Holes in a Quantum Spin Liquid

Magnetic neutron scattering provides evidence for nucleation of antiferromagnetic droplets around impurities in a doped nickel oxide-based quantum magnet. The undoped parent compound contains a spin liquid with a cooperative singlet ground state and a gap in the magnetic excitation spectrum. Calcium doping creates excitations below the gap with an incommensurate structure factor. We show that weakly interacting antiferromagnetic droplets with a central phase shift of pi and a size controlled by the correlation length of the quantum liquid can account for the data. The experiment provides a quantitative impression of the magnetic polarization cloud associated with holes in a doped transition metal oxide.

Fractionated stereotactic radiosurgery for 50 patients with recurrent or residual nasopharyngeal carcinoma

PURPOSE

This study was conducted to evaluate the clinical value of fractionated stereotactic radiosurgery (FSRS) as a boost treatment in 44 patients with residual or recurrent nasopharyngeal carcinoma after conventional radiotherapy (70-80 Gy) or a second course of radiotherapy (50 Gy) or as salvage treatment in 6 patients with recurrent nasopharyngeal carcinoma after a first or second course of radiotherapy at the primary site.

METHODS AND MATERIALS

From September 20, 1995 to December 30, 1998, 50 patients were treated with FSRS with 6 MV of photons. The total FSRS dose was 14-35 Gy (median dose 24) prescribed at 1-4 centers on the 60-90% isodose curves normalized to the isocenter by multiple fractions of 6-8, 12, or 15 Gy, with interfraction intervals of 4-6 days.

RESULTS

Thirty-eight patients (76%) had a complete tumor response, 9 (18%) had a partial response, and 3 (6%) were not assessable. The overall rate of survival was 83.6% at 1 year, 65.0% at 2 years, and 59.6% at 3 years. The overall disease-free survival rate among patients with residual tumor was 89.94% at 1 year, 73.97% at 2 years, and 73.97% at 3 years. Patients who were treated for recurrent lesions or who received FSRS as salvage therapy had a 46.53% rate of disease-free survival at both 1 and 2 years after therapy.

CONCLUSION

FSRS is strongly indicated for recurrent or residual nasopharyngeal carcinoma at the primary site.

Gender comparisons of medical students' psychosocial profiles

OBJECTIVES

This study was designed to compare male and female medical students on selected personality attributes that could influence their academic attainment and personal success.

DESIGN

Participants were 1157 medical students (743 men, 414 women) who completed a set of psychosocial questionnaires measuring intensity and chronicity of loneliness, general anxiety, test anxiety, neuroticism, depression, extraversion, self-esteem, locus of control, perceptions of parents, general health and appraisals of stressful life events. Data were analysed by employing multivariate and univariate analysis of variance and chi-square analysis.

SETTING

Jefferson Medical College.

SUBJECTS

Medical students.

RESULTS

Men scored significantly higher on the intensity of loneliness, and women scored higher on general anxiety, test anxiety and neuroticism scales, but the magnitudes of the effect size estimates were not large. No significant gender difference was observed on measures of chronicity of loneliness, depression, extraversion, self-esteem, external locus of control, perception of general health and perceptions of the mother and the father. Women who experienced stressful life events, such as death in the family or personal illness, appraised these events more negatively than did their male counterparts.

CONCLUSIONS

Implications of the findings for medical education and practice are discussed.

Electrochemiluminescent detection of chlorpromazine by selective preconcentration at a lauric acid-modified carbon paste electrode using tris(2,2'-bipyridine)ruthenium(II)

A new detection scheme for the determination of adsorbable coreactants of Ru(bpy)3(2+) electrochemiluminescent reaction is presented. It is based on selective preconcentration of coreactant onto an electrode, followed by Ru(bpy)3(2+) electrochemiluminescent detection. The coreactant employed is chlorpromazine. It was sensitively detected after 5-min preconcentration onto a lauric acid-modified carbon paste electrode. The linear concentration range was found to occur from 1 x 10(-8) to 3 x 10(-6) mol L-1 with a detection limit of 3.1 x 10(-9) mol L-1. The total analysis time is less than 10 min. As a result of selective preconcentration and medium exchange, such remarkable selectivity is achieved that reproducible quantitation of chlorpromazine in urine is possible.

Cytochrome c release is upstream to activation of caspase-9, caspase-8, and caspase-3 in the enhanced apoptosis of anaplastic thyroid cancer cells induced by manumycin and paclitaxel

We previously demonstrated that the combination of a farnesyltransferase inhibitor, manumycin A, and paclitaxel had a synergistic antineoplastic effect on anaplastic thyroid cancer. In this study we investigated the apoptosis pathway involved. In ARO and KAT-4 cells, manumycin- plus paclitaxel-induced DNA fragmentation was blocked by the inhibitors of caspase-9, caspase-8, and caspase-3. The drug combination enhanced the activation of caspase-9, caspase-8, and caspase-3 and cytochrome c release into the cytosol. Cytochrome c release was not affected by the inhibitors of caspase-9, caspase-8 and caspase-3. In a cell-free reconstitution assay, DNA fragmentation occurred after incubating nuclei purified from untreated KAT-4 cells with deoxy-ATP, exogenous cytochrome c and S-100 extracts from control KAT-4 cells, and also after incubation of purified KAT-4 nuclei with S-100 extracts from KAT-4 cells treated with manumycin-plus-paclitaxel. In both cases, the DNA fragmentation was blocked by the inhibitors of caspase-9, caspase-8 and caspase-3. We concluded that the cytochrome c release was upstream of the activation of caspase-9, caspase-8, and caspase-3 in the enhanced apoptosis of anaplastic thyroid cancer cells treated with manumycin plus paclitaxel, and that the interaction between manumycin and paclitaxel occurred at or upstream of cytochrome c in the apoptosis regulatory pathway in anaplastic thyroid cancer cells.

Expression of TGF-beta signaling genes in the normal, premalignant, and malignant human trophoblast: loss of smad3 in choriocarcinoma cells

We had earlier shown that TGF-beta controls proliferation, migration, and invasiveness of normal human trophoblast cells, whereas premalignant and malignant trophoblast cells are resistant to TGF-beta. To identify signaling defects responsible for TGF-beta resistance in premalignant and malignant trophoblasts, we have compared the expression of TGF-beta signaling molecules in a normal trophoblast cell line (HTR-8), its premalignant derivative (RSVT2/C), and two choriocarcinoma cell lines (JAR and JEG-3). RT-PCR analysis revealed that all these cell lines expressed the mRNA of TGF-beta1, -beta2, and -beta3, TGF-beta receptors type I, II, and III, and post-receptor signaling genes smad2, smad3, smad4, smad6, and smad7 with the exception that TGF-beta2 and smad3 were undetectable in JAR and JEG-3 cells. Immunoblot analysis confirmed the absence of smad3 protein in choriocarcinoma cells. Treatment with TGF-beta1 induced smad3 phosphorylation and smad3 translocation to the nucleus in the normal and premalignant trophoblast cells. These results suggest that loss of smad3 may account for a functional disruption in the TGF-beta signaling pathway in choriocarcinomas, but not in the premalignant trophoblast.

Electrochemiluminescence of tris(2,2'-bipyridine)ruthenium(II) immobilized in poly(p-styrenesulfonate)-silica-Triton X-100 composite thin-films

The electrochemiluminescence (ECL) of tris(2,2'-bipyridine)ruthenium(II) [Ru(bpy)3(2+)] immobilized in poly(p-styrenesulfonate) (PSS)-silica-Triton X-100 composite films was investigated. The cooperative action of PSS, sol-gel and Triton X-100 attached Ru(bpy)3(2+) to the electrode strongly, and the presence of Triton X-100 prevented drying fractures of the sol-gel films during gelation and even on repeated wet-dry cycles. The modified electrode was used for the ECL detection of oxalate, tripropylamine (TPA) and NADH in a flow injection analysis (FIA) system with a newly designed flow cell. The detection scheme exhibited good stability, short response time and high sensitivity. Detection limits were 0.1, 0.1 and 0.5 micromol L(-1) for oxalate. TPA and NADH, respectively, and the linear concentration range extended from 0.001 to 1 mmol L(-1) for the three analytes. Applications of the flow cell in ECL and electrochemical detection, as well as the immobilization of reagents based on the cooperative action, are suggested.

Isolation of a functional homolog of the cell cycle-specific NIMA protein kinase of Aspergillus nidulans and functional analysis of conserved residues

To investigate the degree of conservation of the cell cycle-specific NIMA protein kinase of Aspergillus nidulans, and to help direct its functional analysis, we cloned a homolog (designated nim-1) from Neurospora crassa. Over the catalytic domain NIM-1 is 75% identical to NIMA, but overall the identity drops to 52%. nim-1 was able to functionally complement nimA5 in A. nidulans. Mutational analysis of potential activating phosphorylation sites found in NIMA, NIM-1, and related protein kinases was performed on NIMA. Mutation of threonine 199 (conserved in all NIMA-related kinases) inhibited NIMA beta-casein kinase activity and abolished its in vivo function. This site conforms to a minimal consensus phosphorylation site for NIMA (FXXT) and is analogous to the autophosphorylation site of cyclic-AMP-dependent protein kinases. However, mutation of a unique cysteine residue found only in the catalytic site of NIMA and NIM-1 had no effect on NIMA kinase activity or function. Three temperature-sensitive alleles of nimA that cause arrest in G2 were sequenced and shown to generate three different amino acid substitutions. None of the mutations prevented accumulation of NIMA protein during G2 arrest, but all prevented the p34cdc2/cyclin B-dependent phosphorylation of NIMA normally seen during mitotic initiation even though p34cdc2/cyclin B H1 kinase activity was fully activated.

Hierarchically porous carbon encapsulating sulfur as a superior cathode material for high performance lithium-sulfur batteries

Lithium-sulfur (Li-S) batteries are deemed to be a promising energy storage device for next-generation high energy power system. However, insulation of S and dissolution of lithium polysulfides in the electrolyte lead to low utilization of sulfur and poor cycling performance, which seriously hamper the rapid development of Li-S batteries. Herein, we reported that encapsulating sulfur into hierarchically porous carbon (HPC) derived from the soluble starch with a template of needle-like nanosized Mg(OH)2. HPC has a relatively high specific surface area of 902.5 m(2) g(-1) and large total pore volume of 2.60 cm(3) g(-1), resulting that a weight percent of sulfur in S/HPC is up to 84 wt %. When evaluated as cathodes for Li-S batteries, the S/HPC composite has a high discharge capacity of 1249 mAh g(-1) in the first cycle and a Coulombic efficiency as high as 94% with stable cycling over prolonged 100 charge/discharge cycles at a high current density of 1675 mA g(-1). The superior electrochemical performance of S/HPC is closely related to its unique structure, exhibiting the graphitic structure with a high developed porosity framework of macropores in combination with mesopores and micropores. Such nanostructure could shorten the transport pathway for both ions and electrons during prolonged cycling.

Enhanced electrochemical performance of sulfur cathodes with a water-soluble binder

The LA132 is a promising binder for Li–S batteries due to its strong adhesion ability and non-swellable property.

Cholesterol and oxygenated cholesterol concentrations are markedly elevated in peripheral tissue but not in brain from mice with the Niemann-Pick type C phenotype

Niemann-Pick disease type C (NP-C) is a rare genetic disorder characterized by progressive neurodegeneration, frequent developmental delay and early death. Tissues of affected individuals accumulate large quantities of free cholesterol in lysosomes. Because cytotoxic oxygenated derivatives of cholesterol are known to form readily when cholesterol concentrations are elevated, we searched for these compounds in liver, kidney, spleen and brain from mice with the NP-C phenotype. In order of abundance, we identified 7 alpha- and 7 beta-hydroxycholesterol, 5 alpha, 6 alpha-epoxycholestan-3 beta-ol, 4 beta-hydroxycholesterol, cholest-4-en-3 beta, 7 alpha-diol and cholest-4-en-3 beta, 6 beta-diol in most tissue samples. Cholesterol concentrations in affected mice were increased 3-fold in kidney and 7- to 8-fold in spleen and liver compared to controls (all p < 0.001) but were unchanged in brain. Although oxysterol levels were markedly elevated in nonbrain tissue, the oxysterol and cholesterol concentrations increased proportionally so that oxysterols expressed as percentage of total sterols were the same for all animals (0.34 +/- 0.19% averaged over all organs in affected animals vs 0.40 +/- 0.42% in control mice). In contrast to peripheral tissue, we could not detect any increase in either absolute or relative oxysterol levels in the brains of affected and control mice (49 +/- 61 vs 53 +/- 43 micrograms/g wet weight and 0.45 +/- 0.52 vs 0.47 +/- 0.37%, respectively). Thus, brain sterols are normal in NP-C mice and it is unlikely that an accumulation of cytotoxic oxygenated derivatives of cholesterol could account for the progressive neuropathology seen in the disease.

Reproducing abnormal cholesterol biosynthesis as seen in the Smith-Lemli-Opitz syndrome by inhibiting the conversion of 7-dehydrocholesterol to cholesterol in rats

The Smith-Lemli-Opitz syndrome is a recessive inherited disorder characterized by neurologic developmental defects and dysmorphic features in many organs. Recently, abnormal cholesterol biosynthesis with impaired conversion of 7-dehydrocholesterol to cholesterol has been discovered in homozygotes. To reproduce the biochemical abnormality, BM 15.766, a competitive inhibitor of 7-dehydrocholesterol-delta 7-reductase, the enzyme that catalyzes the conversion of 7-dehydrocholesterol into cholesterol was fed by gavage to rats. After 14 d, plasma cholesterol concentrations declined from 48 mg/dl to 16 mg/dl and 7-dehydro-cholesterol levels rose from trace to 17 mg/dl. Hepatocytes surrounding the central vein developed balloon necrosis. Stimulating cholesterol synthesis with cholestyramine followed by BM 15.766 produced an additional 40% decline (P < 0.05) in plasma cholesterol and 34% increase in 7-dehydrocholesterol levels compared to the inhibitor alone. Adding 2% cholesterol to the diet during the second week of BM 15.766 treatment increased plasma cholesterol threefold and decreased 7-dehydrocholesterol concentrations 55%. Hepatic 3-hydroxy-3-methylglutaryl co-enzyme A (HMG-CoA) reductase activity increased 73% with a 3.9-fold rise in mRNA levels but cholesterol 7 alpha-hydroxylase activity decreased slightly though mRNA levels increased 1.4 times with BM 15.766 treatment. These results demonstrate that BM 15.766 is a potent inhibitor of 7-dehydrocholesterol-delta 7-reductase. The model reproduces abnormal cholesterol biosynthesis as seen in the Smith-Lemli-Opitz syndrome and is useful to test different treatment strategies. Stimulating early steps of cholesterol synthesis worsens the biochemical abnormalities while feeding cholesterol inhibits abnormal synthesis, improves the biochemical abnormalities and prevents liver damage.

Unexpected inhibition of cholesterol 7 alpha-hydroxylase by cholesterol in New Zealand white and Watanabe heritable hyperlipidemic rabbits

We investigated the effect of cholesterol feeding on plasma cholesterol concentrations, hepatic activities and mRNA levels of HMG-CoA reductase and cholesterol 7 alpha-hydroxylase and hepatic LDL receptor function and mRNA levels in 23 New Zealand White (NZW) and 17 Watanabe heritable hyperlipidemic (WHHL) rabbits. Plasma cholesterol concentrations were 9.9 times greater in WHHL than NZW rabbits and rose significantly in both groups when cholesterol was fed. Baseline liver cholesterol levels were 50% higher but rose only 26% in WHHL as compared with 3.6-fold increase with the cholesterol diet in NZW rabbits. In both rabbit groups, hepatic total HMG-CoA reductase activity was similar and declined > 60% without changing enzyme mRNA levels after cholesterol was fed. In NZW rabbits, cholesterol feeding inhibited LDL receptor function but not mRNA levels. As expected, receptor-mediated LDL binding was reduced in WHHL rabbits. Hepatic cholesterol 7 alpha-hydroxylase activity and mRNA levels were 2.8 and 10.4 times greater in NZW than WHHL rabbits. Unexpectedly, cholesterol 7 alpha-hydroxylase activity was reduced 53% and mRNA levels were reduced 79% in NZW rabbits with 2% cholesterol feeding. These results demonstrate that WHHL as compared with NZW rabbits have markedly elevated plasma and higher liver cholesterol concentrations, less hepatic LDL receptor function, and very low hepatic cholesterol 7 alpha-hydroxylase activity and mRNA levels. Feeding cholesterol to NZW rabbits increased plasma and hepatic concentrations greatly, inhibited LDL receptor-mediated binding, and unexpectedly suppressed cholesterol 7 alpha-hydroxylase activity and mRNA to minimum levels similar to WHHL rabbits. Dietary cholesterol accumulates in the plasma of NZW rabbits, and WHHL rabbits are hypercholesterolemic because reduced LDL receptor function is combined with decreased catabolism of cholesterol to bile acids.

Liver and Muscle Contribute Differently to the Plasma Acylcarnitine Pool During Fasting and Exercise in Humans

BACKGROUND

Plasma acylcarnitine levels are elevated by physiological conditions such as fasting and exercise but also in states of insulin resistance and obesity.

AIM

To elucidate the contribution of liver and skeletal muscle to plasma acylcarnitines in the fasting state and during exercise in humans.

METHODS

In 2 independent studies, young healthy males were fasted overnight and performed an acute bout of exercise to investigate either acylcarnitines in skeletal muscle biopsies and arterial-to-venous plasma differences over the exercising and resting leg (n = 9) or the flux over the hepato-splanchnic bed (n = 10).

RESULTS

In the fasting state, a pronounced release of C2- and C3-carnitines from the hepato-splanchnic bed and an uptake of free carnitine by the legs were detected. Exercise further increased the release of C3-carnitine from the hepato-splanchnic bed and the uptake of free carnitine in the exercising leg. In plasma and in the exercising muscle, exercise induced an increase of most acylcarnitines followed by a rapid decline to preexercise values during recovery. In contrast, free carnitine was decreased in the exercising muscle and quickly restored thereafter. C8-, C10-, C10:1-, C12-, and C12:1-carnitines were released from the exercising leg and simultaneously; C6, C8, C10, C10:1, C14, and C16:1 were taken up by the hepato-splanchnic.

CONCLUSION

These data provide novel insight to the organo-specific release/uptake of acylcarnitines. The liver is a major contributor to systemic short chain acylcarnitines, whereas the muscle tissue releases mostly medium chain acylcarnitines during exercise, indicating that other tissues are contributing to the systemic increase in long chain acylcarnitines.

Expression and canalicular localization of two isoforms of the ClC-3 chloride channel from rat hepatocytes

The molecular identities of functional chloride channels in hepatocytes are largely unknown. We examined the ClC-3 chloride channel in rat hepatocytes and found that mRNA for two different isoforms is present. A short form is identical to the previously reported sequence for rat ClC-3, and a long form contains a 176-bp insertion immediately upstream of the translation initiation site. This predicts a 58-amino acid NH(2) terminal insertion. Both long and short form mRNA was expressed in diverse tissues of the rat. Transient transfection of the long form in CHO-K1 cells resulted in currents with an I(-) > B(-) > Cl(-) selectivity sequence, outward rectification, and inactivation at positive voltages. Short form currents had identical ionic selectivity but displayed a more extreme outward rectification and showed no voltage-dependent inactivation. Immunofluorescence and immunoblots localized native ClC-3 preferentially but not exclusively to the canalicular membrane. We have therefore identified a new isoform of rat ClC-3 and shown that expression of both isoforms produces functional channels. In hepatocytes, ClC-3 is located in association with the canalicular membrane.

Changes in gene expression in beta cells after islet isolation and transplantation using laser-capture microdissection

AIMS/HYPOTHESIS

The process of islet isolation can cause chemical and mechanical injury to beta cells. In addition, hyperglycaemia after islet transplantation can compromise beta cell function. The aim of this experiment was to evaluate changes in gene expression in endogenous islets using laser-capture microdissection (LCM).

MATERIALS AND METHODS

Islets from B6AF1 mice were studied in situ in the pancreas as well as those freshly isolated or cultured for 24 h. Fresh islets were transplanted under the kidney capsule of syngeneic diabetic (streptozocin-induced) and non-diabetic mice. Frozen sections from all the samples were prepared for LCM to obtain beta cell-enriched tissue; RNA was extracted and amplified using T7 polymerase. RT-PCR was used to assess expression of selected genes critical for beta cell function (Ins, Ipf1 [previously known as Pdx1], Slc2a2 [previously known as GLUT2] and Ldha) and the stress response (Hmox1 [previously known as HO-1], Gpx1, Tnfaip3 [previously known as A20] and Fas). Immunostaining was also performed.

RESULTS

In freshly isolated and cultured islets, insulin and Ipf1 mRNA levels were decreased by 40% (compared with islets in situ), while stress genes were upregulated. Comparison between in situ pancreatic islets and engrafted beta cells of cured mice showed declines in Ipf1 expression.

CONCLUSIONS/INTERPRETATION

Our experiment, the first report to investigate changes in gene expression in endogenous islets using LCM, indicate that beta cells following islet isolation and residing in a foreign graft environment have decreased expression of genes involved in insulin production and increased expression of stress genes. Our data suggest that an islet graft, even in successful transplantation, may be different from endogenous islets in gene expression.

Ste50p sustains mating pheromone-induced signal transduction in the yeast Saccharomyces cerevisiae

In the yeast Saccharomyces cerevisiae, the heterotrimeric G protein transduces the mating pheromone signal from a cell-surface receptor. Free G beta gamma then activates a mitogen-activated protein (MAP) kinase cascade. STE50 has been shown to be involved in this pheromone signal-transduction pathway. In this study, we present a functional characterization of Ste50p, a protein that is required to sustain the pheromone-induced signal which leads cells to hormone-induced differentiation. Inactivation of STE50 leads to the attenuation of mating pheromone-induced signal transduction, and overexpression of STE50 intensifies the pheromone-induced signalling. By genetic analysis we have positioned the action of Ste50p downstream of the alpha-pheromone receptor (STE2), at the level of the heterotrimeric G protein, and upstream of STE5 and the kinase cascade of STE11 and STE7. In a two-hybrid assay Ste50p interacts weakly with the G protein and strongly with the MAPKKK Ste11p. The latter interaction is absent in the constitutive mutant Ste11pP279S. These data show that a new component, Ste50p, determines the extent and the duration of signal transduction by acting between the G protein and the MAP kinase complex in S. cerevisiae.

Lipophilin, a novel heterodimeric protein of human tears

We identified a novel heterodimeric protein, lipophilin AC, in human tears. One of its components, lipophilin A (69 residues; mass, 7575.1; pI, 9.47) was homologous to the C1 and C2 components of prostatein ('estramustine-binding protein'), the major secreted protein of rat prostate. Human lipophilin C (77 residues; mass, 8854.1; pI, 4.94) was homologous to the rat prostatein C3 component and to human mammaglobin, a protein overexpressed in some mammary carcinomas. Tear lipophilins A and C expand the roster of human uteroglobin superfamily members and provide models for exploring these typically steroid-regulated and steroid-binding molecules.

VP7: an attachment protein of bluetongue virus for cellular receptors in Culicoides variipennis

The importance of VP7 of bluetongue virus (BTV) in the binding of BTV to membrane proteins of the BTV vector Culicoides variipennis was investigated. Core BTV particles, prepared from whole viruses, lacked outer proteins VP2 and VP5 and had VP7 exposed. More core particles and whole viruses bound to membrane preparations of adults of C. variipennis and KC cells, which were cultured from this vector insect, than to membrane preparations of Manduca sexta larvae. More core particles than whole viruses bound to membrane preparations of adults of C. variipennis and KC cells. Polyclonal anti-idiotypic antibodies (anti-Id), which were made against an antigen-combining region of an anti-BTV-10 VP7 antibody and functionally mimicked VP7, bound more to the membrane preparations of adults of C. variipennis and KC cells, and less to cytosol preparations. In Western overalay analysis, the Culicoides plasma membrane preparation reduced binding of an anti-VP7 monoclonal antibody to VP7. Whole and core BTV particles and the anti-Id bound to a membrane protein with a molecular mass of 23 kDa that was present predominantly in membrane preparations of adults of C. variipennis and KC cells. This protein was present in much lower concentrations in membrane preparations of C6/36 and DM-2 insect cells.

Application of capillary electrophoresis in clinical chemistry: the clinical value of urinary modified nucleosides

Urinary modified nucleosides were determined by capillary electrophoresis using a 300 mM SDS-25 mM sodium tetraborate-50 mM sodium dihydrogenphosphate buffer. The nucleosides were extracted from urine by phenylboronate affinity gel chromatography. In cancer patients the levels of the modified nucleosides are generally elevated. By an artificial neural network method breast cancer patients were differentiated from normal individuals, which indicates that the modified nucleosides could be of clinical value as tumor markers.