Femtosecond response of polyatomic molecules to ultra-intense hard X-rays.

X-ray free-electron lasers enable the investigation of the structure and dynamics of diverse systems, including atoms, molecules, nanocrystals and single bioparticles, under extreme conditions. Many imaging applications that target biological systems and complex materials use hard X-ray pulses with extremely high peak intensities (exceeding 1020 watts per square centimetre). However, fundamental investigations have focused mainly on the individual response of atoms and small molecules using soft X-rays with much lower intensities. Studies with intense X-ray pulses have shown that irradiated atoms reach a very high degree of ionization, owing to multiphoton absorption, which in a heteronuclear molecular system occurs predominantly locally on a heavy atom (provided that the absorption cross-section of the heavy atom is considerably larger than those of its neighbours) and is followed by efficient redistribution of the induced charge. In serial femtosecond crystallography of biological objects-an application of X-ray free-electron lasers that greatly enhances our ability to determine protein structure-the ionization of heavy atoms increases the local radiation damage that is seen in the diffraction patterns of these objects and has been suggested as a way of phasing the diffraction data. On the basis of experiments using either soft or less-intense hard X-rays, it is thought that the induced charge and associated radiation damage of atoms in polyatomic molecules can be inferred from the charge that is induced in an isolated atom under otherwise comparable irradiation conditions. Here we show that the femtosecond response of small polyatomic molecules that contain one heavy atom to ultra-intense (with intensities approaching 1020 watts per square centimetre), hard (with photon energies of 8.3 kiloelectronvolts) X-ray pulses is qualitatively different: our experimental and modelling results establish that, under these conditions, the ionization of a molecule is considerably enhanced compared to that of an individual heavy atom with the same absorption cross-section. This enhancement is driven by ultrafast charge transfer within the molecule, which refills the core holes that are created in the heavy atom, providing further targets for inner-shell ionization and resulting in the emission of more than 50 electrons during the X-ray pulse. Our results demonstrate that efficient modelling of X-ray-driven processes in complex systems at ultrahigh intensities is feasible.

Pulse Energy and Pulse Duration Effects in the Ionization and Fragmentation of Iodomethane by Ultraintense Hard X Rays.

The interaction of intense femtosecond x-ray pulses with molecules sensitively depends on the interplay between multiple photoabsorptions, Auger decay, charge rearrangement, and nuclear motion. Here, we report on a combined experimental and theoretical study of the ionization and fragmentation of iodomethane (CH_{3}I) by ultraintense (∼10^{19} W/cm^{2}) x-ray pulses at 8.3 keV, demonstrating how these dynamics depend on the x-ray pulse energy and duration. We show that the timing of multiple ionization steps leading to a particular reaction product and, thus, the product's final kinetic energy, is determined by the pulse duration rather than the pulse energy or intensity. While the overall degree of ionization is mainly defined by the pulse energy, our measurement reveals that the yield of the fragments with the highest charge states is enhanced for short pulse durations, in contrast to earlier observations for atoms and small molecules in the soft x-ray domain. We attribute this effect to a decreased charge transfer efficiency at larger internuclear separations, which are reached during longer pulses.

Erratum: Delayed Onset of Nonthermal Melting in Single-Crystal Silicon Pumped with Hard X Rays [Phys. Rev. Lett. 120, 265701 (2018)].

This corrects the article DOI: 10.1103/PhysRevLett.120.265701.

Asymmetries in core-collapse supernovae from maps of radioactive 44Ti in Cassiopeia A.

Asymmetry is required by most numerical simulations of stellar core-collapse explosions, but the form it takes differs significantly among models. The spatial distribution of radioactive (44)Ti, synthesized in an exploding star near the boundary between material falling back onto the collapsing core and that ejected into the surrounding medium, directly probes the explosion asymmetries. Cassiopeia A is a young, nearby, core-collapse remnant from which (44)Ti emission has previously been detected but not imaged. Asymmetries in the explosion have been indirectly inferred from a high ratio of observed (44)Ti emission to estimated (56)Ni emission, from optical light echoes, and from jet-like features seen in the X-ray and optical ejecta. Here we report spatial maps and spectral properties of the (44)Ti in Cassiopeia A. This may explain the unexpected lack of correlation between the (44)Ti and iron X-ray emission, the latter being visible only in shock-heated material. The observed spatial distribution rules out symmetric explosions even with a high level of convective mixing, as well as highly asymmetric bipolar explosions resulting from a fast-rotating progenitor. Instead, these observations provide strong evidence for the development of low-mode convective instabilities in core-collapse supernovae.

Blastulation of a zygote to a hatched blastocyst without any clear cell division: an observational finding in a time-lapse system after in vitro fertilization.

PURPOSE: To describe an interesting not previously described morphokinetic finding. METHODS: Retrospective case report of a couple undergoing controlled ovarian stimulation (COS) followed by in vitro fertilization and blastocyst transfer. RESULTS: We identified a unique finding of blastulation of a fertilized human zygote after conventional in vitro fertilization. The fertilized zygote did not show any clear cytokinesis until approximately 107 h post insemination, when it started dividing into a blastocyst. By 113 h post insemination, inner cell mass and trophectoderm cells could be clearly distinguished and the blastocyst was completely hatched by 136 h post insemination. CONCLUSION: Time-lapse systems offer more detailed observations of embryonic development. Here, we report an atypical development of an embryo that was not described previously. We hope to become an insightful discussion among peers and incentive the publication of such findings in the future.

Delayed Onset of Nonthermal Melting in Single-Crystal Silicon Pumped with Hard X Rays.

In this work, we monitor the onset of nonthermal melting in single-crystal silicon by implementing an x-ray pump-x-ray probe scheme. Using the ultrashort pulses provided by the Linac Coherent Light Source (SLAC) and a custom-built split-and-delay line for hard x rays, we achieve the temporal resolution needed to detect the onset of the transition. Our data show no loss of long-range order up to 150±40 fs from photoabsorption, which we interpret as the time needed for the electronic system to equilibrate at or above the critical nonthermal melting temperature. Once such equilibration is reached, the loss of long-range atomic order proceeds inertially and is completed within 315±40 fs from photoabsorption.

Demonstration of simultaneous experiments using thin crystal multiplexing at the Linac Coherent Light Source.

Multiplexing of the Linac Coherent Light Source beam was demonstrated for hard X-rays by spectral division using a near-perfect diamond thin-crystal monochromator operating in the Bragg geometry. The wavefront and coherence properties of both the reflected and transmitted beams were well preserved, thus allowing simultaneous measurements at two separate instruments. In this report, the structure determination of a prototypical protein was performed using serial femtosecond crystallography simultaneously with a femtosecond time-resolved XANES studies of photoexcited spin transition dynamics in an iron spin-crossover system. The results of both experiments using the multiplexed beams are similar to those obtained separately, using a dedicated beam, with no significant differences in quality.

CD36 mRNA expression is increased in CD14+ monocytes of patients with coronary heart disease.

1. Blood-derived monocytes/macrophages within the intima of the arterial wall are the main source of inflammatory cytokines and factors contributing to lesion growth, plaque instability and thrombotic events. In the present study, we assessed the hypothesis that mRNA expression levels of candidate genes of atherosclerosis in circulating CD14(+) blood monocytes are associated with coronary heart disease (CHD). 2. We investigated mRNA expression levels using reverse transcription-polymerase chain reaction of genes involved in cholesterol uptake (macrophage scavenger receptor (MSR1), scavenger receptor class B member 1 (SRB1), lectin-like oxidized low-density lipoprotein (LDL) receptor 1 (LOX1), CD36, LDL receptor (LDLR)), reverse cholesterol transport (apolipoprotein E (ApoE), ATP-binding cassette sub-family A member 1 (ABCA1)) and inflammation (tumour necrosis factor-alpha (TNF-alpha), macrophage inflammatory protein-1alpha (MIP-1alpha), interleukin-6 (IL-6), tissue factor) in CD14(+) monocytes from 119 consecutively recruited patients and found that median CD36 mRNA expression levels were significantly increased in patients with CHD compared with controls (111 x 10(3) vs 96 x 10(3) copies/10(6) copies beta-actin, respectively; n = 79 and 40, respectively; P < 0.05), despite a high interindividual variability in gene expression. 3. A common T --> C polymorphism (rs2151916) located only 14 bp upstream of the upstream transcriptional start site did not influence CD36 expression. 4. Expression levels of the other candidate genes investigated in the present study did not show any statistically significant differences between patients with CHD and controls. 5. We conclude that CD36 mRNA expression is significantly increased in patients with CHD and may serve as an indicator of CHD burden.

Attenuated cardiac allograft vasculopathy in mice with targeted deletion of the transcription factor STAT4.

BACKGROUND: To study transcription factor signaling pathways that mediate cardiac allograft vasculopathy, we used mice with targeted gene deletion of signal transducer and activator of transcription (STAT)4 and STAT6 as recipients in our mouse cardiac transplant model of chronic rejection. METHODS AND RESULTS: At day 55 after transplantation, cardiac grafts placed into STAT4 -/- (n=10) had reduced frequency (24+/-2%) and severity (9+/-4%) of vascular occlusion compared with wild-type controls (n=7, frequency 70+/-12% [P<0.001], severity 25+/-6% [P<0.05]). This decrease was associated with reduced intragraft expression ((32)P RT-PCR and immunohistochemistry) of the Th1 signature cytokines interferon-gamma (P<0.001) and interleukin (IL)-2 (P<0.001). Furthermore, cardiac grafts in STAT4 -/- had fewer infiltrating CD45(+) mononuclear cells (99+/-27 cells/mm(3) compared with 551+/-168 cells/mm(3) in wild-type controls [P<0.05]) and reduced expression of P-selectin (P<0.001) and E-selectin (P<0.01) ligand, recently shown to regulate Th1 cell recruitment. In contrast, in grafts placed into STAT6 -/- (n=11), the development of cardiac allograft vasculopathy (frequency 62+/-8%, severity 28+/-6%) and Th2 cytokine profiles (IL-4, IL-10) were comparable to those in wild-type controls. CONCLUSIONS: Hence, we show that immune responses mediated by STAT4, but not STAT6, contribute to the development of cardiac allograft vasculopathy. We speculate that when present, STAT4-mediated signaling pathways may promote cardiac allograft vasculopathy by directing Th1-specific lymphocyte recruitment, activation, and effector functions.

Isolated defect of adenosine-mediated coronary vasodilation: functional evidence for a new microangiopathic entity.

OBJECTIVES: The present study describes an isolated defect of the coronary vasodilation in response to adenosine in five patients examined for clinically suspected coronary microangiopathy. BACKGROUND: Coronary microangiopathies can be defined functionally as dysregulation of the microcirculatory vasomotion. METHODS: The five patients were compared with 24 control subjects. Coronary flow velocity was measured with an intracoronary Doppler guide wire (0.018 in. [0.046 cm], 12 MHz) at rest and during intracoronary administration of adenosine (80 micrograms/min and 160 micrograms/min over 3 min each), papaverine (10-mg bolus) and acetylcholine (30 micrograms/min over 5 min). Diameters of the epicardial coronary arteries were measured by quantitative coronary angiography. RESULTS: All subjects (patients and control) exhibited angiographically normal epicardial coronary arteries and normal and comparable endothelium-independent and -dependent vasomotion, as assessed with papaverine (mean [+/-SD]-relative coronary flow reserve 2.62 +/- 0.66 vs. 2.97 +/- 0.88, p = 0.32) and acetylcholine (volumetric coronary flow reserve 2.61 +/- 0.27 vs. 2.91 +/- 0.67, p = 0.58), respectively. Affected patients were identified by an isolated complete defect of the adenosine-mediated vasodilation compared with control subjects (relative coronary flow reserve in response to 80 micrograms/min of adenosine 1.08 +/- 0.17 vs. 2.45 +/- 0.74 [p < 0.001] and 160 micrograms/min of adenosine 1.03 +/- 0.15 vs. 2.89 +/- 0.65 [p < 0.001]). CONCLUSIONS: These findings are consistent with functional evidence for a new entity of a coronary microangiopathy affecting a subtype of the endothelium-independent vasomotion.

Role of brain natriuretic peptide in risk stratification of patients with congestive heart failure.

OBJECTIVES: Using a prospective study design, we assessed the value of brain natriuretic peptide (BNP) to identify patients with heart failure who have an increased risk of deterioration of their functional status. Furthermore, we examined the relationship between BNP and various clinical characteristics incorporated into an established survival model used for risk stratification. BACKGROUND: Prediction of the clinical course is a crucial part of the decision-making process about the adequate treatment strategy for patients with advanced congestive heart failure (CHF). Although laborious, multivariable indexes have been established for risk stratification, simple plasma BNP measurements may be as useful as prognostic indicators. METHODS: In 78 patients referred to our heart failure clinic, plasma BNP levels were compared with the results of a multivariable prognostic model. To assess the prognostic power of BNP, the clinical course of this cohort was monitored for a median follow-up period of 398 days. RESULTS: At study entry, plasma BNP and the heart failure survival score (HFSS) showed a significant correlation (r = -0.706). During follow-up, Kaplan-Meier estimates of freedom from clinical events differed significantly for patients above and below the 75th percentile concentrations of plasma BNP (p < 0.0001). Changes in plasma BNP were significantly related to changes in limitations of physical activity, as demonstrated by logistic regression analysis (chi-square statistic = 24.9, p < 0.0001). Proportional hazards analysis confirmed BNP as a powerful predictor of functional status deterioration (p < 0.0001). This prognostic information was as powerful as that derived from the multivariable HFSS. CONCLUSIONS: Measurement of plasma BNP concentrations might provide a useful and cost-effective screening tool that helps reduce the need and frequency for more expensive cardiac tests.

Antiadrenergic effect of carbachol but not of adenosine on contractility in the intact human ventricle in vivo.

OBJECTIVES: The purpose of this study was to investigate the antiadrenergic effects of adenosine and carbachol on beta-adrenoceptor-stimulated human ventricular contractility in vivo. In addition, the antiadrenergic effects of adenosine and carbachol were compared in vitro. BACKGROUND: Adenosine is reported to exhibit an antiadrenergic negative inotropic response in the beta-adrenergic-stimulated ventricular myocardium in vitro. The effect of adenosine is similar to the antiadrenergic effect of m-cholinoceptor stimulation in vitro. METHODS: The inotropic response in vivo was assessed in seven healthy volunteers by M-mode echocardiography and simultaneous blood pressure monitoring. It was calculated as the increase in the rate-corrected velocity of circumferential fiber shortening and in the systolic pressure/dimension ratio. All volunteers received pretreatment with 450 mg of dipyridamole/day for 48 h. In addition, the effects of adenosine and carbachol in the presence of 0.03 mumol/liter of isoproterenol on cumulative concentration-response curves of isolated, electrically driven human ventricular muscle strips were compared in vitro (n = 13). RESULTS: The positive inotropic response to continuous infusion of 20 ng/kg per min of isoproterenol (increase of rate-corrected velocity of circumferential fiber shortening [10.2 +/- 2.1% x square root of beats/min per ms] and increase of systolic pressure/dimension ratio 1.09 +/- 0.3 mm Hg/mm) was significantly (p < 0.01) reduced by 3.6 micrograms/kg body weight of intravenous carbachol (4.2 +/- 1.2% x square root of beats/min per ms, 0.21 +/- 0.18 mm Hg/mm) but not by 50 micrograms/kg of intravenous adenosine (8.2 +/- 3.1% x square root of beats/min per ms, 1.35 +/- 0.42 mm Hg/mm), although adenosine induced a significant negative dromotropic effect. In vitro comparison of force of contraction with cumulative concentration-response curves in the presence of 0.03 mumol/liter of isoproterenol demonstrated an EC50 value (concentration producing half-maximal effect) for adenosine 466 times higher than that for carbachol (65.3 vs. 0.14 mumol/liter, p < 0.001). CONCLUSIONS: In contrast to carbachol, adenosine does not attenuate the catecholamine-induced increase in contractility in the human ventricle in vivo. These differences between the A1-adenosine receptor- and m-cholinoceptor-mediated effects could be due to fewer A1-adenosine receptors or a less efficient receptor-effector coupling, or both.

Supernovae. 44Ti gamma-ray emission lines from SN1987A reveal an asymmetric explosion.

In core-collapse supernovae, titanium-44 ((44)Ti) is produced in the innermost ejecta, in the layer of material directly on top of the newly formed compact object. As such, it provides a direct probe of the supernova engine. Observations of supernova 1987A (SN1987A) have resolved the 67.87- and 78.32-kilo-electron volt emission lines from decay of (44)Ti produced in the supernova explosion. These lines are narrow and redshifted with a Doppler velocity of ~700 kilometers per second, direct evidence of large-scale asymmetry in the explosion.

Alloimmune-mediated apoptosis: comparison in mouse models of acute and chronic cardiac rejection.

BACKGROUND: The purpose of the present study was (1) to compare apoptotic activity in models of acute and chronic rejection and (2) to study the cellular distribution of parenchymal versus inflammatory cell apoptosis. METHODS: Heterotopic cardiac mouse transplantation (CBA into C57BL/6) was used to produce allografts undergoing acute (day 7, untreated recipients, n=6) or chronic (day 55, anti-CD4/8 for 28 days, n=6) rejection. As references, we used 55-day isograft controls (n=5) and native hearts (n=6). To assess apoptotic activity, we quantified DNA laddering (32P incorporation), DNA fragmentation (antinucleosome ELISA), and caspase-1 transcript levels (32P-reverse transcriptase-polymerase chain reaction). To localize apoptosis, we performed terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling. RESULTS: DNA laddering and nucleosome levels were increased in allografts undergoing acute or chronic rejection when compared with both controls. Both parameters were twofold higher in acutely compared with chronically rejecting hearts. Caspase-1 transcript levels were increased in acutely (P<0.0001) and chronically rejecting hearts (P=0.004). Acutely rejecting grafts had more terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling-positive nuclei (53+/-3 nuclei/high-powered field) than chronically rejecting grafts (9+/-1 nuclei/high-powered field, P<0.0001), but the distribution between graft-infiltrating inflammatory cells and myocytes was similar. Vascular cells undergoing apoptosis were infrequent in both forms. CONCLUSION: Using four separate indices, apoptotic activity is more pronounced in cardiac allografts undergoing acute compared with chronic rejection. This reflects, in part, the degree of alloimmune response. However, we speculate that the contributions of apoptosis to various forms of rejection are multifactorial. The long-term outcome to the graft may depend upon the magnitude, timing, and target of programmed cell death.

KARMEN time anomaly: search for a neutral particle of mass 33.9 MeV in pion decay

We have searched for the pion decay pi(+)-->&mgr;+X, where X is a neutral particle of mass 33.905 MeV. This process was suggested by the KARMEN Collaboration to explain an anomaly in their observed time distribution of neutrino induced reactions. Having measured the muon momentum spectrum of charged pions decaying in flight, we find no evidence for this process and place an upper limit on the branching fraction eta

Time-dependent decrease of presynaptic inotropic supersensitivity: physiological evidence of sympathetic reinnervation after heart transplantation.

BACKGROUND: Sympathetic cardiac denervation of the transplanted human heart causes a loss of the presynaptic neuronal uptake1-mechanism with consecutive supersensitivity to uptake1-dependent catecholamines. A return of neuronal function (reinnervation) should result in a decrease of supersensitivity to catecholamines subjected to this uptake system and thus may alter the inotropic regulation. METHODS: Inotropic dose-response curves were compared in 12 patients who were studied 3 to 15 months after transplantation (early) and 17 patients who were studied 23 to 156 months after transplantation (late) with isoproterenol (uptake1-independent) and epinephrine (uptake1-dependent). The inotropic response to increasing doses of isoproterenol (5 to 20 ng/kg per min) and epinephrine (10 to 40 ng/kg per min) was assessed with echocardiography as increase of the systolic pressure/dimension ratio (delta P/D) and of the rate-corrected velocity of circumferential fiber shortening (delta Vcfc). RESULTS: Inotropic dose/response curves to isoproterenol were identical in the early and late recipients (during 20 ng/kg per min. isoproterenol: delta P/D 2.07 +/- 1.36 vs 2.18 +/- 1.42 mm Hg/mm; delta Vcfc 1.55 +/- 0.33 vs 1.40 +/- 0.38 square root of min-1 x %/ms), indicating an unchanged inotropic effect mediated by the postsynaptic beta-receptor/effector system. However, the inotropic response to epinephrine in early recipients was significantly attenuated in the late recipients (during 40 ng/kg per min. epinephrine: delta P/D 3.35 +/- 2.06 vs 1.51 +/- 0.68 mm Hg/mm, p < 0.01; delta Vcfc 1.80 +/- 0.42 vs 1.05 +/- 0.35 square root of min-1 x %/ms, p < 0.001). CONCLUSIONS: These findings provide evidence for an at least partial restoration of the neuronal catecholamine uptake and are consistent with a time-dependent sympathetic reinnervation after heart transplantation. Restoration of neuronal uptake seems to be of functional importance, because it profoundly alters the inotropic effect of circulating endogenous catecholamines in long-term survivors after heart transplantation.

Pathogenetic mechanisms of cardiac allograft vasculopathy--impact of nitric oxide.

In the cytokine-enriched environment of the chronically rejecting allograft, nitric oxide (NO) is predominantly produced by the inducible isoform of NOS synthase (NOS2) expressed by recipient-derived infiltrating immune cells as well as donor-derived vascular smooth muscle cells and endothelial cells. Early and persistent upregulation of NOS2 in allografts with cardiac allograft vasculopathy and downregulation of NOS2 coinciding with immunosuppressive attenuation of cardiac allograft vasculopathy have suggested NO as a regulator of cardiac allograft vasculopathy, the hallmark of chronic rejection. Pathogenetically, the development of cardiac allograft vasculopathy can be divided into an early phase, characterized by endothelial dysfunction, and a later phase, characterized by structural changes of vessel wall morphology. Several lines of evidence have shown that NO might play an essential role in both phases. Endothelial dysfunction due to immune-mediated injury of endothelial cells has been suggested as an early response-to-injury event in the pathogenesis of cardiac allograft vasculopathy. Functional studies in human transplant recipients have documented endothelial dysfunction of coronary artery vessels. Administration of L-arginine, the precursor of NO, improved endothelial function of both epicardial coronary arteries and coronary microvasculature indicating a protective effect of NO. To assess the impact of NO on the development of late structural changes, the severity of cardiac allograft vasculopathy was assessed in mice with targeted deletion of NOS2. A significant increase of vascular occlusion in NOS2-knockout mice demonstrated an antiarteriosclerotic effect of NOS2. In part, this effect could be explained by reduced neointimal smooth muscle cell accumulation after alloimmune injury. Taken together, NO plays an important role in maintaining vessel integrity after transplantation. Disruptions in NO pathways seem to play a key role in the progression from endothelial dysfunction to structural changes.

Parasympathetic denervation supersensitivity of the transplanted human ventricle in vivo.

Sympathetic inotropic supersensitivity after transplantation-associated denervation of the cardiac autonomic nervous system has been described in humans previously. Potential changes of the parasympathetic regulation of the human ventricular contractility have not been investigated yet. We studied the antiadrenergic, negative inotropic effect of carbachol (3.6 micrograms/kg) during continuous beta-adrenergic stimulation (with isoproterenol, 20 ng.kg-1.min-1) in seven heart transplant recipients and seven healthy controls. Changes in ventricular contractility were calculated as increase of the systolic pressure-to-dimension ratio (delta P/D) and the rate-corrected velocity of circumferential fiber shortening (delta Vcfc), using M-mode echocardiography. In the control group, the isoproterenol-induced increase in contractility was attenuated only insignificantly by carbachol [delta P/D from 1.53 +/- 0.53 to 0.81 +/- 0.55 mmHg/mm, delta Vcfc from 0.77 +/- 0.20 to 0.63 +/- 0.22% x square root of beats/min (bpm)/ms]. In contrast, the transplant group exhibited a significant reduction of the isoproterenol-induced increase in contractility [delta P/D from 1.27 +/- 0.71 to -0.81 +/- 0.51 mmHg/mm (P < 0.01), delta Vcfc from 1.04 +/- 0.84 to 0.04 +/- 0.43% x square root of bpm/ms (P < 0.01)]. These data are consistent with parasympathetic indirect negative inotropic supersensitivity of the transplanted human heart in vivo.