SEARCH · Search PubMed

Results for “spatial patterning”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 343 records · Page 19Linked to original sources

PubMed1993

Combinatorial interactions between positive and negative cis-acting elements control spatial patterns of 4CL-1 expression in transgenic tobacco.

The phenylpropanoid enzyme 4-coumarate:coenzyme A ligase (4CL) plays a key role in linking general phenylpropanoid metabolism to end-product specific biosynthetic pathways. During vascular system and floral organ differentiation, the parsley 4CL-1 gene is expressed in a restricted set of tissues and cell types where 4CL activity is required to supply precursors for the synthesis of diverse phenylpropanoid-derived products such as lignin and flavonoids. In order to localize cis-acting elements which specify complex patterns of 4CL-1 expression, we analyzed the expression of internally deleted promoter fragment-GUS fusions in tobacco plants and parsley protoplasts. Elements located between -244 and -78 were required for most aspects of developmentally regulated expression. Within this region, three separate promotor domains containing partially redundant cis-elements directed vascular-specific expression when combined with a TATA-proximal domain. A negative cis-acting element which represses phloem expression was revealed in one of the domains and appears to be responsible for restricting vascular expression to the xylem. Distinct but overlapping promoter domain combinations were required for expression in floral organs, suggesting that different combinations of cis-acting elements may direct expression in different organs. Gel retardation assays were used to demonstrate the formation of DNA-protein complexes between factors present in nuclear extracts of parsley tissue culture cells and various tobacco organs and a 4CL-1 promoter fragment. Competition experiments showed that complex formation required the presence of a 42 bp promoter domain shown to be critical for 4CL-1 expression in vascular and floral tissues. The results are discussed in light of the coordinate expression of 4CL and other phenylpropanoid genes.

Base Sequence↗

PubMed1994

Modeling spatial patterns in Dictyostelium.

The life cycle of Dictyostelium discoideum provides a striking example of the transition from single cell behavior to multicellular cooperativity. In this paper the status of the attempts at making semiquantitative models of the aggregation phase of this cycle is reviewed. Specifically, it is discussed how the propagation of cAMP waves is a typical example of excitable signaling, which is then rendered unstable by coupling to cell chemotaxis. To investigate the streaming pattern that emerges from this clumping instability, we next turn to a new simulation strategy, which couples dynamical cell-like entities ("bions") to continuum chemical concentration fields. Finally, we discuss two directions for further research: One is the study of the robustness with respect to the variation of system parameters (such as the cell density) exhibited by the biological system, but not by any simple model. The other concerns going beyond the aggregation phase to tackle the three-dimensional problem of slug formation and motion.

Journal Article↗

PubMed1992

Spatial pattern of cdc2 expression in relation to meristem activity and cell proliferation during plant development.

The p34 protein kinase encoded by the cdc2 gene is a key component of the eukaryotic cell cycle required for the G1- to S-phase transition and entry into mitosis. To study the regulation of plant meristem activity and cell proliferation, we have examined the tissue-specific accumulation of cdc2 transcripts in Arabidopsis thaliana and the related crucifer radish (Raphanus sativus) by in situ hybridization using A. thaliana cdc2 cDNA sequences as a probe. cdc2 transcripts accumulated in leaf primordia and within the vegetative shoot apical meristem. During flower development, high levels of expression were observed in meristems, in the basal regions of developing organs, in the developing vasculature, and associated with rib meristems elaborated late in the development of some floral organs. In root tips, cdc2 transcripts accumulated in the meristematic region and adjacent daughter cells but were not detected in the quiescent center. There was strong hybridization throughout the pericycle, and a further localized accumulation of cdc2 transcripts was observed in the initial stages of the activation of a new meristem at sites of lateral root development. We conclude that cdc2 expression is a critical factor in the regulation of meristem activity and establishment of proliferative competence.

Base Sequence↗

PubMed1992

Spatial pattern of receptor expression in the olfactory epithelium.

A PCR-based strategy for amplifying putative receptors involved in murine olfaction was employed to isolate a member (OR3) of the seven-transmembrane-domain receptor superfamily. During development, the first cells that express OR3 appear adjacent to the wall of the telencephalic vesicle at embryonic day 10. The OR3 receptor is uniquely expressed in a subset of olfactory cells that have a characteristic bilateral symmetry in the adult olfactory epithelium. This receptor and its specific pattern of expression may serve a functional role in odor coding or, alternatively, may play a role in the development of the olfactory system.

Amino Acid Sequence↗

PubMed1994

Experimental specification of cell sorting, tissue spreading, and specific spatial patterning by quantitative differences in cadherin expression.

The sorting-out of embryonic cells from a cell mixture and the selective spreading of one cell population over the surface of another have been attributed to various causes. These include differentials in chemotaxis, in cellular adhesiveness, in cell surface contractility, in speed of cell movement, and in the timing of postulated changes in cellular adhesive and motile properties. One of us earlier predicted on mathematical grounds that two motile cell types differing only in the level of expression of a single cell adhesion system should not only segregate from one another but also arrange themselves with the less cohesive cells enveloping a core of the more cohesive ones. To test these predictions, we combined two populations of L cells transfected with P-cadherin cDNA and expressing this homophilic adhesion molecule in substantially differing amounts. When the two cell populations were intermixed, they segregated to approach a sphere-within-a-sphere configuration, the cell population expressing more P-cadherin forming islands which fused to become an internal "medulla." When the two cell populations were first formed into separate aggregates which were subsequently allowed to fuse, the cell population expressing more P-cadherin was enveloped by its partner, which formed an external "cortex." These observations confirm the early prediction and support the conclusion that both morphogenetic movements and the specific anatomical configurations to which they lead can be determined by particular sets of intercellular adhesive intensities, regardless of how these are generated and in the absence of differentials in other parameters.

Animals↗

PubMed1988

Spatial pattern of myosin phosphorylation in contracting smooth muscle cells: evidence for contractile zones.

We have purified a polyclonal antibody by affinity chromatography which binds specifically to the phosphorylated form of the regulatory light chain (Mr = 20,000) of smooth muscle myosin. This antibody does not stain relaxed, permeabilized smooth muscle cells isolated from guinea pig taenia coli. However, when these cells were stimulated to contract with CaCl2 (100 microM) and ATP (1 mM), the immunofluorescence staining was localized in a series of transverse bands. This distribution of activated myosin appears to reflect an underlying structural organization of the smooth muscle cell cytoskeleton into mechanically coupled contractile zones.

Animals↗

PubMed1969

Spatial patterns of threadlike elements in the axoplasm of the giant nerve fiber of the squid (Loligo pealii L.) as disclosed by differential interference microscopy and by electron microscopy.

The giant nerve fiber of the squid (Loligo pealii L.) has been investigated in situ, and in fresh and fixed preparations, by differential interference microscopy and electron microscopy. A continuous, three-dimensional network, composed of threadlike elements, was disclosed in the axoplasm. The threadlike elements in the axoplasm are twisted as a whole into a steep, right-handed helix. In a peripheral ectoplasmic region, the elements are more parallel to one another and more densely packed than in a central endoplasmic core. The threadlike elements can be resolved into a hierarchy of decreasing order of size. Successive levels of the hierarchy are formed by the association of smaller elements into larger ones. The following levels in the hierarchy of network elements have been distinguished: 1-3-micro-wide threads, 0.1-0.35-micro-wide strands, and 70-250-A-wide unit-filament strands. The differential interference microscope selects, from the network, threads oriented at a specific angle to the long axis of the axon. The specific angle depends upon the orientation of the long axis of the axon relative to the direction of shear. It is postulated that the network configuration is expressed in the solid-state properties of the axoplasm essential for the normal functioning of the nerve fiber.

Animals↗

PubMed2002

Temporal and spatial patterns of seed dispersal in two Cistus species (Cistaceae).

Cistus species are obligate seeding, early colonizers that follow disturbance, particularly fire, in Mediterranean ecosystems. We studied seed release, seed dispersal and soil seed populations in stands of Cistus ladanifer and C. libanotis. Seed release started in mid- to late summer (C. ladanifer) or in early autumn (C libanotis), and continued for a very extended period: 8-10 months in C. ladanifer, and for a mean of 16 months in C. libanotis. The xerochastic capsules of both species released seeds by successive dehiscence of the locules. All capsules begin to dehisce simultaneously at the start of the seed release period, but in C. libanotis capsule fragmentation replaced dehiscence early in the seed release period. In plants of both species, seed shadows were characterized by a peak of density beneath the plant canopy and a very short tail of much lower densities, indicating that seeds are concentrated beneath mother plants when dispersed. Nevertheless, in late May, at the onset of the fire season, soil seed densities beneath plant canopies were low compared with densities expected from seed shadows, but were apparently high enough to allow recovery of the stands if a disturbance, such as fire, had taken place. Seed-eating Bruchidae in summer and granivorous ants during the seed release period were apparently the main causes of seed losses. Results suggest that in both Cistus species, the staggered seed release could constitute an efficient risk-reducing trait. The plant pool of seeds existing throughout most of the year could be a relevant component of Cistus seed banks.

Animals↗

PubMedDate not supplied

Can developmentally significant spatial patterning of the egg be discounted in mammals?

Mammals are generally held to be exceptions to the rule that organization of the egg plays a role in specifying the differentiation of cells, axes, or other aspects of patterning in the early embryo. However, there are several grounds for questioning this conclusion. Not only do certain experimental findings remain unexplained but, more importantly, nearly all have been interpreted specifically in terms of the differentiation of trophectoderm versus inner cell mass. The possibility that egg organization is instrumental in patterning of the early embryo in mammals has so far been almost entirely neglected, notwithstanding evidence that the mouse blastocyst becomes bilaterally symmetrical before it implants. Difficulties confronting attempts to tackle the issue of the significance of egg organization in mammals are discussed with respect to polarity and cytoplasmic differentiation in the oocyte and zygote. Evidence for an enduring influence of the maternal genome during early development is reviewed and weaknesses in the case against a role for egg organization are exposed. Finally, consideration is given to what needs to be done if this issue is to be resolved.

Animals↗

PubMed1997

Objective assessment of risk maps of tick-borne encephalitis and Lyme borreliosis based on spatial patterns of located cases.

BACKGROUND: Clusters of infection can indicate the underlying risk pattern of an endemic disease. Retrospective epidemiological data have been used to map the risk of tick-borne encephalitis (TBE) and Lyme borreliosis (LB) in the Central Bohemian region of the Czech Republic. METHODS: Both reported places of infection and patients' residences were entered in a geographical information system; their distance distribution and census data were used to model density of the population at risk. Point-pattern analysis and non-parametric kernel smoothing of points of infection were applied to compute the risk maps. Tick flagging and direct immunofluorescence assay were used to probe true LB-risk in the field. RESULTS: Tick-borne encephalitis infections proved to be more clustered than those of LB which was widespread; however, the most prominent clusters of both diseases largely correspond to each other. The estimated LB risk correlated well with tangible disease challenge as assessed from the tick abundance and Borrelia infection rates at 15 selected localities surveyed annually. CONCLUSION: The risk of LB is widely and smoothly distributed over the area studied, apparently following tick habitats wherever they occur, while TBE is confined to a subset of these locations.

Czech Republic↗

PubMed1997

Temporal and spatial pattern of expression of the pea phenylalanine ammonia-lyase gene1 promoter in transgenic tobacco.

Genes encoding phenylalanine ammonia-lyase (PAL) form a small multigene family with at least three members in pea. Tissue-specific expression of the promoter of a member of PAL gene family (PSPAL1) was investigated in the transgenic tobacco transformants carrying the different modes of chimeric fusion between the PSPAL1 promoter and a bacterial beta-glucuronidase (GUS) gene. In stems, at least, strict correlation was found between steady-state levels of Gus-mRNA and enzyme activity. Significantly high level of GUS activity was observed in roots, particularly in meristematic tissues and the pigmented region of petals of transgenic tobacco carrying the translational fusion type B (-1,394 to +140 of PSPAL1 connected to Gus), followed by moderately high level of GUS activity carrying the translational fusion type A (-1,394 to +117). GUS expression in tissues of mature leaves, however, was very low in these constructs. Extremely low GUS activity was observed in the transformants of transcriptional fusion type (-1,394 to +5), whilst no activity was detected carrying non-transcription fusion type (-1,394 to -27). Furthermore, the pattern of the PSPAL1 expression was characterized in response to pathogen ingress and woundings in transgenic tobacco carrying the translational fusion type B. Woundings itself triggered marked expression of PSPAL1-driven GUS expression at the wounded sites. Inoculation of nonpathogens, Phytophthora capsici, P. boehmeriae and Erisiphe graminis f. sp. hordei, both caused rapid and very clear GUS expression zone along with the development of hypersensitive cell death area where callose was accumulated, however, the inoculation of a pathogen, P.nicotiana caused slow and hazy GUS expression zone along with the lesion development. These results suggest that the expression of pea PSPAL1 promoter is regulated in a similar fashion, at least in a part, in pea and transgenic tobacco, under the plant development and various environmental cues.

Gene Expression Regulation, Plant↗

PubMed2001

Dynamics of water storage in mature subalpine Picea abies: temporal and spatial patterns of change in stem radius.

Internal water reserves in bark and foliage of trees contribute to transpiration (T) and play an essential role in optimizing water transport by buffering extreme peaks of water consumption. We examined patterns of stem shrinkage and their relationship to tree water dynamics. We measured fluctuations in root radius and stem radius at different stem heights, T of twigs at the top of the crown and sap flow velocities in stem sections of mature subalpine Norway spruce (Picea abies (L.) Karst.) trees over 2 years. The output of each sensor was coupled by physical functions to a mechanistic flow and storage model of tree water relations. The data verified the model-predicted lag in water storage depletion in response to the onset of transpiration and the lag increased with increasing distance from the crown periphery. Between the crown and stem base, the delay ranged from a few minutes to several hours, depending on microclimatic conditions and tree water status. Stem volume changes were proportional to the amount of water exchanged between the elastic tissues of the bark and the rigid xylem, indicating that the "peristaltic" wave of stem contraction along the flow path represented depletion of water stored in bark. On a daily basis, stems lost between 0.2 and 0.5% of their volume as a result of bark dehydration, corresponding to about 2 to 5 l of water. This water contributed directly to T. According to the model based on hydraulic principles, there are three main components underlying the dynamics of water storage depletion: flow resistance, storage capacities of needles and bark, and T of each tree section. The resistances and capacities were proportional to the response delay, whereas T in the lower parts of the tree was inversely proportional. The pattern of T within the crown depended on water intercepted by the branches. Because of these weather-dependent factors, there was no time constant for the response delay along the flow path. Nevertheless, the upper crown and the root section tended to have longer response delays per meter of flow path than the stem. The diurnal course of stem radius fluctuations represents the sum of all external and internal conditions affecting tree water relations; stem radius fluctuations, therefore, provide a sensitive measure of tree water status.

Picea↗

PubMed2003

The formation of spatial patterns in social insects: from simple behaviours to complex structures.

Many of the collective activities performed by social insects result in the formation of complex spatio-temporal patterns. Without centralized control, workers are able to work together and collectively tackle tasks far beyond the abilities of any one individual. The resulting patterns produced by a colony are not explicitly coded at the individual level, but rather emerge from nonlinear interactions between individuals or between individuals and their environment. We present a few selected examples to illustrate some of the basic mechanisms used by social insects, such as templates, stigmergy and self-organization. These mechanisms can be used in combination to organize pattern formation at the colony level.

Adaptation, Physiological↗

PubMed1985