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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
31

Construção e análise de mutantes fluorescentes da troponina I / Construction and analysis of fluorescent mutants of troponin I

Oliveira, Deodoro Camargo Silva Gonçalves de 10 August 2001 (has links)
A troponina (Tn) regula a contração do músculo estriado esquelético de vertebrados. Ela é composta de três subunidades: troponina I (TnI), troponina C (TnC) e troponina T (TnT). A TnI tem a função inibitória que é neutralizada pela ligação de Ca2+ nos sítios regulatórios do N-domínio da TnC, e a TnT posiciona o complexo no filamento fino. Para monitorar o sinal do Ca2+ sendo transmitido da TnC para a TnI as propriedades espectrais únicas do 5-hidroxitriptofano (5HW) foram utilizadas. O 5HW foi incorporado em mutantes pontuais de TnI com um único códon para triptofano. Foram identificadas duas sondas espectrais intrínsecas na TnI capazes de detectar a ligação de Ca2+ na Tn: as TnIs com 5HW nas posições 100 e 121. Complexos troponina reconstituídos com estes mutantes fluorescentes de TnI, Tn-TnIF100HW e Tn-TnIM121HW, apresentaram respectivamente 12 e 70 % de aumento na intensidade do espectro de emissão devido à ligação de Ca2+ na TnC. Nos complexos binários (TnC-TnI) as TnIs com 5HW nas posições 106 e 121 também captam a ligação do Ca2+ na TnC. A análise da fluorescência destas sondas demonstrou que: 1) as regiões da TnI que respondem ao N-domínio regulatório da TnC ocupado com Ca2+ são a região inibitória da TnI, resíduos 96 até 116, e a região vizinha que inclui a posição 121 da TnI; 2) mutações pontuais e a incorporação de 5HW na TnI podem afetar tanto a afinidade como a cooperatividade da ligação de Ca2+ na TnC, confirmando o papel da TnI em modular a afinidade da TnC por Ca2+; 3) as constantes de dissociação de Ca2+ surpreendentemente altas, Kd ~ 10-8 M, calculadas a partir dos sinais das sondas na região inibitória da TnI, sugerem a possibilidade de que os sítios do domínio N-terminal da TnC sejam os sítios de ligação de Ca2+ de maior afinidade no complexo troponina. / Vertebrate striated muscle contraction is regulated by troponin (Tn). Tn is composed of three subunits: troponin I (TnI), troponin C (TnC) and troponin T (TnT). TnI has an inhibitory role that is neutralized by calcium binding to the regulatory sites in the N-domain of TnC, and TnT positions the troponin complex on the thin filament. In order to follow the Ca2+ induced conformational change that is transmitted from TnC to TnI, the unique spectral properties of 5-hydroxytryptophan (5HW) incorporated as point-mutants of TnI were used. It was possible to identify two new TnI intrinsic spectral probes sensitive to Ca2+ binding to Tn: TnI with single 5HW at positions 100 and 121. Trimeric troponin complexes reconstituted with two fluorescent mutants of TnI, Tn-TnIF100HW and Tn-TnIM121HW, showed respectively 12 and 70 % increase in the emission spectra when Ca2+ bound to TnC. In the binary complexes (TnC-TnI) two TnIs with 5HW at positions 106 and 121 were also sensitive to Ca2+ binding to TnC. Fluorescence analysis of these probes showed: 1) the regions in TnI that respond to Ca2+ binding to the regulatory N-domain of TnC are the inhibitory region of TnI (residues 96 to 116), and a neighbor region that includes position 121; 2) point mutations and incorporation of 5HW in TnI can affect both the affinity and the cooperativity of Ca2+ binding to TnC, confirming the role of TnI as a modulator of the Ca2+ affinity of TnC; 3) the high dissociation constant for sites in the N-terminal domain of TnC (Kd ~ 10-8 M), derived from data using probes in the inhibitory region of TnI suggested the possibility that these sites are the high affinity Ca2+ binding sites in the troponin complex.
32

FGF2 de 18kDa e de 22,5kDa: sinalização molecular parácrina e funções biológias / FGF2 species of 18 and 22.5 kDa: paracrine molecular signaling and biological functions

Gilson Masahiro Murata 05 May 2010 (has links)
FGF2 (Fibroblast Growth Factor 2), o fundador da família FGF, tem funções regulatórias na mitogênese, diferenciação, morfogênese e reparo tecidual. Diversas espécies moleculares de FGF2 compartilham uma seqüência C-terminal comum de 155 aminoácidos, pois se originam de diferentes sítios de iniciação de leitura de um único mRNA. O menor, o FGF2-18kDa, é liberado extracelularmente para se ligar a receptores específicos (FGFRs) para disparar as funções parácrinas e autócrinas pelas quais este fator é conhecido. Por outro lado, as espécies maiores (FGF2-21, 22, 22,5 e 34kDa) são intracelulares se ligam a parceiros moleculares desconhecidos para exercer funções intrácrinas ainda indefinidas. O objetivo desta tese foi produzir espécies recombinantes do FGF2-18 e FGF2-22,5, na forma de proteínas de fusão, para analisar funções biológicas e mecanismos de sinalização. Nas células malignas Y1 de camundongo, os recombinantes de FGF2-18kDa (FGF2-18, His-FGF2-18 e His-FGF2-18-ProA) dispararam uma resposta antagônica estimulando as vias de sinalização mitogênica, mas bloqueando o ciclo celular. Nos fibroblastos não tumorigênicos Balb3T3, estes mesmos recombinantes de FGF2-18kDa dispararam apenas a resposta mitogênica clássica. Todos os efeitos biológicos destes recombinantes de FGF2-18kDa foram bloqueados pelo inibidor específico da proteína quinase de tirosina dos FGFRs, PD173074, demonstrando que são respostas intermediadas pelos FGFRs. Portanto, os domínios estruturais adicionados aos recombinantes de FGF2-18kDa não impediram que estas proteínas se ligassem e ativassem os FGFRs. Por outro lado, o recombinante His-FGF2-22,5 dispara apenas as vias de sinalização mitogênica em ambas as células Y1 e 3T3, mas este efeito biológico não é inibido por PD173074. Estes resultados sugerem que a seqüência N-terminal de 55 resíduos, rica em aminoácidos básicos, impede que o FGF2-22,5kDa se ligue e/ou ative os FGFRs. Entretanto, o recombinante His-FGF2-22,5ProA dispara a resposta antagônica característica do FGF2-18kDa. As implicações destes últimos resultados é que o domínio de ProA adicionado ao C-terminal torna o FGF2-22,5kDa um bom ligante dos FGFRs. A interação física entre ligante e receptor das formas recombinantes His-FGF2-18kDa (ou His-FGF2-18ProA) e FGF2-22,5kDa com os putativos FGFRs foi analisada através da técnica de SPR e os resultados mostram KDs aproximados (Kd18=21, 488.10-9 e Kd22,5=20,70393.10-9), enquanto que o número de sítios ligantes em vesículas microssomais das células é significantemente inferior para o FGF2-22,5kDa. Estes resultados são compatíveis com a existência de receptores diferentes para FGF2-18kDa e FGF2-22,5kDa, uma hipótese ainda a ser definitivamente corroborada. Em conclusão, o FGF2-18kDa, mesmo em formas recombinantes como proteína de fusão, dispara todos os efeitos biológicos descritos para FGF2, através dos FGFRs. Diferentemente, o FGF2-22,5kDa, como fator parácrino, só desencadeou a resposta mitogênica clássica de FGF2, provavelmente através de receptores diferentes dos FGFRs. Os resultados e conclusões desta tese têm um potencial indiscutivelmente relevante para a biologia molecular do câncer, com implicações possíveis em terapia oncológica / FGF2 (Fibroblast Growth Factor 2), the founder of the FGF family, has regulatory functions in mitogenesis, differentiation, morphogenesis and tissue repair. Multiple FGF2 molecular species, sharing a C-terminal sequence of 155 amino acids, are translated from different iniciation sites of the same mRNA. The smaller, the FGF2-18kD, is extracellularly released to bind to specific membrane receptors (FGFRs), performing paracrine and autocrine functions. On the other hand, the larger FGF2s (21, 22, 22.5 and 34kDa) are intracellular species that bind to unknown partners to play still undefined intracrine roles. The aim of this thesis was to produce recombinant species of FGF2-18kDa and FGF2-22,5kDa, in the form of fusion proteins, to analyze functions and signaling mechanisms. In mouse Y1 malignant cells, FGF2-18kD recombinants (FGF2-18kDa and His-FGF2-18kDaProA) triggered an antagonistic response activating mitogenic signaling pathways, but blocking the cell cycle. However, in non tumorigenic Balb3T3 fibroblasts, these same FGF2-18kD recombinants only elicited the classical mitogenic response. All biological effects of these FGF2-18kD recombinants were blocked by the specific inhibitor of FGFR-protein-tyrosine-kinases, PD173074, demonstrating that these responses are mediated by FGFRs. Therefore, the new peptide domains added to FGF2-18kD did not prevent these recombinant fusion proteins to bind and activate FGFRs. Conversely, the recombinant His-FGF2-22,5kDa triggered only mitogenic signaling pathways in both Y1 and Balb3T3 cells, a biological effect not inhibited by PD173074. These results suggested that the additional basic-rich N-terminal sequence of 55 amino acid residues, found in FGF2-22,5kDa, prevents this FGF2 species from binding and / or activate FGFRs. However, surprisingly, the recombinant His-FGF2-22kDaProA triggered the antagonistic response characteristic of FGF2-18kDa. These results imply that the ProA-domain added to the C-terminal end rendered the FGF2-22,5kDaProA a good ligand of FGFRs. The physical interaction between recombinants of both His-FGF2-18kD and His-FGF2-22kDa with putative FGFRs, analyzed by SPR, yielded close KD values (KD18=21, 5.10-9 e K D22,5=20,7.10-9), while the number of binding sites in cell microsomal vesicles were significantly lower for the His-FGF2-22,5kDa. These results are consistent with the existence of different receptors for FGF2 and FGF2-18kD-22,5kDa, a hypothesis that has yet to be definitively confirmed. In conclusion, FGF2-18kD, even as recombinant fusion proteins, triggered all biological effects of FGF2, through FGFRs. Conversely, the FGF2-22, 5kDa only triggered the classical mitogenic response, probably via receptors other than FGFRs. The results and conclusions of this thesis are potentially of great interest in cancer molecular biology, with implications in oncologic therapy.
33

Athletes' heart and exercise related sudden cardiac death : across the age span

Wilson, Mathew January 2010 (has links)
Background - Regular exercise reduces the risk of cardiovascular disease and subsequent sudden cardiac death (SCD). However, a small, but notable proportion of athletes die suddenly due to inherited or congenital disorders of the heart that predispose to malignant ventricular arrhythmias. Such tragedies are highly publicised, particularly when high-profile athletes are involved. To date, limited evidence for the efficacy of cardiovascular pre-participation screening exists outside of the Italian experience. Furthermore, limited data exists examining the impact of ethnicity on cardiac adaptations to physical training. Whilst the cardiovascular benefits of exercise are well known, the impact of life-long endurance exercise is less well understood. Long term high-intensity endurance exercise is associated with changes in cardiac morphology together with electrocardiographic alterations that are believed to be physiologic in nature. Recent data however, has suggested a number of deleterious adaptive changes in cardiac structure, function and electrical activity in response to life-long endurance activity. Aims and Objectives - The aims of this PhD were; 1) To find an effective preparticipation screening method that would successfully identify pre-existing cardiovascular abnormalities, 2) To identify the prevalence of hypertrophic cardiomyopathy and Long QT syndrome in elite UK athletes; 3) To examine the impact and significance of ethnicity upon left ventricular remodelling in elite athletes, and 4) To examine the acute and chronic impact of ultra-endurance exercise across the life-span in male endurance athletes. Major Results and Conclusions – 1) Study 2 sought to confirm the efficacy of resting 12-Lead ECG ‘alongside’ personal/family history questionnaires and physical examinations as collective tools to identify diseases that have the potential of causing sudden death within a cohort of elite junior athletes (n=1074) and physically active school children (n=1646). Nine participants were identified with a positive diagnosis of a disease associated with SCD. None of those diagnosed with a disease associated with SCD were symptomatic or had a family history of note. Thus, personal symptoms and family history questionnaires alone are inadequate in the identification of individuals with diseases associated with SCD. In conclusion, resting 12-Lead ECG is paramount when screening for diseases that have the potential of causing sudden death in the young. 2) Study 3 examined 3,500 asymptomatic elite athletes (75% male) with a mean age of 20.5 ± 5.8 years with 12-lead ECG and 2-dimensional echocardiography. None had a known family history of HCM. Of the 3,500 athletes, 53 (1.5%) had LVH (mean 13.6 ± 0.9mm, range 13 to 16mm), and of these 50 had a dilated LV cavity with normal diastolic function to indicate physiological left ventricular hypertrophy. Three (0.08%) athletes with LVH had a non-dilated LV cavity and associated deep T-wave inversion that could have been consistent with HCM. However, none of the 3 athletes had any other phenotypic features of HCM on further non-invasive testing and none had first-degree relatives with features of HCM. In conclusion, the prevalence of HCM in elite athletes is significantly less than in the general population; with the demands of strenuous exercise on the cardiovascular system selecting out most individuals with HCM. Study 4 examined 2000 elite athletes in order to identify the prevalence of Long QT syndrome. Three athletes had a QTc value of >500 ms and all exhibited one of: paradoxical prolongation of QTc during exercise, a confirmatory genetic mutation, or prolonged QTc in a first-degree relative. In contrast, none of the athletes with a QTc value of <500 ms had any other features to indicate LQTS. Accordingly, the prevalence of a prolonged QTc interval in elite British athletes is 0.4%. 3) Study 6 examined 300 nationally ranked UK black male athletes (mean age 20.5 years) in comparison to 150 black and white sedentary individuals and 300 highly-trained white male athletes. Black athletes exhibited greater LV wall thickness and cavity size compared with sedentary black and white individuals. Black athletes had greater LV wall thickness compared with white athletes. A minority of black athlete’s exhibit LVH ≥15 mm; proposing that in the absence of cardiac symptoms or a family history of HCM, an LV wall thickness ≥15 mm in black athletes may represent physiologic LVH when the LV cavity is enlarged and diastolic indexes are normal. 7 black athletes (12%) with LVH displaying deep T-wave inversions in leads V1 to V4. In conclusion, in the absence of obvious pathology, these electrical anomalies in black athletes likely represent a normal spectrum of ECG changes in response to physical training. 4) Study 8 examined 17 male participants (age 33.5 ± 6.5 years, 26–40 years) using cardiac magnetic resonance (CMR) and echocardiography before and after a marathon to investigate the relationship between systolic function and diastolic function against biomarkers of cardiac damage. Results demonstrates biomarkers of myocardial cell damage following an acute bout of prolonged exercise are not associated with either systolic or diastolic functional measures, and do not seem to be associated with any detectable myocardial inflammation, oedema, or scarring using either gold standard techniques of gadolinium enhanced CMR or echocardiography respectively. The impact of multiple episodes of prolonged exercise, as experienced by highly trained veteran endurance athlete is not fully understood. 5) Study 10 examined the cardiac structure and function of 12 life-long, competitive endurance veteran athletes (> 50 yrs, mean ± SD marathons 178 ± 209 (range 20 – 650)) against 17 young male endurance athletes (<40 yrs) using echocardiography and CMR with late gadolinium enhancement (LGE) to assess myocardial fibrosis. Lifelong veteran athletes had smaller LV and RV end-diastolic and end-systolic volumes (p<0.05) but maintained LV and RV systolic function compared with young athletes. In 6 (50%) of the veteran athletes LGE of CMR indicated the presence of myocardial fibrosis; no LGE in the young athletes. The prevalence of LGE in veteran athletes was not associated with the number of competitive marathons or ultra-endurance marathons (>50 miles) completed, age, LV and RV end-diastolic volumes or LV mass (p>0.05). In conclusion, there is limited evidence at present demonstrating that cardiovascular re-modelling following lifelong endurance exercise leads to long-term disease progression, cardiovascular disability or SCD.
34

FGF-2: estudo de estrutura e função / FGF-2: Study of structure and function

Alexandre Dermargos Oliveira 01 October 2007 (has links)
FGFs compreendem um grande família de 24 proteínas, participando de processos chaves nos mais variados tecidos, tendo funções parácrina, autócrina e intrácrina, regulando mitogênese, diferenciação celular, morfogênese e cicatrização. Mas, a relação estrutura-função dos FGFs é pobremente entendida. O membro protótipo desta família é o FGF-2, que apresenta quatro isoformas moleculares incluindo a forma de 18 kDa que é secretada e se liga aos receptores específicos (FGFRs) e dispara uma complexa sinalização. As outras isoformas, de alto peso molecular (21, 22 e 22,5 kDa) são expressas por códons alternativos (CUG) e permanecem no interior da célula interagindo com parceiros moleculares desconhecidos. Para antecipar mecanismos e parceiros do FGF-2 HMW foi realizada modelagem molecular desta isoforma que mostrou: uma estrutura do N-terminal da proteína com motivo &#946;&#8594;&#945;&#8594&#946; e manutenção do barril &#946;. A busca por parceiros intracelulares, foi realizada através da técnica do duplo hibrido de levedura, usando um biblioteca de cDNA de cérebro de rato. Foram encontrados 4 possíveis parceiros: BRD2, UBE2I, BRPF1, PC4. Todas essas interações foram confirmadas através do crescimento da levedura em meio sem histidina, produção de &#946;-galactosidase e ensaios de \"pull-down\" com GST. Analises por FACS confirmam que FGF2 não causa apoptose em células adrenais tumorais Y1 de camundongo, mas promovem um acumulo de células na fase S com bloqueio do ciclo celular e da proliferação, configurando uma forma de senescência. Resultados com as células humanas HEK-ER:Ras permitem fazer a seguinte generalização: FGF2 induz senescência em células malignas transformadas pelos oncogenes raso A superexpressão da proteína de fusão FGF-2(18kDa):protA, mas não a da FGF-2(22,5 kDa):protA, protege a célula Y1 da senescência induzida por FGF-2. Por outro lado, a superexpressão destas mesmas isoformas de FGF-2 fusionadas à proteína A em células imortalizadas Balb3T3 não causou transformação celular e nem alterou a resposta mitogênica destas células ao FGF-2 recombinante adicionado ao meio de cultura. Células Y1 quando tratadas com FGF-2 recombinante produz ROS intracelular e libera anions superóxido no meio extracelular. Além disso, o anti-oxidante NAC protege estas células da indução de senescência induzida por FGF-2, sugerindo que ROS pode ser intermediário no disparo de senescência por FGF-2. / FGFs comprise a large fami1y of 24 proteins that play key roles in a number of tissues as local paracrine, autocrine and intracrine regulators of mitogenesis, cellular differentiation, organ morphogenesis and tissue repair. Structure-function relationship among FGFs is still poorly understood. FGF-2, the fami1y prototype member, exists as four molecular species. The 18 kDa form is released to the extracellular milieu and binds to specific receptors (FGFR), initiating a complex array of signals. Other isoforms of higher molecular weights (21, 22 and 22,5 kDa) are translated from alternative codons (CUG) and remain inside of the cell interacting with unknown partners. Aiming to anticipate mechanisms and partners, we modeled the FGF2-HMW molecule, showing that the protein displays &#946;&#8594;&#945;&#8594&#946; motif in the N-terminal region and maintains the &#946;-barrel structure common to ali FGFs. By the yeast two-hybrid method, using a cDNA rat brain library, we found four possible partners for FGF2-HMW: BRD2, UBE2I, BRP1 and PC4. Ali partners were confirmed by yeast growth without histidine, production of &#946;-galactosidase and \"pull-down\" assays with GST. FACS analyses confirmed that FGF2 does not cause apoptosis in mouse Y1 adrenal tumor cells. But, FGF2 inhibited S phase progression blocking cell cycle and proliferation, characterizing a form of senescence. In addition, results obtained with the human HEK-ER:Ras cells support the following general statement: FGF2 triggers senescence in malignant cells transformed by ras oncogenes. Ectopic expression of the fusion protein FGF-2(18 kDa):protA, but not of FGF-2(22,s kDa):protA, protected Y1 cells senescence induced by FGF-2. On the other hand, ectopic expression of FGF-2 isoforms fusioned to protA in Balb3T3 immortalized cells did not cause transformation and neither modified the mitogenic response of this cell to recombinant FGF2. Recombinant FGF-2 stimules Y1 cells to produce intracellular ROS and to release superoxide anions into intracellular medium. Moreover, the ROS scavenger NAC protect Y1 cells from senescence induced by FGF-2, suggesting that ROS may be mediate senescence triggering induced by FGF-2.
35

Construção e análise de mutantes fluorescentes da troponina I / Construction and analysis of fluorescent mutants of troponin I

Deodoro Camargo Silva Gonçalves de Oliveira 10 August 2001 (has links)
A troponina (Tn) regula a contração do músculo estriado esquelético de vertebrados. Ela é composta de três subunidades: troponina I (TnI), troponina C (TnC) e troponina T (TnT). A TnI tem a função inibitória que é neutralizada pela ligação de Ca2+ nos sítios regulatórios do N-domínio da TnC, e a TnT posiciona o complexo no filamento fino. Para monitorar o sinal do Ca2+ sendo transmitido da TnC para a TnI as propriedades espectrais únicas do 5-hidroxitriptofano (5HW) foram utilizadas. O 5HW foi incorporado em mutantes pontuais de TnI com um único códon para triptofano. Foram identificadas duas sondas espectrais intrínsecas na TnI capazes de detectar a ligação de Ca2+ na Tn: as TnIs com 5HW nas posições 100 e 121. Complexos troponina reconstituídos com estes mutantes fluorescentes de TnI, Tn-TnIF100HW e Tn-TnIM121HW, apresentaram respectivamente 12 e 70 % de aumento na intensidade do espectro de emissão devido à ligação de Ca2+ na TnC. Nos complexos binários (TnC-TnI) as TnIs com 5HW nas posições 106 e 121 também captam a ligação do Ca2+ na TnC. A análise da fluorescência destas sondas demonstrou que: 1) as regiões da TnI que respondem ao N-domínio regulatório da TnC ocupado com Ca2+ são a região inibitória da TnI, resíduos 96 até 116, e a região vizinha que inclui a posição 121 da TnI; 2) mutações pontuais e a incorporação de 5HW na TnI podem afetar tanto a afinidade como a cooperatividade da ligação de Ca2+ na TnC, confirmando o papel da TnI em modular a afinidade da TnC por Ca2+; 3) as constantes de dissociação de Ca2+ surpreendentemente altas, Kd ~ 10-8 M, calculadas a partir dos sinais das sondas na região inibitória da TnI, sugerem a possibilidade de que os sítios do domínio N-terminal da TnC sejam os sítios de ligação de Ca2+ de maior afinidade no complexo troponina. / Vertebrate striated muscle contraction is regulated by troponin (Tn). Tn is composed of three subunits: troponin I (TnI), troponin C (TnC) and troponin T (TnT). TnI has an inhibitory role that is neutralized by calcium binding to the regulatory sites in the N-domain of TnC, and TnT positions the troponin complex on the thin filament. In order to follow the Ca2+ induced conformational change that is transmitted from TnC to TnI, the unique spectral properties of 5-hydroxytryptophan (5HW) incorporated as point-mutants of TnI were used. It was possible to identify two new TnI intrinsic spectral probes sensitive to Ca2+ binding to Tn: TnI with single 5HW at positions 100 and 121. Trimeric troponin complexes reconstituted with two fluorescent mutants of TnI, Tn-TnIF100HW and Tn-TnIM121HW, showed respectively 12 and 70 % increase in the emission spectra when Ca2+ bound to TnC. In the binary complexes (TnC-TnI) two TnIs with 5HW at positions 106 and 121 were also sensitive to Ca2+ binding to TnC. Fluorescence analysis of these probes showed: 1) the regions in TnI that respond to Ca2+ binding to the regulatory N-domain of TnC are the inhibitory region of TnI (residues 96 to 116), and a neighbor region that includes position 121; 2) point mutations and incorporation of 5HW in TnI can affect both the affinity and the cooperativity of Ca2+ binding to TnC, confirming the role of TnI as a modulator of the Ca2+ affinity of TnC; 3) the high dissociation constant for sites in the N-terminal domain of TnC (Kd ~ 10-8 M), derived from data using probes in the inhibitory region of TnI suggested the possibility that these sites are the high affinity Ca2+ binding sites in the troponin complex.
36

Magnetic Resonance Imaging Guided Neuromodulation of Gastric Physiology

Kun-Han Lu (6615527) 25 June 2020 (has links)
The stomach is a digestive organ in the gastrointestinal tract that regulates food intake and paces digestion of nutrients and fluids. The emptying and motility patterns of the stomach are crucial rate-determining processes in maintaining energy homeostasis in the body. Dysregulation of gastric functions often leads to distressing conditions such as gastroesophageal reflux diseases, functional dyspepsia, gastroparesis and obesity. Gastric disorders affect more than 60 million people in the US, producing significant medical and economic burden. These diseases are often chronic and greatly compromise quality of life. As the causes of these diseases remain largely unknown, effects of current pharmacological, dietary, or surgical treatments are often dismal. In this regard, neuromodulation of peripheral nerves emerges as a promising electroceutical therapy for remedying gastric disorders. However, therapeutic effects were shown to be modest, largely due to the inability to validate or calibrate the efficacy and stability of neuromodulation methods with appropriate physiological readouts. To address these problems, here I developed a non-invasive, repeatable online high-resolution magnetic resonance imaging protocol, empowered with advanced image processing algorithms, to track gastric emptying, antral motility, pyloric motility, intestinal filling and absorption in a rat model. The protocol can be used to guide tuning and optimization of stimulation parameters of neuromodulation without perturbing ongoing and spontaneous physiology. The proposed technology and findings are expected to pave the way for the use of gastric MRI to evaluate the efficacy of therapeutics in treating gastric disorders under both preclinical and clinical settings.
37

Structural and biochemical insights into catalytic mechanisms of carotenoid cleavage oxygenases

Sui, Xuewu 08 February 2017 (has links)
No description available.
38

Интеллектуальные системы: от теории к технологии : магистерская диссертация / Intelligent systems: from theory to technology

Томюк, М. А., Tomyuk, M. A. January 2016 (has links)
Интеллектуальные системы применяются человеком во всех сферах жизнедеятельности, при этом существенно изменяя жизненные условия людей. В диссертации рассматриваются теоретические и технологические аспекты интеллектуальных систем. Автор понимает интеллектуальную систему как информационно-вычислительную систему с имеющейся базой знаний, алгоритмом действий и решающую задачи без помощи оператора. Для проектирования интеллектуальных систем важен системный подход. В диссертации искусственный интеллект берется в антропологическом измерении и рассматриваются разные подходы к исследованиям искусственного интеллекта. Интеллектуальные системы в диссертации иследованы в технологическом аспекте, в том числе описаны структурные и функциональные компоненты интеллектуальных систем. В ходе проведенного исследования были рассмотрены возможные варианты взаимодействия в системе «человек – техника» и заявлена актуальность проблемы поиска оптимальных взаимоотношений в системе «человек – интеллектуальная система». / Intelligent systems are used in all spheres of life, thus they significantly are changing the conditions of human life. The dissertation is devoted to theoretical and technological aspects of intelligent systems. The author understands the intelligent system as an information processing system with the existing knowledge base, algorithm of actions and solving problems without operator assistance. The systemic approach is important for the design of intelligent systems. The dissertation takes an artificial intelligence in the anthropological dimension and discusses different approaches to investigations of artificial intelligence. Intelligent systems in the dissertation are taken in the technological aspect, including description of the structural and functional components of intelligent systems. In the represent study the possible options for interaction in the system «man - technique» are examined and there is declared the urgency of the problem of finding the optimal relations in the system «man - intelligent system».
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Estudio de las Proteinas Quinasas C clasicas y su interaccion con ligandos y membranas

Torrecillas Sánchez, Alejandro 12 September 2003 (has links)
La Proteína Quinasa C (PKC) participa en numerosas funciones fisiológicas a través de distintas rutas de señalización celular. Las isoenzimas clásicas están reguladas por diacilglicerol, ésteres de forbol, calcio y fosfolípidos aniónicos. La presencia de insaturaciones en los diacilgliceroles de la membrana modifica la activación de la PKC alfa.Los dominios C2 de PKC clásicas presentan dos tipos de sitios de unión de calcio y enlazan tres cationes de manera similar. La desnaturalización térmica de estos dominios se desplazó hacia mayores temperaturas con concentraciones crecientes de calcio, siendo mayor el efecto en presencia de fosfolípidos aniónicos. La estructura secundaria de los dominios C2 de PKC clásicas así como de la PKC alfa completa mostró una elevada proporción de hoja beta. La adición de fosfolípidos aniónicos y PMA respectivamente provocó un mayor efecto protector frente a la desnaturalización térmica que sólo con calcio. / Protein Kinase C (PKC) plays a key role in several physiological functions through different celullar signalling pathways. The classical isoenzymes are regulated by diacylglycerol, phorbol esters, calcium, and anionic phospholipids.The presence of insaturations in the membrane diacylglycerols modifies the PKC alpha activation.C2 domains of classical PKC have two different binding sites for calcium, and bind three molecules in a similar way. The thermal denaturation of these domains moved to higher temperatures with increasing calcium concentrations, being this effect hingher in the presence of anionic phospholipids. The secondary structure of both C2 domains from classical PKC and PKC alpha showed a high contribution of beta-sheet component. The addition of anionic phospholipids and PMA produced the main protection against thermal denaturation, respectively
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Algebraizace a parametrizace přechodových relací mezi strukturovanými objekty s aplikacemi v oblasti neuronových sítí / Algebraization and Parameterization Transition Relations between Structured Objects with Applications in the Field of Neural Networks

Smetana, Bedřich January 2020 (has links)
The dissertation thesis investigates the modeling of the neural network activity with a focus on a multilayer forward neural network (MLP – Multi Layer Perceptron). In this often used structure of neural networks, time-varying neurons are used, along with an analogy in modeling hyperstructures of linear differential operators. Using a finite lemma and defined hyperoperation, a hyperstructure composed of neurons is defined for a given transient function. There are examined their properties with an emphasis on structures with a layout.

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