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Objective To establish an intestinal organoid-based assay to investigate the radiation mitigation effect of epiregulin in vitro. Methods Intestinal crypts were released from tissue incubated with EDTA. Intestinal crypts seeded in 3D matrigel were irradiated at 24 h after plating. The radiation mitigation effect of epiregulin was evaluated by measuring the survival rate, size and budding numbers of the organoid after irradiation, and the basic FGF was used as a positive control of epiregulin. Results Radiation-induced lethality and dose-dependent survival curve of the intestinal organoid were consistent with in vivo data. Treatment with epiregulin (400 ng/ml) at 24 h post-radiation significantly increased survival rate of 8 Gy X-ray irradiated intestinal organoid in comparison with non-treated group [(12.56 ± 1.02)％vs. (4.73 ± 0.38)％, t=12.43,P<0.05]. Conclusions Epiregulin has radiation mitigation effect on intestinal organoid and could serve as a potential medical countermeasure to mitigate gastrointestinal toxicity.
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Objective To measure the difference of radiosensitivity between small and large intestines toward high dose of radiation and investigate the role of stem cells in this difference.Methods C57BL/6 male mice,6-8 weeks old,were randomly divided as control group and radiation group received 19 Gy whole body γ-ray irridiation.Large and small intestines of the mice were collected 6,12,24,48,72 and 96 h after radiation.The proliferation and apoptosis of the large and small intestines and their stem cells were then detected by immunochemistry,and the change of stem cell number in the large and small intestines were detected by in-situ hybridization.Results HE staining showed that 19 Gy γ-ray irradiation caused more severe injury in the small intestine,and all the crypt in the small intestine were extinct at 48 h post-radiation.However,the proliferation index of crypt in the large intestine was as high as 0.23 (t =4.67,P ＜0.05).Compared with the small intestine,the apoptotic index of epithelial cells in the crypt of large intestine was much lower at 12 and 24 h after irradiation (t =-1.92,-2.42,P＜0.05).The apoptotic population of stem cells in the small intestine at 12 and 24 h post irradiation were significantly lower than that in the large intestine (t =-1.98,-2.33,P ＜ 0.05),and the number of stem cell in the large intestine was significantly higher than that in the small intestine 24,48 h after radiation (t =1.98,3.31,P ＜0.05).Conclusions The radiosensitivity of small intestine toward high dose of irradiation is significantly higher than that of the large intestine,where the difference in radiosensitivity of stem cells between large intestine and small intestine may be involved.
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Objective To study the antibacterial mechanisms of berberine and try to understand the reasons why bacteria cells difficultly resisted to it. Methods Detecting the minimal inhibitory concentration (MIC) of bacterial cultures incubated under sub-MIC concentration of berberine, Huanglian, and Neomycin for more than 200 generations, in order to analyze the bacteria resistance. Detecting the binding kinetics of berberine to DNA, RNA, and proteins. Observing the changes in bacterial cell surface structure with scanning electron microscopy. Detecting the Ca2+ and K.+ released from berberine-treated bacterial cells with atomic absorption spectrum. Detection the absorption of methyl-3H-thymine (3H-dT), 3H-uridine (3H-U), and 3H-tyrosine (3H-Tyr) into berberine-treated bacterial cells. Results MICs of bacterial cultures, growing more than 200 generations in MH medium with 1/2 MIC of berberine (BA200) or Huanglian (HA200), did not increase compared to the control, while remarkably increased in MH medium with 1/2 MIC of Neomycin (NA200). In addition, from the culture NA200 it was easy to isolate resistant mutant strains which could grow in MH medium with more than four times MIC Neomycin, but from the culture BA200 and HA200 it was difficult to isolate berberine or Huanglian mutant strains could grow in MH medium with more than four times MIC berberine or Huanglian. The binding kinetics of berberine to DNA, RNA, and proteins illustrated that berberine could easily and tightly bind to DNA and RNA, and hardly dis-bind from DNA- and RNA-berberine complexes. Berberine could easily bind to protein too, but also easily dis-bind from berberine-protein complex. The bacterial cells treated with berberine sharply decreased the absorption of 3H-dT, 3H-U, and 3H-Tyr, as the radioactive precursors of DNA, RNA, and protein biosynthesis. Berberine could damage bacterial cell surface structure, especially for Gram-negative bacteria. Ca2+ and K+ released from berberine-treated cells increased significantly compared to the control. Conclusion All of above results indicate that bacterial cells could not easily become resistant mutants to berberine. The mechanisms for the bactericidal effect of berberine include: inhibiting DNA duplication, RNA transcription, and protein biosynthesis; influencing or inhibiting enzyme activities; destructing the bacterial cell surface structure and resulting in Ca2+ and K+ released from cells. All of the berberine bactericidal mechanisms are the most essential physiological functions for a live cell, if influenced any one such function, the mutation would be lethal mutation, so that it is difficult to get berberine resistant cells. The results in this paper also prefigure that berberine and its related Chinese medicines would provide a feasible way to control antibiotic resistance problem.
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The structural gene encoding mature peptide of extracellular ? amylase was amplified from the genome DNA of hyperthermophilic archaeon Pyrococcus furiosus by PCR The recombinant plasmid pUC19 amy was constructed by inserting the amplified segment into vector pUC19 The recombinant vector pYX212 amy was constructed by ligate the heterogeneous fragment of pUC19 amy into the multiple cloning site of pYX212, an expression vector of yeast Saccharomyces cerevisiae W303 A1 were transformed with pYX212 amy by electroporation The transformant expressed the activity of the thermophilic ? amylase successfully The recombinant enzyme has the similar enzymatic properties as the extracellular ? amylase produced by Pyrococcus furiosus : it shows an enzymatic activity optimum at pH 5 0, and its optimal temperature for enzymatic activity is about 90℃, more than 50% of its initial enzymatic activity is still detectable after it was incubated at 121℃ for 30 minutes