摘要:

NEURONAL survival during mammalian development crucially depends on target-derived neurotrophic factors. Target loss removes this trophic support and leads in most cases to the transsynaptic retrograde degeneration of the respective afferents. Primary vestibular afferents (PVA) originating from bipolar neurons in the vestibular ganglion (VG) are the first mossy fibers that enter the cerebellum, but little is known about the survival requirements of VG neurons. In the present study the influence of the differential granule cell (GC) target loss on the survival of VG neurons was studied quantitatively using unbiased stereological methods in the cerebellar mutants Purkinje cell degeneration (pcd/pcd), Lurcher (Lc/+), and Weaver (wv/wv). Neither the secondary GC loss in the Purkinje cell deficient mutantspcd/pcdandLc/+, nor the primary loss of GCs inwv/wvproduced any significant reduction in the total number of bipolar neurons in the VG compared to controls. So, PVA neurons are highly resistant to cerebellar target deprivation and survive in the absence of cerebellar granule and Purkinje cells, regardless of whether the target loss occurs before (inwv/wv), during (inLc/+) or after (inpcd/pcd) the mossy fiber-granule cell synaptogenesis.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

THE purpose of this study was to assess thein vivoeffects of melatonin, as an antioxidant, on striatal dopaminergic function in rats with a unilateral 6-hydroxy-dopamine (6-OHDA) lesion of the striatum. Compared with sham-operated controls and expressed as a ratio relative to the contralateral side, there was an increase in the lipid peroxidation product malondialdehyde (MDA, 142%) and a significant reduction in tyrosine hydroxylase (TH) enzyme activity (28%) and dopamine (DA, 32%) and its metabolite dihydroxyphenylacetic acid (DOPAC, 50%) 2 weeks after 6-OHDA injection. Melatonin treatment almost completely restored MDA levels to normal, suggesting thein vivoaction of melatonin as an antioxidant. In parallel, partial, but statistically significant recovery of striatal dopaminergic function, including TH enzyme activity and DA levels, also occurred following melatonin treatment. Taken together with our previous reports showing behavioral and histochemical effects of melatonin on the nigrostriatal dopaminergic system, the present results strongly support the hypothesis that melatonin, as an antioxidant, may have beneficial effects on therapeutic approaches for the treatment of oxidative stress-induced neurodegenerative disease such as Parkinson's disease (PD).

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

ALTHOUGH functional asymmetries in the course of visual information processing have been known for a long time in humans as well as in non-human species, the structural basis of these asymmetries is largely unknown. We now report that due to an asymmetry of commissural projections in the pigeon the left nucleus rotundus of the ascending tectofugal visual system predominantly represents inputs from both eyes while the right nucleus rotundus mainly represents the contralateral left eye. We suggest that a comparable organization exists for several asymmetries in humans. A representation of both hemifields can provide the dominant hemisphere with direct access to all stimulus features when objects cross the vertical meridian.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

WE tested the neuroprotective potential of the Bcl-220–34peptide sequence in hippocampal slices. Treatment with Bcl-2 after fluid percussion trauma significantly improved recovery of CA1 antidromic PS to a mean of 92% ± 1 of initial amplitude, compared with only 16% ± 2 in unmedicated slices. The EC50for trauma protection was 84 μM Bcl-220–34. Protection with Bcl-220–34also extended to long-term potentiation. No protection was seen with the reverse sequence of Bcl-220–34. Treatment with Bcl-220–34also protected against hypoxic damage, with treated slices recovering to 98% ± 2, while unmedicated slices recovered to 14% ± 2. Similar protection was seen against AMPA, NMDA and nitric oxide. These findings indicate that Bcl-220–34provides specific neuroprotection against acute CA1 neuronal injury.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

WE have examined the distribution of androgen receptor (AR) immunoreactivity in L6 and S1 dorsal root ganglia of male rats in order to determine whether the sensory component of reflex circuits is likely to be androgen-sensitive. Nuclear AR immunoreactivity was present in almost half of the neurons, but was decreased markedly by castration; after castration nuclear staining was absent and a few neurons showed dim cytoplasmic staining. Of the neurons possessing AR, half also contained calcitonin gene-related peptide (CGRP); in turn, > 80% of CGRP neurons contained AR. AR staining was present in both large and small CGRP neurons. This study shows that testosterone is likely to influence many sensory neurons and may therefore play an important role in modulating visceral and somatic reflexes.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

WE determined whether exogenous Mg2+and/or mexiletine (Mex), which are reported to be neuroprotective agents, reduced neuronal energy requirements and protected against ischemia, using isolated rabbit retinas. Under non-ischemic conditions, Mex (30 μM) and the combination of Mg2+(1 mM) plus Mex (30 μM) significantly reduced glucose utilization, by 19% and 31%, respectively. The combination of Mg2+plus Mex, but not either agent alone, significantly reduced lactate production (by 18%p< 0.05). When added during 2 h of ischemia (simulated by the reduction of oxygen from 95% to 15% and of glucose from mM to 1 mM), Mg2+plus Mex improved the recovery of glucose utilization (p< 0.01), lactate production (p< 0.05) and neuronal function (p< 0.05) for 3 h following return to control (post-ischemia/recovery) conditions. Thus reducing energy demands by blocking functions during temporary ischemia, protects neurons from irreversible functional damage

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

ITCH sensation is reduced by cooling the skin. We tested whether lowering skin temperature attenuates responses of spinal dorsal horn neurons elicited by intracutaneous (i.c.) microinjection of histamine in anesthetized rats. Cooling the skin to 3°C significantly and reproducibly reduced (to a mean of 48%) i.c. histamine-evoked responses in 20 of 24 wide dynamic range-type dorsal horn neurons. Histamine-evoked responses recovered to control levels after rewarming the skin. Assuming that such neurons play a role in signaling itch, depression of their responses during skin cooling may account for the psychophysical observation that skin cooling relieves itch in humans.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

IN the first of a series of studies aimed at mapping brain stem pathological changes in patients with Alzheimer's disease (AD), we report a new finding regarding the parabrachial nucleus (PBN), a unit of paramount importance in the relay and integration of visceral and nociceptive information as well as in homeostatic control. The brains of 20 patients with AD were surveyed. The PBN contained pervasive neuropathological changes in 100% of the brains from those with early-onset dementia and in 80% from those with late-onset dementia. These changes were entirely absent in all 10 normal controls. The pathological changes of PBN, would cause autonomic dysfunction in patients with AD and perhaps contribute to the disproportionate mortality encountered in these patients.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

BCL-XL and Bcl-2 proteins were identified by paraffin section immunohistochemistry in the neuropil core of the barrelettes of the caudalis spinal trigeminal nucleus 6 h after birth. They were subsequently identified at progressively more rostral levels of the trigeminal pathway, peaking in barreloid neuropil cores in the ventral posterior thalamic nucleus at postnatal day (P)4.5, and in cortical barrel cores at P7. Labelling was confined to the cores of barrel-like structures surrounded by immunonegative shells and became progressively less distinct at all levels from P8. These protein products, which are usually considered to control the onset of apoptosis, may serve other functions in the axon terminal fields of the trigeminal pathway.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

αB-CRYSTALLIN, which is abundantly expressed in the lens but also in a diversity of other tissues, functions as a stress-inducible molecular chaperone and is increased in brain neurodegenerative diseases. We compared retinal αB-crystallin expression in a model of inherited retinal degeneration, th erdmouse, and controls. Northern andin sit uhybridization analysis showe αB-crystallin mRNA to have an altered spatio-temporal pattern with increased levels localized to glial cells in the degenerative state. Immunocytochemistry confirmed increased expression at Müller cells and astrocytes, together with transiently increased localization to the degenerating photoreceptors. These findings suggest that increase dαB-crystallin expression is associated with glial cell reaction to neuronal damage in the retina, and may comprise part of the retina's overall defensive response to the stress of apoptotic photoreceptor cell death.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID