Development of cryopreservation protocols for early stage zebrafish (Danio rerio) ovarian follicles using controlled slow cooling

The Relative Importance of Determinants of the Solar Photovoltaic Industry in China: Analyses by the Diamond Model and the Analytic Hierarchy Process

Within China’s renewable energy industry, the importance of the solar photovoltaic industry has been increasingly recognized. Many Chinese provinces have adopted various measures to develop the solar photovoltaic industry. This study used the diamond model and the analytic hierarchy process to clarify the relative importance of the determinants of the development of the solar photovoltaic industry. A total of 22 determinants in six categories (i.e., factor condition; demand condition; firm strategy, structure, and rivalry; related and support industries; government; and chance) were analyzed. The results show that besides factor condition, demand condition and firm strategy, structure, and rivalry have also had a strong influence on the development of China’s photovoltaic industry. The findings also indicate that some traditional factors, such as labor costs and acquiring land, are very important to the development of the solar photovoltaic industry. The relative importance of the determinants clarified through this study provides a standard for the actions of policymakers and decision makers.

Slow freezing versus vitrification for the cryopreservation of zebrafish (Danio rerio) ovarian tissue

The aim of the present study was to compare the efficiency of vitrification and slow freezing techniques for the cryopreservation of zebrafish ovarian tissue containing immature follicles. In Experiment 1, assessment of cell membrane integrity by trypan blue exclusion staining was used to select the best cryoprotectant solution for each cryopreservation method. Primary growth (PG) oocytes showed the best percentage of membrane integrity (63.5 ± 2.99%) when SF4 solution (2 M methanol + 0.1 M trehalose + 10% egg yolk solution) was employed. The vitrification solution, which presented the highest membrane integrity (V2; 1.5 M methanol + 5.5 M Me₂SO + 0.5 M sucrose + 10% egg yolk solution) was selected for Experiment 2. Experiment 2 aimed to compare the vitrification and slow freezing techniques in the following parameters: morphology, oxidative stress, mitochondrial activity, and DNA damage. Frozen ovarian tissue showed higher ROS levels and lower mitochondrial activity than vitrified ovarian tissue. Ultrastructural observations of frozen PG oocytes showed rupture of the plasma membrane, loss of intracellular contents and a large number of damaged mitochondria, while vitrified PG oocytes had intact mitochondria and cell plasma membranes. We conclude that vitrification may be more effective than slow freezing for the cryopreservation of zebrafish ovarian tissue.

Chilling sensitivity of Steindachneridion parahybae (Siluriformes: Pimelodidae) oocytes in different cryoprotectants

The viability of post-thaw fish oocytes can be affected by different stages of the freezing process, such as cryoprotectant toxicity, cold sensitivity, freezing curves and thawing. Therefore, these steps need to be investigated for the development of a protocol. In the present study, the aim was to investigate chilling sensitivity at different oocyte stages of Steindachneridion parahybae. Immature and mature oocytes were incubated in Hanks' or 90% L15 solutions containing different CPAs (cryoprotectant solutions) per experiment: (1) 0.1-0.4 M sucrose + 1-2 M methanol and (2) 1-4 M methanol X 1-4 M propylene glycol X 1-4 M DMSO for mature oocytes; (3) 0.5 M sucrose or fructose + 2 M methanol or PG or DMSO and (4) 0.25-1 M fructose + 1-4 M DMSO for immature oocytes. All treatments were kept for 120 min at -5.9 ± 2.8°C. For the control treatment, only Hanks' or 90% L15 solutions were carried out. Evaluations were made by viability tests: membrane integrity staining in 0.4% Trypan blue (TB) and fertilization rate (%F) sole for mature oocytes. Results presented that mature oocytes were the most sensitive to lower temperatures, because there was no %F. All cryoprotectants tested in the different concentrations can be used for immature oocytes, however the statistically superior cryoprotectant was CPA with fructose and DMSO, with the low concentration of this CPA being was the best statistically. This may indicate that for this species the immature stages have presented a lower chilling sensitivity than the mature stages.

The Role of Reproductive Sciences in the Preservation and Breeding of Commercial and Threatened Teleost Fishes

The teleost fishes are the largest and most diverse vertebrate group, accounting for nearly half of all known vertebrate species. Teleost fish exhibit greater species diversity than any other group of vertebrates and this is reflected in the unique variety of different reproductive strategies displayed by fish. Fish have always been an important resource for humans worldwide, especially as food. While wild capture fisheries have historically been the main source of fish, the farming of fish (aquaculture) is increasingly becoming the more dominant source of food fish, and is predicted to account for 60% of total global fish production by 2030.Fishes are increasingly threatened by a wide range of anthropogenic impacts, including loss of habitat, pollution, invasive species and over-exploitation. In addition, climate change, especially the consequences of global warming, can impact fish at all levels of biological organization from the individual to the population level, influencing both physiological and ecological processes in a variety of direct and indirect ways. As such, there is an urgent need to protect and conserve the huge genetic diversity offered by this diverse vertebrate group, not just as a source of genes for contemporary breeding and for protection against the consequences of climate change and disease, but also as part of our national heritage. While the cryopreservation of reproductive cells is a means of achieving these objectives, currently only fish sperm can be successfully frozen. Due to their large size, large yolk compartment, low membrane permeability and high chilling sensitivity, successful and reproducible protocols for the cryopreservation of fish oocytes and embryos still remains elusive. However, significant advances have been made in the cryopreservation of primordial germ cells as an alternative means of conserving both paternal and maternal genomes. Although more research needs to be carried out on how these cells can be optimally applied to emerging reproductive technologies, including transplantation techniques and surrogate broodstock technologies, the successful cryopreservation of fish germ cells, and the establishment of genetic resource banks, offers the possibility of both conserving and restoring threatened species. Further, current and future conservation efforts need to consider the impact of climate change in both in situ conservation and reintroduction efforts.In conclusion, it is anticipated that the successful cryopreservation of fish germplasm will result in a range of economic, ecological and societal benefits. In partnership with emerging assisted reproductive technologies, the successful cryopreservation of fish germplasm will lead to more efficient reproduction in aquaculture, assist selective breeding programmes, and be of crucial importance to future species conservation actions.

Development of molecular markers for zebrafish (Danio rerio) ovarian follicle growth assessment following in-vitro culture in cryopreservation studies

Development of in vitro culture protocol for early stage ovarian follicles of zebrafish is important since cryopreserved early stage ovarian follicles would need to be matured in vitro following cryopreservation before they can be fertilised. Development of molecular markers for zebrafish (Danio rerio) ovarian follicle growth assessment following in vitro culture of early stage zebrafish ovarian follicles in ovarian tissue fragments is reported here for the first time although some work has been reported for in vitro culture of isolated early stage zebrafish ovarian follicles. The main aim of the present study was to develop molecular markers in an optimised in vitro culture protocol for stage I and stage II zebrafish ovarian follicles in ovarian tissue fragments. The effect of concentration of the hormones human chorionic gonadotropin and follicle stimulating hormones, and additives such as Foetal Bovine Serum and Bovine Serum Albumin were studied. The results showed that early stage zebrafish ovarian fragments containing stage I and stage II follicles which are cultured in vitro for 24 h in 20% FBS and 100mIU/ml FSH in 90% L-15 medium at 28 °C can grow to the size of stage II and stage III ovarian follicles respectively. More importantly the follicle growth from stage I to stage II and from stage II to stage III were confirmed using molecular markers such as cyp19a1a (also known as P450aromA) and vtg1 genes respectively. However, no follicle growth was observed following cryopreservation and in vitro culture.

Viability assessment of primary growth oocytes following ovarian tissue vitrification of neotropical teleost pacu (Piaractus mesopotamicus)

Vitrification of ovarian tissue containing immature oocytes provides an important tool for protecting the endangered species and genetic diversity in aquatic species. Therefore, the main objective was to assess primary growth (PG) oocytes viability following ovarian tissue vitrification using histological analysis, two staining protocols (trypan blue or fluorescein diacetate combined with propidium iodide) and mitochondrial activity assay (MTT assay). In addition, oocyte histomorphometry was performed to evaluate the morphometric parameters after vitrification and the relationship with the occurrence of damage (nucleus and/or membrane) in PG oocytes. There was no significant difference among the vitrified oocytes using trypan blue dye or FDA + IP staining. Oocyte viability assessed using histological analysis showed that vitrification solution 2.0 M Me₂SO + 2.5 M etilenoglycol +0.5 M sucrose (VS3; 66.43 ± 4.68%) and 1.5 M methanol + 5.5 M Me₂SO + 0.5 M sucrose (VS5; 74.14 ± 3.71%) had the lowest viability rate. Similar results were observed in MTT assay where VS3 (1.63 ± 0.12) and VS5 (1.58 ± 0.09) had the lowest averages when compare with VS1 (2.39 ± 0.14), VS2 (1.78 ± 0.06) and VS4 (2.34 ± 0.19) (P = 0.0002). In membrane damage evaluation by histology, there was no difference among vitrified oocytes and control. However, the highest percentages of nucleus damage were observed in treatments VS3 (26.00 ± 5.55) and VS5 (26.00 ± 5.55). Oocyte diameter did not change after vitrification; however, nucleus diameter was significantly higher in control group (49.03 ± 1.07). Oocyte viability by histological analysis was positive-correlated to the occurrence of nucleus (r² = 0.78) and membrane (r² = 0.45) damage after vitrification/warming. The high viability of PG oocytes obtained after ovarian tissue vitrification of Piaractus mesopotamicus suggests that the protocol applied here might be used successfully in other teleost species for food production.

Cryobanking of aquatic species

This review is focused on the applications of genome cryobanking of aquatic species including freshwater and marine fish, as well as invertebrates. It also reviews the latest advances in cryobanking of model species, widely used by the scientific community worldwide, because of their applications in several fields. The state of the art of cryopreservation of different cellular types (sperm, oocytes, embryos, somatic cells and primordial germ cells or early spermatogonia) is discussed focusing on the advantages and disadvantages of each procedure according to different applications. A special review on the need of standardization of protocols has also been carried out. In summary, this comprehensive review provides information on the practical details of applications of genome cryobanking in a range of aquatic species worldwide, including the cryobanks established in Europe, USA, Brazil, Australia and New Zealand, the species and type of cells that constitute these banks and the utilization of the samples preserved.

STATEMENT OF RELEVANCE

This review compiles the last advances on germplasm cryobanking of freshwater and marine fish species and invertebrates, with high value for commercial aquaculture or conservation. It is reviewed the most promising cryopreservation protocols for different cell types, embryos and larvae that could be applied in programs for genetic improvement, broodstock management or conservation of stocks to guarantee culture production.

Development of Cryopreservation Techniques for Gorgonian (Junceella juncea) Oocytes through Vitrification

Gorgonian corals are slowly declining due to human interaction and environmental impacts. Cryopreservation of gorgonian corals is an ex-situ method of conservation, ensuring future reproduction. The present study assessed the vitrification properties of cryoprotectant (CPT) mixtures using the cryotop, cryoloop and open pulled straw (OPS) cryopereservation methods prior to experimentation on gorgonian (Junceella juncea) oocytes. Investigations of the equilibration and vitrification solutions’ (ES and VS) effect on oocytes throughout different incubation periods were conducted. The cryotop method was found to be the most successful in ensuring vitrification. The most favourable VS was composed of propylene glycol (PG), ethylene glycol (EG) and methanol with concentrations of 3.5M, 1.5M and 2M respectively. Experiments were performed using the cryotop method to cryopreserve Junceella juncea oocytes using VS2, the solution had the least impact on oocytes at 5°C rather than at 26°C. The success of the vitrification procedures was determined by adenosine triphosphate (ATP) levels in cooled-thaw oocytes and the highest viability obtained from the present study was 76.6 ± 6.2%. This study provides information regarding gorgonian corals’ tolerance and viability throughout vitrification to further advance the vitrification protocol on whip corals.

Mathematical model formulation and validation of water and solute transport in whole hamster pancreatic islets

Optimization of cryopreservation protocols for cells and tissues requires accurate models of heat and mass transport. Model selection often depends on the configuration of the tissue. Here, a mathematical and conceptual model of water and solute transport for whole hamster pancreatic islets has been developed and experimentally validated incorporating fundamental biophysical data from previous studies on individual hamster islet cells while retaining whole-islet structural information. It describes coupled transport of water and solutes through the islet by three methods: intracellularly, intercellularly, and in combination. In particular we use domain decomposition techniques to couple a transmembrane flux model with an interstitial mass transfer model. The only significant undetermined variable is the cellular surface area which is in contact with the intercellularly transported solutes, Ais. The model was validated and Ais determined using a 3×3 factorial experimental design blocked for experimental day. Whole islet physical experiments were compared with model predictions at three temperatures, three perfusing solutions, and three islet size groups. A mean of 4.4 islets were compared at each of the 27 experimental conditions and found to correlate with a coefficient of determination of 0.87±0.06 (mean ± SD). Only the treatment variable of perfusing solution was found to be significant (p<0.05). We have devised a model that retains much of the intrinsic geometric configuration of the system, and thus fewer laboratory experiments are needed to determine model parameters and thus to develop new optimized cryopreservation protocols. Additionally, extensions to ovarian follicles and other concentric tissue structures may be made.

Degradation of mitochondrial DNA in cryoprotectant-treated hard coral (Echinopora spp.) oocytes

A critical step for successful cryopreservation is to determine the optimal cryoprotectant treatment that can provide protective effects against cryoinjury during freezing and with minimal toxicity. Most cryoprotectants have chemical and osmotic effects when used at high concentrations. Cryoprotectants can damage coral mitochondrial distributions and membrane potentials, which results in reduced ATP production. As mitochondrial DNA (mtDNA) encodes for components of the electron transport chain (ETC) and plays a critical role in ATP synthesis capacity, we determined the effects of cryoprotectants on mtDNA in hard coral (Echinopora spp.) oocytes using quantitative real-time PCR. Our results showed that an insult from a cryoprotectant may be compensated for by the genetic defense mechanisms of these cells. Methanol was found to have the least effect on coral oocytes with regard to their energy status. A single oocyte without cryoprotectant treatment produced an average of 4,220,645 ± 169,990 mtDNA copies, which was greater than that in mammals. However, relatively lower mtDNA copy numbers (<2,000,000) were observed when oocytes were treated with dimethyl sulfoxide (DMSO), propylene glycol (PG), ethylene glycol (EG), or glycerol at a concentration of 3 M for 20 min. These results provide direct evidence that hard coral (Echinopora spp.) oocytes are extremely susceptible to cryoprotectants and support the concerns with regard to the adverse effects of cryoprotectants.

Generation of functional eggs and sperm from cryopreserved whole testes

The conservation of endangered fish is of critical importance. Cryobanking could provide an effective backup measure for use in conjunction with the conservation of natural populations; however, methodology for cryopreservation of fish eggs and embryos has not yet been developed. The present study established a methodology capable of deriving functional eggs and sperm from frozen type A spermatogonia (ASGs). Whole testes taken from rainbow trout were slowly frozen in a cryomedium, and the viability of ASGs within these testes did not decrease over a 728-d freezing period. Frozen-thawed ASGs that were intraperitoneally transplanted into sterile triploid hatchlings migrated toward, and were incorporated into, recipient genital ridges. Transplantability of ASGs did not decrease after as much as 939 d of cryopreservation. Nearly half of triploid recipients produced functional eggs or sperm derived from the frozen ASGs and displayed high fecundity. Fertilization of resultant gametes resulted in the successful production of normal, frozen ASG-derived offspring. Feasibility and simplicity of this methodology will call for an immediate application for real conservation of endangered wild salmonids.

Use of an adenosine triphosphate assay, and simultaneous staining with fluorescein diacetate and propidium iodide, to evaluate the effects of cryoprotectants on hard coral (Echinopora spp.) oocytes

The objective was to examine the effects of cryoprotectants on oocytes of hard corals (Echinopora spp.) to obtain basic knowledge for cryopreservation procedures. Oocytes were exposed to various concentrations of cryoprotectants (0.25 to 5.0M) for 20 min at room temperature (25 degrees C). Two tests were used to assess ovarian follicle viability: fluorescein diacetate (FDA)+propidium iodide (PI) staining, and adenosine triphosphate (ATP) assay. Both FDA+PI staining and ATP assay indicated that cryoprotectant toxicity to oocytes increased in the order methanol, dimethyl sulfoxide (DMSO), propylene glycol (PG), and ethylene glycol (EG). The no observed effect concentrations for Echinopora spp. oocytes were 1.0, 0.5, 0.25, and 0.25 M for methanol, DMSO, PG, and EG, respectively, when assessed with FDA+PI. The ATP assay was more sensitive than FDA+PI staining (P<0.05). Oocyte viability after 1.0M methanol, DMSO, EG, or PG treatment for 20 min at room temperature assessed with FDA+PI tests and ATP assay were 88.9+/-3.1% and 72.2+/-4.4%, 66.2+/-5.0% and 23.2+/-4.9%, 58.9+/-5.4% and 1.1+/-0.7%, and 49.1+/-5.1% and 0.9+/-0.5%, respectively. We inferred that the ATP assay was a valuable measure of cellular injury after cryoprotectant incubation. The results of this study provided a basis for development of protocols to cryopreserve coral oocytes.