Nonresonant detection of terahertz radiation in high-electron-mobility transistor structure using InAIAs/InGaAs/InP material systems at room temperature

In this paper, we report on nonresonant detection of terahertz radiation using the rectification mechanism of two-dimensional plasmons in high-electron-mobility transistors using InAIAs/InGaAs/InP material systems. The experiments were performed at room temperature using a Gunn diode operating at 0.30 THz as the THz source. The measured response was dependent on the polarization of the incident THz wave; The device exhibited higher response when the electric-field vector of the incident radiation was directed in the source-drain direction. The 2D spatial distribution image of the transistor responsivity extracted from the measured response shows a clear beam focus centered on the transistor position, which ensures the appropriate coupling of the terahertz radiation to the device. The device also demonstrated excellent sensitivity/noise performances of approximately 125 V/W and approximately 10(-11) W/Hz(0.5) under 0.30 THz radiation.

Emission of terahertz radiation from dual grating gate plasmon-resonant emitters fabricated with InGaP/InGaAs/GaAs material systems

This paper reviews recent advances in our original 2D-plasmon-resonant terahertz emitters. The structure is based on a high-electron-mobility transistor and featured with doubly interdigitated grating gates. The dual grating gates can alternately modulate the 2D electron densities to periodically distribute the plasmonic cavities along the channel, acting as an antenna. The device can emit broadband terahertz radiation even at room temperature from self-oscillating 2D plasmons under the DC-biased conditions. When the device is subjected to laser illumination, photo-generated carriers stimulate the plasma oscillation, resulting in enhancement of the emission. The first sample was fabricated with standard GaAs-based heterostructure material systems, achieving room temperature terahertz emission. The second sample was fabricated in a double-decked HEMT structure in which the grating gate metal layer was replaced with the semiconducting upper-deck 2D electron layer, resulting in enhancement of emission by one order of magnitude.

Optical recordings of taste responses from fungiform papillae of mouse in situ

Single taste buds in mouse fungiform papillae consist of approximately 50 elongated cells (TBCs), where fewer than three TBCs have synaptic contacts with taste nerves. We investigated whether the non-innervated TBCs were chemosensitive using a voltage-sensitive dye, tetramethylrhodamine methyl ester (TMRM), under in situ optical recording conditions. Prior to the optical recordings, we investigated the magnitude and polarity of receptor potentials under in situ whole-cell clamp conditions. In response to 10 mM HCl, several TBCs were depolarized by approximately 25 mV and elicited action potentials, while other TBCs were hyperpolarized by approximately 12 mV. The TBCs eliciting hyperpolarizing receptor potentials also generated action potentials on electrical stimulation. A mixture of 100 mM NaCl, 10 mM HCl and 500 mM sucrose depolarized six TBCs and hyperpolarized another three TBCs out of 13 identified TBCs in a taste bud viewed by optical section. In an optical section of another taste bud, 1 M NaCl depolarized five TBCs and hyperpolarized another two TBCs out of 11 identified TBCs. The number of chemosensitive TBCs was much larger than the number of innervated TBCs in a taste bud, indicating the existence of chemosensitivity in non-innervated TBCs. There was a tendency for TBCs eliciting the same polarity of receptor potential to occur together in taste buds. We discuss the role of non-innervated TBCs in taste information processing.

Radiation exposure limits for Japanese astronauts

Starting in 2001, Japanese astronauts will live aboard the International Space Station (ISS) for 3 to 6 months a year. For astronauts, space radiation is primarily hazardous. Therefore, the National Space Development Agency of Japan (NASDA) is developing a system for Space Radiation Safety Operations. This report describes our overall image of Space Radiation Safety Operations aboard the ISS, especially our proceedings in drafting the "Space Radiation Exposure Limits for Japanese ISS Astronauts."

Behçet disease in children: a nationwide retrospective survey in Japan

The purpose of the present study was to evaluate the incidence of Behçet disease among Japanese children and to compare their clinical features with adult patients. A first questionnaire was sent to the department of pediatrics of 1290 hospitals in Japan. Fifty-one cases of Behçet disease among children under 16 years of age were reported. From a second survey, 31 cases satisfied the criteria of the Behçet's Syndrome Research Committee of Japan. Of 31 patients (14 boys and 17 girls), three cases were the complete type, 24 cases were the incomplete type, and four cases were the possible type. As to the specific type of the disease, 10 cases were of the entero-Behçet type, two were a combination of the entero-vasculo-Behçet type, and four were the neuro-Behçet type. In the first 6 months after onset, oral ulcers were observed in 77% of cases, genital ulcers in 45%, uveitis in 10%, and skin lesions were observed in 39% of cases. During the course of the disease, the frequency of oral ulcers was 100%, genital ulcers, 58%; ocular complications, 29%; and skin lesions, 55%. Gastrointestinal signs and symptoms were more frequent in childhood Behçet disease than in adults, while ocular complications were less frequent. The diagnosis of Behçet disease in children is difficult because of the long interval before the onset of enough manifestations to satisfy the diagnostic criteria. Specific diagnostic criteria are necessary, based on a discussion of the many childhood cases of Behçet disease.

Platelet-activating factor mediated potentiation of stimulation-evoked catecholamine release and the rise in intracellular free Ca2+ concentration in adrenal chromaffin cells

The effects of platelet-activating factor (PAF) on catecholamine (CA) release and intracellular free Ca2+ concentration ([Ca2+]i) were studied in cultured bovine adrenal chromaffin cells. PAF (1 nM-1 micron) alone had no effect on [Ca2+]i and basal CA release, but potentiated the [Ca2+]i rise and CA release evoked by acetylcholine (ACh) and by elevated extracellular K+. PAF did not potentiate the responses to caffeine in Ca(2+)-deficient medium or to Bay K 8644. In chromaffin cells pretreated with either BN 50739, tetrodotoxin and amiloride or in Na(+)-deficient medium, PAF failed to potentiate the stimulation-evoked [Ca2+]i rise and CA release. In contrast, neomycin, U 73122, 5-(N-ethyl-N-isopropyl)amiloride or pertussis toxin were ineffective in blocking the potentiating effect of PAF. In a membrane fraction prepared from fresh bovine adrenal medulla, ligand-binding studies using [3H]WEB 2086 identified a PAF-displaceable binding site. These results are consistent with a model in which PAF modulates CA release by activating plasma membrane receptors that can enhance the [Ca2+]i rise via an Na(+)-dependent mechanism.

Cyclic AMP enhances acetylcholine (ACh)-induced ion fluxes and catecholamine release by inhibiting Na+, K(+)-ATPase and participates in the responses to ACh in cultured bovine adrenal medullary chromaffin cells

The effects of cyclic AMP (cAMP) on intracellular Na+ concentration ([Na+]i), membrane depolarization and intracellular Ca2+ concentration ([Ca2+]i) and the involvement of cAMP in acetylcholine (ACh)-induced such cellular events and catecholamine (CA) release were studied in cultured bovine adrenal medullary chromaffin cells. 8-Bromo-cyclic AMP (8Br-cAMP) and forskolin caused a rise in [Na+]i, membrane depolarization and a rise in [Ca2+]i and potentiated these responses and CA release to ACh. The effects of 8Br-cAMP or forskolin on ACh-induced changes of but not on basal level of [Na+]i, membrane potential and [Ca2+]i were blocked by tetrodotoxin (TTX, 1 microM). In Na+ deprivated medium, forskolin failed to produce an increase in basal [Ca2+]i level and to potentiate ACh-induced rise. The similar results as in 8Br-cAMP and forskolin were obtained using ouabain, and 8Br-cAMP or foskolin produced no further effects in the presence of ouabain. Inhibitors of cAMP-dependent protein kinase not only blocked the effects of 8Br-cAMP and forskolin on membrane depolarization, [Ca2+]i rise and CA release, but also reduced these responses to ACh. From the similarity between the effects of cAMP and those of ouabain on the cellular events and the counteraction of the effects of cAMP by ouabain, it may be suggested that cAMP produces its effects on ion fluxes and CA release probably via an inhibition of Na+, K(+)-ATPase in intact chromaffin and cAMP may participate in the responses to ACh.

Possible involvement of nitric oxide in acetylcholine-induced increase of intracellular Ca2+ concentration and catecholamine release in bovine adrenal chromaffin cells

The role of nitric oxide (NO) in neurotransmitter release was studied using bovine adrenal medullary chromaffin cells. L-Arginine and sodium nitroprusside (SNP) slightly increased the intracellular free calcium concentration ([Ca2+]i), and the effects of the agents were dependent on the presence of the extracellular Ca2+ ([Ca2+]o), but were not blocked by verapamil (30 microM) or diltiazem (30 microM). SNP enhanced the acetylcholine (ACh)-induced rise in [Ca2+]i in the presence but not in the absence of [Ca2+]o. The effects of L-arginine but not those of SNP were inhibited by N omega-nitro-L-arginine (L-NNA). L-NNA significantly reduced the ACh-induced rise in [Ca2+]i and catecholamine (CA) release, and the reduction was restored by L-arginine but not by D-arginine. These results suggest a possible involvement of NO in ACh-induced [Ca2+]i rise and CA release in bovine adrenal chromaffin cells.

Cyclic AMP-induced depolarization measured by bis-oxonol fluorescence in bovine adrenal medullary chromaffin cells

Effects of cyclic AMP on membrane potentials were examined by measuring the changes of bis-oxonol fluorescence in bovine adrenal medullary chromaffin cells. 8-Bromo cyclic AMP (8Br-cAMP) or forskolin caused a gradual and long lasting increase of the fluorescence intensity. The effects of 8br-cAMP was blocked by cyclic AMP-dependent protein kinase inhibitor, adenosine-3', 5'-cyclic monophosphothioate, Rp-diastereomer (Rp-cAMPS) and there was no further increase in the fluorescence by 8br-cAMP in the cells depolarized with 56 mM KC1 or gramicidin D. Ouabain or the removal of extracellular K+ ([K+]0 free) which block Na+, K+-ATPase also increased the fluorescence. The effect of 8br-cAMP on the fluorescence was counteracted by ouabain or [K+]0 free and was blocked in the absence of extracellular Na+ but not by tetrodotoxin or the removal of Ca2+ from the medium. These results may suggest that cyclic AMP causes the membrane depolarization by accumulating Na+ through the inhibition of Na+, K+-ATPase in adrenal chromaffin cells.

[A ciclosporin A responsive case of Behçet's disease associated with IgA nephropathy]

A case of Behçet's disease with IgA nephropathy was reported in a 17 year old man. He presented with microscopic hematuria which was pointed out by urinary mass screening for school children at age of 14. As he was subsequently evolved proteinuria, a renal biopsy was performed at age of 16. The specimen showed diffuse proliferation of mesangial cells. Immunofluorescent studies showed granular deposition of IgA. At age of 17, he showed typical symptoms of Behçet's disease, namely aphthous stomatitis, perianal ulcers, erythema nodosum-like lesions, uveitis and genital aphtha. Furthermore he showed an increasing of proteinuria and an impairment of his renal function. Serum IgA level and immune complexes during the exacerbation stage were elevated. The uveitis markedly improved with ciclosporin A therapy. Reduction of proteinuria and improvement of renal function were simultaneously observed. These findings may suggest that IgA nephropathy and Behçet's a disease have common immunological pathogenesis, including circulating immune complexes.

Involvement of Ca2+ entry and inositol trisphosphate-induced internal Ca2+ mobilization in muscarinic receptor-mediated catecholamine release in dog adrenal chromaffin cells

Catecholamine (CA) release from adrenal medulla evoked by muscarinic receptor stimulation has been studied using isolated perfused adrenal gland and cultured chromaffin cells from dogs. Muscarine and oxotremorine (1-100 microM), and bethanechol (0.1-1 mM) dose-dependently stimulated CA release. Muscarine-evoked CA release was antagonized with M1-antagonist, pirenzepine and, to a lesser extent, with atropine; and was reduced either by removal of extracellular Ca2+ or treatment with Ca2+ channel blockers. Muscarine caused an increase of 45Ca uptake and 22Na uptake. Tetrodotoxin (TTX) did not affect muscarine-evoked increase of 22Na uptake and CA release. Under the absence of extracellular Ca2+, muscarine stimulated a 45Ca efflux. Muscarine-induced CA release was attenuated by treating the cells with 8-(N,N-diethylamino)-octyl-3,4,5-trimethoxybenzoate-HCl (TMB-8) which blocks Ca2+ release from the intracellular store. A phospholipase C inhibitor, neomycin, markedly reduced muscarine-induced CA release but not nicotine- and high K(+)-evoked release. Cinnarizine, a Ca2+ channel blocker, attenuated muscarine-evoked but not caffeine-induced CA release and 45Ca efflux in the absence of extracellular Ca2+. Muscarine caused an increase in intracellular free Ca2+ concentration ([Ca2+]i) in the presence of extracellular Ca2+. It caused a similar increase, but to a lesser extent, in the absence of extracellular Ca2+. The increase of [Ca2+]i induced by muscarine without extracellular Ca2+ was reduced by neomycin and cinnarizine. Polymixin B and retinal, which reduced 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced CA release, had little effect on muscarine-induced CA release. Muscarine increased cellular Ins(1,4,5)P3 production, and atropine inhibited this increase.(ABSTRACT TRUNCATED AT 250 WORDS)

Lipoma of the corpus callosum: report of a case and review of the literature

A case of lipoma of the corpus callosum associated with subcutaneous lipoma, whose symptoms were headache and trembling of the extremities, was reported. Roentgenograms showed characteristic findings and computerized tomography revealed a mass of very low density. The literature was reviewed and 15 cases not included in previous compilations were found. Clinical and radiological findings in 89 cases including the present case were analyzed.