Biorheology - Volume 21, issue 4

Authors: Oda, T. | Lehmann, A. | Endrich, B.

Article Type: Research Article

Abstract: In malignant tumors, spontaneous arteriolar vasomotion disappeared already during earliest tumor growth (tumor weight less than 200 mg) suggesting that arterioles supplying a malignant tumor with blood are maximally dilated from the very beginning of tumor growth. As a result, the viscosity of blood becomes a limiting factor of tissue perfusion. To evaluate the effects of isovolemic hemodilution in a malignant tumor, a transparent chamber model was used in conjunction with a subcutaneously growing amelanotic melanoma of the hamster. Quantitative intravital microscopy (video image analysis) and a platinum multiwire electrode were utilized to study the tumor microcirculation. Isovolemic hemodilution was …performed by exchange of blood vs. Dextran 60 to lower the systemic hematocrit to 30% in 21 animals. Capillary flow increased significantly and improved tissue pO2 on the tumor’s surface without any change in capillary density. Since tumor growth was accelerated after hemodilution, these data suggest to combine with hemodilution other treatment modalities to improve blood-mediated tumor therapy. Show more

Keywords: Hemodilution, capillary blood flow, oxygenation, tumor growth, melanoma

DOI: 10.3233/BIR-1984-21410

Citation: Biorheology, vol. 21, no. 4, pp. 509-520, 1984

Authors: Vaupel, P. | Müller-Klieser, W.

Article Type: Research Article

Abstract: Experiments are performed to study the influence of local hemodilution on tumor blood flow, oxygen availability in tumor tissue and O2 consumption of cancer cells. The results obtained clearly show that hemodilution in isolated tumor perfusion can distinctly improve nutritive blood flow through solid tumors. This can be utilized to enhance pharmacokinetics of antitumor drugs. Due to the improved metabolic status, the pharmacodynamics of some antitumor drugs should also be enhanced. To achieve a maximum improvement of the O2 supply to the tumor, hematocrit values should not be decreased below 0.20.

Keywords: Hemodilution, tumor blood flow, O2 supply, oxygenation

DOI: 10.3233/BIR-1984-21411

Citation: Biorheology, vol. 21, no. 4, pp. 521-528, 1984

Authors: Müller-Klieser, W. | Vaupel, P.

Article Type: Research Article

Abstract: Differences in blood perfusion rates between tumors and normal tissue can be utilized to selectively heat many solid tumors. Blood flow in normal tissues is considerably increased at temperatures commonly applied during localized hyperthermia. In contrast, tumor blood flow may respond to localized heat typically in two different blood flow patterns: Flow may either decrease continuously with increasing exposure time and/or temperature or flow may exhibit a transient increase followed by a decline. A decrease in blood flow at high thermal doses can be observed in most of the tumors, whereas an increase in flow at low thermal doses seems …to occur less frequently. The inhibition of blood flow at high thermal doses may lead to physiological changes in the microenvironment of the cancer cells that increase the cell killing effect of hyperthermia. Flow increases at low thermal doses can enhance the efficiency of other treatment modalities, such as irradiation or the administration of antiproliferate drugs. Show more

Keywords: Hyperthermia, tumor blood flow, microcirculation, cellular microenvironment

DOI: 10.3233/BIR-1984-21412

Citation: Biorheology, vol. 21, no. 4, pp. 529-538, 1984

Authors: Dewhirst, M. | Gross, J.F. | Sim, D. | Arnold, P. | Boyer, D.

Article Type: Research Article

Abstract: Single vessel responses to hyperthermia were studied in tumor and normal tissues using a transparent access window chamber. Rates of heating ⩽ .68°C/minute preserved relatively better vascular function in normal than tumor tissue. A rate of heating of 1.0°C/minute lowered normal tissue stasis temperatures so they were no different from tumor. Cooling to 30°C prior to heating slowed normal arteriolar flows to < 5% of 38°C controls. Heating resulted in increased flow in those vessels, but maximum flows never exceeded 5% of flows achieved in similar vessels which were not cooled first. The implications of this work are that rate …of heating and cooling prior to heating can alter normal tissue vascular response to heat in a way that could prove deleterious to maintaining efficient vascular function in that tissue relative to tumor. Show more

Keywords: Microcirculation, Vascular stasis, Heating rate, Tumor, Normal tissue

DOI: 10.3233/BIR-1984-21413

Citation: Biorheology, vol. 21, no. 4, pp. 539-558, 1984

Authors: Schmid-Schönbein, Holger

Article Type: Other

DOI: 10.3233/BIR-1984-21414

Citation: Biorheology, vol. 21, no. 4, pp. 559-564, 1984

Authors: Nerem, R.M.

Article Type: Research Article

Abstract: The evidence for a hemodynamic involvement and possible mechanisms by which hemodynamic-related events could influence the arterial wall, and in particular the vascular endothelium, are reviewed and used to speculate on the role of fluid mechanics in atherogenesis and specifically in lesion localization. The evidence presented suggests that it is vascular geometry, and the way it influences the local detailed flow properties, which is the primary determinant of a hemodynamic effect on the arterial wall and in the initiation of atherosclerosis.

Keywords: atherogenesis, endothelium, hemodynamics, vascular geometry

DOI: 10.3233/BIR-1984-21415

Citation: Biorheology, vol. 21, no. 4, pp. 565-569, 1984

Authors: Liepsch, D. | Moravec, St.

Article Type: Research Article

Abstract: In addition to biochemical factors, hydromechanical influences are responsible for atherogenesis and deposits of blood platelets at bends and bifurcations of human arteries. Hence the flow patterns were simulated in a true-to-scale three-dimensional bifurcation of a human renal artery model and of an arteria femoralis with Newtonian and non-Newtonian blood like fluid. Investigations were made with steady and pulsatile flow. The velocity profiles (at physiological Re-numbers) were measured after the bifurcations with a laser-Doppler-anemometer. In previous works Newtonian fluids were used to investigate the flow in bends and bifurcations of rigid and elastic simplified models. In this paper, …emphasis is placed on the difference between rigid and elastic models and also Newtonian and non Newtonian flow behavior. Differences between Newtonian and non Newtonian fluids may especially be expected to occur after branches where the flow has local strong convective elements such as in reverse zones and flow separation points. Show more

Keywords: Laser-Doppler-Anemometer, velocity measurements, bifurcations, haemodynamic, atherogenesis

DOI: 10.3233/BIR-1984-21416

Citation: Biorheology, vol. 21, no. 4, pp. 571-586, 1984

Authors: Karino, Takeshi | Goldsmith, Harry L.

Article Type: Research Article

Abstract: The relationship between blood flow and the localization of thrombosis and atherosclerosis in vivo was investigated using the approach and techniques of microrheology. The flow patterns and wall-adhesion of platelets were studied in the captive annular vortex formed at a sudden tubular expansion at various hematocrits in steady and pulsatile flow. The adhesion density exhibited a peak within the vortex and just downstream of the reattachment point, which is also a stagnation point. The peaks flattened out with increasing Reynolds number in steady flow and also in pulsatile flow. Platelet adhesion increased markedly with increasing hematocrit. The localization of …adhesion peaks was explained by curvature of the streamlines carrying platelets to the wall on either side of the reattachment point. The relevance of these results to the circulation is that stagnation points are found in regions of disturbed flow at various sites in the arterial and venous circulations. This was shown in experiments using a technique whereby flow was visualized in isolated transparent natural blood vessels prepared from dogs and humans postmortem. In dog saphenous vein bileaflet valves, there was a large primary spiral vortex as well as a smaller secondary vortex, the latter acting as a trap and generator of thrombi. Recirculation zones also existed in the dog aorta at T-junctions of the celiac, cranial mesenteric and renal arteries. Finally, in the human carotid bifurcation, a large standing recirculation zone consisting of spiral secondary flows formed in the carotid sinus at physiological flow conditions. In all these arterial flows there are streamlines impinging radially on the vessel wall which increase the local flux of platelets and plasma proteins and lipids and may lead to the genesis of thrombosis and atherosclerosis. Show more

Keywords: platelet adhesion, vortex, recirculation zone, flow patterns, transparent blood vessel, thrombogenesis, atherogenesis

DOI: 10.3233/BIR-1984-21417

Citation: Biorheology, vol. 21, no. 4, pp. 587-601, 1984

Authors: Niimi, Hideyuki | Kawano, Yosuke | Sugiyama, Ikuo

Article Type: Research Article

Abstract: A fine structure of blood flow through a curved vessel with an aneurysm was studied in in vitro experiments in relation to rheological factors of arterial diseases such as arteriosclerosis or thrombosis. On the basis of the in vivo data related to cerebral circulation, red blood cell suspension was flowed through curved vessel models with an asymmetrical aneurysm. Flow visualization was made with a microscope 16 mm cinecamera-TV monitor system, and the velocity profile was measured using the laser Doppler velocimeter. Vortices induced in aneurysm influenced flow structure and velocity at the presence of the secondary flow due …to the vessel curvature. This suggests strongly that blood flow in curved arteries with an aneurysm must be understood under the influence of the secondary flow. Show more

Keywords: Aneurysm, Blood flow, Cerebral artery, Curved vessel, Secondary flow, Vortices

DOI: 10.3233/BIR-1984-21418

Citation: Biorheology, vol. 21, no. 4, pp. 603-615, 1984

Authors: Remuzzi, Andrea | Dewey Jr., C. Forbes | Davies, Peter F. | Gimbrone Jr., Michael A.

Article Type: Research Article

Abstract: Vascular endothelial cells subjected to fluid shear stress change their shape from polygonal to ellipsoidal and become uniformly oriented with the flow. In order to study the mechanisms of this response, we have measured the relaxation of bovine aortic endothelial cells that were grown on glass coverslips and exposed to fluid shear stress for 72 hours. An image analysis system was developed to quantify the cell shape relaxation that occurs following the cessation of shear stress. This method provides two different quantitative measures of relaxation: the loss of elongated shape by the cells and the change in cell direction with …time. After equilibration to a fluid shear stress level of 8 dynes/cm2 , cells immersed in static medium relax their shape in about 20 hours. After 72 hours in this static condition, the cell elongation is comparable to that of unstressed control cells but vestiges remain of the original orientation in the flow direction. This relaxation process contributes to our understanding of the response of vascular endothelium to fluid shear stress. Show more

Keywords: Endothelial cells, fluid shear stress, vascular endothelium, cell shape relaxation

DOI: 10.3233/BIR-1984-21419

Citation: Biorheology, vol. 21, no. 4, pp. 617-630, 1984

Authors: Chien, Shu | Fan, Foun-chung | Lee, Mary M.L. | Handley, Dean A.

Article Type: Research Article

Abstract: The effects of variations in transmural pressure over a range of 0 to 200 mmHg on transendothelial transport of macromolecules were studied in the canine common carotid artery. The uptake of 125 I-albumin per unit artery weight increased with rising pressure. There was no significant difference in albumin permeability per unit luminal surface area between 0 and 100 mmHg, but permeability nearly doubled when pressure was raised to 200 mmHg. The contribution of an increased rate of transendothelial vesicle diffusion, as evaluated from the experimental determination of the ratio of attached-to-free vesicles and theoretical modeling, was found to be negligible. …The reduction in transendothelial vesicle diffusion distance due to pressure-induced thinning of the peripheral zone contributes to a 25% increase in permeability. with the use of colloidal Ag and Au of various sizes, vesicle loading of particles with diameters ⩾ 15 nm was found to be severely restricted at transmural pressure ⩽ 100 mmHg, but it was significantly enhanced at 200 mmHg, when particles as large as 25 nm became detectable in endothelial vesicles and subendothelial space. This hypertension-induced increase in macromolecular transport across the endothelium may cause an overloading of the arterial wall with low-density lipoproteins and play a significant role in atherogenesis. Show more

Keywords: Albumin, Atherogenesis, Endothelium, Hypertension, Permeability, Vesicles

DOI: 10.3233/BIR-1984-21420

Citation: Biorheology, vol. 21, no. 4, pp. 631-641, 1984

Authors: Lanir, Y.

Article Type: Research Article

Abstract: The possibility of fluid flux within the thickened subendothelial intima is considered. Both the media and the endothelium were already shown to be major hydraulic barriers. It is hypothesized that if the hydraulic conductivity of the inbetween layer of the subendothelial intima is considerably higher, then fluid flux in the downstream (axial) direction is likely to occur within the intima as a result of the luminal blood pressure wave. Macromolecular species (as lipoproteins) would then be transported axially by the fluid. This convective transport may give rise to the formation of early atheromas. The proposed mechanism is in accord with …several clinical and experimental observations. Show more

Keywords: Atherogenesis, Convective Transport, Subendothelial Intima, Hydraulic Conductivity

DOI: 10.3233/BIR-1984-21421

Citation: Biorheology, vol. 21, no. 4, pp. 643-647, 1984

Authors: Wurzinger, L.J. | Blasberg, P. | van de Loecht, M. | Suwelack, W. | Schmid-Schönbein, H.

Article Type: Research Article

Abstract: Experiments with glass models of arterial branchings and bends, perfused with bovine platelet rich plasma (PRP), revealed platelet deposition being strongly dependent on fluid dynamic factors. Predilection sites of platelet deposits are characterized by flow vectors directed against the wall, so-called stagnation point flow. Thus collision of suspended particles with the wall, an absolute prerequisite for adhesion of platelets to surfaces even as thrombogenic as glass, appears mediated by convective forces. The extent of platelet deposition is correlated to the magnitude of flow components normal to the surface as well as to the state of biological activation of the platelets. …The latter could be effective by an increase in hydrodynamically effective volume, invariably associated with the platelet shape change reaction to biochemical stimulants like ADP. The effect of altered rheological properties of platelets upon their deposition and of mechanical properties of surfaces was examined in a stagnation point flow chamber. Roughnesses in the order of 5 µm, probably by creating local flow disturbances, significantly enhance platelet adhesion, as compared to a smooth surface of identical chemical composition. Show more

Keywords: platelet adhesion, stagnation point, atherogenesis, platelet rheology, shape change

DOI: 10.3233/BIR-1984-21422

Citation: Biorheology, vol. 21, no. 4, pp. 649-659, 1984

Article Type: Correction

DOI: 10.3233/BIR-1984-21423

Citation: Biorheology, vol. 21, no. 4, pp. 661-661, 1984