Experimental observation of a magnetic-turbulence threshold for runaway-electron generation in the TEXTOR tokamak.

Magnetic turbulence is observed at the beginning of the current quench in intended TEXTOR disruptions. Runaway electron (RE) suppression has been experimentally found at magnetic turbulence larger than a certain threshold. Below this threshold, the generated RE current is inversely proportional to the level of magnetic turbulence. The magnetic turbulence originates from the background plasma and the amplitude depends strongly on the toroidal magnetic field and plasma electron density. These results explain the previously found toroidal field threshold for RE generation and have to be considered in predictions for RE generation in ITER.

Magnetic topology changes induced by lower hybrid waves and their profound effect on edge-localized modes in the EAST tokamak.

Strong mitigation of edge-localized modes has been observed on Experimental Advanced Superconducting Tokamak, when lower hybrid waves (LHWs) are applied to H-mode plasmas with ion cyclotron resonant heating. This has been demonstrated to be due to the formation of helical current filaments flowing along field lines in the scrape-off layer induced by LHW. This leads to the splitting of the outer divertor strike points during LHWs similar to previous observations with resonant magnetic perturbations. The change in the magnetic topology has been qualitatively modeled by considering helical current filaments in a field-line-tracing code.

Diffusion in a collisional standard map.

Test particle evaluation of the diffusion coefficient in the presence of magnetic field fluctuations and binary collisions is presented. Chaotic magnetic field lines originate from resonant magnetic perturbations (RMPs). To lowest order, charged particles follow magnetic field lines. Drifts and interaction (collisions) with other particles decorrelate particles from the magnetic field lines. We model the binary collision process by a constant collision frequency. The magnetic field configuration including perturbations on the integrable Hamiltonian part is such that the single particle motion can be followed by a collisional version of a Chirikov-Taylor (standard) map. Frequent collisions are allowed for. Scaling of the diffusion beyond the quasilinear and subdiffusive behaviour is investigated in dependence on the strength of the magnetic perturbations and the collision frequency. The appearance of the so called Rechester-Rosenbluth regime is verified. It is further shown that the so called Kadomtsev-Pogutse diffusion coefficient is the strong collisional limit of the Rechester-Rosenbluth formula. The theoretical estimates are supplemented by numerical simulations.

Suppression of pituitary TSH secretion in the patient with a hyperfunctioning thyroid nodule.

10 patients with a single hyperfunctioning thyroid nodule each were studied for pituitary thyrotropin (TSH) suppression. They were judged to be euthyroid on clinical grounds. The total thyroxine (T(4)D), free thyroxine (FT(4)), total triiodothyronine (T(3)D), and free triiodothyronine (FT(3)) were normal in most of the patients. Incorporation of (131)I into the hyperfunctioning thyroid nodules was not suppressed by the administration of physiological doses of T(3). Basal serum TSH concentrations were undetectable (<0.5 - 1.0 muU/ml) in all patients. The metabolic clearance of TSH in one patient before and after excision of the thyroid nodule was unchanged (40 vs. 42 ml/min) whereas the calculated production rate was undetectable before the operation (<29 mU/day) and normal after (103 mU/day). These data, in one patient, suggest that the undetectable concentration of TSH in these patients is a result of suppressed TSH secretion rather than accelerated TSH clearance. In eight patients, basal serum TSH concentrations failed to increase after the intravenous administration of 200 mug of thyrotropin-releasing hormone (TRH); minimal increases in serum TSH concentrations were observed in two patients. The suppression of TSH was evident despite "normal" concentrations of circulating thyroid hormones. The observation that normal serum concentrations of T(4)D, FT(4), T(3)D, and FT(3) may be associated with undetectable basal serum TSH concentrations and suppressed TSH response to TRH was also found in four hypothyroid patients given increasing doses of L-thyroxine and sequential TRH stimulation tests.

Recent developments of in-vessel calibration of mid-IR cameras at JET.

Recent improvements in software tools and methodology have allowed us to perform a more comprehensive in-vessel calibration for all mid-infrared camera systems at JET. A comparison of experimental methods to calculate the non-uniformity correction is described as well as the linearity for the different camera systems. Measurements of the temperature are assessed for the different diagnostics.

Periodate treatment reduces the tetrodotoxin-sensitivity of voltage-gated Na+ channels.

(1) Voltage-clamped nerve fibres of the frog Rana esculenta were treated with periodate in the extracellular solution. (2) Periodate treatment irreversibly reduced the effect of tetrodotoxin (TTX) on the Na+ currents. (3) The effect of saxitoxin (STX) was also reduced but less than that of TTX. (4) The presence of STX during the application of periodate to the nerve fibre almost completely prevented the effect of the chemical reagent on the TTX sensitivity of the Na+ channels. (5) The reduction of the TTX effect is not due to the reaction of small amounts of periodate with the diol group of this toxin, because the effect was seen after prolonged washing with reagent-free Ringer solution with or without high amounts of ribose. (6) Carboxyl groups present in the Na+ channel seem to be quite important for the binding of TTX and STX. Periodate modifies several amino acid side chains, however, it does not attack carboxyl groups in a peptide chain. Thus, these results suggest that periodate modifies a further group critically involved in the binding of TTX and STX.

Purification and characterization of a beta-toxin from the venom of the African scorpion Leiurus quinquestriatus.

The venom of the African scorpion Leiurus quinquestriatus was subjected to high-performance ion-exchange chromatography. Among a large number (greater than 25) of small proteins and other substances, a protein component of approx. 6500 Da was purified. The effect of this toxin was tested on single myelinated nerve fibres of the frog Rana esculenta. Toxin concentrations less than 10 nM produced clear effects. Activation rather than inactivation of the voltage-dependent sodium channel was strongly affected. Thus, this toxin from an African scorpion acts like the beta-toxins present in the venom of North American scorpions.

Effects of flurbiprofen and aspirin on the gastric and duodenal mucosa. An endoscopic comparison.

A single-blind, randomized endoscopic tolerance study was conducted to compare daily doses of flurbiprofen (Ansaid, Upjohn) at 100, 150, and 200 mg per day with 2,600 mg of aspirin per day. Ten normal volunteers were enrolled in each of the flurbiprofen groups, and five were enrolled in the aspirin group. Analysis of the mean gastric mucosal injury scores obtained on day eight revealed statistically significant lower mean scores (p = 0.05) in the 100-mg and 150-mg flurbiprofen treatment groups when compared with the 200-mg flurbiprofen group and the aspirin group. No significant differences were found between any of the treatment groups in duodenal mucosal injury scores. Mean scores for gastric mucosal injury in the three groups receiving flurbiprofen showed a definite dose relationship. The aspirin-treated subjects had significantly decreased uric acid levels (p = 0.006) and a significantly higher incidence of tinnitus (p = 0.04) compared with the flurbiprofen treatment groups. There was a poor correlation between subjective symptomatology and endoscopic pathologic findings.

Placebo-controlled, randomized, evaluator-blinded endoscopy study of risedronate vs. aspirin in healthy postmenopausal women.

BACKGROUND: Bisphosphonates are effective treatments for osteoporosis. Since some primary amino bisphosphonates are associated with oesophageal injury, we conducted a study of the upper gastrointestinal effects of risedronate, a pyridinyl bisphosphonate. METHODS: Healthy, postmenopausal women received risedronate 5 mg (n=26), aspirin 2600 mg (n=27), or placebo (n=27) daily for 14 days and underwent endoscopy at baseline, Day 8 and Day 15. RESULTS: Oesophageal erosions were noted in one subject in the aspirin group, two in the placebo group, and none in the risedronate group, and an ulcer in one aspirin-treated subject. Gastric erosions and ulcers were observed most frequently in the aspirin group. Gastric ulcers were noted in eight subjects in the aspirin group, one in the placebo group, and none in the risedronate group (P=0.010, placebo vs. aspirin; P=0.002, risedronate vs. aspirin). Duodenal erosions and ulcers were observed in the aspirin group only. Gastroduodenal erosion scores of three or more occurred more frequently in the aspirin than in the risedronate and placebo groups (P < 0.001). CONCLUSIONS: Risedronate 5 mg was not associated with oesophageal or gastroduodenal ulcers in healthy, postmenopausal women, a population representative of patients who will receive risedronate in the clinical setting.

Specific inhibition of cyclooxygenase-2 with MK-0966 is associated with less gastroduodenal damage than either aspirin or ibuprofen.

BACKGROUND: Compared with currently available NSAIDs (which inhibit COX-1 and COX-2 isoforms of cyclooxygenase), MK-0966 (a specific COX-2 inhibitor) is expected to cause less gastrointestinal toxicity. AIM: To compare the effect on the upper gastrointestinal mucosae of a high dose of MK-0966 with that of conventional doses of ibuprofen and aspirin. METHODS: Healthy subjects (n = 170; age range 18-54 years) with endoscopically normal gastric and duodenal mucosa were randomized to either MK-0966 250 mg q.d. (n = 51), ibuprofen 800 mg t.d.s. (n = 51), aspirin 650 mg q.d.s. (n = 17), or placebo (n = 51) in this 7-day, double-blind, parallel-group study. The mucosae were evaluated by endoscopy using a predefined scale; scores could range from 0 to 4. The primary end-point was the percentage of subjects who developed a mucosal score >/= 2 (i.e. the development of one or more erosions). To evaluate COX-1 activity, serum thromboxane B2 levels were determined in a subset of the population. RESULTS: The percentage of subjects who developed a mucosal score >/= 2 in the MK-0966 group (12%) was significantly lower (P < 0.001) than that in the ibuprofen (71%) and aspirin (94%) groups, and was similar to that in the placebo group (8%). Only ibuprofen and aspirin significantly (P < 0.0001) reduced baseline thromboxane B2 levels. All treatments were generally well tolerated. CONCLUSIONS: In this acute short-term endoscopic study, MK-0966 250 mg q.d. (a dose at least 10 times higher than that demonstrated to reduce the signs and symptoms of osteoarthritis) produced significantly less gastrointestinal mucosal damage than either ibuprofen 800 mg t.d.s. or aspirin 650 mg q.d.s. and was comparable to placebo in this regard.

Heterogeneous ultrastructure of melanosome formation in the goldfish induced by osmotic stress.

In this study, melanophore cytodifferentiation in the fins of xanthic goldfish that had been exposed to osmotic stress for 18 days was investigated. It was found that multi-vesicular bodies (MVB) are not the only type of premelanosome. Granules having a homogeneous matrix also function as premelanosomes. The presence of acid phosphatase reaction product inside the melanin granules indicated that these organelles in this animal were also related to lysosomes. DOPA-oxidase of tyrosinase, the key enzyme in melanogenesis, was surprisingly not only detected in melanocytes but also in the Golgi stacks of dermal cells. Due to the mechanisms of premelanosome formation it is evident that cytoplasmic material also serves as substrate for melanogenesis. EDX microanalysis was performed to measure the ionic composition of the melanin granules. After aldehyde fixation the newly-formed melanin granules did not contain Na, but had accumulated Ca.

A controlled endoscopic study comparing the toxic effects of sulindac, naproxen, aspirin, and placebo on the gastric mucosa of health volunteers.

Sixty volunteers were endoscopically evaluated to compare gastric mucosal injury following oral administration of sulindac, naproxen, aspirin, or placebo for two consecutive seven-day periods. A single-blind technique was utilized wherein the endoscopist was unaware which drug each volunteer had received. The following dosages were employed for the two study periods: sulindac, 150 and 200 mg, b.i.d., naproxen, 250 and 375 mg, b.i.d., and aspirin, 650 and 975 mg, q.i.d. The only subject who developed a frank ulcer with mucosal bleeding was in the sulindac group, however volunteers taking sulindac demonstrated statistically less significant mucosal injury on endoscopic examination than those receiving naproxen or aspirin.

Preparation of a toxic derivative of sea anemone toxin II from Anemonia sulcata which has peroxidase activity.

Sea anemone toxin II (ATX II) is a useful tool for investigation of sodium channels in excitable membranes. Coupling of ATX II with microperoxidase, a heme-octapeptide, is described. The isolated cross-linked product possesses both toxic and peroxidase activity. The lowest concentration of the modified toxin that affects the action potential and the membrane currents in single cardiac myocytes is 16 nM. The enzymatically active ATX II derivative may be useful for biochemical applications and as a non-radioactive tracer for electron microscopy studies of excitable tissue.

Preparation and properties of fluorescence labeled neuro- and cardiotoxin II from the sea anemone (Anemonia sulcata).

Labeling of the sea anemone toxin II with fluoresceinisothiocyanate is described. The native toxin and low molecular weight fluorescent compounds were completely separated from the derivative. Compared to fluorescein, the fluorescence of the toxin-derivative has a red shift and a decreased quantum yield. Like the native toxin, the fluorescent derivative affects the voltage-dependent sodium channel in nerve membranes. Under voltage-clamp conditions, the effect of the modified toxin on the inactivation of sodium channels was 45% of that of the unlabeled toxin.

Interaction of guanosine 5'-triphosphate binding protein Gq from Sepia officinalis with illuminated rhodopsin bound to concanavalin A.

The heterotrimeric guanosine 5'-triphosphate (GTP)-binding protein Gq was suggested to couple the light receptor rhodopsin with the effector phospholipase C in visual cells of invertebrates. We indirectly linked Gq from Sepia officinalis to a concanavalin A-sepharose column via rhodopsin. Rhodopsin had been solubilized previously with 10 mM n-dodecyl-beta-maltoside from the purified photosensory membrane under illumination. All three subunits of the Gq were released almost pure by elution with 100 microM GTP. The alpha and beta subunits were identified by specific antipeptide antisera. The alpha subunit has a relative molecular mass of 46 kDa, and the beta subunit of 35 kDa. The gamma subunit corresponds to a 9 kDa polypeptide owing to the molecular mass, which is similar to the G gamma subunit of squid. The use of specific antibodies shows that neither actin nor G-protein related to transducin were in the fractions eluted with GTP or alpha-methyl mannoside. We demonstrate that all three subunits of Gq were associated with rhodopsin of invertebrates. Such use of a lectin column might be useful for further investigations of the interaction of rhodopsin and Gq.

Immunoelectron-microscopic study of G-protein distribution in photoreceptor cells of the cephalopod Sepia officinalis.

Previous studies suggest that more than one single light-stimulated transduction pathway seems to be present in photoreceptor cells of invertebrates. Accordingly, more than one light-dependent G-protein has been detected in squid photoreceptor cells. Two different antibodies were used to locate the distribution of G-proteins in Sepia photoreceptors. One antiserum (anti-G alpha-common) has been raised against the peptide CGAGESGKSTIVKQMK. This sequence is found in most G alpha-protein subunits, it is also present in transducin of vertebrates. This sequence however, is conserved only partially in G alpha q from photosensory membranes of the squid. The second antiserum (anti-G alpha q) has been raised against the peptide QLNLKEYNLV. This sequence is present at the C-terminus of e.g. G alpha q from mouse brain and is identical also in squid. Anti-G alpha q very strongly interacted with the rhabdomeres of the photoreceptor cells from Sepia. In the non-rhabdomeric cytoplasm of the photoreceptor cells gold granules (bound to the second antibody) were almost absent. With anti-G alpha-common, only a small number of gold particles could be found at the rhabdomeres. The non-rhabdomeric cytoplasm was not labelled. Thus, further G-proteins that might be involved in a light dependent phototransduction mechanism besides the phosphoinositide pathway can hardly be expected to belong to the group of 'common' G-proteins.

A rotating directional probe for the measurements of fast ion losses and plasma rotation at Tokamak Experiment for Technology Oriented Research.

This work discusses a new directional probe designed for measurements of fast ion losses and the plasma rotation with a high angular resolution in magnetically confined plasmas. Directional and especially Mach probes are commonly used diagnostics for plasma flow measurements, and their applicability for the fast ion losses detection has been demonstrated. A limitation of static Mach probes is their low angular resolution. At the Tokamak Experiment for Technology Oriented Research, the angular resolution is strongly restricted by the finite number of available measurement channels. In a dynamic plasma, where instabilities can lead to local changes of the field line pitch-angle, plasma flow, or fast ion losses, a low angular resolution makes a precise data analysis difficult and reduces the quality of the measured data. The new probe design, the rotating directional probe, combines the features of early directional probes and Mach probes. It consists of two radially aligned arrays of nine Langmuir probe pins with each array facing opposite directions. During the measurement the probe head rotates along its axis to measure the ion saturation current from all directions. As a result, the rotating directional probe simultaneously provides an angular dependent plasma flow and fast ion losses measurement at different radial positions. Based on the angular dependent data, a precise determination of the current density is made. In addition, the simultaneous measurement of the ion saturation current at different radial positions allows for resolving radially varying field line pitch-angles and identifying the radial dynamic of processes like fast ion losses.

Upgrade of the infrared camera diagnostics for the JET ITER-like wall divertor.

For the new ITER-like wall at JET, two new infrared diagnostics (KL9B, KL3B) have been installed. These diagnostics can operate between 3.5 and 5 µm and up to sampling frequencies of ∼20 kHz. KL9B and KL3B image the horizontal and vertical tiles of the divertor. The divertor tiles are tungsten coated carbon fiber composite except the central tile which is bulk tungsten and consists of lamella segments. The thermal emission between lamellae affects the surface temperature measurement and therefore KL9A has been upgraded to achieve a higher spatial resolution (by a factor of 2). A technical description of KL9A, KL9B, and KL3B and cross correlation with a near infrared camera and a two-color pyrometer is presented.