544 research outputs found
Biochemical, electron microscopic and immunohistological observations of cationic detergent-extracted cells: detection and improved preservation of microextensions and ultramicroextensions
BACKGROUND: Filopodia, retraction fibers and microvilli, are fragile microextensions of the plasma membrane that are easily damaged by mechanical force during specimen preparation for microscopy. To preserve these structures for electron microscopy glutaraldehyde is generally used, but it often causes antigen masking. By contrast, formaldehyde is generally used for immunofluorescence light microscopy, but few studies have been concerned with the loss of microextensions. RESULTS: We demonstrate in biochemical experiments that cultured cells needed to be kept in 4% formaldehyde for at least 60 min at room temperature or for 20 min at 37°C to irreversibly crosslink most of the polypeptides. Also, fragmentation of fragile microextensions was observed after Triton X-100 extraction depending on concentration and extent of crosslinking. We also report on a novel fixation procedure that includes the cationic detergent dodecyltrimethylammonium chloride (DOTMAC). Treatment of NIH3T3 cells with DOTMAC resulted in complete removal of membrane lipids and in good preservation of the cytoskeleton in microextensions as well as preservation of ultramicroextensions of <0.05μm in diameter that have not been observed previously unless glutaraldehyde was used. Stress fibers and microextensions of DOTMAC-extracted cells were readily stained with anti-β-actin antibodies, and antibodies to vinculin and moesin stained focal contacts and microextensions, respectively. CONCLUSIONS: Some microextensions were fragmented by the standard Triton X-100 permeabilization method. By contrast, DOTMAC completely extracted membrane lipids while maintaining the cytoskeleton of microextensions. Thus, DOTMAC treatment may provide a valuable new tool for the reliable visualization of previously undetectable or poorly detectable antigens while preserving the actin cytoskeleton of microextensions
Multi-quark baryons and color screening at finite temperature
We study baryons in SU(N) gauge theories at finite temperature according to
the gauge/string correspondence based on IIB string theory. The baryon is
constructed out of D5 brane and fundamental strings to form a color singlet
-quark bound state. At finite temperature and in the deconfining phase, we
could find -quark ``baryons''. Thermal properties of such -quark
baryons and also of the -quark baryon are examined. We study the temperature
dependence of color screening distance and Debye length of the baryon of
-quark and -quark. We also estimate the melting temperature, where the
baryons decay into quarks and gluons completely.Comment: 16 pages, 12 figure
Random invariant densities for Markov operator cocycles and random mean ergodic theorem
In the present paper, we consider random invariant densities and the mean
ergodic theorem for Markov operator cocycles which are applicable to quenched
type random dynamical systems. We give necessary and sufficient conditions for
the existence of random invariant measures for Markov operator cocycles and
establish the mean ergodic theorem for generalized linear operator cocycles
over arbitrary Banach spaces. The advantage of the result is that we show the
implication of weak precompactness for almost every environments to strong
convergence in the global sense
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