Cryo-EM structure of an activated VIP1 receptor-G protein complex revealed by a NanoBiT tethering strategy.

Vasoactive intestinal polypeptide receptor (VIP1R) is a widely expressed class B G protein-coupled receptor and a drug target for the treatment of neuronal, metabolic, and inflammatory diseases. However, our understanding of its mechanism of action and the potential of drug discovery targeting this receptor is limited by the lack of structural information of VIP1R. Here we report a cryo-electron microscopy structure of human VIP1R bound to PACAP27 and Gs heterotrimer, whose complex assembly is stabilized by a NanoBiT tethering strategy. Comparison with other class B GPCR structures reveals that PACAP27 engages VIP1R with its N-terminus inserting into the ligand binding pocket at the transmembrane bundle of the receptor, which subsequently couples to the G protein in a receptor-specific manner. This structure has provided insights into the molecular basis of PACAP27 binding and VIP receptor activation. The methodology of the NanoBiT tethering may help to provide structural information of unstable complexes.

Effect of fluorene groups on the properties of multiblock poly(arylene ether sulfone)s-based anion-exchange membranes.

Two kinds of novel multiblock poly(arylene ether sulfone)s were synthesized via block copolycondensation of telechelic oligomers as a starting material for the preparation of anion-exchange membranes (AEMs). The as-synthesized copolymers have extremely similar main chains. The difference is that the benzylmethyl groups for one are located on the fluorene-sulfone segments and they are located on the isopropylidene-sulfone segments for the other. The benzylmethyl moieties served as precursors to cationic sites and were brominated using N-bromosuccinimide (NBS) and then quaternized with N,N,N',N'-tetramethyl-1,6-diaminohexane (TMHDA). Controlled bromination and quaternization at specific positions of the benzylmethy-containing fluorene-sulfone segments and isopropylidene-sulfone segments can be achieved. 1H NMR spectroscopy, Fourier transform infrared spectroscopy, and gel permeation chromatography were used to characterize the as-synthesized copolymers. Distinct microphase separation in the as-prepared AEMs was observed using small-angle X-ray scattering and transmission electron microscopy. The AEM containing fluorene-sulfone segments (IEC=1.89 meq·g(-1)) showed higher ionic conductivity and methanol permeability than that containing isopropylidene-sulfone segments (IEC=2.03 meq·g(-1)). Moreover, the former showed better alkaline stability than the latter.

Chemical composition and antimicrobial activity of the essential oil of kumquat (Fortunella crassifolia Swingle) peel.

The aim of this study was to determine the main constituents of the essential oil isolated from Fortunella crassifolia Swingle peel by hydro-distillation, and to test the efficacy of the essential oil on antimicrobial activity. Twenty-five components, representing 92.36% of the total oil, were identified by GC-MS analysis. The essential oil showed potent antimicrobial activity against both Gram-negative (E. coli and S. typhimurium) and Gram-positive (S. aureus, B. cereus, B. subtilis, L. bulgaricus, and B. laterosporus) bacteria, together with a remarkable antifungal activity against C. albicans. In a food model of beef extract, the essential oil was observed to possess an effective capacity to control the total counts of viable bacteria. Furthermore, the essential oil showed strongly detrimental effects on the growth and morphological structure of the tested bacteria. It was suggested that the essential oil from Fortunella crassifolia Swingle peel might be used as a natural food preservative against bacteria or fungus in the food industry.

[Effects of metallothionein on rifampicin (RFP)-induced hepatotoxicity in mice].

OBJECTIVE: To investigate the effect of metallothionein (MT) on rifampicin (RFP)-induced hepatotoxicity and the possible mechanisms. METHODS: Male MT- I / II null (MT-/-) and wild type (MT+/+) mice were randomly divided into 4 groups, respectively, and were orally administered RFP (50, 100 or 200 mg/kg) or equal volumes of solvent daily for 15 consecutive days. Levels of plasma alanine aminotransferase (ALT), alkaline phosphatase (ALP) and direct bilirubin (DB) were determined. Liver indexes were calculated and liver histopathologic changes were examined by hematoxylin and eosin (HE) staining. The content of glutathione (GSH) as well as the activities of glutathione peroxydase (GPx) and glutathione reductases (GR) were measured in the liver homogenates. RESULTS: RFP treatment induced significant increases in plasma ALT, AST and DB, as well as liver index. Significant histopathologic changes which were charactered as fatty degeneration in liver were noteced. Moreover, augmentations of GSH content and GR activity and attenuation of GPx activity were observed. More severe hepatic injuries in MT-/- mice were observed as compared to MT+/+ mice, which were evidenced by higher liver/body weight ratio and GR activity, lower GSH content and GPx activity, and more serious fatty degeneration. CONCLUSION: RFP-induced hepatotoxicity was associated with cholestasis and oxidative damage. MT -/- mice were more susceptible than MT +/+ mice to RFP-induced hepatotoxicity and the enhanced hepatotoxicity involves increased oxidative stress.

[Effect of subchronic administered Bismerthlazol on thyroid glands of rats].

OBJECTIVE: To test the impact of subchronically administered Bismerthlazol on the thyroid morphosis of rats. METHODS: One hundred SD rats were randomly divided into one negative control group and four experimental groups with 7.0, 27.9, 111.7, and 447.0 mg/kg daily doses of Bismerthlazol, respectively. The Bismerthlazol was administered by gavage for 90 d. At the end of the experiment, the thyroids of the rats were harvested and weighted. The pathological changes of the thyroids were observed under light microscopes. The positive expression of PCNA in the thyroid glands were examined by histochemistry methods. RESULTS: Increased coefficients of thyroid gland weight were found in the experimental groups (P < 0.01). The thyroid glands showed different hyperplasia of follicular cells. Increased positive cells of PCNA were observed in the experimental groups (P < 0.05 or P < 0.01) except for the 7.0 mg/kg dose group. CONCLUSION: Long-time administered Bismerthlazol causes thyroids hyperplasia in rats. Further study on the mechanisms is warranted.

[Experimental studies on male reproductive toxicity of bisphenol A in vitro and vivo].

OBJECTIVE: To explore the effects of Bisphenol A in adult rats and its possible mechanisms. METHODS: BPA (in corn oil) was administered orally to 9-week-old male Sprague-Dawley rats for 14 days (0, 1 and 5 g/kg bw), and incubated primary Sertoli cells from pubertal SD rats with 0, 10(-7), 10(-6), 10(-5), 10(-4) mol/L BPA. RESULTS: After oral administration, a significant decrease in right testis weight was observed in 5 g/kg dose group, but not in the 1 g/kg bw dose group. Germ cells were detached from basement membrane of seminiferous tubules and Sertoli cells in BPA-treated groups. Administration of BPA at 1 g/kg bw and 5 g/kg bw produced both nucleus pycnosis and vacuolized nucleus in germ cells and Sertoli cells. A marked loss in vimentin staining in Sertoli cells from testis of BPA-treated rats was detected. No change in levels of serum estradiol and testosterone was observed after two-week exposure to BPA. In Sertoli cell primary culture, BPA destroyed the cytoskeleton and cell-cell junctions, and elongated Sertoli cells. CONCLUSION: These results suggest that BPA may injure reproductive function of male rats by destroying the cytoskeleton and changing the form of Sertoli cells.

[A study on the expression of Snap-25 mRNA in rat poisoned by tetramine].

OBJECTIVE: This study sought to reveal the relationship between Snap-25 and tetramine poisoning in order to approach the mechanism of tetramine poisoning. METHODS: The levels of Snap-25 mRNA in the brain tissues of poisoned SD rats were detected by RT-PCR method. RESULTS: After 1 hour of intoxication, the expression level of Snap-25 mRNA did not change in the rat brain. It increased at day 1 and reached its peak at day 3. The expression level of Snap-25 mRNA begain to descend at day 5, but it was still higher than that in the rat brain tissue of control group. CONCLUSION: In this study the expression of Snap-25 of rat poisoned by tetramine was not markedly increased in the early stage of poisoning, indicating that the symptoms of rat poisoned by tetramine are not induced by the changes of the Snap-25 level. The mechanism of high expression in Snap-25 mRNA probably involves the negative feedback of the body, which may increase the releasing of neurohumor and hence mitigate the symptoms of poisoning.

[Exploring the sensitive indicators of uterotrophic assay in immature SD rats exposed to para-nonylphenol].

OBJECTIVE: To investigate the estrogenic activity of para-nonylphenol in immature SD rats and explore the mechanism and sensitive indicators of its action in uterotrophic assay. METHODS: The vehicle control (peanut oil), positive control(estradiol benzoate, E2B, 0.4 mg/kg) and p-NP(60 mg/kg, 90 mg/kg and 120 mg/kg) were given orally (by gavage) q.d. on the 21st, 22nd, 23rd postnatal days. Then the rats were sacrificed 24 hours after the last administration. By using ABC immunohistochemistry, the progesterone receptor (PR), estrogen receptor (ER), and proliferating cell nuclear antigen (PCNA) of the rat uterine were analysed. RESULTS: Uterine weight, uterine/body weight significantly increased in E2B 0.4 mg/kg, p-NP 90 mg/kg and 120 mg/kg groups as compared with those of vehicle control group (P < 0.01), and a dose-response relationship was observed. The expressions of PR, ER and PCNA in the nuclei of stromal and myometrial cells of uterus were detected in all the p-NP groups, and a dose-effect relationship was noted. CONCLUSION: Expressions of PR, ER and PCNA as indicators tested by immunohistochemical technique are more sensitive than uterine weight in uterotrophic assay. Hyperplasia of stromal and myometrial cells of uterus is the reason why the uterine weight of the rat increased.

[The effects of three plastic additives on the proliferation of MCF-7 cell].

OBJECTIVE: To explore the effect of environmental estrogens on the proliferation of breast cancer cell line MCF-7. METHODS: The tested compounds were n-4-nonyphenol, Bisphenol A and dibutylphthalate. Human estradiol-dependent MCF-7 breast cancer cells were grown in DMEM medium containing 10% bovine serum. Five days before the addition of the test compounds, the cells were washed by phosphate-buffered saline, and the medium was substituted with a phenol red-free DMEM medium containing 5% dextral charcoal-stripped FBS. The respective test compound was added in fresh medium and the control cell received only the vehicle (ethanol). The proliferation of MCF-7 was analyzed by the MTT assay, (3)H-TdR incorporation assay and flow cytometry. RESULTS: Compared with the ethanol control, the proliferation and DNA synthesis of the test cells treated with n-4-nonyphenol (8 x 10(-7) mol/L, 96 h), Bisphenol A (8 x 10(-7) mol/L, 96 h) or dibutylphthalate (32 x 10(-6) mol/L, 96 h) treatment was markedly enhanced in a time-dependent and dose-dependent manner. CONCLUSION: n-4-Nonyphenol, Bisphenol A and dibutylphthalate enhanced the proliferation of human breast cancer cell in vitro, which may demonstrate an estrogenic activity.