How does metabolic rate in plant shoot tips change after cryopreservation?

Cryopreservation allows the long-term storage of plant germplasm, but can cause damage to plant tissues, which must be repaired for survival to occur. This repair process is fuelled by the metabolic function of mitochondria; however, little is known about how metabolic function is affected by the cryopreservation process in plants. We compared metabolic rates of shoot tips of two Australian native species, Androcalva perlaria and Anigozanthos viridis. Overall, cryopreservation resulted in a significant reduction in the metabolic rates of shoot tips from both species, even in tissues that regenerated after cryopreservation. Metabolic rate did not increase within 48 h after of thawing, even in shoot tips which later regenerated. When examined in isolation, both pre-treatment on desiccation medium and exposure to cryoprotective agents significantly decreased metabolic rates in regenerating shoot tips of A. viridis, however both caused a significant increase in shoot tips of A. perlaria, suggesting diversity of response to cryopreservation stresses across species. Measurements of shoot tip metabolic rate during cryopreservation will inform investigations into cellular energy production and provide critical information on the state of shoot health after exposure to different cryoprotective treatments, which could play a useful role in guiding protocol optimisation for threatened species to maximise post-cryopreservation regeneration.

Review: The case for studying mitochondrial function during plant cryopreservation

Cryopreservation has several advantages over other ex situ conservation methods, and indeed is the only viable storage method for the long term conservation of most plant species. However, despite many advances in this field, it is increasingly clear that some species are ill-equipped to overcome the intense stress imposed by the cryopreservation process, making protocol development incredibly difficult using traditional trial and error methods. Cryobiotechnology approaches have been recently recognised as a strategic way forward, utilising intimate understanding of biological systems to inform development of more effective cryopreservation protocols. Mitochondrial function is a model candidate for a cryobiotechnological approach, as it underpins not only energy provision, but also several other key determinants of germplasm outcome, including stress response, reduction-oxidation status, and programmed cell death. Extensive research in animal cell and tissue cryopreservation has established a clear link between mitochondrial health and cryopreservation survival, but also indicates that mitochondria are routinely subject to damage from multiple aspects of the cryopreservation process. Evidence is already emerging that mitochondrial dysfunction may also occur in plant cryopreservation, and this research can be greatly expanded by using considered applications of innovative technologies. A range of mitochondria-targeted prophylactic and therapeutic interventions already exist with potential to improve cryopreservation outcomes through mitochondrial function.

Characteristics and Cryopreservation of Semen of Sex-Reversed Females of Salmonid Fish

Sex reversal has been used as a breeding strategy by salmonid fish to produce genetically and phenotypically single sex populations. Production of all-female fish has great importance for the creation of monosex female triploids of salmonid fish, which are valued for their sterility, lack of female maturation, and larger commercial size. Among salmonids, the majority of rainbow trout (Oncorhynchus mykiss) production is based on all-female production with a high proportion of all-female triploid production in Europe. The main aim of this review is to present the recent knowledge regarding sex-reversed females (SRFs) of salmonid fish. We discuss the methods of sex reversal as well as their effects on the morphology and histology of the reproductive tract. We focus on the characteristics of SRF semen as well as the factors determining semen quality. The lower quality of SRF sperm compared to that of normal males has resulted in the need for the artificial maturation of semen. Most importantly, methods of semen storage-both short-term and long-term (cryopreservation)-that can improve hatchery operations are presented with the special emphasis on recent progress in development of efficient cryopreservation procedures and use of cryopreserved semen in hatchery practice. Moreover, we also address the emerging knowledge concerning the proteomic investigations of salmonid sperm, focusing primarily on the proteomic comparison of normal male and SRF testicular semen and presenting changes in SRF rainbow trout sperm proteome after in vitro incubation in artificial seminal plasma.

Seminal characterization of the Amazonian fire-eye tetra Moenkhausia oligolepis (Günther, 1864)

The seminal characteristics of Moenkhausia oligolepis are described. Three males were induced with a single dose of carp pituitary. Semen was collected 6 h after induction, and diluted in dibasic sodium phosphate extender solution. For motility analysis, 1 µl of diluted semen was added to 10 µl of distilled water to achieve gamete activation. The average duration of total motility was 76.67 s; while the average sperm motility rate at intervals of 15 s was 95.3, 85.3, 59.6, 31.7, 13.0, 4.6 and 1.2%. To determine sperm concentration in samples, 0.5 μl of semen was diluted with 500 μl of glutaraldehyde. An aliquot of 10 μl of this dilution was utilized for cell counting. An average count of 4.97 × 109 ± 3.46 sperm/ml was obtained. Morphological analyses were performed using eosin-nigrosine dye; 20.33% of the sperm were observed to be dead. Live sperm, comprising the other 79.67%, had an average length of approximately 30 µm, with a head diameter of 4.488 ± 0.7 µm; and a flagella plus mid-piece length of 26.071 ± 12.4 µm. Of those sperm, 69% had a normal morphology, while 31% had primary and secondary abnormalities. The observed abnormality rate did not have a detrimental effect on artificial fertilization potential for the species. The description of the seminal characteristics of a species is one of the most important sets of information required for artificial reproduction of fish in captivity. It also contributes significantly to the total biological knowledge of the studied species.

Cryopreservation of sperm from farmed Pacific abalone, Haliotis discus hannai

This study aimed to improve a sperm cryopreservation protocol for farmed Pacific abalone, Haliotis discus hannai. Dimethyl sulfoxide (Me₂SO), glycerol, ethylene glycol (EG), propylene glycol (PG), and methanol were chosen as cryoprotectants (CPAs). Four different equilibration time (5, 10, 30, and 60 min), and two types of equilibration temperature (4 °C and 20 °C) were selected at the present experiment. Most equilibration temperatures with each CPA showed significant differences among different equilibration time. Post-thaw sperm motility of five CPAs showed no significant difference at two equilibration temperature. Based on these results, 8% Me₂SO, 8% EG, 6% PG, 2% glycerol, and 2% methanol were chosen to determine optimal conditions for sperm cryopreservation of H. discus hannai. The highest post-thaw sperm motility (8% Me₂SO: 50.6%, 8% EG: 45.6%, 2% glycerol: 44.5%, 6% PG: 28.7%, 2% methanol: 25.4%) was achieved after exposing sperm to liquid nitrogen (LN₂) vapor for 10 min at 5 cm above the LN₂ surface and then submerging them in LN₂ for at least 2 h followed by thawing at 60 °C with seawater and recovering them at 20 °C with seawater. In this study, 8% Me₂SO and 2% glycerol were chosen to check post-thaw sperm quality to estimate percentages of plasma membrane integrity (PMI), mitochondrial potential analysis (MP), and acrosome integrity (AI) using fluorescent techniques. No significant difference in PMI, MP, and AI was found between sperm cryopreserved with 8% Me₂SO and those cryopreserved with 2% glycerol. The current study has demonstrated that 8% Me₂SO was optimal for sperm cryopreservation for H. discus hannai with 5 min of equilibration time, 5 cm of rack height and 60 °C of thawing temperature. The present research provides more effective cryopreservation methods for H. discus hannai sperm than previous studies.

Effects of cryopreservation on cAMP-dependent protein kinase and AMP-activated protein kinase in Atlantic salmon (Salmo salar) spermatozoa: Relation with post-thaw motility

Sperm motility in fish with external fertilization is critical for reproductive efficiency in aquaculture, especially in salmonids. Gamete preservation techniques, such as cryopreservation, however, reduce sperm motility and fertilizing capacity. Very few studies have addressed cryodamage from energetic and cell signalling approaches. In this study, cAMP-dependent protein kinase (PKA) and AMP-activated kinase (AMPK) activities were quantified in fresh and cryopreserved spermatozoa of Atlantic salmon (Salmo salar); and the relation with motility was analysed. Results indicate there was a decrease in membrane integrity and motility in post-thawed spermatozoa compared to fresh samples, however, there was about 30% of cells with intact plasma membrane but incapable of motility. The PKA and AMPK activities were less after cryopreservation, indicating that loss of motility may be related to alteration of these key enzymes. Furthermore, PKA and AMPK activities were positively correlated with each other and with motility; and inhibition decreased motility, indicating there is a functional relationship between PKA and AMPK. The PKA inhibition also decreased AMPK activity, but results from protein-protein docking analyses indicated AMPK activation directly by PKA is unlikely, thus an indirect mechanism may exist. There have been no previous reports of these kinase actions in fish spermatozoa, making these findings worthy of assessment when there are future studies being planned, and may serve as base knowledge for optimization of cryopreservation procedures and development of biotechnologies to improve reproduction efficiency in the aquaculture industry.

Sperm quality in fish: Determinants and affecting factors

Fish sperm quality assessment is helpful for optimizing production and for monitoring the environmental state. Sperm can be monitored relatively easy and, to date, various analyses have been applied and proven to be helpful in this task. Among them, sperm motility parameters such as sperm speed are one of the main performance traits during assisted fish reproduction. Apart from motility the sperm concentration, volume, and seminal plasma pH and osmolality are also frequently evaluated and are the main sperm quality indicators measured in fish sperm. However, other parameters also determine sperm fertilization potential. Recent knowledge reveals several additional parameters of high importance for sperm function. Among them are DNA integration, membrane stability, mitochondria status and enzymatic activity. Measuring all these parameters in fish sperm provides complex knowledge regarding male fertility and helps to improve broodstock maintenance protocols as well as gamete handling and fertilization processes. This review focuses on the presentation of the sperm quality measures for freshwater and marine species of the fish and provides information regarding recent methods of sperm quality evaluation.

Effects of cooling rates on the quality of Prochilodus lineatus (Valenciennes, 1836) sperm

This study aims to investigate the effect of different cooling rates on the semen cryopreservation of curimba (Prochilodus lineatus). Nineteen ejaculates were obtained from adults males and cryopreserved at 15°C/min (CR15), 30°C/min (CR30) (controlled temperature inside and outside straw, speed was stable during freezing) and direct freezing in liquid nitrogen vapour (~35.6°C/min) (CRNV). The straws were thawed and seminal parameters evaluated. DNA fragmentation through the comet assay was assessed. A fresh sperm sample was not frozen and used for analyses. Data were submitted to an analysis of variance (ANOVA), and means were compared by Scott-Knott test (p < 0.05) using the R Software. Mean motility percentage was 100%, and motility duration was 39.5 ± 5.7 s for the fresh sperm (subjective analysis); 58.9 ± 8.0% and 24.5 ± 5.7 s for CR15; 64.8 ± 4.8% and 26.5 ± 7.1 s for CR30; and 50.1 ± 16% and 25.7 ± 4.7 s for CRNV, respectively. Motility percentages were higher and equal between CR15 and CR30 compared to CRNV (p < 0.05). Some sperm motion kinetics, namely average path velocity (VAP) and straight line velocity (VAS), were higher for CR30 (p < 0.05), while curvilinear velocity (VCL) and velocity progression (PRO) were lower for CRNV (p < 0.05). Straightness (STR) and wobble (WOB) were the same among treatments (p > 0.05). Sperm morphology results indicated higher means for total morphological sperm alterations in CRNV. All cooling rates caused sperm DNA fragmentation, although CR30 provided a less harmful effect. This is the first report for cryopreserved P. lineatus sperm preserved under different controlled cooling rates. The cooling rate of 30°C/min is indicated for the cryopreservation of this fish sperm as it led to the lowest detrimental spermatozoa effects.

Protective role of antifreeze proteins on sterlet (Acipenser ruthenus) sperm during cryopreservation

The loss of sperm quality in sterlet (Acipenser ruthenus) due to freeze-thaw process in cryopreservation was investigated in the present study. Two antifreeze proteins (AFPI or AFPIII) were used at different concentrations of 0.1, 1, 10, and 100 μg/mL. We compared motility, curvilinear velocity, and plasma membrane integrity of fresh, cryopreserved sperm, and sperm cryopreserved in the presence of antifreeze proteins. Fresh sperm (control) had 85 ± 4% motility and 160 ± 2 μm/s curvilinear velocity, respectively. After cryopreservation, the motility of frozen-thawed sperm without addition of antifreeze proteins significantly decreased (44 ± 9%), compared to the control. The highest motility of frozen-thawed sperm was obtained in cryopreserved sperm with addition of 1 μg/mL of AFPIII (58 ± 14%). No significant differences were observed in curvilinear velocity between fresh sperm and cryopreserved sperm with/without addition of AFPI or AFPIII. The flow cytometry analysis revealed that fresh sperm contained 94.5 ± 6% live cells, while the cryopreserved sperm only contained 26.6 ± 14% live cells. Supplementation of antifreeze proteins has significantly improved the percentage of live cells in frozen-thawed sperm, except 0.1 μg/ml of AFPI group. No significant difference in percentage of live cells was detected in the sperm cryopreserved with 10 μg/mL of AFPI or AFPIII, compared to fresh sperm. Thus, addition of antifreeze proteins to cryopreservation medium could be considered to improve the post-thawed sperm quality of sterlet.

A Strategy for Sperm Cryopreservation of Atlantic Salmon, Salmo salar, for Remote Commercial-scale High-throughput Processing

Sperm cryopreservation is an essential tool for long-term storage of genetic resources for aquaculture fishes. The goal of this study was to develop an efficient and streamlined protocol for high-throughput processing for sperm cryopreservation in Atlantic salmon, Salmo salar. The objectives were to evaluate: 1) osmolality of blood serum for determining extender osmolality; 2) effects of extenders for fresh sperm dilution and refrigerated storage; 3) effects of methanol and dimethyl sulfoxide (DMSO) on fresh sperm motility, and 4) motility and fertility after thawing. In this study, sperm samples were collected at a hatchery site in Canada, and shipped to a freezing site located 2200 miles (3550 km) away in the United States. Evaluation of three extenders indicated that Mounib solution was suitable for diluting dry sperm for sample processing. Ten percent of methanol or DMSO was less toxic to sperm cells than was 15% within 30 min. Further testing with methanol at 5, 10, and 15%, and sperm solution:extender dilutions (v:v) of 1:1, 1:3, 1:19 (at concentrations of ~5×10⁷; 3×10⁸, and 1×10⁹ cells/mL) indicated that methanol at 5% and 10% showed less toxicity to fresh sperm within 1 hr at sperm: extender dilutions of 1:1 and 1:3. Post-thaw motility of sperm cryopreserved with 10% methanol was significantly higher than that with 10% DMSO, and fertility reflected those results (0-1% in DMSO vs. 38-55% in methanol). Further evaluation of sperm cryopreservation with 10 and 15% methanol at sperm dilution ratios of 1:1, 1:3, 1:19 indicated post-thaw motility in 10% methanol was significantly higher than that in 15% methanol, and post-thaw fertility in 10% methanol at 1:1 and 1:3 dilution ratios had fertilization rates similar to that of fresh sperm controls. Sperm samples from 12 males cryopreserved with 10% methanol showed male-to-male variation in post-thaw motility (0-36%). Overall, a simplified standard protocol was established for cryopreservation of shipped sperm of Atlantic salmon using extender without egg yolk and yielded satisfactory post-thaw motility and fertilization rates. This procedure can be readily adopted by aquaculture facilities to take advantage of high-throughput cryopreservation capabilities at remote service centers. Most importantly, this approach lays the groundwork for an alternative commercial model for commercial-scale production, quality control and development of industrial standards. Control of male variability and sperm quality remain important considerations for future work.

Effect of the age of broodstock males on sperm function during cold storage in the trout (Oncorhynchus mykiss)

The knowledge of sperm quality in the broodstock males of different ages is a prerequisite to identify the reproductive ability of cultivated fish for the hatchery management. Thus, in this work, we analysed sperm function of the semen stored of broodstock males of rainbow trout (Oncorhychus mykiss) in different reproductive ages (2, 3 and 4 years old). Sperm samples of each reproductive age were stored in Storfish^® during 10 days at 4°C, and then, motility, viability, mitochondrial function (MMP), superoxide anion (O2-) level and DNA fragmentation (DNA_frag ) were assessed. The results demonstrated that sperm function parameters were affected significantly by the age of the males and the time of storage. Motility, viability and MMP significantly decreased, and DNA_frag and O2- level increased with the age increment and the time of storage. In conclusion, sperm quality of 2 and 3 years old were superior to those of 4 years old, based on higher quality of various sperm functions such as motility, viability, MMP, DNA integrity and level O2- during short-term storage. This information must be considered for optimum utilization of broodstock males in aquaculture.

Crioconservación de semen de dorada Brycon moorei con dimetilsulfóxido

El objetivo fue evaluar la calidad del semen descongelado de dorada Brycon moorei crioconservado con dimetilsulfóxido (DMSO) a tres porcentajes de inclusión. El semen se obtuvo de nueve machos mantenidos en cautiverio en la Estación Piscícola Repelón (Atlántico, Col), inducidos con extracto pituitario de carpa (4,5 mg/kg). El semen fue diluido en proporción 1:3 con un diluyente compuesto de DMSO a tres porcentajes 5%, 10% y 15%; glucosa al 6% y yema de huevo al 12%; empacado en macrotubos de 2,5 ml, congelados en vapores de nitrógeno y después de tres meses descongelados a 35°C durante 90 s. Semen fresco fue considerando como tratamiento control. En semen descongelado se evaluó movilidad total, tipos de movilidades, progresividad, velocidades y concentración espermática con el programa Sperm Class Analyzer SCA®; adicionalmente en semen fresco se determinó volumen, color y tiempo de activación. El semen fresco presentó movilidad mayor a 80% y tiempo de activación entre 28,5 y 41 s; mientras que, la concentración espermática osciló entre 10188,1 y 14590,2 millones/ml. La movilidad total del semen descongelado fue mayor cuando DMSO se incluyó a 5% (40,1±5,0%) o 10% (43,3±8,7%) (p>0,05); pero a 15% registró la menor movilidad (30,6±7,9%) y el mayor porcentaje de espermatozoides inmóviles (69.4±7.9%) (p<0,05); lo cual sugiere que inclusiones de DMSO por encima de 10% ocasionan mayores daños al espermatozoide de dorada. Los resultados permiten concluir que DMSO debe ser incluido entre 5 y 10%, junto con glucosa al 6% y yema de huevo al 12% para crioconservar semen de dorada.

Amine reactive dyes: an alternative to estimate membrane integrity in fish sperm cells

Fluorescent dyes that binds irreversibly to cellular amines, come in several available emission spectra, and do not poses health concerns were used to evaluate membrane integrity in fish sperm cells. The objectives of the present study were to determine: (1) a working dye concentration for fish sperm samples, and (2) if the traditional propidium iodide/SYBR-14 staining combination was comparable with the amine reactive dye (ARD) methods at identifying cell populations with intact and compromised membranes after sperm activation, refrigerated storage, and exposure to cryoprotectant and surfactant. Zebrafish (Danio rerio) sperm were obtained by stripping, and pooled samples (in triplicate) were used in all tests. Six dilutions of the amine dye (ranging from 0.625 to 0.02 μL/mL) were evaluated, and compared with the traditional staining protocol. A concentration of 0.5 μL/mL ARD was selected to be used in subsequent assays. Sperm suspensions were activated with deionized water to simulate urine contamination. After 10 sec, osmolality was increased to stop activation, and the procedure was repeated in 10-sec intervals until the sperm remained activated for 120 consecutive sec; membrane integrity was analyzed at each time interval. For the storage assay, sperm suspensions were prepared in Hanks' balanced salt solution at 302 mOsm/kg osmolality (HBSS302), HBSS354 and HBSS402, and evaluated every 2 hr for 8 hr, and every 24 hr for 72 hr. Cryoprotectant toxicity was tested by diluting sperm suspensions in HBSS340 with methanol at 5, 10 and 15% final concentrations. Surfactant toxicity was tested by diluting sperm suspensions in HBSS354 with Triton X-100 at 0.2, 0.15 and 0.1 mM final concentrations. In each toxicity assay, membrane integrity was tested every 20 min for 80 min. The number of membrane-intact cells significantly decreased across time in all treatments (p < 0.05). Significant differences between staining protocols were observed after activation and after exposure to methanol at 10 and 15%, and to Triton X-100 (p < 0.05). The average difference, however, was minor (between 1 and 6% in average) in relation to the typical values used for decision making based on this assay. Results showed that this method has the potential to contribute greatly to the standardization of cryopreservation in aquatic species.

Determination of sperm concentration using flow cytometry with simultaneous analysis of sperm plasma membrane integrity in zebrafish Danio rerio

Control of sperm concentration is required to ensure consistent and reproducible results for cryopreservation and in vitro fertilization protocols. Determination of sperm concentration is traditionally performed with a counting chamber (e.g., hemocytometer), or more recently with a spectrophotometer. For small-sized biomedical model fishes, the availability of sperm sample is limited to microliters, so it is desirable to develop fast and accurate approaches for concentration determination that also minimize sample use. In this study, a new approach was developed for sperm concentration determination using a flow cytometer (Accuri C6, BD Biosciences, San Jose, CA) with simultaneous measurement of sperm membrane integrity after fluorescent staining with SYBR(®) -14 and propidium iodide (PI) in sperm from Zebrafish Danio rerio. The goal was to develop a protocol for simultaneous determination of sperm quality and quantity by flow cytometry. The objectives were to (1) determine the effects of sample volume (250 and 500 µl) and analysis volume (10 and 50 µl) on the accuracy of particle counting using standard volumetric validation beads; (2) identify the effective range of sperm concentrations that flow cytometry can measure; (3) test the precision and reproducibility of the sperm concentration measurements; and (4) verify the flow cytometry approach by comparison with measurement with a hemocytometer and a microspectrophotometer. Sample volumes of 250 and 500 µl and analysis volumes of 10 and 50 µl did not affect bead count with the factory-set flow rates of "medium" or "fast," and the precision and accuracy was retained across a concentration range of 1 × 10(3) -1 × 10(7) cells/ml. The approach developed in this study was comparable to traditional methodologies such as hemocytometer or microspectrophotometer. This study provides an efficient, accurate, and rapid method for determination of sperm concentration using flow cytometry while providing simultaneous assessment of sperm membrane integrity. Such approaches can reduce the time needed for quantity assessment and maximize the use of valuable sperm samples. © 2015 International Society for Advancement of Cytometry.

Cryopreservation-induced alterations in protein composition of rainbow trout semen

The aim of this study was to detect cryopreservation-induced alterations in the protein composition of rainbow trout semen using two independent methods 1DE SDS-PAGE prefractionation combined with LC-MS/MS and 2D difference gel electrophoresis followed by MALDI-TOF/TOF identification. Here, we show the first comprehensive dataset of changes in rainbow trout semen proteome after cryopreservation, with a total of 73 identified proteins released from sperm to extracellular fluid, including mitochondrial, cytoskeletal, nuclear, and cytosolic proteins. Our study provides new information about proteins released from sperm, their relation to sperm structure and function, and changes of metabolism of sperm cells as a result of cryopreservation. The identified proteins represent potential markers of cryoinjures of sperm structures and markers of the disturbances of particular sperm metabolic pathways. Further studies will allow to decipher the precise function of the proteins altered during rainbow trout cryopreservation and are useful for the development of extensive diagnostic tests of sperm cryoinjures and for the successful improvement of sperm cryopreservation of this economically important species.

Effect of the addition of six antioxidants on sperm motility, membrane integrity and mitochondrial function in red seabream (Pagrus major) sperm cryopreservation

The present study was to evaluate the effects of six antioxidants on frozen-thawed sperm motility, viability, membrane integrity and mitochondrial function in red seabream (Pagrus major) by computer-assisted sperm analysis system and flow cytometry, respectively. All the parameters tested in this study were determined using one-way ANOVA and identified using the SNK test (P < 0.05). The results demonstrated that on the first day, the highest motility and longevity occurred in 100 mM trehalose (78.34 ± 3.41%, 29 ± 4.00 days) and 50 mM taurine (77.46 ± 1.54%, 29.33 ± 4.04 days), followed by 25 mM vitamin C (79.03 ± 5.37 %, 17 ± 1.00 days), 25 mM vitamin E (69.64 ± 1.64%, 27.67 ± 1.53 days) and 25 mM vitamin A (78.89 ± 2.81%, 9.33 ± 1.53 days), which were all higher than frozen-thawed sperm without antioxidant (control) (66.80 ± 5.55, 5.67 ± 1.15 days). Especially, the percentages of class A sperm with the addition of 100 mM trehalose (40.39 ± 5.20%) and 50 mM taurine (37.78 ± 3.22%) were significantly improved compared to the control (19.63 ± 5.44%). The viability of all groups on the third and sixth day showed a similar trend. Moreover, during the 4 °C storage process, the decrease of frozen-thawed sperm motility was closely associated with the decrease in membrane integrity and mitochondrial function. In conclusion, the present study indicated that antioxidant (100 mM trehalose and 50 mM taurine) provided the most pronounced protective effect in improving frozen-thawed quality of red seabream sperm. The addition of antioxidant may be capable of scavenging the ROS generated during the cryopreservation process and 4 °C storage.

Investigating sperm cryopreservation in a model tunicate, Ciona intestinalis sp. A

In cryopreservation procedures, the capacity to protect the cells from freezing and thawing processes is sensitive to the choice of the cryoprotective agent (CPA) and to its optimal concentration. The advancement of research on Tunicate model species has raised interest in liquid nitrogen cryopreservation for the storage and distribution of genetic resources. Ciona intestinalis (Linnè, 1767) consists of a complex of cryptic taxa that are central to several areas of investigation, from comparative genomics to invasive biology. Here we investigated how five CPAs, three chilling rates and two freezing rates influence semen cryopreservation in C. intestinalis sp. A. By using larval morphology and motility as endpoints, we estimated that long term semen storage requires 10% dimethyl sulfoxide as a protective agent, -1°C/min chilling rate (18°C to 5°C) and -13°C/min freezing rate (5°C to -80°C), followed by immersion in liquid nitrogen.

Evaluation of sperm mitochondrial function using rh123/PI dual fluorescent staining in asthenospermia and oligoasthenozoospermia

Objective

The recent advent of flow cytometry (FCM), coupled with fluorescent dyes, has been successfully applied to assess mitochondrial function. The aim of this study was to investigate the feasibility and clinical significance of detecting sperm mitochondrial function and to evaluate sperm mitochondrial function by using Rhodamine 123/propidium (Rh123/PI) dual fluorescent staining and FCM in asthenospermia and oligoasthenozoospermia.

Methods

Twenty-five fertile men (with normal sperm parameters) and 230 infertile patients were examined. Fifty-five patients of the above 230 patients were selected for idiopathic infertility samples and were divided into two groups: asthenospermia (n = 30) and oligoasthenozoospermia (n = 25). Rh123/PI dual fluorescent staining and FCM were carried out to examine sperm mitochondrial function.

Results

Significant differences were found between the normal and abnormal semen samples (P < 0.05) when Rh123⁺/PI⁻, Rh123⁻/PI⁺ and Rh123⁻/PI⁻ sperm were examined by FCM, but there was no significant difference between the asthenospermia (P = 0.469) and oligoasthenozoospermia group (P = 0.950) when Rh123⁺/PI⁻ and Rh123⁻/PI⁺ sperm were then examined; however, a significant difference was found between the 2 groups (P = 0.003) when Rh123⁻/PI⁻ sperm were examined. There was no correlation between Rh123⁻/PI⁻ sperm and semen parameters in the normal group, but there was a significant negative correlation between the sperm concentration and Rh123⁻/PI⁻ sperm in asthenospermia and oligoasthenozoospermia patients (r = -0.509, -0.660; P = 0.018, 0.038).

Conclusion

Rh123/PI dual fluorescent staining and FCM can provide reliable information to assess the quality of sperm and reveal differences in mitochondrial membrane potential in asthenospermia and oligoasthenozoospermia.

Sources of variation in flow cytometric analysis of aquatic species sperm: The effect of cryoprotectants on flow cytometry scatter plots and subsequent population gating

The use of fluorescent staining and flow cytometry to assess sperm quality in aquatic species has increased over the past decade, but comparisons among studies are difficult or impossible due to variation in application, analysis, and reporting of protocols and data.The goal of the present study was to determine the effect of exposure to two cryoprotectants commonly used for cryopreservation of sperm from aquatic species on the accuracy of flow cytometric assessment of sperm quality.Membrane integrity of zebrafish (Danio rerio) sperm exposed to 10% and 20%methanol and dimethyl sulfoxide (DMSO)in 300 mOsm kg(-1) Hanks' balanced salt solution (HBSS) or calcium-free HBSSwas determined using SYBR 14/propidium iodide staining. Both cryoprotectants significantly affected forward-scatter and side-scatter characteristics of sperm samples, resulting in significant changes in the number of total and gated events, and in the number and percentage of intact cells. These results indicate that it cannot be assumed that the approach to flow cytometric analysis of fresh sperm will be applicable to cryoprotectant-treated or cryopreserved sperm. In total, we document examples of five potentially interacting factors that produce errors of 5 to 50% each, resulting in underestimates and overestimates of total and intact sperm (actual numbers and percentages) in the presence of the two most commonly used cryoprotectants at the concentrations used most often for cryopreservation of sperm from aquatic species. This study provides methods to reduce or eliminate these errors and recommendations necessary for standardization and reporting.

Anormalidades espermáticas de Piaractus mesopotamicus após descongelamento utilizando diferentes metodologias

Avaliou-se a influência de crioprotetores, temperatura e tempo de descongelamento sobre as anormalidades espermáticas de pacu (Piaractus mesopotamicus). Amostras de sêmen de quatro pacus foram coletadas e diluídas em duas soluções crioprotetoras, dimetilsulfóxido (DMSO) 10% e metanol 10%. Após o descongelamento, foram avaliadas anormalidades primárias e secundárias. Não foi verificada interação (P>0,05) nas anormalidades secundárias, nas anormalidades totais e nos espermatozoides normais nos diferentes tratamentos empregados. Nas anormalidades primárias, foi verificada interação temperatura versus tempo de descongelamento, em que a maior temperatura associada ao menor tempo, 60°C por 8s, ou a menor temperatura associada ao maior tempo de descongelamento, 40°C por 12s, proporcionaram menor (P<0,05) porcentagem de espermatozoides com anormalidades primárias. No processo de criopreservação do sêmen de pacu utilizando os crioprotetores DMSO ou o metanol, recomenda-se que o descongelamento seja realizado a 40°C por 12 segundos ou a 60°C por oito segundos.

Effect of hormone implantation on cryopreservation of Atlantic halibut (Hippoglossus hippoglossus L.) sperm

Hormone implantation is widely applied in halibut (Hippoglossus hippoglossus L.) aquaculture to extend the sperm production season of broodstock males. The ability to combine this technique with cryopreservation would increase sperm availability, thereby improving reproduction success and facilitating gene management. In this paper, the cryopreservation ability of sperm from hormone-treated males was examined at three times post-implantation and compared with that of sperm from males that were not hormone-treated. All sperm samples were cryopreserved using the same method. The effectiveness of these techniques was assessed by examining the fertilization rate and motility of thawed sperm. The spermotocrit and concentration of fresh sperm samples were measured to reveal the effect of hormone implantation on sperm characteristics. The reported results indicate that hormone implantation did not affect cryopreservation efficiency. The fertilization rate resulting from thawed sperm of hormone-treated males showed no significant difference from that of untreated males or from fresh sperm. A significant positive relationship was demonstrated between the spermatocrit and concentration of sperm; and a significant decrease of spermatocrit was found in sperm collected from hormone-treated males 14days post-implantation. No significant linear relationship between spermotocrit and fertilization rate of thawed sperm was shown.

Effects of cooling and freezing on the motility of Ostrea edulis (L., 1758) spermatozoa after thawing

The aim of this work was to evaluate the effects of temperature, cryoprotectant agents and freezing curves on sperm motility of Ostrea edulis. All phases of cryopreservation were studied (evaluation of semen motility pattern, choice of cryoprotectants and freezing rates) to restore after thawing the motility characteristics distinctive of fresh semen. To assess the temperature effects on sperm motility, semen was activated using four different temperatures (25, 18, 10 and 3°C). Sperm aliquots were maintained inactive at these temperatures for 1 and 3h, then activated with FSW at same temperature of conservation. Sperm was activated and incubated to 3°C with dimethylsulfoxide (Me(2)SO), ethylene glycol (EG), 1-2 propylene glycol (PG) (5%, 7%, 10% and 15% final concentrations), glycerol (GlOH; 5%, 10% and 15% final concentrations) and methanol (MetOH; 4% and 10% final concentrations) for 10, 20 and 30min. A first evaluation of freezing rates was made by testing four freezing curves: -1, -3, -6 and -10°C/min. Then, an optimization was made by testing four freezing curves: -2.5, -3.0, -3.5 and -4°C/min. The selected temperature for short term conservation has been 3°C, because only this temperature has allowed good sperm motility conservation after 3h of dry-storage; this is a time sufficient to conduct cryopreservation procedures. The sperm showed a particular sensitivity to GlOH and PG to all tested concentrations and to 15% Me(2)SO. EG and MetOH to all concentrations and Me(2)SO to concentrations lower than 15% have not shown significant toxic effects. The freezing rate -3°C/min using 15% EG has shown an highest percentage of RVF (rapid, vigorous and forward) spermatozoa (class 3, about 75% of fresh semen) and an highest sperm motility duration.

Flow-cytometric analyses of viability biomarkers in pesticide-exposed sperm of three aquatic invertebrates

Toxicity studies on sperm often use fertilization success as the end point. This type of assay can be affected by sperm density, egg quality, and sperm-egg compatibility. Testing sperm viability biomarkers with flow cytometry is a fast, high-throughput technique for seminal analysis. In this study, we detected sperm viability biomarkers with several fluorescent reporter dyes using flow cytometry in three aquatic invertebrates (Crassostrea virginica, Dreissena polymorpha, and Lytechinus variegatus) after exposure to a pesticide and herbicide. The pesticide, Bayluscide, appeared to affect mitochondrial membrane potential in the sperm of all three species, as measured with MitoTracker Red CMXRos. A decrease in the percentage of sperm stained with SYBR-14 (indicating uncompromised plasma membrane) was observed in C. virginica and D. polymorpha sperm exposed to Bayluscide, but propidium iodide staining (indicating compromised plasma membranes) appeared to be inhibited by Bayluscide. Acrosome-reacted sperm, as measured by FITC-PNA, decreased after Bayluscide exposure in C. virginica and D. polymorpha sperm. The herbicide, Roundup Ready To-Use-Plus, did not affect the overall percentages of sperm stained with MitoTracker but did cause an increase in MitoTracker fluorescence intensity at 16 mg/L in D. polymorpha. Roundup also caused significant decreases in SYBR-14 staining, significant increases in propidium iodide staining, and significant increases in FITC-PNA staining in D. polymorpha sperm. By not having to rely on egg availability and optimal sperm density, sperm toxicity can be more accurately assessed with flow cytometry as being directly correlated to sperm viability rather than the possibility of altered toxicity results due to sperm-to-egg compatibility.

Effect of Sperm Cryopreservation on the European Eel Sperm Viability and Spermatozoa Morphology

The main objective of the present work was to study the effect of cryopreservation of European eel sperm both on the sperm viability and the spermatozoa head morphology. Spermatozoa morphology was evaluated with computer-assisted morphology analysis after collection in fresh samples, after adding the freezing medium containing dimethyl sulfoxide as cryoprotectant and, finally, after the cryopreservation process and thawing. Cell viability was assessed, in both fresh and thawed samples, by Hoechst 33258 staining. Computer-assisted sperm analysis (CASA) was used to determine the percentage of motile cells and to measure motility parameters in sperm samples. A significant decrease of head perimeter (12.56%) and area (17.90%) was detected from spermatozoa in fresh to thawed samples, indicating that cells do not recover the original size after the cryopreservation process. CASA was used to measure the percentage of motile cells (51.9%) and spermatozoa motility parameters such as curvilinear, straight line and angular path velocities, as well as beating cross frequency. This technique was employed in the fresh sperm samples but proteins present at the freezing medium (L-alpha-phosphatidylcholine) made impossible to use this last technique in thawed samples. When sperm viability was assessed by Hoechst staining, a significant decrease of approximately 15% (73.10 vs 58.26%) of alive spermatozoa was registered from fresh to thawed samples. The percentage of motile cells measured by CASA in fresh samples (51.9%) was lower than the percentage of alive cells determined by Hoechst stainning, suggesting the existence of different batches of spermatozoa in different stages of development, even during the eight to tenth weeks of treatment, when the highest sperm quality was found.

Flow cytometry and ultrastructure of cryopreserved red seabream (Pagrus major) sperm

The objectives were to assess motility, fertilizing capacity, structural integrity, and mitochondrial function in fresh versus frozen-thawed (15% DMSO was used as a cryoprotectant) sperm from red seabream (Pagrus major). Mean (+/-S.D.) rates of motility, fertilization and hatching of frozen-thawed sperm were 81.0+/-5.4, 92.8+/-1.9, and 91.8+/-5.2%, respectively; for fresh sperm, they were 87.5+/-7.7, 95.8+/-2.4, and 93.8+/-4.2%. Although motility was lower in frozen-thawed versus fresh sperm (P<0.05), there was no effect (P>0.05) of cryopreservation on fertilization or hatching. Based on scanning and transmission electron microscopy, 77.8+/-5.6% of fresh sperm had normal morphology, whereas for frozen-thawed sperm, 63.0+/-7.2% had normal morphology, 20.6+/-3.1% were slightly damaged (e.g. swelling or rupture of head, mid-piece and tail region as well as mitochondria), and 16.4+/-4.2% were severely damaged. Sperm were stained with propidium iodide and Rhodamine 123 to assess plasma membrane integrity and mitochondrial function, respectively, and examined with flow cytometry. For fresh sperm, 83.9% had an intact membrane and functional mitochondria, whereas for frozen-thawed sperm, 74.8% had an intact membrane and functional mitochondria, 12.7% had a damaged membrane, 9.9% had nonfunctional mitochondria, and 2.6% had both a damaged membrane and nonfunctional mitochondria. In conclusion, ultrastructure and flow cytometry were valuable for assessment of frozen-thawed sperm quality; cryopreservation damaged the sperm but fertilizing ability was not significantly decreased.

Effects of hCG as spermiation inducer on European eel semen quality

Fish sperm quality has traditionally been estimated by subjective evaluation of motility and sperm concentration. Alternative methods for evaluation of sperm quality have been developed in the last decade and enable estimation of spermatozoa head morphometry, membrane integrity and mitochondrial function. Weekly injections of human chorionic gonadotropin (hCG) induced spermiation in farmed male European eels. The milt volume increased from the 5th to 12th weeks. Sperm concentration significantly increased from the 5th week, reaching the highest values at the 8th week, while best motility results were registered at the 9th week of treatment. Coinciding with these intervals, the percentage of dead spermatozoa determined with Hoechst staining showed a reduction in the 8th to 11th weeks of treatment, while the percentage of mitochondrial functionality determined by JC-1 staining did not show a similar pattern. The automatic sperm morphology analysis (ASMA) of the spermatozoa head length, width, area and perimeter showed a significant growth from the 5th to 8th weeks. However, the analysis of isolated descriptive parameters may be difficult to understand because there is a variability in these parameters for each week, making knowledge of the growth kinetic complex. The global size of the spermatozoa head was calculated by applying principal component analysis (PCA), because this method establishes new components that make the interpretation of results easier, allowing a whole interpretation of the changes in the cell morphology. PC1 defines the global head size and shows a significant increase between the 5th and 8th weeks of treatment, showing shorter changes until 12th week. PC2 shows a significant increase in the spermatozoa width from the 5th to 7th weeks. Considering the results of the variations in the principal components defining European eel spermatozoa morphometry, it may be concluded that hCG maturative treatment produced thick cells during the first weeks of spermiation, and subsequent samplings showed an increase in cell width and length. These changes in sperm morphometry coincide with the highest sperm quality assessed as sperm motility and concentration, as well as with the best results obtained in previous studies reporting the best sperm quality between weeks 8 and 10 of hCG treatment. These results support the use of ASMA and Hoechst staining techniques as alternative methods for the evaluation of fish sperm quality.

Cryopreservation of European eel (Anguilla anguilla) spermatozoa: Effect of dilution ratio, foetal bovine serum supplementation, and cryoprotectants

The main aim of the present study was to investigate the effect of sperm freezing medium dilution ratio (1:1, 1:2, and 1:5 v/v), two cryoprotectants: dimethyl sulphoxide (Me(2)SO) and methanol (MeOH), and the addition of foetal bovine serum (FBS) on the cryopreservation of European eel sperm. The effect of these factors was evaluated comparing post-thawing viability with fluorescent staining (Hoechst bisbenzimide 33258) and the spermatozoa head morphometry, determined with computer-assisted morphology analysis (ASMA). The 1:5 (v/v) dilution ratio resulted in a lower viability in comparison with 1:1 and 1:2 (52.8+/-2.3% vs. 67.4+/-2.3% and 65.1+/-2.3%, respectively, p=0.0001), but without effects on the head morphology. Although the viability was not significantly different between Me(2)SO and MeOH (60.4+/-1.9 vs. 63.2+/-1.9%, respectively, p=0.305), a decrease of spermatozoa head area and perimeter was found when spermatozoa were frozen with methanol (6.19+/-0.01 vs. 6.36+/-0.01 microm(2) and 17.28+/-0.05 vs. 17.49+/-0.05 microm, for area and perimeter and MeOH and Me(2)SO, respectively, p=0.0001). Finally, a higher viability (75.1+/-1.7 vs. 48.5+/-1.7, with or without FBS, respectively, p=0.0001) and higher spermatozoa head size (6.40+/-0.01 vs. 6.15+/-0.01microm(2) and 17.88+/-0.05 vs. 16.89+/-0.05 microm, for area and perimeter, with or without FBS, respectively, p=0.0001) were found when cells were frozen-thawed in freezing media supplemented with FBS. Based on the above findings, dilution ratios lower than 1:5 (v/v) and the addition of serum improved the viability results after cryopreservation. Future studies are required in order to understand the spermatozoa membrane interchange mechanisms in response to the changes in spermatozoa head size caused by cryoprotectants and freezing media supplements.

Assessment of gamete quality for the eastern oyster (Crassostrea virginica) by use of fluorescent dyes

Evaluation of sperm motility is the single most widely used parameter to determine semen quality in mammals and aquatic species. While a good indicator for fresh sperm viability, post-thaw motility is not always effective at predicting fertilizing ability. Techniques using fluorescent dyes can assess functionality of mammalian sperm, but have not been widely applied in aquatic organisms. The eastern oyster Crassostrea virginica is an important mollusk in the United States, and cryopreservation protocols have been developed to preserve sperm and larvae to assist research and hatchery production. In this study, protocols were developed to assess sperm cell membrane integrity and mitochondrial function by flow cytometry and to assess viability of eggs by fluorescence microscopy. The fluorescent dyes SYBR 14 and propidium iodide (PI) (to assess membrane integrity) and rhodamine 123 (R123) (to assess mitochondrial membrane potential) were used to evaluate the quality of thawed oyster sperm previously cryopreserved with different cryoprotectant and thawing treatments. Membrane integrity results were correlated with motility of thawed sperm and mitochondrial membrane potential with fertilizing ability. Fluorescein diacetate (FDA) was used to assess cytotoxicity of cryoprotectant solutions and post-thaw damage to oyster eggs. The results indicated that membrane integrity (P=0.004) and thawing treatments (P=0.04), and mitochondrial membrane potential (P=0.0015) were correlated with motility. Fertilizing ability was correlated with cryoprotectant treatments (P=0.0258) and with mitochondrial membrane potential (P=0.001). The dye FDA was useful in indicating structural integrity of fresh and thawed eggs. Exposure of eggs, without freezing, to dimethyl sulfoxide yielded higher percentages of stained eggs and fertilization rate than did exposure to propylene glycol (P=0.002). Thawed eggs were not stained with FDA (<1%) and larvae were not produced.

Evaluation of DNA damage in rainbow trout (Oncorhynchus mykiss) and gilthead sea bream (Sparus aurata) cryopreserved sperm

Cryopreservation causes several types of damage to spermatozoa, such as loss of plasma membrane integrity and functionality, loss of motility, and ATP content, resulting in decrease of fertility rates. This spermatozoal damage has been widely investigated for several marine and freshwater fish species. However, not much attention has been paid to the nuclear DNA. The objective of this study was to determine the degree to which cryopreservation induces spermatozoal DNA damage in two commercially cultured species, rainbow trout (Oncorhynchus mykiss) and gilthead sea bream (Sparus aurata), both of which could benefit from the development of cryopreservation strategies on a large scale. We have used the single-cell gel electrophoresis, commonly known as Comet assay to detect strand breaks in DNA. This technique was performed on fresh and cryopreserved sperm from both species. In rainbow trout there was a significant increase in the averages of fragmented DNA and Olive tail moment after cryopreservation (11.19-30.29% tail DNA and 13.4-53.48% Olive tail moment in fresh and cryopreserved sperm, respectively), as well as in the proportion of cells with a high percentage of DNA fragmentation. For gilthead sea bream there were no significant differences in the percentage of tail DNA between the control samples and sperm diluted 1:6 and cryopreserved (28.23 and 31.3% DNA(t), respectively). However, an increase in the sperm dilution rate produced an increase in the percentage of DNA fragmentation (41.4%). Our study demonstrates that cryopreservation can induce DNA damage in these species, and that this fact should be taken into account in the evaluation of freezing/thawing protocols, especially when sperm cryopreservation will be used for gene bank purposes.

Evaluation of gilthead sea bream, Sparus aurata, sperm quality after cryopreservation in 5ml macrotubes

Cryopreservation produces several types of damage in spermatozoa, leading to fertility impairment. The reduction arises both from a lower viability post-thaw and from sublethal dysfunctions in some of the surviving cells. In the present study, we have analysed the effect of cryopreservation in 5 ml macrotubes on the quality of post-thawed gilthead sea bream sperm. Several standard sperm quality parameters were determined: pH and osmolarity of seminal plasma, sperm concentration, and motility. An exhaustive determination of sperm quality before and after cryopreservation was investigated. Several parameters related with spermatozoal status were determined: ATP content, plasma membrane integrity and functionality, mitochondrial functionality, and sperm fertility. Our results demonstrated that gilthead sea bream spermatozoa suffer several types of damage after freezing/thawing. The percentage of viable cells slightly decreased after cryopreservation, however plasma membrane was affected by cryopreservation, since cells could not resist the hyperosmotic shock. Mitochondrial status was affected by cryopreservation since there was a decrease in the parameters of sperm motility, ATP content (3.17 nmol ATP/10(5) spermatozoa to 1.7 nmol ATP/10(5) spermatozoa in 1:20 frozen samples) and an increase of the percentage of cells with mitochondrial depolarized membranes (11% for fresh and 27% for 1:20 frozen samples). Fertility rate was similar either using fresh or frozen/thawed sperm (77 and 75% hatched larvae, respectively).

Ultraviolet damages sperm mitochondrial function and membrane integrity in the sea urchin Anthocidaris crassispina

Effects of ultraviolet A (UVA) and ultraviolet B (UVB) on mitochondrial function and membrane integrity of sea urchin sperm were investigated using flow cytometry and fluorescent probes. Both UVA and UVB impaired sperm mitochondrial function in a dose-dependent manner. Covariance analysis further showed that the slopes of change in mitochondrial function in relation to UVA and UVB were significantly different, suggesting that the modes of action were different. UVA did not affect membrane integrity, while membrane integrity showed a linear reduction with increasing UVB doses. Sperm mitochondria function showed significant positive correlations with sperm motility and subsequent fertilization success. Overall, our results showed that both UVA and UVB could decrease sperm motility and fertilization success through impairment of mitochondrial function, whereas UVB alone could cause additional damage through impairing the functional integrity of sperm membrane. Mitochondrial function of sperm may also offer a reliable ecotoxicological biomarker for predicting fertilization success in urchins.

The use of flow cytometry in the evaluation of cell viability of cryopreserved sperm of the marine shrimp (Litopenaeus vannamei)

Although the cryopreservation of penaeid prawn sperm or embryos has definite applications in the aquaculture industry, there is no protocol routinely used for this procedure. One of the main problems relies on the limitations for the determination of sperm cell viability. In this study, we evaluated the toxicity and cryoprotectant effect of four agents, at three different concentrations, in sperm suspension, spermatic mass, and complete spermatophore of the marine shrimp Litopenaeus vannamei. Cells were frozen by fast and slow cooling rates. After thawing, they were analyzed by optical microscopy and flow cytometry, which was also utilized to determine spermatic viability by DNA staining with propidium iodine. Considering viability by morphotype analysis, the best result was obtained when the spermatic mass was frozen by slow cooling rate in the presence of methanol (61.6%). There was a positive correlation between morphotype analysis and flow cytometry, although the percentage of viable cells was always lower when determined by the later. These results show that flow cytometry is a valuable tool to evaluate sperm cell viability in decapod species and it is more sensitive technique than optical microscopy.

Effects of dimethyl sulfoxide and glycine on cryopreservation induced damage of plasma membranes and mitochondria to striped bass (Morone saxatilis) sperm

Intact plasma membrane and functional mitochondria are important attributes for the fertilization capacity of fish sperm. In the present study, dimethyl sulfoxide (Me(2)SO) and glycine were investigated in an effort to improve plasma membrane integrity and mitochondrial function in cryopreserved striped bass (Morone saxatilis) sperm. Prior to freezing, no concentration of Me(2)SO (2.5, 5 or 10%) was found to affect (P>0.05) the integrity of plasma membranes after sperm were exposed for 10 min. However, mitochondrial function decreased (P>0.05) with increasing Me(2)SO concentration. Both fluorescent staining and microscopic examination of the ultrastructure of post-thaw plasma membranes indicated that with increasing Me(2)SO concentration, plasma membranes were better protected, and 10% Me(2)SO had the highest percentage of sperm with plasma membranes intact. However, sperm mitochondrial function decreased (P>0.05) with increasing Me(2)SO concentration. The inverse relationship between plasma membrane integrity and mitochondrial function, given the Me(2)SO concentration, suggests that care must be taken to select Me(2)SO concentration that will maximize the protection of both plasma membranes and mitochondrial function. The addition of glycine to the cryomedia increased (P<0.05) the percentage of sperm with post-thaw functional mitochondria and ATP content. However glycine did not provide (P<0.05) protection to post-thaw plasma membrane integrity. The highest percentage of sperm with both intact plasma membranes and functional mitochondria was obtained with 7.5% Me(2)SO and 75 mM glycine.

Adenosine triphosphate concentration and beta-D-glucuronidase activity as indicators of sea bass semen quality

The most common parameters used to evaluate sperm quality are motility rate and duration and fertilization ability. In this study, chemical and biochemical parameters of sea bass (Dicentrarchus labrax) sperm were investigated to find an alternative method for evaluating sperm fertilization ability before and after cryopreservation. The biochemical and chemical analyses were performed with fresh and frozen-thawed sperm and seminal plasma. To cryopreserve sperm, 250-microl straws were used. Fertilization ability was evaluated by inseminating eggs (obtained from hormonally stimulated females) with fresh and cryopreserved sperm. The results revealed a linear relationship (P < 0.05) between semen fertilization capacity and some seminal plasma (beta-D-glucuronidase activity, potassium concentration) and sperm (ATP concentration, aspartate aminotransferase activity) parameters. Variations in semen fertilization rate could be best described by two multiple regression models: one including the sperm parameters and another including the seminal plasma parameters. For practical application, the use of simple regression models is of value. Fertilization rate in both fresh and cryopreserved sperm was reliably predicted by determining the ATP concentration or the beta-D-glucuronidase activity or both.