Cambial Isoperoxidase Patterns in Castanea

Only 3 major and variable anodal isoperoxidase bands were found in the cambial zone of 10 Castanea species. Even though the numbers of plants tested in several taxa were low, it appeared that certain banding patterns could be characteristic for some species. Thus, C. dentata and other American species (C. alnifolia, C. ashei, C. ozarkensis, C. pumila) exhibited only band A. The Japanese chestnut (C. crenata) and C. seguinii had only band B. The isoenzyme phenotypes A, B, and AB were found in the European chestnut (C. sativa) while our single tree of C. henryii had both A and B bands. Chinese chestnut (C. mollissima) contained trees with 4 isoenzyme phenotypes (A, AB, B, BC). The distribution of isoperoxidase banding patterns, coupled with widespread sexual compatibility, indicated that the categorization of chestnut species into different taxonomic sections may have little importance from a genetic basis. The possible influence of enzyme phenotype on graft compatibility is discussed.

Multicellular origin of fibrosarcomas in mice induced by the chemical carcinogen 3-methylcholanthrene.

The cellular origin of tumors induced by the chemical carcinogen 3-methylcholanthrene (MCA) was studied in mice with X-chromosome inactivation mosaicism. Because only one of the two X-chromosomes is active in XX somatic cells, a female heterozygous at the X-linked phosphoglycerate kinase (PGK-1) locus for the usual Pgk-1b gene and the variant Pgk-1a has two populations of cells, in the cells of one population, Pgk-1b is active and B-type enzyme is synthesized, whereas in cells of the other population, A-type enzyme is produced. Both enzyme types are found in normal tissues from these mosaic mice. A tumor developing from a single cell exhibits only one of the two PGK enzyme types, whereas a tumor with a multicellular origin expresses both enzymes (i.e., it has a double-enzyme phenotype). Five fibrosarcomas developing at the site of injection of 0.2 or 2.0 mg of MCA were analyzed. 36 of 38 fragments from the five tumors had double-enzyme PGK phenotypes. One piece from each of two tumors showed a single-enzyme phenotype. Histological, cell culture, and cloning studies indicate that the double-enzyme phenotypes reflect the presence of both types of malignant cells and not admixture of normal with neoplastic elements in the specimens tested for PGK. The results suggest strongly that these fibrosarcomas have a multicellular origin.