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At least 19 recordsLinked to original sources
PubMed1970

Study of biological pigments by single specimen derivative spectrophotometry.

The single specimen derivative (SSD) method provides an absolute absorption spectrum of a substance in the absence of a suitable reference. Both a reference and a measuring monochromatic beam pass through a single sample, and the specimen itself acts as its own reference. The two monochromatic beams maintain a fixed wavelength difference upon scanning, and the difference in absorbance of the two beams is determined. Thus, the resulting spectrum represents the first derivative of the conventional type absorption spectrum. Tissues and cell fractions have been examined at room and liquid N(2) temperature and chromophoric molecules such as the mitochondrial cytochromes and blood pigments have been detectable in low concentrations. In the case of isolated cellular components, the observed effects of substrates and inhibitors confirm similar studies by conventional spectrophotometry. The extension of the SSD concept to the microscopic level has permitted the study of the tissue compartmentalization and function of cytochromes and other pigments within layered tissue.

Animals↗
PubMed1988

Orientational properties of biological pigments in ordered systems studied with polarized light: photosynthetic pigment-protein complexes in membranes.

A discussion is presented of the problems involved in the interpretation of linear dichroism and fluorescence depolarization experiments on macroscopically ordered membrane systems. Particular attention has been paid to ordered membranes containing photosynthetic pigment-protein complexes, but the mathematical treatment can equally well be applied to other systems. The information about the orientational properties of the pigments is obtained by the application of the theories developed for the characterization of the molecular orientational order in liquid-crystalline materials. It is shown that while linear dichroism only yields the order parameter S mu of the absorption transition moment, fluorescence depolarization experiments yield in addition the order parameter Sv of the emission transition moment as well as three orientational correlation functions of the two transition moments. It is argued that in general the latter information can only be obtained on utilizing a number of experimental scattering geometries. In particular, the merits of angle-resolved experiments are illustrated.

Biophysical Phenomena↗
PubMed1999

The emergence of pigment cell biology: a personal view.

This is a semi-autobiographical coverage of my research career in pigment cell biology presented in the context of the emergence and growth of the discipline. This anecdotal presentation tells about some historical personages in the field. My undergraduate studies at the University of Rochester are related to my graduate work at the University of Iowa. I tell how my dissertation research was derived from a marriage between my interests in experimental embryology and the new field of comparative endocrinology. My early years of research at Iowa and as a young faculty member in Zoology at the University of Arizona were much concerned with the evolution of our knowledge of the chemistry and biology of melanocyte-stimulating hormone (MSH), especially concerning the pigment cells of lower vertebrates. Our developmental, structural, functional, and biochemical characterization of vertebrate chromatophores is described, as is our elucidation of the dermal chromatophore unit. The direct effects of light on changes in pigmentation are considered in descriptions of both the tail-darkening reaction and the role of the pineal gland in melanophore control. Emphasis is placed on the developmental biology of pigmentation, especially on the concept that all pigment cells are derived in common from a stem cell of neural-crest origin, whose expression is influenced by factors, such as melanization-inhibiting factor (MIF), localized in specific areas of the skin to thus produce specific pigmentation patterns. This research is considered in light of what is known about the agouti locus and MSH in the expression of mammalian pigmentation patterns. Part of my work has included ecological considerations, and some of this is touched upon. My role as founder of the journal 'Pigment Cell Research', is presented briefly, as is my involvement in the XIIIth International Pigment Cell Conference and in the establishment of both the International Pigment Cell Society and the International Federation of Pigment Cell Societies. Finally, I comment on the future of research in pigmentation.

Animals↗
PubMed1971

The biology of pigmentation.

Genes are one of the most important control mechanisms of the process of melanin pigmentation and, therefore, changes in pigmentation are important markers of genetic aberrations. Melanin pigmentation is related to four biologic processes: 1) formation of melanosomes in melanocytes; 2) melanization of melanosomes in melanocytes; 3) secretion of melanosomes into keratinocytes and 4) transport (by keratinocytes) of melanosomes within lysosome-like organelles.

Animals↗
PubMed2001

Quantitation and visualization of ultraviolet-induced DNA damage using specific antibodies: application to pigment cell biology.

The major types of DNA damage induced by sunlight in the skin are DNA photoproducts, such as cyclobutane pyrimidine dimers (CPDs), (6-4)photoproducts (6-4PPs) and Dewar isomers of 6-4PPs. A sensitive method for quantitating and visualizing each type of DNA photoproduct induced by biologically relevant doses of ultraviolet (UV) or sunlight is essential to characterize DNA photoproducts and their biological effects. We have established monoclonal antibodies specific for CPDs, 6-4PPs or Dewar isomers. Those antibodies allow one to quantitate photoproducts in DNA purified from cultured cells or from the skin epidermis using an enzyme-linked immunosorbent assay. One can also use those specific antibodies with in situ laser cytometry to visualize and measure DNA photoproducts in cultured cells or in the skin, using indirect immunofluorescence and a laser-scanning confocal microscope. This latter method allows us to reconstruct three-dimensional images of nuclei containing DNA photoproducts and to simultaneously examine DNA photoproducts and histology in multilayered epidermis. Using those techniques, one can determine the induction and repair of these three distinct types of DNA photoproducts in cultured cells and in the skin exposed to sublethal or suberythematous doses of UV or solar simulated radiation. As examples of the utility of these techniques and antibodies, we describe the DNA repair kinetics following irradiation of human cell nuclei and the photoprotective effect of melanin against DNA photoproducts in cultured pigmented cells and in human epidermis.

Animals↗
PubMed2000

The use of expression profiling to study pigment cell biology and dysfunction.

Regulation of gene expression is a fundamental process by which cells respond to both intracellular and extracellular signals. For a pigment cell, alterations in gene expression regulate the processes of cell migration, lineage restriction, differentiation, type of pigment produced, and progression from a normal pigment cell to that of melanoma. To date, the identification of genes involved in normal pigment cell development has been accomplished by the cloning of individual mutant alleles, a single gene at a time. Current advances in technology have now made it possible to use expression profile analysis to investigate, on a genomic scale, the process of pigment cell development and function. This review compares and contrasts the methods of subtractive suppressive polymerase chain reaction (PCR) and differential display with that of cDNA microarray analysis.

Cell Differentiation↗
PubMed1989

Metabolism of arachidonic acid in the retina and retinal pigment epithelium: biological effects of oxygenated metabolites of arachidonic acid.

Most of the research on AA metabolites in the eye has been concerned with the role of prostaglandins in ocular inflammations. For example, it has been postulated that cystoid macular edema (CME) is due to accumulation of prostaglandins produced after cataract surgery and that indomethacin prevents the development of CME (Tennant, 1976; Milch and Yannuzzi, 1987). It is not known if the retina is the source of these prostaglandins. Cyclooxygenase and lipoxygenase activities have been demonstrated in the retina. In this chapter, evidence is presented indicating that eicosanoids can also be involved in retinal neurotransmission and cell to cell interaction. The mammalian retina contains a relatively large amount of AA esterified to membrane phospholipids. A release of AA takes place in the retina under various experimental conditions, e.g., anoxia, K+ polarization, and light exposure. This release of AA, a prerequisite for eicosanoid syntheses, is produced by phospholipases and lipases, some of which are regulated by receptor-mediated G-proteins. Prostaglandins can act as modulators of postsynaptic responses; some can also alter the electroretinographic response, for example PGD2 selectively increases during light stimulation. An increase in LTC4 occurs in the neural retina after Ca+ ionophore stimulation and an increase in LTC4 released from retinal pigment epithelium occurs after light onset before massive shedding, suggesting an involvement of 5-lipoxygenase metabolites in the initial steps of ROS phagocytosis. Although great advances have been made regarding the function of eicosanoids in the central nervous system (of which the retina is a constitutive part), it is yet a very difficult task to determine to what extent eicosanoids are involved in the action of neurotransmitters and whether they may act as neuromodulators. This is due to the complexity of the synaptic circuitry of the retina, which makes it difficult to define their sources and physiological significance.

Animals↗