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PubMed1993

Ecdysteroid induction of embryonic morphogenesis in a parasitic wasp.

Development of the parasitic wasp Copidosoma floridanum (Hymenoptera: Encyrtidae) is unusual in two ways. As many as 3000 embryos are formed from a single egg and embryonic morphogenesis is closely synchronized with the onset of the metamorphosis of its host. Given this extreme synchrony between parasite and host development, we undertook a series of experiments to determine whether host endocrine factors regulate C. floridanum embryonic morphogenesis. Here we report that C. floridanum embryos must develop for 9 days before acquiring the competence to undergo morphogenesis. Furthermore, several pieces of evidence suggest that ecdysteroids of host origin regulate induction of C. floridanum morphogenesis. First, competent embryos initiated morphogenesis when transplanted into host larvae and pupae, host stages possessing elevated ecdysteroid titers, but not when transplanted into adult moths. Second, morphogenesis was arrested by ablation of the host's source of ecdysone, but could be rescued by injection of 20-hydroxyecdysone in a dose-dependent manner. Finally, a segment of DNA encoding a zinc finger nearly identical in sequence to a portion of the ecdysone receptor of Drosophila melanogaster was isolated and characterized from C. floridanum. This putative ecdysone receptor probe indicated that expression of this gene was correlated with the initiation of C. floridanum embryonic morphogenesis. The temporal pattern of putative receptor RNA accumulation increased in association with the onset of morphogenesis, while the spatial pattern of expression was associated with the invagination of cells forming the gastrula. Together, these data suggest that ecdysone of host origin is directly involved in the induction of C. floridanum embryonic morphogenesis.

Amino Acid Sequence↗
PubMed2005

Asymmetric distribution of PAR proteins in the mouse embryo begins at the 8-cell stage during compaction.

In many organisms, like Caenorhabditis elegans and Drosophila melanogaster, establishment of spatial patterns and definition of cell fate are driven by the segregation of determinants in response to spatial cues, as early as oogenesis or fertilization. In these organisms, a family of conserved proteins, the PAR proteins, is involved in the asymmetric distribution of cytoplasmic determinants and in the control of asymmetric divisions. In the mouse embryo, it is only at the 8-cell stage during compaction that asymmetries, leading to cellular diversification and blastocyst morphogenesis, are first observed. However, it has been suggested that developmentally relevant asymmetries could be established already in the oocyte and during fertilization. This led us to study the PAR proteins during the early stages of mouse development. We observed that the homologues of the different members of the PAR/aPKC complex and PAR1 are expressed in the preimplantation mouse embryo. During the first embryonic cleavages, before compaction, PARD6b and EMK1 are observed on the spindle. The localization of these two proteins becomes asymmetric during compaction, when blastomeres flatten upon each other and polarize. PARD6b is targeted to the apical pole, whereas EMK1 is distributed along the baso-lateral domain. The targeting of EMK1 is dependent upon cell-cell interactions while the apical localization of PARD6b is independent of cell contacts. At the 16-cell stage, aPKCzeta colocalizes with PARD6b and a colocalization of the three proteins (PARD6b/PARD3/aPKCzeta can occur in blastocysts, only at tight junctions. This choreography suggests that proteins of the PAR family are involved in the setting up of blastomere polarity and blastocyst morphogenesis in the early mammalian embryo although the interactions between the different players differ from previously studied systems. Finally, they reinforce the idea that the first developmentally relevant asymmetries are set up during compaction.

Adaptor Proteins, Signal Transducing↗
PubMed1998

Adventitial vasa vasorum in balloon-injured coronary arteries: visualization and quantitation by a microscopic three-dimensional computed tomography technique.

OBJECTIVES: The objective of this study was to examine the quantitative response of the adventitial vasa vasorum to balloon-induced coronary injury. BACKGROUND: Recent attention has focused on the role of vasa vasorum in atherosclerotic and restenotic coronary artery disease. However, the three-dimensional anatomy of these complex vessels is largely unknown, especially after angioplasty injury. The purpose of this study was to visualize and quantitate three-dimensional spatial patterns of vasa vasorum in normal and balloon injured porcine coronary arteries. We also studied the spatial growth of vasa vasorum in regions of neointimal formation. A novel imaging technique, microscopic computed tomography, was used for these studies. METHODS: Four pigs were killed 28 d after coronary balloon injury, and four pigs with uninjured coronary arteries served as normal controls. The coronary arteries were injected with a low-viscosity, radiopaque liquid polymer compound. Normal and injured coronary segments were scanned using a microscopic computed tomography technique. Three-dimensional reconstructed maximum intensity projection and voxel gradient shading images were displayed at different angles and voxel threshold values, using image analysis software. For quantitation, seven to 10 cross-sectional images (40 normal and 32 balloon injured cross-sections) were captured from each specimen at a voxel size of 21 microm. RESULTS: Normal vasa vasorum originated from the coronary artery lumen, principally at large branch points. Two different types of vasa were found and classified as first-order or second-order according to location and direction. In balloon-injured coronary arteries, adventitial vasa vasorum density was increased (3.16+/-0.17/mm2 vs. 1.90+/-0.06/mm2, p = 0.0001; respectively), suggesting neovascularization by 28 d after vessel injury. Also, in these injured arteries, the vasa spatial distribution was disrupted compared with normal vessels, with proportionally more second-order vasa vasorum. The diameters of first-order and second-order vasa were smaller in normal compared with balloon-treated coronary arteries (p = 0.012 first-order; p < 0.001, second-order; respectively). The density of newly formed vasa vasorum was proportional to vessel stenosis (r = 0.81, p = 0.0001). Although the total number of vasa was increased after injury, the total vascular area comprised of vasa was significantly reduced in injured vessels compared with normals (3.83+/-0.20% to 5.42+/-0.56%, p = 0.0185). CONCLUSIONS: Adventitial neovascularization occurs after balloon injury. The number of new vessels is proportional to vessel stenosis. These findings may hold substantial implications for the therapy of vascular disease and restenosis.

Angioplasty, Balloon, Coronary↗
PubMedDate not supplied

Spatial variability of nitrous oxide emissions and their soil-related determining factors in an agricultural field.

To evaluate spatial variability of nitrous oxide (N2O) emissions and to elucidate their determining factors on a field-scale basis, N2O fluxes and various soil properties were evaluated in a 100- x 100-m onion (Allium cepa L.) field. Nitrous oxide fluxes were determined by a closed chamber method from the one-hundred 10- x 10-m plots. Physical (e.g., bulk density and water content), chemical (e.g., total N and pH), and biological (e.g., microbial biomass C and N) properties were determined from surface soil samples (0-0.1 m) of each plot. Geostatistical analysis was performed to examine spatial variability of both N2O fluxes and soil properties. Multivariate analysis was also conducted to elucidate relationships between soil properties and observed fluxes. Nitrous oxide fluxes were highly variable (average 331 microg N m(-2) h(-1), CV 217%) and were log-normally distributed. Log-transformed N2O fluxes had moderate spatial dependence with a range of >75 m. High N2O fluxes were observed at sites with relatively low elevation. Multivariate analysis indicated that an organic matter factor and a pH factor of the principal component analysis were the main soil-related determining factors of log-transformed N2O fluxes. By combining multivariate analysis with geostatistics, a map of predicted N2O fluxes closely matched the spatial pattern of measured fluxes. The regression equation based on the soil properties explained 56% of the spatially structured variation of the log-transformed N2O fluxes. Site-specific management to regulate organic matter content and water status of a soil could be a promising means of reducing N2O emissions from agricultural fields.

Air Pollutants↗
PubMed2005

Visual spatial and visual pattern working memory: neuropsychological evidence for a differential role of left and right dorsal visual brain.

According to neurophysiological, neuroimaging, and behavioural evidence, visual working memory (WM) can be separated into a "what" and a "where" component, reflecting the duality of visual processing. Whereas a wealth of empirical data suggests a right-sided fronto-parietal network critical for the maintenance of spatial information, the cortical structures underlying maintenance of object information have remained controversial. Although visual object processing depends on ventral, inferior temporal areas, recent neuroimaging results suggest that maintenance of visual object information involves a left-sided or bilateral fronto-parietal network. The aim of the present study is to further clarify the role of the left and right parietal lobes for pattern and spatial visual WM. Seven patients with left-sided, seven with right-sided parietal brain injury, and two age-matched healthy control groups performed a delayed-matching-to-sample task using either pattern (shape) or spatial (location) information or both. In addition, eight patients with left-sided injury sparing parietal areas were tested to further examine the specific role of the left parietal cortex in pattern WM. Left parietal injury resulted in pattern WM impairment, only, while right parietal injury was associated with pattern and spatial WM deficits. Non-parietal injury was not associated with comparable deficits. These results suggest that visual spatial WM depends critically on right parietal areas; in contrast, pattern WM depends on both, left and right parietal areas.

Adult↗
PubMed1999

Temporal patterns in bovine tuberculosis in a brushtail possum population contiguous with infected cattle in the Ahaura Valley, Westland.

AIMS: To determine temporal and spatial patterns of bovine tuberculosis (Tb) in a population of brushtail possums (Trichosurus vulpecula) free from commercial and recreational hunting and living contiguously with livestock, and to relate these patterns to measures of possum health and density. METHODS: Possums were trapped on 11 lines located on a forest-rough grazing margin in the Ahaura Valley in Westland in 1979-80 and each August from 1992 to 1996, and were examined post mortem for gross lesions indicative of Tb. Infection levels in possums were compared with Th test data from cattle grazing in the same area. RESULTS: Tuberculosis was identified from the trapped sample of possums in 1980. Trapping of further possums on the same trap lines confirmed the presence of the disease each year from 1992 to 1996, and suggested a clustering of infection in time and space. The prevalence of Tb in possums declined with increasing possum population size and well being, and decreasing age. The prevalence of Tb in possums was highest in 1980 and 1992, and appeared to roughly coincide with similar upsurges in Tb in nearby cattle. CONCLUSIONS: Our results suggest that the exceptional levels of Tb recorded in possums in 1992 had a direct effect on possum numbers, and gave rise to very low trap catches in 1993-94. They also suggest that Tb can persist for several years in possum populations existing well below the 5% trap catch targeted by regional councils for Tb possum control.

Journal Article↗
PubMed1982

Human pattern-evoked retinal responses are altered by optic atrophy.

Electrical signals in response to both diffuse flashes of light and phase-alternating spatial patterns were recorded from the eyes and from the occipital scalp of a subject with a traumatic unilateral (right) optic nerve section. Clinical examination disclosed a grossly normal right eye with no light perception, a Marcus Gunn pupil, and an atrophic optic disc. The left eye was normal. The electroretinogram responses on the lesioned side (OD) were normal, but there was no pattern-evoked retinal response (PERR) and no recordable visual-evoked response present. The conclusion is that the optic nerve and ganglion cells appear to be selectively responsible for the PERR potential.

Adolescent↗
PubMed1998

Cooperation of intrinsic and extrinsic signals in the elaboration of regional identity in the posterior cerebral cortex.

Understanding the compartmentalization of the neocortex (isocortex) of the mammalian brain into functional areas is a challenging problem [1-3] . Unlike pattern formation in the spinal cord and hindbrain, it does not involve the specification of distinct cells types: distinct areas differ in their patterns of connectivity and cytoarchitecture. It has been suggested that signals intrinsic to the neocortical neuroepithelium specify regional fate [3]. Alternatively, spatial patterning might be imposed by extrinsic cues such as thalamocortical projections [4-6]. Recent results highlight the ability of early precursor cells of the telencephalic neuroepithelium to 'remember' their spatial position from times before thalamic innervation [7,8] [9-12]. An influence from the thalamus, however, cannot be ruled out as there is a precise invasion of the correct cortical areas by the corresponding projections [13,14]. Furthermore, cortical neuronal progenitors have been proposed to adopt new connection patterns after transplantation [6,7], as well as when the thalamic input is rerouted [15,16]. Here, we describe the transient expression of the homeobox gene Otx2 in the posterior, prospective visual, neocortex and use it to analyze the establishment of posterior cortical fate. The results suggest that whereas intrinsic cortical information is sufficient to specify regional fate, extrinsic signals from the thalamus are involved in the expansion or maintenance of the population of cells expressing Otx2 but not in regionalization.

Amino Acid Sequence↗
PubMed2002

Spatial and temporal pattern of Fgf-8 expression during chicken development.

This study analyzes the temporal and spatial expression pattern of Fgf-8 over a continuous series of developmental stages. Special emphasis is laid on the paraxial mesoderm where Fgf-8 expression is highly dynamic. Whereas the anterior portion of the unsegmented mesoderm is devoid of expression, Fgf-8 is upregulated in the posterior half of a newly formed somite. Soon after somite formation, this highly localized expression gives way to a more diffuse pattern of Fgf-8 expression at low levels in presumptive sclerotomal cells. During later somite maturation, transcripts become restricted to the myotome. Co-staining with the myotome marker MyoD reveals that Fgf-8 expression defines a subpopulation of muscle precursor cells.

Animals↗
PubMed1993

Two different spatiotemporal patterns for Ca2+ oscillations in pancreatic acinar cells: evidence of a role for protein kinase C in Ins(1,4,5)P3-mediated Ca2+ signalling.

The oscillations in cytosolic Ca2+ evoked in pancreatic exocrine acinar cells by submaximal concentrations of the two phosphoinositidase-coupled agonists acetylcholine (ACh) and cholecystokinin octapeptide (CCK-8) have very different temporal patterns. In the present study we use digital video imaging of Fura-2 fluorescence to map the spatial distribution of Ca2+ during the oscillating responses to these two agonists. The spatial patterns induced are very different for each of these agonists. ACh oscillations are sinusoidal and initiated at the secretory pole of these morphologically and functionally polarized cells. As they spread across the cell, pronounced gradients in Ca2+ develop that persist throughout the oscillating response. CCK-8 induces a series of discrete Ca2+ transients of longer duration and lower frequency. These elevations in Ca2+ arise slowly, throughout the cells and without any detectable gradients in Ca2+. We consider that the different spatiotemporal patterns can be explained on the basis of a physiologically relevant interaction between Ins(1,4,5)P3 and protein kinase C in second messenger-mediated Ca2+ signalling.

Acetylcholine↗
PubMed1996

An analysis of alternative classification schemes for medical atlas mapping.

Most national disease atlases adopt a classification scheme based on either the percentile distribution of rates or on the national mean. Although these schemes have a direct interpretation, they are based on the univariate statistical distribution of rates and not on their spatial distribution, and distort the underlying spatial autocorrelation in the data. If the purpose of the maps is to represent spatial patterns, alternative classification schemes might be more appropriate. This research proposes an alternative classification method that maximises spatial similarity among contiguous units in the same class interval. The method has been illustrated using selected data from the German Cancer Atlas published in 1984.

Colonic Neoplasms↗
PubMed2003

Role of Sonic hedgehog in the development of the trachea and oesophagus.

BACKGROUND/PURPOSE: The secreted glycoprotein, Sonic hedgehog (Shh) plays an important patterning role in the development of many organ systems. The authors aimed to study the temporal and spatial pattern of expression of Shh and its receptor Ptc1 during the development of the anterior foregut and to test the hypothesis that the Shh expression pattern is disturbed during the development of oesophageal atresia (OA) and tracheo-oesophageal fistula (TOF) in Adriamycin-treated mouse embryos. METHODS: Saline and Adriamycin-treated (4 mg/kg) CBA/Ca embryos were harvested between embryonic days (E) 10.5 and 12.5, and Shh and Ptc1 expression was studied by whole-mount and section in situ hybridisation using digoxygenin-labelled riboprobes. RESULTS: At E10.5, saline-treated embryos had an undivided foregut in which the ventrally placed prospective tracheal epithelium was positive for Shh, whereas the dorsal part was negative. At E11.5, this pattern had reversed with the separated trachea becoming negative and the oesophagus gaining expression of Shh. Ptc1 was expressed in the mesoderm adjacent to Shh expressing endoderm at both stages. Affected Adriamycin-treated embryos had an undivided foregut at E11.5, the epithelium of which showed diffuse Shh staining that lacked the dorso-ventral patterning seen in controls. CONCLUSIONS: The reversal in the dorso-ventral pattern of Shh expression during the narrow embryologic window in which tracheo-oesophageal separation is initiated suggests that Shh may play an important role in this process. Transient disturbance of this pattern may underlie the abnormal organogenesis in the Adriamycin model.

Animals↗
PubMed1991

Differential expression of three glutamate receptor genes in developing rat brain: an in situ hybridization study.

Non-N-methyl-D-aspartate glutamate receptors (GluRs) are encoded by a gene family, known members of which are designated GluR-1, -2, -3, -4, and -5. The present study examined the developmental pattern of GluR-1, -2, and -3 gene expression in rat brain. In situ hybridization revealed different spatial patterns throughout the brain for the cognate mRNAs at all ages examined, as well as different temporal patterns during development. In the adult all three mRNAs were expressed prominently in the pyramidal and granule layers of the hippocampus and in the Purkinje cell layer of the cerebellum, where detailed differences were apparent at the cellular level. In neocortex, GluR-2 mRNA exhibited prominent lamination and regional differences, which were less marked for GluR-1 and -3 mRNAs. In caudate-putamen GluR-2 mRNA was at high levels, but GluR-1 and -3 mRNAs were not. At early ages transcripts were transiently elevated relative to adult levels. GluR-1 mRNA reached peak expression in cortex at postnatal day 14 (P14) (225% of adult), in striatum at P4 (255% of adult), in hippocampus at P14 (195% of adult), and in cerebellum at P21 (150% of adult). GluR-3 exhibited more modest peaks in neocortex and hippocampus. In contrast, GluR-2 mRNA was at near adult levels throughout the first days of postnatal life and exhibited a peak only in cerebellum at P14 (168% of adult). The finding of differential developmental regulation of the GluR-1, -2, and -3 genes indicates that the receptors they encode may have different influences on synaptic plasticity, neuronal survival, and susceptibility to excitatory amino acid toxicity.

Aging↗
PubMed2003

Local density fluctuations, hyperuniformity, and order metrics.

Questions concerning the properties and quantification of density fluctuations in point patterns continue to provide many theoretical challenges. The purpose of this paper is to characterize certain fundamental aspects of local density fluctuations associated with general point patterns in any space dimension d. Our specific objectives are to study the variance in the number of points contained within a regularly shaped window Omega of arbitrary size, and to further illuminate our understanding of hyperuniform systems, i.e., point patterns that do not possess infinite-wavelength fluctuations. For large windows, hyperuniform systems are characterized by a local variance that grows only as the surface area (rather than the volume) of the window. We derive two formulations for the number variance: (i) an ensemble-average formulation, which is valid for statistically homogeneous systems, and (ii) a volume-average formulation, applicable to a single realization of a general point pattern in the large-system limit. The ensemble-average formulation (which includes both real-space and Fourier representations) enables us to show that a homogeneous point pattern in a hyperuniform state is at a "critical point" of a type with appropriate scaling laws and critical exponents, but one in which the direct correlation function (rather than the pair correlation function) is long ranged. We also prove that the non-negativity of the local number variance does not add a new realizability condition on the pair correlation. The volume-average formulation is superior for certain computational purposes, including optimization studies in which it is desired to find the particular point pattern with an extremal or targeted value of the variance. We prove that the simple periodic linear array yields the global minimum value of the average variance among all infinite one-dimensional hyperuniform patterns. We also evaluate the variance for common infinite periodic lattices as well as certain nonperiodic point patterns in one, two, and three dimensions for spherical windows, enabling us to rank-order the spatial patterns. Our results suggest that the local variance may serve as a useful order metric for general point patterns. Contrary to the conjecture that the lattices associated with the densest packing of congruent spheres have the smallest variance regardless of the space dimension, we show that for d=3, the body-centered cubic lattice has a smaller variance than the face-centered cubic lattice. Finally, for certain hyperuniform disordered point patterns, we evaluate the direct correlation function, structure factor, and associated critical exponents exactly.

Journal Article↗
PubMed2006

Long-range periodic patterns in microbial genomes indicate significant multi-scale chromosomal organization.

Genome organization can be studied through analysis of chromosome position-dependent patterns in sequence-derived parameters. A comprehensive analysis of such patterns in prokaryotic sequences and genome-scale functional data has yet to be performed. We detected spatial patterns in sequence-derived parameters for 163 chromosomes occurring in 135 bacterial and 16 archaeal organisms using wavelet analysis. Pattern strength was found to correlate with organism-specific features such as genome size, overall GC content, and the occurrence of known motility and chromosomal binding proteins. Given additional functional data for Escherichia coli, we found significant correlations among chromosome position dependent patterns in numerous properties, some of which are consistent with previously experimentally identified chromosome macrodomains. These results demonstrate that the large-scale organization of most sequenced genomes is significantly nonrandom, and, moreover, that this organization is likely linked to genome size, nucleotide composition, and information transfer processes. Constraints on genome evolution and design are thus not solely dependent upon information content, but also upon an intricate multi-parameter, multi-length-scale organization of the chromosome.

Bacterial Proteins↗
PubMed2006

A medium-spatial scale distribution pattern of Pseudoscorpionida (Arachnida) in a gradient of topography (altitude and inclination), soil factors, and litter in a central Amazonia forest reserve, Brazil.

In Amazonia, nothing is known about the distribution of the invertebrates on a medium-spatial scale pattern. In a trail system of 64 km2 at Ducke Reserve, we sampled 72 transects using the hand-sorting method and Berlese-Tullgren extraction. The reserve possesses ecosystems of "terra-firme" forest and the trail system represents a gradient of topographic soil factors and vegetation, avoiding categorizations. Considering the abundance and diversity of Pseudoscorpionida, we investigated the relation of the community to environmental factors tested (topography, clay percentage, litter, and soil pH), to the two major drainage basins of the reserve, and if these invertebrates can be used as biological indicators to monitor changes. We registered two species for the first time in the reserve, increasing the known diversity to 17 species. The lack of correlation with the predictor variables and the large home range, indicate that pseudoscorpions are not good biological indicators in the reserve. As the eastern and western watersheds are not separate management units for the community, our results show that they are generalist predators. In spite of our results and lack of knowledge concerning their biology, life history and taxonomy, pseudoscorpions are cosmopolitan and easy to find and measure. Compared with previous studies in the reserve, they have a consistent pattern of abundance and diversity throughout the years showing the stability of the community which can be checked mainly by comparison with environmental changes that would occur in the reserve. An investigation on a medium-spatial scale pattern and over a long-term period including other habitats, and also other predictor variables, like humidity, the structure of the vegetation and canopy closure, will be necessary to reinforce the observed tendencies.

Altitude↗
PubMed1996

Spatiotemporal pattern of ontogenetic expression of calbindin-28/kD in the retinorecipient layers of rat superior colliculus.

Using an antibody against calbindin-28kD, we have studied the spatial pattern of expression of this protein in the superior colliculi (SC) of four strains of mature laboratory rats. In all four strains, calbindin-expressing cells (CECs) formed horizontally oriented tiers in the retinorecipient and intermediate gray layers but were diffusely distributed throughout the deep layers. Ontogenetically, calbindin-28kD was expressed for the first time in the retinorecipient layers at postconceptional day 20 (PCD 20), by cells located in the rostrolateral region where the first born retinal ganglion cells (RGCs) are represented. Although on the day of birth (PCD 22/23), the CECs were distributed more widely, they were still absent in the most medial part of the SC, that is, the region where the latest born RGCs are represented. The spatial distribution of CECs became adultlike only by PCD 29, that is, at the end of the period of the naturally occurring death of the RGCs. Monocular eye enucleations on PCD 23 prevented the expression of calbindin in the medial fifth of the retinorecipient layers of the contralateral SC, while the unilateral removal of the visual cortices had no discernable effect on the numbers and distribution of the CECs in either SC. Thus, the spatiotemporal pattern of ontogenetic expression of calbindin-28kD in the retinorecipient layers of SC reflects the spatiotemporal pattern of generation of the RGCs, and the retinal input appears to induce neuronal expression of calbindin-28kD in these layers.

Animals↗
PubMed1986

Repression and turnover pattern fushi tarazu RNA in the early Drosophila embryo.

Embryonic expression of transcripts from the Drosophila gene fushi tarazu (ftz) progresses through a series of spatial patterns, culminating in a seven-banded pattern at the cellular blastoderm stage. We studied the generation of this pattern using inhibitors of RNA synthesis (alpha-amanitin) and protein synthesis (cycloheximide). Injections of alpha-amanitin revealed that ftz RNA turns over extremely rapidly in the embryo, and we think that this may be essential to effect rapid changes in ftz RNA patterns. Injections of cycloheximide added to the normal domains of ftz expression, creating novel expression patterns that were dependent on the time of injection. These novel patterns suggest that two superimposed systems of repression establish the normal, seven-banded pattern of ftz expression. One system sets up a banded pattern over the entire length of the embryo, and the other restricts actual expression to the middle portion of the embryo.

Amanitins↗