| guanylate cyclase and cyclic guanosine 3':5'-monophosphate phosphodiesterase activities and cyclic guanosine 3':5'-monophosphate levels in normal and transformed fibroblasts in culture. | to investigate the role of guanosine 3':5'-monophosphate (cyclic gmp) in cultured cells we have measured guanylate cyclase and cyclic gmp phosphodiesterase activities and cyclic gmp levels in normal and transformed fibroblastic cells. guanylate cyclase activity is found almost exclusively in the particulate fraction of normal rat kidney (nrk) and balb 3t3 cells. enzyme activity is stimulated 3- to 10-fold by treatment with the detergent lubrol px. however, enhancement of guanylate cyclase by fib ... | 1976 | 4444 |
| the role of thymus subpopulations in "t" leukemia development. | | 1976 | 6155 |
| membrane receptors for murine leukemia viruses: characterization using the purified viral envelope glycoprotein, gp71. | the 71,000 dalton glycoprotein (gp71) purified from rauscher murine leukemia virus (r-mulv) by affinity chromatography specifically binds to murine but not other mammalian cells in culture. binding is prevented by specific antiserum raides to gp71 (anti-gp71). the binding assay as described in this report can detect receptors on as few as 300 murine cells, and with 1 x 10(5) cells gives significant binding with 30 sec. the results show that the purified glycoprotein retians biologic activity and ... | 1976 | 8213 |
| increased survival times of new zealand hybrid mice immunosuppressed by graft-versus-host reactions. | new zealand mice develop autoimmune disease usually accompanied by glomerulonephritis. a graft-versus-host reaction was induced in new zealand black x new zealand white f1 hybrid mice by administration of new zealand white spleen cells. the mice so treated had diminished antibody responses to both an exogenous antigen (sheep red blood cells) and an endogenous antigen (native dna). they had much less glomerulonephritis and increased survival times compared to unmanipulated controls, apparently d ... | 1976 | 8228 |
| adoptive immunotherapy of a gross virus producing lymphoma and a methylcholanthrene-induced fibrosarcoma in tolerant rats. | immunological tolerance to gross virus-specific transplantation antigens in rats given neonatae transfer of donor lymphoid cells beneath the kidney capsule of syngeneic recipient rats. immune or normal donor cells invariably developed a cell-mediated immune reaction in kidneys of gv-tolerant recipients, presumably against gv antigens present on the surface of recipient lymphoid cells in the kidney. spleen and lymph node cells from tolerant rats failed to develop a reaction in tolerant recipients ... | 1976 | 10076 |
| properties of two isolated antigens associated with bovine leukemia virus infection. | we isolated an ether-resistant internal antigen and an ether-sensitive antigen previously described in relation to bovine leukemia virus infection. these two antigens have now been isolated by isoelectric focusing and concanavalin a affinity chromatography, respectively. the ether-resistant antigen exhibited isoelectric heterogeneity with a major peak at ph 7.2 and a minor peak at ph 6.2. its molecular weight, estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (sds-page), was ... | 1976 | 10447 |
| mouse leukemia and solid tumors treated with bone marrow grafting. | | 1976 | 11588 |
| role of endogenous murine leukemia virus in immunologically triggered lymphoreticular tumors. i. development and use of oncogenic cellfree preparations serially passaged in vivo. | cellfree extracts (cfes) prepared from (balb/cj x a/j)f1 (caf1) and (balb/cj x c57bl/6j)f1 (cb6f1) mice in which a graft-versus-host reaction (gvhr) has been induced are known to be oncogenic, but only after a protracted latent period (mean, 16 mo). serial passage of such cfes in successive generations of syngeneic mice inoculated at birth led to the development of two separate oncogenic preparations, the ca serioes in caf, mice and the cb series in cb6f, mice, in which the mean latent period wa ... | 1977 | 13227 |
| antigen-specific nonimmunoglobulin factor that neutralizes xenotropic virus is associated with mouse serum lipoproteins. | a soluble nonimmunoglobulin factor that specifically neutralizes mouse xenotropic c-type virus is found in normal mouse sera. it is stable from ph 2 to neutrality and resists ether extraction, freezing, or brief heating to 100 degrees. it can be separated from immunoglobulins by ultracentrifugation at a density of 1.21 g/cm3. neutralizing activity is only found with the serum lipoproteins in the fraction with density less than 1.21 g/cm3. | 1977 | 13366 |
| expression of endogenous murine leukemia viruses during the course of a protracted immunological disorder. | mice of the low leukemia (balb/cj x a/j)f1 hybrid (caf1) strain express b-and n-tropic infectious murine leukemia virus (mulv) after the age of 6 mo. initation of a protracted immunological disorder, the graft-versus-host reaction (gvhr), at 7 wk of age, accelerates the induction of both these mouse-tropic endogenous viruses, and preferentially enhances the replication of b-tropic mulv. the earlier appearance of b-tropic mulv in a greater proportion of mice and in higher titer is thought to be c ... | 1977 | 16072 |
| recovery of xenotropic virus but not ecotropic virus during graft-versus-host reaction in mice. | | 1977 | 16713 |
| autoimmunity, oncornaviruses, and lymphomagenesis. | the interactions between aberrant immune responses and c-type oncornaviruses in mice are complex. these viruses may be activated during certain immune responses, e.g., histocompatibility reactions, in the face of chronic immunosuppression. oncornaviruses, themselves, may induce autoaggressive cell-mediated responses in certain lymphoid subpopulations, and these autoimmune reactions may be important in subsequent lymphomagenesis. parallel events may occur in other animal models, e.g., the nzb mou ... | 1977 | 17512 |
| differential susceptibility of spleen focus-forming virus and murine leukemia viruses to ansamycin antibiotics. | the streptovaricin complex (svcx) and rifamycin sv derivatives display potent antiviral activity against the polycythemic strain of friend leukemia virus (fv-p), as measured by a reduction in the number of spleen foci produced in mice. such reductions may be explained by inactivation of functions of (i) the spleen focus-forming virus (sffv), (ii) its "helper" murine leukemia virus (mulv), or (iii) both viruses normally present in fv-p. we noted that preincubation of fv-p with fractionation produ ... | 1977 | 18986 |
| helper-independent transformation by unintegrated harvey sarcoma virus dna. | we have studied the unintegrated infectious dna of harvey sarcoma virus (ha-sv) and moloney leukemia virus (mo-mulv). the source of infectious viral dna was the hirt supernatant fraction from cells acutely infected with ha-sv and mo-mulv. to obtain a direct quantitative assay for infectious viral dna, recipient mouse cells were first exposed to calcium phosphate-precipitated viral dna and then treated with dimethyl sulfoxide. infectivity was monitored by focus formation for ha-sv and xc plaque f ... | 1978 | 26810 |
| antitumor action of interferon: animal systems. | | 1977 | 29359 |
| characterization of rauscher murine leukemia virus envelope glycoprotein receptor in membranes from murine fibroblasts. | plasma membrane preparations from ka31 (mouse) cells contained receptors for the binding of rauscher murine leukemia virus (r-mulv) envelope glycoprotein, gp70. this binding was demonstrated by gel filtration of a mixture of the microsomal fraction of the cells and 125i-labeled gp70. a rapid and convenient assay was developed to measure the complex formation between the membrane receptors and gp70 involving specific precipitation of the complex by 3 to 4% polyethylene glycol. the complex formati ... | 1978 | 32403 |
| gross murine leukemia virus-induced alterations in the thymus of preleukemic akr mice. | | 1979 | 32967 |
| inhibition of focus formation of rat cells by mouse sarcoma virus by damavaricin fc derivatives. | | 1979 | 43320 |
| assessment of reactivities of natural antibodies to endogenous rna tumor virus envelope antigens and virus-induced cell surface antigens. | the autogenous humoral immune response of mice to their endogenous leukemia virus (mulv) has been examined with respect to the reactivities of natural antibodies to mulv envelope antigens and virus-induced cells surface antigens. the natural reactivity of mulv envelope antigens was evaluated by means of a radioimmune precipitation assay of intact and disrupted virus, as well as by virus neutralization tests. the specificity of natural antibody for mulv envelope antigens was determined by immunoe ... | 1975 | 45890 |
| different hematological diseases induced by type c viruses chemically activated from embryo cells of different mouse strains. | type c rna viruses can be induced by certain chemicals from cells of many mouse strains. both c58 and balb/c cells have been shown to contain endogenous viruses that are designated n-tropic because they grow preferentially in cells of nih swiss mouse origin. while demonstrating many similar biological and immunological properties, the c58-induced virus is around 10-fold more infectious per physical particle than the n-tropic virus of balb/c cells. in the present studies, inoculation of these vir ... | 1975 | 45891 |
| effect of glucocorticoids on activation of leukemia virus in akr mouse embryo cells. | the effect of glucocorticoids on activation and replication of leukemia virus in akr mouse embryo cells was analyzed. the number of cells detected as positive by fluorescent antibody techniques as well as the virus production in cells chronically producing virus was doubled at optimal concentrations of glucocorticoids. the effect of the hormones in activated cells was found to be not on the process of activation per se but rather on synthesis of the viral components after activation has occurred ... | 1975 | 45895 |
| polypeptides of mammalian oncornaviruses. ii characterization of murine leukemia virus polypeptide (p 15) bearing interspecies reactivity. | | 1975 | 46125 |
| polypeptides of mammalian oncornaviruses. iii. localization of p 15 and reactivity with natural antibody. | | 1975 | 46126 |
| lack of requirement of reverse transcriptase function for the activation of murine leukemia virus by halogenated pyrimidines. | | 1975 | 46650 |
| the morphology of murine oncornaviruses following different methods of preparation for electron microscopy. | the effect of different preparative procedures for electron microscopy on the size and shape of murine oncornaviruses has been studied. with conventional negative staining procedures using neutral sodium phosphotungstate, both murine mammary tumor virus and murine leukemia virus appeared in head-and-tail forms, with a peak head diameter of 122 and 130 nm, respectively. negative staining with uranyl accetate gave round virions with peak diameters of 148 and 130 nm. prefixed virus was round with p ... | 1975 | 46780 |
| the oncornavirus glycoprotein gp69/71: a constituent of the surface of normal and malignant thymocytes. | the oncornavirus related proteins associated with the surface of normal and malignant thymocytes were studied. three virion-associated proteins (gp69/71, p45, p30) were associated with lymphoma cells from about 70% of the tumors studied. two virion-associated proteins (gp69/71 and p45 were associated with normal thymocytes form some but not all strains of mice. in gp69/71- mice, conversion to the gp69/71+ phenotype accompanied leukemogenesis. an interesting difference in the apparent molecular s ... | 1975 | 46909 |
| relation of gix antigen of thymocytes to envelope glycoprotein of murine leukemia virus. | expression of gix surface antigen on thymocytes is an inherited mendelian train of certain strains of mice. we report here the following new findings: (a) gix antigen was found free in the serum of gix+ mouse strains. (b) expression vs. nonexpression of gix antigen was invariably correlated with presence or absence of the group-specific antigen of murine leukemia virus (mulv) gp69/71 in the serum of mice of inbred and segregating populations. (c) gix antigen could be removed from normal gix+ mou ... | 1975 | 46910 |
| purification and characterization of the dna polymerase and rnase h activities in moloney murine sarcoma-leukemia virus. | two rnase h (rna-dna hybrid ribonucleotidohydrolase, ec 3.1.4.34) activities separable by sephadex g-100 gel filtration were identified in lysates of moloney murine sarcoma-leukemia virus (msv). the larger enzyme, which we have called rnase h-i, represented about 10% of the rnase h activity in the virion. rnase h-i (i) copurified with rna-directed dna polymerase from the virus, (ii) had a sedimentation coefficient of 4.4s (corresponds to an apparent mol wt of 70,000), (iii) required mn-2+ (2 mm ... | 1975 | 46924 |
| studies on reverse transcriptase of rna tumor viruses iii. properties of purified moloney murine leukemia virus dna polymerase and associated rnase h. | dna polymerase was purified from a cloned isolate of moloney murine leukemia virus (m-mulv). purified m-mulv dna polymerase, upon analysis by polyacrylamide gel electrophoresis, showed one major polypeptide of mol wt 80,000. estimation of molecular weight from the sedimentation rate of the purifed enzyme in a glycerol gradient was consistent with a structure containing one polypeptide. m-mulv dna polymerase could transcribe ribopolymers, deoxyribopolymers, and heteropolymers as efficiently as di ... | 1975 | 46925 |
| inhibition of oncornavirus functions by 2'-azido polynucleotides. | the 2'-azido analogs of poly(u) and poly(c), poly(duz) [poly(2'-azido-2'-deoxyuridylic acid)], and poly-(dcz [poly(2'-azido-2'-deoxycytidylic acid)], were found to inhibit the rna-directed dna polymerase (reverse transcriptase) activity of murine leukemia (moloney, rauscher) and sarcoma (moloney) virus, and feline leukemia (theilen) and sarcoma (gardner) virus, while under the same conditions the unsubstituted parent compounds failed to do so. in addition, poly(duz) and poly(dcz) inhibited the r ... | 1975 | 47174 |
| mammary tumor virus induction by glucocorticoids. characterization of specific transcriptional regulation. | dexamethasone (1,4-pregnadiene-9-fluor-16alpha-methyl-11beta,17alpha,21-triol-3,20-dione), a potent synthetic glucocorticoid, stimulates mouse mammary tumor virus expression 10- to 20-fold in tissue culture cells. this hormone effect was observed at concentrations as low as 1 times 10-10 m and was maximal at 10-7 to 10-8 m. the time course of induction indicated that detectable increases in extracellular viral dna polymerase were first noted 18 to 24 hours following the addition of dexamethasone ... | 1975 | 47326 |
| the oncogene hypothesis and the search for human cancer virusus. | | 1975 | 47649 |
| cell-mediated immunity to moloney sarcoma virus in mice. i. analysis of antigens responsible for lymphocyte stimulation in regressor mice. | purified viruses, viral antigens, and cell extracts have been tested for their ability to stimulate protein synthesis by msv-m-1 regressor spleen cells from balb/c mice. immune, but not normal cells, responded to msv-m, but not to msv-g virus-1, and to the type-specific viral envelope glycoprotein from msv-m virus. extracts of mouse embryo fibroblasts transformed by either msv-m or msv-g, however, specifically stimulated msv-m regressor spleen cells. cells stimulated by different antigens, and b ... | 1975 | 47841 |
| immunological mechanisms in the pathogenesis of virus-induced murine leukemia. ii. characterization of autoreactive thymocytes. | the nature of the reaction and the type of effector cells involved in the reactivity of thymocytes from moloney murine leukemia virus (mulv-m)-carrier mice against normal syngeneic target cells has been further characterized. the reaction is mediated by viable mulv-infected thymocytes. lysates of carrier thymocytes are not more effective in causing target cell reduction than are lysates of normal thymus cells. soluble mediators do not appear to be involved in the reaction. the thymocytes mediati ... | 1975 | 47845 |
| expression of virus-associated antigens and immune cell functions during spontaneous regression of the friend viral murine leukemia. | spontaneous regression and/or remission of friend virus (fv)-induced splenic erythroblastic leukemia was observed in cd-1 mice infected with several isolates of fv. regression of splenic tumor was accompanied by the loss of both specific fv-induced cell membrane antigen (fvma) and virus group-specific antigens (gsa) from the spleen cells. the frequency (percentage) of immunoglobulin-positive cells (b) and thetapositive cells (t) in the spleen was markedly decreased during leukemia progression, b ... | 1975 | 47847 |
| oncornaviral protein modulation in mouse uterine tissue by estrogen (38467). | treatment of ovariectomized nih swiss mice with estrogens elevated the level of the murine leukemia virus group specific protein and the activity of an rna-directed dna polymerase in the uterus. the extent that these markers were raised was dependent on the relative biological potency of the estrogen and on the time interval following treatment. increases in the levels of both viral marker proteins were evident within 24 hr of treatment and were highest at 48 hr. subsequently, viral protein leve ... | 1975 | 48257 |
| selective immunosuppressive activity of steroids in mice inoculated with the moloney sarcoma virus (38503). | a steroid, 6-chloro-17-hydroxypregna-1,4,6-triene-3,20-doine (chp) that exhibits selective activity in several models of cellular immunity including an apparent inhibitory action on the elicitation of delayed hypersensitivity, was examined in a new, simple experimental model for assessing aspects of host-cell-mediated immunological competence. this model is based upon the capacity of the adult mouse to prevent the progressive growth of tumors induced by the moloney sarcoma virus. two steroids re ... | 1975 | 48258 |
| [biology of mouse rna tumor viruses]. | | 1975 | 48269 |
| a comparative study of the avian reticuloendotheliosis virus: relationship to murine leukemia virus and viruses of the avian sarcoma-leukosis complex. | | 1975 | 48309 |
| virologic and immunologic studies of human prostatic carcinoma. | morphologic, tissue culture, immunologic, and biochemical methods have been used in an attempt to detect and characterize oncogenic viruses or their subviral components in cells derived from human prostatic carcinoma (prca) or benign prostatic hyperplasia (bph). electron microscopy was used to characterize the ultrastructural features of normal and neoplastic prostatic tissue. examination of specimens of prostatic tissue from 34 patients with prca, ten patients with bph, and three patients with ... | 1975 | 48414 |
| quantitation of avian rna tumor virus reverse transcriptase by radioimmunoassay. | a radioimmunoassay was developed that can detect and quantitate 3 ng or more of the avian rna tumor virus reverse transcriptase. the assay detected no antigenic sites in rous sarcoma virus alpha virions or in virions of a murine rna tumor virus. about 70 molecules of reverse transcriptase were found per virion of avian myleloblastosis virus with this assay or with an assay based on antibody inhibition of enzymatic activity. the assay detected about 270 ng of enzyme per mg of cell protein in viru ... | 1975 | 48558 |
| a p60 polypeptide in the feline leukemia virus pseudotype of moloney sarcoma virus with murine leukemia virus p30 antigenic determinants. | a 60,000-dalton polypeptide (p60) has been identified in the feline leukemia virus (felv) pseudotype of moloney sarcoma virus [msv(felv)]. this polypeptide is present in the purified virus complex in concentrations greater than either the murine p30 or the feline p27. purified p60 crossreacts immunologically with murine p30 group antiserum and contains several interspecies determinants, whereas the group specific determinant of felv p27 is not detected. comparison of peptide fingerprints of p60 ... | 1975 | 49060 |
| isolation of mammalian type c rna virus cross-reactive antigen and antibody by immuno-affinity chromatography. | | 1975 | 49291 |
| multiple species-specific and interspecific antigenic determinants of a mammalian type c rna virus internal protein. | | 1975 | 49292 |
| distinction between tumor-specific transplantation antigen and virion antigens in solubilized products from membranes of virus-induced leukemic cells. | a membrane antigen from rbl-5 leukemic cells that was solubilized and partially purified is further characterized in this study. this soluble antigen is capable of immunizating syngeneic hosts to reject neoplastic cells and thus resembles tsta. it also induces cytotoxic antibody in syngeneic hosts capable of specifically lysing rbl-5 cells in vitro. rbl-5, however, releases infectious virus (rlv); it was necessary therefore to rule out virus or structural virion antigens as the effective immunog ... | 1975 | 49326 |
| serological studies with low-molecular-weight polypeptides from the moloney strain of murine leukemia virus. | major virion low-molecular-weight polypeptides were isolated from the moloney strain of murine leukemia virus (type c) by agarose chromatography in 6m guanidine hydrochloride and were shown to have molecular weights of 15,000 (p15), 12,000 (p12), and 10,000 (p10) by their elution volumes and by their relative mobilities in sodium dodecyl sulfate-polyacrylamide gels. each polypeptide could be iodinated and employed in double antibody radioimmunoassay procedures. all three polypeptides demonstrate ... | 1975 | 49441 |
| biological properties of a type c virus isolated from a human x mouse hybrid cell line. | the biological properties of the hmv-1 virus, spontaneously released from a human x c57bl/6 mouse hybrid cell line, were similar to those of radlv, the prototype b-tropic virus of c57bl/6 mice. both viruses replicated on b-type mouse cells and in the wild mouse cell line sc-1. the plaque-forming abilities of the two viruses were relatively low, but gradually increased after passage in new host cells. both viruses were neutralized by akr antisera but not by fmr antisera. hmv-1 virus could rescue ... | 1975 | 49896 |
| studies on virus induction by 5-bromodeoxyuridine in nonproducer murine sarcoma virus-transformed 3t3 cells. | | 1975 | 49978 |
| [inhibition of viral reverse transcriptase and leukemogenesis by modified nucleic acids (author's transl)]. | inhibition of dna polymerase from oncorna viruses by a new class of macromolecular inhibitors is reported. the macromolecule, designated as mercaptopolycytidylic acid (mpc), is a chemically modified polycytidylic acid containing 5-sh cytidylic bases in the polymerase. partially thiolated polycytidylic acids (mpc i-iii, containing 1.7%, 3.5%, and 8.6% 5-mercaptocytidylate units, respectively) inhibited the dna-polymerase of friend leukemia virus (fvl) in the endogenic reaction as well as in the p ... | 1975 | 49986 |
| antibody in cats to mammalian rna tumor virus interspecies antigens. | the studies were undertaken to determine whether the cat, a mammalian species that carries xenotropic endogenous c-type virus(es) and in addition undergoes horizontally transmitted oncogenic c-type rna tumor virus infections, responds immunologically to the mammalian c-type virus interspecies antigens. sera from normal cats and from cats with spontaneous or virus-induced neoplasms were examined for antibodies to interspecies antigen antigen by complement-fixation inhibition, by inhibition of the ... | 1975 | 50133 |
| i. in vitrol transformation of rat embryo cells: correlations with the known tumorigenic activities of chemicals in rodents. | susceptibility to chemically induced transformation changed as a rat embryo cell culture was passaged. for the first 35 to 60 passages, the cultures were diploid and resistant to transformation by chemical carcinogens. however, cultures infected with a murine leukemia virus were transformed by chemicals. for the next 60 passages, the cultures were heteroploid, but retained contact inhibition and were not tumorigenic. even without addition of heterotypic viruses, these heteroploid cultures could ... | 1975 | 50281 |
| blocking of spleen cell activity against target mammary tumor cells by viral antigens. | spleen cells from balb/c females exposed to or neonatally infected with mammary tumor virus (mtv) are cytotoxic to mtv-induced mammary tumor cells in microcytotoxocity assay. this activity can be partially or completely blocked by pretreatment of spleen cells with mtv purified from milk. murine leukemia virus (mulv) has no effect. t cell responses of virgin and multiparous balb/cfc3h females are effectively blocked. non-t cell responses of multiparous balb/cfc3h females or of virgin balb/c femal ... | 1975 | 50346 |
| xenotropic c-type viruses and autoimmune disease. | new zealand black (nzb) mice develop a disease complex which resembles autoimmunity in man. cells from both nzb embryos and adults spontaneously produce an infectious c-type virus which is xenotropic (x-tropic)-capable of being passed only to cells foreign to the host species. it differs from other endogenous murine c-type viruses which are ecotropic, i.e. infectious for cells of their home species. xenotropic viruses are detected in embryos and adult tissues of other strains of mice but at less ... | 1975 | 50450 |
| mitosis is required for production of murine leukemia virus and structural proteins during de novo infection. | cloned 3t3fl cells were synchronized in g1 phase of the cell cycle by deprivation of multiplication stimulatory activity of serum and were then infected with moloney leukemia virus. eclipse period of virus could be made to vary from less than 10 to 34 h. all virus release was completely dependent and occurred immediately after the first mitosis following serum reconstitution. virus yield was not affected by the time of virus inoculation as related to the cell dna synthetic phase. colchicine arre ... | 1975 | 50465 |
| comparison of rna-directed dna polymerases from xenotropic and ecotropic viruses. | | 1975 | 50842 |
| studies on mouse moloney virus induced tumours: i. the detection of p30 as a cytotoxic target on murine moloney leukaemic spleen cells, and on an in vitro moloney sarcoma line by antibody mediated cytotoxicity. | antigenic determinants of p30, the most abundant internal virion protein of c type rna viruses, were detected on the surface of spleen cells from mice bearing moloney leukaemia and on an in vitro line of moloney sarcoma, msc. on both cell types, these determinants on the p30 molecules served as cytotoxic targets in a xenogenic complement dependent antibody mediated 51cr release assay. two antisera were used: a rat anti mlv -m induced lymphoma serum, and an antiserum raised in goats to either dis ... | 1975 | 50852 |
| studies on mouse moloney virus induced tumours: ii. detection of p30 in the serum of mice with moloney leukaemia by in vitro blocking of complement dependent antibody mediated cytotoxicity. | sera from balb/c mice bearing moloney leukaemia block complement dependent antibody mediated cytotoxicity of an antiserum prepared in rats against syngeneic moloney virus induced lymphomata when either spleen cells from mice bearing moloney leukaemia (m) or an in vitro line of moloney virus transformed cells (msc) are used as targets. this antiserum has been shown to recognize p30, the major internal virion protein, as a cytotoxic target on these cells. viral particles were identified by electro ... | 1975 | 50853 |
| effects of nitrosocarbaryl on balb/3t3 cells. | carbaryl(n-methyl-1-naphthylcarbamate) and its nitrosated product, n-nitrosocarbaryl, were tested for their effects of balb/3t3 (clone a31) cells in culture. nitrosocarbaryl, but not carbaryl, caused transformation of the balb/3t3 fibroblasts, but neither chemical induced the complete expression of endogenous murine leukemia virus. transformed cells differed from the parental control cells by loss of contact inhibition, change in morphology, growth in soft agar, growth to higher saturation densi ... | 1975 | 50878 |
| reverse transcriptase and rnase h: present in a murine virus and in both subunits of an avian virus. | | 1975 | 50901 |
| properties of oncornavirus rna-directed dna polymerase, the rna template, and the intracellular products formed early during infection and cell transformation. | we have investigated three aspects of rna turmor virus replication and cell transformation: (1) the properties of the purified avian and mammalian viral rna-directed dna polumerase, (2) some characteristics of the viral 60-70s rna genome, 30-40s rna subunits and intracellular viral rna species, and (3) the interaction of the viral dna polymerase with its rna template early during infection and cell transformation by the murine sarcoma-leukemia virus (msv[mlv]). avian myeloblastosis virus (amv) c ... | 1975 | 50902 |
| quantitation of rna tumor viruses by spectroscopy of density gradient gels. | we have developed a system for virus particle quantitation based on the measurement of the optical absorbance of stained viruses which first have been banded at their buoyant density in an equilibrum 24 to 53% (wt/wt) sucrose density gradient, then fixed in position in the gradient by photopolymerizing an acrylamide-riboflavin mixture in the sucrose, and finally stained and destained. using plasma from mice infected with leukemia virus (rauscher) or chickens infected with avian myeloblastosis vi ... | 1975 | 51099 |
| interferon-directed inhibition of chronic murine leukemia virus production in cell cultures: lack of effect on intracellular viral markers. | extracellular murine leukemia virus (mlv) reverse transcriptase activity was decreased by interferon treatment in four interferon-sensitive mouse cell lines which were chronic mlv producers. in three cell lines which were relatively insensitive to interferon, extracellular enzyme activity remained unchanged by interferon treatment. the concentrations of interferon used had no effect on dna synthesis or cell replication of akr,c+ cells which were chronic producers of akr-mlv. in akr,c+ cultures i ... | 1975 | 51100 |
| characterization of murine sarcoma virus transformation of guinea pig cells and activation of an rna tumor-like virus from nonproducer guinea pig cells. | guinea pig embryo (gep) cells were transformed in vitro by the kirsten strain of mouse sarcoma virus (ki-msv). the transformed cells were found to release infectious virus continuously and produced high titers of group-specific (gs) complement-fixing (cf) antigen characteristics of the murine sarcoma-leukemia virus complex. foci of transformed cells were similar in appearance to those obtained with ki-msv in mouse and rat cells. the transformed cells produced rna dependent dna polymerase and typ ... | 1975 | 51621 |
| erythroid "differentiation" of friend cells. | | 1975 | 51623 |
| lymphomas and immunological tolerance in the rat induced by murine leukemia viruses. | several lines of friend, gross, and rauscher virus-induced rat tumors were able to grow only in friend, gross, and rauscher virus-tolerant rats that had received injections of each of these viruses at birth. when the tumors were transplanted into the virus-tolerant rats that had received injections of the other types of murine leukemia virus (mulv), they grew initially and then regressed. tumors did not grow in normal rats. the same is true in the methylcholanthrene-induced tumors that had been ... | 1975 | 51625 |
| sequences related to the rna tumor viruses in the rna and dna of human leukemias and lymphomas. | dna-rna hybridization was used to explore whether human neoplasias contain rna molecules having sequence homologies to those of the rna tumor viruses known to cause similar diseases in animals. the pattern of specific rnas found in the human tumors showed a remarkable concordance with the predictions deducible from the animal systems. thus human breast cancer contains rna homologous only to that of the murine mammary tumor virus (mmtv). human leukemias, sarcomas, and lymphomas (including hodgkin ... | 1975 | 51626 |
| transplantability, immunological unresponsiveness, and loss of cellular antigenicity in gross virus lymphoma. | the capacity for syngeneic transplantation of rat lymphoma cells, originally induced by gross lymphoma virus (glv), was correlated with the expression of glv-associated antigens by these cells. it was found that lymphoma cells that replicate glv and display membrane and cytoplasmic glv-associated antigens are consistently rejected when transplanted into syngeneic recipients. by contrast, lymphoma cells derived from the same parental cell line and morphologically indistinguishable, that have lost ... | 1975 | 51627 |
| 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 an ... | 1975 | 51634 |
| esp-1 helper virus: characterization of type-specific envelope specificities distinct from those of the murine leukemia viruses. | | 1975 | 51638 |
| transfection of xc plaques with dna from murine leukemia virus producer cells. | | 1975 | 51641 |
| antigenic determinants of the 70,000 molecular weight glycoprotein of woolly monkey type c rna virus. | the 70,000 molecular weight glycoprotein (gp70) of a type-c rna virus originally isolated from a woolly monkey has been partially purified and immunologically characterized. evidence that this viral protein is viral coded was derived from studies showing its antigenic properties to be unaltered by virus passage in cells of different species. a broadly reactive competition immunoassay was developed utilizing antiserum prepared against feline leukemia virus to precipitate 125i-labeled woolly monke ... | 1975 | 51882 |
| anomalous reactions of mouse alloantisera with cultured tumor cells. i. demonstration of widespread occurrence using reference typing sera. | m0use alloantisera produced against different specificities of the k, i, and d regions of the h-2 gene complex reacted as immunogenetically anticipated with normal lymphoid target cells of different haplotypes in cytotoxicity and indirect immunofluorescence tests. these same alloantisera, however, produced anomalous positive reactions when tested on cultured mca-induced sarcoma cells from b10 background h-2 congenic mice. absorption experiments demonstrated that the anomalous activity in these s ... | 1975 | 51886 |
| biochemical properties of the bromodeoxyuridine-induced guinea pig virus. | the biophysical and biochemical properties of the virus particles released by guinea pig embryo cells treated with 5-bromo-2'-deoxyuridine (budr) have been compared to those of the b-type mouse mammary tumor virus (mmtv) and the c-type rauscher murine leukemia virus. the high-molecular-weight (60 to 70s) rna of the budr-induced guinea pig virus (gpv) has a molecular weight of 8 x 106 when measred by mixed agarose polyacylamide gel electrophoresis. the virus particles isolated from the tissue cul ... | 1975 | 51933 |
| variants of n-tropic leukemia virus derived from balb/c mice. | clonal lines derived from cultures of nih/3t3 cells infected with n-tropic leukemia virus from balb/c mice differ in the amount and type of n-tropic virus they produce. three biologically distinguishable n-tropic viruses were found: the large xc plaque-forming virus of hartley et al. (1969) (lp-n), a small xc plaque-forming virus (sp-n), and a non-plaque-forming virus (np-n). sp-n and np-n are less infectious than lp-n. upon prolonged passage in nih/3t3 cells np-n gives rise to highly infectious ... | 1975 | 51938 |
| an antigenically related tryptic polypeptide from several mammalian type c rna virus p30s. | limited tryptic digestion of p30 antigen (the major internal viral protein) of type c viruses isolated from hamster, rat, and gibbon ape yielded a polypeptide fragment with a molecular weight of approximately 10,000 daltons. some antigenic determinants with interspecies specificity were retained on these polypeptides, which in serological tests cross-reacted with antibody produced previously against a similar fragment obtained from mouse p30. exhaustive trypsinization resulted in further fragmen ... | 1975 | 52631 |
| revistin found by screening for inhibitors of reverse transcriptase of an oncogenic virus. | revistin, a substance that strongly inhibits the reverse transcriptase activity of murine leukemia virus in our screening system, was obtained from a cultured broth of a soil streptomyces which was closely related to streptomyces filipinensis. the assay method for the activity was based on the inhibition by a test material of the incorporation of 3h-dtmp into dna synthesized by the reverse transcriptase of an oncogenic rna virus. crude revistin was isolated by serial procedures of salting out wi ... | 1975 | 52648 |
| autogenous immunity to endogenous rna tumor virus: reactivity of natural immune sera to antigenic determinants of several biologically distinct murine leukemia viruses. | sera from normal (c57bl/6xc3h/anf)f1(b6c3f1) mice reacted with several biologically distinct murine leukemia virus(es) (mulv) by radioimmune precipitation assays with the use of purified tritiated leucine-labeled virus. the reactivities of this natural antibody to viral envelope antigens of two laboratory strains (rauscher and moloney) and two endogenous mouse c-type viruses (akr and balb:virus-2) were further analyzed and compared by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. si ... | 1975 | 52718 |
| temperature-dependent rosette formation by mouse lymphoma cells as a result of viral hemadsorption. | cells from several mouse lymphomas formed rosettes with nonsensitized foreign erythrocytes through c-type virus particles clustered on the cell surface in serum-free medium held at 4 degrees c. this type of rosetting was found most typically in a lymphoma induced by rauscher leukemia virus in tissue culture (rd-12), but it also occurred in 23 of 61 spontaneous thymic lymphomas in akr mice. chemically or x-ray-induced leukemias and spontaneous reticulum cell sarcomas did not form rosettes. the na ... | 1975 | 52722 |
| alloantigen expression of a rat moloney sarcoma. | cells of a brown norway (bn) rat moloney sarcoma (mst) failed to express certain bn alloantigen specificities and bound only about 30-50% the amount of labeled alloantibody bound by normal bn spleen cells. mst cells lacked antigen specificities shared by bn and wf rats, but expressed some of the antigen shared by bn and aug rats. further loss of alloantigens that occurred with prolonged in vitro culture was associated with reduced virulence of mst cells for syngeneic hosts and with increased exp ... | 1975 | 52723 |
| specific afferent interference by antiserum of in vivo immunity. | | 1975 | 52846 |
| murine sarcoma virus defectiveness. viral polymerase expression murine and nonmurine host cells transformed by s+l-type murine sarcoma virus. | | 1975 | 52940 |
| relationships between membrane antigens of human leukemic cells and oncogenic rna virus structural components. | leukemic cells from all human chronic granulocytic leukemia (cgl) and some acute myelomonocytic leukemia (amml) donors are lysed by rabbit antisera to a purified glycoprotein of friend murine leukemia virus (flv gp71) in a microcytotoxicity assay. these antisera are not cytotoxic to cells from patients with acute myelocytic leukemia (aml), acute lymphocytic leukemia (all), chronic lymphocytic leukemia (cll), or to peripheral blood lymphocytes from normal donors. a goat antiserum to gradient puri ... | 1976 | 53269 |
| role of carbohydrate in determining the immunochemical properties of the major glycoprotein (gp71) of friend murine leukemia virus. | treatment of friend leukemia virus gp71 with protease-free glycosidase enzymes results in removal of the major portion of the carbohydrate without affecting the amount of protein present. the digested material migrates as protein of about 60,000 to 65,000 molecular weight on sodium dodecyl sulfatepolyacrylamide gel electrophoresis. analyses of the serological properties of gp71 after enzyme treatment indicated that the type, group, and interspecies determinants were not destroyed. in contrast, t ... | 1975 | 53293 |
| thermolabile reverse transcriptase of a mammalian leukemia virus mutant temperature sensitive in its replication and sarcoma virus helper functions. | three temperature-sensitive mutants of the rauscher strain of murine leukemia virus are defective in early post-penetration functions required both for leukemia virus infection and for initiation of transformation of cells by their pseudotypes of murine sarcoma virus. in the present study, the reverse transcriptase of one of these mutants (ts 29) is shown to be thermolabile compared with the enzymes of the wild-type virus and several other temperature-sensitive mutants. these findings provide ev ... | 1975 | 53294 |
| transcription of 70s rna by dna polymerases from mammalian rna viruses. | dna polymerases purified by the same procedure from four mammalian rna viruses, simian sarcoma virus type 1, gibbon ape lymphoma virus, mason-pfizer monkey virus, and rauscher murine leukemia virus are capable of transcribing heteropolymeric regions of viral 70s rna without any other primer. in this reconstituted system the enzymes from simian sarcoma virus type 1, mason-pfizer monkey virus, and rauscher murine leukemia virus transcribe viral 70s rna almost as efficiently as the dna polymerase f ... | 1975 | 53295 |
| [ultracytochemical studies on leukemic cells]. | the present survey of ultracytochemical investigations in the cells of the graffi and rauscher leukaemic systems is intended to throw a light on the place of replication and on the incorporation of cell specific material into the virus. the successful evidence of incorporating certain enzymes associated to the membrane into the virus envelope could have a significance in so far as this process can be used to explain the appearance of cytotropism in certain kinds of virus to a target cell. | 1975 | 54304 |
| cell-mediated immunity to friend virus-induced leukemia. ii. characteristics of primary cell-mediated cytotoxic response. | the primary cell-mediated cytotoxic response to a friend virus-induced leukemia, fbl-3, in c57bl/6 mice was measured by the 125iudr release assay. intraperitoneal (i.p.) inoculation of 1 x 10(1) fbl-3 cells produced progressive tumor growth (progressors); subcutaneous (s.c.) inoculation of as many as 5 x 10(6) fbl-3 cells produced only transient tumor growth (regressors), and these mice would subsequently resist i.p. challenge of fbl-3 cells at 3 days after s.c. inoculation. the kinetics of the ... | 1976 | 54387 |
| cell-mediated immunity to friend virus-induced leukemia. iii. characteristics of secondary cell-mediated cytotoxic response. | by employing the 125iudr release cytotoxicity assay, we have been able to measure the primary and secondary cell-mediated cytotoxic response of c57bl/6 mice to fbl-3 cells, a syngeneic friend virus-induced leukemia. it was found that the secondary cell-mediated cytotoxic response occurred more rapidly after challenge (within 3 days) than the primary response, and the levels of reactivity were considerably higher. as in the primary response, the secondary cytotoxic reactivity of spleen cells was ... | 1976 | 54388 |
| assay in the mouse for delayed-type hypersensitivity to murine leukemia virus. | delayed-type hypersensitivity (dth), assayed by footpad swelling, was induced in 6- to 8-week-old balb/ccr mice immunized with formalin-inactivated, sucrose-banded murine type-c viruses. the dth response was inducible with as little as 11.25 mug sensitizing antigen, was greatest after sc sensitization as compared to im and ip sensitization, and was optimally elicited with a 7-day challenge. a statistical evaluation of the dth assay revealed that the test was consistently reproducible and limited ... | 1975 | 54434 |
| in vitro inhibition of cell-mediated cytotoxicity against syngeneic friend virus-induced leukemia by immunoregulatory alpha globulin. | immunoregulatory alpha-globulin (ira) derived from normal human plasma decreased cytotoxic reactivity as measured by an in vitro 5-iodo-2'-deoxyridine release assay of immune mouse lymphocytes against the syngeneic friend virus-induced leukemia, fbl-3. this inhibitory effect depended on the dose of ira used and was not due to the cytotoxic effects of ira on the effector cells or target tumor cells. we also found elevated levels of serum alpha-gloubins in fbl-3 tumor-bearing mice as compared to n ... | 1975 | 54438 |
| synthesis of long, representative dna copies of the murine rna tumor virus genome. | virions of moloney murine leukemia virus can synthesize two classes of dna molecules complementary to their 70s rna. one class consists of molecules about 200 nucleotides long, which are of limited sequence complexity; these molecules are formed preferentially if the dntp concentration during the reaction is low. the second class consists of very heterogeneous dna molecules with weight-average size of about 1,000 nucleotides containing at least 70% of the viral rna sequences in approximately equ ... | 1975 | 54441 |
| properties of mouse leukemia viruses. x. occurrence of viral structural antigens on the cell surface as revealed by a cytotoxicity test. | | 1976 | 54978 |
| properties of mouse leukemia viruses. xi. immunoelectron microscopic studies on viral structural antigens on the cell surface. | | 1976 | 54979 |
| autogenous immunity to endogenous rna tumor virus: humoral immune response to virus envelope antigens. | autogenous immune sera from several strains of mice have been examined for type-, group-, or interspecies-specific reactivities against leukemia virus envelope antigens and virus-induced cell surface proteins. the natural antibody of these test sera react with gp69/71, gp43, and p15 structural components on murine leukemia viruses including akr, friend, rauscher, moloney, and xenotropic balb:virus-2. furthermore, comparable radioimmune titration curves are obtained when these viruses are used in ... | 1976 | 56222 |
| cell-mediated immunity to leukemia virus- and tumor-associated antigens in mice. | cell-mediated immune reactions appear to play an important role in resistance against growth of leukemia cells in mice. possible mechanisms for in vivo protection in two tumor systems are discussed. these tumor models, which are a friend leukemia virus-induced transplantable tumor, fbl-3, and primary murine sarcoma virus (msv) -induced tumors, are strongly antigenic; under some conditions, tumors regress completely. in mice with regressing fbl-3 tumors, cell-mediated cytotoxicity was measured by ... | 1976 | 56223 |
| x-gp70: a third molecular species of the envelope protein gp70 of murine leukemia virus, expressed on mouse lymphoid cells. | three variants of the gp70 envelope component of mulv are now recognizable serologically: gix-gp70, 0-gp70, and x-gp70. the last of these, x-gp70, has so far been found only in mice or cells producing abundant c-type virus. this distinguishes x-gp70, provisionally, from the gix-gp70 and 0-gp70 variants, each of which can be expressed on normal thymocytes without accompanying virus production, as exemplified by mouse strains 129 and b6, respectively. the x-gp70 genotype, however, is not limited t ... | 1976 | 56420 |
| tumor-bound immunoglobulins: an in vivo phenomenon of masked specificity. | we examined the specificity of the lg "coating" on murine tumor cells grown in vivo. cells were treated in vitro for release of cell-bound lg from ascites tumors. such uncoated cells showed an increased expression of tumor-associated antigens and a parallel decrease in intensity of the lg coat, but displayed no changes in the expressions of other normal membrane antigens. this was shown by a complement-dependent cytotoxicity assay and radioimmunoassay. these changes were attenuated if the tumor ... | 1976 | 56447 |
| inhibition of friend murine leukemia virus production by low-ionic-strength medium. | the effect of medium of low ionic strength on the release of virus from friend leukemia cells has been studied. the release of infectious friend leukemia virus is almost completely inhibited in medium of low ionic strength, as measured by a focus-forming assay (xc assay), by endogenous rna-dependent dna polymerase activity of released virus particles, and by electron microscope studies of the production of c-type particles. friend leukemia virus-transformed proerythroblasts undergo extensive mor ... | 1976 | 56456 |
| purification and serological characterization of the major envelope glycoprotein from akr murine leukemia virus and its reactivity with autogenous immune sera from mice. | the major envelope glycoprotein (gp71) from akr murine leukemia virus (mulv) was purified and its serological reactivity with heterologous and autogenous immune mouse sera was examined. homologous and interspecies competition radioimmunoassays using antisera to rauscher-mulv gp69/71 or friend-mulv gp71 or antisera to feline leukemia virus to precipitate 125i-labeled gp71 from various mulv showed that distinct differences exist between rauscher- or friend-mulv and akr-mulv glycoproteins. characte ... | 1976 | 56459 |
| dissociation of alpha beta dna polymerase of avian myeloblastosis virus by dimethyl sulfoxide. | the alpha beta dna polymerase of avian myeloblastosis virus was treated with dimethyl sulfoxide to dissociate the enzyme subunits. the dimethyl sulfoxide treated enzymes were passed over phosphocellulose to purify and characterize the dissociated subunits as well as to remove the dimethyl sulfoxide. rna-directed dna polymerase, rnase h, and nucleic acid-binding activity were monitored, as well as the subunit structure (on sodium dodecyl sulfate-polyacrylamide gels) of the various enzyme species ... | 1976 | 56461 |