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Abundant Population (abundant + population)
Selected AbstractsLimnological changes in a sub-tropical shallow hypertrophic lake during its restoration: two years of a whole-lake experimentAQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 1 2001F. Scasso Abstract 1.,Lake Rodó is a turbid system, a condition attributed to algal biomass. The proximal source of the eutrophication was stormwater discharges from an ill-defined urban area. This paper describes an attempt to restore the water quality of Lake Rodó, the first time this has been done in Uruguay. In spring 1996 it was drained, sediments were removed and stream inputs were diverted. Groundwater was used to re-fill the lake. Due to its high nutrient concentration a re-circulation system was designed, pumping water from associated pools covered with free-floating plants. 2.,After the lake was refilled, the system was characterized by oxygen saturation or over-saturation, neutral to basic pH, and high phosphorus, nitrogen and silicate concentrations. Ratios of total nitrogen (TN):total phosphorus (TP) and chlorophyll a (Chl a):TP indicated that phosphorus was the primary limiting nutrient during the period of groundwater supply. Once groundwater pumping had ceased, there was a decrease in TN:TP and Chl a:TP ratios, suggesting N-limiting conditions prevailed in some periods. 3.,Before restoration, the phytoplankton community was dominated year-round by Planktothrix agardhii; since restoration the community has been more diverse. This change has favoured grazing by mesozooplankton, and the onset of clear-water phases in spring. 4.,Abundant populations of small omnivorous fish maintained a high predation pressure on zooplankton, restricting the abundance of large-bodied herbivores, which, in turn, allowed an increase in phytoplanton biomass and a decrease in water transparency. Based on this observation, together with the phosphorus concentration and the low abundance of filamentous cyanobacteria compared with previous studies, we suggest that top-down control has played a key role in increasing transparency in Lake Rodó. 5.,A nutrient reduction programme, by the mechanical harvest of floating plants, and a removal of small omnivorous fishes and stocking strictly with piscivores, could be key factors in the achievement of a stable clear-water phase. However, if blooms of Microcystis or other similar genera occur in summer, additional measures (e.g. reduction of the hydraulic residence time) will be needed to improve water transparency. Copyright © 2001 John Wiley & Sons, Ltd. [source] Differential routing of coexisting neuropeptides in vasopressin neuronsEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 11 2003Marc Landry Abstract The functional implications of intraneuronal coexistence of different neuropeptides depend on their respective targeting to release sites. In the rat hypothalamic magnocellular neurons, we investigated a possible differential routing of the coexpressed galanin and vasopressin. The respective location of proteins and messengers was assessed with double immunogold and in situ hybridization combining confocal and electron microscope analysis. The various populations of labelled granules were quantitatively compared in three subcellular compartments: perikarya, local processes and posthypophyseal nerve endings. Three subpopulations of granules were detected in all three compartments, but their respective amount showed significant differences. Galanin alone was immunolocalized in some secretory granules, vasopressin alone in others, and both peptides in a third subpopulation of granules. The major part of the granules containing vasopressin, either alone or in association with galanin, is found in neurohypophyseal nerve endings. In contrast, galanin single-labelled granules represent the most abundant population in dendritic processes, while double-labelled granules are more numerous in perikarya. This indicates a preferential distribution of the two peptides in the different compartments of magnocellular neurons. Furthermore, galanin and vasopressin messenger RNAs were detected at different domains of the endoplasmic reticulum, suggesting that translation might also occur at different locations, thus leading to partial segregation of galanin and vasopressin cargoes between two populations of secretory granules. The present study provides, for the first time in mammals, evidence suggesting that galanin and vasopressin are only partly copackaged and undergo a preferential targeting toward dendrites or neurohypophysis, suggesting different functions, autocrine/paracrine and endocrine, respectively. [source] Differential routing of coexisting neuropeptides in vasopressin neuronsEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 3 2003Marc Landry Abstract The functional implications of intraneuronal coexistence of different neuropeptides depend on their respective targeting to release sites. In the rat hypothalamic magnocellular neurons, we investigated a possible differential routing of the coexpressed galanin and vasopressin. The respective location of proteins and messengers was assessed with double immunogold and in situ hybridization combining confocal and electron microscope analysis. The various populations of labelled granules were quantitatively compared in three subcellular compartments: perikarya, local processes and posthypophyseal nerve endings. Three subpopulations of granules were detected in all three compartments, but their respective amount showed significant differences. Galanin alone was immunolocalized in some secretory granules, vasopressin alone in others, and both peptides in a third subpopulation of granules. The major part of the granules containing vasopressin, either alone or in association with galanin, is found in neurohypophyseal nerve endings. In contrast, galanin single-labelled granules represent the most abundant population in dendritic processes, while double-labelled granules are more numerous in perikarya. This indicates a preferential distribution of the two peptides in the different compartments of magnocellular neurons. Furthermore, galanin and vasopressin messenger RNAs were detected at different domains of the endoplasmic reticulum, suggesting that translation might also occur at different locations, thus leading to partial segregation of galanin and vasopressin cargoes between two populations of secretory granules. The present study provides, for the first time in mammals, evidence suggesting that galanin and vasopressin are only partly copackaged and undergo a preferential targeting toward dendrites or neurohypophysis, suggesting different functions, autocrine/paracrine and endocrine, respectively. [source] Infiltrating cells, related cytokines and chemokine receptors in lesional skin of patients with dermatomyositisBRITISH JOURNAL OF DERMATOLOGY, Issue 4 2004M. Caproni Summary Background, There have been only two reports on immunophenotypic characterization in the cutaneous lesions of dermatomyositis (DM) that emphasize the importance of the infiltrating CD4+ T lymphocytes. Objectives, To characterize the immunophenotype of the cells that infiltrate the lesional skin of DM and to evaluate the possible T-helper (Th) polarization Th1/Th2 through detection of specific cytokines, chemokine receptors and markers of cellular activation. Methods, Skin biopsy specimens derived from pathognomonic lesions (Gottron's papules and Gottron's sign) of eight patients with DM were immunostained with a large panel of monoclonal antibodies to CD3, CD4, CD8, myeloperoxidase (MPO), eosinophil cationic protein, tryptase, CD40, CD40 ligand (CD40L), HLA-DR, interleukin (IL)-2, IL-4, IL-5, IL-13, interferon-,, tumour necrosis factor-,, receptor 3 for CXC chemokines (CXCR3) and receptor 3 for CC chemokines, using the alkaline phosphatase,antialkaline phosphatase method. Control specimens were obtained from five healthy subjects and from six patients with discoid lupus erythematosus. Results, Activated CD4+ Th lymphocytes (HLA-DR+ CD40L+) were the principal infiltrating cells in the lesional skin of DM; the CD4/CD8 ratio was approximately 2·5. A mixed Th1/Th2 profile and higher Th1 cytokine production together with significant staining for CXCR3 were detected. Neutrophil granulocytes were the second most abundant population; eosinophil granulocytes were very poorly represented. Conclusions, Activated CD4+ T cells presumably mediate the main pathogenetic mechanisms in pathognomonic skin lesions. The interaction between CD40 and CD40L could be an important mechanism of cellular activation in cutaneous immune-mediated inflammation by induction of secretion of proinflammatory cytokines and chemokines. Neither Th1 nor Th2 clear polarization was found, although there was a slight Th1 prevalence. There was a significant quantity of MPO+ cells (neutrophil granulocytes) in the inflamed tissue, and they might have a role in sustaining the chronic inflammation. [source] Population responses to natural and human-mediated disturbances: assessing the vulnerability of the common hippopotamus (Hippopotamus amphibius)AFRICAN JOURNAL OF ECOLOGY, Issue 3 2007Rebecca Lewison Abstract Vulnerable wildlife populations can face a suite of anthropogenic activities that may threaten their persistence. However, human-mediated disturbances are likely to be coincident with natural disturbances that also influence a population. This synergism is often neglected in population projection models. Here I evaluate the effects of natural (rainfall fluctuation) and human disturbances (habitat loss and unregulated hunting) using a multi-matrix environmental state population model for the common hippopotamus (Hippopotamus amphibius). By evaluating each disturbance type (natural and human) alone and then together, I explicitly consider the importance of incorporating realistic environmental variability into population projection models. The model population was most strongly affected by moderate habitat loss, which yielded the highest probability of crossing the risk thresholds over the 60 year time period, although these probabilities were relatively low (,0.31). However, the likelihood of crossing the risk thresholds were two to five times as high when human-mediated and natural disturbances were considered together. When these probabilities were calculated per year of the simulation, the results suggested that even relatively mild human disturbances, when considered in conjunction with realistic natural disturbance, resulted in a high probability (>0.50) of substantial declines within decades. The model highlights the importance of integrating realistic natural disturbances into population models, and suggests that, despite locally abundant populations, protected hippopotamus populations may decline over the next 60 years in response to a combination of environmental fluctuations and human-mediated threats. Résumé Les populations sauvages vulnérables peuvent être confrontées à une suite d'activités humaines qui risquent de menacer leur persistance. Cependant, les perturbations causées par l'homme sont susceptibles de coïncider avec des perturbations naturelles qui influencent aussi une population. Cette synergie est souvent négligée dans les modèles de projection des populations. Ici, j'évalue les effets des perturbations naturelles (fluctuations des chutes de pluie) et humaines (perte d'habitat et chasse non réglementée) en utilisant une chaîne de matrices aléatoires pour l'état environnemental d'une population d'hippopotames (Hippopotamus amphibius). En évaluant chaque type de perturbation (naturelle et humaine) seul et ensemble, je considère explicitement l'importance qu'il y a d'intégrer une variabilité environnementale réaliste dans les modèles de projection des populations. La population modèle était surtout affectée par une perte d'habitat modérée, qui réunissait la plus grande probabilité de dépasser les seuils de risque en une période de 60 ans, même si cette probabilitéétait relativement faible (,0,31). Cependant, la probabilité de franchir les seuils de risque était 2 à 5 fois plus grande lorsque les perturbations d'origine humaine et naturelle étaient considérées ensemble. Lorsque ces probabilités étaient calculées par année, les résultats de la simulation suggéraient que même des perturbations humaines faibles, quand on les considérait en conjonction avec une perturbation naturelle réaliste, résultaient en une forte probabilité (>0,50) de déclin substantiel en quelques décennies. Le modèle souligne l'importance qu'il y a d'intégrer les perturbations naturelles réalistes dans les modèles de population et suggère que, malgré des populations localement abondantes, les populations protégées d'hippopotames peuvent décliner au cours des 60 prochaines années en réaction à une combinaison de fluctuations environnementales et de menaces d'origine humaine. [source] 16 Comparisons of macrophyte cover and community primary productivity on two southern california shoresJOURNAL OF PHYCOLOGY, Issue 2003A. M. Bullard Light-saturated net photosynthetic rates and cover of rocky intertidal macrophytes were determined between January and March 2003 at two southern California sites characterized by different macrophyte standing stocks. Overall macrophyte cover at Little Corona del Mar was low (75.4%) and was dominated by articulated corallines, and small, turf-forming crustose algae that provide little habitat structure. Macrophyte cover was higher at Dana Point (99.4%), where larger, frondose seaweeds were more abundant (34% vs < 5% cover). Our light-saturated photosynthetic rates for Little Corona del Mar and Dana Point macrophytes were similar to values for the same species obtained during the 1970s and 1980s. Highest photosynthetic rates were obtained for thinner, sheet-like, and branched, frondose seaweeds, while lowest rates were found for articulated coralline and crustose algae. We estimated the net community productivity of the two sites using photosynthetic rates (calculated as mg C m,2 · h,1) and percent cover data for the most abundant populations. We also compared our community productivity estimates for Little Corona del Mar and Dana Point with values for the same sites calculated using macrophyte cover values obtained during the mid-1970s. Re-sampling studies of these and other regional sites reveal that lower-producing, crustose and coralline algae have become increasingly abundant while the cover of higher-producing, frondose algae has declined on many southern California shores. Our studies at Little Corona del Mar and Dana Point, indicate that changing macrophyte abundances can have significant effects on the primary productivity of rocky intertidal communities. [source] | ||||||||||