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1.
The pericentriolar material in Chinese hamster ovary cells nucleates microtubule formation 总被引:48,自引:38,他引:10
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The structure and function of the centrosomes from Chinese hamster ovary (CHO) cells were investigated by electron microscopy of negatively stained wholemount preparations of cell lysates. Cells were trypsinized from culture dishes, lysed with Triton X-100, sedimented onto ionized, carbon-coated grids, and negatively stained with phosphotungstate. The centrosomes from both interphase and dividing cells consisted of pairs of centrioles, a fibrous pericentriolar material, and a group of virus-like particles which were characteristic of the CHO cells and which served as markers for the pericentriolar material. Interphase centrosomes anchored up to two dozen microtubules when cells were lysed under conditions which preserved native microtubules. When Colcemid-blocked mitotic cells, initially devoid of microtubules, were allowed to recover for 10 min, microtubules formed at the pericentriolar material, but not at the centrioles. When lysates of Colcemid-blocked cells were incubated in vitro with micotubule protein purified from porcine brain tissue, up to 250 microtubules assembled at the centrosomes, similar to the number of microtubules that would normally form at the centrosome during cell division. A few microtubules could also be assembled in vitro onto the ends of isolated centrioles from which the pericentriolar material had been removed, forming characteristic axoneme- like bundles. In addition, microtubules; were assembled onto fragments of densely staining, fibrous material which was tentatively identified as periocentriolar material by its association of CHO can initiate and anchor microtubules both in vivo and in vitro. 相似文献
2.
Slow response of soil organic matter to the reduction in atmospheric nitrogen deposition in a Norway spruce forest 总被引:1,自引:0,他引:1
NICOLE DÖRR KLAUS KAISER ROBERT MIKUTTA GEORG GUGGENBERGER 《Global Change Biology》2010,16(11):2990-3003
Global nitrogen (N) deposition rates in terrestrial environments have quadrupled since preindustrial times, causing structural and functional changes of ecosystems. Different emission reduction policies were therefore devised. The aim of our study was to investigate if, and over what timescale, processes of soil organic matter (OM) transformation respond to a decline in atmospheric N deposition. A N‐saturated spruce forest (current N deposition: 34 kg ha?1 yr?1; critical N load: 14 kg ha?1 yr?1), where N deposition has been reduced to 11.5 kg ha?1 yr?1 since 1991, was studied. Besides organic C and organic and inorganic N, noncellulosic carbohydrates, amino sugars and amino acids were determined. A decline in organic N in litter indicated initial effects at plant level. However, there were no changes in biomarkers upon the reduction in N deposition. In addition, inorganic N was not affected by reduced N deposition. The results showed that OM cycling and transformation processes have not responded so far. It was concluded that no direct N deposition effects have occurred due to the large amount of stored organic N, which seems to compensate for the reduction in deposited N. Obviously, the time span of atmospheric N reduction (about 14.5 years) is too short compared with the mean turnover time of litter to cause indirect effects on the composition of organic C and N compounds. It is assumed that ecological processes, such as microbial decomposition or recycling of organic N and C, react slowly, but may start within the next decade with the incorporation of the new litter. 相似文献
3.
William A Cafruny Richard G Duman Grace HW Wong Suleman Said Pam Ward-Demo Raymond RR Rowland Eric A Nelson 《Virology journal》2006,3(1):1-17
Background
Porcine reproductive and respiratory syndrome virus (PRRSV) is the etiologic agent of PRRS, causing widespread chronic infections which are largely uncontrolled by currently available vaccines or other antiviral measures. Cultured monkey kidney (MARC-145) cells provide an important tool for the study of PRRSV replication. For the present study, flow cytometric and fluorescence antibody (FA) analyses of PRRSV infection of cultured MARC-145 cells were carried out in experiments designed to clarify viral dynamics and the mechanism of viral spread. The roles of viral permissiveness and the cytoskeleton in PRRSV infection and transmission were examined in conjunction with antiviral and cytotoxic drugs.Results
Flow cytometric and FA analyses of PRRSV antigen expression revealed distinct primary and secondary phases of MARC-145 cell infection. PRRSV antigen was randomly expressed in a few percent of cells during the primary phase of infection (up to about 20–22 h p.i.), but the logarithmic infection phase (days 2–3 p.i.), was characterized by secondary spread to clusters of infected cells. The formation of secondary clusters of PRRSV-infected cells preceded the development of CPE in MARC-145 cells, and both primary and secondary PRRSV infection were inhibited by colchicine and cytochalasin D, demonstrating a critical role of the cytoskeleton in viral permissiveness as well as cell-to-cell transmission from a subpopulation of cells permissive for free virus to secondary targets. Cellular expression of actin also appeared to correlate with PRRSV resistance, suggesting a second role of the actin cytoskeleton as a potential barrier to cell-to-cell transmission. PRRSV infection and cell-to-cell transmission were efficiently suppressed by interferon-γ (IFN-γ), as well as the more-potent experimental antiviral agent AK-2.Conclusion
The results demonstrate two distinct mechanisms of PRRSV infection: primary infection of a relatively small subpopulation of innately PRRSV-permissive cells, and secondary cell-to-cell transmission to contiguous cells which appear non-permissive to free virus. The results also indicate that an intact cytoskeleton is critical for PRRSV infection, and that viral permissiveness is a highly efficient drug target to control PRRSV infection. The data from this experimental system have important implications for the mechanisms of PRRSV persistence and pathology, as well as for a better understanding of arterivirus regulation. 相似文献4.
Kiessoun Konaté Jacques Fran?ois Mavoungou Alexis Nicaise Lepengué Ra?ssa RR Aworet-Samseny Adama Hilou Alain Souza Mamoudou H Dicko Bertrand M’Batchi 《Annals of clinical microbiology and antimicrobials》2012,11(1):1-12
Background
The present study reports the antibacterial capacity of alkaloid compounds in combination with Methicillin and Ampicillin-resistants bacteria isolated from clinical samples. The resistance of different bacteria strains to the current antibacterial agents, their toxicity and the cost of the treatment have led to the development of natural products against the bacteria resistant infections when applied in combination with conventional antimicrobial drugs.Method
The antibacterial assays in this study were performed by using inhibition zone diameters, MIC, MBC methods, the time-kill assay and the Fractional Inhibitory Concentration Index (FICI) determination. On the whole, fifteen Gram-positive bacterial strains (MRSA/ARSA) were used. Negative control was prepared using discs impregnated with 10 % DMSO in water and commercially available Methicillin and Ampicillin from Alkom Laboratories LTD were used as positive reference standards for all bacterial strains.Results
We noticed that the highest activities were founded with the combination of alkaloid compounds and conventional antibiotics against all bacteria strains. Then, results showed that after 7 h exposition there was no viable microorganism in the initial inoculums.Conclusion
The results of this study showed that alkaloid compounds in combination with conventional antibiotics (Methicillin, Ampicillin) exhibited antimicrobial effects against microorganisms tested. These results validate the ethno-botanical use of Cienfuegosia digitata Cav. (Malvaceae) in Burkina Faso. Moreover, this study demonstrates the potential of this herbaceous as a source of antibacterial agent that could be effectively used for future health care purposes. 相似文献5.
Chemical composition of the sponge Chondrosia reniformis from [2pt] the Canary Islands 总被引:1,自引:1,他引:0
Jordan Nechev William W. Christie Rafael Robaina Fernando M. de Diego Albena Ivanova Simeon Popov Kamen Stefanov 《Hydrobiologia》2002,467(1-3):91-98
Lake Zempoala was studied throughout 16 months in 1996–1997. It is a shallow monomictic lake situated at 2800 masl at the Neovolcanic Belt, well within the Mexican tropical zone. Most of the phytoplankton species in this lake may be characterized as temperate, according to their geographical distribution. A break down in phytoplankton biomass was observed before the lake's circulation, and open to question if a clear-water phase could be present in a tropical lake. 相似文献
6.
Fernando D. Marián Pilar García-Jiménez Rafael R. Robaina 《Physiologia plantarum》2000,110(4):530-534
The levels of putrescine (Put), spermidine (Spd) and spermine (Spm) were analyzed in naturally collected samples of the marine macroalgae Dyctiota dichotoma, Gelidium canariensis and Grateloupia doryphora . Polyamines (PAs) appeared in free (35–134 μg g−1 fresh weight) and bound TCA-insoluble form (1 667–2 624 μg g−1 fresh weight). Axenic in vitro cultures of sporelings from G. doryphora were established in the medium containing glycerol. This medium promoted growth and morphogenesis and also increased the free and bound PA levels in the sporelings. Tracer experiments using 70 kBq [U-14 C]-glycerol showed significant quantities of radioactivity in Put, Spd and Spm after 20 h of incubation. The effects of glycerol on growth were inhibited by the ornithine decarboxylase (EC 4.1.1.17) inhibitor α -difluoromethylornithine (DFMO). The presence of DFMO in the incubation medium with [U-14 C]-glycerol also reduced the radioactivity in PAs. 相似文献
7.
Analysis of ethylene‐induced gene regulation during carposporogenesis in the red seaweed Grateloupia imbricata (Rhodophyta)
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Pilar Garcia‐Jimenez Montserrat Montero‐Fernández Rafael R. Robaina 《Journal of phycology》2018,54(5):681-689
Ethylene favors carposporogenesis in the red seaweed Grateloupia imbricata. Analyses of cystocarp development in vitro in thalli treated with ethylene suggest an interconnection between polyamine and ethylene biosynthesis pathways. Yet, little is known about molecular mechanisms underlying carposporogenesis. Here, we used droplet digital PCR to analyze genes encoding enzymes related to polyamine (Spermidine [Spd] synthase) and ethylene (ACC synthase) synthesis; a pivotal compound of both pathways (S‐adenosyl methionine synthase, SAMS); the gene that encodes amine oxidase, which is involved in polyamine degradation, and a candidate gene involved in seaweed reproduction (ornithine decarboxylase, ODC). In addition, we analyzed genes encoding proteins related to stress and reactive oxygen species, ascorbate peroxidase (APX), cytochrome P450 and WD 40. We characterized gene expression in fertilized and fertile thalli from G. imbricata that were exposed to ethylene for 15 min at two time points after treatment (1 and 7 d). The differential gene expression of SAMS, Spd synthase, ACC synthase, and cytochrome P450 was related to disclosure and development of cystocarps in fertilized thalli that transitioned from having no visible cystocarps at 1 d to developing cystocarps at 7 d. Likewise, cytochrome P450 was associated with cystocarp disclosure and maturation. In addition, amine oxidase and APX were involved in fine‐tuning polyamine and reactive oxygen species during carposporogenesis, respectively, whereas WD 40 did so in relation to ethylene signaling. Expression of the candidate gene ODC was increased when cystocarps were not visible (fertilized thalli, 1d), as previously described. This analysis suggests developmental stage‐specific roles for these genes during carposporogenesis. 相似文献
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9.
Nicholas J Boddicker Angelica Bjorkquist Raymond RR Rowland Joan K Lunney James M Reecy Jack CM Dekkers 《遗传、选种与进化》2014,46(1):18