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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 226 (1982), S. 133-144 
    ISSN: 1432-0878
    Keywords: Photomechanical movements ; Retina ; Cones ; Pigment epithelium ; Endogenous rhythm
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The retinal rods, cones and epithelial pigment of most lower vertebrates display rhythmic photomechanical (retinomotor) migrations in response to changes in ambient lighting conditions. This study examines the extent of these migrations in the absence of the daily changes in illumination (constant darkness and constant light) in three species of teleosts. Salmo trutta, a crepuscularly active fish, showed two peaks of light adaptation occurring around dawn and dusk when kept in constant darkness. Tinca tinca, a nocturnal species, also showed an endogenous rhythm during extended periods of darkness, but, unlike Salmo trutta, it was light-adapted throughout what would normally have been “day”. At the maximal extent of migration under conditions of continual darkness, the pigment migrated 59% as much as it did during a normal light/dark cycle. Nannacara anomala, a tropical diurnally active species, showed a similar but more pronounced rhythm than Tinea tinea for all 3 days of experimental darkness, behaving essentially identically to fish exposed to a light/dark cycle. Nannacara anomala also displayed a weak rhythm when kept in constant light. It is concluded from these and previous results that the pattern of endogenous photomechanical movement depends both on the activity pattern of a species and on the constancy of the lighting conditions to which it has been exposed during its lifetime.
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 137 (1973), S. 87-95 
    ISSN: 1432-0878
    Keywords: Retina ; Teleosts (Cichlidae) ; Neuron types ; Quantitative distribution ; Silver-impregnation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Description / Table of Contents: Zusammenfassung 1. In 300 Dickschnitten von 15 silberimprägnierten Augen von Nannacara anomala wurden sämtliche Nervenzellen (insgesamt 10435) ausgezählt und nach Wagner (1973, Teil I) klassifiziert. 2. In Foot-Masson gefärbten Querschnitten wurde aus Zählungen an 5 verschiedenen Netzhautregionen die prozentuale Verteilung der Zellklassen ermittelt. In der medio-temporalen Area ergab sich dabei die dichteste und im ventralen Bereich die lockerste Zellpopulation. 3. Beide Methoden führten zu stark abweichenden Werten im prozentualen Verhältnis der Klassen der Retinaneurone. Eine Erklärung dafür liefern die methodischen Fehlerquellen der Golgi-Methode: Neuronenspezifische Unterschiede in der Argyrophilie, unterschiedliche Identifizierbarkeit aufgrund der unterschiedlichen Ausdehnung der Fortsätze und Diffusionshorizonte bei der Stückimprägnation. 4. Den Berechnungen liegt die Annahme zugrunde, daß innerhalb einer Retinaschicht, d. h. einer Zellklasse keine Unterschiede in der Argyrophilie bestehen. Die Verteilung der Neuronenarten läßt sich ermitteln, indem man das prozentuale Verhältnis der silberimprägnierten Zellarten bezogen auf jeweils eine Zellklasse in die prozentuale Verteilung der Zellklassen, wie es aus der Kernfärbung (nach Foot-Masson) hervorgeht, einsetzt. Daraus ergibt sich rechnerisch der relative prozentuale Anteil der einzelnen Zellarten innerhalb aller Retinaneurone. 5. Im Bereich der Äußeren Faserschicht (ÄFS) stimmt der prozentuale Anteil der Stäbchen (a-Zellen) mit dem der riesigen (f) Bipolaren und der Anteil der Zapfen (b- und c-Rezeptoren) mit dem der kleinen (g- und h-) Bipolaren gut überein. 6. Im Bereich der Inneren Faserschicht (IFS) sind die schichtenbildenden sowie die diffusen Amakrinen gleich häufig wie die entsprechenden Ganglienzellen; sie stellen den größten Anteil ihrer Klassen. Demgegenüber kommen asymmetrische Amakrinen sowie radiäre, einkanalige Ganglienzellen nur selten vor. 7. Gemeinsamkeiten in der quantitativen und räumlichen Verteilung von Amakrinen und Ganglienzellen, die auch in ihrer Erscheinungsform übereinstimmen, werden durch Ergebnisse von Vilter (1947, 1953) bestätigt. Ihre funktionelle Bedeutung ist unklar.
    Notes: Summary 1. A total of 10435 nerve cells was counted in 300 thick sections from 15 Golgi impregnated eyes and classified according to part I (Wagner, 1973). 2. The quantitative distribution of retinal neurones was also determined in Foot-Masson stained preparations of 5 different regions of the retina. Cell density was very high in the medio-temporal area whereas in the ventral part it was very low. 3. Both methods result in rather different ratios of the respective retinal neuron classes. This can be attributed to the methodical difficulties of the rapid Golgi method: cell-type-specific differences of argyrophilia, differences in ease of identification due to the various shapes of the processes of the cells, and diffusion bands as a result of block impregnation. 4. The calculations are based on the assumption that there are no differences of argyrophilia within one retinal layer, i.e. one cell class. The distribution of the neuron types can be found by combining the percentage of the silver-impregnated cell-types within one cell-class with the percentage of the cell-classes as follows from the nuclear-staining-method according to Foot-Masson. This results in the calculation of the percentage of the cell-types among all retinal neurones. 5. Within the outer plexiform layer the percentage of rods agrees with that of f-bipolar cells, and the percentage of cones corresponds to that of g- and h-bipolars. 6. In the inner plexiform layer the percentage of the stratified and diffuse amacrine cells is as high as that of the corresponding types of ganglion cells; these amacrine and ganglion cells make up the highest percentage of their respective classes. 7. The similarities in the quantitative and the spatial distributions of amacrines and ganglion cells of corresponding shape are in accordance with the findings of Vilter (1947, 1953). The functional significance is not clear.
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  • 3
    ISSN: 1432-0878
    Keywords: Retina ; Amacrine cells ; Immunocytochemistry ; Neurotensin ; Somatostatin ; Color vision ; Teleosts
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Neurotensin- and somatostatin-like immunoreactivities were localized by pre-embedding techniques in retinal whole-mounts and radial sections of a monochromatic glass catfish (Kryptopterus bicirrhis), a dichromatic cichlid species (Aequidens pulcher), and the tetrachromatic roach (Rutilus rutilus). Both neuropeptides were observed in perikarya and processes of amacrine cells. For a precise identification of cell types, tangential and radial views were correlated with Golgiimpregnated material. The dendritic pattern defining the morphological subtype of amacrine cells was determined by the given neuropeptide or by the species-specific degree of complexity of retinal structure and function. Neurotensin-like immunoreactivity was localized in amacrine cells of intermediate size, radial symmetry and dendrites with numerous varicosities; they were monostratified in sublayer 3 of the inner plexiform layer. This cell type was common to all three species. In the mono and dichromatic retinas, a single type of amacrine cell with somatostatinlike immunoreactivity was found with radially oriented, varicose dendrites in sublayer 5. In the tetrachromatic roach retina, two somatostatin-positive amacrine cell types were found with very different patterns of ramification; furthermore, both of these types occurred in more than one sublayer. Possible functional implications for color vision of neuropeptide-specific amacrine cells with uniform morphology in all three species and those with a more varied morphology in the tetrachromatic roach are discussed.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 137 (1973), S. 63-86 
    ISSN: 1432-0878
    Keywords: Retina ; Teleosts (Cichlidae) ; Neurone types ; Silver-impregnation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Description / Table of Contents: Zusammenfassung 1. Die nervösen Netzhautelemente von 100 Golgi-imprägnierten Augen von Nannacara anomala wurden photographisch und zeichnerisch dargestellt und nach Art und Grad der Verzweigung ihrer Ausläufer und dem Auftreten von Varikositäten klassifiziert. Anstelle der deskriptiven Bezeichnungen von Cajal werden die Zellen nach den kleinen Buchstaben des Alphabets benannt. 2. Die Äußere Faserschicht (ÄFS) ist regelmäßig organisiert und besteht aus den Ausläufern von 3 Rezeptoren-, 2 Horizontalen- sowie 3 Bipolarentypen. Ihre Verschaltungsmöglichkeiten bei Nannacara und anderen Arten werden erörtert. 3. Die Innere Faserschicht (IFS) besteht aus 7 horizontal verlaufenden Schichten, von denen 4 noch weiter unterteilt werden können. Durch Kombination von Quer- und Flachschnitten nach Foot-Masson gefärbter Präparate dieser Schicht wird gezeigt, daß die waagerechte Zonierung in der gesamten Breite der IFS von einem radiären Gitter überlagert wird, das aus dichten und lockeren Faserelementen besteht. 4. Bei den an der Bildung der IFS beteiligten Amakrinen und Ganglienzellen kommen in beiden Zellklassen schichtenbildende, diffuse und radiär orientierte Zelltypen vor. 5. Neben den bisher bekannten Amakrinen werden für die Nannacara-Netzhaut erstmals 1. eine weitere asymmetrische Form (l-Zelle), 2. eine „zwei Schichten bildende“ (n-) Zelle sowie 3. verzweigte und unverzweigte vertikale (o, r) Amakrinen beschrieben. 6. Radiäre (w), „zwei Schichten bildende“ (x) und euterförmig-diffuse (u) Typen von Ganglienzellen waren in der Retina von Teleostiern bisher unbekannt, nicht dagegen in anderen Wirbeltier-Augen. 7. Es werden Kontakte zwischen den Zelltypen der IFS beschrieben und deren funktionelle Bedeutung diskutiert. 8. Zwei Arten von zentrifugalen Neuronen kommen bei Nannacara vor: Neben bereits bekannten Zelltypen in der IFS werden erstmals Verzweigungen weiterer zentrifugaler Zellen in der ÄFS nachgewiesen. 9. Ein Vergleich mit anderen Vertebraten zeigt, daß ein Standardsatz von Neuronen, der allen Wirbeltieren gemeinsam ist, für die Grundprinzipien des Sehvorgangs verantwortlich sein dürfte. Das Vorkommen zusätzlicher Zelltypen kann als Ausdruck spezialisierter, art-spezifischer Anforderungen an das Sehorgan angesehen werden.
    Notes: Summary 1. In 100 Golgi impregnated eyes of Nannacara anomala the retinal neurones were photographed and drawn, and classified according to the kind and the degree of ramification of their branches and to the existence of varicosities. Instead of the descriptive names of Cajal, cells were termed by the small letters of the alphabet. 2. The outer plexiform layer (OPL) is organized regularly; it is formed by the processes of 3 types of receptor cells, 2 horizontal and 3 bipolar cell types. Their possible connections in Nannacara and other species are discussed. 3. The inner plexiform layer (IPL) consists of 7 horizontal layers, 4 of which can be further subdivided. By combining cross- and tangential sections of Foot-Masson stained preparations of this layer, it can be demonstrated that a radially oriented grid of light and dense fibre elements is overlapping the horizontal zones. 4. Both amacrine and ganglion cells, the processes of which form the IPL, consist of stratified, diffuse and radially oriented cell types. 5. In addition to the amacrine cell types known already, 3 new varieties are described for the first time: 1. a further asymmetrical form (1-cell), 2. a two-strata-forming (n-) cell, and 3. branched and non-branched radial amacrine cells. 6. As to the ganglion cells, radial (w), two-strata-forming (x), and diffuse (u) types occurring in other vertebrates, were unknown until now in the teleost retina. 7. Contacts between the cell types of the IPL are described and their functional significance is discussed. 8. Two kinds of centrifugal neurones are found in Nannacara: In addition to a cell type in the IPL, which is already known, there is a new kind of efferent cell with processes in the OPL. 9. Comparison with other vertebrates shows that a standard set of neurones, common to all species, is likely to be responsible for the principles of visual perception. The existence of additional cell types may be interpreted as a sign of special and specific capacities of the eye.
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  • 5
    ISSN: 1432-0878
    Keywords: Retina ; Amacrine cells, sustained, transient ; Horseradish peroxidase ; Inner plexiform layer ; Rutilus rutilus (Teleostei)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Forty amacrine cells in retinae of a cyprinid fish, the roach, were intracellularly labelled with horseradish peroxidase following electrophysiological identification as sustained depolarizing, sustained hyperpolarizing or transient units. Labelled cells were analysed by light microscopy and compared with a catalogue of amacrine cells established in a previous Golgi study on the same species. About 30% of the cell types characterized by the Golgi method were encountered in the present study. When intracellularly labelled cells were differentiated on the basis of their dendritic organization in the plane of the retina, a given electrophysiological response pattern was found to be generated by different morphological types, and vice versa. However, examination of the ramification patterns of the dendrites within the inner plexiform layer (i.e. in the radial dimension of the retina), showed that this morphological parameter of a given amacrine cell could be correlated with its light-evoked response. Several amacrine cell types were found to possess special distal dendrites which arose from the main dendritic branches and extended well over a mm in the retina. Distal dendrites were oriented tangentially with respect to the optic nerve papilla, but did not appear to be involved in any synaptic connectivity. It is concluded that the Golgi-based classification is a valuable tool for identifying intracellularly labelled amacrine cells. However, although the correlation between layering of dendrites in the inner plexiform layer and electrophysiology was generally good, additional physiological parameters would be required to determine whether more extensive parallels exist between structural and functional characteristics of amacrine cells. Alternatively, the considerable morphological diversity of amacrine cells may be of limited physiological significance.
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