X-ray polarization evidence for a 200-year-old flare of Sgr A. Nature 2023:10.1038/s41586-023-06064-x. [PMID: 37344593 DOI: 10.1038/s41586-023-06064-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

The centre of the Milky Way Galaxy hosts a black hole with a solar mass of about 4 million (Sagittarius A^* (Sgr A)) that is very quiescent at present with a luminosity many orders of magnitude below those of active galactic nuclei¹. Reflection of X-rays from Sgr A^* by dense gas in the Galactic Centre region offers a means to study its past flaring activity on timescales of hundreds and thousands of years². The shape of the X-ray continuum and the strong fluorescent iron line observed from giant molecular clouds in the vicinity of Sgr A^* are consistent with the reflection scenario^3-5. If this interpretation is correct, the reflected continuum emission should be polarized⁶. Here we report observations of polarized X-ray emission in the direction of the molecular clouds in the Galactic Centre using the Imaging X-ray Polarimetry Explorer. We measure a polarization degree of 31% ± 11%, and a polarization angle of -48° ± 11°. The polarization angle is consistent with Sgr A^* being the primary source of the emission, and the polarization degree implies that some 200 years ago, the X-ray luminosity of Sgr A^* was briefly comparable to that of a Seyfert galaxy.

Polarized x-rays from a magnetar

Magnetars are neutron stars with ultra-strong magnetic fields, which can be observed in x-rays. Polarization measurements could provide information on their magnetic fields and surface properties. We observe polarized x-rays from the magnetar 4U 0142+61 using the Imaging X-ray Polarimetry Explorer, finding a linear polarization degree of 13.5 ± 0.8% averaged over the 2 to 8 keV band. The polarization changes with energy: the degree is 15.0 ± 1.0% at 2 to 4 keV, drops below the instrumental sensitivity around 4 to 5 keV, and rises to 35.2 ± 7.1% at 5.5 to 8 keV. The polarization angle also changes by 90° around 4 to 5 keV. These results are consistent with a model in which thermal radiation from the magnetar surface is reprocessed by scattering off charged particles in the magnetosphere.

Polarized x-rays constrain the disk-jet geometry in the black hole x-ray binary Cygnus X-1

A black hole x-ray binary (XRB) system forms when gas is stripped from a normal star and accretes onto a black hole, which heats the gas sufficiently to emit x-rays. We report a polarimetric observation of the XRB Cygnus X-1 using the Imaging X-ray Polarimetry Explorer. The electric field position angle aligns with the outflowing jet, indicating that the jet is launched from the inner x-ray emitting region. The polarization degree is 4.01 ± 0.20% at 2 to 8 kiloelectronvolts, implying that the accretion disk is viewed closer to edge-on than the binary orbit. The observations reveal that hot x-ray emitting plasma is spatially extended in a plane perpendicular to the jet axis, not parallel to the jet.

Polarized blazar X-rays imply particle acceleration in shocks

Most of the light from blazars, active galactic nuclei with jets of magnetized plasma that point nearly along the line of sight, is produced by high-energy particles, up to around 1 TeV. Although the jets are known to be ultimately powered by a supermassive black hole, how the particles are accelerated to such high energies has been an unanswered question. The process must be related to the magnetic field, which can be probed by observations of the polarization of light from the jets. Measurements of the radio to optical polarization-the only range available until now-probe extended regions of the jet containing particles that left the acceleration site days to years earlier^1-3, and hence do not directly explore the acceleration mechanism, as could X-ray measurements. Here we report the detection of X-ray polarization from the blazar Markarian 501 (Mrk 501). We measure an X-ray linear polarization degree Π_X of around 10%, which is a factor of around 2 higher than the value at optical wavelengths, with a polarization angle parallel to the radio jet. This points to a shock front as the source of particle acceleration and also implies that the plasma becomes increasingly turbulent with distance from the shock.

Assessing an Automatic Procedure of Extraction of Physiological Parameters from Skin using Video Photoplethysmography

Video Photoplethysmography (vPPG) allows for estimation of blood volume pulse (BVP) from the skin by means of a video camera recording at high frequency rate. The estimation procedure presents several drawbacks in its application to real world conditions, such as light changes or movements that often generate artifacts in the extracted BVP waveform. In addition, the process requires a skin segmentation algorithm to distinguish skin pixels from the background. To date, even the most refined skin segmentation algorithms still need a manual definition that could lead to incorrect pixel classification, and consequently to a decrease in the signal-to-noise ratio (SNR). We here propose a fully autonomic procedure able to extract BVP from video recordings of the skin in real world conditions.The experimental protocol is designed to record the signals of interest and to evaluate changes in the Autonomic Nervous System modulation of the heart during a baseline condition and a controlled breathing phase. Video recordings are gathered from 4 young healthy subjects (age: 21±1 years). vPPG signals are processed in order to extract the BVP waveform, and a peak detection algorithm detects pulse wave peaks that are then used to compute specific measures of heart rate variability (HRV).The procedure is successfully validated by comparing the extracted HRV measures against those extracted using a finger photoplethysmograph (fPPG) using three different skin segmentation algorithms from BVP signals.

Identification and Tracking of Physiological Parameters from Skin using Video Photoplethysmography

In recent years, there has been a growing interest in video Photoplethysmography (vPPG), a technique able to estimate cardiovascular parameters from video recordings of the skin. Despite the growing interest in vPPG technology, there are still problems in extracting the correct waveform of blood volume pulse, mainly due to real world artifacts, such as changes in light condition and movement artifacts. Another important issue is the correct definition of skin against background. Therefore, we propose an algorithm of skin detection that is able to recognize skin pixels solid to variations of luminosity. We recorded the signals of interest during an experimental protocol designed to provide thermal stimulation and observe the resulting Autonomic Nervous System changes. Experimental data were gathered from 10 young healthy subjects (age: 21±2 years). Video recordings are processed using a band-pass filter and then an automatic algorithm of peak detection is applied to detect the pulse wave peaks, then used to estimate heart rate variability (HRV). The efficiency and stability of the algorithm are compared against finger-PPG waveforms. Preliminary results show an overall statistical agreement between time and frequency domain indexes. However, further efforts are required to improve the estimation of frequency components, particularly during rest.

Effects of 12 Weeks of Essential Amino Acids (EAA)-Based Multi-Ingredient Nutritional Supplementation on Muscle Mass, Muscle Strength, Muscle Power and Fatigue in Healthy Elderly Subjects: A Randomized Controlled Double-Blind Study

OBJECTIVE

To counteract muscle mass, muscle strength and power loss during aging, and to study age-related change of neuromuscular manifestation of fatigue in relation to nutritional supplementation.

DESIGN

randomized controlled double-blind study.

SETTING

Twice-daily consumption for 12 weeks of an Essential Amino Acids (EAA)-based multi-ingredient nutritional supplement containing EAA, creatine, vitamin D and Muscle Restore Complex®.

PARTICIPANTS

38 healthy elderly subjects (8 male, 30 female; age: 68.91±4.60 years; body weight: 69.40±15.58 kg; height: 1.60±0.09 m) were randomized and allocated in supplement (SUPP) or placebo (PLA) group. Mean Measurements: Vitamin D blood level; Appendicular Lean Mass (ALM); Visceral Adipose Tissue (VAT); Maximal Voluntary Contraction (MVC) and Peak Power (PP); myoelectric descriptors of fatigue: Fractal Dimension and Conduction Velocity initial values (FD iv, CV iv), their rates of change (FD slopes, CV slopes) and the Time to perform the Task (TtT). Mean Results: Significant changes were found in SUPP compared to baseline: Vitamin D (+8.73 ng/ml; p<0.001); ALM (+0.34 kg; p<0.001); VAT (-76.25 g; p<0.001); MVC (+0.52 kg; p<0.001); PP (+4.82 W; p<0.001). Between group analysis (SUPP Vs. PLA) showed improvements: vitamin D blood levels (+11,72 ng/ml; p<0.001); Legs FFM (+443.7 g; p<0.05); ALM (+0.53 kg; p<0.05); MVC (+1.38 kg; p<0.05); PP (+9.87 W; p<0.05). No statistical changes were found for FD iv, CV iv, FD and CV slopes and TtT, either compared to baseline or between groups. Significant correlations between mean differences in SUPP group were also found.

CONCLUSION

The study demonstrates that in healthy elderly subjects an EAA-based multi-ingredient nutritional supplementation of 12 weeks is not effective to change myoelectric manifestation of fatigue and TtT failure but can positively affect muscle mass, muscle strength, muscle power and VAT, counterbalancing more than one year of age-related loss of muscle mass and strength.

Unresolved Gamma-Ray Sky through its Angular Power Spectrum

The gamma-ray sky has been observed with unprecedented accuracy in the last decade by the Fermi -large area telescope (LAT), allowing us to resolve and understand the high-energy Universe. The nature of the remaining unresolved emission [unresolved gamma-ray background (UGRB)] below the LAT source detection threshold can be uncovered by characterizing the amplitude and angular scale of the UGRB fluctuation field. This Letter presents a measurement of the UGRB autocorrelation angular power spectrum based on eight years of Fermi-LAT Pass 8 data products. The analysis is designed to be robust against contamination from resolved sources and noise systematics. The sensitivity to subthreshold sources is greatly enhanced with respect to previous measurements. We find evidence (with ∼3.7σ significance) that the scenario in which two classes of sources contribute to the UGRB signal is favored over a single class. A double power law with exponential cutoff can explain the anisotropy energy spectrum well, with photon indices of the two populations being 2.55±0.23 and 1.86±0.15.

Multimessenger observations of a flaring blazar coincident with high-energy neutrino IceCube-170922A

Previous detections of individual astrophysical sources of neutrinos are limited to the Sun and the supernova 1987A, whereas the origins of the diffuse flux of high-energy cosmic neutrinos remain unidentified. On 22 September 2017, we detected a high-energy neutrino, IceCube-170922A, with an energy of ~290 tera–electron volts. Its arrival direction was consistent with the location of a known γ-ray blazar, TXS 0506+056, observed to be in a flaring state. An extensive multiwavelength campaign followed, ranging from radio frequencies to γ-rays. These observations characterize the variability and energetics of the blazar and include the detection of TXS 0506+056 in very-high-energy γ-rays. This observation of a neutrino in spatial coincidence with a γ-ray–emitting blazar during an active phase suggests that blazars may be a source of high-energy neutrinos.

Search for Cosmic-Ray Electron and Positron Anisotropies with Seven Years of Fermi Large Area Telescope Data

The Large Area Telescope on board the Fermi Gamma-ray Space Telescope has collected the largest ever sample of high-energy cosmic-ray electron and positron events since the beginning of its operation. Potential anisotropies in the arrival directions of cosmic-ray electrons or positrons could be a signature of the presence of nearby sources. We use almost seven years of data with energies above 42 GeV processed with the Pass 8 reconstruction. The present data sample can probe dipole anisotropies down to a level of 10^{-3}. We take into account systematic effects that could mimic true anisotropies at this level. We present a detailed study of the event selection optimization of the cosmic-ray electrons and positrons to be used for anisotropy searches. Since no significant anisotropies have been detected on any angular scale, we present upper limits on the dipole anisotropy. The present constraints are among the strongest to date probing the presence of nearby young and middle-aged sources.

Time-Resolved Measurement of Interatomic Coulombic Decay Induced by Two-Photon Double Excitation of Ne_{2}

The hitherto unexplored two-photon doubly excited states [Ne^{*}(2p^{-1}3s)]_{2} were experimentally identified using the seeded, fully coherent, intense extreme ultraviolet free-electron laser FERMI. These states undergo ultrafast interatomic Coulombic decay (ICD), which predominantly produces singly ionized dimers. In order to obtain the rate of ICD, the resulting yield of Ne_{2}^{+} ions was recorded as a function of delay between the extreme ultraviolet pump and UV probe laser pulses. The extracted lifetimes of the long-lived doubly excited states, 390(-130/+450)  fs, and of the short-lived ones, less than 150 fs, are in good agreement with ab initio quantum mechanical calculations.

Slow Interatomic Coulombic Decay of Multiply Excited Neon Clusters

Ne clusters (∼5000  atoms) were resonantly excited (2p→3s) by intense free electron laser (FEL) radiation at FERMI. Such multiply excited clusters can decay nonradiatively via energy exchange between at least two neighboring excited atoms. Benefiting from the precise tunability and narrow bandwidth of seeded FEL radiation, specific sites of the Ne clusters were probed. We found that the relaxation of cluster surface atoms proceeds via a sequence of interatomic or intermolecular Coulombic decay (ICD) processes while ICD of bulk atoms is additionally affected by the surrounding excited medium via inelastic electron scattering. For both cases, cluster excitations relax to atomic states prior to ICD, showing that this kind of ICD is rather slow (picosecond range). Controlling the average number of excitations per cluster via the FEL intensity allows a coarse tuning of the ICD rate.

Probe of Multielectron Dynamics in Xenon by Caustics in High-Order Harmonic Generation

We investigated the giant resonance in xenon by high-order harmonic generation spectroscopy driven by a two-color field. The addition of a nonperturbative second harmonic component parallel to the driving field breaks the symmetry between neighboring subcycles resulting in the appearance of spectral caustics at two distinct cutoff energies. By controlling the phase delay between the two color components it is possible to tailor the harmonic emission in order to amplify and isolate the spectral feature of interest. In this Letter we demonstrate how this control scheme can be used to investigate the role of electron correlations that give birth to the giant resonance in xenon. The collective excitations of the giant dipole resonance in xenon combined with the spectral manipulation associated with the two-color driving field allow us to see features that are normally not accessible and to obtain a good agreement between the experimental results and the theoretical predictions.

Search for Spectral Irregularities due to Photon-Axionlike-Particle Oscillations with the Fermi Large Area Telescope

We report on the search for spectral irregularities induced by oscillations between photons and axionlike-particles (ALPs) in the γ-ray spectrum of NGC 1275, the central galaxy of the Perseus cluster. Using 6 years of Fermi Large Area Telescope data, we find no evidence for ALPs and exclude couplings above 5×10^{-12}  GeV^{-1} for ALP masses 0.5≲m_{a}≲5  neV at 95% confidence. The limits are competitive with the sensitivity of planned laboratory experiments, and, together with other bounds, strongly constrain the possibility that ALPs can reduce the γ-ray opacity of the Universe.

Resolving the Extragalactic γ-Ray Background above 50 GeV with the Fermi Large Area Telescope

The Fermi Large Area Telescope (LAT) Collaboration has recently released a catalog of 360 sources detected above 50 GeV (2FHL). This catalog was obtained using 80 months of data re-processed with Pass 8, the newest event-level analysis, which significantly improves the acceptance and angular resolution of the instrument. Most of the 2FHL sources at high Galactic latitude are blazars. Using detailed Monte Carlo simulations, we measure, for the first time, the source count distribution, dN/dS, of extragalactic γ-ray sources at E>50  GeV and find that it is compatible with a Euclidean distribution down to the lowest measured source flux in the 2FHL (∼8×10^{-12}  ph cm^{-2} s^{-1}). We employ a one-point photon fluctuation analysis to constrain the behavior of dN/dS below the source detection threshold. Overall, the source count distribution is constrained over three decades in flux and found compatible with a broken power law with a break flux, S_{b}, in the range [8×10^{-12},1.5×10^{-11}]  ph cm^{-2} s^{-1} and power-law indices below and above the break of α_{2}∈[1.60,1.75] and α_{1}=2.49±0.12, respectively. Integration of dN/dS shows that point sources account for at least 86_{-14}^{+16}% of the total extragalactic γ-ray background. The simple form of the derived source count distribution is consistent with a single population (i.e., blazars) dominating the source counts to the minimum flux explored by this analysis. We estimate the density of sources detectable in blind surveys that will be performed in the coming years by the Cherenkov Telescope Array.

FERMI-LAT OBSERVATIONS OF HIGH- AND INTERMEDIATE-VELOCITY CLOUDS: TRACING COSMIC RAYS IN THE HALO OF THE MILKY WAY

It is widely accepted that cosmic rays (CRs) up to at least PeV energies are Galactic in origin. Accelerated particles are injected into the interstellar medium where they propagate to the farthest reaches of the Milky Way, including a surrounding halo. The composition of CRs coming to the solar system can be measured directly and has been used to infer the details of CR propagation that are extrapolated to the whole Galaxy. In contrast, indirect methods, such as observations of γ-ray emission from CR interactions with interstellar gas, have been employed to directly probe the CR densities in distant locations throughout the Galactic plane. In this article we use 73 months of data from the Fermi Large Area Telescope in the energy range between 300 MeV and 10 GeV to search for γ-ray emission produced by CR interactions in several high- and intermediate-velocity clouds (IVCs) located at up to ~7 kpc above the Galactic plane. We achieve the first detection of IVCs in γ rays and set upper limits on the emission from the remaining targets, thereby tracing the distribution of CR nuclei in the halo for the first time. We find that the γ-ray emissivity per H atom decreases with increasing distance from the plane at 97.5% confidence level. This corroborates the notion that CRs at the relevant energies originate in the Galactic disk. The emissivity of the upper intermediate-velocity Arch hints at a 50% decline of CR densities within 2 kpc from the plane. We compare our results to predictions of CR propagation models.

Non-collinear high-order harmonic generation by three interfering laser beams

High order harmonic generation (HHG) has shown its impact on several applications in Attosecond Science and Atomic and Molecular Physics. Owing to the complexity of the experimental setup for the generation and characterization of harmonics, as well as to the large computational costs of numerical modelling, HHG is generally performed and modelled in collinear geometry. Recently, several experiments have been performed exploiting non-collinear geometry, such as HHG in a grating of excited molecules created by crossing beams. In such studies, harmonics were observed at propagation directions different from those of the driving pulses; moreover the scattered harmonics were angularly dispersed.In this work we report on a new regime of HHG driven by multiple beams, where the harmonics are generated by three synchronized, intense laser pulses organized in a non-planar geometry. Although the configuration we explore is well within the strong-field regime, the scattered harmonics we observe are not angularly dispersed.

High-order harmonic spectroscopy for molecular imaging of polyatomic molecules

High-order harmonic generation is a powerful and sensitive tool for probing atomic and molecular structures, combining in the same measurement an unprecedented attosecond temporal resolution with a high spatial resolution of the order of an angstrom. Imaging of the outermost molecular orbital by high-order harmonic generation has been limited for a long time to very simple molecules, like nitrogen. Recently we demonstrated a technique that overcame several of the issues that have prevented the extension of molecular orbital tomography to more complex species, showing that molecular imaging can be applied to a triatomic molecule like carbon dioxide. Here we report on the application of such a technique to nitrous oxide (N₂O) and acetylene (C₂H₂). This result represents a first step towards the imaging of fragile compounds, a category which includes most of the fundamental biological molecules.

[Growth hormone deficiency associated with 22q11.2 deletion: a case report]

The 22q11.2 microdeletion produces many syndromes, characterized by similar phenotypical features. The most known syndromes are: the DiGeorge syndrome, the velocardiofacial syndrome, the conotruncal anomaly face syndrome. The hallmark features are represented by cardiac anomalies, palate defects, immune and cognitive deficiencies, facial dysmorphisms. Less common disorders include: genito-urinary abnormalities, visual defects, autoimmune disorders and pituitary anomalies, being the last represented by growth hormone and/or insulin growth factor-I deficiency. We present the case of a 8 years old male admitted to our Division for failure to thrive. We found growth hormone deficiency and pituitary hypoplasia associated with some of the anomalies shown above, thus we suspected and confirmed the 22q11.2 deletion syndrome. In literature few cases of associated 22q11.2 deletion syndrome with growth hormone deficiency are described, while short stature between children with and children without cleft palate is reported to be more frequent in the first ones, suggesting that the 22q11.2 deletion syndrome remains undetected in many affected children and that the growth hormone deficiency prevalence in affected children has to be investigated. The wide phenotypical presentation of 22q11.2 deletion syndrome requires a multidisciplinary approach to the affected subject and, from the auxologic point of view, is good to monitoring the growing trend and, if short stature is present, check for the growth hormone deficiency.

[Early diagnosis of Fabry disease in children]

Fabry disease, a rare X-linked lysosomal storage disorder, is caused by deficiency of the enzyme α-galactosidase A. The incidence, ranging from one over 40 000 to one over 11 7000 worldwide is probably underestimated due to its unspecific pattern of presentation. The symptoms, including neurological, gastrointestinal, renal, ophthalmological and dermatologic manifestations, start in childhood and adolescence, cause a significant morbidity and are likely to affect the patient's quality of life. Furthermore, Anderson-Fabry disease always progress leading to a multiorgan dysfunction and life-threatening complications with end-stage renal disease, cardiomyopathy and high incidence of stroke. The estimated life in untreated patients is reduced by 15-20 years respectively in men and women. The enzyme replacement therapy, available in Europe from 2001, results in a reduction of major organs failure, morbidity and mortality. We present the case of an 8-year-old male admitted to our Division for overweight with a previous history of acroparesthesias, severe acute pain in hands and feet, abdominal pain, diarrhoea, constipation, bitemporal headache, dyshidrosis, recurrent fever, exercise intolerance and reduced quality of life. The physical examination was within normal limits. The α-galactosidase A activity was deficient in plasma and normal in peripheral leukocytes; the GLA gene showed a nucleotide substitution c.352C>T (p.Arg 118 Cys) in the eson 2 with a residual enzyme activity of the 29% suggesting the diagnosis of Fabry disease. Blood and urine chemistry, the slit-lamp examination and MRI of kidneys, heart and brain excluded any major organ involvement. The enzyme replacement therapy was then started almost three months ago using agasidase alfa at a dose of 0.2 mg/kg infused intravenously every two weeks but, unfortunately, no relief in the symptoms have been reported so far without any severe adverse reactions. This case report aims to point out the importance of an early diagnosis in order to prevent the progression of the disease, the multiorgan failure and to improve the long-term prognosis.

[Neurofibromatosis type 1 and hypertension in pediatrics: case report]

Neurofibromatosis type 1 (NF1) is an autosomal dominant disorder characterized by cafe-au-lait spots, axillary and inguinal freckling, cutaneous neurofibromas with a variable clinical expression, iris Lisch nodules, and multiple tumors, in particular optic nerve and other central nervous system gliomas. About 6% of patients develop hypertension due to renovascular diseases, mid-aortic syndrome, or pheochromocytoma. We present a case of a 8 year old girl with primary diagnosis of NF1suffering of skin and encefalic neurofibromas, inguinal freckling, café-au-lait spots, optic nerve glioma, headache, facial flushing. The 24-h ambulatory blood pressure revealed hypertension without paroximal attacks. Urinary metanephrines, serum aldosteron, renin and kalemia were constantly normal. Magnetic resonance imaging (MRI) and angioMRI excluded stenoses of the renal arteries or adrenal masses. Standard 2D echocardiography was normal. The antihypertensive medication controlled pressure values. We concluded for hypertension due to a low-grade vasculopathy. The periodic monitoring of blood pressure in NF1 patients, accompanied by appropriate diagnostic modalities and physical examination, is essential to precociously diagnose hypertension and avoid life-threatening organ damages and increased mortality.

Investigation on a focus of human trichinellosis revealed by an atypical clinical case: after wild-boar (Sus scrofa) pork consumption in northern Italy

Trichinellosis is one of the most serious foodborne parasitic zoonoses in Europe. Wild carnivorous and omnivorous hosts are the main reservoirs of Trichinella spp. nematodes in nature. In the winter of 2008-2009, an atypical clinical case of trichinellosis occurred for the consumption of pork from a wild boar (Sus scrofa) hunted in southwestern Alps in Italy. The symptomatic individual showed delayed development of oedemas in the lower limbs and eosinophilia, which appeared three months after infection. Muscle samples harboured 3.8 larvae/g, which were identified as Trichinella britovi. During the epidemiological investigation, anti-Trichinella IgG were detected in five hunters.

Polarization pulse shaping induced by impulsive molecular alignment in optical filamentation and application to high-order harmonic generation

We investigated theoretically and experimentally the ultrafast birefringence induced by impulsive alignment in a molecular gas during optical filamentation. This phenomenon is able to substantially affect the polarization state of an ultrashort laser pulse that propagates through the aligned medium at suitable delays from a first aligning pulse. We exploited this modulation of the polarization state in order to effectively control the high-order harmonic generation (HHG) process, which is strongly dependent on the driving pulse polarization. These results open new and fascinating perspectives for the tailoring of strong-field phenomena by means of polarization pulse shaping.

Efficient continuum generation exceeding 200 eV by intense ultrashort two-color driver

A temporal gating on the high-order harmonic emission process is achieved using an intense 20 fs, 1.45 microm pulse (IR) in combination with an intense 13 fs, 800 nm pulse [visible (VIS)]. Exploiting this two-color gating scheme, a coherent continuous emission extending up to 160 eV using Ar gas and 200 eV using Ne gas is efficiently generated. The IR pulse contributes to significantly extending the harmonic emission to higher photon energies, whereas the VIS pulse improves the conversion efficiency of the process. These results indicate the possibility to produce bright attosecond pulses approaching the soft X spectral region.

Branched-chain amino acid supplementation does not enhance athletic performance but affects muscle recovery and the immune system

Since the 1980's there has been high interest in branched-chain amino acids (BCAA) by sports nutrition scientists. The metabolism of BCAA is involved in some specific biochemical muscle processes and many studies have been carried out to understand whether sports performance can be enhanced by a BCAA supplementation. However, many of these researches have failed to confirm this hypothesis. Thus, in recent years investigators have changed their research target and focused on the effects of BCAA on the muscle protein matrix and the immune system. Data show that BCAA supplementation before and after exercise has beneficial effects for decreasing exercise-induced muscle damage and promoting muscle-protein synthesis. Muscle damage develops delayed onset muscle soreness: a syndrome that occurs 24-48 h after intensive physical activity that can inhibit athletic performance. Other recent works indicate that BCAA supplementation recovers peripheral blood mononuclear cell proliferation in response to mitogens after a long distance intense exercise, as well as plasma glutamine concentration. The BCAA also modifies the pattern of exercise-related cytokine production, leading to a diversion of the lymphocyte immune response towards a Th1 type. According to these findings, it is possible to consider the BCAA as a useful supplement for muscle recovery and immune regulation for sports events.

Evaluation of an enzyme immunoassay for the detection of central nervous system tissue contamination at the slaughterhouse

To protect public health from bovine spongiform encephalopathy, European Commission Regulation EC 1139/2003 on monitoring programs and specified risk material requires that as of 1 October 2003, each member state has in place a sampling plan with an appropriate laboratory test to detect central nervous system (CNS) tissue in bovine head meat harvested at slaughterhouses or cutting plants. With this study, we wanted to evaluate the accuracy and reliability of an enzyme immunoassay, the RIDASCREEN Risk Material 10/5, in targeting a CNS-specific marker, the glial fibrillary acidic protein. A receiver operating characteristics curve was plotted to identify the best cutoff of CNS concentration. Reliability was calculated by Cohen's kappa on data from two diagnostic sessions. Test performance showed high sensitivity and specificity (97.9 and 97.4%, respectively) for a cutoff value between positive and negative at a CNS concentration of 0.049%; reliability of test precision was also very good. When these criteria are applied, the RIDASCREEN Risk Material 10/5 test appears to be a reliable tool for monitoring CNS tissue contamination in meat. This diagnostic procedure should therefore be recommended for national application in monitoring programs.

Autoradiographical study of types 1 and 2 of benzodiazepine receptors in rat brain after chronic ethanol treatment and its withdrawal

The effect of chronic ethanol treatment, and its withdrawal on benzodiazepine binding sites in rat brain is described in this autoradiographical study using the benzodiazepine agonist [3H]flunitrazepam. Several areas of the rat cerebral cortex, hippocampus, mesencephalon, cerebellum and lateral geniculate nucleus were studied in animals, chronically treated with ethanol, and 24 or 48 hr after ethanol withdrawal. The [3H]flunitrazepam binding and the relative percentages of binding to BZ1 and BZ2 sites, using zolpidem as a BZ1 site inhibitor, are described. The cerebellum and red nucleus, which only express BZ1 binding sites, appear to be areas significantly modified by ethanol and its withdrawal. In no other structure did ethanol modify [3H]flunitrazepam binding nor change the relative percentage of BZ1 and BZ2 sites.

Effect of ethanol treatment on rate and equilibrium constants for [3H] muscimol binding to rat brain membranes: alteration of two affinity states of the GABAA receptor

Equilibrium binding curves were biphasic in control and ethanol-treated rats. [3H]Muscimol binds to sites of high (KDA of approximately 10 nM) and low (KDB of approximately 0.3-0.4 microM) affinity. Chronic ethanol treatment produced a decrease in BmaxA value, and the hyperbolic binding profiles were progressively affected by the chronic and in vitro ethanol treatments, with most of this effect corresponding to the high-affinity site. IC50 and Ki values were calculated for several competing ligands, using membranes from both control and ethanol-treated animals. The association and dissociation curves were also biphasic, using a radioligand concentration precluding a significant occupancy of the low-affinity sites, which suggests the existence of two forms or affinity states of the monoliganded receptor. Chronic ethanol treatment did not produce changes in the values of the dissociation rate constants (fast and slow phases). By contrast, we report for the first time a decrease in the values of the association rate constants, with this decrease being higher for the slow phase. Consequently, the dissociation equilibrium constants are two times higher in chronically ethanol-treated animals for both phases.

Differential effect of chronic ethanol treatment on barbiturate and steroid modulation of muscimol-binding to rat brain cortex

We report the differential alterations produced by chronic ethanol treatment on the modulation, by the barbiturate thiopental and the steroid 5 beta-pregnan-3 alpha-ol-20-one, of the binding of [3H]muscimol to membrane preparations from rat brain cortex. We found a clear barbiturate- and steroid-promoted enhancement of muscimol-binding to membranes in both control and ethanol-treated animals. However, the enhancements were higher in control animals, using the barbiturate, and in ethanol-treated rats, using the steroid, Bmax and Kd values were also differentially affected in control and ethanol-treated animals by the presence of the barbiturate or the steroid.

Effect of chronic ethanol treatment on the gamma-aminobutyric acid-mediated enhancement of [3H]flunitrazepam binding in rat cortex and hippocampus

The mechanism by which ethanol affects the gamma-aminobutyric acid (GABA)/benzodiazepine complex is not clear. It is known that ethanol enhances the Cl- influx mediated by the GABAA receptor complex, and although chronic ethanol administration does not change the KD or Bmax for [3H]flunitrazepam binding, some reports have suggested that it could modify the modulation of benzodiazepine binding produced by GABA. In the present work, we studied the effect of chronic ethanol treatment on the modulation by GABA of [3H]flunitrazepam binding, using light microscopic autoradiography. This technique allows the measurement of densities of benzodiazepine receptors in different brain areas, the visual cortex and hippocampus, which appear to constitute the anatomical support for the behavioral and physiological responses affected by ethanol. We found enhancement of benzodiazepine binding by GABA at concentrations of greater than 10(-6) M for the various cortical and hippocampal areas studied from both control and ethanol-treated animals; this enhancement peaked at 10(-4) M GABA but decreased at 10(-3) M GABA. We found a clear effect of ethanol treatment on the modulatory properties of GABAA receptor, in both cortex and hippocampus, although only in cortex were the differences statistically significant between control and ethanol-treated animals.

Autoradiographic study on [3H]flunitrazepam binding in rat cortex and hippocampus after chronic ethanol treatment

Ethanol alters almost all membrane functions, but it behaves essentially like a benzodiazepine-type GABAergic agonist. The mechanism by which ethanol affects the GABA/benzodiazepine complex is not clear. We studied the possible changes in [3H]flunitrazepam binding induced by chronic ethanol treatment, using light microscopic autoradiography, to try to elucidate the controversy underlying this topic. This technique allows us to measure densities of benzodiazepine receptors in different anatomical brain areas--visual cortex and hippocampus--which seem to constitute the anatomical support for the behavioral and physiological responses affected by ethanol. Autoradiographic studies on the visual cortex and hippocampus from rats chronically treated with ethanol do not show statistically significant differences in the binding of [3H]flunitrazepam with respect to control animals. Furthermore, we did not find either rostro-caudal or medio-lateral differences in benzodiazepine receptor densities in each layer of the visual cortex.

Glycoconjugate expression in normal hepatoid glands and hepatoid gland adenomas and carcinomas in dogs

Although neoplastic changes in canine hepatoid perianal glands (HPG) are quite common, the biological behaviour is sometimes difficult to assess on the basis of the histopathological examination. In an attempt to detect differences in the glycoconjugate expression between normal and neoplastic HPG, and to verify their relation to the degree of neoplastic progression, normal and neoplastic HPG were studied in 13 dogs, using 11 biotinylated lectins. In HPG adenomas the majority of the cells did not stain or stained weakly after incubation with pokeweed mitogen, LCA and UEA-I. In HPG carcinoma the basal cells lost the specific binding for WGA while heterogeneous distribution of conconavalin-A staining was observed.