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Arterial and venous blood viscosity in ischemic lower limbs in patients affected by peripheral obliterative arterial disease.

Blood, plasma and serum viscosity, packed red cell volume, and plasma fibrinogen concentration was measured in a group of 13 subjects, suffering from peripheral obliterative arterial disease of the lower limbs (stage III or IV), awaiting surgery, and in 9 control subjects, none of whom showed signs of circulatory disease of the lower limbs either by clinical examination or by instrumental measurements. The blood samples were taken from the: (a) antecubital vein; (b) femoral vein; (c) femoral artery. In the patients venous blood viscosity was significantly higher than arterial blood viscosity. No significant differences have been found between the femoral and the antecubital vein, but in the femoral vein blood viscosity was slightly higher. Packed red cell volume and plasma viscosity were slightly but significantly higher in venous blood, while no difference was seen in serum viscosity and in plasma fibrinogen concentration. In the control subjects blood viscosity values were decidedly lower than in patients and no statistically significant differences were to be found between artery and vein, even if viscosity values were lower in artery. These results support the hypothesis that an interrelation exists between hyperivscosity syndrome and vascular ischaemia-inducing diseases.

Adult↗

[Sputum viscosity and respiratory tract obstruction in chronic unspecific airway diseases].

The relationship between the physico-chemical characteristics of sputum and pulmonary function tests was investigated in patients with chronic nonspecific airway diseases. 141 sputum specimens were categorized on the basis of neutrophil content as slightly inflammatory (mucoid), inflammatory (mucopurulent) and highly inflammatory. "Apparent" viscosity, fucose and N-acetylneuraminic acid content were determined. Forced vital capacity, forced expiratory volume in one second and maximal voluntary ventilation measurements were performed simultaneously for each patient. "Apparent" viscosity and fucose content did not differ among the sputum categories; N-acetylneuraminic acid was slightly increased in the inflammatory sputa. There was a statistically significant inverse correlation between "apparent" viscosity, forced expiratory volume and maximal voluntary ventilation. In contrast, "apparent" viscosity did not correlate with forced vital capacity. As for the bronchial glycoprotein components, fucose correlated directly with "apparent" viscosity, whereas N-acetylneuraminic acid did not. "Apparent" viscosity was approximately the same in all sputum categories; it did not depend on the sputum neutrophil frequency except in the case of the slightly inflammatory, mucoid sputa in which "apparent" viscosity correlated indirectly with the sputum neutrophil frequency. These results show that physicochemical characteristics of sputum or bronchial secretions may play an important role in obstruction of the airways in patients with chronic nonspecific airway diseases. In the case of low inflammation of the bronchi, bronchial glycoproteins produced in the hypertrophied tracheobronchial glands and goblet cells are mainly responsible for increased "apparent" viscosity. With increasing inflammation of the bronchi, factors other than bronchial glycoproteins appear to determine this flow property.

Adult↗

[Hematic and plasmatic viscosity in cyanotic congenital heart diseases (author's transl)].

57 patients with cyanotic congenital heart diseases were studied. 39 patients presented t. of Fallot, 18 patients had patent ductus arterious with pulmonary hypertension and right to left shunt. The average whole blood viscosity in patients with t. of Fallot was 6.86+/-0.32 cps. This parameter was correlated with hematocrit, fibrinogen, euglobulin lysis time, pulmonary output, systemic output, and O2 saturation. The value of "r" resulted as statistically significant only for the correlation between viscosity and hematocrit and between viscosity and fibrinogen (t=13.22, p less than 0.0005; t=3.35, p less than 0.001 respectively). The average value of plasma viscosity in patients with t. of Fallot was 1.61+/-0.024 cps. The correlations of this parameter with fibrinogen, euglobulin lysis time, pulmonary output and systemic output did not result as statistically significant. The average fibrinogen value was 256.10+/-20.63 mg%, whereas that of euglobulin lysis time was 12,67+/-1.50 hours. In patients with patent ductus arteriosus the average blood viscosity was 6.65+/-0.56 cps. Such parameter was correlated with hematocrit, fibrinogen, euglobulin lysis time, pulmonary output, systemic output and O2 saturation. The value of "r" resulted as statistically significant only between blood viscosity and hematocrit and between blood viscosity and O2 saturation (t=9.30, p less than 0.0005; t=5.800, p less than 0.001 respectively). The average value of plasma viscosity was 1.61+/-0.04 cps. This parameter was correlated with fibrinogen, euglobulin lysis time, pulmonary output and systemic output. The correlation index "r" never resulted as statistically significant. The average fibrinogen value was 299.20+/-20.30 mg. The average euglobulin lysis time was 16.02+/-2.73 hours.

Adolescent↗

[Study of blood viscosity for evaluation of peripheral circulation in ischemic heart disease].

An important role in the characterization of the functions of the circulatory system belongs to the interrelationship between blood viscosity and central haemodynamics. Blood viscosity was studied in comparison with the pulse rate, arterial pressure and Robinson's index in patients with chronic forms of ischaemic heart disease. The examinations were conducted at rest and at the peak of sub-maximal bicycle tests. In normal individuals blood viscosity increases along with the increasing workload of the exercise. In patients with ischaemic heart disease performing threshold exercises the shifts in blood viscosity were varidirectional. In patients without circulatory insufficiency blood viscosity was changing in the same way as in normal individuals. In patients with cardiac insufficiency it either remained unchanged, or decreased. An increasing blood viscosity in normals under physical exercises may be interpreted as a mechanism of homeostasis preservation. A lack of growing blood viscosity under threshold exercises in patients with ischaemic heart disease and circulatory insufficiency indicates to disorders in the mechanisms of homeostasis preservation. Increasing blood viscosity may be due to impaired tissue oxygenation.

Adult↗

Viscosity of paraproteinemic sera.

Viscosity was determined in a series of 1402 paraproteinemic sera. Viscosity was measured on an ultrasonic viscosimeter of domestic design and was expressed in relative units(ru). Increased viscosity over 2.1 ru was found in 288 sera, i.e. 20.5%. Clinical symptoms of the hyperviscosity syndrome were found in 44 cases (3%) with viscosity over 4.0 ru. Malignant monoclonal gammopathy as proved in all 44 cases. In 17 determinations with the presence of paraprotein IgM, the mean viscosity was 6.35% +/- 2.6 ru, and the mean paraprotein concentration was 41.12 +/- 11.26g/l. In 17 cases we found paraprotein IgG with a mean viscosity of 6.38 +/- 2.4 ru and a mean concentration of paraprotein was 63.66 +/- 14.52g/l. In 9 determinations with the presence of paraprotein IgA, the mean viscosity as 5.22 +/- 1.02 ru and the mean paraprotein concentration was 49.77 +/- 13.89g/1. In one case we found a double paraproteinemia of IgG-lambda + IgA-kappa (31.9 + 24.2g/l), with a viscosity of 10.5 ru.

Adult↗

Correlation between retinal fluorescein angiography and blood viscosity and other factors in patients with primary open angle glaucoma.

OBJECTIVE: To investigate the correlation among retinal fluorescein angiography, blood viscosity, and other factors in patients with open angle glaucoma (POAG). METHODS: Multiple step regression analysis was made to investigate the correlation between each of the following blood vessel filling times: the arm-choroid (A-CT), arm-retinal artery (A-AT), and retinal artery-venous (A-VT) of the fundus fluorescein angiography (FFA) in 122 eyes with POAG and each of the following related factors in hemorrheology: whole blood apparent viscosity at low, medium and high shear rates, plasma viscosity and hematocrit. Also, the same analysis was applied to investigate the correlation between each of the A-AT, A-VT of the FFA in 70 eyes with POAG and the following factors: systolic blood pressure, diastolic blood pressure, age and whole blood apparent viscosity at low shear rate. RESULTS: The whole blood apparent viscosity at low shear rate was closely related to A-CT and A-AT, while hematocrit was closely related to A-VT of the FFA. The whole blood apparent viscosity at low shear rate and age, especially the whole blood apparent viscosity, was closely related to A-AT, A-VT of the FFA. CONCLUSION: Blood viscosity can affect the filling times of the FFA in POAG.

Blood Viscosity↗

Effective Viscosity of Polymer Solutions: Relation to the Determination of the Depletion Thickness and Thickness of the Adsorbed Layer of Cellulose Derivatives.

The diffusion of silica particles with radii ranging from 12 to 510 nm in dilute solutions of carboxymethyl cellulose (Mw = 180 to 1200 kg mol-1, cCMC = 5 to 1000 mg l-1) was investigated by means of dynamic light scattering at pH 5 in 0.01 mol l-1 NaCl. The viscosity of the polymer solution as experienced by the silica probes (the "microscopic" or effective viscosity, etaeff) differs from the viscosity as determined by capillary viscometry (etap). For small particles etaeff nearly equals the viscosity of the solvent (eta0). The effective viscosity increases with the size of the probe particles and the polymer concentration but remains less than etap. The effective viscosity is interpreted in terms of a model in which the particle is surrounded by a layer of polymer free solution (eta = eta0). The thickness of the polymer-free layer is assumed to be equal to the thickness of the depletion layer (lambdad). Applying this model, a decrease in lambdad as a function of CMC concentration is observed. At low concentration lambdad equals the radius of gyration. The hydrodynamic layer thickness (deltah) of cellulose derivatives (carboxymethyl cellulose and hydroxyethyl cellulose) adsorbed on inorganic oxide surfaces (alpha-Fe2O3 and SiO2) is also investigated by dynamic light scattering. Upon using etap maxima in deltah are found. However, these maxima are a consequence of an incorrect choice of the viscosity. When the viscosity is used as obtained from inert probe diffusion, no anomalies are observed. Copyright 1998 Academic Press.

Journal Article↗

The Viscosity of Solutions of Poly(propylene imine) Dendrimers in Methanol.

The viscosity of solutions of poly(propylene imine) dendrimers in methanol has been determined. An Ubbelohde and a low-shear rotational viscometer have been used. The viscosity was Newtonian for every concentration and shear rate used. The value of the Huggins coefficient indicates soft sphere behavior. The viscosity of the lower generations as a function of the volume fraction can be described with a single exponent, where the exponent is comparable to the intrinsic viscosity. The viscosity of the 4th and 5th generation dendrimers shows a stronger increase from a volume fraction of about 0.15 to 0.30. This increase is much smaller than that expected, using the Krieger-Dougherty formula for hard spheres with the hydrodynamic radius determined from the intrinsic viscosity. This smaller increase and the small value of the Huggins coefficient are interpreted in terms of a breakdown of the solvation layer. At a volume fraction of 0.3 the dendrimers, using the radius of gyration as the radius, start to touch each other. From the dependence of the viscosity on the concentration and the dependence of the viscosity on the molar weight, it can be concluded that dendrimers do not interpenetrate. It is concluded that they deform (collapse). Copyright 2001 Academic Press.

Journal Article↗

Influence of the mechanical properties of a manipulandum on human operator dynamics. II. Viscosity.

The influence of the viscosity of a manipulandum used by a human operator in a position-control pursuit-tracking task was examined. An active servo-system was used to set the viscosity of a manipulandum (motor) connected to the forearm to one of seven levels ranging in a geometric series from 12 to 800 N.s/m. During each condition the viscosity of the motor was held constant by a computer while subjects tracked, by moving their forearm in the sagittal plane, a visually presented target whose position changed randomly every 1.5 s for 255 s. Nonparametric and parametric impulse response functions were calculated between the input (target) and output (position) in each tracking condition. Nonparametric analyses revealed that subjects became sluggish at higher viscosities (above 200 N.s/m) and took longer to reach the target. A second-order low-pass transfer function was found to provide a very good description of tracking performance at each viscous level. The gain and damping parameter of this transfer function were not affected by the manipulandum's viscosity, whereas both the pure delay and natural frequency of the human operator system decreased systematically with increasing manipulandum viscosity. These findings suggest that over the range of viscosities studied, there is no speed-accuracy trade-off in terms of determining an optimal level of manipulandum viscosity for a human operator, and that a less viscous interface will result in faster performance.

Adult↗

On the viscosity of composite suspensions of aluminum and ammonium perchlorate particles dispersed in hydroxyl terminated polybutadiene--New empirical model.

The rheological properties of fuel suspensions with various solid loadings up to close their maximum packing fraction and suspending media having different viscosities are investigated using the rotational viscometer at relatively low shear rates in which suspensions behave as Newtonian fluids. Aluminum (Al) and ammonium perchlorate (AP) particles are major solid components of any solid fuel system which should be distributed uniformly inside a polymeric binder based on hydroxyl terminated polybutadiene (HTPB). The experimental data generated in this investigation indicates that the relative viscosity of the suspensions is independent of viscosity of polymer binder, but in addition to solid content, geometrical aspects of the solid particles affect strongly the relative viscosity of suspensions. Maximum packing fraction of filler is found to be suitable quantitative measure of filler characteristics such as size, size distribution, shape and structure. Consequently, it is revealed that the relative viscosity of fuel suspension is a unique function of reduced volume fraction (Phi). Based on analogy of viscosity enhancement of reactive resin with cure conversion and suspension with filler content, an empirical model with two adjustable parameters originated from resin gelation model is suggested. According to this model and experimental results obtained in this investigation, a generalized model is proposed to describe the relative viscosity as a function of solid content in which the adjustable parameters are found to be general constants. The generalized model which is expressed as mu(r) = (1-Phi)(0.3 Phi-2) is found to be quite accurate to predict the experimental data. Furthermore, the applicability and accuracy of the generalized model are evaluated using the viscosity data of some suspension systems reported in the literature.

Journal Article↗

Viscosity of bimodal and polydisperse colloidal suspensions.

We present a theoretical framework for the viscosity of bimodal and polydisperse colloidal suspensions. For colloidal dispersions both interparticle forces between pairs of particles and many-particle effects such as depletion forces can have a significant effect on rheology. As hydrodynamic interactions are also important for colloidal systems, a theoretical description that includes hydrodynamic and thermodynamic interactions is required. An integral equation theory for multicomponent systems accounts for the contribution of thermodynamic interactions to the viscosity of dispersions. Introduction of small particles into a system of larger particles causes depletion forces between the large particles that increase the viscosity, while replacing large particles with an equal volume fraction of small particles increases the free volume in the system and decreases the viscosity. The integral equations model both of these effects in concentrated suspensions and provide a microscopic interpretation of free volume changes as changes in radial distribution functions. For a bimodal mixture they predict a dependence of the viscosity on size ratio, composition, and total volume fraction. Polydispersity is modeled by a small number of components whose sizes and weights are chosen to match the moments of the size distribution. This theory predicts a reduction in viscosity due to polydispersity and explains conflicting experimental measurement of the viscosity of hard-sphere colloids. Existing theoretical approaches that neglect the multiparticle correlations, included through the integral equations, yield qualitatively incorrect results for the change in the viscosity relative to monodisperse systems.

Journal Article↗

Effect of Metal Cations on the Viscosity of a Pectin-Like Capsular Polysaccharide from the Cyanobacterium Microcystis flos-aquae C3-40.

The properties of purified capsular polysaccharide from the cyanobacterium Microcystis flos-aquae C3-40 were examined by capillary viscometry. Capsule suspensions exhibited similar viscosities between pH 6 and 10 but were more viscous at pH <=4 than at pH 6 to 11. At pH 7, a biphasic effect of metal ion concentration on capsule viscosity was observed: (i) capsule viscosity increased with increasing metal ion concentration until a maximal viscosity occurred at a specific concentration that was a reproducible characteristic of each metal ion, and (ii) the viscosity decreased with further addition of that ion. Because the latter part of the biphasic curve was complicated by additional factors (especially the precipitation or gelation of capsule by divalent metal ions), the effects of various metal chlorides were compared for the former phase in which capsule viscosity increased in the presence of metal ions. Equivalent increases in capsule viscosity were observed with micromolar concentrations of divalent metal ions but only with 10 to 20 times greater concentrations of Na(sup+). The relative abilities of various metal salts to increase capsule viscosity were as follows: CdCl(inf2), Pb(NO(inf3))(inf2), FeCl(inf2) > MnCl(inf2) > CuCl(inf2), CaCl(inf2) >> NaCl. This pattern of metal efficacy resembles known cation influences on the structural integrity of capsule in naturally occurring and cultured M. flos-aquae colonies. The data are the first direct demonstration of an interaction between metal ions and purified M. flos-aquae capsule, which has previously been proposed to play a role in the environmental cycling of certain multivalent metals, especially manganese. The M. flos-aquae capsule and the plant polysaccharide pectin have similar sugar compositions but differ in their relative responses to various metals, suggesting that capsular polysaccharide could be a preferable alternative to pectin for certain biotechnological applications.

Journal Article↗

A simple laboratory measurement for discrimination of transudative and exudative pleural effusion: pleural viscosity.

BACKGROUND: The initial step in establishing the cause of an effusion is to determine whether the fluid is a transudate or exudate. Plasma viscosity is influenced by the concentration of plasma proteins and lipoproteins with the major contribution resulting from fibrinogen. In this study we aimed to evaluate the role of pleural fluid viscosity in discrimination of transudate and exudates. MATERIALS AND METHODS: We studied prospectively 63 consecutive patients with pleural effusion in whom diagnostic or therapeutic thoracentesis had been performed. The criteria of Light were applied to differentiate transudates from exudates: 33 patients (23 male, 13 female, mean age=68+/-4 years) had exudates and 30 patients (17 male, 13 female, mean age=68+/-5) had transudates (due to congestive heart failure). Measurements of pleural fluid and plasma viscosity were performed using a viscometer. RESULTS: There was no statistically significant difference between patients with transudate and exudates in respect to plasma viscosity. However, pleural viscosities of the patients with exudates were significantly higher than those of patients with transudate (1.37+/-0.16 mPa vs 0.93+/-0.03 mPa s p<0.001, respectively). Pleural viscosity has a high sensitivity, specificity (94%, 93%, respectively), positive and negative predictive value (97%, 97%, respectively) for the discrimination of transudative or exudatetive pleural fluid. CONCLUSION: We have demonstrated for the first time that pleural viscosity of the exudative effusion is higher than that of transudative effusion with high sensitivity, specificity, positive and negative predictive value. Regarding the simplicity of this measurement, it may play a valuable role in the accurate and fast discrimination of pleural fluid.

Aged↗

Viscosity of some contemporary contrast media before and after mixing with whole blood.

The viscosity of 7 contrast media was measured using a rotational viscometer. When solutions with similar iodine concentrations were compared, the highest viscosities were found for the nonionic dimers iodixanol and iotrolan, the lowest for diatrizoate, iopamidol, and iopromide, and intermediate values for iohexol and ioxaglate. The viscosity of iohexol and ioxaglate was found to vary linearly with temperature and quadratically with concentration. Whole-blood viscosity was measured for 5 subjects at high and low shear rates before and after mixing with contrast media in various proportions. Low-shear viscosity was found to decrease and high-shear viscosity to increase with contrast medium concentration. It is concluded that the contrast media currently used may affect blood rheology less than previous agents, despite their higher viscosity.

Adult↗

Reversible self-association increases the viscosity of a concentrated monoclonal antibody in aqueous solution.

This study was conducted to investigate the effect of reversible protein self-association on the viscosity of concentrated monoclonal antibody solutions. The viscosities of the monoclonal antibody solutions were measured by either a capillary viscometer or a cone-plate rheometer at different protein concentrations, pH, and ionic strength. Soluble aggregates were determined by size exclusion chromatography, light scattering, and analytical ultracentrifugation. Self-association of protein at high protein concentration was monitored by sedimentation equilibrium analysis using a preparative ultracentrifuge and a microfractionator. The viscosity of one of the monoclonal antibodies investigated is highly dependent on protein concentration, pH, and ionic strength of buffer and charged excipients. This antibody shows the highest viscosity near its pI at low ionic strength conditions. Sedimentation equilibrium analysis suggests that this antibody tends to reversibly self-associate at high protein concentration. The self-association appears to be quite weak and is not detectable by sedimentation velocity and size exclusion chromatography at low protein concentration. There are no significant differences in the amounts of non-dissociable soluble aggregates formed between low viscosity and high viscosity samples. These results suggest that the reversible multivalent self-association of this protein appears to be mediated mainly by electrostatic interactions of charged residues and results in unusually high viscosity of this monoclonal antibody in solution at low ionic strength conditions.

Animals↗

Mass transport in dissolution kinetics. II: Convective diffusion to assess role of viscosity under conditions of gravitational flow.

Dissolution kinetics was studied in a laminar flow cell, through which aqueous solutions of increasing viscosity flowed under the force of gravity, in order to help elucidate the mechanism of drug dissolution. The viscosity was varied by addition of either hydroxypropyl cellulose, sucrose, or glycerin. The dissolution data were evaluated quantitatively in terms of a convective diffusion model for dissolution. It was demonstrated that the decrease in dissolution rate of a test compound due to viscosity in the polymer solution occurs primarily because of a decrease in the rate of shear over the dissolving surface. In solutions of sucrose or glycerin, the decrease in dissolution rate due to viscosity results because of a decrease in the diffusivity of the solute in addition to the decreased rate of shear. Also, the model accounts for the increase in solubility in the glycerin solution. Thus, the influence of viscosity on dissolution depends on whether the viscosity-inducing agent primarily affects only the flow properties of the liquid, or whether it affects diffusivity (i.e., a "micro" viscosity effect, in addition to the flow properties).

Cellulose↗

Blood viscosity in young male diabetics with and without retinopathy.

Blood viscosity (shear rates 100s-1 and 0.94s-1) and several of its major determinants (haematocrit, plasma fibrinogen and plasma viscosity) have been measured in 38 male insulin-treated diabetics, aged 18-50 years, and in 38 non-diabetic control subjects matched for age and smoking habit. Diabetics without fundoscopic retinopathy (n=20) had higher mean blood viscosity than controls at the high shear rate (7.07 cP vs 6.75 cP, p < 0.05) and the low shear rate (21.2 cP vs 18.7 cP, p < 0.025). These differences persisted after correction of blood viscosity to a standard haematocrit, and were associated with increased plasma viscosity (1.41 cP vs 1.34 cP, p < 0.025) and plasma fibrinogen (2.9 g/L vs. 2.5 g/L, p < 0.025). Diabetics with retinopathy (n = 18) had higher mean blood viscosity than diabetics without retinopathy at the high shear rate (7.53 cP vs 7.07 cP, p < 0.05) and the low shear rate (24.3 cP vs. 21.2 cP, p < 0.05), associated with a higher haematocrit (p < 0.05). Blood viscosity and haematocrit correlated with the duration of diabetes (r > 0.32, p < 0.05).

Adolescent↗

The effect of N-acetyl-L-cysteine on the viscosity of ileal neobladder mucus.

N-acetyl-L-cysteine (NAC) proved to be an effective mucolytic in pulmonary secretions. Our goal was to investigate the in vitro effect of NAC on viscosity of ileal neobladder mucus. The urine of a patient with an ileal neobladder was collected during the first 7 days postoperatively and stored in a refrigerator. After precipitation, the urine was decanted. The residue was stirred to a homogeneous suspension. To samples of 4.5 ml mucus, 0.5 ml NAC 10% was added. To the control sample, 0.5 ml water was added. The samples were incubated in a water bath at 37 degrees C for 5, 30 and 60 min. Viscosity was measured in the Bohlin VOR Rheometer. The viscosity of the ileal neobladder mucus decreased quickly after incubating with NAC 10%. Viscosity increased slightly after I h of incubation. The viscosity in the control sample was higher than in the other incubated samples. NAC was found to decrease the viscosity of ileal neobladder mucus, supporting the in vivo experience that NAC can be useful in patients with an ileal neobladder to facilitate the evacuation of mucus by decreasing viscosity.

Acetylcysteine↗