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At least 1,603 records · Page 89Linked to original sources
PubMed2003

Patterns of suicide mortality in Russia.

While Russia perennially has one of the highest suicide rates in the world, researchers had little access to valid data during the Soviet era to examine this issue. Transparency increased following the dissolution of the USSR, and this article employs newly available vital statistics data to describe the demographic, temporal, and spatial patterns of suicide in Russia. The discussion reveals that suicide mortality in Russia is among the highest in the world and is more than three times higher than in the United States; exhibited radical changes between 1984 and 1994; varies widely within the country, with a general increase in rates from west to east; and is highest among working-age males.

Adolescent↗
PubMed1985

Quantitative studies on the nuclei of muscle of congenitally dystrophic mice.

Stereological analyses of the pattern of distribution of heterochromatin and euchromatin in nuclei of muscle fibres are reported. Patterns of distribution found in myonuclei from extensor digitorum longus muscle of C57BL/6Jdy2J/dy2J dystrophic mice were compared with those found in myonuclei from the same muscle of clinically unaffected littermates and of normal control mice. Using a well-known spatial pattern analysis technique, clear differences between these types of nuclei were found. Such differences are clearly of value in helping our understanding of the pathological processes occurring in dystrophic muscle, and may be relevant to future identification and diagnosis of abnormal muscle.

Animals↗
PubMed2006

Benthic impacts of intertidal oyster culture, with consideration of taxonomic sufficiency.

An investigation of the impacts from elevated intertidal Pacific oyster culture in a New Zealand estuary showed enhanced sedimentation beneath culture racks compared with other sites. Seabed elevation beneath racks was generally lower than between them, suggesting that topographic patterns more likely result from a local effect of rack structures on hydrodynamic processes than from enhanced deposition. Compared with control sites, seabed sediments within the farm had a greater silt/clay and organic content, and a lower redox potential and shear strength. While a marked trend in macrofaunal species richness was not evident, species composition and dominance patterns were consistent with a disturbance gradient, with farm effects not evident 35 m from the perimeter of the racks. Of the environmental variables measured, sediment shear strength was most closely associated with the distribution and density of macrofauna, suggesting that human-induced disturbance from farming operations may have contributed to the biological patterns. To evaluate the taxonomic sufficiency needed to document impacts, aggregation to the family level based on Linnean classification was compared with an aggregation scheme based on ;general groups' identifiable with limited taxonomic expertise. Compared with species-level analyses, spatial patterns of impact were equally discernible at both aggregation levels used, provided density rather than presence/absence data were used. Once baseline conditions are established and the efficacy of taxonomic aggregation demonstrated, a ;general group' scheme provides an appropriate and increasingly relevant tool for routine monitoring.

Animals↗
PubMed1991

A comprehensive analysis of the developmental and tissue-specific expression of the isoactin multigene family in the rat.

The present study represents the first comprehensive analysis of isoactin gene expression in the developing rat. Our results clearly demonstrate that the developmental and tissue-specific expression of the actin multigene family is a highly integrated and complex process involving a variety of regulatory paradigms. The distinct temporal patterns of expression reported in this study indicate that there are three key phases in the regulation of expression of the actin multigene family during development. These include early embryonic development, late fetal development, and early postnatal development. The specific spatial patterns of expression observed in this study demonstrate that the expression of the actin multigene family is much more permissive than previously reported. This permissive expression includes a wide range of "ectopic" expression of the striated muscle isoactins as well as an extended expression of the alpha-smooth muscle isoactin. These findings expand our current understanding of the expression of the actin multigene family in development and provide a fundamental basis for future studies directed at investigating these processes.

Actins↗
PubMed1990

Histogenesis of corticotropin releasing factor-like immunoreactive amacrine cells in the rat retina.

The histogenesis of amacrine cells expressing corticotropin releasing factor-like immunoreactivity (CRF-LI) was examined in the rat retina by incorporating [3H]thymidine autoradiography and immunohistochemistry. Our results indicate that, during the period of amacrine cell generation, the population of CRF-LI amacrine cells are generated within a window of time from gestational days (ED)-16 to -20; the majority of them are produced by ED-18. No CRF-LI cells have been found to be 'born' postnatally. The histogenetic pattern of these cells follows a center-to-periphery gradient. Furthermore, CRF-LI cells in both the inner nuclear layer and the ganglion cell layer are generated in the same histogenetic wave and follow an identical temporo-spatial pattern. These results are consistent with and extend our previous findings of a differential change in CRF-LI cell density and total cell number during postnatal development.

Animals↗
PubMed1999

DNA replication in the 1-cell mouse embryo: stimulatory effect of histone acetylation.

Temporal and spatial distribution of the sites of DNA replication were examined in 1-cell mouse embryos. Embryos were labelled with bromodeoxyuridine (BrdU) at hourly intervals after fertilisation, and the incorporation of BrdU was examined by laser-scanning confocal microscopy following immunostaining with an anti-BrdU antibody. DNA replication first started uniformly in both the male and female pronuclei in the intranuclear region and then was observed in the peripheral regions of nucleus and nucleolus. These changes, however, occurred asynchronously in that the female pronucleus required a longer time to complete replication in the intranuclear region but not in the peripheral regions. Inhibiting transcription with alpha-amanitin had no effect on the temporal and spatial patterns of DNA replication. Treatment of the embryos with trapoxin, a specific inhibitor of histone deacetylase, accelerated the completion of replication in the peripheral regions but not in the intranuclear region. These results suggest that DNA replication is temporally and spatially regulated in the 1-cell embryos and that acetylation of histones, but not transcription, is involved in the regulation of DNA replication.

Acetylation↗
PubMed1993

Superfund soil cleanup: developing the Piazza Road remedial design.

A statistical approach was used to develop the remediation and soil sampling strategy at the Piazza Road dioxin site (an EPA Superfund site in Missouri). The source of the dioxin was contaminated waste oil that was used as a dust suppressant. This site was used as a test case to determine if a "surgical" remedial design could be developed. This new approach was compared to the historical approach taken by U.S. EPA Region 7 in Missouri. A pilot study provided information on the local spatial pattern of dioxin, so that sampling designs could be evaluated and costs of remediation could be estimated for different remedial strategies. Sampling designs were evaluated by a Monte Carlo approach, where the laboratory analytical error and sampling error due to spatial variation of dioxin were modeled based on the results of the pilot study and the historical site data. The optimal cleanup unit size was determined to be 14x14 ft, or 1/24th of the historical cleanup unit size. A companion paper describes the performance achieved and the dollar 5,900,000 cost savings that resulted from applying the improved design. This case study clearly shows the value of environmental data, where the use and quality of the data are established as a part of planning the site remediation.

Costs and Cost Analysis↗
PubMed1988

Models of sensorimotor transformations and vestibular reflexes.

The vestibulo-ocular and vestibulo-collic reflexes are well-studied sensorimotor systems with dynamic properties that have been successfully modeled. Recently proposed matrix and tensorial models attempt to describe the spatial organization of these reflexes in three dimensions. Here we describe experiments that test these models. We show that a matrix model of the vestibulo-ocular reflex provides a satisfactory description of its spatial properties. The vestibulo-collic reflex is more complex, but a tensorial model makes close predictions of neck muscle excitation by the vestibulo-collic reflex. In addition, our preliminary data show that the cervico-collic or neck stretch reflex produces essentially the same spatial pattern of neck muscle excitation as the vestibulo-collic reflex, a finding predicted by the tensorial model. We conclude by showing electromyographic and single neuron responses that can be modeled only by combining models of dynamics with models of spatial organization. We believe that the development of such models is the next major challenge in the application of quantitative methods to analysis of reflex behavior.

Animals↗
PubMed1995

Adaptation mechanisms in spatial vision--I. Bleaches and backgrounds.

To examine how the mechanisms of bleaching and background adaptation affect spatial pattern vision, contrast detection thresholds were measured in the fovea for sinusoidal (increment-Gabor) targets, during long-term dark adaptation following full bleaches, and against steady adapting backgrounds of various intensities. The dark-adaptation curves were found to be invariant in shape over the range of spatial frequencies tested (1-15 c/deg); in other words, the amplitude sensitivity functions were invariant during dark adaptation. These results support the hypothesis that bleaching adaptation is local and multiplicative. On the other hand, the background-adaptation curves measured for different spatial frequencies were found to converge as background intensity increased; the amplitude sensitivity functions became flatter. These results reject the equivalent-background hypothesis.

Adaptation, Ocular↗
PubMed1997

Differential features of motor neuron disease mortality in Spain.

BACKGROUND: The objective of this study was to describe the temporal and spatial patterns of motor neuron disease (MND) in Spain. METHODS: We studied data where MND was stated as the principal cause of death in official statistics from Spain. Time trends were analysed for age-, sex-specific and age-adjusted rates for the period 1951-1990. Age-adjusted mortality and relative risk, obtained by Poisson regression adjusting for age, were calculated for each province from deaths during the period 1975-1988. Maps were constructed using log transformed rates. Statistical significance of spatial aggregation was assessed using the Ohno et al. test. RESULTS: The 1951-1990 mortality rate, age- and sex-adjusted to the European population, for the population aged > or = 40 years was 1.49 per 100,000; 1.90 and 1.21 for males and females respectively. In general, mortality increased with age. Age-adjusted rates rose until 1960, dropped by 70% during the 1960s and declined slightly over the 1951-1990 period as a whole. From 1970 onwards MND mortality rose evenly, particularly in the 60-69 age group. A North-South gradient was suggested for both sexes with statistically significant clustering in the Northern coastal regions and--for males alone--in the Midwest provinces. CONCLUSIONS: Mortality from MND in Spain displayed a magnitude and recently rising temporal trend similar to that described in several other countries. Specific traits were: a decrease during the 1960s, which has been described for Japan only, as well as spatial heterogeneity and a predominant recent increase among the 60-69 age group. The determinants of these unusual MND mortality patterns are unknown.

Adult↗
PubMedDate not supplied

[The pattern of the expression of homeo box-containing genes in the mesenchyme of the mammalian limb bud as a coordinate network for subsequent morphogenetic processes].

Hypothesis is developed about mechanisms of determination of limb bud of mammals as a result of expression of homeo box containing genes (hox genes) of known up to date four hox families. Spatial pattern of the expression plays a role of coordinate system for subsequent processes of morphogenesis and differentiation of the limbs. Propositions of the hypothesis are realized in a computer dynamic model. The results of modeling are compared with known data on features of the expression of hox genes in the mesenchyme of developing limb buds in mammals and birds.

Animals↗
PubMed1993

Localization of acidic fibroblast growth factor, basic fibroblast growth factor, and heparan sulphate proteoglycan in rat lens: implications for lens polarity and growth patterns.

PURPOSE: Previous research in this laboratory has shown that fibroblast growth factor stimulates lens epithelial explants to proliferate, migrate, and differentiate into fibers in a progressive dose-dependent manner. The lens has distinct compartments where cells proliferate (germinative zone), migrate, or get displaced (equator) and differentiate into fibers (transitional zone). These compartments occur in an anteroposterior spatial sequence and the authors hypothesized that fibroblast growth factor plays a critical role in determining these spatial patterns of lens growth and lens polarity. To investigate this hypothesis the distribution of fibroblast growth factor in the lens was analyzed. METHODS: Immunohistochemistry was used to localize acidic fibroblast growth factor and basic fibroblast growth factor in the cells and capsule of lenses from neonatal, weanling, and adult rats. Because of its functional relationship with fibroblast growth factor, heparan sulphate proteoglycan was also localized in the lens. RESULTS: In all ages examined, cytoplasmic acidic fibroblast growth factor is present in the germinative and transitional zones of the lens and both acidic fibroblast growth factor and basic fibroblast growth factor are present in the capsule. A major finding is the co-localization of fibroblast growth factor and heparan sulphate proteoglycan reactivity in the lens capsule in the form of laminae. These laminae become more prominent as the capsule thickens and differences in arrangement of laminae between anterior, equatorial, and posterior regions of the capsule also become apparent. CONCLUSIONS: The presence of fibroblast growth factor in lens cells and capsule in neonatal, weanling, and adult rats indicates an important role for fibroblast growth factor in lens cell biology. Moreover, the regional distribution of fibroblast growth factor, particularly in the lens cells, indicates that it may influence determination of lens polarity and growth patterns.

Animals↗
PubMed2004

Spatial avoidance of littoral and pelagic invertebrate predators by Daphnia.

Studies on spatial avoidance behaviour of predators by prey often ignored the fact that prey typically face multiple predators which themselves interact and show a spatial pattern in abundance and predation rates (PRs). In a series of laboratory experiments, we investigated predation risk (PRI) and horizontal migration of the cladoceran Daphnia magna between open water and vegetation in response to two important invertebrate predators with a contrasting spatial distribution: pelagic Choaborus and vegetation-associated Ischnura. As expected, PRI by Chaoborus was higher in open water due to higher numbers and higher PRs of Chaoborus, while for Ischnura, PRI was highest in the vegetation due to higher densities, despite lower PRs of Ischnura. In accordance with this, Daphnia moved into the vegetation in the presence of the pelagic Chaoborus alone. In the presence of Ischnura alone, however, Daphnia showed no response. We hypothesize this may be the result of a constitutive behaviour of Daphnia to avoid pelagic fish, which impedes a response to the open water. In the combined predator treatment, Daphnia migrated to the open water zone. The increased risk of predation in the vegetation, due to a facilitating effect of Chaoborus on Ischnura PRs is believed to have caused this migration of the Daphnia. This response of Daphnia declined through time and Daphnia moved toward the vegetation. A decline in the activity of the Ischnura larvae through time may have switched the risk balance in favour of the vegetation environment.

Animals↗
PubMed2006

Evaluating kriging as a tool to improve moderate resolution maps of forest biomass.

The USDA Forest Service, Forest Inventory and Analysis program (FIA) recently produced a nationwide map of forest biomass by modeling biomass collected on forest inventory plots as nonparametric functions of moderate resolution satellite data and other environmental variables using Cubist software. Efforts are underway to develop methods to enhance this initial map. We explored the possibility of modeling spatial structure to make such improvements. Spatial structure in the field biomass data as well as in residuals from the map was investigated across 18 ecological zones in the Interior Western U.S. Exploratory tools included directional graphs of summary statistics, three dimensional maps, Moran's I correlograms, and variograms. Where spatial pattern was present, field and residual biomass were kriged, and predictions made for an independent test set were evaluated for improvement over predictions in the initial biomass map. While kriging has some potential benefit when analyzing the field data and exploring spatial structure, kriging residuals resulted in little or no improvement in the initial biomass map developed using Cubist software. Stationarity assumptions, variogram behavior, and appropriate model fitting strategies are discussed.

Biomass↗
PubMed1991

Model of peripheral and amblyopic hyperacuity.

Vernier thresholds rise much more rapidly in the periphery than do grating thresholds. A similar dissociation between acuity and hyperacuity has been shown to be present in strabismic but not in anisometropic amblyopia, thus leading to the suggestion that the strabismic fovea is similar to the normal periphery. Here it is shown that a quantitative model for spatial pattern discrimination, which accounts for foveal hyperacuity data, can be extended to encompass both the periphery and amblyopia if appropriate alterations are made. For the periphery it is necessary to increase the size of model receptive fields and to introduce both spatial undersampling and position irregularity (i.e. irregularity in the location of cortical filters). The strabismic fovea also requires spatial undersampling and position irregularity but no change in receptive field size. Defects in the good eye of strabismics can be explained by spatial irregularity. Finally, the anisometropic fovea requires a reduction in mechanism sensitivity but neither spatial undersampling nor position irregularity.

Amblyopia↗
PubMed2003

Alternative brain organization after prenatal cerebral injury: convergent fMRI and cognitive data.

The current study presents both longitudinal behavioral data and functional activation data documenting the effects of early focal brain injury on the development of spatial analytic processing in two children, one with prenatal left hemisphere (LH) injury and one with right hemisphere (RH) injury. A substantial body of evidence has shown that adults and children with early, lateralized brain injury show evidence of spatial analytic deficits. LH injury compromises the ability to encode the parts of a spatial pattern, while RH injury impairs pattern integration. The two children described in this report show patterns of deficit consistent with the site of their injury. In the current study, their longitudinal behavioral data spanning the age range from preschool to adolescence are presented in conjunction with data from a functional magnetic resonance imaging (fMRI) study of spatial processing. The activation results provide evidence that alternative profiles of neural organization can arise following early focal brain injury, and document where in the brain spatial functions are carried out when regions that normally mediate them are damaged. In addition, the coupling of the activation with the behavioral data allows us to go beyond the simple mapping of functional sites, to ask questions about how those sites may have come to mediate the spatial functions.

Adolescent↗
PubMed2000

Voltage- and ligand-gated ryanodine receptors are functionally separated in developing C2C12 mouse myotubes.

In order to further understand the role of voltage- and ligand-gated ryanodine receptors in the control of intracellular Ca2+ signalling during myogenesis, changes in cytosolic free calcium concentration ([Ca2+]i) were investigated by fura-2 videoimaging in C2C12 mouse myotubes developing in vitro. A synchronous [Ca2+]i increase was observed after depolarisation with high [K+], while the Ca2+ response propagated as a wave following caffeine administration. Application of the two stimuli to the same myotube often revealed the existence of cellular zones that were responsive to depolarisation but not to caffeine. Focal application of high [K+] promoted a [Ca2+]i response detectable only in the cellular areas close to the pipette tip, while focal application of caffeine elicited a [Ca2+]i increase which spread as a Ca2+ wave. Buffering of [Ca2+]i by BAPTA did not affect the pattern of the depolarisation-induced [Ca2+]i transient but abolished the Ca2+ waves elicited by caffeine. When high [K+] and caffeine were applied in sequence, reciprocal inhibition of the [Ca2+]i responses was observed. Our results suggest that the different spatial patterns of [Ca2+]i responses are due to uneven distribution of voltage- and ligand-gated ryanodine receptors within the myotube. These two types of receptor control two functionally distinct Ca2+ pools which are part of a common intracellular compartment. Finally, the two differently operated ryanodine receptor channels appear to be independently activated, so that a mechanism of Ca2+-induced Ca2+ release is not required to sustain the global response in C2C12 myotubes.

Animals↗
PubMed1994

[Evaluation and extension of Markov process models for the evolution of DNA].

Markov process models of nucleotide substitution are evaluated. A model proposed by Lanave et al (1984), alleged to need no priori assumption about the substitution pattern, is found to have the assumption of reversibility. Calculations based on the 2-p, 4-p, and 6-p substitution schemes show that site variation of substitution speed leads to serious under-estimation of sequence divergence by various methods. Spatial pattern variation also leads to under-estimation, but the discrepancy is slight. A nonhomogeneous Markov process model is used to study the temporal variations of rates and it is shown that the estimated number of substitutions reflects a rate averaged over time. The implications of those results to evolutionary phylogenetics are discussed.

Biological Evolution↗