Protection of porcine oocytes against apoptotic cell death caused by oxidative stress during In vitro maturation: role of cumulus cells

The present study was conducted to examine the protective effect of cumulus cells on oocyte damage caused by reactive oxygen species (ROS), generated by the hypoxanthine-xanthine oxidase (XOD) system, during in vitro maturation of porcine oocytes. Cumulus-oocyte complexes (COCs) and cumulus-denuded oocytes (DOs) were cultured for 44 h in NCSU37 supplemented with cysteine, gonadotropins, 10% porcine follicular fluid, and hypoxanthine in the presence or absence of XOD. DNA cleavage and damage were analyzed using the terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) method and single cell microgel electrophoresis (comet) assay, respectively, and caspase-3 activity and glutathione (GSH) content were measured in each experimental group. Exposure of DOs to ROS resulted in meiotic arrest and the increase of degenerated oocytes. These degenerated DOs underwent apoptosis, as shown by the TUNEL-positive reaction within their germinal vesicles and the activation of caspase-3. The length of DNA migration in DOs treated with XOD was significantly longer than that of untreated DOs (P: < 0.05). However, irreparable cell damage caused by ROS was not observed in COCs, and no difference was observed in the caspase-3 activity of both COCs treated with and without XOD. A significantly (P: < 0.05) high level of GSH was found in COCs after 44 h of culture, compared with that of oocytes freshly isolated from their follicles, whereas GSH content in DOs markedly decreased after treatment with or without XOD. These findings suggest that cumulus cells have a critical role in protecting oocytes against oxidative stress-induced apoptosis through the enhancement of GSH content in oocytes.

Studies on neplanocin A, new antitumor antibiotic. I. Producing organism, isolation and characterization

Neplanocin A. C11H13N5O3, is a novel carbocyclic analog of adenosine with cyclopentene. It was isolated from the culture filtrate of Ampullariella regularis A11079 by means of ion-exchange, carbon, silica gel adsorption, or partition chromatography. Neplanocin A forms crystals, and is stable at acidic or alkaline pH. Neplanocin A has cytotoxicity against L5178Y cells in culture and showed a remarkable effect on the life prolongation of mice infected with L1210 leukemia.

L-ascorbic acid alpha-glucoside formed by regioselective transglucosylation with rat intestinal and rice seed alpha-glucosidases: its improved stability and structure determination

The definite structure and chemical stability of a new glucoside of L-ascorbic acid (AA) which was enzymatically glucosylated with rat intestinal and rice seed alpha-glucosidases were reported. The stability of this AA derivative in water under aerobic conditions was proved by its remarkable resistance against enhanced oxidative degradation by heat, Cu2+ ion or ascorbate oxidase, and it was found to have no reducing activity toward radicals. These properties were obviously distinguishable from those of AA. This glucoside was effectively hydrolyzed by alpha-glucosidases which possessed the ability to synthesize itself, resulting in the liberation of AA activity. The conjugate was composed of equimoles of AA and glucose. Nuclear magnetic resonance spectra, mass spectra, pH profiles of ultraviolet spectra and pK(a) value of 3.10 supported the coupling of alpha-glucose to the 2-position of AA. From these results, its structure was assigned 2-O-alpha-D-glucopyranosyl-L-ascorbic acid, being distinct from 6-O-alpha-D-glucopyranosyl-L-ascorbic acid formed with Aspergillus niger alpha-glucosidase. These findings indicate that the 2-O-glucoside formed by regioselective transglucosylation withstands oxidative degradation even in aqueous solutions and it can be used as an available active AA source for multicomponent liquid products.

Formation of a stable L-ascorbic acid alpha-glucoside by mammalian alpha-glucosidase-catalyzed transglucosylation

Enzymatic transglucosylation from maltose to L-ascorbic acid (AA) with mammalian tissue homogenates was determined by a high-performance liquid chromatography method and compared with the reaction catalyzed by alpha-glucosidase from Aspergillus niger. The homogenates of small intestine and kidney had a high transglucosylase activity to form a new type of glucosylated AA, which was associated with alpha-glucosidase activity. The new compound was demonstrated to be an equimolar conjugate of AA and glucose by the spectral and quantitative analyses. In particular, it showed a high stability in a neutral solution and no reducing activity toward cytochrome c and a dye. These properties were very different from those of AA and L-ascorbic acid alpha-glucoside formed with alpha-glucosidase from A. niger, but they were consistent with those of L-ascorbic acid 2-O-phosphate and L-ascorbic acid 2-O-sulfate. Moreover, it exhibited a reducing power associated with AA after mild acid hydrolysis or treatment with rat intestinal alpha-glucosidase. These results indicate that it should be assigned the 2-O-alpha-glucoside structure. Consequently, it is concluded that mammalian alpha-glucosidase is able to form a very stable and nonreducing form of glucosylated AA through a specific transglucosylation reaction distinct from that of microbial alpha-glucosidase.

Collagen synthesis in human skin fibroblasts is stimulated by a stable form of ascorbate, 2-O-alpha-D-glucopyranosyl-L-ascorbic acid

We evaluated the effect of 2-O-alpha-D-glucopyranosyl-L-ascorbic acid (AA-2G) on collagen synthesis in cultured human skin fibroblasts and on proliferation of fibroblasts. At concentrations of 0.1-0.5 mmol/L, AA-2G effectively stimulated collagen synthesis with an effectiveness comparable to that of L-ascorbic acid. On the other hand, 6-O-alpha-D-glucopyranosyl-L-ascorbic acid showed a weak effect. The stimulation of collagen synthesis by AA-2G was attenuated by the addition of a collagen synthesis inhibitor, L-azetidine 2-carboxylic acid, in a dose-dependent manner. In addition, AA-2G-induced stimulation of collagen synthesis could be completely inhibited by the addition of castanospermine, an inhibitor of neutral alpha-glucosidase. Relatively high alpha-glucosidase activity, which would contribute to release of ascorbic acid from AA-2G, could be detected in the lysate of cultured fibroblasts. The stimulatory activity of AA-2G on collagen synthesis was observed after 5 d in culture, whereas L-ascorbic acid tended to lose its stimulatory activity. Continuous supplementation of AA-2G (0.25 mmol/L) to culture medium for 24 d enhanced the cell growth four times that of the control. These results indicate that AA-2G is gradually cleaved by the cellular alpha-glucosidase to release L-ascorbic acid, which adequately stimulates collagen synthesis and proliferation of human skin fibroblasts.

Enhancement of developmental competence after in vitro fertilization of porcine oocytes by treatment with ascorbic acid 2-O-alpha-glucoside during in vitro maturation

The present study was conducted to examine the effect of ascorbic acid 2-O-alpha-glucoside (AA-2G), a stable ascorbate derivative, on the sustenance of cytoplasmic maturation responsible for subsequent developmental competence after in vitro fertilization of porcine oocytes. Cumulus-oocyte complexes were cultured for 44 h in North Carolina State University 37 medium supplemented with cysteine, gonadotropins, 10% (v:v) porcine follicular fluid, and 0-750 microM AA-2G. When oocytes were matured in the presence of 250 microM AA-2G, their ability to promote transformation of the sperm nucleus into the male pronucleus (MPN) was strongly enhanced after in vitro fertilization. Similarly, the presence of 25 microM beta-mercaptoethanol (ME) enhanced the degree of progression to MPN of penetrated sperm by associating with the increase in intracellular glutathione (GSH) content. Although the AA-2G treatment during oocyte maturation showed no influence on the GSH concentration, significantly higher levels of ascorbic acid (AsA) were detected in these oocytes than in those oocytes cultured without AA-2G (P < 0.05). The length of DNA migration encompassed by reactive oxygen species (ROS), generated by the hypoxanthine-xanthine oxidase system, was not increased in the oocytes treated with AA-2G, whereas ME treatment could not block the DNA damage by ROS. These findings indicate that AA-2G in maturation medium can potentiate the cellular protection of oocytes against oxidative stress by continuously supplying AsA. The proportion of development to the blastocyst stage after in vitro insemination was significantly increased in oocytes matured with AA-2G (P < 0.05), and this proportion showed no difference in comparison with that of oocytes treated with ME. These findings suggest that a critical concentration of intracellular AsA, supplied by AA-2G during in vitro maturation, plays an important role in supporting the cytoplasmic maturation responsible for developmental competence after fertilization by prevention of oxidative stress against porcine oocytes.

Antiscorbutic activity of L-ascorbic acid 2-glucoside and its availability as a vitamin C supplement in normal rats and guinea pigs

Bioavailability of a newly-synthesized and chemically-stable 2-O-alpha-D-glucopyranosyl-L-ascorbic acid (AA-2G) as a vitamin C supplement was investigated in rats and guinea pigs. Oral administration of AA-2G to the animals resulted in an increase of serum ascorbic acid (AA) levels. However, in these sera the intact form was not detectable by the high performance liquid chromatography (HPLC) method, indicating its hydrolysis through the process of absorption. After an intravenous injection of AA-2G, the intact form diminished rapidly from the serum, followed by prolonged and marked elevation of serum AA levels. Various tissue homogenates from rats and guinea pigs were examined for their releasing activity of AA from AA-2G. High activity was observed in kidney, small intestine and serum of rats and in small intestine and kidney of guinea pigs. These hydrolytic activities were completely inhibited by castanospermine, a specific alpha-glucosidase inhibitor, suggesting the participation of alpha-glucosidase in the in vivo hydrolysis of AA-2G. AA-2G was found to exhibit obvious therapeutic effect in scorbutic guinea pigs by its repeated oral administrations. These results indicate that AA-2G is a readily available source of vitamin C activity in vivo.

Purification and reconstitution properties of human placental aromatase. A cytochrome P-450-type monooxygenase

The hemoprotein component of human placental aromatase (estrogen synthetase) has been purified to a high degree of homogeneity by a combination of affinity and adsorption chromatography on aminohexyl-Sepharose, concanavalin-A-Sepharose, and hydroxyapatite. The monomeric form of the enzyme has an Mr of 55000 +/- 1000 as estimated by sodium dodecyl sulfate gel electrophoresis. Its absolute spectrum shows a high-spin Soret band at 394 nm while its reduced, CO-difference spectrum has a maximum at 447 +/- 1 nm. Full reconstitution of aromatase activity was obtained when it was recombined with a homogeneous preparation of the higher-Mr form of either human placental, or bovine hepatic NADPH-cytochrome P-450 reductase. Critical factors for purification of the very unstable, membrane-bound hemoprotein with good retention of activity were, besides the chromatographic sequence, the use of the zwitterionic detergent 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate (Chaps) during the solubilization, and the stabilizing effect of the aromatase substrate, 4-androstene-3,17-dione, throughout the procedure. In the presence of NADPH, the reconstituted enzyme system smoothly aromatizes 19-oxoandrostenedione, 19-hydroxyandrostenedione and androstenedione in this order of reactivity. The same reconstituted system also aromatized testosterone, but it was inactive towards 19-norandrostenedione. Known cytochrome P-450 inhibitors decreased its activity. We conclude: (a) the terminal oxidase of human placental aromatase is indeed a cytochrome P-450-type monooxygenase; (b) the multistep aromatization reaction of C19 androstenes is catalyzed by a single enzyme; (c) aromatization of 19-norsteroids reported by other authors must be due to a different aromatase. Experimental data obtained with the reconstituted enzyme are fully compatible with the concept of a reaction mechanism for the aromatization sequence involving an all-trans, antiparallel elimination of the 19-methyl group, the 2 beta proton and the 1 alpha proton, rather than the 1 beta proton, as generally assumed.

Differential effect of the antidiabetic thiazolidinediones troglitazone and pioglitazone on human platelet aggregation mechanism

Troglitazone and pioglitazone, antidiabetic thiazolidinediones, are known to improve insulin resistance. However, the effect of these drugs on platelet aggregation remains unclear. The chemical structure of troglitazone contains vitamin E. Accordingly, we studied the effect of troglitazone, pioglitazone, and vitamin E on thrombin-induced platelet aggregation, metabolism of phosphoinositide, protein phosphorylation, protein kinase C (PKC)-alpha and -beta, and phosphatidylinositol (PI) 3-kinase activation in vitro in human platelets. Maximum platelet aggregation by ADP, collagen, and thrombin decreased in the presence of 0.1-1 micromol/l troglitazone and 500 nmol/l vitamin E for 60 min compared with controls. However, pioglitazone did not inhibit ADP-, collagen-, or thrombin-induced platelet aggregation. Pretreatment with troglitazone and vitamin E, but not with pioglitazone, resulted in decreases in thrombin-induced phosphatidic acid production, hydrolysis of phosphatidylinositol 4,5-bisphosphate by phospholipase C, and 47-kDa protein phosphorylation. Thrombin-induced PKC-alpha and -beta activation in membrane fraction was suppressed by pretreatment with troglitazone and vitamin E, but not with pioglitazone. Separately, troglitazone and pioglitazone stimulated PI 3-kinase activity, but thrombin-induced PI 3-kinase activation was suppressed by pretreatment with troglitazone and pioglitazone for 60 min. These results suggest that troglitazone and vitamin E, but not pioglitazone, have a potent inhibitory effect on platelet aggregation via suppression of the thrombin-induced activation of phosphoinositide signaling in human platelets. Finally, the chemical structure of vitamin E may contribute to the inhibitory effect of troglitazone on platelet aggregation in human platelets.

Characteristic distribution of cathepsin E which immunologically cross-reacts with the 86-kDa acid proteinase from rat gastric mucosa

The antiserum raised against the high-molecular-weight acid proteinase from rat gastric mucosa, termed 86-kDa acid proteinase, has been shown to recognize rat cathepsin E, but not cathepsin D (Muto, N. et al. (1987) J. Biochem. 101, 1069-1075). Using this specific antiserum, characteristic distribution of cathepsin E in rats was demonstrated. The enzyme was detected in a limited number of tissues, such as stomach, thymus, spleen, bladder, and erythrocyte membranes. Among them, the highest activity was observed in the stomach. In contrast, cathepsin D immunoreactive with the antiserum specific to rat gastric cathepsin D was demonstrated in all the tissues examined. Cathepsin E-type enzymes partially purified from these five tissues were precipitated in the same manner by the specific antiserum, and they had the same molecular weight, electrophoretic mobility, and resistance against denaturation by 4 M urea. These results indicate that they could be exactly classified as cathepsin E. This type of enzyme was also detectable in mice and guinea pigs, but they showed relatively weak immunoreactivities with the antiserum. Thus, it is concluded that the distribution of cathepsin E is intrinsically different from ordinary cathepsin D, suggesting that it has a different physiological role from cathepsin D.

Mycinamicins, new macrolide antibiotics. I. Taxonomy, production, isolation, characterization and properties

Mycinamicins, novel macrolide antibiotics were obtained from the culture broth of Micromonospora grisseorubida sp. nov. Isolation of five components, mycinamicins I, II, III, IV and V, was accomplished by silica gel adsorption or partition chromatography. Mycinsmicin I and II exhibit a strong UV absorption peak at 218 nm and have a shoulder at 240 nm. Mycinamicin III, IV and V show strong UV absorption peaks at 215 nm and around 280 nm. From their physicochemical and biological properties, the mycinamicins are classified as new macrolide antibiotics.

Characterization and expression of a P-450-like mycinamicin biosynthesis gene using a novel Micromonospora-Escherichia coli shuttle cosmid vector

A 29 kb shuttle cosmid vector, pTYS507, was constructed from a cryptic Micromonospora griseorubida plasmid and the Escherichia coli cosmid pJB8. Subcloning of mycinamicin II biosynthesis genes in pTYS507 led to the identification of a DNA region that could complement a mutant of M. griseorubida that lacked both hydroxylase and epoxidase activities. Nucleotide sequence and mutational analysis suggested that a single P-450-like protein catalyzes both reactions.

Induction of apoptosis by hinokitiol, a potent iron chelator, in teratocarcinoma F9 cells is mediated through the activation of caspase-3

Hinokitiol, a potent iron chelator, has been reported to induce differentiation in teratocarcinoma F9 cells with a reduction of viable cells. In this study, we examined the steps leading to eventual cell death by hinokitiol during differentiation. Hinokitiol induced DNA fragmentation of F9 cells in a concentration- and time-dependent manner. This effect was also observed in a cell-free system using the nuclei from intact cells and the cytosols from hinokitiol-treated cells. In contrast, hinokitiol methyl ether and hinokitiol-Fe (III) complex, which are deficient in iron-chelating activity, showed no DNA fragmentation activity in both cell culture and cell-free systems. These results suggest that iron deprivation by hinokitiol may be involved in the induction of apoptosis of F9 cells. Caspase-3, one of the key enzymes in the apoptotic cascade, was specifically activated by hinokitiol treatment, but not by the other two derivatives. In addition, its specific inhibitor, benzyloxycarbonyl-Val-Ala-Asp-fluoromethyl ketone, strongly blocked hinokitiol-induced DNA fragmentation. These results indicate that iron deprivation by hinokitiol can induce apoptosis of F9 cells through the activation of caspase-3.

Characterization of Bacillus stearothermophilus cyclodextrin glucanotransferase in ascorbic acid 2-O-alpha-glucoside formation

In this study, we characterized cyclodextrin glucanotransferase (CGTase) from Bacillus stearothermophilus in L-ascorbic acid-2-O-alpha-D-glucoside (AA-2G) formation and compared its enzymological properties with those of rat intestinal and rice seed alpha-glucosidases which had the ability to form AA-2G. CGTase formed AA-2G efficiently using alpha-cyclodextrin (alpha-CD) as a substrate and ascorbic acid (AA) as an acceptor. Several AA-2-oligoglucosides were also formed in this reaction mixture, and they could be converted to AA-2G by the additional treatment of glucoamylase. The optimum temperature for AA-2G formation was 70 degrees C and its optimum pH was around 5.0. CGTase also utilized beta- and gamma-CDs, maltooligosaccharides, dextrin, amylose, glycogen and starch as substrates, but not any disaccharides except maltose. CGTase showed the same acceptor specificity as two alpha-glucosidases, whereas its hydrolyzing activity towards AA-2G was very low compared with those of alpha-glucosidases. Cleavage profiles of AA-2-oligoglucosides by CGTase present a possible mechanism for AA-2G formation that CGTase transfers a glucose-hexamer to an acceptor at the first step and then a glucose is stepwisely removed from the non-reducing end of the product through glucoamylase-like action of this enzyme. These results indicate that CGTase is able to synthesize AA-2G more efficiently than rat and rice alpha-glucosidases and utilization of this enzyme makes the mass production of AA-2G possible.

Further studies on rat cathepsin E: subcellular localization and existence of the active subunit form

The subcellular localization of rat neutrophil cathepsin E was examined by a modification of the method of N. Borregaard et al. [(1983) J. Cell Biol. 97, 52-61]. When the postnuclear cavitate of rat neutrophils was subjected to density centrifugation on discontinuous Percoll gradients, three particulate bands, P1 (lowest; azurophil granule rich), P2 (middle; specific granule rich), and P3 (highest; plasma membrane rich), were segregated. A combined application of immunochemical and electrophoretic methods revealed a striking difference in subcellular localization between cathepsin E and cathepsin D: Cathepsin E was associated with P3 and soluble fractions, and cathepsin D was chiefly associated with P1 and P2 fractions. The results thus indicate that cathepsin E is a nonlysosomal acid proteinase in rat neutrophils. It was found that cathepsin E existed in two enzymatically active molecular forms, referred to as CE-I and CE-II, in rat neutrophil extracts. To examine the relationships between the two forms, cathepsin E was purified to homogeneity from rat gastric mucosae. The purified enzyme exhibited a single protein band of 43 kDa on sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis, but electrophoresis without SDS, followed by visualization of activity in the gel, revealed two activity bands corresponding to CE-II and CE-I in neutrophil extracts. Pretreatment of the enzyme with beta-mercaptoethanol or dithiothreitol resulted in an increase in CE-I activity with a concomitant decrease in CE-II activity on gels. Upon gel filtration, the molecular weights of CE-II and CE-I were estimated to be 98,000 and 51,000, respectively, strongly suggesting that they are the dimeric and monomeric forms of the cathepsin E subunit.

The crystal structure and physicochemical properties of L-ascorbic acid 2-glucoside

The stable L-ascorbic acid glucoside produced by the action of the cyclomaltodextrin glucanotransferase (CGTase, EC 2.4.1.19) from Bacillus stearothermophilus was crystallized from an aqueous solution. Determination of the molecular structure by single crystal X-ray analysis showed the compound to be 2-O-alpha-D-glucopyranosyl-L-ascorbic acid (AA-2G). The crystals are orthorhombic, space group P2(1)2(1)2(1), with unit-cell dimensions a = 11.929 A, b = 24.351 A, and c = 4.864 A. The D-glucopyranose residue has the 4C1 conformation. These conclusions are in good agreement with those based on the 13C-NMR spectrum. The general physicochemical properties of crystalline AA-2G are reported.

Purification and properties of a cathepsin D-like acid proteinase from rat gastric mucosa

A unique acid proteinase was purified from rat gastric mucosa by DEAE-Sepharose CL-6B chromatography, gel filtration and isoelectric focusing. The purified enzyme was homogeneous by polyacrylamide disc gel electrophoresis. The molecular weight of the enzyme was estimated to be 86000 by gel filtration on a Sephadex G-100 column. In SDS-polyacrylamide gel electrophoresis, the enzyme showed a single band corresponding to a molecular weight of 42000. So it was concluded that the native enzyme is composed of two identical monomeric units. The enzyme is a glycoprotein and its isoelectric point was determined to be 4.33. The enzyme hydrolyzed bovine hemoglobin with maximum activity at pH 3.0, but it showed considerably lower activity on bovine serum albumin or casein than on bovine hemoglobin. The enzyme was strongly inhibited by pepstatin, but not by urea or thiol-reactive inhibitors. These results lead us to conclude that this enzyme is a cathepsin D-like acid proteinase.

Enhancement by ascorbic acid 2-glucoside or repeated additions of ascorbate of mitogen-induced IgM and IgG productions by human peripheral blood lymphocytes

In this study, the effect of ascorbic acid 2-glucoside (AA-2G), a stable derivative of ascorbic acid (AsA), or repeated additions of ascorbate on antibody productions by human peripheral blood lymphocytes (PBLs) was examined, and the physiological function of AsA was evaluated. When human PBLs were stimulated with Staphylococcus aureus Cowan I or pokeweed mitogen, AA-2G remarkably increased the numbers of IgM- and IgG-secreting cells which were detected by enzyme-linked immunospot assay. Although a single addition of ascorbate was without effect, the effect of AA-2G was remarkably inhibited by the addition of castanospermine, an alpha-glucosidase inhibitor; and moreover, repeated additions of AsA to the culture medium during the culture period enhanced the response to the same level as did a single addition of AA-2G. These results indicate that AsA has the ability to stimulate the immunoglobulin productions by AA-2G. The phytohemagglutinin-induced proliferative response of PBLs was also stimulated by AA-2G. The intracellular AsA content in PBLs cultured with AA-2G was maintained at relatively high levels during the culture period, whereas the content with a single dose of AsA reached nearly zero by the end of the experiment. These in vitro findings suggest that AA-2G and AsA function as potent immunostimulators of antibody production in humans and that the intracellular AsA content is a key parameter for establishing the immune response of PBLs.

Enzymatic formation of a nonreducing L-ascorbic acid alpha-glucoside: purification and properties of alpha-glucosidases catalyzing site-specific transglucosylation from rat small intestine

We have previously found that some mammalian tissue homogenates can catalyze a unique transglucosylation from maltose to L-ascorbic acid (AA), resulting in a chemically stable AA derivative, L-ascorbic acid alpha-glucoside (AAG). In the present study, the enzyme responsible for this transglucosylation was isolated from rat intestinal membrane. The formation of AAG was determined by HPLC with an ODS column. The specific activity of AAG-forming enzyme was increased in parallel with that of alpha-glucosidase (maltose hydrolase) during the purification, and two neutral alpha-glucosidases, termed alpha-glucosidases I and II, were purified to apparent homogeneity. Their enzymological properties showed that they corresponded to maltase [EC 3.2.1.20] and sucrase-isomaltase complex [EC 3.2.1.48/10], respectively. Both enzymes could form AAG by splitting only maltose among the disaccharides examined, although alpha-glucosidase I possessed a considerably higher activity than the other enzyme. Both AAG formation and maltose hydrolysis were dependent on incubation temperature with the maximal activity at 60 degrees C, but there was an apparent difference between their pH optima. AAG thus formed could also be hydrolyzed by the purified enzymes. From these results, it is concluded that membrane-bound neutral alpha-glucosidases from rat intestine have site-specific transglucosylase activity to form nonreducing AAG which is distinct from L-ascorbic acid-6-O-alpha-D-glucoside.

Submandibular Glands Contribute to Increases in Plasma BDNF Levels

Brain-derived neurotrophic factor (BDNF) promotes survival and differentiation of neural cells in the central and peripheral nervous systems. BDNF has been detected in plasma, but its source has not yet been established. Expression of BDNF mRNA has been identified in the submandibular glands when male rats are exposed to acute immobilization stress. In the present study, we investigated whether plasma BDNF is influenced by the submandibular glands in this model. Acute immobilization stress for 60 min significantly increased the level of plasma BDNF. However, plasma BDNF elevation was markedly suppressed in bilaterally sialoadenectomized rats. There were no significant differences between stressed (60 min) and non-stressed rats with respect to the BDNF mRNA expression in the hippocampus, heart, lung, liver, pancreas, or spleen, as determined by real-time polymerase chain-reaction. These findings suggest that the submandibular glands may be the primary source of plasma BDNF in conditions of acute immobilization stress.

Mitogen-activated protein kinase regulates normal transition from metaphase to interphase following parthenogenetic activation in porcine oocytes

The decrease in maturation-promoting factor (MPF) activity precedes that in mitogen-activated protein kinase (MAPK) activity after egg activation, but the cellular functions of this delayed inactivation of MAPK are still unclear. The present study was conducted to examine the essential role of MAPK activity for supporting the transition from metaphase to interphase in porcine oocytes matured in vitro. The increases in the phosphorylated forms of MAPK and the activities of MAPK and histone H1 kinase (H1K) were shown in oocytes arrested at the metaphase II (MII) stage. After additional incubation of MII-arrested oocytes in medium with added U0126, a specific inhibitor of MAPK kinase, 24% of oocytes completed the second meiotic division and underwent entry into interphase with pronucleus (PN) formation, but not second polar body (PB-2) emission. The intensities of the phosphorylated forms of MAPK and the activities of MAPK and H1K in matured oocytes treated with U0126 were significantly decreased by the treatment with U0126. Electrostimulation to induce artificial activation caused both H1K and MAPK inactivation; the inactivation of H1K preceded the inactivation of MAPK and sustained high levels of MAPK activity were detected during the period of PB-2 emission. However, the time sequence required for MAPK inactivation was significantly reduced by the addition of U0126 to the culture medium following electrostimulation, resulting in the dramatic inactivation of MAPK distinct from that of H1K. In these oocytes, PB-2 emission was markedly inhibited but little difference was found in the time course of PN formation compared with oocytes not treated with U0126. These findings suggest that the decrease in MAPK activity is partly involved in driving matured oocytes out of metaphase to induce PN development, and that the delayed MAPK inactivation after the onset of MPF inactivation in activated oocytes has a crucial role for PB-2 emission to accomplish the transition from meiosis to mitosis.

Comparison of ascorbic acid and ascorbic acid 2-O-alpha-glucoside on the cytotoxicity and bioavailability to low density cultures of fibroblasts

Ascorbic acid 2-O-alpha-glucoside (AA-2G) is a stable ascorbate derivative which has vitamin C activity in vivo and in vitro. We studied whether AA-2G exerts a prooxidant action in cultured fibroblasts from chick embryo and human skin, as does ascorbic acid. At concentrations of 0.1-1.0 mM, ascorbic acid markedly reduced the viable cell number of low density cultures within 24 hr, whereas AA-2G had no such effect. The ascorbate cytotoxicity was dependent on the cell density at the time of its addition and it was characteristic of low density cultures. This cytotoxicity was completely prevented by catalase and partially by an Fe3+ ion chelator, desferrioxamine. In the early culture stage at which a morphological change in the fibroblasts began to occur, intracellular ascorbate concentrations in low density cultures after addition of ascorbic acid were much higher than in high density cultures. However, at the same concentrations, AA-2G did not cause an elevation even in low density cultures and it was also effective on collagen synthesis at high and medium densities. These results suggest that the abnormally accumulated ascorbic acid in the cells cultured at low density possibly amplifies the generation of oxygen radicals through the reduction of Fe3+ ions and subsequent oxidative reactions, leading to cell death. Therefore, it is concluded that AA-2G which supplies an adequate amount of ascorbic acid during culture period is a bioavailable ascorbate source without cytotoxicity.

Purification of oestrogen synthetase by high-performance liquid chromatography. Two membrane-bound enzymes from the human placenta

Human placental NADPH-cytochrome P-450 reductase, obtained by 2',5'-ADP-Sepharose affinity chromatography, was separated into two reductase-active peaks on a Pharmacia Mono-Q column. By this short, two-step chromatographic procedure, the two reductases were obtained in a homogeneous state with high retention of activity and in over 900-fold purification. Aromatase-reconstituting activity was present only in the higher-molecular-weight reductase (79 000 D), not in the smaller, 70 000 D reductase, which turned out to be a proteolysis product of the former. Both proteins were eluted as a single peak in reversed-phase high-performance liquid chromatography on a Protesil-diphenyl column. Similar results were obtained with bovine hepatic NADPH-cytochrome P-450 reductases. On the other hand, starting from a reductase-free preparation, we have obtained by high-performance ion-exchange chromatography and high-performance size-exclusion chromatography, only partial purification of the aromatase cytochrome P-450, which showed the following values: aromatase activity, 3.995 nmol/min/mg protein (60-fold purification); cytochrome P-450 content, 1.376 nmol/mg protein (23-fold purification); molecular weight, 165 000 D (estimated as an aggregate by size-exclusion chromatography). Although complete purification of the aromatase component has yet to be accomplished, our results suggest that high-performance ion-exchange chromatography on a Mono-Q column is very useful for the purification of acidic, membrane-bound enzymes with good retention of activity.

Innervation of multiple neck motor nuclei by single reticulospinal tract axons receiving tectal input in the upper cervical spinal cord

Axons of reticulospinal neurons (RSNs) activated monosynaptically by stimulation of the contralateral superior colliculus (SC) were stained with intraaxonal injection of horseradish peroxidase in the cat upper cervical spinal cord. Stem axons of single RSNs gave rise to multiple axon collaterals to laminae IX, VIII and VII over a few cervical segments. Single RSNs made contacts with retrogradely labeled neck motoneurons of different neck muscles. Therefore, RSNs were regarded as mediating output of the SC to functionally different groups of neck muscles simultaneously. The result gave evidence of neural implementation of a functional synergy for a neck movement at a single neuron level.

Requirement for cooperative interaction of interleukin-6 responsive element type 2 and glucocorticoid responsive element in the synergistic activation of mouse metallothionein-I gene by interleukin-6 and glucocorticoid

Metallothionein (MT)-inducing activity of interleukin (IL)-6 depends on the presence of glucocorticoid in hepatic cells. The synergistic action of IL-6 and glucocorticoid was observed in the transcriptional activation of the mouse MT (mMT)-I gene. We found that a 281-bp promoter was sufficient for IL-6 and glucocorticoid stimulation. Our inspection of this region revealed the putative type 1 and 2 IL-6 responsive elements (REs). Functional analyses of these regions were performed using luciferase reporter constructs, and it was observed that the type 2 IL-6RE exerted the major response to the IL-6 signal. The transcriptional factor binding to type 1 IL-6RE, nuclear factor-IL-6, hardly contributed to the activation of the mMT-I promoter by IL-6 and glucocorticoid. A glucocorticoid responsive element (GRE) was also required for the synergistic activation by IL-6 and glucocorticoid. Interestingly, this synergism was not observed when the type 2 IL-6RE and the GRE were kept apart. Therefore, the synergistic activation of the mMT-I gene by IL-6 and glucocorticoid may require not only that signal transducers and activators 3 (Stat3) and the glucocorticoid receptor (GR) bind to their respective responsive elements, but also that Stat3 and the GR physically interact with one another.