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PubMed1989

Early school dropout: configurations and determinants.

This longitudinal study examined behavioral, cognitive, and demographic factors associated with early school dropout. Follow-up assessments were completed on a sample of girls (n = 248) and boys (n = 227) who had first been seen when they were in the seventh grade. School status was determined for all living subjects; 99% of them were interviewed individually in the fifth annual test wave. Overall, 14% of the group had dropped out of school prior to completing grade 11. The clusters of males and females most vulnerable to early school dropout were characterized in grade 7 by high levels of aggressiveness and low levels of academic performance (82% early dropout in males; 47% early dropout in females). In seventh grade, subjects who subsequently dropped out tended to affiliate with persons who were also at risk for dropout. Socioeconomic status, race, and early parenthood were also associated with school dropout. The primary outcomes were supported by convergent variable-oriented and person-oriented analyses. Some developmental dynamics of the phenomena are discussed.

Achievement↗
PubMed2006

Infrequent, but not frequent, reinforcers produce more variable responding and deficient sustained attention in young children with attention-deficit/hyperactivity disorder (ADHD).

BACKGROUND: The underlying behavioral/psychological processes of attention-deficit/hyperactivity disorder are unclear. Motivational factors, related to dopamine dysfunction, may play an important role in the development of the behavioral symptoms. Particularly, infrequent, but not frequent, reinforcers have been suggested to be associated with altered responding and deviant behavior in children with ADHD. The present study was designed to analyze the influence of reinforcement frequency on operationalized measures of hyperactivity, impulsiveness, sustained attention, and response variability. METHODS: Fifty-six boys, half of whom were diagnosed with ADHD, completed a computerized task presented as a game with two squares on the screen. One square was associated with reinforcement. The task required responses by the computer mouse under contingencies alternating between variable interval schedules of short (mean 2 s) and long (mean 20 s) durations. Reinforcers were cartoon pictures and small trinkets. RESULTS: Overall, there was no difference between children with ADHD and comparison children when reinforcers were given frequently. Statistically significant differences on measures of sustained attention and variability, but not hyperactivity and impulsiveness, were found during infrequent reinforcement only. Age effects interacted with group effects on sustained attention, showing that group differences were found in the young children only. Surprisingly, older comparison children showed increased response variability and no learning. CONCLUSIONS: When reinforcers are infrequent, children with ADHD show deficient sustained attention and increased variability in responding. Computer experience may have interfered with measures of hyperactivity and impulsiveness. The unexpectedly poor performance of the older comparison children may have been due to inefficient reinforcers or to verbally governed behavior overruling reinforcer effects. Reinforcer characteristics and experimental procedures are important factors influencing findings in studies investigating motivational factors. The study provides some support for the dynamic developmental theory of ADHD predicting relationships between neurobiological deficits, altered reinforcement mechanisms, and treatment recommendations.

Age Factors↗
PubMed2003

The family experience of "sudden health": the case of intractable epilepsy.

This article reports the experience of "sudden health" among six families who participated in an exploratory qualitative study of families with a member who elects to have corrective surgery for intractable epilepsy. Families were interviewed pre- and post-surgery (6-8 months) and the interviews were analyzed using a constant comparative methodology. Findings indicated that (1) families were organized in two primary ways (nesting and crisis) to deal with epilepsy and the aftermath of surgery and (2) "sudden health" had differing effects on these families depending on their organizational style, emotional communication process, and developmental dynamics.

Activities of Daily Living↗
PubMed2006

Dynamics of development and dispersal in sessile microbial communities: examples from Pseudomonas aeruginosa and Pseudomonas putida model biofilms.

Surface-associated microbial communities in many cases display dynamic developmental patterns. Model biofilms formed by Pseudomonas aeruginosa and Pseudomonas putida in laboratory flow-chamber setups represent examples of such behaviour. Dependent on the experimental conditions the bacteria in these model biofilms develop characteristic multicellular structures through a series of distinct steps where cellular migration plays an important role. Despite the appearance of these characteristic developmental patterns in the model biofilms the available evidence suggest that the biofilm forming organisms do not possess comprehensive genetic programs for biofilm development. Instead the bacteria appear to have evolved a number of different mechanisms to optimize surface colonization, of which they express a subset in response to the prevailing environmental conditions. These mechanisms include the ability to regulate cellular adhesiveness and migration in response to micro-environmental signals including those secreted by the bacteria themselves.

Adaptation, Physiological↗
PubMed2006

Deciphering the underlying mechanism of specification and differentiation: the sea urchin gene regulatory network.

The regulatory genome functions as a vast information processor through development. It processes the initial conditions that are set by asymmetric distributions of cellular components in the egg and translates them into the onset of spatially localized specification states. It regulates the timely differential activation of signaling molecules and transcription factors that divide the emerging domains into subdomains. It also governs the activation of groups of differentiation genes, the genes that encode, at the protein level, the functional and the structural properties of a cell type. The sea urchin endomesoderm gene regulatory network provides a window into the different levels of the regulatory apparatus. It demonstrates how the static physical genomic components define functional connections between the various regulatory genes that act together to conduct the dynamical developmental program.

Animals↗
PubMed1983

Development of neuronal response properties in the cat dorsal lateral geniculate nucleus during monocular deprivation.

We measured response properties of X- and Y-cells from laminae A and A1 of the dorsal lateral geniculate nucleus of monocularly lid-sutured cats at 8, 12, 16, 24, and 52-60 wk of age. Visual stimuli consisted of small spots of light and vertically oriented sine-wave gratings counterphased at a rate of 2 cycles/s. In cats as young as 8 wk of age, nondeprived and deprived neurons could be clearly identified as X-cells or Y-cells with criteria previously established for adult animals. Nonlinear responses of Y-cells from 8- and 12-wk-old cats were often temporally labile; that is, the amplitude of the nonlinear response of nondeprived and deprived cells increased or decreased suddenly. A similar lability was not noted for the linear response component. This phenomenon rarely occurred in older cats. At 8 wk of age, Y-cell proportions (number of Y-cells/total number of cells) in nondeprived and deprived A-laminae were approximately equal. By 12 wk of age and thereafter, the proportion of Y-cells in deprived laminae was significantly lower than that in nondeprived laminae. At no age was there a systematic difference in response properties (spatial resolution, latency to optic chiasm stimulation, etc.) for Y-cells between deprived and nondeprived laminae. Spatial resolution, defined as the highest spatial frequency to which a cell would respond at a contrast of 0.6, was similar for nondeprived and deprived X-cells until 24 wk of age. In these and older cats, the mean spatial resolution of deprived X-cells was lower than that of nondeprived X-cells. This difference was noted first for lamina A1 at 24 wk of age and later for lamina A at 52-60 wk of age. The average latency of X-cells to optic chiasm stimulation was slightly greater in deprived laminae than in nondeprived laminae. No such difference was seen for Y-cells. Cells with poor and inconsistent responses were encountered infrequently but were observed far more often in deprived laminae than in nondeprived laminae. Lid suture appears to affect the development of geniculate X- and Y-cells in very different ways. Not only is the final pattern of abnormalities quite different between these cell groups, but the developmental dynamics of these abnormalities also differ.

Animals↗
PubMed2000

Cortical layer VII and persistent subplate cells in mammalian brains.

Layer VII is the deepest cortical layer in rats, and consists of a thin layer of persistent subplate cells overlain by a cell-sparse, myelin-rich stratum through which many corticocortical axons travel. Layer VII neurons participate in local and long-distance corticocortical connections. The present study was undertaken to determine whether layer VII is a typical feature in rodent brains, and to determine which other mammalian taxa exhibit a layer VII. The adult brains of 144 species from 22 orders were examined. Of these, 43 species in 6 orders exhibit a layer VII. These include the sciurognath Rodentia, Insectivora, Paucituberculata, Paramelemorphia, some Xenarthra, and some Chiroptera. In all taxa interstitial cells were observed scattered throughout the white matter. The observed distribution of layer VII in this sample of mammalian taxa suggests that layer VII is a typical feature in some orders, but is not present in most orders. The heterogeneous distribution of layer VII in the Rodentia and Chiroptera suggests that species-level developmental dynamics are involved. It is hypothesized that the timing of subplate apoptosis in relation to the establishment of corticocortical connections is the major factor that determines whether layer VII is present in the adult stage.

Animals↗
PubMed1998

Enamelysin (matrix metalloproteinase-20): localization in the developing tooth and effects of pH and calcium on amelogenin hydrolysis.

The formation of dental enamel is a precisely regulated and dynamic developmental process. The forming enamel starts as a soft, protein-rich tissue and ends as a hard tissue that is over 95% mineral by weight. Intact amelogenin and its proteolytic cleavage products are the most abundant proteins present within the developing enamel. Proteinases are also present within the enamel matrix and are thought to help regulate enamel development and to expedite the removal of proteins prior to enamel maturation. Recently, a novel matrix metalloproteinase named enamelysin was cloned from the porcine enamel organ. Enamelysin transcripts have previously been observed in the enamel organ and dental papillae of the developing tooth. Here, we show that the sources of the enamelysin transcripts are the ameloblasts of the enamel organ and the odontoblasts of the dental papilla. Furthermore, we show that enamelysin is present within the forming enamel and that it is transported in secretory vesicles prior to its secretion from the ameloblasts. We also characterize the ability of recombinant enamelysin (rMMP-20) to degrade amelogenin under conditions of various pHs and calcium ion concentrations. Enamelysin displayed the greatest activity at neutral pH (7.2) and high calcium ion concentration (10 mM). During the initial stages of enamel formation, the enamel matrix maintains a neutral pH of between 7.0 and 7.4. Thus, enamelysin may play a role in enamel and dentin formation by cleaving proteins that are also present during these initial developmental stages.

Ameloblasts↗
PubMed1986

The Thompson-Patterson Scale of Psychosocial Development: II. Investigation of its use in the assessment of preschool children.

The Thompson-Patterson Scale of Psychosocial Development (TP) is a parent interview questionnaire, each item scored on a 3 point scale and computer analyzed to yield a histogram profile consisting of 11 scale scores. Eight of these scales measure coping styles characteristic of sequential stages of psychosocial development and the remaining 3 are symptom scales. A pilot study was conducted to assess the usefulness of the TP as a diagnostic and therapeutic assessment instrument for preschoolers. The results indicated the following: i) a "healthy" profile emerged in the control group ii) a significant difference existed in the initial assessment profiles of the clinic and control groups; iii) the control group profiles were stable over the period of study; and iv) the profiles of the clinic group showed a movement towards health with treatment that reflected changes in the clinical status of the children. The promising results of this preliminary study suggest there is value in further investigation of the TP scale as an instrument for the dynamic developmental assessment of preschool children.

Adaptation, Psychological↗
PubMed2006

Role of instrumented fetal sheep preparations in defining the pathogenesis of human periventricular white-matter injury.

Periventricular white-matter injury is the major form of brain injury associated with prematurity and the leading cause of cerebral palsy in survivors of premature birth. Progress in understanding the pathogenesis of periventricular white-matter injury requires the development of animal models that are relevant to the unique physiology of the preterm human brain and that replicate the major neuropathologic features of human injury. The sheep is the most extensively studied true fetal preparation. The neurodevelopment of the preterm sheep fetus (0.65 gestation) is comparable to that of the preterm human between approximately 24 and 28 weeks. The size of the fetal sheep permits chronic instrumentation so that well-defined insults can be studied with reliable measurements of blood flow and metabolism in cerebral white-matter. We review here recent developments in the understanding of the role of cerebral hypoxia-ischemia and vulnerable oligodendrocyte progenitors in the pathogenesis of periventricular white-matter injury in the immature sheep fetus. We focus on recent developments in high-resolution spatially defined cerebral blood flow measurements in utero. We determined ovine white-matter maturation between 90 and 120 days' gestation, as defined by immunohistochemical localization of oligodendrocyte lineage-specific antibodies. There was considerable spatial and temporal heterogeneity in oligodendrocyte maturation in the immature periventricular white-matter. Oligodendrocyte maturation in the 90- to 105-day fetal sheep closely coincided with that of the preterm human during the high-risk period for white-matter injury. Hence, the immature state of the 90- to 105-day fetal periventricular white-matter is an optimal and dynamic developmental window to study the role of cellular-maturational factors in the pathogenesis of white-matter injury. We conclude with a review of the significant advantages of the instrumented fetal sheep to accelerate progress in the translation of preventive therapies for periventricular white-matter injury and cerebral palsy.

Animals↗
PubMed2005

Tracking hematopoiesis at the single cell level.

Despite intensive research, many longstanding questions of experimental hematology remain unsolved. One major reason is the fact that hematopoiesis is usually followed by analyzing populations of cells rather than individual cells, at few points in time during an experiment and without knowing (or quickly loosing) the cells' individual identities. The static picture yielded by this approach makes it impossible to appreciate the dynamic developmental processes leading to the generation of the full hematopoietic system from individual hematopoietic stem cells (HSCs). Real-time tracking of individual cells in culture, tissues, or whole organisms would be an extremely powerful approach to fully understand the developmental complexity of hematopoiesis. To this end, a computer-aided culture and bioimaging system is being developed to follow the fate of individual cells over long periods of time. This system is used to follow the development of multilineage cobblestone colonies from adult HSCs in stroma cocultures at the single cell level over many generations. To facilitate noninvasive detection of lineage commitment in these cultures, new subcellular forms of optimized fluorescent proteins have been developed to allow simultaneous marking of multiple hematopoietic lineages within the same animal.

Adult↗
PubMed2006

A comparison of analysis of variance and correlation methods for investigating cognitive development with functional magnetic resonance imaging.

Statistical approaches used in functional magnetic resonance imaging (fMRI) to study cognitive development are varied and evolving. Two approaches have generally been used. These are between-group end-point analysis of variance (ANOVA) and age-related regression. Differences in these 2 approaches could produce different results when applied to a single data set. Event-related fMRI data from a group of typically developing participants (n = 95; age range = 7-35 years) performing controlled lexical processing tasks were analyzed using both methods. Results from the 2 approaches showed significant overlap, but also noteworthy differences. The results suggest that for regions showing age-related changes, correlation was relatively more sensitive to more linear changes whereas ANOVA was relatively more sensitive to less-linear changes. These findings suggest that full characterization of developmental dynamics will require converging methodologies.

Adolescent↗
PubMed2006

Differential zonal expression and adrenocorticotropin regulation of secreted protein acidic and rich in cysteine (SPARC), a matricellular protein, in the midgestation human fetal adrenal gland: implications for adrenal development.

CONTEXT: Matricellular proteins are a group of secreted, multifunctional extracellular matrix glycoproteins that includes thrombospondins (TSPs), tenascin-C, and secreted protein acidic and rich in cysteine (SPARC). They may be implicated in the dynamic developmental processes of the human fetal adrenal (HFA) in which the outer, definitive zone (DZ) cells are postulated to proliferate, migrate centripetally, differentiate, and populate the inner, steroidogenic fetal zone (FZ). OBJECTIVE: The objective of the study was to identify a matricellular molecule that likely plays a major role in HFA development. DESIGN: Studies involved RNA, cryosections, and cell cultures from 14- to 23-wk HFAs and human adult adrenal RNA. MAIN OUTCOME MEASURES: Measures included transcripts encoding matricellular proteins, using real-time quantitative RT-PCR; SPARC localization by immunostaining; and ACTH regulation of SPARC expression and secretion by quantitative RT-PCR and Western blot. RESULTS: SPARC HFA mRNA was 100-, 700-, and 300-fold higher than TSP-1, TSP-2, and tenascin-C mRNA, respectively. HFA SPARC mRNA was 3-fold higher than adult adrenals (P < 0.005), comparable with levels in adult brain (positive control), whereas mRNAs encoding TSP-1 and TSP-2 were lower in fetal than adult adrenals. SPARC immunoreactivity was detected exclusively in the FZ, not DZ. ACTH, a key regulator of HFA growth and function, increased SPARC mRNA (by 1.7-fold at 1 nm, 48 h, P < 0.05) in isolated FZ cells but not DZ cells. ACTH up-regulation of SPARC protein was also detected in FZ cell lysates and culture medium. CONCLUSIONS: Results suggest a possible role for SPARC in development of functional and/or structural zonation of the HFA.

Adrenal Glands↗
PubMed1995

Periaxin expression in myelinating Schwann cells: modulation by axon-glial interactions and polarized localization during development.

Periaxin is a newly described protein that is expressed exclusively by myelinating Schwann cells. In developing nerves, periaxin is first detected as Schwann cells ensheathe axons, prior to the appearance of the proteins that characterize the myelin sheath. Periaxin is initially concentrated in the adaxonal membrane (apposing the axon) but, during development, as myelin sheaths mature, periaxin becomes predominately localized at the abaxonal Schwann cell membrane (apposing the basal lamina). In permanently axotomized adult nerves, periaxin is lost from the abaxonal and adaxonal membranes, becomes associated with degenerating myelin sheaths and is phagocytosed by macrophages. In crushed nerves, in which axons regenerate and are remyelinated, periaxin is first detected in the adoxonal membrane as Schwann cells ensheathe regenerating axons, but again prior to the appearance of other myelin proteins. Periaxin mRNA and protein levels change in parallel with those of other myelin-related genes after permanent axotomy and crush. These data demonstrate that periaxin is expressed by myelinating Schwann cells in a dynamic, developmentally regulated manner. The shift in localization of periaxin in the Schwann cell after completion of the spiralization phase of myelination suggests that periaxin participates in membrane-protein interactions that are required to stabilize the mature myelin sheath.

Animals↗
PubMed2001

Dissection of NT3 functions in vivo by gene replacement strategy.

The development of the peripheral nervous system is governed in part by a family of neurotrophic factors that signal through Trk tyrosine kinase receptors. Neurotrophin 3 (NT3) ablation in mice causes a more severe neuronal phenotype than deletion of its receptor TrkC, suggesting that NT3 acts also through other non-preferred Trk receptors. To study the role of low-affinity ligand receptor interactions in vivo, we have replaced the Nt3 gene with the gene for brain-derived neurotrophic factor (BDNF), a TrkB ligand. As in NT3 and TrkC null mice, the proprioception system of these mutants failed to assemble. However, sensory fiber projections in the embryonic spinal cord suggest chemotropic effects of BDNF in vivo. In the dorsal root ganglia, the developmental dynamic of neuron numbers demonstrates that NT3 is required for activation of TrkB during neurogenesis and that TrkA is required during target tissue innervation. In the inner ear, the ectopic BDNF rescued the severe neuronal deficits caused by NT3 absence, indicating that TrkB and TrkC activate equivalent pathways to promote survival of cochlear neurons. However, specific increased innervation densities suggest unique functions for BDNF and NT3 beyond promoting neuronal survival. This mouse model has allowed the dissection of specific spatiotemporal Trk receptor activation by NT3. Our analysis provides examples of how development can be orchestrated by complex high- and low-affinity interactions between ligand and receptor families.

Animals↗
PubMed1998

Coiled body numbers in the Arabidopsis root epidermis are regulated by cell type, developmental stage and cell cycle parameters.

We have used whole mount immunofluorescence labelling with the antibody 4G3, raised against the human snRNP-specific protein U2B", and whole mount in situ hybridization with an anti-sense probe to a conserved region of U2 snRNA, in combination with confocal microscopy, to examine the organization of spliceosomal components throughout the development of the Arabidopsis thaliana root epidermis. We show that the number of coiled bodies, nuclear organelles in which splicing snRNPs and snRNAs concentrate, is developmentally regulated in the Arabidopsis root epidermis. Firstly, there is a progression from a small number of coiled bodies in the quiescent centre and initial cells, to a larger number in the cell division zone, returning to a lower number in the cell elongation and differentiation zone. Secondly, trichoblasts (root-hair forming epidermal cells) have on average 1.5 times more and often smaller coiled bodies than atrichoblasts (hairless epidermal cells). Moreover, we have shown that these differences in coiled body numbers are related to differences in cell cycle stage, cell type and developmental stage, but are not due to differences in nucleolar or general metabolic activity per se. We discuss possible explanations, including a model in which coiled bodies coalesce during interphase, for the developmental dynamics of coiled bodies.

Arabidopsis↗
PubMed2004

Velocimetric third-harmonic generation microscopy: micrometer-scale quantification of morphogenetic movements in unstained embryos.

We demonstrate the association of third-harmonic generation (THG) microscopy and particle image velocimetry (PIV) analysis as a novel functional imaging technique for automated micrometer-scale characterization of morphogenetic movements in developing embryos. Using a combined two-photon-excited fluorescence and THG microscope, we characterize the optical properties of Drosophila embryos and show that sustained THG imaging does not perturb sensitive developmental dynamics. Velocimetric THG imaging provides a quantitative description of the dynamics of internal structures in unstained wild-type and mutant embryos.

Algorithms↗
PubMed2006

The emotional experience of K.

The author raises the question of the emotional experience of K in Bion's schema of affective links, L, H, and K, suggesting that it is the emotional experience of feeling curious. He explores the central role curiosity has in 'On arrogance' and 'Attacks on linking' and hypothesizes that in Learning from experience the more complex notion of K is introduced in its place. Thus, Bion's affective schema is taken to be a version of Freud's account of experience in terms of instinctual impulses recast in terms of emotional experience. Freud's primary developmental dichotomy, the tensions between the pleasure principle and the reality principle, can be seen as the dichotomy of tensions between the emotional experience of L/H and the emotional experience of K. This suggests that the potential tension between K and L/H is critical to what happens in the consulting room. Finally the author argues that containing as a developmental dynamic is an expression of a K-state-of-mind and thus the container is thus a container-in-K. It concludes that one important aspect of what Bion called -K is an attack on a K-state-of-mind by an intrusion of L/H which has the effect of contaminating and dominating the urge to know.

Drive↗