Effects of magnetic shear on toroidal rotation in tokamak plasmas with lower hybrid current drive.

Application of lower hybrid (LH) current drive in tokamak plasmas can induce both co- and countercurrent directed changes in toroidal rotation, depending on the core q profile. For discharges with q(0) <1, rotation increments in the countercurrent direction are observed. If the LH-driven current is sufficient to suppress sawteeth and increase q(0) above unity, the core toroidal rotation change is in the cocurrent direction. This change in sign of the rotation increment is consistent with a change in sign of the residual stress (the divergence of which constitutes an intrinsic torque that drives the flow) through its dependence on magnetic shear.

Influence of magnetic field ripple on the intrinsic rotation of tokamak plasmas.

Using the unique capability of JET to monotonically change the amplitude of the magnetic field ripple, without modifying other relevant equilibrium conditions, the effect of the ripple on the angular rotation frequency of the plasma column was investigated under the conditions of no external momentum input. The ripple amplitude was varied from 0.08% to 1.5% in Ohmic and ion-cyclotron radio-frequency (ICRF) heated plasmas. In both cases the ripple causes counterrotation, indicating a strong torque due to nonambipolar transport of thermal ions and in the case of ICRF also fast ions.

Stenting of the superior mesenteric vein in midgut carcinoid disease with large mesenteric masses.

BACKGROUND: Midgut carcinoid (MGC) tumors generally develop in the small intestine and in >50% of cases also present with lymph node metastases in the mesentery. The majority of these tumors are surgically resectable, but a fraction are inoperable and may cause obstruction of the superior mesenteric vein (SMV), often associated with stasis of the intestinal wall and severe symptoms. These symptoms include severe abdominal pain, attacks of diarrhea, and malnutrition. METHODS: Seven patients with severe MGC including a large fibrotic inoperable mesenteric mass and severe symptoms were studied. After an obstructed SMV and signs of venous stasis in the small intestine were demonstrated, an expandable stent was inserted after puncturing an intrahepatic portal venous branch. The associated venography, patient symptoms, and radiological signs on computed tomography (CT) scans were evaluated. RESULTS: Four patients demonstrated resolution of their symptoms. In one patient who had intra-abdominal lymph leakage/chyloperitoneum, a complete normalization of the circulation followed and the intra-abdominal lymph leakage stalled. The venographies demonstrated normalization of the venous blood flow through the SMV, and CT scans demonstrated reduction in the thickness of the intestinal wall. In two cases there were no changes in the symptoms, and in one case a slight worsening of the symptoms ensued. In general, reductions of symptoms were associated with the degree of normalization of venous blood flow. CONCLUSIONS: We conclude that in selected patients with MGC stenting of the SMV may improve symptoms.

Fractures of self-expanding metallic stents in periampullary malignant biliary obstruction.

BACKGROUND: Self-expanding metallic stents are widely used for relieving biliary duct obstruction in patients with unresectable periampullary malignancies. However, only a few studies have assessed the occurrence of fractures in these stents. PURPOSE: To determine the prevalence and significance of stent fracture after placement of self-expanding metallic stents for periampullary malignant biliary obstruction. MATERIAL AND METHODS: Over a 5-year period, 48 patients underwent placement of self-expanding metallic stents for periampullary malignant biliary obstructions. Stents were introduced 2-6 weeks after a percutaneous transhepatic biliary decompression. The medical records and relevant images were reviewed for stent patency, stent fracture, type of stent, and stent-related complications. RESULTS: Stent fracture was detected in four of the 48 patients (8%): in one patient at 1 month and in three patients between 10 and 21 months after stenting. All four fractures involved one type of nitinol stent used in 38 patients. In one of the patients, fracture was complicated by life-threatening gastrointestinal bleeding. The mean survival time for all patients was 251 days (standard deviation [SD]+/-275 days) and the mean overall patency time for all stents was 187 days (SD+/-205 days). CONCLUSION: Stent fracture occurs after placement of self-expanding nitinol stents for periampullary malignant biliary obstruction. The low reported incidence of this complication may be due to a lack of awareness of and difficulty in detecting stent fracture. Fracture should be considered as a possible contributing factor in recurrent biliary obstruction after self-expanding metallic stent insertion.

Localization of quinolinic acid metabolizing enzymes in the rat brain. Immunohistochemical studies using antibodies to 3-hydroxyanthranilic acid oxygenase and quinolinic acid phosphoribosyltransferase.

Specific antibodies raised in rabbits against 3-hydroxyanthranilic acid oxygenase (EC 1.13.11.6) and quinolinic acid phosphoribosyltransferase (EC 1.13.11.6) and quinolinic acid phosphoribosyltransferase (EC 2.4.2.19) were used in immunohistochemical studies to map the cellular localization of the quinolinic acid metabolizing enzymes in the adult male rat brain. 3-Hydroxyanthranilic acid oxygenase immunoreactivity was found to be present in glial cells of presumed astroglial identity, as judged by co-localization with glial fibrillary acidic protein. 3-Hydroxyanthranilic acid oxygenase-immunoreactive glial cells were present in all brain regions and within major fiber tracts. The density of 3-hydroxyanthranilic acid oxygenase-immunoreactive glial cells as well as the intensity of staining of these cells differed among brain regions. In general, telencephalic acid diencephalic areas harbored a larger number of 3-hydroxyanthranilic acid oxygenase-positive cells than did mesencephalic regions. In the former regions the caudate nucleus, septum, nucleus accumbens, neocortex and hippocampus were particularly enriched in 3-hydroxyanthranilic acid oxygenase-immunoreactive cells. In the thalamus, regional differences were noted with regard to the intensity of staining among glial cells with high densities of 3-hydroxyanthranilic acid oxygenase cells in the anteroventral, reticular and ventromedial nuclei. In the inferior and superior colliculi, numerous 3-hydroxyanthranilic acid oxygenase-positive glial cells were found in all layers. In the hypothalamus, 3-hydroxyanthranilic acid oxygenase-immunoreactive glial cells were encountered in the zona incerta, the lateral hypothalamic area, the caudal preoptic region and in the dorsomedial nucleus. In the mesencephalon, the substantia nigra contained numerous, moderately stained cells. At caudal levels of the brain-stem, a relatively large number of cells was detected in the nucleus of the solitary tract, the pontine nucleus and in the fascial nerve nucleus, while other nuclei, such as the reticular formation and the area postrema were relatively poor in 3-hydroxyanthranilic acid oxygenase-immunoreactive cells. In addition to staining of glial cells, neuronal cell bodies containing 3-hydroxyanthranilic acid oxygenase immunoreactivity were detected in the main and in the accessory olfactory bulb, as well as in the ventromedial nucleus of the hypothalamus. Quinolinic acid phosphoribosyltransferase immunoreactivity was observed within glial cells and in association with neuronal cell bodies. Some, but not all, quinolinic acid phosphoribosyltransferase positive glial cells contained glial fibrillary acidic protein (Köhl

Origin of the neuropeptide Y innervation of the rat retrohippocampal region.

Using the method of retrograde tracing of Fast Blue in combination with immunohistochemistry, the origins of the retrohippocampal neuropeptide Y (NPY) innervation was studied in the rat brain. The findings suggest that two NPY-immunoreactive (NPY-i) afferent systems, one intrinsic and the other of extrinsic origin give rise to the massive NPY innervation of the retrohippocampal region, including the entorhinal area (EA). The intrinsic projections originate from multipolar and fusiform cells situated primarily in layers IV through VI of the medial and lateral EA, as well as from a small number of NPY-i basket cells situated in layer II. Other NPY-i afferents originate from cortical neurons with long association projections located in the deep layers of the perirhinal area and in the piriform cortex, as well as from cells situated throughout the rostrocaudal extent of the endopiriform nucleus, in the lateral nucleus of amygdala and in the nucleus locus coeruleus.

Co-localization of neuropeptide tyrosine and somatostatin immunoreactivity in neurons of individual subfields of the rat hippocampal region.

The co-localization of neuropeptide tyrosine (NPY) and somatostatin (SOM) in rat hippocampal cells was studied in double labelling experiments using a combination of antibodies against the two peptides on the same tissue section. The individual hippocampal subfields show large variations in the relative number of NPY- and SOM-immunoreactive (-i) neurons. While the entorhinal area is far richer in SOM as compared to NPY-i cells, NPY-i cells predominate in all subfields (e.g. regio superior, regio inferior) of Ammon's horn. Co-localization of both peptides in single neurons was highest in regio inferior and in the area dentata and lowest in the retrohippocampal structures. In the dorsal hippocampus, the number of SOM-i cells containing NPY-i was higher than the number of NPY-i cells containing SOM-i. This pattern was reversed in the retrohippocampal region. At ventral levels the incidence of colocalization of NPY- and SOM-i in single cells increased in all hippocampal subfields.

Immunohistochemical identification of quinolinic acid phosphoribosyltransferase in glial cultures from rat brain.

Glial cell cultures were shown to contain 3 identifiable classes of cells which could be specifically stained with antibodies directed against quinolinic acid phosphoribosyltransferase (QPRT), the catabolic enzyme of the endogenous excitotoxin quinolinic acid. Some, but not all, QPRT-positive cells also contained glial fibrillary acidic protein. These cultures may constitute an in vitro system in which cerebral quinolinic acid metabolism and function can be examined.

Immunohistochemical localization of cytochrome P-450 in the rat brain.

Immunohistochemical localization of cytochrome P-450 in the brains of normal untreated male rats has been demonstrated with polyclonal antibodies raised against hepatic P-450C. These antibodies recognize P-450C and D, two closely related forms of P-450. We have identified P-450C,D immunoreactivity (P-450C,D-i) within both neurons and glial cells. Neuronal cell bodies showing P-450C,D-i were present in several forebrain areas, including the olfactory bulb, the caudate nucleus, the cingulate, the frontal and the entorhinal cortex, the hippocampus and the thalamus. In the brainstem, P-450C,D-i neurons were detected in the substantia nigra, the nucleus locus coeruleus, raphe nucleus, reticular formation and the trigeminal nerve nucleus and the dorsal motor nucleus of the vagus. Glial cells containing P-450C,D-i were situated within myelinated fiber tracts in the forebrain (e.g. the corpus callosum, the internal capsule) and the brainstem (e.g. the superior cerebellar peduncle, the medial longitudinal fasciculus). Some, but not all, of the P-450C,D-i glial cells also stained with an antibody against glial fibrillary acidic protein. The present findings represent the first immunohistochemical demonstration of cytochrome P-450 in the brain and suggest that cytochrome P-450C,D is constitutive in neurons and glial cells of most brain regions throughout the rat neuraxis.

An immunohistochemical study of somatostatin and neurotensin positive neurons in the septal nuclei of the rat brain.

Antibodies to the neuropeptides somatostatin (SOM) and neurotensin were used to study the distribution of the two peptides within the septum of the rat brain. In colchicine treated rats, numerous somatostatin-positive cell bodies were found in the dorsal and ventral subdivisions of the lateral septum, along the border of the nucleus accumbens, in the ventral tip of the horizontal limb of the diagonal band of Broca as well as in the anterior hippocampal rudiment, infralimbic area and several other structures of the basal forebrain (e.g., nucleus accumbens, olfactory tubercle and substantia innominata). Cell bodies containing immunoreactivity for neurotensin were situated in the intermediate and ventral subdivisions of the lateral septum, the medial septal nucleus, the diagonal band of Broca, the rostro-medial continuation of the substantia innominata and the olfactory tubercle. In untreated rats, somatostatin positive processes formed terminal plexuses in the medial septal nucleus and along an area close to the ventricular wall of the lateral septal nucleus. Other septal nuclei, such as the diagonal band of Broca contained a sparse innervation by somatostatin positive fibers. In contrast, the nucleus accumbens, olfactory tubercle, and the substantia innominata contained a rich innervation by somatostatin positive axons and terminals. Within these structures the density of SOM positive processes show great variations with patches of densely packed terminals separated by areas of sparser or no innervation. The neurotensin positive terminals were situated predominantly within the intermediate part of the lateral septum and the medial septal nucleus. Both of these regions contained numerous pericellular baskets of neurotensin positive terminals around septal neurons. In addition to the septal innervation, several of the basal forebrain structures were rich in neurotensin positive processes with the densest innervation found in the nucleus accumbens and substantia innominata. Like the SOM-immunoreactivity distinct islands of dense neurotensin innervation separated by less or no innervation occur throughout the basal forebrain. Taken together, these findings suggest that somatostatin and neurotensin occur in separate neuronal populations and that each may influence important physiological functions within the individual septal nuclei.

Sawtooth-control mechanism using toroidally propagating ion-cyclotron-resonance waves in tokamaks.

The sawtooth control mechanism in plasmas employing off-axis toroidally propagating ion cyclotron resonance waves in tokamaks is reinvestigated. The radial drift excursion of energetic passing ions distributed asymmetrically in the velocity parallel to the magnetic field determines stability when the rational q=1 surface resides within a narrow region centered about the shifted fundamental cyclotron resonance.

Demonstration of effective control of fast-ion-stabilized sawteeth by electron-cyclotron current drive.

In a tokamak plasma, sawtooth oscillations in the central temperature, caused by a magnetohydrodynamic instability, can be partially stabilized by fast ions. The resulting less frequent sawtooth crashes can trigger unwanted magnetohydrodynamic activity. This Letter reports on experiments showing that modest electron-cyclotron current drive power, with the deposition positioned by feedback control of the injection angle, can reliably shorten the sawtooth period in the presence of ions with energies >or=0.5 MeV. Certain surprising elements of the results are evaluated qualitatively in terms of existing theory.

Massive postpartum hemorrhage treated with transcatheter arterial embolization: technical aspects and long-term effects on fertility and menstrual cycle.

BACKGROUND: Transcatheter arterial embolization (TAE) is considered a safe, life-saving procedure in postpartum hemorrhage (PPH), but its long-term effect on menstruation and fertility is unclear. PURPOSE: To investigate technical aspects and the evaluation of complications, focused on menstrual cycle and fertility, using TAE in patients with PPH. MATERIAL AND METHODS: A retrospective study including 20 patients (seven with vaginal and 13 with cesarean delivery) with severe PPH treated with bilateral TAE of the uterine artery was carried out. All patients were asked to answer a questionnaire regarding their post-embolization history. In six patients, the radiation dose was measured. RESULTS: All 20 cases underwent bilateral TAE of the uterine artery. Gelfoam was used as the embolic agent. However, after cesarean delivery in six patients who had clear contrast medium extravasation and/or pseudoaneurysm-like lesion, metallic coils had to be used in order to achieve hemostasis. No major short- or long-term complications were registered. Normal menses resumed in all patients. Four patients had a total of five full-term and two preterm pregnancies, and all delivered healthy infants by cesarean section with no recurrence of PPH. The mean radiation dose to the ovaries was 586 mGy (range 204-729 mGy). CONCLUSION: TAE in patients with PPH is safe and has no major short- or long-term side effects. A patient managed with TAE can expect return of normal menses and preservation of future fertility and successful pregnancies. PPH after cesarean section might need to be embolized with metallic coils in addition to Gelfoam in order to achieve secure hemostasis.

Liver embolization with trisacryl gelatin microspheres (embosphere) in patients with neuroendocrine tumors.

PURPOSE: To report our experience of liver embolization with trisacryl gelatin microspheres (Embospheretrade mark) in patients with metastatic neuroendocrine tumors. MATERIAL AND METHODS: Fifteen patients underwent selective embolization of the right or left hepatic artery with Embosphere. One lobe was embolized in seven patients and both lobes, on separate occasions, in eight patients. Seven patients had midgut carcinoids, two had lung carcinoids, one suffered from a thymic carcinoid, and five had endocrine pancreatic tumors. Eight patients suffered from endocrine symptoms, seven of whom had carcinoid syndrome and one WDHA (watery diarrhea, hypokalemia, achlorhydria) syndrome. RESULTS: Partial radiological response was seen after eight embolizations (in six different patients), stable disease was observed after 13 embolizations (after three of these, necroses occurred), while radiological progression was noted after only two embolizations. Only two patients experienced a biochemical response. Clinical improvement of carcinoid syndrome was observed after five embolizations. There were no major complications. Fever >38 degrees C was seen after all but four embolizations, and urinary tract infections were diagnosed after eight embolizations. CONCLUSION: Selective hepatic artery embolization with Embosphere particles is a safe treatment for patients with metastatic neuroendocrine tumors and may lead to partial radiological response as well as symptomatic improvement of disabling endocrine symptoms.

Three-dimensional rotational angiography of transplanted renal arteries: influence of an extended angle of rotation on beam-hardening artifacts.

PURPOSE: To investigate whether three-dimensional rotational angiography (3D-RA) of the transplant renal artery performed with an extended angle of rotation can reduce beam-hardening artifacts in 3D reconstructed images without image quality being lost or side effects to the transplanted kidney being increased. MATERIAL AND METHODS: 3D-RA with a C-arm rotation of 180 degrees was performed consecutively in 12 renal transplanted patients with suspicion of renal artery stenosis. A 1.7-mm balloon occlusion catheter was placed using the crossover technique and this was compared to a protocol with 160 degrees rotation and a traditional 1.4-mm catheter in 10 patients. The occurrence of beam-hardening artifacts was registered and the effects of the reduced contrast load on image quality and of arterial occlusion on renal function were assessed. RESULTS: The extended angle of rotation, from 160 degrees to 180 degrees, reduced the beam-hardening artifacts. Artifacts were observed in 4/11 patients (36%) in the study group and in all 10 (100%) of the controls. There was no statistical difference regarding image quality between the two protocols. Renal function was equally affected in both protocols. CONCLUSION: 3D-RA with an extended C-arm rotation reduced the beam-hardening artifacts. Image quality was not reduced despite the reduced contrast medium load. The different protocols had no effect on patient outcome.

Current dynamics during disruptions in large tokamaks.

Self-consistent modeling of the evolution of the plasma current during disruptions in large tokamaks is presented, taking into account both the generation of runaway electrons and their backreaction on the electric field. It is found that the current profile changes dramatically, so that the postdisruption current carried by runaway electrons is much more peaked than the thermal predisruption current. Although only a fraction of the thermal current is converted into runaway electrons, the central current density increases significantly for typical parameters in JET and ITER. It is also shown that the radial runaway profile can easily become filamented in the radial direction.

Ion acceleration during reconnection in MAST.

Spontaneous acceleration of ions to suprathermal energies is observed during magnetic reconnection in the Mega-Ampere Spherical Tokamak (MAST). A high-energy tail is observed in the ion-distribution function following each internal reconnection event in Ohmic discharges. This phenomenon is explained in terms of runaway ion acceleration in the electric field induced by the reconnection.

Quinolinic acid metabolism in the rat brain. Immunohistochemical identification of 3-hydroxyanthranilic acid oxygenase and quinolinic acid phosphoribosyltransferase in the hippocampal region.

Quinolinic acid (QUIN) is a potent endogenous excitotoxin, which has been shown to be present in the brain (Wolfensberger et al., 1983). In order to study the cellular localization of QUIN metabolism in the hippocampus, specific antibodies raised against purified rat liver 3-hydroxyanthranilic acid oxygenase (3HAO) and quinolinic acid phosphoribosyltransferase (QPRT), the enzymes directly responsible for QUIN synthesis and catabolism, respectively, were used for immunohistochemical studies in the adult male rat. Cells containing 3HAO immunoreactivity (3HAO-i) were present in all subfields of the hippocampal region, including the area dentata, Ammon's horn, the subicular complex, and the entorhinal area. The highest density of 3HAO-i cells was found in the molecular layer of Ammon's horn and in the hilus of area dentata, while the granular cell layer of area dentata and stratum pyramidale of Ammon's horn contained the lowest number of 3HAO-stained cells. A majority of hippocampal 3HAO-i cells were also stained with monoclonal antibodies against glial fibrillary acidic protein (GFAP) or S-100 protein, suggesting that 3HAO-i is present primarily in astrocytes. At the ultrastructural level, 3HAO-i was found to be distributed uniformly throughout the cytoplasm, with intense immunostaining present in the internal and the external layers of the mitochondria. QPRT-i was detected in 3 morphologically distinct cell types present in all parts of the hippocampus. The total number of QPRT-i cells was lower than that of the 3HAO-i cells. QPRT-i cells were relatively numerous in the molecular and radial layers of Ammon's horn, while they occurred only sporadically in stratum pyramidale of Ammon's horn and in the granular cell layer of area dentata. Many QPRT-i cells stained with antibodies against GFAP and S-100, but the proportion of cells in which QPRT was colocalized with these glial marker proteins was lower than that for 3-HAO-i cells. At the ultrastructural level, 2 types of QPRT-i glial cells were detected. The smaller cell type had a diffuse cytoplasmic staining, while the larger cell type, which also contained glial filaments, showed diffuse cytoplasmic staining and intense staining of lysosomal structures. The observation that 3HAO and QPRT only partially coexist in hippocampal glial cells suggests that while synthesis and catabolism of QUIN may occur in the same glial cells, catabolism of QUIN can also take place in cells lacking the synthetic enzyme.(ABSTRACT TRUNCATED AT 400 WORDS)

Determination of the relative glomerular filtration rate of each kidney in man. Comparison between iohexol CT and 99mTc-DTPA scintigraphy.

Iohexol and 99mTc-DTPA were used in 43 patients to determine the relative glomerular filtration rate (GFR), i.e., the GFR of each kidney in percent of total GFR. The amount of any GFR marker accumulating in Bowman's space, tubuli and renal pelvis within a few minutes after i.v. injection, before any marker had left the kidney via the ureter, was defined as proportional to the GFR of that kidney. The renal accumulation of iohexol was determined by CT using 10 slices of 8-mm thickness 1 to 4 minutes after injection. The renal accumulation of 99mTc-DTPA was determined with a gamma camera within 2 minutes after injection. The correlation coefficient between the two methods was 0.98. Due to the higher radiation dose from CT than from 99mTc-DTPA injection, relative GFR determination with CT should be performed when there is also a diagnostic need to reveal morphology.

Plasma rotation induced by directed waves in the ion-cyclotron range of frequencies.

Changes of the toroidal plasma rotation induced by directed waves in the ion-cyclotron range of frequencies (ICRF) have been identified experimentally for the first time on the JET tokamak. The momentum carried by the waves is initially absorbed by fast resonating ions, which subsequently transfer it to the bulk plasma. Thus, the results provide evidence for the influence of ICRF heated fast ions on plasma rotation.