Evaluating equivalency between response systems: application of the Rasch model to a 3-level and 5-level EQ-5D

BACKGROUND: Expansion of the EQ-5D health state classifier to 5 levels (EQ-5D-5L) has been proposed to improve discriminative and evaluative properties, but current preference-based algorithms were developed for a 3-level (EQ-5D-3L) structure. The objectives were to examine equivalency of meaning between 3L and 5L response systems, and to psychometrically derive a system of weights that facilitate conversion of 3L preference-based algorithms to a 5L system. METHODS: Rasch models were used to examine the equivalency of the 3L and 5L systems using 2 datasets where health status was assessed using the 3L and 5L: a Dutch study of primarily hypothetical health state assessments and a US-based multicenter study of 423 cancer patients. Category-specific mean values of latent person parameters (using maximum likelihood estimation) for the levels of the 3L and 5L systems were estimated. RESULTS: Means on the latent continuum pertaining to level 3 in the 5L system and level 2 in the 3L (some problems) were similar for both datasets, suggesting equivalence of these levels. Extremes of the 5L response structure consistently broadened the measurement continuum. By anchoring "no problems" as 0 disutility, disutility weights from EQ-5D-3L were transformed into weights for EQ-5D-5L using ratios of logit distances between person means for 5L and 3L calibrated for each dimension using the Rasch model. CONCLUSIONS: This study illustrates the rich potential for modern psychometric techniques both to examine equivalency when health status measures are modified as well as to inform preference-based measurement systems using existing value sets.     

Analyses of deep mammalian sequence alignments and constraint predictions for 1% of the human genome

A key component of the ongoing ENCODE project involves rigorous comparative sequence analyses for the initially targeted 1% of the human genome. Here, we present orthologous sequence generation, alignment, and evolutionary constraint analyses of 23 mammalian species for all ENCODE targets. Alignments were generated using four different methods; comparisons of these methods reveal large-scale consistency but substantial differences in terms of small genomic rearrangements, sensitivity (sequence coverage), and specificity (alignment accuracy). We describe the quantitative and qualitative trade-offs concomitant with alignment method choice and the levels of technical error that need to be accounted for in applications that require multisequence alignments. Using the generated alignments, we identified constrained regions using three different methods. While the different constraint-detecting methods are in general agreement, there are important discrepancies relating to both the underlying alignments and the specific algorithms. However, by integrating the results across the alignments and constraint-detecting methods, we produced constraint annotations that were found to be robust based on multiple independent measures. Analyses of these annotations illustrate that most classes of experimentally annotated functional elements are enriched for constrained sequences; however, large portions of each class (with the exception of protein-coding sequences) do not overlap constrained regions. The latter elements might not be under primary sequence constraint, might not be constrained across all mammals, or might have expendable molecular functions. Conversely, 40% of the constrained sequences do not overlap any of the functional elements that have been experimentally identified. Together, these findings demonstrate and quantify how many genomic functional elements await basic molecular characterization.     

28-way vertebrate alignment and conservation track in the UCSC Genome Browser

This article describes a set of alignments of 28 vertebrate genome sequences that is provided by the UCSC Genome Browser. The alignments can be viewed on the Human Genome Browser (March 2006 assembly) at http://genome.ucsc.edu, downloaded in bulk by anonymous FTP from http://hgdownload.cse.ucsc.edu/goldenPath/hg18/multiz28way, or analyzed with the Galaxy server at http://g2.bx.psu.edu. This article illustrates the power of this resource for exploring vertebrate and mammalian evolution, using three examples. First, we present several vignettes involving insertions and deletions within protein-coding regions, including a look at some human-specific indels. Then we study the extent to which start codons and stop codons in the human sequence are conserved in other species, showing that start codons are in general more poorly conserved than stop codons. Finally, an investigation of the phylogenetic depth of conservation for several classes of functional elements in the human genome reveals striking differences in the rates and modes of decay in alignability. Each functional class has a distinctive period of stringent constraint, followed by decays that allow (for the case of regulatory regions) or reject (for coding regions and ultraconserved elements) insertions and deletions.     

脊髓组织工程的体外构建

目的:观察神经干细胞在聚乳酸-羟基乙酸支架上的生长和分化行为,探讨组织工程体外构建人工脊髓修复脊髓损伤。方法:实验于2005-10/2006-06在南京医科大学第一附属医院中心实验室完成。①在聚乳酸-羟基乙酸支架(孔径200～300μm,孔隙率90%,聚乳酸/聚羟基乙酸=75∶25;山东医疗器械研究所)上种植孕14d的胚胎大鼠脑细胞,培养7d。②将培养7d的聚乳酸-羟基乙酸支架置入含体积分数为0.05的胎牛血清和含脑源性神经营养因子20μg/L的DMEM/F12培养基中继续培养5d,诱导其向神经元分化。③用倒置相差显微镜和扫描电镜观察细胞在聚乳酸-羟基乙酸支架上的生长和分化行为;应用免疫组织化学鉴定聚乳酸-羟基乙酸支架上培养的细胞。结果:①神经干细胞生长形态:神经干细胞克隆球充满聚乳酸-羟基乙酸支架孔隙,其形状近似孔隙的不规则几何形状。②神经干细胞超微结构:诱导分化后,大量神经干细胞长出的神经突触跨越支架孔隙的三维空间结构,布满支架的表面和孔隙,并彼此建立了突触联系。③诱导分化前后的聚乳酸-羟基乙酸石蜡切片免疫组织化学鉴定结果:诱导分化前后免疫组织化学鉴定分别为巢蛋白和微管相关蛋白2抗体阳性,说明诱导分化前是神经干细胞,诱导分化后有神经元形成。结论:聚乳酸-羟基乙酸适合神经干细胞的生长和分化,其孔隙结构规范调节了神经干细胞生长增殖的空间排列,而脑源性神经营养因子调控了神经干细胞的分化方向,可以利用该支架的空间结构和细胞因子适度调控神经干细胞在聚乳酸-羟基乙酸上的生长和分化构建脊髓组织。     

Selective inhibition of human diploid fibroblast collagen synthesis by interferons.

The effects of alpha- and gamma-interferons (IFNs) on collagen production by confluent human diploid fibroblasts in culture were examined. It was found that partially purified alpha-IFNs and affinity purified gamma-IFNs caused greater than 50% inhibition of collagen synthesis by these cells independently of their effect on cell proliferation. Recombinant alpha-IFNs showed a similar effect (38.8% inhibition), indicating that collagen synthesis inhibition was a constitutive property of IFNs. Collagen synthesis inhibition by IFNs was concentration dependent. Gel filtration chromatography of the newly synthesized proteins from the media of fibroblasts incubated with partially purified alpha-IFNs demonstrated a selective depression of molecules eluting in the region of procollagen. No detectable increase in collagen degradation products or underhydroxylation of procollagen was observed. Short-term kinetic studies further demonstrated that the major effect of IFNs was due to a net decrease in fibroblast collagen production rather than to impairment of secretion or increased extracellular degradation of the newly synthesized molecules. These results indicate that alpha- and gamma-IFNs are potent inhibitors of human fibroblast collagen production and suggest that they may play an important role in the regulation of normal and pathologic fibrogenesis.     

Drug abusers and poisoned patients: a potential source of organs for transplantation?

One of the major constraints to transplantation of solid organs is lack of availability of grafts and any attempt to use all available donors is to be welcomed. We address the possibility of expanding the transplant donor pool by inclusion of more patients who have suffered intoxication with drugs premortem. Particularly important in this context is the exclusion of organ-specific damage, and also infective risk to the potential recipient due to viral causes in the donor.      

Elevated plasma total homocysteine and C677T mutation of the methylenetetrahydrofolate reductase gene in patients with spina bifida

Total plasma homocysteine (tHcy) was significantly higher in 28 children with spina bifida (median 6.05 mumol/l) as compared with 76 controls (median 4.94 mumol/l). This difference was confined to a subgroup of patients (16/28) with one or two C677T-mutated alleles in the methylenetetrahydrofolate reductase gene. Since we found no significant difference between patients and controls in serum folate, erythrocyte folate, serum cobalamin or serum methylmalonic acid, which were within the normal range for both patients and controls, the elevated tHcy could not be attributed to vitamin deficiencies. Our findings point to an additional genetic defect involving folate- dependent enzymes in a subgroup of patients with neural-tube defects.      

Chronic hepatitis C and B-cell non-Hodgkin's lymphoma

Hepatitis C virus (HCV), a hepatotropic and lymphotropic virus, is the major causative agent of nonA-nonB chronic hepatitis; moreover, it is frequently associated with benign and malignant lymphoproliferative disorders such as mixed cryoglobulinaemia and B-cell non-Hodgkin's lymphoma (NHL). We investigated the clinical and virological features of B-cell NHL complicating chronic hepatitis C in a series of 10 patients (M/F 1/9; mean age 63 +/- 6SD years). The malignancy appeared after median 8 +/- 4SD years from onset and was low-grade in six patients, intermediate in three, and high-grade in one. 'One-tube nested' PCR detected serum HCV RNA and viral ongoing replication in both fresh and cultured peripheral lymphocytes in all ten. Analysis of HCV genotypes showed a relatively higher prevalence of 2a/III type compared with unselected chronic hepatitis C (50% vs. 15%). In one patient, HCV RNA was also found in the neoplastic bone marrow and lymph- node specimens. B-cell NHL can complicate chronic hepatitis C and affect the overall prognosis of the disease. The increasing frequency of chronic hepatitis C worldwide suggests that the actual prevalence of this complication may be underestimated. Careful clinical work-up at diagnosis and during follow-up is particularly recommendable.      

Fixed dosage of low-molecular-weight heparins causes large individual variation in coagulability, only partly correlated to body weight

Summary. Backgrounds: Low‐molecular‐weight heparins (LMWHs) are routinely given without the control of their effect on coagulation. The endogenous thrombin potential (ETP) is a sensitive detector of the heparin effect. Question: What is the interindividual variation in TG after a fixed dose of LMWH in normal volunteers, is it explained by variation in weight? Methods: Subcutaneous (s.c.) injection, in 12 healthy volunteers, of 9000 aXa‐units of unfractionated heparin (UFH) and of three heparins with narrow MW distribution around 10.5, 6.0 and 4.5 kD. Measurement of anti‐thrombin (aIIa) and antifactor Xa (aXa)‐activities and ETP at 11 time points over 24 h. Results: The coefficient of variation (CV) of the AUCs of aXa‐ and aIIa‐activities is 50% for UFH and 22–37% for LMWHs. Because of the hyperbolic form of the dose–response curve, the CV of the inhibition of the ETP is lower: 32% for UFH and 13–21% for the LMWHs. Fixed dosage of LMWH caused under‐dosage in 10–13% of the samples and over‐dosage in 5–11%. High or low response is an individual property independent of the type of heparin injected and only partially explained by variation in body weight. Conclusion: Optimized individual dosage of LMWH is possible through recognition of high and low responders, which requires one measurement of the heparin concentration or, preferably, the heparin effect on the ETP, 2–5 h after a first injection.