Abstract. The majority of malignant melanoma cell types are able to produce melanin and the degree of melanin synthesis in various types of cultured cell line differs. In this study, we evaluated three types of cultured cell line, MNT-1, HM3KO and G-361, with differing melanin production levels. The level was greatest in the MNT-1 cells, lower in the HM3KO cells and lowest in the G-361 cells. In addition, a positive correlation between melanin production and tyrosinase activity was observed. The molecular masses of tyrosinases from HM3KO and G-361 cells were marginally lower than those from MNT-1 cells. Glycosylation inhibitor treatment on MNT-1 cells caused decreases in the molecular mass of tyrosinase, its activity and melanin production. An immunoprecipitation assay using anti-tyrosinase indicated that the immature glycosylated tyrosinases were associated with a type of chaperone, Hsp70. The interaction between tyrosinase and Hsp70 was also detected in HM3KO and G-361 cells. The results indicated that the immature glycosylation of tyrosinase has a critical effect on the melanin-producing ability of melanoma cells. IntroductionMelanin is important in protecting the skin from the harmful effects of ultraviolet irradiation and absorbing toxic drugs and chemicals. Melanin is synthesized in two predominant forms, black-brown pigments (eumelanin) and red-yellow pigments (pheomelanin), within the melanosomes of melanocytes by at least three melanogenic enzymes. Tyrosinase (EC1.14.18.1) is one of the predominant enzymes mediated by the melanin production process in melanosomes (1). The enzyme catalyzes the rate-limiting step of the hydroxylation of tyrosine to dihydroxyphenylalanine (DOPA) and its further oxidation to DOPA-quinone (2). Melanin synthesis is maintained by a number of regulatory processes that act at various steps during the synthesis of the protein in the endoplasmic reticulum (ER), Golgi body and melanosomes, and disorders in any of these processes lead to abnormal pigmentation.Malignant melanoma (MM) cells are derived from epidermal melanocytes and nevi (3), and numerous cultured melanoma cell lines have been established from human and mouse MMs. The majority of MMs produce melanin, and the degree of melanin synthesis differs for each type of cultured cell line (4-6). For example, MNT-1 cells were demonstrated to be highly pigmented MMs (4); however, SK-Mel-28 cells were not able to produce melanin due to a mutation in the endocytic pathway that affected the endosomal trafficking of tyrosinase (5). In addition, B16F10 cells were pigmented; whereas amelanotic melanoma was not pigmented, due to the increased expression of proteasome subunit p27 (6).In this study, three cultured cell lines, MNT-1, HM3KO and G-361, were observed. These cell lines differed in their degrees of melanin synthesis, and thus, the determinants of the degree of melanin synthesis were investigated. Materials and methodsCell culture. The MNT-1 (from Dr VJ Hearing, Laboratory of Cell Biology, National Cancer Institute, National Ins...

The aim of this study was to evaluate the diagnostic potential of whole-body MRI (WB-MRI) for the detection of bone marrow and extramedullary involvement in patients with non-Hodgkin's lymphoma. WB-MRI, which was performed on 34 patients, consisted of the recording of T1-weighted spin-echo images and a fast STIR sequence covering the entire skeleton. The WB-MRI findings for bone marrow and extramedullary involvement were compared with those from (67)Ga and bone scintigraphies and bone marrow biopsy results. Two MRI specialists reviewed the WB-MRI results and two expert radiologists in the field of nuclear medicine reviewed the bone and (67)Ga scintigraphy findings. Bone marrow and extramedullary involvement of non-Hodgkin's lymphoma were confirmed by follow-up radiographs and CT and/or a histological biopsy. The detection rate of WB-MRI was high. More bone marrow involvement was detected by biopsy, and more lesions were detected by scintigraphies. In total, 89 lesions were detected by WB-MRI, whereas 15 were found by biopsy, 5 by (67)Ga scintigraphy, and 14 by bone scintigraphy. WB-MRI could also detect more extramedullary lesions than (67)Ga scintigraphy; i.e., 72 lesions were detected by WB-MRI, whereas 54 were discovered by (67)Ga scintigraphy. WB-MRI is useful for evaluating the involvement of bone marrow and extramedullary lesions throughout the skeleton in patients with non-Hodgkin's lymphoma.

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The respiratory effect of progestin differs among various animal species and humans. The rat does not hyperventilate in response to exogenous progestin. The present study was conducted to determine whether administration of combined progestin and estrogen prompts ventilatory stimulation in the male rat. Ventilation, blood gases, and metabolic rates (O2 consumption and CO2 production) were measured in the awake and unrestrained male Wistar rat. The combined administration of a synthetic potent progestin (TZP4238) and estradiol for 5 days significantly increased tidal volume and minute expiratory ventilation (VE), reduced arterial PCO2, and enhanced the ventilatory response to CO2 inhalation (delta VE/delta PCO2). On the other hand, respiratory frequency, O2 consumption, CO2 production, and body temperature were not affected. The arterial pH increased slightly, with a concomitant decrease in plasma [HCO3-]. Administration of either TZP4238 or estradiol alone or vehicle (Tween 80) had no effect on respiration, blood gases, and ventilatory response to CO2. The results indicated that respiratory stimulation following combined progestin plus estradiol treatment in the male rat involves activation of process(es) that regulate tidal volume and its augmentation during CO2 stimulus.

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