Implementation fidelity of the Falls Management Exercise Programme: a mixed methods analysis using a conceptual framework for implementation fidelity.

OBJECTIVES: Falls in older adults cause significant morbidity and mortality and incur cost to health and care services. The Falls Management Exercise (FaME) programme is a 24-week intervention for older adults that, in clinical trials, improves balance and functional strength and leads to fewer falls. Similar but more modest outcomes have been found when FaME is delivered in routine practice. Understanding the degree to which the programme is delivered with fidelity is important if 'real-world' delivery of FaME is to achieve the same magnitude of outcome as in clinical trials. The objective of this study was to examine the implementation fidelity of FaME when delivered in the community to inform quality improvement strategies that maximise programme effectiveness. STUDY DESIGN: A mixed methods implementation study of FaME programme delivery. METHODS: Data from programme registers, expert observations of FaME classes, and semistructured interviews with FaME instructors were triangulated using a conceptual framework for implementation fidelity. Quantitative data were analysed using descriptive statistics. Interviews were transcribed verbatim and analysed using thematic analysis. RESULTS: In total, 356 participants enrolled on 29 FaME programmes, and 143 (40%) participants completed at least 75% of the classes within a programme. Observations showed that 72%-78% of programme content was delivered, and 80%-84% quality criteria were met. Important content that was most often left out included home exercises, Tai Chi moves, and floor work, whereas quality items most frequently missed out included asking about falls in the previous week, following up attendance absence and explaining the purpose of exercises. Only 24% of class participants made the expected strength training progression. Interviews with FaME instructors helped explain why elements of programme content and quality were not delivered. Strategies for improving FaME delivery were established and helped to maintain quality and fidelity. CONCLUSIONS: FaME programmes delivered in the 'real world' can be implemented with a high degree of fidelity, although important deviations were found. Facilitation strategies could be used to further improve programme fidelity and maximise participant outcomes.

Understanding pathways to social inequalities in childhood unintentional injuries: findings from the UK millennium cohort study.

BACKGROUND: Childhood unintentional injuries (UI) are common but continue to happen more often to children living in less advantaged socioeconomic circumstances (SEC). Our aim was to explore how early life factors mediate the association between SEC and UIs, using the UK Millennium Cohort Study. METHODS: We calculated risk ratios (RR) and 95% confidence intervals (95%CI) for parental report of UI occurring between age 3 and 5 years, using Poisson regression according to family income as a measure of SEC. We explored potentially mediating pathways by controlling associations between SEC and UI for groups of early life risks in three domains: factors that may influence environmental safety, supervision and the MCS child's abilities and behaviours. RESULTS: Twenty eight percent of children had a UI from 3 to 5 years old. Children from the lowest income quintile were more likely to be injured compared to those from the highest (RR 1.20 95%CI 1.05, 1.37). Sequentially controlling for early life factors that may influence environmental safety (RR 1.19 95%CI 1.02, 1.38), then supervision (RR 1.18, 95%CI 1.02, 1.36), and finally adding child's behaviour and abilities (RR 1.15, 95%CI 1.00, 1.34) into the model reduced the RR by 5, 10 and 25% respectively. CONCLUSIONS: Addressing factors that may influence environmental safety and supervision, and the child's abilities and behaviours only partly explains the increased UI risk between the highest and lowest income quintiles. Further research is required to explore factors mediating associations between SEC and specific mechanisms and types of injuries.

Keeping active: maintenance of physical activity after exercise programmes for older adults.

OBJECTIVES: To explore factors associated with maintenance of moderate-to-vigorous physical activity (MVPA) in community-dwelling adults aged ≥65 years after completing a 24-week exercise programme. STUDY DESIGN: This is a cohort study nested within a randomised controlled trial evaluating group- and home-based exercise programmes for older people in England. METHODS: MVPA levels and factors potentially associated with physical activity (PA) were self-reported at recruitment, 6, 12, 18 and 24 months after exercise programme. Multilevel logistic regression estimated odds ratios (ORs) for achieving target MVPA level (150 min/week) 6-24 months after exercise programmes ended. RESULTS: Older people (OR per year increase: 0.89, 95% confidence interval [CI] 0.86, 0.93) and women (OR 0.47, 95% CI 0.33, 0.67) were less likely to achieve target MVPA. Those physically active at recruitment (OR 11.28, 95% CI 7.95, 16.01), with wider social networks (OR per unit increase in Lubben Social Network Scale: 1.06, 95% CI 1.03, 1.10) and performing more sit-to-stands in 30 s (OR for quartile 3 compared with quartile 1: 1.87, 95% CI 1.12, 3.10), were more likely to achieve target MVPA. Negative exercise expectations increased the odds of achieving target MVPA but only among the less active at recruitment (OR per unit increase in Outcome and Expectation for Exercise negative subscale: 1.90, 95% CI 1.39, 2.60). Associations did not differ significantly across the follow-up period. CONCLUSION: A range of factors are associated with maintenance of PA 6-24 months after exercise programmes. Factors are not more strongly associated with shorter vs longer term PA maintenance. Commissioners and providers should consider targeting maintenance interventions to those least likely to maintain PA.

Equity of uptake of a diabetic retinopathy screening programme in a geographically and socio-economically diverse population.

OBJECTIVES: At the time of undertaking the audit, the uptake of diabetic retinopathy screening in Derbyshire was 73%, below the national standard of 80%. To assess equity of access to diabetic retinopathy screening in a geographically and ethnically diverse population and determine predictors for poor uptake that will inform service improvements. STUDY DESIGN: Mixed methods health equity audit. METHODS: Postal questionnaires were issued to 1000 people invited for diabetic retinopathy screening in May 2010 and telephone interviews were conducted with subsample of 32 people who had not made a screening appointment. Routine data from the screening programme was used to identify characteristics of people who did not respond to screening invitation. The adjusted odds ratios (OR) and 95% confidence intervals (95% CI) using multivariate methods were calculated in this study. RESULTS: The response rate to the postal questionnaire was 43%. Of these, 28% of respondents did not recall discussing the importance of diabetic retinopathy screening with their primary care team and 11% of people did not understand the term 'diabetic retinopathy'. Non-uptake of screening was associated with deprivation (OR 1.19, 95% CI 1.10-1.29 for those living in the most deprived areas compared to the least deprived) and young people were over three times more likely not to participate than older people (OR 3.13, 95% CI 2.70-3.64 for men under 40 compared to men over 80 and OR 3.03, 95% CI 1.54-5.98 for people with type 1 diabetes under 40 compared to those over 80). CONCLUSIONS: Ensuring that primary care and other health care and third sector organisations convey the importance of diabetic retinopathy screening with patients and improving patients' understanding of the screening programme may improve uptake. Interventions to increase uptake should be targeted to younger people, especially those with type 1 diabetes and people living in more deprived areas.

Investigation of red blood cell and platelet indices in adult dogs suffered from myxomatous mitral valve disease with and without pulmonary hypertension.

Background: Pulmonary hypertension (PH) is a common complication of cardiopulmonary disease. In dogs, PH commonly occurs secondary to myxomatous mitral valve disease (MMVD). Red blood cell and platelet indices including mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), mean corpuscular hemoglobin concentration (MCHC), red cell distribution width (RDW), mean platelet volume (MPV) and platelet distribution width (PDW), have previously been found to be indicators for predicting and prognosing PH in humans. Therefore, this study aimed to investigate whether these indices are associated with MMVD and/or PH in dogs. Methods: Two hundred and forty-six dogs were retrospectively recruited for the study and classified into 4 groups: normal (n = 49), MMVD (n =102), PH (n =17), MMVD+PH (n =78). A sub-analysis was performed in dogs with MMVD without evidence of PH according to stage B1 (n =20), stage B2 (n =15), stage C (n =67). The data are expressed as median (interquartile range). Results and discussion: No significant differences (p < 0.05) were found in MCV, RDW and MPV among all groups (normal, MMVD, PH and MMVD+PH). However, decreases in MCH and MCHC were found in MMVD [22.40 (20.90-23.50) pg and 35.25 (33.08-36.90) g/dL], MMVD+PH [22.25 (20.85-23.98) pg and 35.65 (33.30-37.33) g/dL] and PH groups [21.20 (20.60-22.20) pg and 33.80 (32.75-35.70) g/dL] compared to the normal dogs [24.29 (23.55-24.90) pg and 38.20 (37.50-39.05) g/dL] (p < 0.001). Decreases in PDW were found in dogs in the MMVD+PH [15.10 (14.98-15.30) %] groups compared to dogs in the normal group [15.30 (15.10-15.50) %] (p = 0.004). Sub-analysis of MMVD dogs without PH showed a decrease in MCH in dogs with stage B2 MMVD [21.00 (20.50-22.90) pg] and stage C MMVD [22.40 (20.90-23.20) pg] compared to normal dogs [24.29 (23.55-24.90) pg] (p < 0.001). MCHC of dogs with stage B1 [36.55 (33.53-37.78) g/dL] (p = 0.004), B2 [32.90 (32.00-35.00) g/dL] (p < 0.001) and C MMVD [35.30 (33.30-36.80) g/dL] (p < 0.001) were lower than those of normal dogs [38.20 (37.50-39.05) g/dL]. PDW in the stage C MMVD group [15.10 (15.00-15.30) %] was reduced compared to the normal group [15.30 (15.10-15.50) %] (p = 0.042) and the stage B1 MMVD group [15.35 (15.23-15.68) %] (p = 0.002). MCH, MCHC and PDW were negatively correlated with the left atrial and left ventricular size. Conclusion: Decreases in MCH and MCHC are related to MMVD, precapillary PH and postcapillary PH while PDW are associated with MMVD severity but not with the presence of PH.

Assessment of microcirculation variables and endothelial glycocalyx using sidestream dark field videomicroscopy in anesthetized dogs undergoing cardiopulmonary bypass.

Introduction: To evaluate microcirculation and endothelial glycocalyx (eGC) variables using sidestream darkfield (SDF) videomicroscopy in canine cardiopulmonary bypass (CPB). Methods: Dogs undergoing CPB for surgical correction of naturally-occurring cardiac disease were prospectively included. Variables collected included patient demographics, underlying cardiac disease, red blood cell flow (Flow), 4-25 µm vessel density (Density), absolute capillary blood volume (CBVabs), relative capillary blood volume (CBVrel) and eGC width assessed by perfused boundary region (PBR). Anesthetized healthy dogs were used as control. Microcirculation and eGC variables were compared at baseline under anesthesia (T0), on CPB prior to cross clamping (T1), after cross clamp removal following surgical correction (T2) and at surgical closure (T3). Results: Twelve dogs were enrolled, including 10 with a complete dataset. Median Flow was 233.9, 79.9, 164.3, and 136.1 µm/s at T0, T1, T2, and T3, respectively, (p = 1.00). Median Density was 173.3, 118.4, 121.0 and 155.4 mm/mm2 at T0, T1, T2, and T3, respectively, (p = 1.00). Median CBVabs decreased over time: 7.4, 6.6, 4.8 and 4.7 103µm3 at T0, T1, T2, and T3, respectively, (p < 0.01). Median CBVrel increased over time: 1.1, 1.5,1.1, and 1.3 103µm3 at T0, T1, T2, and T3, respectively, (p < 0.001). Median PBR increased over time: 1.8, 2.1, 2.4, 2.1 µm at T0, T1, T2, and T3, respectively, (p < 0.001). Compared to control dogs (n = 8), CPB dogs had lower CBVabs at T0. Conclusion: Alterations in eGC thickness and microvascular occur in dogs undergoing CPB for naturally-occurring cardiac disease.

Evaluating the effect of child home safety training upon three family support practitioner groups: a mixed-methods study.

AIMS: Unintentional injuries in the home contribute substantially to preschool child morbidity and mortality. Practitioners such as health visitors, family mentors and children's centre staff are well-positioned to facilitate child injury prevention by providing home safety advice to families, and training may enhance their ability to do so. We aimed to assess the impact of child home safety training for these practitioners. METHODS: An explanatory mixed-methods design was used. Practitioners completed questionnaires before, and up to 7 months after, receiving child home safety training and took part in interviews. Seventy-eight health visitors, 72 family mentors and 11 children's centre staff members completed questionnaires. Items were used to calculate scores on home safety knowledge, confidence to provide home safety advice and belief that child home safety promotion is important. Thematic analysis of interviews with seven health visitors and nine family mentors, open-ended responses to the questionnaires and an additional evaluation form was conducted to explore attendees' perceptions of the training and its impact. In addition, seven health visitors and six children's centre staff who had received no training were interviewed. RESULTS: Knowledge was greater post-training than pre-training across all participants (p < .001). When practitioner groups were analysed separately, there were significant increases in family mentors' knowledge (p < .001) and belief (p = .016), and health visitors' confidence (p = .0036). Qualitative findings indicated that most training session attendees valued the training, believed their practice relating to child home safety had improved as a result, and felt further similar training sessions would be beneficial. Those who had not attended the sessions described a need for more child home safety training. CONCLUSIONS: Delivering training to practitioners providing child home safety promotion to families with preschool children can enhance injury prevention knowledge, beliefs and confidence and positively impact on home safety promotion by practitioners.

Local serotonin mediates cyclic strain-induced phenotype transformation, matrix degradation, and glycosaminoglycan synthesis in cultured sheep mitral valves.

This study addressed the following questions: 1) Does cyclic tensile strain induce protein expression patterns consistent with myxomatous degeneration in mitral valves? 2) Does cyclic strain induce local serotonin synthesis in mitral valves? 3) Are cyclic strain-induced myxomatous protein expression patterns in mitral valves dependent on local serotonin? Cultured sheep mitral valve leaflets were subjected to 0, 10, 20, and 30% cyclic strain for 24 and 72 h. Protein levels of activated myofibroblast phenotype markers, α-smooth muscle actin (α-SMA) and nonmuscle embryonic myosin (SMemb); matrix catabolic enzymes, matrix metalloprotease (MMP) 1 and 13, and cathepsin K; and sulfated glycosaminoglycan (GAG) content in mitral valves increased with increased cyclic strain. Serotonin was present in the serum-free media of cultured mitral valves and concentrations increased with cyclic strain. Expression of the serotonin synthetic enzyme tryptophan hydroxylase 1 (TPH1) increased in strained mitral valves. Pharmacologic inhibition of the serotonin 2B/2C receptor or TPH1 diminished expression of phenotype markers (α-SMA and SMemb) and matrix catabolic enzyme (MMP1, MMP13, and cathepsin K) expression in 10- and 30%-strained mitral valves. These results provide first evidence that mitral valves synthesize serotonin locally. The results further demonstrate that tensile loading modulates local serotonin synthesis, expression of effector proteins associated with mitral valve degeneration, and GAG synthesis. Inhibition of serotonin diminishes strain-mediated protein expression patterns. These findings implicate serotonin and tensile loading in mitral degeneration, functionally link the pathogeneses of serotoninergic (carcinoid, drug-induced) and degenerative mitral valve disease, and have therapeutic implications.

Trifoliate left atrioventricular valve with and without intact septal structures in four dogs: echocardiographic findings and surgical repair.

Trifoliate left atrioventricular (AV) valve with common atrioventricular junction is considered part of the spectrum of atrioventricular septal defect. This valve morphology is typically associated with defects in the AV septum resulting in communication at the atrial or ventricular level, but has also been described as an isolated defect in the setting of a common AV junction without AV septal defect. Trifoliate left AV valve exhibits a line of apposition between the bridging leaflets that is directed toward the inlet interventricular septum, distinguishing it from isolated mitral valve cleft in which the orientation of the bridging leaflets are toward the left ventricular outflow tract. The echocardiographic findings of four dogs with trifoliate left AV valve are described; two with intact septal structures and two with large ostium primum defects. Three dogs underwent open surgical repair using different approaches depending on the presence or absence of a septal defect. One of these underwent concurrent surgical repair for right AV valve dysplasia. One dog with intact septal structures underwent interventional closure of a concurrent patent ductus arteriosus. Current terminology associated with trileaflet left AV valve malformations is reviewed.

Clinical use of tissue plasminogen activator for systemic thrombolysis in dogs and cats.

INTRODUCTION: Systemic administration of tissue plasminogen activator (tPA) is seldomly reported in dogs and cats. ANIMALS: Client-owned animals receiving tPA (2010-2020). MATERIALS AND METHODS: Medical records of dogs and cats receiving tPA for distant known/suspected thrombus were reviewed. Fourteen dog visits (24 injections) and five cat visits (six injections) were included. RESULTS: Canine known/suspected thrombus included pulmonary thromboembolism (n=6), intracardiac thrombus (n=4), aortic thrombus (n=1), cranial vena cava thrombus (n=2), and femoral and iliac veins thrombus (n=1). Various canine primary diseases were represented, but open-heart surgery was the most common cause. Median time between diagnosis/suspicion of thrombus and tPA injection was 24.5 h (range, 3-150 h). Mean total tPA dose was 1.0±0.78 mg/kg. Clinical improvement occurred in 93% of dogs. Non-fatal complications were reported in 14% of dogs. Dogs' survival to discharge was 78.6% without identifiable non-survivor characteristics. Feline known/suspected thrombus included unilateral feline aortic thromboembolism (FATE) (n=2), bilateral FATE (n=2), and right renal artery thrombus. Feline primary diseases included cardiomyopathy (n=5). Median time between diagnosis/suspicion of thrombus and tPA injection was 4 h (range, 2-17 h) and median total tPA dose was 1.0 mg/kg (range, 0.6-1.4 mg/kg).Clinical improvement occurred during 40% of the visits. All cats (n=3) with acute kidney injury (AKI) at admission developed worsening AKI and reperfusion injury. Of the remaining two visits, one developed a non-fatal AKI. Cats' survival to discharge was 40%. CONCLUSIONS: Systemic thrombolysis with tPA seems to be effective and safe in dogs. More investigation is needed in cats.

Phase I clinical trial of an antithrombotic drug protocol combining apixaban and clopidogrel in dogs.

INTRODUCTION: Combining an antiplatelet drug, clopidogrel, with the direct oral Factor Xa inhibitor, apixaban, could provide an effective antithrombotic strategy in dogs. Thus, a limited 3 + 3 phase I dose-escalation clinical trial in healthy dogs was conducted to evaluate bleeding (primary end-point) and pharmacodynamic (PD)/pharmacokinetic (PK) parameters (secondary end-point). ANIMALS: Eleven beagle dogs, median body weight 10.2 kg (9.7-10.9 kg), were enrolled. METHODS: Four doses of apixaban (three dogs/dose) administered for eight days. Clopidogrel dose was fixed at 18.75 mg per os (PO) q 24 h with escalation of apixaban dose at 5 mg PO q 12 h, 5 mg PO q 8 h, 10 mg PO q 12 h, and 10 mg PO q 8 h. Laboratory testing included fecal occult blood, coagulation parameters, Factor X activity, apixaban concentration, platelet aggregometry, and thromboelastography on days 1, 3, and 8. RESULTS: Evidence of bleeding was not observed at any dosage. Dose-dependent changes in PD/PK parameters between baseline and 3 h post-medication were observed including a prolongation of prothrombin time, a prolongation of activated partial thromboplastin time, a decrease of Factor X activity level, and increased apixaban concentration. CONCLUSIONS: The combination of apixaban at a dosage range of approximately 0.5 mg/kg PO q 12 h to 1 mg/kg PO q 8 h and clopidogrel at approximately 1.8 mg/kg PO q 24 h did not cause bleeding over a one-week period in healthy dogs. Clinically relevant changes in PD/PK data occur at all dosage levels. This study provides a starting point for longer-term clinical trials to determine safety and efficacy.

Surgical repair for canine tricuspid valve dysplasia: Technique and case report.

Tricuspid valve dysplasia (TVD) is a congenital malformation of the right atrioventricular valve characterized by restricted leaflet motion, annular dilation, and tricuspid regurgitation (TR). Severe cases typically exhibit progressive right-sided congestive heart failure, affecting the quality of life and survival. This article describes a technique for surgical repair of TVD and a case report with long-term follow-up. A 1.5-year-old intact male Labrador retriever with severe TR underwent surgical repair for TVD. Valve repair was performed under cardiopulmonary bypass and consisted of neochord mobilization of the valve leaflets and partial band annuloplasty. Transthoracic echocardiogram performed 5 days after surgery showed mild TR, a 93% decrease in anatomic regurgitant orifice area, and decreased right chamber dimensions. Forty-eight months after repair, the patient was free of clinical signs, did not have a heart murmur, and was receiving no cardiac medications. Based on this case, surgical repair of TVD is feasible with long-term durability, and the outcome suggests that the described technique may be a viable treatment option for patients with severe TVD.

Tissue-gel electrophoresis enhances antigen removal from porcine aortic valve and bovine pericardium.

BACKGROUND AND AIM OF THE STUDY: A tissue-engineered heart valve could provide a living prosthesis with characteristics of an ideal valve replacement. One approach to scaffolding a tissue-engineered heart valve is through the 'decellularization' of xenogeneic tissues. Concerns regarding the completeness of antigen removal associated with current detergent-based decellularization treatments have been raised. The study aim was to evaluate antigen removal from candidate xenogeneic bioscaffolds using a novel tissue-gel electrophoresis (TGE) method. METHODS: Porcine aortic valve (PAV) conduit and bovine pericardium (BP) were treated sequentially with hypotonic lysis, sodium dodecyl sulfate (SDS), and TGE. The completeness of antigen removal was evaluated by immunoblot analysis of extractable soluble proteins using rabbit anti-PAV or anti-BP serum. Tissues were also evaluated by hematoxylin and eosin histology. RESULTS: TGE enhanced antigen removal from both the PAV and BP. The effects of TGE were shown to depend on the SDS concentration and voltage (60 versus 120 V), but to be independent of time after 4 h. The effects of TGE were detectable both before and after 96 h aqueous washout. Treatment with 1.0% SDS with TGE (120 V for 4 h) resulted in complete acellularity and no detectable soluble protein antigens from the PAV conduit. CONCLUSION: TGE is a promising adjunctive decellularization method for generating non-immunoreactive bioscaffolds from xenogeneic tissues.

Tryptophan hydroxylase 1 expression is increased in phenotype-altered canine and human degenerative myxomatous mitral valves.

BACKGROUND AND AIM OF THE STUDY: Serotonin is a known mediator of myxomatous pathology in heart valves. Tryptophan hydroxylase 1 (TPH1) is the limiting enzyme for peripheral serotonin synthesis, and its expression by valve interstitial cells (IC) could implicate an autocrine serotonin signaling mechanism in primary degenerative myxomatous mitral valve disease. Thus, the expression of TPH1 in canine and human myxomatous mitral valves was determined, and IC phenotypes expressing TPH1 identified. METHODS: TPH1 expression was determined in canine and human myxomatous and normal mitral valves by immunoblot (IB) and immunofluorescence microscopy (IFM). Co-localization of TPH1 expression with markers of IC phenotype transformation, alpha-smooth muscle actin (a-SMA) and non-muscle embryonic myosin (SMemb) was determined using double-IFM. RESULTS: TPH1 expression by IB was increased (p < 0.05) by three- to five-fold in canine early-stage and late-stage myxomatous valves, and in human surgically excised myxomatous valves compared to canine and human normal control valves, respectively. The number of TPH1 immunopositive cells per x400 field was increased (p < 0.005) in canine (14.9 +/- 1.2) and human (14.9 +/- 2.9) myxomatous valves compared to canine (5.0 +/- 2.4) and human (2.9 +/- 0.6) normal control valves, respectively. Patterns for alpha-SMA and SMemb IC phenotype transformation were distinctly different in myxomatous valves. TPH1 expression was more closely associated with the SMemb IC phenotype in canine and human myxomatous valves. CONCLUSION: An increased expression of TPH1 in canine and human myxomatous mitral valves implicates an autocrine serotonin signaling mechanism in primary degenerative myxomatous mitral valves. TPH1 expression is associated with the SMemb-positive IC phenotype.

Megavoltage image contrast with low-atomic number target materials and amorphous silicon electronic portal imagers.

Low-atomic number (Z) targets have been shown to improve contrast in megavoltage (MV) images when using film-screen detection systems. This research aims to quantify the effect of low-Z targets on MV image contrast using an amorphous silicon electronic portal image detector (a-Si EPID) through both experimental measurement and Monte Carlo (MC) simulation. Experimental beams were produced with the linac running in the 6 MeV electron mode and with a 1.0 cm aluminum (Al, Z = 13) target replacing flattening filtration in the carousel, (6 MeV/Al). A 2100EX Varian linac equipped with an aS500 EPID was used with the QC3 MV phantom for the majority of contrast measurements. The BEAMnrc/EGSnrc MC package was used to build a model of the full imaging system including beam generation (linac head), the a-Si detector and the contrast phantom. The model accurately reproduces contrast measurements to within 2.5% for both the standard 6 MV therapy beam and the 6 MeV/Al beam. The contrast advantage of 6 MeV/Al over 6 MV, as quantified with the QC3 phantom, ranged from a factor increase of 1.6 +/- 0.1 to 2.8 +/- 0.2. Only a modest improvement in contrast was seen when the incident electron energy was reduced to 4 MeV (up to factor of 1.2 +/- 0.1 over 6 MeV/Al) or with removal of the copper build-up layer in the detector, (up to factor of 1.2 +/- 0.1 over 6 MeV/Al). Further decreasing the target Z, to beryllium (Be, Z = 4), at 4 MeV showed no significant improvement over 4 MeV/Al. Experimentally, the contrast advantage of 6 MeV/Al over 6 MV was found to decrease with increasing patient thickness, as can be expected due to selective attenuation of low-energy photons. At head and neck-like thicknesses, the low-Z advantage is a factor increase of 1.7 +/- 0.1.

Autocrine serotonin and transforming growth factor beta 1 signaling mediates spontaneous myxomatous mitral valve disease.

BACKGROUND AND AIM OF THE STUDY: Although serotonin and serotoninergic drugs are known to cause myxomatous-like valvulopathy, the role of serotonin in spontaneous myxomatous valve disease (MVD) remains unclear. Tryptophan hydroxylase 1 (TPH1) is the limiting enzyme for peripheral serotonin synthesis, and its expression in myxomatous valves could implicate an autocrine serotonin signaling mechanism. Studies in cultured cells demonstrate a close coupling between serotonin and transforming growth factor beta1 (TGFbeta1) signaling. The study aim was to investigate serotonin and TGFbeta1 signaling in spontaneous MVD. METHODS: In canine normal and myxomatous mitral valves, target signaling proteins including TPH1, serotonin 2B receptor (5HT(2B)R), serotonin transmembrane transporter (SERT), total and phosphorylated extracellular signaling-regulated kinase (ERK) 1/2, latent TGFbeta1 and TGFbeta1 receptors I and II, were studied using immunohistochemistry and immunoblot analysis. In human myxomatous valves, TPH1 was determined using immunofluorescence and immunoblot analysis. RESULTS: In canine mitral valves, both 5HT(2B)R and TPH1 were increased in myxomatous valves, whereas SERT, a key protein in serotonin metabolism, was decreased in myxomatous valves. Phosphorylated, but not total, ERK 1/2 was increased in myxomatous valves, consistent with an enhanced active serotonin signaling. The expression of TGFbeta1 receptors I and II, and of latent TGFbeta1, was increased in myxomatous valves. Human myxomatous mitral valves expressed TPH1. CONCLUSION: The expression of TPH1 by canine and human myxomatous valves demonstrates a capacity for local serotonin production. Key signaling protein expression patterns support active serotonin and TGFbeta1 signaling in canine myxomatous valves. These findings implicate an autocrine serotonin and TGFbeta1 mechanism in the pathogenesis of spontaneous MVD.

Immunoblot detection of soluble protein antigens from sodium dodecyl sulfate- and sodium deoxycholate-treated candidate bioscaffold tissues.

BACKGROUND AND AIMS OF THE STUDY: The detergent-based 'decellularization' of xenogeneic tissues is one approach to scaffolding a tissue-engineered heart valve construct; however, concern persists regarding the immunogenicity of decellularized xenogeneic bioscaffolds. The study aims were to: (i) develop a sensitive and robust immunoblot-based assay for the detection of soluble protein antigens in xenogeneic bioscaffolds; and (ii) evaluate the completeness of protein antigen removal from sodium dodecyl sulfate (SDS)- or sodium deoxycholate (SD)-treated bovine pericardium (BP) or porcine aortic valve (PAV) conduit. METHODS: Homogenized BP or PAV were injected into rabbits to generate immune serum towards these tissues. Soluble proteins were extracted from untreated BP and PAV. Immunoblot analyses of the extracts were performed using pre-immune and 14-, 28-, 42-, 56- and 70-day post-immune serum. BP and PAV were treated sequentially with 4 h hypotonic lysis; with 0, 0.01, 0.025, 0.05, 0.1, 0.25 or 0.5% SDS or SD for 24 h; and with 96 h of aqueous wash-out. Immunoblot analyses of protein extracts from treated tissues were performed using 70-day post-immune rabbit serum. RESULTS: Immunoblot analysis of untreated BP or PAV with pre-immune serum showed no immune banding. The immune banding density increased progressively when immunoblots were performed with 14-day through 70-day post-immune serum. The immunoblot analysis of treated BP and PAV showed that soluble protein antigen removal from SDS- or SD-treated tissues was incomplete. CONCLUSION: Immunoblot analysis is a sensitive and robust assay for detecting soluble protein xenogeneic antigens after the decellularization of xenogeneic bioscaffolds. Under the study conditions, hypotonic lysis, SDS or SD detergent treatment, and aqueous wash-out-based decellularization of bovine pericardium and porcine aortic valve conduit did not completely remove detectable protein antigens.

Does sodium dodecyl sulfate wash out of detergent-treated bovine pericardium at cytotoxic concentrations?

BACKGROUND AND AIM OF THE STUDY: The ionic detergent sodium dodecyl sulfate (SDS) is a proposed treatment for the removal of antigenic proteins from unfixed biological scaffolds used in tissue engineering. However, questions remain about possible cytotoxic effects of SDS-treated tissues. The study aims were to: (i) develop a sensitive SDS assay for physiological solutions; (ii) measure SDS concentrations in the washing media of SDS-treated tissue; and (iii) determine cytotoxic SDS concentrations in cultured ovine vascular cells. METHODS: An assay was developed to monitor SDS concentrations at microM levels, based on attenuated total reflectance infrared spectroscopy. Bovine pericardium was treated with SDS (1.0 to 0.01%) and washed for 96 h. The SDS concentration in the washing media was measured at 24-h intervals; data were expressed as microM/g tissue. Ovine vascular cells were cultured in DME media at 37 degrees C for 48 h in various SDS concentrations (10 to 1000 microM). The cells were then counted, and the percentage live cells expressed, based on trypan blue exclusion (n=5). RESULTS: SDS concentrations > or =10 microM significantly reduced (p < 0.05) the total cell number, while concentrations > or =100 microM reduced (p < 0.05) the percentage live cells of ovine vascular cell cultures. SDS was present in the washing media of SDS-treated bovine pericardium. SDS leaching from bovine pericardium was found to depend on the SDS concentration used for the treatment, and diminished with time. CONCLUSION: SDS leaches from SDS-treated bovine pericardium at concentrations that are potentially cytotoxic. An understanding of the dynamics of SDS washout, based on a sensitive SDS assay, may lead to the creation of protocols for the preparation of biological scaffolds that are free from cytotoxic leaching.

Use of fat-fed rats to study the metabolic and vascular sequelae of obesity and beta-adrenergic antagonism.

Obesity-associated cardiovascular disease exerts profound human and monetary costs, creating a mounting need for cost-effective and relevant in vivo models of the complex metabolic and vascular interrelationships of obesity. Obesity is associated with endothelial dysfunction and inflammation. Free fatty acids (FFA), generated partly through beta-adrenergic receptor-mediated lipolysis, may impair endothelium-dependent vasodilation (EDV) by proinflammatory mechanisms. beta-Adrenergic antagonists protect against cardiovascular events by mechanisms not fully defined. We hypothesized that beta antagonists may exert beneficial effects, in part, by inhibiting lipolysis and reducing FFA. Further, we sought to evaluate the fat-fed rat as an in vivo model of obesity-induced inflammation and EDV. Control and fat-fed rats were given vehicle or beta antagonist for 28 d. Serum FFA were measured to determine the association to serum IL6, TNFalpha, and C-reactive protein and to femoral artery EDV. Compared with controls, fat-fed rats weighed more and had higher FFA, triglyceride, leptin, and insulin levels. Unexpectedly, in control and fat-fed rats, beta antagonism increased FFA, yet inflammatory cytokines were reduced and EDV was preserved. Therefore, reduction of FFA is unlikely to be the mechanism by which beta antagonists protect the endothelium. These results reflect the need for validation of ex vivo models of obesity-induced inflammation and endothelial dysfunction, concurrent with careful control of dietary fat composition and treatment duration.

Epicardial pacemaker implantation in small animals.

Epicardial pacemaker implantation can be performed as a lone procedure or in combination with another thoracic or abdominal surgery. This article reviews the current literature and describes a minimally invasive approach for epicardial pacemaker implantation in small animals. The principal advantage of epicardial pacing is that it avoids contact with blood and intracardiac structures and thereby avoids uncommon but potentially devastating complications associated with endocardial pacemaker implantation. Epicardial pacing as a lone procedure can be accomplished via an abdominal transdiaphragmatic or minimal incision thoracotomy approach (minithoracotomy). A minithoracotomy offers the advantages of being less invasive and providing more direct access to the cardiac surface for suturing of epicardial electrodes. Epicardial pacing is a viable option for smaller animals, animals with pre-existing infections, animals at risk for thrombotic complications, or animals undergoing another thoracic or abdominal surgery.