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PubMed1986

Effect of shear on the apparent viscosity of amorphous carbonate ion containing aluminum hydroxide suspensions.

The application of shear to carbonate ion containing aluminum hydroxide suspensions caused a change in the apparent viscosity by two possible mechanisms: change in the surface charge because of desorption of specifically adsorbed carbonate ion, and aggregate dispersal and formation of more extensive particle networks. The desorption of specifically adsorbed carbonate ion is related to the expansion of the air-liquid interface during shear. Shear-inducing processing equipment which generates a minimal amount of new air-liquid interface was found to produce the least change in pH and, consequently, in surface charge. However, viscosity increases caused by aggregate dispersal and formation of more extensive particle networks may occur without a shear-induced change in surface charge.

Aluminum Hydroxide↗
PubMed1996

The effects of temperature, viscosity, and molecular size on the aluminum-27 QCT NMR of transferrins.

A number of reports in recent years have demonstrated the feasibility of detecting quadrupolar metal ions bound tightly to rather large proteins via the quadrupolar central transition (QCT) NMR approach. In this article, an in-depth investigation of several interesting properties of transferrin-bound 27Al NMR signals, namely, their dependence on temperature, viscosity, and molecular size is presented. It is shown that (1) decreasing temperature and (2) increasing viscosity by adding reagents such as glycerol and ethylene glycol perturb only the linewidths of transferrin-bound 27Al signals, and, in fact, produce a decrease in signal linewidth. These effects are in accord with quadrupolar relaxation theory, which predicts that the linewidth of the central transition of a half-integer quadrupolar nucleus should decrease with increasing correlation time of the protein under nonextreme narrowing conditions. Furthermore, it is demonstrated that these trends, which are completely opposite to those generally observed in NMR spectroscopy, can be exploited to monitor ovotransferrin half-molecule reassociation reactions. In combination with the peculiar properties of transferrin-bound quadrupolar nuclei reported in the literature to date, the phenomena described here provide the basis for understanding the conditions and experimental parameters which may facilitate the application of the QCT NMR technique to the study of other quadrupolar nuclei and proteins.

Aluminum↗
PubMed2000

Effects of olestra and sorbitol consumption on objective measures of diarrhea: impact of stool viscosity on common gastrointestinal symptoms.

The aim of this study was to determine the effects of olestra and sorbitol consumption on three accepted objective measures of diarrhea (stool output >250 g/day, liquid/watery stools, bowel movement frequency >3/day), and how stool composition influences reports of common gastrointestinal symptoms. A double-blind, placebo-controlled study compared the effects of sorbitol (40 g/day in candy), a poorly absorbed sugar-alcohol with known osmotic effects, with those of olestra (20 or 40 g/day in potato chips), a nonabsorbed fat, on objective measures of stool composition and GI symptoms. Sixty-six subjects resided on a metabolic ward for 12 days: 2 days lead-in, 4 days baseline, 6 days treatment. Sorbitol 40 g/day resulted in loose/liquid stools within 1-3 h of consumption. In contrast, olestra resulted in a dose-responsive stool softening effect after 2-4 days of consumption. Subjects reported "diarrhea" when mean stool apparent viscosity (peak force (PF), g) decreased from a perceived "normal" (mean +/- SE, 1355 +/- 224 g PF; firm stool) to loose (260 +/- 68 g PF) stool. Mean apparent viscosity of stool during treatment: placebo, 1363 +/- 280 g (firm); olestra 20 g/day 743 +/- 65 g (soft); olestra 40 g/day, 563 +/- 105 g (soft); and sorbitol 40 g/day, 249 +/- 53 g (loose). Of the 1098 stool samples collected, 38% (419/1098) were rated by subjects as "diarrhea," yet only 2% of treatment days (all in the sorbitol treatment group) met commonly accepted criteria for a clinical diarrhea. Sorbitol, but not olestra, increased the severity of abdominal cramping, urgency and nausea compared to placebo. Olestra consumption, at levels far in excess of normal snacking conditions, resulted in a gradual stool softening effect after several days of consumption, did not meet any of the three objective measures of diarrhea, and did not increase GI symptoms. Sorbitol consumption, at only 80% of the dose requiring a "laxative effect" information label, resulted in rapid onset loose/liquid stools and a significant increase in abdominal cramping, urgency and nausea. Overall, subjects categorized stool as "diarrhea" when stool decreased from their perceived "normal," but the vast majority of these reports were not associated with clinically significant diarrhea.

Adolescent↗
PubMed1990

Residual motion of hemoglobin-bound spin labels and protein dynamics: viscosity dependence of the rotational correlation times.

The residual motion of spin labels bound to cysteine beta 93 and to lysines of methemoglobin has been studied by electron paramagnetic resonance spectroscopy. To separate the influences of the solvent and the protein environment of the label fluctuations, the correlation times, tau, were analyzed as a function of temperature for fixed solvent viscosities, eta. Results show that over a wide range of viscosity the dependence of tau on eta may be empirically described by a power law tau approximately eta kappa. The exponent kappa depends strongly on the location of the label on the protein surface. If one regards the spin labels as artificial amino acid side chains, characteristic values of correlation times and amplitudes of the rotational motion at the surface can be given. For eta = 1 cP and T = 297 K the correlation time of the labels bound to lysines is found to be tau = 9.10(-10) S and the rotational diffusion is nearly isotropic. The spin label bound to cysteine beta 93 occupies a protein pocket, its rotational motion is therefore restricted. The correlation time of the label motion within a limited motion cone of semi angle theta = 30 degrees +/- 3 degrees is found to be tau = 1.3.10(-9) S for eta = 1 cP and T = 297 K.

Animals↗
PubMed1993

Indomethacin decreases viscosity of gallbladder bile in patients with cholesterol gallstone disease.

There is experimental evidence that inhibition of cyclooxygenase with nonsteroidal anti-inflammatory drugs may decrease cholesterol gallstone formation and mitigate biliary pain in gallstone patients. The mechanisms by which NSAIDs exert these effect are unclear. In a prospective, controlled clinical trial we examined the effects of oral indomethacin on the composition of human gallbladder bile. The study included 28 patients with symptomatic cholesterol or mixed gallstones. Of these, 8 were treated with 3 x 25 mg indomethacin daily for 7 days prior to elective cholecystectomy while 20 received no treatment and served as controls. Bile and tissue samples from the gallbladder were obtained during cholecystectomy. Indomethacin tissue levels in the gallbladder mucosa, as assessed by HPLC, were 1.05 +/- 0.4 ng/mg wet weight, a concentration known to inhibit effectively cyclooxygenase activity. Nevertheless, no differences between the treated and untreated groups were found in the concentrations of biliary mucus glycoprotein (0.94 +/- 0.27 versus 0.93 +/- 0.32 mg/ml) or total protein (5.8 +/- 0.9 versus 6.4 +/- 1.3 mg/ml), cholesterol saturation (1.3 +/- 0.2 versus 1.5 +/- 0.2), or nucleation time (2.0 +/- 3.0 versus 1.5 +/- 2.0 days). However, biliary viscosity, measured using a low-shear rotation viscosimeter, was significantly lower in patients receiving indomethacin treatment (2.9 +/- 0.6 versus 5.6 +/- 1.2 mPa.s; P < 0.02). In conclusion, in man oral indomethacin decreases bile viscosity without alteration of bile lithogenicity or biliary mucus glycoprotein content.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗
PubMed1984

Is viscosity important in the production of blood-brain barrier disruption by intracarotid contrast media?

A canine model was used to investigate the effects of intracarotid methylglucamine iothalamate (280 mgI/ml) at different viscosities on the normal blood-brain barrier. To alter viscosity, without changing physiochemical parameters, injections were made at either 23 degrees C or 37 degrees C. The degree of blood-brain barrier damage was assessed using Evans' Blue dye as a visual marker and by contrast enhancement measured by a computed tomographic (CT) scanner. It was found that methylglucamine iothalamate caused more blood-brain barrier damage at 23 degrees C than at 37 degrees C (p less than 0.1). Control studies at each temperature using intracarotid injections of physiological saline showed no temperature effect (p greater than 0.1). The implications of these findings are discussed.

Animals↗
PubMed1996

The influence of bolus volume and viscosity on anterior lingual force during the oral stage of swallowing.

The influence of bolus volume and viscosity on the distribution of anterior lingual force during the oral stage of swallowing was investigated using a new force transducer technology. The maximum force amplitudes from 5 normal adults were measured simultaneously at the mid-anterior, right, and left lateral tongue margins during 10 volitional swallows of 5-, 10-, and 20-ml volumes of water, applesauce, and pudding. Results indicated significant increases in peak force amplitude as viscosity increased. Volume did not significantly influence maximum lingual force amplitudes. Individual subjects demonstrated consistent patterns of asymmetrical force distribution across the lingual margins tested. The results suggest that bolus-specific properties influence the mechanics of oral stage lingual swallowing. This finding has important clinical implications in the assessment and treatment of dysphagic individuals.

Adult↗
PubMed1986

Viscosity of chromatin solutions increases with increasing ionic strength.

Increasing the ionic strength of rat liver chromatin solutions above 0.4 M causes increasing viscosity. This indicates transformation of the compact chromatin molecules to more elongated forms. In the range of 0.4-0.5 M ionic strength histone H1 is dissociating continuously from the chromatin and the quaternary structure chromatin unravels. At ionic strength higher than 0.5 M the viscosities of chromatin solutions are furthermore increasing due to structural deformation. Near 0.7 M ionic strength the core histones H2A and H2B begin to dissociate from the chromatin, and the opening of the nucleosome cores leads to increasing elongation of the chromatin molecules.

Animals↗
PubMed1982

Effects of growth temperature on transport and membrane viscosity in Streptococcus faecalis.

A shift in the growth temperature of Streptococcus faecalis from 37 to 10 degrees C resulted in an 18% increase in the proportion of unsaturated fatty acids. Electron spin resonance spectra of spin-labeled membranes and extracted phospholipids indicated viscosity changes consistent with the alterations in fatty acid composition. Growth temperature had no significant effect on the active transport of leucine and alanine; uptake rates assayed at 10 or 35 degrees C were essentially the same in cells grown at either 10 or 37 degrees C. The relative rapidity of amino acid transport, which presumably contributes to the ability of S. faecalis to thrive in cold environments, is evidently unrelated to adaptive changes in the viscosity of membrane lipids.

Alanine↗
PubMed1989

Blood viscosity in phocid seals: possible adaptations to diving.

1. Mean corpuscular volume (MCV) and mean corpuscular hemoglobin concentration (MCHC) of phocid seal red blood cells (RBC) are elevated compared to those of most terrestrial mammalian species. The influence of these characteristics on blood flow was revealed by viscosity (VIS) measurements. 2. RBC morphology and VIS of whole blood from 7 harbor seals and 5 northern elephant seals were compared with blood of the domestic pig. Samples were analysed for RBC count, white blood cell (WBC) count, total plasma proteins, hematocrit (HCT), MCV and MCHC. Viscosity measurements were made at shear rates from 11.5 to 230.4 s-1 on a Wells-Brookfield cone-plate viscometer at 37 degrees C. 3. Mean values for HCT (%), MCV (micron 3) and MCHC (%) were, respectively: elephant seal: 57, 176, 44; harbour seal: 53, 105, 38; domestic pig: 28, 54, 34. Pig blood was reconstituted to match seal blood HCTs. VIS determinations showed that seal and pig blood conform to the general mammalian dependence of VIS upon shear rate and HCT. 4. Seal blood VIS was 28% (harbour seal) and 16% (elephant seal) less than pig blood VIS at low shear (P less than 0.05). Seal blood carried more hemoglobin per unit volume than did pig blood reconstituted to the same HCT. Fewer, larger RBC with higher MCHC, and hence elevated oxygen storage, accompanied by reduced VIS and reduced flow resistance near stasis suggests that this feature of phocid seal blood is an adaptation to circulatory redistribution during long dives.

Adaptation, Physiological↗
PubMed1985

Viscosity as an additional physico-chemical parameter for studying chromatin structure.

The viscosity values of chromatin in higher order structures, which range from 0.1 to 0.4 dl/g, are considerably lower than those of isolated DNA. These low values are consistent with other physico-chemical parameters, such as sedimentation and diffusion coefficients. When deducing molecular mass and compact shape of chromatin molecules in solvents of nearly physiological ionic strength, all these parameters are in general agreement. A decrease in ionic strength increases viscosity and decreases s-value. Both effects are consistent with a chromatin model postulating a very compact quaternary structure which unravels in low ionic environment to an unfolded but not completely extended tertiary structure.

Animals↗
PubMedDate not supplied

Effects of pentoxifylline (Trental) on blood flow, viscosity, and oxygen transport in young adults with inoperable cyanotic congenital heart disease.

Four polycythemic young adults with inoperable cyanotic congenital heart disease were treated for 12 weeks with 20 mg/kg/day of pentoxifylline in an attempt to increase pulmonary blood flow by improving red blood cell demorability and decreasing whole blood viscosity. Treatment caused a rise in mean arterial oxygen saturation from 75-82%, a fall in the mean oxygen extraction coefficient from 47-40%, and a fall in mean oxygen consumption from 186-169 ml/min/m2. Pentoxifylline decreased whole blood, but not plasma, viscosity at all hematocrits over a range of shear rates. Two patients had significant bleeding episodes during treatment.

Adolescent↗
PubMed1990

Nonsteroidal antiinflammatory drugs exert differential effects on neutrophil function and plasma membrane viscosity. Studies in human neutrophils and liposomes.

Nonsteroidal antiinflammatory drugs (NSAIDs) inhibit neutrophil functions via mechanisms separate from their capacity to inhibit prostaglandin synthesis. We have studied discrete events in the process of signal transduction: NSAIDs but not a related analgesic drug (acetaminophen), inhibited aggregation in response to the chemoattractants f-Met-Leu-Phe (FMLP), leukotriene B4, and C5a. NSAIDs, but not acetaminophen, inhibited binding of radiolabeled FMLP to purified neutrophil membranes. Gpp(NH)p, a GTPase insensitive analog of GTP, also inhibited the binding of FMLP but, paradoxically, enhanced superoxide anion generation and lysozyme release. The inhibition of ligand binding by NSAIDs did not correlate with their capacity to inhibit FMLP-induced increments in diacylglycerol (DG): piroxicam, but not salicylate effectively inhibited appearance of label ([3H]arachidonate, [14C]glycerol) in DG. Finally, NSAIDs exerted differential effects on the viscosity of neutrophil plasma membranes and multilamellar vesicles (liposomes): membrane viscosity was increased by piroxicam and indomethacin, decreased by salicylate, and unaffected by acetaminophen. Thus, the different effects of NSAIDs on discrete pathways are not due to their shared capacity to reduce ligand binding but rather to a capacity to uncouple postreceptor signaling events that depend upon the state of membrane fluidity.

Acetaminophen↗
PubMed1995

Alteration of apparent viscosity of irradiated pepper--a tool for semi-quantitative estimation of irradiation dose.

The feasibility of using apparent viscosity (eta a) as a method for detecting the occurrence of previous irradiation of pepper was studied. Apparent viscosity of heat-treated suspensions of white and black pepper, nonirradiated or irradiated with different doses of ionising radiation (gamma), was measured under different "shear rates". Results of previous research were therefore expanded and their usefulness examined; low shear rate conditions were found to be preferable for the detection and semi-quantitative evaluation of irradiation doses. The experimental methodology for semi-quantitative estimation was developed and its scope and limitations are presented.

Dose-Response Relationship, Radiation↗
PubMed1982

Homologous controlled-viscosity fibrin for endovascular embolization. Part II: catheterization technique, animal experiments.

Part I of the present paper described the development of a substance for endovascular embolization from homologous fibrinogen, aprotinin, thrombin, metrizamide and CaCl2. Part II deals with the applicability of a controlled-viscosity fibrin mixture via different types of arterial catheters. In a flow-dynamic model the embolizing medium injected via a double syringe was shown to block a blood flow corresponding approximately to the flow encountered in cerebral angioma vessels. In the course of animal experiments the embolization of mesenteric arteries of rabbits showed the distribution of the embolizing medium to be dependent on its viscosity; the action of an embolizing medium applied by means of a double syringe was studied in the femoral arteries of rabbits. Scintigraphy was used to study the distribution of the substance in the body of the experimental animal after intravenous (i.v.) application; long-term studies of embolized auricular arteries in rabbits revealed parchment-like necroses after 5 to 10 days and the presence of radiopaque substances in the ear stumps after 6 weeks.

Animals↗
PubMed1978

[Blood viscosity and red cell deformability in primary hyperlipoproteinemia (author's transl)].

In patients with primary hyperlipoproteinemia (types IIa, IV, IIb) we determined by means of a Wells-Brookfield plateconeviscometer and an Ubbelohde capillary-viscometer the serum-, plasma-, apparent and relative apparent blood viscosity as well as the red cell deformability with a filtration technique. All parameters were found to be significantly changed in comparison to those of a normolipidemic control-group: The viscosity values of type IIb showed the greatest increase and of type IIa the smallest, while the red cell deformability was reduced in all types to the same degree.

Blood Viscosity↗
PubMed1986

Erythrocyte Na+-Li+ countertransport and blood viscosity in arterial hypertension.

The aim of this study was to evaluate together the main hemorheologic parameters and one of the transmembrane ion transport systems in erythrocytes of subjects with normal and elevated blood pressure. Three sex-, age-, and weight-matched groups consisting of 15 normotensive subjects (NT) with no parental hypertension, 15 patients with essential hypertension (EH) at stage 1-II WHO, and eight patients with secondary hypertension (Sec.H), respectively, were studied. Red blood cell Na+-Li+ countertransport (CTT), blood viscosity (eta B) at shear rates of 230 X S-1, 115 X S-1, and 46 S-1 and plasma viscosity (eta P) at shear rate of 46 X S-1 were measured. Plasma proteins and fibrinogen were also evaluated. CTT was higher in EH than in NT (P less than 0.01), while no significant difference was found between NT and Sec. H patients. eta B at 115 X S-1 and 46 X S-1 was higher in EH, but not in Sec. H, than in NT patients (P less than 0.05). No difference in eta P, plasma proteins and fibrinogen levels was observed between EH and NT. Elevated eta B and/or CTT may indicate a structural alteration in the erythrocyte membrane of some essential hypertensive patients. This is consistent with the hypothesis that a widespread membrane disorder is involved in the pathogenesis of primary hypertension.

Adolescent↗
PubMed1996

Haemodynamic and rheological effects of contrast media: the role of viscosity and osmolality.

All currently available iodinated contrast media (CM) produce some form of haemodynamic or rheological change when injected. These effects are thought to be due primarily to the osmolality and viscosity of the CM. The new hexa-iodinated contrast agent Visipaque has the advantage of being iso-osmotic with blood at all clinically relevant concentrations, but is more viscous than the monomers at equivalent iodine concentrations. The purpose of this review is to discuss the relative importance of osmolality and viscosity in the clinical situation.

Animals↗