Search PubMed⌕ Search

Biomedical subjects

F Hu

Publications and source records attributed to F Hu.

At least 91 records · Page 5Linked to original sources
PubMed1984

Dermal Merkel cells in the nevus of Ota and leopard syndrome.

We observed dermal Merkel cells around vellus hair follicles in one patient with nevus of Ota and one with leopard syndrome. These Merkel cells were in contact with Schwann cells and nerve endings in the dermis. The question of whether or not Merkel cells exist normally in adult dermis remains unanswered. However, their presence in these abnormal conditions suggests that normally they do occur in the dermis but go undetected because their numbers are so few or they are in a form not readily identifiable by currently available methods.

Abnormalities, Multiple↗
PubMed1983

Changes in melanosomes with age in iridial stromal melanocytes of rhesus macaques.

Iridial ultrasections from eyes of rhesus macaques of different ages were compared. Long, thin melanosomes characteristic of iridial stromal melanocytes occur singly in young monkeys prior to or until adolescence (at or under 3 years of age); as monkeys grow older, they begin to form compound granules by fusions of two or more melanosomes. The frequency of fusions and the number of melanosomes in the fused granules increase in proportion to the age. It appears that long, thin single melanosomes fuse and develop into large ovoid granules characteristic of those in adult choroidal melanocytes and in postnatal pigmented epithelia. We suggest that iridial melanocytes in due time develop into cells with properties identical to those of choroidal melanocytes: they have the same developmental history, and differ only in the timing of their maturation and terminal differentiation.

Aging↗
PubMed1983

Theophylline and melanocyte-stimulating hormone: effects on uveal melanocytes of adult rhesus eyes.

The effects of theophylline and melanocyte-stimulating hormone (MSH) on cultured uveal melanocytes from the eyes of normal adult rhesus macaques were studied by light and electron microscopy and by dopa cytochemistry. The principal effects were changes in melanosome ultrastructure and an increased complexity of Golgi-associated vesicles and cisternae filled with dopa reaction products. The changes were more extensive in iris cells and less remarkable in choroid cells. The effects of theophylline were more pronounced than those of MSH. Our data suggest that normal iridial melanocytes, as do melanogenic murine melanoma cells, respond to theophylline or MSH by increasing tyrosinase synthesis, tyrosinase transfer, and melanization.

Animals↗
PubMed1983

False dopa reaction in studies of mammalian tyrosinase: some characteristics and precautions.

In cytochemical studies of B16 melanoma cells with the dopa reaction for tyrosinase, a false positive result that can easily be confused with authentic reactions has been observed. A preliminary characterization of this false reaction in comparison to authentic reactions with respect to stereospecificity, morphological characteristics, and subcellular localization has been conducted. Modifications of the classic dopa method have been devised that minimize occurrence of the false reaction.

Animals↗
PubMed1982

Theophylline and melanocyte-stimulating hormone effects on gamma-glutamyl transpeptidase and DOPA reactions in cultured melanoma cells.

Gamma-glutamyl transpeptidase (GGT), an enzyme of the gamma-glutamyl cycle, was demonstrated in 3 of 6 cell lines derived from a single B16 murine melanoma. Its activity in these cells varied a great deal, appeared to be correlated with the developmental cycle of the cells, and was greatest in young, actively melanogenic cells. Generally, the activity seemed parallel to that of tyrosinase, an enzyme specific for melanin synthesis. The levels of both enzymes tended to decline with prolonged in vitro cultivation, but could be readily renewed after one animal passage. The 3 cell lines that were GGT-negative were nonpigmented and DOPA-negative; so was a nonmelanogenic and nonmelanocytic rhesus cell line. Melanocyte-stimulating hormone (MSH) and theophylline both enhanced pigmentation in murine melanoma cells. The mechanisms of their action apparently differed. We found that theophylline increased both DOPA- and GGT- reactive cells, whereas MSH only increased DOPA-reactive cells. All 3 GGT-positive lines were tumorigenic, and 2 GGT-negative line were not tumorigenic. Our observations suggest that GGT plays a role in the melanin biosynthetic pathway and the its activity is greater in melanoma cells that are tumorigenic.

Animals↗
PubMed1982

Electron microscopic and cytochemical observations of theophylline and melanocyte-stimulating hormone effects on melanoma cells in culture.

The effects of theophylline and melanocyte-stimulating hormone on B16 melanoma cells in culture cells were studied by electron microscopy and dopa cytochemistry. The data show that theophylline and melanocyte-stimulating hormone enhance melanogenesis by activating tyrosinase synthesis and its transfer but that neither affects the synthesis of the well-organized eumelanosome matrix. Their pigmenting effects appear to be limited to the melanogenic cells and result from a marked increase, particularly in theophylline-treated cells, in pheomelanosome formation.

Animals↗
PubMed1981

Gamma-glutamyl transpeptidase in the pigment cells of rhesus eyes.

We demonstrated that gamma-glutamyl transpeptidase, one of the enzymes of the gamma-glutamyl cycle, is present in the melanocytes of the eyes of rhesus macaques. Enzyme activity was detected in active melaninsynthesizing melanocytes of the iris stoma and in fetal and neonatal retinal pigment epithelium. It was not detected in adults retinal pigment epithelium or choroidal melanocytes, which are ontogenetically more advanced in development and have little melanogenic activity. Our data show that gamma-glutamyl transpeptidase activity correlates well with growth, early differentiation, and active melanogenesis, and support the hypothesis that in addition to tyrosinase, a second enzyme, such as gamma-glutamyl transpeptidase, takes part in the melanin and pheomelanin metabolic pathways.

Animals↗
PubMed1980

Yellow mutant albinism: cytochemical, ultrastructural, and genetic characterization suggesting multiple allelism.

This report describes three sisters, including monozygotic (MZ) twins, with clinical, ultrastructural, and histochemical features typical of yellow mutant albinism; This form of albinism is clinically similar to the tyrosinase-positive type, but hair bulbs showed (1) organelles similar to red hair pheomelanosomes and (2) absence of tyrosinase activity. Classical tyrosinase-negative albinism was found in a maternal cousin of the probands. Pedigree analysis of this family suggests multiple alleles occupying a single locus.

Adult↗
PubMed1980

A reinvestigation of solar lentigines.

Solar lentigines were reinvestigated by a number of different methods to gain a better perspective on their structure. In histologic sections and dopa preparations of split skin, large numbers of melanocytes were seen crowded at the base of the clubbed, budding rete ridges. In split-skin preparations, the scanning electron microscope showed complex systems of ridges, columns, and craters on the underside of the lentiginous epidermis. Oval bodies measuring 15 to 30 mu, with dendrites, were numerous at the apices of the complex epidermal ridges; these bodies were presumed to be melanocytes. In transmission electron micrographs of lentigines, the melanosome complexes inside the keratinocytes were much larger than those found in noninvolved skin. The complex and distinctive architecture of these maculae is probably the result of concurrent proliferation of melanocytes and keratinocytes.

Aged↗
PubMed1979

Aging of melanocytes.

Choroidal melanocytes of the eyes of postnatal animals are classified as postmitotic terminally differentiated cells. They have specific granules, the melanosomes, which undergo changes qualitatively and quantitatively correlated to the animal's increasing age. Epidermal melanocytes, which normally divide only on demand or by stimulation, are classified as intermittent mitotic cells. During their development, lentigines and nevi of the skin show progressive ultrastructural and cytochemical changes similar to those in the choroidal cells, and thus may be considered as aging populations of skin melanocytes. These facts have led to the conclusion that choroidal melanocytes may be used advantageously as a model for studying changes in cells from maturation to senescence.

Age Factors↗
PubMed1979

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.

Animals↗
PubMed1979

Cell interactions in the initial contact between cultured melanoma cells and syngeneic macrophages.

Thioglycolate-induces peritoneal macrophages from melanoma-bearing mice (immune macrophages) or from control mice (control macrophages) were cultured with syngeneic melanoma cells (P51) to determine the surface characteristics of the effector cells during interaction and destruction of the target cells. After a short culture period (3 hours), immune macrophages had extensive connections via filopodia and ruffled membranes to the surfaces of the melanoma cells; control macrophages did not exhibit the same behavior. A dense region in the cytoplasm immediately beneath the macrophage plasmalemma was observed at the point of contact with the target tumor cell. With longer periods of culture (24 hours), effector cells began phagocytosis of the target cells; immune macrophages, however, had more fine filopodial connections and were more cytostatic than were controls. These observations indicate that one of the initial mechanisms of tumor cell destruction was contact-induced lysis, with phagocytosis playing a minor part.

Animals↗
PubMed1977

Characteristics of tyrosinase in B16 melanoma.

Tyrosine hydroxylase, dopa oxidase, and peroxidase activities were studied in soluble fractions of B16 melanoma tumor homogenates by polyacrylamide gel disc electrophoresis. Stained gels were scanned photometrically and gel slices were assayed radiometrically. In these preparations, the two bands of tyrosine hydroxylating activity were completely separated from the peroxidase activity but coincided with two major bands of dopa oxidase activity. The third dopa oxidase band coincided with the single band of peroxidase activity. The soluble fraction of cultured cell homogenates had no peroxidase activity, but the two tyrosine hydroxylase bands coincided exactly with the two dopa oxidase bands. Therefore, in the soluble fraction of the murine melanoma bifunctional tyrosinase does exist as two electrophoretically separable forms which are independent of peroxidase.

Animals↗
PubMed1976

The effect of MSH on thymidine incorporation by keratinocytes in the epidermal melanin unit.

Epidermal melanocytes were observed in the black but not in the white skin of black-and-white spotted guinea pigs. In experiments designed to determine whether melanocyte-stimulating hormone (MSH) affects the incorporation of thymidine by kerationcyte nuclei of the epidermal melanin unit, the labeling index was the same in all skin before MSH administration. After MSH injections, the level of (3H)thymidine incorporation in keratinocytes increased significantly in black skin but not in white. We suggest that through the mediation of melanocytes MSH indirectly afffects keratinocytes in the epidermal melanin unit.

Animals↗