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101.
Takahashi J Fujiwara S Kikyo M Hirokawa Y Tsuzuki M 《Marine biotechnology (New York, N.Y.)》2002,4(1):94-101
We investigated the extent of calcification on the cell surface of the coccolithophorid Pleurochrysis haptonemofera using flow cytometry. Side scattering (SSC) by coccolith-bearing cells was higher than that by naked cells, suggesting the
difference was due to scattering of the laser beam by the coccoliths. SSC of coccolith-bearing cells under acidic conditions
corresponded well to the extracellular Ca content, although SSC could not be used to detect a delicate change in the coccolith
thickness. The increase in SSC during the reproduction of coccoliths after decalcification was consistent with the increase
in the number of coccoliths on the cell surface. The fluorescence after fluorescein-isothiocyanate-labeled lectin staining
suggests that α-d-mannose, α-d-glucose, d-galactose, d-N-acetylgalactosamine, or derivatives of them are included in the coccoliths. Measurement of SSC and fluorescence after fluorescein-isothiocyanate-labeled
lectin staining enabled rapid and quantitative determination of the status on the cell surface and isolation of desirable
cells for physiological studies by cell sorting.
Received May 22, 2001; accepted July 30, 2001. 相似文献
102.
Protoplasts prepared from thalli ofBoergesenia forbesii were subjected to the measurement of tension at the surface by means of the suction method. The tension at the surface just
after completion of spheration was 0.2–0.4 dyne/cm irrespective of the temperature. Since this value is of the same order
of magnitude as those measured in other species of cells without a cell coat, it is suggested that the protoplast just after
spheration is covered with the plasma membrane. The measured tension at the surface was constant and not affected by the degree
of deformation of the protoplast, suggesting that the surface of the protoplast is not elastic.
After some time the tension began to increase abruptly. Both the latent time elapsed prior to the increase in the tension
and the rate of tension increase were strongly dependent on the temperature. As long as protoplasts were treated with cellulase,
increase in the tension was completely inhibited, but it occurred soon after washing out of the cellulase. Protoplasts were
stained with Calcoflour White at around the time when the tension began to increase. These results suggest that the cell wall
formation begins at the time of abrupt increase in the tension at the surface. 相似文献
103.
104.
Yasutaka Chiba 《Biometrical journal. Biometrische Zeitschrift》2009,51(4):670-676
Unmeasured confounders are a common problem in drawing causal inferences in observational studies. VanderWeele (Biometrics 2008, 64, 702–706) presented a theorem that allows researchers to determine the sign of the unmeasured confounding bias when monotonic relationships hold between the unmeasured confounder and the treatment, and between the unmeasured confounder and the outcome. He showed that his theorem can be applied to causal effects with the total group as the standard population, but he did not mention the causal effects with treated and untreated groups as the standard population. Here, we extend his results to these causal effects, and apply our theorems to an observational study. When researchers have a sense of what the unmeasured confounder may be, conclusions can be drawn about the sign of the bias. 相似文献
105.
Clinical isolates of Nocardia brasiliensis from Japan were classified into two groups based on their susceptibility to the carbapenem antibiotic, imipenem (IPM). Of
33 strains tested, 10 belonged to an IPM susceptible group, with MIC of from 0.25 to 2 εg/ml and a MIC80 value of 1.5 εg/ml for this antibiotic. The remaining 23 strains belonged to an IPMresistant group with MIC and MIC80 values of 8–16 εg/ml and >16 εg/ml, respectively. The type strain of N. brasiliensis belonged to this resistant group. Analysis of 16S rDNA genes sequences showed that the IPM susceptible group had characteristic
single nucleotide substitutions at positions 103 (T), 381 (A), and 456 (A), in contrast to the IPM resistant group. This grouping,
however, was not associated with their clinical manifestation. 相似文献
106.
Kanamaru S Ishiwata Y Suzuki T Rossmann MG Arisaka F 《Journal of molecular biology》2005,346(4):1013-1020
Bacteriophage T4 has an efficient mechanism for injecting the host Escherichiacoli cell with genomic DNA. Its gene product 5 (gp5) has a needle-like structure attached to the end of a tube through which the DNA passes on its way out of the head and into the host. The gp5 needle punctures the outer cell membrane and then digests the peptidoglycan cell wall in the periplasmic space. gp5 is normally post-translationally cleaved between residues 351 and 352. The function of this process in controlling the lysozyme activity of gp5 has now been investigated. When gp5 is over-expressed in E.coli, two mutants (S351H and S351A) showed a reduction of cleavage products and five other mutants (S351L, S351K, S351Y, S351Q, and S351T) showed no cleavage. Furthermore, in a complementation assay at 20 degrees C, the mutants that had no cleavage of gp5 produced a reduced number of plaques compared to wild-type T4. The crystal structure of the non-cleavage phenotype mutant of gp5, S351L, complexed with gene product 27, showed that the 18 residues in the vicinity of the potential cleavage site (disordered in the wild-type structure) had visible electron density. The polypeptide around the potential cleavage site is exposed, thus allowing access for an E.coli protease. The lysozyme activity is inhibited in the wild-type structure by a loop from the adjacent gp5 monomer that binds into the substrate-binding site. The same inhibition is apparent in the mutant structure, showing that the lysozyme is inhibited before gp5 is cleaved and, presumably, the lysozyme is activated only after gp5 has penetrated the outer membrane. 相似文献
107.
108.
In the coccolithophorid microalgae acidic polysaccharides are considered to be involved in the formation of the calcified
scale, coccolith. Characteristics of the acidic polysaccharides extracted from the cell surface of the coccolithophorid Pleurochrysis haptonemofera were analyzed. The acidic polysaccharides on the cell surface can be detected by measuring fluorescence of cells after fluorescein-isothiocyanate-labeled
lectin staining by flow cytometry. Flow cytometric analyses revealed that the acidic polysaccharides remained on the cell
surface even after CaCO3 in the coccolith was dissolved by lowering pH, but they were extracted by subsequent EDTA or EGTA treatment, suggesting that
they are bound not into the CaCO3 crystals of the coccolith, but onto the surface via Ca2+. Analyses of the acidic polysaccharides by anion exchange chromatography, colloidal precipitation with divalent cations,
and polyacrylamide gel electrophoresis (PAGE) revealed that P. haptonemofera has 3 types of acidic polysaccharides (Ph-PS-l, -2, and -3). The PAGE patterns suggested that Ph-PS-2 has a repeated structure
with a broad range of molecular weight, as in Pleurochrysis carterae, while Ph-PS-1 and -3 contain several minor components in addition to a major component, respectively. The minor components
in Ph-PS-1 and -3 that have not been found in P. carterae might be characteristic of P. haptonemofera. Analyses of both the cell surface treated by various concentrations of EDTA and EGTA and the extracts suggested that Ph-PS-2,
which is distinguishable by a higher affinity to concanavalin A, is bound onto the coccolith surface more intensely than the
other two types of acidic polysaccharides. 相似文献
109.
Yoshitada Tanabe Fumihito Tajima Yuki Nakamura Eriko Shibasaki Mai Wakejima Takashi Shimomura Rie Murai Yoshiyuki Murawaki Koichi Hashiguchi Takamasa Kanbe Toshiya Saeki Miho Ichiba Yoko Yoshida Masahiro Mitsunari Soichi Yoshida Jun-ichiro Miake Yasutaka Yamamoto Naoki Nagata Tasuku Harada Akihiro Kurimasa Ichiro Hisatome Naoki Terakawa Yoshikazu Murawaki Goshi Shiota 《Biochemical and biophysical research communications》2011,(4):769
110.
Kamata M Yamashita T Imaeda T Tanaka T Terauchi J Miyamoto M Ora T Tawada M Endo S Takekawa S Asami A Suzuki N Nagisa Y Nakano Y Watanabe K Ogino H Kato K Kato K Ishihara Y 《Bioorganic & medicinal chemistry》2011,19(18):5539-5552
Human melanin-concentrating hormone receptor 1 (hMCHR1) antagonists are promising targets for obesity treatment. We identified the tetrahydronaphthalene derivative 1a with modest binding affinity for hMCHR1 by screening an in-house G protein-coupled receptor (GPCR) ligand library. We synthesized a series of 6-aminomethyl-5,6,7,8-tetrahydronaphthalenes and evaluated their activity as hMCHR1 antagonists. Modification of the biphenylcarbonylamino group revealed that the biphenyl moiety played a crucial role in the interaction of the antagonist with the receptor. The stereoselective effect of the chiral center on binding affinity generated the novel 6-aminomethyl-7,8-dihydronaphthalene scaffold without a chiral center. Optimization of the amino group led to the identification of a potent antagonist 2s (4'-fluoro-N-[6-(1-pyrrolidinylmethyl)-7,8-dihydro-2-naphthalenyl][1,1'-biphenyl]-4-carboxamide), which significantly inhibited the nocturnal food intake in rats after oral administration. Pharmacokinetic analysis confirmed that 2s had good oral bioavailability and brain penetrance. This antagonist appears to be a viable lead compound that can be used to develop a promising therapy for obesity. 相似文献