Methods for Cryopreservation of Guinea Fowl Sperm

Conservation of indigenous poultry species is an important part of the new Hungarian agricultural strategy. Semen cryopreservation is the most practical method for the long term storage of poultry genetic material. The objective was to compare four protocols for cryopreservation of guinea fowl sperm (slow and fast programmable, freezing in nitrogen vapor, and pellet) and three cryoprotectants (10% ethylene glycol, 6% dimethyl-formamide and 6% dimethyl-acetamide). The efficiency of the methods was examined by in vitro tests (subjective motility scoring, sperm concentration, morphological and live/dead sperm analysis with eosin-aniline staining). Thereafter, the two most promising methods were tested by artificial insemination of frozen-thawed semen (3 times a week for 3 weeks using 300 million spermatozoa/hen), followed by candling of incubated eggs, assessment of fertilization, embryonic death, and hatching rate. The survival rate of live, intact spermatozoa was greatest (p≤0.05) in pellet method and the slow programmable protocol (with 10% ethylene glycol) (28.6 and 23.5%). The two best protocols (based on in vitro assessment of post-thaw semen quality) were subsequently tested in vivo with artificial insemination. The pellet method yielded a 64% fertility rate compared to slow protocol with only 30% fertility. Regardless, both freezing protocols significantly increased embryonic deaths compared to the control group (16,7; 9,1 and 8,3%, respectively). During the 3-week in vivo trial, fertility increased and early embryonic death decreased over time. According to the results the guinea fowl sperm could tolerate the fast freezing in pellet better than the slower freezing rates and resulted acceptable fertility rate.     

Improving viability of cryopreserved honey bee (Apis mellifera L.) sperm with selected diluents, cryoprotectants, and semen dilution ratios

This is the first study where the systematic application of theories and techniques used in mammalian sperm cryopreservation have been applied to honey bee (Apis mellifera L.) semen as a means to improve postthaw viability of cryopreserved sperm. Six newly designed diluents, three cryoprotectants (dimethyl sulfoxide, DMA, glycerol), and five diluent:semen ratios (1:1, 3:1, 6:1, 9:1, and 12:1) were tested. In addition, the sperm freezing tolerance of three honey bee strains was evaluated. Specific protocols were designed to control semen freezing and thawing rates. Sperm motility was assessed visually, whereas sperm viability was assessed using SYBR-14 and propidium iodide fluorescent stains. Diluent treatments did not affect fresh (nonfrozen) sperm viability yet affected fresh sperm motility (P < 0.05). Based on these assessments, two diluents were chosen and used in all successive cryopreservation experiments. Using the selected diluents, semen was collected at various diluent:semen ratios, along with one of the three cryoprotectants. Semen collected at high dilution ratios, using a hypotonic antioxidant diluent containing catalase, in combination with dimethyl sulfoxide, provided higher postthaw sperm viability than that of all other combinations tested (68.3 ± 5.4%; P < 0.05). Using this combination of dilution ratio, diluent, and cryoprotectant, there were no differences among honey bee strains for postthaw sperm viability (P = 0.805). Nevertheless, these new semen dilution and freezing methods improved postthaw viability of sperm to levels that could theoretically sustain worker populations in colonies, thus providing potential for further optimization of cryopreservation techniques for the genetic preservation and improvement of honey bee genotypes.     

Membrane permeabilization of phosphatidylcholine liposomes induced by cryopreservation and vitrification solutions

Membranes are the primary site of freezing injury during cryopreservation or vitrification of cells. Addition of cryoprotective agents (CPAs) can reduce freezing damage, but can also disturb membrane integrity causing leakage of intracellular constituents. The aim of this study was to investigate lipid-CPA interactions in a liposome model system to obtain insights in mechanisms of cellular protection and toxicity during cryopreservation or vitrification processing. Various CPAs were studied including dimethyl sulfoxide (DMSO), glycerol (GLY), ethylene glycol (EG), dimethyl formamide (DMF), and propylene glycol (PG). Protection against leakage of phosphatidylcholine liposomes encapsulated with carboxyfluorescein (CF) was studied upon CPA addition as well as after freezing-and-thawing. Molecular interactions between CPAs and phospholipid acyl chains and headgroups as well as membrane phase behavior were studied using Fourier transform infrared spectroscopy. A clear difference was observed between the effects of DMSO on PC-liposomes compared to the other CPAs tested, both for measurements on CF-retention and membrane phase behavior. All CPAs were found to inhibit membrane leakiness during freezing. However, exposure to high CPA concentrations already caused leakage before freezing, increasing in the order DMSO, EG, DMF/PG, and GLY. With DMSO, liposomes were able to withstand up to 6 M concentrations compared to only 1 M for GLY. Cholesterol addition to PC-liposomes increased membrane stability towards leakiness. DMSO was found to dehydrate the phospholipid headgroups while raising the membrane phase transition temperature, whereas the other CPAs caused an increase in the hydration level of the lipid headgroups while decreasing the membrane phase transition temperature.     

Sterility in honey bees caused by dimethyl sulfoxide

Honey bee (Apis mellifera) semen was treated as follows: diluted in saline with 10 percent dimethyl sulfoxide (DMSO) and stored at -196 degrees C; same treatment but stored at 12 degrees C; diluted in saline and stored at 12 degrees C; and undiluted, unstored semen. Daughters (queens) produced from the treated spermatozoa were evaluated for total sterility. Only sterile eggs were produced from 3 percent of the queens in both groups that had DMSO (5/166 in group 1, and 6/234 in group 2). They were different (P less than 0.05) from groups 3 and 4 in which no queens were produced that laid only sterile eggs (0/151 and 0/137, respectively). These results demonstrate that, under the conditions used, a low level of sterility is induced by DMSO, and this F1 sterility raises questions about possible genetic damage by DMSO.     

Monthly changes in various drone characteristics of Apis mellifera ligustica and Apis mellifera syriaca

This study was conducted to investigate drone rearing activity and semen production of Apis mellifera ligustica and Apis mellifera syriaca . Tendency of worker bees of both subspecies towards egg laying under semiarid conditions were also monitored in the experiments. Differences were not observed in drone brood production between both honeybee subspecies throughout the investigation. Worker bees of both subspecies needed a significantly shorter time to start egg laying during February and March in comparison with the time those workers needed for laying eggs during the remaining months of the study. Syrian bee workers started egg laying earlier than Italian bee workers. Drones from laying workers were much smaller and produced less sperms with more abnormalities than normal drones. Drones produced from queens in May were heavier and produced more sperms with less abnormalities than those produced during the other months. The drone brood rearing of both subspecies tended to follow the same general cycle in 2005 and 2006. The study suggests that virgin queens have a better chance to receive adequate viable sperm amounts from drones in April and May in semiarid Mediterranean conditions.     

In vivo validation of in vitro quality tests for cryopreserved honey bee semen

Development of cryopreservation protocols for honey bee semen is hampered by the lack of validated laboratory tests that allow the prediction of in vivo performance of frozen-thawed semen. Here we analyzed correlations between seven in vitro tests and indicators of semen performance after insemination. These tests included measures of motility, cell conformation, and membrane permeability before and after exposure to physiochemical stress. We show that the proposed protocol for motility measurement yields results that correlate well with the number of sperm reaching the storage organ of queens (correlation coefficient ρ=0.67) and the proportion of viable eggs in inseminated queens (ρ=0.48). The conventional live/dead assay of membrane permeability by dual fluorescent staining and a new test based on the leakage of the glycolytic enzyme glucose-phosphate-isomerase (GPI) from damaged cells were also correlated to the number of sperm reaching the spermatheca (ρ=0.54 and -0.61, respectively). We conclude that motility, live/dead-staining and the assay for GPI-leakage are valuable tools for the improvement of cryopreservation of honey bee semen.     

Cryopreservation of the Mediterranean mussel (Mytilus galloprovincialis) spermatozoa

The effects of cryoprotectants, cooling rate and freezing on the mussel Mytilus galloprovincialis sperm were evaluated. At the end of each step of the experimental protocol, motility and fertilization ability of sperm were analyzed, compared to fresh semen. Five cryoprotectants were tested in their toxicity level: dimethylsulfoxide, ethylene glycol, 1-2 propylene glycol at 5%, 7%, 10%, 15% and 20% concentration; glycerol and methanol at concentration of 5%, 7% and 10%. The incubation times were 10, 20 and 30 min at 20 ± 1 °C. Only dimethylsulfoxide, ethylene glycol and 1-2 propylene glycol at 5%, 7% and 10% were chosen for the following pre-freezing step. Five adaptation/chilling rates were analyzed: 10 min at 20 ± 1, −2, −1, −0.5 and −0.25 °C/min and the last one was used for testing the best freezing procedure among seven gradients. Particularly, two rapid rates, three slow rates and two double step rates were conducted.Thawing results showed that M. galloprovincialis sperm are very sensitive to rapid pre-freezing and freezing protocols and only a slow procedure assured good motility and fertilization percentages.     

Cryoprotective agent toxicity interactions in human articular chondrocytes

Background

Vitrification is a method of cryopreservation by which cells and tissues can be preserved at low temperatures using cryoprotective agents (CPAs) at high concentrations (typically ?6.0 M) to limit the harmful effects of ice crystals that can form during cooling processes. However, at these concentrations CPAs are significantly cytotoxic and an understanding of their toxicity characteristics and interactions is important. Therefore, single-CPA and multiple-CPA solutions were evaluated for their direct and indirect toxicities on chondrocytes.

Methods

Chondrocytes were isolated from human articular cartilage samples and exposed to various single-CPA and multiple-CPA solutions of five common CPAs (dimethyl sulfoxide (DMSO), ethylene glycol (EG), propylene glycol (PG), glycerol (Gy) and formamide (Fm)) at both 6.0 and 8.1 M concentrations at 0 °C for 30 min. Chondrocyte survival was determined using a fluorescent cell membrane integrity assay. The data obtained was statistically analyzed and regression coefficients were used to represent the indirect toxicity effect which a specific combination of CPAs exerted on the final solution’s toxicity.

Results

Multiple-CPA solutions were significantly less toxic than single-CPA solutions (P < 0.01). The indirect toxicity effects between CPAs were quantifiable using regression analysis. Cell survival rates of approximately 40% were obtained with the four-CPA combination solution DMSO–EG–Gy–Fm. In the multiple-CPA combinations, PG demonstrated the greatest degree of toxicity and its presence within a combination solution negated any benefits of using multiple lower concentration CPAs.

Conclusions

Multiple-CPA solutions are less cytotoxic than single-CPA solutions of the same total concentration. PG was the most toxic CPA when used in combinations. The highest chondrocyte survival rates were obtained with the 6.0 M DMSO–EG–Gy–Fm combination solution.     

Toxicity tests of cryoprotecting agents for Mytilus galloprovincialis (Lamark, 1819) early developmental stages

Global aquaculture production of blue mussel has increased over last years. This work reaffirms the great potential of cryopreservation technique on mussel industry and overcome economic barriers a cause of a traditional and rudimentary management and continue growing. The aim of this work is to set some preliminary basis attending to toxicity of cryoprotecting agents (CPAs) on different development stages of Mytilus galloprovincialis as a start point to develop a stable cryopreservation protocol. Toxicity tests were carried out by using common CPAs (dimethyl-sulfoxide (Me₂SO), glycerol, (GLY), propylene glycol (PG) and ethylene glycol (EG)) in a range from 0.5 to 3 M on fertilized egg, trochophore larva, and D-larva of Mytilus galloprovincialis. Results evidenced more resistance of older development stages to toxicity. Of all CPAs tested, toxicity testing highlights PG or EG as suitable CPAs for cryopreservation of early development stages; whereas D-larva was unaffected by any of the CPAs tested. Preliminary cryopreservation trials were developed to obtain information into cell cryoprotection. Further research should be focused on membrane permeability and other parameters, such as the balance between toxicity and cryoprotective effect of CPAs.     

Molecular Mechanism of the Synergistic Effects of Vitrification Solutions on the Stability of Phospholipid Bilayers

The vitrification solutions used in the cryopreservation of biological samples aim to minimize the deleterious formation of ice by dehydrating cells and promoting the formation of the glassy state of water. They contain a mixture of different cryoprotective agents (CPAs) in water, typically polyhydroxylated alcohols and/or dimethyl sulfoxide (DMSO), which can damage cell membranes. Molecular dynamics simulations have been used to investigate the behavior of pure DPPC, pure DOPC, and mixed DOPC-β-sitosterol bilayers solvated in a vitrification solution containing glycerol, ethylene glycol, and DMSO at concentrations that approximate the widely used plant vitrification solution 2. As in the case of solutions containing a single CPA, the vitrification solution causes the bilayer to thin and become disordered, and pores form in the case of some bilayers. Importantly, the degree of thinning is, however, substantially reduced compared to solutions of DMSO containing the same total CPA concentration. The reduction in the damage done to the bilayers is a result of the ability of the polyhydroxylated species (especially glycerol) to form hydrogen bonds to the lipid and sterol molecules of the bilayer. A decrease in the amount of DMSO in the vitrification solution with a corresponding increase in the amount of glycerol or ethylene glycol diminishes further its damaging effect due to increased hydrogen bonding of the polyol species to the bilayer headgroups. These findings rationalize, to our knowledge for the first time, the synergistic effects of combining different CPAs, and form the basis for the optimization of vitrification solutions.     

Molecular Mechanism of the Synergistic Effects of Vitrification Solutions on the Stability of Phospholipid Bilayers

The vitrification solutions used in the cryopreservation of biological samples aim to minimize the deleterious formation of ice by dehydrating cells and promoting the formation of the glassy state of water. They contain a mixture of different cryoprotective agents (CPAs) in water, typically polyhydroxylated alcohols and/or dimethyl sulfoxide (DMSO), which can damage cell membranes. Molecular dynamics simulations have been used to investigate the behavior of pure DPPC, pure DOPC, and mixed DOPC-β-sitosterol bilayers solvated in a vitrification solution containing glycerol, ethylene glycol, and DMSO at concentrations that approximate the widely used plant vitrification solution 2. As in the case of solutions containing a single CPA, the vitrification solution causes the bilayer to thin and become disordered, and pores form in the case of some bilayers. Importantly, the degree of thinning is, however, substantially reduced compared to solutions of DMSO containing the same total CPA concentration. The reduction in the damage done to the bilayers is a result of the ability of the polyhydroxylated species (especially glycerol) to form hydrogen bonds to the lipid and sterol molecules of the bilayer. A decrease in the amount of DMSO in the vitrification solution with a corresponding increase in the amount of glycerol or ethylene glycol diminishes further its damaging effect due to increased hydrogen bonding of the polyol species to the bilayer headgroups. These findings rationalize, to our knowledge for the first time, the synergistic effects of combining different CPAs, and form the basis for the optimization of vitrification solutions.     

Effects of extenders, cryoprotectants and freezing methods on sperm quality of the threatened Brazilian freshwater fish pirapitinga-do-sul Brycon opalinus (Characiformes)

The objective was to develop a suitable freezing method to cryopreserve Brycon opalinus (Characiformes) sperm. Extenders (NaCl and glucose at 325 and 365 mOsm/kg), cryoprotectants (dimethyl sulfoxide = dimethyl sulfoxide (DMSO) and methyl glycol = methyl glycol (MG)), equilibration times (15 and 30 min), thawing temperatures (30 and 60 °C), and straw sizes (0.5 and 4.0 mL) were tested. Sperm were frozen in a liquid nitrogen vapor vessel at −170 °C and subsequently stored in liquid nitrogen. Post-thaw sperm quality was always evaluated in terms of motility (expressed as percentage of motile sperm), duration of motility and vitality (eosin-nigrosin staining, expressed as percentage of intact sperm). The best freezing method was also tested for fertility and hatching (expressed as the percentage of fertilized eggs). Post-thaw sperm quality was highest when sperm were cryopreserved in Glucose 365 mOsm/kg and MG, after a 30-min equilibration and thawed at 60 °C for 8 s, of regardless straw size: 74 ± 7% motile sperm, 47 ± 4 s of motility duration, 69 ± 3% intact sperm, 64 ± 4% fertilization and 63 ± 3% hatching. The freezing method developed in the present study was efficient and can be used to maximize larvae production for both aquaculture purposes and for conservational programs, since B. opalinus is a threatened species.     

Optimization of the cryopreservation of African clawed frog (Xenopus laevis) sperm

Cryopreservation of testicular sperm in the African clawed frog, Xenopus laevis, was tested using three penetrating cryoprotectants (DMSO, methanol, and glycerol) and three semen diluents (300 mmol/L glucose, 300 mmol/L sucrose, and a motility inhibiting saline [MIS] solution [150 mmol/L NaCl, 3 mmol/L KCL, 1 mmol/L Mg₂SO₄, 1 mmol/L CaCl₂, and 20 mmol/L Tris, pH 8.0]). Three freezing rates and four thawing rates were also tested, and the best freezing/thawing conditions have been determined. The responses of sperm motility, viability, and fertility were assessed. Incubation of the sperm macerates with penetrating cryoprotectants showed that DMSO was the least toxic and methanol the most toxic. Semen in cryodiluents frozen 10 cm above the surface of liquid nitrogen (freezing rate of 20 to 25 °C/min) and thawed at room temperature for 40 sec had significantly higher percentages of motile and viable sperm than that of semen frozen 5 cm or 8 cm above the surface of liquid nitrogen and thawed at 5, 25, or 30 °C for 10, 15, or 60 sec, respectively. Sperm frozen in MIS containing 5% DMSO had a higher hatching rate than that of sperm frozen in sucrose and glucose diluents containing 5% or 10% DMSO and in MIS containing 10% DMSO. Addition of 73 mmol/L sucrose to the sperm extender MIS + 5% DMSO could improve the postthaw sperm motility and fertility. In conclusion, dilution of collected sperm in MIS solution (to have a final concentration of 6.5 × 10⁶ to 8 × 10⁶/mL) containing 5% DMSO and 73 mmol/L sucrose, freezing in a vapor of liquid nitrogen at 10 cm above the surface, and thawing at room temperature for 40 sec was the best cryopreservation protocol. This protocol gave 70% hatching rate, 80% motility rate, and 75% viability rate of fresh hormonally induced sperm.     

The effects of cryoprotectants on sperm motility of the Chinese pearl oyster,Pinctada fucata martensii

Cryopreservation has been widely employed to preserve genetic material of aquatic animals. Although of common use in bivalves, resulting effects due to the toxicity of the cryoprotectants dimethyl sulfoxide (DMSO), propanediol (PG), methanol (MET) and ethylene glycol (EG), upon sperm motility in the Chinese pearl oyster, Pinctada fucata martensii, has remained undocumented. This study endeavors to identify the least toxic among the effective cryoprotectant agents by observing and comparing their toxic effects on sperm motility under varying concentrations and duration of exposure. Sperm samples were exposed during controlled experiments, for 1, 3, 6, 9, 12 and 15 min durations, to each of the listed cryoprotectants at 5, 10, 15, and 20% (volume:volume) concentrations. Sperm motility was observed to diminish when exposed to all cryoprotectant solutions, and observations demonstrated that toxicity increased relative to both concentration and equilibration time. After 6 min of exposure to the cryoprotectants, sperm motility was seen to have diminished significantly in DMSO at just 5% concentration, and in MET, PG and EG at 10% concentrations, respectively (the values of the lowest observed effect concentrations). The relationship between the quantity of immotile sperm and the cryoprotectant concentration was described using the logarithmic regression equation. MET exhibited the lowest effective concentration required to inhibit sperm motility by 50% (EC₅₀), followed by EG, PG and DMSO, in order. Therefore, MET proved most toxic under the test conditions for sperm of P. fucata martensii, whereas DMSO, PG and EG were observed as comparatively safer, suggesting that DMSO, PG and EG warrant further study in the application of cryopreservation of Chinese P. fucata martensii sperm.     

Infrared spectroscopic analysis of hydrogen-bonding interactions in cryopreservation solutions

BackgroundIn this study we investigated hydrogen bonding interactions in hydrated and frozen solutions of different cryoprotective agents (CPAs) including dimethyl sulfoxide, glycerol, ethylene glycol, propylene glycol, and trehalose. We also investigated the effect of CPAs on ice crystal growth during storage and correlated this with storage stability of liposomes.MethodsFTIR spectroscopy was used to study hydrogen bonding interactions in CPA solutions in H₂O and D₂O, and their thermal response was analyzed using van ’t Hoff analysis. The effect of CPAs on ice crystal growth during storage was investigated by microscopy and correlated with storage stability of liposomes encapsulated with a fluorescent dye.ResultsPrincipal component analyses demonstrated that different CPAs can be recognized based on the shape of the OD band region only. Chemically similar molecules such as glycerol and ethylene glycol closely group together in a principal component score plot, whereas trehalose and DMSO appear as condensed separated clusters. The OH/OD band of CPA solutions exhibits an overall shift to higher wavenumbers with increasing temperature and changed fractions of weak and strong hydrogen interactions. CPAs diminish ice crystal formation in frozen samples during storage and minimize liposome leakage during freezing but cannot prevent leakage during frozen storage.ConclusionsCPAs can be distinguished from one another based on the hydrogen bonding network that is formed in solution. DMSO-water mixtures behave anomalous compared to other CPAs that have OH groups. CPAs modulate ice crystal formation during frozen storage but cannot prevent liposome leakage during frozen storage.     

Effects of insemination quantity on honey bee queen physiology

Mating has profound effects on the physiology and behavior of female insects, and in honey bee (Apis mellifera) queens, these changes are permanent. Queens mate with multiple males during a brief period in their early adult lives, and shortly thereafter they initiate egg-laying. Furthermore, the pheromone profiles of mated queens differ from those of virgins, and these pheromones regulate many different aspects of worker behavior and colony organization. While it is clear that mating causes dramatic changes in queens, it is unclear if mating number has more subtle effects on queen physiology or queen-worker interactions; indeed, the effect of multiple matings on female insect physiology has not been broadly addressed. Because it is not possible to control the natural mating behavior of queens, we used instrumental insemination and compared queens inseminated with semen from either a single drone (single-drone inseminated, or SDI) or 10 drones (multi-drone inseminated, or MDI). We used observation hives to monitor attraction of workers to SDI or MDI queens in colonies, and cage studies to monitor the attraction of workers to virgin, SDI, and MDI queen mandibular gland extracts (the main source of queen pheromone). The chemical profiles of the mandibular glands of virgin, SDI, and MDI queens were characterized using GC-MS. Finally, we measured brain expression levels in SDI and MDI queens of a gene associated with phototaxis in worker honey bees (Amfor). Here, we demonstrate for the first time that insemination quantity significantly affects mandibular gland chemical profiles, queen-worker interactions, and brain gene expression. Further research will be necessary to elucidate the mechanistic bases for these effects: insemination volume, sperm and seminal protein quantity, and genetic diversity of the sperm may all be important factors contributing to this profound change in honey bee queen physiology, queen behavior, and social interactions in the colony.     

A new gene, SRP16, differentially expressed in the spermathecae of honeybee queens (Apis mellifera) related with reproduction status

Honey bee queens have the ability to store sperm in spermathecae for fertilizing eggs throughout their life. To investigate mechanisms for sperm storage in Apis mellifera, we employed suppression subtractive hybridization (SSH) to find differentially expressed fragments in spermathecae between virgin queens and newly mated queens. A new gene, named SRP16, was obtained by joining the SSH products with 5′-RACE and 3′-RACE. SRP16 is predicted to encode a 41?kDa protein with 363 amino acid residues. Its expression was found in the spermathecae dominantly in honey bee queens but not in honey bee workers, with the highest expression found in spermathecae of virgin and newly mated queens. SRP16 expression was weak in other tissues of queens other than in the spermathecae and showed no obvious change with reproductive status of queens. The results suggest that SRP16 may play important roles in sperm storage and honey bee reproduction.     

Cryopreservation of flounder (Paralichthys olivaceus) sperm with a practical methodology

A simple and convenient protocol for the cryopreservation of the flounder (Paralichthys olivaceus) sperm was established for "on the spot" cryopreservation of large quantities of semen. The use of three cryoprotectants, dimethyl sulphoxide (DMSO), glycerol (Gly) and methanol was tested in the method. The percentage of motile sperm present in semen after it had been frozen and thawed in the presence of DMSO, Gly or methanol was 60.5+/-3.6, 79.17+/-4.5 and 13.25+/-4.7%, respectively. The fertilization rates of this sperm were 67.06+/-15.1, 76.20+/-10.0 and 44.93+/-22.6%, while the hatching rates of eggs fertilized with this sperm were 37.40+/-8.3, 48.18+/-25.7 and 23.35+/-10.8%, respectively. It was found that Gly and DMSO were better cryoprotectants than methanol, with Gly giving the best overall results. Under scanning electron microscopy, it could be seen that while the majority of the frozen-thawed sperm remained morphologically normal, some exhibited lost or dilated mitochondria, swollen mid-pieces, broken tails, or damaged cell membrane, which probably caused the decrease in motility and fertility of the frozen-thawed sperm.     

不同防冻剂对兔胚胎干细胞慢速冷冻保存的影响

干细胞冷冻保存是干细胞研究和临床应用中的必需技术。为提高兔胚胎干细胞在慢速冻存过程中的保存效果,比较了二甲基亚砜(DMSO)和乙二醇(ethylene glycol,EG)对兔胚胎干细胞冷冻保护效果。对冷冻复苏后的细胞进行台盼蓝染色,并研究其胚胎干细胞分子特性,结果表明DMSO比EG具有更好的冷冻保护效果。再在以10%DMSO为基础的防冻液中添加膜稳定剂海藻糖(trehalose)或谷氨酰胺(glutamine),细胞冷冻复苏后结果显示,谷氨酰胺对兔胚胎干细胞有明显的冷冻保护作用,使细胞存活率从71%提高到83.7%。当谷氨酰胺浓度为0、5、10、20、40mmol/L分别加入防冻液中后,20mmol/L的谷氨酰胺具有最佳的冷冻保护效果。以上结果得出兔胚胎干细胞慢速冷冻的防冻液改进配方为:在胚胎干细胞培养液中添加10%DMSO 20mmol/L谷氨酰胺。     

Cryopreservation of red snapper (Lutjanus argentimaculatus) sperm: Effect of cryoprotectants and cooling rates on sperm motility, sperm viability, and fertilization capacity

Sperm cryopreservation of red snapper (Lutjanus argentimaculatus) is essentially unexplored, although many species of the Lutjanidae family are considered to be high-value commercial species. The objective of this study was to develop a species-specific cryopreservation protocol for red snapper (L. argentimaculatus) sperm by optimizing cryoprotectants and cooling rates in the cryopreservation procedure. Ten cryoprotectants at four concentrations and two freezing protocols were examined in two separate experiments. In the first experiment, toxicity studies of dimethyl sulfoxide (DMSO), glycerol, propylene glycol (PG), ethylene glycol (EG), formamide, methanol, ethanol, sucrose, trehalose, and dimethylacetamide (DMA) on sperm motility were performed. Semen diluted 1:1 in Ringer solution were exposed to cryoprotectants at four final concentrations of 5%, 10%, 15%, or 20% for periods of 10, 20, 30, 40, 50, 60, 90, and 120 min at room temperature (25 °C). The cryoprotectants and concentrations that showed the least toxic effect on sperm motility were selected for cryopreservation trials. In the second experiment, selected cryoprotectants were then assessed for freezing capacity of sperm as follows: DMSO 5% and 10%, PG 5% and 10%, EG 5% and 10%, ethanol 5%, and methanol 5%. Semen was diluted 1:1 in Ringer solution and equilibrated with selected cryoprotectants for 10 min at room temperature. Sperm were frozen in a controlled-rate programmable freezer at four cooling rates of 3, 5, 10, and 12 °C/min from an initial temperature of 25 °C to final temperatures of −40 or −80 °C before plunging into liquid nitrogen. Sperm equilibrated in 10% DMSO and cooled at a rate of 10 °C/min to a final temperature of −80 °C had the highest motility (91.1 ± 2.2%) and viability (92.7 ± 2.3%) after thawing. The fertilization rate of frozen-thawed sperm (72.4 ± 2.4%) was not different (P > 0.05) from that of fresh sperm (75.5 ± 2.4%). This study apparently represents the first reported attempt for cryopreservation of L. argentimaculatus sperm.