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Institute of Physiology and Pathophysiology

Nonlinear Microscopy

Figure 1: SHG signals from myofibrils change under rotation of the excitation laser polarization

Second Harmonic Generation

Second harmonic generation (or frequency doubling) is an effect that can be observed in certain nonlinear optical media, which emit radiation at a doubled frequency 2w when excited by an external electric field of the frequency w. The effect is well known for a number of crystals like quartz, but was also discovered for some biological structures like collagen or skeletal muscle myosin-II.

 

We are interested in the physical properties of second harmonic generation in these biological structures and applications for tissue imaging. The SHG signal intensity, for example, depends on the fiber orientation and the polarization of the incident light. Theoretical predictions for this dependency can be derived from standard equations considering crystal symmetries and then be tested with our experimental setup.

Figure 2: Two-photon excited fluorescence of Bodipy-Fl labeled actin in skeletal muscle

Multiphoton Fluorescence

Two or more photons of an infrared laser can be absorbed simultaneously by a fluorescent molecule to promote it to an excited state. The emission wavelength is the same as for standard single photon excitation.

 

As the effect of multi-photon excitation needs high energy densities, it occures mainly in the small center of the laser focus. Fluorescence is limited to this spot, which provides multi-photon microscopes with inherent high resolution. The main advantage over confocal microscopes is the higher resolution in deep tissue layers.

 


Recent Publications

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Improving electrical properties of iPSC-cardiomyocytes by enhancing Cx43 expression. J Mol Cell Cardiol. 2018 Jul;120:31-41. doi: 10.1016/j.yjmcc.2018.05.010. Epub 2018 May 16.

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Role of CD40 and ADAMTS13 in von Willebrand factor-mediated endothelial cell-platelet-monocyte interaction. Proc Natl Acad Sci U S A. 2018 Jun 12;115(24):E5556-E5565. doi: 10.1073/pnas.1801366115. Epub 2018 May 23.

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The VAMP-associated protein VAPB is required for cardiac and neuronal pacemaker channel function. FASEB J. 2018 Jun 7:fj201800246R. doi: 10.1096/fj.201800246R. [Epub ahead of print]

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Persistent sodium current modulates axonal excitability in CA1 pyramidal neurons. J Neurochem. 2018 Jun 4. doi: 10.1111/jnc.14479. [Epub ahead of print]

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Metabolic modulation of neuronal gamma-band oscillations. Pflugers Arch. 2018 May 28. doi: 10.1007/s00424-018-2156-6. [Epub ahead of print]

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The lncRNA CASC9 and RNA binding protein HNRNPL form a complex and co-regulate genes linked to AKT signaling. Hepatology. 2018 May 23. doi: 10.1002/hep.30102. [Epub ahead of print]

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Early Blood-Brain Barrier Disruption in Ischemic Stroke Initiates Multifocally Around Capillaries/Venules. Stroke. 2018 Jun;49(6):1479-1487. doi: 10.1161/STROKEAHA.118.020927. Epub 2018 May 14.

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Impact of carbonylation on glutathione peroxidase-1 activity in human hyperglycemic endothelial cells. Redox Biol. 2018 Jun;16:113-122. doi: 10.1016/j.redox.2018.02.018. Epub 2018 Mar 1.

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In silico assessment of the conduction mechanism of the Ryanodine Receptor 1 reveals previously unknown exit pathways. Sci Rep. 2018 May 2;8(1):6886. doi: 10.1038/s41598-018-25061-z.

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Astrocytic glutamine synthetase is expressed in the neuronal somatic layers and down-regulated proportionally to neuronal loss in the human epileptic hippocampus. Glia. 2018 May;66(5):920-933. doi: 10.1002/glia.23292. Epub 2018 Jan 19.

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Parallel detection of theta and respiration-coupled oscillations throughout the mouse brain. Sci Rep. 2018 Apr 24;8(1):6432. doi: 10.1038/s41598-018-24629-z.

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Stability and Function of Hippocampal Mossy Fiber Synapses Depend on Bcl11b/Ctip2. Front Mol Neurosci. 2018 Apr 5;11:103. doi: 10.3389/fnmol.2018.00103. eCollection 2018.

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Glycyrrhetinic Acid Antagonizes Pressure-Induced Venous Remodeling in Mice. Front Physiol. 2018 Apr 4;9:320. doi: 10.3389/fphys.2018.00320. eCollection 2018.

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Respiration-Entrained Brain Rhythms Are Global but Often Overlooked. Trends Neurosci. 2018 Apr;41(4):186-197. doi: 10.1016/j.tins.2018.01.007. Epub 2018 Feb 9.

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Hypertension-evoked RhoA activity in vascular smooth muscle cells requires RGS5. FASEB J. 2018 Apr;32(4):2021-2035. doi: 10.1096/fj.201700384RR. Epub 2018 Jan 5.

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Carnosine Catalyzes the Formation of the Oligo/Polymeric Products of Methylglyoxal. Cell Physiol Biochem. 2018 Apr;46(2):713-726. doi: 10.1159/000488727. Epub 2018 Mar 29.

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Bringing European physiologists together. Acta Physiol (Oxf). 2018 Apr;222(4):e13043. doi: 10.1111/apha.13043. Epub 2018 Feb 15.

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Making room for new memories. Science. 2018 Mar 30;359(6383):1461-1462. doi: 10.1126/science.aat1493.

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VCAM-1 expression is upregulated by CD34+/CD133+-stem cells derived from septic patients. PLoS One. 2018 Mar 30;13(3):e0195064. doi: 10.1371/journal.pone.0195064. eCollection 2018.

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Endothelial progenitor cells accelerate endothelial regeneration in an in vitro model of Shigatoxin-2a-induced injury via soluble growth factors. Am J Physiol Renal Physiol. 2018 Mar 7. doi: 10.1152/ajprenal.00633.2017. [Epub ahead of print]


Institute of
Physiology and Pathophysiology

Heidelberg University

Im Neuenheimer Feld 326

69120 Heidelberg

Germany

Phone:+49 6221 54-4035
Fax:+49 6221 54-4038
E-mail:sekretariat.hecker@
physiologie.uni-heidelberg.de