Biorheology - Volume 51, issue 4-5

Authors: Endo, Shunsuke | Goldsmith, Harry L. | Karino, Takeshi

Article Type: Research Article

Abstract: OBJECTIVES: To elucidate the role of fluid mechanical factors in the localized genesis and development of atherosclerotic lesions in man. METHODS: Flow patterns and preferred sites of atherosclerotic lesions in the human aortic arch were studied in detail using isolated transparent aortic trees prepared from humans postmortem and by means of flow visualization of tracer polystyrene microspheres, using cinemicrographic techniques. RESULTS: Under the condition of steady flow that simulated mid-systole, the flow in the aortic arch consisted of three major components; (i) a straight flow to the brachio-cephalic artery located close to the right dorsal wall of the …ascending aorta; (ii) a quasi-parallel undisturbed flow located close to the common median plane of the aortic arch and its side branches, and (iii) a clockwise slow, spiral secondary flow located dominantly near the left ventral wall of the aortic arch. Thus, looking down the aorta from its origin, the flow in the aortic arch appeared as a single helical flow revolving in a clockwise direction. CONCLUSIONS: Atherosclerotic lesions were found mainly in regions of low wall shear stress such as the proximal lip of the orifice of each side branch where a slow recirculation flow formed, and the left ventral wall of the aortic arch where a slow spiral secondary flow formed. Show more

Keywords: Flow visualization, helical flow, recirculation flow, secondary flow, velocity distribution, wall shear stress

DOI: 10.3233/BIR-14005

Citation: Biorheology, vol. 51, no. 4-5, pp. 239-255, 2014

Authors: Endo, Shunsuke | Goldsmith, Harry L. | Karino, Takeshi

Article Type: Research Article

Abstract: OBJECTIVE: As in Part I, to elucidate the role of fluid mechanical factors in the localized genesis and development of atherosclerotic lesions in man, here in the abdominal aorta. METHODS: Flow patterns and preferred sites of atherosclerotic lesions in the aorta were studied in detail using the same isolated transparent aortic trees prepared from humans postmortem and the flow visualization and cinemicrographic techniques as in Part I. RESULTS: Under steady flow simulating mid-systole, the flow was found to be disturbed at the aorto-celiac and aorto-superior mesenteric artery junctions by the formation of complex secondary and adverse flows along …the lateral and posterior walls of the abdominal aorta. More complex secondary and adverse flows formed at the branching sites of the left and right renal arteries. Furthermore, considerable interactions occurred between the secondary and adverse flows formed at the branching sites of the above four arteries, resulting in the formation of a large and long recirculation zone along the lateral and posterior walls of the abdominal aorta corresponding to these branches. The velocity profile was almost flattened throughout the entire length of the descending aorta. CONCLUSIONS: Atherosclerotic lesions were found mainly at the posterior and lateral walls of the abdominal aorta where slow adverse and recirculation flows formed and where wall shear stress was low. Show more

Keywords: Aortic aneurysm, flow visualization, recirculation flow, secondary flow, velocity profile, wall shear stress

DOI: 10.3233/BIR-14006

Citation: Biorheology, vol. 51, no. 4-5, pp. 257-274, 2014

Authors: Li, Lin | Walker, Andrew M. | Rival, David E.

Article Type: Research Article

Abstract: BACKGROUND: Although a blood analog of aqueous glycerol and xanthan gum was found to replicate the viscoelastic behavior of blood, measurements were restricted to laminar flow. OBJECTIVE: To expand the characterization of a non-Newtonian blood analog of aqueous glycerol and xanthan gum to transitional Reynolds numbers to quantify its behavior as a function of both natural and shear-layer-induced mechanisms. METHODS: A Newtonian analog and a shear-thinning aqueous glycerol, xanthan gum solution were circulated through an in vitro flow loop replicating both a straight and obstructed artery where transition was initiated through natural and shear-layer-induced mechanisms respectively. Steady and …pulsatile pressure drop measurements for both fluids were acquired across a range of Reynolds numbers up to 7600 and Womersley numbers of 4 and 6. RESULTS: In steady and pulsatile straight flow, the non-Newtonian analog presented with reduced pressure drops and prolonged laminar flow to Reynolds numbers of 3200 and 3800 respectively. Upon blockage inclusion, non-Newtonian minor losses were comparable to Newtonian in steady flow and greater in pulsatile flow suggesting an elongation of downstream non-Newtonian recirculation. Although non-Newtonian total system pressure drops in both straight and obstructed flows were lower, the ratio of pressure drop difference between the two fluids decreased through shear-layer-induced transition. CONCLUSIONS: These findings not only demonstrated the suitability of using a xanthan gum analog to model blood flow in transitional regimes, but also presented the respective differences in analog behavior as a function of transition mechanism. Show more

Keywords: Blood analog fluids, viscoelastic fluids, natural transition, shear-layer-induced transition

DOI: 10.3233/BIR-14009

Citation: Biorheology, vol. 51, no. 4-5, pp. 275-291, 2014

Authors: Findikoglu, Gulin | Kilic-Toprak, Emine | Kilic-Erkek, Ozgen | Senol, Hande | Bor-Kucukatay, Melek

Article Type: Research Article

Abstract: BACKGROUND: Acute hemorheological responses to different types of aerobic exercises have never been compared in a single study in healthy people. OBJECTIVE: We aimed to compare acute effects of high intensity intermittent exercise (HIIE) and moderate intensity continuous exercise (MICE) on hemorheological parameters, in healthy young subjects. METHODS: A total of 34 sedentary young adults (12 males, 22 females) with a mean age of 20.0±2.1 years were randomly assigned to HIIE, MICE or non-exercise groups. MICE exercised at the power corresponding to 50% of heart rate reserve (HRR) continuously for 25 min. HIIE exercised at the power corresponding …to 100% of HRR for 30 s followed by 30 s rest for 25 min. The non-exercise group rested. Blood samples were collected before and after exercise and studied for blood count, whole blood viscosity (WBV), plasma viscosity (PV) and red blood cell (RBC) elongation at nine different shear stresses. RESULTS: WBV, PV, RBC elongation of MICE and HIIE groups were not found to be statistically different from each other or from the non-exercise group. Compared to the non-exercise group, there was a significant increase in white blood cell (WBC) and RBC counts in the MICE group. CONCLUSIONS: Different types of aerobic exercises, namely MICE, HIIE are not different from each other in terms of hemorheological parameters immediately after exercise. Show more

Keywords: Intermittent exercise, continuous exercise, aerobic, exercise, blood rheology, red blood cell deformability

DOI: 10.3233/BIR-14012

Citation: Biorheology, vol. 51, no. 4-5, pp. 293-303, 2014

Authors: Shao, H.R. | Jin, Y. | Han, G.Y. | Jiang, P. | Zhu, X.Q. | Liu, F. | Song, Z.G. | Li, M. | Ling, P.X.

Article Type: Research Article

Abstract: BACKGROUND: Injection of xanthan gum (XG) has been demonstrated to reduce the symptoms and progression of osteoarthritis (OA) in experimental models. Due to its high viscosity and stability, it may restore the rheological homeostasis of osteoarthritic synovial fluid (SF), and avoid numerous intra-articular injections. OBJECTIVE: The present study investigated the effect of XG on the rheological properties of SF, and determined its residence time in the rabbit joint cavity. METHODS: Rabbit knees were subject to intra-articular injection with XG or XG labeled with green fluorescence, and the SF was collected at different time. Rheological properties of SF with …XG injected were compared with those with sodium hyaluronate injected. Resistance to oxidant damage was tested by adding H2 O2 to the viscosupplement. Fluorescence intensity was measured for the SF with XG labeled with green fluorescence. RESULTS: Results showed that XG could significantly improve the SF viscosity at 24, 96, 168 h, and increase the storage moduli (G′) and loss moduli (G″) tested at frequency of 0.5 and 2.5 Hz. SF with XG injection exhibited a gel-like behavior at 24 h, in that G′ exceed G″ over the entire oscillation frequency range. XG preparation had a high resistance to oxidant damage. Half-life of XG in the joint cavity was 35.9 h, with clearance obeying first-order kinetics. CONCLUSIONS: Intra-articular injection of XG could improve the rheological properties of SF, and this effect could last for several days. Show more

Keywords: Xanthan gum, osteoarthritis, viscosupplementation, intra-articular injection, kinetics

DOI: 10.3233/BIR-14013

Citation: Biorheology, vol. 51, no. 4-5, pp. 305-314, 2014

Authors: Tosato, Maira Gaspar | Orallo, Dalila E. | Churio, M. Sandra | Martin, Airton A. | Soto, Claudio A. Telléz | Dicelio, Lelia E.

Article Type: Research Article

Abstract: BACKGROUND: The amphiphilic nature of polymers allows them to be widely incorporated as carriers in different pharmaceutical applications since they are able to work as vehicles for hydro- or lipo-soluble actives. OBJECTIVE: The aim of this study was to determine the rheological behavior and vibrational spectral variations of two hydrophilic gels prepared with Poloxamer 407 (PO) or Pluronic F-127 (PL) with the addition of the actives mycosporine-like amino acids and gadusol. METHODS: The structures of these polymers in two different concentrations (20% w/w and 27% w/w) were characterized by rheological studies and Raman spectroscopy. RESULTS: Gels prepared …with higher polymer concentration showed larger G′ (storage modulus) values. The C–C stretch and the CH2 rocking predominated in the gels containing PL (20% w/w) and this correlated with a less viscous behavior. The mixture of the actives induced higher contributions of Raman peaks related to trans conformation of the C–C bonds located in hydrophilic polymer blocks, whereas the same peaks decreased in the sample containing only gadusol. CONCLUSIONS: Larger tensile strength and elastic component were observed upon increasing polymer concentration, thus evidencing polymer–polymer and/or polymer–polymer–actives interactions. The presence of the actives affected the mechanical properties of the polymer gels. Gadusol particularly seems to alter the conformation of the polymer chains by favoring gauche orientations, in parallel with rising viscoelastic parameters. More stretched arrangements of the polymer are probably induced in the presence of larger concentration of actives, due to specific interactions with their hydrophilic groups. Show more

Keywords: Triblock copolymers, viscoelastic, mycosporine-like amino acids, gadusol

DOI: 10.3233/BIR-14014

Citation: Biorheology, vol. 51, no. 4-5, pp. 315-328, 2014

Authors: Adams, Rachel A. | Al-Mosawi, Ameena | Bérubé, Kelly | Jones, Tim | Higgins, Timothy | Evans, Shelley-Ann

Article Type: Research Article

Abstract: BACKGROUND: Exposure to particulate air pollution is associated with an increased risk of cardiovascular disease. The mechanism by which exposure increases risk is poorly understood but could involve changes in the flow properties of blood. OBJECTIVE: The aim of this investigation was to assess the effect, in rats, of intratracheal instillation of particulate air pollution on leukocyte flow properties by measurement of polymorphonucleocyte (PMN) and monocyte actin polymerisation. METHODS: Rats were exposed to particulate air pollution by intratracheal instillation of PM10 . Blood was collected from test and control animals at 3 days (n=10) and 6 weeks (n=10) …after dust instillation. Partial differential leukocyte counts were performed. The intracellular F-actin content of blood PMNs and monocytes was determined by staining with FITC-phalloidin and flow cytometric determination of mean florescence intensity (MFI). RESULTS: There were no significant changes in PMN MFI (p=0.369, ANOVA) or cell counts (p=0.753, ANOVA). There was a significant increase in monocyte MFI (p=0.004, ANOVA) and a decrease in monocyte cell count (p=0.003, ANOVA) in instilled rats. CONCLUSIONS: Intratracheal instillation of air pollution particles resulted in an increase in blood monocyte actin polymerisation, which may cause trapping of monocytes. This could be a mechanism by which exposure to air pollution increases the risk of cardiovascular disease. Show more

Keywords: Particles, leukocyte, neutrophil, cytoskeleton, cardiovascular disease

DOI: 10.3233/BIR-14027

Citation: Biorheology, vol. 51, no. 4-5, pp. 329-338, 2014