The recent availability of cell biochemical techniques as ultracentrifugation separation of cell particles and density gradient centrifugation made possible the microdissection of and biochemical studies on melanin-forming cells which have elucidated the steps involved in the formation of melanosomes. A series of experiments along the studies on melanogenesis has been carried out within the last several years. Experimental data obtained from these studies are all compartible with the hypothesis, melanosome concept that tyrosinase is synthesized in ribosomes, transferred via endoplasmic reticulum to the Golgi area, where tyrosinase is separated into small units, each of which is surrounded by a membranous envelope. Within each envelope, the tyrosinase molecules assume an ordered pattern, after which melanin biosynthesis begins and the particle is known as a melanosome. As melanin gradually accumulates, the melanosome is transformed into a uniformly dense and structureless particle, a mature melanosome. The problems described herein are the in vitro experiments on the melanization process of melanosomes and the controling mechanism of thiol-group in melanin formation in melanocyte. The reciprocal relationship between tyrosinase activity and melanization of melanosomes has been demonstrated and data presented herein would be additional evidence to support this concept. Two kinds of melanosomes in defferent developmental stages were prepared from the mouse melanoma. Melanosome No. 1 is less melanized and possesses more tyrosinase activity than melanosome No. 2. Comparison of the rate of incorporation of 14C-DOPA in vitro by melanosome No. 1 and No. 2 was carried out. The experimental results showed that melanosome No. 1, immature melanosome can synthesize and deposit more melanin than melanosome No. 2, mature melanosomes. The melanization mechanism of melanosomes was further studied. Melanosomes isolated from the mouse melanoma were incubated with the excess amount of 14C-DOPA. The amount of melanin formed was dependent on the amount of melanosomes incubated but relationship between them was an upward convex rather than a straight line. It was assumed that there are some kinds of mechanisms which inactivate the enzyme. Kinetic studies were carried out in order to analyze the kind of inactivation mechanisms thought to be present. The exprimental results obtained could not be explained by assuming only one type of inactive enzymeproduct complex. However, they could be explained on the basis of simultaneous formation of two or more types of inactive enzymn-product complex. The sulfhydryl group has been considered as one of the important controling factors in melanin formation in melanocytes. The inhibitory effects of thiol compounds ont yrosine hydroxylase and tyrosinase in melanosomes isolated from mouse melanoma are descrided and an in vitro study of the reaction between an oxidation product of DOPA and glutathione in the presence of mammalian tyrosinase is reported. The formation of new chemical compounds resulted from the presence of DOPA, glutathione and mammalian tyrosinase in solution at pH 6.8. The existence of chemical bonding between glutathione and an oxidation product of DOPA, probably DOPA-quinone was demonstrated. The glutathione-derived reaction product remained soluble in the reaction medium and did not precipitate on the melanosomes. The pKi values of glutathione and cysteine on tyrosine hydroxylase were much smaller than those on tyrosinase. The inhibition of tyrosine melanin formation by sulfhydryl compounds may take place in two ways: by inhibition of the enzyme tyrosinase, and by the formation of new compounds in which intermediates of the tyrosine-tyrosinase reaction are trapped by the sulfhydryl compounds. (to be cotinued)
Precancerous dermatoses, in a narrow sense, includes carcinoma in situ such as Paget’s disease, Bowen’s disease and erythroplasia Queyrat. Furthermore, keratosis senilis, leukoplakia, xeroderma pigmentosum and the like are inculuded in this group of diseases. In a broader sense, however, the precancerous dermatoses, caused by chronic inflammatory process, tissue degeneration, regenerating process, dysplasia and so on, comprise lupus erythematosus discoides, radiodermatitis, cicatrix and many miscellaneous diseases. Firstly, were shown the statistical observations about above-mentioned precancerous dermatoses encountered during recent three years at the Department of Dermatology, Faculty of Medicine, Kyushu University. Secondly, histological features, typical and atypical ones were exhibited, being seclected out of the tissue preparations collected from many hospitals. Moreover, quantitative observations were tried about the size and staining properties of the epithelial cells, especially of its nucleous, constructing the lesions involved in a few cases of Bowen’s disease and keratosis senilis.
Clinical and histopathological observations revealed that burn scars seemed to develop into squamous cell carcinoma via following intermediate stages; (1) atrophic changes, (2) acanthotic changes and (3) acanthotic changes with atypical cells (referred to hereafter precancerous condition). Based upon the avove results, ultrastractural comparisons of the keratinocytes in each of these intermediate stages as well as in squamous cell carcinomas developed on burn scars were performed and obtained following results: 1) keratinocytes in the above precancerous condition displayed nuclei which contained large nucleoli with distinct nucleolonemata, numerous perichromatin granules, and nuclear bodies; The cytoplasm contained well-developed rough endoplasmic reticulum with tubular cisternae and free ribosom es forming polysome; Tonofibrils decreased in number and were irregularly distributed; Desmosomes were scanty and intercellular spaces were mostly widened; Basal laminae often showed irregularity in width and electron density, and/or partial discontinuity; 2) The above changes were observed more conspicuouly in keratinocytes in cancer nests (cancer cells), and increased in grade with the advancement of Broders’ grade of malignancy.
Six cases with malignant melanoma and a case with melanotic freckle Hutchinson, were studied by electronmicroscopically. In the cases with malignant melanoma, numerous long ellipsoid melanosomes and premelanosomes were noted in the 3 cases, while numerous oval, ring like and/or partially melanized melanosomes were observed in the other 2 cases with melanoma arising from melanotic freckle Hutchinson. Melanosomes and premelanosomes in another case, were distinctly small in size and decreased in number. In a case with melanotic freckle Hutchinson, melanosomes and premelanosomes were generally ellipsoid and/or round. A direct communication of endoplasmic reticulum to melanosome was noted in 2 cases.
After ingestion of the azo-dye in rats, the diffuse hyperplasia of hepatocytes appeared in the initial stage, followed by the nodular hyperplasia, and hepatoma production occurred in some of the nodules in the later stage. These progressive alterations of hepatic tissues might be explained by the “summation theory”. If such stepwise transformations are proceeding in the course of the azo-dye carcinogenesis, the manifestatively, but irreversiblly transformed cells should appear at the intermediate stage. This paper deals with the consequence of the “precancerous state” in the early stage of 3’-methyl-4-dimethylaminoazobenzene ingestion.
Hyperplastic nodules developed in rat liver as the result of feeding diets containing 3'-methyl-4-dimethylaminoazobenzene, 2-fluorenyl-acetamide or DL-ethionine. There is evidence that such nodules are in a prodromal stage of cancer. The remarkable changes in ultrastructure as well as in DNA and RNA syntheses occurred in hepatocyte nuclei in the precancer liver. The striking features of these chages were enormous enlargement of nucleoli, disapperance of condensed chromatin aggregates and dense appearance of the inner layer of nuclear envelope. The ultrastructural and autoradiographic patterns of nuclei, especially of nucleoli showed that the transport of nucleolar product into the cytoplasm was blocked, and the turnover of DNA in the hyperplastic precancer cell nuclei was remarkably active as compared with that in the non-nodular portions of the same material or in the normal liver. It was revealed that the ultrastructure of cell nuclei in such diseases as the Bowen’s disease, senile keratosis and leukoplakia was in a similar stage as those in precancerous hepatic nodules. The nuclear body appearing in these diseases was discussed as to the fine structure and origin. The nuclear structure in the Ewing’s sarcoma and osteogenic sarcoma was compared with that of precancerous, cutaneous diseases. The intranuclear inclusions in the precancerous skin diseases were composed from protein, but those of osteogenic sarcoma from crystalline elements consisting of phospholipids.
Six patients with systemic lupus erythematosus were treated with azathioprine in a dosage of 500mg to 100mg per day together with steroids. Four of these patients showed improvements of clinical and laboratory findings in which serum immunoglobulin and antinuclear antibody titer decreased and C′3 increased in a a few cases. Although it is difficult to evaluate the effectiveness of this immunosuppresive agent in view of clinical and laboratory findings, it is deserving of further study as an additional treatment of systemic lupus erythematosus.
Electron microscopic observations were done on the lesion of psoriasis vulgaris topically applied 0.1% vitamin A acid ointment for 2 and 7 days. On the lesion of psoriasis vulgaris, the intercellular spaces were widened in which less dense amorphous materials and infiltrated cells were seen. In the cytoplasm of keratinocyte the irregular shapes of nucleus were seen, and the tonofibrillar formation were observed, and the structureless area of perinuclear part in which contained mitochondria were seen. On the upper parts of the prickle cell layer, a lot of lamellar bodies were seen among the tonofibrils in the cytoplasm, and just over this layer the small keratohyalins were revealed in the cytoplasm. On the parakeratotic layer the tonofibrils, vesicles, mitochondria and ribosomes were revealed. The changes due to vitamin A acid were more remarkable in 7th day’s findings than in 2nd day’s findings. In 7th day’s findings, a lot of vesicles were in the cytoplasm of psoriatic epidermis and the contents of these vesicles were regarded as the mucoid substance.