The role of endogenous and exogenous factors in regulation of synchronous emergence of Trichogramma embryophagum Hartig and T. principium Sug. et Sor. (Hymenoptera, Trichogrammatidae)

The interaction of exogenous and endogenous factors affecting the daily rhythm of emergence of adult parasitoids Trichogramma embryophagum and T. princupium from laboratory strains was studied. Under a constant temperature of 20°C and different photoperiods (photophase of 12, 16, or 20 h), both species demonstrated a distinct rhythm; the majority of adults emerged during 4 first hours after light-on. The fraction of individuals emerged during this period depended on the photoperiod and was different in both the species studied. Experiments with non-periodic regimes (constant light or constant darkness, 20°C) demonstrated that the rhythm is based on the endogenous circadian oscillations that are synchronized with the external photoperiod. The time of emergence however, was not rigidly “programmed” and could be modified by the direct influence of the light and temperature Light-on and/or temperature increase (from 20° up to 30° C) induced the emergence of a certain percentage of individuals virtually at any time of the 24-h-long cycle. The magnitude of the response, estimated as the fraction of adults emerged during 2 h after the stimulation, changed daily under the control of the circadian oscillation. Thus, the plasticity of the daily dynamics of emergence was controlled (to a certain extent) by the endogenous rhythm of sensitivity to the stimuli. The interspecific differences in the relative sensitivity to light-on and temperature increase were revealed. When light and temperature stimuli were applied simultaneously, they caused a synergistic effect, exceeding a simple sum of separate impacts. These results demonstrate an important role of exogenous factors in control of the emergence rhythm in Trichogramma and can also be used in elaboration of methods of regulation and synchronization of emergence in these parasitoids.     

Lack of evidence that feedback from lifestyle alters the amplitude of the circadian pacemaker in humans

Two groups of healthy subjects were studied indoors, first while living normally for 8 days (control section) and then for 18 × 27h “days” (experimental section). This schedule forces the endogenous (body clock-driven) and exogenous (lifestyle-driven) components of circadian rhythms to run independently. Rectal temperature and wrist movement were measured throughout and used as markers of the amplitude of the circadian rhythm, with the rectal temperature also “purified” by means of the activity record to give information about the endogenous oscillator. Results showed that, during the experimental days, there were changes in the amplitude of the overt temperature rhythm and in the relative amounts of out-of-bed and in-bed activity, both of which indicated an interaction between endogenous and exogenous components of the rhythm. However, the amplitude and the amount of overlap were not significantly different on the control days (when endogenous and exogenous components remained synchronized) and those experimental days when endogenous and exogenous components were only transiently synchronized; also, the amplitudes of purified temperature rhythms did not change significantly during the experimental days in spite of changes in the relationship between the endogenous and exogenous components. Neither result offers support for the view that the exogenous rhythm alters the amplitude of oscillation of the endogenous circadian oscillator in humans.     

Origins of life: An operational definition

Two very different models are used for the scientific study of life's origins: in the Troland-Muller model, life is molecular and its defining characteristic is gene function; in the Oparin-Haldane model, life is cellular and its defining characteristic is metabolic function. While each of these models implicitly defines the living, neither provides criteria by which theemergence of life could be recognized in the laboratory.Anoperational definition of the living makes explicit the system logic of metabolic self-production: (1) that whatever form it may take, life is a function of its biochemical processes; (2) that no single biochemical process has integrity apart from an entire network of processes; (3) that a network of processes can have continuity only by being enclosed within a boundary structure, i.e., by the selective partition of a microenvironment as a domain for the bioenergetic-biosynthetic network; and (4) that life is a single phenomenon, distinct in its continuity of capture and storage of energy in such networks, driving the processes that produce its material constituents.This paper presentsautopoiesis as life-defining and discusses the utility of its criteria in our search for the origins of life on Earth. Enactment of the autopoietic criteria would result in aminimal cell and would demonstrate the experimental recapitulation of life's Archaean origins.     

Integration of a vector containing a repetitive LINE-1 element in the human genome.

Mammalian cells contain numerous nonallelic repeated sequences, such as multicopy genes, gene families, and repeated elements. One common feature of nonallelic repeated sequences is that they are homeologous (not perfectly identical). Our laboratory has been studying recombination between homeologous sequences by using LINE-1 (L1) elements as substrates. We showed previously that an exogenous L1 element could readily acquire endogenous L1 sequences by nonreciprocal homologous recombination. In the study presented here, we have investigated the propensity of exogenous L1 elements to be involved in a reciprocal process, namely, crossing-overs. This would result in the integration of the exogenous L1 element into an endogenous L1 element. Of over 400 distinct integration events analyzed, only 2% involved homologous recombination between exogenous and endogenous L1 elements. These homologous recombination events were imprecise, with the integrated vector being flanked by one homologous and one illegitimate junction. This type of structure is not consistent with classical crossing-overs that would result in two homologous junctions but rather is consistent with one-sided homologous recombination followed by illegitimate integration. Contrary to what has been found for reciprocal homologous integration, the degree of homology between the exogenous and endogenous L1 elements did not seem to play an important role in the choice of recombination partners. These results suggest that although exogenous and endogenous L1 elements are capable of homologous recombination, this seldom leads to crossing-overs. This observation could have implications for the stability of mammalian genomes.     

Disentangling demographic co‐effects of predation and pollution on population dynamics

In nature species react to a variety of endogenous and exogenous ecological factors. Understanding the mechanisms by which these factors interact and drive population dynamics is a need for understanding and managing ecosystems. In this study we assess, using laboratory experiments, the effects that the combinations of two exogenous factors exert on the endogenous structure of the population dynamics of a size‐structured population of Daphnia. One exogenous factor was size‐selective predation, which was applied on experimental populations through simulating: 1) selective predation on small prey, 2) selective predation on large prey and 3) non‐selective predation. The second exogenous factor was pesticide exposure, applied experimentally in a quasi‐continuous regime. Our analysis combined theoretical models and statistical testing of experimental data for analyzing how the density dependence structure of the population dynamics was shifted by the different exogenous factors. Our results showed that pesticide exposure interacted with the mode of predation in determining the endogenous dynamics. Populations exposed to the pesticide and to either selective predation on newborns or selective predation on adults exhibited marked nonlinear effects of pesticide exposure. However, the specific mechanisms behind such nonlinear effects were dependent on the mode of size‐selectivity. In populations under non‐selective predation the pesticide exposure exerted a weak lateral effect. The ways in which endogenous process and exogenous factors may interact determine population dynamics. Increases in equilibrium density results in higher variance of population fluctuations but do not modify the stability properties of the system, while changes in the maximum growth rate induce changes in the dynamic regimes and stability properties of the population. Future consideration for research includes the consequences of the seasonal variation in the composition and activity of the predator assembly in interaction with the seasonal variation in exposure to agrochemicals on freshwater population dynamics.     

Quantifying the impact of ecological memory on the dynamics of interacting communities

Ecological memory refers to the influence of past events on the response of an ecosystem to exogenous or endogenous changes. Memory has been widely recognized as a key contributor to the dynamics of ecosystems and other complex systems, yet quantitative community models often ignore memory and its implications.Recent modeling studies have shown how interactions between community members can lead to the emergence of resilience and multistability under environmental perturbations. We demonstrate how memory can be introduced in such models using the framework of fractional calculus. We study how the dynamics of a well-characterized interaction model is affected by gradual increases in ecological memory under varying initial conditions, perturbations, and stochasticity.Our results highlight the implications of memory on several key aspects of community dynamics. In general, memory introduces inertia into the dynamics. This favors species coexistence under perturbation, enhances system resistance to state shifts, mitigates hysteresis, and can affect system resilience both ways depending on the time scale considered. Memory also promotes long transient dynamics, such as long-standing oscillations and delayed regime shifts, and contributes to the emergence and persistence of alternative stable states. Our study highlights the fundamental role of memory in communities, and provides quantitative tools to introduce it in ecological models and analyse its impact under varying conditions.     

Models of dyadic social interaction

We discuss the logic of research designs for dyadic interaction and present statistical models with parameters that are tied to psychologically relevant constructs. Building on Karl Pearson's classic nineteenth-century statistical analysis of within-organism similarity, we describe several approaches to indexing dyadic interdependence and provide graphical methods for visualizing dyadic data. We also describe several statistical and conceptual solutions to the 'levels of analytic' problem in analysing dyadic data. These analytic strategies allow the researcher to examine and measure psychological questions of interdependence and social influence. We provide illustrative data from casually interacting and romantic dyads.     

Cannabinoids as potential new analgesics.

Among other pharmacological properties analgesia is one of the important features of cannabinoids with therapeutical prospects. Cannabinoids have been shown to produce antinociception in experimental animals and humans. Recently a new system of neuromodulation based upon the existence of cannabinoid receptors and their endogenous agonists has emerged. This has been proposed as another of the endogenous pain control systems. Current evidence indicate an interaction between cannabinoid and opioid systems, the latter being of known relevance in nociception. The fact that either exogenous or endogenous opioids enhanced cannabinoid-induced antinociception suggests simultaneous activation of both opioid and cannabinoid receptors by drugs as a new analgesic strategy.     

A genetic code Boolean structure. II. The genetic information system as a Boolean information system

A Boolean structure of the genetic code where Boolean deductions have biological and physicochemical meanings was discussed in a previous paper. Now, from these Boolean deductions we propose to define the value of amino acid information in order to consider the genetic information system as a communication system and to introduce the semantic content of information ignored by the conventional information theory. In this proposal, the value of amino acid information is proportional to the molecular weight of amino acids with a proportional constant of about 1.96×10²⁵ bits per kg. In addition to this, for the experimental estimations of the minimum energy dissipation in genetic logic operations, we present two postulates: (1) the energy E _i (i = 1, 2, ..., 20) of amino acids in the messages conveyed by proteins is proportional to the value of information, and (2) amino acids are distributed according to their energy E _i so the amino acid population in proteins follows a Boltzmann distribution. Specifically, in the genetic message carried by the DNA from the genomes of living organisms, we found that the minimum energy dissipation in genetic logic operations was close to kTLn(2) joules per bit.     

Expert systems in medicine

The emergence of the artificial intelligence (AI) in computer technology and its application in the medical field enables the researchers to carry out such intelligent activities like image processing, medical reasoning systems, clinical decision supporting and natural language understanding, etc. A gastroenterological expert system application is briefly demonstrated in this paper. Similar expert systems can be seen to be useful in the research of gastrointestinal cytoprotection, including the plan of different compounds with cytoprotective effect, experimental and clinical medical research.     

A Dynamic Gene Regulatory Network Model That Recovers the Cyclic Behavior of Arabidopsis thaliana Cell Cycle

Cell cycle control is fundamental in eukaryotic development. Several modeling efforts have been used to integrate the complex network of interacting molecular components involved in cell cycle dynamics. In this paper, we aimed at recovering the regulatory logic upstream of previously known components of cell cycle control, with the aim of understanding the mechanisms underlying the emergence of the cyclic behavior of such components. We focus on Arabidopsis thaliana, but given that many components of cell cycle regulation are conserved among eukaryotes, when experimental data for this system was not available, we considered experimental results from yeast and animal systems. We are proposing a Boolean gene regulatory network (GRN) that converges into only one robust limit cycle attractor that closely resembles the cyclic behavior of the key cell-cycle molecular components and other regulators considered here. We validate the model by comparing our in silico configurations with data from loss- and gain-of-function mutants, where the endocyclic behavior also was recovered. Additionally, we approximate a continuous model and recovered the temporal periodic expression profiles of the cell-cycle molecular components involved, thus suggesting that the single limit cycle attractor recovered with the Boolean model is not an artifact of its discrete and synchronous nature, but rather an emergent consequence of the inherent characteristics of the regulatory logic proposed here. This dynamical model, hence provides a novel theoretical framework to address cell cycle regulation in plants, and it can also be used to propose novel predictions regarding cell cycle regulation in other eukaryotes.     

一体化的光声-荧光显微镜用于活体肿瘤成像

报道了一种利用单一波长激发的同时产生光声和荧光信号的显微成像系统,本成像系统具有超高的成像分辨率(<6μm)。借助外源的造影剂在近红外的吸收特性,利用光声-荧光显微成像系统对活体肿瘤进行光声/荧光成像。实验结果表明,光声-荧光显微镜在早期肿瘤的成像和检测等方面具有潜在的应用价值。因此,通过研究和选择适当的双模态造影剂,该系统在不同病理模型中可以提供更准确的组织信息及生理参数。     

CRISPR-Cas生物传感器研究进展

成簇规律间隔短回文序列(clustered regularly interspaced short palindromic repeats,CRISPR)系统是广泛存在于细菌中的一种特有的免疫防御机制,与特殊的Cas蛋白结合后能够有效的对外源的核酸分子进行特异性片段化,并进一步促进其降解。CRISPR-Cas系统具有独特的靶向性,为开发针对于核酸为底物的生物传感器提供了新的概念。越来越多的研究人员根据不同Cas蛋白的性质,建立了独特的逻辑系统对靶标物质进行准确识别,基于CRISPR技术的生物传感器也开拓了该技术在基因编辑以外领域的应用。介绍了CRISPR-Cas系统的起源、作用机制和科学分类,根据生物传感器的作用方式以及识别底物进行了分类,并对基于CRISPR-Cas系统的高效生物传感器的应用前景进行了展望。     

Melatonin in the multi-oscillatory mammalian circadian world

In mammals, the complex interaction of neural, hormonal, and behavioral outputs from the suprachiasmatic nucleus (SCN) drives circadian expression of events, either directly or through coordination of the timing of peripheral oscillators. Melatonin, one of the endocrine output signals of the clock, provides the organism with circadian information and can be considered as an endogenous synchronizer, able to stabilize and reinforce circadian rhythms and to maintain their mutual phase-relationship at the different levels of the circadian network. Moreover, exogenous melatonin, through an action on the circadian clock, affects all levels of the circadian network. The molecular mechanisms underlying this chronobiotic effect have also been investigated in rats. REV-ERB alpha seems to be the initial molecular target.     

Artificial cell-cell communication in yeast Saccharomyces cerevisiae using signaling elements from Arabidopsis thaliana

The construction of synthetic cell-cell communication networks can improve our quantitative understanding of naturally occurring signaling pathways and enhance our capabilities to engineer coordinated cellular behavior in cell populations. Towards accomplishing these goals in eukaryotes, we developed and analyzed two artificial cell-cell communication systems in yeast. We integrated Arabidopsis thaliana signal synthesis and receptor components with yeast endogenous protein phosphorylation elements and new response promoters. In the first system, engineered yeast 'sender' cells synthesize the plant hormone cytokinin, which diffuses into the environment and activates a hybrid exogenous/endogenous phosphorylation signaling pathway in nearby engineered yeast 'receiver' cells. For the second system, the sender network was integrated into the receivers under positive-feedback regulation, resulting in population density-dependent gene expression (that is, quorum sensing). The combined experimental work and mathematical modeling of the systems presented here can benefit various biotechnology applications for yeast and higher level eukaryotes, including fermentation processes, biomaterial fabrication and tissue engineering.     

Protective effects of S-nitrosoglutathione against amyloid beta-peptide neurotoxicity

Amyloid beta-peptide (Abeta) is a major constituent of senile plaques in the brains of Alzheimer's disease (AD) patients. We have previously demonstrated ceramide production secondary to Abeta-induced activation of neutral sphingomyelinase (nSMase) in cerebral endothelial cells and oligodendrocytes, which may contribute to cellular injury during progression of AD. In this study, we first established the "Abeta --> nSMase --> ceramide --> free radical --> cell death" pathway in primary cultures of fetal rat cortical neurons. We also provided experimental evidence showing that S-nitrosoglutathione (GSNO), a potent endogenous antioxidant derived from the interaction between nitric oxide (NO) and glutathione, caused dose-dependent protective effects against Abeta/ceramide neurotoxicity via inhibition of caspase activation and production of reactive oxygen species (ROS). This GSNO-mediated neuroprotection appeared to involve activation of cGMP-dependent protein kinase (PKG), phosphatidylinositol 3-kinase (PI3K), and extracellular signal-regulated kinase (ERK). Activation of the cGMP/PKG pathway induced expression of thioredoxin and Bcl-2 that were beneficial to cortical neurons in antagonizing Abeta/ceramide toxicity. Consistently, exogenous application of thioredoxin exerted remarkable neuroprotective efficacy in our experimental paradigm. Results derived from the present study establish a neuroprotective role of GSNO, an endogenous NO carrier, against Abeta toxicity via multiple signaling pathways.     

Roles for the two-hybrid system in exploration of the yeast protein interactome

Comprehensive analysis of protein-protein interactions is a challenging endeavor of functional proteomics and has been best explored in the budding yeast. The yeast protein interactome analysis was achieved first by using the yeast two-hybrid system in a proteome-wide scale and next by large-scale mass spectrometric analysis of affinity-purified protein complexes. While these interaction data have led to a number of novel findings and the emergence of a single huge network containing thousands of proteins, they suffer many false signals and fall short of grasping the entire interactome. Thus, continuous efforts are necessary in both bioinformatics and experimentation to fully exploit these data and to proceed another step forward to the goal. Computational tools to integrate existing biological knowledge buried in literature and various functional genomic data with the interactome data are required for biological interpretation of the huge protein interaction network. Novel experimental methods have to be developed to detect weak, transient interactions involving low abundance proteins as well as to obtain clues to the biological role for each interaction. Since the yeast two-hybrid system can be used for the mapping of the interaction domains and the isolation of interaction-defective mutants, it would serve as a technical basis for the latter purpose, thereby playing another important role in the next phase of protein interactome research.     

Melatonin in the multi‐oscillatory mammalian circadian world

In mammals, the complex interaction of neural, hormonal, and behavioral outputs from the suprachiasmatic nucleus (SCN) drives circadian expression of events, either directly or through coordination of the timing of peripheral oscillators. Melatonin, one of the endocrine output signals of the clock, provides the organism with circadian information and can be considered as an endogenous synchronizer, able to stabilize and reinforce circadian rhythms and to maintain their mutual phase‐relationship at the different levels of the circadian network. Moreover, exogenous melatonin, through an action on the circadian clock, affects all levels of the circadian network. The molecular mechanisms underlying this chronobiotic effect have also been investigated in rats. REV‐ERB α seems to be the initial molecular target.     

COEVOLUTION AND THE ARCHITECTURE OF MUTUALISTIC NETWORKS

Although coevolution is widely recognized as an important evolutionary process for pairs of reciprocally specialized species, its importance within species‐rich communities of generalized species has been questioned. Here we develop and analyze mathematical models of mutualistic communities, such as those between plants and pollinators or plants and seed‐dispersers to evaluate the importance of coevolutionary selection within complex communities. Our analyses reveal that coevolutionary selection can drive significant changes in trait distributions with important consequences for the network structure of mutualistic communities. One such consequence is greater connectance caused by an almost invariable increase in the rate of mutualistic interaction within the community. Another important consequence is altered patterns of nestedness. Specifically, interactions mediated by a mechanism of phenotype matching tend to be antinested when coevolutionary selection is weak and even more strongly antinested as increasing coevolutionary selection favors the emergence of reciprocal specialization. In contrast, interactions mediated by a mechanism of phenotype differences tend to be nested when coevolutionary selection is weak, but less nested as increasing coevolutionary selection favors greater levels of generalization in both plants and animals. Taken together, our results show that coevolutionary selection can be an important force within mutualistic communities, driving changes in trait distributions, interaction rates, and even network structure.