Rheological properties of the anterior vaginal fluid from superovulated dairy heifers at estrus

Anterior vaginal fluid samples were collected from 25 dairy heifers induced to superovulation at 12 to 20 hours after estrus detection. Thixotropy and flow behavior were evaluated. In samples from 19 heifers, structural variation was registered and the fluids were considered to be thixotropic; in the remaining samples (6 heifers), structural variation was not registered and the fluids were considered to be nonthixotropic. The mean estradiol concentration of the thixotropic fluids (20.8 pg/ml) was lower (P=0.0002) than of the nonthixotropic samples (56.7 pg/ml). All the nonthixotropic samples of anterior vaginal fluid exhibited Newtonian behavior. Of the 25 thixotropic anterior vaginal fluid samples, 10 exhibited Newtonian behavior while 9 exhibited non-Newtonian behavior. Heifers in which samples exhibited Newtonian behavior had a higher mean estradiol concentration (38.8 pg/ml; P=0.003) than heifers in which samples exhibited non-Newtonian behavior (12.8 pg/ml). Estradiol concentrations were correlated negatively (P=0.02) with the index of consistency (r = -0.46) and were not related to structural variation (P=0.08), although a certain tendency was shown. These results have shown that thixotropic and flow behavior measurements in the anterior vaginal fluid of superovulated estrous heifers vary over a wide range and even qualitatively. This variation is related to estrogen levels: Fluidity increases with increased plasma estrogen values, and the integrity of the gel structure tends toward elimination.     

The relationship of rheological behavior of the vaginal fluid at the time of insemination to the pregnancy rate in dairy cows

The objective of this study was to determine whether rheological properties of the vaginal fluid at the time of insemination could be used as an indicator of potential fertility in dairy cows. Thixotropy and flow behavior were evaluated. Vaginal samples were collected from 347 cows at the time of insemination, within a 12- to 24-h interval after the onset of a natural estrus. Logistic regression analysis showed no significant effects of thixotropy measurements on the pregnancy rate, while flow behavior and the index of consistency (K) had a significant effect. The decrease in the consistency index (K) was related to the increase in the pregnancy rate (odds ratio = 0.99; P = 0.014), and the risk of nonpregnancy was higher (odds ratio = 0.46; P = 0.024) in cows in which vaginal fluid had a Newtonian behavior. Non-Newtonian behavior was recorded in 294 samples (85%) while 53 behaved as Newtonian fluids. For samples from all cows, the mean value of the consistency index was 310 +/- 28.2 milliPascals.second(n) (x +/- SEM) and ranged from 0 to 3881 milliPascals.second(n). In Newtonian samples, the consistency index mean was 2.6 +/- 0.6 milliPascals.second(n) and 367.6 +/- 30.4 milliPascals.second(n) for non-Newtonian samples. Of the 347 cows, 131 (38%) became pregnant. For flow behavior classification, 15 (28.3%) cows in which samples had Newtonian behavior and 116 (39.5%) cows with non-Newtonian samples became pregnant. Therefore, the highest probability of pregnancy was shown by cows in which samples had non-Newtonian behavior and the lowest consistency index values. Our data suggest that flow behavior measurements of the vaginal fluid at the time of insemination may be an indicator of potential fertility in cattle.     

Relationship of sperm migration in anterior vaginal fluid and embryo quality in superovulated dairy heifers

Anterior vaginal fluid samples from 26 superovulated dairy heifers at insemination were classified into 2 grades: 1) with abnormal sperm penetration ability when vanguard sperm migration was randomly oriented; and 2) with normal sperm penetration ability when vanguard sperm migration was parallel and unidirectional. Vanguard sperm behavior and vanguard sperm migration distances were evaluated for their effects on fertilized ova recovery rates and transferable embryo recovery rates. Twelve vaginal fluid samples (46%) showed abnormal sperm penetration ability (Grade 1) and the mean +/- sem distance traveled by the vanguard spermatozoa into these samples (7.3 +/- 0.9 mm) was different (P<0.0001) from the remainder of the samples (48 +/- 3.4 mm) in which sperm penetration was registered as normal (Grade 2). In heifers in which anterior vaginal fluid samples were Grades 1 and 2, the fertilized ova recovery rates were 78.3% and 80.2%, respectively (P=0.91). Transferable embryo recovery rates were 54.2% and 32% for Grades 1 and 2, respectively (P<0.001). Using correlation and linear regression analysis, the sperm migration distance in Grade-2 samples was not related to fertilized ova (P=0.77) or to transferable embryo recovery rates (P=0.97). These results indicate that vanguard sperm movement into capillary tubes varied qualitatively and was related to subsequent embryo quality.     

Rheological behavior of the vaginal fluid of dairy cows at estrus

The present study was conducted to evaluate rheological properties of the vaginal fluid in dairy cows. Thixotropy and flow behavior were evaluated. Vaginal fluid samples were collected in 8 cows at the beginning of a natural estrus and then every 8 h for 24 h. Vaginal samples were also collected from 208 cows at the time of insemination within 12 to 24 h interval after the onset of a natural estrus.Time-dependent variations were registered during the estrus. The limit shear stress for flow production (T_o), the shear stress of equilibrium (T_e) and the consistency index (K) decreased at 8 and 16 h and markedly increased 24 h after the beginning of estrus. At the time of insemination, structural variation was registered and the fluids were considered to be thixotropic in samples of 181 cows (87%); in the remaining samples (27 cows), structural variation was not registered and the fluids were considered to be nonthixotropic. For flow behavior values, 178 samples (85.6%) presented non-Newtonian behavior, while 30 behaved as Newtonian fluids. The mean values of the T_O and the T_e were 6.1 ± 0.69 and 1.9 ± 0.69 pascals, respectively. Consistency index (K) mean was 364.9 ± 41.4 milipascals per secondⁿ Our data show an increase of fluidity at the middle of the estrus period in the cow and a wide variation of rheological measurements of vaginal fluid at the time of insemination.     

Effects of surrounding fluid on motility of hyperactivated bovine sperm

Mammalian spermatozoa in organisms with internal fertilization are required to swim in the cervical and oviductal mucus, whose rheological properties differ substantially from those of water. Moreover, on the way to the oviduct, a change in sperm motility called hyperactivation may occur. In the present study, we focused on the motion characteristics of hyperactivated bovine sperm and investigated the effect of the surrounding fluid on motility. We prepared two kinds of polyacrylamide with high-viscosity non-Newtonian fluid properties, similar to the actual cervical and oviductal mucus. Using semen from Japanese cattle, we evaluated curvilinear velocity (VCL), straight-line velocity (VSL), and average path velocity (VAP). Additionally, we estimated linearity (LIN), straightness (STR), and wobble (WOB) as sperm motility parameters for several surrounding fluids. We successfully induced hyperactivation of bovine sperm in high-viscosity non-Newtonian fluid. Hyperactivation resulted in an increase in VCL and a decrease in VSL. In the high-viscosity non-Newtonian fluid, the hyperactivated sperm moved in a zig-zag pattern with regularity, different from the movement observed in a diluted solution. The increase in WOB in the non-Newtonian fluid suggests that hyperactivated sperm efficiently progress along the groove that exists on the oviductal mucus wall. These results improve our understanding of the motility of bovine sperm when they undergo hyperactivation in the actual cervical and oviductal mucus.     

Absorption of oxygen in highly viscous newtonian and non-Newtonian fermentation model media in bubble column bioreactors

Summary Mean relative gas holdup, slip velocity, bubble size distribution, mean specific interfacial area, and volumetric mass transfer coefficient of oxygen were estimated in sparged columns 14 cm in diameter and 380 and/or 390 cm high with two different aerator types (porous plate and injector nozzle) in highly viscous Newtonian (glycerol solutions) and non-Newtonian (CMC solutions) fluids.For the Newtonian liquids the above properties were estimated as function of the viscosity of the liquid. For the non-Newtonian liquids they were determined as function of the fluid consistency index and flow behavior index. Significant differences between Newtonian and non-Newtonian systems appear. In Newtonian medium k_L a drops with increasing viscosity and already approaches a constant value at =40 cP. In pseudoplastic medium k_L a varies with the fluid consistency and flow behavior indexes in the entire investigated range.In both of these systems the primary bubble population changes into two or three populations along the reactor: the medium bubbles gradually disappear and small and large bubbles are formed.     

自絮凝酵母SPSC01悬浮液的流变行为

用旋转黏度计测定了自絮凝颗粒酵母悬浮液的流变特性,并考察了其流变特性的影响因素,如菌体生物量、葡萄糖质量浓度、温度等。结果表明：自絮凝颗粒酵母悬浮液呈假塑性非牛顿流体,其流变特性服从幂律指数模型,随着菌体浓度的增大,稠度系数增大,流动行为指数减小;絮凝悬浮液的表观黏度随着糖浓度的增加有所增加,同一生物量下稠度系数k随着糖浓度的增加而增加,流动行为指数n随着糖浓度的增加变化很小,悬浮液的表观黏度随着温度的升高而降低;相同生物量下的流变指数随温度的升高而升高,而稠度系数随温度升高有所下降。     

Numerical study of the impact of non-Newtonian blood behavior on flow over a two-dimensional backward facing step

Endothelial cell (EC) responsiveness to shear stress is essential for vasoregulation and plays a role in atherogenesis. Although blood is a non-Newtonian fluid, EC flow studies in vitro are typically performed using Newtonian fluids. The goal of the present study was to determine the impact of non-Newtonian behavior on the flow field within a model flow chamber capable of producing flow disturbance and whose dimensions permit Reynolds and Womersley numbers comparable to those present in vivo. We performed two-dimensional computational fluid dynamic simulations of steady and pulsatile laminar flow of Newtonian and non-Newtonian fluids over a backward facing step. In the non-Newtonian simulations, the fluid was modeled as a shear-thinning Carreau fluid. Steady flow results demonstrate that for Re in the range 50-400, the flow recirculation zone downstream of the step is 22-63% larger for the Newtonian fluid than for the non-Newtonian fluid, while spatial gradients of shear stress are larger for the non-Newtonian fluid. In pulsatile flow, the temporal gradients of shear stress within the flow recirculation zone are significantly larger for the Newtonian fluid than for the non-Newtonian fluid. These findings raise the possibility that in regions of flow disturbance, EC mechanotransduction pathways stimulated by Newtonian and non-Newtonian fluids may be different.     

The influence of the non-Newtonian properties of blood on the flow in large arteries: steady flow in a carotid bifurcation model.

Laser Doppler anemometry experiments and finite element simulations of steady flow in a three dimensional model of the carotid bifurcation were performed to investigate the influence of non-Newtonian properties of blood on the velocity distribution. The axial velocity distribution was measured for two fluids: a non-Newtonian blood analog fluid and a Newtonian reference fluid. Striking differences between the measured flow fields were found. The axial velocity field of the non-Newtonian fluid was flattened, had lower velocity gradients at the divider wall, and higher velocity gradients at the non-divider wall. The flow separation, as found with the Newtonian fluid, was absent. In the computations, the shear thinning behavior of the analog blood fluid was incorporated through the Carreau-Yasuda model. The viscoelastic properties of the fluid were not included. A comparison between the experimental and numerical results showed good agreement, both for the Newtonian and the non-Newtonian fluid. Since only shear thinning was included, this seems to be the dominant non-Newtonian property of the blood analog fluid under steady flow conditions.     

Pulsatile flow of non-Newtonian fluid in distensible models of human arteries

In addition to biochemical factors, hydromechanical influences are responsible for atherogenesis and deposits of blood platelets at bends and bifurcations of human arteries. Hence the flow patterns were simulated in a true-to-scale three-dimensional bifurcation of a human renal artery model and of an arterial femoralis with Newtonian and non-Newtonian blood like fluid. Investigations were made with steady and pulsatile flow. The velocity profiles (at physiological Re-numbers) were measured after the bifurcations with a laser-Doppler-anemometer. In previous works Newtonian fluids were used to investigate the flow in bends and bifurcations of rigid and elastic simplified models. In this paper, emphasis is placed on the difference between rigid and elastic models and also Newtonian and non Newtonian flow behavior. Differences between Newtonian and non Newtonian fluids may especially be expected to occur after branches where the flow has local strong convective elements such as in reverse zones and flow separation points.     

Axial dispersion in packed bed reactors involving viscoinelastic and viscoelastic non-Newtonian fluids

Axial dispersion is an important parameter in the performance of packed bed reactors. A lot of fluids exhibit non-Newtonian behaviour but the effect of rheological parameters on axial dispersion is not available in literature. The effect of rheology on axial dispersion has been analysed for viscoinelastic and viscoelastic non-Newtonian fluids. Aqueous solutions of carboxymethyl cellulose and polyacrylamide have been chosen to represent viscoinelastic and viscoelastic liquid-phases. Axial dispersion has been measured in terms of Bo_L number. The single parameter axial dispersion model has been applied to analyse RTD response curve. The Bo_L numbers were observed to increase with increase in liquid flow rate and consistency index ‘K’ for viscoinelastic as well as viscoelastic fluids. Bodenstein correlation for Newtonian fluids proposed has been modified to account for the effect of fluid rheology. Further, Weissenberg number is introduced to quantify the effect of viscoelasticity.     

Evaluation of fertility status of Murrah buffalo bulls in vitro using zona-free hamster eggs

Cryopreserved semen samples from 10 Murrah buffalo bulls were used for sperm penetration bioassay using zona-free hamster oocytes. The samples were evaluated for sperm motility, viability and acrosome integrity. Actively motile spermatozoa recovered by the swim-up technique were capacitated using calcium ionophore A(2 3 1 8 7). Mature female golden hamsters were superovulated with 50 IU PMSG followed 56 h later by 75 IU hCG. Cumulus mass, recovered by puncture of oviducts at the infundibulum region, was treated with 0.1% hyaluronidase and 0.1% trypsin to obtain zona-free oocytes. After coincubation of zona-free oocytes with capacitated buffalo spermatozoa, scoring was done as fertilization percentage and fertilization index. The correlation coefficients with conception rate were statistically significant with fertilization percentage (r = 0.588, P < 0.05) and fertilization index (r = 0.660, P < 0.01). However, conventional parameters like viability, motility and acrosome integrity showed poor correlation with conception rate.     

Flow investigations in a model of a three-dimensional human artery with Newtonian and non-Newtonian fluids. Part I

Together with biochemical factors, fluid mechanical factors play a role in atherogenesis and the deposition of blood platelets at bends and bifurcations in human arteries. Hence, flow patterns were investigated in a simplified 3-dimensional model of a human renal artery bifurcation using Newtonian (aqueous glycerol) and non-Newtonian (aqueous solution of polyacrylamide) fluids. Studies were carried out in steady as well as pulsatile flow at inflow Reynolds numbers of 498 and 951 with flow rate ratios main tube V1: right branch V4: left branch V3 of 1: 0.25: 0.25 and 1: 0.18: 0.18 respectively. The velocity distribution proximal and distal to the bifurcations was measured using a laser-Doppler anemometer. In steady flow, zones of flow separation and reverse flow were observed distal to the bifurcations. In pulsatile flow using non-Newtonian fluids, there was a significant enlargement of these zones. Differences between the Newtonian and non-Newtonian fluids occurred especially distal to the bifurcations. Shear stresses along all measuring positions were computed from the velocity gradients.     

A single cannula technique for nonsurgical collection of ova from cattle.

The uteri of 34 heifers were flushed for ova six to nine days following estrus using a single cannula nonsurgical technique. The technique involved the infusion of fluid by gravity and agitation within the uterus by to-and-fro action of a syringe followed by unassisted fluid collection. Each horn was flushed five times using 30–150 ml of flushing fluid per flush. Recovered fluid (flushing fluid plus uterine secretion) was an average of 95% of the volume of the fluid inserted. Ova were recovered from 12 of 19 nontreated, single ovulating heifers (63%) and from all of 15 superovulated heifers (mean and S.D. for number of ova, 6.3 ± 4.4/ superovulated heifer; range, 1 to 14 ova). Based on the number of corpora lutea, the ova recovery index was 54% as averaged over the 15 superovulated heifers. The technique has been used in 4 additional superovulated heifers with modification (increased number of flushes to 8) subsequent to the termination of the planned project. Recovery index for the first 5 flushes was 58%. However, some ova were recovered in the 6th, 7th, and 8th flushes resulting in an apparent improved recovery index of 69%.     

Do parameters of seminal quality correlate with the results of on-farm inseminations in rabbits?

This study was conducted to determine if different sperm characteristics correlate with the in vivo fertility of rabbit sperm. A total of 2,765 heterospermic inseminations were performed in commercial rabbitries using 50-pooled samples of fresh semen. Sperm motility and morphological evaluations were performed on each of the heterospermic pooled samples to asses the seminal quality, and the percentage of kindling rate (76.2%) and number of kits born alive (9.3) were recorded. Sperm motility parameters, assessed using a computer-assisted sperm analysis (CASA) system (Sperm Class Analyzer, Microptic, Barcelona, Spain), were: average path velocity, curvilinear velocity, straight-line velocity, linearity, amplitude of lateral head displacement, beat cross-frequency, wobble and percentage of total motile spermatozoa. Morphological analyses included the percentage of sperm with a normal apical ridge, the percentage of sperm with cytoplasmatic droplets and the percentage of abnormal sperm. Significant correlations were observed between kindling rate and the percentage of total motile cells (r=0.31; P<0.05), linearity index (r=-0.32; P<0.05) and the percentage of abnormal sperm in the sample (r=-0.32; P<0.05). Regression models including motility and the morphological parameters explained 45% of the variation in kindling rate. These results indicate that motility parameters, determined by CASA systems, in combination with sperm morphology analyses can provide some information about the fertilizing potential of rabbit sperm.     

Effect of active immunization against inhibin on hormonal concentrations and semen characteristics in Shiba bucks

Active immunization against inhibin increased ovulation rate in females; in males, the effects of active immunization against inhibin on hormonal concentrations and sperm production need more investigation. To test the hypothesis that active immunization against inhibin increases FSH secretion and sperm output, the present study was undertaken to determine the effects of active immunization against inhibin on hormonal profile and sperm production in Shiba bucks. The bucks were actively immunized against inhibin alpha-subunit (immunized group, n=6) or Freund adjuvant (control group, n=5) four times, at 5-weeks intervals. Blood samples were collected twice-weekly and two successive ejaculates of semen were collected (with an artificial vagina) once-weekly. Plasma concentrations of FSH, LH and testosterone were measured by radioimmunoassay (RIA) and sperm motility characteristics were measured by computer-assisted sperm analysis (CASA). All inhibin-immunized bucks produced antibodies against inhibin. Relative to control bucks, in immunized bucks there were significant increases in plasma FSH concentrations and in sperm concentrations from 5 to 9 weeks and from 8 to 11 weeks, respectively, after primary immunization. However, plasma concentrations of LH and testosterone, semen volume, percentage of motile spermatozoa and motility parameters (straight-line velocity, curvilinear velocity and linearity index) were similar in both groups. In conclusion, active immunization against inhibin alpha-subunit increased FSH secretions and enhanced sperm production in bucks, whereas LH and testosterone concentrations, semen volume and sperm motility parameters were unaffected. Active immunization against inhibin could be used to improve fertility in Shiba bucks.     

Increased velocity and induction of chemotactic response in mouse spermatozoa by follicular and oviductal fluids.

The dynamic parameters of mouse sperm cells exposed to follicular and oviductal fluids were assessed. Spermatozoa were tracked on a chemotactic Zigmond chamber and recorded using a videomicroscopy system. The results were evaluated with computer-supported image analysis. Follicular fluid at a dilution of 10(-4) markedly increased the proportion of spermatozoa with high velocity, and stimulated chemotactic behaviour. The highest velocities were observed in sperm cells exposed to oviductal fluid, and a greater proportion of these cells had high velocity compared with those exposed to follicular fluid. Chemotaxis was induced in spermatozoa exposed to oviductal fluid at dilutions of 10(-3) and 10(-5). These results suggest the presence of temporal subpopulations of responsive spermatozoa, considering the distance travelled towards both follicular and oviductal fluids and the proportion of sperm cells migrating towards the gradient in the highest distance ranges. This is the first report on the effect of isolated follicular and oviductal fluids on dynamic parameters and chemotaxis of mouse spermatozoa. The findings support previous work showing that the motility and directionality of mouse sperm cells is increased by factors in the microenvironment of the egg. Although the significance of these factors in vivo is unknown, it is possible that there is a relay mechanism involving sequential activity of both oviductal and follicular fluids to direct the male gametes towards the egg.     

Mass transfer in blood oxygenators using blood analogue fluids

Mass transfer correlations for hollow fiber blood oxygenators have been determined experimentally using Newtonian and non-Newtonian blood analogue fluids. The Newtonian fluids consisted of deionized water and glycerol/water mixtures. The non-Newtonian fluids were prepared by adding small amounts of xanthan gum to the Newtonian blood analogue fluids. The rheological behavior of the non-Newtonian blood analogue fluids was modeled using the power law. The diffusion of oxygen into and out of the Newtonian and non-Newtonian blood analogue fluids has been studied. The liquid stream flowed outside and across bundles of woven hollow fibers, while the gas stream flowed inside the fibers.     

An experimental study of Newtonian and non-Newtonian flow dynamics in a ventricular assist device

The fluid dynamic behavior of a Newtonian water/glycerol solution, a non-Newtonian polymer (separan) solution, and bovine blood were compared in the Penn State Electrical Ventricular Assist Device (EVAD). Pulsed doppler ultrasound velocimetry was used to measure velocities in the near wall region (0.95-2.7 mm) along the perimeter of the pump. Mean velocity, turbulence intensity, local and convective acceleration, and shear rate were calculated from the PDU velocity measurements. Flow visualization provided qualitative information about the general flow patterns in the EVAD. Results indicate that water/glycerol does not accurately model the flow characteristics of bovine blood in the EVAD. The non-Newtonian separan solution produced results closer to those of the bovine blood than did the water/glycerol solution. Near wall velocity magnitudes for the separan were similar to those of the bovine blood, but the profile shapes differed for portions of the pump cycle. All three fluids exhibited periods of stagnation. Bovine blood results indicated the presence of a desired rotational washout pattern at midsystole, while results with the other fluids did not show this feature.     

Flush mounted hot film anemometer measurement of wall shear stress distal to a tri-leaflet valve for Newtonian and non-Newtonian blood analog fluids

Wall shear stress has been measured by flush-mounted hot film anemometry distal to an Ionescu-Shiley tri-leaflet valve under pulsatile flow conditions. Both Newtonian (aqueous glycerol) and non-Newtonian (aqueous polyacrylamide) blood analog fluids were investigated. Significant differences in the axial distribution of wall shear stress between the two fluids are apparent in flows having nearly identical Reynolds numbers. The Newtonian fluid exhibits a (peak) wall shear rate which is maximized near the valve seat (30 mm) and then decays to a fully developed flow value (by 106 mm). In contrast, the shear rate of the non-Newtonian fluid at 30 mm is less than half that of the Newtonian fluid and at 106 mm is more than twice that of the Newtonian fluid. It is suggested that non-Newtonian rheology influences valve flow patterns either through alterations in valve opening associated with low shear separation zones behind valve leaflets, or because of variations in the rate of jet spreading. More detailed studies are required to clarify the mechanisms. The Newtonian wall shear stresses for this valve are low. The highest value observed anywhere in the aortic chamber was 2.85 N/m2 at a peak Reynolds number of 3694.