Esse estudo avaliou o efeito da glicose sobre a atividade da PKA e sua interação com o SGLT1 e os trocadores Na+/H+ (NHE1 e NHE3). As células HEK-293 foram transfectadas com hSGLT1 wild type (WT) ou mutante (S418H) e tratadas 20 dias com DMEM contendo glicose 5 mM ou 25 mM. Foi avaliada a expressão de hSGLT1, hSGLT1+GFP, NHE1, NHE3 e PKA. Foi avaliada a expressão de hSGLT1+GFP e SGLT2 na membrana, com ou sem H-89, Manose, Sucrose e Filipina. Foi avaliada a velocidade de recuperação do pH intracelular (dpHi/dt), onde a solução de NH4Cl foi substituída por uma solução de glicose 5 ou 25 mM ou ambas as soluções na vigência de H-89 ou S3226. Esses dados indicam que o aumento do AMPc pela glicose altera a expressão e atividade dos SGLTs e NHEs. Nossos experimentos utilizando a transfecção do SGLT1 demonstraram que as células regulam a distribuição de SGLT1 e 2 na membrana, frente ao aumento extracelular desse substrato e que as vias ativadas pela glicose afetam a capacidade de recuperação do pH intracelular (pHi), através do NHE3. / This study evaluated the effect of glucose on the PKA activity and its interaction with SGLT1 and the Na+/H+ exchanger (NHE1 and NHE3). The HEK-293 cells were transfected with hSGLT1 wild type (WT) or mutant (S418H) and treated 20 days with DMEM containing glucose 5 mM or 25 mM. The hSGLT1, hSGLT1+GFP, NHE1, NHE3 and PKA expression was analyzed. The surface hSGLT1+GFP and SGLT2 expression with or without H-89, Manose, Sucrose and Filipina was evaluated. The pHi recovery rate (dpHi/dt) was analyzed replacing the NH4Cl solution to glucose 5 or 25 mM solution or both with H-89 or S3226. These data indicate that the glucose increases the cAMP concentration and alters the expression and activity of SGLTs and NHEs. Our experiments using SGLT1 transfection demonstrated that, in the treatment with high glucose concentration, HEK-293 cells regulate the SGLT1 and 2 cellular distribution and that the pathways activated by glucose impair the pHi recovery rate, through the NHE3.

As células glias de Müller são capazes de gerar novos neurônios retinianos em resposta a lesões, atuando como uma possível fonte para regeneração retiniana. Nesse contexto, as GTPases Rho podem ter um papel interessante, visto que regulam múltiplas vias de sinalização que controlam, por exemplo, a transcrição gênica, sobrevivência e proliferação celular. No presente estudo analisamos a participação de um dos membros dessa família (Rac1) na proliferação de células gliais de Müller da retina de galinhas após lesão excitotóxica com N-Metil-D-Aspartato (NMDA). A injeção intraocular de NMDA promoveu extensa proliferação de células gliais de Müller. A inibição de Rac1 com NSC23766 não alterou a quantidade de células que entraram no ciclo celular, mas, provocou um retardo em sua progressão. Esses resultados sugerem um importante papel para a GTPase Rac1 na regulação da proliferação de células gliais de Müller em resposta a lesões retinianas. / Müller glial cells may generate new neurons in response to retinal injury, acting as a potential source for retinal regeneration. In this context, Rho GTPases may have an interesting role, since they regulate multiple signaling pathways that control, for example, gene transcription, cell proliferation and survival. This study analyzed the involvement of a member of this family (Rac1) in the proliferation of Müller glial cells of chick retina after excitotoxic injury with N-methyl-D-aspartate (NMDA). Intraocular injection of NMDA promoted extensive Müller glia proliferation. Rac1 inhibition with NSC23766 did not affect the cell cycle entry, but a delay in cell cycle progression was observed. These results suggest an important role for Rac1 in the regulation of Müller glial cells proliferation in response to retinal injury.

Não consta resumo na publicação. / Pectinesterase (E C 3.1.1.11) was extracted from papaya (Carica papaya L.) tissue and purified 4,48 fold by fractionated ammonium sulphate precipitation, dialysis and chromatography on DEAE-celulose and Sephadex G-100. Extraction conditions of enzyme were studied and their properties characterized. The increase on the activity of pectinesterase was practically followed by increase on the content of soluble pectin, during ripening. The molecular weight of the enzyme eluted in one peak of activity was 53.000 daltons. The pectinesterase has its maximum activity at pH 8,0 and at 0,2 M of NaCl. Optimum temperature for the enzyme assay was 60°C. The enzymatic reaction was linear with the time and protein concentration. With citric pectin as substrate, pectinesterase had a Km of 0,012% and was inhibited competitively by polygalacturonic acid with a Ki of 0,007%. Papaya pectinesterase was inhibited by sucrose, glucose and glicerol.

Não consta resumo na publicação. / Pectinesterase (E C 3.1.1.11) was extracted from papaya (Carica papaya L.) tissue and purified 4,48 fold by fractionated ammonium sulphate precipitation, dialysis and chromatography on DEAE-celulose and Sephadex G-100. Extraction conditions of enzyme were studied and their properties characterized. The increase on the activity of pectinesterase was practically followed by increase on the content of soluble pectin, during ripening. The molecular weight of the enzyme eluted in one peak of activity was 53.000 daltons. The pectinesterase has its maximum activity at pH 8,0 and at 0,2 M of NaCl. Optimum temperature for the enzyme assay was 60°C. The enzymatic reaction was linear with the time and protein concentration. With citric pectin as substrate, pectinesterase had a Km of 0,012% and was inhibited competitively by polygalacturonic acid with a Ki of 0,007%. Papaya pectinesterase was inhibited by sucrose, glucose and glicerol.