Complete Issue - University of Oklahoma

DIS 75 (July 1994) Technque Notes 39
octane, it does decrease the viabilty of embryos exposed between 0 and 3 hrs of age (Strecker et ai., 1994). Embryos
between 3 and 7 hrs old exhbited equaly high viabilty followig hexae exposure as those embryos treated with octane.
Molecules with a molecular mass greater than or equal to 984 daltons were not absorbed into the embryo followig
treatment with either hexae or octane. Given the importance of the Drosophila embryo as a model system for early
development, th procdure should enable investigators to more successfuy introduce smal molecules unormy
throughout livig Drosophila embryos in cultue.
References: Arkig, R. and A Parente 1980, J. Exp. ZoI. 212:183-184; Hil D.L. 1945, Dros. Inf. Servo 19:62;
Limbourg, B. and M. Zalokar 1973, Dev. BioI. 35:382-387; Lynch, D.V., S. P. Myers, S.P. Leibo, RJ. Macintye, and
P.L. Steponk 1988, Dros. Inf. Servo 67:89-90; Mitchion, T J. and J. Sedat 1983, Dev. BioI. 99:261-254;
Nusslein-Volhard 1977, Dros. Inf. Servo 52:166; Strecker, T.R., S. McGhee, S. Shi and D. Ham 1994, Biotech.
Histochem.69:25-3O.
Lin, James h and A. Villavaso. Northwestern State
University, Natchitoches, Louisiana, U.SA. A stepper
motor drven microinjecting device.
Microinjection is a commonly used method in
assaying mutagenicity and toxicity of chemica reagents
in insects. One of the diculties involved in the
application of this technque is to deliver a repeatable
amount of material to each specimen. Turg the
micrometer gauge with figers is quite uneliable, it often baloons up the body or without delivering enough material to
the inect.
To use a stepper motor with precise stepping control has been found to be a very satisfactory improvement over
hand injection. The stepper motor and the stepping control unt are avaiable commercialy as a complete kit or sold by
dierent companes as separate items*. They are not popular enough to be found in most of the electronic stores in the
United States. If you ca buy a kit includig both a motor and a controller, follow the instructions which come with the
kit to assemble the unt, and follow the steps at the end of ths paper to couple the unt with the injector syrge. If not,
the followig schematic diagram (Figue 1) and description wi help you to assemble your own controller board and
decipher the wies coming from the motor in case the colors of the wies are not the same as the ones in the schematic
diagram.
The stepper motor you buy must have to be a 12 V, four-phase (four-coil) unpolar motor (A bipolar motor
. cöìi-e~istance-(in-ohms)~-- - ---
A four-phase (four-coil) stepper motor may have 5 to 8 wies that connect to the coils. See Figue 2 below.
requies two separate voltage supplies, the SAA 1042 chip ca only drve a unpolar stepper), and it doesn't requie
more than 1 ampere. If the coil curent is not given, caculate it by dividig the stepper motor voltage (in volts) by the
If the motor has 8 wies, al the coil ends (terminals 1-8 above) are available externally. A 6-wie motor has two
pais of coils internaly connected, for example, terminals 2-3 internaly connect coils A and B together and terminals 6-7
internaly connect coils C and D together. If the motor has 5 wies, one wire is the common point for al four coils, for
exaple, terminals 2-3-6-7 connected together, with one wie for each coil remaining.
The followig discussion and the schematic diagram provided in Figue 1 use a 6-wie motor confguation. The
colors of the wies from the motor do not follow a standard code; therefore, it is necessar to identif the proper coil
terminal. For a 36-ohm, 6-wie motor, three wies should emerge from each hal of the stator. An ohmmeter should
read 72 ohms across two of the wies (terminal 1-4 and 5-8), and 36 ohms between the other two pais (terminals 1-2 &
3-4 and 5-6 & 7-8). Once the wies are identifed, the stepping sequence of the coils for shaf rotation ca then be
determined. First use a marker pen to put a dot on one side of the shaf to make movement easier to see. Next, connect
the two common wies (terminals 2-3-6-7) to the positive ( + ) terminal of the power source. Arbitrary select one of the
remaig four wies to be phase coil "A" Touch thi wie momentary to the power source ground (-) terminal to
establish the shaf's position. Now, select one of the two unconnected wies from the other stator hal, touch it
momentarily to ground, and observe the diection of rotation of the shaf. If the shaf turns clockwe, this is coil C. If
the shaf doesn't turn clockwse, agai touch the coil A wie momentarily to ground and then touch the other
unconnected wie of the other stator hal momentarily to ground. Th should cause the motor to tu clockwe. This
wie is coil "c." The other unconnected wie from the coil A stator hal is coil "B" and the other unconnected wie from
the coil C stator hal is coil "D." The sequence of coils A-C-B-D being touched to the ground terminal should result in
the continuous movement of the shaf in a clockwe diection. Repeat the pattern of touchig the ground wie
individualy with each of the four wies several more ties to veri the sequence. The connections between each of the
coil (phases) and each of the four motor controller pins in the SAA 1042 ca be made by the schematic in Figue 1.
The switch Sl on the control board in Figue 3 alows the change of a fu step (7.SO to hal step (3.7s' to