Optimising Dynamic Mechanical Analysis experiments on soft rubbers for use in Time Temperature Superposition

Rubbers are ubiquitous in engineering applications where they are often subjected to loading leading to high strain rate deformation. The strong rate and temperature dependence of rubbers and their composites motivates research into understanding their mechanical response under a wide range of conditions. However, experimental characterisation of the rate-temperature dependence of soft rubbers is challenging. In this methods paper, an improved methodology is proposed for conducting Dynamic Mechanical Analysis (DMA) experiments on rubbers. The higher quality data produced can be used in time-temperature superposition (TTS) applications to derive a more accurate definition of the rubber's rate-temperature dependence. Overall, the improvements obtained can be summarised as follows:•

Overall, the proposed methodology can be summarised with the following improvements:

•

Reducing clamping artefacts due to volume expansion

•

Ensuring high quality temperature stability

•

Improving the contact area between the specimen and the clamps

Magnetic resonance imaging in the evaluation of idiopathic frequent premature ventricular complexes with normal ventricular function

Background

The role of cardiac magnetic resonance (CMR) imaging in the diagnostic evaluation of patients with frequent premature ventricular complexes (PVCs) and normal left ventricular ejection fraction (LVEF) remains unclear. Existing data has been predominantly derived from highly selected populations, that may overestimate the true prevalence of abnormal findings on CMR in this patient population.

Purpose

The aim of this study was 2-fold: 1) to establish the prevalence of CMR imaging abnormalities in a cohort with normal LVEF and high PVC burden; 2) to identify predictors of CMR imaging abnormalities in patients with frequent PVCs and normal LVEF.

Methods

In this cohort study, 211 patients (age 53.2±19 years; 41% male) with frequent PVCs (≥5%/24 h), of normal LVEF (≥50% by echocardiography) and no known underlying structural heart disease were prospectively enrolled from 2016–2020. Of these, 166 (79%) patients were symptomatic from their PVCs in the form of palpitations, fatigue, chest pain, dizziness, and/or dyspnea. Patients underwent CMR imaging (1.5 Tesla) with a late gadolinium enhancement (LGE) protocol at the time of enrollment for the detection of scarring and/or fibrosis.

Results

Patients had a median baseline echocardiographic LVEF of 60% (± 5%) with 195 (92%) of patients having a normal native QRS morphology. Median PVC burden of the study cohort was 16% (± 14%). CMR LGE abnormalities were found in 19 (9%) patients including 17 scans with non-ischemic LGE and 2 with ischemic LGE. Age >60 (odds ratio [OR]: 3.20, 95% confidence interval [CI]: 1.20–8.51, p=0.020), male sex (OR: 4.67, 95% CI: 1.61–13.50, p=0.004), history of hypertension (OR: 3.43, 95% CI: 1.31–8.97, p=0.012), native QRS duration (OR: 1.03, 95% CI: 1.00–1.05, p=0.031), and history of non-sustained ventricular tachycardia (OR: 2.81, 95% CI: 1.03–7.68, p=0.044) were significantly associated with the presence of imaging abnormalities on CMR. Dominant PVC origin from the left ventricle had a positive trend (OR: 2.60, 95% CI: 0.99–7.66, p=0.083) to association with CMR imaging abnormalities. On multivariate analysis, male sex (OR: 4.10, 95% CI: 1.40–12.04, p=0.010) and history of hypertension (OR: 2.89, 95% CI: 1.08–7.75, p=0.035) remained significantly associated with the presence of CMR abnormalities. There was no association between CMR imaging abnormalities and the burden of PVCs or the number of PVC morphologies.

Conclusion

In this cohort, only 9% of patients with apparently idiopathic frequent PVCs and normal LVEF had concealed myocardial abnormalities on CMR imaging. Male sex and history of hypertension were associated with a higher rate of CMR abnormalities.

Funding Acknowledgement

Type of funding sources: None.

128 Comparison of multiple maturation times on juvenile invitro embryo transfer (JIVET)-derived oocytes and embryo development in the goat

Juvenile invitro embryo transfer (JIVET) is an assisted reproductive technology (ART) with the potential to produce numerous offspring from a single young female goat at 4 to 8 weeks of age. It has been reported in small ruminants that there can be a marked variable response to the administration of exogenous hormones for superovulation, the subsequent number of oocytes generated, and subsequent embryo developmental potential. The industry standard (as well as the recommendation of commercial media suppliers) invitro maturation time is 21 to 24h for conventionally derived oocytes. This study investigated multiple maturation times for JIVET-derived oocytes: 16, 22, and 28h. Oocytes were collected from four JIVET animals at 6 to 8 weeks of age. The hormonal superovulation regimen used on the juvenile animals consisted of 4×40-mg FSH injections at ∼12h apart and a 400IU of PMSG injection given with the first FSH injection. Surgical recovery of the oocytes via a midline laparotomy was performed the day following the last FSH injection. All of the oocytes were collected via aspirating follicles that were 4mm and larger. Oocytes with compact cumulus cells subsequently underwent IVM, IVF, and invitro culture (IVC) utilising IVF Bioscience media and methods. A single straw of identical cryopreserved/thawed semen from the same buck was utilised for each of the IVF procedures. The results were (37/88) 42%, (37/85) 44%, and (39/91) 43% cleaved and (23/88) 26%, (24/85) 28%, and (28/91) 31% blastocyst rate based on respective maturation times for JIVET-derived ova. Development rate during the cleavage stage and blastocyst stage was analysed using a repeated-measures logistic regression model utilising generalized estimating equations (GEE), with maturation time as fixed effect and a compound symmetry within subject (juvenile goat) covariance structure. The main effect of maturation time on the odds of development during the cleavage stage (P=0.8727) and blastocyst stage (P=0.3857) was not significant. These results indicate that the time in maturation media does not have as profound an effect on development to blastocysts as a factor in the variability reported by other laboratories. The development rate of embryos from one juvenile goat produced very high blastocyst rates of (5/12) 42%, (11/12) 92%, and (11/15) 73%, respectively. Additional logistic regression analysis showed that the odds of development in this juvenile donor was significantly different compared with the other donors (pooled) during the cleavage stage at 16h (P=0.0083) and 28h (P=0.0021) maturation times. Likewise, the odds of development in this donor was significantly different than that of the other donors (pooled) during the blastocyst stage at 22h (P=0.0002) and 28h (P=0.0003) maturation times. This further indicates the wide variation of oocyte quality from JIVET-derived oocytes and indicates potential for higher development rates at 22 and 28h in this specific goat.

Complication rate among people with diabetes at low risk of foot ulceration in Fife, UK: an analysis of routinely collected data

AIMS

To estimate the rate at which people with diabetes and a low risk of foot ulceration change diabetic foot ulceration risk status over time, and to estimate the rate of ulceration, amputation and death among this population.

METHODS

We conducted an observational study of 10 421 people with diabetes attending foot screening in an outpatient setting in NHS Fife, UK, using routinely collected data from a national diabetes register, NHS SCI Diabetes. We estimated the proportion of people who changed risk status and the cumulative incidence of ulceration, amputation and death, respectively, among people with diabetes at low risk of diabetic foot ulceration at 2-year follow-up.

RESULTS

At 2-year follow-up, 5.1% (95% CI 4.7, 5.6) of people with diabetes classified as low risk at their first visit had progressed to moderate risk. The cumulative incidence of ulceration, amputation and death was 0.4% (95% CI 0.3, 0.6), 0.1% (95% CI 0.1, 0.2) and 3.4% (95% CI 3.1, 3.8), respectively.

CONCLUSIONS

At 2-year follow-up, 5% of people at low risk of diabetic foot ulceration changed clinical risk status and <1% of people experienced foot ulceration or amputation. These findings provide information which will help to inform the current debate regarding optimal foot screening intervals.

Machine learning for predicting AF ablation outcomes using daily heart rhythm data at baseline

Background

While numerous studies have shown that catheter ablation is superior to antiarrhythmic drug (AAD) in treating atrial fibrillation (AF), the long term outcomes have been limited by arrhythmia recurrence. Reliable data and methods to predict ablation outcomes will thus be valuable for treatment planning.

Objective

To evaluate the utility of machine learning and various types of input variables, viz. patient characteristics at baseline, and daily heart rhythm data recorded prior to ablation for outcome prediction.

Methods

We acquired permission to analyze data collected from a randomized clinical trial that recorded daily biomeasures from &gt;345 patients who were referred for first catheter ablation due to AF refractory to at least one AAD. After standardizing the dataset, each patient sample is characterized by a set of daily measures, viz. heart rate variability (HRV) and AF burden (AFB), which is the total minutes in AF per day. We next performed comparative analyses on 19 candidate model variants to evaluate each model's ability in identifying patients who were to experience at least one episode of AF recurrence during post-ablation period starting from day 91 up to day 365 post-ablation, per standard guidelines. We examined: i) use of a set of daily biomeasures jointly with baseline sex and age; and ii) observation lengths of the pre-ablation period. We also examined the use of baseline CHA2DS2-VASc scores, left-atrial volume (LAV), atrial diameter, medical history. We conducted multiple sets of 3-fold cross validation (CV) experiments, each fold independently trained a candidate model with 236 samples (two thirds of the dataset) and performed evaluation on the left-out samples. About 50% of cohort belongs to one class. Each fold scored a model and its input variables in terms of sensitivity (SEN), specificity (SPEC), area under receiver operating characteristic curve (AUC), etc. To circumvent risks of overfitting highly parameterized models to our training subset, we shortlisted 19 models that have few hyper-parameters, e.g. stepwise regression, random forest (RF), linear discriminant analysis (LDA).

Results

CV results demonstrated that LDA and RF gave comparable performances, with RF achieving highest AUC of 0.68±0.06 using 30 days of rhythm data prior to ablation (SEN of 65.9±7.82; SPEC of 66.3±0.57). When observation period extended to 90 days prior, AUC improved to 0.691±0.02. In contrast, use of LAV alone was not adequate to predict outcome (AUC∼0.5), and when combined with all aforementioned baseline variables, the best model achieved AUC of 0.58±0.05. Feature analyses from the trained models suggest that AFB had highest relevance in predicting outcome. Using only daily AFB, RF and LDA respectively achieved AUC of 0.608±0.04 and 0.652±0.04.

Conclusions

Our results suggest the value of pre-ablation rhythm data for improving outcome-prediction. Future work will validate these findings using large public datasets.

Funding Acknowledgement

Type of funding source: Public Institution(s). Main funding source(s): Huawei-Data Science Institute Research Program; Natural Sciences and Engineering Research Council of Canada (NSERC)

Generation of goats by nuclear transfer: a retrospective analysis of a commercial operation (1998-2010)

At LFB USA, Inc., the ultimate use for transgenic cloned goats is for the production of recombinant human protein therapeutics in their milk. This retrospective analysis of the Somatic Cell Nuclear Transfer (SCNT) program, spanning from 1998 to 2010, examined parameters potentially affecting the outcomes and efficiencies in this commercial operation. Over 37,000 + ova were utilized in the SCNT protocol producing a total of 203 cloned goats. Fifty one (51) clones were produced from non-transfected (transgenic and non-transgenic animal donor) cell lines and 152 clones were produced from transfected cell lines. Comparisons and summaries of (a) transfected versus non-transfected cell lines, (b) relationship of SCNT parameters to offspring produced, (c) skin versus fetal cells, (d) fresh versus cryopreserved cells, (e) parameters from all cell lines used versus those producing SCNT offspring, (f) variation among cell sources, (g) methods of SCNT parturition management and effects on live offspring, and lastly (h) SCNT variation by program are reported. Findings indicate that (a) non-transfected cell lines were more efficient versus transfected cell lines in generating viable cloned offspring on a per reconstructed embryo transferred basis, (b) transfected fetal fibroblasts had improved efficiency versus transfected skin fibroblasts, (c) the percentage of non-transfected cell lines that produced offspring was statistically higher than transfected cell lines, (d) and induction of parturition improved the percentage of viable offspring. In summary, this retrospective analysis on the SCNT process has identified certain parameters for improved efficiency in producing viable cloned goats in a commercial setting.

154 A method of oviductal semen deposition for use in the goat

The objective of this study was to investigate a method of oviducal semen deposition as a strategy for producing offspring from poor-quality cryopreserved goat sperm. Invitro fertilisation (IVF) and AI are common assisted reproductive technologies used in small ruminants, but they have varied results in the goat. The use of poor-quality cryopreserved-thawed sperm (&lt;50% live/dead ratio at post-thaw) can decrease the rate of success. These procedures were performed in the month of November in Central Massachusetts in the United States (42° N). Seven 10-year-old dairy goats (Saanen, Toggenburg, and Alpine breeds) were synchronised and superovulated using a progesterone implant on Day 0, a prostaglandin injection at Day 7, two daily injections of 36mg of FSH ~12h apart on Days 12-15, and progesterone implant removal on Day 14 followed by an injection of 50µg of gonadotrophin-releasing hormone. Sperm deposition was performed on Day 17 (72 h after implant removal). The animals were anaesthetised using a standardised protocol, intubated, and maintained using isoflurane, and sterile prep was performed before a midline laparotomy procedure. Straws from a single ejaculate from a transgenic founder that was cryopreserved using a commercial two-step glycerol-egg yolk-based extender were used. A straw from this collection was post-thawed 30 days after collection and, using a commercial live/dead stain, 67% live sperm was determined. The optimal type of sperm prep and sperm concentration is unknown and may be dependent on sperm quality. Therefore, different gradient preps using Vitrolife SpermGrad at three volumes (1.5 (used on two animals), 1.0, and 0.5mL) as well as two volumes of IVF Bioscience Bovine BO-SemenPrep (4.0mL (used on two animals) and 2.0mL) were used. All five pellets were diluted in 1.0mL of IVF Bioscience Bovine BO-IVF media. Sperm concentrations ranging from 75×106 to 27×106 spermmL−1 were deposited into one oviduct; then, a 10:1 dilution was performed and 7.5×106 to 2.7×10 spermmL−1 were deposited into the contralateral oviduct. The depositions were performed just proximal to the uterotubal junction in a volume of 0.1mL of diluent via a tuberculin syringe attached to a 20-gauge needle. Two days following the procedure, oviducts were flushed postmortem from three of the seven randomly selected goats. All three had fertilised embryos, and nineteen 8-cell embryos were retrieved. Three of these embryos were surgically transferred to the distal uterine horn of a suitable recipient. The recipient became pregnant and produced a single offspring. The remaining four of seven goats were killed 41 days post-surgery. Two of the four goats were pregnant, with one carrying one fetus and the other carrying five fetuses. Further studies are needed to optimise this method, but these initial results indicate that oviducal semen deposition directly into the oviduct proximal to the uterotubal junction may be a suitable alternative for producing offspring from suboptimal cryopreserved-thawed goat sperm.

P4755Sex differences in admission rates, use of anticoagulation, and outcomes for emergency department presentations of atrial fibrillation

Background

Studies in non-Emergency Department (ED) settings have shown women with non-valvular atrial fibrillation (NVAF) differ in presentation, treatment, and outcomes compared to men. Despite AF being a common reason for ED visit, little is known regarding sex differences in patients presenting to ED.

Purpose

We sought to determine whether sex differences exist in rates of admission among NVAF patients presenting to the ED and if oral anticoagulant (OAC) use and outcomes differ by ED discharge status.

Methods

Patients≥18 years old, presenting to the ED with incident NVAF in two western Canadian provinces (Alberta and British Columbia) from April 2012 to March 2015 were included. ED records were linked to hospital records to identify patients admitted to hospital versus discharged from the ED. Outcomes of interest were 30-day mortality and 1-year stroke, heart failure (HF) and mortality. Pharmaceutical claims were queried for OAC use within 90 days following NVAF ED event.

Results

Of 16,991 ED NVAF patients, 7,770 (46%) were women and 9,221 (54%) were men (p<0.001). Compared to men, women were older (73.9 vs 65.6 years, p<0.001) and presented with higher CHA2DS2-VASc scores (4.0 vs 2.0, p<0.001). Overall, 41% of women and 37% of men were admitted to hospital (p<0.001). OAC rate was 50% among admitted and 37% among discharged (p<0.001). OAC rates were 53% in women and 48% in men among admitted (p<0.001), and 39% in women and 35% in men among discharged (p<0.001). OAC rates were higher in patients with CHA2DS2-VASc ≥1 who were admitted (53% in women (n=2,781) and 52% in men (n=2,683), p=0.63) than in those who were discharged (39% in women (n=4,435) and 45% in men (n=3,866), p<0.01). Women had higher rates of mortality at 30-days and 1-year, and stroke at 1-year compared to men, irrespective of ED discharge status (all p<0.02). Women admitted had higher HF rates at 1-year compared to men (p=0.002). (Table)

Outcomes by Sex and ED Discharge Status Outcome Discharged Admitted Women (N=4,560) Men (N=5,780) p-value Women (N=3,210) Men (N=3,441) p-value 30 Day Mortality, n (%) 63 (1.4) 50 (0.9) 0.01 261 (8.1) 228 (6.6) 0.019 1 Year Mortality, n (%) 270 (5.9) 248 (4.7) <0.001 717 (22.3) 604 (17.6) <0.001 Stroke*, rate (SE) 1.7 (0.19) 0.9 (0.13) <0.001 4.0 (0.37) 2.6 (0.28) 0.001 Heart Failure*, rate (SE) 3.6 (0.28) 3.1 (0.23) 0.16 12.9 (0.62) 10.4 (0.54) 0.002 *Censored on death.

Conclusions

In this population-based study of patients presenting to ED with NVAF, we found women were more likely to be admitted to hospital than men. Women had a worse prognosis than men, irrespective of ED discharge status. Use of OAC was suboptimal, regardless of patient sex.

Acknowledgement/Funding

Heart and Stroke Foundation of Canada, UBC Cardiology, Servier Alberta Innovation Health Fund

194 Superovulation response does not affect embryo development of pronuclear microinjected embryos in the goat

Superovulation of donor animals is essential in the production of transgenic founder goats generated through microinjection. There can be a marked variable response to the exogenous hormones used for superovulation. The objective of this study was to examine how the superovulatory response of individual goats affected the ability of the fertilized, microinjected embryos to develop into offspring. The donors were superovulated using a progesterone implant on Day 0, a prostaglandin injection at Day 7, 2 injections ~12h apart of 32 to 36mg of FSH on Day 12 to 15, progesterone implant removal on Day 14, bred by intact bucks several times starting on Day 15 to 16, an injection of 50μg of gonadotropin-releasing hormone, and surgical collection of 1- to 2-cell embryos from retrograde flushing of the oviduct on Day 17 (~24-48 h, 1-2 days after breeding). Surgical collection allows for an accurate ovulation point (OP) count before the oviduct being retrograde flushed and ova collected and counted. Data from donor animals were grouped by superovulatory response based on OP counts of 1-10, 11-20, 21-30, or &gt;30. The number of donors that contributed per group were 130, 280, 175, and 52, respectively. The recovery rate was 76, 72, 68, and 62%, respectively. After collection, ova were viewed under a dissecting microscope and assessed for fertilization by identifying pronuclei, and 1 pronucleus was microinjected. The fertilization rate was 47, 52, 51, and 56%, respectively. The survivability rate after microinjection was 80, 76, 75, and 76%, respectively. Surviving embryos were transferred (3-5) into recipient goats following a 2- to 6-h in vitro culture (as 1- to 2-cell embryos), allowing for a suitable period to assess viability post-injection. Further in vitro development rates were not assessed because of the short timeframe the embryos stayed in culture. The conception rates were 71, 56, 65, and 53%, respectively, and abortion rates were 23, 10, 14, and 9%, respectively. As some recipients received embryos from multiple donors, this data could not be included in the analysis as identifying which offspring were from the corresponding embryo group could not be confirmed. Data were analysed using SAS software (version 9.4, SAS Institute Inc., Cary, NC, USA). The Wald chi square test under linear regression was used to analyse the number of offspring produced per embryo transferred. No significant differences were found between groups (all P-values were&gt;0.05). This analysis indicated that the range of superovulation response does not affect the developmental competence of the pronuclear microinjected embryo or the ability to produce viable offspring. Table 1.Comparison of the donor ovulation counts, number of embryos transferred, offspring produced and overall efficiency

94 Impact of number of embryos transferred on the number of offspring produced in a commercial transgenic founder production operation

The production of transgenic founder dairy goats (cross-bred Saanens, Alpines, Toggenburgs, and Nubians) involves the collection, microinjection, and transfer of numerous embryos into suitable recipient goats to ultimately produce a transgenic founder(s). The objective of this study was to determine the most efficient number of microinjection embryos to transfer to suitable recipients for transgenic founder generation. This is critically important in a commercial production program, as it impacts the goal for the number of embryos collected from donors, number of recipients utilised, and, hence, the overall number of surgical procedures being performed. The entire embryo collection, transfer, and founder-generation process is continuously being evaluated for ways to become more efficient in producing transgenic animals. During LFB USA’s commercial founder-production campaigns over the years (1997-2017), pronuclear microinjection was performed and 3, 4, or 5 embryos were transferred to female goat recipients. The recipients were synchronized using a progesterone implant on Day 0, a prostaglandin injection at Day 7, an injection of 300-500IU of pregnant mare serum gonadotropin on Day 13, progesterone implant removal on Day 14, and surgical transfer of pronuclear microinjected 1- or 2-cell embryos into the oviduct on Day 17. The individual totals and calculation for offspring per embryos transferred was compared for 3, 4, and 5 embryos transferred per recipient and was determined to be (1659/8637) 0.19, (912/4548) 0.20, and (112/675) 0.17, respectively. These embryo efficacy ratios were not significantly different (P&gt;0.05) using the Wald Chi-squared test under logistic regression, and suggests that the number of offspring born is not impacted by number of embryos transferred. Seasonality was also evaluated in this production environment located in North America, with in-season being considered September to December and out-of-season being January to July. Nulliparous recipients during in-season (September to December) embryo transfer operations produced a significant difference, with totals and calculation for (offspring per embryo transferred) of (470/2346) 0.20, (260/1088) 0.24, and (23/190) 0.12 for 3, 4, and 5 embryo transfers, respectively (Table 1). This data indicates that when using nulliparous recipients during the in-season, transferring 4 embryos is optimal for offspring produced. Table 1.Comparison of the individual totals and the calculation of (offspring/embryo) by parity and season

Cost-effectiveness of alternative changes to a national blood collection service

Objectives

To evaluate the cost‐effectiveness of changing opening times, introducing a donor health report and reducing the minimum inter‐donation interval for donors attending static centres.

Background

Evidence is required about the effect of changes to the blood collection service on costs and the frequency of donation.

Methods/Materials

This study estimated the effect of changes to the blood collection service in England on the annual number of whole‐blood donations by current donors. We used donors' responses to a stated preference survey, donor registry data on donation frequency and deferral rates from the INTERVAL trial. Costs measured were those anticipated to differ between strategies. We reported the cost per additional unit of blood collected for each strategy versus current practice. Strategies with a cost per additional unit of whole blood less than £30 (an estimate of the current cost of collection) were judged likely to be cost‐effective.

Results

In static donor centres, extending opening times to evenings and weekends provided an additional unit of whole blood at a cost of £23 and £29, respectively. Introducing a health report cost £130 per additional unit of blood collected. Although the strategy of reducing the minimum inter‐donation interval had the lowest cost per additional unit of blood collected (£10), this increased the rate of deferrals due to low haemoglobin (Hb).

Conclusion

The introduction of a donor health report is unlikely to provide a sufficient increase in donation frequency to justify the additional costs. A more cost‐effective change is to extend opening hours for blood collection at static centres.

Differential scanning fluorimetry illuminates silk feedstock stability and processability

The ability to design and implement silk feedstock formulations for tailored spinning has so far eluded the bioengineers. Recently, the high throughput screening technique of differential scanning fluorimetry (DSF) demonstrated the link between the instability transition temperature (Ti) and the processability of the silk feedstock. Using DSF we screened a large set of chemicals known to affect solvent quality. A multivariate analysis of the results shows that, regardless of the diversity of chemicals, three groupings are significantly distinguishable: G1 = similar to native silk; G2 = largely dominated by electrostatic interactions; and G3 = dominated by chelating interactions. We propose a thermodynamic analysis based on a pre- and post-transition fit to estimate the van't Hoff enthalpies (ΔHv) and the instability temperature (Ti). Our analysis shows that the ΔTi and ΔHv values were distinct: G1 (ΔTi = 0.23 ± 0.2; ΔHv = -159.1 ± 5.6 kcal mol(-1)), G2 (ΔTi = -7.3 ± 0.7; ΔHv = -191.4 ± 5.5 kcal mol(-1)), and G3 (ΔTi = -19.9 ± 3.3; ΔHv = -68.8 ± 6.0 kcal mol(-1)). Our analysis further combined the ΔTi value and the ΔHv value using stability ΔΔG to find that G1 only marginally stabilizes native silks (ΔΔG = -0.15 ± 0.04 kcal mol(-1)), whereas G2 and G3 destabilize native silk (ΔΔG = 3.8 ± 0.11 and ΔΔG = 3.8 ± 0.3 kcal mol(-1), respectively). Here our analysis shows that native silk has a complex multistep transition that is possibly non-cooperative. However, all three groupings also show a direct and cooperative transition with varied stabilization effects. This analysis suggests that native silks are able to sample multiple substates prior to undergoing (or to delay) the final transition. We conclude by hypothesizing that the observed energetic plasticity may be mediated by a fragile packaging of the silk tertiary structure that is readily lost when the solvent quality changes.

Individual patient data network meta-analysis of mortality effects of implantable cardiac devices

OBJECTIVE

Implantable cardioverter defibrillators (ICD), cardiac resynchronisation therapy pacemakers (CRT-P) and the combination therapy (CRT-D) have been shown to reduce all-cause mortality compared with medical therapy alone in patients with heart failure and reduced EF. Our aim was to synthesise data from major randomised controlled trials to estimate the comparative mortality effects of these devices and how these vary according to patients' characteristics.

METHODS

Data from 13 randomised trials (12 638 patients) were provided by medical technology companies. Individual patient data were synthesised using network meta-analysis.

RESULTS

Unadjusted analyses found CRT-D to be the most effective treatment (reduction in rate of death vs medical therapy: 42% (95% credible interval: 32-50%), followed by ICD (29% (20-37%)) and CRT-P (28% (15-40%)). CRT-D reduced mortality compared with CRT-P (19% (1-33%)) and ICD (18% (7-28%)). QRS duration, left bundle branch block (LBBB) morphology, age and gender were included as predictors of benefit in the final adjusted model. In this model, CRT-D reduced mortality in all subgroups (range: 53% (34-66%) to 28% (-1% to 49%)). Patients with QRS duration ≥150 ms, LBBB morphology and female gender benefited more from CRT-P and CRT-D. Men and those <60 years benefited more from ICD.

CONCLUSIONS

These data provide estimates for the mortality benefits of device therapy conditional upon multiple patient characteristics. They can be used to estimate an individual patient's expected relative benefit and thus inform shared decision making. Clinical guidelines should discuss age and gender as predictors of device benefits.

The contribution of primary prevention medication and dietary change in coronary mortality reduction in England between 2000 and 2007: a modelling study

OBJECTIVE

To analyse the falls in coronary heart disease (CHD) mortality in England between 2000 and 2007 and quantify the relative contributions from preventive medications and population-wide changes in blood pressure (BP) and cholesterol levels, particularly by exploring socioeconomic inequalities.

DESIGN

A modelling study.

SETTING

Sources of data included controlled trials and meta-analyses, national surveys and official statistics.

PARTICIPANTS

English population aged 25+ in 2000-2007.

MAIN OUTCOME MEASURES

Number of deaths prevented or postponed (DPPs) in 2007 by socioeconomic status. We used the IMPACTSEC model which applies the relative risk reduction quantified in previous randomised controlled trials and meta-analyses to partition the mortality reduction among specific treatments and risk factor changes.

RESULTS

Between 2000 and 2007, approximately 20 400 DPPs were attributable to reductions in BP and cholesterol in the English population. The substantial decline in BP was responsible for approximately 13 000 DPPs. Approximately 1800 DPPs came from medications and some 11 200 DPPs from population-wide changes. Reduction in population BP prevented almost twofold more deaths in the most deprived quintile compared with the most affluent. Reduction in cholesterol resulted in approximately 7400 DPPs; approximately 5300 DPPs were attributable to statin use and approximately 2100 DPPs to population-wide changes. Statins prevented almost 50% more deaths in the most affluent quintile compared with the most deprived. Conversely, population-wide changes in cholesterol prevented threefold more deaths in the most deprived quintile compared with the most affluent.

CONCLUSIONS

Population-wide secular changes in systolic blood pressure (SBP) and cholesterol levels helped to substantially reduce CHD mortality and the associated socioeconomic disparities. Mortality reductions were, in absolute terms, greatest in the most deprived quintiles, mainly reflecting their bigger initial burden of disease. Statins for high-risk individuals also made an important contribution but maintained socioeconomic inequalities. Our results strengthen the case for greater emphasis on preventive approaches, particularly population-based policies to reduce SBP and cholesterol.

Dapagliflozin compared with other oral anti-diabetes treatments when added to metformin monotherapy: a systematic review and network meta-analysis

AIMS

Indirect evidence from randomized controlled trials (RCTs) was used to estimate the effect of dapagliflozin, a new agent with a novel mechanism of action (SGLT-2 inhibition), relative to other anti-diabetes therapies after 1 year of treatment.

METHODS

A systematic literature review and Bayesian network meta-analysis (NMA) of RCTs involving anti-diabetes treatments added to metformin were conducted. RCTs enrolling subjects with type 2 diabetes inadequately controlled on metformin monotherapy were included. Comparators included dipeptidyl peptidase-4 (DPP-4) inhibitors, thiazolidinediones (TZDs), sulphonylureas, glucagon-like peptide-1 (GLP-1) analogues and dapagliflozin. Outcomes of interest were mean change from baseline HbA1c, weight and systolic blood pressure, and incidence of hypoglycaemia.

RESULTS

From 4270 abstracts, six RCTs were included in the primary analysis; no RCTs involving GLP-1 analogues met primary inclusion criteria. All RCTs were actively controlled with sulphonylureas. The mean change in HbA1c from baseline was similar across comparators. The treatment effect (95% credible interval) of dapagliflozin on HbA1c was -0.08% (-0.25, 0.10) relative to DPP-4 inhibitors, -0.02% (-0.24, 0.21) relative to TZDs and 0.00% (-0.16, 0.16) relative to sulphonylureas. Non-sulphonylureas showed significantly lower risk of hypoglycaemia relative to sulphonylureas. Dapagliflozin had a significant effect on weight change: the relative difference was -2.74 kg (-5.35, -0.10) compared with DPP-4 inhibitors, and -4.67 kg (-7.03, -2.35) compared with sulphonylureas. Systolic blood pressure was not meta-analysed due to infrequent reporting.

CONCLUSION

Compared with DPP-4 inhibitors, TZDs and sulphonylureas, dapagliflozin offers similar HbA1c control after 1 year, with similar or reduced risk of hypoglycaemia and the additional benefit of weight loss, when added to metformin.

227 SUPEROVULATION AND EMBRYO COLLECTION IN WOOD BISON DURING THE ANOVULATORY SEASON

Brucellosis and tuberculosis are endemic in Wood Buffalo National Park, the largest reserve of wood bison (Bison bison athabascae) in Canada. Our goal is to produce and preserve disease-free embryos for the purpose of wood bison repopulation. This study was designed to determine if embryo collection is feasible in wood bison during the anovulatory season (May–July) and to test if progesterone priming is required for superovulation. A 2-by-2 design was used to determine the effectiveness of LH (Lutropin) or hCG (Chorulon) for induction of ovulation with or without intravaginal progesterone releasing device (PRID) in 32 wood bison cows. Follicular wave emergence was synchronized among bison by transvaginal ultrasound-guided follicle ablation. Synchronized bison were assigned to 4 groups: PRID+LH (n = 12), PRID+hCG (n = 4), no-PRID+LH (n = 12) and no-PRID+hCG (n = 4). A PRID was inserted on the day of follicular ablation in the respective groups. A single SC dose of 400 mg FSH (Folltropin) in a slow-release formulation was given the day after follicular ablation (i.e. on the expected day of a new follicular wave emergence, Day 0). The PRID was removed on Day 4 and either 25 mg LH or 2000 IU hCG was given IM on Day 5. Artificial insemination was done at 24, 36 and 48 h after LH or hCG treatment. Embryos were collected nonsurgically on Day 13 using commercial bovine equipment. Transrectal ultrasonography was done on Days 0, 5, 6, 7, 8 and 13 to record follicular and ovulatory responses. Count data (mean ± SEM) were analysed by two-way ANOVA and proportions by chi square. The number of ovulatory-sized follicles (≥10 mm) on Day 5 did not differ among groups (P = 0.33; Table 1). Ovulation rate (number of ovulations/number of follicles ≥10 mm) was greater in bison treated with hCG (P < 0.05; Table 1). The number of corpora lutea (CL) on Day 13 was greater in bison treated with hCG without a PRID (P < 0.05; Table 1). No differences in number of ova/embryos and transferable embryos were found among groups (P = 0.36 and P = 0.52, respectively; Table 1). In conclusion, progesterone priming (PRID) had no effect on ovarian superstimulation in wood bison in the anovulatory season. The ovulatory response was satisfactory only in bison treated with hCG. Embryo collection is feasible in wood bison, but the reasons for a low embryo collection rate in all groups remain unclear. Table 1.Response to superovulation and embryo collection in wood bison Funded by Advancing Canadian Agriculture and Agri-Food and Agri-Food Innovation.

Transfusion practice in major obstetric haemorrhage: lessons from trauma

The management of massive haemorrhage with blood products is changing as evidence arrives from civilian and military trauma. Rapid early replacement of coagulation factors and platelets is now becoming central to improving outcome, usually given in higher ratios with respect to red cell units than previously recommended and using empiric transfusion based on clinical rather than laboratory parameters. The management of three cases of major obstetric haemorrhage based on these principles is presented. Packed red blood cells, fresh frozen plasma, platelets and cryoprecipitate were transfused in the ratios 5:2:2:1, 4.5:1:1:1 and 4.5:2:1:1. Each patient had acceptable full blood count and coagulation results after surgery and all made an uneventful recovery. These outcomes support the opinion that major obstetric haemorrhage can be managed in a similar fashion to blood loss in trauma. Recommendations from the Association of Anaesthetists of Great Britain and Ireland, and the UK National Patient Safety Agency should be considered during major obstetric haemorrhage.

Fibroblast growth factor 23 (FGF23) and alpha-klotho stimulate osteoblastic MC3T3.E1 cell proliferation and inhibit mineralization

Elevated serum levels of the phosphate-regulating hormone fibroblast growth factor 23 (FGF23) are found in patients with phosphate wasting diseases and chronic kidney disease-mineral and bone disorder (CKD-MBD). These diseases are associated with rickets and renal osteodystrophy, respectively. FGF23 is secreted from osteoblastic cells and signals through FGFRs, membrane coreceptor alpha-Klotho (Klotho), and, possibly, a circulating form of Klotho. Despite the absence of detectable Klotho on osteoblastic cells, studies have suggested that forced FGF23 expression in osteoblasts inhibited mineralization. Thus, we examined the effects of exogenously applied FGF23 on osteoblastic MC3T3.E1 cell proliferation and differentiation, with and without soluble Klotho. MC3T3.E1 cells were cultured in osteoblast differentiation medium, supplemented with FGF23 (0.1-1,000 ng/mL), Klotho (50 ng/mL), the combination FGF23 + Klotho, and FGF2 (100 ng/mL) as a control. Neither FGF23 nor Klotho exposure affected proliferation of day 4 growth phase cells or mineralization of day 14 cultures. In contrast, FGF23 + Klotho resulted in inhibition of mineralization and osteoblast activity markers at day 14, and a slight, reproducible induction of proliferation. Inhibition of FGFR1, but not FGFR2 or FGFR3, completely restored FGF23 + Klotho-induced inhibition of alkaline phosphatase (ALP) activity at day 7. ALP activity was partially restored by the MAPK inhibitor U0126 but not inhibitors p38 and P13K. Thus, soluble Klotho enables FGF23 signaling in MC3T3.E1 cells, likely through FGFR 1(IIIc). Elevated FGF23 actions, in part, appear to parallel FGF2 with lower potency. In addition to affecting bone via indirect phosphate wasting pathways, supraphysiological FGF23 and soluble Klotho may directly impact bone in diseases with elevated FGF23 levels.