Cryoballoon ablation for atrial fibrillation in South Africa: One-year outcome from the Cryo Global Registry

BACKGROUND

Pulmonary vein isolation (PVI) with cryoballoon catheter ablation (CBA) is a well-established and widely adopted method for the treatment of patients with atrial fibrillation (AF) to prevent recurrences of AF. CBA adoption in South Africa (SA) and outcome data in SA patients are limited.

OBJECTIVES

To evaluate real-world usage, safety and effectiveness of CBA in SA.

METHODS

In this sub-analysis of the Cryo Global Registry, 81 participants with paroxysmal AF (PAF) and persistent AF (PsAF) were enrolled between 2017 and 2021 across two private SA hospitals. Baseline characteristics, procedural characteristics, 12-month safety, effectiveness (atrial arrhythmia recurrence), healthcare utilisation (repeat ablation and all-cause hospitalisation), quality of life (QoL; measured by EQ-5D-3L) and predefined symptoms were reported on.

RESULTS

Participants in the SA cohort were a mean (standard deviation) of 60 (12) years old, 19 (23.5%) were female, and 48 (59.3%) presented with PAF. The overall presence of baseline comorbidities in the SA cohort was relatively low compared with the entire Cryo Global Registry cohort. The acute PVI success rate was high (98.8%). Two serious procedure-related adverse events occurred in 2 (2.5%) participants in the SA cohort. Freedom from arrhythmia recurrence was 97.4% (95% confidence interval (CI) 83.2 - 99.6%) in PAF and 78.4% (95% CI 58.1 - 89.7%) in persistent AF (p=0.035). Kaplan-Meier estimates for freedom from repeat ablations and all-cause hospitalisations were 97.0% (95% CI 88.4 - 99.2%) and 98.5% (95% CI 90.0 - 99.8%), respectively. Participants reported significant improvement in EQ-5D-3L index score and symptoms from baseline (0.90 (0.11)) - 12 months (0.97 (0.07), p<0.001).

CONCLUSION

CBA standard-of-care procedures in SA resulted in a high clinical freedom from arrhythmia recurrence, with a low risk of safety events within 12 months post ablation. In addition, participants experienced an improvement in QoL and high freedom from healthcare utilisation at 12 months. The obtained results will be important for guiding clinical decisions around CBA in SA.

Electrophysiology lab efficiency comparison between cryoballoon and point-by-point radiofrequency ablation: a German sub-analysis of the FREEZE Cohort study

BACKGROUND

Pulmonary vein isolation (PVI) is recommended to treat paroxysmal and persistent atrial fibrillation (AF). This analysis aimed to assess the hospital efficiency of single-shot cryoballoon ablation (CBA) and point-by-point radiofrequency ablation (RFA).

METHODS

The discrete event simulation used PVI procedure times from the FREEZE Cohort study to establish the electrophysiology (EP) lab occupancy time. 1000 EP lab days were simulated according to an illustrative German hospital, including 3 PVI cases per day using CBA at one site and RFA at the other.

RESULTS

The analysis included 1560 CBA patients and 1344 RFA patients from the FREEZE Cohort. Some baseline patients' characteristics were different between groups (age, AF type, and some concomitant diseases), without being statistically associated to ablation procedure time. Mean procedure time was 122.2 ± 39.4 min for CBA and 160.3 ± 53.5 min for RFA (p < 0.0001). RFA was associated with a more than five-fold increase of cumulative overtime compared to CBA over the simulated period (1285 h with RFA and 253 h with CBA). 70.7% of RFA lab days included overtime versus 25.7% for CBA. CBA was associated with more days with an additional hour at the end of the EP lab shift compared to RFA (47.8% vs 11.5% days with one hour left, respectively).

CONCLUSION

CBA is faster and more predictable than point-by-point RFA, and enables improvements in EP lab efficiency, including: fewer cumulative overtime hours, more days where overtime is avoided and more days with remaining time for the staff or for any EP lab usage. Clinical trial registration NCT01360008 (first registration 25/05/2011).

p300 or CBP is required for insulin-stimulated glucose uptake in skeletal muscle and adipocytes

While current thinking posits that insulin signaling to GLUT4 exocytic translocation and glucose uptake in skeletal muscle and adipocytes is controlled by phosphorylation-based signaling, many proteins in this pathway are acetylated on lysine residues. However, the importance of acetylation and lysine acetyltransferases to insulin-stimulated glucose uptake is incompletely defined. Here, we demonstrate that combined loss of the acetyltransferases E1A binding protein p300 (p300) and cAMP response element binding protein binding protein (CBP) in mouse skeletal muscle causes a complete loss of insulin-stimulated glucose uptake. Similarly, brief (i.e. 1 h) pharmacological inhibition of p300/CBP acetyltransferase activity recapitulates this phenotype in human and rodent myotubes, 3T3-L1 adipocytes, and mouse muscle. Mechanistically, these effects are due to p300/CBP-mediated regulation of GLUT4 exocytic translocation and occurs downstream of Akt signaling. Taken together, we highlight a fundamental role for acetylation and p300/CBP in the direct regulation of insulin-stimulated glucose transport in skeletal muscle and adipocytes.

618 Management of Rectal Cancer in England And Wales. Is the Rate of Abdominoperineal Excision of Rectum Associated with The Pre-Operative Radiotherapy Rates?

Aim

Rectal cancer treatment has improved over the years, but variations in practice remain. Abdominoperineal resection (APER) is associated with significant morbidity and pre-operative radiotherapy (RT) is only recommended for advanced rectal cancer. As such, APER and RT should be reserved for patients with an appropriate clinical need. The aim of the study is to evaluate the association between the rates of APER and RT, and whether any other factors are associated.

Method

Data on rectal cancer cases was extracted from National Bowel Cancer Audit 2019. Primary outcomes were: APER rate, RT rate. Pearson’s correlation coefficient was calculated. The means for APER and pre-operative radiotherapy were plotted on a four-quadrant matrix. The differences were analysed using Mann-Whitney U and Student T-test.

Results

3,764 patients were included. A mean of 25% (95%CI: 10.3-14.9%) underwent APER and an average of 34% (95%CI: 30.5-36.8%) received RT. There was a weak positive correlation between rates of APER and RT (r = 0.356, p &lt; 0.001). 43 (37%) trusts had proportions of both APER and RT below the overall mean, whilst 30 (26%) had both proportions above. No significant differences were found when comparing other variables between the high to low-rate trusts (p &gt; 0.05).

Conclusions

There is a weak positive correlation between the proportion of rectal cancer patients undergoing APER and the proportion receiving RT in trusts across England and Wales. It is unknown whether this finding has a clinical significance and further analysis on trust/surgeon performance and patient demographics is needed, allowing for prevention strategies to be implemented.

643 How the Straight Leg Raise and Crossed Straight Leg Raise Sign Influence Patient Reported Outcome Measures in Patients with a Lumbar Disc Herniation

Aim

Low back pain (LBP) with associated lumbar radiculopathy is common. Clinical assessment utilises the straight leg raise (SLR) test and the more specific crossed straight leg raise (XSLR) test. Patient reported outcome measure (PROMs) scores can assess the contributary biopsychosocial factors to pain. Evidence shows links between radiculopathy and psychosocial issues, but little has assessed them in relation to clinical examination. The aim of this study was to assess the significance of the SLR and XSLR sign on PROMs in patients with an MRI-confirmed lumbar disc herniation.

Method

Patients with an MRI-confirmed lumbar disc herniation who presented with LBP and lumbar radiculopathy were identified. Collected data included the clinical examination outcome, level and side of disc prolapse, interventions and PROMs scores (VAS, ODI, EQ5D, GAD7, PHQ9). Statistical analysis was performed using SPSS.

Results

216 patients were included in this study (mean age 50.4, 41% female, 59% male), 102 had negative straight leg raise (NSLR), 94 had positive SLR and 20 had both a positive SLR and positive XSLR. Patients with a positive clinical test on examination had ‘worse’ PROMs scores, with a positive XSLR sign associated with the ‘worst’ PROMs scores. For each PROM, t-test analysis reported a significant difference between the NSLR and SLR groups and NSLR and XSLR groups (P &lt; .01).

Conclusions

PROMs scores indicating a lower health-related quality-of-life, increased levels of disability, pain, anxiety and depression and greater expectations are associated with a positive SLR or XSLR test.

635 Expectations and Concerns of Patients Attending a Spinal Outpatient Clinic

Aim

Identifying expectations and concerns of patients is vital during clinical consultation in patient-centred healthcare systems. Most spinal surgery is elective and focussed on improving quality of life. Understanding what patients want from treatment at baseline may improve experience and outcomes.

Method

New patient data from the caseload of a single orthopaedic spinal surgeon (from April 2012-18) was analysed with expectations and concerns reported in the outpatient clinic letter (standard practice for surgeon).

Results

Of 940 patients (498 NHS, 442 private), mean age was 58.3 with 46.0% male and 54.0% female. Nearly 1-in-6 patients underwent previous surgery. The most common expectation was ‘reduce pain’ (41.8%), followed by diagnosis (23.0%), treatment options (13.5%), unsure (10.5%). The most common concern was ‘continuation/worsening of pain’ (27.0%), followed by loss of function (15.9%), work-related (8.3%), permanent disability (7.8%). NHS patients were significantly more unsure of expectations (19.7% vs 4.5%, p&lt;.001) and less frequently raised concerns (39.0% vs 18.8%, p&lt;.001). NHS patients had significantly worse Oswestry Disability Index (ODI) scores (46.8% vs 42.0% p&lt;.001), were more depressed (PHQ-9: 11.5 vs 8.9, p&lt;.001) and anxious (GAD-7: 8.2 vs 5.9, p&lt;.001). Private patients were significantly more likely to report problems sleeping (79.4% vs 51.0%, p&lt;.001). Patients concerned about permanent disability had significantly worse ODI (51.0% vs 42.7%, p&lt;.001), PHQ-9 (12.6 vs 10.2 p=.013) and GAD-7 (9.0 vs 7.1, p=.017) scores.

Conclusions

This study identified patient expectations and concerns in spinal outpatient clinic in both healthcare sectors. Future work should explore these findings in context with clinical outcome.

Teaching a large-scale crystallography school with Zoom Webinar

In order to address the loss of crystallographic training opportunities resulting from the cancelation of conventional schools around the world due to the COVID-19 pandemic, we have started an online crystallography school with live lectures and live Q&A using Zoom Webinar. Since we were trying to reach a large audience in a relatively short period, we have limited the school to ten 1 h lectures covering practical aspects of small molecule crystallography including data collection, data processing, and structure solution. In the school, we also covered some advanced topics that students commonly see in their work: absolute structure determination, twinning, and disorder. To round out the education, we provided lectures on macromolecular crystallography and powder diffraction. For students to practice on their own, we used freely available data reduction and structure solution software, as well as datasets with which to practice. To give students credit for course completion, we provided an online exam and an electronic certificate of completion. In this editorial, we will provide some insight into the issues of holding lectures with up to 750 students of very diverse backgrounds and review the efficacy of the school in teaching crystallography for the two cohorts of students.

Fibrodysplasia ossificans progressiva (FOP): A disorder of osteochondrogenesis

Fibrodysplasia ossificans progressiva (FOP) is an ultra-rare genetic disorder of extraskeletal bone formation, but could appropriately be viewed as a seminal disorder of osteochondrogenesis. Many, if not most, of the musculoskeletal features of FOP are related to dysregulated chondrogenesis including abnormal articular cartilage formation, abnormal diarthrodial joint specification, growth plate dysplasia, osteochondroma formation, heterotopic endochondral ossification (HEO), and precocious arthropathy. In FOP, causative activating mutations of Activin receptor A type I (ACVR1), a bone morphogenetic protein (BMP) type I receptor, are responsible for the osteochondrodysplasia that impacts developmental phenotypes as well as postnatal features of this illustrative disorder. Here, we highlight the myriad developmental and postnatal effects on osteochondrogenesis that emanate directly from mutant ACVR1 and dysregulated bone morphogenetic protein (BMP) signaling in FOP.

Communicating Oncologic Prognosis With Empathy: A Pilot Study of a Novel Communication Guide

Background:

Clear communication between patients, families, and health-care providers is imperative to maximize patient outcomes, particularly for patients diagnosed with incurable cancer who require prompt engagement in decision-making. In response to the need to engage in quality patient-centered communication, an interprofessional team, representing medicine, nursing, social work, spiritual care, and clinical psychology, explored extant literature and developed a simple, single-page communication guide that summarizes the prognosis for patients with incurable cancers. The tool was specifically designed to enhance communication for patients, families, and across all members of the treatment and patient support team.

Purpose:

The purpose of this pilot study was to evaluate the impact of the communication guide on patient’s accurate understanding of prognosis and the feasibility and acceptability of the intervention.

Methods:

The study employed a sequential explanatory mixed-method design. Using pre- and post-tests, participants completed a prognosis and treatment perception survey and were randomized into control or intervention groups based on preference for prognostic information. The oncologist utilized the communication guide with the participants in the intervention group. Finally, 6-week post-test surveys were completed, followed by an exit interview.

Results:

Key findings revealed participants prefer receiving detailed information about prognosis and have differing perceptions compared to the oncologists. Understandings of prognosis for patients and oncologists became more congruent following use of the communication guide. Participants found the tool useful and helpful.

Conclusions:

The communication tool serves as a promising mechanism to enhance patient-centered communication about prognosis for patients with incurable cancer.

Elevated BMP and Mechanical Signaling Through YAP1/RhoA Poises FOP Mesenchymal Progenitors for Osteogenesis

Fibrodysplasia ossificans progressiva (FOP) is a rare genetic disease characterized by the formation of extraskeletal bone, or heterotopic ossification (HO), in soft connective tissues such as skeletal muscle. All familial and sporadic cases with a classic clinical presentation of FOP carry a gain-of-function mutation (R206H; c.617 G > A) in ACVR1, a cell surface receptor that mediates bone morphogenetic protein (BMP) signaling. The BMP signaling pathway is recognized for its chondro/osteogenic-induction potential, and HO in FOP patients forms ectopic but qualitatively normal endochondral bone tissue through misdirected cell fate decisions by tissue-resident mesenchymal stem cells. In addition to biochemical ligand-receptor signaling, mechanical cues from the physical environment are transduced to activate intracellular signaling, a process known as mechanotransduction, and can influence cell fates. Utilizing an established mesenchymal stem cell model of mouse embryonic fibroblasts (MEFs) from the Acvr1R206H/+ mouse model that mimics the human disease, we demonstrated that activation of the mechanotransductive effectors Rho/ROCK and YAP1 are increased in Acvr1R206H/+ cells. We show that on softer substrates, a condition associated with low mechanical signaling, the morphology of Acvr1R206H/+ cells is similar to the morphology of control Acvr1+/+ cells on stiffer substrates, a condition that activates mechanotransduction. We further determined that Acvr1R206H/+ cells are poised for osteogenic differentiation, expressing increased levels of chondro/osteogenic markers compared with Acvr1+/+ cells. We also identified increased YAP1 nuclear localization in Acvr1R206H/+ cells, which can be rescued by either BMP inhibition or Rho antagonism. Our results establish RhoA and YAP1 signaling as modulators of mechanotransduction in FOP and suggest that aberrant mechanical signals, combined with and as a result of the increased BMP pathway signaling through mutant ACVR1, lead to misinterpretation of the cellular microenvironment and a heightened sensitivity to mechanical stimuli that promotes commitment of Acvr1R206H/+ progenitor cells to chondro/osteogenic lineages.

Exploring End-of-Life Care Team Communication: An Interprofessional Simulation Study

Effective team communication is necessary for the provision of high-quality health care. Yet, recent graduates from diverse health-care disciplines report inadequate training in communication skills and end-of-life care. This study explored the impact of a withdrawal of life-sustaining measures interprofessional simulation on team communication skills of students representing medicine, nursing, and social work. The 3-phase simulation required teams to communicate with the patient, family, and one another in the care of a seriously ill patient at the end of life. Team communication in the filmed simulations was analyzed via the Gap-Kalamazoo Communication Checklist. Results revealed fair to good communication across the 9 communication domains. Overall team communication was strongest in “shares information” and lowest in “understands the patient’s and family’s perspective” domains. Field notes revealed 5 primary themes— Team Dynamics, Awkwardness, Empathy is Everything, Build a Relationship, and Communicating Knowledge When You Have It—in the course of the data analysis. Logistical challenges encountered in simulation development and implementation are presented, along with proposed solutions that were effective for this study. This simulation provided an opportunity for interprofessional health-care provider students to learn team communication skills within an end-of-life care context.

ACVR1R206H FOP mutation alters mechanosensing and tissue stiffness during heterotopic ossification

An activating bone morphogenetic proteins (BMP) type I receptor ACVR1 (ACVR1^R206H) mutation enhances BMP pathway signaling and causes the rare genetic disorder of heterotopic (extraskeletal) bone formation fibrodysplasia ossificans progressiva. Heterotopic ossification frequently occurs following injury as cells aberrantly differentiate during tissue repair. Biomechanical signals from the tissue microenvironment and cellular responses to these physical cues, such as stiffness and rigidity, are important determinants of cell differentiation and are modulated by BMP signaling. We used an Acvr1^R206H/+ mouse model of injury-induced heterotopic ossification to examine the fibroproliferative tissue preceding heterotopic bone and identified pathologic stiffening at this stage of repair. In response to microenvironment stiffness, in vitro assays showed that Acvr1^R206H/+ cells inappropriately sense their environment, responding to soft substrates with a spread morphology similar to wild-type cells on stiff substrates and to cells undergoing osteoblastogenesis. Increased activation of RhoA and its downstream effectors demonstrated increased mechanosignaling. Nuclear localization of the pro-osteoblastic factor RUNX2 on soft and stiff substrates suggests a predisposition to this cell fate. Our data support that increased BMP signaling in Acvr1^R206H/+ cells alters the tissue microenvironment and results in misinterpretation of the tissue microenvironment through altered sensitivity to mechanical stimuli that lowers the threshold for commitment to chondro/osteogenic lineages.

Loss of RhoA promotes skin tumor formation and invasion by upregulation of RhoB

Cellular movement is controlled by small GTPases, such as RhoA. Although migration is crucial for cancer cell invasion, the specific role of RhoA in tumor formation is unclear. Inducing skin tumors in mice with a keratinocyte-restricted loss of RhoA, we observed increased tumor frequency, growth and invasion. In vitro invasion assays revealed that in the absence of RhoA cell invasiveness is increased in a Rho-associated protein kinase (ROCK) activation and cell contraction-dependent manner. Surprisingly, loss of RhoA causes increased Rho signaling via overcompensation by RhoB because of reduced lysosomal degradation of RhoB in Gamma-aminobutyric acid receptor-associated protein (GABARAP)+ autophagosomes and endosomes. In the absence of RhoA, RhoB relocalized to the plasma membrane and functionally replaced RhoA with respect to invasion, clonogenic growth and survival. Our data demonstrate for the first time that RhoA is a tumor suppressor in 7,12-dimethylbenz[a]anthracene/12-O-tetradecanoylphorbol 13-acetate skin carcinogenesis and identify Rho signaling dependent on RhoA and RhoB as a potent driver of tumor progression.

Osterix/Sp7 limits cranial bone initiation sites and is required for formation of sutures

During growth, individual skull bones overlap at sutures, where osteoblast differentiation and bone deposition occur. Mutations causing skull malformations have revealed some required genes, but many aspects of suture regulation remain poorly understood. We describe a zebrafish mutation in osterix/sp7, which causes a generalized delay in osteoblast maturation. While most of the skeleton is patterned normally, mutants have specific defects in the anterior skull and upper jaw, and the top of the skull comprises a random mosaic of bones derived from individual initiation sites. Osteoblasts at the edges of the bones are highly proliferative and fail to differentiate, consistent with global changes in gene expression. We propose that signals from the bone itself are required for orderly recruitment of precursor cells and growth along the edges. The delay in bone maturation caused by loss of Sp7 leads to unregulated bone formation, revealing a new mechanism for patterning the skull and sutures.

Abstract OT3-02-02: ROSCO: A randomised phase III, stratified CEP17/TOP2A biomarker trial of neo-adjuvant 5-flourouracil, epirubicin and cyclophosphamide vs docetaxel and cyclophosphamide chemotherapy

Background: Patients with high risk early breast cancer undergoing chemotherapy are frequently treated with both anthracycline and taxane-based chemotherapy exposing patients to multiple toxicities. Molecular predictors of response to specific chemotherapy agents are emerging. Abnormal duplication of the centromeric region of chromosome 17 (CEP17) and either Topoisomerase 2A (TOP2A) gene amplification or deletion, have been identified in a recent meta-analysis as potent markers of anthracycline sensitivity (Bartlett et al JCO 2015). The ROSCO study has been designed to prospectively test the utility of these markers to select anthracycline or taxane based chemotherapy in the neoadjuvant setting.

Key entry criteria: Confirmed invasive breast cancer; centrally confirmed CEP17 duplication and TOP2A status; primary tumour&gt;2cms or documented axillary node metastasis Exclusion criteria include breast cancer with good risk features i.e. Grade 1/2 ER PR rich (Q score 7/8), HER2 negative tumours.

Study treatment: Patients will undergo central testing for CEP-17 and TOP2A and be randomised to 4 cycles of FEC100 (5-Flourouracil 500mg/m2 Epirubicin 100mg/m2 cyclophosphamide 600mg/m2) or 4 cycles of TC (Docetaxel 75mg/m2 Cyclophosphamide 600 mg/m2). Following chemotherapy patients will undergo surgical resection, (Institutional standard). Patients with residual invasive cancer will receive 4 cycles of the alternative chemotherapy to that received in the neoadjuvant setting. HER2 positive patients will receive concurrent trastuzumab and continue standard adjuvant trastuzumab. . Patients with biopsy proven axillary node metastases will undergo combined blue dye and radioisotope tracer guided sentinel lymph node biopsy (SLNB) and axillary lymph node clearance as a single procedure during breast surgery. Adjuvant endocrine and radiation therapy will be Institutional standard

Endpoints: The primary endpoint is pathological complete response (no invasive disease in breast or axilla (pCR)). Secondary endpoints include: clinical and radiological response; rate of breast conservation; patient reported outcomes; safety, tolerability and long term outcomes. In patients with proven nodal involvement the false negative rate of a negative post treatment SLNB compared to axillary node clearance will be reported.

Sample size and stratification: 1050 patients will be randomised in a 1:1 ratio stratified by nodal status, ER, HER2, and biomarker status (CEP-17 amplified or TOP2A amplified/deleted) vs normal (CEP-17 normal TOP2A normal).

Analysis: The primary analysis will assess the interaction between the treatment effect and CEP17/TOP2A status to determine if a differential treatment effect exists between CEP17/TOP2A Normal and CEP17/TOP2A Abnormal patients. pCR will be analysed using a logistic regression model including co-variates for treatment, CEP17/TOP2A status and an interaction term of the two effects Sample size is based on the ability to detect an absolute improvement in pCR in the biomarker abnormal group from 21% in the TC treated group to 30% in the FEC treated group. With 90% power at 10% significance level.

Contact Information: the ROSCO Trial Office ROSCO@trials.bham.ac.uk.

Citation Format: Rea DW, Haywood L, Francis AM, Bowden SJ, Brookes CM, MacKenzie M, Cameron D, Stein R, Earl HM, Thomas J, Abraham J, Stanley A, Starczinski J, McGoldrick T, Treharne-Jones P, Billingham L, Bartlett JM. ROSCO: A randomised phase III, stratified CEP17/TOP2A biomarker trial of neo-adjuvant 5-flourouracil, epirubicin and cyclophosphamide vs docetaxel and cyclophosphamide chemotherapy. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr OT3-02-02.

Hepatitis E virus in patients with decompensated chronic liver disease: a prospective UK/French study

BACKGROUND

In developed countries, hepatitis E is a porcine zoonosis caused by hepatitis E virus (HEV) genotype 3. In developing countries, hepatitis E is mainly caused by genotype 1, and causes increased mortality in patients with pre-existing chronic liver disease (CLD).

AIM

To determine the role of HEV in patients with decompensated CLD.

METHODS

Prospective HEV testing of 343 patients with decompensated CLD at three UK centres and Toulouse France, with follow-up for 6 months or death. IgG seroprevalence was compared with 911 controls.

RESULTS

11/343 patients (3.2%) had acute hepatitis E infection, and three died. There were no differences in mortality (27% vs. 26%, OR 1.1, 95% CI 0.28-4.1), age (P = 0.9), bilirubin (P = 0.5), alanine aminotransferase (P = 0.06) albumin (P = 0.5) or international normalised ratio (P = 0.6) in patients with and without hepatitis E infection. Five cases were polymerase chain reaction (PCR) positive (genotype 3). Hepatitis E was more common in Toulouse (7.9%) compared to the UK cohort (1.2%, P = 0.003). HEV IgG seroprevalence was higher in Toulouse (OR 17, 95% CI 9.2-30) and Truro (OR 2.5, 95% CI 1.4-4.6) than in Glasgow, but lower in cases, compared to controls (OR 0.59, 95% CI 0.41-0.86).

CONCLUSIONS

Hepatitis E occurs in a minority of patients with decompensated chronic liver disease. The mortality is no different to the mortality in patients without hepatitis E infection. The diagnosis can only be established by a combination of serology and PCR, the yield and utility of which vary by geographical location.

A rare human syndrome provides genetic evidence that WNT signaling is required for reprogramming of fibroblasts to induced pluripotent stem cells

WNT signaling promotes the reprogramming of somatic cells to an induced pluripotent state. We provide genetic evidence that WNT signaling is a requisite step during the induction of pluripotency. Fibroblasts from individuals with focal dermal hypoplasia (FDH), a rare genetic syndrome caused by mutations in the essential WNT processing enzyme PORCN, fail to reprogram with standard methods. This blockade in reprogramming is overcome by ectopic WNT signaling and PORCN overexpression, thus demonstrating that WNT signaling is essential for reprogramming. The rescue of reprogramming is critically dependent on the level of WNT signaling: steady baseline activation of the WNT pathway yields karyotypically normal iPSCs, whereas daily stimulation with Wnt3a produces FDH-iPSCs with severely abnormal karyotypes. Therefore, although WNT signaling is required for cellular reprogramming, inappropriate activation of WNT signaling induces chromosomal instability, highlighting the precarious nature of ectopic WNT activation and its tight relationship with oncogenic transformation.

Effect of feeding fescue seed containing ergot alkaloid toxins on stallion spermatogenesis and sperm cells

The cellular effects of tall fescue grass-associated toxic ergot alkaloids on stallion sperm and colt testicular tissue were evaluated. This was a continuation of an initial experiment where the effects of toxic ergot alkaloids on the stallion spermiogram were investigated. The only spermiogram parameter in exposed stallions that was affected by the toxic ergot alkaloids was a decreased gel-free volume of the ejaculate. This study examined the effect of toxic ergot alkaloids on chilling and freezing of the stallion sperm cells. The effect of toxic ergot alkaloids on chilled extended sperm cells for 48 h at 5°C was to make the sperm cells less likely to undergo a calcium ionophore-induced acrosome reaction. The toxic ergot alkaloids had no effect on the freezability of sperm cells. However, if yearling colts were fed toxic ergot alkaloids, then the cytological analysis of meiotic chromosome synapsis revealed a significant increase in the proportion of pachytene spermatocytes showing unpaired sex chromosomes compared to control spermatocytes. There was little effect of ergot alkaloids on adult stallions, but there might be a significant effect on yearling colts.

Expert opinion on the use of anthracyclines in patients with advanced breast cancer at cardiac risk

Anthracyclines are considered to be among the most active agents for the treatment of breast cancer. However, their use is limited by cumulative, dose-related cardiotoxicity. Such cardiotoxicity results in a permanent loss of cardiac myocytes and a progressive reduction in cardiac function following each subsequent dose of anthracycline. Initially, damage to the heart is subclinical; however, increasingly impaired cardiac function can result in cardiovascular symptoms, with serious cardiac injury resulting in chronic heart failure. Since the early detection and treatment of cardiotoxicity can reduce its clinical effects, it is important that oncologists are aware of these adverse effects and manage them appropriately. This review examines the risk factors for anthracycline-associated cardiotoxicity and offers recommendations on strategies to reduce the cardiotoxicity of anthracyclines in the management of patients with advanced breast cancer.

Factors affecting the attrition of community-directed distributors of ivermectin, in an onchocerciasis-control programme in the Imo and Abia states of south-eastern Nigeria

In areas of Nigeria where onchocerciasis is endemic, community-directed distributors (CDD) distribute ivermectin annually, as part of the effort to control the disease. Unfortunately, it has been reported that at least 35% of the distributors who have been trained in Nigeria are unwilling to participate further as CDD. The selection and training of new CDD, to replace those unwilling to continue, leads to annual expense that the national onchocerciasis-programme is finding difficult to meet, given other programme priorities and the limited resources. If the reported levels of attrition are true, they seriously threaten the sustainability of community-directed treatment with ivermectin (CDTI) in Nigeria. In 2002, interviews were held with 101 people who had been trained as CDD, including those who had stopped serving their communities, from 12 communities in south-eastern Nigeria that had high rates of CDD attrition. The results showed that, although the overall reported CDD attrition was 40.6%, the actual rate was only 10.9%. The CDD who had ceased participating in the annual rounds of ivermectin blamed a lack of incentives (65.9%), the demands of other employment (14.6%), the long distances involved in the house-to-house distribution (12.2%) or marital duties (7.3%). Analysis of the data obtained from all the interviewed CDD showed that inadequate supplies of ivermectin (P<0.01), lack of supervision (P<0.05) and a lack of monetary incentives (P<0.001) led to significant increases in attrition. Conversely, CDD retention was significantly enhanced when the distributors were selected by their community members (P<0.001), supervised (P<0.001), supplied with adequate ivermectin tablets (P<0.05), involved in educating their community members (P<0.05), and/or involved in other health programmes (P<0.001). Although CDD who were involved in other health programmes were relatively unlikely to cease participating in the distributions, they were more likely to take longer than 14 days to complete ivermectin distribution than other CDD, who only distributed ivermectin. Data obtained in interviews with present and past CDD appear vital for informing, directing, protecting and enhancing the performance of CDTI programmes, in Nigeria and elsewhere.

A review of internal medicine re-admissions in a peri-urban South African hospital

OBJECTIVE

To measure the re-admission rate and the number of preventable re-admissions in a secondary-level South African hospital, and to identify factors predictive of re-admission.

METHOD

The admission register for the medical wards at Cecilia Makiwane Hospital (CMH) was used to identify re-admitted patients, whose folders were then reviewed. A comparison group of patients who were not re-admitted was randomly generated from the same register.

RESULTS

The re-admission rate for the 7 months ending October 2006 was 8.5% (262/3 083). Patients who were more likely to be re-admitted had chronic respiratory disease (odds ratio (OR) 4.2, 95% confidence interval (CI) 1.2 - 14.6), HIV infection (OR 5.0, CI 2.1 - 12.0), were older than 50 years (OR 5.2, CI 2.5 - 10.9), had a first admission of more than 8 days (OR 3.2, CI 1.5 - 6.6) or a booked medical outpatients followup (OR 5.1, CI 2.6 - 10.3). Age distribution of re-admissions was bimodal, with HIV-positive individuals (27.4% overall) accounting for 50% of all admissions younger than 50 years, but only 9.1% of those 50 years or older. In individuals older than 50 years, 42.1% of admissions were due to chronic cardiorespiratory illnesses. Half of re-admissions were judged to be potentially preventable, mainly through improved patient education.

CONCLUSION

One in 12 general medical patients was readmitted. Chronic diseases and inadequate patient education and discharge planning accounted for the largest group of re-admissions in older patients. Re-admission of HIV/AIDS patients has generated a second peak in younger individuals, and the impact of the antiretroviral roll-out on admission rates warrants further scrutiny.

Studies using Teladorsagia circumcincta in an in vitro direct challenge method using abomasal tissue explants

An in vitro direct challenge (IVDC) method in which abomasal tissue explants maintained at 37 degrees C in Hanks/Hepes solution (pH 7.6) in a high oxygen concentration (incubator gassed with pure oxygen and sealed prior to use) were-challenged with exsheathed third stage larvae of Teladorsagia circumcincta has been used to investigate the tissue association phase of larval establishment. Studies using naïve and recently challenged immune sheep and goat abomasal tissues have shown significant reductions (P < 0.05) in the numbers of tissue associated larvae in material from immune animals. The mechanisms that affect the tissue association process appear to be labile since more larvae were recovered from the tissue digests of previously infected sheep that had not been recently exposed to larval challenge in comparison to those that had been recently challenged (P < 0.05). The method has also been used to demonstrate the influence of protein nutrition on the establishment of larvae in abomasal tissues and region specific differences in the efficacy of exclusion mechanisms. The technique appears to have potential as a means of investigating the crucial first phase of the process of establishment.

A pilot study of adjuvant intraperitoneal 5-fluorouracil using 4% icodextrin as a novel carrier solution

AIM

This pilot study utilised the sustained intraperitoneal (i.p.) dwell properties of an iso-osmotic solution of 4% icodextrin to investigate the tolerability, toxicity and feasibility of home-based i.p. 5FU adjuvant chemotherapy following resective surgery for colorectal cancer.

METHODS

Twenty eligible patients (Dukes' stage B and C with potentially curative resection) underwent perioperative Tenckhoff catheter placement. Ten (6 male, 4 female, aged 46-85; mean 67.5 years) received 5FU chemotherapy. After initial flushing and gradual increase in volumes of 4% icodextrin alone, patients received home-based i.p. 5FU (150-300 mg/m(2)/day given as equal doses at 12-hourly intervals) for 14 days, with a 14-day recovery period, for a maximum of 6 courses. Two incurable patients, treated on compassionate grounds, provided further safety data.

RESULTS

Nine of the 10 patients became proficient in self-treatment with 5FU and two completed 6 courses. Frequent abdominal pain was the main dose-limiting toxicity of 5FU, causing withdrawal of three patients after a high (300 mg/m(2)/day) first course and one following a third course at lower doses. I.p. 5FU concentrations (mean>30000 ngml(-1)) were 1000 fold higher than systemic venous levels. Bacterial peritonitis led to two withdrawals but was not a frequent event (microbiologically confirmed incidence of 1 per 27 catheter-months).

CONCLUSIONS

Home-based i.p. adjuvant chemotherapy is a feasible treatment option in patients with surgically resected colorectal carcinoma.

Senescence and the healing rates of venous ulcers

OBJECTIVE

Premature cellular senescence has been linked to venous hypertension and may contribute to delayed healing of venous ulcers. We hypothesized that the percentage of senescent cells in in vitro populations of fibroblasts isolated from venous ulcers is directly related to the clinical time-to-healing.

METHODS

Biopsy specimens were obtained from ulcer margins and unaffected dermal tissue of the ipsilateral thigh of seven patients with active venous ulcers. Using explant culture techniques, we obtained populations of wound fibroblasts and normal fibroblasts. The percentage of senescence in these cell populations was determined with X-Gal (5-bromo-4-chloro-3-indolyl beta-D-galactoside), which was used as a stain for B-galactosidase, a biomarker for senescent dermal fibroblasts. The X-Gal stain is a peroxidase stain for B-galactosidase. All patients in the study were treated with compression dressings. On a weekly basis, digital images were taken until ulcers healed. Planimetric healing rates were calculated from these images, and an overall time-to-healing was recorded. All cytologic investigations were performed on first passage cells.

RESULTS

The average starting ulcer size was 4.2 cm2. Five of the data points represented healed ulcers. The two remaining patients withdrew from the study to pursue other therapies after having been treated with compression dressings for a long time. Linear regression analysis of healed ulcers identified a relationship between percent of senescence and time-to-healing, which was statistically significant (R2 = 0.81, P =.037). High percentages of senescent cells also had a correlation with slowed planimetric healing, which was not statistically significant.

CONCLUSIONS

This study demonstrates a clinical correlation between quantitative in vitro senescence and time-to-healing. A percentage of senescence that is greater than 15% in populations of cells isolated from venous ulcers may identify a "difficult to heal" ulcer. There is no good clinical indicator for determining the likelihood of ulcer healing, but these results indicate that senescence percentage may have potential in this regard.

An anterior tibial artery aneurysm in a patient with neurofibromatosis

Von Recklinghausen's Type 1 neurofibromatosis (NF) is a genetic disorder of neuroectodermal tissue. Arterial involvement has also been recognized. Stenotic lesions predominate, but aneurysms have been documented as well. Aortoiliac, visceral, and cervical aneurysms are well represented in the literature. Rarely noted, however, have been peripheral aneurysms. Typically in more proximal vessels, subclavian, femoral, and popliteal aneurysms have been mentioned. We present the case of a patient with type 1 NF and an anterior tibial artery aneurysm that was subsequently resected. neurofibromatous invasion of the vessel was confirmed by means of pathological tests. We think this is the first reported case of a tibial artery aneurysm associated with NF.

Cardiac myosin autoantibodies and acute rejection after heart transplantation in patients with dilated cardiomyopathy

OBJECTIVES

To determine whether humoral autoimmune responses associated with dilated cardiomyopathy (DCM) influence the postoperative clinical course following cardiac transplantation.

METHODS

ELISA levels of preformed cardiac myosin (CM) autoantibodies (Abs) in patients with a pretransplant diagnosis of dilated cardiomyopathy (DCM) (n=64) and ischemic heart disease (IHD, n=53) were correlated with cardiac rejection, immunosuppression, and the incidence of endocardial infiltrates after transplantation.

RESULTS

Alpha- and beta-CM autoantibody (IgG and IgM) levels were similar in DCM and IHD patients but were statistically higher than in controls. Distribution of preformed (beta-CM) IgM-Abs in patients with and without rejection in the first postoperative year differed in the two groups. DCM patients rejected earlier P=0.006, and the frequency of rejection at 3 months was statistically higher than in IHD patients. Frequency and reactivity of IgM-Abs in DCM patients with rejection [International Society for Heart and Lung Transplant (ISHLT) grade I and above] was 28% compared with 7% in rejection-free patients, P<0.05. IgM-positive patients had a greater frequency and severity of rejection episodes and required more immunosuppression. These patients had rejection earlier than Ab-negative patients, P<0.009. There was no correlation between antibody status and rejection in IHD patients or with IgG in either group. Distribution of IgG subclass differed in the two diseases. DCM patients had significantly higher IgG3 reactivity; 70% of this activity was present in patients who developed moderate rejection. IgG3-positive patients experienced more frequent rejections, as well as a greater incidence of grade 3A/B rejection as the first episode, than did Ab-negative patients (50% vs. 15%), P<0.05. Frequency of endocardial infiltrates was statistically higher in IgG3-positive patients.

CONCLUSION

Proinflammatory characteristics of preformed IgG3 and IgM antibodies in DCM patients may influence the frequency and severity of cardiac rejection after transplantation.

The potential use of laser capture microdissection to selectively obtain distinct populations of cells for proteomic analysis--preliminary findings

Proteomics-based studies offer a powerful complementary approach to DNA/RNA-based investigations and are now being applied to investigate aspects of many diseases including cancer. However, the heterogeneous nature of tissue samples often makes interpretation difficult. We have undertaken a study into the potential use of a novel laser capture microdissection (LCM) system to isolate cells of interest for subsequent proteomic analysis. Retrieval of selected cells is achieved by activation of a transfer film placed in contact with a tissue section, by a laser beam (30 or 60 microm diameter) which is focused on a selected area of tissue using an inverted microscope. The precise area of film targeted by the laser bonds to the tissue beneath it and these cells are then lifted free of surrounding tissue. Although the technique has been shown to be readily compatible with subsequent analysis of nucleic acids, little information is yet available regarding the application of protein-based analyses to the captured tissue. We report here preliminary data regarding the potential use of the LCM system in combination with two-dimensional electrophoresis to examine protein profiles of selected tissue areas. Electrophoretic profiles of proteins from normal and malignant renal tissue samples showed little change following LCM, nine selected proteins showed identical mass spectrometric sequencing profiles, and two selected proteins retained antigenicity. Dissection of epithelial tissue from a sample of normal human cervix resulted in enrichment of some proteins compared with analysis of the whole tissue. LCM will be a valuable adjunct to proteomic studies although further detailed validation is necessary.

Fibroblasts cultured from distal lower extremities in patients with venous reflux display cellular characteristics of senescence

PURPOSE

Venous reflux precedes the development of venous ulcers. Our earlier work showed that the fibroblasts that are cultured from these wounds display more characteristics of senescence. We evaluated fibroblast senescence in patients with venous reflux but without ulcers to further investigate the role of venous reflux in the predisposition to venous ulcers.

METHODS

Fibroblasts that were isolated from skin biopsy specimens of the "gaiter" area (distal) and of the ipsilateral thigh of the same patient (proximal) were compared. Twelve patients with venous reflux (9 patients in clinical, etiologic, anatomic, and pathologic classification 4; 3 patients in classification 5) with an average venous filling index of 5.45 mL/s and 4 patients without venous reflux were enrolled in the study. The growth rates, the response to basic fibroblast growth factor (b-FGF), and the senescence markers (beta-galactosidase activity at a pH level of 6, unstimulated fibroblasts fibronectin protein, and messenger RNA levels) were determined for each cell population.

RESULTS

The number of senescence-associated beta-galactosidase positive cells (8.3% +/- 1.9% vs 2.2% +/- 0.8%; P =.008) and the level of cellular fibronectin protein (455.7 +/- 80 vs 210 +/- 51; P =.04) and messenger RNA (16.8 +/- 6.8 vs 13.5 +/- 5.7; P =.042) were significantly higher in the distal fibroblasts as compared with the proximal fibroblast cultures. The growth rates of the distal fibroblasts were lower when compared with the proximal fibroblasts (15,746 +/- 4287 cells/day vs 29,550 +/- 5035 cells/day; P <.002) but were not different in the presence of b-FGF (41,717 +/- 9542 cells/day vs 47,030 +/- 6133 cells/day; P =.53). In the patients without venous reflux, no site differences were noted in the growth rates or the senescence markers between the proximal and distal fibroblasts.

CONCLUSION

Distal fibroblasts that are isolated from patients with venous reflux display more senescence characteristics than do proximal fibroblasts and have significantly lower growth rates. Despite senescence, b-FGF restored the distal-fibroblasts growth rate to that of the stimulated proximal fibroblasts, which proposes a therapeutic role for b-FGF. These changes precede ulcer formation and suggest a mechanism that is focal and intrinsically related to venous reflux.

Fibroblasts cultured from venous ulcers display cellular characteristics of senescence

PURPOSE

A well-recognized characteristic of venous ulcers is impaired healing. Fibroblasts cultured from venous ulcers (wound-fb) have been shown to have reduced growth rates and are larger than normal fibroblasts (normal-fb) from the ipsilateral limb. Reduced growth capacity and morphologic changes are 2 well-known traits of cellular senescence. Other molecular changes are overexpression of matrix proteins, such as cellular fibronectin (cFN), and enhanced activity of beta-galactosidase at pH of 6.0 (senescence associated beta-Gal, or SA-beta-Gal). Senescence, an irreversible arrest of cell proliferation with maintenance of metabolic functions, may represent in vivo aging and thus may be related to impaired healing.

METHODS

Cultured normal-fb and wound-fb from 7 venous ulcer patients (average age, 51 years) were obtained by taking punch biopsies of the perimeter of the ulcer and from the ipsilateral thigh of the same patient. Growth rates, SA-beta-Gal activity, and level of cFN protein (immunoblot) and message (Northern blot) were measured.

RESULTS

In all patients, wound-fb growth rates were significantly lower than those of normal-fb (P =.006). A higher percentage of SA-beta-Gal positive cells were found in all wound-fb (average, 6.3% vs. 0.21%; P =.016). The level of cFN, was consistently higher in all wound-fb tested. Also, in 4 patients, the level of cFN messenger RNA (mRNA) was increased.

CONCLUSION

Fibroblasts cultured from venous ulcers exhibited characteristics associated with senescent cells. Accumulation of senescent cell in ulcer environment may be associated with impaired healing.

Release of the angiogenic cytokine vascular endothelial growth factor (VEGF) from platelets: significance for VEGF measurements and cancer biology

Vascular endothelial growth factor (VEGF) is a potent angiogenic factor with a key role in several pathological processes, including tumour vascularization. Our preliminary observations indicated higher VEGF concentrations in serum samples than in matched plasma samples. We have now demonstrated that this difference is due to the presence of VEGF within platelets and its release upon their activation during coagulation. In eight healthy volunteers, serum VEGF concentrations ranged from 76 to 854 pg ml(-1) and were significantly higher (P < 0.01) than the matched citrated plasma VEGF concentrations, which ranged from < 9 to 42 pg ml(-1). Using platelet-rich plasma, mean (s.d.) platelet VEGF contents of 0.56 (0.36) pg of VEGF 10(-6) platelets were found. Immunocytochemistry demonstrated the cytoplasmic presence of VEGF within megakaryocytes and other cell types within the bone marrow. From examination of the effects of blood sample processing on circulating VEGF concentrations, it is apparent that for accurate measurements, citrated plasma processed within 1 h of venepuncture should be used. Serum is completely unsuitable. The presence of VEGF within platelets has implications for processes involving platelet and endothelial cell interactions. e.g. wound healing, and in tumour metastasis, when platelets adhering to circulating tumour cells may release VEGF at points of adhesion to endothelium, leading to hyperpermeability and extravasation of cells.

Ultrasound in the diagnosis and exclusion of intussusception

Intussusception is a major cause of intestinal obstruction in infancy and childhood. Improved results of treatment have followed the increased use of ultrasound imaging and pneumatic reduction. We prospectively studied the value of ultrasound in both the diagnosis and exclusion of intussusception in a peripheral paediatric unit over a four year period from October 1990 to October 1994. In all, 24 patients had a suspected clinical diagnosis of intussusception of which 19 had typical ultrasound findings. The male to female ratio was 8:11 and age at presentation ranged from 2 to 38 months (mean 11.4 months). There were no false negatives and 2 false positives giving a sensitivity to 100% and specificity of 89%. Thus no intussusception was missed by ultrasound examination. Enema reduction was successful in 76% of cases and factors associated with failure of enema reduction included passage of blood per rectum and symptoms for greater than 24 hours. We conclude that ultrasound should be used as a rapid and sensitive screening procedure in the diagnosis and exclusion.

Covert speech behavior during a silent language recitation task

This study tested the prediction that covert speech behavior measured electromyographically from the lips is significantly more prominent during a brief silent-language recitation task than a brief nonlanguage visualization task. Subjects were 20 right-handed, adult volunteers who agreed to participate. Subjects were tested in a multiple-baseline reversal design following an ABAB procedure whereby A1 and A2 were 30-sec. rest periods. B1 and B2 were alternatively assigned 30-sec. silent-language recitation and visualization test periods, respectively. Subjects' dorsal lips and nondominant forearm EMG measures were taken during resting baseline and testing conditions. In addition, subjects' skin surface temperature and heartrate were measured during the rest and test conditions. For the silent-language task, subjects were asked to recite 'mentally' the Pledge of Allegiance to the flag. Subjects were instructed to 'imagine seeing' the American flag for the visualization task. Subjects' mean lip EMG activity increased significantly from rest to the silent-language recitation task, while no significant change in mean lip EMG was observed from rest to the visualization condition.

Prolonged intraperitoneal infusion of 5-fluorouracil using a novel carrier solution

A novel peritoneal carrier solution, Icodextrin 20 (7.5%), has allowed exploration of prolonged, intraperitoneal (i.p.) infusion of the cytotoxic drug 5-fluorouracil (5-FU). A phase I and pharmacokinetic study was performed to determine the toxicities and maximum tolerated dose of prolonged and continuous intraperitoneal 5-FU in patients with peritoneal carcinomatosis. Seventeen patients were entered into this study. Each patient had a Tenckhoff catheter placed into the peritoneal cavity under general anaesthetic. After initial flushing and gradual increase in exchange volumes with Icodextrin 20, 5-FU was administered daily from Monday to Friday, 50% as a bolus in the exchange bag and 50% in an elastomeric infusor device delivering continuous 5-FU to the peritoneal cavity at 2 ml h-1. Treatment was continued for 12 weeks or until intolerable toxicity developed. Abdominal pain and infective peritonitis proved to be the main dose-limiting toxicities. Initial problems with infective peritonitis were overcome by redesign of the delivery system, and it proved possible to deliver 300 mg m-2 5-FU daily (5 days per week) for 12 weeks. Pharmacokinetic studies showed i.p. steady-state 5-FU concentrations (mean 47 500 ng ml-1) that were > 1000-fold higher than systemic venous levels (mean 30 ng ml-1).

Impact of tobacco-free policy on recruitment and retention of adolescents in residential substance abuse treatment

As residential treatment programs consider adopting smoke-free policies, treatment providers question whether such policies interfere with patient recruitment and retention. This study assesses the effect of a smoke-free policy on retention using a sample of 155 low-income, mainly minority youth, randomly assigned to two long-term adolescent residential programs at the New Jersey Substance Abuse Treatment Campus. One of these programs has a smoke-free policy, the other does not. Smoking rates are high for the sample. Eighty-five percent of those adolescents smoke, on average half a pack daily, and 39% smoke a pack or more daily. Differential dropout rates between programs for key time periods related to tobacco withdrawal were analyzed to assess the potential effect of smoking policy on retention. Differential dropout rates at the point of program assignment, in the first two days of residency (p = .43), and for the first two weeks of residency (p = .37) show no differences between programs. While analyses showed heavy smokers are more likely than others to leave treatment early, they were likely to leave from either program regardless of smoking policy. As well, verbal expressions of dissatisfaction with smoking policy did not result in drop outs. These results indicate that smoke-free policies have no detrimental effect on program retention.

The Potential Dependence of the Rate Constant for Charge Transfer at the Semiconductor-Redox Electrolyte Interface

The kinetics of charge transfer at the semiconductor- redox electrolyte interface is described in terms of the Gurney- Gerischer -Marcus (GGM) model by using nuclear configuration potential energy diagrams, electronic configuration potential energy diagrams, density of state distributions and rate constant distributions. The model of identical parabolas for the nuclear configuration diagrams is used; this leads to Gaussian oxidant and reductant distribution functions, g(E), where E is the vertical transition (Franck-Condon) energy. The rate constant distribution, k(E), is obtained from the overlap between occupied and unoccupied state distribution functions of the semiconductor and redox electrolyte. Integration of k(E) gives the rate constant which is calculated as a function of the Helmholtz potential, VH, for various values of the reorganization energy, Ereorg. Three types of semiconductor are considered: intrinsic, doped and highly doped. For intrinsic semiconductors the charge transfer rate constant is relatively small and involves both the conduction and valence bands. For symmetric charge transfer (zero energy change, E0.0, for the reaction) both oxidation and reduction occur between the redox electrolyte and both bands of the semiconductor. For unsymmetrical reactions, charge transfer tends to involve only one of the bands; for net reduction, the valence band is involved, whereas for net oxidation the conduction band is involved. For doped semiconductors the rate constant is larger and only one band is involved; for n-type it is the conduction band, and for p-type it is the valence band. For highly doped semiconductors with the Fermi level in either the conduction or valence bands. the rate constant is even larger and only one band is involved. Changes in Helmholtz potential affect k(E) in a similar way to that for metals. However, unlike for metals, the calculated Tafel plots for highly doped n-type semiconductors are shown to exhibit a Marcus inversion region. This is a consequence of the energy gap between conduction and valence bands of the semiconductor. For doped semiconductors, changes in the Helmholtz potential also produce a maximum in the Tafel plot and because of the relatively low currents involved this maximum should be experimentally observable. For intrinsic semiconductors, variation of Helmholtz potential without inclusion of band bending in the semiconductor produces unexpectedly low Tafel slopes which are related to the ratio of the band gap to the reorganization energy, so that the larger the ratio the smaller the Tafel slope. This unexpected result, which amounts to an assumption of band edge unpinning, is shown to accurately account for the experimentally observed Tafel slopes for reduction at n-WSe2 of the dimethylferrocenium ion in acetonitrile.