Salmonella entry into mammalian cells: different yet converging signal transduction pathways?

Salmonella bacteria have evolved means to subvert host cell signal transduction pathways to induce their uptake. Recently, progress has been made towards defining those pathways. Although it is clear that Salmonella evoke different signalling pathways in different cell lines, it is possible that these responses may be triggered by a common mechanism and that the diverse pathways may converge downstream in common effector molecules.     

Beta-arrestins as regulators of signal termination and transduction: how do they determine what to scaffold?

Over the last decade β-arrestins have emerged as pleiotropic scaffold proteins, capable of mediating numerous diverse responses to multiple agonists. Most well characterized are the G-protein-coupled receptor (GPCR) stimulated β-arrestin signals, which are sometimes synergistic with, and sometimes independent of, heterotrimeric G-protein signals. β-arrestin signaling involves the recruitment of downstream signaling moieties to β-arrestins; in many cases specific sites of interaction between β-arrestins and the downstream target have been identified. As more information unfolds about the nature of β-arrestin scaffolding interactions, it is evident that these proteins are capable of adopting multiple conformations which in turn reveal a specific set of interacting domains. Recruitment of β-arrestin to a specific GPCR can promote formation of a specific subset of available β-arrestin scaffolds, allowing for a higher level of specificity to given agonists. This review discusses recent advances in β-arrestin signaling, discussing the molecular details of a subset of known β-arrestin scaffolds and the significance of specific binding interactions on the ultimate cellular response.     

Post-translational modifications mediated by reactive nitrogen species: Nitrosative stress responses or components of signal transduction pathways?

In animal cells, nitric oxide and NO-derived molecules have been shown to mediate post-translational modifications such as S-nitrosylation and protein tyrosine nitration which are associated with cell signalling and pathological processes, respectively. In plant cells, knowledge of the function of these post-translational modifications under physiological and stress conditions is still very rudimentary. In this addendum, we briefly examine how reactive nitrogen species (RNS) can exert important effects on proteins that could mediate signalling processes in plants.Key words: nitrosative stress, nitric oxide synthase, S-nitrosoglutathione, nitro-tyrosine, post-translational modifications, S-nitrosylation     

Under what conditions signal transduction pathways are highly flexible in response to external forcing? A case study on calcium oscillations

Sensitivity and flexibility are typical properties of biological systems. These properties are here investigated in a model for simple and complex intracellular calcium oscillations. In particular, the influence of external periodic forcing is studied. The main point of the study is to compare responses of the system in a chaotic regime with those obtained in a regular periodic regime. We show that the response to external signals in terms of the range of synchronization is not significantly different in regular and chaotic Ca2+ oscillations. However, both types of oscillation are highly flexible in regimes with weak dissipation. Therefore, we conclude that dissipation of free energy is a suitable index characterizing flexibility. For biological systems this appears to be of special importance since for thermodynamic reasons, notably in view of low free energy consumption, dissipation should be minimized.     

Signal processing and transduction in plant cells: the end of the beginning?

Plants have a very different lifestyle to animals, and one might expect that unique molecules and processes would underpin plant-cell signal transduction. But, with a few notable exceptions, the list is remarkably familiar and could have been constructed from animal studies. Wherein, then, does lifestyle specificity emerge?     

Plants versus animals: do they deal with stress in different ways?

Both plants and animals respond to stress by using adaptationsthat help them evade, tolerate, or recover from stress. In asynthetic paper A. D. Bradshaw (1972) noted that basic biologicaldifferences between plants and animals will have diverse evolutionaryconsequences, including those influencing how they deal withstress. For instance, Bradshaw argued that animals, becausethey have relatively well-developed sensory and locomotor capacities,can often use behavior and movement to evade or ameliorate environmentalstresses. In contrast, he predicted that plants will have toemphasize increased physiological tolerance or phenotypic plasticity,and also that plants should suffer stronger selection and showmore marked differentiation along environmental gradients. Herewe briefly review the importance of behavior in mitigating stress,the behavioral capacities of animals and plants, and examplesof plant responses that are functionally similar to behaviorsof animals. Next, we try to test some of Bradshaw's predictions.Unfortunately, critical data often proved non-comparable: plantand animal biologists often study different stressors (e.g.,water versus heat) and measure different traits (photosynthesisversus locomotion). Nevertheless, we were able to test someof Bradshaw's predictions and some related ones of our own.As Bradshaw predicted, the phenology of plants is more responsiveto climate shifts than is that of animals and the micro-distributionsof non-mobile, intertidal invertebrates ("plant" equivalents)are more sensitive to temperature than are those of mobile invertebrates.However, mortality selection is actually weaker for plants thanfor animals. We hope that our review not only redraws attentionto some fascinating issues Bradshaw raised, but also encouragesadditional tests of his predictions. Such tests should be informative.     

Seasonal changes in blue tit crown color: do they signal individual quality?

Plumage coloration is generally perceived as a static traitand therefore not a good indicator of current condition. However,changing of feather colors after molt does occur and may haveimportant implications for signal function and sexual selection.We studied longitudinal changes in blue tit (Parus caeruleus)crown ultraviolet (UV)/blue color, a sexually selected trait,by repeatedly measuring the same individuals between early winterand late spring. Whereas crown UV reflectance (UV chroma andhue) decreased dramatically over time, brightness and saturationdid not show consistent patterns of change. The magnitude ofthe decline in coloration exceeded sexual and age dichromatismin hue and UV chroma, respectively. Hence, seasonal color changescould have strong effects on blue tit sexual signaling. Between-individualvariation in the decline in UV coloration was large and relatedto attributes of male, but not female, quality, such as sizeand condition. Thus, conspecifics could potentially gain informationabout male phenotypic quality by assessing color change overthe year. However, the degree of decline in male UV color didnot affect breeding success because neither the number of within-pairnor the number of extrapair offspring produced correlated withchanges in crown color. Seasonal changes in the expression ofplumage coloration are probably widespread, and maintainingplumage coloration could thus constitute an additional honesty-enforcingmechanism after molt is completed.     

Social stress models in depression research: what do they tell us?

Interest has recently surged in the use of social stress models, especially social defeat. Such interest lies both in the recognition that stressors of social origin play a major role in human psychopathologies and in the acknowledgement that natural and hence ethologically-based stress models have important translational value. The use of the most recent technology has allowed the recognition of the mechanisms through which social defeat might have enduring psychoneuroendocrine effects, especially social avoidance and anhedonia, two behaviours relevant to human depression. In view of the sensitivity of these behavioural outcomes to repeated antidepressant treatments, the social defeat model has been proposed as a possible animal model of depression. The present survey is aimed at examining the limits of such an interpretation and focuses on methodological aspects and on the relevance of social defeat to the study of anxiety-related pathologies.     

The effects of mowing and fertilization on carbohydrate reserves and regrowth of grasses: do they promote plant coexistence in species-rich meadows?

After the cessation of regular management and after fertilization a single clonal species tends to dominate in many types of grasslands, whereas in regularly managed meadows these potential dominants usually attain a low cover. It has been hypothesized that plants reaching a high dominance in abandoned and fertilized meadows are selectively suppressed by mowing so that a balanced competition is maintained and competitive exclusion is postponed. We compared regeneration capacity and carbohydrate reserves accumulated by three species of clonal grasses, which markedly increase their dominance in irregularly mown, un-mown or fertilized meadows. Above-ground biomass and the amount of storage carbohydrates of the two largest species, (Molinia arundinacea, Calamagrostis epigejos) were reduced in a mown meadow. This effect was weaker in Bromus erectus, which produces smaller shoots. Shoots of Molinia were most impacted by mowing but their regeneration was efficient due to the large carbohydrate reserves in the shoot bases. Fertilization did not affect Bromus and Calamagrostis. In contrast, fertilized plants of Molinia produced larger storage organs and accumulated more carbohydrates. We conclude that plant size and growth form are important features promoting the ability of potential dominants to tolerate mowing and regenerate after it. Our results confirm that taller plants are selectively suppressed by this type of disturbance, thereby potentially promoting plant coexistence.     

Are there protective enzymatic pathways to regulate high local nitric oxide (NO) concentrations in cells under stress conditions?

This paper examines, from a chemical perspective, the hypothesis of the existence of protective enzymes whose role would be to regulate the high local nitric oxide (NO) concentrations that are released in NO-generating cells in situations of response to oxidative stress. These enzymes should play the role, with respect to NO, either of a reductase or of a dismutase. The energetics of the intervening transformations is herein presented, along with a review of pertinent literature. An attempt is made in order to describe the physiognomy of such enzymes, in relation with the literature data. Experimental investigation is needed to further evaluate the validity of such a hypothesis.     

Gluttony and sex in female ixodid ticks: how do they compare to other blood-sucking arthropods?

The central issue dealt with here is the role of copulation in the control of feeding behaviour in ticks and some haematophagous insects. Female ticks of the family Ixodidae normally engorge to approximately 100 x their unfed body weight, and then drop from the host, produce and lay eggs, and die. Virgins, on the other hand, normally do not exceed 5-40% (depending on species) of the normal engorged body weight. But instead of detaching voluntarily at that point most virgins remain fixed to the host for extended periods, waiting for males to find them so they can complete engorgement. Virgin haematophagous insects, and virgin ticks of the family Argasidae display little, if any, reduction in blood meal size compared to mated females, at least not during the first ovarian cycle. During subsequent ovarian cycles, meal size in some virgin insects may be somewhat reduced depending on how many eggs are retained in the reproductive tract, but the reduction is not nearly to the same extent as that observed for virgin ixodid females. The stimulatory effect of copulation on engorgement in the latter is caused by a pair of proteins (voraxin alpha and beta) produced in the testis and transferred to the female with the spermatophore. Here, I propose why it might be adaptive for an ixodid female to remain small until mated. The hypothesis is suggested from the facts that ixodid ticks remain attached to the host for days (rather than minutes), and that virgin ticks, above a certain critical weight, lose all opportunity for producing viable offspring should they be groomed off the host prematurely, or should the host die while ticks are still attached.     

A content analysis of dissemination and implementation science resource initiatives: what types of resources do they offer to advance the field?

Background

The recent growth in organized efforts to advance dissemination and implementation (D & I) science suggests a rapidly expanding community focused on the adoption and sustainment of evidence-based practices (EBPs). Although promising for the D & I of EBPs, the proliferation of initiatives is difficult for any one individual to navigate and summarize. Such proliferation may also result in redundant efforts or missed opportunities for participation and advancement. A review of existing D & I science resource initiatives and their unique merits would be a significant step for the field. The present study aimed to describe the global landscape of these organized efforts to advance D & I science.

Methods

We conducted a content analysis between October 2015 and March 2016 to examine resources and characteristics of D & I science resource initiatives using public, web-based information. Included resource initiatives must have engaged in multiple efforts to advance D & I science beyond conferences, offered D & I science resources, and provided content in English. The sampling method included an Internet search using D & I terms and inquiry among internationally representative D & I science experts. Using a coding scheme based on a priori and grounded approaches, two authors consensus coded website information including interactive and non-interactive resources and information regarding accessibility (membership, cost, competitive application, and location).

Results

The vast majority (83%) of resource initiatives offered at least one of seven interactive resources (consultation/technical assistance, mentorship, workshops, workgroups, networking, conferences, and social media) and one of six non-interactive resources (resource library, news and updates from the field, archived talks or slides, links pages, grant writing resources, and funding opportunities). Non-interactive resources were most common, with some appearing frequently across resource initiatives (e.g., news and updates from the field).

Conclusion

Findings generated by this study offer insight into what types of D & I science resources exist and what new resources may have the greatest potential to make a unique and needed contribution to the field. Additional interactive resources may benefit the field, particularly mentorship opportunities and resources that can be accessed virtually. Moving forward, it may be useful to consider strategic attention to the core tenets of D & I science put forth by Glasgow and colleagues to most efficiently and effectively advance the field.