M. Schoeller

Bio: M. Schoeller is an academic researcher from University of Zurich. The author has an hindex of 1, co-authored 1 publications receiving 46 citations.

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

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.

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.”

Synthese und chromatographische Trennung von [8a-14C]Biopterin und [8a-14C]7-Biopterin

Abstract: Durch chromatographische Trennung an phosphorylierter Cellulose wurden Biopterin und 7-Biopterin erstmals in reiner Form erhalten. Im Gegensatz zum Biopterin ist 7-Biopterin im Wachstumstest bei Crithidia fasciculata inaktiv. Die Ausbeute ist bei der Biopterinsynthese stark von den Reaktionsbedingungen abhangig und liefert unter optimalen Bedingungen 7% Biopterin und 26% 7-Biopterin, bezogen auf eingesetztes 2.4.5-Triamino-6-hydroxy-pyrimidin. Die Radiosynthese der beiden pterine, ausgehend von K14CN, wird beschrieben. Ferner werden die Eigenschaften des 2-Amino-4-hydroxy-6-bzw. 7-[L-erythro-1.2.3-trihydroxy-propyl]-pteridins mitgeteilt.

Der Einfluß des Schirmpigmentgehalts auf die Helligkeits- und Kontrastwahrnehmung bei Drosophila Augenmutanten

Abstract: The function of the facet-separating pigments in the compound eyes of the fruitfly Drosophila melanogaster with hypernormal (se), normal (+), subnormal (wa), and missing (w) pigmentation was studied by investigation of: (1) the in-flight optomotor responses to movement of striped patterns with a mean brightness of 300 cd/m2, and (2) the retinal action potentials evoked by flashes in a program of .0003 cd/m2 average brightness. The pigment deficient mutants (wa, w) are less sensitive to the pattern contrast in the bright adapted state, and more sensitive to the flash intensity in the dark adapted state than either the wild-type (+) or the overpigmented mutant(se). These differences are complementary and can be explained by the increased translucency of the pigment cells. Thus the photoreceptors in the equally illuminated eyes of the normal and mutant animals +, se, wa, and w are expected to receive light in a ratio of about 1∶1∶7∶19. However the sensitivity of the receptors as well as the half-peak widths and the density of their visual fields are apparently independent of the eye pigmentation and seem to be equal at common levels of adaptation. The effects of omnidirectional excess light reaching the receptors of the pigment deficient mutants can be simulated in less translucent eyes: when certain amounts of background illumination were combined with the optomotor stimulus in the visual fields of the wild-type receptors it was possible to elicit the predicted “mutant behavior”.