Clinical Hemorheology and Microcirculation - Volume 60, issue 1

Authors: Yan, Wan | Fang, Liang | Heuchel, Matthias | Kratz, Karl | Lendlein, Andreas

Article Type: Research Article

Abstract: Stress relaxation can strongly influence the shape-memory capability of polymers. Recently a modified Maxwell-Wiechert model comprising two Maxwell units and a single spring unit in parallel has been introduced to successfully describe the shape recovery characteristics of amorphous polyether urethanes. In this work we explored whether such a modified Maxwell-Wiechert model is capable to describe the stress relaxation behavior of a semi-crystalline multiblock copolymer named PCL-PIBMD, which consists of crystallizable poly(ɛ -caprolactone) (PCL) segments and crystallizable poly(3S -isobutylmorpholine-2,5-dione) (PIBMD) segments. The stress relaxation behavior of PCL-PIBMD was explored after uniaxial deformation to different strains ranging from 50 to 900% with …various strain rates of 1 or 10 or 50 mm·min −1 . The modeling results indicated that under the assumption that in PCL-PIBMD both PCL and PIBMD blocks have narrow molecular weight distributions and are arranged in sequence, the two relaxation processes can be related to the amorphous PCL and PIBMD domains and the spring element can be associated to the PIBMD crystalline domains. The first Maxwell unit representing the faster relaxation process characterized by the modulus E 1 and the relaxation time τ 1 is related to the amorphous PCL domains (which are in the rubbery state), while the second Maxwell unit (E 2  ; τ 2 ) represents the behavior of the amorphous PIBMD domains, which are in the glassy state at 50 °C. Increasing strain rates resulted in an increase of E 1 and a significant reduction in τ 1 , whereas the elastic modulus as well as the relaxation time related to the amorphous PIBMD domains remained almost constant. When a higher deformation was applied (ɛ ≥ 200% ) lower values for the elastic moduli of the three model elements were obtained. In general the applied model was also capable to describe the relaxation behavior of PCL-PIBMD at a deformation temperature of 20 °C, where additional crystalline PCL domains are existent. The presented approach using a modified Maxwell-Wiechert model to analyze the stress relaxation behavior can be useful to understand the changes in structure-function relation of amorphous as well as semi-crystalline polymers occurring during its uniaxialdeformation. Show more

Keywords: Degradable polymers, stress relaxation, shape-memory effect, structure-function relation

DOI: 10.3233/CH-151940

Citation: Clinical Hemorheology and Microcirculation, vol. 60, no. 1, pp. 109-120, 2015

Authors: von Tempelhoff, Georg-Friedrich | Tsikouras, Panagiotis | Rath, Werner | Velten, Eva | Csorba, Roland

Article Type: Research Article

Abstract: OBJECTIVE: Patients with a history of severe obstetric complications in the presence of elevated phospholipid antibodies are at high risk for recurrent obstetric debacle. We report a successful immunologic treatment for prevention of HELLP-Syndrome in subsequent pregnancy in a patient with elevated Phospholipid antibodies, while under rheological and hemostaseological monitoring. METHODS: The patient with prior severe HELLP-Syndrome at term in the presence of reconfirmed elevated phospholipid antibodies in her first pregnancy received pooled immunoglobulins (Sandoglobulin 3 g - Novartis) intravenously for immunological treatment every three weeks in addition to low molecular weight heparin (Clexane 40 mg/d s.c.) …and Aspirin (100 mg/d from 2nd trimester) during her subsequent pregnancy. Before each of 10 treatment cycles blood rheological parameters (Red Blood cell {RBC} aggregation stasis E0, low shear E1, RBC - deformability low-, moderate-, and high shear force, plasma viscosity {Pv}), as well as thrombelastometry (ROTEM) and in vitro platelet function (PFA-100) for hemostaseological evaluation was performed. At the same times non-invasive, physical thrombosis screening took place using impedance plethysmography (Filtrass) RESULTS: During pregnancy a constant increase in PV and E1 (>45 S −1 ) was accompanied by a delayed but continuous increase in RBC deformability beginning at the end of the 2nd trimester. Thrombelastometry revealed a continuous reduction of clot formation time (CFT; extem: 84 to 38 sec) and an increase in maximal clot firmness (MCF; extem: 64 to 78 sec) after TF-induced coagulation activation while MCF and CFT after contact activation (intem) was barely unchanged. Platelet bleeding-time after EPI/Coll stimulation was temporary prolonged by the onset of Aspirin intake (>300 sec) but normalized soon after 20th gestational week, while ADP/Coll stimulation revealed a trend towards prolonged bleeding times at the same time. There was a strong and statistically significant inverse correlation between E1 and TF induced CFT (r  =−0.82; p  = 0.002) and a positive correlation between E1 and TF induced MCF (r  = 0.89; p  <  0.001), while the correlation between E1 and contact activated CFT and MCF was weak or absent, respectively. Until GW 38th routine laboratory- (Platelet-count, Haptoglobin, liver enzymes) and clinical findings remained normal, without evidence of HELLP-Syndrome reoccurrence or development of thrombosis. CONCLUSIONS: During immunotherapy in this high risk patient HELLP-Syndrome did not reoccur. The aggregability of RBC was closely related with the formation speed and firmness of clot after TF activated coagulation but not after contact activated coagulation. At the beginning of 3rd trimester RBC aggregation remained dramatically higher as compared to the normal value range of pregnant women found in a large recent trial which may have been an early indicator of imminent HELLP-Syndrome. Show more

Keywords: Pregnancy, antiphospholipid syndrome, HELLP syndrome, plasma viscosity, red blood cell aggregation, immunological treatment, thrombelastometry, platelet function

DOI: 10.3233/CH-151937

Citation: Clinical Hemorheology and Microcirculation, vol. 60, no. 1, pp. 123-131, 2015

Authors: Reviakine, Ilya

Article Type: Research Article

Abstract: Recent years have been ripe with discoveries of non-haemostatic platelet functions. This led to the appreciation of the significant, previously unknown, role played by the platelets in various pathologies and regenerative processes. As a result, exciting opportunities for clinical applications in fields as diverse as regenerative medicine and cancer treatment are emerging. However, their realization depends on the understanding of the regulatory mechanisms governing these diverse platelet functions, so that particular platelet responses could be artificially tailored to specific clinical situations. Current understanding of the signalling pathways controlling haemostatic responses is rooted in the development of quantitative assays for measuring …them and sensitive markers for their quantification. However, the existing assays and markers are not sufficiently sensitive for distinguishing between individual signalling pathways and unravelling inter-pathway connections. Moreover, entirely new approaches are needed for studying non-haemostatic platelet functions, since there are currently no assays or markers for quantifying them. We review the on-going efforts in these directions, including our own recent work on using lectins as sensitive probes for profiling platelet activation. Show more

DOI: 10.3233/CH-151942

Citation: Clinical Hemorheology and Microcirculation, vol. 60, no. 1, pp. 133-152, 2015

Authors: Krüger, A. | Fuhrmann, R. | Jung, F. | Franke, R.P.

Article Type: Research Article

Abstract: The proper morphology and function of the vascular endothelium are prerequisites for a sufficient supply of the tissues. Endothelial cell (EC) dysfunction can lead to circulatory disorders and the development of cardiovascular diseases. The endothelialization of cardiovascular implants is a sophisticated task since EC miss their natural environment and physiological stimuli in vitro . In addition, different studies revealed that the EC behavior and morphology depended on the substrate and the passage number of the EC. Therefore, the comparison of endothelialization studies is very difficult, when passage and substrate are unknown. The aim of this study was to investigate …the growth potential and cell morphology of human venous endothelial cells (HUVEC) as a function of different cell passages and different substrates (pristine polystyrene, tissue-typical ECM-coated polystyrene). The study revealed that HUVEC morphology and growth potential were significantly different on pristine polystyrene compared to the basal lamina-like ECM-coated polystyrene surface. Furthermore, it became obvious that the passage of the cells affected the endothelialization of the polystyrene surface significantly. In conclusion, this study emphasized the need for a critical consideration of EC data whereas a simple comparison of results is not possible if EC age and passage is unknown. Show more

Keywords: Endothelial cells, passage number, extracellular matrix, proliferation, endothelialization

DOI: 10.3233/CH-151943

Citation: Clinical Hemorheology and Microcirculation, vol. 60, no. 1, pp. 153-161, 2015

Authors: Shin, Eun-Seok | Ann, Soe Hee | Brachmann, Johannes | Lam, Yat-Yin | Jung, Friedrich | Park, Jai-Wun

Article Type: Research Article

DOI: 10.3233/CH-151945

Citation: Clinical Hemorheology and Microcirculation, vol. 60, no. 1, pp. 163-169, 2015