Specifity determinants for protein secretion in Bacillus subtilis.

In both prokaryotes and eukaryotes, a large number of proteins that are synthesised in cytoplasmic compartments, are transported across membranes in order to reach their final destination and fulfil their function. Because of the hydrophobic nature of membranes and the necessity to maintain their integrity, complex and strictly organised protein translocation machinery have evolved. ... Zie: Summary

High-salinity growth conditions promote tat-independent secretion of tat substrates in Bacillus subtilis

The Gram-positive bacterium Bacillus subtilis contains two Tat translocases, which can facilitate transport of folded proteins across the plasma membrane. Previous research has shown that Tat-dependent protein secretion in B. subtilis is a highly selective process and that heterologous proteins, such as the green fluorescent protein (GFP), are poor Tat substrates in this organism. Nevertheless, when expressed in Escherichia coli, both B. subtilis Tat translocases facilitated exclusively Tat-dependent export of folded GFP when the twin-arginine (RR) signal peptides of the E. coli AmiA, DmsA, or MdoD proteins were attached. Therefore, the present studies were aimed at determining whether the same RR signal peptide-GFP precursors would also be exported Tat dependently in B. subtilis. In addition, we investigated the secretion of GFP fused to the full-length YwbN protein, a strict Tat substrate in B. subtilis. Several investigated GFP fusion proteins were indeed secreted in B. subtilis, but this secretion was shown to be completely Tat independent. At high-salinity growth conditions, the Tat-independent secretion of GFP as directed by the RR signal peptides from the E. coli AmiA, DmsA, or MdoD proteins was significantly enhanced, and this effect was strongest in strains lacking the TatAy-TatCy translocase. This implies that high environmental salinity has a negative influence on the avoidance of Tat-independent secretion of AmiA-GFP, DmsA-GFP, and MdoD-GFP. We conclude that as-yet-unidentified control mechanisms reject the investigated GFP fusion proteins for translocation by the B. subtilis Tat machinery and, at the same time, set limits to their Tat-independent secretion, presumably via the Sec pathway

The influence of achievement before, during and after medical school on physician job satisfaction

In this longitudinal study, we investigated the relationship between physicians' prior achievements (before, during and after medical school) and job satisfaction, and tested the two lines of reasoning that prior achievements influence job satisfaction positively or negatively, respectively. The participants were graduates who started their medical training in 1982 (n = 147), 1983 (n = 154), 1992 (n = 143) and 1993 (n = 153). We operationalised job satisfaction as satisfaction (on a 10-point scale) with 13 cognitive, affective and instrumental aspects of the participants' jobs. The measures of achievement before, during and after medical school included pre-university grade point average, study progress and a residency position in the specialty of first choice, respectively. We included the effect of curriculum type (problem-based learning versus traditional), gender and years of experience as moderator variables. Higher achievers before and during medical school were more satisfied about their income (beta = .152, p &lt;.01 and beta = .149, p &lt;.05), but less satisfied with their opportunities for personal development (beta = -.159, p &lt;.05). High achievers after medical school were more satisfied with professional accomplishments (beta = .095, p &lt;.05), with appreciation from support personnel (beta = .154, p &lt;.01) and from patients (beta = .120, p &lt;.05). Effect sizes were small. Prior achievements influenced job satisfaction. The direction of the influences depended on the job satisfaction aspect in question, which indicates that it is important to distinguish between aspects of job satisfaction. To optimize job satisfaction of high achievers, it is important for graduates to obtain their preferred specialty. Furthermore, it is vital to provide them with enough opportunities for further development.</p

Cumulative effects assessment: proof of concept marine mammals

This development of the framework and approach for a Cumulative Effects Assessment (CEA) is based on a literature review. The literature identified some key challenges that need to be addressed for CEA to evolve into a consistent, appropriate tool to assist decision-making. These challenges included • A clear distinction of the receptor-led CEA from the dominating stressor-led Environmental Impact Assessment (EIA) approaches and • Enabling CEA to provide ecosystem-relevant information at an appropriate regional scale. Therefore this CEA is explicitly developed to be a receptor-led and fully integrated framework, i.e. involving multiple occurrences of multiple pressures (from single and/or different sources) on multiple receptors, as opposed to other existing approaches dealing with only a subset of those pressures or receptors, hence our use of the phrase iCEA for integrated CEA. As a proof of concept for this iCEA we selected one receptor, the ecosystem component marine mammals. The main conclusions of this exercise (see Chapter 6) are that the iCEA framework and approach presented in this study appear suitable to fulfil its main purpose and ultimately inform the policy process as described in the conception phase. However it should be acknowledged this is only the very first step in a process where through many iterations new information can be introduced and assessed (relative to existing information) based on the criteria provided resulting in an improved iCEA with increasing confidence levels. As more information becomes available the relative importance of impact chains and its corresponding information modules may change giving direction to new areas for research. For further development of this iCEA towards its intended applications we can distinguish between the first purpose, i.e. identification of the main impact chains contributing to the risk that a specific ecosystem component is impacted, which can be achieved with the approach presented here focussing on one specific ecosystem component and the second purpose, i.e. an evaluation of the performance of possible management strategies, which would require all ecosystem components to be included as would be required for ecosystem-based management. Thus to further the development and application of this iCEA towards its (two) purpose(s) the recommendation is to: • Include the available information presented in this report into the iCEA and develop the Bayesian Belief Network such that it can process this information and its associated confidence into an assessment that identifies the main impact chains for the marine mammals. • Extend the framework and approach to (all) the other ecosystem components so that a truly integrated CEA is possible. Note that this is likely to affect the identification of what should be considered the main pressures to guide management. • Improve the information modules that emerged from the evaluation as the most promising to increase the confidence in the outcome of the iCEA. Note that the previous two steps may result in a different prioritisation of the information modules as the importance of pressures and hence impact chains changes

The transcriptomic response to irinotecan in colon carcinoma bearing mice preconditioned by fasting

Background: Irinotecan use is limited due to severe toxicity. Preconditioning by fasting (PBF) protects against side effects of irinotecan while preserving its antitumor activity. The mechanisms underlying the effects of PBF still need to be elucidated. Here, we investigated the transcriptional responses of PBF on irinotecan in both tumor and healthy liver tissue. Experimental approach: Male BALB/c mice were subcutaneously injected with C26 colon carcinoma cells. Twelve days after tumor inoculation, two groups were fasted for three days and two groups were allowed food ad libitum (AL). Subsequently, both groups received one dose of irinotecan. Twelve hours after administration mice were sacrificed and blood, tumor and liver tissue were harvested. Blood samples were analyzed to determine liver, kidney and bone marrow function, tissues were used for transcriptome analyses. Key results: The AL irinotecan group showed worsened organ function and decreased leukocyte numbers. These effects were abated in PBF animals. PBF led to an altered transcriptional response in the liver of irinotecan-treated mice, including decreased cellular injury and increased stress resistance. Hepatic metabolism of irinotecan was also significantly changed due to PBF. The transcriptional response of tumor tissue observed after PBF was hardly affected compared to AL fed animals. Conclusions: Transcriptional changes after PBF to irinotecan treatment showed an improved protective stress response in healthy liver but not in tumor tissue, including changes in irinotecan metabolism. These data help to unravel the mechanisms underlying the effects of fasting on irinotecan and help to improve outcome of chemotherapeutic treatment in cancer patients