The metabolism of glucose in skin maintained in tissue culture

Spectroscopic studies of cutaneous photosensitizing agents--XVI. Disperse blue 35

The photochemistry (Type I and II) of the phototoxic textile dye Disperse Blue (DB-35) and its purified components has been studied using electron spin resonance in conjunction with spin trapping technique and the direct detection of singlet oxygen (1O2) luminescence. The main components of DB-35 (which is synthesized by the successive nitration, reduction and methylation of 1,8-dihydroxy-anthraquinone) were separated by HPLC and identified by mass spectrometry and 2-D NMR as 4,5-diamino-1,8-dihydroxyanthraquinone (4,5-DDHAQ; 62% of total dye) and 2,7-diamino-1,8-dihydroxyanthraquinone (2,7-DDHAQ; 31% of total dye). Minor components included 2,5-diamino-1,8-dihydroxyanthraquinone (2,5-DDHAQ) and a monomethylated derivative of either 4,5-DDHAQ or 2,7-DDHAQ. Irradiation (624 nm) of 4,5-DDHAQ and 2,7-DDHAQ in dimethylsulfoxide resulted in the generation of superoxide which was trapped by 5,5-dimethyl-1-pyrroline-N-oxide (DMPO). Visible light irradiation of the components in ethanol generated 1O2 with the yields decreasing in the following order: 4,5-DDHAQ greater than 2,5-DDHAQ greater than 2,7-DDHAQ. These findings indicate that upon irradiation by visible light DB-35 can generate active oxygen species which may be responsible for the photocontact dermatitis caused by this dye.

Factors controlling the expressed activity of histidine ammonia-lyase in the epidermis and the resulting accumulation of urocanic acid

The synthesis of urocanic acid by histidine ammonia-lyase in guinea-pig epidermis was investigated in various ways. 1. In epidermal homogenates the enzyme obeys Michaelis-Menten kinetics and shows marked dependence of its activity of pH, such that below pH 6 it is inactive. 2. Part-thickness skin samples cultured with radioactive histidine do not accumulate detectable radioactive urocanic acid during 3 days in culture. 3. Very little histidine ammonia-lyase activity can be detected in the living cells of the epidermis. The enzyme is almost completely restricted to the dead cells of the stratum corneum. 4. Radioactive histidine injected into living animals does not result immediately in the accumulation of radioactive urocanic acid. By 3 days after the injection, however, both radioactive urocanic acid and histidine appear, apparently at the expense of radioactive proteins, 5. In isolated stratum corneum, the residual histidine can be converted into urocanic acid by the histidine ammonia-lyase in the tissue only if the natural acidity of the tissue is neutralized. It is concluded from these observations that the biosynthesis of urocanic acid occurs naturally only in the stratum corneum, which contains only dead cells. The amount of urocanic acid accumulated is limited by the availability of free histidine produced by proteolysis of residual protein in these cells and by the penetration into the stratum corneum of the 'acid mantle' of the skin.

Epidermal proteins of cultured human and bovine keratinocytes

Bovine and human epidermal cells were cultured on mitomycin C treated fibroblasts. The cells were carried through four passages and found to synthesize fibrous proteins and insoluble cell envelopes. Acid buffer soluble fibrous protein, prekeratin, and urea soluble fibrous protein were both identified and the latter was the major component in older cultures. Some of the prekeratin polypeptides of intact tissue were not found in cultured cells, but the ones that were present corresponded to those of whole tissue. X-ray diffraction, amino acid analysis and immunological techniques were used to establish that the polypeptides were keratins. The insoluble cell envelopes had a higher proline and 1/2 cystine content than the fibrous protein, similar to what is found in whole epidermis. Histidase, a characteristic enzyme marker of whole epidermis, was not observed in cultured cells. These studies indicate that differentiation occurs in cultured cells but it may not be as complete as in intact tissue.

Growth and characterization of human skin epithelial cell cultures

In 129 of 140 attempts, human skin cells were successfully cultured on the dermal collagen bed of sterile, dead pigskin. Diploid epithelial cells grew selectively on the collagen bed; fibroblasts grew on the glass surfaces of the culture dishes. The cultures could be subdivided physically up to six times at a 1:2 split ratio, but at least 24 to 48 cell generations were produced over the months the cells could be carried. Much of the cell multiplication resulted in maturation into distinct basal, squamous, granular, and keratinized cell layers. The cultured cells were considered epithelial because of their shape, possession of intercellular bridges, desmosomes and tonofibrils, and because they formed maturating epithelium in vitro and upon transplantation back to the original human donor. As the cells grew they digested the pigskin collagen, thus producing clear zones that could be used to monitor and quantitate cell growth. Multiplication of epilthelial cells, rather than migration, was indicated by mitotic figures in colchicine-treated cultures and by DNA synthesis.