DNA methylation biomarker for cumulative lead exposure is associated with Parkinson's disease.

Lead, a known neurotoxicant, has previously received attention in Parkinson's disease (PD) research, but epidemiologic studies have been limited in sample size and findings are equivocal. We generated two methylation-based biomarkers for cumulative tibia and patella bone-measured lead exposure in 1528 PD patients and 1169 controls. PD status was associated with increased levels of the DNAm biomarker for tibia-lead levels. We estimated a meta-OR for PD of 1.89 per unit DNAm tibia-lead increase (95% CI 1.59, 2.24; p = 8.1E-13). The current study supports the notion that chronic and long-term lead exposure tracked via DNAm may contribute to PD pathogenesis.

Blood DNA methylation biomarkers of cumulative lead exposure in adults.

BACKGROUND: Lead is a ubiquitous toxicant following three compartment kinetics with the longest half-life found in bones. Patella and tibia lead levels-validated measures of cumulative exposure-require specialized X-ray-fluorescence-spectroscopy available only in a few centers worldwide. We developed minimally invasive biomarkers reflecting individual cumulative lead exposure using blood DNA methylation profiles-obtainable via Illumina 450K or IlluminaEPIC bead-chip assays. METHODS: We developed and tested two methylation-based biomarkers from 348 Normative Aging Study (NAS) elderly men. We selected methylation sites with strong associations with bone lead levels via robust regressions analysis and constructed the biomarkers using elastic nets. Results were validated in a NAS subset, reporting specificity, and sensitivity. FINDINGS: Participants were 73 years old on average (standard deviation, SD = 6), with moderate lead levels of (mean ± SD patella: 27 ± 18 µg/g; tibia:21 ± 13 µg/g). Methylation-based biomarkers for lead in patella and tibia included 59 and 138 DNA methylation sites, respectively. Estimated lead levels were significantly correlated with actual measured values, (r = 0.62 patella, r = 0.59 tibia) and had low mean square error (MSE) (MSE = 0.68 patella, MSE = 0.53 tibia). Means and distributions of the estimated and actual lead levels were not significantly different across patella and tibia bones (p > 0.05). Methylation-based biomarkers discriminated participants highly exposed (>median) to lead with a specificity of 74 and 73% for patella and tibia lead levels, respectively, with 70% sensitivity. INTERPRETATION: DNA methylation-based lead biomarkers are novel tools that can be used to reconstruct decades' worth of individual cumulative lead exposure using only blood DNA methylation profiles and may help identify the consequences of cumulative exposure.

Early lead exposure and childhood adiposity in Mexico city.

BACKGROUND: Prenatal and early childhood lead exposures have been associated with reduced weight in infants and young children, while studies that have examined such associations in children during peripubescence are rare. OBJECTIVES: We investigated the associations of prenatal and early-life exposure to lead with indices of adiposity in peripubertal children living in Mexico City. METHODS: Maternal bone lead (as a proxy for cumulative fetal exposure) was assessed at 1 month postpartum. Blood samples were obtained from children annually from 1 to 4 years. Multivariable linear regression models were used to examine the association between each lead biomarker and BMI z-score, waist circumference, sum of skinfolds and body fat percentage in 248 children aged 8-16 years. RESULTS: After adjusting for covariates, maternal patella lead was associated with lower child BMI z-score (ß = -0.02, 95% CI: 0.03, -0.01, p = 0.004), waist circumference (ß = -0.12 cm, 95% CI: 0.22, -0.03, p = 0.01), sum of skinfolds (ß = -0.29 mm, 95% CI: 0.50, -0.08, p = 0.007) and body fat percentage (ß = -0.09%, 95% CI: 0.17, -0.01, p = 0.03). No significant associations were detected from the postnatal exposure period. CONCLUSIONS: We observed a significant and inverse association of prenatal lead exposure with body composition in Mexican children, suggesting the potential role of early lead exposure in the fetal programming of child growth. Further research on the biological mechanisms underlying these associations is needed.

Primary pseudomyogenic hemangioendothelioma of bone: case report and review of the literature.

Pseudomyogenic hemangioendothelioma (PMH) represents a multicentric recently characterized tumor type, generally presenting in young adults, of postulated vascular origin and intermediate malignancy. This entity tends to arise in the deep-seated dermal-subcutaneous locations, preferentially limited to one anatomic site, and may extend secondary to bone. PMH restricted to the skeletal system is rare. To our knowledge, only 19 cases with description of both histologic and clinical findings have been reported to date. We report the clinicopathological features of a further intraosseous PMH occurring in a 46-year-old woman involving the right patella. Histologic examination showed an infiltrating growth composed of sheets and fascicles of spindled to epithelioid large cells, with ample eosinophilic cytoplasm, large vesicular nuclei and prominent nucleoli, sometimes resembling rhabdomyoblastic tumor cells, without morphologic signs of vascular differentiation. At immunohistochemical examination, neoplastic cells stained diffusely for AE1/AE3 keratins, vimentin, ERG, FLI-1, INI-1, FOSB with only focal CD31 expression.The morphologic clues leading to the correct diagnosis of intraosseous PMH have been correlated with the data of the literature, and a special emphasis has been given to the differential diagnosis with other neoplasms, particularly epithelioid sarcoma, in order to avoid unnecessary radical surgery and to optimise possible treatment protocols.

Bone Lead Levels and Risk of Incident Primary Open-Angle Glaucoma: The VA Normative Aging Study.

BACKGROUND: Oxidative stress may play an important role in the etiology of primary open-angle glaucoma (POAG). The association between risk of POAG and lead exposure, which is an environmental source of oxidative stress, has not been fully investigated yet. OBJECTIVE: Our objective was to determine the association between bone lead­a biomarker of cumulative lead dose (tibia lead) or an endogenous source of stored lead (patella lead)­and incident POAG. METHODS: We examined a prospective cohort of 634 POAG-free men [mean baseline age=66.8 y of age (SD=6.7)] from the Normative Aging Study (NAS) who had tibia and patella K X-ray fluorescence lead measurements between 1 January 1991 and 31 December 1999. They also had standard ocular evaluations by NAS optometrists until 31 December 2014. POAG cases were identified by consistent reports of enlarged or asymmetric cup-to-disc ratio together with visual field defect or existence of disc hemorrhage. We used Cox proportional hazards regressions to estimate hazard ratios (HRs) of incident POAG and adjusted survival curves to examine changes in the risk of POAG during follow-up according to bone lead quartiles. RESULTS: We identified 44 incident cases of POAG by the end of follow-up (incidence rate=74 per 10,000 person-years; median follow-up=10.6 y). In fully adjusted models, 10-fold increases in patella lead and tibia lead were associated with HRs of 5.06 (95% CI: 1.61, 15.88, p=0.005) and 3.07 (95% CI: 0.94, 10.0, p=0.06), respectively. The HRs comparing participants in the third and fourth quartiles with the lowest quartile were 3.41 (95% CI: 1.34, 8.66) and 3.24 (95% CI: 1.22, 8.62) for patella lead (p-for-trend=0.01), and 3.84 (95% CI: 1.54, 9.55) and 2.61 (95% CI: 0.95, 7.21) for tibia lead (p-for-trend=0.02). CONCLUSIONS: Our study provides longitudinal evidence that bone lead may be an important risk factor for POAG in the U.S. population. https://doi.org/10.1289/EHP3442.

Densitometric changes of the patella in patients undergoing unilateral knee arthroplasty.

INTRODUCTION: Although the intervention of knee arthroplasty became routine, there is no standard reference on the densitometric characteristics of the patella before and after surgery. Scope of this work is the evaluation of patellar bone density before and after unilateral knee arthroplasty. PATIENTS AND METHODS: BMD was assessed by DEXA examination in 146 individuals, who have been divided into three distinct groups. Group I: 68 subjects with a mean age of 70.6 years, with an unilateral femoral-tibial knee prothesis. Group II: healthy subjects of similar age (average: 64) and without implants. Group III: healthy adults with a mean age of 26.6 years. The follow-up was performed at 6 months to a maximum of 2 years post surgery. RESULTS: The results were obtained from 68 subjects examined with the DEXA software dedicated to the forearm, which turned out to be the most appropriate for our purpose. The follow-up performed every 6 months after surgery showed a reduction of the density values in the operated knee in the 1st control with a return to the pre-surgiucal situation in the control performed after 1 year. In subsequent checks there was a further increase of the patellar density of the operated knee. CONCLUSION: Patellar DEXA examination is recommended as an addition to the clinical and radiological standard examination.

Low-Level Cumulative Lead and Resistant Hypertension: A Prospective Study of Men Participating in the Veterans Affairs Normative Aging Study.

Background Bone lead offers a better method over blood lead measurement to discern long-term lead exposure and accumulation. We examined the risk of resistant hypertension based on bone lead levels in a prospective cohort study of NAS (Normative Aging Study). Methods and Results Participants had clinic data on hypertension (systolic blood pressure, diastolic blood pressure, and antihypertension medication), lead (blood, bone-patella, bone-tibia), and demographic and confounding variables. Cases of resistant hypertension were identified by meeting criteria for: (1) inadequate systolic blood pressure (>140 mm Hg) or diastolic blood pressure (>90 mm Hg) while taking 3 medications or (2) requiring >4 medications for blood pressure control. A modified Poisson regression was used for model analysis. Of the 475 participants, 97 cases of resistant hypertension (20.4%) were identified. Among the cases of resistant hypertension, the median tibia and patella lead levels were 20 µg/g and 25 µg/g, respectively, while median tibia and patella lead levels were 20 µg/g and 27.5 µg/g, respectively, in participants without resistant hypertension. Tibia lead demonstrated a significant association with resistant hypertension (relative risk, 1.19; 95% confidence interval, 1.01-1.41 [ P=0.04]) per interquartile range increase in tibia lead (13-28.5 µg/g). Patella lead was not associated with resistant hypertension (relative risk, 1.10; 95% confidence interval, 0.92-1.31 [ P=0.31]) per interquartile range increase in patella lead (18-40 µg/g). Blood lead levels were not significantly associated with resistant hypertension (relative risk, 1.11; 95% confidence interval, 0.88-1.40 [ P=0.38]). Conclusions Tibia lead represents a novel risk factor for resistant hypertension. Our study demonstrates an increased association between tibia lead and resistant hypertension status, with an increased risk of 19% per 1 interquartile range increase in tibia lead.

Evidence of structurally continuous collagen fibrils in tendons.

Tendons transmit muscle-generated force through an extracellular matrix of aligned collagen fibrils. The force applied by the muscle at one end of a microscopic fibril has to be transmitted through the macroscopic length of the tendon by mechanisms that are poorly understood. A key element in this structure-function relationship is the collagen fibril length. During embryogenesis short fibrils are produced but they grow rapidly with maturation. There is some controversy regarding fibril length in adult tendon, with mechanical data generally supporting discontinuity while structural investigations favor continuity. This study initially set out to trace the full length of individual fibrils in adult human tendons, using serial block face-scanning electron microscopy. But even with this advanced technique the required length could not be covered. Instead a statistical approach was used on a large volume of fibrils in shorter image stacks. Only a single end was observed after tracking 67.5mm of combined fibril lengths, in support of fibril continuity. To shed more light on this observation, the full length of a short tendon (mouse stapedius, 125µm) was investigated and continuity of individual fibrils was confirmed. In light of these results, possible mechanisms that could reconcile the opposing findings on fibril continuity are discussed. STATEMENT OF SIGNIFICANCE: Connective tissues hold all parts of the body together and are mostly constructed from thin threads of the protein collagen (called fibrils). Connective tissues provide mechanical strength and one of the most demanding tissues in this regard are tendons, which transmit the forces generated by muscles. The length of the collagen fibrils is essential to the mechanical strength and to the type of damage the tissue may experience (slippage of short fibrils or breakage of longer ones). This in turn is important for understanding the repair processes after such damage occurs. Currently the issue of fibril length is contentious, but this study provides evidence that the fibrils are extremely long and likely continuous.

Associations of cumulative Pb exposure and longitudinal changes in Mini-Mental Status Exam scores, global cognition and domains of cognition: The VA Normative Aging Study.

BACKGROUND: Lead (Pb) exposure has been associated with poorer cognitive function cross-sectionally in aging adults, however the association between cumulative Pb exposure and longitudinal changes in cognition is little characterized. METHODS: In a 1993-2007 subcohort of the VA Normative Aging Study (Mini-mental status exam (MMSE) n=741; global cognition summary score n=715), we used linear mixed effects models to test associations between cumulative Pb exposure (patella or tibia bone Pb) and repeated measures of cognition (MMSE, individual cognitive tests, and global cognition summary). Cox proportional hazard modeling assessed the risk of an MMSE score falling below 25. RESULTS: Among men 51-98 at baseline, higher patella Pb concentration (IQR: 21µg/g) was associated with -0.13 lower baseline MMSE (95% CI: -0.25, -0.004) and faster longitudinal MMSE decline (-0.016 units/year, 95% CI: -0.032, -0.0004) over 15 years. Each IQR increase in patella Pb was associated with increased risk of a MMSE score below 25 (HR=1.21, 95% CI: 0.99, 1.49; p=0.07). There were no significant associations between Pb and global cognition (both baseline and longitudinal change). Patella Pb was associated with faster longitudinal decline in Word List Total Recall in the language domain (0.014 units/year, 95% CI: -0.026, -0.001) and Word List Delayed Recall in the memory domain (0.014 units/year, 95% CI: -0.027, -0.002). We found weaker associations with tibia Pb. CONCLUSIONS: Cumulative Pb exposure is associated with faster declines in MMSE and Word List Total and Delayed Recall tests. These findings support the hypothesis that Pb exposure accelerates cognitive aging.

Toddler temperament and prenatal exposure to lead and maternal depression.

BACKGROUND: Temperament is a psychological construct that reflects both personality and an infant's reaction to social stimuli. It can be assessed early in life and is stable over time Temperament predicts many later life behaviors and illnesses, including impulsivity, emotional regulation and obesity. Early life exposure to neurotoxicants often results in developmental deficits in attention, social function, and IQ, but environmental predictors of infant temperament are largely unknown. We propose that prenatal exposure to both chemical and non-chemical environmental toxicants impacts the development of temperament, which can itself be used as a marker of risk for maladaptive neurobehavior in later life. In this study, we assessed associations among prenatal and early life exposure to lead, mercury, poverty, maternal depression and toddler temperament. METHODS: A prospective cohort of women living in the Mexico City area were followed longitudinally beginning in the second trimester of pregnancy. Prenatal exposure to lead (blood, bone), mercury, and maternal depression were assessed repeatedly and the Toddler Temperament Scale (TTS) was completed when the child was 24 months old. The association between each measure of prenatal exposure and performance on individual TTS subscales was evaluated by multivariable linear regression. Latent profile analysis was used to classify subjects by TTS performance. Multinomial regression models were used to estimate the prospective association between prenatal exposures and TTS performance. RESULTS: 500 mother-child pairs completed the TTS and had complete data on exposures and covariates. Three latent profiles were identified and categorized as predominantly difficult, intermediate, or easy temperament. Prenatal exposure to maternal depression predicted increasing probability of difficult toddler temperament. Maternal bone lead, a marker of cumulative exposure, also predicted difficult temperament. Prenatal lead exposure modified this association, suggesting that joint exposure in pregnancy to both was most toxic. CONCLUSIONS: Maternal depression predicts difficult temperament and concurrent prenatal exposure to maternal depression and lead predicts a more difficult temperament phenotype in 2 year olds. The role of temperament as an intermediate variable in the path from prenatal exposures to neurobehavioral deficits and other health effects deserves further study.

Quadrupole sensitive pulse for signal filtering.

A longstanding problem in quadrupolar NMR of semi-solids is the selection of signals originating from ordered nuclei, i.e. those that experience a non-vanishing quadrupolar coupling. Established techniques, such as for example multiple-quantum filters are not adequate in situations when the radio frequency power is on the order of the quadrupolar coupling or the quadrupolar relaxation rates, such as may be the case on an MRI scanner, or in ex situ applications. In this manuscript we show a new method for the selective excitation of ordered spin-3/2 nuclei, which produces the desired results when the radio frequency power is approximately equal or smaller than quadrupolar frequency. Using a combination of simulations and experiments with (23)Na in NaCl solution, Pf1-solutions, and bovine patellar cartilage samples we further show how the value of the quadrupolar frequency and global features of a quadrupolar coupling distribution can be extracted from these experiments.

Articular cartilage zonal differentiation via 3D Second-Harmonic Generation imaging microscopy.

PURPOSE: The collagen structure throughout the patella has not been thoroughly investigated by 3D imaging, where the majority of the existing data come from histological cross sections. It is important to have a better understanding of the architecture in normal tissues, where this could then be applied to imaging of diseased states. METHODS: To address this shortcoming, we investigated the combined use of collagen-specific Second-Harmonic Generation (SHG) imaging and measurement of bulk optical properties to characterize collagen fiber orientations of the histologically defined zones of bovine articular cartilage. Forward and backward SHG intensities of sections from superficial, middle and deep zones were collected as a function of depth and analyzed by Monte Carlo simulations to extract the SHG creation direction, which is related to the fibrillar assembly. RESULTS: Our results revealed differences in SHG forward-backward response between the three zones, where these are consistent with a previously developed model of SHG emission. Some of the findings are consistent with that from other modalities; however, SHG analysis showed the middle zone had the most organized fibril assembly. While not distinct, we also report bulk optical property values for these different zones within the patella. CONCLUSIONS: Collectively, these results provide quantitative measurements of structural changes at both the fiber and fibril assembly of the different cartilage zones and reveals structural information not possible by other microscope modalities. This can provide quantitative insight to the collagen fiber network in normal cartilage, which may ultimately be developed as a biomarker for osteoarthritis.

Effect modification by vitamin D receptor genetic polymorphisms in the association between cumulative lead exposure and pulse pressure: a longitudinal study.

BACKGROUND: Although the association between lead and cardiovascular disease is well established, potential mechanisms are still poorly understood. Calcium metabolism plays a role in lead toxicity and thus, vitamin D receptor (VDR) polymorphisms have been suggested to modulate the association between lead and health outcomes. We investigated effect modification by VDR genetic polymorphisms in the association between cumulative lead exposure and pulse pressure, a marker of arterial stiffness. METHODS: We examined 727 participants (3,100 observations from follow-ups from 1991 to 2011) from the Normative Aging Study (NAS), a longitudinal study of aging. Tibia and patella bone lead levels were measured using K-x-ray fluorescence. Four single nucleotide polymorphisms (SNPs) in the VDR gene, Bsm1, Taq1, Apa1, and Fok1, were genotyped. Linear mixed effects models with random intercepts were implemented to take into account repeated measurements. RESULTS: Adjusting for potential confounders, pulse pressure was 2.5 mmHg (95% CI: 0.4-4.7) and 1.9 mmHg (95% CI: 0.1-3.8) greater per interquartile range (IQR) increase in tibia lead (15 µg/g) and patella lead (20 µg/g), respectively, in those with at least one minor frequency allele in Bsm1 compared with those with major frequency allele homozygotes. The observed interaction effect between bone lead and the Bsm1 genotype persists over time during the follow-up. Similar results were observed in effect modification by Taq1. CONCLUSIONS: This study suggests that subjects with the minor frequency alleles of VDR Bsm1 or Taq1 may be more susceptible to cumulative lead exposure-related elevated pulse pressure.

Relationships between lead biomarkers and diurnal salivary cortisol indices in pregnant women from Mexico City: a cross-sectional study.

BACKGROUND: Lead (Pb) exposure during pregnancy may increase the risk of adverse maternal, infant, or childhood health outcomes by interfering with hypothalamic-pituitary-adrenal-axis function. We examined relationships between maternal blood or bone Pb concentrations and features of diurnal cortisol profiles in 936 pregnant women from Mexico City. METHODS: From 2007-11 we recruited women from hospitals/clinics affiliated with the Mexican Social Security System. Pb was measured in blood (BPb) during the second trimester and in mothers' tibia and patella 1-month postpartum. We characterized maternal HPA-axis function using 10 timed salivary cortisol measurements collected over 2-days (mean: 19.7, range: 14-35 weeks gestation). We used linear mixed models to examine the relationship between Pb biomarkers and cortisol area under the curve (AUC), awakening response (CAR), and diurnal slope. RESULTS: After adjustment for confounders, women in the highest quintile of BPb concentrations had a reduced CAR (Ratio: -13%; Confidence Interval [CI]: -24, 1, p-value for trend < 0.05) compared to women in the lowest quintile. Tibia/patella Pb concentrations were not associated with CAR, but diurnal cortisol slopes were suggestively flatter among women in the highest patella Pb quantile compared to women in the lowest quantile (Ratio: 14%; CI: -2, 33). BPb and bone Pb concentrations were not associated with cortisol AUC. CONCLUSIONS: Concurrent blood Pb levels were associated with cortisol awakening response in these pregnant women and this might explain adverse health outcomes associated with Pb. Further research is needed to confirm these results and determine if other environmental chemicals disrupt hypothalamic-pituitary-adrenal-axis function during pregnancy.

Optimal variable selection for Fourier transform infrared spectroscopic analysis of articular cartilage composition.

Articular cartilage (AC) is mainly composed of collagen, proteoglycans, chondrocytes, and water. These constituents are inhomogeneously distributed to provide unique biomechanical properties to the tissue. Characterization of the spatial distribution of these components in AC is important for understanding the function of the tissue and progress of osteoarthritis. Fourier transform infrared (FT-IR) absorption spectra exhibit detailed information about the biochemical composition of AC. However, highly specific FT-IR analysis for collagen and proteoglycans is challenging. In this study, a chemometric approach to predict the biochemical composition of AC from the FT-IR spectra was investigated. Partial least squares (PLS) regression was used to predict the proteoglycan content (n=32) and collagen content (n=28) of bovine cartilage samples from their average FT-IR spectra. The optimal variables for the PLS regression models were selected by using backward interval partial least squares and genetic algorithm. The linear correlation coefficients between the biochemical reference and predicted values of proteoglycan and collagen contents were r=0.923 (p<0.001) and r=0.896 (p<0.001), respectively. The results of the study show that variable selection algorithms can significantly improve the PLS regression models when the biochemical composition of AC is predicted.

Clustering of infrared spectra reveals histological zones in intact articular cartilage.

OBJECTIVE: Articular cartilage (AC) exhibits specific zonal structure that follows the organization of collagen network and concentration of tissue constituents. The aim of this study was to investigate the potential of unsupervised clustering analysis applied to Fourier transform infrared (FTIR) microspectroscopy to detect depth-dependent structural and compositional differences in intact AC. METHOD: Seven rabbit and eight bovine intact patellae AC samples were imaged using FTIR microspectroscopy and normalized raw spectra were clustered using the fuzzy C-means algorithm. Differences in mean spectra of clusters were investigated by quantitative estimation of collagen and proteoglycan (PG) contents, as well as by careful visual investigation of locations of spectral changes. RESULTS: Clustering revealed the typical layered structure of AC in both species. However, more distinct clusters were found for rabbit samples, whereas bovine AC showed more complex layered structure. In both species, clustering structure corresponded with that in polarized light microscopic (PLM) images; however, some differences were also observed. Spectral differences between clusters were identified at the same spectral locations for both species. Estimated PG/collagen ratio decreased significantly from superficial to middle or deep zones, which might explain the difference in clustering results compared to PLM. CONCLUSION: FTIR microspectroscopy in combination with cluster analysis allows detailed examination of spatial changes in AC. As far as we know, no previous single technique could reveal a layered structure of AC without any a priori information.

Computed tomography detects changes in contrast agent diffusion after collagen cross-linking typical to natural aging of articular cartilage.

OBJECTIVE: The effect of threose-induced collagen cross-linking on the mechanical and diffusive properties of cartilage was investigated in vitro. In particular, we investigated the potential of Contrast Enhanced Computed Tomography (CECT) to detect changes in articular cartilage after increased collagen cross-linking, which is an age-related phenomenon. METHODS: Osteochondral plugs (Ø=6.0 mm, n=28) were prepared from intact bovine patellae (n=7). Two of the four adjacent samples, prepared from each patella, were treated with threose to increase the collagen cross-linking, while the other two specimen served as paired controls. One sample pair was mechanically tested and then mechanically injured using a material testing device. Contrast agent [ioxaglate (Hexabrix™)] diffusion was imaged in the other specimen pair for 25 h using CECT. Water fraction, collagen and proteoglycan content, collagen network architecture and the amount of cross-links [hydroxylysyl pyridinoline (HP), lysyl pyridinoline (LP) and pentosidine (Pent)] of the samples were also determined. RESULTS: Cartilage collagen cross-linking, both Pent and LP, were significantly (P<0.001) increased due to threose treatment. CECT could detect the increased cross-links as the contrast agent penetration and the diffusion flux were significantly (P<0.05) lower in the threose treated than in untreated samples. The equilibrium modulus (+164%, P<0.05) and strain dependent dynamic modulus (+47%, P<0.05) were both significantly greater in the threose treated samples than in reference samples, but there was no association between the initial dynamic modulus and the threose treatment. The water fraction, proteoglycan and collagen contents, as well as collagen architecture, were not significantly altered by the threose treatment. CONCLUSIONS: To conclude, the CECT technique was found to be sensitive at detecting changes in cartilage tissue due to increased collagen cross-linking. This is important since increased cross-linking has been proposed to be related to the increased injury susceptibility of tissue.

Longitudinal changes in bone lead levels: the VA Normative Aging Study.

OBJECTIVE: Bone lead is a cumulative measure of lead exposure that can also be remobilized. We examined repeated measures of bone lead over 11 years to characterize long-term changes and identify predictors of tibia and patella lead stores in an elderly male population. METHODS: Lead was measured every 3 to 5 years by k-x-ray fluorescence and mixed-effect models with random effects were used to evaluate change over time. RESULTS: A total of 554 participants provided up to four bone lead measurements. Final models predicted a -1.4% annual decline (95% CI: -2.2 to -0.7) for tibia lead and piecewise linear model for patella with an initial decline of 5.1% per year (95% CI: -6.2 to -3.9) during the first 4.6 years but no significant change thereafter (-0.4% [95% CI: -2.4 to 1.7]). CONCLUSIONS: These results suggest that bone lead half-life may be longer than previously reported.

Prospective cohort study of lead exposure and electrocardiographic conduction disturbances in the Department of Veterans Affairs Normative Aging Study.

BACKGROUND: No studies have examined the association between cumulative low-level lead exposure and the prospective development of electrocardiographic conduction abnormalities, which may mediate the association between lead and several cardiovascular end points. OBJECTIVE: We prospectively examined the association between lead exposure and the development of electrocardiographic conduction abnormalities. METHODS: We assessed blood lead, bone lead--a biomarker of cumulative lead exposure--measured with K-shell X-ray fluorescence, and electrocardiographic end points among 600 men in the Normative Aging Study who were free of electrocardiographic abnormalities at the time of the baseline ECG. Of these men, we had follow-up data from a second electrocardiogram for 496 men 8.1 (SD = 3.1) years later, on average. We used repeated measures linear regression to analyze change in electrocardiographic conduction timing and logistic regression to estimate odds ratios (ORs) and 95% confidence intervals (CIs) for developing specific conduction disturbances and adjusted for potential confounders. RESULTS: Mean (± SD) blood (5.8 ± 3.6), patella bone (30.3 ± 17.7), and tibia bone (21.6 ± 12.0) lead concentrations were similar to those found in samples from the general U.S. population and much lower than those reported in occupationally exposed groups. Compared with those in the lowest tertile of tibia lead, those in the highest had a 7.94-ms (95% CI, 1.42-14.45) increase in heart rate-corrected QT (QTc) interval and a 5.94-ms increase in heart rate-corrected QRS (95% CI, 1.66-10.22) duration > 8 years. Those in the highest tertile of tibia lead also had increased odds of QT prolongation (QTc ≥ 440 msec; OR = 2.53; 95% CI, 1.22-5.25) and JT prolongation (heart rate-corrected JT > 360 msec; OR = 2.53; 95% CI, 0.93-6.91). Results were weaker for patella lead. No associations were identified with blood lead. CONCLUSIONS: This study suggests that low-level cumulative exposure to lead is associated with worse future cardiac conductivity in the ventricular myocardium, as reflected in QT interval characteristics.

Assessment of chemical species of lead accumulated in tidemarks of human articular cartilage by X-ray absorption near-edge structure analysis.

A highly specific accumulation of the toxic element lead was recently measured in the transition zone between non-calcified and calcified normal human articular cartilage. This transition zone, the so-called `tidemark', is considered to be an active calcification front of great clinical importance. However, little is known about the mechanisms of accumulation and the chemical form of Pb in calcified cartilage and bone. Using spatially resolved X-ray absorption near-edge structure analysis (µ-XANES) at the Pb L(3)-edge, the chemical state of Pb in the osteochondral region was investigated. The feasibility of the µ-XANES set-up at the SUL-X beamline (ANKA synchrotron light source) was tested and confirmed by comparing XANES spectra of bulk Pb-reference compounds recorded at both the XAS and the SUL-X beamline at ANKA. The µ-XANES set-up was then used to investigate the tidemark region of human bone (two patella samples and one femoral head sample). The spectra recorded at the tidemark and at the trabecular bone were found to be highly correlated with the spectra of synthetic Pb-doped carbonated hydroxyapatite, suggesting that in both of these very different tissues Pb is incorporated into the hydroxyapatite structure.