Biomedical subjects

E Nakamura

Publications and source records attributed to E Nakamura.

At least 37 records · Page 2Linked to original sources

PubMed2000

Wherefore Art Thou Copper? Structures and Reaction Mechanisms of Organocuprate Clusters in Organic Chemistry.

Organocopper reagents provide the most general synthetic tools in organic chemistry for nucleophilic delivery of hard carbanions to electrophilic carbon centers. A number of structural and mechanistic studies have been reported and have led to a wide variety of mechanistic proposals, some of which might even be contradictory to others. With the recent advent of physical and theoretical methodologies, the accumulated knowledge on organocopper chemistry is being put together into a few major mechanistic principles. This review will summarize first the general structural features of organocopper compounds and the previous mechanistic arguments, and then describe the most recent mechanistic pictures obtained through high-level quantum mechanical calculations for three typical organocuprate reactions, carbocupration, conjugate addition, and S(N)2 alkylation. The unified view on the nucleophilic reactivities of metal organocuprate clusters thus obtained has indicated that organocuprate chemistry represents an intricate example of molecular recognition and supramolecular chemistry, which chemists have long exploited without knowing it. Reasoning about the uniqueness of the copper atom among neighboring metal elements in the periodic table will be presented.

Journal Article↗

PubMed2000

Asymmetric construction of quaternary carbon centers by regio- and enantiocontrolled allylzincation

An allylic zinc reagent bearing a chiral bisoxazoline ligand adds to a substituted cyclopropenone acetal to produce an optically active cyclopropanone acetal possessing a quaternary chiral center in high yield with 97.8-99.8% ee. The steric effects of the bulky bisoxazoline ligand overwhelm the regioselectivity inherent to the electronic property of the olefinic acceptor. High pressure exerts favorable effects on the reaction rate without affecting the high enantio- or regioselectivity.

Journal Article↗

PubMed2000

Stepwise Synthesis of Fullerene Cyclopentadienide R(5)C(60)(-) and Indenide R(3)C(60)(-). An Approach to Fully Unsymmetrically Substituted Derivatives.

Fullerene cyclopentadienide (PhCH(2))(2)Ph(3)C(60)(-) and indenide (PhCH(2))(2)PhC(60)(-), each bearing two different organic groups, were efficiently synthesized through regioselective reactions of 1,4-(PhCH(2))(2)C(60) with an organocopper reagent (PhMgBr/CuBr.SMe(2)) or a Grignard reagent (PhMgBr) followed by deprotonation with KO(t)()Bu.

Journal Article↗

PubMed2000

Characterization and functional role of leptin receptor in bovine adrenal medullary cells.

We report here the characterization and functional roles of the leptin receptor (ObR) in bovine adrenal medullary cells. The plasma membranes isolated from bovine adrenal medulla showed a single class of specific binding sites of (125)I-leptin with an apparent K(d) of 6.6 nM and B(max) of 62 fmol/mg protein. ObRa but not ObRb mRNA was detected in bovine adrenal medulla by reverse transcriptase-polymerase chain reaction. Incubation of cultured adrenal medullary cells with leptin (3-30 nM) for 20 min resulted in a significant increase in [(14)C]catecholamine synthesis from [(14)C]tyrosine without any change in catecholamine secretion. These findings suggest that leptin stimulates catecholamine synthesis through its receptors in bovine adrenal medullary cells.

Adrenal Medulla↗

PubMed2000

Syndecan-4 deficiency impairs focal adhesion formation only under restricted conditions.

Two domains of fibronectin deliver two different but cooperative signals required for focal adhesion formation. The signal from the cell-binding domain is mediated by integrins, whereas the signal from the heparin-binding domain is recognized by heparan sulfate proteoglycans, of which syndecan-4 has been hypothesized to be involved in focal adhesion formation. We generated mice deficient in syndecan-4 to study its role directly. Even in fibroblasts from syndecan-4-deficient mice, focal adhesions were formed, and actin fibers terminated normally at focal adhesions when they were cultured on coverslips coated with fibronectin or with a mixture of its cell-binding and heparin-binding fragments. However, when the cells were cultured on the cell-binding fragment and the heparin-binding fragment was added to the medium, focal adhesion formation was impaired in the syndecan-4 null fibroblasts as compared with that in wild-type cells. Therefore, syndecan-4 is essential for promoting focal adhesion formation only when the signal of the heparin-binding domain of fibronectin is delivered as a soluble form, most probably from the apical surface. When the signal is delivered as a substratum-bound form, other molecule(s) also participate(s) in the signal reception.

Actins↗

PubMed2000

Syndecan-4 deficiency impairs the fetal vessels in the placental labyrinth.

Syndecan-4 is a transmembrane protein bearing heparan sulfate chains, involved in anticoagulation and focal adhesion formation. Here, we revealed that syndecan-4 was expressed in the fetal vessels in the placental labyrinth by in situ hybridization and immunohistochemical staining. At 17.5 gestational days, the area of degenerated fetal vessels in the placental labyrinth was more diffuse and larger in Synd4(-/-) embryos than wild-type controls. Calcium and fibrin(ogen) depositions in the degenerated vessels were also more extensive and more severe in the placentas of Synd4(-/-) embryos. These findings suggest that syndecan-4 deficiency impairs the fetal vessels in the placenta, probably due to a deficit in the anticoagulation mechanism. This article is the first report demonstrating that among a large number of core proteins of heparan sulfate proteoglycans, a defect of a single core protein caused impaired anticoagulation in a specific site.

Animals↗

PubMed2000

Arterial pulse wave velocity and risk factors for peripheral vascular disease.

Non-invasive measurement of arterial pulse wave velocity (PWV) is used to diagnose peripheral vascular disease. We examined the relationship between PWV and risk factors related to peripheral vascular disease [body mass index (BMI), systolic blood pressure (SBP), diastolic blood pressure (DBP), serum total cholesterol (TC), high-density lipoprotein-cholesterol (HDL-C), atherogenic index (AI) and blood glucose (GLU)] in 45 healthy male volunteers, aged 25-85 years. The correlation coefficient of PWV with age was r = 0.46, and the correlation coefficients of PWV with DBP, AI and GLU were r = 0.71, 0.56, and 0.22, respectively (P < 0.05). Multiple linear regression analysis revealed that 67% of the variance in PWV could be accounted for by these three variables. The relative contributions of DBP, AI and GLU to PWV were 66%, 26% and 8%, respectively. To test the applicability of PWV for clinical use, a multiple regression equation of PWV derived from these three variables was then applied to male patients with hypertension (n = 53), hyperlipidaemia (n = 35) or hyperglycaemia (n = 39). The results suggest that the multiple regression equation of PWV is an indicator that discriminates between these patient categories and healthy men.

Adult↗

PubMed2000

Nasal NK/T cell lymphoma presenting as transverse myelopathy.

A case of nasal NK/T cell lymphoma with central nervous system (CNS) involvement is reported. A 56-year-old man presented with eyelid edema and transverse myelopathy. Cerebrospinal fluid examination revealed atypical lymphoid cells with azurophilic granules, which were positive for CD2, CD8, and CD56, and negative for CD3 and CD5 by flow cytometry. Because a tumor mass was found involving the ethmoid and maxillary sinuses, CNS involvement was considered to have resulted from local invasion by the nasal lymphoma. In spite of intensive chemotherapy including intrathecal infusion, the patient died 6 months after the initial diagnosis. Autopsy revealed that lymphoma cells were positive for cytotoxic molecules, granzyme B and TIA-1, and EB virus-encoded RNA-1 (EBER-1), and they showed no rearrangement of TCR-beta, -gamma, or -delta genes, suggesting an NK-cell origin of the lymphoma cells. They showed an angiocentric and angiodestructive pattern in the subarachnoid space, focally extending to the cerebral cortex and cranial and spinal nerve roots. Marked demyelination was found in the lateral and posterior funiculi of the spinal cord. Thus, the pathogenesis of this spinal demyelination might be attributed to ischemia secondary to angiocentric and angiodestructive infiltration by lymphoma cells.

Diagnosis, Differential↗

PubMed2000

Nafamostat mesilate treatment during open heart operation in immune thrombocytopenic purpura.

A 58-year old woman with idiopathic thrombocytopenic purpura underwent mitral and aortic valve replacements and tricuspid annuloplasty. Preoperative therapeutic interventions including prednisone and immunoglobulin were successful in elevating the platelet count to 93,000/ mm2. Furthermore, we used nafamostat mesilate for coagulopathy prophylaxis during cardiopulmonary bypass. Postoperative bleeding was average and clinical course was uneventful. The perioperative management for patients with idiopathic thrombocytopenic purpura requiring cardiac operation is reviewed.

Anticoagulants↗

PubMed2000

ATP activates DNA synthesis by acting on P2X receptors in human osteoblast-like MG-63 cells.

In human osteoblast-like MG-63 cells, extracellular ATP increased [(3)H]thymidine incorporation and cell proliferation and synergistically enhanced platelet-derived growth factor- or insulin-like growth factor I-induced [(3)H]thymidine incorporation. ATP-induced [(3)H]thymidine incorporation was mimicked by the nonhydrolyzable ATP analogs adenosine 5'-O-(3-thiotriphosphate) and adenosine 5'-adenylylimidodiphosphate and was inhibited by the P2 purinoceptor antagonist suramin, suggesting involvement of P2 purinoceptors. The P2Y receptor agonist UTP and UDP and a P2Y receptor antagonist reactive blue 2 did not affect [(3)H]thymidine incorporation, whereas the P2X receptor antagonist pyridoxal phosphate-6-azophenyl-2',4-disulfonic acid inhibited ATP-induced [(3)H]thymidine incorporation, suggesting that ATP-induced DNA synthesis was mediated by P2X receptors. RT-PCR analysis revealed that MG-63 cells expressed P2X(4), P2X(5), P2X(6), and P2X(7), but not P2X(1), P2X(2), and P2X(3), receptors. In fura 2-loaded cells, not only ATP, but also UTP, increased intracellular Ca(2+) concentration, and inhibitors for several Ca(2+)-activated protein kinases had no effect on ATP-induced DNA synthesis, suggesting that an increase in intracellular Ca(2+) concentration is not indispensable for ATP-induced DNA synthesis. ATP increased mitogen-activated protein kinase activity in a Ca(2+)-independent manner and synergistically enhanced platelet-derived growth factor- or insulin-like growth factor I-induced kinase activity. Furthermore, the mitogen-activated protein kinase kinase inhibitor PD-98059 totally abolished ATP-induced DNA synthesis. We conclude that ATP increases DNA synthesis and enhances the proliferative effects of growth factors through P2X receptors by activating a mitogen-activated protein kinase pathway.

Adenosine Triphosphate↗

PubMed2000

Neointima formation in a restenosis model is suppressed in midkine-deficient mice.

Neointima formation is a common feature of atherosclerosis and restenosis after balloon angioplasty. To find a new target to suppress neointima formation, we investigated the possible role of midkine (MK), a heparin-binding growth factor with neurotrophic and chemotactic activities, in neointima formation. MK expression increased during neointima formation caused by intraluminal balloon injury of the rat carotid artery. Neointima formation in a restenosis model was strongly suppressed in MK-deficient mice. Continuous administration of MK protein to MK-deficient mice restored neointima formation. Leukocyte recruitment to the vascular walls after injury was markedly decreased in MK-deficient mice. Soluble MK as well as that bound to the substratum induced migration of macrophages in vitro. These results indicate that MK plays a critical role in neointima formation at least in part owing to its ability to mediate leukocyte recruitment.

Angioplasty, Balloon↗

PubMed2000

Immunomodulatory constituents from an ascomycete, Emericella aurantio-brunnea.

Fractionation monitored by the immunomodulatory activity of the AcOEt extract of an Ascomycete, Emericella aurantio-brunnea, afforded two known fungal sesterterpenes, variecolin (1) and variecolactone (2), two new variecolin congeners named variecoacetals A (3) and B (4), and a new sesquiterpenetriol diester named emeremophiline (5), as the immunosuppressive constituents of this fungus. The absolute configuration of 1, which was previously not determined, was determined to be (2S,3S,6R,10S,11R,14S,15R,16S) from the NMR spectral data of the (6R,7R)-dimethyl-1,3,5-trioxacycloheptyl derivative of 1 (7). The absolute configurations of the other variecolin congeners, 2-4, and variecolol (6) are also proposed from biosynthetic considerations.

Adjuvants, Immunologic↗

PubMed2000

[Epididymal sperm aspiration for obstructive azoospermia].

Epididymal sperm aspiration technique combined with assisted reproductive technology (ART) including intracytoplasmic sperm injection (ICSI) has provided new frontiers for the treatment of unreconstructable obstructive azoospermia, including congenital bilateral absence of the vas deferens and failed surgical intervention. Epididymal sperm is obtained by several procedures, including microsurgical epididymal sperm aspiration (MESA), mini-MESA (Modified MESA), macroscopic epididymal sperm aspiration (MaESA) and percutaneous epididymal sperm aspiration (PESA). Since 1991 in our department, epididymal sperm aspiration combined with ART was performed by MESA (26 cases, 41 times) and PESA (3 cases, 4 times). Motile sperm retrieval using MESA and PESA was obtained in 34 out of 36 times (94.4%) and 2 out of 4 times (50%), respectively. MESA-ICSI resulted in a 47.3% 2PN (metaphase II) fertilization rate per eggs and a 28.8% pregnancy rate per transfer. With advancement of ICSI technique in which frozen sperm can be used, elective sperm retrieval can be planned at our convenience. PESA is a convenient, inexpensive and effective outpatient clinic procedure for retrieving sperm assisted with ICSI. In summary, infertile couples need to be given realistic options regarding treatment outcome. The fertility potential and age of the female partner need to be considered when addressing male treatment options.

Epididymis↗

PubMed1999

Inhibitory effect of macrophage-derived factors on the recovery of wounds induced in rat gastric epithelial monolayers.

The effect of macrophage supernatant on the recovery of wounds induced in rat gastric epithelial RGM1 monolayers was investigated. The repair of wounds induced in the monolayers of RGM1 cells was accelerated time-dependently by 10 ng/mL of transforming growth factor-alpha (TGF-alpha). TGF-alpha also significantly stimulated DNA synthesis in RGM1 cells for 24 hr. Upon treatment of the cells with the macrophage supernatant, spontaneous and TGF-alpha-stimulated restoration was inhibited in a time- and concentration-dependent manner. After 24 hr, TGF-alpha-enhanced restoration was eliminated completely by the supernatant at 10(6) cells/mL. Similarly, the macrophage supernatant suppressed the spontaneous and TGF-alpha-stimulated DNA syntheses in a concentration-dependent manner. The macrophage supernatant at 10(6) cells/mL contained 0.4 ng/mL of interleukin-1beta (IL-1beta). Interleukin-1 receptor antagonist (IL-1RA) reversed the inhibition induced by the macrophage supernatant in a concentration-dependent manner. Nonetheless, pretreatment with IL-1RA had no effects on the spontaneous and TGF-alpha-stimulated DNA syntheses. Reverse transcription-polymerase chain reaction analysis revealed that RGM1 cells express mRNA for IL-1 receptor type 1, but not for type 2. These results indicate that macrophages can inhibit the spontaneous and TGF-alpha-stimulated recovery of wounds induced in gastric epithelial monolayers. The inhibitory effects of the supernatant are suggested to be partially mediated through a IL-1beta/IL-1 receptor type 1 pathway.

Animals↗

PubMed1999

The bHLH gene Hes1 is essential for expansion of early T cell precursors.

Mice mutant for the bHLH gene Hes1, which is known to keep cells in a proliferative state, mostly lack thymus. Transfer of Hes1-null fetal liver cells into RAG2-null host mice normally reconstitutes B cells but fails to generate mature T cells in the thymus. In the reconstituted thymus, T cell differentiation is arrested at the CD4(-)CD8(-) double negative (DN) stage. Both the initial T cell receptor (TCR)-independent and the subsequent TCR-dependent selective expansion during the DN stage are severely affected. Thus, Hes1 is essential for the earliest thymocyte expansion in a cell-autonomous manner.

Animals↗

PubMed1999

The site of the anti-emetic action of tachykinin NK1 receptor antagonists may exist in the medullary area adjacent to the semicompact part of the nucleus ambiguus.

NK1 receptor antagonists have been shown to act centrally and to produce a broad-spectrum anti-emetic action. To determine precisely the site of this action, we microinjected GR205171, an NK1 receptor antagonist, into the left medulla oblongata in decerebrate paralyzed dogs. The right medulla was transected 2.5 mm rostral to the obex to eliminate the emetic function of that half. Fictive retching induced by vagal stimulation was still observed after each of 32 injections (0.5-5 microgram in 1-30 microliter) in the area ventrolateral to the solitary complex in six dogs. Retching was also observed for 30 min or more after all but 2 of 30 injections (0.5-1 microgram in 0.5-1 microliter) in the area dorsal to the retrofacial nucleus in 17 dogs. In contrast, retching disappeared within 5-30 min after each of 20 injections (0.5-1 microgram in 1 microliter) in the area adjacent to the semicompact part of the nucleus ambiguus (scAMB) in 15 dogs. The threshold dose for abolition of the retching response was examined in seven dogs and was about 0.1 ng in 1 microliter. The maximum velocity of salivation occurred before the onset of retching and significantly decreased after its abolition. These results suggest that the site of the anti-emetic action of NK1 receptor antagonists may lie in a limited area adjacent to the scAMB, and that neurons in the site induce prodromal signs and retching in a sequential manner.

Animals↗

PubMed1999

4F2 (CD98) heavy chain is associated covalently with an amino acid transporter and controls intracellular trafficking and membrane topology of 4F2 heterodimer.

4F2, also termed CD98, is an integral membrane protein consisting of a heavy chain linked to a light chain by disulfide bond. We have generated a monoclonal antibody to the mouse 4F2 light chain and cloned the cDNA. It encodes a mouse counterpart of rat L-type amino acid transporter-1, and induces system L amino acid transport in Xenopus oocytes in the presence of 4F2 heavy chain. Transfection studies in mammalian cells have indicated that the 4F2 heavy chain is expressed on the plasma membrane on its own, whereas the 4F2 light chain can be transported to the surface only in the presence of 4F2 heavy chain. 4F2 heavy chain is expressed diffusely on the surface of fibroblastic L cells, whereas it is localized selectively to the cell-cell adhesion sites in L cells expressing cadherins. These results indicate that the 4F2 heavy chain is associated covalently with an amino acid transporter and controls the cell surface expression as well as the membrane topology of the 4F2 heterodimer. Although 4F2 heavy and light chains are expressed coordinately in most tissues, the light chain is barely detected by the antibody in kidney and intestine, despite the presence of heavy chain in a complex form. The results predict the presence of multiple 4F2 light chains.

Amino Acid Transport Systems↗

PubMed1999

The tachykinin NK1 receptor antagonist GR205171 abolishes the retching activity of neurons comprising the central pattern generator for vomiting in dogs.

Tachykinin NK1 receptor antagonists are known to act centrally and to have broad-spectrum antiemetic effects, but their precise site of action has not yet been defined. To identify this site, the effects of the NK1 receptor antagonist GR205171 on the activities of neurons comprising the central pattern generator (CPG) for vomiting were observed in decerebrate paralyzed dogs. A non-respiratory neuron in each of nine dogs was considered to be a CPG neuron based on its response to abdominal vagal stimulation, its location in the CPG area in the reticular formation dorsomedial to the retrofacial nucleus, its firing patterns in prodromal and retching phases and its response to apomorphine. In response to vagal stimulation at 3-10 Hz, the firing of these neurons transiently increased at the onset of stimulation (fast component), gradually increased again (slow component), and finally developed into rhythmic bursts synchronous with retching bursts of the phrenic and abdominal muscle nerves. GR205171 (25-50 microg/kg, i.v.) abolished the slow component and retching bursts in the neurons, and the retching activities of both nerves, but did not change the fast component. The responses of these neurons to repetitive pulse-train vagal stimulation exhibited a vigorous 'wind-up' and finally developed into retching bursts. Both the 'wind-up' phenomenon and retching bursts disappeared after the application of GR205171. These results suggest that the site of the antiemetic action of NK1 receptor antagonists is located in the CPG or in the pathway connecting the solitary nucleus to the CPG.

Animals↗