Use of diamond sensors for a high-flux, high-rate X-ray pass-through diagnostic

X-ray free-electron lasers (XFELs) deliver pulses of coherent X-rays on the femtosecond time scale, with potentially high repetition rates. While XFELs provide high peak intensities, both the intensity and the centroid of the beam fluctuate strongly on a pulse-to-pulse basis, motivating high-rate beam diagnostics that operate over a large dynamic range. The fast drift velocity, low X-ray absorption and high radiation tolerance properties of chemical vapour deposition diamonds make these crystals a promising candidate material for developing a fast (multi-GHz) pass-through diagnostic for the next generation of XFELs. A new approach to the design of a diamond sensor signal path is presented, along with associated characterization studies performed in the XPP endstation of the LINAC Coherent Light Source (LCLS) at SLAC. Qualitative charge collection profiles (collected charge versus time) are presented and compared with those from a commercially available detector. Quantitative results on the charge collection efficiency and signal collection times are presented over a range of approximately four orders of magnitude in the generated electron-hole plasma density.

The sourcing and use of high physical resemblance personal protective equipment to train healthcare workers, improve confidence and conserve medical-grade equipment

Personal protective equipment (PPE) is essential for healthcare worker (HCW) safety. Conservation of PPE for clinical use during the COVID-19 pandemic reduced its availability for training, necessitating an innovative approach to sourcing high physical resemblance PPE (HPR-PPE). We present a case study of crowd-sourcing of HPR-PPE to train HCWs. Survey results indicated that HPR-PPE enabled high-fidelity practise of PPE application and removal, aided procedure recall, improved user confidence and was sufficiently similar to medical-grade PPE. HPR-PPE provided a novel and cost-effective alternative. We also demonstrated that medical-grade PPE can be sourced from non-medical institutions and businesses during a pandemic.

142 Improving Functional Outcomes During Covid-19 for Both COVID-19 and Non COVID-19 Positive Older Adults Through the Introduction

Purpose

To improve the functional outcomes of older adults presenting to the Health and Ageing wards during the COVID-19 pandemic through a focussed rehabilitation list. The intended benefits to the older adult and service were for: 1. Daily rehabilitation input for older adults. 2. Older adults to spend less time immobile. 3. Ongoing rehabilitation intervention while awaiting medical clearance for discharge. 4. Increased staff satisfaction 5. Better outcomes on discharge. 6. Rehabilitation ethos on the Health and Ageing wards.

Methods

The quality improvement project was carried out using the Plan, Do, Study, Act (PDSA) cycle. Three iterative PDSA cycles were carried out over the course of the project to deliver proactive interventions as a result of analysis of baseline data and stakeholder involvement. These interventions were aimed at developing communication around the rehabilitation list within the team and sustainability of this list.

Results

The project resulted in better functional outcomes for older adults and increased staff morale. Between May 2020–June 2020, a total of 56 patients were seen on the rehabilitation list, with 84% of these patients seeing improvements in their Elderly Mobility Scores (EMS). 27% of patients on the rehabilitation list saw a change to their initial discharge plan, either needing reduced packages of care or reduced need for ongoing rehabilitation in an external setting.

Conclusions

The quality improvement project found that with focussed rehabilitation older adult inpatients with or without COVID-19 can make significant functional gains. These gains have wider effects on their outcomes on discharge and also for the service through increased morale and job satisfaction. Due to demand and capacity issues in the acute setting, older adults who would often benefit from ongoing input are not always reviewed regularly. This project demonstrates that with focussed rehabilitation older adults can improve and achieve better functional outcomes.

Reduced NT-proBNP threshold for risk prediction in high-risk elderly with subclinical heart failure: support from cardiopulmonary exercise testing

Background

Subclinical heart failure (HF) is divided into Stage A and B (SAHF and SBHF) depending on structural or functional cardiac abnormalities. However, risk of HF progression is not solely dependent on echocardiographic abnormalities. Data on oxygen consumption (VO2) and other prognostic cardiopulmonary exercise test (CPET) markers in subclinical HF, particularly in the elderly, is lacking. VO2 may refine risk prediction and provide pathological insight in subclinical HF.

Methods

Asymptomatic individuals were recruited through primary care if they were ≥65 years with ≥1 non-ischaemic risk factor for HF. Clinical evaluation determined risk profile, biometrics and NT-proBNP. Treadmill CPET was undertaken with a modified Bruce protocol. Low V02 was defined as ≤20th percentile of age and gender specific VO2 in healthy individuals. SBHF defined as systolic (global longitudinal strain, GLS ≤16%), diastolic (E/e' ≥15, E/e' >10 with left atrial enlargement or impaired relaxation with other changes or left ventricular (LV) hypertrophy (LV mass index >95 g/m2 in women or >115 g/m2 in men).

Results

Of the 91 included individuals (age 71±4 years, 53% female), 46 (51%) had SBHF, average NT-proBNP was 60pg/ml (26–99mg/ml) and did not differ by HF stage (59 [26–85] pg/ml vs. 60 [30–99] pg/ml for Stage A vs. B respectively, p=0.94). Average peak VO2 was 19.8 (16–22.6) ml/kg/min and was low in 71 (78%). VO2 did not differ by HF stage (19.9 [17.7–22.4] ml/kg/min vs. 19.7 [16–22.8] ml/kg/min for SAHF vs. SBHF respectively, p=0.62). NT-proBNP was significantly higher in those with abnormal VO2 (66 [34–110] pg/ml vs 31 [20–70] pg/ml, p=0.016). Within each HF stage, low VO2 was associated with higher NT-proBNP (Figure). Of those with NT-proBNP >100pg/ml, 95% (22/23) had low VO2 compared with 72% of those ≤100pg/ml, p=0.02 (non-signifcant for 125pg/ml cut-off). No associations were found between SBHF or individual echo abnormalities and VO2. In logistic regression analysis NT-proBNP was a significant univariable predictor of low VO2 and remained significant after adjustment for other significant univariables (BMI) (OR 1.02 [95% CI 1.0001–1.03], p=0.048).

Conclusion

Low VO2 identifies a high-risk cardiac phenotype within subclinical HF stages, but is not necessarily associated with LV dysfunction. Levels of NT-proBNP beneath the cut-off used for HF exclusion may assist risk stratification in this population.

NT-proBNP by VO2 in subclinical HF

Funding Acknowledgement

Type of funding source: Public Institution(s). Main funding source(s): Dr E Potter is supported by a PhD Scholarship from Monash University, Melbourne, Australia

Effect of DASH diet on oxidative stress parameters: A systematic review and meta-analysis of randomized clinical trials

BACKGROUND AND AIMS

Oxidative stress (OS) is one of the main risk factors for several chronic diseases. The Dietary Approaches to Stop Hypertension (DASH) contain many antioxidants and may contribute to managing OS.

OBJECTIVE

To perform a systematic review and meta-analysis to examine the impacts of the DASH diet on OS parameters.

METHODS

A comprehensive electronic search in MEDLINE, Scopus, EMBASE, and the Cochrane Central Register of Controlled Trials was performed through September 2020 to find related studies evaluating the impact of the DASH diet on OS parameters. Standardized mean differences were pooled using random-effects meta-analysis.

RESULTS

Eight studies with a total of 317 subjects met our inclusion criteria. Four studies included in meta-analysis model with 200 participants (100 in treatment and 100 in control group). The DASH diet was associated with a statistically significant decrease in malondialdehyde (MDA) (SMD: -0.53; 95% CI: -0.89, -0.16; I² = 42.1%), and a significant increase in glutathione (GSH) (SMD: 0.83; 95% CI: 0.36, 1.03; I² = 42.1%). Meta-analysis found no statistically significant effect of DASH diet on nitric oxide (NO) (SMD: -1.40; 95% CI: -0.12, 1.93; I² = 92.6%) or total antioxidant capacity (TAC) levels (SMD: 0.95; 95% CI: -0.10, 1.99; I² = 87.6%).

CONCLUSION

Our results demonstrated that a DASH diet could significantly increase GSH and decrease MDA levels. Furthermore, there is a trend to improve TAC, NO, and f2-isoprostanes by the adherence to the DASH diet. However, long-term, large sample size and well-designed randomized clinical trials are still needed to draw concrete conclusions about DASH diet's effects on OS parameters.

Effect of ginger (Zingiber officinale) on inflammatory markers: A systematic review and meta-analysis of randomized controlled trials

The aim of this systematic review and meta-analysis was to investigate the efficacy of ginger supplementation on circulating levels of C-reactive protein (CRP), high sensitivity C-reactive protein (hs-CRP), tumor necrosis factor-alpha (TNF-α), soluble intercellular adhesion molecule (sICAM), and interleukin-6 (IL-6) concentrations in randomized controlled trials (RCTs). The search included PubMed-Medline, EMBASE, Scopus, Web of Science and Cochrane Library databases to identify randomized clinical trials on the effect of ginger supplementation on circulation levels of CRP, hs-CRP, IL-6, sICAM, and TNF-α published up until February 1st, 2020. We did not restrict articles based on language of publication. Standard mean differences and 95% confidence intervals were calculated for net changes in inflammatory mediators using a random-effects model. Sixteen RCTs comprising 1010 participants were found to be eligible for this meta-analysis. There was a significant reduction of circulating CRP (SMD: -5.11, 95% CI: -7.91, -2.30, I2 = 98.1%), hs-CRP (SMD: -0.88, 95% CI: -1.63, -0.12, I2 = 90.8%) and TNF-α levels (SMD: -0.85, 95% CI: -1.48, -0.21, I2 = 89.4%) following ginger supplementation. However, meta-analysis results did not show any significant impact of ginger supplementation on IL-6 (SMD: -0.45, 95% CI: -1.29, 0.38, I2 = 89.2%), and sICAM levels (SMD: -0.05, 95% CI: -0.36, 0.26, I2 = 00.0%). This systematic review and meta-analysis of RCTs demonstrates a significant impact of ginger in lowering circulating CRP, hs-CRP and TNF-α levels. Large-scale RCTs are still needed to draw concrete conclusions about the effect of ginger on other inflammatory mediators.

Coenzyme Q10 supplementation and oxidative stress parameters: a systematic review and meta-analysis of clinical trials

PURPOSE

Oxidative stress (OS) is associated with several chronic complications and diseases. The use of coenzyme Q10 (CoQ10) as an adjuvant treatment with routine clinical therapy against metabolic diseases has shown to be beneficial. However, the impact of CoQ10 as a preventive agent against OS has not been systematically investigated.

METHODS

A systematic literature search was performed using the PubMed, SCOPUS, EMBASE, and Cochrane Library databases to identify randomized clinical trials evaluating the efficacy of CoQ10 supplementation on OS parameters. Standard mean differences and 95% confidence intervals were calculated for net changes in OS parameters using a random-effects model.

RESULTS

Seventeen randomized clinical trials met the eligibility criteria to be included in the meta-analysis. Overall, CoQ10 supplementation was associated with a statistically significant decrease in malondialdehyde (MDA) (SMD - 0.94; 95% CI - 1.46, - 0.41; I² = 87.7%) and a significant increase in total antioxidant capacity (TAC) (SMD 0.67; 95% CI 0.28, 1.07; I² = 74.9%) and superoxide dismutase (SOD) activity (SMD 0.40; 95% CI 1.12, 0.67; I² = 9.6%). The meta-analysis found no statistically significant impact of CoQ10 supplementation on nitric oxide (NO) (SMD - 1.40; 95% CI - 0.12, 1.93; I² = 92.6%), glutathione (GSH) levels (SMD 0.41; 95% CI - 0.09, 0.91; I² = 70.0%), catalase (CAT) activity (SMD 0.36; 95% CI - 0.46, 1.18; I² = 90.0%), or glutathione peroxidase (GPx) activities (SMD - 1.40; 95% CI: - 0.12, 1.93; I² = 92.6%).

CONCLUSION

CoQ10 supplementation, in the tested range of doses, was shown to reduce MDA concentrations, and increase TAC and antioxidant defense system enzymes. However, there were no significant effects of CoQ10 on NO, GSH concentrations, or CAT activity.

Effect of Cashew Nut on Lipid Profile: A Systematic Review and Meta-Analysis

INTRODUCTION

Nuts are one of the dietary components which appear to have beneficial effects on cardiovascular disease biomarkers. Studies demonstrate beneficial effects of cash-ews on serum lipids concentration, but results in the literature remain inconclusive. We conducted a review to examine the effects of cashew nut supplementation on serum lipid profile.

METHODS

Two reviewers independently searched PubMed, Web of Science, Cochrane Library, Scopus, and EMBASE electronic databases from inception until June 2019 without language limitation. Random- and fixed-effects models were used to calculate 95% confidence intervals (CI) for studies.

RESULTS

Six randomized clinical trials comprising 531 participants were included in this systematic review. Three studies were included in the meta-analysis model. There were no significant changes for total cholesterol (TC) (standardized mean difference [SMD]: -0.02, 95% CI: -0.32, 0.28), triglycerides (TG) (SMD: -0.01, 95% CI: -0.22, 0.20), high-density lipoprotein (HDL) cholesterol (SMD: 0.09, 95% CI: -0.16, 0.34), or low-density lipoprotein (LDL) cholesterol (SMD: -0.18, 95% CI: -0.75, 0.39).

CONCLUSION

The results of this analysis demonstrate that treatment with cashew nut supplementation alone did not significantly change serum levels of LDL, HDL, TC, or TG.

The effects of curcumin supplementation on oxidative stress, Sirtuin-1 and peroxisome proliferator activated receptor γ coactivator 1α gene expression in polycystic ovarian syndrome (PCOS) patients: A randomized placebo-controlled clinical trial

BACKGROUND & AIMS

Curcumin is a biologically active phytochemical ingredient found in turmeric and has antioxidant pharmacologic actions that may benefit patients with polycystic ovarian syndrome (PCOS). The aim in this trial was to evaluate the efficacy of curcumin supplementation on oxidative stress enzymes, sirtuin-1 (SIRT1) and Peroxisome proliferator activated receptor γ coactivator 1α (PGC1α) gene expression in PCOS patients.

METHODS

Seventy-two patients with PCOS were recruited for this randomized, double-blinded, clinical trial. Thirty-six patients received curcumin, 1500 mg (three times per day), and 36 patients received placebo for 3 months. Gene expression of SIRT1, PGC1α and serum activity of glutathione peroxidase (Gpx) and superoxide dismutase (SOD) enzymes were evaluated at the beginning of trial and at 3-month follow-up.

RESULTS

Sixty-seven patients with PCOS completed the trial. Curcumin supplementation significantly increased gene expression of PGC1α (p = 0.011) and activity of the Gpx enzyme (p = 0.045). Curcumin also non-significantly increased gene expression of SIRT1 and activity of the SOD enzyme.

CONCLUSIONS

Curcumin seems to be an efficient reducer of oxidative stress related complications in patients with PCOS. Further studies on curcumin should strengthen our findings.

The future of the amputees with osseointegration: A systematic review of literature

OBJECTIVE

Socket prosthesis attachment is the current gold standard for limb amputees. Osseointegrated implantation is a novel technique that has many proposed advantages over the current gold standard. Clear advantages for its use over socket prosthetic attachment has been well established in literature. It decreases socket problems as pinching, pressure points, chronic skin problems and frequent socket change due to atrophy of muscles.

METHODS

We reviewed primary research articles documenting complication rates and outcome measures in patients with osseointegrated prosthesis implantation after limb amputation.

RESULTS

Nine studies were identified with a total of 211-242 patients. Clinical, radiographic, and functional outcomes, as well as complications were considered. The mean duration of follow-up was greater than 12 months in all studies.

CONCLUSIONS

Osseointegration is an effective alternative to socket prosthesis in transfemoral amputees. Transtibial and upper extremity implants are underreported in the literature and clear indication for their effectiveness over socket prosthesis does not exist. Minor complications are most common, such as soft tissue infections, and may be mitigated in the future by improvements in surgical technique and implant design.The level of evidence is 3.

Radial Plate Fixation of Distal Radius Fracture

Background: A radial incision with radial plate fixation for distal radius fracture has historically been avoided due to its risk to the superficial branch of the radial nerve (SBRN). With careful technique, it is possible to avoid injury to the SBRN, thereby minimizing the soft tissue injury associated with other approaches. We compare subjective and objective functional outcomes of radial plate fixation surgeries that we performed with those of dorsal and volar plate fixation in current literature. Methods: Patients at a single center who underwent radial plate fixation for an AO type A or AO type B distal radius fracture between December 2006 and December 2014 were enrolled in the study. Postoperative grip strength and 3-digit pinch strength were measured systematically in the injured and uninjured wrists. Patients also completed a Quick Disabilities of the Arm, Shoulder and Hand (QuickDASH) questionnaire to assess subjective outcomes. Results: Thirty-six patients met our inclusion criteria and had available medical records. Postoperative grip strength in the injured wrist was significantly lowered-68% compared with the uninjured wrist. After subgroup analysis of dominant and nondominant wrist injuries, there was no significant difference in grip strength between injured and uninjured wrists. There was no significant decrease in postoperative 3-digit pinch strength in the injured wrist-89% compared with the uninjured wrist. The mean QuickDASH score for our study participants was 20.9. Conclusions: Radial plate fixation is an effective approach for distal radius fractures. Objective and subjective outcomes are noninferior to those of a dorsal or volar approach.

Taylor Spatial Frame in Treatment of Equinus Deformity

BACKGROUND

An equinus deformity interferes with activities of daily living. Correction of the deformity ranges from conservative (heel cord stretching, orthotics) to surgical treatment (Baumann, Strayer, Achilles lengthening, soft tissue releases). Severe contractures increase surgical intervention with extensive dissections to release soft tissues. This study investigated the clinical outcomes of gradual overcorrection using a Taylor spatial frame (TSF) with tendo-Achilles lengthening (TAL) added as necessary.

MATERIALS AND METHODS

This retrospective chart review evaluated patients with significant equinus treated with a TSF at a single large tertiary referral centre. Data collected included: diagnosis; patient demographics; laterality; time in frame; additional procedures; complications; degree of equinus deformity preoperatively and at every follow-up visit. Patients were followed at 1 week, 3 weeks, 6 weeks, 3 months, and 6 months intervals, and yearly thereafter.

RESULTS

Twenty-four patients (26 procedures) were treated with a TSF for equinus and had complete preoperative and follow-up measurements over 2 years. The angle of deformity increased from a preoperative -21.5 (range, -69.0 to -1.0) degrees to a postoperative 4.9 (range, -17.0 to 17.0) degrees (z = -4.4573, p = 0.0001, N = 26, Wilcoxon signed-rank test). A secondary outcome was a weak association (not statistically significant) between time in the TSF and the postoperative deformity angle. Four complications occurred during the follow-up (two pin site infections, one broken pin, and one plantar abscess). Three patients had recurrence of equinus deformity at time of last follow-up.

CONCLUSION

Using a TSF for correcting severe, fixed equinus contractures of the ankle joint is successful with minimal soft tissue-related complications. Overcorrection should be achieved in order to compensate for the loss of some dorsiflexion after frame removal. No added benefit was observed from having the frame on for a long time after correcting the deformity. Adding TAL is not necessary in all cases and required only in severe deformities of more than 25°.

HOW TO CITE THIS ARTICLE

Dabash S, Potter E, Catlett G, et al. Taylor Spatial Frame in Treatment of Equinus Deformity. Strategies Trauma Limb Reconstr 2020;15(1):28-33.

Adding deltoid ligament repair in ankle fracture treatment: Is it necessary? A systematic review

BACKGROUND

Deltoid ligament injuries are typically caused by supination-external rotation or pronation injury. Numerous ligament reconstruction techniques have been proposed; however, clear indications for operative repair have not yet been well established in the literature.

METHODS

We reviewed primary research articles comparing ORIF treatment for ankle fracture with versus without deltoid ligament repair.

RESULTS

Five studies were identified with a total of 281 patients. 137 patients underwent ORIF with deltoid repair, while 144 patients underwent ORIF without deltoid ligament repair. Clinical, radiographic, and functional outcomes, as well as complications were considered. The average follow-up was 31 months (range, 5-120).

CONCLUSIONS

Current literature does not provide clear indication for repair of the deltoid ligament at the time of ankle fracture repair. There may be some advantages of adding deltoid ligament repair for patients with high fibular fractures or in patients with concomitant syndesmotic fixation.

LEVEL OF CLINICAL EVIDENCE

III.

P1482Preclinical diastolic dysfunction assessed by left atrial strain and association with incident heart failure

Background

Left atrial strain in the reservoir phase (LASr) measures passive LA stretch and is a sensitive marker of left ventricular diastolic dysfunction (DD). However, reduced LASr has not been prospectively validated against clinical heart failure (HF) endpoints and its place in diastology evaluation is unclear.

Aim

We sought whether DD grades defined by previously validated ranges of LASr predicted incident HF and whether reclassifying indeterminate diastolic function based on reduced LASr could facilitate assessment of HF risk.

Methods

Community dwelling elderly subjects were recruited and underwent baseline clinical and echocardiographic assessment. Where imaging was suitable, speckle-tracking echocardiography assessed LASr and subjects were assigned DD grades based on published ranges: normal >35%, grade 1 24–35%, grade 2 19–24%, grade 3 <19%. Current ASE/EACVI recommendations were used to identify those with indeterminate function; LASr-defined DD (LASr-DD) was defined as LASr ≤23%. Follow-up was ≤2 years and incident HF adjudicated by Framingham criteria.

Results

Of 610 subjects (age 71±5 yrs., 46% male) LASr analysis was feasible in 590 (97%); average LASr was 39% (IQR 34–43%). Incident HF was associated with LASr-DD grade, occurring in 8 (36%) with grade ≥2, 14 (10%) with grade 1 and 39 (9%) with normal function (p<0.001). Adjusted odds ratio for incident HF for LASr-DD grade ≥2 was 3.12 (95% CI 1.06–9.1, p=0.038) Diastolic function was indeterminate in 147 (24%) subjects; of 144 (98%) with LAS analysis, 6 (75%) of those with LASr-DD vs. 15 (11%) with normal LASr experienced incident HF (p<0.001).

Univariable Multivariable* OR (95% CI) p-value OR (95% CI) p-value LASr-DD grade:   1 1.13 (0.59–2.15) 0.7 0.84 (0.42–1.69) 0.63   ≥2 5.7 (2.26–14.5) <0.001 3.12 (1.06–9.1) 0.038 *Adjusted for age, hypertension, diabetes, BMI, global longitudinal strain, E/e', LA volume index, LV mass index (all p<0.1 on univariable analysis).

Incorporating LA strain in practice

Conclusion

DD defined by LASr is predictive of HF for grades ≥2 independent of other diastolic measures. Indeterminate diastolic function with LASr ≤23% is associated with incident HF. LASr may complement current diastolic function assessment recommendations.

Acknowledgement/Funding

Baker Heart and Diabetes Institute

P3431Machine learning applied to energy waveform ECG for prediction of subclinical myocardial dysfunction

Background

Energy waveform (ew) ECG used continuous wavelet transforms (CWT) to create time-frequency energy characterisations. Although ewECG changes reflect myocardial disease, the optimal measures for prediction of subclinical left ventricular dysfunction (sLVD) are unclear.

Aim

Using machine learning, we investigated whether ewECG could predict sLVD in community subjects at risk of heart failure (HF).

Methods

Asymptomatic community subjects aged ≥65 yrs. with ≥1 non-ischaemic risk factor for HF underwent clinical evaluation, MyoVista (HeartSciences, Southlake, TX) ewECG and echocardiographic evaluation. sLVD was defined as systolic (global longitudinal strain, GLS≤16%) or diastolic (E/e' ≥15, E/e'>10 with left atrial enlargement, or impaired relaxation with other changes). A gradient boosting algorithm (supervised machine learning) with regularisation was implemented to predict sLVD using 362 ewECG features. The performance was assessed by precision, recall, F measure, precision-recall (PR) curve and receiver operating characteristic (ROC) curve. Feature importance was inspected by information gain node splitting.

Results

Of 97 subjects (age 71 (68–73) yrs., 53% female) 56 (58%) had sLVD. For prediction of sLVD, ewECG showed areas under PR and ROC curves of 0.86 and 0.8 respectively. The feature of greatest importance, with twice the importance of the second was a CWT frequency related to depolarisation.

Baseline characteristics Hypertension (%) 83 (86) Diabetes Mellitus (%) 34 (36) Atrial Fibrillation (%) 8 (8) BMI (IQR) 31 (27–34) LVMi (SD) 73 (23) Ejection fraction (SD) 60 (6) GLS (SD) 18 (3) E/e' (IQR) 8 (7–10) LAVi (IQR) 33 (28–40) IQR, Interquartile range; BMI, body mass index; LVMi, left ventricular mass index; GLS, global longitudinal strain; LAVi, left atrial volume index.

Prediction model performance

Conclusion

ewECG shows good predictive performance for sLVD in elderly subjects at risk of HF. HF prevention strategies incorporating ewECG to select individuals for echocardiographic evaluation should be considered.

Acknowledgement/Funding

Baker Heart and Diabetes Institute

P5979Impact of disease stage on performance of strain markers for prediction of atrial fibrillation

Background

Efforts to predict incident atrial fibrillation (AF) may be associated with complications, and there is interest in AF prediction in primary prevention (PP; pts with risk factors) and secondary prevention (SP; pts with possible AF complications). These pts have different risk levels, we sought whether that influenced the predictive value of LV dysfunction (measured as global longitudinal strain, GLS) or LA dysfunction (LA reservoir strain).

Methods

The PP cohort comprised 351 community-based pts ≥65 years with ≥1 risk factor for AF (age 70±4y,43% male, median follow-up 22 months) and the SP cohort comprised 532 pts after transient ischaemic attack or stroke (age 68±12y, 51% male, median follow-up 36 months). GLS and LA strain were measured offline (Image Arena-Tomtec, Germany). AF was diagnosed by 12 lead ECG, Holter or by single lead monitor. The clinical and echocardiographic characteristics of those with AF were compared to those in sinus rhythm. Nested Cox-regression models were used to assess for independent and incremental predictive value of LA strain/GLS in both cohorts.

Results

Compared to SP, PP had higher clinical AF risk (CHARGE-AF 5.6±5.5% vs 4.7±12.1%, p=0.02) but a lower thromboembolic risk (CHA2DS2-VASC 3±2 vs. 4±2, p<0.001). AF developed in 42 PP pts (12%) and 61 SP (12%). AF patients were older, with higher CHARGE-AF score, LA volume and LV mass. Pts developing AF had reduced GLS (17±4% vs. 20±3%, p<0.001), reservoir (28±11% vs. 35±8%, p<0.001) and pump strain (13±7% vs. 17±5%, p<0.001). GLS and LA strain had greater AUC in SP (0.84 vs 0.58 for GLS and 0.85 vs 0.57 for reservoir strain, both p<0.001). Nested cox-regression models showed that LA reservoir strain was independently associated with AF in both cohorts (p<0.05). GLS was only independently associated with incident AF in SP (Figure).

Conclusion

LA reservoir strain is independently associated with AF in different risk cohorts and its effect is incremental to clinical parameters and LA volume. GLS may be more useful in AF risk assessment in those in SP.

Acknowledgement/Funding

This study was partially supported by the Tasmanian Community Fund and Siemens Healthcare Australia.

Unstable Ankle Fracture Fixation Using Locked Fibular Intramedullary Nail in High-Risk Patients

Open reduction internal fixation is the gold standard for unstable ankle fracture fixation; however, complications in patients with multiple medical comorbidities are common. Intramedullary nail fixation of the fibula can help to mitigate these difficulties. A retrospective chart review was performed on all patients who underwent fixation for unstable ankle fracture between January 2015 and March 2016 at our level I trauma center. Comorbidities in the patient sample included were one or several of diabetes, renal disease, hypertension, advanced age with osteoporosis, hemorrhagic blisters, and alcoholism. The primary outcomes studied were wound complications, infections, and hardware failure or failure of fixation. Eighteen patients with a mean age of 61 years underwent fibular intramedullary nail fixation, all of whom were considered at high risk for postoperative complications. Patients presented with Weber B or C fracture patterns. All patients had syndesmotic fixation through the nail by one or two 3.5-mm tricortical screws. A medial malleolus was added if needed for stability. The average follow-up time was 291.1 (range 9 to 14 months) days. The prescribed range of time to weightbearing was 2 to 6 weeks. All patients maintained reduction of the fracture and had no wound complications. No syndesmotic screws broke postoperatively, although most patients to failed comply with the postoperative non-weightbearing restrictions. Intramedullary nailing of the fibula with syndesmotic intranail fixation is minimally invasive, quick, and provides adequate fixation strength. It offers a viable treatment option for patients at high risk for complications or who are suspected to have difficulty with follow-up or compliance.

Management of growth arrest: Current practice and future directions

INTRODUCTION

Premature growth arrest can pose a challenge to the orthopedic surgeon. Various options for treating physeal arrest exist.

METHODS

Systematic searches were conducted on PubMed/Medline, ScienceDirect, OVID, and Cochrane Library. Secondary searching was performed, where certain articles from reference lists of the selected studies were reviewed that were not found in the primary search.

RESULTS

This review article discusses the different methods of management for premature growth arrest.

CONCLUSIONS

The use of mesenchymal stem cells provides a promising alternative treatment modality.

Dallas-Fort Worth earthquakes coincident with activity associated with natural gas production

On 31 October 2008 and the following day, numerous Dallas-Fort Worth (DFW) residents called 911 to report experiencing several small earthquakes, accompanied by loud booming noises and the shaking of walls and furniture. Using data recorded by regional seismic stations, the USGS National Earthquake Information Center (NEIC) located nine earthquakes with magnitudes between 2.5 and 3.0. On 16 May 2009, this scenario repeated itself, as local residents felt three earthquakes and the NEIC located four (largest = magnitude 3.3). A third sequence of felt events began on 2 June 2009, approximately 65 km southwest near the city of Cleburne, Texas, but has not yet been studied in detail (Figure 1).

Association of white matter hyperintensity measurements on brain MR imaging with cognitive status, medial temporal atrophy, and cardiovascular risk factors

BACKGROUND AND PURPOSE

White matter hyperintensities (WMHs) are frequently characterized as markers of cerebrovascular disease, whereas medial temporal atrophy (MTA) is a recognized marker of Alzheimer disease (AD). Our purpose was to test the reliability of a visual rating system (VRS) in evaluating WMHs and MTA and in distinguishing healthy from cognitively impaired subjects.

MATERIALS AND METHODS

Subjects (n = 192) enrolled in the Florida Alzheimer's Disease Research Center were diagnosed with no cognitive impairment, nonamnestic mild cognitive impairment (na-MCI), amnestic MCI (a-MCI), or probable AD. The severity of WMHs was assessed on T2-weighted fluid-attenuated inversion recovery axial MR images, and the severity of MTA was evaluated on 1.5-mm-thick coronal MR images by using a computer-based visual rating system. Cardiovascular risk factor scores were calculated as the sum of 10 independent cardiovascular risk factors.

RESULTS

WMH and MTA scores were greater in subjects with probable AD, relative to those with no cognitive impairment and na-MCI. MTA scores differentiated subjects with a-MCI from those with no cognitive impairment and na-MCI. The total WMH score was significantly related to MTA (r = 0.39; P < .001) but not to cardiovascular risk factor scores (r = 0.07; P = not significant). The overall correct classification rate of probable AD versus no cognitive impairment by using MTA scores was 81.8%, improving to 86.5% when combined with WMH scores.

CONCLUSIONS

Both MTA and WMH scores distinguished subjects with no cognitive impairment and probable AD. Combining MTA and WMH scores improved the correct classification rate, whereas WMH scores were significantly related to MTA scores, but not to cardiovascular risk factor scores. This finding suggests that among subjects with a-MCI and probable AD, WMHs on MR images are primarily associated with neurodegenerative disease.

The comparative toxicity to soil invertebrates of natural chemicals and their synthetic analogues

The introduction of Registration, Evaluation and Authorisation of Chemicals (REACH), requires companies to register and risk assess all substances produced or imported in volumes of >1 tonne per year. Extrapolation methods which use existing data for estimating the effects of chemicals are attractive to industry, and comparative data are therefore increasingly in demand. Data on natural toxic chemicals could be used for extrapolation methods such as read-across. To test this hypothesis, the toxicity of natural chemicals and their synthetic analogues were compared using standardised toxicity tests. Two chemical pairs: the napthoquinones, juglone (natural) and 1,4-naphthoquinone (synthetic); and anthraquinones, emodin (natural) and quinizarin (synthetic) were chosen, and their comparative effects on the survival and reproduction of collembolans, earthworms, enchytraeids and predatory mites were assessed. Differences in sensitivity between the species were observed with the predatory mite (Hypoaspis aculeifer) showing the least sensitivity. Within the chemical pairs, toxicity to lethal and sub-lethal endpoints was very similar for the four invertebrate species. The exception was earthworm reproduction, which showed differential sensitivity to the chemicals in both naphthoquinone and anthraquinone pairs. Differences in toxicity identified in the present study may be related to degree of exposure and/or subtle differences in the mode of toxic action for the chemicals and species tested. It may be possible to predict differences by identifying functional groups which infer increased or decreased toxicity in one or other chemical. The development of such techniques would enable the use of read-across from natural to synthetic chemicals for a wider group of compounds.

Medial temporal lobe atrophy on MRI scans and the diagnosis of Alzheimer disease

BACKGROUND

Despite convenience, accessibility, and strong correlation to severity of Alzheimer disease (AD) pathology, medial temporal lobe atrophy (MTA) has not been used as a criterion in the diagnosis of prodromal and probable AD.

METHODS

Using a newly validated visual rating system, mean MTA scores of three bilateral medial temporal lobe structures were compared for subjects with no cognitive impairment (NCI) (n = 117), nonamnestic mild cognitive impairment (MCI) (n = 46), amnestic MCI (n = 45), and probable AD (n = 53). Correlations between MTA scores and neuropsychological test scores at baseline, and predictors of change in diagnosis at 1-year follow-up were evaluated.

RESULTS

With NCI as the reference group, a mean MTA cut score of 1.33 yielded an optimal sensitivity/specificity of 85%/82% for probable AD subjects and 80%/82% for amnestic MCI subjects. MTA and Clinical Dementia Rating Sum of Boxes scores at baseline were independent and additive predictors of diagnosis at baseline, and of transition from NCI to MCI or from MCI to dementia at 1-year follow-up.

CONCLUSION

Medial temporal lobe atrophy (MTA) scores 1) distinguish probable Alzheimer disease (AD) and amnestic mild cognitive impairment (MCI) subjects from nonamnestic MCI and no cognitive impairment (NCI) subjects, 2) help predict diagnosis at baseline, and 3) predict transition from NCI to MCI and from MCI to probable AD. MTA scores should be used as a criterion in the clinical diagnosis of AD.

White matter brain lesions in midlife familial hypercholesterolemic patients at 3-Tesla magnetic resonance imaging

BACKGROUND

Patients with hypercholesterolemia of 60 years and older have an increased risk for white matter brain lesions and dementia.

PURPOSE

To investigate whether patients with familial hypercholesterolemia (FH) develop white matter lesions at 3-Tesla (T) MRI as early as in midlife.

MATERIAL AND METHODS

Non-diabetic, nonsmoking, and non-hypertensive heterozygous FH patients on treatment with maximally tolerated dose of a statin for more than 5 years (n = 14) and matched controls (n = 22) aged 25 to 60 years of age were studied. Imaging was performed at 3T with a fluid-attenuated T2-weighted MR pulse sequence and a T1-weighted spin-echo pulse sequence following 10 ml of i.v. gadopentetate dimeglumine. Images were evaluated by two independent readers. Fasting blood samples were taken. Student's t test was employed at P<0.05.

RESULTS

Three volunteers and one FH patient had white matter lesions (P<0.53). No other evidence of past ischemic stroke was observed. Mean total serum cholesterol and low-density lipoprotein (LDL) cholesterol were significantly higher in the FH group (6.0+/-1.1 vs. 5.1+/-0.9 mmol/l, P<0.02 and 4.1+/-0.9 vs. 3.1+/-0.8 mmol/l, P<0.004, respectively).

CONCLUSION

Heterozygous FH patients on statin treatment in the age range of 25 to 60 years are not at increased risk of white matter lesions at 3T MRI.

The relationship between exercise and hopelessness in prison

This paper reports on the relationship between the levels of self-reported physical exercise and mental well-being (as measured using the Beck Hopelessness Scale) in a cohort of 914 prisoners within New South Wales, Australia. A significant inverse relationship between self-reported exercise in minutes per week and hopelessness was identified. The need to include exercise as a factor in inmate health plans is discussed.

The functional neuroanatomy of corticotropin-releasing factor

Descriptions of the central distribution of corticotropin-releasing factor (CRF) have been taken as generally supporting the proposition that this neuropeptide is involved in the mediation of complementary neuroendocrine, autonomic and behavioural responses to stress. The hypothalamic paraventricular nucleus (PVN) is recognized as the principal source of CRF in hypophysial portal plasma; CRF mRNA and peptide expression in parvocellular neurosecretory neurons are regulated negatively by adrenal steroids and positively by many stressors. Consistent with the latter, the hypophysiotropic zone of the PVN receives a rich, and biochemically differentiated, afferent supply that provides visceral, somatic and special sensory systems with access to the 'CRF neuron'. Within the PVN, CRF is also expressed, and differentially regulated, in oxytocinergic magnocellular neurosecretory neurons and in autonomic-related projection neurons. CRF expression in at least some extrahypothalamic cell groups (olfactory bulb, Barrington's nucleus) is responsive to certain stressful stimuli, but not to perturbations of the steroid environment. Refinement of our understanding of the central distribution of CRF has been provided by the recognition that most CRF antisera cross-react with an amidated dipeptide encoded by the melanin-concentrating hormone precursor, and by the likelihood that some central sites of CRF peptide expression may be muted or masked by the presence of a CRF-binding protein (CRF-BP). The CRF-BP is expressed prominently in the telencephalon, where it is co-localized with CRF in some neurons, and in anterior pituitary corticotrophs.

Oncofoetal fibronectin--a tumour-specific marker in detecting minimal residual disease in differentiated thyroid carcinoma

Supposedly, thyrocyte-specific transcripts such as thyroglobulin (Tg) and thyroid-stimulating hormone receptor (TSH-R) were proposed to be useful for the diagnosis of circulating tumour cells in patients suffering from differentiated thyroid carcinoma (DTC). However, several research groups reported blood-borne Tg transcripts in healthy individuals. This study determines in particular the origin of Tg mRNA in nucleated blood cells and analyses whether other tumour-associated sequences are absent in leukocytes, but widely expressed in DTC. Therefore, expression analyses for Tg, TSH-R, cytokeratin 19 (CK 19), human telomerase reverse transcriptase (hTERT) and oncofoetal fibronectin (onfFN) were carried out using cDNAs derived from (1) leukocyte fractions, (2) 18 follicular thyroid carcinomas (FTCs) and 48 papillary thyroid carcinomas (PTCs), and (3) leukocytes of two thyrocyte-depleted individuals treated for C-cell carcinoma of the thyroid. Expression of onfFN was additionally analysed by semiquantitative RT–PCR and by quantitative fluorescence-based real-time PCR. Tg and TSH-R expression was demonstrated not only in both athyroid individuals, but in all leukocyte subgroups tested, while hTERT was absent in resting CD4⁺ cells and only weakly expressed in the CD8⁺ group. CK 19 was notable in each leukocyte population except for resting CD14⁺, as well as for activated and resting CD19⁺ cells. All blood cell fractions proved negative for onfFN mRNA, whereas its presence in thyroid carcinoma was 78/98% (FTC/PTC). Threshold cycle values were calculated at: porphobilinogen deaminase (PBGD) =25.95±0.73 (FTC)/24.55±5.43 (PTC) (P=0.2878); onfFN=25.48±3.15 (FTC)/21.44±3.44 (PTC) (^*P=0.0001). Finally, onfFN transcripts were detected in blood samples of six out of nine patients with known DTC metastases, demonstrating a reliable assay functionality. We propose that real-time RT–PCR of onfFN mRNA is superior to other markers in monitoring minimal residual disease in DTC with regard to both assay sensitivity and specificity.

Characterization of a CCD-based digital x-ray imaging system for small-animal studies: properties of spatial resolution

A digital x-ray imaging system was designed for small-animal studies. This system is a fiber-optics taper-coupled imaging system with two CCD arrays uniquely jointed. The x-ray source of the system has a small focal spot of 20 microm. This digital imaging system contains specially designed shelves to provide magnification levels, ranging from 1.5x to 5x. The system is characterized in terms of its properties of spatial resolution. An observer-based spatial resolution measurement was conducted with a line-pair target and a sector test pattern. The modulation transfer function of the system, with different magnifications, was studied by use of a 10-microm lead slit. The average resolutions at 50% and 5% modulations at 1x magnification were measured as 3.9 and 8.4 lp/mm, respectively, where lp indicates line pairs. With 5x magnification, the 50% and the 5% modulations provided 13.2- and 29.9-lp/mm, respectively, average spatial resolutions. The measurements showed consistency between the two individual CCD arrays; the difference in resolution between the two CCDs is less than 1%, even at high magnifications.

Ectopic expression of the CRF-binding protein: minor impact on HPA axis regulation but induction of sexually dimorphic weight gain

Corticotrophin-releasing factor (CRF) and urocortin possess a high-affinity binding protein. Although the CRF binding protein (BP) can sequester these ligands and inhibit their activity, the endogenous activity of this protein is not understood. Therefore, transgenic mouse lines that over-express the CRF-BP were created. The transgene was constructed by ligating rat CRF-BP cDNA (1.1 kb) between a mouse metallothionein-I promoter (1.8 kb) and a nonfunctional human growth hormone gene sequence (2.1 kb) in a modified pBR322 plasmid and microinjecting the transgene into C57BL/6 x SJL hybrid ova. The transgene was expressed in 50% in both male and female progeny. All transgenic lines were maintained by crossing transgenic animals with wild-type C57BL/6 mates. Reverse-transcriptase (RT) PCR of the CRF-BP transgene showed that it is widely expressed not only in the brain and pituitary, but also peripheral tissues including the liver, kidney and spleen. Transgenic animals of both sexes showed significant increases in weight gain as established by analysis of variance; however, the weight gain profiles for each sex were distinct. High levels of circulating CRF-BP were detected in the transgenic animals, but the basal ACTH and corticosterone levels were not significantly decreased compared to wild-type littermates. The hypothalamopituitary-adrenal (HPA) axis was stimulated by systemic inflammation induced with lipopolysaccharide (LPS). An expected increase in transgene expression was observed and was accompanied by a significant attenuation of ACTH secretion at 3 h after LPS injection in the transgenic males but not the females. These data suggest that HPA axis regulation is significantly affected only with very high circulating levels of CRF-BP. Moreover, this work supports previous studies that implicate CRF and urocortin in the regulation of appetite and the binding protein expression may play a sexually dimorphic role in regulating this and other responses.

Corticotropin releasing factor (CRF) binding protein: a novel regulator of CRF and related peptides

A 37-kDa corticotropin releasing factor (CRF) binding protein (CRF-BP) was purified from human plasma by repeated affinity purification and subsequently sequenced and cloned. The human and rat CRF-BP cDNAs encode proteins of 322 amino acids with one putative signal sequence, one N-glycosylation site, and 10 conserved cysteines. Human CRF-BP binds human CRF with high affinity but has low affinity for the ovine peptide. In contrast, sheep CRF-BP binds human and ovine CRF with high affinity. The CRF-BP gene consists of seven exons and six introns and is located on chromosome 13 and loci 5q of the mouse and human genomes, respectively. CRF-BP inhibits the adrenocorticotrophic hormone (ACTH) releasing properties of CRF in vitro. CRF-BP dimerizes after binding CRF and clears the peptide from blood. This clearance mechanism protects the maternal pituitary gland from elevated plasma CRF levels found during the third trimester of human pregnancy. CRF-BP is expressed in the brains of all species so far tested but is uniquely expressed in human liver and placenta. In brain, CRF-BP is membrane associated and is predominantly expressed in the cerebral cortex and subcortical limbic structures. In some brain areas CRF-BP colocalizes with CRF and CRF receptors. The protein is also present in pituitary corticotropes, where it is under positive glucocorticoid control, and is likely to locally modulate CRF-induced ACTH secretion. The ligand requirements of the CRF receptor and the CRF-BP can be distinguished in that central human CRF fragments, such as CRF (6-33) and CRF (9-33), have high affinity for CRF-BP but low affinity for the CRF receptor. The binding protein's ability to inhibit CRF-induced ACTH secretion can be reversed by CRF (6-33) and CRF (9-33), suggesting that ligand inhibitors may have utility in elevating free CRF levels in disease states associated with decreased CRF. Thus, by controlling the amount of free CRF which activates CRF receptors, it is likely that the CRF-BP is an important modulator of CRF both in the CNS and in the periphery.

Ligand requirements of the human corticotropin-releasing factor-binding protein

CRF-binding protein (CRF-BP), identified as a 37-kilodalton human serum protein, binds human (h) CRF (Kd = 0.17 +/- 0.01 nM) and blocks hCRF's ability to stimulate ACTH release by pituitary cells in vitro. The present study examines ligand requirements of CRF-BP by testing the affinity of recombinant CRF-BP for synthetic analogs of CRF and peptides in the CRF family. The relative affinities of various fragments of hCRF or related peptides for CRF-BP indicate that residues 9-28 are crucial for ligand binding. CRF-BP binds human/rat CRF and urotensin-I with high affinity, sauvagine with moderate affinity, and ovine (o) CRF with low affinity. The marked difference in the affinity of CRF-BP for oCRF (Ki = 1100 +/- 97 nM) compared to hCRF (Ki = 0.17 +/- 0.01 nM), when considered with the importance of the central domain, suggests that amino acids 22, 23, and/or 25 are critical for binding. Altering oCRF residues 22, 23, or 25 individually or collectively to match those of hCRF increases the affinity of CRF-BP for these ligands; [Ala22, Arg23, Glu25]oCRF, in which all three of these central amino acids are substituted by their hCRF counterparts, binds CRF-BP with an affinity equal to that of hCRF. CRF-BP has differential affinities for CRF receptor antagonists, binding alpha-helical CRF-(9-41) with high affinity and [D-Phe12, Nle21,38]hCRF-(12-41) with low affinity. Thus, the structural requirements for binding to CRF-BP can clearly be distinguished from those for CRF receptor recognition of both agonists and antagonists. Peptides such as hCRF-(9-33), with low biological activity but which retain high affinity for the binding protein, can competitively override the effects of CRF-BP to block CRF-induced ACTH secretion, raising the possibility that whereas endogenous CRF-BP serves to limit the distribution or duration of action of CRF, specific pharmacological inhibitors of the ligand-binding protein interaction might be used to therapeutically elevate free CRF levels.

Distribution of corticotropin-releasing factor receptor mRNA expression in the rat brain and pituitary

Corticotropin-releasing factor (CRF) is a major hypophysiotropic peptide regulating pituitary-adrenal response to stress, and it is also widely expressed in the central nervous system. The recent cloning of cDNAs encoding the human and rat CRF receptors has enabled us to map the distribution of cells expressing CRF receptor mRNA in rat brain and pituitary by in situ hybridization. Receptor expression in the forebrain is dominated by widespread signal throughout all areas of the neo-, olfactory, and hippocampal cortices. Other prominent sites of CRF receptor mRNA expression include subcortical limbic structures in the septal region and amygdala. In the diencephalon, low levels of expression are seen in a few discrete ventral thalamic and medial hypothalamic nuclei. CRF receptor expression in hypothalamic neurosecretory structures, including the paraventricular nucleus and median eminence, is generally low. In the brainstem, certain relay nuclei associated with the somatic (including trigeminal), auditory, vestibular, and visceral sensory systems, constituted prominent sites of CRF receptor mRNA expression. In addition, high levels of this transcript are present in the cerebellar cortex and deep nuclei, along with many precerebellar nuclei. In the pituitary, moderate levels of CRF receptor mRNA expression were detected throughout the intermediate lobe and in a subset of cells in the anterior lobe identified as corticotropes by concurrent immunolabeling. Overall, the central distribution of CRF receptor mRNA expression is similar to, though more expansive than, that of regions reported to bind CRF, and it shows limited overlap with loci expressing CRF-binding protein. Interestingly, CRF receptor mRNA is low or undetectable in several cell groups implicated as central sites of CRF action.

Assignment of disulfide bonds in corticotropin-releasing factor-binding protein

We have previously isolated, cloned, and characterized a protein that specifically binds and inactivates the peptide corticotropin-releasing factor. The integrity of the disulfide bonds in the binding protein is essential for this activity as reduction abolishes the protein's ability to bind corticotropin-releasing factor. The disulfide arrangement of the 10 cysteines present in the mature protein was established by analysis of proteolytically cleaved protein and sequence analysis of cystine containing fragments. A pattern is observed where each cysteine is connected to the next one in a sequential manner. Inspection of the genomic DNA encoding for this protein reveals that four of the domains defined by disulfide linkage coincide with four different exons.

Association of human corticotropin-releasing hormone to its binding protein in blood may trigger clearance of the complex

Late in the last trimester of human pregnancy, as plasma CRH levels rise, the concentration of circulating CRH-binding protein (CRH-BP) falls. We have investigated, using nonpregnant subjects, the hypothesis that CRH has a negative effect on plasma levels of CRH-BP. A specific RIA developed with the aid of recombinant binding protein has been used to measure CRH-BP. Subjects given iv infusions of human CRH for 10 h showed a sustained fall in plasma CRH-BP for the duration of the infusion. Intravenous bolus injection of human CRH produced a rapid reduction in CRH-BP levels to 54% of the basal value, whereas ovine CRH was without effect, even though both peptides are cleared from the plasma at similar rates and have similar effects on the pituitary-adrenal axis. The rapid clearance was concluded to be related to ligand affinity, as ovine CRH has a 200-fold lower affinity than human CRH for CRH-BP. We suggest that the rising levels of CRH are responsible for the reduction in CRH-BP concentrations observed in late pregnancy, and that this reduction is triggered by the binding of CRH-BP to its ligand.