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61.
Georgieva M Roguev A Balashev K Zlatanova J Miloshev G 《Biochimica et biophysica acta》2012,1819(5):366-374
Despite the existence of certain differences between yeast and higher eukaryotic cells a considerable part of our knowledge on chromatin structure and function has been obtained by experimenting on Saccharomyces cerevisiae. One of the peculiarities of S. cerevisiae cells is the unusual and less abundant linker histone, Hho1p. Sparse is the information about Hho1p involvement in yeast higher-order chromatin organization. In an attempt to search for possible effects of Hho1p on the global organization of chromatin, we have applied Chromatin Comet Assay (ChCA) on HHO1 knock-out yeast cells. The results showed that the mutant cells exhibited highly distorted higher-order chromatin organization. Characteristically, linker histone depleted chromatin generally exhibited longer chromatin loops than the wild-type. According to the Atomic force microscopy data the wild-type chromatin appeared well organized in structures resembling quite a lot the "30-nm" fiber in contrast to HHO1 knock-out yeast. 相似文献
62.
Kratzat S Nikolova V Miething C Hoellein A Schoeffmann S Gorka O Pietschmann E Illert AL Ruland J Peschel C Nilsson J Duyster J Keller U 《PloS one》2012,7(5):e37433
The Cks1 component of the SCF(Skp2) complex is necessary for p27(Kip1) ubiquitylation and degradation. Cks1 expression is elevated in various B cell malignancies including Burkitt lymphoma and multiple myeloma. We have previously shown that loss of Cks1 results in elevated p27(Kip1) levels and delayed tumor development in a mouse model of Myc-induced B cell lymphoma. Surprisingly, loss of Skp2 in the same mouse model also resulted in elevated p27(Kip1) levels but exhibited no impact on tumor onset. This raises the possibility that Cks1 could have other oncogenic activities than suppressing p27(Kip1). To challenge this notion we have targeted overexpression of Cks1 to B cells using a conditional retroviral bone marrow transduction-transplantation system. Despite potent ectopic overexpression, Cks1 was unable to promote B cell hyperproliferation or B cell malignancies, indicating that Cks1 is not oncogenic when overexpressed in B cells. Since Skp2 overexpression can drive T-cell tumorigenesis or other cancers we also widened the quest for oncogenic activity of Cks1 by ubiquitously expressing Cks1 in hematopoetic progenitors. At variance with c-Myc overexpression, which caused acute myeloid leukemia, Cks1 overexpression did not induce myeloproliferation or leukemia. Therefore, despite being associated with a poor prognosis in various malignancies, sole Cks1 expression is insufficient to induce lymphoma or a myeloproliferative disease in vivo. 相似文献
63.
64.
Responses of the resurrection plant <Emphasis Type="Italic">Haberlea rhodopensis</Emphasis> to high irradiance 总被引:1,自引:0,他引:1
The effect of high irradiance (HI) during desiccation and subsequent rehydration of the homoiochlorophyllous desiccation-tolerant
shade plant Haberlea rhodopensis was investigated. Plants were irradiated with a high quantum fluence rate (HI; 350 μmol m−2 s−1 compared to ca. 30 μmol m−2 s−1 at the natural rock habitat below trees) and subjected either to fast desiccation (tufts dehydrated with naturally occurring
thin soil layers) or slow desiccation (tufts planted in pots in peat-soil dehydrated by withholding irrigation). Leaf water
content was 5 % of the control after 4 d of fast and 19 d of slow desiccation. Haberlea was very sensitive to HI under all conditions. After 19 d at HI, even in well-watered plants there was a strong reduction
of rates of net photosynthesis and transpiration, contents of chlorophyll (Chl) and carotenoids, as well as photosystem 2
activity (detected by the Chl fluorescence ratio RFd). Simultaneously, the blue/red and green/red fluorescence ratios increased considerably suggesting increased synthesis of
polyphenolic compounds. Desiccation of plants in HI induced irreversible changes in the photosynthetic apparatus and leaves
did not recover after rehydration regardless of fast or slow desiccation. Only young leaves survived desiccation. 相似文献
65.
Alexandrova A Petrov L Georgieva A Kirkova M Kukan M 《Cell biochemistry and function》2008,26(3):392-398
In vivo effects of N-benzyloxycarbonyl (Cbz)-Leu-Leu-leucinal (MG132) on chymotryptic-like (ChT-L), tryptic-like, and post-glutamyl peptide hydrolytic-like proteasome activities, protein oxidation, lipid peroxidation (LP), glutathione (GSH) level, as well as on the activity of antioxidant enzymes (superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px), and glutathione-reductase) in the rat liver were studied. The possibility of MG132 provoking the formation of free oxygen radicals was also assayed in primary hepatocytes. The following results were obtained: (1) In vivo, MG132 did not change the spontaneous LP, but increased Fe-induced LP and the amount of oxidized proteins; it decreased the GSH level in liver. From the proteasome activities studied in liver cytosol only ChT-L activity was significantly decreased after MG132 administration. Furthermore, MG132 increased antioxidant enzyme activities of SOD, CAT, and GSH-Px. (2) In vitro, MG132 increased free radical oxygen species in hepatocytes; this effect disappeared in the presence of CAT or mannitol. In conclusion, since nowadays proteasome inhibitors are entering into the swing of laboratory and clinical practice, the present data could provide useful information for MG132 action. Consequently, future in vivo experiments with MG132 could highlight the possibility of its use at different pathological conditions. 相似文献
66.
Natalia Nikolova Kiril Tenekedjiev Krasimir Kolev 《Central European Journal of Biology》2008,3(4):345-350
Progress curve analysis is a convenient tool for the characterization of enzyme action: a single reaction mixture provides
multiple experimental measured points for continuously varying amounts of substrates and products with exactly the same enzyme
and modulator concentrations. The determination of kinetic parameters from the progress curves, however, requires complex
mathematical evaluation of the time-course data. Some freely available programs (e.g. FITSIM, DYNAFIT) are widely applied
to fit kinetic parameters to user-defined enzymatic mechanisms, but users often overlook the stringent requirements of the
analytic procedures for appropriate design of the input experiments. Flaws in the experimental setup result in unreliable
parameters with consequent misinterpretation of the biological phenomenon under study. The present commentary suggests some
helpful mathematical tools to improve the analytic procedure in order to diagnose major errors in concept and design of kinetic
experiments. 相似文献
67.
Irina Vaseva Dessislava Todorova Jiří Malbeck Alena Trávníčková Ivana Macháčková 《Acta Physiologiae Plantarum》2008,30(2):151-155
Changes in cytokinin pool and cytokinin oxidase/dehydrogenase activity (CKX EC: 1.5.99.12) in response to increasing abscisic
acid (ABA) concentrations (0.5–10 μM) were assessed in the last fully expanded leaves and secondary roots of two pea (Pisum sativum) varieties with different vegetation periods. Certain organ diversity in CKX response to exogenous ABA was observed. Treatment
provoked altered cytokinin pool in the aboveground parts of both studied cultivars. Specific CKX activity was influenced significantly
basically in roots of the treated plants. Results suggest that ABA-mediated cytokinin pool changes are leaf-specific and involve
certain root signals in which CKX activity presents an important link. This enzymatic activity most probably regulates vascular
transport of active cytokinins from roots to shoots. 相似文献
68.
Alkaloid extracts from 12 plant species of the families Amaryllidaceae, Fumariacae and Papaveraceae were studied with respect to their acetylcholinesterase inhibitory activity and alkaloid patterns. Fifty-three alkaloids were identified by GC-MS, including known acetylcholinesterase (AChE) inhibitors such as galanthamine, epigalanthamine, sanguinine and epinorgalanthamine in extracts of Amaryllidaceae plants and protopine in extracts of Fumariaceae and Papaveraceae plants. The galanthamine-containing extracts of the amaryllidaceous plants were found to be the most active while the extract of Corydalis bulbosa was the most active among the extracts of the tested plants from the Fumariaceae and Papaveraceae plants. TLC bioautographic assay, preparative TLC and GC-MS analysis were combined to identify the active compounds in the studied extracts. Galanthamine was isolated from the known AChE inhibitors in the extracts of Amaryllidaceae plants. Corydaline, bulbocapnine and stylopine were found to be active in the extracts of plant species of the families Fumariaceae and Papaveraceae. Available standards of deshydrocorydaline--a precursor of corydaline, corydaline and stylopine--were tested for AChE inhibitory activity. Deshydrocorydaline and corydaline showed potent inhibitory activity comparable with that of the positive control galanthamine. 相似文献
69.
70.