摘要:

THE microtubule-associated protein tau is abnormally hyperphosphorylated in Alzheimer's disease (AD) brain. To date, 21 phosphorylated sites of tau have been identified. In the present study the levels of phosphorylation at Ser199/Ser202, Thr231/Ser235, Ser262/Ser356and Ser396/Ser404of tau in AD brain homogenate and its 100 000 × g supernatant were determined using radioimmuno-dot-blot assay. In homogenate, Ser199/Ser202and Ser262/Ser356were phosphorylated to similar level and were more phosphorylated than Thr231or Ser396/Ser404. In supernatant, there was no significant difference in phosphorylated tau level among the investigated sites except for Thr231/Ser235which was least phosphorylated. These results suggest that Ser199/Ser202and Ser262/Ser356are major sites of phosphorylation of tau in AD brain.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

CEREBELLAR granule cells (CGC) undergo massive DNA fragmentation, an apoptotic marker, in 8-day-old rat cerebellum.In vitro, they survive in the presence of depolarizing concentrations of KCl. Bisindolylmaleimide, a specific PKC inhibitor, blocks CGC apoptosisin vitro. Here I show that PKC δ, which has been involved in apoptosis in different cell lines, is constitutively cleaved in CGC, suggesting that its catalytic subunit is activeper se. Moreover, KCl deprivation induces cyclin D1 expression and accumulation in nuclei. This process is blocked by bisindolylmaleimide. A model is proposed where, in the absence of survival signals, activated PKC δ induces cyclin D1 expression and accumulation in the nucleus, which subsequently, would lead to an aborted cell cycle and apoptosis.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

IN VIVOneuroprotective effects of melatonin on the nigrostriatal dopaminergic system in rats unilateral 6-hydroxydopamine (6-OHDA) lesions were tested. Two weeks after lesioning the dopamine receptor agonist, apomorphine produced rotational asymmetry. In contrast, melatonin treatment significantly reduced the motor deficit following apomorphine challenge. Analysis by tyrosine hydroxylase (TH) immunocytochemistry revealed the loss of cell bodies in the substantia nigra (SN) and absence of terminals in the dorsolateral striatum ipsilaterally. Melatonin treatment also resulted in the survival of dopaminergic neurons in SN and TH-immuoreactive terminals in the dorsolateral striatum. These behavioral and histochemical results may indicate a neuroprotective action of melatonin and suggest a potential pharmacological role in the treatment of Parkinson's disease.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

THE aim of this study was to assess the effect of potential target tissue on regenerating neurones of the snail Lymnaea stagnalis using the three-dimensional collagen gel culture system. Mammalian type I collagen supported the regenerative outgrowth of snail neurones, and the neurofilament antibody SMI31 specifically labelled regenerating processes both within the gel and those growing over the surface of the ganglia. Using these techniques we tested the effect of co-culturing ganglia with either additional nervous tissue, previously shown to produce trophic substances, or buccal muscle on both the amount and direction of outgrowth. We conclude that, under the conditions used, neither target tissue provided trophic or tropic support in collagen gel cultures.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

LUGARO cells are fusiform neurons located just beneath the Purkinje cell layer. Their axon projects profusely in the molecular layer and emits some collaterals in the granular layer. We have analysed the molecular layer postsynaptic targets of a Golgi-impregnated Lugaro cell, using the electronmicroscopic gold-toning procedure and post-embedding anti-GABA immunocytochemistry. All the gold-labeled neuritic and somatic profiles were GABA-positive, thus confirming that the Lugaro cell is an inhibitory interneuron. The axonal varicosities of this cell form multiple symmetrical synaptic junctions with basket and stellate cell somata and proximal dendrites, and, perhaps, with the molecular layer dendrites of Golgi interneurons. Lugaro cells thus seem to exert a feed-back inhibiory control on Purkinje cells.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

IN the normal retinotectal topography established during the embryonic development of the chick visual system, retinal ganglion cell axons from the nasal retina connect to the posterior part and temporal retinal axons connect to the anterior part of the optic tectum. For the investigation of position-specific gene expression along the nasal-temporal axis of the retinal neuroepithelium (RN), differential display PCR was carried out from the nasal or temporal part of the RN at HH11 (E2). We found several genes that are differentially expressed either in the nasal or in the temporal part of the RN and the analysis of the asymmetrically expressed fragments showed at least one cDNA fragment to be exclusively expressed in the nasal RN. This fragment was 550 bp in size.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

ONE issue of continuing debate in language research concerns whether the brain holds separate representations for semantic information through the auditoryvsvisual modalities. Regardless of whether we hear, see or read meaningful information, our brains automatically activate both auditory and visual semantic associations to the sensory input. The prominent models for how the brain makes these cross-modality associations holds that semantic information conveyed through either sensory input modality is represented in a shared semantic system comprising the traditionally identified language areas in the brain. A few recent case reports as well as activation imaging studies, have challenged this notion by demonstrating category-specific organization within the semantic system in spatially discrete brain regions. Neither view posits a role for primary sensory cortices in semantic processing. We obtained positron emission tomographic (PET) images while subjects performed an auditory responsive naming task, an auditory analog to visual object naming. Subjects heard and responded to descriptions of concrete objects while blindfolded to prevent visual stimulation. Our results showed that, in addition to traditional language centres, auditory language input produced reciprocal activation in primary and secondary visual brain regions, just as if the language stimuli had entered in the visual modality. These findings provide evidence for a distributed semantic system in which sensory-specific semantic modules are mutually interactive, operating directly onto early sensory processing centers.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

DIPYRONE, a non-steroidal anti-inflammatory agent, was anticonvulsant in three experimental epilepsy models. At a dose of 300 mg/kg i.p., dipyrone blocked the maximal hind limb extension in the electroshock model in Wistar rats, the tonic-clonic component of acute sound-induced seizures and the limbic component of audiogenic kindling in genetically susceptible Wistar-derived rats, all in 100% of the animals. In the electroshock model higher doses (400 and 500 mg/kg) were also effective but lower doses (100 and 200 mg/kg) were not. In this model dipyrone had no effect on the recovery of the righting reflex and intensified the postictal antinociception in a dose-dependent manner. Other non-steroidal anti-inflammatory agents such as indomethacin, diclofenac and aspirin had no anticonvulsant effect in the electroshock-induced seizures.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

WE previously demonstrated a predominance of contacts by one type of glomerular ending (presumably from unmyelinated fibers) upon postsynaptic sites expressing the GluR1 subunit of the AMPA receptor, and of contacts by another type of glomerular ending (presumably from small myelinated fibers) upon postsynaptic sites expressing GluR2. We here investigate whether any one of three types of primary afferent terminals, two glomerular and one non-glomerular, have direct contacts with postsynaptic sites containing the NMDAR1 subunit. Counts of gold particles revealed that contacts by primary afferents with NMDAR1-positive sites were less frequent than in material processed for AMPA receptor subunits, but that all three types of terminals contact NMDAR1-immunopositive postsynaptic sites in about equal proportions.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

DNA fragmentation, the hallmark of apoptosis, has been recently investigated with contradictory results in several skeletal muscle disorders. Usingin situlabeling of nuclear DNA fragmentation, we have tested the possibility that apoptosis might occur in muscles from patients with mitochondrial respiratory chain defects and other types of metabolic myopathies. A high proportion of apoptotic myonuclei were found in all of 10 patients with mitochondrial myopathies and in one patient with multiple acyl-CoA dehydrogenase deficiency, a disease also affecting mitochondrial metabolism. These findings can be related to the intriguing link existing between apoptosis and mitochondria. It has been demonstrated that a fall of mitochondrial membrane potential constitutes a critical early event in the apoptotic process, and that mitochondrial bcl-2 protein, which protects from apoptosis, apparently functions as an endogenous permeability transition inhibitor.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID