Biomedical subjects

Masato Abe

Publications and source records attributed to Masato Abe.

At least 19 recordsLinked to original sources

PubMed2006

Mode of inhibitory action of Deltalac-acetogenins, a new class of inhibitors of bovine heart mitochondrial complex I.

We have revealed that Deltalac-acetogenins, a new class of inhibitors of bovine heart mitochondrial complex I (NADH-ubiquinone oxidoreductase), act differently from ordinary inhibitors such as rotenone and piericidin A [Ichimaru et al. (2005) Biochemistry 44, 816-825]. Since a detailed study of these unique inhibitors might provide new insight into the terminal electron transfer step of the enzyme, we further characterized their inhibitory action using the most potent Deltalac-acetogenin derivative (compound 1). Unlike ordinary complex I inhibitors, 1 had a dose-response curve for inhibition of the reduction of exogenous short-chain ubiquinones that was difficult to explain with a simple bimolecular association model. The inhibitory effect of 1 on ubiquinol-NAD(+) oxidoreductase activity (reverse electron transfer) was much weaker than that on NADH oxidase activity (forward electron transfer), indicating a direction-specific effect. These results suggest that the binding site of 1 is not identical to that of ubiquinone and the binding of 1 to the enzyme secondarily (or indirectly) disturbs the redox reaction of ubiquinone. Using endogenous and exogenous ubiquinone as an electron acceptor of complex I, we investigated the effect of 1 in combination with different ordinary inhibitors on the superoxide production from the enzyme. The results indicated that the level of superoxide production induced by 1 is significantly lower than that induced by ordinary inhibitors probably because of fewer electron leaks from the ubisemiquinone radical to molecular oxygen and that the site of inhibition by 1 is downstream of that by ordinary inhibitors. The unique inhibitory action of hydrophobic Deltalac-acetogenins may be closely associated with the dynamic function of the membrane domain of complex I.

Acetogenins↗

PubMed2006

Function of the alkyl side chains of Deltalac-acetogenins in the inhibitory effect on mitochondrial complex I (NADH-ubiquinone oxidoreductase).

We synthesized a series of Deltalac-acetogenins in which the two alkyl side chains were systematically modified, and examined their inhibitory effect on bovine heart mitochondrial complex I (NADH-ubiquinone oxidoreductase). The results revealed that the physicochemical properties of the side chains, such as the balance of hydrophobicity and the width (or bulkiness) of the chains, are important structural factors for a potent inhibitory effect of amphiphilic Deltalac-acetogenins. This is probably because such properties decide the precise location of the hydrophilic bis-THF ring moiety in the enzyme embedded in the inner mitochondrial membrane.

Acetogenins↗

PubMed2006

Response of temporomandibular joint intermittent closed lock to different treatment modalities: A multicenter survey.

This study investigated the clinical picture and different treatment methods and results at a number of institutions with the aim of establishing an effective method of treatment for intermittent closed lock (intermittent lock) of the temporomandibular joint (TMJ). The subjects were 104 patients (29 males, 65 females) diagnosed with intermittent lock among 1787 temporomandibular disorder patients. The cases were classified into two types based on the time and occasion when the intermittent lock occurred. The sudden onset type developed in 69.2%, and the habitually occurring type in 29.8%. The most common treatment was disk repositioning exercises alone (in 41 cases) followed by stabilization splints during sleeping. The highest efficacy rate (60.0%) was obtained with the combination of disk repositioning exercise and a repositioning splint followed by a rate of 52.6% with stabilization splints and 41.7% with disk repositioning exercise alone.

Adolescent↗

PubMed2006

Molecular cloning and characterization of a Pichia pastoris ortholog of the yeast Golgi GDP-mannose transporter gene.

There are two structural profiles in the yeast Golgi. The Golgi of Saccharomyces cerevisiae is composed of a number of vesicular compartments dispersed in the cytoplasm as recognized by a large number of Golgi marker proteins. In contrast, the Golgi of Pichia pastoris was reported to be organized in a small number of stacked cisternae located near the transitional endoplasmic reticulum (tER) sites by electron microscopy and immunofluorescent staining of a few marker proteins. The guanosine diphosphate (GDP)-mannose transporter (GMT) is an essential component in the yeast Golgi apparatus. We isolated an ortholog of the GMT gene of P. pastoris and visualized the gene product by epitope tagging to verify the structural characteristics of the Golgi. The tagged product in P. pastoris cell was observed in rod-like compartments in which Och1 mannosyltransferase was also found and the tER marker Sec12 and Sec13 proteins localized very close to them. The present results add further evidence of the restricted localization of the Golgi in P. pastoris cell.

Amino Acid Sequence↗

PubMed2005

Dynamic function of the alkyl spacer of acetogenins in their inhibitory action with mitochondrial complex I (NADH-ubiquinone oxidoreductase).

Studies on the inhibitory mechanism of acetogenins, the most potent inhibitors of mitochondrial complex I (NADH-ubiquinone oxidoreductase), are useful for elucidating the structural and functional features of the terminal electron transfer step of this enzyme. Previous studies of the structure-activity relationship revealed that except for the alkyl spacer linking the two toxophores (i.e., the hydroxylated THF and the gamma-lactone rings), none of the multiple functional groups of these inhibitors is essential for potent inhibition. To elucidate the function of the alkyl spacer, two sets of systematically selected analogues were synthesized. First, the length of the spacer was varied widely. Second, the local flexibility of the spacer was specifically reduced by introducing multiple bond(s) into different regions of the spacer. The optimal length of the spacer for inhibition was approximately 13 carbon atoms. The decrease in the strength of the inhibitory effect caused by elongating the spacer from 13 carbons was much more drastic than that caused by shortening. Local flexibility in a specific region of the spacer was not important for the inhibition. These observations indicate that the active conformation of the spacer is not an extended form, and is not necessarily restricted to a certain rigid shape. Moreover, an analogue in which a spacer covering 10 carbon atoms was hardened into a rodlike shape still maintained a potent inhibitory effect. Our results strongly suggest that the spacer portion is free from steric congestion arising from the putative binding site probably because there is no cavity-like binding site for the spacer portion. The manner of acetogenin binding to the enzyme may not be explained by a simple "key and keyhole" analogy.

Acetogenins↗

PubMed2005

Distinct functional units of the Golgi complex in Drosophila cells.

A striking variety of glycosylation occur in the Golgi complex in a protein-specific manner, but how this diversity and specificity are achieved remains unclear. Here we show that stacked fragments (units) of the Golgi complex dispersed in Drosophila imaginal disk cells are functionally diverse. The UDP-sugar transporter FRINGE-CONNECTION (FRC) is localized to a subset of the Golgi units distinct from those harboring SULFATELESS (SFL), which modifies glucosaminoglycans (GAGs), and from those harboring the protease RHOMBOID (RHO), which processes the glycoprotein SPITZ (SPI). Whereas the glycosylation and function of NOTCH are affected in imaginal disks of frc mutants, those of SPI and of GAG core proteins are not, even though FRC transports a broad range of glycosylation substrates, suggesting that Golgi units containing FRC and those containing SFL or RHO are functionally separable. Distinct Golgi units containing FRC and RHO in embryos could also be separated biochemically by immunoisolation techniques. We also show that Tn-antigen glycan is localized only in a subset of the Golgi units distributed basally in a polarized cell. We propose that the different localizations among distinct Golgi units of molecules involved in glycosylation underlie the diversity of glycan modification.

Animals↗

PubMed2005

Synthesis and inhibition mechanism of Delta lac-acetogenins, a novel type of inhibitor of bovine heart mitochondrial complex I.

We have synthesized Deltalac-acetogenins that are new acetogenin mimics possessing two n-alkyl tails without an alpha,beta-unsaturated gamma-lactone ring and suggested that their inhibition mechanism may be different from that of common acetogenins [Hamada et al. (2004) Biochemistry 43, 3651-3658]. To elucidate the inhibition mechanism of Deltalac-acetogenins in more detail, we carried out wide structural modifications of original Deltalac-acetogenins and characterized the inhibitory action with bovine heart mitochondrial complex I. In contrast to common acetogenins, both the presence of adjacent bis-THF rings and the stereochemistry around the hydroxylated bis-THF rings are important structural factors required for potent inhibition. The inhibitory potency of a derivative possessing an n-butylphenyl ether structure (compound 7) appeared to be superior to that of the original Deltalac-acetogenins and equivalent to that of bullatacin, one of the most potent natural acetogenins. Double-inhibitor titration of steady-state complex I activity showed that the extent of inhibition of compound 7 and bullatacin is not additive, suggesting that the binding sites of the two inhibitors are not identical. Competition tests using a fluorescent ligand indicated that the binding site of compound 7 does not overlap with that of other complex I inhibitors. The effects of compound 7 on superoxide production from complex I are also different from those of other complex I inhibitors. Our results clearly demonstrate that Deltalac-acetogenins are a novel type of inhibitor acting at the terminal electron-transfer step of bovine complex I.

Acetogenins↗

PubMed2004

Localization of GDP-mannose transporter in the Golgi requires retrieval to the endoplasmic reticulum depending on its cytoplasmic tail and coatomer.

The Saccharomyces cerevisiae GDP-mannose transporter (GMT) encoded by the essential gene VRG4/VIG4 is a member of the nucleotide-sugar transporter family in the Golgi apparatus. We examined GMT in the secretory mutant cells to investigate the mechanism of its localization in the Golgi. At the nonpermissive temperature, most GMT was found in the endoplasmic reticulum of sec23ts cells, which have defective COPII, and in the vacuole of sec21ts cells, which have defective COPI. The C-terminal hydrophilic peptide of GMT that is exposed to the cytosol binds to Ret2p, a subunit of the COPI coat. Mutant peptide derivatives that have lost a cluster of lysine in the vicinity of the transmembrane domain had reduced binding activity to Ret2p and the GMT with this sequence was delivered to the vacuole. Our results indicate that GMT escapes from delivery to the vacuole by recycling to the endoplasmic reticulum and retrieval requires the lysine-rich C-terminal tail that can bind to the COPI coat.

Amino Acid Sequence↗

PubMed2004

Analysis of interleukin-13 receptor alpha2 expression in human pediatric brain tumors.

BACKGROUND: Compared with normal brain tissue cells, human malignant glioma cells express higher levels of interleukin-13 receptor (IL-13R). However, whether this receptor is expressed in situ has not been carefully examined. With IL-13R-targeted cytotoxin (IL13-PE38QQR, comprising IL-13 and a mutated form of Pseudomonas exotoxin [PE]) being tested in three Phase I/II clinical trials for the treatment of adult human glioma, and with pediatric studies being planned, the authors set out to analyze pediatric brain tumor tissue specimens for the expression of IL-13R. METHODS: Using in situ hybridization and immunohistochemical staining, the authors examined 58 pediatric brain tumor specimens for expression of the predominant IL-13 binding and internalizing protein (IL-13Ralpha2) chain at the mRNA and protein levels. RESULTS: Overall, approximately 83% of pediatric brain tumor samples expressed IL-13Ralpha2. One hundred percent (11 of 11) high-grade astrocytoma, 79% (26 of 33) low-grade astrocytoma, 67% (4 of 6) medulloblastoma, and 67% (2 of 3) ependymoma samples were positive for IL-13Ralpha2. Among IL-13Ralpha2-positive samples, 88% (42 of 48 samples) had positive expression in > or = 50% of all tumor fields. The results obtained using both assays were consistent with each other. CONCLUSIONS: The current study established that pediatric brain tumor specimens expressed the IL-13Ralpha2 chain. Because the IL-13Ralpha2 chain is a major binding component of the IL-13R complex, these results suggest that the targeting of IL-13R may represent a useful approach for the treatment of pediatric brain tumors.

Adolescent↗

PubMed2004

Direct evidence for the interaction of stigmatellin with a protonated acidic group in the bc(1) complex from Saccharomyces cerevisiae as monitored by FTIR difference spectroscopy and 13C specific labeling.

In this study a combined electrochemical and FTIR spectroscopic approach was applied to monitor the binding of stigmatellin, a Q(o) site inhibitor of the cytochrome bc(1) complex from Saccharomyces cerevisiae. Natural stigmatellin A induced clear shifts in the redox-induced FTIR difference spectra. For data interpretation a stigmatellin derivative (UST) with the conjugated trienes replaced by an aliphatic tail was synthesized, and the carbonyl group shown in crystal structures to interact with His181, the [2Fe-2S] ligand of the Rieske, was specifically (13)C labeled. Electrochemically induced FTIR difference spectra of the inhibitors in CH(3)OD were obtained and revealed signals characteristic for the oxidized and reduced forms of the labeled and unlabeled compounds. On the basis of signals from the inhibitors alone, the binding of the inhibitor to the bc(1) complex was monitored. Direct evidence for the interaction of the carbonyl group with the protein was provided by the observed shift of the nu(C=O) vibrational mode of about 10 cm(-1). In addition, redox-dependent reorganizations of the protein were identified, including protonation changes of acidic residues at 1746 and 1734 cm(-1). The conformational changes observed upon inhibitor binding are discussed with respect to the crystal structures and proposed mechanistic models [Hunte, C., Koepke, J., Lange, C., Rossmanith, T., and Michel, H. (2000) Structure 8, 669-684; Palsdottir, H., Lojero, C. G., Trumpower, B. L., and Hunte, C. (2003) J. Biol. Chem. 278, 31303-31311].

Anti-Bacterial Agents↗

PubMed2004

Synthesis and inhibitory action of novel acetogenin mimics with bovine heart mitochondrial complex I.

Studies on the inhibition mechanism of acetogenins, the most potent inhibitors of complex I, are useful to elucidate the structural and functional features of the terminal electron-transfer step of this enzyme. We synthesized acetogenin mimics that possess two alkyl tails without a gamma-lactone ring, named Deltalac-acetogenin, and examined their inhibitory action on bovine heart mitochondrial complex I. Unexpectedly, the Deltalac-acetogenin carrying two n-undecanyl groups (compound 3) elicited very potent inhibition comparable to that of bullatacin. The inhibitory potency of compound 3 markedly decreased with shortening the length of either or both alkyl tails, indicating that symmetric as well as hydrophobic properties of the inhibitor are important for the inhibition. Both acetylation and deoxygenation of either or both of two OH groups adjacent to the tetrahydrofuran (THF) rings resulted in a significant decrease in inhibitory potency. These structural dependencies of the inhibitory action of Deltalac-acetogenins are in marked contrast to those of ordinary acetogenins. Double-inhibitor titration of steady-state complex I activity showed that inhibition of compound 3 and bullatacin are not additive, though the inhibition site of both inhibitors is downstream of iron-sulfur cluster N2. Our results indicate that the mode of inhibitory action of Deltalac-acetogenins differs from that of ordinary acetogenins. Therefore, Deltalac-acetogenins can be regarded as a novel type of inhibitor acting on the terminal electron-transfer step of complex I.

Acetogenins↗

PubMed2004

Essential structural features of acetogenins: role of hydroxy groups adjacent to the bis-THF rings.

The presence of two hydroxy groups adjacent to the THF ring(s) is a common structural feature of natural acetogenins. To elucidate the role of each hydroxy group in the inhibitory action of acetogenins, we synthesized three acetogenin analogues which lack either or both of the hydroxy groups, and investigated their inhibitory activities with bovine heart mitochondrial complex I. Our results indicate that the presence of either of the two hydroxy groups sufficiently sustains a potent inhibitory effect.

Acetogenins↗

PubMed2004

Synthesis and mitochondrial complex I inhibition of dihydroxy-cohibin A, non-THF annonaceous acetogenin analogue.

To elucidate the inhibitory action of acetogenins, we synthesized an acetogenin derivative which possesses tetraol in place of the tetrahydrofuran ring and examined its inhibitory activity against bovine heart mitochondrial complex I. Our results indicate that these hydroxy groups are an essential structural factor though it is not effective as bis-THF hydroxy groups combination.

Acetogenins↗

PubMed2004

Composite lymphoma arising in the parotid gland: a case report.

A case of composite lymphoma (CL) arisen in the parotid gland in a 58-year-old male is reported. Histologically, most of the tumor region was follicular lymphoma (FL), grade 2. However complicating classical Hodgkin lymphoma (CHL) was noted inside the lesion. There have been a few reports of composite lymphoma, complicated by multiple histologic types in the same organ. Extra-nodal cases are particularly rare. This is a very significant case with regard to differences between B cell-derived non-Hodgkin lymphoma (NHL) and Hodgkin lymphoma (HL) and its histological origin.

Antineoplastic Combined Chemotherapy Protocols↗

PubMed2004

Application of cell-free translation systems to studies of cofactor binding proteins.

To develop applications of in vitro cell-free translation systems for production and characterization of cofactor binding proteins, we investigate the production of apo- or holo-forms of Flavin Mono Nucleotide (FMN)-binding protein from Desulfovibrio vulgaris (Miyazaki F) and purified them. The redox potential analysis and measurements of UV-, visible, and fluorescent spectra of reconstructed holo-protein showed that the FMN correctly bound to the FMN binding site. On the other hand, contrary to our expectation, we found that the apo-protein formed a dimer structure and the incorporation of the FMN led the conformational alterations of the protein. These studies demonstrate the utility of cell-free translation systems to analyses of cofactor-binding proteins.

Bacterial Proteins↗

PubMed2004

Variations in the tensor veli palatini muscle with special reference to its origin and insertion.

OBJECTIVE: Previous research on the tensor veli palatini muscle (TVP) has produced conflicting descriptions of its functions and topographical relationships with other orofacial structures. The goal of this study was to describe the morphology of the TVP in a systematic and comprehensive manner. METHODS: One hundred nineteen sides of 77 human heads from donated cadavers were partially dissected under a binocular microscope. Histological examination of the hard tissue-muscle interfaces was also undertaken. RESULTS: There were two adjacent origins of the TVP: the cranial base origin (CB origin) and the auditory tube cartilage origin (AT origin). The CB origin always lay anterior to the AT origin and there was no septum or loose tissue between the two muscular laminae leading from these origins. The muscle fibers converged on a central tendinous plate in the muscle belly, which gradually became a common tendon that rounded the pterygoid hamulus before inserting into the palatine aponeurosis. Notably, secondary insertions were found on the maxillary tuber (33.6%) and/or in the submucosal tissue near the palatoglossal arch (37.8%). Maxillary insertions were almost exclusively associated with an AT origin that was wide as or wider than the CB origin. Histological observations confirmed that the hamulus acted purely as a pulley and suggested that a connecting band to the tensor tympani had no or few functions of an intermediate tendon. CONCLUSIONS: The TVP appears to act as the dilator tubae and that this function can be maintained by preserving or reconstructing the maxillary insertion during push-back surgery, even if hamulotomy is necessary.

Adult↗

PubMed2003

Synthesis and inhibitory activity of ubiquinone-acetogenin hybrid inhibitor with bovine mitochondrial complex I.

To elucidate the inhibitory action of acetogenins, the most potent inhibitors of mitochondrial complex I, we synthesized an acetogenin analogue which possesses a ubiquinone ring (i.e., the physiological substrate of complex I) in place of the alpha,beta-unsaturated gamma-lactone ring of natural acetogenins, and named it Q-acetogenin. Our results indicate that the gamma-lactone ring of acetogenins is completely substitutable with the ubiquinone ring. This fact is discussed in light of the inhibitory action of acetogenins.

Acetogenins↗

PubMed2003

Afferent and efferent lymph-collecting vessels of the submandibular nodes with special reference to the lymphatic route passing through the mylohyoid muscle.

BACKGROUND: Although metastasis of cancer in the oral region to the submandibular node is well described, there has been no anatomic representation of lymph vessels penetrating the oral floor and draining into the node. MATERIALS AND METHODS: Ninety specimens were obtained from formalin-fixed, donated cadavers. Histologic observations using serial sections followed the macroscopic observations. RESULTS: In 19 of 90 specimens, we found afferent collecting lymph vessels exiting from the mylohyoid surface and draining into the preglandular submandibular node. In 3 of the 19 specimens, collecting vessels passing through the narrow muscle gap with or without arteries, veins, and nerves were identified histologically. The postglandular submandibular node was not evident in the drainage route. CONCLUSIONS: Although it carries a low incidence, because of the direct lymphatic route or pathway between the oral region and preglandular submandibular node, the pathologically positive supraomohyoid node sometimes seems to be found even in elective neck dissection. However, we speculate that sentinel node investigation would reveal the much more critical role of the jugulodigastric node not only as the actual sentinel node but also as the common terminal node along the various drainage routes from the oral region.

Aged↗