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Cardiac arrest is one of the major public health problems with sudden onset, high mortality and high disability rate. The prevalence of cardiovascular disease continues to rise and the burden of cardiac arrest is increasing in China. It is of great significance to explore more effective prevention and treatment measures to improve the prognosis of patients with cardiac arrest. This article discusses the relevant progress on the treatment ability of emergency and critical cardiovascular diseases, medicines and technologies for cardiac arrest care, and registry studies of cardiac arrest, to further promote the effective improvement of key capacities at various stages of the prevention and treatment of cardiac arrest in China.
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Reanimação Cardiopulmonar , Parada Cardíaca , Humanos , Parada Cardíaca/terapia , Prognóstico , Sistema de Registros , Saúde PúblicaRESUMO
The classical B1(NaCl)âB2(CsCl) transitions have been considered as a model for general structural phase transformations, and resolving corresponding phase transition mechanisms under high strain rate shock compression is critical to a fundamental understanding of phase transition dynamics. Here, we use subnanosecond synchrotron x-ray diffraction to visualize the lattice response of single-crystal KCl to planar shock compression. Complete B1-B2 orientation relations are revealed for KCl under shock compression along ⟨100⟩_{B1} and ⟨110⟩_{B1}; the orientation relations and transition mechanisms are anisotropic and can be described with the standard and modified Watanabe-Tokonami-Morimoto model, respectively, both involving interlayer sliding and intralayer ion rearrangement. The current study also establishes a paradigm for investigating solid-solid phase transitions under dynamic extremes with ultrafast synchrotron x-ray diffraction.
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Objective: To understand the status quo of nurses' professional mission and explore the influencing factors of nurses' professional mission. Methods: From November to December, 2018, 316 nurses from three tertiary hospitals in Tianjin were selected as the research objects. The occupational mission scale was used to investigate the sense of professional mission, the nursing work environment scale was used for the nursing work environment survey, and the work family conflict scale was used for the work family conflict investigation. Pearson correlation analysis was used to analyze the correlation among nurses' sense of professional mission, nursing work environment and work family conflict; multiple linear regression analysis was used to analyze the influencing factors of nurses' sense of professional mission. Results: The score of professional mission of nurses was (2.90±0.56) . Average monthly income, nursing work environment and work family conflict were the influencing factors of nurses' professional mission (P<0.05) . The results of hierarchical regression showed that the higher the average monthly income (ß=0.252) , the higher the sense of professional mission of nurses (R(2)=0.064) ; after controlling general data, the two dimensions of nursing work environment: Nurses' participation in hospital affairs (ß=0.263) , high-quality nursing service foundation (ß=0.368) , and work family conflict (ß=-0.145) could explain 43.1% of the total variation of professional mission. Conclusion: The sense of professional mission of nurses is above the middle level. Nursing managers should start with the influencing factors such as average monthly income, nursing working environment and work family conflict, so as to stimulate or improve nurses' sense of professional mission.
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Recursos Humanos de Enfermagem Hospitalar , Estudos Transversais , Hospitais , Humanos , Satisfação no Emprego , Inquéritos e Questionários , Local de TrabalhoRESUMO
Strain tensor measurements are important for understanding elastic and plastic deformation, but full bulk strain tensor measurement techniques are still lacking, in particular for dynamic loading. Here, such a methodology is reported, combining imaging-based strain field mapping and simultaneous X-ray diffraction for four typical loading modes: one-dimensional strain/stress compression/tension. Strain field mapping resolves two in-plane principal strains, and X-ray diffraction analysis yields volumetric strain, and thus the out-of-plane principal strain. This methodology is validated against direct molecular dynamics simulations on nanocrystalline tantalum. This methodology can be implemented with simultaneous X-ray diffraction and digital image correlation in synchrotron radiation or free-electron laser experiments.
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Abnormal blood flow and wall shear stress (WSS) can cause and be caused by cardiovascular disease. To date, however, no standard method has been established for mapping WSS in vivo. Here we demonstrate wide-field assessment of WSS in the rabbit abdominal aorta using contrast-enhanced ultrasound image velocimetry (UIV). Flow and WSS measurements were made independent of beam angle, curvature or branching. Measurements were validated in an in silico model of the rabbit thoracic aorta with moving walls and pulsatile flow. Mean errors over a cardiac cycle for velocity and WSS were 0.34 and 1.69%, respectively. In vivo time average WSS in a straight segment of the suprarenal aorta correlated highly with simulations (PC = 0.99) with a mean deviation of 0.29 Pa or 5.16%. To assess fundamental plausibility of the measurement, UIV WSS was compared to an analytic approximation derived from the Poiseuille equation; the discrepancy was 17%. Mapping of WSS was also demonstrated in regions of arterial branching. High time average WSS (TAWSSxz = 3.4 Pa) and oscillatory flow (OSIxz = 0.3) were observed near the origin of conduit arteries. In conclusion, we have demonstrated that contrast-enhanced UIV is capable of measuring spatiotemporal variation in flow velocity, arterial wall location and hence WSS in vivo with high accuracy over a large field of view.
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Aorta Abdominal/diagnóstico por imagem , Aorta Abdominal/fisiologia , Animais , Artéria Celíaca/diagnóstico por imagem , Artéria Celíaca/fisiologia , Meios de Contraste/farmacologia , Hemodinâmica , Coelhos , Artéria Renal/diagnóstico por imagem , Artéria Renal/fisiologia , Reologia , Estresse Mecânico , UltrassonografiaRESUMO
In situ X-ray diffraction with advanced X-ray sources offers unique opportunities for investigating materials properties under extreme conditions such as shock-wave loading. Here, Singh's theory for deducing high-pressure density and strength from two-dimensional (2D) diffraction patterns is rigorously examined with large-scale molecular dynamics simulations of isothermal compression and shock-wave compression. Two representative solids are explored: nanocrystalline Ta and diamond. Analysis of simulated 2D X-ray diffraction patterns is compared against direct molecular dynamics simulation results. Singh's method is highly accurate for density measurement (within 1%) and reasonable for strength measurement (within 10%), and can be used for such measurements on nanocrystalline and polycrystalline solids under extreme conditions (e.g. in the megabar regime).
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High-frame-rate (HFR) ultrasound (US) imaging and contrast-enhanced US (CEUS) are often implemented using multipulse transmissions, to enhance image quality. Multipulse approaches, however, suffer from degradation in the presence of motion, especially when coherent compounding and CEUS are combined. In this paper, we investigate this effect on the intensity of HFR CEUS in deep tissue imaging using simulations and in vivo contrast echocardiography (CE). The simulation results show that the motion artifact is much higher when the flow is in an axial direction than a lateral direction. Using a pulse repetition frequency suitable for cardiac imaging, a motion of 35 cm/s can cause as much as 28.5 dB decrease in image intensity, where compounding can contribute up to 18.7 dB of intensity decrease (11 angles). These motion effects are also demonstrated for in vivo cardiac HFR CE, where the large velocities of both the myocardium and the blood are present. Intensity reductions of 10.4 dB are readily visible in the chamber. Finally, we demonstrate how performing motion-correction before pulse inversion compounding greatly reduces such motion artifact and improve image signal-to-noise ratio and contrast.
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Deformation twinning plays a vital role in accommodating plastic deformation of hexagonal-close-packed (hcp) metals, but its mechanisms are still unsettled under high strain rate shock compression. Here we investigate deformation twinning in shock-compressed Mg as a typical hcp metal with in situ, ultrafast synchrotron x-ray diffraction. Extension twinning occurs upon shock compression along ⟨112[over ¯]0⟩ and ⟨101[over ¯]0⟩, but only upon release for loading along ⟨0001⟩. Such deformation mechanisms are a result of the polarity of deformation twinning, which depends on directionality and relative magnitude of resolved shear stress and may be common for Mg and its alloys in a wide range of strain rates.
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Polychromatic synchrotron undulator X-ray sources are useful for ultrafast single-crystal diffraction under shock compression. Here, simulations of X-ray diffraction of shock-compressed single-crystal tantalum with realistic undulator sources are reported, based on large-scale molecular dynamics simulations. Purely elastic deformation, elastic-plastic two-wave structure, and severe plastic deformation under different impact velocities are explored, as well as an edge release case. Transmission-mode diffraction simulations consider crystallographic orientation, loading direction, incident beam direction, X-ray spectrum bandwidth and realistic detector size. Diffraction patterns and reciprocal space nodes are obtained from atomic configurations for different loading (elastic and plastic) and detection conditions, and interpretation of the diffraction patterns is discussed.
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PURPOSE: A reduction in ambient pressure or decompression from scuba diving can result in ultrasound-detectable venous gas emboli (VGE). These environmental exposures carry a risk of decompression sickness (DCS) which is mitigated by adherence to decompression schedules; however, bubbles are routinely observed for dives well within these limits and significant inter-personal variability in DCS risk exists. Here, we assess the variability and evolution of VGE for 2 h post-dive using echocardiography, following a standardized pool dive in calm warm conditions. METHODS: 14 divers performed either one or two (with a 24 h interval) standardized scuba dives to 33 mfw (400 kPa) for 20 min of immersion time at NEMO 33 in Brussels, Belgium. Measurements were performed at 21, 56, 91 and 126 min post-dive: bubbles were counted for all 68 echocardiography recordings and the average over ten consecutive cardiac cycles taken as the bubble score. RESULTS: Significant inter-personal variability was demonstrated despite all divers following the same protocol in controlled pool conditions: in the detection or not of VGE, in the peak VGE score, as well as time to VGE peak. In addition, intra-personal differences in 2/3 of the consecutive day dives were seen (lower VGE counts or faster clearance). CONCLUSIONS: Since VGE evolution post-dive varies between people, more work is clearly needed to isolate contributing factors. In this respect, going toward a more continuous evaluation, or developing new means to detect decompression stress markers, may offer the ability to better assess dynamic correlations to other physiological parameters.
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Variação Biológica Individual , Doença da Descompressão/fisiopatologia , Mergulho/efeitos adversos , Embolia Aérea/fisiopatologia , Adulto , Doença da Descompressão/diagnóstico por imagem , Doença da Descompressão/etiologia , Mergulho/fisiologia , Ecocardiografia , Embolia Aérea/diagnóstico por imagem , Embolia Aérea/etiologia , Humanos , Masculino , Pessoa de Meia-Idade , Veias/diagnóstico por imagemRESUMO
We investigate crystallization of Lennard-Jones liquids on substrates under dynamic compression with large-scale molecular dynamics simulations. The substrates examined include single crystals and bicrystals with different crystallographic orientations, and the loading paths include shock and quasi-isentropic loading. Microstructure is characterized with simulated x-ray diffraction and orientation mapping. For shock loading, only heterogeneous nucleation occurs at the simulation scales. Quasi-isentropic loading induces less heating and larger supercooling; as a result, heterogeneous nucleation occurs at low loading strengths, and both heterogeneous and homogeneous nucleation occur at high loading strengths, despite the crystalline substrates. Crystallization depends on the substrate structure (crystal orientation and grain boundary) and loading characteristics. Deformation may induce grain structure change (e.g., reorientation and twinning) of substrates and affect subsequent crystallization. Crystallization rate is anisotropic, inversely proportional to the cosine of the dihedral angle between the substrate plane and a main {111} growth plane.
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The microenvironment of glioblastoma (GBM) contains high levels of inflammatory cytokine interleukin 6 (IL-6), which contributes to promote tumour progression and invasion. The common epidermal growth factor receptor variant III (EGFRvIII) mutation in GBM is associated with significantly higher levels of IL-6. Furthermore, elevated IL-1ß levels in GBM tumours are also believed to activate GBM cells and enhance IL-6 production. However, the crosstalk between these intrinsic and extrinsic factors within the oncogene-microenvironment of GBM causing overproduction of IL-6 is poorly understood. Here, we show that EGFRvIII potentiates IL-1ß-induced IL-6 secretion from GBM cells. Importantly, exacerbation of IL-6 production is most effectively attenuated in EGFRvIII-expressing GBM cells with inhibitors of p38 mitogen-activated protein kinase (p38 MAPK) and MAPK-activated protein kinase 2 (MK2). Enhanced IL-6 production and increased sensitivity toward pharmacological p38 MAPK and MK2 inhibitors in EGFRvIII-expressing GBM cells is associated with increased MK2-dependent nuclear-cytoplasmic shuttling and accumulation of human antigen R (HuR), an IL-6 mRNA-stabilising protein, in the cytosol. IL-1ß-stimulated activation of the p38 MAPK-MK2-HuR pathway significantly enhances IL-6 mRNA stability in GBM cells carrying EGFRvIII. Further supporting a role for the p38 MAPK-MK2-HuR pathway in the development of inflammatory environment in GBM, activated MK2 is found in more than 50% of investigated GBM tissues and correlates with lower grade and secondary GBMs. Taken together, p38 MAPK-MK2-HuR signalling may enhance the potential of intrinsic (EGFRvIII) and extrinsic (IL-1ß) factors to develop an inflammatory GBM environment. Hence, further improvement of brain-permeable and anti-inflammatory inhibitors targeting p38 MAPK, MK2 and HuR may combat progression of lower grade gliomas into aggressive GBMs.
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Neoplasias Encefálicas , Receptores ErbB/farmacologia , Glioblastoma , Interleucina-1beta/farmacologia , Interleucina-6/metabolismo , Sistema de Sinalização das MAP Quinases/fisiologia , Neoplasias Encefálicas/genética , Neoplasias Encefálicas/metabolismo , Neoplasias Encefálicas/patologia , Proteínas ELAV/metabolismo , Proteína Semelhante a ELAV 1 , Glioblastoma/genética , Glioblastoma/metabolismo , Glioblastoma/patologia , Humanos , Inflamação/genética , Inflamação/metabolismo , Peptídeos e Proteínas de Sinalização Intracelular/metabolismo , Proteínas Serina-Treonina Quinases/metabolismo , Células Tumorais Cultivadas , Microambiente Tumoral/efeitos dos fármacos , Microambiente Tumoral/genética , Proteínas Quinases p38 Ativadas por Mitógeno/metabolismoRESUMO
Ultrasound (US) is a widely used clinical imaging modality that offers penetration depths in tissue of >10 cm. However, the spatial resolution in US imaging is fundamentally limited by diffraction to approximately half the wavelength of the sound wave employed. The spatial resolution of optical microscopy is limited by the same fundamental physics, but in recent years super-resolution imaging techniques have been developed that overcome the diffraction limit through the localization of many spatially separated photo-switchable or photo-activatable fluorophores. In this paper, we apply a related approach to demonstrate super-resolution imaging with US. We imaged dilute suspensions of microbubble contrast agents flowing through narrow tube-based phantoms. By spatially localizing multiple spatially isolated microbubbles, we constructed super-resolved microbubble location density maps that clearly resolve features 5.1-2.2 times smaller than the US system point spread function full width half maximum in the lateral and axial directions respectively. Our initial characterization experiment using a fixed 100 µm diameter brass wire and a US frequency of 2 MHz suggests that for an ideal stationary point scatterer the ultimate resolution of the unmodified clinical US system used could be in the range of 2-4 µm.
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Meios de Contraste/farmacologia , Microbolhas , Ultrassonografia/métodos , Acústica , Celulose/química , Meios de Contraste/química , Diagnóstico por Imagem/métodos , Desenho de Equipamento , Corantes Fluorescentes/química , Microscopia/métodos , Óptica e Fotônica , Imagens de Fantasmas , Fatores de Tempo , UltrassomRESUMO
We previously generated and characterized synthesized fatty acid desaturase-1 (sFat-1) transgenic pigs that had increased concentrations of ω-3 unsaturated fatty acid in their meat. The objective was to assess whether the inserted foreign gene in sFat-1 transgenic pigs was able to transfer and integrate into the genome of nontransgenic pigs by suckling or mating. Tests for suckling-mediated horizontal gene transfer (HGT) included sFat-1 transgenic sows nursing nontransgenic piglets and sFat-1 transgenic piglets suckling nontransgenic sows. Tests for mating-mediated HGT were performed by male sFat-1 transgenic pigs mated with nontransgenic females and female sFat-1 transgenic pigs mated with nontransgenic males. Polymerase chain reaction was used to detect the sFat-1 gene fragment in various tissues sampled from nontransgenic pigs. The foreign target gene sFat-1 was not detected in the genomic DNA of various tissues and organs sampled from nontransgenic pigs. Therefore, we concluded that HGT from transgenic pigs to wild type pigs via suckling or mating was unlikely.
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Animais Geneticamente Modificados/genética , Ácidos Graxos Dessaturases/genética , Transferência Genética Horizontal/genética , Sus scrofa/genética , Animais , Animais Lactentes , Cruzamento , DNA/análise , Ácidos Graxos Ômega-3/análise , Feminino , Masculino , Carne/análise , Reação em Cadeia da Polimerase/veterináriaRESUMO
OBJECTIVE: To assess the cognitive phenotype of glucocerebrosidase (GBA) mutation carriers with early-onset Parkinson disease (PD). METHODS: We administered a neuropsychological battery and the University of Pennsylvania Smell Identification Test (UPSIT) to participants in the CORE-PD study who were tested for mutations in PARKIN, LRRK2, and GBA. Participants included 33 GBA mutation carriers and 60 noncarriers of any genetic mutation. Primary analyses were performed on 26 GBA heterozygous mutation carriers without additional mutations and 39 age- and PD duration-matched noncarriers. Five cognitive domains, psychomotor speed, attention, memory, visuospatial function, and executive function, were created from transformed z scores of individual neuropsychological tests. Clinical diagnoses (normal, mild cognitive impairment [MCI], dementia) were assigned blind to genotype based on neuropsychological performance and functional impairment as assessed by the Clinical Dementia Rating (CDR) score. The association between GBA mutation status and neuropsychological performance, CDR, and clinical diagnoses was assessed. RESULTS: Demographics, UPSIT, and Unified Parkinson's Disease Rating Scale-III performance did not differ between GBA carriers and noncarriers. GBA mutation carriers performed more poorly than noncarriers on the Mini-Mental State Examination (p = 0.035), and on the memory (p = 0.017) and visuospatial (p = 0.028) domains. The most prominent differences were observed in nonverbal memory performance (p < 0.001). Carriers were more likely to receive scores of 0.5 or higher on the CDR (p < 0.001), and a clinical diagnosis of either MCI or dementia (p = 0.004). CONCLUSION: GBA mutation status may be an independent risk factor for cognitive impairment in patients with PD.
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Disfunção Cognitiva/genética , Análise Mutacional de DNA , Triagem de Portadores Genéticos , Glucosilceramidase/genética , Testes Neuropsicológicos , Doença de Parkinson/genética , Adulto , Doenças dos Gânglios da Base/diagnóstico , Doenças dos Gânglios da Base/genética , Disfunção Cognitiva/diagnóstico , Demência/diagnóstico , Demência/genética , Transtorno Depressivo/diagnóstico , Transtorno Depressivo/genética , Feminino , Testes Genéticos , Genótipo , Humanos , Serina-Treonina Proteína Quinase-2 com Repetições Ricas em Leucina , Masculino , Transtornos da Memória/diagnóstico , Transtornos da Memória/genética , Entrevista Psiquiátrica Padronizada , Pessoa de Meia-Idade , Transtornos do Olfato/diagnóstico , Transtornos do Olfato/genética , Doença de Parkinson/diagnóstico , Fenótipo , Proteínas Serina-Treonina Quinases/genética , Ubiquitina-Proteína Ligases/genética , beta-Glucosidase/genéticaRESUMO
BACKGROUND: Mutations in parkin are a known genetic risk factor for early onset Parkinson's disease (EOPD) but their role in non-motor manifestations is not well established. Genetic factors for depression are similarly not well characterized. We investigate the role of parkin mutations in depression among those with EOPD and their relatives. METHODS: We collected psychiatric information using the Patient Health Questionnaire and Beck Depression Inventory II on 328 genotyped individuals including 88 probands with early onset PD (41 with parkin mutations, 47 without) and 240 first and second-degree relatives without PD. RESULTS: Genotype was not associated with depression risk among probands. Among unaffected relatives of EOPD cases, only compound heterozygotes (n = 4), and not heterozygotes, had significantly increased risk of depressed mood (OR = 14.1; 95% CI 1.2-163.4), moderate to severe depression (OR = 17.8; 95% CI 1.0-332.0), depression (score ≥ 15) on the Beck Depression Inventory II (BDI-II) (OR = 51.9; 95% CI 4.1-657.4), and BDI-II total depression score (ß = 8.4; 95% CI 2.4-11.3) compared to those without parkin mutations. CONCLUSIONS: Relatives of EOPD cases with compound heterozygous mutations and without diagnosed PD may have a higher risk of depression compared to relatives without parkin mutations. These findings support evidence of a genetic contribution to depression and may extend the phenotypic spectrum of parkin mutations to include non-motor manifestations that precede the development of PD.
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Depressão/genética , Predisposição Genética para Doença/genética , Doença de Parkinson/genética , Doença de Parkinson/psicologia , Ubiquitina-Proteína Ligases/genética , Adulto , Idade de Início , Análise Mutacional de DNA , Feminino , Genótipo , Heterozigoto , Humanos , Masculino , Pessoa de Meia-Idade , Reação em Cadeia da Polimerase Multiplex , Mutação , Testes Neuropsicológicos , Fenótipo , Fatores de RiscoRESUMO
BACKGROUND/AIMS: To confirm in a cohort recruited in 1999-2001 our finding in a cohort recruited in 1992-1994 relating type 2 diabetes (T2D) to late-onset Alzheimer's disease (LOAD). METHODS: Participants were 1,488 persons aged 65 years and older without dementia at baseline from New York City. T2D was ascertained by self-report. Dementia and LOAD were ascertained by standard research procedures. Proportional hazard regression was used for analyses relating T2D and LOAD. RESULTS: The prevalence of T2D was 17%. There were 161 cases of dementia and 149 cases of LOAD. T2D was related to dementia (hazard ratio = 1.7; 95% confidence interval = 1.4-2.9) and LOAD (1.6; 1.0-2.6) after adjustment for age, sex, education, ethnic group and apolipoprotein E ε4. This association was weaker when only AD - excluding cases of mixed dementia - was considered (hazard ratio = 1.3; 95% confidence interval = 0.8-2.2). CONCLUSION: T2D is associated with LOAD. Cerebrovascular disease may be an important mediator.
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Doença de Alzheimer/epidemiologia , Diabetes Mellitus Tipo 2/epidemiologia , Idade de Início , Idoso , Idoso de 80 Anos ou mais , Doença de Alzheimer/complicações , Doença de Alzheimer/diagnóstico , Apolipoproteínas E/genética , População Negra , Estudos de Coortes , Diabetes Mellitus Tipo 2/complicações , Escolaridade , Etnicidade , Feminino , Frequência do Gene , Hispânico ou Latino , Humanos , Estudos Longitudinais , Masculino , Cidade de Nova Iorque/epidemiologia , Modelos de Riscos Proporcionais , Fatores de Risco , Fumar/epidemiologiaRESUMO
BACKGROUND: While Parkinson disease (PD) is consistently associated with impaired olfaction, one study reported better olfaction among Parkin mutation carriers than noncarriers. Whether olfaction differs between Parkin mutation heterozygotes and carriers of 2 Parkin mutations (compound heterozygotes) is unknown. OBJECTIVE: To assess the relationship between Parkin genotype and olfaction in PD probands and their unaffected relatives. METHODS: We administered the University of Pennsylvania Smell Identification Test (UPSIT) to 44 probands in the Consortium on Risk for Early-Onset Parkinson Disease study with PD onset ≤50 years (10 Parkin mutation heterozygotes, 9 compound heterozygotes, 25 noncarriers) and 80 of their family members (18 heterozygotes, 2 compound heterozygotes, 60 noncarriers). In the probands, linear regression was used to assess the association between UPSIT score (outcome) and Parkin genotype (predictor), adjusting for covariates. Among family members without PD, we compared UPSIT performance in heterozygotes vs noncarriers using generalized estimating equations, adjusting for family membership, age, gender, and smoking. RESULTS: Among probands with PD, compound heterozygotes had higher UPSIT scores (31.9) than heterozygotes (20.1) or noncarriers (19.9) (p < 0.001). These differences persisted after adjustment for age, gender, disease duration, and smoking. Among relatives without PD, UPSIT performance was similar in heterozygotes (32.5) vs noncarriers (32.4), and better than in heterozygotes with PD (p = 0.001). CONCLUSION: Olfaction is significantly reduced among Parkin mutation heterozygotes with PD but not among their heterozygous relatives without PD. Compound heterozygotes with PD have olfaction within the normal range. Further research is required to assess whether these findings reflect different neuropathology in Parkin mutation heterozygotes and compound heterozygotes.
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Doença de Parkinson/genética , Olfato , Ubiquitina-Proteína Ligases/genética , Adulto , Feminino , Heterozigoto , Humanos , Masculino , Pessoa de Meia-Idade , Mutação , Doença de Parkinson/fisiopatologiaRESUMO
Ultrasound provides a valuable tool for medical diagnosis offering real-time imaging with excellent spatial resolution and low cost. The advent of microbubble contrast agents has provided the additional ability to obtain essential quantitative information relating to tissue vascularity, tissue perfusion and even endothelial wall function. This technique has shown great promise for diagnosis and monitoring in a wide range of clinical conditions such as cardiovascular diseases and cancer, with considerable potential benefits in terms of patient care. A key challenge of this technique, however, is the existence of significant variations in the imaging results, and the lack of understanding regarding their origin. The aim of this paper is to review the potential sources of variability in the quantification of tissue perfusion based on microbubble contrast-enhanced ultrasound images. These are divided into the following three categories: (i) factors relating to the scanner setting, which include transmission power, transmission focal depth, dynamic range, signal gain and transmission frequency, (ii) factors relating to the patient, which include body physical differences, physiological interaction of body with bubbles, propagation and attenuation through tissue, and tissue motion, and (iii) factors relating to the microbubbles, which include the type of bubbles and their stability, preparation and injection and dosage. It has been shown that the factors in all the three categories can significantly affect the imaging results and contribute to the variations observed. How these factors influence quantitative imaging is explained and possible methods for reducing such variations are discussed.
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OBJECTIVE: To examine changes in levels of plasma amyloid-ß (Aß) peptides, Aß42 and Aß40, in relation to onset of Alzheimer disease (AD) in adults with Down syndrome (DS). METHODS: Plasma Aß42 and Aß40 were measured at initial examination and at follow-up in a community-based cohort of 225 adults with DS who did not have dementia at baseline and were assessed for cognitive/functional abilities and health status and followed at 14- to 20-month intervals. We used Cox proportional hazards modeling to estimate the cumulative incidence of AD by Aß peptide change group (increasing, no change, or decreasing), adjusting for covariates. RESULTS: Sixty-one (27.1%) of the participants developed AD. At follow-up, a decrease in Aß42 levels, a decrease in the Aß42/Aß40 ratio, and an increase in Aß40 levels were related to conversion to AD. Compared with the group with increasing levels of Aß42, the likelihood of developing AD was 5 times higher for those whose plasma Aß42 levels decreased over follow-up (hazard ratio [HR] = 4.9, 95% confidence interval [CI] 2.1-11.4). Decreasing Aß42/Aß40 was also strongly related to AD risk (HR = 4.9, 95% CI 1.8-13.2), while decreasing Aß40 was associated with lower risk (HR = 0.4, 95% CI 0.2-0.9). CONCLUSIONS: Among adults with DS, decreasing levels of plasma Aß42, a decline in the Aß42/Aß40 ratio, or increasing levels of Aß40 may be sensitive indicators of conversion to AD, possibly reflecting compartmentalization of Aß peptides in the brain.