Development of cricket sensory hairs: changes of dynamic mechanical properties

Summary Mechanical oscillation properties of cricket (Acheta domesticus) filiform hair sensilla were measured at different larval stages, as an indication of larval sensory capacities and for comparison with data in the literature on central nervous changes during development. The hairs were stimulated by airborne vibration over a frequency range of 10 to 220 Hz. Best frequency, angular displacement at best frequency, slope of angular-displacement tuning curve and phase of hair deflection relative to air particle velocity were tested for correlation with hair length, which is proportional to the age of a sensillum. The ranges found for the various oscillation parameters in early larval stages were similar to or larger than those in adults. Oscillation properties changed with both the developmental stage of the hair sensilla and that of the whole animal. Four individually identifiable hair sensilla were analysed separately; the sensory neurons of two of them are known to change synaptic properties during maturation. Angular displacement at a given stimulus intensity was maximal for all hairs after differentiation, and decreased during further development. The hairs did not show clear common changes for any of the other oscillation parameters. Yet particular changes were found for individual hairs.     

Mechanosensory afferents innervating the swimmerets of the lobster

Feathered hair sensilla fringe both rami of the lobster (Homarus americanus) swimmeret. The sensory response to hair displacement was characterized by recording afferent impulses extracellularly from the swimmeret sensory nerve while deflecting sensilla with a rigidly-coupled probe or controlled water movements. Two populations of hairs were observed: "distal" hairs localized to the distal 1/3 of each ramus and "proximal" hairs near its base. Distal hairs are not innervated by a mechanosensory neuron but instead act as levers producing strain within adjacent cuticle capable of activating a nearby hypodermal mechanoreceptor. Hair deflections of 25 degrees or more are required to evoke an afferent response and this response is dependent on hair deflection direction. The frequency and duration of the afferent discharge evoked are determined by the velocity of hair displacement. Each proximal hair is innervated by a single mechanosensory neuron responding phasically to hair deflections as small as 0.2 degrees in amplitude. Deflection at frequencies up to 5 Hz elicits a single action potential for each hair movement; at higher frequencies many deflections fail to evoke an afferent response. These sensilla, which are mechanically coupled, may be activated by the turbulent flow of water produced by the swimmerets during their characteristic beating movements.     

A theoretical approach to understanding of the vestibular perception organization in microgravity condition

This paper should be viewed as a part of our attempts to arrive at a quantitative understanding of some contradictory experimental phenomena in the vestibular perception. The most popular remains the Steinhausen's model of perception, in which the endolymph circulation, caused by the angular acceleration, is "measured" by the displacement of cupulae diaphragm. Though displacements of the cupulae top were experimentally observed, the thorough mathematical analysis shows that the applicated stop-stimuli were too much over the range of adequate stimulation conditions, so the cupulae was teared off from its normal position. The more natural mechanism of perception was proposed by McLaren & Hillman. It was experimentally demonstrated that the cupulae diaphragm remained margin attached during the normal stimulation conditions only with its bottom moved according to the value of the applicated angular acceleration. A question only arises, how will be the hair cells excited by low level stimulation, when elastic deformations of the cupulae are small and there is no visible shift of the cupulae bottom? The response is to find in the third mechanism formulated by Schmaltz, which connected the excitation of hair cells with the process of endolymph diffusion through the cupulae towards the subcupulae space.     

Physical dimensions influence the functional property of the semicircular canal

The functional dependence of the semicircular canal upon its physical dimensions was evaluated by measuring the internal radius (r), the radius of curvature (R) and the cupula radius (rC) of the posterior canal in 10 freshly dissected frog labyrinths. These values have been compared to the same parameters of the cat labyrinth. The coefficients I, B, K in the Steinhausen equation were determined for both animals. The A ratio between cupula deflection and endolymph displacement was also calculated by utilizing the Bernard equation. The A ratio is three times larger in the frog than in the cat. It follows that if the same acceleration produces similar endolymph displacements in the posterior canal of both animals, the cupula deflection will be larger in the frog. The solution of the Steinhausen equation in the presence of a constant acceleration, however, reveals that the same stimulus intensity will result in a larger endolymph displacement in the cat posterior canal; similarly, the endolymph displacement directly depends on the duration of the stimulating period in both animals. Contrary to the Bernard assumption, these effects generate a G ratio (psi frog/psi cat) which is less than the Q ratio (A frog/A cat). Moreover, G decreases on increasing the duration of the stimulating period. For stimuli of short duration the semicircular canal of a small animal is expected to exhibit a higher sensitivity than that of a larger one. However, the definitive primary afferent discharge will be largely controlled by the receptor/generator potential properties.     

Ephrin-B2 governs morphogenesis of endolymphatic sac and duct epithelia in the mouse inner ear

Control over ionic composition and volume of the inner ear luminal fluid endolymph is essential for normal hearing and balance. Mice deficient in either the EphB2 receptor tyrosine kinase or the cognate transmembrane ligand ephrin-B2 (Efnb2) exhibit background strain-specific vestibular-behavioral dysfunction and signs of abnormal endolymph homeostasis. Using various loss-of-function mouse models, we found that Efnb2 is required for growth and morphogenesis of the embryonic endolymphatic epithelium, a precursor of the endolymphatic sac (ES) and duct (ED), which mediate endolymph homeostasis. Conditional inactivation of Efnb2 in early-stage embryonic ear tissues disrupted cell proliferation, cell survival, and epithelial folding at the origin of the endolymphatic epithelium. This correlated with apparent absence of an ED, mis-localization of ES ion transport cells relative to inner ear sensory organs, dysplasia of the endolymph fluid space, and abnormally formed otoconia (extracellular calcite-protein composites) at later stages of embryonic development. A comparison of Efnb2 and Notch signaling-deficient mutant phenotypes indicated that these two signaling systems have distinct and non-overlapping roles in ES/ED development. Homozygous deletion of the Efnb2 C-terminus caused abnormalities similar to those found in the conditional Efnb2 null homozygote. Analyses of fetal Efnb2 C-terminus deletion heterozygotes found mis-localized ES ion transport cells only in the genetic background exhibiting vestibular dysfunction. We propose that developmental dysplasias described here are a gene dose-sensitive cause of the vestibular dysfunction observed in EphB–Efnb2 signaling-deficient mice.     

Correction to: Mechanical factors contributing to the Venus flytrap’s rate-dependent response to stimuli

The sensory hairs of the Venus flytrap (Dionaea muscipula Ellis) detect mechanical stimuli imparted by their prey and fire bursts of electrical signals called action potentials (APs). APs are elicited when the hairs are sufficiently stimulated and two consecutive APs can trigger closure of the trap. Earlier experiments have identified thresholds for the relevant stimulus parameters, namely the angular displacement \(\theta \) and angular velocity \(\omega \). However, these experiments could not trace the deformation of the trigger hair’s sensory cells, which are known to transduce the mechanical stimulus. To understand the kinematics at the cellular level, we investigate the role of two relevant mechanical phenomena: viscoelasticity and intercellular fluid transport using a multi-scale numerical model of the sensory hair. We hypothesize that the combined influence of these two phenomena and \(\omega \) contribute to the flytrap’s rate-dependent response to stimuli. In this study, we firstly perform sustained deflection tests on the hair to estimate the viscoelastic material properties of the tissue. Thereafter, through simulations of hair deflection tests at different loading rates, we were able to establish a multi-scale kinematic link between \(\omega \) and the cell wall stretch \(\delta \). Furthermore, we find that the rate at which \(\delta \) evolves during a stimulus is also proportional to \(\omega \). This suggests that mechanosensitive ion channels, expected to be stretch-activated and localized in the plasma membrane of the sensory cells, could be additionally sensitive to the rate at which stretch is applied.

     

Arthropod touch reception: spider hair sensilla as rapid touch detectors

Wandering spiders like Cupiennius salei are densely covered by tactile hairs. In darkness Cupiennius uses its front legs as tactile feelers. We selected easily identifiable hairs on the tarsus and metatarsus which are stimulated during this behavior to study tactile hair properties. Both the mechanical and electrophysiological hair properties are largely independent of the direction of hair displacement. Restoring torques measure 10(-9) to 10(-8) Nm. The torsional restoring constant S changes non-linearly with deflection angle. It is of the order of 10(-8) Nm/rad, which is about 10,000 times larger than for trichobothria. Angular thresholds for the generation of action potentials are ca.1 degrees. Electrophysiology reveals a slow and a fast sensory cell, differing in adaptation time. Both cells are movement detectors mainly responding to the dynamic phase (velocity) of a stimulus. When applying behaviorally relevant stimulus velocities (up to 11 cm s(-1)) threshold deflection for the elicitation of action potentials and maximum response frequency are reached as early as 1.2 ms after stimulus onset and followed by a rapid decline of impulse frequency. Obviously these hairs inform the spider on the mere presence of a stimulus but not on details of its time-course and spatial orientation.     

Relative contributions of organ shape and receptor arrangement to the design of cricket’s cercal system

Understanding the relative contributions of the shape of a sensory organ and the arrangement of receptors to the overall performance of the organ has long been a challenge for sensory biologists. We tackled this issue using the wind-sensing system of crickets, the cerci, two conical abdominal appendages covered with arrays of filiform hairs. Scanning electron microscopy coupled with 3D reconstruction methods were used for mapping of all cercal filiform hairs. The hairs are arranged according to their diameter in a way that avoids collisions with neighbours during hair deflection: long hairs are regularly spaced, whereas short hairs are both randomly and densely distributed. Particle image velocimetry showed that the variation in diameter of the cercus along its length modifies the pattern of fluid velocities. Hairs are subject to higher air flow amplitudes at the base than at the apex of the cercus. The relative importance of interactions between receptors and the air flow around the organ may explain the performance of the cricket's cercal system: it is characterised by a high density of statistically non-interacting short hairs located at the base of the cercus where sensitivity to air currents is the highest.     

Passage of dextran magnetite nanoparticles through the subcupular space of the pigeon.

We examined the permeability of the subcupular space for endolymph flow in the pigeon. A new technique was developed in which nanoparticles consisting of dextran magnetite were attracted by use of a magnet, instead of injecting a dye solution. The method was revealed to prevent an excess pressure application by the injection of dye solution. The Berlin blue color resulting from the dextran magnetite nanoparticles was found mainly within the subcupular space contacting with the sensory hairs. Further formation of the Berlin blue was found within the sensory cells. The result supports the idea that the fluid passes through the subcupular space.     

Sensory pits – Enigmatic sense organs of the nymphs of the planthopper Issus coleoptratus (Auchenorrhyncha,Fulgoromorpha)

The sensory pits of the nymphs of the planthopper Issus coleoptratus were investigated using light and electron microscopic techniques. Sensory pits consist of a bowl-shaped depression in the cuticle (25–70 μm in diameter) covered by a transparent cupola of presumably waxy material. Each pit is equipped with a long sensory hair that emerges from the inner wall of the pit and extends horizontally for about two thirds of the pit diameter. The cupola emerges from the rim of the pit opposite to the socket of this hair. Additional small sensory hairs extend into the base of the cupola. While the ultrastructure of these small hairs resembles that of other mechanoreceptive sensory hairs of insects, that of the long hairs shows several peculiarities. Sensory pits are dispersed over the frontal part of the head, the tergites of thoracic and abdominal segments. On the different parts of the exoskeleton, the orientation of long hairs within the pits varies in a systematic fashion with respect to the body axes. Size, location, and orientation of the pits show almost perfect bilateral symmetry. Their number increases with each moult. Comparative data show that the level of structural complexity of these sense organs varies considerably within this group of insects.     

Differential effects of nitric oxide on the responsiveness of tactile hairs

The responses of tactile hairs located on legs of the desert locust Schistocerca gregaria (Forskål) are modulated by nitric oxide (NO). There are two types of tactile hair on the tibia of the hind leg of the locust which differ in their thresholds for mechanical stimulation, their location on the leg and in the effect of NO on their responses to deflection. The spike response rates of mechanosensory neurons of low-threshold hairs decreased when exposed to elevated NO levels caused by perfusion of the leg with saline containing the NO donor PAPANONOate. In contrast, in high-threshold hairs, which show low responsiveness under control conditions, an increase in spike rates was observed during PAPANONOate application. These opposing effects of NO reduce the differences in the spike responses of the two types of tactile hairs to mechanical stimulation and are likely to have an impact on behaviours elicited by mechanical stimulation of the legs.     

The Novel PMCA2 Pump Mutation Tommy Impairs Cytosolic Calcium Clearance in Hair Cells and Links to Deafness in Mice

The mechanotransduction process in hair cells in the inner ear is associated with the influx of calcium from the endolymph. Calcium is exported back to the endolymph via the splice variant w/a of the PMCA2 of the stereocilia membrane. To further investigate the role of the pump, we have identified and characterized a novel ENU-induced mouse mutation, Tommy, in the PMCA2 gene. The mutation causes a non-conservative E629K change in the second intracellular loop of the pump that harbors the active site. Tommy mice show profound hearing impairment from P18, with significant differences in hearing thresholds between wild type and heterozygotes. Expression of mutant PMCA2 in CHO cells shows calcium extrusion impairment; specifically, the long term, non-stimulated calcium extrusion activity of the pump is inhibited. Calcium extrusion was investigated directly in neonatal organotypic cultures of the utricle sensory epithelium in Tommy mice. Confocal imaging combined with flash photolysis of caged calcium showed impairment of calcium export in both Tommy heterozygotes and homozygotes. Immunofluorescence studies of the organ of Corti in homozygous Tommy mice showed a progressive base to apex degeneration of hair cells after P40. Our results on the Tommy mutation along with previously observed interactions between cadherin-23 and PMCA2 mutations in mouse and humans underline the importance of maintaining the appropriate calcium concentrations in the endolymph to control the rigidity of cadherin and ensure the function of interstereocilia links, including tip links, of the stereocilia bundle.     

Olfaction in the gypsy moth, Lymantria dispar: effect of pH, ionic strength, and reductants on pheromone transport by pheromone-binding proteins

The pheromone-binding proteins (PBPs) are 16-kDa abundant proteins in specialized olfactory hairs in insects. The mechanism by which the PBPs remove the pheromone from the inner surface of sensory hairs and deliver it to the sensory cell remains unclear. Existing qualitative models postulate that pheromone is released near the dendrite by a decrease in pH or by a reduced form of the PBP. This study focuses on the two PBPs from the gypsy moth and the enantiomers of the pheromone cis-2-methyl-7,8-epoxyoctadecane. The pH dependence of pheromone binding has revealed three ionizations that are important. The type of ligand influences two of these ionizations. We propose that the (-)-enantiomer of the pheromone interacts with one of the ionizable residues on the protein while the (+)-enantiomer does not. Simultaneous variation of pH and KCl concentration in the physiological range or reduction of disulfide bridges does not change the affinity of PBP for pheromone. We propose a revised model of pheromone transport from the inner surface of the sensory hair to the sensory neuron.     

Sensilla and Cuticular Appendages on the Female Abdomen of Lasioptera rubi (Schrank) (Diptera,Cecidomyiidae)

Studies by SEM and TEM revealed 6 types of integumental appendages on female uromeres VIII-X in Lasioptera rubi: microtrichia, not innervated; spines, probably without sensory function; nonporous sensory hairs, each containing one dendrite ending with a tubular body indicating a tactile function; uniporous sensory hairs, each innervated partly by 3 dendrites indicating a chemosensory function, partly by an additional dendrite with a tubular body indicating a tactile function; scoop-like sensilla, each containing partly a branched structure of dendrites in the distal half of the sensillum indicating an olfactory function, partly an unbranched dendrite ending at a pore near the base of the sensillum, most probably registrating chemical stimuli by contact or gustation; finally, nonporous bristles, all or some of them innervated, in a manner indicating a tactile function. In addition, two scolopophorous proprioceptors were found inside uromere X. The nonporous sensory hairs, the uniporous sensory hairs and the scolopophores may be used by the midge to determine the mechanical and chemical properties of potential oviposition sites. The spines and nonporous bristles may function as conidia carriers.     

Sensory innervation monitoring movement and position in the mandibular stylets of the aphid, Brevicoryne brassicae

The sensory innervation of the mandibular stylets of the aphid Brevicoryne brassicae (L.) has been examined by electron microscopy. Two groups of sensory neurones are present in the mandible. Each has two neurones, one with a short dendrite extending into the base of the mandible and ending in the base and another with a long microtubular process which extends 500 m? down to the distal tip of the mandible. The two neurones are enclosed by an ensheathing cell comparable to the trichogen cell enveloping the group of neurones innervating pegs and hairs. This ensheathing cell is supported by extensive electron-dense filaments to form a scolopale and is embedded in the mass of stylet-forming cells at the base of the mandible. The inner segments of the dendrites are anchored to the ensheathing cell by desmosome junctions. Desmosome junctions also bind the microtubular outer segments of the short and long dendrite to each other. There is no evidence of a dendritic sheath enclosing the distal portion of the short dendrite which ends while still in the extracellular space within the ensheathing cell. The microtubular process of the long dendrite extends down the lumen of the mandible enclosed by a close-fitting extracellular sheath which penetrates and is attached to the cuticular wall of the mandible tip. Distally this sheath is thickened on one side. Deflection of the mandible would therefore deform the dendritic membrane asymmetrically because the thin walls of the sheath would bend more than the thick walls. This would exert an unequal mechanical strain on the dendritic membrane which could result in depolarization in response to deflection in a particular direction. The arrangement of the dendrites and their sheaths within the mandible is such that deflection to the right would distort one dendrite in the same way as deflection to the left would distort the other.     

External morphology of antennae and their sense organs in the roach Gromphadorhina brunneri (Blattoidea: Dictyoptera)

The antennae and their sense organs in nymphs and adult roaches of Gromphadorhina brunneri, were investigated and described. The number of segments and sensillae of the nymphal antennae depend on the developmental stage. Sexual dimorphism is pronounced. Males have longer antennae than females as well as an abundance of especially long sensory hairs (long wavy hairs), which are probably responsible for the perception of female sex pheromones. They also have more thin-walled sensory hairs, for instance, sensilla trichodea. On a morphological basis the sensillae of Gromphadorhina brunneri, were named and classified. Long wavy hairs and large sensory hairs appear to be present also in a related species, G. portentosa, but are lacking in others. Their distribution on the antennae varies greatly from that in G. portentosa but their structure varies only slightly. These two types of sense organs are considered to be specialized forms of sensilla chaetica. They are contact chemoreceptors, as are two other types of sensilla chaetica. Furthermore, thin-walled chemoreceptors are present, such as sensilla trichodea, sensilla basiconica, sensilla coeloconica and a typical mechanoreceptor, the sensillum campaniformium.     

Sulfolobus chromatin proteins modulate strand displacement by DNA polymerase B1

Strand displacement by a DNA polymerase serves a key role in Okazaki fragment maturation, which involves displacement of the RNA primer of the preexisting Okazaki fragment into a flap structure, and subsequent flap removal and fragment ligation. We investigated the role of Sulfolobus chromatin proteins Sso7d and Cren7 in strand displacement by DNA polymerase B1 (PolB1) from the hyperthermophilic archaeon Sulfolobus solfataricus. PolB1 showed a robust strand displacement activity and was capable of synthesizing thousands of nucleotides on a DNA-primed 72-nt single-stranded circular DNA template. This activity was inhibited by both Sso7d and Cren7, which limited the flap length to 3–4 nt at saturating concentrations. However, neither protein inhibited RNA displacement on an RNA-primed single-stranded DNA minicircle by PolB1. Strand displacement remained sensitive to modulation by the chromatin proteins when PolB1 was in association with proliferating cell nuclear antigen. Inhibition of DNA instead of RNA strand displacement by the chromatin proteins is consistent with the finding that double-stranded DNA was more efficiently bound and stabilized than an RNA:DNA duplex by these proteins. Our results suggest that Sulfolobus chromatin proteins modulate strand displacement by PolB1, permitting efficient removal of the RNA primer while inhibiting excessive displacement of the newly synthesized DNA strand during Okazaki fragment maturation.     

A simple method for alar rim reconstruction

A one-stage repair procedure is described for the reconstruction of small to medium-sized full-thickness alar rim defects with a hinged medially based nasolabial island flap. The operation is performed under local anesthesia as an office procedure and is indicated particularly in older patients. The hinged flap provides both the inner and outer layers of the alar rim. The donor site is closed primarily with no need to mobilize a large skin flap. The procedure leaves no conspicuous scars on the face. This method was found to be simple and safe, providing excellent tissue viability and yielding good color and texture match.     

Die Erregung einzelner Fadenhaare von Periplaneta americana in Abhängigkeit von der Grösse und Richtung der Auslenkung

Zusammenfassung Auf einem Cercus stehen etwa 220 Fadenhaare. Jedes Haar besitzt eine Sinneszelle. Es ist in einer Kuppel eingelenkt und von einem Wall umgeben.Die Haare sind regelmäßig in Längsreihen angeordnet. Haare einer Reihe stimmen in den wesentlichen Merkmalen überein: Die Untersuchungen werden auf eine Reihe beschränkt.Mit der Adhäsionskraft zwischen einer kleinen Lackkugel und dem Haarschaft wird die Richtungsabhängigkeit der rücktreibenden Kraft gemessen: Bei Auslenkung in einer bestimmten Ebene (Vorzugsebene) ist die rücktreibende Kraft besonders klein. In schwachen Luftströmungen bewegen sich deshalb die Haare — unabhängig von der Richtung der Strömung — in ihrer Vorzugsebene.Das Rezeptorpotential und die Impulse eines Fadenhaares werden mit Kapillarelektroden in der Kuppel abgeleitet.Die Richtungsabhängigkeit des Rezeptorpotentials wird untersucht: In der einen Richtung der Vorzugsebene tritt ein maximales phasischtonisches Generatorpotential auf, in der Gegenrichtung maximale Hyperpolarisation. Bei Auslenkung um 12° ändert sich die Höhe des Rezeptorpotentials etwa wie der Kosinus der Auslenkungsrichtung. Die Abweichungen von der cos-Funktion nehmen mit der Größe der Auslenkung zu. Sie werden teilweise durch Strukturen, die die freie Auslenkung des Haares begrenzen, verursacht.Die Abhängigkeit des Generatorpotentials von der Größe der Auslenkung wird in der optimalen Richtung untersucht: Die Höhe der Potentialspitze nimmt logarithmisch und die Höhe des Potentialplateaus linear mit der Größe der Auslenkung zu. Bei 12° Auslenkung schlägt das Haar am Wall an: Bei weiterer Auslenkung fallen die Kennlinien ab.Die Fadenhaare sind zur Rezeption schwacher Luftströmungen hervorragend geeignet: Wenn sie abwechselnd um jeweils 1° in den beiden Richtungen der Vorzugsebene ausgelenkt werden, erreicht das Generatorpotential bereits 40% seiner maximalen Höhe. Der Wall schützt den rezeptiven Apparat vor Überlastung.

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Summary Approximately 220 filiform hairs are to be found on each cercus (Fig. 4). Each hair has a single sensory cell and is located in a sharp walled indentation on top of a mound (Fig. 3).The hairs are arranged in regular columns. In any one column all the hairs are essentially alike (Fig. 5). This paper concerns the hairs of a single column.The elastic forces within the hairs were measured in different directions with the help of adhesion between the hair shaft and a tiny ball of dry varnish. Along one preferential plane the elastic forces were especially small (Fig. 6 and 7). Thus weak air currents bend the hair along this plane regardless of the direction they come from.Receptor potentials and impulses from individual hairs were picked up by glass capillary electrodes inserted in the mound at the base of the hair (Fig. 3 and 8).The amplitude of the receptor potential depends upon the direction in which the hair is bent (Fig. 14). A maximum phasic-tonic generator potential occurs by bending the hair in one direction along the preferential plane and a maximum hyperpolarization by bending it in the opposite direction (Fig. 9 and 13). Within the first 12° of deflection the amplitude of the receptor potential follows fairly closely upon the cosine of the direction of deflection (Fig. 13). The deviation from the cosine function increases with increasing deflection (Fig. 14). This deviation is caused at least in part by structures about the base of the hair which limit its free movement.The amplitude of the generator potential also depends on the degree of deflection along the preferential plane (Fig. 10). The peak generator potential rises with the logarithm whereas the ensuing plateau rises linearly with the degree of deflection (Fig. 12). At 12° the hair shaft reaches the wall of the indentation. Further bending yields lower potentials (Fig. 11).The filiform hairs are excellently adapted to function as receptors for weak air currents. The generator potential rises to 40% of maximum when the hair describes only a two degree arc along the preferential plane, from 1⁰ on one side of the resting position to 1° on the other side (Fig. 12). The steep walls around the base protect the receptive apparatus from excessive strain.

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Dissertation der Naturwissenschaftlichen Fakultät der Universität München.

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Herrn Prof. Dr. H. Autrum danke ich für das Thema und die Unterstützung bei der Arbeit. Die Untersuchungen wurden durch die Deutsche Forschungsgemeinschaft gefördert.