1,25(OH)2D3-mediated phosphate uptake in isolated chick intestinal cells: effect of 24,25(OH)2D3, signal transduction activators,and age

Previous studies have demonstrated that both mechanical perturbation and cell adhesion induced the expression of osteopontin (opn) by osteoblasts (Carvalho et al. [1998] J. Cell. Biochem. 70:376-390). The present study examined if these same stimuli on osteoblasts would induce the expression of other integrin binding proteins, specifically fibronectin (fn) and bone sialoprotein (bsp). All three genes showed three- to four-fold maximal induction in response to both cell adhesion and a single 2-h period of an applied spatially uniform, dynamic biaxial strain of 1.3% at 0.25 Hz. Each gene, however, responded with a different time course of induction to mechanical strain, with bsp, fn, and opn showing their maximal response at 1, 3, and 9 h, respectively, after the perturbation period. In contrast, peak induction to cell adhesion was observed at 24 h for bsp and opn, while fn levels peaked at 8 h. Interestingly, while both opn and fn mRNA expression returned to base line after cell adhesion, bsp mRNA levels remained elevated. Examination of collagen type I and osteocalcin mRNAs showed unaltered levels of expression in response to either type of perturbation. A common feature of the signal transduction pathways, which mediate the gene expression in response to both cell adhesion and mechanical perturbation, was the activation of specific tyrosine kinases based on the ablation of the induction of these genes by the tyrosine kinase inhibitor genistein. While cycloheximide blocked the induction of all three mRNAs in response cell adhesion, it failed to block the induction of any of these genes in response to mechanical perturbation. Such results suggest that the induction of these genes after mechanical perturbation was mediated by an immediate response to signal transduction, while cell adhesion mediated effects secondary to signal transduction. Depolymerization of microfilaments with cytochalasin D had no effect on the overall expression of any of these genes in response to cell adhesion and only blocked the induction of opn expression in response to mechanical perturbation. These results suggest that cytoskeletal integrity is only selectively important in the signal transduction of certain types of stimuli and for the regulation of certain genes. In summary, both mechanical perturbation and cell adhesion stimulated the expression of integrin binding proteins. Furthermore, while there are common features in the signal transduction processes that mediate the induction of these genes in response to both stimuli, specific genes are separately regulated by precise mechanisms that are unique to both forms of stimuli.     

Are ecosystems hormetic?

The phenomenon of hormesis has been observed mainly for the response of individual organisms to stress. A reasonable line of inquiry might explore the possibility of observing hormesis at other levels of ecological organization. This initial examination focuses on ecosystem hormesis. Explorations of hormetic responses of ecosystems to stress cannot be made independently of a fundamental concept of ecosystem. The scale‐dependence of ecosystem dynamics also influences whether an ecological disturbance is in reality a stressor. Ecosystem hormesis might be claimed if one or more components of an ecosystem exhibit hormesis. By this definition, ecosystem hormesis would be a trivial extension of hormesis observed for individual organisms. A non‐trivial extension of ecosystem hormesis would include the observation that integrated (i.e., holistic) measures of ecosystem structure or function displayed an hormetic response to an ecological stressor. Several such examples of ecosystem structural and functional hormesis are presented.     

Ethanol's influence on the stimulus level required to evoke an orienting response in goldfish

In goldfish the heart rate orienting response to periodic photic stimuli was measured by a specially designed computer that also regulated the intensity of the stimuli to maintain the response. When ethanol was administered, the fish then exhibited orienting responses to less intense stimuli; this increased excitability was maintained for the duration of all tests (i.e., a maximum of 26 hours). There also seemed to be a residual increase of excitability lasting as long as 7 days after the ethanol was administered.     

Extended Kalman Filter for Estimation of Parameters in Nonlinear State-Space Models of Biochemical Networks

It is system dynamics that determines the function of cells, tissues and organisms. To develop mathematical models and estimate their parameters are an essential issue for studying dynamic behaviors of biological systems which include metabolic networks, genetic regulatory networks and signal transduction pathways, under perturbation of external stimuli. In general, biological dynamic systems are partially observed. Therefore, a natural way to model dynamic biological systems is to employ nonlinear state-space equations. Although statistical methods for parameter estimation of linear models in biological dynamic systems have been developed intensively in the recent years, the estimation of both states and parameters of nonlinear dynamic systems remains a challenging task. In this report, we apply extended Kalman Filter (EKF) to the estimation of both states and parameters of nonlinear state-space models. To evaluate the performance of the EKF for parameter estimation, we apply the EKF to a simulation dataset and two real datasets: JAK-STAT signal transduction pathway and Ras/Raf/MEK/ERK signaling transduction pathways datasets. The preliminary results show that EKF can accurately estimate the parameters and predict states in nonlinear state-space equations for modeling dynamic biochemical networks.     

Oxylipins and plant abiotic stress resistance

Oxylipins are signaling molecules formed enzymatically or spontaneously from unsaturated fatty acids in all aerobic organisms. Oxylipins regulate growth, development, and responses to environmental stimuli of organisms. The oxylipin biosynthesis pathway in plants includes a few parallel branches named after first enzyme of the corresponding branch as allene oxide synthase, hydroperoxide lyase, divinyl ether synthase, peroxygenase, epoxy alcohol synthase, and others in which various biologically active metabolites are produced. Oxylipins can be formed non-enzymatically as a result of oxygenation of fatty acids by free radicals and reactive oxygen species. Spontaneously formed oxylipins are called phytoprostanes. The role of oxylipins in biotic stress responses has been described in many published works. The role of oxylipins in plant adaptation to abiotic stress conditions is less studied; there is also obvious lack of available data compilation and analysis in this area of research. In this work we analyze data on oxylipins functions in plant adaptation to abiotic stress conditions, such as wounding, suboptimal light and temperature, dehydration and osmotic stress, and effects of ozone and heavy metals. Modern research articles elucidating the molecular mechanisms of oxylipins action by the methods of biochemistry, molecular biology, and genetics are reviewed here. Data on the role of oxylipins in stress signal transduction, stress-inducible gene expression regulation, and interaction of these metabolites with other signal transduction pathways in cells are described. In this review the general oxylipin-mediated mechanisms that help plants to adjust to a broad spectrum of stress factors are considered, followed by analysis of more specific responses regulated by oxylipins only under certain stress conditions. New approaches to improvement of plant resistance to abiotic stresses based on the induction of oxylipin-mediated processes are discussed.     

Forward conditioning with wheel running causes place aversion in rats

Backward pairings of a distinctive chamber as a conditioned stimulus and wheel running as an unconditioned stimulus (i.e., running-then-chamber) can produce a conditioned place preference in rats. The present study explored whether a forward conditioning procedure with these stimuli (i.e., chamber-then-running) would yield place preference or aversion. Confinement of a rat in one of two distinctive chambers was followed by a 20- or 60-min running opportunity, but confinement in the other was not. After four repetitions of this treatment (i.e., differential conditioning), a choice preference test was given in which the rat had free access to both chambers. This choice test showed that the rats given 60-min running opportunities spent less time in the running-paired chamber than in the unpaired chamber. Namely, a 60-min running opportunity after confinement in a distinctive chamber caused conditioned aversion to that chamber after four paired trials. This result was discussed with regard to the opponent-process theory of motivation.     

A comparison of responses and stimuli as time markers

A rat's behavior, as well as a stimulus, may be a time marker. But do they lead to similar performance? Eight rats were trained on a 20-s DRL procedure in which head-entry responses were time markers, i.e., each head-entry response indicated that food would not be delivered for 20 s. Concurrently, eight rats were trained on a control procedure in which light stimuli, yoked to the responses of a rat in the DRL procedure, were time markers, i.e., each light stimulus indicated that food would not be delivered for 20 s. A comparison of performance between the two groups showed a lower response rate in the DRL procedure than in the yoked control procedure. However, similar response patterns between the two groups were observed, suggesting that rats anticipated the food similarly with a stimulus or a response as the time marker.     

Not As Good as You Think? Trait Positive Emotion Is Associated with Increased Self-Reported Empathy but Decreased Empathic Performance

How is positive emotion associated with our ability to empathize with others? Extant research provides support for two competing predictions about this question. An empathy amplification hypothesis suggests positive emotion would be associated with greater empathy, as it often enhances other prosocial processes. A contrasting empathy attenuation hypothesis suggests positive emotion would be associated with lower empathy, because positive emotion promotes self-focused or antisocial behaviors. The present investigation tested these competing perspectives by examining associations between dispositional positive emotion and both subjective (i.e., self-report) and objective (i.e., task performance) measures of empathy. Findings revealed that although trait positive emotion was associated with increased subjective beliefs about empathic tendencies, it was associated with both increases and decreases in task-based empathic performance depending on the target’s emotional state. More specifically, trait positive emotion was linked to lower overall empathic accuracy toward a high-intensity negative target, but also a higher sensitivity to emotion upshifts (i.e., shifts in emotion from negative to positive) toward positive targets. This suggests that trait positive affect may be associated with decreased objective empathy in the context of mood incongruent (i.e., negative) emotional stimuli, but may increase some aspects of empathic performance in the context of mood congruent (i.e., positive) stimuli. Taken together, these findings suggest that trait positive emotion engenders a compelling subjective-objective gap regarding its association with empathy, in being related to a heightened perception of empathic tendencies, despite being linked to mixed abilities in regards to empathic performance. (Word count: 242).     

Differential neural activation for updating rule versus stimulus information in working memory

Establishing what information is actively maintained in working memory (WM) and how it is represented and controlled is essential to understanding how such information guides future behavior. WM has traditionally been investigated in terms of the maintenance of stimulus-specific information, such as locations or words. More recently, investigators have emphasized the importance of rules that establish relationships between those stimuli and the pending response. The current study used a mental arithmetic task with fMRI to test whether updating of numbers (i.e., stimuli) and updating of mathematical operations (i.e., rules) in WM relies on the same neural system. Results indicate that, while a common network is activated by both types of updating, rule updating preferentially activates prefrontal cortex while number updating preferentially activates parietal cortex. The results suggest that both numbers and rules are maintained in WM but that they are different types of information that are controlled independently.     

Cereal host interactions with Russian wheat aphid: A review

Abstract

A lack of understanding the interaction between the Russian wheat aphid (RWA) and its host plant is a limitation in developing effective strategies for controlling the aphid. It is generally assumed that the interaction between aphid and plant is similar to that between plant and pathogen; that is, an elicitor from the insect is recognized by a protein from the host plant and a cascade of signal transduction events follows. However, evidence suggests that RWA feeding is eliciting both the SA- and JA/ethylene-dependent signaling pathways by mimicking aspects of both pathogen and herbivorous insect attacks. Results further suggest that phenotypic symptoms after RWA feeding are under regulation via two independent reactions, namely an immediate response (i.e., leaf rolling) and a downstream event (i.e., chlorosis). These defense responses enable a resistant host plant to defend itself and overcome the stress response, while their susceptible counterparts die. The processes involved in the onset of the defense response are discussed, and mechanisms enabling resistant plants to overcome the stress associated with the feeding process are presented as a working model for RWA-cereal host interaction. Knowledge of genes involved in wheat's defense responses against the RWA and an understanding of their functions may provide additional strategies for developing broad-spectrum resistance in plants.     

Bioinspirations: cell-inspired small-scale systems for enabling studies in experimental biomechanics

Biomechanical forces govern the behaviors of organisms and their environment and examining these behaviors to understand the underlying phenomena is an important challenge. One experimental approach for probing these interactions between organisms and their biomechanical environment uses biologically-inspired, artificial surrogates that reproduce organic mechanical systems. For the case of complex, multicellular organisms, robot surrogates have been particularly effective, such as in the analysis of the fins of fish and insects' wings. This biologically-inspired approach is also exciting when examining cell-scale responses as multicellular organisms' behavior is directly influenced by the integrated interactions of smaller-scale components (i.e., cells). In this review, we introduce the burgeoning field of engineering of artificial cells, which focuses on developing cell-scale entities replicating cellular behaviors. We describe both a bottom-up approach to constructing artificial cells, using molecular components to directly assemble artificial cells, as well as a top-down approach, in which living cells are encapsulated in a single entity whose behavior is determined by its constituent members. In particular, we discuss the potential role of these artificial cells as implantable controllers, designed to alter the mechanical behavior of a host organism. Eventually, artificial cells designed to function as small-scale controllers may help alter organisms' phenotypes.     

Response properties of thick myelinated group II afferents in the medial articular nerve of normal and inflamed knee joints of the cat.

This study investigated the responses to innocuous and noxious mechanical stimuli of joint mechanoreceptors with thick myelinated articular afferents (conduction velocities 21-65 m/sec) in the medial articular nerve of the cat's knee. In nine experiments, we examined whether acute arthritis would modify the discharge properties. The vast majority of the group II afferents were excited by gentle local stimuli and by movements in the working range of the knee. Although they encoded pressure and particular movement stimuli up to the noxious range, their responses were more closely related to the particular type of stimulus (e.g., a movement in a specific direction) than to its intensity (innocuous vs. noxious). In inflamed joints, the response patterns of group II units were similar with regard to local mechanical thresholds, thresholds for passive movements, and patterns of responses to passive movements. In both situations, most units had no resting activity. These results suggest that articular group II afferents do not play a significant role in nociception. Rather, they subserve proprioceptive functions such as deep pressure sensation and kinesthesia in normal as well as inflamed joints.     

Priming and memory of stress responses in organisms lacking a nervous system

Experience and memory of environmental stimuli that indicate future stress can prepare (prime) organismic stress responses even in species lacking a nervous system. The process through which such organisms prepare their phenotype for an improved response to future stress has been termed ‘priming’. However, other terms are also used for this phenomenon, especially when considering priming in different types of organisms and when referring to different stressors. Here we propose a conceptual framework for priming of stress responses in bacteria, fungi and plants which allows comparison of priming with other terms, e.g. adaptation, acclimation, induction, acquired resistance and cross protection. We address spatial and temporal aspects of priming and highlight current knowledge about the mechanisms necessary for information storage which range from epigenetic marks to the accumulation of (dormant) signalling molecules. Furthermore, we outline possible patterns of primed stress responses. Finally, we link the ability of organisms to become primed for stress responses (their ‘primability’) with evolutionary ecology aspects and discuss which properties of an organism and its environment may favour the evolution of priming of stress responses.     

Networks of Causal Linkage Between Eigenmodes Characterize Behavioral Dynamics of Caenorhabditis elegans

Behavioral phenotyping of model organisms has played an important role in unravelling the complexities of animal behavior. Techniques for classifying behavior often rely on easily identified changes in posture and motion. However, such approaches are likely to miss complex behaviors that cannot be readily distinguished by eye (e.g., behaviors produced by high dimensional dynamics). To explore this issue, we focus on the model organism Caenorhabditis elegans, where behaviors have been extensively recorded and classified. Using a dynamical systems lens, we identify high dimensional, nonlinear causal relationships between four basic shapes that describe worm motion (eigenmodes, also called “eigenworms”). We find relationships between all pairs of eigenmodes, but the timescales of the interactions vary between pairs and across individuals. Using these varying timescales, we create “interaction profiles” to represent an individual’s behavioral dynamics. As desired, these profiles are able to distinguish well-known behavioral states: i.e., the profiles for foraging individuals are distinct from those of individuals exhibiting an escape response. More importantly, we find that interaction profiles can distinguish high dimensional behaviors among divergent mutant strains that were previously classified as phenotypically similar. Specifically, we find it is able to detect phenotypic behavioral differences not previously identified in strains related to dysfunction of hermaphrodite-specific neurons.     

Fixed Electrical Charges and Mobile Ions Affect the Measurable Mechano-Electrochemical Properties of Charged-Hydrated Biological Tissues: The Articular Cartilage Paradigm

The triphasic constitutive law [Lai, Hou and Mow (1991)] has been shown in some special 1D cases to successfully model the deformational and transport behaviors of charged-hydrated, porous-permeable, soft biological tissues, as typified by articular cartilage. Due to nonlinearities and other mathematical complexities of these equations, few problems for the deformation of such materials have ever been solved analytically. Using a perturbation procedure, we have linearized the triphasic equations with respect to a small imposed axial compressive strain, and obtained an equilibrium solution, as well as a short-time boundary layer solution for the mechano- electrochemical (MEC) fields for such a material under a 2D unconfined compression test. The present results show that the key physical parameter determining the deformational behaviors is the ratio of the perturbation of osmotic pressure to elastic stress, which leads to changes of the measurable elastic coefficients. From the short-time boundary layer solution, both the lateral expansion and the applied load are found to decrease with the square root of time. The predicted deformations, flow fields and stresses are consistent with the analysis of the short time and equilibrium biphasic (i.e., the solid matrix has no attached electric charges) [Armstrong, Lai and Mow (1984)]. These results provide a better understanding of the manner in which fixed electric charges and mobile ions within the tissue contribute to the observed material responses.     

Comparison studies of dinitrogenase reductase ADP-ribosyl transferase/dinitrogenase reductase activating glycohydrolase regulatory systems in Rhodospirillum rubrum and Azospirillum brasilense.

Reversible ADP ribosylation of dinitrogenase reductase, catalyzed by the dinitrogenase reductase ADP-ribosyl transferase (DRAT)/dinitrogenase reductase activating glycohydrolase (DRAG) regulatory system, has been characterized in both Rhodospirillum rubrum and Azospirillum brasilense. Although the general functions of DRAT and DRAG are very similar in these two organisms, there are a number of interesting differences, e.g., in the timing and extent of the regulatory response to different stimuli. In this work, the basis of these differences has been studied by the heterologous expression of either draTG or nifH from A. brasilense in R. rubrum mutants that lack these genes, as well as the expression of draTG from R. rubrum in an A. brasilense draTG mutant. In general, these hybrid strains respond to stimuli in a manner similar to that of the wild-type parent of the recipient strain rather than the wild-type source of the introduced genes. These results suggest that the differences seen in the regulatory response in these organisms are not primarily a result of different properties of DRAT, DRAG, or dinitrogenase reductase. Instead, the differences are likely the result of different signal pathways that regulate DRAG and DRAT activities in these two organisms. Our results also suggest that draT and draG are cotranscribed in A. brasilense.