Effect of irradiation on Akt signaling in atrophying skeletal muscle

Muscle irradiation (IRR) exposure can accompany unloading during spaceflight or cancer treatment, and this has been shown to be sufficient by itself to induce skeletal muscle signaling associated with a remodeling response. Although protein kinase B/Akt has an established role in the regulation of muscle growth and metabolism, there is a limited understanding of how Akt signaling in unloaded skeletal muscle is affected by IRR. Therefore, we examined the combined effects of acute IRR and short-term unloading on muscle Akt signaling. Female C57BL/6 mice were subjected to load bearing or hindlimb suspension (HS) for 5 days (n = 6/group). A single, unilateral hindlimb IRR dose (0.5 Gy X-ray) was administered on day 3. Gastrocnemius muscle protein expression was examined. HS resulted in decreased AktT308 phosphorylation, whereas HS+IRR resulted in increased AktT308 phosphorylation above baseline. HS resulted in reduced AktS473 phosphorylation, which was rescued by HS+IRR. Interestingly, IRR alone resulted in increased phosphorylation of AktS473, but not that of AktT308. HS resulted in decreased mTORC1 signaling, and this suppression was not altered by IRR. Both IRR and HS resulted in increased MuRF-1 expression, whereas atrogin-1 expression was not affected by either condition. These results demonstrate that either IRR alone or when combined with HS can differentially affect Akt phosphorylation, but IRR did not disrupt suppressed mTORC1 signaling by HS. Collectively, these findings highlight that a single IRR dose is sufficient to disrupt the regulation of Akt signaling in atrophying skeletal muscle

Effect of Deviations from Predicted Lactation Feed Intake on Reproductive Performance in F1 Sows

The objective of this study was to quantify negative deviations from predicted lactation feed intake (LFI) values and the effect of negative deviations on reproductive performance. Daily lactation feed intake values (LFI) were recorded on 10,716 litters farrowed by purebred Yorkshire, Landrace and F1 (Yorkshire x Landrace) sows with an average lactation length of 18.5 days. Daily LFI values were predicted for each litter using the PROC HPMIXED procedure in SAS. An internally studentized residual ≤ -1.71 was characterized as a negative deviation from predicted LFI value (DEV). Total DEV during lactation ranged from 0 occurrences up to 14 negative deviations. However, the occurrence of more than 5 deviations during lactation was rare, and reproductive performance was not statistically affected by additional negative deviations. Twenty-one day litter weaning weight decreased with each additional negative deviation until at least 3 negative deviations occurred in which litter weaning weight remained at a constant value for litters produced by purebred and F1 sows. Wean-to-service interval remained constant when 0, 1, or 2 negative deviations occurred but when the number of negative deviations during lactation reached at least 3, wean-to-service interval began to increase. Limiting the number of DEV during lactation increases the likelihood that a sow will reach her reproductive potential

The effect of radiation dose on mouse skeletal muscle remodeling

BackgroundThe purpose of this study was to determine the effect of two clinically relevant radiation doses on the susceptibility of mouse skeletal muscle to remodeling.Materials and methods.Alterations in muscle morphology and regulatory signaling were examined in tibialis anterior and gastrocnemius muscles after radiation doses that differed in total biological effective dose (BED). Female C57BL/6 (8-wk) mice were randomly assigned to non-irradiated control, four fractionated doses of 4 Gy (4x4 Gy; BED 37 Gy), or a single 16 Gy dose (16 Gy; BED 100 Gy). Mice were sacrificed 2 weeks after the initial radiation exposure.ResultsThe 16 Gy, but not 4x4 Gy, decreased total muscle protein and RNA content. Related to muscle regeneration, both 16 Gy and 4x4 Gy increased the incidence of central nuclei containing myofibers, but only 16 Gy increased the extracellular matrix volume. However, only 4x4 Gy increased muscle 4-hydroxynonenal expression. While both 16 Gy and 4x4 Gy decreased IIB myofiber mean cross-sectional area (CSA), only 16 Gy decreased IIA myofiber CSA. 16 Gy increased the incidence of small diameter IIA and IIB myofibers, while 4x4 Gy only increased the incidence of small diameter IIB myofibers. Both treatments decreased the frequency and CSA of low succinate dehydrogenase activity (SDH) fibers. Only 16 Gy increased the incidence of small diameter myofibers having high SDH activity. Neither treatment altered muscle signaling related to protein turnover or oxidative metabolism.ConclusionsCollectively, these results demonstrate that radiation dose differentially affects muscle remodeling, and these effects appear to be related to fiber type and oxidative metabolism

The Science Performance of JWST as Characterized in Commissioning

This paper characterizes the actual science performance of the James Webb Space Telescope (JWST), as determined from the six month commissioning period. We summarize the performance of the spacecraft, telescope, science instruments, and ground system, with an emphasis on differences from pre-launch expectations. Commissioning has made clear that JWST is fully capable of achieving the discoveries for which it was built. Moreover, almost across the board, the science performance of JWST is better than expected; in most cases, JWST will go deeper faster than expected. The telescope and instrument suite have demonstrated the sensitivity, stability, image quality, and spectral range that are necessary to transform our understanding of the cosmos through observations spanning from near-earth asteroids to the most distant galaxies.Comment: 5th version as accepted to PASP; 31 pages, 18 figures; https://iopscience.iop.org/article/10.1088/1538-3873/acb29