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At least 1,279 records · Page 71Linked to original sources
PubMed1999

Post-transcriptional regulation of Xwnt-8 expression is required for normal myogenesis during vertebrate embryonic development.

The Xenopus Wnt-8 gene is transiently expressed in ventral and lateral mesoderm during gastrulation and plays a critical role in patterning these tissues. In the current study, we show that the spatial and temporal pattern of expression of endogenous Xwnt-8 is regulated, in part, at a post-transcriptional level. We have identified a novel sequence element in the 3' untranslated region of the Xwnt-8 RNA that controls the polyadenylation status of reporter and endogenous Xwnt-8 RNAs, directs rapid RNA degradation beginning precisely at the early gastrula stage, and represses translation of transcripts throughout development. Expression of endogenous Xwnt-8 is normally downregulated within lateral (presomitic) mesoderm following gastrulation. We demonstrate that rapid degradation of Xwnt-8 transcripts, mediated by these regulatory elements in the 3' untranslated region, is essential to this process and that downregulation is required to prevent overcommitment of somitic cells to a myogenic fate. These studies demonstrate a role for post-transcriptional regulation of zygotic gene expression in vertebrate embryonic patterning.

3' Untranslated Regions↗
PubMed1999

Gap junction-mediated transfer of left-right patterning signals in the early chick blastoderm is upstream of Shh asymmetry in the node.

Invariant patterning of left-right asymmetry during embryogenesis depends upon a cascade of inductive and repressive interactions between asymmetrically expressed genes. Different cascades of asymmetric genes distinguish the left and right sides of the embryo and are maintained by a midline barrier. As such, the left and right sides of an embryo can be viewed as distinct and autonomous fields. Here we describe a series of experiments that indicate that the initiation of these programs requires communication between the two sides of the blastoderm. When deprived of either the left or the right lateral halves of the blastoderm, embryos are incapable of patterning normal left-right gene expression at Hensen's node. Not only are both flanks required, suggesting that there is no single signaling source for LR pattern, but the blastoderm must be intact. These results are consistent with our previously proposed model in which the orientation of LR asymmetry in the frog, Xenopus laevis, depends on large-scale partitioning of LR determinants through intercellular gap junction channels (M. Levin and M. Mercola (1998) Developmental Biology 203, 90-105). Here we evaluate whether gap junctional communication is required for the LR asymmetry in the chick, where it is possible to order early events relative to the well-characterized left and right hierarchies of gene expression. Treatment of cultured chick embryos with lindane, which diminishes gap junctional communication, frequently unbiased normal LR asymmetry of Shh and Nodal gene expression, causing the normally left-sided program to be recapitulated symmetrically on the right side of the embryo. A survey of early expression of connexin mRNAs revealed that Cx43 is present throughout the blastoderm at Hamburger-Hamilton stage 2-3, prior to known asymmetric gene expression. Application of antisense oligodeoxynucleotides or blocking antibody to cultured embryos also resulted in bilateral expression of Shh and Nodal transcripts. Importantly, the node and primitive streak at these stages lack Cx43 mRNA. This result, together with the requirement for an intact blastoderm, suggests that the path of communication through gap junction channels circumvents the node and streak. We propose that left-right information is transferred unidirectionally throughout the epiblast by gap junction channels in order to pattern left-sided Shh expression at Hensen's node.

Animals↗
PubMed1999

Extensive zygotic control of the anteroposterior axis in the wasp Nasonia vitripennis.

Insect axis formation is best understood in Drosophila melanogaster, where rapid anteroposterior patterning of zygotic determinants is directed by maternal gene products. The earliest zygotic control is by gap genes, which determine regions of several contiguous segments and are largely conserved in insects. We have asked genetically whether early zygotic patterning genes control similar anteroposterior domains in the parasitoid wasp Nasonia vitripennis as in Drosophila. Nasonia is advantageous for identifying and studying recessive zygotic lethal mutations because unfertilized eggs develop as males while fertilized eggs develop as females. Here we describe recessive zygotic mutations identifying three Nasonia genes: head only mutant embryos have posterior defects, resembling loss of both maternal and zygotic Drosophila caudal function; headless mutant embryos have anterior and posterior gap defects, resembling loss of both maternal and zygotic Drosophila hunchback function; squiggy mutant embryos develop only four full trunk segments, a phenotype more severe than those caused by lack of Drosophila maternal or zygotic terminal gene functions. These results indicate greater dependence on the zygotic genome to control early patterning in Nasonia than in the fly.

Animals↗
PubMed2001

Fate map of early avian cardiac progenitor cells.

Cardiogenic fate maps are used to address questions on commitment, differentiation, morphogenesis and organogenesis of the heart. Recently, the accuracy of classical cardiogenic fate maps has been questioned, raising concerns about the conclusions drawn in studies based on these maps. We present accurate fate maps of the heart-forming region (HFR) in avian embryos and show that the putative cardiogenic molecular markers Bmp2 and Nkx2.5 do not govern the boundaries of the HFR as suggested in the literature. Moreover, this paper presents the first fate map of the HFR at stage 4 and addresses a void in the literature concerning rostrocaudal patterning of heart cells between stages 4 and 8.

Animals↗
PubMed2002

Segmental relationship between somites and vertebral column in zebrafish.

The segmental heritage of all vertebrates is evident in the character of the vertebral column. And yet, the extent to which direct translation of pattern from the somitic mesoderm and de novo cell and tissue interactions pattern the vertebral column remains a fundamental, unresolved issue. The elements of vertebral column pattern under debate include both segmental pattern and anteroposterior regional specificity. Understanding how vertebral segmentation and anteroposterior positional identity are patterned requires understanding vertebral column cellular and developmental biology. In this study, we characterized alignment of somites and vertebrae, distribution of individual sclerotome progeny along the anteroposterior axis and development of the axial skeleton in zebrafish. Our clonal analysis of zebrafish sclerotome shows that anterior and posterior somite domains are not lineage-restricted compartments with respect to distribution along the anteroposterior axis but support a 'leaky' resegmentation in development from somite to vertebral column. Alignment of somites with vertebrae suggests that the first two somites do not contribute to the vertebral column. Characterization of vertebral column development allowed examination of the relationship between vertebral formula and expression patterns of zebrafish Hox genes. Our results support co-localization of the anterior expression boundaries of zebrafish hoxc6 homologs with a cervical/thoracic transition and also suggest Hox-independent patterning of regionally specific posterior vertebrae.

Animals↗
PubMed2002

Patterning of angiogenesis in the zebrafish embryo.

Little is known about how vascular patterns are generated in the embryo. The vasculature of the zebrafish trunk has an extremely regular pattern. One intersegmental vessel (ISV) sprouts from the aorta, runs between each pair of somites, and connects to the dorsal longitudinal anastomotic vessel (DLAV). We now define the cellular origins, migratory paths and cell fates that generate these metameric vessels of the trunk. Additionally, by a genetic screen we define one gene, out of bounds (obd), that constrains this angiogenic growth to a specific path. We have performed lineage analysis, using laser activation of a caged dye and mosaic construction to determine the origin of cells that constitute the ISV. Individual angioblasts destined for the ISVs arise from the lateral posterior mesoderm (LPM), and migrate to the dorsal aorta, from where they migrate between somites to their final position in the ISVs and dorsal longitudinal anastomotic vessel (DLAV). Cells of each ISV leave the aorta only between the ventral regions of two adjacent somites, and migrate dorsally to assume one of three ISV cell fates. Most dorsal is a T-shaped cell, based in the DLAV and branching ventrally; the second constitutes a connecting cell; and the third an inverted T-shaped cell, based in the aorta and branching dorsally. The ISV remains between somites during its ventral course, but changes to run mid-somite dorsally. This suggests that the pattern of ISV growth ventrally and dorsally is guided by different cues. We have also performed an ENU mutagenesis screen of 750 mutagenized genomes and identified one mutation, obd that disrupts this pattern. In obd mutant embryos, ISVs sprout precociously at abnormal sites and migrate anomalously in the vicinity of ventral somite. The dorsal extent of the ISV is less perturbed. Precocious sprouting can be inhibited in a VEGF morphant, but the anomalous site of origin of obd ISVs remains. In mosaic embryos, obd somite causes adjacent wild-type endothelial cells to assume the anomalous ISV pattern of obd embryos. Thus, the launching position of the new sprout and its initial trajectory are directed by inhibitory signals from ventral somites. Zebrafish ISVs are a tractable system for defining the origins and fates of vessels, and for dissecting elements that govern patterns of vessel growth.

Animals↗
PubMed2005

Examination of the Lunatic fringe and Uncx4.1 expression by whole-mount in situ hybridization in the embryo of the CKH-Jsr (jumbled spine and ribs) mouse.

The CKH-Jsr (jumbled spine and ribs) mouse was found as a spontaneous mutant with malformation of vertebrae, that is, a short trunk and kinky tail. We examined Lunatic Fringe (Lfng) and Uncx4.1 expression in the presomitic mesoderm (PSM) and somites of Jsr-mutant (CKH-Jsr/+) embryos to elucidate pathogenesis of the Jsr mutation. Expression pattern of Lfng in the PSM of Jsr-mutant embryos was similar to that of the normal (C57BL/6) embryos. However, expression pattern of Uncx4.1 in the somites of Jsr-mutant embryos was impaired to be irregular and mosaic, suggesting that the anterior-posterior (A-P) polarity is disordered in the Jsr mutant. These results indicate that the Jsr mutation disrupts the A-P polarity of somites during the somitogenesis without altering Lfng expression pattern in the PSM.

Animals↗
PubMed1996

Development, plasticity and evolution of butterfly eyespot patterns.

The developmental and genetic bases for the formation, plasticity and diversity of eyespot patterns in butterflies are examined. Eyespot pattern mutants, regulatory gene expression, and transplants of the eyespot developmental organizer demonstrate that eyespot position, number, size and colour are determined progressively in a developmental pathway largely uncoupled from those regulating other wing-pattern elements and body structures. Species comparisons and selection experiments suggest that the evolution of eyespot patterns can occur rapidly through modulation of different stages of this pathway, and requires only single, or very few, changes in regulatory genes.

Adaptation, Biological↗
PubMed2001

A two-year follow-up of a primary prevention program for negative body image and unhealthy weight regulation.

As a test of a prevention effect, data were collected two years after boys and girls ages 9-11 completed ten one-hour lessons designed to improve nutrition and exercise patterns, enhance body esteem, and discourage unhealthy weight management. Body esteem, use of weight loss techniques, SATAQ scores, weight concerns, and program-related knowledge were compared among three groups of young adolescent girls and boys (N = 509; ages = 11-13): participants in the elementary school program (Smolak, Levine, & Schermer, 1998a, 1998b), control participants from the same elementary schools, and new control participants from schools not included in the original study. Compared to new controls, those adolescents who received the prevention program two years earlier were more knowledgeable, used fewer unhealthy weight management techniques, and had higher body esteem. The latter difference was particularly significant for girls. Original control participants had intermediate scores, suggesting a "spillover" effect. Scores on program-related knowledge were positively correlated with better body esteem and less frequent use of weight loss techniques, and lower SATAQ scores, particularly among the girls. Findings suggest that a curricular program using cognitive social learning and developmental principles may help prevent the development of negative body image and unhealthy weight management techniques in girls and boys as they move from late childhood to early adolescence. Important methodological implications of this study for the meaning of prevention also are discussed.

Journal Article↗
PubMed1989

[Growth curves of body weight changes in laboratory-bred female African green monkeys (Cercopithecus aethiops)].

Nonlinear growth models having three or four parameter family were applied to individual weight data of female African green monkeys for estimating their growth pattern. The body weight was measured continuously from birth to six years of age with five female laboratory-bred monkeys. A total of 95 weight data were collected from each monkey. The average body weight was 330 g with the standard deviation of +/- 15 g at birth, and 2.71 +/- 0.33 kg at four years of age. The body weight of female African green monkeys was judged to reach a plateau after about four years of age. Five growth models (Gompertz, Logistic, Richards, Bertalanffy, Brody) were applied to these weight to age data. The most suitable coefficient of determination between growth data and growth model was obtained by the application of Gompertz equation. Three parameters of Gompertz equation, mature size (A), rate of maturing (K) and inflexion point (e-1 A) were analyzed in relation to age of menarche. Strong correlations between age of menarche and maturing rate, as well as between age of menarche and inflexion point were observed.

Age Factors↗
PubMed1984

Energy exchanges in water.

The thermal physical properties of water make water a medium of high heat transfer relative to air. This paper describes the body temperature pattern during immersion in still and moving water, the avenues for energy exchange, the energy transfer characteristics of humans, and the physiological means by which the body attempts to compensate for the excess heat loss in water. Fat is the major defense against cooling in water when exercising or shivering. Skeletal muscle is a significant additional factor during quiet rest.

Body Temperature↗
PubMed2002

Opponent inhibition: a developmental model of layer 4 of the neocortical circuit.

We model the development of the functional circuit of layer 4 (the input-recipient layer) of cat primary visual cortex. The observed thalamocortical and intracortical circuitry codevelop under Hebb-like synaptic plasticity. Hebbian development yields opponent inhibition: inhibition evoked by stimuli anticorrelated with those that excite a cell. Strong opponent inhibition enables recognition of stimulus orientation in a manner invariant to stimulus contrast. These principles may apply to cortex more generally: Hebb-like plasticity can guide layer 4 of any piece of cortex to create opposition between anticorrelated stimulus pairs, and this enables recognition of specific stimulus patterns in a manner invariant to stimulus magnitude. Properties that are invariant across a cortical column are predicted to be those shared by opponent stimulus pairs; this contrasts with the common idea that a column represents cells with similar response properties.

Action Potentials↗
PubMed1988

Body fat deposition in adult obese women. I. Patterns of fat distribution.

Fat patterning was studied in a sample of 76 obese women before and after weight reduction by principal components analysis. Circumferences were selected as variables rather than skinfolds because circumferences correlated more highly with body composition determined either by total body water or total body potassium. A separate sample of 136 males and females, measured once, was employed to validate the results. The validation sample yielded similar findings. Two significant components were found, the first contrasting upper and lower fatness and the second trunk and extremity fatness. Waist circumference was the best predictor of upper-body fat patterning. For the lower body, thigh circumference loaded more highly than did the iliac crest circumference. Arm circumference did not contribute significantly to upper-lower fat patterning.

Adipose Tissue↗
PubMed2000

Dictyostelium discoideum: a model system for differentiation and patterning.

In Dictyostelium, development begins with the aggregation of free living amoebae, which soon become organized into a relatively simple organism with a few different cell types. Coordinated cell type differentiation and morphogenesis lead to a final fruiting body that allows the dispersal of spores. The study of these processes is having increasing impact on our understanding of general developmental mechanisms. The availability of biochemical and molecular genetics techniques has allowed the discovery of complex signaling networks which are essential for Dictyostelium development and are also conserved in other organisms. The levels of cAMP (both intracellular and extracellular) play essential roles in every stage of Dictyostelium development, regulating many different signal transduction pathways. Two-component systems, involving histidine kinases and response regulators, have been found to regulate intracellular cAMP levels and PKA during terminal differentiation. The sequence of the Dictyostelium genome is expected to be completed in less than two years. Nevertheless, the available sequences that are already being released, together with the results of expressed sequence tags (ESTs), are providing invaluable tools to identify new and interesting genes for further functional analysis. Global expression studies, using DNA microarrays in synchronous development to study temporal changes in gene expression, are presently being developed. In the near future, the application of this type of technology to the complete set of Dictyostelium genes (approximately 10,000) will facilitate the discovery of the effects of mutation of components of the signaling networks that regulate Dictyostelium development on changes in gene expression.

Animals↗
PubMed1993

Functional differentiation of the pituitary gland during development of the domestic ring dove (Streptopelia roseogrisea).

The development and differentiation of the anterior pituitary gland was studied in the domestic ring dove (Streptopelia roseogrisea) and compared with the pattern of body growth. By combining histochemical staining techniques with immunohistochemical methods, cells producing prolactin (PRL), growth hormone (GH), thyrotropic hormone (TSH), and adrenocorticotropic hormone were identified in the pituitary of the developing ring dove. The distribution of the four cell types within the anterior pituitary was illustrated by three-dimensional reconstruction from immunohistochemically stained serial sections. The pattern, which was shown to change through embryonic and juvenile development, was described and compared with examples from other vertebrate classes. The analysis of body growth showed that the development of the nestlings could be divided into two distinct growth phases. The first seven days were characterized by a consistently high rate of body growth, whereas after Day seven the growth rate was markedly reduced. Although GH-immunoreactive cells formed the dominant cell type in the pituitary during the whole postembryonic development, there was no correlation between the rate of body growth and the abundance of GH-immunoreactive cells in the pituitary. In contrast, changes in the abundance of PRL- and TSH-immunoreactive cells were observed simultaneously with the transition from the first to the second growth phase. The proportion of PRL-immunoreactive cells was relatively high during the first seven days, whereas TSH-immunoreactive cells became more abundant during the second growth phase. It is therefore postulated that PRL and TSH play an important role in the regulation of the growth pattern in the ring dove.

Adrenocorticotropic Hormone↗