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  • 1
    Digitale Medien
    Digitale Medien
    Protection against dopaminergic nigrostriatal cell death by excitatory input ablation (2000)
    Oxford, UK : Blackwell Science Ltd
    European journal of neuroscience 12 (2000), S. 0 
    Details
    ISSN: 1460-9568
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: The importance of enhanced glutamatergic neurotransmission in the basal ganglia and related structures has recently been highlighted in the development of Parkinson's disease. The pedunculopontine tegmental nucleus (PPN) is the major origin of excitatory, glutamatergic input to dopaminergic nigrostriatal neurons of which degeneration is well known to cause Parkinson's disease. Based on the concept that an excitatory mechanism mediated by glutamatergic neurotransmission underlies the pathogenesis of neurodegenerative disorders, we made an attempt to test the hypothesis that removal of the glutamatergic input to the nigrostriatal neurons by PPN lesions might prevent 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced parkinsonism in the macaque monkey. The PPN was lesioned unilaterally with microinjection of kainic acid, and, then, MPTP was administered systemically. In these monkeys, the degree of parkinsonian motor signs was behaviourally evaluated, and the histological changes in the dopaminergic nigrostriatal system were analysed by means of tyrosine hydroxylase immunohistochemistry. The present results revealed that nigrostriatal cell loss and parkinsonian motor deficits were largely attenuated in the MPTP-treated monkey group whose PPN had been lesioned, compared with the control, MPTP-treated monkey group with the PPN intact. This clearly indicates that the onset of MPTP neurotoxicity is suppressed or delayed by experimental ablation of the glutamatergic input to the nigrostriatal neurons. Such a protective action of excitatory input ablation against nigrostriatal cell death defines evidence that nigral excitation driven by the PPN may be implicated in the pathophysiology of Parkinson's disease.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1046/j.1460-9568.2000.00062.x
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  • 2
    Digitale Medien
    Digitale Medien
    Down-regulation of metabotropic glutamate receptor 1α in globus pallidus and substantia nigra of parkinsonian monkeys (2005)
    Oxford, UK : Blackwell Science Ltd
    European journal of neuroscience 22 (2005), S. 0 
    Details
    ISSN: 1460-9568
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Enhanced glutamatergic neurotransmission via the subthalamopallidal or subthalamonigral projection seems crucial for developing parkinsonian motor signs. In the present study, the possible changes in the expression of metabotropic glutamate receptors (mGluRs) were examined in the basal ganglia of a primate model for Parkinson's disease. When the patterns of immunohistochemical localization of mGluRs in monkeys administered systemically with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) were analysed in comparison with normal controls, we found that expression of mGluR1α, but not of other subtypes, was significantly reduced in the internal and external segments of the globus pallidus and the substantia nigra pars reticulata. To elucidate the functional role of mGluR1 in the control of pallidal neuron activity, extracellular unit recordings combined with intrapallidal microinjections of mGluR1-related agents were then performed in normal and parkinsonian monkeys. In normal awake conditions, the spontaneous firing rates of neurons in the pallidal complex were increased by DHPG, a selective agonist of group I mGluRs, whereas they were decreased by AIDA, a selective antagonist of group I mGluRs, or LY367385, a selective antagonist of mGluR1. These electrophysiological data strongly indicate that the excitatory mechanism of pallidal neurons by glutamate is mediated at least partly through mGluR1. The effects of the mGluR1-related agents on neuronal firing in the internal pallidal segment became rather obscure after MPTP treatment. Our results suggest that the specific down-regulation of pallidal and nigral mGluR1α in the parkinsonian state may exert a compensatory action to reverse the overactivity of the subthalamic nucleus-derived glutamatergic input that is generated in the disease.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1460-9568.2005.04488.x
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  • 3
    Digitale Medien
    Digitale Medien
    Organization of prefrontal outflow toward frontal motor-related areas in macaque monkeys (2004)
    Oxford, UK : Blackwell Science Ltd
    European journal of neuroscience 19 (2004), S. 0 
    Details
    ISSN: 1460-9568
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Linkage between the prefrontal cortex and the primary motor cortex is mediated by nonprimary motor-related areas of the frontal lobe. In an attempt to analyse the organization of the prefrontal outflow from area 46 toward the frontal motor-related areas, we investigated the pattern of projections involving the higher-order motor-related areas, such as the presupplementary motor area (pre-SMA) and the rostral cingulate motor area (CMAr). Tracer injections were made into these motor-related areas (their forelimb representation) on the medial wall that had been identified electrophysiologically. The following data were obtained from a series of tract-tracing experiments in Japanese monkeys. (i) Only a few neurons in area 46 were retrogradely labelled from the pre-SMA and CMAr; (ii) terminal labelling from area 46 occurred sparsely in the pre-SMA and CMAr; (iii) a dual labelling technique revealed that the sites of overlap of anterograde labelling from area 46 and retrograde labelling from the pre-SMA and CMAr were evident in the rostral parts of the dorsal and ventral premotor cortices (PMdr and PMvr); (iv) and tracer injections into the PMdr produced neuronal cell labelling in area 46 and terminal labelling in the pre-SMA and CMAr. The present results indicate that a large portion of the prefrontal signals from area 46 is not directly conveyed to the pre-SMA and CMAr, but rather indirectly by way of the PMdr and PMvr. This suggests that area 46 exerts its major influence on the cortical motor system via these premotor areas.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.0953-816X.2004.03425.x
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  • 4
    Digitale Medien
    Digitale Medien
    Organization of inputs from cingulate motor areas to basal ganglia in macaque monkey (2001)
    Oxford, UK : Blackwell Science Ltd
    European journal of neuroscience 14 (2001), S. 0 
    Details
    ISSN: 1460-9568
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: The cingulate motor areas reside within regions lining the cingulate sulcus and are divided into rostral and caudal parts. Recent studies suggest that the rostral and caudal cingulate motor areas participate in distinct aspects of motor function: the former plays a role in higher-order cognitive control of movements, whereas the latter is more directly involved in their execution. Here, we investigated the organization of cingulate motor areas inputs to the basal ganglia in the macaque monkey. Identified forelimb representations of the rostral and caudal cingulate motor areas were injected with different anterograde tracers and the distribution patterns of labelled terminals were analysed in the striatum and the subthalamic nucleus. Corticostriatal inputs from the rostral and caudal cingulate motor areas were located within the rostral striatum, with the highest density in the striatal cell bridges and the ventrolateral portions of the putamen, respectively. There was no substantial overlap between these input zones. Similarly, a certain segregation of input zones from the rostral and caudal cingulate motor areas occurred along the mediolateral axis of the subthalamic nucleus. It has also been revealed that corticostriatal and corticosubthalamic input zones from the rostral cingulate motor area considerably overlapped those from the presupplementary motor area, while the input zones from the caudal cingulate motor area displayed a large overlap with those from the primary motor cortex. The present results indicate that a parallel design underlies motor information processing in the cortico-basal ganglia loop derived from the rostral and caudal cingulate motor areas.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1046/j.0953-816x.2001.01789.x
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  • 5
    Digitale Medien
    Digitale Medien
    Detection of hepatocellular carcinoma and its metastases with various pulse sequences using superparamagnetic iron oxide (SHU-555-A) (2000)
    Springer
    Abdominal imaging 25 (2000), S. 151-158 
    Details
    ISSN: 1432-0509
    Schlagwort(e): Key words: SPIO—SHU-555-A—HCC—Metastasis—MRI—CTAP.
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Background: To identify the most useful combinations of various pre- and postcontrast magnetic resonance (MR) image sequences in detecting hepatocellular carcinoma (HCC) and its intrahepatic metastases before and after injection of SHU-555-A. Methods: Thirty-eight lesions in 16 patients were evaluated before and after administration of SHU-555-A by using fast spin echo (FSE), gradient echo (GRE), and echo planar (EP) imaging sequences using a 1.5-Tesla superconducting MR system. The signal intensity ratio (SIR) and contrast-to-noise ratio (CNR) of the lesions, signal-to-noise ratios, and other parameters were calculated. Results: Tumors were better detected after injection of SHU-555-A on all pulse sequences except on out-of-phase T1-weighted (T1W)-GRE sequences. Tumor detectability was higher for precontrast EP imaging and T2*-weighted (T2*W)-GRE sequences, whereas detectability at postcontrast was higher for T2*W-GRE, proton-density-weighted-FSE, and in-phase T1W-GRE sequences. The SIR and CNR at precontrast were highest for EP imaging, and those at postcontrast were highest for T2*W-GRE. Conclusion: SHU-555-A will increase the detectability of HCC and its liver metastases. T1W- and T2*W-GRE sequences would be the sequences of choice.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002619910035
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  • 6
    Digitale Medien
    Digitale Medien
    Thalamic afferents to layer I of anterior sigmoid cortex originating from the VA-VL neurons with entopeduncular input (1987)
    Springer
    Experimental brain research 69 (1987), S. 67-76 
    Details
    ISSN: 1432-1106
    Schlagwort(e): Thalamocortical projection ; VA-VL nuclear complex ; Anterior sigmoid gyrus ; Layer I ; Entopeduncular nucleus
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Seventy seven thalamic neurons in the VA-VL nuclear complex of the cat which projected to the anterior sigmoid gyrus (ASG) were studied extracellularly, and their responses to stimulation of both the cerebellar nuclei (CN) and the entopeduncular nucleus (ENT) were examined. Forty two neurons were inhibited by ENT-stimulation but were not excited by CN-stimulation, while 27 neurons were excited by CN-stimulation but were not inhibited by ENT-stimulation. Eight neurons were inhibited by ENT-stimulation and also excited by CN-stimulation. Distribution of axons in each layer of ASG was examined by means of antidromic activation of the thalamic neurons by microstimulation at various depths of ASG. Almost all (13/14) of the ENT-inhibited neurons examined were antidromically activated by microstimulation in layer I with currents less than 35 μA. On the other hand, most (11/13) of CN-excited neurons were antidromically activated by weak microstimulation in layers deeper than the second, but were not activated by microstimulation in layer I with currents less than 40 μA. VA-VL neurons with inhibitory input from ENT were considered to project mainly to layer I of ASG.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00247030
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  • 7
    Digitale Medien
    Digitale Medien
    Movement-related activity of thalamic neurons with input from the globus pallidus and projection to the motor cortex in the monkey (1991)
    Springer
    Experimental brain research 84 (1991), S. 279-284 
    Details
    ISSN: 1432-1106
    Schlagwort(e): Globus pallidus ; Thalamus ; Motor cortex ; Reaction time task ; Monkey
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Thalamic neurons projecting to the arm area of the motor cortex were identified by their antidromic response to stimulation of that area in two awake monkeys. Neurons were further identified as receiving inputs from the cerebellar nuclei or the internal segment of the globus pallidus by excitatory or inhibitory response to stimulation of these nuclei. Most (33/34) of the thalamic neurons in the cerebello-thalamo-cortical projection and more than half (12/18) of those in the pallido-thalamocortical projection changed their firing rate on the leverlifting hand movement in the reaction-time task. A considerable number of neurons of both groups (14/23 and 3/10) changed their firing rate prior to the onset of the earliest EMG. These findings agree with the model that activities of pallidal as well as cerebellar nuclear neurons related to motor control are transmitted to the motor cortex through the thalamus.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00231447
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  • 8
    Digitale Medien
    Digitale Medien
    Projection on the motor cortex of thalamic neurons with pallidal input in the monkey (1988)
    Springer
    Experimental brain research 71 (1988), S. 658-662 
    Details
    ISSN: 1432-1106
    Schlagwort(e): Pallidum ; Cerebellar nuclei ; Thalamus ; Motor cortex ; Monkey
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The cortical projection areas of thalamic neurons with basal ganglia and/or cerebellar inputs were studied electrophysiologically in unanesthetized monkeys. Thalamic neurons which receive inhibition from the pallidum were found to project to the motor cortex (area 4) as well as to premotor cortex. The neurons with pallidal input and motor cortical projection were located mainly in VLo. This result indicates that the basal ganglia innervate the motor cortex through the thalamus. Thus the basal ganglia can modify the cortical output for controlling movements directly through this pathway as compared with its influence through the prefrontal and premotor cortices.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00248759
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  • 9
    Digitale Medien
    Digitale Medien
    Two-dimensional thick-slice MR digital subtraction angiography for assessment of cerebrovascular occlusive diseases (2000)
    Springer
    European radiology 10 (2000), S. 1858-1864 
    Details
    ISSN: 1432-1084
    Schlagwort(e): Key words: MR imaging – Contrast material – MR angiography – Cerebrovascular disease – Brain
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract. Although spatial resolution of current MR angiography is excellent, temporal resolution has remained unsatisfactory. We evaluated clinical applicability of 2D thick-slice, contrast-enhanced subtraction MR angiography (2D-MR digital subtraction angiography) with sub-second temporal resolution in cerebrovascular occlusive diseases. Twenty-five patients with cerebrovascular occlusive diseases (8 moyamoya diseases, 10 proximal internal carotid occlusions, and 2 sinus thromboses ) were studied with a 1.5-T MR unit. The MR digital subtraction angiography (MRDSA) was performed per 0.97 s continuously just after a bolus injection of 15 ml of gadolinium chelates up to 40 s in sagittal (covering hemisphere) or coronal planes. Subtraction images were generated at a workstation. We evaluated imaging quality and hemodynamic information of MRDSA in comparison with those of routine MR imaging, non-contrast MR angiography, and X-ray intra-arterial DSA. Major cerebral arteries, all of the venous sinuses, and most tributaries were clearly visualized with 2D MRDSA. Also, pure arterial phases were obtained in all cases. The MRDSA technique demonstrated prolonged circulation in sinus thromboses, distal patent lumen of proximal occlusion, and some collateral circulation. Such hemodynamic information was comparable to that of intra-arterial DSA. Two-dimensional thick-slice MRDSA with high temporal resolution has a unique ability to demonstrate cerebral hemodynamics equivalent to that of intra-arterial DSA and may play an important role for evaluation of cerebrovascular occlusive diseases.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s003300000584
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  • 10
    Digitale Medien
    Digitale Medien
    Somatotopical projections from the supplementary motor area to the red nucleus in the macaque monkey (1995)
    Springer
    Experimental brain research 106 (1995), S. 351-355 
    Details
    ISSN: 1432-1106
    Schlagwort(e): Supplementary motor area ; Red nucleus ; Intracortical microstimulation ; Anterograde tracing ; Monkey
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Direct projections from the supplementary motor area (SMA) to the red nucleus were investigated in the Japanese monkey (Macaca fuscata). The anterograde tracer, horseradish peroxidase conjugated to wheat germ agglutinin (WGA-HRP), was injected into various regions of the SMA after intracortical microstimulation mapping. After WGA-HRP injection into the orofacial, forelimb, or hindlimb region of the SMA, anterogradely labeled axon terminals were found, respectively, in the medial, intermediate, or lateral portion of the parvocellular part of the red nucleus, bilaterally with an ipsilateral predominance. The results indicate the clear somatotopical arrangement of corticorubral projections from the SMA.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00241130
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