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PubMed1978

Peripheral circulation in the newborn: interaction of peripheral blood flow, blood pressure, blood volume, and blood viscosity.

Peripheral blood flow and systolic blood pressure (strain-gauge plethysmograph), blood volume (Evans blue) and whole blood viscosity (cone-plate viscometer) have been measured in 66 premature and full-term infants 6 to 144h of age. Blood flow and blood volume were moderately decreased in the infants with respiratory distress. Highly significant (P less than 0.001) correlations were found between blood flow and blood volume (r = 0.77), blood pressure and blood volume (r = 0.50), peripheral resistance and blood volume (r = -0.44), blood flow and blood pressure (r = 0.50), blood flow and peripheral resistance (r = -0.67), peripheral resistance and blood viscosity (r = 0.45), and blood viscosity and haematocrit (r = 0.86). There was no correlation between peripheral blood flow and blood viscosity. However, at given blood volume, peripheral blood flow decreased with increasing blood viscosity. These results indicate that in newborn infants peripheral blood flow, blood pressure and peripheral resistance are influenced by blood volume, but also depend on blood viscosity.

Blood Circulation↗
PubMed1986

Regulation of liver cell ganglioside composition by extracellular fluid viscosity.

The viscosity of plasma and extracellular fluid has been shown to be a regulator of lipoprotein production both in cultured hepatocytes and in vivo. The possibility that this extracellular effect on cell function involves modulation of cell surface membrane components was examined. In the present work, we studied the effect of medium viscosity on liver cell gangliosides known to be involved in various membrane functions and to be located predominantly at the cell surface membrane. Cultivation of isolated hepatocytes as primary cultures markedly reduced the ganglioside content, but this reduction process was attenuated by increasing the viscosity of the culture medium. Elevation of extracellular fluid viscosity inhibited the degradation of the cell gangliosides and secretion of lysosomal enzymes involved in ganglioside degradation. The cellular activity of these enzymes as well as the activity of enzymes involved in ganglioside synthesis, CMP-NANA:GM1 sialyltransferase, CMP-NANAP:GM3 sialyltransferase and UDP-galactose:GD2 galactosyltransferase, were not affected by modulation of the extracellular medium viscosity. It is proposed that the modulation of cell ganglioside content by extracellular fluid viscosity is due to an effect on enzymes involved in ganglioside catabolism.

Acetylglucosaminidase↗
PubMed1997

Oral sensory discrimination of fluid viscosity.

This study was designed to investigate the ability of normal young adult volunteers to sensorially identify Newtonian fluids of specified viscosities. Twenty subjects, 10 men and 10 women between the ages of 18 and 29 years participated. Seven stimuli, consisting of combinations of corn syrup and water, with viscosities ranging from 2 to 2,240 centipoise (cP) were prepared and characterized using a coaxial rotational viscometer. Subjects were presented with two anchor stimuli representing the extremes of the range of viscosities as a basis from which the experimental stimuli were judged. The seven experimental stimuli were randomly presented to each subject 10 times. The accuracy with which the subjects identified the viscosity of the fluid was significant at p < 0.01. The pattern of response was not significantly different across subjects nor gender. There were no differences in performance throughout the duration of the study. The repeat presentation of the anchor points did not significantly affect performance. Further research on oral perception of viscosity, and the processes that mediate changes in swallow physiology resulting from changes in viscosity is required.

Adult↗
PubMed2003

The influence of cement viscosity on the early migration of a tapered polished femoral stem.

It is unclear whether it is best to use high-viscosity or low-viscosity cement for fixation of total hip replacement (THR) femoral components. This study examines the influence of cement viscosity on the migration of the Exeter femoral component using roentgen stereophotogrammetric analysis (RSA). Simplex, CMW1 and CMW3 G cements were examined in a total of 46 patients over a 12-month period. The overall pattern of migration for all cohorts was one of subsidence and rotation into valgus. There was no significant difference in any aspect of migration between the groups. In vitro studies demonstrate that low-viscosity cement forms a more stable bone-cement interface. Several groups have examined the in vivo effect of cement viscosity on stem longevity with conflicting results. For a polished, tapered implant that is designed to subside, cement viscosity does not influence the 1-year migration, and it is therefore unlikely to affect long-term outcome.

Aged↗
PubMed2000

The effect on sound generation of varying both gas flow rate and the viscosity of sputum-like gel in a simple tubular model.

Gas flows of 2, 3, and 4 L/min were directed through a sputum-like gel with viscosities of 100, 150, and 200 P and placed in a tube similar in diameter to a human segmental bronchus (4 mm), which was immersed in a bath of water. The sound produced by gas flow through the gel was recorded with a hydrophone. Sound data were subjected to time-expanded waveforms and fast Fourier transform (FFT) analysis. This study demonstrated that the number of crackles generated was directly related to the flow rate and inversely related to gel viscosity. The initial deflection width (IDW), two-cycle duration (2 CD), and peak-to-peak amplitude of crackles were significantly affected by the gas flow rate but not the viscosity of the gel. A lower gas flow rate generated crackles with longer IDW and 2 CD, but higher gas flow rates generated crackles with higher amplitude. Peak sound intensity measured from FFT increased as flow rate increased but decreased as the viscosity of the gel increased. At low gas flows, no gel-induced crackle sound was generated within the data capture window when the most viscous gel was examined. A digital video image of gas flow through the gel was captured, and this confirmed the absence of bubbles or slug formation at low flows through 200 P gel during the 3 seconds of data acquisition. This study describes some characteristics of crackles generated from different combinations of gas flow and gel viscosity and suggests that "coarse crackles" results from the explosion of gas bubbles in pulmonary secretions. Health care practitioners should consider the combined effect of rate of inspiratory gas flow and sputum viscosity during auscultation of patients' lungs.

Bronchi↗
PubMed2006

Oral and oropharyngeal perceptions of fluid viscosity across the age span.

Research demonstrates that varying sensory input, including the characteristics of a bolus, changes swallow physiology. Altering the consistency of fluids is a common compensatory technique used in dysphagia management to facilitate change. However, it is not known what variations in viscosity can be perceived in the oral cavity or oropharynx or if age affects oral and oropharyngeal perceptions of fluid viscosity. This study aims to establish the ability of normal adults to perceive fluid viscosity in the oral cavity and oropharynx and to determine if, within this population, there are age-related changes in oral and oropharyngeal perceptions. Sensitivity was established by deriving the exponent for the psychophysical law for fluid viscosity in both the oral cavity and the oropharynx, using modulus-free magnitude estimation with Newtonian fluids of corn syrup and water. Sixty normal volunteers, aged 21-84 years, participated. Results indicate that the exponent for oral perception of fluid viscosity was 0.3298, while for oropharyngeal perception it was 0.3148. Viscosity perception deteriorates with increasing age. Men exhibited a more marked deterioration in sensitivity than women. This study contributes to the literature on oral and oropharyngeal perceptions and on aging. The results provide a basis for work with individuals with dysphagia.

Adult↗
PubMed1984

Whole blood viscosity as a determinant of cardiac hypertrophy in systemic hypertension.

The relationships among blood pressure (BP), blood viscosity and echocardiographic left ventricular (LV) muscle mass were evaluated in 24 patients with essential hypertension and in 13 normotensive control subjects. LV mass was greater in the hypertensive patients than in the control subjects (225 +/- 69 vs 170 +/- 31 g, p less than 0.02) as was blood viscosity at a shear rate of 104 sec-1 (4.7 +/- 0.1 vs 4.3 +/- 0.2 cp, p less than 0.005). Among the hypertensive patients, LV mass was most closely related to viscosity at 104 sec-1 (r = 0.80, p less than 0.001), whereas only weak correlations were found between LV mass and systolic or diastolic BP (r = 0.45, p less than 0.05 for both). The 14 hypertensive patients with normal LV mass had viscosity similar to that in control subjects (4.5 +/- 0.3 vs 4.3 +/- 0.2 cp), whereas viscosity was consistently increased (5.0 +/- 0.4 cp, p less than 0.02) in hypertensive patients with LV hypertrophy. Thus, increased blood viscosity may be a determinant of or a response to hypertensive cardiac hypertrophy.

Adult↗
PubMed1980

Increased blood viscosity in young women using oral contraceptives.

Blood viscosity and its major determinants (hematocrit, plasma fibrinogen, and plasma viscosity) were measured in 25 men, 25 women who were not using oral contraceptives, and 25 women who had been using oral contraceptives for at least 3 months. Mean blood viscosity and hematocrit were significantly higher in women using oral contraceptives than in women who were not (p < 0.001), and use of oral contraceptives abolished the normal sex difference in blood viscosity and hematocrit. After correction to a standard hematocrit of 45%, blood viscosity was still higher in users or oral contraceptives, as was plasma fibrinogen (p < 0.05). Plasma viscosity was not significantly increased in users of oral contraceptives.

Adolescent↗
PubMed1993

Longitudinal associations between plasma viscosity and cardiovascular risk factors in a middle-aged French population.

A recent prospective study has suggested that increased plasma viscosity may be associated with higher risk of coronary heart disease. A longitudinal approach was used to investigate associations between plasma viscosity and conventional risk factors in an apparently healthy French population aged 45-56 years (637 men and 431 women) over a 2-year follow-up period. In univariate analysis, change in plasma viscosity was significantly related to changes in smoking status, systolic and diastolic blood pressure, gamma glutamyl transferase (gamma GT), body mass index and triglycerides only in men, and to changes in total cholesterol, low-density lipoprotein (LDL) cholesterol and apolipoprotein (apo) B in both sexes. Change in plasma viscosity was also significantly associated with changes in fibrinogen and hemoglobin levels in both sexes. No association was found with age, high-density lipoprotein (HDL) cholesterol or apo A1 in both sexes, or with changes in smoking and menopausal status in women. In multiple stepwise regression analysis, independent determinants of change in plasma viscosity were changes in smoking status, systolic blood pressure, gamma GT, total cholesterol, fibrinogen and hemoglobin in men, and changes in fibrinogen and apo B in women. These results strengthen the hypothesis that increased plasma viscosity may be one of the mechanisms linking conventional risk factors to the risk of cardiovascular disease and suggest that its decrease may be obtained by appropriate life-style changes.

Age Factors↗
PubMed1988

Determination of whole blood apparent viscosity: experience with a new hemorheologic technique.

A new experimental technique of determining apparent blood viscosity at low rates of shear using a porous bed viscometer (PBV) was evaluated in a study of 213 blood samples from 43 mongrel dogs. Viscosity was measured over a wide range of hematocrit (Hct), 6.5-51%, and plasma fibrinogen (Fib), 11-597 mg%, levels significantly altered (P less than 0.0005) by isovolemic hemodilution. Viscosity was highly correlated with Hct and Fib (r = 0.89), which confirmed the results of previous investigations. An important finding was the ability of the PBV to detect the non-Newtonian behavior of whole blood that occurs under low shear conditions at higher Hct levels. In a subgroup of 10 animals, viscosity was also measured by a precision cone and plate viscometer (CPV) at various shear rates. Although the PBV and CPV measurements showed excellent correlation (r = 0.92), a marked nonlinear deviation of the plotted data from the regression of Hct vs viscosity measured by the PBV at Hct levels greater than or equal to 30% was noted which could not be identified by the CPV. The PBV technique affords valid measurements of the apparent viscosity of normal canine blood. Moreover, the device is apparently sensitive to the anomalous rheologic properties of whole blood attributable to shear-dependent changes in red blood cell aggregation that can become physiologically significant in low-flow states.

Animals↗
PubMedDate not supplied

Blood viscosity in chronically hypoxic rats: an effect independent of packed cell volume.

We compared apparent blood viscosity, measured with a cone-plate viscometer, in normoxic and chronically hypoxic rats. All comparisons were made at equal packed cell volume (PCV) and shear rate conditions. Apparent viscosity of whole blood from the hypoxic rats was significantly lower than that from normoxic littermates and was similar to that of young rats. Apparent viscosity of red cells from hypoxic rats suspended in phosphate buffered saline remained lower than that from the normoxic rats. When blood cells from the hypoxic rats were suspended in plasma from normoxic rats, apparent viscosity was lower than when blood cells from normoxic animals were suspended in plasma from hypoxic rats. The lower viscosity of the blood from hypoxic rats appears to be associated with characteristics present in newly generated red cells. The reduced apparent viscosity of blood in hypoxic rats may partially compensate for the increase in PCV, at least during the early stages of hypoxia.

Aging↗
PubMed1983

Increase in blood viscosity due to alcohol drinking.

To elucidate the effects of alcohol on thrombotic diseases we focussed on blood rheology which is one of the most important factors of blood flow. We measured the viscosity of whole blood and plasma of 18 healthy volunteers (11 males and 7 females) before and after drinking at a dinner party. There were significant increases in whole blood viscosity (7.4%, P less than 0.005) and plasma viscosity (3.0%, P less than 0.005) after drinking. Judging from the significant correlations between changes in blood viscosity and changes in variables related to hemoconcentration, the ability of alcohol to increase blood viscosity is considered to be due mainly to hemoconcentration. Alcohol itself did not increase whole blood viscosity in vitro at concentrations of 0.1, 0.2, 0.3 and 0.4% (w/v).

Adult↗
PubMed1987

Relationship between blood viscosity and cerebral ischemia after surgical treatment of ruptured intracranial aneurysms.

To determine the role of blood viscosity after surgical treatment of ruptured intracranial aneurysms, the relationship between blood viscosity and clinical condition was examined in 17 patients. A total of 213 blood samples were analyzed. An inverse correlation was found between blood viscosity and level of consciousness; in addition, blood viscosity was higher when focal neurologic deficit was observed. Hematocrit was similarly related to clinical condition, although the correlations observed were less strong. Postoperative plasma viscosity was higher in patients with focal neurologic deficit. Regular blood viscosity measurements are of value in patients at risk for developing cerebral ischemia.

Blood Viscosity↗
PubMed1994

Coupling between external viscosity and the intramolecular dynamics of ribonuclease T1: a two-phase model for the quenching of protein fluorescence.

Our recent equilibrium dialysis studies showed that proteins are able to interact preferentially with acrylamide (Punyiczki et al. (1993) Biophys. Chem. 47, 9-19). The presence of considerable amounts of acrylamide--albeit weakly bound--in the protein volume, coupled with the failure of a simple gating model of quenching to rationalise viscosity dependence of the quenching of tryptophan (Trp) fluorescence in Ribonuclease T1 (RNase T1) has prompted us to explore a new model, the two-phase model for quenching. According to this model, the dynamic quenching is accomplished by quencher molecules already in the protein phase at the moment of excitation. Some of the molecules may, at this moment, form an encounter complex with the fluorophore and thus be responsible for the observed static contribution. We use the rate equation derived from our model to study the viscosity dependence of acrylamide quenching of Trp fluorescence in RNase T1. The model allows us to separate co-solvent effects: the chemical effect on the protein and on the distribution of quencher molecules between the bulk and the protein phases and, further, the viscosity effect due to coupling between the bulk viscosity and the local friction affecting intramolecular fluctuations of the protein matrix. We express local friction in terms of bulk viscosity, eta, and a coupling constant kappa (friction = eta kappa). Addition of glycerol up to 65% is characterised by a kappa of 0.50. The viscosity dependence of the apparent bimolecular quenching constant is a combination of two compensating effects: changes in chemical activity and changes in patterns of structural fluctuations.

Acrylamide↗
PubMed1992

Influence of experimentally elevated blood viscosity on the auditory nerve-brainstem evoked response and threshold.

Blood viscosity, due to its effect on blood flow, is one of the determinants of oxygen delivery. Therefore the influence of elevated blood viscosity on hearing was studied in rats using the auditory brainstem response (ABR) threshold, wave 1 latency, brainstem transmission time (BTT) and wave 1/4 amplitude ratio. Whole blood viscosity (WBV) was elevated by 15-21% in two different ways: elevating the hematocrit (Polycythemia) by acclimation in a hypobaric chamber, or elevating the plasma viscosity by infusing a solution of Polyvinylpyrrolidone-360 (PVP). ABR was recorded before and 24 h after the blood viscosity was elevated, so that each rat served as its own control. Paired t-tests showed that there was no statistically significant difference in the ABR parameters in each of the groups as a consequence of blood viscosity elevation. In conclusion, the elevation of WBV to this degree for this duration, using two different techniques had no effect either on the function of the auditory nerve and the more peripheral sites, or on the central auditory pathway as studied by ABR.

Analysis of Variance↗
PubMed1987

The effect of donor age on the flow properties of blood. Part I: Plasma and whole blood viscosity in adult males.

The relationship between blood viscosity and age was studied using heparinized blood samples obtained from 50 normal male blood donors between the ages of 20 and 65 years. There was a slight but significant decline in packed cell volume (hematocrit) with age. Plasma viscosity showed no significant variation with donor age, but the viscosity of blood samples standardized to a packed cell volume of 45 ml/dl showed an increase as the age of the donor rose. The age-related trend to a higher viscosity was present at shear rates below 46 s-1, but not at higher shear rates. This shows that with age there is a rising trend in the red cell contribution to blood viscosity, which is not dependent on the packed red cell volume; this component increases across a wide age range in early and middle adult life, and is not a characteristic appearing exclusively in later age periods. The tendency for the viscosity trend to be greater at lower shear rates indicates increased shear thinning in blood obtained from older subjects, the cause of which may be either diminished red cell deformability in these subjects, or an increased tendency to form aggregates at low shear rates.

Adult↗
PubMedDate not supplied

Elevated blood viscosity in alloxan diabetic dogs and experimentally galactosemic dogs.

Blood viscosity was investigated in alloxan-diabetic dogs and in dogs made experimentally hyperglycemic by a galactose-rich diet. The diabetics were prospectively assigned to levels of glycemic control ranging from poor to good. After up to 5 years of study, the blood viscosity of hyperglycemic diabetic animals was significantly greater than normal at both high (100 sec-1) and low (0.1 sec-1) shear rates. Blood viscosity at the low shear rate correlated closely with fibrinogen concentration, (r = 0.75; p less than 0.02) but not with HbA1 concentration (r = 0.14) in the diabetics. Galactosemic animals likewise had elevated blood viscosity at the low shear rate, but the correlation of viscosity with fibrinogen concentration in those animals was not statistically significant (r = 0.42). Plasma viscosity tended to be elevated in both diabetes and galactosemia, but not to a statistically significant degree.

Animals↗
PubMed2005

Social, behavioral, and metabolic determinants of plasma viscosity in the Whitehall II Study.

PURPOSE: To examine the social, biological, and metabolic associations of plasma viscosity in a large epidemiological study. METHODS: Plasma viscosity was measured from 4548 men and 1837 women that took part in the fifth phase of the Whitehall II Study (1997-1999). Employment grade was used as a measure of social position. RESULTS: A strong inverse relation between employment grade and plasma viscosity was evident (p < 0.0001). This employment grade gradient was apparent overall, and among non-smokers and when participants with poor health were removed from the analyses. Plasma viscosity was associated with a number of biological factors that are themselves socially determined, including fibrinogen (p < 0.001), triglycerides (p < 0.001), fasting insulin (p < 0.001), and height (p < 0.001). Associations with smoking and alcohol intake were apparent in women. In men a U-shaped curve was apparent such that those drinking between 11 and 24 units/week had the lowest plasma viscosity. Alcohol intake, physical activity, and smoking explained 18% of the grade gradient in men and 40% in women while the biological factors examined accounted for 35% in men and 40% in women. CONCLUSION: There is a grade gradient in plasma viscosity which was not fully explained by health related behaviors or measured risk factors for CHD. These data suggest that additional factors that contribute to the rheological properties of plasma may contribute to the explanation for social inequalities in cardiovascular disease.

Adult↗