The degradation of proteins in pinniped skeletal muscle: viability of post-mortem tissue in physiological research

Species-specific responses to di (2-ethylhexyl) phthalate reveal activation of defense signaling pathways in California sea lion but not in human skeletal muscle cells in primary culture

Higher antioxidant defenses in marine than terrestrial mammals allow them to cope with oxidative stress associated with diving-induced ischemia/reperfusion. Does this adaptation translate to inherent resistance to other stressors? We analyzed oxidative stress indicators in cells derived from human and California sea lion (Zalophus californianus) skeletal muscle upon exposure to di (2-ethylhexyl) phthalate (DEHP). Human abdominal muscle biopsies were collected from healthy women undergoing planned cesarean surgery. California sea lion samples were collected postmortem from stranded animals. Skeletal muscle cells derived from each species were exposed to 1 mM DEHP for 13 days (n = 25) or maintained under control (untreated) conditions (n = 25). Superoxide radical (O2•-) production, oxidative damage and antioxidant enzyme activities were measured using spectrophotometric methods. Gene expression was analyzed by RT-qPCR. DEHP exposure increased O2•- production and superoxide dismutase (SOD) activity in both species. Glutathione S-transferase (GST) activity and protein carbonyl levels increased in human but not in California sea lion cells. In contrast, glutathione peroxidase (GPx) and catalase (CAT) activities increased in California sea lion but not in human cells exposed to DEHP. In human cells, DEHP increased microsomal GST1 and GST (κ, μ, θ, ω, and ᴢ), while suppressing 8-oxoguanine DNA glycosylase (OGG1), CAT, glutathione reductase (GR), and nuclear factor erythroid 2-related factor 2 (NRF2) expression, suggesting increased oxidative stress and phase two detoxification processes. In California sea lion cells, DEHP increased OGG1, NRF2, GPx2 and SOD3 expression, suggesting activation of antioxidant defenses, which potentially contribute to maintaining redox homeostasis, avoiding oxidative damage.

Histology of 24 organs from Asian elephant calves (Elephas maximus)

Background

Elephants are the largest and heaviest living terrestrial animals, but information on their histology is still lacking. This study provides a unique insight into the elephant's organs and also provides a comparison between juvenile Asian elephants and adult Asian elephants or other species. Here we report on the histological structure of 24 organs, including the skin, brain (cerebrum, cerebellar hemisphere, vermis, thalamus, midbrain), spinal cord, sciatic nerve, striated skeletal muscle, cardiac muscle, bone (flat bone and long bone), cartilage (hyaline cartilage and fibrocartilage), heart (right atrium, right ventricle), blood vessels (aorta, pulmonary artery and caudal vena cava), trunk, trachea, lung, tongue, esophagus, stomach, small intestine (duodenum, jejunum, ileum), large intestine (cecum, colon, rectum), liver and pancreas, kidney, ovary, uterus (body and horn) and spleen of two juvenile Asian elephants.

Methods

Tissue sections were stained with Harris's hematoxylin and eosin Y.

Results

While almost all structures were similar to those of other species or adult elephants, some structures were different from other mammalian species, such as: plexiform bone was found in flat bone only; a thin trachealismuscle was observed in the trachea; and no serous or mucinous glands were found in the submucosa of the trachea.

Discussion

Histological information from various organs can serve as an important foundation of basal data for future microanatomical studies, and help in the diagnosis and pathogenesis in sick elephants or those with an unknown cause of death.