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1981 (1)
1979 (1)
1Author    KarlH. LeserRequires cookie*
 Title    Effect of Isobutylmethylxanthine and Related Drugs on the Receptor Response (ERG; a-Wave) of the Frog Retina at Various Extracellular Calcium Concentrations  
 Abstract    Various drugs known or expected to increase the levels o f cyclic nucleotides in cells were applied to isolated superfused frog retinae, and their influence on the aspartate-isolated a-wave was studied. Isobutylmethylxanthine (IBMX), triacetylguanosine (TAG), and dimethylaminopurine (DAMP) strongly influenced the responses elicited from dark-adapted retinae by flashes o f light With all three drugs the response amplitude was increased, and latency and time to peak were prolonged. If, on the other hand, the retinae were light-adapted by background light o f various intensities, the drugs showed different effects on the response amplitude: IBMX either did not influence the amplitude at all or even caused a decrease (4 o f 6 experiments), DAMP decreased the amplitude and TAG caused an increase of the amplitude in 2 o f 3 experiments. But latency and time to peak were still prolonged by all three drugs. When dark-adapted retinae were superfused with IBMX or TAG Ringer solution and simul­ taneously calcium concentration was raised, different effects o f calcium on the three measured parameters of the a-wave were observed: By increasing the extracellular calcium concentration the increase of the amplitude caused by the drugs was reversed, down or even below the control level, whereas latency and time to peak remained prolonged. Thus, both an increased calcium level and light adaptation had the same effect, namely to reverse only that part o f the drug effect concerning the amplitude but not latency or time to peak o f the response. The data suggest that calcium and cyclic nucleotides act through different ways in the rod cells. 
  Reference    Z. Naturforsch. 36c, 597—603 (1981); received March 25 1981 
  Published    1981 
  Keywords    Frog Retina, Electroretinogram, IBMX, Calcium 
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 TEI-XML for    default:Reihe_C/36/ZNC-1981-36c-0597.pdf 
 Identifier    ZNC-1981-36c-0597 
 Volume    36 
2Author    W. Schröder, H. Stieve, I. Classen-LinkeRequires cookie*
 Title    Accessibility of Extracellular Space in the Rhabdome of the Living Isolated Retina of the Crayfish  
 Abstract    Diffusion of the tracer enzyme horseradish peroxidase (HRP) into the extracellular spaces of living isolated crayfish retinas was monitored by light-and electronmicroscopic identification of the reaction product obtained after immobilisation of the enzyme by fixation. During the incuba­ tion in enzyme containing saline (up to 3 hours) the extracellularly recorded electroretinogram (ERG) stayed normal and showed no substantial change. The reaction product of the enzyme HRP was found only extracellularly in the space between the microvilli in the rhabdome. The results indicate an exchange of substances via extracellular pathways between the extra­ cellular side of the photosensory membrane and the bathing fluid in the living isolated crayfish retina. 
  Reference    Z. Naturforsch. 34c, 136 (1979); received November 7 1978 
  Published    1979 
  Keywords    Light Microscopy, Electron Microscopy, Horseradish Peroxidase Tracer Labelling, Electroretinogram, Retina, Extracellular Compartments 
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 TEI-XML for    default:Reihe_C/34/ZNC-1979-34c-0136.pdf 
 Identifier    ZNC-1979-34c-0136 
 Volume    34