julilili42/papers huggingface dataset:
Coeval plutonism and metamorphism in a latest Oligocene metamorphic core complex in northwest Turkey
2000-09-01

A metamorphic core complex of latest Oligocene age crops out in the Kazdağ mountain range in northwest Turkey. The footwall of the core complex consists of gneiss, amphibolite and marble metamorphosed at 5 ± 1 kbar and 640° ± 50 °C. The average muscovite and biotite Rb/Sr ages from the gneisses are 19 Ma and 22 Ma, respectively, and imply high temperature metamorphism during latest Oligocene times. The hangingwall is made up of an unmetamorphosed Lower Tertiary oceanic accretionary melange with Upper Cretaceous eclogite lenses. The hangingwall and footwall are separated by an extensional ductile shear zone, two kilometres thick. Mylonites and underlying high-grade metamorphic rocks show a N-trending mineral lineation with the structural fabrics indicating down-dip, top-to-the-north shear sense. The shear zone, the accretionary melange and the high-grade metamorphic rocks are cut by an undeformed granitoid with a 21 Ma Rb/Sr biotite age, analytically indistinguishable from the Rb/Sr biotite ages in the surrounding footwall gneisses. The estimated pressure of the metamorphism, and that of the granitoid emplacement, indicate that the high-grade metamorphic rocks were rapidly exhumed at ∼ 24 Ma from a depth of ∼ 14 km to ∼ 7 km by activity along the shear zone. The subsequent exhumation of the metamorphic rocks to the surface occurred during Pliocene–Quaternary times in a transpressive ridge between two overstepping fault segments of the North Anatolian Fault zone. The high-grade metamorphic rocks of the Kazdağ range are surrounded by voluminous calc-alkaline volcanic and plutonic rocks of Late Oligocene–Early Miocene age, which formed above the northward-dipping Hellenic subduction zone. The magmatic arc setting of the core complex and stratigraphic evidence for subdued topography in northwest Turkey prior to the onset of extension suggest that the latest Oligocene regional extension was primarily related to the roll-back of the subduction zone rather than to the gravitational collapse.
MR Imaging and1H Spectroscopy of Brain Metabolites in Hepatic Encephalopathy: Time-Course of Renormalization after Liver Transplantation
2000-09-01

After successful liver transplantation, renormalization of HE-specific brain metabolite changes is detected at (1)H spectroscopy and precedes the disappearance of BGH. The neuropsychologic signs of subclinical or overt HE follow the changes seen at (1)H spectroscopy rather than those seen at MR imaging.
Reduced Interleukin‐12 and Transforming Growth Factor–β1 in Severe Childhood Malaria: Relationship of Cytokine Balance with Disease Severity
2000-09-01

Interleukin (IL)-12 and transforming growth factor (TGF)-beta1 regulate the balance between pro- and anti-inflammatory cytokines in animal models of malaria. Since the cytokine balance may be an important determinant of whether a protective or a pathogenic immune response develops, plasma cytokine ratios were examined in Gabonese children with various degrees of malarial severity. Severe disease was characterized by high-density parasitemia and severe anemia. IL-12 and TGF-beta1 were significantly lower, whereas tumor necrosis factor (TNF)-alpha and IL-10 were significantly higher in children with severe malaria. The ratios of TGF-beta1/IL-12 and IL-10/IL-12 were significantly higher in the severe, compared with the mild, malaria group. In contrast, ratios of TGF-beta1/TNF-alpha and IL-10/TNF-alpha were significantly lower in the severe malaria group. These results suggest that the inflammatory cascade in severe malaria is characterized by suppression of the protective effects of TGF-beta1 and IL-12, and that overproduction of TNF-alpha may promote deleterious effects, such as severe anemia.
Right-Hemisphere Dominance for the Processing of Sound-Source Lateralization
2000-09-01

Cortical processing of change in direction of a perceived sound source was investigated in 12 human subjects using whole-head magnetoencephalography. The German word "da" was presented either with or without 0.7 msec interaural time delays to create the impression of right- or left-lateralized or midline sources, respectively. Midline stimuli served as standards, and lateralized stimuli served as deviants in a mismatch paradigm. Two symmetrically linked dipoles fitted to the mismatch fields showed stronger moments in the hemisphere contralateral to the side of the deviant. The right dipole displayed equal latencies to both left and right deviants, whereas left dipole latencies were longer for ipsilateral than contralateral deviants. Frequency analysis between 20-70 Hz and statistical probability mapping revealed increased induced gamma-band activity at 53+/-2.5 Hz to both types of deviants. Right deviants elicited spectral amplitude enhancements in this frequency range, peaking at latencies of 160 and 240 msec. These effects were localized bilaterally over the angular gyri and posterior temporal regions. Coherence analysis suggested the existence of two separate interhemispheric networks. For left-lateralized deviants, both spectral amplitude enhancements at 110 and 220 msec and coherence increases were restricted to the right hemisphere. In conclusion, both mismatch dipole latencies at the supratemporal plane and gamma-band activity in posterior parietotemporal areas suggested a right hemisphere engagement in the processing of bidirectional sound-source shifts. In contrast, left-hemisphere regions responded predominantly to contralateral events. These findings may help to elucidate phenomena such as unilateral auditory neglect.
Involvement of the human frontal eye field and multiple parietal areas in covert visual selection during conjunction search
2000-09-01

Abstract Searching for a target object in a cluttered visual scene requires active visual attention if the target differs from distractors not by elementary visual features but rather by a feature conjunction. We used functional magnetic resonance imaging (fMRI) in human subjects to investigate the functional neuroanatomy of attentional mechanisms employed during conjunction search. In the experimental condition, subjects searched for a target defined by a conjunction of colour and orientation. In the baseline condition, subjects searched for a uniquely coloured target, regardless of its orientation. Eye movement recordings outside the scanner verified subjects' ability to maintain fixation during search. Reaction times indicated that the experimental condition was attentionally more demanding than the baseline condition. Differential activations between conditions were therefore ascribed to top‐down modulation of neural activity. The frontal eye field, the ventral precentral sulcus and the following posterior parietal regions were consistently activated: (i) the postcentral sulcus; (ii) the posterior; and (iii) the anterior part of the intraparietal sulcus; and (iv) the junction of the intraparietal with the transverse occipital sulcus. Parietal regions were spatially distinct and displayed differential amplitudes of signal increase with a maximal amplitude in the posterior intraparietal sulcus. Less consistent activation was found in the lateral fusiform gyrus. These results suggest an involvement of the human frontal eye field in covert visual selection of potential targets during search. These results also provide evidence for a subdivision of posterior parietal cortex in multiple areas participating in covert visual selection, with a major contribution of the posterior intraparietal sulcus.
Functional response of leukaemic blasts to stromal cell‐derived factor‐1 correlates with preferential expression of the chemokine receptor CXCR4 in acute myelomonocytic and lymphoblastic leukaemia
2000-09-01

The chemokine stromal cell‐derived factor‐1 (SDF‐1) that is released by bone marrow (BM) stromal cells and contributes to stem cell homing may also play a role in the trafficking of leukaemic cells. We analysed SDF‐1‐induced intracellular calcium fluxes in leukaemic blasts from the peripheral blood of patients with newly diagnosed acute myeloid leukaemia (AML) and lymphoblastic leukaemia (B‐lineage ALL), determined the effect of BM stromal cell‐conditioned medium on in vitro transendothelial migration (TM) and measured expression of the SDF‐1 receptor, CXCR4, by flow cytometry. AML FAB M1/2 blasts did not show calcium fluxes and TM was not stimulated. In myelomonocytic AML (M4/5), however, SDF‐1 induced significant calcium fluxes and TM was increased twofold by the conditioned medium. M3 and M4 blasts with eosinophilia (M4eo) showed intermediate activity and M6 blasts showed no functional activity. In ALL, strong calcium fluxes and increased TM (2.5‐fold) were observed. Accordingly, expression of CXCR4 was low in undifferentiated (M0) AML, myeloid (M1/2) AML and erythroid (M6) AML, but high [mean fluorescence (MF) &gt; 50] in promyelocytic (M3) AML, myelomonocytic (M4/5) AML and B‐lineage ALL. We conclude that, in AML, SDF‐1 is preferentially active in myelomonocytic blasts as a result of differentiation‐related expression of CXCR4. Functional activity of SDF‐1 and high expression of CXCR4 in B‐lineage ALL is in accordance with the previously described activity of SDF‐1 in early B cells. SDF‐1 may contribute to leukaemic marrow infiltration, as suggested by increased CXCR4 expression and migratory response in BM‐derived blasts compared with circulating cells.
Functional and pharmacological characterization of human Na+-carnitine cotransporter hOCTN2
2000-09-01

l-Carnitine is essential for the translocation of acyl-carnitine into the mitochondria for β-oxidation of long-chain fatty acids. It is taken up into the cells by the recently cloned Na + -driven carnitine organic cation transporter OCTN2. Here we expressed hOCTN2 in Xenopus laevis oocytes and investigated with two-electrode voltage- clamp and flux measurements its functional and pharmacological properties as a Na + -carnitine cotransporter. l-carnitine transport was electrogenic. The l-carnitine-induced currents were voltage and Na + dependent, with half-maximal currents at 0.3 ± 0.1 mM Na + at −60 mV. Furthermore,l-carnitine-induced currents were pH dependent, decreasing with acidification. In contrast to other members of the organic cation transporter family, hOCTN2 functions as a Na + -coupled carnitine transporter. Carnitine transport was stereoselective, with an apparent Michaelis-Menten constant ( K m ) of 4.8 ± 0.3 μM for l-carnitine and 98.3 ± 38.0 μM for d-carnitine. The substrate specificity of hOCTN2 differs from rOCT-1 and hOCT-2 as hOCTN2 showed only small currents with classic OCT substrates such as choline or tetraethylammonium; by contrast hOCTN2 mediated transport of betaine. hOCTN2 was inhibited by several drugs known to induce secondary carnitine deficiency. Most potent blockers were the antibiotic emetine and the ion channel blockers quinidine and verapamil. The apparent IC 50 for emetine was 4.2 ± 1.2 μM. The anticonvulsant valproic acid did not induce a significant inhibition of carnitine transport, pointing to a different mode of action. In summary, hOCTN2 mediates electrogenic Na + -dependent stereoselective high-affinity transport ofl-carnitine and Na + . hOCTN2 displays transport properties distinct from other members of the OCT family and is directly inhibited by several substances known to induce systemic carnitine deficiency.
The representation of articulation in the primary sensorimotor cortex
2000-09-01

Bilabial, alveolar and velar sounds are produced at different locations around the oral cavity. fMRI was used to localize cortical representation of articulation in seven healthy subjects during repetitive lip and vertical tongue movements as well as repetitive articulation of /pa/ (bilabial), /ta/ (alveolar), /ka/ (velar consonants) and a combination of all three in /pataka/. Centers of gravity (COG) analysis of fMRI activation in the primary motor (M1) and sensory cortex (S1) revealed /pa/- adjacent to lip representation and /ta/- articulation to tongue representation. The articulation of /pataka/ showed an activation pattern with a combination of the two M1/S1-components and additional activation in the supplementary motor area.
Magnetic properties of synthetic analogues of pyrrhotite ore in the grain size range 1-24 m
2000-09-01

Iron and sulphur in proportions appropriate to Fe7S8 were reacted in evacuated quartz tubes for 24 hr at 500 °C. Quenching produces predominantly hexagonal pyrrhotite, whereas further prolonged annealing at 250 °C produces monoclinic pyrrhotite. We mainly report the properties of material cooled from 500 °C at 10 °C min-1, which is predominantly monoclinic but probably contains hexagonal pyrrhotite together with pyrite, FeS2. This material, which we refer to as 'non-ideal' pyrrhotite, may be a better analogue of pyrrhotite ore than ideal synthetic monoclinic pyrrhotite. The samples were characterized by X-ray, Mössbauer effect and thermomagnetic analyses. The slow-cooled non-ideal monoclinic pyrrhotite exhibits thermal stability intermediate between monoclinic and hexagonal pyrrhotites. One striking observation is that the deviation from ideal monoclinic pyrrhotite increases with decreasing particle size. Particles about 1 μm in size have a low saturation magnetization value of about 6 Am2 kg-1, indicating a lower concentration of ferrimagnetic monoclinic pyrrhotite (saturation magnetization 18 Am2 kg-1) than particles of about 6 μm and above (saturation magnetization 12 Am2 kg-1). On the other hand, magnetization process parameters-coercive force, ratio of saturation remanence to saturation magnetization, coercive force of remanence, median destructive and inductive fields, the magnetic susceptibility-follow well-behaved power law dependences on particle size, similar to monoclinic pyrrhotite. Magnetic domain patterns in the slow-cooled non-ideal pyrrhotite are similar in type and style to those observed in synthetic monoclinic pyrrhotite and in natural pyrrhotite particles in rocks. Dynamic observations of domain walls in changing external alternating and direct magnetic fields are consistent with macroscopic observations of magnetization change with field. The critical size for the monodomain/multidomain transition in synthetic monoclinic pyrrhotite, at about 1 μm, is essentially the same as that previously determined for natural pyrrhotite grains in rocks. The observations suggest that the domain walls lie normal to the c-axis of the structure, consistent with the known magnetocrystalline anisotropy symmetry of monoclinic pyrrhotite. The type and style of the magnetic microstructures of hexagonal pyrrhotite are quite different from those of monoclinic pyrrhotite. The domain patterns are on a much smaller scale, wavy, and sometimes resemble those of a hexagonal material such as magnetoplumbite or cobalt.
A new near-shore marine fauna and flora from the Early Neogene of northwestern Venezuela
2000-09-01

A diverse near-shore marine fauna existed during the early Miocene in what is today an arid inland region about 90 km south of the Caribbean coast of northern Venezuela, a poorly known area geologically and paleontologically. The fossil locality consists of more than 100 m of section exposed in an area of about 1 km 2 . We report the discovery of 20 molluscan species, one crab ( Portunus oblongus ), at least three sharks ( Hemipristis serra and Carcharhinus spp.), one turtle (“ Podocnemis” venezuelensis ), one crocodile (Crocodylidae), two whales (Odontoceti) and a three dimensional cast of the mesocarp or endocarp of a palm fruit. Several taxa are reported for the first time in Venezuela or in northern South America. The fauna indicates, or at least is consistent with, an early Miocene age for the locality, and a near-shore and shallow water marine depositional environment. We suggest that the earliest mammal previously reported from Venezuela, the pyrothere Proticia venezuelensis, was collected in Miocene rocks of the Castillo Formation instead of Eocene rocks of the Trujillo Formation.
Enantiomer separation by capillary electrochromatography on a cyclodextrin-modified monolith
2000-09-01

A chiral monolithic stationary phase was prepared by packing a capillary with bare porous silica and sintering the silica bed at high temperature. The resulting silica monolith was polymer-coated with Chirasil-Dex, a permethylated beta-cyclodextrin covalently linked via an octamethylene spacer to dimethylpolysiloxane. Subsequently, Chirasil-Dex was thermally immobilized on the silica support and a chiral monolith of very high stability (30 kV, more than 400 bar pressure) was obtained. The enantiomer separation of various chiral compounds by monolithic (rod) capillary electrochromatography (rod-CEC) was feasible. This method was compared with capillary liquid chromatography (LC) in a single-column mode using unified equipment. About two to three times higher efficiency was found in the rod-CEC mode as compared to rod-LC. The influence of pressure-driven flow support on efficiency, resolution, elution time and baseline stability was investigated. The amount and nature of organic modifier strongly influences efficiency and resolution.
A NEW NEAR-SHORE MARINE FAUNA AND FLORA FROM THE EARLY NEOGENE OF NORTHWESTERN VENEZUELA
2000-09-01

A diverse near-shore marine fauna existed during the early Miocene in what is today an arid inland region about 90 km south of the Caribbean coast of northern Venezuela, a poorly known area geologically and paleontologically. The fossil locality consists of more than 100 m of section exposed in an area of about 1 km2. We report the discovery of 20 molluscan species, one crab (Portunus oblongus), at least three sharks (Hemipristis serra and Carcharhinus spp.), one turtle ("Podocnemis" venezuelensis), one crocodile (Crocodylidae), two whales (Odontoceti) and a three dimensional cast of the mesocarp or endocarp of a palm fruit. Several taxa are reported for the first time in Venezuela or in northern South America. The fauna indicates, or at least is consistent with, an early Miocene age for the locality, and a near-shore and shallow water marine depositional environment. We suggest that the earliest mammal previously reported from Venezuela, the pyrothere Proticia venezuelensis, was collected in Miocene rocks of the Castillo Formation instead of Eocene rocks of the Trujillo Formation.
Human γδ T Lymphocytes Exert Natural and IL–2–Induced Cytotoxicity to Neuroblastoma Cells
2000-09-01

Human gammadelta T lymphocytes play an important role in nonadaptive reactions to infection and early tumor defense. This is the first report that freshly isolated, native gammadelta T cells of some healthy donors can kill human neuroblastoma cells to varying degrees. Their killing ability was increased and maintained during expansion and cultivation with interleukin-2 (IL-2; 400 IU/mL) for as long as 30 days (100% specific lysis at an effector-to-target cell (E:T) ratio of 20:1). gammadelta T lymphocytes without this spontaneous killing ability gained a specific cytolytic activity of 81% +/- 10.4% SD after stimulation with IL-2 for 24 hours. gammadelta cells were isolated from peripheral blood by positive enrichment (using a magnetic cell sorting system; purity, 95.2% +/- 3.2% SD, n = 21). High natural cytotoxic activity against human neuroblastoma cell lines (>50% specific lysis at an E:T ratio of 20:1) was exhibited by one of 11 donors, whereas two of 11 showed medium cytotoxicity (30% to 50% specific lysis). Eight of 11 donors showed very slight or no lytic activity against human neuroblastoma cells (<30% specific lysis). gammadelta T cells were also cytotoxic against Daudi (32.7% specific lysis at an E:T ratio of 20:1), Raji (10.3%), Colo 205 (23.1%), A 204 (54%), K 562 (100%), and SK-N-MC (100%) cells. Isolated gammadelta T cells were grown in Iscove modified Dulbecco medium with IL-2 (400 IU/mL). Increased cell proliferation (38.5% to 182%) was induced with phytohemagglutinin, IL-15, Clodronat, OKT3, or various combinations of these. Results of cold target inhibition assays suggest a natural killer-like activity of the gammadelta T-cell killing mechanism. Peptidase or papain render neuroblastoma cells unsusceptible to gammadelta T-cell killing, suggesting the involvement of antigen peptide(s) in the process of neuroblastoma cell killing. Treatment with acid phosphatase reduced specific lysis by 66.5% +/- 34.1% SD, which suggests a binding to phosphorylated neuroblastoma cell-surface structures in the killing mechanism of gammadelta T cells. Heat shock did not affect the extent of neuroblastoma killing by gammadelta cells. Recognition of neuroblastoma cells by gammadelta cytotoxic T lymphocytes is negatively regulated by major histocompatibility complex I receptors. Evidence for natural and inducible cell cytotoxicity of gammadelta T cells against human neuroblastoma cells, easy propagation, purification, and missing alloreactivity in mixed lymphocytes cultures indicates a role for this subpopulation of T lymphocytes in adoptive immunotherapy.
Stereospecific Interaction of Ketamine with Nicotinic Acetylcholine Receptors in Human Sympathetic Ganglion-like SH-SY5Y Cells
2000-09-01

Background Surprising clinical evidence suggests a block of sympathetic transmission by ketamine. The action of ketamine on nicotinic acetylcholine receptors (nAChRs) in human ganglions is unknown. Because ganglionic transmission depends on nAChRs, such information may help to clarify whether ketamine impairs ganglionic transmission in men. Because racemic ketamine as well as S(+)-ketamine are used clinically, the authors investigated stereospecific effects on human ganglionic nAChRs. Stereospecific psychomimetic effects have been attributed to voltage-dependent Kv channel inhibition; therefore the effects on nAChRs were compared with those on Kv channels present in the same cells. Methods Whole-cell currents through nAChRs and K channels were measured in SH-SY5Y cells with the patch-clamp technique by application of acetylcholine (1 mm, nAChRs) or by a step depolarization from a holding potential of -80 mV to +40 mV (K channels). Electrolyte conditions were identical for both currents. Results Racemic ketamine and the isomers inhibited nAChRs and K channels in a concentration-dependent and reversible manner. Racemic ketamine inhibited nAChRs and K channels, with the anesthetic concentration inducing the half-maximal effect being 1.4 and 300 micrometer, respectively. Only inhibition of the nAChRs was stereoselective. The half-maximal concentrations were 0.8 and 3.6 micrometer for S(+)- and R(-)-ketamine. The K channels were 350 and 70 times less sensitive to the effects of S(+)- and R(-)-ketamine. Conclusion Ketamine at concentrations found during clinical anesthesia exerts stereospecific effects on human ganglionic nAChRs but not on voltage-dependent K channels. Our results support the view that ketamine impairs sympathetic ganglionic transmission. Nonspecific effects on voltage-dependent K channels may underlie psychomimetic side effects.