摘要:

WE have recorded identified cortico-tectal neurons from the primate parietal cortex to determine whether the depth-related activity in the intraparietal sulcus (area LIP) is transmitted to the superior colliculus. Traditional theory suggests that the superior colliculus is involved in the control of conjugate, saccadic eye movements and thus would not require inputs related to depth. We provide conclusive evidence that area LIP neurons in fact do transmit depth-related information to the superior colliculus.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

AMONG the more frequent oxidative DNA injuries is the formation of abasic sites (AP sites) resulting from removal of purine or pyrimidine bases, estimated to occur at a rate of 1 × 104/genome/24 h. A defect in DNA repair at this level could account for the accumulation of mutations and subsequent genome instability. We have identified missense mutations in the APE gene coding for a multifunctional DNA repair enzyme, AP endonuclease in eight of 11 patients with amyotrophic lateral sclerosis (ALS) and familial ALS. These mutations could affect the repair of abasic sites leading to the accumulation of mutations in neurons, resulting in their degeneration and death. Our findings implicate mutated AP endonuclease in the pathogenesis of ALS.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

THE Flinders Sensitive Line (FSL) rats have been proposed as a genetic animal model of depression because their innately high immobility in the forced swim test is counteracted by antidepressants. This model was used to test the acute and chronic effects of two novel compounds which have either an agonist or antagonist-like effect at melatonin receptors. In the acute study FSL and control Flinders Resistant Line (FRL) rats were unaffected by either the agonist S 20304 (1 or 20 mg/kg) or the antagonist S 20928 (1 or 10 mg/kg) given 1 h prior to a single 5 min swim test. In the chronic study a reduction in immobility in the FSL rats at the highest dose of the agonist was the only significant drug effect. These findings suggest that the melatonin receptor agonist S 20304 may have antidepressant potential.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

THE size or shape of an object, its perceptual features, determine the patterning of an arm and hand action involving that object. Little is known about the role played by the taxonomic semantic attributes of an object for perceptuomotor processing. In this study we investigated whether the semantic relationship between two target stimuli influences the kinematics of a bilateral reach-to-grasp action. The results showed that reach-to-grasp movements preceding the action of putting living-thing pairs together were faster, and showed earlier settings of reach and grasp temporal parameters, than movements involving pairs of non-living things. It is hypothesized that this reflects the recruitment of different categorical perceptuomotor pathways.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

WE investigated the potential for hair cell regeneration in neonatal rat organs of Corti grown in culture following destruction of hair cells by neomycin toxicity. Replacement hair cells were observed by light and scanning electron microscopy in lesion sites in the cultures treated with transforming growth factor-α, epidermal growth factor or a combination of both factors for 5–7 days post-injury. These new cells had morphological characteristics of immature hair cells. Autoradiographic localization of [3H]thymidine-labelled cells on semi-thin sections indicated that these replacement hair cells did not arise through renewed mitotic division, although an important mitotic proliferation was observed outside the area of supporting and sensory cells.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

SOUND conditioning guinea pigs to a 6.3 kHz tone at 78 dB SPL for either 13 or 24 days provides significant physiological (auditory brain stem responses, ABR; and distortion product otoacoustic emissions, DPOAE) and morphological (cochleograms) protection against a subsequent traumatic exposure (6.3 kHz, 100 dB SPL for 24 h) delivered 2 h after sound conditioning. Threshold shifts (ABR, DPOAE) were significantly reduced and the degree of hair cell loss was minimal. When a 1 week pause was given between the end of the sound conditioning and the traumatic exposure, protection was still observed, but to a lesser degree. These findings demonstrate that mid-frequency sound conditioning protects against noise trauma and that the protective effect is maintained for at least 1 week.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

FLUORESCENT tracers were injected into different regions of the caudate nucleus and HRP-WGA in the substantia nigra of the cat in order to analyse the thalamic distribution of retrogradely labelled thalamostriatal neurones and anterogradely labelled nigrothalamic terminals within the thalamus. Overlapping thalamic territories between the thalamostriatal neurones projecting to areas of the caudate nucleus and the nigrothalamic connections were observed in the rostral nuclei of the central thalamic group (ventral anterior nucleus, ventral anterior-ventral lateral complex and ventral medial nucleus) and, more restricted, in the rostral (rhomboid, paracentral, ventral lateral, dorsal mediodorsal nuclei) and caudal intralaminar nuclei (centromedian–parafascicular complex). This study provides evidence of the existence of thalamic areas in which the input and output of the basal ganglia converge.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

SPIRAL ganglion neurones in rat cochlea express three different isoforms of the P2X2receptor subunit which assemble into ATP-gated ion channels. Two of these P2X2R subunit isoforms have previously been detected in other auditory tissues. The third isoform (designated P2X2–3R) has not been described. This isoform lacks 39 bp immediately prior to the stop codon, corresponding to a 13 amino acid deletion of the extreme C-terminus domain. Using directin situRT-PCR, expression of P2X2R mRNA was confined to a subpopulation of type I spiral ganglion neurones. This study supports a role for extracellular ATP as a neurotransmitter for a discrete population of auditory neurones where variation in P2X2R isoform assembly may confer functional heterogeneity, including enhanced desensitization.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

WE examined the cortical areas showing increased activation related to axis orientation discrimination in hand movement and perception by positron emission tomography (PET) in right-handed normal human subjects while they performed a hand orientation (HO) task and an orientation discrimination (OD) task. In the OD task, fields in the parietal cortex and a field in the inferior frontal gyrus showed increased activation relative to the control task. In the HO task, fields in the intraparietal sulcus, the inferior and middle frontal gyri, the fusiform gyrus and the middle temporal gyrus showed increased activation relative to the control task. The results indicate that areas involved in axis orientation discrimination seemed to be segregated in the parietal cortex, with one field in the left intraparietal sulcus related to hand movement and another field in the right intraparietal sulcus related to perception.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

THE hypothalamic neurotransmitter dopamine (DA) regulates pituitary secretion of the glucoregulatory hormones, growth hormone (GH) and adrenocorticotropin (ACTH). The glucose antimetabolite, 2-deoxy-D-glucose (2DG), elicits expression of the protooncogene product Fos, which is expressed in hypothalamic structures where DA is synthesized. These studies utilized dual-label immunocytochemistry to determine whether discrete DA neuron populations in this region of the brain exhibit Fos immunoreactivity (-ir) in response to glucopenia. Ovariectomized female rats implanted s.c. with exogenous estradiol or vehicle were injected with 2DG (400 mg/kg, i.p.) or saline, and sacrificed 2 h later. Whereas Fos-ir was negligible after saline administration, 2DG induced expression of Fos-ir by TH-ir neurons in the paraventricular (PVN), periventricular (Pe) and arcuate nuclei (ARC), and in the anterior hypothalamic area (AHA). TH-ir neurons in the zona incerta did not express Fos-ir following 2DG. Although mean numbers of co-labeled neurons in the Pe, PVN and AHA did not differ between estradiol- and non-steroid-treated rats, the former group exhibited significantly higher numbers of TH-positive plus Fos-positive neurons in the ARC in response to 2DG. These results reveal the functional responsiveness of discrete DA neuron populations to glucoprivation, and indicate that estradiol enhances cellular accumulation of Fos-ir by ARC DA neurons during this metabolic challenge.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID