There have been several attempts to build a unified framework for macroecological patterns. However, these have mostly been based either on questionable assumptions or have had to be parameterized to obtain realistic predictions. Here, we propose a new model explicitly considering patterns of aggregated species distributions on multiple spatial scales, the property which lies behind all spatial macroecological patterns, using the idea we term 'generalized fractals'. Species' spatial distributions were modelled by a random hierarchical process in which the original 'habitat' patches were randomly replaced by sets of smaller patches nested within them, and the statistical properties of modelled species assemblages were compared with macroecological patterns in observed bird data. Without parameterization based on observed patterns, this simple model predicts realistic patterns of species abundance, distribution and diversity, including fractal-like spatial distributions, the frequency distribution of species occupancies/abundances and the species-area relationship. Although observed macroecological patterns may differ in some quantitative properties, our concept of random hierarchical aggregation can be considered as an appropriate null model of fundamental macroecological patterns which can potentially be modified to accommodate ecologically important variables.

• MeSH
• biologické modely * MeSH
• demografie MeSH
• ekosystém * MeSH
• fraktály MeSH
• zachování přírodních zdrojů MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

Phylogenetic and phylogeographic studies suggest that a majority of asexual organisms are evolutionarily recent offshoots of extant sexual taxa and that old clonal lineages tend to be isolated from their sexual and younger asexual counterparts. These observations have often been interpreted as support for the long-term disadvantages of asexuality resulting from the mechanisms of clonal decay. Although clonal decay is likely to be an important mechanism that limits the temporal and spatial distribution of asexual lineages, we argue here that contemporary phylogenetic analyses, which are mostly restricted to simple comparisons of "recent" and "ancient" clones, need to be tested against an appropriate null model of neutrality. We use computer simulations to show that many empirical observations of the distribution of asexuality do not in fact reject a null model of the neutral turnover of clones spawned by sexual relatives. In particular, neutral clonal turnover results in qualitatively similar pattern of clonal spatial distribution and age structure, as does a process that includes clonal decay. Although there are important quantitative differences between predictions made by the two models, we show that published empirical data are still inadequate to distinguish between them. Further work on sexual-asexual complexes is therefore required before clonal turnover can be rejected as a parsimonious explanation of the spatial distribution and age structure of asexual lineages.

• MeSH
• biodiverzita MeSH
• biologická evoluce * MeSH
• biologické modely * MeSH
• časové faktory MeSH
• dlouhověkost genetika   fyziologie   MeSH
• fylogeneze MeSH
• genetická variace MeSH
• hustota populace MeSH
• mutace MeSH
• nepohlavní rozmnožování genetika   fyziologie   MeSH
• počítačová simulace MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

This paper describes tooth development in a basal squamate, Paroedura picta. Due to its reproductive strategy, mode of development and position within the reptiles, this gecko represents an excellent model organism for the study of reptile development. Here we document the dental pattern and development of non-functional (null generation) and functional generations of teeth during embryonic development. Tooth development is followed from initiation to cytodifferentiation and ankylosis, as the tooth germs develop from bud, through cap to bell stages. The fate of the single generation of non-functional (null generation) teeth is shown to be variable, with some teeth being expelled from the oral cavity, while others are incorporated into the functional bone and teeth, or are absorbed. Fate appears to depend on the initiation site within the oral cavity, with the first null generation teeth forming before formation of the dental lamina. We show evidence for a stratum intermedium layer in the enamel epithelium of functional teeth and show that the bicuspid shape of the teeth is created by asymmetrical deposition of enamel, and not by folding of the inner dental epithelium as observed in mammals.

• MeSH
• buněčná diferenciace MeSH
• ještěři embryologie   MeSH
• modely u zvířat * MeSH
• odontogeneze fyziologie   MeSH
• zubní sklovina embryologie   MeSH
• zuby embryologie   MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

QUESTIONS: Traditional null models used to reveal assembly processes from functional diversity patterns are not tailored for comparing different spatial and evolutionary scales. In this study, we present and explore a family of null models that can help disentangling assembly processes at their appropriate scales and thereby elucidate the ecological drivers of community assembly. LOCATION: French Alps. METHODS: Our approach gradually constrains null models by: (1) filtering out species not able to survive in the regional conditions in order to reduce the spatial scale, and (2) shuffling species only within lineages of different ages to reduce the evolutionary scale of the analysis. We first tested and validated this approach using simulated communities. We then applied it to study the functional diversity patterns of the leaf-height-seed strategy of plant communities in the French Alps. RESULTS: Using simulations, we found that reducing the spatial scale correctly detected a signature of competition (functional divergence) even when environmental filtering produced an overlaying signal of functional convergence. However, constraining the evolutionary scale did not change the identified functional diversity patterns. In the case study of alpine plant communities, investigating scale effects revealed that environmental filtering had a strong influence at larger spatial and evolutionary scales and that neutral processes were more important at smaller scales. In contrast to the simulation study results, decreasing the evolutionary scale tended to increase patterns of functional divergence. CONCLUSION: We argue that the traditional null model approach can only identify a single main process at a time and suggest to rather use a family of null models to disentangle intertwined assembly processes acting across spatial and evolutionary scales.

• Klíčová slova
• Assembly rules, Biotic and abiotic filtering, Limiting similarity, Null models, Simulated communities,
• Publikační typ
• časopisecké články MeSH

Patterns of species associations have been commonly used to infer interactions among species. If species positively co-occur, they may form predominantly neutral assemblages, and such patterns suggest a relatively weak role for compensatory dynamics. The main objective of this study was to test this prediction on temporal samples of bird assemblages (n = 19, 10-57 years) by the presence/absence and quantitative null models on assemblage and guild levels. These null model outcomes were further analyzed to evaluate the effects of various data set characteristics on the outcomes of the null models. The analysis of two binary null models in combination with three association indices revealed 20% with significant aggregations, 61% with random associations, and only 19% with significant segregations (n = 95 simulations). The results of the quantitative null model simulations detected more none-random associations: 61% aggregations, 6% random associations, and 33% segregations (n = 114 simulations). Similarly, quantitative analyses on guild levels showed 58% aggregations, 20% segregations, and 22% random associations (n = 450 simulations). Bayesian GLMs detected that the outcomes of the binary and quantitative null models applied to the assemblage analyses were significantly related to census plot size, whereas the outcomes of the quantitative analyses were also related to the mean population densities of species in the data matrices. In guild-level analyses, only 9% of the GLMs showed a significant influence of matrix properties (plot size, matrix size, species richness, and mean species population densities) on the null model outcomes. The results did not show the prevalence of negative associations that would have supported compensatory dynamics. Instead, we assume that a similar response of the majority of species to climate-driven and stochastic factors may be responsible for the revealed predominance of positive associations.

• Klíčová slova
• birds, community ecology, compensatory dynamics, co‐occurrence indices, effects of matrix properties, species association,
• Publikační typ
• časopisecké články MeSH

The success of alien species on oceanic islands is considered to be one of the classic observed patterns in ecology. Explanations for this pattern are based on lower species richness on islands and the lower resistance of species-poor communities to invaders, but this argument needs re-examination. The important difference between islands and mainland is in the size of species pools, not in local species richness; invasibility of islands should therefore be addressed in terms of differences in species pools. Here I examine whether differences in species pools can affect invasibility in a lottery model with pools of identical native and exotic species. While in a neutral model with all species identical, invasibility does not depend on the species pool, a model with non-zero variation in population growth rates predicts higher invasibility of communities of smaller pools. This is because of species sampling; drawing species from larger pools increases the probability that an assemblage will include fast growing species. Such assemblages are more likely to exclude random invaders. This constitutes a mechanism through which smaller species pools (such as those of isolated islands) can directly underlie differences in invasibility.

• Klíčová slova
• Alien species, population growth rate, species pool, species sorting,
• Publikační typ
• dopisy MeSH

Xenograft models represent a promising tool to study the pathogenesis of hematological malignancies. To establish a reliable and appropriate in vivo model of aggressive human B-cell leukemia and lymphoma we xenotransplanted four p53-mutated cell lines and one ATM-mutated cell line into immunodeficient NOD/SCID IL2Rγ-null mice. The cell lines MEC-1, SU-DHL-4, JEKO-1, REC-1, and GRANTA-519 were transplanted intraperitoneally or subcutaneously and the engraftment was investigated using immunohistochemistry and flow cytometry. We found significant differences in engraftment efficiency. MEC-1, JEKO-1 and GRANTA-519 cell lines engrafted most efficiently, while SU-DHL-4 cells did not engraft at all. MEC-1 and GRANTA-519 massively infiltrated organs and the whole intraperitoneal cavity showing very aggressive growth. In addition, GRANTA-519 cells massively migrated to the bone marrow regardless of the transplantation route. The MEC-1 and GRANTA-519 cells can be especially recommended for in vivo study of p53-mutated chronic lymphocytic leukemia and ATM-mutated mantle cell lymphoma, respectively.

• Klíčová slova
• Chronic lymphocytic leukemia, NSG mouse, mantle cell lymphoma, xenograft model,
• MeSH
• ATM protein genetika   MeSH
• biologické markery MeSH
• chronická lymfatická leukemie genetika   metabolismus   patologie   MeSH
• genový knockout MeSH
• heterografty MeSH
• lidé MeSH
• lymfom z plášťových buněk genetika   patologie   MeSH
• modely nemocí na zvířatech MeSH
• mutace * MeSH
• myši inbrední NOD MeSH
• myši knockoutované MeSH
• myši SCID MeSH
• myši MeSH
• nádorové buněčné linie MeSH
• nádorový supresorový protein p53 genetika   MeSH
• receptory interleukinů - společná gama-podjednotka genetika   MeSH
• transplantace heterologní MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• mužské pohlaví MeSH
• myši MeSH
• ženské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• ATM protein MeSH
• biologické markery MeSH
• nádorový supresorový protein p53 MeSH
• receptory interleukinů - společná gama-podjednotka MeSH

Plant clonal spread is ubiquitous and of great interest, owing both to its key role in plant community assembly and its suitability for plant behaviour research. However, mechanisms that govern spreading distance are not well known. Here we link spacer costs and below-ground competition in a simple model of growth in a homogeneous below-ground environment, in which optimal distance between ramets is based on minimizing the sum of these costs. Using this model, we predict a high prevalence of clonal growth that does not employ spacers in resource-poor environments and a nonlinear increase in spreading distance in response to increasing below-ground resource availability. Analysis of database data on clonal growth in relationship to below-ground resource availability revealed that patterns of the spread based on stolons is compatible with the model's predictions. As expected, model prediction failed for rhizomatous species, where spacer sizes are likely to be selected mainly to play roles other than spread. The model's simplicity makes it useful as a null model in testing hypotheses about the effects of environmental heterogeneity on clonal spread.

• Klíčová slova
• below-ground resource availability, clonal growth, clonal plants, lateral spread, model, self-generated heterogeneity,
• MeSH
• biologické modely * MeSH
• ekosystém * MeSH
• fyziologie rostlin * MeSH
• oddenek růst a vývoj   fyziologie   MeSH
• populační dynamika MeSH
• půda MeSH
• vývoj rostlin MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• půda MeSH

Aristolochic acid (AA) causes aristolochic acid nephropathy, Balkan endemic nephropathy, and their urothelial malignancies. To identify enzymes involved in the metabolism of aristolochic acid I (AAI), the major toxic component of AA we used HRN (hepatic cytochrome P450 [Cyp] reductase null) mice, in which NADPH:Cyp oxidoreductase (Por) is deleted in hepatocytes. AAI was demethylated by hepatic Cyps in vitro to 8-hydroxy-aristolochic acid I (AAIa), indicating that less AAI is distributed to extrahepatic organs in wild-type (WT) mice. Indeed, AAI-DNA-adduct levels were significantly higher in organs of HRN mice, having low hepatic AAI demethylation capacity, than in WT mice. Absence of AAI demethylation in HRN mouse liver was confirmed in vitro; hepatic microsomes from WT, but not from HRN mice, oxidized AAI to AAIa. To define the role of hepatic Cyps in AAI demethylation, modulation of AAIa formation by CYP inducers was investigated. We conclude that AAI demethylation is attributable mainly to Cyp1a1/2. The higher AAI-DNA adduct levels in HRN than WT mice were the result of the lack of hepatic AAI demethylation concomitant with a higher activity of cytosolic NAD(P)H:quinone oxidoreductase (Nqo1), which activates AAI. Mouse hepatic Cyp1a1/2 also activated AAI to DNA adducts under hypoxic conditions in vitro, but in renal microsomes, Por and Cyp3a are more important than Cyp1a for AAI-DNA adduct formation. We propose that AAI activation and detoxication in mice are dictated mainly by AAI binding affinity to Cyp1a1/2 or Nqo1, by their turnover, and by the balance between oxidation and reduction of AAI by Cyp1a.

• MeSH
• adukty DNA MeSH
• biotransformace MeSH
• cytochrom P-450 CYP1A1 metabolismus   MeSH
• cytochrom P-450 CYP1A2 metabolismus   MeSH
• játra enzymologie   metabolismus   MeSH
• karcinogeny farmakokinetika   MeSH
• krysa rodu Rattus MeSH
• kyseliny aristolochové farmakokinetika   MeSH
• lidé MeSH
• metylace MeSH
• myši inbrední C57BL MeSH
• myši knockoutované MeSH
• myši MeSH
• NADPH-cytochrom c-reduktasa genetika   metabolismus   MeSH
• spektrometrie hmotnostní - ionizace laserem za účasti matrice MeSH
• vysokoúčinná kapalinová chromatografie MeSH
• zvířata MeSH
• Check Tag
• krysa rodu Rattus MeSH
• lidé MeSH
• myši MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• adukty DNA MeSH
• aristolochic acid I MeSH Prohlížeč
• cytochrom P-450 CYP1A1 MeSH
• cytochrom P-450 CYP1A2 MeSH
• karcinogeny MeSH
• kyseliny aristolochové MeSH
• NADPH-cytochrom c-reduktasa MeSH

The roles of autophagic cell death and apoptosis induced by topoisomerase inhibitor irinotecan in colon cancer cells with deleted p53 were investigated during 48 h. We report that irinotecan-dependent cytotoxicity and proapoptotic activity were reduced in the present model while autophagy levels significantly increased. Upon p53 transfection, cell demise rates increased, with cells bearing the features of apoptosis and autophagic cell death. The subsequent studies into mechanisms of cell death process revealed the important role of Bax in mediating mitochondrial and lysosomal leakage which might serve as leading signals for both apoptosis and autophagic cell death. These results suggest that different modes of cell death in p53 null colon cancer cells treated with cytostatics (irinotecan) may be activated simultaneously. Moreover, their interactions possibly occur at several stages and aren't mutually exclusive. This might thus lead to a potential synergism with interesting therapeutic ramifications.

• MeSH
• apoptóza účinky léků   fyziologie   MeSH
• autofagie účinky léků   fyziologie   MeSH
• buňky HT-29 MeSH
• fytogenní protinádorové látky farmakologie   terapeutické užití   MeSH
• HCT116 buňky MeSH
• irinotekan MeSH
• kamptothecin analogy a deriváty   farmakologie   terapeutické užití   MeSH
• lidé MeSH
• nádorové buněčné linie MeSH
• nádorový supresorový protein p53 nedostatek   genetika   MeSH
• nádory tračníku farmakoterapie   genetika   metabolismus   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• fytogenní protinádorové látky MeSH
• irinotekan MeSH
• kamptothecin MeSH
• nádorový supresorový protein p53 MeSH