The course of culture of human keratinocytes: increase of heat-labile fraction of glucose-6-phosphate dehydrogenase

Human epidermal keratinocytes in cell culture are unique in reorganizing the formation of a stratified cellular sheet and performing terminal differentiation. The course of keratinocytes in culture was delineated over 50 days in the primary culture. The rapid increase in total DNA content commencing 2 weeks after plating corresponded to the appearance of small polygonal keratinocytes in groups. The DNA content reached its maximum after 25 days of cultivation, decreasing gradually thereafter. The protein content increase slowly until 16 to 18 days of cultivation, and then increased rapidly, though slightly behind the rapid increase in DNA. The maximum value of protein content was reached at 32 days, after which the value decreased when the keratinized cells of the uppermost layer began to detach. The heat-labile fraction of glucose-6-phosphate dehydrogenase was increased in 33- and 43-day cultures, when the DNA content was decreasing.

Intrahepatic stones and postoperative choledochoscopy

In 35 out of 38 cases of patients suffering from intrahepatic stones, complete removal of the stones has been carried out with repeated postoperative choledochoscopies, the average being 14.5. A follow-up study revealed that 34 cases remain asymptomatic and are leading a normal social life. The remaining one case died from pancreas carcinoma 22 months after successfully removing the entire stones. With the successful results using postoperative choledochoscopy, we believe that the endoscopy is the preferred approach insofar as it can relieve symptoms, prolong life and render cure in some cases, although it may be only palliative in others. This safer and more reliable procedure as opposed to the blind technique which is carried out under fluoroscopic control should be routinely used for management of intrahepatic stones.

Metabolism of benzo[a]pyrene in human epidermal keratinocytes in culture

The metabolism of benzo[a]pyrene (BP) in cultured human epidermal keratinocytes was investigated using thin layer chromatography, high pressure liquid chromatography and cell-mediated mutagenesis assay. Epidermal keratinocytes were obtained from skin of normal subjects and all experiments were performed on primary cultures. Human epidermal keratinocytes were shown to metabolize BP. Analysis of BP metabolites by high pressure liquid chromatography indicated that epidermal keratinocytes metabolize BP preferentially at non-K-regions such as positions 7, 8, 9 and 10, forming a moderate amount of BP-7,8-dihydrodiol, a precursor of the ultimate metabolite, BP-7,8-dihydrodiol-9,10-epoxide. Conjugate formation was examined by treating the medium with beta-glucuronidase and arylsulfatase. No appreciable amount of conjugates was formed by epidermal keratinocytes, except in one culture which gave small peaks eluted in the phenol regions after beta-glucuronidase treatment. The metabolic activity of human epidermal keratinocytes on BP was further demonstrated by a cell-mediated assay, in which V79 Chinese hamster cells were cultured on top of sheets of keratinocytes and treated with BP for 48 h. Mutation of the V79 cells, demonstrated as ouabain resistance, was induced in a dose-related fashion. The extent of induced mutation was higher than that observed using rat embryo cells as the activating layer, although the shape of the dose-response curves was different.

Stimulation by melanocyte stimulating hormone and dibutyryl adenosine 3'5'-cyclic monophosphate of DNA synthesis in human melanocytes in vitro

The proliferation of human melanocytes in vitro was stimulated by MSH. This stimulation was further intensified by the simultaneous addition of theophylline with MSH. Theophylline alone stimulated proliferation moderately. Dibutyryl cyclic AMP strongly stimulated the proliferation, but sodium butyrate, 5'-AMP and cGMP did not. The stimulation by dibutyryl cyclic AMP was continued up to 4 days so far tested. These findings are directly opposed to those on mouse melanoma cells in culture which responded with retarded growth to MSH and cyclic AMP. It is suggested that the difference of proliferation control may explain the different reaction of the melanocyte and the melanoma cells. The epidermal melanocytes seem to belong to the exceptional group of the cells which responded to cyclic AMP with accelerated proliferation.

Effects of melanocyte stimulating hormone and theophylline on human melanocytes in vitro

The effects of MSH on the human melanocyte in vitro were studied. The addition of MSH up to the concentration of 40 mug/ml into the culture medium did not produce appreciable change on the morphology of the melanocyte. The melanocyte, however, responded to the simultaneous addition of MSH and theophylline with marked increase in the length and complexity of the dendritic process. Melanin synthesis, as indicated by the uptake of tyrosine in the presence of an inhibitor of protein synthesis, was remarkably activated by the simultaneous addition of MSH and theophylline. MSH alone activated the melanin synthesis only slightly, but the increase in the uptake of tyrosine was significant statistically. These results were discussed in terms of the MSH-cyclic AMP cascade in which theophylline worked as an inhibitor of cyclic AMP phosphodiesterase, and increased the intracellular level of cyclic AMP by inhibiting catabolism of cyclic AMP.