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111.
Background
DNA adenine methyltransferase (Dam) activity is absent in many, but not all, disease isolates of Neisseria meningitidis, as a consequence of the insertion of a restriction endonuclease-encoding gene, the 'dam replacing gene' (drg) at the dam locus. Here, we report the results of a survey to assess the prevalence of drg in a globally representative panel of disease-associated meningococci. 相似文献112.
Equine arteritis virus (EAV) induces apoptosis in infected cells. Cell death caused by EAV has been studied mainly using three cell lines, BHK-21, RK-13 and Vero cells. The mechanism of apoptosis varies among cell lines and results cannot be correlated owing to differences in EAV strains used. We evaluated different markers for apoptosis in BHK-21, RK-13 and Vero cell lines using the Bucyrus EAV reference strain. Acridine orange/ethidium bromide staining revealed morphological changes in infected cells, while flow cytometry indicated the extent of apoptosis. We also observed DNA fragmentation, but the DNA ladder was detected at different times post-infection depending on the cell line, i.e., 48, 72 and 96 h post-infection in RK-13, Vero and BHK-21 cells, respectively. Measurement of viral titers obtained with each cell line indicated that apoptosis causes interference with viral replication and therefore decreased viral titers. As an unequivocal marker of apoptosis, we measured the expression of caspase-3 and caspases-8 and -9 as extrinsic and intrinsic markers of apoptosis pathways, respectively. Caspase-8 in BHK-21 cells was the only protease that was not detected at any of the times assayed. We found that Bucyrus EAV strain exhibited a distinctive apoptosis pathway depending on the cell line. 相似文献
113.
Voskamp KE; Noorman N; Mastebroek HA; Van Schoot NE; Den Otter CJ 《Chemical senses》1998,23(5):521-530
Spike trains from individual antennal olfactory cells of tsetse flies
(Glossina spp.) obtained during steady-state conditions (spontaneous as
well as during stimulation with 1-octen-3-ol) and dynamic stimulation with
repetitive pulses of 1-octen-3-ol were investigated by studying the spike
frequency and the temporal structure of the trains. In general, stimulation
changes the intensity of the spike activity but leaves the underlying
stochastic structure unaffected. This structure turns out to be a renewal
process. The only independently varying parameter in this process is the
mean interspike interval length, suggesting that olfactory cells of tsetse
flies may transmit information via a frequency coding. In spike records
with high firing rates, however, the stationary records had significant
negative first- order serial correlation coefficients and were non-renewal.
Some cells in this study were capable of precisely encoding the onset of
the odour pulses at frequencies up to at least 3 Hz. Cells with a rapid
return to pre-stimulus activity at the end of stimulation responded more
adequately to pulsed stimuli than cells with a long increased spike
frequency. While short-firing cells process information via a frequency
code, long-firing cells responded with two distinctive phases: a phasic,
non-renewal response and a tonic, renewal response which may function as a
memory of previous stimulations.
相似文献
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