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Biorheology is an international interdisciplinary journal that publishes research on the deformation and flow properties of biological systems or materials. It is the aim of the editors and publishers of
Biorheology to bring together contributions from those working in various fields of biorheological research from all over the world. A diverse editorial board with broad international representation provides guidance and expertise in wide-ranging applications of rheological methods to biological systems and materials.
The aim of biorheological research is to determine and characterize the dynamics of physiological processes at all levels of organization. Manuscripts should report original theoretical and/or experimental research promoting the scientific and technological advances in a broad field that ranges from the rheology of macromolecules and macromolecular arrays to cell, tissue and organ rheology. In all these areas, the interrelationships of rheological properties of the systems or materials investigated and their structural and functional aspects are stressed.
The scope of papers solicited by
Biorheology extends to systems at different levels of organization that have never been studied before, or, if studied previously, have either never been analyzed in terms of their rheological properties or have not been studied from the point of view of the rheological matching between their structural and functional properties. This biorheological approach applies in particular to molecular studies where changes of physical properties and conformation are investigated without reference to how the process actually takes place, how the forces generated are matched to the properties of the structures and environment concerned, proper time scales, or what structures or strength of structures are required.
Biorheology invites papers in which such 'molecular biorheological' aspects, whether in animal or plant systems, are examined and discussed. While we emphasize the biorheology of physiological function in organs and systems, the biorheology of disease is of equal interest. Biorheological analyses of pathological processes and their clinical implications are encouraged, including basic clinical research on hemodynamics and hemorheology.
In keeping with the rapidly developing fields of mechanobiology and regenerative medicine,
Biorheology aims to include studies of the rheological aspects of these fields by focusing on the dynamics of mechanical stress formation and the response of biological materials at the molecular and cellular level resulting from fluid-solid interactions. With increasing focus on new applications of nanotechnology to biological systems, rheological studies of the behavior of biological materials in therapeutic or diagnostic medical devices operating at the micro and nano scales are most welcome.
Abstract: Passive neutrophils from five different individuals are rapidly aspirated at constant suction pressure and at room temperature into a pipet with a diameter of 4 μ m. The excess suction pressures (i.e., the pressures in excess of the small threshold pressure required to produce continuous flow into the pipet) are 5000, 10000 and 20000 dyn/cm2 (0.5, 1 and 2 kPa) and are comparable to those encountered in the microcirculation. The rate of entry into the pipet is modeled with a linearized version of a theory by Yeung and Evans for the newtonian flow of a neutrophil into a pipet…or pore. From this theory and measurements of the cell size and its rate of entry into the pipet, we can calculate a value for the cytoplasmic viscosity. A linear (newtonian) fit of the theory to the experimental data gives a value for the viscosity of 1050 poise. A non-linear fit predicts a decrease in the “apparent viscosity” from about 1500 poise at zero excess pressure to 1000 poise at an excess aspiration pressure of 20,000 dyn/cm2 . Our experiments and analysis also allow us to calculate a value for the transit time through short pores over a wide range of excess aspiration pressures and pore diameters. For example, for a pore diameter of 3 μ m and an aspiration pressure of 1250 dyn/cm2 , we predict a transit time of about 70 s. At 6 μ m and 20,000 dyn/cm2 , the predicted transit time is only about 0.04 s.
Keywords: Neutrophil, viscosity, pipet, pore, transit time
vol. 27, no. 6, pp. 817-828, 1990
Abstract: Transit times of individual polymorphonuclear leukocytes (PMN) through cylindrical micropores with a diameter of 8 μ m and a length of 19 μ m were measured at pressure gradients of 3 to 10 cm H2 O using the Cell Transit Analyzer (CTA); this system employs a conductometric principle and provides a frequency histogram of transit times for > 1000 cells within 3 to 4 minutes. Salient results included: 1) linear pressure-flow relations (r⩾0.99); 2) mean transit times for PMN on the order of 10-20 milliseconds at a pressure gradient of 4 cm H2 O and thus transit times at least…10-fold longer than for RBC under the same conditions; 3) broad distributions with marked skewness toward longer transit times, indicating a wide range of rheo1ogic properties; 4) increased transit times in either hypotonic or hypertonic media; 5) marked increases of transit times following activation with FMLP; 6) considerable differences between the volume distribution and the transit time distribution of PMN. These results suggest the basic usefulness of the CTA for the analysis of rheologic properties of white blood cells in both normal and pathologic states.
Keywords: micropore filtration, polymorphonuclear leukocytes, transit time, white blood cell rheology, WBC deformability, WBC volume
vol. 27, no. 6, pp. 829-848, 1990
Abstract: Different kinds of leukocytes undergo cytoskeleton-dependent mechanical responses associated wit their specific physiological functions. We have investigated cellular stiffening of several types of leukocytes using a method which measures the force resisting cellular indentation. We have found that lymphocytes stiffen in response to crosslinking cell surface antigens in a process associated with the much studied capping and patching processes. Further studies of myosin-deficient mutants of the ameba Dictyostelium discoideum suggest that this stiffening process results from a myosin dependent contractile process. Rat basophilic leukemia cells and pancreatic islet cells stiffen when triggered to secrete. The function of these cytoskeleton dependent…processes is now unknown, but, at least in the islet cells, may be related to a regulation of the rate of secretion. Primary neutrophils stiffen in response to the chemotactic agent, fMet-Leu-Phe. This stiffening may be responsible for retention of these cells in the pulmonary microcirculation during response to inflammation. These observations pose the challenge of determining the structural basis, mechanism, and physiological function of each of these cellular responses.
Abstract: Recent evidence for a role of granulocytes in ischemic organ injury and in hemorrhagic shock is provided. Compared to red cell, granulocytes are large cells and have a stiff cytoplasm, making them prone to entrapment in the microcirculation. After activation, granulocytes become adhesive, they can elaborate superoxide radicals and release proteolytic enzymes. In the circulation a subgroup of granulocytes are in a spontaneously activated state. If during shock such cells become trapped in the microcirculation they impose a risk for organ injury. In a short term shock protocol, the group of surviving and non-surviving animals can be sharply distinguished by…the number of activated granulocytes before shock. Experimental forms of granulocyte activation in the coronary circulation cause temporary trapping of cells, an increase in vascular resistance, and a transient reduction of muscle contraction even in the presence of a normal perfusion pressure. Detection of spontaneous granulocyte activation requires the development of new tests which can be carried out on fresh un separated blood samples. We provide here also a critical evaluation of experimental neutropenia as a test for granulocyte related hypotheses.
Abstract: It could be claimed that expansion in clinical aspects of haemorheology has largely been fuelled by the development of a simple test of blood flow properties, i.e., analysis of filterability. With time, the level of sophistication in equipment, theory and sample preparation has increased. Theories for the development of flow in the filter have been described and these enable cellular parameters, such as transit times, to be calculated from experimental data. These theories can be quite general, and applied to filtration of red or white cells. Ideally, experimental design requires an understanding of cell behaviour at the filter and of…the effects of factors such as the sample concentration and volume, and the presence of different types of cells or subpopulations. Otherwise, results are susceptible to misinterpretation, particularly if impurities or mixed populations of cells are present. It is thus very important to know accurately the constituents of the test suspension. In clinical applications the trend has been to move away from whole blood filtration, toward use of relatively pure suspension of separated red cells and white cells. In the area of red cell filtration this has led to reappraisal of some previously reported abnormalities. The relatively new study of white cell filtration should benefit from previous experience, but there is the added problem of the reactivity of the cells under test, and their mixed nature. In any case, critical evaluation of the meaning and clinical relevance of results is necessary.
Keywords: Red Blood Cells, White Blood Cells, Filterability
vol. 27, no. 6, pp. 873-882, 1990
Abstract: A brief outline of the background of viscoelasticity of blood is given in order to derive for blood relevant parameters. In this context, especially one method, the sinusoidal oscillating capillary rheometry, is discussed. The determination of different parameters to characterize blood samples, e.g. the viscoelastic phase angle, an aggregation index, a flexibility index, hematocrit and plasma viscosity is described. Most of these parameters show increased values in disease; however they can be influenced by drug treatment.