Translocation of myelin basic protein mRNA in oligodendrocytes requires microtubules and kinesin

Myelin basic protein (MBP) mRNA is localized to the myelin membranes of oligodendrocytes. When exogenous MBP mRNA is microinjected into oligodendrocytes in culture, it is transported along the processes and localized to the myelin compartment in a multistep intracellular RNA trafficking pathway. In the work described here, oligodendrocytes were treated with agents that affect the cytoskeleton including: nocodazole, to disrupt microtubules; taxol, to stabilize microtubules; cytochalasin, to disrupt microfilaments; and kinesin anti-sense oligonucleotide, to suppress kinesin expression. Digoxigenin-labeled MBP mRNA was microinjected into the treated cells and the extent of translocation of the microinjected RNA was determined by confocal microscopy. Nocodazole, taxol, and kinesin anti-sense oligonucleotide inhibited translocation of microinjected MBP mRNA, while cytochalasin B and kinesin sense oligonucleotide did not. These results indicate that translocation of MBP mRNA in oligodendrocytes requires intact microtubules and kinesin but does not require intact microfilaments. The results are discussed in relation to the current multistep model for intracellular RNA trafficking in oligodendrocytes.     

Imprecise Navigation

Conventional models of navigation commonly assume a navigation agents location can be precisely determined. This paper examines the more general case, where an agents actual location cannot be precisely determined. This paper develops a formal model of navigation under imprecision using a graph. Two key strategies for dealing with imprecision are identified and defined: contingency and refinement. A contingency strategy aims to find an instruction sequence that maximizes an agents chances of reaching its destination. A refinement strategy aims to use knowledge gained as an agent moves through the network to disambiguate location. Examples of both strategies are empirically tested using a simulation with computerized navigation agents moving through a road network at different levels of locational imprecision. The results of the simulation indicate that both the strategies, contingency and refinement, applied individually can produce significant improvements in navigation performance under imprecision, at least at relatively fine granularities. Using both strategies in concert produced significant improvements in performance across all granularities.     

Real-time binary phase holograms on a reflective ferroelectric liquid-crystal spatial light modulator

A ferroelectric liquid-crystal spatial light modulator with an active silicon backplane is used to implement reconfigurable reflective phase holograms. Optical results are presented for an optimized computergenerated Fourier hologram.     

Autocatalytic processing of pro-papaya proteinase IV is prevented by crowding of the active-site cleft

The DNA coding for pro-papaya proteinase IV (PPIV) has beencloned and expressed in Escherichia coli. Heterologous expressionof the protein, followed by refolding in vitro, yields an enzymaticallyactive pro-enzyme which fails to autodigest to form the matureprotein. Mutagenesis of the active site of papain to simulatethat of PPIV yields a proenzyme which also fails to autoactivate.Complementarymutagenesis of the pro-region/mature boundary ofPPIV, to introduce its own substrate recognition sequence, has,however, produced a pro-enzyme that will autocatalytically cleave.This is the first report of enzymatic activity in a recombinantpro-cysteine proteinase, and the first time that such a proteinhas been shown to fail to autocatalytically cleave because ofits stringent substrate specificity.     

Autocatalytic processing of pro-papaya proteinase IV is prevented by crowding of the active-site cleft

BACKGROUND: To establish the value of saline-filled appendiceal ultrasonography in the the diagnosis of clinically equivocal acute appendicitis. METHODS: Saline-filled ultrasonography was performed in 43 patients with an equivocal clinical diagnosis of acute appendicitis. RESULTS: Sonography diagnosed 31 of 32 patients without acute appendicitis (97%). A normal appendix was visualized in 15 patients (47%), and we identified a normal appendix in 15 of 22 patients (68%) in whom the colon was cleansed with Golytely(R). Sonography diagnosed 10 of 11 patients with acute appendicitis (91%). In three of 10 patients, the findings corresponded to sonographic pitfalls. CONCLUSION: Saline-filled appendiceal ultrasonography enables the detection of a normal appendix and may overcome sonographic pitfalls in acute appendicitis.     

Radiotracer self-diffusion measurements in poly(ethylene oxide) and poly(propylene oxide) electrolytes

Radiotracer measurements of the ²²Na⁺ and S¹⁴CN^? diffusion coefficients in PEO-NaSCN (x = 6, 8 and 12) and PPO-NaSCN (x = 8) are reported, where PEO = poly(ethylene oxide), PPO = poly(propylene oxide), and x = [EO units]/[NaSCN] or [PO units]/[NaSCN]. The results are compared with ionic conductivity measurements on the same samples. Measurements for the PEO samples were taken above the melting point of pure PEO and the results interpreted, particularly for the sample most dilute in salt, in terms of ‘free ions’ as the dominant charge carriers. For PPO the results are less clear, although there is good evidence for the onset of ion aggregation prior to separation of salt at higher temperatures.