Peptide Variant Detection by a Living Yeast Biosensor via an Epitope-Selective Protease.

We previously demonstrated that we could hijack the fungal pheromone signaling pathway to provide a living yeast biosensor where peptide biomarkers were recognized by G-protein-coupled receptors and engineered to transcribe a readout. Here, we demonstrated that the protease could be reintroduced to the biosensor to provide a simple mechanism for distinguishing single-amino-acid changes in peptide ligands that, otherwise, would likely be difficult to detect using binding-based assays. We characterized the dose-response curves for five fungal pheromone G-protein-coupled receptors, peptides, and proteases-Saccharomyces cerevisiae, Candida albicans, Schizosaccharomyces pombe, Schizosaccharomyces octosporus, and Schizosaccharomyces japonicus. Alanine scanning was carried out for the most selective of these-S. cerevisiae and C. albicans-with and without the protease. Two peptide variants were discovered, which showed diminished cleavage by the protease (CaPep2A and CaPep2A13A). Those peptides were then distinguished by utilizing the biosensor strains with and without the protease, which selectively cleaved and altered the apparent concentration of peptide required for half-maximal activation for 2 peptides-CaPep and CaPep13A, respectively-by more than one order of magnitude. These results support the hypothesis that the living yeast biosensor with a sequence-specific protease can translate single-amino-acid changes into more than one order of magnitude apparent shift in the concentration of peptide required for half-maximal activation. With further engineering by computational modeling and directed evolution, the biosensor could likely distinguish a wide variety of peptide sequences beyond the alanine scanning carried out here. In the future, we envision incorporating proteases into our living yeast biosensor for use as a point of care diagnostic, a scalable communication language, and other applications.

The yield of thyroid fine-needle aspiration in a primary care setting in Riyadh, Saudi Arabia.

Background: Thyroid cancer is the second most common cancer among women. This study was conducted to assess the yield of fine-needle aspiration (FNA) cytology of thyroid nodules in a primary care setting in Riyadh, Saudi Arabia. Materials and Methods: In this retrospective cohort study, primary care patients of both genders with thyroid nodules who underwent FNA above the age of 18 years were enrolled. Patients with a prior history of cancer were excluded. The data was collected from the histopathology reports of FNAs done for thyroid nodules from January 01, 2002 to July 31, 2018. Results: We enrolled 263 patients in this study. The mean age of the study population was 41.3 years old (Standard deviation (SD) ± 10.1), 81.7% were females and 18.3% were males. The rate of abnormal ultrasound (US) was 16%. The mean thyroid-stimulating hormone (TSH) level was 2.3 mU/L (SD ± 5.9). Post-thyroidectomy, 17.5% had carcinoma on pathology reports. Among those who were diagnosed with thyroid cancer, 76.2% had papillary thyroid cancer, 21.4% had follicular thyroid cancer, and 2.4% had medullary thyroid cancer. The mean age for cancer diagnosis was 40 years old (SD ± 8). There was no significant association between FNA findings (benign/malignant) and age, gender, history of smoking, size of the nodule, or TSH level. Conclusion: Thorough investigations including FNA should be considered for patients presenting with suspicious thyroid nodules, regardless of their size or the patients' gender. Access to such investigations and referrals to specialists should be available for primary care physicians.

Characteristics and outcomes of osteoporotic hip fractures: treatment gaps in a tertiary care center in Riyadh, Saudi Arabia.

BACKGROUND: Hip fracture is the most clinically devastating and economically important complication of osteoporosis. Pain, suffering, loss of mobility and independence are some of the devastating consequences of hip fractures. The present study aimed to determine the main characteristics and outcomes of patients with osteoporotic hip fracture and treatment gaps at King Abdulaziz Medical City (KAMC), Riyadh, Saudi Arabia. METHODS: This is a single-center, retrospective cohort study analyzing charts of patients > 45 years who were admitted for hip fracture secondary to low-grade trauma from 2008 to 2012. RESULTS: A total of 264 patients (50.4% males and 49.6% females) were included. The most common fracture types were trochanter (49%) and femoral neck (46%). History of falls was documented in 115 (43.6%) patients. Bone mineral density (BMD) was assessed in only 41 (15.5%) patients. Majority underwent surgery (92%). Surgical complications occurred in 15 (5.7%) patients and medical complications in 21 (7.9%) patients. Vitamin D and calcium were the most common medications, but given only to 45 (17%) patients. Bone mineral density (BMD) assessment was significantly more frequent post-surgery than pre-surgery (p = 0.03). Very few patients received osteoporosis-specific therapy. F ollow-up revealed that 62 (23.5%) patients died 1 year after surgery. CONCLUSION: These present findings warrant urgent reassessment of clinical care and treatments provided to patients with osteoporotic hip fractures to prevent recurrent fractures. The introduction of Fracture Liaison Service (FLS) in institutions caring for patients with hip fractures as internationally recommended will definitely change the current status of care.

Predicting future weight status from measurements made in early childhood: a novel longitudinal approach applied to Millennium Cohort Study data.

BACKGROUND/OBJECTIVE: There are reports that childhood obesity tracks into later life. Nevertheless, some tracking statistics such as correlations do not quantify individual agreement, whereas others such as diagnostic test statistics can be difficult to translate into practice. We aimed to employ a novel analytic approach, based on ordinal logistic regression, to predict weight status of 11-year-old children from measurements at age 5 years. SUBJECTS/METHODS: The UK 1990 growth references were used to generate clinical weight status categories of 12 076 children enrolled in the Millennium Cohort Study. Using ordinal regression, we derived the predicted probability (percent chances) of 11-year-old children becoming underweight, normal weight, overweight, obese and severely obese from their weight status category at age 5 years. RESULTS: The chances of becoming obese (including severely obese) at age 11 years were 5.7% (95% confidence interval: 5.2 to 6.2%) for a normal-weight 5-year-old child and 32.3% (29.8 to 34.8%) for an overweight 5-year-old child. An obese 5-year-old child had a 68.1% (63.8 to 72.5%) chance of remaining obese at 11 years. Severely obese 5-year-old children had a 50.3% (43.1 to 57.4%) chance of remaining severely obese. There were no substantial differences between sexes. Nondeprived obese 5-year-old boys had a lower probability of remaining obese than deprived obese boys: -21.8% (-40.4 to -3.2%). This association was not observed in obese 5-year-old girls, in whom the nondeprived group had a probability of remaining obese 7% higher (-15.2 to 29.2%). The sex difference in this interaction of deprivation and baseline weight status was therefore -28.8% (-59.3 to 1.6%). CONCLUSIONS: We have demonstrated that ordinal logistic regression can be an informative approach to predict the chances of a child changing to, or from, an unhealthy weight status. This approach is easy to interpret and could be applied to any longitudinal data set with an ordinal outcome.

Identification of surrogates and correlates of protection in protective immunity against Mycobacterium bovis infection induced in neonatal calves by vaccination with M. bovis BCG Pasteur and M. bovis BCG Danish.

Vaccination of neonatal calves with Mycobacterium bovis bacillus Calmette-Guérin (BCG) induces a significant degree of protection against infection with virulent M. bovis, the causative agent of bovine tuberculosis (bTB). We compared two strains of BCG, Pasteur and Danish, in order to confirm that the current European human vaccine strain (BCG Danish) induced protective immunity in calves, and we assessed immune responses to determine correlates of protection that could assist future vaccine evaluation in cattle. Both vaccine strains induced antigen (purified protein derivate [PPD])-specific gamma interferon (IFN-γ) in whole-blood cultures. These responses were not significantly different for BCG Pasteur and BCG Danish and peaked at week 2 to 4 postvaccination. Vaccination with either BCG Danish or BCG Pasteur induced significant protection against bTB, with reductions in both lesion score and bacteriological burden evident in both groups of vaccinated calves compared with nonvaccinated control calves. Measurement of IFN-γ-expressing T lymphocytes postvaccination and postchallenge revealed both correlates and surrogates of protective efficacy. The frequency of central memory T lymphocytes present at 12 weeks postvaccination (at the time of M. bovis challenge) correlated significantly with protection. Conversely, the number of IFN-γ-expressing effector T cells present after M. bovis challenge was correlated with disease. These results demonstrate that vaccination of neonatal calves with either BCG Pasteur or BCG Danish induces protective immune responses against TB. In addition, we show that measurement of antigen-specific T lymphocyte populations may provide a reliable means for identifying protective vaccine candidates.

Impact of the changing food environment on dietary practices of an Inuit population in Arctic Canada.

BACKGROUND: Nutritional inadequacies and increasing chronic disease prevalence amongst Inuit in the Canadian Arctic highlight the need to address dietary practices. Research is needed to investigate the individual and environmental factors impacting diet to guide interventions. The present study aimed to explore multiple community perspectives of key factors affecting food choice and availability in Inuit communities in Nunavut, Canada. METHODS: Semi-structured in-depth interviews were conducted with Inuit adults (n=43) in two communities in Nunavut, Canada, and included community members, community leaders, elders, health staff and food shop staff. The interviewer transcribed the audio-taped interviews. Data were analysed using codes and the constant comparative method to determine categories and emergent themes. RESULTS: Thirty-three Inuit (27 females and six males) and 10 non-Inuit (four females and six males) adults participated. Traditional foods procured through hunting and gathering were considered the healthiest by community members, although multiple factors inhibited their procurement, including high petrol cost and decrease in traditional knowledge about hunting and gathering practices. Cost and quality were the main barriers to purchasing healthy foods at the shops. Community leaders and health staff identified multiple barriers to healthy eating in the community, such as skills to prepare some shop-bought foods. Shop managers identified several challenges to providing fresh produce and other perishable foods, such as long transportation routes that increase costs and harsh climatic conditions that may cause spoilage. They also cited factors influencing their decisions regarding whether to stock/discontinue certain foods, such as customers' requests, food cost and shelf-life. CONCLUSIONS: An intervention to reduce chronic disease risk and improve dietary adequacy amongst Nunavut Inuit may be effective by supporting individual behaviour modifications with food environment changes.

Dietary adequacy of Inuit in the Canadian Arctic.

BACKGROUND: Food intake amongst Canadian Inuit is currently in transition with a concurrent increase in diet-related chronic disease. There is a lack of current data on nutrient intake and dietary adequacy in this population. The present study aimed to assess dietary intake and adequacy amongst Inuit adults in a community in Nunavut, Canada. METHODS: Random sampling of 130 households in a remote Inuit community in the Kitikmeot region of Nunavut, Canada, was used for this cross-sectional study. Up to three 24-h dietary recalls were collected on nonconsecutive days, capturing weekday and weekend consumption. Data were analysed to estimate energy and nutrient intake, to determine dietary adequacy, and to summarise the most commonly reported foods and the top food contributors to selected nutrients. RESULTS: The response rate was 69%, with 75 Inuit adults participating (mean (standard deviation (SD)) age 44 (SD=17) years). Mean (SD) daily energy intake was 9.3 (4.4) MJ and 8.7 (3.5) MJ for men and women, respectively. Intakes of dietary fibre, calcium, total folate and vitamins A, D and E were below the Dietary Reference Intakes (Estimated Average Requirements where available) for 60-100% of all men and women. Traditional foods contributed substantially to protein and iron intake, whilst shop-bought foods were primary contributors to total fat, carbohydrate and sugar intake. CONCLUSIONS: The present study reports an in-depth assessment of total dietary quality amongst Inuit adults in Nunavut, Canada. The results obtained indicate inadequate intakes of several essential nutrients, as well as a reliance on a nontraditional diet. A nutrition intervention is needed to prevent a continued rise in diet-related chronic disease incidence.

Socioeconomic indicators and frequency of traditional food, junk food, and fruit and vegetable consumption amongst Inuit adults in the Canadian Arctic.

BACKGROUND: Increasing consumption of non-nutrient-dense foods (NNDF), decreasing consumption of traditional foods (TF) and low consumption of fruit and vegetables (FV) may contribute to increasing chronic disease rates amongst Inuit. The present study aimed to assess the daily frequency and socioeconomic and demographic factors influencing consumption of TF, FV and NNDF amongst Inuit adults in Nunavut, Canada. METHODS: Using a cross-sectional study design and random household sampling in three communities in Nunavut, a food frequency questionnaire developed for the population was used to assess frequency of NNDF, TF and FV consumption amongst Inuit adults. Socioeconomic status (SES) was assessed by education level, ownership of items in working condition, and whether or not people in the household were employed or on income support. Mean frequencies of daily consumption were compared across gender and age groups, and associations with socioeconomic indicators were analysed using logistic regression. RESULTS: Two hundred and eleven participants (36 men, 175 women; mean (standard deviation) ages 42.1 (15.0) and 42.2 (13.2) years, respectively; response rate 69-93%) completed the study. Mean frequencies of consumption for NNDF, TF and FV were 6.3, 1.9 and 1.6 times per day, respectively. On average, participants ≤50 years consumed NNDF (P=0.003) and FV (P=0.01) more frequently and TF (P=0.01) less frequently than participants >50 years. Education was positively associated with FV consumption and negatively associated with TF consumption. Households on income support were more likely to consume TF and NNDF. CONCLUSIONS: These results support the hypothesis that the nutrition transition taking place amongst Inuit in Nunavut results in elevated consumption of NNDF compared with TF and FV.

Important psychosocial factors to target in nutrition interventions to improve diet in Inuvialuit communities in the Canadian Arctic.

BACKGROUND: With increasing chronic disease amongst Inuvialuit in the Canadian Arctic, research on dietary behaviours and their determinants in this population is needed to develop nutritional behaviour change intervention strategies. The present study aimed to assess the knowledge, self-efficacy and intentions towards healthy eating and healthy eating behaviours of Inuvialuit adults in the Northwest Territories (NWT), Canada. METHODS: The Adult Impact Questionnaire was developed from behavioural theories and workshops held in the communities. It was conducted with adult Inuvialuit (≥19 years) from randomly selected households in three NWT communities to collect data on the psychosocial constructs of healthy food knowledge, self-efficacy and intentions, and the dietary behaviours of healthy and unhealthy food acquisition and preparation. Associations between demographic, socioeconomic, psychosocial constructs and behaviours were analysed using multivariate linear regression. RESULTS: The 228 participants [mean (SD) age 43.4 (13.6) years; response rates 65-85%] acquired non-nutrient-dense foods a mean (SD) of 2.7 (3.0) times more frequently than nutrient-dense, low sugar and low fat foods. Increased intention was associated with a greater frequency of acquiring healthy foods (ß=0.17, P=0.012) and a lower frequency of acquiring unhealthy foods (ß=-0.18, P=0.008). Overall, participants reported using food preparation methods that reduce fat content slightly more than methods that add fat [mean (SD) score 0.3 (1.9)]. Use of healthier food preparation methods was associated with higher levels of healthy food knowledge (ß=0.26, P<0.001), self-efficacy (ß=0.29, P<0.001) and intentions (ß=0.22, P=0.001). CONCLUSIONS: Healthy food intention was the construct most significantly associated with all three healthier dietary behaviours. Interventions that target intentions to change food choice and preparation may be effective strategies to improve dietary intake in Inuvialuit populations.

Healthy food intentions and higher socioeconomic status are associated with healthier food choices in an Inuit population.

BACKGROUND: Changing food behaviours amongst Canadian Inuit may contribute to rising chronic disease prevalence, and research is needed to develop nutritional behaviour change programmes. The present study examined patterns of food acquisition and preparation behaviours amongst Inuit adults in Nunavut and associations with psychosocial and socioeconomic factors. METHODS: Developed from behavioural theories and community workshops, Adult Impact Questionnaires were conducted with adult Inuit (≥19 years) from randomly selected households in three remote communities in Nunavut, Canada, to determine patterns of healthy food knowledge, self-efficacy and intentions, frequencies of healthy and unhealthy food acquisition and healthiness of preparation methods. Associations between these constructs with demographic and socioeconomic factors were analysed using multivariate linear regressions. RESULTS: Amongst 266 participants [mean (SD) age 41.2 (13.6) years; response rates 69-93%], non-nutrient-dense foods were acquired a mean (SD) of 2.9 (2.3) times more frequently than nutrient-dense, and/or low sugar/fat foods. Participants tended to use preparation methods that add fat. Intentions to perform healthy dietary behaviours was inversely correlated with unhealthy food acquisition (ß=-0.25, P<0.001), and positively associated with healthy food acquisition (ß=0.22, P<0.001) and healthiness of preparation methods (ß=0.15, P=0.012). Greater healthy food knowledge and self-efficacy were associated with intentions (ß=0.21, P=0.003 and ß=0.55, P<0.001, respectively). Self-efficacy was associated with healthier preparation (ß=0.14, P=0.025) and less unhealthy food acquisition (ß=-0.27, P<0.001), whilst knowledge was associated with acquiring healthy foods (ß=0.13, P=0.035). Socioeconomic status was positively associated with healthy preparation and food acquisition behaviours. CONCLUSIONS: Interventions to improve diet in Nunavut Inuit should target healthy food intentions, knowledge and self-efficacy. Behaviour change strategies emphasising economic benefits of a healthy diet should be employed to target individuals of low socioeconomic status.

Awareness of chronic disease diagnosis amongst family members is associated with healthy dietary knowledge but not behaviour amongst Inuit in Arctic Canada.

BACKGROUND: The extent to which awareness of chronic disease (CD) diagnosis affects one's healthy food knowledge, self-efficacy and intentions or healthy dietary and physical activity (PA) behaviours remains unexplored among Inuit in Canada. METHODS: A food frequency questionnaire and an adult impact questionnaire were used in a cross-sectional study to collect self-reported data on daily energy and nutrient intake, PA and the diagnosis of hypertension, diabetes, heart disease and cancer amongst adult Inuit and their family members. Associations between awareness of personal and family CD status and healthy food knowledge, self-efficacy and intentions, percentage of energy consumed from non-nutrient-dense foods and PA were assessed via ordinal logistic regression. RESULTS: Of the 266 participants, those who self-reported CD for both themselves and their relative(s) were more likely to have high healthy food knowledge [odds ratio (OR)=2.45] than those who did not. Reporting hypertension and heart disease amongst only relatives increased the likelihood of high knowledge (OR=5.20) and intentions (OR=5.10) for healthy eating. Heart disease in both participants and their relatives was associated with high levels of PA (OR=12.24). However, there were no associations when only participants (but not their relatives) reported having CD. A joint effect between a high level of education and awareness of CD was positively related to high food knowledge (OR=38.93). An inverse association between awareness of CD and unhealthy eating was not observed. CONCLUSIONS: Awareness of a relative having a CD was a more important factor in increasing knowledge and, to a lesser degree, self-efficacy or intentions to eat healthy than participants' awareness of personal CD. However, awareness was not associated with lower non-nutrient-dense food intake.

High levels of physical activity and obesity co-exist amongst Inuit adults in Arctic Canada.

BACKGROUND: Existing evidence indicates that Inuit in Arctic Canada are undergoing a lifestyle transition leading to decreased physical activity (PA) and increased body mass index (BMI). Data specific to PA and BMI amongst Inuit in Nunavut, Canada, are currently limited. The present study aimed to characterise current PA and BMI levels in a sample of Inuit adults. METHODS: Inuit adults randomly selected from a cross-sectional survey of three communities in Nunavut, Canada, completed an adapted International Physical Activity Questionnaire (IPAQ) and an anthropometric survey. Data were analysed by gender and age group using standardised IPAQ protocol. RESULTS: Response rates ranged from 69-93%. Two hundred and eighteen Inuit adults [180 women, 38 men; mean (standard deviation (SD)) ages 42.3 (13.0) and 42.4 (14.8) years respectively; age range 19-89 years] completed the IPAQ. All men and 97% of women allowed height and weight measurements; the remainder were self-reported. Mean (SD) BMI was 27.7 (6.3) kg/m(2) for males and 30.3 (8.0) kg/m(2) for females. The largest proportion of women and participants in both age groups had a BMI in the obese category; males were evenly split between the normal and obese categories. Self-reported PA was high, with most men, women and participants ≤50 years in the high category of PA. Participants >50 years were evenly split across the medium and high categories. Most participants (72%) were classified as being overweight or obese, yet reported medium or high levels of PA (89%). CONCLUSIONS: The findings obtained in the present study indicate the co-existence of high BMI and high self-reported PA amongst Inuit adults.

Isoniazid treatment of Mycobacterium bovis in cattle as a model for human tuberculosis.

Cattle infected with Mycobacterium bovis spoligotype 9 were treated with Isoniazid (INH) from three to 14 weeks post infection, rested for fourweeks to allow INH depletion and then challenged with M. bovis spoligotype 35. Post mortem examination (PME) 35 weeks after the initial infection showed partial protection against infectious challenge following INH-attenuated infection compared with the spoligotype 35 challenge controls. Antigen-specific IFN-gamma responses decreased over time with INH therapy, following a similar pattern to that observed in the treatment of M. tuberculosis infection in humans. Following cessation of therapy, specific IFN-gamma responses increased more strongly in those calves that were visibly lesioned at PME. IFN-gamma responses were also used to identify two antigens, TB10.4 and Acr2, that induced anamnestic responses in INH-treated, re-challenged calves, suggesting a role for both antigens in protective immunity. Specific IL-10 responses were observed in all calves following treatment with INH suggesting a role for IL-10 in the resolution of infection.

Kisspeptins: a multifunctional peptide system with a role in reproduction, cancer and the cardiovascular system.

Orphan G-protein-coupled receptors that have recently been paired with their cognate ligand are an often untapped resource for novel drug development. The KISS1 receptor (previously designated GPR54) has been paired with biologically active cleavage peptides of the KiSS-1 gene product, the kisspeptins (KP). The focus of this review is the emerging pharmacology and physiology of the KP. Genetic linkage analysis in humans revealed that mutations in KISS1 (GPR54, AXOR12 or hOT7T175) result in idiopathic hypogonadotrophic hypogonadism and knockout mouse studies confirmed this finding. Identification of KISS1 (GPR54) as a molecular switch for puberty subsequently led to the discovery that KP activate the GnRH cascade. Prior to the role of KISS1 (GPR54) in puberty being described, KP had been shown to be inhibitors of tumour metastasis across a range of cancers. Subsequently the mechanism of this inhibition has been suggested to be via altered cell motility and adhesiveness. PCR detected highest expression of KP and KISS1 (GPR54) in placenta, and changes in KP levels throughout pregnancy and expression in trophoblasts suggests a role in placentation. Placentation and metastasis are invasive processes that require angiogenesis. Investigation of KISS1 (GPR54) and KP in vasculature revealed discrete localisation of KISS1 (GPR54) to blood vessels prone to atherosclerosis and a potent vasoconstrictor action. A role for KP has also been shown in whole body homeostasis. KP are multifunctional peptides and further investigation is required to fully elucidate the complex pathways regulated by these peptides and how these pathways integrate in the whole body system.

Long term metabolic arrest and recovery of HEK293 spheroids involves NF-kappaB signaling and sustained JNK activation.

Understanding how cells withstand a depletion of intracellular water is relevant to the study of longevity, aging, and quiescence because one consequence of air-drying is metabolic arrest. After removal of medium, HEK293 spheroids with intracellular water content of approximately 65% survived partial vacuum, with antistatic control, for weeks in the dark at 25 degrees C. In contrast, only a limited exposure of monolayers to air was lethal; the mitochondrion being a target of this stress. The pathways activated during the long-term arrest and recovery of spheroids depended on both NF-kappaB signaling and sustained JNK activation. A cyclical cascade, presumably originating from an intercellular stress signal, led to endogenous cytokine production (TNF-alpha, IL-1b, and IL-8) and propagation of the cellular stress signal through the co-activation of NF-kappaB and JNK. Increased levels of downstream pathway signaling members, specifically Gadd45beta, c-jun, and ATF3 were observed, as was activation of c-jun (phosphorylation). Activation of these pathways permit cells to survive long-term storage and recovery because chemical inhibition of both NF-kappaB nuclear translocation and JNK phosphorylation led to cell death. The capacity of an immortalized cell to enter, and then exit, a state of long-term quiescence, without genetic or chemical intervention, has implications for the study of cell transformation. In addition, the ability to monitor the relevant signaling pathways at endogenous levels, from effector to transcriptional regulator, emphasizes the utility of multicellular aggregate models in delineating stress response pathways.

Measurement uncertainty associated with overall migration testing.

The results from a single laboratory that took part in a series of check-sample exercises for overall migration were used to calculate the measurement uncertainty for the overall migration methodology. The results span 10 years of proficiency testing and cover a range of plastic materials tested using a variety of time and temperature test conditions. Twelve sets of results for overall migration into olive oil and 10 sets of results for overall migration into volatile simulants were used. The measurement uncertainty associated with the determination of overall migration from plastics into olive oil was estimated as +/- 2.6 mg dm-2 for results between 1.2 and 15.4 mg dm-2. The measurement uncertainty associated with the determination of overall migration into volatile simulants was estimated as +/- 1.4 mg dm-2 for results between 2.1 and 13 mg dm-2. These estimates are within the analytical tolerances set in European Union regulations, of 3 and 2 mg dm-2, respectively. The performance of all laboratories participating in these 22 check sample exercises was also evaluated. A very large majority (93%) of the participants used official test methods, sometimes with minor modifications as stated. For the simulant olive oil, an average of 81% of laboratories (13 rounds with an average of 21 participants in each) using official methods was within the tolerance specified in regulations. For the volatile food simulants, an average of 87% of laboratories (11 rounds with an average of 38 participants in each) using official methods was within the tolerance specified. It is concluded from this evaluation of within- and between-laboratory data that the official European Standard methods for overall migration testing are suitable for the analysis of routine samples.

Fatigue model to characterize cement-metal interface in dynamic shear.

This study evaluated the interface shear strength between vacuum mixed polymethyl-methacrylate and two types of surface enhancements under static and dynamic shear loading. Cobalt chrome coupons with grit blasted or light plasma sprayed surfaces were tested. For each test, two coupons were mounted in a stainless steel chamber such that they were bonded with a 2-mm cement mantle for each test. Pullout and dynamic fatigue tests were performed on an Instron machine. The mean static pullout strength of the grit blasted surfaces was 13.78 (+/- 2.73) MPa, whereas that of the light plasma sprayed surfaces was 18.46 (+/- 1.98) MPa. The rate of degradation of interface strength caused by fatigue was almost identical for both surface treatments. Qualitative analysis showed that the failed light plasma sprayed surface generated more metal and cement particles. These data suggest that light plasma sprayed surfaces sustain higher loads but have a potential for increased debris generation.

Polyethylene wear debris in modular acetabular prostheses.

The longevity of total hip arthroplasty has brought forth the recognition of aseptic loosening of prosthetic components as the leading cause of implant failure. Modularity of implants, although a significant improvement in versatility, may increase debris formation, a recognized cause of implant failure. This study was designed to measure the relative motion, and to assess the polyethylene wear debris production at the interface between the metal acetabular shell and the back side of the polyethylene liner, in modular hip prostheses. Five models from 4 manufacturers with different locking mechanisms and acetabular shell surface treatments were tested under long-term simultaneous sinusoidal and static loading (10(7) cycles at 3 Hz with +/- 2.5 Nmeter and 220 N static load). Results showed that there were marked differences in the security of the acetabular shell and polyethylene liner locking mechanism, wear pattern, damage sites, and amount of polyethylene debris on the acetabular shell and polyethylene liner surfaces. The range of polyethylene liner motion observed among the 5 models during 1 cycle of testing varied from an average of 0.96 degrees to movement too small to be detected by the test machines. Image and scanning electron microscopy analysis showed different wear patterns and a wide range in the average polyethylene liner surface wear area (0.26 cm2-4.61 cm2). In general, a stable locking mechanism and a smooth acetabular shell surface are essential in minimizing polyethylene liner wear and polyethylene debris production.

Development of a device for measuring adherence of skin grafts to the wound surface.

Adherence of a biological graft to the wound surface is the most important factor influencing the ultimate success of graft viability. A machine has been developed to test the adherence of biological graft materials to a substrate such as a wound surface. The peeling mode, which yields reproducible quantitative measurements of adherence, is a standard method for testing adhesives. The device is designed to continuously measure the force required to peel the graft from the substrate at a constant rate. This force is a function of the energy of adhesion per unit area of adhered surface. This device has been used to measure the peeling force of (2 x 2 cm) skin grafts which are applied to full-thickness wounds on mice. Results of tests on adherence of autografts on mice show that the peeling force increases significantly with time over the first 9 days of healing. Thus, this device is useful in quantitative comparison of various skin grafting techniques and artificial grafts.