Responsiveness, effect size, and smallest detectable difference of Magnetic Resonance Imaging in knee osteoarthritis

OBJECTIVE

The aim of this study was to determine the responsiveness, effect size (ES) and smallest detectable difference (SDD) of two Magnetic Resonance Imaging (MRI) measures for osteoarthritis (OA) of the knee: a whole-organ semiquantitative evaluation and cartilage volume.

DESIGN

This analysis was performed on a dataset from a randomized, double-blind trial (Roche NI-15713) conducted in 1998 of a novel therapy in subjects with mild-moderate knee OA, with MRI at baseline and 6-month follow-up. The trial measurements included (1) cartilage volume measured using a proprietary software method; and (2) semiquantitative scoring of other parameters important for "whole organ" evaluation of OA knee joint pathology, using the Whole-Organ MRI Score (WORMS). The analysis initially examined the distributional characteristics of WORMS items, such as cartilage morphology. Standardized response mean (SRM), ES, and SDD between baseline and 6-month follow-up were then calculated in the whole group and the placebo group alone.

RESULTS

In general, the differences were small and this was reflected in the small ESs and SRMs. There was also a suggestion of a treatment effect with reduction in differences between baseline and follow-up in the treatment group.

CONCLUSION

Of the MRI semiquantitative measures, cartilage morphology, synovitis and osteophytes appeared to be responsive to change and the focus of repeat measures should highlight these articular features. In general, the ESs and SRMs were small.

Examining a whole-organ magnetic resonance imaging scoring system for osteoarthritis of the knee using Rasch analysis

OBJECTIVE

The ability to reliably quantify all the structural abnormalities in osteoarthritis (OA) of the knee is a long-standing goal of OA research. On December 5 and 6, 2002, Outcome Measures in Rheumatology Clinical Trials and Osteoarthritis Research Society, International held a Workshop for Consensus on Osteoarthritis Imaging in Bethesda, MD, with the aim of providing a state-of-the-art review of imaging outcome measures for OA of the knee. As part of the Workshop, data from previous clinical trials and epidemiological studies of OA were analysed with respect to the metrological properties of the measurement methods used. The following report outlines the results of analyses aimed at evaluating the internal construct validity of a whole-organ, ordinal (semi-quantitative) magnetic resonance imaging score (WORMS) using Rasch analysis. The fit of data to the Rasch model offers a measure of the validity of summing different items into a subscale score and the degree to which this score behaves as a unidimensional, interval level measurement tool.

METHODS

The Rasch model was applied in two OA studies. The first was a clinical cohort comprising OA knee subjects entering a clinical trial; study entry criteria included patients with at least moderate pain, radiographic osteophytes and a minimum of 1.5mm tibiofemoral joint-space width. The second cohort was from the Boston Osteoarthritis Knee Study, an observational cohort of subjects with symptomatic knee OA with pain on most days and a definite osteophyte in either the tibiofemoral or patellofemoral joints. Baseline WORMS scores from both studies were used for the Rasch analysis, performed with RUMM 2020 software.

RESULTS

There was a substantial proportion of subjects in both study populations with zero scores in several of the subscales of WORMS. Few of the subscales met the requirements of the Rasch measurement model when summated across all sites, and summations of some postulated compartmentally based sites also failed to fit the Rasch model. The existing scoring categories also required rescoring at many sites.

CONCLUSION

There remain important issues in constructing outcome measurements that summate different features across multiple anatomical sites. The whole-organ scoring system evaluated here is no exception. Resolving these issues will improve the ability of imaging studies to assess complex pathological structural change.

In-vitro dynamic micro-probing and the mechanical properties of human prostate tissues

In vitro macro- and micro-indentation test systems have been designed to measure the dynamic micro-mechanical properties of human prostate tissues at actuation frequencies between 5 Hz and 30 Hz, and 0.5 Hz and 20 Hz, respectively. The development of in vitro test systems was aimed at assessing the capacity of such an in vivo medical probe to provide information useful for the diagnosis of various prostate diseases. The macro-indentation test system is an established one, which we have used to determine structure-property relationships in human and canine prostate tissues and here we use it to validate a newly-developed micro-indentation test system using a tissue phantom. Mechanical testing was also carried out on sections of prostate tissue harvested from cystectomy and radical prostatectomy, diagnosed with bladder cancer and benign prostatic hyperplasia. Dynamic probing under displacement control was carried at pre-strains between 5% and 8% for macro-probing and at 5% pre-strain for micro-probing, and the general effect of pre-strain on the dynamic mechanical properties (described by the amplitude ratio between stress and strain, and the phase lag between strain and stress) of phantom and prostate tissues is presented. Specific point probing on epithelial and stromal histological components was also carried out showing a significant difference between the amplitude ratios of epithelial and stromal components for actuation frequencies exceeding 5 Hz. However, no significant difference was found between phase lags for epithelial and stromal tissues.

Infliximab leads to a rapid but transient improvement in endothelial function in patients with primary systemic vasculitis

OBJECTIVE

To assess the immediate effects of tumour necrosis factor alpha (TNFalpha) blockade on endothelial function in systemic vasculitis.

METHODS

Endothelial function was assessed by laser Doppler flowmetry in patients with active vasculitis after 10 infusions of infliximab. For comparison endothelial responses were assessed after five infusions of cyclophosphamide plus methylprednisolone.

RESULTS

Endothelial dependent vasodilatation (EDV) improved significantly within 24 hours of infliximab infusion. The median change in red blood cell flux (interquartile range) was 5.7 (4.3-8.2) before infusion v 8.4 (7.5-10.9) at 24 hours; p=0.027. This was not maintained at day 14. No improvement was seen in EDV after cyclophosphamide plus methylprednisolone infusion.

CONCLUSION

The rapid but transient improvement in EDV after TNFalpha inhibition suggests that TNFalpha may have a direct role in the impairment of endothelial function.

DIFFERENTIAL PROPAGATION OF THE METAZOAN PARASITE MYXOBOLUS CEREBRALIS BY LIMNODRILUS HOFFMEISTERI, ILYODRILUS TEMPLETONI, AND GENETICALLY DISTINCT STRAINS OF TUBIFEX TUBIFEX

Whirling disease, caused by the parasite Myxobolus cerebralis, has infected rainbow trout (Oncorhynchus mykiss) and other salmonid fish in the western United States, often with devastating results to native populations but without a discernible spatial pattern. The parasite develops in a complex 2-host system in which the aquatic oligochaete Tubifex tubifex is an obligate host. Because substantial differences in whirling disease severity in different areas of North America did not seem explainable by environmental factors or features of the parasite or its fish host, we sought to determine whether ecological or genetic variation within oligochaete host populations may be responsible. We found large differences in compatibility between the parasite and various laboratory strains of T. tubifex that were established from geographic regions with different whirling disease histories. Moreover, 2 closely related species of tubificids, Limnodrilus hoffmeisteri and Ilyodrilus templetoni, which occur naturally in mixed species assemblages with T. tubifex, were incompatible with M. cerebralis. Virulence of the parasite was directly correlated with the numbers of triactinomyxon spores that developed within each strain of T. tubifex. Thus, the level of virulence was directly related to the compatibility between the host strain and the parasite. Genetic analyses revealed relationships that were in agreement with the level of parasite production. Differences in compatibilities between oligochaetes and M. cerebralis may contribute to the spatial variance in the severity of the disease among salmonid populations.

Constructing ontology-driven protein family databases

MOTIVATION

Protein family databases provide a central focus for scientific communities as well as providing useful resources to aide research. However, such resources require constant curation and often become outdated and discontinued. We have developed an ontology-driven system for capturing and managing protein family data that addresses the problems of maintenance and sustainability.

RESULTS

Using protein phosphatases and ABC transporters as model protein families, we constructed two protein family database resources around a central DAML+OIL ontology. Each resource contains specialist information about each protein family, providing specialized domain-specific resources based on the same template structure. The formal structure, combined with the extraction of biological data using GO terms, allows for automated update strategies. Despite the functional differences between the two protein families, the ontology model was equally applicable to both, demonstrating the generic nature of the system.

AVAILABILITY

The protein phosphatase resource, PhosphaBase, is freely available on the internet (http://www.bioinf.man.ac.uk/phosphabase). The DAML+OIL ontology for the protein phosphatases and the ABC transporters is available on request from the authors.

CONTACT

kwolstencroft@cs.man.ac.uk.

A methodology to migrate the gene ontology to a description logic environment using DAML+OIL

The Gene Ontology Next Generation Project (GONG) is developing a staged methodology to evolve the current representation of the Gene Ontology into DAML+OIL in order to take advantage of the richer formal expressiveness and the reasoning capabilities of the underlying description logic. Each stage provides a step level increase in formal explicit semantic content with a view to supporting validation, extension and multiple classification of the Gene Ontology. The paper introduces DAML+OIL and demonstrates the activity within each stage of the methodology and the functionality gained.

Neonatal alloimmune thrombocytopenia may be less severe in a subsequent pregnancy

Neonatal alloimmune thrombocytopenia (NAIT) is more common than previously appreciated. Clinical presentation is varied, but it is generally a severe disorder and it is said to be more severe in subsequent pregnancies. The authors present a case of fatal disseminated intravascular coagulation that was diagnosed as NAIT only after presentation of a subsequent surviving sibling with intracranial hemorrhage and thrombocytopenia. Despite the perinatal complications, this second sibling had good neurodevelopmental outcome. This is the first reported case of less severe disease occurring in a subsequent pregnancy.

The comparative sealing ability of hydroxyapatite cement, mineral trioxide aggregate, and super ethoxybenzoic acid as root-end filling materials

A comparison was made of the ability of hydroxyapatite cement, mineral trioxide aggregate, and super ethoxybenzoic acid to prevent the leakage of bacteria from root canals, when used as root-end filling materials. The materials were tested in a double-chamber device in which a root segment connects the upper (delivery) chamber and the lower (receiving) chamber. The root segment was prepared by having the root canal instrumented to a #45 file, and a 3-mm-deep, root-end preparation placed at the apical foramen. The canal of each root segment was filled with gutta-percha, and the root-end preparation was filled with one of three test materials, mixed according to the manufacturer's directions. Negative controls were constructed with sticky wax sealing the apical foramen. A titered suspension of radioactively (3H-thymidine)-labeled bacteria (Enterococcus fecalis) was placed into the delivery chamber, and sterile saline was placed into the receiving chamber such that the apical third of each root section was immersed. At various time points, samples were taken from the receiving chamber, and measured for 3H activity. The results indicated that (a) all the test materials leaked significantly compared with the negative controls; and (b) there was no significant difference found between the leakage rates of the three materials tested.

Interactions of 3T3 fibroblasts and endothelial cells with defined pore features

The colonization of biodegradable polymer scaffolds with cell populations has been established as the foundation for the engineering of a number of tissues, including cartilage, liver, and bone. Within these scaffolds, the cells encounter a porous environment in which they must migrate across the convoluted polymer surface to generate a homogenous cell distribution. Predicting the interactions between cells and pores is important if scaffold characteristics are to be optimized. Therefore, we investigated the behavior of two model cell types over a range of defined pore features. These pore features range from 5 to 90 microm in diameter and have been fabricated by photolithographic techniques. Quantitatively, the behavior of the cells is dependent on three factors: 1) percentage cell coverage of the surface; 2) pore size; and 3) cell type. Fibroblast cells displayed a co-operative pattern of cell spreading in which pores with diameters greater than the cell dimensions were bridged by groups of cells using their neighbors as supports. Endothelial cells were unable to use neighbors as support structures and failed to bridge pores greater than the cell diameter.

Effects of pre- and postnatal corticosterone exposure on the rat hippocampal GABA system

Several lines of evidence have implicated prenatal stress and the hippocampal GABA system in the pathophysiology of schizophrenia, and prenatal stress is believed to increase the risk for schizophrenia through alterations of this neurotransmitter. To explore this hypothesis, we treated male rats pre- and/or postnatally (P48 and P60) with either corticosterone (CORT) or vehicle to establish three study groups: VVV, receiving vehicle at all three time points; VCC, receiving vehicle prenatally and CORT at both postnatal timepoints; and CCC, receiving CORT at all three timepoints. Animals were sacrificed at either 24 h or 5 days after final injection and examined for mRNA levels of GAD65, GAD67, and the GABA(A) receptor subunits alpha2 and gamma2. At 24 h, GAD65 mRNA was decreased in CA1, CA2, CA4, and dentate gyrus (DG) of VCC rats; this effect was either decreased or reversed in CCC-treated animals. No effect was detected in GAD67 mRNA at 24 h. At 5 days, CORT treatment increased GAD67 mRNA levels in CA1, CA3, and DG. Prenatal treatment with CORT was associated with increased responsiveness only in CA3 and DG. For the GABAA receptor, alpha2 subunit mRNA did not show any change in response to CORT treatment, while that for the gamma2 subunit was decreased in CA2 of both VCC- and CCC-treated animals. Consistent with gamma2 subunit mRNA decreases, benzodiazepine (BZ) receptor binding activity was decreased in CA2 with CORT treatment. Prenatal CORT exposure neither increased nor decreased this effect. These results demonstrate that CORT administration is associated with a complex regulation of mRNA expression for pre- and postnatal aspects of the hippocampal GABA system. Under these conditions, prenatal exposure to CORT may sensitize some of these effects, but does not fundamentally alter the nature of this response.