Effect of ultrafine grinding on the structure and physical properties of pregelatinized rice starch.

This study used a combination method of ultrafine grinding and pregelatinization to modify rice starch (RS) to delay its retrogradation and provide a rationale for prolonging rice product shelf life. The structure and physicochemical properties of the pregelatinized ultrafine grinding rice starch (PURS) were compared with those of RS, ultrafine grinding rice starch (URS), and pregelatinized rice starch (PRS). The microstructure, molecular weight, branched starch length distribution, short-range order, crystal structure, and physical properties of RS, URS, PRS, and PURS were analyzed, respectively. Results showed that RS, URS, PRS, and PURS granules exhibited similar spherical or polygonal shapes, and the content of amylose and short-branched starch in PURS increased compared with RS, URS, and PRS. Furthermore, the cross-polarization of PRS and PURS disappeared. Long-chain amylopectin and average molecular weight of PURS decreased significantly after ultrafine grinding. Our study suggested reduced breakdown value and setback value and improved gel stability, and PURS was beneficial for delaying retrogradation compared to RS, URS, and PRS. The ultrafine grinding method improved the water swelling capacity (WSC), solubility, pasting properties, and gelation properties of PRS. The hardness of PURS was reduced by ultrafine grinding. These suggest that the combination of ultrafine grinding and pregelatinization could improve the properties of RS. Pearson's correlation analysis showed that the structure of PURS significantly influenced the physicochemical properties. The present study was helpful in better understanding the importance of ultrafine grinding in improving the anti-retrogradation of PURS and provided new insights into extending the shelf life of rice products by ultrafine grinding and pregelatinization.

[Construction and expression of eukaryotic expression vector of human 4-1BB ligand gene in tumor cells and its antitumor activity in vitro].

AIM: To construct eukaryotic expression vector of human 4-1BB ligand (4-1BBL) gene and express it in HT-29 cell line. To explore the effect on activation and cytotoxicity of human cytotoxic T lymphocytes(CTLs) induced by human 4-1BBL gene transfection into tumor cells in vitro. METHODS: RT-PCR was applied to amplify the full-length of human 4-1BBL gene from Raji cells. After sequencing, the cDNA was recombinated into the eukaryotic expression vector pcDNA3.1(-) and transfected into HT-29 cells through Lipofect AMINE 2000. Human 4-1BBL mRNA and protein expression of transfected cells was detected by RT-PCR and FACS respectively. Human peripheral blood mononuclear cells were stimulated with anti-CD3 mAb and incubated with non-transfected or transfected HT-29 cells, respectively. The MTT colorimetry was used to detect the proliferation and cytotoxic effect of T lymphocytes. Meanwhile, the expression of intracellular IFN-gamma was detected by FCM. RESULTS: The HT-29 cells transfected by pcDNA3.1(-)-h4-1BBL could express human 4-1BBL efficiently. As compared with wild type HT-29 cells, the transfected HT-29 cells had more effect for proliferation, IFN-gamma production and cytotoxic activity of lymphocytes. CONCLUSION: The recombinant eukaryotic expression vector of pcDNA3.1(-)-h4-1BBL is successfully constructed. The transfection of human 4-1BBL gene in HT-29 cells is effctive in enhancing its immunogenicity and inducing antitumor immune response in vitro.

[The role of costimulatory molecule 4-1BB and CD28 in activating of various T cell subsets from human peripheral blood].

AIM: To explore the role of 4-1BB molecule in the activation and proliferation of CD4(+) T cells and CD8(+) T cells and compare it with that of CD28 molecule. METHODS: Human peripheral blood mononuclear cells (PBMCs) were stimulated in-vitro with anti-CD3 mAb. Anti-4-1BB mAb and anti-CD80 mAb were added so as to block respectively costimulatory signals of 4-1BB/4-1BBL and CD28/B7-1. Flow cytometry was used to detect the proliferation ratio of CD4(+) T cells and CD8(+) T cells and the secretion of IFN-gamma. RESULTS: When 4-1BB/4-1BBL and CD28/B7-1 signals were blocked by anti-4-1BBL mAb and anti-CD80 mAb, the proliferative response and the secretion of IFN-gamma by CD4(+) T cells and CD8(+) T cells were obviously decreased. In the group stimulated with anti-CD3 mAb only, the ratio of CD8/CD4 T cells was 1.98+/-0.06. In the groups blocked with anti-4-1BBL mAb and anti-CD80 mAb, the ratios were 0.96+/-0.03 and 2.69+/-0.16, respectively. CONCLUSION: 4-1BB molecule could provide a costimulatory signal for activation and proliferation of CD4(+) T cells and CD8(+) T cells. The costimulatory signal mediated by 4-1BB molecule could mainly induce the proliferative response of CD8(+) T cells, while that mediated by CD28 molecule could induce the activation of CD4(+) T cells mainly.