PubMed Health⌕ Search

Biomedical subjects

B B Knowles

Publications and source records attributed to B B Knowles.

At least 127 records · Page 7Linked to original sources
PubMed1981

Integration pattern of hepatitis B virus DNA sequences in human hepatoma cell lines.

Four human hepatoma cell lines established from primary hepatocellular carcinomas were examined for the presence of hepatitis B virus DNA sequences. Reassociation kinetic analysis indicated that the cell lines HEp-3B 217, HEp-3B 14, HEp-3B F1, and PLC/PRF/5 contained two, one, one, and four genome equivalents per cell, respectively. Southern blot hybridization analysis demonstrated that hepatitis B virus DNA was integrated into the cellular DNAs of these cell lines. Further liquid hybridization studies with 32P-labeled HincII restriction fragments of hepatitis B virus DNA established that DNA sequences from all regions of the HBV genome were represented in the integrated viral sequences. Although the three HEp-3B cell lines were derived from the same tumor, they differed significantly in their patterns of integration of hepatitis B virus DNA, the number of copies of viral DNA per cell, and their ability to produce the virus-coded surface antigen.

Carcinoma, Hepatocellular↗
PubMed1981

A murine stage-specific embryonic antigen (SSEA-2) is expressed on some murine SV40-transformed cells.

A stage-specific embryonic antigen-2 (SSEA-2) found on murine preimplantation embryos is maximally expressed on 4- to 8-cell stage embryos and is present in decreasing amounts of morulae and blastocysts. This antigenic determinant is also expressed on murine teratocarcinoma cells, sperm, and some, but not all, SV40-transformed mouse cell lines. Analysis of solubilized immunoprecipitates by SDS-gel electrophoresis indicates that this cell surface molecule is not the 54,000 m.w. protein shared by teratocarcinoma and SV40-transformed cell lines.

Absorption↗
PubMed1980

Expression of H-2, laminin and SV40 T and TASA on differentiation of transformed murine teratocarcinoma cells.

Murine embryonal carcinoma cells (ECCs) do not express antigens of the major histocompatibility complex (H-2), but do express cell-surface molecules shared with early embryos. ECCs are also characterized by their insusceptibility to infection by various oncogenic viruses, and their ability to differentiate into a variety of adult cell types. Differentiation of ECCs in vitro can occur spontaneously or can be induced. On exposure to retinoic acid the ECC line F9 (ref. 13) differentiates into cells which have the characteristics of parietal endoderm. When ECCs are exposed to simian virus 40 (SV40), the SV40 tumour (T) antigen is not expressed, although the virus genome reaches the nucleus, and a primary transcript of the SV40 A gene is made. However, following exposure to retinoic acid, the differentiated cells, like most mouse somatic cells, are susceptible to SV40 abortive infection and synthesize large T and small t antigens. To monitor the molecular events associated with the expression of the SV40 A gene on differentiation, we have constructed an ECC line (F9 12-1) containing a single integrated copy of the SV40 genome. This was accomplished by introducing a recombinant plasmid consisting of pBR322 linked to the herpes simplex type 1 thymidine kinase gene and SV40 genome into a thymidine kinase-deficient F9 cell line. We report here that in F9 12-1 cells exposed to retinoic acid, synthesis of the SV40 A gene product(s), T and tumour-associated specific antigens (TASA), parallels the appearance of the normal hallmarks of differentiation in this cell line, H-2 antigens and the basement membrane protein laminin.

Animals↗
PubMed1980

A comparative study of eight cell lines derived from human testicular teratocarcinoma.

Eight independent cell lines, derived from human testicular germ-cell tumors, were examined for the expression of various markers. These included major histocompatibility and embryonic antigens, chorionic gonadotropin, alpha fetoprotein, alkaline phosphatase, plasminogen activator, and infectivity by SV40. No line consisted primarily of choriocarcinoma or yolk sac cells, but several contained cells resembling murine embryonal carcinoma; some of these lines formed tumors with the distinctive features of embryonal carcinoma when injected into immunosuppressed animals. It is proposed that human embryonal carcinoma cells, unlike those of the mouse, correspond to a preblastocyst stage of development.

Alkaline Phosphatase↗
PubMed1980

Human hepatocellular carcinoma cell lines secrete the major plasma proteins and hepatitis B surface antigen.

Analysis of the cell culture fluid from two new human hepatoma-derived cell lines reveals that 17 of the major human plasma proteins are synthesized and secreted by these cells. One of these cell lines, Hep 3B, also produces the two major polypeptides of the hepatitis B virus surface antigen. When Hep 3B in injected into athymic mice, metastatic hepatocellular carcinomas appear. These cell lines provide experimental models for investigation of plasma protein biosynthesis and the relation of the hepatitis B viru genome to tumorigenicity.

Blood Proteins↗
PubMed1980

Independent regulation of H-2K and H-2D gene expression in murine teratocarcinoma somatic cell hybrids.

Cells of two teratocarcinoma stem cell lines (PCC4 azaguanine [aza] 1 and F9 5-bromodeoxyuridine [BrdU]) were fused with normal mouse spleen cells and mouse thymoma-derived cells (BW 5147), respectively. Hybrid clones were tested for the expression of molecules coded by the H-2K and -2D genes both by absorption analysis of conventional H-2 sera and by indirect antibody-binding radioimmunoassay with monoclonal antibodies. Somatic cell hybrids between PCC4 aza 1 and spleen cells morphologically resemble teratocarcinoma stem cells and do not express H-2 antigens. However, after differentiation in vitro, one of these hybrid clones expresses the H-2K and -2D gene products of both parental cell lines, one close expresses H-2-D- but not H-2K-coded antigenic determinants, and one clone remains H-2 negative. Somatic cell hybrids between F9 BrdU and BW 5147 resemble fibroblasts. Analysis of a series of hybrid clones revealed some clones that express both the H-2K- and H-2D-coded antigenic specificities of both parental alleles, some that express H-2D gene products strongly and the H-2K gene products very weakly, and some that express H-2D- but not H-2K-coded molecules. These results imply independent regulation of expression of the H-2K and -2D genes. The H-2D gene products appear to be preferentially expressed if the hybrid cells are capable of expressing H-2. The results suggest complex regulatory mechanisms that are H-2K and H-2D specific.

Animals↗
PubMed1980

Metabolic activation of benzo[a]pyrene by a human hepatoma cell line.

The liver-derived human cell line, Hep G2, has high benzo[a]pyrene-metabolizing activity and converts benzo[a]pyrene to intermediates that are mutagenic and that bind to DNA. This cell line will be useful for studying metabolic activation of polycyclic aromatic hydrocarbons and other xenobiotics by human tissue and as an activation system in short-term screening assays for identifying compounds with carcinogenic potential for humans.

Animals↗
PubMed1980

Preferential H-2 association in cytotoxic T cell responses to SV40 tumor-associated specific antigens.

The primary cytotoxic T lymphocyte (CTL) response to the SV40 tumor-associated specific antigen (TASA) has been analyzed in H-2 recombinant mice of the H-2b,d,f,k,q,and s haplotypes, in F1 hybrid mice (of each combination of these six independent haplotypes), and in intra-H-2 recombinant mice. A gradation of responsiveness to SV40 TASA in association with the various H-2 K/D alleles is reported. A weak response is found in association with the H-2 Dd allele, which is strongly affected by the responder status in association with the other H-2 K/D region determinants of the immunized host. Analysis of CTL from F1 mice, after secondary in vitro restimulation with SV40-transformed cells from either parental strain, indicates that in vivo priming to SV40 TASA in association with each K/D associative allele does occur, although efficient CTL are found only in association with specific H-2 K/D determinants after primary immunization. Mechanisms to explain host control of the ability to generate effector T cells to the TASA of this oncogenic virus are discussed.

Alleles↗
PubMed1979

Controlled synthesis of HBsAg in a differentiated human liver carcinoma-derived cell line.

A significant aspect of primary hepatic carcinoma in man is the high positive correlation of hepatocellular carcinoma with infection with hepatitis B virus (HBV)1. Analysis of the relationship between HBV infection and oncogenesis is difficult because natural infection with HBV is limited to man and experimental infection has been achieved only in chimpanzees and gibbons. Furthermore, because HBV has not been successfully propagated in cell culture, basic study of virus-cell interaction of the aetiological agent of one of the most widespread infections of man has been impossible. Recently, however, a cell line (PLC/PRF/5) derived from a human hepatoma biopsy was described which produces the HRV surface antigen (HBsAg) and so provides a tool for the experimental investigation of HBV in viro. We now report the derivation and characterisation of two additional cell lines primary liver carcinomas. In contrast to the PLC/PRF/5 cell line, these cell lines retain the capacity to synthesise many human plasma proteins, including both albumin and alpha-fetoprotein (AFP). One of these lines also produces BHsAg. We also present evidence that HBsAg synthesis and secretion in this cell line are correlated with the growth state of the culture. This finding is in contrast to the continuous HBsAg production found in the PLC/PRF/5 cell line.

Albumins↗
PubMed1978

Cytotoxic T-cell responses in mice infected with influenza and vaccinia viruses vary in magnitude with H-2 genotype.

Secondary effector T-cell populations generated by cross-priming with heterologous influenza A viruses operate only in H-2K or H-2D compatible situations, when assayed on SV40-transformed target cells infected with a range of influenza A viruses. The H2-Kb allele is associated with a total failure in the generation of influenza-immune cytotoxic T cells, though this is not seen for the primary response to vaccinia virus. In both influenza and vaccinia development of effector T cells operating at H-2Db is greatly depressed in B10.A(2R) (kkkddb) and B10.A(4R) (kkbbbb), but not in B10 (bbbbbb), mice. However, there is no defect in viral antigen expression at either H-2Kk or H-2Db in B10.A(2R) target cells. This apparently reflects some inadequacy in the stimulator environment, as (A/J X B6) F1 T cells can be induced to respond at H-2Db when exposed to vaccinia virus in an irradiated B6 but not in a B10.A(4R) recipient. The present report, together with the accompanying paper by Zinkernagel and colleagues, records the first rigorous demonstration of both a nonresponder situation and a probable Ir-gene effect for conventional infectious viruses. Possible implications for the evolution of H-2 polymorphism and mechanisms of Ir gene function are discussed.

Animals↗
PubMed1978

Anti-viral activity induced by culturing lymphocytes with tumor-derived or virus-transformed cells. Identification of the anti-viral activity as interferon and characterization of the human effector lymphocyte subpopulation.

A viral inhibitor(s) is released in the supernate of mixed cultures containing human or mouse lymphocytes and cells from certain lines. The inhibitor is active against a variety of unrelated viruses and is a protein that is not toxic for cells. It does not inactivate viruses directly, but inhibits viral replication through an intracellular mechanism that involves synthesis by the cells of both RNA and protein. These characteristics identify the inhibitor as an interferon. The anti-viral activity is contained in at least two molecular species, of approximately 25,000 and 45,000 daltons, respectively. In addition to the anti-viral activity, the supernates of the mixed cultures display an anti-cellular activity, the inhibition of DNA synthesis and of cell multiplication. The anti-viral and the anti-cellular activities are positively correlated in supernates from various cultures and in partially purified preparations. The human cell population responsible for interferon production is composed mainly of Fc-receptor positive, surface immunoglobulin negative, non-T-cell lymphocytes. The ability of certain cell lines to induce interferon seems to be preferentially associated with tumor origin or with in vitro transformation by certain viruses (Epstein-Barr virus, murine sarcoma virus).

Animals↗