Gerard Redziniak

Decreased biosynthesis of actin and cellular fibronectin during adipose conversion of 3T3-F442A cells. Reorganization of the cytoarchitecture and extracellular matrix fibronectin

Differentiation of 3T3‐F442A cells was accompanied by changes in cell morphology, decreased synthesis and assembly of actin and fibronectin. The network of microfilament stress fibers detected with NBD‐phallacidin was altered during adipose conversion of 3T3‐F442A cells. Parallel to this, the disappearance of fibrillar bundles of extracellular matrix fibronectin was observed by immunofluorescence staining. The pericellular fibronectin content, detected by immunoblotting, strongly diminished during the differentiation process. An altered rate of biosynthesis of both proteins was also measured by [35S]‐methionine pulse‐labeling and immunoprecipitation. A 4–5‐fold decrease in cellular fibronectin synthesis was observed in adipocytes compared to control preadipocytes. Conversely, non‐differentiating 3T3‐C2 control cells did not reorganize either the cytoskeletal architecture or the extracellular matrix fibronectin in the resting state. These results suggest that the decreased rate of biosynthesis of cell‐associated fibronectin is correlated with that of actin. Moreover, both events can essentially be ascribed to differentiation.

C32 human melanoma cell endogenous lectins: Characterization and implication in vesicle-mediated melanin transfer to keratinocytes

To optimize skin pigmentation in order to help body prevention against UV radiation, the mechanism of melanin pigment transfer from melanocytes to keratinocytes must be elucidated. Melanin transfer to keratinocytes requires specific recognition between keratinocytes and melanocytes or melanosomes. Cell surface sugar-specific receptor (membrane lectin) expression was studied in human C32 melanoma cells, an amelanotic melanoma, by flow cytometry analysis of neoglycoprotein binding as an approach to the molecular specificity. Sugar receptors on melanocytes are mainly specific for alpha-L-fucose. Their expression is enhanced upon treatment by the diacylglycerol analogue 1-oleoyl-2-acetylglycerol, which can induce melanin synthesis in amelanotic human melanoma cells in a dose-dependent manner. Flow cytometry analyses showed a small-sized population of vesicles distinguishable from large cells by their fluorescence properties upon neoglycoprotein binding. Sorting indicated that the small-sized subpopulation is composed of vesicles produced by melanocytic cells. Upon vesicle formation, a selective concentration of sugar receptors specific for 6-phospho-beta-D-galactosides appears in the resulting melanocytic vesicles. Vesicles are recognized and taken up by cultured keratinocytes and a partial inhibitory effect was obtained upon cell incubation in the presence of neoglycoproteins, indicating a possible participation of sugar receptors in this recognition. The validity for such a model to help in understanding the natural melanin transfer by melanosomes is confirmed by electron microscopy, which demonstrates the presence of melanin inside keratinocytic cells upon incubation with melanocytic vesicles.

Growth and differentiation of 3T3-F442A preadipocytes in three-dimensional gels of native collagen☆

Three-dimensional gels of native type I collagen have been used as a substrate for growth and differentiation in 3T3 adipocyte precursors. Such hydrated lattices can support a sustained cell growth leading to several 10-fold increases in cell number within 2 weeks. During this period, the cells condense the hydrated collagen lattice to a tissue-like structure one-fourth of the area of the initial gel. From Days 10 to 12, the cells progressively exhibit morphological characteristics of adipocytes and accumulate lipid droplets as evidenced by Oil Red O staining. Lipoprotein lipase activity appears very early; between Days 8 and 22 it sharply increases 15-fold and then remains stable at a very high level (about 30 nmol/min/10(6) cells). The emergence of glycerophosphate dehydrogenase activity is delayed; it becomes detectable at Day 15 and progressively increases up to 700 nmol/min/10(6) cells at Days 35-40. Thus, this adipose tissue equivalent appears to be a potential model for studying adipocyte function.

Phospholipids in Cosmetics: In Vitro Technique Based on Phospholipids Membrane to Predict the in Vivo Effect of Surfactants

In cosmetology, phospholipids in terms of “lecithin extract” (mixture of phospholipids alone or with triglycerids) are used as coemulsifiers and sometimes as moisturizing substances3,4,7,10,11,12,14,15,19.