Aspirin use for cancer prevention: A systematic review of public, patient and healthcare provider attitudes and adherence behaviours.

We undertook a systematic review to synthesise the data on attitudes and behaviour towards the use of aspirin for cancer prevention, and healthcare providers' attitudes towards implementing aspirin in practice. Searches were carried out across 12 databases (e.g. MEDLINE, EMBASE). We used the Mixed Methods Appraisal Tool to evaluate study quality, and conducted a narrative synthesis of the data. The review was pre-registered (PROSPERO: CRD42018093453). Thirty-eight studies were identified. Uptake and adherence data were all from trials. Trials recruited healthy participants, those at higher risk of cancer, and those with cancer. Four studies reported moderate to high (40.9-77.7%) uptake to an aspirin trial among people who were eligible. Most trials (18/22) reported high day-to-day adherence (≥80%). Three trials observed no association between gender and adherence. One trial found no association between adherence and colorectal cancer risk. Three studies reported moderate to high (43.6-76.0%) hypothetical willingness to use aspirin. Two studies found that a high proportion of healthcare providers (72.0-76.0%) perceived aspirin to be a suitable cancer prevention option. No qualitative studies were identified. The likelihood that eligible users of aspirin would participate in a trial evaluating the use of aspirin for preventive therapy was moderate to high. Among participants in a trial, day-to-day adherence was high. Further research is needed to identify uptake and adherence rates in routine care, the factors affecting aspirin use, and the barriers to implementing aspirin into clinical care.

Prevalence, Comorbidities, and Risk Factors of Erectile Dysfunction: Results from a Prospective Real-World Study in the United Kingdom.

Objectives: Assessment of erectile dysfunction (ED) burden could improve health outcomes associated with underlying cardiometabolic and psychological causes of ED. This study provided updated real-world evidence (RWE) on ED epidemiology and quantified healthcare resource utilization (HCRU) and health-related quality of life (HRQoL) burden among men with ED in the UK. Methods: This cross-sectional, prospective real-world evidence study was conducted via a self-reported Internet survey in 2018 in the UK general population. Prevalence of ED was estimated; HCRU and HRQoL were compared between men with ED versus without ED via bivariate analysis. Results: Of 12,490 men included, 41.5% reported ED; 7.5% of men reported severe ED; ED was most prevalent in Wales (44.3%). Men with ED were older (54.1 ± 14.5 vs. 46.8 ± 14.1 years) and often reported modifiable lifestyle risk factors, including smoking (32.8% vs. 26.3%), drinking alcohol (76.1% vs. 71.0%), not exercising (21.7% vs. 19.4%), and being overweight or obese (64.9% vs. 54.6%). Additionally, men with ED more often reported ≥1 comorbid chronic conditions (73.7% vs. 47.7%), including hypertension (31.8% vs. 16.3%), hyperlipidemia (27.6% vs. 14.0%), depression (24.3% vs. 14.6%), anxiety (23.3% vs. 16.6%), and diabetes (15.9% vs. 6.1%) versus men without ED (all, p < 0.001). Nearly half of men with ED (45.3%) were not undergoing treatment for cardiometabolic or psychological comorbidities. Furthermore, men with ED more often reported ≥1 visit to physicians/nurse practitioners and pharmacists in the past year and had significantly lower SEAR total and domain scores than men without ED (all, p < 0.001). Conclusion: ED was highly prevalent in the UK affecting over a quarter of younger men. Cardiometabolic and psychological conditions were common among men with ED and often remained untreated. Higher proportions of modifiable lifestyle risk factors observed among men with ED present an opportunity for healthcare providers to help mitigate the risk of cardiometabolic diseases and incidence of ED.

Barriers and facilitators to using aspirin for preventive therapy: a qualitative study exploring the views and experiences of people with Lynch syndrome and healthcare providers.

BACKGROUND: The National Institute for Health and Care Excellence (NG151) recommends considering daily aspirin for people with Lynch syndrome to reduce colorectal cancer risk. However, deciding whether to initiate aspirin could be a complex decision for patients and their healthcare providers, as both the potential benefits and harms need to be considered. METHODS: We conducted semi-structured interviews to explore the barriers and facilitators to using aspirin for preventive therapy. We recruited 15 people with Lynch syndrome, and 23 healthcare providers across multiple professions in primary, and specialist care (e.g. clinical genetics) in the United Kingdom. Interview schedules were informed by the Theoretical Domains Framework. RESULTS: There were three themes: 1) Considering potential harms and benefits; 2) Healthcare pathway; 3) Patients' level of interest in aspirin. All healthcare providers, across primary and specialist care, viewed general practitioners (GPs) as being responsible for prescribing and overseeing the use of aspirin. However, GPs were unfamiliar with aspirin for preventive therapy, and concerned about prescribing at higher doses (300-600 mg). To support decision-making, GPs wanted clarification from specialist clinicians on the evidence and dose to prescribe. Not all participants with Lynch syndrome received information on aspirin from their healthcare provider, and several were unsure who to discuss aspirin with. GPs were more inclined to prescribe aspirin for patients with expressed preferences for the medication, however several patients were uncertain and wanted further guidance. CONCLUSIONS: Coordinated and multilevel strategies are needed, addressing the needs of both GPs and people with Lynch syndrome, to ensure consistent implementation of national guidance on aspirin for preventive therapy.

Intact calcium signaling in adrenergic-deficient embryonic mouse hearts.

Mouse embryos that lack the ability to produce the adrenergic hormones, norepinephrine (NE) and epinephrine (EPI), due to disruption of the dopamine beta-hydroxylase (Dbh-/-) gene inevitably perish from heart failure during mid-gestation. Since adrenergic stimulation is well-known to enhance calcium signaling in developing as well as adult myocardium, and impairments in calcium signaling are typically associated with heart failure, we hypothesized that adrenergic-deficient embryonic hearts would display deficiencies in cardiac calcium signaling relative to adrenergic-competent controls at a developmental stage immediately preceding the onset of heart failure, which first appears beginning or shortly after mouse embryonic day 10.5 (E10.5). To test this hypothesis, we used ratiometric fluorescent calcium imaging techniques to measure cytosolic calcium transients, [Ca2+]i in isolated E10.5 mouse hearts. Our results show that spontaneous [Ca2+]i oscillations were intact and robustly responded to a variety of stimuli including extracellular calcium (5 mM), caffeine (5 mM), and NE (100 nM) in a manner that was indistinguishable from controls. Further, we show similar patterns of distribution (via immunofluorescent histochemical staining) and activity (via patch-clamp recording techniques) for the major voltage-gated plasma membrane calcium channel responsible for the L-type calcium current, ICa,L, in adrenergic-deficient and control embryonic cardiac cells. These results demonstrate that despite the absence of vital adrenergic hormones that consistently leads to embryonic lethality in vivo, intracellular and extracellular calcium signaling remain essentially intact and functional in embryonic mouse hearts through E10.5. These findings suggest that adrenergic stimulation is not required for the development of intracellular calcium oscillations or extracellular calcium signaling through ICa,L and that aberrant calcium signaling does not likely contribute to the onset of heart failure in this model.

The growing burden of cancer in India: epidemiology and social context.

Cancer can have profound social and economic consequences for people in India, often leading to family impoverishment and societal inequity. Reported age-adjusted incidence rates for cancer are still quite low in the demographically young country. Slightly more than 1 million new cases of cancer are diagnosed every year in a population of 1.2 billion. In age-adjusted terms this represents a combined male and female incidence of about a quarter of that recorded in western Europe. However, an estimated 600,000-700,000 deaths in India were caused by cancer in 2012. In age-standardised terms this figure is close to the mortality burden seen in high-income countries. Such figures are partly indicative of low rates of early-stage detection and poor treatment outcomes. Many cancer cases in India are associated with tobacco use, infections, and other avoidable causes. Social factors, especially inequalities, are major determinants of India's cancer burden, with poorer people more likely to die from cancer before the age of 70 years than those who are more affluent. In this first of three papers, we examine the complex epidemiology of cancer, the future burden, and the dominant sociopolitical themes relating to cancer in India.

GPs' willingness to prescribe aspirin for cancer preventive therapy in Lynch syndrome: a factorial randomised trial investigating factors influencing decisions.

BACKGROUND: The National Institute for Health and Care Excellence (NICE) 2020 guidelines recommends aspirin for colorectal cancer prevention for people with Lynch syndrome. Strategies to change practice should be informed by understanding the factors influencing prescribing. AIM: To investigate the optimal type and level of information to communicate with GPs to increase willingness to prescribe aspirin. DESIGN AND SETTING: GPs in England and Wales (n = 672) were recruited to participate in an online survey with a 23 factorial design. GPs were randomised to one of eight vignettes describing a hypothetical patient with Lynch syndrome recommended to take aspirin by a clinical geneticist. METHOD: Across the vignettes, the presence or absence of three types of information was manipulated: 1) existence of NICE guidance; 2) results from the CAPP2 trial; 3) information comparing risks/benefits of aspirin. The main effects and all interactions on the primary (willingness to prescribe) and secondary outcomes (comfort discussing aspirin) were estimated. RESULTS: There were no statistically significant main effects or interactions of the three information components on willingness to prescribe aspirin or comfort discussing harms and benefits. In total, 80.4% (540/672) of GPs were willing to prescribe, with 19.7% (132/672) unwilling. GPs with prior awareness of aspirin for preventive therapy were more comfortable discussing the medication than those unaware (P = 0.031). CONCLUSION: It is unlikely that providing information on clinical guidance, trial results, and information comparing benefits and harms will increase aspirin prescribing for Lynch syndrome in primary care. Alternative multilevel strategies to support informed prescribing may be warranted.

Acceptability of aspirin for cancer preventive therapy: a survey and qualitative study exploring the views of the UK general population.

OBJECTIVES: Aspirin could be offered for colorectal cancer prevention for the UK general population. To ensure the views of the general population are considered in future guidance, we explored public perceptions of aspirin for preventive therapy. DESIGN: We conducted an online survey to investigate aspirin use, and awareness of aspirin for cancer prevention among the UK general population. We conducted semistructured interviews with a subsample of survey respondents to explore participants' acceptability towards aspirin for cancer preventive therapy. We analysed the interview data using reflexive thematic analysis and mapped the themes onto the Theoretical Domains Framework, and the Necessity and Concerns Framework. SETTING: Online survey and remote interviews. PARTICIPANTS: We recruited 400 UK respondents aged 50-70 years through a market research company to the survey. We purposefully sampled, recruited and interviewed 20 survey respondents. RESULTS: In the survey, 19.0% (76/400) of respondents were aware that aspirin can be used to prevent cancer. Among those who had previously taken aspirin, 1.9% (4/216) had taken it for cancer prevention. The interviews generated three themes: (1) perceived necessity of aspirin; (2) concerns about side effects; and (3) preferred information sources. Participants with a personal or family history of cancer were more likely to perceive aspirin as necessary for cancer prevention. Concerns about taking aspirin at higher doses and its side effects, such as gastrointestinal bleeding, were common. Many described wanting guidance and advice on aspirin to be communicated from sources perceived as trustworthy, such as healthcare professionals. CONCLUSIONS: Among the general population, those with a personal or family history of cancer may be more receptive towards taking aspirin for preventive therapy. Future policies and campaigns recommending aspirin may be of particular interest to these groups. Multiple considerations about the benefits and risks of aspirin highlight the need to support informed decisions on the medication.

Adrenergic deficiency leads to impaired electrical conduction and increased arrhythmic potential in the embryonic mouse heart.

To determine if adrenergic hormones play a critical role in the functional development of the cardiac pacemaking and conduction system, we employed a mouse model where adrenergic hormone production was blocked due to targeted disruption of the dopamine ß-hydroxylase (Dbh) gene. Immunofluorescent histochemical evaluation of the major gap junction protein, connexin 43, revealed that its expression was substantially decreased in adrenergic-deficient (Dbh-/-) relative to adrenergic-competent (Dbh+/+ and Dbh+/-) mouse hearts at embryonic day 10.5 (E10.5), whereas pacemaker and structural protein staining appeared similar. To evaluate cardiac electrical conduction in these hearts, we cultured them on microelectrode arrays (8×8, 200 µm apart). Our results show a significant slowing of atrioventricular conduction in adrenergic-deficient hearts compared to controls (31.4±6.4 vs. 15.4±1.7 ms, respectively, p<0.05). To determine if the absence of adrenergic hormones affected heart rate and rhythm, mouse hearts from adrenergic-competent and deficient embryos were cultured ex vivo at E10.5, and heart rates were measured before and after challenge with the ß-adrenergic receptor agonist, isoproterenol (0.5 µM). On average, all hearts showed increased heart rate responses following isoproterenol challenge, but a significant (p<0.05) 225% increase in the arrhythmic index (AI) was observed only in adrenergic-deficient hearts. These results show that adrenergic hormones may influence heart development by stimulating connexin 43 expression, facilitating atrioventricular conduction, and helping to maintain cardiac rhythm during a critical phase of embryonic development.

Stress-induced switch in Numb isoforms enhances Notch-dependent expression of subtype-specific transient receptor potential channel.

The Notch signaling pathway plays an essential role in the regulation of cell specification by controlling differentiation, proliferation, and apoptosis. Numb is an intrinsic regulator of the Notch pathway and exists in four alternative splice variants that differ in the length of their phosphotyrosine-binding domain (PTB) and proline-rich region domains. The physiological relevance of the existence of the Numb splice variants and their exact regulation are still poorly understood. We previously reported that Numb switches from isoforms containing the insertion in PTB to isoforms lacking this insertion in neuronal cells subjected to trophic factor withdrawal (TFW). The functional relevance of the TFW-induced switch in Numb isoforms is not known. Here we provide evidence that the TFW-induced switch in Numb isoforms regulates Notch signaling strength and Notch target gene expression. PC12 cells stably overexpressing Numb isoforms lacking the PTB insertion exhibited higher basal Notch activity and Notch-dependent transcription of the transient receptor potential channel 6 (TRPC6) when compared with those overexpressing Numb isoforms with the PTB insertion. The differential regulation of TRPC6 expression is correlated with perturbed calcium signaling and increased neuronal vulnerability to TFW-induced death. Pharmacological inhibition of the Notch pathway or knockdown of TRPC6 function ameliorates the adverse effects caused by the TFW-induced switch in Numb isoforms. Taken together, our results indicate that Notch and Numb interaction may influence the sensitivity of neuronal cells to injurious stimuli by modulating calcium-dependent apoptotic signaling cascades.

The political economics of cancer drug discovery and pricing.

Drug discoveries can, when used appropriately, save lives. Since 1970, cancer death rates among people aged under 65 have halved in countries such as the USA and the UK. Despite pharmaceutical market imperfections and fears about the prices of new treatments, further progress should be possible during the 2020s. Anticancer medicine outlays account for 0.1-0.2% of the gross domestic product (GDP) of developed countries. Total cancer service spending typically stands at ∼0.8% of GDP. The affordability of these sums is a political calculation. Improvements in the efficiency of drug development and global access to effective therapies are desirable. However, from a public interest perspective, these goals should not be pursued in ways that understate the value of better treatment outcomes and threaten the funding available for ongoing innovation.

Development of Antimicrobial Stewardship Programmes in Low and Middle-Income Countries: A Mixed-Methods Study in Nigerian Hospitals.

Antimicrobial resistance (AMR) is a major concern facing global health today, with the greatest impact in developing countries where the burden of infectious diseases is much higher. The inappropriate prescribing and use of antibiotics are contributory factors to increasing antibiotic resistance. Antimicrobial stewardship programmes (AMS) are implemented to optimise use and promote behavioural change in the use of antimicrobials. AMS programmes have been widely employed and proven to improve antibiotic use in many high-income settings. However, strategies to contain antimicrobial resistance have yet to be successfully implemented in low-resource settings. A recent toolkit for AMS in low- and middle-income countries by the World Health Organisation (WHO) recognizes the importance of local context in the development of AMS programmes. This study employed a bottom-up approach to identify important local determinants of antimicrobial prescribing practices in a low-middle income setting, to inform the development of a local AMS programme. Analysis of prescribing practices and interviews with prescribers highlighted priorities for AMS, which include increasing awareness of antibiotic resistance, development and maintenance of guidelines for antibiotic use, monitoring and surveillance of antibiotic use, ensuring the quality of low-cost generic medicines, and improved laboratory services. The application of an established theoretical model for behaviour change guided the development of specific proposals for AMS. Finally, in a consultation with stakeholders, the feasibility of the plan was explored along with strategies for its implementation. This project provides an example of the design, and proposal for implementation of an AMS plan to improve antibiotic use in hospitals in low-middle income settings.

The pharmacist's role in improving the treatment of erectile dysfunction and its underlying causes.

Erectile dysfunction (ED), which worldwide is likely to affect in excess of 300 million men by 2025, is often either untreated or insufficiently treated. It can be a prelude to other serious illnesses and may be a cause or consequence of depression in affected individuals. Among men younger than 60 years of age, ED can be a robust early-stage indicator of vascular disease and type 2 diabetes. Untreated or inadequately treated ED can also be a sign of poor communication between health professionals and service users of all ages. Improved treatment of ED could cost-effectively prevent premature deaths and avoidable morbidity. The extension of community pharmacy‒based health care would enable more men living with ED to safely access effective medications, along with appropriate diagnostic services and support for beneficial lifestyle changes such as smoking cessation in conveniently accessible settings. The task of introducing improved methods of affordably addressing problems linked to ED exemplifies the strategic challenges now facing health care systems globally. Promoting professionally supported self-care in pharmacies has the potential to meet the needs of aging populations in progressively more effective ways.

Noninvasive tracking of cardiac embryonic stem cells in vivo using magnetic resonance imaging techniques.

Despite rapid advances in the stem cell field, the ability to identify and track transplanted or migrating stem cells in vivo is limited. To overcome this limitation, we used magnetic resonance imaging (MRI) to detect and follow transplanted stem cells over a period of 28 days in mice using an established myocardial infarction model. Pluripotent mouse embryonic stem (mES) cells were expanded and induced to differentiate into beating cardiomyocytes in vitro. The cardiac-differentiated mES cells were then loaded with superparamagnetic fluorescent microspheres (1.63 microm in diameter) and transplanted into ischemic myocardium immediately following ligation and subsequent reperfusion of the left anterior descending coronary artery. To identify the transplanted stem cells in vivo, MRI was performed using a Varian Inova 4.7 Tesla scanner. Our results show that (a) the cardiac-differentiated mES were effectively loaded with superparamagnetic microspheres in vitro, (b) the microsphere-loaded mES cells continued to beat in culture prior to transplantation, (c) the transplanted mES cells were readily detected in the heart in vivo using noninvasive MRI techniques, (d) the transplanted stem cells were detected in ischemic myocardium for the entire 28-day duration of the study as confirmed by MRI and post-mortem histological analyses, and (e) concurrent functional MRI indicated typical loss of cardiac function, although significant amelioration of remodeling was noted after 28 days in hearts that received transplanted stem cells. These results demonstrate that it is feasible to simultaneously track transplanted stem cells and monitor cardiac function in vivo over an extended period using noninvasive MRI techniques.

Development of a pelvic exenteration service at a tertiary referral centre.

BACKGROUND: Over one-third of primary rectal cancers are locally advanced at diagnosis, and local recurrence of rectal cancer occurs at a rate of 3-10% following primary curative resection. Extended resectional surgery, including pelvic exenteration, is the only proven therapy with curative potential in the treatment of these cancers along with many other pelvic malignancies. A microscopically clear resection margin (R0 resection) is the predominant prognostic factor affecting overall and disease-free survival. The extent and complexity of surgery required to achieve an R0 resection is associated with significant risk of morbidity and mortality. The aim of this paper is to show that pelvic exenterations can be performed with acceptable oncological and safe perioperative results in an appropriately resourced specialist centre. METHODS: Data was collected retrospectively for 61 consecutive patients treated between June 2012 and February 2017. This included patient demographics, tumour characteristics, operative, clinical and histological data, length of hospital stay, morbidity and mortality data. RESULTS: A total of 61 patients underwent surgery. Median age was 57 years (range 27-78 years). Median length of stay was 41 days (range 6-288 days). Median operative time was 624 min (range 239-1035 min); 30-day mortality was 3.3% (n = 2). Resection rates were 91.5% - R0, 6.8% - R1 and 1.7% - R2 resections. Histologically, 86.9% - adenocarcinomas, 3.3% - squamous cell carcinomas and 9.8% - represented by leiomyosarcoma, melanoma, myxoid chondrosarcoma, non-neoplastic processes and undifferentiated carcinoma. CONCLUSION: Our experience confirms that radical resectional pelvic surgery can be safely performed with acceptable results during the establishment phase of a dedicated tertiary service.

Role of chromatin accessibility in the occupancy and transcription of the insulin gene by the pancreatic and duodenal homeobox factor 1.

The pancreatic and duodenal homeobox factor 1 (Pdx-1) is a Hox-like transcription factor that is responsible for the activation of the insulin gene. Previous studies have demonstrated the interaction in vitro of Pdx-1 with short (20-40 nucleotide) DNA fragments corresponding to A boxes of the insulin promoter. Precisely how Pdx-1 binds to DNA in the complex milieu of chromatin, however, has never been studied. In this study, we explored how Pdx-1-DNA interactions might be influenced by chromatin accessibility at the insulin gene in beta-cells (betaTC3) vs. pancreatic ductal cells (mPAC). We demonstrate that Pdx-1 occupies the endogenous insulin promoter in betaTC3 cells but not in mPAC cells, a finding that is independent of the intracellular Pdx-1 protein concentration. Based on micrococcal nuclease protection assays, the difference in promoter binding between the two cell types appears to be secondary to chromatin accessibility at predicted Pdx-1 binding sites between bp -126 to -296 (relative to the transcriptional start site) of the insulin promoter. Binding studies using purified Pdx-1 and reconstituted chromatin in vitro suggest that the positioning of a nucleosome(s) within this crucial region of the promoter might account for differences in chromatin accessibility. Consistent with these observations, fluorescence colocalization studies show that Pdx-1 does not occupy regions of compacted, nucleosome-rich chromatin within the nucleus. Our findings suggest a model whereby insulin transcription in the beta-cell is at least partially facilitated by enhanced chromatin accessibility within a crucial regulatory region between bp -126 to -296, thereby permitting occupancy by transactivators such as Pdx-1.

Apparatus for studies of high-temperature chemical reactions in single particle systems.

We report a compact microgravity flight apparatus for characterization of high-temperature chemical reactions in single particle systems. The apparatus employs an infrared CO(2) laser to ignite 1-5 mm samples while video images, thermocouple measurements, laser on/off status, and XYZ accelerometer signals are synchronously recorded. Different operating modes permit preignition quenching, ignition, and combustion experiments to be performed. The apparatus was successfully utilized during microgravity experiments on board NASA research aircraft.

Catecholamines and development of cardiac pacemaking: an intrinsically intimate relationship.

A generation ago, a melding of imagination and experimental evidence led to the hypothesis that catecholamines were essential in establishing basal cardiac pacemaking rhythm. Subsequent discoveries of depolarizing "pacemaker" currents and viable adult catecholamine-deficient animals raised serious doubts about the necessity of catecholamines in pacemaking. However, the findings that catecholamines are produced in pacemaking regions prior to innervation, and that they are required for embryonic survival during a defined "critical period" of embryonic development have revitalized the original hypothesis. Recent results have further suggested that intrinsic cardiac adrenergic cells can differentiate into pacemaking myocytes, and that protein kinase A, a prominent downstream mediator of beta-adrenergic signaling, is required for pacemaking activity. Here, we discuss how catecholamines and the intrinsic cardiac adrenergic cells that produce them may influence ontological development of cardiac pacemaking.

The transcriptional repressor Nkx6.1 also functions as a deoxyribonucleic acid context-dependent transcriptional activator during pancreatic beta-cell differentiation: evidence for feedback activation of the nkx6.1 gene by Nkx6.1.

In the pancreas, the NK homeodomain transcription factor Nkx6.1 is required for the development of beta-cells and is believed to function as a potent repressor of transcription upon binding to A/T-rich sequences within the promoter region of target genes. Because the nkx6.1 promoter itself contains several such sequences, we considered the possibility that the expression level and restricted pattern of the nkx6.1 gene might be precisely regulated by one or more homeodomain transcription factors, including Nkx6.1 itself. In this report, we identify a novel beta-cell-specific enhancer element in the nkx6.1 gene between -157 and -30 bp (relative to the transcriptional start site) that harbors a conserved A/T-containing sequence flanked by G/C-rich stretches. Although the islet homeodomain-containing activator Pdx-1 was unable to stimulate transcription of a reporter gene through this enhancer element in mammalian cell lines, strikingly, Nkx6.1 robustly activated transcription through direct interaction with the A/T-rich sequence in this element. We demonstrate that this activation is indeed transcriptional in nature (and not secondary to translational effects) and is mediated by a modular acidic sequence within the COOH-terminal domain of Nkx6.1. We show by EMSAs that Nkx6.1 binds to the beta-cell-specific enhancer in vitro and by chromatin immunoprecipitation assays that Nkx6.1 natively occupies this region in vivo in betaTC3 cells. We therefore conclude that Nkx6.1 is a bifunctional transcription factor that serves to maintain the specific expression of its own gene during beta-cell differentiation while simultaneously effecting broader gene repression events.

Quantification of the rat left ventricle force and Ca2+ -frequency relationships: similarities to dog and human.

OBJECTIVE: To measure and quantify the force-frequency (FFR) and Ca(2+)-frequency (CaFR) relationships in isolated rat left ventricular (LV) muscle at physiological heart rates and compare the obtained FFR to that measured in larger mammalian muscle from dog and human using the same experimental protocol. METHODS: Rat papillary muscle was isolated from the LV of adult male Sprague-Dawley rats, and dog and human muscles were from free-wall LV biopsies, loaded with the Ca(2+) indicator Fura-2, allowed to recover from isolation trauma and then subjected to direct electrical stimulation while measuring force production and intracellular Ca(2+) transients. RESULTS: We obtained a positive FFR between 1 and 4 Hz that is qualitatively similar to that found in isolated LV epicardial muscle strips from dogs and humans with normal LV function. The FFR reflects the cytosolic Ca(2+) transients in amplitude. Isoproterenol yielded an enhancement in force, but flattening of the FFR, whereas cyclopiazonic acid caused depression of FFR amplitude without changing frequency-dependent shape. CONCLUSION: We describe an experimental protocol that consistently yields positive FFRs in rat, dog and human LV muscle at stimulation rates between 1 and 4 Hz, without significant qualitative differences. We attribute previously observed negative FFR in rat muscle to an increase in SERCA activity early after excision and preparation of the muscle strips.