A framework for the analysis of self-confirming policies.

This paper provides a general framework for analyzing self-confirming policies. We study self-confirming equilibria in recurrent decision problems with incomplete information about the true stochastic model. We characterize stationary monetary policies in a linear-quadratic setting.

Distinct roles for Distal-less genes Dlx3 and Dlx5 in regulating ectodermal development in Xenopus.

In vertebrates, there are six or more copies of genes related to the Drosophila pattern formation homeodomain gene Distal-less. Among this family, Dlx3 and Dlx5 share extensive sequence homology and have similar, but distinctive, expression patterns, suggesting that these two factors may have substantially redundant developmental functions. Here we show that at the earliest phases of embryogenesis in Xenopus, there are significant differences between Dlx3 and Dlx5 expression and that this correlates with different functions in the restriction of neural crest and neural plate boundaries, respectively.

The human gamma-globin TATA and CACCC elements have key, distinct roles in suppressing beta-globin gene expression in embryonic/fetal development.

The competition model of globin gene regulation states that the gamma-globin gene precludes expression of the beta-globin gene in early development by competing for the enhancing activity of the locus control region. The gamma-globin gene with a -161 promoter is sufficient for suppressing beta-globin gene expression, and the gamma-globin TATA and CACCC elements are necessary for this effect. In this work, stable transfection and transgenic mouse assays have been performed with constructs containing HS3 and HS2 from the locus control region, the gamma-globin gene with promoter mutation(s), and the beta-globin gene. The data indicate that the gamma-globin TATA and CACCC elements together have at least an additive effect on the beta/gamma-globin mRNA ratio in early erythroid cells, suggesting that the elements work coordinately to suppress beta-globin gene expression. The TATA and CACCC are the major gamma-globin promoter elements responsible for this effect. Transgenic mouse experiments indicate that the gamma-globin TATA element plays a role in gamma-globin expression and beta-globin suppression in the embryo and fetus; in contrast, the CACCC element has a stage-specific effect in the fetus. The results suggest that, as is true for the erythroid Krüppel-like factor (EKLF) and the beta-globin promoter CACCC, a protein(s) binds to the gamma-globin CACCC element to coordinate stage-specific gene expression.

Differential regulation of Dlx gene expression by a BMP morphogenetic gradient.

Three members of the vertebrate Distal-less gene family, Dlx3, 5 and 6, are transcribed in early gastrula embryos of Xenopus laevis. This expression is confined to ectoderm and is excluded from the presumptive neural plate region. Expression of all three genes is dependent upon BMP signaling, with significant differences in how the three genes respond to the BMP antagonist chordin. This correlates with the different expression domain boundaries in vivo for Dlx3 compared to Dlx5 and 6, suggesting that BMP signal attenuation could be the primary factor in determining these different patterns in the gastrula ectoderm.

Regulation and function of Dlx3 in vertebrate development.

Dlx3 is a homeodomain transcription factor in vertebrates, related to Distal-less in Drosophila, that is expressed in differentiating epidermal cells, in neural crest, hair follicles, dental epithelium and mesenchyme, the otic and olfactory placodes, limb bud, placenta, and in the cement gland, which is located in the extreme anterior neural plate in Xenopus embryos. This factor behaves as a transcriptional activator, and positively regulates gene expression in the skin, and negatively regulates central nervous system markers in Xenopus epidermis and anterior neural plate. A mutation in the DLX3 gene is associated with a hereditary syndrome in humans, and loss of Dlx3 function is a developmental lethal in gene-targeted mice, where it is essential for proper modeling of the labyrinthine layer of the placenta. In this review, we discuss the evolution, expression, regulation, and function of Dlx3 in mouse, amphibians, and zebrafish. Published 2000 Wiley-Liss, Inc.

Cloning and expression of a novel zinc finger gene, Fez, transcribed in the forebrain of Xenopus and mouse embryos.

We have identified and cloned a novel zinc finger gene, Fez (forebrain embryonic zinc-finger), as a potential downstream determinant of anterior neural plate formation in Xenopus. Fez was isolated as one of several neural-specific genes that was induced by the neuralizing factor, noggin (Smith and Harland, 1992. Cell 70, 829-840), in uncommitted ectoderm. Fez has an open reading frame comprising 466 amino acids, and contains six C(2)H(2) type zinc finger domains, which are highly conserved among Drosophila, zebrafish, mouse, and human. In Xenopus, the expression of Fez begins at stage 12 in the rostral end of the neural plate, and by stage 45, it is localized to several telencephalic regions, including the olfactory bulbs, nervus terminalis, and ventricular zone. The mouse homologue of Fez is similarly expressed in the mouse forebrain by embryonic day 11.

Regulation of early expression of Dlx3, a Xenopus anti-neural factor, by beta-catenin signaling.

The ectoderm of the pre-gastrula Xenopus embryo has previously been shown to be at least partially patterned along the dorsal-ventral axis. The early expression of the anti-neural homeodomain gene Dlx3 is localized to the ventral ectoderm by a mechanism that occurs prior to gastrulation and is independent of the Spemann organizer. The repression of Dlx3 is mediated by signaling though beta-catenin, but is probably not dependent on the induction of the Xnr3 or chordin genes by beta-catenin. We propose a model in which this early regulation of Dlx3 accounts for the pro-neural bias of dorsal ectoderm.

Inhibitory patterning of the anterior neural plate in Xenopus by homeodomain factors Dlx3 and Msx1.

Patterning of the embryonic ectoderm is dependent upon the action of negative (antineural) and positive (neurogenic) transcriptional regulators. Msx1 and Dlx3 are two antineural genes for which the anterior epidermal-neural boundaries of expression differ, probably due to differential sensitivity to BMP signaling in the ectoderm. In the extreme anterior neural plate, Dlx3 is strongly expressed while Msx1 is silent. While both of these factors prevent the activation of genes specific to the nascent central nervous system, Msx1 inhibits anterior markers, including Otx2 and cement gland-specific genes. Dlx3 has little, if any, effect on these anterior neural plate genes, instead providing a permissive environment for their expression while repressing more panneural markers, including prepattern genes belonging to the Zic family and BF-1. These properties define a molecular mechanism for translating the organizer-dependent morphogenic gradient of BMP activity into spatially restricted gene expression in the prospective anterior neural plate.

Comparison of energy estimation equations with measured energy expenditure in obese adolescent patients with cancer.

Obesity is increasing in the US adolescent population. As the number of obese adolescents increases, obesity is becoming a more frequent problem in the hospital setting, sometimes causing patients to have complicated and prolonged hospital stays. Calculation of the energy requirements of obese adolescent patients with chronic diseases such as cancer is complicated by increased energy requirements as a result of disease state and growth. This study examined the accuracy of the commonly used equations for calculating energy requirements. Estimated energy expenditure was compared with measured energy expenditure determined by indirect calorimetry. All energy estimation equations were inaccurate, which indicates the need for a specific equation for determination of energy needs in this special patient population. Until further research is done, indirect calorimetry is recommended for all obese adolescent patients with cancer who require nutrition support.

The gamma-globin promoter has a major role in competitive inhibition of beta-globin gene expression in early erythroid development.

The human gamma-globin gene competitively inhibits beta-globin gene expression in early erythroid development. To identify the gamma-globin gene sequences required for this effect, transgenic mice and stable transfection analyses with constructs containing 5'HS2 from the locus control region, modified gamma-globin genes, and the beta-globin gene were used. The -136 to +56 region of the gamma-globin promoter is necessary for competitive inhibition, as the beta-globin gene was inappropriately expressed in mouse embryos and in K562 and HEL cells containing constructs in which this region was deleted. Independently, the -140 to +56 region of gamma-globin gene was not sufficient to inhibit beta-globin transcription in mouse embryos or in cultured cells. Competitive inhibition of beta-globin gene expression was observed in K562 and HEL cells having a gamma-globin gene with a -161 promoter. The data suggest that the -161 gamma-globin promoter, which includes the CACCC box, two CCAAT boxes, the stage selector element (SSE), and TATA box, has a major role in suppressing beta-globin transcription early in development. Proteins binding to these or other gamma-globin promoter elements may interact with those binding to the locus control region, consequently precluding beta-globin transcription.

The roles of 5'-HS2, 5'-HS3, and the gamma-globin TATA, CACCC, and stage selector elements in suppression of beta-globin expression in early development.

The roles of HS2 and HS3 from the human beta-globin locus control region and of the TATA, CACCC, and stage selector elements of the gamma-globin promoter, in competitive inhibition of beta-globin gene expression in early development, were tested using stable transfections of HEL and K562 cells. Cells with an HS3gamma beta construct demonstrate that HS3 exhibits enhancing activity, but compared with HS2, this site participates less consistently in the inhibition of embryonic/fetal beta-globin expression. In cells with HS3HS2gamma beta constructs, the two HS sites act in concert to more effectively enhance gamma-globin gene expression and to drive stage-specific expression of the gamma- and beta-globin genes. A gamma-globin gene with a -161 promoter can competitively inhibit beta-globin gene expression. HS3HS2gamma beta constructs were used to determine the effects of gamma-globin promoter mutations within this region on competition. The CACCC and TATA elements, but not the stage selector element, inhibit inappropriate embryonic/fetal stage expression of the beta-globin gene. The mutation in the gamma-globin TATA element results in the use of two major alternative transcription start sites. The data suggest that proteins binding to the gamma-globin CACCC and TATA elements interact with those binding to HS2 and/or HS3 to preclude beta-globin transcription in early development.

Transcriptional activation by the homeodomain protein distal-less 3.

PCR-based methods and mobility shift competition assays were used to determine the basic biochemical features of the homeodomain transcription factor Distal-less 3 (Dlx3), including an optimal DNA binding site, the binding constant and dissociation rates of this protein. Expression of Dlx3 protein in either HeLa cells or Xenopus embryos resulted in strong activation of a model target gene construct containing three tandem copies of the Dlx3 binding site upstream from the TATA element. In addition, deletion analysis revealed that transcriptional activation by Dlx3 depends on two subdomains located on either side of the homeobox: removal of either subdomain resulted in complete loss of Dlx3 function. These observations provide new insight regarding the function of Dlx3 in vertebrate development and tissue differentiation and also suggest a mechanism for the dominant inheritance pattern of a hereditary disease resulting from mutation of the DLX3 gene in human.

Placental failure in mice lacking the homeobox gene Dlx3.

Dlx3 is a homeodomain transcription factor and a member of the vertebrate Distal-less family. Targeted deletion of the mouse Dlx3 gene results in embryonic death between day 9.5 and day 10 because of placental defects that alter the development of the labyrinthine layer. In situ hybridization reveals that the Dlx3 gene is initially expressed in ectoplacental cone cells and chorionic plate, and later in the labyrinthine trophoblast of the chorioallantoic placenta, where major defects are observed in the Dlx3 -/- embryos. The expression of structural genes, such as 4311 and PL-1, which were used as markers to follow the fate of different derivatives of the placenta, was not affected in the Dlx3-null embryos. However, by day 10.5 of development, expression of the paired-like homeodomain gene Esx1 was strongly down-regulated in affected placenta tissue, suggesting that Dlx3 is required for the maintenance of Esx1 expression, normal placental morphogenesis, and embryonic survival.

Research utilization and improvement in outcomes after diagnostic cardiac catheterization.

This research utilization project helped summarize the research basis of current practice related to duration of bed rest after cardiac catheterization via the femoral artery. Several physicians have changed their practice as a result of this project, and the safety of patients is being maintained. Interestingly, De Jong and Morton recently published a research analysis of interventions used to control vascular complications after cardiac catheterization. These authors concluded from the review of the literature on duration of bed rest that evidence was sufficient to support a change in practice. Because we thought that the published evidence was insufficient to be used as the sole basis for a change in practice, we continued to follow the Iowa model. Specifically, we integrated scientific principles and expert recommendations with the published research base; recommended a change in practice; and monitored patients' outcomes, which ultimately did confirm the recommendations of De Jong and Morton. We are convinced that the combination of data from our own patients and the review of the literature was helpful to assure our medical and nursing staff that this change in practice was safe. This project illustrates the benefit of using the Iowa Model for Research Based Practice to Promote Quality Care as a guide to improve patients' outcomes.

A methodology for optimally designing console panels for use by a single operator.

A seven-step methodology is presented to determine a dimensionally correct optimal layout of a console panel for a single operator. This methodology integrates the steps in the layout design process and uses a mathematical optimization model from facility design to obtain the optimal panel layout. A major difference in this methodology from previous work is that the mathematical optimization model incorporates factors that are only partially included in previous mathematical models. In addition, it includes the areas of the panel components as a new factor. This methodology is illustrated by the design of a nuclear power plant console panel.

Molecular cloning of Xenopus hatching enzyme and its specific expression in hatching gland cells.

UVS.2 has been known as a cloned cDNA expressed selectively in the hatching gland cells of Xenopus laevis. To determine the molecular identity and function of UVS.2-encoded proteins, antibodies were raised against a bacterially-expressed fusion protein comprising glutathione-S-transferase (GST) and UVS.2. Anti-GST-UVS.2 antibodies inhibited the vitelline envelope digesting activity of the medium (hatching medium) in which dejellied prehatching embryos were cultured. On Western blotting, hatching medium contained 60 kDa and 40 kDa molecules reactive with these antibodies. Whole-mount immunostaining showed a specific localization of UVS.2 protein in the hatching gland cells which appeared first at stage 20, increased in number and intensity to stage 31 then decreased gradually thereafter. Immunoelectron microscopy revealed that UVS.2 protein is localized exclusively in the secretory granules in the hatching gland cells. A cDNA library from the dorsoanterior portion of stage 25 embryos was screened with UVS.2, and a 1.8 kb insert thus cloned contained additional 619bp and 204bp at the 5' and 3' ends of UVS.2, respectively. This clone, designated XHE, contained an open reading frame encoding 514 amino acids including both signal and propeptide sequences. The predicted mature enzyme comprising 425 amino acids consists of about 200 amino acid-long metalloprotease sequence of astacin family at the N-terminus, followed by two repeats of CUB domain each 110 amino acid-length. We conclude that UVS.2 represents an approximately 3/4 C-terminal portion of the hatching enzyme.

Regulation of epidermal differentiation by a Distal-less homeodomain gene.

The Distal-less-related homeodomain gene Dlx3 is expressed in terminally differentiated murine epidermal cells. Ectopic expression of this gene in the basal cell layer of transgenic skin results in a severely abnormal epidermal phenotype and leads to perinatal lethality. The basal cells of affected mice ceased to proliferate, and expressed the profilaggrin and loricrin genes which are normally transcribed only in the latest stages of epidermal differentiation. All suprabasal cell types were diminished and the stratum corneum was reduced to a single layer. These data indicate that Dlx3 misexpression results in transformation of basal cells into more differentiated keratinocytes, suggesting that this homeoprotein is an important regulator of epidermal differentiation.

Disruption of cell adhesion in Xenopus embryos by Pagliaccio, an Eph-class receptor tyrosine kinase.

Pagliaccio (Pag) is a receptor tyrosine kinase of the Eph family that is expressed in Xenopus embryos in a diverse set of localized tissues. Pag is the Xenopus homolog of Hek-8 (human), Sek-1 (mouse), cek8 (chicken), and RTK-1 (zebrafish). We have investigated the function of this protein by injecting RNA encoding an epidermal growth factor receptor-Pag chimera into early Xenopus embryos. Activation of the chimeric receptor results in a kinase-dependent loss of cell-cell adhesion. This dissociation can be reversed by co-injection of RNA encoding C-cadherin, suggesting that one or more cadherins could be the functional targets for Pag activity.

Ventral neural cadherin, a novel cadherin expressed in a subset of neural tissues in the zebrafish embryo.

Cadherins are calcium-binding transmembrane glycoproteins that are important mediators of cell-cell association. Here we describe a novel member of this gene family, zebrafish ventral neural cadherin (VN-cad). Multiple VN-cad transcripts are first detectable by Northern blots at 60% epiboly. In the developing neural tube, VN-cad RNA is first found in the neuroectoderm, directly above the notochord, and later was localized to the neural keel. At the 20-somite stage, VN-cad transcripts are confined to the ventral neural tube, otic vesicle, midbrain, and diencephelon. Transcription of VN-cad RNA continues in adult fish. The embryonic pattern of expression is not significantly disrupted in cyclops or no tail mutants, which lack the floor plate and notochord, respectively. Therefore, neither of these structures is absolutely required for VN-cad expression. The localized pattern of VN-cad expression suggests a possible role for this adhesion molecule in the initial formation and subsequent differentiation of the central nervous system.