Expression of transcriptional repressor ATF3/LRF1 in human atherosclerosis: colocalization and possible involvement in cell death of vascular endothelial cells

Vascular endothelial cell death contributes to the progression of atherosclerotic lesion, and several transcriptional regulators are involved in the process. Activating transcription factor 3/liver regenerating factor-1 (ATF3/LRF-1), a stress-inducible transcriptional repressor, was shown to be highly expressed in vascular endothelial cells and macrophages of human atherosclerotic lesions by immunohistological assay. The expression was colocalized in these cells which were positive for TdT-mediated dUTP nick-end labeling (TUNEL) and annexin V. Treatment of human umbilical vein endothelial cells (HUVECs) by tumor necrosis factor (TNF)-alpha, oxidized low density lipoprotein (oxLDL), and lysophosphatidylcholine (LPC) rapidly induced ATF3/LRF-1, which showed an increased DNA binding to the consensus ATF/CRE sequence by supershift of gel shift assay. Flow cytometry analysis and immunostaining analysis with TUNEL assay showed that ATF3/LRF-1 was highly expressed in cell death induced by these agents. Moreover, antisense ATF3/LRF-1 cDNA partly suppressed the cell death induced by TNF-alpha, oxLDL, and LPC. From these results, it is indicated that ATF3/LRF-1 is one of the immediate early response genes in vascular endothelial cells in response to atherogenic stimuli, and may play a role in the endothelial cell death associated with atherogenesis.

Cell-cycle-dependent regulation of human aurora A transcription is mediated by periodic repression of E4TF1

Human aurora A is a serine-threonine kinase that controls various mitotic events. The transcription of aurora A mRNA varies throughout the cell cycle and peaks during G(2)/M. To clarify the transcriptional mechanism, we first cloned the 1.8-kb 5'-flanking region of aurora A including the first exon. Transient expression of aurora A promoter-luciferase constructs containing a series of 5'-truncated sequences or site-directed mutations identified a 7-bp sequence (CTTCCGG) from -85 to -79 as a positive regulatory element. Electromobility shift assays identified the binding of positive regulatory proteins to the CTTCCGG element. Anti-E4TF1-60 antibody generated a supershifted complex. Furthermore, coexpression of E4TF1-60 and E4TF1-53 markedly increased aurora A promoter activity. Synchronized cells transfected with the aurora A promoter-luciferase constructs revealed that the promoter activity of aurora A increased in the S phase and peaked at G(2)/M. In addition, we identified a tandem repressor element, CDE/CHR, just downstream of the CTTCCGG element, and mutation within this element led to a loss of cell cycle regulation. We conclude that the transcription of aurora A is positively regulated by E4TF1, a ubiquitously expressed ETS family protein, and that the CDE/CHR element was essential for the G(2)/M-specific transcription of aurora A.

Modulation of iron regulatory protein-1 by various metals

Iron regulatory protein-1 (IRP-1) is known as a cytosolic aconitase and a central regulator of iron (Fe) homeostasis. IRP-1 regulates the expression of Fe metabolism-related proteins by interacting with the Fe-responsive element (IRE) in the untranslated regions of mRNAs of these proteins. However, it is less known whether IRP-1 modulates various non-Fe metals. In the present study, we showed that treatment of homogenously purified IRP-1 with non-Fe metals decreased the affinity to IRE in RNA band shift assays and increased aconitase activity. Non-Fe metals also inhibited (55)Fe incorporation into the fourth labile position of the Fe-S cluster of IRP-1. In PLC hepatoma cells, metal loading inactivated binding activity and activated enzyme activity. It also suppressed transferrin receptor mRNA expression in the cells. These results suggest that various non-Fe metals modulate IRP-1 by conversion of the 3Fe-4S apo-form to a [1 non-Fe metal + 3Fe]-4Fe holo-form.

Activation of JNK and transcriptional repressor ATF3/LRF1 through the IRE1/TRAF2 pathway is implicated in human vascular endothelial cell death by homocysteine

Endothelial cell injury underlies an increased occurrence of thromboembolic vascular disease in hereditary hyperhomocysteinemia. We have previously shown that homocysteine causes activation of c-Jun NH(2)-terminal kinase (JNK) and activating transcription factor 3/liver regenerating factor 1 (ATF3/LRF1) and induces apoptosis in human umbilical vein endothelial cells (HUVECs). In this study, the activation of JNK and ATF3 in HUVECs was mediated by the endoplasmic reticulum (ER) resident transmembrane kinase IRE1alpha and beta, which sense and transduce signal of the accumulationj of unfolded proteins in the ER. Moreover, dominant negative mutants of tumor necrosis factor receptor-associated factor 2 and mitogen-activated kinase kinase 4 and 7, as well as antisense ATF3 cDNA, inhibited cell death by homocysteine. These results indicate that the activation of JNK and ATF3 through the ER stress of homocysteine plays a role in the homocysteine-induced cell death. The JNK-ATF3 pathway may be implicated in endothelial cell injury associated with hereditary hyperhomocysteinemia.

Manipulation of the somatosensory cortex modulates stimulus-induced repetitive ear movements in a seizure-sensitive strain of gerbil

Some Mongolian gerbils (Meriones unguiculatus) respond to stimulation by seizures, the pattern of which changes progressively during development. We previously established a seizure-sensitive strain, MGS/Idr, in which all animals exhibit such stimulus-induced seizures. We have now noted that all adults of this strain also show repetitive backward movements of the ears at the ears at the beginning of stimulus-induced seizures, although the incidence varies with the individual. We examined whether the cerebral cortex was involved in these movements and found that electrical stimulation of an area of the somatosensory cortex elicited strong backward movement of the ear on the contralateral side, and that unilateral application of bicuculline, a GABAA receptor antagonist, induced spontaneous repetitive backward movements of the same ear. In this area, sharp waves appeared in the electrocortigram during the repetitive ear movements induced by seizure-inducing stimuli. Unilateral ablation of this area abolished stimulus-induced repetitive movements of the contralateral ear, but had no effects on those of the ipsilateral ear. These results suggest that, in certain types of seizure-susceptible subjects, it may be possible to modify stimulus-induced repetitive movements by manipulating a certain area of the somatosensory cortex which is related to these movements and that this gerbil strain may be useful in research on this subject.

A case of non-functioning pituitary adenoma with Cushing's syndrome upon recurrence

A 49-year-old woman presented with left visual disturbance. No signs of Cushing's disease were evident. Basal levels of serum cortisol and plasma adrenocorticotropic hormone (ACTH) were 16.8 microg/dL and 66.0 pg/mL, respectively. MRI demonstrated an irregularly shaped large pituitary tumor, and the patient then underwent transsphenoidal surgery. By light microscopy the tumor represented a chromophobic adenoma with a few of the adenoma cells showing immunoreactivity for ACTH. On the basis of clinical and light microscopic examinations, the diagnosis of silent corticotroph adenoma was made. Electron microscopy, however, demonstrated the honeycomb Golgi complex that has been reported as a typical finding of gonadotroph adenomas. MRI taken 7 months after the first operation revealed adenoma regrowth. Transcranial surgery was performed, and histology demonstrated a chromophobic pituitary adenoma with most cells immunopositive for ACTH. She was treated with gamma knife postoperatively. Three months later, MRI revealed remarkable shrinkage of the adenoma, but she developed typical signs and symptoms of Cushing's disease. Thus, the hormone immunostaining and biological activity of pituitary adenomas may change with time.

Dextran sodium sulfate-induced colitis in germ-free IQI/Jic mice

This study presents a histological examination of dextran sodium sulfate (DSS)-induced colitis in germ-free (GF) mice. A comparison of the pathology between GF and conventionalized mice (CVz) was made to determine the role that intestinal microflora play in DSS-induced colitis. To induce colitis, GF and CVz IQI/Jic mice were given either 5% or 1% DSS orally. Administration of 5% DSS, a common concentration used to induce colitis in mice, caused gross rectal bleeding and a marked decrease in hematocrit as early as day one in GF mice. These mice died on day three due to massive bleeding into the intestinal lumen. In contrast, CVz mice did not die during the seven-day experimental period. Histopathological examination three days after administration of 5% DSS did not reveal any colitis lesions in GF mice, but CVz mice had developed moderate colitis in the large intestine. Administration of a low concentration of DSS (1%), which only induces mild basal crypt loss in CVz mice, caused severe colitis in the distal colon in GF mice, and they died on day 14. These data suggest that intestinal microflora are not necessary for the induction of colitis. Furthermore, DSS may be highly toxic to GF mice, and when given at a concentration of 5% it causes massive bleeding into the intestinal lumen resulting in death prior to development of colitis.

Transcriptional regulation of Mesp1 and Mesp2 genes: differential usage of enhancers during development

Mesp1 and Mesp2 encode bHLH-type transcription factors, Mesp1 and Mesp2, respectively. The expression of both genes is observed in the nascent mesoderm, and subsequently in the rostral presomitic mesoderm. To determine the regulatory mechanism for gene expression, we attempted to identify enhancer elements by transient transgenic analysis. At least two enhancers, which are responsible for the expression of the two genes in the early mesoderm (early mesodermal enhancer, EME) and the presomitic mesoderm (PSM enhancer, PSME), and one suppressor, which is responsible for the rostrally restricted expression in the presomitic mesoderm, were identified. Deletion studies of these enhancer elements indicate that either gene may use the same enhancer for early mesoderm development, whereas both genes may utilize separate enhancers to regulate their expression in the presomitic mesoderm.

High expression of S-phase kinase-interacting protein 2, human F-box protein, correlates with poor prognosis in oral squamous cell carcinomas

Reduced expression of p27(Kip1), a cyclin-dependent kinase (Cdk) inhibitor, is frequently found in various cancers, including oral squamous cell carcinoma (OSCC), and is attributable to an enhancement of its degradation. Skp2, an F-box protein necessary for DNA replication, is required for the ubiquitinylation and subsequent degradation of p27(Kip1). In the present study, we examined the expression of Skp2 and its correlation with the expression of p27(Kip1) protein or p27(Kip1) degradation in OSCC. Using immunohistochemistry, we found that high expression of Skp2 was present in 49% of OSCCs and only 20% of epithelial dysplasias. Significantly, high expression of Skp2 was correlated with poor prognosis of OSCC patients. We also found an inverse correlation between the expression of Skp2 and p27 by immunohistochemical analysis. A similar correlation was observed in OSCC cell lines and OSCC tissues by Western blot analysis. Interestingly, OSCC tissues with Skp2 expression had high p27(Kip1) degradation activity. These findings indicate that (a) Skp2 may play an important role for the development of OSCC, (b) Skp2 can be a novel target for OSCC treatment as well as a strong prognostic marker, and (c) the reduction in p27(Kip1) protein may be brought about by enhancement of its degradation mediated by increased levels of Skp2 protein.

Homocysteine induces programmed cell death in human vascular endothelial cells through activation of the unfolded protein response

Severe hyperhomocysteinemia is associated with endothelial cell injury that may contribute to an increased incidence of thromboembolic disease. In this study, homocysteine induced programmed cell death in human umbilical vein endothelial cells as measured by TdT-mediated dUTP nick end labeling assay, DNA ladder formation, induction of caspase 3-like activity, and cleavage of procaspase 3. Homocysteine-induced cell death was specific to homocysteine, was not mediated by oxidative stress, and was mimicked by inducers of the unfolded protein response (UPR), a signal transduction pathway activated by the accumulation of unfolded proteins in the lumen of the endoplasmic reticulum. Dominant negative forms of the endoplasmic reticulum-resident protein kinases IRE1alpha and -beta, which function as signal transducers of the UPR, prevented the activation of glucose-regulated protein 78/immunoglobulin chain-binding protein and C/EBP homologous protein/growth arrest and DNA damage-inducible protein 153 in response to homocysteine. Furthermore, overexpression of the point mutants of IRE1 with defective RNase more effectively suppressed the cell death than the kinase-defective mutant. These results indicate that homocysteine induces apoptosis in human umbilical vein endothelial cells by activation of the UPR and is signaled through IRE1. The studies implicate that the UPR may cause endothelial cell injury associated with severe hyperhomocysteinemia.

Mesp1 expression is the earliest sign of cardiovascular development

Understanding the molecular mechanism leading to formation of the heart and vasculature during embryogenesis is critically important because malformation of the cardiovascular system is the most frequently occurring type of birth defect. While the hearts of all vertebrates are derived from bilateral paired fields of primary mesodermal cells that are specified to the cardiac lineage during gastrulation, the mechanism for lineage restriction, and the origin of the myocardium and endocardium have not been defined. Recently, we found that a transcription factor, Mesp1, is expressed in almost all precursors of the cardiovascular system and plays an essential role in cardiac morphogenesis. Mesp1 may play a key role in the early specification for cardiac precursor cells.

Expression of PR-5d and ERF genes in cultured tobacco cells and their NaCl stress-response

The expression of pathogenesis-related protein-5d (PR-5d) and ethylene-responsive transcriptional factors (ERF1-4) for basic PR-proteins was measured in cultured tobacco cells. The PR-5d transcript markedly increased with culture, but only constant levels of transcripts of ERF1 (trans-activator) and ERF3 (repressor) were detected in cells. These different responses of PR-5d and ERF genes were also observed under NaCl stress; PR-5d transcript decreased and ERF levels were constant under NaCl stress. The effect of post-transcriptional regulation of ERF activity, especially ERF3, on the expression of basic PR genes including PR-5d is discussed.

Characterization of ascorbate peroxidases from unicellular red alga Galdieria partita

Galdieria partita, a unicellular red alga isolated from acidic hot springs and tolerant to sulfur dioxide, has at least two ascorbate peroxidase (APX) isozymes. This was the first report to demonstrate that two isozymes of APX are found in algal cells. Two isozymes were separated from each other at the hydrophobic chromatography step of purification and named APX-A and APX-B after the elution order in the chromatography. APX-B accounted for 85% of the total activity. Both isozymes were purified. APXs from Galdieria were monomers whose molecular weights were about 28,000, similar to stromal APX of higher plants. APX-A cross-reacted with monoclonal antibody raised against APX of Euglena gracilis in immunoblotting, but APX-B did not, although the antibody can recognize all other APXs tested. The amino-terminal sequences of APX-A and -B from Galdieria had some homology with each other but little homology with those from other sources. Their Km values for ascorbate and hydrogen peroxide were comparable with those of APX from higher plants. Unlike the green algal enzymes, the donor specificities of Galdieria APXs were as high as those of plant chloroplastic APX. On the contrary, these APXs reduced tertiary-butyl hydroperoxide as an electron acceptor as APXs from Euglena and freshwater Chlamydomonas do. The inhibition of APX-A and -B by cyanide and azide, and characteristics of their light absorbance spectra indicated that they were heme peroxidases.

Influence of organ site and tumor cell type on MUC1-specific tumor immunity

We investigated the influence of organ-specific parameters on tolerance and immunity to human MUC1. C57Bl/6 mice (wild-type) and C57Bl/6 transgenic for MUC1 (MUC1.Tg) were challenged in the pancreas with Panc02-MUC1, a C57Bl/6-syngeneic pancreatic cancer cell line expressing human MUC1. Wild-type mice produced immune responses to MUC1 when presented on tumor cells growing in the pancreas; however, the responses to tumors in the pancreas were less effective than responses produced by tumor challenge at the s.c. site. Tumor immunity specific for MUC1 was produced in wild-type mice by two different procedures: (i) s.c. immunization of wild-type mice with a low dose of Panc02-MUC1 or (ii) adoptive transfer of spleen and lymph node cells harvested from wild-type mice previously immunized s.c. with Panc02-MUC1. This demonstrates that immune responses to MUC1 presented at the s.c. site can be detected and adoptively transferred. MUC1.Tg mice were immunologically tolerant to MUC1; however, some immunological protection against orthotopic challenge with Panc02-MUC1 was conferred by adoptive transfer of CD4+ and CD8+ T cells from wild-type mice. These results show that it is more difficult to produce immune responses to tumors growing at the pancreatic site than the s.c. site. Panc02-MUC1 cells growing in the pancreas were accessible to the immune system, and immune responses evoked by s.c. presentation of this molecule in wild-type mice were effective in rejecting tumor cells in the pancreas of both wild-type and MUC1.Tg mice. No effective anti-tumor immune responses against MUC1 were produced in MUC1.Tg mice.

Glial cells contribute more to iron and aluminum accumulation but are more resistant to oxidative stress than neuronal cells

Iron (Fe) and aluminum (Al) have been implicated in the pathogenesis of Alzheimer's disease (AD). In this study, we examined neuronal and glial cells to clarify which contributes most to metal accumulation after internalization through the transferrin-independent iron uptake (Tf-IU) systems in primary neuronal and glial predominant (NP and GP) cells from rat cerebral cortex, which affect the accumulation of transition metals in a variety of cultured cells. Al more significantly upregulated the Tf-IU activity in GP cells than in NP cells. GP cells were more resistant to Fe and Al exposure than NP cells. However, a chemiluminescence analysis specific for reactive oxygen species (ROS) showed that ROS levels in Fe- or Al-loaded NP cells were twice as high as in Fe- or Al-loaded GP cells. Northern blot analysis and gel retardation assay showed that the Al and Fe exposure taken up by the cells suppress Tf receptor mRNA expression to a greater extent in GP than NP cells, indicating that Al and Fe more markedly accumulate in glial than in neuronal cells. These results suggest that glial cells rather than neuronal cells contribute to the metal accumulation and are more resistant to oxidative stress caused by metals than neuronal cells. The present study may help to explain the pathogenesis of neurodegeneration in AD disorders caused by metal-generated oxidative stress.

Drosophila von Hippel-Lindau tumor suppressor complex possesses E3 ubiquitin ligase activity

Mutations of the von Hippel-Lindau (VHL) tumor suppressor gene predispose individuals to a variety of human tumors, including renal cell carcinoma, hemangioblastoma of the central nervous system, and pheochromocytoma. Here we report on the identification and characterization of the Drosophila homolog of VHL. The predicted amino acid sequence of Drosophila VHL protein shows 29% identity and 44% similarity to that of human VHL protein. Biochemical studies have shown that Drosophila VHL protein binds to Elongins B and C directly, and via this Elongin BC complex, associates with Cul-2 and Rbx1. Like human VHL, Drosophila VHL complex containing Cul-2, Rbx1, Elongins B and C, exhibits E3 ubiquitin ligase activity. In addition, we provide evidence that hypoxia-inducible factor (HIF)-1alpha is the ubiquitination target of both human and Drosophila VHL complexes.

Homocysteine-responsive ATF3 gene expression in human vascular endothelial cells: activation of c-Jun NH(2)-terminal kinase and promoter response element

Activating transcription factor (ATF) 3 is a member of ATF/cyclic adenosine monophosphate (cAMP)-responsive element binding protein (ATF/CREB) family of transcription factors and functions as a stress-inducible transcriptional repressor. To understand the stress-induced gene regulation by homocysteine, we investigated activation of the ATF3 gene in human endothelial cells. Homocysteine caused a rapid induction of ATF3 at the transcriptional level. This induction was preceded by a rapid and sustained activation of c-Jun NH(2)-terminal kinase/stress-activated protein kinase (JNK/SAPK), and dominant negative mitogen-activated protein kinase kinase 4 and 7 abolished these effects. The effect of homocysteine appeared to be specific, because cysteine or homocystine had no appreciable effect, but it was mimicked by dithiothreitol and beta-mercaptoethanol as well as tunicamycin. The homocysteine effect was not inhibited by an active oxygen scavenger. Deletion analysis of the 5' flanking sequence of the ATF3 gene promoter revealed that one of the major elements responsible for the induction by homocysteine is an ATF/cAMP responsive element (CRE) located at -92 to -85 relative to the transcriptional start site. Gel shift, immunoprecipitation, and cotransfection assays demonstrated that a complex (or complexes) containing ATF2, c-Jun, and ATF3 increased binding to the ATF/CRE site in the homocysteine-treated cells and activated the ATF3 gene expression, while ATF3 appeared to repress its own promoter. These data together suggested a novel pathway by which homocysteine causes the activation of JNK/SAPK and subsequent ATF3 expression through its reductive stress. Activation of JNK/SAPK and ATF3 expression in response to homocysteine may have a functional role in homocysteinemia-associated endothelial dysfunction.

Immunohistochemical estimation of in-situ cell cycle time in neoplastic epithelial cells in human large intestine: a new cell proliferation index

In-situ cell cycle time (in-situ Tc) of epithelial cells could be estimated by using a formula; in-situ Tc = cell proliferation rate divided by mitosis rate, on a scale of Tm (cell cycle time in M phase) arbitrary unit (AU), In order to see the nature of in-situ Tc in the adenoma-carcinoma sequence in the human large intestine, the in-situ Tc in 27 cases of adenoma and 71 cases of adenocarcinoma with adenoma components in the human large intestine was estimated by using this formula, counting proliferating cells and mitotic cells in the immunohistochemistry of Ki-67 antigen. C12 antigen was examined as an oncogenic progression indicator in the adenoma-carcinoma sequence. The in-situ Tc tended to shorten in adenoma in accordance with the histological grading of atypia but not in adenoma component. No significant differences in the in-situ Tc was recognized as a whole among adenomas, adenoma components and adenocarcinomas in the mucosa, whereas the in-situ Tc of adenoma components with moderate to severe atypia was significantly longer than that of adenocarcinomas in the mucosa (p = 0.05). The in-situ Tc lengthened in adenocarcinomas invading the submucosa and shortened in adenocarcinomas invading the proper muscular layer. The cases expressing the C12 antigen increased in order of adenoma, adenoma component and adenocarcinoma. The cases expressing the C12 antigen indicated short in situ Tc in the adenomas and adenocarcinomas but not in the adenoma components. Thus, the estimated in-situ Tc is a useful index of the oncogenetic progression, which is different from that detected by the C12 antigen.

Repression of TNF-alpha-induced E-selectin expression by PPAR activators: involvement of transcriptional repressor LRF-1/ATF3

Peroxisome proliferator-activated receptor (PPAR) activators were shown to inhibit the expression of E-selectin of human vascular endothelial cells in response to tumor necrosis factor-alpha (TNF-alpha). Troglitazone, pioglitazone, alpha-clofibrate, and 15-deoxy-Delta12,14-prostaglandin J2 all inhibited the TNF-alpha-stimulated E-selectin gene transcription in reporter assay. To further clarify the underlying transcriptional regulation, nuclear factor(s) that binds to the nuclear factor-endothelial leukocyte adhesion molecule 1 (NF-ELAM1) site of the E-selectin gene promoter was investigated. The activators caused a significant induction of liver regenerating factor 1 (LRF1)/activating transcription factor 3 (ATF3), which bound to the NF-ELAM1 site and repressed the TNF-alpha-induced E-selectin gene expression. From these data, the effect of PPAR activators was mediated, in part, through the induction of LRF1/ATF3. This might provide a novel molecular mechanism of anti-inflammatory effect of PPAR activators.

MesP1 and MesP2 are essential for the development of cardiac mesoderm

The transcription factors, MesP1 and MesP2, sharing an almost identical bHLH motif, have an overlapping expression pattern during gastrulation and somitogenesis. Inactivation of the Mesp1 gene results in abnormal heart morphogenesis due to defective migration of heart precursor cells, but somitogenesis is not disrupted because of normal expression of the Mesp2 gene. To understand the cooperative functions of MesP1 and MesP2, either a deletion or sequential gene targeting strategy was employed to inactivate both genes. The double-knockout (dKO) embryos died around 9.5 days postcoitum (dpc) without developing any posterior structures such as heart, somites or gut. The major defect in this double-knockout embryo was the apparent lack of any mesodermal layer between the endoderm and ectoderm. The abnormal accumulation of cells in the primitive streak indicates a defect in the migratory activity of mesodermal cells. Molecular markers employed to characterize the phenotype revealed a lack of the cranio-cardiac and paraxial mesoderm. However, the axial mesoderm, as indicated by brachyury (T) expression, was initially generated but anterior extension was halted after 8.5 dpc. Interestingly, a headfold-like structure developed with right anterior-posterior polarity; however, the embryos lacked any posterior neural properties. The persistent and widely distributed expression of Cerberus-like-1(Cer1), Lim1 and Otx2 in the anterior endoderm might be responsible for the maintenance of anterior neural marker expression. We also performed a chimera analysis to further study the functions of MesP1 and MesP2 in the development of mesodermal derivatives. In the chimeric embryos, dKO cells were scarcely observed in the anterior-cephalic and heart mesoderm, but they did contribute to the formation of the somites, notochord and gut. These results strongly indicate that the defect in the cranial-cardiac mesoderm is cell-autonomous, whereas the defect in the paraxial mesoderm is a non-cell-autonomous secondary consequence.

Mesp2 initiates somite segmentation through the Notch signalling pathway

The Notch-signalling pathway is important in establishing metameric pattern during somitogenesis. In mice, the lack of either of two molecules involved in the Notch-signalling pathway, Mesp2 or presenilin-1 (Ps1), results in contrasting phenotypes: caudalized versus rostralized vertebra. Here we adopt a genetic approach to analyse the molecular mechanism underlying the establishment of rostro-caudal polarity in somites. By focusing on the fact that expression of a Notch ligand, Dll1, is important for prefiguring somite identity, we found that Mesp2 initiates establishment of rostro-caudal polarity by controlling two Notch-signalling pathways. Initially, Mesp2 activates a Ps1-independent Notch-signalling cascade to suppress Dll1 expression and specify the rostral half of the somite. Ps1-mediated Notch-signalling is required to induce Dll1 expression in the caudal half of the somite. Therefore, Mesp2- and Ps1-dependent activation of Notch-signalling pathways might differentially regulate Dll1 expression, resulting in the establishment of the rostro-caudal polarity of somites.

Studies on thyroid function in rats subjected to repeated oral administration with kojic acid

To elucidate the effects of kojic acid on thyroid function, the compound was given orally to male rats for 4 weeks at 0, 4, 15, 62.5, 250 and 1,000 mg/kg. In 1,000 mg/kg treatment of kojic acid, the rats showed a slight decrease in motility, inhibition of body weight gain, and a decrease in food consumption. An increase in thyroid weight and a morphological change, i.e., hypertrophy of epithelial cells of the thyroid gland follicles, were observed after 1 week of administration. In addition, the uptake of radioactive iodine from blood into the thyroid gland was enhanced and the TCA-precipitable radioactive iodine in the thyroid gland increased in those rats. However, the rates of the iodination in the thyroid gland did not change during the experiment period. Although serum T4 concentration was low in the rats treated with 1,000 mg/kg kojic acid, it was not observed in any changes in TSH concentration. None of these changes were found in the other groups. These observations suggest that massive administration of kojic acid may decrease blood T4 concentration and that thyroid function may be enhanced compensatorily. On the other hand, the absorption of kojic acid was rapid as manifested by the Tmax of blood concentrations of radioactivity, which was as short as 1.0 +/- 0.0 hr, and the t1/2 was 4.8 +/- 0.3 hr. Blood concentrations of radioactivity disappeared nearly completely at 24 hr after administration. This result indicates that the toxic effect observed on the thyroid gland treated with only the largest dosage of kojic acid may depend on a fast decrease following a transient increase of concentration of the compound in the blood.

Characterization of gene expression of NsERFs, transcription factors of basic PR genes from Nicotiana sylvestris

Three genes of NsERFs (EREBPs), transcription factors for GCC box of basic PR genes, were isolated from Nicotiana sylvestris. Analyses of transgenic tobacco carrying the NsERF promoter::GUS genes showed that expression of all NsERF genes in leaves was induced by ethylene. Sequence analyses indicated that the 5'-upstream region of NsERF3 gene has the GCC box. In contrast, the promoter regions of NsERF2 and 4 have no GCC box, whereas NsERF2 has a putative EIN3 binding site. Tissue/cell specific expression is also discussed.