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Search Results: 1 - 10 of 7792 matches for " Denise Rivera;Villac "
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The phytoplankton of Guanabara Bay, Brazil: I. historical account of its biodiversity
Villac, Maria Célia;Tenenbaum, Denise Rivera;
Biota Neotropica , 2010, DOI: 10.1590/S1676-06032010000200030
Abstract: this is a historical account of the biodiversity of phytoplankton in guanabara bay, brazil. it is based on 57 publications that refer to sampling carried out between 1913 and 2004. the publications included are those with direct microscopic identification. although 80% of the studies focus on ecological issues that tend to mention only the most abundant species, 24 publications provide comprehensive check-lists at the species level, especially of taxa > 20 μm. the inventory of species includes, to date, 308 taxa among 199 diatoms, 90 dinoflagellates, 9 cyanobacteria, 5 euglenophyceans, 1 chlorophycean, 1 prasinophycean, 1 silicoflagellate, and 2 ebriids. the most conspicuous species were the dinoflagellate scrippsiella trochoidea and diatoms from the skeletonema costatum complex. the first was the theme of the very first publication in the area (faria 1914) that reported on its bloom associated with the mass mortality of fish due to oxygen depletion; it is still often found in high abundances (106 cell.l-1) in more protected areas. the second was long considered in the literature as a cosmopolitan and opportunistic species, until the recent discovery of cryptic species within the genus; taxonomic re-evaluation of local populations is, therefore, needed. besides these two species, only other 25 species stood out in terms of frequency of occurrence and widespread distribution in the bay, some known to be implicated in harmful blooms elsewhere. the biodiversity of dinoflagellates, especially within the gymnodiniales, and that of other unidentified flagellates (haptophyceae, cryptophyceae, prasinophyceae, raphidophyceae) is largely underestimated because of the use of fixatives that distort/destroy diagnostic characters. from the initial inventory of 124 taxa published in 1917 and the subsequent additions in species numbers, one can have a false perception that the phytoplankton biodiversity has increased throughout the years, despite the overall increase in eutrophicat
Auto- and heterotrophic nanoplankton and filamentous bacteria of Guanabara Bay (RJ, Brazil): estimates of cell/filament numbers versus carbon content
Santos, Viviane Severiano;Villac, Maria Célia;Tenenbaum, Denise Rivera;Paranhos, Rodolfo;
Brazilian Journal of Oceanography , 2007, DOI: 10.1590/S1679-87592007000200006
Abstract: variations of nanoplankton (2-20 μm) and filamentous bacteria (diameter: 0.5-2.0 μm) of guanabara bay (rj, brazil) are presented, considering cell density and carbon content of auto- and heterotrophs. our goal is to contribute to future modeling of local trophic dynamics. subsurface water samples were taken weekly during the year 2000 at two sites: urca (close to the entrance, more saline, eutrophic) and ramos (inner area, less saline, hypertrophic). microscopic analysis was done by epifluorescence and cell density was converted to biomass through cell biovolume. total nanoplankton was about 108 cells.l-1 in most samples (>57%), and total filamentous bacteria densities varied from 105 to 108 fil.l-1. autotroph density was one order of magnitude higher at ramos, both for nanoplankton (md: 108cells.l-1 at ramos and 107cells.l-1 at urca) and for filamentous bacteria (md: 106 fil.l-1 at ramos and 105 fil.l-1 at urca). the same was observed for autotrophic biomass (md: 103μgc.l-1 at ramos and 101μgc.l-1 at urca for nanoplankton; md: 28μgc.l-1 at ramos and 1.4μgc.l-1 at urca for filamentous bacteria). the relative contribution of autotrophs increased after conversion to biomass. seasonal variation was conspicuous for filamentous bacteria at both sites and for nanoplankton only at ramos, with maximum autotrophic abundances during the rainy period (spring-summer).
Protozooplankton characterization of two contrasting sites in a tropical coastal ecosystem (Guanabara Bay, RJ)
Gomes, Eli Ana Traversim;Santos, Viviane Severiano dos;Tenenbaum, Denise Rivera;Villac, Maria Célia;
Brazilian Journal of Oceanography , 2007, DOI: 10.1590/S1679-87592007000100004
Abstract: much time and resources have been invested in understanding plankton dynamics in guanabara bay (brazil), but no attention has been devoted to the protozooplankton. to fulfill this lacuna, abundance and composition of protozooplankton were investigated from january to december - 2000 in fortnightly surface water samplings at two distinct water quality sites (urca - closer to the bay entrance, more saline and cleaner waters; ramos - inner reaches, hypereutrophic waters). the density at urca (103 - 105 cell.l-1) was one to three orders of magnitude lower than at ramos (104 - 105 cell.l-1). a seasonal trend for nanoplankton and protozooplankton was more evident at urca, but both sites had lower densities during the colder period. small heterotrophic dinoflagellates (20-30 mm) were dominant in over 50% of the samples. the protozooplankton abundance and composition reflected the distinct trophic conditions states found at the bay. during the wet-warm season, non-oligotrich ciliates were representative of ramos site with gymnodiniaceae dinoflagellates, while tintinnids and heterotrophic dinoflagellates were predominantly found at urca mainly during the dry-cold season. this first descriptive study towards the understanding of the intricate relationships among the microbial food web components reveals that protozooplankton can be a good indicator of water quality conditions at the bay.
Small time scale plankton structure variations at the entrance of a tropical eutrophic bay (Guanabara Bay, Brazil)
Mariana Guenther,Isabel Lima,Glenda Mugrabe,Denise Rivera Tenenbaum
Brazilian Journal of Oceanography , 2012,
Abstract: The dynamics of the plankton compartments at the entrance of Guanabara Bay (SE Brazil) were assessed during a short-term temporal survey to estimate their trophic correlations. Size-fractioned phytoplankton (picoplankton: < 2μm, nanoplankton: 2-20μm and microplankton: > 20μm) biomass and photosynthetic efficiency, composition and abundance of the auto-and heterotrophic nano-and microplankton, and mesozooplankton were evaluated at a fixed station for 3 consecutive days at 3-h intervals, in the surface and bottom (20m) layers. The variability of almost all plankton compartments in the surface layer was directly dependent on temperature, indicating the great influence of the circulation at the entrance of the bay on plankton structure. In the surface layer, the mesozooplankton seems to be sustained by both autotrophic nano-and picoplankton, this last being channeled through the microzooplankton. Near the bottom, both auto-and heterotrophic microplankton are probably supporting the mesozooplankton biomass. Our findings thus suggest that the entrance of Guanabara bay presents a multivorous food web, i.e., a combination of both grazing and microbial trophic pathways. A dinamica dos vários compartimentos do plancton foi avaliada durante uma série de curta dura o na entrada da baía de Guanabara (SE do Brasil), com o objetivo de estimar suas correla es tróficas. A biomassa e eficiência fotossíntética das três fra es do fitoplancton (picoplancton: < 2μm, nanoplancton: 2-20μm e microplancton: > 20μm), juntamente com a composi o e abundancia do nano-e microplancton auto-e heterótrofos e do mesozooplancton, foram determinadas em uma esta o fixa durante 3 dias consecutivos, a intervalos de 3h, nas camadas de superfície e de fundo (20m). A variabilidade de quase todos os compartimentos do plancton na superfície foi diretamente relacionada à temperatura, indicando forte influência da circula o da entrada da baía na estrutura planct nica. Na camada superficial, o mesozooplancton parece ser alimentado pelo nano-e picoplancton autótrofos, esse último sendo sustentado pelo microzooplancton. Próximo ao fundo, o microplancton auto-e heterótrofo est o possivelmente sustentando a biomassa mesozooplanct nica. Nossos resultados sugerem, portanto, que na entrada da baía de Guanabara esteja estabelecida uma rede trófica multívora, i.e., uma combina o entre as cadeias microbiana e de pastagem.
Evaluación de oncógenes y moléculas de proliferación celular en carcinoma escamoso de cavidad oral
Ponce,José Gregorio; Correnti,María; Rivera,Helen; ávila,Mayra; Lares,Henry; Mattar,Denise; Maissi,Sara;
Revista Venezolana de Oncología , 2008,
Abstract: the oral cavity cancer account for 30 % of all of head and neck cancers, among which 95 % are squamous cell type carcinoma. there are described many risk factors involved, and in the last few years there is been a wide a series development of cell proliferation molecules and oncogenes, in which can be over expressed in the patients with squamous cell cancer of the oral cavity. the objective of this investigation is to evaluate the proliferation cells marker ki-67 and pcna and the p53, p21 oncogenes and the c-erb2 in patients with squamous cell carcinoma, localized in oral cavity and his correlation with clinical and pathological factors in the evaluated group. methods: to the biopsies of 52 patients with squamous cell carcinoma of oral cavity seen in the oncology hospital ?padre machado? between 1995 and 1999 there were evaluated with inmunohistochemestry techniques to determine ki- 67 and pcna cell-proliferation markers and p53, p21, c-erbb2 oncogenes. results: the proportion of positive results found were: in the inmunohistochemestry: 90.4 % pcna, 63.5 % p21, 53.8 % ki-67, 48.1 % p53 and 3.8 % in c-erbb2. in our study, the vascular permeability and the differentiation degree were significant in this study with the correlation of the presence of the p53, p21, c-erbb2, pcna and ki-67. conclusions: the pcna and p21 were the most common found biomarkers. the vascular permeability and the histological grade show a significant statistic relation with all study biomarkers.
Criptosporidiosis intestinal en ni os con HIV/SIDA Intestinal cryptosporidiosis in HIV infected children
Graciela Barboni,Marcela Candi,María Inés Villacé,Araceli Leonardelli
Medicina (Buenos Aires) , 2008,
Abstract: El Cryptosporidium parvum, protozoo parásito intracelular, infecta el epitelio gastrointestinal produciendo diarrea autolimitada en individuos inmunocompetentes pero potencialmente grave en pacientes inmunocomprometidos, especialmente en aquellos con Sida. En este trabajo se evaluó, durante un lap-so de 6 a os, la incidencia de infección intestinal por C. parvum en una población pediátrica con HIV/Sida analizando las características clínicas e inmunológicas de la coinfección. Todos los pacientes iniciaron o continuaron el tratamiento antirretroviral de alta eficacia HAART durante el período de estudio, mientras que la infección intestinal fue tratada con azitromicina. La incidencia de criptosporidiosis fue de 13.7%. 33 de los 240 ni os en seguimiento presentaron diarrea crónica de más de 14 días de evolución o recurrente, sin complicaciones hidroelectrolíticas. Los pacientes evaluados presentaron niveles porcentuales variables de células T CD4+ en sangre periférica, y la presencia del parásito no estuvo en relación con el compromiso inmunitario. Al momento del cuadro entérico 31 de los 33 pacientes tuvieron niveles plasmáticos de carga viral que superaban el límite de detección. Se observó eosinofilia leve o moderada en el 23% de los pacientes y la coinfección con otros parásitos fue detectada en 11 ni os. No se obtuvieron diferencias significativas al relacionar el número de episodios intestinales con los estadios clínico-inmunológicos de los pacientes. La correcta implementación del HAART con la subsecuente restauración de la función inmune se relacionaría con la ausencia de cuadros diarreicos agudos y de las complicaciones hidroelectrolíticas derivadas de la coinfección con C. parvum. Cryptosporydium parvum is an intracellular parasite that infects gastrointestinal epithelium and produces diarrhea that is self-limited in immunocompetent persons but potentially life-threatening in immunocompromised, especially those with the acquired immunodeficiency syndrome (AIDS). C. parvum enteric infection's incidence in a pediatric HIV/AIDS cohort, during a 6 years period, was studied. Clinical and immunologic characteristics of the dual infection were also recorded. Highly active antiretroviral therapy (HAART) was started or continued by all the patients during follow-up. Azithromicyn was used as antiparasitic drug. Cryptosporidiosis incidence was 13.7%; 33 out 240 children showed chronic diarrhea lasting 14 days at least, or recurrent, without dehydration and electrolytic disturbance. Peripheral blood T CD4+ percentage levels of the patients were variable and
Influence of Rainfall Pattern in the Seasonal Variation of Fish Abundance in a Tropical Estuary with Restricted Marine Communication  [PDF]
Manuel Castillo-Rivera
Journal of Water Resource and Protection (JWARP) , 2013, DOI: 10.4236/jwarp.2013.53A032
Pueblo Viejo Lagoon is an estuary with restricted communication with the sea, so the freshwater influence tends to be more important. Therefore, the study focused on testing the hypothesis that the seasonal changes in species abundance would be mainly related to the local rainfall pattern. Monthly samplings were carried out over a one-year, using a seine net. A total of 9108 individuals were caught, corresponding to 66 species of fish, most of them with marine origin. Canonical correspondence analysis revealed that the rainfall-salinity gradient was revealed to be the most important driving force in the seasonal variation of fish composition. In this way, it was observed that seasonal fluctuations in total fish number were linked to preceding fluctuations (one month) in local rainfall. Similar pattern was exhibited by the abundance of Anchoa mitchilli (the most abundant species), Oreochromis mossambicus and Ariopsis felis, and this delayed effect was significant (cross-correlation analyses). In addition, the rainfall showed a direct influence (significant positive correlations) on abundance of D. auratus and M. martinica. The association between fish number and the rainfall regime seems to be related to lagoon productivity and the trophic responses of these species. By contrast, Brevoortia gunteri and Menidia beryllina showed an inverse correlation with rainfall. Other environmental variables (also influenced by rainfall regime) showed a significant relationship with A. hepsetus (salinity), B. chrysoura (depth) and M. curema (turbidity). Thus, at least 12 species showed some relationship with local rainfall, which accounted for 81.27% of the total number of fish collected. Although it is difficult to separate the relative importance of
A Case of Ectopic Growth Hormone Releasing Hormone (GHRH) from Pancreatic Neuroendocrine Tumor Resistant to Therapy  [PDF]
Ohoud Almohareb, Juan Rivera
Open Journal of Endocrine and Metabolic Diseases (OJEMD) , 2013, DOI: 10.4236/ojemd.2013.37037

Introduction: Ectopic secretion of GHRH is a rare cause of acromegaly. However, its recognition is clinically important because different therapeutic approaches are required. Case Presentation: We present a challenging case of acromegaly secondary to ectopic GHRH secretion from pancreatic neuroendocrine tumor in a 52-year-old female. The patient is treated with different modalities which include pegvisomant in an attempt to control the stimulated GH-axis considering the limited data about its use in treatment of ectopic acromegaly. Conclusion: GHRH-secreting tumor is a rare cause of acromegaly. Surgical resection of the tumor is the therapy of choice whenever possible. However, further studies are warranted for unresectable tumor or resistant cases.

Facing the 2013 Gold Rush: A Population Viability Analysis for the Endangered White-Lipped Peccary (Tayassu pecari) in Corcovado National Park, Costa Rica  [PDF]
Christian J. Rivera
Natural Resources (NR) , 2014, DOI: 10.4236/nr.2014.516085
Abstract: The white-lipped peccary (Tayassu pecari) is facing range-wide declines throughout the Neotropics. It has been eliminated from about 89% of its historical range in Costa Rica. Corcovado National Park, in the Osa Peninsula of Costa Rica, is the last remaining stronghold for the white-lipped peccary in the country. In 2013, the Park experienced a sudden gold rush that brought with it a wave of 250 miners and vigorous hunting pressures on the population. Given that the species is endangered and is susceptible to hunting due to its herding behavior and tendency to cohere and attack when threatened rather than flee, it is important to assess its probability of extinction under various hunting scenarios. Incorporating data from studies on the life history of the species throughout its range in the Neotropics and in Corcovado, I used the population viability analysis software VORTEX to simulate the population trajectories and probabilities of extinction of the species under current hunting pressures and under various management scenarios. The results of this study revealed that under the 2013 scenario where 250 miners were present in the Park, the population of white-lipped peccaries has a about a 40% chance of extinction within five years and about a 99% chance of extinction within 10 years. Moreover, there is an “extinction threshold” for the population between the presence of 100 and 150 miners hunting in the Park. At this threshold, the population growth rate, r, drops from a positive growth rate (r = 0.09, SD = 0.08) to a negative one (r = -0.07, SD = 0.29). I suggest that anti-mining and anti-poaching laws be enforced immediately, and that the number of miners be reduced to 100 at a minimum, if not completely, in order to ensure that the population of white-lipped peccaries becomes viable and evades a local extinction.
Applied Linguistic-Tú and Usted Spanish Personal Subject Pronouns  [PDF]
Joel Laffita Rivera
Open Journal of Modern Linguistics (OJML) , 2019, DOI: 10.4236/ojml.2019.91002
Abstract: While the simple phonetics of Spanish language makes it easier to learn and speak irrespective of its grammar complexity, acquiring a good command of this language requires a serious and disciplined study of its grammar. The use of null and overt pronouns and their different grammar related forms in Spanish elevates the level of complexity when it comes to second language acquisition (SLA). In this regard, the teaching and learning of Spanish grammar still remains a subject of interest among linguists. Thereby, the article aimed to provide a guideline through which English language native speakers would gain an insight about language traits, associated with two pronouns and how they should be used in the speaking and writing context of Spanish language communication.
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