Effect of a nitric oxide synthase inhibitor NG-nitro-L-arginine methyl ester on invasion of human colorectal cancer cell line SL-174T

AIML To investigate the effect and mechanism of action of the nitric oxide synthase （NOS） inhibitor NG-nitro-L-arginine methyl ester （L-NAME） on invasion and metastasis of human colorectal cancer cell line SL-174T. METHODS： Human colorectal cancer cel4 line SL-174T was cultured and treated separately with four different dosages of L-NAME for 72 h, Nitric oxide （NO） production was measured with Griess reagent, The effect of L-NAME on invasion and migration of SL-174T cells were evaluated by using Transwell chambers attached with polycarbonate filters and reconstituted basement membrane （Matrigel）, RT-PCR was performed to determine the mRNA levels of matrix metalloproteinase-2 （MMP-2） and tissue inhibitor metalloproteinase-2 （TIMP-2）,RESULTS： L-NAME could significantly inhibit NO production of SL-174T in a dose-dependent manner. After being treated for 72 h with 0.2, 0.4, 0.8, and 1.0 mmol/L L- NAME, respectively, the ability of the L-NAME treated SL- 174T cells to invade the reconstituted basement membrane decreased significantly （t = 8.056, P〈0.05; t= 14.467, P〈0.01; t= 27.785, P〈0.01; and t= 29.405, P〈0.01, respectively） and the inhibition rates were 10.29%, 19.62%, 34.08%, and 42.23%, respectively. Moreover, L-NAME could inhibit migration of SL-174T cells, and the inhibition rates were 20.76%, 24.95%, 39.43%, and 46. 85% for L-NAME at 0.2, 0.4, 0.8, and 1.0 mmol/L, respectively （t = 15.116, P〈0.01）. In addition, after treatment with L-NAME, expression of MMP-2 mRNA was significantly decreased （t = 71.238, P〈0.01） and that of TIMP-2 mRNA was markedly increased （t = -13.020, P〈0.01）. CONCLUSION： L-NAME exerts anti-invasive and anti- metastatic effects on SL-174T cell line via downregulating MNP-2 mRNA expression and upregulating TIMP-2 mRNA expression.

Phase composition and luminescent properties of strontium aluminate long persistence phosphor synthesized by combustion synthesis method with different Sr/Al ratios

Strontium aluminate long persistence phos phors are synthesized by combustion method. By control- ling the raw material ratio （Sr/Al）, the effects of phase composition on subsequent spectroscopic properties of phosphors are studied. Results show that the phase com-position changes from strontium-rich phase to aluminum- rich phase with the decrease of Sr/AI： when the rate of Al/Sr changes from 3：1 to 1：1, the main crystal phase of samples is Sr3Al206, and it exhibits the characteristic fluorescence of Eu^3＋ in the lattice of Sr3Al206; when the rate of Al/Sr is between 1：2 and 2：7, phase composition is the mixture of SrAl204 and SrAl4OT, and it emits the characteristic fluorescence of Eu^2＋ in SrAl204 but not in SrAl4OT; when Al/Sr decreases to 1：4 or even 1：12, the main crystal phase of samples transform into SrAl12019, and the characteristic emission peak is about 470 nm, which corresponds to the characteristic emission of Eu2＋ in SrAl12019. At the end of the article, the influence laws of two different synthesis methods on phase composition of samples between high-temperature solid method and combustion method are compared. Compared with the high-temperature solid method, the rule of influence is similar, but the mole ratio of Al/Sr in products is always higher than the initial ratio of the raw material, and com-pounds like Sr4Al14025 are not obtained by combustion method.

Sintering behavior and properties of SiC/Si_3N_4 composite

SiC/Si_3N_4 composite was pressureless sintered using self-propagating high-temperature combustion synthesis a-Si_3N_4 powder and appropriate amount of b-SiC powder. Both of the sintering additive systems were used,which were YAN（Y_2O_3–Al_2O_3–AlN） and YN（Y_2O_3–AlN）.The influences of b-SiC content on sintering behavior of SiC/Si_3N_4 composite were investigated. The results show that the density, shrinkage, bending strength, hardness, and fracture toughness of the samples with two sintering additive systems increase first with the increase of the contents of b-SiC and then decrease even when b-SiC contents continually increase. The tendency of weight loss of the samples is opposite. The b-SiC content of the samples with the best mechanical properties is different in two systems. For YAN system, the best mechanical properties of the samples are gained when b-SiC content reaches 10 %, while as for YN system it is 5 %. The properties of YN samples are superior to YAN samples. J phase（2Y_2O_3 ·Si_2N_2O） forms in YN system easily. A small amount of M phase（Y_2O_3·Si_3N_4） is observed in YAN system.