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121.
Three methods were adopted for differentiation of aflatoxins B1 and B2 from territrems A and B. They were as follows. (i) Then-layer chromatography coupled with chemical confirmation. A significant decrease in the Rf value of trifluoroacetic acid-treated aflatoxin B1 developed in chloroform-acetone (85:15, vol/vol) was satisfactory in differentiating this toxin from the other three. (ii) High-pressure liquid chromatography monitored synchronously at two wavelengths, 365 and 335 nm. The ratio derived from this double-wavelengh detection could serve as an indicator of the presence of each toxin. (iii) Velasco's flurotoxin meter method, which is used for the determination of aflatoxins within the range of 0 to 50 ng/ml, was not significantly affected by territrems even when they were present in quantities at the microgram-per-milliliter level. 相似文献
122.
High biological activity of the synthetic replicates of somatostatin-28 and somatostatin-25 总被引:4,自引:0,他引:4
Paul Brazeau Nicholas Ling Frederick Esch Peter Böhlen Robert Benoit Roger Guillemin 《Regulatory peptides》1981,1(4):255-264
We have isolated form extracts of ovine hypothalami two molecules characterized as somatostatin-28 and somatostatin-4-28 (referred to as somatostatin-25). They were reproduced by solid hase synthesis. In equimolar ratio and depending upon the experimental conditions, synthetic somatostatin-28 ans somatostatin-25 are 3-14 times more potent than somatostatin-14 to inhibit the basal in vitro secretion of growth hormone or as stimulated by prostaglandin (PGE2). In early studies in vivo, somatostatin-28 and somatostatin-25 are also more potent than somatostatin-14 in inhibiting the secretion of growth hormone acutely stimulated in the rat by injection of morphine; somatostatin-28 is also longer-acting than somatostatin-14. These results suggest that somatostatin-14, as originally isolated, is a biologically active fragment of a larger molecule of greater specific activity; it should be considered as another form of somatostatin with high biological activity present in some tissues and likely secreted y the tissues along with somatostatin-14 and possibly other somatostatin-peptides of diverse sizes. 相似文献
123.
Dominance of colchicine resistance in hybrid CHO cells 总被引:4,自引:0,他引:4
Intraspecific hybrids of colchicine-sensitive with colchicine-resistant (CHR) Chinese hamster ovary cells were constructed, using six different colchicine-resistant clones from two independent series. In each instance, colchicine resistance was expressed in an incompletely dominant manner. Some hybrid clones were examined further for the expression of the pleiotropic CHR phenotype and for the cell surface P glycoprotein. These features of the colchicine-resistant phenotype were also expressed coordinately. 相似文献
124.
An embryogenic callus was obtained from immature panicle of an interspecific hybrid (Oryza sativa x O. latifolia) F1. The medium consisted of HE salts supplemented with 2,4-D, NAA (each 2 mg/l), kinetin (3 mg/l), yeast extract (1360 mg/l) and casein hydrolyzate (300 mg/l). The callus was milk-white in colour compact and granulate in texture. Various developmental stage of embryoid, such as globular, heart-shape, scutellum-shape and mature embryoid were observed in an embryogenic callus. Plantlets were successfully regenerated from 1-month-old callus with more than 80% regenerational frequency in each subculture for 12 passages. 相似文献
125.
The quantitative relationships between the concentrations of solutions of gelatin, polyvinylpyrrolidone, poly(ethylene oxide), polyvinylmethylether, and poly(ethylene glycol), and their ability to reduce the solubility of water for Na citrate are presented. The data in general are in harmony with the polarized multilayer theory of protein (and polymer) dominated water in vitro and in living cells. 相似文献
126.
John H. Collins Bliss Forbush Lois K. Lane Eleanor Ling Arnold Schwartz Anita Zot 《生物化学与生物物理学报:生物膜》1982,686(1):7-12
Highly purified lamb kidney (Na++K+)-ATPase was photoaffinity labeled with the tritiated 2-nitro-5-azidobenzoyl derivative of ouabain (NAB-ouabain). The labeled (Na++K+)-ATPase was mixed with unlabeled carrier enzyme. Two proteolipid (γ1 and γ2) fractions were then isolated by chromatography on columns of Sepharose CL-6B and Sephadex LH-60. The two fractions were interchangeable when rechromatographed on the LH-60 column, suggesting that γ1 is an aggregated form of γ2. The total yield was 0.8–1.5 mol of γ component per mol of catalytic subunit recovered. This indicates that the γ component is present in stoichiometric amounts in the (Na++K+)-ATPase. The proteolipids that were labeled with NAB-ouabain copurified with the unlabeled proteolipids. 相似文献
127.
将水稻(Oryza sativa L.)幼苗悬浮培养于含有羧基化多壁碳纳米管MWCNTs-COOH(0、2.5、5.0、10.0 mg/L)、50 mmol/L混合盐(1NaCl:9Na2SO4:9NaHCO3:1Na2CO3),以及MWCNTs-COOH+混合盐的复合溶液中,10 d后检测叶片生理生化指标变化,研究MWCNTs-COOH复合盐碱胁迫对水稻幼苗的毒性及生态风险。结果显示,与对照组相比,MWCNTs-COOH单一组诱导下水稻叶片O2·-和H2O2的产生不明显,而混合盐组和混合盐+MWCNTs-COOH复合组均诱导了O2·-和H2O2产物的大量累积。MWCNTs-COOH与混合盐复合后,加剧了O2·-和H2O2的累积,并有明显的浓度效应。活性氧(ROS)作为信号分子在一定程度上诱导了各处理组部分抗氧化酶(SOD、CAT、POD、APX)活性的升高;与混合盐组相比,低浓度混合盐+MWCNTs-COOH复合组中叶绿素a和胡萝卜素含量呈一定程度的升高;MWCNTs-COOH与混合盐复合后,抑制了叶片中可溶性糖(SS)和脯氨酸(Pro)的合成,致使相对电导率(REC)和丙二醛(MDA)含量显著升高。上述抗氧化酶活性及叶绿素a和胡萝卜素含量的升高对缓解水稻叶片氧化损伤、维持正常的光合电子传递及对过剩光能的热耗散是有益的,是水稻幼苗重要的防御机制。本研究表明MWCNTs-COOH单一处理在一定程度上诱导了水稻叶片的氧化胁迫和应激响应,与混合盐复合后加剧了叶片的氧化胁迫和应激损伤。 相似文献
128.
Isolation and characterization of a succinimide variant of methionyl human growth hormone. 总被引:4,自引:0,他引:4
G Teshima J T Stults V Ling E Canova-Davis 《The Journal of biological chemistry》1991,266(21):13544-13547
Deamidation of asparagine and glutamine residues, isomerization of aspartic acid side chains, and racemization of the L- to the D-form of the amino acids are common spontaneous chemical reactions known to occur in proteins. Previous studies have implicated succinimides as intermediates in these reactions; however, the evidence has been indirect. Our results demonstrate, for the first time, the presence of a succinimide intermediate in an intact protein. The succinimide (cyclic imide) variant was isolated from thermally stressed recombinant methionyl human growth hormone (hGH) by high performance anion-exchange chromatography, further purified by reversed-phase high performance liquid chromatography, and analyzed by tryptic mapping. A later eluting tryptic peptide, compared with the native T12 peptide (residues 128-134, Leu-Glu-Asp-Gly-Ser-Pro-Arg), was analyzed by mass spectrometry (MS). This variant had a protonated molecular mass of 755.3 atomic mass units (u), as compared with 773.3 u for the native T12 peptide. A difference of 18 u, a loss of water, is consistent with the formation of a succinimide intermediate at Asp-130 of methionyl hGH. MS/MS analysis of the cyclic imide-containing peptide verified that the modification occurred at Asp-130. A difference of 18 u was also observed for the intact cyclic imide methionyl hGH variant (22,238 u), as measured by electrospray mass spectrometry, compared with native methionyl hGH (22,256 u). 相似文献
129.
Ling Yeouruenn 《广西植物》1991,(1):19-35
<正> The paper is a review, in which author showed 1). A view of the classification, including history and taxonomic evidence of the genera, Artemisia L. and Seriphidium (Bess.) Poljak.; 2). the distribution, including migration in geological period, the speciation and present distributional mass center and so-called "3 oblique mass zones" in China, as well as the secondary speciation and developing centers in Hengduang-Himalayan Mts. and 3). the application, mainly in medicine, but also for herbage in steppe and for the windbreaks and assist to sand fixation at the desert and semi-desert areas. 相似文献
130.
Xiaohua Li Ling Song Krystyna Kolasa Richard S. Jope 《Journal of neurochemistry》1992,58(6):2330-2333
Administration of kainate or pentylenetetrazole increased c-fos, c-jun, junB, and junD mRNA levels in rat brain in a dose-dependent manner. Kainate increased these mRNA levels predominantly in the hippocampus, and pentylenetetrazole was more effective in the cortex. Adrenalectomy (3 days) was used to eliminate endogenous glucocorticoid hormones. Adrenalectomy significantly potentiated kainate-induced increases, compared with increases caused by kainate (4 mg/kg) alone, in the hippocampal mRNA levels of c-fos and junB by 6.5-fold and of junD by twofold and tended to augment c-jun mRNA. Corticosterone administration blocked the potentiated stimulation of these mRNA levels caused by adrenalectomy. Adrenalectomy also significantly increased pentylenetetrazole-induced levels of c-fos mRNA in the cortex. These results demonstrate that glucocorticoids modulate immediate early gene expression in the brain, raising the possibility that this interaction contributes to interneuronal and interindividual differences in responses to stimuli and to the effects of stress- or disease-induced changes in glucocorticoid concentrations. 相似文献