Swimming exercise activates peroxisome proliferator-activated receptor-alpha and mitigates age-related renal fibrosis in rats.

Aging results in progressive decline of renal function as well as histological alterations including glomerulosclerosis and interstitial fibrosis. The objective of current study was to test the benefits of moderate swimming exercise in aged rats on renal function and structure and investigate its molecular mechanisms. Aged rats of 21-months old were given moderate swimming exercise for 12 weeks. Swimming exercise in aged rats led to reduced plasma levels of creatinine and blood urea nitrogen. Periodic acid-Schiff staining results revealed reduced renal injury scores in aged rats after swimming exercise. Swimming exercise in aged rats mitigated renal fibrosis and downregulated the mRNA expression of Acta2, Fn, Col1a, Col4a, and Tgfb1 in kidneys. Swimming exercise in aged rats attenuated lipid accumulation and reduced levels of triglyceride in kidneys. Swimming exercise in aged rats abated oxidative stress, evidenced by reduced MDA levels and increased MnSOD activities in kidneys. Swimming exercise in aged rats inhibited NF-κB activities and reduced renal expression of pro-inflammatory cytokines including MCP-1, IL-1ß and IL-6. Mechanistically, swimming exercise restored mRNA and protein expression of PPAR-α in kidney of aged rats. Furthermore, swimming exercise in aged rats increased expression of PPAR-α-targeting microRNAs including miR-21 and miR-34a. Collectively, swimming exercise activated PPAR-α, which partly explained the benefits of moderate swimming exercise in aging kidneys.

[Experimental study on application of the boundary layer theory for determining steady aeration intensity of precoated dynamic membrane bioreactor].

The rheological behaviour of the low sludge concentration liquor in MBR was investigated and made a conclusion that this liquor approximated to the Newtonian fluid while the concentration of the sludge was less than 8000 mg x L(-1). Furthermore, when the laminar flow boundary layer thickness on the surface of flat membrane came up to the thickness of precoated dynamic membrane (PDM), the steady aeration intensity was calculated by using the boundary layer theory in the Newtonian hydrodynamics. In order to ensure the stability of the pre-coated dynamic membrane bioreactor (PDMBR), oxygen supply aeration intensity was chosen to supply the best dissolved oxygen (3-5 mg x L(-1) in the initial stages and gradually increased to the steady aeration intensity. The results indicated that this mode could enhance the stability of PDM. In the experiment period (31 d), effluent COD was less than 12.48 mg x L(-1) and its average removal rate was 97.49%, NH4+ -N was less than 5.27 mg x L(-1) and its average removal rate was 76.13%, while the operational pressure just increased to 27 kPa. During the last period of the experiment, the stability of the PDMBR was studied when the aeration intensity was more than the steady aeration intensity and it was found that the precoated layer had been brushed off from the surface of common filter cloth, so this phenomenon proved that using the boundary layer theory could determine steady aeration intensity of PDMBR.