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BACKGROUND: Numerous studies have shown the effectiveness of testing for hepatitis B (HBV) and hepatitis C (HCV) in emergency departments (ED), due to the elevated prevalence amongst attendees. The aim of this study was to conduct a cost-effectiveness analysis of universal opt-out HBV and HCV testing in EDs based on 2 long-term studies of the real-world effectiveness of testing in 2 large ED's in the UK. METHODS: A Markov model was used to evaluate ED-based HBV and HCV testing versus no ED testing, in addition to current testing practice. The two EDs had a HBV HBsAg prevalence of 0.5-0.9% and an HCV RNA prevalence of 0.9-1.0%. The analysis was performed from a UK health service perspective, over a lifetime time horizon. Costs are reported in British pounds (GBP), and outcomes as quality adjusted life years (QALYs), with both discounted at 3.5% per year. Incremental cost-effectiveness ratios (ICER) are calculated as costs per QALY gained. A willingness-to-pay threshold of £20,000/QALY was used. The cost-effectiveness was estimated for both infections, in both ED's. RESULTS: HBV and HCV testing were highly cost-effective in both settings, with ICERs ranging from £7,177 to £12,387 per QALY gained. In probabilistic analyses, HBV testing was 89-94% likely to be cost-effective at the threshold, while HCV testing was 94-100% likely to be cost-effective, across both settings. In deterministic sensitivity analyses, testing remained cost-effective in both locations at ≥ 0.25% HBsAg prevalence, and ≥ 0.49% HCV RNA prevalence. This is much lower than the prevalence observed in the two EDs included in this study. CONCLUSIONS: HBV and HCV testing in urban EDs is highly cost-effective in the UK, and can be cost-effective at relatively low prevalence. These results should be reflected in UK and European hepatitis testing guidelines.
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We sought to characterize risk factors and patterns of HCV transmission amongst men who have sex with men (MSM). MSM with recently acquired HCV (AHCV) were prospectively recruited ('clinic cohort') between January and September 2017. Clinical data and risk behaviours were identified and blood obtained for HCV whole genome sequencing. Phylogenetic analyses were performed, using sequences from this cohort and two other AHCV cohorts, to identify transmission clusters. Sixteen (40.0%) men in the clinic cohort were HIV-negative MSM. HIV-negative MSM were younger than HIV-positive MSM; most (81.3%) had taken HIV PrEP in the preceding year. Eighteen men (45.0%) reported injection drug use; most (34, 85.0%) reported noninjection drug use in the last year. Most in both groups reported condomless anal sex, fisting and sex in a group environment. Few (7, 17.5%) men thought partners may have had HCV. There were 52 sequences in the HCV genotype 1a phylogeny, 18 from the clinic cohort and 34 from other AHCV cohorts; 47 (90.4%) clustered with ≥1 other sequence. There were 7 clusters of 2-27 sequences; 6 clusters contained HIV-negative and HIV-positive MSM and 1 cluster only HIV-positive MSM. Four of these clusters were part of larger clusters first described in 2007. PrEP-using MSM are at risk of HCV, sharing similar risk factors to HIV-positive MSM. Phylogenetics highlights that PrEP-using and HIV-positive MSM are involved in the same HCV transmission networks. Few men demonstrated HCV awareness and risk reduction strategies should be expanded.
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Infecciones por VIH , Hepatitis C/transmisión , Profilaxis Pre-Exposición , Minorías Sexuales y de Género , Inglaterra , Seropositividad para VIH , Hepacivirus , Homosexualidad Masculina , Humanos , Masculino , Filogenia , Asunción de RiesgosRESUMEN
PURPOSE: With DAAs still only being licensed for chronic HCV infection, the ongoing epidemic of acute hepatitis C (AHC) infection among MSM highlights the need to identify factors allowing for optimal HCV treatment outcome. METHODS: 303 HIV-infected patients from 4 European countries with diagnosed acute HCV infection were treated early with pegylated interferon (pegIFN) and ribavirin (RBV) (n = 273) or pegylated interferon alone (n = 30). RESULTS: All patients were male, median age was 39 years. Main routes of transmission were MSM (95%) and IVDU (3%). 69% of patients were infected with HCV GT 1, 4.3% with GT 2, 10.6% with GT 3, 16.1% with GT 4. Overall SVR rate was 69.3% (210/303). RVR (p ≤ 0.001), 48-w treatment duration (p ≤ 0.001) and GT 2/3 (p = 0.024) were significantly associated with SVR. SVR rates were significantly higher in HCV GT 2/3 receiving pegIFN and RBV (33/35) when compared with pegIFN mono-therapy (6/10) (94% vs. 60 % respectively; p = 0.016). In multivariate analysis, pegIFN/RBV combination therapy (p = 0.017) and rapid virological response (RVR) (p = 0.022) were significantly associated with SVR in HCV GT 2/3. In HCV GT 1/4, RVR (p ≤ 0.001) and 48-w treatment duration (p ≤ 0.001) were significantly associated with SVR. CONCLUSIONS: Treatment of AHC GT 2 and 3 infections with pegIFN/RBV is associated with higher SVR rates suggesting different cure rates depending on HCV genotype similar to the genotype effects seen previously in chronic HCV under pegIFN/RBV. With pegIFN/RBV still being the gold standard of AHC treatment and in light of cost issues around DAAs and very limited licensed interferon-free DAA treatment options for chronic HCV GT 3 infection AHC GT 3 patients might benefit most from early interferon-containing treatment.
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Antivirales/administración & dosificación , Coinfección/tratamiento farmacológico , Infecciones por VIH/complicaciones , Infecciones por VIH/tratamiento farmacológico , Hepatitis C/complicaciones , Hepatitis C/tratamiento farmacológico , Adulto , Quimioterapia Combinada/métodos , Genotipo , Hepacivirus/clasificación , Hepacivirus/genética , Humanos , Interferón-alfa/uso terapéutico , Masculino , Persona de Mediana Edad , Polietilenglicoles/uso terapéutico , Estudios Prospectivos , Proteínas Recombinantes/uso terapéutico , Ribavirina/uso terapéutico , Resultado del TratamientoRESUMEN
AIMS: We evaluated the effectiveness of an intervention to improve the care of people with diabetes undergoing surgery when implemented across multiple organisations. METHODS: This was an observational study using routinely collected data. Eight hospitals in England implemented the Improving the Peri-operative Pathway of People with Diabetes (IP3D) intervention, with pre-implementation data collected from 1st February to 31st July 2019 and post-implementation data collection within the period 1st February to 31st October 2021. Key elements were the use of a patient empowering peri-operative passport and the employment of a peri-operative diabetes specialist nurse. The primary outcome was the change in length of stay. RESULTS: In total 1837 patients at pre-implementation and 1164 patients at post-implementation undergoing elective surgery were included. Pre- and post-implementation 23.8 % and 33.4 % of patients had day-case surgery respectively. For in-patients median length of stay decreased from 3.2 days (inter-quartile range 1.5-6.1) pre-implementation to 2.5 days (inter-quartile range 1.4-5.4) post-implementation. There were also significant improvements in patient experience, hypo- and hyper-glycaemic events, wound complications and diabetes related complications. CONCLUSIONS: The IP3D intervention has the potential to increase efficiency and reduce waiting lists for elective surgery on a nationwide basis.
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Diabetes Mellitus , Humanos , Diabetes Mellitus/cirugía , Inglaterra , Tiempo de InternaciónRESUMEN
BACKGROUND: Glioblastoma (GBM) almost invariably becomes resistant towards conventional treatment of radiotherapy and temozolomide (TMZ) chemotherapy, partly due to subpopulations of intrinsically resistant glioma stem-like cells (GSC). The oncolytic herpes simplex virus-1 G207 is a promising approach for GBM virotherapy although its efficacy in patients with GBM is often limited. Natural killer group 2 member D ligands (NKG2DLs) are minimally expressed by healthy cells but are upregulated by the DNA damage response (DDR) and in malignant cells with chronic DDR signaling, resulting in innate immune activation. METHODS: We have designed a bispecific T-cell engager (BiTE) capable of cross-linking CD3 on T cells with NKG2DL-expressing GBM cells. We then engineered the G207 virus to express the NKG2D BiTE and secrete it from infected cells. The efficacy of the free BiTE and BiTE delivered by G207 was evaluated in combination with conventional therapies in GBM cells and against patient-derived GSCs in the context of T-cell activation and target cell viability. RESULTS: NKG2D BiTE-mediated cross-linking of GBM cells and T cells causes antigen-independent T-cell activation, pro-inflammatory cytokine release, and tumor cell death, thereby combining direct viral oncolysis with BiTE-mediated cytotoxicity. Surface NKG2DL expression was further elevated on GBM cells following pretreatment with sublethal doses of TMZ and radiation to induce the DDR, increasing sensitivity towards G207-NKG2D BiTE and achieving synergistic cytotoxicity. We also demonstrate a novel strategy for targeting GSCs that are non-permissive to G207 infection but remain sensitive to NKG2D BiTE. CONCLUSIONS: We propose a potential model for targeting GSCs in heterogeneous tumors, whereby differentiated GBM cells infected with G207-NKG2D BiTE produce NKG2D BiTE locally, directing T-cell cytotoxicity towards the GSC subpopulations in the tumor microenvironment.
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Glioblastoma , Subfamilia K de Receptores Similares a Lectina de Células NK , Células Madre Neoplásicas , Viroterapia Oncolítica , Humanos , Neoplasias Encefálicas/terapia , Neoplasias Encefálicas/inmunología , Neoplasias Encefálicas/patología , Línea Celular Tumoral , Glioblastoma/tratamiento farmacológico , Glioblastoma/inmunología , Glioblastoma/terapia , Células Madre Neoplásicas/efectos de los fármacos , Células Madre Neoplásicas/metabolismo , Subfamilia K de Receptores Similares a Lectina de Células NK/efectos de los fármacos , Subfamilia K de Receptores Similares a Lectina de Células NK/metabolismo , Viroterapia Oncolítica/métodos , Linfocitos T/efectos de los fármacos , Linfocitos T/inmunología , Linfocitos T/metabolismoRESUMEN
Anandamide is a ligand of the endocannabinoid system. Animals show a depletion following repeated Δ(9)-tetrahydrocannabinol (THC) administration but the effect of cannabis use on central nervous system levels of endocannabinoids has not been previously examined in humans. Cerebrospinal fluid (CSF) levels of the endocannabinoids anandamide, 2-arachidonoylglycerol (2-AG) and related lipids were tested in 33 volunteers (20 cannabis users). Lower levels of CSF anandamide and higher levels of 2-AG in serum were observed in frequent compared with infrequent cannabis users. Levels of CSF anandamide were negatively correlated with persisting psychotic symptoms when drug-free. Higher levels of anandamide are associated with a lower risk of psychotic symptoms following cannabis use.
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Ácidos Araquidónicos/líquido cefalorraquídeo , Endocannabinoides/líquido cefalorraquídeo , Abuso de Marihuana/líquido cefalorraquídeo , Alcamidas Poliinsaturadas/líquido cefalorraquídeo , Trastornos Psicóticos/líquido cefalorraquídeo , Análisis de Varianza , Femenino , Glicéridos/líquido cefalorraquídeo , Humanos , Masculino , Abuso de Marihuana/psicología , Trastornos Psicóticos/etiología , Transducción de Señal/efectos de los fármacos , Adulto JovenRESUMEN
The neurohormone oxytocin regulates many aspects of physiology primarily by binding to its receptor, the oxytocin receptor. The oxytocin receptor gene (Oxtr) has been shown to have alternative transcripts in the mouse brain which may each have different biological functions or be used in specific contexts. A popular animal model for studying oxytocin-dependent social behaviors is the prairie vole, a biparental and monogamous rodent. Alternative transcriptional capacity of Oxtr in prairie voles is unknown. We used 5' rapid amplification of cDNA ends to identify alternative Oxtr transcription start sites in prairie vole brain tissue and uterine tissue. We then validated expression of specific transcripts in fetal brains and assessed the impact of exogenous oxytocin administration in utero on offspring brain development. We identified seven distinct Oxtr transcripts, all of which are present in both brain and uterine tissue. We then demonstrated that maternal oxytocin administration alters expression of a specific subset of Oxtr transcripts and that these different transcripts are under unique epigenetic regulation, such that in the perinatal period only one of the alternative transcripts is associated with DNA methylation in the Oxtr promoter. These data establish the existence of multiple Oxtr transcripts in prairie vole brain and uterine tissue and implicate oxytocin in the regulation of alternative transcript expression. These data have significant implications for our understanding of null mutant models in both mice and voles and translation in human birth and behavior.
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BACKGROUND: Syphilis is a sexually transmitted bacterial infection caused by Treponema pallidum subspecies pallidum. Since 2012, syphilis rates have risen dramatically in many high-income countries, including England. Although this increase in syphilis prevalence is known to be associated with high-risk sexual activity in gay, bisexual, and other men who have sex with men (GBMSM), cases are rising in heterosexual men and women. The transmission dynamics within and between sexual networks of GBMSM and heterosexual people are not well understood. We aimed to investigate if whole genome sequencing could be used to supplement or enhance epidemiological insights around syphilis transmission. METHODS: We linked national patient demographic, geospatial, and behavioural metadata to whole T pallidum genome sequences previously generated from patient samples collected from across England between Jan 1, 2012, and Oct 31, 2018, and performed detailed phylogenomic analyses. FINDINGS: Of 497 English samples submitted for sequencing, we recovered 240 genomes (198 from the UK Health Security Agency reference laboratory and 42 from other laboratories). Three duplicate samples (same patient and collection date) were included in the main phylogenies, but removed from further analyses of English populations, leaving 237 genomes. 220 (92·8%) of 237 samples were from men, nine (3·8%) were from women, and eight (3·4%) were of unknown gender. Samples were mostly from London (n=118 [49·8%]), followed by southeast England (n=29 [12·2%]), northeast England (n=24 [10·1%]), and southwest England (n=15 [6·3%]). 180 (76·0%) of 237 genomes came from GBMSM, compared with 25 (10·5%) from those identifying as men who have sex with women, 15 (6·3%) from men with unrecorded sexual orientation, nine (3·8%) from those identifying as women who have sex with men, and eight (3·4%) from people of unknown gender and sexual orientation. Phylogenomic analysis and clustering revealed two dominant T pallidum sublineages in England. Sublineage 1 was found throughout England and across all patient groups, whereas sublineage 14 occurred predominantly in GBMSM older than 34 years and was absent from samples sequenced from the north of England. These different spatiotemporal trends, linked to demography or behaviour in the dominant sublineages, suggest they represent different sexual networks. By focusing on different regions of England we were able to distinguish a local heterosexual transmission cluster from a background of transmission in GBMSM. INTERPRETATION: These findings show that, despite extremely close genetic relationships between T pallidum genomes globally, genomics can still be used to identify putative transmission clusters for epidemiological follow-up. This could be of value for deconvoluting putative outbreaks and for informing public health interventions. FUNDING: Wellcome funding to the Sanger Institute, UK Research and Innovation, National Institute for Health and Care Research, European and Developing Countries Clinical Trials Partnership, and UK Health Security Agency.
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Minorías Sexuales y de Género , Sífilis , Humanos , Masculino , Femenino , Sífilis/epidemiología , Homosexualidad Masculina , Inglaterra/epidemiología , GenómicaRESUMEN
Fibrosis progression after acute hepatitis C virus (HCV) infection in human immunodeficiency virus (HIV)-infected patients with follow-up >9 months became similar to reported rates from studies in chronic HIV/HCV coinfection, as measured with transient elastometry. The duration of follow-up and serum alanine transaminase correlated with liver stiffness, and short follow-up resulted in high fibrosis progression rates.
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Infecciones por VIH/complicaciones , Hepatitis C/complicaciones , Cirrosis Hepática/diagnóstico , Cirrosis Hepática/epidemiología , Adulto , Alanina Transaminasa/sangre , Diagnóstico por Imagen de Elasticidad/métodos , Estudios de Seguimiento , Humanos , Hígado/enzimología , Hígado/patología , Cirrosis Hepática/patología , Masculino , Prevalencia , Estudios ProspectivosRESUMEN
BACKGROUND: In HIV-1-infected patients impaired IFN-γ responses to purified protein derivative (PPD) are associated with an increased risk of active tuberculosis. Tuberculosis antigen-specific cells are found in the T(H)1/T(H)17 subset of CD4 T cells, which support HIV-1 replication. Selective loss of T(H)1/T(H)17 cells in patients with HIV-1 infection might contribute to reduced tuberculosis-induced immune responses and an increased susceptibility to active tuberculosis. OBJECTIVES: We sought to investigate the association between T(H)1/T(H)17 cells and PPD-specific cytokine responses in HIV-1-infected patients. METHODS: A cross-sectional study was performed on healthy control subjects, HIV-1-infected patients receiving successful antiretroviral therapy (ART(+)), and ART-naive HIV-1-infected patients (ART(-)). All patients studied had evidence of BCG vaccination. Four discrete CD4 T-cell subsets were assessed by flow cytometry: T(H)1/T(H)17 cells (CXCR3(+)CCR6(+)CCR4(-)), T(H)1 cells (CXCR3(+)CCR6(-)CCR4(-)), T(H)17 cells (CXCR3(-)CCR6(+)CCR4(+)), and T(H)2 cells (CXCR3(-)CCR6(-)CCR4(+)). IFN-γ and IL-2 PPD-specific cytokine responses were assessed in PBMCs by using the enzyme-linked immunospot assay. RESULTS: Twenty-nine healthy control subjects, 34 ART(+) patients, and 26 ART(-) patients were recruited. The number and frequency of T(H)1/T(H)17 and T(H)1/T(H)17 CCR5(+) CD4 T cells were significantly reduced in HIV-1-infected patients. IFN-γ and IL-2 PPD responses were significantly lower in ART(-) patients and were partially reconstituted with successful ART. Loss of T(H)1/T(H)17 CCR5(+) cells was associated with reduced IFN-γ and IL-2 PPD responses. CONCLUSIONS: Selective loss of T(H)1/T(H)17 cells may be a risk factor for the development of active tuberculosis in patients with HIV-1 infection and might be a useful biomarker in the development of tuberculosis vaccines.
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Infecciones Oportunistas Relacionadas con el SIDA/inmunología , VIH-1/inmunología , Interferón gamma/inmunología , Interleucina-2/inmunología , Células TH1/inmunología , Células Th17/inmunología , Tuberculina/inmunología , Tuberculosis/inmunología , Adulto , Biomarcadores , Recuento de Linfocito CD4 , Estudios Transversales , Femenino , Humanos , Masculino , Persona de Mediana Edad , Células Th2/inmunologíaRESUMEN
Despite HIV infection being a treatable chronic illness and the many advances in testing for HIV, late diagnosis is still common, with associated avoidable morbidity and mortality. Requirements for explicit consent for HIV testing in the UK differ from those for other blood tests and are major barriers to testing. We argue that the disparity is illogical and outdated. We propose a model for normalising HIV testing that allows for routine testing in various health-care settings via implied consent, where other blood tests are performed. Inclusion of testing for hepatitis B and hepatitis C might also be incorporated into this model. The ethical argument for this approach is principally beneficence towards people with undiagnosed infection and the people they might infect. Patient autonomy would be maintained using systems allowing for individuals to opt out of implied consent.
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Infecciones por VIH , Hepatitis C , Infecciones por VIH/diagnóstico , Prueba de VIH , Hepatitis C/diagnóstico , Humanos , Consentimiento Informado , Tamizaje Masivo , Reino UnidoRESUMEN
Innovative testing approaches and care pathways are required to meet HIV, hepatitis B (HBV) and hepatitis C (HCV) elimination goals. Routine testing for blood-borne viruses (BBVs) within emergency departments (EDs) is suggested by the European Centre for Disease Prevention and Control but there is a paucity of supporting evidence. We evaluated the introduction of routine BBV testing in EDs at a large teaching hospital in northern England. In October 2018, we modified the electronic laboratory ordering system to reflex opt-out HIV, HBV and HCV testing for all ED attendees aged 16-65 years who had a routine blood test for urea and electrolytes (U&Es). Linkage to care (LTC) was attempted for newly diagnosed patients, those never referred and those who had previously disengaged from care. The project operated for 18 months, here we present evaluation of the initial nine months (2 October 2018-1 July 2019). We analysed testing uptake, BBV seropositivity, LTC and treatment initiation within six months post-diagnosis. Over 9 months, 17,026/28,178 (60.4%) ED attendees who had U&Es performed were tested for ≥ 1 BBV. 299 active BBV infections were identified: 70 HIV Ab/Ag-positive (0.4% seroprevalence), 73 HBsAg-positive (0.4%) and 156 HCV RNA-positive (1.0%). Only 24.3% (17/70) HIV Ab/Ag-positive individuals required LTC, compared to 94.9% (148/156) HCV RNA-positive and 53.4% (39/73) HBsAg-positive individuals. LTC was successful in 94.1% (16/17) HIV Ab/Ag-positive and 69.3% (27/39) HBsAg-positive individuals. However, at 6 months LTC was just 39.2% (58/148) for HCV RNA-positive individuals, with 64% (37/58) of these commencing treatment. Universal opt-out ED BBV testing proved feasible and effective in identifying active BBV infections, especially among marginalised populations with reduced healthcare access. Our integrated approach achieved good LTC rates although further service development is necessary, particularly for HCV RNA-positive people who inject drugs.
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Infecciones por VIH , Hepatitis B , Hepatitis C , Humanos , Antígenos de Superficie de la Hepatitis B , Estudios Seroepidemiológicos , Infecciones por VIH/diagnóstico , Infecciones por VIH/epidemiología , Hepatitis C/diagnóstico , Hepatitis C/epidemiología , Hepatitis B/diagnóstico , Hepatitis B/epidemiología , Hepacivirus , Servicio de Urgencia en Hospital , Resultado del Tratamiento , Reino Unido , ARNRESUMEN
Syphilis, which is caused by the sexually transmitted bacterium Treponema pallidum subsp. pallidum, has an estimated 6.3 million cases worldwide per annum. In the past ten years, the incidence of syphilis has increased by more than 150% in some high-income countries, but the evolution and epidemiology of the epidemic are poorly understood. To characterize the global population structure of T. pallidum, we assembled a geographically and temporally diverse collection of 726 genomes from 626 clinical and 100 laboratory samples collected in 23 countries. We applied phylogenetic analyses and clustering, and found that the global syphilis population comprises just two deeply branching lineages, Nichols and SS14. Both lineages are currently circulating in 12 of the 23 countries sampled. We subdivided T. p. pallidum into 17 distinct sublineages to provide further phylodynamic resolution. Importantly, two Nichols sublineages have expanded clonally across 9 countries contemporaneously with SS14. Moreover, pairwise genome analyses revealed examples of isolates collected within the last 20 years from 14 different countries that had genetically identical core genomes, which might indicate frequent exchange through international transmission. It is striking that most samples collected before 1983 are phylogenetically distinct from more recently isolated sublineages. Using Bayesian temporal analysis, we detected a population bottleneck occurring during the late 1990s, followed by rapid population expansion in the 2000s that was driven by the dominant T. pallidum sublineages circulating today. This expansion may be linked to changing epidemiology, immune evasion or fitness under antimicrobial selection pressure, since many of the contemporary syphilis lineages we have characterized are resistant to macrolides.
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Filogenia , Sífilis/microbiología , Treponema pallidum/aislamiento & purificación , Antibacterianos/farmacología , Farmacorresistencia Bacteriana , Genoma Bacteriano , Humanos , Macrólidos/farmacología , Treponema pallidum/clasificación , Treponema pallidum/genética , Treponema pallidum/fisiologíaRESUMEN
Cell biologists generally consider that microtubules and actin play complementary roles in long- and short-distance transport in animal cells. On the contrary, using melanosomes of melanocytes as a model, we recently discovered that the motor protein myosin-Va works with dynamic actin tracks to drive long-range organelle dispersion in opposition to microtubules. This suggests that in animals, as in yeast and plants, myosin/actin can drive long-range transport. Here, we show that the SPIRE-type actin nucleators (predominantly SPIRE1) are Rab27a effectors that co-operate with formin-1 to generate actin tracks required for myosin-Va-dependent transport in melanocytes. Thus, in addition to melanophilin/myosin-Va, Rab27a can recruit SPIREs to melanosomes, thereby integrating motor and track assembly activity at the organelle membrane. Based on this, we suggest a model in which organelles and force generators (motors and track assemblers) are linked, forming an organelle-based, cell-wide network that allows their collective activity to rapidly disperse the population of organelles long-distance throughout the cytoplasm.
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Actinas/metabolismo , Proteínas rab27 de Unión a GTP/metabolismo , Biología Celular , Citoesqueleto/metabolismo , Células HEK293 , Humanos , Microtúbulos/metabolismo , Orgánulos , Filogenia , Proteínas rab27 de Unión a GTP/genéticaRESUMEN
Accurate image quantification requires accurate calibration of the detector and is vital if dosimetry is to be performed in molecular radiotherapy. A dependence on the position of calibration has been observed in single photon emission computed tomography images when attenuation correction (AC) and scatter correction are applied. This work investigates the origin of this dependence in single photon emission computed tomography scans of phantom inserts filled with Lu solution. A 113 ml sphere and inserts representing a mathematical model of a spleen and an anatomical model of a patient spleen were imaged at the centre and edge of elliptical phantoms. For these inserts, the difference in calibration factor between the positions was around 10% for images reconstructed with AC and triple energy window scatter correction. A combination of experimental imaging and Monte Carlo simulation was used to isolate possible causes due to imaging or reconstruction in turn. Inconsistent application of AC between different reconstruction systems was identified as the origin of the positional dependence.
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Procesamiento de Imagen Asistido por Computador , Tomografía Computarizada de Emisión de Fotón Único , Calibración , Dispersión de RadiaciónRESUMEN
The optimised delivery of Molecular Radiotherapy requires individualised calculation of absorbed dose to both targeted lesions and neighbouring healthy tissue. To achieve this, accurate quantification of the activity distribution in the patient by external detection is vital. METHODS: This work extends specific anatomy-related calibration to true organ shapes. A set of patient-specific 3D printed organ inserts based on a diagnostic CT scan was produced, comprising the liver, spleen and both kidneys. The inserts were used to calculate patient-specific calibration factors for 177Lu. These calibration factors were compared with previously reported calibration factors for corresponding organ models based on the Cristy and Eckerman phantom series and for a comparably sized sphere. Monte Carlo calculations of the patient-specific radiation dose were performed for comparison with current clinical dosimetry methods for these data. RESULTS: Patient-specific calibration factors are shown to be dependent on the volume, shape and position of the organ containing activity with a corresponding impact on the calculation of the dose to the patient. The impact of organ morphology on calculated dose is reduced when the dominant contributor to dose is beta particles. This is due to the small range of beta particles in tissue. Overestimations of recovered activity and hence dose of up to 135% are observed. CONCLUSION: For accurate quantification to be performed calibration factors accounting for organ size, shape and position must be used. Such quantification is vital if accurate, patient-specific dosimetry is to be achieved.