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1.
The role of arctic zooplankton in biogeochemical cycles: respiration and excretion of ammonia and phosphate during summer 总被引:1,自引:0,他引:1
M. Alcaraz R. Almeda A. Calbet E. Saiz C. M. Duarte S. Lasternas S. Agustí R. Santiago J. Movilla A. Alonso 《Polar Biology》2010,33(12):1719-1731
The study of the structural and functional properties of key components of polar marine ecosystems has received increased
attention in order to better understand the ecological consequences of future sea temperature rise and seasonal ice retraction.
Owing to this purpose, during the ATOS-Arctic cruise, held in July 2007 in the framework of the 2007–2008 International Polar
Year, we studied the respiratory carbon demand of mesozooplankton as well as their contribution to the regeneration of inorganic
nitrogen and phosphorus (NH4-N and PO4-P) via excretion. The studied area comprised several stations along a latitudinal gradient in the East Greenland current, plus a
network of stations NW of the Svalbard islands. The specific respiratory carbon losses and phosphorus (PO4-P) excretion rates were similar or slightly higher than some reports for Arctic mesozooplankton, but the nitrogen (NH4-N) excretion rates were higher by a factor of 3 when compared with previous data sets. The mesozooplankton respiratory losses
were equivalent to 23% of primary production, and at turn zooplankton contributed by excretion to more than 50% of the N and
P required by phytoplankton. Although C:N, C:P and N:P metabolic atomic quotients almost coincided with the average Redfield’s
stoichiometric ratios, the low C:N values when compared to previous reports suggested a predominance of protein-related metabolic
substrates. The potential consequences of changes observed in the C:N, N:P and C:P metabolic ratios of mesozooplankton for
Arctic marine ecosystems are discussed. 相似文献
2.
Salomé C. Vilchez Larrea Mariana Schlesinger María L. Kevorkian Mirtha M. Flawiá Guillermo D. Alonso Silvia H. Fernández Villamil 《PloS one》2013,8(6)
Trypanosoma cruzi, etiological agent of Chagas’ disease, has a complex life cycle which involves the invasion of mammalian host cells, differentiation and intracellular replication. Here we report the first insights into the biological role of a poly(ADP-ribose) glycohydrolase in a trypanosomatid (TcPARG). In silico analysis of the TcPARG gene pointed out the conservation of key residues involved in the catalytic process and, by Western blot, we demonstrated that it is expressed in a life stage-dependant manner. Indirect immunofluorescence assays and electron microscopy using an anti-TcPARG antibody showed that this enzyme is localized in the nucleus independently of the presence of DNA damage or cell cycle stage. The addition of poly(ADP-ribose) glycohydrolase inhibitors ADP-HPD (adenosine diphosphate (hydroxymethyl) pyrrolidinediol) or DEA (6,9-diamino-2-ethoxyacridine lactate monohydrate) to the culture media, both at a 1 µM concentration, reduced in vitro epimastigote growth by 35% and 37% respectively, when compared to control cultures. We also showed that ADP-HPD 1 µM can lead to an alteration in the progression of the cell cycle in hydroxyurea synchronized cultures of T. cruzi epimastigotes. Outstandingly, here we demonstrate that the lack of poly(ADP-ribose) glycohydrolase activity in Vero and A549 host cells, achieved by chemical inhibition or iRNA, produces the reduction of the percentage of infected cells as well as the number of amastigotes per cell and trypomastigotes released, leading to a nearly complete abrogation of the infection process. We conclude that both, T. cruzi and the host, poly(ADP-ribose) glycohydrolase activities are important players in the life cycle of Trypanosoma cruzi, emerging as a promising therapeutic target for the treatment of Chagas’ disease. 相似文献
3.
Martha L. Bohórquez Alonso Jorge Martínez Cotrina David Aguilar Pardo Enrique Font Miguel Molina-Borja 《Journal of Ethology》2010,28(2):305-311
Many vertebrate species show display behaviors when predators are in their vicinity. Some of these displays may inform the
predator of the improbability of capturing the prey (i.e., pursuit-deterrent displays) and are potentially advantageous to
both predator and prey. Here we present data on a tail display performed by Gonatodes albogularis, a diurnal tropical gecko. We performed transect surveys in three habitats near Bogotá in Colombia. Geckos detected during
transects were approached by the observer in a standardized way, and details of their tail-waving displays were recorded.
In control recordings animals were watched from a distant site without approaching them. Results showed sexual differences
in tail-waving display: when approached by the observer, males performed this behavior more frequently than females. We found
no significant differences between males and females in flight-initiation distances and height above the substratum when they
were initially located. Results also showed that males displayed more frequently when approached than when the simulated predator
remained stationary. We interpret these results as evidence that the display functions as a pursuit-deterrent signal to potential
predators. However, as some tail displays were performed in the presence of conspecifics, the display may also have a social
function. 相似文献
4.
J Ignacio Andrés Jesús Alcázar José M Alonso Adolfo Díaz Javier Fernández Pilar Gil Laura Iturrino Encarna Matesanz Theo F Meert Anton Megens Victor K Sipido 《Bioorganic & medicinal chemistry letters》2002,12(2):249-253
Following the programme started at Janssen Research Foundation searching for 5-HT(2A/2C) antagonists, we now report on the synthesis of a series of substituted 2-(Dimethylaminomethyl)-2,3,3a,8-tetrahydrodibenzo[c,f]isoxazolo[2,3-a]azepine derivatives. The 5-HT(2A), 5-HT(2C) and H(1) receptor affinities as well as the mCPP antagonistic activity of the compounds synthesised is described. 相似文献
5.
6.
7.
A Osuna L M Ruiz-Perez M C Lopez S Castanys F Gamarro D G Craciunescu C Alonso 《The Journal of parasitology》1987,73(2):272-277
The present report deals with the alterations produced by cis-diamminedichloroplatinum (II) (DDP), and 2 of its analogs: cis-Pt(II)(tranylcypromine)2Cl2 and cis-Pt(II)(benzothiazole)2Cl2 in cultured epimastigote forms of Trypanosoma cruzi. Studies have been performed at the ultrastructural level and the inhibitory effect of these complexes on macromolecule synthesis, evaluated by 3H-thymidine, 3H-uridine, and 3H-leucine incorporation, has been investigated. DDP at concentrations of 50 and 100 micrograms/ml does not inhibit significantly the incorporation of radioactive precursors, but a clear decrease was observed with the 2 analogs. Eight hours of treatment at a concentration of 10 micrograms/ml rendered in all 3 cases an increase in autophagic vacuoles and lipids as well as an abnormal condensation of the nucleus chromatin. 相似文献
8.
Summary We have identified a cDNA coding for the murine keratin D from a collection of clones representing F9 teratocarcinoma stem cell mRNA sequences. These sequences are synthesized specifically after the addition of retinoic acid and cAMP to the culture medium. The clone is 1,382 nucleotides long and contains the entire information for the active polypeptide, the complete 3 end and most, if not all, of the 5 non-coding region. The mRNA is found in hepatocytes, in PYS-2 cells (an endodermal cell line) and in differentiated (retinoic-acid-treated) F9 cells, but not in untreated F9 cells. The length of the mRNA is 1.4 kb, as estimated by Northern blot hybridization. Southern hybridization performed under very stringent conditions detects a single fragment hybridizing strongly with the cloned cDNA, suggesting that the mouse genome contains only one or very few copies of this gene. We present the first complete sequence of a keratin expressed in simple epithelia, i.e. keratin D, and discuss its structural features. 相似文献
9.
Of the two mitochondrial enzymes of the urea cycle, carbamoyl phosphate synthetase (CPS) was and ornithine transcarbamylase (OTC) was not inactivated by the Fe3+-oxygen-ascorbate model system for mixed-function oxidation [R. L. Levine, (1983) J. Biol. Chem. 258, 11828-11833]. The susceptibility of OTC was not increased by its substrates, products, or inhibitors, whereas that of CPS was markedly increased by acetylglutamate (its allosteric activator) when ATP was absent. Thus, acetylglutamate binds in the absence of ATP and exposes to oxidation essential groups of the enzyme. We estimate for this binding a KD value of 1.6 mM, which greatly exceeds the KD values (less than 10 microM) determined in the presence of ATP and bicarbonate. ATP, and even more, mixtures of ATP and bicarbonate protected CPS from inactivation. Acetylglutamate exposes the site for the ATP molecule that yields Pi, and it appears that ATP protects by binding at this site. Experiments of limited proteolysis with elastase suggest that oxidation prevents this binding of ATP and show that it accelerates cleavage of CPS by the protease, thus supporting the idea that oxidation may precede proteolysis. Trypsin, chymotrypsin, and papain also hydrolyze the oxidized enzyme considerably faster than the native enzyme. Our results also support the idea that oxidative inactivation is site specific and requires sites on the enzyme for Me2+ and, possibly, for a nucleotide. 相似文献
10.
The rate of hexose transport was approximately 60% lower for both the high- and the low-affinity components of hexose uptake
when a glucose-6-phosphate isomerase mutant ofSaccharomyces cerevisiae was preincubated with glucose, as compared with preincubation with water. Similarly theJ
max value of the high-affinity system of the mutant was 25–35 % of the correspondingJ
max value for normal cells incubated with glucose. Accumulation of glucose 6-phosphate or of some other metabolite, such as fructose
6-phosphate or trehalose, may be responsible for this striking inhibition. 相似文献