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1.
Sci Total Environ ; 722: 137924, 2020 Mar 13.
Artigo em Inglês | MEDLINE | ID: mdl-32208270

RESUMO

Periodic vortex shedding around a building could play an important role in wind-driven single-sided ventilation especially when two free openings are mounted on the leeward wall, in which case "pumping" flow dominates the natural ventilation. In this paper, we investigated the characteristics of vortex shedding and "pumping" flow affected by the arrangements of upstream buildings and opening area ratio of ports on the downstream target building. Computational fluid dynamics (CFD) simulations have been used to predict the instantaneous and mean flow fields. Numerical results indicate that the strength of "pumping" flow could be intensively weakened by two upstream buildings. Vortex shedding from the inner shear layers dominates the vortex shedding from the target building and constrains that from both upstream buildings except at W/B = 0.5, in which case the gap flow is weak and the St is close to that of a single building. The increase of upstream building length leads to decrease of the vortex shedding frequency at the wake of all buildings and ventilation rate of the downstream building. An increase of opening area ratio on the rear wall of the downstream building will raise the Strouhal number but have no positive correlation with ventilation rate. "Pumping" flow oscillating frequency does not have clear correlation with the ventilation rate. Our study on the wake vortex shedding flow across building clusters could benefit the future green design of urban buildings.

2.
J Infect Dis ; 2020 Mar 16.
Artigo em Inglês | MEDLINE | ID: mdl-32179916

RESUMO

Influenza virus can survive on some surfaces, facilitating indirect person-to-person transmission. We collected swab samples weekly from commonly-touched surfaces in 7 kindergartens and primary schools during the 2017/18 winter influenza season in Hong Kong. We detected influenza virus RNA in 12/1352 samples (<1%) collected from 7/11 classrooms (5-2x106 RNA copies/ml). Viral RNA was more frequently recovered from communal items inside classrooms such as bookshelves and doorknobs, suggesting these surfaces may cause greater potential risks of transmission during influenza epidemics. Surface contamination indicates the potential role of fomites in influenza virus transmission in schools.

3.
Indoor Air ; 2020 Mar 23.
Artigo em Inglês | MEDLINE | ID: mdl-32201989

RESUMO

Influenza transmission occurs through the air, but the relative importance of small droplets, or aerosols, in influenza transmission especially within healthcare facilities remains uncertain. Detections of influenza virus in aerosols in cough and exhaled breath from infected patients, and from the air in outpatient or inpatient healthcare facilities have been studied, but most studies were done in adults with very few data involving children. We aimed to assess the potential of influenza transmission via aerosols in pediatric patient rooms. Two-stage cyclone (NIOSH) air samplers were used to collect the air in 5-bed pediatric patient rooms with patients with PCR-confirmed influenza. Influenza A virus RNA was recovered in 15/19 (79%) air sampling occasions, in all size fractions (>4µm, 1-4µm and <1µm), and significantly less for influenza B virus (2/10 occasions, 20%). We estimated a ventilation rate of 1.46 ACH in a similar but unoccupied 5-bed patient room. High quantities of influenza A virus RNA detected in the air in pediatric patient rooms suggests other individuals in paediatric patient rooms including other patients, visitors, caretakers and healthcare workers could be exposed to influenza A virus while caring for infected children.

4.
Proc Natl Acad Sci U S A ; 117(6): 3144-3149, 2020 Feb 11.
Artigo em Inglês | MEDLINE | ID: mdl-32001509

RESUMO

Glycogen plays a central role in glucose homeostasis and is abundant in several types of tissue. We report an MRI method for imaging glycogen noninvasively with enhanced detection sensitivity and high specificity, using the magnetic coupling between glycogen and water protons through the nuclear Overhauser enhancement (NOE). We show in vitro that the glycogen NOE (glycoNOE) signal is correlated linearly with glycogen concentration, while pH and temperature have little effect on its intensity. For validation, we imaged glycoNOE signal changes in mouse liver, both before and after fasting and during glucagon infusion. The glycoNOE signal was reduced by 88 ± 16% (n = 5) after 24 h of fasting and by 76 ± 22% (n = 5) at 1 h after intraperitoneal (i.p.) injection of glucagon, which is known to rapidly deplete hepatic glycogen. The ability to noninvasively image glycogen should allow assessment of diseases in which glucose metabolism or storage is altered, for instance, diabetes, cardiac disease, muscular disorders, cancer, and glycogen storage diseases.

5.
Artigo em Inglês | MEDLINE | ID: mdl-32102305

RESUMO

Knowledge of human behaviors is important for improving indoor-environment design, building-energy efficiency, and productivity, and for studies of infection spread. However, such data are lacking. In this study, we designed a device for detecting and recording, second by second, the 3D indoor positioning and head and body motions of each graduate student in an office. From more than 400 person hours of data. Students spent 92.2%, 4.1%, 2.9%, and 0.8% of their time in their own office cubicles, other office cubicles, aisles, and areas near public facilities, respectively. They spent 9.7% of time in close contact, and each student averagely had 4.0 close contacts/h. Students spent long time on close contact in the office which may lead to high infection risk. The average interpersonal distance during close contact was 0.81 m. When sitting, students preferred small relative face orientation angle. Pairs of standing students preferred a face-to-face orientation during close contact which means this pattern had a lower infection risk via close contact. Probability of close contact decreased exponentially with the increasing distance between two students' cubicles. Data on human behaviour during close contact is helpful for infection risk analysis and infection control and prevention.

6.
BMC Infect Dis ; 20(1): 6, 2020 Jan 03.
Artigo em Inglês | MEDLINE | ID: mdl-31900118

RESUMO

BACKGROUND: An efficient surface cleaning strategy would first target cleaning to surfaces that make large contributions to the risk of infections. METHODS: In this study, we used data from the literature about methicillin-resistant Staphylococcus aureus (MRSA) and developed an ordinary differential equations based mathematical model to quantify the impact of contact heterogeneity on MRSA transmission in a hypothetical 6-bed intensive care unit (ICU). The susceptible patients are divided into two types, these who are cared by the same nurse as the MRSA infected patient (Type 1) and these who are not (Type 2). RESULTS: The results showed that the mean MRSA concentration on three kinds of susceptible patient nearby surfaces was significantly linearly associated with the hand-touch frequency (p < 0.05). The noncompliance of daily cleaning on patient nearby high-touch surfaces (HTSs) had the most impact on MRSA transmission. If the HTSs were not cleaned, the MRSA exposure to Type 1 and 2 susceptible patients would increase 118.4% (standard deviation (SD): 33.0%) and 115.4% (SD: 30.5%) respectively. The communal surfaces (CSs) had the least impact, if CSs were not cleaned, the MRSA exposure to Type 1 susceptible patient would only increase 1.7% (SD: 1.3). The impact of clinical equipment (CE) differed largely for two types of susceptible patients. If the CE was not cleaned, the exposure to Type 1 patients would only increase 8.4% (SD: 3.0%), while for Type 2 patients, it can increase 70.4% (SD: 25.4%). CONCLUSIONS: This study provided a framework to study the pathogen concentration dynamics on environmental surfaces and quantitatively showed the importance of cleaning patient nearby HTSs on controlling the nosocomial infection transmission via contact route.


Assuntos
Busca de Comunicante/métodos , Unidades de Terapia Intensiva , Staphylococcus aureus Resistente à Meticilina/fisiologia , Modelos Teóricos , Infecções Estafilocócicas/transmissão , Busca de Comunicante/estatística & dados numéricos , Infecção Hospitalar/transmissão , Detergentes/farmacologia , Desinfecção , Feminino , Higiene das Mãos/estatística & dados numéricos , Humanos , Controle de Infecções/métodos , Transmissão de Doença Infecciosa do Paciente para o Profissional/estatística & dados numéricos , Transmissão de Doença Infecciosa do Profissional para o Paciente/estatística & dados numéricos , Unidades de Terapia Intensiva/estatística & dados numéricos , Masculino , Resistência a Meticilina/fisiologia , Staphylococcus aureus Resistente à Meticilina/isolamento & purificação , Staphylococcus aureus Resistente à Meticilina/patogenicidade , Propriedades de Superfície
7.
Sci Total Environ ; 713: 136593, 2020 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-31955094

RESUMO

In order to solve problems associated with a short residence time and low conversion efficiency when CO2 gas is aerated directly into raceway ponds, a novel porous nickel-foam filled CO2 absorptive photobioreactor system was developed to promote CO2 conversion to NaHCO3 in a short time to improve photosynthesis of microalgal cells. Numerical simulation showed that the porous nickel-foam promoted the Na2CO3 solution radial velocity and CO2 volume fraction in the CO2 absorption reactor, which enhanced the reaction rate of CO2 gas and soluble Na2CO3. The conversion efficiency of CO2 gas to soluble NaHCO3 gradually increased with an increasing nickel-foam pore diameter and a decreasing CO2 gas outflow rate, while it first increased and then decreased with an increasing relative nickel-foam height in the CO2 absorption reactor. The conversion efficiency from soluble NaHCO3 to microalgal biomass first increased and then decreased with an increasing nickel-foam pore diameter (peaking at 2 mm) and relative height (peaking at 0.24); and CO2 gas outflow rate (peaking at 2 L/min). The chlorophyll fluorescence measurements showed that a sufficient HCO3- supply promoted the quantum ratio used for electron transfer (from 0.19 to 0.23) and the maximum photochemical efficiency (from 0.48 to 0.52), resulting in an increased biomass growth rate (by 1.1 times) when the nickel-foam pore diameter increased from 0.1 to 2 mm.


Assuntos
Microalgas , Fotobiorreatores , Biomassa , Dióxido de Carbono , Níquel , Porosidade
8.
Can J Microbiol ; 66(3): 228-242, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31944857

RESUMO

Rhizosphere bacteria are key determinants of plant health and productivity. In this study, we used PCR-based next-generation sequencing to reveal the diversity and community composition of bacteria in the cotton rhizosphere from samples collected in Xinjiang Province, China. We identified 125 bacterial classes within 49 phyla from these samples. Proteobacteria (33.07% of total sequences), Acidobacteria (19.88%), and Gemmatimonadetes (11.19%) dominated the bacterial community. Marked differences were evident in the α-diversity of rhizosphere bacteria during different cotton plant growth and development stages. The operational taxonomic unit (OTU) numbers were highest in seedling and bud stages and decreased at the flowering and fruit-boll-opening stages. Forty-three OTUs from the Proteobacteria were common to all four periods of cotton development. Proteobacteria were more abundant in the rhizospheres of cotton from southern Xinjiang than from northern Xinjiang, while the opposite trend was observed for Acidobacteria. Gemmatimonadetes frequency was broadly the same in both northern and southern Xinjiang. These results suggest that there is abundant diversity in the microbiota of cotton rhizosphere soil. Proteobacteria and Actinobacteria dominated this microbial niche and bacterial communities in the seedling, bud, flowering, and boll-opening stages appear to be more similar to one another than to communities at the other growth stages.

9.
Environ Pollut ; 256: 113433, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31761597

RESUMO

Epidemiology suggests ambient temperature is the triggers and potential activator of asthma. The role of high and low temperatures on airway inflammation of asthma, and the underlying molecular mechanism are not yet understood. A mouse model of asthma was adopted in our experiment. The BALB/c mice were exposed at different temperature for 4 h (2 h in the morning and 2 h in the afternoon) on weekday. The exposure temperatures were 10 °C, 24 °C and 40 °C. Ovalbumin (OVA) was used to sensitize the mice on days 14, 18, 22, 26, and 30, followed by an aerosol challenge for 30 min from day 32-38. After the final OVA challenge, lung function, serum protein and pulmonary inflammation were assessed. Comparing the OVA with the saline group at 24 °C, we saw a significant increase in: serum Total-IgE (p < 0.05); OVA-sIgE (p < 0.01); IL-4 (p < 0.05); IL-1ß (p < 0.01); IL-6 (p < 0.01); TNF-α (p < 0.01); and the ratio of IL-4/IFN-γ (p < 0.01). At the same time, there was a significant decrease in IFN-γ (p < 0.01). As the temperature increase, there is a U shape for immune proteins and pro-inflammatory factors with a peak value at 24 °C, exception for IFN-γ (inverted U-shape). After the high and low temperature exposure, the Ri and Re increased significantly, while Cldyn decreased significantly compared with the 24 °C group. Histopathological analysis of the OVA groups showed airway remodeling, airway wall thickening and deforming, and subepithelial fibrosis. More obvious changes were found in the high and low temperature exposure groups. The immunohistochemistry suggested that TRPs changed with temperatures. High and low temperatures can aggravate airway inflammation in a mouse model of asthma. TRPs play an important role in temperature aggravation of allergic asthma. The results suggest that asthmatics should avoid exposure to high and low temperatures for too long time.


Assuntos
Asma/fisiopatologia , Temperatura Ambiente , Animais , Líquido da Lavagem Broncoalveolar , Temperatura Baixa , Modelos Animais de Doenças , Feminino , Inflamação , Camundongos , Camundongos Endogâmicos BALB C , Ovalbumina , Pneumonia , Fator de Necrose Tumoral alfa
10.
Clin Infect Dis ; 70(5): 850-858, 2020 Feb 14.
Artigo em Inglês | MEDLINE | ID: mdl-30963180

RESUMO

BACKGROUND: Respiratory virus-laden particles are commonly detected in the exhaled breath of symptomatic patients or in air sampled from healthcare settings. However, the temporal relationship of detecting virus-laden particles at nonhealthcare locations vs surveillance data obtained by conventional means has not been fully assessed. METHODS: From October 2016 to June 2018, air was sampled weekly from a university campus in Hong Kong. Viral genomes were detected and quantified by real-time reverse-transcription polymerase chain reaction. Logistic regression models were fitted to examine the adjusted odds ratios (aORs) of ecological and environmental factors associated with the detection of virus-laden airborne particles. RESULTS: Influenza A (16.9% [117/694]) and influenza B (4.5% [31/694]) viruses were detected at higher frequencies in air than rhinovirus (2.2% [6/270]), respiratory syncytial virus (0.4% [1/270]), or human coronaviruses (0% [0/270]). Multivariate analyses showed that increased crowdedness (aOR, 2.3 [95% confidence interval {CI}, 1.5-3.8]; P < .001) and higher indoor temperature (aOR, 1.2 [95% CI, 1.1-1.3]; P < .001) were associated with detection of influenza airborne particles, but absolute humidity was not (aOR, 0.9 [95% CI, .7-1.1]; P = .213). Higher copies of influenza viral genome were detected from airborne particles >4 µm in spring and <1 µm in autumn. Influenza A(H3N2) and influenza B viruses that caused epidemics during the study period were detected in air prior to observing increased influenza activities in the community. CONCLUSIONS: Air sampling as a surveillance tool for monitoring influenza activity at public locations may provide early detection signals on influenza viruses that circulate in the community.

11.
Indoor Air ; 30(1): 49-59, 2020 01.
Artigo em Inglês | MEDLINE | ID: mdl-31545534

RESUMO

Touching contaminated surfaces might lead to the spread of pathogens, that is, the fomite transmission route. Although hand- and surface-hygiene practices are potentially important non-pharmaceutical interventions for the fomite route, the two interventions have been mostly studied separately in the literature. In this study, we develop a new conceptual model based on the law of mass action, analyze the temporal diffusion of contaminated surfaces and hands, and verify the model with simulations in an assumed norovirus outbreak in a buffet restaurant. A quantitative hygiene criterion is developed for the required frequency of surface disinfection and hand hygiene to control the fomite transmission in indoor environments. To eliminate surface contaminations, the product of pathogen-removal rates (including hygiene and natural death) on hands and surfaces must be no smaller than that of the human hand and surface contact frequency (ie, the net removal product must be non-negative). When the net removal product is negative, the number of contaminated surfaces and hands would show a logistic growth trend and finally approach the equilibrium. Our approach sheds light into how to optimize the combined use of hand hygiene and environmental decontamination for the best effectiveness under different settings.

12.
Indoor Air ; 30(1): 3-6, 2020 01.
Artigo em Inglês | MEDLINE | ID: mdl-31840303
13.
Mol Immunol ; 116: 191-198, 2019 12.
Artigo em Inglês | MEDLINE | ID: mdl-31710976

RESUMO

BACKGROUND: Scars affects the appearance and results in tissue damage. In this research, we preliminarily studied the function and mechanism of curcumin (CUR) on cell proliferation and soluble collagen synthesis in NIH-3T3 cells. METHODS: CCK-8 was used to detect the IC50 of CUR. Moreover, Western blot was used to measure the expression of cell proliferation-related, soluble collagen synthesis and pathway-related proteins. Sircol assay was determined the expression of soluble collagen. Furthermore, reverse transcription quantitative PCR (RT-qPCR) was used to determined miR-29a, α-smooth muscle aorta (α-SMA), soluble collagen 1 (Col 1) and Col 3 expression. RESULTS: CUR inhibited cell viability and proliferation-related proteins expression. Transforming growth factor-ß (TGFß1)-induced heightened the expression of proliferation-related proteins and soluble collagen synthesis-related proteins. CUR inhibited TGFß1-induced proliferation and soluble collagen synthesis. Furthermore, CUR positively related miR-29a and miR-29a mimic inhibited TGFß1-induced proliferation and soluble collagen synthesis. Besides, transfection with miR-29a inhibitor could partly reverse the effects of CUR. CUR inhibited the ERK1/2 and ß-catenin pathways and the miR-29a inhibitor reversed the above results. Otherwise, soluble collagen 1 (Col 1) partly reversed the effects of CUR on proliferation and soluble collagen synthesis and silenced Col 1/3 could inhibit ERK1/2 and ß-catenin signaling pathways. CONCLUSION: CUR restrained TGFß1-induced proliferation and soluble collagen synthesis in NIH-3T3 cells by up-regulation of miR-29a via ERK1/2 and ß-catenin signaling pathways.


Assuntos
Proliferação de Células/efeitos dos fármacos , Colágeno Tipo I/metabolismo , Curcumina/farmacologia , Sistema de Sinalização das MAP Quinases/efeitos dos fármacos , MicroRNAs/metabolismo , Transdução de Sinais/efeitos dos fármacos , beta Catenina/metabolismo , Animais , Linhagem Celular , Sobrevivência Celular/efeitos dos fármacos , Camundongos , Células NIH 3T3 , Fator de Crescimento Transformador beta1/metabolismo , Via de Sinalização Wnt/efeitos dos fármacos
14.
Quant Imaging Med Surg ; 9(9): 1579-1591, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31667143

RESUMO

Background: To develop liposomes loaded with iodinated agents as nanosized CT/MRI bimodal contrast agents for monitoring liposome-mediated drug delivery. Methods: Rhodamine-labeled iodixanol (VisipaqueTM)-loaded liposomes (IX-lipo) were prepared and tested for their properties as a diamagnetic CEST contrast agent in vitro. Mice bearing subcutaneous CT26 colon tumors were injected i.v. with 1 g/kg (535 mg iodine/kg) IX-lipo, and in vivo CT and CEST MR images were acquired on day 3. CT and CEST MR images were also acquired for tumor-bearing mice co-injected with IX-lipo and tumor necrosis factor (TNF-α). Results: In addition to CT contrast, IX-lipo exhibited a strong CEST contrast similar to its non-liposomal form, with a detectability of ~2 nM per liposome. Both CT imaging and CEST MRI showed that i.v. injection of IX-lipo resulted in a rim enhancement of CT26 tumors with a heterogeneous central distribution. In contrast, co-injection of TNF-α caused a significantly augmented CT/MRI contrast in the tumor center. The intratumoral biodistribution of IX-lipo correlated well to the rhodamine patterns observed with fluorescence microscopy. Conclusions: We have developed a CT/MRI bimodal imaging approach for monitoring the delivery and biodistribution of liposomes by loading them with the clinically approved X-ray/CT contrast agent iodixanol. Our approach may be easily adapted for other-FDA approved iodinated agents and thus has great translational potential.

15.
Ecotoxicol Environ Saf ; 184: 109639, 2019 Nov 30.
Artigo em Inglês | MEDLINE | ID: mdl-31525560

RESUMO

BACKGROUND: Although mounting evidence have linked traffic-related air pollution (TRAP) with increased risk of preterm birth (PTB), whether it can interact with indoor environmental factors remains unknown, and its window(s) susceptibility at the stage of gestation is unclear. OBJECTIVE: To explore PTB risk for prenatal exposure to traffic-related air pollution and home environmental factors during pregnancy, so as to identify critical window(s) in the combined effect of traffic air pollution and main home environmental factor(s) on PTB development. METHODS: A retrospective cohort study of 3,509 preschool children was performed in Changsha, China during 2011-2012. The PTB prevalence was reported by the parents based on a questionnaire. We estimated each mother's exposure to traffic-related air pollutant NO2 in different windows of gestation, including conception month, three trimesters, birth month, and whole gestation. Maternal exposure to home environmental factors was considered by renovation (new furniture/redecoration) in pregnancy, and mold/damp stains and window condensation during perinatal period. Associations of PTB with both ambient NO2 and home environmental factors, and their interactions on PTB were evaluated by logistic regression models using odds ratio (OR) with 95% confidence interval (CI). RESULTS: Traffic air pollutant NO2 exposure in utero was significantly associated with PTB, with adjusted odds ratio (OR) (95% CI) of 1.41 (1.00-1.98) for an IQR increase in NO2 exposure during whole pregnancy, particularly in the conception month and 1st trimester. We further found a positive relationship between perinatal exposure to mold/damp stains in the homes and PTB, OR (95% CI) = 1.73 (1.04-2.90). Especially, we detected a significant interaction between outdoor NO2 and indoor mold/damp stains on PTB risk. Male and female foetus were respectively more susceptible to perinatal mold/dampness at home and outdoor NO2 exposure in early gestation. CONCLUSION: Our finding indicates that both outdoor traffic air pollutant and indoor mold/dampness play key roles in PTB development, and their interaction effect in early pregnancy significantly increases PTB risk.


Assuntos
Poluentes Atmosféricos/análise , Poluição do Ar em Ambientes Fechados/análise , Exposição Ambiental/análise , Nascimento Prematuro/epidemiologia , Poluição Relacionada com o Tráfego/análise , Poluentes Atmosféricos/toxicidade , Poluição do Ar em Ambientes Fechados/efeitos adversos , Pré-Escolar , China/epidemiologia , Exposição Ambiental/efeitos adversos , Feminino , Humanos , Recém-Nascido , Modelos Logísticos , Masculino , Exposição Materna/efeitos adversos , Gravidez , Prevalência , Estudos Retrospectivos , Poluição Relacionada com o Tráfego/efeitos adversos
16.
BMC Infect Dis ; 19(1): 755, 2019 Aug 29.
Artigo em Inglês | MEDLINE | ID: mdl-31464601

RESUMO

Although the title of the Special Issue is 'Airborne Microbiome' the manuscripts received have highlighted a variety of peripheral, yet related aspects of this. The contributions are a mixture of primary research, reviews and commentaries, including: new methods to explore environmental niches where such microbes may grow, their detection and characterisation in the human host, which pathogens are present in the respiratory tract and can be exhaled in human breath to potentially spread via the airborne route, and some strategies for their control. Finally, a historical-to-current overview explores human-microbial interactions, including problems with sampling and detection methods, drug resistance, the role of super-spreaders and issues around research funding.


Assuntos
Microbiologia do Ar , Microbiota , Infecções Respiratórias/transmissão , Aerossóis , Expiração , Humanos , Controle de Infecções/métodos , Sistema Respiratório/microbiologia
17.
Sci Adv ; 5(8): eaaw8357, 2019 08.
Artigo em Inglês | MEDLINE | ID: mdl-31453331

RESUMO

Chronic Kidney Disease (CKD) is a cardinal feature of methylmalonic acidemia (MMA), a prototypic organic acidemia. Impaired growth, low activity, and protein restriction affect muscle mass and lower serum creatinine, which can delay diagnosis and management of renal disease. We have designed an alternative strategy for monitoring renal function based on administration of a pH sensitive MRI agent and assessed this in a mouse model. This protocol produced three metrics: kidney contrast, ~4% for severe renal disease mice compared to ~13% and ~25% for moderate renal disease and healthy controls, filtration fraction (FF), ~15% for severe renal disease mice compared to ~79% and 100% for moderate renal disease and healthy controls, and variation in pH, ~0.45 units for severe disease mice compared to 0.06 and 0.01 for moderate disease and healthy controls. Our results demonstrate that MRI can be used for early detection and monitoring of CKD.

18.
Indoor Air ; 29(5): 701-703, 2019 09.
Artigo em Inglês | MEDLINE | ID: mdl-31423675
19.
NMR Biomed ; 32(11): e4168, 2019 11.
Artigo em Inglês | MEDLINE | ID: mdl-31461196

RESUMO

The current study aims to optimize the acquisition scheme for the creatine chemical exchange saturation transfer weighted (CrCESTw) signal on mouse brain at 11.7 T, in which a strong magnetization transfer contrast (MTC) is present, and to further develop the polynomial and Lorentzian line-shape fitting (PLOF) method for quantifying CrCESTw signal with a non-steady-state (NSS) acquisition scheme. Studies on a Cr phantom with cross-linked bovine serum albumin (BSA) as well as on mouse brain demonstrated that the maximum CrCESTw signal was reached with a short saturation time determined by the rotating frame relaxation time of the MTC pool instead of the steady-state saturation. The saturation power for the maximal signal was around 1-1.5 µT for Cr with 20% cross-linked BSA and in vivo applications, but 2 µT was found to be most practical for signal stability. For the CrCEST acquisition with strong MTC interference, the optimal saturation power and length are completely different from those on Cr solution alone. This observation could be explained well using R1ρ theory by incorporating the strong MTC pool. Finally, a high-resolution Cr map was obtained on mouse brain using the PLOF method with the NSS CEST acquisition and a cryogenic coil. The Cr map obtained by CEST showed homogenous intensity across the mouse brain except for regions with cerebrospinal fluid.

20.
Biosens Bioelectron ; 141: 111442, 2019 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-31252256

RESUMO

Phenol contains an exchangeable hydroxyl proton resonant at 4.8 ppm from the resonance frequency of water in the 1H nuclear magnetic resonance (1H NMR) spectrum, enabling itself to be detected at sub-mM concentration by either chemical exchange saturation transfer magnetic resonance imaging (CEST MRI) or exchange-based T2 relaxation enhancement (T2ex) effect under acidic and basic conditions, respectively. We recently investigated the T2ex effects of phenol and its derivatives, but the CEST characteristics of phenols are unknown in detail, and no study on using the natural CEST MRI effects of phenol for detecting enzymatic activity has been conducted. Herein, on the basis of the inherent CEST MR property of phenol, namely phenolCEST, we developed the first MRI approach to detect acid phosphatase (AcP) enzymatic activity. Upon the activity of AcP at pH = 5.0, non-CEST-detectable enzyme substrate phenyl phosphate was converted to CEST-detectable phenol, providing a simple way to quantify AcP activity directly without the need for a second signalling probe. We showed the application of this phenolCEST biosensor for measuring AcP activity in both enzyme solutions and cell lysates of prostate cells. This work opens a door for the utilization of phenolCEST MRI technique in sensor design and development.


Assuntos
Fosfatase Ácida/análise , Meios de Contraste/química , Fenol/química , Técnicas Biossensoriais/métodos , Linhagem Celular , Humanos , Imagem por Ressonância Magnética/métodos , Masculino , Próstata/enzimologia
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