One of the universal characteristics of the long bones and spines of middle-age and older mammals is a loss in bone mass (osteopenia). In humans, if this bone loss is severe enough, it results in osteoporosis, a skeletal disorder characterized by a markedly increased incidence of fractures with sequelae that may include pain, loss of mobility, and in the event of hip fracture, even death within a relatively few months of injury. An important contributing factor to the development of osteoporosis appears to be a diminution in the number and activity of osteoblasts responsible for synthesizing new bone matrix. The findings in the present and other similar studies suggest that this reduction in osteoblast number and activity is due to an age-related diminution in the size and osteogenic potential of the bone marrow osteoblast progenitor cell (OPC or CFU-f) compartment. We previously postulated that these regressive changes in the OPC/CFU-f compartment occurred in old animals because of a reduction in the amount and/or activity of TGF-beta1, an autocrine growth factor important in the promotion of OPC/CFU-f proliferation and differentiation. In support of this hypothesis, we now report that (1) the osteogenic capacity of the bone marrow of 24-month-old BALB/c mice, as assessed in vivo, is markedly reduced relative to that of 3-4-month-old animals, (2) that the matrix of the long bones of old mice contains significantly less TGF-beta than that of young mice, (3) that OPC's/CFU-f's isolated from old mice produce less TGF-beta in vitro than those recovered from young mice, and (4) that OPC's/CFU-f's from old mice express significantly more TGF-beta receptor (Types I, II, and III) than those of young animals and that such cells are more responsive in vitro to exogenous recombinant TGF-beta1. We also find that colony number and proliferative activity of OPC's/CFU-f's of young mice and old mice, respectively, are significantly reduced when incubated in the presence of neutralizing TGF-beta1 antibody. Collectively, these data are consistent with the hypothesis that in old male mice the reduction in the synthesis and, perhaps, availability from the bone matrix of TGF-beta1 contributes to a diminution in the size and development potential of the bone marrow osteoprogenitor pool.
Details of the characterization and motivation of Richard III in William Shakespeare's 'The Tragedy of King Richard the Third' can be used to show one way to explore specifics of connection between the rhetoric of literary texts and philosophical response patterns. Subtleties of Shakespearian rhetoric do not lend themselves to simple connection to a conceptual position. Shakespeare deals with willfully choosing villainy.
A Huckel-type effective Hamiltonian is used to examine the conditions for site-selected reactivity. The example is the dissociation of a positive ion, as in mass spectrometry. Coupling to the dissociative channels is included by a rate operator. We examine the time evolution of the charge and bond order matrices and of the yield of fragments following a localized initial ionization. Dissociation is found to follow the (positive) charge. Variations in the local properties can markedly change the dissociation pattern. A more statistical limit is reached when the migration of charge is unimpeded. (C) 1998 Elsevier Science B.V.
A novel chemiluminescence immunoassay which combines microparticles and microemulsion is described. The method is based on a specific interaction of an antibody with an antigen preadsorbed onto fluorescer (perylene) microparticles (mean diam. 0.8-1.6 μm). Dissolving the particles in a microemulsion-forming mixt. contg. bis(2,4,6-trichlorophenyl) oxalate in toluene (oil phase) and H2O2 in Triton X-100 (surfactant)/2-butanol (cosurfactant)/water leads to chemiluminescence. The dependence of the chemiluminescence intensity on the concns. of antigen, antibody and fluorescer, as well as the kinetics of the chemiluminescence decay, were studied. [on SciFinder(R)]
{{Measurements of the collisional energy transfer of size and energy-selected ammonia cluster ions (NH3)(n)H+
AN Kluger. 1998. “Commute variability and strain.” Journal of Organizational BehaviorJournal of Organizational BehaviorJournal of Organizational Behavior, 19, Pp. 147-165. Abstract
The commute impedance model (e.g. Stokols, Novaco, Stokols and Campbell, 1978) is evaluated through a literature review and a survey of commuters who drive to work (N = 418). A new construct for the study of commuting-commute variability-is introduced and tested in the framework of the survey. Findings from the literature review indicated (a) partial support for the first proposition of the impedance model namely, that impedance-measured as commute distance or time-causes strain (e.g. employee health deficits), but (b) no support for the second proposition of the model namely, that the impedance-strain is moderated by control or the availability of choice. Similarly, the survey showed that (a) commute length (impedance) is consistently correlated with strain, (b) choice is weakly and negatively related to strain, but (c) there is no interactive relationship of choice and length with strain. Furthermore, the results suggest that (a) commute variability is the strongest correlate of commute strain, and that (b) once commute variability is partialled out, most of the partial correlations between impedance and strain are not significant. The paper concludes with an alternative commuting-strain model which includes the new commute-variability construct. (C) 1998 John Wiley & Sons, Ltd.
AN Kluger. 1998. “Commute variability and strain.” Journal of Organizational BehaviorJournal of Organizational Behavior, 19, Pp. 147-165.
The complementarities between tourism and gambling at the local level are examined empirically from two rather different gambling environments (Indiana, USA and Eilat, Israel) in order to show how gambling acts as an import substitution activity and impacts on existing demand. In both contexts, the sources of demand for gambling, the extent to which these are 'tourist' sources and the question of gambling-generated demand displacing existing tourist demand, are examined. Despite the rather different market and political contexts in Indiana and Israel, the findings on the gambling-tourism relationship and the effect of gambling on local economies, are remarkably consistent. In both cases, gambling is seen to be grounded in import-substitution rather than pure 'export' activity. Additionally, in both cases there is evidence that the introduction of gambling displaces tourist demand. The policy implications of these findings point to the need to differentiate between local and national impacts of gambling and between the local fiscal and local economic development impacts.
Fe redox chem. was studied in Lake Kinneret (Sea of Galilee), a mesotrophic, monomictic lake in the central part of the Jordan Rift Valley, Israel. Fe2+ and total Fe concns. in the epilimnion and hypolimnion were measured; relationships between Fe2+ and other parameters (e.g., light, pH) were examd. In addn., lab. expts. were conducted where filtered (biota-free) Lake Kinneret water, sterile unfiltered Lake Kinneret water, and distd. water were spiked with various Fe3+ and Fe2+ concns. Fe3+ and Fe2+ concns. were measured as a function of time in water samples under a variety of pH, O2, and radiation conditions. Fe2+ concns. in the epilimnion were below detection limits (0.04 μM) during nighttime, whereas in daytime, Fe2+ concns. were always above detection limits and changed significantly throughout the year (0.05-0.15 μM). Fe2+:Fe(tot) ratios measured in the lake (3-99%) were higher than expected values for a high pH (pH ∼8), low ionic strength (∼10 mM) aquatic system. In addn. to photo-induced redn. of Fe3+, there was strong evidence that Fe2+ is stabilized in O2-satd. lake water, since Fe2+ concns. were detected at a depth of 10 m, where <10% of light penetrates. Results of oxidn. and photoredn. expts. suggested obsd. rates of Fe redox reactions in sterile lake water were consistent with known chem. (abiotic) rates, but that these rates cannot account for obsd. Fe2+ concns. in epilimnetic water. Therefore, it was proposed that the photo-induced Fe redox cycle in the epilimnion of Lake Kinneret is largely controlled by biol. activity and that abiotic photoredn. of Fe accounts for only a small fraction of Fe2+ in the epilimnion. [on SciFinder(R)]
Translational to electronic energy transfer with or without a concomitant chemical reaction is studied for the Evans-Polanyi model. We explore the possibility of light emission from an electronically excited stare following a high-energy collision. This can be viewed as an inverse process to a Woodward-Hoffmann photochemically allowed four-center reaction. The collision is described using this Evans-Polanyi method where the two diabatic electronic states correlate with the states of the reactants and products. The effective coupling of the diabatic starts is found to be localized and the non-adiabatic regime is transversed rapidly so that facile electronic excitation is possible. (C) 1998 Elsevier Science B.V.
Surface active gelatins were formed by covalent attachment of hydrophobic groups to gelatin mols. by reacting N-hydroxysuccinimide esters of various fatty acids (C4-C16) with the lysine groups. The surface activity was evaluated by emulsification and foaming properties, and by adsorption at the oil-H2O interface. In general, the modified gelatins are more surface active than the native gelatin. The increase in hydrophobic chain length and the no. of attached alkyl chains per gelatin mol. decreases the emulsion droplet's size and to more stable emulsions. Adsorption isotherms, at the o/w interface, show much higher surface concn., at satn., of the modified gelatin than the native gelatin. The modified gelatins also have high foaming ability and a high foam stability, while the maximal foam activity was obtained by the C8 modified gelatin. The foaming properties of the surface-active gelatins were also compared to that of Na dodecyl sulfate (SDS) and below the CMC of SDS, both foam activity and stability were higher for the modified gelatins. However, above the CMC the foam activity of SDS was higher, but the foam stability was lower than for C8-C16-modified gelatins. [on SciFinder(R)]
