Subdivision Of Region Research Articles

The sensory circumventricular organs of the mammalian brain.

The brain's three sensory circumventricular organs, the subfornical organ, organum vasculosum of the lamina terminalis and the area postrema lack a blood brain barrier and are the only regions in the brain in which neurons are exposed to the chemical environment of the systemic circulation. Therefore they are ideally placed to monitor the changes in osmotic, ionic and hormonal composition of the blood. This book describes their. General structure and relationship to the cerebral ventricles Regional subdivisions Vasculature and barrier properties Neurons, glia and ependymal cells Receptors, neurotransmitters, neuropeptides and enzymes Neuroanatomical connections Functions.

Semi-analytical electromagnetic field computation

Any of the numerical methods for electromagnetic field analysis essentially require a subdivision of a problem region. By notifying this subdivision, we have previously proposed a new methodology by applying the analytical solution to each of the discretized parts. The first trial of this semi-analytical electromagnetic filed computational methodology has made it possible to simulate the complex electromagnetic field distributions not obtainable by the conventional numerical schemes, such as finite and boundary elements means. However, our semi-analytical method encounters some difficulty when analyzing the high frequency electromagnetic field distributions because of the displacement currents.In the present paper, we propose a new semi-analytical approach taking the displacement currents into account to overcome this difficulty.

Seismic moment distribution revisited: II. Moment conservation principle

SUMMARY We compare the tectonic rate with earthquake data using several theoretical distributions to approximate the seismic moment‐frequency relation. We derive formulae to estimate parameters of the seismic moment distributions by comparing the earthquake occurrence rate with tectonic strain. We analyse the tectonic moment rate and the earthquake moment distribution for several types of tectonic environments, including subduction zones, plate bounding transform faults and deforming continental regions. In this analysis we use finer subdivisions of tectonic regions to infer whether earthquake size distribution properties established previously for large provinces (Flinn‐Engdahl seismic regions) could be applied to smaller zones extending over a few hundred kilometres. Although the shortness of the available earthquake catalogues makes our results less reliable, several conclusions can be drawn from the analysis. The universality of the β-parameter (the slope of the moment‐frequency relation) is reasonably well confirmed for all of these tectonic regions and their subdivisions. In each region, we estimate the strain rate or relative plate motion from a plate tectonic model, active fault data or geodetic data. According to the moment‐frequency relation, the ratio of the tectonic moment rate to the earthquake rate depends on the β value, the corner magnitude (mc) and the effective seismogenic thickness. We find that this ratio does not vary systematically with the relative plate velocity, the ratio of parallel to perpendicular plate motion, time since the last major earthquake and the length of fault zone segments established by previous earthquake history. We obtain similar results for the western United States and southeast Asia; the corner magnitude is approximately equal to that for the circum-Pacific Rim and there is no systematic dependence of the mc parameter on a geographic region or strain rate. Assuming the commonly accepted values for seismogenic thickness, elastic modulus and 100 per cent seismic coupling, the corner magnitude values for plate boundary zones and continental areas are 8.3‐8.8, i.e. similar to those values obtained by statistical analysis.

Correlation chart of the eastern Grenville Province and its northern foreland

Chart 2: Correlation chart of the eastern Grenville Province and its northern Foreland, including a location map showing regional geological subdivisions and reference list.

Electrophysiological profile of avian hippocampal unit activity: a basis for regional subdivisions.

Electrophysiological activity was recorded from single neurons (units) in the hippocampal formation (HF) of freely moving homing pigeons in order to provide a taxonomy of unit types found in the avian HF; a taxonomy that could be used to define regional subdivisions and be compared with unit types found in the mammalian hippocampus. Two distinct types of unit were observed in the avian HF. One type was uniformly characterized by relatively rapid firing rates and shorter spike widths, and was found throughout the HF. The other type was more variable in activity profile but, compared with the fast-firing units, was characterized by slower firing rates and longer spike widths. However, despite the variable nature of the slow-firing units, most slow-firing units recorded within a given anatomical region displayed similar firing rates, spike widths, and interspike intervals. In general, ventral HF units displayed activity patterns similar to projection cells found in the mammalian Ammon's horn. Most dorsocaudal units displayed activity patterns similar to presumed granular cells in the mammalian dentate gyrus. By contrast, most dorsorostral units displayed activity patterns similar to a type of unit found in the mammalian subiculum. Although different in some details, the overall activity profile of units found in the avian HF, and their regional distribution, is strikingly similar to unit types found in the mammalian hippocampus, suggesting that unit activity profile is one hippocampal dimension conserved through evolution.

A mutation in the Gsk3-binding domain of zebrafish Masterblind/Axin1 leads to a fate transformation of telencephalon and eyes to diencephalon.

Zebrafish embryos homozygous for the masterblind (mbl) mutation exhibit a striking phenotype in which the eyes and telencephalon are reduced or absent and diencephalic fates expand to the front of the brain. Here we show that mbl(-/-) embryos carry an amino-acid change at a conserved site in the Wnt pathway scaffolding protein, Axin1. The amino-acid substitution present in the mbl allele abolishes the binding of Axin to Gsk3 and affects Tcf-dependent transcription. Therefore, Gsk3 activity may be decreased in mbl(-/-) embryos and in support of this possibility, overexpression of either wild-type Axin1 or Gsk3beta can restore eye and telencephalic fates to mbl(-/-) embryos. Our data reveal a crucial role for Axin1-dependent inhibition of the Wnt pathway in the early regional subdivision of the anterior neural plate into telencephalic, diencephalic, and eye-forming territories.

Genetic structure of an introduced pest, grape phylloxera (Daktulosphaira vitifoliaeFitch), in Europe

A model for the genetic structure of grape phylloxera populations in Europe was developed using hierarchical sampling techniques and AFLP-PCR (amplified fragment length polymorphism - polymerase chain reaction) methodology. One-hundred three European and 6 North American phylloxera populations were studied. An additional European sampling set comprising 60 samples was analyzed to study regional subdivision. The populations grouped into two clusters loosely correlated with collection site location. Phylloxera populations collected from northern (above lat 43°) geographic regions were significantly different from southern (below 43°) populations. The northern cluster was more heterogeneous than the southern cluster, possibly reflecting holocyclic versus anholocyclic reproduction. Microgeographic scales of phylloxera genetic structure displayed as much variation within as among host plants. The host plant did not affect the genetic structure of European phylloxera as revealed in two independent experiments.Key words: Daktulosphaira vitifoliae, aphid, genetic structure, AFLP-PCR.

The CA1 region of the human hippocampus is a hot spot in Alzheimer's disease.

Data from an ongoing study of differences in the total number of neurons in the five major subdivisions of the hippocampal regions of the brains of patients with Alzheimer's disease (AD) and normal age-matched controls confirm an earlier finding from our laboratories of a pronounced loss of CA1 neurons associated with AD. In view of an earlier finding that the CA1 region does not suffer normal age-related neuronal loss, these data support the earlier conclusion that the neuropathologic mechanisms involved in the AD-related losses in CA1 are not related to normal aging and that the study of the cellular and molecular events involved in the AD-related loss of CA1 cells can aid in the identification of the unique pathologic processes associated with AD.

Gross Morphology and Topography of the Adult Intestinal Tract of the Tilapian Fish, Oreochromis niloticus L.

The intestinal tract of the Nile tilapia, Oreochromis niloticus L., follows a complex course involving multiple loops and coils arranged in a previously undescribed form. From cranial to caudal, five principal regions were identified and designated as the hepatic loop (HL), proximal major coil (PMC), gastric loop (GL), distal major coil (DMC), and terminal segment (TS). The first four of these regions each possessed a reversal flexure and thus could be divided into proximal and distal limbs. Only the terminal segment was straight and undivided. The PMC and DMC were disposed in a spiral, cone-shaped mass (spiral intestine) – their proximal and distal limbs are thus designated as centripetal and centrifugal limbs. These spiral limbs were arranged with each successive limb nested internal to the previous one. Beginning from the stomach, the complete course of the gut including designations of the subdivisions of the major regions was as follows: proximal limb of the HL, distal limb of the HL, centripetal limb of the PMC, centrifugal limb of the PMC, proximal limb of the GL, distal limb of the GL, centripetal limb of the DMC, centrifugal limb of the DMC, and the TS. Though the topographical relations of the various gut loops permitted ready identification of each, external surface features were so similar among the segments that extirpated segments of gut could not be identified as to region of origin. The nesting of successive intestinal loops of the spiral intestine in this fish is novel among patterns previously described, and also among the more intricate of those that have been described.

ABSTRACT: Regional Stratigraphy and Subdivision, Lower Part of Upper Wilcox, Duval Delta Area, South Texas

ABSTRACT: Regional Stratigraphy and Subdivision, Lower Part of Upper Wilcox, Duval Delta Area, South Texas

High-Resolution Sequence Stratigraphic Analysis of the St. Peter Sandstone and Glenwood Formation (Middle Ordovician), Michigan Basin, U.S.A.

The Middle Ordovician St. Peter Sandstone and Glenwood Formation (Ancell Group) represent a significant target for gas exploration at the base of the Tippecanoe sequence in the Michigan basin. Core and well log data show that the St. Peter-Glenwood interval contains numerous carbonate units that provide the basis for both regional correlation and subdivision of the section into at least 20 high-frequency sequences. The temporal resolution afforded by these sequences allows a detailed analysis of sediment partitioning as the basin evolved. The spatial distribution of the basal sequences illustrates the pronounced east-to-west onlap of the Wisconsin arch. An abrupt increase in sequence thickness upsection indicates that a major episode of basin-centered subsidence began during middle St. Peter deposition and continued through the deposition of the Glenwood Formation. The upper sequences show a significant beveling of the Glenwood Formation and the top of the St. Peter Sandstone in the north, south, and southeast areas of the basin prior to deposition of the overlying Black River carbonates. Although eustatic sea level changes were undoubtedly operating at several scales, the facies distribution of this mixed clastic/carbonate system also documents significant changes of local and regional tectonics.

Genetic structure of an introduced pest, grape phylloxera (<i>Daktulosphaira vitifoliae</i> Fitch), in Europe

A model for the genetic structure of grape phylloxera populations in Europe was developed using hierarchical sampling techniques and AFLP-PCR (amplified fragment length polymorphism--polymerase chain reaction) methodology. One-hundred three European and 6 North American phylloxera populations were studied. An additional European sampling set comprising 60 samples was analyzed to study regional subdivision. The populations grouped into two clusters loosely correlated with collection site location. Phylloxera populations collected from northern (above lat 43 degrees) geographic regions were significantly different from southern (below 43 degrees) populations. The northern cluster was more heterogeneous than the southern cluster, possibly reflecting holocyclic versus anholocyclic reproduction. Microgeographic scales of phylloxera genetic structure displayed as much variation within as among host plants. The host plant did not affect the genetic structure of European phylloxera as revealed in two independent experiments.

Long W tracts are over-represented in the Escherichia coli and Haemophilus influenzae genomes.

The occurrence of DNA tracts of the three binary base combinations: R.Y, K.M and W;S has been mapped in the complete genomes of Haemophilus influenzae and Escherichia coli. A highly significant over-representation of W tracts is observed in both bacteria. The excess of W tracts is particularly striking in the 10% intercoding regions. Subdivision of intercoding regions into divergent (promoting), convergent (terminating) and sequential subregions shows that the excess of W tracts is most concentrated in the promoter regions. A particularly high excess of W tracts is observed in the first 200 bases 5' upstream of coding start sites. The data suggest that W tracts have a role in promoter function. A function as unwinding centers, analogous to the role of R.Y tracts in eukaryotes, is proposed. R.Y and K.M tracts are only modestly over-represented in the two bacteria.

Neurochemical evidence for at least two regional subdivisions within the homing pigeon (Columba livia) caudolateral neostriatum.

The distributions of one neurotransmitter, two neurotransmitter-related substances, and five neuropeptides were examined within the homing pigeon caudolateral neostriatum (NCL). All eight neuroactive substances were found within a tyrosine hydroxylase (TH)-dense region that defines the NCL. Overall regional variation in the relative density of these substances suggested at least two neurochemically distinct portions of NCL. Dorsal NCL contained relatively dense staining for TH, choline acetyltransferase, and substance P, whereas vasoactive intestinal polypeptide was more abundant in ventral portions of NCL. Serotonin and cholecystokinin were found to be densest in intermediate portions of NCL. Somatostatin and leucine-enkephalin were homogeneously distributed throughout NCL. The results suggest that NCL may consist of multiple subdivisions. Investigations into the behavioral importance of these regions are necessary to clarify the role of this brain region in avian behavior.

Characteristics of Australian Land Surface Temperature Variability

A study of the variability of Australian surface maximum and minimum temperature on seasonal and longer time scales for the period 1950 to 1994 is described. Using principal component analysis in the S-mode, it is shown that the variability of Australian temperature is dominated by the large scale, with approximately 80 percent of the temporal variance being explained by five independent modes. The application of orthogonal rotation techniques to these modes, has revealed that this variability displays much simple structure and is physically interpretable in terms of five largely non-overlapping spatial patterns. These five patterns, centred over the east, north, southwest, northwest and southeast of Australia are found when the analysis is performed on maximum and minimum temperature, using monthly, seasonal and annual data and appear to be a natural and optimal subdivision of the Australian region for the description of land surface temperature variability. The highly compressed description of the temperature data provided by the rotated principal component modes is then used to investigate the characteristics and some mechanisms of Australian temperature variability. This analysis confirms the presence of a secular warming trends across much of Australia, but also reveals that some 80 to 90 percent of the temporal variance is unrelated to this trend. The role of rainfall and the El Nino-Southern Oscillation (ENSO) in modulating temperature is also investigated.

Dinoflagellate cysts and microforaminifera of the Lower Cretaceous Yatria River section, Subarctic Ural, NW Siberia (Russia). Biostratigraphy, palaeoenvironmental and palaeogeographic discussion

Rich assemblages of phytoplankton and microforaminifera (foraminifera linings) are found in the marine Lower Cretaceous section from the Yatria River (Subarctic Ural). The Lower Cretaceous (Upper Volgian to Lower Hauterivian) dinocyst and microforaminifera biostratigraphy is calibrated against the ammonite zones. The dinocyst stratigraphy differs from Arctic Canada zonation, except for the Berriasian Paragonyaulacysta? borealis zone, and shows significant similarity with the zonal subdivision of Boreal regions of Europe. The distribution of phytoplankton and microforaminifera is related to relative sea level variations. Consecutive changes of phytoplankton associations (2 in the Berriasian, 3 in the Valanginian-Early Hauterivian, 4 in the Early Hauterivian), lateral zonations of microforaminifera (2 in the Berriasian, 2 in the Valanginian) and their relation to environmental changes in the Lower Cretaceous seas of the Subarctic Ural Basin are established.

Daily rainfall affinity areas in Mediterranean Spain

A subdivision of the Spanish Mediterranean region into daily rainfall affinity areas was conducted using a pluviometric data base of 410 gauges for the period 1964–1993. Areas were derived using principal components analysis on the between-site correlation matrix. Two regionalizations defining 12 areas are offered: the first, non-overlapping, solution is derived by cluster analysis on the most important unrotated PCs extracted, while the second, with overlapping pluviometric regions, is obtained by mapping the obliquely rotated principal components. Both solutions are similar, and emphasize the dominant role exerted by the complex topography of the region on the spatial organization of rainfall through its interaction with the main rain-bearing airflows and systems. A higher-resolution regionalization comprising 20 non-overlapping areas is also included. South and southeast domains, where topography is very prominent and complex, as well as the Balearic Islands, contain most of the additional detail offered by this solution. Copyright © 1999 Royal Meteorological Society

Patterns of gene flow and population genetic structure in the canyon treefrog, Hyla arenicolor (Cope).

Patterns of gene flow and genetic structuring were examined in the canyon treefrog, Hyla arenicolor (Cope). Hierarchical analysis of genetic variation was performed on mitochondrial cytochrome b haplotypes from 323 individuals, representing 32 populations from previously described phylogeographic regions. Results from AMOVA revealed that 60.4-78.9% of the recovered genetic variation was the result of differences in the appointment of genetic variation between subdivisions of the primary phylogeographic regions. In contrast, populations only contained between 13.9 and 30.1% of the observed haplotypic variation. Gene flow estimates based on calculations of phi ST revealed moderate levels of gene flow within phylogeographic regions, but there was no evidence of gene flow between these regions, suggesting that geographical boundaries were probably important in the formation of phylogeographic structure in H. arenicolor. Phylogeographic regions exhibited very different patterns of gene flow. One region showed evidence of recent colonization. Another region exhibited very limited gene flow. Moderate to high estimates of gene flow were obtained for populations from two distinct phylogeographic regions characterized by mesic and xeric environments. Isolation by distance was observed in both regions suggesting that these regions are in genetic equilibrium. Because gene flow is extremely unlikely between the populations in the xeric region, this result is interpreted as historical gene flow. These results indicate that isolation-by-distance effects may still be observed even when population genetic structure and gene flow are the result of historical association.

Cardiosensor Mice and Transcriptional Subdomains of the Vertebrate Heart

Differential regulation of cardiac gene expression in vertebrates has been extensively documented in the context of atrial and ventricular morphogenesis. Recent data, largely from the analysis of transgene and endogenous gene expression patterns, have revealed transcriptional differences between left and right cardiac chambers which suggest that the heart is composed of a series of distinct transcriptional domains. Such phenomena provide regional markers (cardiosensors) for the fine analysis of normal and abnormal heart development. Regional subdivisions and transcriptional heterogeneity within the myocardium emerge in response to patterning of the precardiac mesoderm and early heart tube on the anterior-posterior axis, and to embryonic left-right signals which dictate the direction of cardiac looping. Several families of transcription factors have been characterized which may be implicated in the regionalization of myocardial gene expression.

Use of ring recoveries to monitor long-term changes in the survival rates of British and Irish Cormorants Phalacrocorax carbo

Ring recovery data were used to assess changes in the survival rates of Cormorants in Britain and Ireland between 1965 and 1994. It was found that 99% were ringed as nestlings, thus necessitating an assumption of constant reporting rate across age-classes. The wide geographical spread of ringing effort since 1965 produced sufficient recoveries to enable analyses of trends in survival and reporting rates, but regional subdivisions of the data resulted in high sampling correlations between survival estimates. The assumption of a constant reporting rate across age-classes may be violated for British and Irish Cormorants, because first-year birds are more likely to be shot or caught in fishing nets than older birds and they have a differing seasonal pattern of recoveries. A simple simulation showed that first-year, but not adult, survival estimates were particularly sensitive to age-specific variation in reporting rates. However, the observed trend in first-year survival appeared robust to the assumption of constant reporting rates across age-classes. Declining reporting rates in Britain and Ireland imply that larger numbers of Cormorants will need to be ringed in order to monitor future changes in survival. Regional colour marking schemes for Cormorants have the potential to provide high quality survival information, to supplement that provided by dead recoveries and to offset the observed decline in reporting rates.