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Odor identification: perceptual and semantic dimensions 总被引:8,自引:8,他引:0
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Subcellular localization of DNA-binding protein BA by immunofluorescence and immunoelectron microscopy 总被引:3,自引:2,他引:1
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Nonhistone protein BA has been shown to decrease in amount in the chromatin of growth- stimulated normal rat liver (Yeoman et al. 1975. Cancer Res. 35:1249-1255) and in mitogen-stimulated normal human lymphocytes (Yeoman et al. 1976. Exp. Cell Res. 100:47- 55.). Subsequently, protein BA was purified and was shown to prefer to bind to double- stranded A-T-rich DNAs (Catino et al. 1978. Biochemistry. 17:983-987.). Immunization of rabbits with highly purified protein BA has resulted in the production of a specific antibody. A specific immunoreactivity for chromosomal protein BA has been demonstrated by immunoelectrophoresis and double antibody immunoprecipitation analysis with rabbit anti-BA immunoglobulin and IgG fractions. Light microscope examination of normal rat liver crysections by the indirect immunofluorescence procedure has demonstrated a cytoplasmic as well as a nuclear localization for protein BA with a pronounced perinucleolar fluorescence. Immunoelectron microscopy employing the peroxidase antiperoxidase method of antigen localization has confirmed the immunofluorescence data and has show a heterochromatin localization for protein BA. The relationship of the localization of protein BA to gene control in quiescent cells or to configurations of heterochromatin as well as the marked reduction in the amounts of protein BA which occur in stimulated growth states remains to be defined. 相似文献
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Maize endosperm ADP-glucose pyrophosphorylase SHRUNKEN2 and BRITTLE2 subunit interactions 总被引:4,自引:0,他引:4
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ADP-glucose pyrophosphorylase (AGP) represents a key regulatory step in polysaccharide synthesis in organisms ranging from bacteria to plants. Higher plant AGPs are complex in nature and are heterotetramers consisting of two similar but distinct subunits. How the subunits are assembled into enzymatically active polymers is not yet understood. Here, we address this issue by using naturally occurring null mutants of the Shrunken2 (Sh2) and Brittle2 (Bt2) loci of maize as well as the yeast two-hybrid expression system. In the absence of the maize endosperm large AGP subunit (SH2), the BT2 subunit remains as a monomer in the developing endosperm. In contrast, the SH2 protein, in the absence of BT2, is found in a complex of 100 kD. A direct interaction between SH2 and BT2 was proven when they were both expressed in yeast. Several motifs are essential for SH2:BT2 interaction because truncations removing the N or C terminus of either subunit eliminate SH2:BT2 interactions. Analysis of subunit interaction mutants (sim) also identified motifs essential for protein interactions. 相似文献
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Xavier Didelot David W Eyre Madeleine Cule Camilla LC Ip M Azim Ansari David Griffiths Alison Vaughan Lily O'Connor Tanya Golubchik Elizabeth M Batty Paolo Piazza Daniel J Wilson Rory Bowden Peter J Donnelly Kate E Dingle Mark Wilcox A Sarah Walker Derrick W Crook Tim E A Peto Rosalind M Harding 《Genome biology》2012,13(12):R118
Background
The control of Clostridium difficile infection is a major international healthcare priority, hindered by a limited understanding of transmission epidemiology for these bacteria. However, transmission studies of bacterial pathogens are rapidly being transformed by the advent of next generation sequencing.Results
Here we sequence whole C. difficile genomes from 486 cases arising over four years in Oxfordshire. We show that we can estimate the times back to common ancestors of bacterial lineages with sufficient resolution to distinguish whether direct transmission is plausible or not. Time depths were inferred using a within-host evolutionary rate that we estimated at 1.4 mutations per genome per year based on serially isolated genomes. The subset of plausible transmissions was found to be highly associated with pairs of patients sharing time and space in hospital. Conversely, the large majority of pairs of genomes matched by conventional typing and isolated from patients within a month of each other were too distantly related to be direct transmissions.Conclusions
Our results confirm that nosocomial transmission between symptomatic C. difficile cases contributes far less to current rates of infection than has been widely assumed, which clarifies the importance of future research into other transmission routes, such as from asymptomatic carriers. With the costs of DNA sequencing rapidly falling and its use becoming more and more widespread, genomics will revolutionize our understanding of the transmission of bacterial pathogens. 相似文献17.
The response of human B cells to pokeweed mitogen (PWM) stimulation is potentiated when autologous erythrocytes (E) are added to peripheral blood mononuclear cell (PBMC) cultures. This potentiation has been previously shown to be dependent on interactions between the CD2 molecule on T cells and the lymphocyte function-associated antigen 3 (LFA-3) expressed by autologous erythrocytes. Since in other experimental systems the activation of T cells by CD2/LFA-3 interactions has resulted in increased secretion of interleukin 2 (IL2), we were interested in studying the role of IL2 in PBMC cultures stimulated with PWM and autologous E. The addition of autologous E significantly depressed IL2 levels in PWM-stimulated PBMC cultures. This effect was not secondary to increased expression of IL2 receptors by activated cells, since the addition of anti-TAC antibodies did not result in a significant increase in measurable levels of IL2. The addition of anti-IL2 to PBMC failed to abrogate the potentiating effect of E and it actually further enhanced the production of IgM and IgG from cultures stimulated with PWM + E. These results suggest that the potentiation of B cell function induced by autologous E is not mediated by IL2, either directly or indirectly. It is possible that the effect of autologous E either is mediated by other interleukins or is dependent on cell-to-cell contact with directed release of IL2 and/or other lymphokines without detectable secretion to the extracellular compartment. 相似文献
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Contrasting levels of DNA polymorphism at the autosomal and X-linked visual color pigment loci in humans and squirrel monkeys 总被引:1,自引:0,他引:1
The X-linked color pigment (opsin) locus is known to be highly polymorphic
in the squirrel monkey and other New World monkeys. To see whether this is
also the case for the autosomal (blue) opsin locus, we obtained 32 squirrel
monkey and 30 human blue opsin gene sequences. No amino acid polymorphism
was found in either the squirrel monkey sample or the human sample,
contrary to the situation at the X-linked opsin locus. This sharp contrast
in the level of polymorphism might be due to differences in gene expression
between the autosomal and the X-linked loci. At the X-linked locus,
heterozygote advantage can occur because, owing to X-inactivation, the two
alleles in a heterozygote are expressed in different cone cells, producing
two types of cone cell, whereas at the autosomal locus, heterozygote
advantage cannot occur because the two alleles in a heterozygote are
expressed in the same cone cells, producing only one type of cone cell
(i.e., phenotypically a homozygote). From the sequence data, the levels of
nucleotide diversity (pi, i.e., the number of nucleotide differences per
site) are estimated: for the human sample, pi = 0.00% per nondegenerate
site, 0.00% per twofold degenerate site, and 0.04% per fourfold degenerate
site in the coding regions and 0.01% per site in intron 4; for the squirrel
monkey sample, pi = 0.00% per nondegenerate site, 0.00% per twofold
degenerate site, and 0.15% per fourfold degenerate site in the coding
regions and 0.17% per site in intron 4. The blue opsin genes from the
common and pygmy chimpanzees, the gorilla, the capuchin, and the howler
monkey were also sequenced. Features critical to the function of the opsin
are well conserved in all known mammalian sequences. However, the
interhelical loops are, on average, actually more conservative than the
transmembrane helical regions. In addition, these sequence data and those
from some other genes indicate that the common and pygmy chimpanzees are
not closely related, their divergence data being from one third to one half
the date of the human-chimpanzee divergence.
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