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Results for “Spatial pattern formation”

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At least 775 records · Page 43Linked to original sources

PubMed2000

The role of pyruvate dehydrogenase and acetyl-coenzyme A synthetase in fatty acid synthesis in developing Arabidopsis seeds.

Acetyl-coenzyme A (acetyl-CoA) formed within the plastid is the precursor for the biosynthesis of fatty acids and, through them, a range of important biomolecules. The source of acetyl-CoA in the plastid is not known, but two enzymes are thought to be involved: acetyl-CoA synthetase and plastidic pyruvate dehydrogenase. To determine the importance of these two enzymes in synthesizing acetyl-CoA during lipid accumulation in developing Arabidopsis seeds, we isolated cDNA clones for acetyl-CoA synthetase and for the ptE1alpha- and ptE1beta-subunits of plastidic pyruvate dehydrogenase. To our knowledge, this is the first reported acetyl-CoA synthetase sequence from a plant source. The Arabidopsis acetyl-CoA synthetase preprotein has a calculated mass of 76,678 D, an apparent plastid targeting sequence, and the mature protein is a monomer of 70 to 72 kD. During silique development, the spatial and temporal patterns of the ptE1beta mRNA level are very similar to those of the mRNAs for the plastidic heteromeric acetyl-CoA carboxylase subunits. The pattern of ptE1beta mRNA accumulation strongly correlates with the formation of lipid within the developing embryo. In contrast, the level of mRNA for acetyl-CoA synthetase does not correlate in time and space with lipid accumulation. The highest level of accumulation of the mRNA for acetyl-CoA synthetase during silique development is within the funiculus. These mRNA data suggest a predominant role for plastidic pyruvate dehydrogenase in acetyl-CoA formation during lipid synthesis in seeds.

Acetate-CoA Ligase↗

PubMed2005

Genomic characterisation of a Fgf-regulated gradient-based neocortical protomap.

Recent findings support a model for neocortical area formation in which neocortical progenitor cells become patterned by extracellular signals to generate a protomap of progenitor cell areas that in turn generate area-specific neurons. The protomap is thought to be underpinned by spatial differences in progenitor cell identity that are reflected at the transcriptional level. We systematically investigated the nature and composition of the protomap by genomic analyses of spatial and temporal neocortical progenitor cell gene expression. We did not find gene expression evidence for progenitor cell organisation into domains or compartments, instead finding rostrocaudal gradients of gene expression across the entire neocortex. Given the role of Fgf signalling in rostrocaudal neocortical patterning, we carried out an in vivo global analysis of cortical gene expression in Fgfr1 mutant mice, identifying consistent alterations in the expression of candidate protomap elements. One such gene, Mest, was predicted by those studies to be a direct target of Fgf8 signalling and to be involved in setting up, rather than implementing, the progenitor cell protomap. In support of this, we confirmed Mest as a direct transcriptional target of Fgf8-regulated signalling in vitro. Functional studies demonstrated that this gene has a role in establishing patterned gene expression in the developing neocortex, potentially by acting as a negative regulator of the Fgf8-controlled patterning system.

Animals↗

PubMed1993

Spatial memory in alcohol-dependent subjects: using a push-button maze to test the principle of equiavailability.

The principle of equiavailability states that once the locations in a spatial array are learned, then all locations in the array are simultaneously available in memory (Levine, Jankovic, & Palij, 1982). To test the application of this principle, 21 nonamnesic, alcohol-dependent, male subjects and 20 demographic and ability-matched male control subjects were required to learn a series of push-button maze paths and to perform shortcut or retrace movements on the paths. The results for the control subjects conformed to the principle of equiavailability. In contrast, the alcohol-dependent subjects did not show equiavailability. This pattern of results is interpreted as evidence of a spatial memory deficit in the alcohol-dependent subjects.

Adult↗

PubMed2002

Modeling pattern formation: counting to two in the Drosophila egg.

The EGF receptor pathway patterns the Drosophila egg and specifies the position of its dorsal appendages. A new mathematical analysis of this patterning network has highlighted its crucial features and provided novel insights into the spatial and temporal kinetics controlling patterning.

Animals↗

PubMed2004

Formation and function of the polar body contractile ring in Spisula.

Initial studies suggested that spatial organization of the putative polar body contractile ring was determined by the peripheral aster in Spisula [Biol. Bull. 205 (2003) 192]. Here we report detailed supporting observations, including testing of aster and ring function with inhibitors. The metaphase peripheral aster was confirmed to spread cortically in an umbrella-like pattern, with microtubule-poor center. The aster disassembled during anaphase, leaving the spindle docked at the F-actin-poor center of a newly generated cortical F-actin ring that closely approximated the aster in location, measured diameter range, and pattern. Cytochalasin D and latrunculin-B permitted all events except ring and polar body formation. Nocodazole disassembly or taxol stabilization of the peripheral aster produced poorly defined rings or bulging anaphase asters within the ring center, respectively, inhibiting polar body formation. Polar body extrusion occurred at the ring center, the diameter of which diminished. Ring contractility-previously assumed-was verified using blebbistatin, a myosin-II ATPase inhibitor that permitted ring assembly but blocked polar body extrusion. The data support the hypothesis that peripheral aster spreading, perhaps dynein-driven, is causally related to polar body contractile ring formation, with anaphase entry and aster disassembly also required for polar body biogenesis. Previously reported astral spreading during embryonic micromere formation suggests that related mechanisms are involved in asymmetric somatic cytokinesis.

Actins↗

PubMed1999

Cell cycling and cell enlargement in developing leaves of Arabidopsis.

Cell cycling plays an important role in plant development, including: (1) organ morphogenesis, (2) cell proliferation within tissues, and (3) cell differentiation. In this study we use a cyclin::beta-glucuronidase reporter construct to characterize spatial and temporal patterns of cell cycling at each of these levels during wild-type development in the model genetic organism Arabidopsis thaliana (Columbia). We show that a key morphogenetic event in leaf development, blade formation, is highly correlated with localized cell cycling at the primordium margin. However, tissue layers are established by a more diffuse distribution of cycling cells that does not directly involve the marginal zone. During leaf expansion, tissue proliferation shows a strong longitudinal gradient, with basiplastic polarity. Tissue layers differ in pattern of proliferative cell divisions: cell cycling of palisade mesophyll precursors is prolonged in comparison to that of pavement cells of the adjacent epidermal layers, and cells exit the cycle at different characteristic sizes. Cell divisions directly related to formation of stomates and of vascular tissue from their respective precursors occur throughout the period of leaf extension, so that differing tissue patterns reflect superposition of cycling related to cell differentiation on more general tissue proliferation. Our results indicate that cell cycling related to leaf morphogenesis, tissue-specific patterns of cell proliferation, and cell differentiation occurs concurrently during leaf development and suggest that unique regulatory pathways may operate at each level.

Arabidopsis↗

PubMed2003

Embryonic origins of the two main classes of hemocytes--granular cells and plasmatocytes--in Manduca sexta.

Cell-mediated responses of the moth immune system involve the interaction of two main classes of hemocytes-granular cells and plasmatocytes. During embryogenesis, granular cells arise much earlier than plasmatocytes, and the presence of granular cells is closely coupled with the formation of basal laminae that line the hemocoel occupied by hemocytes. Although epithelial cells contribute the large extracellular matrix protein lacunin to embryonic matrices before granular cells begin contributing this protein to basal laminae, the spatial pattern of lacunin expression in early embryos parallels the later distribution of granular cells over surfaces of basal laminae. Plasmatocytes arise late in embryogenesis, after the cessation of the major morphogenetic movements and the establishment of intact basal laminae. Granular cells are intimately involved with remodeling of basal laminae, and disruptions in the structure of basal laminae can trigger an autoimmune response of granular cells and plasmatocytes. By arising after basal laminae have been molded and remodeled by granular cells, plasmatocytes presumably do not encounter the cues that trigger their aggregation and an autoimmune response.

Animals↗

PubMed2003

Spatial and temporal contribution of somitic myoblasts to avian hind limb muscles.

Skeletal muscles of the avian limb are derived from mononucleated myogenic precursor cells (myoblasts) that migrate into the somatopleural mesoderm of the developing limb bud from the ventrolateral dermomyotome of limb adjacent somites. In the present study, we utilized replication-deficient lacZ-encoding retroviruses to elucidate the source of myoblasts for all hind limb muscles in the chick and define the distinct patterns of myoblast distribution within the limb. We also examined, using the same marker, whether the time of migration from the somites into the limb dictates the spatial contribution the myoblasts make to the developing musculature, particularly in relation to the proximodistal and dorsovental axes. Finally, we used these investigations to examine whether the precursors of both primary and secondary myotubes are derived from somitic mesoderm, a presumption, which up until now, has not been demonstrated in vivo. Overall, the results of our studies demonstrate that individual somites have a selective spatial pattern of participation in the development of the avian hind limb musculature and contribute to both primary and secondary myotubes. We also show that both early and later migrating myoblasts can contribute fully to the formation of the appendicular muscles.

Animals↗

PubMed1987

Adult age differences in integrative spatial ability.

Young and older adults were contrasted in three experiments that involved manipulation of the number of required spatial integration operations (Experiments 1 and 2) and manipulation of the amount of information per operation (Experiment 3). Older adults performed at lower levels of accuracy than did young adults in each experiment. However, the magnitude of the age differences tended to increase with each successive integration operation but was constant across different quantities of relevant information. I interpreted these results as suggesting that one factor responsible for age differences in tests of spatial ability is an age-related reduction in the efficiency of executing operations responsible for the accurate and stable representation of spatial information.

Adolescent↗

PubMed2001

Circuit mechanisms underlying memory encoding and retrieval in the long axis of the hippocampal formation.

Circuits within the hippocampal formation are active during memory processing. Here we used functional magnetic resonance imaging (fMRI) to examine multiple sites across the long axis of the hippocampal formation while subjects performed different phases of an associative memory task, learning to associate faces with names. Viewing faces and hearing names in isolation resulted in separate hippocampal activation patterns. Pairing faces with names resulted a spatially redistributed activation pattern, rather than a simple summation of the activation patterns resulting from viewing faces and hearing names in isolation. Recalling names when cued with faces reactivated a pattern similar to that found during paired training. Finally, the activation patterns representing faces and names were found to be experience dependent, emerging with repeated exposure. Interpreted in the context of hippocampal anatomy and physiology, these findings reveal hippocampal circuit mechanisms that underlie memory encoding and retrieval.

Adult↗

PubMed1981

Strategies for control of pattern formation in Caenorhabditis elegans.

In this paper, strategies for controlling pattern formation in Caenorhabditis elegans are reviewed. The somatic tissues of this small nematode develop, in large part, by invariant cell lineages, whereas the germ-line tissue arises primarily by a variable pattern of divisions. The spatial organization of the germ-line tissue depends on special regulatory cells, the distal tip cells, which appear to influence nearby germ cells to remain in mitosis. In somatic tissues, the problem of specifying that a cell in a particular position assumes a particular fate seems to be controlled by a number of different strategies. These include the production of non-equivalent cells in particular positions of the lineage tree, local interactions between apparently equivalent cells in close contact, and the influence of another special regulatory cell, the anchor cell, over certain neighbouring cells.

Animals↗

PubMed2004

Coarsening in the buoyancy-driven instability of a reaction-diffusion front.

When propagating in a vertical direction an autocatalytic reaction front associated with a change in density can become buoyantly unstable, leading to the formation of a fingerlike pattern. Later on these fingers start to interact. Their temporal evolution is studied experimentally by tracking the horizontal and vertical locations of the extrema of the front pattern. A proceeding development towards larger spatial scales is found. This is reflected in the differences in the vertical speed of neighboring fingers: continually some fingers start to decelerate and vanish finally in the neighboring ones which show a simultaneous acceleration. In addition, weak lateral movements of fingers towards gaps are observed, but there is no evidence for a correlation with the extinction of fingers.

Journal Article↗

PubMed2003

Cell aggregation precedes the onset of Sox9-expressing preSertoli cells in the genital ridge of mouse.

SOX9 is expressed at the onset of the genital ridge formation in both sexes. It is assumed that SRY, the testis determining gene, turns SOX9 on in male embryos because it is turned off in female embryos. Spatial expression of SRY follows a cranio-caudal pattern. Here, we asked if SOX9 is expressed in the same cell lineage and with a similar pattern as SRY. A correlative study between the structural changes in the genital ridge and the immunocytochemical localization of SOX9-positive cells was undertaken. We used a transgenic strain expressing the green fluorescent protein (GFP) that considerably enhanced the cell context where the first SOX9-positive cells appear. Although SOX9-positive cells are located among loose mesenchymal cells by stages of 8-14 tail somites (ts) in both sexes, they are absent in the thickening coelomic epithelium of females. At 15 ts the first SOX9-positive cells appear within the core of the condensed cells only in male genital ridges. At 17 ts, a gradient of SOX9-positive cells in males is apparent, closely following the cranio-caudal pattern of cell aggregation seen in genital ridges of both sexes. Hence, our results suggest that SOX9 is expressed only in loose mesenchymal cells in both sexes and that expression of SOX9 in males requires the prior aggregation of cells in the genital ridges. The correspondence of SOX9 and SRY pattern of expression supports that both genes are expressed in the preSertoli cell lineage in the core of the genital ridges.

Animals↗

PubMed2003

Temperature and the expression of seven muscle-specific protein genes during embryogenesis in the Atlantic cod Gadus morhua L.

Seven cDNA clones coding for different muscle-specific proteins (MSPs) were isolated from the fast muscle tissue of Atlantic cod Gadus morhua L. In situ hybridization using cRNA probes was used to characterize the temporal and spatial patterns of gene expression with respect to somite stage in embryos incubated at 4 degrees C, 7 degrees C and 10 degrees C. MyoD transcripts were first observed in the presomitic mesoderm prior to somite formation, and in the lateral compartment of the forming somites. MyoD expression was not observed in the adaxial cells that give rise to the slow muscle layer, and expression was undetectable by in situ hybridization in the lateral somitic mesoderm after the 35-somite stage, during development of the final approximately 15 somites. RT-PCR analysis, however, confirmed the presence of low levels of the transcript during these later stages. A phylogenetic comparison of the deduced aminoacid sequences of the full-length MyoD cDNA clone and those from other teleosts, and inference from the in situ expression pattern suggested homology with a second paralogue (MyoD2) recently isolated from the gilthead seabream Sparus aurata. Following MyoD expression, alpha-actin was the first structural gene to be switched on at the 16-somite stage, followed by myosin heavy chain, troponin T, troponin I and muscle creatine kinase. The final mRNA in the series to be expressed was troponin C. All genes were switched on prior to myofibril assembly. The troponin C sequence was unusual in that it showed the greatest sequence identity with the rainbow trout Oncorhynchus mykiss cardiac/slow form, but was expressed in the fast myotomal muscle and not in the heart. In addition, the third TnC calcium binding site showed a lower level of sequence conservation than the rest of the sequence. No differences were seen in the timing of appearance or rate of posterior progression (relative to somite stage) of any MSP transcripts between embryos raised at the different temperatures. It was concluded that myofibrillar genes are activated asynchronously in a distinct temporal order prior to myofibrillar assembly and that this process was highly canalized over the temperature range studied.

Actins↗

PubMed1998

Immunohistochemistry and in situ hybridization investigation of transforming growth factor-beta: during odontoblast and ameloblast differentiation.

OBJECTIVE: The purpose of this study was to investigate the expression of transforming growth factor-beta, TGF-beta 1 during odontoblast and ameloblast differentiation. METHODS: The analysis was made on 5-micron serial sections of the glutaraldehyde-fixed and paraffin-embedded mandibular first and second molars of a neonatal mouse. A specific and affinity-purified antibody to TGF-beta 1 and a digoxigenin-labeled cRNA probe were used. RESULTS: The results showed that the TGF-beta 1 was expressed in a spatial and temporal pattern in dental tissues. The immunoreactivity of dental tissues for TGF-beta 1 was consistent with the expression of TGF-beta 1 mRNA revealed by in situ hybridization before dentin matrix formation. The TGF-beta 1 was evenly expressed in dental papilla and inner enamel epithelium. The expression of TGF-beta 1 was increased in the layer of odontoblasts and ameloblasts and in the stratum intermedium with the formation of dentin matrix, where the staining was also observed. CONCLUSIONS: These findings suggest that TGF-beta 1 may have an important role in extracellular matrix formation and cytodifferentation.

Ameloblasts↗

PubMed1998

Errors of morphogenesis and developmental field theory.

Field theory provides a rational basis for birth defects terminology. During blastogenesis in higher metazoa, pattern formation in the primary field leads to the establishment of upstream expression domains of growth and transcription factors, which, in various permutations and at specific sites and times, lay down the pattern of progenitor fields. Further spatially coordinated, temporally synchronized, and epimorphically hierarchical morphogenetic events, mostly during organogenesis, lead to the attainment of final form in the secondary, epimorphic fields. Because of shared molecular determinants, spatial contiguity, and close timing of morphogenetic events during blastogenesis, most malformations arising during blastogenesis are polytopic, i.e., involving two or more progenitor fields, e.g., acrorenal, cardiomelic, gastromelic, or splenomelic anomalies. Defects of organogenesis tend to be monotopic malformations, e.g., cleft palate or postaxial polydactyly. We suggest that what were called "associations" (e.g., VATER, schisis) be designated primary polytopic developmental field defects, or simply polytopic field defects, and that the term "association" be reserved for the original definition of a statistical combination of anomalies (mostly of organogenesis) [Spranger et al. (1982): J Pediatr 100:160-165]. If genetically caused or predisposed, all structures involved in a polytopic or monotopic malformation are genetically abnormal, whereas the parts secondarily affected as a consequence of a malformation sequence (e.g., spina bifida) are genetically normal. Polytopic field anomalies, per se, must be distinguished from pleiotropy, although such anomalies may constitute a part of pleiotropy (e.g., in trisomy 18). Because they are downstream from pattern-forming events in the primary field, multiple anomalies of organogenesis more likely represent syndromal pleiotropy.

Congenital Abnormalities↗

PubMed1991

Selective perturbation of visual input during prehension movements. 2. The effects of changing object size.

1. Subjects were instructed to reach and grasp cylindrical objects, using a precision grip. The objects were two concentric dowels made of translucent material placed at 35 cm from the subject. The inner ("small") dowel was 10 cm high and 1.5 cm in diameter. The outer ("large") dowel was 6 cm high and 6 cm in diameter. Prehension movements were monitored using a Selspot system. The displacement of a marker placed at the wrist level was used as an index for the transport of the hand at the location of the object. Markers placed at the tips of the thumb and the index finger were used for measuring the size of aperture of the finger grip. 2. Kinematics of transport and grasp components were computed from the filtered displacement signals. Movement time (MT), time to peak velocity (TPV) and time to peak deceleration (TPD) of the wrist, time to peak velocity of grip aperture (TGV), time to maximum grip aperture (TGA) were the main parameters used for comparing the movements in different conditions. Spatial paths of the wrist, thumb and index markers were reconstructed in two dimensions. Variability of the spatial paths over repeated trials was computed as the surface of the ellipses defined by X and Y standard deviations from the mean path. 3. Computer controlled illumination of one of the dowels was the signal for reaching toward that dowel. Blocks of trials were made to the small dowel and to the large dowel. Mean MT during blocked trials was 550 ms. The acceleration phase of the movements (measured by parameter TPV) represented 33% of MT. About half of MT (52%) was spent after TPD in a low velocity phase while the hand was approaching the object. This kinematic pattern was not influenced by whether movements were directed at small or large dowels. 4. Grip aperture progressively increased during transport of the hand. TGA corresponded to about 60% of MT, that is, maximum grip aperture was reached during the low velocity phase of transport. Following TGA, fingers closed around the object until contact was made. This pattern of grip formation differed whether the movement was directed at the large or the small dowel: TGA occurred often earlier for the small dowel, and the size of the maximum grip aperture was larger for the large dowel. Variability of both the wrist and finger spatial paths was larger during the first half of MT, and tended to become very low as the hand approached the dowels.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗

PubMed1991

Neurodynamics with spatial self-organizations.

A neural network architecture with self-organization in phase and actual space is proposed and discussed. Special type of differential local interconnections simulating diffusion, dispersion, and convection were investigated. It is shown that these interconnections are responsible for biological pattern formation in a homogeneous neural structure. The model suggests a phenomenological explanation of the mechanisms of edge detection in vision process.

Models, Neurological↗