Type-C particles in human tissues. I. Electron microscopic study of embryonic tissues in vivo and in vitro

Diagnostic virology using electron microscopic techniques

This chapter illustrates the development of the use of electron microscopy in viral diagnosis. The field covered is confined to medical viral diagnosis, but parallel developments have taken place in both veterinary and botanical fields and techniques derived from both these sources are also included where relevant. It is reported that the scanning transmission mode of operation, which can induce image contrast changes electronically, may enhance studies with unstained sections and perhaps facilitate thin section immune electron microscopy (IEM). The application of negative stain IEM has been particularly useful for the study of the antigenic nature of some of the newly discovered noncultivable viruses. Viral antigens can also be detected in thin sections of infected cells by IEM with suitably labeled specific antibodies. Confirmation of viral infection by electron microscopy on tissues originally processed for light microscopy is also frequently useful.

Analysis of family history data for evidence of non-Mendelian inheritance resulting from vertical transmission

A number of infections of man, as well as of other animal and plant species, are heavily dependent upon 'vertical transmission'--that is direct parent-to-progeny transfer--for their maintenance in host populations. Such vertical transmission may be considered as a form of inheritance. It is usually non-Mendelian. This paper discusses the implications of such inheritance for the distribution of disease in families. A method is described for making quantitative predictions of prevalence rates of infection and of disease within different classes of relatives of either infected or uninfected probands. It is pointed out that, whereas a maternal line excess is to be expected among relatives of positive probands, the opposite should be found in families of negative probands. Expected differences between maternal and paternal line prevalence rates of observable disease decline rapidly with distance of relationship from the proband, and are greatly reduced by diagnostic insensitivity (analogous to penetrance). The implications of this analytic method for the design of family history studies are discussed. Published data on familial breast cancer are reviewed, and found to show no evidence that this condition is associated with a non-integrated vertically transmitted agent.

Interactions between endogenous baboon type-C virus and oncogenic viruses. I. Syncytium induction and development of infectivity assay

Cells releasing the endogenous baboon virus (BV) can interact with human KC cells containing the Rous sarcoma virus (RSV) genome, resulting in cell fusion and syncytium formation. This interaction has been utilized in the development of a sensitive infectivity assay for BV. The titration pattern is of a one-hit type, demonstrating a linear relationship between virus concentration and number of syncytial plaques obtained in the KC co-cultivation assay. Endpoint titration comparisons indicate that the KC test is as sensitive as the immunofluorescence or the RNA-directed DNA-polymerase assays. Attempts to develop an XC test for BV failed, indicating that while BV can interact with the RSV genome it will do so in the human KC cells and not in the rat XC cells. Syncytia are also induced when KC cells are directly exposed to cell-free BV; however, a linear dose relationship is not obtained. When syncytium-positive KC cultures are passaged, the syncytia disappear and a chronic BV infection is established. These KC-BV cells then lose the ability to interact with either the endogenous cat RD-114 virus or the Mason-Pfizer virus which are known to form syncytia with KC cells.

Characterization of bromodeoxyuridine-induced endogenous guinea pig virus

An endogenous virus (GPV) was induced after 5-bromodeoxyuridine treatment of cultured guinea pig cells. Compared to Gross murine leukemia virus (G-MuLV) GPV has a reproducibly heterogenous density of about 1.16 to 1.18 g/ml. The virion-associated RNA is slightly larger than that in G-MuLV. Sodium dodecyl sulfate-polyacrylamide gel electrophoretic analysis of dissociated GPV resolved five major structural proteins: I (molecular weight 70,000), II (molecular weight 36,000), III (molecular weight 24,000), IV (molecular weight 18,000), and V (molecular weight 16,000) which are similar to but distinct from G-MuLV proteins. Proteins I and II were demonstrated to be glycoproteins by incorporation of [(3)H]glucosamine. GPV and G-MuLV did not have any appreciable genetic homology or any common group-specific antigens when analyzed by immunodiffusion, radioimmunoassay, and indirect immunofluorescence. Morphogenesis of GPV also differed from that of a typical type C oncornavirus and proceeded via two pathways: (i) a majority of virus particles were formed in cytoplasmic vacuoles and were released after cellular disruption; and (ii) a minor population of particles were assembled in the cytoplasmic matrix and then migrated to the plasma membrane where they budded into the extracellular space. To date, GPV has been unable to initiate or maintain a productive replication in any cell line tested.

Observations of apparent C-type particles in baboon (Papio cynocephalus) placentas

Ultrastructural investigations have revealed the presence of apparent endogenously derived C-type particles in the placental villi of each of 13 baboons studied. Both budding and mature forms were observed in the syncytiotrophoblast of these animals at various stages of pregnancy.