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Biomedical subjects

A Demsey

Publications and source records attributed to A Demsey.

16 recordsLinked to original sources
PubMed1984

Multiple antigens related to the major envelope glycoprotein of murine leukemia virus expressed on B16 melanoma cells as targets of host immune response.

Reactivity of B16 melanoma cell surface proteins with antisera to the major envelope glycoprotein, gp70, of murine leukemia viruses was assessed by radioimmunoprecipitation and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Surface proteins from cultured monolayers of the B16 melanoma and variant lines B16-F1, B16-F1(1r6), B16-F10, and B16-F10(1r6), and from purified B16 melanoma tumor cells, contained three glycosylated components specifically reactive with gp70 antisera, with apparent molecular weights of 70,000, 80,000, and 85,000 (B16-gp70, B16-gp80, and B16-gp85). Antisera raised in syngeneic C57BL/6 mice by immunizing with X-irradiated B16, B16-F10, or B16-F10(1r6) cells immunoprecipitated only solubilized B16-gp70, B16-gp80, and B16-gp85. Absorption of mouse antiserum to B16-gp70/80/85 antigens with purified viruses from various sources indicated that antigens on all three molecules were related to endogenous AKR-type murine leukemia virus antigens. Mice hyperimmunized against melanoma cells were challenged subcutaneously with 4 X 10(4), 10(5), or 2.5 X 10(5) viable B16 or B16-F10 cells, inocula that were lethal and nonmetastatic in unimmunized mice. The lowest cell dose was rejected by 90% of immunized mice. Tumors grew in an average of 58% of immunized mice challenged with 10(5) cells, pulmonary metastases occurring in 61% of those mice. Inocula of 2.5 X 10(5) cells grew in all immunized mice, with a 60% incidence of metastasis. These studies indicate that host immunity to B16-gp70/80/85 antigens can either inhibit or stimulate B16 melanoma tumor progression.

Animals↗
PubMed1983

Reexamination of the morphogenetic block of a putative late-stage, temperature-sensitive mutant of Moloney murine leukemia virus.

The ts3 temperature-sensitive mutant of Moloney murine leukemia virus has been reported to have a morphogenetic block in a late stage of the budding process. As evidence, previously published electron micrographs of cells maintained at the nonpermissive temperature (39 degrees C) revealed numerous budding virions on the cell surface. However, it appears now that these micrographs reflected budding that occurred not at 39 degrees C, but after cells were removed from the incubator before fixation. The morphogenesis of ts3 is actually blocked at an earlier stage of development.

Microbiological Techniques↗
PubMed1980

Structure of and alterations to defective murine sarcoma virus particles lacking envelope proteins and core polyprotein cleavage.

HTG2 hamster cells produce a defective murine sarcoma virus lacking gp70 and, consequently, viral surface projections (knobs), but the lack of knobs appears to have no effect on intramembrane particle distribution. In addition, it has been noted that the core of the virus remains in the "immature" form as a result of the failure of the polyprotein precursor (p65) to undergo cleavage. However, incubation of HTG2 virus with avian myoblastosis virus was found to yield specific cleavage products of p65.

Animals↗
PubMed1977

Application of freeze-drying intact cells to studies of murine oncornavirus morphogenesis.

Using a method for freeze-drying intact cells, uninfected and murine leukemia virus (MuLV)-infected JLSV9 cell surfaces, as well as murine mammary tumor virus (MuMTV)-infected cell surfaces, were examined by electron microscopy. The 10-nm knobs of MuLV and the 5-nm spikes of MuMTV were clearly revealed on the surfaces of budding viruses and were also found dispersed over the cell surface. The MuLV knobs are randomly arranged on the virus surface, whereas the MuMTV spikes are much more ordered. Because freeze-fractured budding viral envelopes are devoid of intramembranous particles, the observed surface particles do not appear to be merely accentuated intramembranous particles. This technique should permit further analysis of the morphogenesis of viral envelopes without the need for externally applied labels.

Cell Line↗
PubMed1976

Characteristics of a surface-adherent subline derived from Friend erythroleukemia cells in continuous suspension culture.

A surface-adherent cell population developed spontaneously from Friend erythroleukemia cells (FLC745) which previously had grown continuously in suspension cultures. The adherent cells have been transferred through more than 60 passages and apparently represent a stable variant, herein designated FLC745-Ad. The cell size, chromosome complement, and tumorigenicity in DBA/2 mice were similar to the parental FLC745 line, although the FLC745-Ad cultures grew at a slightly slower rate and synthesized less hemoglobin in response to dimethyl sulfoxide. Production of C-type particles was abundant in both suspension and adherent cells, but the latter appeared to contain more intracisternal A-type particles. Scanning electron microscopy disclosed that most adherent cells were globoid and nonspreading. They attached to the substrate by a circumferential lamellar skirt of unusual breadth. Adhesion of the FLC745-Ad cells was not influenced by serum concentration, trypsinization, 5-bromodeoxyuridine, or N6, O2'-dibutyryl adenosine 3':5'-monophosphate. Treatment with cytochalasin B increased the cell size and the area of cell attachment.

Animals↗
PubMed1975

Morphological, chemical, and antigenic organization of mammalian C-type viruses.

New features in the architecture of mammalian type C viruses, in particular knoblike surface projections and hexagonally arranged subunits on the core shell could be demonstrated by electron microscopy, taking advantage of newly developed preparation techniques. As examples, murine leukemia viruses (MuLVs) and newly isolated porcine and bovine C viruses are presented. The major proteins of a MuLV were isolated and partially characterized in chemical terms and with respect to their serological and other biological activities, such as interfering and hemagglutinating (HA) capacity. Most of the characterized proteins could be localized in particular substructures of the virion either by selective removal or isolation of electron microscopically identifiable constituents. The information obtained allowed the design of a more detailed model of mammalian C viruses. Special attention was devoted to the further characterization of interspecies antigens of mammalian C viruses. Different antigenic determinants were revealed. Their distribution allows further subgrouping of mammalian C viruses.

AKR murine leukemia virus↗