Diel patterns of leaf and root growth: endogenous rhythmicity or environmental response?

Plants are sessile organisms forced to adjust to their surrounding environment. In a single plant the photoautotrophic shoot is exposed to pronounced environmental variations recurring in a day-night 24?h (diel) cycle, whereas the heterotrophic root grows in a temporally less fluctuating environment. The contrasting habitats of shoots and roots are reflected in different diel growth patterns and their responsiveness to environmental stimuli. Differences between diel leaf growth patterns of mono- and dicotyledonous plants correspond to their different organization and placement of growth zones. In monocots, heterotrophic growth zones are organized linearly and protected from the environment by sheaths of older leaves. In contrast, photosynthetically active growth zones of dicot leaves are exposed directly to the environment and show characteristic, species-specific diel growth patterns. It is hypothesized that the different exposure to environmental constraints and simultaneously the sink/source status of the growing organs may have induced distinct endogenous control of diel growth patterns in roots and leaves of monocot and dicot plants. Confronted by strong temporal fluctuations in environment, the circadian clock may facilitate robust intrinsic control of leaf growth in dicot plants.     

Reactive modifications of the autonomous time structure in the human organism

The spectrum of biological rhythms exhibits characteristic principles of biological time structure which also rule the functional behaviour. With increasing period lengths the rhythms become increasingly complex. In the long-wave section the rhythmic functions find their corresponding cycles in the environment, whereas the shorter waves represent only endogenous autonomous rhythms, which maintain an internal time order by means of frequency- and phase-coordination. Under resting conditions and in a state of complete adaptation only a few spontaneous rhythms dominate in the spectrum. However, under loading conditions as well as in pathological situations further periodicities come up. The spectrum of rhythms can be divided into certain blocks, with the period lengths predominating in each of these whole number frequency ratios forming a harmonic system. Frequency- and phase coordination establish a system of co-action which favours the functional economy of the organism. A tripartite organization of the autonomous rhythms involves different functional behaviours with regard to frequency, amplitude, and phase. Slower rhythms act upon the faster rhythms preferably by modulating their frequencies, while changes of the faster rhythms influence the slower ones by enhancing their amplitudes, multiplying their period lengths and shifting their phases. In principle the reactions of living systems are periodically structured. Reactive periodicity brings to appearance an endogenous time structure, which prefers whole number relationships with the spontaneous rhythms. The phase position of reactive periods depends on the stimulus. The amplitudes dampen down with increasing compensation. From the medical point of view so-called circaseptan (about 7 days) reactive periods are of predominant interest. This periodicity can be observed in numerous adaptive and compensating processes. It does not depend on the external week cycle and was already known to the antiquity.     

Das Leitgewebe gibt den Takt an

Hierarchy in the plant clock shop Higher plants use an endogenous timekeeper, the circadian clock, to adjust to the periodic changes in light and darkness in their environment. It has long been assumed that plant cellular clocks act as stand‐alone systems. Recent evidence points to widespread coupling among clocks in different organs and different cells. Moreover, a hierarchy has been observed between clocks in leaves and roots and even between clocks in individual cell types of the leaf, with the clock in the vasculature being dominant over the clock in mesophyll cells. Thus, the plant circadian system may also show a hierarchical organization reminiscent of the clock system in mammals.     

How does farmer connectivity influence livestock genetic structure? A case‐study in a Vietnamese goat population

Assessing how genes flow across populations is a key component of conservation genetics. Gene flow in a natural population depends on ecological traits and the local environment, whereas for a livestock population, gene flow is driven by human activities. Spatial organization, relationships between farmers and their husbandry practices will define the farmer's network and so determine farmer connectivity. It is thus assumed that farmer connectivity will affect the genetic structure of their livestock. To test this hypothesis, goats reared by four different ethnic groups in a Vietnamese province were genotyped using 16 microsatellites. A Bayesian approach and spatial multivariate analysis (spatial principal component analysis, sPCA) were used to identify subpopulations and spatial organization. Ethnic group frequencies, husbandry practices and altitude were used to create cost maps that were implemented in a least-cost path approach. Genetic diversity in the Vietnamese goat population was low (0.508) compared to other local Asian breeds. Using a Bayesian approach, three clusters were identified. sPCA confirmed these three clusters and also that the genetic structure showed a significant spatial pattern. The least-cost path analysis showed that genetic differentiation was significantly correlated (0.131–0.207) to ethnic frequencies and husbandry practices. In brief, the spatial pattern observed in the goat population was the result of complex gene flow governed by the spatial distribution of ethnic groups, ethnicity and husbandry practices. In this study, we clearly linked the livestock genetic pattern to farmer connectivity and showed the importance of taking into account spatial information in genetic studies.     

Morphology of a human-derived YAC in yeast meiosis

In meiosis of human males DNA is packaged along pachytene chromosomes about 20 time more compactly than in meiosis of yeast. Nevertheless, a human-derived yeast artificial chromosome (YAC) shows the same degree of compaction of DNA as endogenous chromosomes in meiotic prophase nuclei of yeast. This suggests that in yeast meiosis, human and yeast DNA adopt a similar organization of chromatin along the pachytene chromosome cores. Therefore meiotic chromatin organization does not seem to be an inherent chromosomal property but is governed by the host-specific cellular environment. We suggest that there is a correlation between the less dense DNA packaging and the increased rate of recombination that has been reported for human-derived YACs as compared with human DNA in its natural environment.     

Bioinformatic analysis of the origin, sequence and diversification of mu opioid receptors in vertebrates

Opioid receptors are a class of G protein-coupled receptors that mediate the effects of the different families of endogenous opioid peptides and natural alkaloid drugs such as morphine and its synthetic derivatives. In particular, the μ opioid receptor (MOR) represents the principal molecular target for morphine and it plays key roles in opioid analgesia and addiction. In this work, new putative MORs from different vertebrate species were identified in silico and their gene organization and predicted protein products are compared with the previously characterized MORs. Also, for the first time a new genomic organization in euteleleostei teleosts has been identified. Moreover, we suggest that MORs may be specific to craniate lineage. The analysis of functional mapping of MORs we present is an important contribution to the identification of their evolutionarily conserved regions.     

Paleoecology of some molluscan assemblages from the badenian (Miocene) marine sandy facies of Poland

Three molluscan assemblages from the Badenian (Miocene) marine sandy facies of Poland are described in terms of their taxonomic composition, diversity, and trophic structure. The structural variation between the molluscan assemblages seems to be largely controlled by a gradient in water energy which in turn results in gradients in substrate mobility and organic content of bottom sediments. Together with a subordinate factor of local sedimentation rate, these gradients control the distribution of lucinoid mucus tube feeders vs. deep burrowing siphonate suspension feeders, of browsers, and of deposit feeders vs. suspension feeders. Some structural features of the molluscan assemblages are regarded as related to biotic factors. The graphs of cumulative species frequencies vs. the logarithm of cumulative individual frequencies are used as a measure of community organization. These graphs indicate distinct differences in ecological maturity between the molluscan assemblages. On this basis, two different stages of ecological succession in an offshore sandy bottom environment are recognized. The evidence from the comparison of the Miocene molluscan assemblages with their recent counterparts may support the view that the evolutionary stability of species populations of a given community, and long-term stability of the community structure are independent. High environmental variability and stress seem to be correlated with evolutionary stability of species populations rather than with long-term permanence of community structure.     

Organization,control and function of extrasynaptic NMDA receptors

N-methyl d-aspartate receptors (NMDARs) exist in different forms owing to multiple combinations of subunits that can assemble into a functional receptor. In addition, they are located not only at synapses but also at extrasynaptic sites. There has been intense speculation over the past decade about whether specific NMDAR subtypes and/or locations are responsible for inducing synaptic plasticity and excitotoxicity. Here, we review the latest findings on the organization, subunit composition and endogenous control of NMDARs at extrasynaptic sites and consider their putative functions. Because astrocytes are capable of controlling NMDARs through the release of gliotransmitters, we also discuss the role of the glial environment in regulating the activity of these receptors.     

The structure of cell-matrix adhesions: the new frontier

Adhesions between the cell and the extracellular matrix (ECM) are mechanosensitive multi-protein assemblies that transmit force across the cell membrane and regulate biochemical signals in response to the chemical and mechanical environment. These combined functions in force transduction, signaling and mechanosensing contribute to cellular phenotypes that span development, homeostasis and disease. These adhesions form, mature and disassemble in response to actin organization and physical forces that originate from endogenous myosin activity or external forces by the extracellular matrix. Despite advances in our understanding of the protein composition, interactions and regulation, our understanding of matrix adhesion structure and organization, how forces affect this organization, and how these changes dictate specific signaling events is limited. Insights across multiple structural levels are acutely needed to elucidate adhesion structure and ultimately the molecular basis of signaling and mechanotransduction. Here we describe the challenges and recent advances and prospects for unraveling the structure of cell-matrix adhesions and their response to force.     

Zebra stripes and tiger stripes: the spatial frequency distribution of the pattern compared to that of the background is significant in display and crypsis

Some striped animals are camouflaged in their natural environment, whereas others are conspicuous. Mammals are known to have spatial frequency analysers in their visual mechanism, and it is suggested that the spatial characteristics of a striped pattern are different in camouflaged and conspicuous animals. Fourier analysis of the stripes of the zebra shows spatial frequencies in the pattern that are unlikely to be present so strongly in their natural background scene. A similar analysis of the camouflaging stripes of a tiger show that the distribution of spatial frequencies are similar to that in the background scene.     

The role of endogenous bioregulators in formation of cardiogenic reflex effects on circulation

The possible role of endogenous endothelium-derived bioactive substances in organization of cardiogenic depressor reflexes under cardiac receptor stimulation (by veratrine and bradykinin) was investigated in acute experiments on anesthetized rats. The results have shown that endothelium-derived bioactive substances take part in forming of the cardiogenic depressor reflex humoral components of nervous response or nervous modulators. These data contribute to understanding of the role of endogenous endothelium-derived bioactive substances (prostacyclin) and different NOS isoforms in mechanisms of depressor reflex development and species differences in their involvement in reflex vasomotor reactions.     

Does size matter? Examining the drivers of mammalian vocalizations

Previous studies of the vocalization frequencies of mammals have suggested that it is either body mass or environment that drives these frequencies. Using 193 species across the globe from the terrestrial and aquatic environments and a model selection approach, we identified that the best‐supported model for minimum and maximum frequencies for vocalization included both body mass and environment. The minimum frequencies of vocalizations of species from all environments retained the influence of body mass. For maximum frequency however, aquatic species are released from such a trend with body mass having little constraint on frequencies. Surprisingly, phylogeny did not have a strong impact on the evolution of the maximum frequency of mammal vocalizations, largely due to the pinniped species divergence of frequency from their carnivoran relatives. We demonstrate that the divergence of signal frequencies in mammals has arisen from the need to adapt to their environment.     

Automated biochemical, morphological, and organizational assessment of precancerous changes from endogenous two-photon fluorescence images

Background

Multi-photon fluorescence microscopy techniques allow for non-invasive interrogation of live samples in their native environment. These methods are particularly appealing for identifying pre-cancers because they are sensitive to the early changes that occur on the microscopic scale and can provide additional information not available using conventional screening techniques.

Methodology/Principal Findings

In this study, we developed novel automated approaches, which can be employed for the real-time analysis of two-photon fluorescence images, to non-invasively discriminate between normal and pre-cancerous/HPV-immortalized engineered tissues by concurrently assessing metabolic activity, morphology, organization, and keratin localization. Specifically, we found that the metabolic activity was significantly enhanced and more uniform throughout the depths of the HPV-immortalized epithelia, based on our extraction of the NADH and FAD fluorescence contributions. Furthermore, we were able to separate the keratin contribution from metabolic enzymes to improve the redox estimates and to use the keratin localization as a means to discriminate between tissue types. To assess morphology and organization, Fourier-based, power spectral density (PSD) approaches were employed. The nuclear size distribution throughout the epithelial depths was quantified by evaluating the variance of the corresponding spatial frequencies, which was found to be greater in the normal tissue compared to the HPV-immortalized tissues. The PSD was also used to calculate the Hurst parameter to identify the level of organization in the tissues, assuming a fractal model for the fluorescence intensity fluctuations within a field. We found the range of organization was greater in the normal tissue and closely related to the level of differentiation.

Conclusions/Significance

A wealth of complementary morphological, biochemical and organizational tissue parameters can be extracted from high resolution images that are acquired based entirely on endogenous sources of contrast. They are promising diagnostic parameters for the non-invasive identification of early cancerous changes and could improve significantly diagnosis and treatment for numerous patients.     

Nuclear plasmids in the Dictyostelium slime molds

Cellular slime molds are one of only three types of eukaryotes known to contain circular nuclear plasmids. Unlike the 2-microns circle in Saccharomyces, different strains of Dictyostelium can carry different, nonhomologous plasmids. Covalently closed, circular DNA plasmids have been identified in D. discoideum, D. mucoroides, D. giganteum, and D. purpureum. These plasmids range in size from 1.3-27 kb and in copy number from 50-300 molecules per cell. Plasmids have been identified in approximately one-fifth of all isolates examined. The organization of their DNA in nucleosomes establishes their presence in the nucleus. We have successfully cotransformed endogenous Dictyostelium plasmids into D. discoideum using the G418 resistance shuttle vector B10S. Transformants carrying D. discoideum plasmids are recovered at much higher frequency than those carrying plasmids from the other Dictyostelium species. We have constructed recombinant plasmids based on the D. discoideum plasmid Ddp2 and the G418 resistance gene. With these extrachromosomal vectors, transformed cells are recovered at frequencies of up to 10(-4) per input cell, the vectors are stably maintained at high copy number in the absence of selection, and the vectors can be used to introduce foreign DNA sequences into D. discoideum cells.     

Functional dynamics of plant growth and photosynthesis--from steady-state to dynamics--from homogeneity to heterogeneity

Plants are much more dynamic than we usually expect them to be. This dynamic behaviour is of paramount importance for their performance under natural conditions, when resources are distributed heterogeneously in space and time. However, plants are not only the cue ball of their physical and chemical environment. Endogenous rhythms and networks controlling photosynthesis and growth buffer plant processes from external fluctuations. This review highlights recent evidence of the importance of dynamic temporal and spatial organization of photosynthesis and of growth in leaves and roots. These central processes for plant performance differ strongly in their dependence on environmental impact and endogenous properties, respectively. Growth involves a wealth of processes ranging from the supply of resources from external and internal sources to the growth processes themselves. In contrast, photosynthesis can only take place when light and CO2 are present and thus clearly requires 'input from the environment'. Nevertheless, growth and photosynthesis are connected to each other via mechanisms that are still not fully understood. Recent advances in imaging technology have provided new insights into the dynamics of plant-environment interactions. Such processes do not only play a crucial role in understanding stress response of plants under extreme environmental conditions. Dynamics of plants under modest growth conditions rise from endogenous mechanisms as well as exogenous impact too. It is thus an important task for future research to identify how dynamic external conditions interact with plant-internal signalling networks to optimize plant behaviour in real time and to understand how plants have adapted to characteristic spatial and temporal properties of the resources from their environment, on which they depend on.     

Maize and wheat mitochondrial tRNAPro coding regions have similar sequences but different organizations.

The nucleotide sequences of two maize mitochondrial DNA regions containing a tRNAPro gene and an incomplete tRNAPro gene have been compared with the corresponding regions of wheat mitochondrial DNA. These regions have similar sequences but their organization is modified due to different recombination events involving the tRNAPro immediate environment.     

UHF-dielectrometry in the assessment of the structural organization of salt solutions and interstitial fluids in normal and cicatricial tissues

The complex dielectric permittivity of salt solutions with positive and negative salvation as well as healthy and cicatricially changed human skin in situ at the frequencies of 42 and 56.6 GHz was measured. The relation between the dielectric characteristics of water and diluted salt solutions and changes in their structural organization conditioned by different temperatures of samples and the type of salvation of electrolytes was studied. The differences in the dielectric characteristics of healthy and cicatricially changed skin are interpreted in terms of the dependence of the structural organization of interstitial fluids on the morphological and functional state of biological tissues.     

Targeted disruption of nebulette protein expression alters cardiac myofibril assembly and function

To evaluate nebulette's role in cardiac myofibrils, cardiomyocytes expressing green fluorescent protein (GFP)-nebulette constructs were monitored for their ability to contract and myofilament protein distribution was analyzed. Cells expressing full-length GFP-nebulette appear unaffected and exhibit normal beating frequencies. Expression of the GFP linker and SH3 results in loss of the endogenous nebulette and tropomyosin; however, Z-line and thick filaments are undisturbed. Cells expressing either of these domains have dramatically reduced beating frequencies, consistent with the loss of thin filament proteins. This loss was inhibited by the addition of protease inhibitors during culturing. The GFP repeat domain disrupts both myofibrillogenesis and contraction in spreading cardiomyocytes, whereas introduction of this protein into well-spread cardiomyocytes results in localization at the Z-line and a 50% reduction in beating frequency. Ultimately, these cells form bundles containing the GFP repeat and many myofilament proteins. Interestingly, butanedione monoxime inhibition of contraction inhibited the formation of these bundles. These results show that the GFP-nebulette domains have a dominant-negative effect on the distribution and function of the sarcomeric proteins. Taken together with the observation that nebulette colocalizes with alpha-actinin in the pre-, nascent, and mature myofibrils, our data demonstrate the importance of this cardiac-specific nebulin isoform in myofibril organization and function.     

From Ultradian to Infradian Rhythms: LH Releases Patterns In Vitro

In the present study, we examined in vitro luteinizing hormone (LH) release patterns from pituitaries and from pituitary cell cultures (3 and 7 days in culture) to elucidate the endogenous period generated by the gonadotroph cell population and to evaluate the relationship between the basic period generated at the cellular level and the output pattern observed at the organ level. In addition, we examined the effect of photic environmental signals perceived by the animals on LH release patterns from pituitaries in vitro. When the animals were exposed to circadian photoperiodic signals, the in vitro LH release pattern from the pituitaries exhibited ultradian, circadian, and infra-dian frequencies. When the animals were exposed to continuous illumination, the in vitro patterns exhibited only ultradian and infradian frequencies. Furthermore, free running is a process, not a state. This process is driven by a change in the relative dominance of different frequencies that construct the pattern without changing the basic period length. Evaluation of the relative dominance of the different frequencies that construct the pattern indicates that, although infradian oscillators may take part in shaping the output pattern, the basic rhythm generated by the pituitary cells is in the ultradian domain. The results obtained from the examined system suggest that an endogenous oscillator is a cellular entity with ultradian periodicity, and that the rhythmic output of many biological variables is structured by various ultradian components that construct the circadian and infradian output rhythms.