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1Author    Ursula Hamm, M. Aroli, K. Chandrashekaran, W. Olfgang EngelmannRequires cookie*
 Title    Temperature Sensitive Events between Photoreceptor and Circadian Clock?  
 Abstract    The phase shifting action of low temperature pulses of 6 °C and 2 h duration administered to the various phases of the D rosoph ila pseudoobscu ra circadian rhythm and the action of light pulses given 30 min after the beginning of these low temperature pulses have been investigated. The phase response curve obtained from experiments with light pulses during low temperature cannot be ex­ plained on the basis of a straightforward and sequential phase shifting of the oscillation by the various transitions in the pulses. The response curve, after the slight phase shifting action of the temperature pulses is corrected for, resembles the standard phase response curve 4 for light pulses (at 20 °C) in its wave form but n ot in its time course. Our curve is shifted in time in a manner that indicates that the light pulses accompanying the low temperature pulses arrived at phase points 1.5 h later than the actual phases at which they were given. We attribute this delay to a slowing down of the information that is apparently transmitted by a process that is temperature dependent. 
  Reference    (Z. Naturforsch. 30c, 240 [1975]; received November 22 1974) 
  Published    1975 
  Keywords    Circadian Rhythm, Photoreceptor, Temperature, D rosophila pseudoobscura 
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 TEI-XML for    default:Reihe_C/30/ZNC-1975-30c-0240.pdf 
 Identifier    ZNC-1975-30c-0240 
 Volume    30 
2Author    A. Ndreas Schleicher, KlausPeter HofmannRequires cookie*
 Title    Proton Uptake by Light Induced Interaction between Rhodopsin and G-Protein  
 Abstract    The light-induced proton uptake of rod outer segment disc membranes has been investigated in the absence and presence of G-protein. Proton uptake was measured as the alkalisation of the suspending medium using a pH electrode and/or the indicator dye bromocresol purple. It was found that besides the known proton uptake of photolysed rhodopsin additional uptake of one proton accompanies formation of the complex between rhodopsin and G-protein. No measurable proton uptake was found under conditions of rapid redissociation of the complex indicating an only transient protonation during its lifetime. Proton uptake was the same in washed membra­ nes recombined with G-protein and in ordinarily stacked rod outer segments. The additional proton uptake reported here is not due to enhanced metarhodopsin II. 
  Reference    Z. Naturforsch. 40c, 400—405 (1985); received January 14/February 25 1985 
  Published    1985 
  Keywords    Photoreceptor, Protein-Protein Interaction, GTP-Binding Protein, Rhodopsin 
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 TEI-XML for    default:Reihe_C/40/ZNC-1985-40c-0400.pdf 
 Identifier    ZNC-1985-40c-0400 
 Volume    40 
3Author    PeterH. OchstrateRequires cookie*
 Title    Photoresponses from Cells in the Fly's Eye which are not Visual Cells  
 Abstract    It is shown that light elicits distinct responses from cells in the fly's eye which are different from photoreceptors. These cells are designated as "slow cells" because o f their sluggish response characteristics. Like the visual cells the slow cells depolarize upon light stim ulation, but the time course o f their responses is clearly different from that o f the photoreceptors. Furtherm ore, the intensity necessary to evoke a given response amplitude is considerably higher in slow cells than in photoreceptors. Several lines of evidence indicate that the slow cell response is caused by light absorption through the visual pigment rhodopsin in the peripheral photoreceptors R l —6. The slow cells are electrically coupled among each other, as dem onstrated by application of local light stimuli and injection of the fluorescent dye Lucifer Y ellow . The identity o f the slow cells and the mechanism o f response generation are discussed. 
  Reference    Z. Naturforsch. 44c, 867 (1989); received May 17/June 13 1989 
  Published    1989 
  Keywords    V ision, Fly, Photoreceptor, R hodopsin, Pigment Cells 
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 TEI-XML for    default:Reihe_C/44/ZNC-1989-44c-0867.pdf 
 Identifier    ZNC-1989-44c-0867 
 Volume    44 
4Author    EricJ W Arrant, RobertB. PinterRequires cookie*
 Title      
 Abstract    Intracellular recordings o f angular sensitivity from the photoreceptors o f Aeschnid dragonflies (Hemianax papuensis and Aeschna brevistyla) are used to determine the magnitude and time course o f acuity changes follow ­ ing alterations o f the state o f light or dark adaptation. Acuity is defined on the basis o f the acceptance angle, A q (the half-width o f the angular-sensitivity function). The maximally light-adapted value o f A q is half the dark-adapted value, indicating greater acuity during light adaptation. Following a change from light to dark adaptation, A q increases slowly, requiring at least 3 min to reach its dark-adapted value. In contrast, the reverse change (dark to light) induces a rapid reduction o f A q , and at maximal adapting luminances, this reduction takes place in less than 1 0 sec. 
  Reference    Z. Naturforsch. 45c, 137—141 (1990); received September 14 1989 
  Published    1990 
  Keywords    Compound Eye, Adaptation, Photoreceptors, Spatial Acuity, Dragonfly 
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 TEI-XML for    default:Reihe_C/45/ZNC-1990-45c-0137_n.pdf 
 Identifier    ZNC-1990-45c-0137_n 
 Volume    45 
5Author    Ulrich SchraermeyerRequires cookie*
 Title    Effects of Chloroquine on the Photosensory Membrane Turnover and the Ultrastructure of Lysosome-Related Bodies of the Crayfish Photoreceptor  
 Abstract    The effect o f chloroquine in combination with bright light on the ultrastructure o f crayfish (Orconectes limosus R.) photoreceptors was investigated in vivo. Chloroquine had several ef­ fects upon the crayfish retina. Multivesicular bodies (M VB) that are involved in lysosom al degradation o f photosensory membrane were altered in ultrastructure. M VB frequently con­ tained smaller M VB in a state o f more advanced membrane degradation. A dditionally screen­ ing pigment-like granules appeared in MVB. MVB accumulated in and filled the retinular cell cytoplasm just proximal or distal to the basement membrane which indicated inhibition o f photosensory membrane degradation. Under chloroquine treatment rhabdom degradation appeared to be inhibited, as rhabdom diameter was less reduced under these conditions. A lso chloroquine caused accumulation o f screening pigment granules in glial cells within the lamina ganglionaris. 
  Reference    Z. Naturforsch. 47c, 420 (1992); received January 17 1992 
  Published    1992 
  Keywords    Electron M icroscopy, Chloroquine, Crayfish, Photoreceptor, Screening Pigment Granules 
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 TEI-XML for    default:Reihe_C/47/ZNC-1992-47c-0420.pdf 
 Identifier    ZNC-1992-47c-0420 
 Volume    47 
6Author    Nikolaus TrojeRequires cookie*
 Title    Spectral Categories in the Learning Behaviour of Blowflies  
 Abstract    Wavelength discrimination in the flower visiting blowfly Lucilia spec, was investigated in an attempt to elucidate the mechanisms underlying colour vision in this insect. The flies were sub­ jected to a classical conditioning procedure in which they had to discriminate between a re­ warded and an unrewarded monochrom atic light stimulus. The results reveal large wavelength ranges within which no discrimination occurs, between which, however, a very distinct dis­ crimination is found. The first range consists o f the UV region up to 400 nm (U V). The second range comprises wavelengths between 400 nm and 515 nm (B L U E) and the third range all wavelengths longer than 515 nm (YELLOW). A simple model consisting o f two colour oppo­ nent subsystems (R 7 p /R 8 p and R 7 y /R 8 y) can explain these results. Each o f the two subsys­ tems is assumed to evaluate only whether the sign o f the difference between the excitations o f R 7 and R 8 is positive or negative. For the whole system there are thus four possible condi­ tions: p +y +, p +y", p~y+, p "y~. Three o f them correspond to the experim entally obtained wave­ length ranges. The fourth condition (p+y~) might represent a still hypothetical PU R PLE cate­ gory in which the stimulus is made up o f both short and long wavelengths. 
  Reference    Z. Naturforsch. 48c, 96—104 (1993); received January 7 1993 
  Published    1993 
  Keywords    Blowfly, W avelength Discrimination, Colour Categories, Learning, Photoreceptors 
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 TEI-XML for    default:Reihe_C/48/ZNC-1993-48c-0096.pdf 
 Identifier    ZNC-1993-48c-0096 
 Volume    48 
7Author    Ulrich Schraermeyer, Hennig Stieve, Michael RackRequires cookie*
 Title    Cytochemical Localization of Guanylate and Adenylate Cyclase in Photoreceptor Cells of the Fly  
 Abstract    In photoreceptor cells o f invertebrates light triggers an enzyme cascade in which the phos-phoinositide pathway is crucially involved. Likewise, there is growing evidence of an impor­ tant role of cyclic nucleotides, too. To localize these enzymes able to catalyze the formation of cGM P and cAMP, the spatial distribution of guanylate cyclase (EC 4.6.1.2) and adenylate cyclase (EC 4.6.1.1) was determined in photoreceptor cells of the fly. In photoreceptor cells of the blowfly (Calliphora erythrocephala), the electron dense reaction product o f guanylate cyclase was found within the phototransducing region, the rhabdomeral microvilli and in the mitochondria. Staining was also observed throughout the cytoplasm of the microvilli. With the same cytochemical method, reaction product for adenylate cyclase was found on the tips of the photosensory membrane, and not in the cytoplasm o f the rhabdomeral microvilli. The results presented here further argue for an important role of one or possibly two cyclic nucleotides in the photoreceptor cells, and possibly in the process o f phototransduction of in­ vertebrates. 
  Reference    Z. Naturforsch. 50c, 695—6 (1995); received May 24/July 10 1995 
  Published    1995 
  Keywords    Electron Microscopy, Guanylate Cyclase, Adenylate Cyclase, Photoreceptor, Fly 
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 TEI-XML for    default:Reihe_C/50/ZNC-1995-50c-0695.pdf 
 Identifier    ZNC-1995-50c-0695 
 Volume    50