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PubMed1982

Morphologic and internal viscosity aspects of RBC rheologic behavior.

The influence of cellular morphology on the rheologic behavior of human red blood cells (RBC) was examined for both fresh and ATP-depleted erythrocytes. Rheologic measurements included cone-plate viscometry, cell deformation by high-speed centrifugation and direct microscopic observation via a counter-rotating Rheoscope. Evaluation of the experimental observations indicated the importance of RBC shape as a determinant of RBC deformability such that either echinocytic or stomatocytic shape alterations resulted in decreased deformability. the influences of both intracellular viscosity and the ratio of intracellular to suspending medium viscosity on age-separated RBC rheologic behavior were also investigated via the rheoscope. Deformation at a given stress level increased with increasing media viscosity; at constant media viscosity and shear stress, young cells deformed more than old. However, identical cellular deformation could be achieved by comparing RBC at equal ratios of internal to external viscosity. The above mentioned results appear relevant to measurements of SS RBC mechanical behavior when dealing with either non-biconcave cells (e.g., ISC or low oxygen tension) or with cells having altered internal viscosity (e.g., ISC, increased MCHC, gel formation). The relative importance of these effects is, however, as yet unknown.

Adenosine Triphosphate↗

PubMed1980

[Viscosity studies of tracheobronchial secretions post tracheostomy (author's transl)].

In 14 patients post tracheostomy viscosity of the tracheobronchial secretion was studied. No daytime fluctuation of the viscosity could be detected. There was a clear correlation between viscosity and duration since tracheostomy. Infection had less impact on viscosity than the appearance of mucous structures. antibiotics decreased, ionizing radiation of the patient increased viscosity. Humidification of the inspired air by means of an "artificial nose" increase volume and viscosity of the secretions.

Aged↗

PubMed1997

Liver transplantation from non-heart beating donors in rats: influence of viscosity and temperature of initial flushing solutions on graft function.

BACKGROUND: We evaluated the effect of warm (37 degrees C) versus cold (4 degrees C) solutions as the initial flush for liver preservation from non-heart beating donors in rats. METHODS: An initial flush was performed just before donor hepatectomy with cold or warm University of Wisconsin solution (UW), UW without hydroxyethyl starch, sodium lactobionate sucrose solution, or lactated Ringer's solution as the control group. A separate group also used as control received no initial flushing. Liver transplantation was performed, and the graft function was determined by survival and assessment of enzyme release. The viscosity of each solution and the vascular resistance of the graft were measured. RESULTS: The 7-day survival rate was 83% and 100% in the warm and cold sodium lactobionate sucrose solution groups and 60% and 50% in the warm and cold lactated Ringer's solution groups, respectively. In the no-initial-flush group, rats did not survive. The 7-day survival rate was 67% and 0% in the warm and cold UW groups, respectively. Eliminating the hydroxyethyl starch from the cold UW improved the survival to 67%. Serum alanine aminotransferase levels 1 day after transplantation in the no-initial-flush and the cold UW groups were significantly higher than those of the remaining groups. At 4 degrees C the viscosity was higher in the UW (86.2 cp) compared to hydroxyethyl starch-free UW solution (30.9 cp), lactated Ringer's solution (24.5 cp), and sodium lactobionate sucrose solution (32.7 cp). The viscosity of UW at 37 degrees C was 34.7 cp. Vascular resistance correlated well with the viscosity. Livers flushed with solutions with a low viscosity showed lower vascular resistance than those flushed with cold UW and led to better survival. CONCLUSIONS: These data suggest that the viscosity of the initial flushing solution may play an important role in determining the outcome of organ procurement from non-heart beating donors.

Adenosine↗

PubMed1998

Whole blood viscosity and haematocrit are associated with internal carotid atherosclerosis in men.

BACKGROUND: Alterations in blood viscosity and haematocrit have been described in patients with coronary and cerebrovascular diseases. The results have not been conclusive, as modifications of these parameters are often associated with the presence of coronary heart disease (CHD) risk factors. The aim of this study was to verify whether blood viscosity and haematocrit are increased in patients with carotid atherosclerosis, independently of the presence of CHD risk factors. METHODS: Male patients with internal carotid atherosclerosis (ICA+, n = 28) were selected from participants in a cardiovascular disease prevention campaign. Controls (ICA-, n = 28), also participating in the prevention campaign, were matched for age and all the classical CHD risk factors. Plasma lipids, glucose and fibrinogen were determined by routine methods. Cigarette smoking and current drug therapy was established by questionnaire. Whole blood viscosity was measured at shear rates of 450 and 225/s, using a cone-plate viscometer. Echo-Doppler of carotid arteries was performed with an ATL Ultramark 9 HDI using a 5-10 MHz multifrequency probe. RESULTS: Blood pressure, plasma lipids, glucose, body mass index, fibrinogen and plasma viscosity were similar in the two groups. ICA+ patients, compared with the ICA- group, had significantly greater values of blood viscosity (4.52 +/- 0.37 cP compared with 4.18 +/- 0.45 cP, P < 0.005 respectively; shear rate 450/s) and haematocrit (48.57 +/- 3.19% compared with 45.57 +/- 4.81%, P < 0.008 respectively). CONCLUSIONS: Our findings demonstrate that blood viscosity and haematocrit are increased in men with internal carotid atherosclerosis, independently of the presence of risk factors for atherosclerosis.

Adipose Tissue↗

PubMedDate not supplied

[Effect on viscosity and yield value of addition of different vegetable fat sources used in chocolate].

Viscosity and Yield Value of Casson are two chocolate properties. They are very important in the technological processes and they affect to the final product acepptation. In this study viscosity, yield value and fatty acid composition were determined of chocolates elaborated with different fat sources. A correlation study was made between these three variables. Viscosity and yield value were calculated with the Casson's education using a viscometer brookfield and fatty acids composition by gas-chromatography. Positive correlations between viscosity and yield value with stearic and palmitic acids contents have been found. Negative correlations between yield value and lauric content and viscosity and oleic acid content have been observed. The viscosity variations were relationed with total content of cocoa butter of different chocolates.

Cacao↗

PubMed1998

Effects of tourniquet application on plasma viscosity measurements.

Reliable plasma viscosity measurements are required for cardiovascular risk factor assessment. This study was designed to examine the influence of tourniquet pressure and duration on plasma viscosity measurement with a coaxial cylinder at 37 degrees C. Plasma viscosity was evaluated at low (40 mm Hg) and high (mean arterial blood pressure plus 10 mm Hg) tourniquet pressure and at two time intervals following (0-1 and 4-5 min) of tourniquet application in 38 healthy adults. Longer duration of tourniquet application was accompanied by a significant increase in plasma viscosity at both low (1.356 +/- 0.067 mPa s versus 1.393 +/- 0.067 mPa s (p = 0.0001)) and high (1.321 +/- 0.071 mPa s versus 1.430 +/- 0.086 mPa s (p = 0.0002)) tourniquet pressures. Plasma viscosity values were not influenced by the magnitude of tourniquet pressure. The accuracy of plasma viscosity measurements can be improved by sample acquisition within 1 min following tourniquet application.

Adult↗

PubMed1998

Docosahexaenoic acid inhibits blood viscosity in stroke-prone spontaneously hypertensive rats.

Increased blood viscosity facilitates the formation of thrombosis. This is an important risk factor in the occurrence of cerebral infarctions. The present study was undertaken to elucidate whether docosahexaenoic acid (DHA) inhibits blood viscosity, hematocrit and fibrinogen in the disease animal model, stroke-prone spontaneously hypertensive rats (SHRSP). An attempt was also made to clarify the effect of DHA on blood pressure in SHRSP. Blood viscosity, hematocrit and fibrinogen in non-treated SHRSP increased significantly when compared with levels in age-matched non-treated Wistar Kyoto rats (WKY). SHRSP rats which were administered DHA for 5 weeks displayed significant decreases in blood viscosity, hematocrit and fibrinogen when compared with the values in non-treated SHRSP. The blood pressure of DHA-treated SHRSP was significantly lower than that of non-treated SHRSP. A positive correlation existed between blood pressure and blood viscosity. These findings suggest that decreased blood viscosity induced by DHA appears to be associated with the reduction of thrombosis formation and hypotensive action in SHRSP.

Aging↗

PubMed1999

Concentration and shear-rate dependence of the viscosity of an exocellular polysaccharide

The viscosity of an exocellular polysaccharide (EPS) produced by the bacterium Lactococcus lactis subsp. cremoris B40 was studied in aqueous solution at an ionic strength of 0.10M. First, the zero-shear viscosity was determined as a function of the concentration. From the data in the low concentration range, the intrinsic viscosity was determined. In addition, the shear-thinning behavior was measured at several concentrations. By combining existing theories, a new equation is proposed that describes and predicts the intrinsic viscosity and the concentration dependence of the (zero-shear) viscosity of B40 EPS solutions from the molar mass and the hydrodynamic radius of the polysaccharide. Based on the Rouse theory, the shear-rate dependence of the viscosity also could be described and predicted from the molecular characteristics, i.e., molar mass and radius of gyration. It is shown that these equations can be applied to all random coil polysaccharides. Copyright 1999 John Wiley & Sons, Inc.

Journal Article↗

PubMed2002

Stilbene photochrome-fluorescence-spin molecules: covalent immobilization on silica plate and applications as redox and viscosity probes.

We report herein on the development of a new photochrome-fluorescence-spin method for the quantitative analysis of the redox status and viscosity of a medium. The method of the viscosity measurement is based on the use of double fluorescence-nitroxide molecules. In such hybrid compounds the nitroxide moiety quenches the fluorescence of the fluorophore (stilbene moiety). The reduction of nitroxide by an antioxidant (ascorbic acid) causes a rise of fluorescence of the fluorophore. The rate constant of the stilbene fragment photoisomerization in such systems is dependent upon the viscosity of the media. The synthesized dual stilbene-nitroxide probe was covalently immobilized onto the surface of a quartz plate as an eventual fiber-optic sensor. The immobilization procedure included a cyanogen bromide surface activation followed by smoothing with a protein tether. The rate of fluorescence change was monitored in aqueous-glycerol solutions of different viscosities and content of ascorbic acid. Good correlation was found: (a) between the concentration of ascorbic acid in the sample and the rate of fluorescence increase due to the reduction of the nitroxide moiety, and (b) between the rate constant of photoisomerization and the viscosity of the media. Appropriate calibration would make the determination of the viscosity of a media possible (in a range 1-500 cP), as well as ascorbate content, in a range (1-9) x 10(-4) M, with fast single measurement.

Antioxidants↗

PubMed1998

Environmental influence on age-related changes of human lymphocyte membrane viscosity using severe combined immunodeficiency mice as an in vivo model.

Peripheral blood lymphocytes (PBL) of healthy elderly people show increased plasma membrane viscosity compared to young subjects, that inversely correlates with lymphocyte proliferation after mitogen stimulation in vitro. Maintenance of a constant membrane viscosity, which is necessary for proper cell function, is crucially dependent on the membrane lipid composition. The cellular lipid metabolism, and thus lymphocyte function, may be subject to modulation by diet or drugs. To study the susceptibility of membrane viscosity to environmental conditions, we established an in vivo model using severe combined immunodeficiency (SCID) mice: human peripheral blood lymphocytes from healthy young and old subjects were engrafted for three days intraperitoneally into SCID mice to offer identical environmental conditions. First, we demonstrate that human lymphocytes can take up and utilize murine lipoproteins: engrafted human PBL can participate in the mouse lipid metabolism, and an exchange of membrane lipids in vivo is, therefore, possible. Second, plasma membrane viscosity was determined before and after engraftment: before engraftment, PBL from the elderly showed a significantly higher membrane viscosity than that from young controls, but this difference vanished during engraftment into SCID mice, wherein cells from both age groups exhibited nearly identical values. It was, therefore, concluded that lymphocyte membrane viscosity is influenced by environmental factors, and that the age-related increase is, in principle, reversible.

Adult↗

PubMed2005

Viscosity increase with temperature in cationic surfactant solutions due to the growth of wormlike micelles.

Wormlike micellar solutions based on ionic surfactants typically show an exponential decrease in viscosity upon heating. Here, we report the unusual observation of an increasing viscosity with temperature in certain cationic wormlike micellar solutions. The solutions contain a cationic surfactant with an erucyl (C22, mono-unsaturated) tail and an organic salt, sodium hydroxynaphthalene carboxylate (SHNC). When these solutions are heated, their zero-shear viscosity increases over a range of temperatures. In some cases, the viscosity reaches a peak at a certain temperature and then decreases with further heating. The magnitude of the viscosity increase, the onset of this increase, and the peak temperature can all be tuned by varying the SHNC concentration. Small-angle neutron scattering is used to study the origin of this unusual rheological behavior. The data reveal that the contour length of the micelles increases with temperature, in tandem with the rise in viscosity. A possible explanation for the contour length increase, based on a temperature-dependent counterion binding, is discussed.

Journal Article↗

PubMed2005

Crystalline cellulose reduces plasma glucose concentrations and stimulates water absorption by increasing the digesta viscosity in rats.

Although cellulose is generally considered not to affect the viscosity of the digesta in the upper gastrointestinal tract, we found previously that the ingestion of cellulose elevated the viscosity of the gastric, small intestinal, and cecal contents when particulate matter was included in the measurements. We hypothesized that the digesta viscosity influences absorption. Here, we examined the effects of crystalline cellulose on plasma glucose concentrations by infusing control and cellobiose- and cellulose-containing artificial digesta of approximately 30 mL into the small intestine of rats. Cellulose, but not cellobiose, decreased the postinfusion plasma glucose concentration (P < 0.05), although cellulose did not cause adsorption or dilution of glucose. Among the physical properties of the artificial digesta, only viscosity was responsible for the decrease in the plasma glucose concentration, whereas water content, free water, bound water, and osmotic pressure were not. The cellulose-induced increase in digesta viscosity may delay glucose diffusion in the lumen, as found in our previous study. Cellulose also stimulated water absorption from the small intestine (P < 0.05), which may be attributable to increases in the water potential of the digesta moving through the small intestine. The ingestion of cellulose with meals, which increases digesta viscosity, is likely to modulate the postprandial plasma glucose concentration and to reduce the incidence of diarrhea associated with enteral nutrition.

Animals↗

PubMed1999

Relation of shear viscosity and self-diffusion coefficient for simple liquids.

A Stokes-Einstein-type relation is derived for the potential part of the shear viscosity of a simple liquid by means of statistical mechanics. The product of the shear viscosity and the self-diffusion coefficient is shown to be expressible in terms of the pair correlation function and the intermolecular force as well as the density. The shear viscosity formula, consisting of kinetic and potential parts and given in terms of the self-diffusion coefficient, is tested against experimental data with regard to the temperature and density dependence of the shear viscosity. Given the self-diffusion coefficient determined by experiment or simulations, the viscosity formula involving the Stokes-Einstein relation obtained produces the shear viscosity of argon, krypton, and xenon, in good agreement with experiment in the case of temperatures well away from the triple point. However, in the neighborhood of the triple point of argon examined, a cutoff parameter, which is a measure of the range of density variation, is needed to account for the experimental data. The applicability of the Stokes-Einstein relation to molecular particles is assessed, and it is found to remain applicable in the range of density and temperature examined.

Journal Article↗

PubMed2001

Computation of the viscosity of a liquid from time averages of stress fluctuations.

The shear viscosity can be calculated from the standard deviation of an equilibrium ensemble of time averages of the shear stress computed along finite duration phase space trajectory segments. The mean square of the segment averages of the shear stress is proportional to the shear viscosity and inversely proportional to the duration of the trajectory segments and the number of particles. We test the fluctuation relation for the shear viscosity and show that it provides a simple but viable means of computing the zero strain rate shear viscosity. We decompose the shear viscosity computed using this fluctuation method, into its "kinetic" and "configurational" components. We also calculate the relevant relaxation times. We compare the computed results with standard nonequilibrium molecular dynamics simulations. Finally we compute the bulk viscosity using an analogous fluctuation method.

Journal Article↗

PubMed1998

Effects of proteins, blood cells and glucose on the viscosity of cerebrospinal fluid.

It has long been assumed that cerebrospinal fluid (CSF) is a newtonian fluid with viscosity similar to water, yet high protein content, has been postulated to increase the viscosity of CSF in vivo. Such an increase in viscosity may have serious implications for the effectiveness of surgical shunts implanted to re-establish the CSF flow in cases of abnormal CSF circulation. In this study, glucose content, total protein content and blood cell count in the CSF of 23 patients undergoing brain surgery were measured. Viscosity measurements were performed on duplicate CSF samples over a range of shear strain rates of 25-1,460 s-1. The results indicated that high protein or high cell concentration in CSF does not significantly affect the viscosity of the cerebral fluid at those shear rates. CSF is clearly newtonian, and its viscosity at 37 degreesC is in the range of 0.7-1 mPa.s.

Adolescent↗

PubMed1996

Influence of density and viscosity of fluids on extracorporeal shock wave lithotripsy of gallstones in vitro.

BACKGROUND: It is hitherto still questionable which of the physical properties of the bile fluid influence the outcome of extracorporeal shock wave lithotripsy (ESWL). METHODS: In this study the influence of the density and viscosity of bile simulating fluid on ESWL was tested in vitro by applying CsCl solutions of densities 1.0, 1.3, 1. 5, 1.7 and 1.9 g/ml. Five almost identical "sister" stones from one patient were fragmented in these five fluids. The number of shock waves required for adequate fragmentation (fragments < 4 mm) was measured for comparison. This was repeated on a further seven patients (five "sister" stones per patient). Subsequently, the influence of the viscosity of the fluid on ESWL was tested using polyethylene glycol (PEG) solutions of the viscosities 1, 5, 17, 30 and 59 mPa.s. Analogous to the first part of this investigation, 40 gallstones from an additional eight patients (again five almost identical sister stones) were fragmented, registering the number of shock waves required for adequate fragmentation. RESULTS AND CONCLUSIONS: The density of the fluid did not reveal any monotone correlation to the number of shock waves required. In contrast to the density of the fluid there was a distinct correlation (r subsets = 0.84; p < 0.001) between its viscosity and the number of shock waves required. On average, the number of shock waves required in a fluid with a viscosity of 59 mPa . s must be more than three times that required in water, which has a viscosity of 1 mPa.s.

Cholelithiasis↗

PubMed1975

The influence of viscosity on dilution methods. Its problems in the determination of serum sodium.

Dilution with a roller-pump is a well known procedure in clinical chemistry. This method may be influenced by viscosity. A higher viscosity of the sample yields a lower sample output and consequently a larger dilution. If the substance to be determined in the diluted sample can be measured accurately, the influence of viscosity may be analysed easily. This was performed for serum sodium. It was shown that with extreme pathological viscosities (as are found e.g. in multiple myeloma and Waldenström's macroglobinemia) underestimations of more than 15% may occur. Especially for serum sodium, the physiological range of which is fairly small, this may provoke serious diagnostic and therapeutic problems. We propose to use viscosity independent dilution systems.

Blood Proteins↗

PubMed2002

Measurement of blood viscosity using mass-detecting sensor.

A newly designed mass-detecting capillary viscometer is extended to measure the viscosity of whole blood over a range of shear rates without the use of anticoagulants in a clinical setting. In the present study as proof of principle, a single measurement of liquid-mass variation with time replaces the flow rate and pressure drop measurements that are usually required for the operation of a capillary tube viscometer. Using a load cell and capillary, we measured the change of mass flowing through capillary tube with respect to the time, m(t), from which viscosity and shear rate were mathematically calculated. For water and adulterated bloods, excellent agreement was found between the results from the mass-detecting capillary viscometer and those from a commercially available rotating viscometer. Also, the mass-detecting capillary viscometer measured the viscosity of unadulterated whole blood without heparin or EDTA. This new method overcomes the drawbacks of conventional viscometers in the measurement of the whole blood viscosity. First, the mass-detecting capillary viscometer can accurately and consistently measure the unadulterated blood viscosity over a range of shear rates in less than 2 min without any anticoagulants. Second, this design provides simplicity (i.e. ease of operation, no moving parts, and disposable) and low cost.

Anticoagulants↗