Biomedical subjects

S Noji

Publications and source records attributed to S Noji.

At least 19 recordsLinked to original sources

PubMed1998

lefty-1 is required for left-right determination as a regulator of lefty-2 and nodal.

lefty-1, lefty-2, and nodal are expressed on the left side of developing mouse embryos and are implicated in left-right (L-R) determination. The role of lefty-1 was examined by analyzing mutant mice lacking this gene. The lefty-1-deficient mice showed a variety of L-R positional defects in visceral organs. Unexpectedly, however, the most common feature of lefty-1-/- mice was thoracic left isomerism (rather than right isomerism). The lack of lefty-1 resulted in bilateral expression of nodal, lefty-2, and Pitx2 (a homeobox gene normally expressed on the left side). These observations suggest that the role of lefty-1 is to restrict the expression of lefty-2 and nodal to the left side, and that lefty-2 or nodal encodes a signal for "leftness."

Animals↗

PubMed1998

Pitx2, a bicoid-type homeobox gene, is involved in a lefty-signaling pathway in determination of left-right asymmetry.

Signaling molecules such as Activin, Sonic hedgehog, Nodal, Lefty, and Vg1 have been found to be involved in determination of left-right (L-R) asymmetry in the chick, mouse, or frog. However, a common signaling pathway has not yet been identified in vertebrates. We report that Pitx2, a bicoid-type homeobox gene expressed asymmetrically in the left lateral plate mesoderm, may be involved in determination of L-R asymmetry in both mouse and chick. Since Pitx2 appears to be downstream of lefty-1 in the mouse pathway, we examined whether mouse Lefty proteins could affect the expression of Pitx2 in the chick. Our results indicate that a common pathway from lefty-1 to Pitx2 likely exists for determination of L-R asymmetry in vertebrates.

Animals↗

PubMed1998

Hypoplasia of pancreatic islets in transgenic mice expressing activin receptor mutants.

Activin, a member of the TGF-beta superfamily, regulates the growth and differentiation of a variety of cell types. Based on the expression of activin in pancreatic rudiments of rat embryos and stimulation of insulin secretion from adult rat pancreatic islets by activin, activin is implicated in the development and function of islets. To examine the significance of activin signaling in the fetal and postnatal development of islets, transgenic mice expressing a dominant negative form of activin receptor (dn-ActR) or a constitutively active form of activin receptor (ActR-T206D) in islets were generated together with the transgenic mice expressing intact activin receptor (intact ActR) as a negative control. Transgenic mice with both dn-ActR and ActR-T206D showed lower survival rates, smaller islet area, and lower insulin content in the whole pancreas with impaired glucose tolerance when compared with transgenic mice with intact ActR or littermates, but they showed the same alpha cell/beta cell ratios as their littermates. In addition to islet hypoplasia, the insulin response to glucose was severely impaired in dn-ActR transgenic mice. It is suggested that a precisely regulated intensity of activin signaling is necessary for the normal development of islets at the stage before differentiation into alpha and beta cells, and that activin plays a role in the postnatal functional maturation of islet beta cells.

Activin Receptors↗

PubMed1998

Expression of peroxisome proliferator-activated receptor alpha (PPAR alpha) in primary cultures of human vascular endothelial cells.

The peroxisome proliferator-activated receptor (PPAR) is a member of the steroid nuclear receptor superfamily. Three types of PPARs have been described in humans: PPAR alpha, PPAR beta, and PPAR gamma. Here we investigated the levels of PPAR alpha mRNA in primary cultures of human umbilical venous endothelial cells (HUVEC), human umbilical arterial endothelial cells (HUAEC), human coronary arterial endothelial cells (HCAEC), and human aortic endothelial cells (HAEC), using the reverse transcriptase-polymerase chain reaction (RT-PCR). The HUVEC, HAEC, and HCAEC, but not the HUAEC, showed relatively low expression of PPAR alpha in comparison with liver, which was used as a positive control. Moreover, the partial sequences of the PCR-amplified products from HUVEC, HAEC, and HCAEC were similar to that of the PPAR alpha from human liver. The expression of PPAR alpha in cultured HAEC, which were induced by dexamethasone, was inhibited by insulin. In addition, PPAR alpha expression was also increased by benzafibrate or eicosapentaenoic acid with the physiological concentration. These results suggest that the PPAR alpha in endothelial cells may have the same physiological role as the expression of PPAR alpha in the liver.

Aorta↗

PubMed1998

Bone morphogenetic protein signaling is required for maintenance of differentiated phenotype, control of proliferation, and hypertrophy in chondrocytes.

To examine the role of bone morphogenetic protein (BMP) signaling in chondrocytes during endochondral ossification, the dominant negative (DN) forms of BMP receptors were introduced into immature and mature chondrocytes isolated from lower and upper portions of chick embryo sternum, respectively. We found that control sternal chondrocyte populations expressed type IA, IB, and II BMP receptors as well as BMP-4 and -7. Expression of a DN-type II BMP receptor (termed DN-BMPR-II) in immature lower sternal (LS) chondrocytes led to a loss of differentiated functions; compared with control cells, the DN-BMPR- II-expressing LS chondrocytes proliferated more rapidly, acquired a fibroblastic morphology, showed little expression of type II collagen and aggrecan genes, and upregulated type I collagen gene expression. Expression of DN-BMPR-II in mature hypertrophic upper sternal (US) chondrocytes caused similar effects. In addition, the DN-BMPR-II-expressing US cells exhibited little alkaline phosphatase activity and type X collagen gene expression, while the control US cells produced both alkaline phosphatase and type X collagen. Both DN-BMPR-II-expressing US and LS chondrocytes failed to respond to treatment with BMP-2 . When we examined the effects of DN forms of types IA and IB BMP receptors, we found that DN-BMPR-IA had little effect, while DN-BMPR-IB had similar but weaker effects compared with those of DN-BMPR-II. We conclude that BMP signaling, particularly that mediated by the type II BMP receptor, is required for maintenance of the differentiated phenotype, control of cell proliferation, and expression of hypertrophic phenotype.

Animals↗

PubMed1998

Bezafibrate has an antioxidant effect: peroxisome proliferator-activated receptor alpha is associated with Cu2+, Zn2+-superoxide dismutase in the liver.

Administration of bezafibrate in rats significantly reduced the levels of plasma thiobarbituric acid-reactive substances (TBARS) in comparison with those obtained in rats fed a soy or lard chow. Moreover, an elevation of in vitro conjugated diene production and linoleic acid levels in the high-density lipoproteins and low-density lipoproteins induced by a soy or lard chow, was reduced by bezafibrate administration. In addition, the liver Cu2+, Zn2+-superoxide dismutase (SOD) gene expression showed a significant positive correlation with the liver peroxisome proliferator-activated receptor alpha (PPARalpha) mRNA level (R=0.769, p<0.0001). This unique characteristic of bezafibrate, which possesses both a hypolipidemic effect and antioxidant activity, may be beneficial in preventing vascular complications in hyperlipidemia.

Acyl-CoA Oxidase↗

PubMed1998

Sonic hedgehog expression in developing chicken digestive organs is regulated by epithelial-mesenchymal interactions.

Sonic hedgehog (Shh) gene encodes a secreted protein that acts as an important mediator of cell-cell interactions. A detailed analysis of Shh expression in the digestive organs of the chicken embryo was carried out. Shh expression in the endoderm begins at stage 7, when the formation of the foregut commences, and is found as narrow bands in the midgut. Shh expression around the anterior intestinal portal at stage 15 is restricted to the columnar endoderm lined by the thick splanchnic mesoderm, suggesting that the existence of thick splanchnic mesoderm might be necessary for Shh expression in the columnar endoderm. After the gut is closed, Shh expression is found universally in digestive epithelia, including the cecal epithelium. However, its expression ceases in the epithelium of the proventricular glands, the ductus choledochus and ductus pancreaticus that protrude from the main digestive duct. When the gizzard epithelium differentiated into glands under the influence of the proventricular mesenchyme, the glandular epithelium lost the ability to express Shh. These findings suggest that Shh expression in the epithelium may be regulated by surrounding mesenchyme throughout organogenesis of the digestive organs and is closely involved in epithelial-mesenchymal interactions in developing digestive organs.

Animals↗

PubMed1998

Correlation of wing-leg identity in ectopic FGF-induced chimeric limbs with the differential expression of chick Tbx5 and Tbx4.

It has been reported that members of the fibroblast growth factor (FGF) family can induce additional limb formation in the flank of chick embryos. The phenotype of the ectopic limb depends on the somite level at which it forms: limbs in the anterior flank resemble wings, whereas those in the posterior flank resemble legs. Ectopic limbs located in the mid-flank appear chimeric, possessing characteristics of both wings and legs; feather buds are present in the anterior halves with scales and claws in the posterior halves. To study the mechanisms underlying the chimerism of these additional limbs, we cloned chick Tbx5 and Tbx4 to use as forelimb and hindlimb markers and examined their expression patterns in FGF-induced limb buds. We found that Tbx5 and Tbx4 were differentially expressed in the anterior and posterior halves of additional limb buds in the mid-flank, respectively, consistent with the chimeric patterns of the integument. A boundary of Tbx5/Tbx4 exists in all ectopic limbs, indicating that the additional limbs are essentially chimeric, although the degree of chimerism is dependent on the position. The boundary of Tbx5/Tbx4 expression is not fixed at a specific position within the interlimb region, but dependent upon where FGF was applied. Since the ectopic expression patterns of Tbx5/Tbx4 in the additional limbs are closely correlated with the patterns of their chimeric phenotypes, it is likely that Tbx5 and Tbx4 expression in the limb bud is involved in determination of the forelimb and hindlimb identities, respectively, in vertebrates.

Amino Acid Sequence↗

PubMed1997

Differential expression of the two closely related LIM-class homeobox genes LH-2A and LH-2B during limb development.

We have isolated the chicken homeobox genes LH-2A and LH-2B encoding two related LIM domain-containing homeodomain proteins and examined the expression pattern during chick limb development. LH-2A is most closely related to human and rat LH-2, while LH-2B is less conserved. Although both LH-2A and LH-2B are expressed in the limb mesenchyme throughout stage 16 to stage 32, LH-2A transcripts are detectable in the distal limb bud and LH-2B transcripts are detectable in the anterior limb bud. Signals from the apical ectodermal ridge positively regulate LH-2A expression, since removal of the apical ectoderm resulted in the rapid reduction of LH-2A expression in the distal limb mesenchyme. Ectopic expression of the sonic hedgehog gene in the anterior margin of the limb bud resulted in the rapid reduction of LH-2B expression accompanying respecification of the positional value to the posterior phenotype. These results suggest that LH-2A and LH-2B play important roles in the determination and specification of the proximal-distal and anterior-posterior positional values, respectively.

Amino Acid Sequence↗

PubMed1997

The peroxisome proliferator-activated receptor alpha (PPAR alpha) regulates the plasma thiobarbituric acid-reactive substance (TBARS) level.

We investigated whether liver expression of the peroxisome proliferator-activated receptor alpha (PPAR alpha) gene is related to the plasma thiobarbituric acid-reactive substance (TBARS) level, as well as to plasma cholesterol (TC) level and plasma triglyceride (TG) level in rats fed a high fat chow containing a variety of fatty acids. Only the plasma TBARS level showed a significant negative correlation with the liver PPAR alpha mRNA level (TC, R = 0.001, p = 0.9967; TG, R = 0.248, p = 0.1276; TBARS, R = 0.439, p = 0.0046). Although further studies are needed to clarify whether the increase of the liver PPAR alpha mRNA level confers a reduction in plasma TBARS levels, it is likely that PPAR alpha activity plays a regulatory role in the pathogenesis of hyperlipidemia and atherosclerosis.

Animals↗

PubMed1997

Induction of osteogenic differentiation by hedgehog proteins.

In this study we asked whether members of the hedgehog gene family are involved in osteogenesis. C3H10T1/2 cells and MC3T3-E1 cells expressed the putative hedgehog receptor patched (Ptc) gene. Medium conditioned by chicken embryo fibroblast cultures expressing either Indian hedgehog or Sonic hedgehog stimulated alkaline phosphatase (APase) activity in cultures of the mouse mesenchymal cell line C3H10T1/2 and the osteoblastic cell line MC3T3-E1. These stimulatory effects were synergistically enhanced by bone morphogenetic protein-2 (BMP-2). Treatment with the amino-terminal portion of recombinant Sonic hedgehog proteins (rShh-N) up-regulated the expression of the Ptc gene within 12 h and increased production of APase in C3H10T1/2. rShh-N and BMP-2 also synergistically stimulated APase activity. rShh-N treatment did not affect the expression levels of Bmp-2, -4, -5, -6 and -7 genes. These findings indicate that hedgehog proteins directly act on osteogenic precursor cells and osteoblasts and stimulate osteogenic differentiation of these cells in co-operation with BMPs.

3T3 Cells↗

PubMed1997

Identification of alpha-fodrin as a candidate autoantigen in primary Sjögren's syndrome.

It is unclear whether organ-specific autoantigens are critical for the development of primary Sjögren's syndrome (SS). A 120-kilodalton organ-specific autoantigen was purified from salivary gland tissues of an NFS/sld mouse model of human SS. The amino-terminal residues were identical to those of the human cytoskeletal protein alpha-fodrin. The purified antigen induced proliferative T cell responses and production of interleukin-2 and interferon-gamma in vitro. Neonatal immunization with the 120-kilodalton antigen prevented the disease in mice. Sera from patients with SS reacted positively with purified antigen and recombinant human alpha-fodrin protein, whereas those from patients with systemic lupus erythematosus and rheumatoid arthritis did not. Thus, the immune response to 120-kilodalton alpha-fodrin could be important in the initial development of primary SS.

Amino Acid Sequence↗

PubMed1997

Fibroblasts expressing Sonic hedgehog induce osteoblast differentiation and ectopic bone formation.

We investigated the role of Sonic hedgehog (SHH) in osteoblast differentiation and bone formation. The numbers of ALP-positive cells in the mouse fibroblastic cell line C3H10T1/2 and the mouse osteoblastic cell line MC3T3-E1 were increased by co-culture with chicken fibroblasts transfected with chicken Shh cDNA encoding amino-terminal peptide (Shh-N). The conditioned medium of Shh-N-RCAS-transfected chicken fibroblast cultures also significantly increased ALP activity in both C3H10T1/2 and MC3T3-E1 cells. Intramuscular transplantation of Shh-N-RCAS-transfected chicken fibroblasts into athymic mice induced ectopic bone formation. These results indicate that SHH induces osteoblast differentiation and ectopic bone formation.

3T3 Cells↗

PubMed1997

Induction of additional limb at the dorsal-ventral boundary of a chick embryo.

In the early chick embryo, an apical ectodermal ridge (AER) is formed from the overlying ectoderm of the presumptive limb bud region at the dorsal-ventral (DV) boundary. We report here that the ectopic DV boundary formed in the presumptive wing, flank, and leg fields induces an ectopic AER structure. Dorsal tissue (ectoderm and mesoderm) from the presumptive wing field of stage 10 to 17 embryos was inserted into a slit in the somatopleure of the future ventral side of host embryos. The same method was used to implant ventral tissue into the future dorsal side of host embryos. After the implantation, ectopic AER was induced and an additional limb or limb-like structure developed. In related experiments, ectoderm-free presumptive wing tissue was implanted, which resulted in a considerably decreased frequency of ectopic AER formation. Further analysis of chick and quail chimeras suggests that the ectopic AER was formed from the ectodermal cells overlying the boundary of host and graft mesodermal cells. These results indicate that the DV boundary organizes the AER structure in the limb bud field of early-stage chick embryos and that the ectoderm of the grafted tissues plays an important role in this process.

Animals↗

PubMed1997

Acarbose controls postprandial hyperproinsulinemia in non-insulin dependent diabetes mellitus.

We investigated how fasting or postprandial insulin levels were altered by treatment with acarbose or sulfonylureas. Plasma glucose and serum insulin, C-peptide, and proinsulin levels were measured before as well as 1 and 2 h after breakfast in 23 patients with non-insulin-dependent diabetes mellitus and 17 patients with impaired glucose tolerance. In the diabetic patients, 12 weeks of acarbose therapy decreased the postprandial levels of glucose (1 h: -60.0%; 2 h: -67.6%), insulin (1 h: -67.5%; 2 h: -72.2%) and proinsulin (1 h: -55.2%; 2 h: -46.7%), and proinsulin (1 h: -20.9%; 2 h: -57.5%). In contrast, sulfonylurea treatment increased postprandial insulin and proinsulin levels. Since increased in the serum insulin or proinsulin levels are associated with a higher risk of cardiovascular disease, the present findings suggest that the acarbose-induced reduction of the postprandial serum insulin or proinsulin responses to food intake might be useful for preventing vascular complications in patients with diabetes.

Acarbose↗

PubMed1997

A chick wingless mutation causes abnormality in maintenance of Fgf8 expression in the wing apical ridge, resulting in loss of the dorsoventral boundary.

We analyzed a Japanese chick wingless mutant (Jwg) to know a molecular mechanism underlying wing development. We observed expression patterns of eleven marker genes to characterize the mutant. Expressions of dorsoventral (DV) and mesenchymal marker genes were intact in nascent Jwg limb buds. However, expression of Fgf8, a marker gene for the apical ectodermal ridge (AER), was delayed and shortly disappeared in the wing regressing AER. Later on, ventral expression of dorsal marker genes of Wnt7a and Lmx1 indicated that the wing bud without the AER became bi-dorsal. In addition, the posterior mesoderm became defective, as deduced from the impaired expression patterns of Sonic hedgehog (Shh), Msx1, and Prx1. We attempted to rescue a wing by implanting Fgf8-expressing cells into the Jwg wing bud. We found that FGF8 can rescue outgrowth of the wing bud by maintaining Shh expression. Thus, the Jwg gene seems to be involved in maintenance of the Fgf8 expression in the wing bud. Further, it is suggested that the AER is required for maintenance of the DV boundary and the polarizing activity of the established wing bud.

Animals↗

PubMed1997

The mesenchymal factor, FGF10, initiates and maintains the outgrowth of the chick limb bud through interaction with FGF8, an apical ectodermal factor.

Vertebrate limb formation has been known to be initiated by a factor(s) secreted from the lateral plate mesoderm. In this report, we provide evidence that a member of the fibroblast growth factor (FGF) family, FGF10, emanates from the prospective limb mesoderm to serve as an endogenous initiator for limb bud formation. Fgf10 expression in the prospective limb mesenchyme precedes Fgf8 expression in the nascent apical ectoderm. Ectopic application of FGF10 to the chick embryonic flank can induce Fgf8 expression in the adjacent ectoderm, resulting in the formation of an additional complete limb. Expression of Fgf10 persists in the mesenchyme of the established limb bud and appears to interact with Fgf8 in the apical ectoderm and Sonic hedgehog in the zone of polarizing activity. These results suggest that FGF10 is a key mesenchymal factor involved in the initial budding as well as the continuous outgrowth of vertebrate limbs.

Amino Acid Sequence↗

PubMed1997

Pax-6 is involved in the specification of hindbrain motor neuron subtype.

Pax-6 is a member of the vertebrate Pax gene family, which is structurally related to the Drosophila pair-rule gene, paired. In mammals, Pax-6 is expressed in several discrete domains of the developing CNS and has been implicated in neural development, although its precise role remains elusive. We found a novel Small eye rat strain (rSey2) with phenotypes similar to mouse and rat Small eye. Analyses of the Pax-6 gene revealed one base (C) insertion in an exon encoding the region downstream of the paired box of the Pax-6 gene, resulting in generation of truncated protein due to the frame shift. To explore the roles of Pax-6 in neural development, we searched for abnormalities in the nervous system in rSey2 homozygous embryos. rSey2/rSey2 exhibited abnormal development of motor neurons in the hindbrain. The Islet-1-positive motor neurons were generated just ventral to the Pax-6-expressing domain both in the wild-type and mutant embryos. However, two somatic motor (SM) nerves, the abducent and hypoglossal nerves, were missing in homozygous embryos. By retrograde and anterograde labeling, we found no SM-type axonogenesis (ventrally growing) in the mutant postotic hindbrain, though branchiomotor and visceral motor (BM/VM)-type axons (dorsally growing) were observed within the neural tube. To discover whether the identity of these motor neuron subtypes was changed in the mutant, we examined expression of LIM homeobox genes, Islet-1, Islet-2 and Lim-3. At the postotic levels of the hindbrain, SM neurons expressed all the three LIM genes, whereas BM/VM-type neurons were marked by Islet-1 only. In the Pax-6 mutant hindbrain, Islet-2 expression was specifically missing, which resulted in the loss of the cells harboring the postotic hindbrain SM-type LIM code (Islet-1 + Islet-2 + Lim-3). Furthermore, we found that expression of Wnt-7b, which overlapped with Pax-6 in the ventrolateral domain of the neural tube, was also specifically missing in the mutant hindbrain, while it remained intact in the dorsal non-overlapping domain. These results strongly suggest that Pax-6 is involved in the specification of subtypes of hindbrain motor neurons, presumably through the regulation of Islet-2 and Wnt-7b expression.

Animals↗