Demonstrating Agreement between Radio and Fluorescence Measurements of the Depth of Maximum of Extensive Air Showers at the Pierre Auger Observatory

We show, for the first time, radio measurements of the depth of shower maximum (X_{max}) of air showers induced by cosmic rays that are compared to measurements of the established fluorescence method at the same location. Using measurements at the Pierre Auger Observatory we show full compatibility between our radio and the previously published fluorescence dataset, and between a subset of air showers observed simultaneously with both radio and fluorescence techniques, a measurement setup unique to the Pierre Auger Observatory. Furthermore, we show radio X_{max} resolution as a function of energy and demonstrate the ability to make competitive high-resolution X_{max} measurements with even a sparse radio array. With this, we show that the radio technique is capable of cosmic-ray mass composition studies, both at Auger and at other experiments.

Observation of high-energy neutrinos from the Galactic plane

The origin of high-energy cosmic rays, atomic nuclei that continuously impact Earth's atmosphere, is unknown. Because of deflection by interstellar magnetic fields, cosmic rays produced within the Milky Way arrive at Earth from random directions. However, cosmic rays interact with matter near their sources and during propagation, which produces high-energy neutrinos. We searched for neutrino emission using machine learning techniques applied to 10 years of data from the IceCube Neutrino Observatory. By comparing diffuse emission models to a background-only hypothesis, we identified neutrino emission from the Galactic plane at the 4.5σ level of significance. The signal is consistent with diffuse emission of neutrinos from the Milky Way but could also arise from a population of unresolved point sources.

Limits to Gauge Coupling in the Dark Sector Set by the Nonobservation of Instanton-Induced Decay of Super-Heavy Dark Matter in the Pierre Auger Observatory Data

Instantons, which are nonperturbative solutions to Yang-Mills equations, provide a signal for the occurrence of quantum tunneling between distinct classes of vacua. They can give rise to decays of particles otherwise forbidden. Using data collected at the Pierre Auger Observatory, we search for signatures of such instanton-induced processes that would be suggestive of super-heavy particles decaying in the Galactic halo. These particles could have been produced during the post-inflationary epoch and match the relic abundance of dark matter inferred today. The nonobservation of the signatures searched for allows us to derive a bound on the reduced coupling constant of gauge interactions in the dark sector: α_{X}≲0.09, for 10^{9}≲M_{X}/GeV<10^{19}. Conversely, we obtain that, for instance, a reduced coupling constant α_{X}=0.09 excludes masses M_{X}≳3×10^{13}  GeV. In the context of dark matter production from gravitational interactions alone, we illustrate how these bounds are complementary to those obtained on the Hubble rate at the end of inflation from the nonobservation of tensor modes in the cosmological microwave background.

Evidence for neutrino emission from the nearby active galaxy NGC 1068

A supermassive black hole, obscured by cosmic dust, powers the nearby active galaxy NGC 1068. Neutrinos, which rarely interact with matter, could provide information on the galaxy’s active core. We searched for neutrino emission from astrophysical objects using data recorded with the IceCube neutrino detector between 2011 and 2020. The positions of 110 known gamma-ray sources were individually searched for neutrino detections above atmospheric and cosmic backgrounds. We found that NGC 1068 has an excess of 79 − 20 + 22 neutrinos at tera–electron volt energies, with a global significance of 4.2σ, which we interpret as associated with the active galaxy. The flux of high-energy neutrinos that we measured from NGC 1068 is more than an order of magnitude higher than the upper limit on emissions of tera–electron volt gamma rays from this source.

Search for Unstable Sterile Neutrinos with the IceCube Neutrino Observatory

We present a search for an unstable sterile neutrino by looking for a resonant signal in eight years of atmospheric ν_{μ} data collected from 2011 to 2019 at the IceCube Neutrino Observatory. Both the (stable) three-neutrino and the 3+1 sterile neutrino models are disfavored relative to the unstable sterile neutrino model, though with p values of 2.8% and 0.81%, respectively, we do not observe evidence for 3+1 neutrinos with neutrino decay. The best-fit parameters for the sterile neutrino with decay model from this study are Δm_{41}^{2}=6.7_{-2.5}^{+3.9}  eV^{2}, sin^{2}2θ_{24}=0.33_{-0.17}^{+0.20}, and g^{2}=2.5π±1.5π, where g is the decay-mediating coupling. The preferred regions of the 3+1+decay model from short-baseline oscillation searches are excluded at 90% C.L.

Strong Constraints on Neutrino Nonstandard Interactions from TeV-Scale ν_{μ} Disappearance at IceCube

We report a search for nonstandard neutrino interactions (NSI) using eight years of TeV-scale atmospheric muon neutrino data from the IceCube Neutrino Observatory. By reconstructing incident energies and zenith angles for atmospheric neutrino events, this analysis presents unified confidence intervals for the NSI parameter ε_{μτ}. The best-fit value is consistent with no NSI at a p value of 25.2%. With a 90% confidence interval of -0.0041≤ε_{μτ}≤0.0031 along the real axis and similar strength in the complex plane, this result is the strongest constraint on any NSI parameter from any oscillation channel to date.

Search for Relativistic Magnetic Monopoles with Eight Years of IceCube Data

We present an all-sky 90% confidence level upper limit on the cosmic flux of relativistic magnetic monopoles using 2886 days of IceCube data. The analysis was optimized for monopole speeds between 0.750c and 0.995c, without any explicit restriction on the monopole mass. We constrain the flux of relativistic cosmic magnetic monopoles to a level below 2.0×10^{-19}  cm^{-2} s^{-1} sr^{-1} over the majority of the targeted speed range. This result constitutes the most strict upper limit to date for magnetic monopoles with β≳0.8 and up to β∼0.995 and fills the gap between existing limits on the cosmic flux of nonrelativistic and ultrarelativistic magnetic monopoles.

Measurement of the Fluctuations in the Number of Muons in Extensive Air Showers with the Pierre Auger Observatory

We present the first measurement of the fluctuations in the number of muons in extensive air showers produced by ultrahigh energy cosmic rays. We find that the measured fluctuations are in good agreement with predictions from air shower simulations. This observation provides new insights into the origin of the previously reported deficit of muons in air shower simulations and constrains models of hadronic interactions at ultrahigh energies. Our measurement is compatible with the muon deficit originating from small deviations in the predictions from hadronic interaction models of particle production that accumulate as the showers develop.

eV-Scale Sterile Neutrino Search Using Eight Years of Atmospheric Muon Neutrino Data from the IceCube Neutrino Observatory

The results of a 3+1 sterile neutrino search using eight years of data from the IceCube Neutrino Observatory are presented. A total of 305 735 muon neutrino events are analyzed in reconstructed energy-zenith space to test for signatures of a matter-enhanced oscillation that would occur given a sterile neutrino state with a mass-squared differences between 0.01 and 100  eV^{2}. The best-fit point is found to be at sin^{2}(2θ_{24})=0.10 and Δm_{41}^{2}=4.5  eV^{2}, which is consistent with the no sterile neutrino hypothesis with a p value of 8.0%.

Characteristics of the Diffuse Astrophysical Electron and Tau Neutrino Flux with Six Years of IceCube High Energy Cascade Data

We report on the first measurement of the astrophysical neutrino flux using particle showers (cascades) in IceCube data from 2010-2015. Assuming standard oscillations, the astrophysical neutrinos in this dedicated cascade sample are dominated (∼90%) by electron and tau flavors. The flux, observed in the sensitive energy range from 16 TeV to 2.6 PeV, is consistent with a single power-law model as expected from Fermi-type acceleration of high energy particles at astrophysical sources. We find the flux spectral index to be γ=2.53±0.07 and a flux normalization for each neutrino flavor of ϕ_{astro}=1.66_{-0.27}^{+0.25} at E_{0}=100  TeV, in agreement with IceCube's complementary muon neutrino results and with all-neutrino flavor fit results. In the measured energy range we reject spectral indices γ≤2.28 at ≥3σ significance level. Because of high neutrino energy resolution and low atmospheric neutrino backgrounds, this analysis provides the most detailed characterization of the neutrino flux at energies below ∼100  TeV compared to previous IceCube results. Results from fits assuming more complex neutrino flux models suggest a flux softening at high energies and a flux hardening at low energies (p value ≥0.06). The sizable and smooth flux measured below ∼100  TeV remains a puzzle. In order to not violate the isotropic diffuse gamma-ray background as measured by the Fermi Large Area Telescope, it suggests the existence of astrophysical neutrino sources characterized by dense environments which are opaque to gamma rays.

Features of the Energy Spectrum of Cosmic Rays above 2.5×10^{18} eV Using the Pierre Auger Observatory

We report a measurement of the energy spectrum of cosmic rays above 2.5×10^{18}  eV based on 215 030 events. New results are presented: at about 1.3×10^{19}  eV, the spectral index changes from 2.51±0.03(stat)±0.05(syst) to 3.05±0.05(stat)±0.10(syst), evolving to 5.1±0.3(stat)±0.1(syst) beyond 5×10^{19}  eV, while no significant dependence of spectral features on the declination is seen in the accessible range. These features of the spectrum can be reproduced in models with energy-dependent mass composition. The energy density in cosmic rays above 5×10^{18}  eV is [5.66±0.03(stat)±1.40(syst)]×10^{53}  erg Mpc^{-3}.

Time-Integrated Neutrino Source Searches with 10 Years of IceCube Data

This Letter presents the results from pointlike neutrino source searches using ten years of IceCube data collected between April 6, 2008 and July 10, 2018. We evaluate the significance of an astrophysical signal from a pointlike source looking for an excess of clustered neutrino events with energies typically above ∼1  TeV among the background of atmospheric muons and neutrinos. We perform a full-sky scan, a search within a selected source catalog, a catalog population study, and three stacked Galactic catalog searches. The most significant point in the northern hemisphere from scanning the sky is coincident with the Seyfert II galaxy NGC 1068, which was included in the source catalog search. The excess at the coordinates of NGC 1068 is inconsistent with background expectations at the level of 2.9σ after accounting for statistical trials from the entire catalog. The combination of this result along with excesses observed at the coordinates of three other sources, including TXS 0506+056, suggests that, collectively, correlations with sources in the northern catalog are inconsistent with background at 3.3σ significance. The southern catalog is consistent with background. These results, all based on searches for a cumulative neutrino signal integrated over the 10 years of available data, motivate further study of these and similar sources, including time-dependent analyses, multimessenger correlations, and the possibility of stronger evidence with coming upgrades to the detector.

Recent results from the KASCADE-Grande data analysis

KASCADE, together with its extension KASCADE-Grande measured individual air showers of cosmic rays in the primary energy range of 100 TeV to 1 EeV. The data collection was fully completed at the end of 2013 and the experiment was dismantled. However, the data analysis is still in progress. Recently, we published a new result on upper limits to the flux of ultra-high energy gamma rays, which set constraints on some fundamental astrophysical models. We also use the data to investigate the validity of the new hadronic interactions models like SIBYLL version 2.3c or EPOS-LHC. In addition, we updated and improved the webbased platform of the KASCADE Cosmic Ray Data Centre (KCDC), where now the data from KASCADE and KASCADE-Grande of more than 20 years measurements is available, including corresponding Monte-Carlo simulated events based on three different hadronic interaction models. In this contribution, recent results from KASCADE-Grande and the update of KCDC is briefly discussed.

Study of themuon content of high-energy air showers with KASCADE-Grande

In this work, we report measurements on the muon content (Eth > 230 MeV) of extensive air showers (EAS) induced by cosmic rays with primary energy from 10 PeV up to 1 EeV performed with the KASCADE-Grande experiment. The measurements are confronted with SIBYLL 2.3. The results are focused on the dependence of the total muon number and the lateral density distribution of muons in EAS on the zenith angle and the total number of charged particles in the shower. We also present updated results of a detailed study of the attenuation length of shower muons, which reveal a deviation between the measured data and the predictions of the post-LHC hadronic interaction models SIBYLL 2.3, QGSJET-II-04 and EPOS-LHC.

Summary of the main results of the KASCADE and KASCADE-Grande experiments

The KASCADE and KASCADE-Grande experiments operated in KIT-Campus North, Karlsruhe (Germany) from 1993 to 2012. The two experiments studied primary cosmic rays in the energy range from 1014 eV to 1018 eV, investigating the change of slope of the spectrum detected at 2 - 4 × 1015 eV, the so called knee. We briefly review the performance of the experiments and then the main results obtained in the operation of both experiments: the test of hadronic interaction models, the all particle primary spectrum, the elemental composition of primary cosmic rays (with the first claim of a knee-like feature of the heavy primaries spectrum) and the search for large scale anisotropies.

Tests of the SIBYLL 2.3 high-energy hadronic interaction model using the KASCADE-Grande muon data

The KASCADE-Grande observatory was a ground-based air shower array dedicated to study the energy and composition of cosmic rays in the energy interval E = 1 PeV –1 EeV. The experiment consisted of different detector systems which allowed the simultaneous measurement of distinct components of air showers (EAS), such as the muon content. In this contribution, we study the total muon number and the lateral density distribution of muons in EAS detected by KASCADE-Grande as a function of the zenith angle and the total number of charged particles. The attenuation length of the muon content of EAS is also measured. The results are compared with the predictions of the SIBYLL 2.3 high-energy hadronic interaction model.

Testing Hadronic Interactions at Ultrahigh Energies with Air Showers Measured by the Pierre Auger Observatory

Ultrahigh energy cosmic ray air showers probe particle physics at energies beyond the reach of accelerators. Here we introduce a new method to test hadronic interaction models without relying on the absolute energy calibration, and apply it to events with primary energy 6-16 EeV (E_{CM}=110-170  TeV), whose longitudinal development and lateral distribution were simultaneously measured by the Pierre Auger Observatory. The average hadronic shower is 1.33±0.16 (1.61±0.21) times larger than predicted using the leading LHC-tuned models EPOS-LHC (QGSJetII-04), with a corresponding excess of muons.

Measurement of the Radiation Energy in the Radio Signal of Extensive Air Showers as a Universal Estimator of Cosmic-Ray Energy

We measure the energy emitted by extensive air showers in the form of radio emission in the frequency range from 30 to 80 MHz. Exploiting the accurate energy scale of the Pierre Auger Observatory, we obtain a radiation energy of 15.8±0.7(stat)±6.7(syst)  MeV for cosmic rays with an energy of 1 EeV arriving perpendicularly to a geomagnetic field of 0.24 G, scaling quadratically with the cosmic-ray energy. A comparison with predictions from state-of-the-art first-principles calculations shows agreement with our measurement. The radiation energy provides direct access to the calorimetric energy in the electromagnetic cascade of extensive air showers. Comparison with our result thus allows the direct calibration of any cosmic-ray radio detector against the well-established energy scale of the Pierre Auger Observatory.

Search for patterns by combining cosmic-ray energy and arrival directions at the Pierre Auger Observatory

Energy-dependent patterns in the arrival directions of cosmic rays are searched for using data of the Pierre Auger Observatory. We investigate local regions around the highest-energy cosmic rays with [Formula: see text] eV by analyzing cosmic rays with energies above [Formula: see text] eV arriving within an angular separation of approximately 15[Formula: see text]. We characterize the energy distributions inside these regions by two independent methods, one searching for angular dependence of energy-energy correlations and one searching for collimation of energy along the local system of principal axes of the energy distribution. No significant patterns are found with this analysis. The comparison of these measurements with astrophysical scenarios can therefore be used to obtain constraints on related model parameters such as strength of cosmic-ray deflection and density of point sources.

First Experimental Characterization of Microwave Emission from Cosmic Ray Air Showers

We report the first direct measurement of the overall characteristics of microwave radio emission from extensive air showers. Using a trigger provided by the KASCADE-Grande air shower array, the signals of the microwave antennas of the Cosmic-Ray Observation via Microwave Emission experiment have been read out and searched for signatures of radio emission by high-energy air showers in the GHz frequency range. Microwave signals have been detected for more than 30 showers with energies above 3×10^{16}  eV. The observations presented in this Letter are consistent with a mainly forward-directed and polarized emission process in the GHz frequency range. The measurements show that microwave radiation offers a new means of studying air showers at E≥10^{17}  eV.

[The White man's burden - a case study caught between bipolar affective disorder and Huntington's disease]

We report upon a case of a 55 year old patient with a bipolar affective disorder, presenting herself with a depressive symptomatology in addition to a severe motor perturbation. The main emphasis upon admittance was perfecting and improving her latest medication. Four weeks prior to her stay at our clinic a thorough neurological examination had taken place in terms of an invalidity pension trial which did not result in any diagnostic findings. Therefore a neurological disease seemed at first highly unlikely. Even though the prior testing was negative, the ensuing neurological examination at our clinic resulted in movement disorders very much indicative of Huntington's Disease. A detailed investigation in regards to the particular family history of the patient was positive for Huntington's Disease. However, whether the patient's mother had also been a genetic carrier of Huntington's Disease was still unknown at the time the patient was admitted to our clinic. It was nevertheless discovered that her mother had also suffered from a bipolar affective disorder. A genetic testing that followed the neurological examination of the patient proved positive for Huntington's Disease. Neuro-imaging resulted in a bicaudate-index of 2.4 (the critical value is 1.8). In a clinical psychological test battery the ensuing results were highly uncommon for patients with solely a bipolar affective disorder people. Under the medical regimen of Quetiapine, Citalopram and Tiaprid the patient's mood could be stabilized and there was some improvement of her motor pertubation.

Measurement of the proton-air cross section at √s=57 TeV with the Pierre Auger Observatory

We report a measurement of the proton-air cross section for particle production at the center-of-mass energy per nucleon of 57 TeV. This is derived from the distribution of the depths of shower maxima observed with the Pierre Auger Observatory: systematic uncertainties are studied in detail. Analyzing the tail of the distribution of the shower maxima, a proton-air cross section of [505±22(stat)(-36)(+28)(syst)] mb is found.

Kneelike structure in the spectrum of the heavy component of cosmic rays observed with KASCADE-Grande

We report the observation of a steepening in the cosmic ray energy spectrum of heavy primary particles at about 8×10(16) eV. This structure is also seen in the all-particle energy spectrum, but is less significant. Whereas the "knee" of the cosmic ray spectrum at 3-5×10(15) eV was assigned to light primary masses by the KASCADE experiment, the new structure found by the KASCADE-Grande experiment is caused by heavy primaries. The result is obtained by independent measurements of the charged particle and muon components of the secondary particles of extensive air showers in the primary energy range of 10(16) to 10(18) eV. The data are analyzed on a single-event basis taking into account also the correlation of the two observables.

Voxel-based morphometry in individual patients: a pilot study in early Huntington disease

BACKGROUND AND PURPOSE

Voxel-based morphometry (VBM) has proved a powerful method to detect subtle changes of gray matter (GM) at the group level but the role of VBM for the detection of GM changes in single subjects, especially in those with suspected neurodegenerative disorder, remains uncertain. Here, we performed single subject analyses in 22 patients in early stages of Huntington disease (HD), a neurodegenerative disorder with a well-known and characteristic pattern of GM loss.

MATERIALS AND METHODS

We applied an ANCOVA with age and gender as covariates and corrected for multiple statistical tests by false discovery rate (P < 0.05). Each patient was compared to 133 healthy controls. The same procedure was applied to 22 of the controls matched for age and gender in a pair-wise manner.

RESULTS

Our analyses yielded biologically plausible results in HD patients in which GM decrease within the caudate nucleus could be identified in 15 of the 16 most affected patients while GM decrease was found in only 1 control subject. Lowering the size of the control group yielded comparable results with 99 and 66 control subjects whereas sensitivity decreased with 33 control subjects.

CONCLUSIONS

Our pilot study demonstrates a potential role of VBM for the detection of cerebral GM changes in single subjects with suspected neurodegenerative disorder.

Voxel-based morphometry indicates relative preservation of the limbic prefrontal cortex in early Huntington disease

In Huntington disease (HD), both the genetic defect and mutant gene product huntington are known but the exact mechanisms that lead to neuronal loss are poorly understood. Until now, the distribution of tissue loss throughout the brain has been investigated intensively. Here we searched for areas that, antipodal to the striatum, display grey-matter (GM) preservation. We performed high resolution T1-weighted magnetic resonance imaging and voxel-based morphometry in 46 patients in early HD and 46 healthy controls. We applied an analysis of covariance (ANCOVA) model with the total GM volume of each participant as covariate. In accordance with earlier reports, group comparisons revealed GM decrease in the striatum, insula, and thalamus as well as in dorsolateral frontal and occipital areas. In contrast, the limbic prefrontal cortex displayed GM preservation. Our findings support hypotheses that postulate differential involvement of frontosubcortical circuits in the pathophysiology of HD.

Detection and imaging of atmospheric radio flashes from cosmic ray air showers

The nature of ultrahigh-energy cosmic rays (UHECRs) at energies >10(20) eV remains a mystery. They are likely to be of extragalactic origin, but should be absorbed within approximately 50 Mpc through interactions with the cosmic microwave background. As there are no sufficiently powerful accelerators within this distance from the Galaxy, explanations for UHECRs range from unusual astrophysical sources to exotic string physics. Also unclear is whether UHECRs consist of protons, heavy nuclei, neutrinos or gamma-rays. To resolve these questions, larger detectors with higher duty cycles and which combine multiple detection techniques are needed. Radio emission from UHECRs, on the other hand, is unaffected by attenuation, has a high duty cycle, gives calorimetric measurements and provides high directional accuracy. Here we report the detection of radio flashes from cosmic-ray air showers using low-cost digital radio receivers. We show that the radiation can be understood in terms of the geosynchrotron effect. Our results show that it should be possible to determine the nature and composition of UHECRs with combined radio and particle detectors, and to detect the ultrahigh-energy neutrinos expected from flavour mixing.

Neural correlates associated with impaired disgust processing in pre-symptomatic Huntington's disease

Disturbances in recognizing facial expressions of disgust have been reported previously in pre-symptomatic and manifest Huntington's disease. Given the substantial role of the insula and basal ganglia in the perception of disgust as revealed by functional imaging, lesion studies and intracerebral recordings, we propose dysfunction within the insula and/or basal ganglia as the underlying neural substrate. Using functional MRI (fMRI), we studied a group of nine pre-symptomatic Huntington's disease gene carriers and nine healthy controls, matched for age, gender, intelligence and years of education, while they were viewing disgusted facial expressions. As control conditions, surprised and neutral expressions were presented. Compared with healthy controls, Huntington's disease gene carriers showed reduced responses within the left dorsal anterior insula during processing of disgusted facial expressions. Moreover, processing of disgust was associated with significant activation of the left dorsal anterior insula and putamen in healthy controls, but not in Huntington's disease gene carriers. Furthermore, behavioural assessment revealed a selective impairment in recognizing facial expressions displaying disgust in Huntington's disease gene carriers. Our finding of dysfunctional decreased insula activation in pre-symptomatic Huntington's disease provides an explanation for the clinical deficit in recognizing facial expression of disgust. Furthermore, it underscores the role of the insula in the emotion of disgust.

The N-methyl-D-aspartate antagonist memantine retards progression of Huntington’s disease

According to the excitotoxicity hypothesis, neurotoxicity due to glutamate is regarded as potential factor in the progredient neurodegeneration of Huntington's disease (HD). Memantine, as a glutamate receptor antagonist, should counteract this mechanism. Its effectiveness (up to 30 mg/day) with regard to retardation of progression was thus examined in 27 HD patients in a two year, open and multicentre trial. The results suggest that memantine treatment of HD may be useful in terms of retardation of the progression of the disorder.

Increased cerebral iron uptake in Wilson's disease: a 52Fe-citrate PET study

Toxicity of abundant copper is the main cause of brain and liver tissue damage in patients with Wilson's disease (WD). However, there is also evidence of a disturbed iron metabolism in this genetically determined disorder. This PET study was undertaken to assess cerebral iron metabolism in WD patients.

METHODS

We used 52Fe-citrate, which converts to 52Fe-transferrin in blood plasma, to study basic pharmacokinetic features of the cerebral iron transport in 6 WD patients and in 16 healthy volunteers (control subjects). A 2-tissue-compartment model and multiple time graphic plotting were used to calculate 52Fe-transferrin distribution volumes and transport rates.

RESULTS

Net iron uptake (Ki) from plasma into brain tissue was significantly (P < 0.001) higher in WD patients (Ki [mean +/- SEM] = 15.1E-05 +/- 7.13E-05 [1/min]) than in healthy volunteers (Ki = 2.66E-05 +/- 0.351E-05 [1/min]). There was no difference of tracer iron distribution in the cerebral plasma volume between patients and healthy volunteers. Iron uptake values resulting from 2 methods to model PET data of patients and healthy volunteers were highly correlated (P < 0.001).

CONCLUSION

An abnormally increased cerebral 52Fe-transferrin uptake was found in WD patients.

Progressive degeneration of dopamine system functions after transient cerebral oligemia in rats

A reduction in cerebral blood flow to oligemic levels was achieved in pentobarbital-anesthetized adult rats by clamping both carotid arteries (BCCA) for 60 min. To assess the extent to which the animals' dopaminergic system was affected over an increasing time span, their spontaneous locomotor activity in an unfamiliar environment and in response to the subcutaneous administration of apomorphine was tested at various times after either BCCA or sham operation. Eight to 14 days after the operation, it was possible to observe a diminished locomotor activity in response to apomorphine injection in BCCA as compared with sham-operated animals, while oral stereotypical behavior such as licking was increased. At 3 months, there was only a subtle decrease in apomorphine-induced locomotor activity, and stereotypical behavior was similar in both groups. At 7 months, the BCCA rats covered shorter distances than sham-operated controls during the habituation phase; after apomorphine injection, more stereotypic movements, such as, e.g., sniffing, were observed, and less running. Twelve months after surgery, no further differences could be observed between the two groups during the habituation phase, but the injection of apomorphine led to increased stereotypic sniffing movements, rearing and locomotor activity in BCCA animals to a greater extent than in the controls. At 12 months, sensorimotor disturbances elicited by the rota rod test, which were only transiently observed at 11 weeks and 7 months, did not appear any different from the normal age-related motor decline of the sham-operated controls. The animals' motor co-ordination in the chimney test was not significantly disturbed during the time between 7 and 12 months after surgery. At 15 months, nocturnal locomotor activities in BCCA rats were significantly decreased. In situ hybridization (ISH) histochemistry revealed decreased D1 receptor mRNA (D1RmRNA) in striatal neurons 19 months after surgery, while D2 receptor mRNA (D2RmRNA) and the neuronal number remained the same. The present results show that just as is already known for the immature rat brain, the adult rat brain, too, reacts to a transient decrease in its blood supply by appearance of long-lasting alterations in function, and that even a single oligemic episode is capable of inducing progressive dopaminergic dysfunctions and ultimately the partial loss of striatal D1RmRNA.

Sensory processing in Parkinson's and Huntington's disease: investigations with 3D H(2)(15)O-PET

There is conjoining experimental and clinical evidence supporting a fundamental role of the basal ganglia as a sensory analyser engaged in central somatosensory control. This study was aimed at investigating the functional anatomy of sensory processing in two clinical conditions characterized by basal ganglia dysfunction, i.e. Parkinson's and Huntington's disease. Based on previously recorded data of somatosensory evoked potentials, we expected deficient sensory-evoked activation in cortical areas that receive modulatory somatosensory input via the basal ganglia. Eight Parkinson's disease patients, eight Huntington's disease patients and eight healthy controls underwent repetitive H(2)(15)O-PET activation scans during two experimental conditions in random order: (i) continuous unilateral high-frequency vibratory stimulation applied to the immobilized metacarpal joint of the index finger and (ii) rest (no vibratory stimulus). In the control cohort, the activation pattern was lateralized to the side opposite to stimulus presentation, including cortical [primary sensory cortex (S1); secondary sensory cortex (S2)] and subcortical (globus pallidus, ventrolateral thalamus) regional cerebral blood flow (rCBF) increases (P < 0.001). Between-group comparisons (P < 0.01) of vibration-induced rCBF changes between patients and controls revealed differences in central sensory processing: (i) in Parkinson's disease, decreased activation of contralateral sensorimotor (S1/M1) and lateral premotor cortex, contralateral S2, contralateral posterior cingulate, bilateral prefrontal cortex (Brodmann area 10) and contralateral basal ganglia; (ii) in Huntington's disease, decreased activation of contralateral S2, parietal areas 39 and 40, and lingual gyrus, bilateral prefrontal cortex (Brodmann areas 8, 9, 10 and 44), S1 (trend only) and contralateral basal ganglia; (iii) in both clinical conditions relative enhanced activation of ipsilateral sensory cortical areas, notably caudal S1, S2 and insular cortex. Our data show that Parkinson's disease and Huntington's disease, beyond well-established deficits in central motor control, are characterized by abnormal cortical and subcortical activation on passive sensory stimulation. Furthermore, the finding that activation increases in ipsilateral sensory cortical areas may be interpreted as an indication of either altered central focusing and gating of sensory impulses, or enhanced compensatory recruitment of associative sensory areas in the presence of basal ganglia dysfunction. Altered sensory processing is thought to contribute to pertinent motor deficits in both conditions.

D2 receptor binding in dopa-responsive dystonia

We have studied dopamine D2 receptor binding by [11C]raclopride positron emission tomography in 14 patients with dopa-responsive dystonia (DRD). Data were compared with 16 levodopa-treated patients with Parkinson's disease (PD) and 26 healthy controls. The results revealed an elevated [11C]raclopride binding index in the putamen and caudate nucleus of DRD patients compared with controls as well as a significant elevation in the caudate nucleus compared with PD patients. The increase of [11C]raclopride binding may be interpreted either as reduced tracer displacement by endogenous dopamine, or as an alteration of the receptor features due to chronic dopamine deficiency. The difference in [11C]raclopride binding in DRD and PD patients in the caudate nucleus suggests that this structure may be of pathophysiological relevance in the presentation of the clinical features of both diseases.

Heterogeneous dopamine D2 receptor subtype messenger ribonucleic acid expression in clinically nonfunctioning pituitary adenomas

Little is known about differences in the expression, localization, and function of the two dopamine D2 receptor subtypes, D2short and D2long (D2s and D2l), in either normal or adenomatous pituitary. We investigated the messenger RNA (mRNA) expression of the D2 receptor (D2R) subtypes in clinically nonfunctioning pituitary adenomas by in situ hybridization using subtype-specific oligonucleotides. The five normal pituitaries studied expressed similar ratios of D2R subtypes mRNA with a predominant expression of the D2l isoform. In 2 of 18 clinically inactive adenomas no D2R mRNA was found, whereas in 16 a heterogeneous expression of D2R isoforms was observed. Six adenomas expressed only the D2l and 2 adenomas only the D2s subtype mRNA; the remaining 8 expressed extremely varying proportions of the two subtypes. The D2R was found only in a subset of the nonfunctioning adenoma cells. In gonadotropin-immunopositive adenomas, the D2R was mainly localized in LH- and FSH-immunopositive cells. Probably because of the heterogeneous D2R subtype expression, suppression of cell proliferation was observed in only 3 of 9 adenoma cell cultures in which the growth inhibitory effect of bromocriptine was studied. Although there is some evidence that the presence of the D2s receptor subtype favors the growth inhibitory response to bromocriptine, further studies with a larger number of inactive adenomas are needed to confirm this speculation.