格网尺度下典型旅游城市生态服务价值估算和时空分异特征——以三亚为例

以典型旅游城市三亚市为案例地，利用2006-2018年4期Landsat遥感影像数据，借助ENVI、ArcGIS平台定量识别土地利用演变特征，在1km×1km格网尺度下估算旅游地生态系统服务价值，并结合空间探索性数据分析揭示生态系统服务价值时空分异特征及其与旅游地发展的时空耦合关系。结果表明：（1）2006-2018年间，三亚市生态系统服务价值总量呈逐年下降趋势，由6.73×10⁹元降至5.76×10⁹元，累计减少9.78×10⁸元；（2）空间格局上，三亚市呈"南低北高"空间分异格局，2006-2018年增值区域连片分布于崖州区、天涯区、吉阳区南部区域，且呈逐年减少趋势，减值区域集聚于天涯区东北部、海棠区；（3）空间集聚上，生态系统服务价值截面各年份均呈显著空间正相关且相关性先降后增。高高集聚区位于天涯区北部区域，低低集聚区分布于沿海、海湾地区；（4）旅游发展与生态系统服务价值时空演化特征关联性较强。三亚市天涯区北部林地生态环境良好，生态系统服务价值略有下降但绝对数值稳定，是生态系统服务价值主要来源；旅游发展较为迅速的三亚湾、崖州湾以及海棠湾，相对增值区域较多，但绝对生态系统服务价值损失显著，严重滞后于其他区域。     

Col V plasmids and the resistance of Escherichia coli to divalent copper ions

Free organisms of both plasmid-free and plasmid-carrying strains of Escherichia coli were killed by incubation in water containing low levels of cupric ions. Sensitivity was temperature-dependent with killing being more marked at 20° or 25°C than at 10° or 15°C. In contrast to the effects of other inhibitors from natural waters (which affect free Col V⁺organisms more than Col^-ones), free Col^-and Col V⁺organisms were equally sensitive to kill by Cu²⁺. Attachment to glass beads essentially abolished sensitivity to cupric ions with full survival after exposure to 15 μ g/ml. This applied to both p⁺and p^-strains but attachment would have more effect on the survival of p⁺organisms in natural waters because some plasmids markedly enhance attachment.     

Kinetic Basis for the Conjugation of Auxin by a GH3 Family Indole-acetic Acid-Amido Synthetase

The GH3 family of acyl-acid-amido synthetases catalyze the ATP-dependent formation of amino acid conjugates to modulate levels of active plant hormones, including auxins and jasmonates. Initial biochemical studies of various GH3s show that these enzymes group into three families based on sequence relationships and acyl-acid substrate preference (I, jasmonate-conjugating; II, auxin- and salicylic acid-conjugating; III, benzoate-conjugating); however, little is known about the kinetic and chemical mechanisms of these enzymes. Here we use GH3-8 from Oryza sativa (rice; OsGH3-8), which functions as an indole-acetic acid (IAA)-amido synthetase, for detailed mechanistic studies. Steady-state kinetic analysis shows that the OsGH3-8 requires either Mg²⁺ or Mn²⁺ for maximal activity and is specific for aspartate but accepts asparagine as a substrate with a 45-fold decrease in catalytic efficiency and accepts other auxin analogs, including phenyl-acetic acid, indole butyric acid, and naphthalene-acetic acid, as acyl-acid substrates with 1.4–9-fold reductions in k_cat/K_m relative to IAA. Initial velocity and product inhibition studies indicate that the enzyme uses a Bi Uni Uni Bi Ping Pong reaction sequence. In the first half-reaction, ATP binds first followed by IAA. Next, formation of an adenylated IAA intermediate results in release of pyrophosphate. The second half-reaction begins with binding of aspartate, which reacts with the adenylated intermediate to release IAA-Asp and AMP. Formation of a catalytically competent adenylated-IAA reaction intermediate was confirmed by mass spectrometry. These mechanistic studies provide insight on the reaction catalyzed by the GH3 family of enzymes to modulate plant hormone action.     

酸敏感离子通道与脑梗死

急性脑梗死约占全部脑卒中的70%,病死率和致残率高,且极易复发。但目前针对急性脑梗死在时间窗内溶栓、抗凝等治疗手段不能从根本上切实有效地修复受损脑组织,且伴有出血等风险。寻找脑梗死形成发展的原因并予以治疗迫在眉睫。酸中毒是引起缺血性脑损伤的重要机制。大量实验研究表明,酸中毒能加重神经元的缺血性损伤,且其梗死面积与酸中毒的程度直接相关。但缺血产生的酸中毒如何引起神经元损伤的确切机制尚不明确。最近研究发现酸中毒能激活一种在中枢及周围神经中广泛存在的膜通道,即酸敏感离子通道,它对Ca2+通透,能引起细胞内Ca2+超载,同时能激活胞内酶引起细胞内蛋白质、脂类及核酸的降解,加重缺血后脑损伤。本文就酸敏感离子通道1a与脑梗死做一综述。     

Sealpox in captive grey seals (Halichoerus grypus) and their handlers

Histopathologic, ultrastructural, and negative-staining studies indicated that nodular lesions on the flippers, head, and necks of recently weaned, captive grey seals (Halichoerus grypus) were similar to sealpox lesions reported from several other species of seals. Virions associated with the nodules were characteristic of the parapoxvirus subgroup of pox viruses. Two of the three persons handling the seals developed nodular lesions similar to "milker's nodules," the characteristic lesion in persons infected with parapoxvirus. The clinical course of the parapoxvirus infection in both the grey seals and their handlers is described. It was concluded that although sealpox is transmissible to man, the mild clinical manifestations place it in the nuisance category of zoonotic diseases.     

Effects of sodium butyrate on human colonic adenocarcinoma cells. Induction of placental-like alkaline phosphatase

We have examined the effects of the "differentiating agent," sodium butyrate, on the induction of alkaline phosphatase in human colonic tumor cell line LS174T. Culture of these cells in the presence of 2 mM butyrate caused this activity to increase from less than 0.0001 unit/mg of protein to greater than 0.7 unit/mg of protein over an 8-day period. This induction proceeded in a nonlinear fashion with a lag time of 2-3 days occurring before enzymatic activity began to rise. These increases in activity were accompanied by elevations in the content of a placental-like isozyme of alkaline phosphatase as demonstrated by "Western" immunoblots. Dome formation, indicative of differentiation in cultured cells, also required 3 days treatment with butyrate before becoming evident. The rate of biosynthesis of the enzyme, examined using metabolic labeling with L-[35S]methionine and immunoprecipitation, was found to increase continuously between days 2 and 6 of butyrate treatment. "Northern" blot analysis indicated that treatment of these cells with butyrate caused greater than 20-fold induction of a 2700-base mRNA that hybridized to a cDNA probe for placental alkaline phosphatase. The mRNA for alkaline phosphatase produced by these cells upon butyrate treatment was approximately 300-400 bases smaller than the mRNA for alkaline phosphatase found in placenta. Human small intestine also contained two mRNAs that hybridized relatively weakly with the placental alkaline phosphatase probe. These results indicate that a placental alkaline phosphatase-like protein and mRNA are induced by butyrate in LS174T cells with a time course consistent with cellular differentiation preceding induction.     

cDNA sequence and tissue distribution of the mRNA for bovine and murine p11, the S100-related light chain of the protein-tyrosine kinase substrate p36 (calpactin I)

We have isolated and sequenced cDNA clones of bovine and murine p11 mRNAs. The nonpolyadenylated mRNAs are predicted to be 614 and 600 nucleotides, respectively. The p11 mRNAs both contain a 291 nucleotide open reading frame, preceded by a 5'-untranslated region of 73 nucleotides in bovine p11 mRNA and of 68 nucleotides in murine p11 mRNA. The deduced bovine p11 amino acid sequence is identical to the previously published partial bovine and complete porcine p11 protein sequence except for an additional COOH-terminal lysine residue. The bovine and murine p11 proteins are 92% homologous, whereas at the nucleotide level the conservation is 89% in the coding region and 75% in the 3'-untranslated region. Southern analysis of murine genomic DNA detected a single p11 gene, less than 10 kilobase pairs in size, containing as many as three introns. The p11 gene has been assigned to mouse chromosome 3 by analysis of interspecific hybrid cell panels and recombinant inbred mouse strains. The p11 gene is closely linked to the Xmmv-65 endogenous leukemia virus env gene and the guanylate binding protein-1 gene. Northern analyses of RNAs from mouse tissues and cell lines indicated that p11 mRNA levels vary widely. They are very low in liver, heart, and testes, moderate in brain, spleen, and thymus, and high in kidney, intestine, and lung. Analysis of the same RNA samples for p36 mRNA levels showed that expression of p11 and p36 mRNAs is not always coordinated. Brain and the mouse embryonal carcinoma cell line F9 contain moderate to high levels of p11 mRNA with very low levels of p36 mRNA. Sequence homology between p11 and the S100 proteins, and the serum-induced 2A9 gene product, as well as possible functions of p11 are discussed.     

Different rhodopsin monoclonal antibodies reveal different binding patterns on developing and adult rat retina

We used a battery of 10 monoclonal antibodies directed against different identified peptide sequences within the carboxyl, transmembrane loop, and amino terminal regions of rhodopsin to label retinas from early postnatal and adult rats. Intensity of label, age of initial appearance of staining, and distribution of label varied depending on the antibody. Most antibodies showed detectable labeling at postnatal day 1, and were eventually observed binding to the cell bodies and the inner and outer segments of the photoreceptors. One amino terminal and two carboxyl terminal antibodies, however, showed no detectable labeling until postnatal day 5 and were only transiently detectable in the cell body region. These patterns cannot be explained by accessibility of binding site, binding affinity, fixation artifact, or crossreactivity. The results indicate that physiological and experimental parameters can alter the apparent immunocytochemical localization of conformationally active molecules such as rhodopsin. The results also suggest that rhodopsin can undergo light-dependent conformational changes in several different compartments within rat retinal photoreceptors before the time of eye opening.