E. Hadorn

Bio: E. Hadorn is an academic researcher from University of Zurich. The author has an hindex of 4, co-authored 4 publications receiving 172 citations.

Fluoreszierende Stoffe aus Drosophila melanogaster: die roten Augenfarbstoffe. 5. Mitteilung

Abstract: Der „wasserlosliche rote Augenfarbstoff” von Drosophila melanogaster wurde isoliert und weiter untersucht. Die Papierchromatographie zeigt, dass das Pigment in Wirklichkeit eine Mischung von drei roten, gelborange fluoreszierenden Stoffen ist, deren chemische und physikalische Eigenschaften sehr ahnlich sind. Sowohl die Behandlung dieser Stoffe mit Laugen als auch die Oxydation mit KMnO4 oder NaJO4 bauen alle drei zu Pteridin-8-carbonsaure ab. Demnach ist ihre Zugehorigkeit zur Pterinklasse bewiesen. Diese drei Stoffe werden als Neodrosopterin, Drosopterin und Isodrosopterin bezeichnet.

Isolierung fluoreszierender Stoffe aus Drosophila melanogaster. Vorläufige Mitteilung

Abstract: Es werden die Isolierung von vier fluoreszierenden Stoffen aus Drosophila melanogaster und deren Eigenschaften kurz beschrieben

Fluoreszierende Stoffe aus Drosophila melanogaster. 3. Mitteilung

Abstract: Das aus Drosophila melanogaster isolierte, stark fluoreszierende Pterin HB2 besitzt nicht die fruher zur Diskussion gestellte Formel, was durch den oxydativen Abbau der Substanz zu Acetaldehyd bewiesen wird. Eine Strukturformel kann auf Grund der bisherigen Versuchsergebnisse noch nicht vorgeschlagen werden.

Fluoreszierende Stoffe aus Drosophila melanogaster. 2. Mitteilung

Abstract: Es werden die Konstitutionsaufklarung von zwei fluoreszierenden Stoffen und die Isolierung von 2-Amino-6-oxy-pterin-8-carbonsaure aus Drosophila melanogaster beschrieben.

The visual system of insects

Abstract: Publisher Summary This chapter focuses on the structural organization of compound eyes, which are the principal photoreceptors of adult insects. They are composed of structural units called ommatidia. Compound eyes can be divided into two groups: photopic eyes and scotopic eyes. The former are characteristic of diurnal insects active in bright light, while the latter are found in nocturnal or crepuscular species and have short, fat rhabdoms that are separated from the crystalline cones by a relatively large distance. The chapter further illustrates examples of insect ommatidia. Many insects, particularly males, have eyes divided into two regions that are characterized by markedly different sizes and pigmentation of ommatidia. In some dragonflies, the dorsal facets are nearly twice the diameter of the ventral.

The growth and nutrition of Crithidia fasciculata.

Abstract: The conditions for luxuriant axenic cultivation of the trypanosomid flagellate Crithidia fasciculata in chemically-defined media were determined. Improvements over the hitherto published media include higher concentrations of amino acids, folic acid (where this is the sole source of pteridine) and purines and the inclusion of threonine and Tween 80. Increased oxygenation was obtained by incubating liquid cultures in tubes in a sloped position. Under these conditions consistently excellent growth (up to 2 × 108 organisms/ml.) was obtained and the useful incubation period could be decreased to 4 days. Using the improved medium, qualitative and quantitative studies on the nutritional requirements of the organism were carried out. Growth failed when any one of the following amino acids was omitted from the basal medium: histidine, phenylalanine, isoleucine, leucine, valine, lysine, arginine, tyrosine, methionine, tryptophan. The omission of threonine caused drastically decreased growth rates and lower yields. It was found that phenylpyruvic acid could replace phenylalanine; cysteine, cystathionine or homocysteine could replace methionine; and citrulline, but not ornithine, could replace arginine for C. fasciculata. In addition to the amino acid requirements a nutritional need for the following was demonstrated: a carbohydrate, haemin, a purine, thiamine, riboflavin, pantothenic acid, nicotinic acid or its amide, pyridoxal or pyridoxamine, biotin, folic acid and an unconjugated pteridine (biopterin). The natural purines, their nucleosides and nucleotides are nearly equivalent, on a molar basis, in growth promotion. Numerous substituted purines were also tested for their ability to supply the purine requirement. No exogenous source of pyrimidine for nucleic acid synthesis is necessary provided folic acid is present. Folic acid can be omitted from the growth medium provided thymine and methionine are present. The absolute requirement for biotin could not be demonstrated in the present medium without the use of avidin.

The Biology of Pteridines in Insects

Abstract: Publisher Summary The term “pteridine” was confined to a chemically recognizable group of substances mainly responsible for wing pigmentation in Pieridae. Other groups of chemical substances also take part in the total pigmentation pattern: ommochromes, melanins, flavines, purines and various lipid pigments. The chemical composition of the pteridines became known a few years later when the structure of leucopterin was discovered. An evolutionary sequence starts with the development of hydrogenated pterines from purines or purine precursors. The primary metabolic role must have been, and still is, in their function as co-factors in hydroxylation reactions. The direct oxidation and excretion of the hydrogenated pterines must have replaced their reentry into purine metabolism for energetic reasons. The auto-chelating properties of simple pterines, resulting in high insolubility under normal physiological conditions or the binding of the eye pterines onto carrier granules, must be the basis of the development of various types of deposition. The knowledge and insight of the biological role of pterines in insects exemplifies a pattern of common biological interest: a fundamental physiological process common to all organisms (the biosynthesis of a co-factor from a purine precursor), provides the starting point for a new selection process in physiological development.

Genetic Aspects of Ommochrome and Pterin Pigments

Abstract: Publisher Summary This chapter discusses the genetic aspects of pterins and ommochromes that are complementary to one another. The ommochromes and pterins represent interesting groups of naturally occurring compounds, whose structure, biosynthesis, and physiological interrelationships are elucidated by the study of mutants affecting them. The action of genes results in the specific pattern of phenes, comprising the phenotype of the organism. Gene-dependent formation of ommochromes and pterin pigments presents models in which morphological phenes are relatively closely connected with gene-controlled chemical processes. The chapter focuses on the mutations that block ommochrome synthesis. Biochemical assays for the presence of enzymes involved in ommochrome synthesis from the gene groups in Drosophila melanogaster and D. pseudoobscura offer a promising opportunity to gain information about homologous genes and evolution of genic complexes in Drosophila. Pterins are found in the eyes, the Malpighian tubules, and in the testis. In many cases, the patterns of pterins or of compounds connected with ommochrome metabolism as “phenes” of a certain genotype are reflections of the degree of relationship. The present state of knowledge offers two possibilities for the pathway of synthesis of “eye pterins.”