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41.
A simplified method for the preparation of rotifers for transmission and scanning electron microscopy 总被引:1,自引:0,他引:1
Tor TEM and SEM prepatations, rotifers are placed in little panels made of plastic Beem capsules normally used for embedding, with their conical parts cut off and closed by plankton filter cloth. Thus, the risk of losing animals is considerably reduced. 相似文献
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Gause M Webber HA Misulovin Z Haller G Rollins RA Eissenberg JC Bickel SE Dorsett D 《Chromosoma》2008,117(1):51-66
Drosophila Nipped-B is an essential protein that has multiple functions. It facilitates expression of homeobox genes and is also required
for sister chromatid cohesion. Nipped-B is conserved from yeast to man, and its orthologs also play roles in deoxyribonucleic
acid repair and meiosis. Mutation of the human ortholog, Nipped-B-Like (NIPBL), causes Cornelia de Lange syndrome (CdLS),
associated with multiple developmental defects. The Nipped-B protein family is required for the cohesin complex that mediates
sister chromatid cohesion to bind to chromosomes. A key question, therefore, is whether the Nipped-B family regulates gene
expression, meiosis, and development by controlling cohesin. To gain insights into Nipped-B’s functions, we compared the effects
of several Nipped-B mutations on gene expression, sister chromatid cohesion, and meiosis. We also examined association of Nipped-B and cohesin
with somatic and meiotic chromosomes by immunostaining. Missense Nipped-B alleles affecting the same HEAT repeat motifs as CdLS-causing NIPBL mutations have intermediate effects on both gene expression and mitotic chromatid cohesion, linking these two functions and
the role of NIPBL in human development. Nipped-B colocalizes extensively with cohesin on chromosomes in both somatic and meiotic
cells and is present in soluble complexes with cohesin subunits in nuclear extracts. In meiosis, Nipped-B also colocalizes
with the synaptonemal complex and contributes to maintenance of meiotic chromosome cores. These results support the idea that
direct regulation of cohesin function underlies the diverse functions of Nipped-B and its orthologs.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
Gause, Webber, and Misulovin provided equal contributions. 相似文献
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The Escherichia coli (E. coli) SOS response is the largest, most complex, and best characterized bacterial network induced by DNA damage. It is controlled by a complex network involving the RecA and LexA proteins. We have previously shown that the SOS response to DNA damage is inhibited by various elements involved in the expression of the E. coli toxin-antitoxin mazEF pathway. Since the mazEF module is present on the chromosomes of most E. coli strains, here we asked: Why is the SOS response found in so many E. coli strains? Is the mazEF module present but inactive in those strains? We examined three E. coli strains used for studies of the SOS response, strains AB1932, BW25113, and MG1655. We found that each of these strains is either missing or inhibiting one of several elements involved in the expression of the mazEF-mediated death pathway. Thus, the SOS response only takes place in E. coli cells in which one or more elements of the E. coli toxin-antitoxin module mazEF or its downstream pathway is not functioning. 相似文献
47.
Several phenotypic properties of dissociated rat embryo cerebral cells cultivated in the absence of serum on poly(l-lysine) coated surfaces were investigated. A great enrichment of neuronal cells is attained after 3–4 weeks in culture as a result of cessation of nonneuronal cell proliferation. The monolayer pattern of cell-cell reassociation and neuritic sprouting is promoted by poly(l-lysine) and it is independent of serum presence or the existence of a layer of nonneuronal cells. Synaptic profiles and typical regions of neuropil are prominent. The neuronal plasma membrane is often characterized by irregular foldings at points of cell-cell contacts. A few biochemical parameters investigated lend support to the suggestion that the cerebral neurons acquire a certain state of functional maturation. It is proposed that substances secreted by the cells or released as a result of cell death may be conspicuous components for long-term survival of the cerebral neurons. 相似文献
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Bacteriocins are antimicrobial peptides generally active against bacteria closely related to the producer. Escherichia coli produces two types of bacteriocins, colicins and microcins. The in vitro efficacy of isolated colicins E1, E6, E7, K and M, was assessed against Escherichia coli strains from patients with bacteraemia of urinary tract origin. Colicin E7 was most effective, as only 13% of the tested strains were resistant. On the other hand, 32%, 33%, 43% and 53% of the tested strains exhibited resistance to colicins E6, K, M and E1. Moreover, the inhibitory activity of individual colicins E1, E6, E7, K and M and combinations of colicins K, M, E7 and E1, E6, E7, K, M were followed in liquid broth for 24 hours. Resistance against individual colicins developed after 9 hours of treatment. On the contrary, resistance development against the combined action of 5 colicins was not observed. One hundred and five E. coli strains from patients with bacteraemia were screened by PCR for the presence of 5 colicins and 7 microcins. Sixty-six percent of the strains encoded at least one bacteriocin, 43% one or more colicins, and 54% one or more microcins. Microcins were found to co-occur with toxins, siderophores, adhesins and with the Toll/Interleukin-1 receptor domain-containing protein involved in suppression of innate immunity, and were significantly more prevalent among strains from non-immunocompromised patients. In addition, microcins were highly prevalent among non-multidrug-resistant strains compared to multidrug-resistant strains. Our results indicate that microcins contribute to virulence of E. coli instigating bacteraemia of urinary tract origin. 相似文献
50.
Caburet S Zavadakova P Ben-Neriah Z Bouhali K Dipietromaria A Charon C Besse C Laissue P Chalifa-Caspi V Christin-Maitre S Vaiman D Levi G Veitia RA Fellous M 《PloS one》2012,7(3):e33412