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Abstract: In response to hypoxia, chemoreceptor cells of the carotid body (CB) release transmitters, which acting on the petrosal ganglion (PG) neuron terminals, increase the chemoafferent discharge. Additionally, vasoactive molecules produced within the CB may modulate hypoxic chemoreception by controlling blood flow and tissue PO2. Endothelin-1 (ET-1) increases basal CB chemosensory discharges in situ, probably due to its vasoconstrictor action. However, the actions of ET-1 on PG neurons or its expression in the PG are not known. Using immunohistochemistry, we found that endothelin-like peptides are expressed in the cat PG and CB under normoxic conditions. Exogenous applications of ET-1 increased the chemosensory activity in the vascularly perfused CB but were ineffective on either the CB or PG superfused preparations, both of which are devoid of vascular control. Thus, our data indicate that the excitatory effect of ET-1 in the carotid chemoreceptor system appears to be mainly due to a vasoconstrictor effect in the CB blood vessels. [Copyright &y& Elsevier]

The article discusses various reports published within the issue, including one by Luc Anselin, Ibnu Syabri and Youngihn Kho which provides an overview of GeoDa, a free program supporting interactive exploratory spatial data analysis and another by Roger Bivand which provides an overview of work implementing functions for spatial statistical analysis in the open-source R language environment.

Space–Time Analysis of Regional Systems (STARS) is an open-source package designed for the dynamic exploratory analysis of data measured for areal units at multiple points in time. STARS consists of four core analytical modules: Anselin (1995) exploratory spatial data analysis; Anselin (2003) inequality measures; Carlino and Mills (1993) mobility metrics; and Christakos, Bogaert, and Serre (2001) spatial Markov. Developed using the Python object-oriented scripting language, STARS lends itself to three main modes of use. Within the context of a command line interface (CLI), STARS can be treated as a package which can be called from within customized scripts for batch-oriented analyses and simulation. Alternatively, a graphical user interface (GUI) integrates most of the analytical modules with a series of dynamic graphical views containing brushing and linking functionality to support the interactive exploration of the spatial, temporal, and distributional dimensions of socioeconomic and physical processes. Finally, the GUI and CLI modes can be combined for use from the Python shell to facilitate interactive programming and access to the many libraries contained within Python. This article provides an overview of the design of STARS, its implementation, functionality, and future plans. A selection of its analytical capabilities are also illustrated that highlight the power and flexibility of the package. [ABSTRACT FROM AUTHOR]

The carotid body (CB) chemoreceptors may play an important role in the enhanced hypoxic ventilatory response induced by chronic intermittent hypoxia (CIH). We studied the effects of cyclic hypoxic episodes of short duration on cat cardiorespiratory reflexes, heart rate variability, and CB chemosensory activity. Cats were exposed to cyclic hypoxic episodes (PO2 ∼ 75 Torr) repeated during 8 h for 2-4 days. Cats were anaesthetized with sodium pentobarbitone (40 mg kg-1 I.R, followed by 8-12 mg i.v.), and ventilatory and cardiovascular responses to NaCN (0.1-100 µg kg-1 i.v.) and several isocapnic levels of oxygen (PO2 ∼ 20-740 Torr) were studied. After studying the reflex responses, we recorded the CB chemosensory responses induced by the same stimuli. Results showed that CIH for 4 days selectively enhanced cat CB ventilatory (VT and VI) responses to hypoxia, while responses to NaCN remained largely unchanged. Similarly, basal CB discharges and responses to acute hypoxia (PO2 < 100 Torr) were larger in CIH than in control cats, without modification of the responses to NaCN. Exposure to CIH did not increase hasal arterial pressure, heart rate, or their changes induced by acute hypoxia or hyperoxia. However, the spectral analysis of heart rate variability of CIH cats showed a marked increase of the low-/high-frequency ratio and an increase of the power spectral distribution of low frequencies of heart rate variability. Thus, the enhanced CB reactivity to hypoxia may contribute to the augmented ventilatory response to hypoxia, as well as to modified heart rate variability due to early changes in autonomic activity. [ABSTRACT FROM AUTHOR]

Explores the influence of Walter Isard on analytical human geography.

This article examines the publication patterns in five core regional science journals during the 1990s. Attention is paid to the thematic distribution of articles for each journal and across journals. The journals am also compared with respect to citation counts, areas of concentration, and authorship patterns. The impact of each article is examined through an analysis of citations over the decade. Productivity of individual scholars is measured using article counts, page counts, and citation indices. [ABSTRACT FROM AUTHOR]

In this paper we move away from a static view of neighbourhood inequality and investigate the dynamics of neighbourhood economic status, which ties together spatial income inequality at different moments in time. Using census data from three decades (1980–2010) in 294 metropolitan statistical areas, we use a statistical decomposition method to unpack the aggregate spatiotemporal income dynamic into its contributing components: stability, growth and polarisation, providing a new look at the economic fortunes of diverse neighbourhoods. We examine the relative strength of each component in driving the overall pattern, in addition to whether, how, and why these forces wax and wane across space and over time. Our results show that over the long run, growth is a dominant form of change across all metros, but there is a very clear decline in its prominence over time. Further, we find a growing positive relationship between the components of dispersion and growth, in a reversal of prior trends. Looking across metro areas, we find temporal heterogeneity has been driven by different socioeconomic factors over time (such as sectoral growth in certain decades), and that these relationships vary enormously with geography and time. Together these findings suggest a high level of temporal heterogeneity in neighbourhood income dynamics, a phenomenon which remains largely unexplored in the current literature. There is no universal law governing the changing economic status of neighbourhoods in the US over the last 40 years, and our work demonstrates the importance of considering shifting dynamics over multiple spatial and temporal scales. [ABSTRACT FROM AUTHOR]

A recent review noted important differences in the results of the local Moran's Ii statistic depending on the inference method. These differences had significant practical implications. In closing, the authors speculated the differences may be due to local spatial heterogeneity. In this article, we propose that different null hypotheses, not heteroskedasticity, generate these differences. To test this, we examine the null hypotheses implicit in common statistical significance tests of local Moran's Ii. We design an experiment to assess the impact of local heterogeneity on tests conducted under the two most common null hypotheses. In this experiment, we analyze the relationship between measures of local variance, such as the local spatial heteroskedasticity (LOSH) statistic, and components of the local Moran's Ii statistic. We run this experiment with controlled synthetic heteroskedastic data and with uncontrolled real‐world data with varying degrees and patterns of local heteroskedasticity. We show that, in both situations, estimates that use the same null are extremely similar, regardless of estimation method. In contrast, all estimates (regardless of the null) are moderately affected by spatial heteroskedasticity. Ultimately, this article demonstrates that there are important conceptual and computational differences about null hypothesis in local testing frameworks, and these differences can have significant practical implications. Therefore, researchers must be aware as to how their choices may shape the observed spatial patterns. [ABSTRACT FROM AUTHOR]

Explores the extension of integrated econometric/input-output models from a single to a multiregional context. Importance of integrated econometric/input-output models; Multiregional linkages in regional econometric models; Integrated approaches towards multiregional linkages; Empirical illustrations; Discussion of results; Conclusions.

Choropleth mapping is an essential visualization technique for exploratory spatial data analysis. Visualizing multiple choropleth maps is a technique that spatial analysts use to reveal spatiotemporal patterns of one variable or to compare the geographical distributions of multiple variables. Critical features for effective exploration of multiple choropleth maps are (1) automated computation of the same class intervals for shading different choropleth maps, (2) dynamic visualization of local variation in a variable, and (3) linking for synchronous exploration of multiple choropleth maps. Since the 1990s, these features have been developed and are now included in many commercial geographic information system (GIS) software packages. However, many choropleth mapping tools include only one or two of the three features described above. On the other hand, freely available mapping tools that support side-by-side multiple choropleth map visualizations are usually desktop software only. As a result, most existing tools supporting multiple choropleth-map visualizations cannot be easily integrated with Web-based and open-source data visualization libraries, which have become mainstream in visual analytics and geovisualization. To fill this gap, we introduce an open-source Web-based choropleth mapping tool called the Adaptive Choropleth Mapper (ACM), which combines the three critical features for flexible choropleth mapping. [ABSTRACT FROM AUTHOR]

We report microplastic densities on windward beaches of Oahu, Hawai'i, USA, an island that received about 6 million tourist visits a year. Microplastic densities, surveyed on six Oahu beaches, were highest on the beaches with the coarsest sands, associated with high wave energy. On those beaches, densities were very high (700–1700 particles m-2), as high as those recorded on other remote island beaches worldwide. Densities were higher at storm tide lines than high tide lines. Results from our study provide empirical data on the distribution of microplastics on the most populated and visited of the Hawaiian islands. [ABSTRACT FROM AUTHOR]

Income mobility measures provide convenient and concise ways to reveal the dynamic nature of regional income distributions. Statistical inference about these measures is important especially when it comes to a comparison of two regional income systems. Although the analytical sampling distributions of relevant estimators and test statistics have been asymptotically derived, their properties in small sample settings and in the presence of contemporaneous spatial dependence within a regional income system are underexplored. We approach these issues via a series of Monte Carlo experiments that require the proposal of a novel data generating process capable of generating spatially dependent time series given a transition probability matrix and a specified level of spatial dependence. Results suggest that when sample size is small, the mobility estimator is biased while spatial dependence inflates its asymptotic variance, raising the Type I error rate for a one-sample test. For the two-sample test of the difference in mobility between two regional economic systems, the size tends to become increasingly upward biased with stronger spatial dependence in either income system, which indicates that conclusions about differences in mobility between two different regional systems need to be drawn with caution as the presence of spatial dependence can lead to false positives. In light of this, we suggest adjustments for the critical values of relevant test statistics. [ABSTRACT FROM AUTHOR]

The article presents information on the role of hypoxia-inducible factor (HIF)-1 in the promotion of breast cancer. Breast cancer patients with increased HIF-1levels in their tumor biopsies have significantly reduced survival. HIF-1dependent expression of platelet-derived growth factor B enhances lymphatic metastasis of hypoxic breast cancer cells.

Monitoring market share changes over space and time is an essential and continuous task for commercial companies and their third-party local agents to adjust their sale campaigns and marketing efforts for profit maximisation. This paper uses social media data as a cheap and up-to-date source to reveal the implicit semantics that are embedded in the meta-data of public geosocial datasets. We use Twitter data as a prime example of rich geosocial data. These data are associated with several meta-data attributes. Using this meta-data, we perform a geospatial analysis for the source platform from which a tweet is posted, e.g. from Apple or Android device. Our analysis studies all counties in US connected states over 2 years 2016-2017. We show that market structure at the national level masks substantial variation at the county scale. Moreover, we find strong spatial autocorrelation in platform distribution and market share in the US. In addition, we show interesting changes over the 2 years that motivates further analysis at different spatial and temporal levels. Our results are supported with visual maps of location quotients and market dominance, in addition to formal test results of spatial autocorrelation, and spatial Markov analysis. [ABSTRACT FROM AUTHOR]

Urbanization is a natural and social process involving simultaneous changes to the Earth’s land systems, energy flow, demographics, and the economy. Understanding the spatiotemporal pattern of urbanization is increasingly important for policy formulation, decision making, and natural resource management. A combination of satellite remote sensing and patch-based models has been widely adopted to characterize landscape changes at various spatial and temporal scales. Nevertheless, the validity of this type of framework in identifying long-term changes, especially subtle or gradual land modifications is seriously challenged. In this paper, we integrate annual image time series, continuous spatial indices, and non-parametric trend analysis into a spatiotemporal study of landscape dynamics over the Phoenix metropolitan area from 1991 to 2010. We harness local indicators of spatial dependence and modified Mann-Kendall test to describe the monotonic trends in the quantity and spatial arrangement of two important land use land cover types: vegetation and built-up areas. Results suggest that declines in vegetation and increases in built-up areas are the two prevalent types of changes across the region. Vegetation increases mostly occur at the outskirts where new residential areas are developed from natural desert. A sizable proportion of vegetation declines and built-up increases are seen in the central and southeast part. Extensive land conversion from agricultural fields into urban land use is one important driver of vegetation declines. The xeriscaping practice also contributes to part of vegetation loss and an increasingly heterogeneous landscape. The quantitative framework proposed in this study provides a pathway to effective landscape mapping and change monitoring from a spatial statistical perspective. [ABSTRACT FROM AUTHOR]

Within residential electricity consumption there exists significant variability from home-to-home due to the differences in building thermal properties, appliances, and inhabitants. Electricity analyses at sub-city scales using predefined geographies, such census tracts, might artificially split areas with homogenous characteristics leading to analyses that don't effectively contrast the drivers of energy use. The objective of this study is to use the spatial relationships between demographics, building types, and electricity consumption to form new geographies with less variability for use in residential energy assessment. Using Los Angeles and New York City as case studies, differences in energy use variability within predefined geographies (e.g., census tract) are compared to geographies defined by clustering on socio-technical characteristics. Socio-technical clustering, regardless of the chosen subset of variables, reduces the energy consumption variability over pre-defined geopolitical boundaries with high statistical significance (p<<0.0001). By clustering, intra-regional variability is reduced by 13% in Los Angeles and 29% in New York, therefore improving opportunities for prediction and forecasting. This is the first study to examine the role of spatial boundaries in urban energy assessment. The creation of socio-technical geographies for electricity assessment creates opportunities for improving predictions and forecasts for future sub- and cross-city energy studies. [ABSTRACT FROM AUTHOR]

Racial segregation in public education has been declared as unconstitutional for over 60 years in the United States. Yet many public school districts remain largely separate and unequal. A commonly used approach to reduce school segregation is redelineating school attendance zones to create more racially diverse classrooms. However, there is a need for a school districting approach that can minimize racial or socioeconomic segregation at the district level. In this paper, we develop a spatial optimization model that delineates school attendance zones with the aim of minimizing racial segregation of school district to enable the assessment of the impacts of school attendance zones on the racial segregation of school district. Applications of this model to Riverside Unified School District (RUSD) and San Diego Unified School District (SDUSD) in California, USA show that it is possible to reduce racial segregation by 64% at RUSD and 56% at SDUSD, demonstrating the potential of the proposed model. • Develop a method that assigns students to schools with the goal of minimizing racial segregation. • Highlight the potential of school districts to reduce segregation by adjusting student assignment. • The applications demonstrate a significant reduction of racial segregation. [ABSTRACT FROM AUTHOR]

Obstructive sleep apnea patients and chronic intermittent hypoxia (CIH) animal models present increased cardiovascular responses. Therefore, it is possible that increased chemoreflexes and decreased baroreflex sensitivity (BRS) would elicit sympathetic overactivity, inducing hypertension. We previously showed that exposure of cats to CIH for 4 days increases the carotid body chemosensory and ventilatory responses to hypoxia. Thus, we studied the effect of brief exposure to CIH in cats for 4 days on sympathetic tone and BRS, using spectral analysis of heart rate variability (HRV), blood pressure variability (BPV) and BRS determination with the sequence method. In anesthetized cats we evaluated the effect of acute hypoxia on heart rate and blood pressure. Data was digitized with a PowerLab 8SP A/D interface and stored in a PC computer. For HRV and BPV analysis, we used autoregressive methods for estimation of the spectral density at the low-frequency (LF, 0.025-0.15) and high-frequency (HF, 0.15-0.833) bands. We compared control (normoxic) cats with animals exposed to sham-CIH and CIH. We found that CIH-treated cats showed enhanced tachycardic responses to acute severe hypoxia, with reduced HRV and BRS. Our data suggests that CIH exposure for 4 days induced early autonomic changes that favor an enhanced sympathetic outflow and decreased baroreflex control on blood pressure. [ABSTRACT FROM AUTHOR]

This article focuses on the subject and author indexes that list all articles and comments published in the 2002 issues of the included journals. The subject index is arranged alphabetically by author within eighty-six categories. Articles are listed in only one category, so readers are advised to examine the listings in categories related to their primary interests.

Offers information on subject and author indexes of articles pertaining to regional science.

Abstract. Recent research on integrated econometric+input-output modeling for regional economies is reviewed. The motivations for and the alternative methodological approaches to this type of analysis are examined. Particular attention is given to the issues arising from multiregional linkages and spatial effects in the implementation of these frameworks at the sub-national scale. The linkages between integrated modeling and spatial econometrics are outlined. Directions for future research on integrated econometric and input-output modeling are identified. [ABSTRACT FROM AUTHOR]

The best obstacle avoiding path in continuous space, referred to as the Euclidean shortest path, is important for spatial analysis, location modeling and wayfinding tasks. This problem has received much attention in the literature given its practical application, and several solution techniques have been proposed. However, existing approaches are limited in their ability to support real time analysis in big data environments. In this research a multicore computing approach is developed that exploits spatial knowledge through the use of geographic information system functionality to efficiently construct an optimal shortest path. The approach utilizes the notion of a convex hull for iteratively evaluating obstacles and constructing pathways. Further, the approach is capable of incrementally improving bounds, made possible through parallel processing. Wayfinding routes that avoid buildings and other obstacles to travel are derived and discussed. [ABSTRACT FROM AUTHOR]

In this paper, we report efforts to develop a parallel implementation of thep-compact regionalization problem suitable for multi-core desktop and high-performance computing environments. Regionalization for data aggregation is a key component of many spatial analytical workflows that are known to be NP-Hard. We utilize a low communication cost parallel implementation technique that provides a benchmark for more complex implementations of this algorithm. Both the initialization phase, utilizing a Memory-based Randomized Greedy and Edge Reassignment (MERGE) algorithm, and the local search phase, utilizing Simulated Annealing, are distributed over available compute cores. Our results suggest that the proposed parallelization strategy is capable of solving the compactness-driven regionalization problem both efficiently and effectively. We expect this work to advance CyberGIS research by extending its application areas into the regionalization world and to make a contribution to the spatial analysis community by proposing this parallelization strategy to solve large regionalization problems efficiently. [ABSTRACT FROM PUBLISHER]

The industrial composition of places has received considerable attention because of the widespread belief that industrial diversity buffers regional economies from economic shocks. Subsequently, a variety of toolkits and indices have been developed with the goal of better capturing the compositional dynamics of regions. Although useful, a key drawback of these indices is their static nature, which limits the utility of these indices in a space-time context. This paper provides an overview of and applications of an interface called interactive visualization tool for indices of industrial diversity, which is a visual analytics tool developed specifically for the analysis and visualization of local measures of industrial composition for areal data. This overview will include a discussion of its key features, as well as a demonstration of the utility of the interface in exploring questions surrounding diversity and the dynamic nature of composition through space and time. A focus of this demonstration is to highlight how the interactivity and query functionality of this interface overcome several of the obstacles to understanding composition through space and time that prior toolkits and comparative static approaches have been unable to address. [ABSTRACT FROM AUTHOR]

Abstract: Common to all tests of space–time interaction is the assumption that the population underlying the events of interest exhibits a trajectory of growth that is consistent through time and across space. In practice, however, this assumption is often untenable and, when violated, can introduce population shift bias into the results of these tests. While this problem is widely recognized, more work remains to compare its effect across tests and to determine the extent to which it is a problem for study short periods. This paper quantifies and compares the population shift bias present in the results of the Knox, Mantel, and Jacquez tests of space–time interaction. A simulation study is carried out which quantifies the bias present in each test across a variety of population movement scenarios. Results show a positive relationship between population shift bias and the heterogeneity in population growth across all the tests. They also demonstrate variability in the size of the bias across the three tests for space–time interaction considered. Finally, the results illustrate that population shift bias can be a serious problem for short study periods. Collectively, these findings suggest that an unbiased approach to assessing the significance of space–time interaction test results is needed whenever spatially heterogeneous population change is identified within a study area. [Copyright &y& Elsevier]

ABSTRACT In this paper, we introduce a new spatially constrained clustering problem called the max- p-regions problem. It involves the clustering of a set of geographic areas into the maximum number of homogeneous regions such that the value of a spatially extensive regional attribute is above a predefined threshold value. We formulate the max- p-regions problem as a mixed integer programming (MIP) problem, and propose a heuristic solution. [ABSTRACT FROM AUTHOR]

Impaired wound healing in the elderly represents a major clinical problem. Delineating the cellular and molecular mechanisms by which aging impairs wound healing may lead to the development of improved treatment strategies for elderly patients with non-healing wounds. Neovascularization is an essential step in wound healing, and bone marrow-derived angiogenic cells (BMDACs) play an important role in vascularization. Using a mouse full-thickness burn wound model, we demonstrate that perfusion and vascularization of burn wounds were impaired by aging and were associated with dramatically reduced mobilization of BMDACs bearing the cell surface molecules CXCR4 and Sca1. Expression of stromal-derived factor 1 (SDF-1), the cytokine ligand for CXCR4, was significantly decreased in peripheral blood and burn wounds of old mice. Expression of hypoxia-inducible factor (HIF)-1α was detected in burn wounds from young (2-month-old), but not old (2-year-old), mice. When BMDACs from young donor mice were injected intravenously, homing to burn wound tissue was impaired in old recipient mice, whereas the age of the BMDAC donor mice had no effect on homing. Our results indicate that aging impairs burn wound vascularization by impairing the mobilization of BMDACs and their homing to burn wound tissue as a result of impaired HIF-1 induction and SDF-1 signaling. [ABSTRACT FROM AUTHOR]

Using a cell-based reporter gene assay, we screened a library of drugs in clinical use and identified the anthracycline chemotherapeutic agents doxorubicin and daunorubicin as potent inhibitors of hypoxia-inducible factor 1 (HIF-1)-mediated gene transcription. These drugs inhibited HIF-1 by blocking its binding to DNA. Daily administration of doxorubicin or daunorubicin potently inhibited the transcription of a HIF-1-dependent reporter gene as well as endogenous HIF-1 target genes encoding vascular endothelial growth factor, stromal-derived factor 1, and stem cell factor in tumor xenografts. CXCR4+/sca1+, VEGFR2+/CD34+, and VEGFR2+/ CD117+ bone-marrow derived cells were increased in the peripheral blood of SCID mice bearing prostate cancer xenografts but not in tumor-bearing mice treated for 5 days with doxorubicin or daunorubicin, which dramatically reduced tumor vascularization. These results provide a molecular basis for the antiangiogenic effect of anthracycline therapy and have important implications for refining the use of these drugs to treat human cancer more effectively. [ABSTRACT FROM AUTHOR]

In the absence of information on functional manifestations of carotid body (CB) inflammation, we studied an experimental model in which lipopolysaccharide (LPS) administration to pentobarbitone-anaesthetized cats was performed by topical application upon the CB surface or by intravenous infusion (endotoxaemia). The latter caused: (i) disorganization of CB glomoids, increased connective tissue, and rapid recruitment of polymorphonuclear cells into the vascular bed and parenchyma within 4 h; (ii) increased respiratory frequency and diminished ventilatory chemoreflex responses to brief hypoxia (breathing 100% N2 for 10 s) and diminished ventilatory chemosensory drive (assessed by 100% O2 tests) during normoxia and hypoxia; (iii) tachycardia, increased haematocrit and systemic hypotension in response to LPS i.v.; and (iv) increased basal frequency of carotid chemosensory discharges during normoxia, but no change in maximal chemoreceptor responses to brief hypoxic exposures. Lipopolysaccharide-induced tachypnoea was prevented by prior bilateral carotid neurotomy. Apoptosis was not observed in CBs from cats subjected to endotoxaemia. Searching for pro-inflammatory mediators, tumour necrosis factor-α (TNF-α) was localized by immunohistochemistry in glomus and endothelial cells; reverse transcriptase-polymerase chain reaction revealed that the CB expresses the mRNAs for both type-1 (TNF-R1) and type-2 TNF-α receptors (TNF-R2); Western blot confirmed a band of the size expected for TNF-R1; and histochemistry showed the presence of TNF-R1 in glomus cells and of TNF-R2 in endothelial cells. Experiments in vitro showed that the frequency of carotid nerve discharges recorded from CBs perfused and superfused under normoxic conditions was not significantly modified by TNF-α, but that the enhanced frequency of chemosensory discharges recorded along responses to hypoxic stimulation was transiently diminished in a dose-dependent manner by TNF-α injections. The results suggest that the CB may operate as a sensor for immune signals, that the CB exhibits histological features of acute inflammation induced by LPS, that TNF-α may participate in LPS-induced changes in chemosensory activity and that some pathophysiological reactions to high levels of LPS in the bloodstream may originate from changes in CB function. [ABSTRACT FROM AUTHOR]

Question: What changes in species composition and cover have occurred in chaparral as a function of fire history across an ecoregion? Location: San Diego County, California, USA. Methods: Stands in which 40 mid-elevation chaparral vegetation plots (each 400 m² in area) were located in the 1930s were resurveyed in 2001. We stratified the stands into Infrequently versus Frequently burned (0-1 versus 2 or more fires recorded in the 91-yr period), and Immature versus Mature (≤31 yr versus >31 yr since last fire), resulting in four groups. Ten stands were randomly selected from each of these groups for survey. Results: There were no major shifts in life form composition, e.g., live oak trees were not invading chaparral that had experienced little or no fire, nor were subshrubs or herbaceous species replacing shrubs in areas that had experienced more frequent fires. However, there was a notable increase in the frequency of the subshrub Eriogonum fasciculatum across all fire history groups. In the mature stands with infrequent fire, average cover of resprouting shrubs increased (from 72 to 91%) and cover of obligate seeding shrubs (species with firecued germination) decreased (from 21 to 6%) significantly. Mature stands with frequent fire showed a significant decrease in resprouter cover (from 87 to 80%) and increase in obligate seeders (from 10 to 16%). Conclusions: While the tremendous changes in land use in southern California have been predicted to cause shifts in chaparral composition, these shifts are difficult to detect because species longevity and fire cycles are on the order of decades to a century. In this study, the expected trends could only be detected in groups that were mature at the time of the second survey. [ABSTRACT FROM AUTHOR]

We tested the hypothesis that nitric oxide (NO) produced within the carotid body is a tonic inhibitor of chemoreception and determined the contribution of neuronal and endothelial nitric oxide synthase (eNOS) isoforms to the inhibitory NO effect. Accordingly, we studied the effect of NO generated from S-nitroso-Nacetylpenicillamide (SNAP) and compared the effects of the nonselective inhibitor N[sub ω]-nitro-L-arginine methyl ester (LNAME) and the selective nNOS inhibitor 1-(2-trifluoromethylphenyl)-imidazole (TRIM) on chemosensory dose-response curves induced by nicotine and NaCN and responses to hypoxia (Po[sub 2] ≈ 30 Torr). CBs excised from pentobarbitoneanesthetized cats were perfused in vitro with Tyrode at 38°C and pH 7.40, and chemosensory discharges were recorded from the carotid sinus nerve. SNAP (100 µM) reduced the responses to nicotine and NaCN. L-NAME (1 mM) enhanced the responses to nicotine and NaCN by increasing their duration, but TRIM (100 µM) only enhanced the responses to high doses of NaCN. The amplitude of the response to hypoxia was enhanced by L-NAME but not by TRIM. Our results suggest that both isoforms contribute to the NO action, but eNOS being the main source for NO in the cat CB and exerting a tonic effect upon chemoreceptor activity. [ABSTRACT FROM AUTHOR]

Reflects on encounters with scholar William Alfonso. Achievements of Alfonso; Views on Alfonso.

Presents subject index to the 1998 'International Regional Science Review' and related journal literature.'

Aim Regional patterns of forest composition in West Polynesia were analysed to determine the relative importance of dispersal limitation, speciation, environmental filtering and biotic interactions. Location West Polynesia (Fiji, Tonga, Samoa). Methods We applied clustering and indicator species analysis to presence/absence data for 397 tree taxa in 338 forest plots to detect groups of plots sharing similar species composition. Patterns of plot composition and co-occurrence of congeneric species were compared between archipelagos for evidence of dispersal limitation, speciation, and environmental filtering versus competitive displacement or niche differentiation across the three archipelagos at the local (plot) and regional scales. Results Dispersal limitation was evident in the compositional segregation of inland rain forests across the three archipelagos, whereas compositional overlap was widespread for coastal forests, which are composed of species dispersed by water. Within genera, species numbers attenuated from Fiji to Tonga to Samoa, but speciation also contributed to compositional differences in all three island groups. Environmental filtering was suggested by the distinct composition of both secondary and mature inland rain forest versus coastal forest. At the local scale, however, clumping of congeners, which might suggest fine-scale environmental filtering, was observed for only a minority of inland forest genera. Most genera showed either overdispersion, suggesting competitive displacement or niche differentiation, or patterns not significantly different from random. Main conclusions Well-established biogeographical patterns of dispersal limitation and speciation contribute to West Polynesian tree diversity at the community scale. Environmental filtering and competitive displacement further structure forest communities; the evidence from this study suggests that environmental filtering is more important at a landscape scale, while competitive displacement may be more important at a local scale, although their relative importance varies considerably among taxa. [ABSTRACT FROM AUTHOR]

Abstract: Vegetation characteristics of a watershed can be important in estimating hydrological response variables (HRVs) such as streamflow (Q), evapotranspiration (ET), and river yield (Q/P). Quantifying the relationship between satellite-derived vegetation metrics and hydrological response to precipitation (P) has the potential to facilitate prediction of HRVs for ungauged watersheds, and/or aid in the assessment of watershed similarity as an initial phase of hydrological regionalization. The utility of Moderate Resolution Imaging Spectroradiometer (MODIS) satellite data to estimate HRVs of watersheds at the regional scale (southern and central California) is tested in this study. An exhaustive statistical regression analysis was conducted to quantify the relationships between MODIS vegetation metrics and HRVs using both ordinary least squares and spatially varying parameter models. Additionally a confirmatory analysis was conducted to test the effect precipitation and potential evaporation have on the exploratory regression results. Results from both the exploratory and confirmatory analyses suggest that (1) while there are limitations in the water balance approach to estimating ET (errors associated with changes in storage and meteorological data are unknown), moderate statistical relationships exist between MODIS vegetation metrics and HRVs; (2) these relationships are heavily influenced by vegetation–precipitation relationships and general precipitation magnitudes; (3) relationships between MODIS metrics and precipitation/HRVs are strongest when drought conditions prevail; and (4) LAI has the strongest relationship with precipitation and HRVs compared to other MODIS vegetation metrics. [ABSTRACT FROM AUTHOR]

HIF-1 is a heterodimeric transcription factor that mediates adaptive responses to hypoxia and plays critical roles in cancer progression. Using a cell-based screening assay we have identified acriflavine as a drug that binds directly to HIF-1α and HIF-2α and inhibits HIF-1 dimerization and transcriptional activity. Pretreatment of mice bearing prostate cancer xenografts with acriflavine prevented tumor growth and treatment of mice bearing established tumors resulted in growth arrest. Acriflavine treatment inhibited intratumoral expression of angiogenic cytokines. mobilization of angiogenic cells into peripheral blood, and tumor vascularization. These results provide proof of principle that small molecules can inhibit dimerization of HIF-1 and have potent inhibitory effects on tumor growth and vascularization. [ABSTRACT FROM AUTHOR]

A library of drugs that are in clinical trials or use was screened for inhibitors of hypoxia-inducible factor 1 (HIF-1). Twenty drugs inhibited HIF-1-dependent gene transcription by >88% at a concentration of 0.4 μM. Eleven of these drugs were cardiac glycosides, including digoxin, ouabain, and proscillaridin A, which inhibited HIF-1α protein synthesis and expression of HIF-1 target genes in cancer cells. Digoxin administration increased latency and decreased growth of tumor xenografts, whereas treatment of established tumors resulted in growth arrest within one week. Enforced expression of HIF-1α bytransfection was not inhibited by digoxin, and xenografts derived from these cells were resistant to the anti-tumor effects of digoxin, demonstrating that HIF-1 is a critical target of digoxin for cancer therapy. [ABSTRACT FROM AUTHOR]

Amyloid-beta plaques and neurodegeneration are hallmarks of Alzheimer's disease, where glial cells are responsible for sustained neuroinflammation. Here we show that hippocampal-microglia co-cultures exposed to proinflammatory mediators, amyloid-beta- and amyloid-beta protein precursor construct-conjugated beads increased their production of nitrites. In contrast, inflammation was unable to significantly induce cell death by itself, whereas inflammation plus amyloid-beta or amyloid-beta protein precursor induced a significant increment of cell death and a 6-fold increase of production of Interleukin 1beta. Those effects were not observed in the absence of microglia or when hippocampal cells were co-cultured with microglia for one day. In contrast, a 2-fold increase of transforming growth factor beta1 was observed in hippocampal cultures exposed to inflammatory stimuli for 4 days, whereas induction of transforming growth factor beta1 by inflammation plus amyloid-beta and amyloid-beta protein precursor was nearly abolished by microglia. Our results indicate that neurotoxicity induced by amyloid-beta or amyloid-beta protein precursor was a slow process depending on activated microglia and additional stimuli. The observed cytotoxicity could be consequence of a vicious cycle in which elevated concentrations of Interleukin 1beta and radical species along with decreased secretion of neuroprotective cytokines such as transforming growth factor beta1 support persistent activation of glial cells and cell damage. [ABSTRACT FROM AUTHOR]

Summary: Phytomonitoring techniques for irrigation of avocado orchards indicate that plants respond very rapidly to fluctuations in soil water content. Root to leaf abscicic acid transport cannot fully explain the almost immediate response of stomata to either irrigation and/or sudden changes in climatic conditions. Therefore, we studied the existence of a fast conducting signal between roots and leaves, and the possible involvement of such a signal in the regulation of stomatal behavior. Two-year-old avocado trees were subjected to drying and re-watering cycles or changes in incident radiation (light or darkness). The difference in extracellular electrical potential between the leaf petiole and the base of stem (ΔV L–S) was continuously recorded. Stomatal conductance (gs) was also recorded for the same leaves that were used for voltage difference measurements. A sudden change in soil water content induced by root drying and re-watering was accompanied by a slow, significant change in the recorded ΔV L–S signal, which was fully developed at 52 and 32min for root drying and re-watering, respectively. We found an inverse correlation (r=−0.56) between the change of ΔV L–S and the gs difference measured before and after each soil-drying treatment. Plants that were girdled to disrupt the phloem and then irrigated tended to have lower ΔV L–S differences over time than non-girdled irrigated plants, suggesting that the electrical signal was transmitted in the phloem. The existence of a fast signal transmitted from the root to the leaf that can be measured and correlated with stomatal control opens the possibility of developing a new phytomonitoring technique and/or artificially modifying plant responses by imposing agronomic management strategies aimed at rapid stomatal adaptation to changes in soil water content. [Copyright &y& Elsevier]