Influence of the major histocompatibility complex (H-2) on glucocorticoid-stimulated pulmonary surfactant synthesis in two congenic mouse strains.

Mice with different histocompatibility alleles in otherwise identical backgrounds (congenic inbred strains of H-2a and H-2b haplotypes), were used to study the possible influence of the major histocompatibility complex (MHC) upon glucocorticoid-stimulated pulmonary surfactant synthesis during embryonic and fetal stages of mouse lung development. Pregnant C57BL/10SnJ (H-2b) and congenic B10.A/SnSgJ (H-2a) mice were administered single or consecutive intraperitoneal injections of betamethasone during the period of 14 through 17 days gestation.

Differentiation of cultured palatal shelves from alligator, chick, and mouse embryos.

Palatal shelves from embryonic alligators, chicks, and mice were explanted at various stages of development and organ cultured in either chemically defined, serumless media or the same media supplemented with 10% fetal calf serum. Shelves from each vertebrate were either cultured singly or in contact, and heterologous combinations of palatal shelves from different animals were made: chick/mouse, chick/alligator, and mouse/alligator. Epithelial differentiation (particularly that of the medial shelf edge) was assayed by vital staining, histology, and scanning electron microscopy.

Does anterior (non-polarizing region) tissue signal in the developing chick limb?

The morphogenetic properties of embryonic chick limb bud tissue from anterior positions and from the posterior (polarizing) region are compared. Quail grafts, which possess the distinctive nucleolar cell marker, and gamma-irradiation are used. Supernumerary limb structures induced by anterior tissue wedge grafts are found to be nearly exclusively graft, donor tissue derived.

Enamel gene products during murine amelogenesis in vivo and in vitro.

Epithelial-mesenchymal interactions regulate determination and differentiation of amelogenesis. Our attention has focused on identification of ameloblast gene products, the regulation of enamel mRNA synthesis, and subsequent translation into enamel proteins in vivo and in vitro. Enamel proteins are the most abundant gene products synthesized in fully-differentiated ameloblasts.

Effects of ultraviolet light on the activity of an avian limb positional signalling region.

Cells from a region on the posterior margin of the developing avian limb bud (the polarizing region) can signal positional information to responding anterior cells. Polarizing activity may be assayed by disaggregation of the tissue into single cells, followed by reaggregation and grafting of cell pellet. This method enables treatments of the cells while in single-cell suspension.

Epithelial-derived basal lamina regulation of mesenchymal cell differentiation.

The mechanisms by which epithelial-mesenchymal interactions result in differentiation are not known. A number of recombinations between vertebrate tissues associated with epidermal organs (e.g.

Positional signal transmission in the developing chick limb.

It has been suggested that the pattern along the antero-posterior axis of the embryonic developing chick limb arises from a gradient of diffusible morphogen produced by a special region of cells on the posterior margin of the limb bud, called the polarizing region. Grafts of posterior polarizing-region tissue to an anterior site in an embryonic chick wing bud result in mirror-image duplication of the limb bud; typically three extra wing digits are produced (Fig. 1f, g).

Effects of biochemical inhibitors on positional signalling in the chick limb bud.

In 3- to 4-day embryonic chick limb buds, a region at the posterior margin of the limb, the zone of polarizing activity, appears to be responsible for signalling positional information along the anteroposterior axis. Our experiments were designed to test which biosynthetic processes are required for polarizing activity. We have treated polarizing regions with biochemical inhibitors, and then assayed their abilities to induce limb reduplications when grafted into anterior sites on host limb buds and also measured their capacities for protein, RNA, and DNA synthesis.

Microtubule protein preparations from C6 glial cells and their spontaneous polymer formation.

C6 cell tubulin is indistinguishable from hog brain tubulin with respect to its molecular weight, amino acid composition, and colchicine-binding activity. Moreover, microtubule assembly systems from both sources form the same structures: rings, ribbons, tubules, and drug-induced polymers. There is, nevertheless, a difference between the cultured cell and brain systems which lies in the nature of their microtubule-associated accessory proteins.

Identification of tubulin from the yeast Saccharomyces cerevisiae.

A tubulin-like protein was identified in the lower eukaryote Saccharomyces cerevisiae. The following criteria were used: (i) copolymerization of the 35S-labeled yeast protein with porcine brain tubulin; (ii) immunoprecipitation of the 35S-labeled yeast protein with antiflagellar tubulin antibody; (iii) the presence of the yeast protein as a constituent of isolated yeast nuclei; and (iv) splitting of the yeast protein in a gel electrophoretic system containing sodium dodecyl sulfate that resolved the alpha- and beta-tubulin chains from other sources. This protein did not appear to have significant affinity for the plant alkaloid, Colcemid.