• MeSH
• virová interference MeSH
• viry hmyzu růst a vývoj   MeSH

Variation partitioning of species composition into components explained by environmental and spatial variables is often used to identify a signature of niche- and dispersal-based processes in community assembly. Such interpretation, however, strongly depends on the quality of the environmental data available. In recent studies conducted in forest dynamics plots, the environment was represented only by readily available topographical variables. Using data from a subtropical broad-leaved dynamics plot in Taiwan, we focus on the question of how would the conclusion about importance of niche- and dispersal-based processes change if soil variables are also included in the analysis. To gain further insight, we introduced multiscale decomposition of a pure spatial component [c] in variation partitioning. Our results indicate that, if only topography is included, dispersal-based processes prevail, while including soil variables reverses this conclusion in favor of niche-based processes. Multiscale decomposition of [c] shows that if only topography was included, broad-scaled spatial variation prevails in [c], indicating that other as yet unmeasured environmental variables can be important. However, after also including soil variables this pattern disappears, increasing importance of meso- and fine-scaled spatial patterns indicative of dispersal processes.

• MeSH
• biologické modely MeSH
• demografie MeSH
• druhová specificita MeSH
• ekosystém * MeSH
• nadmořská výška MeSH
• půda chemie   MeSH
• stromy MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Geografické názvy
• Taiwan MeSH

The modification of biomaterial surfaces has become increasingly relevant in the context of ongoing advancements in tissue engineering applications and the development of tissue-mimicking polymer materials. In this study, we investigated the layer-by-layer (LbL) deposition of polyelectrolyte multilayer protein reservoirs consisting of poly-l-lysine (PLL) and hyaluronic acid (HA) on the hydrophobic surface of poly(glycerol sebacate) (PGS) elastomer. Using the methods of isothermal titration calorimetry and surface plasmon resonance, we systematically investigated the interactions between the polyelectrolytes and evaluated the deposition process in real time, providing insight into the phenomena associated with film assembly. PLL/HA LbL films deposited on PGS showed an exceptional ability to incorporate bone morphogenetic protein-2 (BMP-2) compared to other growth factors tested, thus highlighting the potential of PLL/HA LbL films for osteoregenerative applications. The concentration of HA solution used for film assembly did not affect the thickness and topography of the (PLL/HA)10 films, but had a notable impact on the hydrophilicity of the PGS surface and the BMP-2 release kinetics. The release kinetics were successfully described using the Weibull model and hyperbolic tangent function, underscoring the potential of these less frequently used models to compare the protein release from LbL protein reservoirs.

• MeSH
• kyselina hyaluronová * chemie   MeSH
• nanočástice layer-by-layer MeSH
• polyelektrolyty MeSH
• polylysin * chemie   MeSH
• polymery MeSH
• Publikační typ
• časopisecké články MeSH

UNLABELLED: The hexameric lattice of an immature retroviral particle consists of Gag polyprotein, which is the precursor of all viral structural proteins. Lentiviral and alpharetroviral Gag proteins contain a peptide sequence called the spacer peptide (SP), which is localized between the capsid (CA) and nucleocapsid (NC) domains. SP plays a critical role in intermolecular interactions during the assembly of immature particles of several retroviruses. Published models of supramolecular structures of immature particles suggest that in lentiviruses and alpharetroviruses, SP adopts a rod-like six-helix bundle organization. In contrast, Mason-Pfizer monkey virus (M-PMV), a betaretrovirus that assembles in the cytoplasm, does not contain a distinct SP sequence, and the CA-NC connecting region is not organized into a clear rod-like structure. Nevertheless, the CA-NC junction comprises a sequence critical for assembly of immature M-PMV particles. In the present work, we characterized this region, called the SP-like domain, in detail. We provide biochemical data confirming the critical role of the M-PMV SP-like domain in immature particle assembly, release, processing, and infectivity. Circular dichroism spectroscopy revealed that, in contrast to the SP regions of other retroviruses, a short SP-like domain-derived peptide (SPLP) does not form a purely helical structure in aqueous or helix-promoting solution. Using 8-Å cryo-electron microscopy density maps of immature M-PMV particles, we prepared computational models of the SP-like domain and indicate the structural features required for M-PMV immature particle assembly. IMPORTANCE: Retroviruses such as HIV-1 are of great medical importance. Using Mason-Pfizer monkey virus (M-PMV) as a model retrovirus, we provide biochemical and structural data confirming the general relevance of a short segment of the structural polyprotein Gag for retrovirus assembly and infectivity. Although this segment is critical for assembly of immature particles of lentiviruses, alpharetroviruses, and betaretroviruses, the organization of this domain is strikingly different. A previously published electron microscopic structure of an immature M-PMV particle allowed us to model this important region into the electron density map. The data presented here help explain the different packing of the Gag segments of various retroviruses, such as HIV, Rous sarcoma virus (RSV), and M-PMV. Such knowledge contributes to understanding the importance of this region and its structural flexibility among retroviral species. The region might play a key role in Gag-Gag interactions, leading to different morphological pathways of immature particle assembly.

• MeSH
• cirkulární dichroismus MeSH
• elektronová kryomikroskopie MeSH
• konformace proteinů MeSH
• Masonův-Pfizerův opičí virus fyziologie   MeSH
• molekulární modely MeSH
• nukleokapsida - proteiny chemie   genetika   metabolismus   ultrastruktura   MeSH
• sestavení viru * MeSH
• uvolnění viru z buňky MeSH
• virové plášťové proteiny chemie   genetika   metabolismus   ultrastruktura   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

Functional trait differences among species are increasingly used to infer the effects of biotic and abiotic processes on species coexistence. Commonly, the trait diversity observed within communities is compared to patterns simulated in randomly generated communities based on sampling within a region. The resulting patterns of trait convergence and divergence are assumed to reveal abiotic and biotic processes, respectively. However, biotic processes such as competition can produce both trait divergence and convergence, through either excluding similar species (niche differences, divergence) or excluding dissimilar species (weaker competitor exclusion, convergence). Hence, separating biotic and abiotic processes that can produce identical patterns of trait diversity, or even patterns that neutralize each other, is not feasible with previous methods. We propose an operational framework in which the functional trait dissimilarity within communities (FDcomm) is compared to the corresponding trait dissimilarity expected from the species pool (i.e., functional species pool diversity, FDpool). FDpool includes the set of potential species for a site delimited by the operating environmental and dispersal limitation filters. By applying these filters, the resulting pattern of trait diversity is consistent with biotic processes, i.e., trait divergence (FDcomm > FDpool) indicates niche differentiation, while trait convergence (FDcomm < FDpool) indicates weaker competitor exclusion. To illustrate this framework, with its potential application and constraints, we analyzed both simulated and field data. The functional species pool framework more consistently detected the simulated trait diversity patterns than previous approaches. In the field, using data from plant communities of typical Northern European habitats in Estonia, we found that both niche-based and weaker competitor exclusion influenced community assembly, depending on the traits and community considered. In both simulated and field data, we demonstrated that only by estimating the species pool of a site is it possible to differentiate the patterns of trait dissimilarity produced by operating biotic processes. The framework, which can be applied with both functional and phylogenetic diversity, enables a reinterpretation of community assembly processes. Solving the challenge of defining an appropriate reference species pool for a site can provide a better understanding of community assembly.

• MeSH
• biologické modely MeSH
• druhová specificita MeSH
• ekosystém MeSH
• fyziologie rostlin MeSH
• rostliny klasifikace   MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Geografické názvy
• Estonsko MeSH

Assembly of immature retroviral particles is a complex process involving interactions of several specific domains of the Gag polyprotein localized mainly within capsid protein (CA), spacer peptide (SP), and nucleocapsid protein (NC). In the present work we focus on the contribution of NC to the oligomerization of CA leading to assembly of Mason-Pfizer monkey virus (M-PMV) and HIV-1. Analyzing in vitro assembly of substitution and deletion mutants of DeltaProCANC, we identified a "spacer-like" sequence (NC(15)) at the M-PMV NC N terminus. This NC(15) domain is indispensable for the assembly and cannot be replaced with oligomerization domains of GCN4 or CREB proteins. Although the M-PMV NC(15) occupies a position analogous to that of the HIV-1 spacer peptide, it could not be replaced by the latter one. To induce the assembly, both M-PMV NC(15) and HIV-1 SP1 must be followed by a short peptide that is rich in basic residues. This region either can be specific, i.e., derived from the downstream NC sequence, or can be a nonspecific positively charged peptide. However, it cannot be replaced by heterologous interaction domains either from GCN4 or from CREB. In summary, we report here a novel M-PMV spacer-like domain that is functionally similar to other retroviral spacer peptides and contributes to the assembly of immature-virus-like particles.

• MeSH
• buněčné linie MeSH
• DNA primery genetika   MeSH
• DNA virů genetika   MeSH
• Escherichia coli genetika   ultrastruktura   virologie   MeSH
• HIV-1 fyziologie   genetika   MeSH
• lidé MeSH
• Masonův-Pfizerův opičí virus fyziologie   genetika   ultrastruktura   MeSH
• molekulární sekvence - údaje MeSH
• multimerizace proteinu MeSH
• mutageneze MeSH
• nukleokapsida - proteiny fyziologie   genetika   chemie   MeSH
• rekombinantní proteiny genetika   chemie   metabolismus   MeSH
• sekvence aminokyselin MeSH
• sekvence nukleotidů MeSH
• sekvenční homologie aminokyselin MeSH
• sestavení viru fyziologie   genetika   MeSH
• terciární struktura proteinů MeSH
• transmisní elektronová mikroskopie MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• zvířata MeSH
• Publikační typ
• práce podpořená grantem MeSH
• Research Support, N.I.H., Extramural MeSH

BACKGROUND: Alternative organism designs (i.e. the existence of distinct combinations of traits leading to the same function or performance) are a widespread phenomenon in nature and are considered an important mechanism driving the evolution and maintenance of species trait diversity. However, alternative designs are rarely considered when investigating assembly rules and species effects on ecosystem functioning, assuming that single trait trade-offs linearly affect species fitness and niche differentiation. SCOPE: Here, we first review the concept of alternative designs, and the empirical evidence in plants indicating the importance of the complex effects of multiple traits on fitness. We then discuss how the potential decoupling of single traits from performance and function of species can compromise our ability to detect the mechanisms responsible for species coexistence and the effects of species on ecosystems. Placing traits in the continuum of organism integration level (i.e. traits hierarchically structured ranging from organ-level traits to whole-organism traits) can help in choosing traits more directly related to performance and function. CONCLUSIONS: We conclude that alternative designs have important implications for the resulting trait patterning expected from different assembly processes. For instance, when only single trade-offs are considered, environmental filtering is expected to result in decreased functional diversity. Alternatively, it may result in increased functional diversity as an outcome of alternative strategies providing different solutions to local conditions and thus supporting coexistence. Additionally, alternative designs can result in higher stability of ecosystem functioning as species filtering due to environmental changes would not result in directional changes in (effect) trait values. Assessing the combined effects of multiple plant traits and their implications for plant functioning and functions will improve our mechanistic inferences about the functional significance of community trait patterning.

• MeSH
• biodiverzita MeSH
• ekosystém * MeSH
• fenotyp MeSH
• fyziologie rostlin MeSH
• rostliny * MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

V posledním desetiletí došlo k prudkému rozvoji metody nazvané funkční MR, která mapuje regionální změny mozkové perfuze a nepřímo tak měří neuronální aktivaci ve vyšetřovaných částech mozku. Její přínos ke studiu kognitivních funkcí dosud není zcela jednoznačný. Metodou „event-related" funkční MR (efMRI) autoři provedli vyšetření sluchového „oddball" úkolu u 10 zdravých dobrovolníků. Získané výsledky porovnávali s nálezy předchozích efMRI a intracerebrálních ERP studií s cílem posoudit míru shody mezi oblastmi s hemodynamicky významně odlišnou odpovědí na vzácné terčové podněty a známými intracerebrálními generátory P3 potenciálu ERP. Obě metody shodně prokázaly aktivaci řadj oblastí především parietálního a frontálního laloku (lobulus parietalis superior, inferior, gyrus supramarginalis, gyrus cinguli, laterálního prefrontálního kortexu, gyrus temporalis superior a thalamu). Ve shodě s předpokládanou významnou rolí neurokognitivní sítě pro záměrnou pozornost v průběhu detekce terčových podnětů byla ve většině těchto struktur pozorována výraznější hemodynamická odezva na pravé straně. Oproti očekávání nebyla v prezentovaném experimentu, ani v žádné z před¬ chozích efMRI studií prokázána signifikantní hemodynamická odpověď na terčové podněty v místě nejvýraznějšího P3 generátoru - v amygdalohipokampálním komplexu. Rozdílné výsledky byly obdrženy také při vyšetřování dalších oblastí, např. rostrálního cingula. Ačkoli je tedy přínos efMRI k poznání neuroanatomického korelátu mentálních pochodů extrémně vysoký, sama o sobě není schopna poskytnout kompletní mapu aktivovaných mozkových oblastí v průběhu kognitivních operací. Důvodem je nejspíše neschopnost plně reflektovat tranzientní krátce trvající funkční změny neuronalních populací. Nadále je tak nutno vnímat ji jako metodu komplementární a její výsledky posuzovat s maximální obezřetností.

During the last decade occurred brisk development of the method of functional MR which maps regional changes of cerebral perfusion and indirectly assesses also the neuronal activation in the examined parts of the brain. Its contribution to investigations of cognitive functions is not quite unequivocal so far. Using the method of „event-related" functional MR (efMRI) the authors examined the auditory „oddball" task in 10 healthy volunteers. They compared the assembled results with the results of previous efMRI and intracerebral ERP studies with the objective to evaluate the extent of agreement between areas with a haemodynamically significantly different response to rare target stimuli and known intracerebral generators of the P3 potential. Both methods proved the activation of several areas in particular the parietal and frontal lobe (lobulus parietalis superior, inferior, gyrus suprarginalis, gyrus cinguli. of the lateral prefrontal cortex, gyrus temporalis superior and of the thalamus). Consistent with the assumed significant role of the neurocognitive network for directed attention in the course of detection of target stimuli in the majority of these structures a more marked haemodynamic response was observed on the right side. Against expectation in the presented experiment nor in any previous efMRI studies a significant haemodynamic response to target stimuli was not proved at the site of the most marked P3 generator in the amygdalohippocampal complex. Different results were also obtained on examination of further areas, e.g. the rostral cingulum. Thus although the contribution of efMRI to recognition of the neuroanatomical correlate of mental processes is extremely high, it is unable to provide alone a complete map of activated cerebral areas in the course of cognitive operations. The reason is most probably the inability to reflect fully transient short-term functional changes of the neuronal populations. Thus it has to be conceived also in future as a complementary method and its results must be evaluated with maximum caution.

• MeSH
• duševní procesy MeSH
• finanční podpora výzkumu jako téma MeSH
• hemodynamika MeSH
• kognice MeSH
• lidé MeSH
• magnetická rezonanční tomografie metody   přístrojové vybavení   MeSH
• mapování mozku MeSH
• neurony fyziologie   MeSH
• podněty MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• přehledy MeSH
• srovnávací studie MeSH

Proper assembly and disassembly of both immature and mature HIV-1 hexameric lattices are critical for successful viral replication. These processes are facilitated by several host-cell factors, one of which is myo-inositol hexaphosphate (IP6). IP6 participates in the proper assembly of Gag into immature hexameric lattices and is incorporated into HIV-1 particles. Following maturation, IP6 is also likely to participate in stabilizing capsid protein-mediated mature hexameric lattices. Although a structural-functional analysis of the importance of IP6 in the HIV-1 life cycle has been reported, the effect of IP6 has not yet been quantified. Using two in vitro methods, we quantified the effect of IP6 on the assembly of immature-like HIV-1 particles, as well as its stabilizing effect during disassembly of mature-like particles connected with uncoating. We analyzed a broad range of molar ratios of protein hexamers to IP6 molecules during assembly and disassembly. The specificity of the IP6-facilitated effect on HIV-1 particle assembly and stability was verified by K290A, K359A, and R18A mutants. In addition to IP6, we also tested other polyanions as potential assembly cofactors or stabilizers of viral particles.IMPORTANCE Various host cell factors facilitate critical steps in the HIV-1 replication cycle. One of these factors is myo-inositol hexaphosphate (IP6), which contributes to assembly of HIV-1 immature particles and helps maintain the well-balanced metastability of the core in the mature infectious virus. Using a combination of two in vitro methods to monitor assembly of immature HIV-1 particles and disassembly of the mature core-like structure, we quantified the contribution of IP6 and other small polyanion molecules to these essential steps in the viral life cycle. Our data showed that IP6 contributes substantially to increasing the assembly of HIV-1 immature particles. Additionally, our analysis confirmed the important role of two HIV-1 capsid lysine residues involved in interactions with IP6. We found that myo-inositol hexasulphate also stabilized the HIV-1 mature particles in a concentration-dependent manner, indicating that targeting this group of small molecules may have therapeutic potential.

• MeSH
• genové produkty gag - virus lidské imunodeficience chemie   genetika   metabolismus   MeSH
• HIV-1 chemie   genetika   MeSH
• missense mutace MeSH
• polymery chemie   MeSH
• sestavení viru * MeSH
• substituce aminokyselin MeSH
• vztahy mezi strukturou a aktivitou MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

Profilin controls actin nucleation and assembly processes in eukaryotic cells. Actin nucleation and elongation promoting factors (NEPFs) such as Ena/VASP, formins, and WASP-family proteins recruit profilin:actin for filament formation. Some of these are found to be microtubule associated, making actin polymerization from microtubule-associated platforms possible. Microtubules are implicated in focal adhesion turnover, cell polarity establishment, and migration, illustrating the coupling between actin and microtubule systems. Here we demonstrate that profilin is functionally linked to microtubules with formins and point to formins as major mediators of this association. To reach this conclusion, we combined different fluorescence microscopy techniques, including superresolution microscopy, with siRNA modulation of profilin expression and drug treatments to interfere with actin dynamics. Our studies show that profilin dynamically associates with microtubules and this fraction of profilin contributes to balance actin assembly during homeostatic cell growth and affects micro-tubule dynamics. Hence profilin functions as a regulator of microtubule (+)-end turnover in addition to being an actin control element.

• MeSH
• aktiny metabolismus   MeSH
• buněčná adheze MeSH
• buněčné kultury MeSH
• cytoskelet metabolismus   MeSH
• fetální proteiny metabolismus   MeSH
• fluorescenční mikroskopie MeSH
• fokální adheze metabolismus   MeSH
• HEK293 buňky MeSH
• jaderné proteiny metabolismus   MeSH
• lidé MeSH
• malá interferující RNA MeSH
• melanom experimentální MeSH
• mikrofilamenta metabolismus   MeSH
• mikrofilamentové proteiny metabolismus   MeSH
• mikrotubuly metabolismus   MeSH
• pohyb buněk fyziologie   MeSH
• profiliny metabolismus   MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH