Bis-(2-propylheptyl)phthalate (DPHP) metabolites emerging in 24h urine samples from the German Environmental Specimen Bank (1999-2012).

Bis-(2-propylheptyl)-phthalate (DPHP) has been introduced as a substitute for other high molecular weight phthalates primarily used in high temperature applications (e.g. cable wires, roofing membranes). The aim of this study was to investigate how the increased usage of DPHP is reflected in urine samples collected over the last 14 years and to evaluate the current extent of exposure. We analyzed 300 urine samples (24h voids) from the German Environmental Specimen Bank collected in the years 1999, 2003, 2006, 2009 and 2012, 60 samples per year, from 30 male and 30 female volunteers (age: 20-30 years) for three specific, secondary oxidized DPHP metabolites (with hydroxy, oxo and carboxy modifications of the alkyl side chain). We determined DPHP metabolites with a previously developed GC-HRMS method, enabling us to unambiguously distinguish DPHP metabolites from co-eluting, structurally isomeric di-iso-decyl phthalate (DIDP) metabolites. All samples were blinded before analysis. We detected no DPHP metabolites in urine samples from the years 1999, 2003 and 2006. Thereafter, detection rates increased from 3.3% in 2009 to 21.7% in 2012. Mono-oxo-propylheptylphthalate (oxo-MPHP) was the most abundant metabolite, with concentrations between

German health-related environmental monitoring: assessing time trends of the general population's exposure to heavy metals.

The German system of a health-related environmental monitoring is based upon two instruments: The German Environmental Survey (GerES) and the Environmental Specimen Bank (ESB). The ESB is a tool to describe time trends of human exposure. Each year approx. 500 students from 4 sampling locations are analysed for their heavy metal contents in blood, blood plasma, and urine. GerES is a nationwide representative cross-sectional study that has been conducted four times up to now. Both instruments have been used to measure heavy metals over the last decades and thus provide complementary information. Both instruments are useful to describe time trends. However, combining the two has an added value, which is demonstrated for heavy metals for the first time in this paper. Major results and the changing importance of sources of exposure to heavy metals (Pb, Cd, Hg, Au, Pt, U and Ni) are shown. This leads to the following conclusion about the today's relevance of exposure in Germany. For the study participants of the city of Muenster, lead in whole blood decreased from about 70 µg/l in 1981 to levels below 15 µg/l in 2009. GerES data of young adults confirmed this time trend and GerES IV on children revealed the decreasing relevance of lead in outdoor air and in drinking water. The concentrations of mercury in urine decreased because in Germany it is no longer recommended to use amalgam fillings for children. However, GerES IV and ESB data also demonstrate that despite the decline of these heavy metals exposures to nickel and uranium originating from drinking water are still of importance.

Dioxins and dioxin-like PCBs in different fish from the river Elbe and its tributaries, Germany.

In a long-term program polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) as well as dioxin-like polychlorinated biphenyls (DL-PCBs) were analyzed in the muscle tissue of eels (Anguilla anguilla), bream (Abramis brama), European chub (Leuciscus cephalus) and ide (Leuciscus idus) from the river Elbe and its tributaries Mulde and Saale. The variation of the PCDD/F and DL-PCB concentrations in all fish samples is very large, whereby the DL-PCBs predominate in comparison to the PCDD/Fs. In the eels, the concentrations (pg WHO-TEQ/g ww) for the PCDD/Fs lie in the range of 0.48-22 and for the DL-PCBs between 8.5 and 59. In the whitefish, the concentration range is 0.48-12 for the PCDD/Fs and 1.2-14 for the DL-PCBs. Statistical analysis using relative congener patterns for PCDD/Fs allow spatial correlations to be examined for sub-populations of eels and whitefish. The results are compared to the maximum levels laid down in the European Commission Regulation (EC) No. 466/2001 and the action levels of the European Commission Recommendation 2006/88/EC. Eels caught directly after the major flood in August 2002 as well as eels near Hamburg (years 1996 and 1998) show high concentration peaks. Compared to the eels whitefish is less contaminated with PCDD/Fs and DL-PCBs.

Survivorship and clinical outcome of modular endoprosthetic reconstruction for neoplastic disease of the lower limb.

We reviewed retrospectively the results in 211 consecutive patients who had undergone limb salvage for bone neoplasia with endoprosthetic reconstruction of the proximal femur (96), distal femur (78), proximal tibia (30) and total femur (7). Their mean age was 50 years (11 to 86) and the mean follow-up period was 37.3 months (1 to 204). A total of 35 (16.6%) prostheses failed. Overall, implant survival was 78% (95% confidence interval (CI) 0.29 to 0.54) at five years, 60% (95% CI 0.93 to 2.35) at ten years and 60% (95% CI 1.27 to 3.88) at 15 years. Survivorship of the limb was 97.6% (95% CI 1.73 to 3.35) at ten years. The gender, age, diagnosis and location of the tumour were not prognostic variables for failure. Modular endoprosthetic replacement in the lower limb is a durable long-term reconstructive option, with the implants generally outlasting the patient.

Contamination of the alluvial plain, feeding-stuffs and foodstuffs with polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans (PCDD/Fs), dioxin-like polychlorinated biphenyls (DL-PCBs) and mercury from the River Elbe in the light of the flood event in August 2002.

Meadow soils, feeding-stuffs and foodstuffs from the alluvial plain of the river Elbe were analyzed in respect of PCDD/Fs, DL-PCBs and mercury with a view to assessing the consequences of the extreme flood of August 2002. The PCDD/F concentrations in the soils range from 3 to 2100 ng WHO-TEQ/kg dm, and for the DL-PCBs the range was 0.32 to 28 ng WHO-TEQ/kg dm. On the basis of established threshold values >40% of the areas are only fit for restricted usage. Mercury concentrations range from 0.11 to 17 mg/kg dm, whereby the action value of 2 mg/kg dm is exceeded in about 50% of the soil samples. A cumulative memory effect from past floods rather than a recent contamination from August 2002 is documented. Soils taken from behind broken dykes showed significantly lower concentrations. Grass, hay and grass silage originating from pasture land in Lower Saxony were taken before and immediately after the flooding. PCDD/Fs range from 0.29 to 16 ng WHO-TEQ/kg, the maximum permitted value of 0.75 ng WHO-TEQ/kg was exceeded in about 50% of the samples. Muscle-tissue from cattle, sheep, lamb and a roe deer as well as untreated milk from individual cows returned values ranging from 0.76 to 5.9 pg WHO-PCDD/F-TEQ/g fat, and 10% of the samples returned values higher than the permitted maximum of 3 pg WHO-PCDD/F-TEQ/g fat. The action value of 2 pg WHO-PCDD/F-TEQ/g fat was exceeded in 33% of the samples. No direct connection between these results and the effects of the flood could be established. A major input path for PCDD/Fs is the tributary Mulde, which discharges contaminated sediments from its catchment area into the Elbe.

Inflamed human periodontal versus peri-implant gingival tissues: an immunohistochemical differentiation of the extracellular matrix.

Inflamed human periodontal and peri-implant (ITI Bonefit) gingival tissues were studied immunohistochemically to evaluate the possible presence of structural differences in the extracellular matrix protein localization. Collagen types I, III, IV, V, VI, and VII and fibronectin showed a similar distribution in these tissues. Data show that morphologic structural differences between these inflamed tissues are not present. According to these findings, the connective tissue response of inflamed peri-implant as well as periodontal gingival tissues should be similar during treatment when the inflammation is localized only in the soft tissue level.

The cost of overseas visitors to an inner city accident and emergency department.

OBJECTIVE: To estimate, in a metropolitan accident and emergency (A&E) department, the annual cost of treating overseas visitors whose countries of origin do not have reciprocal arrangements with Britain. METHODS: The study was retrospective. A 24 h period (00.01 h to 24.00 h inclusive) on consecutive days in consecutive weeks (that is, Monday in week 1, Tuesday in week 2, etc) was costed over 52 weeks (1.8.92-31.7.93 inclusive) and extrapolated to 365 days. All visitors between those dates were divided into eligible (from countries with a reciprocal agreement) or non-eligible (from countries without a reciprocal agreement). Costs were calculated for medical and nursing care, investigation and treatment, and fixed costs. RESULTS: The annual St Mary's Hospital A&E budget for the study period (01/08/92 to 31/07/93) was 2,612,200 pounds; the average medical and nursing cost per major or minor case was 66.88 pounds and 20.08 pounds respectively. Investigation, treatment, and fixed costs were 16.31 pounds per patient. In total 2704 non-eligible patients (498 major and 2206 minor cases) were treated at a cost of 121,705 pounds (95% confidence interval 114,234 pounds to 129,176 pounds), which was 4.7% of the total annual budget. CONCLUSIONS: The cost of non-eligible patients to the NHS is substantial. One possible solution would be for visitors from countries which do not offer subsidised emergency treatment to British nationals to purchase health insurance compulsorily on or before entry to Britain. The revenue could be used to improve standards of care for all A&E patients.

Health human periodontal versus peri-implant gingival tissues: an immunohistochemical differentiation of the extracellular matrix.

Healthy human periodontal and peri-implant (ITI Bonefit) keratinized gingival tissues were studied immunohistochemically to evaluate the possible presence of structural differences in the extracellular matrix protein localization. Collagen types I, III, IV, and VII and fibronectin showed similar distribution in these tissues. Compared to the periodontal tissues, collagen type V was localized in higher amounts in the lamina propria of the peri-implant gingival tissues. Collagen type VI stained the periodontal tissues as a delicate microfibrillar network contrasting to the not well-stained peri-implant gingival tissues. The data show that structural differences between these tissues are present. The structural differences may be responsible for the defense of peri-implant keratinized gingival connective tissues to bacterial penetration, because of the high amount of the collagen type V component, which is responsible for the higher collagenase stability.

Extracellular matrix interactions during the in vivo degradation of collagen membranes in the rat skin: immunohistochemical distribution of collagen types IV, V, and VI.

The role of collagen implant material (CIM) in periodontology is of considerable interest to the clinical dentist because of the capacity of connective tissue (CT) regeneration and partial prevention of epithelial cell migration onto the root surface. The aim of this study was to demonstrate alterations of the CT matrix after the use of CIM in subcutaneous pockets in the rat skin. We used 15 rats in this study. After sedation, two subcutaneous pockets (2 cm in length) were surgically made in the animals' backs. Collagen membranes were implanted in one of the two pockets (test site). The other pocket served as control. Then, 4, 7, 14, 21, and 28 days after implantation, the animals were sacrificed and biopsies preserved for histologic and immunohistochemical examination. Incubation with antibodies against CT matrix components (collagen type IV, V, and VI) were used for immunostaining. Histologically, the CIM was migrated by inflammatory cells in the first 7 days. Newly formed fibroblasts and blood vessels (BV) were present 14 days postimplantation. Collagen type IV was localized in the basement membranes of the epithelium, BV, and nerves. An increase in the BV amount was demonstrated around (and later in) the implant material. Collagen type V was found in a filament pattern of distribution and was inserted into the implant after 4 weeks of healing. Collagen type VI showed a microfibrillar pattern of distribution with a delayed formation in the graft mass. The data showed the alterations of the matrix after implantation of collagen type I membranes in the rat skin.(ABSTRACT TRUNCATED AT 250 WORDS)

Matrix changes during long-term cultivation of cartilage (organoid or high-density cultures).

In high density (organoid or micromass) cultures of prechondrogenic mesenchymal cells from limb buds of 12-day-old mouse embryos typical cartilaginous tissue develops after 3 days. Immunomorphological investigations have shown that it contains the typical components of the cartilaginous matrix, such as collagen type II and cartilage-specific proteoglycans. After a 2-week cultivation period hypertrophic cartilage cells develop to an increasing extent. Many of these cells as well as normal chondroblasts detach from the matrix from the 2nd week in vitro onwards to assume a fibroblast-like appearance. At the same time thick (25-65 nm) collagenous fibrils occur at the surface of these cells. These thick fibrils contain collagen type I, as shown by immunomorphology. Hence, in these older cartilage cultures chondroblasts change their synthesis programme or direction of differentiation. Consequently, a model for the study of "dedifferentiation" of cartilage and possibly also transformation of cartilage cells to osteoblasts has become available.

Distribution of type-VII collagen in xenografted human carcinomas.

The distribution of type-VII collagen, the main molecular component of the anchoring fibrils (AF) attaching the basal lamina (BL, lamina densa of the basement membrane) to the surrounding connective tissue, was investigated in four xenografted human carcinomas of the hypopharynx (H-Stg 1), the lung (L 261), the sigmoid colon (CA 1), and the rectum (R 85). The studies were performed with a recently prepared, affinity-purified and highly specific antibody to type-VII collagen by using the indirect immunofluorescence and the APAAP (alkaline phosphatase anti-alkaline phosphatase) techniques. For comparison, the localization of the intrinsic BL components laminin and type-IV collagen were additionally analyzed in all four carcinomas. It was shown that type-VII collagen usually colocalized to laminin and type-IV collagen and was deposited at the borderline between carcinoma cell clusters and the surrounding strands of connective tissue in a similar, but more diffuse and less continuous distribution than both intrinsic BL components. In the squamous cell carcinoma H-Stg 1 and the adenocarcinoma L261, type-VII collagen was additionally accumulated in enlarged extracellular spaces between carcinoma cells, away from the contact zone to the connective tissue and again colocalized to laminin and type-IV collagen. Numerous carcinoma cells of both xenografts showed remarkable intracytoplasmic immunoreactivity for the antibody to type-VII collagen. Even in the case of the gastrointestinal carcinomas CA 1 and R 85, faint immunoreactivity for type-VII collagen was found at the contact zone between the mucosal epithelium and the surrounding connective tissue. These results confirm that epithelial carcinoma cells are obviously involved with the synthesis of the main molecular component of AF usually attaching the BL to the adjacent connective tissue and hint at a possible correlation between the localization of type-VII collagen and the observed pattern of the BL. However, it cannot be decided whether there is a direct causal relation between both phenomena or whether they are both the consequence of an independent but common cause, such as abnormal cellular differentiation of carcinoma cells. In no case, can the discontinuities in the distribution of type-VII collagen be explained by active tumor cell invasion since xenografted human carcinomas neither invade nor metastasize.

Localization of collagen type VI in articular cartilage of young and adult mice.

Collagen type VI was demonstrated immunomorphologically in articular cartilage (distal femur) of young (2-8 weeks) and adult mice by fluorescence and electron microscopy (gold-labelled second antibody--sandwich method) using pre- and post-embedding techniques. This collagen type was mainly seen in the vicinity of chondrocytes, and in larger amounts in adult cartilage. Electron-microscopic inspection (pre-embedding technique) revealed labelling above plaques that were 40-160 nm in size, and from which up to 7 fine filaments (< or = 10 nm) per unit sectional plane radiated. Using the post-embedding technique, only labelled plaques could be demonstrated; fine filaments were not perceptible. This was partly a result of the low contrast. It is assumed that the globular ends of up to 20 of the fine type VI filaments are anchored in one plaque and that the antibodies bind to the non-collagenous globular domains. Filaments radiated from the plaques and formed a three-dimensional network that stabilized the structures of the cartilaginous matrix. Antibodies against fibronectin also labelled similar plaques. The ends of the type VI filaments are possibly linked into the plaques by fibronectin.

Matrix production of smooth muscle cells from rat aorta in vitro.

Immunofluorescence microscopic methods served to demonstrate the production of the following matrix components in cultures of vascular smooth muscle cells from rat aorta: fibronectin; nidogen; heparan sulphate-proteoglycan (HS-PG); laminin; and collagen types I, III, IV, V, and VI. A time-dependence of synthesis and secretion could be shown for a number of components of the extracellular matrix (ECM), such as laminin. The results revealed the following estimated quantitative differences of the collagen types: type I > type III > types V and VI. A filamentous/fibrillar matrix and also occasionally a typical basal lamina could be demonstrated electron microscopically around the smooth muscle cells.

Type I collagen synthesis in cultured aortic smooth muscle cells from spontaneously hypertensive rats and normotensive control, Wistar-Kyoto rats.

An inhibition ELISA was used to quantify the amount of type I collagen synthesized in culture media and cell layers from aortic smooth muscle cells (SMCs) of spontaneously hypertensive rats (SHR) and normotensive control, Wistar-Kyoto rats (WKY). Cultured cells were also observed by electron microscopy. Collagen content in the culture media was strongly increased after 6 days in both cultures. Collagen and protein contents in the medium and cell layer from SHR were significantly higher than those in WKY at day 14. However, cell density in SHR-derived cells was also higher than that of WKY. No significant differences were detected in the rates of collagen content between SHR and WKY on a per cell basis. The main differences between SHR and WKY in collagen and protein levels may be due to the greater number of SHR cells and increased amounts of extracellular matrix components. The assay system outlined here should be useful for studying the control of extracellular-matrix synthesis.

Extracellular matrix analysis of nifedipine-induced gingival overgrowth: immunohistochemical distribution of different collagen types as well as the glycoprotein fibronectin.

The purpose of this study was to demonstrate the localization of collagen types I, III, IV, V, VI and VII as well as the glycoprotein fibronectin in nifedipine-induced gingival overgrowth. The slices, after the use of indirect immunofluorescence (incubation with antibodies against these extracellular matrix components), showed a diffuse distribution with the anti-types I and III in the stroma and fluorescent staining of the basement membranes of the epithelium, blood vessels and nerves with collagen type IV antibodies. The increased number of vessels was localized near the surface of the lesion. Collagen type V - seen as a filamentous - and collagen type VI - as microfibrillar - components were also localized in the tissue, showing completely different patterns of distribution. Collagen type V appeared "crater"-like and type VI displayed a "honeycomb"-shaped structural model. The blood vessels were not stained but the area around their walls demonstrated an intense fluorescence with these antibodies. Collagen type VII showed a characteristic linear staining near to the epithelial basement membrane. In contrast to this, fibronectin localized with a varied intensity in the different areas of the tissues and presented a "cloud"-like structure. This shows differences between the matrix components in nifedipine-induced hyperplasia and confirms the heterogeneity of the matrix in health and in gingival alterations.

Zonal differentiation of the marmoset (Callithrix jacchus) endometrium.

The differentiation of the marmoset (Callithrix jacchus) endometrium under different steroid hormone levels was investigated by electron microscopy and by the binding of different antibodies directed against collagen types. Based on differences in the glandular and interglandular compartments, the endometrium of sexually mature common marmosets consists of 3 zones: basal, adluminal and luminal. Hormone-dependent appearances are characterised. With low steroid concentrations, intercellular spaces between glandular epithelial cells occurred in the adluminal and the luminal areas. Epithelial cells of the basal region exhibited coated pits and phagolysosomes together with large apical protrusions. Under oestrogen dominance, phagolysosomes, fat vesicles and apical protrusions were evident in epithelial cells in the adluminal region. Secretory granules and concentric glycogen accumulations were a characteristic feature in epithelial cells of the adluminal and basal regions. With high progesterone concentrations, large empty vesicles were found with a higher frequency in adluminal than in basal epithelial cells. Using FITC-labelled antibodies against types V and VI collagen, binding was apparent adluminally in close vicinity to basement membranes, whereas reactivity was seen in the entire interglandular region of the basal area during this phase. Our findings indicate specific microenvironments with distinctive structural characteristics in the marmoset endometrium that are hormone dependent during all phases of the endometrial cycle. They are not related to menstruation, appear to be characteristic for primates and could reflect epithelial-mesenchymal interaction.

Distribution of fibronectin in healthy, inflamed and drug-induced gingival hyperplasia.

The distribution of fibronectin (FN) in the healthy, inflamed and hyperplastic human gingiva was investigated by indirect immunofluorescence. FN appeared as a fibrillar structure in the lamina propria of the healthy gingivae. In the inflamed specimens, FN demonstrated parallel fibres, especially in the coronal areas of the tissue. In the phenytoin gingival overgrowth, tissue FN was observed as thin fibres with variable length. The thin fibres gave the appearance of penetrating the basement membrane of the epithelium. Cyclosporin A gingival enlargement could be differentiated by phenytoin lesions because of the higher length and the parallel distribution of the FN. Finally, FN was observed in the nifedipine gingival overgrowth, where a microfibrillar delicate network gave the appearance of a "cloud"-pattern of distribution. In all of the specimens, blood vessels and nerves could not be stained. These findings show that FN distribution could differentiate the structure of the gingival lesions.

Immunohistochemical localization of collagenous components in healthy periodontal tissues of the rat and marmoset (Callithrix jacchus). I. Distribution of collagen types I and III.

The distribution of collagen types I and III was demonstrated in healthy periodontal tissues of the rat and marmoset using immunofluorescent localization after decalcification of the maxillae and mandiblae in 0.2 N HCl. An intense fluorescence in the alveolar bone and cementum matrix, as well as in the soft periodontal tissue, was demonstrated with anti-collagen type I antibodies. In the gingival connective tissue and in the periodontal ligament thick fibers of collagen type I could be observed. The fluorescent reaction in the rat periodontal ligament was not strong in comparison to the marmoset periodontal ligament. Sharpey's fibers, inserting into the cementum and alveolar bone, were also stained. On the other hand, collagen type III could not be demonstrated in the hard periodontal tissues, but could be in the bone marrow stroma and the incremental lines as well as around the Sharpey's fibers of the cementum, in accordance to previous studies. In the gingival connective tissue a strong staining was evident, especially near the basement membrane. The periodontal ligament showed an intense fluorescence that was, in some areas, continuous with Sharpey's fibers inserting into the cementum. The distribution of collagen types I and III was demonstrated with immunohistochemical techniques in the rat and marmoset periodontium. These results provide necessary information on healthy tissues that will be required for future studies on the effects of pathological, reparative and regenerative processes.

Extracellular matrix in the rat spiral limbus.

The matrix of the spiral limbus is obviously a special form of the intercellular substance. In the present study, the rat's spiral limbus was investigated by electron microscopy after fixation with ruthenium red and tannic acid and immunofluorescence to demonstrate matrix components. Collagen types I, II, V, VI, VII, IX and XI and fibronectin were not observed. Collagen type II and cartilage-specific proteoglycans, however, occurred in large quantities. The basal lamina of interdental cells and inner sulcus cells did not contain any collagen type IV, while the basal lamina of the capillaries had only minor amounts. Laminin and nidogen appeared in large amounts in the basal lamina. After fixation with tannic acid, the matrix between the interdental cells and the capillaries contained 20- to 22-nm-thick single and irregularly running fibrils as well as plaques of a fine granular material. After fixation with ruthenium red, 30- to 60-nm-thick, electron-dense granules occurred and most probably consisted of proteoglycans. These findings indicate that the composition of the matrix of the spiral limbus is similar to that of cartilage but not identical.

Effects of ofloxacin on chondrogenesis in murine cartilage organoid culture.

The fluoroquinolone, ofloxacin, a widely used antimicrobial agent, has been shown to cause athropathogenic syndromes in juvenile animals. In the present study, the effect of ofloxacin on chondrogenesis in cartilage organoid cultures of limb-bud mesenchymal cells obtained from day-12 mouse embryos was investigated. Cultures treated with increasing concentrations of ofloxacin (10, 30 and 100 mug/ml medium) for 6 days showed no significant changes in overall protein content and dry weight. Collagen type II, as a specific marker for cartilage, and collagen type I, as a marker protein in the internodular loose connective tissue in this culture system, were estimated by an inhibition-ELISA after cyanogen-bromide digestion. The collagen type I content of treated cultures remained constant, but the collagen type II level decreased in a dose-dependent manner to about 40% of that of the controls. There was no detectable increase in the concentration of collagen type II in the medium suggesting that ofloxacin inhibits synthesis rather than stimulate degradation of collagen type II. Cultures treated with 100 mug ofloxacin/ml were further investigated by indirect immunofluorescence and electron microscopy. Anticollagen type II antibodies demonstrated irregularities, several defects in the cartilage nodules, and much weaker staining in the treated cultures compared with controls. Similar results were obtained with antibodies directed against the core protein of large chondroitin sulphate proteoglycan monomers. Using monoclonal antibodies specific for unsulphated, 4-sulphated and 6-sulphated disaccharide "stubs" that remain attached to the core protein after chondroitinase ABC digestion of proteoglycans, different changes in these glycosaminoglycans were observed. While unsulphated chondroitin seemed to disappear nearly completely from the cartilage matrix, the level of chondroitin 4-sulphate remained unchanged and in the case of chondroitin 6-sulphate a slight increase in staining intensity was observable in the ofloxacin-treated cultures. Ultrastructurally, there was a reduction in the number of collagenous fibrils in the cartilage matrix of treated cultures and necrotic chondroblasts could be demonstrated. The present results resemble, in some aspects, observations that have been made in vivo after ofloxacin treatment, indicating that this in vitro model may provide a suitable system for examining the mechanism of quinolone-induced athropathia.