Carbohydrate composition and electrophoretic properties of tomato polygalacturonase isoenzymes

Two polygalacturonase isoenzymes, PG I and PG II, were extracted from Murrieta tomato and purified by gel exclusion and ion-exchange chromatography. The kinetic constants and activation energies of the purified isoenzymes have been determined. Polygalacturonase I has two polypeptide chains (Mr = 47 500 and 41 400) whereas polygalacturonase II is a single polypeptide (Mr = 47 500) as shown by electrophoresis in polyacrylamide gels in the presence of sodium dodecyl sulphate. Both isoenzymes are glycoproteins. Through gas liquid chromatography, polygalacturonase II was shown to contain 4.6% neutral hexoses and 1.5% amino sugars. There are eight D-mannose, two L-fucose, two D-xylose and three N-acetylglucosamine residues per mole of PG II. The carbohydrate portion of PG II was shown to be attached to the protein part through an N-acetylglucosaminylasparaginyl bond.     

Effect of Phloroglucinol and Resorcinol on the Clingstone Peach Polyphenol Oxidase-catalyzed Oxidation of 4-Methylcatechol

Phloroglucinol and resorcinol are not substrates for clingstone peach (Prunus persica) polyphenol oxidase, but they react with 4-methyl-o-quinone, produced either enzymatically or nonenzymatically, to give an intense red or red-brown color with a maximal absorption at about 470 nanometers. Several colored products were isolated from an ethyl acetate extract of the reaction by two-dimensional thin layer chromatography. Based on thin layer chromatographic and spectral studies of the enzymatic and nonenzymatic reactions, polyphenol oxidase does not play a role in the reaction between 4-methyl-o-quinone and phloroglucinol, resorcinol, d-catechin, or orcinol. In such reactions, the function of polyphenol oxidase is the formation of 4-methyl-o-quinone which then reacts nonenzymatically with the above phenols. Activation energies of both enzymatic and nonenzymatic reactions were determined.     

小麦颖果果皮绿色层内同化物的合成与分配

小麦幼嫩颖果中,果皮内侧发育出由内表皮与亚表皮组成的一薄层绿色组织。显微与亚显微结构观察表明,虽绿色层只接受到自然光照的1/4～1/8,叶绿体仍能正常发育,叶绿素含量与叶绿体数量均高出旗叶。大量胞间连丝联接相邻的绿色细胞,并在一定时期形成开放的胞间通道,显然有利于同化物的快速胞间运输。离体颖果饲喂~14CO_2试验证明,新合成的同化物从绿色细胞输向胚珠。绿色层产生的同化物可能通过合点端的珠心进入胚乳或通过珠孔直接汇聚到胚珠和分化中的原胚。     

Syntaxin-1通过激活突触递质传递加速早期突触的形成

Syntaxin-1是一种多结构域蛋白,通过与synaptobrevin-2和SNAP-25形成SNARE复合体调节囊泡融合.然而,syntaxin-1在突触形成过程中是否发挥作用,目前尚不清楚.本研究显示syntaxin-1的表达水平与突触形成过程高度相关.Syntaxin-1的R151A和I155A突变影响其在突触形成中的促进作用,而Habc结构域或跨膜结构域在突触形成中无显著作用.结果表明,syntaxin-1通过激活突触囊泡释放来加速突触的形成.     

Gli as a Novel Therapeutic Target in Malignant Pleural Mesothelioma

Malignant pleural mesothelioma (MPM) is a highly aggressive tumor with poor prognosis. Current treatment is rarely curative, thus novel meaningful therapies are urgently needed. Inhibition of Hedgehog (Hh) signaling at the cell membrane level in several cancers has shown anti-cancer activity in recent clinical studies. Evidence of Hh-independent Gli activation suggests Gli as a more potent therapeutic target. The current study is aimed to evaluate the potential of Gli as a therapeutic target to treat MPM. The expression profiles of Gli factors and other Hh signaling components were characterized in 46 MPM patient tissue samples by RT-PCR and immunohistochemistry. Cultured cell lines were employed to investigate the requirement of Gli activation in tumor cell growth by inhibiting Gli through siRNA or a novel small molecule Gli inhibitor (Gli-I). A xenograft model was used to evaluate Gli-I in vivo. In addition, a side by side comparison between Gli and Smoothened (Smo) inhibition was conducted in vitro using siRNA and small molecule inhibitors. Our study reported aberrant Gli1 and Gli2 activation in a large majority of tissues. Inhibition of Gli by siRNAs or Gli-I suppressed cell growth dramatically both in vitro and in vivo. Inhibition of Gli exhibited better cytotoxicity than that of Smo by siRNA and small molecule inhibitors vismodegib and cyclopamine. Combination of Gli-I and pemetrexed, as well as Gli-I and vismodegib demonstrated synergistic effects in suppression of MPM proliferation in vitro. In summary, Gli activation plays a critical role in MPM. Inhibition of Gli function holds strong potential to become a novel, clinically effective approach to treat MPM.     

Optimal policies of non-cross-resistant chemotherapy on Goldie and Coldman’s cancer model

Mathematical models can be used to study the chemotherapy on tumor cells. Especially, in 1979, Goldie and Coldman proposed the first mathematical model to relate the drug sensitivity of tumors to their mutation rates. Many scientists have since referred to this pioneering work because of its simplicity and elegance. Its original idea has also been extended and further investigated in massive follow-up studies of cancer modeling and optimal treatment.     

NF-κB is involved in the LPS-mediated proliferation and apoptosis of MAC-T epithelial cells as part of the subacute ruminal acidosis response in cows

Objectives

To determine the effect of NF-κB on cell proliferation and apoptosis, we investigate the expression of inflammation and apoptosis-related factors in the bovine mammary epithelial cell line, MAC-T.

Results

MAC-T cells were cultured in vitro and MTT and LDH assays used to determine the effects of lipopolysaccharide (LPS) on proliferation and cytotoxicity respectively. RT-PCR and western blotting were used to evaluate the effect of LPS and NF-κB inhibition [pyrrolidine dithiocarbamate (PDTC) treatment] on the expression of inflammation and apoptosis-related factors. LPS significantly inhibited MAC-T cell proliferation in a dose- and time-dependent manner. Furthermore, LPS promoted apoptosis while the NF-кB inhibitor PDTC attenuated this effect. After LPS treatment, the NF-кB signaling pathway was activated, and the expression of inflammation and apoptosis-related factors increased. When PDTC blocked NF-кB signaling, the expression of inflammation and apoptosis-related factors were decreased in MAC-T cells.

Conclusions

LPS activates the TLR4/NF-κB signaling pathway, inhibits proliferation and promotes apoptosis in MAC-T cells. NF-кB inhibition attenuates MAC-T cell apoptosis and TLR4/NF-κB signaling pathway. NF-кB inhibitor alleviating MAC-T cell apoptosis is presumably modulated by NF-кB.

     

广东省蛇类新纪录——菱斑小头蛇

2007年6月23日,在广东省南昆山省级自然保护区采集到一条菱斑小头蛇(Oligodon catenata),为广东省蛇类新纪录。该新分布区的发现说明菱斑小头蛇在我国可能并非间断分布。     

Spectroscopic properties, catalytic activities and mechanism studies of [(TpPh)Co(X)(CH3OH)m] . nCH3OH: bicarbonate dehydration in the presence of inhibitors

Two inhibitor-containing 'half-sandwich' cobalt(II) complexes [(TpPh)Co(X)(CH3OH)m] x nCH3OH ((TpPh) = hydrotris (3-phenylpyrazolyl)borate; 1: X- = N3-, m = 1, n = 2; 2: X- = NCS-, m = 0, n = 0) have been synthesized and used as the catalysts in the bicarbonate dehydration reaction. The structures of 1 and 2 were determined by X-ray diffraction analysis, which shows that N3- and NCS- coordinate to the Co(II) ions of 1 and 2, respectively, with the Co-N bond lengths of 1.992(6) A and 1.901(3) A. The coordination geometries of the Co(II) complexes in solution are five-coordinated trigonal bipyramid as revealed by the spectroscopic measurements. The dehydration kinetic measurements of HCO3- are performed by the stopped-flow techniques at pH < 7.9. The apparent dehydration rate constant k(obs) varies linearly with Co(II) complex and H+ concentrations, respectively, and the catalytic activity of 2 is lower than that of 1. The aqua Co(II) complex must be the reactive catalytic species in the catalyzed dehydration reaction and the rate-determining step is the substitution of the labile water molecule by HCO3-. The k(obs) values increase with increasing reaction temperature, and the large negative entropy of activation also indicates the associative activation mode. The inhibition ability of NCS- is stronger than that of N3-, which can be rationalized by the decreases in the Co-N(N3-/NCS-) bond lengths and effective atomic charges of the Co(II) ions based on the X-ray crystallographic data and theoretical calculations in this work.     

Evaluation of Prey-Stage Preference as an Indicator of Life-Style Type in Phytoseiid Mites

Discriminant analysis (DA) models were developed and applied to examine the use of prey-stage preference (Tetranychus urticae Koch egg versus larval prey) in the classification of phytoseiid mites into life-style types. Prey-stage preferences and developmental times when preying on T. urticae, and relative ovipositional rates on six food categories were determined for four phytoseiid species occurring on apple in central and eastern Oregon, USA: Galendromus flumenis (Chant), Galendromus occidentalis (Nesbitt), Metaseiulus citri (Garman and McGregor) and Typhlodromus caudiglans Schuster. In terms of all three aspects studied, the phytoseiid species showed a consistent polarization of G. occidentalis < or = G. flumenis < or = T. caudiglans < M. citri. Specifically, G. occidentalis ('The Dalles' strain) had a significant preference for eggs, G. flumenis had no preference, and T. caudiglans and M. citri had significant preferences for larvae; G. occidentalis had the shortest developmental time, followed by G. flumenis and T. caudiglans, while M. citri had the longest developmental time; and diet breadth was most narrow for G. occidentalis and progressively broader from G. flumenis, T. caudiglans through M. citri, which was able to sustain oviposition on the broadest range of prey and pollens. Species were classified somewhat differently depending on which traits were considered in a given DA. Prey-stage preference was not included as an indicator in the parsimonious DA model when all species and all traits were considered, but in general this trait performed well as an indicator alone (single-trait DA) and somewhat improved the classifications of multitrait discriminant analyses.