Much of the present-day volume of Earth's continental crust had formed by the end of the Archean Eon, 2.5 billion years ago, through the conversion of basaltic (mafic) crust into sodic granite of ...tonalite, trondhjemite and granodiorite (TTG) composition. Distinctive chemical signatures in a small proportion of these rocks, the so-called high-pressure TTG, are interpreted to indicate partial melting of hydrated crust at pressures above 1.5 GPa (>50 km depth), pressures typically not reached in post-Archean continental crust. These interpretations significantly influence views on early crustal evolution and the onset of plate tectonics. Here we show that high-pressure TTG did not form through melting of crust, but through fractionation of melts derived from metasomatically enriched lithospheric mantle. Although the remaining, and dominant, group of Archean TTG did form through melting of hydrated mafic crust, there is no evidence that this occurred at depths significantly greater than the ~40 km average thickness of modern continental crust.
Sudden emotional distress, such as that caused by an unexpected death, can sometimes produce severe transient left ventricular dysfunction. This stress-induced cardiomyopathy appears to be a form of ...myocardial stunning associated with marked sympathetic stimulation.
Sudden emotional distress, such as that caused by an unexpected death, can sometimes produce severe transient left ventricular dysfunction.
The potentially lethal consequences of emotional stress are deeply rooted in folk wisdom, as reflected by phrases such as “scared to death” and “a broken heart.” In the past decade, cardiac contractile abnormalities and heart failure have been reported after acute emotional stress,
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but the mechanism remains unknown. We evaluated 19 patients with “stress cardiomyopathy,” a syndrome of profound myocardial stunning precipitated by acute emotional stress, in an effort to identify the clinical features that distinguish this syndrome from acute myocardial infarction and the cause of transient stress-induced myocardial dysfunction.
Methods
Study Patients
Nineteen previously healthy patients were admitted . . .
In this work, we report a unified methodology to express the molecular wavefunctions of water in both vapor and liquid phases by means of a single-center approach. These latter are then used as input ...data in a theoretical treatment--previously published and successfully tested--for describing the water ionization process in the first Born approximation (Champion et al 2006 Phys. Rev. A 73 012717). The multi-differential and total cross sections also obtained are reported for the two thermodynamical phases investigated and compared to the rare existing experimental and theoretical data.
Prognosis in pulmonary hypertension (PH) is largely determined by RV function. However, uncertainty remains about what metrics of RV function might be most clinically relevant. The purpose of this ...study was to assess the clinical relevance of metrics of RV functional adaptation to increased afterload.
Patients referred for PH underwent right heart catheterisation and RV volumetric assessment within 48 h. A RV maximum pressure (Pmax) was calculated from the RV pressure curve. The adequacy of RV systolic functional adaptation to increased afterload was estimated either by a stroke volume (SV)/end-systolic volume (ESV) ratio, a Pmax/mean pulmonary artery pressure (mPAP) ratio, or by EF (RVEF). Diastolic function of the RV was estimated by a diastolic elastance coefficient β. Survival analysis was via Cox proportional HR, and Kaplan-Meier with the primary outcome of time to death or lung transplant.
Patients (n=50; age 58±13 yrs) covered a range of mPAP (13-79 mm Hg) with an average RVEF of 39±17% and ESV of 143±89 mL. Average estimates of the ratio of end-systolic ventricular to arterial elastance were 0.79±0.67 (SV/ESV) and 2.3±0.65 (Pmax/mPAP-1). Transplantation-free survival was predicted by right atrial pressure, mPAP, pulmonary vascular resistance, β, SV, ESV, SV/ESV and RVEF, but after controlling for right atrial pressure, mPAP, and SV, SV/ESV was the only independent predictor.
The adequacy of RV functional adaptation to afterload predicts survival in patients referred for PH. Whether this can simply be evaluated using RV volumetric imaging will require additional confirmation.
Much of the current volume of Earth's continental crust had formed by the end of the Archaean eon
(2.5 billion years ago), through melting of hydrated basaltic rocks at depths of approximately 25-50 ...kilometres, forming sodic granites of the tonalite-trondhjemite-granodiorite (TTG) suite
. However, the geodynamic setting and processes involved are debated, with fundamental questions arising, such as how and from where the required water was added to deep-crustal TTG source regions
. In addition, there have been no reports of voluminous, homogeneous, basaltic sequences in preserved Archaean crust that are enriched enough in incompatible trace elements to be viable TTG sources
. Here we use variations in the oxygen isotope composition of zircon, coupled with whole-rock geochemistry, to identify two distinct groups of TTG. Strongly sodic TTGs represent the most-primitive magmas and contain zircon with oxygen isotope compositions that reflect source rocks that had been hydrated by primordial mantle-derived water. These primitive TTGs do not require a source highly enriched in incompatible trace elements, as 'average' TTG does. By contrast, less sodic 'evolved' TTGs require a source that is enriched in both water derived from the hydrosphere and also incompatible trace elements, which are linked to the introduction of hydrated magmas (sanukitoids) formed by melting of metasomatized mantle lithosphere. By concentrating on data from the Palaeoarchaean crust of the Pilbara Craton, we can discount a subduction setting
, and instead propose that hydrated and enriched near-surface basaltic rocks were introduced into the mantle through density-driven convective overturn of the crust. These results remove many of the paradoxical impediments to understanding early continental crust formation. Our work suggests that sufficient primordial water was already present in Earth's early mafic crust to produce the primitive nuclei of the continents, with additional hydrated sources created through dynamic processes that are unique to the early Earth.
Objectives The aim of this study was to report a series of patients with stress cardiomyopathy precipitated by the intravenous administration of catecholamines and beta-receptor agonists. Background ...Stress cardiomyopathy is a syndrome of transient cardiac dysfunction precipitated by intense emotional or physical stress. Excessive sympathetic stimulation is believed to be central to the pathogenesis of this disorder, but a causal link has not been convincingly demonstrated. Methods We observed 9 cases of stress cardiomyopathy precipitated immediately by the intravenous administration of epinephrine (n = 6) or dobutamine (n = 3). Patients were evaluated with coronary angiography and with serial echocardiography, electrocardiography, and cardiac enzymes. Results The median age was 44 years (interquartile range IQR: 30 to 48 years), and 7 (78%) were woman. Troponin-I was mildly elevated (median 4.07 ng/ml, IQR: 0.47 to 5.63 ng/ml), but none of the patients undergoing angiography had obstructive coronary disease. All patients developed corrected QT interval (QTc interval) prolongation (median QTc interval 504 ms, IQR: 477 to 568 ms) within 24 h of receiving drug. All 3 previously described variants of left ventricular “ballooning” (apical, midventricular, and basal) were observed. The median ejection fraction on admission was 35% (IQR: 35% to 40%). During follow-up (median 7 days, IQR: 4 to 13 days) there was recovery of left ventricular systolic function in all patients (median ejection fraction 55%, IQR: 40% to 60%, p < 0.001 vs. admission). Conclusions Exposure to catecholamines and beta-receptor agonists used routinely during procedures and diagnostic tests can precipitate all the features of stress cardiomyopathy, including cardiac isoenzyme elevation, QTc interval prolongation, and rapidly reversible cardiac dysfunction. These observations strongly implicate excessive sympathetic stimulation as central to the pathogenesis of this unique syndrome.
Sustained cardiac pressure overload induces hypertrophy and pathological remodeling, frequently leading to heart failure. Genetically engineered hyperstimulation of guanosine 3',5'-cyclic ...monophosphate (cGMP) synthesis counters this response. Here, we show that blocking the intrinsic catabolism of cGMP with an oral phosphodiesterase-5A (PDE5A) inhibitor (sildenafil) suppresses chamber and myocyte hypertrophy, and improves in vivo heart function in mice exposed to chronic pressure overload induced by transverse aortic constriction. Sildenafil also reverses pre-established hypertrophy induced by pressure load while restoring chamber function to normal. cGMP catabolism by PDE5A increases in pressure-loaded hearts, leading to activation of cGMP-dependent protein kinase with inhibition of PDE5A. PDE5A inhibition deactivates multiple hypertrophy signaling pathways triggered by pressure load (the calcineurin/NFAT, phosphoinositide-3 kinase (PI3K)/Akt, and ERK1/2 signaling pathways). But it does not suppress hypertrophy induced by overexpression of calcineurin in vitro or Akt in vivo, suggesting upstream targeting of these pathways. PDE5A inhibition may provide a new treatment strategy for cardiac hypertrophy and remodeling.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Analysis of heart rate variability (HRV) is a recognized tool in the assessment of autonomic nervous system (ANS) activity. Indeed, both time and spectral analysis techniques enable us to obtain ...indexes that are related to the way the ANS regulates the heart rate. However, these techniques are limited in terms of the lack of thresholds of the numerical indexes, which is primarily due to high inter-subject variability. We proposed a new fetal HRV analysis method related to the parasympathetic activity of the ANS. The aim of this study was to evaluate the performance of our method compared to commonly used HRV analysis, with regard to i) the ability to detect changes in ANS activity and ii) inter-subject variability. This study was performed in seven sheep fetuses. In order to evaluate the sensitivity and specificity of our index in evaluating parasympathetic activity, we directly administered 2.5 mg intravenous atropine, to inhibit parasympathetic tone, and 5 mg propranolol to block sympathetic activity. Our index, as well as time analysis (root mean square of the successive differences; RMSSD) and spectral analysis (high frequency (HF) and low frequency (LF) spectral components obtained via fast Fourier transform), were measured before and after injection. Inter-subject variability was estimated by the coefficient of variance (%CV). In order to evaluate the ability of HRV parameters to detect fetal parasympathetic decrease, we also estimated the effect size for each HRV parameter before and after injections. As expected, our index, the HF spectral component, and the RMSSD were reduced after the atropine injection. Moreover, our index presented a higher effect size. The %CV was far lower for our index than for RMSSD, HF, and LF. Although LF decreased after propranolol administration, fetal stress index, RMSSD, and HF were not significantly different, confirming the fact that those indexes are specific to the parasympathetic nervous system. In conclusion, our method appeared to be effective in detecting parasympathetic inhibition. Moreover, inter-subject variability was much lower, and effect size higher, with our method compared to other HRV analysis methods.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
In addition to conventional short-lived radionuclides, longer-lived isotopes are becoming increasingly important to positron emission tomography (PET). The longer half-life both allows for ...circumvention of the in-house production of radionuclides, and expands the spectrum of physiological processes amenable to PET imaging, including processes with prohibitively slow kinetics for investigation with short-lived radiotracers. However, many of these radionuclides emit 'high-energy' positrons and gamma rays which affect the spatial resolution and quantitative accuracy of PET images. The objective of the present work is to investigate the positron range distribution for some of these long-lived isotopes. Based on existing Monte Carlo simulations of positron interactions in water, the probability distribution of the line of response displacement have been empirically described by means of analytic displacement functions. Relevant distributions have been derived for the isotopes 22Na, 52Mn, 89Zr, 45Ti, 51Mn, 94mTc, 52mMn, 38K, 64Cu, 86Y, 124I, and 120I. It was found that the distribution functions previously found for a series of conventional isotopes (Jødal et al 2012 Phys. Med. Bio. 57 3931-43), were also applicable to these non-conventional isotopes, except that for 120I, 124I, 89Zr, 52Mn, and 64Cu, parameters in the formulae were less well predicted by mean positron energy alone. Both conventional and non-conventional range distributions can be described by relatively simple analytic expressions. The results will be applicable to image-reconstruction software to improve the resolution.
Positron range impairs resolution in PET imaging, especially for high-energy emitters and for small-animal PET. De-blurring in image reconstruction is possible if the blurring distribution is known. ...Furthermore, the percentage of annihilation events within a given distance from the point of positron emission is relevant for assessing statistical noise. This paper aims to determine the positron range distribution relevant for blurring for seven medically relevant PET isotopes, 18F, 11C, 13N, 15O, 68Ga, 62Cu and 82Rb, and derive empirical formulas for the distributions. This paper focuses on allowed-decay isotopes. It is argued that blurring at the detection level should not be described by the positron range r, but instead the 2D projected distance δ (equal to the closest distance between decay and line of response). To determine these 2D distributions, results from a dedicated positron track-structure Monte Carlo code, Electron and POsitron TRANsport (EPOTRAN), were used. Materials other than water were studied with PENELOPE. The radial cumulative probability distribution G2D(δ) and the radial probability density distribution g2D(δ) were determined. G2D(δ) could be approximated by the empirical function 1 - exp(-Aδ2 - Bδ), where A = 0.0266 (Emean)−1.716 and B = 0.1119 (Emean)−1.934, with Emean being the mean positron energy in MeV and δ in mm. The radial density distribution g2D(δ) could be approximated by differentiation of G2D(δ). Distributions in other media were very similar to water. The positron range is important for improved resolution in PET imaging. Relevant distributions for the positron range have been derived for seven isotopes. Distributions for other allowed-decay isotopes may be estimated with the above formulas.
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