Probiotic administration improves sperm quality in asthenozoospermic human donors

The objective of this study is to analyse the effect of the ingestion of two selected antioxidant probiotics strains (Lactobacillus rhamnosus CECT8361 and Bifidobacterium longum CECT7347) on sperm quality parameters in asthenozoospermic males after three and six weeks of administration. Nine asthenozoospermic men without any medical treatment under similar diet conditions participated in the study. The quality of individual sperm samples was evaluated before (previous to ingestion), during (after 3 and 6 weeks of ingestion) and after probiotic administration (3 and 6 weeks after finishing the treatment). Sperm motility was evaluated by computer-assisted sperm analysis system, DNA fragmentation by sperm chromatin structure assay, cell viability by flow cytometry and measurement of intracellular H₂O₂ (reactive oxygen species; ROS) by flow cytometry using dichloro-dihydrofluorescein diacetate. Sperm motility was drastically improved after the treatment (approximately 6 fold change), DNA fragmentation was statistically reduced after probiotic administration from (approximately 1.2 fold change) and intracellular H₂O₂ level was decreased (approximately 3.5 fold change). Cell viability was not affected by the treatment. The significant improvement in sperm motility and the decrease in DNA fragmentation reported in this study provide preliminary evidence that probiotics could be administrated to improve motility and decrease DNA fragmentation and ROS levels in asthenozoospermic human males.

Effect of captivity and cryopreservation on ROS production in Solea senegalensis spermatozoa

Reactive oxygen species have a great impact on spermatozoa function. Gametes from sole males born in captivity (F1) display lower quality than those from wild individuals. In this paper, the percentage of cells positive for dichlorofluorescein (DCF(+)) was determined by flow cytometry in wild and F1 animals, the effect of cryopreservation on DCF(+) cells was evaluated in both groups and the distribution of H2O2 within the cell was studied by confocal microscopy. Our results indicated that there are no differences in either viability or DCF(+) cells between wild and F1 animals when fresh samples were evaluated. However, when data were analyzed considering two different sperm populations in terms of motility, a significant decrease in viability and DCF(+) cells was reported in low-motile F1 spermatozoa. Cryopreservation did not alter the viability or the presence of DCF(+) cells in sperm samples from wild animals, but significantly decreased the viability in F1 samples. Distribution patterns of H2O2 have been established by confocal microscopy in Solea senegalensis spermatozoa: co-localization of H2O2 with active mitochondria (MitoTracker(+)) and co-localization with nuclear DNA (DAPI). Compared with H2O2 distribution in other marine species such as Scophthalmus maximus, Solea senegalensis spermatozoa showed widespread presence of H2O2 particularly in the nuclei, which could potentially compromise DNA integrity.

Selection of nonapoptotic sperm by magnetic-activated cell sorting in Senegalese sole (Solea senegalensis)

Senegalese sole (Solea senegalensis) is a promising species in aquaculture. However, owing to decreased sperm quality in F1 generations and the absence of courtship in those individuals born in captivity, artificial fertilization is being used to generate new progenies. The objective of this study was to implement a sperm selection method for nonapoptotic sperm subpopulation recovery before sperm cryopreservation. In particular, magnetic-activated cell sorting is used to eliminate apoptotic spermatozoa. This study represents the proof-of-concept for magnetic-activated cell sorting applicability in teleost species relevant in aquaculture. Apoptotic cell population was studied by flow cytometry using YO-PRO-1 and a caspase detection kit. Also, reactive oxygen species were measured in sperm samples. Our data demonstrated that caspase detection is more specific than YO-PRO-1 in the identification of apoptotic cells in S senegalensis seminal samples. The results showed that the percentage of apoptotic cells (caspase positive) was significantly higher (P = 0.04) in seminal samples from F1 than that from wild individuals. Magnetic-activated cell sorting removed a significant number of apoptotic cells from the samples (54% and 75% in wild and F1 individuals, respectively), decreasing the level of cells positive for reactive oxygen species (P = 0.17). In conclusion, this technique reduces the percentage of nonfunctional spermatozoa in a seminal sample before cryopreservation. This novel technique can be applied directly in the aquaculture industry.

Current concepts on microscopic colitis: evidence-based statements and recommendations of the Spanish Microscopic Colitis Group

BACKGROUND

Microscopic colitis (MC) is an underdiagnosed inflammatory bowel disease.

AIM

To develop an evidence-based clinical practice guide on MC current concepts.

METHODS

Literature search was done on the Cochrane Library, EMBASE and MEDLINE electronic databases, which were consulted covering the period up until March 2015. Work groups were selected for each of the reviewed topics, with the purpose of drafting the initial statements and recommendations. They subsequently underwent a voting process based on the Delphi method. Each statement/recommendation was accompanied by the result of the vote the level of evidence, and discussion of the corresponding evidence. The grade of recommendation (GR) using the GRADE approach was established for diagnosis and treatment recommendations.

RESULTS

Some key statements and recommendations are: advancing age increases the risk of developing MC, mainly in females. The symptoms of MC and IBS-D may be similar. If MC is suspected, colonoscopy taking biopsies is mandatory. Treatment with oral budesonide is recommended to induce clinical remission in patients with MC. Oral mesalazine is not recommended in patients with collagenous colitis for the induction of clinical remission. The use of anti-TNF-alpha drugs (infliximab, adalimumab) is recommended for the induction of remission in severe cases of MC that fail to respond to corticosteroids or immunomodulators, as an alternative to colectomy.

CONCLUSIONS

This is the first consensus paper on MC based on GRADE methodology. This initiative may help physicians involved in care of these patients in taking decisions based on evidence.

Inhibition of zygotic DNA repair: transcriptome analysis of the offspring in trout (Oncorhynchus mykiss)

Zygotic repair of the paternal genome is a key event after fertilization. Spermatozoa accumulate DNA strand breaks during spermatogenesis and can suffer additional damage by different factors, including cryopreservation. Fertilization with DNA-damaged spermatozoa (DDS) is considered to promote implantation failures and abortions, but also long-term effects on the progeny that could be related with a defective repair. Base excision repair (BER) pathway is considered the most active in zygotic DNA repair, but healthy oocytes contain enzymes for all repairing pathways. In this study, the effects of the inhibition of the BER pathway in the zygote were analyzed on the progeny obtained after fertilization with differentially DDS. Massive gene expression (GE; 61 657 unique probes) was analyzed after hatching using microarrays. Trout oocytes are easily fertilized with DDS and the high prolificacy allows live progeny to be obtained even with a high rate of abortions. Nevertheless, the zygotic inhibition of Poly (ADP-ribose) polymerase, upstream of BER pathway, resulted in 810 differentially expressed genes (DEGs) after hatching. DEGs are related with DNA repair, apoptosis, telomere maintenance, or growth and development, revealing a scenario of impaired DNA damage signalization and repair. Downregulation of the apoptotic cascade was noticed, suggesting a selection of embryos tolerant to residual DNA damage during embryo development. Our results reveal changes in the progeny from defective repairing zygotes including higher malformations rate, weight gain, longer telomeres, and lower caspase 3/7 activity, whose long-term consequences should be analyzed in depth.

Human genetics. The genetics of Mexico recapitulates Native American substructure and affects biomedical traits

Mexico harbors great cultural and ethnic diversity, yet fine-scale patterns of human genome-wide variation from this region remain largely uncharacterized. We studied genomic variation within Mexico from over 1000 individuals representing 20 indigenous and 11 mestizo populations. We found striking genetic stratification among indigenous populations within Mexico at varying degrees of geographic isolation. Some groups were as differentiated as Europeans are from East Asians. Pre-Columbian genetic substructure is recapitulated in the indigenous ancestry of admixed mestizo individuals across the country. Furthermore, two independently phenotyped cohorts of Mexicans and Mexican Americans showed a significant association between subcontinental ancestry and lung function. Thus, accounting for fine-scale ancestry patterns is critical for medical and population genetic studies within Mexico, in Mexican-descent populations, and likely in many other populations worldwide.

Effect of intrathecal baclofen on evoked pain perception: an evoked potentials and quantitative thermal testing study

BACKGROUND AND OBJECTIVES

Somatic antinociceptive effects of baclofen have been demonstrated in animal models. We hypothesized that if enhanced thermal or pain sensitivity is produced by loss of gamma-aminobutyric acid (GABA)-ergic tone in the central nervous system, spinal administration of GABA agonists might be predicted to be effective in thermal and/or pain perception changes and pain-related evoked potentials in candidates for intrathecal baclofen (ITB) treatment.

METHODS

Eleven patients with severe spinal cord injury (SCI) who suffered from severe spasticity were evaluated during a 50-μg ITB bolus test. Warm and heat pain thresholds, evoked heat pain perception, and contact heat-evoked potentials (CHEPs) were determined above SCI level from the right and left sides. Nine age- and gender-matched healthy volunteers undergoing repeat testing without any placebo injection served as control group.

RESULT

In patients, heat pain perception threshold increased, and evoked pain perception and amplitude of CHEPs decreased significantly after ITB bolus application in comparison with baseline (p < 0.005), with no change in warm perception threshold. In controls, no significant changes were observed in repeat testing over time.

CONCLUSION

Our findings indicate that ITB modulates heat pain perception threshold, evoked heat pain perception and heat pain-related evoked potentials without inducing warm perception threshold changes in SCI patients. This phenomenon should be taken into account in the clinical evaluation and management of pain in patients receiving baclofen.

Estimation of distribution algorithms as logistic regression regularizers of microarray classifiers

OBJECTIVES

The "large k (genes), small N (samples)" phenomenon complicates the problem of microarray classification with logistic regression. The indeterminacy of the maximum likelihood solutions, multicollinearity of predictor variables and data over-fitting cause unstable parameter estimates. Moreover, computational problems arise due to the large number of predictor (genes) variables. Regularized logistic regression excels as a solution. However, the difficulties found here involve an objective function hard to be optimized from a mathematical viewpoint and a careful required tuning of the regularization parameters.

METHODS

Those difficulties are tackled by introducing a new way of regularizing the logistic regression. Estimation of distribution algorithms (EDAs), a kind of evolutionary algorithms, emerge as natural regularizers. Obtaining the regularized estimates of the logistic classifier amounts to maximizing the likelihood function via our EDA, without having to be penalized. Likelihood penalties add a number of difficulties to the resulting optimization problems, which vanish in our case. Simulation of new estimates during the evolutionary process of EDAs is performed in such a way that guarantees their shrinkage while maintaining their probabilistic dependence relationships learnt. The EDA process is embedded in an adapted recursive feature elimination procedure, thereby providing the genes that are best markers for the classification.

RESULTS

The consistency with the literature and excellent classification performance achieved with our algorithm are illustrated on four microarray data sets: Breast , Colon , Leukemia and Prostate . Details on the last two data sets are available as supplementary material.

CONCLUSIONS

We have introduced a novel EDA-based logistic regression regularizer. It implicitly shrinks the coefficients during EDA evolution process while optimizing the usual likelihood function. The approach is combined with a gene subset selection procedure and automatically tunes the required parameters. Empirical results on microarray data sets provide sparse models with confirmed genes and performing better in classification than other competing regularized methods.

Cryoprotective effects of antifreeze proteins delivered into zebrafish embryos

Fish embryo cryopreservation, which is useful in aquaculture or biodiversity conservation, is still far from being achieved. Structural barriers reduce the entrance of cryoprotectants into embryo compartments. Previous studies demonstrated a better ability for freezing in Arctic species which naturally express antifreeze proteins (AFPs). In this study, AFPs were delivered in early zebrafish embryos by incubation in media containing protein. Their cryoprotective effects were then analyzed. Chilling sensitivity was evaluated at 4 degrees C and -10 degrees C. Survival rates significantly increased in embryos incorporating AFPI and kept at -10 degrees C. To analyze their effects on cryopreservation, 5-somite embryos were vitrified. Incorporation of AFPI reduced the percentage of embryos that collapsed at thawing (14.2% of AFPI-treated embryos and 48.9% of controls). Cellular damage caused by vitrification was assessed after thawing by cell dissociation and further analysis of cell survival in culture (SYBR-14/IP labeling). The percentage of viable cells at thawing ranged from 25 to 50%, considered incompatible with embryo development. Cells recovered from frozen-control embryos did not survive in culture. However, the incorporation of AFPs allowed survival similar to that of cells recovered from non-frozen embryos. Blastomere cryopreservation trials incorporating AFPI in the extender also demonstrated a significant increase in viability after freezing. Our findings demonstrated that delivery of AFPs into zebrafish embryos by incubation in media containing protein at early stages is a simple and harmless method that increases cryoprotection of the cellular compartment. This beneficial effect is also noticed in blastomeres, encouraging their use in further protocols for embryo cryopreservation.

Incorporation of antifreeze proteins into zebrafish embryos by a non-invasive method

The cryopreservation of fish embryos is a challenge because of their structure, with multiple compartments and permeability barriers, and their high chilling sensitivity. Vitrification at advanced developmental stages is considered to be the more promising option. Nevertheless, all reported attempts have failed. Previous studies demonstrated a better ability for freezing in species that naturally express antifreeze proteins (AFPs). These proteins have been delivered into other fish embryos using time-consuming techniques like microinjection. In the present study, the introduction of FITC labelled AFPs was assayed in zebrafish embryos at early developmental stages (from 2-cell to high blastula stage), before the formation of the yolk syncytial layer, by an easy and non-invasive method and evaluated by fluorescence and confocal microscopy. Incubation with AFPs at 128-cell or high blastula stage provides incorporation of the protein in 50-90% of embryos without affecting hatching. Incubation in media containing protein is a simple, harmless and effective method which makes it possible to treat several embryos at the same time. AFPs remain located in derivatives from marginal blastomeres: the yolk syncytial layer, the most cryosensitive and impermeable barrier, and different digestive organs. Our findings demonstrate that delivery of AFP type I and AFP type III into zebrafish embryos by incubation in media containing protein is a simple and harmless method that may improve cryoprotection of the cellular compartment.

Effects of feeding frequency on intake, ruminal fermentation, and feeding behavior in heifers fed high-concentrate diets1

Four ruminally fistulated Holstein heifers (BW = 385 +/- 6.2 kg) were used in a 4 x 4 Latin square experiment to determine the effect of feeding frequency on intake, water consumption, ruminal fermentation, and feeding and animal behavior. The treatments consisted of different feeding frequencies: a) once daily (T1); b) twice daily (T2); c) 3 times daily (T3); and d) 4 times daily (T4). Heifers were offered ad libitum access to concentrate and barley straw. Feeding frequency did not affect DMI (P >0.10), but water consumption tended to increase linearly as feeding frequency increased (P = 0.08). Average ruminal pH was not affected (P >0.10) by feeding frequency, but at 12 h after feeding ruminal pH was greater for T2 than for the other treatments. Total VFA concentration and VFA proportions were not affected (P >0.10) by feeding frequency, except valerate proportion, which increased linearly (P = 0.05) as feeding frequency increased. The concentration of ammonia-N was affected (P <0.05) cubically as feeding frequency increased (greatest for T3 = 9.3 mg of N/100 mL; lowest for T2 = 7.2 mg of N/100 mL). Feeding frequency had no effect on daily percentages of behavioral activities (P >0.05), except for observational behavior, for which there was a linear decrease as feeding frequency increased (P = 0.02). Heifers spent the same time on chewing activities, independent of feeding frequency. However, meal criteria tended to be affected (P = 0.07) by feeding frequency, with T2 (39.4 min) showing the longest intermeal interval. Total daily meal time, meal frequency, and meal size were not affected by feeding frequency (P >0.10), whereas meal length and eating rate showed cubic tendencies (P = 0.10 and P = 0.06, respectively) as feeding frequency increased. These results suggest that in the present experimental conditions, with heifers fed high-concentrate diets and with noncompetitive feeding, a smaller range of ruminal pH values was observed when feed was offered twice daily. Although heifers spent the same time on chewing activities, more stable ruminal conditions were probably achieved by feeding twice daily due to the rumination pattern, which was more constant during daytime in T2 than in T1. Moreover, when daytime and nighttime ruminating activity were analyzed separately, this activity was different in T1 (17.3 vs. 30.8%, respectively; P <0.05) but not in T2 (21.5 vs. 28.0%, respectively; P >0.05).

The antifreeze protein type I (AFP I) increases seabream (Sparus aurata) embryos tolerance to low temperatures

To date, all attempts at fish embryo cryopreservation have failed. One of the main reasons for this to occur is the high chilling sensitivity reported in fish embryos thus emphasizing the need for further testing of different methods and alternative cryoprotective agents (CPAs) in order to improve our chances to succeed in this purpose. In this work we have used the antifreeze protein type I (AFP I) as a natural CPA. This protein is naturally expressed in sub-arctic fish species, and inhibits the growth of ice crystals as well as recrystallization during thawing. Embryos from Sparus aurata were microinjected with AFP I at different developmental stages, 2 cells and blastula, into the blastomere-yolk interface and into the yolk sac, respectively. Control, punctured and microinjected embryos were subjected to chilling at two different temperatures, 0 degrees C (1h) and -10 degrees C (15min) when embryos reached 5-somite stage. Embryos were subjected to -10 degrees C chilling in a 3M DMSO extender to avoid ice crystal formation in the external solution. Survival after chilling was established as the percentage of embryos that hatch. To study the AFP I distribution in the microinjected embryos, a confocal microscopy study was done. Results demonstrate that AFP I can significantly improve chilling resistance at 0 degrees C, particularly in 2-cell microinjected embryos, displaying nearly 100% hatching rates. This fact is in agreement with the confocal microscopy observations which confirmed the presence of the AFP protein in embryonic cells. These results support the hypothesis that AFP protect cellular structures by stabilizing cellular membranes.

Vitrification assays with embryos from a cold tolerant sub-arctic fish species

Pseudopleuronectes americanus is a Northern teleost species that produces antifreeze proteins (AFPs) to protect them from freezing during the winter. These AFPs bind to ice crystals to inhibit their growth, and they also protect cell membranes at low temperatures. In this study, vitrification trials were done with fish embryos at three different developmental stages, using two different protocols for incorporating the vitrifying solutions. Toxicity of the cryoprotectants and permeability to dimethyl sulfoxide were analyzed. Embryos were vitrified in 0.5 ml straws by direct immersion in liquid nitrogen, and their morphology and development analyzed following thaw. The embryos responded well to vitrification as evidenced by the high percentage that exhibited good morphology following thaw. Although none of the embryos hatched, a small percentage (0.92%) of them showed active movements within the chorion and continued to develop for a number of days following thaw. This is the first record of post-thaw development of vitrified fish embryos.

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).

Effect of a vitrification protocol on the lactate dehydrogenase and glucose-6-phosphate dehydrogenase activities and the hatching rates of Zebrafish (Danio rerio) and Turbot (Scophthalmus maximus) embryos

Vitrification, is the most promising option for the cryopreservation of fish embryos but requires high concentrations of potentially toxic cryoprotectants. In this study, embryos from Turbot and Zebrafish, each in two developmental stages, were submitted to a four stepwise cryoprotectant incorporation protocol. After incubation in the vitrificant solution (5M dimethyl sulfoxide, 2M methanol, 1M ethylen-glycol and 10% sucrose) embryos were loaded in straws and plunged into liquid nitrogen. The activity of two cytoplasmic enzymes, LDH and G6PDH, and the hatching rates were analyzed in control embryos, those subjected to the cryoprotectant solutions and in frozen/thawed embryos. Results showed that the cryoprotectants incorporation protocol did not have important effects on the analyzed enzymatic activities, which remained at similar levels to that in control embryos but significantly reduced the hatching rates. Turbot was less sensitive than Zebrafish to the toxic effect of the cryoprotectants, achieving hatching rates of 74.8% in comparison with fresh control embryos at G stage, whereas in Zebrafish only 17.7% of hatching was reported with five somites-treated embryos. In Turbot, G stage was more resistant to the cryoprotectants and thus more convenient for further vitrification studies. After vitrification no survival was recorded and enzymatic activities dropped significantly, particularly in Zebrafish, indicating cell damage and loss of cytoplasmic enzymes. Nevertheless, total cell lysis was not produced, and once again Turbot was more resistant to the effect of vitrification, particularly at the later stage. In that stage, Turbot embryos showed around 50% of G6PDH activity after vitrification, in comparison with the control, indicating the preservation of some cellular activity after freezing-thawing, despite the loss of developmental ability.

Effect of different cryoprotectants and vitrificant solutions on the hatching rate of turbot embryos (Scophthalmus maximus)

Vitrification could provide a promising tool for the cryopreservation of fish embryos. However, in order to achieve a vitrifiable medium, a high concentration of permeable cryoprotectants must be employed, and the incorporation of high molecular weight compounds should also be considered. The toxicity of these permeable and non-permeable agents has to be assessed, particularly when high concentrations are required. In the present study, permeable and non-permeable cryoprotectant toxicity was determined in turbot embryos at two development stages (F stage-tail bud and G stage-tail bud free). Embryos treated with pronase (2mg/ml, 10 min at 22 degrees C) were incubated in dimethyl sulfoxide (Me2SO), methanol (Meth.) or ethylene glycol (EG) in concentrations ranging from 0.5 to 6M for periods of 10 or 30 min, and in 5, 10, and 15% polyvinylpyrrolidone (PVP), 10, 15, and 20% sucrose or 0.1, 1, and 2% X-1000 for 2 min. The embryos were then washed well and incubated in seawater until hatching. The toxicity of permeable cryoprotectants increased with concentration and exposure time. There were no significant differences between permeable cryoprotectants. However, embryos tolerated higher concentrations of Me2SO than other cryoprotectants. Exposure to permeable cryoprotectants did not affect the hatching rate except at G stage with X-1000 treatment and 20% sucrose. Taking into account the cryoprotectant toxicity and the vitrification ability of cryoprotectant mixtures, three vitrification solutions (V1, V2, and V3), and one protocol for stepwise incorporation were designed. The tested solutions contained 5M Me2SO+2M Meth+1M EG plus 5% PVP, 10% sucrose or 2% X-1000. The hatching rate of embryos that had been exposed to the the vitrification solutions was analyzed and no significant differences were noticed compared with the controls. Our results demonstrate that turbot embryos can be subject to this cryoprotectant protocol without deleterious effect on the hatching rate.

Vitrification of turbot embryos: preliminary assays

Successful fish embryo cryopreservation is still far from being achieved. Vitrification is considered the most promising option. Many factors are involved in the success of the process. The choice of a proper vitrification solution, the enzymatic permeabilization of embryos to increase cryoprotectant permeability, the adequate container for embryo loading, and the temperature for thawing, were the parameters considered at different developmental stages in the present study. After vitrification, embryo morphology was evaluated under stereoscopic microscopy, establishing the percentage of intact embryos. Two of the studied parameters yielded differences in this percentage, the volume of straw used for embryo loading (1 ml straws were significantly better than 0.5 ml straws, with regard to post-thawed embryo morphologies), and the thawing temperature, achieving 49% of embryos with intact morphology after thawing at 0 degrees C. After thawing, the intact embryos were incubated and periodically observed to detect morphological changes. Changes in the perivitelline space, shrinkage of the yolk and chorion ruptures as well as a progressive whitening of the embryo and yolk were observed. After 8 h all embryos showed clear signs of degradation and during this incubation period no embryo showed any developmental ability.

Dimethyl sulfoxide influx in turbot embryos exposed to a vitrification protocol

The particular characteristics of fish embryos require the development of specific methods for cryopreservation. One of the main obstacles is related to the presence of membranes and compartments with different water and cryoprotectant permeability. To assess dimethyl sulfoxide (Me2SO4) permeability, we exposed turbot embryos (Scophthalmus maximus) at F stage (tail bud) to the cryoprotectant solutions used in a vitrification protocol and then evaluated the Me2SO4 content inside the embryo using high-performance liquid chromatography (HPLC). The Me2SO4 influx was analyzed in normal embryos and in embryos treated with pronase (2mg/ml) in order to increase chorion permeability. The evaluation was made after each step of cryoprotectant incorporation and removal. Three embryo compartments were distinguished: the perivitelline space (PVS), the yolk sac (YS) and the cellular compartment (CC), and the relative volumes of each, estimated using stereoscopic microscopy imaging, were 11.37, 81.23 and 7.40%, respectively. The Me2SO4 concentration inside the embryos was calculated based on their entrance into one, two or three compartments. Results suggest high entrance of Me2SO4 into the PVS and a low concentration of this cryoprotectant inside the other compartments. Pronase did not significantly increase Me2SO4 influx, but facilitated its elimination during the washing steps.