bluuebunny/crossref_metadata_2025 huggingface dataset:
Regulation of Sertoli Cell Tight Junction Dynamics in the Rat Testis via the Nitric Oxide Synthase/Soluble Guanylate Cyclase/3′,5′-Cyclic Guanosine Monophosphate/Protein Kinase G Signaling Pathway: an in Vitro Study
Authors: Lee Nikki P. Y. , Yan Cheng C.
Published: March 2003

Nitric oxide (NO) synthase (NOS) catalyzes the oxidation of l-arginine to NO. NO plays a crucial role in regulating various physiological functions, possibly including junction dynamics via its effects on cAMP and cGMP, which are known modulators of tight junction (TJ) dynamics. Although inducible NOS (iNOS) and endothelial NOS (eNOS) are found in the testis and have been implicated in the regulation of spermatogenesis, their role(s) in TJ dynamics, if any, is not known. When Sertoli cells were cultured at 0.5–1.2 × 106 cells/cm2 on Matrigel-coated dishes or bicameral units, functional TJ barrier was formed when the barrier function was assessed by quantifying transepithelial electrical resistance across the cell epithelium. The assembly of the TJ barrier was shown to associate with a significant plummeting in the levels of iNOS and eNOS, seemingly suggesting that their presence by producing NO might perturb TJ assembly. To further confirm the role of NOS on the TJ barrier function in vitro, zinc (II) protoporphyrin-IX (ZnPP), an NOS inhibitor and a soluble guanylate cyclase inhibitor, was added to the Sertoli cell cultures during TJ assembly. Indeed, ZnPP was found to facilitate the assembly and maintenance of the Sertoli cell TJ barrier, possibly by inducing the production of TJ-associated proteins, such as occludin. Subsequent studies by immunoprecipitation and immunoblotting have shown that iNOS and eNOS are structurally linked to TJ-integral membrane proteins, such as occludin, and cytoskeletal proteins, such as actin, vimentin, and α-tubulin. When the cAMP and cGMP levels in these ZnPP-treated samples were quantified, a ZnPP-induced reduction of intracellular cGMP, but not cAMP, was indeed detected. Furthermore, 8-bromo-cGMP, a cell membrane-permeable analog of cGMP, could also perturb the TJ barrier dose dependently similar to the effects of 8-bromo-cAMP. KT-5823, a specific inhibitor of protein kinase G, was shown to facilitate the Sertoli cell TJ barrier assembly. Cytokines, such as TGF-β and TNF-α, known to perturb the Sertoli cell TJ barrier, were also shown to stimulate Sertoli cell iNOS and eNOS expression dose dependently in vitro. Collectively, these results illustrate NOS is an important physiological regulator of TJ dynamics in the testis, exerting its effects via the NO/soluble guanylate cyclase/cGMP/protein kinase G signaling pathway.
Structural and Functional Evidence for the Interaction of Insulin-Like Growth Factors (IGFs) and IGF Binding Proteins with Vitronectin
Authors: Kricker Jennifer A. , Towne Chris L. , Firth Sue M. , Herington Adrian C. , Upton Zee
Published: April 2003

Previous studies demonstrated that IGF-II binds directly to vitronectin (VN), whereas IGF-I binds poorly. However, binding of VN to integrins has been demonstrated to be essential for a range of IGF-I-stimulated biological effects, including IGF binding protein (IGFBP)-5 production, IGF type-1 receptor autophosphorylation, and cell migration. Thus, we hypothesized that a link between IGF-I and VN must occur and may be mediated through IGFBPs. This was tested using competitive binding assays with VN and 125iodine-labeled IGFs in the absence and presence of IGFBPs. IGFBP-4, IGFBP-5, and nonglycosylated IGFBP-3 were shown to significantly enhance binding of IGF-I to VN, whereas IGFBP-2 and glycosylated IGFBP-3 had a smaller effect. Furthermore, binding studies with analogs indicate that glycosylation status and the heparin-binding domain of IGFBP-3 are important in this interaction. To examine the functional significance of IGFs binding to VN, cell migration in MCF7 cells was measured and found to be enhanced when VN was prebound to IGF-I in the presence of IGFBP-5. The effect required IGF:IGFBP:VN complex formation; this was demonstrated by use of a non-IGFBP-binding IGF-I analog. Together, these data indicate the importance of IGFBPs in modulating IGF-I binding to VN and that this binding has functional consequences in cells.
Regulation of Niemann-Pick C1 Gene Expression by the 3′5′-Cyclic Adenosine Monophosphate Pathway in Steroidogenic Cells
Authors: Gévry Nicolas Y. , Lalli Enzo , Sassone-Corsi Paolo , Murphy Bruce D.
Published: March 2003

The Niemann Pick-C1 (NPC-1) protein is essential for intracellular transport of cholesterol derived from low-density lipoprotein import in mammalian cells. The role of the protein kinase A (PKA) pathway in regulation of expression of the NPC-1 gene was investigated. NPC-1 promoter activity was induced by treatment with dibutryl cAMP (dbcAMP), alone or in combination with the cAMP response element (CRE) binding protein (CREB) overexpressed in adrenal Y-1 cells. When the catalytic subunit of PKA was overexpressed in Y-1 cells, there were similar increases in NPC-1 promoter activity in the presence of CREB. Responses were attenuated by blockade of the PKA pathway, and in the Kin-8 cell line deficient in PKA. Promoter deletion analysis revealed that this response was present in promoter fragments of 186 bp and larger but not present in the 121-bp fragment. Two promoter regions, one at −430 and one at −120 upstream of the translation initiation site, contained CRE consensus sequences. These bound recombinant CREB in EMSA, confirming their authenticity as CREB response elements. Promoters bearing mutations of both CRE displayed no response to dbcAMP. The orphan nuclear receptor, steroidogenic factor-1 (SF-1), was implicated in NPC-1 transactivation by the presence of SF-1 target sequence that formed a complex with recombinant SF-1 in EMSA. Furthermore, transfection of a plasmid that overexpressed SF-1 into ovarian granulosa cells increased promoter activity in response to dbcAMP, an effect abrogated by mutation of the SF-1 target sequence. Chromatin immunoprecipitation assays demonstrated that the CRE region of the endogenous and transfected NPC-1 promoter associated with both acetylated and phosphorylated histone H-3 and that this association was increased by dbcAMP treatment. Treatment with dbcAMP also increased the association of the CRE region of the promoter with CREB binding protein, which has histone acetyltransferase activity. Together, these results demonstrate a mechanism of regulation of NPC-1 expression by the cAMP-PKA pathway that includes PKA phosphorylation of CREB, recruitment of the coactivator CREB binding protein and the phosphorylation and acetylation of histone H-3 to transactivate the NPC-1 promoter.
Gene Expression Profiling Reveals Progesterone-Mediated Cell Cycle and Immunoregulatory Roles of Hoxa-10 in the Preimplantation Uterus
Authors: Yao Mylene W. M. , Lim Hyunjung , Schust Daniel J. , Choe Sung E. , Farago Anna , Ding Yueyun , Michaud Sebastien , Church George M. , Maas Richard L.
Published: March 2003

Human infertility and recurrent pregnancy loss caused by implantation defects are poorly understood. Hoxa-10-deficient female mice have severe infertility and recurrent pregnancy loss due to defective uterine implantation. Gene expression profiling experiments reveal that Hoxa-10 is an important regulator of two critical events in implantation: stromal cell proliferation and local immunosuppression. At the time of implantation, Hoxa-10 mediates the progesterone-stimulated proliferation of uterine stromal cells. Hoxa-10 mutants express a stromal cell proliferation defect that is accompanied by quantitative or spatial alterations in the expression of two cyclin-dependent kinase inhibitor genes, p57 and p15. Hoxa-10 deficiencyFS also leads to a severe local immunological disturbance, characterized by a polyclonal proliferation of T cells, that occurs in place of the normal progesterone-mediated immunosuppression in the periimplantation uterus.
Dax-1 (Dosage-Sensitive Sex Reversal-Adrenal Hypoplasia Congenita Critical Region on the X Chromosome, Gene 1) Gene Transcription Is Regulated by Wnt4 in the Female Developing Gonad
Authors: Mizusaki Hirofumi , Kawabe Ken , Mukai Tokuo , Ariyoshi Etsuko , Kasahara Megumi , Yoshioka Hidefumi , Swain Amanda , Morohashi Ken-ichirou
Published: March 2003

Dax-1 [dosage-sensitive sex reversal-adrenal hypoplasia congenita critical region on the X chromosome, gene 1 (NR0B1)] is an orphan nuclear receptor acting as a suppressor of Ad4 binding protein/steroidogenic factor 1 [Ad4BP/SF-1 (NR5A1)] and as an anti-Sry factor in the process of gonadal sex differentiation. The roles of these nuclear receptors in the differentiation of the gonads and the adrenal cortex have been established through studies of the mutant phenotype in both mice and humans. However, the mechanisms underlying transcriptional regulation of these genes remain largely unknown. Here, we examined the relationship between Dax-1 gene transcription and the Wnt4 pathway. Reporter gene analysis revealed that Dax-1 gene transcription was activated by β-catenin, a key signal-transducing protein in the Wnt pathway, acting in synergy with Ad4BP/SF-1. Interaction between β-catenin and Ad4BP/SF-1 was observed using yeast two-hybrid and in vitro pull-down assays. The region of Ad4BP/SF-1 essential for this interaction consists of an acidic amino acid cluster, which resides in the first helix of the ligand-binding domain. Mutation of the amino acid cluster impaired transcriptional activation of Dax-1 as well as interaction of Ad4BP/SF-1 with β-catenin. These results were supported by in vivo observations using Wnt4 gene-disrupted mice, in which Dax-1 gene expression was decreased significantly in sexually differentiating female gonads. We thus conclude that Wnt4 signaling mediates the increased expression of Dax-1 as the ovary becomes sexually differentiated.
Short-Term Plasticity of Cyclic Adenosine 3′,5′-Monophosphate Signaling in Anterior Pituitary Corticotrope Cells: The Role of Adenylyl Cyclase Isotypes
Authors: Antoni Ferenc A. , Sosunov Alexander A. , Haunsø Anders , Paterson Janice M. , Simpson James
Published: March 2003

Anterior pituitary corticotropes show a wide repertory of responses to hypothalamic neuropeptides and adrenal corticosteroids. The hypothesis that plasticity of the cAMP signaling system underlies this adaptive versatility was investigated. In dispersed rat anterior pituitary cells, depletion of intracellular Ca2+ stores with thapsigargin combined with ryanodine or caffeine enhanced the corticotropin releasing-factor (CRF)-evoked cAMP response by 4-fold, whereas reduction of Ca2+ entry alone had no effect. CRF-induced cAMP was amplified 15-fold by arginine-vasopressin (AVP) or phorbol-dibutyrate ester. In the presence of inhibitors of cyclic nucleotide phosphodiesterases and phorbol-dibutyrate ester, the depletion of Ca2+ stores had no further effect on CRF-induced cAMP accumulation. Adenohypophysial expression of mRNAs for the Ca2+-inhibited adenylyl cyclases (ACs) VI and IX, and the protein kinase C-stimulated ACs II and VII was demonstrated. ACIX was detected in corticotropes by immunocytochemistry, whereas ACII and ACVI were not present. The data show negative feedback regulation of CRF-induced cAMP levels by Ca2+ derived from ryanodine receptor-operated intracellular stores. Stimulation of protein kinase C by AVP enhances Ca2+-independent cAMP synthesis, thus changing the characteristics of intracellular Ca2+ feedback. It is proposed that the modulation of intracellular Ca2+ feedback in corticotropes by AVP is an important element of physiological control.
Mitogen-Activated Protein Kinase Regulates Nuclear Association of Human Progesterone Receptors
Authors: Qiu Ming , Olsen Abby , Faivre Emily , Horwitz Kathryn B. , Lange Carol A.
Published: March 2003

Breast cancers often have increased MAPK activity; this pathway may drive breast cancer cell growth by targeting steroid hormone receptors. MAPK phosphorylates human progesterone receptors (PRs) on Ser294, thus regulating several aspects of PR activity. To study the role of PR Ser294 phosphorylation on subcellular distribution, we stably expressed wild-type (wt) or S294A (Ser294 to Ala) PR-B in several cell types. PRs phosphorylated on Ser294 were nuclear. Activation of MAPK induced Ser294 phosphorylation and rapid nuclear translocation of wt, but not S294A, PR-B; both receptors concentrated in the nucleus after progestin treatment. The MAPK kinase inhibitor, U0126, blocked epidermal growth factor but not progestin-induced Ser294 phosphorylation and translocation of wt PR, indicating a novel mechanism for nuclear localization. After progestin treatment, wt PR-B underwent ligand-dependent down-regulation, while S294A PR-B persisted in nuclei. Prolonged treatment with U0126 or the nuclear export inhibitor, leptomycin B, promoted nuclear accumulation of wt PR-B and blocked ligand-dependent PR down-regulation, suggesting that PR degradation occurs in the cytoplasm and requires MAPK-dependent nuclear export. Stabilization of PRs by leptomycin B also blocked PR transcriptional activity, indicating a link between nucleocytoplasmic shuttling, receptor stability, and function. These results support a regulatory role for MAPK in nuclear steroid hormone receptor subcellular localization and coupling to multiple PR functions.
Liver X Receptors Interact with Corepressors to Regulate Gene Expression
Authors: Hu Xiao , Li Suzhen , Wu Jun , Xia Chunsheng , Lala Deepak S.
Published: April 2003

Liver X receptors (LXRs) are members of the nuclear receptor superfamily that regulate gene expression in response to oxysterols and play a critical role in cholesterol homeostasis by regulating genes that are involved in cholesterol transport, catabolism, and triglyceride synthesis. Oxysterols and synthetic agonists bind LXRs and activate transcription by recruiting coactivator proteins. The role of LXRs in regulating target gene expression in the absence of ligand is unknown. Here we show that LXRs interact with corepressors, N-CoR (nuclear receptor corepressor) and SMRT (silent mediator of retinoic acid receptor and thyroid receptor), which are released upon binding agonists. The LXR-corepressor interaction is isoform selective, wherein LXRα has a very strong interaction with corepressors and LXRβ only shows weak interaction. LXRs also exhibit a preference for interacting with N-CoR vs. SMRT. Similar to other nuclear receptors, mutations in the LXR helix 3 and 4 region abolish corepressor interaction. Using a transient transfection assay, we demonstrate that LXR represses transcription that can be further increased by cotransfecting N-CoR into cells. Chromatin immunoprecipitation experiments further indicated that N-CoR is recruited onto endogenous LXR target genes, and addition of LXR agonists releases N-CoR from their promoters. Collectively, these results suggest that corepressors play an important role in regulating LXR target gene expression.
Functional Cooperation between Multiple Regulatory Elements in the Untranslated Exon 1 Stimulates the Basal Transcription of the Human GnRH-II Gene
Authors: Cheng Chi Keung , Hoo Ruby L. C. , Chow Billy K. C. , Leung Peter C. K.
Published: April 2003

The wide distribution of GnRH-II and conservation of its structure over all vertebrate classes suggest that the neuropeptide possesses vital biological functions. Although recent studies have shown that the expression of the human GnRH-II gene is regulated by cAMP and estrogen, the molecular mechanisms governing its basal transcription remain poorly understood. Using the neuronal TE-671 and placental JEG-3 cells, we showed that the minimal human GnRH-II promoter was located between nucleotide −1124 and −750 (relative to the translation start codon) and that the untranslated exon 1 was important to produce full promoter activity. Two putative E-box binding sites and one Ets-like element were identified within the first exon, and mutational analysis demonstrated that these cis-acting elements functioned cooperatively to stimulate the human GnRH-II gene transcription. EMSAs, UV cross-linking, and Southwestern blot analyses indicated that the basic helix-loop-helix transcription factor AP-4 bound specifically to the two E-box binding sites, whereas an unidentified protein bound to the Ets-like element. The functional importance of AP-4 in controlling human GnRH-II gene transcription was demonstrated by overexpression of sense and antisense full-length AP-4 cDNAs. Taken together, our present data demonstrate a novel mechanism in stimulating basal human GnRH-II gene transcription mediated by cooperative actions of multiple regulatory elements within the untranslated first exon of the gene.
Neuroglian activates Echinoid to antagonize theDrosophilaEGF receptor signaling pathway
Authors: Islam Rafique , Wei Shu-Yi , Chiu Wei-Hsin , Hortsch Michael , Hsu Jui-Chou
Published: March 2003

echinoid (ed) encodes an cell-adhesion molecule (CAM)that contains immunoglobulin domains and regulates the EGFR signaling pathway during Drosophila eye development. Based on our previous genetic mosaic and epistatic analysis, we proposed that Ed, via homotypic interactions, activates a novel, as yet unknown pathway that antagonizes EGFR signaling. In this report, we demonstrate that Ed functions as a homophilic adhesion molecule and also engages in a heterophilic trans-interaction with Drosophila Neuroglian (Nrg), an L1-type CAM. Co-expression of ed and nrg in the eye exhibits a strong genetic synergy in inhibiting EGFR signaling. This synergistic effect requires the intracellular domain of Ed, but not that of Nrg. In addition, Ed and Nrg colocalize in the Drosophila eye and are efficiently co-immunoprecipitated. Together,our results suggest a model in which Nrg acts as a heterophilic ligand and activator of Ed, which in turn antagonizes EGFR signaling.
Impaired cumulus mucification and female sterility in tumor necrosis factor-induced protein-6 deficient mice
Authors: Fülöp Csaba , Szántó Sándor , Mukhopadhyay Durba , Bárdos Tamás , Kamath Rajesh V. , Rugg Marylin S. , Day Anthony J. , Salustri Antonietta , Hascall Vincent C. , Glant Tibor T. , Mikecz Katalin
Published: March 2003

Mucification of the cumulus layer around the oocyte is an obligatory process for female fertility. Tumor necrosis factor-induced protein-6 (TNFIP6 or TSG6) has been shown to be specifically expressed during this process. We have generated TNFIP6-deficient mice and tested the ability of their cumulus cells to undergo mucification. Cumulus cell-oocyte complexes fail to expand in TNFIP6-deficient female mice because of the inability of the cumulus cells to assemble their hyaluronan-rich extracellular matrix. The impaired cumulus matrix formation is due to the lack of covalent complexes between hyaluronan and the heavy chains of the inter-α-trypsin inhibitor family. As a consequence, TNFIP6-deficient females are sterile. Cultured TNFIP6-deficient cumulus cell-oocyte complexes also fail to expand when stimulated with dibutyryl cyclic AMP or epidermal growth factor. Recombinant TNFIP6 is able to catalyze the covalent transfer of heavy chains to hyaluronan in a cell-free system, restore the expansion of Tnfip6-null cumulus cell-oocyte complexes in vitro, and rescue the fertility in Tnfip6-null females. These results provide clear evidence that TNFIP6 is a key catalyst in the formation of the cumulus extracellular matrix and indispensable for female fertility.
A novel role for retinoids in patterning the avian forebrain during presomite stages
Authors: Halilagic Aida , Zile Maija H. , Studer Michèle
Published: March 2003

Retinoids, and in particular retinoic acid (RA), are known to induce posterior fates in neural tissue. However, alterations in retinoid signalling dramatically affect anterior development. Previous reports have demonstrated a late role for retinoids in patterning craniofacial and forebrain structures,but an earlier role in anterior patterning is not well understood. We show that enzymes involved in synthesizing retinoids are expressed in the avian hypoblast and in tissues directly involved in head patterning, such as anterior definitive endoderm and prechordal mesendoderm. We found that in the vitamin A-deficient (VAD) quail model, which lacks biologically active RA from the first stages of development, anterior endodermal markers such as Bmp2,Bmp7, Hex and the Wnt antagonist crescent are affected during early gastrulation. Furthermore, prechordal mesendodermal and prospective ventral telencephalic markers are expanded posteriorly, Shhexpression in the axial mesoderm is reduced, and Bmp2 and Bmp7 are abnormally expressed in the ventral midline of the neural tube. At early somite stages, VAD embryos have increased cell death in ventral neuroectoderm and foregut endoderm, but normal cranial neural crest production, whereas at later stages extensive apoptosis occurs in head mesenchyme and ventral neuroectoderm. As a result, VAD embryos end up with a single and reduced telencephalic vesicle and an abnormally patterned diencephalon. Therefore, we propose that retinoids have a dual role in patterning the anterior forebrain during development. During early gastrulation, RA acts in anterior endodermal cells to modulate the anteroposterior (AP) positional identity of prechordal mesendodermal inductive signals to the overlying neuroectoderm. Later on, at neural pore closure, RA is required for patterning of the mesenchyme of the frontonasal process and the forebrain by modulating signalling molecules involved in craniofacial morphogenesis.
Netrin 1 mediates spinal cord oligodendrocyte precursor dispersal
Authors: Tsai Hui-Hsin , Tessier-Lavigne Marc , Miller Robert H.
Published: March 2003

In spinal cord, oligodendrocyte precursors that give rise to myelin-forming cells originate in a restricted domain of the ventral ventricular zone. During development, these cells migrate widely throughout the spinal cord. Netrin 1 is expressed at the ventral ventricular zone during oligodendrocyte precursors emigration, and, in vitro, netrin 1 acts as chemorepellent and antagonizes platelet-derived growth factor (PDGF) chemoattraction. Oligodendrocyte precursors express the netrin receptors DCC and UNC5 and function-blocking anti-DCC antibody inhibits chemorepulsion of ventral spinal cord explants and netrin-secreting cells. In spinal cord slice preparations, addition of function-blocking anti-DCC antibody or netrin 1 dramatically inhibits oligodendrocyte precursor migration from the ventral ventricular zone. These data indicate the initial dispersal of oligodendrocyte precursors from their localized origin is guided by a chemorepellent response to netrin 1.
Two suppressors ofsel-12encode C2H2zinc-finger proteins that regulate presenilin transcription inCaenorhabditis elegans
Authors: Lakowski Bernard , Eimer Stefan , Göbel Christine , Böttcher Andreas , Wagler Babett , Baumeister Ralf
Published: March 2003

Mutations in presenilin genes are associated with familial Alzheimer's disease in humans and affect LIN-12/Notch signaling in all organisms tested so far. Loss of sel-12 presenilin activity in Caenorhabditis elegans results in a completely penetrant egg-laying defect. In screens for extragenic suppressors of the sel-12 egg-laying defect, we have isolated mutations in at least five genes. We report the cloning and characterization of spr-3 and spr-4, which encode large basic C2H2 zinc-finger proteins. Suppression of sel-12 by spr-3 and spr-4 requires the activity of the second presenilin gene, hop-1. Mutations in both spr-3and spr-4 de-repress hop-1 transcription in the early larval stages when hop-1 expression is normally nearly undetectable. As sel-12 and hop-1 are functionally redundant, this suggests that mutations in spr-3 and spr-4 bypass the need for one presenilin by stage-specifically de-repressing the transcription of the other. Both spr-3 and spr-4 code for proteins similar to the human REST/NRSF (Re1 silencing transcription factor/neural-restrictive silencing factor) transcriptional repressors. As other Spr genes encode proteins homologous to components of the CoREST co-repressor complex that interacts with REST, and the INHAT (inhibitor of acetyltransferase) co-repressor complex, our data suggest that all Spr genes may function through the same mechanism that involves transcriptional repression of the hop-1locus.
Hoxb13is required for normal differentiation and secretory function of the ventral prostate
Authors: Economides Kyriakos D. , Capecchi Mario R.
Published: March 2003

The murine prostate is a structure that is made up of four distinct lobes;the dorsal and lateral prostates (often grouped together as the dorsolateral prostate), the anterior (coagulating gland) and the ventral prostate. Previous work has implicated Hox genes in the development of these structures,but how each lobe acquires unique identities for specific functions has not been addressed. In this study, the ventral prostate-specific function of Hoxb13 is described. Mice lacking Hoxb13 function show normal numbers of duct tips, but mice mutant for both Hoxb13 and Hoxd13exhibit severe hypoplasia of the duct tips, revealing a role for Hoxb13 in ventral prostate morphogenesis. Additionally, a ventral lobe-specific defect was identified in Hoxb13 mutants wherein the epithelium is composed of simple cuboidal cells rather than of tall columnar cells. Ventral prostate ducts appear devoid of contents and do not express the ventral prostate-specific secretory proteins p12, a kazal-type protease inhibitor and p25, a spermine binding protein. These defects are not due to reduction of Nkx3.1 expression or to a global effect on androgen receptor signaling. These results suggest a specific role for Hoxb13in a differentiation pathway that gives the ventral prostate epithelium a unique identity, as well as a more general role in ventral prostate morphogenesis that is redundant with other Hox13 paralogs.
GDNF availability determines enteric neuron number by controlling precursor proliferation
Authors: Gianino Scott , Grider John R. , Cresswell Jennifer , Enomoto Hideki , Heuckeroth Robert O.
Published: March 2003

To clarify the role of Ret signaling components in enteric nervous system(ENS) development, we evaluated ENS anatomy and intestinal contractility in mice heterozygous for Ret, GFRα1 and Ret ligands. These analyses demonstrate that glial cell line-derived neurotrophic factor (GDNF) and neurturin are important for different aspects of ENS development. Neurturin is essential for maintaining the size of mature enteric neurons and the extent of neuronal projections, but does not influence enteric neuron number. GDNF availability determines enteric neuron number by controlling ENS precursor proliferation. However, we were unable to find evidence of programmed cell death in the wild type ENS by immunohistochemistry for activated caspase 3. In addition, enteric neuron number is normal in Bax–/– and Bid–/– mice, suggesting that, in contrast to most of the rest of the nervous system, programmed cell death is not important for determining enteric neuron numbers. Only mild reductions in neuron size and neuronal fiber counts occur in Ret+/– and Gfra1+/– mice. All of these heterozygous mice,however, have striking problems with intestinal contractility and neurotransmitter release, demonstrating that Ret signaling is critical for both ENS structure and function.
Role of glypican 4 in the regulation of convergent extension movements during gastrulation inXenopus laevis
Authors: Ohkawara Bisei , Yamamoto Takamasa S. , Tada Masazumi , Ueno Naoto
Published: March 2003

Coordinated morphogenetic cell movements during gastrulation are crucial for establishing embryonic axes in animals. Most recently, the non-canonical Wnt signaling cascade (PCP pathway) has been shown to regulate convergent extension movements in Xenopus and zebrafish. Heparan sulfate proteoglycans (HSPGs) are known as modulators of intercellular signaling, and are required for gastrulation movements in vertebrates. However, the function of HSPGs is poorly understood. We analyze the function of Xenopusglypican 4 (Xgly4), which is a member of membrane-associated HSPG family. In situ hybridization revealed that Xgly4 is expressed in the dorsal mesoderm and ectoderm during gastrulation. Reducing the levels of Xgly4 inhibits cell-membrane accumulation of Dishevelled (Dsh), which is a transducer of the Wnt signaling cascade, and thereby disturbs cell movements during gastrulation. Rescue analysis with different Dsh mutants and Wnt11 demonstrated that Xgly4 functions in the non-canonical Wnt/PCP pathway, but not in the canonical Wnt/β-catenin pathway, to regulate gastrulation movements. We also provide evidence that the Xgly4 protein physically binds Wnt ligands. Therefore, our results suggest that Xgly4 functions as positive regulator in non-canonical Wnt/PCP signaling during gastrulation.
Isolation ofCOV1, a gene involved in the regulation of vascular patterning in the stem ofArabidopsis
Authors: Parker Garry , Schofield Rebecca , Sundberg Björn , Turner Simon
Published: March 2003

The molecular mechanisms that control the ordered patterning of vascular tissue development in plants are not well understood. Several models propose a two-component system for vascular differentiation. These components include an inducer of vascular tissue development and an inhibitor that prevents the formation of vascular bundles near pre-existing bundles. We have identified two recessive allelic mutants in Arabidopsis, designated continuous vascular ring (cov1), that display a dramatic increase in vascular tissue development in the stem in place of the interfascicular region that normally separates the vascular bundles. The mutant plants exhibited relatively normal vascular patterning in leaves and cotyledons. Analysis of the interaction of cov1 with a known auxin signalling mutant and direct analysis of auxin concentrations suggests that cov1 affects vascular pattering by some mechanism that is independent of auxin. The COV1 protein is predicted to be an integral membrane protein of unknown function, highly conserved between plants and bacteria. In plants, COV1 is likely to be involved in a mechanism that negatively regulates the differentiation of vascular tissue in the stem.
Notch activates sonic hedgehog and both are involved in the specification of dorsal midline cell-fates inXenopus
Authors: López Silvia L. , Paganelli Alejandra R. , Siri María V. Rosato , Ocaña Oscar H. , Franco Paula G. , Carrasco Andrés E.
Published: March 2003

We analysed the role of Notch signalling during the specification of the dorsal midline in Xenopus embryos. By activating or blocking the pathway we found that Notch expands the floor plate domain of sonic hedgehog and pintallavis and represses the notochordal markers chordin and brachyury, with a concomitant reduction of the notochord size. We propose that within a population of the early organiser with equivalent potential to develop either as notochord or floor plate, Notch activation favours floor plate development at the expense of the notochord,preferentially before mid gastrula. We present evidence that sonic hedgehog down-regulates chordin, suggesting that secreted Sonic hedgehog may be involved or reinforcing the cell-fate switch executed by Notch. We also show that Notch signalling requires Presenilin to modulate this switch.
Controlled Evaporation as an Easy Method of Constructing Novel Nano Objects from Amphiphilic Diblock Molecules
Authors: Qin Lidong , Li Hongbo , Wu Lixin , Qiu Dengli , Zhang Xi , Shen Jiacong
Published: March 2003

Novel nano “island” and “ribbon” morphologies could be fabricated just by changing the air-substrate interface of cast films during evaporation. Speeding up or slowing down evaporation of cast films 100-fold allowed diblock molecules containing oligo (phenylene vinylene) dimer as the rod segment and poly (ethylene oxide) as the coil segment to form two different self-assembled nano objects on mica: “islands” and “ribbons,” respectively.
GHz Range Absorption Properties of α-Fe/Y2O3 Nanocomposites Prepared by Melt-spun Technique
Authors: Liu Jiu Rong , Itoh Masahiro , Machida Ken-ichi
Published: March 2003

Nanocomposite materials of α-Fe/Y2O3 prepared by melt-spun technique exhibited good electromagnetic wave absorption properties (RL<−20 dB) in a 2.0-3.5 GHz range as absorbers with thickness ranging from 3 to 5 mm, and a minimum reflection loss of −36 dB was obtained at 2.6 GHz with an absorber thickness of 4 mm.
Synthesis and Facile Rearrangement of 10,10-Dicarbonyl-substituted [4.3.1]Propellane Derivatives
Authors: Tobe Yoshito , Kusumoto Takuji , Minakata Shiho , Umeda Rui , Sonoda Motohiro , Naemura Koichiro
Published: March 2003

While an attempt to prepare 10,10-diformyl[4.3.1]propella-1,4-diene was not successful owing to its facial skeletal rearrangement, the corresponding diacetyl derivative was isolated, which would serve as a useful precursor of carbene sources.
Direct Detection of Horseradish Peroxidase as a Marker Molecule Encapsulated in Liposomes via Use of Fluorescein Chemiluminescence
Authors: Kamidate Tamio , Ishida Yoshiki , Tani Hirofumi , Ishida Akihiko
Published: March 2003

A method for direct detection of horseradish peroxidase (HRP) as a marker molecule trapped in liposomes by the use of HRP-catalyzed fluorescein chemiluminescence (CL) with hydrogen peroxide has been developed. Maximum CL emission in the direct detection of HRP in liposomes increased by a factor of 13 times compared with that in the detection of HRP dissolved in lipid-free buffer solution.
Preparation and Characterization of Hydroxo-zinc(II) Complex Surrounded with Hydrogen Bonding and Hydrophobic Interaction Groups. A Structural/Functional Model of Carbonic Anhydrases
Authors: Yamaguchi Syuhei , Tokairin Isao , Wakita Yoko , Funahashi Yasuhiro , Jitsukawa Koichiro , Masuda Hideki
Published: March 2003

A novel Zn(II)–OH complex surrounded with hydrogen bonding and hydrophobic interaction groups has been prepared as a structural/functional model of carbonic anhydrases, and characterized by X-ray structure analysis and ESIMS and 1H- and 13C-NMR spectroscopies. The complex has been found to exhibit a reversible binding of CO2.
IR Observation of Hydrogen Adsorption on Active and Inactive Pt/SO42−–ZrO2
Authors: Wang Ping , Yang Shuwu , Kondo Junko N , Domen Kazunari , Yamada Takashi , Hattori Hideshi
Published: March 2003

The formation of H2O and OH groups on an active Pt/SO42−–ZrO2 (Pt/SZ) catalyst was observed upon hydrogen adsorption at 523 K, whereas only OH groups were formed on an inactive Pt/SZ catalyst.
[2.0.2.0]Metacyclophane-1,15-diynes. A Potential Fragment of Double-Helical Conjugated Systems
Authors: Utsumi Keiichiro , Kawase Takeshi , Oda Masaji
Published: March 2003

The title cyclophanes as a potential fragment of double-helical π-conjugated system were synthesized, and the spectroscopic and crystallographic characterization shows the strained nature of the π-system; variable-temperature NMR spectra also reveal that the cyclophanes exist as an equilibrium mixture between the meso- and dl-forms in solution.
Mountain waves over the Hohe Tauern: Influence of upstream diabatic effects
Authors: Doyle James D. , Smith Ronald B.
Published: March 2003

The structure and intensity of large‐amplitude trapped lee waves over the Hohe Tauern range of the Alps on 20 September 1999 are investigated through the analysis of in situ aircraft observations, airborne lidar, Global Positioning System dropsondes, rapid‐scan satellite imagery, and a suite of linear and nonlinear model simulations. Observations indicate that the lee waves attained a maximum vertical velocity of more than 9 m s−1, potential‐temperature perturbations greater than 10 K, and a horizontal wavelength of approximately 12–15 km. High‐resolution nonlinear simulations accurately capture the trapped‐wave evolution and characteristics. Blocking of the southerly flow upstream of the Hohe Tauern decreases the depth of the layer that ascends the mountain crest, and modulates the wave response. Vertically propagating waves are partially ducted into a train of lee waves as a result of weak stability aloft, which forms due to diabatic processes associated with precipitation upstream of the Hohe Tauern crest. Linear analytic solutions confirm the importance of the weak‐stability layer in the upper‐troposphere for the development of the non‐hydrostatic evanescent waves. Results from idealized two‐dimensional nonlinear simulations suggest that the vertical depth of diabatic heating associated with the upstream precipitation is important. In this case, latent heating over a relatively shallow depth tunes the atmosphere for a nonlinear resonance that leads to strong descent in the lee and reinforcement of the lee waves. Copyright © 2003 Royal Meteorological Society.
Orographic precipitation and air mass transformation: An Alpine example
Authors: Smith Ronald B. , Jiang Qingfang , Fearon Matthew G. , Tabary Pierre , Dorninger Manfred , Doyle James D. , Benoit Robert
Published: March 2003

A case of orographic precipitation in the Alps on 20 September 1999 was studied using several models, along with rain‐gauge and radar data. The objective of the study is to describe the orographic transformation of an air mass, including multi‐scale aspects. Several new and some conventional diagnostic quantities are estimated, including drying ratio, precipitation efficiency, buoyancy work, condensed‐water residence time, parcel changes in heat, moisture and altitude, and dominant space‐ and time‐scales.

For the case considered, the drying ratio was about 35%. Precipitation efficiency values are ambiguous due to repeated ascent and descent over small‐scale terrain. The sign of buoyancy work changed during the event, indicating a shift from stratiform orographic to weak convective clouds. Cloud‐water residence times are different for the two mesoscale models (400 compared to 1000 s) due to different cloud–physical formulations. The two mesoscale models agree that the dominant spatial‐scale of lifting and precipitation is about 10 km; smaller than the scale of the main Alpine massif. Trajectory analysis of air crossing the Alps casts doubt on the classic model of föhn. Few parcels exhibit classic pattern of moist ascent followed by dry descent. Parcels that gain latent heat descend only briefly, before rising into the middle troposphere. Parcels that descend along the lee slope, originate in the middle troposphere and gain little, or even lose, latent heat during the transit. As parcels seek their proper buoyancy level downstream, a surprising scrambling of the air mass occurs.

Radar data confirm the model prediction that the rainfall field is tightly controlled by local terrain on scales as small as 10 km, rather than the full 100 km cross‐Alpine scale. A curious pulsing of the precipitation is seen, indicating either drifting moisture anomalies or weak convection. Copyright © 2003 Royal Meteorological Society.
The convective storm system during IOP 2a of MAP: Cloud‐to‐ground lightning flash production in relation to dynamics and microphysics
Authors: Seity Y. , Soula S. , Tabary P. , Scialom G.
Published: March 2003

This paper presents a study about correlation between cloud‐to‐ground lightning flash (CG) activity, and the dynamics and microphysics of thunderclouds. Data collected during Intense Observation Period (MAP IOP) 2a of the Mesoscale Alpine Programme Special Observing Period (SOP) over the Lago Maggiore Target Area (LMTA) in northern Italy are used. IOP 2a was the most electrically active period during the SOP, representing 75% of the total CG activity. Thunderclouds were strongly vertically developed (the 30 dBZ echo tops were sometimes higher than 12 km) and produced large amounts of rainfall and some hail. Doppler and polarimetric radar data allow us to retrieve the three‐dimensional wind and radar‐reflectivity fields from two synchronous Doppler radars, and particle‐type fields in the thunderclouds from the S‐Pol polarimetric radar. Both polarities of CGs are distinguished. Temporal and spatial relationships from the global activity over the LMTA are first studied. Then, the temporal correlation between CG rates and dynamics or microphysics for five individual cells is considered. A very strong correlation is observed between CG and the presence of a mixture of graupel and hail, which strongly supports a non‐inductive charging mechanism. CG impacts seem to be located underneath large radar‐reflectivity values and around the maximum vertical velocities. Two individual cells are studied in more detail, in order to better understand their different electrical behaviours: the first produced mainly negative CGs, and the second produced 61% positive CGs in the second phase of its lifetime. The association of positive CGs with severe weather and especially with the presence of hail is observed. Copyright © 2003 Royal Meteorological Society.
The nature of the mistral: Observations and modelling of two MAP events
Authors: Jiang Qingfang , Smith Ronald B. , Doyle James
Published: March 2003

Two mistral events observed in 1999 during the Mesoscale Alpine Programme (MAP) are studied using observational data and high‐resolution mesoscale‐model simulations from the US Navy's Coupled Ocean Atmosphere Mesoscale Prediction System (COAMPS). Radiosondes suggested that both mistral wind events were associated with the passage of cold fronts and post‐frontal air descent. EuroSat Rapidscan images indicated a stationary and persistent cloud edge along the lee of the Massif Central. The cloud edge marks the beginning of mistral flow acceleration and descent according to COAMPS simulations. Narrow persistent cloud banners were identified trailing from the Mont Lozére in the Massif Central during both mistral events. COAMPS indicated that these cloud banners were associated with a deeper turbulent boundary layer in wakes induced by hydraulic jumps. The cloud banner and wake defined the western boundary of the mistral.

Analysis of dropsonde data and in situ flight data indicated the presence of a sharp shear line separating the cold severe mistral wind from the warm calm wake flow to the lee of the French Alps. Trajectory analysis of model data suggested that air parcels on the two sides of the shear line had different histories. Copyright © 2003 Royal Meteorological Society.
Coupled runoff simulations as validation tools for atmospheric models at the regional scale
Authors: Jasper Karsten , Kaufmann Pirmin
Published: March 2003

High‐resolution atmospheric forecasting systems are characterized by an increasing complexity which renders validation and interpretation of the model results more and more demanding. This is especially evident in complex terrain. In such areas, the limited density of meteorological observing stations does not allow an accurate evaluation of high‐resolution weather forecasts. Accordingly, advanced tools for the validation of atmospheric models are necessary and of great interest to forecasters. In this paper we address this issue, and present the possibilities and advantages offered by coupling atmospheric and hydrological models. A distributed hydrological model has been used to estimate the forecast quality of two different weather prediction models at different resolutions for the mesoscale Ticino–Verzasca–Maggia watershed, a high catchment located in the southern European Alps draining from the north into the Lago Maggiore. For this area, several hydrological forecast‐driven model experiments have been carried out as one‐way nested simulations using hourly time steps and 0.5 × 0.5 km grid resolution. The availability of meteorological forecast sequences allowed continuous atmospheric– hydrological simulations covering non‐overlapping periods of 3.5 years and 2.5 months. The model results have been analysed using multiple comparisons including rainfall and runoff measurements, as well as observation‐driven model results of river runoff and water balances at the catchment‐scale. It is shown that the hydrological model is sufficiently sensitive to provide substantial information for the validation of atmospheric models. Copyright © 2003 Royal Meteorological Society.
Analysis and simulation of local and regional conditions for the rainfall over the Lago Maggiore Target Area during MAP IOP 2b
Authors: Asencio N. , Stein J. , Chong M. , Gheusi F.
Published: March 2003

The Mesoscale Alpine Programme (MAP) operational and research network collected a large variety of measurements during the two days of Intensive Observing Period (IOP) 2b (19 and 20 September 1999), which is one of the most intense rainfall episodes during the Special Observing Period over the Lago Maggiore area. The synoptic situation is a typical one of a southerly flow and associated convection over Alpine orography. Simulations with the non‐hydrostatic Meso‐NH model are used to describe the rainfall conditions and are successfully validated at the different scales allowed by the MAP data. The two types of pre‐frontal orographically triggered convective episodes are described: (1) Sporadic and shallow convection occurs over the coastal mountains and propagates over the Po Valley. The chronology and the intensity of these convective episodes are driven by two main features: the low‐level humidity anomalies and the middle‐troposphere dry anomaly present over the Mediterranean Sea. (2) The Lago Maggiore orographic convection has a very long duration and is mainly controlled by both the intensity of the easterly low‐level wind in the north part of the Po Valley and the upper‐level clouds of the cold front. The different origins of the air masses transported by this easterly barrier wind and the associated local circulations are detailed. Copyright © 2003 Royal Meteorological Society.
A comparison of ground‐based Doppler lidar and airborne in situ wind observations above complex terrain
Authors: Durran Dale R. , Maric Tomislav , Banta Robert M. , Darby Lisa S. , Hardesty R. Michael
Published: March 2003

Airborne wind observations collected by the National Oceanic and Atmospheric Administration's (NOAA) WP‐3D aircraft are compared with the winds retrieved by the NOAA/Environmental Technology Laboratory's ground‐based scanning Doppler lidar within the Wipp Valley during the Special Observing Period of the Mesoscale Alpine Programme. Comparisons are performed along individual flight tracks and over an aggregated dataset consisting of all pairs of WP‐3D and lidar observations that were approximately coincident in time and space. The impact of several different quality‐control thresholds on the root mean square (r.m.s.) difference between the two observations is explored. The overall quality‐controlled r.m.s. difference between radial wind speeds measured by each platform was 3.0 m s−1, with larger r.m.s. errors in the region up valley from the lidar than in the region down valley. A bias was also evident, in which the wind speeds from the WP‐3D exceeded those from the lidar; this bias was small down valley (0.4 m s−1) and much larger up valley (2.4 m s−1). Copyright © 2003 Royal Meteorological Society.
Determination of airflow across the Alpine ridge by a combination of airborne Doppler lidar, routine radiosounding and numerical simulation
Authors: Reitebuch Oliver , Volkert Hans , Werner Christian , Dabas Alain , Delville Patricia , Drobinski Philippe , Flamant Pierre H. , Richard Evelyne
Published: March 2003

The Wind Infrared Doppler lidar (WIND) instrument was flown on board the aircraft Falcon of the Deutsches Zentrum für Luft‐ und Raumfahrt on two missions during the Special Observing Period (SOP) of the Mesoscale Alpine Programme (MAP). During the first flight two complete sections of horizontal wind speed and direction were sampled up to a height of 7 km from Innsbruck to the Po basin and back. From the second mission 11 WIND soundings from 11 km downwards are presented along a route from a jet stream of up to 45 m s−1 above Berlin towards the Alps. A routine radiosounding from Milano and episode‐type simulations with the Meso‐NH modelling system are used for detailed comparisons and to obtain comparative statistics. Copyright © 2003 Royal Meteorological Society.