DNA damage in human sperm is related to urinary levels of phthalate monoester and oxidative metabolites

BACKGROUND

The ubiquitous use of phthalate esters in plastics, personal care products and food packaging materials results in widespread general population exposure. In this report, we extend our preliminary study on the relationship between urinary concentrations of phthalate metabolites and sperm DNA damage among a larger sample of men and include measurements of mono-(2-ethyl-5-hydroxyhexyl) phthalate (MEHHP) and mono-(2-ethyl-5-oxohexyl) phthalate (MEOHP), two oxidative metabolites of di-(2-ethylhexyl) phthalate (DEHP).

METHODS

Among 379 men from an infertility clinic, urinary concentrations of phthalate metabolites were measured using isotope-dilution high-performance liquid chromatography-tandem mass spectrometry. Sperm DNA damage measurements, assessed with the neutral comet assay, included comet extent (CE), percentage of DNA in tail (Tail%) and tail distributed moment (TDM).

RESULTS

Monoethyl phthalate (MEP), a metabolite of diethyl phthalate, was associated with increased DNA damage, confirming our previous findings. Mono-(2-ethylhexyl) phthalate (MEHP), a metabolite of DEHP, was associated with DNA damage after adjustment for the oxidative DEHP metabolites. After adjustment for MEHHP, for an interquartile range increase in urinary MEHP, CE increased 17.3% [95% confidence interval (CI) = 8.7-25.7%], TDM increased 14.3% (95% CI = 6.8-21.7%) and Tail% increased 17.5% (95% CI = 3.5-31.5%).

CONCLUSIONS

Sperm DNA damage was associated with MEP and with MEHP after adjusting for DEHP oxidative metabolites, which may serve as phenotypic markers of DEHP metabolism to 'less toxic' metabolites. The urinary levels of phthalate metabolites among these men were similar to those reported for the US general population, suggesting that exposure to some phthalates may affect the population distribution of sperm DNA damage.

Nicotine delays tendon-to-bone healing in a rat shoulder model

BACKGROUND

Many studies have shown that nicotine negatively impacts fracture healing and bone fusion processes. However, very little is known about its effect on tendon and ligament healing. The goal of the present study was to evaluate the effect of nicotine on tendon-to-bone healing.

METHODS

Supraspinatus tendons in both shoulders of seventy-two rats were transected and repaired to the humeral head. Osmotic pumps were implanted subcutaneously, and nicotine or saline solution was delivered for ten, twenty-eight, or fifty-six days. Cell morphology was evaluated with use of histologic sections. Cells were counted, and proliferating cell nuclear antigen (PCNA) immunohistochemistry was performed to assess cellular proliferation. In situ hybridization was performed to measure type-I collagen mRNA expression. Biomechanical and geometric properties were assessed.

RESULTS

Inflammation persisted longer in the nicotine group than in the saline solution group. Cellular proliferation was higher in the saline solution group than in the nicotine group at the early time-points. Type-I collagen expression was higher in the saline solution group at twenty-eight days. Mechanical properties increased over time in both groups. Maximum stress was significantly lower in the nicotine group than in the saline solution group at ten days. Maximum force was significantly lower in the nicotine group than in the saline solution group at twenty-eight days. Maximum force was significantly higher in the nicotine group than in the saline solution group at fifty-six days. Stiffness was not different between the groups at any time-point.

CONCLUSIONS

Nicotine caused a delay in tendon-to-bone healing in a rat rotator cuff animal model. Mechanical properties increased over time in both groups, but the properties in the nicotine group lagged behind those in the saline solution group. Chronic inflammation and decreased cell proliferation may partly explain the inferior biomechanical properties in the nicotine group as compared with the saline solution group.

CLINICAL RELEVANCE

Failure of rotator cuff repair is a major clinical problem. The adverse effect of nicotine on rotator cuff healing noted in this clinically appropriate animal model may be an important clinical consideration.

Resistance to white rust in pak choi and Chinese cabbage at the cotyledon stage

The biothrofic pathogen Albugo candida (Pers.) attacks all the cultivated Brassica species and several wild crucifers causing the disease known as white rust. The symptoms consist on the initial appearance of more or less conspicuous white sori on the plant leaves and stems, followed by severe distortions of the affected organs, especially flowers and siliqua. On delicate vegetable types of Brassica rapa L., like pak choi (B. rapa var. chinensis L.) and chinese cabbages (B. rapa var. pekinensis L.) even a slight white rust infection can render all the production unmarketable. Development of resistant cultivars is the best way to control the disease and to insure low pesticide spraying and residues in vegetables. The objective of this work were: i) the screening of a collection of B. rapa accessions from several seed banks for sources of resistance to white rust; and ii) the study of the inheritance of resistance in the most resistant accessions. Forty three accessions of B. rapa chinensis and 19 accessions of B. rapapekinensis were screened at the cotyledon stage following the methods of Santos and Dias (2004) with a Portuguese A. candida isolate Ac506 (Br) collected from turnip leaves. Four accessions of B. rapa chinensis presented more than 50% of resistant plants: the pak choi (BRA 117) was the most resistant accession with 85% of resistant plants, followed by pak choi (BRA227) with 73%, pai tsai 'Ex China 1' (B00083) with 60% and pak choi 'Ai Jiao Huang' (BRA 225) with 53%. On the opposite, B. rapa pekinensis accessions were all consider as susceptible presenting only 0-11% of resistant plants. The inheritance of resistance was studied in two crosses between pak choi BRA 117 and the rapid cycling B. rapa plant line CrGC 1.19. Selfed parents and F1 and F2 generations were produced, and screened at the cotyledon stage as previously described. Analysis of the results suggests that inheritance of resistance to Ac506 in pak choi BRA 117 is controlled by two nuclear genes with dominant recessive interaction.

Aureobasidium pullulansas a biocontrol agent of blue mold in "Rocha" pear

The blue mold of "Rocha" pear caused by Penicillium expansum is an important postharvest disease which is adequately controlled by application of synthetic fungicides. In recent years, strategies like biological control have been considered a desirable alternative to chemicals. Several studies have demonstrated the potential of the yeast-like fungus Aureobasidium pullulans for control of postharvest decay of pear. A Portuguese isolate of Aureobasidium pullulans was characterized and evaluated for its activity in reducing postharvest blue mold decay of "Rocha" pear caused by Penicillium expansum. Study of optimal conditions for antagonist growth was carried out in six different culture media. The effect of four maturity stages of fruits in the development of A. pullulans was also studied. Biocontrol studies were performed with two concentrations of the antagonist (3 x 10(8) and 4 x 10(9) CFU/ml). A. pullulans growth was significantly different (P < or = 0.001) according to the various media and time of incubation. Best results were obtained in Corn Meal Agar (CMA) and Potato Dextrose Agar (PDA) media which contains the higher concentration of glucose (20 mg/l). Medium resulted from fruits of the first harvest date presented lower colony diameter. Inoculation of A. pullulans at 3 x 10(8) and 4 x 10(9) CFU/ml reduced the incidence of the disease by 23 and 63%, and reduced the lesion diameter by 36 and 46%, respectively.

Delayed repair of tendon to bone injuries leads to decreased biomechanical properties and bone loss

INTRODUCTION

Repair of the torn rotator cuff tendon is a common procedure performed in the shoulder. In the clinical setting, a significant delay between rotator cuff tear and subsequent repair often exists. The purpose of this study was to investigate the biomechanical properties and bone density of the tendon to bone repair site after acute and delayed repair.

METHODS

The supraspinatus tendons in bilateral shoulders of 60 rats were transected from the bone. In the acute group, the tendons were immediately repaired with suture. In the delayed group, the tendons were allowed to retract and repaired in a second procedure after a 3-week delay. Cross sectional area and biomechanical properties were evaluated. Bone density of the humeral head was assessed using peripheral quantitative computed tomography. Histologic sections were obtained and examined.

RESULTS

At 10 days the repair tissue displayed vascular and fibroblast proliferation accompanied by predominantly mononuclear infiltrate. At 28 days the inflammatory process gradually decreased. No significant histologic differences were noted between the acute and delayed repair specimens. Cross-sectional area was higher in the delayed group at the early time points (44% at 10 days and 31% at 28 days). Viscoelastic properties were greater in the acute group at the early time points and significantly less at the latest time point, compared to the delayed group. Bone density was markedly decreased (8% and 12%, 28 and 56 days respectively) in the delay group.

DISCUSSION

Inferior rotator cuff healing was demonstrated when there was a delay between injury and repair. Viscoelastic properties of the acute repairs were increased compared to the delayed group at 10 days, indicating tendon stiffening during the 3-week delay before repair. Viscoelastic properties of the acute repairs were decreased compared to the delayed group at 56 days indicating deterioration of properties over time in the delayed group. The deterioration in properties in the delayed group coincide with bone density decreases in the greater tuberosity. These results indicate that bone loss may a significant factor in poor healing.

Supplementary core sutures increase resistance to gapping for flexor digitorum profundus tendon to bone surface repair - an in vitro biomechanical analysis

We evaluated the effects of two types of supplementary core sutures on the tensile properties and resistance to gap formation of flexor digitorum profundus (FDP) tendon-bone repairs. Forty-five human cadaver FDP tendons were sharply released from their insertion sites and repaired to bone utilizing one of three repair techniques: four-strand modified Becker core suture (Becker only), modified Becker plus a figure-of-eight supplementary core suture (Becker plus figure-of-eight), and modified Becker plus a supplementary core suture using a bone anchor (Becker plus anchor). Ultimate (maximum) force did not differ between repair groups. However, addition of a supplementary suture significantly increased repair-site stiffness and the 1, 2 and 3 mm gap forces, while decreasing the gap at 20 N compared to the Becker only suture (P<0.05). The only difference between the two supplementary suture groups was that the Becker plus anchor group had increased stiffness compared to the Becker plus figure-of-eight group. In conclusion, a supplementary figure-of-eight suture and a supplementary suture using a bone anchor provide enhanced resistance to gap formation for FDP tendon-bone repairs.

Ligamentous versus physeal failure in murine medial collateral ligament biomechanical testing

This study examines the age at which a femoral physeal failure ceased to occur in a mouse model of medial collateral ligament (MCL) testing. Biomechanical testing of the MCL with load to failure can result in physeal failure rather than MCL failure in skeletally immature animals. Failure mode depended significantly on age (p<0.05). Sixty percent of the knees tested at 4 months failed at the physis rather than at the ligament, whereas, only ten percent of the knees tested at 5 and 6 months failed at the physis. The mean ultimate force to failure for the specimens in which the failure occurred at the ligament was 8.1 N with a higher values for the right side versus the left (p<0.05). For the specimens in which the failure occurred at the physis, the mean ultimate force to failure was 11.2 N. We now consider that 5 month old mice are functionally skeletally mature and old enough to be tested biomechanically with few failures at the physis.

Experimental and finite element analysis of the rat ulnar loading model-correlations between strain and bone formation following fatigue loading

The rat forelimb compression model has been used widely to study bone response to mechanical loading. We used strain gages to assess load sharing between the ulna and radius in the forelimb of adult Fisher rats. We used histology and peripheral quantitative computed tomography (pQCT) to quantify ulnar bone formation 12 days after in vivo fatigue loading. Lastly, we developed a finite element model of the ulna to predict the pattern of surface strains during compression. Our findings indicate that at the mid-shaft the ulna carries 65% of the applied compressive force on the forelimb. We observed large variations in fatigue-induced bone formation over the circumference and length of the ulna. Bone formation was greatest 1-2 mm distal to the mid-shaft. At the mid-shaft, we observed woven bone formation that was greatest medially. Finite element analysis indicated a strain pattern consistent with a compression-bending loading mode, with the greatest strains occurring in compression on the medial surface and lesser tensile strains occurring laterally. A peak strain of -5190 microepsilon (for 13.3N forelimb compression) occurred 1-2 mm distal to the mid-shaft. The pattern of bone formation in the longitudinal direction was highly correlated to the predicted peak compressive axial strains at seven cross-sections (r2 = 0.89, p = 0.014). The in-plane pattern of bone formation was poorly correlated to the predicted magnitude of axial strain at 51 periosteal locations (r2 = 0.21, p < 0.001), because the least bone formation was observed where tensile strains were highest. These findings indicate that the magnitude of bone formation after fatigue loading is greatest in regions of high compressive strain.

Accuracy of peripheral quantitative computed tomography (pQCT) for assessing area and density of mouse cortical bone

Peripheral quantitative computed tomography (pQCT) is increasingly used for measurement of cortical bone geometry and density in mice. We evaluated the accuracy of pQCT for area and density measurements of thin-walled aluminum phantoms and mouse femora. Aluminum tubes with varying wall thicknesses and femora from 1- to 6-month-old C3H/HeJ (C3H) and C57B1/6J (B6) mice (average cortical thickness 0.14-0.29 mm) were scanned at 70- or 90-microm resolution. pQCT values of area were compared to optical values determined after sectioning, while pQCT density (vBMD) was compared to solid aluminum density or correlated to bone ash content. For the aluminum phantoms, the error in pQCT area and density depended strongly on wall thickness, and density was consistently underestimated. For mouse femora, threshold values were found that produced zero error in bone area for each strain and age group, although the optimal threshold differed between groups. pQCT vBMD correlated strongly with ash content (r2=0.7), although the regression equations differed between strains and the magnitude of the inter-strain difference in vBMD was fourfold greater than the difference in ash content. This finding suggests that pQCT can overestimate the differences in volumetric mineral density between inbred mouse strains whose bones are of different thickness (e.g., C3H vs. B6). In conclusion, both area and density values obtained by pQCT depend strongly on specimen thickness, consistent with a partial volume averaging artifact. Investigators using pQCT to assess cortical bones in mice should be aware of the potential for cortical thickness-dependent errors.

[Determination of tissue optical parameters using HF modulation spectroscopy]

Radio frequency modulation spectroscopy is a capable method to determine tissue optical parameters in-vivo. For the eventual purpose of clinical measurements we have developed and tested an rf laser spectroscopy device which enables a measurement of the spatial amplitude and phase shift profiles of backscattered modulated laser light. Spectral absorption and scattering coefficients are computed by inverse formulas derived from analytical solutions of the diffusion model of light transport in a semi-infinite geometry.

Haplotype study of microsatellites flanking the t(15;17) breakpoint in acute promyelocytic leukemia patients from North Portugal

A higher frequency of acute promyelocytic leukemia (APL) has been noted in countries of Southern Europe and among 'Latino' patients of the United States with acute myeloid leukemia (AML). In order to discover whether there is any genetic predisposition to the disease, we analyzed microsatellites flanking PML and RARalpha genes in 29 t(15;17) APL patients from North Portugal and compared them with a control group of 123 healthy individuals. Fluorescent PCR products were analyzed using an automated capillary electrophoresis system and allele and haplotype frequencies of the two populations were determined. No significant differences were found, suggesting the same genetic origin of patients and healthy individuals. As suggested by the four microsatellites screened, MSI (microsatellite instability) does not explain the increased incidence of t(15;17) APL in this Portuguese population. These results intend to be a new approach to the study of APL, reflecting the particularity of the disease.

Low frequency noise and whole-body vibration cause increased levels of sister chromatid exchange in splenocytes of exposed mice

Chronic exposure to low frequency (LF) noise and whole-body vibration (WBV) induces both physiological and psychological alterations in man. Recently, we have shown that long-term occupational exposure to LF noise and WBV produces genotoxic effects in man expressed as an increase in sister chromatid exchange (SCE) levels in lymphocytes. The objectives of the present study were to investigate whether the observed effect could be reproduced in a murine model and, if so, which of the agents, LF noise alone or in combination with WBV, would be instrumental in the SCE induction. SCEs were analyzed in spleen lymphocytes of mice exposed to LF noise alone and in combination with WBV for 300 and 600 hr. An effect at the cell cycle kinetics level was also investigated. The results revealed significant increases in the mean SCE number per cell and in the proportion of cells with high frequency of SCEs (HFCs) in lymphocytes of mice submitted to combined noise and WBV over controls. No significant differences were found between single noise-exposed and control mice. A cell cycle delay was observed exclusively in the noise and WBV exposure groups. In conclusion, we demonstrated that, as in exposed workers, prolonged exposure to the combination of LF noise and WBV determines an increase in SCE level in mice while LF noise alone is not effective in SCE induction.

BMP-12 gene transfer augmentation of lacerated tendon repair

Bone morphogenetic protein (BMP) 12 is a recently discovered member of the human BMP family. It is the human homolog of mouse growth/differentiation factor (GDF)-7. Previously we reported that injection of mesenchymal progenitor cells transferred with the BMP-12 gene into the muscles of nude mice induced tendon-like tissue formation. In this study, we further investigated the effect of BMP-12 gene transfer on tendon cells. We observed that adenovirus mediated in vitro BMP-12 gene transfer into chicken tendon cells increased type I collagen synthesis. No change in alkaline phosphatase activity was observed following BMP-12 gene transfer. We also determined that BMP-12 gene transfer into a complete tendon laceration chicken model resulted in a two-fold increase of tensile strength and stiffness of repaired tendons, indicating improved tendon healing in vivo. We conclude that BMP-12 gene transfer is a promising procedure for improving the tendon repair process.

The influence of cross-sectional area on the tensile properties of flexor tendons

Clinicians have long noted substantial variation in the cross-sectional size of flexor tendons in the hand; however, data indicating that surgical repair techniques of lacerated flexor tendons should be altered according to size are unavailable. Our objectives were to evaluate the cross-sectional size differences among tendons within the same hand and to correlate tendon size with tensile mechanical properties after suture repair. Fifty human cadaver flexor digitorum profundus tendons were measured with digital calipers to determine radioulnar and volardorsal diameters. Twenty tendons were used to measure resistance to suture pull-through; tendons were transected at the A2 pulley, and a transverse double-stranded 4-0 Supramid suture (S. Jackson, Inc, Alexandria, VA) was passed through the radioulnar plane of the tendon 1 cm from the transection site. The remaining tendons were transected and repaired by using a modified Kessler repair with double-stranded 4-0 Supramid suture. Both tendon repairs and tendon-suture pull-through specimens were tested to failure in tension by using a material testing machine. Dorsovolar tendon height and tendon cross-sectional area varied significantly between digits, with an average difference of approximately 40% between the values of the smallest (fifth) and largest (third) fingers. Yield and ultimate force determined by pull-through tests of the simple transverse suture correlated positively with tendon radioulnar width. Tensile properties of tendons repaired with a double-stranded modified Kessler repair, however, did not depend significantly on tendon size. These results indicate that the strength of the commonly used Kessler suture technique is not dependent on tendon cross-sectional size within the clinically relevant range of tendons evaluated.

The effect of variations in applied rehabilitation force on collagen concentration and maturation at the intrasynovial flexor tendon repair site

The biochemical means by which accelerated rehabilitation alters intrasynovial flexor tendon repair site collagen synthesis and extracellular matrix maturation are not fully understood. We hypothesized that an increased level of applied rehabilitative force in a clinically relevant animal model would hasten the maturation of the repair site extracellular matrix as demonstrated by total collagen and collagen cross-link assessment. Twenty-eight flexor digitorum profundus tendons from 14 adult dogs were transected and repaired. The animals received either low- or high-force rehabilitation and were killed 10, 21, and 42 days after surgery. A 10-mm segment of tendon surrounding the repair site was obtained. Biochemical analysis showed that total collagen concentration was significantly reduced at each time point, that the reducible cross-link ratio of dihydroxylysinonorleucine to hydroxylysinonorleucine was significantly increased at each time point, and that the nonreducible pyridinoline cross-link content was significantly decreased at 10 days in both rehabilitative groups. Total collagen content did not vary to a statistically significant degree with either time or as a function of rehabilitation type. Based on these findings several clinically relevant observations can be made. Increasing collagen concentration and repair site maturation do not explain the previously demonstrated increased tensile properties of tendon that occur between 3 and 6 weeks after repair. Higher force rehabilitation does not alter the biochemical composition of the healing tendon through 6 weeks. Coupled with other recent data these findings suggest that high-force rehabilitation does not stimulate accelerated healing after intrasynovial flexor tendon repair.

A new species of Calomys (Rodentia, Sigmodontinae) from Central Brazil identified by its karyotype

Ten species of small rodents of genus Calomys are found in South America. Three of these ten species are known to occur in Brazil: C. tener, C. laucha and C. expulsus (= C. callosus expulsus). Almost all Calomys karyotypes are made up of acrocentric pairs. In this paper we describe a new karyotype with 2n = 46 (FN = 66), including 11 meta/submetacentric and 11 acrocentric autosomal pairs. This is not related to any described Calomys karyotype. The X chromosome is a medium submetacentric and the Y is a small acrocentric. This new karyotype is briefly compared to karyotype of the sympatric species C. tener (2n = 66, FN = 66). The reduced diploid number and small amount of pericentromeric heterochromatin observed in the biarmed chromosomes that contrasts to large blocks seen in acrocentrics seem to indicate that centric fusion and loss of constitutive heterochromatin have led to the new karyotype. Cytogenetic evidence suggests strongly that a new species with 2n = 46 from Central Brazil should be described in the genus Calomys.

Intrasynovial flexor tendon repair. An experimental study comparing low and high levels of in vivo force during rehabilitation in canines

BACKGROUND

Rehabilitation methods that generate increased tendon force and motion have been advocated to improve results following intrasynovial flexor tendon repair. However, the effects of rehabilitation force and motion on tendon-healing may be masked by the high stiffness produced by newer suture methods. Our objective was to determine whether the biomechanical properties of tendons repaired by one of two multistrand suture methods were sensitive to an increased level of applied rehabilitation force.

METHODS

Two hundred and fourteen flexor digitorum profundus tendons from 107 adult dogs were transected and repaired. Dogs were assigned to one of four groups based on the rehabilitation method (low force [<5 N] or high force [17 N]) and the repair technique (four-strand or eight-strand core suture) and were killed between five and forty-two days after the procedure. Repair-site structural properties were determined by tensile testing, and digital range of motion was assessed with use of a motion-analysis system.

RESULTS

Tensile properties did not differ between the low and high-force rehabilitation groups, regardless of the repair technique (p > 0.05). In contrast, tensile properties were strongly affected by the repair technique, with tendons in the eight-strand group having an approximately 35% increase in ultimate force and rigidity compared with those in the four-strand group (p < 0.05). Ultimate force did not change significantly with time during the first twenty-one days (p > 0.05); there was no evidence of softening in either of the repair or rehabilitation groups. Force increased significantly from twenty-one to forty-two days, while rigidity increased throughout the forty-two-day period (p < 0.05).

CONCLUSIONS

Increasing the level of force applied during postoperative rehabilitation from 5 to 17 N did not accelerate the time-dependent accrual of stiffness or strength. Suture technique was of primary importance in providing a stiff and strong repair throughout the early healing interval.

CLINICAL RELEVANCE

Our findings suggest that there be a reexamination of the concept that increases in force produced by more vigorous mobilization protocols are beneficial to tendon-healing. While more vigorous rehabilitation may help to improve hand function, we found no evidence that it enhances tissue-healing or strength in the context of a modern suture repair.

The effects of repetitive physiologic loading on bone turnover and mechanical properties in adult female and male rats

Repetitive physiologic loading is widely believed to be beneficial in maintaining skeletal integrity. However, repetitive loading is also associated with bone injuries, including stress fractures and osteoporotic fractures, indicating that under certain conditions repetitive physiologic loading decreases the functional capacity of bone. Our objective was to identify the response of bone to excessive repetitive loading in adult rats. Male and female rats (8-9 months old) were exposed to 2 hours of treadmill running each day for 10 or 30 consecutive days. We examined bone response using biochemical, densitometric, and monotonic, relaxation, and cyclic mechanical outcomes. Urinary deoxypyridinoline, a marker of bone resorption, was not significantly affected by running nor were tibial or femoral bone mineral density (BMD) (P > 0.05). Tibial mechanical properties following running were not decreased (P > 0.05). We did observe a slight decrease in displacement to failure (P < 0.05) and energy to failure (P = 0.10) of the proximal femur. These findings indicate that 14,000 physiologic loading cycles per day did not increase systemic bone resorption levels or substantially degrade the mechanical properties of long bone in adult rats. The lack of response to low magnitude, high cycle number physiologic loading is consistent with the view that a metabolic bone disturbance, in addition to repetitive loading, may be necessary for the development of the stress injury in the adult skeleton.

Raman spectroscopic detection of changes in bioapatite in mouse femora as a function of age and in vitro fluoride treatment

Laser Raman microprobe spectroscopy, which characterizes the molecular structure of a mineral, was used to analyze microscopically small regions of bioapatite in mouse femora in order to study the effect of mouse age and in vitro fluoride treatment on the bone mineral (i.e., mineral identity and degree of crystallinity). Both femora that had and those that had not undergone in vitro NaF treatment underwent point analysis of 1 micron spots in the center of the compact bone's cross-section. The Raman spectra of bones treated with fluoride showed a peak up-shift of the PO4 vibration mode from 961 to 964 delta cm-1 indicating a conversion from a carbonated hydroxylapatitic to a carbonated fluorapatitic mineral phase. The spectral band width of the 961 delta cm-1 PO4 vibration in femora of 4-, 10-, and 24-week-old mice showed that aging, as well as in vitro treatment with 1.5 M NaF for 12 hours, significantly increases the degree of crystallinity of the bioapatite. In vitro fluoridation of 10-week-old mouse femora increased the bioapatite's degree of crystallinity to about the same degree as did aging to 24 weeks. Four-point bending tests indicated that the age-related increase in crystallinity of untreated bones was associated with decreased deformation to failure, i.e., increased brittleness. In contrast, the increased crystallinity following fluoridation of 10-week-old bones was associated with increased deformation, i.e., increased ductility, perhaps due to the altered mineral composition. This study shows that the laser Raman microprobe readily detects the conversion of carbonated hydroxylapatite to carbonated fluorapatite, as well as changes in crystallinity of either mineral phase, in microscopically small regions of a bone sample.

Integrin expression is upregulated during early healing in a canine intrasynovial flexor tendon repair and controlled passive motion model

To explore crucial early molecular events involved in contact healing of the intrasynovial flexor tendon, integrin expression was evaluated at the transcriptional and post-transcriptional levels during the first two weeks following injury, repair and controlled passive motion in a canine model. Specifically, immunohistochemical and reverse transcription polymerase chain reaction (RT-PCR) techniques were employed to evaluate expression of the fibronectin, vitronectin and endothelial cell binding integrin receptor subunits alpha5, alphav and alpha6, along with the common beta1 subunit. The two techniques revealed increasing expression of the four subunits over the two week post-repair period. Immunohistochemistry revealed that beta1 and alpha5 expression was concentrated in the epitenon layer near the repair site and interiorly within the wound area, while alpha6 was associated with capillary-forming endothelial cells near the wound. RT-PCR and quantitation by NIH image analysis demonstrated peak messenger RNA expression of beta1 and alpha5 at ten days post-repair and peak expression of alpha6 and alphav at 15 days. The results in this study correlate well with previous results demonstrating increased fibronectin deposition and angiogenesis during the same time period in a similar injury/repair model.

Levels of seven urinary phthalate metabolites in a human reference population

Using a novel and highly selective technique, we measured monoester metabolites of seven commonly used phthalates in urine samples from a reference population of 289 adult humans. This analytical approach allowed us to directly measure the individual phthalate metabolites responsible for the animal reproductive and developmental toxicity while avoiding contamination from the ubiquitous parent compounds. The monoesters with the highest urinary levels found were monoethyl phthalate (95th percentile, 3,750 ppb, 2,610 microg/g creatinine), monobutyl phthalate (95th percentile, 294 ppb, 162 microg/g creatinine), and monobenzyl phthalate (95th percentile, 137 ppb, 92 microg/g creatinine), reflecting exposure to diethyl phthalate, dibutyl phthalate, and benzyl butyl phthalate. Women of reproductive age (20-40 years) were found to have significantly higher levels of monobutyl phthalate, a reproductive and developmental toxicant in rodents, than other age/gender groups (p < 0.005). Current scientific and regulatory attention on phthalates has focused almost exclusively on health risks from exposure to only two phthalates, di-(2-ethylhexyl) phthalate and di-isononyl phthalate. Our findings strongly suggest that health-risk assessments for phthalate exposure in humans should include diethyl, dibutyl, and benzyl butyl phthalates.

Quantitative detection of eight phthalate metabolites in human urine using HPLC-APCI-MS/MS

Because of the ubiquity of phthalates and their potential role in increasing risk for cancer and reproductive dysfunction, the need for human exposure assessment studies is urgent. In response to this need, we developed a high-throughput, robust, sensitive, accurate, and precise assay for simultaneous measurement of trace levels of eight phthalate metabolites in human urine by HPLC-MS/MS. Human urine samples were processed using enzymatic deconjugation of the glucuronides followed by solid-phase extraction. The eluate was concentrated, and the phthalate metabolites were chromatographically resolved by reversed-phase HPLC, detected by APCI-tandem mass spectrometry, and quantified by isotope dilution. This selective analytical method permits rapid detection (7.7 min total run time) of eight urinary metabolites of the most commonly used phthalates with detection limits in the low nanagram per milliliter range. Assay precision was improved by incorporating 13C4-labeled internal standards for each of the eight analytes, as well as a conjugated internal standard to monitor deconjugation efficiency. This selective, sensitive, and rapid method will help elucidate potential associations (if any) between human exposure to phthalates and adverse health effects.