Significance of kidney biopsy in autosomal dominant tubulointerstitial kidney disease-UMOD: is kidney biopsy truly nonspecific?

BACKGROUND: Autosomal dominant tubulointerstitial kidney disease (ADTKD) is a rare hereditary disease caused by a variety of genetic mutations. Carriers of a mutation in the responsible genes are at risk of reaching end-stage kidney disease typically in middle age. The frequency of this disease is assumed to be underestimated because of a lack of disease-specific signs. Pathological findings obtained from kidney of uromodulin related ADTKD (ADTKD-UMOD) patients are regarded as non-specific and less-informative for its diagnosis. This research was undertaken to evaluate the significance of kidney biopsy in ADTKD-UMOD patients. METHODS: Thirteen patients from 10 families with nine identified uromodulin (UMOD) gene mutations who underwent kidney biopsy in the past were studied. Their kidney tissues were stained with anti-UMOD antibody in addition to conventional methods such as PAS staining. When positive, the numbers of tubules with visible UMOD protein accumulations were calculated based on the total numbers of UMOD expressing tubules. Pathological findings such as tubulointerstitial fibrosis, atrophy, inflammation and glomerulosclerosis were also evaluated and analyzed. RESULTS: Interstitial fibrosis and tubular atrophy were present in all 13 patients. Most atrophic tubules with thickening and lamellation of tubular basement membranes showed negative UMOD staining. In all but two patients with C94F mutations, massive accumulation of UMOD proteins was observed in the renal endoplasmic reticulum. UMOD accumulations were also detectable by PAS staining as polymorphic unstructured materials in the 11 patients at frequencies of 2.6-53.4%. 80.4% of the UMOD accumulations were surrounded by halos. The detection rate of UMOD accumulations positively correlated with eGFR. Glomerulosclerosis was detected in 11/13 patients, with a frequency of 20.0 to 61.1%, while no cystic dilatations of glomeruli were detected. CONCLUSIONS: Massively accumulated UMOD proteins in ADTKD-UMOD kidneys are detectable not only by immunostaining using anti-UMOD antibody but also by conventional methods such as PAS staining, although their detection is not easy. These findings can provide important clues to the diagnosis of ADTKD-UMOD. Kidney biopsy in ADTKD-UMOD may be more informative than assumed previously.

Terahertz Spectroscopy of Individual Carbon Nanotube Quantum Dots.

We have investigated the electronic structures of metallic carbon nanotube quantum dots (CNT QDs) by terahertz-induced photocurrent spectroscopy. Sharp peaks due to intersublevel transitions in the CNT QDs are observed at the sublevel energy spacings expected from the linear band dispersion. The line width of the photocurrent peak is as narrow as 0.3 meV and is governed by the tunnel coupling with the electrodes, indicating that the scattering time of electrons in the present CNTs is comparable to or longer than 10 ps. The observation of a sharp absorption peak at the bare quantization energy was not consistent with the Tomonaga-Luttinger liquid theory.

Unusual O-alkylation of 2-hydroxy-1,4-naphthoquinone utilizing alkoxymethyl chlorides.

A new type of O-alkylation of 2-hydroxy-1,4-naphthoquinone with alkoxymethyl chlorides is described. The reaction course can be controlled by the choice of base and yields O-alkylated or O-alkoxymethylated products in high yield with high selectivity.

Electrophysiological characterization of human Na⁺/taurocholate cotransporting polypeptide (hNTCP) heterologously expressed in Xenopus laevis oocytes.

The Na(+)/taurocholate cotransporting polypeptide (NTCP) plays a major role in Na(+)-dependent bile acid uptake into hepatocytes. The purpose of the present study was to establish the heterologous expression of human NTCP (hNTCP) in Xenopus laevis oocytes and to elucidate whether the transport of bile acid via hNTCP is electrogenic using electrophysiological techniques. First, we evaluated the uptake of taurocholate (TCA) by hNTCP heterologously expressed in Xenopus oocytes utilizing [(3)H]-labeled TCA. The uptake of 1.2 µM TCA by cRNA-injected oocytes increased more than 100-fold compared to H2O-injected oocytes, indicating that hNTCP is robustly expressed in the oocytes. hNTCP-mediated transport of TCA is saturable with a Michaelis constant of 10.5 ± 2.9 µM. The Na(+)-activation kinetics describing the relationship between the concentration of Na(+) and the magnitude of the TCA uptake rate by hNTCP were sigmoidal with a Hill coefficient of 2.3 ± 0.4, indicating the involvement of more than one Na(+) in the transport process. Ntcp in primary cultured hepatocytes from rats exhibited similar Na(+)-activation kinetics of TCA uptake rate with a Hill coefficient of 1.9 ± 0.1, suggesting that hNTCP could be expressed properly in the oocytes and exhibit the electrogenic property of Na(+)-coupled TCA transport. The transport of TCA via hNTCP was subsequently determined in the oocytes by the inward currents induced via TCA uptake under voltage (-50 mV). Two hundred micromolar TCA induced significant inward currents that were entirely abolished by the substitution of Na(+) with N-methyl-d-glucamine (NMDG) in the perfusate, indicating that the TCA-induced currents were obligatorily dependent on the presence of Na(+). The TCA-induced currents were saturable, and the substrate concentration needed for half-maximal induction of the current was consistent with the Michaelis constant. Transportable substrates, such as rosuvastatin and fluvastatin, also induced currents. These results in the hNTCP heterologously expressed in Xenopus oocytes directly demonstrated that hNTCP is an electrogenic Na(+)-dependent transporter.

Evaluation of a new image-enhanced endoscopic technology using band-limited light for detection of esophageal squamous cell carcinoma.

BACKGROUND: The aim of the present study was to evaluate the clinical utility of a new image-enhanced endoscopy (IEE) technology called optical enhancement imaging (OEI-1, -2, -3) by quantitatively evaluating diagnostic performance in superficial esophageal squamous cell carcinoma (SCC) in order to facilitate detection and characterization of gastrointestinal tumors. PATIENTS AND METHODS: The study involved 10 esophageal SCC resected endoscopically at our hospital. Ex vivo observation of the boundary area between normal and SCC was done using each mode (white light image [WLI], OEI-1, OEI-2, and OEI-3) with and without magnification. The additional effect of OEI on WLI was evaluated by calculating the color difference (expressed as ΔE94 ) between SCC and normal epithelium, and that between the intraepithelial papillary capillary loop (IPCL) and inter-vascular background coloration (IVBC). RESULTS: Mean ΔE94 values between SCC and normal epithelium for WLI, OEI-1, OEI-2, and OEI-3 were 9.37 ± 4.64, 13.82 ± 4.46,13.26 ± 4.73, and 16.44 ± 4.83, respectively; the corresponding values between IPCL and IVBC were 17.57 ± 10.17, 29.32 ± 9.95, 25.41 ± 11.72, and 23.71 ± 11.58, respectively. Compared with WLI, all OEI exhibited significant additional effect on ΔE94 . Furthermore, we found significant additional effect of OEI-3 in observing SCC and normal epithelium, and of OEI-1 in observing IPCL and IVBC, compared with other OEI. CONCLUSION: These results suggest that OEI improves endoscopic detection and characterization of esophageal SCC compared with WLI. Moreover, the data indicate that OEI-3 is useful for detection and OEI-1 is useful for characterization of esophageal SCC.

Factors predictive of inaccurate determination of horizontal extent of intestinal-type early gastric cancers during endoscopic submucosal dissection: a retrospective analysis.

BACKGROUND: Certain tumor characteristics may pose challenges when endoscopically determining the horizontal extent of early gastric cancers (EGC). In the present study, clinicopathological features related to inaccurate endoscopic evaluation of horizontal extent of intestinal-type EGC were analyzed. PATIENTS AND METHODS: We analyzed 431 lesions with intestinal-type EGC treated by endoscopic submucosal dissection (ESD) at our hospital. We focused on whether pretreatment demarcation was accurate by comparing positional relationships between marking dots and tumor edges in resected specimens, and factors related to inaccurate evaluation were analyzed. Gender, age, tumor size, location, circumference, depth, ulceration, macroscopic type, presence of a flat (0-IIb) component, predominant histological type, mixture of diffuse-type adenocarcinoma, mixed histology, and use of magnification endoscopy with narrow band imaging were analyzed. Reasons for inaccurate evaluation were also investigated by re-examining endoscopic images and prepared histological slides. RESULTS: Rate of inaccurate evaluation of horizontal extent was 7.4% (32/431 lesions). Multivariate analysis revealed the following significant independent variables contributing to inaccurate endoscopic evaluation: presence of a flat component, large size, and predominant histological findings of moderately differentiated adenocarcinoma. Re-examination of prepared histological slides of inaccurately evaluated cases revealed a marginal flat spreading area in 28 of the 32 lesions (87.5%). In 14 of the 32 lesions (43.8%), tumor margins were composed of moderately differentiated adenocarcinoma. CONCLUSIONS: For lesions with a flat component, large lesions, and moderately differentiated adenocarcinoma, determination of the horizontal extent can be challenging in EGC indicated for ESD, even with the best available endoscopic tools.

1,8-cineole, a TRPM8 agonist, is a novel natural antagonist of human TRPA1.

BACKGROUND: Essential oils are often used in alternative medicine as analgesic and anti-inflammatory remedies. However, the specific compounds that confer the effects of essential oils and the molecular mechanisms are largely unknown. TRPM8 is a thermosensitive receptor that detects cool temperatures and menthol whereas TRPA1 is a sensor of noxious cold. Ideally, an effective analgesic compound would activate TRPM8 and inhibit TRPA1. RESULTS: We screened essential oils and fragrance chemicals showing a high ratio of human TRPM8-activating ability versus human TRPA1-activating ability using a Ca2+-imaging method, and identified 1,8-cineole in eucalyptus oil as particularly effective. Patch-clamp experiments confirmed that 1,8-cineole evoked inward currents in HEK293T cells expressing human TRPM8, but not human TRPA1. In addition, 1,8-cineole inhibited human TRPA1 currents activated by allyl isothiocyanate, menthol, fulfenamic acid or octanol in a dose-dependent manner. Furthermore, in vivo sensory irritation tests showed that 1,8-cineole conferred an analgesic effect on sensory irritation produced by TRPA1 agonists octanol and menthol. Surprisingly, 1,4-cineole, which is structurally similar and also present in eucalyptus oil, activated both human TRPM8 and human TRPA1. CONCLUSIONS: 1,8-cineole is a rare natural antagonist of human TRPA1 that has analgesic and anti-inflammatory effects possibly due to its inhibition of TRPA1.

Rebamipide induces dendritic cell recruitment to N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)-exposed rat gastric mucosa based on IL-1ß upregulation.

Rebamipide is usually used for mucosal protection, healing of gastric ulcers, treatment of gastritis, etc., but its effects on gastric malignancy have not been elucidated. Using Lewis and Buffalo rat strains treated with peroral administration of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), we evaluated the effect of rebamipide on the induction of tumor-suppressive dendritic cells, which are known to be heterogeneous antigen-presenting cells of bone marrow origin and are critical for the initiation of primary T-cell responses. Using CD68 as a marker for dendritic cells, the stomach pyloric mucosae of Lewis and Buffalo rats were immunohistochemically analyzed in the presence or absence of rebamipide and MNNG. After a 14-day treatment of rebamipide alone, no significant change in number of CD68-expressing cells was detected in either rat strain. However, after concurrent exposure to MNNG for 14 days, treatment with rebamipide slightly increased CD68-positive cells in the Lewis strain, and significantly increased them in the Buffalo strain. Analysis of two chemotactic factors of dendritic cells, IL-1ß and TNF-α, in the gastric cancer cells showed that expression of IL-1ß, but not TNF-α, was induced by rebamipide in a dose-dependent manner. A luciferase promoter assay using gastric SH-10-TC cells demonstrated that an element mediating rebamipide action exists in the IL-1ß gene promoter region. In conclusion, rebamipide has potential tumor-suppressive effects on gastric tumorigenesis via the recruitment of dendritic cells, based on the upregulation of the IL-1ß gene in gastric epithelial cells.

Lifestyle factors affecting gastroesophageal reflux disease symptoms: a cross-sectional study of healthy 19864 adults using FSSG scores.

BACKGROUND: Gastroesophageal reflux disease (GERD) is a very common disorder worldwide, comprised of reflux esophagitis (RE) and non-erosive reflux disease (NERD). As more than half of GERD patients are classified into the NERD group, precise evaluation of bothersome epigastric symptoms is essential. Nevertheless, compared with many reports targeting endoscopic reflux esophagitis, large-scale studies focusing on GERD symptoms have been very scarce. METHODS: To elucidate lifestyle factors affecting GERD symptoms, 19,864 healthy adults in Japan were analyzed. Sub-analyses of 371 proton pump inhibitor (PPI) users and 539 histamine H2-receptor antagonist (H2RA) users were also performed. Using the FSSG (Frequency Scale for the Symptoms of GERD) score as a response variable, 25 lifestyle-related factors were univariately evaluated by Student's t-test or Pearson's correlation coefficient, and were further analyzed with multiple linear regression modelling. RESULTS: Average FSSG scores were 4.8 ± 5.2 for total subjects, 9.0 ± 7.3 for PPI users, and 8.2 ± 6.6 for H2RA users. Among the total population, positively correlated factors and standardized coefficients (ß) for FSSG scores are inadequate sleep (ß = 0.158), digestive drug users (ß = 0.0972 for PPI, ß = 0.0903 for H2RA, and ß = 0.104 for others), increased body weight in adulthood (ß = 0.081), dinner just before bedtime (ß = 0.061), the habit of midnight snack (ß = 0.055), lower body mass index (ß = 0.054), NSAID users (ß = 0.051), female gender (ß = 0.048), lack of breakfast (ß = 0.045), lack of physical exercise (ß = 0.035), younger age (ß = 0.033), antihyperglycemic agents non-users (ß = 0.026), the habit of quick eating (ß = 0.025), alcohol drinking (ß = 0.025), history of gastrectomy (ß = 0.024), history of cardiovascular disease (ß = 0.020), and smoking (ß = 0.018). Positively correlated factors for PPI users are female gender (ß = 0.198), inadequate sleep (ß = 0.150), lack of breakfast (ß = 0.146), antihypertensive agent non-users (ß = 0.134), and dinner just before bedtime (ß = 0.129), whereas those for H2RA users are inadequate sleep (ß = 0.248), habit of midnight snack (ß = 0.160), anticoagulants non-users (ß = 0.106), and antihypertensive agents non-users (ß = 0.095). CONCLUSIONS: Among many lifestyle-related factors correlated with GERD symptoms, poor quality of sleep and irregular dietary habits are strong risk factors for high FSSG scores. At present, usual dose of PPI or H2RA in Japan cannot fully relieve GERD symptoms.

Pretransplantation combined therapy with plasmapheresis and rituximab in a second living-related kidney transplant pediatric recipient with a very high risk for focal segmental glomerulosclerosis recurrence.

Prophylactic PP can provide some protection against post-transplantation recurrences of FSGS, but it cannot prevent recurrences in all cases. Therefore, new preventive therapies are needed. We report on a 7.9-yr-old girl treated with pretransplantation prophylactic combined therapy consisting of four sessions of PP and one dose of rituximab before a second living-related KTX. The patient had a very high risk of post-transplantation FSGS recurrence because this had occurred after the first KTX. During the 36 months since the second transplantation, she has had no evidence of proteinuria or significant infectious complications. Although our experience is too preliminary to draw any generalizable conclusions, pretransplantation combined therapy with PP and rituximab might be a possible option for the prevention of FSGS recurrence in very high-risk recipients undergoing living-donor KTXs.

Endoscopic mucosal resection with a ligation device or endoscopic submucosal dissection for rectal carcinoid tumors: an analysis of 24 consecutive cases.

AIMS: Endoscopic submucosal dissection (ESD) has several advantages over conventional endoscopic mucosal resection, including a higher en bloc resection rate and more accurate pathological estimation. However, ESD is a complex procedure that requires advanced endoscopic skills. The aim of our study is to evaluate the efficacy of endoscopic mucosal resection with a ligation device (EMR-L) compared to ESD for rectal carcinoid tumors. METHODS: Between September 2003 and April 2011, 24 rectal carcinoid tumors in 24 patients treated by ESD or EMR-L were retrospectively analyzed. The indications for endoscopic treatment were node-negative rectal carcinoid tumors. We compared the therapeutic outcomes of the ESD group (n = 13) and the EMR-L group (n = 11). RESULTS: Both groups had similar mean tumor sizes (ESD: 5.5 ± 2.1 mm; EMR-L: 4.4 ± 2.2 mm). The rates of en bloc and complete resection were, respectively, 100% and 92.3% for ESD, and 100% and 100% for EMR-L. Perforations did not occur in either group. Postoperative bleeding occurred in one EMR-L case, and it was endoscopically managed. However, there were no differences in therapeutic outcomes between the two groups. The mean procedure time was longer in the ESD group (28.8 ± 16.2 min) than in the EMR-L group (17.4 ± 4.4 min), without a significant difference. The mean hospitalization period was significantly shorter in the EMR-L group (1.8 ± 3.1 day) than in the ESD group (6.2 ± 2.1 day), and eight EMR-L cases were treated in an outpatient setting. CONCLUSIONS: EMR-L is a simple and effective procedure that compares favorably to ESD for small rectal carcinoid tumors.

Postprandial fullness correlates with rapid inflow of gastric content into duodenum but not with chronic gastritis.

BACKGROUND: The aim of this study is evaluating the correlation of postprandial fullness with chronic gastritis or rapid inflow of gastric content into duodenum, based on double-contrast barium X-ray imaging. METHODS: 253 healthy subjects who underwent upper gastrointestinal barium X-ray examination were analyzed. Chronic gastritis was judged from mucosal atrophy and hypertrophic thickened folds on barium X-ray images. For the gastric excretion, the tips of barium flow on the single-contrast frontal barium X-ray images of the stomach were classified into four categories; V type (all the barium remained in the stomach), V-H type (some barium had flowed into the duodenum but the tip of barium remained in the proximal half of the duodenal bulb), H-V type (some barium had flowed into the duodenum and the tip of barium was in the distal half of duodenal the bulb, but no barium was observed in the descending part of the duodenum), and H type (some barium had flowed into the descending part of the duodenum). The chi-square test and Cochran-Mantel-Haenzel test were used for evaluation. RESULTS: Chronic gastritis was observed in 72 subjects, among which 21 subjects (29.2%) presented with postprandial fullness. For the remaining 181 subjects without chronic gastritis, 53 subjects (29.3%) complained of postprandial fullness. There is no significant correlation between chronic gastritis and postprandial fullness (p = 0.973). For the rapid flow of gastric content into duodenum, all the 253 subjects comprised 136 subjects with V type (in the stomach), 40 subjects with V-H type (in the proximal half of the duodenal bulb), 21 subjects with H-V type (in the distal half of the duodenal bulb), and 56 subjects with H type (in the descending part of the duodenum). Postprandial fullness was present in 30 subjects with V type (22.1%), 9 subjects with V-H type (22.5%), 8 subjects with H-V type (38.1%), and 27 subjects with H type (48.2%). There is a distinct correlation between postprandial fullness and gastric barium excretion on barium X-ray imaging (p = 0.002). CONCLUSIONS: Bothersome postprandial fullness correlates with rapid inflow of gastric content into duodenum, but not with chronic gastritis.

Simultaneous determination of histamine and prostaglandin D2 using an LC-ESI-MS/MS method with positive/negative ion-switching ionization modes: application to the study of anti-allergic flavonoids on the degranulation of KU812 cells.

A new method for simultaneous determination of histamine and prostaglandin D(2) (PGD(2)) by liquid chromatography-electrospray ionization tandem mass spectrometry operated in positive and negative ionization switching modes was developed and validated without a previous derivatization step. This method was used to measure histamine and PGD(2) release following degranulation of KU812 human basophilic cells, using pyrazol and d(4)-PGD(2) as internal standards. Analyses were performed on a liquid chromatography system employing a Cosmosil 5C(18) PAQ column and an isocratic elution with mixed solution of methanol-water (7:3, v/v) with 0.0015% trifluoroacetic acid at a flow rate of 0.2 mL/min. A triple-quadrupole mass spectrometer operating in selected reaction monitoring mode simultaneously monitored using the following transitions: positive m/z 112/95 for histamine and negative m/z 351/271 for PGD(2). The retention times of histamine and pyrazol were 4.2 and 5.0 min, respectively. PGD(2) and d(4)-PGD(2) had retention times of 8.5 min. The limits of detection were 0.3 and 0.5 ng/mL for histamine and PGD(2), respectively. The relative standard deviations of the retention time and peak area for histamine were between 1.6% and 7.7%, and were 1.2% and 7.8% for PGD(2). This method was used to evaluate the anti-allergic effects of 26 flavonoids and sodium cromoglicate which are first-line anti-allergic drugs. Of these compounds, baicalein and morin were the most potent inhibitors.

A case of a 6-year-old girl with anti-neutrophil cytoplasmic autoantibody-negative pauci-immune crescentic glomerulonephritis.

A 6-year-old girl was admitted to our hospital with proteinuria, hematuria, skin rash and joint pain of the lower limbs. Due to rapid progression of renal insufficiency, hemodialysis and peritoneal dialysis were performed. She was diagnosed with rapidly progressive glomerulonephritis. Kidney biopsy showed severe crescent formation (50% of glomeruli) and no deposition of any immunoglobulins or complements. Serologically, anti-neutrophil cytoplasmic autoantibody (ANCA) was negative not only by ELISA against proteinase-3 and myeloperoxidase-ANCA but also by indirect immunofluorescent assay against cytoplasmic and perinuclear ANCA. Anti-glomerular basement membrane antibody was also negative. In the acute phase, proinflammatory cytokines such as soluble tumor necrosis factor receptor 1 (sTNFR1), soluble interleukin (IL)-2 receptor (sIL2R), IL-6 and chemokine IL-8 were elevated. The patient was diagnosed with ANCA-negative pauci-immune crescentic glomerulonephritis (CrGN). Intensive treatment with methylprednisolone pulse therapy, plasma exchange, and multiple drug therapy including prednisolone and cyclophosphamide resulted in histopathological improvement and complete remission of proteinuria. There was a possibility that sTNFR1, sIL2R, IL-6 and IL-8 might be involved in the initiation and progression of ANCA-negative pauci-immune CrGN, and to remove and suppress these cytokines might be an effective way to treat ANCA-negative pauci-immune CrGN.

ERK5 activation enhances mesangial cell viability and collagen matrix accumulation in rat progressive glomerulonephritis.

The mitogen-activated protein kinase (MAPK) cascade plays an important role in the regulation of various cellular functions in glomerulonephritis (GN). Here, we investigated whether extracellular signal-regulated kinase 5 (ERK5), a member of the MAPK family, is involved in the pathogenesis of chronic mesangioproliferative GN, using a rat model induced by uninephrectomy and anti-Thy-1 antibody injection. Immunostaining of kidneys obtained at different time points revealed that phospho-ERK5 was weakly expressed in control glomeruli but dramatically increased in a typical mesangial pattern after 28 and 56 days of GN. A semiquantitative assessment indicated that glomerular phospho-ERK5 expression closely paralleled the accumulation of extracellular matrix (ECM), collagen type I, as well as glomerular expression of reactive oxygen species (ROS) and ANG II. On the other hand, phospho-ERK1/2 expression increased on day 7 during the phase of enhanced mesangial cell (MC) proliferation and decreased thereafter. H(2)O(2) and ANG II each induced ERK5 phosphorylation by cultured rat MCs. Costimulation with both H(2)O(2) and ANG II synergistically increased ERK5 phosphorylation in MCs. Cultured MCs transfected with ERK5-specific small interference RNA showed a significant decrease in H(2)O(2) or ANG II-induced cell viability and soluble collagen secretion compared with control cells. Treatment of GN rats with an ANG II type 1 receptor blocker resulted in significant decreases in phospho-ERK5 expression and collagen accumulation accompanied by remarkable histological improvement. Taken together, these results suggest that MC ERK5 phosphorylation by ANG II or H(2)O(2) enhances cell viability and ECM accumulation in an experimental model of chronic GN.

Fabrication of quantum-dot devices in graphene.

We describe our recent experimental results on the fabrication of quantum-dot devices in a graphene-based two-dimensional system. Graphene samples were prepared by micromechanical cleavage of graphite crystals on a SiO2/Si substrate. We performed micro-Raman spectroscopy measurements to determine the number of layers of graphene flakes during the device fabrication process. By applying a nanofabrication process to the identified graphene flakes, we prepared a double-quantum-dot device structure comprising two lateral quantum dots coupled in series. Measurements of low-temperature electrical transport show the device to be a series-coupled double-dot system with varied interdot tunnel coupling, the strength of which changes continuously and non-monotonically as a function of gate voltage.

Coupled quantum dots in a graphene-based two-dimensional semimetal.

We present an experimental demonstration of a graphene-based double quantum dot system, which exhibits single-electron transport of two lateral quantum dots coupled in series. Low-temperature transport measurements revealed honeycomb charge stability diagrams with a varied (from weak to strong) interdot tunnel-coupling regime, and we have extracted the relevant parameters associated with the double quantum dot system. These results are important for the realization of integrated quantum circuits in graphene-based electronics.

Characterization of emodin metabolites in Raji cells by LC-APCI-MS/MS.

A rapid, simple, and sensitive liquid chromatography-atmospheric pressure chemical ionization tandem mass spectrometry (LC-APCI-MS/MS) method was developed for the identification and quantification of emodin metabolites in Raji cells, using aloe-emodin as an internal standard. Analyses were performed on an LC system employing a Cosmosil 5C(18) AR-II column and a stepwise gradient elution with methanol-20mM ammonium formate at a flow rate of 1.0 mL/min operating in the negative ion mode. As a result, the starting material emodin and its five metabolites were detected by analyzing extracts of Raji cells that had been cultivated in the presence of emodin. The identification of the metabolites and elucidation of their structures were performed by comparing their retention times and spectral patterns with those of synthetic samples. In addition to the major metabolite 8-O-methylemodin, four other metabolites were assigned as omega-hydroxyemodin, 3-O-methyl-omega-hydroxyemodin, 3-O-methylemodin (physcion), and chrysophanol.

Development of an LC-ESI-MS/MS method for the determination of histamine: application to the quantitative measurement of histamine degranulation by KU812 cells.

A rapid, simple, and sensitive liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS) method was developed for the identification and quantification of histamine without a previous derivatization step or the addition of general ion-pairing reagents to the mobile phase. This method was used to measure histamine release following degranulation of KU812 human basophilic cells, using pyrazol as an internal standard. Analyses were performed on an LC system employing a Cosmosil 5C(18) PAQ column and an isocratic elution with methanol-0.005% trifluoroacetic acid (1:1) at a flow rate of 0.2 mL/min. A triple-quadrupole mass spectrometer, equipped with an electrospray ionization interface was employed, operating in the positive ion mode. The retention time of histamine and the internal standard were 4.0 and 5.0 min, respectively. The relative standard deviations (R.S.D.s) of the retention time and peak area were between 0.47% and 2.03%. Micropipette tip solid-phase extraction (SPE) using LooseTip C(18) allowed for not only rapid sample preparation, but also decreased suppression effects, improving peak shape. This method was used to evaluate the anti-allergic effects of compounds contained in Taxus yunnanensis extracts. Four constituents that were isolated from the wood extracts of T. yunnanensis and sodium cromoglicate, which is used as a first line anti-allergic drug, were tested in an in vitro histamine release inhibition assay. Of these compounds, taxiresinol and isotaxiresinol were more inhibitory than sodium cromoglicate.