Experimental oxygen concentration influences rates of mitochondrial hydrogen peroxide release from cardiac and skeletal muscle preparations

Mitochondria utilize the majority of oxygen (O2) consumed by aerobic organisms as the final electron acceptor for oxidative phosphorylation (OXPHOS) but also to generate reactive oxygen species (mtROS) that participate in cell signaling, physiological hormesis, and disease pathogenesis. Simultaneous monitoring of mtROS production and oxygen consumption ( Jo2) from tissue mitochondrial preparations is an attractive investigative approach, but it introduces dynamic changes in media O2 concentration ([O2]) that can confound experimental results and interpretation. We utilized high-resolution fluorespirometry to evaluate Jo2 and hydrogen peroxide release ( Jh2o2) from isolated mitochondria (Mt), permeabilized fibers (Pf), and tissue homogenates (Hm) prepared from murine heart and skeletal muscle across a range of experimental [O2]s typically encountered during respirometry protocols (400–50 µM). Results demonstrate notable variations in Jh2o2 across tissues and sample preparations during nonphosphorylating (LEAK) and OXPHOS-linked respiration states at 250 µM [O2] but a linear decline in Jh2o2 of 5–15% per 50-µM decrease in chamber [O2] in all samples. Jo2 was generally stable in Mt and Hm across [O2]s above 50 µM but tended to decline below 250 µM in Pf, leading to wide variations in assayed rates of Jh2o2/O2 across chamber [O2]s and sample preparations. Development of chemical background fluorescence from the H2O2 probe (Amplex Red) was also O2 sensitive, emphasizing relevant calibration considerations. This study highlights the importance of monitoring and reporting the chamber [O2] at which Jo2 and Jh2o2 are recorded during fluorespirometry experiments and provides a basis for selecting sample preparations for studies addressing the role of mtROS in physiology and disease.

Functional Changes Induced by Short Term Caloric Restriction in Cardiac and Skeletal Muscle Mitochondria

Caloric restriction (CR) is widely known to increase life span and resistance against different types of injuries in several organisms. We have previously shown that mitochondria from livers or brains of CR animals exhibit higher calcium uptake rates and lower sensitivity to calcium-induced mitochondrial permeability transition (mPT), an event related to the resilient phenotype exhibited by these organs. Given the importance of calcium in metabolic control and cell homeostasis, we aimed here to uncover possible changes in mitochondrial calcium handling, redox balance and bioenergetics in cardiac and skeletal muscle mitochondria. Unexpectedly, we found that CR does not alter the susceptibility to mPT in muscle (cardiac or skeletal), nor calcium uptake rates. Despite the lack in changes in calcium transport properties, CR consistently decreased respiration in the presence of ATP synthesis in heart and soleus muscle. In heart, such changes were accompanied by a decrease in respiration in the absence of ATP synthesis, lower maximal respiratory rates and a reduced rate of hydrogen peroxide release. Hydrogen peroxide release was unaltered by CR in skeletal muscle. No changes were observed in inner membrane potentials and respiratory control ratios. Together, these results highlight the tissue-specific bioenergetic and ion transport effects induced by CR, demonstrating that resilience against calcium-induced mPT is not present in all tissues.

604 Comparing Disinfection of Different Dosages of Vaporized Hydrogen Peroxide in Burn Ward

Introduction The objective of this study is to compare the disinfection effects using the vaporized hydrogen peroxide disinfection method in critical burn ward. Methods A 110m3 empty ward of the burn center was selected as the experimental site. The Bacillus subtilis var. niger spores were opened and placed in 15 unprepared positions (with 0 m, 1 m, 2 m, 3 m, and 4 m from the disinfection machine, each of which was divided into upper, middle, and The lower 3 planes), as well as the 15 points of the cloth (the same position as before), are fixed with hydrogen peroxide indicating tape. The amount of hydrogen peroxide was calculated according to the size of the ward (8 g/m3, 12 g/m3, respectively), and disinfected at a rate of 10 g/min of hydrogen peroxide release flow. After 5 hours of disinfection, the chemical indicator tape and the bacteria pieces were taken out. Observe the discoloration of the chemical indicating tape. The bacteria pieces were placed in a test tube containing the broth culture medium, and the results were observed after incubation in a 37 ° C incubator for 7*24 hours. Results (1) Under the condition of no cover, the two disinfecting dose chemical indicating tapes are all discolored, and in the case of obstruction, they cannot be completely discolored; (2) When the amount of hydrogen peroxide disinfection is 8g/m3 and 12g/m3 respectively, The positive rates of unobstructed specimens were 6.67% and 2.67%, respectively, no significant difference (P= >0.05), and there was no difference in disinfection effect between the positions (P >0.05); (3) 8g/m3 disinfection dose The peak concentration is 255.9g, the peak concentration is 1h48min; the peak concentration is 337.6g at 12g/m3 disinfection, and the peak concentration is 2h26min. When the two disinfection doses were disinfected for 8 hours, the peak concentrations of the chambers were basically the same(1) Under the condition of no cover, the two disinfecting dose chemical indicating tapes are all discolored, and in the case of obstruction, they cannot be completely discolored; (2) When the amount of hydrogen peroxide disinfection is 8g/m3 and 12g/m3 respectively, The positive rates of unobstructed specimens were 6.67% and 2.67%, respectively, no significant difference (P= >0.05), and there was no difference in disinfection effect between the positions (P >0.05); (3) 8g/m3 disinfection dose The peak concentration is 255.9g, the peak concentration is 1h48min; the peak concentration is 337.6g at 12g/m3 disinfection, and the peak concentration is 2h26min. When the two disinfection doses were disinfected for 8 hours, the peak concentrations of the chambers were basically the same. Conclusions The use of vaporized hydrogen peroxide for terminal disinfection should be as full as possible to expose the items to be disinfected. Applicability of Research to Practice Disinfection.