ISSN:
1432-2307
Keywords:
Melanin
;
Teratoma
;
Tyrosinase
;
Tyrosine hydroxylase
;
Immunofluorescence
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Summary A pigmented tumor fraction, designated IB-9, obtained following cellular dissociation and elutriation procedures applied to the solid transplants of the OTT-6050 mouse teratoma cell line, was characterized enzymatically and by immunofluorescence for the presence of tyrosinase and tyrosine hydroxylase (TH). Enzymatic assays of the pigmented tumors were compared with those obtained on non-pigmented teratoma-derived tumors, on pigmented tumors obtained from the mouse melanoma B16 line as a control for tyrosinase activity, and on whole brains of adult 129/J mice as a control for TH activity. All the teratoma-derived tumors, including the IB-9 fraction, showed a predominance of TH over tyrosinase activity. The levels of TH activity appeared independent of the presence or the extent of melanin pigment. All pigmented teratoma-derived tumors showed low levels of tyrosinase activity. On the basis of the enzymatic assays, the IB-9 tumors were divided into two groups: group I, which showed low enzyme activity, almost certainly entirely tyrosinase; and group II, in which the enzyme activity appeared largely due to TH, with presumably a very low background of tyrosinase activity. Immunofluorescence demonstrated the localization of TH activity to non-pigmented cells of the IB-9 fraction, whereas the pigmented cells showed absence of TH activity. These findings, taken in conjunction with the presence by electron microscopy of premelanosomes and melanosomes, indicate that pigment formation associated with melanosomal differentiation in the neural cells of IB-9 with the histologic patterns of primitive CNS neuroepithelium results from tyrosinase activity only and is therefore unrelated to the metabolic pathways involved in catecholamine synthesis and degradation. It is suggested that, at this stage of differentiation and in this system, the expression of catecholamine synthesis via tyrosine hydroxylase in neuroepithelial cells, and of melanin pigment via tyrosinase, are probably mutually exclusive.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00430868
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