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  • 1
    ISSN: 1432-0509
    Keywords: Key words: SPIO—SHU-555-A—HCC—Metastasis—MRI—CTAP.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: 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.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1106
    Keywords: Key words Putamen ; Primary motor cortex ; Supplementary motor area ; Premotor cortex ; Motor control
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  It is an important issue to address the mode of information processing in the somatic motor circuit linking the frontal cortex and the basal ganglia. In the present study, we investigated the extent to which corticostriatal input zones from the primary motor cortex (MI), the supplementary motor area (SMA), and the premotor cortex (PM) of the macaque monkey might overlap in the putamen. Intracortical microstimulation was performed to map the MI, SMA, and dorsal (PMd) and ventral (PMv) divisions of the PM. Then, two different anterograde tracers were injected separately into somatotopically corresponding regions of two given areas of the MI, SMA, PMd, and PMv. With respect to the PMd and PMv, tracer injections were centered on their forelimb representations. Corticostriatal input zones from hindlimb, forelimb, and orofacial representations of the MI and SMA were, in this order, arranged from dorsal to ventral within the putamen. Dense input zones from the MI were located predominantly in the lateral aspect of the putamen, whereas those from the SMA were in the medial aspect of the putamen. On the other hand, corticostriatal inputs from forelimb representations of the PMd and PMv were distributed mainly in the dorsomedial sector of the putamen. Thus, the corticostriatal input zones from the MI and SMA were considerably segregated though partly overlapped in the mediolateral central aspect of the putamen, while the corticostriatal input zone from the PM largely overlapped that from the SMA, but not from the MI.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-1084
    Keywords: Key words: Magnetic resonance angiography ; Digital subtraction angiography ; Two-dimensional Brain tumor ; Gadolinium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract. The aim of this study was to evaluate clinical applicability of two-dimensional (2D) thick-slice, contrast-enhanced magnetic resonance digital subtraction angiography (MRDSA) with high temporal resolution in diagnosis of brain tumors. Forty-four patients with brain tumors including, 15 meningiomas, 8 gliomas, 6 metastatic tumors, 4 neuromas, and 2 hemangioblastomas, were studied with 2D MRDSA with frame rate approximately 1 s. Images were continuously obtained following the initiation of bolus injection of gadolinium chelates for 40 s and subtraction images were generated in a workstation. We evaluated visualization of normal cranial vessels on MRDSA and compared MRDSA and intra-arterial digital subtraction angiography (IADSA) with regard to hemodynamic information. Large cerebral arteries, all venous sinuses, and most tributaries were clearly visualized. A stain was present in hypervascular tumors including all 15 meningiomas and 2 hemangioblastomas on MRDSA. Presence of a stain demonstrated on MRDSA and that on IADSA coincided in 16 of 20 cases (Spearman rank correlation value was 0.85). The location, shape, and phase of the stain on MRDSA were similar to those on IADSA. Two-dimensional MRDSA with high temporal resolution has a unique ability to demonstrate cerebral hemodynamics, such as IADSA, and can play an important role in assessing brain tumors.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 106 (1995), S. 351-355 
    ISSN: 1432-1106
    Keywords: Supplementary motor area ; Red nucleus ; Intracortical microstimulation ; Anterograde tracing ; Monkey
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: 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.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 69 (1987), S. 67-76 
    ISSN: 1432-1106
    Keywords: Thalamocortical projection ; VA-VL nuclear complex ; Anterior sigmoid gyrus ; Layer I ; Entopeduncular nucleus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: 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.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: 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.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    European journal of neuroscience 19 (2004), S. 0 
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: 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.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: 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.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    European journal of neuroscience 12 (2000), S. 0 
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: 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.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1432-1084
    Keywords: Key words: MR imaging – Contrast material – MR angiography – Cerebrovascular disease – Brain
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: 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.
    Type of Medium: Electronic Resource
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