摘要:

The effects of electromagnetic fields (EMF) emitted by cellular phones on the ERD/ERS of the 4–6 Hz, 6–8 Hz, 8–10 Hz and 10–12 Hz EEG frequency bands were studied in 16 normal subjects performing an auditory memory task. All subjects performed the memory task both with and without exposure to a digital 902 MHz EMF in counterbalanced order. The exposure to EMF significantly increased EEG power in the 8–10 Hz frequency band only. Nonetheless, the presence of EMF altered the ERD/ERS responses in all studied frequency bands as a function of time and memory task (encoding vs retrieval). Our results suggest that the exposure to EMF does not alter the resting EEGper sebut modifies the brain responses significantly during a memory task.

ISSN:0959-4965    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

In order to study the pharmacological action of the NO donor SIN-1 upon laryngeal motoneurons, we focally iontophoresed SIN-1 onto single motoneurons identified by antidromic stimulation of the recurrent nerve. SIN-1 produced opposing effects on motoneuron activities. Of 34 identified motoneurons, 38.2% showed a statistically significant decrease (decreasing group), while 29.4% showed an increase in their antidromic response to SIN-1 application (increasing group), respectively. The remaining neurons did not show any change (no change group). When the antidromic spike amplitude during the precontrol period was compared between the three groups, both the increasing and decreasing groups exhibited larger antidromic spikes than those measured in the no change group. The results are discussed in terms of dual pharmacological actions of NO.

ISSN:0959-4965    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

The pathological hallmarks of Prion disease are cortical spongi-form changes and neuronal loss, which are induced by the accumulation of the scrapie-isoform prion protein (PrPSc). PrPScis derived from a post-translational modification of the cellular form of prion protein (PrPC). Heat-shock proteins, a group of molecular chaperones, are involved in the degradation of denatured proteins and post-translational folding of newly synthesized polypeptides. In an attempt to examine any possible relationship between heat shock stress and an induction of prion protein (PrP), human NT-2 cells were treated with heat shock at 42°C for 30 min. After heat-shock treatment, both the level of mRNA and PrPCprotein were analyzed at various time points by Northern and Western blot, respectively. There was a 1.5-to 2.5-fold increase in PrP mRNA levels 1 and 3 h following heat shock. In addition, a two-fold increase in protein level of PrP was found 3 h after heat-shock treatment. These results suggest that cellular stress induces the elevation of both PrP mRNA and protein synthesis. The up-regulation of prion-protein mRNA and protein, implies that PrP may play a role in cellular stress.

ISSN:0959-4965    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

A fundamental property of the human brain is the ability to make predictions of future sensory and motor events. We have recently found that steering manoeuvres when walking along curvilinear trajectories are controlled by an anticipatory guidance of the direction of head (and eyes). However it is unclear whether a time-related or space-related signal triggers such anticipatory head orienting movements. By simulating navigation along a multi-legged virtual corridor we show that anticipatory orienting movements are triggered (in standing subjects) by reaching specific locations rather than by the time to the approaching corridor's bend. Similar to what happens in car driving, specific spatial features of the route rather than time to collision seem to drive steering.

ISSN:0959-4965    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

The interstitial nucleus of Cajal (iC) is a center of the velocity-to-position integration for vertical and torsional eye movements. In addition, iC has projections to and from the vestibular nuclei. Therefore the vestibular influence on the binocular alignment of vertical–torsional nystagmus after unilateral reversible iC inactivations was investigated in the alert monkey using 3D binocular search-coil recordings. The nystagmus was compared with the eye muscle rotation axes, which were corrected for the tonic ocular torsion elicited by the iC inactivation. Rotation axes of nystagmus were different for both eyes and revealed a co-activation of eye muscles similar to the effects of electrical stimulation of the anterior canal nerve. This suggests that, in addition to the deficient neural integrator, a vestibular imbalance contributes to the vertical–torsional nystagmus after iC inactivations.

ISSN:0959-4965    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

Regional cerebral blood flow (rCBF) was measured using PET and H215O in Parkinson's disease (PD) patients with predominantly right-sided akinetic-rigid symptoms and in control subjects during the execution of an externally cued motor task either with the left or the right hand. During the execution of the task with the left, non-akinetic, hand, cerebral activation in PD patients appeared similar to that of controls. Activated areas were the primary motor cortex, premotor cortex, parietal cortex and cerebellum. When the task was executed with the right, akinetic, hand cerebral activation in PD patients differed from that of controls subjects. The most important change was a bilateral activation of the primary motor cortex. We conclude that overactivation of primary motor cortex is asymmetrical in hemiparkinsonian patients.

ISSN:0959-4965    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

The aim of our study was to investigate the influence of gonadal steroids on the expression of different GAD isoforms. Here we show that, in addition to the adult GAD forms, the two embryonic splice variants of GAD67 mRNA and the truncated GAD25 are present in the adult rat olfactory bulb, a brain region with high synaptic plasticity, which has preserved some features of the developing brain. By Western blot analysis, we could demonstrate that the expression of the embryonic GAD25 is cyclic in females: its quantity is higher on estrus day. Furthermore, in ovariectomized animals 17-β-estradiol treatment induced an increase of GAD25 within 3 h, reaching a maximum at 9–12 h. Our data are compatible with the interpretation that the embryonic GAD isoforms may play a role in the neuroplastic changes induced by sexual steroids.

ISSN:0959-4965    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

We tested whether familial aggregation of Down syndrome and Alzheimer's disease (AD) is present for trisomies of other autosomes. We compared rates of Alzheimer-like dementia in the parents of women with trisomic pregnancy losses (n= 109) with those in parents of women with chromosomally normal losses (n= 151) and births (n= 216). Relative risks of Alzheimer-like dementia in parents of women with trisomic losses were 1.2 (95% Cl 0.6, 2.2) and 0.9 (95% Cl 0.5, 1.5) in comparison to parents of women with chromosomally normal losses and births, respectively. Associations were similar among women whose index pregnancy occurred before age 35 or later. Our data do not support an association between the occurrence of AD and trisomy of all autosomal chromosomes. They raise the possibility that familial aggregation with AD is specific to trisomy 21.

ISSN:0959-4965    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

Calcitonin gene-related peptide (CGRP), a neuropeptide synthesized by motor neurons, stimulates the expression of AChR and AChE at the vertebrate neuromuscular junctions. The signaling mechanism of CGRP-induced AChE expression in muscle was determined bothin vitroandin vivo. In cultured chick myotubes, the intracellular cAMP-dependent protein kinase (PKA) activity increased to ∼2-fold after the application of CGRP or PKA activators; the induction was blocked by PKA inhibitors.in vivotransfection analysis on chick gastrocnemius muscles showed that the transfection of cDNA encoding constitutively active mutant Gαsincreased the expression of AChE mRNA and protein to ∼2-fold, while the constitutively active mutant GαicDNA transfection showed an opposite effect. The induced catalytic subunit of AChE at ∼105 kDa was determined by specific antibody. These findings indicate that the CGRP-induced AChE expression in chick muscle is mediated by a PKA-dependent pathway.

ISSN:0959-4965    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

S100B is a calcium binding protein expressed and secreted by astrocytes. Extracellular S100B stimulates the proliferation of astroglial cells and the survival of neurons. Extracellular signal regulated kinases (ERK) are involved in the transduction of proliferating signals in astrocytes. Here we report that S100B significantly increases the activity of ERK in primary cultures of astrocytes, a result which may be related to previous observations of the effect of this protein on glial proliferation. We further confirm that conversion of S100B to its covalent dimer by oxidation of cysteine residues increases its extracellular activity. Although we cannot exclude S100B involvement in other mechanisms of signal transduction, these results suggest that ERK activity in astrocytes is modulated by extracellular S100B.

ISSN:0959-4965    

出版商:OVID    

年代:2000

数据来源: OVID