Antibiotic Exposure and Dental Health: A Systematic Review

CONTEXT

The use of antibiotics in young children is widespread and may lead to adverse effects on dental health, including staining, developmental defects, and dental caries.

OBJECTIVE

To systematically review the effects of early childhood antibiotic exposure on dental health.

DATA SOURCES

Medline (Ovid/PubMed), Embase (Ovid) and Cochrane databases. Study bias was assessed using the Newcastle-Ottawa Scale.

STUDY SELECTION

English language articles that reported antibiotic exposure before 8 years of age and 1 or more of the relevant outcomes (dental caries, intrinsic tooth staining, or developmental defects of enamel) were included.

DATA EXTRACTION

Data on study population, design, type of antibiotic, outcome measurement, and results were extracted from the identified studies.

RESULTS

The initial search yielded 1003 articles of which 34 studies were included. Five of the 18 studies on tetracycline described a dose response relationship between exposure to tetracycline doses of > 20 mg/kg per day and dental staining. Early childhood exposure to doxycycline (at any dose) was not associated with dental staining. There was no clear association between any early childhood antibiotic exposure and dental caries or enamel defects.

LIMITATIONS

In all included studies, the main limitations and sources of bias were the lack of comparison groups, inconsistent outcome measures, and lack of adjustment for relevant confounders.

CONCLUSIONS

There was no evidence that newer tetracycline formulations (doxycycline and minocycline) at currently recommended dosages led to adverse effects on dental health. Findings regarding antibiotic exposure and developmental defects of enamel or dental caries were inconsistent. Further prospective studies are warranted.

A health promotion intervention for vulnerable schools (BeE-school): a cluster-randomized trial

Background

Noncommunicable diseases (NCDs) share key determinants like unhealthy diet, unhealthy 24h- movement behaviour (sleep, sedentary behaviour and physical activity), leading to other risks including overweight, obesity and raised blood pressure. Although the manifest of the NCDs in childhood is rare, risk behaviours, obesity, and raised blood pressure that accelerates their development begin during childhood. The current study aims to analyze the effectiveness of the intervention program based on the promotion of health literacy and lifestyles, on children’s health literacy, lifestyles (e.g. dietary intake, 24hmovement behaviour) and overweight and obesity.

Methods

478 children (6 schools) aged 6-12years old will participate in this cluster-randomized trial, having schools as the unit of randomization, assigned into intervention (239-3schools) and the control arm (239-3schools). This project is currently performing social listening (online and offline) and stakeholders’ involvement. Data collection includes sociodemographics, health literacy and infodemic resilience, dietary intake and children’s 24-h movement behaviour (e.g. accelerometry), anthropometry (e.g. weight, height and waist circumference) and blood pressure. It will occur at baseline and after the intervention (follow-up, 6 months after the beginning of the intervention).

Results

Expected outputs and outcomes include the 1-creation of a model for characterizing NCDs and health topics based on artificial intelligence techniques (e.g. deep learning, social network analysis methods).2- improved health literacy and infodemic resilience of children, families and teachers.3- enhanced children’s lifestyles. 4- reduce NCDs’ physical risk factors (e.g. overweight, raised blood pressure).

Conclusions

A feasible intervention program for school-aged children with vulnerabilities enhances tailored policies about health promotion and NCDs’ prevention, respecting the contextś singularities.

Key messages

• Health promotion and NCDs prevention are crucial for the well-being of our societies.

• Feasible intervention programs advocates for evidence-based policies that respect local singularities.

Digital health literacy and online information queries in Portuguese university students

Background

Worldwide there is an overwhelming amount of information about COVID-19 circulating online, also named infodemic. Misinformation (the unintentional) and disinformation (the intentional) spreading of false information have proven to be very dangerous to public health. Hence, more than ever, people need skills for searching, evaluating and integrating information related to health in daily life, i.e., health literacy. Until now, little is known about the digital health literacy of university students and their information-seeking behaviour. Hence, this study aimed to analyse the associations between university students' digital health literacy and online information queries during the beginning of the COVID-19 pandemic (and infodemic) in Portugal.

Methods

A cross-sectional study of 3.084 Portuguese university students (75.7% females), with an average age of 24.2 (SD = 7.5), was conducted using an online survey. We used sociodemographic data (sex, age, subjective social status) and the digital health literacy questionnaire adapted to the specific COVID-19 context. Online information queries included the topics related to SARS-CoV-2 and COVID-19 searched by students. Logistic regression models were performed.

Results

Online information queries (e.g., individual measures to protect against infection, current spread of the virus, current situation assessments and recommendations) were associated with an increased odds of achieving sufficient digital health literacy.

Conclusions

Online information queries related to epidemiological and public health topics are significantly associated with digital health literacy in times of COVID-19. Further studies are needed, including programs that improve digital health literacy among university students and increase the availability of high-quality content information.

NF-κB-mediated effects on behavior and cartilage pathology in a non-invasive loading model of post-traumatic osteoarthritis

OBJECTIVE

This study aimed to examine the temporal activation of NF-κB and its relationship to the development of pain-related sensitivity and behavioral changes in a non-invasive murine knee loading model of PTOA.

METHOD

Following knee injury NF-κB activity was assessed longitudinally via in vivo imaging in FVB. Cg-Tg (HIV-EGFP,luc)8Tsb/J mice. Measures of pain-related sensitivity and behavior were also assessed longitudinally for 16 weeks. Additionally, we antagonized NF-κB signaling via intra-articular delivery of an IκB kinase two antagonist to understand how local NF-κB inhibition might alter disease progression.

RESULTS

Following joint injury NF-κB signaling within the knee joint was transiently increased and peaked on day 3 with an estimated 1.35 p/s/cm2/sr (95% CI 0.913.1.792 p/s/cm2/sr) fold increase in signaling when compared to control joints. Furthermore, injury resulted in the long-term development of hindpaw allodynia. Hyperalgesia withdrawal thresholds were reduced at injured knee joints, with the largest reduction occurring 2 days following injury (estimate of between group difference 129.1 g with 95% CI 60.9,197.4 g), static weight bearing on injured limbs was also reduced. Local delivery of an NF-κB inhibitor following joint injury reduced chondrocyte death and influenced the development of pain-related sensitivity but did not reduce long-term cartilage degeneration.

CONCLUSION

These findings underscore the development of behavioral changes in this non-invasive loading model of PTOA and their relationships to NF-κB activation and pathology. They also highlight the potential chondroprotective effects of NF-κB inhibition shortly following joint injury despite limitations in preventing the long-term development of joint degeneration in this model of PTOA.

[SAMHD1 acts at stalled replication forks to prevent interferon induction]

DNA replication is an extremely complex process, involving thousands of replication forks progressing along chromosomes. These forks are frequently slowed down or stopped by various obstacles, such as secondary DNA structures, chromatin-acting proteins or a lack of nucleotides. This slowing down, known as replicative stress, plays a central role in tumour development. Complex processes, which are not yet fully understood, are set up to respond to this stress. Certain nucleases, such as MRE11 and DNA2, degrade the neo-replicated DNA at the level of blocked forks, allowing the replication to restart. The interferon pathway is a defense mechanism against pathogens that detects the presence of foreign nucleic acids in the cytoplasm and activates the innate immune response. DNA fragments resulting from genomic DNA metabolism (repair, retrotransposition) can diffuse into the cytoplasm and activate this pathway. A pathological manifestation of this process is the Aicardi-Goutières syndrome, a rare disease characterized by chronic inflammation leading to neurodegenerative and developmental problems. In this encephalopathy, it has been suggested that DNA replication may generate cytosolic DNA fragments, but the mechanisms involved have not been characterized. SAMHD1 is frequently mutated in the Aicardi-Goutières syndrome as well as in some cancers, but its role in the etiology of these diseases was largely unknown. We show that cytosolic DNA accumulates in SAMHD1-deficient cells, particularly in the presence of replicative stress, activating the interferon response. SAMHD1 is important for DNA replication under normal conditions and for the processing of stopped forks, independent of its dNTPase activity. In addition, SAMHD1 stimulates the exonuclease activity of MRE11 in vitro. When SAMHD1 is absent, degradation of neosynthesized DNA is inhibited, which prevents activation of the replication checkpoint and leads to failure to restart the replication forks. Resection of the replication forks is performed by an alternative mechanism which releases DNA fragments into the cytosol, activating the interferon response. The results obtained show, for the first time, a direct link between the response to replication stress and the production of interferons. These results have important implications for our understanding of the Aicardi-Goutières syndrome and cancers related to SAMHD1. For example, we have shown that MRE11 and RECQ1 are responsible for the production of DNA fragments that trigger the inflammatory response in cells deficient for SAMHD1. We can therefore imagine that blocking the activity of these enzymes could decrease the production of DNA fragments and, ultimately, the activation of innate immunity in these cells. In addition, the interferon pathway plays an essential role in the therapeutic efficacy of irradiation and certain chemotherapeutic agents such as oxaliplatin. Modulating this response could therefore be of much wider interest in anti-tumour therapy.

A twin study of body mass index and dental caries in childhood

Sub-optimal nutrition and dental caries are both common with significant short and long-term implications for child health and development. We applied twin statistical methods to explore the relationship between body mass index (BMI) and dental caries. We measured BMI at 18 months and six years of age and cumulative dental caries experience at six years in 344 twin children. Dental caries in primary teeth was categorised into ‘any’ or ‘advanced’ and BMI was analysed as both a continuous and categorical variable. Statistical analyses included multiple logistic regression using generalized estimating equations and within/between-pair analyses. There was no association between BMI and ‘any’ dental caries experience at either time-point, neither overall nor in within/between pair analyses. However, ‘advanced’ dental caries at six years was associated with a within-pair difference in BMI of −0.55 kg/m² (95% CI −1.00, −0.11, p = 0.015). A within-pair increase of 1 kg/m² in BMI was associated with a lower within-pair risk of advanced dental caries (OR 0.68, 95% CI 0.52, 0.90, p = 0.007). These findings reveal a possible causal relationship between lower BMI and dental caries. As dental outcomes were only measured at one time point, the direction of this potentially causal relationship is unclear.

Getting ahead of the oral health game: it starts before we're born?

Dental caries is one of the most common chronic diseases affecting individuals of all ages. Caries in the primary dentition is one of the main risk factors for caries in the permanent dentition. Preventing the development of the first carious lesion is fundamental not only to long term health and wellbeing but to reducing the burden of this disease on individuals, families and the community. Described as the developmental origins of health and disease, events from the prenatal period are increasingly recognised as having a significant impact on later health outcomes. While social and behavioural factors from this period have long been linked with oral health, emerging evidence of the influence of epigenetics and early life programming of microbiome and host response suggests that the prenatal period provides a timely opportunity for preventive interventions. Pregnancy is an ideal time to focus on health promoting activities as most women have regular interaction with health care professionals who can target risk factors before the onset of disease. This paper summarizes contemporary understanding of the role of pre- and perinatal factors on child oral health and describes how this evidence might be used by all health professionals to ensure infants start life ahead in the oral health game.

Genetic and Early-Life Environmental Influences on Dental Caries Risk: A Twin Study

OBJECTIVES

To explore the relative contributions of genetic and environmental influences on dental caries risk and to investigate fetal and developmental risk factors for dental caries.

METHODS

We recruited children from 250 twin pregnancies midgestation and collected demographic, health, and phenotypic data at recruitment, 24 and 36 weeks' gestational age, birth and 18 months, and 6 years of age. 25-hydroxyvitamin D was quantified in mothers at 28 weeks' gestation and in infants at birth. Dental caries and enamel defects were measured at six years of age. We compared concordance for the presence of any caries and advanced caries in monozygotic and dizygotic twin pairs. To investigate environmental risk factors for caries, we fitted multiple logistic regression models using generalized estimating equations to adjust for twin correlation.

RESULTS

A total of 345 twins underwent dental assessment, with 111 (32.2%) showing signs of any caries and 83 (24.1%) having advanced caries. There was no evidence of higher concordance in monozygotic twins compared with dizygotic twins, with a difference of 0.05 (95% confidence interval -0.14 to 0.25; P = .30) and 0.00 (95% confidence interval -0.26 to 0.26; P = .50) for any caries and advanced caries, respectively, suggesting that environmental factors, rather than genetics, are the predominant determinant of caries risk. After adjusting for potential confounders, lack of community water fluoridation, hypomineralized second primary molars, dichorionic placenta, and maternal obesity were associated with caries.

CONCLUSIONS

Environmental rather than genetic factors drive dental caries risk and arise as early as prenatal life.

Abstract PD1-06: A phase 1b dose-escalation and expansion study of the BCL-2 inhibitor venetoclax combined with tamoxifen in ER and BCL-2–positive metastatic breast cancer (MBC)

Background: Venetoclax, a potent and selective inhibitor of the survival protein BCL-2 (recently approved in CLL and in development in other hematopoietic malignancies), has yet to be evaluated in pts with solid tumors. BCL-2 is overexpressed in ˜85% of ER+ breast cancer. Pre-clinical findings using patient-derived xenograft breast tumor models suggest that venetoclax synergizes with endocrine therapy by increasing apoptosis. Here we report mBEP, an investigator-initiated phase 1b study of venetoclax with tamoxifen in 33 pts with ER+ (>1%), BCL-2+ (>10%, 2-3+ intensity) and HER2– MBC.

Methods: We conducted a 3+3 dose escalation study comprising cohorts receiving venetoclax 200, 400, 600 or 800 mg/d with tamoxifen 20 mg/d (continued until progression). The primary endpoint was to determine the maximum tolerated dose (MTD), define dose-limiting toxicities (DLTs) and identify the recommended phase 2 dose (RP2D). In a dose expansion phase (at the RP2D), secondary endpoints including safety and tolerability, response at 24 wks (RECIST v1.1), clinical benefit rate (CBR) and progression-free survival (PFS) were studied.

Results: In the escalation phase (n=15 pts), treatment was well tolerated with no DLTs or high-grade (Gd 3/4) adverse events observed, apart from asymptomatic on-target lymphopenia (Gd 3, 2/15 pts). MTD was not reached. The 800 mg/d dose was selected as the RP2D and the cohort expanded to include 24 pts with ≥24 wks follow up (range 24-105 wks). Fifteen pts had received prior regimens for MBC (median 3, range 1-9) that included tamoxifen in 5/15.

For the RP2D cohort (n=24), overall responses (OR) included 1 CR (4%) and 12 PR (50%), with 5 SD (21%), corresponding to a CBR of 75%. The 9 pts treated in the first line setting experienced a 78% OR (7/9 pts) and 11% SD (1/9 pts), equating to an 89% CBR. The data are immature for determining median PFS for the RP2D cohort (currently 40+ wks).

Treatment responses were pre-empted by metabolic responses (FDG-PET) at 4 wks (seen in 13/16 (81%) pts studied), and correlated with serial changes in circulating tumor DNA (ctDNA). Intriguingly, responses and clinical benefit were observed in pts with plasma-detected ESR1 mutations (4/10 and 7/10, respectively).

The most common treatment-related AEs (CTCAE v4.0) for all pts were lymphopenia in 29/33 (88%; 57% Gd 1-2, 30% Gd 3-4), neutropenia in 24/33 (73%; 67% Gd 1-2, 6% Gd 3), nausea in 22/33 (67%; all ≤Gd 2), anemia in 13/33 (39%; 33% Gd 1-2, 6% G3), thrombocytopenia in 11/33 (33%; all ≤Gd 2), vomiting in 11/33 (33%, all ≤Gd 2), diarrhea in 10/33 (30%; 24% Gd 1-2, 6% Gd 3), infection in 9/33 (27%; 18% Gd 2, 9% Gd 3) and fatigue in 7/33 (21%; all ≤Gd 2). There was one possible treatment-related SAE (infection).

Conclusions: In the first clinical study to evaluate venetoclax in a solid tumor, we demonstrate that combining venetoclax with endocrine therapy has a tolerable safety profile and elicits remarkable activity in ER+ and BCL-2+ MBC. These findings support further investigation of combination therapy for patients with BCL-2-positive breast cancer.

Sponsor: The Royal Melbourne Hospital (ACTRN12615000702516)

Citation Format: Lindeman GJ, Lok SW, Whittle JR, Siow ZR, Bergin AR, Dawson S-J, Desai J, Gray DH, Liew D, Mann GB, Murugasu A, Roberts AW, Rosenthal MA, Shackleton K, Sherman P, Silva MJ, Teh C, Travers A, Vaillant F, Visvader JE. A phase 1b dose-escalation and expansion study of the BCL-2 inhibitor venetoclax combined with tamoxifen in ER and BCL-2–positive metastatic breast cancer (MBC) [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr PD1-06.

Etiology of Hypomineralized Second Primary Molars: A Prospective Twin Study

The etiology of hypomineralized second primary molars (HSPM) is unclear, but genetic and environmental factors have been proposed. The aim of this study was to investigate the relative contribution of genes and environment to the etiology of HSPM and to identify potential environmental risk factors in a longitudinal twin cohort. Children from twin pregnancies ( N = 250) were recruited antenatally, and detailed demographic, health, and phenotypic data were collected at recruitment, 24- and 36-wk gestation, birth, and 18 mo of age. 25-Hydroxyvitamin D was quantified for mothers at 28-wk gestation and infants at birth. Dental examinations were conducted on the twins at 6 y of age to determine the presence, severity, and extent of HSPM per standardized criteria. To investigate associations of environmental risk factors with HSPM, multiple logistic regression models were fitted with generalized estimating equations to adjust for twin correlation. Within- and between-pair analyses were performed for unshared continuous variables: birthweight and birth 25-hydroxyvitamin D. Twin-twin concordance for monozygotic (MZ) and dizygotic (DZ) pairs was calculated and compared after adjusting for identified risk factors. A total of 344 twins underwent the 6-y-old dental assessment; HSPM occurred in 68 (19.8%). After adjusting for potential confounders, vitamin D levels at birth, infantile eczema, dizygosity, in vitro fertilization, socioeconomic position, and maternal smoking beyond the first trimester of pregnancy demonstrated the strongest associations with HSPM. Overall concordance for HSPM was 0.47 (95% CI, 0.32 to 0.62) with weak evidence ( P = 0.078) of higher concordance in MZ twins (0.63; 95% CI, 0.38 to 0.89) as compared with DZ twins (0.41; 95% CI, 0.24 to 0.58). After adjusting for known risk factors, there was no evidence ( P = 0.172) for an additive genetic influence. These findings suggest that shared and unshared environmental factors, such as maternal smoking later in pregnancy and infantile eczema, are important in the etiology of HSPM.

Etiology of molar incisor hypomineralization - A systematic review

OBJECTIVES

Molar incisor hypomineralization (MIH) is a common developmental dental defect of permanent teeth, which can increase the risk of dental caries, infection and hospitalization. The etiology is currently unclear although prenatal or early childhood health factors are suspected. The aim of this systematic review was to assess the strength of evidence linking etiological factors with MIH.

METHODS

A systematic search was conducted using the Medline and Embase electronic databases for studies investigating environmental etiological factors of MIH. Two reviewers assessed the eligibility of studies. The level of evidence and bias was determined for all eligible studies according to Australian National Health and Medical Research Council guidelines for systematic reviews of etiology and the Newcastle-Ottawa Scale.

RESULTS

From a total of 2254 studies identified through electronic and hand searching, 28 were eligible for inclusion. Twenty-five of these investigated MIH and three investigated a related condition in primary teeth, hypomineralized second primary molars (HSPM), and these were analysed separately. A limited number of studies reported significant associations between MIH and pre- and perinatal factors such as maternal illness and medication use in pregnancy, prematurity and birth complications. Early childhood illness was implicated as an etiological factor in MIH in several studies, in particular fever, asthma and pneumonia. The studies investigating HSPM revealed an association with maternal alcohol consumption, infantile fever and ethnicity. However, the validity of these findings is impaired by study design, lack of adjustment for confounders, lack of detail and consistency of exposures investigated and poor reporting.

CONCLUSIONS

Childhood illness is likely to be associated with MIH. Further prospective studies of the etiology of MIH/HSPM are needed.

Early response of mouse joint tissue to noninvasive knee injury suggests treatment targets

OBJECTIVE

Joint trauma can lead to a spectrum of acute lesions, including cartilage degradation, ligament or meniscus tears, and synovitis, all potentially associated with osteoarthritis (OA). This study was undertaken to generate and validate a murine model of knee joint trauma following noninvasive controlled injurious compression in vivo.

METHODS

The right knees of 8-week-old mice were placed in a hyperflexed position and subjected to compressive joint loading at 1 of 3 peak forces (3N, 6N, or 9N) for 60 cycles in a single loading period and harvested on days 5, 9, and 14 after loading (n = 3-5 for each time point and for each loading). The left knees were not loaded and were used as the contralateral control. Histologic, immunohistochemical, and enzyme-linked immunosorbent assay analyses were performed to evaluate acute pathologic features in chondrocyte viability, cartilage matrix metabolism, synovial reaction, and serum cartilage oligomeric matrix protein (COMP) levels.

RESULTS

Acute joint pathology was associated with increased injurious loads. All loading regimens induced chondrocyte apoptosis, cartilage matrix degradation, disruption of cartilage collagen fibril arrangement, and increased levels of serum COMP. We also observed that 6N loading induced mild synovitis by day 5, whereas at 9N, with tearing of the anterior cruciate ligament, severe posttraumatic synovitis and ectopic cartilage formation were observed.

CONCLUSION

We have established a murine model of knee joint trauma with different degrees of overloading in vivo. Our results suggest that immediate therapies particularly targeted to apoptosis and synovial cell proliferation could affect the acute posttraumatic reaction to potentially limit chronic consequences and OA.

The early inflammatory response after flexor tendon healing: a gene expression and histological analysis

Despite advances in surgical techniques over the past three decades, tendon repairs remain prone to poor clinical outcomes. Previous attempts to improve tendon healing have focused on the later stages of healing (i.e., proliferation and matrix synthesis). The early inflammatory phase of tendon healing, however, is not fully understood and its modulation during healing has not yet been studied. Therefore, the purpose of this work was to characterize the early inflammatory phase of flexor tendon healing with the goal of identifying inflammation-related targets for future treatments. Canine flexor tendons were transected and repaired using techniques identical to those used clinically. The inflammatory response was monitored for 9 days. Temporal changes in immune cell populations and gene expression of inflammation-, matrix degradation-, and extracellular matrix-related factors were examined. Gene expression patterns paralleled changes in repair-site cell populations. Of the observed changes, the most dramatic effect was a greater than 4,000-fold up-regulation in the expression of the pro-inflammatory factor IL-1β. While an inflammatory response is likely necessary for healing to occur, high levels of pro-inflammatory cytokines may result in collateral tissue damage and impaired tendon healing. These findings suggest that future tendon treatment approaches consider modulation of the inflammatory phase of healing.

Determining oxidative and non-oxidative genotoxic effects driven by estuarine sediment contaminants on a human hepatoma cell line

Estuarine sediments may be reservoirs of hydrophilic and hydrophobic pollutants, many of which are acknowledged genotoxicants, pro-mutagens and even potential carcinogens for humans. Still, studies aiming at narrowing the gap between ecological and human health risk of sediment-bound contaminant mixtures are scarce. Taking an impacted estuary as a case study (the Sado, SW Portugal), HepG2 (human hepatoma) cells were exposed in vitro for 48 h to extracts of sediments collected from two areas (urban/industrial and Triverine/agricultural), both contaminated by distinct mixtures of organic and inorganic toxicants, among which are found priority mutagens such as benzo[a]pyrene. Comparatively to a control test, extracts of sediments from both impacted areas produced deleterious effects in a dose-response manner. However, sediment extracts from the industrial area caused lower replication index plus higher cytotoxicity and genotoxicity (concerning total DNA strand breakage and clastogenesis), with emphasis on micronucleus induction. On the other hand, extracts from the rural area induced the highest oxidative damage to DNA, as revealed by the FPG (formamidopyrimidine-DNA glycosylase) enzyme in the Comet assay. Although the estuary, on its whole, has been classified as moderately contaminated, the results suggest that the sediments from the industrial area are significantly genotoxic and, furthermore, elicit permanent chromosome damage, thus potentially being more mutagenic than those from the rural area. The results are consistent with contamination by pro-mutagens like polycyclic aromatic hydrocarbons (PAHs), potentiated by metals. The sediments from the agriculture-influenced area likely owe their genotoxic effects to metals and other toxicants, probably pesticides and fertilizers, and able to induce reactive oxygen species without the formation of DNA strand breakage. The findings suggest that the mixtures of contaminants present in the assayed sediments are genotoxic to HepG2 cells, ultimately providing a useful approach to hazard identification and an effective line-of-evidence in the environmental monitoring of anthropogenically-impacted coastal ecosystems.

Human hepatoma cells exposed to estuarine sediment contaminant extracts permitted the differentiation between cytotoxic and pro-mutagenic fractions

Complex toxicant mixtures present in estuarine sediments often render contaminant screening unfeasible and compromise determining causation. HepG2 cells were subjected to bioassays with sediment extracts obtained with a series of progressively polar solvents plus a crude extract. The sediments were collected from an impacted area of an estuary otherwise regarded as pristine, whose stressors result mostly from aquaculture effluents and hydrodynamic shifts that enhance particle deposition. Compared to a reference scenario, the most polar extracts yielded highest cytotoxicity while higher genotoxicity (including oxidative damage) was elicited by non-polar solvents. While the former caused effects similar to those expected from biocides, the latter triggered effects compatible with known pro-mutagens like PAHs, even though the overall levels of toxicants were considered of low risk. The results indicate that the approach may constitute an effective line-of-evidence to infer on the predominant set of hazardous contaminants present in complex environmental mixtures.

Intrasynovial flexor tendon repair: a biomechanical study of variations in suture application in human cadavera

To improve the functional outcomes of intrasynovial tendon suture, prior experiments evaluated individual technical modifications used in the repair process. Few studies, however, have assessed the combinatorial effects of those suture modifications in an integrated biomechanical manner, including a sample size sufficient to make definitive observations on repair technique. Two hundred fifty-six flexor tendon repairs were performed in human cadavera, and biomechanical properties were determined. The effects of five factors for flexor tendon repair were tested: core suture caliber (4-0 or 3-0), number of sutures crossing the repair site (four- or eight-strand), core suture purchase (0.75 or 1.2 cm), peripheral suture caliber (6-0 or 5-0), and peripheral suture purchase (superficial or 2 mm). Significant factors affecting the properties of the repair were the number of core suture strands and the peripheral suture purchase. The least significant factors were core suture purchase and peripheral suture caliber. The choice of core suture caliber affected the properties of repair marginally. Based on these results, we recommend that surgeons continue to focus on multi-strand repair methods, as the properties of eight-strand repairs were far better than those of four-strand repairs. To resist gap formation and enhance repair strength, a peripheral suture with 2 mm purchase is also recommended. Finally, since core suture caliber affected some biomechanical properties, including the failure mode, a 3-0 suture could be considered, provided that future in vivo studies can confirm that gliding properties are not adversely influenced.

Screening of Jatropha curcas genotypes to anthracnose caused by Colletotrichum gloeosporioides

Anthracnose caused by Colletotrichum gloeosporioides is an important physic nut (Jatropha curcas) disease causing damages on leaves, stems and fruits and consequently a decrease in seed quantity and quality. Physic nut is a native plant of Central America that has gained international attention due to its potential as biodiesel crop. However despite its highest relevance, studies concerning the response of different Jatropha genotypes to infection with this disease are very limited. The main objective of this study is the evaluation of susceptibility of 38 Jatropha curcas genotypes from a worldwide germplasm collection to Colletotrichum gloeosporioides. A simple method using wounded detached leaves inoculated with a 5-mm mycelia plug was used. Observations (lesion diameter and % of infection) were made after 3 and 7 days under controlled conditions (25 degrees C and 85% RH). Results showed significantly differences (P < or = 0.001) in both percentage of infection and lesion diameter among the tested accessions. Two genotypes from Brazil and Cape Verde, presented no lesions after 7 days of treatment, while the others presented between 67 and 100% of infection. Lesion diameter showed an increase with time of incubation and proved to be a useful tool for evaluation of plant susceptibility.

Associations between urinary metabolites of di(2-ethylhexyl) phthalate and reproductive hormones in fertile men

Widely used man-made chemicals, including phthalates, can induce hormonal alterations through a variety of cellular and molecular mechanisms. A number of rodent and observational studies have consistently demonstrated the anti-androgenic effect of several phthalates. However, there are only limited data on the relationship between exposure to these chemicals and reproductive hormone levels in men. All men (n=425) were partners of pregnant women who participated in the Study for Future Families in five US cities and provided urine and serum samples on the same day. Eleven phthalate metabolites were measured in urine and serum samples were analysed for reproductive hormones, including follicle-stimulating hormone, luteinizing hormone, testosterone, inhibin B and oestradiol and sex hormone-binding globulin (SHBG). Pearson correlations and parametric tests were used for unadjusted analyses, and multiple linear regression analysis was performed controlling for appropriate covariates. We observed weak or no associations with urinary phthalates other than di(2-ethylhexyl) phthalate (DEHP). All measures of testosterone [total, calculated free testosterone and the free androgen index (FAI)] were inversely correlated with the urinary concentrations of four DEHP metabolites. After adjustment by appropriate covariates, there was no longer an association between urinary DEHP metabolite concentrations and total testosterone levels; however, FAI was significantly associated with the urinary concentrations of several DEHP metabolites. SHBG was positively related to the urinary concentrations of mono(2-ethylhexyl) phthalate, but not with other DEHP metabolites, an association that was attenuated after adjustment. Our results suggest that DEHP exposure of fertile men is associated with minor alterations of markers of free testosterone.

Genomics and proteomics approaches to the study of cancer-stroma interactions

Background

The development and progression of cancer depend on its genetic characteristics as well as on the interactions with its microenvironment. Understanding these interactions may contribute to diagnostic and prognostic evaluations and to the development of new cancer therapies. Aiming to investigate potential mechanisms by which the tumor microenvironment might contribute to a cancer phenotype, we evaluated soluble paracrine factors produced by stromal and neoplastic cells which may influence proliferation and gene and protein expression.

Methods

The study was carried out on the epithelial cancer cell line (Hep-2) and fibroblasts isolated from a primary oral cancer. We combined a conditioned-medium technique with subtraction hybridization approach, quantitative PCR and proteomics, in order to evaluate gene and protein expression influenced by soluble paracrine factors produced by stromal and neoplastic cells.

Results

We observed that conditioned medium from fibroblast cultures (FCM) inhibited proliferation and induced apoptosis in Hep-2 cells. In neoplastic cells, 41 genes and 5 proteins exhibited changes in expression levels in response to FCM and, in fibroblasts, 17 genes and 2 proteins showed down-regulation in response to conditioned medium from Hep-2 cells (HCM). Nine genes were selected and the expression results of 6 down-regulated genes (ARID4A, CALR, GNB2L1, RNF10, SQSTM1, USP9X) were validated by real time PCR.

Conclusions

A significant and common denominator in the results was the potential induction of signaling changes associated with immune or inflammatory response in the absence of a specific protein.

Enhanced flexor tendon healing through controlled delivery of PDGF-BB

A fibrin/heparin-based delivery system was used to provide controlled delivery of platelet derived growth factor BB (PDGF-BB) in an animal model of intrasynovial flexor tendon repair. We hypothesized that PDGF-BB, administered in this manner, would stimulate cell proliferation and matrix remodeling, leading to improvements in the sutured tendon's functional and structural properties. Fifty-six flexor digitorum profundus tendons were injured and repaired in 28 dogs. Three groups were compared: (1) controlled delivery of PDGF-BB using a fibrin/heparin-based delivery system; (2) delivery system carrier control; and (3) repair- only control. The operated forelimbs were treated with controlled passive motion rehabilitation. The animals were euthanized at 7, 14, and 42 days, at which time the tendons were assessed using histologic (hyaluronic acid content, cellularity, and inflammation), biochemical (total DNA and reducible collagen crosslink levels), and biomechanical (gliding and tensile properties) assays. We found that cell activity (as determined by total DNA, collagen crosslink analyses, and hyaluronic acid content) was accelerated due to PDGF-BB at 14 days. Proximal interphalangeal joint rotation and tendon excursion (i.e., tendon gliding properties) were significantly higher for the PDGF-BB-treated tendons compared to the repair-alone tendons at 42 days. Improvements in tensile properties were not achieved, possibly due to suboptimal release kinetics or other factors. In conclusion, PDGF-BB treatment consistently improved the functional but not the structural properties of sutured intrasynovial tendons through 42 days following repair.

Measurement of eight urinary metabolites of di(2-ethylhexyl) phthalate as biomarkers for human exposure assessment

Human metabolism of di(2-ethylhexyl) phthalate (DEHP) is complex and yields mono(2-ethylhexyl) phthalate (MEHP) and numerous oxidative metabolites. The oxidative metabolites, mono(2-ethyl-5-oxohexyl) phthalate (MEOHP), mono(2-ethyl-5-hydroxyhexyl) phthalate (MEHHP), mono(2-ethyl-5-carboxypentyl) phthalate (MECPP) and mono(2-carboxymethylhexyl) phthalate (MCMHP), have been considered to be better biomarkers for DEHP exposure assessment than MEHP because urinary levels of these metabolites are generally higher than MEHP, and their measurements are not subject to contamination. The urinary levels of the above metabolites, and of three other recently identified DEHP oxidative metabolites, mono(2-ethyl-3-carboxypropyl) phthalate (MECPrP), mono-2-(1-oxoethylhexyl) phthalate (MOEHP), and mono(2-ethyl-4-carboxybutyl) phthalate (MECBP), were measured in 129 adults. MECPP, MCMHP and MEHHP were present in all the samples analysed. MEHP and the other oxidative metabolites were detected less frequently: MEOHP (99%), MECBP (88%), MECPrP (84%), MEHP (83%) and MOEHP (77%). The levels of all DEHP metabolites were highly correlated (p<0.0001) with each other, confirming a common parent. The ? and ?-1 oxidative metabolites (MECPP, MCMHP, MEHHP and MEOHP) comprised 87.1% of all metabolites measured, and thus are most likely the best biomarkers for DEHP exposure assessment. The percentage of the unglucuronidated free form excreted in urine was higher for the ester linkage carboxylated DEHP metabolites compared with alcoholic and ketonic DEHP metabolites. The percentage of the unglucuronidated free form excreted in urine was higher for the DEHP metabolites with a carboxylated ester side-chain compared with alcoholic and ketonic metabolites. Further, differences were found between the DEHP metabolite profile between this adult population and that of six neonates exposed to high doses of DEHP through extensive medical treatment. In the neonates, MEHP represented 0.6% and MECPP 65.5% of the eight DEHP metabolites measured compared to 6.6% (MEHP) and 31.8% (MECPP) in the adults. Whether the observed differences reflect differences in route/duration of the exposure, age and/or health status of the individuals is presently unknown.

Assessment of human exposure to di-isodecyl phthalate using oxidative metabolites as biomarkers

Di-isodecyl phthalate (DiDP), primarily used as a plasticiser, is a mixture of isomers with predominantly ten-carbon branched side chains. Assessment of DiDP exposure has not been conducted before because adequate biomarkers were lacking. In 129 adult volunteers with no known exposure to DiDP, the urinary concentrations of three oxidative metabolites of DiDP: monocarboxyisononyl phthalate (MCiNP), monooxoisodecyl phthalate (MOiDP) and monohydroxyisodecyl phthalate (MHiDP), previously identified in DiDP-dosed rats, were estimated by solid-phase extraction coupled to high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) using the respective oxidative metabolites of di(2-ethylhexyl)phthalate since authentic standards of the DiDP oxidative metabolites were unavailable. Interestingly, the hydrolytic monoester of DiDP, monoisodecyl phthalate (MiDP), was not detected in any of the samples, while MCiNP, MHiDP and MOiDP were detected in 98%, 96% and 85%, respectively, of the samples tested. MCiNP was excreted predominantly in its free form, whereas MOiDP was excreted as its glucuronide. MCiNP, MHiDP and MOiDP eluted as clusters of multiple peaks from the HPLC column probably due to the presence of numerous structurally similar isomers present in commercial DiDP formulations. The urinary concentrations of these oxidative metabolites correlated significantly (p < 0.0001) with each other, thus confirming a common precursor. The urinary concentrations of these DiDP oxidative metabolites also correlated significantly (p < 0.0001) with oxidative metabolites of di-isononyl phthalate (DiNP) suggesting the potential presence of DiNP isomers in commercial DiDP or simultaneous use of DiDP and DiNP in consumer products. The concentrations presented are semiquantitative estimates and should be interpreted cautiously. Nevertheless, the higher frequency of detection and higher urinary concentrations of MCiNP, MHiDP and MOiDP than of MiDP suggest that these oxidative metabolites are better biomarkers for DiDP exposure assessment than MiDP. These data also suggest that unless oxidative metabolites are measured, the prevalence of exposure to DiDP will probably be underestimated.

[Results from applying the monaural compressed speech test in Spanish at 75% and 100% in cases of stuttering and controls]

AIM

To evaluate the results obtained from applying the monaural compressed speech test in Spanish at 75% and 100% in cases of stutterers and controls.

SUBJECTS AND METHODS

The study involved 50 cases with ages ranging from 8 to 36 years, 25 of whom were stutterers and 25 controls, who were paired one to one by age, sex and schooling. Severe cases of stuttering were not included. Subjects had to have normal auditory functioning, which was evaluated by means of audiometry and peripheral vocal audiometry, and also normal cognitive functioning, which was assessed using TONI-2 in children and by the Spanish version of the Mini-Mental State Examination in adults.

RESULTS

The average number of correct answers on the CSTS at 75% was 60.98% in cases of stutterers and 82.04% in the group of controls (Student's t = -7.4; p = 0.0001), and on the CSTS at 100% the figures were 56.56% and 73.16%, respectively, (Student's t = -5.9; p = 0.0001). Sensitivity and specificity were calculated for each test by means of ROC curves, together with the cut-off point.

CONCLUSION

Applying the CSTS in individuals who stutter helped us to identify disorders in the temporal processing of auditory information.

Temporal variability in urinary concentrations of phthalate metabolites, phytoestrogens and phenols among minority children in the United States

BACKGROUND

Exposure to endocrine disruptors (EDs), including some phthalates, phytoestrogens and phenols can be quantified using biomarkers of exposure. However, reliability in the use of these biomarkers requires an understanding of the timeframe of exposure represented by one measurement. Data on the temporal variability of ED biomarkers are sparse, especially among children.

OBJECTIVE

To evaluate intraindividual temporal variability in 19 individual urinary biomarkers (eight phthalate metabolites from six phthalate diesters, six phytoestrogens (two lignans and four isoflavones) and five phenols) among New York City children.

METHODS

Healthy Hispanic and Black children (N=35; 6-10 years old) donated several urine samples over 6 months. To assess temporal variability we used three statistical methods: intraclass correlation coefficient (ICC), Spearman correlation coefficients (SCC) between concentrations measured at different timepoints, and surrogate category analysis to determine how well the tertile categories based on a single measurement represented a 6-month average concentration.

RESULTS

Surrogate category analysis indicated that a single sample provides reliable ranking for all analytes; at least three of four surrogate samples predicted the 6-month mean concentration. Of the 19 analytes, the ICC was >0.2 for 18 analytes and >0.3 for 10 analytes. Correlations among sample concentrations throughout the 6-month period were observed for all analytes; 14 analyte concentrations were correlated at 16 weeks.

CONCLUSIONS

The reasonable degree of temporal reliability and the wide range of concentrations of phthalate metabolites, phytoestrogens and phenols suggest that these biomarkers are appropriate for use in epidemiologic studies of environmental exposures in relation to health outcomes in children.

Atopic disease and body mass index

BACKGROUND

Obesity and atopy are two increasingly important population health issues. Excess weight and obesity are potential risk factors for atopy (specifically asthma).

OBJECTIVE AND METHODS

To determine the body mass index (BMI) in children with atopic disease compared with nonatopic children, and to determine whether obesity is associated to more severe disease. Children aged 5 to 16 years with diagnosed atopic disease that attended the Ambulatory Hospital Center where eligible as cases. Children aged 5 to 16 years without atopic disease from a school in the same geographic area were used as controls.

RESULTS

A total of 228 children where included in the analysis: 112 children with atopy (75.9% asthma, 21.4% rhinitis and 2.7% eczema) and 116 children without atopy. The median age was 10.5 and 10.3 years for the atopic and non-atopic children, respectively. The prevalence of overweight or obese subjects was significantly greater in the atopic group (44.6% vs 31.9%, p 0.05). The obese asthmatic children had a significantly higher prevalence of sleep disturbances due to wheezing in the last 12 months (45.5% vs 15.9%, p 0.05). They also reported dry cough at night more often (50% vs 28.6%, p = 0.07), and a higher number of wheezing attacks in the past 12 months (72.7% vs 50.8%, p = 0.074), than the non-obese asthmatic children. Most of the obese atopic children were already overweight or obese at the time of the diagnosis (66.6%). None of the associations were significantly different for boys or girls.

DISCUSSION

There is some evidence of an association between excess body weight or obesity and atopy--particularly asthma.

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.