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61.
Conserved sequences in enzymes of the UDP-GlcNAc/MurNAc family are essential in hamster UDP-GlcNAc:dolichol-P GlcNAc-1-P transferase 总被引:1,自引:0,他引:1
The UDP-GlcNAc/MurNAc family of eukaryotic and prokaryotic enzymes use
UDP-GlcNAc or UDP-MurNAc-pentapeptide as donors, dolichol-P or polyprenol-P
as acceptors, and generate sugar-P-P-polyisoprenols. A series of six
conserved sequences, designated A through F and ranging from 5 to 13 amino
acid residues, has been identified in this family. To determine whether
these conserved sequences are required for enzyme function, various
mutations were examined in hamster UDP- GlcNAc:dolichol-P GlcNAc-1-P
transferase (GPT). Scramble mutations of sequences B-F, generated by
scrambling the residues within each sequence, demonstrated that each is
important in GPT. While E and F scrambles appeared to prevent stable
expression of GPT, scrambling of B- D resulted in GPT mutants that could be
stably expressed and bound tunicamycin, but lacked enzymatic activity.
Further, the C and D scramble mutants had an unexpected sorting defect.
Replacement of sequences B-F with prokaryotic counterparts from either the
B.subtilis mraY or E.coli rfe genes also affected GPT by preventing
expression of the mutant protein (B, F) or inhibiting its enzymatic
activity (C-E). For the C-E replacements, no acquisition of acceptor
activity for polyprenol-P, the fully unsaturated natural bacterial
acceptor, was detected. These studies show that the conserved sequences of
the UDP- GlcNAc/MurNAc family are important, and that the eukaryotic and
prokaryotic counterparts are not freely interchangeable. Since several
mutants were efficiently expressed and bound tunicamycin, yet lacked
enzymatic activity, the data are consistent with these sequences having a
direct role in product formation.
相似文献
62.
63.
Mara Proca-Ciobanu Gh. Lupascu Al. Petrovici M.D. Ionescu 《International journal for parasitology》1975,5(1):49-56
Along general lines, the fine structure of the Acanthamoeba castellani Sn cell corresponds to the aspects described by other authors in the free forms. Of particular interest was the presence in the amoeba cytoplasm of some free formations, with a cell envelop and internal bacteria-like structure. The presence of these bacterial bodies free in the amoeba cytoplasm and without a surrounding host cell membrane as well as the aspects suggestive of cell division, led the authors to consider them as integrated in the Acanthamoeba Sn economy, correlating them with bacterial endosymbionts. Similar endosymbionts have not yet been described in Acanthamoeba and might be implicated in the pathogenic potential of the Sn strain. 相似文献
64.
V V Morariu M S Ionescu M Frangopol R Grosescu M Lupu P T Frangopol 《Biochimica et biophysica acta》1987,900(1):73-78
The effect of procaine hydrochloride and its metabolites on the diffusional water exchange through erythrocyte membranes was investigated at 37 degrees C and at concentrations ranging between 5 X 10(-5) M and 5 X 10(-1) M by using the NMR manganese doping method. Procaine hydrochloride and 2-diethylaminoethanol have a moderate stimulating effect on the water exchange, of up to 20% at concentrations ranging between 10(-3) and 10(-2) M, while an increasing inhibitory effect was found at higher concentrations. The p-aminobenzoic acid has no effect on the water exchange up to 10(-2) M and, at higher concentrations, and apparent decreasing inhibition was noticed which is thought to be an artefact due to the uptake of Mn2+ by the cells. The temperature dependence studies suggest that procaine HCl enhances the uptake of Mn2+ by the cells. An opposite effect was found for rigid erythrocytes. The p-aminobenzoic acid and 2-diethylaminoethanol appeared to be more effective than procaine hydrochloride in increasing the uptake of Mn2+. 相似文献
65.
JB Parentes-Vieira PV Lopes-Costa CG Pires AR dos Santos JD Pereira-Filho BB da Silva 《International Seminars in Surgical Oncology : ISSO》2007,4(1):22
Background
The objective of this study was to evaluate angiogenesis according to CD34 antigen expression in estrogen receptor (ER)-positive and negative breast carcinomas.Methods
This study comprised 64 cases of infiltrating ductal carcinoma in postmenopausal women divided into two groups: Group A: ER-positive, n = 35; and Group B: ER-negative, n = 29. The anti-CD34 monoclonal antibody was used as a marker for endothelial cells. Microvessel count was carried out in 10 fields per slide using a 40× objective lens (magnification 400×). Statistical analysis of the data was performed using Student's t-test (p < 0.05).Results
The mean number of vessels stained with the anti-CD34 antibody in the estrogen receptor-positive and negative tumors was 23.51 ± 1.15 and 40.24 ± 0.42, respectively. The number of microvessels was significantly greater in the estrogen receptor-negative tumors (p < 0.001).Conclusion
ER-negative tumors have significantly greater CD34 antigen expression compared to ER-positive tumors.66.
Dieni S Matsumoto T Dekkers M Rauskolb S Ionescu MS Deogracias R Gundelfinger ED Kojima M Nestel S Frotscher M Barde YA 《The Journal of cell biology》2012,196(6):775-788
Although brain-derived neurotrophic factor (BDNF) regulates numerous and complex biological processes including memory retention, its extremely low levels in the mature central nervous system have greatly complicated attempts to reliably localize it. Using rigorous specificity controls, we found that antibodies reacting either with BDNF or its pro-peptide both stained large dense core vesicles in excitatory presynaptic terminals of the adult mouse hippocampus. Both moieties were ~10-fold more abundant than pro-BDNF. The lack of postsynaptic localization was confirmed in Bassoon mutants, a seizure-prone mouse line exhibiting markedly elevated levels of BDNF. These findings challenge previous conclusions based on work with cultured neurons, which suggested activity-dependent dendritic synthesis and release of BDNF. They instead provide an ultrastructural basis for an anterograde mode of action of BDNF, contrasting with the long-established retrograde model derived from experiments with nerve growth factor in the peripheral nervous system. 相似文献
67.
Danny Ionescu Sigrid Penno Maya Haimovich Branko Rihtman Aram Goodwin Daniel Schwartz Lena Hazanov Mark Chernihovsky Anton F. Post & Aharon Oren 《FEMS microbiology ecology》2009,69(3):425-438
Using a polyphasic approach, we examined the presence of Archaea in the Gulf of Aqaba, a warm marine ecosystem, isolated from major ocean currents and subject to pronounced seasonal changes in hydrography. Catalyzed reported deposition FISH analyses showed that Archaea make up to >20% of the prokaryotic community in the Gulf. A spatial separation between the two major phyla of Archaea was observed during summer stratification. Euryarchaeota were found exclusively in the upper 200 m, whereas Crenarchaeota were present in greater numbers in layers below the summer thermocline. 16S rRNA gene-based denaturing gradient gel electrophoresis confirmed this depth partitioning and revealed further diversity of Crenarchaeota and Euryarchaeota populations along depth profiles. Phylogenetic analysis showed pelagic Crenarchaeota and Euryarchaeota to differ from coral-associated Archaea from the Gulf, forming distinct clusters within the Marine Archaea Groups I and II. Endsequencing of fosmid libraries of environmental DNA provided a tentative identification of some members of the archaeal community and their role in the microbial community of the Gulf. Incorporation studies of radiolabeled leucine and bicarbonate in the presence of different inhibitors suggest that the archaeal community participates in autotrophic CO2 uptake and contributes little to the heterotrophic activity. 相似文献
68.
Microbial communities and processes within a hypersaline gypsum crust in a saltern evaporation pond (Eilat,Israel) 总被引:1,自引:0,他引:1
Aharon Oren Ketil B. Sørensen Don E. Canfield Andreas P. Teske Danny Ionescu André Lipski Karlheinz Altendorf 《Hydrobiologia》2009,626(1):15-26
Gypsum crusts containing multicolored, stratified microbial communities develop in the evaporation ponds of a commercial saltern
in Eilat, Israel at salt concentrations between 190 and 240 g l−1. The upper 0.5–2 cm of the crust is densely populated by orange-brown unicellular cyanobacteria. Below, a layer of green-colored
filamentous cyanobacteria is found. Underneath, a bright purple layer of anoxygenic phototrophs is present, below which a
reduced black layer is found. We have investigated the biological properties of this crust using a wide variety of techniques,
and we here review the results of these interdisciplinary studies. The tests performed included microscopic examination of
the biota, phylogenetic analyses based on 16S rRNA gene clone libraries and denaturing gradient gel electrophoresis, fatty
acid analysis, light intensity and light quality measurements, microelectrode studies of oxygen profiles and oxygen evolution,
determination of sulfate reduction using radioisotope methods, and measurement of methane evolution. The stable vertical stratification
in the system enabled separate analyses of the different layers with a high spatial resolution. It was therefore possible
to combine the different approaches and obtain information on the activities of the different types of oxygenic and anoxygenic
phototrophs, dissimilatory sulfate reducers and methanogens in the different layers, as well as phylogenetic information on
the nature of the microorganisms responsible for these processes. The gypsum crust thus becomes a paradigm for the study of
a wide variety of microbial processes and their interrelationships in the presence of high salt concentrations.
Guest Editors: J. John & B. Timms
Salt Lake Research: Biodiversity and Conservation—Selected papers from the 9th Conference of the International Society for
Salt Lake Research 相似文献
69.
ADRIANA ARÁNGUIZ‐ACUÑA RODRIGO RAMOS‐JILIBERTO NANDINI SARMA S.S.S. SARMA RAMIRO O. BUSTAMANTE VERÓNICA TOLEDO 《Freshwater Biology》2010,55(10):2114-2122
1. A key aspect of the ecology and evolution of adaptive prey responses to predator risk is the timing by which the former develop a defensive trait in response to inducing signals released by the latter. This property, called reactivity, has been shown to affect population stability and persistence. 2. Theoretically, the minimal predator density required by prey to exhibit induced defences is expected to increase with the effectiveness of the defence and decrease with its cost. Likewise, the time required for the prey population to exhibit an induced defence is expected to increase together with cost. 3. The freshwater rotifers Brachionus calyciflorus and B. havanaensis and their predator Asplanchna brightwelli were used to test the hypothesis that prey species exhibiting defences that offer a larger fitness benefit and lower fitness cost are more reactive to predator signals, in terms of requiring shorter exposure time and lower signal concentration to trigger a morphological defence reaction. 4. Our results showed that both prey species exhibited costly and effective defences after induction by predator infochemicals. Faster reactions were observed at higher levels of predator cues. Nevertheless, the observed relationship between reactivity and benefit/cost of defences did not agree with our expectations. 5. To our knowledge, this is the first study in which the timing of induction of morphological defences is experimentally assessed over a gradient of risk signals. We propose new research directions to disentangle the mechanisms and project the consequences of prey decisions at the morphological level. 相似文献
70.
Transformation of NIH 3T3 cells by enhanced PAR expression 总被引:2,自引:0,他引:2
Platica M Ivan E Ionescu A Holland JF Mora G Tindall DJ Mandeli J Unger PD Platica O 《Biochemical and biophysical research communications》2004,314(3):891-896
Prostate androgen regulated (PAR) is a 1038bp novel gene located on chromosome 1 in epidermal differentiation complex. The gene is ubiquitously expressed in normal tissues and is overexpressed in most of their malignant counterparts. PAR cellular function is unknown. Here we report the effect of increased PAR expression induced by transfection of PAR cDNA on NIH3T3 cell phenotype. PAR-NIH3T3 transfectants expressing 3- to 4-fold higher PAR levels compared to controls grew faster in tissue cultures, formed colonies in soft agar, and exhibited a shortening of G1 and S phases of cell cycle and formed tumors in SCID mice. Transfection of NIH3T3 cells with increased ectopic PAR expression with a 22 mer oligonucleotide in antisense orientation with PAR mRNA abrogated their ability to form colonies in soft agar. The data presented here along with our previously reported results on DU145 cells transfected with antisense PAR cDNA suggest that PAR gene behaves like a proto-oncogene. 相似文献