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Observations of ctenophore species were made in the Gulf ofTrieste between 2003 and 2006. We examined native ctenophorespecies with special attention to representatives of the ordersLobata and Beroida, and we recorded among them two non-nativectenophores: Mnemiopsis leidyi A. Agassiz 1865 and Beroe ovatasensu Mayer, 1912. The validity of the Mediterranean speciesBeroe ovata is discussed. We determined that among the nativespecies, it is not Beroe ovata but rather Beroe cucumis sensuMayer, 1912 that occurs in the Mediterranean Sea. 相似文献
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The herbivory of the marine cladoceran Peniliaavirostris was studied in the Gulf of Trieste(Northern Adriatic) from June 1993 to December1994 using the gut fluorescence method. P. avirostrisoccurred from June to December, butreached its greatest abundance in the summer months.A significant correlation between the gut pigmentcontent and chlorophyll a concentration in thesurface layer was established. Observations with anepifluorescence microscope revealed that the guts werefilled with fluorescing nanoplankton and picoplankton(cyanobacteria). Quantitative estimates indicated thatP. avirostris grazed less than 5% of theavailable chlorophyll a in more than half of allmeasurements, but removed most of the availablechlorophyll a in the surface layer during someperiods in September. It can therefore be concludedthat P. avirostris, together with planktonicprotists, plays an important role within the microbialloop. 相似文献
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Oleoyl-CoA is not an immediate substrate for fatty acid elongation in developing seeds of Brassica napus 总被引:1,自引:1,他引:0
Alenka Hlousek-Radojcic Hiroyuki Imai Jan G. Jaworski 《The Plant journal : for cell and molecular biology》1995,8(6):803-809
The substrate specificity of fatty acid elongase was studied using an oil body fraction from developing seeds of Brassica napus. ATP was essential for high rates of elongase activity, but there was no apparent requirement for oleoyl-CoA, oleic acid (18:1) or CoA. Furthermore, 14C from 18:1-CoA was incorporated into eicosenoic (20:1) and erucic (22:1) acids at a much slower rate than 14C from malonyl-CoA. Incubation of [14C]18:1-CoA with the oil body fraction resulted in a rapid loss of [14C]18:1-CoA into several lipid fractions whether in the absence or presence of ATP, but the loss of 18:1-CoA had a comparatively small effect on the overall rate of elongation. Acyl-CoAs were derivatized to their respective acylbutylamide and analyzed by gas chromatography-mass spectrometry. This analysis of acyl-CoAs demonstrated that there was no detectable 20:1-CoA or 22:1-CoA at 0 min incubation, while newly synthesized 20:1-CoA and 22:1-CoA were present at 10 min. Analysis of the %14C of the substrates and products of the elongation reaction revealed that the endogenous pool of 18:1-CoA is quite small in elongase preparations. In addition, [14C]18:1-CoA added to the incubation, although incorporated into lipids, was not significantly diluted by turnover or new synthesis. In contrast, the %14C of the 20:1-CoA was two- to threefold less than that of the 18:1-CoA. Taken together, these results indicate that the [14C]18:1 from the [14C]18:1-CoA was diluted in an intermediate 18:1 pool and that the 18:1-CoA was not the major donor of the acyl group to the elongase reaction. 相似文献
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Alenka Jejcic Robert Daniels Laura Goobar-Larsson Daniel N. Hebert Anders Vahlne 《Journal of virology》2009,83(19):10075-10084
Human immunodeficiency virus type 1 (HIV-1) is dependent on its envelope glycoprotein (Env) to bind, fuse, and subsequently infect a cell. We show here that treatment of HIV-1-infected cells with glycyl-prolyl-glycine amide (GPG-NH2), dramatically reduced the infectivity of the released viral particles by decreasing their Env incorporation. The mechanism of GPG-NH2 was uncovered by examining Env expression and maturation in treated cells. GPG-NH2 treatment was found to affect Env by significantly decreasing its steady-state levels, its processing into gp120/gp41, and its mass by inducing glycan removal in a manner dependent on its native signal sequence and the proteasome. Therefore, GPG-NH2 negatively impacts Env maturation, facilitating its targeting for endoplasmic reticulum-associated protein degradation, where Env is deglycosylated en route to its degradation. These findings illustrate that nontoxic drugs such as GPG-NH2, which can selectively target glycoproteins to existing cellular degradation pathways, may be useful for pathogen therapy.The endoplasmic reticulum (ER) contains a number of molecular chaperones and folding factors that aid in the maturation of proteins that traverse the secretory pathway. This process is strictly monitored by the ER quality control system, which selects properly folded proteins for export to the Golgi (16) and targets misfolded proteins for destruction through the ER-associated protein degradation pathway (ERAD) (4, 28). Once an ER protein is selected as a substrate for ERAD, it is translocated from the ER lumen to the cytosol through an ER translocon. This retrotranslocation process is thought to be driven by either the cytosolic AAA-ATPase p97 (39) or the 19S proteasome cap (23). Upon entrance into the cytosol, the ERAD substrate is ubquitinated, and its glycans are removed by an N-glycanase to prepare it for proteasomal degradation (11, 28).Viral envelope glycoproteins utilize the host cell secretory pathway for their proper maturation and trafficking to the site of viral assembly. The human immunodeficiency virus type 1 (HIV-1) encodes the envelope glycoprotein (Env), which initiates HIV-1 infections by mediating attachment and fusion of the viral envelope with the host cell membrane (17). Therefore, infectious HIV-1 particle production relies on the ability of Env to pass the rigorous ER quality control system.Env is initially synthesized as a type I membrane precursor glycoprotein termed gp160, which is cotranslationally targeted to the ER by its 30-amino-acid N-terminal signal sequence (24). Within the ER, gp160 receives ∼30 N-linked glycans and is assisted in its maturation by the chaperones BiP, calnexin, and calreticulin as it undergoes extensive disulfide bond formations (15, 21, 31). Once gp160 has reached its native state with ten disulfide bonds and its signal sequence has been cleaved posttranslationally (21, 25), it assembles into trimers (26) and is exported to the Golgi. Within the Golgi, gp160 is cleaved by cellular endoproteases, yielding the transmembrane protein gp41 and the noncovalently associated surface protein gp120 (27). Thereafter, this complex is transported to the plasma membrane, where it is incorporated into the envelope of assembling HIV-1 particles.We have previously shown that a tripeptide amide corresponding to a conserved motif of the HIV-1 Env, glycyl-prolyl-glycine amide (GPG-NH2), suppressed the replication of all 47 HIV-1 laboratory strains and clinical isolates examined with a 50% inhibitory concentration of ∼10 μM, a concentration that is 200- to 2,000-fold less than what affected cell growth or had other toxic effects on peripheral blood mononuclear cells (35). However, this suppression was not, as we had anticipated, due to interactions of the peptide with the early events of the HIV-1 replication cycle, such as attachment or entry (36). In the present study, we demonstrate that GPG-NH2 reduced Env incorporation into HIV-1 particles during replication by targeting Env toward the ERAD pathway. The ability of GPG-NH2 to target Env for degradation was dependent on the presence of functional proteasomes and required the full-length Env signal sequence. These findings illustrate that small molecules may be utilized therapeutically to specifically target unwanted pathogenic proteins for degradation by the existing cellular machinery. 相似文献
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Jessica Rehdorf Alenka Lengar Uwe T. Bornscheuer Marko D. Mihovilovic 《Bioorganic & medicinal chemistry letters》2009,19(14):3739-3743
A set of various linear aliphatic β-hydroxyketones was investigated as substrates in the enzymatic kinetic and regioselective Baeyer–Villiger oxidation catalyzed by 12 Baeyer–Villiger monooxygenases from different bacterial origin. Excellent enantioselectivities (E >100) could be observed with 4-hydroxy-2-ketones. After acyl migration, the ester undergoes hydrolysis followed by the formation of optically active 1,2-diols. Furthermore, resolution of 5-hydroxy-3-ketones gave access to the ‘abnormal’ esters, which broadens applicability of these enzymes in organic chemistry. Additionally, it was noticed, that several substrates were converted by different enzymes in an enantiocomplementary way and with high optical purities. 相似文献
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Dessardo NS Dessardo S Sasso A Sarunić AV Dezulović MS 《Collegium antropologicum》2010,34(Z2):217-221
Idiopathic intracranial hypertension (IIH) is a clinical condition characterized by elevated intracranial pressure and absence of clinical, laboratory or radiographic evidence of central nervous system infection, vascular malformation, intracranial space occupying lesion or hydrocephalus. In the last years the raising understanding of pediatric IIH, especially concerning its demographics and epidemiology, has brought up to a redefinition of diagnostic criteria and reevaluation of pathogenesis and treatment. The authors reviewed the records of nineteen consecutive children with newly diagnosed IIH in order to compare demographic characteristics, clinical pictures and ophthalmologic aspects as optic disc evaluation and visual field evaluation, as well as treatment modalities and follow up. Beside obesity and female gender, potential alternative risk factors remains to be investigated, which need a good collaboration between neuro-ophthalmologists and pediatric neurologists. 相似文献
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Lake Cerknica is an intermittent wetland with seasonal water level fluctuations. This paper discusses the possible changes of ecosystem services due to altered ecosystem functions caused by regional climate change. For this purpose, the lake's water regime was analysed and biomass production of common reed (Phragmites australis), the prevailing species, was related to ambient temperatures and water level. The effect of the latter was also examined for reed transpiration rate and plant diversity. The results revealed a gradual loss of seasonality of floods and droughts. High water level in winter months and temperatures at the beginning as well as the end of vegetation period were found to have a significant influence on reed biomass. The plant diversity research in six subsequent years in three different aquatic habitats revealed trends of a decrease due to increased water depth during the vegetation period. The complexity of the system and consequently ecosystem services might also be affected due to changes of other processes, which revealed to be related to water level; namely transpiration rate, plant mycorrhizal colonisation and soil mineralisation. 相似文献
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Marina Štukelj Zdravko Valenčak Mladen Krsnik Alenka Nemec Svete 《Acta veterinaria Scandinavica》2010,52(1):19