Docosahexaenoic acid supplementation in vegetarians effectively increases omega-3 index: A randomized trial

Low red blood cell (RBC) membrane content of FPA+DHA (hereafter called omega-3 index) has recently been described as an indicator for increased risk of death from coronary heart disease. The relationship between plasma and RBC FA, focusing on omega-3 index, and the response to DHA supplementation were investigated in a double-blind, randomized, placebo-controlled, intervention study. Healthy vegetarians (87 f, 17 m) consumed daily a microalgae oil from Ulkenia sp. (0.94 g DHA/d) or olive oil (placebo) for 8 wk. DHA supplementation significantly increased DHA in RBC total lipids (7.9 vs. 4.4 wt%), in RBC PE (12.1 vs. 6.5 wt%), in RBC PC (3.8 vs. 1.4 wt%), and in plasma phospholipids (PL) (7.4 vs. 2.8 wt%), whereas EPA levels rose to a much lesser extent. Microalgae oil supplementation increased the omega-3 index from 4.8 to 8.4 wt%. After intervention, 69% of DHA-supplemented subjects (but no subject of the placebo group) reached an omega-3 index above the desirable value of 8 wt%. Omega-3 index and EPA+DHA levels in RBC PE, RBC PC, and plasma PL were closely correlated (r always >0.9). We conclude that an 8-wk supplementation with 0.94 g DHA/d from microalgae oil achieves a beneficial omega-3 index of ≥8% in most subjects with low basal EPA+DHA status. RBC total FA analyses can be used instead of RBC lipid fraction analyses for assessing essential FA status, e.g., in clinical studies.     

Structural mean models for compliance analysis in randomized clinical trials and the impact of errors on measures of exposure

Partial compliance with assigned treatment regimes is common in drug trials and calls for a causal analysis of the effect of treatment actually received. As such observed exposure is no longer randomized, selection bias must be carefully accounted for. The framework of potential outcomes allows this by defining a subject-specific treatment-free reference outcome, which may be latent and is modelled in relation to the observed (treated) data. Causal parameters enter these structural models explicitly. In this paper we review recent progress in randomization-based inference for structural mean modelling, from the additive linear model to the structural generalized linear models. An arsenal of tools currently available for standard association regression has steadily been developed in the structural setting, providing many parallel features to help randomization-based inference. We argue that measurement error on exposure is an important practical complication that has, however, not yet been addressed. We show how standard additive linear structural mean models are robust against unbiased measurement error and how efficient, asymptotically unbiased inference can be drawn when the degree of measurement error bias is known. The impact of measurement error is illustrated in a blood pressure example and finite sample properties are verified by simulation. We end with a plea for more and careful use of this methodology and point to directions for further development.     

Monitoring the development of hepatocellular carcinoma in woodchucks using 31P-MRS

The woodchuck is one of the only lab animal models of chronic viral hepatitis infection and the development of hepatocellular carcinoma. Using this model, changes in tissue energetics in the liver due to the development of hepatocellular carcinoma can be monitored by repeated magnetic resonance imaging and localized phosphorus spectroscopy. Age- and sex-matched control (n=5) and chronically infected (n=5) adult woodchucks were imaged four times in a six-month period in a 7-T horizontal-bore magnet. Using a custom-built doubly tunable quadrature volume coil, sagittal and axial FLASH images (128×128, slice thickness = 5 mm, TR/TE=1000/4.1, 8 averages) were acquired to locate the largest portion of the liver with the least amount of signal contamination from surrounding abdominal muscle. Two-dimensional 31P chemical-shift imaging (2D-CSI) was acquired (16×16 data matrix, 24×24×2 cm³, 1024 data points, 16 averages) for all animals. The extent of liver injury was determined using serum gamma glutamyltransferase (GGT). The livers of infected woodchucks showed a significant increase (p=0.01) in phosphomonoesters (PME):β-adenosine triphosphate (NTP). Chronically infected woodchucks had higher levels of serum GGT compared to uninfected woodchucks (p=0.002). An increase in the PME:β-NTP ratio indicates cellular proliferation within the malignant tumor.     

Acute toxicity removal in textile finishing wastewater by Fenton's oxidation, ozone and coagulation-flocculation processes

This study evaluates the effectiveness of Fenton's oxidation (FO) process and ozone (O3) oxidation compared with a coagulation-flocculation (CF) process to remove effluent toxicity as well as colour and COD from a textile industry wastewater. Daphnia magna was used to test acute toxicity in raw and pre-treated wastewater. The operational parameters for each process were determined on the basis of complete toxicity removal. The FO process removed COD at a higher rate (59%) than O3 (33%) while colour removal was similar (89% and 91%, respectively). The CF process removed both COD and colour at rates similar to the FO process. A colour range of 150-250 platin-cobalt (Pt-Co) unit was assessed for toxicity.     

Relative vs. absolute statistical analysis of compositions: a comparative study of surface waters of a Mediterranean river

Most hydrogeological research includes some sort of statistical study, which is generally conducted on the raw measures of chemical variables, though there are several theoretical and practical studies warning against this practice. Arguments refer mainly to the positive character of this type of data, and to the fact that they carry only information about the relative abundance of each component on the whole, what makes techniques based on correlation, like the widely used Principal Component Analysis (PCA), loose their meaning. The solution proposed by Aitchison (1982, Journal of the Royal Statistical Society, Series B 44(2), 139-177)-based on working with log-ratios of observations-is equivalent to define a new distance between compositions and to adapt usual statistical techniques to it. To illustrate its effect, our study compares the performance of the biplot-a PCA graphical technique-according to the usual Euclidean and to the Aitchison distance. The study is conducted on a set of 14 molarities measured monthly through the years 1997-1999 at 30 different stations along the Llobregat River and its tributaries (Barcelona, NE Spain). Ordinary analysis, implicitly based on an Euclidean distance, presents some deficiencies, mainly because it only captures major ion variations and the inferred relationship between them actually depends on other non-relevant variables, such as water mass. An analysis based on compositional distances captures variations of all the ions; it is robust against the inclusion of non-relevant variables in the analysis; and it offers a way to build factors expressed as equilibrium equations. In our case, two promising factors are extracted, showing the different anthropogenic and geological pollution sources of the rivers.     

A hip wear simulator with 100 test stations

A novel high-capacity hip wear simulator of the pin-on-disc type was designed, built, and validated. This so-called Super-CTPOD (circularly translating pin-on-disc) device has as many as 100 separate test stations, being an advanced version of the previously validated 12-station CTPOD. A validity test was done so that in all stations the specimens and the test conditions were as similar as possible. Hence, for the first time in this field, an adequate number of similar tests was done for a proper statistical analysis of wear data. The pins were conventional, gamma-sterilized ultra-high molecular weight polyethylene, and the discs were polished CoCr. The lubricant was diluted calf serum and the test length 3 million cycles. In the course of the test, the pins became highly polished, whereas the discs remained practically unchanged. The majority of the polyethylene wear particles were rounded, with a mean diameter of 0.25 microm. The 100 wear factor values computed from the 100 steady state wear rate values of the pins were normally distributed, the mean +/- 95 per cent confidence interval being 1.63 +/- 0.017 x 10(-6) mm3 /N m. The standard deviation was 5.4 per cent of the mean. There were no outliers. The wear mechanisms and the wear factor agreed well with clinical findings. Altogether, the Super-CTPOD test system was shown to be a unique combination of validity, low variation, capacity, efficiency, reliability, productivity, economy, ease of operation, and compact size.     

Effect of interface conditions between ultrahigh molecular weight polyethylene and polymethyl methacrylate bone cement on the mechanical behaviour of total shoulder arthroplasty

The aim of this study was to investigate the effect of the interface condition between polymethyl methacrylate (PMMA) bone cement and the ultrahigh molecular weight (UHMWPE) glenoid component on cement stresses and glenoid component tilting in a finite element (FE) model. The background of this research is that most FE models assume bonding between the PMMA bone cement and the UHMWPE component, although it is very doubtful that this bonding is present. An FE model of a cemented glenoid component was developed and a joint compression force and subluxation force of 725 and 350 N respectively were applied. The maximal principal stresses in the cement layer ranged between 21.30 and 32.18 MPa. Glenoid component tilting ranged between 0.943 degrees and 0.513 degrees. It was found that the interface condition has a large effect on the maximal principal stresses and glenoid component tilting. Whether adhesion between the UHMWPE component and PMMA bone cement occurs is unknown beforehand and, as a result, design validation using the FE technique should be carried out both by using contact elements in combination with a coefficient of friction as well as by a full bonding at this interface.     

Microvascular growth, development, and remodeling in the embryonic avian kidney: the interplay between sprouting and intussusceptive angiogenic mechanisms

Embryonic development is associated with extensive vascular growth and remodeling. We used immunohistochemical, light and electron microscopical techniques, as well as vascular casting methods to study the developing chick embryo kidney with special attention to the interplay between sprouting and intussusceptive vascular growth modes. During inauguration at embryonic day 5 (E5), the early mesonephros was characterised by extensive microvascular sprouting. By E7, the vascular growth mode switched to intussusception, which contributed to rapid kidney vasculature growth up to E11, when the first obvious signs of vascular degeneration were evident. The metanephros underwent similar phases of vascular development inaugurating at E8 with numerous capillary sprouts and changing at E13 to intussusceptive growth, which was responsible for vascular amplification and remodeling. A phenomenal finding was that future renal lobules arose as large glomerular tufts, supplied by large vessels, which were split into smaller intralobular feeding and draining vessels with subsequent formation of solitary glomeruli. This glomerular duplication was achieved by intussusception, i.e., by formation of pillars in rows and their successive merging to delineate the vascular entities. Ultimately, the maturation of the vasculature was achieved by intussusceptive pruning and branching remodeling. An interesting finding was that strong VEGF expression was associated with the sprouting phase of angiogenesis while bFGF was upregulated during the phase of intussusceptive microvascular growth. We conclude that microvascular growth and remodeling in avian kidney follows an adroitly crafted pattern, which entails a precise spaciotemporal interplay between sprouting and intussusceptive angiogenic growth modes supported partly by VEGF and bFGF.