Suppressor cells prevent host resistance to tumor growth

The role of immunosuppressor cells in preventing host immune rejection of tumor cells is described. The growth of Lewis lung carcinoma (3LL) in syngeneic C57BL mice is accompanied by a weak and transient anti-tumor cytotoxic response that is later on replaced by tumor-enhancing activity. This enhancing activity is correlated with the generation of suppressor cells in 3LL-bearing mice. Such suppressors were demon strated in two ways: (a) Elimination of the hydrocortisone(HC)-sensitive lymphoid population from tumorbearing mice (TBM) resulted in a significant increase in the anti-tumor cytotoxic response and in a marked delay in tumor development. It is assumed that HC inactivates precursors of suppressor lymphocytes whereas the mature suppressor cells themselves are HC-resistant. (b) The increased resistance against the tumor could be partially re-suppressed by restoring the HC-treated TBM with spleen or thymus cells from normal C57BL. Suppression, however, was more pronounced if the resistant mice were restored with spleen or thymus cells from TBM. HC-resistant spleen cells from TBM that appear to be enriched for mature suppressor cells were capable of suppressing in vitro the secondary sensitization of spleen cells from TBM against tumor cells.     

Metabolism of the explosive hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) in a contaminated vadose zone

The aim of this study was to explore biodegradation potential of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) in a deep contaminated unsaturated zone over Israel's coastal aquifer. While anaerobic biodegradation potential was observed throughout the profile down to the water table at a depth of 45 m, aerobic biodegradation was limited to the surface of the unsaturated zone. Traces of nitroso-RDX intermediates were detected in the soil samples, indicating possible in situ activity. Polymerase chain reaction and denaturing gradient gel electrophoresis analysis revealed that the microbial population in the soil consisted of protobacteria, but no known RDX degraders were detected. However, a 16S rRNA gene sequence most similar to Sphingomonas sp. was detected at all depths. Biodegradation rates were faster in the surface (0 and 1m) versus deeper soil samples (22 and 45 m) and were not affected under anaerobic conditions by the presence of nitrate, indicating a concurrent reduction of both compounds. RDX half-life in the surface soil was mostly dependent on carbon content and to lesser extent on soil moisture. Biomineralization of RDX to CO(2) was confirmed by incubating surface soil with (14)C-labeled RDX. An aerobic RDX-degrading bacterium, identified as Gordonia sp., was isolated from the soil: it degraded RDX aerobically and produced 4-nitro-2,4-diazabutanal. This study, the first to explore RDX biodegradation in the deep vadoze zone, indicates biodegradation potential throughout the profile, which is likely to support natural attenuation.     

Quantifying RDX biodegradation in groundwater using δ15N isotope analysis

Isotope analysis was used to examine the extent of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) biodegradation in groundwater along a ca. 1.35-km contamination plume. Biodegradation was proposed as a natural attenuating remediation method for the contaminated aquifer. By isotope analysis of RDX, the extent of biodegradation was found to reach up to 99.5% of the initial mass at a distance of 1.15–1.35 km down gradient from the contamination sources. A range of first-order biodegradation rates was calculated based on the degradation extents, with average half-life values ranging between 4.4 and 12.8 years for RDX biodegradation in the upper 15 m of the aquifer, assuming purely aerobic biodegradation, and between 10.9 and 31.2 years, assuming purely anaerobic biodegradation. Based on the geochemical data, an aerobic biodegradation pathway was suggested as the dominant attenuation process at the site. The calculated biodegradation rate was correlated with depth, showing decreasing degradation rates in deeper groundwater layers. Exceptionally low first-order kinetic constants were found in a borehole penetrating the bottom of the aquifer, with half life ranging between 85.0 to 161.5 years, assuming purely aerobic biodegradation, and between 207.5 and 394.3 years, assuming purely anaerobic biodegradation.The study showed that stable isotope fractionation analysis is a suitable tool to detect biodegradation of RDX in the environment. Our findings clearly indicated that RDX is naturally biodegraded in the contaminated aquifer. To the best of our knowledge, this is the first reported use of RDX isotope analysis to quantify its biodegradation in contaminated aquifers.     

An evaluation of a bed instability index as an indicator of habitat quality in mountain streams of the northwestern United States

Managers of aquatic resources benefit from indices of habitat quality that are reproducible and easy to measure, demonstrate a link between habitat quality and biota health, and differ between human-impacted (i.e., managed) and reference (i.e., nonimpacted or minimally impacted) conditions. The instability index (ISI) is an easily measured index that describes the instability of a streambed by relating the tractive force of a stream at bankfull discharge to the median substrate size. Previous studies have linked ISI to biological condition but have been limited to comparisons of sites within a single stream or among a small number of streams. We tested ISI as an indicator of human impact to habitat and biota in mountain streams of the northwestern USA. Among 1428 sites in six northwestern states, ISI was correlated with other habitat measures (e.g., residual pool depth, percent fine sediment) and indices of biotic health (e.g., number of intolerant macroinvertebrate taxa, fine sediment biotic index) and differed between managed and reference sites across a range of stream types and ecoregions. While ISI could be useful in mountain streams throughout the world, this index may be of particular interest to aquatic resource managers in the northwestern USA where a large dataset, from which ISI can be calculated, exists.     

Age,work experience,and the psychological contract

The purpose of the current paper is to examine the ways in which age and work experience shape how individuals experience psychological contract breaches. We first introduce the concepts of contract malleability (the degree to which individuals can tolerate deviations from contract expectations) and contract replicability (the degree to which individuals believe that their psychological contracts can be replicated elsewhere). Next, we discuss the variety of reasons why contract malleability and replicability become greater with age and work experience and how contract malleability and replicability may temper negative reactions to psychological contract breaches. We also address the different ways contract malleability and replicability mediate the relationships between age and work experience, on one hand, and exit, voice, loyalty, and neglect behaviors on the other. We consider the moderating effects of age similarity and dissimilarity here as well. The paper concludes with a discussion of the implications for future research designs and for managing older and more experienced workers. Copyright © 2009 John Wiley & Sons, Ltd.     

Age and innovation‐related behavior: The joint moderating effects of supervisor undermining and proactive personality

Previous research has yielded mixed results regarding the effects of age on innovation‐related behavior (IRB; i.e., generating, disseminating, and implementing new ideas). This paper hypothesizes that the relationship of age with IRB is jointly moderated by undermining behavior on the part of the supervisor and the extent to which the employee possesses a proactive personality. We collected data from 196 employees at three points in time over a one‐year period. Results supported the hypothesized 3‐way interaction of age, supervisor undermining, and proactive personality on IRB. As predicted, highly proactive older workers responded to high supervisor undermining with more IRB, whereas older workers low on proactive personality responded to high supervisor undermining with less IRB. On the other hand, when supervisor undermining was low, proactive personality did not moderate the relationship of age with IRB. Copyright © 2012 John Wiley & Sons, Ltd.     

Within-tree life process models of the southern pine beetle, dendroctonus frontalis

This paper develops models of gallery construction, emergence and re-emergence for use in a general population dynamics model of the southern pine beetle, Dendroctonuc frontalis Zimmermann. Models of these processes were originally developed from laboratory data, and are extended here to account for fluctuating temperatures and variable attack densities under field conditions. The resulting models were tested using data from three natural populations (infestations) from east Texas. These tests reveal that the laboratory-derived models closely predict the timing and length of gallery, and the timing of emergence and re-emergence in the field.