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Temporal Relationships (temporal + relationships)
Selected AbstractsWorld phylogeography and male-mediated gene flow in the sandbar shark, Carcharhinus plumbeusMOLECULAR ECOLOGY, Issue 10 2010DAVID S. PORTNOY Abstract The sandbar shark, Carcharhinus plumbeus, is a large, cosmopolitan, coastal species. Females are thought to show philopatry to nursery grounds while males potentially migrate long distances, creating an opportunity for male-mediated gene flow that may lead to discordance in patterns revealed by mitochondrial DNA (mtDNA) and nuclear markers. While this dynamic has been investigated in elasmobranchs over small spatial scales, it has not been examined at a global level. We examined patterns of historical phylogeography and contemporary gene flow by genotyping 329 individuals from nine locations throughout the species' range at eight nuclear microsatellite markers and sequencing the complete mtDNA control region. Pairwise comparisons often resulted in fixation indices and divergence estimates of greater magnitude using mtDNA sequence data than microsatellite data. In addition, multiple methods of estimation suggested fewer populations based on microsatellite loci than on mtDNA sequence data. Coalescent analyses suggest divergence and restricted migration among Hawaii, Taiwan, eastern and western Australia using mtDNA sequence data and no divergence and high migration rates, between Taiwan and both Australian sites using microsatellite data. Evidence of secondary contact was detected between several localities and appears to be discreet in time rather than continuous. Collectively, these data suggest complex spatial/temporal relationships between shark populations that may feature pulses of female dispersal and more continuous male-mediated gene flow. [source] Granularity in Relational Formalisms,With Application to Time and Space RepresentationCOMPUTATIONAL INTELLIGENCE, Issue 4 2001Jérôme Euzenat Temporal and spatial phenomena can be seen at a more or less precise granularity, depending on the kind of perceivable details. As a consequence, the relationship between two objects may differ depending on the granularity considered. When merging representations of different granularity, this may raise problems. This paper presents general rules of granularity conversion in relation algebras. Granularity is considered independently of the specific relation algebra, by investigating operators for converting a representation from one granularity to another and presenting six constraints that they must satisfy. The constraints are shown to be independent and consistent and general results about the existence of such operators are provided. The constraints are used to generate the unique pairs of operators for converting qualitative temporal relationships (upward and downward) from one granularity to another. Then two fundamental constructors (product and weakening) are presented: they permit the generation of new qualitative systems (e.g. space algebra) from existing ones. They are shown to preserve most of the properties of granularity conversion operators. [source] Tonically active neurons in the primate striatum and their role in the processing of information about motivationally relevant eventsEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 11 2002Paul ApicellaArticle first published online: 11 DEC 200 Abstract Analysis of recordings of single neuronal activity in the striatum of monkeys engaged in behavioural tasks has shown that tonically active neurons (TANs) can be distinguished by their distinct spontaneous firing and functional properties. As TANs are assumed to be cholinergic interneurons, the study of their physiological characteristics allows us to gain an insight into the role of a particular type of local-circuit neuron in the processing of information at the striatal level. In monkeys performing various behavioural tasks, the change in the activity of TANs, unlike the diversity of task-related activations exhibited by the phasically active population of striatal neurons, involves a transient depression of the tonic firing related to environmental events of motivational significance. Such events include primary rewards and stimuli that have acquired a reward value during associative learning. These neurons also respond to an aversive air puff, indicating that their responsiveness is not restricted to appetitive conditions. Another striking feature of the TANs is that their responses can be modulated by predictions about stimulus timing. Temporal variations in event occurrence have been found to favour the responses of TANs, whereas the responses are diminished or abolished in the presence of external cues that predict the time at which events will occur. These data suggest that the TANs respond as do detectors of motivationally relevant events, but they also demonstrate that these neurons are influenced by predictive information based on past experience with a given temporal context. TANs represent a unique subset of striatal neurons that might serve a modulatory function, monitoring for temporal relationships between environmental events. [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] Psychological aspects of hair diseaseJOURNAL OF COSMETIC DERMATOLOGY, Issue 2 2005Ramon Grimalt Summary Balding men are viewed as less desirable in a physical, personal, and social sense. Given the stereotype, it is not surprising that some men with androgenetic alopecia (AGA) appear to have a lower self-image, depression resulting in increased introversion, and increased feelings of unattractiveness. Ours is a culture that places a premium on physical appearance. In this context, appearance-altering conditions can be psychosocially insidious, especially conditions such as AGA with an uncertain course and a negative social meaning. To date, little or no data have been available regarding the psychosocial and quality-of-life aspects of AGA in a representative sample of community men. It is unknown whether AGA is a causal factor in the development of low self-esteem, depression, introversion, and feeling of unattractiveness, or whether there are underlying problems in certain patients prior to hair loss. Longitudinal studies will be important to investigate the temporal relationships between the degree of hair loss and psychosocial variables associated with AGA. A patient with male pattern baldness will be better treated and consequently more satisfied (better quality of life) if he receives effective anti-alopecia agents and simultaneously is evaluated and treated, if needed, for his psychological disorder. [source] Interactions between non-native plant species and the floristic composition of common habitatsJOURNAL OF ECOLOGY, Issue 6 2006L. C. MASKELL Summary 1We investigated the role of non-native species (neophytes) in common British plant communities using botanical data from two stratified random surveys carried out in 1990 and 1998. 2We found that from 16 851 plots surveyed in 1998 there were 123 non-native species found mostly in arable, tall grass/herb and fertile grassland habitats. Invasive non-native species, e.g. Fallopia japonica, Impatiens glandulifera and Rhododendron ponticum, were uncommon in this survey. 3Between 1990 and 1998 the total number of non-native species increased but the mean number of species per sample plot decreased. The mean cover of non-natives increased from 1.2% to 1.9%. 4There were positive spatial and temporal relationships between non-native and native species diversity. However, there was a weak negative relationship between changes in non-native cover and native diversity. 5The species composition and ecological traits of communities containing non-natives were very different from those that did not contain them. 6In the British countryside non-native species were mainly found in habitats with anthropogenic associations, high fertility, high number of ruderal species and high diversity. There is also an indication that successional shifts where competitive invasive species dominate involve non-native species. 7National-scale changes in plant community composition are likely to be closely correlated with external land-use impacts. Changes such as eutrophication, nitrogen deposition and increased fertility in infertile habitats are likely to benefit both native and non-native invasive species; however, currently these trends benefit native species much more often than non-natives. 8Non-native species are known to have significant effects on native species at local scales in many countries; however, at the landscape scale in Great Britain they are best considered as symptoms of disturbance and land-use change rather than a direct threat to biodiversity. [source] Drinking Alcohol before Age 13 and Negative Outcomes in Late AdolescenceALCOHOLISM, Issue 11 2009Neta Peleg-Oren Background:, Research has shown that adolescents who begin drinking at an early stage in life are at greater risk of developing alcohol dependency, as well as a variety of negative outcomes, for instance, delinquent behavior. Most of these studies have focused on those who begin drinking in middle adolescence, but little attention has been paid to youth who initiate drinking under the age of 13. Twenty percent of adolescents have begun using alcohol by the age of 13. The purpose of the study is to examine whether initiating alcohol use before the age of 13 exacerbates negative outcomes in late adolescence. Methods:, Data for the study were derived from 2 school-based statewide surveys conducted in Florida: the 2005 YRBS and the 2006 FYSAS. The sample included 12,352 11th and 12th grade students divided into 3 groups: students who initiated alcohol use under the age of 13, students who initiated alcohol use at age 13 or later, and students who never used alcohol. Results:, Results showed that after adjusting for gender, ethnicity/race, and grade, adolescents who initiated alcohol use before age 13 were more likely to report problems with school performance and display delinquent behaviors (carrying a gun, carrying a weapon to school, and recent marijuana use). Conclusion:, Although no temporal relationships can be determined between drinking alcohol before age 13 and delinquent behavior outcomes, the results suggested that adolescents under the age of 13 need to be included in national epidemiological surveys on alcohol use and more efforts need to be directed toward the implementation of prevention programs early in elementary and middle schools. [source] Changes in Plasma Concentrations of LH, FSH, Estradiol 17- , and Progesterone During Oestrus in Mithun (Bos frontalis)REPRODUCTION IN DOMESTIC ANIMALS, Issue 2 2006A Dhali Contents The objective of the present study was to establish the changes in plasma concentrations of LH, FSH, estradiol 17- , (E2) and progesterone (P4), as well as to understand their temporal relationships during oestrus in mithun (Bos frontalis). The experiment was conducted on 11 mithuns during third or fourth postpartum oestrous cycle. Since oestrus onset the jugular vein blood samples were collected every 2 h for 72 and 96 h, respectively from the animals without and with standing heat. The LH, FSH, E2 and P4 concentrations were estimated in plasma. The P4 concentration was fluctuated throughout the oestrus period and the average P4 concentration was found significantly (p < 0.05) lower on the day of oestrus onset. The multiple rises in LH and FSH concentrations above the basal level in spike like fashion were observed throughout the oestrus period irrespective of the occurrence of standing heat. A significant (p < 0.01) gradual increase in the average daily E2 concentration was observed till day 2 following oestrus onset irrespective of the occurrence of standing heat. A significant (p < 0.05) simultaneous increase in LH, FSH and E2 concentrations and a transient increase in P4 concentration at approximately the time of standing heat onset were observed. During investigation a definite temporal coupling between LH and FSH rises was absent throughout the oestrus period. The results suggest that (1) the multiple short-duration low-amplitude LH and FSH surges during oestrus may be crucial for the final maturation of ovulatory follicle and subsequent ovulation in mithun; (2) a differential mechanism for controlling LH and FSH secretions probably exists in mithun. [source] Live cell fluorescence microscopy to study microbial pathogenesisCELLULAR MICROBIOLOGY, Issue 4 2009Adam D. Hoppe Summary Advances in microscopy and fluorescent probes provide new insight into the nanometer-scale biochemistry governing the interactions between eukaryotic cells and pathogens. When combined with mathematical modelling, these new technologies hold the promise of qualitative, quantitative and predictive descriptions of these pathways. Using the light microscope to study the spatial and temporal relationships between pathogens, host cells and their respective biochemical machinery requires an appreciation for how fluorescent probes and imaging devices function. This review summarizes how live cell fluorescence microscopy with common instruments can provide quantitative insight into the cellular and molecular functions of hosts and pathogens. [source] | |||||||||||||