Search PubMed⌕ Search

Biomedical subjects

M R Bernfield

Publications and source records attributed to M R Bernfield.

31 records · Page 2Linked to original sources
PubMed1972

Acid mucopolysaccharide (glycosaminoglycan) at the epithelial-mesenchymal interface of mouse embryo salivary glands.

Acid mucopolysaccharide (glycosaminoglycan) has been demostrated at the epithelial-mesenchymal interface of mouse embryo submandibular glands by (a) specific staining for polymeric sulfate with Alcian blue 8 GX at various magnesium concentrations, (b) specific staining for polymeric uronic acid by selective oxidation of these residues to Schiff-reactive compounds, (c) electron microscope localization of ruthenium red staining, (d) radioautographic localization of glucosamine-(3)H and (35)SO(4), and (e) by susceptibility of the glucosamine radioactivity at the interface to digestion with protease-free hyaluronidase. Moreover, material labeled with glucosamine-(3)H and (35)SO(4) and with chemical characteristics identical with those of acid mucopolysaccharide were isolated from the glands. Acid mucopolysaccharide is distributed over the entire epithelial surface. The amount of acid mucopolysaccharide, as revealed by the staining procedures, is nearly equivalent at all sites. In contrast, the rate of accumulation of glucosamine-labeled mucopolysaccharide is greater at the surface of the distal ends of the growing and branching lobules. This distribution of newly synthesized acid mucopolysaccharide at the sites of incipient cleft formation suggests that surface-associated acid mucopolysaccharide is involved in the morphogenetic process. A mechanism of branching morphogenesis is proposed which accounts for the distribution of collagen fibers and total and newly synthesized acid mucopolysaccharide at the epithelial surface.

Ammonia↗
PubMed1972

Dependence of salivary epithelial morphology and branching morphogenesis upon acid mucopolysaccharide-protein (proteoglycan) at the epithelial surface.

The morphogenetic role of the acid mucopolysaccharide (glycosaminoglycan) at the epithelial surface of mouse embryo submandibular glands has been studied by comparing the in vitro morphogenesis of epithelia from which the mucopolysaccharide was removed with that of those that retained the mucopolysaccharide. Epithelia isolated free of mesenchyme by procedures which retain the bulk of surface mucopolysaccharide maintain their lobular shape and undergo uninterrupted branching morphogenesis in culture in direct combination with fresh mesenchyme. Under identical culture conditions, epithelia from which surface mucopolysaccharide was removed lose their lobules and become spherical masses of tissue. During continued culture, the spherical epithelia produce outgrowths from which branching morphogenesis resumes. The morphogenetically active mucopolysaccharide is localized within the basal lamina of the epithelial basement membrane and appears to be bound to protein. During culture in combination with mesenchyme, epithelia undergoing uninterrupted morphogenesis show maximal accumulation of newly synthesized surface mucopolysaccharide at the distal ends of the lobules, the sites of incipient branching. In contrast, the material accumulates nearly equivalently over the surface of the spherical epithelia, with the exception that there is greater accumulation of the material at the surfaces of the budding outgrowths, the sites where morphogenesis will resume. Rapidly proliferating cells are localized within the lobules of epithelia undergoing uninterrupted morphogenesis, but are distributed uniformly in the cortex of the spherical epithelia, except for the outgrowths which show a greater localization of proliferating cells. It is concluded that normal salivary epithelial morphology and branching morphegenesis require the presence of acid mucopolysaccharide-protein within the epithelial basal lamina.

Ammonia↗
PubMed1970

A specific hepatic transfer RNA for phosphoserine.

Radioactive O-phosphoryl-L-serine was detected after alkaline deacylation of rat and rooster liver [(3)H]seryl-tRNA acylated in vitro with homologous synthetases. Ribonuclease treatment of this tRNA yielded a compound with the properties of phosphoseryl-adenosine. Benzoylated DEAE-cellulose chromatography of seryl-tRNA yielded four distinct peaks, only one of which contained phosphoserine. A unique fraction for phosphoserine was also found on chromatography of nonacylated tRNA. In ribosome binding studies, this fraction responded very slightly with poly(U,C), but not with any of the known serine trinucleotide codons. Substantial incorporation of [(3)H]-serine into protein from this tRNA species was observed in an aminoacyl-tRNA dependent polysomal system derived from chick oviducts. No phosphoserine was found in Escherichia coli or yeast seryl-tRNA acylated with homologous enzymes, nor in E. coli seryl-tRNA acylated with liver synthetase. In the absence of tRNA, free phosphoserine was not formed in reaction mixtures, which suggests that phosphoseryl-tRNA arises by phosphorylation of the unique seryl-tRNA species. These results demonstrate a discrete tRNA(Ser) species in rat and rooster liver containing phosphoserine and suggest that this tRNA is involved in ribosomal polypeptide synthesis.

Amino Acids↗