Control Of Color Change Research Articles

Tunable Temperature Response of a Thermochromic Photonic Gel Sensor Containing N-Isopropylacrylamide and 4-Acryloyilmorpholine.

In this study, thermochromic photonic gels were fabricated using 2-hydroxyethyl methacrylate (HEMA) as a hydrogel building block, and 4-Acryloyl morpholine (ACMO) and N-isopropylacrylamide (NIPAAM) as thermoresponsive monomers with different critical solution temperature behaviors. Rapid photopolymerization of opal-templated monomer mixtures of varying ACMO contents formed five individual thermochromic inverse opal photonic gels integrated on a single substrate. With temperature variation from 10 °C to 80 °C, the changes in reflective colors and reflectance spectra of the respective thermochromic gels were noted, and λpeak changes were plotted. Because NIPAAM exhibits a lower critical solution temperature (LCST) at 33 °C, the NIPAAM-only gel showed a steep slope for dλpeak/dT below 40 °C, whereas the slope became flatter at high temperatures. As the ACMO content increased in the thermochromic gel, the curve of dλpeak/dT turned out to be gradual within the investigated temperature range, exhibiting the entire visible range of colors. The incorporation of ACMO in NIPAAM-based thermochromic gels therefore enabled a better control of color changes at a relatively high-temperature regime compared to a NIPAAM-only gel. In addition, ACMO-containing thermochromic gels exhibited a smaller hysteresis of λpeak for the heating and cooling cycle.

Dimerization of melanocortin receptor 1 (MC1R) and MC5R creates a ligand-dependent signal modulation: Potential participation in physiological color change in the flounder

Vertebrates produce α-melanocyte-stimulating hormone (α-MSH), which contains an N-terminal acetyl group, and desacetyl-α-MSH, which does not contain an N-terminal acetyl group. In teleosts and amphibians, α-MSH-related peptides stimulate pigment dispersion via melanocortin receptors 1–5 (MC1R–MC5R), which are members of the G-protein-coupled receptor (GPCR) family. We previously reported an interesting phenomenon associated with physiological color changes in the skin of a flatfish, barfin flounder (bf). Specifically, pigments in xanthophores expressing only the bfMC5R gene were dispersed by both α-MSH and desacetyl-α-MSH, whereas those in melanophores expressing both the bfMC1R and bfMC5R genes were dispersed by desacetyl-α-MSH, but not by α-MSH. In this study, we examined whether heterodimers of bfMC1R and bfMC5R can act as significant inhibitory receptors for the N-terminal acetylation of α-MSH in mammalian Chinese hamster ovary cells. Immunofluorescence analyses showed that bfMC1R and bfMC5R were localized together at the plasma membrane when expressed in the same cells. Indeed, after coexpression of Flag-bfMC1R and HA-bfMC5R, immunoprecipitation with anti-Flag antibodies resulted in the presence of anti-HA immunoreactivity in the precipitate, and vice versa. Importantly, cyclic AMP assays showed that cotransfection of bfMC1R with bfMC5R inhibited the cyclic AMP accumulation induced by α-MSH to a greater extent than that observed after transfection of bfMC1R alone. Of note, this inhibitory response was not caused by desacetyl-α-MSH. Thus, we show a ligand-dependent signaling through functional heterodimerization of MC1R and MC5R in mammalian cells. The ligand-selective receptor complex also provide the first mechanistic implication that may play a role in the control of color change in teleosts.

Possible involvement of nitric oxide in signaling pigment dispersion in teleostean melanophores.

The possible involvement of nitric oxide (NO) in regulating the motile activities of teleostean melanophores was studied in the dark chub Zacco temmincki (Cyprinidae, Cypriniformes) and in the translucent glass catfish Kryptopterus bicirrhis (Siluridae, Siluriformes). NO donors, including (+/-)-(E)-methyl-2-[(E)-hydroxyimino]-5-nitro-6-methoxy-3-hexaneamide (NOR1), molsidomine (MSD), sodium nitroprusside (SNP) and glyceryl trinitrate (GTN), had no pigment-aggregating action on melanophores, but actively dispersed melanosomes in those cells. Among those reagents, NOR 1, a spontaneous releaser of NO, was the most effective. Inhibitors for nitric oxide synthase (NOS), i.e. N omega-nitro-L-arginine methyl ester (L-NNA), N omega-nitro-L-arginine (L-NAME) and N omega-monomethyl-L-arginine (L-NMMA), showed melanosome-aggregating effects. A membrane-permeable analogue of cyclic guanosine-3',5'-monophosphate (8-Br-cGMP) was effective in dispersing melanosomes. The sum of these results suggests that NO plays an active role in the elaborate control of color changes in teleosts by dispersing pigment in melanophores via activation of soluble guanylyl cyclase to increase cytosolic levels of cGMP.

Progress in Clinical and Biological Research, Volume 256: Advances in Pigment Cell Research

This book is a compilation of symposia proceedings and lectures from the 13th International Pigment Cell Conference held in Tucson, Ariz, October 5 through 9, 1986. There are 135 contributors, including a number of international authorities in the field. The book is organized into nine sections or symposia. Each section consists of five or nine reports selected from a symposium. These nine sections include the structure and development of vertebrate pigment cells, melanogenesis, acquired pigmentary disorders, recent advances in the molecular genetics of pigment cells, human melanoma, control of color change (invertebrates), photoaging and pigmentation, melanin-concentrating hormones, a novel chromatophore-regulating hormone, immunology, and pigmentation. "... may be of limited interest to the ophthalmologist in clinical practice..." The book also includes four special lectures presented at the conference: biochemical mechanisms of tumor invasion and metastases by L. A. Liotta et al, protein and active-site structure of tyrosinase by Konrad Lerch, some

Relationship of Finishes and Wood Care Products to Color Change of Wood Surfaces after Exposure to Interior Daylight

Color change can occur in the wood surface materials used in today's interiors with exposure to interior daylight. The objective of this research was to examine the color change of red oak after exposure to interior daylight in order to determine if control of color change is possible through application of a finish and/or wood care product. Results of the one year study indicated 1) no wood finishes tested prevented significant color change after exposure to interior daylight: and 2) no wood care product protected all finishes from significant additional color change (beyond that related to exposure). Therefore, the wood finish should be considered when specifying a wood care product to control color change due to exposure to interior daylight.

Evidence for the participation of a melanin-concentrating hormone in physiological colour change in the eel.

The hormonal and nervous control of colour change in the eel has been investigated. The only bioactive forms of MSH found in eel pituitary extracts or secreted by eel pituitary cultures were forms of alpha-MSH; no beta-MSH was detected. After transfer of eels from a black to a white background, the melanin concentration in skin melanophores was accompanied by a rapid decline in plasma alpha-MSH titres. Hypophysectomy resulted in melanin concentration, and pituitary extracts injected into hypophysectomized eels caused melanin dispersion. This effect was eliminated if the pituitary extracts were first incubated with a specific alpha-MSH antiserum or if the antiserum was injected into the hypophysectomized eel. However, injection of alpha-MSH antiserum into intact, black-adapted eels failed to result in melanin concentration although the same antiserum was effective in causing pallor in black-adapted toads. Partially purified preparations of teleost melanin-concentrating hormone (MCH), free from catecholamines, induced melanin concentration when injected into black-adapted eels and this effect was significantly potentiated by injections of alpha-MSH antiserum. The denervation of melanophores on the pectoral fin had only a slight effect on the responses of the melanophores to humoral agents. It is concluded that the control of physiological colour change in the eel is largely hormonal, and involves the antagonistic effects of alpha-MSH and a melanin-concentrating agent which is probably MCH.

Studies on the colour-change mechanism in a fresh-water teleost,Nandus nandus (Ham.) I. Neural control

The existence and nature of chromatic fibres controlling the colour-change mechanism in the teleost, Nandus nandus has been studied by means of spinal sectioning at various vertebral levels of the animal between vertebrae 3 to 10. Spinal sectioning at or anterior to 5th vertebra completely eliminated the neural control of colour-change. As a result, the animal darkened to its maximum and the neural responses of different backgrounds were abolished. Spinal sectioning at or posterior to vertebra 6 did not affect the melanophores and at the same time did not interfere with the normal background responses of the animal. This study clearly shows that the chromatic fibres in this species run in the spinal cord and leave the latter at 5/6th vertebral level. Effect of adrenaline in the chromatic spinal-sectioned fish shows that the fibres innervating the melanophores are aggregating in nature and adrenergic in character. The results also suggest that the dispersed condition of pigment in the melanophores represents the "resting state" of the melanophores when they are under no stimulation.

Endocrine Regulation of Pigmentation in Fish

This article reviews the development of knowledge of physiological and morphological color change in fishes. Emphasis is placed on research in the last three years. Although direct evidence may not be available at present, an attempt is made to show a unifying theme. It is apparent that those circumstances that lead to pigment dispersion as a physiological color change also favor the development of a dark morphological color and vice versa for pigment aggregation. There is ample evidence that control of color change in fishes ranges from fully nervous to fully hormonal. It may be that both neural and endocrine agents exert their effects upon the melanophore by causing changes in the amount of cyclic AMP in the cell. Rhythmic color change, which appears to be a special instance of physiological color change is discussed, but no conclusions are drawn. A tentative scheme for the unification of physiological and morphological color change is advanced with the note that direct evidence is not currently available to support all of it.

Pituitary innervation and control of colour change in the skates Raia naevus, R. clavata, R. montagui, and R. radiata

In a preliminary attempt to analyse the mechanisms controlling colour change in species of skate of the Genus Raia, the hypothalamoneurohypophyseal neurosecretory tracts have been sectioned at various points, the preoptic nucleus region removed, and the neurointermediate lobe of the pituitary grafted on to the dorsal surface of the brain. All these treatments resulted in irreversible darkening of the fish, the first two producing the response significantly faster than when white-adapted fish are placed on a black background. Although the results suggest that the preoptic neurons may control release of melanophore-stimulating hormone, such a conclusion is premature until more is known about the detailed histology of the preoptic area vis à vis other secretory neurons and tracts which may have been removed or damaged as a result of ablation of the preoptic nucleus. It has also been shown that the neurointermediate lobe in an ectopic site can maintain the melanophores of R. montagui in a state of maximal expansion for at least 8 months, that rostral lobectomy, carefully carried out, has no effect on colour change, and that R. clavata and R. batis, contrary to earlier reports, show normal paling responses on a white background.

Cellular aspects of the control of color changes. AAAS Symposium, 29 December 1968 Dallas, Texas.

Cellular aspects of the control of color changes. AAAS Symposium, 29 December 1968 Dallas, Texas.

Control of Colour Change in Amphibians

THE adaptation of colour in anurans to the background is controlled by hormones. Direct innervation of the melanophores is of little or no importance in controlling the degree of dispersion of the melanin-containing granules within the melanophores1. It is generally agreed that a melanin-dispersing hormone is produced in the pars intermedia of the hypophysis and that this hormone, intermedin, is responsible for the darkening of the skin. It is, however, controversial whether the paling upon transfer to a white, illuminated background is due to the disappearance of intermedin from the blood, or to the secretion of a whitening hormone.