Beta-alanine and adaptation in Drosophila

Populations of Drosophila melanogaster show melanistic polymorphism. Adult melanization is inversely related to the rate of incorporation of beta-alanine into tanning cuticles. Light tan pigmentation is directly related to this incorporation. Beta-alanine induced tanning serves to protect pupae from ultraviolet light damage. Flies which do not fail to incorporate injected beta-alanine into developing cuticles, but which exhibit inhibited beta-alanine synthesis (flies homozygous for the gene ‘b’) are not only protected, as pupae, from ultraviolet damage by beta-alanine injection but also show enhanced mating success when injected as newly emerged adults. The metabolic block in this mutant appears in the pathway from orotic acid through uracil to beta-alanine.     

Quantitative variation of melanins in llama (Lama glama L.)

The amount of melanin pigments was investigated in 80 Argentinean llama, representative of seven phenotypes and four different fleece colours, by means of spectrophotometric assays: SpEM (spectrophotometric eumelanin), SpPM (spectrophotometric pheomelanin), SpASM (spectrophotometric alkali soluble melanin), and SpTM (spectrophotometric total melanin). It was found that, although to a different extent, the quantitative variation of these pigments was affected both by phenotypes and fleece colours and, hence, it was possible to identify and to distinguish homogeneous groups on the basis of these two factors. In particular, SpEM revealed the most reliable parameter for a discrimination among these groups. Low concentrations of this pigment characterize red, wild, and red black phenotypes and distinguish them from black and tan and non-agouti black ones, both showing high concentrations; low concentrations also distinguish reddish brown fleece colour from very dark red and black ones.     

Role of beta-alanine in cuticular tanning,sclerotization, and temperature regulation in Drosophila melanogaster

Injection of 20 nl of 1.0 M beta-alanine, about the minimal amount needed to produce wild-type tanned phenomenocopies from newly eclosed mutant black Drosophila melanogaster, increases stiffness and puncture-resistance of the wing cuticle. Increasing the concentration of beta-alanine to 2.0 M increases puncture-resistance further. Injection of 1.0 M of the beta-alanine analogue beta-aminoisobutyric acid, does not induce tanning or puncture-resistance, nor does injection of 1.0 M dopamine. However, injection of 1.0 M beta-alanine and 1.0 M dopamine increases puncture-resistance more than an injection of 1.0 M beta-alanine, though not more than an injection of 2.0 M beta-alanine alone. Within 10 min after injection of [3-³H]beta-alanine into newly eclosed normal flies, ³H becomes 8.7 times more concentrated in the cuticle than in an equal area of underlying epidermis. ³H is excluded from the epidermis or cuticle of ebony strains. Ebony strains show a deficiency of cuticular electron-absorbing material, and the cuticular lamellae show a tendency to separate from each other. Compaction of the chitinous lamellae is induced in alkali-detanned pupal sheaths by exposure to nascent quinones of N-acetyldopamine or N-beta-alanyldopamine. Glucosamine, but not N-acetylglucosamine, reacts with such quinones in tanning reactions. Under an infrared beam, black cuticular pigmentation induces more rapid heating of haemocoel fluids than does tan pigmentation. A theory of pigmentation and sclerotization relative to environmental adaptation is presented.     

New mechanism of melanosomes transport into hair of lambs of different breeds and genotypes.

By light microscopic investigation of skin and wool specimens of newborn lambs, we discovered a previously unknown mechanism for melanosomes transport in the process of dermal papilla melanocytes regular mitosis and migration into the hair shaft. This mechanism plays a great role in hair pigmentation especially in dominant (ED/ED) and recessive (Aa/Aa) black lambs of all investigated breeds. The rate of pigment cell mitosis, proliferation, and migration differs greatly in lambs of investigated color genotypes. In black genotypes the rate of melanocyte mitosis is very high and is approximately the same as in the hair bulb matrix cells, whereas in brown and red genotypes this rate is much lower. Melanocyte mitosis in the light red and tan groups was not found.     

New Mechanism of Melanosomes Transport into Hair of Lambs of Different Breeds and Genotypes

By light microscopic investigation of skin and wool specimens of newborn lambs, we discovered a previously unknown mechanism for melanosomes transport in the process of dermal papilla melanocytes regular mitosis and migration into the hair shaft. This mechanism plays a great role in hair pigmentation especially in dominant (E^D/E^D) and recessive (A^a/A^a) black lambs of all investigated breeds. The rate of pigment cell mitosis, proliferation, and migration differs greatly in lambs of investigated color genotypes. In black genotypes the rate of melanocyte mitosis is very high and is approximately the same as in the hair bulb matrix cells, whereas in brown and red genotypes this rate is much lower. Melanocyte mitosis in the light red and tan groups was not found.     

The absorption of orally supplied β-alanine and its effect on muscle carnosine synthesis in human vastus lateralis

Summary. β-Alanine in blood-plasma when administered as A) histidine dipeptides (equivalent to 40 mg · kg⁻¹ bwt of β-alanine) in chicken broth, or B) 10, C) 20 and D) 40 mg · kg⁻¹ bwt β-alanine (CarnoSyn™, NAI, USA), peaked at 428 ± SE 66, 47 ± 13, 374 ± 68 and 833 ± 43 μM. Concentrations regained baseline at 2 h. Carnosine was not detected in plasma with A) although traces of this and anserine were found in urine. Loss of β-alanine in urine with B) to D) was <5%. Plasma taurine was increased by β-alanine ingestion but this did not result in any increased loss via urine. Pharmacodynamics were further investigated with 3 × B) per day given for 15 d. Dietary supplementation with I) 3.2 and II) 6.4 g · d⁻¹ β-alanine (as multiple doses of 400 or 800 mg) or III) L-carnosine (isomolar to II) for 4 w resulted in significant increases in muscle carnosine estimated at 42.1, 64.2 and 65.8%.     

Comparison of the structural and physical properties of human hair eumelanin following enzymatic or acid/base extraction

Eumelanin was isolated from a sample of black, Indonesian human hair using three different published procedures: two different acid/base extractions and an enzymatic extraction. The morphology and spectroscopic properties of the isolated pigments differ significantly. The acid/base procedures both yield an amorphous material, while enzymatic extraction yields ellipsoidal melanosomes. Amino acid analysis shows that there is protein associated with the isolated pigments, accounting for 52, 40 and 14% of the total mass for the two acid/base extractions and the enzymatic extraction, respectively. The amino acid compositions do not correlate with those of keratin or tyrosinase. Metal elemental analysis shows that the acid/base extraction removes a majority of many metal ions bound to the pigment. Chemical degradation analysis by KMnO4/H+ and H2O2/OH- indicates significant differences between the pigments isolated by acid/base and enzymatic extraction. After correction for the protein mass in the two pigments, the lower yields of both pyrrole-2,3,5-tricarboxylic acid and pyrrole-2,3-dicarboxylic acid, eumelanin degradation products, indicate acid/base extraction modifies the chemical structure of the melanin, consistent with the result of Soluene solubilization assay. While the optical absorption spectra of the bulk pigments are similar, the spectra of the molecular weight less than 1000 mass fractions differ significantly. The data clearly indicate that pigment obtained from human hair by acid/base extraction contains significant protein, exhibits destruction of the melanosome, and possesses altered molecular structure. The acid/base extracted hair melanin is not representative of the natural material and is a poor model system for studying the physical and biological properties of melanins. The enzymatically extracted hair melanin, on the contrary, retains the morphology of intact melanosomes and is an excellent source of human melanin.     

Brown pigmentation in Serratia marcescens cultures associated with tyrosine metabolism

Serratia marcescens produced a brown pigment when grown in minimal medium in the presence of tyrosine and high concentrations of copper(II) ion. The pigment was not related to the melanin pigments, but was similar to the pigment produced by autooxidation and polymerization of 3,4-dihydroxyphenylacetate, which is synthesized in S. marcescens from tyrosine through the 3,4-dihydroxyphenylacetate catabolic pathway. The enzymes of this pathway were induced under pigment production conditions; however, 3,4-dihydroxyphenylacetate 2,3-dioxygenase remained at low activity levels, permitting the accumulation and excretion of the substrate. Mutants unable to use tyrosine as a sole carbon and energy source were able to produce brown pigments only if the step blocked by the mutation was after the synthesis of 3,4-dihydroxyphenylacetate. The ability to produce brown pigments was common to all the S. marcescens strains tested.     

The production of chimeric rats and their use in the analysis of the hooded pigmentation pattern

New, improved media and procedures for making rat chimeric embryos and culturing them in vitro have been developed. We have produced 27 rat chimeras: 20 males and 7 females. This ratio of males to females is consistent with that seen in mouse chimeras, suggesting that rat sex chimeras develop as phenotypic males. By aggregating embryos containing appropriate genetic markers for pigment cell differentiation, it is possible to produce chimeras that elucidate the site of action of the hooded gene. The coat color patterns of black ? black hooded chimeras display a white belly spot. In black ? albino hooded chimeras, small patches of white hair appear on the head and a large white spot occurs on the belly. Black ? agouti hooded chimeras display both agouti and nonagouti pigmentation over the entire surface of the chimera. These animals are fully pigmented with no white spots. In black ? albino non-hooded chimeras, rather small irregular patches of black and white hairs are distributed throughout the pelage. Histological examination of sections of hair follicles obtained from the white areas in the head of black ? albino hooded chimeras revealed amelanotic melanocytes. On the other hand, hair bulbs from the white belly spots do not contain any such melanocytes. Thus the white hairs of the head are due to the presence of albino melanocytes, but the white hairs of the belly are due to the total absence of melanocytes. All these observations are consistent with the conclusion that the hooded gene acts within melanoblasts, probably to retard their migration from the neural crest and/or to prevent their entrance into the hair follicles of the white areas of hooded rats.     

The dark side of white hair? Artificial light irradiation reduces cortisol concentrations in white but not black hairs of cattle and pigs

Analysing hair cortisol concentrations (HCCs) is a minimally invasive way to retrospectively assess long-term stress, and its application in studies of animal welfare and stress has attracted considerable interest. However, not only stress-related effects but also hair-specific characteristics and external influences can affect HCCs and interfere with the interpretation of results. Thus, it was the aim of this study to investigate the impact of daylight and UV irradiation on cortisol concentrations in the hairs of pigs and cattle. We also examined whether a potential irradiation effect on HCCs depended on the colour of the hair. For this purpose, black and white hair samples from 18 Saddleback pigs and 18 Holstein Friesian cattle were exposed to artificial light (both visible and UV) and compared with control hair samples from the same animals kept in the dark. Exposure to artificial light significantly decreased HCCs in both pigs (P < 0.05) and cattle (P < 0.001), and hair colour had an influence on HCCs, with black hair showing higher cortisol levels than white hair (cattle: P < 0.001, pigs: P = 0.07). The interaction between light exposure and hair colour was significant in both pigs (P < 0.01) and cattle (P < 0.001), so light exposure reduced HCCs in porcine white hair but not black hair. In cattle, light-exposed white hair exhibited lower hair cortisol levels than control white hair or black hair. These results demonstrate that artificial light irradiation degrades hair cortisol or favours its elimination by structural changes of the hair matrix. However, this effect was only detectable in white hair, indicating that the melanin pigments in black hair absorbed radiation, thereby reducing the effects of photodegradation. Compared with other known influencing factors on HCCs, such as age and body region, the influence of light irradiation was relatively low in this in vitro experiment. However, further studies should investigate this influence under real-life animal conditions, such as outdoor and indoor housing.     

Relation between phenotype and banal melanocytic naevi.

In a study of risk factors for the development of melanocytic naevi in relation to the pathogenesis of malignant melanoma 197 white adults were examined by four dermatologists and naevus counts correlated with several other features. Highly significant associations were found between large numbers of banal acquired melanocytic naevi and the ability to tan easily without burning (skin types 3 and 4; relative risk 4.6), brown or hazel eyes (relative risk 3.5), green or grey eyes (relative risk 3.5) and brown or black hair (relative risk 3.7). No significant associations with numbers of naevi were shown for parity or use of oral contraceptives or other steroid hormones. This is the first study to find any relation between melanocytic naevi and phenotypic factors in a white population.     

Comparative Analysis of Melanins and Melanosomes Produced by Various Coat Color Mutants

Pigmentation in the skin, hair, and eyes of animals is influenced by a number of genes that modulate the activity of melanocytes, the intervention of enzymatic controls at different stages of the melanogenic process, and the physico-chemical properties of the final pigment. The results of combined phenotypic, ultrastructural, biochemical, and chemical analyses of hairs of a variety of defined genotypes on a common genetic background performed in this study are consistent with the view that pigmentation of dark to black hairs results from the incorporation of eumelanin pigments whereas that of yellow hairs results from the incorporation of eu- and pheomelanins. It is also clear that relatively minor differences in melanin content can have dramatic effects on visible hair color. A good correlation was found for expression of (and enzyme activities associated with) TRP1 and TRP2 with eumelanin synthesis and eumelanosome production.     

Observations on the pigmentation of the pigeon iris

There are three genetically controlled iris types found in the pigeon, two of which contain stromal pigment cells, the third lacks pigment cells. The yellow (gravel) and white (pearl) iris types have pigment cells that contain birefringent pigment granules (crystals) and are ultrastructurally similar to iridophores of poikilothermic vertebrates. Both these iris types contain guanine as a major "pigment" and, in addition, the yellow iris contains at least two yellow fluorescing pigments that are tentatively identified as pteridines. The pigment cells of the yellow and white irises are structurally identical differing only in the presence or absence of these yellow pigments. The stromal pigment cells of the white iris correspond in structure and pigment chemistry to classical iridophores although they lack strong irridescence and are therefore perhaps best considered leucophores. The pigment cells of the yellow iris can be considered "reflecting xanthophores" having the combined properties of both classical xanthophores and iridophore/leucophores.     

Ultraviolet radiation induces dose-dependent pigment dispersion in crustacean chromatophores

Pigment dispersion in chromatophores as a response to UV radiation was investigated in two species of crustaceans, the crab Chasmagnathus granulata and the shrimp Palaemonetes argentinus. Eyestalkless crabs and shrimps maintained on either a black or a white background were irradiated with different UV bands. In eyestalkless crabs the significant minimal effective dose inducing pigment dispersion was 0.42 J/cm(2) for UVA and 2.15 J/cm(2) for UVB. Maximal response was achieved with 10.0 J/cm(2) UVA and 8.6 J/cm(2) UVB. UVA was more effective than UVB in inducing pigment dispersion. Soon after UV exposure, melanophores once again reached the initial stage of pigment aggregation after 45 min. Aggregated erythrophores of shrimps adapted to a white background showed significant pigment dispersion with 2.5 J/cm(2) UVA and 0.29 J/cm(2) UVC. Dispersed erythrophores of shrimps adapted to a black background did not show any significant response to UVA, UVB or UVC radiation. UVB did not induce any significant pigment dispersion in shrimps adapted to either a white or a black background. As opposed to the tanning response, which only protects against future UV exposure, the pigment dispersion response could be an important agent protecting against the harmful effects of UV radiation exposure.     

Isolation and characterization of mammalian eumelanins from hair and irides

A new enzymatic procedure was developed for isolation of eumelanin from black human hair which might provide a substantially intact pigment for structural characterization. Sequential digestion with protease, proteinase K and papaine in the presence of dithiothreitol afforded a pigment with a 6% w/w protein content. HPLC analysis of pyrrole acids resulting from alkaline H(2)O(2) degradation, carboxyl content determination, and ferricyanide titration showed that the isolated pigment is made up of 5,6-dihydroxyindole (DHI)- and 5, 6-dihydroxyindole-2-carboxylic acid (DHICA)-derived units at a 6:1 ratio, exhibiting a significant degree of oxidative degradation. For comparison, a different eumelanin isolated from black bovine irides by a similar enzymatic procedure was analyzed. Matrix-assisted laser desorption ionization (MALDI) mass spectrometry of the final pigment provided evidence for homologous series of DHICA oligomers, while chemical analysis allowed an estimate of 2:1 DHICA/DHI-derived units in the polymer, with a substantial proportion of intact o-diphenolic functions. Iris melanin proved able to promote the Fenton oxidation of deoxyribose while hair melanin was ineffective. Overall, these results provide, for the first time, unambiguous evidence for marked structural differences of mammalian eumelanins which may be directly related to the diversity of the sites of biosynthesis and storage, as well as to functional role of these pigments.     

Brilliant skyblue pigment formation from gardenia fruits

It is well known that blue pigment is formed by the reaction of amino acids with genipin, the hydrolyzate of geniposide from gardenia fruits. We studied the effect of the amino acid on blue pigment formation and found a linear relationship between the molecular weight of the neutral amino acid and the λ_max of the blue pigment formed. Thin layer chromatographic analysis revealed brilliant skyblue components of the blue pigments formed from glycine, alanine, leucine, phenylalanine and tyrosine. Furthermore, a brilliant skyblue color was obtained by a reverse phase column chromatography (HP-20) of blue pigments formed from glycine, leucine and phenylalanine. The λ_max of these purified pigments lay above 600 nm, and the peaks were sharper than those of crude pigments. After standing for two weeks at 40°C in 40% ethanol solution, the brilliant skyblue pigment formed from genipin and glycine remained stable, losing none of its initial absorbance.     

蝗虫复眼光谱敏感性的比较研究——Ⅱ.视网膜电图的光谱敏感曲线

(1)用视网膜电图(ERG)方法测定了9种蝗虫在黑暗、蓝光和橙光适应下的光谱敏感性。(2)9种蝗虫的碚适应光谱敏感曲线峰值均在520—546nm 之间。(3)橙光或蓝光明适应导致不同程度的峰值位移,蓝区的相对敏感性提高,这与光引起屏蔽色素移动效应有关。(4)黑背蝗和稻蝗复眼表面均没有黑白间,橙光适应时出现第二个峰值在蓝区,而蓝光适应则压抑蓝区的敏感性。可能这两种蝗虫还具有蓝敏视色素。(5)佛蝗和黄脊蝗复眼表面均有明显的黑白相间的区域,在有色光适应下这两种蝗虫的光谱敏感性变化最小,没有证据说明多于一种光敏色素。     

Tissue microenvironment and the genetic control of hair pigment patterns in mice

This study was conducted to assess microenvironmental variability within integumental tissue of genetically identical mice with respect to a specific cellular response: cyclic synthesis of yellow and black pigment by hair bulb melanocytes. Crosses were performed within and between inbred strains of mice that were isogenic with the exception of a single gene substitution at the agouti locus. Agouti locus genes included the A^vy, A^w, A, a^td, a^t, a^x, a^m, and a alleles. The pigment patterns of dorsal, flank, and ventral hairs of the first and third hair generations and of hairs growing in special integumentary areas such as the pinna, tail, and hind foot were studied. It was found that the amount of yellow pigment synthesized by hair bulb melanocytes within genetically identical mice is both agedependent and conditioned by the integumentary environment. Furthermore, the special integumentary regions produce hairs with a variety of pigment patterns in which the distribution and relative amounts of black and yellow pigments do not necessarily conform to dominance relationships expected among agouti locus alleles as judged by their effects on the pigmentation of the dorsal pelage. We conclude that within genetically uniform integumental tissues, microenvironmental differences occur and are reflected as alterations in the metabolic pattern of differentiated cells.