Effects of unilateral electrical stimulation of various thalamic nuclei on the release of dopamine from dendrites and nerve terminals of neurons of the two nigrostriatal dopaminergic pathways

The role of several motor and intralaminar thalamic nuclei in the regulation of dopamine release from terminals and dendrites of the nigrostriatal dopaminergic neurons was investigated in halothane-anaesthetized cats. For this purpose, the effects of the unilateral electrical stimulation of various thalamic nuclei on the release of newly synthesized [3H]dopamine were simultaneously determined in both substantiae nigrae and caudate nuclei using the push-pull cannula method. The electrical stimulation of the motor nuclei was the only one to induce asymmetric changes in the four structures since [3H]dopamine release was enhanced in the ipsilateral caudate nucleus and reduced in the contralateral structure while opposite responses were observed in the corresponding substantiae nigrae. A reduction of [3H]dopamine release occurred in the four structures or only in the contralateral substantia nigra and caudate nucleus following the stimulation of the parafascicularis nucleus and the adjacent posterior part of the nucleus centrum medianum or of the nucleus centralis lateralis and the adjacent paralaminar part of the nucleus medialis dorsalis, respectively. The stimulation of the anterior part of the nucleus centrum medianum, which in contrast to other thalamic nuclei examined, receives few nigral inputs, selectively enhanced [3H]dopamine release in the contralateral substantia nigra. No significant changes in [3H]dopamine release were seen either in the substantiae nigrae or in the caudate nuclei following the stimulation of midline thalamic nuclei. These results indicate that the motor and intralaminar thalamic nuclei exert multiple and selective influences on the release of dopamine from terminals and/or dendrites of the dopaminergic neurons. They also further support a role of thalamic nuclei in the transfer of information from one substantia nigra to the contralateral dopaminergic neurons. The possible involvement of connections between paired thalamic nuclei was underlined by the observations of evoked potentials in contralateral homologous nuclei following unilateral stimulation of motor, or some intralaminar, nuclei. The present report provides new insights on the mechanisms contributing to the reciprocal and/or bilateral regulations of nigrostriatal dopaminergic pathways.     

Effects of nigral application of muscimol on release of [3H]γ-aminobutyrate and on multi-unit activity in various cat thalamic nuclei

The release of [³H]γ-aminobutyrate (GABA) neosynthesized from [³H]glutamine was estimated in one substantia nigra and in the ipsilateral thalamus of halothane-anesthetized cats by perfusing a [³H]glutamine-enriched physiological medium through a push-pull cannula implanted in the two structures under investigation. After two hours of superfusion, muscimol (10^?6 M) was delivered through the nigral push-pull cannula for 50–60 min and local- and distal-evoked changes of [³H]GABA release were analyzed. In some experiments, changes of global neuronal activity induced by muscimol application were recorded in different thalamic nuclei, using a bipolar electrode. In a few of the above experiments, biochemical and electrophysiological determinations were simultaneously performed in the substantia nigra and the thalamus. The nigral application of muscimol (10^?6 M) induced locally an activation of the substantia nigra reticulata cells, as well as an increase in release of [³H]GABA.Distally, in the thalamus, two types of biochemical and electrophysiological responses were observed according to the localization of the tip of the push-pull cannula or the electrode. (1) An increased release of [³H]GABA and a depression of the global multi-unit cellular activity were obtained in the ventralis medialis-ventralis lateralis, the centralis lateralis and the paracentralis nuclei. These effects could reflect an activation of the GABAergic nigrothalamic neurons projecting to these different thalamic nuclei. (2) In contrast, in the medialis dorsalis paralamellar zone adjacent to the intralaminar nuclei of the thalamus, a decrease of [³H]GABA release and an activation of the multi-unit activity were obtained. These latter results may suggest either a polysynaptic response or the non-GABAergic nature of the nigrothalamic neurons afferent to the medialis dorsalis paralamellar zone.     

Evaluation of the ICT Malaria Pf test for rapid post-mortem diagnosis of Plasmodium falciparum malaria in corpses examined for forensic reasons

To test the diagnostic value of a rapid and simple immunochromatographic test (ICT) based on the detection of Plasmodium falciparum histidine-rich protein 2 (PfHRP2) for post-mortem examination, blood samples from 30 consecutive corpses were analysed by ICT and Giemsa-stained blood films. Compared to microscopy, ICT had 100% sensitivity and 100% specificity even after a considerable time had passed between the presumed time of death and testing or after prolonged storage of whole blood samples. The ICT yielded positive results for four travellers who had returned from Kenya and died from Pl. falciparum malaria. The ICT might therefore serve as an additional tool for rapid malaria diagnosis, especially in non-endemic countries where experience with microscopic malaria detection is limited. Received: 5 August 1999 / Received in revised form: 7 October 1999     

Dematin,a human erythrocyte cytoskeletal protein,is a substrate for a recombinant FIKK kinase from Plasmodium falciparum

P. falciparum causes the most deadly form of malaria, resulting from the adherence of infected red blood cells to blood vessels. During the blood stage of infection, the parasite secretes a large number of proteins into the host erythrocyte. The secretion of a 20-member family of protein kinases known as FIKK kinases, after a conserved Phe-Ile-Lys-Lys sequence motif, is unique to P. falciparum. Identification of physiological substrates of these kinases may provide perspective on the importance of FIKK kinase activity to P. falciparum virulence. We demonstrate, for the first time, the heterologous expression and purification of a FIKK kinase (PfFk4.1, PFD1165w). The recombinant kinase is active against general substrates and phosphorylates itself. Having demonstrated kinase activity, we incubated recombinant Fk4.1 with parasite and human erythrocyte lysates. No parasite-derived substrates were identified. However, treatment of erythrocyte ghosts shows that the FIKK kinase Fk4.1 phosphorylates dematin, a cytoskeletal protein found at the red blood cell spectrin–actin junction.     

Pattern of antibodies to the Duffy binding like domain of Plasmodium falciparum antigen Pf332 in Senegalese individuals

Acquisition of antibodies against blood stage antigens is crucial in malaria immunity and the Plasmodium falciparum antigen Pf332, which is present in close association with the infected red blood cell membrane, is one such antigen. In this study, the antibody response to a Duffy binding like fragment of Pf332, termed Pf332-DBL was investigated in sera from naturally exposed individuals living in Dielmo village, Senegal, with regard to immunoglobulin classes (IgG, IgM, IgE) and IgG subclasses (IgG1–4). While the levels of IgM, IgG, IgG1 and IgG2 only displayed a moderate trend to increase with age, Pf332-DBL specific IgG3 levels increased significantly in the older villagers. In multivariate analysis, when controlling for confounding factors, and in a linear model with a Poisson distribution, anti-Pf332-DBL IgG3 as well as the ratio of cytophilic to non cytophilic anti-Pf332-DBL antibodies were found significantly associated with a reduced risk of malaria attack. This association was also present when the IgG3:IgG1 ratio was tested. Finally, two subgroups of villagers with the same mean age, were delineated by IgG3 concentrations either lower or higher than the median value. A total of 45.2% of the individuals with low anti-Pf332-DBL-IgG3 levels but only 21.4% of the villagers in the group with high levels of such antibodies had a clinical malaria attack during a period of 3 years of continuous follow-up after the blood sampling. In conclusion, Pf332-DBL induces naturally the acquisition of antibodies, and Pf332-DBL-specific IgG3 appears to be associated with protection against malaria in this endemic setting.     

恶性疟原虫11.1基因3个重复片段的克隆及表达

目的　克隆和表达恶性疟原虫 (Pf) 11 1基因产物中的 3个重复片段 3R、6R和 9R。方法　利用设计的引物从培养的恶性疟原虫 3D7株的基因组DNA中扩增出 3个重复片段。PCR产物被克隆入pT7载体中以进双向测序。测序结果用GENETYX MAC软件进行分析。扩增的片段亚克隆入pET32a(+ )或pET32b(+ ) ,并由IPTG诱导在大肠杆菌BL2 1中表达重组蛋白。结果　用PCR方法成功地扩增出 3R、6R和 9R片段 ,大小分别为 5 5 2、630和44 4bp。测序结果显示 ,3D7株的Pf11 1基因比PaloAlto株的Pf11 1基因多 4个 3AA和 1个 6AA重复单元 ,两原虫株的 3R和 6R片段的同源性分别 92 8%和 95 1%。扩增出的 9R片段含有 13个 9AA重复单元。在BL2 1菌株中表达出三个重组蛋白 ,分子量分别为 45、60和 42kDa。结论　用PCR方法分别获得 3R、6R和 9R重复片段并在大肠杆菌中成功表达。 3D7株的Pf11 1基因与PaloAlto株具有高度同源性     

恶性疟原虫Pf332基因片段的分泌型、非分泌型真核表达重组质粒的构建

目的 构建包含恶性疟原虫Pf332基因片段的分泌型、非分泌型真核表达重组质粒。方法 从FCCl／HN株基因组DNA中PCR扩增P1332基因片段，P332-RO、P332-R1和P332-R2；用PCR扩增法合成鼠IgG轻链信号肽的编码序列。用定向克隆法分别构建分泌型重组质粒pcDNA3-s—P332-R0、pcDNAl-s—P332-R1、pcDNA3-s—P332-R2和非分泌型重组质粒pcDNA3-s—P332-R0、pcDNA3—s—P332-R1、pcDNA3—s—P332-R2。阳性克隆的重组质粒DNA经酶切、PCR扩增及测序鉴定。结果 PCR扩增得到特异的FCCl／HN株P1332基因片段，P332-R0、P332-R1、P332-R1，大小分别为489、429和393bp。用PCR扩增法合成63bp的Balb／c小鼠IgG轻链信号肽的编码序列。酶切、PCR及测序鉴定表明获得了正确的含P1332基因片段的分泌型、非分泌型重组质粒。结论 成功构建分别包含恶性疟原虫P1332基因片段-1332-R0、P332-R1和P332-R2的分泌型、非分泌型真核表达重组质粒。     

Reversible attenuation of neuropathic-like manifestations in rats by lesions or local blocks of the intralaminar or the medial thalamic nuclei

BACKGROUND AND AIM: Thalamic somatosensory nuclei have been classified into medial and lateral systems based on their role in nociception. An imbalance between these two systems may result in abnormal somatic sensations and spontaneous pain. This study aims to investigate the effects of transient or permanent block of the medial and intralaminar nuclear groups on the neuropathic-like behavior in a rat model for mononeuropathy. METHODS: Neuropathy was induced on one hind paw in different groups of rats following the spared nerve injury model. When the resulting hyperalgesia and allodynia (tactile and cold) reached a maximum plateau, the rats received either chemical or electrolytic lesion or lidocaine (2%) microperfusion, placed in the various thalamic nuclear groups. RESULTS: All procedures produced transient but significant decrease of neuropathic manifestations. The magnitude and duration of decrease depended on the type and the site of the block. These effects can be ranked in increasing order as follows, electrolytic相似文献   

Recognition of synthetic polypeptides corresponding to the N- and C-terminal fragments of Plasmodium falciparum Exp-1 by T-cells and plasma from human donors from African endemic areas

The present work describes the recognition of three synthetic polypeptides encompassing the N- and C-terminal regions of the transmembrane Exp-1 protein of the parasite Plasmodium falciparum by plasma and peripheral blood mononuclear cells from naturally exposed individuals living in African endemic areas. The three polypeptides comprise the sequences 23-105, 73-162 and 101-162, and overlap at the transmembrane domain (73-105). Thus, they permitted characterization of the immune response specific to the N- and C-terminal domains in an independent fashion. Two different populations were evaluated, one in the village of Safo in Mali and the other in the villages of Somnaway, Kabortenga and Toussouktenga in Burkina Faso. Antibodies to the sequence 73-162 of Pf Exp-1 were found in 70% of adult Mali donors and in all of the donors tested from Burkina Faso. Strikingly, the N-terminal fragment Pf Exp-1 23-105 was only weakly recognized by a few donors. Evaluation of the T-cell response indicated that the peptide Pf Exp-1 23-105 was more potent than Pf Exp-1 73-162 in inducing a proliferative response. A correlation between peptide-specific interferon-gamma and interleukin-6 production and proliferation to peptide Pf Exp-1 23-105 was observed. Further studies are needed to evaluate this molecule as a vaccine candidate.     

Single thalamic neurons which project to both the rostral cortex and caudate nucleus studied with the fluorescent double labeling method

After injections of fast blue into the rostral cortex and Evans blue into the caudate nucleus in cats, doubly labeled neurons were present in the ventral anterior, ventral lateral, rhomboid, and mediodorsal thalamic nuclei. Doubly labeled cells were also found in most members of the intralaminar group, including the central medial, paracentral, central lateral, and parafascicular nuclei. Although the centromedian nucleus contained large numbers of cells labeled with Evans blue which project to the caudate nucleus, and a few fast-blue labeled cells which projected to the cortex, doubly labeled neurons were absent from this posterior intralaminar nucleus in this study.