needles similar to ours to ‘tow’ neurons at a constant rate using a motorized hydraulic device10. There are many alternative means of applying forces to cells which include: stepper motors11, magnetic beads12, microfabricated beams13 and fluid flows14. The latter are similar to our approach in that the cellula…
The authors have nothing to disclose.
We gratefully acknowledge the important contributions of Dr. Robert E. Buxbaum in the development of this methodology.
Material Name | Type | Company | Catalogue Number | Comment |
---|---|---|---|---|
R-6 cap. Tube | Drummond Scientific Co., Broomall, PA, USA | 9-000-3111 | R-6 glass OD 0.9mm, ID 0.6 mm, 8″ | |
BB-CH puller | Mecanex S.A., Geneva, Switzerland | BB-CH puller | Use Mode 4 Alt by CP=100, PP=10, SP1=1000, SP2=1000 | |
0.001″ Chromel wire | Omega Engineering, Stamford, CT, USA | SPCH-001-50 | unsheathed, themocouple wire, 50ft spool now called Chromega | |
0.003″ Constatan wire | Omega Engineering, Stamford, CT, USA | SPCI-003-50 | unsheathed, themocouple wire, 50 ft spool | |
fine forceps | Fine Science Tools, USA | 91150-20 | Dumont Inox #5 | |
universal microscope boom stand | Nikon | 76135 or 90430 | most brands or types of boom stand will work for this use | |
mechanical micromanipulator | Narishige | M-152 | three-axis direct-drive coarse micromanipulator | |
hydraulic micromanipulator | Narishige | MO-203 | now available as MMO-203, three movable axis type | |
needle holder | Leica Microsystems | 11520145 | set of 3 | |
single instrument holder | Leica Microsystems | 11520142 | ||
double instrument holder | Leica Microsystems | 11520143 | ||
mechanical micromanipulator | Leica Microsystems | 39430001 | post mount,1 prob holder, RH Model 430001 | |
joystick mech. micromanipulator | Leica Microsystems | 11520137 | ||
Leica DM IRB | Leica Microsystems | inverted microscope | ||
Vibraplane isolation table | Kinetic System, Boston, MA, USA | 1200 series | ours is model 1201-02-12 | |
Ringcubator | self manufactured see reference 19 | reference 19, requires updated controller listed below | ||
programable temperature controller | Instrumart.com | Fuji Electric PXR3 | replaces the retired PXV3 temperature controller | |
Nikon Diaphot TMD | Nikon Instruments, Inc. | inverted microscope, circa 1980 | ||
Nikon SMZ-10 binocular dissecting | Nikon Instruments, Inc. | other dissecting microscopes will work |