Home About us Contact
|
Home About us Contact | ||
|
|
||
Particular Locations (particular + locations)
Selected AbstractsDorsal/ventral hippocampus, fornix, and conditioned place preferenceHIPPOCAMPUS, Issue 2 2001Janina Ferbinteanu Abstract Conditioned place preference (CPP) is a learning paradigm requiring formation of associations between reward and particular locations. White and McDonald (Behav Brain Res 1993;55:269,281) demonstrated that amygdala (AMG) lesions impair, while fornix (Fx) lesions enhance learning of this task. In the present experiments, we replicated the effects of AMG and Fx lesions, but we also found that complete hippocampal (HPC) lesions interfere with normal performance. Thus, the effects of Fx and HPC lesions on CPP are opposite. This is in contrast with spatial learning in the water maze. Because it has been demonstrated that damage of dorsal HPC interferes to a greater extent with spatial learning than damage of ventral HPC, we also tested animals with either dorsal or ventral HPC disruptions on CPP. Lesions limited to dorsal HPC were followed by impairment on this task. In contrast, lesions limited to ventral HPC resulted in enhanced learning. We argue that Fx and HPC lesions do not have interchangeable effects in all learning paradigms. To explain the complex pattern of results presently obtained, we propose a novel hypothesis regarding behavioral functions of HPC neural circuits. Implications regarding the interaction between memory systems are also considered. Hippocampus 2001;11:187,200. © 2001 Wiley-Liss, Inc. [source] Symposium 8: Regulation of Oligodendrocyte DevelopmentJOURNAL OF NEUROCHEMISTRY, Issue 2002R. H. Miller Oligodendrocyte precursors arise in restricted regions of the developing neuroepithelium due to local signals that include sonic hedgehog. In the spinal cord the founder cells of the oligodendrocyte lineage develop in a specific domain of the ventral ventricular zone. These cells or their progeny subsequently migrate long distances to populate the entire spinal cord and myelinate axons in the peripheral presumptive white matter. The majority of migration in the oligodendrocyte lineage is accomplished by immature precursors, which then stop, proliferate and differentiate in the appropriate location. Several distinct mechanisms appear to regulate this migration. The initial dispersal of cells from the ventral ventricular zone is guided by chemorepellent cues including netrin-1 present in the ventral ventricular domain. Migratory precursors are arrested in particular locations within the developing spinal cord as the result of the localized expression of the chemokine, CXCL1 by astrocytes. This chemokine, signalling through the CXCR2 receptor combines with PDGF to inhibit cell migration and enhance cell proliferation thereby facilitating the local expansion of the oligodendrocyte lineage and myelination of all relevant axons. [source] WELCOME TO THE NEIGHBORHOOD: HOW CAN REGIONAL SCIENCE CONTRIBUTE TO THE STUDY OF NEIGHBORHOODS?,JOURNAL OF REGIONAL SCIENCE, Issue 1 2010Ingrid Gould Ellen ABSTRACT We argue in this paper that neighborhoods are highly relevant for the types of issues at the heart of regional science. First, residential and economic activity takes place in particular locations, and particular neighborhoods. Many attributes of those neighborhood environments matter for this activity, from the physical amenities, to the quality of the public and private services received. Second, those neighborhoods vary in their placement in the larger region and this broader arrangement of neighborhoods is particularly important for location choices, commuting behavior and travel patterns. Third, sorting across these neighborhoods by race and income may well matter for educational and labor market outcomes, important components of a region's overall economic activity. For each of these areas we suggest a series of unanswered questions that would benefit from more attention. Focused on neighborhood characteristics themselves, there are important gaps in our understanding of how neighborhoods change , the causes and the consequences. In terms of the overall pattern of neighborhoods and resulting commuting patterns, this connects directly to current concerns about environmental sustainability and there is much need for research relevant to policy makers. And in terms of segregation and sorting across neighborhoods, work is needed on better spatial measures. In addition, housing market causes and consequences for local economic activity are under researched. We expand on each of these, finishing with some suggestions on how newly available data, with improved spatial identifiers, may enable regional scientists to answer some of these research questions. [source] A field and laboratory method for monitoring the concentration and isotopic composition of soil CO2RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 4 2008Dan Breecker The stable isotope composition of nmol size gas samples can be determined accurately and precisely using continuous flow isotope ratio mass spectrometry (IRMS). We have developed a technique that exploits this capability in order to measure ,13C and ,18O values and, simultaneously, the concentration of CO2 in sub-mL volume soil air samples. A sampling strategy designed for monitoring CO2 profiles at particular locations of interest is also described. This combined field and laboratory technique provides several advantages over those previously reported: (1) the small sample size required allows soil air to be sampled at a high spatial resolution, (2) the field setup minimizes sampling times and does not require powered equipment, (3) the analytical method avoids the introduction of air (including O2) into the mass spectrometer thereby extending filament life, and (4) pCO2, ,13C and ,18O are determined simultaneously. The reproducibility of measurements of CO2 in synthetic tank air using this technique is: ±0.08, (,13C), ±0.10, (,18O), and ±0.7% (pCO2) at 5550,ppm. The reproducibility for CO2 in soil air is estimated as: ±0.06, (,13C), ±0.06, (,18O), and ±1.6% (pCO2). Monitoring soil CO2 using this technique is applicable to studies concerning soil respiration and ecosystem gas exchange, the effect of elevated atmospheric CO2 (e.g. free air carbon dioxide enrichment) on soil processes, soil water budgets including partitioning evaporation from transpiration, pedogenesis and weathering, diffuse solid-earth degassing, and the calibration of speleothem and pedogenic carbonate ,13C values as paleoenvironmental proxies. Copyright © 2008 John Wiley & Sons, Ltd. [source] Study of Regions of Extended Homozygosity Provides a Powerful Method to Explore Haplotype Structure of Human PopulationsANNALS OF HUMAN GENETICS, Issue 2 2008D. Curtis Summary Previous investigations have reported linkage disequilibrium occurring between nearby polymorphisms, a block-like structure for such relationships, some instances where surprisingly few haplotypes are found and regions of extended homozygosity which are especially marked around centromeres and which are especially common on the X chromosome. We investigated the distribution and nature of regions of extended homozygosity in a sample of 1411 subjects included in a genome wide association study. Regions of extended homozygosity over 1Mb are common, with an average of 35.9 occurring per subject, and containing on average 73 homozygous markers. They have a markedly non-random distribution. They are relatively common on the X chromosome and are seen at centromeres but are also concentrated at other chromosomal regions where presumably recombination is rare. They seem to be a consequence of some haplotypes being very common in the population and although sometimes this reflects the effect of a very common haplotype we also note that there are examples of two or three common haplotypes, each very different from each other, underlying this effect. Regions of extended homozygosity are commoner than previously appreciated. They result from the presence of extended haplotypes with high population frequency. Such regions concentrate in particular locations. The haplotypes involved are sometimes markedly disparate from each other. These regions offer a valuable opportunity for further investigation, in particular with regard to their ancestral history. [source] Insight into initiator,DNA interactions: a lesson from the archaeal ORCBIOESSAYS, Issue 3 2008Shusuke Tada Although initiation of DNA replication is considered to be highly coordinated through multiple protein,DNA and protein,protein interactions, it is poorly understood how particular locations within the eukaryotic chromosome are selected as origins of DNA replication. Here, we discuss recent reports that present structural information on the interaction characteristics of the archaeal orthologues of the eukaryotic origin recognition complex with their cognate binding sequences.1,2 Since the archaeal replication system is postulated as a simplified version of the one in eukaryotes, by analogy, these works provide insights into the functions of the eukaryotic initiator proteins. BioEssays 30:208,211, 2008. © 2008 Wiley Periodicals, Inc. [source] | ||||||||||