Spatio-Temporal Processes in Plant Communities

Ecological systems evolve in space and time. Until recently, however, research in ecology separately has focused either on the spatial domain (patterns) or on the temporal domain (processes). In this paper we describe novel approaches for progressing towards an integration of pattern and process, a goal long called for in ecology. First, we present a sequence of alternative stochastic models of spatially extended processes. Second, we advance two new methods for the estimation, or calibration, of model parameters from spatio-temporal processes observed in the field. Third, we provide tools for reducing the complexity of spatially extended ecological processes to manageable dynamical systems. Steps and techniques are illustrated in the context of data from a montane grassland community from the Czech Republic

Mechanistic explanations of community structure: Introduction

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/75364/1/j.1654-1103.1999.tb00597.x.pd

S-matrix oriented simulation of a looped-back four channel add-drop multiplexer

A design tool for simulation of complex photonic integrated circuits is described. An example simulation of a four-channel add-drop multiplexer is presented and results are in good agreement with measurement

Invloed van de pH op het aantonen van bacteriegroeiremmende stoffen in rauwe melk

Een hoeveelheid melk wordt toegevoegd aan een vaste voedingsbodem, waaraan sporen van Bacillus stearothermophilus var. calidolactis ATCC 10149, broomcresolpurper en trimethoprim zijn toegevoegd. Normale groei van en zuurproduktie door het micro-organisme veroorzaakt een kleurverandering van de pH indicator van paars naar geel. De aanwezigheid in de melk van stoffen die remmend werken op de groei van het micro-organisme, hebben tot gevolg dat de kleur van de pH indicator paars blijft. Nagegaan is of verhoging van de pH van de vaste voedingsbodem deze screeningsmethode gevoeliger maakt voor het opsporen van bacterie groeiremmende stoffen welke een hogere activiteit vertonen in een basisch milieu

Disturbance indicator values for European plants

Motivation Indicator values are numerical values used to characterize the ecological niches of species and to estimate their occurrence along gradients. Indicator values on climatic and edaphic niches of plant species have received considerable attention in ecological research, whereas data on the optimal positioning of species along disturbance gradients are less developed. Here, we present a new data set of disturbance indicator values identifying optima along gradients of natural and anthropogenic disturbance for 6382 vascular plant species based on the analysis of 736,366 European vegetation plots and using expert-based characterization of disturbance regimes in 236 habitat types. The indicator values presented here are crucial for integrating disturbance niche optima into large-scale vegetation analyses and macroecological studies. Main types of variables contained We set up five main continuous indicator values for European vascular plants: disturbance severity, disturbance frequency, mowing frequency, grazing pressure and soil disturbance. The first two indicators are provided separately for the whole community and for the herb layer. We calculated the values as the average of expert-based estimates of disturbance values in all habitat types where a species occurs, weighted by the number of plots in which the species occurs within a given habitat type. Spatial location and grain Europe. Vegetation plots ranging in size from 1 to 1000 m(2). Time period and grain Vegetation plots mostly sampled between 1956 and 2013 (= 5th and 95th quantiles of the sampling year, respectively). Major taxa and level of measurement Species-level indicator values for vascular plants. Software format csv file

A phase I study with MAG-camptothecin intravenously administered weekly for 3 weeks in a 4-week cycle in adult patients with solid tumours

In MAG-camptothecin (MAG-CPT), the topoisomerase inhibitor camptothecin is linked to a water-soluble polymer. Preclinical experiments showed enhanced antitumour efficacy and limited toxicity compared to camptothecin alone. Prior phase I trials guided the regimen used in this study. The objectives were to determine the maximum tolerated dose, dose-limiting toxicities, safety profile, and pharmacokinetics of weekly MAG-CPT. Patients with solid tumours received MAG-CPT intravenously administered weekly for 3 weeks in 4-week cycles. At the starting dose level ( 80 mg m(-2) week(-1)), no dose-limiting toxicities occurred during the first cycle (n = 3). Subsequently, three patients were enrolled at the second dose level ( 120 mg m(-2) week(-1)). Two of three patients at the 80 mg m(-2) week(-1) cohort developed haemorrhagic cystitis ( grade 1/3 dysuria and grade 2/3 haematuria) during the second and third cycles. Next, the 80 mg m(-2) week(-1) cohort was enlarged to a total of six patients. One other patient at this dose level experienced grade 1 haematuria. At 120 mg m(-2) week(-1), grade 1 bladder toxicity occurred in two of three patients. Dose escalation was stopped at 120 mg m(-2) week(-1). Cumulative bladder toxicity was dose-limiting toxicity at 80 mg m(-2) week(-1). Pharmacokinetics revealed highly variable urinary camptothecin excretion, associated with bladder toxicity. Due to cumulative bladder toxicity, weekly MAG-CPT is not a suitable regimen for treatment of patients with solid tumours

A pharmacokinetic and pharmacodynamic study on metronomic irinotecan in metastatic colorectal cancer patients

The pharmacokinetics (PK) and pharmacodynamics (PD) of metronomic irinotecan have not been studied in cancer patients. The aim of the study is to investigate the PK/PD profile of irinotecan/SN-38 administered by metronomic schedule. Twenty chemotherapy-refractory or chemotherapy-resistant patients with metastatic colorectal carcinoma were enrolled. Irinotecan was infused continuously as follows: irinotecan 1.4 mg m−2 day−1 (n=7), 2.8 mg m−2 day−1 (n=5) and 4.2 mg m−2 day−1 (n=8). Drug levels were examined by HPLC, whereas ELISAs and real-time RT-PCR were used, respectively, for the measurement of plasma levels and gene expression in peripheral blood mononuclear cells of vascular endothelial growth factor/thrombospondin-1. Pharmacokinetic analysis demonstrated that the steady-state levels (Css) of SN-38 were between 1 and 3.3 ng ml−1. From a PD point of view, higher thrombospondin-1 (TSP-1) plasma levels (153.4±30.1 and 130.4±9.2% at day 49 vs pretreatment values at 1.4 and 2.8 mg m−2 day−1 dose levels, respectively) and increased gene expression in PBMC were found during the metronomic irinotecan infusion, especially at the lower doses. Four patients (20%) obtained a stable disease (median 3.9 months) despite progressing during previous standard irinotecan schedule. Toxicities >grade 1 were not observed. Metronomic irinotecan administration is very well tolerated and induces an increase of gene expression and plasma concentration of TSP-1 at low plasma SN-38 concentrations

Temporal dynamics of the shrub and herbaceous layer of an area of moist grassland in Alto Paraíso de Goiás, Brazil

Este trabalho avaliou a dinâmica estrutural e fl orística de uma comunidade de espécies herbáceo-arbustivas de uma área de campo limpo úmido em Alto Paraíso de Goiás, o primeiro inventário realizado em 2000 (T0) e o segundo em 2007 (T1). A diversidade de Shannon entre os períodos foi comparada pelo teste-t de Hutcheson e a similaridade fl orística, pelo índice de similaridade de Chao-Sørensen. As relações fl orísticas e a cobertura, entre os períodos e as linhas, foram avaliadas por meio de análises de correspondência retifi cada (DCA). Foram amostradas 98 espécies, 88 no T0 e 67 no T1, sendo 31 exclusivas do T0 e 10 do T1. A diversidade fl orística na comunidade foi elevada nos dois períodos, porém diferente entre esses (t = 7,12; p < 0,001), devido a variação no número e cobertura das espécies. A similaridade entre os dois inventários foi alta (Chao-Sørensen ± IC = 0,841 ± 0,074). A ordenação por DCA indicou relações entre a composição fl orística e a cobertura com o gradiente de umidade e de matéria orgânica no solo identifi cados em T0. Houve modifi cações nas linhas em zonas sazonais, as quais se tornaram mais semelhantes às linhas constantemente saturadas por água. Em um intervalo de sete anos o campo limpo úmido apresentou mudanças na composição fl orística e, principalmente na estrutura devido o aumento da cobertura de espécies perenes, cespitosas e entouceiradas, que foram favorecidas pela maior umidade no solo em resposta à elevação da pluviosidade da região. __________________________________________________________________________________________ ABSTRACTTh is study evaluated the fl oristic and structural dynamics of a community of herbaceous-shrub species in an area of moist grassland in Alto Paraíso de Goiás. Th e fi rst inventory was undertaken in 2000 (T0) and the second in 2007 (T1). Shannon’s diversity between the periods was compared by Hutchesons´s t-test, and the fl oristic similarity by the Chao-Sørensen similarity index. Floristic composition and cover, between periods and lines, were evaluated by detrended correspondence analysis (DCA). We sampled 98 species, 88 at T0 and 67 at T1; 31 were unique to T0 and 10 to T1. Floristic diversity in the community was high in both periods, but diff erent between them (t = 7.12, p <0.001), due to variation in species number and coverage. Similarity between the two surveys was high (Chao-Sørensen CI = ± 0.841 ± 0.074). Th e DCA ordination indicated relationships between the fl oristic composition and cover with a gradient of moisture and organic matter in the soil identifi ed in T0. Th ere were changes in the lines in the seasonal zones, which became more similar in those constantly saturated with water. During an interval of seven years the moist grassland showed changes in fl oristic composition and mainly in structure due to increased cover of the clumped tussock perennial species, which were favored by higher soil moisture due to high rainfall in the region

Deficient activation of CD95 (APO-1/ Fas)-mediated apoptosis: a potential factor of multidrug resistance in human renal cell carcinoma

The pronounced resistance of human renal cell carcinoma (RCC) to anticancer-induced apoptosis has primarily been related to the expression of P-glycoprotein and effective drug detoxification mechanisms. Because the CD95 system has recently been identified as a key mediator of anticancer drug-induced apoptosis, we analysed the contribution of the CD95 system to chemotherapy-induced apoptosis in four newly established RCC cell lines. Here, we demonstrate that all RCC cell lines expressed CD95-receptor and -ligand. Exposure to agonistic anti-CD95 antibodies resulted in induction of apoptosis and significant (P< 0.05) reduction of cell number in three out of four cell lines, indicating that the essential components for CD95-mediated apoptosis were present and functionally intact in the majority of these RCC cell lines. Moreover, treatment of cultures with bleomycin or topotecan, a novel topoisomerase I inhibitor with little substrate affinity for P-glycoprotein, led to induction of apoptosis and significant (P< 0.05) dose-dependent reduction of cell number in all RCC cell lines. Both anticancer drugs also induced upregulation of CD95 ligand expression in all cell lines. Additionally, augmentation of CD95 receptor expression was found in three RCC cell lines, including one p53-mutated cell line, whereas another p53-mutated cell line showed no or only a weak CD95 receptor upregulation after exposure to topotecan or bleomycin, respectively. Despite this upregulation of CD95 receptor and ligand, antagonistic antibodies directed against CD95 receptors or ligands could not inhibit induction of apoptosis by topotecan and bleomycin in any cell line. Thus, although a functionally intact CD95 signalling cascade is present in most RCC cell lines, the anticancer drugs topotecan and bleomycin that induce upregulation of CD95 receptor and ligand fail to effectively activate CD95-mediated apoptosis. This deficient activation of CD95-mediated apoptosis might be an important additional factor for the multidrug resistance phenotype of human RCCs. © 2000 Cancer Research Campaig