Matrix changes in articular cartilage in the knee of patients with rheumatoid arthritis after biological therapy: 1-year follow-up evaluation by T2 and T1ρ MRI quantification.

AIM: To estimate the morphological changes in the articular cartilage of the knees of patients with rheumatoid arthritis treated with biological disease-modifying anti-rheumatic drugs (bDMARDs). MATERIALS AND METHODS: Cartilage-specific magnetic resonance imaging (MRI) results, including T2 and T1ρ mapping of the femorotibial joint of 17 patients, were obtained before and 1 year after starting treatment with bDMARDs. Regions of interest were selected on the sagittal images of the cartilage of the medial and lateral femoral condyles (MFC, LFC) and the tibial plateau (MTP, LTP). Cartilage thickness, T2, and T1ρ were measured, and the correlations of their changes were evaluated. RESULTS: The mean changes in cartilage thickness tended to decrease in all four condyles, and the rate was significant in the MFC. T2 and T1ρ tended to increase, and T2 in the MFC significantly increased. Changes in cartilage thickness after 1 year showed a moderate correlation with the baseline T2 in the MFC as well as changes in T2 in the MTP. CONCLUSIONS: Decreasing cartilage thickness and matrix changes appeared in the MFC after 1 year of treatment with bDMARDs. Microstructural damage of the cartilage at baseline is a predictor for further cartilage damage in the knee joint, even if treatment with bDMARDs is effective.

The impact of paralytic bovine rabies transmitted by vampire bats in Latin America and the Caribbean.

The effective control of dog rabies in Latin America is justifiably seen as a major success in the struggle to limit this devastating zoonosis. However, rabies remains a problem, due to the presence of the virus in bat populations throughout the region, including vampire bats. Vampire bats obtain nutrition exclusively through consuming blood by biting mammals and birds. This makes the species a highly efficient vector of the rabies virus, responsible for sporadic outbreaks of rabies in human populations and numerous cases of rabies in livestock. This, in turn, causes economic losses to the farming industry in countries throughout the region. For over four decades, efforts to control rabies have been directed at controlling the reservoir species and vaccinating cattle. However, this approach has not eliminated rabies in livestock. A major barrier to innovation in vampire rabies control is a lack of consistent surveillance to establish the extent of the problem. This precludes any calculation of its cost to the economy or the cost of potential solutions, such as vaccinating livestock. This paper outlines the problem of livestock rabies in Latin America and considers factors that influence the economic cost of potential solutions to this continuing challenge to human and livestock health.

Les résultats enregistrés en matière de lutte contre la rage canine en Amérique latine sont considérés avec raison comme un succès majeur sur la voie du contrôle de cette zoonose dévastatrice. Toutefois, la rage continue de poser un problème car le virus circule toujours parmi les populations de chauves-souris de la région, en particulier chez les chauves-souris hématophages. Ces dernières se nourrissent exclusivement de sang de mammifères ou d'oiseaux, en mordant leurs proies. Les espèces de chauves-souris hématophages sont donc des vecteurs extrêmement efficaces du virus de la rage et sont à l'origine de foyers sporadiques de rage dans les populations humaines ainsi que de nombreux cas de rage affectant le bétail. Cela occasionne des pertes économiques dans le secteur de l'élevage de tous les pays de la région. Depuis plus de quarante ans, les mesures appliquées pour lutter contre la rage ont essentiellement porté sur le contrôle des espèces réservoirs et sur la vaccination des bovins. Or, cette méthode n'a pas réussi à éliminer la rage chez le bétail. L'un des principaux obstacles à l'innovation en matière de lutte contre la rage chez les chauves-souris est qu'aucune surveillance n'est exercée de manière cohérente pour établir avec précision la portée du problème. Cela empêche d'évaluer le coût économique associé à la maladie ainsi que le coût des solutions envisageables, par exemple la vaccination du bétail. Les auteurs soulignent l'importance de la problématique de la rage chez les animaux d'élevage en Amérique latine et examinent les facteurs qui influent sur le coût économique des solutions à ce défi permanent pesant sur la santé humaine et celle du bétail.

El eficaz control de la rabia canina en América Latina se considera, con razón, un gran éxito en la lucha por contener esta devastadora zoonosis. La rabia, sin embargo, sigue planteando problemas por la presencia del virus en poblaciones de murciélagos de toda la región, en particular en murciélagos vampiro. Los vampiros se nutren exclusivamente de la sangre que sorben al morder a mamíferos y aves, lo que hace de ellos un vector sumamente eficaz del virus de la rabia, responsable de brotes esporádicos en poblaciones humanas y de numerosos casos de rabia bovina. Ello, a su vez, causa pérdidas económicas al sector pecuario de toda la región. Durante más de cuatro decenios, las medidas de lucha antirrábica han pasado esencialmente por el control de las especies que ejercen de reservorio y la vacunación de las reses. Esta lógica, sin embargo, no ha servido para acabar con la enfermedad en el ganado. Uno de los grandes obstáculos que impiden innovar en la lucha contra la rabia transmitida por los vampiros es la ausencia de una vigilancia sistemática que permita determinar el alcance del problema. Ello hace imposible calcular los costos que la enfermedad impone a la economía o el costo de eventuales soluciones, como la vacunación del ganado. Los autores exponen a grandes rasgos el problema de la rabia en el ganado latinoamericano y examinan los factores que influyen en el costo económico de las posibles soluciones a esta permanente amenaza para la salud de personas y animales.

Deep venous thrombosis was not detected after total knee arthroplasty in Japanese patients with haemophilia.

Combined thrombo-prophylaxis with mechanical and pharmacological methods is recommended in patients undergoing total knee or hip arthroplasty. As patients with 'untreated inherited bleeding disorders such as haemophilia' are at risk of bleeding, no prophylaxis has been prescribed for these patients. However, a retrospective study reported subclinical deep venous thrombosis (DVT) in 10% of patients with haemophilia undergoing major orthopaedic surgery. In this study, we aimed to evaluate the risk of DVT after total knee arthroplasty (TKA). We examined 38 TKA in 33 Japanese patients with haemophilia using ultrasonography. We did not detect DVT. The risk of DVT in patients with haemophilia after TKA may be lower than that in the general population. However, as patients with haemophilia progress in age, venous thromboembolism should be considered as a potential problem.

Endoplasmic reticulum stress-induced apoptosis contributes to articular cartilage degeneration via C/EBP homologous protein.

OBJECTIVE: When endoplasmic reticulum (ER) stress, i.e., the excessive accumulation of unfolded proteins in ER, endangers homeostasis, apoptosis is induced by C/EBP homologous protein (Chop). In osteoarthritis (OA) cartilage, Chop expression and apoptosis increase as degeneration progresses. We investigated the role of Chop in murine chondrocyte apoptosis and in the progression of cartilage degeneration. METHOD: We induced experimental OA in Chop-knockout (Chop(-/-)) mice by medial collateral ligament transection and meniscectomy and compared cartilage degeneration, apoptosis, and ER stress in Chop(-/-)- and wild-type (Chop(+/+)) mice. In our in vitro experiments we treated murine Chop(-/-) chondrocytes with the ER stress inducer tunicamycin (TM) and evaluated apoptosis, ER stress, and chondrocyte function. RESULTS: In vivo, the degree of ER stress was similar in Chop(-/-)- and Chop(+/+) mice. However, in Chop(-/-) mice apoptosis and cartilage degeneration were lower by 26.4% and 42.4% at 4 weeks, by 26.8% and 44.9% at 8 weeks, and by 26.9% and 32.3% at 12 weeks after surgery than Chop(+/+) mice, respectively. In vitro, the degree of ER stress induction by TM was similar in Chop(-/-)- and Chop(+/+) chondrocytes. On the other hand, apoptosis was 55.3% lower and the suppression of collagen type II and aggrecan mRNA was 21.0% and 23.3% less, and the increase of matrix metalloproteinase-13 mRNA was 20.0% less in Chop(-/-)- than Chop(+/+) chondrocytes. CONCLUSION: Our results indicate that Chop plays a direct role in chondrocyte apoptosis and that Chop-mediated apoptosis contributes to the progression of cartilage degeneration in mice.

The risk of elective orthopaedic surgery for haemophilia patients: Japanese single-centre experience.

Haemophilic arthropathy causes pain and a severely restricted range of motion, and results in a significant reduction in quality of life. When conservative treatments have failed, orthopaedic surgery is recommended for these patients with severe haemophilic arthropathy. However, surgery for haemophilia patients is challenging due to high complication rate such as infection, delayed wound healing and mortality. The aim of this study was to evaluate the incidence of early complications and identify preoperative risk factors of surgery for haemophilia patients. We report a series of haemophilia patients undergoing elective orthopaedic surgery between 2006 and 2012. During this period, 119 surgeries in 81 patients were prepared and 118 surgeries in 80 patients were actually performed. Four deep bacterial infections and four delayed wound healings occurred within 6 months postoperatively. One patient died preoperatively and four patients died postoperatively. Only the presence of inhibitor was a significant risk factor for infection. We found no risk factor related to delayed wound healing. Our data revealed alkaline phosphatase, albumin, platelet, alpha-fetoprotein, presence of ascites and child classification C as predictors of perioperative mortality following elective orthopaedic surgery. Our role is to identify potential patients who present with risk factors for complications and attempt to seek the best determination of treatment strategy for these people.

Evaluation of estimation of physiologic ability and surgical stress (E-PASS) to predict the postoperative risk for hip fracture in elder patients.

INTRODUCTION: The Estimation of Physiologic Ability and Surgical Stress (E-PASS) scoring system is comprised of a preoperative risk score (PRS), a surgical stress score (SSS), and a comprehensive risk score (CRS) determined by both the PRS and SSS. E-PASS predicts the postoperative risk by quantifying the patient's reserve and surgical stress in general surgery. This study aims to evaluate the usefulness of this scoring system for the hospitalization outcomes in hip fracture. PATIENTS AND METHODS: A consecutive series of 419 elderly patients who underwent surgery with osteosynthesis or arthroplasty for hip fracture were prospectively assessed for the E-PASS scoring system, which was compared with their postoperative course. RESULTS: The postoperative morbidity and mortality rates in hospital increased linearly as the PRS and CRS increased, with significant correlation (rho = 0.2, P < 0.01) in both operations. The cost of hospital stay also related significantly to the SSS (r = 0.6, P < 0.0001) and CRS (r = 0.4, P < 0.0001). CONCLUSION: These results suggest that E-PASS may be useful for predicting postoperative risk and estimating medical expense for surgical cases with hip fracture.

Healing of full-thickness defects of the articular cartilage in rabbits using fibroblast growth factor-2 and a fibrin sealant.

We have investigated in vitro the release kinetics and bioactivity of fibroblast growth factor-2 (FGF-2) released from a carrier of fibrin sealant. In order to evaluate the effects of the FGF-2 delivery mechanism on the repair of articular cartilage, full-thickness cylindrical defects, 5 mm in diameter and 4 mm in depth, which were too large to undergo spontaneous repair, were created in the femoral trochlea of rabbit knees. These defects were then filled with the sealant. Approximately 50% of the FGF-2 was released from the sealant within 24 hours while its original bioactivity was maintained. The implantation of the fibrin sealant incorporating FGF-2 successfully induced healing of the surface with hyaline cartilage and concomitant repair of the subchondral bone at eight weeks after the creation of the defect. Our findings suggest that this delivery method for FGF-2 may be useful for promoting regenerative repair of full-thickness defects of articular cartilage in humans.

MRI T1ρ and T2 mapping for the assessment of articular cartilage changes in patients with medial knee osteoarthritis after hemicallotasis osteotomy.

OBJECTIVES: The purpose of this study was to clarify the appearance of the reparative tissue on the articular surface and to analyse the properties of the reparative tissue after hemicallotasis osteotomy (HCO) using MRI T1ρ and T2 mapping. METHODS: Coronal T1ρ and T2 mapping and three-dimensional gradient-echo images were obtained from 20 subjects with medial knee osteoarthritis. We set the regions of interest (ROIs) on the full-thickness cartilage of the medial femoral condyle (MFC) and medial tibial plateau (MTP) of the knee and measured the cartilage thickness (mm) and T1ρ and T2 relaxation times (ms). Statistical analysis of time-dependent changes in the cartilage thickness and the T1ρ and T2 relaxation times was performed using one-way analysis of variance, and Scheffe's test was employed for post hoc multiple comparison. RESULTS: The cartilage-like repair tissue appeared on the cartilage surface of the medial compartment post-operatively, and the cartilage thickness showed a significant increase between the pre-operative and one-year post-operative time points (MFC; p = 0.003, MTP; p < 0.001). The T1ρ values of the cartilage-like repair tissue showed no difference over time, however, the T2 values showed a significant decrease between the pre-operative and one-year post-operative time points (MFC; p = 0.004, MTP; p = 0.040). CONCLUSION: This study clarified that the fibrocartilage-like repair tissue appeared on the articular surface of the medial compartment after HCO as evidenced by MRI T1ρ and T2 mapping.Cite this article: H. Nishioka, E. Nakamura, J. Hirose, N. Okamoto, S. Yamabe, H. Mizuta. MRI T1ρ and T2 mapping for the assessment of articular cartilage changes in patients with medial knee osteoarthritis after hemicallotasis osteotomy. Bone Joint Res 2016;5:294-300. DOI: 10.1302/2046-3758.57.BJR-2016-0057.R1.

Metal coordination geometry of ternary complex between cobalt-bovine carbonic anhydrase and multidentate ligands.

Interaction of cobalt(II) bovine carbonic anhydrase with 3- and 4-pyridinecarboxylates, 2-pyridinecarboxylate, and 2,6-pyridinedicarboxylate has been investigated by the spectrophotometric method. The apparent formation constant of the ternary complex (ligand : cobalt ion : apoenzyme = 1 : 1 : 1) was determined from spectral data. The spectroscopic data of the ternary complex indicate that the 3- or 4-pyridinecarboxylate adduct has a five-coordination geometry through three donor atoms of the protein part of the enzyme, the carboxyl group of 3- or 4-pyridinecarboxylate, and a water molecule. 3- or 4-Pyridinecarboxylate behaves as a monodentate ligand. The spectrum of the ternary complex of 2-pyridinecarboxylate was very different from that of 3- or 4-pyridinecarboxylate. The spectra data indicate that 2-pyridinecarboxylate adduct has a five-coordination geometry and that it behaves as a bidentate ligand. The ternary complex of 2,6-pyridinedicarboxylate was so unstable that the spectrum of the ternary complex was determined by the indirect method. The spectrum of 2,6-pyridinedicarboxylate adduct shows lower molar absorption than that of 2-pyridinecarboxylate adduct. This result indicates that 2,6-pyridine dicarboxylate behaves possibly as a tridentate ligand.

Antibodies against (1R,2R)-cyclohexanediamineplatinum(II)-DNA adduct recognize the conformational differences of isomeric analogues of cyclohexanediamine.

Antibodies reactive to (1R,2R)-cyclohexanediamineplatinum(II)-DNA ((1R,2R)-cyclohexanediamine: 1R,2R-dach) adducts were elicited by immunization of rabbit with calf thymus DNA modified by Pt(1R,2R-dach)Cl2 at a ratio of bound platinum per nucleotide ((D/N)b) of 0.0335. In an enzyme-linked immunosorbent assay (ELISA), the binding of specific antibodies to Pt(1R,2R-dach)-DNA adduct (60 microliters of 1.235 x 10(-7) M Pt in each wells) on the assay plate was competitively inhibited by Pt(1R,2R-dach)-DNA adduct ((D/N)b = 0.0653) in the solution. Almost equal inhibition was observed with Pt(1S,2S-dach)-DNA ((D/N)b = 0.0412), an optical isomer of 1R,2R-dach. Pt(1R,2S-dach)-DNA ((D/N)b = 0.0371) and Pt(1R,3S-dach)-DNA ((D/N)b = 0.0281) in which the cyclohexane ring is stereochemically perpendicular to the platinum chelate plane, also inhibited antibody binding, but these adducts gave only incomplete inhibition at higher Pt-DNA adduct concentrations. Although Pt(1R,2R-dach)-d(GpG) and Pt(1R,2R-dach)(NH3)2 inhibited antibody binding, the affinity of the antibody for Pt(1R,2R-dach)(NH3)2 was lower than with Pt(1R,2R-dach)-DNA, and the inhibition behavior of Pt(1R,2R-dach)-d(GpG) was biphasic, i.e., at the lower concentration the inhibition curve was consistent with that of Pt(1R,2R-dach)-DNA, but at the higher concentration it shifted to that of Pt(1R,2R-dach)(NH3)2. The affinity of the antibody for cis-DDP was markedly lower than with Pt(1R,2R-dach)(NH3)2. These facts suggest that the antibodies may bind to the substituents (the platinum and its surroundings) of the various Pt complexes rather than the DNA structure altered by platinum binding.

Copper binding selectivity of N- and C-sites in serum (human)- and ovo-transferrin.

Copper binding selectivity of the N- and C-sites in serum (human)- and ovo-transferrin was investigated through copper binding constants, copper dissociation rate constants, and EPR spectra. At pH 7.4, stepwise copper binding constants of serum (human)-transferrin were K1 = 1.8 (+/- 0.6) x 10(12) M-1 and K2 = 1.2 (+/- 0.5) x 10(11) M-1, and those of ovo-transferrin were K1 = 1.9 (+/- 0.5) x 10(11) M-1 and K2 = 2.1 (+/- 0.4) x 10(11) M-1. Absorbance changes resulting from copper binding to the C- or N-site at various ratios of Cu2+/apo-transferrin were separated by a kinetic method. It was clearly indicated that, in serum (human)-transferrin, the copper binding affinity for the C-site was much larger than that for the N-site, whereas in ovo-transferrin, the C- and N-sites have almost the same affinity for copper ions. In the presence of anions (0.1 M KCl or 0.1 M NaClO4), the stepwise copper binding constants of serum (human)-transferrin were almost 10-times smaller than those in the absence of the anions. The selectivity in binding the copper ions to both sites of serum (human)-transferrin in the presence of 0.1 M NaClO4 is much smaller than that in the presence of 0.1 M KCl or in the absence of the anions (0.1 M KCl and 0.1 M NaClO4). EPR spectra of the copper ions of the N-site in dicupric serum-transferrin are dramatically changed respectively by the addition of 0.1 M KCl, 0.1 M NaCl, and 0.1 M NaClO4. This suggests that the change in the coordination geometry of the copper ions occurs at the N-site.

Construction of hybrid biphenyl (bph) and toluene (tod) genes for functional analysis of aromatic ring dioxygenases.

Multicomponent enzyme complexes of biphenyl (BP) dioxygenase (Dox) encoded by the gene cluster, bphA1A2A3A4 in Pseudomonas pseudoalcaligenes strain KF707 [Taira et al., J. Biol. Chem. 267 (1992) 4844-4858] and toluene Dox encoded by the gene cluster, todC1C2BA in P. putida strain F1 [Zylstra et al., J. Biol. Chem. 264 (1989) 14940-14946], show high homologies (approx. 60%) for the corresponding subunit component in spite of the fact that they have discrete substrate specificities. We constructed hybrid gene clusters by replacing the gene component(s) between the large and small subunits of terminal Dox in the bph and tod gene clusters, and analyzed the function of a novel hybrid aromatic ring Dox. Escherichia coli cells expressing the hybrid gene clusters, todC1::bphA2A3A4, todC1C2::bphA3A4 and bphA1::todC2::bphA3A4, gained the ability to convert benzene-toluene and their derivatives to the dihydrodiols, indicating that the hybrid terminal Dox composed of TodC1::BphA2 and BphA1::TodC2 forms a functionally active multicomponent Dox associated with ferredoxin (Fer) (BphA3) and Fer reductase (BphA4). Moreover, hybrid Dox (composed of TodC1::BphA2A3A4 and TodC1C2::BphA3A4) showed a wide substrate specificity rather similar to that of the wild-type toluene Dox (TodC1C2BA). On the other hand, the hybrid Dox (BphA1::TodC2::BphA3A4) showed oxidative activities for the same compounds, but the rate of oxidation was dependent upon the substrate. These results suggest that (i) the two subunits of terminal Dox are critically involved in the substrate specificity for BP, benzene and their derivatives, and (ii) the electron transport proteins, Fer and Fer reductase, are exchangeable with one another between the BP Dox and toluene Dox complexes.

Photoreversible antigen-antibody reactions.

A monoclonal antibody (Z1H01) for an oligopeptide carrying an azobenzene group, was prepared under conditions where the azobenzene group is in the trans form. The antibody bound the hapten peptide effectively when the hapten peptide is in the trans form (K = 5 x 10(7) M-1), but the antibody released the hapten under irradiation with UV light where the hapten is in the cis form. The antibody bound the hapten again, when the hapten reverted to the trans form after irradiation with visible light.

Nucleocapsid specific T and B cell responses in humans after rabies vaccination.

The importance of the immune response directed to the internal component of the rabies virus, the nucleocapsid (NC), was evaluated in humans after rabies vaccination. T cell activation was measured with a bulk proliferative assay and relative frequencies of circulating NC-specific PBL were calculated with the limiting dilution technique. Vaccinees were classified into two groups: NC responders and NC non-responders. In NC responders, the frequency of NC-specific circulating lymphocytes was up to 6 times higher than the frequency of virus-specific lymphocytes. In non-responders, NC-specific lymphocytes were up to 25 times less common than virus-specific ones. The NC capacity to induce a secondary antibody response was tested in vitro. After a stimulation with complete virus, lymphocytes originating from donors vaccinated with tissue culture vaccine produced a secondary antibody-response composed mainly of glycoprotein-specific neutralizing antibodies, whereas lymphocytes from suckling mouse brain vaccines produced essentially NC-specific antibodies. This result confirmed the serological status of suckling mouse brain vaccinees, who usually developed high titres of NC-specific antibodies. After an in vitro NC stimulation, lymphocytes collected from NC responders produced not only NC-specific antibodies, provided they have NC-specific B cells at the time of blood sampling, but most surprisingly, they also produce glycoprotein-specific neutralizing antibodies. This finding indicates that NC free of glycoprotein is capable, in some individuals, of boosting an heterologous glycoprotein response.

Pulmonary plasma cell granuloma improves with corticosteroid therapy.

Two cases of pulmonary plasma cell granuloma that progressed after respiratory infectious disease are described. The men, 48 and 32 years old, were admitted to the hospital with blood-streaked sputum and mass or nodular shadow on chest radiograph. Close examination revealed that these tumors were plasma cell granulomas, which are known as postinflammatory pseudotumors. Biopsy specimens, obtained by way of transbronchial biopsy, demonstrated proliferation of mature plasma cells and infiltration of lymphocytes supported by granulation tissue, and there was no evidence of malignancy or tuberculosis. Although surgery is common in the treatment of pulmonary plasma cell granuloma, some cases relapse or invade the mediastinum. Therefore, we decided to treat these patients with prednisolone, 30 mg/d, an anti-inflammatory and immunosuppressive agent. Two or 4 weeks later, these tumors disappeared completely and they have never recurred. As middle-dosage corticosteroid therapy is not cytotoxic, it is useful for the treatment of pulmonary plasma cell granuloma, especially in multifocal, unresectable, and/or relapsing cases.

Insulin insensitivity in nonobese, nondiabetic essential hypertension and its improvement by an alpha 1-blocker (bunazosin).

To investigate insulin insensitivity and its reversibility, we performed an insulin sensitivity test using the steady state plasma glucose (SSPG) method in 10 lean hypertensive subjects with normal glucose tolerance before and after treatment with alpha 1-blocker bunazosin, and 14 age body mass index-adjusted healthy control subjects. Steady state plasma glucose was significantly higher in the hypertensive subjects compared with the control group (182 +/- 10 mg/dL v 104 +/- 7, P < .01, mean +/- standard error of the mean (SEM). Steady state plasma glucose significantly decreased to 136 +/- 12 mg/dL (P < .01) after the treatment with alpha 1-blocker bunazosin, with a decrease of blood pressure. Hypertensive subjects had shown an increased area under the curve of glucose and insulin during the oral glucose tolerance test compared with normal controls. The glucose area decreased significantly, but the insulin area did not change after the treatment. There was no difference in plasma epinephrine, norepinephrine, and fractional excretion of Na between normal and hypertensive subjects both before and after treatment with bunazosin at basal and during insulin sensitivity tests (2 h). Serum total cholesterol level decreased and HDL cholesterol increased significantly after treatment with bunazosin. A significant correlation was observed between SSPG and blood pressure, but not between insulin level and blood pressure. The results indicate that insulin sensitivity is better related than hyperinsulinemia to hypertension and that this insensitivity is partially reversible by alpha 1-blocker, bunazosin.

Coordination chemical studies on metalloenzymes. II. Kinetic behavior of various types of chelating agents towards bovine carbonic anhydrase.

In order to investigate the kinetics and mechanism of the removal of zinc ions from bovine carbonic anhydrase [EC 4.2.1.1] (BCA), several chelating agents with various stability constants were used to remove zinc from BCA. The second-order rate constants (kaap) of zinc removal from BCA were found to be in the following order; 2,6-pyridinedicarboxylic acid greater than 2-pyridinecarboxylic acid greater than 2,4-pyridinedicarboxylic acid greater than 2,3-pyridinedicarboxylic acid greater than or approximately 1,10-phenanthroline greater than or approximately 5-methyl-1,10-phenanthroline greater than 2,2'-bipyridine. With similar chelating agents the greater the stability constant, the faster was the rate of removal of zinc ions from BCA. With EDTA, trans-1,2-cyclohexanediaminetetraacetic acid, and nitrilotriacetic acid, the rate of zinc ion removal from the native enzyme was governed by the rate of spontaneous dissociation of zinc enzyme. The rate constants for the removal of zinc ions from BCA were governed by the affinity of the chelating agents for the metal ion and the conformation of the chelating agents. Based on these findings, reaction pathways for various chelating agents are proposed.