Clyde J. Dawe

HISTOCHEMICAL DEMONSTRATION OF COLLAGEN FIBERS IN ASCORBIC-ACID-FED CELL CULTURES

SummaryNine cultures of fibroblast cell types and 13 epithelial-like cell types were maintained for 1 week in media supplemented with L-asborbic acid (50 μg per ml). All fibroblast-like cultures produced extracellular fibers that stained positively by a silver-impregnation reticulin stain. Nine of the 13 epithelial-like cultures produced fibers that stained positively for reticulin. Nearly all cultures not supplemented with ascorbic acid showed no fiber staining. Those few lines that stained positively for reticulin in the absence of ascorbic-acid supplementation demonstrated only slight reticulin formation. Reticulin from one fibroblast culture and one epithelial culture was examined by electron microscopy, and the silver-impregnated fibrils were morphologically identical to collagen. The reticulin was digestible with collagenase, providing further evidence that the silver-impregnation reticulin stain identifies collagen in culture. The demonstration of collagen can be performed easily in histology laboratories using Formalin-fixed cells, and provides a means of assaying a functional property of cells in culture which is characteristic of connective tissue fibroblasts in general as well as certain specialized epithelia.

Epigenetic Factors in the Neoplastic Response to Polyoma Virus

One could hardly speak of epigenetic matters before an audience at the University of Chicago without taking cognizance of the outstanding contributions that have come from that institution to the field of epigenetics. Among them, and quite relevant to the work described in this report, are the classical works of Dr. F. R. Lillie and Dr. Hsi Wang on the formation of feathers. In a series of experiments that lead to the delineation of the specific morphogenetic functions of the epithelial and the mesenchymal components of feather follicles (1), Dr. Lillie and Dr. Wang developed a pattern of analysis that has found increasing use in developmental biology, and is beginning to find application in experimental oncology. It is safe to predict that the debt of oncologists to those original investigations will continue to increase.

Microcinematographic demonstration of synchronous and asynchronous myoepithelial contractions in mouse submandibular gland rudiments in organotypic culture.

SummaryTime-lapse phase-contrast cinematography revealed contractile activity within mouse submandibular salivary gland rudiments in organotypic culture. Three types of contraction were distinguishable. In type I (voiding contractions), all portions of the gland contracted synchronously, and the active state ranged from 30 min to 2 hr. In type II (priming contractions), all portions of the gland contracted synchronously, but the active state was shorter, ranging from 4 to 10 min. In type III (churning contractions), isolated foci in lobules or secretory units throughout the gland contracted asynchronously and had very short active states of about 1 min. By electron microscopy, myoepithelial cells could first be demonstrated in submandibular glands developing either in vitro or in vivo, at 21 days postconception. Contractions in the cultured rudiments began as early as 18 days postconception. Since neither smooth nor striated muscle could be identified in these glands by electron microscopy, the contractions are believed to result from myoepithelial activity that apparently may begin before ultrastructural evidence of myoepithelial differentiation is contractile function and indirect evidence has lent ample support to this presumption, the present study represents the first direct cinematographic demonstration and characterization of myoepithelial contractions, under conditions in vitro.

Some Comparative Morphological Aspects of Renal Neoplasms in Rana pipiens and of Lymphosarcomas in Amphibia

Those who first began to compare neoplasms of man with those of other animals had practical expectations in mind. One was that neoplasms resembling each other and arising from homologous organs and cells might have the same etiology, regardless of species differences among the hosts. While this hope springs eternal in the breast of the comparative oncologist, it has been learned from experience that such hope is not to be Scized upon without a good deal of circumspection, though it ought not be abandoned.

Differentiation in relation to neoplasia in old and new organisms

It is a stimulating exercise to look for common processes in the normal and abnormal development of organisms at various levels in phylogeny. Such an exercise is indeed a reaching for some of the principal objectives of comparative embryology and comparative oncology. These two disciplines may be combined if one accepts the premise that the development of cancer is a deviation within the realm