Mareike Sausemuth

Home Institution
Friedrich Schiller Universität Jena

Host Institution
Feinberg Cardiovascular Research Institute,
Feinberg Medical School, Northwestern University, Chicago

E-Mail:
mareike.sausemuth@uni-jena.de

Research Topic
see Abstract
Personal Reactions to the U.S. Experience
I had a unforgettable time! The welcome in my institute was so friendly and nice. Thanks to all of them for their help and for making this experience so unique for me!
I was integrated into the lab from the first day. I had the chance to work on my own project and the supervision was excellent. Even the office doors of the professors have been open nearly all time, so that you always had the chance to step in and ask your questions without any prior appointments. My supervisor and his wife showed me a lot of typical American activities and traditions, and I was invited for Thanksgiving and Christmas dinners.
My institute was close to the hospital complex, so I had the chance to take part in Grand Rounds and other clinical conferences, and to get some clinical experience as well. I was introduced to important persons for research and the clinic. This is relevant especially if you are planning to come back for further training either in the lab or in the clinic.
Chicago was a great city in which to live and work. When I arrived there for the first time I sometimes felt like I was in a movie: buildings with an unbelievable altitude, millions of lights, wide streets with four or more lanes in each direction, hectic people and the shore of Lake Michigan located right downtown.
There have been a lot of things I was afraid of while planning my experience abroad: the distance from home, language more than cultural barriers, the challenges in the lab and the clinic. But all these things have been much easier for me to handle than I ever thought in before!
Greatest Difficulties Encountered
I had the greatest difficulties in getting my visa procedure done while still in Germany. Once in the U.S. everything worked very well.
Most humorous incident
I experienced of some kinds of traditional American sports. Going to an original American football game with a tailgating party before the game started, was as incredible fun as spending an evening in the huge Basketball Center to see the legendary Chicago Bulls playing.

Helpful Hints for Future Students

  • Take care about your visa procedure as early as possible and do not hesitate to call your U.S. university and the responsible offices again and again to ask for the status of your paperwork!
  • Winter in Chicago is extremely cold and windy. Stay warm!
  • Check out the "Blue Chicago" Blues Club.
  • Living in a safe area of the city can be very expensive, even if you decide to stay in a student dormitory, so make sure that you have enough money with you ($1000-1500/ month are required).
  • Stay open-minded.
  • Check out www.digitalcity.com/chicago for all that's going on in the city.

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Abstract on Research Topic
The Role of cardiac TnI phosphorylation in the pathogenesis of hibernation and stunnend myocardium

Authors:
Mareike Sausemuth, Robert S. Decker

Institution:
Feinberg Cardiovascular Research Institute, Northwestern University, Chicago

Purpose/Background:
Reversible contractile dysfunction can be observed after transient episodes of low-flow ischemia: hibernation versus stunned myocardium. In hibernation myocardium you have an adaptive rather than injurious response to low-flow ischemia with a normal match between flow and function. In contrast, stunnend myocardium is viable but hypocontractile, so you have a flow-function mismatch. Although the subcellular mechanisms that regulate contractile function remain unresolved. Troponin I is a part of the Troponin I/Troponin C and Troponin T-complex and is responsible for the inhibition of the crossbridge formation in non-activity.We hypothesised that TnI, depending on his phosphorylation state, may play a crucial role in these processes. Two different protein kinases (PKA and PKC) are responsible for the phosphorylation of the five phosphorylation sites of Troponin I in the heart. Two sites are phosphorylated by PKA and the other three sites are phosphorylated by PKC. But a crossphosphorylation especially of the PKA sites by PKC is possible. Can a change in the phosphorylation state of Troponin I be responsible for a reduction in function after an ischemic period? Do these two kinases have different effects on contractility after phosphorylation?

Materials and Methods:
Frozen tissue samples from mongrel dogs were used for Western Blot Analysis to get a first impression of the phosphorylation state under different conditions of ischemia (hibernation and stunning). To further investigate the role of TnI phosphorylation with regard to the influence of PKA and PKC in this process, we tried to do 2-dimensional-isoelectric focusing. With this method the protein is separated by its isoelectric point, and this point varies within the phosphorylation state of the protein. The first dimension of focusing is followed by a second dimension (SDS-PAGE), where the protein is separated by mass additionally. After that, we transferred the gel to a PVDF membrane and incubated with a PKA site (Ser23/24) specific antibody.

Results/Conclusion:
From our Western Blots we could conclude that there might be a different regulation of these two protein kinases under low-flow ischemia.