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Differential Responses (differential + response)
Selected AbstractsEffect of Osteoblast-Targeted Expression of Bcl-2 in Bone: Differential Response in Male and Female Mice,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 8 2005Alexander G Pantschenko Abstract Transgenic mice (Col2.3Bcl-2) with osteoblast-targeted human Bcl-2 expression were established. Phenotypically, these mice were smaller than their wildtype littermates and showed differential effects of the transgene on bone parameters and osteoblast activity dependent on sex. The net effect was an abrogation of sex differences normally observed in wildtype mice and an inhibition of bone loss with age. Ex vivo osteoblast cultures showed that the transgene had no effect on osteoblast proliferation, but decreased bone formation. Estrogen was shown to stimulate endogenous Bcl-2 message levels. These studies suggest a link between Bcl-2 and sex regulation of bone development and age-related bone loss. Introduction: Whereas Bcl-2 has been shown to be an important regulator of apoptosis in development, differentiation, and disease, its role in bone homeostasis and development is not well understood. We have previously showed that the induction of glucocorticoid-induced apoptosis occurred through a dose-dependent decrease in Bcl-2. Estrogen prevented glucocorticoid-induced osteoblast apoptosis in vivo and in vitro by preventing the decrease in Bcl-2 in osteoblasts. Therefore, Bcl-2 may be an important regulator of bone growth through mechanisms that control osteoblast longevity and function. Materials and Methods: Col2.3Bcl-2 mice were developed carrying a 2.3-kb region of the type I collagen promoter driving 1.8 kb of human Bcl-2 (hBcl-2). Tissue specific expression of hBcl-2 in immunoassays validated the transgenic animal model. Histomorphometry and DXA were performed. Proliferation, mineralization, and glucocorticoid-induced apoptosis were examined in ex vivo cultures of osteoblasts. The effect of estrogen on mouse Bcl-2 in ex vivo osteoblast cultures was assayed by RT-PCR and Q-PCR. Results and Conclusions: Two Col2.3Bcl-2 (tg/+) founder lines were established and appeared normal except that they were smaller than their nontransgenic wildtype (+/+) littermates at 1, 2, and 6 months of age, with the greatest differences at 2 months. Immunohistochemistry showed hBcl-2 in osteoblasts at the growth plate and cortical surfaces. Nontransgenic littermates were negative. Western blots revealed hBcl-2 only in type I collagen-expressing tissues. Histomorphometry of 2-month-old mice showed a significant decrease in tg/+ calvaria width with no significant differences in femoral trabecular area or cortical width compared with +/+. However, tg/+ males had significantly more trabecular bone than tg/+ females. Female +/+ mice showed increased bone turnover with elevated osteoblast and osteoclast parameters compared with +/+ males. Col2.3Bcl-2 mice did not show such significant differences between sexes. Male tg/+ mice had a 76.5 ± 1.5% increase in ObS/BS with no significant differences in bone formation rate (BFR) or mineral apposition rate (MAR) compared with male +/+ mice. Transgenic females had a significant 48.4 ± 0.1% and 20.1 ± 5.8% decrease in BFR and MAR, respectively, compared with +/+ females. Osteoclast and osteocyte parameters were unchanged. By 6 months, femurs from female and male +/+ mice had lost a significant amount of their percent of trabecular bone compared with 2-month-old mice. There was little to no change in femoral bone in the tg/+ mice with age. Ex vivo cultures of osteoblasts from +/+ and Col2.3Bcl-2 mice showed a decrease in mineralization, no effect on proliferation, and an inhibition of glucocorticoid-induced apoptosis in Col2.3Bcl-2 cultures. Estrogen was shown to increase mouse Bcl-2 transcript levels in osteoblast cultures of wildtype mice, supporting a role for Bcl-2 in the sex-related differences in bone phenotype regulated by estrogen. Therefore, Bcl-2 differentially affected bone phenotype in male and female transgenic mice, altered bone cell activity associated with sex-related differences, and decreased bone formation, suggesting that apoptosis is necessary for mineralization. In addition, Bcl-2 targeted to mature osteoblasts seemed to delay bone development, producing a smaller transgenic mouse compared with wildtype littermates. These studies suggest that expression of Bcl-2 in osteoblasts is important in regulating bone mass in development and in the normal aging process of bone. [source] ,-Arrestin2 Regulates the Differential Response of Cortical and Trabecular Bone to Intermittent PTH in Female Mice,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 4 2005Mary L Bouxsein PhD Abstract Cytoplasmic arrestins regulate PTH signaling in vitro. We show that female ,-arrestin2,/, mice have decreased bone mass and altered bone architecture. The effects of intermittent PTH administration on bone microarchitecture differed in ,-arrestin2,/, and wildtype mice. These data indicate that arrestin-mediated regulation of intracellular signaling contributes to the differential effects of PTH at endosteal and periosteal bone surfaces. Introduction: The effects of PTH differ at endosteal and periosteal surfaces, suggesting that PTH activity in these compartments may depend on some yet unidentified mechanism(s) of regulation. The action of PTH in bone is mediated primarily by intracellular cAMP, and the cytoplasmic molecule ,-arrestin2 plays a central role in this signaling regulation. Thus, we hypothesized that arrestins would modulate the effects of PTH on bone in vivo. Materials and Methods: We used pDXA, ,CT, histomorphometry, and serum markers of bone turnover to assess the skeletal response to intermittent PTH (0, 20, 40, or 80 ,g/kg/day) in adult female mice null for ,-arrestin2 (,-arr2,/,) and wildtype (WT) littermates (7-11/group). Results and Conclusions: ,-arr2,/, mice had significantly lower total body BMD, trabecular bone volume fraction (BV/TV), and femoral cross-sectional area compared with WT. In WT females, PTH increased total body BMD, trabecular bone parameters, and cortical thickness, with a trend toward decreased midfemoral medullary area. In ,-arr2,/, mice, PTH not only improved total body BMD, trabecular bone architecture, and cortical thickness, but also dose-dependently increased femoral cross-sectional area and medullary area. Histomorphometry showed that PTH-stimulated periosteal bone formation was 2-fold higher in ,-arr2,/, compared with WT. Osteocalcin levels were significantly lower in ,-arr2,/, mice, but increased dose-dependently with PTH in both ,-arr2,/, and WT. In contrast, whereas the resorption marker TRACP5B increased dose-dependently in WT, 20-80 ,g/kg/day of PTH was equipotent with regard to stimulation of TRACP5B in ,-arr2,/,. In summary, ,-arrestin2 plays an important role in bone mass acquisition and remodeling. In estrogen-replete female mice, the ability of intermittent PTH to stimulate periosteal bone apposition and endosteal resorption is inhibited by arrestins. We therefore infer that arrestin-mediated regulation of intracellular signaling contributes to the differential effects of PTH on cancellous and cortical bone. [source] Sleep Loss Induces Differential Response Related To Genotoxicity in Multiple Organs of Three Different Mice StrainsBASIC AND CLINICAL PHARMACOLOGY & TOXICOLOGY, Issue 1 2010Vanessa Kahan Swiss, C57BL/6j and hairless (HRS/j) mice were submitted to PSD by the multiple platform technique for 72 hr, and DNA damage was evaluated. Statistically significant differences in DNA damage were found in blood cells of the Swiss mice strain when compared to negative controls. By contrast, no statistically significant differences were found in the C57BL/6j or hairless mice strains. With regard to the liver, extensive genotoxic effects were found in the Swiss strain. The hairless and C57BL/6j mice strains did not show any signs of genotoxocity in this organ. The same lack of effect was noted in kidney and heart cells of all strains evaluated. In conclusion, our results reveal that sleep deprivation exerted genetic damage in the form of DNA breakage in blood and liver cells of the Swiss mice strain only. This type of approach should be considered when studying noxious activities on genetic apparatus induced by sleep deprivation in mice since the Swiss strain is more suitable for this purpose. [source] Differential Responses of the Activities of Antioxidant Enzymes to Thermal Stresses between Two Invasive Eupatorium Species in ChinaJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 4 2008Ping Lu Abstract The effect of thermal stress on the antioxidant system was investigated in two invasive plants, Eupatorium adenophorum Spreng. and E. odoratum L. The former is sensitive to high temperature, whereas the latter is sensitive to low temperature. Our aim was to explore the relationship between the response of antioxidant enzymes and temperature in the two invasive weeds with different distribution patterns in China. Plants were transferred from glasshouse to growth chambers at a constant 25 °C for 1 week to acclimatize to the environment. For the heat treatments, temperature was increased stepwise to 30, 35, 38 and finally to 42 °C. For the cold treatments, temperature was decreased stepwise to 20, 15, 10 and finally to 5 °C. Plants were kept in the growth chambers for 24 h at each temperature step. In E. adenophorum, the coordinated increase of the activities of antioxidant enzymes was effective in protecting the plant from the accumulation of active oxygen species (AOS) at low temperature, but the activities of catalase (CAT), guaiacol peroxidase (POD), ascorbate peroxidase (APX), glutathione reductase (GR), and monodehydroascorbate reductase (MDAR) were not accompanied by the increase of superoxide dismutase (SOD) during the heat treatments. As a result, the level of lipid peroxidation in E. adenophorum was higher under heat stress than under cold stress. In E. odoratum, however, the lesser degree of membrane damage, as indicated by low monodehydroascorbate content, and the coordinated increase of the oxygen. Detoxifying enzymes were observed in heat-treated plants, but the antioxidant enzymes were unable to operate in cold stress. This indicates that the plants have a higher capacity for scavenging oxygen radicals in heat stress than in cold stress. The different responses of antioxidant enzymes may be one of the possible mechanisms of the differences in temperature sensitivities of the two plant species. [source] Differential Responses of Germination and Seedling Establishment in Populations of Tragopogon pratensis (Asteraceae)PLANT BIOLOGY, Issue 1 2007L. D. Jorritsma-Wienk Abstract: The establishment phase is an important bottleneck in the life cycle of plants. It consists of two steps that are rarely separated, i.e., the germination of seeds and the establishment of seedlings. Here we report the results of two experiments in which we independently investigated germination and seedling establishment in the greenhouse, under different grass vegetation treatments representing different regeneration niches. Seeds of Tragopogon pratensis from six populations and two habitat types were studied, three from roadside verges and three from hayfields. Germination percentages and germination speed were higher for seeds from roadside verges than for seeds from hayfields, but were little affected by treatment. In contrast, seedling growth was much lower in the tall grass vegetation, than in the short grass and especially the bare soil treatment. Seedling sizes were generally similar for different populations and habitat types. Our results thus show that the two early steps in the establishment phase of plants may respond very differently to the micro-environment, and may have a different selection history. Insight into the ecology and evolution of life histories may require that germination and establishment are considered separately. [source] Differential response to bypassing agents complicates treatment in patients with haemophilia and inhibitorsHAEMOPHILIA, Issue 1 2009E. BERNTORP Summary., The bypassing agents factor eight inhibitor bypassing activity (FEIBA) anti-inhibitor coagulant complex and recombinant activated factor VII (rFVIIa) have been established as safe and effective therapies for treating bleeding episodes in haemophilia patients with inhibitors. However, the efficacy of each bypassing agent can vary, and neither agent is universally effective. The reasons for such variability have yet to be confirmed, but may involve patient-specific factors and the mechanisms of action (MOAs) and pharmacokinetic profiles of these two agents. This issue underscores the necessity of both products in the comprehensive care of patients with haemophilia and inhibitors. The objective of this review is to discuss the evidence of a differential haemostatic response to bypassing agents and the potential roles of MOA and patient-specific factors in contributing to the differences in response. [source] Differential response to phytoestrogens in endocrine sensitive and resistant breast cancer cells in vitroINTERNATIONAL JOURNAL OF CANCER, Issue 3 2006Jane L. Limer Abstract Women approaching menopause increasingly investigate alternatives to hormone replacement therapy. Plant phytoestrogens are being promoted as "natural" alternatives but there is a lack of substantive data to advocate their safe use in breast cancer patients receiving tamoxifen (TAM), or in those who have relapsed. The aim of our study was to investigate the proliferative effects and mode of action of the phytoestrogens genistein, daidzein and coumestrol on TAM-sensitive (-s) and resistant (-r) breast cancer cells under in vitro conditions designed to mimic the hormonal environment of the pre- and post-menopausal breast. At physiological concentrations (<10 ,M) and under reduced estrogen (E2) conditions, genistein was mitogenic to TAM-s cells with TAM-r cells generally refractory. Daidzein and coumestrol were growth stimulatory irrespective of TAM sensitivity. Transcriptional activity was ERE-mediated. Combining phytoestrogens with E2 (simulating the pre-menopausal breast environment) had no effect on growth of TAM-s or TAM-r cells. Addition of 4-HT mimicked the hormonal environment in post-menopausal breast cancer patients receiving TAM. The growth inhibitory effects of 4-HT were abrogated in TAM-s cells when combined with genistein and coumestrol, and to a lesser extent, daidzein, where significant growth stimulatory effects were observed. In TAM-r cells, proliferation did not exceed control values. At phytoestrogen concentrations above 10 ,M, growth inhibitory effects were seen, irrespective of estrogenic environment or cell sensitivity to TAM. Our in vitro data suggests that phytoestrogens could have potentially adverse mitogenic effects on tumour cells and should probably be avoided by patients who remain sensitive to TAM or in those with pre-existing and possibly undiagnosed breast tumours. © 2006 Wiley-Liss, Inc. [source] Differential response of platelets to chemokines: RANTES non-competitively inhibits stimulatory effect of SDF-1,JOURNAL OF THROMBOSIS AND HAEMOSTASIS, Issue 1 2004B. Shenkman Summary.,Background:,Among the chemokines related to CXC and CC receptor groups and released from platelets, leukocytes and endothelial cells, SDF-1, TARC and MDC have been found to be platelet agonists. Platelets do not contain SDF-1,. In contrast, RANTES is constitutively present in platelet ,-granules and released upon platelet activation. Objectives:,To study a possible role of RANTES as a modulator of SDF-1, effect on platelets, in relation to CXCR4 and various CC receptors. Methods:,CXCR-4 (CXCL12) receptor expression and platelet activation were evaluated by flow cytometry, platelet deposition was studied by cone and plate(let) analyzer, and platelet aggregation by turbidometric aggregometry. Results:,Flow cytometry studies revealed similar expression of CXCR-4, the specific receptor of SDF-1, on intact, inactivated, and activated platelets. Preincubation of platelets with RANTES affected neither CXCR-4 expression, nor SDF-1, binding to the platelet membrane. In the presence of fibrinogen, SDF-1, activated gel-filtered platelets. RANTES did not activate platelets, but substantially (by 70%) inhibited SDF-1,-induced fibrinogen binding. Similarly, RANTES abrogated the promoting effect of SDF-1, on whole blood platelet adhesion to endothelial cell monolayer under venous flow conditions. In platelet-rich plasma, RANTES moderately inhibited SDF-1,-induced platelet aggregation, while it did not affect aggregation induced by thrombin-receptor activation peptide, adenosine diphosphate, or phorbol 12-myristate 13-acetate. A synergistic inhibitory effect of RANTES and prostaglandin E1 used at subthreshold concentrations, on SDF-1,-induced aggregation and SDF-1,-induced fibrinogen binding to platelets was observed, which may suggest involvement of RANTES in a cAMP-dependent signal transduction pathway. Conclusions:,RANTES non-competitively inhibits activation of platelets by SDF-1,, and thus may play a regulatory role in platelet response to inflammation. [source] Differential response of Amaranthus tuberculatus (Moq ex DC) JD Sauer to glyphosatePEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 10 2005Ian A Zelaya Abstract Midwest USA farmers have reported inconsistent control of Amaranthus tuberculatus (= rudis) (Moq ex DC) JD Sauer by glyphosate in glyphosate-resistant crops. The potential of selection for decreased A tuberculatus sensitivity to glyphosate was therefore investigated in a reportedly resistant Everly, IA population (P0,EV). Evaluation of six A tuberculatus populations from the Midwest USA estimated a seedling baseline sensitivity of 2.15 mM glyphosate. Based on these results, three generations of divergent recurrent selection were implemented on P0,EV to isolate resistant and susceptible populations. A seedling assay was developed to screen large amounts of seeds and thus expedite the selection process. Whole-plant and seedling rate responses of P0,EV and a known pristine A tuberculatus population from Paint Creek, OH (P0,WT) identified no significant difference in response to glyphosate; however, greater phenotypic variance was ostensibly evident in P0,EV. The first recurrent generation selected for resistance at 3.2 mM glyphosate (RS1,R) had a 5.9- and 1.7-fold resistance increase at the seedling and whole-plant levels, respectively, compared with the susceptible generation selected at 32 µM glyphosate. After three cycles of recurrent selection, 14.6-fold difference in resistance at the seedling level and 3.1-fold difference at the whole-plant level were observed when comparing the populations selected for resistance (RS3,R) and susceptibility (RS3,S). Overall, recurrent selection increased the frequency of resistant individuals and decreased the variability to glyphosate at the population level. Nevertheless, variability for glyphosate resistance was still evident in RS3,R. Results herein suggested that A tuberculatus is inherently variable to glyphosate and that selection decreased the sensitivity to glyphosate. We purport that evolved glyphosate resistance in A tuberculatus may require multiple cycles of selection under field conditions. Historic estimated use of glyphosate alludes to the evolution of tolerant weed populations. Copyright © 2005 Society of Chemical Industry [source] Differential response of antioxidant compounds to salinity stress in salt-tolerant and salt-sensitive seedlings of foxtail millet (Setaria italica)PHYSIOLOGIA PLANTARUM, Issue 4 2000N. Sreenivasulu The modulation of antioxidant components was comparatively analysed in a salt-tolerant (cv. Prasad) and salt-sensitive (cv. Lepakshi) cultivar of foxtail millet (Setaria italica L.) under different NaCl concentrations. Under conditions of salt stress, the salt-tolerant cultivar exhibited increased total superoxide dismutase (SOD) and ascorbate peroxidase (APX) activity, whereas both enzyme activities decreased in acutely salt-stressed seedlings of the sensitive cultivar. At 200 mM NaCl, the tolerant foxtail millet cultivar responded with induction of cytosolic Cu/Zn-SOD and the Mn-SOD isoform at the protein level. The induced accumulation of the cytosolic Cu/Zn-SOD protein/activity is positively correlated with an elevated level of the cytosolic APX gene activity. The elevated cytosolic Cu/Zn-SOD and cytosolic APX activity correlates with an induced accumulation of their transcripts. Tolerant 5-day-old seedlings grown during high salinity treatment (200 mM NaCl) contained a lower amount of Na+ ions and showed a lower electrolyte leakage than sensitive seedlings. In conclusion, our comparative studies indicate that salt-induced oxidative tolerance is conferred by an enhanced compartment-specific activity of the antioxidant enzymes in response to compartment-specific signals. [source] Differential responses to NMDA receptor activation in rat hippocampal interneurons and pyramidal cells may underlie enhanced pyramidal cell vulnerabilityEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 12 2005E. Avignone Abstract Hippocampal interneurons are generally more resistant than pyramidal cells to excitotoxic insults. Because NMDA receptors play a crucial role in neurodegeneration, we have compared the response to exogenous NMDA in CA1 pyramidal cells and interneurons of the stratum oriens using combined whole-cell patch-clamp recording and ratiometric Ca2+ imaging. In voltage-clamp, current-clamp or in nominally Mg2+ -free medium, NMDA (10 µm; 3,5 min exposure in the presence of tetrodotoxin) induced a markedly larger inward current and Ca2+ rise in pyramidal cells than in interneurons. Pyramidal cells also showed a more pronounced voltage dependence in their response to NMDA. We hypothesized that this enhanced response to NMDA receptor activation in pyramidal cells could underlie their increased vulnerability to excitotoxicity. Using loss of dye as an indicator of degenerative membrane disruption, interneurons tolerated continuous exposure to a high concentration of NMDA (30 µm) for longer periods than pyramidal cells. This acute neurodegeneration in pyramidal cells was independent of intracellular Ca2+, because high intracellular BAPTA (20 mm) did not prolong survival time. Thus, a plausible explanation for the enhanced sensitivity of pyramidal neurons to excitotoxic insults associated with cerebral ischemia is their greater response to NMDA receptor activation, which may reflect differences in NMDA receptor expression and/or subunit composition. [source] Acacia species turnover in space and time in an African savannaJOURNAL OF BIOGEOGRAPHY, Issue 1 2001William J. Bond Aim Patterns of species turnover along environmental gradients are better studied than their causes. Competitive interactions, or physiological tolerance are most often cited as determinants of turnover. Here we investigate differential tree species response to disturbance by fire and mammal browsing as causes of changing dominance of species within and among sites along an altitudinal gradient. Methods We documented the distribution of two Acacia species using maps and sample transects. We explored possible causes of species turnover by studying differences between the species in tolerance to grass competition using pot experiments, to browsers by observing patterns of shoot damage, and to fire by comparing the size structure of populations burnt at different frequencies and intensities. Results Acacia karroo woodlands were rare and occur at higher elevations than the much more common A. nilotica woodlands. Woodland composition seems set to change in future since the pattern of dominance was reversed in juvenile stages. A. karroo juveniles were very widespread and far more abundant than A. nilotica juveniles. A. karroo juveniles were most abundant in tall fire-prone grasslands and were rare on grazing lawns whereas A. nilotica showed the reverse pattern. In the pot experiments, growth of both species was suppressed by grasses but there were no significant differences in response between the two species. Juveniles of A. karroo were more heavily browsed than those of A. nilotica. However juveniles of A. nilotica were less tolerant of frequent intense burns than juvenile A. karroo. Main conclusions Disturbance gradients, from high fire frequency and low herbivore density at high altitudes, to lower fire frequency and higher herbivore density at low altitudes, are responsible for the shift in community structure along the spatial gradient. Differential responses to browsing and fire may also explain temporal turnover from A. nilotica in the past to A. karroo in the present. Changes in the area burnt annually, and in faunal composition, suggest a landscape-scale shift from grazing-dominated short-grass landscapes in the 1960s, favouring A. nilotica, to fire-dominated tall grasslands in the 1990s favouring A. karroo. We suggest that species turnover due to differential responses along disturbance gradients may be much more widespread than the current paucity of studies suggests. [source] Differential interaction of Phytophthora infestans on tubers of potato cultivars with different levels of blight resistancePLANT PATHOLOGY, Issue 3 2001W. G. Flier Differential interactions in tuber blight attack between potato cultivars and Phytophthora infestans isolates were studied using whole tuber and tuber slice assays. Tuber blight incidence and severity were studied in a whole tuber assay, whilst necrosis and mycelium coverage were evaluated in a tuber slice assay. The overall defence reaction of the potato cultivars tested varied considerably. Cultivars like Kartel and Producent showed resistant reactions, whilst Bintje and, to a lesser extent, Astarte reacted more susceptibly after inoculation with aggressive strains of P. infestans. A highly significant cultivar by year interaction was observed when tuber blight incidence was evaluated in two successive years. Differential responses were revealed by changing ranked order of cultivars after exposure to aggressive isolates of P. infestans. The results show that cultivar by isolate interactions existed for all components of tuber blight resistance studied. The quantitative nature of the observed resistance responses suggests the presence of quantitative trait loci governing resistance to tuber blight. The consequences of differential interactions in relation to the stability of tuber resistance are discussed. [source] Differential responses to branched and unsaturated aliphatic hydrocarbons in the rat olfactory systemTHE JOURNAL OF COMPARATIVE NEUROLOGY, Issue 4 2006Sabrina L. Ho Abstract In an effort to understand mammalian olfactory processing, we have been describing the responses to systematically different odorants in the glomerular layer of the main olfactory bulb of rats. Previously, we demonstrated chemotopically organized and distinct olfactory responses to a homologous series of straight-chained alkanes that consisted of purely hydrocarbon structures, indicating that hydrocarbon chains could serve as molecular features in the combinatorial coding of odorant information. To better understand the processing of hydrocarbon odorants, we now have examined responses to other types of chemical changes in these kinds of molecules, namely, branching and carbon,carbon bond saturation. To this end, we used the [14C]2-deoxyglucose method to determine glomerular responses to a group of eight-carbon branched alkane isomers, unsaturated octenes (double-bonded), and octynes (triple-bonded). In contrast to the differential responses we observed previously for straight-chained alkanes of differing carbon number, the rat olfactory system was not particularly sensitive to these variations in branching and bond saturation. This result was unexpected, given the distinct molecular conformations and property profiles of the odorants. The similarity in activity patterns was paralleled by a similarity in spontaneous perceptual responses measured using a habituation assay. These results demonstrate again the functional relationship between bulbar activity patterns and odor perception. The results further suggest that the olfactory system does not respond equally to all aspects of odorant chemistry, functioning as a specific, rather than a general, chemical analysis system. J. Comp. Neurol. 499:519,532, 2006. © 2006 Wiley-Liss, Inc. [source] Associative learning and memory in a chimpanzee fetus: Learning and long-lasting memory before birthDEVELOPMENTAL PSYCHOBIOLOGY, Issue 2 2004Nobuyuki Kawai Abstract We tested whether a chimpanzee fetus could form an association between an extrauterine tone and vibroacoustic stimulation (VAS) using classical conditioning treatment. Two kinds of pure tone were used as the conditioned stimuli, one where a 500-Hz tone was always followed by a VAS of 80 Hz (110 gal), the unconditioned stimulus (US), and another where a 1000-Hz tone was never followed by a VAS. This treatment was repeated 156 times in total until natural labor at 233 days of gestational age. Behavioral tests on the 33rd and 58th days after birth revealed a differential response to the tones: The infant displayed an exaggerated response to the 500-Hz tone, but not to the 1000-Hz tone. Other naïve chimpanzee infants did not show any response to either tone, which suggests that a chimpanzee fetus can distinguish between tones and form an association, and that it retains such information for at least 2 months after birth. © 2004 Wiley Periodicals, Inc. Dev Psychobiol 44: 116,122, 2004. [source] GENETIC STUDY: Polymorphisms of the dopamine D4 receptor gene (DRD4 VNTR) and cannabinoid CB1 receptor gene (CNR1) are not strongly related to cue-reactivity after alcohol exposureADDICTION BIOLOGY, Issue 2 2007Esther Van Den Wildenberg ABSTRACT Polymorphisms in the D4 dopamine receptor gene (DRD4) and the CB1 cannabinoid receptor gene (CNR1) have been associated with a differential response to alcohol after consumption. The goal of the present study was to investigate whether heavy drinkers with these polymorphisms would respond with enhanced cue-reactivity after alcohol exposure. Eighty-eight male heavy drinkers were genotyped for the DRD4 variable number of tandem repeats (VNTR) [either DRD4 long (L) or short (S)] and the CNR1 rs2023239 polymorphism (either CT/CC or TT). Participants were exposed to water and beer in 3-minute trials. Dependent variables of main interest were subjective craving for alcohol, subjective arousal and salivary reactivity. Overall, no strong evidence was found for stronger cue-reactivity (= outcome difference between beer and water trial) in the DRD4 L and CNR1 C allele groups. The DRD4 VNTR polymorphism tended to moderate salivary reactivity such that DRD4 L participants showed a larger beverage effect than the DRD4 S participants. Unexpectedly, the DRD4 L participants reported, on average, less craving for alcohol and more subjective arousal during cue exposure, compared with the DRD4 S participants. As weekly alcohol consumption increased, the CNR1 C allele group tended to report more craving for alcohol during the alcohol exposure than the T allele group. The DRD4 and CNR1 polymorphisms do not appear to strongly moderate cue-reactivity after alcohol cue exposure, in male heavy drinkers. [source] Differential effects of histone deacetylase inhibitors on phorbol ester- and TGF-,1 induced murine tissue inhibitor of metalloproteinases-1 gene expressionFEBS JOURNAL, Issue 8 2005David A. Young Expression of the tissue inhibitor of metalloproteinases-1 (Timp-1) gene can be induced by either phorbol myristate acetate (PMA) or transforming growth factor ,1 (TGF-,1), although the signalling pathways involved are not clearly defined. Canonically, histone deacetylase inhibitors (HDACi) such as trichostatin A (TSA) or sodium butyrate (NaB) increase total cellular histone acetylation and activate expression of susceptible genes. Remarkably, PMA and TGF-,1 stimulation of Timp-1 show a differential response to TSA or NaB. TSA or NaB potentiate PMA-induced Timp-1 expression but repress TGF-,1-induced Timp-1 expression. The repression of TGF-,1-induced Timp-1 by TSA was maximal at 5 ng·mL,1, while for the superinduction of PMA-induced Timp-1 expression, the maximal dose is >,500 ng·mL,1 TSA. A further HDACi, valproic acid, did not block TGF-,1-induced Timp-1 expression, demonstrating that different HDACs impact on the induction of Timp-1. For either PMA or TGF-,1 to induce Timp-1 expression, new protein synthesis is required, and the induction of AP-1 factors closely precedes that of Timp-1. The effects of the HDACi can be reiterated in transient transfection using Timp-1 promoter constructs. Mutation or deletion of the AP-1 motif (,59/,53) in the Timp-1 promoter diminishes PMA-induction of reporter constructs, however, the further addition of TSA still superinduces the reporter. In c-Jun,/, cells, PMA still stimulates Timp-1 expression, but TSA superinduction is lost. Transfection of a series of Timp-1 promoter constructs identified three regions through which TSA superinduces PMA-induced Timp-1 and we have demonstrated specific protein binding to two of these regions which contain either an avian erythroblastosis virus E26 (v-ets) oncogene homologue (Ets) or Sp1 binding motif. [source] Carry-over effects of embryonic acid conditions on development and growth of Rana temporaria tadpolesFRESHWATER BIOLOGY, Issue 1 2002K. RÄsänen 1.,Conditions experienced during the early stages of development may have carry-over effects on performance during later life. The egg laying period and embryonic development of temperate and boreal zone amphibians often coincides with peak acidity resulting from spring snow-melt, but the effects of acid conditions during embryonic stage on subsequent performance are unknown. 2.,We investigated the potential carry-over effects of acidity during the embryonic stage on performance up to metamorphosis in the common frog (Rana temporaria) tadpoles. There were four combinations of acid (4.5) and neutral (7.5) pH treatments applied to the egg and larval stages in a factorial laboratory experiment. In addition, we studied the difference in embryonic and larval tolerance of acidity between two populations originating from circumneutral (pH 6.6) and acidic conditions (pH 4.8). 3.,The effects of acid conditions during the embryonic stage were sublethal, as indicated by delayed development and reduced size. Under acid conditions, tadpoles that had been raised in neutral water as embryos at first grew more slowly than tadpoles raised under acid conditions as embryos. At metamorphosis, no effects of embryonic acidity were detectable indicating that tadpoles were able to compensate fully for the initial reduction in growth. 4.,Acid conditions during the larval period had a strongly negative effect on survival, size and age at metamorphosis. The amount of food consumed was lower under acid conditions, suggesting that reduced food consumption was at least partly responsible for the negative effects. 5.,Although the two populations differed in the length of larval period, there was no indication of a differential response to the treatments in any of the metamorphic traits studied. 6.,These results suggest that, although moderate acid conditions during embryonic development affect growth and development negatively, this influence does not persist after conditions have returned to normal. However, even moderately acid conditions during the larval period may have a strong negative influence on survival and performance of the tadpoles. [source] BDNF variability in opioid addicts and response to methadone treatment: preliminary findingsGENES, BRAIN AND BEHAVIOR, Issue 5 2008R. De Cid Brain-derived neurotrophic factor (BDNF) signaling pathways have been shown to be essential for opioid-induced plasticity. We conducted an exploratory study to evaluate BDNF variability in opioid addict responders and nonresponders to methadone maintenance treatment (MMT). We analyzed 21 single nucleotide polymorphisms (SNPs) across the BDNF genomic region. Responders and nonresponders were classified by means of illicit opioid consumption detected in random urinalysis. Patients were assessed by a structured interview (Psychiatric Research Interview for Substance and Mental Disorders (PRISM)-DSM-IV) and personality was evaluated by the Cloninger's Temperament and Character Inventory. No clinical, environmental and treatment characteristics were different between the groups, except for the Cooperativeness dimension (P < 0.001). Haplotype block analysis showed a low-frequency (2.7%) haplotype (13 SNPs) in block 1, which was more frequent in the nonresponder group than in the responder group (4/42 vs. 1/135; Pcorrected = 0.023). Fine mapping in block 1 allows us to identify a haplotype subset formed by only six SNPs (rs7127507, rs1967554, rs11030118, rs988748, rs2030324 and rs11030119) associated with differential response to MMT (global P sim = 0.011). Carriers of the CCGCCG haplotype had an increased risk of poorer response, even after adjusting for Cooperativeness score (OR = 20.25 95% CI 1.46,280.50, P = 0.025). These preliminary results might suggest the involvement of BDNF as a factor to be taken into account in the response to MMT independently of personality traits, environmental cues, methadone dosage and psychiatric comorbidity. [source] Impacts of extreme winter warming in the sub-Arctic: growing season responses of dwarf shrub heathlandGLOBAL CHANGE BIOLOGY, Issue 11 2008S. BOKHORST Abstract Climate change scenarios predict an increased frequency of extreme climatic events. In Arctic regions, one of the most profound of these are extreme and sudden winter warming events in which temperatures increase rapidly to above freezing, often causing snow melt across whole landscapes and exposure of ecosystems to warm temperatures. Following warming, vegetation and soils no longer insulated below snow are then exposed to rapidly returning extreme cold. Using a new experimental facility established in sub-Arctic dwarf shrub heathland in northern Sweden, we simulated an extreme winter warming event in the field and report findings on growth, phenology and reproduction during the subsequent growing season. A 1-week long extreme winter warming event was simulated in early March using infrared heating lamps run with or without soil warming cables. Both single short events delayed bud development of Vaccinium myrtillus by up to 3 weeks in the following spring (June) and reduced flower production by more than 80%: this also led to a near-complete elimination of berry production in mid-summer. Empetrum hermaphroditum also showed delayed bud development. In contrast, Vaccinium vitis-idaea showed no delay in bud development, but instead appeared to produce a greater number of actively growing vegetative buds within plots warmed by heating lamps only. Again, there was evidence of reduced flowering and berry production in this species. While bud break was delayed, growing season measurements of growth and photosynthesis did not reveal a differential response in the warmed plants for any of the species. These results demonstrate that a single, short, extreme winter warming event can have considerable impact on bud production, phenology and reproductive effort of dominant plant species within sub-Arctic dwarf shrub heathland. Furthermore, large interspecific differences in sensitivity are seen. These findings are of considerable concern, because they suggest that repeated events may potentially impact on the biodiversity and productivity of these systems should these extreme events increase in frequency as a result of global change. Although climate change may lengthen the growing season by earlier spring snow melt, there is a profound danger for these high-latitude ecosystems if extreme, short-lived warming in winter exposes plants to initial warm temperatures, but then extreme cold for the rest of the winter. Work is ongoing to determine the longer term and wider impacts of these events. [source] C3 grasses have higher nutritional quality than C4 grasses under ambient and elevated atmospheric CO2GLOBAL CHANGE BIOLOGY, Issue 9 2004Raymond V. Barbehenn Abstract Grasses with the C3 photosynthetic pathway are commonly considered to be more nutritious host plants than C4 grasses, but the nutritional quality of C3 grasses is also more greatly impacted by elevated atmospheric CO2 than is that of C4 grasses; C3 grasses produce greater amounts of nonstructural carbohydrates and have greater declines in their nitrogen content than do C4 grasses under elevated CO2. Will C3 grasses remain nutritionally superior to C4 grasses under elevated CO2 levels? We addressed this question by determining whether levels of protein in C3 grasses decline to similar levels as in C4 grasses, and whether total carbohydrate : protein ratios become similar in C3 and C4 grasses under elevated CO2. In addition, we tested the hypothesis that, among the nonstructural carbohydrates in C3 grasses, levels of fructan respond most strongly to elevated CO2. Five C3 and five C4 grass species were grown from seed in outdoor open-top chambers at ambient (370 ppm) or elevated (740 ppm) CO2 for 2 months. As expected, a significant increase in sugars, starch and fructan in the C3 grasses under elevated CO2 was associated with a significant reduction in their protein levels, while protein levels in most C4 grasses were little affected by elevated CO2. However, this differential response of the two types of grasses was insufficient to reduce protein in C3 grasses to the levels in C4 grasses. Although levels of fructan in the C3 grasses tripled under elevated CO2, the amounts produced remained relatively low, both in absolute terms and as a fraction of the total nonstructural carbohydrates in the C3 grasses. We conclude that C3 grasses will generally remain more nutritious than C4 grasses at elevated CO2 concentrations, having higher levels of protein, nonstructural carbohydrates, and water, but lower levels of fiber and toughness, and lower total carbohydrate : protein ratios than C4 grasses. [source] Affect expression in prenatally psychotropic exposed and nonexposed mother,infant dyadsINFANT MENTAL HEALTH JOURNAL, Issue 4 2002Pratibha N. Reebye This prospective study examined infant, maternal, and dyadic affective profiles at three months postpartum in infant,mother dyads that were exposed to psychotropic medications in utero compared with nonexposed control dyads. Control dyads of nondepressed mothers and their infants showed many similarities in affect expression with mother,infant dyads who were exposed to selective serotonin reuptake inhibitors (SSRIs) alone for treatment of maternal depression. In contrast, mothers who received SSRIs and Rivotril (Benzodiazepine derivative) for treatment of depression and anxiety expressed both positive and negative affect towards their infants. Clinical implications regarding use of psychotropic medications such as SSRIs alone or in combination with other drugs for treatment of maternal anxiety and depression during pregnancy are discussed. Clinicians should be aware of the possible differential response in maternal,infant interaction in a mixed diagnosis group (i.e., depression and anxiety) regarding infant temperament, possibly suggesting latent behavioral teratogenicity with psychotropics. ©2002 Michigan Association for Infant Mental Health. [source] Correlation between the high expression of C/EBP, protein in F442A cells and their relative resistance to antiadipogenic action of TCDD in comparison to 3T3-L1 cellsJOURNAL OF BIOCHEMICAL AND MOLECULAR TOXICOLOGY, Issue 2 2002Phillip C. C. Liu Abstract We compared the ability of two clonally derived murine preadipocyte cell lines, 3T3-L1(L1) and 3T3-F442A (F442A), to differentiate after treatment by 2,3,7,8-tetrachlorodibenzo- p -dioxin (TCDD), and found that the former cell line was clearly suppressed by TCDD but the latter was not. It was initially postulated that the easiest way to explain the lack of response to TCDD in F442A cells could be an alteration in aryl hydrocarbon receptor (AhR) functionality. This hypothesis was tested first, but no differences were found in the levels or functions of AhR. To find an alternate explanation for such a differential effect of TCDD, we tested the action of several diagnostic agents on the process of adipocyte differentiation of these two cells. No differences were found between these two lines of cells in the susceptibility to the antiadipogenic action of 12-0-tetradecanoylphorbol-13-acetate (TPA), or to TNF,, indicating that the basic biochemical components engaged in the antiadipogenic actions of these agents in these two cell lines are similar. In contrast, F442A cells were found to be more resistant to the antiadipogenic action of EGF or TGF, than L1 cells which were tested side by side. Based on the knowledge that TNF, preferentially affects C/EBP, and that TGF, specifically controls C/EBP, and , in their antiadipogenic action, we hypothesized that the major cause for the differential response of these two similar cell lines could be the insensitivity of C/EBP, and/or , of F442A cells to the action of TCDD. We could obtain supporting data for this hypothesis, showing that in F442A cells, the level of C/EBP, is already high even before the addition of adipocyte differentiation factors and that TCDD did not cause any significant changes in the titer of C/EBP,. © 2002 Wiley Periodicals, Inc. J Biochem Mol Toxicol 16:70,83, 2002; Published online in Wiley Interscience (www.interscience.wiley.com). DOI 10.1002/jbt.10020 [source] Differential cytokine expression by human dendritic cells in response to different Porphyromonas gingivalis capsular serotypesJOURNAL OF CLINICAL PERIODONTOLOGY, Issue 10 2009Rolando Vernal Abstract Aim: Capsular polysaccharides play an important role in the virulence of Gram-positive and Gram-negative bacteria. In Porphyromonas gingivalis, six serotypes have been described based on capsular antigenicity and its pathogenicity has been correlated both in vitro and in animal models. This study aimed to investigate the differential response of human dendritic cells (DCs) when stimulated with different P. gingivalis capsular serotypes. Materials and Methods: Using different multiplicity of infection (MOI) of the encapsulated strains K1,K6 and the non-encapsulated K, strain of P. gingivalis, the mRNA expression levels for interleukin (IL)-1,, IL-2, IL-5, IL-6, IL-10, IL-12, IL-13, interferon (IFN)- ,, tumour necrosis factor (TNF)- ,, and TNF- , in stimulated DCs were quantified by real-time reverse transcription-polymerase chain reaction. Results: All P. gingivalis capsular serotypes induced a T-helper type 1 (Th1) pattern of cytokine expression. K1- and K2-stimulated DCs expressed higher levels of IL-1,, IL-6, IL-12p35, IL-12p40, and IFN- , and at lower MOI than DCs stimulated with the other strains. Conclusions: These results demonstrate a differential potential of P. gingivalis capsular serotypes to induce DC responses and a higher capacity of strains K1 W83 and K2 HG184 than other K serotypes to trigger cytokine expression. [source] Facilitation research in marine systems: state of the art, emerging patterns and insights for future developmentsJOURNAL OF ECOLOGY, Issue 6 2009Fabio Bulleri Summary 1. Positive species interactions are increasingly recognized as important drivers of community structure and ecosystem functioning. Although the literature on facilitative interactions in terrestrial environments has been reviewed and emerging patterns have been synthesized, comparable attempts are lacking for the marine realm. 2. By means of a quantitative survey of the literature, I provide a critical summary of current knowledge on positive species interactions in marine environments. In particular, I (i) assess how marine facilitation research compares to that carried out in terrestrial environments in terms of focus and philosophical approach; (ii) illustrate the mechanisms by which facilitation takes place in different habitats; (iii) assess whether benefactor and beneficiary species are more likely to belong to the same or to a different trophic level; and (iv) provide examples of how including facilitation into ecological theory might advance our understanding of the mechanisms that regulate ecosystem functioning. 3. Except for some studies in intertidal habitats, few studies in marine environments have been framed within mainstream facilitation theory (e.g. the Stress Gradient Hypothesis) and research does not seem to be organized in a self-contained theme. Amelioration of physical conditions appears to be the most common mechanism of facilitation in intertidal habitats, whilst associational defence predominates in the subtidal. 4. In contrast to the terrestrial literature, dominated by plant,plant interactions, marine benefactors and beneficiary species often belong to different trophic levels. This might imply little overlapping of resource niches or a differential response to environmental conditions or consumer pressure, with implications for the persistence of facilitative effects at the extreme ends of stress gradients. 5. Recent research shows that facilitation can enhance temporal variability and invasibility of marine communities and emphasizes the central role of positive species interactions in regulating the functioning of natural ecosystems. 6.Synthesis. Studies encompassing a wide variety of life histories and environmental conditions are central to achieving a unified facilitation theory. Research in marine environments can provide new insights into the mechanisms underlying variations in the strength and direction of species interactions, but this will require greater awareness and consideration of facilitation. [source] Metamorphic phase relations in orthopyroxene-bearing granitoids: implication for high-pressure metamorphism and prograde melting in the continental crustJOURNAL OF METAMORPHIC GEOLOGY, Issue 4 2009S. K. BHOWMIK Abstract In this work, the factors controlling the formation and preservation of high-pressure mineral assemblages in the metamorphosed orthopyroxene-bearing metagranitoids of the Sandmata Complex, Aravalli-Delhi Mobile Belt (ADMB), northwestern India have been modelled. The rocks range in composition from farsundite through quartz mangerite to opdalite, and with varying K2O, Ca/(Ca + Na)rock and FeOtot + MgO contents. A two stage metamorphic evolution has been recorded in these rocks. An early hydration event stabilized biotite with or without epidote at the expense of magmatic orthopyroxene and plagioclase. Subsequent high-pressure granulite facies metamorphism (,15 kbar, ,800 °C) of these hydrated rocks produced two rock types with contrasting mineralogy and textures. In the non-migmatitic metagranitoids, spectacular garnet ± K-feldspar ± quartz corona was formed around reacting biotite, plagioclase, quartz and/or pyroxene. In contrast, biotite ± epidote melting produced migmatites, containing porphyroblastic garnet incongruent solids and leucosomes. Applying NCKFMASHTO T,M(H2O) and P,T pseudosection modelling techniques, it is demonstrated that the differential response of these magmatic rocks to high-pressure metamorphism is primarily controlled by the scale of initial hydration. Rocks, which were pervasively hydrated, produced garnetiferous migmatites, while for limited hydration, the same metamorphism formed sub-solidus garnet-bearing coronae. Based on the sequence of mineral assemblage evolution and the mineral compositional zoning features in the two metagranitoids, a clockwise metamorphic P,T path is constrained for the high-pressure metamorphic event. The finding has major implications in formulating geodynamic model of crustal amalgamation in the ADMB. [source] Effects of Fusaric Acid on Reactive Oxygen Species and Antioxidants in Tomato Cell CulturesJOURNAL OF PHYTOPATHOLOGY, Issue 10 2001E. Ku Generation of O2, and H2O2 as well as the activities of superoxide dismutase, catalase, ascorbate peroxidase, guaiacol peroxidase, dehydroascorbate reductase and ascorbate content were studied in tomato cell cultures in response to fusaric acid , a nonspecific toxin of phytopathogenic Fusarium species. Toxin treatment resulted in decreased cell viability which was preceded by culture medium alkalinization up to 0.65 pH unit and enhanced extracellular O2, production. The H2O2 level was not significantly affected. In toxin-treated cultures, a transient, significant increase occurred in intracellular superoxide dismutase, catalase, guaiacol peroxidase and ascorbate peroxidase activities. Fusaric acid-induced ascorbate turnover modulation led to up to a twofold increase in dehydroascorbic acid accumulation, and a decrease in the associated ascorbate redox ratio. It was concomitant with a significant decrease in dehydroascorbate reductase activity. These results support previous observations that the pro- and anti-oxidant systems are involved in response to fusaric acid treatment although differential response of H2O2 and its metabolism-related enzymes between the whole leaf and cell culture assays was found. [source] A Within-Group Design of Nontreatment Seeking 5-HTTLPR Genotyped Alcohol-Dependent Subjects Receiving Ondansetron and SertralineALCOHOLISM, Issue 2 2009George A. Kenna Background:, Serotonergic mechanisms are associated with the development of alcohol dependence (AD), however, studies evaluating serotonergic medications have produced conflicting results. One hypothesis suggests that differential response may be due to a functional polymorphism of the 5-HTTLPR promoter region of the serotonin re-uptake transporter (5-HTT). The L/L genotype is postulated to be associated with early onset alcoholism and the S/S or S/L genotypes associated with late onset alcoholism. The aim of this study was to match and mismatch L/L, S/S, or S/L genotypes with administration of ondansetron and sertraline. Methods:, Fifteen nontreatment seeking alcohol-dependent individuals were randomized to 1 of 2 counterbalanced arms to receive either 200 mg/d of sertraline or ondansetron 0.5 mg/d for 3 weeks followed by an alcohol self-administration experiment (ASAE), then received placebo for 3 weeks followed by a second ASAE. Participants then received the alternate drug for 2 weeks followed by a third ASAE. Results:, At the first ASAE compared to sertraline, ondansetron significantly improved drinking outcomes for the L/L genotype for the ASAE volume consumed (100% reduction based on between-subjects comparison, t = 2.35), and for drinks per drinking day during the 7 days prior to the ASAE (79% reduction and t = 4.34). Compared with ondansetron for S/S or S/L genotypes, outcomes at ASAE 1 for sertraline and S/S or S/L genotypes are opposite than hypothesized. Overall, subjects reduced drinking across their participation in the trial, as there appears to be an order effect. Conclusion:, This study suggests that ondansetron may reduce alcohol consumption in alcohol-dependent individuals who have the L/L genotype as measured naturalistically and during the ASAE. By contrast there was no support that sertraline reduces alcohol use in individuals who have S/S or S/L genotypes. Evidence in the literature suggests that AD in some individuals may be influenced by a gene by socio-environmental interaction making pharmacological treatment with serotonergic drugs complex. Research must consider that typologies may predict successful treatment of AD in future trials. [source] Pollen-based biome reconstructions for Colombia at 3000, 6000, 9000, 12 000, 15 000 and 18 000 14C yr ago: Late Quaternary tropical vegetation dynamicsJOURNAL OF QUATERNARY SCIENCE, Issue 2 2002Robert Marchant Abstract Colombian biomes are reconstructed at 45 sites from the modern period extending to the Last Glacial Maximum (LGM). The basis for our reconstruction is pollen data assigned to plant functional types and biomes at six 3000-yr intervals. A reconstruction of modern biomes is used to check the treatment of the modern pollen data set against a map of potential vegetation. This allows the biomes reconstructed at past periods to be assessed relative to the modern situation. This process also provides a check on the a priori assignment of pollen taxa to plant functional types and biomes. For the majority of the sites, the pollen data accurately reflect the potential vegetation, even though much of the original vegetation has been transformed by agricultural practices. At 18 000 14C yr BP, a generally cool and dry environment is reflected in biome, assignments of cold mixed forests, cool evergreen forests and cool grassland,shrub; the latter extending to lower altitudes than presently recorded. This signal is strongly recorded at 15 000 and 12 000 14C yr BP, the vegetation at these times also reflecting a relatively cool and dry environment. At 9000 14C yr BP there is a shift to biomes thought to result from slightly cooler environmental conditions. This trend is reversed by 6000 14C yr BP; most sites, within a range of different environmental settings, recording a shift to more xeric biome types. There is an expansion of steppe and cool mixed-forest biomes, replacing tropical dry forest and cool grassland,shrub biomes, respectively. These changes in biome assignments from the modern situation can be interpreted as a biotic response to mid-Holocene climatic aridity. At 3000 14C yr BP the shift is mainly to biomes characteristic of slightly more mesic environmental conditions. There are a number of sites that do not change biome assignment relative to the modern reconstruction, although the affinities that these sites have to a specific biome do change. These ,anomalies' are interpreted on a site-by-site basis. Spatially constant, but differential response of the vegetation to climatic shifts are related to changes in moisture sources and the importance of edaphic controls on the vegetation. The Late Quaternary reconstruction of large-scale vegetation dynamics in Colombia allows an understanding of the environmental controls on these to be developed. In particular, shifts in the character of the main climatic systems that influence Colombian vegetation are described. Copyright © 2002 John Wiley & Sons, Ltd. [source] Molecular approach to aquatic environmental bioreporting: differential response to environmental inducers of cytochrome P450 monooxygenase genes in the detritivorous subalpine planktonic Crustacea, Daphnia pulexMOLECULAR ECOLOGY, Issue 9 2003P. David Abstract In order to examine the usefulness of detoxifying genes as molecular markers in different chemical environments, isolation of cytochrome P450 genes (CYPs) belonging to the CYP4 family was performed in different samples from two subalpine populations of Daphnia pulex. The use of degenerate primers allowed us to isolate seven cDNAs. Four of them were assigned to the CYP4C subfamily, and were closely related to previously isolated crustacean CYP4s while the others were assigned to new CYP4AN and CYP4AP subfamilies. Expression studies, using semiquantitative polymerase chain reaction (PCR) followed by Southern blot hybridization with specific probes revealed differences in CYP4C32 and CYP4AP1 expressions between the two populations, which differ in the polyphenol richness of the vegetation surrounding their aquatic habitat. Further exposure to toxic dietary polyphenols showed different CYP induction patterns. Taken together, these preliminary results suggest a possible involvement of CYP4s in the ecological differentiation of subalpine D. pulex populations related to the polyphenol richness of the environmental vegetation. CYP4s may thus be considered as possible molecular markers in aquatic environmental bioreporting. [source] | |||||||||||||||||||||||||||||||||||||||||||