Frozen-thawed bovine spermatozoa diluted by slow or rapid dilution method: Measurements on occurrence of osmotic shock and sperm viability

Cryopreservation of sperm from the gudgeon, Microphysogobio rapidus (Cyprinidae): Effects of cryoprotectant, diluents, and dilution ratio

We investigated methods for cryopreserving sperm from the endangered gudgeon, Microphysogobio rapidus, by examining the effects of cryoprotective agent (CPA) concentration, diluent, and dilution ratio on post-thaw sperm quality. The quality of frozen sperm was evaluated in terms of motility and kinematic parameters, viability, DNA damage, and fertilization rate. We evaluated methanol, glycerol, dimethyl sulfoxide (DMSO), and ethylene glycol as CPAs. Sperm motility, velocity, and viability were significantly higher when methanol was used as the CPA (p < 0.05). The diluents tested were Ringer's solution, Kurokura's Extender, Common Carp Sperm Extender (CCSE), and buffered sperm motility-inhibiting saline solution (BSMIS); post-thaw motility was highest when Ringer's solution was used as the diluent. Next, various quantities of methanol were combined with Ringer's solution to identify the optimal dose of methanol. The dilution ratios tested ranged from 1:1 to 1:7. Cryopreserved sperm was thawed at 20 °C for 15 s. The use of 10% methanol with Ringer's solution at a dilution ratio of 1:5 resulted in the highest post-thaw sperm motility, viability, and velocity including VAP, VCL, and VSL. Post-thaw sperm showed significantly greater DNA damage than the control (fresh sperm) (p < 0.05). The fertilization rate was highest with fresh sperm (p < 0.05), followed by sperm frozen with 10% methanol + Ringer's solution. We recommend that the best way to preserve sperm in the studied species is to use a combination of Ringer's solution and 10% methanol at a 1:5 dilution ratio. Our findings will facilitate the artificial fertilization of M. rapidus.

Cryopreservation of Roughscale Sole (Clidoderma asperrimum) Sperm: Effects of Cryoprotectant, Diluent, Dilution Ratio, and Thawing Temperature

Simple Summary

The roughscale sole, Clidoderma asperrimum, is found in the East and West Seas of Korea, waters north of Hokkaido in Japan, as well as the East China Sea, the East Pacific, and the Canadian Maritimes. In 2021, this fish was categorized as an endangered species. Thus, there is a need to maintain gametes by freezing sperm. This study investigated the impacts of the cryoprotective agent, diluent, dilution ratio, and thawing temperature on the cryopreservation of fish sperm. In this investigation, sperm dilution 1:1 with a mixture of 10% dimethyl sulfoxide + Stein’s solution and thawing at 10 °C provided the most effective DNA damage prevention. These results support the development of a roughscale sole sperm cryopreservation procedure.

Abstract

The roughscale sole, Clidoderma asperrimum is categorized as an endangered species. Sperm freezing is essential for preserving gametes. This study examined the CPA concentration, diluent, dilution ratio, and thawing temperature to design a sperm cryopreservation protocol for roughscale sole. The variables examined included sperm motility and kinematics, cell survival, fertilization, and DNA fragmentation. Sperm motility parameters were assessed via computer-assisted sperm analysis using a CEROS II instrument. Cell survival rate and DNA damage were assessed using the Cell Counting Kit-8 and single-cell gel electrophoresis assay, respectively. Sperm preservation was tested using several CPAs, including ethylene glycol, dimethyl sulfoxide (DMSO), glycerol, propylene glycol, and methanol. The diluents tested were 300 mM sucrose, 300 mM glucose, Stein’s solution, Ringer’s solution, and Hank’s solution. The optimal conditions for sperm cryopreservation were 10% DMSO + Stein’s solution. After thawing, sperm motility was highest with a 1:1 dilution ratio (sperm to CPA + diluent), at 69.20 ± 0.32%; thawing at 10 °C was optimal for post-thaw motility (72.03 ± 0.95%). The highest fertilization rate (40.00 ± 1.22%) was obtained using DMSO. The fresh sperm had the lowest tail DNA, followed by 10% DMSO + Stein’s solution. The developed cryopreservation methods can be used in roughscale sole hatcheries.

Improving Cell Recovery: Freezing and Thawing Optimization of Induced Pluripotent Stem Cells

Achieving good cell recovery after cryopreservation is an essential process when working with induced pluripotent stem cells (iPSC). Optimized freezing and thawing methods are required for good cell attachment and survival. In this review, we concentrate on these two aspects, freezing and thawing, but also discuss further factors influencing cell recovery such as cell storage and transport. Whenever a problem occurs during the thawing process of iPSC, it is initially not clear what it is caused by, because there are many factors involved that can contribute to insufficient cell recovery. Thawing problems can usually be solved more quickly when a certain order of steps to be taken is followed. Under optimized conditions, iPSC should be ready for further experiments approximately 4-7 days after thawing and seeding. However, if the freezing and thawing protocols are not optimized, this time can increase up to 2-3 weeks, complicating any further experiments. Here, we suggest optimization steps and troubleshooting options for the freezing, thawing, and seeding of iPSC on feeder-free, Matrigel™-coated, cell culture plates whenever iPSC cannot be recovered in sufficient quality. This review applies to two-dimensional (2D) monolayer cell culture and to iPSC, passaged, frozen, and thawed as cell aggregates (clumps). Furthermore, we discuss usually less well-described factors such as the cell growth phase before freezing and the prevention of osmotic shock during thawing.

Effects of Cryoprotective Medium Composition, Dilution Ratio, and Freezing Rates on Spotted Halibut (Verasper variegatus) Sperm Cryopreservation

The spotted halibut is species that has a high potential market value in Korea, but the supply of seed is unstable because of the limited milt production of males. The objective of this research was to explore different aspects, such as CPAs, diluents, dilution ratio, and freezing rates, to develop an optimal sperm cryopreservation. The parameters assessed were movable sperm ratio, sperm activity index, survival rate, and DNA damage. The CPAs tested in this research were propylene glycol, dimethyl sulfoxide (DMSO), methanol, ethylene glycol, and glycerol. Different diluents, including 300 mM sucrose, 300 mM glucose, Stain's solution, and Ringer's solution, were investigated. The previous experiment showed that the optimal CPA for cryopreservation was DMSO with a concentration of 15% with 300 mM as diluent. To determine the effect of the dilution ratio, sperm was diluted to 1:1, 1:2, 1:10, 1:100, and 1:1000 with 300 mM sucrose containing DMSO at a final concentration of 15%. Lastly, the optimal freezing rate of the sperm was evaluated with four different freezing rates (-1, -5, -10, and -20 °C/min). Post-thaw sperm motility was higher with a dilution ratio lower than 1:2, and the freezing rate was less than -5 °C/min. In conclusion, these findings represent the development of a cryopreservation protocol for spotted halibut.

Impact of different dilution techniques on boar sperm quality and sperm distribution of the extended ejaculate

The dilution of ejaculates is a fundamental step for the production of liquid-preserved boar semen. For a long time, it has been recommended to add the extender to the ejaculate. The aim of the present study was to first compare the effect of the position ('center' vs. 'wall') where the extender is added to the semen-mixing cylinder (height 32.5cm; diameter 12.7cm) using an automatic dispenser (n=11). In experiment 2 (n=30), we analyzed the two main dilution methods (extender to the semen ('control') vs. 'reverse'). Experiment 3 was carried out to study the dilution effect on kinematics. In Experiments 1 and 2, the sperm distribution 10min after the dilution and the sperm quality parameters during long-term storage (d1, d3, d5, and d7) were evaluated. In Experiment 3, sperm quality was assessed during short-term storage at 0, 10, 20, 30 and 60min after semen dilution ('control' vs. 'reverse'; n=6). There were no significant differences (P>0.05) between the treatments in the specific response to bicarbonate, mitochondrial activity, membrane status, thermo-resistance or sperm motility immediately after dilution or long-term storage. The sperm distribution was significantly (P=0.029) affected by the dilution method in Experiment 2. In summary, treatment with the extender first, which is used by only a few European boar studs, leads to comparable results in sperm quality during storage and better results in sperm distribution after dilution. This procedure is also less time consuming, less foam formation occurs during the semen dilution and the procedure is more hygienic.

Effect on sperm quality of different cryoprotectants in sperm of Chinchilla lanigera

Chinchilla lanigera is an endangered species therefore the development of cryopreservation protocols for its gametes is a useful tool in the application of assisted reproduction techniques. A study of the functionality of the spermatozoa punctured from the cauda epididymis was performed on fresh or frozen–thawed samples with three cryoprotective media (test-yolk buffer, sucrose and glycerol). The effect that these media had on sperm physiology during the freezing, storage and later thawing process was analysed. A decrease in the percentages of viability, motility, membrane integrity and capacity to undergo the induced acrosome reaction was found with all the media assayed, an increase in the percentages of DNA fragmentation was also observed. The comparative analysis of the effect of the different cryoprotectants assayed showed that the best medium to use to cryopreserve epididymal sperm in this species is test-yolk buffer. This medium had the least effect on the abovementioned physiological parameters, especially at the level of genetic material.

Effects of cryoprotectant treatments on bovine sperm function and osmolyte content

The hypothesis that addition and removal of cryoprotectants to and from spermatozoa would initiate regulatory volume decrease, and lead to osmolyte loss and reduced sperm function, was tested. Common cryoprotectants, in the absence of freezing and thawing, affected bovine ejaculated spermatozoa by lowering their total and progressive motility in medium, reducing their migration through surrogate cervical mucus, damaging sperm head membranes and inducing sperm tail coiling. Sperm function was slightly better maintained after cryoprotectants were added and removed in multiple small steps rather than in a single step. The intracellular content of the polyol osmolytes, D-sorbitol and myo-inositol, exceeded that of the zwitterion osmolytes, L-carnitine and L-glutamate. Certain cryoprotectants reduced intracellular L-carnitine and L-glutamate concentration but not that of myo-inositol or D-sorbitol. Multistep treatments with some cryoprotectants had advantages over one-step treatments in mucus penetration depending on the original amount of intracellular carnitine and glutamate in the spermatozoa. Overall, sperm quality was best maintained by multistep treatment with glycerol and propanediols that were associated with decreased intracellular glutamate concentration. Bovine spermatozoa seem to use glutamate to regulate cryoprotectant-induced cell swelling.

Relationships among frozen-thawed sperm characteristics assessed via the routine semen analysis, sperm functional tests and fertility of bulls in an artificial insemination program

Frozen semen specimens from 22 Holstein bulls representing a wide range of field fertility levels or nonreturn rates (NRR) were used in this study. Semen specimens were thawed at 37 degrees C for a minimum of 30 sec, followed by assessment via a routine semen analysis (RSA) and other sperm functional tests. The RSA was performed by assessing sperm count, motility and morphological characteristics. Other sperm functional tests were performed by assessing the acrosomal membrane integrity, sperm penetration into the cervical mucus and the sperm membrane functional integrity. Following assessment of sperm characteristics, the fertility data of the various bulls were compared to the RSA and the functional tests results. Bulls of high and low fertility were similar in terms of sperm count and progressive motility (P > 0.05). Other characteristics measured by the RSA and functional tests were significantly higher in high fertility bulls (P < 0.05). Correlation coefficients among the various sperm characteristics and fertility of bulls were highly significant (P < 0.01). The highest correlation coefficients between sperm characteristics and fertility were obtained for motility (r = 0.53; P < 0.01), normal morphology (r = 0.59; P < 0.01) and swollen spermatozoa (r = 0.57; P < 0.01). Analysis of specific sperm swelling patterns showed that those patterns considered to reflect maximal sperm swelling were indicative of high fertility.

Prognostic value of spermatological parameters as predictors of in vitro fertility of frozen-thawed bull semen

Cryopreservation imposes irreversible damage to sperm membranes, such as swelling and disruption of plasma and acrosome membranes, changes in membrane fluidity, altered influx of calcium, and changes in enzyme activity. Morphological integrity of the sperm plasma membrane has been widely studied using different techniques, including exposure of spermatozoa to hypoosmotic solutions (provides information concerning the biochemical activity of the sperm tail membrane), supravital test using eosin stain (yields information regarding sperm head membrane integrity), and Trypan-blue Giemsa stain (TBG; reveals both sperm plasma membrane and acrosome integrity). The objective of this study was to combine these tests in order to provide information about the integrity of the whole sperm surface, as well as acrosome status, and determine if the results of these tests were associated with sperm in vitro fertilizing ability. Stepwise regression analyses yielded a model in which fertility (maintain variable) was expressed as a combination of the results of different spermatological parameters (independent variables). The results of a test combining supravital eosin staining of samples previously submitted to hypoosmotic swelling test (STHOS) accounted for the greatest proportion of variation in fertilization rates (78%). Inclusion of the results of dual staining with TBG increased the proportion of variation in fertility rate that could be accounted for to 82%. Therefore, sperm plasma membrane integrity and function, and acrosome integrity can be considered important variables for normal sperm function and STHOST and TBG could be used for the prognosis of the potential fertility of bovine semen samples used for IVF or AI.

The effect of colloid osmotic pressure in human spermatozoa exposed to hypoosmotic conditions

The use of a protein source such as serum and albumin had been extensively employed as supplements of culture media for handling and culture of gametes and embryos. Protein molecules behave as colloids in solution and contribute to the osmotic pressure of fluids. The interaction of proteins in solution and spermatozoa needs to be assessed in order to determine their possible role in osmoregulation. The aim of this study was to assess possible osmoregulatory mechanisms of protein supplementation against exposure to hypoosmotic conditions by assessing the sperm's response to those environments. A stock hypoosmotic solution (HOS) was prepared by using a mixture of fructose and sodium citrate and adjusted to an osmotic pressure of 150 mOsm l-1. Another stock solution was prepared by diluting a preparation of synthetic serum supplement [SSS; 6% (v/v) total protein] with distilled water to obtain an osmotic pressure of 150 mOsm l-1 (hypoosmotic SSS or H-SSS). Three additional solutions were prepared by mixing the stock HOS and H-SSS solutions in the following proportions (v/v): (i) 75% H-SSS/25% HOS, (ii) 50% H-SSS/50% HOS and (iii) 25% H-SSS/75% HOS. Aliquots of washed spermatozoa from 18 men were diluted 1 : 10 (v/v) with each of the testing solutions and incubated for 60 min. Specimens were assessed on wet mounts for total and specific swelling patterns. Swelling patterns were classified as maximal (>50% tail length swollen) and minimal (<50% tail length swollen) swelling with or without associated sperm motility. The major finding of this study was that increasing the concentration of protein supplementation resulted in a decrease in the proportion of maximal sperm tail swelling patterns and an increase in the proportion of minimal tail swelling patterns. A proportion of spermatozoa which exhibited minimal swelling patterns were still motile in all solutions tested, and the percentage of those spermatozoa increased as the protein supplementation was also increased in the testing solutions. Incorporation of protein supplementation as described in this study delays the effect of sperm swelling in hypoosmotic conditions.

Effects of spermatozoal concentration and post-thaw dilution rate on survival after thawing of dog spermatozoa

The objectives of this study were to evaluate the effects and interactions of freezing dog semen using 4 different sperm concentrations (50 x 10(6), 100 x 10(6), 200 x 10(6) and 400 x 10(6) spermatozoa/mL) in 0.5-mL straws and diluting the thawed semen at 4 different rates (1:0, 1:1, 1:2 and 1:4) on post-thaw survival and longevity of dog spermatozoa during incubation at 38 degrees C. Fifteen ejaculates were collected from 12 dogs and pooled. The semen pool was divided into 4 aliquots containing respectively 4,200 x 10(6), 2,100 x 10(6), 1,050 x 10(6) and 525 x 10(6) spermatozoa, which were centrifuged. Sperm pellets were rediluted with TRIS-glucose-egg yolk extender containing 5% glycerol and 0.5% of Equex STM Paste to obtain the designated sperm concentrations. The semen was frozen in 0.5-mL straws 4 cm above liquid nitrogen (LN2). The straws were thawed at 70 degrees C for 8 sec and the contents of each straw were divided into 4 aliquots and diluted with TRIS buffer at 38 degrees C at rates of 1:0, 1:1, 1:2 and 1:4 (semen:buffer), respectively, making a total of 16 treatments. Sperm motility was subjectively evaluated after thawing and at 1-h intervals during 8 h of incubation at 38 degrees C. Plasma membrane integrity and acrosomal status were evaluated at 1, 3, 6, 12 and 18 h post-thaw using a triple-staining procedure and flow cytometry. For data pooled across the post-thaw dilution rate, motility was higher (P< 0.001) in samples frozen with 200 x 10(6) spermatozoa/mu. The integrity of sperm plasma membranes after 18 h incubation was higher (P<0.05) in samples frozen with 200 x 10(6) and 400 x 10(6) spermatozoa/mL. For data pooled across sperm concentration, samples diluted at a rate of 1:2 or 1:4 had better (P<0.001) motilities after 8 h of incubation than undiluted samples or those diluted at 1:1. The integrity of the sperm plasma membranes was higher (P<0.001) at increasing dilution rates. When the 16 treatments were compared, the best longevity was obtained when semen packaged at a concentration of 200 x 10(6) spermatozoa/mL was diluted immediately after thawing at 1:4 dilution rate.

Activity of Chinchilla laniger spermatozoa collected by electroejaculation and cryopreserved

Because reproductive studies and the application of assisted reproductive techniques are relevant issues for an endangered species such as Chinchila laniger, the availability of a source of viable spermatozoa becomes of utmost importance. In this paper, we evaluate several functional parameters (motility, viability, response to hypoosmotic swelling test and acrosomal integrity) of fresh or frozen-thawed spermatozoa. Electro-ejaculation trials (50-cyc/sec sinusoidal wave was applied for 5 of every 10 sec) were successful in all unanesthetized animals. After volume (108.3 +/- 12.0 microL, n = 15) and concentration (421.8 +/- 34.4 x 10(6) cells/mL, n = 15) measurements, the above mentioned parameters were determined. In frozen-thawed semen samples sperm motility, viability, hypoosmotic swelling test and acrosomal integrity were significantly lower than in fresh semen samples. The results clearly indicated that electro-ejaculation is a useful method for evaluating spermatozoa for genetic analysis or for used in Al in this species. In addition, the cryopreservation procedure in this study preserved adequate levels of functional sperm activity.

Survival of bull sperm frozen at different rates in media varying in osmolarity

The effects of freezing procedures, osmolarity, trehalose, and sucrose on survival of bull sperm in whole milk (WM) and egg yolk-Tris (EYT), semen extenders used worldwide, were studied. Sperm were added to extenders at 25 degreesC, cooled slowly to 5 degreesC, glycerolated, packaged in 0.5-ml straws, and frozen. Different freezing rates were accomplished in two steps. Straws were transferred from +5 degreesC to nitrogen vapor at temperatures ranging from -10 to -100 degreesC in the first step and to liquid nitrogen in the second step. Straws were thawed in water at 35 degreesC. A substantial decrease in sperm motility occurred between -10 and -20 degreesC, as abrupt nucleation occurred following supercooling to -13 degreesC. To study the interactions between osmolarity x cooling rate, WM and EYT extenders were prepared to yield media measuring 220 to 420 mOsm/L. The optimal first-step range of cooling in the two-step procedure was -30 to -70 degreesC, and the highest proportions of motile sperm after freezing and thawing were 61 to 62 in 260 to 300 mOsm/L WM and 63 to 64% in 300 to 340 mOsm/L EYT, equivalent to the results with the control procedure used commercially. As the cooling rate increased (first step to -100 degreesC) sperm motility was much higher in hypertonic than in hypotonic extenders (P < 0.05), indicating the importance of partial dehydration before rapid cooling. Replacing part of EYT and WM with equivalent solutions (same mOsm/L) of sucrose or trehalose had no appreciable effect. These results provide a basis for further investigating simple freezing systems that might be more effective in preserving bull sperm than those currently available.

Evaluation of techniques for the cryopreservation of washed spermatozoa: comparisons between Ham's F-10 and TEST-yolk media

The objective of this study was to develop new techniques for the cryopreservation of washed spermatozoa. Two media (Ham's F-10 and nonthermoprecipitated TEST-yolk buffer [NT-TYB]) containing 7% (v/v) glycerol were compared to semen cryopreservation by adding glycerol directly to the semen. Twenty four men collected a semen specimen each after 4 days of sexual abstinence via the use of a semen collection device at intercourse. Specimens were assessed for volume (ml), count (x 10(6)), percentage and grade of motility, morphology (% normal) and acrosomal status (% intact acrosomes). Each ejaculate was split into 3 aliquots (Aliquots 1 to 3) and processed for freezing. Aliquot 1 was prepared for cryopreservation by adding glycerol (7% [v/v] final concentration) directly via a dropwise mode. Aliquot 2 and 3 were diluted 1:1 (v/v) with Ham's F-10 and NT-TYB, respectively. Aliquots 2 and 3 were then centrifuged (400 x g for 10 minutes) and resuspended into the corresponding media containing 7% (v/v) glycerol to complete the sperm wash procedure. All aliquots were frozen in 0.5 ml french straws. Sperm specimens were frozen in liquid nitrogen (LN2) vapor from +23 degrees C to -68 degrees C at a slow rate (2.3 degrees C/minute), after which the specimens were plunged directly into LN2 and stored for 30 days. The quality of the spermatozoa were monitored throughout each step of the overall procedure by measuring the motility characteristics of the spermatozoa. Straws corresponding to each aliquot were thawed in a water bath at 37 degrees C for 2 minutes, followed by assessment of sperm motility and acrosomal status. The percentage of motility after thawing was 31.6 +/- 5.6%, 32.8 +/- 1.8% and 37.3 +/- 1.9% in Aliquots 1 to 3, respectively. Similarly, the grade of motility was 2.4 +/- 0.2, 2.6 +/- 0.1 and 3.0 +/- 0.1 in Aliquots 1 to 3, respectively. The acrosomal status (% intact acrosomes) in Aliquots 1 to 3 was 41.2 +/- 2.6, 43.1 +/- 3.6 and 51.6 +/- 4.5, respectively. The results suggest that the characteristics of spermatozoa washed and frozen in NT-TYB (Aliquot 3) were improved over those spermatozoa prepared via direct addition of glycerol to the semen (Aliquot 1) or by using Ham's F-10 (Aliquot 2). The most significant reduction noted during freezing was in the loss of acrosomal integrity. The results obtained in this study point out that washed spermatozoa can be cryopreserved with some success and that the recovered spermatozoa could be used for intrauterine insemination in an artificial insemination program using husband's or donor sperm, or for the various assisted reproductive technology procedures. It is the opinion of the authors that the information generated in this study is of importance for those scientists and clinicians involved in the handling and manipulation of cryopreserved spermatozoa.

Sperm membrane functional integrity and response of frozen-thawed bovine spermatozoa during the hypoosmotic swelling test incubation at varying temperatures

The objective of this study was to assess the sperm membrane integrity and permeability of frozen-thawed bovine spermatozoa, processed at varying temperatures during and after thawing, by exposing the spermatozoa to standardized hypoosmotic conditions. The hypoosmotic swelling (HOS) test was employed to measure changes in sperm membrane functional status and permeability. Frozen specimens (from 5 bulls) were thawed at 37h degrees C for 10 sec and transferred to a water bath at 37 (Aliquot 1), 21 (Aliquot 2) or 5 degrees C (Aliquot 3) to complete thawing (1 to 2 min). The specimens were maintained and processed at these temperatures for additional 5 to 10 min. Specimens were slowly diluted 1:1 (v/v) and washed with Ham's F-10 media containing 3% (w/v) BSA. The HOS test was performed by adding 0.1 ml of the sperm specimen to 1.0 ml of a 100 mOsm/L HOS diluent. The following treatments were performed: 1) Aliquot 1 (control), specimens were incubated in HOS solutions at 37 degrees C for 5 min; 2) Aliquot 2, specimens were incubated in HOS solutions at 21 or 37 degrees C for 5 min; and 3) Aliquot 3, specimens were incubated in HOS solutions at 5 or 37 degrees C for 5 min. Samples were obtained from the sperm specimen-HOS diluent mixtures at 1 min intervals (during the 5 min incubation period), fixed and assessed for sperm swelling patterns. The sperm response to the HOS test for specimens processed at temperatures below 37 degrees C was higher when samples were incubated in HOS diluents at 37 degrees C. This finding indicates that the potential for sperm swelling (measurement of sperm membrane functional status) can be maintained when spermatozoa are processed at temperatures below 37 degrees C. The highest response to the HOS test was observed in spermatozoa processed at 21 degrees C and incubated in a HOS solution at 37 degrees C. The response to the HOS test was superior to the one observed in specimens maintained and processed at 37 degrees C throughout. Thawing of spermatozoa at 37 degrees C, followed by processing at 21 degrees C seems to reduce the negative effects associated with osmotic shock and results in the preservation of the sperm membrane functional status during the in vitro handling of frozen-thawed bovine spermatozoa.

Quantitative and qualitative characteristics of frozen-thawed bovine spermatozoa recovered via a conventional and a standardized swim-up technique

The objective of this study was to use the bovine as a model to evaluate the recovery of frozen-thawed spermatozoa via a conventional and a standardized swim-up technique. Frozen-thawed semen specimens (3 bulls) were washed and reconstituted with 2.9% (w/v) sodium citrate extender containing 20% (v/v) chicken egg yolk (SC-EY). Reconstituted sperm specimens were used for selection via conventional swim-up and the standardized ZSC method. The swim-up method consisted of overlayering the sperm specimen with 0.7 to 1.0 ml of isolation media (Ham's F-10), followed by 1 hr of incubation. The ZSC consisted of a conical cavity on the bottom of a glass column. The sperm specimen was placed into the conical cavity until the surface of the specimen was at the same level as the upper boundaries of the conical cavity. The surrounding periconical and epiconical areas were filled with 0.7 to 1.0 ml of isolation media followed by 1 hr of incubation. The isolation media was removed (harvesting) from swim-up (80% volume) and ZSC specimens (100% volume) at the end of incubation. Recovered specimens were assessed for volume (ml), sperm concentration (x10(6) spermatozoa/ml), the percentage and grade of motility (0 to 4), the occurrence of osmotic shock and the percentage of spermatozoa reactive to the hypoosmotic swelling (HOS) test. Swim-up and ZSC selected specimens were qualitatively similar to each other. However, higher numbers of spermatozoa were recovered when sperm specimens were processed via the ZSC method (1.6 fold increase) than with the conventional swim-up technique. Because the ZSC method enabled the recovery of up to 100% of the overlayered media, it also enabled the recovery of most of the spermatozoa that migrated from the sperm specimen into the isolation media with no possibility of mixing the two, which was the case with the swim-up method, and which could also contaminate the recovered specimen with dead and immotile spermatozoa. Thus, the ZSC technique enabled the harvesting of the medium closest to the underlayered sperm specimen, which contributed to maximize the number of sperm recovered. When all assessed parameters were noted and all clinical improvements and efficiency of the method were compared to the swim-up technique, the sperm manipulation procedure of choice was clearly the ZSC method.

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.

Measurement of the sperm motility index via the sperm quality analyzer and its relationship to other qualitative sperm parameters

Sperm parameters such as the concentration and percentage of motile spermatozoa are commonly used to assess semen quality. The sperm quality analyzer (SQA) is a device that detects variations in the optical density of motile spermatozoa, providing a sperm motility index (SMI) that is based on various sperm parameters including the concentration, morphology and acrosomal status of motile spermatozoa. The relationship between SMI values of frozen-thawed bovine spermatozoa undergoing swelling in a hypoosmotic medium (100 mOsm/L) and other sperm parameters were evaluated. Frozen semen specimens from 3 bulls were thawed and washed with Ham's F-10 supplemented with 3% BSA and split into 3 (0.2 mL) aliquots. The aliquots were diluted with 1.0 mL of Ham's F-10 (Aliquot 1), isotonic sodium citrate (Aliquot 2), and hypotonic sodium citrate (Aliquot 3). The osmotic pressure of the media used for dilution of Aliquots 1 and 2 was 300 mOsm/L, while that for Aliquot 3 was 100 mOsm/L. Following dilution, the aliquots were incubated for 30 min and manually assessed at 5-min intervals for the percentage and grade of motility (Grades 0 to 4) as well as for the percentage of swollen spermatozoa. Sperm samples were simultaneously evaluated by SQA to obtain the SMI values at the same 5-min intervals during the 30-min incubation. Significant correlations were observed between SMI values and other sperm parameters in Aliquot 3 (P < 0.05). The results indicated that the SMI values obtained from frozen-thawed bovine spermatozoa exposed to a 100 mOsm/L diluent, which causes optimal swelling of spermatozoa, are highly correlated to other sperm parameters. The SQA unit, as applied in this study, can be used for rapid and reliable screening of sperm samples.

Thawing and processing of cryopreserved bovine spermatozoa at various temperatures and their effects on sperm viability, osmotic shock and sperm membrane functional integrity

The objective of this study was to evaluate the effects of thawing and processing temperatures on post-thaw sperm viability, occurrence of osmotic shock and sperm membrane functional status. The occurrence of osmotic shock, characterized by increased spermatozoa with coiled tails, eventually results in reduced sperm viability and sperm membrane integrity. The effects of different thawing temperatures were assessed by thawing frozen specimens at 37, 21 or 5 degrees C for 1 to 2-min, followed by processing at these temperatures. A subset of frozen specimens were thawed at 37 degrees C for 10 to 15-sec and transferred to a water bath at 21 or 5 degrees C for 1 to 2-min to complete thawing, followed by processing at these temperatures. Sperm processing (washing) consisted of dilution, centrifugation and resuspension to remove glycerol from the medium and to gradually return the spermatozoa to isotonic conditions. Post-thawed specimens (0.5 mL) were slowly diluted 1:1 (v/v) at a rate of 0.1 mL/min, centrifuged, and resuspended to 0.5 mL (37 degrees C). Diluted specimens were equilibrated for 1 to 2-min after dilution and for 5-min after resuspension. The specimens were then incubated for 2-h (37 degrees C) and assessed at 60-min intervals for the percentage of motility, for progressive motility (Grades 0 to 4), for the percentage of spermatozoa with coiled tails, and for the percentage of swollen spermatozoa. The percentage of swollen spermatozoa (measurement of sperm membrane integrity) was assessed by exposing spermatozoa to a modified hypoosmotic swelling (HOS) test. The results obtained seem to indicate that physiological thawing and processing temperatures (37 degrees C) are required to maintain sperm motility. However, thawing and processing at lower temperatures (< 37 degrees C) seems to prevent the occurrence of osmotic shock and to maintain sperm membrane functional integrity. In this study, thawing at 37 degrees C (10 to 15-sec) and transfer to a water bath at 21 degrees C (1-min) to complete thawing, followed by processing at 21 degrees C, yielded better results in terms of increased sperm viability, reduced occurrence of osmotic shock and higher reactivity to the HOS test.