Biomedical subjects

M Naito

Publications and source records attributed to M Naito.

At least 325 records · Page 18Linked to original sources

PubMed1995

[The role of some cellular components of bacterial parasites in determining the incidence of tuberculosis: studies on mycobacterial antigens, with special reference to mycobacterial immunoreactive ribosomal and secreted proteins].

Tuberculosis remains as major disease, affecting more than 20 million people. The elimination of the disease with vaccination, rapid diagnosis, and and efficient therapy is an important objective of our study. To realize the objective, the characterization of antigens is essential. We have chosen two kinds of antigens for our study, the ribosomal antigens and and an antigenic proteins secreted by mycobacteria. The biochemical and immunological characterization of ribosomal fraction was carried out. Ribosomal proteins were purified and assessed for DTH reaction. The N-terminal amino acids sequences were determined. Total structures of S19, S7 and S12 in 30S and L7/L12 in 50S subunits were elucidated. L7/L12 had 66% homology with analogue from S. griseus which showed GTPase activity in protein synthesis. This protein was secreted in culture medium and induced strong DTH. Secreted antigenic proteins are of great interest for us. Secreted antigens may be recognized rapidly by immune system and therefore may induce rapid and high level immune response. It is also expected that it may contain protective antigens, since live BCG protect disease more efficiently than heat killed BCG. We have determined and published the total structure of four proteins (MPB64, MPB70, MPB57 and alpha antigen). We attempted to utilize this antigen for the diagnosis and the design of vaccine. The structures of alpha antigens from M. avium, M. intracellulare, M. scrofulaceum, M. kansasii and BCG were determined and its potential for application to diagnosis was presented. Using the operon of M. kansasii, alpha antigen and V3 region of HIV-1 were expressed by recombinant BCG which induced CTL in mice.

Animals↗

PubMed1995

A recessive mutant of the U937 cell line acquired resistance to anti-Fas and anti-p55 tumor necrosis factor receptor antibody-induced apoptosis.

Human monocytic leukemia U937 cells readily undergo apoptosis when cells are treated with various stimuli including antitumor agents, tumor necrosis factor (TNF)-alpha and anti-Fas antibody. However, the signal transduction mechanism resulting in apoptosis is unclear. To study the mechanism of apoptosis, we isolated and characterized a mutant, UK110, from U937 cells, which was resistant to TNF-alpha and anti-Fas antibody-induced apoptosis but was less resistant to etoposide-induced apoptosis. TNF-alpha induced signals are mediated by two types of TNF receptors (TNFR), p55- and p75-TNFR, and p55-TNFR is homologous to the Fas antigen. Interestingly, UK110 cells showed resistance to apoptosis by agonistic anti-p55-TNFR antibody, indicating that UK110 cells were resistant to Fas- and p55-TNFR-mediated apoptosis. Because expression of apoptosis-associated molecules, such as c-Myc, Bcl-2, and Bax, was similar between U937 and UK110 cells an undetermined pathway for apoptosis through Fas and p55-TNFR could be mutated in UK110 cells. To clarify the genetic phenotype of UK110 cells, we performed somatic cell hybridization with parental U937 and the UK110 cells. All of the hybrid clones were as sensitive as the parental U937 cells to apoptosis by both anti-Fas and anti-p55-TNFR antibodies, indicating that the apoptosis resistance in UK110 cells resulted from recessive genotype.

Antibodies↗

PubMed1994

The histidine interruption of an alpha-helical coiled coil allosterically mediates a pH-dependent ligand dissociation from macrophage scavenger receptors.

Macrophage scavenger receptors uptake modified low density lipoproteins (LDLs) through receptor-mediated endocytosis. In the alpha-helical coiled coil domain, 2 histidines (His168 and His260) disrupt leucine or isoleucine heptad repeats. Substitution of His168 or/and His260 to leucine had no effect on AcLDL binding activities. However, the His260-replaced receptors had their ligand degradation activities diminished. Cell surface ligand release experiments under acidic pH clarified that His260 mutants lost their ligand dissociation activities at 37 degrees C. Furthermore, immunoelectron microscopic experiments using anti-scavenger receptor antibody showed that the His260 replaced receptors were not able to release gold-labeled AcLDL in endosomes. Here we propose an allosterical ligand dissociation mechanism by His260 in macrophage scavenger receptors.

Allosteric Regulation↗

PubMed1994

Biphasic effect of estrogen on neuronal constitutive nitric oxide synthase via Ca(2+)-calmodulin dependent mechanism.

Estrogen is known to retard the development of atherosclerosis and to work in the brain, but the mechanism of hormonal action is completely unknown. We investigated the effect of estrogen on the activity of neuronal constitutive nitric oxide synthase (NNOS). A low concentration of estrogen (10(-10)(-7) M) enhanced the activity of homogenates of the cytosol fraction of rabbit cerebellums and also that of partially purified NNOS, and high dose (10(-6)(-5) M) attenuated them. The study using estrogen receptor antagonists, tamoxifen, clomiphene, and ICI182780 suggested that estrogen receptor did not relate significantly to those effects of 17 beta-estradiol. 17 alpha-estradiol or progesterone did not change significantly it in low doses, although moderately inhibited it in high doses. Estrogen enhanced the fluorescence of dansyl-calmodulin in low doses and attenuated it in high doses, suggesting that estrogen affects Ca(2+)-calmodulin directly. This study demonstrated that estrogen has a biphasic effect on the activity of NNOS through a Ca(2+)-calmodulin.

Amino Acid Oxidoreductases↗

PubMed1994

Transport of cyclosporin A across the brain capillary endothelial cell monolayer by P-glycoprotein.

P-glycoprotein, a multidrug transporter protein, exists in the brain capillary endothelium. To study the function of P-glycoprotein in brain capillary endothelium as a barrier against cyclosporin A, we examined the interaction of cyclosporin A with P-glycoprotein expressed in cultured brain capillary endothelial cells (MBEC4). P-glycoprotein of MBEC4 specifically bound [125I]iodoaryl azidoprazosin, and the binding was inhibited by cyclosporin A and vincristine. Intracellular accumulation of cyclosporin A in MBEC4 was about one-third the amount accumulated in mouse aortic endothelial cells (MAEC3), a cell line that did not express P-glycoprotein. The reduced accumulation of cyclosporin A in MBEC4 was increased by verapamil, a competitive inhibitor of transport function of P-glycoprotein. Cyclosporin A was preferentially transported from basal to apical side when the cell monolayer of MBEC4 was formed; however this transendothelial transport was not observed across cell monolayer of MAEC3. Verapamil inhibited the transendothelial transport of cyclosporin A across the MBEC4 monolayer. Thus P-glycoprotein in brain capillary endothelium could transport cyclosporin A across the endothelium from the basal to the apical side. These observations suggest that P-glycoprotein is involved in the complex function of the blood-brain barrier as a secretory detoxifying transporter of cyclosporin A.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1994

Nonenzymatic reductive activation of 7-N-((2-([2-(gamma-L-glutamylamino)ethyl]dithio)ethyl))mitomycin C by thiol molecules: a novel mitomycin C derivative effective on mitomycin C-resistant tumor cells.

7-N-((2-([2-(gamma-L-Glutamylamino)ethyl]dithio)ethyl))mitomycin C (KW-2149) is an analogue of mitomycin C (MMC) and has prominent activities against various tumors. We studied the antitumor effects of KW-2149 in MMC-resistant variants of human colon carcinoma HT-29 (HT-29/MMC) and mouse hepatoma Hepa-I (C4, B13NBii1) cells, which are deficient in DT-diaphorase and cytochrome P450 reductase, respectively. These enzymes mediate the reductive activation of MMC in the cells. Although HT-29/MMC and C4, B13NBii1 cells showed significant resistance to MMC, they showed sensitivity tl KW-2149 comparable to their parental tumors, indicating that DT-diaphorase and cytochrome P450 reductase could not be involved in the activation of KW-2149. In studying the activation mechanism of KW-2149, we found that glutathione (GSH) and cysteine significantly enhanced the cytotoxicity of KW-2149 in HT-29 cells. The DNA adduct of KW-2149 was increased when HT-29 cells or the isolated nuclei of the cells were incubated with KW-2149 in the presence of physiological concentrations of GSH and cysteine. KW-2149 alkylated calf thymus DNA in the presence of GSH and cysteine in vitro. These results indicate that activation of KW-2149 by thiol molecules, unlike MMC, could be an important activation mechanism of KW-2149 to form DNA adduct and to exert its cytotoxicity. This is the reason why KW-2149 is effective against MMC-resistant tumors with deficiencies in the MMC activation enzymes.

Buthionine Sulfoximine↗

PubMed1994

Magnetic resonance imaging of the olfactory apparatus.

The magnetic resonance imaging visualization of the olfactory apparatus is reported in this article. We used a superconductor-type magnetic resonance device (Siemens Magnetom H15 (1.5 T) with a surface coil. The subjects were patients with posttraumatic anosmia. The olfactory bulbs were clearly visualized in the frontal plane magnetic resonance images, the olfactory bulbs and the foramina of the cribriform plate were visualized in the sagittal section, and the olfactory bulbs, tracts, and other structures were visualized in the coronal sections. The olfactory nerves could not be seen.

Brain Diseases↗

PubMed1994

Immunophenotypic and ultrastructural heterogeneity of macrophage differentiation in bone marrow and fetal hematopoiesis of mouse in vitro and in vivo.

The present in vitro study revealed marked differences in immunophenotypic expression and ultrastructure among macrophage colony-stimulating factor (M-CSF)-derived, granulocyte-macrophage colony-stimulating factor (GM-CSF)-derived, and multi-CSF-derived macrophages. M-CSF-derived macrophages were larger and had more markedly differentiated intracellular organelles and more cytoplasmic projections than GM-CSF-or multi-CSF-derived macrophages. By the combined method of ultrastructural peroxidase cytochemistry and immunoelectron microscopy, ER-MP12 was demonstrated mainly on blastic cells; ER-MP20 on promonocytes, monocytes, and immature macrophages; and F4/80 or BM8 on immature and mature macrophages and monocytes. Macrophage heterogeneity was demonstrated to occur at the stage of macrophage precursor cells, and macrophage differentiation was different between bone marrow hematopoiesis and early fetal hematopoiesis. In vivo, F4/80- or BM8-positive (+) macrophages and ER-MP12 (+) cells developed in the yolk sac prior to the appearance of ER-MP20 (+) monocytic cell series. These results imply that CSFs are important factors for the generation of phenotypic heterogeneity of macrophage populations not only in bone marrow but also in fetal hematopoiesis, suggesting that there are different pathways of macrophage differentiation.

Animals↗

PubMed1994

Introduction of exogenous DNA into somatic and germ cells of chickens by microinjection into the germinal disc of fertilized ova.

The plasmid DNA, pAcZ, containing Escherichia coli beta-galactosidase (lacZ) gene under the control of chicken beta-actin gene promoter was injected in a linearized form into the germinal disc of fertilized chick ova at the single-cell stage. The manipulated embryos were cultured by the method of Naito et al. (1990) until hatching. The rate of hatching was 11.8% (31/263), and 19 males and 6 females were matured. DNA from blood and semen samples of the 25 matured chickens was analyzed for the presence of the injected DNA by Southern blot hybridization. The injected DNA was detected in the blood DNA of one male and in the sperm DNA of another male up to 13 months after hatching, indicating that the injected DNA was stably maintained in these chickens. Restriction digestion analysis of the injected DNA suggested that it was not rearranged and was organized as head-to-tail multimers. The copy numbers of the DNA were 0.07-0.02 in the blood DNA of one male per diploid genome, and 0.02-0.015 in the sperm DNA of another male, indicating that the exogenous DNA was present in limited populations of blood and sperm cells.

Animals↗

PubMed1994

Liposome-mediated DNA transfer into chicken primordial germ cells in vivo.

In embryogenesis, avian primordial germ cells (PGCs) circulate temporarily in the blood vessels at stages 10-15 (Hamburger and Hamilton, 1951), before reaching the gonads. In an attempt to transfer cloned genes into PGCs, liposome consisting of reporter plasmid DNA and N-[1-(2,3-Dioleoyloxy)propyl]-N,N,N-trimethylammoniummethylsulf ate was injected into the marginal veins of embryos at stages 11-15. As reporter plasmids, pRSVZ and pAcZ harboring the Escherichia coli lacZ gene driven, respectively, by the Rous sarcoma virus (RSV) promoter and the chicken beta-actin gene promoter were used. First, 55 embryos were injected with liposome containing pRSVZ and stained for the bacterial beta-galactosidase activity 24 hr after injection. In all the embryos, cells positive for beta-galactosidase activity were observed among the blood cells, endothelial cells, and endocardium cells of the heart, suggesting that transfection took place within the circulatory system. Then, embryos were injected with liposome containing pRSVZ or pAcZ, and stained 2 or 3 d after injection. PGCs positive for beta-galactosidase activity were observed in the gonads in four out of 44 embryos injected with pRSVZ, and 29 out of 71 embryos injected with pAcZ, indicating that the plasmid DNA was transferred into PGCs developing normally. The average number of positive PGCs per embryo was 0.2 and 2.1, respectively, when pRSVZ and pAcZ were introduced. The difference in the number of positive PGCs detected after introduction of the two plasmids suggests that the actin promoter has a higher level of transcriptional activity in PGCs than does the RSV promoter.

Animals↗

PubMed1994

Production of germline chimeric chickens, with high transmission rate of donor-derived gametes, produced by transfer of primordial germ cells.

Germline chimeric chickens were produced by transfer of primordial germ cells from White Leghorn to Barred Plymouth Rock, and vice versa. Blood was collected from stage 13-15 embryos and primordial germ cells were concentrated by Ficoll density gradient centrifugation. Approximately 200 primordial germ cells were injected into the bloodstream through the dorsal aorta of stage 14-15 recipient embryos from which blood had been drawn via the dorsal aorta prior to the injection. Intact embryos were also prepared as recipients for White Leghorns only. The manipulated embryos were cultured in recipient eggshells until hatching. Germline chimerism of the chickens reaching maturity was examined by mating them with Barred Plymouth Rocks and donor-derived offspring were identified based on their feather color. The efficiency of production of germline chimeras was 95% (19/20). When primordial germ cells were transferred from White Leghorn to Barred Plymouth Rock, the average frequency of donor-derived offspring was 81% for three male chimeras (96% for one female chimera), and it was approximately 3.5 times higher for transfer in the opposite direction (23% for 6 male chimeras). Removing blood from recipient embryos prior to primordial germ cell injection enhanced the frequency of donor-derived offspring by 10% in resulting male chimeras. Male chimeras produced donor-derived offspring more frequently (approximately 3.8 times) than female chimeras. Increases, decreases, or no changes were observed in the frequency of donor-derived offspring from the germline chimeras with increasing age.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1994

Resistance to antitumor agent-induced apoptosis in a mutant of human myeloid leukemia U937 cells.

Human monocytic leukemia U937 cells underwent apoptosis when the cells were treated with a variety of antitumor drugs. We isolated and characterized a mutant, UK711, that was resistant to apoptosis induced by antitumor agents. When U937 cells were treated with etoposide (VP-16), an inhibitor of DNA topoisomerase II, apoptosis occurred in a large number of cells, and flow-cytometric analysis revealed that the majority of cells in S phase underwent apoptosis within 2 h of the end of treatment. Such treatment, however, induced apoptosis in only a few UK711 cells. The levels of protein-DNA covalent links and DNA double-strand breaks caused by VP-16 were similar in both cell lines, indicating that the initial DNA damage caused by VP-16 were comparable, whereas the following cellular responses that resulted in apoptosis differed between these cell lines. UK711 cells also showed resistance to apoptosis induced by such antitumor agents as 1-(beta-D-arabinofuranosyl) cytosine (Ara-C), adriamycin, mitomycin C, camptothecin, and by cytotoxic stimuli such as staurosporine, cycloheximide, and uv irradiation. UK711 cells, however, were sensitive to apoptosis induced by tumor necrosis factor (TNF), as were U937 cells. In accordance with resistance to apoptosis induced by antitumor agents, UK711 cells showed significant actual drug resistance to these antitumor agents. The present results indicate that UK711 cells acquired resistance to apoptosis induced by a variety of cytotoxic stimuli resulting in actual anticancer drug resistance. This cell line may be useful in studying the mechanism of apoptosis induced by cytotoxic agents.

Antineoplastic Agents↗

PubMed1994

Canal-expansive laminoplasty in 83 patients with cervical myelopathy. A comparative study of three different procedures.

We have reviewed 83 patients who had undergone canal-expansive laminoplasty for the treatment of cervical myelopathy between 1982 and 1991. The procedures used for laminoplasty were a Z-plasty in 35 patients, unilateral laminoplasty in 19, and sagittal splitting of the spinous processes in 29. At an average follow-up of more than two years and five months, there were no significant differences in clinical results among the three operations, and excellent or good results were obtained in more than 70% of the patients. However, Z-plasty was the least preferable because this procedure had the longest operating time and the greatest intraoperative blood loss. The sagittal splitting procedure is recommended in routine laminoplasty in order to avoid complications at the site of osteotomy, and to allow simultaneous posterior fusion to be easily performed.

Adult↗

PubMed1994

A solid and cystic tumor of the pancreas in a 10-year-old girl: report of a case and review of the literature.

We report herein the unusual case of a 10-year-old girl in whom a neoplasm developed in the head of the pancreas. Complete extirpation of the tumor was performed, which was histologically classified as a "solid and cystic tumor of the pancreas." Postoperative DNA analysis revealed a diploid pattern. The patient remains well with no sign of tumor recurrence 2 years after her operation. Thus, complete tumor extirpation without pancreatectomy is recommended for pediatric patients when there is no direct invasion to the adjacent organs or distant tumor metastasis.

Carcinoma, Acinar Cell↗

PubMed1994

Chelation of copper reduces inhibition by oxidized lipoproteins of endothelium-dependent relaxation in porcine coronary arteries.

We examined the effect of dialyzing oxidized low-density lipoprotein (oLDL) against Krebs-Ringer solution, in the absence (yielding d-oLDL) or presence (yielding EDTA-oLDL) of ethylenediamine tetraacetic acid (EDTA), to investigate the mechanism that underlies the inhibition of endothelium-dependent relaxation (EDR) by o-LDL. Oxidation of LDL by exposure to Cu2+ resulted in the formation of a thiobarbituric acid-reacting substance (TBARS) and lipid hydroperoxide (LPO). At a concentration of 5 mg/dl, d-oLDL markedly attenuated EDR in the porcine coronary artery. Analysis of d-oLDL by gel filtration revealed that TBARS was ditributed in both the lipoprotein and the aqueous phases, whereas LPO was present only in the lipoprotein particles. Lysophosphatidylcholine (LPC), which has been suggested to be responsible for the impairment of EDR by oLDL, was present not only in the lipoprotein but also in the aqueous phase. However, EDR inhibitory activity was observed only in the oLDL particles, not in the aqueous phase. Almost all Cu2+ associated with the oLDL particles was removed by dialysis of oLDL against Krebs-Ringer solution containing EDTA. EDTA-oLDL or native LDL, at concentrations as high as 75 mg/dl, exerted only a moderate inhibitory action on EDR, Both TBARS and LPO in EDTA-oLDL were distributed only in the lipoprotein particles, not in the aqueous phase. These results demonstrate that the impairment of EDR by oLDL is related both to LPO and to transition metal ions such as Cu2+ associated with the lipoprotein particles, not to the amount of the TBARS or negative charge, and that factors other than LPC may affect EDR.

Animals↗

PubMed1994

Comparative toxicity of oxidatively modified low-density lipoprotein and lysophosphatidylcholine in cultured vascular endothelial cells.

Oxidative modification of low-density lipoprotein (LDL) may play an important role in the initiation and progression of atherosclerosis. We previously showed that the cytotoxicity of oxidized LDL (oxLDL) depended on the level of lipid hydroperoxides. Meanwhile, it has been shown that during LDL oxidation, a significant part of the LDL phosphatidylcholine (PC) is degraded to lysophosphatidylcholine (LPC) by an intrinsic phospholipase A2-like activity, and that LPC is toxic to various cells. In the present study, we compared the toxicity of oxLDL with that of LPC in cultured bovine aortic endothelial cells. Cytotoxicity induced by LPC, assessed by the release of lactate dehydrogenase (LDH), reached a plateau within 1 h. LDH release induced by oxLDL occurred much later, at about 3 h, and increased linearly until nearly all the LDH was released at 10 h. The addition of deferoxamine, a Fe3+ chelator, to the reaction medium prevented the toxic effects of oxLDL, but not of LPC. Native LDL and oxLDL inhibited the toxicity of LPC, while native LDL promoted the toxicity of oxLDL. Albumin inhibited the toxicity of LPC but not of oxLDL. Preincubation of endothelial cells with an antioxidant, probucol, protected against oxLDL toxicity, but not against LPC toxicity. These results suggest that lipid hydroperoxides associated with the oxLDL particle, not LPC, constitute the toxic moiety of oxLDL. These substances may generate lipid peroxyl and alkoxyl radicals in the presence of ionic iron, probably from intracellular iron stores in endothelial cells, and produce cytotoxicity.

Animals↗

PubMed1994

Long-term results after nonshunt operations for esophageal varices in children.

The clinical results of nonshunt operations for esophageal varices in 15 children were evaluated. The varices were caused by congenital extrahepatic portal obstruction (EHPO) in 10, liver cirrhosis or fibrosis (C/F) in 3, and idiopathic portal hypertension (IPH) in 2. The operative procedures were transthoracic esophageal transection with paraesophageal devascularization (TR) for 2 EHPO patients under 5 years of age, TR combined with splenectomy and paragastric devascularization (Sugiura procedure) for 11 (8 EHPO, 3 C/F), and splenectomy with devascularization (SP) or splenectomy for the 2 IPH patients. In the EHPO patient under 5 years of age, TR is associated with a likelihood of gastric or esophageal hemorrhage resulting from hypersplenism, gastric congestion, or persistent distal esophageal varices, which can be treated with partial splenic arterial embolization (PSE), endosclerotherapy, or an additional abdominal procedure. The Sugiura procedure has provided satisfactory long-term results, without rebleeding from esophageal varices, in patients with EHPO and C/F for 1 to 20 years. But EHPO patients who undergo the Sugiura procedure before age 6 can have gastric hemorrhage, because of mucosal congestion, for more than 10 years after the procedure, and selective gastric arterial embolization (GAE) might be necessary. In some EHPO patients, especially young ones who have variceal bleeding, a significant increase in hepatopetal portal flow may not develop, but hepatofugal natural shunts may progress. Therefore we recommend direct operative procedures, ie, TR for patients < or = 6 years of age and a one- or two-stage Sugiura procedure for those over 7 years old.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1994

Leukemic cell membrane from acute myelogenous leukemias with massive mast cell infiltration has a mast cell differentiation activity under culture condition containing interleukin 3.

Five cases of acute myelogenous leukemia with massive mast cell infiltration in bone marrow and leukemic tumors of the soft tissue were examined to elucidate the relationship between leukemic cells and mast cells. Leukemic cells in each case showed no basophil/mast cell features and differentiated to neutrophil-like cells in liquid culture. Isolated mast cells failed to proliferate with or without growth factors used irrespective of culture conditions. Mononuclear cell fraction obtained from all patients gave rise to relatively numerous mast cells in interphase culture using IL-3 but not in other culture systems. The simultaneous addition of leukemic cell membrane and IL-3 or delayed addition of leukemic cell membrane produced more numerous and mature mast cells in the upper layer of interphase culture using IL-3. However, addition of leukemic cell membrane alone failed to increase the number of mast cells. Similar results were obtain using mononuclear cells obtained from volunteers and cord blood cells. These results indicate that a cell to cell contact or interstitial substance together with IL-3 are essential requirements for growth and maturation of mast cell precursors and that the cell membrane itself in some cases of leukemia has the ability to induce maturation of mast cell precursors.

Adolescent↗