摘要:

The interaction of listening to words and watching sign language in short-term and long-term cochlear implant (CI) users who have learned sign language after becoming deaf was measured using PET. In short-term CI users the auditory cortex was inactive while in long-term CI users it was fully activated with the simultaneous presentation of auditory and visual input. The result suggests the possibility that the interference of rival modalities may be diminished with experience and the preference switchover from the visual input to the auditory input could be accomplished by means of the neural plasticity persisting in the mature human auditory cortex.

ISSN:0959-4965    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

The slow auditory evoked (wave Nlm) and mismatch field (MMF) elicited by sequences of pure tones of 1000 Hz and deviant tones of 1050, 1010 and 1005 Hz were measured before, during and 3 weeks after subjects were trained at frequency discrimination for 15 sessions (over 3 weeks) using an odd-ball procedure. The task of the subject was to detect deviants differing by progressively smaller frequency shifts from the standard stimulus. Frequency discrimination improved rapidly in the first week and was followed by small but constant improvements thereafter. Nlm and MMF responses to the deviant stimuli increased in amplitude during training. This enhancement persisted until training was finished, but decreased 3 weeks later. The results suggest a plastic reorganization of the cortical representation for the trained frequencies.

ISSN:0959-4965    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

Succinate dehydrogenase (SDH) activities and cross-sectional areas (CSAs) of tibialis anterior motoneurons and muscle fibers were determined in 20-, 40-, and 60-week-old male senescence-accelerated mice (SAMP6), and compared with those in age-matched accelerated-senescence resistant mice (SAMR1). The mean CSA of motoneurons in SAMP6 decreased at 60 weeks, primarily due to a selective loss of large (> 400 μm2) motoneurons. The mean SDH activity of motoneurons with CSAs between 100 and 400 μm2decreased in SAMP6, but not SAMR1, at 60 weeks. The mean muscle fiber SDH activities and CSAs in SAMP6 decreased at 60 weeks. There were no differences in the mean SDH activity or CSA of motoneurons or muscle fibers among 20-, 40-, and 60-week-old SAMR1. These results demonstrate that mice which have been shown to have a variety of accelerated-senescent features also have an earlier onset of age-related changes in motoneurons and the muscle fibers that they innervate when compared with age-matched accelerated-senescence resistant mice.

ISSN:0959-4965    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

The possible effect of a cholecystokinin-8 agonist (caerulein) and antagonists (MK-329 and L365,260) on the development of morphine dependence and withdrawal were investigated in rats. Caerulein treatment (0.01 and 0.1 mg/kg) increased the incidence of naloxone-induced withdrawal syndromes and delayed the extinction of morphine-conditioned place preference in morphine-dependent animals. The signs of the morphine withdrawal syndromes and the formation of morphine-conditioned place preference were suppressed by pretreatment with L365,260 (0.1 and 1 mg/kg) and not affected by pretreatment with MK-329 (0.1 and 1 mg/kg). The present study demonstrated CCK, acting on CCK-B receptors, participates in the development of the opiate dependence. These findings suggest that CCK-B receptor antagonists might be of some value in the treatment and prevention the relapse of opiate addicts.

ISSN:0959-4965    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

The early expression of neurotransmitters and receptors in the developing brain has brought attention to their potential contribution in modulating neuronal developmental processes. Monoamines are among the first neurotransmitter systems to develop during embryogenesis. Depletion of neocortical serotonin or catecholamine afferents with selective neurotoxins resulted in a permanent alteration of the dendritic arborization of calretinin-containing interneurons, and a transient delay of parvalbumin and calbindin expression in a number of cortical neurones during the second postnatal week. The expression pattern of other developmentally regulated proteins, such as two subunits of the GABAAreceptor, was not altered. Depletion of serotonin, and in part catecholamines, appeared to perturb several developmental processes of the cerebral cortex which would interfere with both its maturation and adult circuitry.

ISSN:0959-4965    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

The distribution of activated NF-κB (p65) was studied in granule cells of the rat fascia dentata using confocal laser scanning microscopy and preembedding immunogold electron microscopy. Activated NF-κB, detected with a monoclonal antibody specific for the nuclear localization signal-epitope, was found in proximal dendrites, somata, and nuclei but not in axon terminals of granule cells. Within the nuclei of granule cells, clusters of NF-κB immunoreactivity were detected. These data are in line with the proposed function of NF-κB as a retrograde signal transducer which transports information from synaptic sites to the nucleus to initiate gene expression.

ISSN:0959-4965    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

Inflammation of the temporomandibular joint (TMJ) produces an increase in preprodynorphin (PPD) mRNA expression in the spinal trigeminal nucleus (Vsp) and paratrigeminal nucleus (Pa5) of the rat. In this study, we further demonstrated that a portion of the TMJ inflammation-induced PPD mRNA positive neurons in the Vsp and Pa5 projected to the parabrachial nucleus (PB). In inflamed rats, the percentage of trigemino-and paratrigeminoparabrachial neurons with up-regulation of PPD mRNA was significantly increased in the ipsilateral Vsp(5.7 ± 1.8%) and Pa5 (22.8 ± 7.4%,n= 3) when compared with the contralateral side and with saline-treated controls (p< 0.05). These results suggest that the selective up-regulation of PPD mRNA in the Vsp and Pa5 following TMJ inflammation involves ascending trigeminal nociceptive pathways.

ISSN:0959-4965    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

Innervation of the γ straddler vibrissa and distribution of individual γ vibrissal sensory nerve fibers within infraorbital nerve branches were investigated in adult rats. In the close vicinity (2 mm) of the whisker-pad, one-fifth of the nerve fibers innervating the γ vibrissa were still located in nerves to neighboring (β, δ, C1 and D1) whiskers, while one-tenth of the innervating fibers were placed in nerves of more distant sinus hairs. This convergence of γ vibrissal sensory nerve fibers to single vibrissa from neighboring nerves is suggested to be a consequence of overlapping vibrissal representation in the Gasserian ganglion.

ISSN:0959-4965    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

Vestibular ganglion (VG) neurons are bipolar neurons that relay peripheral vestibular information to the CNS. Neuron counts in normal humans provide a basis for quantitative studies on the effects of aging or pathological conditions in the audiovestibular systems. No prior study has employed unbiased stereological technique to count human VG neurons. This study used unbiased stereology in the form of the optical fractionator to estimate the total number of human VG neurons in archival temporal bone specimens. An average (± s.d.) of 27 330 ± 2593 neurons was found in specimens from five patients with no history of vestibular pathology. This result, a significant departure from results of past studies, provides the first unbiased baseline value to compare with future stereologically based studies on the human VG.

ISSN:0959-4965    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

Radiolabeled probes for the transcription factor, activator protein-1 (AP-1), bound differentially to nuclear fractions of discrete structures of the guinea pig cochlea (organ of Corti, lateral wall tissues, and spiral ganglion). Noise exposure (4 kHz octave band, 115 dB, for 5 h) significantly increased AP-1 binding in both the organ of Corti and lateral wall tissues but not in the spiral ganglion. Supershift analysis using an antibody against c-Fos protein demonstrated that enhancement of AP-1/DNA binding was at least in part due to the expression of c-Fos protein. These results suggest that AP-1 is involved in the molecular mechanism(s) mediating noise-induced cochlear damage.

ISSN:0959-4965    

出版商:OVID    

年代:2000

数据来源: OVID