Figure - PMC

Skip to main content

An official website of the United States government

Here's how you know

Here's how you know

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

View full-text article in PMC

. 2021 Apr 28;11:9168. doi: 10.1038/s41598-021-88392-4

Search in PMC
Search in PubMed
View in NLM Catalog
Add to search

© The Author(s) 2021

Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.

PMC Copyright notice

Characterization of the hindlimb muscles among three experimental groups: GC, AG, and MG. (A) Overview of the MHU-1 study. Twelve male mice were launched by SpaceX-9 from the Kennedy Space Center in Florida on July 18, 2016. After arrival at the ISS, six of the mice were housed in HCU under microgravity (MG) for approximately 34.6 days, while the other six mice were housed in an artificial 1 g onboard environment (AG) induced by centrifugation for approximately 34.1 days during the approximate 37-day berthing period. After approximately 35 days of habitation on the ISS, all 12 mice were loaded into the Dragon capsule and kept under microgravity for approximately 1.3 days before undocking. The capsule subsequently splashed down in the Pacific Ocean near Southern California on August 26, 2016. The mice were then transported to a laboratory for behavioral tests and other analyses after approximately 2 days of undocking. Graphical representations of the study design using the multiple artificial-gravity research system (MARS). Three experimental groups, namely, ground control (GC), artificial 1 g onboard environment (AG), and microgravity (MG) in the ISS, are color-coded as green, blue, and red, respectively, in the following bar graphs. (B) Quantification of the change in individual skeletal muscle weights: soleus (Sol), gastrocnemius (Gas), plantaris (Pla), tibialis anterior (TA), and extensor digitorum longus (EDL), among GC (n = 6), AG (n = 5), and MG (n = 4) groups, normalized by body weight and graphed in the Tukey boxplot. P-value from Tukey’s test is indicated as follows: *P < 0.05 and **P < 0.01. (C) Hematoxylin–eosin staining of soleus and EDL sections. Scale bars indicate 100 μm. (D) Immunostaining of the myosin heavy chain using muscle fiber-specific antibodies (type I; blue, type IIa; red, type IIb; green) in the soleus muscle. The unstained fibers were predicted to be of type IIx fibers (black). Scale bars indicate 100 μm. (E, F) Frequency (E) and cross-sectional areas (CSA) (F) of each fiber type in the soleus muscles of the GC (n = 3), AG (n = 3), and MG (n = 3). P-value from Student’s t-test is indicated as follows: *P < 0.05 and **P < 0.01.