BookOfAbstracts_ICMFM-XIX Page 183.pdf (original) (raw)
Related papers
Optimal investments with convex–concave revenue: a focus-node distinction
Optimal Control Applications and Methods, 2004
This paper considers a capital accumulation model in which revenue is a convex-concave function of the capital stock. While for certain capital values increasing returns to scale are reasonable, usually this property does not hold in general. In particular for large capital stock values the situation usually changes to decreasing returns to scale because it becomes increasingly di¢cult and thus expensive to produce more and more because of limitations of resources or infrastructure, lack of trained personnel in the region etc. We give a complete classi…cation under which parameter constellations a saddle point equilibrium is optimal, under which parameter constellations it is optimal to close down by choosing zero investment and when history dependent equilibria occur. In the last scenario we distinguish between di¤erent types of the unstable equilibrium, which can each have their own implication for the …rm's investment policy.
Proteomics of Arabidopsis seed germination and priming
The biology of seeds: recent research advances. Proceedings of the Seventh International Workshop on Seeds, Salamanca, Spain, 2002, 2003
Under optimal conditions (25°C), dry mature Arabidopsis seeds (ecotype Landsberg erecta) started to germinate at 1.6 d of imbibition and it took almost 2.2 d for 50% of the seeds to germinate (T 50 ) on water. Proteins were extracted from various seed samples (dry mature seeds, 1d-and 2-d-imbibed seeds, corresponding to germination sensu stricto and radicle protrusion, respectively), and analyzed by two-dimensional (2-D) gel electrophoresis as described (Gallardo et al., 2002b). A comparison of 2-D gels for the various protein extracts allowed classifying seed proteins from their specific accumulation patterns ).
Murine Cerberus Homologue mCer-1: A Candidate Anterior Patterning Molecule
Developmental Biology, 1998
Xenopus cerberus (Xcer) is a cytokine expressed in anterior mesendoderm overlapping and surrounding Spemann's gastrula organiser. When misexpressed in blastomeres, Xcer can induce ectopic heads with well-defined brain, cement gland, olfactory placodes, cyclopic eye, and occasionally liver and heart. We report here the identification of mCer-1, a murine gene related to cerberus. Both mCer-1 and Xcer appear to belong to the cystine knot superfamily, which includes TGFbs and BMPs. In Xenopus animal cap assays, mCer-1 and Xcer induced cement glands and markers of anterior neural tissue and endoderm, characteristic of BMP inhibition. Furthermore, both antagonised the ventrolateral mesoderm-inducing activity of coexpressed BMP4. In mouse embryos, mCer-1 was expressed at early gastrulation in a stripe of primitive endoderm along the future anterior side of the egg cylinder, a region essential for anterior patterning. A second phase of expression was detected in anterior embryonic mesendoderm, and by late-streak stages most of the anterior half of the embryo was positive, except for the node and cardiac progenitors. Expression was later seen in the cranial portion of the two most-recently formed somites and in two stripes within presomitic mesoderm. In embryos lacking Otx2, a homeogene with a demonstrated role in anterior patterning, mCer-1 was still expressed in an anterior zone, although often abnormally. The data suggest that mCer-1 shares structural, functional, and expression characteristics with Xcer and may participate in patterning the anterior of the embryo and nascent somite region, in part, through a BMP-inhibitory mechanism. ᭧
Corporate Investment, Irreversibilities and Lumpiness: An Empirical Model
2008
We study the role of irreversibility and non convexities in …rm investment decisions. For such purpose, we posit a dynamic structural investment model with irreversibility and nonconvex adjustment costs. We focus on the …rm decision about whether to invest or not, which is characterized by means of a discrete choice dynamic programming problem. The adjustment cost parameters behind the investment decision are estimated with a longitudinal sample of Spanish manufacturing …rms between 1990 and 2002. For these …rms, we con-…rm that inaction and investment episodes account for a signi…cant fraction of them. As estimation procedure, we apply the Nested Pseudo-Likelihood (NPL) algorithm by .
Developmental Biology, 1999
The zinc finger transcription factors Spalt and Spalt-related have been implicated in multiple developmental processes. In the wing they are regulated by the secreted protein Decapentaplegic and participate in the positioning of the wing veins. The function of Spalt has been also analyzed during tracheal development and embryonic segmentation. Here, we present the isolation and characterization of novel spalt/spalt-related alleles, which analysis indicates that these genes cannot substitute for each other in the developmental processes studied. The mutants present embryonic or pupal lethality, with phenotypes consistent with the loss of spalt function. We also present a detailed functional analysis of the DNA regions implicated in the regulation of these genes. This regulation is complex, integrating the information from both negative and positive regulators, and it is modular, with discrete fragments of DNA directing expression to discrete regions in embryonic and larval tissues.
Nuclear hormone receptor antagonism with AP1 by inhibition of the JNK pathway
Genes & Development, 1997
The activity of c-Jun, the major component of the transcription factor AP-1, is potentiated by amino-terminal phosphorylation on serines 63 and 73 (Ser-63/73). This phosphorylation is mediated by the Jun amino-terminal kinase (JNK) and required to recruit the transcriptional coactivator CREB-binding protein (CBP). AP-1 function is antagonized by activated members of the steroid/thyroid hormone receptor superfamily. Recently, a competition for CBP has been proposed as a mechanism for this antagonism. Here we present evidence that hormone-activated nuclear receptors prevent c-Jun phosphorylation on Ser-63/73 and, consequently, AP-1 activation, by blocking the induction of the JNK signaling cascade. Consistently, nuclear receptors also antagonize other JNK-activated transcription factors such as Elk-1 and ATF-2. Interference with the JNK signaling pathway represents a novel mechanism by which nuclear hormone receptors antagonize AP-1. This mechanism is based on the blockade of the AP-1 activation step, which is a requisite to interact with CBP. In addition to acting directly on gene transcription, regulation of the JNK cascade activity constitutes an alternative mode whereby steroids and retinoids may control cell fate and conduct their pharmacological actions as immunosupressive, anti-inflammatory, and antineoplastic agents.
Developmental Biology, 1997
the gene is under the control of a tissue-specific promoter/enhancer. To investigate whether it is possible to generate transgenic zebrafish which reliably express a reporter gene in specific tissues, we have isolated a zebrafish muscle-specific actin (a-actin) promoter and generated transgenic zebrafish in which the green fluorescent protein (GFP) reporter gene was driven by this promoter. In total, 41 GFP-expressing transgenic lines were generated with a frequency of as high as 21% (41 of 194), and GFP was specifically expressed throughout muscle cells in virtually all of the lines (40 of 41). Nonexpressing transgenic lines were rare. This demonstrates that a tissue-specific promoter can reliably drive reporter gene expression in transgenic zebrafish in a manner identical to the control of the endogeneous expression of the gene. Levels of GFP expression varied greatly from line to line; i.e., fluorescence was very weak in some lines, while it was extremely high in others. We also isolated a zebrafish cytoskeletal b-actin promoter and generated transgenic zebrafish using a b-actin-GFP construct. In all of the four lines generated, GFP was expressed throughout the body like the b-actin gene, demonstrating that consistent expression could also be achieved in this case. In the present study, we also examined the effects of factors which potentially affect the transgenic frequency or expression levels. The following results were obtained: (i) expression levels of GFP in the injected embryo were not strongly correlated to transgenic frequency; (ii) the effect of the NLS peptide (SV40 T antigen nuclear localization sequence), which has been suggested to facilitate the transfer of a transgene into embryonic nuclei, remained to be elusive; (iii) a plasmid vector sequence placed upstream of the construct might reduce the expression levels of the reporter gene. ᭧ 1997 Academic Press
Coalitions and networks in industrial organization
This paper provides a selective survey of recent approaches to coalition and network formation in Industrial Organization, and o¤ers a uni…ed framework in which the di¤erent approaches can be compared. We focus on two extreme forms of cooperation -collusive agreements and costreducing alliances. We show that bilateral negotiations yield higher levels of cooperation than multilateral agreements, that the formation of a cartel depends on the sequentiality of the procedure of coalition formation, and that the size of alliances depends on the membership rule. JEL Classi-…cation Number: D43, L13.
Suppression of SHP2 and ERK Signalling Promotes Self-Renewal of Mouse Embryonic Stem Cells
Developmental Biology, 1999
The propagation of pluripotent mouse embryonic stem (ES) cells depends on signals transduced through the cytokine receptor subunit gp130. Signalling molecules activated downstream of gp130 in ES cells include STAT3, the protein tyrosine phosphatase SHP-2, and the mitogen-activated protein kinases, ERK1 and ERK2. A chimaeric receptor in which tyrosine 118 in the gp130 cytoplasmic domain was mutated did not engage SHP-2 and failed to activate ERKs. However, this receptor did support ES cell self-renewal. In fact, stem cell colonies formed at 100-fold lower concentrations of cytokine than the unmodified receptor. Moreover, altered ES cell morphology and growth were observed at high cytokine concentrations. These indications of deregulated signalling in the absence of tyrosine 118 were substantiated by sustained activation of
Developmental Biology, 2001
srfA displays a complex temporal and cell type-specific pattern of expression in Dictyostelium and is expressed by most of its cell types at some stage of their development. This complexity is achieved by the use of alternative promoters. The promoter activity of the proximal region was found to be restricted to a subset of prestalk cells. Little or no associated expression was observed in the lower cup and basal disc during culmination. The middle promoter region was preferentially active in prestalk cells under usual conditions of filter development. Interestingly, during slug migration, the activity of this promoter in posterior prespore cells was strongly induced. The distal region displayed a dual pattern of expression. Thus, before culmination, this region drove lacZ expression in a few cells scattered along the entire structure. However, intense lacZ staining was found in the spores by the end of culmination. We have previously reported that srfA expression is essential for spore differentiation (R. Escalante and L. Sastre, Development 125, 3801-3808). Our novel finding of the expression of the gene in prestalk cells before culmination suggested that it might play additional roles in Dictyostelium development. The study of knockout strains revealed that srfA is also required for proper slug migration. Spore differentiation and slug migration defects were rescued by reexpression of srfA in the null mutant background, under the appropriate promoter control. The expression of srfA under the activity of the distal promoter region was able to rescue spore differentiation but not slug migration. Conversely, reexpression under the control of the middle promoter rescued slug morphogenesis and migration. Our results demonstrate that the correct spatial and temporal pattern of expression of srfA is essential for the different functions that this transcription factor plays in development.