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At least 865 records · Page 48Linked to original sources
PubMed2004

Self-organization of tree form: a model for complex social systems.

The branches of a tree can be viewed as redundant organs: they have the same functional roles and the same unlimited developmental potential. The most prominent aspect of tree form, here considered as an example of dynamic self-organization, is the relations among these branches. A branch is a source of information about its size, state and environment. A response to this information is the oriented vascular differentiation which connects the branch with the rest of the plant. A known phytohormone, auxin, is formed by shoot tissues and replaces this orienting influence of a shoot. This accounts for neighboring branches having specific, even competing, effects without any other branch specificity. The same phytohormone also elicits different processes throughout the plant, integrating their occurrence without recourse to a central control. Self-organization requires a positive feedback that enhances the development of a successful branch, and an inhibitory influence that reduces similar branch growth. Both roles could depend on the oriented vascular differentiation that is specified by auxin. Actual tree form at any given time is a transient dynamic state. One reason for this is that competition between branches is a long-term, gradual process. A second reason is that a periodic surfeit of root supplies enhances a seasonal formation of many branches which 'search' environmental possibilities, and most of these branches decline only gradually. The various aspects of tree form could thus depend on remarkably simple and robust principles, requiring only limited genetic information. Much of the necessary information about the details of tree form is generated by a Darwinian-like process of developmental selection, reaching a predictable overall outcome without following any strict plan. It is a case of self-organization in which the component structures, the tree branches, do not move, but do undergo long term developmental changes.

Animals↗
PubMed2005

Biological sensitivity to context: I. An evolutionary-developmental theory of the origins and functions of stress reactivity.

Biological reactivity to psychological stressors comprises a complex, integrated, and highly conserved repertoire of central neural and peripheral neuroendocrine responses designed to prepare the organism for challenge or threat. Developmental experience plays a role, along with heritable, polygenic variation, in calibrating the response dynamics of these systems, with early adversity biasing their combined effects toward a profile of heightened or prolonged reactivity. Conventional views of such high reactivity suggest that it is an atavistic and pathogenic legacy of an evolutionary past in which threats to survival were more prevalent and severe. Recent evidence, however, indicates that (a) stress reactivity is not a unitary process, but rather incorporates counterregulatory circuits serving to modify or temper physiological arousal, and (b) the effects of high reactivity phenotypes on psychiatric and biomedical outcomes are bivalent, rather than univalent, in character, exerting both risk-augmenting and risk-protective effects in a context-dependent manner. These observations suggest that heightened stress reactivity may reflect, not simply exaggerated arousal under challenge, but rather an increased biological sensitivity to context, with potential for negative health effects under conditions of adversity and positive effects under conditions of support and protection. From an evolutionary perspective, the developmental plasticity of the stress response systems, along with their structured, context-dependent effects, suggests that these systems may constitute conditional adaptations: evolved psychobiological mechanisms that monitor specific features of childhood environments as a basis for calibrating the development of stress response systems to adaptively match those environments. Taken together, these theoretical perspectives generate a novel hypothesis: that there is a curvilinear, U-shaped relation between early exposures to adversity and the development of stress-reactive profiles, with high reactivity phenotypes disproportionately emerging within both highly stressful and highly protected early social environments.

Environment↗
PubMed1999

Psychopathology as risk for adolescent substance use disorders: a developmental psychopathology perspective.

Examines several issues on psychiatric diagnoses as risk factors for adolescent drug use and substance use disorders. The articles in this special section are discussed in terms of dynamic models of risk and protective factors, stages of research needed for establishing causal mechanisms in the etiology of drug use disorders, conceptualizing drug use and abuse in the context of the developmental organization of the individual, equifinality and multifinality in developmental pathways to drug use and abuse, and issues in conceptualizing drug use problems as mental disorders. Future directions for research on the etiology of problem drug use, guided by principles of developmental psychopathology and prevention science, are provided.

Adolescent↗
PubMed2000

L-Type calcium channels mediate calcium oscillations in early postnatal Purkinje neurons.

Ca(2+) signaling is important in many fundamental neuronal processes including neurotransmission, synaptic plasticity, neuronal development, and gene expression. In cerebellar Purkinje neurons, Ca(2+) signaling has been studied primarily in the dendritic region where increases in local Ca(2+) have been shown to occur with both synaptic events and spontaneous electrical activity involving P-type voltage-gated Ca(2+) channels (VGCCs), the predominant VGCC expressed by Purkinje neurons. Here we show that Ca(2+) signaling is also a prominent feature of immature Purkinje neurons at developmental stages that precede expression of dendritic structure and involves L-type rather than P-type VGCCs. Immature Purkinje neurons acutely dissociated from postnatal day 4-7 rat pups exhibit spontaneous cytoplasmic Ca(2+) oscillations. The Ca(2+) oscillations require entry of extracellular Ca(2+), are blocked by tetrodotoxin, are communicated to the nucleus, and correlate closely with patterns of endogenously generated spontaneous and evoked electrical activity recorded in the neurons. Immunocytochemistry showed that L-, N-, and P/Q-types of VGCCs are present on the somata of the Purkinje neurons at this age. However, only the L-type VGCC antagonist nimodipine effectively antagonized the Ca(2+) oscillations; inhibitors of P/Q and N-type VGCCs were relatively ineffective. Release of Ca(2+) from intracellular Ca(2+) stores significantly amplified the Ca(2+) signals of external origin. These results show that a somatic signaling pathway that generates intracellular Ca(2+) oscillations and involves L-type VGCCs and intracellular Ca(2+) stores plays a prominent role in the Ca(2+) dynamics of early developing Purkinje neurons and may play an important role in communicating developmental cues to the nucleus.

Action Potentials↗
PubMed2006

From the "Modern Synthesis" to cybernetics: Ivan Ivanovich Schmalhausen (1884-1963) and his research program for a synthesis of evolutionary and developmental biology.

Ivan I. Schmalhausen was one of the central figures in the Russian development of the "Modern Synthesis" in evolutionary biology. He is widely cited internationally even today. Schmalhausen developed the main principles of his theory facing the danger of death in the totalitarian Soviet Union. His great services to evolutionary and theoretical biology are indisputable. However, the received view of Schmalhausen's contributions to evolutionary biology makes an unbiased reading of his texts difficult. Here we show that taking all of his works into consideration (including those only available in Russian) paints a much more dynamic and exciting picture of what he tried to achieve. Schmalhausen pioneered the integration of a developmental perspective into evolutionary thinking. A main tool for achieving this was his approach to living objects as complex multi-level self-regulating systems. Schmalhausen put enormous effort into bringing this idea into fruition during the final stages of his career by combining evolutionary theory with cybernetics. His results and ideas remain thought-provoking, and his texts are of more than just historical interest.

Biological Evolution↗
PubMed1991

Serving rural families of developmentally disabled children: a case management model.

Family-centered, community-based case management is a key feature of new federal legislation mandating educational and preschool services for all developmentally disabled children. Social work skills, including counseling, planning, coordination, and knowledge of family and community dynamics, are germane to this task. The goal of family-centered case management is the empowerment of parents as caretakers and planners for their children. Highly skilled case managers will be particularly needed in rural areas where families must deal with scarce resources and other environmental constraints. The authors describe a program employing master's-level social work case managers who serve rural Appalachian families with developmentally disabled children. Included is a case illustration that delineates both case management activities and the contextual elements important in working in an Appalachian rural community.

Child, Preschool↗
PubMed2005

Rapid separation of protein isoforms by capillary zone electrophoresis with new dynamic coatings.

Many cellular functions are regulated through protein isoforms. Changes in the expression level or regulatory dysfunctions of isoforms often lead to developmental or pathological disorders. Isoforms are traditionally analyzed using techniques such as gel- or capillary-based isoelectric focusing. However, with proper electro-osmotic flow (EOF) control, isoforms with small pI differences can also be analyzed using capillary zone electrophoresis (CZE). Here we demonstrate the ability to quickly resolve isoforms of three model proteins (bovine serum albumin, transferrin, alpha1-antitrypsin) in capillaries coated with novel dynamic coatings. The coatings allow reproducible EOF modulation in the cathodal direction to a level of 10(-9) m2V(-1)s(-1). They also appear to inhibit protein adsorption to the capillary wall, making the isoform separations highly reproducible both in peak areas and apparent mobility. Isoforms of transferrin and alpha1-antitrypsin have been implicated in several human diseases. By coupling the CZE isoform separation with standard affinity capture assays, it may be possible to develop a cost-effective analytical platform for clinical diagnostics.

Animals↗
PubMed1987

Bureaucratic aspects of international health agencies.

In this paper the large international health agencies are viewed as bureaucracies, i.e. in Max Weber's sense as rational administrative organizations. The kinds of activities in which they engage, and the effectiveness of their programs, are interpreted as a function of their structural and dynamic characteristics, and of the professional assumptions held by administrators, planners and technical specialists. International health agency activities are placed in the context of the 'donor-recipient' model that characterizes post-World War II international developmental assistance programs. Some of the strengths and weaknesses of these organizations are noted, and linked to the organizations' structural, dynamic and professional characteristics.

Community Participation↗
PubMed2026

Functions and mechanisms of BRCA1 in early embryonic development.

Breast Cancer Gene 1 (BRCA1) is a critical regulator of genome integrity whose dysfunction greatly increases lifetime risk of breast and ovarian cancers. While BRCA1 has been extensively studied in the contexts of adult biology and cancer, its diverse functions, including homologous recombination-mediated DNA repair, cell cycle checkpoint activation, protein ubiquitination, and transcriptional regulation, have many underexplored implications. In early embryonic development, the maternal-to-zygotic transition (MZT) and subsequent developmental processes place extraordinary demands on DNA replication fidelity, cell cycle regulation, transcriptional activation, and chromatin remodeling. These critical processes overlap strikingly with canonical functions of BRCA1, yet its function in early development is poorly characterized. In this review, we investigate BRCA1 conservation across species and connect its well-established functions to findings from developmental studies to assess its role in development. We highlight evidence of BRCA1 mitigating genome integrity loss from diverse sources, maintaining the proliferative activity needed for successful germ layer formation and early tissue morphogenesis, and regulating transcription and epigenetic modifications. Together, this synthesis supports a model where BRCA1 acts as a multi-functional and dynamic regulator of early embryogenesis. Building on this, we propose outstanding questions that could further illuminate these developmental roles. Characterization of BRCA1 in early development may not only provide important insight into the origin and progression of cancer susceptibility but may also elucidate fundamental mechanisms shaping early development.

BRCA1 Protein↗
PubMed2001

The quest for modern manhood: masculine stereotypes, peer culture and the social significance of homophobia.

This paper explores the use of homophobic terms by boys and young men and the meanings they invoke when using them. Highly detailed interviews were conducted with young men from diverse backgrounds about their own experiences while growing up and their observations of schools, teachers, family and peers. Homophobia was found to be more than a simple prejudice against homosexuals. Homophobic terms like "poofter" and "faggot" have a rich developmental history and play a central role in adolescent male peer-group dynamics. Homophobic terms come into currency in primary school. When this happens, words like poofter and faggot rarely have sexual connotations. Nevertheless, far from being indiscriminate terms of abuse, these terms tap a complex array of meanings that are precisely mapped in peer cultures, and boys quickly learn to avoid homophobia and to use it decisively and with great impact against others. Significantly, this early, very powerful use of homophobic terms occurs prior to puberty, prior to adult sexual identity and prior to knowing much, if anything, about homosexuality. An effect of this sequence is that early homophobic experiences may well provide a key reference point for comprehending forthcoming adult sexual identity formation (gay or not) because powerful homophobic codes are learned first.

Adult↗
PubMed1995

International adoption: a case review of Korean children.

In contrast to the controversial transracial adoption of African American children by Caucasian families in the U.S., international, transracial adoption of Asian children has not received much scientific or societal attention. There has been a steady increase in this unnoticed minority group, made up largely of Korean children. This paper reviews the developmental characteristics of post-adoption adjustments among Korean adoptees and discusses the dynamics of their positive adjustments. Sociopolitical issues of international adoptions are also addressed.

Acculturation↗
PubMed2005

Actin redistribution in mosquito malpighian tubules after a blood meal and cyclic AMP stimulation.

Fluid secretion by mosquito Malpighian tubules is critical to maintaining fluid and electrolyte balance after a blood meal. Endogenous cAMP levels increase in Malpighian tubules after a blood meal. Here, we determined if corresponding changes in intracellular actin distribution occur after a blood meal or dibutyryl-cAMP (db-cAMP) stimulation and whether altering actin turnover inhibits secretion. In untreated Malpighian tubules, beta-actin immunostaining was more intense in the apical region of adult Malpighian tubules than in the cytoplasm. Stimulation by a blood meal or db-cAMP significantly decreased beta-actin immunostaining in the non-apical region of the cell. Db-cAMP had similar effects in larvae and pupae Malpighian tubules. In contrast, no detectable shift in F-actin distribution was detected; however, F-actin bundles within the cytoplasm increased in size after treatment with db-cAMP. Pretreatment of Malpighian tubules with agents perturbing actin fiber assembly and disassembly decreased basal secretion rates and inhibited the stimulatory effects of db-cAMP. Our results show (1) beta-actin redistributes toward the apical membrane after a blood meal and this correlates temporally with increase urine flow rate and intracellular cAMP levels, (2) Malpighian tubules from all developmental stages exhibit this same response to db-cAMP-stimulation, and (3) dynamic assembly and disassembly of beta-actin is required for db-cAMP-stimulated secretion.

Actins↗
PubMed1987

Fetal surgery for obstructive uropathy: rational considerations.

The widespread use of high resolution dynamic ultrasound imaging methods in obstetrics now permits recognition of structural and/or functional developmental anomalies of fetal genitourinary tract with some considerable accuracy. Detection of congenital obstructive uropathy in the human fetus may occur as early as 16 weeks gestation. In the fetal lamb model, experimental occlusion of the outflow tract results in progressive hydronephrosis, pulmonary hypoplasia, and oligohydramnios. The renal parenchymal changes vary with the fetal age at obstruction ranging from simple hydronephrosis with later obstruction to dysgenesis with earlier obstruction. The pulmonary damage, and to some extent the renal damage, may be halted or even reversed with release of obstruction. These advances in diagnosis and an understanding of the pathophysiology have prompted attempts at chronic in utero diversion therapy in the human fetus with obstructive uropathy yielding encouraging, but as of yet, unproven success. In this report, the methods for such therapy, the rationale for the therapy, and the results of the therapy is reviewed.

Amniotic Fluid↗
PubMed2000

dADAR, a Drosophila double-stranded RNA-specific adenosine deaminase is highly developmentally regulated and is itself a target for RNA editing.

We have identified a homolog of the ADAR (adenosine deaminases that act on RNA) class of RNA editases from Drosophila, dADAR. The dADAR locus has been localized to the 2B6-7 region of the X chromosome and the complete genomic sequence organization is reported here. dADAR is most homologous to the mammalian RNA editing enzyme ADAR2, the enzyme that specifically edits the Q/R site in the pre-mRNA encoding the glutamate receptor subunit GluR-B. Partially purified dADAR expressed in Pichia pastoris has robust nonspecific A-to-I deaminase activity on synthetic dsRNA substrates. Transcripts of the dADAR locus originate from two regulated promoters. In addition, alternative splicing generates at least four major dADAR isoforms that differ at their amino-termini as well as altering the spacing between their dsRNA binding motifs. dADAR is expressed in the developing nervous system, making it a candidate for the editase that acts on para voltage-gated Na+ channel transcripts in the central nervous system. Surprisingly, dADAR itself undergoes developmentally regulated RNA editing that changes a conserved residue in the catalytic domain. Taken together, these findings show that both transcription and processing of dADAR transcripts are under strict developmental control and suggest that the process of RNA editing in Drosophila is dynamically regulated.

Adenosine Deaminase↗
PubMed2004

Religion as a resource for positive youth development: religion, social capital, and moral outcomes.

Although existing literature demonstrates that developmental benefits are associated with religion for adolescents, little is understood about the dynamics of this relationship. Drawing on social capital theory, this study tested a conceptual model exploring socially embedded religious influences on moral outcomes. A three-dimensional model of social capital demonstrated how social interaction, trust, and shared vision enable social ties associated with religiousness to influence moral behavior. Structural equation modeling was used with data gathered from 735 urban youths to test a proposed model of the effects of religiousness on moral outcomes. Results suggested that religiously active youths report higher levels of social capital resources and that the influence of adolescent religiousness on moral outcomes was mediated through social capital resources. Suggestions for further research and implications for faith-based youth development organizations are considered.

Adolescent↗
PubMed2003

Nanolitre-scale assays to determine the activities of enzymes in individual plant cells.

There are a variety of methods for characterising gene expression at the level of individual cells and for demonstrating that the cells also contain the encoded proteins. However, measuring the activity of enzymes at the resolution of single cells in complex tissues, such as leaves, is problematic. We have addressed this by using single-cell sampling to extract 10-100 pl droplets of sap from individual plant cells and then measuring enzyme activities in these droplets with nanolitre-scale fluorescence-based assays. We have optimised these assays and used them to measure and characterise the activities of acid phosphatase, cysteine protease and nitrate reductase in sap samples from epidermal and mesophyll cells of barley (Hordeum vulgare L.) and Arabidopsis thaliana leaves exposed to different developmental and environmental conditions. During leaf senescence in barley, we found that the dynamics with which acid phosphatase and protease activities changed were different in each cell type and did not mirror the changes occurring at the whole-leaf level. Increases in nitrate reductase activities after exposure of barley plants to nitrate were large in mesophyll cells but small in epidermal cells. The technique was applied successfully to Arabidopsis and, as in barley, revealed cell-specific differences in the activities of both acid phosphatase and nitrate reductase. The assays add to the spectrum of techniques available for characterising cells within complex plant tissues, thus extending the opportunity to relate gene expression to biochemical activities at the single-cell level.

Acid Phosphatase↗
PubMed2003

p57Kip2 regulates actin dynamics by binding and translocating LIM-kinase 1 to the nucleus.

p57Kip2 is the only cyclin-dependent kinase (Cdk) inhibitor shown to be essential for mouse embryogenesis. The fact suggests that p57 has a specific role that cannot be compensated by other Cdk inhibitors. LIM-kinase 1 (LIMK-1) is a downstream effector of the Rho family of GTPases that phosphorylates and inactivates an actin depolymerization factor, cofilin, to induce the formation of actin fiber. Here we demonstrate that p57 regulates actin dynamics by binding and translocating LIMK-1 from the cytoplasm into the nucleus, which in turn results in a reorganization of actin fiber. The central region of p57, a unique feature among the Cdk inhibitors, and the N-terminal region of LIMK-1, which contains the LIM domains were essential for the interaction. Expression of p57, but not p27Kip1 or a p57 mutant, with a deletion in the central region was shown to induce marked reorganization of actin filament and a translocation of LIMK-1. Our findings indicate p57 may act as a key regulator in embryogenesis by bearing two distinct functions, the regulation of cell cycle through binding to Cdks and the regulation of actin dynamics through binding to LIMK-1, both of which should be important in developmental procedure.

Actins↗
PubMed2002

Developing and establishing bee species as crop pollinators: the example of Osmia spp. (Hymenoptera: Megachilidae) and fruit trees.

The development of a bee species as a new crop pollinator starts with the identification of a pollination-limited crop production deficit and the selection of one or more candidate pollinator species. The process continues with a series of studies on the developmental biology, pollinating efficacy, nesting behaviour, preference for different nesting substrates, and population dynamics of the candidate pollinator. Parallel studies investigate the biology of parasites, predators and pathogens. The information gained in these studies is combined with information on the reproductive biology of the crop to design a management system. Complete management systems should provide guidelines on rearing and releasing methods, bee densities required for adequate pollination, nesting materials, and control against parasites, predators and pathogens. Management systems should also provide methods to ensure a reliable pollinator supply. Pilot tests on a commercial scale are then conducted to test and eventually refine the management system. The process culminates with the delivery of a viable system to manage and sustain the new pollinator on a commercial scale. The process is illustrated by the development of three mason bees, Osmia cornifrons (Radoszkowski), O. lignaria Say and O. cornuta (Latreille) as orchard pollinators in Japan, the USA and Europe, respectively.

Animals↗