Ultrastructure of the chromatophores of Palaemon affinis Heilprin (crustacea: decapoda). The structural basis of pigment migration

The relationships between pigment granules and the prominent smooth endoplasmic reticulum in the chromatophores of the shrimp, Palaemon affinis Heilprin, were investigated by transmission electron microscopy. Different types of pigment granules within the chromatophores were found to exhibit a close structural continuity with the cisternal membranes. The membranes of membrane-bound pigment granules were seen to be continuous with those of the ER cisternae, while pigment granules lacking membranes appear to adhere to the external cisternal surfaces. The reticulum, which seems to form a network enmeshing the pigment granules, is proposed to be part of a continuum linking these granules with their translocating force.     

Action Spectra for Step-Up Photophobic Response in Blepharisma

ABSTRACT The cells of Blepharisma which possess red pigment (blepharismin) show step-up photophobic response (temporal ciliary reversal induced by a sudden increase in light intensity). Bleaching of the cells by cold shock raised a threshold light intensity for the response, Oxidation of red pigment that produced blue pigment did not raise the threshold for the response. The action spectrum for the step-up photophobic response of the cells which possess normal red pigment had peaks at about 580, 540 and 490 nm, a value which coincided with peaks of an absorption spectrum of the red pigment. The absorption spectrum of oxidized pigment (blue pigment) shifted 20 nm toward infrared light. The action spectrum for the response of the cells which possess blue pigment also shifted 20 nm toward infrared light. Results suggest that red pigment might be involved in the step-up photophobic response. Key words. Blepharismin, ciliary reversal, photoreceptors, photoresponse.     

Eggshell spot scoring methods cannot be used as a reliable proxy to determine pigment quantity

Eggshell maculation of most passerines is due to the deposition of the pigment protoporphyrin which is produced during biosynthesis of blood haem. Its functional significance has only received empirical attention in recent years. This interest has generated a number of hypotheses of which some remain untested partly because the quantification of protoporphyrin is analytically challenging and can be prohibitively expensive. Many studies have therefore used the extent of eggshell spotting as a proxy for total eggshell protoporphyrin concentration, although this has not been formally tested. Pigment scoring involves recording visible eggshell pigment attributes, such as spot intensity, distribution and size. Since even immaculate eggs can contain some protoporphyrin, there remains doubt over the degree to which visible pigment correlates with total pigment content of the shell. In this study, we test whether visible pigment scoring can be used as a proxy for protoporphyrin concentration of an eggshell. We use pigmented eggshells of two common British passerine species to compare eggshell spot intensity, distribution and spot size (as used by the visual pigment scoring method) with direct measures of eggshell protoporphyrin concentration. In addition, we compared an alternative method of pigment scoring, the pixel pigment scoring method, using a computer programme to quantify the number of pixels exceeding a specified colour threshold. We demonstrate that although results from both scoring methods were positively correlated with eggshell protoporphyrin concentrations, the correlations were not sufficiently strong to be used as surrogates in studies where actual pigment concentrations are required.     

红穗醋栗色素理化性质的研究

本试验研究了红穗醋栗色素的理化性质,结果表明:红穗醋栗色素热稳定性很好,而光照对其有一定的降解作用。pH值对该色素影响明显,宜在酸性食品中应用。几种金属离子Na~ 、Ca~(2 )、Al~(3 )、Zn~(2 )。Cu~(2 )对该色素的色泽没有影响;而Fe~(3 )、Sn~(2 )则有不良影响。食品中常含的几种添加物葡萄糖、蔗糖、淀粉和抗坏血酸对该色素无不良影响。红穗醋栗色素对Na_2SO_3的还原性耐性较强,对H_2O_2的耐氧化性很差。防腐剂苯甲酸钠对该色素也有一定的不良影响。     

Reactivated melanophore motility: differential regulation and nucleotide requirements of bidirectional pigment granule transport

To study the molecular basis for organized pigment granule transport, procedures were developed to lyse melanophores of Tilapia mossambica under conditions in which pigment granule movements could be reactivated. Gentle lysis of the melanophores resulted in a permeabilized cell model, which, in the absence of exogenous ATP, could undergo multiple rounds of pigment granule aggregation and dispersion when sequentially challenged with epinephrine and cAMP. Both directions of transport required ATP, since aggregation or dispersion in melanophores depleted of nucleotides could be reactivated only upon addition of MgATP or MgATP plus cAMP, respectively. Differences between the nucleotide sensitivities for aggregation and dispersion were demonstrated by observations that aggregation had a lower apparent Km for ATP than did dispersion and could be initiated at a lower ATP concentration. Moreover, aggregation could be initiated by ADP, but only dispersion could be reactivated by the thiophosphate ATP analog, ATP gamma S. The direction of pigment transport was determined solely by cAMP, since pigment granules undergoing dispersion reaggregated when cAMP was removed, and those undergoing aggregation dispersed when cAMP was added. These results provide evidence that pigment granule motility may be based on two distinct mechanisms that are differentially activated and regulated to produce bidirectional movements.     

A Streptomyces avermitilis gene encoding a 4-hydroxyphenylpyruvic acid dioxygenase-like protein that directs the production of homogentisic acid and an ochronotic pigment in Escherichia coli.

A 1.5-kb genomic fragment isolated from Streptomyces avermitilis that directs the synthesis of a brown pigment in Escherichia coli was characterized. Since pigment production in recombinant E. coli was enhanced by the addition of tyrosine to the medium, it had been inferred that the cloned DNA might be associated with melanin biosynthesis. Hybridization studies, however, showed that the pigment gene isolated from S. avermitilis was unrelated to the Streptomyces antibioticus melC2 determinant, which is the prototype of melanin genes in Streptomyces spp. Sequence analysis of the 1.5-kb DNA that caused pigment production revealed a single open reading frame encoding a protein of 41.6 kDa (380 amino acids) that resembled several prokaryotic and eukaryotic 4-hydroxyphenylpyruvate dioxygenases (HPDs). When this open reading frame was overexpressed in E. coli, a protein of about 41 kDa was detected. This E. coli clone produced homogentisic acid (HGA), which is the expected product of the oxidation of 4-hydroxyphenylpyruvate catalyzed by an HPD, and also a brown pigment with characteristics similar to the pigment observed in the urine of alkaptonuric patients. Alkaptonuria is a genetic disease in which inability to metabolize HGA leads to increasing concentrations of this acid in urine, followed by oxidation and polymerization of HGA to an ochronotic pigment. Similarly, the production of ochronotic-like pigment in the recombinant E. coli clone overexpressing the S. avermitilis gene encoding HPD is likely to be due to the spontaneous oxidation and polymerization of the HGA accumulated in the medium by this clone.     

The Production and Some Properties of the Brown Pigment of Aeromonas Liquefaciens

The optimum conditions for pigment production by Ae. liquefaciens was found to be 30 °C and aerobic incubation, and the properties of the pigment are shown to be similar to those of the synthetic dopa-melanin referred to. The enzyme phenol oxidase was demonstrated in the culture filtrates, but not in extracts of disintegrated cells. As precursors for the pigment production, which was shown to be strictly pH dependent, DL-tyrosine, DL-dopa and catechol were used with success, while numerous other amino acids failed. The significance of the pigment as a criterium for the identification of strains which are pathogenic to certain animals or fishes, is not known.     

Regulation of the distribution of carotenoid droplets in goldfish xanthophores and possible implication to secretory processes

In goldfish xanthophores, the formation of pigment aggregate requires: 1) that a pigment organelle (carotenoid droplet) protein p57 be in the unphosphorylated state; 2) that self-association of pigment organelles occur in a microtubule-independent manner; and 3) that pigment organelles via p57 associate with microtubules. In the fully aggregated state, the pigment organelles are completely stationary. Pigment dispersion is initiated by activation of a cAMP-dependent protein kinase, which phosphorylates p57 and allows pigment dispersion via an active process dependent on F-actin and a cytosolic factor. This factor is not an ATPase, and its function is unknown. However, its abundance in different tissues parallels secretory activity of the tissues, suggesting a similarity between secretion and pigment dispersion in xanthophores. The identity of the motor for pigment dispersion is unclear. Experimental results show that pigment organelles isolated from cells with dispersed pigment have associated actin and ATPase activity comparable to myosin ATPase. This ATPase is probably an organelle protein of relative molecular mass approximately 72,000, and unlikely to be an ion pump. Isolated pigment organelles without associated actin have 5x lower ATPase activity. Whether this organelle ATPase is the motor for pigment dispersion is under investigation. The process of pigment aggregation is poorly understood, with conflicting results for and against the involvement of intermediate filaments.     

Elimination of egg pigment from developing ocular tissues in the frog Rana pipiens

The method by which egg pigment is eliminated from the developing retina, corneal epithelium and lens in Rana pipiens was studied with light and electron microscopy. The retina expells egg pigment into the space between the retina and pigment epithelium. This pigment is then engulfed by the pigment epithelial cells. The corneal epithelium eliminates egg pigment directly to the outside via the free surface of the epithelial cells. Egg pigment accumulates in a few cells in the lens. These cells probably degenerate and are extruded. These ectodermal derivatives in the eye are free of egg pigment long before ectodermal derivatives in other parts of the embryo lose their pigment. The early elimination of egg pigment from ocular tissues may related to the fact that these tissues must be transparent in order that light may pass freely to the photoreceptors.     

Extrusion of a Protein-Pigment Complex from Blepharisma undulans

SYNOPSIS. Blepharisma undulans , a purple-coloured ciliate protozoan, contains pigment granules in the ectoplasm. Treating the cells with 0.9% NaCl extruded the pigment into the medium without injury to the cells. The extrusion was instantaneous and with a single treatment about 35% of the total pigment oozed out. The pigment in the cells as well as in the saline extract was found to be associated with proteins and particulate fractions. The protozoa regenerated the pigment when transferred to culture fluid but not in dilute solution of saline, where they continued to live without regenerating the pigment. In addition to NaCl, sulphates of monovalent and divalent cations and calcium-binding agents induced the extrusion, which, however, was prevented by calcium in all cases. It is proposed that the removal of calcium from the outer membrane by chemicals disintegrates the pellicle and produces the extrusion, since a majority of the pigment granules are in the subpellicular layers of the cell.     

雪白白僵菌红色素的初步鉴定及其与环孢菌素A对底物缬氨酸的竞争

【目的】分离鉴定雪白白僵菌红色素,分析红色素与环孢菌素A对底物缬氨酸的竞争和相互影响。【方法】对红色素进行分离纯化,利用UV、IR和ESI-MS对红色素进行初步鉴定。采用缬氨酸分批补料培养,通过控制溶氧水平,以及添加红色素,分析红色素与环孢菌素A合成之间的竞争关联及相互影响。【结果】经鉴定,雪白白僵菌红色素分子式为C15H10O5,推测为含有芳环结构的蒽醌类化合物。在补加缬氨酸和高DO条件下,环孢菌素的产量高于低DO水平,相反红色素在低DO条件下合成量大于高DO水平。在不补加缬氨酸条件下,实验结果与补加缬氨酸培养一致,但是红色素和环孢菌素A的产量都显著降低。进一步添加外源纯化的红色素时,随着添加量的增加出现了环孢菌素A合成先减弱后增加的变化。【结论】发现并证实了雪白白僵菌红色素与环孢菌素A合成都以缬氨酸为共同底物,但两者的途径又相互独立。     

Dynein, dynactin, and kinesin II's interaction with microtubules is regulated during bidirectional organelle transport

The microtubule motors, cytoplasmic dynein and kinesin II, drive pigmented organelles in opposite directions in Xenopus melanophores, but the mechanism by which these or other motors are regulated to control the direction of organelle transport has not been previously elucidated. We find that cytoplasmic dynein, dynactin, and kinesin II remain on pigment granules during aggregation and dispersion in melanophores, indicating that control of direction is not mediated by a cyclic association of motors with these organelles. However, the ability of dynein, dynactin, and kinesin II to bind to microtubules varies as a function of the state of aggregation or dispersion of the pigment in the cells from which these molecules are isolated. Dynein and dynactin bind to microtubules when obtained from cells with aggregated pigment, whereas kinesin II binds to microtubules when obtained from cells with dispersed pigment. Moreover, the microtubule binding activity of these motors/dynactin can be reversed in vitro by the kinases and phosphatase that regulate the direction of pigment granule transport in vivo. These findings suggest that phosphorylation controls the direction of pigment granule transport by altering the ability of dynein, dynactin, and kinesin II to interact with microtubules.     

The orange-yellow pigment of heartwater-infected angora goats

Heartwater is a highly fatal disease of ruminants in South Africa, caused by the parasite Cowdria ruminantium. A consistent pigment, associated with serum albumin, could be readily extracted from heartwater exudates and serum samples using n-butanol. The pigment gave a characteristic absorption spectrum between 400 and 500 nm which was absent in control serum samples. RP-HPLC of the isolated pigment revealed two components with absorption maxima at 440 and 460 nm and mol. wts of 558 and 1239. The pigment closely resembled bilirubin and/or its conjugates when compared by HPLC.     

Red Pigment Produced by the Reaction of Dehydro-l-ascorbic Acid with α-Amino Acid

At the initial stage of the browning reaction of dehydro-l-ascorbic acid (DHA) with α-amino acid, a kind of red pigment was produced. The pigment was isolated as very hygroscopic red powder from non-aqueous reaction system, and its characterization was made. It was revealed that it had the same structure with that of the red pigment produced by the oxidation of l-scorbamic acid, an intermediate amino-reductone expected to be produced by Strecker degradation. Formation mechanism of the pigment which was considered to be an intermediate of browning reaction of DHA with α-amino acid was also discussed.     

Retinal pigment epithelial cell proliferation

The human retinal pigment epithelium forms early in development and subsequently remains dormant, undergoing minimal proliferation throughout normal life. Retinal pigment epithelium proliferation, however, can be activated in disease states or by removing retinal pigment epithelial cells into culture. We review the conditions that control retinal pigment epithelial proliferation in culture, in animal models and in human disease and interpret retinal pigment epithelium proliferation in context of the recently discovered retinal pigment epithelium stem cell that is responsible for most in vitro retinal pigment epithelial proliferation. Retinal pigment epithelial proliferation-mediated wound repair that occurs in selected macular diseases is contrasted with retinal pigment epithelial proliferation-mediated fibroblastic scar formation that underlies proliferative vitreoretinopathy. We discuss the role of retinal pigment epithelial proliferation in age-related macular degeneration which is reparative in some cases and destructive in others. Macular retinal pigment epithelium wound repair and regression of choroidal neovascularization are more pronounced in younger than older patients. We discuss the possibility that the limited retinal pigment epithelial proliferation and latent wound repair in older age-related macular degeneration patients can be stimulated to promote disease regression in age-related macular degeneration.     

Non-local interactions between light induced processes inCalliphora photoreceptors

Summary The prolonged depolarizing afterpotential (PDA) is a phenomenon which is tightly linked to visual pigment conversion. In order to determine whether processes underlying PDA induction and depression can spread in space, the PDA was recorded intracellularly in white-eyedCalliphora R1-6 photoreceptors and used to examine interactions between processes induced by activating statistically different photopigment molecules (Figs. 3–6). It was found that a PDA induced by converting some fraction of rhodopsin (R) molecules forward into the metarhodopsin (M) state can be completely depressed by equal or smaller amounts of pigment conversion, backward from metarhodopsin to rhodopsin even when largely different sets of pigment molecules were shifted in the respective directions, in agreement with previous experiments conducted on the barnacle. The characteristics of the afterpotentials obtained following the cessation of strong blue and green light stimuli which did not cause a net pigment conversion was examined (Figs. 7, 8). It was found that these afterpotentials, obtained when nonet R to M conversion took place, could not be depressed by an opposite net large M to R pigment conversion. Accordingly we propose to restrict the term PDA to an afterpotential which can be depressed by a net M to R pigment conversion. It is concluded: (a) that some processes underlying PDA induction and depression inCalliphora must interact at a distance which extends at least to the nearest neighboring pigment molecule, and (b) that inCalliphora photoreceptors net pigment conversion is required in order to induce and depress a PDA.Abbreviations R rhodopsin - M metarhodopsin - R to M rhodopsin to metarhodopsin pigment conversion - M to R metarhodopsin to rhodopsin pigment conversion - PDA prolonged depolarizing afterpotential - ERG electroretinogram - M potential metarhodopsin potential - ERP early receptor potential     

Granadaene: Proposed Structure of the Group B Streptococcus Polyenic Pigment

The goal of this work was to determine the chemical nature of the red pigment produced by Streptococcus agalactiae, which has been thought to be a carotene. We extracted the pigment with 0.1 M KOH and purified it by column chromatography on Sephadex LH. Data from elemental analysis and mass and nuclear magnetic resonance spectra lead us to propose the structure to be that of a new ornithine rhamno-polyene with 12 conjugated double bonds, to which we have assigned the trivial name granadaene.     

Production of purple pigment from green malt and dry malt grains by fermentation without steaming

Summary A large amount of high-molecular-mass anthocyanin pigment was produced by fermentation of malt grains without steaming, in which the malts were used as raw materials. The formation of a purple pigment from green malt was the most prominent from all malt grains tested. The precursor of the purple pigment was presumed to be a polyphenol (proanthocyanidin). When malt was used as the raw material, it allowed the production of pigment without using the glucoamylase preparation that is used for the fermentation of barley bran. In addition, the pigment was produced even from dry malt that had been treated with heat (80°C).     

金鱼总色素及色素组分的比较研究

用色谱和光谱两种方法对金鱼总色素和色素组分进行了研究。研究结果表明,红鲫、草金鱼和红龙睛等红色金鱼总色素光谱在可见光区(472nm附近)有一个吸收峰,黑鲫和黑龙睛等黑色金鱼在可见光区(450nm和472nm附近)有两个吸收峰出现,且红色金鱼所含色素组分以红色(虾青素)为主,黑色金鱼所含色素组分以杏黄色和橙色为主,其他色素组分为辅。金鱼黑色色斑形成是由于黑色素存在时,其他各色素组分的颜色被掩盖的结果;金鱼其他各种色斑的形成则是由于其体内各色素组分以不同比例相互搭配组合的结果。亲缘关系越近的金鱼其总色素组成就越相似,红鲫和黑鲫均含有四种近乎相同的色素组分,红龙睛和黑龙睛均含有六种近乎相同的色素组分,草金鱼虽也含有四种与红鲫和黑鲫相近的色素组分,但Rf值略有差异。据此推测,红鲫和黑鲫、红龙睛和黑龙睛可能分别具有较近的亲缘关系,而草金鱼则可能是介于黑鲫和龙睛鱼之间,且与黑鲫具有较近的亲缘关系。该研究有望为金鱼增色饵料的研制与开发提供理论依据,使金鱼的观赏价值和经济价值得到进一步提高。     

Structure of green pigment formed by the reaction of caffeic acid esters (or chlorogenic acid) with a primary amino compound.

A marked greening observed in some foods such as sweet potato, burdock, and others during food processing was shown to be due to green pigment formation by the condensation reaction of two molecules of chlorogenic acid or caffeic acid ester with one molecule of a primary amino compound under aeration in alkaline solution. Reduction of the green pigment by ascorbic acid or NaBH4 gave a yellow product, which readily turn green and then blue in air. The reduced and acetylated product of the green pigment was identified to be a novel trihydroxy benzacridine derivative, and the yellowish ethanol solution of this product immediately turned green upon addition of butyl amine or diluted alkali. Therefore, the green pigment was assumed to be an oxidized quinone type product of trihydroxy benzacridine. This identification of the structure was supported by the correspondence of the measured absorption spectra with those calculated by the molecular orbital method. A possible charge transfer complex between products of different oxidation steps in green solution was proposed.