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61.
Patricio H. Manríquez Ricardo Guiñez Alberto Olivares Marcela Clarke Juan Carlos Castilla 《Marine Biology Research》2018,14(5):462-477
Reproduction in tunicates is considered to be particularly vulnerable to changes in seawater temperature. In the present study we investigated the effects of sea surface temperature and temperature anomalies on reproductive traits of the non-native sessile tunicate Pyura praeputialis. Reproductive traits of this species were investigated over the course of 67 months, based on samples collected at two localities (eastern and western shorelines) of the Bay of Antofagasta. The study period included years with different oceanic and atmospheric conditions: a warm event, El Niño (June 1997 to July 1998); a cold event, La Niña (August 1998 to December 2000); and post-La Niña (January 2000 to December 2002). We compared two common indices (condition and gonadosomatic) and histological sections to evaluate the maximum reproduction index of this introduced species that dominates a large part of the rocky intertidal habitat in the Bay of Antofagasta. We found sexually mature individuals all year-round and a decrease in both reproductive indices matching the reduction in the sea surface temperature during the austral autumn and winter months. The results suggest that gonad development in this species is sensitive to sea surface temperature and thermal anomalies. We conclude that future thermal anomalies or projected global average sea surface warming associated with climate change might have no negative consequences on these reproductive traits of P. praeputialis. This suggests this species is ecologically resilient and that the ecosystem services that this species provides for other invertebrate and algal species will be maintained. 相似文献
62.
Ingrid Olivares Dirk N. Karger Michael Kessler 《Biological reviews of the Cambridge Philosophical Society》2018,93(4):1874-1890
Is there a maximum number of species that can coexist? Intuitively, we assume an upper limit to the number of species in a given assemblage, or that a lineage can produce, but defining and testing this limit has proven problematic. Herein, we first outline seven general challenges of studies on species saturation, most of which are independent of the actual method used to assess saturation. Among these are the challenge of defining saturation conceptually and operationally, the importance of setting an appropriate referential system, and the need to discriminate among patterns, processes and mechanisms. Second, we list and discuss the methodological approaches that have been used to study species saturation. These approaches vary in time and spatial scales, and in the variables and assumptions needed to assess saturation. We argue that assessing species saturation is possible, but that many studies conducted to date have conceptual and methodological flaws that prevent us from currently attaining a good idea of the occurrence of species saturation. 相似文献
63.
Steven D. Allison Adriana L. Romero‐Olivares Ying Lu John W. Taylor Kathleen K. Treseder 《Global Change Biology》2018,24(7):2884-2897
The magnitude and direction of carbon cycle feedbacks under climate warming remain uncertain due to insufficient knowledge about the temperature sensitivities of soil microbial processes. Enzymatic rates could increase at higher temperatures, but this response could change over time if soil microbes adapt to warming. We used the Arrhenius relationship, biochemical transition state theory, and thermal physiology theory to predict the responses of extracellular enzyme Vmax and Km to temperature. Based on these concepts, we hypothesized that Vmax and Km would correlate positively with each other and show positive temperature sensitivities. For enzymes from warmer environments, we expected to find lower Vmax, Km, and Km temperature sensitivity but higher Vmax temperature sensitivity. We tested these hypotheses with isolates of the filamentous fungus Neurospora discreta collected from around the globe and with decomposing leaf litter from a warming experiment in Alaskan boreal forest. For Neurospora extracellular enzymes, Vmax Q10 ranged from 1.48 to 2.25, and Km Q10 ranged from 0.71 to 2.80. In agreement with theory, Vmax and Km were positively correlated for some enzymes, and Vmax declined under experimental warming in Alaskan litter. However, the temperature sensitivities of Vmax and Km did not vary as expected with warming. We also found no relationship between temperature sensitivity of Vmax or Km and mean annual temperature of the isolation site for Neurospora strains. Declining Vmax in the Alaskan warming treatment implies a short‐term negative feedback to climate change, but the Neurospora results suggest that climate‐driven changes in plant inputs and soil properties are important controls on enzyme kinetics in the long term. Our empirical data on enzyme Vmax, Km, and temperature sensitivities should be useful for parameterizing existing biogeochemical models, but they reveal a need to develop new theory on thermal adaptation mechanisms. 相似文献
64.
L C Reis A C Almeida P L Cedraz-Mercez E L Olivares A Marinho Jr C M Thomaz 《Revista brasleira de biologia》2005,65(2):353-361
We investigated participation of the brain serotonergic system in food intake control by using oral and systemic administration of serotonin precursors in quails (Coturnix japonica). Dietary supplemental tryptophan (0.1-50.0 g/kg) provoked a dose-dependent inhibition of food intake during a 5-h observation period, which persisted up to 24 h for doses of 30.0 and 50.0 g/kg. Normally fed and fasted animals treated with hydroxytryptophan (12.5-50.0 mg/kg) by the intracoelomic route showed an acute inhibition of food intake. Hypophagia in fasted birds was only effective when the precursor was administered immediately before food presentation. A similar response was obtained by administering serotonin (0.125-2.5 mg/kg, sc), with animals showing a hypnogenic response within the first ten minutes after administration, suggesting that, in contrast to mammals, the amine crosses the blood-brain barrier in quails. Administration of hydroxytryptophan at all doses tested induced significant dipsogenic behavior despite the concomitant hypnogenic response. The results suggest the involvement of serotonergic pathways in food intake control in quails and also show, for the first time, hypnogenic action induced by serotonin and a hyperdipsic effect elicited by hydroxytryptophan. 相似文献
65.
66.
Reis Veronica Massena Olivares Fábio Lopes de Oliveira André Luiz Martinez Bueno dos Reis Junior Fábio Baldani José Ivo Döbereiner Johanna 《Plant and Soil》1999,206(2):205-211
Micropropagated plantlets of sugar cane were inoculated with the N2-fixing bacterium Acetobacter diazotrophicus. Various modifications
on the basic plant culture medium MS were made for the plant/bacteria association. The protocol required the inoculation of
the bacteria at the end of the rooting period in a medium without hormones or vitamins, and with the concentration of sugar
and mineral nutrients reduced by a factor of 10. Individual plants were inoculated with A. diazotrophicus and maintained under
the appropriate light and temperature condition used for micropropagation up to 7 days. The system favored the infection and
the establishment of the bacteria within the plant tissue. Bacteria colonized the plant tissue and accumulated in inter-cellular
cavities and the region of lateral root emergence and also colonizes the xylem vessels. The inoculated plantlets were subsequently
transferred to the acclimatization phase and after 30 days it was possible to isolate the bacteria from plant tissue. This
protocol permitted studies of infection and comparison among strains. 相似文献
67.
68.
Second-site reversion of a human immunodeficiency virus type 1 reverse transcriptase mutant that restores enzyme function and replication capacity. 下载免费PDF全文
69.
Araya JE Cornejo A Orrego PR Cordero EM Cortéz M Olivares H Neira I Sagua H da Silveira JF Yoshida N González J 《Microbes and infection / Institut Pasteur》2008,10(8):892-900
During Trypanosoma cruzi cell invasion, signal transduction pathways are triggered in parasite and host cells, leading to a rise in intracellular Ca(2+) concentration. We posed the question whether calcineurin (CaN), in particular the functional regulatory subunit CaNB, a Ca(2+)-binding EF-hand protein, was expressed in T. cruzi and whether it played a role in cell invasion. Here we report the cloning and characterization of CL strain CaNB gene, as well as the participation of CaNB in cell invasion. Treatment of metacyclic trypomastigotes (MT) or tissue-culture trypomastigotes (TCT) with the CaN inhibitors cyclosporin or cypermethrin strongly inhibited (62-64%) their entry into HeLa cells. In assays using anti-phospho-serine/threonine antibodies, a few proteins of MT were found to be dephosphorylated in a manner inhibitable by cyclosporin upon exposure to HeLa cell extract. The phosphatase activity of CaN was detected by a biochemical approach in both MT and TCT. Treatment of parasites with antisense phosphorothioate oligonucleotides directed to TcCaNB-CL, which reduced the expression of TcCaNB and affected TcCaN activity, resulted in approximately 50% inhibition of HeLa cell entry by MT or TCT. Given that TcCaNB-CL may play a key role in cell invasion and differs considerably in its primary structure from the human CaNB, it might be considered as a potential chemotherapeutic target. 相似文献
70.
Aline C. Intorne Marcos Vinicius V. de Oliveira Mariana L. Lima Juliana F. da Silva Fábio L. Olivares Gonçalo Apolinário de Souza Filho 《Archives of microbiology》2009,191(5):477-483
Gluconacetobacter diazotrophicus is a plant-growth-promoting bacterium, which is able to colonize sugarcane and other plant species of economic importance.
The potentially beneficial effects promoted by this bacterium on plants are nitrogen-fixation, production of phythormones,
action against pathogens and mineral nutrient solubilization. In this study, the molecular mechanisms associated with phosphorus
and zinc solubilization were analyzed. A transposon mutant library was constructed and screened to select for mutants defective
for phosphorous [Ca5(PO4)3OH] and zinc (ZnO) solubilization. A total of five mutants were identified in each screen. Both screenings, performed independently,
allowed to select the same mutants. The interrupted gene in each mutant was identified by sequencing and the results demonstrate
that the production of gluconic acid is a required pathway for solubilization of such nutrients in G. diazotrophicus.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
A. C. Intorne and M. V. V. de Oliveira contributed equally to this work. 相似文献