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91.
Abstract.— Direct development in benthic marine invertebrates is usually associated with narrow geographical range, low rates of colonization, and low levels of gene flow. Paradoxically, the small brittle star Amphipholis squamata broods its larvae to a crawl-away juvenile stage, yet has a cosmopolitan distribution. Using sequence and restriction-fragment-length-polymorphisms (RFLP) analyses of nuclear and mitochondrial DNA from 16 coastal populations throughout New Zealand, we tested whether the species is indeed a poor disperser, as may be expected from its brooding habit. We predicted that local and regional populations would be genetically structured according to isolation by distance. We also suspected that this ubiquitous "species" is composed of a variety of cryptic taxa in different geographic areas, as has been discovered in an increasing number of marine invertebrates. We found evidence of four genetically divergent and reproductively isolated lineages that can exist in syntopy. Lineages vary in abundance, haplotype diversity, and geographic distribution. The partitioning of genetic variation within the most common lineage, as well as the geographic distribution of the four lineages, suggest a north/south split. This pattern is consistent with known New Zealand marine biogeographic zones and appears to be linked to the regime of oceanic circulation, which is characterized by subtropical, southward-moving water masses in the north, and sub-Antarctic, northward-moving water in the south. We conclude that the dispersal ability of A. squamata is regionally restricted but with sporadic long-distance dispersal, which serves to increase local genetic variation. Our results support the idea that dispersal occurs through passive transport by drifting or rafting on macroalgae, which A. squamata commonly inhabits, and emphasize that poor dispersal ability is not necessarily a corollary of direct development. 相似文献
92.
Hobe G Schön R Goncharov N Katsiya G Koryakin M Gesson-Cholat I Oettel M Zimmermann H 《Steroids》2002,67(11):883-893
17Alpha-estradiol (1,3,5(10)-estratriene-3,17alpha-diol) together with a tracer dose of the tritium-labeled compound was administered orally and sublingually to male volunteers. The serum concentrations of 17alpha-estradiol (free and liberated by enzymatic hydrolysis) were quantified by GC/MS, and the serum total radioactivity and urinary radioactivity excretion were determined. After oral administration, 17alpha-estradiol was rapidly and intensively conjugated; only tiny quantities of the free steroid (<1% of total) appeared in serum. Sublingual administration resulted in temporary (up to 3 h p.a.) higher serum levels of the free compound. The metabolite patterns obtained by TLC of extracts from serum and urine demonstrated that 17alpha-estradiol is the subject of a poor phase I metabolism in man. A great discrepancy was found in the serum concentrations of 17alpha-estradiol (free + conjugated) determined by GC/MS and the serum radioactivity expressed in 17alpha-estradiol equivalents. By TLC analysis of the steroid conjugates extracted from serum, various 17alpha-estradiol conjugate peaks were found. By enzymatic hydrolysis with beta-glucuronidase/aryl sulfatase from Helix pomatia they were only partially cleaved. Thus, the difference between the serum radioactivity and the 17alpha-estradiol levels determined by GC/MS had to be attributed to an incomplete conjugate hydrolysis. It has been shown with the synthesized 17alpha-estradiol sulfate conjugates that only the 3-sulfate is cleaved by enzymatic hydrolysis, whereas the 17-sulfate group resists enzymatic hydrolysis. The methanolysis procedure (acetyl chloride in MeOH) has proved to be an efficient method for cleaving both the 3-sulfate group and the 17-sulfate group. In contrast to the 17alpha-estradiol conjugates in serum, the urinary conjugates were intensively split by the enzyme preparation. From this, it has to be concluded that the serum conjugates were deconjugated and newly reconjugated before urinary excretion. 相似文献
93.
Canines are preserved among Multituberculata only in the upper jaw of the Paulchoffatiidae, the Pinheirodontidae and the North American genusGliodon Engelmann &; Callison, 1999. They resemble the anterior premolars (p1–3) in the morphology of their crown, but they differ from them by the presence of only one root. In the present paper, 126 isolated canines of the Paulchoffatiidae from the Guimarota coal-pit in Portugal are treated. They show a wide morphological variation, from bicuspid to pentacuspid expression, and they can be grouped into 18 morphological units (Tab. 1). The bicuspid canines (11 specimens) show one buccal and one lingual cusp, arranged side by side, the latter normally being larger than the former. In the tricuspid canines (32 specimens) the cusps (one buccal and two lingual) are arranged in a triangle, with a great variation in the position of the cusps to each other. Tetracuspid canines (69 specimens) are the dominating group. Two buccal and two lingual cusps are present, which differ markedly in their largeness and their position to each other. The teeth differ also much in the shape of their crown. The pentacuspid canines (14 specimens) show two buccal and three lingual cusps. The variation in the arrangement of the cusps and in the shape of the crown is similar as in the tetracuspid specimens. One or two small cuspules can be present at the anterior border of the crown additionally to the main cusps in the canines. Tricuspid and tetracuspid canines are present also in the skulls of the Paulchoffatiidae, whereas bicuspid and pentacuspid canines are known only as isolated specimens. In the Pinheirodontidae the canines are tricuspid or tetracuspid, inGlirodon they are unicuspid. The Paulchoffatiidae and Pinheirodontidae — Paulchoffatiid line sensuKielan-Jaworowska &; Hurum, 2001 — are characterized by increasing premolarization of the upper canines. With that they differ markedly from all other multituberculates where the canini become reduced. 相似文献
94.
Surface diversity in Mycoplasma agalactiae is driven by site-specific DNA inversions within the vpma multigene locus 下载免费PDF全文
The ruminant pathogen Mycoplasma agalactiae possesses a family of abundantly expressed variable surface lipoproteins called Vpmas. Phenotypic switches between Vpma members have previously been correlated with DNA rearrangements within a locus of vpma genes and are proposed to play an important role in disease pathogenesis. In this study, six vpma genes were characterized in the M. agalactiae type strain PG2. All vpma genes clustered within an 8-kb region and shared highly conserved 5' untranslated regions, lipoprotein signal sequences, and short N-terminal sequences. Analyses of the vpma loci from consecutive clonal isolates showed that vpma DNA rearrangements were site specific and that cleavage and strand exchange occurred within a minimal region of 21 bp located within the 5' untranslated region of all vpma genes. This process controlled expression of vpma genes by effectively linking the open reading frame (ORF) of a silent gene to a unique active promoter sequence within the locus. An ORF (xer1) immediately adjacent to one end of the vpma locus did not undergo rearrangement and had significant homology to a distinct subset of genes belonging to the lambda integrase family of site-specific xer recombinases. It is proposed that xer1 codes for a site-specific recombinase that is not involved in chromosome dimer resolution but rather is responsible for the observed vpma-specific recombination in M. agalactiae. 相似文献
95.
Engineered CD4- and CXCR4-using simian immunodeficiency virus from African green monkeys is neutralization sensitive and replicates in nonstimulated lymphocytes 下载免费PDF全文
König RR Flory E Steidl S Neumann J Coulibaly C Holznagel E Holzammer S Norley S Cichutek K 《Journal of virology》2002,76(21):10627-10636
During human immunodeficiency virus type 1 (HIV-1) infection, disease progression correlates with the occurrence of variants using the coreceptor CXCR4 for cell entry. In contrast, apathogenic simian immunodeficiency virus (SIV) from African green monkeys (SIVagm), specifically the molecular virus clone SIVagm3mc, uses CCR5, Bob, and Bonzo as coreceptors throughout the course of infection. The influence of an altered coreceptor usage on SIVagm3mc replication was studied in vitro and in vivo. The putative coreceptor binding domain, the V3 region of the surface envelope (SU) glycoprotein, was replaced by the V3 loop of a CD4- and CXCR4-tropic HIV-1 strain. The resulting virus, termed SIVagm3-X4mc, exclusively used CD4 and CXCR4 for cell entry. Consequently, its in vitro replication was inhibited by SDF-1, the natural ligand of CXCR4. Surprisingly, SIVagm3-X4mc was able to replicate in vitro not only in interleukin-2- and phytohemagglutinin-stimulated but also in nonstimulated peripheral blood mononuclear cells (PBMCs) from nonhuman primates. After experimental infection of two pig-tailed macaques with either SIVagm3-X4mc or SIVagm3mc, the coreceptor usage was maintained during in vivo replication. Cell-associated and plasma viral loads, as well as viral DNA copy numbers, were found to be comparable between SIVagm3mc and SIVagm 3-X4mc infections, and no pathological changes were observed up to 14 months postinfection. Interestingly, the V3 loop exchange rendered SIVagm3-X4mc susceptible to neutralizing antibodies present in the sera of SIVagm3-X4mc- and SIVagm3mc-infected pig-tailed macaques. Our study describes for the first time a successful exchange of a V3 loop in nonpathogenic SIVagm resulting in CD4 and CXCR4 usage and modulation of virus replication in nonstimulated PBMCs as well as sensitivity toward neutralization. 相似文献
96.
Zidorn C Spitaler R Ellmerer-Müller EP Perry NB Gerhäuser C Stuppner H 《Zeitschrift für Naturforschung. C, Journal of biosciences》2002,57(7-8):614-619
A novel tyrolobibenzyl derivative, 1-->beta-D-apiosyl-beta-D-glucopyranosyl 4-[2-(4-hydroxyphenyl)ethyl]benzofuran-2-carboxylate 3 (tyrolobibenzyl D) was isolated from Scorzonera humilis L. and its structure established by mass spectrometry and 1D- and 2D-NMR spectroscopy. The biological activities of the new compound and related tyrolobibenzyls A-C (1-2, 4) and the semi-synthetic peracetyl derivatives of tyrolobibenzyls B (2a) and C (4a) were assessed. The results revealed no cytotoxic activity against P388 cells and neither anti-bacterial activity against Bacillus subtilis nor antifungal activity against Candida albicans and Trichophyton mentagrophytes for any of the investigated compounds. An evaluation of potential chemopreventive activity of 2, 2a, 4, and 4a also revealed no pronounced activity in any of the employed assaying systems. 相似文献
97.
Hemphill A Stettler M Walker M Siles-Lucas M Fink R Gottstein B 《Trends in parasitology》2002,18(10):445-451
This article reviews the use of an in vitro culture model for the maintenance and proliferation of Echinococcus multilocularis metacestodes and the formation of protoscoleces. This model has been used to identify and characterize parasite molecules involved in host-parasite interactions, and is a suitable tool to perform in vitro drug-screening assays. The development of a simple and easy-to-handle assay to determine the effects of drugs on parasite viability, without the need for time-consuming animal experimentation, has opened the way for larger-scale in vitro drug screening. 相似文献
98.
The lung is protected against oxidative stress by a variety of antioxidants and type II pneumocytes seem to play an important role in antioxidant defense. Previous studies have shown that inhalation of NO2 results in acute and chronic lung injury. How the expression and enzyme activity of antioxidant enzymes are influenced in type II cells of different inflammatory stages has yet not been studied. To elucidate this question, we exposed rats to 10 ppm NO2 for 3 or 20 days to induce acute or chronic lung injury. From these and air-breathing rats, type II pneumocytes were isolated. The mRNA expression and protein content of CuZnSOD and MnSOD as well as total SOD-specific enzyme activity were determined. For the acute lung injury (3 d NO2), the expression of CuZnSOD mRNA was significantly increased, while MnSOD expression was significantly reduced after 3 days of NO 2 exposure. For the chronic lung injury (20 d NO2), CuZnSOD expression was still enhanced, while MnSOD expression was comparable to control. In parallel to CuZnSOD mRNA expression, the protein amount was significantly increased in acute and chronic lung injury however MnSOD protein content exhibited no intergroup differences. Total SOD enzyme activity showed a significant decrease after 3 days of NO2 exposure and was similar to control after 20 days. We conclude that during acute and chronic lung injury in type II pneumocytes expression and protein synthesis of CuZnSOD and MnSOD are regulated differently. 相似文献
99.
Schöps R Schierhorn A Schäffner I Mansfeld J Ulbrich-Hofmann R 《Journal of Protein Chemistry》2002,21(6):407-411
Recently, the genes of two isoenzymes of phospholipase D from white cabbage (PLD1 and PLD2) with molecular masses of 91.7 and 91.9 kDa, respectively, have been sequenced and expressed in Escherichia coli [Schäffner, I., Rücknagel, K.-P., Mansfeld, J., and Ulbrich-Hofmann, R. (2002). Eur. J. Lipid Sci. Technol.
104: 79–87]. Both enzymes are highly homologous (91% identity) and behave very similarly. Phospholipase D purified from white cabbage leaves (PLDcab) is compared with the two recombinant enzymes in sodium dodecylsulfate and native polyacrylamide gel electrophoresis, isoelectric focusing, N-terminal sequencing, and mass spectrometry after tryptic digestion. As a result, PLDcab clearly can be assigned to PLD2. In contrast to recombinant PLD2, however, PLDcab is N-terminally acetylated. 相似文献
100.
7,8-Dihydroneopterin and neopterin are secreted by human and primate macrophages after activation by interferon-gamma in a ratio of 2:1. 7,8-Dihydroneopterin is known to suppress radical-mediated processes, but it is also able in the presence of iron ions to generate superoxide radical anion and hydroxyl radicals from molecular oxygen. Effects of 7,8-dihydroneopterin were investigated on (met)myoglobin and (met)hemoglobin. Addition of 7,8-dihydroneopterin to heme proteins in air-saturated solution resulted in dose-dependent cleavage of the porphyrin moiety. The liberation of non-heme iron and carbon monoxide originating from the cleaved porphyrin was quantified. Both were generated at equimolar concentrations with a linear correlation coefficient of 0.9. Addition of ferrous iron significantly accelerated the pteridine-mediated cleaving of the porphyrin. However, the total yield of porphyrin cleaved was controlled by the pterin rather than by the ferrous ion concentration. 7,8-Dihydroneopterin is assumed to reduce the heme iron in intact protein molecules, thereby preparing the conditions for binding of oxygen and carbon monoxide as ligands. Beyond that, it is concluded that hydroxyl radicals might be generated via reduction of molecular oxygen to superoxide anion in the autoxidation process and dismutation to hydrogen peroxide and subsequent Fenton reaction. 相似文献