Insights Into the Inhibition of MOX-1 β-Lactamase by S02030, a Boronic Acid Transition State Inhibitor

The rise of multidrug resistant (MDR) Gram-negative bacteria has accelerated the development of novel inhibitors of class A and C β-lactamases. Presently, the search for novel compounds with new mechanisms of action is a clinical and scientific priority. To this end, we determined the 2.13-Å resolution crystal structure of S02030, a boronic acid transition state inhibitor (BATSI), bound to MOX-1 β-lactamase, a plasmid-borne, expanded-spectrum AmpC β-lactamase (ESAC) and compared this to the previously reported aztreonam (ATM)-bound MOX-1 structure. Superposition of these two complexes shows that S02030 binds in the active-site cavity more deeply than ATM. In contrast, the SO₃ interactions and the positional change of the β-strand amino acids from Lys315 to Asn320 were more prominent in the ATM-bound structure. MICs were performed using a fixed concentration of S02030 (4 μg/ml) as a proof of principle. Microbiological evaluation against a laboratory strain of Escherichia coli expressing MOX-1 revealed that MICs against ceftazidime are reduced from 2.0 to 0.12 μg/ml when S02030 is added at a concentration of 4 μg/ml. The IC₅₀ and K_i of S02030 vs. MOX-1 were 1.25 ± 0.34 and 0.56 ± 0.03 μM, respectively. Monobactams such as ATM can serve as informative templates for design of mechanism-based inhibitors such as S02030 against ESAC β-lactamases.

Structural and functional analysis of miraculin-like protein from Vitis vinifera

The so-called miraculin-like proteins (MLPs) are homologous to miraculin, a homodimeric protein with taste-modifying activity that converts sourness into sweetness. The identity between MLPs and miraculin generally ranges from 30% to 55%, and both MLPs and miraculin are categorized into the Kunitz-type soybean trypsin inhibitor (STI) family. MLP from grape (Vitis vinifera; vvMLP) exhibits significant homology to miraculin (61% identity), suggesting that vvMLP possesses miraculin-like properties. The results of size-exclusion chromatography and sensory analysis illustrated that vvMLP exists as a monomer in solution with no detectable taste-modifying activity. Crystal structure determination revealed that vvMLP exists as a β-trefoil fold, similarly as other MLPs and Kunitz-type protein inhibitors. The conformation of the loops, including the so-called reactive loop in the STI family, was substantially different between vvMLP and STI. Recombinant vvMLP had inhibitory activity against trypsin (K_i = 13.7 μM), indicating that the protein can act as a moderate trypsin inhibitor.

Structural Basis of Sequential Allosteric Transitions in Tetrameric d-Lactate Dehydrogenases from Three Gram-Negative Bacteria

d-Lactate dehydrogenases (d-LDHs) from Fusobacterium nucleatum (FnLDH) and Escherichia coli (EcLDH) exhibit positive cooperativity in substrate binding, and the Pseudomonas aeruginosa enzyme (PaLDH) shows negatively cooperative substrate binding. The apo and ternary complex structures of FnLDH and PaLDH have been determined together with the apo-EcLDH structure. The three enzymes consistently form homotetrameric structures with three symmetric axes, the P-, Q-, and R-axes, unlike Lactobacillus d-LDHs, P-axis-related dimeric enzymes, although apo-FnLDH and EcLDH form asymmetric and distorted quaternary structures. The tetrameric structure allows apo-FnLDH and EcLDH to form wide intersubunit contact surfaces between the opened catalytic domains of the two Q-axis-related subunits in coordination with their asymmetric and distorted quaternary structures. These contact surfaces comprise intersubunit hydrogen bonds and hydrophobic interactions and likely prevent the domain closure motion during initial substrate binding. In contrast, apo-PaLDH possesses a highly symmetrical quaternary structure and partially closed catalytic domains that are favorable for initial substrate binding and forms virtually no intersubunit contact surface between the catalytic domains, which present their negatively charged surfaces to each other at the subunit interface. Complex FnLDH and PaLDH possess highly symmetrical quaternary structures with closed forms of the catalytic domains, which are separate from each other at the subunit interface. Structure-based mutations successfully converted the three enzymes to their dimeric forms, which exhibited no significant cooperativity in substrate binding. These observations indicate that the three enzymes undergo typical sequential allosteric transitions to exhibit their distinctive allosteric functions through the tetrameric structures.

Mechanistic insight into the substrate specificity of 1,2-β-oligoglucan phosphorylase from Lachnoclostridium phytofermentans

Glycoside phosphorylases catalyze the phosphorolysis of oligosaccharides into sugar phosphates. Recently, we found a novel phosphorylase acting on β-1,2-glucooligosaccharides with degrees of polymerization of 3 or more (1,2-β-oligoglucan phosphorylase, SOGP) in glycoside hydrolase family (GH) 94. Here, we characterized SOGP from Lachnoclostridium phytofermentans (LpSOGP) and determined its crystal structure. LpSOGP is a monomeric enzyme that contains a unique β-sandwich domain (Ndom1) at its N-terminus. Unlike the dimeric GH94 enzymes possessing catalytic pockets at their dimer interface, LpSOGP has a catalytic pocket between Ndom1 and the catalytic domain. In the complex structure of LpSOGP with sophorose, sophorose binds at subsites +1 to +2. Notably, the Glc moiety at subsite +1 is flipped compared with the corresponding ligands in other GH94 enzymes. This inversion suggests the great distortion of the glycosidic bond between subsites −1 and +1, which is likely unfavorable for substrate binding. Compensation for this disadvantage at subsite +2 can be accounted for by the small distortion of the glycosidic bond in the sophorose molecule. Therefore, the binding mode at subsites +1 and +2 defines the substrate specificity of LpSOGP, which provides mechanistic insights into the substrate specificity of a phosphorylase acting on β-1,2-glucooligosaccharides.

Validation of the distress and impact thermometer and the changes of mood during the first 6 months of treatment in gynecological cancer patients: a Kansai Clinical Oncology Group (KCOG)-G1103 prospective study

PURPOSE

To verify distress and impact thermometer (DIT) for screening emotional distress in gynecological cancer patients by Hospital Anxiety and Depression Scale total (HADS-T) as gold standard and to assess emotional changes by DIT and HADS-T.

METHODS

A prospective study was conducted in newly diagnosed gynecological cancer patients during the peri-treatment period after the cancer diagnosis followed by 6-month. We defined a HADS-T score of ≥11 as being indicative of emotional distress.

RESULTS

117 patients were enrolled between May 1, 2011 and March 31, 2012, and 95 were eligible. The median age was 54 years (range 31-77). (1) From the baseline to 3-month, distress (DIT-D) ≥4 with Impact (DIT-I) ≥2 exhibited sensitivity, specificity, positive predictive value (PPV), and negative predictive values (NPV) of 0.776 [95 % confidential interval (CI) 0.688, 0.850], 0.889 (95 % CI 0.824, 0.954), 0.868 (95 % CI 0.792, 0.949), and 0.808 (95 % CI 0.731, 0.886), respectively. (2) At 6-month, DIT-D ≥2 with DIT-I ≥1 exhibited sensitivity, specificity, PPV and NPV of 0.893 (95 % CI 0.778, 1), 0.825 (95 % CI 0.707, 0.942), 0.781 (95 % CI 0.638, 0.928), and 0.917 (95 % CI 0.826, 1). (3) At 6-month, the HADS-T, DIT-D, and DIT-I scores in individual patients were significantly reduced by a mean of 4.57 (p < 0.0001), 2.34 (p < 0.0001), and 1.10 (p = 0.0031), respectively, compared with those scores of baseline (Student's paired t test), but still remained high.

CONCLUSIONS

(1) On acute phase within 3-month setting, DIT; DIT-D ≥4 with DIT-I ≥2, is a reliable cut-off to screen emotional distress among gynecological cancer patients. (2) The patients' moods had improved, but not completely recovered at 6-month after the diagnosis.

Diverse allosteric and catalytic functions of tetrameric d-lactate dehydrogenases from three Gram-negative bacteria

NAD-dependent d-lactate dehydrogenases (d-LDHs) reduce pyruvate into d-lactate with oxidation of NADH into NAD⁺. Although non-allosteric d-LDHs from Lactobacilli have been extensively studied, the catalytic properties of allosteric d-LDHs from Gram-negative bacteria except for Escherichia coli remain unknown. We characterized the catalytic properties of d-LDHs from three Gram-negative bacteria, Fusobacterium nucleatum (FNLDH), Pseudomonas aeruginosa (PALDH), and E. coli (ECLDH) to gain an insight into allosteric mechanism of d-LDHs. While PALDH and ECLDH exhibited narrow substrate specificities toward pyruvate like usual d-LDHs, FNLDH exhibited a broad substrate specificity toward hydrophobic 2-ketoacids such as 2-ketobutyrate and 2-ketovalerate, the former of which gave a 2-fold higher k_cat/S_0.5 value than pyruvate. Whereas the three enzymes consistently showed hyperbolic shaped pyruvate saturation curves below pH 6.5, FNLDH and ECLDH, and PALDH showed marked positive and negative cooperativity, respectively, in the pyruvate saturation curves above pH 7.5. Oxamate inhibited the catalytic reactions of FNLDH competitively with pyruvate, and the PALDH reaction in a mixed manner at pH 7.0, but markedly enhanced the reactions of the two enzymes at low concentration through canceling of the apparent homotropic cooperativity at pH 8.0, although it constantly inhibited the ECLDH reaction. Fructose 1,6-bisphosphate and certain divalent metal ions such as Mg²⁺ also markedly enhanced the reactions of FNLDH and PALDH, but none of them enhanced the reaction of ECLDH. Thus, our study demonstrates that bacterial d-LDHs have highly divergent allosteric and catalytic properties.

The core of allosteric motion in Thermus caldophilus L-lactate dehydrogenase

For Thermus caldophilus L-lactate dehydrogenase (TcLDH), fructose 1,6-bisphosphate (FBP) reduced the pyruvate S(0.5) value 10(3)-fold and increased the V(max) value 4-fold at 30 °C and pH 7.0, indicating that TcLDH has a much more T state-sided allosteric equilibrium than Thermus thermophilus L-lactate dehydrogenase, which has only two amino acid replacements, A154G and H179Y. The inactive (T) and active (R) state structures of TcLDH were determined at 1.8 and 2.0 Å resolution, respectively. The structures indicated that two mobile regions, MR1 (positions 172-185) and MR2 (positions 211-221), form a compact core for allosteric motion, and His(179) of MR1 forms constitutive hydrogen bonds with MR2. The Q4(R) mutation, which comprises the L67E, H68D, E178K, and A235R replacements, increased V(max) 4-fold but reduced pyruvate S(0.5) only 5-fold in the reaction without FBP. In contrast, the P2 mutation, comprising the R173Q and R216L replacements, did not markedly increase V(max), but 10(2)-reduced pyruvate S(0.5), and additively increased the FBP-independent activity of the Q4(R) enzyme. The two types of mutation consistently increased the thermal stability of the enzyme. The MR1-MR2 area is a positively charged cluster, and its center approaches another positively charged cluster (N domain cluster) across the Q-axis subunit interface by 5 Å, when the enzyme undergoes the T to R transition. Structural and kinetic analyses thus revealed the simple and unique allosteric machinery of TcLDH, where the MR1-MR2 area pivotally moves during the allosteric motion and mediates the allosteric equilibrium through electrostatic repulsion within the protein molecule.

Paclitaxel plus Carboplatin Chemotherapy for Primary Peritoneal Carcinoma: A Study of 22 Cases and Comparison with Stage III-IV Ovarian Serous Carcinoma

The aim of this study was to assess the clinical characteristics and outcome of patients with either primary peritoneal carcinoma (PPC) or ovarian serous carcinoma (OSC) treated with paclitaxel plus carboplatin chemotherapy. We retrospectively identified 22 PPC patients and 55 stage III–IV OSC patients treated between 2002 and 2007. After exploratory laparotomy, all patients received paclitaxel and carboplatin every 3 weeks, with the goal of optimal cytoreduction. There were no statistically significant differences between the PPC and OSC groups with regard to tumor stage, residual tumor after debulking surgery (initial or interval), serum cancer antigen (CA) 125 levels at diagnosis, and completion of first-line chemotherapy. The progression-free survival (PFS) durations were 12.7 months (95% CI, 6.3–18.5) in the patients with PPC and 15.9 months (95% CI, 13.3–18.5) in those with OSC (p = 0.016). However, the median survival durations were 26.5 months (95% CI, 14.6–38.3) in the patients with PPC and 38 months (95% CI, 23.8–53.8) in those with OSC (p = 0.188). Survival was longer for all patients whose CA125 levels normalized to 26 U/ml during and after treatment. Overall survival (OS) of the patients with PPC was similar to that of the patients with OSC, suggesting that management for advanced-stage OSC would be similar to that for PPC. The combination of optimal debulking with paclitaxel plus carboplatin chemotherapy may offer patients the most effective treatment. The CA125 nadir after cytoreductive surgery can be considered a prognostic factor for OS and PFS in patients with PPC.

Use of high-dose cisplatin with aprepitant in an outpatient setting

Chemotherapy-induced nausea and vomiting (CINV) and nephrotoxicity are adverse events induced by cisplatin administration. These effects can be reduced by treatment regimens with low-dose cisplatin, but high-dose cisplatin is still used. In Japan, high-dose cisplatin is usually administered in an inpatient setting to permit management of CINV. However, with use of new-generation antiemetic agents such as aprepitant, CINV and nephrotoxicity are controllable in an outpatient setting. Here, we discuss issues related to the management of high-dose cisplatin administration in outpatients. Grade 2 or worse CINV induced by high-dose cisplatin occurs in more than 40% of patients without treatment with aprepitant, but is controllable by administration of a 5-HT3 receptor antagonist, steroids and aprepitant. Moreover, prevention of CINV using these drugs is cost-effective, since outpatient settings have advantages with regard to health economics and patient quality of life. These findings suggest that shifting high-dose cisplatin administration to the outpatient setting may be achieved with co-administration of aprepitant. Available facilities and the status of the patient should be considered when selecting whether an outpatient setting is suitable for administration of cisplatin, but the use of aprepitant and adequate oral hydration should allow use of cisplatin in this setting.

CRISPR inhibition of prophage acquisition in Streptococcus pyogenes

Streptococcus pyogenes, one of the major human pathogens, is a unique species since it has acquired diverse strain-specific virulence properties mainly through the acquisition of streptococcal prophages. In addition, S. pyogenes possesses clustered regularly interspaced short palindromic repeats (CRISPR)/Cas systems that can restrict horizontal gene transfer (HGT) including phage insertion. Therefore, it was of interest to examine the relationship between CRISPR and acquisition of prophages in S. pyogenes. Although two distinct CRISPR loci were found in S. pyogenes, some strains lacked CRISPR and these strains possess significantly more prophages than CRISPR harboring strains. We also found that the number of spacers of S. pyogenes CRISPR was less than for other streptococci. The demonstrated spacer contents, however, suggested that the CRISPR appear to limit phage insertions. In addition, we found a significant inverse correlation between the number of spacers and prophages in S. pyogenes. It was therefore suggested that S. pyogenes CRISPR have permitted phage insertion by lacking its own spacers. Interestingly, in two closely related S. pyogenes strains (SSI-1 and MGAS315), CRISPR activity appeared to be impaired following the insertion of phage genomes into the repeat sequences. Detailed analysis of this prophage insertion site suggested that MGAS315 is the ancestral strain of SSI-1. As a result of analysis of 35 additional streptococcal genomes, it was suggested that the influences of the CRISPR on the phage insertion vary among species even within the same genus. Our results suggested that limitations in CRISPR content could explain the characteristic acquisition of prophages and might contribute to strain-specific pathogenesis in S. pyogenes.

Isolated latent tricuspid regurgitation caused by blunt trauma

Isolated tricuspid regurgitation with rupture of the chordae tendinae caused by blunt trauma is uncommon. We present a 20-year-old man who was asymptomatic for four months after a traffic accident, but then developed severe tricuspid regurgitation, caused by rupture of the chordae tendinae. We performed minimally invasive tricuspid valve repair with chordal reconstruction and annuloplasty. We discuss the optimal treatment of traumatic valve insufficiency in a young patient and review the literature.

Ferroelectricity induced by spin-dependent metal-ligand hybridization in Ba₂CoGe₂O₇

We have investigated the variation of induced ferroelectric polarization under a magnetic field with various directions and magnitudes in a staggered antiferromagnet Ba₂CoGe₂O₇. While the ferroelectric polarization cannot be explained by the well-accepted spin current model nor the exchange striction mechanism, we have shown that it is induced by the spin-dependent p-d hybridization between the transition metal (Co) and ligand (O) via the spin-orbit interaction. On the basis of the correspondence between the direction of electric polarization and the magnetic state, we have also demonstrated the electrical control of the magnetization direction.

Real-time quantum dynamics of interacting electrons: self-organized nanoscale structure in a spin-electron coupled system

We investigate the quantum evolution of the excited electronic states combined with the classical dynamics of the order parameter field in a spin-electron coupled system. It is found that the nanoscale spatial structure of the spins evolves spontaneously accompanied by the localization of the electronic wave functions, and the nonadiabatic quantum transitions through a resonant mutual precession analogous to the electron spin resonance (ESR) process.

Novel multiferroic state of Eu1-xYxMnO3 in high magnetic fields

Magnetic and dielectric properties of Eu1-xYxMnO3 (x=0 and 0.4) are studied in pulsed magnetic fields up to 55 T. For x=0, application of magnetic fields higher than 20 T along the b axis causes magnetic transitions accompanied by generation of electric polarization (P) along the a axis. Similar first-order transitions are also observed in crystals of x=0.4, in which the ground state at zero magnetic field is already a ferroelectric P parallel a phase of different origin. Realistic model calculation indicates the presence of a novel multiferroic state induced by the spin exchange striction mechanism in high magnetic fields as an essential nature of the frustrated Mn spin system in this class of manganites.

Dynamics of multiferroic domain wall in spin-cycloidal ferroelectric DyMnO3

We report the dielectric dispersion of the giant magnetocapacitance (GMC) in multiferroic DyMnO3 over a wide frequency range. The GMC is found to be attributable not to the softened electromagnon but to the electric-field-driven motion of multiferroic domain wall (DW). In contrast to conventional ferroelectric DWs, the present multiferroic DW motion holds an extremely high relaxation rate of approximately 10;{7} s;{-1} even at low temperatures. This mobile nature as well as the model simulation suggests that the multiferroic DW is not atomically thin as in ferroelectrics but thick, reflecting its magnetic origin.

Evidence for an electric-dipole active continuum band of spin excitations in multiferroic TbMnO3

The wide range optical spectra on a multiferroic prototype TbMnO3 have been investigated to clarify the origin of spin excitations observed in the far-infrared region. We elucidate the full band structure, whose high energy edge (133 cm;{-1}) exactly corresponds to twice of the highest-lying magnon energy. Thus the origin of this absorption band is clearly assigned to two-magnon excitation driven by the electric field of light. There is an overlap between the two-magnon and phonon energy ranges, where the strong coupling between them is manifested by the frequency shift and transfer of oscillator strength of the phonon mode.

Spontaneous formation of vanadium "molecules" in a geometrically frustrated crystal: AlV2O4

We investigated the charge-ordered (CO) state in spinel AlV2O4 by electron diffraction, synchrotron x-ray diffraction, and magnetic measurements. It was found that the CO structure appearing below 700 K is characterized by the formation of V clusters (heptamers), each of which is consisting of 7 vanadium atoms and is in a spin-singlet state as a total. Theoretical consideration indicates that this unique molecularlike V heptamer is stabilized by a strong bonding of vanadium t(2g) orbitals.

Daily inhibition of postprandial hyperglycaemia with JTT-608, a novel oral antidiabetic agent, ameliorates pancreatic function in neonatally streptozotocin-treated rats

AIM

Chronic glycaemic control, in particular, the control of postprandial hyperglycaemia, is essential for preventing the development of diabetic complications. We therefore evaluated the chronic treatment effect of a new antidiabetic agent, JTT-608 [trans-4-(methylcyclohexyl)-4-oxobutyric acid], in neonatally streptozotocin-treated rats.

METHODS

The rats were maintained with liquid meal three times a day and treated orally with JTT-608 10 min before each meal for 12 weeks. Haemoglobin A1C (HbA1C) and fasting blood glucose levels were measured at 4-week intervals, and effects of JTT-608 on pancreatic function and diabetic complications were examined after dosing period.

RESULTS

The postprandial hyperglycaemia was suppressed by JTT-608 administration, and both HbA1C levels and fasting blood glucose levels were reduced during the experimental period. After the treatment period of 12 weeks, JTT-608 further improved the early insulin secretion and the impaired glucose tolerance after meal loading in the diabetic rats. Also, pathological examination revealed that JTT-608 reduced the incidence of the decrease in immunoreactivity of insulin. In examination of other diabetic complications, JTT-608 ameliorated the reduced motor nerve conduction velocities observed in diabetic rats and inhibited the incidence of cataracts with diabetes.

CONCLUSIONS

We conclude that a newly developed antidiabetic agent, JTT-608, improves the pancreatic function and prevents the development of diabetic complications by inhibition of daily postprandial hyperglycaemia and could be useful for the treatment of diabetic subjects with impaired insulin secretion.

Association of verrucous skin lesions and skin ulcers on the feet in patients with diabetic neuropathy

We report the simultaneous or chronological association of verrucous skin lesions and diabetic ulcers on the feet of three diabetic patients. All three patients had poor diabetic control and were suffering from complications such as neuropathy, retinopathy and nephropathy at the time of presentation. In patient 1, verrucous skin lesions on the feet in diabetic neuropathy (VSLDN) and a diabetic skin ulcer developed simultaneously. In patient 2, VSLDN preceded the development of diabetic ulcers, while in patient 3, diabetic ulcers preceded VSLDN. These associations suggest that VSLDN and diabetic ulcers are closely related in their aetiology and pathogenesis. Strategies for the treatment and prevention of VSLDN should include multiple treatment modalities combined with foot care as proposed by the international working group on the diabetic foot.

Glutaminergic vagal afferents may mediate both retching and gastric adaptive relaxation in dogs

We previously reported that intra-4th-ventricular (i.4th.v.) administration of a non-NMDA receptor antagonist, NBQX, abolished vagally induced retching. This study was undertaken to ascertain whether or not the neuronal response in the solitary tract nucleus (NTS) to vagal stimulation and the vago-vagal gastric reflexes induced by non-emetic stimulation are also abolished by NBQX with a similar latency as in the case of retching. Ketamine and thiopental- or chloralose-anesthetized dogs were decerebrated, and the dorsal surface of the medulla was exposed. This study consisted of two series of experiments. In the first series, extracellular neuronal responses in the NTS to pulse-train vagal stimulation were recorded. Effects of NBQX on the neural response and vagally induced fictive retching were observed. In the second series, effects of glutamate receptor antagonists on gastric corpus responses to esophageal or gastric antral distension were observed. Retching was abolished 5-15 min after an i.4th.v. application of NBQX. and the neuronal responses disappeared within 14 min after application in nine of 10 NTS neurons. On the other hand, corpus contractility was inhibited by esophageal distension, and inhibited and/or enhanced by antral distension. While the inhibitory responses disappeared within 17 min after NBQX, the enhanced response remained even after NBQX and vagotomy, but was abolished by i.v. administration of hexamethonium. These results suggest that adaptive relaxation in the corpus, as well as retching, may be mediated by glutaminergic vagal afferents and non-NMDA receptors in the NTS.

Syntheses and properties of ditelluroxanes and oligochalcogenoxanes: hypervalent oligomers with Te-O apical linkages in the main chain

The reaction of ditelluroxanes [Ar2Te-O-TeAr]2+[X]2- (2) (Ar = p-tolyl) with a telluroxide 1, a selenoxide 7, or a carboxylate 10 to produce oligochalcogenoxanes with hypervalent Te-O apical linkages in their main chain is described. The 125Te NMR chemical shifts of 2 (2a: X- = CF3SO3-, 2b: X- = CF3CO2-, 2c: X- = CH3CO2-, 2d: X- = Cl-) are shifted downfield with decreasing nucleophilicity of the counteranions. This result reflects both the cationic character and the reactivity of the Te atoms of 2. The reaction of 2a with one, two, three, or four equivalents of telluroxide 1a (Ar = p-tolyl) selectively gave a tritelluroxane 3a, tetratelluroxane 4a, pentatelluroxane 5a, and hexatelluroxane 6a, respectively. In contrast, the reaction of 2b with an excess of 1a produced only tritelluroxane 3b. An equilibrium between the oligotelluroxanes was confirmed by crossover experiments of the reactions of 2a with 4a and of 2a with 1b (Ar = Ph). The selective equilibrium formation of a selenoxaditelluroxane 8 or a bis(selenoxa)ditelluroxane 9 was achieved by the reaction of 2a with one or two equivalents of selenoxide 7, respectively. The association constant of 2a with 7 to form 8 was estimated to be Ka = (2.18+/-0.12) x 10(4) M(-1) in CD3CN at -40 degrees C. The reaction of 2a with two equivalents of carboxylates 10a-d gave a mixture of bis(carboxylate)ditelluroxanes and diaryldicarboxytelluranes 12b-d, respectively, in which the product ratio of these depended upon the electron-withdrawing ability of 10. The reaction of 3a with two equivalents of 10a-d afforded 11a-d in all cases. The present results suggest that the sigma*-n orbital interaction plays an essential role in the reactivity of ditelluroxanes and in the formation of self-assembled oligochalcogenoxanes, and that a hypervalent bond via a sigma*-n orbital interaction is viable as a new supramolecular synthon for molecular assembly.

Evidence for intermolecular interaction between sulfonium and sulfide sulfur atoms and its application to synthesis of cyclic bis(disulfide) dimer

On the basis of the remote Pummerer reaction of p-bis(alkylthio)-aromatic S-oxides, the intermolecular interaction between the sulfonium and sulfide sulfur atoms is described. (1) In marked contrast to the Pummerer reaction of 1b-d(3) with (CF(3)CO)(2)O (J. Org. Chem. 1999, 64, 3190-3195), the reaction of 3,3',5,5'-tetramesityl-4-(trideuteriomethylsulfinyl)-4'-(methylthio)biphenyl (1a-d(3)) as a sterically hindered analogue of 1b gave only 2a-d(2). (2) Both reactions of the two unsymmetrical regioisomers of 1-(ethylthio)-4-(methylthio)benzene S-oxide (5a and 5b) with (CF(3)CO)(2)O afforded a mixture of the mono-Pummerer products 6a and 6b, the bis-Pummerer product 7, and the bis-sulfide 8 in a similar ratio. The quenching at the initial stage of both reactions produced 5a, 5b, 8, and the bis-sulfoxide 10 in a similar ratio. These results indicate the equilibrium in the intermolecular interaction between the sulfur atoms. (3) The reaction of the p-bis(benzylthio)-aromatic S-oxide 16 with (CF(3)SO(2))(2)O gave the cyclic bis(disulfide) dimer 17 for the diphenyl sulfide and diphenylmethane spacers or the cyclic tetrakis(disulfide) tetramer 19 for the benzene and biphenyl spacers via the debenzylation of an intermolecular dithia dication. The cyclic bis(dithia dication) dimer A resulting from the intermolecular interaction between the sulfonium and sulfide sulfur atoms is proposed as an intermediate throughout the present reactions.

DOPA cyclohexyl ester, a competitive DOPA antagonist, protects glutamate release and resultant delayed neuron death by transient ischemia in hippocampus CA1 of conscious rats

In rat striata, DOPA released is a causal factor for glutamate release and resultant delayed neuron death by four-vessel occlusion. Nanomolar DOPA cyclohexyl ester (CHE), a potent and relatively stable competitive DOPA antagonist, protects these events. We tried to clarify whether DOPA CHE protects these events in hippocampal CA1 pyramidal cell layers most vulnerable against ischemia. Five to 10 min ischemia caused slight to mild glutamate release in 10 min samples during microdialysis and mild to severe neuron death 96 h after reperfusion. DOPA and dopamine were under assay limit in this design, but were basally detected by 20 min sampling and released by 20 min ischemia. In 10 min samples, intrahippocampal perfusion of 100 nM DOPA CHE 10 min before ischemia for 70 min did not inhibit glutamate release by 10 min ischemia, while it abolished glutamate release and protected delayed neuron death by 5 min ischemia. DOPA CHE is neuroprotective under a mild ischemic condition in rat hippocampus CA1.

Endogenously released DOPA is a causal factor for glutamate release and resultant delayed neuronal cell death by transient ischemia in rat striata

Glutamate is implicated in neuronal cell death. Exogenously applied DOPA by itself releases neuronal glutamate and causes neuronal cell death in in vitro striatal systems. Herein, we attempt to clarify whether endogenous DOPA is released by 10 min transient ischemia due to four-vessel occlusion during rat striatal microdialysis and, further, whether DOPA, when released, functions to cause glutamate release and resultant delayed neuronal cell death. Ischemia increased extracellular DOPA, dopamine, and glutamate, and elicited neuronal cell death 96 h after ischemic insult. Inhibition of striatal L-aromatic amino acid decarboxylase 10 min before ischemia increased markedly basal DOPA, tripled glutamate release with a tendency of decrease in dopamine release by ischemia, and exaggerated neuronal cell death. Intrastriatal perfusion of 10-30 nM DOPA cyclohexyl ester, a competitive DOPA antagonist, 10 min before ischemia, concentration-dependently decreased glutamate release without modification of dopamine release by ischemia. At 100 nM, the antagonist elicited a slight ceiling effect on decreases in glutamate release by ischemia and protected neurons from cell death. Glutamate was released concentration-dependently by intrastriatal perfusion of 0.3-1 mM DOPA and stereoselectively by 0.6 mM DOPA. The antagonist elicited no hypothermia during and after ischemia. Endogenously released DOPA is an upstream causal factor for glutamate release and resultant delayed neuronal cell death by brain ischemia in rat striata. DOPA antagonist has a neuroprotective action.

Identification of a cis-acting element and a novel trans-acting factor of the human insulin receptor gene in HepG2 and rat liver cells

The liver is a major target organ of insulin and is important for glucose homeostasis. We analyzed the tissue specific regulation of the insulin receptor gene in the liver by studying the cis-acting element and trans-acting factor of the human insulin receptor gene in human hepatoma cell line, HepG2 cells. In the chloramphenicol acetyl transferase (CAT) assay with chimeric plasmids containing various deletions and insertions of the human insulin receptor promoter/CAT gene, a HepG2 cell specific cis-acting element was identified between nt -592 to -577 of the promoter. In electrophoretic mobility shift assay and UV cross-link analysis, a 35-kDa nuclear protein that bound to 5'-TCCCTCCC-3' (nt -588 to -581) sequence was identified in HepG2 cells as well as in rat hepatocytes. This nuclear protein, designated as hepatocyte-specific transcription factor of the insulin receptor gene (HTFIR), might play an important role in tissue-specific expression of the insulin receptor gene in the liver.

Prognostic results of cisplatin IP and carboplatin IV with G-CSF in patients with ovarian cancer

We performed a dose-escalation study of carboplatin combined with a fixed dose of intraperitoneal cisplatin and G-CSF in patients with epithelial ovarian cancer, and analyzed the progression-free and overall survival. Six of the patients who entered the study with stage IC and II disease are still alive with no evidence of disease. The five-year survival rate was 61% for the 18 patients with stage III and IV disease; progression-free survival over 5 years was 32%. Our results show this to be an effective treatment regimen for epithelial ovarian cancer. Prognosis is good with this combined carboplatin/cisplatin/G-CSF therapy, especially for those patients with microscopic or no residual disease.

Group-II phospholipase A(2) enhances oxidized low density lipoprotein-induced macrophage growth through enhancement of GM-CSF release

Inflammatory process plays an important role in the development and progression of atherosclerotic lesions. Recently, group-II phospholipase A(2) (PLA(2)), an inflammatory mediator, was reported to exist in human atherosclerotic lesions and to enhance the development of murine atherosclerotic lesions. Oxidized low density lipoprotein (Ox-LDL) stimulates the growth of several types of macrophages in vitro. Since proliferation of macrophages occurs in atherosclerotic lesions, it is possible to assume that the Ox-LDL-induced macrophage proliferation might be involved in the progression of atherosclerosis. In this study, the role of group-II PLA(2) in the Ox-LDL-induced macrophage growth was investigated using thioglycollate-elicited mouse peritoneal macrophages. Thioglycollate-elicited macrophages significantly expressed group-II PLA(2) and released it into the culture medium. The Ox-LDL-induced thymidine incorporation into thioglycollate-elicited macrophages was three times higher than that into resident macrophages, whereas under the same conditions, granulocyte/macrophage colony-stimulating factor (GM-CSF) equally induced thymidine incorporation into both types of macrophages. Moreover, the Ox-LDL-induced GM-CSF release from thioglycollate-elicited macrophages was significantly higher than that from resident macrophages. In addition, the Ox-LDL-induced thymidine incorporation into macrophages obtained from human group-II PLA(2) transgenic mice and the GM-CSF release from these cells were significantly higher than those from their negative littermates, and the Ox-LDL-induced thymidine incorporation into human group-II PLA(2) transgenic macrophages was significantly inhibited by a polyclonal anti-human group-II PLA(2) antibody. These results suggest that the expression of group-II PLA(2) in thioglycollate-elicited macrophages may play an enhancing role in the Ox-LDL-induced macrophage growth through the enhancement of the GM-CSF release.

Observation of anomalous single-magnon scattering in half-metallic ferromagnets by chemical pressure control

The temperature variation of the resistivity rho and specific heat C have been measured for prototypical half-metallic ferromagnets, R0. 6Sr 0.4MnO3, by controlling the one-electron bandwidth W. We have found variations in the temperature scalings of rho from approximately T2 ( R = La, and Nd) to approximately T3 ( R = Sm), and have interpreted the T3 law in terms of the anomalous single-magnon scattering process in the half-metallic system.