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Results for “developmental dynamics”

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At least 1,459 records · Page 81Linked to original sources
PubMed2004

Synchronism of leaf and tiller emergence relative to position and to main stem development stage in a rice cultivar.

BACKGROUND AND AIMS: Tillering is an essential factor when estimating yield, but investigations rarely include both the temporal and spatial changes that occur in tillers. This study analyses the morphology and development dynamics of each tiller, based on its topological location, the timing of appearance and main stem development stage. METHODS: An indica cultivar of rice, 'Ir64', glasshouse-grown (25/20 degrees C, 12 h photoperiod), was used to examine the emergence, phenology and morphology of each axis starting at the third leaf stage up to heading. KEY RESULTS: Little variability was observed in the structural and morphological characteristics of the tillers, and the rice population appeared to be hierarchical. Blade length initially increased with leaf rank and then decreased sharply for the last three leaves. The number of phytomers per axis decreased with branching order and rank. An analysis of plant dynamics showed synchronous emergence of the leaves on the main stem and on the tillers up to flowering. Axillary bud development into tillers depended on their topological location and plant developmental stage. CONCLUSIONS: The timing and frequency of flowering tillers complied with rules of priority depending on their order, rank and emergence time. Precise description of plant topology in grasses is a useful tool that can be used to quantify growth events and predict tillering in terms of location, structure and fate according to growing conditions.

Flowers↗
PubMed1996

Simulating development and survival of Aedes vexans (Diptera: Culicidae) preimaginal stages under field conditions.

Ecology and population dynamics of Aedes vexans (Meigen), were studied for 3 yr in southern Switzerland. Demographic data were compiled into single and multicohort stage-frequency lifetables that indicated variability in individual developmental times and losses caused by mortality. The structure of life table matrices suggested an analysis using a timevarying distributed delay model with attrition. Field data then were used to construct and validate a simulation model that input the number of 1st instars and output the number of emerging adults. The delay was the time required to complete development and attrition corresponded to mortality. Under optimal food supply, temperature was the most important driving variable. The model was parameterized with data obtained from laboratory experiments and evaluated with field data. Development and survival of preimaginal Ae. vexans were simulated reasonably well under 2 different pool habitats. Addition of a hydrology component to the model would enhance control operations by predicting hatch rates in the field.

Aedes↗
PubMed2002

Ethanol induces morphological and dynamic changes on in vivo and in vitro neural crest cells.

BACKGROUND: Fetal alcohol syndrome (FAS) is an embryopathology related to maternal alcohol drinking. The information concerning the factors involved in the prenatal mechanisms of ethanol action at the cellular and molecular levels is scarce. Because several abnormal changes in FAS involve regions colonized by cell lineages derived from neural crest cells (NCCs), it is reasonable to propose that epigenetic alteration of this cell population can represent an important component of the etiopathogeny. The aim of this work was to evaluate the direct effect of ethanol on a chick embryo model, as well as on in vitro NCC morphology and dynamic behavior. METHODS: After ethanol treatment, in ovo or cultured chick embryos were used to determine the anatomical development of and to quantify the migratory parameters and apoptosis of NCCs. Scanning electron microscopy was performed on ethanol-perfused (and control) cultures of cephalic and trunk NCCs; the actin cytoskeleton was evaluated, and morphometric and dynamic parameters were determined after time-lapse videorecording. Recovery capacity after ethanol treatment was also determined. RESULTS: Chick embryos submitted to conditions sufficient to induce FAS in mammals displayed developmental disruptions frequently accompanied by cephalic/facial anomalies. In vitro studies also indicated that cephalic and trunk NCCs exposed to ethanol exhibited significant and permanent changes regarding cell shape, surface morphology, apoptotic cell death, cytoskeleton, and distance and velocity traveled, as well as an abnormal pattern of migration. CONCLUSIONS: Taking into account that even a limited period of abnormal behavior may imply serious consequences in the final cues of an embryonic cell population, our results indicate that the biological effects of ethanol on early development-even during a short time-could induce permanent ontogenetic perturbations of NCCs, with potentially dramatic effects on embryonic morphogenesis. These results support an important participation of NCCs in the etiopathogeny of FAS.

Animals↗
PubMed2006

Localization of metabotropic GABA receptor subunits GABAB1 and GABAB2 relative to synaptic sites in the rat developing cerebellum.

The highest densities of the two metabotropic GABA subunits, GABAB1 and GABAB2, have been reported as occurring around the glutamatergic synapses between Purkinje cell spines and parallel fibre varicosities. In order to determine how this distribution is achieved during development, we investigated the expression pattern and the cellular and subcellular localization of the GABAB1 and GABAB2 subunits in the rat cerebellum during postnatal development. At the light microscopic level, immunoreactivity for the GABAB1 and GABAB2 subunits was very prominent in the developing molecular layer, especially in Purkinje cells. Using double immunofluorescence, we demonstrated that GABAB1 was transiently expressed in glial cells. At the electron microscopic level, immunoreactivity for GABAB receptors was always detected both pre- and postsynaptically. Presynaptically, GABAB1 and GABAB2 were localized in the extrasynaptic membrane of parallel fibres at all ages, and only rarely in GABAergic axons. Postsynaptically, GABAB receptors were localized to the extrasynaptic and perisynaptic plasma membrane of Purkinje cell dendrites and spines throughout development. Quantitative analysis and three-dimensional reconstructions further revealed a progressive developmental movement of the GABAB1 subunit on the surface of Purkinje cells from dendritic shafts to its final destination, the dendritic spines. Together, these results indicate that GABAB receptors undergo dynamic regulation during cerebellar development in association with the establishment and maturation of glutamatergic synapses to Purkinje cells.

Animals↗
PubMed2001

Synthetic hammerhead ribozymes as tools in gene expression.

The assessment of genetic controls for sequential developmental processes such as tooth formation and biomineralization is often difficult in transgenic "knockout" models, where phenotypes reflect only the permanent eradication of a gene, and reveal little about the dynamic range of expression for the gene(s) involved. One promising strategy to overcome this problem is through the use of ribozymes, a class of metalloenzymes made entirely of ribonucleic acid (RNA), that are capable of cleaving other RNA molecules in a catalytic fashion. Their activity can be targeted against specific mRNAs by selection of unique sequences flanking a conserved catalytic motif. In synthetic ribozymes, specificity, stability, and cell permeability can be dramatically improved by the incorporation of chemically modified ribonucleotides. This review focuses on the design and application of hammerhead ribozymes, the best-known and most widely used class of RNA-based enzymes. So far, except for a few conserved structures at the catalytic core, no one particular model or superior ribozyme design has been identified. It may well be that each cell, tissue, and organism has different requirements for the uptake, activity, and stability of hammerhead ribozymes. However, designed ribozymes can be highly effective agents for timed and localized elimination of gene products. As the 3D structures of active hammerhead molecules are revealed, more effective ribozymes will be developed. Today, developments in ribozyme-mediated sequence-specific blocking of gene expression hold great promise for active RNA enzymes as tools in biomolecular research and for eliminating unwanted gene expression in human diseases.

Animals↗
PubMed2003

The exocyst component Sec5 is required for membrane traffic and polarity in the Drosophila ovary.

The directed traffic of membrane proteins to the cell surface is crucial for many developmental events. We describe the role of Sec5, a member of the exocyst complex, in directed membrane traffic in the Drosophila oocyte. During oogenesis, we find that Sec5 localization undergoes dynamic changes, correlating with the sites at which it is required for the traffic of membrane proteins. Germline clones of sec5 possess defects in membrane addition and the posterior positioning of the oocyte. Additionally, the impaired membrane trafficking of Gurken, the secreted ligand for the EGF receptor, and Yolkless, the vitellogenin receptor, results in defects in dorsal patterning and egg size. However, we find the cytoskeleton to be correctly oriented. We conclude that Sec5 is required for directed membrane traffic, and consequently for the establishment of polarity within the developing oocyte.

Animals↗
PubMed2006

Identification of a nuclear localization signal in mouse polycomb protein, M33.

The mouse Polycomb group (PcG) protein M33 forms nuclear complexes with the products of other PcG members and maintains repressed states of developmentally important genes, including homeotic genes. In this context, nuclear localization is a prerequisite for M33 to exert its function. However, we previously found that M33 in mouse liver shuttles dynamically between the nucleus and the cytoplasm, depending on the proliferative states of cells, coupled with phosphorylation and dephosphorylation of M33 protein. To understand the mechanism and significance of this phenomenon, we identified the functional nuclear localization signal (NLS) of M33 protein. Deletion mutants that lack a particular one of three putative NLS motifs failed to localize in the nucleus. Green fluorescent protein (GFP) fused to this motif specifically localized in the nucleus. We conclude that this amino-acid stretch in M33 acts as the functional NLS for this protein.

Animals↗
PubMed1990

Facilitating growth and development: a paradigm case for modeling and role-modeling.

This article describes an example of a paradigm case for the nursing theory of modeling and role-modeling. A synthesis of the mid-range theoretical linkages of basic need satisfaction, object attachment, and growth and developmental processes derived from the theory and paradigm are described. These theoretical linkages guide the assessment, implementation, and evaluation of the nursing care and provide the basis for describing the dynamic nurse-client relationship.

Adult↗
PubMedDate not supplied

Control issues in toilet training.

There are many control issues surrounding toilet training that involve the child, the family, and the environment. Loss of control by the child during this period can result in significant physical and psychologic consequences as well as a failure to complete the developmental task of autonomy. A review of both professional and lay literature showed various approaches to toilet training with little reference to the control issues involved. Toilet training is a dynamic process that does not always go smoothly. Constipation often develops during toilet training and may be related to control issues. Neuman's Systems Model is used to identify the types of control issues often involved in toilet training. Anticipatory guidance specifically developed to address issues of control may help alleviate problems in the toilet training process. Changes for current practice are recommended.

Child, Preschool↗
PubMedDate not supplied

[Population and economics in Quintana Roo state: some considerations from recent experience].

"This article focuses on the explosive population growth in Quintana Roo [Mexico] during the last few years and its...implications [for] the local economy. First, the article briefly describes population structure, emphasizing some migratory and socioeconomic aspects. Next it considers the status sectoral and regional production structure, which [emphasize] the strong dependence on tourism and its concentration in Cancun. In the conclusions population and economic aspects entwine, providing a more comprehensive developmental perspective." (SUMMARY IN ENG)

Americas↗
PubMed1990

Family functioning 2 to 4 years after preterm birth.

The purpose of the study was to determine if selected risk factors related to preterm birth continued to be associated with family functioning when preterm children were 2 to 4 years of age. A convenience sample of 55 mothers and 27 fathers participated in the survey. Parents completed the Family Dynamics Measure and the family APGAR. Multiple regression analyses were computed to examine the associations between the dependent variables for family functioning and the independent variables, which included child's developmental status, neonatal hospitalization length, adequacy of family economics, parental age, and marital status. Of these risk factors, longer neonatal hospitalizations continued to be associated with poorer family role functioning for mothers (R2 = .237, F = 2.43, p = .039).

Adaptation, Psychological↗
PubMed1979

Learning general practice--the experience of one trainee.

I report my experiences in learning general practice as a vocational trainee with 12 months divided between two general practices at the end of a three-year course. A parallel between developmental milestones and a trainee's educational development is drawn and the reasons which brought patients to me as a trainee are analysed.I suggest the trainee year should be a dynamic time of learning and that trainees should be in an educational environment including progressively less authority. The trainer/trainee relationship, like the doctor/patient relationship, is all important.

Attitude of Health Personnel↗
PubMed2006

Endosome dynamics during development.

Endocytosis has traditionally been studied in isolated cells. More recently, however, the analysis of protein trafficking in whole organisms has revealed that it plays exciting roles during development. Endocytic trafficking of cell adhesion molecules regulates epithelial polarity and cell migration. Developmental signaling pathways are regulated by the trafficking of receptors and their ligands through the endocytic pathway. Finally, impairment of the endocytic machinery can affect proliferation control and contribute to tumor development.

Animals↗
PubMed2005

Signaling to cytoskeletal dynamics during chemotaxis.

We review insights in signaling pathways controlling cell polarization and cytoskeletal organization during chemotactic movement in Dictyostelium amoebae and neutrophils. We compare and contrast these insights with our current understanding of pathways controlling chemotactic movements in more-complex multicellular developmental contexts.

Actins↗
PubMed2007

The developmental nephrome: systems biology in the developing kidney.

PURPOSE OF REVIEW: A set of important genes and signaling pathways involved in kidney development is emerging from analyses of mutant mice, in-vitro models, and global gene expression patterns. Conversion of data into dynamic models or networks through the synthesis of information at multiple levels is crucial for a better understanding of kidney development. RECENT FINDINGS: Genetic and in-vitro evidence is beginning to provide a limited sense of the network topology in stages of kidney development. Intriguing data from other fields suggest how, with the aid of large-scale gene expression studies, these stages might be represented as dynamic attractor states. It is also suggested how branching morphogenesis of the epithelial ureteric bud may be sustained by an autocatalytic set of proteins whose interactions lead to repeated rounds of tip and stalk generation. Accumulating data in lower organisms suggest network topologies may be quite flexible, and the implications of these results for varieties of tubulogenesis and renal regeneration after acute injury are discussed. SUMMARY: Currently it may be feasible to build tentative dynamic multistage models of nephrogenesis that facilitate experimental thinking. As data accumulate, it may become possible to test their predictive value.

Animals↗
PubMed2025

Complex and Dynamic Gene-by-Age and Gene-by-Environment Interactions Underlie Functional Morphological Variation in Adaptive Divergence in Arctic Charr (Salvelinus alpinus).

The evolution of adaptive phenotypic divergence requires heritable genetic variation. However, it is underappreciated that trait heritability is molded by developmental processes interacting with the environment. We hypothesized that the genetic architecture of divergent functional traits was dependent on age and foraging environment. Thus, we induced plasticity in full-sib families of Arctic charr (Salvelinus alpinus) morphs from two Icelandic lakes by mimicking prey variation in the wild. We characterized variation in body shape and size at two ages and investigated their genetic architecture with quantitative trait locus (QTL) analysis. Age had a greater effect on body shape than diet in most families, suggesting that development strongly influences phenotypic variation available for selection. Consistent with our hypothesis, multiple QTL were detected for all traits and their location depended on age and diet. Many of the genome-wide QTL were located within a subset of duplicated chromosomal regions suggesting that ancestral whole genome duplication events have played a role in the genetic control of functional morphological variation in the species. Moreover, the detection of two body shape QTL after controlling for the effects of age provides additional evidence for genetic variation in the plastic response of morphological traits to environmental variation. Thus, functional morphological traits involved in phenotypic divergence are molded by complex genetic interactions with development and environment.

Animals↗
PubMed2026

A novel iPSC model of Bryant-Li-Bhoj neurodevelopmental/neurodegenerative syndrome demonstrates the role of histone H3.3 in chromatin dynamics, neuronal differentiation, and maturation.

BACKGROUND: Bryant-Li-Bhoj neurodevelopmental syndrome (BLBS) is neurogenetic disorder caused by variants in H3-3A and H3-3B, the two genes that encode histone H3.3. Ninety-nine percent of individuals with BLBS show developmental delay/intellectual disability, but the mechanism by which variants in H3.3 result in these phenotypes is not yet understood, limiting the therapeutic interventions available to individuals living with BLBS. METHODS: Here, we investigate how one BLBS-causative variant, H3-3B p.Leu48Arg (L48R), affects neurodevelopment using an induced pluripotent stem cell model differentiated to 2D neural progenitor cells (NPCs), 2D forebrain neurons (FBNs), and 3D dorsal forebrain organoids (DFBOs). We employ a multi-omic approach in the 2D models to quantify the resulting changes in gene expression and chromatin accessibility. We used immunofluorescence (IF) staining to define the identities of cells in the 3D DFBOs and whole-cell patch clamp to investigate the electrophysiological properties of neurons in DFBOs. RESULTS: In the 2D systems, we found dysregulated gene expression and chromatin accessibility affecting neuronal fate, adhesion, neurotransmission, and excitatory/inhibitory balance. Immunofluorescence of DFBOs corroborated altered proportions of radial glia and mature neuronal populations. Patch clamp recordings revealed decreased electrical activity in neurons from L48R DFBOs compared to control DFBOs. CONCLUSIONS: These data provide the first mechanistic insights into the pathogenesis of BLBS from a human-derived model of neurodevelopment, which suggest that H3.3 L48R increases H3-3B expression, resulting in the hyper-deposition of H3.3 into the nucleosome, which underlies changes in gene expression and chromatin accessibility. Functionally, this causes dysregulation of cell adhesion, neurotransmission, and the balance between excitatory and inhibitory signaling. These results are a crucial step towards preclinical development and testing of targeted therapies for this and related disorders.

Histones↗
PubMed2002

Demecolcine-induced oocyte enucleation for somatic cell cloning: coordination between cell-cycle egress, kinetics of cortical cytoskeletal interactions, and second polar body extrusion.

Studies were designed to further explore the use of pharmacological agents to produce developmentally competent enucleated mouse oocytes for animal cloning by somatic cell nuclear transfer. Metaphase II oocytes from CF-1 and B6D2F1 strains were activated with ethanol and subsequently exposed to demecolcine at various times postactivation. Chromosome segregation, spindle dynamics, and polar body (PB) extrusion were monitored by fluorescence microscopy using DNA-, microtubule-, and microfilament-selective probes. Exposure to demecolcine did not affect rates of oocyte activation induced by ethanol but did disrupt the coordination of cytokinesis and karyokinesis, suppressing the extent and completion of spindle rotation and second PB extrusion in a strain-dependent manner. Moreover, strain- and treatment-specific variations in the rate of oocyte enucleation were also detected. In particular, CF1 oocytes were more efficiently enucleated relative to B6D2F1 oocytes, and demecolcine treatments initiated early after activation resulted in higher enucleation rates than when treatment was delayed. The observed strain differences are possibly caused by a combination of factors, such as the time course of meiotic cell-cycle progression after ethanol activation, the degree of spindle rotation, and the extent of second PB extrusion. These results suggest that developmentally competent cytoplasts can be produced by timely exposure of activated oocytes to agents that disrupt spindle microtubules. However, the utility of the demecolcine-induced enucleation protocol will require further investigation into factors linking karyokinesis to cytokinesis at the levels of cell-cycle control and oocyte cytoskeletal remodeling following artificial or natural means of egg activation.

Animals↗