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N Satoh

Publications and source records attributed to N Satoh.

At least 127 records · Page 7Linked to original sources
PubMed1998

Isolation and characterization of endostyle-specific genes in the ascidian Ciona intestinalis.

The endostyle is a special organ in the pharynx of Urochordata, Cephalochordata, and Cyclostomata. It may have arisen in the common ancestor of these taxa, along with a shift to internal feeding for extracting suspended food from the water. In addition, the endostyle has a functional homology to the vertebrate thyroid gland. The endostyle is therefore one of the structures key to the understanding of the origin and evolution of chordates. In the present study, we isolated and characterized cDNA clones for four endostyle-specific genes, CiEnds1, CiEnds2, CiEnds3, and CiEnds4, of the ascidian Ciona intestinalis. Although the predicted amino acid sequences of the gene products CiENDS1, CiENDS2, and CiENDS3 showed no similarity to known proteins, their mean hydropathy profiles suggest that they are secretory proteins. In addition, CiENDS3 contained a unique repeat of 10 amino acids [R(QPCI)-(RRPC)I]. CiEnds1 and CiEnds2 were expressed in zone 6, a protein-secreting glandular element of the endostyle, and CiEnds3 was expressed in zone 2, another secretory zone. CiEnds4, a cytoplasmic actin gene, was predominantly expressed in zones 3 and 5, which are supporting elements of the endostyle. The amino acid sequences of CiENDS1 and CiENDS2 resembled each other. In addition, they resembled a zone-6-specific gene product (HrENDS2) of another ascidian, Halocynthia roretzi. The results suggest that these genes are conserved among ascidian species, and therefore they (as well as CiEnds3 for the protein with a unique motif) may be useful probes for further analyses of molecular mechanisms involved in endostyle development.

Amino Acid Sequence↗
PubMed1998

Involvement of apoptosis and cyclin D1 gene repression in growth inhibition of T-47D human breast cancer cells by methylglyoxal bis(cyclopentylamidinohydrazone).

Polyamines are considered to be important intracellular molecules for the proliferation of the cancer cells. In this study, effects of methylglyoxal bis(cyclopentylamidinohydrazone) (MGBCP), a potent inhibitor of the polyamine biosynthetic pathway, on the growth and cell cycle of T-47D human breast cancer cells were investigated. MGBCP dose-dependently inhibited the growth of T-47D cells, in which the contents of spermine, spermidine and putrescine decreased concomitantly. The gene expression of cyclin D1 was also repressed by the MGBCP treatment. The MGBCP-treated cells clearly exhibited morphological changes indicating the blebbing and chromatin condensation which are characteristic of apoptosis. Flow cytometric analysis showed hypo-diploid subpopulations due to apoptotic cells, and characteristic oligonucleosomal-sized DNA fragments were clearly observed for MGBCP-treated cells as the concentration of the drug was increased. These findings suggest that the inhibition of polyamine synthesis results in the repressions of cyclin D1 expression and cell cycle progression, eventually inducing apoptosis in these human breast cancer cells.

Antineoplastic Agents↗
PubMed1998

Analysis of uveitogenic sites in phosducin molecule.

PURPOSE: Phosducin, a retinal photoreceptor protein, induces experimental autoimmune uveitis (EAU). In this study, we attempted to determine the numbers of uveitogenic sites in phosducin using synthetic peptides. METHODS: Antigen peptides were synthesized according to the amino acid sequence of the rat-derived phosducin with a peptide-synthesizer and purified by reversed-phase HPLC. First, 13 peptides covering the entire sequence of phosducin were synthesized, and each was injected into the hind footpad of Lewis rats for immunization, and induction of EAU was examined clinically and histologically. Next, peptides that appeared to contain sequences of a uveitogenic site were newly synthesized and examined clinically and immunologically. RESULTS: Of the 13 peptides used in the first immunization, 7 induced inflammation. Similar to other EAU antigens, clinical changes began with fibrin deposition in the anterior segment and posterior synechia, followed by posterior chamber hypopyon. Histologically, inflammation was observed mainly in the outer segment of photoreceptor cells and outer nuclear layer, and serous retinal detachment was found in cases of severe inflammation. Infiltration of inflammatory cells in the pineal gland was also observed. In experiments designed to further specify the uveitogenic sites, the presence of inflammation-inducing sequences was inferred for amino acid sequences 1-20, 23-37, 79-91, 127-142 and 198-212. The rats immunized with these peptides also exhibited high value on lymphocyte proliferation assay. CONCLUSION: Phosducin has 5 uveitogenic sites. Among others, one of them has potent and others weak uveitogenicity.

Amino Acid Sequence↗
PubMed1998

Characterization of an ascidian maternal T-box gene, As-mT.

The T-box genes encode a novel family of transcriptional factors that seem to play crucial roles in various processes of animal development, in particular, mesoderm formation of chordate embryos. The ascidian egg has been regarded as a typical mosaic egg, in which several types of embryonic cells are specified autonomously dependent on prelocalized maternal factors or determinants. In the present study, we investigated a possible role of a maternal T-box gene (As-mT) of the ascidian Halocynthia roretzi. A cDNA clone we obtained predicted As-mT protein of 891 amino acids with a distinct T-domain, which was divergent from those of other T-box genes. Expression of As-mT was exclusively maternal. Although the transcript became barely detectable by the gastrula stage, no zygotic expression was evident during embryogenesis. The maternal transcript was distributed rather evenly within eggs and early embryos without any special localization. Injection of synthetic As-mT mRNA into fertilized eggs induced retardation of embryogenesis. Although cleavage occurred normally, the initiation of gastrulation was delayed, and delay in the morphogenesis resulted in dumpy larvae. Expression of a muscle-specific actin gene, a notochord-specific Brachyury gene, and an epidermis-specific gene was not detected at the early gastrula stage, all of the three genes being expressed in normal embryos at that stage. However, the expression of these genes as well as a mesenchyme-specific gene and histochemical activity of endoderm-specific alkaline phosphatase were evident by the mid-tailbud stage.

Amino Acid Sequence↗
PubMed1997

Posterior end mark 2 (pem-2), pem-4, pem-5, and pem-6: maternal genes with localized mRNA in the ascidian embryo.

The posterior-vegetal cytoplasm of an ascidian egg contains maternal factors required for pattern formation and cell specification of the embryo. We report here the isolation and characterization of cDNA clones for novel maternal genes, posterior end mark 2 (pem-2), pem-4, pem-5, and pem-6. We obtained these clones from a cDNA library of Ciona savignyi fertilized egg mRNAs subtracted with gastrula mRNAs by examining the localization of the corresponding mRNAs of randomly selected clones by whole-mount in situ hybridization. As in the case of pem, all of these mRNAs were localized in the posterior-vegetal cytoplasm of the egg, and they later marked the posterior end of early embryos. The predicted amino acid sequence suggested that PEM-2 contains a signal for nuclear localization, an src homology 3 (SH3) domain, and a consensus sequence of the CDC24 family guanine nucleotide dissociation stimulators (GDSs). PEM-4 has a signal for nuclear localization and three C2H2-type zinc finger motifs, while PEM-5 and PEM-6 show no similarity to known proteins. These results provide further evidence that the ascidian egg contains maternal messages that are localized in the posterior-vegetal cytoplasm.

Amino Acid Sequence↗
PubMed1997

Neural tube is partially dorsalized by overexpression of HrPax-37: the ascidian homologue of Pax-3 and Pax-7.

The origin and elaboration of the central nervous system played an important role in chordate and vertebrate history. All chordates possess a dorsal tubular central nervous system, but elaboration of dorsoventral and segmental pattern is far more pronounced in cephalochordates and vertebrates than in the more basal urochordates. Analysis of the urochordates, therefore, should allow deduction of the neural organization and neuronal patterning mechanisms that predated overt dorsoventral and segmental complexity. Here we report functional studies of the ascidian Pax gene (HrPax-37). The spatiotemporal expression pattern of HrPax-37 has suggested involvement in two distinct developmental processes: specification of dorsal cell fates of ectoderm during neurulation, and regional differentiation of the neural tube in later stages. Here we show that HrPax-37 is descendent from the precursor of the Pax-3 and Pax-7 genes implicated in specification of dorsal fate in the vertebrate neural tube. We also demonstrate that injection of HrPax-37 RNA into fertilized eggs causes ectopic expression of the dorsal neural marker tyrosinase gene in neurulae, confirming a regulatory role in dorsal patterning of the neural tube comparable to its vertebrate homologues. These results suggest that dorsal specification in the neural tube by Pax-3/7 subfamily genes was established in the ancestors of extant chordates during emergence of the dorsal tubular nervous system.

Amino Acid Sequence↗
PubMed1997

The arcuate nucleus as a primary site of satiety effect of leptin in rats.

The obese (ob) gene encodes a fat cell-derived circulating satiety factor (leptin) that is involved in the regulation of energy homeostasis. In the present study, we examined effects of i.c.v. injection of recombinant human leptin on food intake and body weight gain in rats. We also studied effects of direct microinjections of leptin into the arcuate nucleus (Arc), ventromedial hypothalamus (VMH), and lateral hypothalamus (LH). A single i.c.v. injection of recombinant human leptin (0.25-2.0 micrograms/rat) reduced significantly and dose-dependently food intake and body weight gain in rats. Microinjections (0.125-0.5 microgram/site) into the bilateral Arc, VMH, and LH caused dose-related decreases in food intake and body weight gain as compared with vehicle-treated groups with a rank order of potency; Arc > VMH = LH. The present study provides the first direct evidence that the Arc is a primary site of satiety effect of leptin.

Animals↗
PubMed1997

Ascidian tyrosinase gene: its unique structure and expression in the developing brain.

Tadpole larvae of ascidians have two sensory pigment cells in the brain. One is the otolith cell that functions as a gravity receptor, the other pigment cell is part of a primitive photosensory structure termed the ocellus. These sensory cells, like vertebrate pigment cells, contain membrane-bounded melanin granules and are considered to reflect a crucial position in the evolutionary process of this cell type. To investigate the molecular changes accompanying the evolution of pigment cells, we have isolated from Halocynthia roretzi a gene encoding tyrosinase, a key enzyme in melanin biosynthesis. The cDNA has an open reading frame (ORF) of 596 amino acids, which is 36-39% identical in amino acid sequence to vertebrate tyrosinases. In addition, the sequence analysis of both cDNA and genomic clones reveals an unusual organization of the tyrosinase gene, an extraordinary 3' untranslated region of the transcripts with significant homology to the coding sequence, and a single short intron in the sequence encoding a cytoplasmic domain. Expression of the gene is detected first in two pigment precursor cells positioned in the neural plate of early neurulae, and later in two melanin-containing pigment cells within the brain of late tailbud embryos. Its expression pattern correlates well with the appearance of tyrosinase enzyme activity in the developing brain. These results provide the first description of pigment cell differentiation at the molecular level in the ascidian embryo, and also will contribute to a better understanding of the evolution of chordate pigment cells.

Amino Acid Sequence↗
PubMed1997

Characterization of a potent uveitopathogenic site derived from rat phosducin.

Phosducin is a retinal and pineal phosphoprotein assumed to play an important role in visual phototransduction. Phosducin is also a uveitopathogenic retinal antigen, but its potency has been reported to be mild. During the course of studies aimed at identifying uveitopathogenic sites in phosducin, we found that rat phosducin possessed a potent uveitopathogenic site. In this study, we characterize the potent uveitopathogenic site by using synthetic peptides. Several synthetic peptides from this region plus adjuvants were injected into Lewis rats, and the uveitopathogenic core sequence was defined. We also determined the pivotal amino acid residues by using synthetic peptides with single residue substitution. Immunization with PDC(R)65-96 (amino acid residues 65 through 96 derived from rat phosducin) at doses of 0.83 nmol or more induced severe experimental autoimmune uveitis (EAU) in all rats within 12 days. Experimental autoimmune pinealitis (EAP) was also observed in all rats after immunization with 0.83 nmol or higher doses of the peptide. The lowest dose of the peptide to induce EAU and EAP was 0.24 nmol. The smallest peptide that induced EAU as severe as PDC(R)65-96 was PDC(R)77-87, which consisted of 11 amino acid residues (YELIHQDKEDE). The core sequence within the uveitopathogenic site was a pentapeptide (LIHQD), amino acid residues from 79 to 83. To determine the role of individual residues within PDC(R)77-87, we tested the uveitopathogenicity of analogues of PDC(R)75-85 and PDC(R)77-89, respectively, in which each of the residues from 77 to 87 was replaced by alanine (A). Analogous peptides bearing a single residue substitution at 80 (I-->A) and 82 (Q-->A), respectively, were not uveitopathogenic. Our findings demonstrated the presence of a potent uveitopathogenic site in PDC(R)65-96 whose potency in Lewis rats was comparable to that of S-antigen. The pivotal amino acid residues for uveitopathogenicity were the residues at 80 (I) and 82 (Q). The clinical and histological features of this EAU closely resembled those of the EAU induced by S-antigen and recoverin.

Adoptive Transfer↗
PubMed1997

Evolution of chordate actin genes: evidence from genomic organization and amino acid sequences.

The origin and evolutionary relationship of actin isoforms was investigated in chordates by isolating and characterizing two new ascidian cytoplasmic and muscle actin genes. The exon-intron organization and sequences of these genes were compared with those of other invertebrate and vertebrate actin genes. The gene HrCA1 encodes a cytoplasmic (nonmuscle)-type actin, whereas the MocuMA2 gene encodes an adult muscle-type actin. Our analysis of these genes showed that intron positions are conserved among the deuterostome actin genes. This suggests that actin gene families evolved from a single actin gene in the ancestral deuterostome. Sequence comparisons and molecular phylogenetic analyses also suggested a close relationship between the ascidian and vertebrate actin isoforms. It was also found that there are two distinct lineages of muscle actin isoforms in ascidians: the larval muscle and adult body-wall isoforms. The four muscle isoforms in vertebrates show a closer relationship to each other than to the ascidian muscle isoforms. Similarly, the two cytoplasmic isoforms in vertebrates show a closer relationship to each other than to the ascidian and echinoderm cytoplasmic isoforms. In contrast, the two types of ascidian muscle actin diverge from each other. The close relationship between the ascidian larval muscle actin and the vertebrate muscle isoforms was supported by both neighbor-joining and maximum parsimony analyses. These results suggest that the chordate ancestor had at least two muscle actin isoforms and that the vertebrate actin isoforms evolved after the separation of the vertebrates and urochordates.

Actins↗
PubMed1997

Autonomy of ascidian fork head/HNF-3 gene expression.

We have characterized the expression pattern of a class I fork head/HNF-3 gene (HrHNF3-1) of the ascidian Halocynthia roretzi. Zygotic HrHNF3-1 expression was detectable as early as the 16-cell stage, and the transcript was evident in blastomeres of the endoderm, notochord and mesenchyme lineages of the early embryos. After the late gastrula stage, HrHNF3-1 was also expressed in the presumptive spinal cord cells and some brain cells. The spinal cord of the ascidian tadpole consists of four layers of cells; the dorsal layer, two lateral layers and the ventral layer, the latter of which simply lies on the notochord. Cross-sections of in situ hybridized specimens showed that HrHNF3-1 was expressed in cells of the ventral layer, reminiscent of the floor plate of vertebrate embryos. In addition, we found autonomy in the initiation of early HrHNF3-1 expression, because the gene was expressed in blastomeres continuously dissociated from the first cleavage until the 16-cell stage.

Amino Acid Sequence↗
PubMed1997

The rectus abdominis myocutaneous flap combined with vascularized costal cartilages in reconstructive craniofacial surgery.

The efficacy of osteocutaneous or vascularized bone flaps for reconstruction of massive skeletal and soft-tissue defects has been supported by recent descriptions in the literature. In this article we presented an alternative technique, which is the rectus abdominis myocutaneous flap combined with vascularized eighth and ninth costal cartilages, for reconstruction of midfacial composite defects. The vascular pedicle of the composite flap is the deep inferior epigastric artery and vein. The costal cartilages are supplied by the perichondrial vascular network through the anterior intercostal vessels connecting with the deep epigastric vascular system. Vascularized costal cartilages are considered to reduce the incidence of postoperative complications and resorption of this material. This technique is a useful tool for restoration of craniofacial contour in reconstructive head and neck surgery.

Abdominal Muscles↗
PubMed1997

Pathophysiological significance of the obese gene product, leptin, in ventromedial hypothalamus (VMH)-lesioned rats: evidence for loss of its satiety effect in VMH-lesioned rats.

To explore the pathophysiological significance of the obese (ob) gene product, leptin, in ventromedial hypothalamus (VMH)-lesioned rats, we examined the synthesis and secretion of leptin and its satiety effect in VMH-lesioned rats compared with those in sham-operated rats. Northern blot analysis revealed that ob gene expression is markedly augmented in the mesenteric and sc white adipose tissue, but remained unchanged in the epididymal white adipose tissue during the development of obesity in VMH-lesioned rats. Plasma leptin levels were relatively constant in sham-operated rats, but were elevated during the development of obesity in VMH-lesioned rats. In sham-operated rats, a single i.v. (1.0 mg/rat) or intracerebroventricular (2.0 micrograms/rat) injection of recombinant human leptin reduced food intake and body weight gain in sham-operated rats. By contrast, no significant effect on food intake or body weight gain was observed in VMH-lesioned rats. The present study provides evidence that VMH-lesioned rats overproduce leptin and increase its release but cannot respond to it and suggests that the loss of its satiety effect contributes to the development of obesity and the obesity-related phenotypes in VMH-lesioned rats.

Animals↗
PubMed1997

Functional analysis of an ascidian homologue of vertebrate Bmp-2/Bmp-4 suggests its role in the inhibition of neural fate specification.

The ascidian tadpole larva is thought to be close to a prototype of the ancestral chordate. The vertebrate body plan is established by a series of inductive cellular interactions, whereas ascidians show a highly determinate mode of development. Recent studies however, suggest some roles of cell-cell interaction during ascidian embryogenesis. To elucidate the signaling molecules responsible for the cellular interaction, we isolated HrBMPb, an ascidian homologue of the vertebrate bone morphogenetic protein (BMP) gene, from Halocynthia roretzi. The amino acid sequence of HrBMPb closely resembled those of vertebrate BMP-2 and BMP-4 and of Drosophila Decapentaplegic (DPP). In addition to the sequence similarity, HrBMPb overexpression induced the ventralization of Xenopus embryos, suggesting functional conservation. The zygotic expression of HrBMPb was first detected around gastrulation. HrBMPb expression was maintained in some cells at the lateral edges of the neural plate through gastrulation to neurulation, although that in the presumptive muscle cells was downregulated. HrBMPb was not expressed in the presumptive epidermis during gastrulation. When HrBMPb mRNA was injected into fertilized Halocynthia eggs, cells that normally give rise to the neural tissue differentiated into epidermis, causing a loss of anterior neural tissue in the larva. In addition, HrBMPb might function synergistically with HrBMPa, an ascidian homologue of BMPs-5 to 8. However, HrBMPb overexpression did not affect differentiation of the notochord and muscle cells. These results suggest that HrBMPb functions as a neural inhibitor and as an epidermal inducer but not as a ventralizing agent in ascidian development.

Amino Acid Sequence↗
PubMed1997

Relation of urinary sodium excretion to blood pressure, glucose metabolism, and lipid metabolism in residents of an area of Japan with high sodium intake.

To evaluate the effects of prolonged intake of a high-sodium diet on glucose and lipid metabolism, we examined the relation of daily urinary sodium excretion to blood pressure, glucose metabolism, and lipid metabolism in 140 Japanese adults who lived in a region where the average daily consumption of sodium was high and stable during the past 15 yr; no subject had received any treatment for hypertension or metabolic disorders. Each subject was admitted to our health examination center for 2 d for measurement of blood pressure, sampling of blood, and glucose tolerance testing. A 24-h urine specimen was collected by each subject after discharge. Multiple regression analysis revealed that urinary sodium excretion was significantly independent of the mean blood pressure and was unrelated to the area under the serum glucose curve after glucose administration. The urinary sodium level was also unrelated to low-density lipoprotein cholesterol, and high-density lipoprotein cholesterol. The prevalence of hypertension in the group with a daily sodium excretion below 140 mEq (low sodium group) was 0%, while that in the group with a daily sodium excretion above 280 mEq (high sodium group) was 44%; this difference was significant (p < 0.01). No significant difference was observed in the prevalence of metabolic disorders between the two groups. Our results suggest that sodium intake has little influence on glucose and lipid metabolism but has a significant influence on blood pressure in normotensive and untreated hypertensive subjects who reside in an area with a relatively high sodium intake.

Adult↗
PubMed1997

The recently-described ascidian species Molgula tectiformis is a direct developer.

Molgula tectiformis is a new ascidian species recently described by Nishikawa (1991). In Otsuchi Bay, Iwate, Japan, they are easily obtainable from cages for culturing scallops. We report here that M. tectiformis is another example of a direct developer: their embryonic development is lacking the tadpole larva. The fertilized egg is orange and about 150 microns in diameter. At 18 degrees C, the egg cleaves at about 20 min intervals and gastrulation occurs about 5 hr after fertilization. In contrast to conventionally-developing ascidians, M. tectiformis does not form a tadpole larva. Immediately before hatching, three stolons or ampullae begin to extend from the tailless embryo. After hatching the stolons mediate the attachment of the juvenile body to the substratum. Histochemistry for tissue-specific enzyme activity did not detect muscle-specific acetyl-cholinesterase, endoderm-specific alkaline phosphatase, and pigment cell-specific tyrosinase. In addition, in situ hybridization could not prove the presence of muscle actin gene transcripts in the embryo. These results suggest that these larval tissues do not differentiate in M. tectiformis embryos. Because M. tectiformis is common and gravid year-around in Otsuchi Bay, this direct developer provides the opportunity for further analysis of molecular changes during evolution that cause an alternative mode of development.

Acetylcholinesterase↗
PubMed1997

Expression of actin genes in the arrow worm Paraspadella gotoi (Chaetognatha).

Arrow worms (the phylum Chaetognatha), one of the major marine planktonic animals, exhibit features characteristic to both deuterostomes and protostomes, and their ancestry therefore remains unknown. As the first step to elucidate the molecular bases of arrow worm phylogeny, physiology and embryology, we isolated cDNA clones for three different actin genes (PgAct1, PgAct2 and PgAct3) from the benthic species Paraspadella gotoi, and examined their expression patterns in adults and juveniles. The amino acid sequences of the three actins resembled each other, with identities ranging from 86% to 92%. However, the patterns of the spatial expression of the genes were independent. The PgAct1 gene might encode a cytoplasmic actin and was expressed in oogenic cells, spermatogenic cells, and cells in the ventral ganglion. The PgAct2 and PgAct3 genes encoded actins of divergent types. The former was expressed in well-developed muscle of the head (gnathic) region and trunk muscle cells, whereas the latter was expressed in muscle of the trunk and tail regions and oogenic cells. These results suggest that, similarly to other metazoans, the chaetognath contains multiple forms of actins, which are expressed in various manners in the adult and juvenile arrow worm.

Actins↗