Henry S. Di Stefano

Cytological observations of “nonproducer” Rous sarcoma cells☆

Abstract “Nonproducer” cells, obtained by infection of cultivated chick embryo fibroblasts with Rous sarcoma virus (Bryan strain), were compared and contrasted with similarly infected cells that were producing virus in large quantities and with uninfected control cells. Both types of infected cells differed markedly from uninfected cells but, despite quantitative differences between them, the morphology of the two types of infected cells was essentially the same. Inasmuch as the “nonproducer” cells did not involve infection with the “helper” Rous-associated virus, the alterations observed reflected only infection with Rous sarcoma virus.

Substructure of membranes in cultivated chick embryo fibroblasts

SummaryElectron microscope examination of the plasma membrane of chick embryo fibroblasts cultured in vitro revealed the presence of a single osmiophilic layer about 90 Å thick and a substructure composed of ovoid sub-units associated with an amorphous component. These ovoid sub-units measured approximately 112 Å along the major axis and 75 Å along the minor axis and were composed of a central core, approximately 30 Å by 60 Å, surrounded by a peripheral component.Examination of other membranous components of these cells revealed a similar ovoid subunit structure in a single layered membrane. Differences in thickness and in the sizes of ovoid sub-units were seen in these membranes. The ergastoplasmic membranes, the outer nuclear membranes, the outer mitochondrial and the Golgi membranes were found to be the thinnest.These varied in thickness from approximately 75 Å to 80 Å. The thickest membranes seen were the inner nuclear membranes. These were approximately 100 Å thick. The dimensions of the ovoid sub-units corresponded with differences in the thickness of the various membranes. These findings support the concept of a particulate substructure of cell membranes.

EFFECTS OF ALLOXAN AND REDUCED FOOD INTAKE ON LIVER DEOXYRIBOSE NUCLEIC ACID OF THE RAT

Effects of alloxan, reduced food intake, starvation and biopsy procedure on the deoxyribose nucleic acid (DNA) content of rat liver tetraploid nuclei have been investigated. It was found that: (1) Alloxan treatment resulted in an increased amount of DNA. (2) Reduced food intake of treated animals Played no part in this increase. (3) Complete starvation for a period of six days did not effect the amount of DNA in these nuclei. (4) An increased amount of DNA was found in tetraploid nuclei of rat liver 13 days after removal of a small biopsy sample. The increased DNA in tetraploid liver nuclei of alloxan diabetic rats may be explained on the basis of regeneration of liver tissue due to some submicroscopic liver damage caused by the drug.

Corpuscular and trilaminar appearance of cultivated chick embryo fibroblast plasma membranes

SummaryElectron microscope examination of chick embryo fibroblasts grown in tissue culture and fixed in a variety of osmium fixatives as well as in fixatives not containing osmium revealed a limiting cell membrane with a corpuscular substructure. A trilaminar appearance was more difficult to demonstrate in plasma membranes of cells fixed in osmium or glutaraldehyde solutions followed by osmication, while many extensive regions of membranes with this appearance were observed after fixation in buffered potassium permanganate.A study of the conditions favorable to the demonstration of a trilaminar appearance indicated that the level of focus of the electron microscope image and alteration of the intrinsic structure of the summits within the membrane played significant roles in producing this appearance.