摘要:

THIS study investigated the role of the plantar cutaneous information in controlling human balance. We hypothesized that the cutaneous afferent messages from the main supporting zones of the feet have sufficient spatial relevance to inform the CNS about the body position with respect to the vertical reference and consequently to induce adapted regulative postural responses. Skin mechanoreceptors of anterior and/or posterior areas of one or both soles of 10 standing subjects were activated by superficial mechanical vibration with high frequency and low amplitude. Variations of the subject's center of pressure (CoP) were recorded. Spatially oriented whole-body tilts were observed for every subject. Their direction depended on the foot areas stimulated and was always opposite to the vibration-simulated pressure increase. These responses are found to subserve a postural regulative function and we suggest that co-processing of the various cutaneous messages followed a vector addition mode.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

AN important issue regarding the neural basis of major depression is whether the functional brain changes associated with the affect disturbance seen in this syndrome are similar to those that accompany transient sadness in normal subjects. To address this question, we carried out an fMRI study using an emotional activation paradigm. Brain activity associated with passive viewing of an emotionally laden film clip aimed at inducing a transient state of sadness was contrasted with that associated with passive viewing of an emotionally neutral film clip in patients suffering from unipolar depression and in normal control subjects. Results showed that transient sadness produced significant activation in the medial and inferior prefrontal cortices, the middle temporal cortex, the cerebellum and the caudate in both depressed and normal subjects. They also revealed that passive viewing of the emotionally laden film clip produced a significantly greater activation in the left medial prefrontal cortex and in the right cingulate gyrus in depressed patients than in normal control subjects. These findings suggest that these two cortical regions might be part of a neural network implicated in the pathophysiology of major depression. Taken together, these results strongly support the view that activation paradigms represent an extremely useful and powerful way of delineating the functional anatomy of the various symptoms that characterize major depression.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

COPPER homeostasis in the brain must be strictly maintained, since copper is an essential trace element and is potentially toxic. To understand the mechanism of copper homeostasis in the brain, we cloned several mouse homologues of copper trafficking genes and performedin situhybridization histochemistry. mCTR1, mATX1, and mATP7a were highly expressed in the choroid plexus, indicating that the choroid plexus uses the trafficking pathway from uptake to efflux to transport copper to the cerebrospinal fluids. We suggest that these genes may regulate copper concentration in the brain through the choroid plexus.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

THE latency of components of the auditory evoked neuromagnetic field has been shown to reflect, or encode, stimulus attributes. In particular, the M100 component, occurring ∼100 ms post stimulus onset has a latency that depends on stimulus pitch, spectral complexity and presentation level. This study used magnetoencephalography to record neuromagnetic fields evoked by presentation of two-tone complexes consisting of various proportions of 100 Hz and 1 kHz energy. These are perceived categorically, as evidenced by classification and reaction time measurements. It is found that the M100 latency also varies categorically, that is, characterized by two plateau regions with a sharp interface. Thus, we find that not only does the M100 latency reflect acoustic attributes of a stimulus, but also such perceptual characteristics.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

NEUROPEPTIDE Y (NPY) concentrations were investigated by radioimmunoassay and immunohistochemistry in a murine model of cutaneous leishmaniasis, using a susceptible (BALB/c) and a resistant (C57BL/6) mouse strain. The analyses were performed on the skin, secondary lymphoid organs and dorsal root ganglia (DRG) at 1, 3, 6 and 9 weeks postinfection. An overall reduction in the NPY concentrations in the studied organs was observed in both mouse strains; the reduction in the skin and draining lymph nodes was more evident and progressive in the susceptible strain. Using immunohistochemistry there seemed to be a reduction in NPY immunoreactivity in all inflamed tissues analysed compared to the controls. These observations might indicate a possible pathophysiological role for NPY in murine cutaneous leishmaniasis.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

THE effects of chronic 17β-estradiol (E2) depletion, via ovariectomy (OVX), and its repletion, on cortical cerebral blood flow (CBF) and EEG activities during forebrain ischemia, as well as post-ischemic recovery and neuropathology, were assessed and compared with results obtained in normal female rats. We also examined whether neuronal nitric oxide synthase (nNOS) activity is affected by OVX and E2replacement and whether NOS-derived NO supports vasodilation during ischemia. OVX females displayed a significantly lower CBF during ischemia (10% of baseline) than did normal females (23% of baseline). In OVX rats, given chronic low-dose E2treatment (0.1 mg kg−1day−1), intra-ischemic CBF was similar to normal females (25% of baseline). However, at supraphysiologic E2doses (≥ 0.5 mg kg−1day−1), that benefit was diminished or lost. Intra-ischemic EEG power reductions and post-ischemic survival rates, neurological dysfunction, and histopathology displayed similar relative differences among groups as the CBF findings. Intra-ischemic CBF was reduced by nNOS inhibition, with ARL 17477, in normal and low-dose E2-treated OVX rats (4–8% baseline). The repressed intra-ischemic vasodilating function in OVX rats may be due to reductions in nNOS activity, because untreated OVX rats showed a 50% lower cortical nNOS activity than that in normal rats and in rats treated with low or high dose (5 mg kg−1day−1) E2. However, the inability to restore vasodilating function despite normalization of nNOS activity indicates that another mechanism is responsible for the repression of vasodilatory function in the high-dose group. These findings suggest that E2, at levels within the physiological range, promotes ischemic neuroprotection via improving vasodilating capacity. One possible mechanism may relate to E2enhancing brain nNOS expression and activity.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

NUMEROUS mutations in the presenilin (PS) genes cause early onset familial Alzheimer's disease (FAD). Here we characterize the expression of two naturally occurring alternative PS2 transcripts which lack either exons 3 and 4 (PS2 Δexon 3,4) or exons 3, 4, and 8 (PS2 Δexon 3,4,8). These transcripts do not contain the natural initiation codon within exon 3. The transcripts are efficiently translated as N-terminal truncated proteins. These deleted proteins are still able to regulate formation of endogenous PS fragments, indicating that the C-terminal half of the PS2 protein is sufficient for this phenomenon. Although ∼50% of the PS1 and both PS2 mutations occur within the N-terminal region lacking in the PS2 Δexon3,4 and PS2 Δexon3,4,8 proteins, expression of these truncated proteins does not affect pathological generation of amyloidβ-peptide (Aβ). This suggests that point mutations causing AD are gain of function mutations.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

THE role of the amygdala in major depression was investigated. Resting regional cerebral metabolic rate (rCMRglu) was measured with [18F]fluorodeoxyglucose positron emission tomography (PET) in two samples of subjects using two different PET cameras. The samples consisted of 10 and 17 medication-free depressives and 11 and 13 controls, respectively. Using coregistration of PET and magnetic resonance images, regions were individually delineated for the amygdala and thalamus, the latter of which was used as a control region. Within the depressed groups, right amygdalar rCMRgluwas positively correlated with negative affect. Thalamic rCMRgluwas not related to negative affect, and amygdalar rCMRgluaccounted for a significant portion of variance in depressives' negative affect scores over and above the contribution of thalamic rCMRglu.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

THE effect of a Ca2+resting current on spiking and intra-cellular Ca2+concentration [Ca2+]iof isolated cockroach dorsal unpaired median neurons was investigated by combining microfluometry (Fura2) with patchclamping. The resting current was reduced by 10 μM 5-nitro-2-(3-phenylpropylamino) benzoic acid (NPPB) and 10m μM mefenamic acid, which caused slower spiking of cells. Up-modulation of the resting current by neurohormone D (NHD, 100 fM to 10 pM) transiently increased [Ca2+]i. This Ca2+transient was largely reduced by the ryanodine receptor antagonist dantrolene (10 μM) but it was not reduced by the IP3-receptor antagonist heparin which indicates Ca2+-induced Ca2+release. The NHD-effect on [Ca2+]iwas strongly attenuated by NPPB and mefenamic acid. Thus, NHD caused Ca2+-induced Ca2+release by enhancing the Ca2+resting current.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

THIS study assessed the effect of peripherally applied opioids on the electromyographic activity reflexly evoked in digastric and masseter muscles by injection of the small-fiber excitant and inflammatory irritant mustard oil (MO) into the temporomandibular joint. In 39 anaesthetized rats, local pretreatment of joint tissues with morphine (15 nmol) significantly depressed the jaw muscle responses compared with saline, and the depression was antagonized by simultaneous local injection of the opiate antagonist naloxone (2.7 nmol); systemic morphine pretreatment (15 nmol, i.v.) did not influence the muscle responses. The naloxone-reversible depression of the MO-evoked muscle responses by local, but not systemic morphine, supports the presence of peripheral opioid receptors that may have a role in modulating nociceptive responses.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID