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At least 1,621 records · Page 90Linked to original sources
PubMed1990

A new outlook on body fluid viscosity and cell function: concluding remarks and discussion.

The area neglected so far in the fields of clinical and theoretical haemorheology is that of interaction between viscosity and chemical reactions in the cells. The reintroduction of teinochemical principle opens entirely new doors for investigation both in vitro and in vivo. Effect of extracellular fluid viscosity on synthesis (i.e. lipids) and on possible enzymatic and catalytic functions influences our opinion that haemorheology has to go back to fundamentals.

Animals↗
PubMed1981

An instrument suitable for viscosity determination of chick intestinal fluids.

A rotating cylinder viscometer was described which was modeled after a Zimm viscometer. Regression of power input (watts) to the instrument versus angular velocity (radians per second) for standard fluids at fixed temperature produced linear equations with intercepts at the origin. The ratio of the slopes of these lines to the slope for water produced values that were good estimates of the relative viscosity of the standard fluids. The instrument was capable of determining the relative viscosity of .75 ml of intestinal fluid taken from young growing chicks.

Animals↗
PubMed2000

Method of stimulation, mouth movements, concentration, and viscosity: effects on the degree of taste adaptation.

Although sensory adaptation, the gradual loss of sensation during prolonged stimulation, has been demonstrated in laboratory taste experiments, a comparable loss of taste intensity is not experienced in real-life eating situations. This discrepancy may be due to differences in the proximal stimuli or to differences in the ways the taste receptors are stimulated. In two experiments, the effects of four potentially relevant variables were investigated: stimulus intensity, stimulus viscosity, mouth movements, and presentation method. During the initial seconds of stimulation, adaptation to the weakest of the two solutions was faster. Although more viscous stimuli were less sweet, viscosity as such did not affect adaptation rate, nor did mouth movements. Among the three presentation methods, a sucrose-soaked filter paper on the tongue produced more adaptation than either sipping the solution or flowing it over the tongue. This suggests that even mouth movements far more subtle than those still present in the no-movement condition of a sip-and-spit experiment can disrupt the adaptation process.

Adolescent↗
PubMed1993

Separate contributions of large- and small-scale dynamics to the heat capacity of proteins. A new viscosity approach.

We present here a theoretical description and experimental verification of a novel method of separating large-scale (LS) and small-scale (SS) dynamics contributions to the heat capacities of proteins in solution by using viscosity dependences. It was assumed that the LS dynamics, related to the thermal fluctuations of domains and subunits, is dependent on solvent viscosity within a sucrose concentration of 0-15% w/v, in contrast with the SS dynamics, which are related to fluctuations of atoms and amino acid residues. The results obtained with immunoglobulin G, hemoglobin and cytochrome c were in reasonable accordance with the previous data achieved by a spin-label method: the LS dynamics decrease, whereas the SS dynamics increase within the temperature elevation. The changes are dependent on the stage of the active sites of the proteins. The internal compensation of molecular dynamics between the LS and SS fluctuations may be an important factor in the design of thermostable enzymes and proteins. A new phenomenon concerning the ability of macromolecules to increase free volume in water as a result of ice-like clusters stabilization is revealed.

Hot Temperature↗
PubMedDate not supplied

[Action of dopamine on blood flow of the limbs and on blood viscosity (author's transl)].

The observation of several cases of gangrene in the lower limbs of subjects treated with an infusion of dopamine has encouraged the authors to study the action of the drug, in a dose capable of increasing the arterial pressure, on the blood flow in the lower limbs and on the viscosity of the blood in a group of normal middle aged subjects. A significant reduction in the values of the blood flow with a simultaneous increase in the blood viscosity was observed. There results confirm the ischemic action of the drug with the doses used at the muscular and cutaneous level in the lower limbs.

Blood Circulation↗
PubMed1999

[Rheologic modifications induced by heparin therapy. Capillary blood viscosity, erythrocyte deformability, aggregation index].

BACKGROUND: The most important problem with which doctors have to deal every day in their practice, is occlusive vascular disease, at the basis of which there is commonly a process of thrombosis. For this reason, it is very important to define early the subjects at thrombosis risk and an appropriate therapeutic strategy. METHODS: We considered 13 inpatients at thrombosis risk, c/o sezione di Clinica Medica I, dipartimento di Medicina Interna e Terapia Medica, Università di Pavia, IRCCS Policlinico S. Matteo, and 12 healthy volunteers, between March and June 1998, evaluating age, sex, weight, diseases and ongoing therapy, hemocytological, hemocoagulational and hemorheological tests before and after heparinic therapy. RESULTS: General blood viscosity, measured by the rotational and double-filtration method, presented no significant changes; on the contrary, capillary blood viscosity and erythrocyte deformability, measured by our new double-filtration method, showed respectively an increase and a decrease. CONCLUSIONS: Calcium heparin is the most frequently used antithrombotic drug in thrombotic diseases and their prevention, but its action on the hemorheological profile is not clear. This study showed that it increases erythrocyte aggregation rate and decreases erythrocyte deformability, having a negative effect on the microcirculation.

Anticoagulants↗
PubMed1975

[The use of energy in casting and the viscosity of zinc oxide-eugenol pastes].

The recorded diagrams give information on the viscosity (consistency) at any given time. The force data indicate the difference in the viscosity (consistency). The line in the graph reflects the setting behavior. A flow test should be included in the specification of impression materials. The consistency test provided for in the ADA specification does not have any clinical significance, neither have changes in the load.

Energy Metabolism↗
PubMed1975

[Changes in plasma and whole blood viscosity during starvation (author's transl)].

More than 6000 parameters were collected during a 21-day period of starvation in 51 obese patients aged 17 to 65 years and stored as data bank on a CDC CYBER 74 at the calculating centre of the University of Technology in Vienna. Samples for multiple linear regression were obtained on the basis of various selective criteria. The essential results of this analysis are the depression of plasma viscosity, which correlates positively with the decrease in blood lipids and the reduction of overweight, as well as the unexpected increase in whole blood viscosity. The latter can probably be explained by an altered erythrocytic fluidity due to the metabolic changes which take place during a longer period of starvation.

Adolescent↗
PubMed2000

Morning increase of whole blood viscosity in obstructive sleep apnea syndrome.

OBJECTIVE: Patients affected by obstructive sleep apnea syndrome (OSAS) have an increased risk of cardiovascular diseases such as stroke and myocardial infarction. The pathophysiological mechanisms leading to increased vascular risk are still matter of debate. A relative morning hyperviscosity could be one of the leading mechanisms of cardiovascular morbidity which is actually known to be especially high in the morning hours. METHODS: Whole blood viscosity (WBV) at seven shear rates, ranging from 0.47 to 118 sec(-1), haematocrit (Hct), and plasma fibrinogen (F) concentration, were measured on venous blood samples in 12 patients with OSAS and in 8 healthy controls at 8-9 p.m. and at 7-8 a.m. the morning after. WBV values were normalized on Hct by the computation of the standardised normal deviate z on the normal database of the laboratory. RESULTS: No changes were observed in controls. Hct, F and normalized WBV (independently from Hct changes) significantly increased in the morning hours in OSAS patients. CONCLUSIONS: Viscosity of whole blood increases in the morning in OSAS patients but not in healthy controls. This condition may be related to the increased susceptibility to cerebral ischemia in patients affected by OSAS, particularly evident in the early morning.

Adult↗
PubMed2000

Effect of viscosity on digestion of nutrients in conventional and germ-free chicks.

A study was conducted with conventional and germ-free broiler chicks to obtain more information on the role of the intestinal microflora in the anti-nutritive effects of NSP in broiler chicks. As the NSP source, highly methylated citrus pectin (HMC) was used at a dose level of 30 g/kg in a maize-based diet. The diets fed to the germ-free chicks were gamma-irradiated, whereas those fed to the conventional chicks were not. Feeding the HMC diet to conventional birds depressed weight gain and food utilization (P < 0.05), whereas in germ-free birds only weight gain was reduced (P < 0.05). Feeding the HMC diet to conventional birds reduced digestibilities of energy and starch at the end of the jejunum. Ileal digestibilities of starch and energy were not strongly affected when birds were fed on the HMC-containing diet. Faecal digestibilities of organic matter, crude fat, starch and amino acids, N retention and metabolizable energy were reduced when conventional chicks were fed on the HMC diet. Feeding the HMC diet to germ-free birds hardly affected faecal digestibility of nutrients and N retention, whereas metabolizable energy was increased. Feeding the HMC diet to conventional or germ-free birds increased the viscosity of the digesta in the small intestine. This increase in digesta viscosity was more pronounced in conventional than in germ-free birds. The pH of ileal digesta was reduced when HMC was added to the diet of conventional chicks, but not in germ-free chicks. Feeding the HMC diet to conventional birds markedly affected morphology of the gut wall, whereas in germ-free chicks very little effect was found on gut morphology. Based on the results of the present study, it is concluded that the gastrointestinal microflora mediates the magnitude of the anti-nutritive effects of HMC in broiler chicks. However, the exact role of the microflora in chicks in the magnitude of the anti-nutritional effects of HMC could not be derived from the present study, since the results might have been influenced by gamma-irradiation of the diets fed to the germ-free chicks.

Animals↗
PubMed2000

Relationships between blood viscosity and insulin-like growth factor I status in athletes.

Exercise training is known (1) to enhance the function of the GH-IGF-I system, which has profound effects on body fluid status; (2) to increase blood fluidity. Thus, we investigated during an exercise-test in 39 male elite sportsmen (age 23.7+/-0.72 years; body mass index 23.7+/-0.28 kg/m2) the possible relationships between GH and IGF-I status and the rheological properties of blood. Two correlations indicate a relationship between body hydration and fitness: isometric handgrip strength is correlated with the percentage of extracellular water in total body water (r = 0.432, p = 0.02) and the aerobic working capacity W170 is negatively correlated with hematocrit (r = -0.341, p = 0.039). Water loss during exercise appears to be inversely related to fitness as evaluated by W170 (r = -0.529, p = 0.05), and is positively correlated with the score of signs of overtraining (r = 0.725, p = 0.003) and with the red blood cell aggregation index (r = 0.584, p = 0.036). Finally, while the GH peak value is correlated with the extracellular water volume (r = 0.393, p = 0.02), IGF-I is correlated with blood viscosity (r = 0.546, p = 0.0003), suggesting that when IGF-I values are within the upper quintile (>340 ng/ml) IGF-I may unfavourably affect blood rheology. Among factors of blood viscosity, IGF-I exhibits a borderline correlation (p = 0.05) with "Tk" and the ratio IGF1/IGFBP3 which reflects free circulating IGF-I is correlated with red cell aggregability measured with the Myrenne "M" (r = 0.485, p = 0.014) and S60 (r = 0.396, p = 0.494). These findings confirm the importance of hydration and dehydration as determinants of both blood rheology and exercise performance. Moreover, they suggest that values of IGF-I within the upper quintile are associated with an impairment of blood fluidity, possibly due to a direct effect of IGF-I on red cell deformability and aggregability.

Adult↗
PubMedDate not supplied

Effect of sealant viscosity on the penetration of resin into etched human enamel.

This study was designed to investigate the relationship between the etched depth, penetration of sealants and marginal seal. Sixty unerupted lower first premolars extracted from patients for orthodontic reasons were thoroughly cleaned and stored in an antiseptic Ringer's solution at 4 degrees C. A "window" on the occlusal of 15 of the premolars, including both mesial and distal pits, was developed by painting nail varnish around the border of the occlusal surfaces. Etching was then done with 35% phosphoric acid for 60 seconds to all 60 premolars. Five of the "window" teeth were evaluated by microradiography to determine the etched depth of the superficial and subsurface enamel. Five were prepared for SEM analysis to observe the change of the superficial etched enamel surface. Another five "window" teeth were embedded in epoxy resin and sectioned parallel to the long axis of the tooth through the fissures in order to observe the subsurface depth of the etch by SEM analysis. The other 45 teeth were divided into three groups of 15 teeth each. Fissures of each group of teeth were sealed using Prisma-Shield (LD Caulk), Concise White Sealant (3M Dental Products) or Teethmate A (Kuraray) sealants and stored in water (37 degrees C) for 24 hours. They were then sectioned and demineralized before being examined by a scanning electron microscope. Photographs of secondary electron image (SEI) were done to gradate the resin-infiltrated enamel and resin tags for these sealants. After SEM observation, the 15 samples of each applied sealant were polished to a high gloss again and placed in a silver nitrate solution for 24 hours before being examined under the SEM equipped with a back-scatter electron detector. Data were then analyzed using the Welch and Student t-tests. Results showed that fissured enamel of unerupted human lower first premolars became porous after etching with 35% phosphoric acid. The low viscosity sealant Teethmate A (approximately 260 mPa.s), penetrated fully and formed a resin-infiltrated layer in enamel beyond the etched depth. However, the high viscosity sealants (Prisma-Shield and Concise White Sealant) did not penetrate enough to ensure that the acid-etched enamel was infiltrated sufficiently by the sealant to insure good marginal seals.

Acid Etching, Dental↗
PubMedDate not supplied

[Relation between the viscosity of enteral diets and mechanical complications in their administration according to the nasogastric catheters].

OBJECTIVE: The use of enteral nutrition has increased enormously over the last few years and at the same time the standard indications for parenteral nutrition, whether in hospitals or at home, have gradually been defined. The most common way to administer enteral nutrition is intermittently and using gravity, through a nasogastric catheter or through gastrostomy. In our daily practice it has been observed that there was at times a considerable delay in the administration of the diet by means of a nasogastric catheter and the tube was sometimes blocked due to its small calibre and/or the excessive viscosity of the formula. It was therefore proposed to study the viscosities of polymeric enteral diets with and without fibre at this hospital to identify the relationship with the time taken for their intermittent, gravity-driven administration through different calibres of nasogastric catheter at the maximum flow rate. RESULTS: Some of the enteral diets under study exceeded the recommended time for intermittent administration by gravity (20-40 minutes). CONCLUSIONS: We feel it is essential for the product label to provide information on the optimal calibre of the nasogastric catheter required for administration of the product.

Drug Labeling↗
PubMedDate not supplied

Erythrocyte rate and plasma viscosity in health and disease.

Erythrocyte sedimentation rate(ESR) and plasma viscosity (PV) were assessed in patients with the following disorders: pulmonary tuberculosis (PTB); malignant lymphomas (ML) and sickle cell anaemia (SCA). Normal healthy individuals (controls) and pregnant women were also investigated. The degree of correlation between erythrocyte sedimentation rate and plasma viscosity was assessed in each case. The mean ESR values for the controls, pregnant subjects, sickle cell anaemia, pulmonary tuberculosis and malignant lymphomas patients were 14.02 +/- 16.15, 50.26 +/- 32.56, 9.12 +/- 8.84, 102.54 +/- 27.64 and 79.73 +/- 51.75 mm/hr, respectively. Similarly, their relative PV were found to be 1.69 +/- 0.13, 1.72 +/- 0.16, 1.86 +/- 0.18 2.01 +/- 0.52 and 0.24 +/- 2.18, respectively. The ESR was significantly higher in pulmonary tuberculosis, malignant lymphomas and in pregnancy but lower in SCA when compared with the control. With the exception of SCA patients, regression analysis showed that haematocrit and sex significantly influenced ESR values but not PV values. Erythrocyte sedimentation rate correlated positively with PV in patients with pulmonary tuberculosis and malignant lymphomas but not in pregnant women, SCA and normal controls. Therefore PV cannot reliably replace ESR as a routine laboratory test either in health or in disease conditions such as SCA.

Adult↗
PubMedDate not supplied

[Effect of haloperidol on transmembrane potential and viscosity of thymocyte membrane lipids].

A damaging effect of the neuroleptic haloperidol on thymocytes was studied in vivo. The integral state of energetic processes in the cells was described by the electric transmembrane potential of thymocytes delta psi equal to the sum of potential on the plasmic and mitochondrial membranes. The effect of haloperidol was also evaluated by the content of lipid peroxidation (LPO) products and by the structural and functional characteristics of thymocyte membranes (lipid viscosity, protein-lipid interaction). A single administration of haloperidol (0.4 mg/kg) decreased the delta psi of thymocytes and increases the viscosity of lipids in the cell membranes. The content of LPO products--primary (diene conjugates) and secondary (Schiff bases)--was not affected. The obtained results indicate that the combination of methods employed can be used for analysis of the structural and functional characteristics of blood cell membranes (in leukocytes and lymphocytes) for evaluating the side effects of haloperidol in the human organism.

Animals↗
PubMed2002

Fibrinogen, viscosity and white blood cell count predict myocardial, but not cerebral infarction: evidence from the Caerphilly and Speedwell cohort.

Fibrinogen, plasma viscocity, and the white blood cell count predict ischaemic heart disease, but there is less certainty for their predictive power for ischaemic stroke. Studying stroke and ischaemic heart disease in the same cohort prospectively allows comparison of predictive strengths. The Caerphilly and Speedwell cohorts consist of a population sample of 4,860 men aged 45-59 years at recruitment who had baseline measurements of fibrinogen, plasma viscosity, and white blood cell counts. After 15-19 years of follow-up, men in the two cohorts experienced 312 ischaemic strokes and 557 ischaemic heart disease events. Mean fibrinogen, plasma viscosity and white blood cell counts differed significantly after adjustment for confounding factors between men with and without ischaemic heart disease, 0.25 g/l (95% CIs 0.1 8-0.32); 0.036 cp (95% CIs 0.027-0.044); 0.67 x 10(9)/l (95% CIs 0.50-0.84) respectively. The same measurements showed no significant differences after adjustment for the same confounding factors for men with and without ischaemic stroke, 0.05 g/l (95% CIs -0.04-0.14); 0.008 cp (95% CIs -0.003-0.019); 0.16 x 10(9)/l (95% CIs -0.06-0.38) respectively.

Blood Viscosity↗
PubMed1975

[Effect of a decrease in viscosity on myocardial blood flow and function in myocardial infarct].

In 5 dogs the effect of a decrease in blood viscosity on myocardial blood flow (radioactive microspheres) and left ventricular function (Sarnoff curves) following ligation of the left anterior descending coronary artery was tested. Moderate anaemia produced a significant increase in coronary blood flow to the total left ventricle (+ 100%) and to the ischemic area (+ 400%). Depressed left ventricular function after coronary ligation alone was restored when blood viscosity was lowered only slightly. Severe anaemia further increased coronary blood flow but left ventricular function worsened.

Animals↗
PubMed2002

Assessing microleakage in resin composite restorations rebonded with a surface sealant and three low-viscosity resin systems.

OBJECTIVES: The aim of this study was to assess the ability of three low-viscosity resin systems (Unibond, Single Bond, and Fluorseal), used as rebonding agents, and a specific surface-penetrating sealant (Fortify) to prevent microleakage in Class V resin composite restorations. METHOD AND MATERIALS: Fifty Class V cavities with the occlusal margin in enamel and the cervical margin in dentin and cementum were prepared on both the buccal and lingual surfaces of sound extracted premolars and restored with a hybrid light-cured resin composite. After finishing and polishing, restorations were randomly assigned to one of five equal groups (n = 10): a control, without surface sealing, and four experimental groups in which margins were etched and rebonded. Specimens were thermocycled, immersed in a 50% silver nitrate solution, sectioned longitudinally, and analyzed for leakage at the occlusal and cervical interfaces. RESULTS: Statistical analysis showed significantly less leakage at the enamel margins for all groups. Fortify and Unibond were statistically similar and provided better marginal sealing at dentin and cementum interfaces. Fluorseal showed the poorest ability to prevent microleakage. CONCLUSION: The rebonding technique may substantially minimize microleakage at dentin and cementum margins of composite restorations, when a resin system with sufficiently low viscosity is used as a surface sealant, regardless of whether it has been specified for such a purpose.

Acid Etching, Dental↗