Mannich反应中酸组分与胺组分亲核性及其选择

本文通过对该反应二组分亲核性这一影响因素的分析探讨，提出了解决二组分亲核性对某些Mannich反应的不利影响的一些方法．

两点法确定混胺中两组分的电位滴定终点

利用两点法确定了液体推进剂混胺中两组分——三乙胺和二甲苯胺的电位滴定终点,并与常规的弧切作图法和二阶微分法确定的滴定终点进行了配对t检验,显示结果之间不存在显著差异,或可予校正。两点法简单快速,结果可靠,特别适宜于大量样品的快速分析。

Ghrelin and gastric acid secretion

Ghrelin, a novel growth hormone-releasing peptide, was originally isolated from rat and human stomach. Ghrelin has been known to increase the secretion of growth hormone (GH), food intake, and body weight gain when administered peripherally or centrally. Ghrelin is also known to stimulate the gastric motility and the secretion of gastric acid. In the previous studies, the action of ghrelin on acid secretion was shown to be as strong as that of histamine and gastrin in in-vivo experiment. In the studies, the mechanism for the action of ghrelin was also investigated. It was shown that vagotomy completely inhibited the action of ghrelin on the secretion of gastric acid suggesting that vagal nerve is involved in the mechanism for the action of ghrelin on acid secretion. As famotidine did not inhibit ghrelin-in-duced acid secretion in the study by Masuda et al, they concluded that histamine was not involved in the action of ghrelin on acid secretion. However, we have shown that famotidine completely inhibited ghrelin-induced acid secretion and histidine decarboxylase (HDC) mRNA was increased in gastric mucosa by ghrelin injection which is inhibited by vagotomy Our results indicate that histamine is involved in the action of ghrelin on acid secretion. Furthermore synergistic action of gastrin and ghrelin on gastric acid secretion was shown. Although gastrin has important roles in postprandial secretion of gastric acid, ghrelin may be related to acid secretion during fasting period or at night. However, further studies are needed to elucidate the physiological role of ghrelin in acid secretion.

Expression of fragile histidine triad in primary hepatocellular carcinoma and its relation with cell proliferation and apoptosis

AIM: To evaluate the expression of fragile histidine triad (FHIT) gene protein, product of a candidate tumor suppressor, and to investigate the relationship between FHIT, cell apoptosis and proliferation, and pathological features of primary hepatocellular carcinoma (HCC). METHODS: Forty-seven HCC and ten normal liver specimens were collected during surgical operation between 2001 and 2003. FHIT and proliferating cell nuclear antigen (PCNA) expression were detected by immunohistochemistry, and apoptotic level was evaluated by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) assay on the tissue sections. RESULTS: All normal liver tissues showed a strong expression of FHIT, whereas 28 of 47 (59.6%) carcinomas showed a significant loss or absence of FHIT expression (P= 0.001). The proportion of reduced FHIT expression in those carcinomas at stages Ⅲ-Ⅳ (70.6%) and in those with extrahepatic metastasis (86.7%) showed an increasing trend compared with those at stages HI (30.8%, P= 0.013) and those without metastasis (46.9%, P = 0.010) respectively. Apoptotic incidence in advanced TNM stage carcinoma and those with positive FHIT expression was higher than that in early stage carcinoma (P=0.030) and in those with negative FHIT expression (P=0.044) respectively. The proliferating potential of hepatocellular carcinoma was associated with FHIT expression (P= 0.016) and the aggressive feature (P = 0.019). Kaplan-Meier analysis demonstrated that the survival time of these 47 patients correlated with TNM stage, FHIT expression and metastasis. CONCLUSION: There is marked loss or absence of FHIT expression, as well as abnormal apoptosis-prdiferation balance in HCC. FHIT may play an important role in carcinogenesis and development of HCC.

Recent advances in fixation of CO_(2) into organic carbamates through multicomponent reaction strategies

Carbon dioxide(CO_(2)) is the main greenhouse gas and also an ideal C1 feedstock in organic synthesis because it is abundant,nontoxic,nonflammable,and renewable.The synthesis of organic carbamates using CO_(2) as a phosgene alternative has attracted extensive attention because of the importance of carbamates in organic synthesis and in the pharmaceutical and agrochemical industries.In recent decades,many multicomponent reaction strategies have been designed for constructing different types of organic carbamate molecules.Most of these methods rely on the in situ generation of carbamate anions from CO_(2) and amines,followed by reactions with other coupling partners.Synthetic strategies for acyclic carbamates include nucleophile‐electrophile coupling,nucleo‐phile‐nucleophile oxidative coupling,difunctionalization of unsaturated hydrocarbons,and C–H bond functionalization.Strategies for the synthesizing cyclic carbamates include carboxylative cyclization of in situ‐generated unsaturated amines and difunctionalization of unsaturated amines with CO_(2) and other electrophilic reagents.This review summarizes the recent advances in the synthesis of organic carbamates from CO_(2) using different multicomponent reaction strategies.Future perspectives and challenges in the incorporation of CO_(2) into carbamates are also presented.

Synthesis of Oligohydroxynapthylenes and Their Use in Making of Heat-Stable and Electro-Conducting Rubbers

By oxidative polycondensation of 1-naphthol and their copolycondensation with aniline or p-phenylenediamine the polyfucntional polyconjugated oligomers consisting of hydroxynaphthylene links have been prepared. These soluble and meltable oligomers showing thermostability, semiconducting and paramagnetic properties and also high reactivity at reactions characteristic for aromatic hydroxyl groups were used as active filler at preparation of rubbers from butyl and butadiene-nitrile rubbers. It has been shown that in partial or full substitution of carbon black by oligohydroxynaphthylenes or cooligohydroxynaphthylenephenylamines in composition of vulcanizate the prepared rubbers are characterized by noticeably high heat-physical, physical-mechanical and electrical properties （Pv = 10^8 - 10^6Om. cm ）.

Increased expression of chondroitin sulphate proteoglycans in rat hepatocellular carcinoma tissues

AIM:To investigate the expression of chondroitin sulphate proteoglycans(CSPGs)in rat liver tissues of hepatocellular carcinoma(HCC).METHODS:Thirty male Sprague Dawley rats were randomly divided into two groups:control group(n=10) and HCC model group(n=20).Rats in the HCC model groups were intragastrically administrated with 0.2%(w/v)N-diethylnitrosamine(DEN)every 5 d for 16 wk,whereas 0.9%(w/v)normal saline was administered to rats in the control group.After 16 wk from the initiation of experiment,all rats were killed and livers were collected and fixed in 4%(w/v)paraformaldehyde.All tissues were embedded in paraffin and sectioned.Histological staining(hematoxylin and eosin and Toluidine blue)was performed to demonstrate the onset of HCC and the content of sulphated glycosaminoglycan(sGAG).Immunohistochemical staining was performed to investigate the expression of chondroitin sulphate(CS)/dermatan sulphate(DS)-GAG,heparan sulphate(HS)-GAG,keratan sulphate(KS)-GAG in liver tissues.Furthermore,expression and distribution of CSPG family members,including aggrecan,versican,biglycan and decorin in liver tissues,were also immunohistochemically determined.RESULTS:After 16 wk administration of DEN,malignant nodules were observed on the surface of livers from the HCC model group,and their hepatic lobule structures appeared largely disrupted under microscope.Toluidine blue staining demonstrated that there was an significant increase in sGAG content in HCC tissues when compared with that in the normal liver tissues from the control group[0.37±0.05 integrated optical density per stained area(IOD/area)and 0.21± 0.01 IOD/area,P<0.05].Immunohistochemical studies demonstrated that this increased sGAG in HCC tissues was induced by an elevated expression of CS/DS(0.28±0.02 IOD/area and 0.18±0.02 IOD/area,P< 0.05)and HS(0.30±0.03 IOD/area and 0.17±0.02 IOD/area,P<0.01)but not KS GAGs in HCC tissues.Further studies thereby were performed to investigate the expression and distribution of several CSPG components in HCC tissues,including aggrecan,versican,biglycan and decorin.Interestingly,there was a distinct distribution pattern for these CSPG components between HCC tissues and the normal tissues.Positive staining of aggrecan,biglycan and decorin was localized in hepatic membrane and/or pericellular matrix in normal liver tissues;however,their expression was mainly observed in the cytoplasm,cell membranes in hepatoma cells and/or pericellular matrix within HCC tissues.Semi-quantitative analysis indicated that there was a higher level of expression of aggrecan(0.43± 0.01 and 0.35±0.03,P<0.05),biglycan(0.32±0.01 and 0.25±0.01,P<0.001)and decorin(0.29±0.01 and 0.26±0.01,P<0.05)in HCC tissues compared with that in the normal liver tissues.Very weak versican positive staining was observed in hepatocytes near central vein in normal liver tissues;however there was an intensive versican distribution in fibrosis septa between the hepatoma nodules.Semi-quantitative analysis indicated that the positive rate of versican in hepatoma tissues from the HCC model group was much higher than that in the control group(33.61%and 21.28%,P <0.05).There was no positive staining in lumican and keratocan,two major KSPGs,in either normal or HCC liver tissues.CONCLUSION:CSPGs play important roles in the onset and progression of HCC,and may provide potential therapeutic targets and clinical biomarkers for this prevalent tumor in humans.

Syntheses of N-sulfonyl-N,N-disubstituted amidines via a three-component free-radical coupling reaction of tertiary amines and arenesulfonyl azides with terminal alkynes

A facile and efficient synthesis of N-sulfonyl-N,N-disubstituted amidines has been achieved via a CuI-catalyzed three-component free-radical coupling reaction of tertiary amines and arenesulfonyl azides with terminal alkynes in the presence of azodiisobutyronitrile(AIBN).The reaction mechanism of this reaction has also been studied.

Surface analysis and electrochemical behaviour of the self-assembled polydopamine/dodecanethiol complex films in protecting 304 stainless steel

A self-assembled 1-dodecanethiol film assisted with the preferential adhesion of polydopamine was prepared on the non-etching 304 stainless steel surfaces by a simple dip-coating method.The formation and surface structure of the film were characterized by water contact angle measurement,atomic force microscopy(AFM),and X-ray photoelectron spectroscopy(XPS).The corrosion behavior of the complex films was evaluated by Tafel polarization curve and electrochemical impedance spectroscopy(EIS).The excellent corrosion resistance property could be attributed to the compact hybrid film structure and superior seawater stability for modified 304 stainless steel surface.