A non-invasive micronucleus assay in the rat liver

The potent rat-liver mitogen 4-acetylaminofluorene (4AAF) is shown here to provide an effective replacement for the surgical procedure of 2/3 partial hepatectomy (2/3PH) in the in vivo rat-liver micronucleus assay described by Tates and his colleagues. This protocol modification enables the assay to be conducted on a routine basis. Control observations for both 2/3PH and 4AAF-treated rats are presented, together with evidence indicating 4AAF itself to be without activity in the assay, irrespective of the mitogenic stimulus. The activities of the rat carcinogens DMN, 2AAF, DMH and 6BT, and of the non-carcinogens 4AAF and 4N are demonstrated. Recommendations for the conduct of the modified assay are made.     

The function of mucous secretions in the cushion star Pteraster tesselatus Ives

In all previous studies involving the behavior of the cushion star Pteraster tesselatus Ives, the possibility that this asteroid's copious secretions of mucus are defensive in nature has been suggested, but never studied to any degree.

Our research shows that discharge of mucus from Pteraster was triggered not only by physical stimulation, but also from contact with the asteroid-consuming sea stars Solaster dawsoni Verrill and Pycnopodia helianthoides (Brandt). It was also found that mucus repelled these two asteroids so effectively that it provided Pteraster tesselatus with protection from predation for essentially 100% of the time.

Pteraster specimens were easily and harmlessly rendered defenseless by removing their mucous-cell-containing supradorsal membranes by dissection. Without the mucous secretions available for discharge, it was shown that P. tesselatus was easily preyed upon by both Solaster dawsoni and Pycnopodia helianthoides.     

Alterations to controls of cellular DNA synthesis by adenovirus infection.

Human adenovirus type 5 and temperature-sensitive mutants ts36, ts37, and ts125 induced cellular DNA synthesis in quiescent rodent cells at both permissive and nonpermissive temperatures. Cellular DNA synthesis induced by adenovirus type 5 or by serum required protein synthesis for both initiation and continuation, whereas viral DNA synthesis was not dependent upon continued protein synthesis once it was initiated. Both cellular and viral DNA replication was induced in adenovirus type 5-infected cells in the presence of dibutyryl cyclic AMP at concentrations which inhibited induction by serum which suggested that some of the controls of DNA synthesis in serum-treated and virus-infected cells are different. After adenovirus infection of quiescent cells, there was a decrease in the number of cells with G1 DNA content and an increase in cells with G2 diploid and greater DNA contents. Thus, adenovirus type 5 induces a complete round of cellular DNA replication, but in some cells, it induces a second round without completion of a normal mitosis. These results suggest that adenovirus type 5 is able to alter cell growth cycle controls in a way which may be related to its ability to transform cells.