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No description available.

by Chan Chun-wai, Francis. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1993. / Includes bibliographical references (leaves 105-116). / Abstract --- p.I / Acknowledgments --- p.III / Abbreviations --- p.IV / Objectives --- p.VI / Content --- p.VII / Chapter Section 1 --- Introduction / Chapter I. --- Preamble --- p.1 / Chapter II. --- Characteristics of Cell Death Process --- p.1 / Chapter II.1. --- Necrosis --- p.1 / Chapter II.2. --- Apoptosis-Programmed Cell Death --- p.5 / Chapter III. --- Triggering of Programmed Cell Death --- p.10 / Chapter IV. --- DNA Fragmentation and Activation of Endogenous Endonuclease --- p.12 / Chapter V. --- Signal Transduction Leading to Programmed Cell Death --- p.14 / Chapter V.1. --- Role of Calcium Ion --- p.14 / Chapter V.2. --- Role of Protein Kinase C --- p.15 / Chapter V.3. --- Protein Dephosphorylation by Phosphatases --- p.16 / Chapter V.4. --- Role of Adenosine 3':5'-cyclic Monophosphate --- p.17 / Chapter V.5. --- Other Signaling Mechanisms --- p.17 / Chapter VI. --- Gene Regulation in Programmed Cell Death --- p.19 / Chapter VI. 1. --- Gene Expression in Programmed cell death --- p.19 / Chapter VI. 1.1 . --- Tissue Transglutaminase --- p.19 / Chapter VI. 1.2. --- Poly (ADP-ribose) Polymerase --- p.20 / Chapter VI. 1.3. --- Testosterone-Repressed Prostate Message-2 Gene --- p.20 / Chapter VI. 1.4. --- Other Programmed Cell Death Associated Gene Expressions --- p.21 / Chapter VI.2. --- Protooncogene Regulation in Programmed Cell Death --- p.22 / Chapter VI.2.1. --- bcl-2 Expression --- p.22 / Chapter VI.2.2. --- c-myc Expression --- p.23 / Chapter VII. --- Concanavalin A and succinylated Concanavalin A --- p.25 / Chapter VII. 1. --- Physiochemical Characterization --- p.25 / Chapter VII.2. --- Cellular Response to Concanavalin A --- p.29 / Chapter VIII. --- Features of Murine Macrophage Cell Line PU5-1.8 and Normal Macrophages --- p.32 / Chapter Section 2 --- Materials and Methods / Chapter I. --- Materials --- p.33 / Chapter II. --- Cell Culture --- p.33 / Chapter III. --- [Methyl-3H]-Thymidine Incorporation Assay --- p.34 / Chapter IV. --- [Methyl-3H]-Thymidine Release Assay --- p.34 / Chapter V. --- "3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT ) Cell Death Assay" --- p.35 / Chapter VI. --- Identification of Cell Death using DNA Chelating Fluorescence Probes´ؤFluorescent Microscopy and Confocal Laser Microscopy --- p.35 / Chapter VII. --- Analysis of DNA Fragmentation --- p.37 / Chapter VIII. --- Determination of Fluxes by Confocal Laser Microscopy --- p.38 / Chapter IX. --- Determination of PKC Activation by Western Blotting and Immunocytochemistry --- p.39 / Chapter X. --- Statistical Analysis --- p.41 / Chapter Section 3 --- Results / Chapter I. --- Concanavalin A was a Cell Death Causing Agent in PU5-1.8 cells --- p.42 / Chapter I.1 --- Con A Reduced the Cell Proliferation in PU5-1.8 cells --- p.42 / Chapter I.2. --- Con A Exhibited Cytotoxic Effect to PU5-1.8 cells --- p.44 / Chapter I.3. --- Con A Exhibited Cytotoxic Effect on Normal Peritoneal Macrophages --- p.46 / Chapter I.4. --- Succinylated Concanavalin A Showed a Weaker Cytotoxic Effect in the PU5-1.8 cells --- p.46 / Chapter I.5. --- α-D-Methylmannopyranoside Inhibited the Cytotoxic Effect of Con A in PU5-1.8 cells --- p.50 / Chapter I.6. --- FCS Inhibited the Con A-induced cell death of PU5-1.8 cells --- p.52 / Chapter II. --- Concanavalin A was an Apoptosis Causing Agentin PU5-1.8 cells --- p.57 / Chapter II. 1. --- Con A Induced Apoptosis in PU5-1.8 cells --- p.57 / Chapter II. 2. --- Con A Enhanced the Release of DNA in PU5-1.8 cell --- p.63 / Chapter II. 3. --- Con A Induced DNA fragmentation in PU5-1.8 cells --- p.63 / Chapter II.4. --- Cycloheximide Inhibited the Con A-Induced Cell Death in PU5-1.8 cells --- p.67 / Chapter II.5. --- Nicotinamide Inhibited the Con A-Induced Cell Death in PU5-1.8 cells --- p.71 / Chapter III. --- Signaling elicited by Concanavalin A --- p.74 / Chapter III.1. --- Con A Increased Intracellular Free Calcium Ion Concentration of PU5-1.8 cells --- p.74 / Chapter III. 1.1. --- Con A Induced Ca2+ Mobilization in PU5-1.8 cells --- p.74 / Chapter III. 1.2. --- Con A Induced the Ca2+ Influx and Intracellular Ca2+ Mobilization --- p.78 / Chapter III. 1.3. --- BAPTA-AM Inhibited the Ca2+ Mobilization in PU5-1.8 cells Stimulated by Con A --- p.80 / Chapter III.2. --- Role of Protein kinase C --- p.86 / Chapter III.2.1. --- Con A Increased the amount of PKC in PU5-1.8 cells --- p.86 / Chapter III.2.2. --- Con A translocated the Protein Kinase C from Cytosol into Subnuclear Region --- p.86 / Chapter III.2.3. --- The Cell Death Induced by Con A Is Partially Inhibited by PKC Depletion But not by Staurosporine --- p.89 / Chapter Section 4 --- Discussions / Chapter I. --- PU5-1.8 cells as a Model for the Study of Cell Deathin Macrophages --- p.94 / Chapter II. --- Concanavalin A caused Cell Death in PU5-1.8 cells --- p.95 / Chapter III. --- Concanavalin A induced Programmed Cell Death in PU5-1.8 cells --- p.97 / Chapter IV. --- Increase in Intracellular Calcium was not Required in Con A-induced Cell Death --- p.100 / Chapter V. --- Activation of Protein Kinase C was Partially Required for Con A-induced Cell Death --- p.101 / Chapter VI. --- General Discussions --- p.102 / Chapter Section 5 --- Bibliography --- p.104 / Reference --- p.104

Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico / Os PeptÃdeos NatriurÃticos (NPs) tÃm significativa participaÃÃo na regulaÃÃo na homeostasia cardiovascular, renal e endÃcrina, e tÃm sido descritos nos venenos de serpentes peÃonhentas. A Crotalus durissus cascavella, uma serpente terrÃcola caracterÃstica da caatinga do Nordeste do Brasil, possui em seu veneno total um NP (NPCdc), ao qual sÃo relatados efeitos vasculares e renais. O objetivo desse trabalho foi sintetizar em fase sÃlida o NPCdc e avaliar suas aÃÃes renais atravÃs da perfusÃo de rim isolado e em cultura de cÃlulas tubulares renais da linhagem MDCK e LLC-MK2. Rins de ratos Wistar machos, pesando entre 250-300 g, foram excisados cirurgicamente e perfundidos com soluÃÃo de Krebs-Henseleit modificada com 6% p/v de albumina bovina previamente dialisada. Foram investigados os efeitos do NPCdc em quatro concentraÃÃes (0,03 Âg/mL; 0,1 Âg/mL; 0,3 Âg/mL e 1 Âg/mL; n=6). As cÃlulas MDCK e LLC-MK2 foram cultivadas em meio de cultura RPMI 1640 suplementado com 10% v/v de Soro Bovino Fetal e entÃo avaliadas na presenÃa do NPCdc em diversas concentraÃÃes em um perÃodo de incubaÃÃo de 24 horas. ApÃs esse perÃodo, foram realizados ensaios de viabilidade celular. Os dados foram comparados estatisticamente considerando P<0,05. Houve aumento na pressÃo de perfusÃo (PP) em 0,03 Âg/mL e reduÃÃo em 1 Âg/mL. A resistÃncia vascular renal (RVR) apresentou aumento em 0,03 Âg/mL. O fluxo urinÃrio (FU) aumentou em 0,03 Âg/mL e diminuiu em 0,1 Âg/mL e 1 Âg/mL. O ritmo de filtraÃÃo glomerular (RFG) encontrou-se diminuÃdo nas quatro concentraÃÃes testadas. O clearance osmolar (COsm) apresentou-se aumentado em 0,03 &#956;g/mL e reduzido em 0,1 &#956;g/mL e 1 &#956;g/mL. O percentual de transporte tubular total e proximal de sÃdio (%TNa+ e %TpNa+, respectivamente) e cloreto (%TCl- e %TpCl-, respectivamente) apresentaram reduÃÃes nas quatro concentraÃÃes testadas. JÃ o percentual de transporte tubular total e proximal de potÃssio (%TK+ e %TpK+, respectivamente) apresentaram-se reduzidos em 0,03 &#956;g/mL e 0,3 &#956;g/mL. A anÃlise histopatolÃgica mostrou a presenÃa de alteraÃÃes morfolÃgicas significativas, como degeneraÃÃo hidrÃpica concentraÃÃo-dependente em todas as concentraÃÃes, juntamente com discreta a moderada deposiÃÃo de material proteÃceo nos tÃbulos na concentraÃÃo de 0,03 &#956;g/mL. Na cultura de cÃlulas MDCK e LLC-MK2, porÃm, o NPCdc nÃo foi capaz de diminuir a viabilidade celular. Esses resultados demonstram que o NPCdc modificou todos os parÃmetros avaliados na perfusÃo de rim isolado, alÃm de revelar alteraÃÃes de carÃter citotÃxico na anÃlise histopatolÃgica dos mesmos, todavia, nÃo as apresentando em culturas de cÃlulas tubulares renais. / Natriuretic Peptides (NPs) have significant interest in regulating the cardiovascular, renal and endocrine homeostasis, and have been described in the venom of venomous snakes. Crotalus durissus cascavella, a characteristic terrestrial snake of caatinga biome of northeastern Brazil, has in his whole venom an NP (NPCdc), of which are reported vascular and renal effects. The aim of this study was to synthesize NPCdc in solid phase and evaluate its renal actions through isolated kidney perfusion and culture of renal tubular cells of MDCK and LLC-MK2 line. Kidneys from male Wistar rats weighing 250-300 g were surgically excised and perfused with modified Krebs-Henseleit solution with 6 g% of previously dialyzed bovine serum albumin. The effects of NPCdc were investigated in four concentrations (0.03 &#956;g/mL, 0.1 &#956;g/mL, 0.3 &#956;g/mL and 1 &#956;g/mL, n=6). MDCK and LLC-MK2 cells were cultured in RPMI 1640 culture medium supplemented with 10% v/v Fetal Bovine Serum and then evaluated in presence of several concentrations of NPCdc at an incubation period of 24 hours. After this period, cell viability assays were performed. Data were statistically compared considering P<0.05. There was increase in perfusion pressure (PP) in 0.03 &#956;g/mL and reduction in 1 &#956;g/mL. Renal vascular resistance (RVR) was increased at 0.03 &#956;g/mL. Urinary flow (UF) increased in 0.03 &#956;g/mL and decreased in 0.1 &#956;g/mL and 1 &#956;g/mL. The glomerular filtration rate (GFR) was reduced at all the concentrations tested. Osmolar clearance (OsmC) was increased in 0.03 &#956;g/mL and reduced in 0.1 &#956;g/mL and 1 &#956;g/mL. Percentage of the total and proximal tubular transport of sodium (%TNa+ and %pTNa+, respectively) and chloride (TCl-% and pTCl-%, respectively) showed reductions at all concentrations tested. Percentage of the total proximal tubular transport and potassium (%TK+ and pTK+%, respectively) were reduced in 0.03 &#956;g/mL and 0.3 &#956;g/mL. The histopathological analysis revealed the presence of significant morphological changes, such as concentration-dependent hydropic degeneration at all concentrations, along with mild to moderate deposition of proteinaceous material in the tubules in concentration 0.03 &#956;g/mL. In the culture of MDCK and LLC-MK2 cells, however, NPCdc was not able to lower cell viability. These results demonstrate that NPCdc modified all parameters assessed in renal perfusion of isolated kidney, and showed cytotoxic alterations in histopathological analysis, however, not presenting it in cultures of renal tubular cells.

No description available.

Thesis (Ph. D.)--Case Western Reserve University, 2005. / [School of Medicine] The Molecular Virology Training Program. Includes bibliographical references. Available online via OhioLINK's ETD Center.

A new nanodosimetry-based cell survival model for mixed high- and low-LET radiations has been developed. The new model employs three dosimetry quantities and three biological quantities. The three dosimetry quantities are related to energy depositions at two nanometer scales, 5nm and 25nm. The three biological quantities are related to lesion production and interaction probabilities, and lesion repair rate. The model assumes that the lesions created at the two nanometer scales are directly or indirectly responsible for cell death depending on the lesions interaction and repair rate. The cell survival fraction derived from the new model can be expressed by the familiar dose-dependent linear quadratic formula. The coefficients alpha and beta are based on the three nanodosimetry quantities and the three biological quantities. Validation of the new model has been performed both by using published data and by the experimental data obtained. Published cell survival curves for V-79 Chinese hamster cells irradiated with various LET of radiations were used for validation. The new model was applied to radiation therapy by irradiating V-79 cells with mixed fission neutron and gamma-rays. The results show that the new model has been successfully used in a mixed n+g field to predict the synergistic effect between neutron and gamma-ray lesions and the RBE for fission neutrons.

Procedimentos endodônticos regenerativos proporcionaram mudanças no tratamento de pacientes com dentes imaturos e periodontite apical possibilitando desenvolvimento radicular completo e menor incidência de fratura dental. Medicações intracanal são utilizadas para a realização da desinfecção; entretanto, o efeito delas sobre às células da papila apical é pouco elucidado. Adicionalmente, pouco se conhece a respeito do efeito destas substâncias sobre células previamente submetidas à condição pró- inflamatória. O objetivo deste estudo foi avaliar a citotoxicidade de medicações intracanal empregadas em procedimentos regenerativos em Endodontia sobre células de papila humana em cultura em condição fisiológica e ativada. Cultura de células foi estabelecida a partir da papila apical removida de um terceiro molar imaturo extraído. As substâncias estudadas foram a pasta tripla antibiótica modificada: ciprofloxacina, metronidazol e cefalosporina (1:1:1); CFC: ciprofloxacina, metronidazol e hidróxido de cálcio (1:1:2) e CFC modificado: ciprofloxacina, metronidazol e hidróxido de cálcio (2:2:1). Parte das células foram estimuladas previamente por ácido lipoteicóico (LTA) de Enterococcus faecalis por 7 dias. Após plaqueamento, células foram expostas a concentrações crescentes das medicações por 1, 3, 5 e 7 dias. Foram avaliados viabilidade celular por meio de brometo de 3-(4,5-dimetiliazol-2-il)-2,5-difeniltetrazólio (MTT) e liberação de óxido nítrico (NO) pelo método de Griess. A análise estatística foi realizada por meio de análise de variância a 1 critério (ANOVA) seguida de pós teste de Tukey, com nível de significância de 5%. O CFC modificado foi a medicação que demonstrou menor efeito citotóxico sobre a viabilidade celular nos tempos experimentais estudados, o CFC promoveu queda da viabilidade celular especialmente após 7 dias de contato. A pasta tripla antibiótica modificada resultou em comprometimento importante da viabilidade podendo ser considerada a mais citotóxica. A ativação celular por LTA resultou em níveis aumentados de atividade mitocondrial para todas as medicações sendo mais evidente nos períodos experimentais mais longos. A ativação celular também contribuiu para níveis maiores de óxido nítrico. Conclui-se que o efeito citotóxico das medicações testadas é dependente de sua concentração, tempo de contato e condição celular, sendo a pasta tripla antibiótica modificada a mais citotóxica em concentrações elevadas podendo implicar clinicamente na diminuição da viabilidade das células da papila apical podendo diminuir o sucesso dos procedimentos regenerativos. / Regenerative Endodontic procedures have provided changes in treatment of patients with immature teeth and apical periodontitis enabling full root development and lower incidence of dental fracture. Intracanal dressings are used for disinfection; however, their effect on apical papilla cells is poorly elucidated. Additionally, the effect of these substances on cells previously subjected to proinflammatory condition is still unknown. The aim of this study was to evaluate the cytotoxicity of intracanal dressings used in Endodontics regenerative procedures on cultured human apical papilla cells at physiologic and activated condition. Cell culture was established from the apical papilla removed from an extracted immature third molar. The substances studied were triple antibiotic modified paste: ciprofloxacin, metronidazole and cephalosporin (1:1:1); CFC: ciprofloxacin, metronidazole and calcium hydroxide (1:1:2) and modified CFC: ciprofloxacin , metronidazole and calcium hydroxide (2:2:1). Part of the cells was stimulated previously with lipotheichoic acid (LTA) of Enterococcus faecalis por 7 days. Once plated, cells were exposed to increasing concentration of the medications for 1, 3, 5 and 7 days. Cell viability was evaluated by means of 3-bromide (4.5-dimetiliazol-2-yl) -2.5-difeniltetraze (MTT) and Nitric Oxide (NO) release was assessed by the Griess method. The statistical analysis was done through analysis of variance with 1 criteria (ANOVA) followed by Tukey test with 5% of significance level. Modified CFC was the medication that demonstrated the less cytotoxic effect on cell viabilityat the experimental periods studied while CFC promoted significant decrease on cell viability specially after 7 days of contact. The modified triple antibiotic paste resulted in important alteration of cell viability being considered the most citotoxic. Cellular activation by LTA resulted in increased levels of mitochondrial activity for all medications being more evident at the longer experimental periods. Cellular activation also contributed to higher levels of nitric oxide release. In conclusion, the cytotoxic effect of the tested medications is dependent on concentration, time of contact and cellular condition, being the triple antibiotic modified paste the most cytotoxic in high concentrations leading clinically in the decreased of the cells viability of the apical papilla, decreasing the success of regenerative procedures.

Com a evolução do Biomateriais houve melhorias nas opções de tratamentos e atualmente são utilizados em substituição de partes do corpo que foram perdidas e promovem a recuperação de funções biológicas. Dentre eles existem as chamadas Biocerâmicas, que incluem alumina, zircônia e derivadas de fosfato de cálcio. A hidroxiapatita possui composição e estrutura minerais semelhantes à fase mineral óssea e apresenta como propriedades a biocompatibilidade, osteocondutividade e bioatividade. O trabalho avaliou a viabilidade celular em cerâmica de hidroxiapatita experimental de origem bovina em comparação com dois tipos de zircônia comerciais e liga de titânio comercialmente puro, para que futuramente possa ser utilizada como material base para implantes dentários. A avaliação in vitro foi realizada por meio de testes nos quais células pré-osteoblásticas cultivadas de linhagem murina MC3T3-E1 foram colocadas em contato indireto e direto com estes materiais. Para viabilidade celular (n=8) foram feitos testes de ensaio MTT e Cristal Violeta em duplicata e após 24, 48 e 72 horas os níveis de absorbâncias foram analisados por meio de espectrofotometria no leitor de Elisa. Para as analises por microscopia eletrônica de varredura (n=6) as células foram plaqueadas diretamente sobre as superfícies dos discos, fixadas em vapor de tetróxido de ósmio 2% após 24 e 48 horas, seguido da metalização após 48 horas da fixação das células para análise em Microscópio Eletrônico de Varredura. Os resultados para viabilidade indireta foram submetidos ao teste paramétrico ANOVA, seguido de teste de Tukey (p<0,05). Tanto no teste de MTT quanto no Cristal Violeta, de acordo com o grupo controle positivo, todos os grupos apresentaram resultados satisfatórios. A cerâmica de hidroxiapatita não apresentou diferença estatística significante, demonstrando não ser um material citotóxico. Pelas imagens geradas no MEV do teste de viabilidade direta, verificou-se que houve adesão e proliferação das células nos dois períodos sobre as superfícies dos materiais. Portanto, pode-se afirmar que a cerâmica de hidroxiapatita apresentou-se como um material biocompatível. / With the evolution biomaterials there were improvements in treatment options, and are currently used in replacement body parts that were lost and promote the recovery of biological functions. Among them are the bioceramic which include alumina, zirconia and calcium phosphate derivative. Hydroxyapatite has mineral composition and structure similar to bone mineral phase and can be used as a biomaterial having biocompatibility, osteoconductivity and bioactivity. The study evaluated the cell viability in experimental hydroxyapatite ceramic bovine compared the two types of commercial zirconia and titanium alloy commercially pure, so that in future it can be used as base material for dental implants. In vitro evaluation was carried by means of tests in which the pre-osteoblastic cells MC3T3-E1 murine lineage cultured were placed in indirect and direct contact with these materials. For cell viability (n=8) were carried MTT assay and Crystal Violet tests in duplicate and after 24, 48 and 72 hours the absorbance levels were analyzed by spectrophotometry Elisa reader. For analysis by Scanning Electron Microscope variable pressure (n = 6) cells were plated directly on the discs surfaces, fixed in osmium tetroxide steam 2% after 24 and 48 hours, followed by metallization after 48 of cells fixation. The results for the cell viability were submitted to parametric test ANOVA, followed by Tukey test (p<0.05). Both in the MTT assay as Crystal Violet all groups exhibited satisfactory results absent cytotoxicity. By means of the SEM images produced, it was found that there was adhesion and proliferation of cells on the materials surfaces in the two periods. Therefore, it can be stated that the hydroxyapatite ceramic was presented as a biocompatible material.

Procedimentos endodônticos regenerativos proporcionaram mudanças no tratamento de pacientes com dentes imaturos e periodontite apical possibilitando desenvolvimento radicular completo e menor incidência de fratura dental. Medicações intracanal são utilizadas para a realização da desinfecção; entretanto, o efeito delas sobre às células da papila apical é pouco elucidado. Adicionalmente, pouco se conhece a respeito do efeito destas substâncias sobre células previamente submetidas à condição pró- inflamatória. O objetivo deste estudo foi avaliar a citotoxicidade de medicações intracanal empregadas em procedimentos regenerativos em Endodontia sobre células de papila humana em cultura em condição fisiológica e ativada. Cultura de células foi estabelecida a partir da papila apical removida de um terceiro molar imaturo extraído. As substâncias estudadas foram a pasta tripla antibiótica modificada: ciprofloxacina, metronidazol e cefalosporina (1:1:1); CFC: ciprofloxacina, metronidazol e hidróxido de cálcio (1:1:2) e CFC modificado: ciprofloxacina, metronidazol e hidróxido de cálcio (2:2:1). Parte das células foram estimuladas previamente por ácido lipoteicóico (LTA) de Enterococcus faecalis por 7 dias. Após plaqueamento, células foram expostas a concentrações crescentes das medicações por 1, 3, 5 e 7 dias. Foram avaliados viabilidade celular por meio de brometo de 3-(4,5-dimetiliazol-2-il)-2,5-difeniltetrazólio (MTT) e liberação de óxido nítrico (NO) pelo método de Griess. A análise estatística foi realizada por meio de análise de variância a 1 critério (ANOVA) seguida de pós teste de Tukey, com nível de significância de 5%. O CFC modificado foi a medicação que demonstrou menor efeito citotóxico sobre a viabilidade celular nos tempos experimentais estudados, o CFC promoveu queda da viabilidade celular especialmente após 7 dias de contato. A pasta tripla antibiótica modificada resultou em comprometimento importante da viabilidade podendo ser considerada a mais citotóxica. A ativação celular por LTA resultou em níveis aumentados de atividade mitocondrial para todas as medicações sendo mais evidente nos períodos experimentais mais longos. A ativação celular também contribuiu para níveis maiores de óxido nítrico. Conclui-se que o efeito citotóxico das medicações testadas é dependente de sua concentração, tempo de contato e condição celular, sendo a pasta tripla antibiótica modificada a mais citotóxica em concentrações elevadas podendo implicar clinicamente na diminuição da viabilidade das células da papila apical podendo diminuir o sucesso dos procedimentos regenerativos. / Regenerative Endodontic procedures have provided changes in treatment of patients with immature teeth and apical periodontitis enabling full root development and lower incidence of dental fracture. Intracanal dressings are used for disinfection; however, their effect on apical papilla cells is poorly elucidated. Additionally, the effect of these substances on cells previously subjected to proinflammatory condition is still unknown. The aim of this study was to evaluate the cytotoxicity of intracanal dressings used in Endodontics regenerative procedures on cultured human apical papilla cells at physiologic and activated condition. Cell culture was established from the apical papilla removed from an extracted immature third molar. The substances studied were triple antibiotic modified paste: ciprofloxacin, metronidazole and cephalosporin (1:1:1); CFC: ciprofloxacin, metronidazole and calcium hydroxide (1:1:2) and modified CFC: ciprofloxacin , metronidazole and calcium hydroxide (2:2:1). Part of the cells was stimulated previously with lipotheichoic acid (LTA) of Enterococcus faecalis por 7 days. Once plated, cells were exposed to increasing concentration of the medications for 1, 3, 5 and 7 days. Cell viability was evaluated by means of 3-bromide (4.5-dimetiliazol-2-yl) -2.5-difeniltetraze (MTT) and Nitric Oxide (NO) release was assessed by the Griess method. The statistical analysis was done through analysis of variance with 1 criteria (ANOVA) followed by Tukey test with 5% of significance level. Modified CFC was the medication that demonstrated the less cytotoxic effect on cell viabilityat the experimental periods studied while CFC promoted significant decrease on cell viability specially after 7 days of contact. The modified triple antibiotic paste resulted in important alteration of cell viability being considered the most citotoxic. Cellular activation by LTA resulted in increased levels of mitochondrial activity for all medications being more evident at the longer experimental periods. Cellular activation also contributed to higher levels of nitric oxide release. In conclusion, the cytotoxic effect of the tested medications is dependent on concentration, time of contact and cellular condition, being the triple antibiotic modified paste the most cytotoxic in high concentrations leading clinically in the decreased of the cells viability of the apical papilla, decreasing the success of regenerative procedures.