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Joint Meeting of the Federation of European Physiological Societies and the Austrian Physiological Society

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09/13/2017 - Hall C1 | 11:30am - 12:30pm 
European Young Physiologists’ Symposium (EYPS)

Chairs: A. Assinger (Vienna, Austria); N.D. Ullrich (Heidelberg, Germany)

Advanced-level analysis of spiking EEG activity potentiated by high dietary methionine: contribution of purinergic signaling
*Dragan Hrncic1, Aleksandra Rasic Markovic1, Nikola Sutulovic1, Zeljko Grubac1, Marko Vorkapic1, Anida Ademovic1, Mirjana Colovic2, Danijela Krstic3, Bojana Rankov Petrovic1, Veselinka Susic1,4, Dragan Djuric1, Olivera Stanojlovic1
1 Belgrade University Faculty of Medicine, Institute of Medical Physiology "Richard Burian", Belgrade, Serbia
2 Institute of Nuclear Sciences VInca, , Belgrade, Serbia
3 Belgrade University Faculty of Medicine, Department of Medical Chemistry, Belgrade, Serbia
4 Serbian Academy of Sciences and Arts, , Belgrade, Serbia
Abstract text :

Questions: Hypersynchronous firing of neuronal networks is a key feature of epilepsy manifested as spiking EEG activity. High methionine diet results in hyperhomocysteinemia and elevated susceptibility to epileptogenesis Purinergic signaling has been recognized to be involved in a wide range of activities of the nervous system. The aim of this study was to investigate the effects of high dietary methionine on spiking EEG activity and involvement of ecto-nucleoside triphosphate diphosphohydrolase (E-NTPDase) activity in the rat brain.

Methods: Male Wistar rats were used in this study. They were fed during 30 days either with standard (control group) or diet containing high level of methionine (7.7 g/kg, experimental group). EEG activity was recorded for 90 min upon homocysteine thiolactone (HCT) convulsive trigger dose at 512 Hz sampling rate. Number and duration of SWD were analyzed in EEG traces, by using visual inspection and fast-Fourier transform, continuous and discreet wavelet transform. Rats were decapitated and E-NTPDase activity was determined spectrophotometrically in synaptic plasma membranes isolated from the brain.

Results: Experimental and control group showed different patterns of brain activity. Rats on high dietary methionine had an increased number of SWD, as well as prolongation of individual SWD elicited by HCT compared to control group. Further analysis showed that the activity of E-NTPDase, an enzyme of purinergic signalig patways, was higher in the brains of the rats from experimental comparing to control group.

Conclusions: These results suggest that ectonucleotidase pathway may play a contributory role in potentiation of spiking EEG activity by high dietary methionine/ hyperhomocysteinemia related to epileptogenesis.

Platelet PI3K in Acute Lung Injury
*Julia B. Kral-Pointner1, Waltraud C. Schrottmaier1, Manuel Salzmann1, Birgit Birnecker1, Yasemin Ekici1, Stefan Heber2, Alice Assinger1, Gernot Schabbauer1
1 Medical University of Vienna, Department for Vascular Biology and Thrombosis Research, Vienna, Austria
2 Medical University of Vienna, Institute of Physiology, Vienna, Austria
Abstract text :

Platelets are anuclated blood cells, which are critical for hemostasis. However, increasing evidence indicates that activated platelets influence immune responses, as they interact with leukocytes. This interaction promotes leukocyte trafficking to inflammatory sites, e.g. induced by acute lung injury (ALI). As phosphatidylinositol 3-kinase (PI3K) is central in conducting platelet activation and neutrophils are important in ALI, we wanted to elucidate the effect of platelet PI3K on ALI.

Hence, we bred mice with a platelet-specific p85α deficiency, a regulatory subunit of the PI3K. Platelet activation was examined by detecting surface activation markers via flow cytometry and platelet aggregation via light transmission aggregometry. To induce ALI we treated mice intra-tracheally with hydrochloric acid and analyzed pulmonary leukocyte influx by flow cytometry.

We found that platelets lacking p85α had reduced CD62P and CD40L surface expression compared to wild-type platelets in response to AY-NH2 (PAR4 agonist) and convulxin (GPIV agonist). Further, platelet aggregation upon thrombin stimulation was diminished. Challenging platelet p85α-deficient mice and wild-type littermates with ALI, we observed attenuated pulmonary leukocyte accumulation. Moreover p85α deficiency provoked impaired platelet-neutrophil/ monocyte aggregate formation.

Our results indicate that PI3K is important for platelet activation. Lack of platelet PI3K reduced platelet-leukocyte interactions and therefore likely diminished leukocyte extravasation, may leading to ameliorated symptoms in ALI. Thus, platelet PI3K is not only crucially involved in platelet-mediated hemostasis, it is also essential for their immunological functions.

The role of Aflibercept and Ranibizumab against oxidative stress in Retinal Pigment epithelium cells (ARPE-19). Mechanisms related to nitric oxide release and apoptosis, autophagy modulation.
*Serena Farruggio1
1 University of Eastern Piedmont, , Novara, Italy
Abstract text :

The Age-Related Macular Degeneration is the leading cause of severe and irreversible loss of vision in developed countries. In the mechanisms of action of the anti-VEGF agents the involvement of nitric oxide (NO), and the modulation of mitochondria function and of apoptosis/ autophagy have not been examined, yet. In the present study, we planned to evaluate the effects of Aflibercept and
Ranibizumab in human retinal pigment epithelium cells (RPE; ARPE-19) cultured in physiologic/peroxidative conditions on cell viability/proliferation and mitochondria function. Mechanisms related to NO release, apoptosis/autophagy, and Akt and ERK1/2 expression/activation were examined, as well. RPE, either or not subjected to peroxidation were administrated Ranibizumab (0.025-0.20 mg/ml) and Aflibercept (0.025-0.50 mg/ml) for 1, 5 and 30 min. The modulation of NO release, cell viability/proliferation, oxidant/antioxidant system, mitochondrial membrane potential were examined by specific dyes. eNOS/iNOS, markers of apoptosis/autophagy and kinases activation/expression were analyzed by Western Blot. In RPE, Aflibercept and Ranibizumab increased NO release in a dose and time-dependent way in physiologic condition. In the presence of hydrogen peroxide both the anti-VEGF agents prevented the collapse of mitochondrial membrane potential and cell viability. In the presence of the NOS inhibitor, the effects on NO release were reduced or abolished. Those findings were accompanied by modulation of apoptosis/autophagy and of above kinases activation. The present results have shown protective effects elicited by Aflibercept and Ranibizumab on RPE undergone peroxidation through the modulation of NO release, apoptosis and autophagy.

Influence of compression aids on baroreflex function in patients with cervical spinal cord injury
*Jana Svacinova1, Katarina Ondrusova1, Michal Javorka2,3, Marie Novakova1, Zuzana Novakova1
1 Faculty of Medicine, Masaryk University, Department of Physiology, Brno, Czech Republic
2 Jessenius Faculty of Medicine, Comenius University in Bratislava, Department of Physiology, Martin, Slovakia
3 Jessenius Faculty of Medicine, Comenius University in Bratislava, Biomedical Center Martin, Martin, Slovakia
Abstract text :

Patients after cervical spinal cord injury (cSCI) often suffer from orthostatic hypotension (OH). Although vagal cardiac chronotropic effect is preserved in cSCI, baroreflex vascular tone regulation is impaired due to interrupted sympathetic pathways below the cSCI level. Patients usually use compression aids (CA, e.g. stockings, abdominal corset) to mitigate blood pressure (BP) drop during orthostasis. This study aimed to assess the influence of CA on baroreflex function in cSCI patients during orthostasis.

BP was continuously recorded in 9 cSCI patients during passive orthostasis without and with CA. Beat-to-beat systolic blood pressure (SBP) and inter-beat intervals (IBI) sequences were obtained from continuous non-invasive BP recording. Pulse pressure (PP) was evaluated as a mean of beat-to-beat differences between SBP and diastolic pressures. Closed loop of SBP IBI interaction was mathematically opened by bivariate autoregressive model; causal coherence (a measure of IBI and SBP synchronization) and gain estimating baroreflex sensitivity (BRS) were calculated in baroreflex direction (from SBP to IBI).

When CA were applied, coherence and PP were significantly increased as compared to orthostasis without CA (p < 0.05). CA application was also associated with an increase of BRS (borderline significant; p = 0.059). Patients reported less OH symptoms when wearing CA.

Use of CA increased venous return and consequently stroke volume expressed as an increase of PP in this study. This probably prevented the baroreflex sensitivity decrease during orthostasis. We suppose that positive influence of CA on blood pressure regulation during orthostasis weakened OH symptoms in cSCI.

Grants: MUNI/A/1355/2016, APVV-0235-12.