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PubMed1992

The influence of erythrocyte shape on suspension viscosities.

Erythrocyte shape changes are known to occur in vivo and can readily be induced in vitro. We have analysed the influence of increasing stomatocytosis produced by 0-0.64 mmol l-1 chlorpromazine and increasing echinocytosis induced with 0-120 mmol l-1 salicylate or 0-8 mmol l-1 2,4-dinitrophenol on suspension viscosities. The morphological index of each sample was determined and related to the suspension viscosity. It was found that the viscosity was increased by echinocytosis in dextran-free solutions, where no aggregation occurred. The viscosity could be normalized by retransforming echinocytes into discocytes. Under conditions with erythrocyte aggregation (suspension with 4 g dl-1 dextran 70, low shear rate: 0.1 s-1) a small degree of echinocytosis produced the highest viscosity, whereas at higher degrees of echinocytosis the ability to aggregate was reduced and the viscosity was similar to that of discocytes or stomatocytes. Erythrocytes incubated in hypotonic medium (constant cell number/volume) had a higher viscosity than cells in iso- or hypertonic medium. Severely hypotonic medium led to sphering of erythrocytes which reduced the ability of these cells to aggregate and hence decreased the viscosity of suspensions with dextran at low shear rate. The results indicate that discocytes have the lowest viscosity and thus the best oxygen transport efficiency and that iso- to hypertonicity provides a lower viscosity and better oxygen transport efficiency than hypotonicity. These results may contribute to the understanding of blood flow in health and disease.

Blood Viscosity↗

PubMed1987

Whole blood viscosity during normal pregnancy.

In a serial study the changes in whole blood viscosity at different shear rates and its major determinants were determined in 24 healthy women with normal pregnancies. Whole blood viscosity and plasma viscosity were measured with a rotational viscometer. Red cell aggregation was measured by syllectometry. During normal pregnancy we found a decrease in whole blood viscosity at all shear rates until 29 weeks gestation, followed by a smaller increase between 30 and 37 weeks, which was most pronounced at higher shear rates, especially in nulliparae. The changes in whole blood viscosity were to a great extent determined by the changes in haematocrit and plasma viscosity. Haematocrit was more important for whole blood viscosity at lower shear rates, while plasma viscosity had more influence on high shear blood viscosity. The continuous increase in red cell aggregation had no demonstrable influence on low shear blood viscosity as measured in vitro in a rotational viscometer.

Blood Viscosity↗

PubMed2000

Plasma viscosity and cerebral blood flow.

We hypothesized that the response of cerebral blood flow (CBF) to changing viscosity would be dependent on "baseline" CBF, with a greater influence of viscosity during high-flow conditions. Plasma viscosity was adjusted to 1.0 or 3.0 cP in rats by exchange transfusion with red blood cells diluted in lactated Ringer solution or with dextran. Cortical CBF was measured by H(2) clearance. Two groups of animals remained normoxic and normocarbic and served as controls. Other groups were made anemic, hypercapnic, or hypoxic to increase CBF. Under baseline conditions before intervention, CBF did not differ between groups and averaged 49.4 +/- 10.2 ml. 100 g(-1). min(-1) (+/-SD). In control animals, changing plasma viscosity to 1. 0 or 3.0 cP resulted in CBF of 55.9 +/- 8.6 and 42.5 +/- 12.7 ml. 100 g(-1). min(-1), respectively (not significant). During hemodilution, hypercapnia, and hypoxia with a plasma viscosity of 1. 0 cP, CBF varied from 98 to 115 ml. 100 g(-1). min(-1). When plasma viscosity was 3.0 cP during hemodilution, hypercapnia, and hypoxia, CBF ranged from 56 to 58 ml. 100 g(-1). min(-1) and was significantly reduced in each case (P < 0.05). These results support the hypothesis that viscosity has a greater role in regulation of CBF when CBF is increased. In addition, because CBF more closely followed changes in plasma viscosity (rather than whole blood viscosity), we believe that plasma viscosity may be the more important factor in controlling CBF.

Anemia↗

PubMed1996

Blood viscosity in broilers: influence on pulmonary hypertension syndrome.

Elevation in apparent blood viscosity may enhance the pulmonary hypertension that leads to pulmonary hypertension syndrome (PHS) and ascites in fast-growing broilers. We investigated the importance of packed cell volume (PCV) and shear rate in modifying apparent viscosity of the blood from broilers assigned to normal, preascites, and ascites groups. Apparent viscosity of broiler blood increased at all shear rates as PCV increased; the increase in apparent viscosity became greater as the shear rate decreased at PCV above 0.30. At the PCV of normal broilers (0.30 or below), apparent viscosity was nearly shear rate independent, at least down to 11.25 per second, the lowest shear rate studied. Apparent viscosity, at any given PCV and shear rate, was significantly lower in the blood of birds with ascites than in normal birds; however, the relative viscosity was not different between those groups, indicating that lower plasma viscosity in the birds with PHS was responsible for the finding. The results show that the principal factor responsible for increased apparent viscosity of blood in birds with PHS is the increase in PCV. The increased resistance to flow of blood as the result of higher blood viscosity may contribute to the pulmonary hypertension.

Animals↗

PubMed2002

[The whole blood and plasma viscosity changes in course of acute myocardial infarction].

The whole blood and plasma viscosity changes in course of acute myocardial infarction were examined. The examination were performed at the beginning of acute phase of myocardial infarction (period 1), at second to third day (period 2) and after about 10 days of infarction episode (period 3). 77 patients (mean age 56.8 +/- 9.8 years) suffered from myocardial infarction were examined. The whole blood viscosity at following shear rates [s-1]: 0.116; 1.0; 4.59; 150 and plasma viscosity were performed. Besides the viscometric examinations the total cholesterol, LDL-cholesterol, HDL-cholesterol, triglycerides, glucose and fibrinogen as well as blood morphology and ESR were determined. All rheological measurements were carried out at the temperature of 37 degrees C immediately after blood drawing. The control group consisted of 110 healthy persons (aged 56.6 +/- 10 years). Some persons of control group have got risk factors of atherosclerosis as: obesity, artery hypertension and cigarette smoking. The following additional parameters were investigated: hematocrit, the artery pressure, the body mass index, total cholesterol concentration, serum LDL-cholesterol, HDL-cholesterol, fibrinogen and blood morphology. The corrected whole blood viscosity was adjusted to 45% of hematocrit. It was stated that the native whole blood viscosity was disturbed at all periods of disease. The corrected whole-blood viscosity in all periods of acute myocardial infarction comparing with controls increased. The greatest rise of corrected whole blood viscosity was especially observed in second period of acute myocardial infarction. Plasma viscosity in patients with acute myocardial infarction is increased in all periods. The greatest rise of plasma viscosity was in second period of disease. The rheological blood and plasma disturbances were connected with increase of total cholesterol, LDL-cholesterol, triglycerides and fibrinogen. These disturbances of blood and plasma viscosity may play a role in promoting myocardial infarction factors.

Adult↗

PubMed1992

Hematocrit and whole blood viscosity in newborns: analysis of 100 cases.

Hematocrit (Hct) and whole blood viscosity was studied at a mean age of ten hours in 100 neonates. Group A (n = 25), were term normal newborns, Group B (n = 25) were preterms, Group C (n = 20) were term small for gestation (SGA) and Group D (n = 30) had perinatal hypoxia. Blood viscosity was estimated in all cases at shear rates 94.5, 51.2, 20.4 and 8.1 and intergroup variability in viscosity compared at shear rate 51.2. The mean hematocrit (Hct) (59.4%) and viscosity (8.2 cps) was higher in Group A as compared to other groups, but the difference was not significant (p greater than 0.05). The upper limit of viscosity in Group C (11.9 cps) was higher than in all other groups but this difference was also not significant (p greater than 0.05). With decrease in shear rates a reciprocal increase in viscosity was noted in all four groups. Seventeen neonates (17%) had polycythemia of which eight (47.5%) were SGA. Twelve per cent preterms were polycythemic. Only 3% of neonates had hyperviscosity. The mean Hct and viscosity of the 17 cases with polycythemia was 70.9 and 9.21 cps, respectively, which was significantly higher than mean Hct and viscosity of Group A (p less than 0.05). Partial exchange transfusions were done in five neonates with Hct greater than 75%, of which only one had hyperviscosity. Post-exchange viscosity was not estimated. Whereas, three neonates with polycythemia were symptomatic, none of these had hyperviscosity. A linear correlation between Hct and viscosity was observed (r = 0.67).

Blood Viscosity↗

PubMed1991

Effect of hydroxypropylmethylcellulose on gastrointestinal transit and luminal viscosity in dogs.

The effects of hydroxypropylmethylcellulose on upper gastrointestinal transit, viscosity, and water flux were studied in six dogs fistulated at the proximal duodenum and/or mid-jejunum. Combinations of different grades of hydroxypropylmethylcellulose were prepared as 2% or 3.3% solutions to yield input viscosities of low (approximately 5000 cp at 37 degrees C and 1 s-1), medium (15,000 cp), or high (30,000 cp) viscosity. Hydroxypropylmethylcellulose modified intralumenal viscosity, with a linear relationship existing between input and lumenal viscosity. With regard to transit, the lag time before the onset of chyme recovery increased linearly as a function of luminal viscosity. There was also a pronounced decrease in the first-order emptying rate constant as lumenal viscosity increased from water to low-viscosity hydroxypropylmethylcellulose, but as viscosity was further increased there was little additional change. These results indicate that water-soluble fibers can exert a significant influence on both the lumenal viscosity and the transit profile in the upper gastrointestinal tract.

Animals↗

PubMed1988

The effect of hemodialysis on whole blood, plasma and erythrocyte viscosity.

The effect of hemodialysis (HD) on blood viscosity has not been adequately investigated. We studied blood viscosity during HD employing coneplate viscometry. Ten patients with end-stage renal disease were studied before and immediately after HD. To dissect the possible effects of HD on plasma and red blood cell (RBC) determinants, we measured whole blood, plasma, and reconstituted erythrocyte viscosities. The latter consisted of RBC's suspended in a buffered saline solution (pH = 7.4 units). In addition, serum, electrolytes and hematocrit (HCT) were measured. The results revealed a significant rise in whole blood viscosity after dialysis. Likewise, plasma viscosity rose considerably with dialysis. However, when the RBC's were reconstituted to a constant HCT, no significant difference was noted before and after HD. As expected, body weight, blood urea nitrogen (BUN) and creatinine concentrations fell while HCT and protein concentration rose with HD. A significant correlation was found between the observed rise in HCT, and dialysis-induced rise in whole blood viscosity. Likewise, the observed rises in plasma viscosity after dialysis significantly correlated with the rise in protein concentration. In addition, the change in whole blood and plasma viscosity values correlated with the degree of ultrafiltration (weight loss). In conclusion, whole blood and plasma viscosity rises with hemodialysis. The observed rise in viscosity is primarily due to hemoconcentration.

Acid-Base Equilibrium↗

PubMed1977

Blood viscosity in Waldenström macroglobulinemia.

Patients with Waldenström macroglobulinemia were studied for the presence or absence of the hyperviscosity syndrome, the relative serum viscosity value, and the calculated whole blood viscosity to identify a level at which symptoms occurred. The majority of symptomatic patients had whole blood viscosity values above 8.0 centipoises. There was a direct correlation between whole blood viscosity and relative serum viscosity, r = 0.75. One patient with central nervous system abnormalities was identified as having a high whole blood viscosity but a low serum viscosity. It was concluded that the vast majority of patients with the hyperviscosity syndrome will be identified by measuring the relative serum viscosity. In patients with central nervous system findings and a low serum viscosity, the whole blood viscosity should be determined either by direct measurement or by calculation.

Blood Viscosity↗

PubMed1996

Apparent viscosity of the synovial fluid from mid-carpal, tibiotarsal, and distal interphalangeal joints of horses.

OBJECTIVE: To compare the apparent viscosity of normal synovial fluid of the mid-carpal, tibiotarsal, and interphalangeal joints of horses. DESIGN: Viscosity evaluation over a range of shear rates was used to characterize the apparent viscosity of synovial fluids from the 3 joints. ANIMALS: 60 clinically normal adult horses. PROCEDURE: Viscosity data for synovial fluid samples were obtained over a shear rate range of 10 to 250/s and apparent viscosity was calculated at 50, 100, 150, 200, and 250/s. Effect of shear rate on apparent viscosity was determined, using a two-way ANOVA, with significant differences tested, using a Tukey's test at a significance level of P < 0.05. RESULTS: Synovial fluid from all these joints indicated shear thinning behavior: decreased apparent viscosity with increased shear rate. Apparent viscosity of synovial fluid from the 3 joints was not significantly different over the shear rate range of 50 to 250/s. CONCLUSION: Results of this study indicate that the apparent viscosity of the distal interphalangeal joint is not less than that of other joints, as has been reported. CLINICAL RELEVANCE: The observation of decreased synovial fluid viscosity of distal interphalangeal joint fluid should be considered as suggestive of joint disease.

Analysis of Variance↗

PubMed1998

Opposite effects of low-density and high-density lipoprotein on blood viscosity in fasting subjects.

Given the enlarging body of evidence implicating increased blood viscosity in atherogenesis, the authors hypothesize that lipoproteins modulate the atherogenic process by affecting blood viscosity. In order to define the magnitude of the effect of lipoproteins on blood viscosity, capillary viscometry was performed on blood from 16 healthy, fasting subjects, and results were correlated with lipoprotein-cholesterol levels. Low-density lipoprotein-cholesterol was positively associated with blood viscosity (r = 0.610, p = 0.01). High-density lipoprotein-cholesterol was negatively associated with blood viscosity (r = -0.479, p = 0.06). A multiple regression model was developed with these data, revealing that 54% of variation in blood viscosity was attributable to these lipoproteins. This model was validated on a second dataset, in which these lipoproteins accounted for 28% of variation in blood viscosity. A second model, including hematocrit, serum viscosity, and high-density lipoprotein-cholesterol levels, explained 73% of variation in blood viscosity. By modulating blood viscosity and flow, lipoproteins may affect the residence time of atherogenic particles and atherogenesis.

Adult↗

PubMed2005

Effects of Viscoseal, a synovial fluid substitute, on recovery after arthroscopic partial meniscectomy and joint lavage.

This was a pilot, single blind, randomised, controlled study in patients requiring partial meniscectomy. The aim was to assess whether replacing the synovial fluid lost during arthroscopy with a hyaluronic acid-containing synovial fluid substitute (Viscoseal) would reduce the severity and duration of post-operative symptoms during the 4 weeks post-surgery, in comparison to the standard arthroscopy procedure alone. Fifty patients were randomly assigned to either undergo arthroscopic partial meniscectomy alone (control group: n=25) or to receive 10 ml Viscoseal into the joint at the end of the procedure (Viscoseal group: n=25). Forty patients (20 per group) completed the study. Despite the small patient population in this pilot study, some interesting results were obtained. On Day 1 after surgery, the mean values for pain at rest (VAS) increased in both groups but this increase was lower in the Viscoseal group (8.9+/-23.1 mm) than in the standard therapy group (20.0+/-25.9 mm) (Mann-Whitney statistic MW-S: P=0.0525) and remained in favour of Viscoseal for the first 3 days after surgery. Joint swelling decreased to a greater extent in the Viscoseal group with an observed superiority at Day 7 (MW-S: P=0.1187) and a proven superiority at Days 12 (MW-S: P=0.015) and 28 (MW-S: P=0.0072). Diclofenac intake was lower in the Viscoseal group from Day 3 to Day 28 with a proven superiority (LB-CI > 0.5) in favour of Viscoseal on Days 3 (MW-S: P = 0.0093), 4 (MW-S: P= 0.0075), and 7 (MW-S: P = 0.0195) indicating that the product had an NSAID-sparing effect. Viscoseal was safe and well-tolerated and no adverse reactions occurred during the study. These findings indicate that Viscoseal may be useful as a synovial fluid substitute after arthroscopy.

Activities of Daily Living↗

PubMed2003

A modified model for non-newtonian viscosity behavior of Aureobasidium pullulans culture fluid.

The culture fluid of the fungus Aureobasidium pullulans and the exopolysaccharide solution obtained by removal of the microbial cells exhibit a marked shear dependence of viscosity. The viscosity in a high shear rate region was a little higher than that predicted by a non-Newtonian viscosity equation derived previously on the basis of the concept of traveling force. In a sample exhibiting such high shear rate dependence, a hydrodynamic effect based on the fluid structure of the binding of contacting polymers and suspended microbial cells on viscosity becomes comparatively significant. A model for the shear rate dependence of the viscosity is needed to elucidate the mechanism of the viscosity behavior. A term concerning the increase in viscosity caused by the binding of polymers and the microbial cells suspended in a medium was added to the previous viscosity equation. The experimental shear dependence of the viscosity was well simulated by the modified viscosity equation.

Journal Article↗

PubMed2005

Pressure dependence of viscosity.

We reanalyze the pressure dependence of viscosity of liquids of constant composition under isothermal conditions. Based exclusively on very general considerations concerning the relationship between viscosity and "free volume," we show that, at moderate values of pressure, viscosity increases, as a rule, with increasing pressure, provided the liquid is in stable or metastable (undercooled) equilibrium states. However, even if the behavior of the viscosity is governed by free volume effects, deviations from a positive pressure dependence are possible, when the liquid's thermal expansion coefficient is negative. We derive an equation that allows one to quantitatively determine the pressure dependence of viscosity, which requires, in the simplest case, only the knowledge of the temperature dependence of viscosity at constant pressure, the thermal expansion coefficient, and the isothermal compressibility of the liquid. As an example, the negative pressure dependence of water in the range of temperatures 0-4 degrees C and of several silicate liquids, such as albite, jadeite, dacite, basalts, etc., could be explained in such a way. Other glass-forming liquids initially (for moderate pressures) show a positive pressure dependence of viscosity that changes to a negative one when subjected to high (approximately GPa) isostatic pressure. A detailed analysis of water and already mentioned silicate melts at GPa pressures shows that, in addition to free volume effects, other pressure induced structural transformations may have to be accounted for in a variety of cases. By this reason, the theoretical analysis is extended (i) in order to describe the pressure dependence of viscosity for systems that are in frozen-in thermodynamic nonequilibrium states (glasses, i.e., undercooled liquids below the glass transition temperature Tg) and (ii) to systems which undergo, in addition to variations of the free volume, pressure induced changes of other structural parameters. In such cases a decrease of viscosity with increasing pressure may occur, in principle, even if the thermal expansion coefficient is positive. In this way, the present analysis grants a general tool to estimate the pressure dependence of viscosity and supposedly settles the controversy in the current literature.

Journal Article↗

PubMed2000

In vitro and in vivo determination of the UV protection factor for lightweight cotton and viscose summer fabrics: a preliminary study.

BACKGROUND: One of the most important elements in the prevention of skin cancer is the use of comfortable UV-protective clothing. Owing to their low weight, cotton fabrics, and especially viscose fabrics made from filament yarns, are ideal for summer clothing and in fact enjoy a high degree of acceptance among consumers. Two methods are available for determining the UV protection factor (UPF) of textiles: the in vitro method is based on the spectrophotometric determination of the transmission of UV radiation through these fabrics; the in vivo method is based on the determination of the minimal erythema dose for a test subject with and without textiles. OBJECTIVE: This study was performed to assess the UPF of lightweight cotton and viscose fabrics and whether the use of these two methods to determine the UPF of viscose fabrics and cotton fabrics produces congruent results. METHODS: We tested 7 different viscose fabrics and 7 different cotton fabrics. Three of the viscose fabrics (ENKA SUN) had been specially treated, by depositing pigments in the fibers, to confer UV-protective properties. The determination of the in vitro and in vivo UPF was performed with a spectrophotometer and sun simulator, respectively. RESULTS: The in vivo measurements on the untreated viscose fabrics produced UPF values lower than those obtained from the in vitro measurements. For one of these untreated viscose fabrics, the difference between the in vivo UPF and the in vitro UPF was statistically significant (P <.05). In contrast, the in vivo measurements on the specially treated viscose textiles and on the cotton fabrics resulted in UPF values higher than the in vitro UPF values. For one specially treated viscose fabric and 4 cotton fabrics, this difference was statistically significant (P < .05). CONCLUSION: Our results suggest, however, that-depending on the type of fabric-determination of the UPF by the in vitro method is not in agreement with the in vivo method. In vivo measurements made with lightweight specially treated UV-protective clothing showed in contrast to the untreated viscose fabrics that these garments offer very good protection against UV radiation. These results underscore the importance of developing and refining such UV-protective materials.

Adult↗

PubMed2003

Evaluation of a new high-viscosity octylcyanoacrylate tissue adhesive for laceration repair: a randomized, clinical trial.

OBJECTIVE: Tissue adhesives have recently been approved for skin closure. Their low viscosity may result in inadvertent migration. The authors compared the tendency of the adhesive to migrate after laceration closure with a high- or low-viscosity octylcyanoacrylate (OCA). METHODS: This was a randomized, clinical trial set in university and community-based emergency departments. Participants included patients with simple traumatic lacerations. Patients were randomized to laceration closure with low- or high-viscosity OCA tissue adhesive. The outcome measured was immediate adhesive migration (interobserver agreement, kappa = 0.90). Data analysis was performed with proportions compared with chi-square and Fisher's exact tests. RESULTS: Eighty-four patients were randomized to low- (n = 42) or high- (n = 42) viscosity OCA tissue adhesive. Groups were similar in baseline patient and wound characteristics. The high-viscosity OCA was less likely to migrate than the lower-viscosity agent (21% vs. 78%, p < 0.001; odds ratio = 0.3, 95% confidence interval = 0.1 to 0.5). The proportion of patients who noted a sensation of heat during OCA application was higher in the high-viscosity groups (44% vs. 26% respectively, p = 0.11); however, all such patients in both groups would use the device again. At 14 days, there were no wound infections in either group. There was one dehiscence in the high-viscosity group. CONCLUSIONS: The high-viscosity OCA tissue adhesive was less likely to migrate than the lower-viscosity device. Wound dehiscence and infection rates were acceptably low in both treatment groups.

Adolescent↗

PubMedDate not supplied

The influence of suspending phase viscosity on the passage of red blood cells through capillary-size micropores.

Much attention has been paid to the study of blood flow in long, narrow tubes. While the influence of tube diameter and driving pressure have been examined in detail, the influence of suspending phase viscosity has generally been assumed only to affect the blood viscosity in a linearly proportional manner, hence the practice of normalizing apparent blood viscosity values by the suspending phase viscosity to give a relative viscosity (e.g., Pries et al., 1992). While this assumption is probably valid for long tubes, it apparently does not hold for blood flow in short tubes (and by extension also for flow in short or branching capillary segments in vivo) in which RBC deformation plays a more significant role. In this paper we present a series of experiments using the Cell Transit Analyzer (CTA) in which the influence of driving pressure and suspending phase viscosity on RBC passage through short, narrow tubes has been systematically evaluated. Over the range studied (1 to 10 cm water), the influence of driving pressure was found to be unremarkable, in that RBC velocity scaled directly and linearly with pressure. This finding is consistent with previous studies. However, a distinct intercept was observed in the linear relationship between RBC pore transit time and suspending phase viscosity, which presumably arises as a consequence of RBC deformation either at the pore entrance or within the pore. Two simple mathematical models for the suspending phase-viscosity/transit-time relationship were considered. The results show that making CTA measurements over a range of suspending medium viscosities is a simple and practical way to obtain additional information about RBC mechanical properties.

Blood Pressure↗

PubMed1998

Effect of viscosity on metachrony in mucus propelling cilia.

In the present work we report that increasing the viscosity of the medium caused not only a decrease in the ciliary beat frequency but also changes in the metachrony and correlation between cilia. The study was performed using double and triple simultaneous photoelectric measurements on cultured ciliary cells from the frog esophagus in the viscosity range of 1-2,000 cp. We observed that increasing the viscosity intensified the fluctuations in all the measured parameters. Ciliary beat frequency decreased moderately. Even at quite high viscosities (circa 2000 cp.), cilia were still active with beating frequencies of 3-5 Hz. In addition, the degree of correlation between cilia parallel to the effective stroke direction (ESD) decreased, while that perpendicular to the ESD at a low range of viscosities remained unchanged and even increased at high viscosities. Medium viscosities in the range of 30-1,500 cp. altered the metachronal wave properties of cultured frog esophagus. The metachronal wavelength increased by up to 50%, and the wave direction changed towards more orthoplectic type of coordination. According to our recently suggested model [Gheber and Priel, 1990: Cell Motil. Cytoskeleton 16:167-181], these effects can be explained by a decrease in the temporal asymmetry of the ciliary beat. Since similar results were observed in water propelling cilia of Paramecium subjected to medium viscosity ranges of up to 40 cp. [Machemer, 1972: J. Exp. Biol. 57:239-259], we conclude that hydrodynamic interactions govern the metachronal wave properties of both mucus and water propelling cilia, though mucus propelling cilia, with their better adaptation to increased load, are affected at much higher viscosities than water propelling cilia.

Animals↗