Trypanosoma brucei species are vector-borne protozoan parasites that cause Human African typanosomiasis (HAT) and nagana in cattle. In humans, the diseases caused by these parasites are fatal if left untreated. Treatments for these diseases are complicated because the approved drugs for treatment are ineffective against the parasites and have many toxic side effects associated with their use. There is a clear need to identify new therapeutics that are less toxic and more effective against T. brucei. Our approach for identifying new therapies is to identify novel targets in the parasite that can be modulated by small molecules. The mitogen-activated protein kinases (MAPK) pathway is a three-tiered signaling cascade that regulates cell responses to stimuli and are involved in essential processes. MAPKs can regulate differentiation, virulence, apoptosis, cell cycle and gene expression, which makes MAPKs interesting drug targets in T. brucei. The extracellular-signal regulated kinase 8 homolog in T. brucei (TbERK8) is essential for survival in bloodstream form T. brucei. The work in this dissertation involves characterizing this T. brucei MAPK to better understand its biological function and identify small molecules that can inhibit its activity to kill the parasite. Here, we report that TbERK8 is an atypical MAPK kinase that is able to autophosphorylate and no upstream kinases that activate TbERK8 have been identified. We have demonstrated that TbERK8 is able to phosphorylate the proliferating cell nuclear antigen homolog in T. brucei (TbPCNA). This is in contrast to the reported function the human ERK8 and PCNA homologs that form a stable complex in normal breast cells which does not result in PCNA phosphorylation. We also report here that TbPCNA is phosphorylated on three residues localized to a unique insertion loop by TbERK8. TbPCNA is tightly regulated in the parasites such that either upregulating or downregulating its expression arrests T. brucei proliferation. Although, this mechanism of phosphorylation is unique to TbPCNA, the role that such phosphorylation has in regulating TbPCNA is not known. Finally, we have identified small molecules that can selectively inhibit either TbERK8 or HsERK8, demonstrating that TbERK8 can be selectively inhibited to kill the parasite. The unique properties of TbERK8 can be exploited by small molecules that can be developed into new parasite-specific therapies that kill T. brucei with fewer side effects to the patients. / Ph. D.

Diss. (sammanfattning) Stockholm : Karol. inst., 2003. / Härtill 5 uppsatser.

Diss. (sammanfattning) Umeå : Umeå universitet, 2008. / Härtill 4 uppsatser.

Thesis (Ph.D.)--University of Florida, 2004. / Typescript. Title from title page of source document. Document formatted into pages; contains 87 pages. Includes Vita. Includes bibliographical references.

Made available in DSpace on 2014-06-11T19:25:35Z (GMT). No. of bitstreams: 0 Previous issue date: 2006-12-18Bitstream added on 2014-06-13T19:12:32Z : No. of bitstreams: 1 caetano_mc_me_araca.pdf: 1024075 bytes, checksum: aa12fb1ffe3cd0c2176481b1472ff87e (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / As células-tronco (stem cells) têm um papel fundamental nos processos reparativos e regenerativos da córnea. A exata localização destas é bem conhecida no olho do homem, bem como as suas funções. Entretanto, as mesmas ainda não foram descritas em medicina veterinária, sequer a sua localização em olhos de animais de companhia, tratando-se assim, de assunto que merece novas e originais investigações. Anticorpos monoclonais que reagem superficialmente com as citoqueratinas são empregados para determinar este tipo celular presente nos tecidos, no entanto, existem outros marcadores capazes de reagir antigenicamente com núcleos celulares. Entre eles, o PCNA (antígeno nuclear de proliferação celular) e o Ki-67 (antígeno de proliferação Ki-67) são capazes de marcar células em proliferação. Uma vez que isso nunca fora descrito anteriormente, e considerando-se a necessidade e importância científica em se determinar a localização de células em proliferação na superfície ocular de cães, o presente estudo teve por objetivos: 1) determinar a expressão de células em proliferação pela marcação imunoistoquímica com anticorpos monoclonais anti-PCNA e anti-MIB-1 (anticorpo monoclonal anti-Ki-67), bem como, sua localização na superfície ocular; 2) comparar se há diferença estatística significante na marcação dessas células em diferentes idades. Para tanto, foram utilizados 24 cães jovens e adultos, sadios, dos quais o bulbo ocular esquerdo foi removido, fixado e corado pela H.E. (hematoxilina e eosina), além da imunoistoquímica empregando-se os anticorpos monoclonais anti-PCNA e anti-MIB-1. Concluiu-se que a presença de células em proliferação imunomarcadas pelo PCNA e pelo MIB-1 foi observada em diferentes tecidos da superfície ocular de cães, sendo os tecidos mais marcados: o limbo e o epitélio da córnea... / The stem-cells has a fundamental paper in process of cornea s tissue repair and regeneration. In man, the well-know localization and functions had been descriebed a long time ago, however the same ones had not yet been descriebed in veterinary medicine, at least your localization in eyes of company animals, what deserve new and original inquiries. Monoclonais antibodies that react superficially with the cytokeratins are used to determine this cell type presence in ocular surface. However, exist another markers capable to react with cell nucleoli, for example, PCNA and MIB-1 are capable to mark proliferation cells. Considering the necessity and scientific importance to determining the localization of proliferation cells on dog s ocular surface, a time that, never was descriebed previously, the present study had for objectives: 1) determineted the expression of proliferation cells immunohistochemically by PCNA and MIB-1 and its localization in ocular surface; 2) compare if has statistically significant difference in immunoexpression of proliferation cells in different ages. In the study was used 24 healthy dogs, young and adults, witch had the left eyes removed, fixed in buffered formalin and stained with H.E. (hematoxilin and eosin) and with monoclonal antibodies anti-PCNA and anti-MIB-1. The presence of immunostained cells was most observed in corneal ephithelium and limbo. Probably the immunostained cells are stem-cells in dog s ocular surface, however for such evidence it is necessary ...(Complete abstract click electronic address below)

Orientador: Alexandre Lima de Andrade / Banca: Adriana Morales / Banca: Renée Laufer Amorim / Resumo: As células-tronco (stem cells) têm um papel fundamental nos processos reparativos e regenerativos da córnea. A exata localização destas é bem conhecida no olho do homem, bem como as suas funções. Entretanto, as mesmas ainda não foram descritas em medicina veterinária, sequer a sua localização em olhos de animais de companhia, tratando-se assim, de assunto que merece novas e originais investigações. Anticorpos monoclonais que reagem superficialmente com as citoqueratinas são empregados para determinar este tipo celular presente nos tecidos, no entanto, existem outros marcadores capazes de reagir antigenicamente com núcleos celulares. Entre eles, o PCNA (antígeno nuclear de proliferação celular) e o Ki-67 (antígeno de proliferação Ki-67) são capazes de marcar células em proliferação. Uma vez que isso nunca fora descrito anteriormente, e considerando-se a necessidade e importância científica em se determinar a localização de células em proliferação na superfície ocular de cães, o presente estudo teve por objetivos: 1) determinar a expressão de células em proliferação pela marcação imunoistoquímica com anticorpos monoclonais anti-PCNA e anti-MIB-1 (anticorpo monoclonal anti-Ki-67), bem como, sua localização na superfície ocular; 2) comparar se há diferença estatística significante na marcação dessas células em diferentes idades. Para tanto, foram utilizados 24 cães jovens e adultos, sadios, dos quais o bulbo ocular esquerdo foi removido, fixado e corado pela H.E. (hematoxilina e eosina), além da imunoistoquímica empregando-se os anticorpos monoclonais anti-PCNA e anti-MIB-1. Concluiu-se que a presença de células em proliferação imunomarcadas pelo PCNA e pelo MIB-1 foi observada em diferentes tecidos da superfície ocular de cães, sendo os tecidos mais marcados: o limbo e o epitélio da córnea...(Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The stem-cells has a fundamental paper in process of cornea’s tissue repair and regeneration. In man, the well-know localization and functions had been descriebed a long time ago, however the same ones had not yet been descriebed in veterinary medicine, at least your localization in eyes of company animals, what deserve new and original inquiries. Monoclonais antibodies that react superficially with the cytokeratins are used to determine this cell type presence in ocular surface. However, exist another markers capable to react with cell nucleoli, for example, PCNA and MIB-1 are capable to mark proliferation cells. Considering the necessity and scientific importance to determining the localization of proliferation cells on dog’s ocular surface, a time that, never was descriebed previously, the present study had for objectives: 1) determineted the expression of proliferation cells immunohistochemically by PCNA and MIB-1 and its localization in ocular surface; 2) compare if has statistically significant difference in immunoexpression of proliferation cells in different ages. In the study was used 24 healthy dogs, young and adults, witch had the left eyes removed, fixed in buffered formalin and stained with H.E. (hematoxilin and eosin) and with monoclonal antibodies anti-PCNA and anti-MIB-1. The presence of immunostained cells was most observed in corneal ephithelium and limbo. Probably the immunostained cells are stem-cells in dog’s ocular surface, however for such evidence it is necessary ...(Complete abstract click electronic address below) / Mestre

No description available.

In sheep, large ovarian antral follicles grow in waves with a periodicity of every 4 to 5 days; each wave is initiated by a peak in serum concentrations of follicle stimulating hormone (FSH). In the present thesis, follicular data and hormone estimations acquired from daily ultrasonography and blood samples, respectively, were used to study mechanisms regulating the number of follicular waves per estrous cycle. Using additional approaches such as implants releasing estradiol-17â and or progesterone, immunization against gonadotropin releasing hormone (GnRH), and injections of GnRH, the role of pulsed luteinizing hormone (LH) secretion and FSH peaks in follicular wave emergence and growth and the dependency of FSH peaks on pulsed GnRH secretion, were studied in sheep. The viability of aged follicles was also addressed.<p> The results of the present studies showed that ewes with three or four waves per cycle had cycles of the same length. The inter-wave interval was longer for the first and the last or ovulatory wave of the cycle in three compared to four wave cycles. The length of the lifespan and regression phase of the largest follicle of a wave declined across the cycle as FSH peak concentration and amplitude decreased. The maximum follicular diameter of the largest follicle growing in the first wave and the last or ovulatory wave of the cycle was greater compared to other waves of the cycle. Treatment of anestrous ewes with estradiol releasing implants alone completely abolished pulsed LH secretion and suppressed follicular wave development; however, FSH secretion was only minimally affected and the pool of small follicles was not affected. When pulsed secretion of LH was restored by frequent injections of GnRH, follicular waves were re-established. Treatment of anestrous ewes with implants releasing estradiol and progesterone, decreased FSH peak amplitude and abolished LH pulses and follicular waves; the size of the pool of small follicles increased. Immunization against GnRH in anestrous ewes abolished pulsatile LH secretion and suppressed follicular wave emergence; however, FSH peaks continued to occur for several weeks. In cyclic ewes, creating an LH pulse frequency typical of the follicular phase, during the luteal phase of the cycle by giving GnRH, increased maximum diameter of the largest follicle in a wave and serum concentrations of estradiol and progesterone. The enhanced growth of follicles in a wave blocked the next expected FSH peak and its associated follicular wave. Decreasing LH pulse frequencies lower than the minimal frequency seen in the luteal phase, by implants releasing progesterone, did not affect the growth of follicular waves.<p> It was previously demonstrated that treatment of non-prolific WWF ewes with Prostaglandin F2á (PGF2á) and medroxy progesterone acetate (MPA) increased the ovulation rate by adding ovulations from the penultimate wave in addition to the final wave of the cycle; however, fertility was not improved. In the last study of my thesis, we collected follicles, with an extended lifespan, from the penultimate wave of the cycle in ewes given the PGF2á and MPA treatment. We compared their quality with follicles from the final wave of the cycle by looking at the expression of markers of follicular development. The results showed that theca cells of follicles from the final wave had significantly higher mRNA expression for vascular endothelial growth factor (VEGF) compared to follicles from the penultimate wave. Granulosa cells of follicles from the final wave had significantly higher mRNA expression for connexion 43 (Cx43) compared to follicles from the penultimate wave. Protein expression for Cx43, proliferating cell nuclear antigen (PCNA) and Factor VIII was greater in follicles from the final compared to the penultimate wave.<p> We concluded from the present studies that: 1) the mechanism that makes a three wave or four wave cycle is unclear; 2) some level of pulsatile LH secretion is required for an FSH peak to trigger emergence of follicular waves in anestrous ewes; 3) progesterone enhances the inhibitory effects of estradiol on FSH secretion in anestrous ewes, suppressing specifically FSH peak amplitude; 4) an endogenous rhythm may exist that drives the peaks in FSH secretion independent of secretory products from the follicles growing in a wave and pulsed GnRH secretion; 5) follicular waves in ewes, when exposed to an LH pulse frequency similar to the follicular phase, during the luteal phase of the cycle, when serum progesterone concentrations are high, can grow and function like ovulatory follicles growing in the follicular phase of the cycle; 6) expression of some markers of vascularization/ angiogenesis, gap-junctional communication and cell proliferation, appeared to be decreased in follicles from the penultimate compared to the final wave of an estrous cycle, when the lifespan of follicles from the penultimate wave was extended such that they were present in the ovary with follicles from the final wave of the cycle.

In sheep, large ovarian antral follicles grow in waves with a periodicity of every 4 to 5 days; each wave is initiated by a peak in serum concentrations of follicle stimulating hormone (FSH). In the present thesis, follicular data and hormone estimations acquired from daily ultrasonography and blood samples, respectively, were used to study mechanisms regulating the number of follicular waves per estrous cycle. Using additional approaches such as implants releasing estradiol-17â and or progesterone, immunization against gonadotropin releasing hormone (GnRH), and injections of GnRH, the role of pulsed luteinizing hormone (LH) secretion and FSH peaks in follicular wave emergence and growth and the dependency of FSH peaks on pulsed GnRH secretion, were studied in sheep. The viability of aged follicles was also addressed.<p> The results of the present studies showed that ewes with three or four waves per cycle had cycles of the same length. The inter-wave interval was longer for the first and the last or ovulatory wave of the cycle in three compared to four wave cycles. The length of the lifespan and regression phase of the largest follicle of a wave declined across the cycle as FSH peak concentration and amplitude decreased. The maximum follicular diameter of the largest follicle growing in the first wave and the last or ovulatory wave of the cycle was greater compared to other waves of the cycle. Treatment of anestrous ewes with estradiol releasing implants alone completely abolished pulsed LH secretion and suppressed follicular wave development; however, FSH secretion was only minimally affected and the pool of small follicles was not affected. When pulsed secretion of LH was restored by frequent injections of GnRH, follicular waves were re-established. Treatment of anestrous ewes with implants releasing estradiol and progesterone, decreased FSH peak amplitude and abolished LH pulses and follicular waves; the size of the pool of small follicles increased. Immunization against GnRH in anestrous ewes abolished pulsatile LH secretion and suppressed follicular wave emergence; however, FSH peaks continued to occur for several weeks. In cyclic ewes, creating an LH pulse frequency typical of the follicular phase, during the luteal phase of the cycle by giving GnRH, increased maximum diameter of the largest follicle in a wave and serum concentrations of estradiol and progesterone. The enhanced growth of follicles in a wave blocked the next expected FSH peak and its associated follicular wave. Decreasing LH pulse frequencies lower than the minimal frequency seen in the luteal phase, by implants releasing progesterone, did not affect the growth of follicular waves.<p> It was previously demonstrated that treatment of non-prolific WWF ewes with Prostaglandin F2á (PGF2á) and medroxy progesterone acetate (MPA) increased the ovulation rate by adding ovulations from the penultimate wave in addition to the final wave of the cycle; however, fertility was not improved. In the last study of my thesis, we collected follicles, with an extended lifespan, from the penultimate wave of the cycle in ewes given the PGF2á and MPA treatment. We compared their quality with follicles from the final wave of the cycle by looking at the expression of markers of follicular development. The results showed that theca cells of follicles from the final wave had significantly higher mRNA expression for vascular endothelial growth factor (VEGF) compared to follicles from the penultimate wave. Granulosa cells of follicles from the final wave had significantly higher mRNA expression for connexion 43 (Cx43) compared to follicles from the penultimate wave. Protein expression for Cx43, proliferating cell nuclear antigen (PCNA) and Factor VIII was greater in follicles from the final compared to the penultimate wave.<p> We concluded from the present studies that: 1) the mechanism that makes a three wave or four wave cycle is unclear; 2) some level of pulsatile LH secretion is required for an FSH peak to trigger emergence of follicular waves in anestrous ewes; 3) progesterone enhances the inhibitory effects of estradiol on FSH secretion in anestrous ewes, suppressing specifically FSH peak amplitude; 4) an endogenous rhythm may exist that drives the peaks in FSH secretion independent of secretory products from the follicles growing in a wave and pulsed GnRH secretion; 5) follicular waves in ewes, when exposed to an LH pulse frequency similar to the follicular phase, during the luteal phase of the cycle, when serum progesterone concentrations are high, can grow and function like ovulatory follicles growing in the follicular phase of the cycle; 6) expression of some markers of vascularization/ angiogenesis, gap-junctional communication and cell proliferation, appeared to be decreased in follicles from the penultimate compared to the final wave of an estrous cycle, when the lifespan of follicles from the penultimate wave was extended such that they were present in the ovary with follicles from the final wave of the cycle.

Scar-free wound healing and regeneration are uncommon phenomena permitting the near complete restoration of damaged tissues, organs and structures. Although rare in mammals, many lizards are able to undergo scarless healing and regeneration following loss of the tail. This study investigated the spontaneous and intrinsic capacity of the leopard gecko (Eublepharis macularius) tail to undergo scar-free wound healing and regeneration following two different forms of tail loss: autotomy, a voluntary and evolved mechanism of tail shedding at fracture planes; and surgical amputation, involuntary loss of the tail outside the fracture planes. Furthermore, I investigated the ability of the regenerate tail to regenerate by amputating a regenerate tail (previously lost by autotomy). To investigate these phenomena I imaged wound healing and regenereating tails daily (following autotomy and amputation) to document gross morphological changes. I used histochemistry to document tissue structure and immunohistochemistry to determine the tissue/cellular location of my five proteins of interest (PCNA, MMP-9, WE6, α-sma, TGF-β3). Each of these proteins of interest has been previously documented during wound healing and/or regeneration in other wound healing/regeneration model organisms (e.g. mice, urodeles, lizards, zebrafish). Scar-free wound healing and regeneration occurred following autotomy, amputation of the original tail and amputation of the regenerate tail, indicating that the leopard gecko tail has an instrinsic scar-free wound healing and regenerative capacity that is independent of the mode of tail loss (autotomy or amputation). Furthermore immunohistochemistry revealed a conserved sequence and location of the expression of the five proteins of interest following both forms of tail loss. These results provide the basis for further studies investigating scar-free wound healing and regeneration in a novel amniote model, the leopard gecko. / NSERC