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961.
Nuclei of nonviable ovine somatic cells develop into lambs after nuclear transplantation 总被引:9,自引:0,他引:9
Loi P Clinton M Barboni B Fulka J Cappai P Feil R Moor RM Ptak G 《Biology of reproduction》2002,67(1):126-132
Here we report on the successful reprogramming of nuclei from somatic cells rendered nonviable by heat treatment. Granulosa cells from adult sheep were heated to nonphysiological temperatures (55 degrees C or 75 degrees C) before their nuclei were injected into enucleated metaphase II oocytes. Reprogramming was demonstrated by the capacity of the reconstructed embryos to develop to the blastocyst stage in vitro and into fetuses and viable offspring in suitable foster mothers. To our knowledge, this is the first report of cloned mammalian offspring originating from nonviable cells. In addition, our experiments show that heat-treating donor nuclei destabilizes higher-order features of chromatin (but leaves intact its nucleosomal organization) and results in a high proportion of reconstructed embryos developing to the blastocyst stage and beyond. 相似文献
962.
Uthman A Rezaie S Dockal M Ban J Söltz-Szöts J Tschachler E 《Biochemical and biophysical research communications》2002,299(5):688-692
Azole antifungals are widely used to treat infections with dermatophyte fungi. Whereas it is well established that this class of drugs interferes with fungal ergosterol synthesis, little is known about its potential other biological effects. Here we report the isolation and structural organization of Microsporum canis metallothionein gene and demonstrate that fluconazole is able to downregulate the baseline as well as copper-induced expression of this gene. Since this effect occurred within 30 min after exposure of the fungus to fluconazole, it is unlikely that it is due to impaired ergosterol synthesis. Our additional demonstration that fluconazole enhances copper toxicity for M. canis suggests that inhibition of metallothionein expression by fluconazole is biologically relevant and may represent an important additional mode of the antifungal action of this drug. Therefore our data indicate that antifungal effects of azole derivatives might not only be due to interference with cell wall synthesis but may also affect other biological circuits within the fungal cells. 相似文献
963.
964.
Ackerman JD 《American journal of botany》2002,89(7):1119-1127
The dispersion and capture of differently shaped particles within a Zostera marina L. (eelgrass; Zosteraceae) bed were examined to understand submarine pollination and other dispersals. During periods of moderate flow in the canopy, the capture rate of "spherical" (the shape of ancestral pollen) and "filamentous" (the shape of eelgrass pollen) particles was greater for particles released at the top of the canopy (3.07 and 4.53% × 10(-5) cm(-2) of collector; i.e., percentage of particles captured normalized to collector area) and greater for filamentous than for spherical particles (4.51% × 10(-5) cm(-2) vs. 2.01% × 10(-5) cm(-2)). Estimates of the horizontal P (Joseph-Sendner diffusion velocity) and the vertical diffusivity (Gaussian K) of filamentous particles were small (P ≈ 4 × 10(-4) m/s; K ≈ 10(-4) m(2)/s) compared to theoretical values that do not consider plant canopies. These findings support the concept that eelgrass canopies modify the fluid dynamics (i.e., reduced turbulent mixing) within their canopies. These results indicate that 1000-10?000 Z. marina pollen are required to pollinate a single flower. Similarly, it was estimated that under some conditions, the probability of particle impaction on eelgrass vegetation approaches certainty. These results provide insight into the evolution of filamentous pollen and submarine pollination, as well as dispersal and other mass transport phenomena within macrophyte canopies. 相似文献
965.
Watanabe T Nakagawa K Ohata S Kitagawa D Nishitai G Seo J Tanemura S Shimizu N Kishimoto H Wada T Aoki J Arai H Iwatsubo T Mochita M Watanabe T Satake M Ito Y Matsuyama T Mak TW Penninger JM Nishina H Katada T 《Developmental biology》2002,250(2):332-347
Mice lacking the stress-signaling kinase SEK1 die from embryonic day 10.5 (E10.5) to E12.5. Although a defect in liver formation is accompanied with the embryonic lethality of sek1(-/-) mice, the mechanism of the liver defect has remained unknown. In the present study, we first produced a monoclonal antibody specifically recognizing murine hepatoblasts for the analysis of liver development and further investigated genetic interaction ofsek1 with tumor necrosis factor-alpha receptor 1 gene (tnfr1) and protooncogene c-jun, which are also responsible for liver formation and cell apoptosis. The defective liver formation in sek1(-/-) embryos was not protected by additionaltnfr1 mutation, which rescues the embryonic lethality of mice lacking NF-kappaB signaling components. There was a progressive increase in the hepatoblast cell numbers of wild-type embryos from E10.5 to E12.5. Instead, impaired hepatoblast proliferation was observed in sek1(-/-) livers from E10.5, though fetal liver-specific gene expression was normal. The impaired phenotype in sek1(-/-) livers was more severe than in c-jun(-/-) embryos, and sek1(-/-) c-jun(-/-) embryos died more rapidly before E8.5. The hepatoblast proliferation required no hematopoiesis, since liver development was not impaired in AML1(-/-) mice that lack hematopoietic functions. Stimulation of stress-activated protein kinase/c-Jun N-terminal kinase by hepatocyte growth factor was attenuated in sek1(-/-) livers. Thus, SEK1 appears to play a crucial role in hepatoblast proliferation and survival in a manner apparently different from NF-kappaB or c-Jun. 相似文献
966.
Josef Hölzl 《Plant Systematics and Evolution》1958,104(4-5):342-369
Ohne ZusammenfassungEs ist mir eine angenehme Pflicht, Herrn Univ. Prof. Dr. R.Biebl vom pflanzenphysiologischen Institut der Universität Wien für die kritische Durchsicht des Manuskripts und wertvolle Verbesserungsvorschläge meinen verbindlichsten Dank auszusprechen. 相似文献
967.
968.
Josef Ullepitsch 《Plant Systematics and Evolution》1884,34(10):363-368
Ohne Zusammenfassung 相似文献
969.
Gerhard Stehlik Josef Kainzbauer Helmut Tausch Otto Richter 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》1982,232(2):295-303
ExtrelutR extraction and glass capillary gas chromatography were applied to the routine determination of nicotine and its metabolites cotinine, nicotine-1′-N-oxide and cotinine-1-N-oxide in urine and plasma. After extraction of nicotine and cotinine both N-oxides and phendimetrazine-N-oxide (used as internal standard) were reduced to their bases by SO2 on-column and eluted by a mixture of diethyl ether and dichloromethane. The minimum detectable concentrations are 0.03 μg/ml for urinary nicotine and cotinine and 0.1 μg/ml for the N-oxides. In plasma samples the corresponding values are 5 ng/ml and 15 ng/ml, respectively, with sample values as small as 2 ml. The advantage of the direct determination of all four compounds of interest in one sample reduced the amount of plasma required. The straightforward and rapid extraction and reduction procedure as well as the long-term stability of the gas chromatographic separation system make the method suitable for routine application. 相似文献
970.
H. Josef Trier 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1926,4(3):305-330
Zusammenfassung An frisch entnommenem oder im Thermostaten aufbewahrtem Panseninhalte von Schafen wurde zu verschiedenen Zeiten nach verschiedenartiger Fütterung des Wirtstieres die Aufnahme und Verarbeitung der Nahrung durch die Panseninfusorien mikrochemisch verfolgt. Es lassen sich dabei, unter Zuhilfenahme der Fütterung der Infusorien im Thermostaten, der Vorgang der Nahrungsaufnahme und besonders der Kohlehydratstoffwechsel mikroskopisch beobachten. Stärkekörner werden als Ganzes aufgenommen und innerhalb des Nahrungssackes arrodiert und aufgelöst; dafür tritt im Ektoplasma Ablagerung von Glykogen auf. Diese erfolgt auch bei Fütterung mit Traubenzucker oder Milchzucker. Das Glykogen wird bei mangelnder weiterer Nahrungszufuhr sehr bald wieder aufgelöst und im ZellstoffWechsel verarbeitet.Im Gegensatze zu der gierigen Aufnahme von Stärke wird tierisches Eiweiß von den Infusorien nicht aufgenommen. Stets aber finden sich in ihrem Zelleibe normalerweise Bruchstücke pflanzlicher Nahrung und besonders grüne Pflanzenteile, ohne deren Aufnahme seitens des Wirtstieres die Infusorien aus dem Pansen verschwinden, um sich mit ihrer Neuaufnahme wieder einzustellen. Auch die grünen Pflanzenteile, die mit ihrem Bestand an Chlorophyll und Zellulose ebenfalls sowohl im Pansen wie auch von im Thermostaten aufbewahrten Infusorien aufgenommen werden, Werden im Innern der Infusorien in charakteristischer Weise verändert und aufgelöst. 相似文献