Intracisternal A particles and C particles

Characterization of human cells transformed in vitro by N-methyl-N'-nitro-N-nitrosoguanidine

Human osteosarcoma (HOS) clonal cells transformed in vitro by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) were characterized, and compared to non-producer HOS cells transformed by Kirsten murine sarcoma virus (Ki-MSV). The MNNG- and virus-transformed cells grew in the aggregate form above an agar base, grew in soft agar, and had a high fibrinolytic activity. When inoculated into nude mice, all the chemically or virally altered cells produced tumors or tumor nodules. When transplanted into ATS-treated hamsters, the cells transformed by MNNG (0.01 mug/ml) and Ki-MSV produced tumors but MNNG (0.1 mug/ml) transformed cells did not produce tumors. The control HOS cells did not grow in the aggregate form but formed colonies in soft agar, and had low fibrinolytic activity and no capacity to form tumors in nude mice and ATS-treated hamsters. However, one of the control clonal lines had a high level of fibrinolytic activity. Cellular aggregation properties of human transformed cells did appear to correlate with tumorigenicity in nude mice.

Ultrastructural studies of human prostatic neoplasia

Forty-two specimens of human prostatic neoplasia (32 carcinomas, eight benign hyperplasia, two bladder tumors infiltrating prostatic tissue, and 15 tissue cultures derived from prostatic neoplasia) were examined by electron microscopy. Intracisternal viruslike particles, 150-200 nm in diameter and budding, were found in epithelial cells of four carcinomas. In some of these particles, an electron-dense central core or two concentric layers were discernible. In addition, particles resembling type C virus particles, 90-130 nm in diameter, were observed in intracytoplasmic vacuoles in five cases of carcinomas and in one case of benign prostate hyperplasia. Thus, viruslike particles were found in 9 of 32 cases of prostate carcinoma and in one of eight cases of benign prostate hyperplasia. Virus particles have, so far, not been found in any of the tissue culture specimens. Further studies are required to determine the nature of these particles and their relationship to the origin of human prostatic neoplasia. Additional observations in both benign hyperplasia and carcinoma include intranuclear mitochondria, multilayered nuclear inclusions, bundles of intranuclear fibrils, intracytoplasmic tubules, extracellular tubulo-filamentous structures, and cilia.ltilayered nuclear inclusions, bundles of ilo-filamentous structures, and cilia.

Characterization of C-type particles produced by a tissue culture-adapted murine myeloma

C-type particles produced by a tissue culture-adapted BALB/c myeloma were characterized. It was determined that although the particles were morphologically and antigenically similar to murine leukemia and sarcoma virus, the size of their RNA was different, they lacked RNA-dependent DNA polymerase, they were unstable in NET buffer, sucrose and citrate but were stable in glycerol and Earle balanced salt solution, and they behaved differently from oncornaviruses when treated with ether and detergent.

Mason-Pfizer virus characterization: a similar virus in a human amniotic cell line

Mason-Pfizer monkey virus (MP-MV) is a RNA virus with an RNA-instructed DNA polymerase first isolated from a rhesus monkey mammary adenocarcinoma in 1970. Until recently, there have been no other isolates. A continuous human amnion cell line, AO, was found to be producing a virus indistinguishable or closely related to the Mason-Pfizer virus as measured by morphological, immunological, and biochemical methods. By thin-section electron microscopy, the extracellular virus particle in AO line is 115 to 130 nm in diameter and has a preformed nucleoid (80 to 90 nm) before budding, properties which are also characteristic of MP-MV. Two proteins of the virus from the AO line were studied. By immunodiffusion, sera which react specifically with MP-MV give a line of identity with virus from the AO line. The AO viral RNA-instructed DNA polymerase purified by phosphocellulose chromatography was specifically inhibited by anti-MP-MV polymerase sera, and the AO cells contained both DNA and RNA sequences related to MP-MV (3)H-DNA. Viruses thus far indistinguishable from MP-MV have also recently been found by others in different human lines, raising again the question of the species of origin of MP-MV. Because the virus in the AO cells cannot be differentiated from MP-MV, we attempted to determine the origin of MP-MV virus by measuring DNA sequences related to MP-MV (3)H-DNA in uninfected human and rhesus monkey cells. The quantity of MP-MV-like DNA sequences in uninfected primate tissues was found to be much lower than the amount of DNA sequences of murine type-B or type-C viruses in uninfected murine tissues. Thus, it was not possible to determine whether the virus produced by AO cells or MP-MV was of human or monkey origin, or both.