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排序方式: 共有8200条查询结果,搜索用时 15 毫秒
31.
Carmen Cristea Janvin Jan Petter Larsen David P Salmon Douglas Galasko Kenneth Hugdahl Dag Aarsland 《Movement disorders》2006,21(3):337-342
We describe the pattern of cognitive profiles within a community-based sample of patients with Parkinson's disease (PD) and dementia (PDD) using cluster analyses, and compare the results with data from patients with Alzheimer's disease (AD) and dementia with Lewy bodies (DLB). Fifty patients with PDD and 39 with AD from Stavanger, Norway, and 62 patients with DLB from San Diego, CA, USA were diagnosed by either standardized clinical procedures or criteria (all PDD and all AD cases) or necropsy (all DLB cases). Four subgroups were identified: two subgroups with a subcortical cognitive profile (one with mild and one with moderate dementia severity), one subgroup with global impairment and severe dementia, and one subgroup with a cortical cognitive profile and moderate dementia. Of the patients with PDD and with DLB, 56% and 55%, respectively, had a subcortical cognitive profile, compared with only 33% of the AD patients. Conversely, 30% of the patients with PDD and 26% of those with DLB had a cortical cognitive profile, compared with 67% of the patients with AD. These findings suggest that in some patients with PDD, frontosubcortical changes are the main contributing factor to dementia, whereas in other patients, cortical and hippocampal changes are more important. 相似文献
32.
K. Hamby A. Trexler T. C. Pearson C. P. Larsen M. R. Rigby L. S. Kean 《American journal of transplantation》2007,7(8):1884-1896
We have used a sensitive and specific in vivo killing assay to monitor the kinetics, anatomic location and mechanisms controlling NK-mediated rejection of Balb/c bone marrow by C57BL/6 natural killer (NK) cells. We find that NK killing of fully allogeneic bone marrow is a rapid, highly efficient process, leading to substantial rejection of transplanted marrow within 6 h of transplant and elimination of 85% of the transplanted cells within 2 days. NK-mediated rejection occurred predominantly in the spleen, with sparing of rejection in the bone marrow and lymph nodes. Rejection was dependent on Perforin gene function, but was independent of interferon-gamma. Finally, rejection of Balb/c bone marrow by B6 NK cells required signaling through the Ly49D receptor, but occurred despite blockade of NKG2D, which distinguishes these results from previous studies using semiallogeneic transplant pairs. These results identify NK cells as highly active mediators of bone marrow rejection, and suggest that inhibiting NK function early during transplantation may increase the efficiency of engraftment and allow successful engraftment of limiting doses of donor bone marrow. 相似文献
33.
Neural classifier construction using regularization, pruning and test error estimation 总被引:1,自引:0,他引:1
Mads Hintz-Madsen Lars Kai Hansen Jan Larsen Morten With Pedersen Michael Larsen 《Neural networks》1998,11(9):1659-1670
In this paper we propose a method for construction of feed-forward neural classifiers based on regularization and adaptive architectures. Using a penalized maximum likelihood scheme, we derive a modified form of the entropic error measure and an algebraic estimate of the test error. In conjunction with optimal brain damage pruning, a test error estimate is used to select the network architecture. The scheme is evaluated on four classification problems. 相似文献
34.
The long term outcome of open total and partial meniscectomy related to the quantity and site of the meniscus removed 总被引:1,自引:0,他引:1
Summary Two hundred patients were randomly selected for either a partial or a total meniscectomy for a meniscal tear during open operation. They were followed for a median of 7.8 years after operation. After partial meniscectomy, posterior horn tears had the worst outcome, but this was only apparent when more than two-thirds of the meniscus had been removed. The amount of meniscal tissue excised was inversely related to the function of the knee, except with bucket-handle tears treated by partial meniscectomy. Patients with bucket-handle, anterior and posterior horn tears had similar functional results after total meniscectomy. Preservation of the peripheral rim of the meniscus following partial meniscectomy produces the best functional results.
Résumé Deux cents patients atteints de lésion méniscale ont été répartis en cours d'opération, de façon randomisée, entre méniscectomie partielle et méniscectomie totale. Ces patients ont été revus, au dernier examen, de 6.3 à 9.8 ans après l'intervention (à 7.8 ans en moyenne). Après méniscectomie partielle c'étaient les lésions de la corne postérieure qui avaient les moins bons résultats fonctionnels, mais les différences de résultat selon les types de lésion n'étaient observées que lorsque plus d'un tiers de la surface méniscale avait été réséquée. La quantité de tissu méniscal enlevé était inversement proportionnelle à la qualité de la fonction du genou, sauf dans les déchirures en anse de seau traitées par méniscectomie partielle. Ces lésions étaient celles où la plus forte proportion de tissu méniscal avait été réséquée, mais dont les résultats fonctionnels étaient meilleurs que ceux des lésions de la corne postérieure. Les patients présentant des anses de seau, des lésions de la corne antérieure ou de la corne postérieure, avaient des résultats fonctionnels similaires après méniscectomie totale. La conservation de la périphérie du ménisque après méniscectomie partielle est le facteur essentiel d'un bon résultat fonctionnel post-opératoire.相似文献
35.
F G Larsen F Nielsen-Kudsk P Jakobsen K Weismann K Kragballe 《Clinical pharmacokinetics》1992,23(1):42-61
The retinoids are a class of compounds that includes the natural forms and synthetic analogues of vitamin A. Isotretinoin, often referred to as a first generation retinoid, may be of considerable benefit to patients with severe, recalcitrant acne. Etretinate and acitretin, 2 aromatic compounds representing the second generation, have found their major success in the treatment of psoriasis, particularly in combination with more traditional therapies. Retinoid therapy is associated with a distinctive adverse effect profile typical of hypervitaminosis A; thus, it is especially important that fertile women undergoing retinoid therapy adhere to a contraceptive regimen. These drugs are extensively metabolised and only traces of unchanged drugs are eliminated in urine. The terminal elimination half-lives of isotretinoin, etretinate and acitretin after long term treatment are up to 20h, 120 days and 48h, respectively. Because of lack of definite correlation between plasma concentration and desired pharmacological effects, in conjunction with the very pronounced inter- and intraindividual variation in systemic availability (15 to 90%) after oral administration of these drugs, initial dosages in individual patients can only be roughly judged on the basis of the general pharmacokinetics of the agents. Later dosage adjustments should be made on the basis of monitoring of both plasma drug (and possible metabolite) concentrations, and the efficacy and tolerability of the drugs. 相似文献
36.
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A series of water soluble aliphatic solutes were chosen for study. Fifty percent effective doses (ED50) to block propagated compound action potentials (AP's) were obtained by examining dose–response relations for each solute. All solutes used were liquids at room temperature and are typically used as solvents. The solutes studied were dimethylsulfoxide (DMSO), dimethylformamide (DMF), dimethylacetamide, acetone, and hexamethylphosphoramide (HMPA); the octanol/water partition coefficients for these test substances form an ordered sequence that increased 40-fold from DMSO to HMPA. AP's were recorded from desheathed frog sciatic nerves using the sucrose-gap technique; test solutes were added to Ringer's solution and applied externally to the nerve. ED50’s for the solutes could be predicted as a function of the molar volume (dV/dn), polarity (P), and the hydrogen bond acceptor basicity (β). Voltage-clamp experiments employing the vaseline-gap technique on single muscle fibers showed that each solute reduced Na+current with little change in their kinetics at all voltages studied. Experiments using DMSO or DMF showed that Na+channel block alone is insufficient to explain the respective ED50 values of AP block. Experiments conducted using a chloride transport-sensitive membrane fluidity assay, using rat pancreas secretory granules, suggested that each of the solutes act to increase membrane fluidity at doses below and above ED50 values. Light microscopic observations of fixed thick sections of whole nerves previously exposed to DMSO or DMF show structural changes; however, ED50 values cannot be simply explained by osmotic alterations of nerve structure. ED50’s are likely to be produced by a combination of effects including osmotically induced nerve structural changes, ion channel block, and fluidity changes. The toxicity (lethal doses or toxic concentrations) of each of these five solutes correlates well with the ED50 and could be predicted as a function of dV/dn, P, and β. 相似文献
39.
Frank S. Stay Albert Katko Christina M. Rohm Melissa A. Fix David P. Larsen 《Archives of environmental contamination and toxicology》1989,18(6):866-875
Comparisons were made among Leffler microcosms developed from four different natural communities and exposed to 0, 20, 100, 200, 500, 1,000, and 5,000 g/L atrazine, a commonly used herbicide. Atrazine reduced net primary productivity, pH, and net productivity/respiration ratios in all four microcosm communities. In three of the four communities, the lowest observed (P < 0.05) effect concentration (LOEL) was 100 g/L. In the fourth community the LOEL was 200 g/L atrazine.The sensitivity and accuracy of bioassays with four different microcosm communities were evaluated by comparing results with values reported for acute and chronic single species bioassays, other types of microcosms, and experimental ponds exposed to similar concentrations of atrazine. The ranges of sensitivity noted in these experiments were less than the range reported for single species bioassays using common test organisms and similar to those reported for other microcosms. The similarity between Leffler microcosm results and the responses reported for the experimental ponds suggests that the Leffler microcosms accurately reflected concentrations causing ecosystem level changes in the experimental ponds. 相似文献
40.
Lawrence SM Larsen JO Horch KW Riso R Sinkjaer T 《Journal of biomedical materials research》2002,63(5):501-506
Polymer-based longitudinal intrafascicular electrodes (polyLIFEs) were chronically implanted into the sciatic nerve of white New Zealand rabbits (n=8) for a period of 6 months (hereafter referred to as the long-term group). The impact of the implantation procedure, as observed 6 months post surgery, was evaluated in a sham-treated control group (n=9). The contralateral sciatic nerve served as the control for each animal. Nerve-fiber counts, fiber diameters, and myelin thickness were estimated at the level of the implant site, 1.5 cm proximally, and 1.5 cm distally for both nerves in sham-treated and long-term groups. Implantation of polyLIFEs had no significant effect on fiber counts, nerve-fiber diameter, or myelin thickness. A slight increase in connective tissue in the vicinity of the implant site was evident in the long-term group, including a thin but dense capsule immediately surrounding the implanted electrode. 相似文献