80 MARY ELMORE SAUER AND DONALD DUNCAN 



known situation, nuclear division regularly occurs without cytoplasmic divi- 

 sion, and one of the daughter nuclei degenerates to become a DNA-contain- 

 ing cytoplasmic inclusion. Since origin from degenerating nuclei in this case 

 is undisputed, Wigglesworth inferred such origin for all cases. Linder's 

 (1956; Linder and Anderson, 1956) more recent observations support this 

 conclusion. 



Gliicksmann (1951) in his classic review listed numerous descriptions of 

 prominent, dark-staining bodies usually interpreted as degenerating cells in 

 normal embryos. The Feulgen stain, whenever carried out, indicated nuclear 

 material. Gliicksmann concluded that the bodies in all cases represented nu- 

 clear degeneration which typically began with pyknosis, further changes 

 occurring either in the isolated remnant or inside a neighboring cell that 

 had resorbed it. Chang (1940) pointed out the large number and wide dis- 

 tribution of the bodies in mouse embryos. He held that the bodies are within 

 the cytoplasm, being phagocytized fragments of dead cells. According to 

 Hamburger and Levi-Montalcini (1949), the entire body resembles a macro- 

 phage in its reaction to vital stains. 



Nucleic acid normally moves from nucleus to cytoplasm by submicroscopic 

 particles, but the same function may occasionally be accomplished by trans- 

 port of large bodies. Here probably belong the examples of cytoplasmic DNA 

 granules in certain plants (Sparrow and Hammond, 1947; Chayen and Nor- 

 ris, 1953). A number of species of nematodes and insects undergo a chro- 

 matin diminution process in connection with the segregation of the germ 

 cells from somatic cells, whereby the somatic cells regularly cast out into the 

 cytoplasm what may be a large part of the chromosomes (Wilson, 1934; 

 Painter, 1959). 



Extranuclear DNA in nonexperimental pathologic states is usually inter- 

 preted as degenerating nuclear remnants (Barthels and Voit, 1931). Other 

 possibilities, especially in malignant cells, are nuclear buds which become 

 enclosed in the cytoplasm, explained as an adjustment of the nuclear-cyto- 

 plasmic surface ratio, and a direct extrusion of chromatin into the cytoplasm, 

 leaving a hypochromatic nucleus (Ludford, 1942). Von Sallmann et al. 

 (1955) in studying radiation-induced changes in the lens of laboratory ani- 

 mals, where extranuclear Feulgen-positive bodies apparently are the pre- 

 dominant pathologic finding, pointed out the striking analogy with age- 

 induced changes. They considered the bodies to be extruded from the nu- 

 cleus. Loewenthal (1957) interpreted the Feulgen-positive bodies found in 

 large numbers in chick embryos homozygous for the "creeper" mutation as 

 degenerating nuclei. Cytoplasmic inclusions containing DNA characterize a 

 number of virus diseases. Leuchtenberger et al. (1956) recently applied 

 electron microscopy and quantitative measurements of the DNA to the 

 bodies constantly present in rectal polypoid tumors and concluded that they 

 were viral. 



