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排序方式: 共有1283条查询结果,搜索用时 234 毫秒
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DD Lund FM Faraci H Ooboshi BL Davidson DD Heistad 《Canadian Metallurgical Quarterly》1999,30(1):120-125
OBJECTIVE: Regional presynaptic dopaminergic function and its regulation by dopamine agonists in different stages of PD can be measured by L-[11C]dopa and PET. In the current investigation, we studied the effects of therapeutic apomorphine on L-[11C]dopa uptake in patients with early and advanced PD. BACKGROUND: With disease progression and chronic dopamine agonist treatment, motor response complications supervene in a majority of PD patients. It is assumed that both presynaptic and postsynaptic changes in the dopaminergic system act to modify dopaminergic efficacy. METHODS: Patients with early and advanced stages of PD were included in the study. All patients were investigated twice with PET and L-[11C]dopa drug free and during a subsequent standardized therapeutic apomorphine infusion. RESULTS: Subregional analysis of the striatum showed differences in the effects of apomorphine infusion on the L-[11C]dopa influx rate in the two patient categories. In patients with early and uncomplicated PD, apomorphine infusion decreased the L-[11C]dopa influx rate. This decrease was most pronounced in the dorsal part of the putamen. In advanced PD patients, apomorphine did not affect the striatal L-[11C]dopa influx rate. CONCLUSIONS: We suggest that in mild and stable PD an upregulated presynaptic inhibitory feedback regulation, particularly in the dorsal putamen, acts to maintain congruity within the dopaminergic system in response to antiparkinsonian medication. However, this inhibitory feedback regulation is diminished with the progression of nigrostriatal degeneration and chronic dopamine agonist treatment. 相似文献
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JD Amsterdam F Garcia-Espana J Fawcett FM Quitkin FW Reimherr JF Rosenbaum C Beasley 《Canadian Metallurgical Quarterly》1999,19(1):9-14
PURPOSE: To evaluate the potential diagnostic role of mediastinal sonography in patients with cystic fibrosis (CF), we screened the mediastinum of adult CF patients with and without signs of infection and healthy controls. METHODS: Fifty-four consecutive adult patients with CF and 53 healthy volunteers underwent high-resolution mediastinal sonography. The paratracheal region and aorticopulmonary window of each subject were examined for lymph nodes. Each patient was screened for clinical signs of infection. RESULTS: Lymph nodes were detectable in the mediastinum of 39 of 50 CF patients (78%); the mean total lymph node volume was 1.5 +/- 1.7 cm3. Lymph nodes were detectable in the mediastinum of 31 of 50 controls (62%); the mean total lymph node volume in this group was 0.3 +/- 0.3 cm3 (p < 0.001). In the 30 CF patients with signs of infection, the mean total lymph node volume was larger (2.0 +/- 1.8 cm3) than in the 20 CF patients without signs of infection (0.7 +/- 0.9 cm3; p = 0.002). CONCLUSIONS: These results indicate that lymph node volume determination by high-resolution mediastinal sonography may help assess inflammatory activity in patients with CF. 相似文献
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AK Metzger G Mohapatra YA Minn AW Bollen K Lamborn FM Waldman CB Wilson BG Feuerstein 《Canadian Metallurgical Quarterly》1999,90(2):306-314
OBJECT: This study was conducted to determine whether comparative genomic hybridization (CGH) is a more sensitive method for detecting genetic aberrations than other tests currently in use. METHODS: The authors used CGH to examine 40 primary and 13 recurrent adenomas obtained from 52 patients for loss and gain of genetic material. Copy number aberrations (CNAs) were detected in 25 (48%) of the 52 patients studied. The chromosomes affected were, in order of decreasing frequency, 11, 7, X, 1, 8, 13, 5, 14, 2, 6, 9, 10, 12, 3, 18, 21, 4, 16, 15, 19, 22, and Y. Endocrinologically active adenomas were more likely to contain (p = 0.009) and had a greater number (p = 0.003) of CNAs. Of 26 adenomas with CNAs, 18 showed multiple aberrations involving entire chromosomes or chromosome arms. The most frequent CNA involving a chromosome subregion, which was present in four (8%) of 53 adenomas, was the loss of all chromosome 11 material except for a preserved common segment containing 11q13. Immunoperoxidase staining did not detect cyclin D1 expression in those four cases, making cyclin D1 an unlikely target of this rearrangement. CONCLUSIONS: These findings indicate that genetic abnormalities are present in pituitary adenomas at a higher rate than previously reported, are associated with endocrinological activity, and often involve several chromosomes. Rearrangement at 11q13 may inactivate a tumor suppressor gene or activate an oncogene that is important in the initiation or progression of sporadic pituitary adenomas. 相似文献
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A. I. Y. Tok F. Y. C. Boey M. K. A. Khor 《Journal of Materials Engineering and Performance》1999,8(4):469-472
The production of ceramic green tapes is integral to the production of multilayer ceramic packages and capacitors. This article
presents a batch type process for producing alumina ceramic green tape down to 150 μm thickness. The process parameters relevant
to the precise control of the thickness of an aluminabased ceramic tape have been investigated using a float glass tape caster.
Results indicate that the cast tape thickness was dependent on the blade gap until it reached a limiting value. This limiting
thickness in turn was dependent on the casting speed, with a higher speed producing thinner tapes. Optimal casting was shown
to exist when the blade gap was set at or beyond the limiting value, with the casting speed the controlling factor for the
final thickness. 相似文献
8.
Anode-supported solid oxide fuel cells (SOFC) based on gadolinia-doped ceria (GDC) are developed in this study. A carbonate co-precipitation method is used to synthesize the nano-sized GDC powders. A dense GDC electrolyte thin film supported by a Ni–GDC porous anode is fabricated by dry-pressing and spin-coating processes, respectively. In comparison with dry pressing, it is easy to prepare a thinner electrolyte film by the novel spin-coating method. Cell performance is examined using humidified (3% H2O) hydrogen as fuel and air as oxidant in the temperature range of 500–700 °C. Cell performance is strongly dependent on the electrolyte thickness. With a porous Ni–GDC anode, a dense 19-μm GDC electrolyte film and a porous La0.6Sr0.4Co0.2Fe0.8O3–GDC cathode, the cell exhibits maximum power densities of 130, 253, 386 and 492 mW cm−2 at 500, 550, 600 and 650 °C, respectively. It is also found that at the low operating temperature about 500 °C, the cell resistance is significantly dominated by the electrode polarization resistance. 相似文献
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FM Duh SW Scherer LC Tsui MI Lerman B Zbar L Schmidt 《Canadian Metallurgical Quarterly》1997,15(13):1583-1586
By direct sequencing of cosmids using primers designed from the known cDNA sequence, we identified 19 exons in the human MET proto-oncogene, and sequenced the corresponding 5' and 3' exon-intron junctions. By homology search in the database of the Washington University Genome Sequence Center (GSC), we identified one additional exon. These 20 exons, together with a previously reported exon, bring the total exon number of MET to 21. Oligonucleotide primers were designed to amplify each exon and adjacent intronic sequences to permit examination of each exon for mutations. By restriction mapping, we assembled a 110 kb genomic contig that covered almost the entire MET proto-oncogene. This information is relevant for the screening of recently reported mutations of the MET gene which cause hereditary papillary renal carcinomas and for the search for additional mutations of the same gene which may play a role in the pathogenesis of common human carcinomas including carcinomas of the breast, ovary and pancreas. 相似文献