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1. 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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2. 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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3. Genetic and physiological mechanisms of freezing tolerance in locally adapted populations of a winter annual

   https://doi.org/10.1002/ajb2.1385  

   Sanderson, Brian J. ; Park, Sunchung ; Jameel, M. Inam ; Kraft, Joshua C. ; Thomashow, Michael F. ; Schemske, Douglas W. ; Oakley, Christopher G. ( November 2019 , American Journal of Botany)

   Despite myriad examples of local adaptation, the phenotypes and genetic variants underlying such adaptive differentiation are seldom known. Recent work on freezing tolerance and local adaptation in ecotypes ofArabidopsis thalianafrom Italy and Sweden provides an essential foundation for uncovering the genotype–phenotype–fitness map for an adaptive response to a key environmental stress.

   We examined the consequences of a naturally occurring loss‐of‐function (LOF) mutation in an Italian allele of the gene that encodes the transcription factorCBF2,which underlies a major freezing‐tolerance locus. We used four lines with a Swedish genetic background, each containing aLOFCBF2allele. Two lines had introgression segments containing the ItalianCBF2allele, and two contained deletions created usingCRISPR‐Cas9. We used a growth chamber experiment to quantify freezing tolerance and gene expression before and after cold acclimation.

   Freezing tolerance was lower in the Italian (11%) compared to the Swedish (72%) ecotype, and all four experimentalCBF2LOFlines had reduced freezing tolerance compared to the Swedish ecotype. Differential expression analyses identified 10 genes for which allCBF2LOFlines, and theITecotype had similar patterns of reduced cold responsive expression compared to theSWecotype.

   We identified 10 genes that are at least partially regulated byCBF2that may contribute to the differences in cold‐acclimated freezing tolerance between the Italian and Swedish ecotypes. These results provide novel insight into the molecular and physiological mechanisms connecting a naturally occurring sequence polymorphism to an adaptive response to freezing conditions.

    

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4. 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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5. Cold tolerance in the genus Arabidopsis

   https://doi.org/10.1002/ajb2.1442  

   Armstrong, Jessica J. ; Takebayashi, Naoki ; Wolf, Diana E. ( February 2020 , American Journal of Botany)

   Cold tolerance is an important factor limiting the geographic distribution and growing season for many plant species, yet few studies have examined variation in cold tolerance extensively within and among closely related species and compared that to their geographic distribution.

   This study examines cold tolerance within and among species in the genusArabidopsis. We assessed cold tolerance by measuring electrolyte leakage from detached leaves in multiple populations of fiveArabidopsistaxa. The temperature at which 50% of cells were lysed was considered the lethal temperature (LT₅₀).

   We found variability within and among taxa in cold tolerance. There was no significant within‐species relationship between latitude and cold tolerance. However, the northern taxa,A. kamchatica,A. lyratasubsp.petraea, andA. lyratasubsp.lyrata, were more cold tolerant thanA. thalianaandA. hallerisubsp.gemmiferaboth before and after cold acclimation. Cold tolerance increased after cold acclimation (exposure to low, but nonfreezing temperatures) for all taxa, although the difference was not significant forA. hallerisubsp.gemmifera. For all taxa exceptA. lyratasubsp.lyrata, theLT₅₀values for cold‐acclimated plants were higher than the January mean daily minimum temperature (T_min), indicating that if plants were not insulated by snow cover, they would not likely survive winter at the northern edge of their range.

   Arabidopsis lyrataandA. kamchaticawere far more cold tolerant thanA. thaliana. These extremely cold‐tolerant taxa are excellent candidates for studying both the molecular and ecological aspects of cold tolerance.

    

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