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PubMed1964

SCALING OF APPARENT VISCOSITY.

Observers made numerical judgments of the apparent viscosities of silicone liquids whose absolute viscosities ranged from 10.3 to 95,000 centipoises. Judgments were made by three procedures: shaking or turning a bottle containing the liquid, stirring the liquid with a rod with the eyes blindfolded, and stirring with the eyes open. For all these methods of judging, apparent viscosity was found to grow as the absolute viscosity raised to a fractional power. The exponents ranged from 0.42 to 0.46. The perception of viscosity follows the psychophysical power law that seems to govern prothetic perceptual continua.

Biophysical Phenomena↗
PubMed1990

Viscosity measurements of suspensions of hemoglobin-containing liposomes of varying lipid composition.

The viscosity of suspensions of hemoglobin-containing liposomes (Hb liposomes) and of liposomes without Hb was determined as a function of the shear rate. Liposomes of varying lipid composition were prepared by detergent dialysis. All liposome suspensions showed non-Newtonian viscous behavior, as did erythrocyte suspensions. The viscosity of suspensions of Hb liposomes with a bilayer consisting of egg yolk lecithin and phosphatidylserine was almost identical to erythrocyte suspension viscosity. When cholesterol was included in the lipid component of the Hb liposomes, the dependence of viscosity on the shear rate decreased (flattening of the curve), but overall suspension viscosity became higher than that of erythrocyte suspensions. Evidence is provided for the lipid concentration at which liposomes can be applied intravenously.

Blood Substitutes↗
PubMed1982

Decreased viscosity of human erythrocyte suspension due to drug-induced spherostomatocytosis.

The effect of two cationic drugs (chlorpromazine and isoxsuprine) on the suspension viscosity of human erythrocytes were examined, comparing with the effect of anionic drugs. (1) As increasing the drug concentrations, the cationic drugs transformed the erythrocytes to stomatocytes, then to spherostomatocytes, while trinitrobenzene sulfonate, dehydroepiandrosterone sulfate and lysolecithin induced echinocytes, as well known. (2) The suspension viscosity decreased in parallel with the appearance of spherostomatocytes, but it increased in echinocytosis. (3) The membrane fluidity, measured by spin label method, was not a major determinant for the suspension viscosity in these cases, because of no systematic correlation. (4) The rheoscopic observation under shear force demonstrated that the spherostomatocytes deformed easily to ellipsoid with smooth cell surface, while the echinocytes less easily deformed to ellipsoid on which the small spikes persisted at higher shear. These distinct difference in deformed shape under high shear force could be related to the decreased suspension viscosity of spherostomatocytes. (5) In addition, the transformation to spherostomatocytes, thus the decreased viscosity, was primarily determined by the intramembraneous drug concentration.

Blood Viscosity↗
PubMed1964

BLOOD VISCOSITY IN HEALTHY SUBJECTS AND PATIENTS WITH CORONARY HEART DISEASE.

Viscosity of whole blood and plasma was measured in 258 apparently healthy subjects of both sexes from 5 to 60 years of age, and in 86 patients with unequivocal evidence of chronic coronary heart disease. Children and young healthy females had the lowest viscosity readings. Healthy young and middle-aged males had significantly higher blood viscosity than females. Patients with coronary heart disease had significantly higher blood viscosity values than healthy groups of the same sex. It is suggested that the higher viscosity of whole blood and of plasma is a contributory factor in development of clinical manifestations of coronary heart disease and possibly of the basic vascular lesion itself.

Adolescent↗
PubMed2002

Microchannel DNA sequencing matrices with switchable viscosities.

We review the variety of thermo-responsive and shear-responsive polymer solutions with "switchable" viscosities that have been proposed for application as DNA sequencing matrices for capillary and microfluidic chip electrophoresis. Generally, highly entangled polymer solutions of high-molar mass polymers are necessary for the attainment of long DNA sequencing read lengths (> 500 bases) with short analysis times (< 3 h). However, these entangled polymer matrices create practical difficulties for microchannel electrophoresis with their extremely high viscosities, necessitating high-pressure loading into capillaries or chips. Shear-responsive (shear-thinning) polymer matrices exhibit a rapid drop in viscosity as the applied shear force is increased, but still require a high initial pressure to initiate flow of the solution into a microchannel. Polymer matrices designed to have thermo-responsive properties display either a lowered (thermo-thinning) or raised (thermo-thickening) viscosity as the temperature of the solution is elevated. These properties are generally designed into the polymers by the incorporation of moderately hydrophobic groups in some part of the polymer structure, which either phase-separate or hydrophobically aggregate at higher temperatures. In their low-viscosity states, these matrices that allow rapid loading of capillary or chip microchannels under low applied pressure. The primary goal of work in this area is to design polymer matrices that exhibit this responsive behavior and hence easy microchannel loading, without a reduction in DNA separation performance compared to conventional matrices. While good progress has been made, thermo-responsive matrices have yet to offer sequencing performance as good as nonthermo-responsive networks. The challenge remains to accomplish this goal through the innovative design of novel polymer structures.

Electrophoresis, Capillary↗
PubMed1975

Evaluation of high viscosity contrast media in canine selective coronary arteriography.

A special high viscosity preparation of water soluble radiopaque contrast media was explored in animals for its suitability in selective coronary angiography. The high viscosity required power injection to accomplish adequate filling during selective coronary arteriography. The anticipated angiographic advantages, such as prolonged visualization and coating of the vascular walls, were marginal. Comparison with conventional preparations of the same contrast agent suggests that the high viscosity itself exerts some protective effect with regard to the immediate side effects on the electrocardiogram and mechanical function of the myocardium. However, the high viscosity preparation induced electrocardiographic signs compatible with myocardial ischemia not usually seen to follow the injection of conventional contrast agents. These were followed by mechanical heart failure or ventricular fibrillation resulting in death of 6 of the 10 experimental animals. It was concluded that high viscosity contrast media preparations are unsuitable for use in clinical selective coronary arteriography as presently practiced.

Angiography↗
PubMed2007

Influence of initial component temperature on the apparent viscosity and handling characteristics of acrylic (PMMA) bone cement.

The flow and polymerization characteristics of poly(methylmethacrylate) (PMMA) bone cement can be changed by manipulating the temperature of the bone cement components or the environment that they are prepared in. To quantify the effects of the initial component temperature (T(ic)) of acrylic bone cement on the rheological and handling characteristics, ASTM F451-99a compliant methods and clinically relevant testing methods were utilized. A rheometer was designed and fabricated using the dimensions of a clinical, commercially available, cement gun and nozzle. The influence on the apparent viscosity and handling characteristics (setting time, working time, and peak exotherm temperature) for a high viscosity (HV) commercially-available acrylic bone cement, Palacos R, were determined. The values of T(ic) used were 23 degrees C (room), 6 degrees C (refrigerator), and -14 degrees C (freezer). Using the apparent viscosity of a medium viscosity (MV) bone cement as a benchmark (Simplex P at room temperature), it was found that by adjusting the T(ic) the HV cement was able to mimic the flow characteristics of the MV cement. Lowering the T(ic) lowered the apparent viscosity of the bone cement. The effects of T(ic) on the polymerization of bone cement were studied in dynamic and static conditions. The dynamic test recorded temperature and torque from stirring resistance. Setting times were also determined using the ASTM exotherm mold method. The setting times determined by the dynamic testing conditions were consistently shorter than those determined by the ASTM method. Lowering the T(ic) increased the working and setting times; however, it did not have a significant effect on the peak exotherm temperature.

Bone Cements↗
PubMed2000

Stiffness, viscosity, and upper-limb inertia about the glenohumeral abduction axis.

To evaluate the dynamic properties of the shoulder and understand how they are controlled by the central nervous system, glenohumeral-joint stiffness and viscosity and upper-limb inertia were quantified under various levels of muscle contraction in seven healthy human subjects. Through a cast attachment, the upper limb was perturbed in a precise pattern by a computer-controlled servomotor to manifest the dynamic properties of the joint. The recorded joint position and torque were used to estimate joint stiffness and viscosity and upper-limb inertia. With moderate muscle contraction, the stiffness and viscosity increased several fold. A stiffer shoulder joint associated with stronger muscle contraction made the shoulder more stable and protected it from potential injuries during strenuous tasks. Joint viscosity, especially the stronger viscous damping associated with more strenuous contraction, smoothed shoulder movement and stabilized the joint. From the control viewpoint, the glenohumeral joint responded to the central nervous system more quickly with increasing muscle contraction, which was useful during strenuous tasks. On the other hand, the central nervous system controlled stiffness and viscosity synchronously so that it dealt with only a nearly constant damping ratio of the joint over various levels of contraction, which simplified its task substantially. This approach quantified the dynamic and static properties of the shoulder under various levels of contraction more accurately and completely than a manual test, and it can potentially be used to evaluate changes in these properties caused by musculoskeletal injuries and their surgical treatments.

Adult↗
PubMed1975

Viscosities of acacia and sodium alginate after sterilization by cobalt-60.

Acacia and sodium alginate powders were sterilized by cobalt-60 irradiation to a total dose of 2.5 Mrad with no increase in residual radioactivity of the gums as a result of the treatment. Viscosity measurements showed an 11% reduction in the viscosity of acacia in water and a 16% decrease in the intrinsic viscosity in barium chloride solution due to the irradiation. Viscosities of sodium alginate solutions in 0.1 N sodium chloride showed a 70% decrease in intrinsic viscosity, indicating changes in the molecular structure corresponding to degradation to 30% of the original degree of polymerization. This dose of gamma-radiation from cobalt-60 is not an appropriate method of sterilization for these gums.

Acacia↗
PubMed1997

Cell type and spatial location dependence of cytoplasmic viscosity measured by time-resolved fluorescence microscopy.

Information on the cell type and spatial location dependence of cytoplasmic viscosity would be very useful in understanding some of the processes occurring in the cell. For this purpose, fluorescent dye kiton red (sulforhodamine B) was loaded into a variety of cells such as Swiss 3T3 fibroblasts, human mononuclear cells, Sarcoma-180 tumor cells, Chinese hamster ovary cells, plant cells from Digitalis lanata, stamen hair cells of Tradescantia, and guard mother cells of Allium cepa. Space-resolved measurements of cytoplasmic viscosity were carried out by using an experimental set-up wherein a picosecond laser system was coupled with an epifluorescence microscope. The spatial resolution of this set-up was approximately 1.0 micron, and reliable dynamic fluorescence measurements could be obtained from 10(2) to 10(3) fluorescent molecules. Fluorescence lifetime measurements showed that a large fraction (approximately 70%) of kiton red was in the free form. Fluorescence anisotropy decay of kiton red in cells was analyzed by a two population (free and bound) model. The microviscosity of cytoplasm was estimated from the anisotropy decay kinetics of the free probe. It was found that the cytoplasmic viscosity is dependent on both the cell type and spatial location within a cell. Furthermore, both the average value of viscosity and spatial variation within a cell were larger in the plant cells when compared to the animal cells. Model studies in various simpler systems have shown that the higher viscosity observed in some part of the cell could be due to either physical restriction and/or the presence of high concentrations of small solutes and macromolecules.

3T3 Cells↗
PubMed2000

Aluminum modifies the viscosity of filamentous actin solutions as measured by optical displacement microviscometry.

A microtechnique has been developed that is capable of measuring the viscosity of filamentous actin (F-actin) solutions. This method, called optical displacement microviscometry (ODM), was utilized to determine the changes in viscosity of solutions of rabbit muscle, human platelet, and maize pollen actin when measured in the absence and presence of aluminum. Measurements demonstrated that the viscosity of the different actin solutions decreased with aluminum concentration. In contrast, increases in viscosity were observed when aluminum was added to F-actin solutions containing filamin (chicken gizzard), a protein that bundles actin filaments. Confocal fluorescence imaging of pure actin solutions in the presence of aluminum showed a disrupted actin network composed of fragmented actin filaments in the form of small aggregates. In contrast, in the presence of filamin, aluminum promoted the formation of thicker actin filaments. These measurements demonstrate that aluminum can affect actin filaments differentially depending on the presence of an actin-binding protein. In addition, a strong correlation is observed between the changes in viscosity as measured by ODM and the thickness and assembled state of bundles of actin filaments.

Actins↗
PubMed1993

Antifreeze glycoproteins increase solution viscosity.

A new microsensor that can analyze microliter volume samples was used to measure the viscosity of aqueous solutions of antifreeze glycoproteins as a function of temperature and concentration. The results show that at physiological concentrations which naturally occur in the fish, the antifreeze proteins significantly increase aqueous solution viscosity. The probability for ice nucleation is inversely proportional to viscosity. Therefore, the increased viscosity could explain, in part, reports on the beneficial effects of antifreeze glycoproteins during cryopreservation by vitrification. Reducing the probability for ice nucleation could be also beneficial for the survival of cold-water fish in their natural habitat. Millimolar concentrations of antifreeze proteins increase aqueous solution viscosity to values comparable with those of conventional cryoprotectants in molar concentrations.

Animals↗
PubMed2000

Pharmacological concentrations of arginine influence human whole blood viscosity independent of nitric oxide synthase activity in vitro.

l-Arginine, the natural precursor of NO, is infused in patients to restore endothelial function. Concentrations up to 7.5 mM l-arginine have been measured after parenteral administration. We investigated whether such high concentrations of amino acids influence blood viscosity in vitro. Incubation of whole blood from healthy volunteers with l-arginine, d-arginine, which has no effect on stereospecific NO synthases (NOS), the NOS substrate L-AME, the NOS inhibitor L-NNA, the amino acids l-lysine and l-glutamic acid, and finally NaCl dose-dependently decreased (up to 30% at 10(-2) M) low shear viscosity, which is primarily determined by erythrocyte aggregation. In contrast, the lipophilic NOS inhibitor L-NAME had no effect on low shear viscosity. All molecules failed to influence high shear viscosity, which is primarily determined by red cell deformability, and the erythrocyte shape remained unaltered. We conclude that high concentrations amino acids may decrease blood viscosity at low shear rate independent of NOS activity. This effect may contribute to the improved blood flow after intravascular administration of l-arginine.

Adult↗
PubMed1977

Gastric mucus viscosity and peptic ulcer.

The following observations have been made: 1. The viscosity of a substance as complex as mucus requires study at different rates of shear and shear stresses. 2. Visible gastric mucus behaves as a pseudoplastic substance. 3. Duodenal ulcer patients have a higher gastric mucus viscosity than controls. 4. Pentagastrin stimulation in duodenal ulcer patients leads to the secretion of gastric mucus of low viscosity. 5. This decrease in the viscosity of gastric mucus on pentagastrin stimulation does not occur in patients with gastric ulcer. 6. Truncal vagotomy leads to an increase in the viscosity of gastric mucus under basal and stimulted conditions.

Duodenal Ulcer↗
PubMed1984

Comparative evaluation of blood viscosity in diabetic retinopathy.

The viscosity of the whole blood, plasma and serum, haematocrit and plasma fibrinogen were studied in diabetic patients with (DR) and without (D) retinopathy and in non-diabetic control subjects (C). Blood viscosity was significantly higher in diabetics than in controls. No significant differences in viscosity of the whole blood were found when various types of retinopathy were compared according to the severity of retinal damage. Plasma viscosity was significantly higher (P less than 0.01) than controls (C) only in diabetic patients with retinopathy (DR). Serum viscosity was significantly increased compared with controls (C) only in diabetic patients affected by proliferative retinopathy. Plasma fibrinogen was significantly higher than controls (C) both in diabetics with retinopathy (DR) and without retinopathy (D). Haematocrit did not show a significant difference in the three groups considered (C, D, DR).

Adult↗
PubMed1991

The release of gentamicin after total hip replacement using low or high viscosity bone cement. A prospective, randomized study.

Low viscosity bone cement is expected to give improved long term fixation of prosthetic components by increased intrusion into cancellous bone. Fixation is more difficult to achieve after revision for infection because of the inferior quality of the bone. We have compared the amount of gentamicin released from high viscosity and low viscosity bone cements in 41 patients undergoing total hip replacement. The concentration of gentamicin in serum and the wound secretion, and the amount recovered from the urine, was about three times higher for low viscosity cement. A possible explanation for this is an increase in surface area of the cement body because of improved intrusion of cement into bone. The improved mechanical fixation and the high concentration of gentamicin of the bone cement interface favours the use of low viscosity cement, especially in revision for deep infection.

Aged↗
PubMed1995

Elaboration of amylase activity and changes in paste viscosity of some common Indian legumes during germination.

The effect of germination upto 120 hours on malting loss, amylase activity and viscosity of nine common Indian legumes was investigated. The amylase activity increased on progressive germination in all legumes, the increase being particularly high for green gram, horse gram, moth bean and black gram. Malted samples had lower cooked paste viscosity than native ones. Samples with high amylase activity exhibited proportionately lower viscosity. Maximum reduction in viscosity was observed in green gram, followed by moth bean, horse gram, black gram and cowpea within 48 hours of germination. Malting losses ranged between 12 to 27 percent over a period of 48 hours in all legumes. Germination beyond 48 hours resulted in considerably higher malting losses without much effect on viscosity.

Amylases↗
PubMed1979

Influence of clofibrate on blood viscosity in primary hyperlipoproteinemia.

In patients with primary hyperlipoproteinemia (23 patients type II a and II b, 13 patients type IV), changes in lipoprotein concentrations (lipid fraction), fibrinogen concentrations, in kinematic serum and plasma viscosity (determined by means of a capillary viscosimeter) and changes in relative apparent viscosity at shear rate 46 s-1 and 115 s-1 (determined by means of a plate-cone-viscosimeter) were measured before and after a clofibrate therapy (2 X 1 g/day) lasting for 7 to 9 weeks. Serum and plasma viscosity was lowered significantly in both types II and IV. The apparent viscosity decreased at shear rate 46 s-1 in type IV, whereas it remained unchanged in type II. Moreover, there exists a qualitative correlation between changes in serum viscosity and changes in lipoprotein concentration. Fibrinogen concentration remained unaltered.

Blood Viscosity↗