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排序方式: 共有1481条查询结果,搜索用时 15 毫秒
1.
Rik C. Schoemaker Joop M. A. van Gerven Adam F. Cohen 《Journal of pharmacokinetics and pharmacodynamics》1998,26(5):581-593
The most widely applied model relating drug concentrations to effects is the Emax
model. In practice, concentration–effect relationships often deviate from a simple linear relationship but without reaching a clear maximum because a further increase in concentration might be associated with unacceptable or distorting side effects. The parameters for the Emax
model can only be estimated with reasonable precision if the curve shows sign of reaching a maximum, otherwise both EC50
and Emax
estimates may be extremely imprecise. This paper provides a solution by introducing a new parameter (S0
) equal to Emax/EC50
that can be used to characterize potency adequately even if there are no signs of a clear maximum. Simulations are presented to investigate the nature of the new parameter and published examples are used as illustration. 相似文献
2.
G Harry Van Lenthe Marieke M. M. Willems Nico Verdonschot Maarten C De Waal Malefijt Rik Huiskes 《Acta orthopaedica》2002,73(6):630-637
Although the revision rates for modern knee prostheses have decreased drastically, the total number of revisions a year is increasing because many more primary knee replacements are being done. At the time of revision, bone loss is common, which compromises prosthetic stability. To improve stability, intramedullary stems are often used. The aim of this study was to estimate the effects of a stem, its diameter and the interface bonding conditions on patterns of the bone remodeling in the distal femur.
We created finite element models of the distal half of a femur in which 4 types of knee prostheses were placed. The bone remodeling process was simulated using a strain-adaptive bone remodeling theory. The amount of such remodeling was determined by calculating the changes in bone mineral density in 9 regions of interest from simulated DEXA scans.
The computer simulation model showed that revision prostheses tend to cause more bone resorption than primary ones, especially in the most distal regions. Predicted long-term bone loss due to a revision prosthesis with a thin stem equalled that around a prosthesis with an intercondylar box. However, strong regional differences were found- the stemmed prostheses having more bone loss in the most distal areas and some bone gain in the more proximal ones. A prosthesis with a thick stem led to an increase in bone loss. When the prosthesis-cement interface was bonded, more bone loss was predicted than with an unbonded interface. These results suggest that a stem which increases stability initially may reduce stability in the long term. This is due to an increase in stress shielding and bone resorption. 相似文献
We created finite element models of the distal half of a femur in which 4 types of knee prostheses were placed. The bone remodeling process was simulated using a strain-adaptive bone remodeling theory. The amount of such remodeling was determined by calculating the changes in bone mineral density in 9 regions of interest from simulated DEXA scans.
The computer simulation model showed that revision prostheses tend to cause more bone resorption than primary ones, especially in the most distal regions. Predicted long-term bone loss due to a revision prosthesis with a thin stem equalled that around a prosthesis with an intercondylar box. However, strong regional differences were found- the stemmed prostheses having more bone loss in the most distal areas and some bone gain in the more proximal ones. A prosthesis with a thick stem led to an increase in bone loss. When the prosthesis-cement interface was bonded, more bone loss was predicted than with an unbonded interface. These results suggest that a stem which increases stability initially may reduce stability in the long term. This is due to an increase in stress shielding and bone resorption. 相似文献
3.
4.
Scalp electrical recording during paralysis: quantitative evidence that EEG frequencies above 20 Hz are contaminated by EMG. 总被引:2,自引:0,他引:2
Emma M Whitham Kenneth J Pope Sean P Fitzgibbon Trent Lewis C Richard Clark Stephen Loveless Marita Broberg Angus Wallace Dylan DeLosAngeles Peter Lillie Andrew Hardy Rik Fronsko Alyson Pulbrook John O Willoughby 《Clinical neurophysiology》2007,118(8):1877-1888
OBJECTIVE: To identify the possible contribution of electromyogram (EMG) to scalp electroencephalogram (EEG) rhythms at rest and induced or evoked by cognitive tasks. METHODS: Scalp EEG recordings were made on two subjects in presence and absence of complete neuromuscular blockade, sparing the dominant arm. The subjects undertook cognitive tasks in both states to allow direct comparison of electrical recordings. RESULTS: EEG rhythms in the paralysed state differed significantly compared with the unparalysed state, with 10- to 200-fold differences in the power of frequencies above 20 Hz during paralysis. CONCLUSIONS: Most of the scalp EEG recording above 20 Hz is of EMG origin. Previous studies measuring gamma EEG need to be re-evaluated. SIGNIFICANCE: This has a significant impact on measurements of gamma rhythms from the scalp EEG in unparalysed humans. It is to be hoped that signal separation methods will be able to rectify this situation. 相似文献
5.
6.
B. Willem Schreurs Pieter T. J. Spierings Rik Huiskes Tom J. J. H. Slooff 《Acta orthopaedica》1988,59(4):403-409
We investigated four acrylic cement preparation techniques for their effects on cement porosity: hand mixing, pressurization in a pneumatic pistol, centrifugation, and vacuum mixing. All the techniques were tested on three types of cement with different viscosity characteristics. The best results were obtained with vacuum mixing using a newly designed experimental system, yielding porosity reductions of 60-80 percent relative to hand mixing. Vacuum mixing with a commercial system was also effective, but to a somewhat lesser extent.
Pressurization and centrifugation had no substantial effect on the overall porosity. Centrifugation led to considerable nonuniformity in the distribution of pores and additives. 相似文献
Pressurization and centrifugation had no substantial effect on the overall porosity. Centrifugation led to considerable nonuniformity in the distribution of pores and additives. 相似文献
7.
8.
High responsiveness of HLA-B57-restricted Gag-specific CD8+ T cells in vitro may contribute to the protective effect of HLA-B57 in HIV-infection 总被引:1,自引:0,他引:1
Jansen CA Kostense S Vandenberghe K Nanlohy NM De Cuyper IM Piriou E Manting EH Miedema F van Baarle D 《European journal of immunology》2005,35(1):150-158
HLA-B57 has been shown to be associated with long-term asymptomatic HIV-1 infection. To investigate the biological mechanism by which the HLA-B57 allele could protect from HIV-1 disease, we studied both the number of CD8(+) T cells as well as CD8(+) T cell responsiveness directed to different HIV-1 Gag peptides presented by HLA-A2, -B8 or -B57. T cells specific for the HLA-B57 peptide KAFSPEVIPMF responded more readily and to a higher extend to antigenic stimulation in vitro than T cells specific for the HLA-A2 peptide SLYNTVATL or the HLA-B8 peptide EIYKRWII. This phenomenon was reproducible with T cells from individuals expressing HLA-B57 in combination with one or both of the other alleles and was persistent during long-term follow-up. Lower reactivity of A2- and B8-restricted T cells was not explained by mutations in the B8- or A2-restricted Gag-peptides. Moreover, no correlation between peptide mutation frequency and IFN-gamma production by the corresponding Gag-specific T cells was observed. In conclusion, functional differences were observed between T cells specific for HIV epitopes derived from the same protein presented by different HLA molecules. B57-restricted KAFSPEVIPMF-specific CD8(+) T cells have relatively high responsiveness, which could contribute to the protective effect of HLA-B57 in HIV infection. 相似文献
9.
Comparative genomic hybridization pattern distinguishes T-cell/histiocyte-rich B-cell lymphoma from nodular lymphocyte predominance Hodgkin's lymphoma 总被引:3,自引:0,他引:3 下载免费PDF全文
Franke S Wlodarska I Maes B Vandenberghe P Achten R Hagemeijer A De Wolf-Peeters C 《The American journal of pathology》2002,161(5):1861-1867
Several lines of evidences suggest that T cell/histiocyte-rich B-cell lymphoma (T/HRBCL) represents an aggressive variant of the clinically indolent entity nodular lymphocyte predominance Hodgkin's lymphoma (LPHL). Still, this view has not yet been supported by firm genetic evidence. In this study, we analyzed 17 T/HRBCL cases using comparative genomic hybridization (CGH) combined with microdissection of single CD20+ neoplastic cells and DNA amplification by degenerate oligonucleotide primed-polymerase chain reaction, an approach we previously used in LPHL. Genomic imbalances were detected in all cases (in total, 80 changes). The most common imbalances included gain of Xq, 4q13q28, Xp21p11, and 18q21, and loss of 17p. Of note, a partial gain of 4q, a rare change in lymphoma, is also among the genomic imbalances most frequently encountered in LPHL. On the other hand, the CGH profiles of T/HRBCL and LPHL showed several distinct features, in particular with respect to the number of genomic imbalances (average of 4.7 in T/HRBCL versus 10.8 in LPHL) and their distribution (usually 1 to 5 in T/HRBCL versus 6 to 22 in LPHL). Altogether, our CGH findings of shared as well as distinctive cytogenetic features in both diseases suggest that T/HRBCL constitutes a separate lymphoma entity, possibly originating from the same precursor cell as LPHL. 相似文献
10.
A novel C202F mutation in the connexin26 gene (GJB2) associated with autosomal dominant isolated hearing loss 下载免费PDF全文
Morlé L Bozon M Alloisio N Latour P Vandenberghe A Plauchu H Collet L Edery P Godet J Lina-Granade G 《Journal of medical genetics》2000,37(5):368-370
Mutations in the GJB2 gene encoding connexin26 (CX26) account for up to 50% of cases of autosomal recessive hearing loss. In contrast, only one GJB2 mutation has been reported to date in an autosomal dominant form of isolated prelingual hearing loss. We report here a novel heterozygous 605G→T mutation in GJB2 in all affected members of a large family with late childhood onset of autosomal dominant isolated hearing loss. The resulting C202F substitution, which lies in the fourth (M4) transmembrane domain of CX26, may impair connexin oligomerisation. Finally, our study suggests that GJB2 should be screened for heterozygous mutations in patients with autosomal dominant isolated hearing impairment, whatever the severity of the disease.
Keywords: C202F mutation; connexin26 gene (GJB2); autosomal dominant hearing loss 相似文献
Keywords: C202F mutation; connexin26 gene (GJB2); autosomal dominant hearing loss 相似文献