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Chance Encounters (chance + encounter)
Selected AbstractsManipulating CD4+ T cells by optical tweezers for the initiation of cell-cell transfer of HIV-1JOURNAL OF BIOPHOTONICS, Issue 4 2010Gregory P. McNerney Abstract Cell-cell interactions through direct contact are very important for cellular communication and coordination , especially for immune cells. The human immunodeficiency virus type I (HIV-1) induces immune cell interactions between CD4+ cells to shuttle between T cells via a virological synapse. A goal to understand the process of cell-cell transmission through virological synapses is to determine the cellular states that allow a chance encounter between cells to become a stable cell-cell adhesion. We demonstrate the use of optical tweezers to manipulate uninfected primary CD4+ T cells near HIV Gag-iGFP transfected Jurkat T cells to probe the determinants that induce stable adhesion. When combined with fast 4D confocal fluorescence microscopy, optical tweezers can be utilized not only to facilitate cell-cell contact, but also to simultaneously track the formation of a virological synapse, and ultimately to probe the events that precede virus transfer. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Temporal changes in replicated experimental stream fish assemblages: predictable or not?FRESHWATER BIOLOGY, Issue 9 2006WILLIAMJ. Summary 1.,Natural aquatic communities or habitats cannot be fully replicated in the wild, so little is known about how initially identical communities might change over time, or the extent to which observed changes in community structure are caused by internal factors (such as interspecific interactions or traits of individual species) versus factors external to the local community (such as abiotic disturbances or invasions of new species). 2.,We quantified changes in seven initially identical fish assemblages, in habitats that were as similar as possible, in seminatural artificial streams in a 388-day trial (May 1998 to May 1999), and compared the change to that in fish assemblages in small pools of a natural stream during a year. The experimental design excluded floods, droughts, immigration or emigration. The experimental fish communities diverged significantly in composition and exhibited dissimilar trajectories in multivariate species space. Divergence among the assemblages increased from May through August, but not thereafter. 3.,Differences among the experimental assemblages were influenced by differences that developed during the year in algae cover and in potential predation (due to differential survival of sunfish among units). 4.,In the natural stream, fish assemblages in small pools changed more than those in the experimental units, suggesting that in natural assemblages external factors exacerbated temporal variation. 5.,Our finding that initially identical assemblages, isolated from most external factors, would diverge in the structure of fish assemblages over time suggests a lack of strong internal, deterministic controls in the assemblages, and that idiosyncratic or stochastic components (chance encounters among species; vagaries in changes in the local habitat) even within habitat patches can play an important role in assemblage structure in natural systems. [source] Feeding history effects on feeding responses of Rhagoletis indifferens (Dipt., Tephritidae) to GF-120 and NulureJOURNAL OF APPLIED ENTOMOLOGY, Issue 9-10 2006W. L. Yee Abstract:, Effects of feeding history on feeding responses of western cherry fruit fly, Rhagoletis indifferens Curran, to the commercial protein baits GF-120 and Nulure were determined in the laboratory. Flies were kept on 5% sucrose alone or yeast extract and sucrose (Y + S) for 3,7 or 14,16 days and exposed to 24-h-old GF-120 or Nulure drops on artificial leaves. Numbers and durations of feeding events on leaves and durations of non-feeding events were recorded over 1-h periods. Experiments were also conducted to determine effects of Y + S feeding sequences on responses to Nulure, of starvation after sucrose or Y + S feeding on responses to Nulure, and of feeding history on mortality after exposure to GF-120 and Nulure. Protein-deprived flies consistently fed more times on GF-120 and Nulure than protein-fed flies and fed longer. One day of exposure to Y + S or 16 h of starvation after exposure to sucrose caused greater feeding on Nulure than 7 days of exposure to Y + S or 16 h of starvation after exposure to Y + S. Durations of non-feeding events on leaves with sucrose or bait were similar in protein-deprived and -fed flies. Responses of 4- to 6-day-old flies kept on sucrose to 0- and 24-h-old GF-120 or Nulure were similar. More flies kept on sucrose were paralysed or dead at 6,32 h after exposure to GF-120 or Nulure with spinosad than flies kept on Y + S. Results show that complete or long periods of protein deprivation and starvation after sucrose feeding increased feeding responses to GF-120 and Nulure. The general lack of differences in durations of non-feeding events on leaves with sucrose or GF-120 or Nulure in protein-deprived and -fed flies suggests that most protein-deprived flies found baits through chance encounters following normal movement. [source] Intensity of case managers' participation in organizational decision making,RESEARCH IN NURSING & HEALTH, Issue 5 2001L. Michele Issel Abstract Prior research has indicated that registered nurse (RN) participation in decision making (PDM) is related to better outcomes in nursing homes and hospitals. Little is known, however, about the roles of community-based case managers (CMs), most of whom are RNs. Data from 68 prenatal case management programs were used to test hypotheses about the intensity of CM PDM and to describe their patterns of involvement in decision activities and mechanisms. CMs were most involved in the activity of "raising the issue" and least involved in "choosing the alternative." However, "choosing the alternative" was the strongest predictor of perceived CM influence over the final choice. When CMs were involved in informal meetings and chance encounters with administrators, they were more likely to be perceived as having influence over the final choices made. Intensity of CM PDM varied by decision level and content, supporting two of the three hypotheses. The findings are discussed in light of prior research and complexity theory. © 2001 John Wiley & Sons, Inc. Res Nurs Health 24:361,372, 2001 [source] | |||||||||||||