Long-term survival has been one of the most studied of the extraordinary physiological characteristics of cryptobiosis in micrometazoans such as nematodes, tardigrades and rotifers. In the available studies of long-term survival of micrometazoans, instances of survival have been the primary observation, and recovery conditions of animals or subsequent reproduction are generally not reported. We therefore documented recovery conditions and reproduction immediately following revival of tardigrades retrieved from a frozen moss sample collected in Antarctica in 1983 and stored at -20°C for 30.5 years. We recorded recovery of two individuals and development of a separate egg of the Antarctic tardigrade, Acutuncus antarcticus, providing the longest records of survival for tardigrades as animals or eggs. One of the two resuscitated individuals and the hatchling successfully reproduced repeatedly after their recovery from long-term cryptobiosis. This considerable extension of the known length of long-term survival of tardigrades recorded in our study is interpreted as being associated with the minimum oxidative damage likely to have resulted from storage under stable frozen conditions. The long recovery times of the revived tardigrades observed is suggestive of the requirement for repair of damage accrued over 30 years of cryptobiosis. Further more detailed studies will improve understanding of mechanisms and conditions underlying the long-term survival of cryptobiotic organisms.
The holding time (HT) is the period during which an ejaculate, either in a raw or diluted state, is held at 17°C before further processing for cold-storage. In boars, the HT positively influences select sperm quality parameters of semen cooled from 15 to 5°C, a range in temperature during which plasma membrane remodeling occurs. Objective insight into the effect of HT on plasma membrane organization remains unknown. Therefore, the present work sought to elucidate if HT contributes to minimizing alterations in boar sperm plasma membrane fluidity at the initial step of the cooling process in a cryopreservation practice (holding at 5°C) and in relation with select sperm quality parameters. Nineteen ejaculates from five boars were collected and processed according to different treatments: T1) Fresh diluted semen, 0 h at 17°C; T2) Fresh diluted semen, 24 h at 17°C (HT); T3) Sperm from T1 in a lactose-egg yolk (LEY) extender, 3 h at 5°C; T4) Sperm from T2 in LEY, 3 h at 5°C; T5) Sperm from T1 in LEY, 24 h at 5°C; T6) Sperm from T2 in LEY, 24 h at 5°C. Sperm motility was assessed using CASA, and sperm plasma membrane integrity and fluidity were evaluated by flow cytometry with dual labeling (M540/YO-PRO®-1). Results demonstrated that the lack of exposure to a HT (T5) results in reduced sample motility compared to those having a HT (T6), with sperm exposed to HT exhibiting less plasma membrane fluidity. Collectively, these results provide empirical evidence that incorporation of a HT in semen processing protects boar sperm against cold injury through maintenance of lipid architecture of the plasma membrane.
Slush nitrogen (SN) is used to avoid the Leidenfrost effect, which is problematic when using liquid nitrogen (LN). Slush nitrogen’s usefulness has been demonstrated by its requirement for the successful cryopreservation of insect embryos. To convert LN to SN, typically, the pressure above a Dewar of LN is reduced, using a vacuum pump in a sealed system until conversion occurs. It has been observed that LN from a fresh tank will readily produce SN; however, repeated use of the same LN results in the inability to form SN in subsequent trials. The current experiments were designed to identify the cause of this phenomenon. The hypothesis is that gaseous oxygen from the surrounding, ambient air condenses and mixes with the LN to form a mixture with a lower freezing point and; therefore, prevents the formation of SN. The hypothesis was tested and found to be true.
This study dealt with the development of cryopreservation protocol for Nandus nandus, which entailed a number of experiments. Sperm was collected by sacrificing males. The collected sperm was suspended in extenders. Activation of sperm motility was evaluated in different osmolalities of NaCl. Motility of sperm decreased as the osmolality of the extender increased and was completely inhibited at almost 319mOsmol/kg. To evaluate the toxicity of cryoprotectant, sperm was incubated with DMSO, methanol and ethanol at 5%, 10% and 15% concentrations, respectively, for 5-35min. Five and ten percent of cryoprotectants produced better motility during 5 and 10min incubation. Sperm incubated with 15% cryoprotectant seemed to be toxic and this concentration was excluded in the subsequent trials. Three extenders, namely, Alsever’s solution, egg-yolk citrate and urea egg-yolk and three cryoprotectants, DMSO, methanol and ethanol were employed to preserve the sperm. Alsever’s solution with 10% DMSO showed best performance producing 90.0±1.8% and 75.0±2.5% equilibration and post-thaw motility followed by that of 82.5±4.2% and 62.5±5.5% with Alsever’s solution plus methanol, respectively. Between two diluents, sperm preserved with Alsever’s solution plus DMSO produced highest fertilization (76.7±3.3%) and hatching (43.8±7.9%) while fresh sperm yielded 83.3±6.7% and 64.0±10.4% fertilization and hatching, respectively. The protocol developed through the study can be applied for long-term conservation of genetic materials of the endangered fish N. nandus and the cryopreserved sperm can be used in artificial breeding for generating new individuals.
Factors limiting the hypothermic preservation of hepatocytes on gelatin gels at 10°C were investigated. Following 4days of preservation, uniform morphological changes started to appear. The cells exhibited halos that increased in size. The particulate matter of the cell was confined to the central region. Cell viability was reduced from day 7 onwards. Neither fresh media changes nor the use of conditions to minimise free radical formation improved cell survival. However, haloing was decreased by short term temperature elevation to 37°C (3h), to reactivate the cells, and could be prevented completely by a stepwise increase in the sucrose concentration of the medium. The addition of sucrose in increments of 50mM, at four day intervals, was found to inhibit morphological change. Prevention of haloing enabled the cells to be preserved for at least two weeks. The preserved cells attached to supports and spread as if freshly isolated. The procedure allows extended preservation of cells at non-freezing temperatures.
The present study aimed to evaluate the effect of methyl-β-cyclodextrin (MβCD) as a cholesterol loader to change oocyte plasma membrane and increase its tolerance toward cryopreservation. The first and second experiments were conducted to investigate if MβCD could improve nuclear and cytoplasmic maturation after oocyte exposure to cold stress for 10 or 30min, respectively. No differences (P>0.05) in either experiment in the metaphase II (MII) rate of oocytes exposed to MβCD and cold stress; but these oocytes presented lower maturation rates than control groups. In the second experiment, a lower percentage of oocytes showed degenerated chromatin (P<0.05) after exposure to 2mg/mL of MβCD compared to the group exposed to 0mg/mL. However, no differences among treatments were observed in cytoplasmic maturation. Groups exposed to cold stress demonstrated a lower (P<0.05) capacity for embryonic development compared to the control groups. In the third experiment immature oocytes were exposed to MβCD and then, vitrified (cryotop). After warming, we observed that the ability to reach MII and chromatin degeneration were altered (P<0.05) by MβCD. The blastocysts rate (P<0.05) on D7 was higher in the 2mg/mLMβCD group, but an identical finding was not observed on D8 (P>0.05). Chromatin degeneration was higher in the vitrification groups. We conclude that MβCD improved nuclear maturation by reducing oocyte degeneration after cold stress or vitrification; however, more studies are required to clarify the usefulness of MβCD use in oocyte cryopreservation.
We aimed in the first part of our work to study the effect of cryopreservation on the human sperm DNA integrity and the activation of caspase 3, the main apoptosis indicator. In the second part, we were interested in testing the effect of quercetin, as an antioxidant, in preventing sperm damage during the freeze-thawing process. Seventeen semen samples were obtained from 17 men recruited for infertility investigations. Liquefied sperm was cryopreserved using spermfreeze®. Nine of the used samples were divided into two aliquots; the first one was cryopreserved with spermfreeze only (control) and the second one was cryopreserved with spermfreeze supplemented with quercetin to a final concentration of 50μM. Sperm motility and viability were assessed according to WHO criteria. We used TUNEL assay and the Oxy DNA assay to assess sperm DNA integrity. Activated caspase 3 levels were measured in spermatozoa using fluorescein-labeled inhibitor of caspase (FLICA). Cryopreservation led to a significant increase in sperm DNA fragmentation, DNA oxidation and caspase 3 activation (p<0.01). Supplementation of the cryopreservation medium with quercetrin induced a significant improvement in post thaw sperm parameters, compared to those of control, regarding sperm motility (p=0.007), viability (p=0.008) and DNA integrity (p=0.02); however, it had no effect on caspase 3 activation (p=0.3). We conclude that oxidative stress plays a major role in inducing sperm cryodamage but implication of apoptosis in this impairment requires further investigations. Quercetin could have protective effect during cryopreservation but further research is needed to confirm this effect.
The intracellular ice formation (IIF) behavior of Haliotis diversicolor (small abalone) eggs is investigated in this study, in relation to controlling the cooling rate and the concentration of dimethyl sulfoxide (DMSO). The IIF phenomena are monitored under a self-developed thermoelectric cooling (TEC) cryomicroscope system which can achieve accurate temperature control without the use of liquid nitrogen. The accuracy of the isothermal and ramp control is within ±0.5°C. The IIF results indicate that the IIF of small abalone eggs is well suppressed at cooling rates of 1.5, 3, 7 and 12°C/min with 2.0, 2.5, 3.0 and 4.0 M DMSO in sea water. As 2.0 M DMSO in sea water is the minimum concentration that has sufficient IIF suppression, it is selected as the suspension solution for the cryopreservation of small abalone eggs in order to consider the solution’s toxicity effect. Moreover, IIF characteristics of the cumulative probability of IIF temperature distribution are shown to be well fitted by the Weibull probabilistic distribution. According to our IIF results and the Weibull distribution parameters, we conclude that cooling at 1.5°C/min from 20 to -50°C with 2.0 M DMSO in sea water is more feasible than other combinations of cooling rates and DMSO concentrations in our experiments. Applying this protocol and observing the subsequent osmotic activity, 48.8% of small abalone eggs are osmotically active after thawing. In addition, the higher the cooling rate, the less chance of osmotically active eggs. A separate fertility test experiment, with a cryopreservation protocol of 1.5°C/min cooling rate and 2.0 M DMSO in sea water, achieves a hatching rate of 23.7%. This study is the first to characterize the IIF behavior of small abalone eggs in regard to the cooling rate and the DMSO concentration. The Weibull probabilistic model fitting in this study is an approach that can be applied by other researchers for effective cryopreservation variability estimation and analysis.
The aims of this study were to determine the stability of Podoviridae coliphage CA933P during lyophilization and storage in different media, and to establish similarities between the results obtained and those expected through mechanisms described for proteins stabilization during freeze-drying. PBS and SM buffer were assayed as lyophilization media. The effect of inorganic salts concentration as well as the addition of disaccharides on phage stability during freeze-drying and storage was also studied. The addition of low sucrose concentration (0.1 mol l(-1)) to SM buffer stabilized phage during freezing and drying steps of the lyophilization process, but higher sugar concentrations were detrimental to phage stability during freeze-drying. Sucrose stabilized phage during storage for at least 120 days. The lyoprotective effect of low concentrations of disaccharides during the drying step of the lyophilization of proteins as well as the stabilization of the freeze-dried product in time correlated with the results obtained for phage CA933P.
Lanan (1971) working on oyster sperm and Asahina and Takahashi (1977) on sea urchin sperm and embryos can be considered the pioneers in marine invertebrate cryopreservation. It was from the 90s onwards when the number of references began to increase and diversify not only the range of species of interest but also in the cell types and fields of application. This work is an attempt to summarize the research published on marine invertebrates in a wide variety of journals regarding the development and the applications of marine invertebrate cryopreservation protocols. This paper reviews factors and trends, the obtained results, remaining technical constraints and the immediate future of marine invertebrate cryopreservation.