Bau und optische Leistungen des Komplexauges der StielaugenfliegeCyrtodiopsis dalmanni Wiedemann

Zusammenfassung Die großen Sehfelder der Komplexaugen der malayischen StielaugenfliegeCyrtodiopsis dalmanni überschneiden sich 3–4 mm vor den Augen. Eine Entfernungswahrnehmung von Objekten, die sich in den Sehfeldern beider Facettenaugen befinden, ist deshalb sehr wahrscheinlich.Interferometrische Messungen amCyrtodiopsis-Auge führten zu gleichen Brechungsquotienten für die Ommatidienstrukturen wie beiCalliphora erythrocephala. Die geometrischoptischen Berechnungen ergaben für den dioptrischen Apparat des Ommatidiums imCyrtodiopsis-Auge eine objektseitige Brennweite von 29 m. Hieraus und aus den Durchmessern der Rhabdomeren-Kappen — sie liegen in der Brennebene — resultieren die Öffnungswinkel von2,5° für die Rhabdomere 1–6 und von1,6° für das 7. Rhabdomer. Diese Öffnungswinkel sind kleiner als die der Ommen, die bei8,8° liegen. Im einzelnen Ommatidium kann eine höhere Auflösung erzielt werden, da die Beugungsscheibe jeweils nur eine Kappe bedeckt.

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Morphology and physiology of the compound eye of the stalked-eye flyCyrtodiopsis dalmanni Wiedemann

Summary The large visual fields of the compound eyes of the Malayan flyCyrtodiopsis dalmanni overlap 3–4 mm in front of the eyes. Depth perception of objects placed within the visual fields of both eyes is therefore very probable. Interferometrical studies on theCyrtodiopsis eye indicated that refractive indices of the ommatidial structures are the same as in the blowfly. The focal length of the dioptric apparatus of the stalked-eye fly ommatidium was found to be 29 m on the object side. The angles of aperture calculated from this focal length and from the diameters of the corresponding rhabdomeric prolongations—located in the focal plane-are 2.5° for the rhabdomeres 1–6, and 1.6° for the rhabdomere 7. These opening angles are smaller than those of the ommatidia, which are about 8.8°. Calculations based on the diffraction theory lead to the conclusion that higher resolution is obtained in the single ommatidium because the airy disc covers only one rhabdomeric prolongation.

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Mit Unterstützung der Deutschen Forschungsgemeinschaft.     

Electrophysiological studies on the compound eye of a stalked-eye fly,Cyrtodiopsis dalmanni (Diopsidae,Diptera)

Summary The mass response (ERG) of the compound eye of the Malaysian stalked-eye flyCyrtodiopsis dalmanni was recorded by means of conventional electrophysiological techniques. The ERG consists of a positive on-effect, a sustained negative potential during illumination and a negative off-effect, it resembles that ofCalliphora as described by Autrum (1950). As compared with data derived fromCalliphora under identical conditions the eye ofCyrtodiopsis is more sensitive to weak stimuli and shows considerable adaptation. The spectral response curve reveals peaks at 360 nm, around 450 nm and around 490 nm. Above 550 nm the response curve rises steeply, even with stimuli above 700 nm reactions may be elicited. Most probably this effect is caused by weak absorption of long wavelength radiation in the screening pigments.With simple techniques it is fairly easy to record impulse activity from single units of the optic tract within the eye-stalk. This makesCyrtodiopsis a favorable object for experimental studies on data processing in insect optic centers.The characteristics of the diopsid eye are discussed in context with the environmental conditions in the biotop.I would like to thank the colleagues at the University of Malaya, Kuala Lumpur, Malaysia, for help and hospitality.The investigations were supported by a grant from the Sonderforschungsbereich Vergleichende Sinnes- und Nervenphysiologie at the University of Frankfurt (Main).     

Accumulation of anthracotic particles along lymphatics of the human lung: Relevance to “hot spot” formation after inhalation of poorly soluble radionuclides

Summary Large lung sections of humans of advanced adult age revealed a markedly nonuniform retention pattern of dense anthracotic particle aggregates, with an impressive accumulation of this material along pulmonary lymphatics, i.e. the deep (peribronchial), septal (perivenous) and superficial (pleural) networks. Conversely, the alveolar parenchyme contained only occasional, small aggregates of macrophages heavily loaded with carbon, representing little more than 2% of this material in lung tissue. Although translocation kinetics of anthracotic particles cannot readily be compared to those of highly toxic -emitting, poorly soluble radionuclides such as²³⁹PuO₂, lymphatic drainage of the latter over the years may also be expected to lead to a concentration of radioactive material along lymph vessels. Since human data on the effects of inhaled²³⁹PuO₂ are virtually lacking, the above distribution pattern is apt to help in identifying cells and other tissue components most heavily at risk. Findings are also relevant to the problem of hot spot formation in vivo and its possible sequelae. The latter are briefly discussed with regard to both stochastic and non-stochastic effects.Dedicated to Prof. L.E. Feinendegen on the occasion of his 60th birthday     

Formation of 70S ribosomes: large activation energy is required for the adaptation of exclusively the small ribosomal subunit

Association of ribosomal subunits is an essential reaction during the initiation phase of protein synthesis. Optimal conditions for 70S formation in vitro were determined to 20 mM Mg2+ and 30 mM K+. Under these conditions, the association reaction proceeds with first order kinetics, suggesting a conformational change to be the rate-limiting step. 70S formation separates into two sub-reactions, the adaptation of the ribosomal subunits to the association conditions and the association step itself. The activation energy of the process was determined to 78 kJ/mol and revealed to be required exclusively for the adaptation of the small subunit, rather than the large subunit or the association step. The presence of mRNA [poly(U)] together with cognate AcPhe-tRNA, accelerates the association rate significantly, forming a well-defined 70S peak in sucrose gradient profiles. mRNA alone provokes an equivalent acceleration, however, the resulting 70S couple impresses as an ill-defined, broad peak, probably indicating the readiness of the ribosome for tRNA binding, upon which the ribosome flips into a defined state.