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91.
N Shastri D J Kawahara A Miller E E Sercarz 《Journal of immunology (Baltimore, Md. : 1950)》1984,133(3):1215-1221
Hen egg-white lysozyme (HEL)-specific Thy-1+, Lyt-1+2- T cell lines and clones were derived from the nonresponder C57BL/6 strain. Although the antigen-specific proliferative response of these T cells in the presence of syngeneic irradiated spleen cells as a source of antigen-presenting cells (APC) was normal, the same cells were incapable of stimulating B cells to secrete antibody in vitro. This deficiency could, however, be corrected by the addition of an excess of normal T cells or a supernatant from concanavalin A-stimulated rat spleen cells. Alternatively, the use of highly cross-reactive ring-necked pheasant lysozyme in the cultures allowed expression of efficient help, ruling out any inherent deficiency in the T cells. The antibody response was specific and required MHC compatibility between the T lines and responding B cells. By using (H-2b X H-2d)F1 B cells and another H-2d-restricted HEL-specific T line, it was shown that only the H-2b-restricted T-B collaboration required exogenous factors, and the H-2d-restricted collaboration did not. Because both proliferative and helper responses are dependent upon MHC-restricted antigen presentation by macrophage-APC and B cells, respectively, these results suggest that the defect in the nonresponder H-2b-restricted T-B collaborative pathway may relate to the inability of B cells to adequately process and present HEL to clonal T cells. 相似文献
92.
We released seeds of two sympatric tree species, Corylus mandshurica (seed with thinner seed hull, higher nutrition) and C. heterophylla (seeds with thicker seed hull, lower nutrition) in the masting year of C. mandshurica in 2008, and C. heterophylla in 2009, respectively, to investigate how seed masting of the two sympatric Corylus species affects seed removal and dispersal fitness of the two species differently at both intra- and inter-specific levels.
At intra-specific level, the authors found mast seeding of both C. mandshurica and C. heterophylla significantly reduced seed removal, seed consumption, but increased seed dispersal distance and seed dispersal fitness of
the released seeds. Mast seeding of C. mandshurica increased seed caching of C. mandshurica. At inter-specific level, the authors found mast seeding of C. mandshurica reduced seed removal of C. heterophylla, but mast seeding of C. heterophylla did not significantly reduce seed removal of C. mandshurica. Mast seeding of C. mandshurica reduced seed consumption of C. heterophylla, while mast seeding of C. heterophylla reduced seed consumption of C. mandshurica. We found mast seeding of C. mandshurica significantly reduced seed dispersal distance of C. heterophylla, while mast seeding of C. heterophylla significantly increased seed dispersal distance of C. mandshurica. We found that mast seeding of C. mandshurica significantly increased seed dispersal fitness of C. heterophylla, while mast seeding of C. heterophylla did not significantly increase seed dispersal fitness of C. mandshurica. More studies are needed to reveal the ecological consequences of mast seeding at inter-specific or community-level. Seed
traits may attribute the differences of mast seeding at inter-specific level. Because seeds with thinner seed hull and higher
nutrition were more harvested and eaten by rodents, mast seeding of C. mandshurica might have reduced seed removal and seed consumption, but increased dispersal fitness of C. heterophylla (seeds with thicker seed hull, lower nutrition). Therefore, synchrony among species is, or is not, selectively beneficial
to the focus species depends on seed traits which determine gains from mast seeding at inter-specific level. 相似文献
93.
E. B. Burova I. S. Smirnova A. N. Shatrova I. V. Gonchar N. N. Nikolskii 《Cell and Tissue Biology》2011,5(1):9-14
Interferon gamma (IFNγ) is known to inhibit the proliferation of some transformed cell lines. Recently, we demonstrated the
transactivation of the epidermal growth factor receptor (EGFR) in response to IFNγ (Burova et al., 2007) and provided direct
evidence for the dependence of IFNγ-induced EGFR transactivation on the EGFR expression level in epithelial cells (Gonchar
et al., 2008). This study examines an antiproliferative effect of IFNγ on human epithelial cell lines—A431 and HeLa that express
high levels of EGFR, as well as HEK293 that expresses low levels of EGFR. To characterize the IFNγ-induced changes in these
cells, we studied cell growth, the cell cycle, and induction of apoptosis. The response to IFNγ differed in the compared cell
lines; cell growth was inhibited in both A431 and HeLa cells, but not in HEK293 cells, as was shown by the cell count and
MTT. The cell-cycle phases analyzed by flow cytometry were disturbed in A431 and HeLa cells in response to IFNγ. On the contrary,
in HEK293 cells, the IFNγ treatment did not alter distribution by cell cycle phases. Our results indicate that IFNγ produces
an antiproliferative effect that depends on the increased expression of EGFR in A431 and HeLa cells. Furthermore, it was demonstrated
that IFNγ induced the caspase 3 activation in A431 cells, which suggests the involvement of active caspase 3 in the IFNγ-induced
apoptosis. 相似文献
94.
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97.
S. T. Zakhidov T. L. Marshak E. A. Malolina A. Yu. Kulibin I.A. Zelenina S. M. Pavluchenkova V. M. Rudoi O. V. Dement’eva S. G. Skuridin Yu. M. Evdokimov 《Biochemistry (Moscow) Supplemental Series A: Membrane and Cell Biology》2010,4(3):293-296
The effect of gold nanoparticles on mouse epididymal sperm has been studied using the model system of nuclear chromatin decondensation
in vitro. It is shown that the treatment of gametes, preliminary membrane-freed by sodium dodecyl sulfate, in the mediums
containing gold nanoparticles (with diameter ∼2.5 nm) in concentrations 1.0 × 1015 or 0.5 × 1015 particles/ml and following incubation in dithiothreitol solution (DTT) resulted in failure of chromatin decondensation process
and nucleus structure. We conclude that gold nanoparticles possess spermatotoxicity. The mechanism of cytotoxic effect of
gold nanoparticles may be related with their interaction with molecules of double-helix DNA. The model system studied in this
research is applicable for further investigations of cytotoxic effects of nanoparticles of different origin and made of different
metals. 相似文献
98.
99.
100.
THE high-sulphur proteins of α-keratins, which constitute the non-filamentous matrix between the microfibrils, comprise several major groups of proteins, each group consisting of a number of closely related components. They are obtained in a soluble form by reduction of the disulphide bonds of wool and preferential extraction with alkaline thioglycollate at high ionic strength1. The thiol groups are subsequently stabilized by alkylation with iodoacetic acid. 相似文献