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At least 667 records · Page 37Linked to original sources
PubMed1978

[Viscosity changes of zinc phosphate cements in setting process (author's transl)].

A better understanding of setting process of zinc phosphate cements is important to obtain optimum conditions of manipulation. Viscosity changes of zinc phosphate cements in setting process were investigated using a rotational viscometer in various conditions. The results obtained were as follows. 1) The viscosity of the cement mixture increased exponentially as a function of time. 2) The setting process of the cements was characterized by two parameters, the coefficient of setting speed and the setting time. The coefficient of setting speed was defined as the slope of the linear portion of log viscosity versus time curve, and the setting as the time required to reach a certain level of viscosity after the start of the mixing. 3) Shear rate was observed to affect on the time-related changes of viscosity. As the shear rate increased, the coefficient decreased and the setting time increased. These changes were more remarkable in the lower range of shear rate. 4) The coefficient of setting speed was found to be dependent on environmental temperature in accordance with Arrhenius' low. 5) Apparent activation energy calculated 16.41 kcal/mol by Arrhenius' equation. The coefficient increased by a factor of 2.6, when the temperature was raised from 20 degrees to 30 degrees C. 6) A decrease of the P/L ratio caused the logarithm of the coefficient to increase linearly and the setting time to decrease. 7) All the four commerical zinc phosphate cements tested showed different values of both the coefficient and the setting time.

Time Factors↗
PubMed1988

Blood viscosity in ocular hypertension.

Blood viscosity and its determinants were measured in 27 patients with primary open-angle glaucoma, 15 patients with ocular hypertension and 18 healthy control subjects matched for sex, blood pressure and smoking habits. The mean blood viscosity value was significantly higher in the glaucoma group than in the two other groups at all three shear rates studied; there was no difference in viscosity between the hypertension group and the control group. The mean hematocrit value was significantly lower in the hypertension group than in the two other groups. The results suggest that blood viscosity may contribute to nerve damage in patients with primary open-angle glaucoma. The low hematocrit observed in the patients with ocular hypertension may, by contributing to low viscosity, in some measure protect this group from optic nerve damage.

Blood Viscosity↗
PubMed1986

[Blood viscosity in osteonecrosis of the femur head].

The viscosity of total venous blood was studied in 21 patients with osteonecrosis (ON) of the femoral head, and compared with the viscosity of 43 control patients, blood donors of the same mean age, and with the viscosity of 17 patients suffering from hip arthrosis. Measurements were carried out on a rotary resistance meter with coaxial cylinders. Along with the viscosity, certain biological, hematological and biochemical parameters, making up the main macro-rheological parameters, were measured in the same blood samples. Statistical analysis of the results confirms the hyperviscosity of total venous blood in patients with ON of the femoral head. This hyperviscosity does not seem correlated with the biological parameters studied, contrary to the viscosity of the blood in the control group. It is likely secondary to other factors, intrinsic to ON, and especially microrheological factors.

Adult↗
PubMed1986

Plasma viscosity elevations with simulated weightlessness.

Bed rest studies which simulate weightlessness have demonstrated marked changes in the state of hydration of subjects as well as decrements in aerobic capacity. These two phenomena may be linked through increases in blood viscosity which is altered by a loss of free water and which, in turn, influences blood flow needed for aerobic muscular work. This study examines changes in the rheologic properties of blood which attend changes in plasma volume with bed rest in humans and correlates these changes with alterations in aerobic capacity. Eight healthy human subjects were studied on the 6th day of bed rest during two consecutive 10-d bed rest periods separated by a 14-d recovery interval designed to simulate the flight-layover schedule of shuttle astronauts. Plasma viscosity was measured with a Wells-Brookfield viscometer, plasma volume by dye dilution, and maximal aerobic capacity (VO2max) by recumbent cycle ergometry. Bed rest resulted in significant increases in hematocrit and in total plasma protein concentration and fibrinogen concentration, both of which contribute to an elevation in plasma viscosity. The greater than 20% increase in fibrinogen concentration was much greater than could be explained by hemoconcentration. VO2max decreased significantly in the first but not the second bed rest cycle. In many individuals, a decrease in plasma volume and aerobic capacity was coupled with elevated plasma viscosity and hematocrit; however, significant correlations between these variables were lacking. Although significant rheologic perturbations do occur with bed rest, in this study, blood viscosity elevation failed to directly correlate with the reduction in VO2max.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1979

Dynamic study of the blood viscosity of insulin-dependent diabetics by means of an artificial pancreas.

The blood viscosity of 15 insulin-dependent, poorly controlled, diabetic subjects was determined by using a microviscosimeter at low shear rates, with cylindrical cuvettes of the Couette type. It was found that the blood viscosity of these diabetics was more elevated than that of control patients (p less than 0.001). In ten diabetics, the return to a strict metabolic control over a period of more than 24 h by means of an artificial pancreas resulted in a significant systematic lowering of blood viscosity. These results suggest that the metabolic control of diabetes influences blood viscosity, and they underline the importance of an artificial pancreas for the dynamic study of the factors affecting blood viscosity during the course of diabetes.

Adolescent↗
PubMed1985

[Effects of reduction of blood viscosity at constant hematocrit on the cerebral blood flow].

It is well established that cerebral blood flow (CBF) is low in patients with high hematocrit and is high in anemic patients. An inverse relationship between CBF and hematocrit has been found. Furthermore, if hematocrit is reduced, CBF increases. There is some debate as to whether these observations are due to viscosity or to oxygen carrying capacity of the blood. In order to further elucidate this problem, CBF, blood viscosity and hematocrit were measured in 4 patients with paraproteinemias before and after paraproteins had been removed by plasmapheresis without changes in hematocrit. After plasmapheresis, blood viscosity significantly decreases and CBF increases by a mean of 24.4 ml/100 g/min. Mean arterial blood pressure and hematocrit were not influenced by plasmapheresis. These results indicate that blood viscosity is an important factor in determining CBF. This does not exclude the role of oxygen transport as an associated factor, but it is evident that oxygen transport and blood viscosity are independent variables in the control of CBF.

Blood Viscosity↗
PubMed1983

Blood viscosity and haemostasis in the nephrotic syndrome.

Blood viscosity and its major determinants (haematocrit, plasma viscosity and fibrinogen) as well as several haemostatic variables were measured in 21 patients with the nephrotic syndrome, and 21 controls matched for age, sex, smoking habit and serum creatinine. Blood viscosity was significantly increased in the nephrotic group, measured at a low shear rate (mean increase 41%, p less than 0.01) and at a high shear rate (mean increase 25%, p less than 0.01). Haematocrit was not significantly increased, but plasma viscosity was significantly higher (p less than 0.01), associated with increased plasma macroglobulins especially fibrinogen, which was increased to double the plasma concentration of the control group (p less than 0.01). Nephrotic subjects also had increased plasma levels of alpha 2-macroglobulin, factor VIII activity, factor VIII antigen and beta-thromboglobulin; differences in antithrombin III, fibrin degradation products, plasminogen, and platelet count were not significant. We suggest that increased blood and plasma viscosity may play a role in the vascular complications of the nephrotic syndrome.

Adult↗
PubMed1984

Relationship between paired plasma and serum viscosity and plasma proteins in the horse.

The relationship between paired plasma and serum viscosity measurements and plasma proteins, including fibrinogen, were compared in 106 horses with both normal and abnormal serum protein levels. There is a highly significant positive correlation between serum viscosity and total serum proteins and total globulin levels. The difference between plasma and serum viscosity correlated well with clottable fibrinogen concentration. Albumin levels showed a negative correlation with plasma and serum viscosity, globulins and fibrinogen. Simultaneous estimation of serum and plasma viscosity improves the diagnostic value of the latter test without appreciable increase in cost or time and should prove useful for screening large numbers of samples for the presence or absence of abnormal levels of globulins and, or, fibrinogen.

Animals↗
PubMed1984

[Measurement of sputum viscosity with the Jenssen viscometer].

The authors measured the viscosity of sputum with a Jenssen type capillary viscometer. The repeated assessment of the viscosity of the same sample of sputum showed that the results are reproducible and the instrument does not disrupt markedly the structure of the sputum. After measuring the viscosity of 35 patients with different types of pulmonary disease the authors state, in accordance with the data found in literature, that the measurement of the viscosity of sputum by itself cannot help in the differential diagnosis of pulmonary diseases. The authors suggest the determination of the Biochemical constituents of sputum to supplement the measurement of the viscosity of sputum.

Bronchitis↗
PubMed1981

Relationship between serum viscosity and intravascular IgA polymer concentration in IgA myeloma.

The relative serum viscosity (RSV) at 37 degrees C was measured at presentation in all 179 patients with IgA myeloma admitted to the IIIrd and IVth British Medical Research Council trials until January 1981. An elevated relative serum viscosity (greater than 1.7) was noted in 83%. Hyperviscosity, as defined by a relative serum viscosity greater than 5, was a comparatively rare presenting feature (5.0%). The relationship between relative serum viscosity and IgA polymer equivalent concentration was examined in 33 of the 179 patients, selected to cover a wide range of serum viscosity. A significant correlation was observed between the two parameters (rs=0.7928, P less than 0.001). The sera from two patients with marked serum hyperviscosity (RSV=9.51 and 9.76) were clearly distinct from this relationship. Protein aggregation appeared to be a major determinant in the development of serum hyperviscosity in these two patients.

Biopolymers↗
PubMedDate not supplied

Erythrocyte sedimentation, viscosity, and plasma proteins in disease detection.

In order to assess the relationships of erythrocyte sedimentation rates (ESR) and various acute phase reactants in diagnosing and following the remissions and exacerbations of various chronic diseases, multiple tests were performed on patients for whom an ESR was ordered. The Wintrobe and Westergren ESR, plasma and serum viscosity, hemoglobin, blood cell indices, fibrinogen, serum protein electrophoresis, triglycerides, and complement (C-3) were performed. A discussion of the relative merits of correcting the Wintrobe ESR by the Wintrobe anemia correction chart of the Hynes and Whitby method is presented. Although many significant correlations exist, only the Wintrobe and Westergren ESRs and plasma viscosity approached the same number of abnormal results. If the results of the Wintrobe and Westergren are combined 67 abnormal results are observed. The plasma viscosity exhibited a 10.4 percent false positive rate compared to the combined ESR's and a 6.0 percent false negative rate. The plasma viscosity was not only highly significantly correlated with the ESR's (P < < 0.001), but also with all acute phase reactants measured as well as total protein, albumin, and gamma-globulin. The plasma viscosity appears to give the best overall summation of the many non-specific changes observed in chronic disease.

Adolescent↗
PubMed1995

Effects of chemically-induced stress on blood viscosity of rabbits.

Disease-induced stress in a living system needs its characterization before quantification. We address this problem by studying the flow behaviour of blood of rabbits. The flow behaviour of rabbit blood, both normal and streptozotocin-induced diabetic was observed by plotting viscosity levels against known shear stress. The curves obtained from normal animals showed a curvilinear relationship between eta and tau, whereas the curves obtained from the blood of the induced diabetic animals showed a 'thixotropic' nature i.e. viscosity varies inversely with shear stress. The results obtained were (a) increased viscosity associated with increasing doses, (b) the lower the shear stress, higher was the viscosity and (c) significant variation of viscosity levels between normal and induced-diabetic rabbits observed by increased stress. The possible interpretation of the results in the light of rheological properties of blood is discussed.

Animals↗
PubMed1994

The viscosity of red blood cell membranes in patients with beta-thalassaemia.

The purpose of this work was to study the viscoelastic behaviour of the red blood cell membrane (RBCM) in cells from patients with beta-thalassaemia and to investigate whether the precipitated haemoglobin, which is one of the main features of thalassaemic syndromes, influences the membrane viscosity. RBCM viscosities were determined using the micropipet aspiration method. A negative pressure of about 50 Pa was applied in steps at the membrane surface so as to cause partial aspiration of the cell and the entry process was analyzed automatically by a TV-line analyzer. This analysis enabled estimation of the characteristic times (tau 1, tau 2) and corresponding values of the viscosity (eta 1, eta 2). Results were as follows: eta 1 = (1.87 +/- 0.55) microNs/m and eta 2 = (51.42 +/- 20) microNs/m for erythrocytes from normal donors; eta 1 = (3.97 +/- 0.98) microNs/m and eta 2 = (110.40 +/- 35) microNs/m for erythrocytes from patients. Inclusions (Heinz Bodies) were produced artificially in normal cells and the characteristic times (tau 1, tau 2) and corresponding viscosities (eta 1, eta 2) derived in the same manner. For three types of RBC containing increasing numbers of inclusions, the values were: eta 1 = (3.26 +/- 1.70) microNs/m and eta 2 = (77.33 +/- 46.96) microNs/m; eta 1 = (4.21 +/- 1.49) microNs/m and eta 2 = (129.60 +/- 47.90) microNs/m; eta 1 = (7.93 +/- 2.62) microNs/m and eta 2 = (206.60 +/- 93.19) microNs/m. It is concluded that the association of inclusion bodies with the membrane, either in disease or through artificial production, increases the membrane viscosity.

Adult↗
PubMed1994

[Significance of perioperative elevation of blood viscosity in patients with esophageal or cardiac carcinoma].

The blood viscosity of 21 patients with esophageal or cardiac carcinoma during preoperative period was measured and compared with that of 25 healthy persons. The results indicate that the blood viscosity in patients is higher than that in the control group (P < 0.001) immediately and one day after operation. Elevation of blood viscosity is not only related to myocardial infarction, but also may be one of the causes for the poor therapeutic effect in patients with carcinomas. It is suggested that proper measures should be taken to control the elevating blood viscosity in patients, especially the elderly ones during the perioperative period. Colloid fluid which is believed to increase blood viscosity should be avoided within the first two days after operation to prevent cardiac complications.

Aged↗
PubMed1977

[Experimental investigations on the effect of various doses of streptokinase on blood viscosity (author's transl)].

The decrease in blood viscosity induced by streptokinase (SK) in the present investigation in proportional to the streptokinase concentration up to a concentration of 2000 IE/ml blood. A maximum decrease in viscosity is attained with a dosage of between 200 and 300 IE/ml blood. The decrease in viscosity is already clearly detectable at 10 minutes at all investigated doses and is completed after 20 to 30 minutes. An increase in SK resistance delays the decrease in viscosity. Prevention of the decrease, however, only seems to occur with a very high SK resistance and a very low SK dosage (50 IE/ml blood). The optimum dosage of SK to achieve a maximum decrease in viscosity is 200 IE/ml blood.

Blood Viscosity↗
PubMed1996

Decreased blood viscosity and serum levels of erythropoietin after anti-hypertensive treatment with amlodipine or metoprolol: results of a cross-over study.

The increased viscosity of blood of hypertensive patients can be assumed to be a risk factor for the development of cardiovascular diseases. The aim of the present study was to elucidate whether anti-hypertensive treatment has any impact on blood rheology. Twenty patients with previously untreated hypertension who consecutively attended our outpatient hypertension clinic were included in this prospective, open, cross-over study. The patients were randomly selected to treatment with amlodipine or metoprolol. The anti-hypertensive therapy was switched after 4 months. Haemorheological and haemodynamic variables were measured with rotational viscometry and impedance cardiography, respectively. Fifteen and 16 patients could be evaluated after amlodipine or metoprolol treatment respectively. The mean blood pressure (BP) decreased from 159 +/- 22/105 +/- 7 to 139 +/- 21/91 +/- 6 mm Hg on amlodipine and from 162 +/- 22/104 +/- 5 to 145 +/- 24/90 +/- 8 mm Hg on metoprolol therapy. After amlodipine treatment, the total peripheral resistance index decreased whereas metoprolol treatment was accompanied by a decrease in the cardiac index. Decreases in whole blood viscosity, haematocrit and serum erythropoietin were found after amlodipine as well as metoprolol treatment. After amlodipine the plasma viscosity decreased and the erythrocyte deformability increased in the majority of patients. Plasma fibrinogen decreased after metoprolol treatment. Despite the differences in haemodynamic mechanisms underlying the decrease in BP, amlodipine and metoprolol exert beneficial effects on blood viscosity. Haemodilution and a decrease in serum erythropoietin may be factors underlying this decrease in blood viscosity.

Adult↗
PubMedDate not supplied

Neonatal whole blood hyperviscosity: the important factor influencing later neurologic function is the viscosity and not the polycythemia.

The neurologic outcome of 23 seven-year old children who had cord blood hyperviscosity was compared with that of children with normal cord blood viscosity in a randomised, controlled and blinded study. Viscosity was measured using a coaxial narrow-gap couette viscometer. Sixteen (69.6%) of the children with hyperviscous cord blood had a disability; this incidence being three times greater (22.7%) than in children whose cord blood was not hyperviscous (P < 0.01). In three children with cord-blood hyperviscosity, the disability was severe. No child had a severe disability with normal cord blood viscosity. Of the eight children whose cord blood was hyperviscous, but not polycythemic, six (75.0%) had a disability and in one child the disability was severe. These results demonstrate an association between cord blood hyperviscosity and later neurologic development. Cord studies are non-invasive and result in the rapid diagnosis of the neonatal hyperviscosity syndrome, so allowing earlier treatment. This may be crucial in altering the effects of hyperviscosity on the developing brain in the early neonatal period. Because the neurologic outcome of children was similar whether polycythemia was present or not, the prime factor was the viscosity and not the hematocrit level. We suggest it may be necessary to perform cord blood viscosity studies routinely.

Blood Viscosity↗
PubMedDate not supplied

[Blood viscosity analyzer].

An analyzer that determines blood viscosity at different shift speed has been designed. Its operation principle is based on the use of rotation viscosity measurement using a rotor freely floating in the sample. A blood sample is placed between the stationary thermostabilized measuring cylinder and a free floating rotor. The system creates a rotating magnetic field which makes the rotor rotate with a preset speed, determines shift stress, calculates the magnitude of viscosity and indicates it on the display. The magnitude of viscosity is proportional to the square of the current drawn in the windings of a stator, which divided by the rotational speed of a rotor. The analyzer provides viscosity measurements in the range of 0.7-14 mPa.sec at shift rate of 20-200 sec-1, the sample volume is less than 1 cm3. The device can be used for the diagnosis of the diseases whose pathogenesis microcirculatory and coagulative disorders play an important role in.

Blood Viscosity↗