CYTOPATHOGENICITY OF INFLUENZA VIRUS (H4 N3)

Monolayer tissue cultures of chicken embryo fibroblast ( CEF ) cells infected with avian influenza virus isolate were examined by the hematoxylie and eosin (H&E) staining and indirect immunoperoxidase test for studying the cytopathogenic effect of the virus. Cytopathological changes which occurred in the uncleus of infected cells included nuclear and nucleolar hypertropy, chromatin margination and intranuclear inclusions. The most striking cytoplasmic change were the presence of perinuclear. eosinophilic inclusions at 22-36 hours post inoculation ( p. i.). Vacuolization, and granulation were also observed. Indirect immunoperoxidase ( IP ) test demonstrated the localization of influenza virus antigens in infected cells. A positive peroxidase reaction observed in the nucleus and cytoplasm were similar to those shown hematoxyline and eosin staining.

Novel cytonuclear combinations modify Arabidopsis seed physiology and vigor

The influence of intraspecific variation in cytoplasmic genomes and cytonuclear interactions on key seed traits that can impact adaptation and agriculture has not been thoroughly explored, so far. Here, dormancy, germination performance and longevity of seeds have been assessed in Arabidopsis plants with novel cytonuclear combinations that disrupt coadaptation between natural variants of nuclear and cytoplasmic genomes. Although all three traits were affected by cytonuclear reshuffling, the sensitivity of seed traits to cytoplasmic change was dependent on the nuclear background. Both deleterious and, more surprisingly, favorable effects of novel cytonuclear combinations (in comparison with the nuclear parent) were observed, suggesting suboptimal genetic combinations exist in natural populations for these traits. Significant changes on dormancy and germination performance due to specific cytonuclear interacting combinations mainly occurred in opposite directions, in accordance with the previously proposed ‘dormancy continuum’. Consistently, reduced sensitivity to exogenous ABA and faster endogenous ABA decay during germination were observed in a novel cytonuclear combination that also exhibited enhanced longevity and better germination performance, compared to its natural nuclear parent. Cytoplasmic genomes, therefore, represent an additional resource of natural variation for breeding seed vigor traits.Issue sectionGrowth and developmentHighlightNatural variation in Arabidopsis organelles and cytonuclear interactions influence seed dormancy, longevity and germination performance. Enhanced seed vigor was obtained through the creation of novel cytonuclear combinations.

Cytoplasmic fine-structure

In any attempt to reach an integrated conception of the cytoplasm in variation and development, a study of the fine-structure of the cytoplasm and its relation to the nucleus must take its proper place. It is the object of our paper to survey, as adequately as we are able in a limited space, selected data on cytoplasmic fine-structure and we hope that this will provide the Discussion with a background against which to consider a morphological basis for that variation which genetical studies may show to be due to changes in the organization of the cytoplasm. It is possibly too early as yet to hope that examination of the morphology of cells by means of the electron microscope will reveal cytoplasmic differences between organisms which differ from one another in the characteristics studied in genetical experiments; it would be useful to the future study of the problem of Cytoplasmic change, however, to know within what limits speculation must be reasonably confined by the nature of the fine-structure of the cytoplasm. It is now becoming apparent that though cells of organisms widely separated phylogenetically have basic similarities, cellular specialization has led to some diversity in the fine-structure. In the first part of the paper we shall briefly consider the development of electron-microscope methods, e.g. the thin-sectioning procedures, which have made it possible to examine biological material at a resolution which allows comparatively small macromolecular units to be distinguished (10 to 50 Å); at the same time we shall emphasize the danger of overestimating the significance of the observations that have been made. In the second part we shall consider certain selected features of the cell in some detail; in view of the large body of literature on cell fine-structure that is now available (publications numbered over 100 during the last 6 months of 1956) no attempt will be made to review all the findings which have been published during the last few years. Rather we will consider, in general terms, the structure of each component, then compare the variations in structural form noted in different cell types and indicate where there is direct disagreement in the findings of various authorities.