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  • 1
    Electronic Resource
    Electronic Resource
    An equivalent circuit for the quantitative description of inter-receptor coupling in the retina of the desert antCataglyphis bicolor (1980)
    Springer
    Journal of comparative physiology 139 (1980), S. 277-285 
    Details
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 1. An ionic equivalent circuit model is developed for the purpose of quantifying the strengths of electrical coupling existing between certain receptor cells in the compound eye ofCataglyphis bicolor which show wavelength dependence in the slopes of their ‘V logI’ relations and orientations of maximum PS (Mote and Wehner, 1980). It combines the pure electrical equivalent of the plasma membrane, as proposed by Finkelstein and Mauro (1963), and a closed series circuit such that Kirchhoff's laws are applicable. 2. The model is applied to hypothetical pairs of cells with different sensitivities and different strengths of interaction. It predicts that cells are most strongly coupled when at rest and most weakly coupled when most active. When one is active and the second is not then “apparent rectification” can occur since the coupling strength is not symmetrical. This means that both “resting” and “dynamic” coupling coefficients must be considered. Transition between these modes causes irregularities in the ‘V logI’ relation of a weakly excited cell which is coupled to a strongly excited cell. 3. The model is then applied to data obtained from photoreceptors in the compound eye ofCataglyphis. It adequately simulates the wavelength dependence of both the ‘V logI’ relation (Fig. 6) and the orientation of maximum PS (Fig. 7) measured in these cells. In its simplest form the model permits an estimate of the coupling coefficients which are greater than 0.6 for strongly coupled cells and less than 0.4 for weakly coupled cells. 4. A hypothetical treatment of pairs of coupled cells under conditions approaching the natural situation in the animal's environment suggests that super-numerary analyzers of polarized light in the u.v. could arise through receptor coupling in certain ommatidial types found in the eye ofCataglyphis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00610459
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  • 2
    Electronic Resource
    Electronic Resource
    Color receptors in marine crustaceans: A second spectral class of retinular cell in the compound eyes ofCallinectes andCarcinus (1982)
    Springer
    Journal of comparative physiology 145 (1982), S. 549-554 
    Details
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 1. Spectral and polarizational sensitivities of dark adapted retinular cells in the ventral regions of the compound eye of the crabsCallinectes andCarcinus have been measured with intracellular recording of responses to flashes of monochromatic light. The majority was maximally sensitive to green light (508 nm,n=108) and showed a mean sensitivity in the blue violet that was higher than expected from a rhodopsin like pigment (Fig. 1). 2. A small number of cells (n = 6) showed a maximum sensitivity to blue light (440 nm) and had a sensitivity function which was considerably wider than a nomogram pigment (Fig. 2). These cells were recorded in the ventral regions of the eye and ERG measurements under selective adaptation revealed statistically significant changes in the relative sensitivities to blue and red stimuli (Figs. 4 and 5). 3. PS values ranged from 1 to 13 when measured in green cells with 508 nm stimuli (n = 69) with the modal value being 3. When PS was tested at 410 nm, 508 nm, and 605 nm in the same cell there was a statistically significant (0.07 log,P 〈 0.01) elevation of PS in the orange region of the spectrum. 4. The results are discussed in relation to the possibility of color vision in marine crustaceans.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00612820
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  • 3
    Electronic Resource
    Electronic Resource
    An ultrastructural morphometric study of the papillary muscle of the right ventricle of the cat (1983)
    Springer
    Cell & tissue research 230 (1983), S. 543-552 
    Details
    ISSN: 1432-0878
    Keywords: Myocardium ; Ultrastructure ; Myocardial biopsy ; Morphometry ; Papillary muscle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The papillary muscle of the cat heart's right ventricle has not been studied previously with quantitative ultrastructural techniques despite its wide use for functional studies. This tissue was perfusion-fixed, processed for electron microscopy, and morphometric techniques were used to assess the ultrastructural characteristics of the papillary muscle as well as the working myocardial cells. The results of this study were that 73.5% of the papillary muscle was composed of muscle cells, 9.7% of blood vessels, and the remainder of interstitial connective tissue. In the muscle cell the volume fraction of mitochondria was 17.3%, that of myofibrils was 49.8%, and that of the nucleus was 2.0%. The mitochondria to myofibrils ratio was 0.36 and the surface to volume ratio was 0.309. In a quantitative ultrastructural comparison of perfusion and immersion fixed tissue it was found that significant differences in the volume density of the blood vessel lumen existed between the two groups. In addition, there were significant differences in the volume fraction of mitochondria and nucleus between perfusion-fixed and immersion-fixed muscle cells. A concurrent significant decrease between the two groups was also found for the ratio of mitochondria to myofibrils. The perfusion-fixed tissue can be considered to provide only normal baseline data for the papillary muscle of the right ventricle. These data are important as they can be used in future structure-function studies on normal and pathological heart tissue.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00216200
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    Paper (German National Licenses)
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