Thesis (Ph. D.)--University of Queensland, 2002. / Includes bibliographical references.

Early adolescence is a period marked by increases in internalizing problems, particularly depression. In childhood, the rates of depressive symptomatology are between .6% and 1.7%, but by adolescence, rates rise to 8.0%. Two key correlates of adolescent depression are behavioral inhibition and poor peer relations. Yet, it is unclear whether these factors simply co-occur with depressive symptoms or are instrumental across development in regulating them. In this study, using data from the NICHD Study of Early Child Care, we examine whether increases in inhibition in late childhood may undermine peer relationships in predicting increases in adolescent depressive symptoms. Specifically, we test whether inhibition promotes depressive symptoms by undermining two aspects of peer relationships – popularity and friendship quality. Findings revealed that increases in inhibition from childhood to adolescence lead to increases in adolescent depressive symptoms. Decreases in popularity mediated the relation of inhibition, friendship quality and increases in adolescent depressive symptoms. / text

The extensive infiltration of immune cells in the joints of patients affected by rheumatoid arthritis (RA), and the subsequent production of pro-inflammatory cytokines triggers bone erosion through the extensive stimulation of bone resorbing osteoclasts (OCs). The activity of γδ T cells has been implicated to influence the onset and severity of the disease pathology in murine models of human RA. With this study the effects of γδ T cells for influencing OC differentiation and resorptive activity were assessed in vitro. Activated γδ T cells exerted inhibitory effects on OC differentiation and resorptive activity, these effects were mediated by the release of soluble factors, since similar inhibitory effects were obtained using conditioned medium (CM) from activated γδ T cells. The primary mediator of such effects was determined to be IFN, since neutralisation markedly restored OC differentiation and resorptive activity. γδ T cell proliferation, activation and survival following culture with autologous mature OCs were assessed by flow cytometry. Interestingly, OCs and OC-derived CM induced activation of γδ T cells as determined by the expression of the early activation marker CD69. A mediator of this stimulatory effect on T cells was found to be TNF, since neutralisation of TNFα decreased the stimulatory effect of OCs on CD69 expression. Consistently, OCs, but not OC-derived CM, increased the proliferation of IL-2-stimulated γδ T cells and also supported the survival of resting γδ T cells. This study provides new insights into the in vitro interactions between human γδ T cells and OCs, moreover it defines osteoclasts as immune competent cells capable of influencing the activation status and the viability of T lymphocytes, and provide evidence for a novel stimulatory effect of OCs on γδ T cells.

An inhibition-based fan effect was explored with two different negative priming tasks. Experiment 1 used a modified flanker-type colour blob task in both children and adults (Pritchard & Neumann, 2004), where two additional conditions were included (C2 and IR2). Each set of the colour blobs for the additional conditions consist of two distractor colours instead of one distractor colour. Experiment 2 used Navon’s (1977) global-local letter task, where a global letter contains one, two, or three local letters as distractors to see if an inhibitory fan effect operated on the should-be-ignored local letters. Results from both experiments did not support for the inhibition-based fan effect hypothesis. However, in line with Pritchard and Neumann (2004) and Frings et al. (2007), there was evidence for the claim that selective control mechanism are developed much earlier in young children than previously thought.

The purpose of this study was to determine under which of several conditions preschool children would delay gratification longer given the choice between a smaller immediate, and a larger delayed reward in a non-instrumental paradigm.Prior to the experiment 70 subjects from a pool of 81 subjects were randomly assigned to 8 treatment groups with 4 males and 3 females in each group. When a subject was eliminated from the study another subject of the same sex was randomly selected from the remaining pool of subjects and assigned to the treatment condition. In all 31 males and 24 females completed the experiment. -Four experimenters, 2 male and 2 female, were randomly assigned to subjects such that experimenter sex, subject sex, and experimental condition were distributed evenly across cells.In each group the preschool child could obtain a less preferred reward immediately or wait for-a a more preferred reward. 1ne eight treatment groups varied subject sex, nature of the distractor, degree of distraction, and presence of reward. Reward presence was varied by either leaving the rewards on a table in front of the subject during the waiting period or covering the rewards and placing them under the table. Nature of distractor, internal or external, was varied by leaving the subject to his own thought distractions (internal), or by making paper and crayons available to the subject during the waiting period (external). Degree of distraction, structured or non-structured, was varied by the experimenter informing the subject of pleasant activities to engage in during the waiting period (structured) or by the experimenter refraining from making suggestions for activities (non-structured).The data were subjected to a univariate analysis of variance. The F value which was obtained for subject sex was Statistically significant at the .01 level with female subect3 waiting longer than male subjects. The first null h7-pothesis that there would be no statistically significant differences between males and females was, therefore, rejected. The F values for the other three null hypotheses: there will be'no statistically significant difference between those subjects waiting under the conditions of external distractor and those subjects waiting under the condition of internal distractor; there will be no statistically significant difference between those subjects waiting under the condition of a positive structured task and those waiting under the condition of a neutral unstructured task; and there will be no statistically significant difference between those subjects waiting under the condition of reward present and those subjects waiting under the condition of reward absent failed to be significant at the .05 level of confidence.Because three of the four major null hypotheses failed to be rejected and because the study was a partial replication, the data were further subjected to a series of post-hoc analyses in an attempt to account for differences between the present study and previous studies. Analyses of criterion time; subject age; experimenter sex, subject sex, and individual experimenter differences; preference for the rewards; use of the materials; and testing order failed to account for differences between studies.

Synaptic inhibition in the vertebrate central nervous system is largely mediated by type A GABA receptors (GABA(_A)R). The clustering of (GABA(_A)R) at discrete and functionally significant domains on the nerve cell surface is an important determinant in the integration of synaptic inputs. To discern the role that specific GABA(_A)R subunits play in determining the receptor's cell surface topography and mobility, recombinant GABA(_A)Rs, comprising different GABA(_A)R subunit combinations, were transiently expressed in COS7, HEK293 and PC12 cells. In addition, a series of domain swapping experiments were performed in order to elucidate which regions of the protein are important in mobility/anchoring of receptors. The cellular localization and lateral mobility of the recombinantly expressed GABA(_A)Rs were determined by immunocytochemistry and Fluorescence Photobleach Recovery (FPR), respectively. The results presented in this thesis show that GABA(_A)R al subunits are recruited by the β3 subunits from an internally sequestered pool and assembled into a population of GABA(_A)Rs that are spatially segregated into clusters and also immobilised on the cell surface. FPR experiments on recombinant GABA(_A)R containing al-a6 subunits expressed in COS? cells showed restricted mobilities consistent with mobility constants determined for native GABA(_A)Rs expressed on cerebellar granule cells. Furthermore, the intracellular loop domain M3/M4 of the a1 subunits was found to be required for anchoring recombinantly expressed GABA(_A)Rs in C0S7 and cerebellar granule cells in culture, but not for GABA(_A)R clustering at the cell surface.

Although the integrated relationship that exists between the lumbar spine and hip joints is frequently acknowledged in scientific journals and by medical professionals, specific functional and injury relationships, are speculative and have not been substantiated. Lumbar spine and hip dysfunctions are suspected to be associated with inhibition of the surrounding extensor musculature, particularly the gluteal muscles, and facilitation of the flexor musculature. This phenomenon has been observed in other joints following effusion and is often termed ‘arthrogenic inhibition’. Its apparent occurrence about the hip has never been validated. The primary objective of this thesis was to investigate whether arthrogenic inhibition occurred about the hip. If inhibition was found to exist, its relationship with volume vs pressure was investigated to determine if either of these factors were a more appropriate predictor of inhibition. Finally, compensatory motor patterns in response to apparent inhibition were of interest. Participants were allocated to the following groups: 1) Control 2) Intervention I (magnetic resonance arthrogram) or 3) Intervention II (therapeutic arthrogram). Electromyography was collected on the rectus abdominis, erector spinae, gluteus maximus and semimenbranosis bilaterally during hip rehabilitation exercises prior to and following the intervention. Intra-capsular pressure was measured during the intervention. The findings provided support for the presence of extensor-inhibition in the hip following infusion of intra-articular fluid with intra-capsular pressure being the most appropriate predictor of the magnitude of inhibition. Hip extensor inhibition appeared to be compensated for by lumbar spine extensors during the selected tasks. Arthrogenic inhibition should be considered in the clinical evaluation and management of patients with hip joint effusions and/or elevated intra-capsular pressure.

To achieve goal-orientated behaviour, selective attention is often needed to filter out irrelevant information. Past research has shown that working memory (WM) plays a critical role in selective attention, with high WM load leading to more distractor interference than low WM load. However, because WM load is usually manipulated by requiring participants to hold in memory either one or several digits that were presented simultaneously while performing a selective attention task, the extent of attentional focus was not controlled. The present study examined the effect of WM load on distractor inhibition while keeping attentional focus constant by presenting one digit (low load condition) or six digits (high load condition) sequentially. The participants in the high-load condition demonstrated greater distractor interference than the participants in the low-load condition, suggesting that WM load influences distractor inhibition even when the extent of attentional focus was controlled. This result provides converging evidence to Lavie's (1995, 2005) load theory of attention and cognitive control.

Diss. (sammanfattning). Uppsala : Sveriges lantbruksuniv., 2003. / Härtill 4 uppsatser.

Thesis (Ph.D.)--University of Wollongong, 2003. / Typescript. Bibliographical references: leaf 285-306.