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Cytogenetic studies of African cane rat (Thryonomys swinderianus) established a diploid chromosome number for this species 2n=44. Among 21 pairs of autosomes, one pair of large submetacentric chromosomes possess secondary constriction and satellites on the shorter arms. The X chromosomes are the largest metacentrics while the Y chromosomes is the smallest of the complement. The karyotypic similarities between African cane rat and other hystricomorph rodents are briefly discussed.

Epstein-Barr virus obtained by superinfection of Raji cells with Epstein-Barr virus recovered from P3HR1 cells (HRI virus) transformed human lymphocytes, but it did not superinfect Raji cells. A human lymphoblastoid cell line, HLB, established by such transformation contained 22 Epstein-Barr virus genomes per cell and Epstein-Barr virus-associated nuclear antigen, and a few cells contained early or viral capsid antigen complexes. Chromosomal analysis revealed that HLB-cells were diploid with normal female karyotypes. Replication of Epstein-Barr virus DNA and inhibition of host cell DNA synthesis were observed in HLB cells after superinfection with HR1 virus.

Genetic analyses have defined a single gene ( src ) as that portion of the avian sarcoma virus (ASV) genome which encodes the protein directly responsible for ASV-induced neoplastic transformation. We have recently identified the polypeptide product of the src gene of the Schmidt-Ruppin (SR) strain of ASV, a 60,000-dalton phosphoprotein designated pp60 src , and have further determined that pp60 src acts as a protein kinase. Essential to the identification and characterization of the pp60 src protein of SR-ASV was the use of serum (TBR serum) from rabbits bearing SR-ASV-induced tumors. TBR serum was, however, strain specific, recognizing pp60 src from SR-ASV-transformed cells only. We report here that sera from marmosets bearing tumors induced by the Bryan or SR strains of ASV (TBM sera) contain antibody which precipitates the transforming gene product from cells transformed by the SR, Bryan, Prague, or Bratislava strains of ASV. In contrast, rabbits bearing tumors induced by either the Bratislava or Bryan strains of ASV, or hamsters with SR-ASV-induced tumors did not produce antibody to pp60 src from any strain of ASV. The 60,000-dalton polypeptides immunoprecipitated with TBM serum from cells transformed by each of the above virus strains are phosphoproteins. One-dimensional peptide mapping by limited proteolysis revealed that the pp60 src proteins are structurally very similar, but not identical. Furthermore, all of the viral pp60 src proteins have an associated phosphotransferase activity. In addition to detecting the viral src proteins, TBM serum was able to immunoprecipitate an antigenically related protein from normal uninfected avian cells.

Cytogenetic analysis of the native African pig revealed the presence of auto-somal mosaicism (38/37) in bone marrow tissue. The population of cells with 37 chromosomes show unbalanced karyotype, lacking on large autosomal acrocentric chromosome. The significance of this finding in relation to the karyotype of the European domestic pig (Sus scrofa) and intraspecies hybrids is discussed.

Human osteosarcoma and mammary carcinoma cells were cultured separately in a medium supplemented with fetal calf serum, until they were confluent. The medium was then replaced by serum-free medium supplemented with heparin. Both cell cultures secreted collagenase, and this activity was inhibited by a cartilage-derived protein of low molecular weight. Since cartilage is rarely invaded by neoplasms, the presence of this inhibitor may play an important role in the regulation of tumor invasion.