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PubMed1974

Effect of viscosity on swimming velocity of bacteria.

A theory is given for the swimming velocity of a flagellated bacterium and its variation with the viscosity of the surrounding fluid. The theory is shown to agree fairly well with the experimental observations of Schneider and Doetsch on Pseudomonas aeruginosa for viscosities greater than 2 centipoise. However, it fails to account for the decrease of velocity observed when the viscosity decreases from 2 to 1.1 centipoise.

Bacterial Physiological Phenomena↗

PubMed2005

Viscosity effects on eukaryotic nitrate reductase activity.

Rate-limiting processes of catalysis by eukaryotic molybdenum-containing nitrate reductase (NaR, EC 1.7.1.1-3) were investigated using two viscosogens (glycerol and sucrose) and observing their impact on NAD(P)H:NaR activity of corn leaf NaR and recombinant Arabidopsis and yeast NaR. Holo-NaR has two "hinge" sequences between stably folded regions housing its internal electron carriers: 1) Hinge 1 between the molybdenum-containing nitrate reducing module and cytochrome b domain containing heme and 2) Hinge 2 between cytochrome b and cytochrome b reductase (CbR) module containing FAD. Solution viscosity negatively impacted the activity of these holo-NaR forms, which suggests that the rate-limiting events in catalysis were likely to involve large conformational changes that restrict or "gate" internal electron-proton transfers (IET). Little effect of viscosity was observed on recombinant CbR module and methyl viologen nitrate reduction by holo-NaR, suggesting that these activities involved no large conformational changes. To determine whether Hinge 2 is involved in gating the first step in IET, the effects of viscosogen on cytochrome c and ferricyanide reductase activities of holo-NaR and ferricyanide reductase activity of the recombinant molybdenum reductase module (CbR, Hinge 2, and cytochrome b) were analyzed. Solution viscosity negatively impacted these partial activities, as if Hinge 2 were involved in gating IET in both enzyme forms. We concluded that both Hinges 1 and 2 appear to be involved in gating IET steps by restricting the movement of the cytochrome b domain relative to the larger nitrate-reducing and electron-donating modules of NaR.

Amino Acid Sequence↗

PubMed1981

The effect of guar gum on the viscosity of the gastrointestinal contents and on glucose uptake from the perfused jejunum in the rat.

1. Male Wistar rats were meal-fed for at least 10 d a control semi-synthetic diet containing no guar gum, or one of three similar test diets containing 3, 10 or 20 g dry guar gum/kg. 2. Rats were killed 6 h after feeding, and contents of stomach, small and large intestine were collected separately. The apparent viscosities of stomach and small intestine contents from animals fed on diets containing 10 and 20 g guar gum/kg were increased relative to control animals, but large intestine contents were unchanged. 3. In the second part of this study, male Wistar rats were anaesthetized and two consecutive lengths of jejunum were perfused, initially with Ringer only (control) or Ringer plus 5 or 6 g guar gum/1 (test). Following this pre-perfusion, both segments were perfused with Ringer containing glucose (10 mM), [3H]glucose and [14C]inulin, and the rate of glucose absorption was determined. 4. The rate of glucose absorption was decreased relative to control values in segments pre-perfused with both 5 and 6 g guar gum/1 solution, but this reduction was significant only in the instance of the 6 g/l solution (P less than 0.001). 5. These results provide evidence to support previous assumptions that ingestion of guar gum will increase the apparent viscosity of the contents of the stomach and small intestine. We propose that a possible mechanism by which guar reduces post-prandial glycaemia is a reduction of glucose absorption from the small intestine, resulting from an increase in viscosity of the contents.

Animals↗

PubMed1995

The effects of diffusion and viscosity on ruminant faecal excretion of markers in a simple compartmental model.

Using equations obtained in a previous analysis, results are computed numerically which illustrate the effects of diffusion and viscosity on faecal excretion patterns of markers in ruminants. Results are first given for plug flow, a velocity gradient produced by viscosity, and diffusion, each mechanism operating alone. Plug flow gives a period during which no marker appears in the faeces, then a sharp increase in faeces marker concentration, followed by rapid washout. A velocity gradient gives a more gradual appearance of marker in the faeces followed by a slower washout. Diffusion alone (although not realistic for ruminant marker kinetics) can give early appearance of marker followed by slow washout. Combining diffusion with a velocity gradient produced by viscosity can give a range of behaviour, depending on the effective diffusion coefficient, D'; an approximate method is used to compute these solutions. Because plug flow with no velocity gradient plus diffusion gives results similar to convective flow with a velocity gradient plus diffusion, we believe it will not be possible to determine the main mechanisms defining marker outflow patterns from observations of marker kinetics alone, and more detailed investigations will be needed. Although estimates of quantities such as mean transit time are unaffected by detailed mechanism, the interpretations of measures such as sigmoidicity, sharpness of the faecal marker concentration v. time curve, and length and nature of the washout tail are highly dependent on mechanism.

Animals↗

PubMed2006

High-viscosity carboxymethylcellulose reduces carbachol-stimulated intestinal chloride secretion in weaned piglets fed a diet based on skimmed milk powder and maltodextrin.

High-viscosity carboxymethylcellulose (CMC) promotes gastrointestinal disorders, tissue alterations and bacterial overgrowth in pigs. The impact of CMC on intestinal absorptive and secretory physiology is not known. We hypothesised that CMC consumption alters intestinal Na-dependent glucose absorption and stimulates electrogenic chloride secretion. For testing this hypothesis, twenty-four piglets were weaned at 21 d of age and pair-fed for 13 d a starter diet based on skimmed milk powder and maltodextrin containing cellulose (control) or CMC. Body weight and faecal total aerobe and coliform counts were measured kinetically. At slaughter, digesta were weighed and characterised for viscosity and pH. Gastrointestinal tissues were weighed and sampled for physiology in Ussing chambers, morphometry and enzymology. Glucose absorption tended to be higher (P = 0.08) and carbachol-stimulated chloride secretion was lower (P = 0.01) with CMC in the small intestine, without changes in the colon. Aerobes were transiently higher at day 7 (P < 0.05) but coliform counts remained unchanged (P = 0.78) and beta-haemolitic Escherichia coli were virtually absent. Stomach and small-intestinal segments were heavier, and viscosity higher with CMC (0.001 < P < 0.05). The pH in the stomach was higher, and in the caecum and proximal colon lower with CMC (0.001 < P < 0.05). Jejunal villus area was slightly reduced with CMC (P < 0.05) without effects on enzyme activities (P > 0.10). In conclusion, CMC supplementation had pro-absorptive effects on the small intestine, possibly due to the absence of pathogenic E. coli in the present study.

Animals↗

PubMed2005

The effect of conditioning temperature and exogenous xylanase addition on the viscosity of wheat-based diets and the performance of broiler chickens.

1. A total of 1920 Ross broiler chicks were used in a 6 treatment by 8 replicate growth study to investigate the effect of conditioning temperature and exogenous xylanase addition on diet characteristics and bird performance. 2. Increasing conditioning temperature from 80 to 90 degrees C increased the viscosity of the diets by approximately 6 mPa.s and reduced body weight gain of the broiler chickens by 7%. 3. Furthermore, there was a significant interaction between temperature and the addition of exogenous xylanase, with a proportionately greater positive response to added xylanase in the diets that were pelleted at higher temperatures. 4. Addition of exogenous xylanase also increased the proportion of soluble arabinoxylan in the feed and reduced dietary viscosity, which is likely to be related to the degree of polymerisation of the soluble carbohydrate. 5. These results suggest that conditioning temperature should be considered as a factor when attempting to predict the response of broilers to added xylanase, especially when high-viscosity or 'low-quality' wheat is being used. 6. It can be concluded that pelleting wheat-based diets above 80 degrees C can compromise bird performance and that, if higher temperatures are to be employed, the use of exogenous xylanase is critical to maintain productivity.

Animal Feed↗

PubMed2000

Blood viscosity, plasma adrenaline and fasting insulin in hypertensive patients with left ventricular hypertrophy. ICARUS, a LIFE Substudy. Insulin CARotids US Scandinavica.

We have seen relationships between whole blood viscosity (WBV) and components of the metabolic cardiovascular syndrome in borderline hypertensive young men and suggested that sympathetic nervous system (SNS) activity may be a mediator. In the present study we aimed to test this hypothesis in established hypertension and to investigate the relationship between WBV and cardiac dimensions. Unmedicated patients (n = 42) with stage II-III hypertension and electrocardiographic left ventricular hypertrophy (LVH) underwent hyperinsulinemic isoglycemic glucose clamp to assess glucose disposal rate (GDR) and echocardiographic studies. WBV, plasma catecholamines and insulin were measured in arterialized venous blood. WBV at high shear rate correlated with baseline plasma adrenaline (r = 0.33, p = 0.04) and fasting insulin (r = 0.34, p = 0.04) while there was a negative trend for GDR (r = -0.21, p = 0.2). WBV at low shear rate correlated with plasma adrenaline (r = 0.49, p = 0.002) and resting heart rate (r = 0.36, p = 0.02). WBV was higher in smokers than in non-smokers (p = 0.02) and in males than in females (p = 0.02). Fasting insulin independently explained 12% of the variation in WBV at high shear, while baseline adrenaline independently explained 17% of the variation in WBV at low shear. Systolic blood pressure explained 31% of the variation in LV mass index. Thus, we demonstrate positive relationships between blood viscosity versus plasma adrenaline and fasting insulin in hypertensive patients with LVH. We suggest that adrenergic activity may increase hematocrit and viscosity and hence reduce insulin sensitivity.

Aged↗

PubMed2005

Water-binding capacity and viscosity of Australian sweet lupin kernel fibre under in vitro conditions simulating the human upper gastrointestinal tract.

There is currently little understanding of the physicochemical properties in the human gastrointestinal tract of Australian sweet lupin (Lupinus angustifolius) kernel fibre (LKF), a novel food ingredient with potential for the fibre enrichment of foods such as baked goods. Since physicochemical properties of dietary fibres have been related to beneficial physiological effects in vivo, this study compared water-binding capacity and viscosity of LKF with that of other fibres currently used for fibre-enrichment of baked goods, under in vitro conditions simulating the human upper gastrointestinal tract. At between 8.47 and 11.07 g water/g dry solids, LKF exhibited water-binding capacities that were significantly higher (P < 0.05) than soy fibre, pea hull fibre, cellulose and wheat fibre at all of the simulated gastrointestinal stages examined. Similarly, viscosity of LKF was significantly higher (P < 0.05) than that of the other fibres at all simulated gastrointestinal stages. The relatively high water-binding capacity and viscosity of LKF identified in this study suggests that this novel fibre ingredient may elicit different and possibly more beneficial physiological effects in the upper human gastrointestinal tract than the conventional fibre ingredients currently used in fibre-enriched baked goods manufacture. We are now performing human studies to investigate the effect of LKF in the diet on health-related gastrointestinal events.

Absorption↗

PubMed1999

Viscosity, energy density and osmolality of gruels for infants prepared from locally produced commercial flours in some developing countries.

Forty market samples of locally produced (33) and imported (7) cereal-based flours used for complementary feeding in some African countries and Vietnam were studied in order to characterise their macronutrient content and, when prepared as gruels, their viscosity, energy density, and osmolality. The results show that less than half were fairly balanced with respect to their protein and lipid content. When prepared as gruels following the manufacturers' instructions, out of the 21 locally produced flours with complete instructions, ten had energy densities too low to provide sufficient energy to complement breastmilk for 9-11-month-old infants even at three meals a day (< 77 kcal or 322 kJ/100 g), nine were satisfactory if fed more than twice a day, and two if fed twice a day (> 116 kcal or 485 kJ/100 g). Two of the 11 with acceptable energy density had osmolality values higher than those reported in literature for complementary feeding (< 660 mOsm/kg H2O). In addition, when prepared as gruels with viscosities within the range of viscosity (1 to 3 Pa.s) usually observed in African countries, 14 of the 32 (44%) locally produced flours had insufficient energy densities to meet the energy requirements of infants even at three meals a day. These results call for greater concern and effort towards improving the nutritive value and energy density of cereal-based complementary foods produced in developing countries.

Cameroon↗

PubMed2004

Viscosity of animal erythrocyte suspensions mixed with a perflurocarbon emulsion.

Artificial blood substitutes (ABS) offer an alternative to donated blood. Increasing the oxygen carrying capacity of blood plasma through the addition of a Perfluorocarbon emulsion (PFE) is one approach in creating a blood substitute. The peripheral resistance of the circulatory system may be altered depending on the rheological properties of the ABS. Measurements of the rheological behavior of mixtures of a PFE, Oxygent, and erythrocyte suspensions were conducted at room temperature at different hematocrits using sheep (nonaggregating) and swine (aggregating) erythrocytes. The pure PFE was found to be shear thinning. Adding 6 and 12 g per 100 mL of sheep blood at the various hematocrits increased the viscosity of the suspension from as low as 4% (6 g PFE/40% Hct) to as high as 26.5% (12 g PFE/plasma). The nonaggregating sheep erythrocyte and PFE mixtures exhibited Newtonian behavior. Shear thinning behavior continued upon addition of 6 and 12 g per 100 mL of swine blood at the various hematocrits, with a slight increase in viscosity in most cases. It was observed that adding 12 g of PFE (approximately 3 x intended clinical dose) to 40% Hct swine blood at room temperature led to a significant decrease in viscosity.

Animals↗

PubMed2001

Effects of low-viscosity sodium hyaluronate preparation on the pulmonary absorption of rh-insulin in rats.

PURPOSE: A low-viscosity formulation for pulmonary delivery of rh-insulin as model peptide drugs was developed using a solution of sodium hyaluronate. METHOD: The effects of different concentrations and pH values of low-viscosity solutions of hyaluronate on the pulmonary absorption of rh-insulin were examined after intratracheal administration in rats. The permeation of fluorescein isothiocyanate (FITC)-dextran (molecular weight 4300; FD-4) and insulin through excised rat trachea in vitro were also examined. RESULTS: The hyaluronate (2140 kDa) solutions (0.1% and 0.2% w/v) at pH 7.0 significantly enhanced the pharmacological availability (PAB) of insulin compared to the aqueous solution of insulin at pH 7.0. The absorption-enhancing effect at a concentration of 0.1% w/v hyaluronate was greater than that at a concentration of 0.2% w/v hyaluronate. Furthermore, the greatest absorption-enhancing effect was obtained, regardless of the molecular weight of hyaluronate, when the concentration of hyaluronate was adjusted to 0.47 microM. Absorption-enhancing effects were consistent with the effect of a 0.1 w/v hyaluronate preparation at pH 4.0 and 7.0 on the permeation of FITC-dextran and insulin through excised rat trachea in vitro. CONCLUSION: Low-viscosity hyaluronate preparation was shown to be a useful vehicle for pulmonary delivery of peptide drugs.

Absorption↗

PubMed2001

Effects of light intensity, n-alcohols, water-soluble colorants, and solution viscosity on photoisomerization of sorivudine.

Effects of various factors, such as light intensity, polarizability of n-alcohol solvents, addition of colorants, and viscosity of solutions on the kinetics of the photoisomerization of therapeutically effective E-isomer of sorivudine to its less effective Z-isomer were studied. Solutions of known concentrations of E-isomer or Z-isomer in water or in a series of n-alcohols were directly exposed to ultraviolet (UV) A light, or visible light of 400 or 900 foot candles (fc). E-isomer solutions containing various colorants at 1% w/v, or in a series of poloxamer solutions of different viscosities, were also exposed to 400 or 900 fc light. Using the stability-indicating HPLC assay, which showed mass-balance between the starting isomer and the converting isomer, the kinetics of photoisomerization were monitored. The photoisomerization reaction, which takes place on the vinyl side chain, was found to be a first-order reversible reaction. In water, the rate of conversion of E-isomer to Z-isomer was faster than that of Z-isomer to E-isomer, since, E-isomer with higher extinction coefficient absorbed substantially more light than Z-isomer. The rate of photoisomerization increased with the intensity of the visible light and was very rapid in the presence of UV A light (300 to 400 nm), which is to be expected based on the 239 nm and 283 nm absorption maxima of sorivudine. Addition of water-soluble colorants retarded the photoisomerization process significantly, especially as the maximum absorption wavelengths (lambda max) of the colorants approached the UV region. The rate of photoisomerization increased with increasing polarizability (alpha s) of the n-alcohol solvents. Polarizable solvents such as alcohols could compensate for the electron density built up in the excited state, and thus facilitated the photoisomerization process. The rate of photoisomerization decreased as the viscosity of solution increased. This may be attributed to the fact that the twisting of the C=C bond in the excited state can be inhibited by the friction imposed by the viscous medium.

Alcohols↗

PubMed2000

Influence of drying temperature and granulation liquid viscosity on the inter- and intragranular drug migration in tray-dried granules and compacts.

The influence of the drying temperature and granulation liquid viscosity on the inter- and intragranular migration of a poorly water-soluble compound in a granulation mass and in a compact was quantitatively assessed. The intergranular migration kinetics were investigated by evaluating the drug distribution at different drying-time intervals. The results were analyzed by use of two-factor, three-level, face-centered, central composite designs. Riboflavin was mixed with alpha-lactose monohydrate 90 M and granulated with distilled water, except for the viscosity experiments in which an aqueous polyvinylpyrrolidone (PVP) (Kollidon K90) solution was used. The wet granules were dried in a hot-air oven or compacted prior to drying. The drug concentration at different locations inside the granulated mass and the compacts after drying was determined spectrophotometrically and by use of diffuse light reflectance measurements. The riboflavin distribution in the granulation masses and in the compacts was characterized by drug-enriched outer layers and drug-depleted inner regions, indicating a strong migration phenomenon. It was clear that the drying temperature had no influence on the inter- and intragranular drug distribution. The intergranular migration was avoided using the PVP as a binder in the granulation liquid, whereas a minimal granulation liquid viscosity of 100 mPa.sec was necessary to avoid the intragranular migration. The diffuse light reflectance measurements can be used for the in-process control of granule samples containing low drug concentrations without the destruction of the samples.

Hot Temperature↗

PubMed2004

A blood-oxygenation-dependent increase in blood viscosity due to a static magnetic field.

As the magnetic field of widely used MR scanners is one of the strongest magnetic fields to which people are exposed, the biological influence of the static magnetic field of MR scanners is of great concern. One magnetic interaction in biological subjects is the magnetic torque on the magnetic moment induced by biomagnetic substances. The red blood cell is a major biomagnetic substance, and the blood flow may be influenced by the magnetic field. However, the underlying mechanisms have been poorly understood. To examine the mechanisms of the magnetic influence on blood viscosity, we measured the time for blood to fall through a glass capillary inside and outside a 1.5 T MR scanner. Our in vitro results showed that the blood viscosity significantly increased in a 1.5 T MR scanner, and also clarified the mechanism of the interaction between red blood cells and the external magnetic field. Notably, the blood viscosity increased depending on blood oxygenation and the shear rate of the blood flow. Thus, our findings suggest that even a 1.5 T magnetic field may modulate blood flow.

Adult↗

PubMed2004

In vitro effects of helium-neon laser irradiation on human blood: blood viscosity and deformability of erythrocytes.

OBJECTIVE: The purpose of this study was to investigate the in vitro effects of He-Ne laser irradiation on some rheological factors of human blood, such as blood viscosity, erythrocyte deformability, and sedimentation rate. BACKGROUND DATA: The intravascular irradiation of low power laser has been applied in pre-clinical and clinical to treat various pathological processes. However, the mechanism is not fully understood so far. Especially the interaction and related mechanism between the laser and blood are unclear. In this work, by measuring the change of the main rheological factors after laser irradiation, the interaction and mechanism were explored. METHODS: A30-mW He-Ne laser was used for irradiation with a 4-5-mm-diameter beam spot on blood samples, with a fluence rate of about 150 mW/cm.(2) The irradiation time was 60 min, so the total dose of irradiation was 540 J/cm.(2) The pathological samples of blood were obtained from patients (volunteers), and each sample was divided into two tubes for irradiation and control. The blood viscosity, erythrocyte deformability, and sedimentation rate were measured after laser irradiation and compared with un-irradiated control. The blood samples with poor erythrocyte deformability were prepared by adding Ca(2+) to the normal erythrocytes of a healthy person for investigating the laser effect on erythrocyte deformability further. RESULTS: Laser irradiation reduced the erythrocyte sedimentation rate of blood samples, which had a hyper-sedimentation rate originally. The blood viscosity of samples in hyper-values was lowered by laser irradiation in all shear rates measured (10-110 S(-1)), with a relative variation of approximately 10%. The deformability of erythrocytes from pathological samples and Ca(2+)-treated samples was improved after laser irradiation. CONCLUSIONS: The positive effects of laser irradiation on improving the rheological properties of blood were demonstrated in vitro.

Blood Sedimentation↗

PubMed1988

Copper deficiency anemia: altered red blood cell lipids and viscosity in rats.

To investigate membrane lipid abnormalities and their possible role in copper deficiency anemia, we studied lipids, osmotic fragility, and viscosity of red blood cells (RBCs) of rats fed diets containing 1.1 mg Cu/kg (deficient, Cu-) and 6.0 mg Cu/kg (supplemented, Cu+) at age 3 wk for 9 wk. Data show an increase in cholesterol of 43% and in phospholipids of 38% per cell in Cu- compared with Cu+ rats. Thin-layer chromatography of RBC lipids showed an increased amount of phospholipid-malonyldialdehyde adduct in Cu- (0.70 +/- 0.35% [means +/- SD] of total phospholipids) compared with Cu+ (0.29 +/- 0.19%) rats, suggesting increased membrane lipid peroxidation in Cu- RBC. Osmotic fragility of RBCs from Cu- rats was lower. RBC viscosity was significantly higher in Cu- than in Cu+ rats at shear rates of 23, 11.5, and 5.75 shear/s and was similar at shear rates 115 and 46 shear/s. Increased cell viscosity caused by lipid loading and crosslinking of membrane components caused by lipid peroxidation may have a role in the reduced RBC survival and anemia in Cu deficiency.

Animals↗

PubMed1990

Plasma viscosity, fibrinogen and haematocrit in the course of unstable angina.

Plasma viscosity, fibrinogen and haematocrit were measured in 80 patients with unstable angina on the 1st, 2nd and 5th day of hospitalization. In the group of patients who developed acute myocardial infarction (AMI) during hospitalization (20 patients), plasma viscosity was elevated during the entire observation period (1.69 +/- 0.05 cp, normal range 1.38-1.48 cp), while in patients who did not develop AMI, plasma viscosity was only mildly elevated (1.59 +/- 0.05 cp, P less than 0.001 vs the group who developed AMI) and tended to normalize towards the 5th day of hospitalization. Fibrinogen and haematocrit showed similar variations between the two groups. In a group of 20 patients who received heparin, the studied parameters were similar to the group who did not develop AMI. The importance of haemorheological factors in the clinical course of unstable angina is thus emphasized.

Adult↗

PubMed1975

Viscosity and molecular weight of hyaluronic acids.

The intrinsic viscosity ([eta]) and the molecular weight (M) by sedimentation equilibrium were determined for hyaluronic acids of low (M=104--7.2X10(4)) and high (M=3.1X10(5)--1.5X10(6)) molecular weights. Double logarithmic plot of [eta] against M gave different lines for the two groups. The relationship between [eta] and M was [eta]=3.0X10(6)XM1,20 for the former and [eta]=5.7X10(-4)XM0.46 for the latter group. The molecular weight at the point of intersection of the two lines was about 1.5X10(5). The rheological behavior of the hyaluronic acids below M=2.1X10(4), for which the value of reduced viscosity was independent of concentration, was different from that of the hyaluronic acids above M=5.1X10(4), for which the value of reduced viscosity increased with concentration.

Female↗