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We present simple procedures for estimating non linear panel data models in the presence of unobserved heterogeneity and possible endogeneity with respect to time-varying unobservables. We combine a correlated random effects approach with a control function approach while accounting for missing time periods for some units. We examine the performance of the approach in comparisons with standard estimators using Monte Carlo simulation. We apply the methods to estimate the effects of school spending on student pass rates on a standardized math exam. We find that a 10% increase in spending leads to an approximately 2 percentage point increase in math pass rates. [ABSTRACT FROM AUTHOR]

Dopamine is a catecholamine neurotransmitter produced by the brain which affects the stimulation of nerves. Alteration in the number or activity of the cell receptors that bind dopamine is thought to be involved in diseases such as Parkinson's disease and schizophrenia. Drugs that have an effect on the dopamine receptors are given to patients with these diseases. The physiological effects of dopamine occur by its binding with two types of receptors: D1 receptors, which stimulate a second enzyme known as adenylyl cyclase; and D2 receptors, which inhibit adenylyl cyclase. These receptors are G protein-coupled receptors, receptors which bind G proteins. The receptors act as a bridge, sending a message inside the cell from a signal generated by the binding of a substance such as dopamine to a receptor on the cell surface. The enzyme adenylyl cyclase stimulates the activation of the cell. The authors report that the gene encoding a dopamine D1 receptor in humans has been isolated and characterized. The D2 receptor gene had already been isolated and characterized. The protein that is encoded by the gene is similar to that of other G protein-coupled receptors, and encodes a region that spans the cell membrane seven times. When the protein that is encoded by the gene was expressed in cells, the receptor was functional. It bound dopamine and stimulated the activity of adenylyl cyclase. It is thought that other subtypes of the D1 dopamine receptor may exist. The cloning of this gene will allow for further research so that the function of this gene, and how it is activated and regulated in both normal and disease states, can be understood. (Consumer Summary produced by Reliance Medical Information, Inc.)

Hirschsprung disease (HD) and anorectal malformations (ARMs) result from alterations in hindgut development. It has long been recognized that both recur in families and thus result, at least in part, from genetic factors. Progress in the understanding of the genetic basis of HD has been made by the application of findings from genetic animal models of altered enteric nervous system development to human beings. Several genes have been shown to be important for human enteric nervous system development, and current work is progressing to identify genetic interactions that may explain the variable phenotype of HD. By contrast, understanding of the genetic factors underlying ARMs is much less developed. We and others have shown that genetic factors play an important role in the pathogenesis of ARMs, and many mouse genetic models suggest molecular pathways that may be altered in ARMs. [Copyright &y& Elsevier]

Background & Aims: Following massive small bowel resection (SBR), the remnant intestine undergoes an adaptive process characterized by increases in a number of physiologic and morphologic parameters. These changes are the result of a stimulus that increases crypt cell mitosis and augments cellular progression along the villus axis. To better define this process, we identified patterns of gene expression specifically within adapting intestinal crypt cells following SBR. Methods: Laser capture microdissection was used to isolate mouse intestinal crypt cells following SBR or sham operation. Multiple biological and technical complementary DNA microarray replicates allowed rigorous statistical analyses for identification of important expression profiles. Major groups of genes were classified as to site of action, functional pathway, and possible regulatory groups. Results: A total of 300 genes differentially expressed at significant levels within adapting crypt enterocytes were analyzed. Comparison of this list of differentially expressed adapting crypt cell genes with a generalized mouse gene expression database (from 82 developing and adult mouse tissues) showed the greatest overlap with developing and immature intestinal tissues. We identified prominent groups of genes involved with cell growth, signal transduction, and nucleic acid binding. Genes not previously shown to be involved with adaptation or development and maturation were identified. Conclusions: Identification of similar genes coordinately regulated during both adaptation and development, processes that share key morphologic features, provides a basis for new mechanistic insights into these shared characteristics. [Copyright &y& Elsevier]

Background: Development of the enteric nervous system (ENS) requires interactions between migrating neural crest cells and the nascent gastrointestinal tract that are dependent upon genes expressed by both cell compartments. Hlx, a homeobox transcription factor gene that is expressed in mouse intestinal and hepatic mesenchyme, is required for normal embryonic growth of intestine and liver, and the Hlx-/- genotype is embryonic lethal. We hypothesized that Hlx is required for ENS development. Results: Enteric neurons were identified in Hlx+/+ and Hlx-/- mouse embryos by immunostaining of embryo sections for the neural markers PGP9.5 and Phox2b, or by staining for β- alactosidase in whole-mount embryos containing the dopamine β-hydroxylase- LacZ transgene. In Hlx+/+ embryos, neural crest cells/enteric neurons have moved from the stomach into the intestine by E10.5. By contrast, neural crest cells/enteric neurons remain largely restricted to the lateral stomach mesenchyme of Hlx-/- embryos, with only a few scattered neural crest cells/enteric neurons in the intestine between E10.5-16.5. Conclusion: The Hlx homeobox transcription factor is required for early aspects of ENS development. [ABSTRACT FROM AUTHOR]

Abstract: Hlx is a homeobox transcription factor gene that is expressed in intestinal and hepatic mesenchyme of the developing mouse embryo and is essential for normal intestinal and hepatic development. Because of the morphological and molecular similarities in the development of the digestive system across species, we hypothesized that the Hlx gene and protein sequences and expression patterns would be conserved among vertebrates. Comparison of the Hlx gene orthologues of human, chimpanzee, mouse, rat, pufferfish (Fugu) and zebrafish demonstrates that these six genes share an identical organization with four exons and three introns. Comparison of the inferred Hlx protein sequences from these and three additional species (chick, Spanish ribbed newt and rainbow trout) reveals significant sequence identity, with identical homeodomains. The expression of Hlx in the mesenchyme of developing chick embryos is highly similar to that of mouse. Fugu Hlx is expressed in a tissue-specific manner that is similar though not identical to that of mouse, suggesting a conservation of Hlx function between mammals and birds. The mammalian and fish Hlx genes share a putative 5′ upstream enhancer as well as an inverted repeat containing CCAAT boxes on opposite strands that we have previously shown to be important for mouse Hlx gene expression. These results suggest that the function of Hlx and the mechanisms regulating its expression are highly conserved in mammals, birds, amphibians and fish. [Copyright &y& Elsevier]