Increased glomerular hydrostatic pressure is an important determinant of glomerulosclerosis and can be modeled by in vitro exposure of mesangial cells to cyclic mechanical strain. Stretched mesangial cells increase extracellular matrix protein production, the hallmark of glomerulosclerosis. Recent data indicate that the serine/threonine kinase Akt may be involved in matrix modulation. Thus, Akt activation and matrix synthesis in stretched mesangial cells were studied. Exposure of mesangial cells to 1 Hz cyclic strain led to prompt Akt activation, which was biphasic to 24 h. Activation was dependent on signaling through phosphatidylinositol-3-kinase and required EGF receptor transactivation. Inhibition of signaling through the PDGF receptor, Src kinase, or cytoskeletal disruption failed to prevent strain-induced Akt activation. Collagen type 1A1 transcript expression, promoter activation, and protein secretion were increased by stretch at 24 h and were dependent on phosphatidylinositol-3 kinase. Overexpression of dominant-negative Akt inhibited strain-induced collagen 1A1 production. Conversely, overexpression of constitutively active Akt led to increased collagen 1A1 upregulation and secretion. Finally, Akt activation was observed in the glomeruli of remnant rat kidneys, a model marked by increased intraglomerular pressure. The authors conclude that mechanical strain induces Akt activation in mesangial cells through a mechanism requiring phosphatidylinositol-3-kinase and EGF receptor transactivation. Type 1 collagen production is dependent on Akt and can be induced by Akt overexpression. Akt activation is observed in remnant kidneys in vivo. Thus, the role of Akt in progression of chronic hemodynamic glomerular disease is worthy of further exploration.

To investigate the effect of restricted grazing time on behavior of Tan sheep on desert steppe, forty 4-months old male Tan sheep with an original body weight (BW) of 15.62±0.33 kg were randomly allocated to 4 grazing groups which corresponded to 4 different restricted grazing time treatments of 2 h/d (G2), 4 h/d (G4), 8 h/d (G8) and 12 h/d (G12) access to pasture. The restricted grazing times had a significant impact on intake time, resting time, ruminating time, bite rate and movement. As the grazing time decreased, the proportion of time spent on intake, bite rate and grazing velocity significantly (p<0.05) increased, but resting and ruminating time clearly (p<0.05) decreased. The grazing months mainly depicted effect on intake time and grazing velocity. In conclusion, by varying their foraging behavior, Tan sheep could improve grazing efficiency to adapt well to the time-limited grazing circumstance.

The beneficial effects on meat quality of adding vitamin E to diets have been extensively studied in cattle and lamb. However, how supplemental vit E affects the performance and meat quality of ʽTanʼ sheep has not been reported. Thirtyfive male lambs of ʽTanʼ sheep (20-30 d after weaning) with similar body weight were randomly divided into five groups of seven each to receive a basal diet plus five levels of vit E supplementation: 0 (control group, CG), 20, 100, 200, and 2000 IU d -1 lamb -1 . The results showed: 1) no differences were observed in animal growth performance between CG and vit E treated groups (VG) (P > 0.05); 2) vit E supplementation levels over 200 IU d -1 lamb -1 dramatically suppressed subcutaneous fat deposition and similarly that above 100 IU d -1 lamb -1 considerably reduced drip loss and pH 24 h of Longissimus dorsi (LD) muscle in VG lambs compared to those of CG (P < 0.01), but with no significant effect on other carcass characteristics (P > 0.05); 3) although vit E supplementation generally did not affect the fatty acid composition of intramuscular lipids in LD muscle, the percentage of n-6 polyunsaturated fatty acids (PUFA) and the ratio of n-6/n-3 PUFA were significantly enhanced (P < 0.05) and an increasing tendency (P < 0.1) for both total PUFA proportion and the ratio of PUFA/saturated fatty acids (SFA) was also observed in ʽTanʼ sheep lambs treated with vit E. In conclusion, vit E supplementation of male ʽTanʼ sheep lambs did not influence growth performance, significantly reduced subcutaneous fat deposition, drip loss, pH 24 h and tended to improve fatty acid profile of LD muscle.

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