Effect of dietary roughage level on chewing activity, ruminal pH, and saliva secretion in lactating Holstein cows.

Increasing dietary roughage level is a commonly used strategy to prevent subacute ruminal acidosis. We hypothesized that high-roughage diets could promote chewing activity, saliva secretion, and hence more alkaline to buffer rumen pH. To verify the hypothesis, 12 multiparous Holstein cows in mid lactation were randomly allocated to 4 treatments in a triplicated 4 × 4 Latin square experiment with one cow in each treatment surgically fitted with a ruminal cannula. Treatments were diets containing 40, 50, 60, or 70% of roughage on a DM basis. Increasing dietary roughage level decreased DM, CP, OM, starch, and NEL intake, increased ADF intake, and decreased milk yield linearly. Intake of NDF was quite stable across treatments and ranged from 7.8 to 8.1 kg/d per cow. Daily eating time increased linearly with increased roughage level. The increase in eating time was due to increased eating time per meal but not number of meals per day, which was stable and ranged from 8.3 to 8.5 meals per day across treatments. Increasing dietary roughage level had no effect on ruminating time (min/d), the number of ruminating periods (rumination periods per d), and chewing time per ruminating period (min/ruminating period). Ruminating time per kilogram of NDF intake and total chewing time per kilogram of ADF intake were similar across treatments (57.4 and 183.8 min/kg, respectively). Increasing dietary roughage level linearly increased daily total chewing time; linearly elevated the mean, maximum, and minimum ruminal pH; and linearly decreased total VFA concentration and molar proportion of propionate in ruminal fluid. Saliva secretion during eating was increased, the secretion during rumination was unaffected, but the secretion during resting tended to decrease with increased dietary roughage level. As a result, total saliva secretion was not affected by treatments. In conclusion, the results of the present study did not support the concept that high-roughage diets elevated ruminal pH through increased salivary recycling of buffering substrates.

[Experimental study on the in vitro osteogenic differentiation of dental pulp stem cells encapsulated in Pluronic F-127 hydrogel].

OBJECTIVE: To evaluate the biocompatibility and viability of nonionic triblock copolymer Pluronic F-127 as a cell scaffold for osteogenic differentiation of dental pulp stem cells(DPSC). METHODS: DPSC were obtained via enzymatic digestion method and purified bylimited dilution method. The freeze dried hydrogel of 20% Pluronic F-127 was prepared and itsstructurewas observed usingscanning electron microscopy(SEM). After the encapsulation of cells of passage 3 in Pluronic F-127, the effects of hydrogel on the proliferations of DPSC were assessed with methyl thiazolyl terazolium(MTT) after one day and 3, 5, 7 days of incubations, respectively. On day 14, osteogenic abilities of DPSC encapsulated in the hydrogel were estimated by means of alizarin red S, immunocytochemical staining and real-time quantitative PCR(RT-qPCR). RESULTS: DPSC were isolated and cultured successfully in the present study. SEM observations showed that porous structures which might be suitable for cell culture. A570 values of MTT were then normalized. A570 values of the cells in 2D cultures were 0.30±0.06, 0.30±0.17, 0.35±0.04 and 0.25±0.06 and A570 values of DPSC in 3D cultures were 0.36±0.06, 0.54±0.18, 0.70±0.10 and 0.32±0.10 on day 1, 3, 5 and 7, respectively. A570 value peaks were found on day 5 in both groups. The proliferation of 3D cultured DPSC was higher than that of 2D cultured cells(P<0.05). After 14 days of osteogenic induction, there were no calcium nodules observed in the control group and the numbers of calcium nodulesin the 2D and 3D groups had no significant difference(P>0.05). Inmmunocytochemical staining demonstrated strong expression of osteoblast marker Runt-related transcription factor 2(RUNX2), type Ⅰ collagen(Col-Ⅰ) and relatively low expression of osteocalcin(OCN). Moreover, RT-qPCR showed no differences between the relative expression of ALP, RUNX-2, OCN in the 2D and 3D groups (P>0.05), but a higher relative expression of Col-Ⅰ was observed in the 3D group(P=0.023). CONCLUSIONS: Pluronic F-127 is a promising cell scaffold or cell carrier for the osteobalst differentiation of dental pulp stem cells.

[Determination of aluminium and barium in silicon-aluminium-barium alloy with internal standard by ICP-AES].

A method for the determination of aluminium and barium in silicon-aluminium-barium alloy with the internal standard by ICP-AES was studied. The method of melting sample, the interference of dissolved acid and coexisting elements and the working parameters were experimented. The sample was melted by appropriate acid, was changed into solution, the calculating lines were made by standard solution of aluminium and barium, then the concentrations of aluminium and barium were determined by ICP-AES. The linear rang, detection limits and RSD of the method were examined. The method was simple and the results were accurate.