4,657 research outputs found
Lipids and Cardiovascular Organ Damage in Type 2 Diabetes Mellitus
One of the mechanisms underlying increased cardiovascular (CV) risk in patients with type 2 diabetes mellitus is atherogenic dyslipidemia, that is characterized by elevated triglycerides and free fatty acids (FFAs) levels, low levels of high-density lipoprotein cholesterol (HDL) and an excess of small dense low-density lipoprotein particles (sdLDLs). Each component of atherogenic dyslipidemia is associated with CV events and triggers alterations at different levels of CV system through different pathways. FFAs and sdLDLs induce endothelial dysfunction, intima-media thickening, plaque formation and arterial stiffening through increase in oxidative stress and inflammation and promoting lipid accumulation and smooth muscle cells (SMCs) proliferation in vascular wall. In contrast, HDL exerts protective effect on arterial wall by increasing nitric oxide availability, by reverse cholesterol transport and by suppression of SMCs proliferation and migration. FFAs overload results in a switch in myocardial substrate utilization, causing changes in myocardial energy metabolism and an increase in baseline oxygen consumption. Accumulation of toxic lipid intermediates in myocardium provokes damage of cellular membrane integrity, organelle dysfunction and apoptosis with consequent decrease in myocardial performance. The structural and functional changes in myocardium can be reversed by therapy with reconstructed HDL. Therefore, the impact of atherogenic dyslipidemia on CV system is not limited on accelerated atherosclerosis, but causes different organ damages that must be considered in their complexity
Therapeutic implications of immunogenic cell death in human cancer
Dendritic cells (DCs) are central to the adoptive immune response, and their function is regulated by diverse signals in a context-specific manner. Different DCs have been described in physiologic conditions, inflammation, and cancer, prompting a series of questions on how adoptive immune responses, or tolerance, develop against tumors. Increasing evidence suggests that tumor treatments induce a dramatic change on tumor-infiltrating lymphocytes and, in particular, on some DC subtypes. In this review, we summarize the latest evidence on the role of DCs in cancer and preliminary evidence on chemotherapy-associated antigens identified in human cancers
Carotid-femoral pulse wave velocity estimated by an ultrasound system
To date, regional aortic stiffness can be evaluated by the reference tonometric technique via the pulse wave velocity (PWV) measured in two points: the carotid and the femoral arteries. Based on a similar intersecting tangent algorithm, we have developed a new method for the determination of carotid-femoral PWV using a high-resolution echo tracking ultrasound system. Herein, PWV can be computed from the measurement of the transit time between the foot of the carotid diameter waveform and the foot of the femoral diameter waveform.
The study was carried out on 50 consecutive patients at rest (29 men, mean age 30 ± 18 yrs) recruited on the occasion of a vascular screening for atherosclerosis. Carotid-femoral PWV was determined by a trained operator using a tonometric technique, (PWVpp, PulsePen, Italy), and an echotracking ultrasound system, (PWVus, e-tracking Alpha 10, Aloka, Japan). Relationship between PWVpp and PWVus was evaluated by linear regression.
A Pearson’s correlation coefficient of r=0.95 was found between both variables (95% confidence interval 0.90-0.99; P<0.0001; PWVus= 0,91*PWVpp+0.44). The Bland–Altman plot comparing PWVpp and PWVus showed a systematic offset of -0.07 m.s-1 with a limit of agreement from -1,33 to 1,19 m.s-1.
Our results show an excellent and significant correlation between both techniques which confirms that ultrasound system can provide a reliable estimate of the regional aortic stiffness like the tonometric technique does. Additional studies are now needed to show the simplicity of the measurement using ultrasound system while maintaining reliability even in overweight patients
Combined Diffusion-Relaxometry MRI to Identify Dysfunction in the Human Placenta
Purpose: A combined diffusion-relaxometry MR acquisition and analysis
pipeline for in-vivo human placenta, which allows for exploration of coupling
between T2* and apparent diffusion coefficient (ADC) measurements in a sub 10
minute scan time.
Methods: We present a novel acquisition combining a diffusion prepared
spin-echo with subsequent gradient echoes. The placentas of 17 pregnant women
were scanned in-vivo, including both healthy controls and participants with
various pregnancy complications. We estimate the joint T2*-ADC spectra using an
inverse Laplace transform.
Results: T2*-ADC spectra demonstrate clear quantitative separation between
normal and dysfunctional placentas.
Conclusions: Combined T2*-diffusivity MRI is promising for assessing fetal
and maternal health during pregnancy. The T2*-ADC spectrum potentially provides
additional information on tissue microstructure, compared to measuring these
two contrasts separately. The presented method is immediately applicable to the
study of other organs
Mapping complex cell morphology in the grey matter with double diffusion encoding MR: a simulation study
This paper investigates the impact of cell body (soma) size and branching of
cellular projections on diffusion MR imaging (dMRI) and spectroscopy (dMRS)
signals for both standard single diffusion encoding (SDE) and more advanced
double diffusion encoding (DDE) measurements using numerical simulations. The
aim is to study the ability of dMRI/dMRS to characterize the complex morphology
of brain grey matter, focusing on these two distinctive features. To this end,
we employ a recently developed framework to create realistic meshes for Monte
Carlo simulations, covering a wide range of soma sizes and branching orders of
cellular projections, for diffusivities reflecting both water and metabolites.
For SDE sequences, we assess the impact of soma size and branching order on the
signal b-value dependence as well as the time dependence of the apparent
diffusion coefficient (ADC). For DDE sequences, we assess their impact on the
mixing time dependence of the signal angular modulation and of the estimated
microscopic anisotropy, a promising contrast derived from DDE measurements. The
SDE results show that soma size has a measurable impact on both the b-value and
diffusion time dependence, for both water and metabolites. On the other hand,
branching order has little impact on either, especially for water. In contrast,
the DDE results show that soma size has a measurable impact on the signal
angular modulation at short mixing times and the branching order significantly
impacts the mixing time dependence of the signal angular modulation as well as
of the derived microscopic anisotropy, for both water and metabolites. Our
results confirm that soma size can be estimated from SDE based techniques, and
most importantly, show for the first time that DDE measurements show
sensitivity to the branching of cellular projections, paving the way for
non-invasive characterization of grey matter morphology
ConFiG: Contextual Fibre Growth to generate realistic axonal packing for diffusion MRI simulation
This paper presents Contextual Fibre Growth (ConFiG), an approach to generate
white matter numerical phantoms by mimicking natural fibre genesis. ConFiG
grows fibres one-by-one, following simple rules motivated by real axonal
guidance mechanisms. These simple rules enable ConFiG to generate phantoms with
tuneable microstructural features by growing fibres while attempting to meet
morphological targets such as user-specified density and orientation
distribution. We compare ConFiG to the state-of-the-art approach based on
packing fibres together by generating phantoms in a range of fibre
configurations including crossing fibre bundles and orientation dispersion.
Results demonstrate that ConFiG produces phantoms with up to 20% higher
densities than the state-of-the-art, particularly in complex configurations
with crossing fibres. We additionally show that the microstructural morphology
of ConFiG phantoms is comparable to real tissue, producing diameter and
orientation distributions close to electron microscopy estimates from real
tissue as well as capturing complex fibre cross sections. Signals simulated
from ConFiG phantoms match real diffusion MRI data well, showing that ConFiG
phantoms can be used to generate realistic diffusion MRI data. This
demonstrates the feasibility of ConFiG to generate realistic synthetic
diffusion MRI data for developing and validating microstructure modelling
approaches
Impact of within-voxel heterogeneity in fibre geometry on spherical deconvolution
Axons in white matter have been shown to have varying geometries within a
bundle using ex vivo imaging techniques, but what does this mean for diffusion
MRI (dMRI) based spherical deconvolution (SD)? SD attempts to estimate the
fibre orientation distribution function (fODF) by assuming a single dMRI fibre
response function (FRF) for all white matter populations and deconvolving this
FRF from the dMRI signal at each voxel to estimate the fODF. Variable fibre
geometry within a bundle however suggests the FRF might not be constant even
within a single voxel. We test what impact realistic fibre geometry has on SD
by simulating the dMRI signal in a range of realistic white matter numerical
phantoms, including synthetic phantoms and real axons segmented from electron
microscopy. We demonstrate that variable fibre geometry leads to a variable FRF
across axons and that in general no single FRF is effective to recover the
underlying fibre orientation distribution function (fODF). This finding
suggests that assuming a single FRF can lead to misestimation of the fODF,
causing further downstream errors in techniques such as tractography
Sorgo para pastejo/corte e cobertura do solo no período de outono/inverno (safrinha) em Mato Grosso do Sul.
Em Mato Grosso do Sul, as principais culturas utilizadas para cobertura de solo na safrinha são o milheto, a aveia e o nabo (Hernani et al., 1995; Machado, 2003). Para pastejo, também são utilizadas essas espécies, com exceção do nabo. Devido ao risco de geadas, as espécies adaptadas ao clima frio, como a aveia e o nabo, são mais utilizadas na região sul do Estado. Na região norte, o milheto e o sorgo são mais produtivos no período de outono, porque o clima, apesar de seco, é quente, favorecendo as espécies tropicais. Em regiões com esta condição, o sorgo é muito utilizado para a produção de grãos, sendo recente sua utilização para a produção de palha e forragem. Pela sua tolerância a déficit hídrico e a baixas temperaturas, a cultura vem ganhando importância econômica no Estado. Este estudo teve como objetivo selecionar genótipos de sorgo para pastejo na safra de outono/inverno, em sucessão a soja.bitstream/item/38771/1/BP-200416.pd
Left ventricular ejection time, not heart rate, is an independent correlate of aortic pulse wave velocity.
Salvi P, Palombo C, Salvi GM, Labat C, Parati G, Benetos A. Left
ventricular ejection time, not heart rate, is an independent correlate of
aortic pulse wave velocity. J Appl Physiol 115: 1610–1617, 2013. First
published September 19, 2013; doi:10.1152/japplphysiol.00475.2013.—
Several studies showed a positive association between heart rate and
pulse wave velocity, a sensitive marker of arterial stiffness. However, no
study involving a large population has specifically addressed the dependence
of pulse wave velocity on different components of the cardiac
cycle. The aim of this study was to explore in subjects of different age the
link between pulse wave velocity with heart period (the reciprocal of
heart rate) and the temporal components of the cardiac cycle such as left
ventricular ejection time and diastolic time. Carotid-femoral pulse wave
velocity was assessed in 3,020 untreated subjects (1,107 men). Heart
period, left ventricular ejection time, diastolic time, and early-systolic
dP/dt were determined by carotid pulse wave analysis with high-fidelity
applanation tonometry. An inverse association was found between pulse
wave velocity and left ventricular ejection time at all ages (25 years,
r2 0.043; 25–44 years, r2 0.103; 45–64 years, r2 0.079; 65–84
years, r2 0.044; 85 years, r2 0.022; P 0.0001 for all). A
significant (P 0.0001) negative but always weaker correlation between
pulse wave velocity and heart period was also found, with the exception
of the youngest subjects (P0.20). A significant positive correlation was
also found between pulse wave velocity and dP/dt (P 0.0001). With
multiple stepwise regression analysis, left ventricular ejection time and
dP/dt remained the only determinant of pulse wave velocity at all ages,
whereas the contribution of heart period no longer became significant.
Our data demonstrate that pulse wave velocity is more closely related to
left ventricular systolic function than to heart period. This may have
methodological and pathophysiological implications
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