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Professor Glendinning and I studied taste receptors of caterpillars
(Manduca sexta) last summer. The caterpillars have a limited
number of taste receptors (about 52), which is a small number compared
to other species. Our experiments were divided into two parts: electrophysiology
and behavioral studies. In the electrophysiology studies, we recorded
the responses of receptors to stimulation. We used three major stimuli,
myo-inositol, aristolochic acid, and a mixture of the two compounds.
In the behavior experiments, we gave the caterpillars filter paper
disks containing a fixed concentration of myo-inositol, aristolochic
acid, or the mixture, and we measured their responses to the different
stimuli. These two experiments were complementary because they looked
at different types of responses to the same compounds.
In the electrophysiology studies, we used
animals of a convenient size to fit into a tube containing KCL solution.
The KCL facilitated the conductivity of the electric current. It
also kept the animals in a good physiological condition. The apparatus
was placed under the microscope, and we used three electrodes to
measure the animals' responses. We put either 10ml of inositol,
.05ml of aristolochic acid, or the mixture into the electrode and
marked electrodes with different colors to avoid confusing them.
The responses to the stimuli were recorded with the Spike program,
which was a very powerful tool we used to count the number of spikes
in a specific time.
To conduct the behavioral tests, young caterpillars
were chosen and deprived of food for 30 minutes. Meanwhile, we treated
paper disks with 450ml of chloroform. After food deprivation, the
animal was put on the disk with water. The numbers of bites were
recorded. We used the same method to test the animal with the experimental
solutions of the three stimuli. After the feeding period was completed,
we scanned the disks to calculate the area eaten. I found the work
interesting because it allowed me to use my knowledge of Biology,
Chemistry, Math, and Physics. I had many responsibilities in the
lab. Every morning before beginning the experiment I had to check
the caterpillars in a special room designed with the appropriate
temperature, lighting, and housing. It was where the caterpillars
reproduced themselves. We followed the whole developmental process
from eggs to moths. I had to look for black caterpillars, isolate
them and freeze them because they carried a disease. Then I had
to select some animal for the experiment. The selection depended
on the type of experiment we wanted to conduct that day.
In the lab, I set up the experimental.
If we were out of electrodes I had to go to another lab to make
them by heating a glass tube to cut it into two parts with pointed
ends. Also, when we ran out of caterpillar diet, I had to cook it
for them. On days when I wanted to do electrophysiology, I had to
set up the microscope, and the rest of the accessories, including
the KCI solution. In both cases, we use the computer to record and
keep our data and analyze them. At the end of each day, after we
transferred the data to a secure Zip disk, we went to the bug room
to clean the cage, give new diet, put two day old eggs on the diet,
and put a new tobacco leaf in the adults' cage. We also transferred
large caterpillars to a pupation box. Finally I took care of the
tobacco plants.
This summer program was very helpful. It
helped me to develop some personal skills and interpersonal ones.
It also increased my knowledge in many scientific domains such as
mathematics, physics, chemistry and biology. Another most important
thing was the practice; it gave a pre-taste of what the scientific
workplace is like. If I have another opportunity I will be glad
to do it again.
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