摘要:

WE simultaneously measured extracellular glutamate ([Glu]e) elevation and local CBF using a real-time monitoring method and laser-Doppler flowmetry, respectively, in the rat striatum in a modified graded global ischemia model. Ischemic brain temperatures were kept at 32°C, 37°C and 39°C. Three distinct types of intraischemic [Glu]e elevation, reflecting mild, moderate and massive glutamate release, were observed. Brain temperature plays an important role in determining CBF thresholds for each of the three types of [Glu]e elevation. CBF thresholds for [Glu]e elevations shifted to a lower level range as brain temperature was reduced. In mild or moderate ischemia, there is no exposure to sustained [Glu]e elevation, which is seen only in relatively severe ischemia characterized by biphasic [Glu]e elevation.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

THE rat suprachiasmatic (SCN) contains a dense plexus of low-affinity p75 neurotrophin receptor (p75NTR) immunoreactivity. In some SCN neurons, p75NTR is co-localized with vasoactive intestinal peptide (VIP). The present study examines the effect of third ventricle administration of 192 IgG-saporin immunotoxin on p75NTR and VIP immunoreactivity in the rat SCN. The 192 IgG-saporin immunotoxin abolished p75NTR immunoreactivity in the SCN. VIP immunoreactivity in the SCN of saporin-lesioned animals was not significantly different from that of control animals. Immunolesions of the p75NTR-ir cell population in the SCN may prove useful in clarifying the role of p75NTR in circadian timing.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

TO investigate whether abnormally accumulated βAPP may be responsible for denervation of muscle fibers that are present in hereditary inclusion-body myopathy (h-IBM) and sporadic inclusion-body myositis (s-IBM), we cultured five h-IBM and eight normal muscle biopsies. In eight other experiments, a 3 kb human 751-βAPP-cDNA was transferred, using adenovirus vector, into cultured normal myotubes immediately after myoblast fusion. In all experiments, cultured muscle fibers were co-cultured with fetal rat spinal cord. Controls had no detectable βAPP epitopes, whereas βAPP epitopes were greatly increased in cultured h-IBM muscle and in cultured normal muscle after βAPP-gene transfer. Innervated normal cultured muscle fibers were continuously contracting and fully cross-striated, and they had acetylcholine receptors (AChRs) and acetylcholinesterase (AChE) accumulated only at the neuro-muscular junctions (NMJs). By contrast, both groups of βAPP-overexpressing cultured muscle fibers were not contracting and not cross-striated; and did not have NJMs containing AChRs and AChE. Our results suggest that over-expression of βAPP in cultured muscle fibers inhibits their innervation, and that the accumulation of βAPP in muscle fibers of both h- and s-IBM patients may be responsible for their not becoming or remaining properly innervated or reinnervated, i.e. a ‘myogenous-dysinnervation’ mechanism.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

BRIEF exposure of neuronally differentiated human NT2/D1 cells to hydrogen peroxide induced cell death by apoptosis with an ED50of 30 μM, whereas a 70-fold higher concentration was required to obtain an ED50effect in undifferentiated NT2/D1 neuronal precursor cells. This enhanced sensitivity in NT2/D1 neurons was correlated with an 8-fold lower level of intracellular glutathione. Pretreatment with N-acetyl-L-cysteine, an agent that is able to raise the levels of intracellular glutathione, promoted the survival of hydrogen peroxide-treated NT2/D1 neurons. Thus, the low glutathione level may contribute to the high sensitivity of NT2/D1 neurones to hydrogen peroxide-induced apoptosis. This study indicates that neuronal susceptibility to oxidative damage is developmentally regulated.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

REFERRED pain arising in orofacial pain states is probably due to convergence of different somatosensory input onto the medullary dorsal horn (MDH). To examine convergence between nociceptive and nonnociceptive input onto the MDH, the blink reflex (BR) was applied. R1-and R2-components can be evoked by innocuous stimuli, but only the R2 is elicited by painful heat. The BR was elicited by innocuous electrical stimuli applied to the supraorbital nerve. A conditioning painful heat pulse which did not evoke any BR was homotopically applied to the left forehead preceding the electrical stimulus by 75 ms. While R1 remained unchanged, the R2 was facilitated by about 30%. This study demonstrates a convergence of low-threshold mechanoreceptive and nociceptive inputs onto interneurons of the MDH in man.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

GLUTAMATE is considered an important pain transmitter and responsible for inflammatory hyperalgesia, but quantitative and topographical changes in glutamate release in the dorsal horn during peripheral inflammation have not been characterized. To address this issue, image analysis with a confocal laser scanning microscope was performed for quantitatively mapping capsaicin-evoked glutamate release from the lumbar cord slice of rats following unilateral adjuvant inoculation to the hind-paw. Capsaicin induced glutamate release from laminae I, II and X in the spinal cord of the adjuvant-treated and untreated sides, without apparent release from laminae III–V. The concentration of released glutamate in laminae I, II and X was higher on the adjuvant-treated side than on the untreated side. The results suggest that adjuvant inflammation increases glutamate release from capsaicin-sensitive primary afferents in laminae I, II and X.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

THE physical process of cell suspension preparation from embryonic ventral mesencephala (VM) may be responsible for the low numbers of dopaminergic (DA) neurons that survive following neural transplantation orin vitroculture. In particular, the disruption of cell to extra-cellular matrix attachment may result in cell death through deactivation of a cAMP-dependent protein kinase involved in cell survival signalling. In an attempt to reduce this death, dibutyryl cAMP was included in all solutions from explant collection to final dissociation. Pretreatment with 700μM dibutyryl cAMP resulted in 90% survival of the DA neurons originally plated, compared with only 40% in the untreated cultures, after 5 daysin vitro. Treatment of VM explants in this manner may result in major improvements in neural transplantation as a technique for the treatment of Parkinson's disease.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

MOBILE phones emit a pulsed high-frequency electromagnetic field (PEMF) which may penetrate the scalp and the skull. Increasingly, there is an interest in the interaction of this pulsed microwave radiation with the human brain. Our investigations show that these electromagnetic fields alter distinct aspects of the brain's electrical response to acoustic stimuli. More precisely, our results demonstrate that aspects of the induced but not the evoked brain activity during PEMF exposure can be different from those not influenced by PEMF radiation. This effect appears in higher frequency bands when subjects process task-relevant target stimuli but was not present for irrelevant standard stimuli. As the induced brain activity in higher frequency bands has been proposed to be a correlate of coherent high-frequency neuronal activity, PEMF exposure may provide means to systematically alter the pattern fluctuations in neural mass activity.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

CURRENT brain models of emotion processing hypothesize that positive (or approach-related) emotions are lateralized towards the left hemisphere, whereas negative (or withdrawal-related) emotions are lateralized towards the right hemisphere. Brain imaging studies, however, have so far failed to document such hemispheric lateralization. In a functional magnetic resonance imaging (fMRI) study, 14 female subjects viewed alternating blocks of emotionally valenced positive and negative pictures. When the experience of valence was equated for arousal, overall brain reactivity was lateralized towards the left hemisphere for positive pictures and towards the right hemisphere for negative pictures. This study provides direct support for the valence hypothesis, under conditions of equivalent arousal, by means of functional brain imaging.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

LOW doses of fenvalerate (a Type II pyrethroid) were applied to the beetleTenebrio molitorat pupation, to ascertain its effects on the developing olfactory system. Doses of fenvalerate that prevent the formation of glomeruli in the primary olfactory neuropil (antennal lobes) also inhibit olfactory orientation behavior for different odors, despite the fact that sensory neurons developed responses to these odors. Even when lower amounts of fenvalerate that allowed glomeruli to develop were applied to pupae, the olfactory behavior was affected. Therefore, the formation of glomerular structures within the antennal lobe is not sufficient to establish olfactory behavior. A possible reason for this developmental effect of fenvalerate is a change in the odotopic arrangement of sensory axons within the glomeruli.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID