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During the Pleistocene in the northern part of Europe and Asia, the presence of ice sheets not only limited the range of species but also influenced landscape and thus the contemporary habitat system that determines the pattern of biodiversity. The aim of the research was to find out whether and how a lowland landscape, which formed as a result of subsequent Pleistocene glaciations (five) that in Eurasia covered various and generally successively smaller areas, affected the genetic differentiation of a species. The research was carried out in eastern Poland on the root vole Microtus oeconomus (Arvicolinae, Rodentia), a model boreal and hygrophilous species. Samples were collected from 549 vole individuals at 33 locations. Based on the analysis of 12 microsatellite loci and the 908 bp of cytochrome b sequences (mitochondrial DNA), the genetic structure of M. oeconomus in the landscape zones of the Polish Lowlands was determined. The results show that the latitudinal variability of the relief in eastern Poland (resulting from different ranges of Pleistocene ice sheets) and the related specific configuration of hydrogenic habitats are reflected in the genetic differentiation of the root vole. Therefore, it may be concluded that the history of landscape development affects the genetic structure of hydrophilic species.
Mollusc seashells grow through the local deposition and calcification of material at the shell opening by a soft and thin organ called the mantle. Through this process, a huge variety of shell structures are formed. Previous models have shown that these structural patterns can largely be understood by examining the mechanical interaction between the deformable mantle and the rigid shell aperture to which it adheres. In this paper we extend this modelling framework in two distinct directions. For one, we incorporate a mechanical feedback in the growth of the mollusc. Second, we develop an initial framework to couple the two primary and orthogonal modes of pattern formation in shells, which are termed antimarginal and commarginal ornamentation. In both cases we examine the change in shell morphology that occurs due to the different mechanical influences and evaluate the hypotheses in light of the fossil record.
City road networks have been extensively studied for their social significance or to quantify their connections and centralities, but often their geographical origin is forgotten. This work focuses on the spatial-geographical and geometrical aspects of the road network skeleton. Following previous work, a multi-scale object, the way, is constructed, based only on the local geometry at road crossings. The best method to reconstruct significant elements is investigated. The results show that this object is geographically meaningful, with many particular characteristics. A new indicator, structurality, is introduced and compared with previous indicators, on the cities of Paris and Avignon. Structurality appears to be stable over the borders of the map sample, and is able to reveal the underlying coherence of the road network. This stability can be interpreted as coming from the particular way the network developed in time, and was later preserved. This link with the historical development of the cites, which deserves to be further studied, is exemplified in the cases of Villers-sur-Mer (France) and Manaus (Brazil). The construction method, the results, and their potential meaning are discussed in detail so that they can be used in various related disciplines, such as sociology, town planning, geomatics, and physics.
The presence of permafrost in Poland north of the line indicating the maximum ice extent of the Vistulian (Weichselian) glaciation after retreat of the land-ice cap has been a subject of debate for a long time. Investigations in an area at the line of the maximum ice extent of the Pomeranian phase prove that permafrost existed, indeed, after the ice retreat. This conclusion is drawn on the basis of morphological data (the presence of oriented kettle holes), sedimentological data (the nature of the infilling of the kettle holes) and pedological data (permafrost-affected horizons in soil profiles). It appears that the permafrost mostly developed in the ice-free zone that appeared after the retreat of the land-ice cap, but it is likely that some relict permafrost that had originated earlier in front of advancing ice was also still present. The landscape of northern Poland owes its relief partly to the Late Glacial permafrost.
The morphogenesis and morphology of the marine benthic ciliate Certesia quadrinucleata collected from seawater in Nagasaki Mie Port, Japan, were investigated using microscopic observation of live and protargol-stained specimens. In terms of its morphology, the current isolate possesses diagnostic features of the genus and the species: a row of left marginal cirri, a prominent paroral membrane, 11 frontoventral cirri scattered in frontoventral area, five highly developed transverse cirri, four macronuclear nodules, five dorsal kineties and a caudally located contractile vacuole. Its morphogenesis belongs to the ‘Certesia’ subtype, and main events can be summarized as follow: (1) the oral primordium in the opisthe develops de novo in a subcortical pouch; (2) the old paroral membrane is completely replaced by the new one in the proter, but the parental adoral zone of membranelles is wholly inherited; (3) five streaks of cirral anlagen are formed in a primary mode for the proter and the opisthe, which gives rise to cirri in the pattern of 3:3:3:3:3 from left to right; (4) the leftmost frontoventral cirrus develops de novo on the cell surface in both dividers, and has no connection with the undulating membrane anlage; and (5) the anlagen for marginal cirri and dorsal kineties occur intrakinetally. Current observations confirm the separation of Certesiidae from other euplotids at the familial level.
Osteohistological characteristics of the large temnospondyl amphibian Metoposaurus diagnosticus from the Upper Triassic of Poland (Krasiejów locality) were determined using vertebral intercentra thin-sections from different regions and growth stages. The intercentra showed a trabecular structure in both the endochondral and periosteal domains. Endochondral ossification developed first, and the primary bone occurs near the periphery with a higher degree of remodelling in the centre. Periosteal bone deposition begins later; first on the ventral side, continuing laterally and finally onto the dorsal side. Periosteal growth rate was initially very rapid, and then subsequently decreased in rate. In all sections, numerous remains of calcified cartilage are visible, which may indicate a juvenile, paedomorphic or plesiomorphic character. The four histologic ontogenetic stages (HOS) of sampled vertebrae were determined based on growth marks. Most of the sampled bones belong to juvenile individuals (HOS 1 to 3), apart from one atlas and the largest anterior dorsal intercentrum, which represent the oldest described stage (HOS 4). Sharpey's fibres are preserved in ventro-lateral cortical regions, around parapophyses and on the posterior side of the neural arch.
Plants and animals have highly ordered structure both in time and in space, and one of the main questions of modern developmental biology is the transformation of genetic information into the regular structure of organism. Any multicellular plant begins its development from the universal unicellular state and acquire own species-specific structure in the course of cell divisions, cell growth and death, according to own developmental program. However the cellular mechanisms of plant development are still unknown. The aim of this work was to elaborate and verify the formalistic approach, which would allow to describe and analyze the large data of cellular architecture obtained from the real plants and to reveal the cellular mechanisms of their morphogenesis. Two multicellular embryos of Calla palustris L. (Araceae) was used as a model for the verification of our approach. The cellular architecture of the embryos was reconstructed from the stack of optical and serial sections in three dimensions and described as graphs of genealogy and space adjacency of cells. In result of the comparative analysis of these graphs, a set of regular cell types and highly conservative pattern of cell divisions during five cell generations were found. This mechanism of cellular development of the embryos could be considered as a developmental program, set of rules or grammars applied to the zygote. Also during the comparative analysis the finite plasticity in cell adjacency was described. The structural equivalence and the same morphogenetic potencies of some cells of the embryos were considered as the space-temporal symmetries. The symmetries were represented as a set of regular cell type permutations in the program of development of the embryo cellular architecture. Two groups of cell type permutations were revealed, each was composed of two elements and could be interpreted as the mirror and rotational space symmetries. The results obtained as well as the developed approach can be used in plant tissue modelling based on the real, large and complex structural data.
The anatomy of the human and other vertebrates has been well described since the days of Leonardo da Vinci and Vesalius. The causative origin of the configuration of the bones and of their shapes and forms has been addressed over the ensuing centuries by such outstanding investigators as Goethe, Von Baer, Gegenbauer, Wilhelm His and D'Arcy Thompson, who sought to apply mechanical principles to morphogenesis. However, no coherent causative model of morphogenesis has ever been presented.
This paper presents a causative model for the origin of the vertebrate skeleton, based on the premise that the body is a mosaic enlargement of self-organized patterns engrained in the membrane of the egg cell. Drawings illustrate the proposed hypothetical origin of membrane patterning and the changes in the hydrostatic equilibrium of the cytoplasm that cause topographical deformations resulting in the vertebrate body form.
Cell-based, mathematical models help
make sense of morphogenesis—i.e. cells organizing into
shape and pattern—by capturing cell behavior in simple, purely
descriptive models. Cell-based models then predict the
tissue-level patterns the cells produce collectively. The first
step in a cell-based modeling approach is to isolate
sub-processes, e.g. the patterning capabilities of one or a
few cell types in cell cultures. Cell-based models can then
identify the mechanisms responsible for patterning in vitro.
This review discusses two cell culture models of morphogenesis
that have been studied using this combined
experimental-mathematical approach: chondrogenesis (cartilage
patterning) and vasculogenesis (de novo blood vessel growth). In
both these systems, radically different models can equally
plausibly explain the in vitro patterns. Quantitative
descriptions of cell behavior would help choose between
alternative models. We will briefly review the experimental
methodology (microfluidics technology and traction force
microscopy) used to measure responses of individual cells to their
micro-environment, including chemical gradients, physical forces
and neighboring cells. We conclude by discussing how to include
quantitative cell descriptions into a cell-based model: the
Cellular Potts model.
Modular organization of colonial hydroids is based on cyclic morphogenesis during growth of their body. In many thecate hydroids (Hydrozoa: Leptomedusae) the shoots of the colony consist of a few distinct elements and possess complex spatial organization. In most cases, the evolutionary sequence of morphogenetic modifications that led to present-day organization of shoots is obscure and not obvious. One of the approaches that allow getting insight into the morphogenetic evolution in colonial thecate hydroids is to analyse the spectrum of different minor morphotypes presented in the population of the certain species. In our opinion, some rare morphotypes allow understanding and reconstructing the scenario of morphogenetic evolution of species under consideration. We describe the application of such an approach for reconstruction of the morphogenetic evolution of Dynamena pumila (L.) (Sertulariidae) with some additional conclusions.
The stomatogenesis and morphology of the marine planktonic ciliate Philasterides armatalis collected from mollusc-culturing waters off the coast of Qingdao, China, were studied using a differential interference contrast microscope for observations in vivo and protargol impregnation. In terms of its infraciliature, this species possesses typical characteristics of the genus Philasterides: bipartite paroral membrane, the anterior part double-rowed and the posterior part in a zig-zag-formation, and three well-defined membranelles arranged in Paranophrys-pattern. This investigation confirms the dual origin of the buccal apparatus in the opisthe, one derived from the scutica and the other from the paroral membrane. Its stomatogenesis belongs to the ‘Philasterides’ sub-type, although it differs from its only congener P. armata, in that paroral membrane 1 gives rise to the paroral membrane and the scutica in the proter, and paroral membrane 2 forms the paroral membrane, membranelles 1 and 2 and the scutica in the opisthe. Based on stomatogenetic data, the phylogenetic positions of several genera in the suborder Philasterina are reconsidered.
The effect of the feeding period on larval development was investigated in European sea bass larvae by considering the expression level of some genes involved in morphogenesis. Larvae were fed a control diet except during three different periods (period A: from 8 to 13d post-hatching (dph); period B: from 13 to 18dph; period C: from 18 to 23dph) with two compound diets containing high levels of vitamin A or PUFA. European sea bass morphogenesis was affected by these two dietary nutrients during the early stages of development. The genes involved in morphogenesis could be modulated between 8 and 13dph, and our results indicated that retinoids and fatty acids influenced two different molecular pathways that in turn implicated two different gene cascades, resulting in two different kinds of malformation. Hypervitaminosis A delayed development, reducing the number of vertebral segments and disturbing bone formation in the cephalic region. These malformations were correlated to an upregulation of retinoic acid receptor γ, retinoid X receptor (RXR) α and bone morphogenetic protein (BMP)4. An excess of PUFA accelerated the osteoblast differentiation process through the upregulation of RXRα and BMP4, leading to a supernumerary vertebra. These results suggest that the composition of diets devoted to marine fish larvae has a particularly determining effect before 13dph on the subsequent development of larvae and juvenile fish.
At least four cell types in mouse mammary epithelium, three in human, and three in cow are now known to be proliferation competent. Some evidence indicates that pregnancy may confer proliferative competency on a new cell type. These cells are widely seen as stem and progenitor cells that maintain the epithelium and produce lactational units during pregnancy. Evolutionarily conserved developmental signaling pathways active in germinal and neuronal stem cell proliferation and differentiation in drosophila and mammalian development are implicated in mammary tumorigenesis. In adult tissues this signaling is retained, is regulated by stem cell niches and operates to create new tissue and maintain tissue form and integrity. Disruption of this signaling may abrogate maintenance of the stem cell niche and lead to preneoplastic conditions.
The development of isidia in thalli of Pseudevernia furfuracea from the Carnic Alps (North-eastern Italy), and the effects of these structures on CO2 gas exchanges were investigated. The ontogenetic events were studied by comparison of sections stained with different histochemical tests and SEM observations. A high cell turnover rate in both symbiotic partners is the first sign of isidium development, followed by an increased aplanosporogenesis of algae and growth of neighbouring medullary hyphae which become oriented upwards. Large nuclei and an intense cytoplasm activity characterize the mycobiont cells. The surface of very young isidia shows an irregular structure of spherical to ovoid protruding tips of perpendicular cortical hyphae, that are later organised in a pseudomeristematic area similar to that observed in the apex of growing lobes. CO2 gas exchange measurements carried out in the laboratory confirmed the high metabolic activity of isidia. At optimal water content and favourable light conditions, isolated isidia had rates of gross photosynthesis and dark respiration that were twice those of non-isidiate lobes. Isolated isidia also had a very low CO2 saturation point, probably because of their favourable surface/volume ratio, and a high light saturation, probably linked to their high content of photosynthetic pigments. The different roles played by isidia in the biology of Pseudevernia furfuracea, and particularly their rejuvenating effect on aged lobes, are discussed, and the presence of thalloconidia is briefly mentioned.
The cell lineage heterogeneity is an essential component of early morphogenesis and is associated with the maintenance of developmental potential for the embryo. The mammalian embryo has long been considered to exhibit remarkable regulative capacity, presumably reflecting a plasticity in developmental potential to combat different environmental conditions. Cell contact patterns between blastomeres have a major influence on this dynamic state. While compaction and epithelial cell polarisation at the 8-cell stage is mediated by cell adhesion, contact patterns remain effective in steering developmental pathways throughout the cleavage period. The capacity to recavitate and re-form trophectoderm-like outer cells is progressively lost when inner cell masses (ICMs) are isolated from older, more expanded blastocysts which then form predominantly primary endoderm-like structures. The cell contact pattern, either asymmetric or symmetric, maintaining trophectoderm and ICM lineage pathways respectively, acts upstream of signal transduction mechanisms regulating phenotypic status.
Most nematode-trapping fungi are dependent on specific hyphal structures on or in which nematodes can be trapped mechanically or by adhesion. These structures are a prerequisite for the ability of the fungus to invade a host and are thus crucial for survival as well as virulence. The diversity of trapping structures is large and highly dependent on the environment of the fungus. Within one single species, Arthrobotrys oligospora, not only adhesive nets are formed but also so-called conidial traps, hyphal coils around hyphae of other fungi, and appressoria in the rhizosphere of agricultural crops. In this article these structures and the conditions for their development are described. Since the trapping structures influence the survival and the virulence of their producer, it is important that we know more about the molecular background of their development and function. The application of genomics to understand the function and the development of infection structures, therefore, has substantially increased the potential of A. oligospora to become a model system for fungal morphogenesis.
The development of the male duct and spermatheca is studied in three species of the marine Limnodriloidinae (Tubificidae): Limnodriloides rubicundus; Tectidrilus bori; Thalassodrilides ineri. All tubificids are hermaphroditic with paired male ducts, female ducts and, as a rule, spermathecae. The male duct comprises a funnel, followed by a vas deferens, an atrium and, frequently, a copulatory structure. There may also be a diffuse or compact prostate gland in association with the male duct. In the three species studied, the funnel and vas deferens originate from peritoneal (mesodermal) cells in the posterior septa of the testes segment. The atrium develops from an invagination of the epidermis (ectoderm). The vas deferens and atrium subsequently connect to each other, and a continuous duct from the testes segment to the exterior is formed. The prostate gland originates from large peritoneal cells occurring in a delimited area on the outer surface of the atrium; other small peritoneal cells surrounding the whole atrium give rise to muscle fibres. The spermatheca develops from an invagination of the epidermis, and is thus of ectodermal origin. The morphology and position of the genital ducts have been and are important for the classification of the oligochaetes. However, different parts of the male duct have been named without regard to whether they are homologous or not. One way to establish stronger primary hypotheses of homology is to study the detailed morphology and/or the development of the genital ducts.
The aim of this present study was to identify the earliest point at which riboflavin deficiency affects post-weaning bowel development in rats. After weaning, eighty Wistar rats were weight-matched as pairs, one animal being fed a normal synthetic diet and the other being fed the same diet but deficient in riboflavin. Body weight, feeding and rates of growth were monitored and eight pairs of animals were taken for analysis at 45, 69, 93, 117 and 141 h. Riboflavin status was monitored by determining the erythrocyte glutathione reductase activation coefficient (EGRAC), and hepatic flavins were measured by a fluorescence assay. Changes to the number and dimensions of villi and crypts in the duodenum were determined, as well as crypt division (bifurcation) and the DNA synthesis index of the crypt epithelium by bromodeoxyuridine (BrdU) labelling. Riboflavin deficiency was established in the experimental rats, as demonstrated by a significant increase in EGRAC after 45 h (P<0·001) and decreased liver flavins after 96 h (P<0·001). After 96 h a significant increase in the size and cellularity of the crypts (P<0·001 in both cases) was seen in these riboflavin-deficient animals, with a decreased incidence of bifurcating crypts and of BrdU-labelled cells. No changes to villus number or size were observed. The present study has demonstrated that developmental changes to the duodenal crypt arise shortly after circulating riboflavin measurements show evidence of deficiency. These changes primarily affect cell proliferation and crypt bifurcation, and precede long-term changes such as the reduction of villus number.
Objective: Using a newly acquired archive of previously prepared material, we sought to re-examine the origin of the pulmonary vein in the human heart, aiming to determine whether it originates from the systemic venous sinus (“sinus venosus”), or appears as a new structure draining to the left atrium. In addition, we examined the temporal sequence of incorporation of the initially solitary pulmonary vein to the stage at which four venous orifices opened to the left atrium. Methods: We studied 26 normal human embryos, ranging from 3.8 mm to 112 mm crown-rump length, and representing the period from the 12th Carnegie stage to 15 weeks of gestation. Results: The pulmonary vein canalised as a solitary vessel within the mediastinal tissues so as to connect the intraparenchymal pulmonary venous networks to the heart, using the regressing dorsal mesocardium as its portal of cardiac entry. The vein was always distinct from the tributaries of the embryonic systemic venous sinus. The orifice of the solitary vein became committed to the left atrium by growth of the vestibular spine. During development, a marked disparity was seen between the temporal and morphological patterns of incorporation of the left-sided and right-sided veins into the left atrium. The pattern of the primary bifurcation was asymmetrical, a much longer tributary being formed on the left than on the right. Contact between the atrial wall and the venous tributary on the left initially produced a shelf, which became effaced with incorporation of the two left-sided veins into the atrium. Conclusions: The initial process of formation of the human pulmonary vein is very similar to that seen in animal models. The walls of the initially solitary vein in humans become incorporated by a morphologically asymmetric process so that four pulmonary veins eventually drain independently into the left atrium. Failure of incorporation on the left side may provide the substrate for congenital division of the left atrium.