摘要:

PATIENTS with striate cortical damage causing a hemianopic field defect can nevertheless demonstrate residual visual capacities in their blind field. Previous research investigating blindsight required patients to respond explicitly to stimuli appearing in the blind field by making forced choice judgements. We present data from a patient with a left occipital lesion resulting in a homonymous hemianopia, using the flanker task. This patient displayed a significant flanker congruency effect (FCE) for colour and letter stimuli even when they appeared in the blind field. A control patient with a lesion of the right thalamus showed no FCE in the blind field. This suggests that thalamo-extrastriate neural pathways are necessary for residual functioning in blindsight.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

GLIAL cell-line derived neurotrophic factor (GDNF) and neurturin (NTN) are members of a new family of factors within the transforming growth factor-βb(TGFβ) super-family. Signaling by GDNF and NTN depends on the tyrosine kinase receptor Ret and on GFRα−1 and −2. We have investigated by competitive RT-PCR the developmental expression of these molecules within the rat hippocampus. All transcripts reach high expression levels between postnatal day 0 and 14 (P0–P14), a critical period of hippocampal differentiation, suggesting roles for these molecules in this process. All mRNAs (with the exception of Ret) can be detected as early as embryonic day 14 E14. The absence of Ret expression at E14 suggests that both GDNF and NTN may employ an additional, unknown receptor. NTN expression shows a biphasic expression pattern, with maximum expression levels at E14 and P5.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

THYROID hormone receptor β–deficient (TRβ–/–) mice have defective auditory-evoked brain stem responses (ABR). Sincein vitro, TRβ binds to DNA as homodimers or as heterodimers with retinoid X receptors (RXRs), we investigated whether the TRβ–/– phenotype may reflect loss of RXR-TRβ heterodimer or TRβ homo-dimer function. Normal ABR thresholds were recorded in RXRβ–/–, RXRγ–/– RXRα–/+ and RXR compound mutant mice. When RXR mutations were introduced onto TRβ–/+ or TR–/– backgrounds, thresholds were dictated solely by TRβ and not RXR genotype. TRβ–/– mice also over-produce thyroid hormones and thyroid stimulating hormone; however, levels of these hormones were unaltered by RXR mutations. This suggests that, contrary toin vitromodels, RXRs may be dispensable and that TRβ may functionin vivoby an RXR-independent mechanism in the auditory system and pituitary–thyroid axis.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

ALTHOUGH several studies have shown that L-threo-3,4-dihydroxyphenylserine (DOPS) may provide a neuroprotective effect against ischemic brain damage, its protective mechanism is not fully understood. Glutamate release and hippocampal blood flow in ischemia with administration of DOPS were investigated to elucidate the neuroprotective mechanism of DOPS. Pre- (but not post-) ischemic administration of DOPS rescued 73% of hippocampal CA1 neurons (p< 0.001, compared with ischemia only) 1 week after transient global ischemia in gerbils. While glutamate release induced by ischemia was not affected, the increase of hippocampal blood flow during reperfusion was significantly suppressed by DOPS. These results demonstrate that DOPS may prevent reperfusion injury by suppression of hyperemia after ischemia, resulting in neuroprotection.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

EVENT-RELATED brain potentials (ERPs) to intact faces and to faces without eyes were compared to ERPs elicited by houses to find out whether the face-specific N170 component reflects the activity of a cortical eye processor. When compared to houses, face stimuli elicited a posterior negativity (N170) and a frontocentral positivity. N170 amplitude was not affected by the presence or absence of eyes, but N170 was delayed in response to faces without eyes. It is concluded that the N170 is not directly related to the activity of cortical regions sensitive to the presence of eyes, and is more likely to reflect processes involved in the structural encoding of face components.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

AUDITORY stimuli elicit auditory evoked magnetic fields (AEFs) called P50m and N100m, which index preconscious auditory processing in human. We investigated with a whole-head magnetometer whether Parkinson's disease (PD) impairs parallel preattentive auditory processing between the hemispheres. Stimulus blocks consisting of standard (80%) and deviant (20%) tones were monaurally presented in a passive condition to 11 PD patients with unilateral motor symptoms and to 11 age-matched healthy controls. The constant interstimulus intervals (ISIs) were 0.5 s and 2.5 s in separate blocks. The interhemispheric latency differences of the P50m and N100m were significantly lengthened in PD patients in the left-ear condition. This might be caused by the basal ganglia dysfunction in PD together with the simultaneous age-related neural degeneration predominant in the left auditory cortex.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

SCHIZOPHRENIA is associated with both increased dopaminergic activity and perinatal complications. To test whether dopamine-mediated behavior can be altered by birth complications, we investigated effects of amphetamine (AMPT) on activity levels in adult rats that had been born vaginally or by Caesarean section (C-section) from isoflurane-anesthetized dams with or without addition of D min global anoxia. For comparison with our previous results, we also included rats born by C-section from decapitated dams. The main finding is that rats born by C-section from isoflurane-anesthetized dams, either with or without added anoxia, showed greater AMPT-induced activity as adults compared to vaginally born controls. C-section from decapitated dams also enhanced AMPT-induced activity, however the time course differed from that following maternal anesthesia. Thus subtle alterations in birth procedure can produce long-lasting increases in dopamine-mediated behavior, supporting a role for birth complications in the pathophysiology of schizophrenia.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

FMRFAMIDE immunoreactivity is widespread in the tissues of bivalve molluscs, but some of this immunoreactivity may represent distinct related peptides (FaRPs) rather than the exact tetrapeptide FMRFamide. We have cloned the first full-length cDNA encoding the precursor protein for FMRFamide from this class of molluscs to investigate the possibility that additional peptides may be produced. The precursor contains one copy each of NFLRFamide, FLRFamide, ALAGDHFFRFamide and 16 copies of FMRFamide. This precursor is expressed in all three ganglia of the central nervous system. Since the gene encoding the FMRFamide precursor in pulmonate molluscs is alternatively spliced to give two distinct messages, we searched for evidence that the FMRFamide gene ofMytiluis also alternatively spliced. No evidence of alternative splicing was found.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

AN experimental mouse model of thromboembolic stroke is presented, in which standardized fibrin-rich emboli (15 0μm diameter, 1.5 mm or 4 mm length) are injected into the internal carotid artery. Injection of six or eight 1.5 mm clots (corresponding to 0.16 or 0.2 μl clot material) led to a variable decrease in laser Doppler flow (LDF), but did not result in reproducible infarcts of the middle cerebral artery (MCA) territory, as determined by triphenyltetrazolium chloride (TTC) staining 2 4 h after embolization. Injection of ten 1.5 mm clots (0.2 7 μl) or four 4 mm clots (μl), however, caused a persistent LDF decline to about 20–30% of baseline and led to reproducible infarcts covering the entire MCA territory. The method establishes a clinically relevant, reproducible stroke model for the study of molecular mechanisms of ischemic brain injury in genetically engineered mice.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

TRANSPLANTED olfactory ensheathing cells (OECs) have previously been demonstrated to support axonal growth and myelination in the adult rat CNS. Here, the capacity of donor OECs to control the direction of axonal regeneration has been investigated following transplantation, as elongated columns, into the thalamus of adult rats. The OECs formed a ‘glial bridge’ which extended from the thalamus to the hippocampus. Transplanted OECs rapidly adopted a spindle-shaped morphology which was orientated along the vertical axis of the transplant. Numerous host axons grew into the transplants and followed the highly orientated OEC cell matrix across the choroid fissure. Thus, the spontaneous elongation and orientation of donor OECs may support highly directional host axonal growth across natural barriers within the CNS.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID