Efficacy of four density gradient separation media to remove erythrocytes and nonviable sperm from canine semen

The objective was to compare four commercially available density gradient centrifugation (DGC) media (ISolate [Irvine Scientific; Santa Ana, CA, USA], Percoll [Pharmacia; Uppsala, Sweden], PureCeption [SAGE In-Vitro Fertilization, Inc.; Trumbull, CT, USA], PureSperm 100 [Nidacon International AB; Molndal, Sweden]) for their ability to separate viable, motile sperm from contaminant nonviable (immotile and/or dead) sperm and red blood cells (RBC). Pooled sperm-rich fractions from four healthy dogs were assessed using Spermvison SAR (Minitube of America). For this, 1 mL of the blood/sperm admixture was pipetted over 4 mL of DGC media: 50%/90% ISolate (Irvine Scientific), 45%/90% Percoll (Pharmacia), 40%/80% PureCeption (SAGE In-Vitro Fertilization, Inc.), and 40%/80% PureSperm 100 (Nidacon International AB). After centrifugation, five 1-mL fractions (A, B, C, D, and E) and the sperm pellet (bottom fraction F) were separated. Sperm morphology and red blood cell/sperm ratio (RBC/S) per fraction were determined on stained slides. All DGC media separated RBC from sperm; the highest red blood cell/sperm ratio was present in ISolate (Irvine Scientific) and Percoll (Pharmacia) fraction A (29.4 ± 29.7 and 28.2 ± 20.8, respectively), and in fractions A and B of both PureCeption (SAGE In-Vitro Fertilization, Inc.) (37.0 ± 22.8 and 39.6 ± 24.3, respectively) and PureSperm 100 (Nidacon International AB) (25.2 ± 5.9 and 23.0 ± 3.9, respectively). The fractions with the highest total sperm recovery, motile sperm recovery, as well as overall motility were ISolate (Irvine Scientific) and Percoll (Pharmacia) fraction D (33.9 ± 29.4%; 40.99 ± 27.9%; 71.2 ± 21.8% and 36.4 ± 14.5%; 39.3 ± 15.8%; 88.6 ± 2.3%, respectively), and for PureCeption (SAGE In-Vitro Fertilization, Inc.) and PureSperm 100 (Nidacon International AB), the sperm pellet, fraction F (78.8 ± 28.3%; 88.0 ± 17.4%; 70.2 ± 11.1% and 73.1 ± 21.0%; 75.4 ± 24.6%; 80.6 ± 17.1%, respectively). In the pellet for PureCeption (SAGE In-Vitro Fertilization, Inc.), more sperm and motile sperm were recovered than in ISolate (Irvine Scientific) and Percoll (Pharmacia) fractions D (P < 0.0163). Therefore, DGC media should be considered for canine semen purification when contaminated with blood or when separation of motile versus immotile sperm is needed.     

Brown bear sperm double freezing: Effect of elapsed time and use of PureSperm® gradient between freeze–thaw cycles

The use of sexed spermatozoa has great potential to captive population management in endangered wildlife. The problem is that the sex-sorting facility is a long distance from the semen collection place and to overcome this difficulty two freeze–thaw cycles may be necessary. In this study, effects of refreezing on brown bear electroejaculated spermatozoa were analyzed. We carried out two experiments: (1) to assess the effects of the two freezing–thawing cycles on sperm quality and to analyze three different elapsed times between freezing–thawing cycles (30, 90 and 180 min), and (2) to analyze the use of PureSperm between freezing–thawing cycles to select a more motile and viable sperm subpopulation which better survived first freezing. The motility, viability and undamaged acrosomes were significantly reduced after the second thawing respect to first thawing into each elapsed time group, but the elapsed times did not significantly affect the viability and acrosome status although motility was damaged. Our results with the PureSperm gradient showed higher values of viability in freezability of select sample (pellet) respect to the rest of the groups and it also showed a significant decrease in the number of acrosome damaged. In summary, the double freezing of bear semen selected by gradient centrifugation is qualitatively efficient, and thus could be useful to carry out a sex-sorting of frozen–thawed bear spermatozoa before to send the cryopreserved sample to a biobank. Given the low recovery of spermatozoa after applying a selection gradient, further studies will be needed to increase the recovery rate without damaging of the cell quality.     

Effect of heparin on cleavage rates and embryo production with four bovine sperm preparation protocols

Heparin is often added to fertilization media to induce sperm capacitation. However, recent observations from the bovine IVF industry have indicated that heparin may not be necessary to induce sperm capacitation when cryopreserved bovine sperm are separated through Percoll gradients. The objective of these studies was to determine if the addition of heparin to fertilization media was required following separation of frozen-thawed bovine sperm. Experiment 1 was conducted to determine the effect of heparin on cleavage rates and embryo production when using Percoll, BSA or washing sperm separation protocols. Experiment 2 was conducted to determine the effect of heparin on cleavage rates and embryonic development when using a new sperm separation protocol (PureSperm). In Experiment 1, regardless of sperm separation protocol, heparin increased cleavage rates and embryo production (P<0.05). Further, cleavage rates and embryo production were higher for the Percoll procedure compared to either BSA or washing sperm separation protocols (P<0.05). In Experiment 2, there was no difference between Percoll and PureSperm separation protocols on cleavage rates or embryo production (P>0.05). However, heparin increased cleavage rates for both protocols and improved embryo production for the PureSperm protocol (P<0.05). In conclusion, use of heparin in fertilization media improves in vitro embryo production when using cryopreserved bovine sperm. Furthermore, PureSperm can be used as an alternative to Percoll for bovine sperm separation.     

Brown bear sperm double freezing: Effect of elapsed time and use of PureSperm® gradient between freeze–thaw cycles

The use of sexed spermatozoa has great potential to captive population management in endangered wildlife. The problem is that the sex-sorting facility is a long distance from the semen collection place and to overcome this difficulty two freeze–thaw cycles may be necessary. In this study, effects of refreezing on brown bear electroejaculated spermatozoa were analyzed. We carried out two experiments: (1) to assess the effects of the two freezing–thawing cycles on sperm quality and to analyze three different elapsed times between freezing–thawing cycles (30, 90 and 180 min), and (2) to analyze the use of PureSperm between freezing–thawing cycles to select a more motile and viable sperm subpopulation which better survived first freezing. The motility, viability and undamaged acrosomes were significantly reduced after the second thawing respect to first thawing into each elapsed time group, but the elapsed times did not significantly affect the viability and acrosome status although motility was damaged. Our results with the PureSperm gradient showed higher values of viability in freezability of select sample (pellet) respect to the rest of the groups and it also showed a significant decrease in the number of acrosome damaged. In summary, the double freezing of bear semen selected by gradient centrifugation is qualitatively efficient, and thus could be useful to carry out a sex-sorting of frozen–thawed bear spermatozoa before to send the cryopreserved sample to a biobank. Given the low recovery of spermatozoa after applying a selection gradient, further studies will be needed to increase the recovery rate without damaging of the cell quality.     

Evaluation of the qualitative and quantitative effectiveness of three media of centrifugation (Maxifreeze, Cushion Fluid Equine, and PureSperm 100) in preparation of fresh or frozen-thawed brown bear spermatozoa

Centrifugation is a crucial procedure in sperm cryopreservation protocols of brown bear (Ursus arctos), because the semen must be processed to increase sperm concentration and/or clean urine-contaminated samples. The efficacy of three media for centrifugation (Maxifreeze [IMV technologies, L'Aigle, France], Cushion Fluid Equine (Minitübe, Tiefenbach, Germany), and PureSperm [Nidacon, Gothenburg, Sweden]) on the quality of bear spermatozoa was evaluated. In experiment one, two cushioned media used for protecting against mechanical stress during centrifugation were analyzed. In experiment two, a density gradient based on PureSperm was assessed in relation to the maximum retrieval and the quality of fresh spermatozoa, and the freezability of the spermatozoa selected in this density gradient was studied in experiment three. Finally, the selection of frozen-thawed sperm using PureSperm was analyzed in experiment four. Our results indicate that the use of dense isotonic cushion solutions (Maxifreeze, Cushion Fluid Equine) in centrifugation did not improve the quality of recovered spermatozoa compared with standard centrifugation. However, a density gradient prepared with PureSperm improved the quality of spermatozoa in fresh semen and frozen-thawed semen, but the spermatozoa selected from the fresh sample with this density gradient did not show a better resistance to freezing with this density gradient in comparison with the control sample.     

Changes in the structures of motile sperm subpopulations in dog spermatozoa after both cryopreservation and centrifugation on PureSperm(®) gradient

The aims of the present study were to: (1) determine if discrete motile sperm subpopulations exist and their incidence in fresh dog ejaculates, (2) evaluate the effects of cryopreservation on the distribution of spermatozoa within the different subpopulations, and (3) determine the effect of the discontinuous PureSperm(?) gradient on the sperm subpopulation structure of frozen-thawed dog spermatozoa. Semen from 5 dogs were collected and cryopreserved following a standard protocol. After thawing, semen samples were selected by centrifugation on PureSperm(?). Sperm motility (assessed by computerized-assisted semen analysis, CASA) was assessed before freezing, just after thawing and after preparation on the PureSperm(?) gradients. Cryopreservation had a significant (P<0.001) effect on CASA-derived parameters. PureSperm(?) centrifugation yielded sperm suspensions with improved motility (P<0.01). A multivariate clustering procedure separated 19414 motile spermatozoa into four subpopulations: Subpopulation 1 consisting of poorly active and non-progressive spermatozoa (20.97%), Subpopulation 2 consisting of slow and low-linear spermatozoa (18.24%), Subpopulation 3 consisting of highly active but non-progressive spermatozoa (20.75%), and Subpopulation 4 consisting of high speed and progressive spermatozoa (40.03%). Although, cryopreservation had a significant (P<0.001) effect on both the frequency distribution of spermatozoa within subpopulations and the motion characteristics of each subpopulation, the sperm subpopulation structure was perfectly maintained after freezing and thawing. The selected sperm samples was enrich in Subpopulation 4, reaching a proportion of 31.9% of the present spermatozoa, in contrast with the unselected sperm samples, where this sperm subpopulation accounted for 24.9% of the total. From these results, we concluded that four well-defined motile sperm subpopulations were present either in fresh semen, in unselected sperm samples or in selected preparations from dogs. The discontinuous PureSperm(?) gradient is a simple method to improve the quality of canine frozen-thawed semen samples, since Subpopulation 4 (high-speed and progressive spermatozoa) was more frequently observed after preparation on the gradient. Finally, this study also demonstrated that the general motile sperm structure present in dog remains constant despite the effect caused by either cryopreservation or separation on PureSperm(?) gradient.     

Fertilization rates and in vitro embryo production using sexed or non-sexed semen selected with a silane-coated silica colloid or Percoll

The aim of this study was to evaluate sperm fertilization rates and in vitro embryo development rates for sexed and non-sexed semen selected using a silane-coated silica colloid method (Isolate) or Percoll. Frozen/thawed, sexed and unsexed semen samples from four Holstein bulls were randomly allocated to one of two different density gradient selection methods. Sperm quality (motility, concentration, morphology and membrane integrity) were evaluated and compared before and after sperm selection. Sperm motility and morphology improved (P < 0.005) after the sperm selection process with no differences between the two methods. For non-sexed semen, Percoll gradient increased the mean (± SEM) percentage of sperm recovered (57.3 ± 2.8) compared to Isolate (46.0 ± 1.8; P < 0.01). However, membrane integrity was higher after Isolate than Percoll (sexed semen: 41.0 ± 0.6 vs. 38.8 ± 0.8 and non-sexed semen 60.8 ± 1.6 vs. 58.8 ± 0.5; P < 0.05). The percentage of blastocysts produced was higher when either sexed or non-sexed semen was selected by Isolate (14.0 ± 1.0; 22.0 ± 1.1) than by Percoll (10.5 ± 1.5; 17.0 ± 2.1, respectively; P < 0.05). In summary, Isolate was a more effective method for the recovery of high quality sperm for in vitro fertilization embryo production.     

A comparison of BoviPure and Percoll on bull sperm separation protocols for IVF

In the present study, we have examined the effect of density gradient preparations BoviPure and Percoll on bull sperm separation and the in vitro fertilization (IVF) and culture (IVC) results. Frozen/thawed semen from five simmental bulls were pooled. Sperm quality parameters such as sperm motility, concentration, membrane activity (HOS assay), membrane integrity (SYBR-14/PI assay) and acrosomal status (EthD-1/FITC-PSA assay) were evaluated before and after sperm processing for IVF using BoviPure and Percoll density gradient separations. The results of the evaluated parameters before sperm processing were: motility 50%, concentration 82.33x10(6)spz/mL, membrane activity 39.05%, membrane integrity 42.97% and the acrosomal status 46.90% of the live spermatozoa with intact acrosomes. After sperm processing with BoviPure and Percoll the motility was 66.67 and 64.17%, the concentration was 25.50x10(6) and 27.67x10(6)spz/mL, the membrane activity was 53.78 and 56.58%, the membrane integrity was 70.85 and 68.76% of and the acrosomal status was 74.16 and 67.46% of the live spermatozoa with intact acrosomes, respectively. Percentages were referred to the total number of spermatozoa. There were significant differences (P<0.05) between the evaluated parameters before and after sperm processing for both separation protocols. We found no significant differences (P>0.05) regarding sperm evaluation parameters between the protocols. A total of 492 oocytes were matured and fertilized in vitro and cultured in SOFaaBSA in six replicates. The cleavage (D2) and blastocysts (D7) rate were significantly higher (P<0.05) for the BoviPure group compared to the Percoll group: 75.80 and 28.21%; 61.58 and 20.83%, respectively. However, the number of hatched blastocysts (D10) did not differ significantly between sperm separation protocols (P>0.05). Our results indicate that both protocols gave suitable sperm for IVF. This finding and the similarity between those two density gradient preparations suggests that BoviPure is a good alternative for sperm separation in bovine IVF.     

Loss of plasma membrane proteins of bull spermatozoa through the freezing-thawing process

The widespread application of A. I. and realization of its full potential depends largely on the use of frozen semen. However, fertility resulting from A. I. is poorer than that from fresh semen in most species. The objective of this study was to compare the protein composition of fresh and frozen-thawed bull sperm plasma membrane surface. The effect of Tween 20 on protein removal from fresh and frozen sperm plasma membrane surface was studied and compared. The effect of incubation with different detergent concentrations on sperm motility and viability was examined. Approximately 2 x 10(8) frozen-thawed bull spermatozoa washed through a discontinuous Percoll gradient were incubated for 15 min at 20 degrees C with 0.01, 0.03 and 0.05% Tween 20. Sperm motility was completely eliminated at all 3 assayed detergent concentrations, while the initial sperm viability of 52% was decreased to 26, 10 and 5%, respectively, at the 3 concentrations. The removal of sperm plasma membrane proteins also increased from 0.72 mg to 2 mg with 0.05% Tween 20. Similar results were found with fresh semen samples. Although the amount of extracted proteins was significantly lower than that obtained with frozen spermatozoa, fresh sperm motility was likewise eliminated by the detergent treatment, and sperm viability was decreased. A semen sample with an initial sperm viability of 59% had a value of only 8% after treatment with 0.05% Tween 20. Comparative SDS-PAGE analysis of the extracted fractions from fresh and frozen-thawed semen treated with Tween 20 showed that the higher amount of extracted proteins in the frozen semen samples corresponded to the egg yolk lipoproteins in the cryoprotectant medium. However, it is worth noting that 4 more bands were found in the sample obtained from fresh semen than from frozen semen. These results indicate that some cell membrane proteins are lost through the freezing-thawing process.     

Fractionation of cells and subcellular particles with Percoll

At present, centrifugation is the most common method for separation and isolation of cells and subcellular particles. The technique can be used for a wide range of applications. During latter years it has become obvious what a powerful method density gradient centrifugation is, especially when used in conjunction with sensitive assays or clinical treatments. The most active areas for use of density gradient centrifugation include purification for in vitro fertilization of sperm of both human and bovine origin, isolation of cells for cell therapy of patients receiving chemo- and radiation therapy and basic research both on cellular and subcellular levels. These treatments and investigations require homogeneous populations of cells and cell organelles, which are undamaged after the separation procedure. Percoll, once introduced to reduce convection during centrifugation, has proved to be the density gradient medium of choice since it fulfills almost all criteria of an ideal density gradient medium. Recently good results have also been obtained after silanization of colloidal silica particles, e.g. BactXtractor. The latter medium has proved to be useful in recovery of microorganisms from food samples free of inhibitors to the Polymer Chain Reaction (PCR). The separation procedures described for Percoll in this review seem to be applicable to any cells or organelles in suspension for which differences in size or bouyant density exist. Furthermore, since Percoll media are inert, they are well suited for the separation of fragile elements like enveloped viruses.     

Schistosoma mansoni: rapid isolation and purification of schistosomula of different developmental stages by centrifugation on discontinuous density gradients of Percoll

Step gradients of polyvinylpyrolidone-coated colloidal silica particles (Percoll) were used to isolate and purify early development stages of Schistosoma mansoni (cercariae, skin stage, and 5-day-old schistosomula). With this method, mechanically transformed schistosomula can be isolated in higher purity and yield than that obtained with conventional procedures. In addition, use of the method revealed that schistosomula undergo a dramatic change in density during the first hours after transformation from cercariae. In other experiments, 5-day-old schistosomula were effectively purified from contaminating lung tissue by means of the Percoll gradient procedure. After purification on Percoll, schistosomula display no evidence of damage when examined by light microscopy and no loss in viability as judged by recovery of adult worms from mice.     

The viability of cells grown or centrifuged in a new density gradient medium, Percoll(TM)

A new density gradient medium, Percoll (a modified colloidal silica), has been tested for toxicity in primary cultures of rat liver and calf testicle cells, and in continuous cultures of pig kidney and HeLa cells. The presence of Percoll did not appreciably affect the growth or viability of the cells as judged from cell counts and morphology. The various cells were also centrifugea in gradients of Percoll and subsequently cultured. The in vitro growth of the cells was similar to that of untreated cells. Rat liver cells were labelled in vivo with [¹²⁵I]asialoceruloplasmin (parenchymal cells) or heat-denatured [¹²⁵I]albumin (non-parenchymal cells). After dispersion of the cells and iso-pycnic centrifugation in Percoll the non-parenchymal cells banded preferentially at a lower density (1.04−1.05 g/ml) than parenchymal cells (1.07−1.09 g/ml). The two types of cells showed very different morphology in cell culture. The non-parenchymal cells retained their phagocytic properties during culture. Injured cells and cell debris band at the top of the Percoll gradients in contrast to their behaviour in gradients containing low molecular weight substances. Centrifugation in Percoll can be used to enrich viable cells.     

Functional changes and motility characteristics of Japanese Black bull spermatozoa separated by Percoll

Spermatozoa from two Japanese Black bulls (Bull-ATF and Bull-KTG) were separated by centrifugation at 700 x g for 15min in modified TALP with or without 45-90% Percoll. Control washed spermatozoa and those collected from the bottom of 45 and 90% Percoll fractions were examined for viability and membrane integrity (using Hoechst bis-benzimide 33258 or propidium iodide and 6-carboxyfluorescein diacetate (PI-CFDA)), acrosomal status (using fluorescence isothiocyanate (FITC) conjugated Pisum Sativum agglutinin (PSA) and Peanut agglutinin (PNA), Naphthol Yellow S and Erythrosin B (NE) or triple staining (TS)), capacitation status (using chlortetracycline (CTC)), motility characteristics (using a computer-assisted sperm motion analysis system (CASA)) and for in vitro fertility. Percoll-separated spermatozoa showed greater viability and membrane integrity than controls, as determined by supravital staining. Differences were observed in the results regarding viability and acrosomal status of spermatozoa among sperm staining methods. Bull-ATF, which showed significantly greater in vitro fertility than Bull-KTG (P<0.05), showed a significantly higher rate of CTC-B-pattern (capacitated) spermatozoa (P<0.01) than Bull-KTG. The motility characteristics of control washed spermatozoa and those separated by 45-90% Percoll were analyzed by CASA. More motile and progressively motile spermatozoa were observed in the fraction at the bottom of the 90% Percoll solution than in the 45% Percoll fraction or in controls (P<0.01). Moreover, the spermatozoa of Bull-KTG, which showed lower in vitro fertility than Bull-ATF, did not show significant differences in motility from those of Bull-ATF. These results provided basic information about Japanese Black bull spermatozoa, and suggested that spermatozoa with greater motility and viability can be obtained by Percoll separation than without separation. However, Percoll separation did not enhance their in vitro fertility.     

Motility, acrosome integrity, membrane integrity and oocyte cleavage rate of sperm separated by swim-up or Percoll gradient method from frozen-thawed buffalo semen

Frozen-thawed semen of five buffalo bulls was used to compare efficacy of swim-up and Percoll gradient methods for separating viable spermatozoa. Sperm separated by the two methods were also tested to differentiate buffalo bulls on the basis of in vitro fertilization (IVF) rates. Recovery of motile sperm (%), increase in membrane integrity (%) and acrosome integrity (%) were compared after two sperm separation methods in experiment I, and in vitro fertilization rate (cleavage rate and cleavage index) was compared in experiment II. Swim-up separated sperm showed a higher motility (P<0.05), while percent recovery of motile sperm was higher with Percoll separation (P<0.05). Membrane integrity (%) of sperm separated with swim-up was significantly higher (P<0.05) as compared to sperm separated with Percoll gradient. Swim-up separated sperm gave a higher cleavage rate and cleavage index (P<0.001). Sperm separated by swim-up showed significant difference among the bulls in cleavage rate and cleavage index (P<0.05), while the Percoll gradient method did not. It has been concluded that separation of sperm from frozen-thawed buffalo semen by swim-up method can be more expedient for IVF in buffalo.     

Preparation and recovery of frozen-thawed bovine spermatozoa via various sperm selection techniques employed in assisted reproductive technologies

A number of semen manipulative techniques are currently available to remove the undesirable spermatozoa, debris and other factors and to increase sperm quality. The use of motility stimulants such as caffeine or others could optimize the recovery and quality of frozen-thawed spermatozoa processed by a variety of sperm selection techniques. Frozen-thawed specimens from 5 bulls were slowly diluted and washed with Ham's F-10 medium containing 3% BSA (w/v) and 0 or 2 mM caffeine. Aliquots containing approximately 50 x 10(6) total sperm cells were used for conventional sperm wash, swim-up, Percoll density gradient centrifugation (80, 70, 55 and 40% Percoll gradients) and Sephadex (SpermPrep I) filtration. Quantitative and qualitative characteristics of selected spermatozoa included: total sperm (x 10(6)), percentage and grade (0 to 4) of motility, percentage of spermatozoa with coiled tails and response to the hypoosmotic swelling (HOS) test (percentage of swollen spermatozoa). When compared to washed specimens, fewer spermatozoa were recovered via the swim-up, Percoll and SpermPrep I filtration methods. Quantitative and qualitative characteristics of these spermatozoa improved further after processing with Ham's F-10 containing 2 mM caffeine, followed by selection via the various techniques. Enhancement of sperm motility, in conjunction with the most appropriate sperm selection technique, represents an efficient method for the recovery of spermatozoa with improved qualitative characteristics.     

Evaluation of cryopreserved stallion semen from Tori and Estonian breeds using CASA and flow cytometry

Methods to evaluate the quality of frozen-thawed stallion semen are still needed, particularly those considering the sperm function. The present study evaluated sperm motility, membrane and acrosome integrity and the capacitation status of frozen-thawed spermatozoa from seven Tori and six Estonian breed stallions by way of computer assisted sperm analysis (CASA), a triple fluorophore stain combination and Merocyanine 540, respectively, the latter ones using flow cytometry. Two ejaculates from each stallion were cryopreserved using the Hannover method in 0.5 ml plastic straws. Two straws per ejaculate per stallion were thawed at 37 degrees C for 30s. Motility was analysed with CASA immediately after thawing, while for flow cytometry spermatozoa were cleansed by 70:40% Percoll discontinuous density gradient separation before analysed for sperm viability, acrosome integrity (stained with SNARF, PI and FITC-PSA) and capacitation status (stained with Merocyanine 540/Yo-Pro-1). Results (as least square means) were as follows: the motility of frozen-thawed semen was 43.4% for Tori stallions and 42.3% for Estonian stallions (P>0.05). After Percoll separation 79.3% of the spermatozoa from Tori stallions had intact acrosomes and 1.7% of them showed early signs of capacitation. The same parameters for Estonian stallions were 84.5 and 2.3%, respectively. There were no statistically significant differences between breeds or ejaculates within breed for any evaluated parameter. We conclude that triple staining and flow cytometry are valuable techniques to evaluate frozen-thawed stallion spermatozoa, and that no differences in quality of frozen semen were registered between Tori and Estonian breed stallions, allowing implementation of this technology in the Estonian horse population.     

Integrated morphophysiological assessment of two methods for sperm selection in bovine embryo production in vitro

Extensive work was done regarding the ability of Swim up and Percoll gradient to select functional sperm for in vitro embryo production (IVP) systems. The aim of this work was to compare Swim up and Percoll as methods of sperm selection by ultrastructural, biochemical and functional studies. Frozen-thawed semen from two bulls (Experiments 1 and 2, respectively) were treated using Swim up or Percoll discontinuous gradients. Motility, sperm membrane ultrastructure, sperm proteins, in vitro embryo production (insemination doses, cleavage, embryo yield and quality) and embryo sex ratio were scored and compared. Electron transmission microscopy of outer sperm membranes showed higher (P<0.05) percentage of sperm with lost acrosomes in Percoll treated samples compared to Swim up. A differential protein pattern was also detected. When in vitro embryo production was performed, Percoll gradient produced higher (P<0.05) number of fertilizing doses (7.6 versus 5.9, Bull 1; 13.5 versus 7.8, Bull 2) and higher sperm motility (90% versus 76.6%, Bull 1; 81.7% versus 68.3%, Bull 2) than Swim up. The percentage of cleavage (Day 3) was similar in both treatment groups, whereas embryo production rate (Day 7) was higher (39.4% versus 30.2%, Bull 1; 38% versus 32.4%, Bull 2; P<0.05) when Percoll gradient was used. The percentage of hatched embryos (Day 11) and sex ratio did not differ. Total cell counting and embryo differential staining (inner cell mass and trophoblast cells) of Day 7 embryos showed that Percoll treated sperm produced better quality embryos compared to Swim up. We concluded that Percoll had a better performance selecting sperm and an enhanced capacity for embryo production when compared with the Swim up procedure; this could be attributed to a better acrosome exocytosis, associated to the absence of certain membrane proteins.     

Production of Ficoll, Percoll, and albumin gradients by the freeze-thaw method.

Ficoll, sucrose, albumin, and Percoll, a modified colloidal silica centrifugation medium, all form density gradients upon freezing and thawing. The data suggest that any density gradient material will form gradients upon freezing and thawing, provided the material is stable to freezing.     

Effects of centrifugation through three different discontinuous Percoll gradients on boar sperm function

In this study, different combinations of 2-step, discontinuous gradient centrifugation were used, consisting of three different combinations of isotonic Percoll (45/60, 60/75 and 45/90%) that allowed us to select different sperm subpopulations from fertile and normozoospermic boars. Our objective in this study is to evaluate the effects of centrifugation through three different discontinuous Percoll gradients on sperm function parameters (motility, viability, morphology, acrosome status, chromatin condensation, DNA fragmentation, ROS generation, tyrosine phosphorylation and intracellular calcium concentration) and the sperm penetrating capacity in an IVF system. All the Percoll treatments evaluated increased the percentage of spermatozoa with normal morphology, the proportion of un-damaged DNA, normal chromatin condensation, motion parameters measured by CASA and the percentage of capacitated spermatozoa with tyrosine phosphorylated proteins compared to control group. Finally, the in vitro oocyte penetrating capacity of boar spermatozoa was significantly affected by Percoll centrifugation. All the Percoll treatments increased the penetration rates and mean number of sperm per penetrated oocyte. Despite the efficiency of all three of the sperm treatments tested in selecting spermatozoa with improved sperm parameters and capacity to penetrate oocytes in vitro, the optimum performance of this system was demonstrated after preselecting spermatozoa by centrifugation on a discontinuous 45/90 Percoll gradient. The P45/90 treatment leads to obtain a higher percentage of spermatozoa which develop properly the capacitation process as it was shown measuring tyrosine phosphorylation and intracellular calcium concentration.