“…Attempts have been made in the discussion to reconcile these findings with previous estimates of the liberation period and to integrate them with histologic observations and electron micrographs of thin sections of infected allantoic membranes having a bearing on the mode of liberation.…”
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“…It was found that the membranes always contained relatively more non-infectious hemagglutinins (NIHA) than the media and, correspondingly, the ratios between infectious virus and hemagglutinin units (ID(50)/HA) in the tissues were up to 1.5 log(10) units lower than in the liberated progeny. These differences were seen not only following inoculation of undiluted ST, ΔST, and UP seeds, the progenies of which always contain considerable proportions of NIHA, but also when dilute ST inocula were employed which lead to the liberation of only infectious virus. …”
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“…Thereafter, a sharp rise in infectivity occurs 2 to 3 hours before liberation of the new generations of active virus into the allantoic fluid can be detected. …”
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“…Growth curves in intact chick embryos or in deembryonated eggs (differential yields) revealed that non-infectious hemagglutinins appeared in the tissues or were liberated therefrom as soon as any virus activity became detectable. …”
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“…The value of the technic is demonstrated by the fact that liberation of virus from infected cells can be detected earlier than in the intact egg. …”
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“…The influenza A and swine influenza strains showed constant periods of 5 to 6 hours before newly formed virus was liberated from the infected cells, whereas 8 to 10 hours elapsed in the case of the influenza B strains. …”
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“…With undiluted infected allantoic fluid as seed only 4 to 5 hours elapsed before new generations of virus were liberated. With increasing 10-fold dilution of the seed the constant period became increasingly longer until it stabilized at 8 to 10 hours. …”
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“…Following injection of various types of seeds NIHA appeared in the allantoic fluids as soon as liberation of virus became detectable. This time relationship and the rates of release of non-infectious virus components seemed to exclude that the NIHA obtained consisted entirely of infectious virus which had been inactivated during incubation in ovo. …”
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“…Cells from persistently infected cultures, which are free of infectious virus at the time of transfer, failed to liberate virus at a later time during incubation periods of up to 4 weeks. …”
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