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  • 1
    Electronic Resource
    Electronic Resource
    Oxford [u.a.] : International Union of Crystallography (IUCr)
    Acta crystallographica 55 (1999), S. 576-578 
    ISSN: 1600-5759
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: In vivo and in vitro experiments on the endocrine relationships of epidermal glands in the tokay Gekko gecko, and the common house gecko Hemidactylus bowringii are reported. The results show that certain aspects of ß-gland differentiation involve a synergistic action between androgens and those hormones responsible for controlling the normal shedding cycle, while other aspects are solely under androgenic control. Pre-anal organ activity appears to be solely under androgenic control.
    Additional Material: 3 Tab.
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  • 3
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    ISSN: 0887-6266
    Keywords: latex films ; particle coalescence ; cross-linking ; small-angle neutron scattering (SANS) ; dynamic micromechanical analysis (DMA) ; chain segment mobility ; diffusion coefficient ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Interdiffusion of polymer chains across particle-particle interfaces in latex films is one of the key issues, because this further coalescence process usually controls the cohesive strength of the films. Here we examined local dynamics of polymer chains within latex films and showed that it is related to the occurrence of particle coalescence. For this purpose, structural and dynamic micromechanical properties of partly cross-linked polymer films from styrenebutadiene (SB) copolymer latexes were investigated. The gel fraction of the emulsion copolymers was varied within a large range (15-90%) by adding different chain transfer agents during the polymerization process. The structure of the films was determined using small-angle neutron scattering (SANS) and transmission electron microscopy (TEM). A qualitative description of the mechanism that likely triggers further coalescence in latex films is given, based on critical disjoining pressure exerted by particle cores on interfacial membranes. In addition, from dynamic micromechanical analysis (DMA) spectra, a key molecular parameter reflecting local segmental mobility was derived. Average diffusion coefficients of polymer segments were calculated and shown to be consistently related to the occurrence of particle coalescence as evidenced from SANS and TEM structural investigations. Finally, the noncovalent physical intermolecular interaction loci, which act as cross-link knots, were shown to play a significant part in the restriction of the coalescence process, increasing the state of constraints encountered by free chain segments embedded in the covalent network. © 1995 John Wiley & Sons, Inc.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 235 (1993), S. 183-190 
    ISSN: 0003-276X
    Keywords: Mitosis ; Cell rounding ; Surface area ; Endocytosis ; Intracellular pH ; BCECF ; Neutral red ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The rounding up of mitotic human Chang liver cells in monolayer culture was studied quantitatively. It was surprising to find significant reduction in cell surface area considering that endocytosis has been demonstrated to be at a complete standstill in M phase. Uptake studies using impermeant BCECF (2′,7′-bis(2-carboxyethyl)-4(5)-carboxyfluorescein free acid) pH indicator and particulate neutral red dye in aqueous buffer showed preferential internalization into mitotic cells in direct contrast to expectation since interphase cells do not have arrested endocytosis. However, infolded plasma membrane ruffles and internalized extracellular material were demonstrated in prophase cells, much like those seen in interphase rounding via the induction of intracellular alkalinizations. Raised intracellular pH (pHi) is a universal and consistent finding in M phase cells. Despite cessation of small pit endocytosis, it remains possible for plasma membrane internalization to be a causal factor in the observed surface area reduction in mitotic rounding. © 1993 Wiley-Liss, Inc.
    Additional Material: 9 Ill.
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  • 5
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The high-resolution nmr spectrum of the anticodon hairpin from E. coli tRNAfMet has been obtained at a number of different temperatures. The positions of the resonances from interior Watson-Crick base pairs are well accounted for (within 0.1 ppm) by a semi-empirical ring current shift theory, but the terminal base pairs are susceptible to the exact orientation of adjacent bases in single-stranded regions. From a careful examination of the exact way in which resonances disappear at elevated temperatures, we conclude that melting in the nmr experiments occurs when the lifetime of a base pair is reduced to several milliseconds. On the basis of these experiments we are able to assign an nmr Tm to each individual base pair and these should be useful in interpreting the melting behavior of the intact molecule. An “extra” resonance is observed at ∼11.3 ppm and, on the basis of its position and temperature sensitivity, it is tentatively assigned to the ring nitrogen proton of a “protected” U residue in the anticodon loop. A strong preference for stacking of a nonbase-paired A residue on an adjacent GC base pair is observed even at temperatures in excess of 52°C.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Journal of Raman Spectroscopy 23 (1992), S. 479-481 
    ISSN: 0377-0486
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: An amplified spontaneous emission (ASE) seeded broadband pulsed stimulated Raman gain spectroscopy (SRGS) technique is described. The ASE of a dye laser and the dye laser itself are used as a broadband probe and the pump beam, respectively. The overall optical arrangement is simple and easy to implement. The technique has been demonstrated to have excellent background fluorescence rejection capability. Raman spectra of low-concentration NO3 - and SO42- dissolved in a strongly fluorescent solution have been obtained.
    Additional Material: 3 Ill.
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  • 7
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: We show that, for rigid body dynamics, the mid-point rule formulated in body co-ordinates exactly conserves energy and the norm of the angular momentum for incremental force-free motions, but fails to conserve the direction of the angular momentum vector. Further, we show that the mid-point rule formulated in the spatial representation is, in general, physically and geometrically meaningless. An alternative algorithm is developed which exactly preserves energy, and the total spatial angular momentum in incremental force-free motions. The implicit version of this algorithm is unconditionally stable and second order accurate. The explicit version conserves exactly angular momentum in incremental force-free motions. Numerical simulations are presented which illustrate the excellent performance of the proposed procedure, even for incremental rotations over 65 degrees. The procedure is directly applicable to transient dynamic calculations of geometrically exact rods and shells.
    Additional Material: 14 Ill.
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  • 8
    ISSN: 0003-276X
    Keywords: Flow cytometric analysis of BCECF ratios ; Neutral red uptake and propidium iodide-DNA bindings ; Ao apoptotic peak ; two million mol.wt dextrans ; Macrophagic internalizations ; Large channel endocytosis ; Image analysis ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Background: The early stages of apoptosis (programmed cell death) are said to be characterized by internucleosomal DNA fragmentation and “condensation of the cytoplasm” in which cells round up, detach, and increase in density. We studied the causation of apoptotic rounding.Methods: Human Chang liver cells in normal monolayer culture were compared with apoptotic counterparts derived from serum growth factor deprivation. Cell-by-cell analysis using the Coulter EPICS PROFILE II flow cytometer studied (1) the cell cycle from propidium iodide-DNA bindings, (2) uptake of neutral red (NR) dye, a viable cell marker, and (3) cytosolic pH (pHi) modulations from 2′,7′-bis(2-carboxyethyl)-5(and-6)-carboxyfluorescein (BCECF) fluorescence ratios with NH4Cl prepulsing and forward scatter bitmapping of cell surface area. Morphometric studies were done in the Quantimet 570 image analyser. Uptake of trypan blue, neutral red, and 2 million mol.wt fluoresceinated dextrans was studied by light microscopy. Cytological profiles were examined in light microscopy and transmission and scanning electron microscopy.Results: Three days of serum growth factor deprivation caused confluent flat substrate-attached cells to retract and round up, tethering tenuously to the substrate via thin microvillus attachments only. Ninety percent of cell surface area was lost with this flat-to-round change. There was high trypan blue staining with total loss of proliferative potential, and the entire genome was just fragmented DNA making up the solitary Ao (apoptotic) peak in cell cycle profiles. However, these rounded apoptotic cells also internalized huge 2 million mol.wt dextran particles and impermeant neutral red which is an established viable cell marker. The rounded apoptotic cells had an intensely acidic (pH 5.6) cytosol and therefore a steep [H+]i/[H+]o gradient promoting proton extrusion. The pHi upshifted dynamically upon acidification, recovering and even exceeding resting level by a whole pH unit. Surface area reduction occurred concomitantly in real time with pHi upshifts in these apoptotic cells. Acidification and recovery in apoptotic cells also produced enhanced uptake of neutral red. Cytological profiles showed abundant large endocytic channels and endosomes in the rounded apoptotic cells.Conclusion: Gross surface area reduction with evidence of distinctive endocytic activity including uptake of huge 2 million mol.wt dextran particles suggested large channel endocytic internalization as a causal factor in apoptotic rounding, in common with rounding in M-phase and interphase cells with pHi upshifting where concomitant surface area reduction and uptake of impermeant particles were similarly demonstrable. The reduction in size of the cell envelope, together with consequential concentration pressures, could account for the observed rise in cell density and shrinkage in cell size. As a symptom of continual pHi upshifting, apoptotic rounding appears to be a recovery-associated response rather than a direct consequence of the disruptive forces causing its death. © 1994 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
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  • 9
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The high-resolution (300 MHz) proton nmr spectrum of E. coli tRNAfMet has been examined in 0.17M NaCl, with and without Mg2+, and at various temperatures. In light of recent studies of other E. coli tRNA and fragments of tRNAfMet, some low field (11-15 ppm) resonances previously assigned to secondary structure base pairs are reassigned to a tertiary structure A14-S4U8 base pair and a protected uridine residue in the anticodon loop. These two resonances and other low field resonances which are assigned to secondary structure base pairs are used to monitor the thermal unfolding of the molecule. In the absence of Mg2+ the tertiary structure base pair is present only to ∼45°C, but in the presence of Mg2+ it remains until at least 70°C. Analysis of the temperature dependence of other low field resonances indicates that the melting of the dihydrouridine stem occurs more or less simultaneously with the loss of tertiary structure. The observation of the resonance from the A14-S4U8 base pair proves that tertiary structure is present in this molecule below 40°C, even in the absence of Mg2+.
    Additional Material: 5 Ill.
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