Your browser doesn't support javascript.
Mostrar: 20 | 50 | 100
Resultados 1 - 19 de 19
Filtrar
Mais filtros










Base de dados
Intervalo de ano de publicação
1.
Artigo em Inglês | MEDLINE | ID: mdl-32260284

RESUMO

Climate change has a distinct impact on agriculture in China, particularly in the northeast, a key agriculture area sensitive to extreme hydroclimate events. Using monthly climate and agriculture data, the influence of drought on maize and soybean yields-two of the main crops in the region-in northeast China since 1961 to 2017 were investigated. The results showed that the temperature in the growing season increased by 1.0 °C from the period 1998-2017 to the period 1961-1980, while the annual precipitation decreased slightly. However, precipitation trends varied throughout the growing season (May-September), increasing slightly in May and June, but decreasing in July, August and September, associated with the weakening of the East Asian summer monsoon. Consequently, the annual and growing season drought frequency increased by 15%, and 25%, respectively, in the period 1998-2017 relative to the period 1961-1980. The highest drought frequency (55%) was observed in September. At the same time, the drought intensity during the growing season increased by 7.8%. The increasing frequency and intensity of drought had negative influences on the two crops. During moderate drought years in the period 1961-2017, 3.2% and 10.4% of the provincial maize and soybean yields were lost, respectively. However, during more severe drought years, losses doubled for soybean (21.8%), but increased more than four-fold for maize (14.0%). Moreover, in comparison to the period 1961-1980, a higher proportion of the yields were lost in the period 1998-2017, particularly for maize, which increased by 15% (increase for soybean was 2.4%). This change largely depends on increasing droughts in August and September, when both crops are in their filling stages. The impact of drought on maize and soybean production was different during different growth stages, where a strong relationship was noted between drought and yield loss of soybean in its filling stage. Given the sensitivity of maize and soybean yields in northeast China to drought, and the observed production trends, climate change will likely have significant negative impacts on productivity in the future.

2.
Artigo em Inglês | MEDLINE | ID: mdl-31575015

RESUMO

The Tibetan plateau is one of the most sensitive areas in China and has been significantly affected by global warming. From 1961 to 2017, the annual air temperature increased by 0.32 °C/decade over the Tibetan Plateau, which is the highest in the whole of China. Furthermore, this is a trend that is projected to continue by 0.30 °C/decade from 2018 to 2050 due to global warming using the Regional Climate Model version 4 (RegCM4). The increased temperature trend in recent decades has been highest in winter, which has been positive for the safe dormancy of winter wheat. In order to investigate agricultural adaptation to climate change in the Tibetan plateau, we used the World Food Studies (WOFOST) cropping systems model and weather data from the regional climate model RegCM4, to simulate winter wheat production in Guide county between 2018 and 2050. The simulated winter wheat potential yields amounted to 6698.3 kg/ha from 2018 to 2050, which showed the wheat yields would increase by 81%, if winter wheat was planted instead of spring wheat in the Tibetan Plateau with the correct amount of irrigation water. These results indicate that there are not only risks to crop yields from climate change, but also potential benefits. Global warming introduced the possibility to plant winter wheat instead of spring wheat over the Tibetan Plateau. These findings are very important for farmers and government agencies dealing with agricultural adaptation in a warmer climate.


Assuntos
Agricultura/métodos , Aquecimento Global , Triticum/crescimento & desenvolvimento , Estações do Ano , Temperatura , Tibet
3.
Sci Total Environ ; 690: 189-196, 2019 Nov 10.
Artigo em Inglês | MEDLINE | ID: mdl-31288110

RESUMO

Winter wheat is one of China's most important staple food crops, and its growth and productivity are influenced by climate. Given its importance, we investigated the influence of excess precipitation under recent climate change on winter wheat in east-central China during 1961-2017. Although annual precipitation in the studied region decreased slightly, it increased during the winter wheat flowering and maturity period (May to June). Concurrently, the number of late growing season sunshine hours decreased. Our results showed that about 44% of the years with excess precipitation and less than normal radiation (16 years) were associated with decreasing winter wheat yields. Furthermore, during most years, precipitation of 50% above normal resulted in large decreases in winter wheat production in Jiangsu and Anhui provinces, some of the wetter parts of the studied region. These results indicated that the grain yield variability of winter wheat was mainly influenced by excess precipitation in May, where precipitation could explain 70%-78% of yield variability in the wet parts. Moreover, excess precipitation can induce Fusarium head blight as well as wheat sprouting of pre-harvest, both affecting the grain quality of winter wheat. Projected increases in precipitation throughout the 21st century in the studied region, warrants further studies of how to maintain the winter wheat production in a changing climate.

4.
Magn Reson Med ; 75(6): 2464-72, 2016 06.
Artigo em Inglês | MEDLINE | ID: mdl-26997332

RESUMO

PURPOSE: We explore the advantages of using a double-ring radiofrequency (RF) array and slice orientation to design parallel transmission (pTx) multiband (MB) pulses for simultaneous multislice (SMS) imaging with whole-brain coverage at 7 Tesla (T). METHODS: A double-ring head array with 16 elements split evenly in two rings stacked in the z-direction was modeled and compared with two single-ring arrays consisting of 8 or 16 elements. The array performance was evaluated by designing band-specific pTx MB pulses with local specific absorption rate (SAR) control. The impact of slice orientations was also investigated. RESULTS: The double-ring array consistently and significantly outperformed the other two single-ring arrays, with peak local SAR reduced by up to 40% at a fixed excitation error of 0.024. For all three arrays, exciting sagittal or coronal slices yielded better RF performance than exciting axial or oblique slices. CONCLUSIONS: A double-ring RF array can be used to drastically improve SAR versus excitation fidelity tradeoff for pTx MB pulse design for brain imaging at 7 T; therefore, it is preferable against single-ring RF array designs when pursuing various biomedical applications of pTx SMS imaging. In comparing the stripline arrays, coronal and sagittal slices are more advantageous than axial and oblique slices for pTx MB pulses. Magn Reson Med 75:2464-2472, 2016. © 2016 Wiley Periodicals, Inc.


Assuntos
Encéfalo/diagnóstico por imagem , Processamento de Imagem Assistida por Computador/métodos , Imagem por Ressonância Magnética/instrumentação , Imagem por Ressonância Magnética/métodos , Desenho de Equipamento , Humanos , Modelos Biológicos , Imagens de Fantasmas
5.
J Magn Reson Imaging ; 43(6): 1279-87, 2016 06.
Artigo em Inglês | MEDLINE | ID: mdl-26584144

RESUMO

PURPOSE: To develop and evaluate a sterilizable multichannel endorectal coil (ERC) for use in combination with an external surface array (ESA) for high-resolution anatomical and functional studies of the prostate at 7T. MATERIALS AND METHODS: A two-loop ERC (ERC-2L) and a microstrip-loop ERC (ERC-ML) were compared at 7T in terms of transmit and receive performance. The best-performing ERC was evaluated alone and in combination with the ESA through 1) simulations on both phantom and an anatomically correct numerical human model to assess B1+ transmit and specific absorption rate (SAR) efficiencies, and 2) phantom experiments to calculate B1+ transmit efficiency and signal-to-noise ratio (SNR). Phantom studies were also performed to look at heating when using the ERC as a transmitter and for comparing the new coil against a single-channel balloon-type ERC (ERC-b). High-resolution magnetic resonance imaging (MRI) acquisitions were performed on a single healthy subject using the two-channel ERC combined with the ESA. RESULTS: Compared to the ERC-ML, the ERC-2L demonstrated 20% higher SAR efficiency and higher SNR 3 cm from the coil. The presence of a tuned and detuned ERC-2L did not alter the peak local SAR of the ESA alone; however, the detuned ERC-2L had 45% less peak local SAR around the rectum compared to the tuned ERC-2L. The receive-only version of the ERC-2L improved the SNR 4.7-fold and 1.3-fold compared to the ESA and ERC-b, respectively. In combination with the ESA, the ERC-2L supported in-plane voxel-size of 0.36 × 0.36 mm(2) in T2 -weighted anatomic imaging. CONCLUSION: The reusable ERC-2L combined with an ESA offers a high SNR imaging platform for translational studies of the prostate at 7T. J. Magn. Reson. Imaging 2016;43:1279-1287.


Assuntos
Aumento da Imagem/instrumentação , Imagem por Ressonância Magnética/instrumentação , Neoplasias da Próstata/diagnóstico por imagem , Transdutores , Desenho Assistido por Computador , Desenho de Equipamento , Análise de Falha de Equipamento , Humanos , Magnetismo/instrumentação , Masculino , Imagens de Fantasmas , Neoplasias da Próstata/patologia , Reprodutibilidade dos Testes , Sensibilidade e Especificidade
6.
Wei Sheng Yan Jiu ; 44(4): 543-8, 2015 Jul.
Artigo em Chinês | MEDLINE | ID: mdl-26454948

RESUMO

OBJECTIVE: To explore the relationship between polymorphism of interferon regulatory factor 6 (IRF6) gene rs642961 locus and nonsyndromic cleft lip with or without cleft palate (NSCL ± P). METHODS: There were 88 NSCL ± P nuclear families and 116 healthy people as control recruited from Chinese northern area. The polymorphism of IRF6 rs642961 locus was detected by tetra-primer amplification refractory mutation system-polymerase chain reaction (tetra-primer ARMS-PCR). Case-control analysis, transmission-disequilibrium test (TDT), haplotype-based haplotype relative risk analysis (HHRR) and family-based association test (FBAT) were carried out. RESULT: There was significant difference in rs642961 of IRF6 locus between the NSCL P group and control group, whether in children or parents (P < 0.05). The odds ratio (OR) of AG and AA versus GG is above one, and its 95% confidence interval did not include 1 in offspring, father and mother group, which meant genetic variant of rs642961 of IRF6 could increase the risk of occurrence of NSCL ± P. The allele transmission disequilibrium for rs642961 of IRF6 variant in NSCL ± P families was found by TDT analysis (P < 0.05). HHRR calculation also showed that there was association between the genetic variant and the occurrence of NSCL ± P (P < 0.05). While FBAT test showed that there was relationship between the genetic variant and the occurrence of NSCL ± P in addictive model. CONCLUSION: Polymorphism IRF6 gene locus is associated with NSCL ± P in northern Chinese population.


Assuntos
Fenda Labial/genética , Fissura Palatina/genética , Fatores Reguladores de Interferon/genética , Polimorfismo Genético/genética , Alelos , Grupo com Ancestrais do Continente Asiático/genética , Estudos de Casos e Controles , Criança , Fenda Labial/sangue , Fissura Palatina/sangue , Primers do DNA , Predisposição Genética para Doença , Variação Genética , Haplótipos , Humanos , Reação em Cadeia da Polimerase
7.
NMR Biomed ; 28(10): 1332-44, 2015 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-26332290

RESUMO

The performance of multichannel transmit coil layouts and parallel transmission (pTx) RF pulse design was evaluated with respect to transmit B1 (B1 (+)) homogeneity and specific absorption rate (SAR) at 3 T for a whole body coil. Five specific coils were modeled and compared: a 32-rung birdcage body coil (driven either in a fixed quadrature mode or a two-channel transmit mode), two single-ring stripline arrays (with either 8 or 16 elements), and two multi-ring stripline arrays (with two or three identical rings, stacked in the z axis and each comprising eight azimuthally distributed elements). Three anatomical targets were considered, each defined by a 3D volume representative of a meaningful region of interest (ROI) in routine clinical applications. For a given anatomical target, global or local SAR controlled pTx pulses were designed to homogenize RF excitation within the ROI. At the B1 (+) homogeneity achieved by the quadrature driven birdcage design, pTx pulses with multichannel transmit coils achieved up to about eightfold reduction in local and global SAR. When used for imaging head and cervical spine or imaging thoracic spine, the double-ring array outperformed all coils, including the single-ring arrays. While the advantage of the double-ring array became much less pronounced for pelvic imaging, with a substantially larger ROI, the pTx approach still provided significant gains over the quadrature birdcage coil. For all design scenarios, using the three-ring array did not necessarily improve the RF performance. Our results suggest that pTx pulses with multichannel transmit coils can reduce local and global SAR substantially for body coils while attaining improved B1 (+) homogeneity, particularly for a "z-stacked" double-ring design with coil elements arranged on two transaxial rings.


Assuntos
Imagem por Ressonância Magnética/instrumentação , Algoritmos , Simulação por Computador , Desenho de Equipamento , Humanos , Modelos Teóricos , Software
8.
Zhongguo Zhong Yao Za Zhi ; 39(4): 733-7, 2014 Feb.
Artigo em Chinês | MEDLINE | ID: mdl-25204156

RESUMO

OBJECTIVE: To investigate the effect of Zige lyophilized powder for injection in improving the acute cerebral microcirculation disturbance in rats. METHOD: Window craniotomy was performed for rats after the drug administration for 14 days. The experimental microcirculation disturbance model was duplicated with high molecule dextran. After the drug administration, the micro-vein diameters of cerebral pla mater of various groups were observed and recorded under the biological microscope. The blood flow volume was monitored by laser Doppler flow-meter. HCT was measured by the electric resistance method. The hemorheological indexes were detected by the auto-hemorheological instrument. RESULT: Zige lyophilized powder for injection (16.40, 32.70, 65.40 mg x kg(-1)) could significantly expand the micro-vein diameter of cerebral pla mater, improve the downward trend of the blood flow volume, and reduce the various hemorheological indexes. CONCLUSION: Zige lyophilized powder for injection shows the effect in improving the cerebral microcirculation.


Assuntos
Isquemia Encefálica/tratamento farmacológico , Circulação Cerebrovascular/efeitos dos fármacos , Medicamentos de Ervas Chinesas/administração & dosagem , Animais , Encéfalo/irrigação sanguínea , Encéfalo/efeitos dos fármacos , Isquemia Encefálica/fisiopatologia , Humanos , Masculino , Pós/administração & dosagem , Ratos , Ratos Sprague-Dawley
9.
Magn Reson Med ; 72(4): 1141-50, 2014 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-24259413

RESUMO

PURPOSE: To study in vivo radiofrequency (RF) heating produced due to power deposition from a 3T (Larmour frequency = 123.2 MHz), birdcage, whole body coil. METHODS: The RF heating was simulated in a digital swine by solving the mechanistic generic bioheat transfer model (GBHTM) and the conventional, empirical Pennes bioheat transfer equation for two cases: 1) when the swine head was in the isocenter and 2) when the swine trunk was in the isocenter. The simulation results were validated by making direct fluoroptic temperature measurements in the skin, brain, simulated hot regions, and rectum of 10 swine (case 1: n = 5, mean animal weight = 84.03 ± 6.85 kg, whole body average SAR = 2.65 ± 0.22 W/kg; case 2: n = 5, mean animal weight = 81.59 ± 6.23 kg, whole body average SAR = 2.77 ± 0.26 W/kg) during 1 h of exposure to a turbo spin echo sequence. RESULTS: The GBHTM simulated the RF heating more accurately compared with the Pennes equation. In vivo temperatures exceeded safe temperature thresholds with allowable SAR exposures. Hot regions may be produced deep inside the body, away from the skin. CONCLUSION: SAR exposures that produce safe temperature thresholds need reinvestigation.


Assuntos
Temperatura Corporal/fisiologia , Temperatura Corporal/efeitos da radiação , Calefação/métodos , Imagem por Ressonância Magnética/métodos , Modelos Biológicos , Imagem Corporal Total/métodos , Irradiação Corporal Total/métodos , Absorção de Radiação , Animais , Simulação por Computador , Desenho de Equipamento , Análise de Falha de Equipamento , Calefação/instrumentação , Imagem por Ressonância Magnética/instrumentação , Doses de Radiação , Ondas de Rádio , Suínos , Imagem Corporal Total/instrumentação , Irradiação Corporal Total/instrumentação
10.
Chin J Nat Med ; 11(6): 588-95, 2013 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-24345499

RESUMO

The treatment of cerebral ischemic disease by natural medicines has a long history, and has accumulated a rich theoretical knowledge and treatment experience. The objective of this review is to critically evaluate the experimental research situation of the protective effect of the individual compounds from natural medicine on cerebral ischemia in the past ten years, emphasizing the major mechanisms underlying cerebral ischemic pathophysiology. Sixteen representative compounds from natural medicines which are often used to treat stroke are discussed. The results indicate that these components possess a protective effect on cerebral ischemia, and that these components have different mechanisms, including inhibiting excitotoxicity by ginkgolide B, antiapoptosis of breviscapine, influencing astrocytic activation and proliferation of tanshinone IIA, influencing free radicals by ginsenoside Rd, impairing blood-brain barrier disruption by baicalin, and the anti-inflammatory activity of tetramethylpyrazine. Moreover, some components have multiple neuroprotective mechanisms. Therefore, the combination of individual compounds from natural medicines, considering the mechanisms of cerebral ischemia, may be beneficial to patients with cerebral ischemia in the future. This approach will provide a direction for the further application and exploitation of new drug development in the treatment of cerebral ischemia.


Assuntos
Isquemia Encefálica/prevenção & controle , Medicamentos de Ervas Chinesas/uso terapêutico , Fitoterapia/tendências , Plantas Medicinais/química , Animais , Isquemia Encefálica/tratamento farmacológico , Humanos
11.
Circulation ; 127(9): 997-1008, 2013 Mar 05.
Artigo em Inglês | MEDLINE | ID: mdl-23371930

RESUMO

BACKGROUND: The use of cells derived from human induced pluripotent stem cells as cellular therapy for myocardial injury has yet to be examined in a large-animal model. METHODS AND RESULTS: Immunosuppressed Yorkshire pigs were assigned to 1 of 3 groups: A myocardial infarction group (MI group; distal left anterior descending coronary artery ligation and reperfusion; n=13); a cell-treatment group (MI with 4×10(6) vascular cells derived from human induced pluripotent stem cells administered via a fibrin patch; n=14); and a normal group (n=15). At 4 weeks, left ventricular structural and functional abnormalities were less pronounced in hearts in the cell-treated group than in MI hearts (P<0.05), and these improvements were accompanied by declines in scar size (10.4±1.6% versus 8.3±1.1%, MI versus cell-treatment group, P<0.05). The cell-treated group displayed a significant increase in vascular density and blood flow (0.83±0.11 and 1.05±0.13 mL·min(-1)·g(-1), MI versus cell-treatment group, P<0.05) in the periscar border zone (BZ), which was accompanied by improvements in systolic thickening fractions (infarct zone, -10±7% versus 5±5%; BZ, 7±4% versus 23±6%; P<0.05). Transplantation of vascular cells derived from human induced pluripotent stem cells stimulated c-kit(+) cell recruitment to BZ and the rate of bromodeoxyuridine incorporation in both c-kit(+) cells and cardiomyocytes (P<0.05). Using a magnetic resonance spectroscopic saturation transfer technique, we found that the rate of ATP hydrolysis in BZ of MI hearts was severely reduced, and the severity of this reduction was linearly related to the severity of the elevations of wall stresses (r=0.82, P<0.05). This decline in BZ ATP utilization was markedly attenuated in the cell-treatment group. CONCLUSIONS: Transplantation of vascular cells derived from human induced pluripotent stem cells mobilized endogenous progenitor cells into the BZ, attenuated regional wall stress, stimulated neovascularization, and improved BZ perfusion, which in turn resulted in marked increases in BZ contractile function and ATP turnover rate.


Assuntos
Trifosfato de Adenosina/metabolismo , Células-Tronco Pluripotentes Induzidas/transplante , Infarto do Miocárdio/metabolismo , Miocárdio/metabolismo , Transplante de Células-Tronco/métodos , Remodelação Ventricular/fisiologia , Animais , Células Cultivadas , Feminino , Humanos , Imunossupressão/métodos , Células-Tronco Pluripotentes Induzidas/fisiologia , Recém-Nascido , Infarto do Miocárdio/patologia , Infarto do Miocárdio/cirurgia , Miocárdio/citologia , Suínos
12.
J Sep Sci ; 35(19): 2659-64, 2012 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-23001886

RESUMO

In this study, the bioactive component harpagoside and angroside C in the root of Scrophularia ningpoensis Hemsley was simultaneously separated by high-speed counter-current chromatography (HSCCC). A two-phase solvent system containing chloroform/n-butanol/methanol/water (4:1:3:2, v/v/v/v) was selected following consideration of the partition coefficient of the target compound. The crude extract (200 mg) was loaded onto a 280-mL HSCCC column and yielded 22 mg harpagoside and 31 mg angroside C with the purity of higher than 98 and 98.5%, respectively. It is feasible to isolate active compounds harpagoside and angroside C from S. ningpoensis using HSCCC.


Assuntos
Distribuição Contracorrente/métodos , Glicosídeos/isolamento & purificação , Extratos Vegetais/isolamento & purificação , Piranos/isolamento & purificação , Scrophularia/química , Glicosídeos/análise , Extratos Vegetais/análise , Raízes de Plantas/química , Piranos/análise
13.
Neuroimage ; 63(3): 1313-20, 2012 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-22917678

RESUMO

Ultra high fields (UHF) permit unprecedented explorations of functional organizations and insight into basic neuronal processes. Increases in the signal and contrast to noise ratios have allowed increases in the spatial resolution of T(2) weighted gradient echo (GE) echo planar imaging (EPI). Furthermore, while the use of T(2) weighted imaging methods at UHF (e.g. spin echo (SE) EPI, gradient and spin echo (GRASE) EPI) can also permit higher resolution images, they in addition allow for increased spatial specificity of functional responses, permitting the in-vivo study of functional organizations down to the columnar level of the cortex. The study of the visual cortex has, thus far, benefitted the most from higher resolution T(2) weighted studies as achieving the required transmit B(1) magnitude at 7T is more challenging in other brain regions, such as the auditory cortex. As such, auditory fMRI studies at UHF have been limited to T(2) weighted GE sequences. Recent advances in multi-channel RF transmission (e.g. B(1) shimming) have enabled procedures to efficiently address deficiencies in transmit B(1) profiles. However, these techniques, shown to be advantageous in anatomical imaging at UHF, are not generally utilized to facilitate T(2) weighted fMRI studies. Here we investigate the feasibility of applying B(1) shimming to achieve efficient RF transmission in the human auditory cortex. We demonstrate that, with B(1) shimming, functional responses to simple tones and to complex sounds (i.e. voices, speech, animal cries, tools and nature) can be efficiently measured with T(2) weighted SE-EPI in the bilateral human auditory cortex at 7T without exceeding specific absorption rate (SAR) limits.


Assuntos
Córtex Auditivo/fisiologia , Mapeamento Encefálico/métodos , Interpretação de Imagem Assistida por Computador/métodos , Imagem por Ressonância Magnética/métodos , Imagem Ecoplanar/métodos , Feminino , Humanos , Masculino
14.
Artigo em Chinês | MEDLINE | ID: mdl-21619792

RESUMO

OBJECTIVE: To detect the expression and the CpG island methylation status of tumor suppressor gene p15 after exposure to 1,4-benzoquinone (1,4-BQ) in primary cultivated C57BL/6J mouse bone marrow cells in vitro. METHODS: The mouse bone marrow cells were isolated in vitro. The effect of 0, 0.1, 1, 5, 10, 20, and 40 µmol/L 1,4-BQ on cell viability (CKK-8) was detected. 0, 0.1, 1, 10 µmol/L 1,4-BQ were used to intoxicate the mouse bone marrow cells for 24 h; Real-time PCR was employed to analyze the mRNA expression level of p15; The bisulfite sequencing PCR (BSP) was used to look into the methylation status of CpG islands in p15 promoter region. RESULTS: 1,4-BQ exhibited dose-dependent toxicity to mouse bone marrow cells, and the LC(50) was 8.3 µmol/L (95%CI: 4.6 - 10.6 µmol/L). The mRNA expression of p15 in 10 µmol/L group was only equivalent to 43% of control group. Compared with control group, the decrease of p15 mRNA expression in1 and 10 µmol/L concentration were obvious, and the differences had statistical significance (P < 0.05 or P < 0.01). BSP sequencing results were same between the exposure groups and control group, the 56 CpG sites on CpG islands remained in the state of unmethylated. CONCLUSION: mRNA expression of p15 gene decreases after exposure to 1,4-BQ, but the CpG islands methylation status in promoter is not affected, suggesting that methylation does not participate in 1,4-BQ-mediated p15 gene expression decrease, other effect mechanisms still need to be investigated.


Assuntos
Benzoquinonas/toxicidade , Células da Medula Óssea/metabolismo , Inibidor de Quinase Dependente de Ciclina p15/genética , Metilação de DNA , Exposição Ambiental , Animais , Sequência de Bases , Células Cultivadas , Ilhas de CpG , Camundongos , Camundongos Endogâmicos C57BL , Regiões Promotoras Genéticas , RNA Mensageiro/genética
15.
Magn Reson Med ; 66(1): 255-63, 2011 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-21337423

RESUMO

Temperatures were measured in vivo in four pigs (mean animal weight = 110.75 kg and standard deviation = 6.13 kg) due to a continuous wave radiofrequency (RF) power irradiation with a 31.75 cm internal diameter and a 15.24 cm long, 7 T (296 MHz), eight channel, transverse electromagnetic head coil. The temperatures were measured in the subcutaneous layer of the scalp, 5, 10, 15, and 20 mm deep in the brain, and rectum using fluoroptic temperature probes. The RF power was delivered to the pig's head for ∼3 h (mean deposition time = 3.14 h and standard deviation = 0.06 h) at the whole head average specific absorption rate of ∼3 W kg(-1) (mean average specific absorption rate = 3.08 W kg(-1) and standard deviation = 0.09 W kg(-1)). Next, simple bioheat transfer models were used to simulate the RF power induced temperature changes. Results show that the RF power produced uniform temperature changes in the pigs' heads (mean temperature change = 1.68°C and standard deviation = 0.13°C) with no plateau achieved during the heating. No thermoregulatory alterations were detected due to the heating because the temperature responses of the pre-RF and post-RF epochs were not statistically significantly different. Simple, validated bioheat models may provide accurate temperature changes.


Assuntos
Encéfalo/efeitos da radiação , Temperatura Alta , Imagem por Ressonância Magnética/instrumentação , Ondas de Rádio , Animais , Humanos , Modelos Animais , Segurança , Suínos
16.
Biol Trace Elem Res ; 141(1-3): 119-25, 2011 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-20490709

RESUMO

Amblyopia is a common cause of vision damage in children, and some aspects of its etiology are not clear. A number of mineral elements have important effects on the nerve and visual nerve systems. However, little is known about the relationship between amblyopia and nutritional mineral elements. In this study, hair samples were collected from 67 children with amblyopia and 57 age-matched control groups. The height and weight of each child was measured, and body mass index (BMI) was calculated. Mineral elements were determined by atomic absorption spectrometry and inductively coupled plasma-atomic emission spectrometry. The calcium and magnesium levels in the hair of amblyopic children were higher (p < 0.006), but the level of manganese were lower compared with those in the control groups (p < 0.006). Other elements measured were found to have an insignificant difference between the two groups (p > 0.006). The BMI of amblyopic children was higher (p < 0.001). These results show that mineral elements may play an important role in the visual development of children. Therefore, studies should pay more attention to investigating the impact of mineral elements on child vision.


Assuntos
Ambliopia/metabolismo , Cabelo/química , Minerais/análise , Oligoelementos/análise , Ambliopia/epidemiologia , Estudos de Casos e Controles , Criança , Pré-Escolar , China/epidemiologia , Feminino , Cabelo/metabolismo , Humanos , Masculino , Minerais/metabolismo , Oligoelementos/metabolismo
17.
J Magn Reson Imaging ; 32(3): 600-7, 2010 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-20815057

RESUMO

PURPOSE: To study the effect of the extracranial portion of a deep brain stimulation (DBS) lead on radiofrequency (RF) heating with a transmit and receive 9.4 Tesla head coil. MATERIALS AND METHODS: The RF heating was studied in four excised porcine heads (mean animal head weight = 5.46 +/- 0.14 kg) for each of the following two extracranial DBS lead orientations: one, parallel to the coil axial direction; two, perpendicular to the coil axial direction (i.e., azimuthal). Temperatures were measured using fluoroptic probes at four locations: one, scalp; two, near the second DBS lead electrode-brain contact; three, near the distal tip of the DBS lead; and four, air surrounding the head. A continuous wave RF power was delivered to each head for 15 min using the coil. Net, delivered RF power was measured at the coil (mean whole head average specific absorption rate = 2.94 +/- 0.08 W/kg). RESULTS: RF heating was significantly reduced when the extracranial DBS lead was placed in the axial direction (temperature change = 0-5 degrees C) compared with the azimuthal direction (temperature change = 1-27 degrees C). CONCLUSION: Development of protocols seems feasible to keep RF heating near DBS electrodes clinically safe during ultra-high field head imaging.


Assuntos
Encéfalo/efeitos da radiação , Estimulação Encefálica Profunda/efeitos adversos , Estimulação Encefálica Profunda/métodos , Temperatura Alta/efeitos adversos , Imagem por Ressonância Magnética/métodos , Animais , Artefatos , Encéfalo/fisiopatologia , Modelos Animais de Doenças , Eletrodos Implantados , Técnicas In Vitro , Imagens de Fantasmas , Reprodutibilidade dos Testes , Suínos , Termografia
18.
Magn Reson Med ; 61(1): 244-8, 2009 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-19097214

RESUMO

The objective of this study was to investigate the feasibility of whole-body imaging at 7T. To achieve this objective, new technology and methods were developed. Radio frequency (RF) field distribution and specific absorption rate (SAR) were first explored through numerical modeling. A body coil was then designed and built. Multichannel transmit and receive coils were also developed and implemented. With this new technology in hand, an imaging survey of the "landscape" of the human body at 7T was conducted. Cardiac imaging at 7T appeared to be possible. The potential for breast imaging and spectroscopy was demonstrated. Preliminary results of the first human body imaging at 7T suggest both promise and directions for further development.


Assuntos
Algoritmos , Mama/anatomia & histologia , Aumento da Imagem/métodos , Interpretação de Imagem Assistida por Computador/métodos , Imagem Corporal Total/métodos , Estudos de Viabilidade , Feminino , Humanos , Projetos Piloto , Reprodutibilidade dos Testes , Sensibilidade e Especificidade
19.
Magn Reson Med ; 56(6): 1274-82, 2006 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-17075852

RESUMO

This work reports the preliminary results of the first human images at the new high-field benchmark of 9.4T. A 65-cm-diameter bore magnet was used together with an asymmetric 40-cm-diameter head gradient and shim set. A multichannel transmission line (transverse electromagnetic (TEM)) head coil was driven by a programmable parallel transceiver to control the relative phase and magnitude of each channel independently. These new RF field control methods facilitated compensation for RF artifacts attributed to destructive interference patterns, in order to achieve homogeneous 9.4T head images or localize anatomic targets. Prior to FDA investigational device exemptions (IDEs) and internal review board (IRB)-approved human studies, preliminary RF safety studies were performed on porcine models. These data are reported together with exit interview results from the first 44 human volunteers. Although several points for improvement are discussed, the preliminary results demonstrate the feasibility of safe and successful human imaging at 9.4T.


Assuntos
Aumento da Imagem/instrumentação , Imagem por Ressonância Magnética/instrumentação , Proteção Radiológica/instrumentação , Transdutores , Queimaduras por Corrente Elétrica/etiologia , Queimaduras por Corrente Elétrica/prevenção & controle , Tontura/etiologia , Tontura/prevenção & controle , Desenho de Equipamento , Análise de Falha de Equipamento , Humanos , Aumento da Imagem/métodos , Imagem por Ressonância Magnética/efeitos adversos , Imagem por Ressonância Magnética/métodos , Projetos Piloto , Proteção Radiológica/métodos , Medição de Risco
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA