De Quervain tendinitis after total trapeziometacarpal joint arthroplasty: Biomechanical evaluation of tendon excursion in the first extensor tendon compartment.

De Quervain's tenosynovitis is the most common complication after total trapeziometacarpal joint replacement. Etiology is unclear. Implantation of a ball-in-socket implant changes the biomechanics of the normal trapeziometacarpal saddle joint and increases its range of motion. The present study demonstrates that this procedure also significantly increases excursion of the abductor pollicis longus and extensor pollicis brevis tendons during thumb flexion-extension, and not during thumb abduction-adduction. Increased tendon gliding under the retinaculum of the first extensor tendon compartment could predispose to the development frictional tenosynovitis and play a role in the development of de Quervain's syndrome after total trapeziometacarpal joint replacement. LEVEL OF EVIDENCE: Not applicable (laboratory study).

Trapeziometacarpal total joint arthroplasty: The effect of capsular release on range of motion.

It has been suggested that trapeziometacarpal total joint arthroplasty be combined with complete release of the joint capsule to prevent ligament tethering and implant dislocation. Our goal was to evaluate the consequences of capsular release on range of motion. Trapeziometacarpal joint motion was measured with a 3D motion tracking system in seven fresh frozen human cadaver hands before and after capsular release and total joint arthroplasty with subsequently longer neck lengths. Relative to the native trapeziometacarpal joint with intact joint capsule, mean flexion-extension was significantly increased after the arthroplasty with released capsule and lengthening up to 6 mm. Mean abduction-adduction did not increase significantly. Total joint replacement combined with capsular release increases the trapeziometacarpal joint's range of motion, but not beyond the limits of most trapeziometacarpal implant designs. Lengthening of the implant neck progressively decreases the excess motion.

Analysis of spectinomycin by liquid chromatography with pulsed electrochemical detection.

Until now, no LC method is described to determine the purity and content of spectinomycin without prior derivatization. A reversed-phase ion-pair LC method using a base deactivated column and pulsed electrochemical detection is described. The mobile phase consisted of an aqueous solution containing 5.8 g/l pentafluoropropionic acid, 1.25 g/l potassium dihydrogen phosphate and 5.5 ml/l tetrahydrofuran. The pH was adjusted to 6.25 using dilute NaOH solution. An experimental design was used to optimize the chromatographic parameters and to check the robustness. The quality of separation was investigated on different stationary phases. The method allows the separation of spectinomycin from its related substances as well as some other components of unknown identity. The total time of analysis is 65 min. A number of commercial samples were examined using this method.

8-Azido-ATP labelling of the FecE protein of the Escherichia coli iron citrate transport system.

The iron(III) transport system via citrate displays the characteristics of a binding protein-dependent transport mechanism through the cytoplasmic membrane. One of the five transport proteins, FecE, contains the two motifs found in ATP-binding proteins. Cloned overexpressed FecE was photoaffinity-labelled with [32P]8-azido-ATP. Labelling was inhibited by 1 mM ATP, ADP, GTP and less by CTP, demonstrating the specificity of the reaction. It is suggested that ATP is the principal energy source for iron(III) citrate transport through the cytoplasmic membrane of Escherichia coli.

Novel two-component transmembrane transcription control: regulation of iron dicitrate transport in Escherichia coli K-12.

Citrate and iron have to enter only the periplasmic space in order to induce the citrate-dependent iron(III) transport system of Escherichia coli. The five transport genes fecABCDE form an operon and are transcribed from fecA to fecE. Two genes, termed fecI and fecR, that mediate induction by iron(III) dicitrate have been identified upstream of fecA. The fecI gene encodes a protein of 173 amino acids (molecular weight, 19,478); the fecR gene encodes a protein of 317 amino acids (molecular weight, 35,529). Chromosomal fecI::Mu d1 mutants were unable to grow with iron(III) dicitrate as the sole iron source and synthesized no FecA outer membrane receptor protein. Growth was restored by transformation with plasmids encoding fecI or fecI and fecR. FecA and beta-galactosidase syntheses under transcription control of the fecB gene (fecB::Mu d1) were constitutive in fecI transformants and were regulated by iron(III) dicitrate in fecI fecR transformants. The amino acid sequence of the FecI protein contains a region close to the carboxy-terminal end for which a helix-turn-helix motif is predicted, which is typical for DNA-binding regulatory proteins. The FecI protein was found in the membrane, and the FecR protein was found in the periplasmic fraction. It is proposed that the FecR protein is the sensor that recognizes iron(III) dicitrate in the periplasm. The FecI protein activates fec gene expression by binding to the fec operator region. In the absence of citrate, FecR inactivates FecI. The lack of sequence homologies to other transmembrane signaling proteins and the location of the two proteins suggest a new type of transmembrane control mechanism.

Nucleotide sequences of the fecBCDE genes and locations of the proteins suggest a periplasmic-binding-protein-dependent transport mechanism for iron(III) dicitrate in Escherichia coli.

The fec region of the Escherichia coli chromosome determines a citrate-dependent iron(III) transport system. The nucleotide sequence of fec revealed five genes, fecABCDE, which are transcribed from fecA to fecE. The fecA gene encodes a previously described outer membrane receptor protein. The fecB gene product is formed as a precursor protein with a signal peptide of 21 amino acids; the mature form, with a molecular weight of 30,815, was previously found in the periplasm. The fecB genes of E. coli B and E. coli K-12 differed in 3 nucleotides, of which 2 gave rise to conservative amino acid exchanges. The fecC and fecD genes were found to encode very hydrophobic polypeptides with molecular weights of 35,367 and 34,148, respectively, both of which are localized in the cytoplasmic membrane. The fecE product was a rather hydrophilic but cytoplasmic membrane-bound protein of Mr 28,189 and contained regions of extensive homology to ATP-binding proteins. The number, structural characteristics, and locations of the FecBCDE proteins were typical for a periplasmic-binding-protein-dependent transport system. It is proposed that after FecA- and TonB-dependent transport of iron(III) dicitrate across the outer membrane, uptake through the cytoplasmic membrane follows the binding-protein-dependent transport mechanism. FecC and FecD exhibited homologies to each other, to the N- and C-terminal halves of FhuB of the iron(III) hydroxamate transport system, and to BtuC of the vitamin B12 transport system. FecB showed some homology to FhuD, suggesting that the latter may function in the same manner as a binding protein in iron(III) hydroxamate transport. The close homology between the proteins of the two iron transport systems and of the vitamin B12 transport system indicates a common evolution for all three systems.