Worm Breeder's Gazette 11(4): 7

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Worm Injection Setup and Parts List

Craig Mello and Victor Ambros

Figure 1

The accompanying diagram shows the system which we use to pressurize 
our microinjection setup.  The key feature of this system is the three 
way ball valve through which pressure at the needle is applied and 
then rapidly relieved during each injection.  Pressure must be off 
between injections because the high flow associated with optimal 
injections will float animals off the pad before the needle can be 
inserted.  It may be possible to adapt your current system to include 
such a valve, or to construct a similar system with other parts.
[See Figure 1]
1) Leitz  microinstrument collar (part no.  520145).  Holds the 
injection needle.
2) 3/32' outside diameter (1/32' I.D.) Tygon  tubing.  This tubing, 
once stretched, will fit snugly down the opening in the back of the 
microinstrument collar.  This junction is taped with electrical tape.  
The tape keeps this joint from getting worked loose during the 
frequent handling of the microtool collar.  The tape should not be 
necessary to make the pressure seal.
3) 21g metal tube (cut off of a syringe needle).  Fitted halfway 
within the 3/32' tubing, the protruding portion is inserted into the 
1/16' tubing and serves as a connecter.  This connection is also 
wrapped with electrical tape.
4) 1/16' polyethylene tubing (rigid plastic or nylon tubing works 
best with the Swagelok  adapters).  Note; if you plan to HF treat your 
needles (Worm Breeders Gazette 11-1:18), then this tubing should be 
long enough to reach a nearby dissecting scope.
S) Swagelok  reducer (part no.  B-100-R-2).  Connects the 1/16' 
tubing to the Swagelok  1/8 connector which comes with the three way 
6) Swagelok  three way ball valve (part no.  B-41XS2).  Should be 
mounted or clamped in place.  This valve is used during each injection 
to apply pressure at the needle.  It should be placed within easy 
reach but should not be on the vibration free table.
7) Swagelok  male connector (part no.  B-100-1-4).  This connector 
threads into the 1/4 NPT female socket of the STREET TEE.
8) CAJON  STREET TEE connector (part no.  B-4-ST).  Male end threads 
into the pressure regulator.  Female ends accept the tubing connector 
and the pressure release valve.
9) Swagelok  toggle operated shut off valve (B-1GM4-S4).  This valve 
opens the system to allow a quick release of pressure.  This is 
necessary when using the pressure regulator to make downward 
adjustments in pressure, for example if there is too much flow at the 
10) Pressure regulator.  Must have a 1/4 NPT Female thread in order 
to accept the STREET TEE described above.  Allows the pressure to be 
increased or decreased.  Pressures required for adequate flow range 
from 10- to 100-lbs/sq.in.  depending on the needle; higher pressures 
tend to blow connections or to propel the needle out of the holder at 
high velocity.
11) Nitrogen tank.  Should be positioned so that the regulator 
handle can be reached easily without getting up during injection.

Figure 1