Biochemical and hematologic effects of polyvinylpyrrolidone-wrapped fullerene C60 after oral administration.

The fullerene C60 is used in consumer products such as cosmetics owing to its antioxidative effects and is being developed for nanomedical applications. However, knowledge regarding the safety of fullerene C60, especially after oral administration, is sparse. Here, we examined the safety of fullerene C60 in mice after 7 d of exposure to orally administered polyvinylpyrrolidone (PVP)-wrapped fullerene C60 (PVP-fullerene C60). Mice treated with PVP-fullerene C60 showed few changes in the plasma levels of various markers of kidney and liver injury and experienced no significant hematologic effects. Furthermore, the histology of the colon of PVP-fullerene C60-treated mice was indistinguishable from that of control mice. These results suggest that PVP-fullerene C60 lacks toxicity after high-dose oral administration and indicate that PVP-fullerene C60 can be considered safe for oral medication. These data provide basic information that likely will facilitate the production of safe and effective forms of fullerene C60.

Effect of dried bonito (katsuobushi) and some of its components on GABAA receptors.

Katsuobushi, a popular Japanese food additive and traditional flavour enhancer, is produced from a fish, bonito, by a variety of processes, including boiling, sun drying, smoking and mould culturing. Aqueous katsuobushi (AK), which is produced from katsuobushi powder by extraction with water, and some of its aroma components, such as 2-ethyl-3-methylpyrazine and phenol derivatives, potentiated dose-dependently the response of the GABAA receptors expressed in Xenopus oocytes. When AK, 2-ethyl-3-methylpyrazine or 3-methoxyphenol were injected into mice prior to an intraperitoneal administration of pentobarbital, the pentobarbital-induced sleeping time increased. In an elevated plus maze test, intraperitoneal administration of 2-ethyl-3-methylpyrazine to mice increased significantly both the number of entries into the open arms and the duration of stay in the open arms, indicating anti-anxiety activity. Katsuobushi and its aroma components may modulate human mood or consciousness through acting on GABAA receptors in the brain.

[Extremely elderly patient in whom the pacing lead was implanted via the femoral vein].

We report on an extremely elderly patient in whom we were unable to insert a pacing lead via the subclavian or internal jugular vein because of a superior vena cava obstruction; we instead inserted the pacing lead via the femoral vein. The patient was a 98-year-old male. Thirty-nine years previously, pacemaker implantation was performed for complete atrioventricular block. Afterwards, pacemaker replacement and reimplantation had been performed a total of 15 times. The patient was recently admitted because of pacing failure. Pacemaker replacement was performed, but pacing was not possible because of disconnection of the pacing lead. Insertion of a new pacing lead was attempted via both subclavian veins and the right jugular vein but failed; this approach was abandoned and temporary pacing was done. Superior vena cava obstruction was noted on chest computed tomography (CT), and pacing lead insertion through the superior vena cava was deemed unfeasible. Myocardial electrode implantation was also considered, but general anesthesia was deemed problematic because of the patient's extreme age. A pacing lead was inserted via the right femoral vein, and the generator was implanted in the right lower abdomen. Postoperative pacing was satisfactory.

Crystal structure of an aromatic ring opening dioxygenase LigAB, a protocatechuate 4,5-dioxygenase, under aerobic conditions.

BACKGROUND: Sphingomonas paucimobilis SYK-6 utilizes an extradiol-type catecholic dioxygenase, the LigAB enzyme (a protocatechuate 4,5-dioxygenase), to oxidize protocatechuate (or 3,4-dihydroxybenzoic acid, PCA). The enzyme belongs to the family of class III extradiol-type catecholic dioxygenases catalyzing the ring-opening reaction of protocatechuate and related compounds. The primary structure of LigAB suggests that the enzyme has no evolutionary relationship with the family of class II extradiol-type catecholic dioxygenases. Both the class II and class III enzymes utilize a non-heme ferrous center for adding dioxygen to the substrate. By elucidating the structure of LigAB, we aimed to provide a structural basis for discussing the function of class III enzymes. RESULTS: The crystal structure of substrate-free LigAB was solved at 2.2 A resolution. The molecule is an alpha2beta2 tetramer. The active site contains a non-heme iron coordinated by His12, His61, Glu242, and a water molecule located in a deep cleft of the beta subunit, which is covered by the alpha subunit. Because of the apparent oxidation of the Fe ion into the nonphysiological Fe(III) state, we could also solve the structure of LigAB complexed with a substrate, PCA. The iron coordination sphere in this complex is a distorted tetragonal bipyramid with one ligand missing, which is presumed to be the O2-binding site. CONCLUSIONS: The structure of LigAB is completely different from those of the class II extradiol-type dioxygenases exemplified by the BphC enzyme, a 2,3-dihydroxybiphenyl 1,2-dioxygenase from a Pseudomonas species. Thus, as already implicated by the primary structures, no evolutionary relationship exists between the class II and III enzymes. However, the two classes of enzymes share many geometrical characteristics with respect to the nature of the iron coordination sphere and the position of a putative catalytic base, strongly suggesting a common catalytic mechanism.

Inactivation of Streptomyces subtilisin inhibitory by chemical modifications.

1. The inhibitory activity of an alkaline protease inhibitor, (Streptomyces subtilisin inhibitor) towards subtilisin is found to decrease by photooxidation sensitized by methylene blue with a clear pH dependence, the midpoint of which is about 6.0. 2. Amino acid analyses of photooxidized Streptomyces subtilisin inhibitor indicate that one of the two histidyl residues and the three methionyl residues are destroyed, concomittant with the loss of inhibitory activity. 3. In accordance with this observation, one of the clearly resolved nuclear magnetic resonances from C2-protons of the two histidyl residues is selectively diminished. This histidyl residue, sensitive to photooxidation and giving a proton magnetic resonance peak at lower field, is assigned to His-106 from peptide analyses. 4. Independent modification of methionyl residues by a reaction with H2O2 or Cl2 also decreases the inhibitory activity of Streptomyces subtilisin inhibitor. 5. Modification of lysyl, tyrosyl and tryptophanyl residues by diazonium-1-H-tetrazole does not lead to the loss of the inhibitory activity. 6. The above results indicate that one or more methionyl residue(s) are essential to the inhibitory activity of Streptomyces subtilisin inhibitor, whereas lysyl, tyrosyl and tryptophanyl residues are not essential to the inhibitory activity. Modification of His-106 is also strongly related to the loss of activity, although its distinct participation in the inactivation mechanism has not been demonstrated.

Kinetic study of lipoxygenase-hydroperoxylinoleic acid interaction.

Interaction of lipoxygenase with hydroperoxylinoleic acid, which is the product of this enzyme reaction and acts as an activator, was studied kinetically by the fluorescence stopped-flow method. The kinetic features are consistent with a two-step mechanism involving a fast bimolecular association process followed by a slow unimolecular process. The dissociation constant of the bimolecular process was 3 (+/-2) - 10(-5) M, which was appreciably dependent on temperature and pH, in contrast to the rate constant of the latter process. The enthalpy and the entropy of activation for the unimolecular process were estimated to be 21 kcal/mol and 20 e.u., respectively. The pH dependence of the rate constant indicated that an ionizable group with pK of about 8.6 is involved in the interaction. Linoleic acid, the substrate of lipoxygenase, and oleic acid inhibited the interaction between the lipoxygenase and the hydroperoxylinoleic acid by reducing the rate. A series of saturated monohydric alcohols also reduced the rate of the interaction as the chain length of the alcohols increases, though methanol and ethanol increased the rate of the interaction.

Peptide hydrogen exchange rates in Streptomyces subtilisin inhibitor.

The exchange reaction of the peptide NH protons of a microbial protease inhibitor (Streptomyces subtilisin inhibitor) with deuterium atoms in 2H2O (p2H 6.8) has been studied by proton magnetic resonance in the temperature range 56-71 degrees C. Both slowly and rapidly exchanging processes have been observed. The number of slowly exchanging protons is estimated to be 25 +/- 2 per subunit of the protein molecule. The decay of the slowly exchanging proton signals follows a single time-exponential function at each temperature. The observed first-order rate constants have been analyzed to give the denaturated fraction of the protein as a function of temperature with a consequent enthalpy (56 kcal/mol) and an entropy (137 cal/degree per mol) of denaturation. The results indicate the high conformational stability of this protein against heat denaturation.

Cloning of a cDNA for a constitutive NRT1 transporter from soybean and comparison of gene expression of soybean NRT1 transporters.

We have isolated a cDNA for a putative transporter, named GmNRT1-3, in the NRT1 family from soybean. It was predicted to have a similar topological structure not only to both GmNRT1-1 and GmNRT1-2 reported previously, but also to other members of the family. Two other cDNAs isolated have parts of the sequence for putative NRT1 transporters, GmNRT1-4 and GmNRT1-5, suggesting that at least five NRT1 transporters occur in soybean. These GmNRT1 genes and the GmNRT2 gene, encoding a soybean NRT2 nitrate transporter, showed different expression patterns to each other under various nitrogen conditions. Specifically, GmNRT1-3 was constitutively expressed in both roots and leaves, while GmNRT1-2 was gradually expressed as the roots developed in the presence of ammonium as a nitrogen source, but not in the presence of both ammonium and nitrate. Based on these results, we discussed the possible regulation in the expression and role of these transporters in nitrate uptake.

Generation of free radicals during lipid hydroperoxide-triggered apoptosis in PC12h cells.

The compound 13-L-hydroperoxylinoleic acid (LOOH) triggered the death of clonal rat pheochromocytoma PC12h cells (LD50 = about 8 microM). LOOH induced nuclear condensation and DNA fragmentation, which was prevented by cycloheximide (a protein synthesis inhibitor) and NGF, indicating that LOOH triggered apoptosis in PC12h cells. LOOH produced reactive oxygen species (ROS) in PC12h cells in a time- and dose-dependent manner, as measured by flow cytometry using the ROS-specific fluorescent indicator, 6-carboxy-2,7-dichorodihydrofluorescein diacetate, di(acetoxymethyl ester) (C-DCDHF-DA). Antioxidants such as N,N'-diphenyl-p-phenylenediamine (DPPD), vitamin E and N-acetylcysteine, and a ferric iron chelator, deferoxamine, inhibited the LOOH-triggered apoptosis and simultaneously decreased the generation of ROS, whereas an inhibitor of glutathione synthesis, buthionine sulfoximine (BSO), enhanced the apoptosis and increased the generation of ROS. These results indicate that LOOH triggers the apoptosis of PC12h cells by increasing the production of ROS. A confocal analysis with the Ca(2+)-specific fluorescent indicator, fluo-3, demonstrated that LOOH at concentrations up to 200 microM, did not increase the intracellular Ca2+ concentration. These data indicate that LOOH induces apoptosis of PC12h cells through the enhanced production of ROS, not through increasing the permeability of Ca2+.

Characterization of the gntT gene encoding a high-affinity gluconate permease in Escherichia coli.

We characterized the gntT gene encoding a high-affinity gluconate permease of Escherichia coli K-12. Primer extension and lacZ-operon fusion analyses revealed that gntT has one strong and two weak promoters, all of which are regulated positively by cAMP-CRP and negatively by GntR. The weak promoters became constitutive when separated from the upstream region including the strong promoter that overlaps a putative GntR-binding sequence. Gluconate-specific uptake activity was observed with cells harboring the gntT plasmid clone, which was enhanced by the presence of gntK encoding gluconate kinase.

Circadian variation of urinary type I collagen crosslinked C-telopeptide and free and peptide-bound forms of pyridinium crosslinks.

This study was performed to investigate the circadian variation of urinary CrossLaps (CTx), which was the type I collagen peptide released during bone matrix degradation, and peptide-bound and free forms of urinary pyridinium crosslinks. Urine was obtained during the 24 h of the study in seven separate collections as follows: from 23:00 h to the first void (FV) followed by FV at 11:00, 11:00-14:00, 14:00-17:00, 17:00-20:00, 20:00-23:00, and 23:00 h to FV the next morning. Total, free, and peptide-bound pyridinoline (Pyr) and deoxypyridinoline (Dpyr) excretion measured by high-performance liquid chromatography (HPLC) and CTx measured by enzyme-linked immunosorbent assay in nine premenopausal women aged 22-40 years and nine osteoporotic women aged 65-83 years was analyzed. Among three parameters of Pyr measured by HPLC, a significant day and night difference was found only in total Pyr (21.9% higher at night than during the day in premenopausal women and 24.0% in osteoporotic women, whereas no significant day and night variation was found in free and peptide-bound Pyr in either group. In contrast, total and peptide-bound Dpyr were significantly (37.9% and 66.9%) higher at night than those during the day in premenopausal women (38.0%) and osteoporotic women (48.8%). For free Dpyr, there were no day and night differences in the two groups. The day and night variances were significantly greater in peptide-bound Dpyr than with total Dpyr in both groups. In urinary CTx, a significant circadian variation with a peak at night and a nadir at 17:00 h was found (p < 0.0001) (premenopausal was 54.0% higher at night than during the day; osteoporotic was 38.4%. In conclusion, urinary CTx represented remarkable circadian variation compared with urinary pyridinium crosslinks measured by HPLC. Furthermore, free pyridinium crosslinks did not undergo a circadian variation. Peptide-bound crosslinks might contribute mostly to the circadian variation of total excretion of pyridinium crosslinks.

Acetylcholine receptor-mediated membrane current in oocytes injected with Electrophorus electricus mRNA: analyses of nicotine, succinylcholine, and decamethonium responses on the basis of the minimal model.

Nicotinic acetylcholine receptor was synthesized in Xenopus oocytes after injection of the mRNA purified from Electrophorus electricus electroplax. Nicotine, succinylcholine, and decamethonium (agonist)-elicited membrane currents in the injected oocytes were measured electrophysiologically by the voltage-clamping method. The following four different measurements were made to establish the relationship between the agonist concentration and the membrane current: 1) the agonist-induced membrane current before desensitization, 2) the agonist-induced membrane current after desensitization equilibrium, 3) the fraction of the active form of the receptors after desensitization equilibrium, 4) the rate of recovery of desensitized receptors upon removal of the agonist. These results were analyzed on the basis of the minimal model proposed from receptor-mediated ion translocation measurements. The equilibrium and rate constants of the model were evaluated for nicotine, succinylcholine, and decamethonium, and could explain the observed electrical responses in the injected oocyte, i.e. the characteristics of the receptor response caused by these agonists.

Inhibition schemes for acetylcholine receptor-mediated ion translocation in the presence of various kinds of inhibitors.

Some basic inhibition schemes for acetylcholine receptor (AChR)-mediated ion translocation in the presence of agonist, cholinergic ligand, and inhibitors are proposed on the basis of the minimum reaction scheme (Hess, G.P., Cash, D.J., & Aoshima, H. (1983) Annu. Rev. Biophys. Bioeng. 12, 443-473). Equations for the rate coefficients of ion flux before and after desensitization, JA and JD, and for desensitization, a, were derived from each scheme, assuming that binding of inhibitors to AChR does not affect the values of rate and equilibrium constants of cholinergic ligand to the receptor. In the presence of inhibitors, AChR-mediated transmembrane Li+ influx caused by carbamylcholine (Carb) was measured by using Electrophorus electricus membrane vesicles, a simple filtration assay and flame emission spectroscopy. The dependence of the ratios of rate coefficients on the concentration of ligand and inhibitors was examined in detail. The inhibition constants of d-tubocurarine and caffeine were estimated to be about 31 nM and 0.84 mM, respectively, on the basis of a simple competitive inhibition scheme, and that of procaine was estimated to be 0.11 mM on the basis of a simple noncompetitive one.

High performance liquid chromatography of the hydroperoxides produced by lipoxygenases.

Separation of 13-hydroperoxylinoleic acid or 13-hydroperoxylinolenic acid from linoleic acid or linolenic acid, respectively, was carried out easily and quickly by high performance liquid chromatography on porous polymer gel (TSK-Gel LS-140) using n-hexane/ethanol as an eluent. An eluent containing a large amount of n-hexane (96%) made possible the separation of 9- and 13-hydroperoxylinoleic acids. These methods were applicable for analyses of the products obtained by the incubation of soybean lipoxygenase-1 [linoleate: oxygen oxidoreductase, EC 1.13.11.12] with linoleic acid or 13-hydroperoxylinoleic acid.

Acetylcholine receptor-controlled ion translocation caused by phenyltrimethylammonium and nereistoxin: simple estimation of equilibrium constants of the minimal model.

The rate of slow Li+ influx and the fraction of active form of acetylcholine receptor (AChR) of Electrophorus electricus membrane vesicles at equilibrium between the active and desensitized forms of the receptor were measured in the presence of various concentrations of phenyltrimethylammonium (PTA) and nereistoxin (NTX), by a simple filtration assay and flame emission spectroscopy. The equilibrium constants of these ligands in the minimal model, which accounts for the AChR-mediated ion flux, were estimated simply from these two measurements, since the equilibrium constants for acetylcholine (ACh) and carbamylcholine (Carb) estimated from two kinetic measurements agreed well with those estimated from five sophisticated kinetic measurements of AChR-mediated ion fluxes. PTA showed high potency but not high efficacy, and showed inhibition when large doses were applied. NTX showed both low potency and low efficacy and acted as an inhibitor when it was added with Carb. The apparent dissociation constants of these three agonists evaluated from the minimal model and the equilibrium constants agreed with those obtained by assay of inhibition of radiolabeled ligand binding.

Inhibition of ionotropic neurotransmitter receptors by antagonists: strategy to estimate the association and the dissociation rate constant of antagonists with very strong affinity to the receptors.

Since binding of an agonist to an ionotropic neurotransmitter receptor causes not only channel opening, but also desensitization of the receptor, inhibition of the receptor by the antagonist sometimes becomes very complicated. The transient state kinetics of ligand association and dissociation, and desensitization of the receptor were considered on the basis of the minimal model proposed by Hess' group, and the following possibilities were proposed. 1) When an agonist is simultaneously applied to the receptor with an antagonist whose affinity to the receptor is extremely strong and different from that of the agonist, it is usually impossible to estimate the real inhibition constant exactly from the responses because desensitization of the receptor proceeds before the equilibrium of the ligand binding. Simultaneous addition of the antagonist with strong affinity to the receptor may apparently accelerate inactivation (desensitization) of the receptor. The association rate constant of the antagonist can be estimated by analyses of the rate of the inactivation in the presence and the absence of the antagonist. 2) A preincubated antagonist with a slow dissociation rate constant, i.e., a very effective inhibitor, may cause apparent noncompetitive inhibition of the receptor, since the receptor is desensitized by an agonist as soon as the antagonist dissociates from the receptor and the dissociation of the antagonist from the receptor becomes the rate-determining step. A nicotinic acetylcholine receptor (nAChR) was expressed in Xenopus oocytes by injecting mRNA prepared from Electrophorus electricus electroplax and used for the experiments on inhibition by an antagonist.(ABSTRACT TRUNCATED AT 250 WORDS)

Electron spin resonance studies on the lipoxygenase reaction by spin trapping and spin labelling methods.

The rate of oxygenation and that of trapping linoleic acid free radicals in the lipoxygenase [EC 1.13.11.12] reaction were measured in the presence of linoleic acid, oxygen, and nitrosobenzene at various concentrations, with a Clark oxygen electrode and ESR spectroscopy. The results were interpreted under the assumption that the free radical of linoleic acid, an intermediate of the lipoxygenase reaction, reacts competitively with oxygen or nitrosobenzene. The oxidation of the iron in the active site of lipoxygenase caused by the spin label reagent, 2-(10-carboxydecyl)-2-hexyl-4,4-dimethyl-3-oxazolidinyloxyl, was also observed by ESR- and fluorescence-spectroscopy.

Minimal model analyzing response of glycine receptors expressed in Xenopus oocyte: inhibition by a lipid hydroperoxide.

Glycine receptor (GlyR) was expressed in Xenopus oocytes by injecting rat brain mRNA. Glycine (Gly)-elicited responses in the oocyte were measured by the voltage-clamping method. The following measurements were made to establish the relationship between Gly concentration and the current: 1) Gly-induced membrane current before desensitization, 2) Gly-induced membrane current after desensitization equilibrium, 3) fraction of the active form of the receptor after desensitization equilibrium, 4) rate of recovery of the desensitized receptors upon removal of Gly. These results were analyzed on the basis of the minimal model proposed for nicotinic acetylcholine and gamma-aminobutyric acid A receptor. The equilibrium and rate constants of the model were evaluated for GlyR. The effects of procaine and 13-L-hydroperoxylinoleic acid (LOOH) on GlyR were examined electrophysiologically. LOOH noncompetitively inhibited the receptor with the inhibition constant of 27 microM, while 1 mM procaine, a local anesthetic, did not inhibit GlyR at all.

Kinetic analyses of alcohol-induced potentiation of the response of GABA(A) receptors composed of alpha(1) and beta(1) subunits.

To investigate the kinetics of both the potentiation and desensitization of the response of ionotropic GABA receptors (GABA(A) receptors) in the presence of various compounds, we expressed receptors composed of alpha(1) and beta(1) subunits by injecting cells with the cRNAs synthesized from cloned bovine GABA(A) receptor cDNAs and measured the electrical responses of the cells electrophysiologically with or without the compounds. The potentiation of the GABA(A) receptor-mediated response was quantitatively analyzed using a simple model with the assumption that the receptors have two identical binding sites for GABA molecules with a dissociation constant of K(1), and one potentiation site for the compound with a dissociation constant of K(p), and that the binding of the compound to the potentiation site only increases the affinity of the GABA binding sites, changing K(1) to K(1p). The estimated K(p) and K(1p) were dependent on the functional groups and the chain length of the compounds. These results could be satisfactorily analyzed using this simple model. The potentiation of the GABA(A) receptor-mediated response by the components of essential oils used for aromatherapy was also examined. These compounds accelerated the decay of the response, possibly due to desensitization of the receptors, which was also analyzed on the basis of the model.

A minimal model to account for the response of N-Methyl-D-aspartate receptors expressed in Xenopus oocyte injected with rat brain mRNA.

N-Methyl-D-aspartate (NMDA) receptors were expressed in Xenopus oocytes by injecting rat brain mRNA. NMDA-elicited responses in the oocytes were measured by the voltage-clamping method. The following measurements were made in the presence of 50 microM glycine (Gly) to establish the relationship between the NMDA concentration and the current: (1) the NMDA-induced membrane current before desensitization; (2) the NMDA-induced membrane current after desensitization equilibrium; (3) the fraction of the active form of the receptor after desensitization equilibrium in the presence and absence of 50 microM Gly; (4) the rate of the recovery of desensitized receptors upon removal of NMDA. Gly was essential for not only the activation of NMDA receptors but also their desensitization. These results were analyzed on the basis of a minimal model where one agonist and one Gly binding site were assumed. The equilibrium and rate constants of the model were evaluated for NMDA in the presence of saturating amounts of Gly. This model will be useful for systematically explaining the complicated responses of NMDA receptors.