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1.
Volker Sommer 《Animal behaviour》2011,82(5):1213-1214
2.
Sequence of the mglB gene from Escherichia coli K12: comparison of wild-type and mutant galactose chemoreceptors 总被引:1,自引:0,他引:1
Annette Scholle Jörg Vreemann Volker Blank Annette Nold Winfried Boos Michael D. Manson 《Molecular & general genetics : MGG》1987,208(1-2):247-253
Summary The mglB gene of Escherichia coli codes for a galactose-binding protein (GBP) that serves both as the galactose chemoreceptor and as the recognition component of the -methylgalactoside transport system. The mglB551 mutation eliminates the chemotactic function of GBP without altering its transport or substrate-binding properties. To investigate the interaction between GBP and Trg, the chemotactic signal transducer for galactose, we sequenced the mglB genes from wild-type and mglB551 mutant strains. The mutation causes the replacement of Gly74 of GBP by Asp. This residue is located in alpha-Helix III at the tip of the P domain in the GBP tertiary structure farthest removed from the substrate-binding cleft between the P and Q domains. We conclude that Helix III must be part of, or at least adjacent to, the recognition site for Trg. Our sequence also included part of the mglA gene, which is immediately distal to mglB. The amino acid sequence deduced for the beginning of the MglA protein showed homology with a family of polypeptides that contain an ATP-binding site and are components of binding-protein-dependent transport systems. 相似文献
3.
Cell walls of Zea mays (cv L.G.11) seedlings labeled with 14C were treated with α-amylase from Bacillus subtilis to remove starch and mixed linkage glucans. These walls released arabinose, xylose, galactose, and galacturonic acid in addition to glucose when they were allowed to autolyze. Methylation analysis was performed on samples of wall which had been incubated autolytically and the results indicated that degradation of the major polymer of the wall, the glucoarabinoxylan, had occurred. A number of glycanases could be dissociated from the wall by use of 3 m LiCL. The proteins which were released were found to contain a number of exoglycosidase activities in addition to being effective in degrading the polysaccharide substrates, araban, xylan, galactan, laminarin, mannan, and polygalacturonic acid. The effects of these enzymes on the wall during autolysis appear to result from endo-activity in addition to exo-activity. The structural changes that occurred in the cell walls during autolysis were found to be related to the changes previously found to occur in cell walls during auxin induced extension. 相似文献
4.
Volker Hartenstein Eberhard Rudloff Jose A. Campos -Ortega 《Development genes and evolution》1987,196(8):473-485
Summary The pattern of neuroblast divisions was studied in thoracic and abdominal neuromeres of wild-type Drosophila melanogaster embryos stained with a monoclonal antibody directed against a chromatin-associated antigen. Since fixed material was used, our conclusions are based upon the statistical evaluation of a large number of accurately staged embryos, covering the stages between the formation of the cephalic furrow up to shortened germ band. Our observations point to a rather stereotypic pattern of proliferation, consisting of several parasynchronous cycles of division. The data suggest that all SI neuroblasts divide at least eight times, all SII neuroblasts six or seven times and all SIII neuroblasts at least five times. This conclusion is based on the mapping of mitotic neuroblasts and is supported by the progressive reduction of the neuroblast volume and by the results of cell countings performed on embryos of increasing age. No conclusive evidence was obtained concerning the fate of the neuroblasts after their last mitosis, i.e. it cannot be decided whether the neuroblasts degenerate or become incorporated as inconspicuous cells in the larval ventral cord. The duration of the cycles of division of the neuroblasts was found to be 40–50 min each, while in the case of ganglion mother cells about 100 min are required to complete one cell cycle. 相似文献
5.
Based on cross-sectional and longitudinal data collected in 1967–1988 by various observers, male reproductive success was
studied in the Hanuman langurs of Jodhpur, India. The harem-structured social organization ensures a high degree of paternity
certainty. Births occur throughout the year, with significant peaks and minima in March and November, respectively (n =398).The interbirth interval averages 16.7 months (n = 114).The duration of harem residencies varies between 3 days and ≥ 74.0 months, with a mean of 26.5 (n = 64). Harem holder replacements
occur during all months of the year. No male achieves residency in more than one troop, suggesting that residency is associated
with a distinct peak in the resource holding potential of a given male. Reproductive success among males varies considerably.
Male mortality is high due to migration and intrasexual competition, leading to an adult sex ratio of 1:4.9. It is estimated
that one-quarter of all adult males will never gain harem residency. Conceptions achieved outside harem residencies are so
rare (4.7%) that a viable low-risk strategy, opting for longevity instead of harem residency, is unlikely. Tenure length has
a stronger influence on male reproductive success than harem size because interbirth intervals are significantly shorter in
small harems than in larger ones. It is assumed that females in one-male breeding structures compete for sperm and that such
competition is more intense in larger harems. 相似文献
6.
The activity of beta-adrenergic receptors at the plasma membrane level was investigated in viable, electropermeabilized C6 glioma cells. Electric field pulses were applied directly to the plated cells without any previous proteinase treatment. The affinity for isoproterenol and the density of the beta-adrenergic receptors, as judged from the number of [3H]CGP-12177 binding sites, were not affected by the electropermeabilization whereas the isoproterenol-stimulated cAMP accumulation was transiently impaired. This decrease in activity is due to an electropermeabilization-induced GTP leak. Normal activity could be obtained either by treating the cells by the electric field in a GTP-containing buffer, or by spontaneous recovery of the cells after the resealing of the plasma membrane, with a delay depending on the temperature. The activity of the receptors was not affected by the structural organization of the membrane associated to its electropermeabilization. 相似文献
7.
3H]U-69593 labels a subtype of kappa opiate receptor with characteristics different from that labeled by [3H]ethylketocyclazocine 总被引:1,自引:0,他引:1
[3H]U-69593 is an opiate agonist that has been reported to bind in vitro with high affinity and selectivity to the kappa receptor subtype. The studies reported here were designed to determine the optimal conditions for labeling kappa receptors with [3H]U-69593 and to further characterize the binding site. The effects of temperature and NaCl on [3H]U-69593 binding were of particular interest because previous studies reported that [3H]ethylketocyclazocine ([3H]EKC) and [3H]bremazocine binding to kappa receptors was optimal at 4 degrees C in the presence of NaCl. Those conditions were not found to be optimal for [3H]U-69593 binding. Although the pharmacological specificity and Bmax of [3H]U-69593 binding was similar at room temperature and at 4 degrees C, the binding affinity was approximately three times lower at 4 degrees C than at room temperature. In addition, NaCl had an effect on [3H]U-69593 binding that was opposite that on [3H]EKC binding at 4 degrees C (100 nM DAGO and 100 nM DADLE were included in all [3H]EKC assays to prevent binding to mu and delta receptors), i.e. NaCl decreased, rather than increased, [3H]U-69593 binding at 4 degrees C. These differences between [3H]U-69593 and [3H]EKC binding at 4 degrees C were accentuated by a vast difference in the density of the binding sites [Bmax approximately equal to 12 fmol/mg protein for [3H]U-69593 vs approximately equal to 375 fmol/mg protein for [3H]EKC at 4 degrees C in the presence of NaCl) and suggested that [3H]U-69593 might bind selectively to a kappa receptor subtype. This concept was supported by competition experiments. In particular, the site labeled by [3H]EKC at 4 degrees C was found to be relatively insensitive (compared to [3H]U-69593 and [3H]EKC binding at room temperature) to the kappa agonist U-50488H, a close analog to U-69593. Based on these findings, we propose that [3H]U-69593 (and U-50488H) labels a kappa receptor subtype which differs from that labeled by [3H]EKC at 4 degrees C. 相似文献
8.
Volker Nicolai 《Oecologia》1988,75(4):575-579
Summary Factors influencing decomposition in European forests growing on different soils were studied in stands dominated by the European
beechFagus sylvatica L. Phenolic contents of freshly fallen leaves ofF. sylvatica growing on nutrient-poor soils (acid sandy soil) were higher than those of similar leaves on nutrient-rich soils (calcareous
mull soil). Analysis of fallen leaves of different ages showed rapid decay of phenolics during the first winter on the ground.
After 1 year the phenolic content of leaves ofF. sylvatica growing on nutrient-poor soils was still twice as high as in similar leaves on nutrient-rich soils. Field and laboratory
experiments showed that a major decomposer (Oniscus asellus, Isopoda) preferred leaves from trees on nutrient-rich soils. Mineral contents of leaves ofF. sylvatica growing on different soils differed: on rich soils leaves had higher contents of Ca, Mg, Na, and K. These elements are important
nutrients for decomposers. The distribution of major decomposers reflects the mineral content of their diet, which in turn
reflects soil type. Different rates of leaf turnover and nutrient turnover in different forest ecosystems (even when the same
tree species is dominant) are due to the decomposing system, which is influenced by the phenolic and mineral contents of the
leaves. 相似文献
9.
A serum free medium was developed, that could be used for the large scale propagation of various cell lines in bioreactors. The medium is based on a 1:1 mixture of Iscove's Modified Dulbecco's Medium and Ham's Medium F12, supplemented with transferrin, insulin and a BSA/oleic acid complex. Several myelomas, hybridomas derived from different myelomas and spleen cells, and other lymphoid and non-lymphoid cell lines were cultivated at growth rates comparable to those observed using serum-supplemented media. There was furthermore no reduction in the formation of products such as monoclonal antibodies or recombinant human interleukin-2.Abbreviations Ag8
Mouse myeloma cell line P3-X63-Ag8.653
- BME
Basal Medium Eagle
- BSA
Bovine Serum Albumin
- DMEM
Dulbecco's Modified Eagle's Medium
- EDTA
Ethylenediaminete-traacetic Acid
- e-PC
Phosphatidyl choline from egg yolk
- FCS
Fetal Calf Serum
- FGF
Fibroblast Growth Factor
- GHL
Glycyl-histidyl-lysine
- HDL
High Density Lipoprotein
- HPL
Human Plasma Lipid
- IF
1:1 mixture of IMDM and Ham's F12
- IMDM
Iscove's Modified Dulbecco's medium
- LDL
Low Density Lipoprotein
- NS1
Mouse myeloma cell line NSI-1-Ag4-1
- PBS
Phosphate Buffered Saline
- s-PC
Phosphatidylcholine from soy beans
- s-PE
Phosphatidylethanolamine from soy beans
- s-lecithin
lecithin from soy beans 相似文献
10.