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PubMed2002

Xylanase, beta-glucanase, and other side enzymatic activities have greater effects on the viscosity of several feedstuffs than xylanase and beta-glucanase used alone or in combination.

This study was carried out to evaluate the effects of a pure xylanase, a pure beta-glucanase, a mix of the two pure enzymes, and a commercial enzyme preparation (Quatrazyme HP, Nutri-Tomen Les Ulis, France) on the viscosity exhibited by water-soluble nonstarch polysaccharides of several feedstuffs (Rialto wheat, Sidéral wheat, Isengrain wheat, triticale, rye, barley, oats, corn, wheat bran, rice bran, wheat screenings, soybean meal, rapeseed meal, sunflower meal, and peas). The viscosity depended on the feedstuffs and varieties of the same feedstuff. There was a correlation (R (2) = 0.86) between viscosity of cereals and their arabinoxylan and beta-glucan contents. The correlation was greater (R (2) = 0.99) when the type of cereal was taken into account. The addition of pure xylanase significantly decreased the viscosity of all feedstuffs except sunflower meal (P < or = 0.05). However, pure beta-glucanase was unable significantly to decrease the viscosity of Isengrain wheat, corn, rice bran, wheat screenings, soybean meal, and sunflower meal. There was a greater decrease in viscosity with the combination of xylanase and beta-glucanase than with addition of xylanase or beta-glucanase alone. This synergistic action of xylanase and beta-glucanase was observed only in Rialto wheat, Sidéral wheat, triticale, rye, barley, oats, and peas. Finally, the commercial enzyme preparation produced a greater reduction (P < or = 0.05) in viscosity for all feedstuffs compared to xylanase or beta-glucanase used alone or in combination. The greater effectiveness of the commercial enzyme preparation was due to the presence of side enzymatic activities (arabinofuranosidase, xylosidase, glucosidase, galactosidase, cellulase, and polygalacturonase).

Animal Feed↗
PubMed2003

15N relaxation study of the cold shock protein CspB at various solvent viscosities.

For a detailed NMR study of the dynamics of the cold shock protein CspB from Bacillus subtilis, we determined (15)N transverse and longitudinal relaxation rates and heteronuclear nuclear Overhauser effects at different solvent viscosities. Up to a relative viscosity of 2, which is equivalent to 27% ethylene glycol (EG), the overall correlation time follows the linear Stokes-Einstein equation. At a relative viscosity of 6 (70% EG) the correlation time deviates from linearity by 30%, indicating that CspB tumbles at a higher rate as expected from the solvent viscosity probably due to a preferential binding of water molecules at the protein surface. The corresponding hydrodynamic radii, determined by NMR diffusion experiments, show no variation with viscosity. The amplitudes of intramolecular motions on a sub-nanosecond time scale revealed by an extended Lipari-Szabo analysis were mainly independent of the solvent viscosity. The lower limit of the NMR 'observation window' for the internal correlation time shifts above 0.5 ns at 70% EG, which is directly reflected in the experimentally derived internal correlation times. Chemical exchange contributions to the transverse relaxation rates derived from the Lipari-Szabo approach coincide with the experimentally determined values from the transverse (1)H-(15)N dipolar/(15)N chemical shift anisotropy relaxation interference. These contributions originate from fast protein folding reactions on a millisecond timescale, which get retarded at increased solvent viscosities.

Bacillus↗
PubMed2000

Paradoxical effects of viscosity on the VentrAssist rotary blood pump.

The ability of the VentrAssist blood pump to perform at its optimum design point is determined by a number of factors such as geometry of the pump, surface roughness, and fluid properties. Once the fluid properties are known, the performance characteristics of the pump can be optimized for that fluid. It is important to understand the effects of dynamic viscosity mu (called simply viscosity hereafter) on the performance characteristics and stability of the pump. The performance envelope of the pump and the needs of the patient must be matched. The VentrAssist pump has no shaft, seals, or fixed bearings and relies on the fluid-dynamic forces to maintain its effective performance. A number of different fluids have been tested to determine the effects of viscosity and density on pump performance. These include aqueous glycerol, red blood cells (RBCs) suspended in phosphate buffered saline solution (PBS), and Haemaccel. The effects of viscosity on the bearing stiffness, stage efficiency, and the pressure-flow rate (HQ) are characterized. The experimental results show a slight increase in the pressure rise across the pump shown as a positive upward shift of the H-Q curves with a decrease in viscosity; however, this is relatively small. A paradox in system efficiency exists: for a given fluid asymptotic viscosity, the system efficiency (product of magnetic and stage efficiency) using Haemaccel or PBS is greater than for the same viscosity of aqueous glycerol.

Blood Viscosity↗
PubMed2000

In vivo effects of Hb solutions on blood viscosity and rheologic behavior of RBCs: comparison with clinically used volume expanders.

BACKGROUND: Hb-based oxygen carriers (HbOCs) have vasoactive effects that are still poorly understood. Factors known to have vasoactive effects, such as plasma, whole-blood viscosity, and the rheologic behavior of RBCs, are modulated by HbOCs in vitro, but few in vivo studies have been performed. STUDY DESIGN AND METHODS: Rabbits were phlebotomized (30%) and resuscitated with unmodified stroma-free Hb (SFHb), dextran-tetracarboxylate-Hb (Dex-BTC-Hb), O-raffinose-polymerized Hb (OrpHb), HSA, or hydroxyethyl starch 200 (HES). Plasma viscosity was assessed with a capillary viscometer and whole-blood viscosity with a rotational viscosimeter. RBC aggregation kinetics were determined by analysis of back-scattered light in a rotating device. RESULTS: As compared to that in the control RBC suspension, resuscitation with SFHb, OrpHb, or HSA decreased plasma and whole-blood viscosity as well as RBC aggregation; resuscitation with Dex-BTC-Hb increased whole-blood viscosity at low shear rates as well as RBC aggregation, whereas that with HES decreased whole-blood viscosity but increased RBC aggregation. CONCLUSION: HbOCs have different rheologic effects in vitro and in vivo. There are marked differences among the Hb solutions in their in vivo effects on viscosity and RBC rheologic behavior (especially at low shear rates encountered in the venous circulation and the microcirculation), which may be related to the chemical modifications applied to hemoprotein. These results could contribute to an understanding of the vasoactive effects of HbOCs.

Adult↗
PubMed1987

Treatment of claudication with pentoxifylline: are benefits related to improvement in viscosity?

Forty-five patients with short-distance claudication were treated with pentoxifylline. The initial claudication distance increased significantly (32.5 m, p = 0.02) and the absolute claudication distance (ACD) increased significantly (49.5 m, p = 0.001) while the patients were receiving pentoxifylline. Patients with initial elevated viscosity levels were more likely to have decreased viscosity with pentoxifylline than were patients with normal viscosity levels (p = 0.01). No significant improvement in ACD or viscosity was noted in 51% of patients. Both ACD and viscosity improved in 15% of patients, viscosity improved without improvement in ACD in 9%, and ACD improved without improvement in viscosity in 25%.

Blood Viscosity↗
PubMed1997

Viscosity discrimination: a comparison of an adaptive two-alternative forced-choice and an adjustment procedure.

Differential thresholds for viscosity were measured in ten subjects with the use of an adaptive two-alternative forced-choice procedure. An electromagnetic linear motor was connected to each wrist and the viscosity of the motors was under computer servo control. For each block of 50 trials the viscosity of one motor was fixed at a reference value which ranged from 4 to 512 N s m-1, and the viscosity of the other motor varied according to the subject's responses. On each trial subjects were required to indicate which motor had the greater viscosity and were given feedback of the correct response. By this procedure the Weber fraction for viscosity was calculated to be 19%, which is lower than the Weber fraction of 34% estimated by using the method of adjustment. The criterion used for determining the threshold differs in the two procedures (71% and 84% correct, respectively), and the results from the two studies were found to be consistent. They suggest that the Weber fraction for viscosity remains remarkably stable despite differences in the methods of measurement.

Adult↗
PubMed2002

Influence of cement viscosity on cement interdigitation and venous fat content under in vivo conditions: a bilateral study of 13 sheep.

In a sheep model permitting standardized bilateral, simultaneous cement pressurization, we studied the effect of different cement viscosities on fat and bone marrow intravasation and cement penetration in vivo. High viscosity cement (Palacos) was used on one side and low viscosity cement (Osteopal) on the other. Catheters were inserted into both external iliac veins to collect blood during bilateral simultaneous cement pressurization. After bone preparation and pulsatile lavage, both femora were filled with cement followed by simultaneous cement pressurization. A quantitative fat analysis of the blood collected was done. We used microradiographs to determine cement penetration in a left versus right comparison of both viscosity groups. The low viscosity cement yielded lower rates of cement penetration despite adequate and sustained pressurization. Cement applied at low viscosity state seems to take the path of least resistance into the venous system before more deeper cement penetration can occur. The use of high viscosity cement ran a higher risk of fat embolism, but improved cement interdigitation.

Animals↗
PubMed2001

Nutrient digestibility and intestinal viscosities in broiler chickens fed on wheat diets, as compared to maize diets with added guar gum.

1. Three maize diets containing 0, 1 or 3 g of guar gum per kg and 2 wheat diets were given to male broiler chickens for measurements of growth performance and nutrient digestibility. 2. The intestinal viscosities found with wheat diets were within the range of those observed with the 3 maize diets. The correlations between in vivo and in vitro viscosities were higher with real than with potential applied viscosity. 3. The gain:food ratio decreased (P < 0.05) with the addition of 3 g guar gum/kg. The mean gain:food ratio observed for wheat diets was lower (P = 0.007) than the mean value found for the 3 maize diets. 4. The negative effects of increased intestinal viscosity due to guar gum addition on nutrient digestibility were highest for lipids and lowest for starch. 5. Wheat diets resulted in much lower (P < 0.001) starch apparent digestibility compared to maize diets with added guar gum despite similar mean intestinal viscosities in the 2 groups of diets. Apparent lipid digestibility with wheat diets was lower (P < 0.01) than the value predicted from intestinal viscosity, the predictive model having been calculated with the guar gum added maize diets. Apparent protein digestibility did not differ between wheat diets and guar gum added maize diets. 6. It was concluded that the low apparent digestibilities of starch and lipid observed with wheats could not be attributed only to intestinal viscosity and that other factors appear to be implicated in the low digestibilities observed with the wheat samples tested in the present experiment.

Animal Feed↗
PubMed1991

Low viscosity in the aqueous domain of cell cytoplasm measured by picosecond polarization microfluorimetry.

Information about the rheological characteristics of the aqueous cytoplasm can be provided by analysis of the rotational motion of small polar molecules introduced into the cell. To determine fluid-phase cytoplasmic viscosity in intact cells, a polarization microscope was constructed for measurement of picosecond anisotropy decay of fluorescent probes in the cell cytoplasm. We found that the rotational correlation time (tc) of the probes, 2,7-bis-(2-carboxyethyl)-5-(and-6-)carboxyfluorescein (BCECF), 6-carboxyfluorescein, and 8-hydroxypyrene-1,3,6-trisulfonic acid (HPTS) provided a direct measure of fluid-phase cytoplasmic viscosity that was independent of probe binding. In quiescent Swiss 3T3 fibroblasts, tc values were 20-40% longer than those in water, indicating that the fluid-phase cytoplasm is only 1.2-1.4 times as viscous as water. The activation energy of fluid-phase cytoplasmic viscosity was 4 kcal/mol, which is similar to that of water. Fluid-phase cytoplasmic viscosity was altered by less than 10% upon addition of sucrose to decrease cell volume, cytochalasin B to disrupt cell cytoskeleton, and vasopressin to activate phospholipase C. Nucleoplasmic and peripheral cytoplasmic viscosities were not different. Our results establish a novel method to measure fluid-phase cytoplasmic viscosity, and indicate that fluid-phase cytoplasmic viscosity in fibroblasts is similar to that of free water.

Animals↗
PubMed1997

Effects of milk viscosity on gastric emptying and lactose intolerance in lactose maldigesters.

The possibility of delaying gastric emptying and improving lactose digestion and tolerance by increasing milk viscosity was studied in 13 lactose maldigesters who ingested three test milks with different viscosities (range: 33-1892 mPa.s) in random order at intervals of 1 wk. Each test portion was 500 mL and provided approximately equal to 1900 kJ and 18 g lactose. The different viscosities were obtained by adding varying proportions of rice starch and maltodextrin to a basic milk formula. A combined [13C]glycine-hydrogen breath test was used to measure gastric emptying and lactose digestion simultaneously. Participants reported their gastrointestinal symptoms by using a four-grade scale. Mean (+/- SEM) gastric-emptying half times were 78 +/- 5.7 min for low-viscosity milk (30 mPa.s), 86 +/- 5.0 min for moderate-viscosity milk (80 mPa.s), and 78 +/- 4.5 min for high-viscosity milk (1.9.10(3) mPa.s). Mean orocecal transit times (180 +/- 24, 163 +/- 23, and 180 +/- 24 min, respectively) were not significantly different. There were no milk-dependent differences in breath-hydrogen excretion or in the severity of gastrointestinal symptoms. The milks were well tolerated; > 50% of the subjects reported nondisturbing symptoms or none. We conclude that gastric emptying, orocecal transit time, and lactose digestion and tolerance were not affected by altering milk viscosity. This may have been due to the high energy content of the test milks, which in itself led to slow gastric emptying.

Adult↗
PubMed1993

Dietary fiber viscosity and endogenous protein excretion at the terminal ileum of growing rats.

The effect of dietary fiber viscosity on the excretion of endogenous nitrogen and amino acids from the small intestinal lumen of growing rats was investigated. Rats were fed for 12 d protein-free diets containing 5% cellulose (negligible viscosity) or 5% carboxymethylcellulose of low (20 cP), medium (800 cP) or high (2000 cP) viscosity, as the sole dietary fiber source. As dietary fiber viscosity increased from 0 to 2000 cP, there was a significant (P < 0.05) linear increase in the flow of endogenous nitrogen, aspartic acid, serine, glutamic acid, proline, threonine, glycine, alanine, isoleucine, histidine, valine, methionine, leucine and lysine at the terminal ileum. The amino acid composition of the ileal digesta was unaffected by changes in fiber viscosity. It seems that either endogenous protein of a similar origin was secreted in larger amounts or that the digestion and absorption of endogenous amino acids was inhibited as dietary fiber viscosity increased. There was a significant (P < 0.05) linear increase in the concentration of sialic acids relative to chromic oxide in the small intestinal contents with increasing fiber viscosity, indicating an increase in mucoproteins.

Animals↗
PubMed1993

Viscosity and fermentability as attributes of dietary fiber responsible for the hypocholesterolemic effect in hamsters.

The attribute(s) of soluble dietary fibers responsible for cholesterol lowering is currently uncertain. A series of experiments were conducted in which viscosity and fermentability was assessed independently for their effect on plasma and liver cholesterol concentration. Hamsters were divided into four dietary groups and fed diets containing 0.12% cholesterol and 5% fiber as high viscosity hydroxypropyl methylcellulose (HV-HPMC group), low viscosity hydroxypropyl methylcellulose (LV-HPMC group), high viscosity guar gum (HV-GG group) or low viscosity guar gum (LV-GG group). Hydroxypropyl methylcellulose is essentially nonfermentable, whereas guar gum is highly fermentable. Plasma cholesterol concentrations at 3, 6 and 11 wk and liver cholesterol concentrations at 6 and 11 wk were significantly lower in the HV-HPMC group relative to the LV-HPMC group (P < 0.05). Intestinal content viscosities of the LV-HPMC and HV-GG groups were similar; consequently, these two groups were compared to examine the independent effect of fermentation. Plasma and liver cholesterol were significantly lower in the HV-GG group compared with the LV-HPMC group at 6 wk (P < 0.05), but not at 3 or 11 wk. Hepatic sterol synthesis rates were not affected by any of the diets. This study shows that greater viscosity of intestinal contents is strongly associated with cholesterol reduction, but that the contribution of fiber fermentation remains uncertain.

Animals↗
PubMed1996

Increased intestinal contents viscosity reduces cholesterol absorption efficiency in hamsters fed hydroxypropyl methylcellulose.

This study was conducted to test the hypothesis that increased intestinal contents viscosity lowers plasma cholesterol concentrations by decreasing cholesterol absorption. Male Golden Syrian hamsters were fed for 4 wk diets containing 0.12% cholesterol, and either 4% cellulose or four different viscosity grades of hydroxypropyl methylcellulose (HPMC). Dietary HPMC confers viscosity in the small intestine but is resistant to fermentation. Cholesterol absorption efficiency was measured using the dual isotope ratio method, and plasma and liver cholesterol concentrations were determined enzymatically. Ex vivo viscosity of intestinal contents supernatants was measured using a Wells-Brookfield cone/plate viscometer, and the means of treatment groups ranged from 6 to 6532 mPa.s. Relative to dietary cellulose, all viscosity grades of HPMC resulted in significantly lower cholesterol absorption efficiency, lower plasma cholesterol concentration, and lower liver cholesteryl ester content. The logarithm of intestinal contents ex vivo viscosity was inversely correlated with dietary cholesterol absorption (r2 = 0.84, P = 0.028). Furthermore, dietary cholesterol absorption was positively correlated with plasma cholesterol concentration (r2 = 0.89, P = 0.017) and liver cholesteryl ester content (r2 = 0.96, P = 0.0031). Thus, the data suggest an independent role of intestinal contents viscosity in lowering plasma cholesterol concentration and liver cholesteryl ester content by reducing cholesterol absorption efficiency.

Animals↗
PubMed2000

Evaluating the efficacy of enzyme preparations and predicting the performance of leghorn chicks fed rye-based diets with a dietary viscosity assay.

We studied whether a single-step dietary viscosity assay could be used to evaluate the efficacy of an enzyme when added to a poultry diet. The results demonstrated a linear relationship between the log of the dietary viscosity change in vitro, as determined with the new assay and the log of the enzyme activity (xylanase) added to a rye-based diet. The sensitivity of the dietary viscosity assay was high, as little as 0.19 U of xylanase per gram of diet could be detected. In addition, there was a high correlation (r > or = 0.97; P < 0.005) between chick performance and the log of the amount of enzyme added to the diet or the log of its viscosity change in rye-based diets that contained different amounts of xylanase, as determined by the in vitro dietary viscosity assay. Further, the dose response data from the dietary viscosity assay, when incorporated into a log-linear model that we developed, was able to distinguish between the efficacy of two enzymes with regards to their ability to hydrolyze the viscosity factor in rye grain. Therefore, it was possible to accurately evaluate the efficacy of enzyme preparations in a rye diet and to predict chick performance using the new assay in conjunction with a model equation.

Animals↗
PubMedDate not supplied

Effect of erythropoietin administration on blood and plasma viscosity in hemodialysis patients.

The effect of recombinant human erythropoietin (EPO) on whole blood and plasma viscosity was studied in six anemic hemodialysis (HD) patients, and five equally anemic placebo treated HD patients. Viscosity was determined pre- and postdialysis using cone-plate viscometry. Predialysis values for hematocrit and whole blood viscosity increased significantly over a 12 week period in the EPO but not the placebo treated group; plasma viscosity did not change in either group. Whole blood viscosity measured before and after a single HD session during week 12 revealed a significant rise. This change, expressed as a percent of the predialysis values, was similar in the two groups. Thus, the rise in whole blood viscosity seen in EPO treated patients is a result of the increase in erythrocyte concentration and not a result of an effect of EPO on plasma. In addition, EPO does not seem to alter the acute effect of HD on blood viscosity.

Adult↗
PubMed1995

Influence of viscosity on WIN 39996 as a contrast agent for gastrointestinal magnetic resonance imaging.

RATIONALE AND OBJECTIVES: The authors discuss the influence of viscosity on the imaging properties of WIN 39996 suspension. WIN 39996 suspension is a magnetically susceptible iron ferrite that provides negative (darkening) contrast enhancement in magnetic resonance imaging of the gastrointestinal tract. METHODS: The viscosity of WIN 39996 suspension was altered by various stress conditions (1 week to 4.5 months storage at temperatures of 5 degrees to 70 degrees C) or by various amounts of xanthan gum. Magnetic resonance imaging was performed in vitro on phantoms and in vivo on the gastrointestinal tract of anesthetized dogs. RESULTS: The results indicated that in vitro and in vivo imaging efficacies of WIN 39996 suspension depended on the viscosity, irrespective of the means by which the viscosity was altered. Specifically, the imaging quality was suitable at viscosities > or = 36.6 cp for in vitro imaging, and > 25 cp for in vivo imaging. The lower in vivo viscosity limit for magnetic resonance imaging compared with the in vitro limit may be due to gastrointestinal peristaltic activities continuously mixing the WIN 39996 suspension to prevent gravitational settling, and the enhancement of signal blackening by intraluminal WIN 39996 that was above and below the plane of image. CONCLUSIONS: It is speculated that the imaging quality of WIN 39996 suspension depends on the degree of dispersion of the magnetically susceptible iron ferrite in the WIN 39996 suspension, and that a minimum viscosity is needed to ensure such dispersion.

Animals↗
PubMed1996

The effect of omeprazole on gastric juice viscosity, pH and bacterial counts.

BACKGROUND: In vitro studies have shown that pH is an important determinant of mucus structure and function, but the relationship in vivo is unclear. Omeprazole increases intragastric pH and also allows bacterial overgrowth. In this study we have assessed the effect of omeprazole on gastric juice viscosity and examined the influence of pH and bacterial overgrowth on the resulting change. METHODS: Gastric juice specific viscosity, pH and total bacterial counts were measured in nine healthy male volunteers before and after omeprazole 20 mg twice daily for 1 week. The effect of incubation at pH 2 and 7 was also determined. Viscosity changes were compared with changes in pH and bacterial counts. RESULTS: Mean viscosity fell (P < 0.05) following treatment, though there was a wide range in viscosity both before and after treatment. The decrease was reproduced by incubation of pre-treatment juice at pH 7 but not pH 2. The fall in viscosity was correlated (P < 0.05) with change pH. CONCLUSION: Omeprazole decreases gastric juice, and hence gastric mucus, viscosity by increasing intragastric pH. This could be important if it allows improved penetration of antimicrobials to Helicobacter pylori within the mucus layer.

Adult↗
PubMed2006

The effect of temperature on viscosity of root canal sealers.

AIM: To test the hypothesis that there was no significant (alpha = 0.05) change in viscosity of commercially available root canal sealers with increase in temperature using a high-performance Advanced Rheometric Expansion System (ARES) rheometer. METHODOLOGY: Materials tested were Apexit, Tubliseal EWT, Grossman's, AH Plus and Ketac-endo. Cone-and-plate geometry was used (25-mm diameter, 0.1 radian and gap 0.051 mm). Measurements were carried out for steady-state viscosity at 25 and 37 degrees C in the shear rate range of 0.001-50 s(-1) at standardized relative humidity and within 30 min from the start of mixing. Five samples were taken for each sealer at each temperature. RESULTS: At 25 degrees C all sealers demonstrated shear thinning. At 37 degrees C Grossman's (powder : liquid ratio 2 : 1 and 3 : 1) and Ketac-endo had a rapid rise in viscosity and early set whereas the other sealers were shear thinning. On increasing temperature from 25 degrees C to 37 degrees C, Apexit, Tubliseal and AH Plus had reduced viscosity whereas Grossman's 2 : 1, Grossman's 3 : 1 and Ketac-endo had increased viscosity, which varied with the shear rate. The change in viscosity with change in temperature was significant (P < 0.05) for all sealers except AH Plus. CONCLUSIONS: There was a variation in the effect of increasing temperature on each sealer depending on the shear rate. With the exception of AH Plus, a significant (P < 0.05) change in viscosity was found, and the null hypothesis was rejected.

Calcium Hydroxide↗