Fibronectin production by cultured human lung fibroblasts in three-dimensional collagen gel culture

Summary In vivo, fibroblasts are distributed in a three-dimensional (3-D) connective tissue matrix. Fibronectin is a major product of fibroblasts in routine cell culture and is thought to regulate many aspects of fibroblast biology. In this context, we sought to determine if the interaction of fibroblasts with a 3-D matrix might affect fibronectin production. To examine this hypothesis, fibronectin production by fibroblasts cultured in a 3-D collagen gel or on plastic dishes was measured by ELISA. Fibroblasts in 3-D gel culture produced more fibronectin than those in monolayer culture. Fibroblasts in 3-D culture produced increasing amounts of fibronectin when the collagen concentration of the gel was increased. The 3-D nature of the matrix appeared to be crucial because plating the fibroblasts on the surface of a plastic dish underneath a collagen gel was not different from plating them on a plastic dish in the absence of collagen. In addition to increased fibronectin production, the distribution of the fibronectin produced in 3-D culture was different from that of monolayer culture. In monolayer culture, more than half of the fibronectin was released into the culture medium. In 3-D culture, however, approximately two-thirds remained in the collagen gel. In summary, the presence of a 3-D collagen matrix increases fibroblast fibronectin production and results in greater retention of fibronectin in the vicinity of the producing cells.     

Radiation effects on erythrocyte membrane structure studied by the intrinsic fluorescence.

The changes in the intrinsic fluorescence, primarily from tryptophan residues, of sheep erythrocyte membranes following X-irradiation (0--4000 R) were investigated. The experiments showed that there was (1) a decrease in the intensity of fluorescence with increasing dose of X-rays, (2) a small shift of fluorescence emission to longer wavelengths, (3) a decrease in the fluorescence polarization, and that (4) treatment of membranes with a perturbing solvent, 2-chloroethanol, can eliminate the effects of X-rays. The amount of tryptophan in the membranes was not altered after X-irradiation. It was also shown that sulphydryl reagents, N-ethylmaleimide and 2,2'-dithiodipyridine, induced similar fluorescence changes. From these results it was concluded that the fluorescence changes could result from a change in the environment surrounding tryptophan residues, from being relatively non-polar to being more polar, implying that conformational changes of membrane proteins are brought about by low doses of X-rays.     

Erythrocyte membrane glycerophospholipid organization is normal in multiple sclerosis

The phospholipid composition of erythrocyte membranes from patients with multiple sclerosis (MS) was found to be normal, in agreement with previous reports. The transbilayer asymmetry of the glycerophospholipids in MS red cells was probed using bee venom phospholipase A₂ and was also found not to be significantly different from normal. Abnormal membrane glycerophospholipid organisation is therefore not involved in the increased red cell size, osmotic fragility, and electrophoretic mobility associated with MS.     

Application of colour laser microscope for observing living biological specimens

Pollen-mother cells from Lilium longiflorum, human metaphase chromosomes and human spermatozoa, were observed under a colour laser microscope. Helical mitochondrial strands were clearly evident in the middle piece of human spermatozoa. The technique enables living specimens to be conveniently and effectively examined.     

Identification of cellular factors that recognize UV-damaged DNA in Drosophila melanogaster.

Using a gel electrophoresis DNA band-shift assay, we have identified 2 DNA-binding protein complexes in wild-type Drosophila embryonic cells which have high affinity for UV-irradiated, double-stranded DNA. Screening of Drosophila mutants deficient in DNA repair led to the identification of 5 mutants which lacked either one of the 2 protein complexes. Four excision repair-deficient mutants (mus-201, phr, mus-308 and mus-205) lacked one protein complex (Factor 2). The other protein complex (Factor 1) was not detectable in the post-replication repair-deficient mutant mus-104. These findings might suggest the possible involvement of these gene products in lesion recognition and repair of UV-induced photoproducts in DNA.     

Phosphorylation state of the histone variant H2A.X controls human stem and progenitor cell fate decisions

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