Nucleic acid guanine: reaction with the carcinogen N-acetoxy-2-acetylaminofluorene

Reaction of N-acetoxy-2-acetylaminofluorene with DNA or RNA at pH 7 causes marked increase in absorption at 280 to 320 millimicrons and marked decrease in guanine content. Reaction with guanosine-8-(14)C yields a radioactive fluorescent derivative. The data suggest that metabolic esters of N-hydroxy-2-acetylaminofluorene may be intermediates in the binding of this proximate carcinogen to nucleic acids in vivo.     

Reduction of intestinal carcinogen absorption by carcinogen-specific secretory immunity

A secretory immune response to the carcinogen 2-acetylaminofluorene (AAF) was elicited in rabbits by directly immunizing the small intestine with an AAF-cholera toxin conjugate. High-titer, high-affinity secretory immunoglobulin A (IgA) antibody to AAF was secreted into the intestinal lumen in response to this immunogen. Immune secretions reduced the transepithelial absorption of a 125I-labeled derivative of AAF by more than half. This reduction of absorption by hapten-specific IgA suggests that oral vaccines against carcinogens and toxicants could be developed for humans.     

菜籽多酚级分-2的体外抗氧化作用及其机理

测定了菜籽多酚级分-2在化学模拟体系、小鼠线粒体、小鼠血清与肝匀浆中的抗氧化作用.结果表明: 在化学反应体系中, 菜籽多酚级分-2具有还原能力,能清除活性氧,抑制脂肪氧合酶的活性.在体外试验中,菜籽多酚级分-2能抑制线粒体膜的肿胀,增加小鼠血清抗活性氧能力,抑制小鼠肝线粒体与小鼠肝组织匀浆MDA(丙二醛)的生成.以上试验表明: 菜籽多酚级分-2在生物体内具有明显的抗氧化作用,高的还原能力与抑制生物体内氧化酶是菜籽多酚级分-2抗氧化的机理.     

Chemical carcinogenesis: persistence of bound forms of 2-fluorenylacetamide

The persistent binding of metabolites of hepatic carcinogen, 2-fluorenylacetamide, to glycogen and to DNA in a new population of liver cells, hyperplastic nodules, and to glycogen in liver cancer cells weeks to months after the carcinogen was removed from the animals' diet is indicated by spectrophotometric, chromatographic, and mass spectrographic data. This persistence of binding does not appear to occur in the nonhyperplastic or nonneoplastic liver surrounding the nodules or the cancer.     

Binding of SH2 domains of phospholipase C gamma 1, GAP, and Src to activated growth factor receptors

Phospholipase C gamma 1 (PLC gamma 1) and p21ras guanosine triphosphatase (GTPase) activating protein (GAP) bind to and are phosphorylated by activated growth factor receptors. Both PLC gamma 1 and GAP contain two adjacent copies of the noncatalytic Src homology 2 (SH2) domain. The SH2 domains of PLC gamma 1 synthesized individually in bacteria formed high affinity complexes with the epidermal growth factor (EGF)- or platelet derived growth factor (PDGF)-receptors in cell lysates, and bound synergistically to activated receptors when expressed together as one bacterial protein. In vitro complex formation was dependent on prior growth factor stimulation and was competed by intracellular PLC gamma 1. Similar results were obtained for binding of GAP SH2 domains to the PDGF-receptor. The isolated SH2 domains of other signaling proteins, such as p60src and Crk, also bound activated PDGF-receptors in vitro. SH2 domains, therefore, provide a common mechanism by which enzymatically diverse regulatory proteins can physically associate with the same activated receptors and thereby couple growth factor stimulation to intracellular signal transduction pathways.     

Inhibition by alcohols of the localization of radioactive nitrosonornicotine in sites of tumor formation

Oral administration of ethanol, n-butanol, or t-butanol to mice 20 minutes before injection of carbon-14-labeled nitrosonornicotine inhibited the localization of radioactivity in bronchial and salivary duct epithelium and in the liver. Localization of radioactivity in the nasal epithelium and esophagus was not significantly reduced. These alcohols therefore may selectively inhibit tumor formation in three of the five sites where this carcinogen typically acts.     

Gender disparity in liver cancer due to sex differences in MyD88-dependent IL-6 production

Hepatocellular carcinoma (HCC), the most common liver cancer, occurs mainly in men. Similar gender disparity is seen in mice given a chemical carcinogen, diethylnitrosamine (DEN). DEN administration caused greater increases in serum interleukin-6 (IL-6) concentration in males than it did in females. Furthermore, ablation of IL-6 abolished the gender differences in hepatocarcinogenesis in mice. DEN exposure promoted production of IL-6 in Kupffer cells (KCs) in a manner dependent on the Toll-like receptor adaptor protein MyD88, ablation of which also protected male mice from DEN-induced hepatocarcinogenesis. Estrogen inhibited secretion of IL-6 from KCs exposed to necrotic hepatocytes and reduced circulating concentrations of IL-6 in DEN-treated male mice. We propose that estrogen-mediated inhibition of IL-6 production by KCs reduces liver cancer risk in females, and these findings may be used to prevent HCC in males.     

Reactive metabolites from the bioactivation of toxic methylfurans

An important mechanism of toxicity of furans involves the cytochrome P-450 monooxygenase-catalyzed bioactivation of the compound in situ directly within the target tissues to highly reactive electrophilic products. The unsaturated aldehydes acetylacrolein and methylbutenedial have been identified as the principal reactive intermediates of 2- and 3-methylfuran, respectively, that are produced and bound covalently to tissue macromolecules in hepatic and pulmonary microsomal systems in vitro.     

Binding of benzo[a]pyrene 7,8-diol-9,10-epoxides to DNA, RNA, and protein of mouse skin occurs with high stereoselectivity

The formation, stereostructure, and cellular reactions of the 7,8-diol-9,10-epoxide metabolites of the carcinogen benzo[a]pyrene have been examined after topical application of benzo[a]pyrene to the skin of mice. In this known target tissue, polymer adducts from diastereomeric diol epoxides, (+)-(7S, 8R, 9R, 10R) and (+)-(7R, 8S, 9R, 10R), were formed stereospecifically from their corresponding 7,8-dihydrodiols. Both diol epoxides bind with proteins, RNA, and DNA in vivo. For the nucleic acids, binding occurs preferentially at the 2-amino group of guanine in cellular RNA and DNA in vivo. Methods for establishing the structure of the cellular adducts as well as the possible biological implications of their formation are discussed.     

低温胁迫对菜用大豆生长、叶片活性氧及多胺代谢的影响

选用两种耐低温性不同的菜用大豆品种——‘沪宁95-1’(耐低温)和‘台湾75’(低温敏感),对低温胁迫下两者的生长、叶片活性氧及多胺代谢进行了比较。结果表明,低温胁迫后两者生物量积累显著受到抑制,但‘沪宁95-1’受抑制程度显著小于‘台湾75’;低温胁迫下两者叶片抗氧化酶活性、O·-2生成速率、H2O2和MDA含量均显著升高,但‘沪宁95-1’叶片抗氧化酶活性显著高于‘台湾75’,O·-2生成速率、H2O2和MDA含量则显著低于‘台湾75’;低温胁迫后‘沪宁95-1’叶片不同形态腐胺、亚精胺和精胺含量均显著上升,‘台湾75’叶片不同形态腐胺含量显著下降,游离态、结合态亚精胺和精胺含量显著上升,束缚态亚精胺和精胺含量变化不显著。以上结果表明,低温胁迫下不同形态腐胺、束缚态亚精胺和精胺与‘沪宁95-1’较低的生长抑制、较低的氧化损伤以及较高的保护酶活性有关,可能在菜用大豆耐寒性方面发挥重要作用。     

Binding of HTLV-III/LAV to T4+ T cells by a complex of the 110K viral protein and the T4 molecule

Human T-lymphotropic virus type III (HTLV-III) or lymphadenopathy-associated virus (LAV) is tropic for human T cells with the helper-inducer phenotype, as defined by reactivity with monoclonal antibodies specific for the T4 molecule. Treatment of T4+ T cells with monoclonal antibodies to T4 antigen blocks HTLV-III/LAV binding, syncytia formation, and infectivity. Thus, it has been inferred that the T4 molecule itself is a virus receptor. In the present studies, the surfaces of T4+ T cells were labeled radioactively, and then the cells were exposed to virus. After the cells were lysed, HTLV-III/LAV antibodies were found to precipitate a surface protein with a molecular weight of 58,000 (58K). By blocking and absorption experiments, this 58K protein was identified as the T4 molecule. No cell-surface structures other than the T4 molecule were involved in the antibody-antigen complex formation. Two monoclonal antibodies, each reactive with a separate epitope of the T4 molecule, were tested for their binding capacities in the presence of HTLV-III/LAV. When HTLV-III/LAV was bound to T4+ T cells, the virus blocked the binding of one of the monoclonal antibodies, T4A (OKT4A), but not of the other, T4 (OKT4). When HTLV-III/LAV was internally radiolabeled and bound to T4+ T cells which were then lysed, a viral glycoprotein of 110K (gp110) coprecipitated with the T4 molecule. The binding of gp110 to the T4 molecule may thus be a major factor in HTLV-III/LAV tropism and may prove useful in developing therapeutic or preventive measures for the acquired immune deficiency syndrome.     

ITGB1基因表达与鹅肥肝形成的关系

为探究ITGB1基因与鹅肥肝形成的关系,选取30只70日龄健康朗德公鹅,随机分为填饲组与对照组并进行24 d填饲.运用ITGB1基因序列进行生物信息学分析,采用RT-qPCR技术检测不同填饲阶段(填饲12d与24d)鹅肝脏中ITGB1基因的表达水平,同时,使用不同剂量的脂肪肝形成相关因子(胰岛素、葡萄糖、油酸、亚油酸和棕榈酸)处理鹅原代肝细胞,检测ITGB1基因的表达水平.结果 发现:全长CDS共2418 bp,编码805个氨基酸,与鸭的同源性高于98％,可编码1种亲水性蛋白;与对照相比,填饲12d与24 d时,鹅肝脏中ITGB1基因的表达均显著上调(P＜0.05);0.5 mmol·L-1油酸、亚油酸和棕榈酸均能显著地诱导鹅原代肝细胞中ITGB1基因上调(P＜0.05);200mmol·L-1葡萄糖能极显著地诱导鹅原代肝细胞中ITGB1基因上调(P＜0.01);此外,0.2 mmol·L-1胰岛素也能在一定程度上有诱导其表达上调的趋势(P=0.098).结果 表明,ITGB1基因表达上调与鹅肥肝形成密切相关,受脂肪肝形成相关因子诱导,提示ITGB1基因表达上调可能会促进鹅肥肝的形成.     

Genetic defect in biosynthesis of the precursor form of the fourth component of complement

Under cell-free conditions, liver polysomes from guinea pigs genetically deficient in the fourth component of complement (C4) did not synthesize pro-C4 (the precursor of C4), but did synthesize nascent C4 polypeptides which remained polysome bound. The defect was specific for pro-C4 synthesis since the amounts of total protein and albumin synthesis and release from C4-deficient polysomes were similar to that in normal guinea pig liver polysomes.     

Enzyme-catalyzed reactions of the carcinogen N-hydroxy-2-fluorenylacetamide with nucleic acid

A protein fraction obtained by gel filtration of a 105,000g supernatant of rat liver catalyzes three reactions of the hepatocarcinogen N-hydroxy-2-fluorenylacetamide with nucleic acid. Cofactor requirements and isotopic studies suggest that the reactive intermediates involved may be N-2-fluorenylhydroxylamine, and phosphate and sulfate esters of N-hydroxy-2-fluorenylacetamide.     

肉桂游离酚提取物改善非酒精性肝细胞脂肪变性的活性研究

【目的】分析云野肉桂中不同存在形式酚类物质的含量，并探究其不同存在形式酚类提取物对非酒精性脂肪肝（Non-alcoholic fatty liver disease，NAFLD）的影响，为热带亚热带植物肉桂资源的深加工及相关功能性食品的开发和利用提供理论依据。【方法】用福林酚法及硼氢化钠—四氯对苯醌法分析肉桂中不同存在形式的酚类物质及黄酮类物质的含量；体外以游离脂肪酸诱导剂（油酸钠∶棕榈酸=2∶1）诱导HepG2细胞为模型，分析不同浓度的肉桂游离酚/结合酚提取物对NAFLD细胞模型脂滴形成及甘油三酯（TG）含量的影响；体内以高脂饮食结合链脲佐菌素诱导的NAFLD小鼠为模型，探究体外筛选的强活性酚类提取物对小鼠血脂及肝脏中TG和游离脂肪酸含量的影响。【结果】肉桂多酚主要以游离酚（55.99±0.45 mg GAE/g）的形式存在，含有一定比例的结合酚（3.21±0.12 mg GAE/g），其中黄酮类物质（46.49±4.75 mg CE/g）是肉桂的主要酚类物质之一。云野肉桂游离酚提取物可有效降低NAFLD细胞模型胞内TG的水平。与模型组相比，经中和高剂量的肉桂游离酚提取物作用后，细胞内TG含量显著降低（P<0.05，下同），分别降低17.07%和26.83%，而结合酚提取物作用后细胞内TG水平与模型组相比无显著差异（P>0.05）。动物试验结果表明，高剂量的游离酚提取物干预后，不仅可以显著降低小鼠血清中TG、胆固醇（TC）和低密度脂蛋白胆固醇（LDL-C）含量，还能显著降低小鼠肝脏中TG和游离脂肪酸含量，分别降低42.21%和22.22%。液相色谱串联质谱（LC-MS/MS）分析结果表明，肉桂游离酚提取物主要由原花青素C1、原花青素B2、原花青素A2、原花青素B3和原花青素B₁等物质组成。【结论】肉桂游离酚提取物对NAFLD可能具有较好的改善作用，且原花青素类物质可能是发挥改善肝细胞脂肪变性作用的主要物质基础。     

Detection of DNA sequences in nuclei in suspension by in situ hybridization and dual beam flow cytometry

This report describes the fluorescence hybridization of DNA sequence probes to interphase nuclei in suspension and the quantification of bound probe by dual beam flow cytometry. Nuclear proteins were first cross-linked with dimethylsuberimidate to prevent disintegration of the nuclei during denaturation and hybridization. To demonstrate that in situ hybridization can be performed in suspension, stabilized mouse thymocyte nuclei were hybridized with a probe for mouse satellite DNA sequences. The DNA probes were labeled with 2-acetylaminofluorene. After hybridization, an indirect immunofluorescent labeling procedure was used to visualize the target sequences. With dual beam flow cytometry, both the amount of hybridized probe and the DNA content of individual nuclei were determined. Thus, the specificity of DNA hybridization can be combined with the speed and quantitative analysis provided by flow cytometry.     

Free-radical oxidants in natural waters

Photooxidation of cumene (isopropylbenzene) and pyridine in dilute solution in natural waters gives products characteristic of reactions with alkylperoxy (RO(2).) and hydroxyl (HO.) radicals. On the basis of the rates of formation of the products, the average concentrations of RO(2). and HO. are estimated to be about 10(-9) and 10(-17) mole per liter, respectively. The concentration of RO(2). is large enough that, for some classes of reactive chemicals, oxidation can be an important process in natural waters.     

Polysomes and protein synthesis in cells infected with a DNA virus

In HEp-2 cells infected with herpes simplex virus the rate of protein synthesis at first decline, is stimulated between 4 and 8 hours after infection, and progressively and irreversibly declines from 9 to 16 hours later. The increase and decrease in rates coincide with corresponding changes in the amounts of cytoplasmic polysomes and amounts of labeled amino acids in nascent peptides bound to polysomes. The data indicate that (i) early and late inhibition and intervening stimulation of protein synthesis are due to the corresponding breakdown and formation of polysomes, and (ii) the bulk of viral proteins is probably made on cytoplasmic polysomes.     

Liver cancer: neonatal estrogen enhances induction by a carcinogen

A single injection of 100 micrograms of estradiol benzoate into newborn rats was followed after weaning by dietary treatment with one of two dosages of the carcinogen N-hydroxy-N-2-fluorenylacetamide. Autopsies 26 weeks later showed a higher incidence of liver cancer in male and, particularly, female rats injected with hormone than in controls. The weights of livers were greater but gonads were smaller in size in the estradiol groups. Endocrine and possibly centralnervous-system factors may play roles in formation of liver tumors.