A unique vacuolar processing enzyme responsible for conversion of several proprotein precursors into the mature forms

AbstractProprotein precursors of vacuolar components are transported from the endoplasmic reticulum into vacuoles, where they are proteolytically processed into their mature forms. However, the processing mechanism in plant vacuoles is very obscure. Characterization of a purified processing enzyme is required to determine whether a single enzyme is responsible for processing many vacuolar proteins with a large variability of molecular structure. If this is true, how can it recognize the numerous varieties of processing sites? We have now purified a processing enzyme (Mt=37 000) from castor bean seeds. Our results show that the purified enzyme can process 3 different proproteins isolated from either the endoplasmic reticulum or transport vesicles in cotyledon cells to produce the mature forms of these proteins which are found at different suborganellar locations in the vacuole: the 2S protein found in the soluble matrix, the 11S globulin found in the insoluble crystalloid and the 51 kDa protein associated with the membrane. Thus a single vacuolar processing enzyme is capable of converting several proprotein precursors into their respective mature forms

Mechanisms of thrombin-Induced myometrial contractions: Potential targets of progesterone

Intrauterine bleeding during pregnancy is a major risk factor for preterm birth. Thrombin, the most abundant coagulation factor in blood, is associated with uterine myometrial contraction. Here, we investigated the molecular mechanism and signaling of thrombin-induced myometrial contraction. First, histologic studies of placental abruption, as a representative intrauterine bleeding, revealed that thrombin was expressed within the infiltrating hemorrhage and that thrombin receptor (protease-activated receptor 1, PAR1) was highly expressed in myometrial cells surrounding the hemorrhage. Treatment of human myometrial cells with thrombin resulted in augmented contraction via PAR1. Thrombin-induced signaling to myosin was then mediated by activation of myosin light chain kinase- and Rho-induced phosphorylation of myosin light chain-2. In addition, thrombin increased prostaglandin-endoperoxidase synthase-2 (PTGS2 or COX2) mRNA and prostaglandin E2 and F2α synthesis in human myometrial cells. Thrombin significantly increased the mRNA level of interleukine-1β, whereas it decreased the expressions of prostaglandin EP3 and F2α receptors. Progesterone partially blocked thrombin-induced myometrial contractions, which was accompanied by suppression of the thrombin-induced increase of PTGS2 and IL1B mRNA expressions as well as suppression of PAR1 expression. Collectively, thrombin induces myometrial contractions by two mechanisms, including direct activation of myosin and indirect increases in prostaglandin synthesis. The results suggest a therapeutic potential of progesterone for preterm labor complicated by intrauterine bleeding

ヒト白血病K562細胞でクロトリマゾールにより誘発される細胞死に対するマイクロモル濃度の亜鉛の影響

Our recent study showed that the simultaneous application of clotrimazole with CdCI2 or PbCI2 exerted potent cytotoxic action in rat thymocytes although respective agents were ineffective. It was also the case of ZnCl2 and clotrimazole in preliminary study using rat thymocytes. Since clotrimazole is supposed to be a candidate for anticancer drug, we examined the effects of clotrimazole, ZnCI2, and their combination on human leukemia K562 cells. The combination of clotrimazole and ZnCl2 exerted potent cytotoxic effects on the growth and lethality of K562 cells by presumably modifying the process of cell death. The result suggests the possibility that endogenous Zn2+ may modify the action of clotrimazole

ヒト白血病K562細胞におけるアドリアマイシン作用のクレモフォールELによる修飾

Adriamycin and paclitaxel are simultaneously used for cancer treatment in some cases. The formula of paclitaxel contains cremophor EL as a solvent. Since this solvent exerts diverse biological actions, the modification of adriamycin action by cremophor EL has been studied on human leukemia K562 cells. Cremophor EL did not significantly affect the concentration-response relation for antiproliferative action of adriamycin and the cell cycle changed by adriamycin. However, the induction of morphological change by adriamycin was significantly augmented by cremophor EL. The simultaneous application of cremophor EL increased the intensity of fluorescence from adriamycin trapped inside the cells in a concentration-dependent manner, suggesting an increase in intracellular concentration of adriamycin by cremophor EL. Adriamycin alone at concentrations higher than those to completely inhibit the growth induced morphological change in K562 cells. Therefore, cremophor EL may potentiate some of actions induced by adriamycin when adriamycin and paclitaxel are simultaneously applied

Basic limnological study in an alpine Lake Puma Yumco, the pre-Himalayas, China

Lake Puma Yumco is a typical alpine lake (altitude; 5,030m) located in the pre-Himalayas of Tibet, China. This study was the first limnologicak investigation. Puma Yumco (28°34'N,90°24'E) has the following morphometric properties: maximum length of 31 km; maximum width of 14 km; mean width of 9 km; shoreline of 90 km; surface area of 280 km²; shoreline development of 1.5. Transparency was approximately 10 m. Dissolved oxygen was l7 mg O₂ L⁻¹ and showed saturated values. Saljnity was 360 mg L⁻¹. The chemical type of the lake water was Mg-Ca-HCO₃-SO₄. Total nitrogenous nutrients and phosphate were extremely low at 1μM and 0.02 μM, respetively. Chlorophyll-a concentration was 0.2 mg chl.a m⁻³. Phytoplankton and zooplankton were dominated by Aphanocapsa. and Diaptomidae. The grain size of lake sediment was that of silt in most cases.Article信州大学山地水環境教育研究センター研究報告 2: 83-90(2004)departmental bulletin pape

Variable-grasping-mode underactuated soft gripper with environmental contact-based operation

A novel robotic gripper with soft surfaces and underactuated joints was proposed. The soft surface was fabricated from a deformable rubber bag filled with incompressible fluid and a microgripper inside the fluid. A ratchet was installed at the underactuated joint so that the joint\u27s rotation caused by contact with an environment, such as a supporting surface, can be preserved, and the actions of scooping and enveloping an object are realized. With one actuator, the gripper realized three modes, i.e., parallel gripper, pinching, and enveloping. The range of graspable objects was wide and included soft, rigid, deformable, fragile, small (boundary length less than 30 mm), large (more than 80 mm long), thin (less than 0.5 mm), and heavy (more than 3 kg) objects.INSPEC Accession Number: 1671251

Nitroprusside increases intracellular Zn2+ concentration without affecting cellular thiol content : A model experiment using rat thymocytes and FluoZin-3

Nitric oxide (NO) is cytotoxic under some conditions although it has physiological roles. It is recently proposed that the cytotoxicity of NO is resulted from its interaction with glutathione and zinc. Since we have revealed that a decrease in cellular content of non-protein thiols, presumably glutathione, induces intracellular Zn2+ release, there is a possibility that the cytotoxicity of nitroprusside, a donor of NO, is resulted from the interaction of NO with cellular thiols, leading to an increase in intracellular Zn2+ concentration. To test the possibility, the effects of nitroprusside on cell lethality, intracellular thiol content, and intracellular Zn2+ concentration were examined in rat thymocytes by using a flow cytometer with propidium iodide and FluoZin-3. Nitroprusside at concentrations of 0.3 mM or more (up to 10 mM) significantly augmented FluoZin-3 fluorescence, indicating an increase in intracellular Zn2+ concentration. It was also the case under external Zn2+-free condition, suggesting nitroprusside-induced release of intracellular Zn2+. However, nitroprusside at 10 mM did not affect cell lethality and cellular thiol content. Thus, it can be concluded that nitroprusside-induced increase in intracellular Zn2+ concentration is not related to its cytotoxicity

Tetracaine decreases intracellular Zn2+ concentration by inhibiting Zn2+ influx in rat thymocytes

In this study to examine the cytotoxic property of tetracaine, we cytometrically examined the effect of tetracaine on intracellular Zn2+ concentration by the use of FluoZin-3, a fluorescent indicator of intracellular Zn2+. Lidocaine was used as a reference drug. The incubation of rat thymocytes with tetracaine decreased the intensity of FluoZin-3 fluorescence while that with lidocaine increased the intensity. The incubation with 10 μM DTPA, a chelator for extracellular Zn2+, attenuated the tetracaine-induced decrease in fluorescence intensity. The application of ZnCl2 augmented FluoZin-3 fluorescence. The augmentation by ZnCl2 was a temperature-sensitive. Tetracaine attenuated the ZnCl2-induced augmentation of FluoZin-3 fluorescence. Taken together, the results suggest that tetracaine attenuates membrane Zn2+ influx, resulting in a decrease in intracellular Zn2+ concentration in rat thymocytes. Although the cells in this study are not targets for actions of local anesthetics, the result may give one clue to explain the difference between the cytotoxicity of local anesthetics since the action of tetracaine on FluoZin-3 fluorescence was opposite to that of lidocaine