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  • 1
    ISSN: 1432-1106
    Keywords: Cochlea ; Perfusion ; Elevated potassium ; Electrical potentials ; Recovery
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Scala tympani (ST) in guinea pig was perfused with modified Ringer's solutions containing 5–50 mM potassium; tone-induced cochlear responses from the basal turn of ST were compared before, during and after perfusions. The compound nerve action potential (N1) and afterpotential (a/p) amplitudes were reduced, especially above 20 mM; the summating potential (SP) was variable, but its onset shape changed consistently with 13–20 mM levels. However, the cochlear microphonic amplitude (CM) remained substantially unchanged even at the 35 mM level. K+ concentration was monitored in ST with ion-sensitive pipettes. Stable levels were reached within 2 min, but N1 responses continued to fall beyond this time. Recovery to normal K+ levels took place spontaneously and the concentration curve which resulted showed a 2-slope characteristic. These experiments question whether elevated potassium concentration in scala tympani depolarizes the hair cells, and if it does, whether the hair cell resting potential is involved in the generation of the CM.
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  • 2
    ISSN: 1432-1106
    Keywords: Excitatory amino acids ; Thalamus ; Somatosensory system ; CNQX ; CPP
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Sensory synaptic responses of rat ventrobasal thalamus neurones were challenged with iontophoretic applications of the excitatory amino acid antagonists CNQX and CPP. CNQX, applied with currents which were selective for non-NMDA receptors, antagonised responses of VB neurones to both 10 ms and 2000 ms air jet stimulation of the peripheral receptive field. In contrast, CPP only antagonised the latter type of response. These results suggest a differential involvement of excitatory amino acid receptors in sensory synaptic transmission to the ventrobasal thalamus, with an initial synaptic component being mediated by non-NMDA receptors (including kainate receptors), and a further NMDA receptor-mediated component being manifested upon maintained sensory stimulation. The expression of this latter component appears to be largely dependent upon the integrity of the non-NMDA receptor-mediated component.
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  • 3
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 322 (1986), S. 263-265 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Recordings, using extracellular iontophoretic electrodes, were made from single neurones in the ventrobasal thalamus of rats anaesthetized with urethane (1.2 g per kg intraperitoneal). Responses of VB neurones to physiological stimulation of hair or vibrissa follicle afferents (using an air jet) ...
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  • 4
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: SUMMARY. 1. Diet composition and the production of embryos were measured in Asplanchna girodi and Asplanchna priodonta collected through 3 years in the San Joaquin-Sacramento delta of California. The two species are sympatric in low to moderate densities for 5 months of the year.2. Despite marked differences in the structure of the trophi, both species consumed the same array of prey species. Percentage composition of the diet varied both intra- and interspecifically. The food niches of the two species appear to differ little from one another.3. Individuals of Asplanchna girodi had a larger mean number of prey in the gut per individual than did those of A.priodonta, due to their larger size. Per unit volume, each species prey gathering performance was the same. Asplanchna priodonta produced more embryos per calculated unit volume of prey ingested than did A.girodi.4. During spring, when both species were present in the plankton, A.priodonta did not capture Size Class 2 and 5 animals (volumes 0.09–1.0 μm3×106 and 3.0–3.5 μm3X106 respectively) nor large Synchaeta. Both these prey classes were in the diet during the summer and autumn months. Several hypotheses are examined as possible explanations for this phenomenon.
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Anaesthesia 31 (1976), S. 0 
    ISSN: 1365-2044
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
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  • 6
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Anaesthesia 31 (1976), S. 0 
    ISSN: 1365-2044
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Anaesthesia 30 (1975), S. 0 
    ISSN: 1365-2044
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
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  • 8
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Anaesthesia 32 (1977), S. 0 
    ISSN: 1365-2044
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
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  • 9
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    ISSN: 1550-7408
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: SYNOPSIS. In 3 species of carnivorous protozoa, the rate of individual food intake per generation declines with an increase in the density of the population. In all, the rate of division remains constant. Three hypotheses may be proposed to explain these phenomena: the individual size decreases, thus bringing about a decline in food need; the individuals in the earlier stages of population growth consume excess food which is passed on to later generations to supplement their food intake; an increase in density within the carnivore population decreases the activity rate, thus reducing the food requirement. Experiments using Didinium nasutum as the carnivore and Paramecium aurelia, syngen 4, as the food source were conducted to test these 3 hypotheses. The results contradicted the 1st hypothesis and part of the 2nd. A new working hypothesis based on the remaining hypotheses is proposed.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Hydrobiologia 147 (1987), S. 271-281 
    ISSN: 1573-5117
    Keywords: Rotifera ; feeding behavior ; Asplanchna ; Brachionus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Feeding behavior of a rotifer can be broken into two classes of activities: the rate of successful search and the handling process. The former consists of the following components: Perceptual field (in planktonic rotifers the area of the corona), swimming rate, and attack rate. The second class consists of capture rate, handling time, rejection rate, ingestion, digestion, and assimilation. All evidence indicates that the perceptual field cannot be varied by the rotifer. Swimming rate is variable and under rotifer control, but does not appear to vary with degree of starvation. Attack rate is also under control of the rotifer, at least in the genus Asplanchna. Capture rates vary with the species of food item from zero to 100%. Handling times are longer than one would expect, as are rejection times. Digestion and assimilation appear to vary inversely with rate of ingestion. There is some suggestion in the literature that feeding behavior on very small particles differs from that on larger ones.
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