Pterine als Wirkstoffe und Pigmente

Time Flies-Age Grading of Adult Flies for the Estimation of the Post-Mortem Interval

The estimation of the minimum time since death is one of the main applications of forensic entomology. This can be done by calculating the age of the immature stage of necrophagous flies developing on the corpse, which is confined to approximately 2–4 weeks, depending on temperature and species of the first colonizing wave of flies. Adding the age of the adult flies developed on the dead body could extend this time frame up to several weeks when the body is in a building or closed premise. However, the techniques for accurately estimating the age of adult flies are still in their beginning stages or not sufficiently validated. Here we review the current state of the art of analysing the aging of flies by evaluating the ovarian development, the amount of pteridine in the eyes, the degree of wing damage, the modification of their cuticular hydrocarbon patterns, and the increasing number of growth layers in the cuticula. New approaches, including the use of age specific molecular profiles based on the levels of gene and protein expression and the application of near infrared spectroscopy, are introduced, and the forensic relevance of these methods is discussed.

Marginal Differentiation between the Sexual and General Carotenoid Pigmentation of Guppies (Poecilia reticulata) and a Possible Visual Explanation

We present the first detailed analysis of carotenoid pigmentation of the integument of guppies (Poecilia reticulata Peters), quantifying variation in carotenoid content and composition of wild guppies from three drainages on Trinidad (1) between the sexual and general pigmentation of males, (2) between the sexes, and (3) geographically in relation to carotenoid availability. We report that the carotenoid pigments in the integument of guppies are predominantly esters of tunaxanthin. The peak wavelength of carotenoids in the orange spots of males lay only ca. 2.8 nm higher than that of pigments outside of the orange spots, and the peak wavelength of carotenoids in the male whole integument does not differ from that in the female whole integument. Carotenoid composition of the general integument of females and the non-orange spot fraction of males, but not of the orange spot fraction of males, varied with diet, correlating with the ratio beta-carotene to lutein in the different streams. Male guppies deposit higher concentrations of carotenoids in their orange spots than in the rest of the integument (five to nine times higher), but not at the expense of the general integument, which was similarly endowed as the general integument of females, even in carotenoid-poor streams. Presumably males absorb/retain more pigments than females. Photoreceptor-based simulations suggest that tunaxanthin provides both greater brightness and chroma than would 4-keto-carotenoids such as astaxanthin.

The pteridine pathway in zebrafish: regulation and specification during the determination of neural crest cell-fate

This review describes pteridine biosynthesis and its relation to the differentiation of neural crest derivatives in zebrafish. During the embryonic development of these fish, neural crest precursor cells segregate into neural elements, ectomesenchymal cells and pigment cells; the latter then diversifying into melanophores, iridophores and xanthophores. The differentiation of neural cells, melanophores, and xanthophores is coupled closely with the onset of pteridine synthesis which starts from GTP and is regulated through the control of GTP cyclohydrolase I activity. De novo pteridine synthesis in embryos of this species increases during the first 72-h postfertilization, producing H4biopterin, which serves as a cofactor for neurotransmitter synthesis in neural cells and for tyrosine production in melanophores. Thereafter, sepiapterin (6-lactoyl-7,8-dihydropterin) accumulates as yellow pigment in xanthophores, together with 7-oxobiopterin, isoxanthopterin and 2,4,7-trioxopteridine. Sepiapterin is the key intermediate in the formation of 7-oxopteridines, which depends on the availability of enzymes belonging to the xanthine oxidoreductase family. Expression of the GTP cyclohydrolase I gene (gch) is found in neural cells, in melanoblasts and in early xanthophores (xanthoblasts) of early zebrafish embryos but steeply declines in xanthophores by 42-h postfertilization. The mechanism(s) whereby sepiapterin branches off from the GTP-H4biopterin pathway is currently unknown and will require further study. The surge of interest in zebrafish as a model for vertebrate development and its amenability to genetic manipulation provide powerful tools for analysing the functional commitment of neural crest-derived cells and the regulation of pteridine synthesis in mammals.

The erythrophore in the larval and adult dorsal skin of the brown frog, Rana ornativentris: its differentiation, migration, and pigmentary organelle formation

To determine whether or not the erythrophore originates from xanthophores in the dorsal skin of the brown frog, Rana ornativentris, we morphologically examined the differentiation and migration of the two chromatophore types and their pigmentary organelle formation. At an early tadpole stage, three kinds of chromatophores, xanthophores, iridophores, and melanophores, appeared in the subdermis, whereas the erythrophore did so just before the foreleg protrusion stage. By the middle of metamorphosis, most chromatophores other than erythrophores had migrated to the subepidermal space. Erythrophores, which appeared late in the subdermis, proliferated actively there during metamorphosis and finished moving into the subepidermal space by the completion of metamorphosis. Carotenoid vesicles and pterinosomes within the erythrophores and xanthophores showed several significant differences in structure. In xanthophores, carotenoid vesicles were abundant throughout life, whereas those in erythrophores decreased in number with the growth of the frogs. The fibrous materials contained in the pterinosomes were initially scattered but soon formed a concentric lamellar structure. In erythrophores, the lamellar structure began to form at the periphery of the organelles but at the center in xanthophores. In addition, the pterinosomes of erythrophores were uniform in size throughout development, while those of xanthophores showed a tendency to become smaller after metamorphosis. The pterinosomes of xanthophores were significantly larger than those of erythrophores. These findings suggest that an erythrophore is not a transformed xanthophore, although they resemble each other closely in many respects.

Characterization of the reflective materials and organelles in the bright irides of North American blackbirds (Icterinae)

The reflective materials in the iris stroma of bright-irised American blackbirds (Icterinae, Emberizidae) and the red-eyed vireo (vireo olivaceus) (Vireonidae) were characterized using high-performance liquid chromatography (HPLC) and diode-array detection. Two purines, guanine and hypoxanthine, and two pteridines, leucopterin and xanthopterin, were detected in large amounts in all bright irides. The brown iris of the red-winged blackbird (Agelaius phoeniceus) by comparison contained only small amounts of these and additional unidentified compounds. The absolute and relative amounts of light-absorbing compounds in the iris varied somewhat among species of blackbirds with bright irides, and markedly within one species (brewer's blackbird, Euphagus cyanocephalus) between sexes and age classes that very in eye color. Differences in the types, numbers, and sizes of pigment organelles in the irides appeared to underlie the differences in amounts of light-absorbing compounds. Guanine was the most abundant light-absorbing compound in all bright irides, accounting for about 90% of the total absorption at 250 nm. A wide range of concentrations of guanine, from 96 to 9 micrograms per iris, produced bright irides. The primary pigment organelles of pigment cells in bright irides were reflecting platelets, which typically appeared as open spaces on electron micrographs. In the red-eyed vireo there were in addition red pterinosome-like pigment organelles in the pigment cells on the anterior surface of the iris stroma. Guanine was present even in irides with no overt reflecting platelets.

Biotechnological applications of research on animal pigmentation

The implications of primary research on pigmentation for the colour manipulation of animal species of economic importance, and the facilitation of specific processes in biotechnology are discussed. Pigment technologists, especially poultry and fish nutritionists, are concerned with achieving the often specific type and degree of coloration demanded by consumers of various products (notably egg yolk, eggshell, broiler skin and salmon flesh). In most instances involving melanin (pelage, plumage and integument) and porphyrin (eggshell) pigments, the desired coloration is achieved through the use of alternate alleles at gene loci controlling the characters of interest. In contrast, coloration involving carotenoids is controlled primarily through pigment supplementation in the diet. The difference between carotenoids and other pigments involves the strict dietary origin of the former. Factors other than pigment availability, such as body condition, hormonal status and genetic constitution, also affect coloration. Although day-old chicks can be sexed by visual inspection of their genitalia, matings resulting in sex-associated phenotypes are in wide use. The genetic markers involved affect the colour of the plumage. The cloning of genes involved in pigmentation offers the prospect of deciphering the genetic control of animal pigmentation and modifying it to meet specific pigmentation needs.

Pteridines as reflecting pigments and components of reflecting organelles in vertebrates

This paper reviews evidence for the presence of pteridines in iridophores, leucophores, and xanthophores in a wide variety of vertebrate chromatophores, and argues that the chemical and functional distinction between pterinosomes and reflecting platelets is not as clear-cut as previously believed. Observations indicate that: (1) Pteridines may, either alone or in conjunction with purines, form pigment granules that reflect light, (2) these pigment granules are highly variable ranging from fibrous pterinosomes to typical reflecting platelets and may be colored, reflect white light, or be iridescent, and (3) many "leucophores" probably contain typical pterinosomes and presumed associated colorless pteridines and are therefore more closely related to erythrophores and xanthophores than to iridophores with which they are usually classified. We propose that the classification of pigment cells should be modified to reflect these facts.

[Pterins: pigments, cofactors and signal connections in cell interactions]

Pteridines were originally described as pigments of insects and lower vertebrates. The electron-donating function of tetrahydrobiopterin for aromatic amino acid hydroxylation and thus, for neurotransmitter biosynthesis adduced the participation of unconjugated pterins in cellular metabolism. There has been increasing evidence moreover that they are signal molecules for intercellular recognition in primitive eucaryotes, as well as modifiers of signal polypeptides in higher vertebrates.

Biopterin level in blood cells as a marker for hemopoietic cell proliferation during autologous bone marrow transplantation in beagle dogs

Bone marrow aplasia was induced by fractionated whole body irradiation with 3000 R and restitution was started by autologous bone marrow transplantation. During the period of aplasia the amount of buffy coat biopterin clearly followed the decline of leukocytes and, vice versa, during reconstitution it largely paralleled their increase in number. The amount of red cell biopterin closely correlated with the number of reticulocytes rather than with the fairly constant values for hematocrit or of erythrocytic protein. Thereby it clearly followed the various periods of red cell recovery. The amount of cellular biopterin, its concentration with respect to cell number or to unit of protein and the percentage distribution of biopterin among the cell fractions are presented as characteristics of the activity of hemopoietic cell proliferation.

Purification and properties of the enzymes from Drosophila melanogaster that catalyze the synthesis of sepiapterin from dihydroneopterin triphosphate

Sepiapterin synthase, the enzyme system responsible for the synthesis of sepiapterin from dihydroneopterin triphosphate, has been partially purified from extracts of the heads of young adult fruit flies (Drosophila melanogaster). The sepiapterin synthase system consists of two components, termed "enzyme A" (MW 82,000) and "enzyme B" (MW 36,000). Some of the properties of the enzyme system are as follows: NADPH and a divalent cation, supplied most effectively as MgCl2, are required for activity; optimal activity occurs are pH 7.4 and 30 C; the Km for dihydroneopterin triphosphate is 10 microM; and a number of unconjugated pterins, including biopterin and sepiapterin, are inhibitory. Dihydroneopterin cannot be used as substrate in place of dihydroneopterin triphosphate. Evidence is presented in support of a proposed reaction mechanism for the enzymatic conversion of dihydroneopterin triphosphate to sepiapterin in which enzyme A catalyzes the production of a labile intermediate by nonhydrolytic elimination of the phosphates of dihydroneopterin triphosphate, and enzyme B catalyzes the conversion of this intermediate, in the presence of NADPH, to sepiapterin. An analysis of the activity of sepiapterin synthase during development in Drosophila revealed the presence of a small amount of activity in eggs and young larvae and a much larger amount in late pupae and young adults. Sepiapterin synthase activity during development corresponds with the appearance of sepiapterin in the flies. Of a variety of eye color mutants of Drosophila melanogaster tested for sepiapterin synthase activity, only purple (pr) flies contained activity that was significantly lower than that found in the wild-type flies (22% of the wild-type activity). Further studies indicated that the amount of enzyme A activity is low in purple flies, whereas the amount of enzyme B activity is equal to that present in wild-type flies.

The quantitative relations between variation in red eye pigment and related pteridine compounds in Drosophila melanogaster

The relations between the quantity of red eye pigment and related pteridine compounds ofDrosophila melanogasterhave been studied in a variety of genotypes, which include strains selected for high or low pigment content, various derivatives of these lines and also lines in which one or other of the major autosome pairs were represented by homozygous chromosome pairs, derived by random sampling from the base population and also inbred lines. The quantity of red pigment was defined by the optical density when whole heads were extracted in a suitable solvent, while the pteridines were separated by chromatography and their amounts estimated by means of their characteristic fluorescence.

The evidence from selection, inbreeding and chromosome sampling from the base population demonstrated the presence of substantial genetic variation for pigment content and amounts of related pteridines.

The genetic and biochemical properties of the selected lines differed according to the direction of selection. High lines remained heterozygous after many generations of selection and displayed dominance and epistasis in favour of higher pigment content in crosses to the unselected stock. Selection for low pigment content led to fixation of recessive effects, attributable to particular chromosomes. The dominance-recessive relationship in red pigment differences was also applicable to the associated pteridines.

The metabolic pattern in all lines with reduced pigment content is compatible with the assumption of reduced enzyme activity at particular steps of the pathway leading to the drosopterins (red eye pigments). The two steps accessible to study are subject to genetic variation in the base population, while inbreeding or selection for low pigment content leads to genetically fixed alterations at one or other of these steps. The genetic analysis was consistent with the biochemical evidence.

Increase in pigment content above the normal level, either by selection or chance fixation, is accompanied by correlated increase in all the precursors. Several alternatives are possible but it is suggested that this may be due to an increase in early precursors, before the stages which have been altered in the low pigment lines.

Attention is drawn to the similarity in genetic behaviour between pigment content and body size. Particular emphasis is laid on the value of selection as a means of creating biochemical differences which offer a basis for relating biochemical function and genetic behaviour.