The key components of a successful model of midwifery-led continuity of carer, without continuity at birth: findings from a qualitative implementation evaluation.

BACKGROUND: Recent UK maternity policy changes recommend that a named midwife supports women throughout their pregnancy, birth and postnatal care. Whilst many studies report high levels of satisfaction amongst women receiving, and midwives providing, this level of continuity of carer, there are concerns some midwives may experience burnout and stress. In this study, we present a qualitative evaluation of the implementation of a midwife-led continuity of carer model that excluded continuity of carer at the birth. METHODS: Underpinned by the Conceptual Model for Implementation Fidelity, our evaluation explored the implementation, fidelity, reach and satisfaction of the continuity of carer model. Semi-structured interviews were undertaken with midwives (n = 7) and women (n = 15) from continuity of carer team. To enable comparisons between care approaches, midwives (n = 7) and women (n = 10) from standard approach teams were also interviewed. Interviews were recorded, transcribed and analysed using thematic analysis. RESULTS: For continuity of carer team midwives, manageable caseloads, extended appointment times, increased team stability, and flexible working patterns facilitated both care provided and midwives' job satisfaction. Both continuity of carer and standard approach midwives reported challenges in providing postnatal continuity given the unpredictable timing of labour and birth. Time constraints, inadequate staffing and lack of administrative support were reported as additional barriers to implementing continuity of carer within standard approach teams. Women reported continuity was integral to building trust with midwives, encouraged them to disclose mental health issues and increased their confidence in making birth choices. CONCLUSIONS: Our evaluation highlighted the successful implementation of a continuity of carer model for ante and postnatal care. Despite exclusion of the birth element in the model, both women and midwives expressed high levels of satisfaction in comparison to women and midwives within the standard approach. Implementation successes were largely due to structural and resource factors, particularly the combination of additional time and smaller caseloads of women. However, these resources are not widely available within the resources of maternity unit budgets. Future research should further explore whether a continuity of carer model focusing on antenatal and postnatal care delivery is a feasible and sustainable model of care for all women.

Field Studies Measuring the Aerosolization of Endotoxin During the Land Application of Class B Biosolids.

Endotoxins are a component of Gram-negative bacteria cell walls and are known to be present in biosolids. Endotoxins have been shown to be potent stimulators of the innate immune response causing airway irritation and shortness of breath. Class B biosolids are routinely applied to agricultural lands to enhance soil properties and can be used as an alternative to chemical fertilizers. This study investigated the aerosolized endotoxin dispersed during the land application of Class B biosolids on agricultural land and a concrete surface at two sites in Colorado, USA. Aerosolized endotoxin was captured using HiVol samplers fitted with glass fiber filters, polycarbonate filter cassettes (both open and closed) and BioSampler impinger air samplers. Endotoxins were also measured in the biosolids to allow for correlating bulk biosolids concentrations with aerosol emission rates. Endotoxin concentrations in biosolids, impinger solutions and filter extracts were determined using the kinetic Limulus amebocyte lysate assay. Aerosolized endotoxin concentration was detected from all sites with levels ranging from 0.5 to 642 EU/m3. The four types of sampling apparatus were compared, and the HiVol and open-faced cassette samplers produced higher time-weighted average (TWA) measurements (EU/m3) than the impinger and closed cassette samplers. Ambient wind speed was found to be the variable best describing the observed results with optimal wind speed for highest deposition estimated at 5 m s-1. It is argued that HiVol air samplers are a particularly reliable approach and subsequent analyses relating TWA measurements to wind speed and biosolids characteristics were based on the measurements collected with those samplers.

Small-for-gestational age and large-for-gestational age thresholds to predict infants at risk of adverse delivery and neonatal outcomes: are current charts adequate? An observational study from the Born in Bradford cohort.

OBJECTIVES: Construct an ethnic-specific chart and compare the prediction of adverse outcomes using this chart with the clinically recommended UK-WHO and customised birth weight charts using cut-offs for small-for-gestational age (SGA: birth weight <10th centile) and large-for-gestational age (LGA: birth weight >90th centile). DESIGN: Prospective cohort study. SETTING: Born in Bradford (BiB) study, UK. PARTICIPANTS: 3980 White British and 4448 Pakistani infants with complete data for gestational age, birth weight, ethnicity, maternal height, weight and parity. MAIN OUTCOME MEASURES: Prevalence of SGA and LGA, using the three charts and indicators of diagnostic utility (sensitivity, specificity and area under the receiver operating characteristic (AUROC)) of these chart-specific cut-offs to predict delivery and neonatal outcomes and a composite outcome. RESULTS: In White British and Pakistani infants, the prevalence of SGA and LGA differed depending on the chart used. Increased risk of SGA was observed when using the UK-WHO and customised charts as opposed to the ethnic-specific chart, while the opposite was apparent when classifying LGA infants. However, the predictive utility of all three charts to identify adverse clinical outcomes was poor, with only the prediction of shoulder dystocia achieving an AUROC>0.62 on all three charts. CONCLUSIONS: Despite being recommended in national clinical guidelines, the UK-WHO and customised birth weight charts perform poorly at identifying infants at risk of adverse neonatal outcomes. Being small or large may increase the risk of an adverse outcome; however, size alone is not sensitive or specific enough with current detection to be useful. However, a significant amount of missing data for some of the outcomes may have limited the power needed to determine true associations.

Agreement between routine and research measurement of infant height and weight.

UNLABELLED: In many countries, routine data relating to growth of infants are collected as a means of tracking health and illness up to school age. These have potential to be used in research. For health monitoring and research, data should be accurate and reliable. This study aimed to determine the agreement between length/height and weight measurements from routine infant records and researcher-collected data. METHODS: Height/length and weight at ages 6, 12 and 24 months from the longitudinal UK birth cohort (born in Bradford; n=836-1280) were compared with routine data collected by health visitors within 2 months of the research data (n=104-573 for different comparisons). Data were age adjusted and compared using Bland Altman plots. RESULTS: There was agreement between data sources, albeit weaker for height than for weight. Routine data tended to underestimate length/height at 6 months (0.5 cm (95% CI -4.0 to 4.9)) and overestimate it at 12 (-0.3 cm (95% CI -0.5 to 4.0)) and 24 months (0.3 cm (95% CI -4.0 to 3.4)). Routine data slightly overestimated weight at all three ages (range -0.04 kg (95% CI -1.2 to 0.9) to -0.04 (95% CI -0.7 to 0.6)). Limits of agreement were wide, particularly for height. Differences were generally random, although routine data tended to underestimate length in taller infants and underestimate weight in lighter infants. CONCLUSIONS: Routine data can provide an accurate and feasible method of data collection for research, though wide limits of agreement between data sources may be observed. Differences could be due to methodological issues; but may relate to variability in clinical practice. Continued provision of appropriate training and assessment is essential for health professionals responsible for collecting routine data.

A comparison of South Asian specific and established BMI thresholds for determining obesity prevalence in pregnancy and predicting pregnancy complications: findings from the Born in Bradford cohort.

OBJECTIVE: To describe how maternal obesity prevalence varies by established international and South Asian specific body mass index (BMI) cut-offs in women of Pakistani origin and investigate whether different BMI thresholds can help to identify women at risk of adverse pregnancy and birth outcomes. DESIGN: Prospective bi-ethnic birth cohort study (the Born in Bradford (BiB) cohort). SETTING: Bradford, a deprived city in the North of the UK. PARTICIPANTS: A total of 8478 South Asian and White British pregnant women participated in the BiB cohort study. MAIN OUTCOME MEASURES: Maternal obesity prevalence; prevalence of known obesity-related adverse pregnancy outcomes: mode of birth, hypertensive disorders of pregnancy (HDP), gestational diabetes, macrosomia and pre-term births. RESULTS: Application of South Asian BMI cut-offs increased prevalence of obesity in Pakistani women from 18.8 (95% confidence interval (CI) 17.6-19.9) to 30.9% (95% CI 29.5-32.2). With the exception of pre-term births, there was a positive linear relationship between BMI and prevalence of adverse pregnancy and birth outcomes, across almost the whole BMI distribution. Risk of gestational diabetes and HDP increased more sharply in Pakistani women after a BMI threshold of at least 30 kg m(-2), but there was no evidence of a sharp increase in any risk factors at the new, lower thresholds suggested for use in South Asian women. BMI was a good single predictor of outcomes (area under the receiver operating curve: 0.596-0.685 for different outcomes); prediction was more discriminatory and accurate with BMI as a continuous variable than as a binary variable for any possible cut-off point. CONCLUSION: Applying the new South Asian threshold to pregnant women would markedly increase those who were referred for monitoring and lifestyle advice. However, our results suggest that lowering the BMI threshold in South Asian women would not improve the predictive ability for identifying those who were at risk of adverse pregnancy outcomes.

Measuring placental transfusion for term births: weighing babies with cord intact.

OBJECTIVE: To estimate the volume and duration of placental transfusion at term. DESIGN: Prospective observational study. SETTING: Maternity unit in Bradford, UK. POPULATION: Twenty-six term births. METHODS: Babies were weighed with umbilical cord intact using digital scales that record an average weight every 2 seconds. Placental transfusion was calculated from the change in weight between birth and either cord clamping or when weighing stopped. Start and end weights were estimated using both a B-spline and inspection of graphs. Weight was converted to volume, 1 ml of blood weighing 1.05 g. MAIN OUTCOME MEASURES: Volume and duration of placental transfusion. RESULTS: Twenty-six babies were weighed. Start weights were difficult to determine because of artefacts in the data as the baby was placed on the scales and wrapped. The mean difference in weight was 116 g [95% confidence interval (CI), 72-160 g] using the B-spline and 87 g (95% CI, 64-110 g) using inspection. Converting this to the mean volume of placental transfusion gave 110 ml (95% CI, 69-152 ml) and 83 ml (95% CI, 61-106 ml), respectively. Placental transfusion was usually complete by 2 minutes, but sometimes continued for up to 5 minutes. Based on the B-spline, placental transfusion contributed 32 ml (95% CI, 30-33 ml) per kilogram of birth weight to blood volume, but 24 ml (95% CI, 19-32 ml) based on inspection. This equates to 40% (95% CI, 37-42%) and 30% (24-40%), respectively, of total potential blood volume. CONCLUSION: Inspection of the graphs probably underestimates placental transfusion. For term infants, placental transfusion contributes between one-third and one-quarter of total potential blood volume at birth.

The importance of postpartum glucose tolerance testing after pregnancies complicated by gestational diabetes.

AIMS: To review postpartum glucose tolerance in women with gestational diabetes and evaluate the role of formal 75 g oral glucose tolerance testing vs. fasting plasma glucose in screening for persistent abnormalities. METHODS: Retrospective study of 985 pregnancies over a 10 year period in a mixed ethnic cohort of women who underwent follow-up glucose tolerance testing at 6 weeks postpartum. Diagnosis obtained by oral glucose tolerance test was tested against that from the fasting plasma glucose value. RESULTS: There were 272 abnormal postpartum oral glucose tolerance test results (27.6%), with 109 women identified as having frank diabetes. Eleven of these (10%) had fasting plasma glucose < or =6.0 mmol/l, as did 62 of 114 cases of impaired glucose tolerance. A fasting plasma glucose concentration of > or =6.1 mmol/l correctly identified abnormal glucose tolerance in 199 of 272 cases (sensitivity 0.73). South Asian women were much more likely to have persistent abnormalities of glucose tolerance than were Europeans (32 vs. 15%, chi(2)P < 0.0001). CONCLUSIONS: A postpartum fasting plasma glucose measurement alone is not sensitive enough in our population to classify glucose tolerance status accurately. A formal postpartum oral glucose tolerance test is therefore needed to facilitate early detection and treatment.

Recovery of depleted uranium fragments from soil.

A "proof of concept" was conducted to determine the effectiveness of a survey method for cost-effective recovery of depleted uranium (DU) fragments from contaminated soil piles at Sandia National Laboratories. First, DU fragments ranging from less than a gram up to 48 g were covered by various thicknesses of soil and used for detector efficiency measurements. The efficiencies were measured for three different sodium iodide detectors: a 5.1-cm by 5.1-cm (2-inch by 2-inch) detector, a 7.6-cm by 7.6-cm (3-inch by 3-inch) detector, and a Field Instrument for the Detection of Low Energy Radiation (FIDLER) detector. The FIDLER detector was found to be superior to the other detectors in each measurement. Next, multiple 7.6-cm (3-inch) layers of soil, taken from the contaminated piles, were applied to a clean pad of soil. Each layer was scanned by an array of eight FIDLER detectors pulled by a tractor. The array, moving 10.2 to 12.7 cm s(-1) (4 to 5 inches per second), automatically recorded radiation count data along with associated detector coordinates at 3-s intervals. The DU fragments were located and identified with a handheld system consisting of a FIDLER detector and a positioning system and then removed. After DU removal, the affected areas were re-scanned and a new lift of contaminated soil was applied. The detection capability of the system as a function of DU fragment mass and burial depth was modeled and determined to be sufficient to ensure that the dose-based site concentration goals would be met. Finally, confirmation soil samples were taken from random locations and from decontaminated soil areas. All samples had concentrations of U that met the goal of 400-500 pCi g(-1).

Lipidomic analysis reveals prostanoid profiles in human term pregnant myometrium.

Prostanoids modulate the activity of human pregnant myometrium and their functional role can be appreciated through characterisation of prostanoid receptors and tissue concentration of prostanoids. We have applied a lipidomic approach to elucidate the profile of prostanoids in human non-labouring and labouring myometrium. We have identified a total of nineteen prostanoids including prostacyclin, thromboxanes, prostaglandins and dihydro-prostaglandins. Prostacyclin was the predominant prostanoid in both non-labouring and labouring myometria, with PGD(2) and PGF(2alpha) being the second most abundant. Although the total amount of prostanoids was increased in the labouring tissue, PGE(2) and 13,14-dihydro-15-keto-PGE(2) were the only prostanoids to increase significantly at early and late labour (p< or =0.001). Our data suggest that PGF(2alpha) plays an important role in parturition, whilst the increase in PGE(2) could occur to facilitate cervical dilation and relaxation of the lower myometrium during labour. Although the elevation in TXA(2) was less marked than expected, in terms of translation to function even a relatively small increase in the level of this potent spasmogen may have significant effects.

Application of discriminant analysis with clustered data to determine anthropogenic metals contamination.

Environmental site assessments involve, among other things, characterization of the nature and extent of contamination. In general, environmental assessors are interested in empirical methodologies that can be applied to a broad range of environmental media (e.g., soils, sediments, etc.) and situations. To date, no unified guidance has been adopted, and site investigations usually involve a tiered process with multiple analyses. We propose a multivariate analysis methodology utilizing discriminant analysis with clustered chemical concentrations as a novel application to environmental site assessments that determine, in relative order of magnitude, contaminated chemicals. Finite mixture models are presented as a means to assess latent chemical clusters with some basis in statistical inference. The methodology is illustrated with a typical localized data set containing total metal and metalloid (i.e., chemical) concentrations, extracted from bulk soil collected from reference and site-related locations, obtained from a former military installation in the southeast United States. The illustration is particularly applicable because site-related soils inherently possessed higher background chemical levels than reference soils, which biased conventional analyses. However, contrasting chemical compositions were inferred within site-related samples illustrating the versatility of the proposed methodology. Using these results along with known information regarding the history of contamination at the site, a qualitative and quantitative assessment of contaminated chemicals was made. Results are intended for illustration purposes only and are discussed within the context of environmental site assessment.

BORIS, a paralogue of the transcription factor, CTCF, is aberrantly expressed in breast tumours.

BORIS (for brother of the regulator of imprinted sites), a paralogue of the transcription factor, CTCF, is a novel member of the cancer-testis antigen family. The aims of the present study were as follows: (1) to investigate BORIS expression in breast cells and tumours using immunohistochemical staining, western and real-time RT-PCR analyses and (2) assess potential correlation between BORIS levels in tumours with clinical/pathological parameters. BORIS was detected in all 18 inspected breast cell lines, but not in a primary normal breast cell culture. In 70.7% (41 of 58 cases) BORIS was observed in breast tumours. High levels of BORIS correlated with high levels of progesterone receptor (PR) and oestrogen receptor (ER). The link between BORIS and PR/ER was further confirmed by the ability of BORIS to activate the promoters of the PR and ER genes in the reporter assays. Detection of BORIS in a high proportion of breast cancer patients implies potential practical applications of BORIS as a molecular biomarker of breast cancer. This may be important for diagnosis of the condition and for the therapeutic use of BORIS. The ability of BORIS to activate promoters of the RP and ER genes points towards possible involvement of BORIS in the establishment, progression and maintenance of breast tumours.

Continuous subcutaneous insulin infusion versus multiple daily injections of insulin for pregnant women with diabetes.

BACKGROUND: Diabetes causes a rise in blood glucose above normal physiological levels causing damage to many systems including the cardiovascular and renal systems. Pregnancy causes a physiological reduction in insulin action; for those women who have pre-gestational diabetes, this results in an increasing insulin requirement. There are several methods of administering insulin. Conventionally, insulin has been administered subcutaneously, formally referred to as intensive conventional treatment, but now more usually referred to as multiple daily injections (MDI). An alternative insulin administration method is the continuous subcutaneous insulin infusion pump (CSII). OBJECTIVES: To compare continuous subcutaneous insulin infusion with MDI of insulin for pregnant women with diabetes. SEARCH STRATEGY: We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (November 2006). SELECTION CRITERIA: Randomised controlled trials comparing CSII with MDI for pregnant women with diabetes. DATA COLLECTION AND ANALYSIS: Three authors independently assessed studies and extracted data. MAIN RESULTS: Two studies (60 women with 61 pregnancies) were included. There was a significant increase in mean birthweight associated with CSII as opposed to MDI (weighted mean difference 220.56, 95% confidence interval (CI) -2.09 to 443.20; two trials, 61 participants). However, taking into consideration the lack of significant difference in rate of macrosomia (birthweight greater than 4000 g) (relative risk (RR) 3.20, 95% CI 0.14 to 72.62; two trials, 61 participants), this is not viewed by the authors as clinically significant. No significant differences were found in any other outcomes measured, which may reflect the small number of trials suitable for meta-analysis and the small number of participants in the included studies. No significant differences were found in perinatal mortality (RR 2.00, 95% CI 0.20 to 19.91), fetal anomaly (RR 1.07, 95% CI 0.07 to 15.54), maternal hypoglycaemia (RR 3.00, 95% CI 0.35 to 25.87) or maternal hyperglycaemia (RR 7.00, 95% CI 0.39 to 125.44). AUTHORS' CONCLUSIONS: There is a dearth of robust evidence to support the use of one particular form of insulin administration over another for pregnant women with diabetes. The data are limited because of the small number of trials appropriate for meta-analysis, small study sample size and questionable generalisability of the trial population. Conclusions cannot be made from the data available and therefore a robust randomised trial is needed. The trial should be adequately powered to assess the efficacy of continuous subcutaneous insulin infusion versus multiple daily injections in terms of appropriate outcomes for women with diabetes.

In vitro susceptibilities in lymphocytes from mothers and cord blood to the monofunctional alkylating agent EMS.

It has been reported that children may experience different levels of chemical exposures than adults and that their sensitivities to chemical toxins may be increased or decreased when compared to adults. The perinatal period is one period in which these susceptibilities may be examined. Midwives at the Bradford Royal Infirmary collected venous blood samples from mothers at the time of birth and venous cord blood post-delivery. Lymphocytes were isolated from both blood types and examined in the alkaline comet assay using the monofunctional alkylating agent ethyl methanesulphonate (EMS). There were no biologically significant differences when subjects were categorized into subgroups based on lifestyle habits and physical characteristics, and overall there were no statistically significant differences in levels of DNA damage in mothers (n=22) and babies (n=22), except at the basal level (P<0.05), but mean values in babies were always lower over the EMS dose range. Whole blood was used in the micronucleus (MN) assay, and there was a significantly (P<0.05) higher rate of MN in mothers (n=17), per 1000 binucleates, as compared with lymphocytes from their offspring (n=17) at the basal level. This may be accounted for by age and endogenous factors. Overall, this current study cannot provide statistically significant evidence that children have either increased or decreased levels of susceptibility to a chemical toxin in comparison to adults when EMS is examined in vitro.

Volatile organic compounds in selected micro-environments.

A program of sampling for volatile organic compounds (VOCs) in ambient air was undertaken in selected locations and micro-environments in Perth, Western Australia to characterise concentrations of target VOCs and to determine the relative strength of the contributing sources to ambient air in different micro-environments in a major Australian city. Twenty-seven locations were sampled and, of the forty-one target compounds, 26 VOCs were detected in the samples collected. The highest concentrations were recorded for benzene, toluene, ethylbenzene, xylenes (BTEX), chloroform and styrene. The maximum 12-h toluene and benzene concentrations observed were from a basement carpark and were 24.7 parts per billion (ppb) and 5.6 ppb, respectively. The maximum xylenes concentration was 29.4 ppb and occurred in a nightclub where styrene was also detected. A factor analysis of the data was undertaken. Two key factors emerge that appear to be associated with petroleum and motor vehicles and environmental tobacco smoke. A third significant occurrence was a high concentration of chloroform that was observed at a sports centre complex with a swimming pool text and was uncorrelated with other compounds in the data set. This study indicates that locations associated with motor vehicles and petrol fuel, tobacco and wood smoke and chlorinated water represent the major risks for personal exposure to VOCs in Perth.

Cement from nanocrystalline hydroxyapatite: effect of calcium phosphate ratio.

Nanocrystalline hydroxyapatite (nHA) can be mixed with phosphoric acid to form a brushite cement; a degradable inorganic bone filling material. nHA was precipitated from reactants of calcium to phosphate (Ca/P) ratio 0.8 to 2.0 and mixed with phosphoric acid, which resulted in the formation of a brushite cement. Cement was also formed by mixing microcrystalline calcium phosphates, beta-tricalcium phosphate, hydroxyapatite and tetracalcium phosphate with phosphoric acid solution. Cement produced with nHA was stronger in compression than that formed with crystalline calcium phosphate phases. Setting time, strength and composition of cement produced with nHA was dependant on both the Ca/P ratio of nHA and the concentration of phosphoric acid in cement slurry. Increasing phosphoric acid concentration increased compressive strength whilst reducing the initial setting time of cement. Reducing the Ca/P ratio of nHA precipitation reactants retarded the setting and increased the extent of reaction of cements. This finding was unexpected and suggests that Ca/P ratio may strongly affect dissolution behaviour and this parameter is more important than stoichiometry in determining extent of reaction in this system. This study demonstrated that the wide variation in stoichiometry that may be attained in nanocrystalline apatite may be utilised to change cement performance and setting behaviour.

Cement from magnesium substituted hydroxyapatite.

Brushite cement may be used as a bone graft material and is more soluble than apatite in physiological conditions. Consequently it is considerably more resorbable in vivo than apatite forming cements. Brushite cement formation has previously been reported by our group following the mixture of nanocrystalline hydroxyapatite and phosphoric acid. In this study, brushite cement was formed from the reaction of nanocrystalline magnesium-substituted hydroxyapatite with phosphoric acid in an attempt to produce a magnesium substituted brushite cement. The presence of magnesium was shown to have a strong effect on cement composition and strength. Additionally the presence of magnesium in brushite cement was found to reduce the extent of brushite hydrolysis resulting in the formation of HA. By incorporating magnesium ions in the apatite reactant structure the concentration of magnesium ions in the liquid phase of the cement was controlled by the dissolution rate of the apatite. This approach may be used to supply other ions to cement systems during setting as a means to manipulate the clinical performance and characteristics of brushite cements.

Penetration of ammonium perfluorooctanoate through rat and human skin in vitro.

Rat and human epidermal membranes were mounted onto in vitro diffusion cells with an exposure area of 0.64 cm2, and skin integrity was confirmed using electrical impedance. Following membrane selection, Fluorad FC-118, a 20% aqueous solution of ammonium perfluorooctanoate (AFPO), was applied to the epidermal surface of each skin replicate at approximately 150 microL/cm2 and the donor chamber opening occluded with Parafilm. Serial receptor fluid samples were collected hourly from 1 to 6 h and at 12, 24, 30, and 48 h and analyzed by liquid chromatography-mass spectrometry (LC-MS) for APFO anion (PFO-). For rat skin, the time to steady-state penetration (6500+/-3000 ng APFO x cm(-2) x h(-1)) occurred in less than 12 h, which was sustained until termination (48 h). Based on the concentration of the applied test material, the permeability coefficient (Kp) for APFO in rat skin was calculated to be 3.25+/-1.51 x 10(-5) cm/h. By end of the 48-h exposure period, only a small portion of the total APFO applied (1.44+/-1.13%) had penetrated through rat skin. For human skin, steady-state penetration of APFO (190+/-57 ng APFO x cm(-2) x h(-1)) was reached by 12 h. Based on the concentration of the applied test material, the permeability coefficient for APFO in human skin was calculated to be 9.49+/-2.86 x 10(-7) cm/h. By the end of the 48-h exposure period, only a negligible amount of the total APFO applied (0.048+/-0.01%) had penetrated through human skin. Thus, under infinite dose and occlusive conditions, the steady-state penetration of APFO from a 20% solution was approximately 34-fold faster through rat skin than human skin.

Degradation of poly-L-lactide. Part 2: increased temperature accelerated degradation.

Poly-L-lactide (PLLA) is one of the most significant members of a group of polymers regarded as bioresorbable. The degradation of PLLA proceeds through hydrolysis of the ester linkages in the polymer's backbone; however, the time for the complete resorption of orthopaedic devices manufactured from PLLA is known to be in excess of five years in a normal physiological environment. To evaluate the degradation of PLLA in an accelerated time period, PLLA pellets were processed by compression moulding into tensile test specimens, prior to being sterilized by ethylene oxide gas (EtO) and degraded in a phosphate-buffered solution (PBS) at both 50 degrees C and 70 degrees C. On retrieval, at predetermined time intervals, procedures were used to evaluate the material's molecular weight, crystallinity, mechanical strength, and thermal properties. The results from this study suggest that at both 50 degrees C and 70 degrees C, degradation proceeds by a very similar mechanism to that observed at 37 degrees C in vitro and in vivo. The degradation models developed also confirmed the dependence of mass loss, melting temperature, and glass transition temperature (Tg) on the polymer's molecular weight throughout degradation. Although increased temperature appears to be a suitable method for accelerating the degradation of PLLA, relative to its physiological degradation rate, concerns still remain over the validity of testing above the polymer's Tg and the significance of autocatalysis at increased temperatures.

Cements from nanocrystalline hydroxyapatite.

Calcium phosphate cements are used as bone substitute materials because they may be moulded to fill a void or defect in bone and are osteoconductive. Although apatite cements are stronger than brushite cements, they are potentially less resorbable in vivo. Brushite cements are three-component systems whereby phosphate ions and water react with a soluble calcium phosphate to form brushite (CaHPO4 x 2H2O). Previously reported brushite cement formulations set following the mixture of a calcium phosphate, such as beta-tricalcium phosphate (beta-TCP), with an acidic component such as H3PO4 or monocalcium phosphate monohydrate (MCPM). Due to its low solubility, hydroxyapatite (HA) is yet to be reported as a reactive component in calcium phosphate cement systems. Here we report a new cement system setting to form a matrix consisting predominantly of brushite following the mixture of phosphoric acid with nanocrystalline HA. As a result of the relative ease with which ionic substitutions may be made in apatite this route may offer a novel way to control cement composition or setting characteristics. Since kinetic solubility is dependent on particle size and precipitation temperature is known to affect precipitated HA crystal size, the phase composition and mechanical properties of cements made from HA precipitated at temperatures between 4 and 60 degrees C were investigated.

Processing, annealing and sterilisation of poly-L-lactide.

Poly-L-lactide (PLLA) is one of the most significant members of a group of polymers regarded as bioabsorbable. Degradation of PLLA proceeds through hydrolysis of the ester bonds in the polymer chains and is influenced significantly by the polymer's molecular weight and crystallinity. To evaluate the effects of processing and sterilisation on these properties, PLLA pellets were either compression moulded or extruded, subjected to annealing at 120 degrees C for 4h and sterilised by ethylene oxide (EtO) gas. Procedures were used to evaluate the mechanical properties, molecular weight and crystallinity. Upon processing, the crystallinity of the material fell from 61% for the PLLA pellets to 12% and 20% for the compressed and extruded components, respectively. After annealing, crystallinity increased to 43% for the compression-moulded material and 40% for the extruded material. Crystallinity further increased upon EtO sterilisation. A slight decrease in molecular weight was observed for the extruded material through processing, annealing and sterilisation. Young's modulus generally increased with increasing crystallinity, and extension at break and tensile strength decreased. The results from this investigation suggest that PLLA is sensitive to processing and sterilisation, altering properties critical to its degradation rate.