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At least 1,603 records · Page 89Linked to original sources
PubMed1990

Whole blood viscosity and red cell filterability as factors in sensorineural hearing impairment in the elderly.

Deficiencies in blood supply can lead to impairments in cochlear function. We have reported significant associations of both measures of whole blood viscosity and derived measures of red cell rigidity with hearing threshold levels in individuals with sensorineural hearing impairments. This paper describes direct measures of red cell filterability in a group balanced across the variables of hearing threshold level and age to facilitate dissociation of the effects of factors correlated with age. After controlling for effects of age, sex and social class, there were strong correlations between whole blood viscosity at high shear rate and hearing threshold levels at 250, 500, and 1,000 and 2,000 Hz. At 4,000 and 8,000 Hz, hearing threshold level was related to red cell filterability. When the data are divided into subgroups by age, the younger age group exhibited a pattern similar to the overall one, but in the older age group the effect of red cell filterability was more apparent, extending down to 1,000 Hz. The data support a strong association between aspects of blood rheology and sensorineural hearing impairment, but in a more complex manner than suggested by previous studies. They imply that there are two processes associated with sensorineural hearing impairment, one of which can be considered as due to bulk rheological properties, while the other appears more related to the properties of individual red cells. The bulk properties are more important at lower frequencies, while the cellular properties are more influential at higher frequencies.

Aged↗
PubMed1992

Efficacy of a topical nasal decongestant in different formulations: the effect of viscosity.

Factors affecting the absorption of drugs through the nasal mucosa are increasingly being studied. Dosage form factors, i.e. the viscosity of the excipients, have been claimed to be of importance for enhanced nasal absorption due to prolongation of contact time between drug and mucosa. In the present study, a comparison was made of the effect of a local nasal sympathomimetic when administered intranasally in formulations with different viscosities. Volunteers received the test drugs as nasal sprays in a randomized cross-over design by a rhinomanometric technique, the effect of the drug being recorded for up to 5 h after administration. No significant differences in effects were observed when the test formulations were compared.

Absorption↗
PubMed1980

The importance of lysozyme for the viscosity of sputum from patients with chronic obstructive lung disease.

Addition of lysozyme (1 g/l) to sputum from patients with chronic obstructive lung disease increased the viscosity of the material significantly. The effect was prevented by addition of salt (LiCl) in the high concentration (0.25 mol/l). The sole addition of salt decreased the viscosity of native sputum. These results together with our earlier [5] studies of the interaction between the positively charged lysozyme and the negatively charged mucin molecules in model systems, indicate that lysozyme acts as a cross-linking agent in mucus by an electrostatic mechanism. Lysozyme is thus, at least partly, responsible for building up a macromolecular network giving mucus its characteristic gel-like properties.

Chlorides↗
PubMed1978

The effect of sterculia bulk on the viscosity of stomal output from twelve patients with ileostomy.

The addition of 15g of sterculia bulk (Inolaxol) to the daily food patients with ileostomy increased the viscosity of the stomal output by roughly 100%. The clinical result of this change was beneficial in 9 out of 12 patients in terms of diminished bandaging difficulties. Adding bulk to the diet of patients with ileostomy may thus facilitate the management of the stoma by increasing the viscosity of the output.

Adult↗
PubMed1995

Changes of blood viscosity in patients treated with 5-fluorouracil--a link to cardiotoxicity?

Cardiotoxicity is a serious but relatively unknown side-effect of treatment with 5-fluorouracil (5-FU). The underlying mechanism of 5-FU cardiotoxicity has not been defined. The aim of the present study was to determine whether hemorheological factors might in part explain 5-FU cardiotoxicity. Changes of blood and plasma viscosity, fibrinogen and hematocrit were studied in 11 patients treated by 5-FU. The study showed a decrease in blood and plasma viscosity during treatment with 5-FU, probably caused by a decrease of plasma fibrinogen. Reversible cardiotoxic effects were demonstrated in four patients.

Adult↗
PubMed1984

Blood viscosity, finger systolic pressure and effect of dazoxiben treatment in primary vasospastic disease.

Whole blood viscosity, plasma viscosity, erythrocyte deformability, and finger systolic pressure (FSP) were measured in ten patients with primary vasospastic (Raynaud's) disease before and after a controlled double-blind prospective trial involving dazoxiben (a thromboxane inhibitor, Pfizer). Five of the patients were assigned to dazoxiben and five to placebo. Before treatment, the FSP at 10 degrees C in the patient groups was significantly lower than that in a normal reference group, but all rheologic variables, measured at 37 and 10 degrees C, were normal. There was no significant correlation between FSP and rheology. Dazoxiben did not yield any subjective relief or give any objective effect.

Adult↗
PubMed1985

Blood viscosity and finger systolic pressure in primary and traumatic vasospastic disease.

Vasospastic reactions to cold have been suggested to be related to altered blood rheology, as has been reported in both primary (PVD) and traumatic (TVD) vasospastic disease. Measurements of whole blood viscosity, plasma viscosity, erythrocyte deformability and finger systolic pressure (FSP) were performed in 18 patients with PVD (Raynaud's disease) and 15 patients with TVD. FSP at 10 degrees C was significantly lower in both patient groups than in a normal reference group. All rheologic variables at 37 and 10 degrees C were normal, apart from increased erythrocyte deformability at 37 degrees C in the PVD group.

Adult↗
PubMed1986

The modulatory effect of membrane viscosity on structural and functional properties of the anion exchange protein of human erythrocytes.

The sterol content of human erythrocyte membranes was modified by polyvinylpyrrolidone (PVP)-mediated enrichment or depletion of cholesterol (CHL) or incorporation of cholesteryl hemisuccinate (CHS). The effects of these modifications on osmotic fragility and anion exchange protein (AEP) disposition and function were evaluated. CHS enrichment was fast (1 hr, 37 degrees C) and led to a concentration-dependent crenation as well as a decrease in osmotic cell fragility, in parallel with increased membrane microviscosity. CHL caused similar but considerably less marked effects due to slower incorporation rates into membranes. CHS enrichment of cells induced susceptibility of AEP to trypsin, a protease which otherwise does not affect AEP in intact cells. Although transport rates of monosaccharides, nucleosides, and anions were markedly slowed down by CHS enrichment of cells in parallel with increased membrane viscosity, anion transport was the most affected. The temperature profile of anion transport in CHS-enriched cells revealed a 10-kcal/mol increase in the enthalpy of activation relative to normal cells. Anion transport measured in heteroexchange conditions (Cl in--pyruvate out) and (Cl in-sulfate out) was relatively more susceptible to CHS modification than when it was measured in homoexchange conditions (Cl in-Cl out). The results of these measurements indicate that CHS-mediated increase in membrane viscosity affects AEP translocation capacity and transmembrane disposition via changes in lipid compressibility. Specific effects of CHS on AEP function, however, could not be ruled out.

Anion Transport Proteins↗
PubMed1986

Blood viscosity: a pathogenetic factor in the development of essential hypertension?

Inhibition of the ouabain-sensitive Na-K-ATPase by digoxin significantly decreases erythrocyte deformability (5). Since first a decrease in this transport system has been discussed as a pathogenetic factor in the development of essential hypertension and second an increase in blood viscosity, due to an increased hematocrit has been observed in elderly hypertensives, hemorheology and sodium transport systems were examined in adolescent hypertensives and compared with age-matched normotensive controls. 73 normotensives (N; mean blood pressure 127/80 mmHg) and 53 hypertensives (H; mean blood pressure 147/94 mmHg) aged 23-27 yrs were randomly selected from an epidemiological survey, covering 1342 adolescents. While apparent whole blood viscosity at different shear rates, hematocrit, plasma fibrinogen were not significantly different, erythrocyte deformability, measured with a positive pressure filter system (pore phi 5 mu) and expressed as Q = delta P/ery.susp.Hct 10%/delta P/plasma was significantly attenuated with Q = 1.77 +/- 0.05 in H, compared to 1.64 +/- 0.04 in N (p less than 0.05) The decrease in erythrocyte deformability was not accompanied by an inhibition of the Na-K-pump nor of total K+-uptake in erythrocytes, both measured with the 86Rb uptake. There was only a slight increase in Na+-excretion in urine of 184.4 + 12.2 mval in H, compared to 162.0 +/- 10.4 mval in N (n.s.). K-/+-excretion and serum electrolytes did not show any difference. Whether the decrease in erythrocyte deformability may contribute to an increase in peripheral vascular resistance in essential hypertension has to be further clarified.

Adult↗
PubMed1983

A comparison of the mechanical properties of Simplex, Zimmer, and Zimmer low viscosity bone cements.

Many different methods have been used to compare polymethylmethacrylate bone cements. In this paper the three currently available cements were compared in regard to dough and set times, heat of polymerization, compressive, tensile, 3 and 4 point bending strengths, fracture toughness, flexural modulus, void density distribution, and viscosity. Methods used were ASTM designated for bone cement or plastics in general whenever possible. Significant differences in set and dough times and heat of polymerization were noted. All cements were equal in compressive, tensile, and fracture toughness testing; Zimmer Regular Cement was significantly weaker (p less than 0.001) in flexural testing and had a significantly (p less than 0.001) decreased modulus of elasticity when compared to LVC and Simplex Cements. Void density distributions were not significantly different. Viscosity was shown to vary between these cements as well. This data was analysed both to determine differences between various brands of cement and to assess the relevance to clinical use and failure modes in vivo of these different means of testing.

Bone Cements↗
PubMed1995

A rheological equation to express the relations among hemoglobin contents, hematocrits, and viscosity of hemosome.

The relations among hemoglobin contents, hematocrit and viscosity of hemosome at a fixed shear rate have been studied. These relations can be well fitted by a rheological equation with internal viscosity of hemosome, (Tk)h, as a parameter. Where, (Tk)h are correlated (r = 0.996) with logarithm of hemoglobin content of hemosome by an equation: (Tk)h = 0.315 ln (hemoglobin contents of hemosome) + 0.435. The correlation can serve as an alternative way to predict hemoglobin content of hemosome instead of Benesch's method. The results of this study serve as a reference to determine an optimal conditions for in vivo tests of hemosome.

Animals↗
PubMed1975

Viscosity and gelation studies in deer hunting hemoglobins.

Sickling, viscosity and gelling properties of the red cells and the hemoglobins of three Virginia white-tailed deer homozygous for types II and III (the sickling types) and V (the nonsickling type), respectively, have been analyzed. The sickling of erythrocytes of deer with type II or III is inhibited by urea and cyanate at concentrations which are comparable to those used in in vitro studies of red cells from patients with sickle cell anemia. No differences were observed between the viscosities of the three deer hemoglobin types at temperatures of 12 degrees C or above. High concentrations of deer hemoglobin types II and III gelled at 1 degree C and at pH values of 7.4-7.7; the minimum gelling concentration of type II was 33.5 g% and of type III was 38 g%. Gel formation was not observed at pH values between 6.7-7.1. Hemoglobin type V did not gel and prevented the formation of gels of type II and III in mixtures at pH 7.6-7.7.

Anemia, Sickle Cell↗
PubMed1984

The OP-Rheometer system, a new device for analysis of viscosity and viscoelasticity of blood: description and clinical application.

OP-Rheometer is a rotational viscometer of concentric type, which was developed to measure blood viscosity at low shear rate (0.2-40 sec-1) and viscoelasticity at 0.1-3.0 Hz in the context of clinical medicine. This system consists of a mechanical unit, a control unit (console), a data processing unit and a printer. The dynamic or steady state flow data are automatically printed out. An outer cylinder (sample container) is connected to a torsion wire assembly supported by a pair of magnetic bearings. The angular displacement is detected by a pair of variable differential transformers. In clinical application of this rheometer, authours have confirmed that the viscosity and viscoelasticity of blood from diabetic patients are higher than for normal subjects.

Adult↗
PubMed1984

Blood viscosity measurements in both extensional and shear flow by a falling ball viscometer.

A falling ball viscometer is used to measure whole blood and plasma viscosities. The principle of the device is to determine the fall time of a ball contained in a disposable syringe; the periodic run of the sphere prevents blood sedimentation during the measuring cycle but does not prevent the aggregation process which takes place with a short relaxation time. The analysis of the flow field is discussed relative to previous papers. The study of the dynamics of the falling ball provides two characteristic rates of deformation for the mixed extensional and shear flow field. The Reynolds numbers are calculated using different velocities and radii. Results on blood and plasma viscosity of patients suffering from rheumatoid arthritis are given in relation with clinical and biological indexes.

Arthritis, Rheumatoid↗
PubMed1984

Dependence of capillary flow resistance upon the width of the marginal layer and the viscosity of the axial core.

Capillary blood flow may be considered as the flow of two compartments a.) the low viscous cell free marginal layer, surrounding b.) the higher viscous axial core. If the flow of both compartments is calculated separately according to Poiseuille, the addition of the two calculations allows to adapt Poiseuille's law to the non-Newtonian blood flow in small capillaries. The modified law correlates theoretical and experimental data with R2 = 0.99. (H = 0.3 - 0.7, tau W = 0.1 - 1.2 Pa, blood viscosity 5 to 20 mPa X s, capillary I.D. 0.3 mm). The width of the marginal was calculated by relating the shear dependent change in electrical resistance in blood perfused capillaries to the development of a cell free marginal layer. The viscosity of the core was determined with a bended glass fibre (phi = 10 microns).

Blood Physiological Phenomena↗
PubMed1987

Effect of temperature dependent changes in mechanical stability of red cell aggregates on relative apparent whole blood viscosity.

As the temperature dependence of relative apparent whole blood viscosity eta rel is still controversial, the relation between the temperature dependence of red cell aggregation (RCA) and that of eta rel was examined in normal donors and in patients with venous ulcers of the leg. Apparent whole blood viscosity was measured in the DEER-rheometer (0.01 Pa less than tau less than 2.9 Pa) at 10 degrees C, 20 degrees C, 30 degrees C and 37 degrees C. The instrument was calibrated for each temperature to correct for changes in viscometer geometry. Simultaneously the minimal shear stress tau Tmin to keep RCA dispersed was determined by photometric aggregometry. eta rel was found to increase with decreasing temperature. By basing the relative cold induced increase in eta rel on the state of RCA as defined by the ratio of tau/tau Tmin the relation between both features is verified: With increasing RCA the cold induced increase in eta rel is progressively enhanced.

Blood Viscosity↗
PubMed1988

A method for analyzing non-Newtonian blood viscosity data in low shear rates.

Viscosity measurements were made using a coaxial rotating cylinder viscometer for blood having various volume fractions of red cells. A method is described for analyzing non-Newtonian blood viscosity in low shear rates by taking account of an increase or a decrease in size of red cell aggregates induced by shear. Our results are compared with empirical formulae presented by Scott Blair, Weaver-Evans-Walder and Thurston.

Blood Viscosity↗
PubMed1988

A new analysis method for the membrane viscosity from steady-state fluorescence depolarization.

The absolute value of the viscosity in membrane lipid bilayers, which is different from the microviscosity advocated by Shinitzky, could be calculated from steady-state fluorescence depolarization of a hydrocarbon fluorophore, 1,6-diphenyl-1,3,5-hexatriene (DPH). This method was based on the theory of time-resolved fluorescence anisotropy and empirical relationships between fluorescence life time and the anisotropy parameters such as half cone angle in wobbling motion and wobbling diffusion rate of the fluorescent probe. Obtained viscosity values of various membranes from this method were consistent with those from time resolved method within experimental error.

Animals↗