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PubMed1991

The role of pentoxifylline in endotoxin-induced alterations of red cell deformability and whole blood viscosity in the neonate.

Endotoxin induces alterations in the neonatal red cell membrane that result in decreased deformability and an increase in whole blood viscosity. These rheologic alterations are detrimental to flow in the microcirculation. Pentoxifylline (PTX), a methyl xanthine derivation, increases red cell deformability presumably through its effect on intracellular adenosine 5-triphosphate. The purpose of this study was to evaluate the effect of PTX on endotoxin-induced alterations in the neonatal red blood cell. Anticoagulated whole blood specimens obtained from the cord of 12 neonates at birth were used to study the effects of Escherichia coli endotoxin (LPS) with and without PTX (50 micrograms/mL) on red cell deformability and whole blood viscosity. LPS resulted in a significant (P less than .001) decrease in deformability compared with controls. PTX reversed these endotoxin-induced alterations (P less than .01), normalizing deformability to control values (P = NS). LPS resulted in a significant increase (P less than .005) in blood viscosity that was reversed by PTX (P = NS). Pentoxifylline reverses the detrimental rheologic effect of endotoxin in the neonate. This activity may be helpful in sustaining normal microcirculation in neonatal sepsis.

Blood Viscosity↗

PubMed1977

Viscosity of elastomeric impression materials.

(1) Some elastomeric impression materials (Omniflex and Impregum) exhibited extreme shear thinning properties. This property was considered useful and these materials can be considered all-purpose. (2) The use of impression materials in syringing applications should not be precluded simply because the substances are thick or heavy during spatulation. A tenfold reduction in viscosity with increasing shear rate was found for three of the materials tested. (3) Viscosity characteristics of the impression rubbers were linked to filler content. (4) The viscosity rise during cross-linking was monitored for various impression products. It was found that each manufacturer's specifications of the length of time for syringing were relatively accurate.

Chemical Phenomena↗

PubMed1996

Viscosity of bovine serum albumin aqueous solutions as a function of temperature and concentration.

This paper presents the results of viscosity determinations on aqueous solutions of bovine serum albumin (BSA) at a wide range of concentrations and at temperatures ranging from 5 degrees C to 45 degrees C. On the basis of these measurements a general formula connecting the relative viscosity eta r with temperature T and concentration c of the dissolved proteins was established: [formula: see text] The quantities alpha, beta, B, D and delta E are described in the text below. A simple substantiation of the formula was also given. This relation gives immediately the Mooney approximation and allows the prediction of the values of the parameter S and a self-crowding factor K in this approximation. By applying an asymptotic form of the formula such rheological quantities as the intrinsic viscosity and Huggins coefficient were calculated.

Animals↗

PubMed1982

Kinetics of acetylthiocholine binding to electric eel acetylcholinesterase in glycerol/water solvents of increased viscosity. Evidence for a diffusion-controlled reaction.

Steady-state kinetic studies were made on the very efficient enzyme hydrolysis of acetylthiocholine by electric eel acetylcholinesterase (acetylcholine acetylhydrolase, EC 3.1.1.7) in glycerol/water solvents of increased viscosity. Determinations of the very fast minimum substrate association rate constants kmin, (2 . 10(8) M-1 . s-1 at I approximately 0.1 M and 25 degrees C) from the Michaelis parameters, V/(Km[E0]), were made at low substrate concentrations in order to obtain kmin directly. kmin was shown to be strongly dependent upon viscosity, which is characteristic of a diffusion-controlled reaction. kmin is as large or larger than plausible models for a simple diffusion-controlled reaction between a charged enzyme and substrate would suggest. Enhancement of the diffusion-controlled reaction through nonspecific binding of substrate to the highly negatively charged acetylcholinesterase followed by two-dimensional surface diffusion in a random walk to the active site may be a factor in this enzyme mechanism. Evidence for this comes from the viscosity dependence of kmin. Using the surface diffusion model it is estimated that the binding-site target area on acetylcholinesterase is effectively increased a minimum of 8-fold.

Acetylcholinesterase↗

PubMed1990

Direct measurement of the internal viscosity of sickle erythrocytes as a function of cell density.

The rotational dynamics of TEMPAMINE can be used to study directly the intracellular environment. The extracellular signal from TEMPAMINE is broadened away by the use of potassium ferricyanide which does not enter the cell. The EPR signal which results when 1 mM TEMPAMINE, 120 mM ferricyanide, and erythrocytes are mixed together arises from TEMPAMINE only in the intracellular aqueous space. The relative viscosity measured by the motion of TEMPAMINE in various control environments is: water at 37 degrees C = 1; human plasma at 37 degrees C = 1.1; internal aqueous environment of washed erythrocytes or whole blood at 37 degrees C = 4.92 +/- 0.32. Erythrocytes can be fractionated by density. In sickle-cell anemia (SS), the percentage of cells we find with density greater than 1.128 g/ml is 15-40%, in normals (AA) and sickle trait (AS) 1%. By direct spin-label measurements with TEMPAMINE we show, for the first time, that the relative internal viscosity (eta mu) of these dense erythrocytes is markedly elevated and density-dependent. Our results show that (1) eta mu increases with increasing cell density; (2) eta mu obtained from sickle cells is higher than eta mu obtained from normal cells at a given density, and this effect is greater at 37 degrees C than at 20 degrees C; (3) eta mu is proportional to MCHC, but eta mu in erythrocytes is higher than eta mu obtained from in vitro preparations of hemoglobin S at equivalent concentrations. We conclude that the relative internal viscosity of erythrocytes is affected by three factors: the state of cell hydration, the amount of hemoglobin polymer present, and the potential interactions of the cell membrane with intracellular hemoglobin.

Anemia, Sickle Cell↗

PubMed1991

Relationship of viscosity to porosities in automixed elastomeric impressions.

Porosities commonly presenting as voids have been recognized as an inherent problem in elastomeric impressions. Automixing of the impression has been found to be effective in reducing voids. The purpose of this study was to compare formation of voids in medium-viscosity and putty-wash materials in four automixed addition silicone elastomers. Impressions of a master model were made according to manufacturers' recommendations on manipulation of materials. Voids presenting on a predetermined surface were counted under a binocular microscope at a magnification factor of 7x. Results showed that Express exhibited a significantly higher number of voids than other materials in both categories. Putty-wash impressions generated significantly less voids than medium-viscosity impressions for all materials except Reprosil. The findings of this study suggested that putty-wash impressions produced significantly less porosities than medium-viscosity impressions and, consequently, offer better tear strength for impressions.

Dental Impression Materials↗

PubMedDate not supplied

Changes in blood viscosity and plasma proteins in myocardial infarction.

A clinical study of some biological and biochemical factors was carried out on patients with acute myocardial infarction. It was shown that: (i) the plasma viscosity was highly correlated to the clinical evolution of myocardial infarction; (ii) the variations of plasma viscosity were related to changes in the connection of fibrinogen and globulin; (iii) the highest correlation was between the plasma viscosity and alpha2-globulin concentration. The monitoring of these may be useful in the clinical evaluation of myocardial infarction.

Adult↗

PubMed1996

Analytical model for effects of shear rate on rouleau size and blood viscosity.

In this paper, a theoretical model is proposed by using the reversible kinetic equation of colloid coagulation to reveal the effects of erythrocyte aggregation and shear rate on the rouleau size and the blood viscosity. With this model, shear rate gamma dependences of the average size of rouleaux n(e) and the viscosity eta in concentrated red blood cell suspension are derived analytically. In this model, we consider not only the shear rate effect but also the rouleau size effect on the aggregation and degradation mechanism. By comparing with experimental results obtained by Shiga et al., some theoretical parameters have been determined. The variation of rate of rouleau formation with shear rate derived in our model is in fairly good agreement with the experimental results, and the viscosity of the concentrated red cell suspension derived in our model showing shear thinning agrees qualitatively with the experimental results obtained by Chien and Sung.

Animals↗

PubMed1981

Increased blood viscosity as the pathogenic agent in minimal change nephrosis: a new hypothesis.

It is proposed that minimal change nephrosis (MCN) is the result of impaired glomerular blood flow to slightly increased blood viscosity or to an abnormality of an autoregulatory mechanism controlling glomerular perfusion pressure or to unusually small efferent arterioles, or to combinations of these factors. The functional response to any of such changes would be an increase in intraglomerular pressure. If the pressure exceeded a critical level albumin would be able to pass into Bowman's space after deforming the pressure-dependent thixotropic basement membrane. In response to the presence of albumin in Bowman's space, epithelial cell foot process retraction would be initiated. The concentration of albumin capable of stimulating this reversible change in unknown. If it can be shown that MCN is a consequence of increased blood viscosity, then drugs having direct effects on blood viscosity might offer alternatives to steroid treatment.

Albuminuria↗

PubMed1988

Acute local inflammation causing generalized increased ground substance viscosity: guttate psoriasis, Reiter's syndrome, adjuvant disease, cancer regression.

It is known that at sites of acute inflammation there is increased ground substance formation and fibroblast proliferation. There is also increased serum glycoprotein following localized acute inflammation. The author proposes that a severe acute inflammatory response in a localized area of the body induces a generalized increase in ground substance viscosity (generalized ground substance adaptive phenomenon). This would increase host resistance to invasion and heighten the inflammatory response. There are multiple clinical and experimental facts which could be explained by this response. These include guttate psoriasis, pustular psoriasis, pustular bacterid of Andrew's, Reiter's syndrome, and others. This response would include some aspects of adjuvant disease. Increased generalized ground substance viscosity could also explain the beneficial effects of streptococcal cell fractions and streptococcal infections on tumor regression. A number of other clinical observations could be explained. Connective tissue-activating peptide released at the inflammation site could be having a systemic effect. It could be generally beneficial to have generalized increased ground substance viscosity when acute inflammation is occurring in a localized area. A few patients who already have a highly reactive inflammatory level could develop excess inflammation especially at sites of trauma, or preexisting inflammation.

Acute-Phase Reaction↗

PubMed1989

Pyridoxine deficiency and antagonism produce increased ground substance viscosity with resulting seborrheic dermatitis and increased tumor resistance.

Pyridoxine deficiency and 4'-deoxypyridoxine produce acrodynia in rats and seborrheic dermatitis in man. They also produce tumor inhibition in man and animals. Pyridoxine is extensively involved in metabolism and its relationship to the inhibitor 4'-deoxypyridoxine is complex. Pyridoxine deficiency and antagonism increases ground substance viscosity. This increase the inflammatory reactivity of the skin to produce acrodynia in rats and seborrheic dermatitis in man. The increase in ground substance viscosity would explain the increased resistance to tumors in man and animals. Pyridoxine is important in protein metabolism. The protein moiety of glycosaminoglycans in ground substance is small but plays a major role in tissue viscosity. Pyridoxine deficiency or antagonism by itself does not offer a definitive answer for tumors. Combined with substances that stimulate fibroblast or glycosaminoglycans production it may have a significant additive effect.

Acrodynia↗

PubMed1991

Aphthous stomatitis (canker sores): a consequence of high oral submucosal viscosity (the role of extracellular matrix and the possible role of lectins).

Recurrent aphthous stomatitis (RAS) or canker sores occur in 20-60% of all persons. The lesion occurs because of increased viscosity of oral submucosal extracellular matrix (ECM). The lesions begin in the second decade and peak in the third decade. Sex hormones are an important influence on fibroblasts, especially in the early phase of exposure. Sex hormones are known to concentrate, to a degree, in the bucal mucosa in animals. Lesions of RAS localize clinically and experimentally at sites of trauma. In the skin, edema is known to trigger early cellular inflammation. Increased viscosity of ECM heightens the response. The histopathology of the ulcerated lesions is similar to that which occurs under sites of acute inflammation in the skin. Systemic corticosteroids completely supress the lesions. Caustics, such as silver nitrate and phenol, stop the growth and pain of lesions. Irritants are known to break ECM viscosity. The oral mucosa exerts some control on underlying ECM. Substances such as lectins influencing the mucosa could influence ECM. Soluble substances in food or organisms could also penetrate to influence ECM. A number of different foods have been incriminated as trigger agents in individual cases. This includes gluten in patients with gluten sensitive enteropathy. Gluten is known to alter the mucosa of the small intestine in persons with celiac disease.

Extracellular Matrix↗

PubMed1989

Effects of ovariectomy on blood and plasma viscosity, fibrinogen and whole blood filterability.

Blood and plasma viscosity, fibrinogen concentrations and whole blood filterability (VB) were evaluated before surgery and 7 and 30 days postoperatively in 2 groups of subjects, one of which comprised 10 hysterectomized women and the other 14 women who had undergone both hysterectomy and ovariectomy. Oestrogens and various metabolic haematological parameters were measured and correlated with the haemorrheological data. By day 7 after surgery fibrinogen concentrations and plasma viscosity had increased, while VB had decreased. Plasma viscosity and fibrinogen levels correlated negatively with VB in the non-ovariectomized women. Three weeks later almost complete normalization of all parameters was observed in all of the subjects, except for the persistence of low oestrogen concentrations and a further decrease in VB values in the ovariectomized patients, these parameters showing a positive correlation. This study demonstrates that haemorrheological alterations occur after hysterectomy (with or without ovariectomy) in the early post-operative period. The striking decrease in VB values and its correlation with the oestrogen concentrations observed 1 mth after ovariectomy suggest that the fall in oestrogen levels might be responsible for the decrease in whole blood filterability.

Adult↗

PubMed1994

Measurements of viscosity and permeability of two phase miscible fluid flow in rock cores.

This paper describes the application of 1H magnetic resonance imaging (MRI) to the measurement of fluid viscosity and rock core plug permeability during two phase miscible displacements in certain rock types. The core plug permeability was determined by monitoring glycerol solutions displacing D2O. Simple physical principles were used to calculate the core permeability from the measured displacement angle for a set of Lochaline sandstone core plugs. In a further experiment the viscosity of polyacrylamide solution 1500 ppm was determined in the core plug. The permeability and viscosity results compared well to conventional core analysis methods.

Acrylic Resins↗

PubMed1990

The effect of malonyldialdehyde on viscosity of normal and sickle red blood cells.

This study has examined the effect of MDA, an end product of lipid peroxidation, on the viscosity of AA and SS RBC suspensions. MDA accumulation in RBC was accomplished in vitro in human RBC by treating them with exogenous standard MDA. MDA accumulation assessed by the thiobarbituric acid reactivity of in vitro MDA-treated RBC was comparable to that of the RBC in vivo in hemolytic anemias. There was a significant increase in the viscosity of both AA and SS RBC suspensions after in vitro treatment with MDA. The increase in viscosity or RBC was significantly positively correlated with the extent of MDA accumulation.

Anemia, Sickle Cell↗

PubMed2005

Influence of cement viscosity and cement mantle thickness on migration of the Exeter total hip prosthesis.

The effect of bone cement viscosity and cement mantle thickness on the migration of the Exeter total hip prosthesis was studied in a prospective, randomized, double-blind clinical Roentgen Stereophotogrammetric Analysis study. Forty-one cemented total hip arthroplasty in 39 patients were included and randomized into a low/medium Simplex P cement group and a high-viscosity Simplex AF cement group. At time of stem introduction, 5 minutes after mixing, the Simplex AF was more viscous than Simplex P. No statistical difference existed between the 2 cement groups, for neither translation nor rotation migration data. Subsidence of the stem at 2-year follow-up was 1.1 +/- 0.56 mm for Simplex AF cement and 1.5 +/- 1.00 mm for Simplex P cement. The mean rotation of the acetabular components about the sagittal axis was 1.7 degrees +/- 3.8 degrees in the Simplex AF group and 0.7 degrees +/- 2.1 degrees for the Simplex P group. No effect of cement mantle thickness on migration of neither the acetabular cups nor the femoral stems was found. Although there were no differences in migration data for the cups and the stems, 2 acetabular cups in the Simplex AF group (almost 10%) were revised because of mechanical loosening. Because of these findings, we suggest caution before using this new high-viscosity bone cement for fixation of acetabular components.

Acetabulum↗

PubMed2005

Membrane viscosity is a major modulating factor of the enterocin CRL35 activity.

Enterocin CRL35 activity is deeply influenced by the membrane viscosity as could be demonstrated performing determinations of the minimal inhibitory concentrations (MIC) at different temperatures and analyzing the membrane viscosity in these cells as well as in resistant bacteria. In all the cases, bacteriocin activity was linked to higher levels of viscosity. This finding was confirmed studying the interaction of enterocin CRL35 with liposomes composed of dimyristoyl phosphatidylcholine: dimyristoyl phosphatidylglycerol (9:1) in both gel and liquid-crystalline phases. It could be establish, from peptide insertion analysis following the tryptophan fluorescence and microviscosity experiments that this peptide is able to interact more efficiently with membranes having a more structured hydrophobic core.

Bacteriocins↗

PubMed2006

In vitro release of a water-soluble agent from low viscosity biodegradable, injectable oligomers.

Low-molecular-weight poly(epsilon-caprolactone-co-1,3-trimethylene carbonate) and poly(1,3-trimethylene carbonate) are potential vehicles for the regio-specific delivery of water-soluble agents. In this paper, the characteristics and the mechanism governing the in vitro release of a model water-soluble drug, vitamin B12, from these polymer vehicles were determined. The loading of vitamin B12 was kept to 1 w/w%. The oligomers examined ranged from amorphous, high viscosity to crystalline but low viscosity. The oligomers did not degrade appreciably in vitro. The total fraction of vitamin B12 released increased as the crystallinity of the oligomers decreased, reaching nearly total release only for the completely amorphous oligomers. The rate of release was fastest for the amorphous oligomers and dependent on their viscosity. Inclusion of a more osmotically active agent, trehalose, into the vitamin B12 particles through co-lyophilization resulted in enhanced total fraction released and a faster release rate. The results are consistent with an osmotically driven release mechanism.

Caproates↗