Comparison of Power of Trend Tests for Toxicological Application Based on Dose-Response Profiles Enumerated Using a Nonparametric Algorithm

Tests for dose-response trend may be used to support conclusions on the toxicity of a substance in a range of doses evaluated in a comparative experiment. Criteria are proposed for evaluating and comparing alternative tests, and are applied in a comparison of certain tests applicable with continuous responses, namely, a multiplicity-adjusted pairwise comparison procedure, a trend test based on a single contrast, and four multiple-contrast trend tests. Methods considered treat dose as ordinal information. A particular focus was comparison of the simple test of a single contrast, with coefficients proportional to dose rank, with the multiple-contrast methods available with modern computing. To explore the role of the dose-response curve shape, regular dose-response shapes (or profiles), defined by the mean response for each dose level, using a simple grid-based algorithm were generated. Power for individual profiles may be used to illustrate the effect of curve shape on the power of alternative tests. To facilitate selection of tests, we report average power over profiles, averaging at different levels of granularity, first separately for each of several curve shape categories, and then over all profiles, weighting shape categories equally. Power results for the six tests evaluated at least provide clear distinctions between some procedures that are more-preferred, versus less-preferred. Our analyses expand the comparisons of tests available and contribute a methodology for choice of statistical methods for toxicological data analysis. Environ Toxicol Chem 2022;41:1754-1764. Published 2022. This article is a U.S. Government work and is in the public domain in the USA.

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.

The effect of continuous diffusion of oxygen treatment on cytokines, perfusion, bacterial load, and healing in patients with diabetic foot ulcers

To evaluate continuous diffusion of oxygen therapy (CDO) on cytokines, perfusion, and bacterial load in diabetic foot ulcers we evaluated 23 patients for 3 weeks. Tissues biopsies were obtained at each visit to evaluate cytokines and quantitative bacterial cultures. Perfusion was measured with hyperspectral imaging and transcutaneous oxygen. We used paired T tests to compare continuous variables and independent T tests to compare healers and nonhealers. There was an increase from baseline to week 1 in TGF-β (P = .008), TNF-α (P = .014), VEGF (P = .008), PDGF (P = .087), and IGF-1 (P = .058); baseline to week 2 in TGF-β (P = .010), VEGF (P = .051), and IL-6 (P = .031); and baseline to week 3 with TGF-β (P = .055) and IL-6 (P = .054). There was a significant increase in transcutaneous oxygen after 1 week of treatment on both medial and lateral foot (P = .086 and .025). Fifty-three percent of the patients had at least a 50% wound area reduction (healers). At baseline, there were no differences in cytokines between healers and nonhealers. However, there was an increase in CXCL8 after 1 week of treatment (P = .080) and IL-6 after 3 weeks of treatment in nonhealers (P = .099). There were no differences in quantitative cultures in healers and nonhealers.

Lyopreserved amniotic membrane is cellularly and clinically similar to cryopreserved construct for treating foot ulcers

We compared cellular viability between cryopreserved and lyopreserved amniotic membranes and clinical outcomes of the lyopreserved construct in a prospective cohort study of 40 patients with neuropathic foot ulcers. Patients received weekly application of lyopreserved membrane for 12 weeks with standard weekly debridement and offloading. We evaluated the proportion of foot ulcers that closed, time to closure, closure trajectories, and infection during therapy. We used chi-square tests for dichotomous variables and independent t-tests for continuous variables with an alpha of α = .10. Cellular viability was equivalent between cryo- and lyopreserved amniotic tissues. Clinically, 48% of subjects' wounds closed in an average of 40.0 days. Those that did not close were older (63 vs 59 years, P = .011) and larger ulcers at baseline (7.8 vs 1.6 cm² , P = .012). Significantly more patients who achieved closure reached a 50% wound area reduction in 4 weeks compared with non-closed wounds (73.7% vs 47.6%, P = .093). There was no difference in the slope of the wound closure trajectories between closed and non-closed wounds (0.124 and 0.159, P = .85), indicating the rate of closure was similar. The rate of closure was 0.60 mm/day (SD = 0.47) for wounds that closed and 0.50 mm/day (SD = 0.58) for wounds that did not close (P = .89).

The infected diabetic foot: Can serum biomarkers predict osteomyelitis after hospital discharge for diabetic foot infections?

The aim of this study is to evaluate serum biomarkers to monitor high-risk patients for reinfection of bone. Thirty-five patients were prospectively enrolled with moderate to severe diabetic foot infections with suspicion of osteomyelitis. Bone samples were obtained for culture and histology. Clinical characteristics and outcomes of patients were compared using χ² square test. Biomarkers (white blood cell count, erythrocyte sedimentation rate, c-reactive protein, procalcitonin, interleukin-6, interleukin-8, and monocyte chemoattractant protein 1) were assessed at baseline, 3, and 6 weeks after treatment initiation and evaluated for correlation with reinfection of bone. After 6 weeks of antibiotic treatment, ESR at 73.5 mm/h (sensitivity 62.5%, specificity 100%, area under the receiver operating characteristic (AUROC) 0.7839, 95% CI 0.54-1.00, P < .01) and IL-8 at 15.09 mg/dL (sensitivity 42.9%, specificity 92.0% AUROC 0.6286, 95% CI 0.36-0.90, P = .0496) were associated with reinfection of bone. An increase in IL-8 from week 0 to 6 >0.95 mg/dL was associated with reinfection (sensitivity 71%, specificity 72% AUROC 0.7057, 95% CI 0.49-0.92, P = .04). An ESR change from week 0-6 of -16.5% (sensitivity 71.4%, specificity 86.4% AUROC 0.7403, 95% CI 0.48-1.00, P = .02), CRP (-)74.4% (sensitivity 66.7%, specificity 91.3% AUROC 0.7174, 95% CI 0.40-1.00, P = .04), IL-6 (-)49.9% (sensitivity 71.4%, specificity 76% AUROC 0.7371, 95% CI 0.47-1.00, P = .04), and IL-8 29% (sensitivity 85.7%, specificity 56.0% AUROC of 0.7343, 95% CI 0.54-0.93, P = .048) were associated with increased risk of reinfection. Pilot data suggest that serum biomarkers (ESR, IL8 and IL6, MCP-1) may be correlated with developing osteomyelitis and could be used to monitor high-risk patients for reinfection.

Randomized clinical study to compare negative pressure wound therapy with simultaneous saline irrigation and traditional negative pressure wound therapy for complex foot infections

The aim of this study was to compare the efficacy of different negative pressure wound therapy (NPWT) devices and NPWT with and without simultaneous irrigation in patients admitted to hospital with moderate and severe foot infections. Ninety patients were randomized in a 12‐week prospective, randomized noninferiority trial to compare wound healing in patients with moderate and severe infected foot wounds treated with NPWT after surgery. Inclusion criteria included ABI > 0.5 or toe pressures >30 PVR/mmHg, >18 years of age and exclusion included active Charcot arthropathy, collagen vascular disease, HIV, and hypercoagulable state. We compared two different traditional devices, NPWT‐K (KCI, VAC Ulta) and NPWT‐C (Cardinal, PRO), and NPWT‐I with saline irrigation (Cardinal, PRO). All patients had therapy delivered at 125 mmHg continuous pressure. In patients who received simultaneous saline irrigation (NPWT‐I), the administration rate was 15 ml per hour. The primary outcome was the proportion of healed wounds in 12 weeks. Secondary outcomes included surgical wound closure, number of surgeries, length of stay, and time to wound healing. Continuous data was presented as mean ± standard deviation. Analysis of variance was used to compare continuous variables and chi‐square to compare dichotomous variables with an alpha of 0.05. There were no differences in outcomes among NPWT‐I, NPWT‐C, and NPWT‐K groups in proportion of healed wounds (63.3%, 50.0%, 46.7% p = 0.39), surgical wound closure (83.3%, 80.0%, 63.3%, p = 0.15), number of surgeries (2.0 ± 0.49, 2.4 ± 0.77, 2.4 ± 0.68, p = 0.06), length of stay (16.3 ± 15.7, 14.7 ± 7.4, 15.3 ± 10.5 days, p = 0.87), time to wound healing (46.2 ± 22.8, 40.9 ± 18.8, 45.9 ± 28.3 days, p = 0.78). We did not identify any significant differences in clinical outcomes or adverse events between patients treated with different NPWT devices or NPWT with and without irrigation.

Blood Usage in an Australian Intensive Care Unit: Have We Met Best Practice Goals?

The transfusion of blood products, especially red cell concentrates, in critically ill patients is controversial and benefits of red cell concentrate transfusion in these patients have not been clearly demonstrated.

We performed a prospective observational study to compare best evidence to actual practice of red cell concentrate and other blood product administration in an intensive care unit (ICU) in a university-associated tertiary hospital. All primary admissions during a 28-day period were included in the study and data collected included transfusion of red cells and blood products, patient demographics and ICU and hospital outcome.

One hundred and seventy-five admissions were studied; 44% followed cardiac surgery. Forty-one patients (23%) received red cell concentrates in ICU, with 120 units transfused in 61 separate episodes. Other blood product usage was minimal. One third (20/61) of red cell concentrate transfusion episodes were of a single unit. The mean (±SD) pre-transfusion haemoglobin was 7.9±1.1 g/dl. Despite transfusion, such patients left ICU with a lower haemoglobin concentration compared with untransfused ICU patients (9.5±1.0 versus 10.5±2.1 g/dl; P<0.001). Cardiac surgical patients received similar red cell transfusion to general ICU patients. Univariate analysis showed no significant difference in mortality between patients who did or did not receive red cell concentrate transfusion (P=0.17). However, red cell concentrate transfusion was associated with a reduced adjusted mortality both in ICU (OR 0.13, 95% CI 0.02-0.73) and in hospital at 28 days (OR 0.10, 95% CI 0.02-0.58). The low red cell concentrate and blood product usage in our ICU were consistent with restrictive transfusion practice and selective red cell concentrate transfusion was associated with reduced mortality.

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.

Control of cytotoxic T lymphocyte memory development by beta2-adrenergic receptor signaling

Cytotoxic T lymphocytes (CTLs) play a critical role in immune responses to intracellular pathogens. CTL responses are initiated by T cell receptor signaling, and they can be modulated by secreted factors, such as cytokines and other extracellular signals. Previous research from our lab demonstrated that the acute effector functions of CTLs are regulated by the neurotransmitter norepinephrine (NE) via beta2-adrenergic receptor (ADRB2) signaling in vitro. We now demonstrate that ADRB2 signaling intrinsically modulates in vivo memory development in response to viral infection using an adoptive transfer model. Expansion of ADRB2-deficient CTLs is unaffected during the initial priming phase in response to the model pathogen, vesicular stomatitis virus. However, ADRB2-deficient CTLs contract rapidly and do not yield any detectable pools of memory cells when compared to wild-type counterparts. Transcriptome analysis revealed a variety of differentially expressed genes, both expressed in resting naïve cells as well as in cells obtained during the primary expansion phase of infection. Among them, we found that the expression of the high affinity IL-2Ra (CD25) was reduced during the activation phase in ADRB2-deficient cells, which was confirmed at the protein level by flow cytometry. While IL-2 responsiveness is a key determinant in programming memory cell development, treatment with IL-2/anti-IL-2 complexes during early phases of infection failed to rescue memory formation of ADRB2-deficient cells, despite a restoration of CD25 expression on day 5 post-infection. Future experiments will dissect the role of ADRB2 signaling during CTL development on the capacity to form memory upon antigen exposure.

Beta-2 adrenergic receptor signaling prevents hyperinflammation through early release of IL-10

Innervation of the lymphoid tissues by catecholaminergic nerve endings allow the sympathetic nervous system to communicate with immune cells through the release of norepinephrine (NE). NE signals through adrenergic receptors, which are widely expressed by immune cells. We have identified a novel pathway where NE can suppress pro-inflammatory cytokine secretion from bone marrow-derived macrophages in response to multiple TLR agonists. This pathway operates through the beta2-adrenergic receptor (ADRB2), and the suppressive effect of NE depends on the early induction of the anti-inflammatory cytokine IL-10. We assessed the in vivo role of this pathway using a LPS endotoxemia model and found that ADRB2 knockout (KO) animals rapidly succumbed to a sub-lethal LPS challenge. This sensitivity is correlated with elevated serum levels of TNFα and suppressed IL-10 in ADRB2 KO animals. The lethality in the ADRB2 KO animals was rescued by administering exogenous IL-10. Additionally, the ADRB2-specific agonist salmeterol rescued wild-type animals from a lethal LPS challenge, which was reversed by neutralizing anti-IL-10 antibody. These observations suggest that ADRB2 signaling is critical for controlling inflammation through the rapid induction of IL-10. Through transcriptome analysis, the NR4A nuclear orphan family members were induced by NE, and the presence of several putative NR4A binding sites within the IL-10 promoter suggests that these factors may directly regulate IL-10 expression in response to ADRB2 signaling. Further studies will directly test the control of IL-10 expression by NR4A factors. Understanding this pathway will provide new insights into how the nervous and immune systems communicate through ADRB2 signaling.

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

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.

Type I interferon negatively regulates acute IL-5 and IL-13 expression in human memory Th2 cells (IRM6P.717)

IFN-α/β is a potent antiviral cytokine that induces the expression of hundreds of interferon-sensitive genes (ISGs). ISGs are positively regulated by IFN-α/β signaling and collectively interfere with various aspects of viral replication. Although the positive regulatory aspects of IFN-α/β signaling through STAT activation have been studied at length, less is known about its role as a negative regulator. Previously, we demonstrated that IFN-α/β suppresses Th2 development in human naïve CD4+ T cells by negatively regulating GATA3 expression, leading to the suppression of Th2 cytokines. In the current study, we found that IFN-α/β also suppressed Th2 cytokine expression from fully committed Th2 cells responding to recall antigen stimulation. Human memory CD4+ T cells acutely stimulated in the presence of IFN-α showed suppressed IL-5 and IL-13 gene expression, however, IL-4 expression was unaffected. Nuclear run-on studies demonstrated that IFN-α signaling suppressed de novo transcription of IL-5 and IL-13, which did not require new protein synthesis. Our data suggest that IFN-α/β was able to acutely repress specific genes by directly inhibiting their transcription. We are assessing direct STAT2 binding by ChIP-Seq, which will identify cis-regulatory regions necessary for gene repression at these cytokine promoters. Taken together, these results demonstrate that IFN-α/β is a key negative regulator of the Th2 response in humans.

The nervous system modulates CD8+ T cell function through the beta2-adrenergic receptor (IRC2P.456)

There is growing evidence to suggest that various aspects of immune function are controlled by neural networks. Both cholinergic and adrenergic receptors are expressed by various major immune cell types. Specifically, expression of the β2-adrenergic receptor (ADRB2) has been characterized in different cells of the immune system; however, our lab has demonstrated for the first time a differential expression of this receptor in subsets of effector and memory CD8+ T cells. We found that the ADRB2 is upregulated in human effector memory CD8+ T cells compared to central memory/naïve counterparts. Further, human CD8+ T cells that are acutely activated in the presence of the ADRB2 natural ligand, nor-epinephrine (NE), secrete significantly less IFN-γ and TNF-α. Similarly, the cytolytic capacity of these cells is reduced when NE is present. This downregulation by NE was reversed in the presence of a ADRB2-specific antagonist, but not a pan α-adrenergic or β1-adrenergic receptor specific antagonists. Additionally, mouse CD8+ T cells behaved similarly to human cells to these antagonists, suggesting species conservation of this neural-immune network. Moreover, ADRB2-KO CD8+ T cells were completely resistant to the effects of NE. Current experiments using an adoptive transfer model will elucidate how ADRB2 signaling modulates CD8+ T cell function in vivo. These experiments will provide insight into how the nervous system controls CD8+ T cell function during the course of an infection.

Neural control of innate immunity by beta2-adrenergic receptor (INC5P.323)

The nervous system controls a variety of physiological responses through the release of several chemical messengers. Although the immune system has been thought to be a self-regulated system, there is growing evidence that the immune system and the nervous system are capable of reciprocally regulating their function. We recently identified a unique role for adrenergic signaling in modulating the innate response to pathogen-associated molecular patterns. First, we found that norepinephrine (NE) can suppress pro-inflammatory cytokine secretion from bone marrow-derived macrophages and dendritic cells in response to TLR signaling in vitro. This suppressive effect depends on the early induction of the anti-inflammatory cytokine IL-10, where neutralizing the autocrine IL-10 signaling restores the cytokine secretion. NE exerts its effects by signaling through the beta2-adrenergic receptor (ADRB2). Second, upon challenging mice with a sub-lethal dose of Listeria monocytogenes, ADRB2 knockout mice present with splenomegaly and enhanced bacterial clearance. Additionally, treatment of whole human blood with TLR ligands in the presence of the ADRB2 agonist albuterol suppresses TNFα secretion, demonstrating the presence of this pathway in humans. This supports the hypothesis that ADRB2 signaling is a negative regulator of TLR signaling and suggests that this pathway plays an important role in immune activation and homeostasis.

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.

Application of Computer Modeling in Systemic VAD Support of Failing Fontan Physiology

Although the Fontan procedure has been enormously successful in palliation of single-ventricle patients, many seem to experience progressive failure of the Fontan circulation over time. Ventricular assist devices (VADs) have developed into stable platforms for long-term support of adult patients with heart failure. Given the success of axial flow devices, it was hypothesized that the technology could provide clinical benefit to failing Fontan patients. The aim of this study was to use a computer model to evaluate VAD support in failing Fontan physiology. A computer model of Fontan circulation with heart failure was developed and the HeartMate II (HM II) (Thoratec Corp) axial flow ventricular assist device was connected to this model in a systemic configuration to examine its impact. Cardiac catheterization data from 7 patients (8 catheterization studies) with failing Fontan physiology were applied to this model to evaluate the impact of using the HM II in this manner. When the HM II was used in a systemic configuration at 8000 rpm, there was a 35% decrease in the systemic venous pressure in the Fontan circuit and a 63% decrease in pulmonary capillary wedge pressure with a resultant 41% increase in CI. The model also predicted patient-specific parameters where the VAD may not benefit the patient, such as fixed elevated pulmonary vascular resistance, low systemic ventricular end-diastolic pressure, and high unresponsive systemic vascular resistance. These data suggest a potential benefit from application of axial flow VAD technology in the management of failing Fontan physiology. Clinical correlation will allow for refinement of this model as a predictive tool in discerning which patients may benefit from placement of a VAD and what issues must be addressed prior to implanting the device.

The potential of electron beam radiation for simultaneous surface modification and bioresorption control of PLLA

Bioresorbable polymers have been widely investigated as materials exhibiting significant potential for successful application in the fields of tissue engineering and drug delivery. Further to the ability to control degradation, surface engineering of polymers has been highlighted as a key method central to their development. Previous work has demonstrated the ability of electron beam (e-beam) technology to control the degradation profiles and bioresorption of a number of commercially relevant bioresorbable polymers (poly-l-lactic acid (PLLA), L-lactide/DL-lactide co-polymer (PLDL) and poly(lactic-co-glycolic acid (PLGA)). This work investigates the further potential of e-beam technology to impart added biofunctionality through the manipulation of polymer (PLLA) surface properties. PLLA samples were subjected to e-beam treatments in air, with varying beam energies and doses. Surface characterization was then performed using contact angle analysis, X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and atomic force microscopy. Results demonstrated a significant increase in surface wettability post e-beam treatment. In correlation with this, XPS data showed the introduction of oxygen-containing functional groups to the surface of PLLA. Raman spectroscopy indicated chain scission in the near surface region of PLLA (as predicted). However, e-beam effects on surface properties were not shown to be dependent on beam energy or dose. E-beam irradiation did not seem to affect the surface roughness of PLLA as a direct consequence of the treatment.

Abstract 194: Pre-Operative Health Status is Only Weakly Associated With Mortality or Hospitalization Following Continuous-Flow Left Ventricular Assist Device Implantation

Background: Health status predicts death and hospitalization in heart failure and cardiac surgery, but its prognostic value in the setting of left ventricular assist device (LVAD) placement is unknown. We hypothesized that baseline health status could help identify patients at risk for adverse post-operative outcomes and improve patient selection for LVAD therapy.

Methods: We examined the association of pre-operative health status, as measured by the Kansas City Cardiomyopathy Questionnaire (KCCQ) overall summary score (OSS), with overall mortality and hospitalization in 965 patients undergoing LVAD placement as part of two clinical trials of the HeartMate II device. Unadjusted statistical analyses were performed using Cox proportional hazard models and Kruskal-Wallis non-parametric tests.

Results: Baseline OSS of survivors (median: 25.5, inter quartile range (IQR): 15.6-38.6) was similar to those who died (median: 23.4, IQR 12.9-39.2, p=0.06). Patients in the lowest quartile of KCCQ scores (OSS<14.8) had worse survival as compared with the upper 3 quartiles (unadjusted HR: 1.30. 95% CI 1.03-1.63, p=0.03). Patients in the lowest quartile of baseline OSS also spent more time in the hospital (median 25 days, IQR 19-42) as compared with the upper 3 quartiles (median 23 days, IQR 17-35, p=0.009). Outcomes for the 3 higher OSS quartiles were not significantly different. When comparing KCCQ sub-domain scores of patients who died during follow-up to those who did not, lower total symptom score was significantly associated with worse survival (p=0.009); all other KCCQ sub-domains were not.

Conclusion: Only patients with very low baseline health status (KCCQ <15) were at increased risk for mortality and hospitalization following LVAD implantation, with the absolute differences being very small. This weak association between baseline KCCQ and post-operative outcomes suggests that LVAD implantation, unlike chronic heart failure and other cardiac surgeries, represents a unique clinical situation in which the benefits of the intervention may outweigh the anticipated risks of worse health status.

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.

Analysis of degradation data of poly(l-lactide-co-l,d-lactide) and poly(l-lactide) obtained at elevated and physiological temperatures using mathematical models

The degradation of resorbable polymeric devices often takes months to years. Accelerated testing at elevated temperatures is an attractive but controversial technique. The purposes of this paper include: (a) to provide a summary of the mathematical models required to analyse accelerated degradation data and to indicate the pitfalls of using these models; (b) to improve the model previously developed by Han and Pan; (c) to provide a simple version of the model of Han and Pan with an analytical solution that is convenient to use; (d) to demonstrate the application of the improved model in two different poly(lactic acid) systems. It is shown that the simple analytical relations between molecular weight and degradation time widely used in the literature can lead to inadequate conclusions. In more general situations the rate equations are only part of a complete degradation model. Together with previous works in the literature, our study calls for care in using the accelerated testing technique.

Performance of calcium deficient hydroxyapatite-polyglycolic acid composites: an in vitro study

The strategic incorporation of bioresorbable polymeric additives to calcium-deficient hydroxyapatite cement may provide short-term structural reinforcement and modify the modulus to closer match bone. The longer-term resorption properties may also be improved, creating pathways for bone in-growth. The aim of this study was to investigate the resorption process of a calcium phosphate cement system containing either in polyglycolic acid tri-methylene carbonate particles or polyglycolic acid fibres. This was achieved by in vitro aging in physiological conditions (phosphate buffered solution at 37 degrees C) over 12 weeks. The unreinforced CPC exhibited an increase in compressive strength at 12 weeks, however catastrophic failure was observed above a critical loading. The fracture behaviour of cement was improved by the incorporation of PGA fibres; the cement retained its cohesive structure after critical loading. Gravimetric analysis and scanning electron microscopy showed a large proportion of the fibres had resorbed after 12 weeks allowing for the increased cement porosity, which could facilitate cell infiltration and faster integration of natural bone. Incorporating the particulate additives in the cement did not provide any mechanism for mechanical property augmentation or did not demonstrate any appreciable level of resorption after 12 weeks.

The degradation properties of co-continuous calcium phosphate polyester composites: insights with synchrotron micro-computer tomography

This study investigates the in vitro degradation properties of composites consisting of a porous tricalcium phosphate (TCP) foam filled with degradable poly(dl-lactic acid) (PDLLA) via either in situ polymerization or infiltration. The motivation was to develop a material for bone repair that would be initially mechanically strong and would develop porosity during degradation of one of the components. A thorough analysis of the physical in vitro degradation properties has been conducted and reported by the same authors elsewhere. Synchrotron micro-computer tomography analysis (conducted at ID19, ESRF, Grenoble, France) allowed detailed insights to be gained into the process of the composites' degradation, which was discovered to be strongly influenced by the manufacturing method. The polymer phase of in situ-polymerized TCP-PDLLA degraded as a bulk sample, with faster degradation in the centre of the sample as a whole. In contrast, the polymer phase of infiltrated TCP-PDLLA degraded as individual polymer spheres with faster degradation in the centre of each sphere.

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.

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.

Lithocholate--a promising non-calcaemic calcitriol surrogate for promoting human osteoblast maturation upon biomaterials

BACKGROUND AND AIMS

Calcitriol, an active vitamin D metabolite, has a limited application in bone repair because of its undesirable hypercalcaemic action. However it has emerged that lithocholic acid (LCA) is a non-calcaemic vitamin D receptor ligand but whether this steroid can support osteoblast maturation has not been reported. Using the human osteoblast cell line, MG63, we explored the potential of LCA and LCA derivatives to secure osteoblast maturation.

RESULTS

The co-stimulation of cells with LCA, LCA acetate or LCA acetate methyl ester (0.5-5 microM) and lysophosphatidic acid (LPA, 20 microM) resulted in clear, synergistic increases in MG63 maturation that was both time and dose dependent. Cells grown upon both titanium and hydroxyapatite, two widely used implant materials, responded well to co-treatment with LCA acetate (5 microM) and LPA (20 microM) as demonstrated by stark, synergistic increases in ALP activity. Evidence of activator protein-1 (AP-1) stimulation by LCA acetate (30 microM) was demonstrated using an AP-1 luciferase reporter assay. Synergistic increases in ALP activity, and therefore osteoblast maturation, were observed for MG63 cells co-stimulated with LCA acetate (5 microM) and either epidermal growth factor (10 ng/ml) or transforming growth factor-beta (10 ng/ml). Ligands acting on either the farnesoid X receptor or pregnane X receptor could not substitute for the action of LCA acetate on MG63 maturation.

CONCLUSIONS

Lithocholate is able to act as a calcitriol surrogate in generating mature osteoblasts. Given that LCA is non-calcaemic it is likely to find an application in bone repair/regeneration by aiding matrix calcification at implant sites.

Cytoskeletal reorganisation, 1alpha,25-dihydroxy vitamin D3 and human MG63 osteoblast maturation

Bone tissue is especially receptive to physical stimulation and agents with the capacity to mimic the signalling incurred via mechanical loading on osteoblasts may find an application in a bone regenerative setting. Recently this laboratory revealed that the major serum lipid, lysophosphatidic acid (LPA), co-operated with 1alpha,25-dihydroxy vitamin D3 (D3) in stimulating human osteoblast maturation. Actin stress fiber accrual in LPA treated osteoblasts would have generated peripheral tension which in turn may have heightened the maturation response of these cells to D3. To test this hypothesis we examined if other agents known to trigger stress fiber accumulation co-operated with D3 in stimulating human osteoblast maturation. Colchicine, nocodazole and LPA all co-operated with D3 to promote MG63 maturation in a MEK dependent manner. In contrast, calpeptin, a direct activator of Rho kinase and stress fiber accumulation did not act with D3 to secure MG63 differentiation. Herein we describe how the signalling elicited via microtubule disruption cooperates with D3 in the development of mature osteoblasts.