Biomedical subjects

A Yamamoto

Publications and source records attributed to A Yamamoto.

At least 55 records · Page 3Linked to original sources

PubMed2002

Loss of mRNA levels, binding and activation of GTP-binding proteins for cannabinoid CB1 receptors in the basal ganglia of a transgenic model of Huntington's disease.

Data obtained from the basal ganglia of postmortem Huntington's disease (HD) brains have revealed that the level of cannabinoid CB1 receptors in striatal efferent neurons decreases in parallel to the dysfunction and subsequent degeneration of these neurons. These findings, and others from rat models of HD generated by lesions with mitochondrial toxins, suggest that the loss of CB1 receptors may be involved in the pathogenesis of the disease. To explore further the changes in the endocannabinoid system, as well as the potential of endocannabinoid-related compounds, we examined the status of CB1 receptors in the HD94 transgenic mouse model of HD. These mice express huntingtin exon 1 with a polyglutamine tract of 94 repeats in a tissue-specific and conditional manner using the tet regulatable system. They develop many features of HD, such as striatal atrophy, intraneuronal aggregates and progressive dystonia. In these animals, we analyzed mRNA levels for the CB1 receptor, in addition to the number of specific binding sites and the activation of GTP-binding proteins by CB1 receptor agonists. mRNA transcripts of the CB1 receptor were significantly decreased in the caudate-putamen of HD transgenic mice compared to age-matched littermate controls. The decrease concurred with a marked reduction in receptor density in both the caudate-putamen and its projection areas such as the globus pallidus, entopeduncular nucleus and substantia nigra pars reticulata. Furthermore, the efficacy of CB1 receptor activation was reduced in the globus pallidus, as determined by agonist-induced [35S]GTPgammaS binding, and tended towards a decrease in the substantia nigra. None of these changes was seen in the cerebral cortex and hippocampus, despite high levels of expression of the mutant protein in these regions. The decrease in CB1 receptor levels was accompanied by a decrease in the proenkephalin-mRNA levels but not in substance P-mRNA levels. Taken together, these results suggest that the loss of CB1 receptor might be preferential to the enkephalinergic CB1 receptor-containing striatopallidal neurons, and further implicate the CB1 receptor to the subsequent HD symptomatology and neuropathology.

Animals↗

PubMed2002

Superconducting gap in MgB(2): electronic Raman scattering measurements of single crystals.

Polarization-resolved Raman scattering measurements were performed on MgB(2) single crystals to determine the magnitude, symmetry, and temperature dependence of the superconducting gap. A single sharp peak due to Cooper pair breaking appears in the electronic continuum below T(c), reaching a maximum Raman shift of 105 +/- 1 cm(-1) [2 Delta(0)/k(B)T(c) = 3.96 +/- 0.09] and showing up to 5 cm(-1) anisotropy between polarized and depolarized spectra. The temperature dependence of 2 Delta follows that predicted from BCS theory, while the anisotropy decreases with decreasing temperature. It is concluded that the Raman results are consistent with a slightly anisotropic s-wave gap in a conventional BCS superconductor.

Journal Article↗

PubMed2002

Measurements of cosmic-ray low-energy antiproton and proton spectra in a transient period of solar field reversal.

The energy spectra of cosmic-ray low-energy antiprotons ( *p's) and protons ( p's) have been measured by BESS in 1999 and 2000, during a period covering reversal at the solar magnetic field. Based on these measurements, a sudden increase of the *p/p flux ratio following the solar magnetic field reversal was observed, and it generally agrees with a drift model of the solar modulation.

Journal Article↗

PubMed2002

Exponential temperature dependence of the penetration depth in single crystal MgB2.

The temperature dependence of the London penetration depth, lambda(T), was measured in both single crystal and polycrystalline MgB2 samples by a high-resolution, radio frequency technique. A clear exponential temperature dependence of lambda(T) was observed at low temperature, indicating s-wave pairing. A BCS fit to the lowest temperature data gives an in-plane energy gap Delta of 30+/-2 K (2Delta/T(c) = 1.5+/-0.1), which is significantly smaller than the standard BCS weak coupling value of 3.5. We find that the data are best described by a two-gap model.

Journal Article↗

PubMed2002

An essential amino acid residue for catalytic activity of the dextranase of Streptococcus mutans.

Dextranase (Dex) is an enzyme that hydrolyzes glucan, a polymer of glucose synthesized from sucrose by glucosyltransferases (GTFs). By comparing amino acid sequences of Dexs and GTFs, we found that the Dex enzymes of Streptococcus mutans, Streptococcus sobrinus, Streptococcus downei and Streptococcus salivarius had similar amino acid sequences to those of the catalytic sites of GTFs of mutans streptococci. We therefore examined the amino acid essential in Dex catalysis by molecular genetic approaches in this study. Site-directed mutagenesis was used to convert the Asp-385 of the Dex molecule of S. mutans Ingbritt to Glu, Asn, Thr or Val. Replacement of Asp-385 with any of the amino acids resulted in complete disappearance of Dex activity. However, replacement of other Asp residues did not affect the enzyme activity. The inactive enzymes still retained dextran-binding ability. These results suggest that Asp-385 of the Dex of S. mutans Ingbritt was essential for enzyme activity and the catalytic and substrate-binding sites were located at different sites within the Dex molecule.

Amino Acid Sequence↗

PubMed2002

Role of reactive oxygen species in neutrophil apoptosis following ingestion of heat-killed Staphylococcus aureus.

Neutrophils, short-lived leucocytes that die by apoptosis, play an important role in the first stage of defense against bacterial infections. It has been reported that phagocytosis of intact bacteria or Candida albicans can accelerate neutrophil apoptosis. However, the mechanism of phagocytosis-mediated neutrophil apoptosis is not well characterized. In this study, we evaluated whether ingestion of heat-killed Staphylococcus aureus (S. aureus) enhances neutrophil apoptosis and whether this type of apoptosis is mediated by oxidative stress by using antioxidants and polymorphonuclear leucocytes (PMNs) from patients with chronic granulomatous disease (CGD). Co-culture of PMNs with varying doses of S. aureus resulted in accelerated PMN death in a dose- and time-dependent manner. Increased PMN apoptosis was observed by both Annexin V and PI staining. Similar results were observed in PMNs of CGD patients. Dimethyl sulphoxide (DMSO, an OH* scavenger) did not significantly inhibit either S. aureus-ingested PMN apoptosis or spontaneous PMN apoptosis. On the other hand glutathione (GSH, an H2O2 scavenger) significantly inhibited both types of apoptosis. Our findings suggest that oxygen-independent pathways may mainly operate in the process of phagocytosis-induced apoptosis.

Adult↗

PubMed2002

Analysis of a dextran-binding domain of the dextranase of Streptococcus mutans.

AIMS: To examine the dextran-binding domain of the dextranase (Dex) of Streptococcus mutans. METHODS AND RESULTS: Deletion mutants of the Dex gene of Strep. mutans were prepared by polymerase chain reaction and expressed in Escherichia coli cells. Binding of the truncated Dexs to dextran was measured with a Sephadex G-150 gel. Although the Dexs which lacked the N-terminal variable region lost enzyme activity, they still retained dextran-binding ability. In addition, further deletion into the conserved region from the N-terminal did not influence the dextran-binding ability. However, the Dex which carried a deletion in the C-terminus still possessed both enzyme activity and dextran-binding ability. Further deletion into the conserved region from the C-terminal resulted in complete disappearance of both enzyme and dextran-binding activities. CONCLUSIONS: Deletion analysis of the Dex gene of Strep. mutans showed that the C-terminal side (about 120 amino acid residues) of the conserved region of the Dex was essential for dextran-binding ability. SIGNIFICANCE AND IMPACT OF THE STUDY: The dextran-binding domain was present in a different area from the catalytic site in the conserved region of the Dex molecule. The amino acid sequence of the dextran-binding domain of the Dex differed from those of glucan-binding regions of other glucan-binding proteins reported.

Amino Acid Sequence↗

PubMed2002

Simple curettage without bone grafting for enchondromata of the hand: with special reference to replacement of the cortical window.

We studied 23 patients (25 bones) with enchondromata of the hand which were treated with simple curettage without bone grafting. The cortical window was replaced in 18 bones (group A), whereas it was not replaced in six bones (group B). In one bone, only half of the cortical window was replaced. Local recurrence was not seen in any patient. Although bone grafting was not performed, new bone formation was observed in all the patients. Radiographic and functional results were excellent in most bones. Restoration of the continuity of the cortex was seen at 3 (range, 1.5-4) months in group A and 8 (range, 6-12) months in group B. This restoration is important for the recovery of mechanical strength and we therefore consider that the cortical window should be replaced, unless this is impractical.

Adult↗

PubMed2002

Evaluation of 5-S-cysteinyldopa as a marker of melanoma progression: 10 years' experience.

5-S-Cysteinyldopa (5-S-CD) has been used as a biochemical marker of melanoma progression. In this study, we measured serum levels of 5-S-CD in 2648 samples taken from 218 patients in order to evaluate the usefulness of this parameter in following melanoma progression and prognosis. 5-S-CD levels were significantly elevated above the upper limit of the normal range (10 nmol/l) in stage IV melanoma patients. The sensitivity of elevated serum 5-S-CD levels in detecting distant metastasis was 73%, while the specificity was 98% and the positive predictive value 94%. The sensitivity was improved to 77% when cases of amelanotic melanoma were excluded. Patients without metastases had elevated 5-S-CD values in 5% of the 1480 serum samples. Changes in serum 5-S-CD levels were followed during disease progression until the end stage in 49 patients. In 33% of the patients, elevation of serum 5-S-CD levels preceded clinical detection of visceral metastases, and in 37% elevation of 5-S-CD levels occurred at the same time as visceral metastasis. Patients with elevated 5-S-CD levels before or after surgical treatment had significantly shorter survival times than those with normal levels. These results show that the level of 5-S-CD in the serum is a sensitive and specific marker in predicting distant metastases. Elevated serum levels of 5-S-CD, before or after surgical treatment, is associated with a poor prognosis.

Adolescent↗

PubMed2002

[The usefulness of induction chemotherapy in cases with tumors showing border-line pathological aspects between thymoma and thymic carcinoma].

We present 2 surgically treated cases with thymoma classified as Masaoka stage III and IV a (type B 3 thymoma), which showed the border-line pathological aspects between the thymoma and thymic carcinoma. Induction chemotherapy [CAV-PVP (cyclophosphamide, adriamycin, vincristine sulfate, etoposide) therapy in one case and ADOC (adriamycin, cisplatin, vincristine sulfate, cyclophosphamide) therapy in another case] preluded their surgical resection resulted in reduction of the tumor's size moderately or severely. After achievement of induction chemotherapy, these tumors were resected with the midsternotomy approach, along with resection of the right upper lobe and the left brachiocephalic vein replacing the expanded pdytetrafluoroethylene (ePTFE) graft following mediastinal lymphnodes dissection in one case and leaving the tumor tissue around the pulmonary trunk in another case. Postoperative irradiation of 40 Gy in one case and 60 Gy in another case were performed in the mediastinal regions. From pathological aspects especially in second case, though the specimen by preoperative needle biopsy stained positive for bcl-2 and strong immunoreactivity (20%) for MIB-1, specimens excised operatively after induction chemotherapy showed negative staining for bcl-2 and little staining (lower than 5%) for MIB-1. This fact indicates that the induction chemotherapy makes the tumor less malignant, in other words, from the face of thymic carcinoma to the face of thymoma. Induction chemotherapy performed for the purpose of reducing the tumor size was very advantage in these 2 cases with type B 3 thymoma.

Antineoplastic Combined Chemotherapy Protocols↗

PubMed2001

XBP1 mRNA is induced by ATF6 and spliced by IRE1 in response to ER stress to produce a highly active transcription factor.

In yeast, the transmembrane protein kinase/endoribonuclease Ire1p activated by endoplasmic reticulum stress cleaves HAC1 mRNA, leading to production of the transcription factor Hac1p that activates the unfolded protein response (UPR). In mammals, no Hac1p counterpart has yet been discovered despite the presence of Ire1p homologs in the endoplasmic reticulum. Instead, the transcription factor ATF6 specific to the mammalian UPR is regulated by intramembrane proteolysis. Here, we identified the transcription factor XBP1, a target of ATF6, as a mammalian substrate of such an unconventional mRNA splicing system and showed that only the spliced form of XBP1 can activate the UPR efficiently. Our results reveal features of the UPR conserved during evolution and clarify the relationship between IRE1- and ATF6-dependent pathways.

Activating Transcription Factor 6↗

PubMed2001

Human Nck-associated protein 1 and its binding protein affect the metabolism of beta-amyloid precursor protein with Swedish mutation.

Alzheimer's disease (AD) is a neurodegenerative disorder of the central nervous system, and beta-amyloid precursor protein (betaAPP) plays a pivotal role in AD pathology. We previously reported that the suppression of human Nck-associated protein 1 (Nap1) whose expression was down-regulated in sporadic AD led to apoptosis in human neuroblastoma cells, and also its binding protein, hNap1BP was identified. Here, we examined whether these molecules were involved in the regulation of betaAPP metabolism. Human Nap1 and hNap1BP were found not to effect the amount of intracellular betaAPP but induced sAPPalpha secretion. Interestingly, they didn't reduce but slightly increased the extracellular level of Abeta. Furthermore, neither human Nap1 nor hNap1BP influenced the ratio of Abeta42/43 to total Abeta. Taken together, human Nap1 and hNap1BP may play a role in regulation of beta-secretase activity in the processing of betaAPP.

Adaptor Proteins, Signal Transducing↗

PubMed2001

Molecular cloning and characterization of the Cl(-) pump-associated 55-kDa protein in rat brain.

The Cl(-)-ATPase/pump in the plasma membrane of the rat brain is a candidate for active outwardly directed Cl(-) translocating systems. We recently isolated a Cl(-) pump, 520- or 580-kDa protein complex, which consisted of 51-, 55-, 60-, and 62-kDa proteins. In this study, we cloned a cDNA encoding a 55-kDa glycoprotein, designated as ClP55, which contained an open reading frame of 1512 base pairs encoding a protein of 504 amino acids including a signal peptide of 28 amino acids. Northern and Western blot analyses demonstrated expression of ClP55 mainly in the cerebrum. Application of antisense phosphorothioate oligonucleotides to cultured neurons resulted in a marked increase in the intracellular Cl(-) concentration ([Cl(-)](i)). Immunohistochemical analysis indicated that ClP55 was localized to the plasma membranes of neurons such as hippocampal pyramidal neurons and cerebellar Purkinje cells. Taken together, these results suggest that ClP55 is one of the Cl(-) pump subunits responsible for Cl(-) pump activity.

Adenosine Triphosphatases↗

PubMed2001

Neuronal nitric oxide synthase generates superoxide from the oxygenase domain.

When l-arginine is depleted, neuronal nitric oxide synthase (nNOS) has been reported to generate superoxide. A flavoprotein module construct of nNOS has been demonstrated to be sufficient for superoxide production. In contrast, nNOS was reported not to be involved in superoxide formation, because such formation occurred with a mixture of the boiled enzyme and redox-active cofactors. We aimed to resolve these controversial issues by examining superoxide generation, without the addition of redox-active cofactors, by recombinant wild-type nNOS and by C415A-nNOS, which has a mutation in the haem proximal site. In a superoxide-sensitive adrenochrome assay, the initial lag period of C415A-nNOS was increased 2-fold compared with that of native nNOS. With ESR using the spin trap 5,5-dimethyl-1-pyrroline-N-oxide, prominent signals of the superoxide adduct were obtained with wild-type nNOS, whereas an enzyme preparation boiled for 5 min did not produce superoxide. Higher concentrations of NaCN (10 mM) decreased superoxide formation by 63%. Although the activity of the reductase domain was intact, superoxide generation from C415A-nNOS was decreased markedly, to only 10% of that of the wild-type enzyme. These results demonstrate that nNOS truly catalyses superoxide formation, that this involves the oxygenase domain, and that full-length nNOS hinders the reductase domain from producing superoxide.

Animals↗

PubMed2001

Proteasomal-dependent aggregate reversal and absence of cell death in a conditional mouse model of Huntington's disease.

Neuronal intranuclear inclusions are a histopathological hallmark of Huntington's disease. Nevertheless, the precise mechanism by which they are formed and their relevance to neuronal cell death and/or dysfunction remains unclear. We recently generated a conditional mouse model of Huntington's disease (HD94) in which silencing expression of mutated huntingtin led to the disappearance of intranuclear aggregates and amelioration of the behavioral phenotype. Here, we analyze primary striatal neuronal cultures from HD94 mice to explore the dynamics of aggregate formation and reversal, the possible mechanisms involved, and the correlation between aggregates and neuronal death. In parallel, we examine symptomatic adult HD94 mice in similar studies and explored the relationship between aggregate clearance and behavioral reversal. We report that, in culture, aggregate formation and reversal were rapid processes, such that 2 d of transgene expression led to aggregate formation, and 5 d of transgene suppression led to aggregate disappearance. In mice, full reversal of aggregates and intranuclear mutant huntingtin was more rapid than reported previously and preceded the motor recovery by several weeks. Furthermore, the proteasome inhibitor lactacystin inhibited the aggregate clearance observed in culture, thus indicating that aggregate formation is a balance between the rate of huntingtin synthesis and its degradation by the proteasome. Finally, neither expression of the mutant huntingtin nor aggregates compromised the viability of HD94 cultures. This correlated with the lack of cell death in symptomatic HD94 mice, thus demonstrating that neuronal dysfunction, and not cell loss, triggered by mutant huntingtin underlies symptomatology.

Acetylcysteine↗

PubMed2001

Tumor antigens isolated from a patient with vitiligo and T-cell-infiltrated melanoma.

Serological identification of tumor antigens by cDNA expression cloning is a technique used to isolate cDNAs encoding tumor antigens that are recognized by IgG antibodies in sera from cancer patients. It is also useful for the isolation of tumor antigens recognized by T cells. We applied this method to identify melanoma antigens recognized by the serum from a patient with a good prognosis who had T-cell-infiltrated melanoma and vitiligo. By screening a lambda phage cDNA library constructed from a highly pigmented melanoma cell line, SKmel23, with the patient's serum, 50 positive cDNA clones consisting of 26 distinct antigens were isolated. Of these, 20 encoded known proteins, and 6 encoded previously uncharacterized ones. The most frequently isolated clone, which we named KU-MEL-1, was unknown previously but was homologous to partial cDNA sequences registered in the expressed sequence tag database. Reverse transcription-PCR and Northern blot analysis demonstrated that KU-MEL-1 was strongly expressed in most melanoma cell lines, melanoma tissue samples, and cultured melanocytes and weakly expressed in cell lines derived from other types of tumors, as well as in some normal tissues, including testis. Western blot analysis with polyclonal murine antibody generated by immunization with the recombinant KU-MEL-1 protein demonstrated that the KU-MEL-1 protein was preferentially expressed in melanoma cells and melanocytes. IgG antibodies against KU-MEL-1 were detected in the sera from 9 of 26 melanoma patients and from some patients with other cancers, including brain tumor, esophageal cancer, colon cancer, and chronic myelogenous leukemia, but were not detected in sera from 30 healthy individuals. Although the IgG specific for KU-MEL-1 was not detected in sera from 12 vitiligo patients, it was detected in sera from 7 of 11 patients with Vogt-Koyanagi-Harada disease that is thought to be an autoimmune disease against melanocytes. These results suggest that KU-MEL-1 may be a useful target for the development of diagnostic and therapeutic methods for patients with various cancers, particularly with melanoma, as well as patients with autoimmune diseases against melanocytes.

Aged↗

PubMed2001

Efficient antigen gene transduction using Arg-Gly-Asp fiber-mutant adenovirus vectors can potentiate antitumor vaccine efficacy and maturation of murine dendritic cells.

Dendritic cells (DCs), the most effective antigen-presenting cells, are being studied as adjuvants or antigen delivery vehicles for eliciting T-cell-mediated antitumor immunity. Gene delivery to DCs provides an intracellular source of antigen for efficient and persistent loading to MHC class I molecules capable of activating CD8(+) CTLs, which play a central role in antitumor immunity. We previously reported that the fiber-mutant adenovirus vector (Ad) harboring the Arg-Gly-Asp (RGD) sequence in the HI loop of its fiber knob could more efficiently transduce the LacZ gene into both murine DC lines and normal human DCs than conventional Ad. In the present study, we compared immunological properties and vaccine efficacy of DC2.4 cells, an immature murine DC line, transduced with an ovalbumin (OVA) gene by fiber-mutant Ad (Ad-RGD-OVA) or conventional Ad (Ad-OVA). Ad-RGD-OVA-infected DC2.4 cells could more efficiently present OVA peptides via MHC class I molecules in a vector particle-dependent manner and induce OVA-specific CTL response by vaccination than Ad-OVA-infected DC2.4 cells. This result was correlated with the efficiency of gene transduction into DC2.4 cells by both types of Ad. Moreover, vaccination with Ad-RGD-OVA-infected DC2.4 cells could achieve an equal or greater antitumor effect against challenge with E.G7-OVA tumor cells with lower doses of Ad on infection or fewer cells for immunization than the vaccination procedure using Ad-OVA-infected DC2.4 cells. In addition, the maturation of DC2.4 cells was promoted by efficient expression of the antigen gene by the Arg-Gly-Asp fiber-mutant Ad. Flow cytometric analysis indicated enhanced expression of MHC class I and II molecules as well as CD80, CD86, CD40, and CD54, and reverse transcription-PCR analysis revealed increased levels of interleukin 12 p40 mRNA. However, infection by Ad-OVA or Ad that did not contain the cDNA of interest (Ad-Null and Ad-RGD-Null) contributed little to phenotypical changes in DC2.4 cells. On the basis of these results, we propose that DC manipulation using the Arg-Gly-Asp fiber-mutant Ad system could advance the development of more effective vaccines and allow for more convenient administration of DC-based gene immunotherapy.

Adenoviridae↗

PubMed2001

Absorption of water-soluble compounds with different molecular weights and.

The absorption of water soluble compounds with different molecular weights, such as phenol red (MW 354), trypan blue (MW 960), fluorescein isothiocyanate dextrans, (MW 4400 and 9100) was studied in the lung, nasal cavity, buccal cavity, small and large intestine of rats. For all the compounds, maximal absorption was observed when administered to the lung. The rank order of absorption of each compound from various administration sites was lung>small intestine> or =nasal cavity> or =large intestine> or =buccal cavity. In addition, the relationship between logarithm absorption % of the compounds from various administration sites and logarithm molecular weights of these compounds was examined. The absorption of compounds gradually decreased with increasing molecular weight for each site of administration. Moreover, the absorption of [Asu1.7]-eel calcitonin (ECT) from these sites and the effect of 10 mM sodium glycocholate, an absorption enhancer, on its absorption were also investigated in rats. When ECT alone was administered into these sites, the lung had the best absorption site of ECT, followed by the nasal cavity, the large intestine, the small intestine and the buccal cavity. Therefore, the absorption of ECT was also dependent on the administration site, although the rank order of absorption % of ECT was different from the other compounds. Sodium glycocholate (NaGC) remarkably increased ECT absorption from the small intestine, while we found marginal increase in its absorption from the lung even in the presence of NaGC. These findings provided useful fundamental information that might aid in the selection of administration routes for drugs of differing molecular weights including peptide drugs as far as the degree of drug absorption is concerned.

Absorption↗