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71.
Delta (δ) subunit containing GABAA receptors are expressed extra‐synaptically and mediate tonic inhibition. In cerebellar granule cells, they often form a receptor together with α6 subunits. We were interested to determine the architecture of these receptors. We predefined the subunit arrangement of 24 different GABAA receptor pentamers by subunit concatenation. These receptors (composed of α6, β3 and δ subunits) were expressed in Xenopus oocytes and their electrophysiological properties analyzed. Currents elicited in response to GABA were determined in presence and absence of 3α, 21‐dihydroxy‐5α‐pregnan‐20‐one and to 4,5,6,7‐tetrahydroisoxazolo[5,4‐c]‐pyridin‐3‐ol. α6‐β3‐α6/δ receptors showed a substantial response to GABA alone. Three receptors, β3‐α6‐δ/α6‐β3, α6‐β3‐α6/β3‐δ and β3‐δ‐β3/α6‐β3, were only uncovered in the combined presence of the neurosteroid 3α, 21‐dihydroxy‐5α‐pregnan‐20‐one with GABA. All four receptors were activated by 4,5,6,7‐tetrahydroisoxazolo[5,4‐c]‐pyridin‐3‐ol. None of the functional receptors was modulated by physiological concentrations (up to 30 mM) of ethanol. GABA concentration response curves indicated that the δ subunit can contribute to the formation of an agonist site. We conclude from the investigated receptors that the δ subunit can assume multiple positions in a receptor pentamer composed of α6, β3 and δ subunits. 相似文献
72.
Vronique Boudolf Tim Lammens Joanna Boruc Jelle Van Leene Hilde Van Den Daele Sara Maes Gert Van Isterdael Eugenia Russinova Eva Kondorosi Erwin Witters Geert De Jaeger Dirk Inz Lieven De Veylder 《Plant physiology》2009,150(3):1482-1493
The mitosis-to-endocycle transition requires the controlled inactivation of M phase-associated cyclin-dependent kinase (CDK) activity. Previously, the B-type CDKB1;1 was identified as an important negative regulator of endocycle onset. Here, we demonstrate that CDKB1;1 copurifies and associates with the A2-type cyclin CYCA2;3. Coexpression of CYCA2;3 with CDKB1;1 triggered ectopic cell divisions and inhibited endoreduplication. Moreover, the enhanced endoreduplication phenotype observed after overexpression of a dominant-negative allele of CDKB1;1 could be partially complemented by CYCA2;3 co-overexpression, illustrating that both subunits unite in vivo to form a functional complex. CYCA2;3 protein stability was found to be controlled by CCS52A1, an activator of the anaphase-promoting complex. We conclude that CCS52A1 participates in endocycle onset by down-regulating CDKB1;1 activity through the destruction of CYCA2;3. 相似文献
73.
Benjamin Sommer Karl Friehs Erwin Flaschel Michael Reck Frank Stahl Thomas Scheper 《Journal of biotechnology》2009,140(3-4):194-202
Recombinant proteins are essential products of today's industrial biotechnology. In this study we address two crucial factors in recombinant protein production: (i) product accessibility and (ii) product recovery. Escherichia coli, one of the most frequently used hosts for recombinant protein expression, does not inherently secrete proteins into the extracellular environment. The major drawback of this expression system is, therefore, to be found in the intracellular protein accumulation and hampered product accessibility. We have constructed a set of expression vectors in order to facilitate extracellular protein production and purification. The maltose binding protein from E. coli is used as fusion partner for several proteins of interest allowing an export to the bacteria's periplasm via both the Sec and the Tat pathway. Upon coexpression of a modified Cloacin DF13 bacteriocin release protein, the hybrid proteins are released into the culture medium. This essentially applies to a distinguished reporter molecule, the green fluorescent protein, for which an extracellular production was not reported so far. The sequestered proteins can be purified to approximate homogeneity by a simple, rapid and cheap procedure which utilizes the affinity of the maltose binding protein to α-1,4-glucans. 相似文献
74.
Erwin Märtlbauer Ewald Usleber Richard Dietrich Elisabeth Schneider 《Mycotoxin Research》2009,25(4):175-186
In a long-term study (1990–1997) on ochratoxin A (OTA) in human blood serum, 102 serum samples from 36 persons of the Munich
Institute for Hygiene and Technology of Food of Animal Origin were analysed by enzyme immunoassay (EIA), and by high performance
liquid chromatography (HPLC) for control. Detection limits were at 50 pg/ml (EIA) and 50–70 pg/ml (HPLC), recoveries were
80–120% (EIA) and 30–60% (LC). OTA was detected in 98% (EIA, 368 ± 217 pg/ml) and 93% (HPLC, 271 ± 170 pg/ml) of samples (maximum
1,290 pg/ml). Using published conversion factors for serum/intake estimates (1.34 or 1.97), the mean daily OTA intake of these
36 persons was 493–725 pg/kg bw. Long-term individual mean OTA levels of nine persons ranged from 162 ± 80 pg/ml to 549 ± 172 pg/ml.
Our data were compared with published OTA serum levels (1985–2008) for apparently healthy persons from a total of 30 countries.
On a worldwide basis, the mean of means for OTA in human serum was estimated to be 700 pg/ml, corresponding to a mean daily
OTA intake of 940–1380 pg/kg bw. This level, which was relatively stable over the last decades, is well below published tolerable
daily intake values (14,000–18,000 pg/kg bw). 相似文献
75.
Carina Nielsen Maximilian Casteel Andrea Didier Richard Dietrich Erwin Märtlbauer 《Mycotoxin Research》2009,25(2):77-84
Trichothecene cytotoxicity of type A (T-2 toxin and HT-2 toxin), type B (deoxynivalenol, DON, and nivalenol, NIV), and type
D (satratoxins G and H) compounds was determined comparatively by using eight permanent human cell lines (Hep-G2, A549, CaCo-2,
HEp-2, A204, U937, RPMI 8226, and Jurkat). Viability of cells was measured by a water-soluble tetrazolium (WST-1) reagent
cell proliferation assay assessing mitochondrial metabolic activity. Toxicity was expressed as the toxin concentration inhibiting
50% of cell viability (IC50). Depending on the chemotype of the tested trichothecenes, relative cytotoxic activity differed by a factor of 100–1,000,
and the corresponding IC50 values were in the range from 2.2 nmol/l (satratoxin H on Jurkat and U937 cells) to 4,900 nmol/l (deoxynivalenol on HEp-2
cells). In contrast, the specific toxicity of each individual mycotoxin towards different cell lines was within remarkable
close limits, and between-cell line differences were much smaller than previously reported. For the cell lines tested, IC50 values were 4.4–10.8 nmol/l for T-2 toxin, 7.5–55.8 mol/l for HT-2 toxin, 600–4,900 nmol/l for DON, 300–2,600 nmol/l for
NIV, and 2.2–18.3 nmol/l for satratoxins G/H. In addition, for the first time, the toxic activity of trichothecenes on primary
cell culture of human endothelial cells (HUVEC) was tested. The susceptibility of this cell line was comparable to the other
cell lines tested, with IC50 values ranging from 16.5 nmol/l (T-2 toxin) to 4,500 nmol/l (DON). The results suggest that the current focus of cytotoxicological
studies on trichothecenes on lymphoid cell lines may lead to an underestimate of their potential on other target cell systems. 相似文献
76.
Wetlands and global climate change: the role of wetland restoration in a changing world 总被引:11,自引:0,他引:11
Kevin L. Erwin 《Wetlands Ecology and Management》2009,17(1):71-84
Global climate change is recognized as a threat to species survival and the health of natural systems. Scientists worldwide are looking at the ecological and hydrological impacts resulting from climate change. Climate change will make future efforts to restore and manage wetlands more complex. Wetland systems are vulnerable to changes in quantity and quality of their water supply, and it is expected that climate change will have a pronounced effect on wetlands through alterations in hydrological regimes with great global variability. Wetland habitat responses to climate change and the implications for restoration will be realized differently on a regional and mega-watershed level, making it important to recognize that specific restoration and management plans will require examination by habitat. Floodplains, mangroves, seagrasses, saltmarshes, arctic wetlands, peatlands, freshwater marshes and forests are very diverse habitats, with different stressors and hence different management and restoration techniques are needed. The Sundarban (Bangladesh and India), Mekong river delta (Vietnam), and southern Ontario (Canada) are examples of major wetland complexes where the effects of climate change are evolving in different ways. Thus, successful long term restoration and management of these systems will hinge on how we choose to respond to the effects of climate change. How will we choose priorities for restoration and research? Will enough water be available to rehabilitate currently damaged, water-starved wetland ecosystems? This is a policy paper originally produced at the request of the Ramsar Convention on Wetlands and incorporates opinion, interpretation and scientific-based arguments. 相似文献
77.
Kristen J. Skvorak Elizabeth J. Hager Erland Arning Teodoro Bottiglieri Harbhajan S. Paul Stephen C. Strom Gregg E. Homanics Qin Sun Erwin E.W. Jansen Cornelis Jakobs William J. Zinnanti K. Michael Gibson 《生物化学与生物物理学报:疾病的分子基础》2009,1792(10):1004-1010
Skvorak et al. [1] demonstrated the therapeutic efficacy of HTx in a murine model of iMSUD, confirming significant metabolic improvement and survival. To determine the effect of HTx on extrahepatic organs, we examined the metabolic effects of HTx in brain from iMSUD animals. Amino acid analysis revealed that HTx corrected increased ornithine, partially corrected depleted glutamine, and revealed a trend toward alloisoleucine correction. For amino acid and monoamine neurotransmitters, decreased GABA was partially corrected with HTx, while the l-histidine dipeptide of GABA, homocarnosine, was decreased in iMSUD mice and hypercorrected following HTx. Elevated branched-chain amino acids (BCAA; leucine, isoleucine, and valine) in MSUD can deplete brain tyrosine and tryptophan (the precursors of monoamine neurotransmitters, dopamine (DA) and serotonin (5-hydroxytryptamine; 5-HT)) through competition via the large neutral amino acid transporter. HTx corrected decreased DA levels and the DA metabolite, 3-methoxytyramine, and partially corrected the DA intermediate 3,4-dihydroxyphenylacetate (DOPAC) and 5-HT levels, despite normal tyrosine and tryptophan levels in iMSUD mouse brain. We further observed enhanced intracellular turnover of both DA and 5-HT in iMSUD mouse brain, both of which partially corrected with HTx. Our results suggest new pathomechanisms of neurotransmitter metabolism in this disorder and support the therapeutic relevance of HTx in iMSUD mice, while providing proof-of-principle that HTx has corrective potential in extrahepatic organs. 相似文献
78.
Boonthida Kositsup Pierre Montpied Poonpipope Kasemsap Philippe Thaler Thierry Améglio Erwin Dreyer 《Trees - Structure and Function》2009,23(2):357-365
The aim of this study was to assess the temperature response of photosynthesis in rubber trees (Hevea brasiliensis Müll. Arg.) to provide data for process-based growth modeling, and to test whether photosynthetic capacity and temperature
response of photosynthesis acclimates to changes in ambient temperature. Net CO2 assimilation rate (A) was measured in rubber saplings grown in a nursery or in growth chambers at 18 and 28°C. The temperature response of A was measured from 9 to 45°C and the data were fitted to an empirical model. Photosynthetic capacity (maximal carboxylation
rate, V
cmax, and maximal light driven electron flux, J
max) of plants acclimated to 18 and 28°C were estimated by fitting a biochemical photosynthesis model to the CO2 response curves (A–C
i curves) at six temperatures: 15, 22, 28, 32, 36 and 40°C. The optimal temperature for A (T
opt) was much lower in plants grown at 18°C compared to 28°C and nursery. Net CO2 assimilation rate at optimal temperature (A
opt), V
cmax and J
max at a reference temperature of 25°C (V
cmax25 and J
max25) as well as activation energy of V
cmax and J
max (E
aV and E
aJ) decreased in individuals acclimated to 18°C. The optimal temperature for V
cmax and J
max could not be clearly defined from our response curves, as they always were above 36°C and not far from 40°C. The ratio J
max25/V
cmax25 was larger in plants acclimated to 18°C. Less nitrogen was present and photosynthetic nitrogen use efficiency (V
cmax25/N
a) was smaller in leaves acclimated to 18°C. These results indicate that rubber saplings acclimated their photosynthetic characteristics
in response to growth temperature, and that higher temperatures resulted in an enhanced photosynthetic capacity in the leaves,
as well as larger activation energy for photosynthesis. 相似文献
79.
Sander A. Peters Erwin Datema Dóra Szinay Marjo J. van Staveren Elio G.W.M. Schijlen Jan C. van Haarst Thamara Hesselink Marleen H.C. Abma-Henkens Yuling Bai Hans de Jong Willem J. Stiekema René M. Klein Lankhorst Roeland C.H.J. van Ham 《The Plant journal : for cell and molecular biology》2009,58(5):857-869
80.
Blind Source Separation Techniques for the Decomposition of Multiply Labeled Fluorescence Images 总被引:1,自引:0,他引:1
Richard A. Neher Frank Kirchhoff Erwin Neher Fabian J. Theis André Zeug 《Biophysical journal》2009,96(9):3791-3800
Methods of blind source separation are used in many contexts to separate composite data sets according to their sources. Multiply labeled fluorescence microscopy images represent such sets, in which the sources are the individual labels. Their distributions are the quantities of interest and have to be extracted from the images. This is often challenging, since the recorded emission spectra of fluorescent dyes are environment- and instrument-specific. We have developed a nonnegative matrix factorization (NMF) algorithm to detect and separate spectrally distinct components of multiply labeled fluorescence images. It operates on spectrally resolved images and delivers both the emission spectra of the identified components and images of their abundance. We tested the proposed method using biological samples labeled with up to four spectrally overlapping fluorescent labels. In most cases, NMF accurately decomposed the images into contributions of individual dyes. However, the solutions are not unique when spectra overlap strongly or when images are diffuse in their structure. To arrive at satisfactory results in such cases, we extended NMF to incorporate preexisting qualitative knowledge about spectra and label distributions. We show how data acquired through excitations at two or three different wavelengths can be integrated and that multiple excitations greatly facilitate the decomposition. By allowing reliable decomposition in cases where the spectra of the individual labels are not known or are known only inaccurately, the proposed algorithms greatly extend the range of questions that can be addressed with quantitative microscopy. 相似文献