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At least 1,207 records · Page 67Linked to original sources
PubMed1998

Cytokinesis in flowering plants: cellular process and developmental integration.

In phragmoplast-assisted cytokinesis of somatic cells, vesicle fusion generates a cell plate that matures into a new cell wall and its flanking plasma membranes. Insight into this dynamic process has been gained in the past few years and additional molecular components of the basic machinery of cytokinesis have been identified. Specialized modes of cytokinesis occur in meiosis and gametophyte development, and recent studies indicate that they are genetically distinct from somatic cytokinesis.

Cell Cycle↗
PubMed2004

Solution structure and backbone dynamics of the pleckstrin homology domain of the human protein kinase B (PKB/Akt). Interaction with inositol phosphates.

The programmed cell death occurs as part of normal mammalian development. The induction of developmental cell death is a highly regulated process and can be suppressed by a variety of extracellular stimuli. Recently, the ability of trophic factors to promote survival have been attributed, at least in part, to the phosphatidylinositide 3'-OH kinase (PI3K)/Protein Kinase B (PKB, also named Akt) cascade. Several targets of the PI3K/PKB signaling pathway have been identified that may underlie the ability of this regulatory cascade to promote cell survival. PKB possesses a N-terminal Pleckstrin Homology (PH) domain that binds specifically and with high affinity to PtIns(3,4,5)P(3) and PtIns(3,4)P(2), the PI3K second messengers. PKB is then recruited to the plasma membrane by virtue of its interaction with 3'-OH phosphatidylinositides and activated. Recent evidence indicates that PKB is active in various types of human cancer; constitutive PKB signaling activation is believed to promote proliferation and increased cell survival, thereby contributing to cancer progression. Thus, it has been shown that induction of PKB activity is augmented by the TCL1/MTCP1 oncoproteins through a physical association requiring the PKB PH domain. Here we present the three-dimensional solution structure of the PH domain of the human protein PKB (isoform beta). PKBbeta-PH is an electrostatically polarized molecule that adopts the same fold and topology as other PH-domains, consisting of a beta-sandwich of seven strands capped on one top by an alpha-helix. The opposite face presents three variable loops that appear poorly defined in the NMR structure. Measurements of (15)N spin relaxation times and heteronuclear (15)N[(1)H]NOEs showed that this poor definition is due to intrinsic flexibility, involving complex motions on different time scales. Chemical shift mapping studies correctly defined the binding site of Ins(1,3,4,5)P(4) (the head group of PtIns(3,4,5)P(3)), as was previously proposed from a crystallographic study. More interestingly, these studies allowed us to define a putative alternative low-affinity binding site for Ins(1,4,5)P(3). The binding of this sugar to PKBbeta-PH might also involve non-specific association that could explain the stabilization of the protein in solution in the presence of Ins(1,4,5)P(3).

Apoptosis↗
PubMed1992

Developmental pattern of gene-specific DNA methylation in the mouse embryo and germ line.

Methylation patterns of specific genes have been studied by polymerase chain reaction and found to undergo dynamic changes in the germ line and early embryo. Some CpG sites are methylated in sperm DNA and unmodified in mature oocytes, indicating that the parental genomes have differential methylation profiles. These differences, however, are erased by a series of early embryonic demethylation and postblastula remodification events, which serve to reestablish the basic adult methylation pattern prior to organogenesis. During gametogenesis, all of these sites are unmethylated in primordial germ cells but eventually become remodified by 18.5 days postcoitum in both males and females. The final methylation profile of the mature germ cells is then formed by a multistep process of site-specific demethylation events. These results form a basis for the understanding of the biochemical mechanisms and role of DNA methylation in embryonic development.

Animals↗
PubMed2004

Dynamics of fruiting body morphogenesis.

Myxobacteria build their species-specific fruiting bodies by cell movement and then differentiate spores in specific places within that multicellular structure. New steps in the developmental aggregation of Myxococcus xanthus were discovered through a frame-by-frame analysis of a motion picture. The formation and fate of 18 aggregates were captured in the time-lapse movie. Still photographs of 600 other aggregates were also analyzed. M. xanthus has two engines that propel the gliding of its rod-shaped cells: slime-secreting jets at the rear and retractile pili at the front. The earliest aggregates are stationary masses of cells that look like three-dimensional traffic jams. We propose a model in which both engines stall as the cells' forward progress is blocked by other cells in the traffic jam. We also propose that these blockades are eventually circumvented by the cell's capacity to turn, which is facilitated by the push of slime secretion at the rear of each cell and by the flexibility of the myxobacterial cell wall. Turning by many cells would transform a traffic jam into an elliptical mound, in which the cells are streaming in closed orbits. Pairs of adjacent mounds are observed to coalesce into single larger mounds, probably reflecting the fusion of orbits in the adjacent mounds. Although fruiting bodies are relatively large structures that contain 10(5) cells, no long-range interactions between cells were evident. For aggregation, M. xanthus appears to use local interactions between its cells.

Morphogenesis↗
PubMed1997

Tubulin synthesis and assembly in differentiating neurons.

Neurons are highly polarized cells that extend long processes, the axons and dendrites, to form contacts with target cells. The formation and maintenance of this specialized morphology relies on the assembly of an organized microtubule array that is the predominant component of the neuronal cytoskeleton. During this process there is an evolution in the composition and dynamics of microtubules, resulting in stable microtubule bundles that provide structural support and function in intracellular transport along the axon. In this essay we provide an overview of the mechanisms regulating the synthesis and assembly of tubulin in differentiating neurons with particular attention to the roles of multiple tubulin isotypes, posttranslational modifications of tubulin, and microtubule-associated proteins. We conclude that, ultimately, the developmental regulation of microtubules in neurons may require the coordinated expression and posttranslational modifications of tubulin and microtubule-associated proteins to provide biochemical forms that favour specific interactions, each combination conferring distinctive dynamic and functional properties.

Animals↗
PubMed2001

Developmental changes of tau protein and mRNA in cultured rat brain oligodendrocytes.

Oligodendrocytes elaborate an extensive network of multibranched processes and flat membranous sheets. Microtubules (MT) participate in the elaboration and stabilization of myelin-forming processes and are essential for cellular sorting processes. Microtubule-associated proteins (MAPs) are involved in the regulation and stabilization of the dynamic MT network. It has been shown previously that oligodendrocytes express the MAP tau, a phosphoprotein most abundant in neurons of the CNS. In this article, we demonstrate for the first time that oligodendrocytes contain all six tau isoforms, and that tau mRNA and protein expression is developmentally regulated. Immunoblot analysis reveals that tau protein is more abundant, and mature isoforms are more prominent at later stages of development. During the first week of culture maturation, a marked decrease in phosphorylation is observable. Using an RT-PCR approach, we can show that oligodendrocytes express small amounts of exon 3 containing isoforms and that during culture maturation, tau mRNA splice products with 3 MT-binding domains (3R) decrease and mRNA with 4 MT-binding domains (4R) increase. In situ hybridization study demonstrates that tau mRNA is present in precursor cells and in mature oligodendrocytes. Tau mRNA is actively transported into the cellular processes, is specifically present in the primary and some of the secondary processes, enriched at the turning and branching points and the growing tips, and often appears as small patches. Hence, localized tau translation at specific sites in the cellular extensions might contribute to the regulation of MT stability during process formation, early axonal contact establishment, and myelination.

Aging↗
PubMed2026

Integrative dual-track transcriptomics reveals stage-specific coordination, regulatory divergence, and HSP90AA1-associated remodeling in human folliculogenesis.

Human folliculogenesis depends on coordinated yet non-identical developmental remodeling in the oocyte and its surrounding granulosa cells. When these two compartments remain synchronized and when they diverge into lineage-specific regulatory states, however, remains incompletely resolved. Here we performed an integrative dual-track re-analysis of the human RNA-seq dataset GSE107746, modeling oocytes and granulosa cells as distinct but developmentally linked compartments across follicular progression. Analysis of 148 sequencing libraries showed that compartment identity was the dominant source of transcriptomic variation, supporting compartment-aware downstream interpretation. Within this framework, oocytes followed a relatively continuous developmental trajectory, with substantial transcriptional remodeling already evident across adjacent stages, whereas granulosa cells showed weaker early-stage contrasts but markedly stronger late-stage reorganization, particularly around the antral and preovulatory transitions. Functional enrichment indicated that oocyte maturation was associated with RNA-processing and broader genome-regulatory remodeling, whereas granulosa maturation was dominated by progressive mitochondrial and bioenergetic activation. Co-expression analysis showed that both compartments contained strong late-stage programmes together with inverse early-state modules, indicating a shared systems-level architecture of maturation, although the hub-gene composition and biological content of these programmes were largely compartment-specific. Machine-learning validation reinforced this asymmetry: oocyte stage classification was best recovered from a compact eigengene-based representation, whereas granulosa stage discrimination was better resolved by a broader differential-expression-derived feature set. At the gene level, HSP90AA1 emerged as a stage-associated marker with compartment-specific behavior, showing progressive attenuation across oocyte development, assignment to the selected oocyte blue module, and sharper transitional dynamics in granulosa cells. Together, these findings support a model in which human folliculogenesis proceeds through coordinated but non-equivalent transcriptomic remodeling, with shared developmental logic at the systems level but distinct molecular execution in germline and somatic compartments.

Co-expression networks↗
PubMed2006

Depolymerized hyaluronan induces vascular endothelial growth factor, a negative regulator of developmental epithelial-to-mesenchymal transformation.

Cardiac malformations constitute the most common birth defects, of which heart septal and valve defects are the most frequent forms diagnosed in infancy. These cardiac structures arise from the endocardial cushions through dynamic interactions between cells and the extracellular matrix (cardiac jelly). Targeted deletion of the hyaluronan synthase-2 (Has2) gene in mice results in an absence of hyaluronan (HA), cardiac jelly, and endocardial cushions, a loss of vascular integrity, and death at embryonic day 9.5. Despite the requirements for Has2 and its product, HA, in the developing heart, little is known about the normal processing and removal of HA during development. Cell culture studies show that HA obtains new bioactivity after depolymerization into small oligosaccharides. We previously showed reduction in Has2 expression and diminished presence of HA at later stages of heart development as tissue remodeling formed the leaflets of the cardiac valves. Here we show that small oligosaccharide forms of HA (o-HA) act antagonistically to developmental epithelial-to-mesenchymal transformation (EMT), which is required to generate the progenitor cells that populate the endocardial cushions. We further show that o-HA induces vascular endothelial growth factor (VEGF), which acts as a negative regulator of EMT. This is the first report illustrating a functional link between oligosaccharide HA and VEGF. Collectively, our data indicate that following endocardial cell EMT, native HA is likely processed to o-HA, which stimulates VEGF activity to attenuate cardiac developmental EMT.

Animals↗
PubMed2006

Experience-dependent plasticity in adult visual cortex.

Experience-dependent plasticity is a prominent feature of the mammalian visual cortex. Although such neural changes are most evident during development, adult cortical circuits can be modified by a variety of manipulations, such as perceptual learning and visual deprivation. Elucidating the underlying mechanisms at the cellular and synaptic levels is an essential step in understanding neural plasticity in the mature animal. Although developmental and adult plasticity share many common features, notable differences may be attributed to developmental cortical changes at multiple levels. These range from shifts in the molecular profiles of cortical neurons to changes in the spatiotemporal dynamics of network activity. In this review, we will discuss recent progress and remaining challenges in understanding adult visual plasticity, focusing on the primary visual cortex.

Animals↗
PubMed2000

Selective deficits of vibrotactile sensitivity in dyslexic readers.

Developmental dyslexia is a disability of literacy skill that has also been associated with sensory processing deficits, primarily for the detection of dynamic auditory and visual stimuli. Here we examined whether analogous deficits extend into the domain of somatosensory perception. Detection thresholds for each of three frequencies of vibration were obtained for 11 readers with a prior history of dyslexia and 14 similarly aged adult controls. The poor readers were significantly less sensitive to vibration at 3 Hz (P<0. 01) but not at either 30 or 100 Hz. Detection of each of these three vibration rates is mediated primarily by a separate somatosensory fiber tract; deficits selective to 3 Hz therefore suggest an impairment within the slow-adapting I (SAI) fiber system beginning with Merkel-cell mechanoreceptors in the glabrous skin. Such evidence is compatible with the hypothesis of a generalized, multisensory deficit of temporal processing functions in dyslexia.

Adolescent↗
PubMed2005

The psychodynamics of borderline personality disorder: a view from developmental psychopathology.

This article provides a contemporary view of the psychodynamics of borderline personality disorder (BPD) from a developmental psychopathology perspective. We first briefly describe the evolution of the borderline construct in psychoanalysis and psychiatry. Then we provide clinically and empirically informed model of domains of personality function and dysfunction that provides a roadmap for thinking about personality pathology from a developmental psychopathology standpoint and examine the nature and phenomenology of BPD in terms of these domains of functioning. Next, we describe prominent dynamic theories of etiology of BPD and examine these in relation to the available research. Finally, we describe psychodynamic conceptions of treatment and the way BPD phenomena manifest in treatment, followed again by consideration of relevant research, particularly on transference-countertransference constellations empirically identified in the treatment of patients with BPD.

Adolescent↗
PubMed2005

The neurodevelopmental model of schizophrenia: update 2005.

Neurodevelopmental models of schizophrenia that identify longitudinal precursors of illness have been of great heuristic importance focusing most etiologic research over the past two decades. These models have varied considerably with respect to specificity and timing of hypothesized genetic and environmental 'hits', but have largely focused on insults to prenatal brain development. With heritability around 80%, nongenetic factors impairing development must also be part of the model, and any model must also account for the wide range of age of onset. In recent years, longitudinal brain imaging studies of both early and adult (to distinguish from late ie elderly) onset populations indicate that progressive brain changes are more dynamic than previously thought, with gray matter volume loss particularly striking in adolescence and appearing to be an exaggeration of the normal developmental pattern. This supports an extended time period of abnormal neurodevelopment in schizophrenia in addition to earlier 'lesions'. Many subtle cognitive, motor, and behavioral deviations are seen years before illness onset, and these are more prominent in early onset cases. Moreover, schizophrenia susceptibility genes and chromosomal abnormalities, particularly as examined for early onset populations (ie GAD1, 22q11DS), are associated with premorbid neurodevelopmental abnormalities. Several candidate genes for schizophrenia (eg dysbindin) are associated with lower cognitive abilities in both schizophrenic and other pediatric populations more generally. Postmortem human brain and developmental animal studies document multiple and diverse effects of developmental genes (including schizophrenia susceptibility genes), at sequential stages of brain development. These may underlie the broad array of premorbid cognitive and behavioral abnormalities seen in schizophrenia, and neurodevelopmental disorders more generally. Increased specificity for the most relevant environmental risk factors such as exposure to prenatal infection, and their interaction with susceptibility genes and/or action through phase-specific altered gene expression now both strengthen and modify the neurodevelopmental theory of schizophrenia.

Adult↗
PubMed2005

Altered parvalbumin-positive neuron distribution in basal ganglia of individuals with Tourette syndrome.

Tourette syndrome (TS) is a childhood neuropsychiatric disorder characterized by motor and vocal tics. Imaging studies found alterations in caudate (Cd) and putamen volumes. To investigate possible alterations in cell populations, postmortem basal ganglia tissue from individuals with TS and normal controls was analyzed by using unbiased stereological techniques. A markedly higher total neuron number was found in the globus pallidus pars interna (GPi) of TS. In contrast, a lower neuron number and density was observed in the globus pallidus pars externa and in the Cd. An increased number and proportion of the GPi neurons were positive for the calcium-binding protein parvalbumin in tissue from TS subjects, whereas lower densities of parvalbumin-positive interneurons were observed in both the Cd and putamen of TS subjects. This change is consistent with a developmental defect in tangential migration of some GABAergic neurons. The imbalance in striatal and GPi inhibitory neuron distribution suggests that the functional dynamics of cortico-striato-thalamic circuitry are fundamentally altered in severe, persistent TS.

Adult↗
PubMedDate not supplied

The development of infants' reaches for stationary and moving targets.

The organization of infants' reaching skill for stationary and moving targets was examined. While 58 term, healthy infants at 5.5, 8.5, and 11.5 months of age reached for and grasped a cloth-covered dowel, their reaches were videotaped for later slow-motion analysis. Analyses addressed infants' anticipatory adjustment of hand alignment, use of information from spinning and oscillating targets to update ongoing reaches, and ability to capture targets moving in depth. Infants at all ages made anticipatory adjustments of hand alignment, although the effectiveness of these adjustments improved with age. Regardless of age, infants also used dynamic information from spinning and oscillating targets to update ongoing reaches, but the way infants used this information was related to age. Developmental constancy characterized infants' reaches for approaching targets. By observing infants' reaches for stationary, spinning, and approaching targets, the study expands the range of conditions under which adaptive reaching skill has been examined and provides insight into the roles of anticipation and updating in the development of early manual skill.

Age Factors↗
PubMed1996

Aspects of anima and animus in Oedipal development.

This paper aims to insert the contrasexual archetype into the dynamic narrative of the Oedipus complex. Jung used the terms 'anima' and 'animus' to classify observed phenomena but did not explore the developmental origins of these phenomena in terms of personal history and experience. Some typical manifestations of anima and animus are described and shown to be rooted in the vicissitudes of Oedipal development. The contrasexual archetype is initially mediated by the oedipally loved parent and subsequent manifestations bear the imprint not only of the parent himself or herself but of the entire complex of object relationships in which Oedipal love is embedded. Successful resolution of the Oedipus complex depends on freeing the anima/animus from its Oedipal bonds so that its function as a bridge to the unconscious can be realized. This function is connected with the emergence of a symbolic capacity through which anima and animus can be recognized and valued as imaginal rather than external realities. The clinical material explores the damaging impact of a split parental couple on this process and the positive role of idealization as a stimulus to psychic development.

Adult↗
PubMedDate not supplied

Components of soft tissue deformations in subjects with untreated angle's Class III malocclusions: thin-plate spline analysis.

While the dynamics of maxillo-mandibular allometry associated with treatment modalities available for the management of Class III malocclusions currently are under investigation, developmental aberration of the soft tissues in untreated Class III malocclusions requires specification. In this study, lateral cephalographs of 124 prepubertal European-American children (71 with untreated Class III malocclusion; 53 with Class I occlusion) were traced, and 12 soft-tissue landmarks digitized. Resultant geometries were scaled to an equivalent size and mean Class III and Class I configurations compared. Procrustes analysis established statistical difference (P < 0.001) between the mean configurations. Comparing the overall untreated Class III and Class I configurations, thin-plate spline (TPS) analysis indicated that both affine and non-affine transformations contribute towards the deformation (total spline) of the averaged Class III soft tissue configuration. For non-affine transformations, partial warp 8 had the highest magnitude, indicating large-scale deformations visualized as a combination of columellar retrusion and lower labial protrusion. In addition, partial warp 5 also had a high magnitude, demonstrating upper labial vertical compression with antero-inferior elongation of the lower labio-mental soft tissue complex. Thus, children with Class III malocclusions demonstrate antero-posterior and vertical deformations of the maxillary soft tissue complex in combination with antero-inferior mandibular soft tissue elongation. This pattern of deformations may represent gene-environment interactions, resulting in Class III malocclusions with characteristic phenotypes, that are amenable to orthodontic and dentofacial orthopedic manipulations.

Age Factors↗
PubMed2001

In vitro fertilized human eggs. An electron microscopic study.

This paper describes by scanning and transmission electron microscopy the ultrastructure of the human fertilized egg and its vestments (cumulus oophorus and zona pellucida). Data are reported on the ultrastructure of a. conventional in vitro fertilized eggs (pronuclear eggs and cleaving eggs at two-to-four cell stage); b. eggs at the same developmental stage deriving fro intracytoplasmic sperm injection. The present results showed that: 1. The cumulus-enclosed fertilized egg is a highly dynamic structure in which egg vestments play a crucial role, positively affecting fertilization and healthy embryo development; 2. Intracytoplasmic sperm injection technique does not seem to significantly alter fertilized egg morphology.

Cell Nucleus↗