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Biomedical subjects

Y Imai

Publications and source records attributed to Y Imai.

At least 163 records · Page 9Linked to original sources
PubMed2000

Mutations of the AML1 gene in myelodysplastic syndrome and their functional implications in leukemogenesis.

The AML1 gene encodes a DNA-binding protein that contains the runt domain and is the most frequent target of translocations associated with human leukemias. Here, point mutations of the AML1 gene, V105ter (single-letter amino acid code) and R139G, (single-letter amino acid codes) were identified in 2 cases of myelodysplastic syndrome (MDS) by means of the reverse transcriptase-polymerase chain reaction single-strand conformation polymorphism method. Both mutations are present in the region encoding the runt domain of AML1 and cause loss of the DNA-binding ability of the resultant products. Of these mutants, V105ter has also lost the ability to heterodimerize with polyomavirus enhancer binding protein 2/core binding factor beta (PEBP2beta/CBFbeta). On the other hand, the R139G mutant acts as a dominant negative inhibitor by competing with wild-type AML1 for interaction with PEBP2beta/CBFbeta. This study is the first report that describes mutations of AML1 in patients with MDS and the mechanism whereby the mutant acts as a dominant negative inhibitor of wild-type AML1.

Amino Acid Substitution↗
PubMed2000

Regulation of the development of allodynia by intrathecally administered P2 purinoceptor agonists and antagonists in mice.

Effects of agonists and antagonists of P2X-purinoceptors on the regulation of the development of allodynia were examined in mice; the drugs were administered intrathecally to the spinal cord. Suramin (5, 10 microg) and pyridoxalphosphate-6-azophenyl-2', 4'-disulfonic acid (PPADS), antagonists of P2X receptors, inhibited prostaglandin (PG) E(2)-induced allodynia. PPADS did not block glutamate-induced allodynia. alpha,beta-Methylene ATP (alpha, beta-meATP), an agonist of P2X receptor, elicited allodynia. alpha, beta-me ATP-induced allodynia was blocked by co-administration of alpha,beta-meATP with PPADS, MK 801 or N(omega)-nitro-L-arginine methyl ester (L-NAME). Suramin at higher doses (20, 40 microg) induced allodynia, which was inhibited by MK 801 or L-NAME. These results suggest that ATP P2X receptors in the spinal cord are involved in the regulation of tactile allodynia. Glutamate receptor and nitric oxide systems play an important role in the development of allodynia produced by alpha,beta-meATP and suramin.

Adenosine Triphosphate↗
PubMed2000

HCO3- transport in a mathematical model of the pancreatic ductal epithelium.

We have used computer modeling to investigate how pancreatic duct cells can secrete a fluid containing near isotonic (approximately 140 mM) NaHCO3. Experimental data suggest that NaHCO3 secretion occurs in three steps: (i) accumulation of HCO3- across the basolateral membrane of the duct cell by Na(HCO3)n cotransporters, Na+/H+ exchangers and proton pumps; (ii) secretion of HCO3- across the luminal membrane on Cl-/HCO3- antiporters operating in parallel with Cl- channels; and (iii) diffusion of Na+ through the paracellular pathway. Programming the currently available experimental data into our computer model shows that this mechanism for HCO3- secretion is deficient in one important respect. While it can produce a relatively large volume of a HCO3(-)-rich fluid, it can only raise the luminal HCO3- concentration up to about 70 mM. To achieve secretion of 140 mM NaHCO3 by the model it is necessary to: (i) reduce the conductive Cl- permeability and increase the conductive HCO3- permeability of the luminal membrane of the duct cell, and (ii) reduce the activity of the luminal Cl-/HCO3- antiporters. Under these conditions most of the HCO3- is secreted via a conductive pathway. Based on our data, we propose that HCO3- secretion occurs mainly by the antiporter in duct segments near the acini (luminal HCO3- concentration up to approximately 70 mM), but mainly via channels further down the ductal tree (raising luminal HCO3- to approximately 140 mM).

Animals↗
PubMed2000

Substitutions for hydrophobic amino acids in the N-terminal domains of IGFBP-3 and -5 markedly reduce IGF-I binding and alter their biologic actions.

Insulin-like growth factor-binding protein-3 and -5 (IGFBP-3 and -5) have been shown to bind insulin-like growth factor-I and -II (IGF-I and -II) with high affinity. Previous studies have proposed that the N-terminal region of IGFBP-5 contains a hydrophobic patch between residues 49 and 74 that is required for high affinity binding. These studies were undertaken to determine if mutagenesis of several of these residues resulted in a reduction of the affinity of IGFBP-3 and -5 for IGF-I. Substitutions for residues 68, 69, 70, 73, and 74 in IGFBP-5 (changing one charged residue, Lys(68), to a neutral one and the four hydrophobic residues to nonhydrophobic residues) resulted in an approximately 1000-fold reduction in the affinity of IGFBP-5 for IGF-I. Substitutions for homologous residues in IGFBP-3 also resulted in a >1000-fold reduction in affinity. The physiologic consequence of this reduction was that IGFBP-3 and -5 became very weak inhibitors of IGF-I-stimulated cell migration and DNA synthesis. Likewise, the ability of IGFBP-5 to inhibit IGF-I-stimulated receptor phosphorylation was attenuated. These changes did not appear to be because of alterations in protein folding induced by mutagenesis, because the IGFBP-5 mutant was fully susceptible to proteolytic cleavage by a specific IGFBP-5 protease. In summary, residues 68, 69, 70, 73, and 74 in IGFBP-5 appear to be critical for high affinity binding to IGF-I. Homologous residues in IGFBP-3 are also required, suggesting that they form a similar binding pocket and that for both proteins these residues form an important component of the core binding site. The availability of these mutants will make it possible to determine if there are direct, non-IGF-I-dependent effects of IGFBP-3 and -5 on cellular physiologic processes in cell types that secrete IGF-I.

Amino Acid Substitution↗
PubMed2000

Novel chiral bisoxazoline ligands with a biphenyl backbone: preparation, complexation, and application in asymmetric catalytic reactions

Novel C(2)-symmetric chiral bisoxazoline ligands 1 were easily prepared from enantiomerically pure 2-amino alcohols and achiral 2, 2'-biphenyldicarboxylic acid via the corresponding amide and mesylate as intermediates. Since these ligands bear only two ortho-substituents on the biphenyl backbone, the biphenyl axis is not fixed, and the two diastereomers of these ligands exist in equilibrium in solution. Interestingly, when the ligands 1 were coordinated with a metal ion, only one of the two possible diastereomer complexes, an (S,aS,S)-complex, can be formed depending on the combination of the ligand and the metal ion. Thus, copper(I) afforded only the (S,aS,S)-complexes with all ligands 1, while zinc(II), palladium(II), and silver(I) afforded the (S,aS, S)-complexes as the sole product only with 1b, which has a bulky tert-butyl group on the oxazoline ring, and a mixture of the two diastereomer complexes with 1a,c,d. The copper(I)-catalyzed asymmetric cyclopropanation of styrene with diazoacetate proceeded successfully with these ligands and good to excellent enantioselectivities were afforded.

Journal Article↗
PubMed2000

Insertional mutation of the murine kisimo locus caused a defect in spermatogenesis.

Spermatogenesis is a developmental process that occurs in several phases and is regulated by a large number of gene products. An insertional transgenic mouse mutant (termed kisimo mouse) has been isolated that results in abnormal germ-cell development, showing abnormal elongated spermatids in the lumina of seminiferous tubules. We cloned the disrupted locus of kisimo and identified a novel testis-specific gene, THEG, which is specifically expressed in spermatids and was disrupted in the transgenic mouse. The yeast two-hybrid screening method revealed that THEG protein strongly interacts with chaperonin containing t-complex polypeptide-1epsilon, suggesting that THEG protein functions as a regulatory factor in protein assembly. Our findings indicate that the kisimo locus is essential for the maintenance of spermiogenesis and that a gene expression disorder may be involved in male infertility.

3',5'-Cyclic-GMP Phosphodiesterases↗
PubMed2000

Precision wavelength measurement of the 14.4 keV Mössbauer photon.

The wavelength of the 14.4 keV Mössbauer photon has been determined by using undulator radiation and diffraction of FZ silicon crystals. For the wavelength determination a goniometer equipped with a laser rotary encoder and a sine-bar angle optical interferometer was developed; a temperature-monitoring system and X-ray optics related to the experiment were also developed. The mean wavelength was 0.08602557 nm with an uncertainty of 0.6 p.p.m., derived from 16 measurements of three pieces of FZ Si(840) crystals.

Journal Article↗
PubMed2000

Development of bacterial expression system with high yield of CYP3A7, a human fetus-specific form of cytochrome P450.

In an E. coli expression system for human cytochrome P450 3A7 (CYP3A7), holo-CYP3A7 was not expressed as judged by CO-difference spectra, although apo-CYP3A7 was clearly detected by Western blot analysis. Unlike CYP3A7, CYP3A4 was expressed efficiently as a hemoprotein in E. coli transformed with a CYP3A4 expression plasmid. To achieve the high yield of the holo-CYP3A7 in E. coli, we examined a causal residue(s) preventing the expression of the holo-CYP3A7 using the chimeric gene of CYP3A4 with CYP3A7. It was found that the region between residues 405 and 503 of CYP3A7 was responsible for the prevention of the holo-CYP3A7 expression in E. coli. Among amino acids examined, substitution of Thr at position 485 in CYP3A7 with Pro, which is at the corresponding position of CYP3A4, resulted in an increase in the amount of holo-CYP3A7. The Thr residue was adjacent to the heme-binding region of CYP3A7. Thus, it appeared that the incorporation of heme into CYP3A7 was possibly affected by this particular amino acid residue. Moreover, holo-CYP3A7 was expressed efficiently when CYP3A7 was co-expressed with molecular chaperone GroEL, known to assist the correct folding of unfolded proteins. Dehydroepiandrosterone 16alpha-hydroxylation was catalyzed by CYP3A7 expressed in the presence of GroEL.

Amino Acid Sequence↗
PubMed2000

Utility of blasts with a clear halo around the nucleolus as a predictive indicator for disease progression in patients with myelodysplastic syndromes and aplastic anemia.

This study was designed to evaluate the utility of blasts with a clear halo around their nucleoli (BCHN) as a predictive indicator of disease progression in myelodysplastic syndromes (MDSs) and aplastic anemia (AA). Bone marrow aspirates from 75 patients with MDSs and 18 with AA were fixed in 95% ethanol solution or 10% neutral formalin and stained with the Papanicolaou method. BCHNs were detected in 57 of 75 patients with MDSs and in 10 of 18 AA patients. Disease progression was restrictedly observed in 17 patients with MDSs who had BCHNs at onset and in 1 patient with AA. The proportion of BCHNs increased with disease progression in these 16 of 17 patients with MDSs. The presence of BCHNs at onset and the increase in proportion of BCHNs during the clinical course of MDSs were significant indications for predicting disease progression.

Anemia, Aplastic↗
PubMed2000

A mouse model of vascular injury that induces rapid onset of medial cell apoptosis followed by reproducible neointimal hyperplasia.

Genetically modified mice serve as a powerful tool to determine the role of specific molecules in a wide variety of biological phenomena including vascular remodeling. Several models of arterial injury have been proposed to analyze transgenic/knock-out mice, but many questions have been raised about their reproducibility and physiological significance. Here, we report a new mouse model of vascular injury that resembles balloon-angioplasty. A straight spring wire was inserted into the femoral artery via arterioctomy in a small muscular branch. The wire was left in place for one minute to denude and dilate the artery. After the wire was removed, the muscular branch was tied off and the blood flow of the femoral artery was restored. The lumen was enlarged with rapid onset of medial cell apoptosis. While the circumference of the external elastic lamina remained enlarged, the lumen was gradually narrowed by neointimal hyperplasia composed of smooth muscle cells. At 4 weeks, a concentric and homogeneous neointimal lesion was formed reproducibly in the region where the wire had been inserted. Similar exuberant hyperplasia could be induced in all strains examined (C57BL/6J, C3H/HeJ, BALB/c, and 129/SVj). This model may be widely used to study the molecular mechanism of post-angioplasty restenosis at the genetic level.

Angioplasty, Balloon↗
PubMed2000

Protective effect of riluzole on MPTP-induced depletion of dopamine and its metabolite content in mice.

The neuroprotective effects of riluzole (2-amino-6-trifluoromethoxy benzothiazole), a Na+ channel blocker with antiglutamatergic activity, MK-801, a blocker of N-methyl-D-aspartate (NMDA) receptors and monoamine oxidase (MAO) inhibitor pargyline were compared in the model of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced depletion of dopamine and its metabolite 3,4-dihydroxyphenylacetic acid (DOPAC) levels in mice. The mice received four intraperitoneal injections of MPTP (10 mg/kg) at 1-hr intervals and then the brains were analyzed at 1, 3 and 7 days after the treatments. Dopamine and DOPAC levels were significantly decreased in the striatum from 1 day after MPTP treatments. A severe depletion in dopamine and DOPAC levels was found in the striatum 3 and 7 days after MPTP treatments. Riluzole dose-dependently antagonized the MPTP-induced decrease in dopamine and DOPAC levels in the striatum. Pargyline also protected against MPTP-induced decrease in dopamine levels in the striatum. However, this drug showed no significant change in the striatal DOPAC levels. On the other hand, MK-801 failed to protect against MPTP-induced decrease in dopamine levels in the striatum. However, MK-801 reversed the MPTP-induced decrease in DOPAC levels. These results suggest that riluzole can protect against MPTP-induced striatal dopamine and DOPAC depletion in mice. This protective effect may be caused by inactivation of voltage-dependent Na+ channels by riluzole. Furthermore, the present study suggests that the activation of NMDA receptors does not mainly contribute to MPTP-induced neurodegeneration, whereas MAO, especially MAO type B(MAO-B) plays a crucial role in MPTP-induced degeneration of the nigrostriatal dopaminergic neuronal pathway.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed2000

The usefulness of 99mTc-HMPAO-labeled leukocyte scintigraphy in the diagnosis of skeletal metastases of cancers.

The usefulness of bone marrow scintigraphy with 99mTc-HMPAO-labeled leukocytes (leukocyte bone marrow scintigraphy) in the diagnosis of skeletal metastases of cancers was investigated in 70 lesions in 27 patients with various types of cancer. The final diagnosis of skeletal metastases was based on one or more criteria consisting of histological confirmation, typical findings of metastases by bone radiograph, CT and MRI, or progressive swellings of the lesions with severe pain due to nerve compression. Of the 70 lesions, 55 were finally diagnosed as metastases, and 15 as benign lesions. Leukocyte bone marrow scintigraphy showed photopenic defects in 52 of the 55 metastatic lesions (sensitivity 95%), and the remaining 3 negative lesions were found positive for metastases by MRI. In contrast, MRI could evaluate only 39 of the 55 lesions because 16 lesions in the ribs, scapula and sternum were not visualized. Of these 39 lesions, MRI showed positive findings for metastases in 33 (sensitivity 85%), and negative findings in 6 with photopenic defects found by leukocyte bone marrow scintigraphy. Of the 15 benign lesions, 3 were false positive for metastases on leukocyte bone marrow scintigraphy (specificity 80%). We conclude that 99mTc-HMPAO-labeled leukocyte bone marrow scintigraphy may be useful in the diagnosis of skeletal metastases of cancers, particularly when MRI fails to evaluate the lesions.

Adult↗
PubMed2000

Autologous tissue-fragmented extracardiac conduit with rapid, stable endothelialization due to angiogenesis.

OBJECTIVES: Autologous angiogenic cytokines are known to activated by mincing stimulation, and well regulated in vivo. We applied this tissue fragmentation technique to a low-pressure pulmonary extracardiac conduit to obtain rapid endothelialization and stable neointima formation due to angiogenesis. METHODS: Subcutaneous adipose tissue was obtained, minced, suspended, and sieved through highly porous fabric vascular prosthesis by pressurized injection. The adipose tissue fragmented graft with an autologous fresh pericardial monocusp valve was implanted between the right ventricle and the pulmonary artery in 13 dogs. The same grafts without fragments were implanted in 8 dogs as controls. No anticoagulation therapy was given. RESULTS: Grafts were removed 6 to 1,128 days after implantation. In the developed grafts, angiogenesis occurred throughout the interstices of the graft wall from the adventitial side, and host cells proliferated and migrated. Endothelialization was completed throughout developed grafts at 2 weeks. The intima was still thin up to 1,128 days and free of degenerative changes. In control grafts, however, capillary infiltration was limited to perigraft tissue at 2 weeks and endothelialization was not completed by 3 months. Under the endothelial cell layer, laminal elastic fibers were formed through the developed graft wall by 4 months and still maintained at 1,128 days. CONCLUSIONS: The results demonstrated that adipose tissue fragmented extracardiac conduits induce rapid endothelialization and maintained thin intima with laminal elastic fibers. Long-term durability is expected based on results from using this technique in a low-pressure pulmonary system in dogs.

Adipose Tissue↗
PubMed2000

Definite improvement in left ventricular function at six years after the Takeuchi procedure.

We report a case of a six-year-old girl who underwent the Takeuchi procedure for anomalous origin of the left coronary artery from the pulmonary artery at the age of 4 months. The left ventricular function was severely deteriorated before the initial operation and at 6 years after the procedure showed a remarkable improvement. Mitral regurgitation disappeared during the 6 years. The intrapulmonary tunnel was sufficiently patent to provide adequate blood flow for the anomalous coronary artery. This patient showed supravalvular stenosis due to shrinkage and thickening in the equine pericardium used for reconstruction of the pulmonary artery, and this stenosis was successfully released by autologous pericardial patch angioplasty.

Cardiac Surgical Procedures↗
PubMed2000

Initial steps in lymph node metastasis formation in an experimental system: possible involvement of recognition by macrophage C-type lectins.

We used histological observations and experiments with fluorescent cell tracers to investigate the roles of tissue macrophages in recognition through a galactose/N-acetylgalactosamine-specific C-type lectin (mMGL) in lymph node metastasis formation by mouse ovarian tumor OV2944-HM-1 (HM-1) cells. Lymph node metastasis from subcutaneous sites was shown to be initiated by the entry of tumor cells into the subcapsular sinus of lymph nodes where mMGL-positive cells were mainly located. To investigate whether mMGL-positive cells contributed to host resistance against lymph node metastasis, we repeatedly treated mice bearing transplanted tumors with an mMGL-blocking monoclonal antibody that was known to inhibit mMGL binding to its ligands. The number of HM-1 cells recovered from lymph nodes 2 weeks after subcutaneous injections was significantly greater when the mice were treated with the blocking anti-mMGL antibody. These results suggested that mMGL-positive macrophages contributed to the host's defense against lymph node metastasis.

Animals↗
PubMed2000

Colonoscopic diagnosis and management of nonpolypoid early colorectal cancer.

Nonpolypoid colorectal neoplasms are grossly classified into three groups: slightly elevated (small flat adenomas), laterally spreading, and depressed. Flat adenomas are not invasive until they are rather large, whereas depressed lesions can invade the submucosa even when they are extremely small. Nonpolypoid lesions are difficult to detect and are often overlooked. Keys to detect them are their slight color change, interruption of the capillary network pattern, slight deformation of the colonic wall, spontaneously bleeding spots, shape change of the lesion with insufflation and deflation of air, and interruption of the innominate grooves. Spraying of indigo carmine dye helps to clarify the lesions. A pit pattern analysis with a zoom colonoscope is useful for the diagnosis and staging of early colorectal cancer. Small flat adenomas are thought to be precursors of protruded polyps and lateral spreading tumors, whereas depressed lesions are thought to grow endophytically and become advanced cancers. Small depressed lesions are treated with an endoscopic mucosal resection (EMR) technique; but when they massively invade the submucosa, surgical resection is indicated. Laterally spreading tumors are not as invasive despite their large size and therefore are good indications for the EMR or piecemeal EMR method. Small flat adenomas need not be treated urgently, as almost none is invasive. Accurate diagnosis with dye-spraying and zoom colonoscopy is vital for deciding the treatment strategy.

Adenoma↗
PubMed2000

The evaluation of meconium disease by distribution of cathepsin D in intestinal ganglion cells.

Meconium disease (MD) results in intestinal obstruction in the neonate where tenacious meconium is found in the distal ileum and proximal colon. The obstructive symptoms improve at several days of age after some of the meconium is passed. We observed premature infants with MD who underwent ileostomy for intestinal obstruction due to tenacious meconium. Afterward, meconium was passed well and the clinical symptoms improved. After closing the ileostomy, growth and defecation became normal. The MD in our cases was documented by histologic changes in the maturation of ganglion cells observed at the time of ileostomy creation and closure. For an objective evaluation of the maturation of intestinal ganglion cells (IGC), we attempted to distinguish immature from mature cells by the expression of cathepsin D. We examined the distribution of cathepsin D in IGC in patients with MD to test the hypothesis that ganglion-cell immaturity might be related to MD. In ganglion cells at the time of ileostomy, cathepsin D was detected in the perinuclear cytoplasm (immature staining pattern), while at the time of ileostomy closure it was detected in intense granules throughout the cytoplasm (mature staining pattern). We propose that it would be possible to evaluate the maturation of IGC by the intracellular distribution of cathepsin D in MD and suggest that immaturity of IGC might be the cause of MD.

Cathepsin D↗