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At least 919 records · Page 51Linked to original sources
PubMed1981

The effects of mannitol on blood viscosity.

To determine the effect of mannitol on blood viscosity, serial measurements were carried out on venous blood in patients undergoing craniotomies for intracranial aneurysms. Blood samples were drawn immediately prior to, and 30 minutes, 2, and 4 hours after administration of mannitol. Complete blood counts, serum osmolarities, and erythrocyte microsieving studies were also performed on each sample. Whole-blood viscosity decreased at 30 minutes and 2 hours, but not at 4 hours after mannitol administration. This decreased appeared at high shear rates only, where erythrocyte deformability is critical viscosity. This effect was independent of the hematocrit. Removal of mannitol from the suspension returned red cell deformability to preadministration values indicating that the increased erythrocyte deformability required the presence of mannitol and the relative hyperosmolarity induced by this agent. The reduced erythrocyte rigidity and subsequent decreased whole-blood viscosity should enhance tissue perfusion in the microcirculation.

Blood Viscosity↗
PubMed1983

Mannitol causes compensatory cerebral vasoconstriction and vasodilation in response to blood viscosity changes.

There is no proof that osmotic agents such as mannitol lower intracranial pressure (ICP) by decreasing brain water content. An alternative mechanism might be a reduction in cerebral blood volume through vasoconstriction. Mannitol, by decreasing blood viscosity, would tend to enhance cerebral blood flow (CBF), but the cerebral vessels would constrict to keep CBF relatively constant, analogous to pressure autoregulation. The cranial window technique was used in this study to measure the pial arteriolar diameter in cats, together with blood viscosity and ICP changes after an intravenous bolus of 1 gm/kg of mannitol. Blood viscosity decreased immediately; the greatest decrease (23%) occurred at 10 minutes, and at 75 minutes there was a "rebound" increase of 10%. Vessel diameters decreased concomitantly, the largest decrease being 12% at 10 minutes, which is exactly the same as the 12% decrease in diameter associated with pronounced hyperventilation (PaCO2 30 to 19 mm Hg) in the same vessels; at 75 minutes vessel diameter increased by 12%. With hyperventilation, ICP was decreased by 26%; 10 minutes after mannitol was given, ICP decreased by 28%, and at 75 minutes it showed a rebound increase of 40%. The correlation between blood viscosity and vessel diameter and between vessel diameter and ICP was very high. An alternative explanation is offered for the effect of mannitol on ICP, the time course of ICP changes, "rebound effect," and the absence of influence on CBF, all with one mechanism.

Animals↗
PubMed1982

Microstructural and peripheral-layer viscosity effects on peristaltic transport of seminal fluid.

Most of the physiological fluids are transported through peristalsis of the walls which is the inherent neuromuscular property of tube smooth muscle structure. The present paper deals with the transport of seminal fluid introducing the microstructural effects and peripheral-layer viscosity effects on the flow rate and the drag for the system. It has been observed that the flow rate increases tremendously with the decrease of the peripheral layer viscosity whereas a reverse trend has been noted for the frictional drag. Further other sub-structural effects i.e. the effects of relative rotational viscosity and viscosity gradients have also been broughtout and discussed.

Animals↗
PubMed1986

Viscosity and order in erythrocyte membranes studied with nanosecond fluorometry.

The viscosity and the order in the interior of human erythrocyte membranes were investigated by the fluorescence depolarization technique in the nanosecond region with 1,6-diphenyl-1,3,5-hexatriene (DPH). After pulsed excitation with a polarized light, the fluorescence anisotropy ratio of DPH in membranes rapidly decreased and gave a final value (r infinity). The rate of initial decrease and the value of r infinity related to the viscosity in the interior of the membranes and a wobbling angle of DPH which reflects a size of range for the phospholipid motion relating to the order of membrane structure. For normal human erythrocyte membranes the viscosity and the wobbling angle were obtained to be 0.82 poise and 42 degrees, at 37 degrees C. Similar values were obtained for spectrin-free membranes. Hardened membranes by the cross-linking of the cytoskeletal proteins with glutaraldehyde showed a small wobbling angle of 37 degrees, but the viscosity of them was unchanged.

Blood Viscosity↗
PubMed1987

The effects of experimental hypo- and hyperthyroidism on blood viscosity and other blood parameters in the rat.

Three groups of male Sprague Dawley rats received methimazole without or with Na-thyroxine in drinking water (3 and 0.33 mg T4/l, respectively) to induce characteristic alterations of their thyroid status (hypothyroid, hyperthyroid, euthyroid). A fourth group served as an untreated control without any additive to the drinking water. With respect to the different thyroid status, the following changes in the blood parameters were found: increasing plasma-T3-levels caused a reduction in plasma viscosity, in total plasma protein and in alpha 1-globulin, but an increase in hematocrit, whole blood viscosity, the number of erythrocytes and leukocytes, alpha 2-globulin and beta-globulin. It was concluded that the increase in the plasma viscosity in the hypothyroid status is mainly due to an alteration of the plasma protein pattern, and that the increase in whole blood viscosity in the hyperthyroid rat is a consequence of increased hematocrit.

Animals↗
PubMed1990

Solvent viscosity effects on protein dynamics studied by ultrasonic absorption.

Solvent viscosity is known to play an important role in the kinetics of biochemical reactions, and has been suggested to modulate the dynamic structure of proteins. The effect of viscous cosolvents, of various molecular sizes, on the apparent ultrasonic absorption of bovine serum albumin in solution, at 37 degrees, has been measured in attempt to investigate the following phenomena: 1) The predicted modulating effect of viscous cosolvents on the "internal friction" of proteins, and 2) Possible differences between the microscopic and macroscopic pictures of the solvent viscosity concerning the proposed effect. We have found that A) The absorption of ultrasound (3-17 MHz) by the protein increases with increasing the cosolvent concentration. B) That increase correlates with the solvent viscosity for small cosolvent molecules, but not with macromolecular cosolvents, and C) Dextran solutions with the same concentration by weight, reveal similar ultrasonic absorption, in spite of large differences in their viscosity. A possible explanation is discussed.

Absorption↗
PubMedDate not supplied

Non-Newtonian viscosity of human blood: flow-induced changes in microstructure.

Flow-induced changes in the red cell microstructure of human blood are identified from mechanical and optical evidence. On initiation of steady flow, a new microstructure develops as the shear strain increases through unit strain. This structure is identified with the formation of layers of red cells that slide on plasma layers (Thurston, 1989). At low shear rates, the cell layers are composed of aggregated cells, but at higher shear rates, the aggregates degrade to form thinner layers of oriented, compacted cells. The viscosity is determined by the hematocrit, the degree of compaction and viscosity within the cell layers, and the plasma viscosity. Degradation of cell aggregates is controlled by 1) the time required for the strain to increase by one unit (delta t1 = 1/shear rate) and 2) the dominant viscoelastic relaxation times of the red cell structures. Structures having relaxation times > delta t1 are degraded by cell disaggregation; when delta t1 is less than the shortest relaxation time of the layered cells, disaggregation and (cell and plasma) layer formation are nearly complete. Analyses of the non-Newtonian viscosity and cell layer characteristics are given for both normal and hardened cells.

Biomechanical Phenomena↗
PubMed1981

The viscosity interaction of barley beta-glucan with Trichoderma viride cellulase in the chick intestine.

A culture filtrate from Trichoderma viride was used as a source of cellulose degrading enzymes. This filtrate, when added to a barley ration fed to chicks, improved growth and feed efficiency by 19% and 8%, respectively. The response was saturable since increasing amounts of filtrate above 50 mg/kg produced no further improvement. Barley eta-glucan was added to a corn-based diet (10 g/kg) to evaluate the effect of the culture filtrate on the viscosity of beta-glucan in the chick intestinal contents. Barley beta-glucan increased the viscosity of the supernatant of the chick intestinal contents threefold and the culture filtrate reduced the viscosity to near control levels when combined with the diet containing beta-glucan. The presence of beta-glucan in barley probably limits growth of chicks by increasing viscosity of intestinal contents.

Animals↗
PubMed1976

[Sputum viscosity and pulmonary function measurements during a one-week parenteral treatment with a standardized oxidation product of oil of turpentine and terpin hydrate].

In 23 patients with chronic obstructive lung diseases, viscosity, airway resistance, arterial blood gases and acid-base balance, and sputum aspect were measured before and after one-week treatment with Ozothin, a substance from oxidation products of ol. terebinth. and terpinum hydratum. Within this time, viscosity of the sputum was reduced, airway resistance decreased, and arterial oxygen pressure slightly increased, whereas arterial carbon dioxide tension obvious change of sputum aspect could be observed. Correlation calculations revealed no significant relations between viscosity and the above cited lung function values. The results indicate that administration of Ozothin may liquefy viscous secretion and reduce sputum viscosity.

Adult↗
PubMed1999

Abnormal plasma and serum viscosity in systemic lupus erythematosus (SLE): a Jamaican study.

Vascular complications occur frequently in SLE, and their development may be related to haemorheological derangements. However, the range of rheological abnormality in Jamaican SLE patients have not been studied. The present investigation was aimed at determining the changes in the three major blood proteins, namely fibrinogen, albumin and globulin, and their effect on plasma and serum viscosity in SLE patients during the course of treatment. The concentrations of fibrinogen and globulin were significantly increased (p<0.001), while albumin was decreased (p<0.05) in the SLE patients as compared with the control group. This increase in the fibrinogen and globulin contributed significantly to the rise of both serum and plasma viscosity. SLE patients with more severe disease had higher serum viscosity values, suggesting that serum viscosity values may provide an important marker for disease severity.

Adult↗
PubMed1999

Changes in viscosity of low shear rates and viscoelastic properties of oxidative erythrocyte suspensions.

We exposed erythrocytes in soluble hemoglobin and Fe+2, in which hydroxyl radical (OH*) might be generated, and measured low shear rate viscosity and viscoelasticity of erythrocyte suspensions at Hct of 40%. The quantities of the lipid peroxidation product, malonyldialdehyde (MDA), for oxidized samples were higher than that for control (e.g., 2.20 +/- 0.46 nmol and 1.70 +/- 0.42 nmol, n = 6, p = 0.01, respectively). The viscosity values of oxidized erythrocyte suspensions for all tested shear rates were higher than those for the control samples (p < 0.05 or better, n = 6). Dynamic viscosity (eta') of oxidized erythrocyte samples was higher than that of control samples at the tested shear stress of 30 mPa whereas it was not observed in elasticity values (eta"). We tentatively concluded from the study, that oxidized erythrocytes would be more prone to form aggregates and increase viscosity of blood at low shear rates. Therefore, they might impair blood flow in the microcirculation.

Adult↗
PubMed1999

[Blood and serum viscosity in cardiologic X syndrome].

UNLABELLED: The aim of this study was to explore if are there blood rheological disturbances in cardiac syndrome X. Two groups were examined: 23 patients (aged 41 divided by 72 years) suffering from cardiac syndrome X (typical anginal pain positive stress test and no lesion in coronary angiograms) and 20 healthy (aged 32 divided by 57 years). Blood samples were drawn from the cubital vein prior to the angiogram. Blood viscosity measurements were performed using the Brookfield Cone/Plate Viscosimeter at 150 s-1 shear rate, and by means of low-shear Contraves viscometer at 1 s-1 (a)nd 4.59 s-1 shear rates. The plasma viscosity was measured by means of Ubbelohde's capillary viscometer. Besides the viscometric examinations the total cholesterol, LDL-cholesterol, HDL-cholesterol, triglycerides and glucose plasma concentration as well as blood morphology and ESR were determined. All rheological measurements were carried out at the temperature of 37 degrees C immediately after blood drawing. It was stated that blood and plasma viscosity were significantly elevated in syndrome X compared with the control group (p < 0.001). CONCLUSION: The examinations indicate that in patients suffering from Cardiological Syndrome X the whole blood and plasma viscosity are increased.

Adult↗
PubMed2000

[Estimation of blood viscosity in woman at puerperium].

Marks of blood viscosity in different states of physiology and of pathology of man are well-supplied documentary evidence. One recognized also influence of blood viscosity on disclosure of some disease processes. Period pregnancy and labour joins with changes of volume and of composition of blood circulation. Authors decided to price blood viscosity in period puerperal and to compare these given to universally coming to light anaemia's woman in puerperium. Investigations one passed in groups pregnant and woman in puerperium from different degree exacerbations of anaemia. Obtained results of stickiness one achieved to morphological parameters of blood. One ascertained, that blood viscosity is less at woman in puerperium than at women pregnant and grows less together from degree anaemia's.

Adolescent↗
PubMedDate not supplied

[Method of the anomalous time dependence of viscosity for registration of changes in conformational state of Escherichia coli cell genome].

The sensitivity of the anomalous time dependence of viscosity to the concentration of the DNA-protein complexes (DNA + histone-like proteins of bacteria or, in other words, the genome) such as chromatin and the conformations of these complexes in lysates of E. coli AB1157 cells were studied. A linear region of the anomalous viscosity time dependence on the concentration of E. coli cells was found in which the interactions between single DNA-protein complexes can be neglected. The response of the genome of E. coli to ethidium bromide at concentrations of 0.0003-3 mg/ml was studied. Significant differences in the effect of ethidium bromide on E. coli cells in the stationary and logarithmic growth phases were found. The effect of heating cell lysates, the molar concentration of NaCl in lysates, and the addition of proteins into lysates on the parameters of the anomalous viscosity time dependence was studied. It was shown that proteins do not contribute significantly to the effect of anomalous viscosity time dependence. The results obtained confirm that the method is sensitive to changes in the conformational state of the genome of E. coli cells.

Bacterial Proteins↗
PubMed2001

Theoretical and experimental analysis of the sedimentation kinetics of concentrated red cell suspensions in a centrifugal field: determination of the aggregation and deformation of RBC by flux density and viscosity functions.

The flow properties of blood are mostly determined using various viscometric approaches, and described in terms of a shear rate or shear stress dependent apparent viscosity. The interpretation of results are rather difficult, especially at low shear rates when particle sedimentation and migration within the viscometer gap are significant. By contrast, analysing the separation process in concentrated RBC suspensions in a centrifugal field also yields information about the viscosity function, including particle-particle interaction and deformation parameters. In this paper, the sedimentation process is approached by means of the theory of kinematic waves and theoretically described by solving the corresponding one-dimensional quasi-linear partial differential equation based on viscosity/flow function as a function of volume concentration. The sedimentation kinetics of rigid spherical RBC suspended in saline and normal RBC suspended in Dx-saline solutions were investigated by means of a separation analyser (LUMiFuge 114). The instrument detects the light transmission over the total length of the cell containing the suspension. During centrifugation the analyser automatically determines the position of the particle free fluid/suspension interface or the sediment by means of a special algorithm. The data obtained with sedimentation of rigid spherical RBC at different volume concentrations demonstrate that, in the case of suspensions rotated in containers of constant cross section, there is good agreement between the theory of kinematic waves developed by Anestis and Schneider (1983) and the results of the experiments. Such good agreement was obtained even though a restrictive one-dimensional model was used to obtain the theoretically derived sedimentation time course. In addition, we describe an algorithm enabling the experimental determination of the viscosity and related flux density function to be made for any suspension. Through this approach, we investigated in detail the rheological behavior of suspended rigid spheres at low Reynolds numbers ranging from 10(-6) to 10(-3). The method here introduced also enabled us to investigate RBC suspensions with respect to the deformability and interactions of the cells by means of the separation analysis. Normal, rigid as well as aggregating RBC exhibited marked differences in the sedimentation kinetics, which were quantified by means of the flux and viscosity functions based on the theory of kinematic waves.

Blood Sedimentation↗
PubMed1979

[Monoclonal immunoglobulins and serum viscosity: contribution of the idea of activation energy to the paraprotein concept (author's transl)].

The simultaneous study of dynamic and cinematic viscosity in 34 control sera and 49 paraprotein sera showed that there was a simple relationship between the viscosity and the total serum protein content both in normal sera and in paraprotein sera. When the ratio of monoclonal immunoglobulins/total proteins is less than 55%, the viscosity is little or not modified in the case of the IgGk paraproteins studied, whereas it was increased in the case of IgA, IgM and IgG LAMBDA SERA. Beyond 2 cSt, it is not however possible to incriminate a particular type of heavy chain nor even a light chain. The measurement of the viscosity in relation to the temperature permitted us to show that the IgA, IgG, and IgM sera studied all presented an activation energy of outflow (E in Kcal) higher than that of normal sera and the highest rise is due to IgA paraproteins. The concept of energy activation permits us to say that paraproteins have a different behaviour from normal proteins, probably due to disorders in their structural arrangement.

Blood Viscosity↗
PubMed2001

[Comparative effects of decreasing viscosity in different preparations of Chinese angelica root and ginseng].

OBJECTIVE: To compare the effects of different preparations of Chinese angilica root and ginseng on decreasing whole blood viscosity and plasma viscosity in rats. METHOD: The hemorheological method was used in vivo or in vitro and a Decreasing Viscosity Index (DIV) was defined as a comparative scalar. RESULTS: In the effect of the groups of Chinese angilica root on decreasing viscosity, the effect of whole root group was the best and the effect of main root group was better than that of the tributary root group. Meanwhile the same effect of transplant wild ginseng group was greater than that of dried raw ginseng group. CONCLUSION: This work provided some fundamental evidences for clinical application and pharmacological data for the quality evaluation.

Angelica sinensis↗
PubMed2001

[The effect of medium viscosity on actin polymerization].

A comparative study of the influence of two factors--excluded volume effect, and medium viscosity--on actin polymerization was carried out. Dextrane--500 (1%), poly(ethylene)glycol--6000 (2.7%), Ficol (1.8%), methyl cellulose (0.04%), saccharose (10%), and glycerine (10%) were used for creating a viscous medium. The concentrations of these agents in actin solution made approximately the same viscosity commensurable with the cytoplasm viscosity. By this it was possible to bring conditions of actin polymerization in vitro closer to those in vivo. It is shown that the medium viscosity in contrast to the excluded volume effect, prolongs the nucleation phase during actin polymerization. A conclusion is made that in the cell both factors can be involved in the regulation of actin filament formation.

Actins↗