Funan Hu

Pigment cell development in rhesus monkey eyes: an electron microscopic and histochemical study☆

Abstract The ontogeny of pigment cells in the eyes of rhesus monkeys was studied by electron microscopy and histochemistry. In 60- to 80-day-old fetuses, the pigment epithelium of the iris and retina has already differentiated whereas stromal melanocytes of the uveal tract differentiate much later. The morphological and histochemical difference between melanocytes of the iris stroma and the choroid suggests that during embryonic development melanocytes migrate from the iris toward the ciliary body and choroid. Similarly, melanosomes of pigmented epithelial cells may have their origin in the epithelium of the anterior layer of the iris, which is metabolically more active than both the posterior layer and the pigment epithelium of the ciliary body and retina.

Effects of dicarboxylic acids on normal and malignant melanocytes in culture

We have shown that dicarboxylic acids (C9 and C12), known competitive inhibitors of tyrosinase, are selectively cytotoxic to malignant melanogenic melanocytes but not to normal pigmented cells or to amelanotic or non‐melanogenic melanoma cells. The main target of this toxicity appears to be the mitochondria, which become markedly swollen and vacuolated. The mechanism of their action has been thought to be due to interference with oxidoreductases in the mitochondria. However, our results suggest that this cytotoxicity most probably does not result simply from inhibition of mitochondrial enzymes, but is closely related to the melanin biosynthesis pathway.

Gossypol effects on cultured normal and malignant melanocytes

SummaryGossypol, a polyphenolic compound known to interfere with spermatogenesis, was found to have differential cytotoxic effects on normal and malignant melanocytes in culture. Ultrastructurally it caused marked swelling and vacuolization of mitochondria; there was an almost complete loss of cristae but the outer mitochondrial membrane was retained. The cytotoxicity seemed to be selective for actively proliferating cells, regardless of normal or malignant origin. An endothelial cell line (RF/6A) derived from the choroid-retina of the eye of a rhesus fetus was extremely sensitive to its toxic effect. The mechanism of action is still unknown. The fact that mitochondria are predominantly damaged suggests that toxicity involves a perturbation of energy metabolism and the membrane transport system.

Somatic cell hybrids derived from terminally differentiated rhesus cells and established mouse cell lines.

The mechanisms of normal cell differentiation in vivo may be related to some features of cellular aging in vitro in that both are considered to be under genetic control. Diploid rhesus choroidal melanocytes and purified peripheral lymphocytes were fused by means of inactivated Sendai virus with three long-term murine cell lines which lacked either hypoxanthine-guanine phosphoribosyl transferase or thymidine kinase. Cell hybrids were selected by their growth in medium containing hypoxanthine, aminopterin, thymidine, and glycine. G-banded chromosomes were analyzed and elements from both the rhesus and the established mouse cell lines were identified in all metaphases. Hybrids derived from choroid X mouse cells contained more than one chromosome set from the mouse, but those between lymphocytes and established cell lines had only one. However, in every combination continuously replicating hybrids were produced; most of them have undergone more than 40 subculture passages. Our results demonstrate not only that DNA synthesis can be re-initiated in postreplicative cells, but also that DNA continues to replicate in a manner consistent with the life span of the long-term cell line parent.

Microspectrofluorometric analysis of surface antigens of murine melanoma and hamster peritoneal cell hybrids: comparisons of species antigenicity, chromosome number, and tumorigenicity.

Somatic cell hybrids from viral fusions of murine melanoma (PAZG) X Chinese hamster peritoneal cells (CH) were compared with respect to surface antigenicity, karyotype and tumorigenicity. One line, F57-(9), which arose from the hybridization of two CH cells and one PAZG cell, had slight (6%) CH chromosome loss but 80%PAZG chromosome loss after 10 months in culture. These cells expressed CH antigens strongly and PAZG antigens weakly. In comparison, another hybrid, F57-(7), formed from one CH and one PAZG cell, lost 20% of its chromosomes after 10 months in vitro. These cells had a stronger expression of PAZG antigens and weaker expression of CH antigens than F57-(9). These findings indicate a direct relationship between chromosome number and antigenicity; tumorigenicity, however, does not appear to depend on the chromosome numbers of the parental cells.