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Increased Variability (increased + variability)
Selected AbstractsDifferent methods of creatinine measurement significantly affect MELD scoresLIVER TRANSPLANTATION, Issue 4 2007Evangelos Cholongitas Bilirubin (Bil) interferes with creatinine (Cr) measurement. Different laboratory methods are used to overcome this problem. Model for end-stage liver disease (MELD) scoring incorporates Cr and is used to prioritize patients for liver transplantation. Thus, MELD scores may vary with different Cr measurements influencing patients' priority. Our aim was to evaluate 4 different Cr assays (O'Leary modified Jaffe [mJCr], compensated [rate blanked] kinetic Jaffe [cJCr], enzymatic [ECr], and standard kinetic Jaffe [JCr]) in patients with abnormal liver function tests and assess changes in MELD score. A total of 403 consecutive samples from 158 patients' Cr assays were evaluated.. Bland-Altman plots and MELD scores were also evaluated for each assay. Agreement was found to be poor among all Cr assays. Increased variability in Cr occurred with increasing Bil concentrations: Bil <100 ,mol/L ,3-point MELD variation - 3-point difference in 2%; Bil ,400,mol/L ,7-point MELD variation - ,3-point difference in 78%. When MELD was ,25 (mJCr as reference; mean, 30.5 points), MELD variation was greatest: mean, 28 (MELD cJCr), 27.5 (MELD ECr), and 28.4 (MELD JCr) (P < 0.001). In conclusion, there is poor agreement among different assays for Cr. As Bil concentration rises, there is greater variability in each creatinine measurements and thus greater variability in MELD scores that, this affect prioritization for liver transplantation. Liver Transpl, 2006. © 2006 AASLD. [source] Effects of aging and gender on the spatial organization of nuclei in single human skeletal muscle cellsAGING CELL, Issue 5 2010Alexander Cristea Summary The skeletal muscle fibre is a syncitium where each myonucleus regulates the gene products in a finite volume of the cytoplasm, i.e., the myonuclear domain (MND). We analysed aging- and gender-related effects on myonuclei organization and the MND size in single muscle fibres from six young (21,31 years) and nine old men (72,96 years), and from six young (24,32 years) and nine old women (65,96 years), using a novel image analysis algorithm applied to confocal images. Muscle fibres were classified according to myosin heavy chain (MyHC) isoform expression. Our image analysis algorithm was effective in determining the spatial organization of myonuclei and the distribution of individual MNDs along the single fibre segments. Significant linear relations were observed between MND size and fibre size, irrespective age, gender and MyHC isoform expression. The spatial organization of individual myonuclei, calculated as the distribution of nearest neighbour distances in 3D, and MND size were affected in old age, but changes were dependent on MyHC isoform expression. In type I muscle fibres, average NN-values were lower and showed an increased variability in old age, reflecting an aggregation of myonuclei in old age. Average MND size did not change in old age, but there was an increased MND size variability. In type IIa fibres, average NN-values and MND sizes were lower in old age, reflecting the smaller size of these muscle fibres in old age. It is suggested that these changes have a significant impact on protein synthesis and degradation during the aging process. [source] Spectrum separation resolves partial-volume effect of MRSI as demonstrated on brain tumor scansNMR IN BIOMEDICINE, Issue 10 2008Yuzhuo Su Abstract Magnetic resonance spectroscopic imaging (MRSI) is currently used clinically in conjunction with anatomical MRI to assess the presence and extent of brain tumors and to evaluate treatment response. Unfortunately, the clinical utility of MRSI is limited by significant variability of in vivo spectra. Spectral profiles show increased variability because of partial coverage of large voxel volumes, infiltration of normal brain tissue by tumors, innate tumor heterogeneity, and measurement noise. We address these problems directly by quantifying the abundance (i.e. volume fraction) within a voxel for each tissue type instead of the conventional estimation of metabolite concentrations from spectral resonance peaks. This ,spectrum separation' method uses the non-negative matrix factorization algorithm, which simultaneously decomposes the observed spectra of multiple voxels into abundance distributions and constituent spectra. The accuracy of the estimated abundances is validated on phantom data. The presented results on 20 clinical cases of brain tumor show reduced cross-subject variability. This is reflected in improved discrimination between high-grade and low-grade gliomas, which demonstrates the physiological relevance of the extracted spectra. These results show that the proposed spectral analysis method can improve the effectiveness of MRSI as a diagnostic tool. Copyright © 2008 John Wiley & Sons, Ltd. [source] The Hybrid Permit Cum Price Ceiling Policy Proposal: Intuition From The Prices Versus Quantities LiteratureOPEC ENERGY REVIEW, Issue 4 2000Gary W. Yohe The social value of choosing a marketable permit cum price ceiling mechanism over an unencumbered marketable permit scheme to limit the emission of greenhouse gases is explored. Insight from the prices versus quantities literature instructs that this relative valuation weighs the benefit of increased variability in emissions as economic conditions warrant against an increase in the expected cost of climate change. The value of the hybrid scheme is high and carries a low price ceiling when, ceteris paribus, the marginal benefit of emissions reduction is not very sensitive to changes in the regulatory environment, when the marginal cost of reducing emissions is sensitive to that environment, when the variance in marginal cost is high and/or when the distortion created by the initial allocation of permits is large. The value is correspondingly low and the ceiling high when the opposite conditions hold. [source] Menstrual cycle variability and the perimenopauseAMERICAN JOURNAL OF HUMAN BIOLOGY, Issue 4 2001Kathleen A. O'Connor Menopause, the final cessation of menstrual cycling, occurs when the pool of ovarian follicles is depleted. The one to five years just prior to the menopause are usually marked by increasing variability in menstrual cycle length, frequency of ovulation, and levels of reproductive hormones. Little is known about the mechanisms that account for these characteristics of ovarian cycles as the menopause approaches. Some evidence suggests that the dwindling pool of follicles itself is responsible for cycle characteristics during the perimenopausal transition. Another hypothesis is that the increased variability reflects "slippage" of the hypothalamus, which loses the ability to regulate menstrual cycles at older reproductive ages. This paper examines the underlying cause of the increasing variability in menstrual cycle length prior to the menopause. A model of ovarian cycles is developed, based on the process of follicular growth and depletion. Under this model, the follicular phase of each menstrual cycle is preceded by an inactive phase, a period of time when no ovarian follicles have left the resting state and begun secreting steroids in response to gonadotropin stimulation. The model makes predictions about the variability in menstrual cycles across the reproductive life span based on the size of the surviving pool of ovarian follicles. We show that the model can explain several characteristics of the perimenopause in humans and macaques and illustrate how the model can be applied to research on the biological and cultural correlates of the timing of menopause. J. Hum. Biol. 13:465,478, 2001. © 2001 Wiley-Liss, Inc. [source] Control of blood pressure in the absence of sympathetic nerves: Is it all about increased variability?CLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 1 2010Jacqueline Kathleen Phillips No abstract is available for this article. [source] | |||||||||||||