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Developmental Shift (developmental + shift)
Selected AbstractsDevelopmental shift in bidirectional functions of taurine-sensitive chloride channels during cortical circuit formation in postnatal mouse brainDEVELOPMENTAL NEUROBIOLOGY, Issue 2 2004Mika Yoshida Abstract Taurine (2-aminoethanesulfonic acid) is the most abundant free amino acid in the developing mammalian cerebral cortex, however, few studies have reported its neurobiological functions during development. In this study, by means of whole-cell patch-clamp recordings, we examined the effects of taurine on chloride channel receptors in neocortical neurons from early to late postnatal stages, which cover a critical period in cortical circuit formation. We show here that taurine activates chloride channels in cortical neurons throughout the postnatal stages examined (from postnatal day 2 to day 36). The physiological effects of taurine changed from excitatory to inhibitory due to variations in the intracellular Cl, concentration during development. An antagonist blocking analysis also demonstrated a developmental shift in the receptor target of taurine, from glycine receptors to GABAA receptors. Taken together, these results may reflect genetically programmed, bidirectional functions of taurine. At the early developmental stage, taurine acting on glycine receptors would serve to promote cortical circuit formation. As cortical circuit has to be regulated in the later stages, taurine would serve as a safeguard against hyperexcitable circuit. © 2004 Wiley Periodicals, Inc. J Neurobiol 60: 166,175, 2004 [source] Developmental shift from long-term depression to long-term potentiation in the rat medial vestibular nuclei: role of group I metabotropic glutamate receptorsTHE JOURNAL OF PHYSIOLOGY, Issue 2 2003Julien Puyal The effects of high frequency stimulation (HFS) of the primary vestibular afferents on synaptic transmission in the ventral part of the medial vestibular nuclei (vMVN) were studied during postnatal development and compared with the changes in the expression of the group I metabotropic glutamate receptor (mGluR) subtypes, mGluR1 and mGluR5. During the first stages of development, HFS always induced a mGluR5- and GABAA -dependent long-term depression (LTD) which did not require NMDA receptor and mGluR1 activation. The probability of inducing LTD decreased progressively throughout the development and it was zero at about the end of the second postnatal week. Conversely, long-term potentiation (LTP) appeared at the beginning of the second week and its occurrence increased to reach the adult value at the end of the third week. Of interest, the sudden change in the LTP frequency occurred at the time of eye opening, about the end of the second postnatal week. LTP depended on NMDA receptor and mGluR1 activation. In parallel with the modifications in synaptic plasticity, we observed that the expression patterns and localizations of mGluR5 and mGluR1 in the medial vestibular nuclei (MVN) changed during postnatal development. At the earlier stages the mGluR1 expression was minimal, then increased progressively. In contrast, mGluR5 expression was initially high, then decreased. While mGluR1 was exclusively localized in neuronal compartments and concentrated at the postsynaptic sites at all stages observed, mGluR5 was found mainly in neuronal compartments at immature stages, then preferentially in glial compartments at mature stages. These results provide the first evidence for a progressive change from LTD to LTP accompanied by a distinct maturation expression of mGluR1 and mGluR5 during the development of the MVN. [source] Developmental shifts in gene expression in the auditory forebrain during the sensitive period for song learningDEVELOPMENTAL NEUROBIOLOGY, Issue 7 2009Sarah E. London Abstract A male zebra finch begins to learn to sing by memorizing a tutor's song during a sensitive period in juvenile development. Tutor song memorization requires molecular signaling within the auditory forebrain. Using microarray and in situ hybridizations, we tested whether the auditory forebrain at an age just before tutoring expresses a different set of genes compared with later life after song learning has ceased. Microarray analysis revealed differences in expression of thousands of genes in the male auditory forebrain at posthatch day 20 (P20) compared with adulthood. Furthermore, song playbacks had essentially no impact on gene expression in P20 auditory forebrain, but altered expression of hundreds of genes in adults. Most genes that were song-responsive in adults were expressed at constitutively high levels at P20. Using in situ hybridization with a representative sample of 44 probes, we confirmed these effects and found that birds at P20 and P45 were similar in their gene expression patterns. Additionally, eight of the probes showed male,female differences in expression. We conclude that the developing auditory forebrain is in a very different molecular state from the adult, despite its relatively mature gross morphology and electrophysiological responsiveness to song stimuli. Developmental gene expression changes may contribute to fine-tuning of cellular and molecular properties necessary for song learning. © 2009 Wiley Periodicals, Inc. Develop Neurobiol 2009 [source] Developmental shifts in watermelon growth and reproduction caused by the squash bug, Anasa tristisNEW PHYTOLOGIST, Issue 2 2002Maciej Biernacki Summary ,,Compared with leaf-feeding herbivores, little is known about how sap-feeding herbivores affect plant growth, morphology and reproduction. This study examines effects of the sap-feeding squash bug ( Anasa tristis ) on watermelon ( Citrullus lanatus ) root, leaf and reproductive structures. ,,Plants at the four-leaf stage were exposed to different densities of caged squash bugs for 67 d (to plant maturity). ,,Initial effects were on roots. Herbivory was associated with a significant reduction in mean total root length, root surface area and number of root tips, as well as an increase in root diameters. Herbivore-exposed plants had significantly more leaves, although leaf lifespan was decreased. Both total plant dry mass and fruit dry mass per unit leaf area were significantly greater in controls. Significant effects of herbivores on plant reproductive traits included delayed flower formation (by 7,12 d), change in floral sex ratio (in favor of femaleness), increased fruit abortion, and smaller fruit size. ,,Developmental consequences were related to changes in plant water relations, including decreased water-use efficiency. Water use in treated plants was three to nine times greater per unit of plant dry mass than in controls. [source] A subclass of myosin XI is associated with mitochondria, plastids, and the molecular chaperone subunit TCP-1, in maizeCYTOSKELETON, Issue 4 2004Zhengyuan Wang Abstract The role and regulation of specific plant myosins in cyclosis is not well understood. In the present report, an affinity-purified antibody generated against a conserved tail region of some class XI plant myosin isoforms was used for biochemical and immunofluorescence studies of Zea mays. Myosin XI co-localized with plastids and mitochondria but not with nuclei, the Golgi apparatus, endoplasmic reticulum, or peroxisomes. This suggests that myosin XI is involved in the motility of specific organelles. Myosin XI was more than 50% co-localized with tailless complex polypeptide-1, (TCP-1,) in tissue sections of mature tissues located more than 1.0 mm from the apex, and the two proteins co-eluted from gel filtration and ion exchange columns. On Western blots, TCP-1, isoforms showed a developmental shift from the youngest 5.0 mm of the root to more mature regions that were more than 10.0 mm from the apex. This developmental shift coincided with a higher percentage of myosin XI /TCP-1, co-localization, and faster degradation of myosin XI by serine protease. Our results suggest that class XI plant myosin requires TCP-1, for regulating folding or providing protection against denaturation. Cell Motil. Cytoskeleton 57:218,232, 2004. © 2004 Wiley-Liss, Inc. [source] Developmental shift in bidirectional functions of taurine-sensitive chloride channels during cortical circuit formation in postnatal mouse brainDEVELOPMENTAL NEUROBIOLOGY, Issue 2 2004Mika Yoshida Abstract Taurine (2-aminoethanesulfonic acid) is the most abundant free amino acid in the developing mammalian cerebral cortex, however, few studies have reported its neurobiological functions during development. In this study, by means of whole-cell patch-clamp recordings, we examined the effects of taurine on chloride channel receptors in neocortical neurons from early to late postnatal stages, which cover a critical period in cortical circuit formation. We show here that taurine activates chloride channels in cortical neurons throughout the postnatal stages examined (from postnatal day 2 to day 36). The physiological effects of taurine changed from excitatory to inhibitory due to variations in the intracellular Cl, concentration during development. An antagonist blocking analysis also demonstrated a developmental shift in the receptor target of taurine, from glycine receptors to GABAA receptors. Taken together, these results may reflect genetically programmed, bidirectional functions of taurine. At the early developmental stage, taurine acting on glycine receptors would serve to promote cortical circuit formation. As cortical circuit has to be regulated in the later stages, taurine would serve as a safeguard against hyperexcitable circuit. © 2004 Wiley Periodicals, Inc. J Neurobiol 60: 166,175, 2004 [source] Something old, something new: a developmental transition from familiarity to novelty preferences with hidden objectsDEVELOPMENTAL SCIENCE, Issue 2 2010Jeanne L. Shinskey Novelty seeking is viewed as adaptive, and novelty preferences in infancy predict cognitive performance into adulthood. Yet 7-month-olds prefer familiar stimuli to novel ones when searching for hidden objects, in contrast to their strong novelty preferences with visible objects (Shinskey & Munakata, 2005). According to a graded representations perspective on object knowledge, infants gradually develop stronger object representations through experience, such that representations of familiar objects can be better maintained, supporting greater search than with novel objects. Object representations should strengthen with further development to allow older infants to shift from familiarity to novelty preferences with hidden objects. The current study tested this prediction by presenting 24 11-month-olds with novel and familiar objects that were sometimes visible and sometimes hidden. Unlike 7-month-olds, 11-month-olds showed novelty preferences with both visible and hidden objects. This developmental shift from familiarity to novelty preference with hidden objects parallels one that infants show months earlier with perceptible stimuli, but the two transitions may reflect different underlying mechanisms. The current findings suggest both change and continuity in the adaptive development of object representations and associated cognitive processes. [source] The development of gaze following and its relation to languageDEVELOPMENTAL SCIENCE, Issue 6 2005Rechele Brooks We examined the ontogeny of gaze following by testing infants at 9, 10 and 11 months of age. Infants (N = 96) watched as an adult turned her head toward a target with either open or closed eyes. The 10- and 11-month-olds followed adult turns significantly more often in the open-eyes than the closed-eyes condition, but the 9-month-olds did not respond differentially. Although 9-month-olds may view others as ,body orienters', older infants begin to register whether others are ,visually connected' to the external world and, hence, understand adult looking in a new way. Results also showed a strong positive correlation between gaze-following behavior at 10,11 months and subsequent language scores at 18 months. Implications for social cognition are discussed in light of the developmental shift in gaze following between 9 and 11 months of age. [source] Density-dependent polyphenism and geographic variation in size among two populations of lubber grasshoppers (Romalea microptera)ECOLOGICAL ENTOMOLOGY, Issue 5 2009JASON E. JANNOT Abstract. 1. Density-dependent phase polyphenism occurs when changes in density during the juvenile stages result in a developmental shift from one phenotype to another. Density-dependent phase polyphenism is common among locusts (Orthoptera: Acrididae). 2. Previously, we demonstrated a longitudinal geographic cline in adult body size (western populations = small adults; eastern populations = large adults) in the eastern lubber grasshopper (Romalea microptera) in south Florida. As lubbers are confamilial with locusts, we hypothesised that the longitudinal size cline was partly due to density-dependent phase polyphenism. 3. We tested the effect of density, population, and density×population interaction on life-history traits (pronotum length, mass, cumulative development time, growth rate) of, and proportion surviving to, each of the five instars and the adult stage in a 2 × 3 factorial laboratory experiment with two lubber populations, each reared from hatchling to adult at three different densities. 4. The effect of density on life history and survival was independent of the effects of population on life history and survival. Higher densities led to larger adult sizes (pronotum, mass) and lower survivorship. The western population had smaller adult masses, fewer cumulative days to the adult stage, and higher survivorship than the eastern population. 5. Our data suggest that lubber grasshoppers exhibit density-dependent phase polyphenism initiated by the physical presence of conspecifics. However, the plastic response of adult size to density observed in the laboratory is not consistent with the relationship between phenotypes and adult density in the field. Genetic differences between populations observed in the laboratory could contribute to size and life-history differences among lubber populations in the field. [source] The More the Scarier: Adult Richardson's Ground Squirrels (Spermophilus richardsonii) Assess Response Urgency Via the Number of Alarm SignallersETHOLOGY, Issue 5 2008Jennifer L. Sloan Richardson's ground squirrels (RGS) produce alarm calls that warn conspecifics of potential predators. We presented free-living adult and juvenile RGS with playbacks of repetitive alarm calls from one vs. two juvenile callers broadcast sequentially through two spatially separated loudspeakers. Adult RGS spent a greater proportion of time vigilant in response to two vs. one calling squirrel, whereas juvenile RGS did not respond differentially to two vs. one caller. Apparently then, the relative inexperience of juvenile RGS with alarm calls and the context in which such calls are emitted precludes their enumeration of alarm callers. Taken together with our earlier finding that adult but not juvenile RGS ignore information regarding response urgency encoded in the rate of juvenile produced repetitive calls, our present results suggest a developmental shift in response-urgency perception. Adult RGS selectively extract information regarding response urgency via discrimination of the number of callers, ignoring less reliable information encoded in the rate of repetitive calls issued by inexperienced juvenile signallers. [source] Postnatal maturation of Na+, K+, 2Cl, cotransporter expression and inhibitory synaptogenesis in the rat hippocampus: an immunocytochemical analysisEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 2 2002Serge Marty Abstract GABA, a major inhibitory neurotransmitter, depolarizes hippocampal pyramidal neurons during the first postnatal week. These depolarizations result from an efflux of Cl, through GABAA -gated anion channels. The outward Cl, gradient that provides the driving force for Cl, efflux might be generated and maintained by the Na+, K+, 2Cl, cotransporter (NKCC) that keeps intracellular Cl, concentration above electrochemical equilibrium. The developmental pattern of expression of the cotransporter in the hippocampus is not known. We studied the postnatal distribution pattern of NKCC in the hippocampus using a monoclonal antibody (T4) against a conserved epitope in the C-terminus of the cotransporter molecule. We also examined the temporal relationships between the developmental pattern of NKCC expression and the formation of perisomatic GABAergic synapses. This study was aimed at determining, with antivesicular inhibitory amino acid transporter (VIAAT) antibodies, whether perisomatic GABAergic synapses are formed preferentially at the time when GABA is depolarizing. During the first postnatal week, NKCC immunolabelling was restricted to cell bodies in the pyramidal cell layer and in the strata oriens and radiatum. In contrast, at postnatal day 21 (P21) and in adult animals little or no labelling occurred in cell bodies; instead, a prominent dendritic labelling appeared in both pyramidal and nonpyramidal neurons. The ultrastructural immunogold study in P21 rat hippocampi corroborated the light-microscopy results. In addition, this study revealed that a portion of the silver-intensified colloidal gold particles were located on neuronal plasmalemma, as expected for a functional cotransporter. The formation of inhibitory synapses on perikarya of the pyramidal cell layer was a late process. The density of VIAAT-immunoreactive puncta in the stratum pyramidale at P21 reached four times the P7 value in CA3, and six times the P7 value in CA1. Electron microscopy revealed that the number of synapses per neuronal perikaryal profile in the stratum pyramidale of the CA3 area at P21 was three times higher than at P7, even if a concomitant 20% increase in the area of these neuronal perikaryal profiles occurred. It is concluded that, in hippocampal pyramidal cells, there is a developmental shift in the NKCC localization from a predominantly somatic to a predominantly dendritic location. The presence of NKCC during the first postnatal week is consistent with the hypothesis that this transporter might be involved in the depolarizing effects of GABA. The depolarizing effects of GABA may not be required for the establishment of the majority of GABAergic synapses in the stratum pyramidale, because their number increases after the first postnatal week, when GABA action becomes hyperpolarizing. [source] Identifying meta-clusters of students' interest in science and their change with ageJOURNAL OF RESEARCH IN SCIENCE TEACHING, Issue 9 2009Ayelet Baram-Tsabari Abstract Nearly 6,000 science questions collected from five different web-based, TV-based and school-based sources were rigorously analyzed in order to identify profiles of K-12 students' interest in science, and how these profiles change with age. The questions were analyzed according to their topic, thinking level, motivation for and level of autonomy in raising the question, the object of interest and its magnitude, and psychological distance of the object in question from the asker. Characteristics of the asker, such as gender, grade level, and country of origin were also considered, alongside characteristics of the data source, such as language, setting (Internet, school, TV), and the potential science-attentiveness of the users. Six meta-clusters of children's and adolescents' interest in science were identified using cluster analysis of their self-generated science questions. A developmental shift in interest from non-classical to classical school science subjects was noted. Other age-related developments, such as an increase in thinking level as reflected by the questions, a decrease in organization level and the psychological distance of the object in question with age were also explored. Advantages and shortcomings of web-based data collection for educational research are discussed, as are the implications of the results obtained using this methodology for formal science education. © 2009 Wiley Periodicals, Inc. J Res Sci Teach 46: 999,1022, 2009 [source] Survival of juvenile European eels (Anguilla anguilla), transferred among salinities, and developmental shifts in their salinity preferenceJOURNAL OF ZOOLOGY, Issue 1 2005S. R. Crean Abstract After their oceanic migration, juvenile European eels Anguilla anguilla enter estuaries as glass eels, develop into pigmented elvers and migrate into fresh water. Fisheries often transfer such eels abruptly between salinities, principally glass eels and elvers from estuarine to fresh water. It is usually assumed that survival rates are high, but this required systematic investigation. Survival was found to be 100% over 21 days of glass eels and semi-pigmented elvers transferred abruptly from estuary conditions into fresh water, 50% sea water and full sea water. Fully pigmented elvers, however, showed significantly reduced survival when transferred into sea water. Salinity preference experiments with juvenile eels have historically been inconclusive. Here, in a choice chamber design, a clear developmental shift in salinity preference was found, with glass eels preferring 100% sea water, semi-pigmented elvers showing no clear preference and fully pigmented elvers preferring fresh water. We conclude that eel fisheries enhancement by abrupt transfer of juveniles among salinities is largely vindicated. In addition, developmental shifts in salinity preference have been clarified and this aids in the interpretation of eel migration patterns. [source] Embryogenesis and ossification of Emydura subglobosa (Testudines, Pleurodira, Chelidae) and patterns of turtle developmentDEVELOPMENTAL DYNAMICS, Issue 11 2009Ingmar Werneburg Abstract Using the Standard Event System (SES) to study patterns of vertebrate development, we describe a series of 17 embryos of the pleurodire turtle Emydura subglobosa. Based on a sequence heterochrony analysis including 23 tetrapod taxa, we identified autapomorphic developmental shifts that characterise Testudines, Cryptodira, and Pleurodira. The main results are that Testudines are characterised by an autapomorphic late neck development, whereas pleurodires and cryptodires show a different developmental timing of the mandibular process. Additionally, we described the ossification pattern of E. subglobosa and compared the data to those of five other turtles. Pleurodires show the epiplastron to ossify before or simultaneously with maxilla and dentary. In contrast, cryptodires show a later ossification of this bone. Because evolutionary developmental studies on turtles have previously focused only on "model organisms" that all belong to Cryptodira, we underline the necessity to include a pleurodire taxon for a more comprehensive, phylogenetically more informative approach. Developmental Dynamics 238:2770,2786, 2009. © 2009 Wiley-Liss, Inc. [source] Developmental changes in habitat associations of tropical treesJOURNAL OF ECOLOGY, Issue 3 2007LIZA S. COMITA Summary 1Recent studies have documented local-scale associations between tree species and topographic and edaphic habitat types in forests worldwide. To determine whether such associations form at early life stages, we compared species' positive associations with five habitat types (high plateau, low plateau, slope, streamside, and swamp) at two life stages for 80 tree and shrub species in a Panamanian lowland forest. 2Nineteen significant, positive habitat associations were detected at the small tree stage (seedlings and saplings , 20 cm tall and < 1 cm d.b.h.), and 18 at the large tree stage (individuals , 1 cm d.b.h.), according to results of torus-translation randomization tests. The majority of species did not show consistent associations at the two stages. Of the 30 species significantly associated with a habitat, only five were associated with the same habitat at both stages. Overall, more species were associated with the wetter slope habitat at the large tree stage compared with the small tree stage. 3For a subset of species, we examined the relationship between observed habitat associations and seed dispersal and seedling establishment patterns by using species-specific seed dispersal kernels to predict seed rain into each habitat. 4Two-thirds of species associated with a habitat at the large tree stage had higher predicted seed densities in the associated habitat relative to other habitat types, indicating that limited seed dispersal acts to reinforce habitat associations for most species. In contrast, only one-third of the species associated with a habitat at the large tree stage showed evidence of higher seedling establishment rates in the associated habitat compared with other habitats, and an equal number of species appeared to have lower rates of establishment in the habitat that large trees of the species were associated with. 5Overall, our results indicate that habitat associations of large trees typically do not form at early life stages. Rather, many species appear to exhibit different ecological habitat preferences across life stages. Future studies of species' habitat associations should therefore include multiple life stages in order to detect developmental shifts in ecological preferences. [source] Survival of juvenile European eels (Anguilla anguilla), transferred among salinities, and developmental shifts in their salinity preferenceJOURNAL OF ZOOLOGY, Issue 1 2005S. R. Crean Abstract After their oceanic migration, juvenile European eels Anguilla anguilla enter estuaries as glass eels, develop into pigmented elvers and migrate into fresh water. Fisheries often transfer such eels abruptly between salinities, principally glass eels and elvers from estuarine to fresh water. It is usually assumed that survival rates are high, but this required systematic investigation. Survival was found to be 100% over 21 days of glass eels and semi-pigmented elvers transferred abruptly from estuary conditions into fresh water, 50% sea water and full sea water. Fully pigmented elvers, however, showed significantly reduced survival when transferred into sea water. Salinity preference experiments with juvenile eels have historically been inconclusive. Here, in a choice chamber design, a clear developmental shift in salinity preference was found, with glass eels preferring 100% sea water, semi-pigmented elvers showing no clear preference and fully pigmented elvers preferring fresh water. We conclude that eel fisheries enhancement by abrupt transfer of juveniles among salinities is largely vindicated. In addition, developmental shifts in salinity preference have been clarified and this aids in the interpretation of eel migration patterns. [source] | ||||||||||