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At least 955 records · Page 53Linked to original sources
PubMed1990

Branch retinal vein occlusion: the pathogenetic role of blood viscosity.

The pathogenesis of branch retinal vein occlusion has not been completely clarified. The role of abnormal blood viscosity in the appearance and evolution of the disease has recently been advocated. We studied 54 patients with long-standing branch retinal vein occlusion from a hemorrheologic point of view. Depending on the extension of retinal ischemia, two subgroups were identified. Hematocrit, blood and plasma viscosity, whole blood filterability, cell deformability, and fibrinogen levels were investigated. Thirty-five subjects of similar age, sex, and risk factors of diabetes and hypertension served as controls. Our results showed that blood viscosity is higher in patients with occlusion and particularly in those with severe retinal ischemia. Statistical analysis showed a direct correlation between blood viscosity and hematocrit.

Adult↗
PubMed1990

Reduction in blood viscosity by treatment with coenzyme Q10 in patients with ischemic heart disease.

The effects of coenzyme Q10 (CoQ10) on blood viscosity were studied in twelve patients (mean age 49 +/- 16 years) with ischemic heart disease. Twenty mg of CoQ10 was orally administered three times daily for two months (total dose 60 mg per day). Blood viscosity was measured with a cone-plate type viscometer at the shear rates of 37.5, 75, 150, and 375 s-1. Yield shear stress was calculated from Casson's plot. Blood viscosity decreased at each shear rate after the administration of CoQ10. Yield shear stress decreased significantly by the treatment with CoQ10. Hematocrit and fibrinogen were also measured, but showed no significant change. These results suggest that CoQ10 decreases the blood viscosity, i.e., improves the rheological properties of blood in ischemic heart disease.

Administration, Oral↗
PubMed1990

[Experimental studies of the so-called emulsification behavior of silicone oil: effect of viscosity].

The stability of intraocularly applied silicone oils plays an important role in their biocompatibility. The clinically used silicone oils are not a unique group of materials. There are important differences regarding viscosity and the amount of low molecular and ionic components. A sign of bioinstability of silicone oils is silicone oil emulsification. According to clinical experience and experimental studies, less viscous silicone oils seem to emulsify earlier then more viscous oils. Therefore, we investigated three highly purified polydimethylsiloxanes with defined physicochemical characteristics and viscosities of 1,000 cs, 5,000 cs and 10,000 cs for their in vitro stability. As detergents, we used fibrin, fibrinogen, gammaglobulins, acidic alpha-1-glycoprotein, very-low-density lipoprotein (VLDL), and serum. The oil with a viscosity of 1000 cs was the most unstable silicone oil whereas the oils of 5,000 cs and 10,000 cs reacted similarly. The most effective detergents were fibrin, fibrinogen and serum-causing emulsification for all silicone oils investigated whereas gamma-globulins, acidic alpha-1-glycoprotein and VLDL only emulsified the less viscous oil of 1,000 cs. Our results show the importance of viscosity for the stability of silicone oils and the effect of biologically potential detergents.

Drug Stability↗
PubMed1990

Effects of pentoxifylline administration on blood viscosity and leukocyte cytoskeletal function in patients with intermittent claudication.

We have previously shown that pentoxifylline, a drug used in intermittent claudication, causes depolymerization of actin in leukocytes in vitro. In this study we evaluated several parameters in peripheral blood obtained from 17 patients receiving pentoxifylline, before therapy and at 1 and 2 months after initiation of drug therapy. Total blood viscosity decreased at 1 month and was further reduced at 2 months. The plasma viscosity remained unchanged during the course of the therapy (1.770 +/- 0.147, 1.776 +/- 0.162, and 1.772 +/- 0.164 centipoise at 0, 1, and 2 months, respectively; mean +/- SD, n = 14 to 17). No changes were observed in stimulus-induced actin polymerization in granulocytes, concanavalin A-induced capping in granulocytes and lymphocytes, and anti-IgG-induced caps in lymphocytes, before and after therapy. Similarly, there was no difference in the magnitude of depolymerization caused by pentoxifylline when added in vitro. Thus none of the parameters altered by pentoxifylline treatment in vitro have been observed ex vivo in patients receiving this drug. However, the decrease in total blood viscosity along with unaltered plasma viscosity suggests that the rheology of the cellular elements is being affected by the administered drug. In addition to the direct effects on the cell membrane and the cytoskeleton, pentoxifylline may exert indirect effects through its inhibitory action on cytokine production. Subtle changes in a number of parameters in leukocytes, which taken alone fail to show demonstrable changes, might ultimately be responsible for the therapeutic benefit noted with pentoxifylline.

Actins↗
PubMed1989

[Study of pit and fissure sealants. The effect of viscosity of the sealants and type of the applicators on the administration time and the sealed area].

From the standpoint of the durability of the sealants, it is assumed that the sealants should be applied only to the bottom part of the pit and fissure to avoid marginal fracture and wear of the materials. Because of this, a minimum area for the sealant to be applied is required for a stable prevention of dental caries. The purpose of this study was to investigate the effect of viscosity of the sealants and various applicators in the techniques for minimum-area-sealing. Three sealants with various degrees of viscosity were applied to the stone models of a lower first molar by means of four types of applicators. Three operators conducting the experiment were a dentist with two years of experience, a dentist with one year of experience and a student. The time required for administration and the area of sealed pits and fissures were evaluated. The following results were obtained. 1. The sealants with a lower degree of viscosity revealed a shorter administration time and a narrower sealed area. 2. The applicators with thinner nozzles brought about a shorter administration time and a narrower sealed area. 3. The administration time did not exhibit significant differences among the operators, while the sealed area exhibited significant differences. 4. The longer the period of the clinical experience of the operator, the narrower the sealed area obtained. From the above results, it is recommended to select a sealant with low viscosity and utilize an applicator with a thin nozzle or a brush with a fine tip to obtain the minimum-sealing-area. Additionally, prior to the clinical trial, one should become acquainted with the characteristics of the sealant as well as the manipulation of the applicator.

Pit and Fissure Sealants↗
PubMed1989

[Erythrocyte filterability and relative viscosity in liver cirrhosis and chronic hepatitis].

Fifty patients with liver disease, of whom twenty-four had chronic active hepatitis and twenty-three had liver cirrhosis, were studied and compared with thirty-nine age- and sex-matched controls. Whole blood, plasma and their relative viscosities and the main factors capable of influencing these parameters (Ht, fibrinogen, triglycerides, cholesterol, plasma glucose, total proteins and gamma-globulins) were tested. Whole blood filterability time and velocity of red blood cells (VRBC) were also determined. In ten patients deformability of erythrocytes was determined both in whole blood and in suspensions of RBC in buffer at a Ht of 10%. Whole blood filterability time was significantly increased in all subjects with liver disease. Corrected filterability time was increased only in the cirrhotic group associated with a significant decrease of Ht and fibrinogen and a slight increase in gamma globulins and plasma viscosity. Whole blood viscosity was in the normal range while relative viscosity was decreased in all patients. These findings suggest that both shape alterations of red cells (such as echinocytic shape) and modifications of plasma proteins probably lead to a decrease of red cell filtration in cirrhotic patients.

Adult↗
PubMedDate not supplied

Air pollution by gasoline exhaust fumes: effect on platelet function and blood viscosity.

Air pollution induced by automobile exhaust fumes seems to be involved in increased cardiovascular and respiratory morbidity. The effects of inhalation of such pollutant gases on platelet function and blood viscosity have not been sufficiently investigated, even if these parameters seem to be in strict correlation with cardiovascular function. Twelve healthy non-smoking volunteers were exposed for 30 minutes in a closed room to air polluted by automobile fumes. Platelet aggregation, blood viscosity, HbCO levels and P50 STD were determined before and after exposure. Cardiovascular parameters (blood pressure, heart rate and ECG) were also measured. At the end of the test, HbCO levels were significantly increased, but P50 STD was significantly reduced; an impairment of both platelet function and blood viscosity was observed. No significant changes in cardiovascular parameters were recorded. The decreases in platelet aggregation and blood viscosity were not directly correlated with either the increase in carbon monoxide levels or with the reduced P50 STD levels. It can be reasonably concluded that gasoline exhaust fumes could have been responsible for the observed alterations.

Adult↗
PubMed1986

Blood and plasma viscosity in experimentally induced hyper- and hypo-fibrinogenaemia.

For some time now fibrinogen has been attributed considerable importance in influencing blood and plasma viscosity. This paper attempts to experimentally confirm this statement in vivo: two groups of arteriopathic patients were selected for investigating viscosity in hyper- and hypo-fibrinogenaemia induced by PTA and a cycle of fibrinolytic treatment with urokinase respectively. Although fibrinogenaemia exhibited highly significant changes under such conditions, there was no important change in viscosity. Probably the role of fibrinogen in influencing viscosity has been overestimated in the past and it is likely that there are other more important factors.

Afibrinogenemia↗
PubMed1987

[Effect of smoking on blood viscosity and arterial rigidity in normal and hypertensive subjects].

The purpose of the study was to assess whether cigarettes smoking could induce blood hyperviscosity and arterial rigidity in 30 normotensive and 70 hypertensive men aged from 24 to 65 years. Of those, 20 normotensive and 20 hypertensive were cigarettes smokers, while the remaining subjects were non smokers. Age and weight were similar in the 4 groups of subjects. A couette viscometer with coaxial cylinders allowed the measurements of blood viscosity over a wide range of shear rates (0.033 to 241 sec-1) mimicking the flow condition of the circulation, and two strain gauge transducers permitted the measurements of the brachial to radial pulse wave velocity as an index of arterial wall distensibility. In normotensive subjects cigarettes smoking increased pulse wave velocity from 7.1 + 1 to 9.2 + 0.6 m/sec. (P less than 0.05) as well as blood viscosity, which increased both at higher shear rates (+10% from 52 to 241 sec-1, P less than 0.05) and lower shear rates (+20% from 11.2 to 0.2 sec-1, P less than 0.02). In hypertensives, cigarettes smoking increased pulse wave velocity (9.8 + 0.3 to 11.3 + 0.4; P less than 0.05) and blood viscosity (4% at higher shear rate P less than 0.05 and 10% at lower shear rates P less than 0.02). Although hypertensive patients had increased pulse wave velocity and blood viscosity compared to normotensive controls, these variables were not significantly different when hypertensive non smokers were compared to normotensive. The present study demonstrated that cigarettes smoking produced in normotensive and hypertensive men significant rheological disturbances of flow and wall arteries.2

Adult↗
PubMed1988

Blood and plasma viscosity after acipimox treatment in hypertriglyceridemic patients.

Acipimox, a nicotinic acid analog, is known to reduce the plasma lipid concentration in hyperlipidemic patients. In a study to check whether the drug improved hemo-rheological parameters, 21 patients (17 M, 4 F) with asymptomatic hypertriglyceridemia were treated with acipimox (250 b.i.d.) for 30 days. Plasma lipid concentrations were measured before and after therapy, together with blood and plasma viscosity. Mean plasma cholesterol and triglyceride levels decreased from 234 +/- 51 (SD) mg/dl to 202 +/- 53 mg/dl (p less than 0.01) and from 515 +/- 231 mg/dl to 298 +/- 130 mg/dl (p less than 0.01) respectively. Blood viscosity decreased (p less than 0.05 and less than 0.01) (range of reduction 6-20%) at all shear rates examined (from 2.25 s-1 to 450 s-1); plasma viscosity was significantly reduced only at lower shear rates (2.25 and 4.50 s-1). Changes in blood and plasma viscosity after acipimox treatment were not related to changes in plasma triglycerides. Acipimox seems to act beneficially on hemo-rheological parameters, independently of its hypolipidemic effect and could be usefully prescribed to patients with clinical signs of arteriosclerosis.

Adolescent↗
PubMedDate not supplied

Dependence of tissue valve leaflet motion on the viscosity of blood analogue fluid.

The dependence of the leaflet motion of bioprosthetic heart valves on the viscosity of the blood analogue fluid was studied in this work. A pericardial and a porcine tissue valve were mounted in a pulse duplicator and high-speed films were taken to record the motion of the valve leaflets. The blood analogue fluids used were physiological saline with a viscosity coefficient of 1.0 cP, and glycerol solution with a viscosity of 3.5 cP. The transvalvular pressure drop and percentage of regurgitation were also measured with the time-averaged flow rate maintained at 6.00 +/- 0.05 litres/min. Our results show that the leaflets did not stiffen with up to 15 days' exposure to glycerol. Also, there was no substantial difference in the time of opening of the leaflets or in the area of opening of the valves with the two blood analogue fluids. However, the leaflets closed substantially later in the cardiac cycle in the case of glycerol solution, owing to the interaction between the leaflets and the viscosity of the fluid. For proper comparison of the flow dynamics past prosthetic valves at comparable Reynolds number and Womersley number, our results suggest that glycerol solution should be used as the blood analogue fluid for tissue valves also.

Animals↗
PubMed1979

[Variations of hematic and plasmatic viscosity as a function of flow velocity, analyzed by means of an experimental model].

The authors have determined the hematic and plasmatic viscosity in 60 sound subjects, 30 men and 30 women respectively, at different values of cut drop, corresponding to the values that can be found at different levels of circulatory system. These subjects had value of Ht, total protidemy, cholesterolemy and trigliceryds, included in normal limits. For these determinations, made at constant temperature, they have used Well-Brookfield with a divergent angle of 0,8 degrees. In this way they could determinate the normality limits of hematic and plasmatic viscosity, in men and women, in connection with the physiologic modifications of flux speed. It has been confirmed the tixotropo behaviour of blood, whose viscosity increases exponentially for lessenings of cut drop and we have put this fact in touch with genesis of thrombosis. They haven't shown any expressive difference in the behaviour of the curves of two undergroups; the curve of middle values is higher for men, and it seems that this difference is owing to Ht. esclusively. In the end they have considered the curves of subjects that had values of viscosity different from normality; in this way they have found three different curves, in pathologic conditions.

Blood Flow Velocity↗
PubMed1977

[Structural viscosity of the blood].

In 34 healthy normal persons (19 females, 15 males) measurings of the blood viscosity in 7 shearing degrees between 218.7 and 1,312 sec-1 with the rotation viscosimeter Rheotest 2 were carried out. In the medium shearing degrees a large degrease of viscosity with increasing shearing degree was to be established, which corresponds to the structural-viscous behaviour of the blood. In high shearing degrees this decrease of viscosity was only slightly to be proved. As explanation for this we increasingly regard Newton's flowing qualities of the blood in high flowing speed. Statistically ascertained correlations between the height of viscosity and the haematocrit value, the number of erythrocytes and the level of plasma fibrinogen within the normal groups could be performed.

Blood Viscosity↗
PubMed1980

Effect of blood viscosity decrease on exercise ST segment depressions in hyperlipidemia.

In order to study the possible relation between blood viscosity and exercise ST segment depressions in hyperlipidemia the former was lowered by infusion of dextran and by treatment with clofibrate 1 g twice daily. Acute decrease of blood viscosity with dextran infusion in two cases increased the ST segment depressions during work. Nine subjects with asymptomatic hyperlipidemia, hyperfibrinogenemia and exercise ST segment depressions were treated with clofibrate in order to lower plasma fibrinogen and serum lipids. This did not influence the area of ST segment depression with either Frank leads or CH leads as determined by computer estimation. As the plasma fibrinogen level is of major importance for the blood viscosity it is concluded that the ischaemic ST segment depression seen in hyperlipidemia is not due to increased blood viscosity but more likely to a premature subclinical coronary atherosclerosis.

Blood Viscosity↗
PubMed1983

[Effect of anticoagulants on blood viscosity].

In 21 cases the blood viscosity of native blood was determined in comparison to heparin blood at a shear rate of 218.7 and 1312 sec-1 by using the rotational viscosimeter Rheotest 2. As a result, a low viscosity of the heparin blood could be found. In addition, the impact of phenprocoumon treatment on several rheologic parameters was examined in 20 healthy test persons. With the haematocrit and fibrinogen level remaining constant, a reduction of blood viscosity could be observed when the Quick value decreased. This was detected with Rheotest 2 at 7 different shear rate between 218.7 and 1312 sec-1. The influence of anticoagulants on the erythrocyte deformability is discussed as a possible cause underlying the obtained decreases of viscosity. This would have to be proved by investigations using erythrocyte filters.

4-Hydroxycoumarins↗
PubMed1983

Blood viscosity in proliferative diabetic retinopathy and complicated retinal vein thrombosis.

Forty-two patients with longstanding retinal vein thrombosis and 36 patients with diabetes had their blood viscosity levels measured. In both conditions blood viscosity, plasma viscosity, and plasma fibrinogen levels were significantly higher in those patients with capillary non-perfusion and/or new vessels on fluorescein angiography, compared to those patients without these complications. The possible role of abnormal blood viscosity in producing capillary non-perfusion and its sequelae in both conditions is discussed.

Aged↗
PubMed1980

Studies on the reduction of sputum viscosity in cystic fibrosis using an orally absorbed protected thiol.

The viscosity of cystic fibrosis fluids leads to clinical difficulties in adequate clearance of the respiratory and gastrointestinal tracts and in delivery of gases and nutrients to their respective sites. Various sulfhydryl agents are effective in reducing in vitro sputum viscosity. Present therapy for cystic fibrosis involves the aerosolization of N-acetylcysteine, presenting problems of toxicity and inadequate delivery to the small airways. We have been assessing various prodrugs which would liberate the free thiol in vivo and which would be orally absorbed. The free thiol of WR 2721, at a concentration of 1 mM, reduces sputum viscosity by 70% in 15 min. WR 2721 is hydrolyzed to the free thiol chemically at an acid pH and enzymatically by homogenates of the liver and gut. It is well absorbed (23%) after oral administration to rabbits. Clinical studies indicate that orally administered WR 2721 is without toxicity and reduces sputum viscosity in cystic fibrosis patients in 30 to 60 min after administration.

Adolescent↗
PubMed1983

[Effect of prostacyclin on erythrocyte deformability and blood viscosity].

The aim of our research was to investigate the effect of prostacyclin (PGI2) on red blood cell deformability and blood viscosity. Ten non-smokers healthy subjects (aged from 25 to 40) were examined. Different PGI2 concentrations were added to the blood sample and then red blood cell deformability and blood viscosity were measured: 1.2 and 2.4 ng/ml PGI2 concentrations, corresponding to plasma PGI2-like activity in man, increased red blood cell deformability and reduced blood viscosity. The PGI2 capacity of affecting red blood cell deformability and blood viscosity seems to be of clinical interest in conditions where the PGI2 production is reduced, such as ischemic heart disease, peripheral artery disease and diabetes mellitus.

Adult↗