Neutrophil apoptosis is associated with a reduction in CD16 (Fc gamma RIII) expression

Resolution of inflammation involves removal of recruited neutrophils from inflamed sites via a noninflammatory mechanism, possibly involving neutrophil apoptosis and engulfment/phagocytosis by macrophages. In this study, we describe the reduction in surface expression (> 90%) of the neutrophil molecule Fc gamma RIII (CD16) during in vitro culture at 37 degrees C, which was found to be temporally associated with the appearance of neutrophils with apoptotic morphology during in vitro culture and inhibitable by granulocyte-macrophage colony-stimulating factor (GM-CSF), which postpones apoptosis in the neutrophil. By using dual fluorescence analysis, CD16 "low" expressing neutrophils showed reduced staining with the DNA-binding dye propidium iodide, suggesting that CD16 low expressing neutrophils were apoptotic. Separation of CD16 "high" and CD16 "low" expressing neutrophils by fluorescence-activated cell sorting revealed that morphologically apoptotic cells exhibited the CD16 low phenotype. We did not observe similar marked changes in expression of other neutrophil surface molecules (including other phosphatidylinositol (PI)-linked molecules), indicating that generalized loss of surface molecules does not occur during apoptosis. We believe this to be the first reported cell type-specific membrane alteration in a surface glycoprotein associated with apoptosis, suggesting that the program of cell death in the neutrophil, in addition to morphologic and nuclear changes, includes alterations in expression of surface receptors.     

Impaired Higher Order Implicit Sequence Learning on the Verbal Version of the Serial Reaction Time Task in Patients With Parkinson's Disease.

Although neuroimaging studies have strongly implicated basal ganglia involvement in implicit sequence learning, serial reaction time (SRT) studies with Parkinson's disease (PD) patients have yielded mixed results. The present research sought to examine the ability of people with PD to implicitly learn sequences with different sequential structures and to objectively assess explicit knowledge. A version of the SRT task that reduces motor demands was used to compare 19 patients with PD but not dementia and 37 matched controls. PD patients showed less implicit sequence-specific learning for both sequences and reduced response time improvement over sequential trials for the more complex sequence. A closer examination revealed that the deficit involved higher order sequential associations as well as the learning of pairwise information. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Applications drive VR interface selection

Physical interfaces to virtual environments fall into two broad categories: devices for navigation and physical interaction (such as deskbound and flying “mice”, gestural devices and navigation controls built into viewing devices); and viewing devices (such as head-mounted displays, counterbalanced displays, shutter glasses and a new class of immersive “desktop” viewers). The visual image is critical to creating an effective virtual experience. Beginning with immersive displays, this survey describes the range of available devices and discusses how application considerations affect the selection of components when configuring a virtual reality (VR) system     

Enhancing the biofiltration of geosmin by seeding sand filter columns with a consortium of geosmin-degrading bacteria

Geosmin is a secondary metabolite that can be produced by many species of cyanobacteria and Actinomycetes. It imparts a musty/earthy taste and odour to drinking water which can result in consumer complaints and a general perception that there is a problem with the water quality. As geosmin is recalcitrant to conventional water treatment, processes are sought to ensure effective removal of this compound from potable water. Biological filtration (biofiltration) is an attractive option for geosmin removal as this compound has been shown to be biodegradable. However, effective biofiltration of geosmin can be site specific as it is highly dependent upon the types of organism present and there is often an extended acclimation period before efficient removals are achieved. We report here, a novel approach to enhance the biofiltration of geosmin by seeding sand filter columns with a bacterial consortium previously shown to be capable of effectively degrading geosmin. Geosmin removals of up to 75% were evident through sand columns which had been inoculated with the geosmin-degrading bacteria, when compared with non-inoculated sand columns where geosmin removals were as low as 25%. These low geosmin removals through the non-inoculated sand columns are consistent with previous studies and were attributed to physical/abiotic losses. The presence of an existing biofilm was shown to influence geosmin removal, as the biofilm allowed for greater attachment of the geosmin-degrading consortium (as determined by an ATP assay), and enhanced removals of geosmin. Minimal difference in geosmin removal was observed when the geosmin-degrading bacteria were inoculated into the sand columns containing either an active or inactive biofilm.     

Genetic analysis of sterile mutants in the dpy-5 unc-13 (I) genomic region of Caenorhabditis elegans

Essential genes were identified in the 1.5-map unit dpy-5 unc-13 region of chromosome I in the Caenorhabditis elegans genome by rescuing lethal mutations using the duplication sDp2. In this paper, we report the mapping and complementation testing of lethal mutations, 45 of which identify 18 new, essential genes. This analysis brings the number of essential genes defined by the sDp2 rescue of lethal mutants to 97; 64 of these map between dpy-5 and unc-13. 61% of these essential genes are identified by more than one allele. Positioning of the mutations was done using the breakpoints of six duplications. The mutant phenotypes of 14 loci essential for fertility were characterized by Nomarski microscopy and DAPI staining. None of the mutants were rescued by wild-type male sperm. The cytological data showed that four genes produced mutants with defects in gonadogenesis. let-395. let-603, let-605 and let-610. Mutations in seven genes, let-355, let-367, let-384, let-513, let-544, let-545 and let-606, affected germ cell proliferation or gametogenesis. Mutants for the remaining three genes, let-370, let-599 and let-604, produced eggs that failed to develop or hatch. thereby acting as maternal effect lethals. We observed a nonrandom distribution of arrest phenotypes with regard to map position.     

Site-directed mutagenesis of Arg60 and Cys271 in ornithine transcarbamylase from rat liver

We have investigated the putative carbamylphosphate- and ornithine-bindingdomains in ornithine transcarbamylase from rat liver using site-directedmutagenesis. Arg60, present in the phosphate-binding motif X-Ser-X-Arg-Xand therefore implicated in the binding of the phosphate moietyof carbamylphosphate has been replaced with a leucine. Thisresults in a dramatic reduction of catalytic activity, althoughthe enzyme is synthesized in cells stably transfected with themutant clone and imported, correctly processed and assembledinto a homotrimer in mitochondria. The sole cysteine residue(Cys271) has been implicated in ornithine binding by the chemicalmodification studies of Marshall and Cohen in 1972 and 1980(J. Biol. Chem., 247, 1654–1668, 1669–1682; 255,7291–7295, 7296–7300). Replacement of this residuewith serine did not eliminate enzyme activity but affected theMichaelis constant for ornithine (K_b, increasing it 5-fold from0.71 to 3.7 mM and reduced the k_cat at pH 8.5 by 20-fold. Thesechanges represent a loss in apparent binding energy for theenzyme - ornithine complex of 2.9 kcal/mol, suggesting thatCys271 is normally involved in hydrogen bonding to the substrate,ornithine. The cysteine to serine substitution also caused thedissociation constant (Kä for the competitive inhibitor,L-norvaline to be increased 10-fold, from 12 to 120 µM.The small loss in binding energy and relatively high residualcatalytic activity of the mutant strongly suggests that a numberof other residues are involved in the binding of ornithine.The effect of replacement of Cys271 with serine was restrictedto the ornithine binding site of the enzyme since both the bindingconstant for carbamyl-phosphate (K_ia) and Michaelis constant(K_a) were not appreciably different for mutant and wild-typeenzymes. The pH optimum of the wild-type enzyme (8.6) is increasedto > 9.6 in the Ser271 mutant.     

Synthesis and performance of an active microstrip antenna

This article discusses the application of a synthesis method for, and the subsequent experimental characterization, of an active microstrip patch antenna. The active antenna incorporates a GaAs MESFET on the patch periphery and the circuit acts as a self-oscillating radiating element. The MESFET and the antenna are mounted on the same side of the circuit, thereby preserving the conformal nature of the structure. The synthesis approach described is based on the method of harmonic balance and allows optimal FET terminations to be selected for a predefined, added power at a specified frequency of operation. Application of a time domain simulator is illustrated in order to demonstrate start-up performance and limit cycle formation in the presence and absence of a frequency entrainment signal. The issue of stability of the active element is also addressed using a modified device/load line method. Theoretical and experimental results are presented for the external quality factor, locking power/phase variation, and power and frequency pushing characteristics of the active antenna. Finally, the effect on oscillator behavior of the mutual coupling between the microstrip patch and the active antenna distributed embedding elements is discussed.     

Indirect Learning of Event Sequences: The Effects of Divided Attention and Stimulus Continuity.

In a serial reaction time (SRT) task, the learning curve is steeper when the stimuli are presented in a repeating sequential manner rather than in random order (Nissen & Bullemer, 1987). This is true even when subjects report being unaware of the presence of the repeating sequence. The present study examines the nature of this learning under conditions designed to reduce attentional resources and to disrupt the continuity of stimuli. In the first three experiments, subjects were trained in the SRT task, with or without the addition of a secondary tone counting task, and with repeating or non-repeating sequences. The results suggest that some sequence learning occurred despite the presence of a secondary task. Experiment 4 examined the extent of sequence learning when the inter-stimulus interval was varied between trials. The overall results suggest that despite reduced attentional allocation and discontinuous stimulus presentation, some sequence learning occurs. This result supports other work suggesting a dissociation between learning when measured explicitly, and when assessed through performance indicators. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cellular location of thymus-leukemia (TL) antigen as shown by immuno-cryoultramicrotomy

Thymus-leukemia (TL) antigen is a class I molecule of the major histocompatibility complex that is expressed on the surface of mouse cortical thymocytes. Though not expected, it has been reported that TL antigen can be found on isolated mitochondria of TL⁺ cells. We used immuno-cryoultramicrotomy to look for TL on mitochondria in situ, thereby avoiding the plasma membrane contamination that occurs when isolating organelles. Establishing optimal fixation conditions was crucial, as mitochondrial structure was not preserved by the low concentrations of fixative needed for detection of antibody labeling. The plasma membranes of tissue culture and thymus cells were labeled well with anti-TL antibody and protein A-gold conjugate, while mitochondria within the cells were not labeled. Isolation of mitochondria on a one-step Ficoll gradient resulted in a purer organelle preparation than did isolation of mitochondria by centrifugation alone. Generally, mitochondria within this purer preparation were not labeled. Our data show that under conditions where contamination by plasma membrane is not a major concern, TL antigen cannot be detected on mitochondria.     

Developing cognitive task analysis and the importance of socio-cognitive competence/insight for professional practice

Accelerating the cognitive expertise of professionals is a critical challenge for many organizations. This paper reports a collaborative, longitudinal, academic practitioner project which aimed to elicit, document, and accelerate the cognitive expertise of engineering professionals working with the manufacture and management of petroleum additives. Twenty-five engineering experts were trained by three academic psychologists to use applied cognitive task analysis (ACTA) interview techniques to document the cognition of their expert peers. Results had high face validity for practitioners who elicited hot/sensory-based cognition, a number of perceptual skills and mental models, highlighting undocumented context specific expertise. We conclude from a peer review of findings, combined with experienced CTA analysts that ACTA techniques can be advanced in context by the explicit recognition and development of socio-cognitive competence/insight.