Bibliothek

Notizen: This work examines the effects of Ag on stoichiometric and nonstoichiometric BaTiO3 in terms of the unit cell dimensions, the polycrystalline microstructure, and the dielectric properties. Stoichiometric BaTiO3 and compositions with 0.5 mol% TiO2 excess and 0.5 mol% BaO excess were prepared via solid-state synthesis with varying amounts of Ag up to 0.3 mol%. Experimental results indicate that stoichiometry plays a significant role in the solubility of Ag and its effects on the physical properties. Overall, the solubility of Ag was negligible in stoichiometric BaTiO3. However, compositions with excess TiO2 stabilized the solubility of Ag as evidenced from changes in the unit cell dimensions and dielectric properties. Based on these data, it is proposed that Ag occupies the A-site in the perovskite structure with an upper limit of Ag solubility of 0.06 mol% Ag in BaTiO3 with 0.5 mol% excess TiO2. Dielectric measurements showed that Ag concentrations approaching 0.3 mol% gave rise to an increase in the space charge effect, especially at temperatures above TC. In both nonstoichiometric compositions, the presence of a liquid Ag phase during thermal processing was found to affect microstructural development and sintering.

Notizen: The GoLoco motif is a 19-amino-acid sequence with guanine nucleotide dissociation inhibitor activity against G-alpha subunits of the adenylyl-cyclase-inhibitory subclass. The GoLoco motif is present as an independent element within multidomain signaling regulators, such as Loco, RGS12, RGS14, and Rap1GAP, as well as in tandem arrays in proteins, such as AGS3, G18, LGN, Pcp-2/L7, and Partner of Inscuteable (Pins/Rapsynoid). Here we discuss the biochemical mechanisms of GoLoco motif action on G-alpha subunits in light of the recent crystal structure of G-alpha-i1 bound to the RGS14 GoLoco motif. Currently, there is sparse evidence for GoLoco motif regulation of canonical G-protein-coupled receptor signaling. Rather, studies of asymmetric cell division in Drosophila and Caenorhabditis elegans, as well as mammalian mitosis, implicate GoLoco proteins, such as Pins, GPR-1/GPR-2, LGN, and RGS14, in mitotic spindle organization and force generation. We discuss potential mechanisms by which GoLoco/Galpha complexes might modulate spindle dynamics.

Notizen: The GoLoco motif is a 19-amino-acid sequence with guanine nucleotide dissociation inhibitor activity against G-alpha subunits of the adenylyl-cyclase-inhibitory subclass. The GoLoco motif is present as an independent element within multidomain signaling regulators, such as Loco, RGS12, RGS14, and Rap1GAP, as well as in tandem arrays in proteins, such as AGS3, G18, LGN, Pcp-2/L7, and Partner of Inscuteable (Pins/Rapsynoid). Here we discuss the biochemical mechanisms of GoLoco motif action on G-alpha subunits in light of the recent crystal structure of G-alpha-i1 bound to the RGS14 GoLoco motif. Currently, there is sparse evidence for GoLoco motif regulation of canonical G-protein-coupled receptor signaling. Rather, studies of asymmetric cell division in Drosophila and Caenorhabditis elegans, as well as mammalian mitosis, implicate GoLoco proteins, such as Pins, GPR-1/GPR-2, LGN, and RGS14, in mitotic spindle organization and force generation. We discuss potential mechanisms by which GoLoco/Galpha complexes might modulate spindle dynamics.

Notizen: Background:  Accumulating evidence indicates that there are intergenerational continuities in antisocial behavior, and that parenting patterns play a role in these continuities. Very few studies, however, enable assessment across two generations of children at comparable ages, employing independent reporters and comparable measurements. The present study addresses the extent to which antisocial behavior in parents predicts antisocial behavior in children in two successive generations; the degree to which a man's childhood antisocial behavior predicts antisocial behavior in his own children; the extent to which parenting problems are related to child antisocial behavior similarly in two successive generations; and the extent to which intergenerational continuities in antisocial behavior are mediated by parenting variables.Methods:  Questions are addressed with prospective longitudinal data from the Cambridge Study in Delinquent Development (CSDD). The CSDD includes data on 411 Inner London males (Generation 2, or G2), their female partners, their parents (G1) and their children (G3). At time 1, when G2 were aged 8–10, data on G2 child conduct problems and G1 parenting and convictions were available. At time 2 when G2 males were aged 32, data were available on the parenting of 178 G2 fathers with G3 children aged 3–15, and on their G3 children's behavior. Time 1 data come predominantly from G1 mothers, whereas time 2 data come predominantly from G2 fathers.Results:  Between generations, antisocial G1 mothers and fathers predicted conduct problems in G2 and G3 children, but G2 child conduct problems did not predict G3 child conduct problems. Within generations, G2 child conduct problems predicted G2 adult antisocial behavior and antisocial partnerships, which in turn predicted G3 conduct problems. Parental conflict and authoritarian parenting were similarly related to early childhood conduct problems in two successive generations. There was relatively little continuity between G1 and G2 parenting except that G2 males who were poorly supervised by their parents were themselves poor supervisors as fathers. Both G1 and G2 generations displayed assortative mating, with antisocial males tending to partner antisocial female peers.Conclusions:  There are between-generation and within-generation continuities in antisocial behavior, although assessment of such continuities is complicated by inevitable design and measurement limitations. Parenting partly mediated the impact of parental antisocial behavior on child antisocial behavior in two successive generations, but the relation between antisocial parents and antisocial children is not fully mediated by parenting variables.

Notizen: 1. During late spring 1993–1995, the U.S. Environmental Protection Agency's Environmental Monitoring and Assessment Program (EMAP) sampled 490 wadeable streams in the mid-Atlantic Highlands (MAH) of the U.S. for a variety of physical, chemical and biological indicators of environmental condition. We used the resulting data set to evaluate the importance of differing levels of macroinvertebrate taxonomic resolution in bioassessments by comparing the ability of family versus genus to detect differences among sites classified by type and magnitude of human impact and by stream size. We divided the MAH into two physiographic regions: the Appalachian Plateau where mine drainage (MD) and acidic deposition are major stressors, and the Ridge and Valley where nutrient enrichment is a major stressor. Stream sites were classified into three or four impact classes based on water chemistry and habitat. We used stream order (first to third Strahler order) in each region as a measure of stream size. Ordination, 2 × 2 chi-square and biotic metrics were used to compare the ability of family and genus to detect differences among both stressor and size classes.2. With one notable exception, there were only a small number of different genera per family (interquartile range = 1–4). Family Chironomidae, however, contained 123 different genera. As a result, significant information loss occurred when this group was only classified to family. The family Chironomidae did not discriminate among the predefined classes but many chironomid genera did: by chi-square analysis, 10 and 28 chironomid genera were significant in discriminating MD and nutrient impacts, respectively.3. Family and genus data were similar in their ability to distinguish among the coarse impacts (e.g. most severe versus least severe impact classes) for all cases. Though genus data in many cases distinguished the subtler differences (e.g. mixed/moderate impacts versus high or low impacts) better than family, differences in significance levels between family and genus analyses were relatively minor. However, genus data detected differences among stream orders in ordination analyses that were not revealed at the family level. In the ordinations, both family and genus levels of analysis responded to similar suites of environmental variables.4. Our results suggest that identification to the family level is sufficient for many bioassessment purposes. However, identifications to genus do provide more information in genera-rich families like Chironomidae. Genus or finer levels of identification are important for investigating natural history, stream ecology, biodiversity and indicator species. Decisions about the taxonomic level of identification need to be study specific and depend on available resources (cost) and study objectives.

Notizen: We investigated the natural history of atopic dermatitis (AD) in a population-based birth cohort and assessed whether children at risk of visible eczema at 5 years of age can be identified from total immunoglobulin E (IgE) levels measured at 8, 12 and 18 months. AD data collected included a whole body examination for visible eczema at 49 months (4 years) and 61 months (5 years) of age and parent completed questionnaire data throughout their early lives. Children were divided into four groups based on their natural history of early AD: persistent (AD at 1, 6, 18, 30 and 42 months, n = 34), intermittent early onset (before 18  months of age, n = 495), intermittent late onset (18–42 months of age, n = 273) and unaffected (n = 429). Visible eczema at 5 years of age was present in 12.2% (117/957) (95% confidence interval [CI] 10.1–14.3%) of the children. Levels of total IgE at 8, 12 and 18 months of age were associated with early onset of AD, but not with AD of later onset. For all four natural history groups, the geometric mean total IgE at 12 months was higher in those who subsequently had visible eczema than those who did not. However, the degree of overlap was such that total IgE at 12 months of age was a poor predictor of eczema at age five. A cutoff point of 78 kU/l had the highest positive predictive value for visible eczema at 5 years of age of 28.6%, with a sensitivity of 12% and specificity of 95%.

Notizen: Rab proteins are small GTPases involved in intracellular trafficking. Among the 60 different Rab proteins described in mammals, Rab3a is the most abundant in brain, where it is involved in synaptic vesicle fusion and neurotransmitter release. Rab3a constitutive knockout mice (Rab3a−/−) are characterized by deficient short- and long-term synaptic plasticity in the mossy fiber pathway and altered circadian motor activity, while no effects on spatial learning have been reported so far for these mice. The goals of this study were to analyse possible behavioral consequences of the lack of synaptic plasticity in the mossy fiber pathway using a broad battery of sensitive behavioral measures that has been used previously to analyse the behavior of Gdi1 mice lacking a protein thought to regulate Rab3a. Rab3a−/− mice showed normal acquisition but moderately impaired platform reversal learning in the water maze including reference memory and episodic-like memory tasks. A mild deficit in spatial working memory was also observed when tested in the radial maze. Analysis of explorative behavior revealed increased locomotor activity and enhanced exploratory activity in open field, O-maze, dark/light box and novel object tests. Spontaneous activity in normal home cage settings was unaffected but Rab3a−/− mice showed increased motor activity when the home cage was equipped with a wheel. No differences were found for delayed and trace fear conditioning or for conditioned taste aversion learning. Congruent with earlier data, these results suggest that Rab3a-dependent synaptic plasticity might play a specific role in the reactivity to novel stimuli and behavioral stability rather than being involved in memory processing. On the other hand, the phenotypic changes in the Rab3a−/− mice bore no relation to the behavioral changes as observed in the Gdi1 mice. Such divergence in phenotypes implies that the putative synaptic interaction between Gdi1 and Rab3a should be reconsidered and re-analysed.

Notizen: Four rhesus monkeys (Macaca mulatta) were trained preoperatively in a test of object-in-place scene memory. They were presented daily with lists of unique computer-generated scenes each containing a spatial array of multiple individual objects. Within each scene, objects to be discriminated appeared in the foreground, each occupying a unique location, and monkeys were required to correctly discriminate the rewarded object to receive a food reward. Once this preoperative criterion was attained, the monkeys received bilateral entorhinal cortex ablation performed as either one or two surgical operations with a period of testing following each. Postoperatively, they were significantly impaired in learning new object-in-place scene problems. These results show that the entorhinal cortex, like anatomically related structures including the perirhinal cortex and the fornix, contributes to object-in-place scene learning.

Notizen: Myelin-derived molecules inhibit axonal regeneration in the CNS. The Long–Evans Shaker rat is a naturally occurring dysmyelinated mutant, which although able to express the components of myelin lacks functional myelin in adulthood. Given that myelin breakdown exposes axons to molecules that are inhibitory to regeneration, we sought to determine whether injured dorsal column axons in a Shaker rat would exhibit a regenerative response absent in normally myelinated Long–Evans (control) rats. Although Shaker rat axons did not regenerate beyond the lesion, they remained at the caudal end of the crush site. Control rat axons, in contrast, retracted and died back from the edge of the crush. The absence of retraction/dieback in Shaker rats was associated with a reduced phagocytic reaction to dorsal column crush around the caudal edge of the lesion. Systemic injection of minocycline, a tetracycline derivative, in control rats reduced both the macrophage response and axonal retraction/dieback following dorsal column injury. In contrast, increasing macrophage activation by spinal injection of the yeast particulate zymosan had no effect on axonal retraction/dieback in Shaker rats. Schwann cell invasion was reduced in minocycline-treated control rats compared with untreated control rats, and was almost undetectable in Shaker rats, suggesting that like axonal retraction/dieback, spinal Schwann cell infiltration is dependent upon macrophage-mediated myelin degeneration. These results indicate that following spinal cord injury the phagocyte-mediated degeneration of myelin and subsequent exposure of inhibitory molecules to the injured axons contributes to their retraction/dieback.

Notizen: We examine whether gang membership is associated with higher levels of delinquency because boys predisposed to delinquent activity are more likely than others to join. We use 10 years of longitudinal data from 858 participants of the Pittsburgh Youth Study to identify periods before, during and after gang membership. We build on prior research by controlling for ages and calendar time, by better accounting for gang memberships that occurred before the study began, and by using fixed effects statistical models. We find more evidence than has been found in prior studies that boys who join gangs are more delinquent before entering the gang than those who do not join. Even with such selective differences, however, we replicate research showing that drug selling, drug use, violent behaviors and vandalism of property increase significantly when a youth joins a gang. The delinquency of peers appears to be one mechanism of socialization. These findings are clearest in youth self-reports, but are also evident in reports from parents and teachers on boys' behavior and delinquency. Once we adjust for time trends, we find that the increase in delinquency is temporary, that delinquency falls to pre-gang levels when boys leave gangs.