Armin Hinterwirth    

Rotations during my first year of graduate school at UW

Rotation Project 1: Abdominal steering in Manduca sexta

A model by Stacey Combes and Tom Daniel suggests that in large insects, such as Manduca sexta, abdominal flexion can act as a mechanism to control body rotations initiated by the wings. We wanted to see to which degree we can elicit body rotations by electrically stimulating nerves that innervate the appropriate muscles that move the abdomen. I created an 8-pronged electrode array (made of tungsten and epoxy) that plugs into a flexible patch of cuticle between the ventral thorax and abdomen. The electrodes achieve a wide-field stimulation of efferents branching off the ventral connective and I was able to move a moth's abdomen in 4 directions by choosing the right stimulus geometry.

The photo above on the left shows the electrode array plugged into the moth with fine leads leading backwards. The graph on the right illustrates that the amount of abdominal deflection can be varyied by changing certain stimulus parameters.

Rotation Project 2: Drosophila Development ---> Lineage 15

My second rotation project in the Truman lab at UW introduced me to the world of Drosophila genetics and especially the MARCM system that allows expression of a GFP marker in specific cell lineages. I screened Drosophila maggots for a lineage that is known to arise from a single neuroblast in each thoracic hemineuromere and has projections to the leg imaginal disks. In order to see what this "lineage 15" (Truman et al. 2005) looks like when it's grown-up, I waited until the screened maggots turned into flies, dissected the ventral nervous system & the legs, amplified the GFP signal via immunocytochemisty, and put the legs under a confocal microscope.

Result: Motor neurons of lineage 15 project into the leg and innervate leg muscles.

Research Assistant at The Rockefeller University

Before I started in the graduate program at the University of Washington, I worked as a research assistant in Dr. A.J. Hudspeth’s laboratory at the Rockefeller University, which is broadly concerned with mechanisms of hearing.

My main project was to convert a conventional research microscope into a sensitive interferometer that responds to sub-nanometer movements of transparent optical structures and measures displacements at two different locations within the field of view of the microscope. The interferometer is used to investigate the characteristics of thermal noise of hair bundles to validate certain predictions of a mathematical model of the active process in auditory sensory transduction. Working in the Hudspeth lab was a great experience and I learned an immense amount about how to set up an experiment.

Undergraduate years in Vienna

I received my undergraduate degree in zoology (M. sci.) at the University of Vienna, where I focused on neurophysiology and ecology. For my "Magister" thesis I investigated peripheral olfactory processing in receptor cells located on the antennae of an insect. Together with other members of the lab of Harald Tichy, I looked into how a certain type of receptor reacts to changes in food odor concentration. We characterized two receptor cells that work antagonistically when charged with various kinds of food odor.

One cell reacts to the onset of odor with an excitatory signal, i.e. the firing rate of the neuron increases with increasing odor concentration. The behavior of this ON cell is therefore not too surprising. The other cell, on the other hand, stops firing when the odor concentration reaches a certain level. The most interesting result, however, is that this OFF cell actually responds to a decrease in odor concentration with an excitatory signal.

Having excitatory signals that represent the animal leaving an odor plume could be a good way to improve the temporal and spatial resolution of the olfactory channel.

In addition to the work on "the nose" of the American cockroach, I worked on the anatomy of the thermoreceptive organ in the mosquito Aedes aegyti. Ewald Gingl (in an electrophysiological prepartion that one can describe as borderline-insane because of the minute structures involved) characterized the warm and cold receptors that sit at the very tip of the antennae. I provided the SEM pictures for this project.