Many naturally occurring C-type RNA viruses are of endogenous origin. The genetic information for synthesizing these RNA viruses is present in the DNA of normal mouse cells, probably as part of their ...chromosomal DNA. Some C-type viruses infect mouse cells (homotropic virus), while others infect certain tissue culture cells from other species but not mouse fibroblasts (xenotropic virus). All mouse strains studied appear to contain endogenous xenotropic viral genomes. However, based on the regularity with which homotropic virus is detected, inbred mice can be divided into high, low, and non-virus-yielding strains. Nucleic acid hybridization studies have shown that DNA from high virus strains contains several copies of the homotropic virus genome, while that from low virus strains contains fewer copies, and DNA from nonvirus strains lacks a significant portion of the homotropic virus genome. In vivo and in vitro genetic studies support the nucleic acid hybridization results. In addition, high virus mouse strains are more likely than low virus strains to release virus that will replicate efficiently in their own cells. Methods for the activation and detection of endogenous C-type virus in tissue culture are discussed.
Background. Recurrence in the peritoneum occurs in up to 50% of patients after a potentially curativepancreaticoduodenectomy. Previous authors have implicated preoperative fine-needle aspiration ...(FNA) as a cause of intraperitoneal tumor dissemination, although prior studies of peritoneal cytology findings have largely involved patients with locally advanced disease.
Methods. A consecutive series of patients referred to our institution between 1991 and 1993 with suspected or biopsy-proven adenocarcinoma of the pancreatic head was studied prospectively. All patients fulfilled criteria for resectability as assessed by computed tomography: no metastatic disease, no encasement of the superior mesenteric or hepatic arteries, and a patent superior mesenteric-portal venous confluence. Peritoneal washings were obtained at the time of staging laparoscopy and/or at subsequent laparotomy. Data regarding peritoneal cytology results, previous FNA, preoperative chemoradiation, eventual resection, pattern of disease recurrence, and survival were collected.
Results. A total of 80 peritoneal washings from 60 consecutive patients were prospectively examined. Forty-nine (82%) of 60 patients underwent FNA before peritoneal washings were obtained. A total of four patients (7%) had positive peritoneal cytology findings: three (6%) of 49 who underwent prior FNA and one (9%) of 11 with no prior FNA. Similarly, no differences in eventual peritoneal failure or short-term survival were observed for patients who underwent prior FNA compared with patients who did not. All four patients with positive peritoneal cytology findings had metastatic disease (liver, three; peritoneum, one) at a median of 4.8 months after diagnosis; three of the four died of disease at a median of 8 months.
Conclusions. Positive peritoneal cytology findings are rare in patients with radiologically resectable adenocarcinoma of the pancreas. When found, positive peritoneal washings are an indicator of advanced disease characterized by unresectability, early metastasis, and short survival. Computed tomographic-guided FNA does not appear to increase the risk for positive peritoneal washings and represents a valid approach to the pretreatment diagnosis of patients with suspected pancreatic malignancy.
Harvey murine sarcoma virus is a retrovirus which transforms cells by means of a single virally encoded protein called p21 has. We have determined the nucleotide sequence of 1.0 kilobase in the ...5$^{\prime}$ half of the viral genome which encompasses the has coding sequences and its associated regulatory signals. The nucleotide sequence has identified the amino acid sequence of two additional overlapping polypeptides which share their reading frames and the carboxyl termini with p21 but which contain additional NH$_{2}$-terminal amino acids.
The spleen focus-forming virus (SFFV), a replication-defective murine leukemia virus that causes the rapid transformation of certain hematopoietic target cells, has acquired specific xenotropic viral ...genetic information not contained in Friend helper virus. In the current studies, it is shown that a cDNA that represents a xenotropic virus portion of SFFV detects genetic sequences derived from the env gene region of murine xenotropic virus. The significance of the acquisition of these xenotropic viral sequences by SFFV is discussed with regard to their possible role in the rapid leukemogenicity of SFFV, and an analogy is drawn between the formation of SFFV and the formation of the Kirsten and Harvey sarcoma viruses.
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