Regularities and cellular mechanism of spontaneous mutations in enterobacteria

The regularities and a possible mechanism of the formation of spontaneous mutations in enterobacteria were studied. Possible causes and the mechanism of these processes were analyzed. It was shown that the mechanism of formation of spontaneous mutations is not related to the replication process and DNA polymerase errors. Mutations arise abruptly within 10-20 min due to a cosmophysical factor of unknown origin. It is assumed that cosmophysical radiation makes cell membranes excitable. Upon membrane pulsation, different volumes (portions) of cell substance are ejected through expanding pores. From this substance, viable heteromorphous mutant forms of colonies and cells (bio- and serum variants, L-forms, "parastrains", and new ecoforms of bacteria) are formed.     

Chronobiological analysis of subarctic features of long-term dynamics of biological processes

The analysis of a large number of chronobiological observations (heliospheric modulations, cosmophysical factors, weak low-frequency electromagnetic influences, etc.) allows us to make a conclusion about the possibility of direct and indirect exogenous (relative to the biosphere) modulations of biological processes in avroral and arctic zones. A nonequivalence of various seasons for the performance of introduction experiments was established. It was shown that the intensive fluctuations of environmental conditions are very important for the survival of living forms introduced into subarctic regions.     

Discrete macroscopic fluctuations in processes of various nature

The data of 30-year investigations of macroscopic fluctuations are generalized in this review. The results of measuring processes of different nature (from biochemical reactions to radioactive decay) fluctuate. They are presented by certain discrete values. The discreteness of corresponding spectra of states can be probably explained by both pure mathematical causes and cosmophysical factors. The fluctuation amplitude and the shape of the spectrum of the states of objects with different nature depend on the universal external cosmophysical factors. General problems arising in connection with the analysis of the "scatter in the results" and "nonreproducibility of measurements" are discussed.     

Can micro-imaging based analysis methods quantify structural integrity of rat vertebrae with and without metastatic involvement?

This study compares the ability of μCT image-based registration, 2D structural rigidity analyses and multimodal continuum-level finite element (FE) modeling in evaluating the mechanical stability of healthy, osteolytic, and mixed osteolytic/osteoblastic metastatically involved rat vertebrae. μMR and μCT images (loaded and unloaded) were acquired of lumbar spinal motion segments from 15rnu/rnu rats (five per group). Strains were calculated based on image registration of the loaded and unloaded μCT images and via analysis of FE models created from the μCT and μMR data. Predicted yield load was also calculated through 2D structural rigidity analysis of the axial unloaded μCT slices. Measures from the three techniques were compared to experimental yield loads. The ability of these methods to predict experimental yield loads were evaluated and image registration and FE calculated strains were directly compared. Quantitatively for all samples, only limited weak correlations were found between the image-based measures and experimental yield load. In comparison to the experimental yield load, we observed a trend toward a weak negative correlation with median strain calculated using the image-based strain measurement algorithm (r=-0.405, p=0.067), weak significant correlations (p<0.05) with FE based median and 10th percentile strain values (r=-0.454, -0.637, respectively), and a trend toward a weak significant correlation with FE based mean strain (r=-0.366, p=0.09). Individual group analyses, however, yielded more and stronger correlations with experimental results. Considering the image-based strain measurement algorithm we observed moderate significant correlations with experimental yield load (p<0.05) in the osteolytic group for mean and median strain values (r=-0.840, -0.832, respectively), and in the healthy group for median strain values (r=-0.809). Considering the rigidity-based predicted yield load, we observed a strong significant correlation with the experimental yield load in the mixed osteolytic/osteoblastic group (r=0.946) and trend toward a moderate correlation with the experimental yield load in the osteolytic group (r=0.788). Qualitatively, strain patterns in the vertebral bodies generated using image registration and FEA were well matched, yet quantitatively a significant correlation was found only between mean strains in the healthy group (r=0.934). Large structural differences in metastatic vertebrae and the complexity of motion segment loading may have led to varied modes of failure. Improvements in load characterization, material properties assignments and resolution are necessary to yield a more generalized ability for image-based registration, structural rigidity and FE methods to accurately represent stability in healthy and pathologic scenarios.     

Random fluctuations in readings of measurement devices: cosmophysic effects?

Fluctuations of "computer time" provided by the PC quartz generator were studied. It was shown that variations in the yearly course of the quartz generator frequency occur with periodicities of 13-15 days and 28-30 days. Regular fluctuations with periods of 0.5 and 1.0 min are typical of the short-term spectral component. Impulses of sharp and intense deceleration of "computer time" are often observed against the background of these regular fluctuations. The conclusion is made that fluctuations of "computer time" are of cosmophysical origin.     

Can the past predict the future? Experimental tests of historically based population models

A frequently advocated approach for forecasting the population‐level impacts of climate change is to project models based on historical, observational relationships between climate and demographic rates. Despite the potential pitfalls of this approach, few historically based population models have been experimentally validated. We conducted a precipitation manipulation experiment to test population models fit to observational data collected from the 1930s to the 1970s for six prairie forb species. We used the historical population models to predict experimental responses to the precipitation manipulations, and compared these predictions to ones generated by a statistical model fit directly to the experimental data. For three species, a sensitivity analysis of the effects of precipitation and grass cover on forb population growth showed consistent results for the historical population models and the contemporary statistical models. Furthermore, the historical population models predicted population growth rates in the experimental plots as well or better than the statistical models, ignoring variation explained by spatial random effects and local density‐dependence. However, for the remaining three species, the sensitivity analyses showed that the historical and statistical models predicted opposite effects of precipitation on population growth, and the historical models were very poor predictors of experimental responses. For these species, historical observations were not well replicated in space, and for two of them the historical precipitation‐demography correlations were weak. Our results highlight the strengths and weaknesses of observational and experimental approaches, and increase our confidence in extrapolating historical relationships to predict population responses to climate change, at least when the historical correlations are strong and based on well‐replicated observations.     

Identifying kinetic gating mechanisms for ion channels by using two-dimensional distributions of simulated dwell times.

Ion channels are integral membrane proteins that regulate ionic flux through cell membranes by opening and closing (or gating) their pores. The gating can be monitored by observing step changes in the current flowing through single channels. Analysis of the durations of the open and closed intervals and of the correlations among the interval durations can give insight into the gating mechanism. Although it is well known that the correlation information can be essential to distinguish among possible gating mechanisms, it has been difficult to use this information because it has not been possible to correct the predicted correlations for the distortion of the single-channel data because of filtering and noise. To overcome this limitation we present a method based on a comparison of simulated and experimental two-dimensional dwell-time distributions constructed by analysing simulated and experimental single-channel currents in an identical manner. The simulated currents incorporate the true effects of filtering and noise, the two-dimensional distributions retain the correlation information, and the identical analysis allows direct maximum-likelihood comparison of the simulated and experimental two-dimensional distributions. We show that the two-dimensional simulation method has a greatly increased ability to distinguish among models, compared with methods that use one-dimensional distributions.     

Urinary electrolyte excretion,alcohol consumption,and blood pressure in the Scottish heart health study.

As part of a study of risk factors for coronary heart disease 24 hour urine collections were obtained from 7354 men and women aged 40-59 selected at random from 22 districts throughout Scotland (Scottish heart health study). The mean of two standardised measurements of blood pressure was related to the reported consumption of alcohol and measurements of height, weight, pulse rate, and electrolyte excretion. Several significant correlations were found with both systolic and diastolic pressure, but only the coefficients for age, body mass index, and pulse rate were greater than 0.1. Alcohol consumption showed a weak positive correlation with blood pressure in men. Sodium excretion showed a weak positive correlation with blood pressure in both sexes, and potassium excretion showed weak negative correlations. In multiple regression analysis age, pulse rate, body mass index, alcohol consumption, and potassium excretion had significant independent effects but sodium excretion did not. Although measuring blood pressure twice on one occasion and 24 hour urinary sodium excretion only once may have weakened any potential correlation, the most likely explantation of these results is that the relation between sodium and blood pressure in the population is weak and that potassium and alcohol are of greater importance.     

Bringing to Light Hidden Elasticity in the Liquid State Using In-Situ Pretransitional Liquid Crystal Swarms

The present work reveals that at the sub-millimeter length-scale, molecules in the liquid state are not dynamically free but elastically correlated. It is possible to “visualize” these hidden elastic correlations by using the birefringent properties of pretransitional swarms persistent in liquids presenting a weak first order transition. The strategy consists in observing the optical response of the isotropic phase of mesogenic fluids to a weak (low energy) mechanical excitation. We show that a synchronized optical response is observable at frequencies as low as 0.01Hz and at temperatures far away from any phase transition (up to at least 15°C above the transition). The observation of a synchronized optical signal at very low frequencies points out a collective response and supports the existence of long-range elastic (solid-like) correlations existing at the sub-millimeter length-scale in agreement to weak solid-like responses already identified in various liquids including liquid water. This concept of elastically linked molecules differs deeply with the academic view of molecules moving freely in the liquid state and has profound consequences on the mechanisms governing collective effects as glass formation, gelation and transport, or synchronized processes in physiological media.     

Stochastic resonance as a possible mechanism of amplification of weak electric signals in living cells

The most important but still unresolved problem in bioelectromagnetics is the interaction of weak electromagnetic fields (EMFs) with living cells. Thermal and other types of noise pose restrictions in cell detection of weak signals. As a consequence, some extant experimental results that indicate low-intensity field effects cannot be accounted for, and this renders the results themselves questionable. One way out of this dead end is to search for possible mechanisms of signal amplification. In this paper, we discuss a general mechanism in which a weak signal is amplified by system noise itself. This mechanism was discovered several years ago in physics and is known, in its simplest form, as a stochastic resonance. It was shown that signal amplification may exceed a factor of 1000, which renders existing estimations of EMF thresholds highly speculative. The applicability of the stochastic resonance concept to cells is discussed particularly with respect to the possible role of the cell membrane in the amplification process. © 1994 Wiley-Liss, Inc.     

Biological detector of weak cosmic fields]

Possibility of use of biological object as a detector of faint cosmophysical fields is discussed. The signals of free induction and electric echo caused by a short-term effect of light with an intensity of approximately 0.2 mWt/sm2 on biological systems were observed. The experiments with Blatella germanica, Muska domestica were performed in vivo and with red and green seaweeds and yeast cells in vitro. The signals were detected by means of the dielectric permeability measurement in a dynamic regime. Main features of the observed responses are described and assumption on mechanisms of their origin are given. An example of registration of the Lunar eclipse on a detector with in active element of Blatella germanica is given.     

The relationship between tree biodiversity and biomass dynamics changes with tropical forest succession

Theory predicts shifts in the magnitude and direction of biodiversity effects on ecosystem function (BEF) over succession, but this theory remains largely untested. We studied the relationship between aboveground tree biomass dynamics (Δbiomass) and multiple dimensions of biodiversity over 8–16 years in eight successional rainforests. We tested whether successional changes in diversity–Δbiomass correlations reflect predictions of niche theories. Diversity–Δbiomass correlations were positive early but weak later in succession, suggesting saturation of niche space with increasing diversity. Early in succession, phylogenetic diversity and functional diversity in two leaf traits exhibited the strongest positive correlations with Δbiomass, indicating complementarity or positive selection effects. In mid‐successional stands, high biodiversity was associated with greater mortality‐driven biomass loss, i.e. negative selection effects, suggesting successional niche trade‐offs and loss of fast‐growing pioneer species. Our results demonstrate that BEF relationships are dynamic across succession, thus successional context is essential to understanding BEF in a given system.     

Electrostatic Potential of B-DNA: Effect of Interionic Correlations

Modified Poisson-Boltzmann (MPB) equations have been numerically solved to study ionic distributions and mean electrostatic potentials around a macromolecule of arbitrarily complex shape and charge distribution. Results for DNA are compared with those obtained by classical Poisson-Boltzmann (PB) calculations. The comparisons were made for 1:1 and 2:1 electrolytes at ionic strengths up to 1 M. It is found that ion-image charge interactions and interionic correlations, which are neglected by the PB equation, have relatively weak effects on the electrostatic potential at charged groups of the DNA. The PB equation predicts errors in the long-range electrostatic part of the free energy that are only ∼1.5 kJ/mol per nucleotide even in the case of an asymmetrical electrolyte. In contrast, the spatial correlations between ions drastically affect the electrostatic potential at significant separations from the macromolecule leading to a clearly predicted effect of charge overneutralization.     

Combining genetic variation and phenotypic plasticity in tradeoff modelling

Tradeoffs lead to antagonistic relationships between phenotypic traits and are thought to be determined both genetically and environmentally. We present here an allocation model that distinguishes between the genetic and environmental components of variation in resource allocation. In this model we introduced plasticity of resource allocation which was considered to be an adaptive response to environmental variations. The results show that resource allocation plasticity is a key parameter for the existence of environmental (i.e. inter environments and intra genotype) correlations and is therefore necessary to detect environment-induced tradeoffs. We also investigated the impact of the resource allocation plasticity and other factors on genetic (i.e. inter genotypes) correlations. Our results show that resource allocation plasticity induces a masking effect of tradeoffs when studying genetic correlations and increases the masking effect of resource variation by making apparent correlations positive when negative correlations are expected. In addition, by simulating different sources of resource acquisition variation, we demonstrated that resource variation might have different effects on correlations according to the experimental design and the studied biological material. Further development of this model may be used to investigate the theoretical implications of tradeoffs in evolutionary biology and to improve design and interpretation of experimental studies.     

Diversity effects on invasion vary with life history stage in marine macroalgae

Most experimental studies of diversity effects on invasibility have reported negative relationships while observational studies have often found positive correlations between the numbers of exotic and native taxa. Nearly all of these studies have been done with terrestrial plants or aquatic invertebrates. We investigated effects of native macroalgal diversity on invasion success of the introduced macroalga Sargassum muticum (Yendo) Fensholt (Phaeophyceae: Fucales) on the west coast of Vancouver Island. We conducted both observational field surveys of the correlation between native diversity and exotic cover, and experimental manipulations of native diversity in constructed 25×25 cm communities. Field surveys found higher cover of S. muticum in plots with low native diversity, suggesting a negative relationship between diversity and invasibility at the neighbourhood scale. The experiment found initial cover of S. muticum germlings was highest in plots with greater diversity. Over the duration of the experiment cover of settled germlings increased fastest in the low diversity plots, so that there was a weak negative effect of diversity on final cover of the invader after 77 days. The slope of the relationship reversed over time, with field patterns and experimental results converging at the end of the experiment. Our results suggest native diversity has contrasting effects on different stages of invasion. Diversity facilitates invader recruitment of S. muticum but decreases growth and or survivorship.     

Multivariate stabilizing selection and pleiotropy in the maintenance of quantitative genetic variation

Abstract. We investigate maintenance of quantitative genetic variation at mutation-selection balance for multiple traits. The intrinsic strength of real stabilizing selection on one of these traits denoted the "target trait" and the observed strength of apparent stabilizing selection on the target trait can be quite different: the latter, which is estimable, is much smaller (i.e., implying stronger selection) than the former. Distinguishing them may enable the mutation load to be relaxed when considering multivariate stabilizing selection. It is shown that both correlations among mutational effects and among strengths of real stabilizing selection on the traits are not important unless they are high. The analysis for independent situations thus provides a good approximation to the case where mutant and stabilizing selection effects are correlated. Multivariate stabilizing selection can be regarded as a combination of stabilizing selection on the target trait and the pleiotropic direct selection on fitness that is solely due to the effects of real stabilizing selection on the hidden traits. As the overall fitness approaches a constant value as the number of traits increases, multivariate stabilizing selection can maintain abundant genetic variance only under quite weak selection. The common observations of high polygenic variance and strong stabilizing selection thus imply that if the mutation-selection balance is the true mechanism of maintenance of genetic variation, the apparent stabilizing selection cannot arise solely by real stabilizing selection simultaneously on many metric traits.     

QUANTITATIVE GENETIC DIVERGENCE AND STANDING GENETIC (CO)VARIANCE IN THERMAL REACTION NORMS ALONG LATITUDE

Although the potential to adapt to warmer climate is constrained by genetic trade‐offs, our understanding of how selection and mutation shape genetic (co)variances in thermal reaction norms is poor. Using 71 isofemale lines of the fly Sepsis punctum, originating from northern, central, and southern European climates, we tested for divergence in juvenile development rate across latitude at five experimental temperatures. To investigate effects of evolutionary history in different climates on standing genetic variation in reaction norms, we further compared genetic (co)variances between regions. Flies were reared on either high or low food resources to explore the role of energy acquisition in determining genetic trade‐offs between different temperatures. Although the latter had only weak effects on the strength and sign of genetic correlations, genetic architecture differed significantly between climatic regions, implying that evolution of reaction norms proceeds via different trajectories at high latitude versus low latitude in this system. Accordingly, regional genetic architecture was correlated to region‐specific differentiation. Moreover, hot development temperatures were associated with low genetic variance and stronger genetic correlations compared to cooler temperatures. We discuss the evolutionary potential of thermal reaction norms in light of their underlying genetic architectures, evolutionary histories, and the materialization of trade‐offs in natural environments.     

Fisher's sons’ effect in sexual selection: absent,intermittent or just low experimental power?

The Fisherian sexual selection paradigm has been called the null model of sexual selection. At its heart is the expectation of a genetic correlation (r_G) between female preference and male trait. However, recent meta‐analysis has shown estimated correlations are often extremely weak and not statistically significant. We show here that systematic failure of studies to reject the null hypothesis that r_G = 0 is almost certainly due to the low power of most experimental designs used. We provide an easy way to assess experimental power a priori and suggest that current data make it difficult to definitively test a key component of the Fisher effect.     

Plasmodesmatal pores in the torus of bordered pit membranes affect cavitation resistance of conifer xylem

The pit membrane in bordered pits of conifer tracheids is characterized by a porous margo and central thickening (torus), which is traditionally considered to function as an impermeable safety valve against air-seeding. However, electron microscopy based on 33 conifer species, including five families and 19 genera, reveals that pores occur in the torus of 13 of the species studied. The pores have a plasmodesmatal origin with an average diameter of 51 nm and grouped arrangement. Evidence for embolism spreading via pores in tori is supported by the pore sizes, which correspond relatively well with the pressure inducing cavitation. Predictions based on earlier correlations between pit structure and cavitation resistance were only weakly supported for species with punctured tori. Moreover, species with punctured tori are significantly less resistant to cavitation than species with non-punctured tori. Nevertheless, absolute pore diameters must be treated with caution and correlations between theoretical and measured air-seeding pressures are weak. Because most pores appear not to traverse the torus but are limited to one torus pad, only complete pores would trigger air-seeding. Embolism spreading through a leaky torus is not universal across gymnosperms and unlikely to represent the only air-seeding mechanism.