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  • 1
    ISSN: 1420-9098
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Résumé Des enregistrements de température ont été effectués depuis le moment où de jeunes reines deBombus (Pyrobombus) impatiens se sont enfouies dans le sol jusqu'au moment où elles sortent de terre au printemps suivant. Les relations entre l'émergence, la radiation solaire et la température ont fait l'objet d'une analyse statistique.
    Notes: Summary Temperature records were kept from the time the new queens ofBombus (Pyrobombus) impatiens burrowed into the soil until they emerged the following spring. Statistical analysis is presented on the relationship of solar radiation and temperature as they affected emergence.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of comparative physiology 79 (1972), S. 15-27 
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 1. Potamotrygon lacks ampullae of Lorenzini (defined by their long canals), otherwise general for elasmobranchs. There are present however microscopic ampullary organs with extremely short canals. A brief histologic description is provided, together with counts of their abundance in various parts of the body. They are chiefly concentrated ventrally in the head region. 2. The skin has a relatively high resistance compared to marine rays. This is measured in the physiologically significant way, by measuring the potential distribution in and around a living ray placed in a homogenous electric field. 3. The microscopical size of the ampullary organs and the high skin resistance are believed to be a specialization maintaining the electroreceptive function in the low conductivity, fresh water medium. 4. These rays are shown to be responsive to d.c. and low-frequency a.c. electric fields. They give specific movements seemingly related to feeding. They seem to be less sensitive than marine sharks and rays. The threshold stimulus is probably less than 120 μV/cm (corresponding to 0.03 μA/cm2 with water resistivity of 4 kOhm · cm). 5. Potamotrygon circularis appears to lack Savi's vesicles. However, an organ which may be equivalent is a tubular, subcutaneous, receptor in the Submandibular region. It does not open to the outside or connect to the skin or to the skeleton. Its spontaneous background nerve impulses and the increases in firing with mechanical stimuli are described.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 17 (1973), S. 229-241 
    ISSN: 1432-1106
    Keywords: Weakly electric fish ; Midbrain nucleus ; Unipolar (adendritic) neurons ; Club endings ; Cup-like terminals ; Rapid electrosensory pathway
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary 1. A particular area of the midbrain called magnocellular mesencephalic nucleus (MMN), characteristic of several weakly electric fishes, was examined by different histological methods in Gymnotus carapo, Gymnotidae. 2. This area contains a dense network of thick fibers in which large neurons are scattered: it contains also a great number of small neurons. 3. The large neurons (25–35 μ) are unipolar with a profusely branching axon that gives rise to the main part of the network within the nucleus. At least one branch of the axonal arborisation leaves the nucleus towards the torus semicircularis, i.e. in the ventral direction. The small neurons (5–12 μ) are uni- or bipolar and display a profuse arborisation of their axon near the soma. 4. Large and small neurons are preferentially localized in the postero-ventral part of the nucleus. 5. Large neurons are contacted by multiple club endings originating partly from the rhombencephalon. The unipolar small neurons receive a single cup-like terminal. 6. The total number of club endings extablishing synaptic contacts on the surface of a large neuron was counted on serial semithin sections. 7. The present findings provide new information about the mesencephalic nucleus, which according to previous electrophysiological observations (Szabo, 1967; Szabo and Sakata, 1967) has been shown to represent a relay in the rapid electrosensory pathway.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 18 (1973), S. 323-339 
    ISSN: 1432-1106
    Keywords: Fish ; Rhombencephalon ; Lateral lobe
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The cyto- and fiber architecture of the lateral lobe (LL) of Gymnotus carapo was investigated using Nissl, Golgi and reduced silver stains as well as 1 μ semi-thin sections. The neurons and fiber tracts are distributed in six layers. The first layer is subdivided into two sublayers: 1A where the primary afferent fibers run in rostro-caudal direction and 1B where these fibers terminate and the large multipolar neurons can be found. The 2nd layer consists of a single row of adendritic, pear-shaped neurons. The axons of these neurons enter the 4th layer and leave the lateral lobe in medial direction. The 3rd layer contains the granular cells of two different types: granular cells with two dendritic trunks directed into dorsal and ventral directions respectively, and granular cells in which, instead of the dendritic trunk, the axon emerges from the dorsal pole of the perikaryon. The axon can be followed up to the 6th layer. The 4th layer consists of bundles of nerve fibers. Beside the axons of the pear-shaped neurons the bundles contain also the axons of the pyramidal neurons (5th layer) leaving the lateral lobe. The 5th layer contains the perikarya of the pyramidal neurons. They have two separate dendritic arborizations, one directed ventrally and entering layer 1B and another directed dorsally and penetrating into the 6th layer. Their axons join the 4th layer and run in medial, rostro-medial or rostral direction depending upon the localization of the neurons in the lateral lobe. The 6th layer (crista cerebellaris) consists of three sublayers. Sublayer 6A contains fine myelinated fibers of unknown origin; sublayer 6B contains fine, mainly non-myelinated fibers originating from the mesencephalon, sublayer 6C is built up of non-myelinated fibers originating from the cerebellum. — A preliminary diagram of the neuron circuits and of the synaptic arrangements involved in the relay of lateral-line organ impulses is suggested.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1432-1106
    Keywords: Synaptology ; Pacemaker ; Gymnotoid electric fish
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The general organization and synaptology of the medullary command (pacemaker) nucleus (MCN) was investigated in the high frequency weakly electric fish, Apteronotus leptorhynchus. This study was undertaken in order to establish differences and similarities between the MCN of A. leptorhynchus and that of the closely related species, Apteronotus albifrons which has been studied previously. The basic morphology and synaptology of the MCN in A. leptorhynchus is similar to that of A. albifrons. The MCN of A. leptorhynchus consists of large (relay) and small (pacemaker) cells; both cell types receive synaptic input or large club endings with electrotonic gap junctions and bouton-like terminals with polarized chemical synapses. Club endings originate from thick meyelinated fibres belonging to the small (pacemaker) cells, whereas the bouton-like terminals issue from thin myelinated fibers of extranuclear origin. Via their club endings, the small (pacemaker) cells are connected both to each other and to the large (relay) cells. Besides the similarities, there are distinct and characteristic differences between the MCN of the two species, which mainly concern the synaptology of the nucleus. In A. leptorhynchus, the large (relay) cells possess long dendritic processes, covered exclusively with bouton-like terminals; the axon initial segment of large (relay) cells receives boutons, in addition to club endings. Small (pacemaker) cells have short dendritic protrusions receiving input from club endings and boutons; furthermore, the small pacemaker cells axon initial segment receives both club endings and bouton-like terminals. These differences are discussed in terms of the functional organization of the MCN in certain gymnotoids and draw attention to the fact that the morphological and ultrastructural aspects of the central command of the electric organ discharge reveal several differences not only between different gymnotoid fish (Apteronotus and Eigenmannia) but also between closely related species such as A. albifrons and A. leptorhynchus.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1432-1106
    Keywords: Electromotoneurons ; Motoneurons ; Electric fish ; HRP ; EM
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Two types of neurons were identified by light and electron microscopy in the spinal cord of Gymnarchus niloticus following HRP injections at different peripheral sites: one, situated in the mediodorsal region, is labelled after injection into the electric organ; the other, situated in the lateroventral region, is labelled in addition after injections extending beyond to the lateral muscle. The cells of the first type, thus shown to be electromotoneurons (EMNs), are spherical and do not have dendritic processes; some of them are connected by somato-somatic gap junctions. The EMNs are surrounded by dense glial processes and embedded in a network of myelinated axons of large diameter. Synaptic contacts with the EMNs are of axosomatic type, exhibiting mostly gap junctions and, less frequently, mixed or chemical junctions. Some endings establish gap junctions simultaneously, with two electromotoneurons, the somatic membrane of which may be joined. The initial segment does not bear any endings. The second type of cells, identified as motoneurons, are pyriform and have large dendritic processes. The motoneurons are surrounded by myelinated axons of small diameter. They receive axosomatic endings with chemical synapses.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    European journal of pediatrics 157 (1998), S. 782-782 
    ISSN: 1432-1076
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1600-0625
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: While the enormous clinical and psychosocial importance of pruritus in many areas of medicine and the detrimental effects of chronic ‘itch’ on the quality of life of an affected individual are widely appreciated, the complexity of this sensation is still often grossly underestimated. The current Controversies feature highlights this complexity by portraying pruritus as a truly interdisciplinary problem at the crossroads of neurophysiology, neuroimmunology, neuropharmacology, protease research, internal medicine, and dermatology, which is combated most successfully if one keeps the multilayered nature of ‘itch’ in mind and adopts a holistic treatment approach – beyond the customary, frequently frustrane monotherapy with histamine receptor antagonists. In view of the often unsatisfactory, unidimensional, and altogether rather crude standard instruments for pruritus management that we still tend to use in clinical practice today, an interdisciplinary team of pruritus experts here critically examines recent progress in pruritus research that future itch management must take into consideration. Focusing on new insights into the neuroimmunological, neuroendocrine, and neurophysiological bases of pruritus, and discussing available neuropharmacological tools, specific research avenues are highlighted, whose pursuit promises to lead to novel, and hopefully more effective, forms of pruritus management.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Analytical Biochemistry 77 (1977), S. 286-288 
    ISSN: 0003-2697
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Comparative Biochemistry And Physiology 27 (1968), S. 625-627 
    ISSN: 0010-406X
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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