Dans la majorité des cas, les mitochondries sont nécessaires à la tumorigenèse et à la réponse des cellules cancéreuses aux signaux générés par les facteurs micro-environnementaux (exemples : privation de nutriments, hypoxie) ou par les traitements anticancéreux (exemples : chimiothérapie, radiothérapie). Presque toutes les protéines mitochondriales sont codées par le génome nucléaire et importées dans l'organelle. Des machineries d'import ont donc évolué afin de répondre aux besoins d'import protéique. Dans ce contexte, la machinerie régulée par CHCHD4/Mia40 fonctionne dans l’espace intermembranaire et contrôle l’import d’un groupe de protéines (substrats) qui joue des rôles importants dans la survie et la réponse au stress. Les substrats de CHCHD4/Mia40 sont impliqués dans un vaste panel d’activités mitochondriales qui inclut la biogenèse des complexes de la chaîne respiratoire, l’homéostasie lipidique, le stockage du calcium, ainsi que l'ultrastructure et la dynamique mitochondriale. Ce programme de thèse a été dédié à l’étude de la voie d’import CHCHD4/Mia40 dans les cellules cancéreuses et a porté un intérêt tout particulier à l'un des substrats CHCHD4/Mia40 qui façonne l'ultrastructure mitochondriale. En utilisant des techniques d’ARN interférence et de sur-expression de protéines recombinantes, dans un modèle de cancer du côlon, nous avons montré que l’expression du substrat étudié a un effet crucial sur la prolifération et la croissance tumorale. Nos données ont également impliqué cette protéine dans la réponse aux traitements anticancéreux. Dans l'ensemble, ces travaux ouvrent un nouveau champ d'investigations qui non seulement permettra de mieux comprendre la plasticité métabolique des cellules cancéreuses, mais aidera également à identifier de nouveaux biomarqueurs métaboliques. / In the vast majority of cases, mitochondria are required for tumorigenesis and also for the tumoral response to signals generated by the microenvironmental factors (e.g. nutrient deprivation, hypoxia) or to the effects of anti-cancer treatments (e.g. chemotherapy, radiotherapy). As almost all mitochondrial proteins are nuclear-encoded and imported into the organelle, specialized import machineries have evolved in order to meet the need for protein import. Among these machineries, the one that operates in the intermembrane space and is controlled by CHCHD4/Mia40, regulates the import of a group of proteins (substrates) that play important roles in survival and stress response. Substrates of CHCHD4/Mia40 are involved in a broad panel of mitochondrial activities that includes the biogenesis of respiratory chain complexes, lipid homeostasis, calcium storage, as well as ultrastructure and mitochondrial dynamics. This thesis program was dedicated to the study of the CHCHD4/Mia40 import pathway in cancer cells, with a particular interest for one of the CHCHD4/Mia40 substrates that shapes mitochondrial ultrastructure. Using RNA interference approach and recombinant protein overexpression technique, in a colon cancer model, we showed that the expression of this substrate had a crucial effect on proliferation and tumor growth. Our data also involved this protein in the response to anti-cancer treatments. All together, this work opens a new field of investigations that will not only shed new lights on the metabolic plasticity of cancer cells but also help to identify new metabolic biomarkers.

Thesis (MMed (Biomedical Sciences. Anatomy and Histology))--University of Stellenbosch, 1993. / Glial fibrillary acidic protein (GFAP) is found in varying amounts in the cytoplasm of most normal and neoplastic cells of astroglial origin. Though not glial specific, immunoelectron microscopy has shown that vimentin and GFAP are coexpressed as monomers of glial intermediate filaments. These structures display irreversible assembly and a slow metabolic turnover. Although currently applied as astroglial markers, these intermediate filament proteins may reflect the functional and developmental differentiation status of the cells in which they are expressed. Some authors have tried to apply these aspects as diagnostic parameters for grades of malignancy and anaplasia whilst other workers have indicated variable concentrations of GFAP in different astroglial cell types and entities. Different processing protocols, including the use of epoxy and acrylic resins, omission of osmium tetroxide and variations in concentration and incubation time of primary fixatives, were evaluated to find a compromise between antigen availability and acceptable ultrastructure. Thin sections were labelled on grid for GFAP (Dako A561) and vimentin (Dako M725) by means of the indirect immunogold method. For semi- quantification of relative antigen concentrations, a novel method was devised to calculate the labelling density, percentage heterogeneity of the particle distribution and the surface area investigated. This allowed expression of labelling results as a three figure unit. Standardized post-embedding immunoelectron microscopy was performed on 11 normal and neoplastic human tissue specimens. The tissue was exposed to conventional immersion fixation in glutaraldehyde and osmium tetroxide prior to modified embedding in LR White resin. The validity of these results was verified by correlation with conventional histopathological, immunohistochemical and clinical data obtained for each specimen. The presence of epoxy resin in thin sections was shown to reduce antigen availability to such an extent that very low to negative labelling was encountered. Acrylic LR White resin allowed more acceptable immunodetection, but at the cost of inferior ultrastructure and greater instability of thin sections in the electron beam. This masked the effects of glutaraldehyde fixation on the density of the tissuefixative matrix which included destruction of the vimentin and some GFAP associated epitopes. Although osmium tetroxide was required for acceptable ultrastructure, it reduced the labelling sensitivity by 20% and was responsible for premature curing of acrylic resin during impregnation of tissue. Despite superior resolution gained by electron microscopy and the advantage of semi-quantification of labeling results, the labelling sensitivity of this technique is lesser than that of light microscopical immunohistochemistry. Immunoelectron microscopy confirmed the association between GFAP and glial intermediate filaments in almost all the glial tumours studied, correlating well with GFAP expression in matching specimens demonstrated at light microscopical level. In the absence of intermediate filaments, no positivity for GFAP or vimentin was found in oligodendroglial components of mixed tumours. GFAP positivity in astrocytomas was demonstrated by between 17 and 126 particles / µm2, whilst lower figures were obtained for the glioblastoma (PD = 8) and some of the mixed gliomas (Pd = 6). Rosenthal fibres showed both peripheral and central positive labelling for GFAP, thus providing more evidence for their hypothetical degenerative, astroglial nature. The meningioma studied, was GFAP negative, but produced low density positivity for vimentin. Coexpression of GFAP and vimentin was demonstrated in an astroblastoma and degenerative infant brain tissue, thus supporting the presence of both these proteins development of glial structures. Although sites of likely glial intermediate filament synthesis were found, the antigen availability for vimentin was too low to allow a reliable assessment of specific vimentin localization and determination of the GFAP : vimentin ratio in individual intermediate filaments and/or astroglial fibres. Variations in particle densities (PD) which demonstrated GFAP in the various astroglial entities studied, were considered to be a result of variable technical and tissue processing factors rather than truly significant differences in expression of GFAP in individual intermediate filaments. This lead to the conclusion that the GFAP concentration / glial intermediate filament area is likely to be constant for mature glial intermediate filaments and therefore cannot be used to distinguish between different astroglial cells or entities. Whether each cell has a different number of glial intermediate filaments, has not been established satisfactorily. Following complementary conventional immunohistochemistry and careful orientation of biopsy material, the procedure can be applied to suitable specimens for the electron microscopical localization of high concentrations of aldehyde resistant, cytoplasmic antigens.

Understanding the lignin effect and related structural parameters relevant to the recalcitrance of the plant cell wall and the individual and cooperative effects on enzymatic saccharification are vital for improving current processing and conversion methods for cellulosic biofuels. Data were collected from several pretreatment technologies (Hot-water, organo-solv, lime, lime-oxidant, dilute acid, and dilute acid-oxidant pretreatments) on cellulose ultrastructure, partial delignification followed by dilute acid pretreatment, dilute acid pretreatment of enzymatic isolated lignin, and melt rheology test of organo-solv lignin. Results showed minimal cellulose ultrastructural changes occurred due to lime and lime-oxidant pretreatments, which however especially at short residence time displayed relatively high enzymatic glucose yield. Dilute acid and dilute acid-oxidant pretreatments resulted in the largest increase in cellulose crystallinity, para-crystalline, and cellulose-Iβ allomorph content as well as the largest increase in cellulose microfibril or crystallite size. Organo-solv pretreatment generated the highest glucose yield, which was accompanied by the most significant increase in cellulose microfibril or crystallite size and decrease in relatively lignin contents. Lignin acted as a barrier which restricted cellulose crystallinity increase and cellulose crystallite growth during dilute acid pretreatment, and that partial delignification instead of complete lignin removal during DAP would benefit the increase of sugar yield. Furthermore, a deeper understanding of the structural change of lignin in the absence of cellulose-hemicellulose matrix during dilute acid pretreatment confirmed that delignification had the most beneficial effect in poplar, but for switchgrass was the xylan removal. In addition, investigation on the structural change of organo-solv lignin during melt rheology test indicated that high purity lignin isolated from plant biomass with the lowest S/G (syringyl/guaiacyl) ratios will exhibit superior processing performance characteristics to produce high-quality carbon fibers. These findings can aid both in the development of improved enzymes that contain activities to decompose recalcitrant structures and in the design of various processing conditions that efficiently convert specific biomass feedstock into sugars. They can also help in the design of new chemical modifications on lignin and innovative biosynthesis strategies for producing linear-fiber-forming lignin with high-performance.

Pinus radiata is the dominant species of the plantations forests in New Zealand. The forest industry in New Zealand is heavily dependant on it. However, Pinus radiata can develop wood quality flaw called 'intra-ring checking'. The checks or splits appear in wood during kiln drying and usually affect the earlywood region of the wood. It lowers value of appearance grade timber leading to huge economic loses for the forest industry. This thesis presents a study that was undertaken as a part of ongoing collaborative work that is being carried out to understand wood quality issues in Pinus radiata, with a vision of improving its wood quality. This study was a part of that effort and was conducted with an aim to gain an insight into intra-ring checking, and the process of xylogenesis in Pinus radiata. The investigations for this study were carried out in two steps. The first step was to understand intra-ring checking. The location of intra-ring checking was determined by observing the checks using various microscopy techniques. Scanning electron microscopy confirmed that checking was as an intercell failure that usually occurs at the cm1/S1 boundary. A comparative study was also conducted to see if the checked wood had some inherent properties that made it more susceptible to checking. It was found that checking could be influenced by tracheid geometry and cell wall thickness. If the wood had large tracheids with thin walls, it was more likely to develop checks during drying. Lignin distribution in the cell wall layers was also seen to play an important role in checking. Lower lignin levels and disruption in the pattern of lignification of the cell wall layers increased the tendency of the wood to develop checks. Similarly, it the tracheids have larger pits then their tendency to check increases. Structural features that disrupt the uniformity of the interlocking pattern of the tracheid such as rays and resin canals could also play a role in checking. Checked wood tends to have more surface area occupied by ray tissue. However, resin canals do not seem to be directly involved in checking, though their arrangement could indicate disturbances during xylogenesis. The second step was to understand the process of xylogenesis in Pinus radiata especially with respect to the influence of auxin and boron on it. Nutrient and organ culture methods were manipulated and successfully used to study xylogenesis. An exhaustive comparative study was carried out to observe and measure selected wood properties. Microscopy and image analysis revealed that auxin and boron changes in the medium led to the alterations in the cell division, expansion and lignification. However, the analysis of the measurements and the observations displayed complex 'between-tree' and 'within-culture variations'. Clear trends did not emerge from the analysis hence, a confident conclusion on the association between auxin, boron and lignification could not be drawn from this organ culture study. The study has added to the knowledge about checking and wood properties associated with it. A new tool of organ culture had been established that can hlep future research on the process of xylogenesis in Pinus radiata.

The aim of this research was to identify the mechanisms that underpin changes in respiratory capacity during acclimation to temperature. Dark respiration, enzyme activities and leaf ultrastructure were measured from ryegrass (Lolium perenne) in controlled environmental chambers and two species of native grass (Chionochloa rubra & C. pallens) growing at different altitudinal ranges on Mount Hutt, Canterbury, New Zealand. The overall hypothesis was that the changes in both mitochondrial numbers and enzyme activity underpin the greater respiratory capacity observed in response to decreasing temperatures. Gas exchange measurements were carried out to measure rates of dark respiration (Rd) in leaves of both ryegrass and tussocks. Respiratory homeostasis (full acclimation) was achieved in ryegrass leaves but only partial acclimation in both species of tussock plants. Dark respiration rates for warm-grown ryegrass were greatly reduced compared to cool-grown grasses. Rd was lower for C. rubra growing at the base of the mountain (450m) compared to plants at a higher altitude (1060m). The dark respiration rates were also lower for C. pallens growing at 1070m than at 1600m. When comparing Rd between high and low altitude plants, it was significantly lower in low altitude plants at 450m than at 1600m. Oxygen consumption was measured in intact leaves and roots, crude mitochondria and isolated mitochondria from ryegrass to investigate whether a change in respiratory capacity was involved with changes in Rd. Mitochondrial respiratory capacity was slightly reduced in warm leaves and roots (not significantly). The respiratory capacity results from isolated mitochondria for C. rubra (at 450m and 1060m) and C. pallens (at 1070m and 1600m) were consistent with the hypothesis that plants from warm sites have lower respiratory capacity in comparison to plants from cool sites. Based on these results and those of previous studies, it was concluded that respiratory flux for any given temperature is not simply determined by maximal capacities of the respiratory apparatus but rather a combination of the availability of substrate supply, the demand for respiratory products (i.e. ATP) and/or the maximal capacity of respiratory enzymes. Utilizing transmission electron micrographs, it was found that mitochondria were significantly less abundant in warm-grown than cool-grown ryegrass mesophyll cells. Mitochondria dimensions increased slightly between the cool and warm treatment. At lower altitudes (C. rubra), there was a significant decrease in mitochondria numbers with decreasing elevation. At higher altitudes (C. pallens), there was no noticeable change in mitochondria numbers between 1070m and 1600m. It was concluded that mitochondrial abundance for the controlled and field experiments, and mitochondrial sizes in the field, were associated with changes in Rd. The maximal activities of fumarase and succinate dehydrogenase (SDH) in isolated mitochondria from leaves of ryegrass and tussock were measured spectrophotometrically. The results in the controlled experiment indicate that enzymes other than fumarase and SDH could be responsible for the increased respiratory capacity observed in cold acclimated leaves of ryegrass. However, fumarase maximal activity was significantly reduced in C. rubra at low altitude compared with C. pallens growing at high altitude - this suggests that it may be involved in the differences in respiratory capacity and Rd between the two sites. Succinate dehydrogenase did not differ significantly in response to altitude. The large difference between the two field sites for fumarase activity is comparable to the large difference in Rd and reduction in mitochondrial abundance and dimensions seen between the two sites. This supports the overall hypothesis that cool-grown plants keep up with energy demands at low temperatures by increasing enzyme concentrations/capacity. The results of this study are supportive of the hypothesis that growth in low altitudes and warm conditions will result in the reduction of Rd as a consequence of: (1) temperature sensitivity of the respiratory apparatus, resulting in the reduction of the respiratory capacities of mitochondria; (2) a reduction in mitochondria size and numbers; and as a consequence of this (3) a reduction in the activities of mitochondrial enzymes. However, these responses are species specific and vary according to the range of temperatures experienced by plants in the field and controlled environments.

Ephedra (Gnetales) is a gymnosperm genus with a long evolutionary history; the first dispersed pollen grains with affinity to the group are known already from the Permian. This thesis focuses on the evolutionary history of the group and different aspects of its pollination mechanisms. Despite the limited number of extant species of the genus (50-60), and a low morphological and genetic divergence among species, there is variation in pollination syndrome in the genus. The prevailing state in Ephedra, and most gymnosperms, is wind pollination. It is therefore surprising that one species, E. foeminea, is insect-pollinated. Together with co-workers I documented the pollination syndromes of E. foeminea and a sympatric species, E. distachya, based on long term field experiments in north-eastern Greece and aerodynamic investigations and calculations. Placing the results into an evolutionary framework reveals that the insect-pollinated species E. foeminea is sister to the remaining (mostly wind-pollinated) genus, and indicates that insect pollination is the ancestral state in the Gnetales. During the course of evolution of the group there has been a shift to wind pollination, which may have played a crucial role for the diversification of the crown group in the Paleogene. Pollination biology is often correlated with the morphology of the pollen such that pollen grains of anemophilous plants are small with a smooth surface, whereas pollen grains of entomophilous plants are larger with an ornamented surface and a covering of pollenkitt. The pollen morphology of Ephedra can be broadly divided into two types: an ancestral type with an unbranched pseudosulcus between each pair of plicae, and a derived type with a branched pseudosulcus between each pair of plicae. Further, the pollen morphology and ultrastructure of the pollen wall in Ephedra are to some degree correlated with the pollination syndrome and capability of long distance dispersal. Pollen of E. foeminea has a denser ultrastructure, as a result a higher settling velocity and is therefore capable of flying shorter distances than does pollen of the anemophilous E. distachya, and other investigated anemophilous species that show a more spacious ultrastructure of the pollen grain. These results can be useful in the reconstruction of the pollination mechanism of extinct taxa of the Ephedra-lineage in the future.

Description of Trichobilharzia regenti as a new species of nasal bird schistosome in 1998 was only the first step in our knowledge of this extraordinary parasite. Natural definitive hosts of T. regeni are anseriform birds, but infective larvae - cercariae - are able to penetrate also into mammalian hosts including humans. There they are causative agents of hypersensitive skin immune reaction called cercarial dermatitis or swimmer's itch. Contrary to other schistosomes, miracidia of T. regenti hatch directly inside the definitive host tissue. Schistosomula migrate through the nervous system of vertebrates and, together with adult worms, they have predominantly extravascular localization in definitive hosts. Adult worms have a short lifespan and low degree of sexual dimorphism, connected with lower dependence of adult females on long-term contact with males. During the life cycle, T. regenti can be found within three different environments (freshwater, tissue of intermediate molluscan host and tissue of vertebrate host). Each of the seven developmental stages has a different role in the life cycle which corresponds with different organization of various organ systems. The introductory part of the thesis is focused entirely on ontogenetic changes of surface ultrastructure and body musculature of...

Orientador: Daniela Carvalho dos Santos / Resumo: O bicho-da-seda, Bombyx mori (Lepidoptera: Bombycidae), é o inseto de maior importância econômica na produção de seda. A lagarta se alimenta de folhas de amoreira e é altamente sensível a agrotóxicos, assim o uso destes em culturas agrícolas circunvizinhas às plantações de amoreira pode afetar o desenvolvimento de B. mori, acarretando em desequilíbrio nas suas funções metabólicas e, consequentemente, comprometendo a produção de casulos. Entre estes agrotóxicos, destaca-se o Novaluron, inseticida inibidor da síntese de quitina nos insetos e empregado no controle de insetos pragas de culturas agrícolas próximas as plantações de amoreira. Assim, investigamos os efeitos tóxicos de Novaluron no desenvolvimento de B. mori. Lagartas de B. mori, foram separadas em dois grupos experimentais: grupo controle (GC) e grupo tratamento (GT: tratado com 0, 15 mL/L de Novaluron). Após ecdise do 2° para o 3° instar, lagartas do GT foram alimentadas por 24 horas com folhas de amoreira tratadas com o inseticida. Paralelamente foi realizada uma nova exposição, porém em lagartas que realizavam a ecdise do 4° para o 5° instar. Lagartas, pupas e adultos de B. mori foram anestesiadas e segmentos do intestino médio, glândula da seda e órgãos reprodutores retirados e processados convencionalmente para técnicas de microscopias de luz, eletrônica e imunohistoquímica. Além disso, os efeitos no desenvolvimento, reprodução e qualidade do casulo também foram avaliados. O Novaluron provocou efeitos citotóxico... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The silkworm, Bombyx mori (Lepidoptera: Bombycidae is the insect of major economic importance in the production of silk. The larvae feeds on mulberry leaves and is highly sensitive to agrochemicals, thus the use of these in agricultural crops surrounding the mulberry plantations can affect the development of B. mori, causing an imbalance in its metabolic functions and, consequently, compromising the production of cocoons. Among these agrochemicals, stands out the Novaluron, an insecticide inhibitor of the synthesis of chitin in insects and used in the control of insect pests of crops near mulberry plantations. Thus, we investigated the lethal and sublethal effects of Novaluron on the development of B. mori. Larvae were selected into two experimental groups: control group (CG) and treatment group (TG: treated with 0, 15 mL/L Novaluron). After ecdysis from the 2nd to the 3rd instar, the TG larvae were fed for 24 hours with mulberry leaves treated with the insecticide. In parallel, a new exposition was carried out, however in larvae that carry out the ecdysis from the 4th to the 5th instar. B. mori larvae, pupae and adults were anesthetized and segments of the midgut, silk gland and reproductive organs were removed and processed conventionally for light microscopy, electron microscopy and immunohistochemistry. In addition, the effects on the development, reproduction and quality of the cocoon were also evaluated. Novaluron caused cytotoxic effects on the midgut and the silk glan... (Complete abstract click electronic access below) / Doutor

O Gambá-de-Orelha-Branca (Didelphis albiventris) é um marsupial que ocupa uma ampla variedade de habitats, desde florestas até áreas urbanas, em diversos biomas brasileiros e apresenta um importante papel na disseminação de sementes. O objetivo desta pesquisa é estudar a morfologia lingual desta espécie. As línguas foram coletadas de animais encontrados mortos em estradas no estado do Rio Grande do Sul ou ainda de cadáveres de animais oriundos do Núcleo de Reabilitação da Fauna Silvestre (NURFS/ UFPel). As amostras foram submetidas para processamento para as técnicas de microscopias de luz (ML) e eletrônicas de varredura (MEV) e transmissão (MET). Através da ML observamos o epitélio estratificado pavimentoso e o brotamento das papilas em fetos, o desenvolvimento das papilas linguais em animais infantis e as características das papilas totalmente desenvolvidas em adultos. Pelas colorações de Azan e Picrosirius observamos que o colágeno está localizado principalmente sob o epitélio. Através da MEV a análise da camada epitelial revelou três tipos de papilas filiformes com diferentes morfologias de acordo com a região. As papilas fungiformes estão dispersas pelo ápice e corpo linguais, e parcialmente cobertas por uma elevação de mucosa. Papilas circunvaladas são em número de 3 e formam um triângulo na raiz lingual. Papilas foliadas são pequenas e delgadas elevações no bordo caudolateral da língua, em número varíavel de 13-18 projeções. Os tecidos subepiteliais das papilas fungiformes, circunvaladas e foliadas apresentam uma superfície irregular com algumas depressões dorsalmente. Através da MET o estrato córneo demonstrou, para adultos e fetos, o processo de renovação epitelial através da liberação das células mais superficiais; na camada granular observamos tonofilamentos e grânulos de querato-hialina; a camada espinhosa se mostrou similar em ambas as idades e esteve marcada pela grande quantidade de desmossomos intercelulares. As características até então observadas na língua de D. albiventris são semelhantes às observadas em outras espécies de marsupiais. Os procedimentos experimentais foram aprovados pela Comissão de Ética no Uso de Animais (CEUA/FMVZ/USP). / The White-eared Opossum (Didelphis albiventris) is a marsupial that occupies a wide variety of habitats, ranging from forests to urban areas, in several Brazilian biomes and plays an important role in the dissemination of seeds. The objective of this research is to study the lingual morphology of this species. The tongues were collected from animals found dead on roads in the state of Rio Grande do Sul or by cadaver donation from the Núcleo de Reabilitação da Fauna Silvestre (NURFS / UFPel). The samples were submitted to light and scanning (SEM) and transmission (TEM) electron microscopy techniques. Through light microscopy we observed the epithelium stratified squamous and the budding of the papillae in fetuses, the development of the lingual papillae in infants and the characteristics of the fully developed papillae in adults. By the staining of Azan and Picrosirius we observed that the collagen is located mainly under the epithelium. Through the SEM the analysis of the epithelial layer revealed three filiform papillae with different morphologies according to the region. The fungiform papillae are scattered at the apex and body lingual, and partially covered by an elevation of mucosa. Circumvallate papillae are 3 in number and form a triangle at the lingual root. Foliate papillae are small and slender elevations in the caudolateral border of the tongue, in varying numbers of 13-18 projections. The subepithelial tissues of fungiform, circumvallate and foliate papillae have an irregular surface with some dorsal depressions. Through MET, the stratum corneum demonstrated, for adults and fetuses, the process of epithelial renewal through the release of the most superficial cells; in the granular layer we observed tonofilaments and granules of kerato-hyaline; The spinous layer was similar in both ages and was marked by the great amount of intercellular desmosomes. The characteristics previously observed in the tongues of D. albiventris are similar to those observed in other species of marsupials. The experimental procedures were approved by the Committee on Ethics in the Use of Animals (CEUA / FMVZ / USP).

Biotécnicas aplicadas à reprodução animal são empregadas com o intuito de melhorar qualitativa e quantitativamente os rebanhos. A superovulação assim como a estimulação do folículo dominante utilizando-se doses suprafisiológicas de eCG (gonadotrofina coriônica eqüina) são empregadas em bovinos e bubalinos, mas nem sempre alcançam os resultados esperados. Entretanto, foram relatadas alterações morfofuncionais em corpos lúteos (CL) de animais submetidos a estes tratamentos, o que implica, necessariamente, em levantamento de hipóteses relativas ao(s) mecanismo(s) pelo(s) qual(is) as gonadotrofinas exógenas alteram as funções celulares nos folículos e corpos lúteos resultantes. Com o intuito de melhor compreensão do papel exercido pelo eCG sobre a célula luteínica bovina, 16 vacas foram sincronizadas e submetidas (grupos tratados) ou não (grupo controle) ao tratamento com eCG. O tratamento foi realizado previamente (superovulação) ou posteriormente (estimulação do folículo dominante) ao desvio folicular. No dia 6 após a ovulação, estes animais foram abatidos e os CL coletados para realização de análises histológicas e ultra-estruturais, assim como o sangue coletado para dosagem de progesterona. Para comparação dos dados obtidos entre os diferentes grupos utilizou-se o programa GraphPrism e as médias foram consideradas diferentes quando p < 0.05. Em relação à densidade de mitocôndrias e densidade numérica das mitocôndrias elipsóides não houve diferença significativa entre os grupos estudados. Quando se calculou o volume total das mitocôndrias no CL bovino, houve diferença significativa do grupo superovulado em relação aos outros grupos. Já para as mitocôndrias esferóides observou-se diferença significativa do grupo estimulado comparado aos grupos controle e superovulado. À imunofluorescência os animais do grupo superovulado apresentaram visualmente uma marcação mais fluorescente intensa para mitocôndrias quando comparados aos grupos controle e estimulado; e o grupo estimulado apresentou uma marcação mais intensa em relação ao grupo controle. Houve diferença significativa entre os três grupos em relação à quantidade das células luteínicas grandes. Quando se corrigiu o número de células luteínicas grandes pelo volume do CL, os mesmos resultados foram encontrados. Quanto às medidas do maior diâmetro das células luteínicas grandes houve uma diferença significativa quando comparado o grupo estimulado com os demais. Aspectos qualitativos da microvascularização do CL em animais controle e superovulados revelam vascularização mais abundante no grupo tratado. Estes dados apontam para modificações morfológicas da célula luteínica e do CL bovino direcionadas à maior produção hormonal após tratamento com eCG e indicam que doses diferentes aplicadas em momentos diferentes do ciclo estral levam à respostas diversas da célula luteínica e do próprio CL. / Biotechnologies applied to animal reproduction are employed in order to improve livestock quality and quantity. Superovulation and the stimulation of the dominant follicle using supraphysiological doses of eCG (equine chorionic gonadotropin) are used in cattle and buffaloes, but not always achieve the expected results. However, morphofunctional changes in corpora lutea (CL) derived from animals submitted to these treatments were reported, which necessarily implies a survey of hypotheses regarding the mechanism(s) by which exogenous gonadotrophins result in altered cellular functions in the follicles and corpora lutea. In order to better understand the role played by eCG on bovine luteal cells, 16 cows were synchronized and submitted (treated groups) or not (control group) to treatment with eCG. The treatment was performed previously (superovulation) or after (stimulation of the dominant follicle) follicular deviation. At 6 days after ovulation, animals were slaughtered and the CL collected for histological and ultrastructural analysis, as well as blood for determining plasmaprogesterone.For statistical analysis the program Graph Prism was used and mean considered significant different when p < 0.05. In relation to mitochondria number and volume density there were no differences among the studied groups. Values of mitochondria total volume in CL were different if stimulated was compared to the other groups. Imunofluoresce for mitochondria showed a more intensive signal for animals from the superovulated group, followed by animals belonging to the stimulated group. The number of large luteal cells was different among all groups. Even though this number was corrected by CL volume, the same results were found. The biggest diameter of large luteal cells was compared among the groups and stimulated group showed higher values. Qualitative aspects of CL microvascularization in control and superovulated animals reveal more abundant vascularization in treated group. These data point towards morphological modification of bovine CL and luteal cell directed to increased hormonal production after eCG treatment. Moreover, results indicate that different eCG dosis applied in different time points of estrous cycle lead to different responses from CL and luteal cells.