Home About us Contact
|
Home About us Contact | ||
|
|
||
Background Colour (background + colour)
Selected AbstractsDemonstration of Postsynaptic Receptor Plasticity in an Amphibian Neuroendocrine InterfaceJOURNAL OF NEUROENDOCRINOLOGY, Issue 11 2002B. G. Jenks Abstract Pituitary pars intermedia melanotrope cells are often used as a model to study mechanisms of neuroendocrine integration. In the amphibian Xenopus laevis, the synthesis and release of ,-melanophore-stimulating hormone (,-MSH) from these cells is a dynamic process dependent upon the colour of background. In animals on a black background, there is a higher level of synthesis and secretion of ,-MSH than in animals on a white background, and, consequently, there is skin darkening in animals on a black background. The melanotropes are innervated by hypothalamic neurones that produce neuropeptide Y (NPY), a peptide that inhibits ,-MSH secretion via the NPY Y1 receptor. The inhibitory neurones have a higher expression of NPY in animals adapted to a white background and both the size and the number of inhibitory synapses on the melanotrope cells are enhanced. The purpose of the present study was to determine if this presynaptic plasticity displayed by the inhibitory neurones is reciprocated by postsynaptic plasticity (i.e. if there is an enhanced expression of the Y1 receptor in melanotropes of animals adapted to a white background). For this purpose quantitative real-time reverse transcriptase-polymerase chain reaction was used to determine the level of Y1 receptor mRNA in melanotropes of animals undergoing the process of background adaptation. The results showed that there is a higher Y1 receptor mRNA expression in melanotropes of white-adapted animals. We conclude that the inhibitory neuroendocrine interface in the Xenopus pars intermedia displays postsynaptic plasticity in response to changes of background colour. To our knowledge, this is the first demonstration of a physiological environmental change leading to changes in postsynaptic receptor expression in a fully identified vertebrate neuroendocrine reflex. [source] Influence of abutment substrate and ceramic thickness on the colour of heat-pressed ceramic crownsJOURNAL OF ORAL REHABILITATION, Issue 9 2002T. NAKAMURA Summary All-ceramic crowns made of leucite-based heat-pressed ceramics are widely used to restore non-vital teeth in conjunction with various post and core materials. However, as some light passes through the ceramic, the colour of the abutment substrate can negatively affect the final aesthetic appearance of the all-ceramic crown. In this study, we made background specimens simulating gold-alloy cast posts and other simulating porcelain veneered cast posts, overlaid different thickness of heat-pressed ceramic on these background specimens, and measured the shifts in colour. We found that, when the background specimen was a gold alloy, the background colour had an effect on the apparent colour, unless the ceramic was more than 1·6 mm thick. When the background specimen was porcelain veneered, the background colour had no evident effect, even when the ceramic was not very thick. Therefore, when making a restoration using a leucite-based heat-pressed ceramic crown, it is advisable to use tooth-coloured materials such as a porcelain veneered cast post, if you will not be able to make the ceramic more than 1·6 mm thick. [source] Effects of hatchling body colour and rearing density on body colouration in last-stadium nymphs of the desert locust, Schistocerca gregariaPHYSIOLOGICAL ENTOMOLOGY, Issue 1 2007KOUTARO MAENO Abstract The influences of hatchling character and rearing density on body colour at the last-nymphal stadium are investigated for the desert locust, Schistocerca gregaria. Hatchlings are divided into five groups based on the darkness of the body colour and reared either under isolated or crowded conditions. Two types of body colour variation at the last-nymphal stadium are separately analysed (i.e. the background colour and black patterns). Under isolated conditions, the background body colour is either greenish or brownish. Most individuals are greenish and the highest percentage of brownish insects is obtained from hatchlings with the darkest body colour. Under crowded conditions, the background colour is yellow or orange and the percentage of yellowish nymphs tends to decrease when they are darker at hatching. The intensity of black patterns differs depending on the body colour at hatching and subsequent rearing density. Most isolated-reared nymphs exhibit few or no black patterns but nymphs with some black patterns also appear, particularly among those that had been dark at hatching. Under crowded conditions, the black patterns become more intense when they are darker at hatching. Therefore, last-stadium nymphs with typical solitarious or gregarious body colouration appear when they have the phase-specific body colouration at hatching as well. The present results demonstrate that both body colour at hatching and rearing density during nymphal development influence body colouration at the last-nymphal stadium. [source] Changes in skin colour and cortisol response of Australian snapper Pagrus auratus (Bloch & Schneider, 1801) to different background coloursAQUACULTURE RESEARCH, Issue 5 2009Ben J Doolan Abstract A two-factor experiment was carried out to investigate the change in skin colour and plasma cortisol response of cultured Australian snapper Pagrus auratus to a change in background colour. Snapper (mean weight=437 g) were held in black or white tanks and fed diets containing 39 mg unesterified astaxanthin kg,1 for 49 days before being transferred from white tanks to black cages (WB) or black tanks to white cages (BW). Skin colour values [L* (lightness), a* (redness) and b* (yellowness)] of all snapper were measured at stocking (t=0 days) and from cages of fish randomly assigned to each sampling time at 0.25, 0.5, 1, 2, 3, 5 and 7 days. Plasma cortisol was measured in anaesthetized snapper following colour measurements at 0, 1 and 7 days. Fish from additional black-to-black (BB) and white-to-white (WW) control treatments were also sampled for colour and cortisol at those times. Rapid changes occurred in skin lightness (L* values) after altering background colour with maximum change in L* values for BW and WB treatments occurring within 1 day. Skin redness (a*) of BW snapper continued to steadily decrease over the 7 days (a*=7.93 × e,0.051 × time). Plasma cortisol concentrations were highest at stocking when fish were held at greater densities and were not affected by cage colour. The results of this study suggest that transferring dark coloured snapper to white cages for 1 day is sufficient to affect the greatest benefit in terms of producing light coloured fish while minimizing the reduction in favourable red skin colouration. [source] Extraction and analysis of colourful eggshell pigments using HPLC and HPLC/electrospray ionization tandem mass spectrometryBIOMEDICAL CHROMATOGRAPHY, Issue 6 2009A. Gorchein Abstract The literature on the pigments of avian eggshells is critically reviewed. Methods using methanolic sulfuric acid or hydrochloric acid to extract eggshell pigments are unsuitable to detect the occurrence of zinc protoporphyrin or zinc biliverdin because they demetallate these compounds. Extraction methods are described here using EDTA and acetonitrile,acetic acid or acetonitrile,dimethyl sulfoxide, which do not demetallate zinc protoporphyrin. Such extracts were prepared from eggshell of the common nighthawk, Chordeiles minor, and from another six bird species. Protoporphyrin and biliverdin were identified and fully characterized by HPLC/electrospray ionization tandem mass spectrometry (HPLC/ESI-MS/MS) in all samples, but none contained zinc protoporphyrin. The zinc complex of biliverdin, claimed to be an additional pigment responsible for eggshell background colours, was labile to EDTA and acid pH and if occurring naturally could not be extracted intact by the published or the modified protocols. An explanation is advanced for the exceptional report that all porphyrins from uroporphyrin to protoporphyrin were found in eggshells of the fowl Gallus domesticus. Copyright © 2009 John Wiley & Sons, Ltd. [source] | ||||||||||