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81.
Juan Rull Solana Abraham Adalecio Kovaleski Diego F. Segura Mariana Mendoza M. Clara Liendo M. Teresa Vera 《Entomologia Experimentalis et Applicata》2013,148(3):213-222
Tropical tephritids are ideally suited for studies on population divergence and speciation because they include species groups undergoing rapid radiation, in which morphologically cryptic species and sister species are abundant. The fraterculus species group in the Neotropical genus Anastrepha is a case in point, as it is composed of a complex of up to seven A. fraterculus morphotypes proposed to be cryptic species. Here, we document pre‐ and post‐zygotic barriers to gene flow among adults of the Mexican A. fraterculus morphotype and three populations (Argentina, Brazil, and Peru) belonging to two separate morphotypes (Brazilian 1 and Peruvian). We unveiled three forms of pre‐zygotic reproductive isolation resulting in strong assortative mating. In field cages, free‐ranging male and female A. fraterculus displayed a strong tendency to form couples with members of the opposite sex belonging to their own morphotype, suggesting that male pheromone emission, courtship displays, or both intervene in shaping female choice before actual contact and coupling. In addition, males and females of the Peruvian morphotype became receptive and mated significantly later than adults of the Mexican and Brazilian 1 morphotypes. After contact, Mexican females exhibited greater mating discrimination than males when facing adults of the opposite sex belonging to either the Peruvian or the Brazilian 1 morphotype as evidenced by vigorous resistance to penetration once they had been forcefully mounted by heterotypic males. Forced copulations resulted in production of F1 hybrids that were either less viable (and partially fertile) than parental crosses or even sterile. Our results suggest that the Mexican morphotype is a distinct biological entity and that pre‐zygotic reproductive isolation through divergence in courtship or male‐produced pheromone and other mechanisms appear to evolve faster than post‐zygotic isolation in the fraterculus species group. 相似文献
82.
Maria Carolina S. Soares Vera L. M. Huszar Marcela N. Miranda Mariana M. Mello Fabio Roland Miquel Lürling 《Hydrobiologia》2013,717(1):1-12
Based on a literature survey, we evaluated the periods of cyanobacterial dominance in Brazil. We hypothesized that variability of environmental forces along the country will promote or facilitate temporal and spatial mosaic in cyanobacterial dominance. The most striking outcomes are related to the dominance of Cylindrospermopsis, Dolichospermum, and Microcystis. Although they share important adaptive strategies (e.g., aerotopes, large size and toxins production), our findings suggest that they have different environmental preferences. Dolichospermum and Microcystis dominated mainly in warm-rainy periods whereas Cylindrospermopsis was more common during dry periods and in mixed systems, or formed perennial dominance. Maximum phosphorus concentrations were observed in reservoirs dominated by Cylindrospermopsis. Although the main genera reached high biomass levels individually, different abilities to form dominance and co-dominance were observed. The number of co-dominance of Chroococales and Nostocales was almost the same as the individual occurrence of the main genera from these groups. This dataset reveals patterns of dominance of these cyanobacteria and also indicates that physiological features will cause differences in the mechanisms of interactions between species. The understanding of these processes and their relationship to environmental conditions will promote better understanding of cyanobacterial dominance and increase our ability to predict and manage these events. 相似文献
83.
Mariana Budovská Martina Pilátová Lenka Varinská Ján Mojžiš Roman Mezencev 《Bioorganic & medicinal chemistry》2013,21(21):6623-6633
An effective synthesis of analogs of the indole phytoalexin cyclobrassinin with NR1R2 group instead of SCH3 was developed starting from indole-3-carboxaldehyde. The target compounds were prepared by spirocyclization of 1-Boc-thioureas with the formation of isolable spiroindoline intermediates, followed by the trifluoroacetic acid-induced cascade reaction consisting of methanol elimination, deprotection and rearrangement of the iminium ion. The structures of novel products were elucided by the 1H and 13C NMR spectroscopy, including HMBC, HSQC, COSY, NOESY and DEPT measurements. Several newly synthesized compounds demonstrated significant antiproliferative/cytotoxic activity against human leukemia and solid tumor cell lines, as well as remarkable selectivity of these effects against cancer cells relative to the non-malignant HUVEC cells. 相似文献
84.
Mariana Richero Mariana Barraco Vega Maria Pía Cerdeiras Gianna Cecchetto 《Trees - Structure and Function》2013,27(1):249-257
The genus Eucalyptus includes over 700 species, some of which are the most widely planted hardwoods worldwide. Each species and subspecies of Eucalyptus present different characteristics regarding its wood quality and yield. This fact makes it very important to work with known species/subspecies so as to optimize handling and conservation of forest resources. Some of them are morphologically very similar, making it difficult to differentiate by simple observation. This is the case with Euclyptus globulus ssp globulus and E. globulus ssp maidenii, which can only be distinguished in the adult tree. These issues can be avoided using well-characterized seeds. This can be quite expensive, especially for the small growers. An alternative approach is to develop simple methods for the differentiation of the two subspecies. In this work, we develop a quick method, based on SCAR molecular markers derived from RAPD molecular markers, for the differentiation of the subspecies of E. globulus, in particular E. globulus ssp globulus and E. globulus ssp maidenii. 相似文献
85.
Disturbances, elevation, topography and spatial proximity drive vegetation patterns along an altitudinal gradient of a top biodiversity hotspot 总被引:1,自引:0,他引:1
Pedro V. Eisenlohr Luciana F. Alves Luís Carlos Bernacci Maíra C. G. Padgurschi Roseli B. Torres Eduardo M. B. Prata Flavio Antonio M. dos Santos Marco Antônio Assis Eliana Ramos André Luís C. Rochelle Fernando R. Martins Mariana C. R. Campos Fernando Pedroni Maryland Sanchez Larissa S. Pereira Simone A. Vieira José Ataliba M. A. Gomes Jorge Y. Tamashiro Marcos A. S. Scaranello Cora J. Caron Carlos Alfredo Joly 《Biodiversity and Conservation》2013,22(12):2767-2783
The correlation between vegetation patterns (species distribution and richness) and altitudinal variation has been widely reported for tropical forests, thereby providing theoretical basis for biodiversity conservation. However, this relationship may have been oversimplified, as many other factors may influence vegetation patterns, such as disturbances, topography and geographic distance. Considering these other factors, our primary question was: is there a vegetation pattern associated with substantial altitudinal variation (10–1,093 m a.s.l.) in the Atlantic Rainforest—a top hotspot for biodiversity conservation—and, if so, what are the main factors driving this pattern? We addressed this question by sampling 11 1-ha plots, applying multivariate methods, correlations and variance partitioning. The Restinga (forest on sandbanks along the coastal plains of Brazil) and a lowland area that was selectively logged 40 years ago were floristically isolated from the other plots. The maximum species richness (>200 spp. per hectare) occurred at approximately 350 m a.s.l. (submontane forest). Gaps, multiple stemmed trees, average elevation and the standard deviation of the slope significantly affected the vegetation pattern. Spatial proximity also influenced the vegetation pattern as a structuring environmental variable or via dispersal constraints. Our results clarify, for the first time, the key variables that drive species distribution and richness across a large altitudinal range within the Atlantic Rainforest. 相似文献
86.
Fungyi Chow Marianne Pedersén Mariana C. Oliveira 《Journal of applied phycology》2013,25(6):1847-1853
Nitrate reductase (NR), a key enzyme in nitrogen metabolism, has been implicated in the production of nitric oxide (NO) in plants. The effect of photosynthetic electron transport chain inhibitors and NO scavengers or donors on NR activity of Gracilaria chilensis was studied under experimental laboratory conditions. Effective quantum yield (Φ PSII) and NR activity were significantly diminished by 3-(3,4-dichlorophenyl)-1,1-dimethylurea and 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone, two photosynthetic electron flux inhibitors of photosystem (PS) II and PSI, respectively, but not by diphenyleneiodonium, a NADPH oxidase inhibitor, indicating a direct dependence of NR activity on the PSII and PSI electron flux. Nitrate reductase activity was sensitive to a decrease or increase of NO levels when NO scavenger (2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide) and NO donor (sodium nitroprusside) were added. Moreover, the addition of 8Br-cGMP, a secondary signal molecule, stimulated NR activity. These results evidence a modulation of the photosynthetic electron transport chain and NO balance on G. chilensis NR activity. This association could be linked to the crucial tight modulation of nitrogen assimilation and carbon metabolism to guarantee nitrite incorporation into organic compounds and to avoid toxicity by nitrite, reactive oxygen species, or nitric oxide in the cells. Nitric oxide showed to be an important signaling molecule regulating NR activity and cGMP could participate as secondary messenger on this regulation by phosphorylation and desphosphorylation processes. 相似文献
87.
Magdalena Sarah Volz Vanessa Suarez-Contreras Mariana E. Mendonca Fernando Santos Pinheiro Lotfi B. Merabet Felipe Fregni 《PloS one》2013,8(1)
Background/Objective
Transcutaneous electrical stimulation has been proven to modulate nervous system activity, leading to changes in pain perception, via the peripheral sensory system, in a bottom up approach. We tested whether different sensory behavioral tasks induce significant effects in pain processing and whether these changes correlate with cortical plasticity.Methodology/Principal Findings
This randomized parallel designed experiment included forty healthy right-handed males. Three different somatosensory tasks, including learning tasks with and without visual feedback and simple somatosensory input, were tested on pressure pain threshold and motor cortex excitability using transcranial magnetic stimulation (TMS). Sensory tasks induced hand-specific pain modulation effects. They increased pain thresholds of the left hand (which was the target to the sensory tasks) and decreased them in the right hand. TMS showed that somatosensory input decreased cortical excitability, as indexed by reduced MEP amplitudes and increased SICI. Although somatosensory tasks similarly altered pain thresholds and cortical excitability, there was no significant correlation between these variables and only the visual feedback task showed significant somatosensory learning.Conclusions/Significance
Lack of correlation between cortical excitability and pain thresholds and lack of differential effects across tasks, but significant changes in pain thresholds suggest that analgesic effects of somatosensory tasks are not primarily associated with motor cortical neural mechanisms, thus, suggesting that subcortical neural circuits and/or spinal cord are involved with the observed effects. Identifying the neural mechanisms of somatosensory stimulation on pain may open novel possibilities for combining different targeted therapies for pain control. 相似文献88.
Alipio Pinto Mariana Jacobsen Patricia A. Geoghegan Adriana Cangelosi María Laura Cejudo Carla Tironi-Farinati Jorge Goldstein 《PloS one》2013,8(7)
Shiga toxin 2 (Stx2)-producing Escherichia coli (STEC) causes hemorrhagic colitis and hemolytic uremic syndrome (HUS) that can lead to fatal encephalopathies. Neurological abnormalities may occur before or after the onset of systemic pathological symptoms and motor disorders are frequently observed in affected patients and in studies with animal models. As Stx2 succeeds in crossing the blood-brain barrier (BBB) and invading the brain parenchyma, it is highly probable that the observed neurological alterations are based on the possibility that the toxin may trigger the impairment of the neurovascular unit and/or cell damage in the parenchyma. Also, lipopolysaccharide (LPS) produced and secreted by enterohemorrhagic Escherichia coli (EHEC) may aggravate the deleterious effects of Stx2 in the brain. Therefore, this study aimed to determine (i) whether Stx2 affects the neurovascular unit and parenchymal cells, (ii) whether the contribution of LPS aggravates these effects, and (iii) whether an inflammatory event underlies the pathophysiological mechanisms that lead to the observed injury. The administration of a sub-lethal dose of Stx2 was employed to study in detail the motor cortex obtained from a translational murine model of encephalopathy. In the present paper we report that Stx2 damaged microvasculature, caused astrocyte reaction and neuronal degeneration, and that this was aggravated by LPS. Dexamethasone, an anti-inflammatory, reversed the pathologic effects and proved to be an important drug in the treatment of acute encephalopathies. 相似文献
89.
Joshua P. Vogel Maria Regina Torloni Armando Seuc Ana Pilar Betrán Mariana Widmer Jo?o Paulo Souza Mario Merialdi 《PloS one》2013,8(8)
Background
Twin pregnancies in low- and middle-income countries (LMICs) pose a high risk to mothers and newborns due to inherent biological risks and scarcity of health resources. We conducted a secondary analysis of the WHO Global Survey dataset to analyze maternal and perinatal outcomes in twin pregnancies and factors associated with perinatal morbidity and mortality in twins.Methods
We examined maternal and neonatal characteristics in twin deliveries in 23 LMICs and conducted multi-level logistic regression to determine the association between twins and adverse maternal and perinatal outcomes.Results
279,425 mothers gave birth to 276,187 (98.8%) singletons and 6,476 (1.2%) twins. Odds of severe adverse maternal outcomes (death, blood transfusion, ICU admission or hysterectomy) (AOR 1.85, 95% CI 1.60–2.14) and perinatal mortality (AOR 2.46, 95% CI 1.40–4.35) in twin pregnancies were higher, however early neonatal death (AOR 2.50, 95% CI 0.95–6.62) and stillbirth (AOR 1.22, 95% CI 0.58–2.57) did not reach significance. Amongst twins alone, maternal age <18, poor education and antenatal care, nulliparity, vaginal bleeding, non-cephalic presentations, birth weight discordance >15%, born second, preterm birth and low birthweight were associated with perinatal mortality. Marriage and caesarean section were protective.Conclusions
Twin pregnancy is a significant risk factor for maternal and perinatal morbidity and mortality in low-resource settings; maternal risk and access to safe caesarean section may determine safest mode of delivery in LMICs. Improving obstetric care in twin pregnancies, particularly timely access to safe caesarean section, is required to reduce risk to mother and baby. 相似文献90.
Ronan A. Lyons Denise Kendrick Elizabeth M. L. Towner Carol Coupland Mike Hayes Nicola Christie Judith Sleney Sarah Jones Richard Kimberlee Sarah E. Rodgers Samantha Turner Mariana Brussoni Yana Vinogradova Tinnu Sarvotham Steven Macey 《PloS one》2013,8(4)