Effect of intra-articular versus systemic anti-inflammatory drugs in a rabbit model of temporomandibular joint inflammation

PURPOSE: In an attempt to better understand the time course of inflammatory mediator production or release in inflammatory joint disease, a rabbit model of acute temporomandibular joint (TMJ) inflammation was established. This model was used to evaluate the effects of specific anti-inflammatory agents administered either systemically (intraperitoneal, IP) or locally (intra-articular, IA) on the modulation of in vivo tissue levels of two prototypic inflammatory mediators, prostaglandin E2 (PGE2) and bradykinin (BK). MATERIALS AND METHODS: An experimental model of inflammation was created by administering carrageenan (carra) into one joint and an equivalent volume of saline (control) into the contralateral joint of 42 male New Zealand White rabbits. The development of hyperthermia was assessed by placement of a microthermister probe into the joint space. The inflammatory mediators, immunoreactive PGE2 (iPGE2) and BK (iBK), were recovered with microdialysis probes, and samples were assayed in conjunction with specific pharmacologic interventions. In the first part of the study, the time course for the release or production of iBK and iPGE2 was determined. In the second part, the effects of IP versus IA administration of dexamethasone and a nonsteroidal anti-inflammatory drug, ketorolac tromethamine, were compared. Dexamethasone and ketorolac were administered at 3 hours and 1 hour, respectively, before the peak release of the inflammatory mediators. RESULTS: The onset of IA hyperthermia, an index of inflammation, was evident by 90 minutes post-carra and reached a maximum of 1.2 degrees C above core temperature by 150 minutes post-carra. Intra-articular levels of iPGE2 and iBK peaked at 240 minutes (3.35+/-1.9 nmol/L) and 270 minutes (0.45+/-0.29 nmol/L), respectively, after the induction of inflammation in the superior joint space. iBK levels within the superior joint space were significantly decreased by dexamethasone and ketorolac. Ketorolac (50 microg) decreased iBK and iPGE2 levels when given IA or IP. With dexamethasone (3 mg), the levels of iBK were significantly reduced, and iPGE2 levels were not changed. CONCLUSIONS: This study shows that the rabbit model of TMJ inflammation, with concurrent collection of iBK and iPGE2 via microdialysis, is a reproducible and reliable method to investigate the time course of inflammatory mediator release and their modulation by either the local or systemic administration of anti-inflammatory medications.     

Characterization of an altered DNA catalysis of a camptothecin-resistant eukaryotic topoisomerase I

We investigated topoisomerase I activity at a specific camptothecin-enhanced cleavage site by use of a partly double-stranded DNA substrate. The cleavage site belongs to a group of DNA topoisomerase I sites which is only efficiently cleaved by wild-type topoisomerase I (topo I-wt) in the presence of camptothecin. With a mutated camptothecin-resistant form of topoisomerase I (topo I-K5) previous attempts to reveal cleavage activity at this site have failed. On this basis it was questioned whether the mutant enzyme has an altered DNA sequence recognition or a changed rate of catalysis at the site. Utilizing a newly developed assay system we demonstrate that topo I-K5 not only recognizes and binds to the strongly camptothecin-enhanced cleavage site but also has considerable cleavage/religation activity at this particular DNA site. Thus, topo I-K5 has a 10-fold higher rate of catalysis and a 10-fold higher affinity for DNA relative to topo I-wt. Our data indicate that the higher cleavage/religation activity of topo I-K5 is a result of improved DNA binding and a concomitant shift in the equilibrium between cleavage and religation towards the religation step. Thus, a recently identified point mutation which characterizes the camptothecin-resistant topo I-K5 has altered the enzymatic catalysis without disturbing the DNA sequence specificity of the enzyme.     

Anticomplementary activity in serum samples from patients with acute parvovirus B19 infection

Of 65 serum samples submitted for diagnostic purposes which proved to be anti-complementary by complement fixation test, 49 were parvovirus B19 IgM positive. Forty four of the 49 serum samples were from patients with arthropathy. Acute parvovirus B19 infection should be suspected when a patient has symptoms of disease of the joints and the serum is anticomplementary.     

Impact of particles on sediment accumulation in a drinking water distribution system

Discolouration of drinking water is one of the main reasons customers complain to their water company. Though corrosion of cast iron is often seen as the main source for this problem, the particles originating from the treatment plant play an important and potentially dominant role in the generation of a discolouration risk in drinking water distribution systems. To investigate this thesis a study was performed in a drinking water distribution system. In two similar isolated network areas the effect of particles on discolouration risk was studied with particle counting, the Resuspension Potential Method (RPM) and assessment of the total accumulated sediment. In the ‘Control Area’, supplied with normal drinking water, the discolouration risk was regenerated within 1.5 year. In the ‘Research Area’, supplied with particle-free water, this will take 10-15 years. An obvious remedy for controlling the discolouration risk is to improve the treatment with respect to the short peaks that are caused by particle breakthrough.     

L-allo-threonine aldolase from Aeromonas jandaei DK-39: gene cloning, nucleotide sequencing, and identification of the pyridoxal 5'-phosphate-binding lysine residue by site-directed mutagenesis

We have isolated the gene encoding L-allo-threonine aldolase (L-allo-TA) from Aeromonas jandaei DK-39, a pyridoxal 5'-phosphate (PLP)-dependent enzyme that stereospecifically catalyzes the interconversion of L-allo-threonine and glycine. The gene contains an open reading frame consisting of 1,014 nucleotides corresponding to 338 amino acid residues. The protein molecular weight was estimated to be 36,294, which is in good agreement with the subunit molecular weight of the enzyme determined by polyacrylamide gel electrophoresis. The enzyme was overexpressed in recombinant Escherichia coli cells and purified to homogeneity by one hydrophobic column chromatography step. The predicted amino acid sequence showed no significant similarity to those of the currently known PLP-dependent enzymes but displayed 40 and 41% identity with those of the hypothetical GLY1 protein of Saccharomyces cerevisiae and the GLY1-like protein of Caenorhabditis elegans, respectively. Accordingly, L-allo-TA might represent a new type of PLP-dependent enzyme. To determine the PLP-binding site of the enzyme, all of the three conserved lysine residues of L-allo-TA were replaced by alanine by site-directed mutagenesis. The purified mutant enzymes, K51A and K224A, showed properties similar to those of the wild type, while the mutant enzyme K199A was catalytically inactive, with corresponding disappearance of the absorption maximum at 420 nm. Thus, Lys199 of L-allo-TA probably functions as an essential catalytic residue forming an internal Schiff base with PLP of the enzyme to catalyze the reversible aldol reaction.