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M Bernfield

Publications and source records attributed to M Bernfield.

97 records · Page 6Linked to original sources
PubMed1981

Type I collagen reduces the degradation of basal lamina proteoglycan by mammary epithelial cells.

When mouse mammary epithelial cells are cultured on a plastic substratum, no basal lamina forms. When cultured on a type I collagen gel, the rate of glycosaminoglycan (GAG) synthesis is unchanged, but the rate of GAG degradation is markedly reduced and a GAG-rich, basal lamina-like structure accumulates. This effect of collagen was investigated by comparing the culture distribution, nature, and metabolic stability of the 35S-GAG-containing molecules produced by cells on plastic and collagen. During 48 h of labeling with 35SO4, cultures on collagen accumulate 1.4-fold more 35S-GAG per microgram of DNA. In these cultures, most of the extracellular 35S-GAG is immobilized with the lamina and collagen gel, whereas in cultures on plastic all extracellular 35S-GAG is soluble. On both substrata, the cells produce several heparan sulfate-rich 35S-proteoglycan fractions that are distinct by Sepharose CL-4B chromatography. The culture types contain similar amounts of each fraction, except that collagen cultures contain nearly four times more of a fraction that is found largely bound to the lamina and collagen gel. During a chase this proteoglycan fraction is stable in cultures on collagen, but is extensively degraded in cultures on plastic. Thus, collagen-induced formation of a basal lamina correlates with reduced degradation and enhanced accumulation of a specific heparan sulfate-rich proteoglycan fraction. Immobilization and stabilization of basal laminar proteoglycan(s) by interstitial collagen may be a physiological mechanism of basal lamina maintenance and assembly.

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PubMed1981

Basal lamina formation by normal and transformed mouse mammary epithelial cells duplicated in vitro.

Cells from low-passage (LP) cultures of a mouse mammary epithelial line (NMuMG cells) form a basal lamina when they are cultured on a type I collagen gel substratum. A high-passage (HP) strain of this line maintained the morphologic, serologic, and karyologic properties of the LP cells. For the determination of whether transformation of the NMuMG cells might lead to defects in the basal lamina, cells from LP cultures were compared in vivo and in vitro with cells of HP cultures for tumorigenicity, growth characteristics, and ability to form a lamina. The LP NMuMG cells had a typical epithelial morphology and showed no cytologic evidence of cancer. They formed an ultrastructurally normal continuous basal lamina in vivo when they were injected into athymic nude mice. In contrast, the HP cells were pleomorphic and highly invasive when injected into nude mice where they showed frequent and large basal lamina defects. These cells also accumulated only traces of lamina-like materials when cultured on a collagen gel, indicating that neoplastic transformation had markedly reduced the ability of NMuMG cells to form a basal lamina both in vivo and in vitro. Because the collagen gel culture system duplicated the in vivo situation with regard to basal lamina integrity, the basis for this lack of in vitro basal lamina formation may be physiologically relevant for the mechanism of malignant invasion.

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PubMedDate not supplied

The distribution of syndecan during murine secondary palate morphogenesis.

The distribution of syndecan, an integral membrane proteoglycan, has been immunohistochemically mapped during the course of murine secondary palate morphogenesis, gestational days 12-15. Syndecan has been shown to mediate cell adhesion and shape change and to be involved in epithelial-mesenchymal interactions during the morphogenesis of several structures. Changes in epithelial cell architecture accompany and may serve to direct the reorientation of the murine secondary palatal shelves from a vertical position on either side of the tongue to a horizontal and adhering position above it. Using a monoclonal antibody made to the core protein of the ectodomain of syndecan, staining was observed to correlate with epithelial cell shape, packing and degree of differentiation. Staining of condensing mesenchyme was also observed. Syndecan may be involved in modulating epithelial cell shape, architecture and fates during both major phases of secondary palate morphogenesis: shelf reorientation and midline epithelial seam dissolution.

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