First-principles study of lithium aluminosilicate glass scintillators.

Radiation sensors are an important enabling technology in several fields, such as medicine, scientific research, energy, defence, meteorology, and homeland security. Glass-based scintillators have been in use for more than 50 years and offer many benefits, including their ability to respond to different types of radiation, and to be readily formed into various shapes. There is, however, the prospect to develop new and improved glass scintillators, with low self-absorption, low refractive indices, and high radiative recombination rates. To investigate the factors limiting the improvement of glass scintillator properties, this work provides insight from atomic scale simulations of the cerium-doped lithium aluminosilicate (SiO2-Al2O3-MgO-Li2O-Ce2O3) glass scintillator system. Three glass compositions were studied using molecular dynamics and density functional theory to investigate the effect of the ratio (with RAl/M = [0.1, 0.8 and 1.2]) on the structural and electronic properties. For a ratio RAl/M > 1, it has been shown that glasses with increased polymerization allow for more effective incorporation of Ce3+ cations. The structural analysis also showed that the bond order of Al-O can be affected in the presence of a lithium-rich environment. Electronic density of states and Bader charge analysis indicate a decline in the population of localized trapping states with increasing RAl/M. This suggests a higher probability of radiative recombination which can increase the photon yield of these scintillators. These findings provide valuable guidance for optimizing Li-glasses in neutron detection systems by highlighting the intricate challenges.

Anthracycline-induced cardiotoxicity in patients with early-stage breast cancer: the Canadian Cancer Trials Group (CCTG) MA.21 experience.

PURPOSE: Anthracyclines are frequently used in adjuvant treatment for early-stage breast cancer (ESBC). The purpose of this study was to evaluate cardiotoxic effects in the first five years after treatment with different anthracycline-based regimens. METHODS: CCTG MA.21 (NCT000142) was a phase III trial in ESBC that compared cyclophosphamide (75 mg/m2) orally for 14 days, epirubicin (60 mg/m2) and fluorouracil, IV days one and eight (CEF) for six cycles; dose-dense epirubicin (120 mg/m2) and cyclophosphamide, IV every 2 weeks for six cycles with concurrent G-CSF then paclitaxel every 2 weeks for four cycles (ddEC/T); doxorubicin (60 mg/m2) and cyclophosphamide (600 mg/m2) every 3 weeks for four cycles then four cycles q3 weekly paclitaxel (175 mg/m2) (AC/T). ENDPOINTS: LVEF decline; LV function changes (heart failure), or Grade 3-4 cardiac ischemia/infarction. A competing risk analysis was performed with endpoints of cardiotoxicity or recurrence in first 5 years after completion of chemotherapy. RESULTS: 2104 women were randomized. Compliance with cardiac LVEF assessments was 70% at 5 years in all arms. The 5-year cumulative risks of any cardiac event for CEF, ddECT, and AC/T were 22.3% (95%CI 18.9 to 25.7), 14.2% (95%CI 11.0 to 17.3), and 8.1% (95%CI 5.8 to 10.4), respectively, p < 0.0001. At 5 years, women in the ddEC/T and AC/T group had significantly lower risk of cardiotoxicity than those given CEF (HR 0.599 and 0.371, respectively). Most events were asymptomatic drop in LVEF. CONCLUSIONS: Asymptomatic changes in LVEF accounted for most of the cardiotoxicity. The majority of cardiac events occurred in year one although occurrence of cardiotoxicity over time highlights the need for improved risk stratification to guide cardiac surveillance strategies.

Optimization of a new interatomic potential to investigate the thermodynamic properties of hypo-stoichiometric mixed oxide fuel U1-y Pu y O2-x.

The behaviour of stoichiometric U1-y Pu y O2 compounds used as nuclear fuel is relatively well understood. Conversely, the effects of stoichiometry deviation on fuel performance and fuel stability are intricate and poorly studied. In order to investigate what affect these have on the thermophysical properties of hypo-stoichiometric U1-y Pu y O2-x mixed oxide fuel, new interaction parameters based on the many-body CRG (Cooper-Rushton-Grimes) potential formalism were optimized. The new potential has been fitted to match experimental lattice parameters of U0.70Pu0.30O1.99 (O/M = 1.99) and U0.70Pu0.30O1.97 (O/M = 1.97), where M represents the total amount of metallic cations, through a rigorous procedure combining classical molecular dynamic and classical molecular Monte Carlo simulation methods. This new potential provides an excellent description of the U1-y Pu y O2-x system. Concerning lattice parameter, although fitted on only one Pu content (30%) and two stoichiometries (1.99 and 1.97), our potential allows good predictions compared to available experimental results as well as to available recommendations in wide ranges of O/M ratio, Pu content and temperature. For the U0.70Pu0.30O2-x hypo-stoichiometric system (30% Pu content and O/M ratio ranging from 1.94 to 2.00), some direct properties (lattice parameter and enthalpy) and some derivative properties (linear thermal expansion coefficient and specific heat) were systematically investigated from room temperature up to the expected melting temperatures and a good agreement with experiments is found. Moreover, our potential shows good transferability to the plutonium sesquioxide Pu2O3 system.

Clinical experience of patients referred to a multidisciplinary cardio-oncology clinic: an observational cohort study.

Introduction: Cardiovascular disease is the 2nd leading cause of long-term morbidity and mortality in cancer survivors. Cardio-oncology clinics (cocs) have emerged to address the issue; however, there is a paucity of data about the demographics and clinical outcomes of patients seen in the coc setting. Methods: Cancer patients referred to The Ottawa Hospital coc were included in this retrospective observational study. Data collected were patient demographics, cancer type and stage, reason for referral, cardiac risk factors, cardiac assessments and treatment, and clinical outcomes. Results: Between 2008 and 2015, 779 patients (516 women, 66%; 263 men, 34%) were referred to the coc. Median age of the patients at cancer diagnosis was 60 years (range: 18-90 years). The most frequent reasons for referral were decreased left ventricular ejection fraction (33%), pre-chemotherapy assessment (14%), and arrhythmia (14%). Treatment with cardiac medication was given in 322 patients (41%), 181 (56%) of whom received more than 2 cardiac medications, with 57 (18%) receiving an angiotensin-converting enzyme inhibitor (acei), 46 (14%) receiving an acei and a beta-blocker, and 38 (12%) receiving a beta-blocker. Of 163 breast cancer patients, 129 (79%) were able to complete targeted therapy with coc co-management. Most of the 779 patients (n = 643, 83%) were alive at the time of the last data collection. Conclusions: This cohort study is one of the largest to report characteristics and clinical outcomes of patients referred to a coc. Collaboration between oncologists and cardiologists resulted in completion of cancer therapy in most patients. Ongoing analysis of referral patterns, management plans, and patient outcomes will help to guide the cardiac care of oncology patients, ultimately optimizing cancer and cardiac outcomes alike.

An international survey of healthcare providers' knowledge of cardiac complications of cancer treatments.

BACKGROUND: Cardio-oncology is a young sub-specialty that addresses the needs of cancer patients at risk of, or who have experienced cancer therapy related cardiac dysfunction (CTRCD). This study assessed clinicians' understanding of cardio-oncology, opinions towards current practice, and approach to diagnosing and managing CTRCD. METHODS: A 45-question survey was administered online via Survey Monkey and WeChat to health care providers (HCPs) comprising of cardiologists, oncologists, and others from September 2017 to March 2018. Implementation of the survey followed a modified Dillman's Total Design Method. RESULTS: In total, 160 responses were collected from 22 countries; majority were from cardiologists (53.8%) and oncologists (32.5%). The remaining 13.7% identified themselves as "others," including general internists, cardio-oncologists, pediatric oncologists, radiation oncologists, cardiac rehabilitation therapists, nurse practitioners, research students, and pharmacists. In the setting of metastatic cancer, there was a difference in risk tolerance for cardiotoxicity between subspecialties. In this case, more cardiologists (36.7%) accepted a 5-10% risk of cardiotoxicity compared to oncologists (20.0%). Majority of cardiologists felt that cardiotoxicity should be monitored, even in asymptomatic cancer patients (55.8%). Only 12% of oncologists selected this response. In contrast, 50.0% of oncologists reported that cardiologists should be involved only when patients develop cardiotoxicity. In comparison, 6.5% of cardiologists selected this response. Majority of cardiologists stated that cardio-oncology clinics would significantly improve cancer patients' prognosis (88.3%); only 45.8% of oncologists shared this opinion. Of all respondents, 66.9% stated they were familiar with a variety of international guidelines for managing cardiotoxicity. Of all oncologists, 65.3% indicated that they referred to these guidelines for clinical decision making. CONCLUSIONS: Despite the growth of cardio-oncology clinics, there are significant knowledge gaps regarding prevention and treatment strategies for CTRCD among health care providers. Knowledge translation from guidelines and collaboration between cardiologists and oncologists are needed to improve cardiovascular outcomes of cancer patients.

The Framingham risk score underestimates the risk of cardiovascular events in the HER2-positive breast cancer population.

INTRODUCTION: Patients with breast cancer (bca) who overexpress her2 (the human epidermal growth factor receptor 2) are at risk for cardiotoxicity when treated with anthracycline-based chemotherapy and her2-targeted agents. The Framingham risk score (frs) is a validated tool that stratifies patients into high-, intermediate-, or low-risk groups and calculates their 10-year risk of developing cardiovascular disease (cvd) based on past medical history, systolic blood pressure, and measurement of serum lipids. We retrospectively analyzed patients with her2-positive bca to determine whether the frs predicts adverse cardiovascular (CV) events or cardiotoxicity in patients treated using anthracyclines or her2-targeted therapy, or both. METHODS: The frs was determined for patients with bca referred to The Ottawa Hospital Cardiology-Oncology Clinic from October 2008 to August 2014. The patients were stratified into high (≥20%), intermediate (10%-20%), and low (<10%) 10-year cv risk groups. Primary outcomes included cvd-related hospitalizations and deaths, and cardiotoxicity [drop in left ventricular ejection fraction (lvef) of >10% to a lvef ≤50%]. RESULTS: Of the 152 patients included in the analysis (median follow-up: 40.7 months; range: 3.5-263 months), 47 (31%) were classified as high risk; 36 (24%), as intermediate risk; and 69 (45%), as low-risk. The number of cvd-related hospitalizations and deaths was 22, for an overall prevalence of 14%, with significantly more events occurring in high-risk than in low-risk patients (odds ratio: 4.18; 95% confidence limits: 1.47, 11.89). The frs predicted a 10-year risk of any cv event of 11.2% and underestimated the actual rate of cv events in the entire cohort. High frs was not associated with cardiotoxicity (p = 0.82). CONCLUSIONS: In a population of patients with her2-positive bca referred to a cardiology-oncology clinic, the frs does not accurately predict the risk of cv events or cardiotoxicity.

Trastuzumab-induced cardiotoxicity: testing a clinical risk score in a real-world cardio-oncology population.

BACKGROUND: Trastuzumab has improved survival for women with her2-positive breast cancer, but its use is associated with an increased risk of cardiotoxicity. With increased survivorship, the long-term effects of cancer treatment are an important consideration for clinicians and patients. We reviewed the current literature on predicting trastuzumab-related cardiotoxicity and tested a clinical risk score (crs) in a real-world breast cancer population to assess its utility in predicting permanent cardiotoxicity. METHODS: In this retrospective exploratory cohort study of breast cancer patients referred to a cardio-oncology clinic at a tertiary care centre between October 2008 and August 2014, a crs was calculated for each patient, and a sensitivity analysis was performed. RESULTS: Of the 143 patients included in the study, 62 (43%) experienced a cardiac event, and of those 62 patients, 43 (69%) experienced full recovery of cardiac function. In applying the crs, 119 patients (83%) would be considered at low risk, 14 (10%) at moderate risk, and 10 (7%) at high risk to develop heart failure or cardiomyopathy. When applied to the study population, the high-risk cut-off score had a sensitivity of 0.13 [95% confidence interval (ci): 0.08 to 0.20] and a specificity of 0.94 (95% ci: 0.87 to 0.97). The positive predictive value was 0.07 (95% ci: 0.03 to 0.13), and the negative predictive value was 0.93 (95% ci: 0.87 to 0.96). CONCLUSIONS: The crs demonstrated good specificity and negative predictive value for the development of permanent cardiotoxicity in a real-world population of breast cancer patients, suggesting that intensive cardiac monitoring might not be warranted in low-risk patients, but that high-risk patients might benefit from early referral to cardio-oncology for optimization. Further study using the crs in a larger breast cancer population is warranted to identify patients at low risk of long-term trastuzumab-related cardiotoxicity.

Thermophysical properties and oxygen transport in (Thx,Pu1-x)O2.

Using Molecular Dynamics, this paper investigates the thermophysical properties and oxygen transport of (Thx,Pu1-x)O2 (0 ≤ x ≤ 1) between 300-3500 K. In particular, the superionic transition is investigated and viewed via the thermal dependence of lattice parameter, linear thermal expansion coefficient, enthalpy and specific heat at constant pressure. Oxygen diffusivity and activation enthalpy are also investigated. Below the superionic temperature an increase of oxygen diffusivity for certain compositions of (Thx,Pu1-x)O2 compared to the pure end members is predicted. Oxygen defect formation enthalpies are also examined, as they underpin the superionic transition temperature and the increase in oxygen diffusivity. The increase in oxygen diffusivity for (Thx,Pu1-x)O2 is explained in terms of lower oxygen defect formation enthalpies for (Thx,Pu1-x)O2 than PuO2 and ThO2, while links are drawn between the superionic transition temperature and oxygen Frenkel disorder.

Development of Xe and Kr empirical potentials for CeO2, ThO2, UO2 and PuO2, combining DFT with high temperature MD.

The development of embedded atom method (EAM) many-body potentials for actinide oxides and associated mixed oxide (MOX) systems has motivated the development of a complementary parameter set for gas-actinide and gas-oxygen interactions. A comprehensive set of density functional theory (DFT) calculations were used to study Xe and Kr incorporation at a number of sites in CeO2, ThO2, UO2 and PuO2. These structures were used to fit a potential, which was used to generate molecular dynamics (MD) configurations incorporating Xe and Kr at 300 K, 1500 K, 3000 K and 5000 K. Subsequent matching to the forces predicted by DFT for these MD configurations was used to refine the potential set. This fitting approach ensured weighted fitting to configurations that are thermodynamically significant over a broad temperature range, while avoiding computationally expensive DFT-MD calculations. The resultant gas potentials were validated against DFT trapping energies and are suitable for simulating combinations of Xe and Kr in solid solutions of CeO2, ThO2, UO2 and PuO2, providing a powerful tool for the atomistic simulation of conventional nuclear reactor fuel UO2 as well as advanced MOX fuels.

Age-related changes in mesenchymal stem cells identified using a multi-omics approach.

Mesenchymal stem cells (MSC) are capable of multipotent differentiation into connective tissues and as such are an attractive source for autologous cell-based treatments for many clinical diseases and injuries. Ageing is associated with various altered cellular phenotypes coupled with a variety of transcriptional, epigenetic and translational changes. Furthermore, the regeneration potential of MSCs is reduced with increasing age and is correlated with changes in cellular functions. This study used a systems biology approach to investigate the transcriptomic (RNASeq), epigenetic (miRNASeq and DNA methylation) and protein alterations in ageing MSCs in order to understand the age-related functional and biological variations, which may affect their applications to regenerative medicine. We identified no change in expression of the cellular senescence markers. Alterations were evident at both the transcriptional and post-transcriptional level in a number of transcription factors. There was enrichment in genes involved in developmental disorders at mRNA and differential methylated loci (DML) level. Alterations in energy metabolism were apparent at the DML and protein level. The microRNA miR-199b-5p, whose expression was reduced in old MSCs, had predicted gene targets involved in energy metabolism and cell survival. Additionally, enrichment of DML and proteins in cell survival was evident. Enrichment in metabolic processes was revealed at the protein level and in genes identified as undergoing alternate splicing. Overall, an altered phenotype in MSC ageing at a number of levels implicated roles for inflamm-ageing and mitochondrial ageing. Identified changes represent novel insights into the ageing process, with implications for stem cell therapies in older patients.

Wellness Beyond Cancer Program: building an effective survivorship program.

BACKGROUND: The Wellness Beyond Cancer Program (wbcp) was launched in 2012, first accepting patients with colorectal cancer (crc) and, subsequently, those with breast cancer (bca), with the aim of standardizing and streamlining the discharge process from our cancer centre. Patients are discharged either to the wbcp nurse practitioner or to their primary care provider (pcp). The program incorporates survivorship care plans (scps) and education classes; it also has a rapid re-entry system in case of recurrence. The objective of this paper is to describe the process by which a cancer survivorship program was developed at our institution and to present preliminary evaluation results. METHODS: Qualitative surveys were mailed to patients and pcps 1 year after patients had been referred to the wbcp. The surveys addressed knowledge of the program content, satisfaction on the part of patients and providers, and whether scp recommendations were followed. Questions were scored on the level of agreement with each of a list of statements (1 = strongly disagree to 5 = strongly agree). RESULTS: From March 2012 to November 2014, 2630 patients were referred to the wbcp (809 with crc, 1821 with bca). Surveys were received from 289 patients and 412 pcps. Patients and pcps gave similar scores (average: 4) to statements about satisfaction; pcps gave scores below 4 to statements about communication with the wbcp. CONCLUSIONS: At 1 year after discharge, patients and pcps were satisfied with program content, but there is an opportunity to improve on communication and provision of cancer-specific information to the pcps. Using the wbcp to ensure a safe transition to the most appropriate health care provider, we have standardized the discharge process for crc and bca patients.

Genetics of superionic conductivity in lithium lanthanum titanates.

The self-diffusion of ions is a fundamental mass transport process in solids and has a profound impact on the performance of electrochemical devices such as the solid oxide fuel cell, batteries and electrolysers. The perovskite system lithium lanthanum titanate, La2/3-xLi3xTiO3 (LLTO) has been the subject of much academic interest as it displays very high lattice conductivity for a solid state Li conductor; making it a material of great technological interest for deployment in safe durable mobile power applications. However, so far, a clear picture of the structural features that lead to efficient ion diffusion pathways in LLTO, has not been fully developed. In this work we show that a genetic algorithm in conjunction with molecular dynamics can be employed to elucidate diffusion mechanisms in systems such as LLTO. Based on our simulations we provide evidence that there is a three-dimensional percolated network of Li diffusion pathways. The present approach not only reproduces experimental ionic conductivity results but the method also promises straightforward investigation and optimisation of the properties relating to superionic conductivity in materials such as LLTO. Furthermore, this method could be used to provide insights into related materials with structural disorder.

Thermal conductivity and energetic recoils in UO2 using a many-body potential model.

Classical molecular dynamics simulations have been performed on uranium dioxide (UO2) employing a recently developed many-body potential model. Thermal conductivities are computed for a defect free UO2 lattice and a radiation-damaged, defect containing lattice at 300 K, 1000 K and 1500 K. Defects significantly degrade the thermal conductivity of UO2 as does the presence of amorphous UO2, which has a largely temperature independent thermal conductivity of ∼1.4 Wm(-1) K(-1). The model yields a pre-melting superionic transition temperature at 2600 K, very close to the experimental value and the mechanical melting temperature of 3600 K, slightly lower than those generated with other empirical potentials. The average threshold displacement energy was calculated to be 37 eV. Although the spatial extent of a 1 keV U cascade is very similar to those generated with other empirical potentials and the number of Frenkel pairs generated is close to that from the Basak potential, the vacancy and interstitial cluster distribution is different.

Impact of uniaxial strain and doping on oxygen diffusion in CeO2.

Doped ceria is an important electrolyte for solid oxide fuel cell applications. Molecular dynamics simulations have been used to investigate the impact of uniaxial strain along the <100> directions and rare-earth doping (Yb, Er, Ho, Dy, Gd, Sm, Nd, and La) on oxygen diffusion. We introduce a new potential model that is able to describe the thermal expansion and elastic properties of ceria to give excellent agreement with experimental data. We calculate the activation energy of oxygen migration in the temperature range 900-1900 K for both unstrained and rare-earth doped ceria systems under tensile strain. Uniaxial strain has a considerable effect in lowering the activation energies of oxygen migration. A more pronounced increase in oxygen diffusivities is predicted at the lower end of the temperature range for all the dopants considered.

Treatment outcomes for male breast cancer: a single-centre retrospective case-control study.

BACKGROUND: Male breast cancer (bc) is a rare disease, and the availability of information on treatment outcomes is limited compared with that for female bc. The objective of the present study was to compare disease-free (dfs) and overall survival (os) for men compared with women having early-stage bc. METHODS: This retrospective case-control study compared men and women treated for stage 0-iiib bc at a single institution between 1981 and 2009. Matching was based on age at diagnosis, year of diagnosis, and stage. Treatment, recurrence, and survival data were collected. Kaplan-Meier analysis was used to calculate os and dfs. RESULTS: For the 144 eligible patients (72 men, 72 women), median age at diagnosis was 66.5 years. Treatments included mastectomy (72 men, 38 women), radiation (29 men, 44 women), chemotherapy (23 men, 20 women), and endocrine therapy (57 men, 57 women). Mean dfs was 127 months for women compared with 93 months for men (p = 0.62). Mean os was 117 months for women compared with 124 months for men (p = 0.35). In multivariate analysis, the only parameter that affected both dfs and os was stage at diagnosis. CONCLUSIONS: This case-control study is one of the largest to report treatment outcomes in early-stage male bc patients treated in a non-trial setting. Male patients received systemic therapy that was comparable to that received by their female counterparts, and they had similar os and dfs. These results add to current evidence from population studies that male sex is not a poor prognostic factor in early-stage breast cancer.

A many-body potential approach to modelling the thermomechanical properties of actinide oxides.

A many-body potential model for the description of actinide oxide systems, which is robust at high temperatures, is reported for the first time. The embedded atom method is used to describe many-body interactions ensuring good reproduction of a range of thermophysical properties (lattice parameter, bulk modulus, enthalpy and specific heat) between 300 and 3000 K for AmO2, CeO2, CmO2, NpO2, ThO2, PuO2 and UO2. Additionally, the model predicts a melting point for UO2 between 3000 and 3100 K, in close agreement with experiment. Oxygen-oxygen interactions are fixed across the actinide oxide series because it facilitates the modelling of oxide solid solutions. The new potential is also used to predict the energies of Schottky and Frenkel pair disorder processes.

The influence of coronal tooth tissue in the diagnosis of apical pathosis.

AIM: To assess the influence of the status of the crown of the tooth on the observers' periapical radiological assessment. METHODOLOGY: Seven clinical tutors, eight postgraduate students and seven undergraduate students were recruited. Each evaluated 24 periapical radiographs comprising 12 radiographs with teeth restored with small to medium coronal restorations and 12 radiographs displaying teeth which were either heavily restored or exhibited gross caries. Two viewing sessions, separated by several weeks, were undertaken using ideal viewing conditions. In the first viewing teeth were examined in their entirety and in the second the coronal aspects of the teeth were obscured. RESULTS: An analysis of variance found no significant differences between the groups of observers during the first viewing. When the crowns were masked, undergraduate students had a significantly lower sensitivity (P = 0.008) compared with postgraduates and clinical tutors. Paired t-tests found a significant increase in the sensitivity of the postgraduate students between the first and second viewing (P = 0.037). Mean sensitivity and specificity for the undergraduates decreased from 0.67 to 0.63 and 0.64 to 0.60 for the first and second viewing, respectively, whilst mean sensitivity for postgraduates and clinical tutors increased from 0.59 to 0.79 and 0.69 to 0.80, respectively. Specificity increased from 0.72 to 0.78 for the postgraduates between viewings, whilst the tutors recorded 0.80 for each viewing. CONCLUSION: The status of coronal tooth tissue had a major impact on the diagnostic accuracy of the observers with limited radiological experience supporting the need for earlier radiological training within the undergraduate curriculum.

Induction of hepatitis B virus gene expression at low temperature.

There is a limited understanding of the cellular regulation of HBV gene expression in differentiated hepatocytes. We previously demonstrated that HBV replication inversely correlates with cell proliferation and DNA synthesis. In this report, temperature-induced modulation of cell growth was used as a novel approach to study HBV gene expression in the absence of indirect effects from drugs or serum deprivation. We observed markedly elevated levels of hepatic HBV mRNA expression from integrated and episomal HBV DNA at 32 degrees C. Additionally, hepatoblastoma cells cultured at 32 degrees C expressed increased levels of albumin mRNA and decreased levels of c-myc mRNA, which demonstrates that liver-derived cells cultured at low temperature exhibit characteristics of functional and differentiated hepatocytes. In transiently transfected HepG2 cells cultured at 32 degrees C, the HBV enhancer 1 activated the X promoter and core/pregenomic promoter by 7.3- and 28-fold, respectively. In the absence of enhancer 1, core/pregenomic promoter activity was 2.4-fold higher than the X promoter in HepG2 cells at 32 degrees C. In contrast, enhancer 1 exclusively activated the X promoter in transfected non-liver cells at 32 degrees C. Therefore, the core/pregenomic promoter exhibits strict liver-specificity at low temperature. This work supports the hypothesis that HBV replication and gene expression are optimal in non-activated hepatocytes, and provides a novel system for delineating molecular aspects of the HBV replication process.

Sodium/proton antiporter in the euryhaline crab Carcinus maenas: molecular cloning, expression and tissue distribution.

Gill epithelial cells of euryhaline crustaceans demonstrate net inward transport of sodium ions, possibly via apical Na+/H+ antiporters, Na+/K+/2Cl- cotransporters or Na+ channels working in series with the basolateral Na(+) + K(+)-ATPase. We have identified and sequenced the cDNA coding for a crustacean Na+/H+ antiporter, starting with mRNA isolated from gills of the euryhaline green shore crab Carcinus maenas. The complete 2595-base-pair cDNA includes an open reading frame coding for a 673-amino-acid protein. A search of GenBank revealed more than 20 high-scoring matches, all Na+/H+ antiporter sequences from mammalian, amphibian, teleost and nematode species. Injection of Xenopus laevis oocytes with cRNA transcribed from the cloned crab sequence substantially enhanced Na(+)-dependent H+ efflux from the oocytes. Analysis of crab tissue antiporter mRNA levels by semi-quantitative reverse transcription-polymerase chain reaction revealed that posterior and anterior gills of Carcinus maenas expressed this antiporter the most strongly, followed in decreasing order by skeletal muscle, hepatopancreas, hypodermis and heart. Hydropathy and transmembrane alpha-helix analysis suggested a 10-helix membrane-spanning topology of the antiporter protein. It is clear from this study that Carcinus maenas gills vigorously transcribe a gene coding for a Na+/H+ antiporter. Whether these gills also express a gene coding for an epithelial Na+ channel or Na+/K+/2Cl- cotransporter remains to be demonstrated.