尼罗罗非鱼染色体的C带、Ag带和减数分裂联会复合体的研究

以Sumner法和界面铺张-硝酸银技术观察, 表明尼罗罗非鱼的2n=44, 核型可分为3组,各具4对亚中着丝粒染色体、17对亚端着丝粒染色体和1对端着丝粒的特大染色体。结构异染色质主要分布于着丝粒附近, 其中Nos.6、8、15亚中着丝粒染色体短臂全部深染。带有银染核仁组织者(Ag-NORs)染色体的数目为2—6条, NORs均位于6、8、15亚中着丝粒染色体短臂。银染色可清楚显示联会复合体(SC)结构和减数分裂行为。SC组型与有丝分裂染色体的组型有较好的一致性 。图版2图2表2参13

Transport of anti-sperm monoclonal IGA and IGC into murine male and female genital tracts from blood - Effect of sex hormones

Ab levels in the genital tract may be important in fertility and in preventing sexually transmitted diseases, In this study, I-125-labeled polymer or monomer mAb IgA (C4pIgA or C4mIgA) and IgC2b (C4IgC) to murine lactate dehydrogenase C4 and a polymer mAb IgA (npIgA) not cross-reacting with mouse sperm were intravenously injected into BALB/c mice, and the relative distribution of these Abs was determined. Polymer IgA was transported much more efficiently into the genital tract, trachea, and duodenum of both sexes than C4IgG and C4 mIgA (p < 0.01), The transport of polymer IgA (C4pIgA and npIgA) into the male genital tract greatly increased following orchiectomy (p < 0.01); this change was not affected by testosterone, suggesting that the unknown regulatory factor(s) from the testis may suppress polymer IgA transport, However, the transport of polymer IgA into female genital tissues was significantly decreased by ovariectomy (p < 0.01); this decline can be rectified by P-estradiol but not progesterone treatment, suggesting that estradiol may stimulate polymer IgA transport, Furthermore, the transport of C4IgG into tissues of the Fallopian tubes and the uterus was significantly decreased by treatment with progesterone (p < 0.01). Together, these findings indicate that serum polymer IgA can be transported selectively into the genital tracts of both sexes, that this transport is strongly under the control of gonads, and that transport of Ige into the Fallopian tubes and uterus is downregulated by progesterone.

Molecular modeling on some human interleukins sharing gamma c of interleukin-2 receptor, and structure-function relationships

Five models for human interleukin-7 (HIL-7), HIL-9, HIL-13, HIL-15 and HIL-17 have been generated by SYBYL software package. The primary models were optimized using molecular dynamics and molecular mechanics methods. The final models were optimized using a steepest descent algorithm and a subsequent conjugate gradient method. The complexes with these interleukins and the common gamma chain of interleukin-2 receptor (IL-2R) were constructed and subjected to energy minimization. We found residues, such as Gln127 and Tyr103, of the common gamma chain of IL-2R are very important. Other residues, e.g. Lys70, Asn128 and Glu162, are also significant. Four hydrophobic grooves and two hydrophilic sites converge at the active site triad of the gamma chain. The binding sites of these interleukins interaction with the common gamma chain exist in the first helical and/or the fourth helical domains. Therefore, we conclude that these interleukins binds to the common gamma chain of IL-2R by the first and the fourth helix domain. Especially at the binding sites of some residues (lysine, arginine, asparagine, glutamic acid and aspartic acid), with a discontinuous region of the common gamma chain of IL-2R, termed the interleukins binding sites (103-210). The study of these sites can be important for the development of new drugs. (C) 2000 Elsevier Science B.V. All rights reserved.

Independent Transport and Sorting of Functionally Distinct Protein Families in Tetrahymena thermophila Dense Core Secretory Granules

Dense core granules (DCGs) in Tetrahymena thermophila contain two protein classes. Proteins in the first class, called granule lattice (Grl), coassemble to form a crystalline lattice within the granule lumen. Lattice expansion acts as a propulsive mechanism during DCG release, and Grl proteins are essential for efficient exocytosis. The second protein class, defined by a C-terminal beta/gamma-crystallin domain, is poorly understood. Here, we have analyzed the function and sorting of Grt1p (granule tip), which was previously identified as an abundant protein in this family. Cells lacking all copies of GRT1, together with the closely related GRT2, accumulate wild-type levels of docked DCGs. Unlike cells disrupted in any of the major GRL genes, Delta GRT1 Delta GRT2 cells show no defect in secretion, indicating that neither exocytic fusion nor core expansion depends on GRT1. These results suggest that Grl protein sorting to DCGs is independent of Grt proteins. Consistent with this, the granule core lattice in Delta GRT1 Delta GRT2 cells appears identical to that in wild-type cells by electron microscopy, and the only biochemical component visibly absent is Grt1p itself. Moreover, gel filtration showed that Grl and Grt proteins in cell homogenates exist in nonoverlapping complexes, and affinity-isolated Grt1p complexes do not contain Grl proteins. These data demonstrate that two major classes of proteins in Tetrahymena DCGs are likely to be independently transported during DCG biosynthesis and play distinct roles in granule function. The role of Grt1p may primarily be postexocytic; consistent with this idea, DCG contents from Delta GRT1 Delta GRT2 cells appear less adhesive than those from the wild type.

Effects of adrenergic agonists on the extrahepatic expression of vitellogenin Ao1 in heart and brain of the Chinese rare minnow (Gobiocypris rarus)

Teleost vitellogenins (VTGs) are large multidomain apolipoproteins and traditionally considered as the estrogen responsive precursors of the major egg yolk proteins. We identified five clones encoding VTGs, about 16% of the random EST clones from our constructed cDNA library from Chinese rare minnow liver tissue treated with 17 beta-estradiol (E2). Full-length vtgAo1 has been obtained based on the sequence information of four partial cDNA inserts by RACE. The inducibility of the vtgAo1 expression in liver by E2 was confirmed by RT-PCR. The presence of vtgAo1 transcripts have been observed primarily in liver. However. a significant level of the vtgAo1 was found in an unexpected location, heart, particularly in atrial cells by RT-PCR and whole mount in situ hybridization analyses. The vtgAo1 mRNA expression in heart and liver tissue could be suppressed by both alpha-adrenergic agonist, phenylephrine (PE) and beta-adrenergic agonist, isoproterenol (ISO). The expression of VTG in the heart observed in the present studies suggested it may provide protection from surplus intracellular lipids in fish cardiomyocytes as triglyceride transport proteins do in mammals. The results also indicated that the production of teleost vtg in vivo can be regulated by riot only estrogenic agents, but adrenergic signals as well. (c) 2008 Elsevier B.V. All rights reserved.

Characterization of C-C chemokine receptor subfamily in teleost fish

Chemokines and their receptors play important roles in nervous and immune systems. Little information, however, exists concerning this gene family in teleost fish. In the present Study, 17 C-C chemokine receptors genes were identified from Danio rerio, 9 from Gasterosteus aculeatus, 10 from Oryzius latipes, 8 from Takifugu rubripes and 5 from Tetraodon nigroviridis. Phylogenetic analysis showed that the orthologs to mammalian CCR6, 7, 8, 9 and CCRL1 receptors were evident in zebrafish, but the clear orthologs to mammalian CCR1, 2, 3, 4, 5 and 10 were not found in zebrafish. The gene structure of zebrafish CCR (zfCCR) was further analyzed. The open reading frame of zfCCR3-1, zfCCR3-3, zfCCR6-1, zfCCR6-2, zfCCR8-2 contain one exon, and two exons were identified for zfCCR2-1, zfCCR2-2, zfCCR4 and zfCCRLI-1, three exons for zfCCR3-2, zfCCR5 and zfCCR7, four exons for zfCCR8-1 and zfCCR9-1. The expression analyses showed that in zebrafish, most C-C chemokine receptor genes Were expressed in fertilized eggs and oocytes, and all the receptor genes were expressed in larval stages. The zfCCR2-2, zfCCR3-1, zfCCR4 and zfCCR6-2 genes were expressed in all normal organs examined, whereas not for zfCCR2-1, zfCCR3-3, zfCCR6-1, zfCCR8-1, zfCCR9-2 and zfCCRL1-2. The expression of zfCCR3-2, zfCCR5, zfCCR7, zfCCR9-1 and zfCCRLI-1 were detected in the majority organs. and zfCCR8-2 and zfCCR8-3 detected only in brain. The differential expression pattern of different paralogues in organs may indicate their difference in function, which requires further investigation. (C) 2008 Elsevier Ltd. All rights reserved.

In vivo studies on the toxic effects of microcystins on mitochondrial electron transport chain and ion regulation in liver and heart of rabbit

This study examined the toxic effects of microcystins on mitochondria of liver and heart of rabbit in vivo. Rabbits were injected i.p. with extracted microcystins (mainly MC-RR and -LR) at two doses, 12.5 and 50 MCLReq. mu g/kg bw, and the changes in mitochondria of liver and heart were studied at 1, 3,12, 24 and 48 h after injection. MCs induced damage of mitochondrial morphology and lipid peroxidation in both liver and heart. MCs influenced respiratory activity through inhibiting NADH dehydrogenase and enhancing succinate dehydrogenase (SDH). MCs altered Na+-K+-ATPase and Ca2+-Mg2+-ATPase activities of mitochondria and consequently disrupted ionic homeostasis, which might be partly responsible for the loss of mitochondrial membrane potential (MMP). MCs were highly toxic to mitochondria with more serious damage in liver than in heart. Damage of mitochondria showed reduction at 48 h in the low dose group, suggesting that the low dose of MCs might have stimulated a compensatory response in the rabbits. (C) 2008 Elsevier Inc. All rights reserved.

Degradation of 17 alpha-ethinylestradiol in aqueous solution by ozonation

This study investigates the ozonation of 17 alpha-ethinylestradiol (EE2) in aqueous solution. The affecting factors on the degradation of EE2 were studied and described in details, such as initial EE2 concentration, initial pH value and ozone concentration. In addition, some parameters such as pH. electrical conductivity, mineralization efficiency and degradation products were monitored during the process. The mineralization efficiency of EE2 could reach 53.9%. During the ozonation process the rapid decrease of pH and the sharp increase of electrical conductivity indicated the fort-nation of acidic by-products, small fragments and ions which were confirmed by high performance liquid chromatography (HPLC) and gas chromatography-mass spectrometry (GUMS) analysis. Results showed that there were intermediate products of smaller molecule with higher polarity produced during the course of EE2 degradation. Then a possible reaction pathway for EE2 degradation involving all intermediates detected is proposed. During the ozonation process EE2 was first oxidized into hydroxyl-semiquinone isomers which were subsequently degraded into low molecular weight compounds such as oxalic acid, malonate, glutarate, and so on. Furthermore. these organic acids are easily oxidized by ozone into carbon dioxide (CO2). This work shows that ozonation process is promising for the removal of EE2. The results can provide some useful information for the potential treatment of EE2 by ozonation in aqueous solution. (c) 2005 Elsevier B.V. All rights reserved.

Interference in transport through double barriers in interacting quantum wires

We investigate interference effects of the backscattering current through a double-barrier structure in an interacting quantum wire attached to noninteracting leads. Depending on the interaction strength and the location of the barriers, the backscattering current exhibits different oscillation and scaling characteristics with the applied voltage in the strong and weak interaction cases. However, in both cases, the oscillation behaviors of the backscattering current are mainly determined by the quantum mechanical interference due to the existence of the double barriers.

Band-tail shape and transport near the metal-insulator transition in Si-doped

In the present work, an infrared light-emitting diode is used to photodope molecular-beam-epitaxy-grown Si: Al0.3Ga0.7As, a well-known persistent photoconductor, to vary the effective electron concentration of samples in situ. Using this technique, we examine the transport properties of two samples containing different nominal doping concentrations of Si [1 x 10(19) cm(-3) for sample 1 (S1) and 9 x 10(17) cm(-3) for sample 2 (S2)] and vary the effective electron density between 10(14) and 10(18) cm(-3). The metal-insulator transition for S1 is found to occur at a critical carrier concentration of 5.7 x 10(16) cm(-3) at 350 mK. The mobilities in both samples are found to be limited by ionized impurity scattering in the temperature range probed, and are adequately described by the Brooks-Herring screening theory for higher carrier densities. The shape of the band tail of the density of states in Al0.3Ga0.7As is found electrically through transport measurements. It is determined to have a power-law dependence, with an exponent of -1.25 for S1 and -1.38 for S2.

Spin-dependent transport and spin polarization in coupled quantum wells

We theoretically investigate the electron transport and spin polarization of two coupled quantum wells with Dresselhaus spin-orbit interaction. In analogy with the optical dual-channel directional coupler, the resonant tunneling effect is treated by the coupled-mode equations. We demonstrate that spin-up and -down electrons can be completely separated from each other for the system with an appropriate system geometry and a controllable barrier. Our result provides a new approach to construct spin-switching devices without containing any magnetic materials or applying a magnetic field. (C) 2008 American Institute of Physics. [DOI: 10.1063/1.2981204]

Electron transport properties of In0.53Ga0.47As/In0.52Al0.48As quantum wells with two occupied subbands

Magnetotransport properties of two-dimensional electron gas have been investigated for three In0.53Ga0.47As/In0.52Al0.48As quantum well samples having two occupied subbands with different well widths. When the intersubband scattering is considered, we have obtained the subband density, transport scattering time, quantum scattering time and intersubband scattering time, respectively, by analyzing the result of fast Fourier transform of the first derivative of Shubnikov-de Haas oscillations. It is found that the main scattering mechanism is due to small-angle scattering, such as ionized impurity scattering, for the first subband electrons.

Studies of tetragonal PbTiO3 subjected to uniaxial stress along the c-axis

Tetragonal PbTiO3 under uniaxial stress along the c-axis is investigated from first-principles. The structural parameters, polarization, and squares of the lowest optical phonon frequencies for E(1TO) and A(1)(1TO) modes at Gamma show abrupt changes near a stress sigma(c) of 1.04 GPa, which is related to the dramatic change of elastic constant c(33) resulting from the uniaxial stress applied along the c-axis. We also find that the uniaxial compressive stress could enhance the piezoelectric stress coefficients, whereas the uniaxial tensile stress could enhance the piezoelectric strain coefficients. It is also found that when the magnitude of uniaxial compressive stress sigma(33) is greater than 12 GPa, PbTiO3 is transformed to the paraelectric tetragonal phase.

Investigation of native defects and property of bulk ZnO single crystal grown by a closed chemical vapor transport method

Hall effect, Raman scattering, photoluminescence spectroscopy (PL), optical absorption (OA), mass spectroscopy, and X-ray diffraction have been used to study bulk ZnO single crystal grown by a closed chemical vapor transport method. The results indicate that shallow donor impurities (Ga and Al) are the dominant native defects responsible for n-type conduction of the ZnO single crystal. PL and OA results suggest that the as-grown and annealed ZnO samples with poor lattice perfection exhibit strong deep level green photoluminescence and weak ultraviolet luminescence. The deep level defect in as-grown ZnO is identified to be oxygen vacancy. After high-temperature annealing, the deep level photoluminescence is suppressed in ZnO crystal with good lattice perfection. In contrast, the photoluminescence is nearly unchanged or even enhanced in ZnO crystal with grain boundary or mosaic structure. This result indicates that a trapping effect of the defect exists at the grain boundary in ZnO single crystal. (C) 2007 Elsevier B.V. All rights reserved.