Search for Gamma-Ray Spectral Lines from Dark Matter Annihilation up to 100 TeV toward the Galactic Center with MAGIC.

Linelike features in TeV γ rays constitute a "smoking gun" for TeV-scale particle dark matter and new physics. Probing the Galactic Center region with ground-based Cherenkov telescopes enables the search for TeV spectral features in immediate association with a dense dark matter reservoir at a sensitivity out of reach for satellite γ-ray detectors, and direct detection and collider experiments. We report on 223 hours of observations of the Galactic Center region with the MAGIC stereoscopic telescope system reaching γ-ray energies up to 100 TeV. We improved the sensitivity to spectral lines at high energies using large-zenith-angle observations and a novel background modeling method within a maximum-likelihood analysis in the energy domain. No linelike spectral feature is found in our analysis. Therefore, we constrain the cross section for dark matter annihilation into two photons to ⟨σv⟩≲5×10^{-28} cm^{3} s^{-1} at 1 TeV and ⟨σv⟩≲1×10^{-25} cm^{3} s^{-1} at 100 TeV, achieving the best limits to date for a dark matter mass above 20 TeV and a cuspy dark matter profile at the Galactic Center. Finally, we use the derived limits for both cuspy and cored dark matter profiles to constrain supersymmetric wino models.

Bounds on Lorentz Invariance Violation from MAGIC Observation of GRB 190114C.

On January 14, 2019, the Major Atmospheric Gamma Imaging Cherenkov telescopes detected GRB 190114C above 0.2 TeV, recording the most energetic photons ever observed from a gamma-ray burst. We use this unique observation to probe an energy dependence of the speed of light in vacuo for photons as predicted by several quantum gravity models. Based on a set of assumptions on the possible intrinsic spectral and temporal evolution, we obtain competitive lower limits on the quadratic leading order of speed of light modification.

MiR-138 indirectly regulates the MDR1 promoter by NF-κB/p65 silencing.

MicroRNAs (miRNAs) are known to mediate post-transcriptional gene silencing in the cytoplasm and recent evidence indicates that may also possess nuclear roles in regulating gene expression. A previous study showed that miR-138 is involved in the multidrug resistance of leukemia cells through down-regulation of the drug efflux pump P-glycoprotein (P-gp), the protein encoded by the human multidrug-resistant ABCB1/MDR1 gene. However, the transcriptional regulatory mechanisms responsible remain to be elucidated. To deepen the description of the mechanism of transcriptional gene silencing on the MDR1 promoter, we initially performed a bioinformatics search for potential miR-138 binding sites in the MDR1 gene promoter sequence. Interestingly, we did not find miR-138 binding sites in this region, suggesting an indirect regulation. From six representative transcriptional factors involved in MDR1 gene regulation, an in silico analysis revealed that NF-κB/p65 has a specific binding site for miR-138. The results of luciferase reporter assay, western blot and flow cytometry shown here suggest that miR-138 might modulate the human MDR1 expression by inhibiting NF-κB/p65 as an indirect mechanism of MDR1 regulation. Furthermore, employing the human macrophage-like cell line U937 we observed comparable results with NF-κB/p65 down-regulation and we also observed a significant reduction in the IL-6 and TNF-α mRNA, as well as in their secreted pro-inflammatory cytokines following miR-138 expression, suggesting that canonical NF-κB target genes might also be potential targets for miR-138 in leukemia cells.

Black hole physics. Black hole lightning due to particle acceleration at subhorizon scales.

Supermassive black holes with masses of millions to billions of solar masses are commonly found in the centers of galaxies. Astronomers seek to image jet formation using radio interferometry but still suffer from insufficient angular resolution. An alternative method to resolve small structures is to measure the time variability of their emission. Here we report on gamma-ray observations of the radio galaxy IC 310 obtained with the MAGIC (Major Atmospheric Gamma-ray Imaging Cherenkov) telescopes, revealing variability with doubling time scales faster than 4.8 min. Causality constrains the size of the emission region to be smaller than 20% of the gravitational radius of its central black hole. We suggest that the emission is associated with pulsar-like particle acceleration by the electric field across a magnetospheric gap at the base of the radio jet.

Observation of pulsed gamma-rays above 25 GeV from the Crab pulsar with MAGIC.

One fundamental question about pulsars concerns the mechanism of their pulsed electromagnetic emission. Measuring the high-end region of a pulsar's spectrum would shed light on this question. By developing a new electronic trigger, we lowered the threshold of the Major Atmospheric gamma-ray Imaging Cherenkov (MAGIC) telescope to 25 giga-electron volts. In this configuration, we detected pulsed gamma-rays from the Crab pulsar that were greater than 25 giga-electron volts, revealing a relatively high cutoff energy in the phase-averaged spectrum. This indicates that the emission occurs far out in the magnetosphere, hence excluding the polar-cap scenario as a possible explanation of our measurement. The high cutoff energy also challenges the slot-gap scenario.

Very-high-energy gamma rays from a distant quasar: how transparent is the universe?

The atmospheric Cherenkov gamma-ray telescope MAGIC, designed for a low-energy threshold, has detected very-high-energy gamma rays from a giant flare of the distant Quasi-Stellar Radio Source (in short: radio quasar) 3C 279, at a distance of more than 5 billion light-years (a redshift of 0.536). No quasar has been observed previously in very-high-energy gamma radiation, and this is also the most distant object detected emitting gamma rays above 50 gigaelectron volts. Because high-energy gamma rays may be stopped by interacting with the diffuse background light in the universe, the observations by MAGIC imply a low amount for such light, consistent with that known from galaxy counts.

Testosterone, androstenedione, and 5alpha-dihydrotestosterone on male sexual behavior and penile spines in the hamster.

The expression of masculine sexual behavior (MSB) in male hamsters is optimally stimulated by aromatizable androgens like androstenedione (AD) and testosterone (T), while the non-aromatizable androgen, 5alpha-dihydrotestosterone (DHT), exerting potent androgenic peripheral effects, only in high doses maintains MSB after castration. No data exist on the ability of these androgens to restore long intromissions after castration. In this study, AD, T, and DHT were administered to four-week gonadectomized, sexually experienced male hamsters, for three weeks, in doses of 25 microg/day or up to 1000 microg/day to compare their potency in restoring MSB, penile size, and penile spines growth. Plasma levels of these steroids and the metabolites estrone and estradiol, were determined at the end of the treatment period. Gonadectomy completely suppressed MSB and induced a regression of penile spines. AD was more potent than T in restoring MSB, ejaculatory behavior being displayed by most castrated subjects with a lower dose of AD (50 microg/day) than of T (300 microg/day), and long intromissions being shown by all AD-treated castrated hamsters but only by 20% of T-treated ones, when doses of 1000 microg/day were given. DHT did not stimulate any copulatory response. The three androgens, even at the lowest dose, partially stimulated penis and penile epithelium growth, DHT showing the highest potency. Treatment of castrated hamsters with AD (50 microg/day), restored steroid levels to similar values as those of intact animals. These results show that AD and T restored MSB even with a partial stimulation of penile spines growth, AD being more potent than T. In contrast, DHT did not restore MSB in the hamster in spite of its peripheral androgenic potency.

Variable very-high-energy gamma-ray emission from the microquasar LS I +61 303.

Microquasars are binary star systems with relativistic radio-emitting jets. They are potential sources of cosmic rays and can be used to elucidate the physics of relativistic jets. We report the detection of variable gamma-ray emission above 100 gigaelectron volts from the microquasar LS I 61 + 303. Six orbital cycles were recorded. Several detections occur at a similar orbital phase, which suggests that the emission is periodic. The strongest gamma-ray emission is not observed when the two stars are closest to one another, implying a strong orbital modulation of the emission or absorption processes.

Employment of liver tissue slice analysis to assay hepatotoxicity linked to replicative and nonreplicative adenoviral agents.

Whereas virotherapy has emerged as a novel and promising approach for neoplastic diseases, appropriate model systems have hampered preclinical evaluation of candidate conditionally replicative adenovirus agents (CRAds) with respect to liver toxicity. This is due to the inability of human viral agents to cross species. We have recently shown the human liver tissue slice model to be a facile means to validate adenoviral replication. On this basis, we sought to determine whether our ex vivo liver tissue slice model could be used to assess CRAd-mediated liver toxicity. We analyzed and compared the toxicity of a conditionally replicative adenovirus (AdDelta24) to that of a replication incompetent adenovirus (Adnull [E1-]) in mouse and human liver tissue slices. To accomplish this, we examined the hepatic apoptosis expression profile by DNA microarray analyses, and compared these results to extracellular release of aminotransferase enzymes, along with direct evidence of apoptosis by caspase-3 immunhistochemical staining and TUNEL assays. Human and mouse liver tissue slices demonstrated a marked increase in extracellular release of aminotransferase enzymes on infection with AdDelta24 compared to Adnull. AdDelta24-mediated liver toxicity was further demonstrated by apoptosis induction, as detected by caspase-3 immunohistochemical staining, TUNEL assay and microarray analysis. In conclusion, concordance of CRAd-mediated apoptosis in both the human and the mouse liver tissue slice models was demonstrated, despite the limited replication ability of CRAds in mouse liver slices. The results of this study, defining the CRAd-mediated apoptosis gene expression profiles in human and mouse liver, may lay a foundation for preclinical liver toxicity analysis of CRAd agents.

17beta-estradiol differentially activates mitogen-activated protein-kinases and improves survival following reperfusion injury of reduced-size liver in mice.

Ischemia-reperfusion injury (I/R-I), which is unavoidable in liver transplantation, impairs liver regeneration and predisposes to liver failure. The three major mitogen-activated protein-kinases (MAPKs): ERK, p38, and JNK, are critical in the transmission of signals triggered by proinflammatory cytokines, by stress, and by growth factors. JNK and p38alpha activation have been associated with apoptosis; p38beta with cell survival; and ERK with proliferation. Previous studies have demonstrated gender dimorphism in hepatocellular dysfunction after experimental trauma and hemorrhage. Female mice are protected to a much greater extent from I/R-I than male mice. We assessed the effects of 17beta-estradiol (17beta-E) on liver function, host survival, and cellular activation of MAPK in a murine model of I/R-I in reduced-size livers. C57BL/6 mice were subjected to 45 minutes of warm ischemia (70% of the liver mass). After reperfusion, the nonischemic lobes were excised. Vehicle, 17beta-E or the estrogen receptor antagonist ICI-182780, was delivered 1 hour before the injury. We evaluated AST and apoptosis as well as activation of JNK, p38, and ERK. Female mice showed a lower level of hepatocellular injury (AST = 445 +/- 82 IU/L) after I/R-I compared with male mice (AST = 1400 +/- 210). 17beta-E decreased the liver injury in male mice (AST = 522 +/- 77), an effect that was partially reversed by ICI-182,780 (910 +/- 92). A higher rate of apoptosis was observed in male animals given saline (enrichment factor = 7.22 +/- 0.8) versus those treated with 17beta-E (5.85 +/- 0.3, P < .05). A significant increase in liver regeneration, as assessed by the percentage of liver weight/body weight was demonstrated in females (184% +/- 24%) and male mice given 17beta-E (168% +/- 22%) compared with male mice given vehicle (9% +/- 4%). 17beta-E significantly down-regulated JNK and p38alpha activities, whereas I/R-I promoted p38beta and ERK activation. These results suggest that the cytoprotective effects of 17beta-E on I/R-I to reduced-size livers are associated with selective modulation of MAPK kinases.

Ultrastructural morphology and morphometry of epididymal sperm in the volcano rabbit (Romerolagus diazi).

Sperm characteristics of Romerolagus diazi, an endemic endangered rabbit from Mexico's Higlands, are poorly known. Knowledge of gamete characteristics are urged for any conservation-oriented strategy and morphometry-based taxonomical database. Sperm lagomorph comparisons have been made at light microscopy resolution. Our goal was to analyze the ultrastructure of the R. diazi male gamete. Two wild animals were kept in captivity and the epididymus were obtained. Fixed gametes show a characteristic spatula-like morphology with a dilated forefront. The nucleus has an arrow head morphology lightly thicker at the base. Tail ultrastructure is similar to that of laboratory rabbits with an end piece thicker than that of human sperm. Morphometry data could be used for construction of a male gamete data base for further studies.

Gene transfer of the Bcl-2 gene confers cytoprotection to isolated adult porcine pancreatic islets exposed to xenoreactive antibodies and complement.

BACKGROUND: Exposing adult porcine pancreatic islets (PI) to xenoreactive natural antibodies (XNA) induces brisk inflammatory injury that involves activation of the complement system. Gene transfer of Bcl-2 has been shown to protect PI from apoptosis and necrosis in several models. In this study, we investigated the effect of Bcl-2 gene transfer on protection of PI from primate XNA and complement-mediated injury. METHODS: The PI were isolated from adult female sows. Only islet preparations that exhibited >90% viability and purity were used. Fresh rhesus monkey serum served as the XNA source. Gene transfer of Bcl-2 was achieved with an adenoviral vector (AdBcl-2) at 500 particle forming units (pfu)/cell. The Bcl-2 expression was confirmed by Western blot technique. Untransfected and transfected PI were incubated in 50% fresh complete serum (CS) or heat-inactivated (HI) rhesus serum for 24 hours. The PI viability was analyzed with acridine orange and ethidium bromide staining. Antibody and complement-mediated cytotoxicity were tested by intracellular lactate dehydrogenase (LDH) release. The PI function was assessed in vitro by static incubation studies and in vivo after intraportal transplantation in diabetic severe combined immunodeficiency (SCID) mice. RESULTS: The AdBcl-2 gene transfer resulted in Bcl-2 gene expression in >90% of PI cells. Following exposure to XNA, <15% of the untransfected cells were viable. Similar results were obtained in PI transfected with a similar recombinant adenovirus encoding the reporter gene E coli beta-galactosidase (AdLacZ), an irrelevant gene. A significant increase in LDH release was observed in control PI after exposure to CS compared with PI that overexpressed Bcl-2 (82.89% +/- 7.78% vs 34.31% +/- 5.4%, P <.005). Higher insulin release was observed in vitro in PI transfected with Bcl-2 compared with untransfected PI or islets transfected with AdLacZ (stimulation index of 0.9 +/- 0.31, 0.9 +/- 0.3 vs 2.67 +/- 0.4, respectively). Only PI treated with AdBcl-2 were able to achieve euglycemia after exposure to XNA and complement after transplantation. CONCLUSIONS: Transfer of the antiapoptotic and antinecrotic Bcl-2 gene into PI can reduce primate XNA and complement-mediated lysis. Cytoprotection of PI with Bcl-2 has potential to improve survival of PI xenotransplants.

A tripartite anoikis-like mechanism causes early isolated islet apoptosis.

BACKGROUND: This study examines the mechanisms of early isolated islet apoptosis (II-APO) and loss of functional islet mass. METHODS: Rhesus islets were isolated for transplantation, and an aliquot was used for in vitro molecular studies of II-APO. These studies used Western blotting to examine caspase activation and perinuclear envelope protein cleavage that are associated with II-APO and used immunofluorescence analysis of Annexin V and mitochondrial permeability index to examine spontaneous and tripartite anoikis-like (TRAIL) mechanism--induced II-APO. RESULTS: Caspase 6 was prominently activated in association with spontaneous II-APO, which occurred after overnight culture. In contrast, caspase 7, 8, and 9 were not activated. Cleavage of focal adhesion kinase and Lamin, substrates of caspase 6, was also evident in spontaneous II-APO. II-APO was exaggerated by the addition of the TRAIL mechanism. The TRAIL mechanism--induced II-APO was blocked by the caspase 6 inhibitor, VEID, and by the soluble fusion proteins, DR4 or DR5, which act as decoy receptors. In vivo studies in diabetic severe combined immunodeficiency disease mice showed that rhesus islets were cytoprotected by either ex vivo gene transfer of Bcl-2 or treatment of the isolated islet with VEID. CONCLUSIONS: These studies suggest 3 major mechanisms involved in II-APO: caspase 6 activation, a TRAIL-induced apoptosis pathway, and the mitochondrial-associated apoptosis pathway. Inhibition of these II-APO pathways may improve isolated islet survival and reduce functional islet mass loss, which compromises the stable reversal of diabetes.

Phenotypic and functional analysis of T-cell recovery after anti-CD3 immunotoxin treatment for tolerance induction in rhesus macaques.

T-cell reduction utilizing specific antibody has been widely used in human transplantation, and is a cornerstone of several tolerance induction strategies in nonhuman primates. We have established a population of long-term tolerant rhesus macaques induced with an anti-CD3epsilon immunotoxin (IT). This treatment effects transient, specific and profound ablation of T cells in blood and lymphoid tissues. In most instances the IT was used in combination with the NF-kappaB inhibitor, 15-Deoxyspergualin. This 2-week long protocol produces a "window of opportunity" for tolerization in which the animal exhibits an enduring quiescent state of unresponsiveness to the allograft, all accomplished without maintenance immunosuppressive drugs. During this induction period, the treated immune system bears some resemblance to that of the neonate, in that T cell numbers are abnormally low and antigen presentation by dendritic cells is precluded by an arrest in their NF-kappaB dependant maturation. In addition, IL-4 production is prominent during and after the tolerance induction interval. For this study we focused on measuring the monkey's ability to repopulate T cells with particular emphasis on the memory T-cell phenotype. Three "memory" phenotypes were utilized; CD3(+)CD45RO(+), CD3(+)CRTH2(+), and CD3(+)CD4(+)CD8(+). All three phenotypes exhibited different patterns of recovery, all of which included transient bursts in their numbers during repopulation. We also estimated thymic activity after T-cell ablation with the use of a newly-described RTE or recent thymic émigré phenotype (a naïve CD8(+)CD103(+) T cell). This marker revealed production of RTE cells including supranormal levels at approximately 6 months post-transplant, implicating thymic function in the repopulation of T-cells. Finally, we measured antibody responses to a panel of antigens (vaccines, environmental antigen, and foreign proteins) that indicated there was no apparent loss of immunologic function during or after the tolerance induction period. Results of studies of T-cell receptor repertoire expression suggest preservation of the pretreatment repertoire, which is consistent with rapid recovery of immune competence to the test antigens. Taken together, these results suggest that while aggressive, this tolerance induction protocol does not appear to incur a prolonged immunologically-compromised state, if at all.

Cytoprotection of pancreatic islets before and soon after transplantation by gene transfer of the anti-apoptotic Bcl-2 gene.

Isolated pancreatic islet transplantation is a promising alternative to conventional insulin-dependent diabetes treatment but is not yet a practical clinical therapy. In the first few days after pancreatic islet transplantation, substantial donor pancreatic islet dysfunction and apoptosis commonly occur. Islet apoptosis has been documented after extracellular matrix disruption and exposure to proinflammatory cytokines, and during hypoxia before islet revascularization and rejection. These studies show that targeting the apoptosis pathway by adenoviral-mediated gene transfer of the anti-apoptotic Bcl-2 gene exerts a major cytoprotective effect on isolated macaque pancreatic islets. Bcl-2 transfection ex vivo protects these islets from apoptosis induced by disruption of the islet extracellular matrix during pancreatic digestion. Additionally, overexpression of Bcl-2 confers long-term, stable protection and maintenance of functional islet mass after transplantation of macaque islets into diabetic severe combined immunodeficency mice. Notably, genetic modification of pancreatic islets also reduced the islet mass required to achieve stable euglycemia. Ex vivo gene transfer of anti-apoptotic genes has potential as a therapeutic approach to both minimize loss of functional islet mass after transplant and reduce the high donor islet requirement currently needed for successful stable reversal of insulin-dependent diabetes.

Successful reversal of streptozotocin-induced diabetes with stable allogeneic islet function in a preclinical model of type 1 diabetes.

The recent focus on islet transplantation as primary therapy for type 1 diabetes has heightened interest in the reversal of type 1 diabetes in preclinical models using minimal immunosuppression. Here, we demonstrated in a preclinical rhesus model a consistent reversal of all measured glycemic patterns of streptozotocin-induced type 1 diabetes. The model used single-donor islet transplantation with induction of operational tolerance. The term "operational tolerance" is used to indicate durable survival of single-donor major histocompatibility complex (MHC)-mismatched islet allografts without maintenance immunosuppressive therapy and without rejection or loss of functional islet mass or insulin secretory reserve. In this operational tolerance model, all immunosuppression was discontinued after day 14 posttransplant, and recipients recovered with excellent health. The operational tolerance induction protocol combined peritransplant anti-CD3 immunotoxin to deplete T-cells and 15-deoxyspergualin to arrest proinflammatory cytokine production and maturation of dendritic cells. T-cell deficiency was specific but temporary, in that T-cell-dependent responses in long-term survivors recovered to normal, and there was no evidence of increased susceptibility to infection. Anti-donor mixed lymphocyte reaction responses were positive in the long-term survivors, but all showed clear evidence of systemic T-helper 2 deviation, suggesting that an immunoregulatory rather than a deletional process underlies this operational tolerance model. This study provides the first evidence that operational tolerance can protect MHC nonhuman primate islets from rejection as well as loss of functional islet mass. Such an approach has potential to optimize individual recipient recovery from diabetes as well as permitting more widespread islet transplantation with the limited supply of donor islets.

Combined cardiac surgery and liver transplantation.

During evaluation for liver transplantation, a 63-year-old man with cirrhosis secondary to hepatitis C was diagnosed with severe aortic stenosis (aortic valve area, 0.87 cm(2)) and coronary artery disease. A combined procedure involving aortic valve replacement (pericardial xenograft), coronary artery bypass surgery, and orthotopic liver transplantation was performed. Convalescence was uneventful, and at 2 years after the procedure, the patient has normal cardiac function, good prosthetic valve function, and biochemically normal liver function.

Experience with renal transplantation in the nonhuman primate: a modified ureteroneocystostomy to prevent urologic complications.

Nonhuman primates provide an optimal model for the evaluation of tolerance in the preclinical setting. Transplantation and management of nonhuman primates are technically demanding, and the purpose of this article is to review our extensive experience in renal transplantation in non-human primates, with particular emphasis on modifications of surgical techniques on urologic complications. We retrospectively reviewed our results with 329 renal transplants in rhesus monkeys over an 18-year period. The surgical technique and, in particular, the ureteroneocystostomy have evolved over this period of time. This review extensively details our current technique, the surgical and urologic complications, and their management. There were 329 renal transplants performed. There were 85 early deaths, or animals euthanized, within 30 days of the transplant operation. In the first 15 years, there were 27 (10.68%) surgical complications that required euthanasia, and in the last 3 years the complication rate has been reduced to 5 (7.3%, p < .05). The routine use of microsurgical techniques has reduced the incidence of arterial thrombosis (6.2% vs. 2.9%, p < .05). The incidence of ureteral strictures (15 vs. 0, p < .005) has been reduced by a modification of the ureteroneocystostomy technique detailed in the text. Renal transplantation in small rhesus monkeys is technically demanding. The routine use of microsurgical techniques and a modified ureteroneocystostomy has reduced the incidence of surgical complications.

Serotonin and sexual behavior in the male rabbit.

Sexual behavior was evaluated in sexually experienced male rabbits after the administration of different serotonergic drugs. The serotonin1A receptor agonist 8-OH-DPAT, 1 mg/kg, inhibited male rabbit sexual behavior when animals were tested 15 min after subcutaneous (SC) administration of this compound. Lower doses, 0.25 and 0.5mg/kg, were ineffective at a test 30 min after drug injection. Furthermore, 8-OH-DPAT, 0.25mg/kg, failed to revert the inhibitory effects upon sexual behavior produced by lidocaine application to the rabbit penis. Stimulation of 5-HT1B/2C receptors by TFMPP, at doses between 0.625 and 2.5 mg/kg, produced a drastic inhibition of sexual behavior when the drug was administered SC 30 min before behavioral observation. Doses below 5mg/kg were ineffective when given intraperitoneally 15 min before test. When the 5-HT1D/2C receptors were stimulated by the agonist mCPP a reduced number of mounts and ejaculations was observed after the SC administration of 1.25 and 2.5 mg/kg. Similarly, the mixed 5-HT agonist/antagonist lisuride reduced the percentage of rabbits displaying mounting behavior at doses of 0.25 and 0.5 mg/kg SC. All compounds tested produced a clear inhibition of male rabbit sexual behavior independently of the receptor subtype activated. These results are at variance with previous observations in rats where 8-OH-DPAT and lisuride produced a drastic facilitation of masculine coital behavior. Moreover, while the inhibition of male sexual behavior in rats produced by TFMPP and mCPP is associated with a disruption of the execution of this behavior, in rabbits these compounds reduced sexual motivation. These results indicate that the effects of serotonergic drugs on sexual behavior are species specific.