Energy transfer and dual cascade in kinetic magnetized plasma turbulence.

The question of how nonlinear interactions redistribute the energy of fluctuations across available degrees of freedom is of fundamental importance in the study of turbulence and transport in magnetized weakly collisional plasmas, ranging from space settings to fusion devices. In this Letter, we present a theory for the dual cascade found in such plasmas, which predicts a range of new behavior that distinguishes this cascade from that of neutral fluid turbulence. These phenomena are explained in terms of the constrained nature of spectral transfer in nonlinear gyrokinetics. Accompanying this theory are the first observations of these phenomena, obtained via direct numerical simulations using the gyrokinetic code AstroGK. The basic mechanisms that are found provide a framework for understanding the turbulent energy transfer that couples scales both locally and nonlocally.

Gyrokinetic simulations of solar wind turbulence from ion to electron scales.

A three-dimensional, nonlinear gyrokinetic simulation of plasma turbulence resolving scales from the ion to electron gyroradius with a realistic mass ratio is presented, where all damping is provided by resolved physical mechanisms. The resulting energy spectra are quantitatively consistent with a magnetic power spectrum scaling of k(-2.8) as observed in in situ spacecraft measurements of the "dissipation range" of solar wind turbulence. Despite the strongly nonlinear nature of the turbulence, the linear kinetic Alfvén wave mode quantitatively describes the polarization of the turbulent fluctuations. The collisional ion heating is measured at subion-Larmor radius scales, which provides evidence of the ion entropy cascade in an electromagnetic turbulence simulation.

Caffeic acid is a selective inhibitor for leukotriene biosynthesis.

.eukotrienes are significantly involved in immunoregulation and in a variety of diseases, including asthma, inflammation and various allergic conditions. They are initially biosynthesized by 5-lipoxygenase from arachidonic acid, which can also be metabolized to prostaglandin endoperoxide by cyclooxygenase. The specific inhibitors for 5-lipoxygenase would be useful not only as tools for investigating the regulation mechanism of leukotriene biosynthesis, but also as drugs for clinical use. Although recently a few selective inhibitors have been reported, most of them are difficult to obtain, since they are new compounds. We found that caffeic acid, which is one of the most common reagents, is a selective inhibitor for 5-lipoxygenase and therefore for leukotriene biosynthesis. The inhibitory effect of its methyl ester on 5-lipoxygenase (ID50 = 4.8 X 10(-7) M) was stronger than that of caffeic acid itself (ID50 = 3.7 X 10(-6) M). Caffeic acid inhibited 5-lipoxygenase in a non-competitive manner. Caffeic acid and its methyl ester did not inhibit prostaglandin synthase activity at all, at least up to 5 X 10(-4) M, but rather stimulate at higher doses. The biosynthesis of leukotriene C4 and D4 in mouse mast tumor cells was also inhibited completely with 10(-4) caffeic acid. Besides, caffeic acid had little effect on arachidonic acid metabolism in platelet at less than 1 X 10(-5) M, but at higher doses it showed a definite inhibitory effect, i.e., thromboxane B2, HHT (12(S)-hydroxy-5,8,10-heptadecatetraenoic acid) and 12-HETE (12(S)-hydroxy-5,8,10,14-eicosatetraenoic acid) syntheses were inhibited 33, 40 and 80% at 1 X 10(-4) M, respectively. Platelet aggregation induced by arachidonic acid was also inhibited by caffeic acid at high dose, while platelet aggregation induced by ADP is not influenced by caffeic acid at all. The observations on caffeic acid and its derivatives may contribute to leukotriene research.

Basic FGF, NGF, and IGFs protect hippocampal and cortical neurons against iron-induced degeneration.

Iron is believed to contribute to the process of cell damage and death resulting from ischemic and traumatic insults by catalyzing the oxidation of protein and lipids. Exposure of cultured rat hippocampal neurons to iron (FeSO4) caused a dose-dependent reduction in neuronal survival, which was potentiated by ascorbate. Damage to neurons was associated with a significant level of oxygen radical in the culture medium. The iron chelator desferal prevented both the neuronal degeneration caused by FeSO4 and the production of oxygen radical, demonstrating that ionic iron was responsible for the cell damage. Iron neurotoxicity was associated with an elevation of [Ca2+]i and was attenuated by NMDA receptor antagonists. Since recent findings demonstrated neuroprotective effects of growth factors in cell culture and in vivo models of ischemia, we examined the effects of growth factors on iron-induced damage. Basic fibroblast growth factor (bFGF), nerve growth factor (NGF), and insulin-like growth factors (IGF-I and IGF-II) each protected neurons against iron-induced damage. Both rat hippocampal and human cortical neurons were protected by these growth factors. Taken together, the data suggest that the neuroprotective effects of growth factors against excitotoxic/ischemic insults may result, in part, from a prevention or attenuation of oxidative damage.

Selective inhibition of 5-lipoxygenase by natural compounds isolated from Chinese plants, Artemisia rubripes Nakai.

Three of four natural compounds, which are caffeic acid, eupatilin and 4'-demethyleupatilin, isolated from Chinese plant, Artemisia rubripes Nakai selectively inhibited 5-lipoxygenase of cultured mastocytoma cells. Half-inhibition doses (ID50) for caffeic acid, eupatilin and 4'-demethyleupatilin were 3.7, 14 and 18 X 10(-6) M, respectively. The inhibition by caffeic acid was non-competitive types. Prostaglandin synthase activities were little inhibited by eupatilin and 4'-demethyleupatilin, but rather stimulated by caffeic acid. The formation of leukotriene C4 and D4 by mast tumor cells was almost completely suppressed by these compounds at 10(-4) M.

Tricyclic quinoxalinediones: 5,6-dihydro-1H-pyrrolo[1,2,3-de] quinoxaline-2,3-diones and 6,7-dihydro-1H,5H-pyrido[1,2,3-de] quinoxaline-2,3-diones as potent antagonists for the glycine binding site of the NMDA receptor.

A series of tricyclic quinoxalinediones, 5,6-dihydro-1H-pyrrolo[1,2,3-de]quinoxaline-2,3-diones and 6,7-dihydro-1H,5H-pyrido[1,2,3-de]quinoxaline-2,3-diones, were synthesized and was evaluated for their affinity for the glycine binding site of the NMDA receptor using a [3H]-5,7-dichlorokynurenic acid binding assay. The six-membered ring-fused tricyclic quinoxalinedione 18g (Ki = 9.9 nM) displayed high affinity for the glycine site. The anilide derivative 20g (Ki = 2.6 nM) was 4-fold more potent than 18g and as potent as L-689,560, one of the most potent glycine antagonists so far prepared. Although the carboxylic acid derivative of the corresponding five-membered ring-fused tricyclic quinoxalinedione 18e (Ki = 7.3 nM) had affinity comparable to that of 18g, the anilide derivative 20e largely decreased in the affinity in contrast to 20g. Enantiomers 23g, 24g, 25g, and 26g were prepared and tested. Only the S enantiomer 25g (Ki = 0.96 nM) retained the affinity among the anilide derivatives, whereas both enantiomers 23g (Ki = 2.3 nM) and 24g (Ki = 9.6 nM) were active among the carboxylic acid derivatives. The origin of the high affinity of carboxylic acid derivatives such as 18e and 18g would be a charge-charge interaction between the anionic carboxylate residues of the compounds and the cationic proton-donor site in the receptor.

BDNF attenuates retinal cell death caused by chemically induced hypoxia in rats.

PURPOSE: To investigate the neuroprotective effects of brain-derived neurotrophic factor (BDNF) against potassium cyanide (KCN)-induced retinal damage. METHODS: Rats were injected intravitreally with iodinated BDNF. Two days later, eyeballs were dissected into various parts, and the level of radioactivity in each part was measured. Retinal damage was induced by incubating rat eyeballs with 5 mM KCN. BDNF was injected intravitreally 2 days before KCN treatment, and subsequent morphometric analysis was carried out to evaluate the retinal cell damage. To elucidate the mechanisms of BDNF's neuroprotective effects, the intravitreal concentrations of amino acids and the expression of calretinin were investigated. RESULTS: Intravitreally injected BDNF was distributed evenly throughout the eyes, and the incorporation of iodinated BDNF into the retina was three times higher than in other ocular tissues. Immunohistochemical analysis demonstrated that exogenous BDNF diffused throughout the retina and was especially concentrated in the inner (INL) and outer nuclear layer. Morphometric analysis showed that the number of INL cells of the posterior area, 880 microm from the optic nerve head, was 190 +/- 4 with KCN treatment and 284 +/- 9 in control animals. Cell death appeared to be necrotic. When eyes injected with either phosphate-buffered saline (PBS) or BDNF were subjected to treatment with KCN, the number of INL cells was 186 +/- 5 in the PBS-treated controls and 253 +/- 8 in eyes treated with BDNF. Also, BDNF increased the number of calretinin-positive cells in the INL and reduced the KCN-induced elevation of intravitreal glutamate levels. CONCLUSIONS: BDNF injected intravitreally reaches the retina and attenuates the INL cell death caused by KCN-induced metabolic insult. The neuroprotective effects of BDNF are partly ascribed to the upregulation of a calcium-binding protein and the attenuation of glutamate release into the vitreous body.

Analysis of effects and pharmacokinetics of subcutaneously administered BDNF.

Brain-derived neurotrophic factor (BDNF) belongs to the neurotrophin family and has been shown to be a potent and effective trophic factor for motor neurons and other neurons of the peripheral and central nervous. Little is known, however, about the relationship between the efficacy and pharmacokinetics of s.c. administered BDNF. In this study, the efficacy of BDNF on motor neuron protection in sciatic or facial nerve axotomy models was examined and compared with the concommitant concentrations of BDNF in plasma. Delayed treatment (started at 1 week after surgery) of BDNF was also shown to retard choline acetyltransferase reduction in sciatic nerve axotomy models.

Regulation of nerve growth factor secretion in L-M cells by catechol derivatives.

We investigated the mechanism responsible for the stimulation of nerve growth factor (NGF) secretion by catechol derivatives in L-M cells, using L-threo-3,4-dihydroxyphenylserine (L-DOPS). Treatment of the cells with L-DOPS increased the NGF content in the L-M cell medium by approximately 3-fold. This stimulatory effect was not blocked by a decarboxylase inhibitor, or by alpha- or beta-adrenergic blockers. Intracellular cAMP levels were not changed by exposure to L-DOPS. The antioxidants, ascorbic acid and sodium pyrosulfite, completely prevented the stimulatory effect of L-DOPS, and radical scavengers (superoxide dismutase plus catalase) caused a significant partial inhibition of the response to L-DOPS. Quinone derivatives (adrenochrome, 4-n-propyl-1,2-benzoquinone), which are the oxidative products of the catechol derivatives, increased the NGF content in the medium, and their potency was greater than that of the catechol derivatives themselves. These findings suggest that L-DOPS and other catechol derivatives might be oxidized in the medium to form quinone derivatives, and that it is these which predominantly express a stimulatory effect on NGF secretion by a novel cAMP-independent mechanism in L-M cells.

Neuroprotective effects of brain-derived neurotrophic factor in eyes with NMDA-induced neuronal death.

PURPOSE: To determine if brain-derived neurotrophic factor (BDNF) has a neuroprotective effect against N-methyl-D-aspartate (NMDA)-induced cell death in retina. METHODS: NMDA was injected into the vitreous of rat eyes. NMDA-induced neuronal death was measured by morphometric analyses on cell counts of ganglion cell layer cells and thickness of retinal layers. Also, we conducted additional experiment using retrograde labeling with a fluorescent tracer (Fluoro-Gold) for exact counting of retinal ganglion cells (RGCs). In addition, intravitreal glutamate levels were measured with the use of a high-performance liquid chromatography (HPLC) system. RESULTS: Morphometric analysis of retinal damage in NMDA-injected eyes showed that BDNF could protect inner retinal cells from glutamate receptor-mediated neuronal death. Also, counts of RGCs labeled with a fluorescent tracer showed that BDNF could protect RGCs from glutamate receptor-mediated neuronal death. Furthermore, measurements of intravitreal glutamate levels indicated an increase in this excitatory amino acid in the vitreous after NMDA injection. CONCLUSIONS: Exogenous BDNF can protect inner retinal cells (possible RGCs and amacrine cells) from NMDA-induced neuronal death. However, increased intravitreal glutamate levels in response to NMDA-mediated neurotoxicity may augment retinal degeneration.

Autoradiographic localization and pharmacological characterization of [3H]tandospirone binding sites in the rat brain.

The regional distribution and pharmacological properties of [3H]tandospirone binding sites in the rat brain were investigated using quantitative autoradiography. [3H]Tandospirone binding was notably high in the dentate gyrus and CA1 area of the hippocampus, lateral septum, entorhinal cortex, interpeduncular nucleus and dorsal raphe nucleus. The distribution profiles of [3H]tandospirone binding sites significantly correlated with that of serotonin (5-HT)1A receptors identified using [3H]8-OH-DPAT. In competitive binding studies, [3H]tandospirone binding was inhibited by 5-HT, 8-OH-DPAT, pindolol, buspirone and N-(a,a,a-trifluoro-m-tolyl)-piperazine. The potencies of these ligands correlated with their affinities for 5-HT1A receptors. In addition, there was no significant difference in the dissociation constant of [3H]tandospirone binding between the dentate gyrus, CA1 area, dorsal raphe nucleus, lateral septum and entorhinal cortex (about 10 nM) suggesting that [3H]tandospirone binds to 5-HT1A receptors with same affinities in these brain structures. The distribution pattern of binding sites for [3H]tandospirone was also compared with that of benzodiazepine receptors identified using [3H]fludiazepam to find common effector sites for different types of anxiolytics. Some similarities were observed. It is evident in the hippocampal formation that an overlap of intense binding occurred. 5-HT1A receptors in the hippocampus may participate in the anxiolytic effects of tandospirone.

Inhibition by 8-hydroxy-2-(di-n-propylamino) tetralin and SM-3997, a novel anxiolytic drug, of the hippocampal rhythmical slow activity mediated by 5-hydroxytryptamine1A receptors.

Electrophysiological studies using spectral analysis techniques were undertaken in rabbits to determine whether or not hippocampal rhythmical slow activity (RSA, theta wave activity) was affected by the 5-hydroxy-tryptamine1A (5-HT1A) agonists 8-hydroxy-2-(di-n-propyl-amino) tetralin (8-OH-DPAT) and 3a alpha, 4 beta, 7 beta, 7a alpha-hexahydro-2-(4-(4-(2-pyrimidinyl)-1-piperazinyl)-butyl)-4, 7-methano-1H-isoindole-1,3(2H)-dione dihydrogen citrate (SM-3997, a newly synthesized anxiolytic drug). Intravenous administration of 8-OH-DPAT and SM-3997 induced a desynchronized pattern with low-amplitude slow wave activity in the hippocampal EEG and inhibited RSA generation following stimulation of the midbrain reticular formation. RSA was also inhibited by 5-HT1A related anxiolytics such as buspirone, gepirone, and ipsapirone. The effects of 8-OH-DPAT and SM-3997 on the hippocampal RSA were blocked by pindolol, which has 5-HT1A antagonistic activity. Direct microinjection of these 5-HT1A selective agonists into the hippocampus inhibited generation of the hippocampal RSA. These findings indicated that 8-OH-DPAT and SM-3997 inhibited the hippocampal RSA by acting on hippocampal 5-HT1A receptors.

Trichothecene structure and toxicity to the green alga Chlorella pyrenoidosa.

Using the paper-disk method with Chlorella-seeded agar plates, 15-acetoxyscirpenol, HT-2 toxin, acetyl T-2 toxin and neosolaniol inhibited growth at a concentration of 1 mg/ml, whereas verrucarol, T-2 tetraol, nivalenol, fusarenon-X, deoxynivalenol and 3-acetyldeoxynivalenol were inactive. Taking into account that verrucarin A, roridin A, T-2 toxin and diacetoxyscirpenol had previously been found to strongly inhibit Chlorella growth, esterification at R15 appears to be important for growth inhibitory activity. The most active agents are also esterified at R4. Inhibition of protein synthesis appears to be involved in the toxicity.

Acceleration of actin polymerization and rapid microfilament reorganization in cultured hepatocytes by cyclochlorotin, a hepatotoxic cyclic peptide.

Cyclochlorotin (= chloropeptide, CC) is a hepatotoxic mycotoxin of Penicillium islandicum Sopp. The effect of CC on actin polymerization was examined by the measurement of changes in fluorescence intensity using pyrene-labeled actin and high shear viscosity. In the presence of CC, the time course of actin polymerization was accelerated in a dose dependent manner (2.5 ng/ml-2.5 microg/ml), without affecting the final level of viscosity. CC exerted a strong stabilizing effect on actin, enabling it to maintain its filamentous form in the presence of members of actin-binding proteins, including those of the gelsolin family prepared from hepatocytes. Microscopic observation revealed that in cultured hepatocytes, 1.0 microg/ml of CC induced bleb formation and changes in the microfilament. These observations indicated that after contact of the hepatocyte with CC, the following events were probable. The toxin passed through the cell membrane by a transport system and immediately reacted with the actin-actin binding proteins underlying the lipid bilayer. Bleb formation and hepatotoxicity were thus induced.

Enhanced mRNA expression of Th1 cytokines and IL-12 in active pulmonary sarcoidosis.

BACKGROUND AND AIM OF THE WORK: Active sarcoidosis is considered to be a Th1 dominant condition. We examined whether Th1 cytokines are highly expressed at inflammed lesions of Japanese patients with sarcoidosis. METHODS: To investigate the mRNA expression of Th1 cytokines and IL-12 in sarcoid BAL cells, we used semiquantitative reverse transcription--polymerase chain reaction method. RESULTS: The mRNA expressions of Th1 cytokines (IFN-gamma and IL-2) in active sarcoid BAL cells were significantly elevated as compared with those in healthy volunteers. The proportion of positive IL-4 mRNA expression in sarcoid BAL cells was not significantly higher than that in healthy volunteers. Further, there was no significant difference in IFN-gamma mRNA levels between the groups positive and negative for IL-4 mRNA expression. Although the proportion of positive expression of IL-12 mRNA in active sarcoid BAL cells was not significantly higher than that in healthy volunteers, the group positive for IL-12 mRNA expression had significantly elevated levels of IFN-gamma mRNA than did the negative group. CONCLUSIONS: These results may indicate that IL-12 induces IFN-gamma expression and subsequent Th1 dominant condition in Japanese patients with sarcoidosis.

Characterization of the putative anxiolytic SM-3997 recognition sites in rat brain.

In order to clarify the mechanism of action of the putative nonbenzodiazepine anxiolytic SM-3997 [3a alpha,4 beta,7 beta,7a alpha)-Hexahydro-2-(4-(4-(2-pyrimidinyl)-1- piperazinyl)-butyl)-4,7-methano-1H-isoindole-1,3 (2H)-dione dihydrogen citrate), in vitro binding studies with radiolabeled compound were performed. 3H-SM-3997 bound rapidly, reversibly and in a saturable manner with high affinity to rat brain hippocampal membranes (Kd = 9.4 nM, Bmax = 213 fmol/mg protein). This specific binding was displaced by 5-hydroxytryptamine (5-HT) and related compounds. Especially, 8-OH-DPAT, a 5-HT-1A selective agonist, bound with the highest affinity to these binding sites. 3H-SM-3997 binding, however, was not displaced by a variety of other neurotransmitters, neuropeptides and some other drugs. EDTA and physiological concentration of Na+ inhibited this specific binding, but several divalent cations, Mn2+, Ca2+ and Mg2+, enhanced this binding. GTP decreased the affinity of these binding sites for 3H-SM-3997 without changing the number of binding sites, but GMP and ATP did not influence 3H-SM-3997 binding. Furthermore, 3H-SM-3997 bound with marked regional selectivity to hippocampal membranes. These characteristics and the regional distribution of 3H-SM-3997 binding sites were very similar to those of 3H-8-OH-DPAT binding sites (5-HT-1A receptors). Therefore, these results indicate that SM-3997 binds selectively and with high affinity to 5-HT-1A receptors in rat brain and may be an agonist.

Effects of the putative anxiolytic SM-3997 on central monoaminergic systems.

The effects of SM-3997 on central monoaminergic systems were evaluated by ex vivo measurement of monoamines and their metabolite levels in rat brain after intraperitoneal treatment of drugs and by in vitro measurement of monoamine uptake into rat brain slices. The effects of SM-3997 were also compared with those of other new nonbenzodiazepine anxiolytic compounds. SM-3997, buspirone, gepirone and ipsapirone showed no effects on serotonin uptake and dopamine uptake, and a weak inhibition of norepinephrine uptake at the concentration of 100 microM. SM-3997 decreased the serotonin metabolite (5-hydroxyindole-3-acetic acid) level without changing the serotonin level in hippocampus and increased dopamine metabolite (3,4-dihydroxyphenylacetic acid, homovanillic acid) level with no effect on the dopamine level in striatum. SM-3997 also produced an increase in the norepinephrine metabolite (3-methoxy-4-hydroxyphenylglycol) level with a decrease in the norepinephrine levels in hippocampus. Similar effects on serotonin metabolites and norepinephrine metabolites were observed in several other regions. Although the serotonergic effect of SM-3997 was similar to that of buspirone, gepirone and ipsapirone, the dopaminergic effect of SM-3997 was much weaker than that of buspirone.

Vortex solitons: mass, energy, and angular momentum bunching in relativistic electron-positron plasmas.

It is shown that the interaction of large amplitude electromagnetic waves with a hot electron-positron (e-p) plasma (a principal constituent of the universe in the MeV epoch) leads to a bunching of mass, energy, and angular momentum in stable, long-lived structures. Electromagnetism in the MeV epoch, then, could provide a possible route for seeding the observed large-scale structure of the universe.

Angular momenta creation in relativistic electron-positron plasma.

Creation of angular momentum in a relativistic electron-positron plasma is explored. It is shown that a chain of angular momentum carrying vortices is a robust asymptotic state sustained by the generalized nonlinear Schrödinger equation characteristic to the system. The results may suggest a possible electromagnetic origin of angular momenta when it is applied to the MeV epoch of the early Universe.

Statistical characterization of the interchange-instability spectrum of a separable ideal-magnetohydrodynamic model system.

A Suydam-unstable circular cylinder of plasma with periodic boundary conditions in the axial direction is studied within the approximation of linearized ideal magnetohydrodynamics (MHD). The normal mode equations are completely separable, so both the toroidal Fourier harmonic index n and the poloidal index m are good quantum numbers. The full spectrum of eigenvalues in the range 1< or = m < or = m(max) is analyzed quantitatively, using asymptotics for large m, numerics for all m, and graphics for qualitative understanding. The density of eigenvalues scales like m(2)(max) as m(max) -->infinity . Because finite-m corrections scale as 1/ m(2)(max) , their inclusion is essential in order to obtain the correct statistics for the distribution of eigenvalues. Near the largest growth rate, only a single radial eigenmode contributes to the spectrum, so the eigenvalues there depend only on m and n as in a two-dimensional system. However, unlike the generic separable two-dimensional system, the statistics of the ideal-MHD spectrum departs somewhat from the Poisson distribution, even for arbitrarily large m(max) . This departure from Poissonian statistics may be understood qualitatively from the nature of the distribution of rational numbers in the rotational transform profile.