Glutamine supplementation improves contractile function of regenerating soleus muscles from rats

This study evaluated the effects of glutamine supplementation immediately after freezing injury on morphological and contractile function of regenerating soleus muscles from rats. Young male Wistar rats were subjected to cryolesion of soleus muscles, and immediately after received a daily supplementation of glutamine (1 g/kg/day). The muscles were evaluated on post-injury days 3 and 10. Glutamine-supplemented injured muscles had a lower number of CD11b positive immune cells and higher mRNA levels of IL-4 compared to those from the cryolesioned muscles analyzed on post-injury day 3. The mRNA and protein expression levels of the myogenic transcription factor MyoD were also higher in glutamine-supplemented injured muscles than in injured muscles examined on post-cryolesion day 3. In addition, glutamine-supplemented injured muscles had a higher size of their regenerating myofibers, attenuated decline in maximum tetanic strength and improved fatigue resistance compared to those from injured muscles evaluated on post-cryolesion day 10. No effect was observed in uninjured muscles supplemented with glutamine. Our results suggest that glutamine supplementation improves the resolution of inflammation, as well as the size and functional recovery of regenerating myofibers from soleus muscles by accelerating the up-regulation of IL-4 and MyoD expression. Future non-pharmacological rehabilitation studies are warranted to investigate the effect of glutamine supplementation on the outcome of injured skeletal muscles.

Physiological and biochemical responses of strawberry crown and leaf tissues to freezing stress

BACKGROUND

In northern Iran and other cold regions, winter freezing injury and resultant yield instability are major limitations to strawberry production. However, there is scarcity of information on the physiological and biochemical responses of strawberry cultivars to freezing stress. This study aimed to investigate the physiological and biochemical responses of strawberry cultivars (Tennessee Beauty, Blakemore, Kurdistan, Queen Elisa, Chandler, Krasnyy Bereg, and Yalova) to different freezing temperature treatments (- 5, - 10, - 15, - 20, and - 25 °C) under controlled conditions.

RESULTS

All measured physiological and biochemical features were significantly affected by the interaction effect between low temperatures and cultivars. Tennessee Beauty showed the highest RWC at - 25 °C. The highest Fv/Fm was observed in Queen Elisa. Krasnyy Bereg had the least freezing injury (FI) in crown and leaf, while Yalova and Chandler showed the highest crown and leaf FI, respectively. At - 20 to - 25 °C, the highest carbohydrates contents of crown and leaf were noted in Blakemore and Krasnyy Bereg cultivars, respectively. The Yalova showed the highest protein content in both crown and leaf tissues at - 25 °C. The Tennessee Beauty and Blackmore cultivars showed the highest proline in crowns and leaves at - 15 °C, respectively. The highest ThioBarbituric Acid Reactive Substances (TBARS) contents in the crown and leaf were observed in Kurdistan and Queen Elisa, respectively. Queen Elisa and Krasnyy Bereg cultivars showed SOD and POD peaks in the crown at - 15 °C, respectively.

CONCLUSION

Freezing stress was characterized by decreased Fv/Fm and RWC, and increased FI, TBARS, total carbohydrates, total proteins, proline content, and antioxidant enzyme activity. The extent of changes in above mentioned traits was cultivar dependent. FI and TBARS were the best traits among destructive parameters for evaluating freezing tolerance. Moreover, maximum quantum yield of PSII (Fv/Fm index), as non-destructive parameters, showed a significant efficiency in rapid assessment for screening of freezing tolerant strawberry cultivars. The cultivars Krasnyy Bereg, Queen Elisa, and Kurdistan were the most tolerant cultivars to freezing stress. These cultivars can be used as parents in breeding programs to develop new freezing tolerant cultivars.

Optimizing the spray parameters of a cryospray process

Smaller spray zone of single-hole nozzle (SHN) constrains cryospray as a treatment method suitable for lesions having diameter larger than 15 mm on the skin surface. The present study is an attempt to resolve this issue, through the improvement in conventional technique of spraying liquid nitrogen on cancerous lesion. A multi-hole nozzle (MHN) with 5 holes is fabricated to demarcate the variation in outcome when cryogen is sprayed through customised MHN instead of conventional SHN. Special emphasis is placed on reducing the number of sitting required for completion of treatment and increasing the feasibility of cryospray process for larger lesions. Commercial SHN having a hole diameter of 0.8 mm is selected to compare results with the customised MHN having 5 holes of 0.8 mm diameter (4 holes are arranged in a circle of radius 2 mm around the central hole). Single freeze-thaw cycle is carried out to spray liquid nitrogen on tissue mimicking gel. Temperature profile accessed through infrared images advocates that lethal area formed through application of MHN is twice larger than the lethal area formed through the application of SHN on the surface of gel for same spraying distance (z). Thermocouples placed at various locations strengthen the fact that higher cooling rate (CR) corresponding to MHN ensures 15 mm spread of necrotic zone from the centre of spray (CS) and up to a depth of 2 mm from the gel surface while in case of SHN, it is limited to the vicinity of CS. On the basis of observations made through thermal images and digital images, it can be said that the ratio of lateral spread to penetration depth of ice ball remains almost same for SHN and MHN. However, the lateral spread of ice ball formed through the application of MHN is twice larger than SHN while the axial depth of ice ball does not record such increment. This reflects that MHN provides more destruction to superficial skin than SHN. Among the three spraying distances selected (i.e. z = 13 mm, 18 mm and 23 mm), the most optimised spraying distance (z) for MHN is also explored in this study. It has been found that cryoablation is not inversely proportional to the spraying distance. Spraying distance of z = 18 mm provided the most optimised result in terms of cryoablation.

Genetic suppression of cryoprotectant toxicity

We report here a new, unbiased forward genetic method that uses transposon-mediated mutagenesis to enable the identification of mutations that confer cryoprotectant toxicity resistance (CTR). Our method is to select for resistance to the toxic effects of M22, a much-studied whole-organ vitrification solution. We report finding and characterizing six mutants that are resistant to M22. These mutants fall into six independent biochemical pathways not previously linked to cryoprotectant toxicity (CT). The genes associated with the mutations were Gm14005, Myh9, Nrg2, Pura, Fgd2, Pim1, Opa1, Hes1, Hsbp1, and Ywhag. The mechanisms of action of the mutations remain unknown, but two of the mutants involve MYC signaling, which was previously implicated in CT. Several of the mutants may up-regulate cellular stress defense pathways. Several of the M22-resistant mutants were also resistant to dimethyl sulfoxide (Me2SO), and many of the mutants showed significantly improved survival after freezing and thawing in 10% (v/v) Me2SO. This new approach to overcoming CT has many advantages over alternative methods such as transcriptomic profiling. Our method directly identifies specific genetic loci that unequivocally affect CT. More generally, our results provide the first direct evidence that CT can be reduced in mammalian cells by specific molecular interventions. Thus, this approach introduces remarkable new opportunities for pharmacological blockade of CT.

Bark cells and xylem cells in Japanese white birch twigs initiate deacclimation at different temperatures

Appropriate timing of cold deacclimation is an important component of winter survival of perennial plants, such as trees, in temperate and boreal zones. Recently, concerns about predicted global climate change disturbing deacclimation timing have been increasing. The relationship between ambient temperatures and the manner by which cells' freezing resistance changes is essential for forecasting the timing of deacclimation. In this study, Japanese white birch twigs that underwent deacclimation treatment at a constant temperature of -2, 0, 4, 10, or 20 °C were separated into bark in which cells adapted to subfreezing temperatures by extracellular freezing and xylem in which cells adapted to subfreezing temperatures by deep supercooling, and the freezing resistance of cells in each tissue type was investigated by measuring percentage electrolyte leakage. Birch cells deacclimated in a different manner according to tissue type. Within 7 days under deacclimation treatment, xylem cells decreased their freezing resistance significantly at a high subfreezing temperature (-2 °C). In contrast, bark cells required a temperature of 10 or 20 °C for a detectable decrease in freezing resistance to occur within the same period. At a temperature lower than 0 °C, bark cells did not decrease their freezing resistance, even after 28 days of treatment. The difference in freezing behavior of cells might involve the difference in how deacclimation occurred in bark and xylem cells.