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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Psychopharmacology 28 (1973), S. 351-362 
    ISSN: 1432-2072
    Keywords: Ethanol ; Operant Performance ; Dose-Response Analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effects of various doses of ethanol on DRL performance was examined in rats under conditions of cued and non-cued DRL tasks and under conditions of low versus high baseline performance criteria. The dose-level at which ethanol produced a significant reduction in number of responses and reinforcements interacted in a complex fashion with level of baseline performance, the cue conditions, and the order of DRL tasks. Generally, performance was impaired at a lower dose level for groups initially trained to a low criterion of DRL performance than for groups later trained to a higher criterion of DRL performance, regardless of cue condition. Further, the dose level at which ethanol impaired performance (as indicated by number of reinforcements obtained) under non-cued DRL conditions was lower than that for the cued DRL conditions, but only on the initial task where baseline DRL performance criterion was lower. Finally, the group with a higher baseline level of responding (i.e., poorer DRL performance) was more vulnerable to the disrupting effects of ethanol on this measure than groups with lower baseline response rates.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Psychopharmacology 37 (1974), S. 311-321 
    ISSN: 1432-2072
    Keywords: Rats ; Ethanol ; Ethanol Reinforcement ; Acquisition ; Schedule-Induced-Polydipsia ; Ethanol Concentration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Daily 6-h sessions were run during which each lever press by rats produced brief access to water, or to 8
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-2072
    Keywords: Ethanol ; Ethanol Drinking ; Water-Ethanol Choice ; Concurrent Schedules ; Ethanol Concentration ; Ethanol Reinforcement ; Rats
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Water and ethanol solutions were concurrently made available on a continuous reinforcement schedule to 4 food-deprived male albino rats during daily 1-hr sessions in an operant conditioning chamber equipped with 2 levers and 2 liquid dippers. The number of ethanol reinforcements substantially exceeded the number of water reinforcements for each rat at each concentration studied (8, 16, and 32% w/v). Water reinforcements were low in number and did not vary with ethanol concentration. As the ethanol concentration was increased, the number of ethanol reinforcements obtained decreased, while the quantity consumed (mg/100 g of body weight/hr) increased. The highest rate of responding occurred at the beginning of the session.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 132 (1972), S. 167-192 
    ISSN: 1432-0878
    Keywords: Microfilaments ; Contractility ; Morphogenesis ; Ascidians ; Cytochalasin B
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary During tail resorption in Distaplia occidentalis the caudal epidermis contracts to 8.5% of its initial length in about 6 minutes and forces the axial complex (muscle, notochord and nerve cord) into a coiled configuration in the trunk. The contraction of the caudal epidermal cells is accompanied by rapid alignment of arrays of circa 50 Å (diameter) filaments parallel to the axis of contraction in the apical cytoplasm of each epidermal cell. Normal metamorphosis (including tail resorption) can be instantly induced by treating tadpole larvae with 0.5% dimethylsulfoxide. Cytochalasin B, (CCB) 〉 0.25 μg/ml rapidly inhibits contraction of the caudal epidermis. The tail stops shortening, then partly re-extends. When CCB is removed by washing immediately after relaxation, tail resorption resumes. Cytochalasin B reversibly disrupts the organization of central and subterminal arrays of apical filaments in the contractile caudal epidermal cells. Membrane associated filaments near the junctional complexes are not disrupted by 0.25–1.0 μg/ml of CCB. This suggests that CCB does not degrade the filaments into subunits. It is more likely that CCB blocks contraction by disrupting the binding forces between overlapping filaments and facilitates the disorganization of unattached filaments. A second type of filament with a fusiform configuration has been detected in the epidermal cells after CCB treatment. The possibility that these are myosinoid proteins is considered. The data presented in this paper strengthen the hypothesis that the filaments in the epidermal cells are part of a contractile apparatus.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 107 (1970), S. 157-173 
    ISSN: 1432-0878
    Keywords: Ascidians ; Metamorphosis ; Blood cells ; Epidermis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary During the first 10 minutes after the onset of metamorphosis in the ascidian Amaroucium constellatum there is a massive emigration of blood cells (granulocytes) from the hemocoel, across the epidermis, into the tunic. Electron microscopy has been employed to extend some of the classical observations of the last century. The new findings are compatible with the hypothesis that the blood cells follow a transcellular pathway. Our interpretation is as follows: an emigrating cell enters the basal part of an epidermal cell and becomes enclosed within a vacuole. The vacuole and the blood cell move to the apex of the epidermal cell. The vacuole fuses with the plasmalemma releasing the blood cell into the tunic. Blood cells can therefore pass through the epidermis without leaving a hole and without rupturing intercellular junctions.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 200 (1979), S. 453-473 
    ISSN: 1432-0878
    Keywords: Metamorphosis ; Settlement ; Morphogenetic movements ; Adhesive organs ; Ascidians
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The cup-shaped adhesive papillae of Distaplia occidentalis evert at the onset of metamorphosis and each transforms into a hyperboloidal configuration. The rate of transformation is a function of temperature. At 14° C complete eversion takes about 30 seconds. Myoepithelial cells that extend from the rim to the base on the cup contract. Simultaneously the central part of the papilla advances 60–70 μm. During the last phases of eversion, collocytes (cells that secrete adhesives) on the inner wall of the cup and on the sides of the axial protrusion flow outward and form a collar-like structure. The myoepithelial cells contain arrays of thick and thin filaments. These become compacted during contraction. The surfaces of these cells become extensively folded as they shorten to about 1/3 of rest length. According to the proposed model the myoepithelial cells are the driving force in papillary eversion. Immediately after eversion is completed the papillae begin to retract. Eversion of the papillae is not inhibited by cytochalasin B, but the process of retraction is reversibly inhibited. Some histological characteristics of five types of everting papillae in four families of ascidians are compared.
    Type of Medium: Electronic Resource
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