ResearchPad - environmental-physiology https://www.researchpad.co Default RSS Feed en-us © 2020 Newgen KnowledgeWorks <![CDATA[Effect of somatic maturity on the aerobic and anaerobic adaptations to sprint interval training]]> https://www.researchpad.co/article/Nee9d9b91-1e50-4da1-ad79-8a26873d15df After 4 weeks of sprint interval training, improvements in aerobic and anaerobic exercise performance were observed in youth male athletes. However, prepubertal participants had no changes following training.

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<![CDATA[The effect of acute exercise on environmentally induced symptoms of dry eye]]> https://www.researchpad.co/article/N70a39e83-f5fd-4a95-b441-b886ea493768

Abstract

The purpose of this study was to investigate the effects of acute exercise on environmentally induced symptoms of dry eye. Twelve participants without dry eye disease volunteered to complete three experimental visits in a randomized order; (1) control condition seated for 1 h at a relative humidity (RH) of 40% (CONT), (2) dry condition seated for 1 h at a RH of 20% (DRY), and (3) exercise condition seated for 40 min followed by 20 min of cycling exercise at a RH of 20% (EXER). Tear volume, tear matrix metalloproteinase 9 (MMP‐9), perception of dry eye symptoms (frequency and severity), core temperature, and ocular surface temperature (OST) were measured at the end of each exposure. The perception of dry eye frequency and MMP‐9 concentration were significantly higher in DRY compared to CONT (P < 0.012), with no differences in EXER compared to CONT. The results suggest that an acute bout of exercise may attenuate symptoms of environmentally induced dry eye, and warrant further research.

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<![CDATA[The effects of hibernation and forced disuse (neurectomy) on bone properties in arctic ground squirrels]]> https://www.researchpad.co/article/5b016cce463d7e4814341d83

Abstract

Bone loss is a well‐known medical consequence of disuse such as in long‐term space flight. Immobilization in many animals mimics the effects of space flight on bone mineral density. Decreases in metabolism are also thought to contribute to a loss of skeletal mass. Hibernating mammals provide a natural model of disuse and metabolic suppression. Hibernating ground squirrels have been shown to maintain bone strength despite long periods of disuse and decreased metabolism during torpor. This study examined if the lack of bone loss during torpor was a result of the decrease in metabolic rate during torpor or an evolutionary change in these animals affording protection against disuse. We delineated changes in bone density during natural disuse (torpor) and forced disuse (sciatic neurectomy) in the hind limbs of the arctic ground squirrel (AGS) over an entire year. We hypothesized that the animals would be resistant to bone loss due to immobilization and disuse during the winter hibernation season when metabolism is depressed but not the summer active season. This hypothesis was not supported. The animals maintained bone density (dual‐energy X‐ray absorptiometry) and most bone structural and mechanical properties in both seasons. This was observed in both natural and forced disuse, regardless of the known metabolic rate increase during the summer. However, trabecular bone volume fraction (microcomputed tomography) in the distal femur was lower in neurectomized AGS at the study endpoint. These results demonstrate a need to better understand the relationship between skeletal load (use) and bone density that may lead to therapeutics or strategies to maintain bone density in disuse conditions.

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<![CDATA[Carbonic anhydrase 2‐like in the giant clam, Tridacna squamosa: characterization, localization, response to light, and possible role in the transport of inorganic carbon from the host to its symbionts]]> https://www.researchpad.co/article/5b467fed463d7e5f40bc6df3

Abstract

The fluted giant clam, Tridacna squamosa, lives in symbiosis with zooxanthellae which reside extracellularly inside a tubular system. Zooxanthellae fix inorganic carbon (Ci) during insolation and donate photosynthate to the host. Carbonic anhydrases catalyze the interconversion of CO 2 and HCO3, of which carbonic anhydrase 2 (CA2) is the most ubiquitous and involved in many biological processes. This study aimed to clone a CA2 homolog (CA2‐like) from the fleshy and colorful outer mantle as well as the thin and whitish inner mantle of T. squamosa, to determine its cellular and subcellular localization, and to examine the effects of light exposure on its gene and protein expression levels. The cDNA coding sequence of CA2‐like from T. squamosa comprised 789 bp, encoding 263 amino acids with an estimated molecular mass of 29.6 kDa. A phenogramic analysis of the deduced CA2‐like sequence denoted an animal origin. CA2‐like was not detectable in the shell‐facing epithelium of the inner mantle adjacent to the extrapallial fluid. Hence, CA2‐like is unlikely to participate directly in light‐enhanced calcification. By contrast, the outer mantle, which contains the highest density of tertiary tubules and zooxanthellae, displayed high level of CA2‐like expression, and CA2‐like was localized to the tubule epithelial cells. More importantly, exposure to light induced significant increases in the protein abundance of CA2‐like in the outer mantle. Hence, CA2‐like could probably take part in the increased supply of inorganic carbon (Ci) from the host clam to the symbiotic zooxanthellae when the latter conduct photosynthesis to fix Ci during light exposure.

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