An melanotic line of Bomirski Hamster Melanoma (BHM Ma) was implanted into the anterior chamber of the hamster eye and the ensuring vascular system was studied using scanning electron microscopy ...(SEM) of vascular corrosion casts.
The tumor vasculature, induced mainly from the host iris vessels, showed generally disorganized and irregular patterns. Tortuous tumor capillaries of uneven contour with local dilatations and constrictions were drained by markedly dilated, thin-walled, venous vessels connected with the eye veins. Vascular sprouting and, less frequently, intussusceptive formation of new vessels were observed at the periphery and also within the tumor mass. The presence of numerous nodular outgrowths, varying in size, on the surface of dilated venules and venous vessels represent morphological evidence for continuous remodeling of the tumor vasculature. The observed features of the vascular system seem to provide a pathway for further tumor expansion.
Our study showed that BHM Ma line, originating from an aggressive skin melanotic melanoma, implanted to the eye anterior chamber gave rise to rapidly growing tumors with the capability of inducing abundant vasculature which allows metastasis to the lungs, kidneys and regional lymph-nodes.
Inhibition of melanoma metastases by fenofibrate GRABACKA, Maja; PLACHA, Wojciech; PLONKA, Przemyslaw M ...
Archives of Dermatological Research,
07/2004, Letnik:
296, Številka:
2
Journal Article
Recenzirano
The effect of fenofibrate, a ligand of peroxisome proliferator-activated receptor (PPAR) alpha, on the growth and metastatic potential of Bomirski hamster melanoma s.c. tumors, pigmented line (BHM ...Ma) was investigated in vivo. RT-PCR and Western-blot analyses revealed the presence of mRNA and protein of PPAR alpha in BHM Ma cells. The animals treated orally with fenofibrate developed significantly fewer metastatic foci in the lungs, as compared to the control group; however, primary tumor growth remained unaltered. This observation is interesting in respect of the potential use of fenofibrate in melanoma chemoprevention.
: We characterized the melanogenic apparatus in a family of transplantable gerbil melanomas (melanotic and amelanotic) using a combination of biophysical, ultrastructural and biochemical methods. ...Melanotic melanomas produced pure eumelanin but in vesiculo‐globular melanosomes (‘pheomelanosomes’); the eumelanosomes, characteristically ellipsoidal in shape with fibrillar or fibrillo‐lamelar matrix, were never noticed. Melanotic melanomas also had significant tyrosinase activity and Zn, Pb/S, Ca and P content; all higher than in the amelanotic variants. The amelanotic variant, which was devoid of melanin pigment and melanosomes, had clearly detectable tyrosinase activity (albeit at 20% of that in the melanotic variant). Thus, with these multidirectional approaches we demonstrate that pure eumelanin can be synthesized in organelles ultrastructurally defined as pheomelanosomes, but a defect in the formation of melanosomes can prevent in vivo melanin synthesis despite the presence of detectable tyrosinase activity. We conclude that this melanoma system provides an excellent experimental model for the study of molecular components determining pheo‐ and/or eumelanogenesis. The information generated can be used for defining the roles of melanogenesis and of tyrosinase expression in the regulation of melanoma behavior and the effect of their modification on the course of the disease.
A family of serially transplanted melanomas in gerbils is described. These tumors were derived from the cutaneous melanotic melanoma that arose in 1 of 44 gerbils injected postnatally with ...N-ethyl-N-nitrosourea. It consists of a slow growing heavily melanotic parental line and two fast growing melanotic (FGM) and amelanotic (A-FGM) lines that appeared abruptly during serial transplantation of the parental tumor. The FGM melanotic line originated after a sudden acceleration of growth of the parental line during the 4th in vivo passage that was accompanied by a decrease in both pigmentation and metastasizing potential. The A-FGM derived from the depigmented tissue of the 7th in vivo passage of the FGM line and has been characterized by an amelanotic phenotype, an increased metastasizing potential and similar growth rate to that of the FGM. Once established, both lines expressed considerable phenotypic stability during serial transplantation in gerbils. Thus, the Zeman UJ melanomas represent the first established family of transplantable melanomas in gerbils, which serve as a model for pigmented cell and melanoma research and as a subject for a retrospective analysis of the phenomenon of tumor evolution.
Effect of melanin on radiation response of CHO cells Hopwood, L E; Swartz, H M; Pajak, S
International journal of radiation biology and related studies in physics, chemistry and medicine,
01/1985, Letnik:
47, Številka:
5
Journal Article
Recenzirano
The effect of the presence of melanin on the response of mammalian cells to ionizing radiation was investigated in a model system utilizing the ability of Chinese hamster ovary cells to incorporate ...melanin by endocytosis. Cells were incubated in monolayer cultures from 2 to 20 hours with melanin prepared from 'beef eye' or synthesized by air oxidation of 3,4-dihydroxyphenylalanine. For asynchronous cultures, the survival curve parameters for cells incubated with both types of melanin were indistinguishable from those of the same cells without added melanin. The radiation response to fractionated doses of 6 Gy separated by various periods did not indicate any effect of melanin on the extent or kinetics of repair of sublethal damage. Likewise, the repair of potentially lethal damage in plateau phase cultures was unaffected by the presence of melanin. Thus the explanation for the clinical radiation resistance of melanomas in the absence of a direct radiation effect might more likely be found in consideration of other factors such as the role of melanin in oxygen consumption or in differentiation.
