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Results for “spatial patterning”

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PubMed1987

Developmental and spatial patterns of expression of the mouse homeobox gene, Hox 2.1.

The Hox 2.1 gene forms part of a cluster of homeobox-containing genes on mouse chromosome 11. Analysis of Hox 2.1 cDNAs isolated from an 8 1/2-day p.c. mouse embryo library predicts that the gene encodes a 269 amino acid protein (Mr, 29,432). This deduced protein contains a homeobox 15 amino acids from the carboxy terminus and is very rich in serine and proline. A second partially conserved region present in several other genes containing homeoboxes, the hexapeptide Ile-Phe-Pro-Trp-Met-Arg, is located 12 amino acids upstream of the homeodomain and is encoded by a separate exon. Analysis of Hox 2.1 gene expression reveals a complex and tissue-specific series of RNA transcripts in a broad range of fetal tissues (lung, spinal cord, kidney, gut, spleen, liver and visceral yolk sac). Comparison of the temporal patterns of gene expression during development and in the adult suggests that Hox 2.1 is regulated independently in different tissues. Evidence is also presented that transcripts from other loci have extensive homology to the Hox 2.1 gene in sequences outside of the homeobox. In situ hybridization shows that Hox 2.1 transcripts are regionally localized in the spinal cord in an apparent anterior-posterior gradient extending from the hind brain. The distribution of RNA also displays a cell-type specificity in the lung, where mesodermal cells surrounding the branching epithelial cell layer accumulate high levels of Hox 2.1 transcripts.

Amino Acid Sequence↗
PubMed2004

The spatial pattern of atrial cardiomyocyte calcium signalling modulates contraction.

We examined the regulation of calcium signalling in atrial cardiomyocytes during excitation-contraction coupling, and how changes in the distribution of calcium impacts on contractility. Under control conditions, calcium transients originated in subsarcolemmal locations and showed local regeneration through activation of calcium-induced calcium release from ryanodine receptors. Despite functional ryanodine receptors being expressed at regular (approximately 2 microm) intervals throughout atrial myocytes, the subsarcolemmal calcium signal did not spread in a fully regenerative manner through the interior of a cell. Rather, there was a diminishing centripetal propagation of calcium. The lack of regeneration was due to mitochondria and SERCA pumps preventing the inward movement of calcium. Inhibiting these calcium buffering mechanisms allowed the globalisation of action potential-evoked responses. In addition, physiological positive inotropic agents, such as endothelin-1 and beta-adrenergic agonists, as well as enhanced calcium current, calcium store loading and inositol 1,4,5-trisphosphate infusion also led to regenerative global responses. The consequence of globalising calcium signals was a significant increase in cellular contraction. These data indicate how calcium signals and their consequences are determined by the interplay of multiple subcellular calcium management systems.

Animals↗
PubMed1993

Changing spatial patterns of DNA replication in the noise-damaged chick cochlea.

The purpose of the present study was to examine the spatio-temporal pattern of cell proliferation in the chick cochlea in response to the sensory hair cell loss induced by a 1.5 kHz pure tone at 120 dB SPL (1 dB = 20 muPa) for 48 h. DNA replication was evaluated with the bromodeoxyuridine (BrdU) pulse-fix technique. One group of birds was given multiple injections of BrdU (50 mg/kg) over a period of 8 h at various starting times during or after the exposure. Afterwards, their cochleas were removed and processed as whole mounts for BrdU immunohistochemistry. The cochleas of a second group of acoustically traumatized chicks were evaluated by scanning electron microscopy in order to determine the spatio-temporal pattern of hair cell loss. Hair cell loss was first observed 12 h after the start of the exposure and DNA replication started near the inferior edge of the hair cell lesion 24-32 h after the start of the exposure, i.e. 12-20 h after the first sign of hair cell loss. The site of hair cell loss and DNA replication shifted toward the superior edge of the basilar papilla as the exposure continued. The rate of DNA replication accelerated and reached its peak near the end of the 48 h exposure. The estimated latency of cell proliferation after hair cell loss was faster and the duration of DNA replication shorter than that observed in other sensory systems. The spatio-temporal pattern of DNA replication follows the spatio-temporal gradient of hair cell loss, suggesting that cell proliferation is triggered by hair cell loss itself rather than by intrinsic positional cues or gradients.

Animals↗
PubMed2005

Single-cell transcriptional profiles and spatial patterning of the mammalian olfactory epithelium.

In order to gain insights into the regulatory control of neuronal diversity in the mammalian olfactory system, we have identified the transcriptional profile of individual olfactory neurons. A single cell microarray strategy was performed to search for candidate genes involved in the molecular specification of dorso-ventral zones of olfactory receptor (OR) expression. Several transcripts were identified that display differential expression in distinct OR zones, including a novel family of genes, the Lozenge-like (Lzl) genes which share sequence consensus motifs with Lozenge, a transcription factor involved in the patterning of the Drosophila olfactory and visual systems.

Amino Acid Sequence↗
PubMed2003

Spatial patterns of spontaneous local field activity in the monkey visual cortex.

Spontaneous activity among visually responsive neurons is often considered to consist of random neural events, or perhaps to reflect an irrelevant by-product of brain homeostasis. However, recent studies have emphasized that such ongoing activity is strongly synchronized over large cortical distances, and can have a marked impact on the responsiveness of neurons to visual stimuli, suggesting that such activity may indeed be highly relevant to the brain's interpretation of its sensory input. In the current study, we examined the spatiotemporal nature of local field potential (LFP) fluctuations in the visual cortex of two macaque monkeys that were awake, but in a state of relaxation with minimal visual stimulation. Using an array of 16 electrodes spaced by several millimeters, we simultaneously monitored the LFP at many sites over a large region of the visual cortex. In agreement with the literature, we found that the coherence in the raw LFP signal fell off quickly with both frequency and distance. However, when we examined slower fluctuations in the LFP power, we found that power signals, including those derived from the high y-range frequencies, had high coherence that fell off only very slowly with cortical distance. Finally, we performed an additional experiment, with several electrodes placed on either side of a sulcus, to demonstrate that the decline in local field synchrony with cortical distance was so reliable that the interruption in the cortical sheet corresponding to the opening of the sulcus could be easily identified by monitoring just a few minutes of spontaneous LFP activity. These experiments reveal that a significant portion of spontaneous LFP fluctuations in the visual cortex is contributed by global mechanisms, imposing synchrony that is, first and foremost, a function of cortical separation between any two points.

Animals↗
PubMed2003

Quantifying spatial patterns of landscapes.

In this paper we discuss information theoretical landscape indices based on data from digitized maps in grid format: measures based on Shannon's entropy, e.g. the measures of diversity and contagion; and measures based on conditional entropy, e.g. a new index which can be seen as an alternative to the measure of contagion that does not have the disadvantage of being highly correlated to the measure of diversity. We also introduce a measurement on how much information is contained in a coarse-scale map about a fine-scale map.

Entropy↗
PubMed2001

Temporal and spatial patterns on serra, Scomberomorus brasiliensis (Teleostei, Scombridae), catches from the fisheries on the Maranhão coast, Brazil.

The displacement pattern of the serra, Scomberomorus brasiliensis, in North-eastern Brazil was analyzed from landing data recorded form the fleet fishing serra. Serra fishery has two seasons: from Septemer to February (demersal species plus serra), and from March to August (almost only large amounts of serra). S. brasilienisis relative abundance increases similarly along the coast from March. but decreases first on the West coast from June. Records indicate that serra is near the coast at least until September/October in Eastern grounds. From October to March (strongest spawning season) there is no record of shoals on the coast. We concluded that the Maranhão coast is just a part of the migration circuit of S. brasilienisis that may exceed 300 nautical miles.

Animals↗
PubMed1999

Temporal and spatial patterns of malaria reinfection in northeastern Venezuela.

We stratified the risk of malaria transmission (Plasmodium vivax) in 35 villages along a coastal range in northeastern Venezuela (51 km2) where the main vector is the mosquito Anopheles aquasalis. After 20 years without local malaria transmission, reinfection of the entire area occurred from May to December 1985 by local (continuous) and jump (discontinuous) dispersal. Epidemiologic, environmental, and vector variables were investigated with the aid of a Geographic Information System. Risk factors for malaria transmission were human population density, proximity to pre-adult mosquito habitats (< 500 m), and the number of pre-adult habitats nearby. Most inhabitants, immature mosquito habitats, and malaria cases were located at low elevations and on gentle slopes. High prevalence of malaria during the dry seasons was associated with the presence of permanent bodies of water containing An. aquasalis. Occurrence of a La Niña event in 1988 (wet and cool phase of the El Niño Southern Oscillation) triggered malaria transmission to unusually high levels, consolidating infection in the area, and rendering traditional control efforts useless. We recommend tracking malaria persistence per village and associated risk factors as methods to reduce the cost of malaria control programs.

Adolescent↗
PubMedDate not supplied

Spatial patterns of out-migration in Maharashtra: 1961-71.

In view of the importance of migration in Maharashtra state. India an attempt is made to identify the areas of out-migration, and to assess the probable causes for it. The analysis is confined to the decade 1961-1971 and based on secondary data, with the taluka as the unit of analysis. The total number of births and deaths in each taluka for the period of study was complied and enabled the natural increase of population to be computed. A comparison of this with the actual increase as indicated by the census made it possible to identify the areas of out-migration. The study revealed that the out-migration talukas were located in 3 areas and that the relative significance of out-migration varied. The analysis indicated that the causes of out-migration were probably unfavorable relief efforts, susceptibility to drought, closure of household industries, and the 'pull' effect of metropolitan centers like Bombay.

Asia↗
PubMedDate not supplied

Spatial pattern of migration of plantation labour and its dynamics.

"This study examines the issue of migration trends being witnessed by areas of plantation agriculture [in India]. The focus is on the linkages between structural changes in local economies, the overall development policy and people's responses to plantation agriculture both as an economic activity and as a way of life. Based on field data, it is a case study of Hassan district, Karnataka."

Agriculture↗
PubMed1992

Population change in the Republic of Ireland 1981-1991: trends and spatial patterns.

"Demographic trends in the Republic of Ireland have gradually moved closer to Western European norms during the past two decades. Birth rates have continued to fall and internal migration flows have become diversified. External migration has continued to play an important role in population change, however, and in the most recent census period has contributed to net decline. Geographical patterns of change within the state reflect a concentration of growth in the environs of the larger centres of population." (SUMMARY IN FRE)

Demography↗