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PubMed1986

The effect of barium suspension viscosity on the delineation of areae gastricae.

The viscosity of a barium suspension is an important and controllable variable that influences the quality of mucosal detail demonstrated by double-contrast upper gastrointestinal examination. High-density barium suspensions show a notable viscosity response to seemingly trivial changes in the amount of water added. A double-blind trial involving 600 patients used E-Z-HD of the same batch number suspended with 65-70 ml water. Overall, areae gastricae covering at least 25% of the stomach surface were seen in 68.3%; no or minimal areae gastricae were seen in 31.7%. The corresponding figures for the suspension of optimal viscosity were 80% and 20%, respectively.

Barium Sulfate↗
PubMed1981

Changes in cerebral blood flow relating to haematocrit and viscosity.

Evidence suggests that haematocrit and viscosity are important factors in the control of cerebral blood flow (CBF). Conditions in which the haematocrit is raised, such as polycythaemia rubra vera and relative polycythaemia are associated with a low CBF. Following reduction in haematocrit, there is a significant rise in CBF. It is likely that two factors are responsible for this. Firstly there is a fall in oxygen carrying capacity with venesection. Secondly there is a marked fall in whole blood viscosity. Both these changes tend to result in a rise in CBF. Further studies in patients with paraproteinaemias suggest that oxygen carriage and blood viscosity are independent variables in the control of CBF.

Animals↗
PubMed2003

Rheological properties of concentrated skim milk: importance of soluble minerals in the changes in viscosity during storage.

Properties of condensed milks prior to spray drying dictate to a large extent the functionality of the resulting milk powder. Rheological properties of concentrated skim milk, with total solids content of 45% but different mineral content, were studied as a function of shear rate and storage time at 50 degrees C. These milks are proposed as a model to study the effects of minerals on rheology and age gellation of condensed milk prior to drying. During storage of the concentrated milk, the apparent viscosity, particularly after 4 h, increased markedly at all shear rates studied. The yield stress also increased steeply after 4 h of storage at 50 degrees C. The changes in apparent viscosity of concentrated milk stored for up to 4 h were largely reversible under high shear, but irreversible in samples stored for longer time. The appearance of yield stress suggested the presence of reversible flocculation arising from weak attraction between casein micelles, with a transition from reversible to irreversible aggregation during storage. Particle size analysis confirmed irreversible aggregation and fusion of casein micelles during storage. Gradual reduction of mineral content of concentrated milks resulted in a marked decrease in the apparent viscosity and casein micelle aggregation during storage, while addition of minerals to milk had the opposite effect. The results demonstrated that the soluble mineral content is very important in controlling the storage-induced changes in the rheology of concentrated milks.

Animals↗
PubMed1997

Influence of protein standardization by ultrafiltration on the viscosity, color, and sensory properties of skim and 1% milk.

Permeate and retentate (concentration factor ca. 2x) from UF of skim milk were combined, and cream was added to produce skim milk (0.1% fat) and 1% milk with a range of true protein contents (1.0 to 4.8%) within each fat level. A panel that had been trained for descriptive sensory analysis evaluated the appearance, aroma, flavor, and textural attributes of milks. Relative viscosity and Hunter color values for whiteness (L value), greenness to redness (a value), and blueness to yellowness (b value) increased when either protein or fat was increased. The rate of change of L, a, and b values as protein content changed was greater for skim milk than for 1% milk and was greater as protein contents decreased. Sensory scores for several descriptors of appearance, texture, and flavor had a stronger positive correlation with objective measurements of whiteness than with objective measurements of viscosity. Thus, the judgment of panelists about milk texture and flavor in milks that differed in protein content was influenced more by appearance than by viscosity. As the protein content of skim and 1% milk was increased from 2.9 to 4.8% true protein, the sensory properties of the milks were made more like those of higher fat milk, particularly those of skim milk, mainly because of whiter appearance. Panelists perceived changes in the sensory characteristics of both skim and 1% fat milk when the true protein content was increased by 0.9%, the smallest increase that was studied in the experiment.

Animals↗
PubMed1982

Modifications of the erythrocyte deformability alter the effect of temperature on the relative viscosity of human blood.

The relative viscosity of normal red cell suspensions is independent of temperature at high shear rates. The relative viscosity of suspensions with normovolemic sphered erythrocytes having a reduced deformability, however, is higher at 37 degrees C then at 20 degrees C. It is concluded that the changes of the lipoprotein configuration within the erythrocyte membrane which are proposed to be involved in the disc-sphere-transformation of the red cell, depend on temperature and are responsible for the increased relative viscosity at 37 degrees C.

Blood Viscosity↗
PubMed1983

Theory of non-Newtonian viscosity of red blood cell suspension: effect of red cell deformation.

The effects of the deformation of red blood cells on non-Newtonian viscosity of a concentrated red cell suspension are investigated theoretically. To simplify the problem an elastic spherical shell filled with an incompressible Newtonian fluid is considered as a model of a normal red cell. The equation of the surface of the shell suspended in a steady simple shear flow is calculated on the assumption that the deformation from a spherical shape is very small. The relative viscosity of a concentrated suspension of such particles is obtained based on the "free surface cell" method proposed by Happel. It is shown that the relative viscosity decreases as the shear rate increases.

Blood Viscosity↗
PubMed1983

Complex viscosity of bovine red blood cells in suspensions.

The complex viscosity eta* has been measured of bovine red blood cells suspended in a medium of isotonic NaCl solutions including dextran and buffered with potassium phosphate at pH 7.0. A multiple lumped resonator apparatus was used at the frequencies of 144, 572, 1491, 3742, and 8026 Hz at 20.0 degrees C. Due to the high molecular weight of dextran the medium also exhibited some visco-elasticity eta s*. So we adopted the complex specific viscosity eta sp* = (eta*-eta s*)/[eta s*]. At 20.0 degrees C eta sp* decreased with the frequency where the hematocrit was 0.233 and eta s 0.34 poise. The measurements were made for the medium with different viscosity at 5.0 degrees C and 25.0 degrees C. The results are compared with the theory of elastic shells.

Animals↗
PubMed1987

Measurements of viscosity of synthetic erythrocyte suspensions.

Measurements were made of the viscosity of suspensions of synthetic erythrocytes composed of hemoglobin solutions encapsulated in liposomes, as a function of shear rate, temperature, suspension concentration, lipid membrane composition, and the viscosity of the suspending medium. It was found that the viscous behavior of the synthetic erythrocyte suspensions was non-Newtonian and nearly the same as that of suspensions of natural erythrocytes prepared similarly, with the major difference being that synthetic erythrocyte suspensions are somewhat more viscous. Suspensions of Fluosol FC-43 prepared similarly were found to be essentially Newtonian fluids, and substantially different and more viscous than either erythrocyte suspension. The higher viscosity of synthetic erythrocyte suspensions probably accounts for the ability of these suspensions to maintain normal systemic vascular resistance in transfusion experiments, in spite of the fact that synthetic erythrocytes are smaller than natural erythrocytes.

Blood Proteins↗
PubMed1988

Effects of viscoelasticity of cytoplasm on the complex viscosity of red blood cell suspensions.

To consider the effects of the viscoelasticity of cytoplasm on the relaxation phenomenon of red blood cell suspensions, we calculate the complex intrinsic viscosity [eta*] = lim(eta* - eta)/eta c of the disperse system of spherical c----0 cells as a function of the frequency, where eta* is the complex viscosity in suspensions, eta the medium viscosity and c the volume concentration of the cells. The cell consists of a viscoelastic membrane and a viscoelastic cytoplasm. The viscoelasticity of the membrane is described by the Voigt model, while the viscoelasticity of the cytoplasmic region is described either by the Maxwell model or by the Voigt model. The interfacial tension is taken into account on both the interfaces of the membrane. The results of [eta*] are compared with the ones in the case in which the cytoplasmic region is purely viscous liquid.

Animals↗
PubMed1990

The role of viscosity in oxygen binding to respiratory proteins.

Investigations of Myoglobin, Hemoglobin and, more recently of Hemerythrin, suggest that the inward and outward motion of the oxygen ligand is governed by fluctuations between open and closed paths in the protein and that the driving force is the local brownian motion of protein residues. Reaction rates involving protein internal motions are strongly influenced by the viscosity of the solvent, whereas the ultimate binding of oxygen at the protein's active site remains viscosity independent. The description of a protein reaction therefore requires the introduction of a free energy surface with a conformation coordinate accounting for the viscosity-dependent protein transitions in addition to the usual reaction coordinate which only describes the system of reactants in a fixed protein conformation.

Hemerythrin↗
PubMed1990

The viscosity of neutrophils and their transit times through small pores.

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 microns. 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, 10,000 and 20,000 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 microns and an aspiration pressure of 1250 dyn/cm2, we predict a transit time of about 70 s. At 6 microns and 20,000 dyn/cm2, the predicted transit time is only about 0.04 s.

Blood Flow Velocity↗
PubMed1991

The effect of the solvent viscosity on the migration of small molecules through the structure of myoglobin.

The migration rate of small molecules through the structure of proteins can be monitored by quenching the light emitted from an excited optical probe located within the protein. In the present study we examined the influence of the solvent viscosity on the migration rate of the quencher anthraquinone sulfonate through myoglobin towards an excited Zn protoporphyrin molecule at the binding site of the protein. The solvent viscosity was increased by adding dextrans of different molecular weight but forming isoviscous solutions. The results demonstrate that the migration rate in the protein decreases with increasing solvent viscosity. This suggests that the fluctuations on the protein structure, which make the above migration possible, are affected by the solvent macroviscosity.

Animals↗
PubMed1988

Effect of extender viscosity on the insemination dose for chickens.

When semen was diluted 1:2 with Beltsville poultry semen extender (BPSE) containing 4% (w/v) carboxymethyl cellulose (CMC), seminal viscosity was 14 times greater than that of semen similarly extended with BPSE and 2.2 times more viscous than neat semen. Under these conditions, CMC was not spermicidal (P greater than .05). Increased seminal viscosity did not enhance fertility (P greater than .05) over a 20-day interval following a single insemination of 33 or 100 X 10(6) spermatozoa/hen. In the case of semen extended with BPSE as well as BPSE containing CMC, the insemination dose of 100 x 10(6) spermatozoa gave superior fertility (P less than .05) compared with results of insemination with 33 X 10(6) spermatozoa. However, when fertility data from the 1st wk of egg collection were compiled, there was no difference in fertility (P greater than .05) due to insemination dose. These results demonstrate that although a conventional insemination dose could be reduced in order to use semen more efficiently, increasing seminal viscosity may not be warranted for artificial insemination programs.

Animals↗
PubMedDate not supplied

The role of blood viscosity in the development and progression of coronary artery disease.

BACKGROUND: Although a great deal of attention has been directed to the risk factors for atherosclerotic coronary artery disease, relatively little research has been focused on the role of the circulating blood itself. OBJECTIVES: To review the possible role of increased plasma viscosity and decreased cellular deformability in the pathogenesis of atherosclerotic coronary artery disease. SUMMARY: Increased plasma viscosity or decreased erythrocyte deformability may reduce blood flow in areas where blood flow is already low, such as at arterial branch points and bifurcations as well as in advanced coronary artery narrowing. Further, these factors may favor the development and progression of atherosclerotic coronary artery disease through direct mechanical effects on either the vascular endothelium or existing atheromatous plaques. Beyond their potential direct effects, each may represent a common link between recognized risk factors and the resulting disease process. CONCLUSIONS: Accumulating evidence suggests that increased blood viscosity is an independent risk factor for atherosclerotic heart disease and its complications.

Adult↗
PubMed1990

Viscosity of dental porcelains in glass transition range.

Changes in the viscosity of dental porcelain as a function of temperature are the controlling factor determining incompatible stresses in porcelain-fused-to-metal restorations. A new method was used to estimate viscosity using a viscoelastic analytical model that considers the relation between the heating rate and deformation temperature (Td) of dental porcelain with stress applied during heating. The activation energy of viscous flow and the viscous constant in the Arrhenius equation were calculated for six kinds of commercial body and opaque porcelains. The effect of the heating rate on the instantaneous coefficient of thermal expansion was also measured. Tg onset was graphically determined using data on thermal deformation and agreed well with the strain point as defined by viscosity. The data gathered in this study was also compared to the experimental results of previous works by others.

Dental Porcelain↗
PubMed1987

Usefulness of blood parameters, especially viscosity, for the diagnosis and elucidation of pathogenic mechanisms of the hand-arm vibration syndrome.

In the present study it was found that, in vibrating-tool operators with Raynaud's phenomenon, whole blood viscosity was significantly higher than in operators without Raynaud's phenomenon at shear rates from 230 to 11.5 s-1. In addition rats were experimentally exposed to local vibration (60 Hz, 5 g) on their hind limbs for 4 h/d for 30 or 90 d. In the case of 30-d exposure, the small arteries in the exposed site did not change. However, after exposure for 90 d, disruption of the internal elastic lamina was observed in the small arteries. The disruption was followed by focal cell proliferation with regenerative formation of collagen and elastic fibers. The fibro-cellular thickening of the intima was further augmented, and, in addition, a complete stenosis of the small lumen of the small artery was observed. Medial thickness did not show significant differences between the control and exposed groups for either exposure duration. The whole blood viscosity was significantly increased by the 90-d but not by the 30-d exposure. These results suggest that there are some relationships between the increase in whole blood viscosity and the intimal thickening of some small arteries in the exposed site.

Animals↗
PubMed1976

[Viscosity of blood, plasma and serum, in the vessels of the lesser and greater circulation in rheumatic mitral heart defect].

The study was conducted in 44 patients with rheumatic mitral and combined mitral valve disease in its inactive phase with circulatory insufficiency of Stage II, III or IV, according to the classification by A. N. Bakulev and E. A. Damir, and in 30 normal individuals. The viscosity of blood and serum flowing in different organs and tissues was found to undergo no changes and to be not dependent on the severity of circulatory insufficiency. It was concluded that the viscosity of blood in a peripheral vein may be used for judging its ability to flow in various points of the vascular bed. The viscosity of plasma was found to alter when passing through the brain, muscle tissue, splanchnic organs and the lungs.

Adolescent↗
PubMed1997

[Effect of jiangtangkang on blood glucose, sensitivity of insulin and blood viscosity in non-insulin dependent diabetes mellitus].

OBJECTIVE: To study the hypoglycemic effect of Jiangtangkang (JTK), a Chrysanthemum product and its influence on sensitivity of insulin in non-insulin dependant diabetes mellitus (NIDDM). METHODS: Newly discovered (71 cases) and poorly controlled (117 cases) NIDDM were divided to JTK, 8 g each time, 3 times per day, and the control (Glibenclazide in newly discovered, no treatment in poorly controlled) group respectively. RESULTS: After 2 months of treatment, the fasting blood glucose (FBG), postprandial blood glucose (PBG), glucosylated hemoglobin (GHb) improved remarkably and insulin of plasma remained unchanged in JTK group, their blood viscosity and triglyceride decreased after 6-month reatment, the FBG, PBG lowered in the control group while their viscosity and lipids were unaffected. Insulin tolerance test on newly discovered NIDDMs showed an increased sensitivity to insulin, their serum chromium elevated, and the urinary albumin in poorly controlled persons lowered significantly. CONCLUSIONS: JTK might improve the sensitivity to insulin and decrease the blood viscosity in NIDDM.

Adult↗