Ograniczanie wyników

Czasopisma help
Autorzy help
Lata help
Preferencje help
Widoczny [Schowaj] Abstrakt
Liczba wyników

Znaleziono wyników: 23

Liczba wyników na stronie
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 2 Następna strona wyników Pięć stron wyników wprzód Ostatnia strona wyników

Wyniki wyszukiwania

Wyszukiwano:
w słowach kluczowych:  DNA fragmentation
help Sortuj według:

help Ogranicz wyniki do:
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 2 Następna strona wyników Pięć stron wyników wprzód Ostatnia strona wyników
There is still no clarity on whether the endonuclease incisions in apoptotic cells are induced randomly in the genome or induced in some preferable sites. In order to evaluate the intensity of DNA fragmentation in the chicken alpha-globin domain, AEV-virus transformed chicken erythroblasts (HD3) were incubated in a serum free medium, and their DNA was Southern blotted and hybridised with probes representing different fragments of the domain. Probes corresponding to the upstream areas of the domain mostly hybridised with high molecular weight DNA. Unlike these, the probe corresponding to the 2 Kb BamHI-BamHI fragment, containing the alphaA globin gene (B18), revealed a 5 Kb band on the hybridisation autoradiographs. The probe to the neighbouring upstream fragment did not reveal this band, but it was clearly seen on hybridisations with a downstream 1 Kb BamHI-BamHI fragment. The intensity of the band increased with overall apoptotic DNA degradation, hence its appearance should be coupled to apoptosis. Hybridisation of BamHI-digested DNA with B18 probe revealed a shortening of the 2 Kb band in preparations of DNA from apoptotic cells. The presumable positions of the cuts correspond to the formerly described DNase hypersensitive sites in the domain. Slot-blot and Northern hybridisation of RNA extracted from apoptotic HD3 cells revealed that the excision of the area of the B18 gene is coupled to a decrease in the intensity of alphaA globin gene transcription. Transcription of the non-erythroid NIK gene, transcribed in the upstream part of the domain, did not depend on the level of apoptotic DNA fragmentation.
The aim of the study was to investigate the competence of in vivo- and in vitro-derived pig expanded blastocysts by analysing DNA fragmentation using TUNEL. A total of 533 porcine expanded blastocysts were examined, and results were evaluated using Fisher’s test. Significant differences in the incidence of fragmented nuclei (detected by the TUNEL reaction) and all nuclei (detected by DAPI) were identified between in vivo- and in vitro-derived embryos at the expanded blastocyst stage. The total numbers of nuclei observed in in vivo-derived embryos were significantly different from those in in vitro-cultured embryos (89.1±13.4 and 47.7±25.1, respectively). TUNEL index in In vitro-cultured embryos (28.3%) was significantly higher (P<0.01) than in in vivo-derived blastocysts (4%). These findings indicate that in vivo- and in vitro-derived expanded blastocysts consisting of a small number of cells are characterized by a high incidence of DNA fragmentation. The total number of nuclei in in vivo- and in vitro-derived blastocysts correlated negatively with the number of TUNEL-positive nuclei (r = -0.51; P<0.0001) and the TUNEL index (r = -0.69; P<0.0001), whereas the number of TUNEL-positive nuclei was positively correlated with the TUNEL index (r = 0.95;P<0.0001). Moreover, significant differences were observed between embryos collected from individual experiments.
Intracerebral haematoma was produced in 25 adult rats by infusion of 100 µl of autologous blood into the striatum. The animals’ brains were removed at 1, 3, 7, 14 and 21 days after production of the haematoma. The TUNEL method was used to detect DNA fragmentation and TUNEL-positive cells were qualified. TUNEL-positive cells were already found on the first day of observation and were present for three weeks after haematoma production. These results provide evidence that programmed cell death is associated with intracerebral haemorrhage.
In this paper we are presenting a critical review of works demonstrating that at the early stages of apoptosis eukaryotic DNA is cleaved to large fragments the length of which is several tens of thousands of nucleotide pairs. Evidence is presented that this fragmentation proceeds in a specific fashion and that the character of the fragmentation reflects the general principle of eukaryotic genome organization into structural-functional domains.
The sequential generation of large-scale DNA fragments followed by internucleosomal chromatin fragmentation is a biochemical hallmark of apoptosis. One of the nucleases primarily responsible for genomic DNA fragmentation during apoptosis is called DNA Fragmentation Factor 40 (DFF40) or Caspase-activated DNase (CAD). DFF40/CAD is a magnesium-dependent endonuclease specific for double stranded DNA that generates double strand breaks with 3'-hydroxyl ends. DFF40/CAD is activated by caspase-3 that cuts the nuclease's inhibitor DFF45/ICAD. The nuclease preferentially attacks chromatin in the internucleosomal linker DNA. However, the nuclease hypersensitive sites can be detected and DFF40/CAD is potentially involved in large-scale DNA fragmentation as well. DFF40/CAD-mediated DNA fragmentation triggers chromatin condensation that is another hallmark of apoptosis.
Sequential cleavage of genomic DNA into large-scale DNA fragments of 50-300-kb, followed by formation of mono- and oligonucleosomal DNA fragments, is a biochemical hallmark of programmed, cell death (apoptosis). The endonuclease DFF40/CAD mediates regulated internucleosomal DNA fragmentation and chromatin condensation in cells undergoing apoptosis. DFF40 hypersensitive sites were detected in purified HeLa cell nuclei, and excision of 50-kb DNA fragments preceded formation of oligonucleosomal DNA ladders in nuclei treated with the nuclease. Topoisomerase II, but not topoisomerase I, stimulates DFF40 activity on plasmid DNA substrates. This suggests that interactions of DFF with the nuclear matrix-bound topoisomerase II may be involved in formation of DFF40 hypersensitive sites.
The present study was undertaken to investigate the effect of various concentrations of cobalamin (vitamin B₁₂) in Bioexcell® extender on the spermatozoa quality of Simmental bulls. The semen was collected from 12 bulls by means of an artificial vagina. Vitamin B₁₂ at concentrations of 1.50, 2.50, 3.50, and 5.00 mg/mL was added to bovine Bioexcell® extender. The semen aliquots were cooled and preserved at 4°C. Their quality was evaluated during pre-freezing, and then the cooled semen samples were packaged into 0.25 ml straws. The straws were frozen in the vapor of liquid nitrogen, and stored at -196ºC in a container. The straws were thawed one day later, and the characteristics of spermatozoa were examined. The results showed that the effect of vitamin B₁₂ on the viability, DNA fragmentation and motility of spermatozoa was significant under both pre- and post-freezing conditions (p <0.05), and revealed that supplementation of the extender with B₁₂ improved the post-thaw spermatozoa quality in bulls.
UVC-induced apoptotic symptoms such as morphological changes, DNA fragmentation, Bcl-2 and Bax protein expression were examined in primary splenocyte cultures from young (3 months) and old (24 months) rats. The activities of AP-1 and CRE transcription factors in UVC-irradiated splenocytes were also assessed. At 24 h after UVC irradiation 40% of cells derived from young rats were found to be apoptotic, which was twice as much as in splenocytes from old rats. Apoptosis in cells from old rats did not give typical symptoms like a DNA ladder and Bcl-2 protein downregulation, in contrast to splenocytes from young rats. No AP-1 transcription factor activity was found in UVC-irradiated splenocytes from old animals and only a trace activity in splenocytes from young animals. This indicates that, UVC-induced apoptosis in rat splenocytes is practically AP-1 independent and that cells from old rats are less sensitive to UVC irradiation than splenocytes from young rats.
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 2 Następna strona wyników Pięć stron wyników wprzód Ostatnia strona wyników
JavaScript jest wyłączony w Twojej przeglądarce internetowej. Włącz go, a następnie odśwież stronę, aby móc w pełni z niej korzystać.