Structure of air shower disc near the core

The longitudinal structure of the air shower disk is studied by measuring the arrival time distributions of air shower particles for showers with electron size in the range 3.2 x 10 to the 5.5. power to 3.2 x 10 to the 7.5 power in the Akeno air-shower array (930 gcm squared atmospheric depth). The average FWHM as a parameter of thickness of air shower disk increases with core distances at less than 50m. AT the present stage, dependence on electron size, zenith angle and air shower age is not apparent. The average thickness of the air shower disk within a core distance of 50m could be determined by an electromagnetic cascade starting from the lower altitude

Search for long-lived massive particles in extensive air showers

Air showers containing delayed sub-showers which may be produced by a long-lived massive particle have been investigated by using twelve detectors. Ten events have been selected out as the candidates. However, a definite conclusion cannot be reached at the present time

Evidence for the tonic inhibition of spinal pain by nicotinic cholinergic transmission through primary afferents

<p>Abstract</p> <p>Background</p> <p>We have proposed that nerve injury-specific loss of spinal tonic cholinergic inhibition may play a role in the analgesic effects of nicotinic acetylcholine receptor (nAChR) agonists on neuropathic pain. However, the tonic cholinergic inhibition of pain remains to be well characterized.</p> <p>Results</p> <p>Here, we show that choline acetyltransferase (ChAT) signals were localized not only in outer dorsal horn fibers (lamina I–III) and motor neurons in the spinal cord, but also in the vast majority of neurons in the dorsal root ganglion (DRG). When mice were treated with an antisense oligodeoxynucleotide (AS-ODN) against ChAT, which decreased ChAT signals in the dorsal horn and DRG, but not in motor neurons, they showed a significant decrease in nociceptive thresholds in paw pressure and thermal paw withdrawal tests. Furthermore, in a novel electrical stimulation-induced paw withdrawal (EPW) test, the thresholds for stimulation through C-, Aδ- and Aβ-fibers were all decreased by AS-ODN-pretreatments. The administration of nicotine (10 nmol i.t.) induced a recovery of the nociceptive thresholds, decreased by the AS-ODN, in the mechanical, thermal and EPW tests. However, nicotine had no effects in control mice or treated with a mismatch scramble (MS)-ODN in all of these nociception tests.</p> <p>Conclusion</p> <p>These findings suggest that primary afferent cholinergic neurons produce tonic inhibition of spinal pain through nAChR activation, and that intrathecal administration of nicotine rescues the loss of tonic cholinergic inhibition.</p

Characterization of three different sensory fibers by use of neonatal capsaicin treatment, spinal antagonism and a novel electrical stimulation-induced paw flexion test

In the present study, we first report an in vivo characterization of flexor responses induced by three distinct sine-wave stimuli in the electrical stimulation-induced paw flexion (EPF) test in mice. The fixed sine-wave electric stimulations of 5 Hz (C-fiber), 250 Hz (Aδ-fiber) and 2000 Hz (Aβ-fiber) to the hind paw of mice induced a paw-flexion response and vocalization. The average threshold for paw flexor responses by sine-wave stimulations was much lower than that for vocalization. Neonatally (P3) pretreatment with capsaicin to degenerate polymodal substance P-ergic C-fiber neurons increased the threshold to 5 Hz (C-fiber) stimuli, but not to 250 Hz (Aδ-fiber) and 2000 Hz (Aβ-fiber). The flexor responses to 5 Hz stimuli were significantly blocked by intrathecal (i.t.) pretreatment with both CP-99994 and MK-801, an NK1 and NMDA receptor antagonist, respectively, but not by CNQX, an AMPA/kainate receptor antagonist. On the other hand, the flexor responses induced by 250 Hz stimuli were blocked by MK-801 (i.t.) but not by CP-99994 or CNQX. In contrast, flexor responses induced by 2000 Hz stimuli were only blocked by CNQX treatment. These data suggest that we have identified three pharmacologically different categories of responses mediated through different primary afferent fibers. Furthermore, we also carried out characterization of the in vivo functional sensitivity of each of the sensory fiber types in nerve-injured mice using the EPF test, and found that the threshold to both 250 Hz and 2000 Hz stimulations were markedly decreased, whereas the threshold to 5 Hz stimulations was significantly increased. Thus we found opposing effects on specific sensory fiber-mediated responses as a result of nerve injury in mice. These results also suggest that the EPF analysis is useful for the evaluation of plasticity in sensory functions in animal disease models

Pathological study of chronic pulmonary toxicity induced by intratracheally instilled Asian sand dust (Kosa): possible association of fibrosis with the development of granulomatous lesions

Introduction. Exposure to Asian sand dust (ASD) is associated with enhanced pulmonary morbidity and mor­tality, and the reporting of such cases has rapidly increased in East Asia since 2000. The purpose of the study was to assess chronic lung toxicity induced by ASD. Material and methods. A total of 174 ICR mice were randomly divided into 5 control and 17 exposure groups. Suspensions of low dose (0.2, 0.4 mg) and high dose (3.0 mg) of ASD particles in saline were intratracheally instilled into ICR mice, followed by sacrifice at 24 hours, 1 week, and 1, 2, 3 and 4 months after instillation. Paraffin sections of lung tissues were stained with hematoxylin and eosin and by immunohistochemistry to detect α-smooth muscle actin, collagen III, matrix metalloproteinase-9 (MMP-9), tissue inhibitor of metalloproteinases-1 (TIMP-1), CD3, CD20, immunoglobulin G, interleukin-1β and inducible nitric oxide synthase. Results. A lung histological examination revealed similar patterns in the lesions of the groups treated with high (3.0 mg) or low dose (0.4 mg) of ASD. Acute inflammation was observed 24 h after treatment and subsided after 1 week; persistent granulomatous changes were observed at 2 months, focal lymphocytic infiltration at 3 months, and granuloma formation at 4 months. An increase in the size of granulomatous lesions was observed over time and was accompanied by collagen deposition in the lesions. The cytoplasm of macrophages in inflammatory lesions showed positive immunolabeling for MMP-9 at 24 h, 1 and 2 months after instillation of 3.0 mg of ASD. Positive immunolabeling for TIMP-1 was demonstrated in the cytoplasm of macrophages at 2 and 4 months after instillation of 3.0 mg of ASD. These findings suggest association between the expression of MMP-9 and TIMP-1 with the development of lung granulomatous lesions. Conclusions. These findings suggest that collagen deposition resulting from the altered regulation of extracel­lular matrix is associated with granuloma formation in the lungs of mice treated with ASD

Pathological study of pulmonary toxicity induced by intratracheally instilled Asian sand dust (Kosa): effects of lowered serum zinc level on the toxicity

Introduction. We have previously reported that Asian sand dust (ASD) induced acute and chronic inflammatory changes in the lung of mice. Zinc (Zn) is reported to influence inflammation and wound healing. The purpose of the study was to assess the effects of lowered serum Zn levels on the lung toxicity induced by ASD. Material and methods. Mice that were fed diets containing normal (group 1) or low (group 2) content of Zn for 8 weeks were intratracheally instilled with 3.0 mg of ASD, followed by sacrifice at 24 hours, 2 weeks, and 1, 2 and 3 months after instillation. Paraffin sections of lung tissues were stained by hematoxylin and eosin and by immunohistochemistry to detect tumor necrosis factor (TNF) and interleukin (IL)-1β as well as inflammasome (NALP3), autophagy (LC-3) and lysosome (LAMP-1) markers. Selected samples of lung tissue were examined by electron microscopy. Results. Following histological examination of the lung, similar patterns of inflammatory changes were observed in mice with normal and low serum Zn concentrations; however, they were more prominent and persistent in mice with low serum Zn level. These changes were both purulent (acute) and pyogranulomatous (chronic) in nature. In the lung lesions of group 2 mice the changes within the cytoplasmic vacuoles of enlarged ASD-containing macrophages (Mo) were clearly visible. The macrophages expressed TNF and IL-1β, and semi-quantitative analysis revealed a larger number of TNF-positive Mo in mice with normal level of serum Zn and a larger number of IL-1β-positive Mo in mice with low level of serum Zn. Decreased positive LC-3 staining and dilated lysosomes containing ASD particles were observed in the cytoplasm of Mo in mice with low serum Zn concentration. Conclusions. These findings suggest that low serum zinc concentration may induce the modulation of cytokine expression and lysosomal malfunction by phagocytotic and/or autophagic mechanisms, and may result in interstitial pyogranulomatous inflammation in the lungs of mice treated with ASD

Ultrahigh Energy Gamma Ray Cascading in the Geomag- netic Field and Its Development in the Atmosphere

Abstract Extensive simulations of the longitudinal development of air showers from ultrahigh (UHE) energy gamma rays have been carried out. The shower development is affected by the geomagnetic cascading before entering the atmosphere and by the Landau-Pomeranchuk-Migdal effect in the atmosphere. AIRES code as well as our original code have been used for cascade simulations in the atmosphere. The analysis of the results shows that the longitudinal development of the showers depend strongly on both primary energy and incident direction. This feature may provide reliable conclusions about the photon fraction in the UHE ( &gt; 5 × 10 19 eV) cosmic ray flux