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  • 1
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Journal of agricultural and food chemistry 41 (1993), S. 537-539 
    ISSN: 1520-5118
    Source: ACS Legacy Archives
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Journal of agricultural and food chemistry 43 (1995), S. 1489-1492 
    ISSN: 1520-5118
    Source: ACS Legacy Archives
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Journal of agricultural and food chemistry 40 (1992), S. 2260-2262 
    ISSN: 1520-5118
    Source: ACS Legacy Archives
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Journal of agricultural and food chemistry 43 (1995), S. 9-12 
    ISSN: 1520-5118
    Source: ACS Legacy Archives
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract During early embryogenesis of the nematode Parascaris univalens (2n=2) the processes of chromatin diminution and segregation of the germ and somatic cell lineages take place simultaneously. In this study we analyzed the nucleolar cycle in early embryos, both in germinal and somatic blastomeres, by means of silver staining and antibodies against the nucleolar protein fibrillarin. We observed an identical nucleolar cycle in both types of blastomeres, hence, the chromatin diminution process has no effect on the nucleolar cycle of somatic blastomeres. We report the existence of outstanding differences between this cycle and those previously reported during early embryogenesis of other species. There is a true nucleolar cycle in early embryos that shows a peculiar nucleolar disorganization at prophase, and a preferential localization of prenucleolar bodies only on the euchromatic regions during nucleologenesis. Moreover, fibrillarin does not form a perichromosomal sheath in metaphase or anaphase holocentric chromosomes, probably owing to their special centromeric organization. The number and location of nucleolus organizer regions (NORs) in the chromosomal complement have been determined using silver impregnation, chromomycin A3/distamycin A staining, and fluorescent in situ hybridization using an rDNA probe. There are only two NORs, one per chromosome, and these are lost in blastomeres after chromatin diminution. Moreover, the constant presence of two nucleoli in somatic blastomeres suggests that NORs are not affected during the fragmentation of euchromatic regions when this process occurs.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The two nucleolus organizing chromosome pairs of the grasshopper Pyrgomorpha conica can carry a proximal supernumerary heterochromatic segment. We employed different cytological techniques to characterize and analyze the possible origin of this segment. The supernumerary segment and the nucleolus organizing regions (NORs) show similar responses after C-banding plus either Giemsa or acridine orange, and chromomycin A3/distamycin A staining to detect GC-rich chromosome regions. Fluorescence in situ hybridization with a biotinylated rDNA probe demonstrated that the segment originated by amplification of the rDNA genes. However, as the silver staining indicates, the ribosomal genes present in the segment are not active since no nucleolus is formed. The use of in situ digestion with the isoschizomeric MspI and HpaII restriction endonucleases and subsequent Giemsa, ethidium bromide or chromomycin A3/distamycin A staining, suggests that the segment has been inactivated by DNA methylation.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1432-1106
    Keywords: Inferior olive ; Deep cerebellar nuclei ; Pontine nuclei ; Very short-term potentiation ; Attentional movements ; Cats
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Field potentials induced in deep cerebellar nuclei by the electrical stimulation of contralateral red, pontine and reticularis tegmenti pontis oralis nuclei, the restiform body and the inferior olive were recorded in the alert cat. Recording sites in interpositus and fastigial nuclei were selected with the aid of antidromic field potentials induced by red nucleus and restiform body stimulation, respectively. Pontine and reticularis tegmentipontis oralis nuclei stimulation induced small, but constant amplitude, field potentials consisting of one or two negative waves. Control field potentials induced by inferior olive stimulation consisted of a negative wave at 2–3 ms followed by a late (4–6 ms) positivity. Conditioning stimuli applied to the pontine and reticularis tegmenti pontis oralis nuclei greatly enhanced the amplitude of the inferior olive-evoked synaptic field potential for a time window of about 40 ms. In contrast, inferior olive conditioning stimulation failed to modify the field potentials induced by pontine nuclei stimulation. These facilitatory effects on field potential amplitude showed no long-lasting modifications. The transient modification of inferior olive-induced field potentials could be related to attentional movements made by the animal to natural or electrically-induced sensory cues.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    European journal of neuroscience 5 (1993), S. 0 
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The electrical activity of antidromically identified abducens internuclear neurons selectively deprived of their target motoneurons was recorded in chronic alert cats. Target motoneurons were killed by the injection of the cytotoxic lectin of Ricinus communis into the medial rectus muscle. Following target removal, the discharge pattern of abducens internuclear neurons showed an overall decrease in firing rate, a significant reduction in their sensitivity to eye position and velocity, and the presence of anomalous responses such as bursts of spikes associated with off-directed saccades. The decreased excitability of abducens internuclear neurons correlated well with a marked reduction in the synaptic efficacy of their inputs. Thus, both excitatory and inhibitory synaptic potentials of vestibular origin showed a noticeable decrease in amplitude. The alterations in firing properties and synaptic transmission were only observed during an initial period of 3 weeks following ricin injection. Within 1 month the electrophysiological parameters returned to control values and remained unaltered for 1 year. Retrograde labelling of abducens internuclear neurons revealed that no cell death occurred after target loss. The anterograde axonal labelling of these neurons showed a progressive decrease in the density of their axonal terminals, and no sign of redistribution to other areas was found. These findings indicate that abducens internuclear neurons are not dependent on the presence of their natural target cells, either for the survival or for the maintenance of appropriate physiological signals.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The ability of four different brainstem motoneuron pools to perform a newly acquired motor task was studied in alert cats. A classical conditioning of eyelid responses was carried out in (i) unoperated animals, and in animals with (ii) transection, 180° rotation, and re-suture of the zygomatic facial nerve branch, (iii) a crossed anastomosis of the buccal to the zygomatic facial nerve branch and (iv) a hypoglossal–facial nerve anastomosis. Animals were conditioned with a delay paradigm using a tone (350 ms, 600 Hz, 90 dB) as conditioned stimulus, followed 250 ms later by an air puff (100 ms, 3 kg/cm2) as unconditioned stimulus. Animals with zygomatic nerve rotation performed conditioned responses (CRs) at control rate, with significantly larger amplitude, area and velocity, but a de-synchronized oscillatory pattern. Animals with buccal–zygomatic anastomosis acquired CRs at control rate, but these CRs had significantly smaller amplitude than those of controls and a de-synchronized pattern. Animals with a hypoglossal–facial anastomosis were unable to perform CRs. The trigeminal hyper-reflexia triggered by the axotomy was probably the origin of the large CRs after zygomatic nerve rotation. Trigeminal hyper-reflexia could also contribute to generation of the small CRs recorded after buccal–zygomatic anastomosis. Although trigeminal hyper-reflexia was also present following hypoglossal–facial anastomosis, hypoglossal motoneurons did not reach their firing threshold to perform CRs. In accordance with the embryonic origin of involved motoneurons, animals with buccal–zygomatic and hypoglossal–facial anastomoses moved the ipsilateral eyelid synchronously to mouth-related activities. It is suggested that there is a gradient of adaptability in motoneuron pools forced to perform new motor tasks through foreign muscles, which depends on their embryological origins and functional properties.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Adult heterozygous Lurcher mice show a degeneration of almost all Purkinje cells and 90% of the granular cells of the cerebellum, resulting in ataxia or general deficits in motor coordination. These mice are therefore an excellent model for studying the role of the cerebellar cortex in motor performance, including the acquisition of new motor abilities. The performance of 3-month-old Lurcher mice was studied in various behavioural (fall, horizontal bar, rotating cylinder, and ladder), spatial orientation (water maze) and associative learning (eyelid classical conditioning) tasks and compared with that of wild-type mice. Behavioural tasks indicated a deficit for motor abilities in Lurcher mice but with some adaptation to the tests and improvement in performance. Wild-type and Lurcher mice performed swimming equally, but the latter learned the task significantly more slowly than the former. The late component of reflex blinks was smaller in amplitude and had a longer latency in Lurcher mice than in controls. Learning curves for Lurcher mice during classical conditioning of eyelid responses were similar to controls, but the amplitude of the learned response in Lurcher mice was significantly lower. The startle response to a severe tone was similar in both control and Lurcher mice but the latter were unable to produce prepulse inhibition. These results suggest that the cerebellar cortex is not indispensable for the performance of this complete set of skeletal and facial tasks, or for the acquisition of new motor abilities, but it is for the appropriate execution and adjustment of any of these motor activities.
    Type of Medium: Electronic Resource
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