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Aaron Mendez-Bermudez Alberto Hidalgo-Bravo Victoria E. Cotton Athanasia Gravani Jennie N. Jeyapalan Nicola J. Royle 《Nucleic acids research》2012,40(21):10809-10820
Approximately 10% of all cancers, but a higher proportion of sarcomas, use the recombination-based alternative lengthening of telomeres (ALT) to maintain telomeres. Two RecQ helicase genes, BLM and WRN, play important roles in homologous recombination repair and they have been implicated in telomeric recombination activity, but their precise roles in ALT are unclear. Using analysis of sequence variation present in human telomeres, we found that a WRN– ALT+ cell line lacks the class of complex telomere mutations attributed to inter-telomeric recombination in other ALT+ cell lines. This suggests that WRN facilitates inter-telomeric recombination when there are sequence differences between the donor and recipient molecules or that sister-telomere interactions are suppressed in the presence of WRN and this promotes inter-telomeric recombination. Depleting BLM in the WRN– ALT+ cell line increased the mutation frequency at telomeres and at the MS32 minisatellite, which is a marker of ALT. The absence of complex telomere mutations persisted in BLM-depleted clones, and there was a clear increase in sequence homogenization across the telomere and MS32 repeat arrays. These data indicate that BLM suppresses unequal sister chromatid interactions that result in excessive homogenization at MS32 and at telomeres in ALT+ cells. 相似文献
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Hierarchical down-modulation of hemopoietic growth factor receptors 总被引:31,自引:0,他引:31
Granulocytes and macrophages can be produced in vitro when progenitor cells from mouse bone marrow are stimulated by any of four distinct colony stimulating factors, Multi-CSF (IL-3), GM-CSF, G-CSF, and M-CSF (CSF-1). At 0 degrees C the four CSFs do not cross-compete for binding to bone marrow cells, indicating that each has a specific cell surface receptor. However, at 21 degrees C or 37 degrees C, Multi-CSF inhibits binding of the other three CSFs and GM-CSF inhibits binding of G-CSF and M-CSF. Rather than competing directly for receptor binding, the binding of Multi-CSF, GM-CSF, or G-CSF to their own receptor induces the down-modulation (and thus activation) of other CSF receptors at 37 degrees C. The pattern and potency of down-modulation activity exhibited by each type of CSF parallels the pattern and potency of its biological activity. We propose a model in which the biological interactions of the four CSFs are explained by their ability to down-modulate and activate lineage-specific receptors. 相似文献
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Nicola Borri 《Cell and tissue research》1939,29(2):128-137
Riassunto Nella cornea del ratto, in tutta quella parte del parenchima che è al margine con la sclerotica, esistono due cospicue formazioni a plesso, una vascolare e l'altra nervosa, in stretto reciproco rapporto topografico e verosimilmente anche funzionale.Il plesso nervoso è formato da fibre di varia provenienza, mieliniche ed amieliniche, fra loro mescolate ed anastomizzate, soprattutto mediante la rete diffusa alla quale danno origine.È molto probabile che a queste due formazioni, vascolare e nervosa, non sia riservato il solo compito di assicurare la nutrizione della cornea; ma penso che esse non siano estranee al meccanismo regolatore dell'umore acqueo.
Zusammenfassung Der Verfasser hat mit der Bielschowsky-Grosschen Methode und vor allem mit der Schwarzreaktion von Golgi in Epymis norv. die angehäufte Zahl von Nerven studiert, die im Zusammenhang mit dem Hornhautrand stehen und von denen weder die Topographie noch ihre Bedeutung sonderlich bekannt war. Indem der Verfasser diese Methoden mit der Injektion des Blutgefäßsystems verband, hat er festgestellt, daß der plexiforme Nervenapparat enge topographische und funktionelle Beziehungen zu dem sich ringförmig in der gleichen Zone erstreckenden Gefäßplexus hat.Der Verfasser legt außerdem klar, daß dieser vasculonervöse Plexus zur Hornhaut und nicht zu anderen Bildungen gehört. Er schließt ferner, daß diesem angesichts seiner großen Entwicklung eine bemerkenswertere Aufgabe zukommt als jene, lediglich die Ernährung der Hornhaut zu sichern und daß er ein Teil des sinnreichen Regulationsmechanismus des Kammerwassers sei.相似文献
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Granulocyte-colony stimulating factor (G-CSF) is a glycoprotein hemopoietic growth factor which regulates the production of granulocytes and macrophages. Reversed-phase microbore high-performance liquid chromatography was employed to purify a number of tryptic and Staphylococcus aureus V8 proteinase peptides generated from approximately 400 pmol G-CSF purified from medium conditioned by lungs from mice previously injected with endotoxin. N-Terminal amino-acid sequence analyses were performed on the parent polypeptide and on four tryptic peptides and one Staphylococcus aureus V8 protease peptide, yielding 68 unique amino-acid assignments; this corresponds to approximately 38% of the molecule. 相似文献
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Giorgio Di Marco Nicola D'Ambrosio Maria T. Giardi Angelo Massacci Domenico Tricoli 《Photosynthesis research》1989,21(2):117-122
We investigated several photosynthetic parameters of a virescent mutant of durum wheat and of its wild-type. Electron transport rate to ferricyanide was the same in the two genotypes when expressed on leaf area basis while O2 evolution of the leaf tissue in saturating light and CO2 was slightly higher in the yellow genotype. RuBPCase was also slightly higher. Quantum yield per absorbed light was similar in the two genotypes. P700 and Cyt f were less concentrated in the mutant while PS II was only marginally lower. The light response curve of CO2 assimilation indicated higher level of photosynthesis of the mutant in high light, which corresponded to a lower non-photochemical quenching compared to the wild-type. It is concluded that the reaction centres, cyt f and chlorophyll are not limiting factors of electron transport in wheat seedlings and that electron transport capacity is in excess with respect to that needed for driving photosynthesis. Since the differences in photosynthesis reflect differences in RuBPCase activity, it is suggested that this enzyme limits photosynthesis in wheat seedlings also at high light intensities.Abbreviations cyt f
cytochrome f
- chl
chlorophyll
- PS II
photosystem II
- Pnmax
maximum photosynthesis
- RuBCase
Ribulose, 1-5,bisphosphate carboxylase 相似文献
10.
Extension of previous investigations at this laboratory regarding life shortening and tumor induction in the mouse has provided more complete dose-response information in the low dose region of X rays and neutrons. A complete observation of survival and late pathology has been carried out on over 2000 BC3F1 female mice irradiated with single doses of 1.5 MeV neutrons (0.5, 1, 2, 4, 8, 16 cGy) and, for comparison, of X rays (4, 8, 16, 32, 64, 128, 256 cGy). Data analysis has shown that a significant life shortening is observable only for individual neutron doses not lower than 8 cGy. Nevertheless, assuming a linear nonthreshold form for the overall dose-effect relationships of both radiation qualities, an RBE value of 12.3 is obtained for the 1.5 MeV neutrons. The induction of solid tumors by neutrons becomes statistically significant at individual doses from 8 cGy and by X rays for doses larger than 1 Gy. Linear dependence on neutron dose appears adequate to interpret the data at low doses. A separate analysis of ovarian tumor induction substantiates the hypothesis of a threshold dose for the X rays, while this is not strictly needed to interpret the neutron data. A trend analysis conducted on the neoplasm incidence confirms the above findings. Death rates have been analyzed, and a general agreement between the shift to earlier times of these curves and tumor induction was found. 相似文献