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1.
A Volbeda M C Feiters M G Vincent E Bouwman B Dobson K H Kalk J Reedijk W G Hol 《European journal of biochemistry》1989,181(3):669-673
Single-crystal ultraviolet spectroscopy, X-ray absorption spectroscopy and EPR measurements have been used to examine the oxidation and oxygenation state of the dinuclear copper site of several types of hemocyanin crystals. The crystals contain Panulirus interruptus hemocyanin which forms hexameric molecules with a molecular mass of approximately 470 kDa. Three types of crystals have been investigated. Type-I monoclinic crystals, which have been used for the X-ray structure determination, contain virtually only deoxyhemocyanin. Type-II monoclinic crystals, which are less well ordered than the type-I crystals, contain a mixture of deoxy, oxy and met forms. Older crystals contain relatively more methemocyanin. A third, hexagonal, crystal form is also partially oxygenated, and, like the type-II monoclinic form, subject to gradual conversion to methemocyanin. 相似文献
2.
David Fowler Mhairi Coyle Ute Skiba Mark A. Sutton J. Neil Cape Stefan Reis Lucy J. Sheppard Alan Jenkins Bruna Grizzetti James N. Galloway Peter Vitousek Allison Leach Alexander F. Bouwman Klaus Butterbach-Bahl Frank Dentener David Stevenson Marcus Amann Maren Voss 《Philosophical transactions of the Royal Society of London. Series B, Biological sciences》2013,368(1621)
Global nitrogen fixation contributes 413 Tg of reactive nitrogen (Nr) to terrestrial and marine ecosystems annually of which anthropogenic activities are responsible for half, 210 Tg N. The majority of the transformations of anthropogenic Nr are on land (240 Tg N yr−1) within soils and vegetation where reduced Nr contributes most of the input through the use of fertilizer nitrogen in agriculture. Leakages from the use of fertilizer Nr contribute to nitrate (NO3−) in drainage waters from agricultural land and emissions of trace Nr compounds to the atmosphere. Emissions, mainly of ammonia (NH3) from land together with combustion related emissions of nitrogen oxides (NOx), contribute 100 Tg N yr−1 to the atmosphere, which are transported between countries and processed within the atmosphere, generating secondary pollutants, including ozone and other photochemical oxidants and aerosols, especially ammonium nitrate (NH4NO3) and ammonium sulfate (NH4)2SO4. Leaching and riverine transport of NO3 contribute 40–70 Tg N yr−1 to coastal waters and the open ocean, which together with the 30 Tg input to oceans from atmospheric deposition combine with marine biological nitrogen fixation (140 Tg N yr−1) to double the ocean processing of Nr. Some of the marine Nr is buried in sediments, the remainder being denitrified back to the atmosphere as N2 or N2O. The marine processing is of a similar magnitude to that in terrestrial soils and vegetation, but has a larger fraction of natural origin. The lifetime of Nr in the atmosphere, with the exception of N2O, is only a few weeks, while in terrestrial ecosystems, with the exception of peatlands (where it can be 102–103 years), the lifetime is a few decades. In the ocean, the lifetime of Nr is less well known but seems to be longer than in terrestrial ecosystems and may represent an important long-term source of N2O that will respond very slowly to control measures on the sources of Nr from which it is produced. 相似文献
3.
Distribution and budget of dissolved and biogenic silica in the Bohai Sea and Yellow Sea 总被引:2,自引:0,他引:2
Jun Liu Jiaye Zang Lex Bouwman Sen Liu Zhigang Yu Xiangbin Ran 《Biogeochemistry》2016,130(1-2):85-101
4.
Concomitant loss of cell surface fibronectin and laminin from transformed rat kidney cells 总被引:8,自引:11,他引:8 下载免费PDF全文
Both fibronectin and laminin were found by immunofluorescence as a matrix at the surface of normal rat kidney cells. These matrices were absent from the surface of virally transformed rat kidney cells. Soluble fibronectin and laminin were detected in the culture media of the transformed as well as the normal cells. Culture supernates of the transformed cells contained even more fibronectin than the supernates of the transformed cells contained even more fibronectin than the supernates of the normal cells while laminin was present in similar amounts in both culture media. This shows that the loss of fibronectin and laminin from the surface of the transformed cells is caused by failure of the cells to deposit these proteins into an insoluble matrix and not caused by inadequate production. Fibronectins isolated from culture media of the normal and transformed cells were similar in SDS polyacrylamide gel electrophresis. Laminin isolated from culture media by affinity chromatography on heparin-Sepharose followed by immunoprecipitation was composed of three main polypeptides, one with a molecular weight of 400,000 and two with a molecular weight close to 200,000 in both cell types. Fibronectins from both cell types were equally active in promoting cell attachment. Rat fibronectin from transformed cells, like normal cells, when applied to culture dishes coated with fibronectin, readily attached and spread on the substratum, requiring approximately the same amount of fibronectin as the normal cells. On the basis of these results it seem that the failure of the transformed cells to incorporate fibronectin into an insoluble cell surface matix is not a consequence of a demonstrable change in the functional characteristics of the fibronectin molecule or in the ability of the cells to interact with fibronectin. It may depend on as yet unidentified interactions of the cell surface. Similar interactions may be needed for the deposition of laminin into the matrix, because laminin was also absent from the surface of transformed cells, despite its being synthesized by these cells. 相似文献
5.
van der Sluis C Smit BA Hartmans S ter Schure EG Tramper J Wijffels RH 《Enzyme and microbial technology》2000,27(1-2):151-156
To elucidate the growth inhibitory effect of threonine, the regulation of the aspartate-derived amino-acid metabolism in Zygosaccharomyces rouxii, an important yeast for the flavor development in soy sauce, was investigated. It was shown that threonine inhibited the growth of Z. rouxii by blocking the methionine synthesis. It seemed that threonine blocked this synthesis by inhibiting the conversion of aspartate. In addition, it was shown that the growth of Z. rouxii, unlike that of Saccharomyces cerevisiae, was not inhibited by the herbicide sulfometuron methyl (SMM). From enzyme assays, it was concluded that the acetohydroxy acid synthase in Z. rouxii, unlike that in S. cerevisiae, was not sensitive to SMM. Furthermore, the enzyme assays demonstrated that the activity of threonine deaminase in Z. rouxii, like in S. cerevisiae, was strongly inhibited by isoleucine and stimulated by valine. From this work, it is clear that the aspartate-derived amino-acid metabolism in Z. rouxii only partly resembles that in S. cerevisiae. 相似文献
6.
Visinoni S Fam BC Blair A Rantzau C Lamont BJ Bouwman R Watt MJ Proietto J Favaloro JM Andrikopoulos S 《American journal of physiology. Endocrinology and metabolism》2008,295(5):E1132-E1141
Increased endogenous glucose production (EGP) predominantly from the liver is a characteristic feature of type 2 diabetes, which positively correlates with fasting hyperglycemia. Gluconeogenesis is the biochemical pathway shown to significantly contribute to increased EGP in diabetes. Fructose-1,6-bisphosphatase (FBPase) is a regulated enzyme in gluconeogenesis that is increased in animal models of obesity and insulin resistance. However, whether a specific increase in liver FBPase can result in increased EGP has not been shown. The objective of this study was to determine the role of upregulated liver FBPase in glucose homeostasis. To achieve this goal, we generated human liver FBPase transgenic mice under the control of the transthyretin promoter, using insulator sequences to flank the transgene and protect it from site-of-integration effects. This resulted in a liver-specific model, as transgene expression was not detected in other tissues. Mice were studied under the following conditions: 1) at two ages (24 wk and 1 yr old), 2) after a 60% high-fat diet, and 3) when bred to homozygosity. Hemizygous transgenic mice had an approximately threefold increase in total liver FBPase mRNA with concomitant increases in FBPase protein and enzyme activity levels. After high-fat feeding, hemizygous transgenics were glucose intolerant compared with negative littermates (P < 0.02). Furthermore, when bred to homozygosity, chow-fed transgenic mice showed a 5.5-fold increase in liver FBPase levels and were glucose intolerant compared with negative littermates, with a significantly higher rate of EGP (P < 0.006). This is the first study to show that FBPase regulates EGP and whole body glucose homeostasis in a liver-specific transgenic model. Our homozygous transgenic model may be useful for testing human FBPase inhibitor compounds with the potential to treat patients with type 2 diabetes. 相似文献
7.
Summary Cirripedes are fascinating models for studying both functional constraints and diversity in larval development. Adult cirripedes display an amazing variation in morphology from sessile suspension feeders that still retain many crustacean characters to parasites that have lost virtually all arthropod traits. In contrast, cirripede larval development follows a common scheme with pelagic larvae comprising a series of nauplii followed by a cyprid. Variations are mostly concerned with whether or not the nauplii are feeding and the degree of abbreviation of development, culminating in species where the larvae hatch as cyprids. The cypris larvae are very similar among the ingroups of the Cirripedia, but interesting variations occur in structures used for substrate location and attachment. The cyprid is specialized to both swim through the water and actively explore the substratum by walking on the antennules and using an array of sensory organs in search for a suitable site to attach. This unique morphology and behavior of the cyprid have enabled the Cirripedia to colonize widely different habitats ranging from hard rock to soft animal tissue. Yet, the cyprid can metamorphose into juveniles as different as a setose feeding barnacle and the vermiform stages of the parasitic forms. This emphasizes the importance of the cyprid as one of the key features for the evolutionary success of the Cirripedia. 相似文献
8.
Autotaxin, a secreted lysophospholipase D, is essential for blood vessel formation during development 总被引:10,自引:0,他引:10 下载免费PDF全文
van Meeteren LA Ruurs P Stortelers C Bouwman P van Rooijen MA Pradère JP Pettit TR Wakelam MJ Saulnier-Blache JS Mummery CL Moolenaar WH Jonkers J 《Molecular and cellular biology》2006,26(13):5015-5022
Autotaxin (ATX), or nucleotide pyrophosphatase-phosphodiesterase 2, is a secreted lysophospholipase D that promotes cell migration, metastasis, and angiogenesis. ATX generates lysophosphatidic acid (LPA), a lipid mitogen and motility factor that acts on several G protein-coupled receptors. Here we report that ATX-deficient mice die at embryonic day 9.5 (E9.5) with profound vascular defects in yolk sac and embryo resembling the Galpha13 knockout phenotype. Furthermore, at E8.5, ATX-deficient embryos showed allantois malformation, neural tube defects, and asymmetric headfolds. The onset of these abnormalities coincided with increased expression of ATX and LPA receptors in normal embryos. ATX heterozygous mice appear healthy but show half-normal ATX activity and plasma LPA levels. Our results reveal a critical role for ATX in vascular development, indicate that ATX is the major LPA-producing enzyme in vivo, and suggest that the vascular defects in ATX-deficient embryos may be explained by loss of LPA signaling through Galpha13. 相似文献
9.
HENRIK GLENNER MARKJ. GRYGIER JENS T. HØEG PETER G.JENSEN FREDERICK R. SCHRAM F.L.S. 《Zoological Journal of the Linnean Society》1995,114(4):365-404
We present a cladistic analysis of the Cirripedia Thoracica using morphological characters and the Acrothoracica and Ascothoracida as outgroups. The list of characters comprised 32 shell and soft body features. The operational taxonomic units (OTUs) comprised 26 well-studied fossil and extant taxa, principally genera, since uncertainty about monophyly exists for most higher ranking taxonomic units. Parsimony analyses using PAUP 3.1.1 and Hennig86 produced 189 trees of assured minimal length. We also examined character evolution in the consensus trees using MacClade and Clados. The monophyly of the Balanomorpha and the Verrucomorpha sensu stricto is confirmed, and all trees featured a sister group relationship between the ‘living fossil Neoverruca and me Brachylepadomorpha. In the consensus trees the sequential progression of ‘pedunculate‘sister groups up to a node containing Neolepas also conforms to current views, but certain well-established taxa based solely on plesiomorphies stand out as paraphyletic, such as Pedunculata (= Lepadomorpha); Eolepadinae, Scalpellomorpha and Chthamaloidea. The 189 trees differed principally in the position of shell-less pedunculates, Neoverruca, the scalpelloid Capitulum, and the interrelationships within the Balanomorpha, although the 50% majority rule consensus tree almost fully resolved the latter. A monophyletic Sessilia comprising both Verrucomorpha and Balanomorpha appeared among the shortest trees, but not in the consensus. A tree with a monophyletic Verrucomorpha including Neoverruca had a tree length two steps longer than the consensus trees. Deletion of all extinct OTUs produced a radically different tree, which highlights the importance of fossils in estimating cirripede phylogeny. Mapping of our character set onto a manually constructed cladogram reflecting die most recent scenario of cirripede evolution resulted in a tree length five steps longer than any of our shortest trees. Our analysis reveals that several key questions in cirripede phylogeny remain unsolved, notably the position of shell-less forms and the transition from ‘pedunculate‘to ‘sessile‘barnacles. The inclusion of more fossil species at this point in our understanding of cirripede phylogeny will only result in even greater levels of uncertainty. When constructing the character list we also identified numerous uncertainties in the homology of traits commonly used in discussing cirripede evolution. Our study highlights larval ultrastructure, detailed studies of early ontogeny, and molecular data as the most promising areas for future research. 相似文献
10.
Rick Hursel Pilou L. H. R. Janssens Freek G. Bouwman Edwin C. Mariman Margriet S. Westerterp-Plantenga 《PloS one》2014,9(9)