{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,6,10]],"date-time":"2026-06-10T15:01:19Z","timestamp":1781103679415,"version":"3.54.1"},"reference-count":0,"publisher":"National Academy of Sciences","issue":"10","content-domain":{"domain":["www.pnas.org"],"crossmark-restriction":true},"short-container-title":["Proc. Natl. Acad. Sci. U.S.A."],"published-print":{"date-parts":[[1971,10]]},"abstract":"<jats:p>\n                    Extracts of cultured human leukemic tissues increased the spleen focus-forming activity of Friend leukemia virus preparations in BALB\/c and other partially resistant mice. Such mice carry the\n                    <jats:italic>\n                      Fv-1\n                      <jats:sup>b<\/jats:sup>\n                    <\/jats:italic>\n                    gene, which inhibits the expression of helper virus indigenous to the Friend virus complex, and allows co-infecting leukemia viruses of mice, cats, or chickens to substitute for the inhibited helper virus and increase the expression of the spleen focus-forming virus. The helper activity of extracts from human leukemic tissues shared several important properties with that associated with known leukemogenic viruses of animals.\n                  <\/jats:p>","DOI":"10.1073\/pnas.68.10.2391","type":"journal-article","created":{"date-parts":[[2006,5,31]],"date-time":"2006-05-31T02:25:16Z","timestamp":1149042316000},"page":"2391-2395","update-policy":"https:\/\/doi.org\/10.1073\/pnas.cm10313","source":"Crossref","is-referenced-by-count":7,"title":["Helper Activity of Human Leukemic Tissue Extracts for Leukemia Virus Expression in Mice"],"prefix":"10.1073","volume":"68","author":[{"given":"Richard A.","family":"Steeves","sequence":"first","affiliation":[{"name":"Department of Experimental Biology, Roswell Park Memorial Institute, Buffalo, New York 14203"},{"name":"Department of Viral Oncology, Roswell Park Memorial Institute, Buffalo, New York 14203"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Audrey","family":"Fjelde","sequence":"additional","affiliation":[{"name":"Department of Experimental Biology, Roswell Park Memorial Institute, Buffalo, New York 14203"},{"name":"Department of Viral Oncology, Roswell Park Memorial Institute, Buffalo, New York 14203"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Edwin A.","family":"Mirand","sequence":"additional","affiliation":[{"name":"Department of Experimental Biology, Roswell Park Memorial Institute, Buffalo, New York 14203"},{"name":"Department of Viral Oncology, Roswell Park Memorial Institute, Buffalo, New York 14203"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"341","published-online":{"date-parts":[[1971,10]]},"container-title":["Proceedings of the National Academy of Sciences"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/pnas.org\/doi\/pdf\/10.1073\/pnas.68.10.2391","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2022,4,13]],"date-time":"2022-04-13T10:47:35Z","timestamp":1649846855000},"score":1,"resource":{"primary":{"URL":"https:\/\/pnas.org\/doi\/full\/10.1073\/pnas.68.10.2391"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[1971,10]]},"references-count":0,"journal-issue":{"issue":"10","published-print":{"date-parts":[[1971,10]]}},"alternative-id":["10.1073\/pnas.68.10.2391"],"URL":"https:\/\/doi.org\/10.1073\/pnas.68.10.2391","relation":{},"ISSN":["0027-8424","1091-6490"],"issn-type":[{"value":"0027-8424","type":"print"},{"value":"1091-6490","type":"electronic"}],"subject":[],"published":{"date-parts":[[1971,10]]},"assertion":[{"value":"1971-10-01","order":2,"name":"published","label":"Published","group":{"name":"publication_history","label":"Publication History"}}]}}