ABSTRACT
OBJECTIVE: The dynamic mechanism underlying cervical spine involvement in rheumatoid arthritis (RA) remains unidentified. The purpose of the current study was to determine the in vivo cervical segmental motion in RA patients with atlantoaxial subluxation (AAS) using a patient-based three-dimensional magnetic resonance imaging (MRI) computer model. METHODS: Healthy volunteers and RA patients with AAS (all females, n=10) underwent MRI examination of the cervical spine. Each vertebral body from the occipital bone (Oc) to the first thoracic vertebra (T1) was reconstructed from slices of T2-weighted sagittal MR images in the neutral, flexion, and extension positions. Using volume merge methods, each reconstructed vertebral body was virtually rotated and translated. Rotational segmental and translational segmental motions were obtained in three major planes. RESULTS: Overall, the axial translational motions in the RA group were lower than those in the healthy volunteers; however the axial translational motion at only C1-C2 during flexion was at the same level as that in the healthy volunteers and was greater on the bottom side than that at other intervertebral levels. The frontal rotational motions at C1-C2 during extension were greater in the RA patients than those in the healthy volunteers (p<0.05). CONCLUSION: The atlantoaxial joints in the RA patients with AAS showed great frontal rotational motion during extension and great axial translation on the bottom side during flexion. The current noninvasive MRI-based method could be useful in evaluating the 3-D dynamic mechanism underlying cervical involvement in RA in vivo.
Subject(s)
Arthritis, Rheumatoid/physiopathology , Atlanto-Axial Joint/physiopathology , Cervical Vertebrae/physiopathology , Joint Instability/physiopathology , Range of Motion, Articular/physiology , Spine/physiopathology , Adult , Aged , Atlanto-Axial Joint/diagnostic imaging , Biomechanical Phenomena , Case-Control Studies , Cervical Vertebrae/diagnostic imaging , Computer Simulation , Female , Humans , Magnetic Resonance Imaging , Middle Aged , Radiography , Spine/diagnostic imagingABSTRACT
OBJECTIVE: Methotrexate (MTX) is most widely used for the treatment of rheumatoid arthritis (RA). However, it has certain drawbacks with regard to individual differences in its therapeutic effects as well as the differences in the patients' response to MTX therapy. We investigated whether multi-drug resistance-1 (ABCB1) C3435T, reduced folate carrier-1 (RFC1) G80A, 5-aminoimidazole-4-carboxamide ribonucleotide transformylase (ATIC) C347G and a 6bp-deletion polymorphism in the 3'-untranslated region of the thymidylase synthase (TYMS) gene are predictive of MTX sensitivity and its adverse effects. METHODS: Patients whose last maintenance dosage of MTX was
Subject(s)
Antirheumatic Agents/therapeutic use , Arthritis, Rheumatoid/drug therapy , Drug Resistance, Multiple/genetics , Methotrexate/therapeutic use , Organic Anion Transporters/genetics , Polymorphism, Genetic , ATP Binding Cassette Transporter, Subfamily B , ATP Binding Cassette Transporter, Subfamily B, Member 1 , Antirheumatic Agents/adverse effects , Arthritis, Rheumatoid/genetics , Arthritis, Rheumatoid/physiopathology , Female , Genotype , Health Status , Humans , Hydroxymethyl and Formyl Transferases/genetics , Joints/physiopathology , Male , Membrane Transport Proteins/genetics , Methotrexate/adverse effects , Middle Aged , Multienzyme Complexes/genetics , Nucleotide Deaminases/genetics , Retrospective Studies , Severity of Illness Index , Thymidylate Synthase/genetics , Treatment OutcomeABSTRACT
Escherichia coli heat-labile enterotoxin (LT) is a holotoxin which consists of one A and five B subunits. Although B subunit monomers released into periplasm can associate into pentameric structures in the absence of the A subunit, the A subunit accelerates the assembly. To express the function, A subunit constructs the proper spatial structure. However, the regions involved in the construction are unknown. To identify the regions, we substituted arginine residues near position 146 of the A subunit with glycine by oligonucleotide-directed site-specific mutagenesis and obtained the mutants expressing LT(R141G), LT(R143G), LT(R146G), LT(R143G, R146G), LT(R141G, R143G, R146G) and LT(R143G, R146G, R148G). We purified these mutant LTs by using an immobilized D-galactose column and analyzed the purified mutant LTs by SDS-PAGE to examine the amount of A subunit associated with B-subunit oligomer. The substitution of an arginine residue at any position did not induce a significant alteration in the amount of A subunit associated with B-subunit oligomer. However, the substitution of more than two arginine residues induced a significant decrease in the amount of A subunits associated with the B-subunit oligomer. Subsequently, we measured the level of the intracellular B-subunit oligomer of these mutant strains. The measurement revealed that the amount of B-subunit oligomer in cells decreased as the number of substituted arginine residues increased. These results show that all arginine residues near position 146 are important for the construction of the functional A subunit, and thus for holotoxin formation, although each individual arginine residue is not an absolute requirement.