In-situ investigation of supercooling behaviour during high-pressure shift freezing of pure water and sucrose solution

Supercooling is a main controllable factor for the fundamental understanding the high-pressure shift freezing (HPSF). In the study, a self-developed device based on the diamond anvil cell (DAC) and confocal Raman microscopy was utilized to realize an in-situ investigation of supercooling behaviour during HPSF of the pure water and sucrose solution. The spectra were used to determine the freezing point which is shown as a spectral phase marker (SD). The hydrogen bond strengths of water and sucrose solution under supercooling states were estimated by peak position and peak area ratio of sub-peaks. The results showed that the OH stretching bands had redshift under supercooling states. Moreover, the addition of sucrose molecules could strengthen the hydrogen bonding strength of water molecules under supercooling states. Thus, the DAC combined with Raman spectroscopy could be considered a novel strategy for a deep understanding of the supercooling behaviour during HPSF.

Effect of high pressure pretreatment on the inhibition of ice nucleation and biochemical changes in pork loins during supercooling preservation

In this study, the effect of high pressure (HP) pretreatment on the stability of pork loins during supercooling (SC) preservation was investigated, and the freshness and postmortem metabolism of pork loins preserved by SC was evaluated. Based on the differential scanning calorimetry (DSC), the peak enthalpies of 200 MPa treatment were lower than those of 50 MPa treatment (P < 0.05). For the nuclear magnetic resonance (NMR) relaxometry, extramyofibrillar water in pork loins was decreased with increasing intermyofibrillar water at >100 MPa (P < 0.05). Compared to unpressurized control all HP treatment had less α-helix structure while random coil was dominated from the Fourier transform infrared (FTIR) spectroscopy (P < 0.05). A 200 MPa was selected to estimate the relationship between HP pretreatment and stability of SC preservation of pork loins. The HP-treated pork loins showed high stability during SC preservation under the relatively low temperature algorithm. Compared to fresh control, HP pretreatment caused physicochemical changes of pork loins which did not recover even after 2 weeks of preservation. Nevertheless, HP followed by SC preservation was able to reduce property changes better than pork loins preserved by normal refrigeration. According to the analyses of transmission electron microscopy (TEM), the HP pretreatment influenced the postmortem biochemical metabolism of pork loins, however, it did not affect the freshness and quality parameters of pork loins due to the subsequently applied low preservation temperature of SC. Therefore, this study demonstrated that moderate HP pretreatment was a potential pretreatment for SC preservation of pork loins.

Identifying Ice-Binding Proteins in Nature

Organisms inhabiting freezing terrestrial, polar, and alpine environments survive because they have evolved adaptations to tolerate sub-freezing temperatures. Among these adaptations are ice-binding proteins (IBPs) which in the case of fishes and some insects have antifreeze properties which allow them to avoid freezing even at their lowest environmental temperatures. Other organisms, including some insects, microorganisms, and plants, tolerate freezing and also contain IBPs. Unlike fish and insects, their antifreeze properties (hysteresis) are minimal, but most are potent ice recrystallization inhibitors (IRIs). Microbes secrete IBPs into their immediate environment where they are thought to modify ice growth in a way that ensures a liquidous habitat in the ice and also reduces ice recrystallization. With plants, IBPs are found in the small amount of apoplastic fluid associated with the extracellular spaces and show a weak hysteresis but are potent IRIs.Techniques are described for drawing blood and hemolymph from fish and insects, respectively, in order to determine whether there is a hysteresis present (separation of the freezing and melting points) indicative of an antifreeze protein. For microbes, which secrete very small amounts of IBPs into their environment, a technique is described where their spent growth media causes the pitting of the basal plane of an ice crystal at a temperature slightly below the media freezing point. In plants, IBPs are isolated from the apoplastic fluids of the leaves by vacuum infiltration of a fluid into the extracellular spaces and then recovering the fluid by centrifugation.The pitting of the basal plane again can be used to verify the presence of IBPs in the concentrated apoplastic fluid.The techniques describe how to collect fluids from a variety of organisms to determine if IBPs are present using nanoliter osmometry or using the ice basal plane pitting technique.

Supercooling: A Promising Technique for Prolonged Organ Preservation in Solid Organ Transplantation, and Early Perspectives in Vascularized Composite Allografts

Ex-vivo preservation of transplanted organs is undergoing spectacular advances. Machine perfusion is now used in common practice for abdominal and thoracic organ transportation and preservation, and early results are in favor of substantially improved outcomes. It is based on decreasing ischemia-reperfusion phenomena by providing physiological or sub-physiological conditions until transplantation. Alternatively, supercooling techniques involving static preservation at negative temperatures while avoiding ice formation have shown encouraging results in solid organs. Here, the rationale is to decrease the organ's metabolism and need for oxygen and nutrients, allowing for extended preservation durations. The aim of this work is to review all advances of supercooling in transplantation, browsing the literature for each organ. A specific objective was also to study the initial evidence, the prospects, and potential applications of supercooling preservation in Vascularized Composite Allotransplantation (VCA). This complex entity needs a substantial effort to improve long-term outcomes, marked by chronic rejection. Improving preservation techniques is critical to ensure the favorable evolution of VCAs, and supercooling techniques could greatly participate in these advances.

Osmotic and metabolic responses to cold acclimation and acute cold challenge in a freeze avoidant lizard, Podarcis siculus

Ectotherms survive exposure to subzero temperatures through freeze tolerance or freeze avoidance. Among vertebrate ectotherms, glucose is commonly used as a cryoprotectant in freeze tolerant strategies and as an osmolyte in freeze avoidant strategies, while also functioning as a metabolic substrate. Whereas some lizard species are capable of both freeze tolerance and freeze avoidance, Podarcis siculus is limited to freeze avoidance through supercooling. We hypothesized that, even in a freeze-avoidant species such as P. siculus, plasma glucose would accumulate with cold acclimation and would increase in response to acute exposure to subzero temperatures. To investigate this, we tested whether plasma glucose concentration and osmolality would increase in response to a subzero cold challenge before and after cold acclimation. In addition, we examined the relationship between metabolic rate, cold acclimation, and glucose by measuring metabolic rate during the cold challenge trials. We found that plasma glucose increased during the cold challenge trials, and that the increase was more pronounced after cold acclimation. However, baseline plasma glucose decreased throughout cold acclimation. Interestingly, total plasma osmolality did not change, and the increase in glucose only slightly altered freezing point depression. Metabolic rate during the cold challenge decreased after cold acclimation, and changes in respiratory exchange ratio suggest an increased relative use of carbohydrates. Overall, our findings demonstrate an important role for glucose in the response of P. siculus to an acute cold challenge, thus adding evidence for glucose as an important molecule for overwintering ectotherms that use freeze avoidant strategies.

Chilling injury in human kidney tubule cells after subzero storage is not mitigated by antifreeze protein addition

By preventing freezing, antifreeze proteins (AFPs) can permit cells and organs to be stored at subzero temperatures. As metabolic rates decrease with decreasing temperature, subzero static cold storage (SZ-SCS) could provide more time for tissue matching and potentially lead to fewer discarded organs. Human kidneys are generally stored for under 24 h and the tubule epithelium is known to be particularly sensitive to static cold storage (SCS). Here, telomerase-immortalized proximal-tubule epithelial cells from humans, which closely resemble their progenitors, were used as a proxy to assess the potential benefit of SZ-SCS for kidneys. The effects of hyperactive AFPs from a beetle and Cryostasis Storage Solution were compared to University of Wisconsin Solution at standard SCS temperatures (4 °C) and at -6 °C for up to six days. Although the AFPs helped guard against freezing, lower storage temperatures under these conditions were not beneficial. Compared to cells at 4 °C, those stored at -6 °C showed decreased viability as well as increased lactate dehydrogenase release and apoptosis. This suggests that this kidney cell type might be prone to chilling injury and that the addition of AFPs to enable SZ-SCS may not be effective for increasing storage times.

Effect of supercooling on storage ability of different beef cuts in comparison to traditional storage methods

The effect of supercooling on different beef cuts was evaluated compared with traditional storage methods. Beef striploins and topsides were stored under freezing, refrigeration, or supercooling conditions and their storage ability and quality were analyzed during 28 days of storage. The total aerobic bacteria, pH, and volatile basic nitrogen were higher in the supercooled beef than in the frozen beef, but lower than in the refrigerated one, regardless of the type of cut. In addition, the discoloration of frozen and supercooled beef was slower than that of refrigerated beef. The results in storage stability and color indicate that supercooling can prolong the shelf-life of beef compared to refrigeration due to its temperature characteristic. In addition, supercooling minimized the problems of freezing and refrigeration, including ice crystal formation and enzyme-based deterioration; therefore, the qualities of topside and striploin were less affected. Collectively, these results indicate that supercooling can be a beneficial storage method for extending the shelf-life of different beef cuts.

Crystallization of emulsified anhydrous milk fat: The role of confinement and of minor compounds. A DSC study

We examined the crystallization and melting of anhydrous milk fat (AMF)-in-water emulsions stabilized by sodium caseinate. Various additives at low concentrations (<5 wt%), differing in their hydrocarbon chain length (propionic vs. palmitic acid), unsaturation (palmitic vs. oleic acid), and esterification state (palmitic acid vs. tripalmitin) were used to modulate AMF crystallization kinetics. Three emulsions with different average droplet diameters were cooled down from 60 °C to 4 °C. Fat crystallization was followed by DSC under dynamic (cooling) and static (isothermal) conditions. Propionic acid did not have any noticeable effect. Oleic acid favored supercooling and the formation of unstable polymorphs at short times but its impact faded after 48 h of isothermal storage. The impact of palmitic acid was related to its amphiphilic properties and vanished after 48 h. Tripalmitin influenced crystallization via volume effects that were persistent. It formed mixed crystals which extended the melting range of AMF.

Effect of static magnetic field extended supercooling preservation on beef quality

Supercooling can preserve beef without freezing damage, whereas maintaining the supercooled state is difficult. An innovative method of static magnetic field extended supercooling (SM-ES) was proposed to maintain the non-frozen state of beef. Effect of SM-ES (-4 °C + SMF) compared with refrigerated (4 °C), slow-frozen (-4 °C) and frozen (-18 °C) treatment on beef quality was investigated. Results demonstrated that SM-ES successfully preserved beef at -4 °C without ice nucleation for 14 days. The SEM images revealed that the microstructure of slow-frozen/frozen samples was damaged due to crystallizing, while the ice nucleation was not observed in SM-ES treated beef. Compared with refrigerated, slow-frozen and frozen treatment, the drip loss of SM-ES decreased by 21.9%, 47.8% and 30.9%, respectively. The lipid oxidation degree of beef decreased following SM-ES treatment. SM-ES treatment extended the shelf-life of beef for more than 6 days compared with refrigeration while prevented its crystallizing.

Responses of the Plant Cell Wall to Sub-Zero Temperatures: A Brief Update

Our general understanding of plant responses to sub-zero temperatures focuses on mechanisms that mitigate stress to the plasma membrane. The plant cell wall receives comparatively less attention, and questions surrounding its role in mitigating freezing injury remain unresolved. Despite recent molecular discoveries that provide insight into acclimation responses, the goal of reducing freezing injury in herbaceous and woody crops remains elusive. This is likely due to the complexity associated with adaptations to low temperatures. Understanding how leaf cell walls of herbaceous annuals promote tissue tolerance to ice does not necessarily lead to understanding how meristematic tissues are protected from freezing by tissue-level barriers formed by cell walls in overwintering tree buds. In this mini-review, we provide an overview of biological ice nucleation and explain how plants control the spatiotemporal location of ice formation. We discuss how sugars and pectin side chains alleviate adhesive injury that develops at sub-zero temperatures between the matrix polysaccharides and ice. The importance of site-specific cell-wall elasticity to promote tissue expansion for ice accommodation and control of porosity to impede ice growth and promote supercooling will be presented. How specific cold-induced proteins modify plant cell walls to mitigate freezing injury will also be discussed. The opinions presented in this report emphasize the importance of a plant's developmental physiology when characterizing mechanisms of freezing survival.

Towards increasing stallion sperm longevity by storage at subzero temperatures in the absence of ice

The aim of cell preservation technologies is to slow down damaging reactions by lowering the storage temperature. Upon dilution in a stabilizing extender, stallion sperm can be stored at refrigerator temperatures for several days. Cryopreservation allows storage for decades, but freezing and thawing cause damage and viability losses. It is assumed that by storing cells at subzero temperatures in a non-frozen supercooled state, the damaging effects of ice formation can be avoided. In this study, we have investigated if stallion sperm can be stored at -10°C in the absence of ice, and compared viability during supercooled storage with that during storage at 5°C. We found that addition of 2% Ficoll-400 to buffered saline and covering with mineral oil depressed the sample freezing point and inhibited surface-catalyzed nucleation. This allowed storage in a supercooled state at -10°C for up to 7 days. Supplementing specimens with sperm, however, increased the incidence of sample freezing. Nonetheless, with 50×10⁶ sperm mL^-1, about 40% of the samples turned out to be non-frozen. Adding 100 mM sucrose was found to preserve sperm membrane intactness during supercooled storage, although this resulted in lower percentages as found with refrigerated storage. Sperm motility appeared to be lost during supercooled storage but could be partly restored by substituting buffered saline with a milk-based extender as base medium. Percentages of membrane intact sperm, however, were found to be lower. Supercooled storage holds promise for semen preservation, but further optimization of the storage solution is required to preserve sperm motility.

Changes in the quality of pork loin after short-term (ten-day) storage in a supercooling refrigerator

The study aimed to evaluate pork loin quality after short-term (ten-day) storage in a supercooling refrigerator. Pork loin samples were stored for 10 days in a traditional refrigerator (control) and a commercially available supercooling refrigerator (SC). Pork quality measurements included meat pH, meat color, water holding capacity (drip loss and cooking loss), tenderness (hardness), and a sensory evaluation. Temperature changes of 0.45 ± 0.2°C and 0.02 ± 0.25°C occurred in the control and the SC, respectively, during 10 days of storage. The temperature in the SC chamber did not remain below freezing point, failing to meet expectations. Regarding the pork quality measurements, only the drip losses in the control and the SC were significantly different (4.45% vs. 2.59%, p < 0.01) after 10 days of storage. There were no significant differences between the two types of refrigerator in terms of the other measurements. Additionally, the overall acceptability of the pork loin did not vary significantly between the control and the SC when the sensory evaluation was performed. Therefore, a commercial SC could prove beneficial in terms of water holding capacity during the short-term storage of meat. Further research should be performed to evaluate quality changes that occur during long-term storage of meat in SC s and evaluate a wide range of meat, such as beef and chicken.

Freezing resistance and behavior of winter buds and canes of wine grapes cultivated in northern Japan

In high-latitude regions, the cold hardiness of buds and canes of grapevine is important for budburst time and yield in the next season. The freezing resistance of buds and canes sampled from six wine grapes currently cultivated in Hokkaido, Japan, all of them grown from autumn to winter, was investigated. A significant difference between the cultivars in their freezing resistance was detected in the buds harvested in winter. In addition, outstanding differences in the lower temperature exotherms (LTE) related to the supercooling ability of tissue cells happened in the winter buds, and there is a close relationship between freezing resistance and LTE detected in the winter buds. This suggests that the supercooling ability of tissue cells in winter buds is strongly related to the freezing resistance. However, detailed electron microscopy exposed that the differences in freezing resistance among cultivars appeared in freezing behavior of leaf primordium rather than apical meristem. This indicated that as the water mobility from the bud apical meristem to the spaces around the cane phloem progressed, the slightly dehydrated cells improved the supercooling ability and increased the freezing resistance.

Factors contributing to ice nucleation and sequential freezing of leaves in wheat

Anatomical, metabolic and microbial factors were identified that contribute to sequential freezing in wheat leaves and likely contribute to supercooling in the youngest leaves and potentially meristematic regions. Infrared thermography (IR) has been used to observe wheat leaves freezing independently and in an age-related sequence with older leaves freezing first. To determine mechanisms that might explain this sequence of freezing several analytical approaches were used: (1) The size of xylem vessels, in proximity to where freezing initiated, was measured to see if capillary freezing point depression explained sequential freezing. The sequence of freezing in the four youngest leaves was correlated, with the largest vessels freezing first. (2) Carbohydrate and amino acids were analyzed to determine if solute concentrations as well as interactions with membranes explained the freezing sequence. Sucrose was highly correlated to the freezing sequence for all leaves suggesting a prominent role for this sugar as compared to other simple sugars and fructans. Among individual free amino acids proline and serine were correlated to the freezing sequence, with younger leaves having the highest concentrations. (3) Microflora within and on leaf surfaces were determined to measure potential freezing initiation. Levels of bacteria and fungi were correlated to the freezing sequence for all leaves, and species or genera associated with high ice nucleation activity were absent in younger leaves. Moisture content and transcript expression of ice binding proteins were also measured. As expected, our results show that no single mechanism explains the freezing sequence observed via infrared analyses. While these multiple mechanisms are operative at different levels according to the leaf age, they seem to converge when it comes to the protection of vital meristematic tissues. This provides potential phenotypic characters that could be used by breeders to develop more winter-hardy genotypes.

Cryo-scanning electron microscopy reveals that supercooling of overwintering buds of freezing-resistant interspecific hybrid grape 'Yamasachi' is accompanied by partial dehydration

Dormant compound buds of grapevines adapt to subfreezing temperatures through a freezing avoidance mechanism. One still-unclear question, however, is whether supercooled water in primordial cells of dormant grape buds are partially dehydrated under subfreezing temperatures. In this study, we used differential thermal analysis (DTA) and cryo-scanning electron microscopy (cryo-SEM) to look for partial dehydration of primordial cells of the freezing-resistant interspecific hybrid cultivar 'Yamasachi'. According to DTA, the freezing temperature of supercooled water in primary buds was not significantly affected by cooling rates between 2 and 5 °C/h; however, maintaining the bud temperature at -15 °C for 12 h followed by cooling at a rate of 5 °C/h depressed the freezing temperature. As revealed by cryo-SEM observation, many wrinkles were present on inner surfaces of walls and outer surfaces of plasma membranes of leaf primordial cells in dormant buds frozen to -15 °C. These results suggest the existence of partial dehydration in dormant-bud primordial cells under subfreezing temperatures. The apparent absence of extracellular ice crystals in bud primordial tissues under subfreezing temperatures suggests that Yamasachi dormant buds adapt to subfreezing temperatures by extraorgan freezing. When we coated primary buds with silicone oil to inhibit freeze dehydration of primordial cells, the freezing temperature of buds was slightly but significantly increased. This result suggests that the partial dehydration of cells promotes bud supercooling capability and has an important role in the freezing adaptation mechanism of grapevines.

Characterization of Ice-Binding Proteins from Sea-Ice Microalgae

Several species of polar microalgae are able to live and thrive in the extreme environment found within sea ice, where ice crystals may reduce the organisms' living space and cause mechanical damage to the cells. Among the strategies adopted by these organisms to cope with the harsh conditions in their environment, ice-binding proteins (IBPs) seem to play a key role and possibly contribute to the success of microalgae in sea ice. Indeed, IBPs from microalgae predominantly belong to the so-called "DUF 3494-IBP" family, which today represents the most widespread IBP family. Since IBPs have the ability to control ice crystal growth, their mechanism of function is of interest for many potential applications. Here, we describe methods for a classical determination of the IBP activity (thermal hysteresis, recrystallization inhibition) and further methods for protein activity characterization (ice pitting assay, determination of the nucleating temperature).

[Advances in supercooling liver preservation]

Liver transplantation is currently the only effective treatment for end-stage liver disease. The preservation of donor liver before transplantation is important. But both traditional static cold storage and machine perfusion are limited by the preservation time, so that the allotment space of donor liver is limited, which inevitably leads to the abandonment of part of donor liver.At present, to find a preservation technology that not only guarantees the quality of donor liver but also has a longer effective preservation time is the direction of joint efforts of all clinicians. Supercooling liver preservation(SLP) to find a preservation technology that not only guarantees the quality of donor liver but also has a longer effective preservation time is the direction of joint efforts of all clinicians. SLP, a new method based on using cryoprotectants to keep donor liver under -6 ℃ and recovering the graft with subnormothermic machine perfusion that enables long-term transplantation survival following 4 days of liver preservation, made a revolutionary breakthrough in the field of liver preservation, carved out a new field for the research of liver preservation. This article reviews the latest experimental research progress of SLP in the field of liver transplantation.

Supercooling preservation technology in food and biological samples: a review focused on electric and magnetic field applications

Freezing has been widely recognized as the most common process for long-term preservation of perishable foods; however, unavoidable damages associated with ice crystal formation lead to unacceptable quality losses during storage. As an alternative, supercooling preservation has a great potential to extend the shelf-life and maintain quality attributes of fresh foods without freezing damage. Investigations for the application of external electric field (EF) and magnetic field (MF) have theorized that EF and MF appear to be able to control ice nucleation by interacting with water molecules in foods and biomaterials; however, many questions remain open in terms of their roles and influences on ice nucleation with little consensus in the literature and a lack of clear understanding of the underlying mechanisms. This review is focused on understanding of ice nucleation processes and introducing the applications of EF and MF for preservation of food and biological materials.

Critical steps during the prilling process of molten lipids: Main stumbling blocks due to pharmaceutical excipient properties

Prilling by ultrasonic jet break-up is an efficient process to produce perfectly spherical microparticles homogeneous in size. However, the material properties could affect the manufacturability and the final product properties especially with lipid-based excipients which often exhibit complex structural properties. This work presents the characterisation of six lipid-based excipients differing by their melting point and polymorphic behaviour which were used to produce microspheres using a pilot-scale prilling equipment. The experimental results were compared to theoretical calculations, especially the droplet solidification time which is a key-parameter for this process. This work highlighted that monotropic polymorphism of excipients and supercooling effect have a significant impact on process parameters which should be considered with care during formulation design.

Fat body disintegration after freezing stress is a consequence rather than a cause of freezing injury in larvae of Drosophila melanogaster

Extracellular freezing of insect body water may cause lethal injury either by direct mechanical stress exerted by growing ice crystals on cells and tissues or, indirectly, by deleterious physico-chemical effects linked to freeze-induced cell dehydration. Here we present results showing that the macroscopic damage (cell ruptures, tissue disintegration) to fat body of Drosophila melanogaster is not directly caused by mechanical forces linked to growth of ice crystals but rather represents a secondary consequence of other primary freeze injuries occurring at subcellular or microscopic levels. Larvae of D. melanogaster were acclimated to produce variants ranging from freeze susceptible to freeze tolerant. Then, larvae were exposed to supercooling and freezing stresses at different subzero temperatures. The larval survival and macroscopic damage to fat body tissue was scored in 1632 larvae exposed to cold stress. In most cases, fat body damage was not evident immediately following cold stress but developed later. This suggests that the fat body disintegration is a consequence rather than a cause of cold injury. Analysis of fat body membrane phospholipids revealed that increased freeze tolerance was associated with increased relative proportion of phosphatidylethanolamines (PEs) at the expense of phosphatidylcholines (PCs). The PE/PC ratio increased from 1.08 in freeze-susceptible larvae to 2.10 in freeze-tolerant larvae. The potential effects of changing PE/PC ratio on phospholipid bilayer stability upon supercooling and freezing stress are discussed.

Supercooled Liquid Serum Physiologic Solution Instantly Crystallized on the Nurse Table Used for Cooling of Periorbital Region During Rhinoplasty

INTRODUCTION

Formation of less periorbital ecchymosis in post-operative period of rhinoplasty is a popular trend. We present the use of instantly crystallizing supercooled serum physiologic solution for periorbital cooling.

PHYSICS OF SUPERCOOLING

There are circumstances in which water temperature drops below its freezing point, but no phase transition happens while water remains in the liquid phase. This is called supercooling. Pure water can be supercooled below the freezing temperature without transforming into ice. Tap water will not supercool because it contains impurities that serve as nucleation sites for crystallization. For freezer temperatures in the range of - 4 °C, - 6 °C, and - 8 °C, nucleation was not observed and pure water remained in the supercooled condition for a long time.

DESCRIPTION OF THE TECHNIQUE

Sterile serum physiologic solution at + 5 °C can be supercooled in the freezer at - 14 °C only between the 257 and 277 min time interval. But when it is supercooled in the freezer at - 8 °C it is possible to save it in liquid form for at least 7 days as we have observed in our trials.

CLINICAL USE AND DISCUSSION

It is easily possible to transform this supercooled liquid sterile serum physiologic within a few seconds into moldable snow-like ice that can be used safely and more nicely rather than solid ice for periorbital cooling in rhinoplasty operations. Its sterile inner bag is held tight and struck over the sterile nurse table and it crystallizes within a few seconds. For frozen solutions, tearing of the inner plastic bag and extracting the ice and then crushing of big masses of ice to small pieces is exhaustive and a time-consuming process. The temperature of the supercooled fluid will be zero at the moment of nucleation with no risk of frostbite. The crystallized serum physiologic solution preserves its ice-gel form for nearly 25 min.

CONCLUSION

The instant crystallization of supercooled liquid serum physiologic solution can be applied as a tissue cooling method in rhinoplasty and in several other surgical procedures.

LEVEL OF EVIDENCE IV

This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Supercooling and freezing as eco-physiological alternatives rather than mutually exclusive strategies: A case study in Pyrrhocoris apterus

Overwintering insects are categorized either as freeze tolerant or freeze avoiding (supercooling) based on their ability or inability, respectively, to tolerate the formation of ice in their body. The freeze tolerant insects set their supercooling point (SCP) higher for winter to stimulate freezing at higher temperatures, while freeze avoiding insects survive winter in a supercooled state by depressing their SCP. Some supercooling insects, however, were found to survive in frozen state when freezing occurred through inoculation by external ice at mild subzero temperatures. Here, we assessed the potential relevance of inoculative freezing and freeze tolerance strategy in an insect that was so far considered as a classical example of a 'supercooler', the linden bug (Pyrrhocoris apterus). Microclimatic conditions of the overwintering microhabitat of P. apterus (leaf litter layer with buffered temperature fluctuations, mild sub-zero extremes, high humidity, and presence of ice) present a potentially high risk of inoculative freezing. We found that P. apterus is highly susceptible to inoculation by external ice. The temperature at which inoculative freezing occurred (above -3°C) was much higher compared to SCP (-16 °C to -20 °C in winter). The insects were inoculated through body openings and across cuticle and were able to survive after freezing. There was, however, a distinct critical ice fraction, corresponding to 38.7-42.8% of total body water, beyond which survival rapidly decreased to zero. We found that P. apterus adaptively reduces the actual ice fraction below critical ice fraction for winter season. Since many insect species overwinter in habitats similar to that of P. apterus, the ability to tolerate freezing after inoculation by external ice crystals could be much more common among 'supercooling' insects than it is currently appreciated.

Screening of cold tolerance in fifteen springtail species

Springtails (Collembola) are ubiquitous and help ecosystem processes such as the decomposition of dead plant material. Their ability to survive low winter temperatures is an important trait that partly defines their geographic distribution. The cold tolerances of 15 laboratory-reared species of springtails were investigated. Springtails were cold acclimated in the laboratory over two months in order to simulate a seasonal change in temperature during autumn. Springtails were then exposed to decreasing sub-zero temperatures and at the same time simulating the moisture conditions in frozen soil. The cold tolerance of the species reflected well the climate of region of origin. Differential scanning calorimetry of individual springtails showed that melting points of body fluids did not become lower due to long-term cold acclimation (from 20° to 1.5°C). However, both water content and melting point of two arctic species (Hypogastrura viatica and Protaphorura macfadyeni) decreased drastically during exposure to sub-zero temperatures indicating cryoprotective dehydration (CPD). These arctic species survived exposure to - 9 °C for two weeks and - 20 °C for at least one week using CPD. Four other subarctic or cool temperate species also used CPD and survived - 9 °C for weeks, whereas springtails in culture from less cool temperate regions had poor cold tolerance.

Supercooling of Water Controlled by Nanoparticles and Ultrasound

Nanoparticles, including Al₂O₃ and SiO₂, and ultrasound were adopted to improve the solidification properties of water. The effects of nanoparticle concentration, contact angle, and ultrasonic intensity on the supercooling degree of water were investigated, as well as the dispersion stability of nanoparticles in water during solidification. Experimental results show that the supercooling degree of water is reduced under the combined effect of ultrasound and nanoparticles. Consequently, the reduction of supercooling degree increases with the increase of ultrasonic intensity and nanoparticle concentration and decrease of contact angle of nanoparticles. Moreover, the reduction of supercooling degree caused by ultrasound and nanoparticles together do not exceed the sum of the supercooling degree reductions caused by ultrasound and nanoparticles separately; the reduction is even smaller than that caused by ultrasound individually under certain conditions of controlled nanoparticle concentration and contact angle and ultrasonic intensity. The dispersion stability of nanoparticles during solidification can be maintained only when the nanoparticles and ultrasound together show a superior effect on reducing the supercooling degree of water to the single operation of ultrasound. Otherwise, the aggregation of nanoparticles appears in water solidification, which results in failure. The relationships among the meaningful nanoparticle concentration, contact angle, and ultrasonic intensity, at which the requirements of low supercooling and high stability could be satisfied, were obtained. The control mechanisms for these phenomena were analyzed.

Ice Nucleation Activity in Plants: The Distribution, Characterization, and Their Roles in Cold Hardiness Mechanisms

Control of freezing in plant tissues is a key issue in cold hardiness mechanisms. Yet freeze-regulation mechanisms remain mostly unexplored. Among them, ice nucleation activity (INA) is a primary factor involved in the initiation and regulation of freezing events in plant tissues, yet the details remain poorly understood. To address this, we developed a highly reproducible assay for determining plant tissue INA and noninvasive freeze visualization tools using MRI and infrared thermography. The results of visualization studies on plant freezing behaviors and INA survey of over 600 species tissues show that (1) freezing-sensitive plants tend to have low INA in their tissues (thus tend to transiently supercool), while wintering cold-hardy species have high INA in some specialized tissues; and (2) the high INA in cold-hardy tissues likely functions as a freezing sensor to initiate freezing at warm subzero temperatures at appropriate locations and timing, resulting in the induction of tissue-/species-specific freezing behaviors (e.g., extracellular freezing, extraorgan freezing) and the freezing order among tissues: from the primary freeze to the last tissue remaining unfrozen (likely INA level dependent). The spatiotemporal distributions of tissue INA, their characterization, and functional roles are detailed. INA assay principles, anti-nucleation activity (ANA), and freeze visualization tools are also described.

Spectroscopic and thermal studies on 2- and 4-phenyl-1H-imidazoles

The polarized IR spectra of isotopically neat and isotopically substituted monocrystalline samples of 2-phenyl-1H-imidazole (2PI) and 4-phenyl-1H-imidazole (4PI) were recorded at two temperatures of 293 K and 77 K. The room-temperature ATR-FTIR and Raman spectra of 2PI and two polymorphic forms of 4PI were also recorded. Theoretical analysis of the vibrational spectra of selected imidazole derivatives reflected similar characteristics of their hydrogen-bond networks and allowed us to obtain the information about the mechanism of the H/D isotopic "self-organization" phenomenon. The distribution of protons and deuterons in the lattices of the isotopically diluted crystalline samples of 2PI and 4PI was found to be non-random. In the crystals of the hydrogen- and deuterium-bonded imidazole derivatives the strongest vibrational exciton interactions favored the intrachain ("tail-to-head")-type exciton coupling widespread at 77 K via the π-electrons. At room temperature a weak interchain ("through-space")-type exciton coupling was also partially responsible for the IR spectra generation. Differential scanning calorimetry (DSC) measurements showed that the two polymorphic forms of 4PI exhibit an extensive supercooling of crystallization process and cold crystallization on reheating. Additionally, both polymorphic modifications of 4PI are monotropically related. 2PI exhibits only the crystallization and melting processes.

Daily thermal fluctuations to a range of subzero temperatures enhance cold hardiness of winter-acclimated turtles

Although seasonal increases in cold hardiness are well documented for temperate and polar ectotherms, relatively little is known about supplemental increases in cold hardiness during winter. Because many animals are exposed to considerable thermal variation in winter, they may benefit from a quick enhancement of cold tolerance prior to extreme low temperature. Hatchling painted turtles (Chrysemys picta) overwintering in their natal nests experience substantial thermal variation in winter, and recently, it was found that brief subzero chilling of winter-acclimated hatchlings decreases subsequent chilling-induced mortality, increases blood concentrations of glucose and lactate, and protects the brain from cryoinjury. Here, we further characterize that phenomenon, termed 'cold conditioning', by exposing winter-acclimated hatchling turtles to -3.5, -7.0, or -10.5 °C gradually or repeatedly via daily thermal fluctuations over the course of 5 days and assessing their survival of a subsequent cold shock to a discriminating temperature of -12.7 °C. To better understand the physiological response to cold conditioning, we measured changes in glucose and lactate concentrations in the liver, blood, and brain. Cold conditioning significantly increased cold-shock survival, from 9% in reference turtles up to 74% in cold-conditioned turtles, and ecologically relevant daily thermal fluctuations were at least as effective at conferring cryoprotection as was gradual cold conditioning. Cold conditioning increased glucose concentrations, up to 25 μmol g^-1, and lactate concentrations, up to 30 μmol g^-1, in the liver, blood, and brain. Turtles that were cold conditioned with daily thermal fluctuations accumulated more glucose in the liver, blood, and brain, and had lower brain lactate, than those gradually cold conditioned. Given the thermal variation to which hatchling painted turtles are exposed in winter, we suggest that the supplemental protection conferred by cold conditioning, especially that induced by daily thermal fluctuations, may be important for their overwinter survival. Investigation into the duration of the cold-conditioning induced protection and its occurrence in natural field conditions is needed to better understand its ecological significance. We suggest that future work exploring the underlying mechanisms of cold conditioning should focus on non-colligative effects of glucose, expression of small Hsps, changes in membrane structure, and ion homeostasis.

A first test of the hypothesis of biogenic magnetite-based heterogeneous ice-crystal nucleation in cryopreservation

An outstanding biophysical puzzle is focused on the apparent ability of weak, extremely low-frequency oscillating magnetic fields to enhance cryopreservation of many biological tissues. A recent theory holds that these weak magnetic fields could be inhibiting ice-crystal nucleation on the nanocrystals of biological magnetite (Fe3O4, an inverse cubic spinel) that are present in many plant and animal tissues by causing them to oscillate. In this theory, magnetically-induced mechanical oscillations disrupt the ability of water molecules to nucleate on the surface of the magnetite nanocrystals. However, the ability of the magnetite crystal lattice to serve as a template for heterogeneous ice crystal nucleation is as yet unknown, particularly for particles in the 10-100 nm size range. Here we report that the addition of trace-amounts of finely-dispersed magnetite into ultrapure water samples reduces strongly the incidence of supercooling, as measured in experiments conducted using a controlled freezing apparatus with multiple thermocouples. SQUID magnetometry was used to quantify nanogram levels of magnetite in the water samples. We also report a relationship between the volume change of ice, and the degree of supercooling, that may indicate lower degassing during the crystallization of supercooled water. In addition to supporting the role of ice-crystal nucleation by biogenic magnetite in many tissues, magnetite nanocrystals could provide inexpensive, non-toxic, and non-pathogenic ice nucleating agents needed in a variety of industrial processes, as well as influencing the dynamics of ice crystal nucleation in many natural environments.

Supercooling, ice nucleation and crystal growth: a systematic study in plant samples

This paper presents an innovative technological platform which is based on infrared video recording and is used for monitoring multiple ice nucleation events and their interactions, as they happen in 96 well microplates. Thousands of freezing curves were obtained during this study and the following freezing parameters were measured: cooling rate, nucleation point, freezing point, solidus point, degree of supercooling, duration of dendritic phase and duration of crystal growth. We demonstrate the use of this platform in the detection of ice nuclei in plant samples. Future applications of this platform may include breeding for frost tolerance, cryopreservation, frozen food technology and atmospheric sciences.

Polyethylene glycol protects primary hepatocytes during supercooling preservation

Cold storage (at 4°C) offers a compromise between the benefits and disadvantages of cooling. It allows storage of organs or cells for later use that would otherwise quickly succumb to warm ischemia, but comprises cold ischemia that, when not controlled properly, can result in severe damage as well by both similar and unique mechanisms. We hypothesized that polyethylene glycol (PEG) 35 kDa would ameliorate these injury pathways and improve cold primary hepatocyte preservation. We show that reduction of the storage temperature to below zero by means of supercooling, or subzero non-freezing, together with PEG supplementation increases the viable storage time of primary rat hepatocytes in University of Wisconsin (UW) solution from 1 day to 4 days. We find that the addition of 5% PEG 35 kDa to the storage medium prevents cold-induced lipid peroxidation and maintains hepatocyte viability and functionality during storage. These results suggest that PEG supplementation in combination with supercooling may enable a more optimized cell and organ preservation.

Polyethylene glycol protects primary hepatocytes during supercooling preservation

Cold storage (at 4°C) offers a compromise between the benefits and disadvantages of cooling. It allows storage of organs or cells for later use that would otherwise quickly succumb to warm ischemia, but comprises cold ischemia that, when not controlled properly, can result in severe damage as well by both similar and unique mechanisms. We hypothesized that polyethylene glycol (PEG) 35 kDa would ameliorate these injury pathways and improve cold primary hepatocyte preservation. We show that reduction of the storage temperature to below zero by means of supercooling, or subzero non-freezing, together with PEG supplementation increases the viable storage time of primary rat hepatocytes in University of Wisconsin (UW) solution from 1 day to 4 days. We find that the addition of 5% PEG 35 kDa to the storage medium prevents cold-induced lipid peroxidation and maintains hepatocyte viability and functionality during storage. These results suggest that PEG supplementation in combination with supercooling may enable a more optimized cell and organ preservation.

Effect of simulated fall heat waves on cold hardiness and winter survival of hemlock looper, Lambdina fiscellaria (Lepidoptera: Geometridae)

The hemlock looper (Lambdina fiscellaria) is an important pest of eastern Canadian forests. The ongoing climate warming could modify the seasonal ecology of this univoltine species that lays eggs at the end of summer and overwinters at this stage. Indeed, the increase in frequency and intensity of extreme climatic events such as fall heat waves could interfere with the winter metabolism of the hemlock looper. Moreover, the host plant quality, which influences the quantity of insect energetic reserves, the geographic origin of populations and the conditions prevailing during the cold acclimation period, could cause various responses of this pest to climate warming. The main objective of this study is to determine the impact of these factors on hemlock looper winter biology. In October 2010, hemlock looper eggs initially collected from two geographic areas in the province of Québec, and from parents reared on two host plants, were exposed to fall heat waves of different intensities during 5 consecutive days. Supercooling points and cryoprotectant levels were measured on eggs on four different dates in 2010-2011 and survival rate was measured in April 2011. Our results show that hemlock looper eggs have a very low supercooling point and high levels of trehalose, glucose and mannitol in September and November. However, there is no clear relationship between the concentration of these compounds and the decrease in supercooling points. Contents in trehalose, glucose and mannitol were significantly influenced by fall heat waves and by the origin of the population. Winter survival of eggs from the temperate population was negatively affected by strong heat waves while the boreal population was not affected. This study suggests that the metabolism and winter survival of temperate hemlock looper populations in Québec will be more affected by fall heat waves that will increase in frequency due to climate change, than boreal populations.

Ice barriers promote supercooling and prevent frost injury in reproductive buds, flowers and fruits of alpine dwarf shrubs throughout the summer

Over-wintering reproductive buds of many woody plants survive frost by supercooling. The bud tissues are isolated from acropetally advancing ice by the presence of ice barriers that restrict ice growth. Plants living in alpine environments also face the risk of ice formation in summer months. Little knowledge exists, how reproductive structures of woody alpine plants are protected from frost injury during episodic summer frosts. In order to address this question, frost resistance of three common dwarf shrubs, Calluna vulgaris, Empetrum hermaphroditum and Loiseleuria procumbens was measured and ice formation and propagation were monitored in twigs bearing reproductive shoots during various stages of reproductive development (bud, anthesis, and fruit) throughout the alpine summer. Results indicated that, in the investigated species, ice barriers were present at all reproductive stages, isolating the reproductive shoots from ice advancing from the subtending vegetative shoot. Additionally, in the reproductive stems ice nucleating agents that are active at warm, sub-zero temperatures, were absent. The ice barriers were 100% effective, with the exception of L. procumbens, where in 13% of the total observations, the ice barrier failed. The ice barriers were localized at the base of the pedicel, at the anatomical junction of the vegetative and reproductive shoot. There, structural aspects of the tissue impede or prevent ice from advancing from the frozen stem into the pedicel of the reproductive shoot. Under the experimental conditions used in this study, ice nucleation initially occurred in the stem of the vegetative shoot at species-specific mean temperatures in the range of -4.7 to -5.8 °C. Reproductive shoots, however, remained supercooled and ice free down to a range of -7.2 to -18.2 °C or even below -22 °C, the lowest temperature applied in the study. This level of supercooling is sufficient to prevent freezing of reproductive structures at the lowest air temperature occurring at the altitude of the upper distribution boundary of the natural habitat of the investigated species which is between -8 and -10 °C in summer. Frost resistance assays indicated that reproductive shoots are much less frost resistant than vegetative stems, and in contrast to vegetative shoots, are not ice tolerant. Supercooling of reproductive shoots in alpine, woody plant species is an effective mechanism that protects developing offspring from potential frost damage resulting from episodic summer freezing events.

Analysis of supercooling activities of surfactants

Supercooling-promoting activities (SCAs) of 25 kinds of surfactants including non-ionic, anionic, cationic and amphoteric types were examined in solutions (buffered Milli-Q water, BMQW) containing the ice nucleation bacterium (INB) Erwinia ananas, silver iodide (AgI) or BMQW alone, which unintentionally contained unidentified ice nucleators, by a droplet freezing assay. Most of the surfactants exhibited SCA in solutions containing AgI but not in solutions containing the INB E. ananas or BMQW alone. SCAs of many surfactants in solutions containing AgI were very high compared with those of previously reported supercooling-promoting substances. Cationic surfactants, hexadecyltrimethylammonium bromide (C16TAB) and hexadecyltrimethylammonium chloride (C16TAC), at concentrations of 0.01% (w/v) exhibited SCA of 11.8 °C, which is the highest SCA so far reported. These surfactants also showed high SCAs at very low concentrations in solutions containing AgI. C16TAB exhibited SCA of 5.7 °C at a concentration of 0.0005% (w/v).

Physiology of cold tolerance in the bark beetle, Pityogenes chalcographus and its overwintering in spruce stands

The seasonal development of physiological features underlying gradual acquisition of relatively high cold tolerance in overwintering adults of the bark beetles, Pityogenes chalcographus was described. Prior to overwintering, the beetles accumulated carbohydrate reserves in the form of glycogen and trehalose. These reserves were partially converted to glycerol during peaking winter so that glycerol concentration reached 1.4M in average, which corresponds to approximately one quarter of the beetle dry mass. Whole body supercooling points decreased from -12.8°C in average at the beginning of dormancy (August) to -26.3°C in average during peaking winter (January). More than 75% of January-collected beetles survived at -5°C for 30days, at -15°C for 60days and more than 40% of them survived at -26°C for 12h. High resistance against inoculation of body fluids with external ice crystals, and low mortality, was observed when January-collected beetles were encased in an ice block for 14days. Thus, the physiological limits of cold tolerance measured at individual level in laboratory were safely sufficient for survival of P. chalcographus at any conceivable cold spell that may occur in Central Europe. In contrast, the field experiment showed that winter survival fluctuated between 23.8% and 69.2% at a population level depending on microclimatic conditions in different altitudes and overwintering locations (standing tree trunk or ground level). The meaning of laboratory-assessed physiological limits of cold tolerance for predictions of population winter survival in the field is discussed.

Recombinant Dendroides canadensis antifreeze proteins as potential ingredients in cryopreservation solutions

Expanding cryopreservation methods to include a wider range of cell types, such as those sensitive to freezing, is needed for maintaining the viability of cell-based regenerative medicine products. Conventional cryopreservation protocols, which include use of cryoprotectants such as dimethylsulfoxide (Me2SO), have not prevented ice-induced damage to cell and tissue matrices during freezing. A family of antifreeze proteins (AFPs) produced in the larvae of the beetle, Dendroides canadensis allow this insect to survive subzero temperatures as low as -26°C. This study is an assessment of the effect of the four hemolymph D. canadensis AFPs (DAFPs) on the supercooling (nucleating) temperature, ice structure patterns and viability of the A10 cell line derived from the thoracic aorta of embryonic rat. Cryoprotectant solution cocktails containing combinations of DAFPs in concentrations ranging from 0 to 3mg/mL in Unisol base mixed with 1M Me2SO were first evaluated by cryomicroscopy. Combining multiple DAFPs demonstrated significant supercooling point depressing activity (∼9°C) when compared to single DAFPs and/or conventional 1M Me2SO control solutions. Concentrations of DAFPs as low as 1 μg/mL were sufficient to trigger this effect. In addition, significantly improved A10 smooth muscle cell viability was observed in cryopreservation experiments with low DAFP-6 and DAFP-2 concentrations in combination with Me2SO. No significant improvement in viability was observed with either DAFP-1 or DAFP-4. Low and effective DAFP concentrations are advantageous because they minimize concerns regarding cell cytotoxicity and manufacturing cost. These findings support the potential of incorporating DAFPs in solutions used to cryopreserve cells and tissues.

Effect of supercooling and freezing on photosynthesis in freezing tolerant leaves of Afroalpine 'giant rosette' plants

The effect of supercooling and freezing on the photosynthetic capability of representatives of the permanent frost hardy giant rosette plants Dendrosenecio keniodendron, D. brassica and Lobelia telekii, of the tropical alpine regions was investigated with the non-invasive chlorophyll a fluorescence technique. While supercooling, normal chlorophyll a fluorescence kinetics exhibiting the sequence 0, I, (D), P, S, M, were recorded, however with some retardation of both, the fast and the slow characteristics as compared to those obtained at day-time temperature. As long as the leaves remained unfrozen, the rise of the variable fluorescence F _ν from the level 0 to P was inversely related to a drop of the temperature from about 0°C to-8°C. The increase of F _ν with lower temperature is understood to result from a decrease of the velocity of the quenching reactions while photoreduction of the primary electron acceptor appeared to be unimpeded. The second fluorescence maximum (M), usually interpreted to indicate the commencement of the biochemical reactions of photosynthesis was consistenly to be observed during supercooling. Fluoescence induction kinetics of frozen leaves showed only fast rise to presumably F _max which was not followed by a significant decay for as long as 4 min. The lack of substantial quenching indicates that in the freeze-dehydrated state neither reoxidation of the primary acceptor nor energetization of the thylakoid membrane was accomplished. This effect however was immediately and fully reserved upon thawing of the leaves when the usual fluorescence induction kinetics as well as normal rates of CO₂-uptake were observed. Thus the permanent frost-hardy afroalpine plants do not exhibit any even short-term memory effect of the nocturnal frost on such a delicate process as is photosynthesis.