T lymphocytes play a critical role in adaptive immunity by eliciting and regulating specific immune responses against viral and bacterial pathogens. The development of T cells occurs within the highly specialized thymus and follows a defined set of stage-specific differentiation steps. However, the molecular and cellular events occurring at early stages of human T-cell development remain to be fully elucidated. This was in part due to the inability to obtain substantial numbers of T-lineage cells from hybrid/human fetal thymic organ culture (FTOC) and the inability to recapitulate human T-lymphopoiesis using other systems. To address the molecular and cellular events occurring during early human T-lymphopoiesis, human umbilical cord-blood (UCB) hematopoietic stem cells (HSCs) were induced to differentiate to the T-lineage utilizing OP9-DL1 stromal cells. A developmental program involving a sequential and temporally discrete expression of key differentiation markers was revealed. In addition, this Thesis demonstrates that in vitro-generated CD34+CD7++ progenitors effectively engrafted the thymus of immunodeficient mice. In addition, two distinct progenitor subsets, CD34+CD45RA+CD7++CD5-CD1a- (proT1) and CD34+CD45RA+CD7++CD5+CD1a- (proT2), were identified with proT2 cells showing a 3-fold enhanced engrafting capacity than the proT1 subset. As proT2 cells exhibit superior engrafting capacity, these cells were tested for their ability to enhance T cell generation following hematopoietic stem cell transplant (HSCT). We observe that when HSCs are coinjected with proT2 cells, a dramatic improvement in HSC-derived T-lymphopoiesis is observed. This Thesis demonstrates that in vitro-derived proT2 cells reorganize the thymus stromal compartment of the host NOD/SCID/γcnull mouse compared to the highly disorganized cortical and medullary compartments in mice not receiving proT cells. This alteration in thymic architecture likely favours the recruitment of BM derived progenitors. Lastly, we address whether functional CD8 T cells can be generated in vitro using hematopoietic stem cells (HSCs) in coculture with OP9-DL1 cells and indeed these cells were capable of proliferating, and secreting effector molecules typical of cytotoxic T cells. Taken together, the ability to generate proT cells and mature T cells from Notch-ligand cultures offers a new tool to study human T cell development.

The processes localized to biological membranes are of great interest, both from a scientific and pharmaceutical point of view. Understanding aspects such as the detailed mechanism and regulation of these processes requires investigation of the structure and function of the membrane-bound proteins in which they take place. The study of these processes is often complicated by the need to create in vitro systems that mimic the environment in which these proteins are normally found in vivo. This thesis describes some of the methods available for membrane-protein studies in membrane-mimetic systems, as well as our work aimed at developing such systems. Furthermore, results from studies using these systems are described. In the first two studies, described in Papers I &amp; II, we investigated the use of silica particle-supported lipid bilayers, both for membrane-protein studies and as possible drug-delivery vehicles. Successful reconstitution of a multisubunit proton-pump, cytochrome c oxidase is described and characterized. Initial attempts to develop drug-delivery systems with two different targeting peptides are also described in the thesis. The second part of this thesis revolves around our work with membraneprotein dependent pathways. Results from studies of systems where the proton- pump bo3 oxidase and ATP synthase work in concert are described. The results show a surprising lipid-composition dependence for the coupled bo3- ATP-synthase activity (Paper III). Finally, a new system utilizing synaptic vesicle-fusion proteins for coreconstitution of membrane proteins is described, showing successful coreconstitution of a small respiratory chain, delivery of soluble proteins to preformed liposomes and reconstitution of ATP synthase in native membranes (Paper IV). / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Manuscript. Paper 4: Manuscript.</p>

Trijų sudėčių sluoksniuoti dvigubi hidroksidai (SDH) Mg/Al, Co/Mg/Al ir Ni/Mg/Al susintetinti bendro nusodinimo esant mažoms koncentracijoms metodu. Šie SDH buvo termiškai suskaidyti, ir gautieji mišrūs metalų oksidai reformuoti vandenyje ir pirmą kartą magnio nitrato tirpale. Naudojant XRF ir TG duomenis pasiūlytos susintetintų bendro nusodinimo metodu SDH formulės. XRD analizės rezultatai parodė, kad SDH ir mišrių metalų oksidų faziniai kitimai reformavimo metu priklauso nuo proceso temperatūros ir terpės prigimties. Co ir Ni turinčių SDH mėginių sluoksninės struktūros atstatymas kambario temperatūros vandenyje vyksta nepilnai, tačiau pakėlus temperatūrą iki 80 °C pašalinės oksidų fazės reformuotuose pavyzdžiuose nebelieka. Kai SDH atstatymui buvo naudojamas magnio nitrato tirpalas, katijonų sudėtis pakito dėl padidėjusio sluoksninėje struktūroje magnio kiekio. Ryškus temperatūros ir vandeninės terpės poveikis stebimas ne tik reformavimui, bet ir gautų SDH kristalitų dydžiams. Iškaitinus SDH gautų oksidų morfologija priklauso nuo jų sudėtyje esančio pereinamojo metalo ir reformavimui naudoto tirpalo prigimties. Praktiniai panaudojimai reformuotų SDH tirti NOx pašalinimo reakcijose ir gazifikacijos metu gaunamų dujų valyme. / Three layered double hydroxides Mg/Al, Co/Mg/Al and Ni/Mg/Al were successfully synthesized by the low supersaturation method, thermally decomposed and derived mixed metal oxides reformed to layered structures in water and for first time to our knowledge in magnesium nitrate media. XRD measurements provided direct evidence for phase transformation processes during calcination and reformation of layered structure at different temperatures. From XRF and TG analyses data the formulas of synthesized LDH were proposed. Incomplete regeneration of Co and Ni containing LDH samples at room temperature in aqueous media has been observed. However, with increasing temperature up to 80 °C the reconstitution process of LDH proceeds fully. Changes of cations composition after reformation could be explained by the increase of magnesium content when the reconstitution in magnesium nitrate solution followed. The hydration causes the formation of LDH with higher crystallite size in comparison with the LDH samples reformed in magnesium nitrate media. In most of the cases, with increasing the temperature of reconstitution media to 80ºC the crystallite size also increased. Reformation media had a considerable influence to the morphology of mixed metal oxides. Moreover, the effects for nickel or cobalt containing samples were found to be different. Catalysts prepared from LDH containing cobalt were tested in the removal of NOx and nickel containing LDH were tested in gasification gas cleaning.

<p>Hematopoietic stem cell (HSC) self-renewal, proliferation and differentiation are regulated by signaling through protein tyrosine kinases (PTK) such as c-kit, Flt-3 and Tie2. PTKs work in concert with receptor protein tyrosine phosphatases (PTPs) to maintain cellular equilibrium. The functions of PTPs in counterbalancing PTK signaling in HSCs however remain incompletely understood. Our laboratory has demonstrated that a heparin binding growth factor, Pleiotrophin (PTN), promotes the expansion of murine long-term (LT)-HSCs via binding to a PTP, protein tyrosine phosphatase receptor type Z (PTPRZ). The addition of PTN to murine PTPRZ-/- c-Kit+Sca-1+Lineage- (KSL) cells caused no expansion of HSCs in culture, suggesting that PTPRZ mediates PTN effects on HSC growth. We subsequently screened for the expression of other receptor PTPs in murine HSCs. Among 21 different receptor PTPs, we found that protein tyrosine phosphatase receptor type S (PTPRS) was significantly overexpressed in mouse and human HSCs compared to more mature hematopoietic cells. Ptprs-/- mice displayed no difference in mature blood counts or phenotypic HSC frequency compared to Ptprs+/+ mice. However, competitive transplantation of bone marrow (BM) cells from Ptprs-/- mice resulted in more than 8-fold increased multilineage hematopoietic repopulation in primary and secondary recipient mice compared to mice transplanted with BM cells from Ptprs+/+ mice. While Ptprs-/- mice displayed no differences in cell cycle status, HSC survival or homing capability compared to Ptprs+/+ mice, PTPRS-/- BM cells expressed significantly increased levels of activated Rac1, a RhoGTPase which regulates HSC engraftment capacity, compared to PTPRS+/+ BM cells. PTPRS-/- BM cells displayed significantly increased transendothelial migration capacity and cobblestone area forming cells (CAFC), consistent with increased Rac1 activation. Furthermore, inhibition of Rac1 abrogated the increased transendothelial migration capacity of PTPRS-/- BM cells, suggesting that the augmented engraftment capacity of PTPRS-/- BM cells was mediated via Rac1. Translationally, we demonstrated that negative selection of human cord blood Lin-CD34+CD38-CD45RA- cells for PTPRS expression yielded a 15-fold enrichment for human long term HSCs compared to Lin-CD34+CD38-CD45RA- cells or Lin-CD34+CD38-CD45RA- PTPRS+ cells. These data suggest that PTPRS regulates HSC repopulating capacity via inhibition of Rac1 and selection of human PTPRS - negative HSCs is a translatable strategy to significantly enrich human cord blood HSCs for transplantation.</p> / Dissertation

A Savana Estépica Parque, formação vegetacional campestre do Bioma Pampa, tem sua área de ocorrência no Brasil restrita ao extremo oeste do Rio Grande do Sul, no município de Barra do Quaraí. Com o objetivo estudar a história vegetacional desta formação e suas mudanças ao longo do Holoceno tardio, foi desenvolvida a pesquisa em um afloramento localizado na margem brasileira do rio Quaraí (30°16’27.9”S e 57°26’33.6”O), com a coleta de 86 amostras. Para determinação do espectro polínico atual, foram coletadas 15 amostras superficiais em diferentes ambientes do Parque do Espinilho (PESP). Um total de 81 táxons foi identificado nas amostras sedimentares do afloramento (10 férteis) e 114 nas amostras superficiais. Análises a partir dos diagramas polínicos foram realizadas apoiadas por datações radiocarbônicas e análises granulométricas. Os resultados indicam que entre 3.380 ± 25 e 2.350 ± 25 anos AP a área era composta por uma planície de inundação recoberta por gramíneas que formava corpos d’água de pequena profundidade, possibilitando o desenvolvimento de colônias de algas. Entre 2.328 e 2.262 anos AP observa-se diminuição da umidade e aumento de temperatura, evidenciado pelo desaparecimento das algas e maior frequência de briófitos. Entre 2.130 e 1.940 ± 20 anos AP é registrado aumento de umidade refletido na maior diversidade de táxons arbóreos, com expansão da Mata Ciliar. Os dados de granulometria corroboram com os dados palinológicos. O espectro polínico das amostras superficiais refletiu a composição taxonômica da flora do PESP, de acordo com a particularidade ecológica de cada ponto de amostragem. Este constitui o primeiro trabalho de palinologia desenvolvido na Savana Estépica Parque nos três países em que ocorre (Argentina Uruguai e Brasil). Os resultados aqui apresentados contribuirão para melhor compreensão da origem e desenvolvimento desta formação vegetacional, importante pelo endemismo de suas espécies e que está sob forte pressão antrópica por ocorrer em planícies de inundação, área de interesse para atividades agrícolas. / The “Savana Estépica Parque”, constitutes a vegetational formation of the Pampa Biome, recorded in Brazil only on the extreme west of Rio Grande do Sul state, in the municipality of Barra do Quaraí. This study aims to know the history of this vegetational formation and its changes during the late Holocene. Material is derived from an outcrop located on the Brazilian side of the Quaraí river (30 ° 16'27 .9 "S and 57 ° 26'33 .6" W). To determine the current pollen spectrum, 15 surface samples were collected in different environments of the Espinilho Park (PESP). A total of 81 taxa were identified from the samples of the sedimentary outcrop (10 fertiles) and 114 from surface samples. Analyzes from the pollen diagrams were performed supported by radiocarbon dating and granulometry analysis. The results indicate that between 3,380 ± 25 and 2,350 ± 25 yr BP the area was composed of a flood plain covered with grasses that formed bodies of water of little depth, enabling the development of colonies of algae. Between 2,328 and 2,262 years BP observed decrease in humidity and temperature increase, evidenced by the disappearance of algae and higher frequency of bryophytes. Between 2,130 and 1,940 ± 20 yr BP is recorded an increasing of humidity reflected by the greater diversity of arboreal taxa, with an expansion of “Mata Ciliar”. The granulometry data corroborates palynological analysis. The pollen spectra of surface samples reflected the taxonomic composition of the PESP flora, according to ecological particularities of each local point of sampling. This is the first work in palynology developed from “Savana Estépica Parque” amongst the three countries that it occurs (Argentina Uruguay and Brazil). The results presented here will contribute to the better understanding of the origin and development of this vegetation of formation, which is very important taking into account the record of endemic species, as well as the intense anthropogenic pressure that affect flood plains, that constitute areas for agricultural activities.

Le département de la Meuse est essentiellement rural et agricole. Les communautés rurales de 1880 à 1914 ne sont pas figées. Elles se transforment par la synthèse d'éléments issus de la tradition et de facteurs liés au contexte général. Elles ne sont ni réfractaires au progrès ni passéistes. Le département devient une terre de guerre. Les paysages et les patrimoines sont bouleversés et métamorphosés. Les rapports sociaux sont modifiés. À l'armistice, la situation rend le système d'avant-guerre obsolète. La loi de réparation des dommages de guerre offre un espoir de relèvement. Les bilans des destructions sont conséquents. La reconstruction est une période charnière. L'argent apparaît être le nerf de la reconstruction. Elle devient un moyen de moderniser et de rationaliser les communes rurales. Le territoire se mémorialise et de nouveaux éléments d'identification et de reconnaissance modifient la tradition / The department of the Meuse is mainly rural and agricultural. The rural communities from 1880 to 1914 are not fixed. They are transformed by the synthesis of elements from tradition and factors related to the general context. They are neither refractory to progress nor past. The department became a land of war. Landscapes and heritages are overturned and transformed. Social relations are modified. At the armistice, the situation made the pre-war system obsolete. The war damage compensation law offers hope of recovery. The results of the destruction are substantial. Reconstruction is a pivotal period. Money appears to be the nerve of reconstruction. It becomes a means of modernizing and rationalizing rural communes. The territory is memorized and new elements of identification and recognition change the tradition

Made available in DSpace on 2014-06-11T19:32:21Z (GMT). No. of bitstreams: 0 Previous issue date: 2003-12-18Bitstream added on 2014-06-13T20:03:46Z : No. of bitstreams: 1 grego_mibm_dr_rcla.pdf: 5936303 bytes, checksum: c48d07b5a345f3c0f0bbbd508557d304 (MD5) / Acumulaçoes de gás no centro de bacias sedimentares (Basin-centered gas accumulations, BCGA) diferem significantemente das acumulações convencionais em características geológicas e de produção. Enquanto um sistema petrolífero convencional contém elementos e processos necessários para acumulação de óleo e gás existir, no BCGS o foco está na interação dos componentes que formam apenas gás em condições peculiares. O propósito desta tese é demonstrar que o campo de gás de Elsinore, Texas (EUA), constitui acumulação dc gás não convencional (BCGA) utilizando métodos geoestatísticos para identificar as características diagnósticas. Os reservatórios ocorrem em três unidades de diferentes idades (ordo-silu-devoniana); são compostos de gás (60%: metano 53%, CO2 45%) e água (40%); são fraturas em chert e porosidade secundária em dolomitos; são profundos (média 4.051 m); mostram pressão inicial alta (média 0.38 psi/fl); estão em trapas estruturais (antiformas, fraturas) e estratigráficos. Migração do gás ocorreu através das falhas NW cm mais de um estágio de acordo com mecanismos de pressão. Selos de topo são litológicos, folhelhos e carbonatos; selos laterais e de base são blocos-selantes com água capilar. A reconstituição da história de soterramento e termal foi importante para determinar as relações temporais entre a geração, expulsão, migração e armadilhas do gás formado. / Gas accumulations in center of sedimentary basin (Basin-centered gas accumulations, BCGA) di/fer signficantly from conventional accumulations in geological and production characteristics. While a conventional petroleum system has elements and process needed for an ou and gas accumulation to exist, in the BCGS the focus is in interaction of these components lo form only gas in peculiar conditions. The purpose of lhis thesis is to demonstrate that the Elsinore gas field, Texas (US), constitutes unconventional gas accumulation (BCGA) using geostatistics to identfy diagnosed characteristics. The reservoirs occur in four units ofvarious ages (Ordovician-Devonian): are composed by gas (60% total gases - methane 53%, CO2 45%) and water (40%); are in cheri fractures, and secondary porosity in dolomites; are deep (avg 4.051 m); high initialpressure (avg 0.38 psi/ft); gas are in structural traps (antforms, fractures) and stratigraphic ones. Gas migralion happened through the NWfaults in more than one stage according to pressure echanisms. Top seals are litologic, shales and limestones; lateral and base seals are capillary water block-seals. The reconstitution of thermal and burial history was important lo determine the temporal relationships among generation, expulsion, migration, and traps offormed gas.

Submitted by Ana Carla Almeida (ana.almeida@ucsal.br) on 2016-10-06T18:13:34Z No. of bitstreams: 1 Nathalie-UCSAL(22-08).pdf: 1133368 bytes, checksum: 1ca70db5dec04fe371d3d5d7449241f5 (MD5) / Approved for entry into archive by Maria Emília Carvalho Ribeiro (maria.ribeiro@ucsal.br) on 2016-11-25T21:57:09Z (GMT) No. of bitstreams: 1 Nathalie-UCSAL(22-08).pdf: 1133368 bytes, checksum: 1ca70db5dec04fe371d3d5d7449241f5 (MD5) / Made available in DSpace on 2016-11-25T21:57:09Z (GMT). No. of bitstreams: 1 Nathalie-UCSAL(22-08).pdf: 1133368 bytes, checksum: 1ca70db5dec04fe371d3d5d7449241f5 (MD5) Previous issue date: 2013-05-24 / O presente estudo de casos múltiplos tem como objetivo estudar como filhos de casais que se separaram experienciaram esta separação Optou-se pela pesquisa de tipo qualitativo por meio de questionário semi-estruturado, com perguntas fechadas e abertas, devido à possibilidade de uma coleta de dados mais abrangente. A pesquisa focalizou características da rede social familiar e dos relacionamentos pessoais. A coleta de dados foi realizada entre os anos de 2012 a 2013, na cidade de Alagoinhas, localizada no estado da Bahia. Teve a participação de sete mulheres, filhas de pais separados, com idades entre 25 e 33 anos, de classe média. Os resultados estão, em parte, apresentados sob a forma de registro das falas dos indivíduos pesquisados, para que se possa ter a dimensão emocional do contexto que vivenciaram – o ambiente familiar. A pesquisa traz como resultados que filhos podem compreender a separação dos pais de forma positiva, assim como a redefinição do seu lugar na família. É o caso daqueles que experimentaram uma nova composição familiar, tornando-se enteados e/meios-irmãos, a partir do surgimento de um novo relacionamento parental. O estudo indicou que o rompimento conjugal é vivenciado de forma diferenciada para os pais e para os filhos, logo não deve ser analisado de forma unificada. / The present study aims to study, from specific cases, such as the children of couples who separated experienced the separation of their parents. This is a study that is not intended exhaustive, however aims to launch another look at the issue of separation, in this case experienced by children. The research presents a point of view to qualitative methodology with regard to the characteristics of the social network of family and personal relationships that respondents experienced. We opted for semi structured research because of the possibility and flexibility to adapt to the context of the respondent, or their reactions permit a more comprehensive data collection. Data collection was conducted between the years2012 to 2013, the city of Alagoinhas, located in the state of Bahia, was attended by7 women daughters of divorced parents, aged 25and 33 years, responding to a questionnaire of questions closed and open. The results a represented in part in the form of record of the speech of individuals surveyed, so you can have the emotional dimension of context that experienced-the family environment. The research results that bring as many children realize a positive separation. Likewise, the redefinition of its place in the family can be a positive experience: the case of those who have experience da new family composition, becoming step children and /stepbrothers, from the emergence of a new relationship which currently live his father or mother. The study shows that children of divorced parents do not always play with negativity, and can understand positively the separation and the emergence of a new family constitution.

Orientador: Paulo César Soares / Banca: Edson José Milani / Banca: Paulo Milton Barbosa Landim / Banca: Mário Luis Assine / Banca: Cláudio Riccomini / Resumo: Acumulaçoes de gás no centro de bacias sedimentares (Basin-centered gas accumulations, BCGA) diferem significantemente das acumulações convencionais em características geológicas e de produção. Enquanto um sistema petrolífero convencional contém elementos e processos necessários para acumulação de óleo e gás existir, no BCGS o foco está na interação dos componentes que formam apenas gás em condições peculiares. O propósito desta tese é demonstrar que o campo de gás de Elsinore, Texas (EUA), constitui acumulação dc gás não convencional (BCGA) utilizando métodos geoestatísticos para identificar as características diagnósticas. Os reservatórios ocorrem em três unidades de diferentes idades (ordo-silu-devoniana); são compostos de gás (60%: metano 53%, CO2 45%) e água (40%); são fraturas em chert e porosidade secundária em dolomitos; são profundos (média 4.051 m); mostram pressão inicial alta (média 0.38 psi/fl); estão em trapas estruturais (antiformas, fraturas) e estratigráficos. Migração do gás ocorreu através das falhas NW cm mais de um estágio de acordo com mecanismos de pressão. Selos de topo são litológicos, folhelhos e carbonatos; selos laterais e de base são blocos-selantes com água capilar. A reconstituição da história de soterramento e termal foi importante para determinar as relações temporais entre a geração, expulsão, migração e armadilhas do gás formado. / Abstract: Gas accumulations in center of sedimentary basin (Basin-centered gas accumulations, BCGA) di/fer signficantly from conventional accumulations in geological and production characteristics. While a conventional petroleum system has elements and process needed for an ou and gas accumulation to exist, in the BCGS the focus is in interaction of these components lo form only gas in peculiar conditions. The purpose of lhis thesis is to demonstrate that the Elsinore gas field, Texas (US), constitutes unconventional gas accumulation (BCGA) using geostatistics to identfy diagnosed characteristics. The reservoirs occur in four units ofvarious ages (Ordovician-Devonian): are composed by gas (60% total gases - methane 53%, CO2 45%) and water (40%); are in cheri fractures, and secondary porosity in dolomites; are deep (avg 4.051 m); high initialpressure (avg 0.38 psi/ft); gas are in structural traps (antforms, fractures) and stratigraphic ones. Gas migralion happened through the NWfaults in more than one stage according to pressure echanisms. Top seals are litologic, shales and limestones; lateral and base seals are capillary water block-seals. The reconstitution of thermal and burial history was important lo determine the temporal relationships among generation, expulsion, migration, and traps offormed gas. / Doutor

A Savana Estépica Parque, formação vegetacional campestre do Bioma Pampa, tem sua área de ocorrência no Brasil restrita ao extremo oeste do Rio Grande do Sul, no município de Barra do Quaraí. Com o objetivo estudar a história vegetacional desta formação e suas mudanças ao longo do Holoceno tardio, foi desenvolvida a pesquisa em um afloramento localizado na margem brasileira do rio Quaraí (30°16’27.9”S e 57°26’33.6”O), com a coleta de 86 amostras. Para determinação do espectro polínico atual, foram coletadas 15 amostras superficiais em diferentes ambientes do Parque do Espinilho (PESP). Um total de 81 táxons foi identificado nas amostras sedimentares do afloramento (10 férteis) e 114 nas amostras superficiais. Análises a partir dos diagramas polínicos foram realizadas apoiadas por datações radiocarbônicas e análises granulométricas. Os resultados indicam que entre 3.380 ± 25 e 2.350 ± 25 anos AP a área era composta por uma planície de inundação recoberta por gramíneas que formava corpos d’água de pequena profundidade, possibilitando o desenvolvimento de colônias de algas. Entre 2.328 e 2.262 anos AP observa-se diminuição da umidade e aumento de temperatura, evidenciado pelo desaparecimento das algas e maior frequência de briófitos. Entre 2.130 e 1.940 ± 20 anos AP é registrado aumento de umidade refletido na maior diversidade de táxons arbóreos, com expansão da Mata Ciliar. Os dados de granulometria corroboram com os dados palinológicos. O espectro polínico das amostras superficiais refletiu a composição taxonômica da flora do PESP, de acordo com a particularidade ecológica de cada ponto de amostragem. Este constitui o primeiro trabalho de palinologia desenvolvido na Savana Estépica Parque nos três países em que ocorre (Argentina Uruguai e Brasil). Os resultados aqui apresentados contribuirão para melhor compreensão da origem e desenvolvimento desta formação vegetacional, importante pelo endemismo de suas espécies e que está sob forte pressão antrópica por ocorrer em planícies de inundação, área de interesse para atividades agrícolas. / The “Savana Estépica Parque”, constitutes a vegetational formation of the Pampa Biome, recorded in Brazil only on the extreme west of Rio Grande do Sul state, in the municipality of Barra do Quaraí. This study aims to know the history of this vegetational formation and its changes during the late Holocene. Material is derived from an outcrop located on the Brazilian side of the Quaraí river (30 ° 16'27 .9 "S and 57 ° 26'33 .6" W). To determine the current pollen spectrum, 15 surface samples were collected in different environments of the Espinilho Park (PESP). A total of 81 taxa were identified from the samples of the sedimentary outcrop (10 fertiles) and 114 from surface samples. Analyzes from the pollen diagrams were performed supported by radiocarbon dating and granulometry analysis. The results indicate that between 3,380 ± 25 and 2,350 ± 25 yr BP the area was composed of a flood plain covered with grasses that formed bodies of water of little depth, enabling the development of colonies of algae. Between 2,328 and 2,262 years BP observed decrease in humidity and temperature increase, evidenced by the disappearance of algae and higher frequency of bryophytes. Between 2,130 and 1,940 ± 20 yr BP is recorded an increasing of humidity reflected by the greater diversity of arboreal taxa, with an expansion of “Mata Ciliar”. The granulometry data corroborates palynological analysis. The pollen spectra of surface samples reflected the taxonomic composition of the PESP flora, according to ecological particularities of each local point of sampling. This is the first work in palynology developed from “Savana Estépica Parque” amongst the three countries that it occurs (Argentina Uruguay and Brazil). The results presented here will contribute to the better understanding of the origin and development of this vegetation of formation, which is very important taking into account the record of endemic species, as well as the intense anthropogenic pressure that affect flood plains, that constitute areas for agricultural activities.