Lytic to temperate switching of viral communities.

Microbial viruses can control host abundances via density-dependent lytic predator-prey dynamics. Less clear is how temperate viruses, which coexist and replicate with their host, influence microbial communities. Here we show that virus-like particles are relatively less abundant at high host densities. This suggests suppressed lysis where established models predict lytic dynamics are favoured. Meta-analysis of published viral and microbial densities showed that this trend was widespread in diverse ecosystems ranging from soil to freshwater to human lungs. Experimental manipulations showed viral densities more consistent with temperate than lytic life cycles at increasing microbial abundance. An analysis of 24 coral reef viromes showed a relative increase in the abundance of hallmark genes encoded by temperate viruses with increased microbial abundance. Based on these four lines of evidence, we propose the Piggyback-the-Winner model wherein temperate dynamics become increasingly important in ecosystems with high microbial densities; thus 'more microbes, fewer viruses'.

Association between imaging response and survival following neoadjuvant chemotherapy in patients with resectable colorectal liver metastases: A cohort study.

BACKGROUND: The association between the imaging response (structural or metabolic) to neoadjuvant chemotherapy (neoCT) before colorectal liver metastasis (CRLM) and survival is unclear. METHOD: A total of 201 patients underwent their first CRLM resection. A total of 94 (47%) patients were treated with neoCT. A multivariable, Cox proportional hazard regression analysis was performed to compare overall survival (OS) and progression-free survival (PFS) between response groups. RESULTS: Multivariable regression analysis of the CT/MRI (n = 94) group showed no difference in survival (OS and PFS) in patients who had stable disease/partial response (SD/PR) or complete response (CR) versus patients who had progressive disease (PD) (OS: HR, 0.36 (95% CI: 0.11-1.19) p = .094, HR, 0.78 (95% CI: 0.13-4.50) p = .780, respectively), (PFS: HR, 0.70 (95% CI: 0.36-1.35) p = .284, HR, 0.51 (0.18-1.45) p = .203, respectively). In the FDG-PET group (n = 60) there was no difference in the hazard of death for patients with SD/PR or CR versus patients with PD for OS or PFS except for the PFS in the small CR subgroup (OS: HR, 0.75 (95% CI: 0.11-4.88) p = .759, HR, 1.21 (95% CI: 0.15-9.43) p = .857), (PFS: HR, 0.34% (95% CI: 0.09-1.22), p = .097, HR, 0.17 (95% CI: 0.04-0.62) p = .008, respectively). CONCLUSION: There was no convincing evidence of association between imaging response to neoCT and survival following CRLM resection.

Comparison of Low Dose Recombinant Factor VIIa and 4-Factor Prothrombin Complex Concentrate for Treatment of Bleeding Related to Cardiac Surgery.

Background: Recombinant factor VIIa (rFVIIa) and prothrombin concentrate complex (PCC) are used for uncontrolled bleeding in cardiac surgery (CS), however, there are limited direct comparisons of these agents. Objective: To evaluate the efficacy and safety of rFVIIa and PCC in CS related bleeding. Methods: This retrospective study included adult CS patients who received either low dose rFVIIa (<30 mcg/kg) or 4-factor PCC. The primary outcome was transfusion requirements of packed red blood cells (pRBC) within 6 hours of factor administration. Secondary efficacy outcomes included transfusion requirements 0-18 hours, doses of additional factor product, thrombotic events, and acute kidney injury (AKI). Results: A total of 179 patients were included (n = 78 rFVIIa; n = 101 PCC). Of patients who received blood products, there was no difference in the requirement of pRBCs within 6 hours (73.8 vs 68.9%, P = .5359) or in the median amount of pRBC transfused (500 mL vs 640 mL, P = .0723) in the rFVIIa and PCC groups respectively. Patients in the PCC group were more likely to require additional factor products (24.4% vs 47.5%, P = .0015), develop AKI (12.8% vs 25.7%, P = .0325), have longer ICU lengths of stay [2 (IQR 1-5) vs 4 (IQR 2-6), P = .0487] and greater in-hospital mortality (2.6% vs 10.9%, P = .033). There was no difference in thrombotic events. Conclusion: Although, there was no difference in pRBC transfusion requirements between PCC and rFVIIa, more patients in the PCC group required additional factor products and had increased adverse effects. Further comparisons of PCC and rFVIIa are warranted.

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.

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).

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.

Simian virus 40 (SV40)-transgenic mice that develop tumors are specifically tolerant to SV40 T antigen.

The ability to mount an immune response to simian virus 40 (SV40) T antigen was evaluated using mice from two distinct SV40 transgenic lines derived from injection of the same gene construct. Our studies demonstrate functional immune tolerance to SV40 T antigen in a SV40 transgenic line that consistently develops tumors of the choroid plexus by 7 mo of age. Antibodies to SV40 T antigen are undetectable in the serum of these animals; furthermore, mice from this line are unable to generate SV40-specific CTL after primary or secondary immunization with the virus, although they mount a normal CTL response to vaccinia virus when appropriately immunized. In contrast, we find that mice from a second transgenic line of low tumor incidence can mount a humoral response to SV40 T antigen, and upon immunization they generally respond with a vigorous cytotoxic T cell response to SV40 T antigen. These data suggest that specific immune tolerance to the product of an integrated viral oncogene may be induced, and is likely a reflection of the time in development at which the gene product first appears. Immune tolerance or responsiveness to the endogenous oncogene product may in turn play a role in the tumorigenic potential of such genes.

Complement-mediated antiserum cytotoxic reactions to human chromosome 7 coded antigen(s): immunoselection of rearranged human chromosome 7 in human-mouse somatic cell hybrids.

Immunoselection via complement-dependent lysis of human-mouse somatic cell hybrids containing chromosome 7, with antisera reactive to cell surface antigen(s) coded for by chromosome 7, has resulted in growth of somatic cell hybrids containing rearranged human chromosome 7s. Investigation of these hybrids has localized the gene(s) coding for the relevant cell surface antigen(s) to the short arm of human chromosome 7. The simian virus 40 integration site and the gene coding for human beta-glucuronidase appear to be localized to the long arm of chromosome 7 in this hybrid clone.

Drosophila singed, a fascin homolog, is required for actin bundle formation during oogenesis and bristle extension.

Drosophila singed mutants were named for their gnarled bristle phenotype but severe alleles are also female sterile. Recently, singed protein was shown to have 35% peptide identity with echinoderm fascin. Fascin is found in actin filament bundles in microvilli of sea urchin eggs and in filopodial extensions in coelomocytes. We show that Drosophila singed is required for actin filament bundle formation in the cytoplasm of nurse cells during oogenesis; in severe mutants, the absence of cytoplasmic actin filament bundles allows nurse cell nuclei to lodge in ring canals and block nurse cell cytoplasm transport. Singed is also required for organized actin filament bundle formation in the cellular extension that forms a bristle; in severe mutants, the small disorganized actin filament bundles lack structural integrity and allow bristles to bend and branch during extension. Singed protein is also expressed in migratory cells of the developing egg chamber and in the socket cell of the developing bristle, but no defect is observed in these cells in singed mutants. Purified, bacterially expressed singed protein bundles actin filaments in vitro with the same stoichiometry reported for purified sea urchin fascin. Singed-saturated actin bundles have a molar ratio of singed/actin of approximately 1:4.3 and a transverse cross-banding pattern of 12 nm seen using electron microscopy. Our results suggest that singed protein is required for actin filament bundle formation and is a Drosophila homolog of echinoderm fascin.

The use of flow microbluorimetry in the analysis of the phenotype expression of mouse histocompatibility antigens.

Quantitation of the expression of cell surface antigens has hitherto been limited to analysis by either cytotoxicity tests or radioimmune assays (5, 15). We report here the use of a new methodology to analyze and quantitate the expression of mouse histocompabililty antigens (H-2 locus) in hybrid clones and parental cell types. The binding of fluorescein-tagged antibody is measured on a cell-to-cell basis in large viable cell populations using flow microfluorimetric techniques. These techniques have been used to measure hapten and immunoglobulin binding to lymphocyte populations (8, 9, 14). However, this is the first report in which these techniques have been used to examine the expression of the H-2 locus. The advantage of this approach is twofold: first, a large and statistically significant sample population may be analyzed one cell at a time, thus revealing the fine detail of heterogeneity in the expression of the cell surface markers within a population. Second, as has been demonstrated for analysis of specific components of the immune system, this method does permit fluorescence-activated sorting of cell types according to their different surface populations (8, 9, 14).

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.

Biosynthesis and processing of a human precursor complement protein, pro-C3, in a hepatoma-derived cell line.

A 180,000-dalton single-chain molecule (human pro-C3) is the precursor of the third component of human complement (C3), a disulfide-linked two-chain protein. The pro-C3 is converted by limited proteolysis to C3. The relationship between pro-C3 and C3 was established with the use of Hep G2, a cell line derived from a human hepatocellular carcinoma, which synthesizes at least 17 plasma proteins.

Metastatic hibernomas in transgenic mice expressing an alpha-amylase-SV40 T antigen hybrid gene.

Mice transgenic for a hybrid gene containing the liver promoter of the mouse amylase gene (Amy-1a) fused to the SV40 tumor antigen coding region unexpected developed malignant brown adipose tissue tumors (malignant hibernomas). Expression of the alpha-amylase gene had previously been thought to be confined to the liver parotid, and pancreas; however, analysis of white and brown adipose tissue from nontransgenic mice revealed expression of the endogenous Amy-1a gene in these tissues. Gene constructs driven by the Amy-1a liver promoter thus provide a means of targeting gene expression to the adipocyte cell lineage in transgenic mice. Moreover the high frequency of metastases in the liver, lungs, spleen, heart, and adrenals of these mice provides an experimental system in which to study the development of disseminated malignancy.

Less absorbed solar energy and more internal heat for Jupiter.

The radiant energy budget and internal heat are fundamental properties of giant planets, but precise determination of these properties remains a challenge. Here, we report measurements of Jupiter's radiant energy budget and internal heat based on Cassini multi-instrument observations. Our findings reveal that Jupiter's Bond albedo and internal heat, 0.503 ± 0.012 and 7.485 ± 0.160 W m-2 respectively, are significantly larger than 0.343 ± 0.032 and 5.444 ± 0.425 Wm-2, the previous best estimates. The new results help constrain and improve the current evolutionary theories and models for Jupiter. Furthermore, the significant wavelength dependency of Jupiter's albedo implies that the radiant energy budgets and internal heat of the other giant planets in our solar system should be re-examined. Finally, the data sets of Jupiter's characteristics of reflective solar spectral irradiance provide an observational basis for the models of giant exoplanets.

The specialized cytoskeleton of the Drosophila egg chamber.

The Drosophila egg chamber is emerging as a uniquely versatile system for studying cytoskeletal rearrangements during development. Initial determination of the oocyte fate and subsequent growth of the oocyte depend on a series of highly coordinated changes in cell architecture. Homologs or relatives of many known cytoskeletal proteins play key roles in these events.

Complement biosynthesis by the human hepatoma-derived cell line HepG2.

The human hepatoma-derived cell line, HepG2, synthesized and secreted functional complement proteins C1r, C1s, C2, C3, C4, C5, factor B, C1 inhibitor, C3b inactivator, a small amount of C6, and trace amounts of C8; but failed to produce detectable C1q, C7, or C9. Immunochemically, C2, C3, C4, C5, and B were isolated from culture medium as proteins with molecular sizes and subunit structures identical to the corresponding components isolated from serum. C2 and factor B from cellular lysates had slightly lower molecular weights than the corresponding proteins in culture medium. C3, C4, and C5 were detected as single chain precursor molecules in cellular lysates. These results demonstrate that human C5, like C3 and C4, is synthesized as a single chain precursor that is converted by limited proteolysis to the native two-chain molecule. It also establishes the precursor-product relationship for human pro-C4 and native C4, pro-C5, and native C5.

Biosynthesis and glycosylation of the epidermal growth factor receptor in human tumor-derived cell lines A431 and Hep 3B.

Biosynthesis of the receptor for epidermal growth factor was investigated in two human tumor-derived cell lines, Hep 3B and A431. When grown in the presence of tunicamycin, both cells expressed a receptor-related species p135, the presumptive aglycosylated form of the biosynthetic precursor, gp145, of the mature form of the receptor, gp165, expressed at the cell surface. Two additional receptor-related species, p115 and p70, were detected when A431, but not Hep 3B, cells were treated with tunicamycin. Furthermore, digestion of the A431 receptor-related proteins with endoglycosidase F resulted in the detection of these three aglycosylated species. P70 appears to be the aglycosylated form of gp95, the presumptive intracellular precursor of the receptor-related species gp120 that is secreted by A431 but not Hep 3B cells; gp120 has a complex pattern of N-linked glycosylation, with consequent molecular weight and charge heterogeneity. P115 may be the aglycosylated form of a third biosynthetic intermediate, possibly a gp135 species detected in the early time points of pulse-chase labeling. Alternatively, p115 and gp135 may be derived co- or post-translationally by Ca2+-mediated proteolysis from p135 and gp145, respectively. The implications of the complexity of the biosynthesis of this molecule with regard to the multiple opportunities it affords the cell to modulate cell proliferation are discussed.

Expression and biosynthetic variation of the epidermal growth factor receptor in human hepatocellular carcinoma-derived cell lines.

Expression of the epidermal growth factor (EGF) was analyzed in six human hepatocellular carcinoma-derived and one human hepatoblastoma-derived cell line, each of which retained the differentiated phenotype and functions of the parenchymal hepatocyte. The level of receptor expression of each hepatoma cell line was similar to that of the normal human fibroblast, approximately 10(5) molecules per cell. However, NPLC/PRF/5, a subline of the PLC/PRF/5 cell line obtained following reestablishment of a xenograft tumor in vitro, was found to express 4 x 10(6) high-affinity EGF receptor molecules per cell. Proliferation of the NPLC/PRF/5 cell line was inhibited in the presence of nanomolar quantities of ligand. Receptor overexpression was found to result from EGF receptor gene amplification without apparent rearrangement of the EGF receptor coding sequences. Although cell-specific variability in posttranslational processing of EGF receptor N-linked oligosaccharides in the hepatoma cell lines was found, no difference between the receptors in PLC/PRF/5 and NPLC/PRF/5 was observed and no aberrant receptor-related species were detected. EGF receptor gene amplification in the NPLC/PRF/5 cell line is probably a reflection of genome instability and selection of variants with augmented growth potential in limiting concentrations of EGF in vivo. When viewed in this light, EGF receptor overexpression could represent a manifestation of tumor progression in the EGF-responsive hepatocyte.