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81.
Christian Sturmbauer Corinna Fuchs Georg Harb Elisabeth Damm Nina Duftner Michaela Maderbacher Martin Koch Stephan Koblmüller 《Hydrobiologia》2008,615(1):57-68
Lake Tanganyika, the second-oldest and second-deepest lake in the world, harbors an impressive cichlid fish fauna counting about 250 endemic species that are characterized by a great level of ecological, morphological, and behavioral specialization. This study describes and compares cichlid fish communities at two rocky shores with differential human impact in the south of Lake Tanganyika. Species inventories and depth-dependent abundances were elaborated. About 41 and 46 sympatric cichlid species were recorded in the two study sites, respectively. Variabilichromis moorii was the most abundant species (29–60% of total number of fishes), followed by Aulonocranus dewindti (3–19%), Tropheus moorii (12%), Ophthalmotilapia ventralis (4–10%), Eretmodus cyanostictus (6–11%), and Cyathopharynx furcifer (0.01–9%). All other species had abundances below 5%. It further emerged that large cichlids such as Petrochromis species, Cyathopharynx furcifer, and Lobochilotes labiatus were very rare at one location, with frequencies of 0.55% or less. Territorial sizes of three particularly abundant species, Variabilichromis moorii, Aulonocranus dewindti, and Tropheus moorii, were assessed by behavioral observations. We distinguished between territorial core areas and total defended area, yielding average core areas between 0.4 (V. moorii) and 1.6 m2 (T. moorii), and total defended areas averaging for each species between 1.6 (V. moorii) and 5.0 m2 (A. dewindti) with no significant differences between the two study sites. The data on individual densities are also relevant for evolutionary studies, in that they allow more accurate calculations of effective population sizes. 相似文献
82.
Doris Ribitsch Sonja Heumann Eva Trotscha Enrique Herrero Acero Katrin Greimel Regina Leber Ruth Birner‐Gruenberger Sigrid Deller Inge Eiteljoerg Peter Remler Thomas Weber Petra Siegert Karl‐Heinz Maurer Ilaria Donelli Giuliano Freddi Helmut Schwab Georg M. Guebitz 《Biotechnology progress》2011,27(4):951-960
From a screening on agar plates with bis(benzoyloxyethyl) terephthalate (3PET), a Bacillus subtilis p‐nitrobenzylesterase (BsEstB) was isolated and demonstrated to hydrolyze polyethyleneterephthalate (PET). PET‐hydrolase active strains produced clearing zones and led to the release of the 3PET hydrolysis products terephthalic acid (TA), benzoic acid (BA), 2‐hydroxyethyl benzoate (HEB), and mono‐(2‐hydroxyethyl) terephthalate (MHET) in 3PET supplemented liquid cultures. The 3PET‐hydrolase was isolated from non‐denaturating polyacrylamide gels using fluorescein diacetate (FDA) and identified as BsEstB by LC‐MS/MS analysis. BsEstB was expressed in Escherichia coli with C‐terminally fused StrepTag II for purification. The tagged enzyme had a molecular mass of 55.2 kDa and a specific activity of 77 U/mg on p‐nitrophenyl acetate and 108 U/mg on p‐nitrophenyl butyrate. BsEstB was most active at 40°C and pH 7.0 and stable for several days at pH 7.0 and 37°C while the half‐life times decreased to 3 days at 40°C and only 6 h at 45°C. From 3PET, BsEstB released TA, MHET, and BA, but neither bis(2‐hydroxyethyl) terephthalate (BHET) nor hydroxyethylbenzoate (HEB). The kcat values decreased with increasing complexity of the substrate from 6 and 8 (s?1) for p‐nitrophenyl‐acetate (4NPA) and p‐nitrophenyl‐butyrate (4NPB), respectively, to 0.14 (s?1) for bis(2‐hydroxyethyl) terephthalate (BHET). The enzyme hydrolyzed PET films releasing TA and MHET with a concomitant decrease of the water‐contact angle (WCA) from 68.2° ± 1.7° to 62.6° ± 1.1° due to formation of novel hydroxyl and carboxyl groups. These data correlated with a fluorescence emission intensity increase seen for the enzyme treated sample after derivatization with 2‐(bromomethyl)naphthalene. © 2011 American Institute of Chemical Engineers Biotechnol. Prog., 2011 相似文献
83.
The dielectric dispersion in the MHz range of the zwitterionic dipolar phosphocholine head groups has been measured from 0–70°C for various mixtures of (DPPC) and cholesterol. The abrupt change in the derived relaxation frequency observed for pure DPPC at the gel-to-liquid crystalline phase transition at 42°C reduces to a more gradual increase of frequency with temperature as the cholesterol content is increased. In general the presence of cholesterol increases the DPPC head group mobility due to its spacing effect. Below 42°C no sudden changes in are found at 20 or 33 mol% cholesterol, where phase boundaries have been suggested from other methods. Above 42°C, however, a decrease in at cholesterol contents up to 20–30 mol% is found. This is thought to be partly due to an additional restricting effect of the cholesterol on the number of hydrocarbon chain conformations and consequently on the area occupied by the DPPC molecules. 相似文献
84.
Peter J. Gebicke-Haerter Andr s Seregi Angelika Schobert Georg Hertting 《Neurochemistry international》1988,13(4):475-480
The role of protein kinase C (PKC) and calcium in the stimulation of prostaglandin D2 (PGD2) synthesis was investigated in primary rat astroglial cultures using the phorbol esters phorbol 12-myristate, 13-acetate (PMA), phorbol 12,13-dibutyrate (PDB) and the calcium ionophore A23187. Both phorbol esters and the ionophore were able to stimulate PGD2 synthesis in a concentration dependent manner. The inactive stereoisomers of PMA and PDB had no significant effect. Combinations of subthreshold concentrations of phorbol esters (10 nM PMA or 10 nM PBD) potentiated PG formation induced by 100 nM A23187. An even more pronounced effect was observed when phorbol ester concentrations were increased to 100nM. The contribution of extra- and intracellular calcium in phorbol ester or A23187 stimulated PGD2 synthesis was evaluated by carrying out experiments with calcium-free media plus EGTA or with the intracellular calcium-chelating agent TMB-8. Ionophore stimulated PGD2 release was shut down to basal values upon removal of extracellular calcium, whereas phorbol ester stimulated PGD2 formation persisted at a reduced level. It was unabated also upon further addition of EGTA. In the presence of TMB-8, however, phorbol ester stimulated PGD2 synthesis was completely suppressed. These data strongly suggest that PKC has an additional effect on the activation of phospholipase A2 and subsequent prostanoid synthesis, which is independent from extracellular calcium and, thus, support the concept of more than one metabolic pathway in astrocytes that synergistically regulate phospholipase A2 activity. 相似文献
85.
Kumar Sanath Parvathi Ammini George Jeffy Krohne Georg Karunasagar Indrani Karunasagar Iddya 《World journal of microbiology & biotechnology》2009,25(3):527-531
Biofilms formed by the human pathogen Listeria monocytogenes in food-processing environments can be a potential source of contamination. In this study, we investigated the ability of
L. monocytogenes wild type and its laboratory-derived isogenic mutants in cwhA, prfA, agrA, flaA, degU, ami and sigB to adhere to and form biofilms on abiotic surfaces. The results suggest that inactivation of the two component regulatory
system degU completely abolished biofilm formation, while inactivation of the flagellar gene flaA, two component response regulator agrA and the autolysin-adhesin gene ami lead to severe impairment of initial attachment and the subsequent development of a mature biofilm by L. monocytogenes. Mutants in the global regulator of virulence prfA and the alternative sigma factor sigB were unaffected and formed biofilms similar to wild type L. monocytogenes. 相似文献
86.
Christian Weiss Joanna Weiss Jens Boy Issi Iskandar Robert Mikutta Georg Guggenberger 《Ecology and evolution》2016,6(14):5043-5056
Mangroves play an important role in carbon sequestration, but soil organic carbon (SOC) stocks differ between marine and estuarine mangroves, suggesting differing processes and drivers of SOC accumulation. Here, we compared undegraded and degraded marine and estuarine mangroves in a regional approach across the Indonesian archipelago for their SOC stocks and evaluated possible drivers imposed by nutrient limitations along the land‐to‐sea gradients. SOC stocks in natural marine mangroves (271–572 Mg ha?1 m?1) were much higher than under estuarine mangroves (100–315 Mg ha?1 m?1) with a further decrease caused by degradation to 80–132 Mg ha?1 m?1. Soils differed in C/N ratio (marine: 29–64; estuarine: 9–28), δ15N (marine: ?0.6 to 0.7‰; estuarine: 2.5 to 7.2‰), and plant‐available P (marine: 2.3–6.3 mg kg?1; estuarine: 0.16–1.8 mg kg?1). We found N and P supply of sea‐oriented mangroves primarily met by dominating symbiotic N2 fixation from air and P import from sea, while mangroves on the landward gradient increasingly covered their demand in N and P from allochthonous sources and SOM recycling. Pioneer plants favored by degradation further increased nutrient recycling from soil resulting in smaller SOC stocks in the topsoil. These processes explained the differences in SOC stocks along the land‐to‐sea gradient in each mangrove type as well as the SOC stock differences observed between estuarine and marine mangrove ecosystems. This first large‐scale evaluation of drivers of SOC stocks under mangroves thus suggests a continuum in mangrove functioning across scales and ecotypes and additionally provides viable proxies for carbon stock estimations in PES or REDD schemes. 相似文献
87.
Alfred Lindner Erich Hofmann Markus Naumann Georg Becker Heinz Reichmann 《Molecular and cellular biochemistry》1997,174(1-2):297-303
Nineteen patients (9 females, 10 males) with mitochondrial encephalomyopathies (ME) were studied. The diagnosis was established according to clinical and histopathological criteria. Leading clinical features were chronic progressive external ophthalmoplegia (CPEO) and muscle weakness in 95% of the patients. Pigmentary retinopathy was seen in 63%, and was always associated with CPEO. Hypacusis was present in 47% and cerebellar ataxia in 63% of patients. Clinical or electrophysiological signs of involvement of the central nervous system (CNS) were found in 21% of the patients. In muscle biopsy ragged red fibers were the predominant histopathological findings (100% of the patients), while COX-negative fibers were seen in 74%, deletions of the mitochondrial DNA in 42%, and defects of the respiratory chain in 32% of the patients. Increased blood lactate levels were found in 79% of the patients. Needle electromyography revealed myopathic features in 74%, features of denervation in 16%, and w as normal in the remainder. Imaging studies showed cerebral atrophy in 58%, cerebellar atrophy in 16%, and hyperintense lesions of the white matter, pyramidal tract or extrapyramidal system in 16% of the cases. It is concluded that the clinical manifestations of ME can be very variable. Diagnosis of ME should be always considered in young patients presenting with CPEO and muscle weakness. In most cases, diagnosis can be made by a few selected investigations, while detection of genetic abnormalities may lead to the diagnosis in the remaining cases. (Mol Cell Biochem 174: 297–303, 1997) 相似文献
88.
Barthélemy X Bouvier G Radunz A Docquier S Schmid GH Franck F 《Photosynthesis research》2000,64(1):63-76
The localization of protochorophyllide (Pchlide) and of NADPH-protochlorophyllide oxidoreductase (POR, EC 1.6.99.1) within
(etio)chloroplasts has been investigated at selected stages of greening of barley seedlings. Pchlide pigment and POR protein
contents were evaluated in different plastid membrane fractions by fluorescence spectroscopy and immunoblot analysis using
a monospecific polyclonal antibody raised against the purified enzyme. Fluorescence analysis showed the presence of Pchlide
in both the envelope and thylakoid membranes. During greening, the Pchlide content, expressed on a total protein basis, decreased
in thylakoid membranes, whereas it increased in the envelope membranes. POR proteins were detected mainly in thylakoid membranes
at early greening stages. In contrast, the weak amount of POR proteins was associated more specifically with envelope membranes
of mature chloroplasts. Whatever the greening stage, thylakoid-bound Pchlide and POR proteins were more abundant in the thylakoid
regions which remained unsolubilized after mild Triton treatment used as standard procedure to prepare PS II particles. This
suggests the preferential association of Pchlide and POR to the appressed regions of thylakoids.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
89.
Michaela Pape Georg von Samson-Himmelstjerna Thomas Schniede 《International journal for parasitology》1999,29(12):126
mRNA and genomic DNA were isolated from adult Cylicocyclus nassatus, and the mRNA was reverse transcribed. The cDNA was PCR amplified using degenerate primers designed according to the alignment of the β-tubulin amino acid sequences of other species. To complete the coding sequence, the 3′ end was amplified with the 3′-RACE, and for amplification of the 5′ end the SL1-primer was used. The cDNA of the β-tubulin gene of C. nassatus spans 1429 bp and encodes a protein of 448 amino acids. Specific primers were developed from the cDNA sequence to amplify the genomic DNA sequence and to analyse the genomic organisation of the β-tubulin gene. The complete sequence of the genomic DNA of the β-tubulin gene of C. nassatus has a size of 2652 bp and is organised into nine exons and eight introns. The identities with the exons of the gru-1 β-tubulin gene of Haemonchus contortus range between 79% and 97%. 相似文献
90.
Georg Neubauer Stefan Cecil Wolfram Giczi Benjamin Petric Patrick Preiner Jürg Fröhlich Martin Röösli 《Bioelectromagnetics》2010,31(7):535-545
The selection of an adequate exposure assessment approach is imperative for the quality of epidemiological studies. The use of personal exposimeters turned out to be a reasonable approach to determine exposure profiles, however, certain limitations regarding the absolute values delivered by the devices have to be considered. Apart from the limited dynamic range, it has to be taken into account that these devices give only an approximation of the exposure due to the influence of the body of the person carrying the exposimeter, the receiver characteristics of the exposimeter, as well as the dependence of the measured value on frequency band, channel, slot configuration, and communication traffic. In this study, the relationship between the field strength measured close to the human body at the location of the exposimeter and the exposure, that is, the field strength at the location of the human body without the human body present, is investigated by numerical means using the Visible Human model as an anatomical phantom. Two different scenarios were chosen: (1) For FM, GSM, and UMTS an urban outdoor scenario was examined that included a transmitting antenna mounted on the roof of one of four buildings at a street crossing, (2) For WLAN an indoor scenario was investigated. For GSM the average degree of underestimation by the exposimeter (relation of the average field levels at the location of the exposimeter to the field level averaged over the volume of the human body without the body present) was 0.76, and for UMTS 0.87; for FM no underestimation was found, the ratio was 1. In the case of WLAN the degree of underestimation was more pronounced, the ratio was 0.64. This study clearly suggests that a careful evaluation of correction factors for different scenarios is needed prior to the definition of the study protocol. It has to be noted that the reference scenario used in this study does not allow for final conclusions on general correction factors. Bioelectromagnetics 31:535–545, 2010. © 2010 Wiley‐Liss, Inc. 相似文献