Neuropathic-like pain features and cross-sectional associations in rheumatoid arthritis

IntroductionIncreasing evidence indicates that features suggestive of neuropathic pain may also be present in patients with common rheumatic conditions. The objective of this study was to examine neuropathic-like pain symptoms and associated factors in patients with rheumatoid arthritis.MethodsWe used the painDETECT screening tool to identify possible or likely neuropathic pain in 159 outpatients with rheumatoid arthritis. Patients additionally completed other self-reported measures, while clinical measures were assessed to calculate the 28-joint Disease Activity Score. Univariate analyses and multivariable logistic regression were used to identify factors associated with neuropathic pain features.ResultsAccording to the painDETECT, 27 patients (17.0 %) were classified as having likely neuropathic pain and 34 patients (21.4 %) as having possible neuropathic pain. Besides reporting more severe pain, patients with likely or possible neuropathic pain were more likely to meet the diagnostic criteria for fibromyalgia, to use analgesics, and to have more tender joints and a worse physical and mental health status as measured by the 36-item Short-Form health survey. In multivariable analysis, physical (P < 0.001) and mental health status (P = 0.006) remained significantly associated with neuropathic pain features, even after controlling for pain severity.ConclusionsThese findings suggest that a sizeable proportion of patients with relatively well-controlled rheumatoid arthritis report symptoms suggestive of neuropathic pain. Neuropathic-like pain symptoms are independently associated with worse self-reported physical and mental health.     

Using a logical model to predict the growth of yeast

Background  

A logical model of the known metabolic processes in S. cerevisiae was constructed from iFF708, an existing Flux Balance Analysis (FBA) model, and augmented with information from the KEGG online pathway database. The use of predicate logic as the knowledge representation for modelling enables an explicit representation of the structure of the metabolic network, and enables logical inference techniques to be used for model identification/improvement.     

Adaptive nature of chromosomal rearrangement: differential fitness in pocket gophers

A chromosomal centric fusion polymorphism in populations of the plains pocket gopher, Geomys bursarius, was studied to determine the relative fitness associated with the karyotypic phenotypes. There was a greater number of heterozygous individuals than expected χ₁ ²=8.58, P=0.001. Calculations indicate that the viabilities of the two chromosomal homozygotes were only 35 and 76 percent or that of the heterozygote. Differences in fitness values for the chromosomal morphs for Geomys strongly emphasize the possible adaptive nature of the karyotype and provides a primary mechanism for chromosomal evolution, even in species composed of demes of relatively large size. This is the first case of positive chromosomal heterosis in vertebrates. The plains pocket gopher can now be added to the few empirically documented samples of balanced polymorphism.     

PEG-mediated plastid transformation in higher plants

Summary Plastids are surrounded by an envelope consisting of a double membrane. This barrier has to be penetrated or overcome by the DNA when transforming the plastome. Both the biolistic and polyethylene glycol-mediated transformation techniques accomplish this task, albeit by different mechanisms. We were the first laboratory to successfully use the polyethylene glycol (PEG)-method for plastid transformation, yet we use the particle gun when appropriate. In this report we compare the two methods and discuss their shortcomings and advantages. Plastid transformations with various constructs, mainly using theaadA gene as a selective marker, were performed. We point to potential problems likely to be encountered during the transformation and selection processes and offer possibilities for improvement. We give further examples of the successful application of plastome transformation and show its merits in addressing biological questions concerning the elucidation of plastid sequences of unknown function and the control of plastid gene expression. Based on a presentation in the symposium “Organelle Transformation” during the 1997 SIVB Congress held in Washington, DC June 14–18, 1997. An erratum to this article is available at .     

Flux detectors versus concentration detectors: two types of chemoreceptors

Dose-response curves relating the external stimulus concentration to receptor occupancy differ in two types of chemoreceptor organs. In 'concentration detectors' the receptor molecules at the receptor cell membrane are directly exposed to the external stimulus concentration; these organs exhibit the well-known hyperbolic dose-response relationship reflecting the association-dissociation of stimulus and receptor molecules. In contrast, 'flux detectors' accumulate the stimulus molecules in a perireceptor compartment. In flux detectors, deactivation of stimulus molecules may be in balance with arrival, as a prerequisite for producing a constant effective stimulus concentration at constant adsorptive flux of stimulus molecules. In a simple model of a flux detector in which receptor molecules themselves catalyze the deactivation, the dose-response relationship is linear. It reflects the rate of stimulus deactivation. If the deactivation is catalyzed by a separate enzyme, the dose-response relationship can be close to hyperbolic, or linear. In all cases, the receptor molecules are maximally occupied if the adsorptive flux equals or exceeds the maximum rate of stimulus deactivation. The time course of the receptor potential recorded from moths' pheromone receptors depends on the odor compound, which suggests that a peripheral process, possibly the stimulus deactivation, is the slowest, rate-limiting process of the transduction cascade. Further evidence comes from experiments with stimuli oversaturating the mechanism responsible for the decline of the receptor potential.