Farbstoffgehalt und Grösse der Augen bei verschiedenen Mutanten von Drosophila melanogaster

Zusammenfassung Quantitative Untersuchungen über den Farbstoffgehalt der Drosophilaaugen haben schon wiederholt gezeigt, daß die Werte bei bestimmten Mutanten von der Erwartung abweichen. So fand man regelmäßig bei den rotäugigen Mutanten v bzw. cn weniger Pterin und bei der braunäugigen Mutante bw weniger Ommochrom als bei Wildfliegen.Wir haben diese Befunde zunächst mit Hilfe einer vereinfachten Extraktions- und Meßtechnik nachgeprüft und bestätigt. Die genauere Analyse ergab dann aber, daß das Farbstoffdefizit der Mutanten v, cn und bw lediglich darauf beruht, daß diese Tiere kleinere Augen haben als die Wildfliegen. Die Augenverkleinerung ist jedoch nicht, wie gelegentlich vermutet wurde, die Folge einer polyphänen Wirkung der Gene v, cn und bw, sondern nur eine besondere Eigenschaft bestimmter Fliegenstämme, die heute in fast allen Laboratorien gehalten werden.Die Erscheinung selbst beruht auf der Wirkung augenverkleinernder Modifikationsgene, die bei diesen Stämmen zufällig mit den Farbgenen gekoppelt sind, durch geeignete Kreuzungen aber eliminiert werden können. Unsere so erhaltenen neuen v-, cn- und bw-Stämme besitzen nicht nur ebenso große Augen wie die Wildfliegen, sondern enthalten auch die theoretisch erwarteten Mengen an Augenfarbstoffen. Der Zusammenhang zwischen der Größe der Augen und ihrem Farbstoffgehalt hat u. a. zur Folge, daß die Männchen, die ja stets kleinere Augen haben als die Weibchen, bei allen Mutanten weniger Augenpigment besitzen als jene.Der Farbstoffgehalt der Augen hängt außerdem von der Zucht-temperatur ab. Fliegen, die sich bei 18° C entwickeln, besitzen weniger Pterin aber mehr Ommochrom als solche, die bei 26° C aufgezogen werden. Auch die Melaninsynthese im Integument der Tiere wird durch Temperaturerniedrigung begünstigt; aus 18°-Zuchten stammende Fliegen sind deutlich dunkler als die entsprechenden 26°-Tiere.     

Untersuchungen über die Insulinmikromelie am Hühnerembryo

Ohne ZusammenfassungDie Arbeit wurde auf Anregung von Herrn Prof. Dr. H.Wurmbach ausgeführt. Ich danke ihm für die freundliche Förderung der Arbeit, sowie Herrn Prof. Dr. A.Goebel, Pathol. Inst. d. Univ. Köln, für wertvolle Hinweise. Die Untersuchungen wurden von derDeutschen Forschungsgemeinschaft, Bad Godesberg, gefördert.     

Reaction intensification for biocatalytic production of polyphenolic natural product di-C-β-glucosides

Polyphenolic aglycones featuring two sugars individually attached via C-glycosidic linkage (di-C-glycosides) represent a rare class of plant natural products with unique physicochemical properties and biological activities. Natural scarcity of such di-C-glycosides limits their use-inspired exploration as pharmaceutical ingredients. Here, we show a biocatalytic process technology for reaction-intensified production of the di-C-β-glucosides of two representative phenol substrates, phloretin (a natural flavonoid) and phenyl-trihydroxyacetophenone (a phenolic synthon for synthesis), from sucrose. The synthesis proceeds via an iterative two-fold C-glycosylation of the respective aglycone, supplied as inclusion complex with 2-hydroxypropyl β-cyclodextrin for enhanced water solubility of up to 50 mmol/L, catalyzed by a kumquat di-C-glycosyltransferase (di-CGT), and it uses UDP-Glc provided in situ from sucrose by a soybean sucrose synthase, with catalytic amounts (≤3 mol%) of UDP added. Time course analysis reveals the second C-glycosylation as rate-limiting (0.4–0.5 mmol/L/min) for the di-C-glucoside production. With internal supply from sucrose keeping the UDP-Glc at a constant steady-state concentration (≥50% of the UDP added) during the reaction, the di-C-glycosylation is driven to completion (≥95% yield). Contrary to the mono-C-glucoside intermediate which is stable, the di-C-glucoside requires the addition of reducing agent (10 mmol/L 2-mercaptoethanol) to prevent its decomposition during the synthesis. Both di-C-glucosides are isolated from the reaction mixtures in excellent purity (≥95%), and their expected structures are confirmed by NMR. Collectively, this study demonstrates efficient glycosyltransferase cascade reaction for flexible use in natural product di-C-β-glucoside synthesis from expedient substrates.     

The influence of prey consumption and demographic stochasticity on population growth rate of Isle Royale wolves Canis lupus

The relationship between the rates of prey capture and predator population growth is a fundamental aspect of predation, yet it is rarely measured for vertebrate predators. For the isolated wolf population on Isle Royale, annual variation in kill rate explains 22% of the variation in wolf population growth rate. From the slope of this relationship, we estimate that the production efficiency (ratio of production to respiration) of wolves is between 0.5% and 1.5%. More generally, we assess the relative extent to which wolf population growth rate is affected by density dependence, prey availability (moose, Alces alces ), winter weather, and demographic stochasticity. Prey availability explains the most variation in wolf growth rate (42%), but this is only recognized after accounting for the influence of a disease-induced population crash and age structure of the prey population (i.e. number of vulnerable moose, >9 years of age). Demographic stochasticity accounts for approximately 30% of the variation in wolf growth rate. This recognition is important, but not surprising, given that the average population size of Isle Royale wolves is 22. Previous work indicates that the effect of winter climate, as mediated through prey vulnerability and kill rates, is substantial. This work indicates that the direct effect of winter climate is weak, and explains only about 4% of the variation in wolf growth rate (P=0.10).     

Regional ventilation in statically and dynamically hyperinflated dogs

Hubmayr, Rolf D., and Susan S. Margulies. Regionalventilation in statically and dynamically hyperinflated dogs.J. Appl. Physiol. 81(4):1815-1821, 1996.Using the parenchymal marker technique innormal anesthetized dogs, we compared the dynamics of regional lungexpansion between two ventilation strategies designed to increase meanthoracic volume. Dynamic hyperinflation (DH) was produced byventilating the lungs at a rate of 50 breaths/min and with a duty cycleof 0.5. Static hyperinflation (SH) was produced throughthe application of extrinsic positive end-expiratory pressure while thelungs were ventilated at a rate of 15 breaths/min and with a duty cycleof 0.15. Regional tidal volume(VT,r), regional functionalresidual volume, and the time delay between regional expansion and the flow signal at the common airway were computed for upto 100 regions/lobe in 5 animals. Ventilation strategy had no effect onthe overall variance of VT,rwithin lobes. Although the VT,rmeasured during SH correlated withVT,r measured during DH, theaverage correlation coefficient was only 0.69. Ventilation rate-relateddifferences in VT,r and regionalfunctional residual capacity varied with the regional time delay inways qualitatively consistent with parallel inhomogeneity of unit timeconstants. However, a large component of frequency-dependent behaviorremains unexplained by established mechanisms. We conclude that DH and SH should not be considered equivalent lung unit recruitmentstrategies.

     

Biotransformation of diphenyl ether by the yeastTrichosporon beigelii SBUG 752

Trichosporon beigelii SBUG 752 was able to transform diphenyl ether. By TLC, HPLC, GC, GC-MS, NMR- and UV-spectroscopy, several oxidation products were identified. The primary attack was initiated by a monooxygenation step, resulting in the formation of 4-hydroxydiphenyl ether, 2-hydroxydiphenyl ether and 3-hydroxydiphenyl ether (48:47:5). Further oxidation led to 3,4-dihydroxydiphenyl ether. As a characteristic product resulting from the cleavage of an aromatic ring, the lactone of 2-hydroxy-4-phenoxymuconic acid was identified. The possible mechanism of ring cleavage to yield this metabolite is discussed.     

Crown alterations induced by decline: a study of relationships between growth rate and crown morphology in beech (Fagus sylvatica L.)

One of the first symptoms expressed by declining trees is reduced growth in stem diameter and length increment. The possibility of a relationship between length increment and crown thinning in beech (Fagus sylvatica L.) was investigated by developing a computer model to simulate first order branching patterns of the apical 2 m of monopodially branching beech trees, 70–100 years old, for a range of length increment rates. The model was based on values for branching angle, main axis and branch length increment, number of branches produced per year and branch mortality rates for six healthy and declining trees. Shoot growth rates in the apical 2 m of the sample trees ranged from about 5 cm/year (decline class 3) to 43 cm/ year (healthy). Simulations of branching patterns in the apical 2 m of trees growing at different rates indicated that, when growth rate exceeded about 20 cm/year, total first order branch length and area explored were independent of growth rate. When growth rates fell below this value there was a reduction in total area explored and first order branch length due primarily to the formation of fewer branches. More acute branching angles contributed to a reduction in the area explored. Growth rate-related crown thinning could increase the risk of bark necrosis and secondary pathogen infection during dry and/or hot spells.     

ATP and the processivity of Xenopus laevis DNA polymerase α

We use specific restriction fragments as defined primers for DNA synthesis on single-stranded circular phage fd DNA. These structures are relatively poor templates for a highly purified DNA polymerase α from Xenopus laevis eggs. However, DNA synthesis is stimulated about 5-fold by addition of ATP to the reaction mixture. We show that the deoxynucleotide polymers, synthesized in the presence of ATP, are significantly longer than those produced in the absence of ATP. We also show that this effect is due to a more tenacious binding of DNA polymerase α to DNA and conclude that ATP increases the processivity of the enzyme.