Hyuk Kim

Bupivacaine Induces Apoptosis via ROS in the Schwann Cell Line

Local anesthetics have been generally accepted as being safe. However, recent clinical trials and basic studies have provided strong evidence for the neurotoxicity of local anesthetics, especially through apoptosis. We hypothesized that local anesthetics cause neural complications through Schwann cell apoptosis. Among local anesthetics tested on the Schwann cell line, RT4-D6P2T, bupivacaine significantly induced cell death, measured by the methyl tetrazolium (MTT) assay, in a dose- (LD50 = 476 μM) and time-dependent manner. The bupivacaine-induced generation of reactive oxygen species (ROS), which was initiated within 5 hrs and preceded the activation of caspase-3 and poly ADP-ribose polymerase (PARP) degradation, was suggested to trigger apoptosis, exhibited by Hoechst 33258 nuclear staining and DNA fragmentation. Furthermore, concomitant block of ROS by anti-oxidants significantly inhibited bupivacaine-induced apoptosis. Among the local anesthetics for peripheral neural blocks, bupivacaine induced apoptosis in the Schwann cell line, which may be associated with ROS production.

On the Volume Formula for Hyperbolic Tetrahedra

Abstract. We present a volume formula for arbitrary hyperbolic tetrahedra and give applications for Coxeter tetrahedra.

Mechanism of Azithromycin Treatment on Gingival Overgrowth

Azithromycin is effective for the remission of cyclosporine A-induced gingival overgrowth (CIGO) in persons who have undergone renal transplant. To explain its mechanism in alleviating the clinical symptoms of these indivduals, we examined the effect of azithromycin on cell proliferation and collagen turnover modified by cyclosporin A in human gingival fibroblasts from healthy persons and from persons who had undergone renal transplant. Cyclosporin A-induced proliferation of renal transplant fibroblasts and normal fibroblasts was inhibited by azithromycin. Azithromycin elevated the reduced metalloproteinase (MMP)-1 and MMP-2 activities in cyclosporine A-treated renal transplant fibroblasts and normal fibroblasts. In cyclosporine A-treated renal transplant fibroblasts, azithromycin blocked the accumulation of total collagen in culture media and the increase in type I collagen mRNA level, but recovered the reduced MMP-2 mRNA level to the control. These results suggest that azithromycin may improve CIGO by blocking cyclosporine A-induced cell proliferation and collagen synthesis, and by activating MMP-2 in gingival fibroblasts of persons with cyclosporine A-induced gingival overgrowth.

Optimistic limits of Kashaev invariants and complex volumes of hyperbolic links

Yokota suggested an optimistic limit method of the Kashaev invariants of hyperbolic knots and showed it determines the complex volumes of the knots. His method is very effective and gives almost combinatorial method of calculating the complex volumes. However, to describe the triangulation of the knot complement, he restricted his method to knot diagrams with certain conditions. Although these restrictions are general enough for any hyperbolic knots, we have to select a good diagram of the knot to apply his theory. In this paper, we suggest more combinatorial way to calculate the complex volumes of hyperbolic links using the modified optimistic limit method. This new method works for any link diagrams, and it is more intuitive, easy to handle and has natural geometric meaning.

Impact of the cation composition on the electrical performance of solution-processed zinc tin oxide thin-film transistors.

This study examined the structural, chemical, and electrical properties of solution-processed (Zn,Sn)O3 (ZTO) films with various Sn/[Zn+Sn] ratios for potential applications to large-area flat panel displays. ZTO films with a Zn-rich composition had a polycrystalline wurtzite structure. On the other hand, the Sn-rich ZTO films exhibited a rutile structure, where the Zn atom was speculated to replace the Sn site, thereby acting as an acceptor. In the intermediate composition regions (Sn/[Zn+Sn] ratio from 0.28 to 0.48), the ZTO films had an amorphous structure, even after annealing at 450 °C. The electrical transport properties and photobias stability of ZTO thin film transistors (TFTs) were also examined according to the Sn/[Zn+Sn] ratio. The optimal transport property of ZTO TFT was observed for the device with an amorphous structure at a Sn/[Zn+Sn] ratio of 0.48. The mobility, threshold voltage, subthreshold swing, and on/off current ratio were 4.3 cm(2)/(V s), 0 V, 0.4 V/decade, and 4.1 × 10(7), respectively. In contrast, the device performance for the ZTO TFTs with either a higher or lower Sn concentration suffered from low mobility and a high off-state current, respectively. The photoelectrical stress measurements showed that the photobias stability of the ZTO TFTs was improved substantially when the ZTO semiconducting films had a lower oxygen vacancy concentration and an amorphous structure. The relevant rationale is discussed based on the phototransition and subsequent migration mechanism from neutral to positively charged oxygen vacancies.

Antinociceptive curcuminoid, KMS4034, effects on inflammatory and neuropathic pain likely via modulating TRPV1 in mice

BACKGROUND Curcumin, the active ingredient of turmeric (Curcuma longa), has a wide range of beneficial effects including anti-inflammation and analgesia. However, poor bioavailability of curcumin hinders its clinical application. To overcome this limitation, we modified the structure of curcumin and synthesized new derivatives with favourable pharmacokinetic profiles. Recently, curcumin has been shown to have an antagonizing effect on transient receptor potential vanilloid type 1 (TRPV1) ion channels. We investigated the antinociceptive activity of KMS4034 which had the most favourable pharmacokinetics among the tested curcumin derivatives. METHODS To evaluate the mechanism of the antinociceptive effects of KMS4034, capsaicin (I(CAP))- and heat (I(heat))-induced currents in TRPV1 expressing HEK293 cells were observed after the application of KMS4034. Nociceptive behavioural measurement using the hot-plate test, formalin test, and chronic constriction injury (CCI) model were evaluated in mice. Also, calcitonin gene-related peptide (CGRP) was stained immunohistochemically in the L4/5 dorsal horns in mice with neuropathic pain. RESULTS I(CAP) (P<0.01) and I(heat) (P<0.05) of TRPV1 were significantly blocked by 10 μM KMS4034. Behaviourally, noticeable antinociceptive effects after 10 mg kg(-1) of KMS4034 treatment were observed in the first (P<0.05) and second phases (P<0.05) of the formalin and hot-plate tests. The mechanical threshold of CCI mice treated with 10 mg kg(-1) KMS4034 was significantly increased compared with control. Immunohistochemical CGRP expression was decreased in the lamina I-II of the lumbar dorsal horns in KMS4034-treated CCI mice compared with the control (P<0.05). CONCLUSIONS KMS4034 may be an effective analgesic for various pain conditions.

Only tetracaine and not other local anaesthetics induce apoptosis in rat cortical astrocytes

BACKGROUND The potential risks of neurotoxicity due to local anaesthetics after regional anaesthesia have been suggested recently. To evaluate the neurotoxicity of commonly used local anaesthetics, primary cultured rat cortical astrocytes were treated with lidocaine, ropivacaine, bupivacaine, levobupivacaine, and tetracaine. METHODS Cell death after local anaesthetic treatment was evaluated with a lactate dehydrogenase (LDH) assay. To examine the mechanisms of cell death, reactive oxygen species (ROS) measurement and western blots of poly-ADP ribose polymerase (PARP), procaspase-3, and mitogen-activated protein kinases family members were performed. RESULTS Of the local anaesthetics, which were applied at <1 mM for 18 h, only tetracaine significantly increased LDH leakage (P<0.05) and cell death in a dose- and time-dependent manner. Hoechst 33258-propidium iodide staining and western blots with PARP and procaspase-3 antibodies suggested that tetracaine induced apoptosis. ROS levels increased 2-fold at 30 min after tetracaine treatment compared with the control and then decreased. The antioxidants, N-acetylcysteine and trolox, markedly inhibited tetracaine-induced apoptosis. CONCLUSIONS Tetracaine induced apoptosis through ROS generation. Further studies focusing on the neurotoxicity of tetracaine are needed.

A CHARACTERIZATION OF CAYLEY HYPERSURFACE AND EASTWOOD AND EZHOV CONJECTURE

Eastwood and Ezhov generalized the Cayley surface to the Cayley hypersurface in each dimension, proved some characteristic properties of the Cayley hypersurface and conjectured that a homogeneous hypersurface in affine space satisfying these properties must be the Cayley hypersurface. We will prove this conjecture when the domain bounded by a graph of a function defined on ℝn is also homogeneous giving a characterization of Cayley hypersurface. The idea of the proof is to look at the problem of affine homogeneous hypersurfaces as that of left symmetric algebras with a Hessian type inner product. This method gives a new insight and powerful algebraic tools for the study of homogeneous affine hypersurfaces.

Effect of sputter power on the photobias stability of zinc-tin-oxide field-effect transistors

This study examined the effect of sputtering power on the performance of zinc-tin-oxide field-effect transistors and the stability under photobias stress. Large improvements in the saturation mobility and subthreshold swing were found in devices fabricated at higher sputtering powers; 13.80 cm2/V·s, 0.33 V/decade at a power of 400 W compared with 2.70 cm2/V·s, 1.19 V/decade at a power of 50 W. The threshold voltage shift under negative bias illumination stress (NBIS) for the device fabricated at a power of 400 W shows superior properties (−2.41 V) compared with that (−5.56 V) of the device fabricated at 50 W. The improvements in electrical performance and NBIS stability were attributed to the formation of a denser film and the reduced dielectric/channel interfacial trap densities due to the more energetic bombardment used under high power sputtering conditions.

On radicals of a left-symmetric algebra

(1999). On radicals of a left-symmetric algebra. Communications in Algebra: Vol. 27, No. 7, pp. 3161-3175.