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1. The role of antifreeze glycoprotein (AFGP) and polyvinyl alcohol/polyglycerol (X/Z-1000) as ice modulators during partial freezing of rat livers

   https://doi.org/10.3389/fphy.2022.1033613  

   Tessier, Shannon N. ; Haque, Omar ; Pendexter, Casie A. ; Cronin, Stephanie E. ; Hafiz, Ehab O. ; Weng, Lindong ; Yeh, Heidi ; Markmann, James F. ; Taylor, Michael J. ; Fahy, Gregory M. ; et al ( December 2022 , Frontiers in Physics)

   Introduction:The current liver organ shortage has pushed the field of transplantation to develop new methods to prolong the preservation time of livers from the current clinical standard of static cold storage. Our approach, termed partial freezing, aims to induce a thermodynamically stable frozen state at high subzero storage temperatures (−10°C to −15°C), while simultaneously maintaining a sufficient unfrozen fraction to limit ice-mediated injury.

   Methods and results:Using glycerol as the main permeating cryoprotectant agent, this research first demonstrated that partially frozen rat livers showed similar outcomes after thawing from either −10°C or −15°C with respect to subnormothermic machine perfusion metrics. Next, we assessed the effect of adding ice modulators, including antifreeze glycoprotein (AFGP) or a polyvinyl alcohol/polyglycerol combination (X/Z-1000), on the viability and structural integrity of partially frozen rat livers compared to glycerol-only control livers. Results showed that AFGP livers had high levels of ATP and the least edema but suffered from significant endothelial cell damage. X/Z-1000 livers had the highest levels of ATP and energy charge (EC) but also demonstrated endothelial damage and post-thaw edema. Glycerol-only control livers exhibited the least DNA damage on Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining but also had the lowest levels of ATP and EC.

   Discussion:Further research is necessary to optimize the ideal ice modulator cocktail for our partial-freezing protocol. Modifications to cryoprotective agent (CPA) combinations, including testing additional ice modulators, can help improve the viability of these partially frozen organs.

    

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2. Temperature modulates the osmosensitivity of tilapia prolactin cells

   https://doi.org/10.1038/s41598-023-47044-5  

   Malintha, G. H. T. ; Woo, Daniel W. ; Celino-Brady, Fritzie T. ; Seale, Andre P. ( November 2023 , Scientific Reports)

   In euryhaline fish, prolactin (Prl) plays an essential role in freshwater (FW) acclimation. In the euryhaline and eurythermal Mozambique tilapia,Oreochromis mossambicus,Prl cells are model osmoreceptors, recently described to be thermosensitive. To investigate the effects of temperature on osmoreception, we incubated Prl cells of tilapia acclimated to either FW or seawater (SW) in different combinations of temperatures (20, 26 and 32 °C) and osmolalities (280, 330 and 420 mOsm/kg) for 6 h. Release of both Prl isoforms, Prl₁₈₈and Prl₁₇₇, increased in hyposmotic media and were further augmented with a rise in temperature. Hyposmotically-induced release of Prl₁₈₈, but not Prl₁₇₇, was suppressed at 20 °C. In SW fish, mRNA expression ofprl₁₈₈increased with rising temperatures at lower osmolalities, while andprl₁₇₇decreased at 32 °C and higher osmolalities. In Prl cells of SW-acclimated tilapia incubated in hyperosmotic media, the expressions of Prl receptors,prlr1 and prlr2,and the stretch-activated Ca²⁺channel,trpv4,decreased at 32 °C, suggesting the presence of a cellular mechanism to compensate for elevated Prl release. Transcription factors,pou1f1,pou2f1b,creb3l1,cebpb,stat3,stat1aandnfat1c, known to regulateprl₁₈₈andprl₁₇₇,were also downregulated at 32 °C. Our findings provide evidence that osmoreception is modulated by temperature, and that both thermal and osmotic responses vary with acclimation salinity.

    

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3. Thermal acclimation influences the growth and toxin production of freshwater cyanobacteria

   https://doi.org/10.1002/lol2.10197  

   Layden, Tamara J. ; Kremer, Colin T. ; Brubaker, Delaney L. ; Kolk, Maeve A. ; Trout‐Haney, Jessica V. ; Vasseur, David A. ; Fey, Samuel B. ( May 2021 , Limnology and Oceanography Letters)

   Understanding how altered temperature regimes affect harmful cyanobacterial bloom formation is essential for managing aquatic ecosystems amidst ongoing climate warming. This is difficult because algal performance can depend on both current and past environments, as plastic physiological changes (acclimation) may lag behind environmental change. Here, we investigate how temperature variation on sub‐weekly timescales affects population growth and toxin production given acclimation. We studied four ecologically important freshwater cyanobacterial strains under low‐ and high‐nutrient conditions, measuring population growth rate after acclimation and new exposure to a range of temperatures. Cold‐acclimated populations (15.7°C) outperformed fully acclimated populations (held in constant conditions) across 65% of thermal environments, while hot‐acclimated populations (35.7–42.6°C) underperformed across 75% of thermal environments. Over a 5‐day period, cold‐acclimatedMicrocystis aeruginosaproduced ~2.5‐fold more microcystin than hot‐acclimated populations experiencing the same temperature perturbation. Our results suggest that thermal variation and physiology interact in underappreciated ways to influence cyanobacterial growth, toxin production, and likely bloom formation.

    

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4. A large-effect fitness trade-off across environments is explained by a single mutation affecting cold acclimation

   https://doi.org/10.1073/pnas.2317461121  

   Lee, Gwonjin ; Sanderson, Brian J. ; Ellis, Thomas J. ; Dilkes, Brian P. ; McKay, John K. ; Ågren, Jon ; Oakley, Christopher G. ( February 2024 , Proceedings of the National Academy of Sciences)

   Identifying the genetic basis of local adaptation and fitness trade-offs across environments is a central goal of evolutionary biology. Cold acclimation is an adaptive plastic response for surviving seasonal freezing, and costs of acclimation may be a general mechanism for fitness trade-offs across environments in temperate zone species. Starting with locally adapted ecotypes ofArabidopsis thalianafrom Italy and Sweden, we examined the fitness consequences of a naturally occurring functional polymorphism inCBF2. This gene encodes a transcription factor that is a major regulator of cold-acclimated freezing tolerance and resides within a locus responsible for a genetic trade-off for long-term mean fitness. We estimated the consequences of alternate genotypes ofCBF2on 5-y mean fitness and fitness components at the native field sites by comparing near-isogenic lines with alternate genotypes ofCBF2to their genetic background ecotypes. The effects ofCBF2were validated at the nucleotide level using gene-edited lines in the native genetic backgrounds grown in simulated parental environments. The foreignCBF2genotype in the local genetic background reduced long-term mean fitness in Sweden by more than 10%, primarily via effects on survival. In Italy, fitness was reduced by more than 20%, primarily via effects on fecundity. At both sites, the effects were temporally variable and much stronger in some years. The gene-edited lines confirmed thatCBF2encodes the causal variant underlying this genetic trade-off. Additionally, we demonstrated a substantial fitness cost of cold acclimation, which has broad implications for potential maladaptive responses to climate change.

    

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5. Cryopreserved red blood cells maintain allosteric control of oxygen binding when utilizing trehalose as a cryoprotectant

   https://doi.org/10.1016/j.cryobiol.2023.104793  

   Elder, Charles A. ; Smith, Jensen S. ; Almosawi, Mustafa ; Mills, Ethan ; Janis, Brett R. ; Kopechek, Jonathan A. ; Wolkers, Willem F. ; Menze, Michael A. ( March 2024 , Cryobiology)

   One of the most common life-saving medical procedures is a red blood cell (RBC) transfusion. Unfortunately, RBCs for transfusion have a limited shelf life after donation due to detrimental storage effects on their morphological and biochemical properties. Inspired by nature, a biomimetics approach was developed to preserve RBCs for long-term storage using compounds found in animals with a natural propensity to survive in a frozen or desiccated state for decades. Trehalose was employed as a cryoprotective agent and added to the extracellular freezing solution of porcine RBCs. Slow cooling (-1 C min-1) resulted in almost complete hemolysis (1 ± 1 % RBC recovery), and rapid cooling rates had to be used to achieve satisfactory cryopreservation outcomes. After rapid cooling, the highest percentage of RBC recovery was obtained by plunging in liquid nitrogen and thawing at 55 C, using a cryopreservation solution containing 300 mM trehalose. Under these conditions, 88 ± 8 % of processed RBCs were recovered and retained hemoglobin (14 ± 2 % hemolysis). Hemoglobin’s oxygen-binding properties of cryopreserved RBCs were not significantly different to unfrozen controls and was allosterically regulated by 2,3-bisphosphoglycerate. These data indicate the feasibility of using trehalose instead of glycerol as a cryoprotective compound for RBCs. In contrast to glycerol, trehalose-preserved RBCs can potentially be transfused without time-consuming washing steps, which significantly facilitates the usage of cryopreserved transfusible units in trauma situations when time is of the essence. 

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