Las terapias utilizadas actualmente para el tratamiento de infecciones fúngicas invasoras causadas por levaduras oportunistas están lejos de ser las óptimas. Estas infecciones afectan principalmente a pacientes inmunocomprometidos, dando lugar a tasas de mortalidad muy elevadas. Aunque varias especies de Candida son las responsables del mayor porcentaje de infecciones fúngicas invasoras causadas por levaduras oportunistas, otros géneros, como Cryptococcus, Trichosporon, Blastoschizomyces, Rhodotorula y Sporobolomyces ocasionan también infecciones de incidencia creciente y de difícil tratamiento, existiendo pocos estudios, tanto in vitro como in vivo, acerca de la eficacia de nuevos antifúngicos. El objetivo de la presente tesis es contribuir al desarrollo experimental de nuevos tratamientos o a la mejora de los tratamientos ya existentes. Para ello, se han realizado estudios in vitro para evaluar la eficacia in vitro de los antifúngicos, para posteriormente, comprobar la eficacia de los fármacos en modelos animales adecuados para cada estudio. Las diferentes cepas de Trichosporon asahii estudiadas han mostrado ser resistentes in vitro a los antifúngicos usualmente utilizados en los tratamientos de las infecciones diseminadas por levaduras (la anfotericina B y el fluconazol), siendo por el contrario sensibles a los nuevos triazoles, voriconazol, ravuconazol y albaconazol.. Además el voriconazol ha resultado eficaz en el tratamiento de la tricosporonosis diseminada experimental en el cobaya inmunodeprimido, sugiriendo su potencial utilidad en la terapia de las infecciones humanas producidas por T. asahii. También se ha estudiado la actividad de varias combinaciones de antifúngicos, obteniéndose con la combinación de micafungina y anfotericina B un 100% de interacciones sinérgicas in vitro frente a T. asahii. Esta asociación de antifúngicos ha mostrado una excelente eficacia en el tratamiento experimental de la infección diseminada producida por T. asahii en el ratón. Se ha desarrollado por primera vez un modelo animal de infección diseminada por Blastoschizomyces capitatus en el que se ha estudiado la eficacia del tratamiento con diferentes antifúngicos, clásicos y de reciente introducción. El fluconazol a dosis elevadas ha demostrado ser el tratamiento más efectivo de los ensayados frente a la infección experimental causada por B. capitatus. La combinación de la micafungina con la anfotericina B ha mostrado el mayor porcentaje de interacciones sinérgicas in vitro frente a 40 cepas estudiadas pertenecientes a las cuatro especies de Cryptococcus de mayor relevancia clínica. Se ha estudiado por primera vez el tratamiento con voriconazol en un modelo experimental de criptococosis cerebral en el ratón, demostrándose una eficacia excelente, lo que sugiere la potencial utilidad de este antifúngico en el tratamiento de la infección humana. Se ha evaluado la actividad in vitro de la micafungina combinada con la anfotericina B frente a 115 cepas pertenecientes a las siete especies de Candida de mayor importancia clínica. La disparidad de resultados obtenida en función del criterio de lectura de la CMI, evidencia la necesidad de definir los puntos de corte adecuados para la lectura de las pruebas de sensibilidad in vitro frente a combinaciones de antifúngicos cuando se utiliza la técnica del damero. Se ha estudiado la actividad in vitro de 8 antifúngicos y de las combinaciones de la micafungina con 5 de ellos frente a diferentes cepas de Rhodotorula glutinis y Sporobolomyces salmonicolor. Únicamente la anfotericina B, el ravuconazol y el albaconazol mostraron actividad in vitro frente a R. glutinis. Los triazoles itraconazol, voriconazol, ravuconazol y albaconazol y la terbinafina presentaron buena actividad in vitro frente a S. salmonicolor. Todas las combinaciones de antifúngicos estudiadas con excepción de la combinación de la micafungina con el fluconazol mostraron un alto porcentaje de interacciones sinérgicas frente a R. glutinis. La combinación de la micafungina con el itraconazol dio lugar al mayor porcentaje de interacciones sinérgicas frente a S. salmonicolor. / The conventional antifungal therapies commonly used for the treatment of systemic fungal infections due to opportunistic pathogenic yeasts are far to be the optimal. These infections affect mainly immunocompromised patients, causing high mortality rates. Although Candida spp. are the most common cause of fungal infections, other genera such as Cryptococcus, Trichosporon, Blastoschizomyces, Rhodotorula and Sporobolomyces, have also frequently reported. In general, these latter genera are less susceptible to conventional antifungal treatments and the number of in vitro and in vivo studies about the efficacy of new antifungal treatment against them is very scarce. The main objective of this thesis is to evaluate both in vitro and in animal models the efficacy of new therapeutical strategies. We have evaluated the in vitro activity of micafungin combined with amphotericin B against 115 strains belonging to the seven species of Candida most commonly found in clinical samples (20 of C. albicans, 20 of C. dubliniensis, 15 of C. glabrata, 20 of C. krusei, 10 of C. lusitaniae, 15 of C. parapsilosis and 15 of C. tropicalis).. When we used the MIC-2 endpoint criterion such combination showed synergism against all the species tested. We have evaluated the in vitro activity of micafungin combined with each of the following drugs: amphotericin B, fluconazole, itraconazole, voriconazole and ravuconazole, against 37 strains belonging to the four most clinically relevant species of Cryptococcus i.e. C. neoformans, C. gattii, C. albidus and C. laurentii. The combination micafungin with amphotericin B showed the best synergism, with 70% of synergistic interactions. Voriconazole showed an excellent activity in a murine model of central nervous system infection by Cryptococcus neoformans. We studied the efficacy of voriconazole administered at 10, 40 and 60 mg/kg/day, and amphotericin B administered at 1.5 mg/kg/day. All treatments significantly prolonged survival of mice infected with the three strains of C. neoformans tested with respect to the control group. In addition, all the treatments reduced significantly the fungal loads versus controls. However, the best results were obtained with voriconazole administered at 60 mg/kg/day. Trichosporon asahii is an opportunistic fungus usually resistant in vitro to the conventional antifungals used in systemic infections caused by yeasts. On the other hand, the new triazoles, voriconazole, albaconazole and ravuconazole, have shown an excellent activity. We have evaluated the efficacy of voriconazole in a guinea pig model of trichosporonosis by T. asahii. Voriconazole was effective in resolving such infection. asahii and may represent an important advance in the therapy of this disease. We studied also the efficacy of combined therapy against T. asahii infections. In an in vitro study we tested micafungin combined with five antifungal drugs against ten strains of T. asahii. The combination micafungin with amphotericin B showed 100% of synergistic interactions. With the other combinations tested (micafungin combined with fluconazole, itraconazole, voriconazole or ravuconazole) we obtained between 40 and 20% of synergistic interactions. We selected the combinations that showed the best results i.e, micafungin plus amphotericin B or fluconazole, in the same murine model. Both combinations were effective in prolonging the mean survival time and also significantly reducing the fungal load respect the control group, but only the combination of micafungin with amphotericin B was able to improve the results obtained with monotherapies. We established a reproducible murine model of disseminated blastoschizomycosis to evaluate the effectiveness of the most commonly used antifungal therapies against this infection. We evaluate the efficacy of amphotericin B at 1 and 3 mg/kg/day, fluconazole at 40 and 80 mg/kg/day, flucytosine at 60 mg/kg/day and voriconazole at 40 mg/kg/day, all them against two strains of B. capitatus. This study demonstrated the potential use of this murine model for evaluating therapies against systemic blastoschizomycosis and the highest efficacy of FLC administered at 80 mg/kg/day. Combined therapy has not yet been investigated in blastoschizomycosis and this could be a good alternative for those infections caused by azole-resistant isolates which are increasing among clinical yeasts in general. Since several cases of FLC failure in B, capitatus infections have been documented we decided to evaluate the efficacy of amphotericin B combined with voriconazole, flucytosine or micafungin, using the murine model developed in our previous study. In general, the combinations tested showed better results than the control group and their monotherapies, but they could not improve the efficacy of FLC at high doses. We have also studied the in vitro activity of eight antifungals (amphotericin B, fluconazole, itraconazole, voriconazole, ravuconazole, albaconazole, micafungin and terbinafine) and the interactions of micafungin with five antifungals (amphotericin B, fluconazole, itraconazole, voriconazole or ravuconazole) against 10 strains of Rhodotorula glutinis and 10 of Sporobolomyces salmonicolor. Only amphotericin B, ravuconazole and albaconazole showed low MIC values against R. glutinis. For this reason, we consider interesting the finding that all the antifungal combinations showed a high percentage of synergic interactions (60-80%) with the exception of micafungin plus fluconazole that only showed 20%. Against S. salmonicolor, the amphotericin B MICs were very variable with a 6-fold difference between the lowest and the highest values (0.25-16 mg/L). The best combination was micafungin plus itraconazole with 60% synergic interactions. The other combinations only showed 20-40% synergic interactions. Although these percentages are not so high as for the other species tested, some of these combined therapies could be helpful when amphotericin B fails.

Els estudis inclosos a la present tesi s'han centrat en el desenvolupament de noves teràpies antifúngiques per a infeccions causades per diverses espècies de Candida i per Cladophialophora bantiana. D'aquesta tesi s'han extret les següents conclusions:-La micafungina ha demostrat una eficàcia similar a la d'antifúngics tradicionals per al tractament experimental d'infeccions per C.glabrata. En combinació amb l'amfotericina B, aquest antifúngic ha demostrat, també, una gran eficàcia.-S'ha demostrat l'eficàcia del posaconazole per al tractament experimental d'infeccions disseminades per C.krusei i C.tropicalis.-L'anidulafungina, la caspofungina i la micafungina han estat efectives per al tractament d'infeccions experimentals disseminades per C.dubliniensis.-S'ha comprovat l'eficàcia de dues noves formulacions d'amfotericina B per al tractament d'infeccions experimentals per Candida.-La combinació de la micafungina amb l'itraconazole ha demostrat una bona activitat in vitro envers el gènere Candida.-La combinació del posaconazole, la micafungina i la flucitosina ha demostrat ser efectiva envers C. bantiana. / The studies included in this thesis focused on the development of new antifungal therapies for infections caused by various species of Candida and also Cladophialophora bantiana. The following conclusions were obtained in this thesis:-Micafungin demonstrated to be as effective as some traditional antifungal agents for the treatment of experimental infections by C.glabrata. This drug in combination with amphotericin B has also shown great efficacy.- Posaconazole demonstrated to be effective for the treatment of experimental infections by C.krusei and C.tropicalis. -Anidulafungin, micafungin and caspofungin were effective for the treatment of experimental disseminated infections by C.dubliniensis. -The effectiveness of two new formulations of amphotericin B has been proven for the treatment of experimental disseminated Candida infections. -The combination of micafungin with itraconazole showed good in vitro activity against the genus Candida. -The combination of posaconazole, micafungina and flucytosine has proven to be effective against C. bantiana.

Introdução: A energia elétrica e ultrasônica são utilizadas com freqüência na prostatectomia radical laparoscópica e podem lesar os nervos cavernosos adjacentes através da dissipação térmica. Em contrapartida, a energia laser tem potencial para proporcionar uma dissecção precisa, com boa hemostasia e pequena lesão dos tecidos adjacentes. Este estudo avalia o efeito do laser KTP na dissecção laparoscópica do feixe neuro-vascular cavernoso em modelo experimental canino. Material e Métodos: Um total de 36 cães foi dividido igualmente em três grupos. Realizou-se a dissecção unilateral do feixe neurovascular cavernoso utilizando (1) laser KTP (KTP), (2) bisturi ultrasônico (BU), e (3) tesoura e clipes metálicos (TC), mantendo o lado contralateral intacto. Realizou-se a análise do tempo operatório e sangramento em cada grupo, assim como a análise funcional, através do coeficiente entre a pressão intracavernosa e pressão arterial média (PIC/PAM) durante a estimulação do feixe neurovascular cavernoso. Metade dos animais de cada grupo foi mantida viva por 30 dias e submetidos à nova neuroestimulação. Foram avaliados ainda os efeitos da dissipação térmica através da análise termográfica em fragmentos de peritôneo parietal e a extensão histológica da necrose tecidual na fáscia prostática desde a superfície de corte de cada instrumento. Resultados: O tempo de dissecção do feixe neuro-vascular cavernoso foi similar entre os grupos (KTP vs. BU p=0.21, KTP vs. TC p=0.81, BU vs. TC p=0.22). A dissecção utilizando o BU resultou em um prejuízo significativo na resposta à neuroestimulação quando comparado aos grupos TC e KTP no experimento agudo (BU vs. KTP p<0.001, BU vs. TC p<0.001), e crônico (BU vs. KTP p=0.02, BU vs. TC p=0.02). A análise histológica demonstrou uma área de necrose desde a superfície de corte com a utilização do laser KTP de aproximadamente 500 um, enquanto que com o uso do BU essa área se extendeu em média por 2 mm. A avaliação termográfica mostrou uma dissipação térmica significativamente maior do BU comparado ao laser KTP (laser KTP 0.98 mm vs. BU 6.25 mm, p<0.0001). Conclusão: O uso do laser KTP na dissecção laparoscópica do feixe neuro-vascular cavernoso apresentou resultado funcional semelhante à técnica sem emprego de energia térmica utilizando tesoura e clipes, enquanto o bisturi ultrasônico foi associado a um prejuízo significativo na função dos nervos cavernosos. / Introduction: Electrical and ultrasonic energy used in nerve-sparing laparoscopic radical prostatectomy can compromise cavernous nerve function. Laser energy may potentially allow fine dissection with good hemostasis and minimal adjacent tissue injury. This study examines the electrophysiological, histological and thermal mapping features of KTP laser dissection on cavernous nerve function in the survival canine model. Materials and Methods: A total of 36 dogs were divided into 3 groups. Laparoscopic unilateral neurovascular bundle (NVB) mobilization was performed using either: (1) KTP laser (n=12), (2) ultrasonic shears (US) (n=12), or (3) athermally with cold scissors (AT) (n=12). The contralateral NVB remained undissected as an internal control. NVB function was assessed acutely in all dogs, and after 1-month survival in 50% of the dogs of each group. Peak intracavernosal pressure response to cavernous nerve stimulation was measured as a percentage of mean arterial pressure (ICP/MAP). Strips of peritoneum were sectioned ex-vivo with the KTP laser and US shears for thermographic mapping. Histological evaluation of prostatic fascia necrosis from the cutting surface was also performed. Results: Comparing KTP and AT groups, the erectile response to nerve stimulation was similar acutely and at 1 month (acute ICP/MAP: KTP 92%, AT 96% p=0.54; chronic ICP/MAP: KTP 95%, AT 98% p=0.71). In contrast, US dissection resulted in a significant decrease in the ICP response compared to the KTP and AT groups (acute ICP/MAP: US 49%, KTP 92%, AT 96%. US vs. KTP p<0.001, US vs. AT p<0.001; chronic ICP/MAP: US 58%, KTP 95%, AT 98%, US vs. KTP p=0.02, US vs. AT p=0.02). Mean NVB dissection times were similar (KTP 27.5min, US 19.9min, AT 26.6min, KTP vs. US p=0.21, KTP vs. AT p=0.81, US vs. AT p=0.22). Histopathology demonstrated an acute zone of laser-induced necrosis of approximately 500 um compared to 2 mm with US dissection. Thermographic assessment demonstrated significantly less collateral thermal spread from the KTP laser compared to US (mean thermal spread >60 oC KTP 0.98 mm vs. US 6.25 mm, p<0.0001). Conclusions: Use of KTP laser for NVB mobilization preserved cavernous nerve function comparable to standard athermal techniques using cold scissors and was superior to ultrasonic shears.

Introdução: A energia elétrica e ultrasônica são utilizadas com freqüência na prostatectomia radical laparoscópica e podem lesar os nervos cavernosos adjacentes através da dissipação térmica. Em contrapartida, a energia laser tem potencial para proporcionar uma dissecção precisa, com boa hemostasia e pequena lesão dos tecidos adjacentes. Este estudo avalia o efeito do laser KTP na dissecção laparoscópica do feixe neuro-vascular cavernoso em modelo experimental canino. Material e Métodos: Um total de 36 cães foi dividido igualmente em três grupos. Realizou-se a dissecção unilateral do feixe neurovascular cavernoso utilizando (1) laser KTP (KTP), (2) bisturi ultrasônico (BU), e (3) tesoura e clipes metálicos (TC), mantendo o lado contralateral intacto. Realizou-se a análise do tempo operatório e sangramento em cada grupo, assim como a análise funcional, através do coeficiente entre a pressão intracavernosa e pressão arterial média (PIC/PAM) durante a estimulação do feixe neurovascular cavernoso. Metade dos animais de cada grupo foi mantida viva por 30 dias e submetidos à nova neuroestimulação. Foram avaliados ainda os efeitos da dissipação térmica através da análise termográfica em fragmentos de peritôneo parietal e a extensão histológica da necrose tecidual na fáscia prostática desde a superfície de corte de cada instrumento. Resultados: O tempo de dissecção do feixe neuro-vascular cavernoso foi similar entre os grupos (KTP vs. BU p=0.21, KTP vs. TC p=0.81, BU vs. TC p=0.22). A dissecção utilizando o BU resultou em um prejuízo significativo na resposta à neuroestimulação quando comparado aos grupos TC e KTP no experimento agudo (BU vs. KTP p<0.001, BU vs. TC p<0.001), e crônico (BU vs. KTP p=0.02, BU vs. TC p=0.02). A análise histológica demonstrou uma área de necrose desde a superfície de corte com a utilização do laser KTP de aproximadamente 500 um, enquanto que com o uso do BU essa área se extendeu em média por 2 mm. A avaliação termográfica mostrou uma dissipação térmica significativamente maior do BU comparado ao laser KTP (laser KTP 0.98 mm vs. BU 6.25 mm, p<0.0001). Conclusão: O uso do laser KTP na dissecção laparoscópica do feixe neuro-vascular cavernoso apresentou resultado funcional semelhante à técnica sem emprego de energia térmica utilizando tesoura e clipes, enquanto o bisturi ultrasônico foi associado a um prejuízo significativo na função dos nervos cavernosos. / Introduction: Electrical and ultrasonic energy used in nerve-sparing laparoscopic radical prostatectomy can compromise cavernous nerve function. Laser energy may potentially allow fine dissection with good hemostasis and minimal adjacent tissue injury. This study examines the electrophysiological, histological and thermal mapping features of KTP laser dissection on cavernous nerve function in the survival canine model. Materials and Methods: A total of 36 dogs were divided into 3 groups. Laparoscopic unilateral neurovascular bundle (NVB) mobilization was performed using either: (1) KTP laser (n=12), (2) ultrasonic shears (US) (n=12), or (3) athermally with cold scissors (AT) (n=12). The contralateral NVB remained undissected as an internal control. NVB function was assessed acutely in all dogs, and after 1-month survival in 50% of the dogs of each group. Peak intracavernosal pressure response to cavernous nerve stimulation was measured as a percentage of mean arterial pressure (ICP/MAP). Strips of peritoneum were sectioned ex-vivo with the KTP laser and US shears for thermographic mapping. Histological evaluation of prostatic fascia necrosis from the cutting surface was also performed. Results: Comparing KTP and AT groups, the erectile response to nerve stimulation was similar acutely and at 1 month (acute ICP/MAP: KTP 92%, AT 96% p=0.54; chronic ICP/MAP: KTP 95%, AT 98% p=0.71). In contrast, US dissection resulted in a significant decrease in the ICP response compared to the KTP and AT groups (acute ICP/MAP: US 49%, KTP 92%, AT 96%. US vs. KTP p<0.001, US vs. AT p<0.001; chronic ICP/MAP: US 58%, KTP 95%, AT 98%, US vs. KTP p=0.02, US vs. AT p=0.02). Mean NVB dissection times were similar (KTP 27.5min, US 19.9min, AT 26.6min, KTP vs. US p=0.21, KTP vs. AT p=0.81, US vs. AT p=0.22). Histopathology demonstrated an acute zone of laser-induced necrosis of approximately 500 um compared to 2 mm with US dissection. Thermographic assessment demonstrated significantly less collateral thermal spread from the KTP laser compared to US (mean thermal spread >60 oC KTP 0.98 mm vs. US 6.25 mm, p<0.0001). Conclusions: Use of KTP laser for NVB mobilization preserved cavernous nerve function comparable to standard athermal techniques using cold scissors and was superior to ultrasonic shears.

Diss. (sammanfattning) Stockholm : Karol. inst., 2004. / Härtill 5 uppsatser.

A toxoplasmose ocular é atribuída ao parasita, mas a auto-imunidade pode participar do processo. Soros humanos com IgG positiva para T. gondii mostraram níveis altos de IgG anti-retina para diferentes antígenos, se comparados com soros negativos para T. gondii, uveítes de outras origens também tiveram títulos elevados. Hamsters imunizados e/ou infectados não mostraram estes anticorpos sem mimetismo antigênico. A retinocoroidite por Toxoplasma induz resposta humoral auto-imune contra antígenos da retina, provavelmente piorando o efeito direto do agente. Estes anticorpos podem ser usados como marcadores de doença ocular em pacientes soropositivos para toxoplasmose pela triagem de lesão ocular. / Ocular toxoplasmosis is attributed to the parasite, but autoimmunity could have a role in this process. Human sera, positive of anti-T. gondii IgG, show high levels of anti-retina IgG, measured by several antigens, as compared to T. gondii seronegative samples. Sera from patients with uveitis from other origins also had higher anti-retina abs levels. Challenged and/or immunized hamsters showed low anti-retina abs levels, without antigen mimicry. Toxoplasmic retinochoroiditis presents a humoral anti-retina abs, probably worsening the parasite direct effect. Those antibodies could be used as markers of eye involvement in toxoplasmosis seropositive patients, as a screening for eye examination.

A toxoplasmose ocular é atribuída ao parasita, mas a auto-imunidade pode participar do processo. Soros humanos com IgG positiva para T. gondii mostraram níveis altos de IgG anti-retina para diferentes antígenos, se comparados com soros negativos para T. gondii, uveítes de outras origens também tiveram títulos elevados. Hamsters imunizados e/ou infectados não mostraram estes anticorpos sem mimetismo antigênico. A retinocoroidite por Toxoplasma induz resposta humoral auto-imune contra antígenos da retina, provavelmente piorando o efeito direto do agente. Estes anticorpos podem ser usados como marcadores de doença ocular em pacientes soropositivos para toxoplasmose pela triagem de lesão ocular. / Ocular toxoplasmosis is attributed to the parasite, but autoimmunity could have a role in this process. Human sera, positive of anti-T. gondii IgG, show high levels of anti-retina IgG, measured by several antigens, as compared to T. gondii seronegative samples. Sera from patients with uveitis from other origins also had higher anti-retina abs levels. Challenged and/or immunized hamsters showed low anti-retina abs levels, without antigen mimicry. Toxoplasmic retinochoroiditis presents a humoral anti-retina abs, probably worsening the parasite direct effect. Those antibodies could be used as markers of eye involvement in toxoplasmosis seropositive patients, as a screening for eye examination.

A atresia das vias biliares é afecção hepática da infância. A etiologia é desconhecida, e o diagnóstico baseia-se na biópsia hepática, cujo achado é a proliferação ductular. A ligadura do ducto biliar comum em ratos é modelo utilizado para estudo das doenças colestáticas. A proposta do trabalho foi estudar, em modelo experimental de obstrução biliar, as alterações histológicas hepáticas em ratos jovens e compará-las com o animal adulto. Avaliou-se a semiquantificação da proliferação ductular e inflamação pelo HE; quantificação da fibrose portal e periportal pelo picrosírius; semiquantificação da expressão de desmina e a-actina de músculo liso pelas células estreladas e miofibroblastos. Apesar das respostas de proliferação ductular e inflamação mais lentas no rato jovem, a fibrose e a expressão de desmina foram mais intensas neste grupo / Biliary atresia is an hepatic disease of infancy. Etiology is unknown, and diagnosis is made by liver biopsy, with ductular proliferation being the main histological feature. Bile duct ligation in rats is an useful experimental model of biliary obstruction. The aim of this study of extra-hepatic cholestasis was analyse hepatic histological alterations in young rats compared to adult animals. The responses were studied by semiquantification of ductular proliferation and inflammatory infiltrated by HE stain; quantification of portal and periportal fibrosis with the sirius-red stain; semiquantification of the expression of desmin and a-smooth muscle actin by the hepatic stellated cells and myofibroblasts. In young animals, despite the very slow response of ductular proliferation and inflammation observed with HE, there were significantly more fibrosis and expression of desmin than in adult group

A atresia das vias biliares é afecção hepática da infância. A etiologia é desconhecida, e o diagnóstico baseia-se na biópsia hepática, cujo achado é a proliferação ductular. A ligadura do ducto biliar comum em ratos é modelo utilizado para estudo das doenças colestáticas. A proposta do trabalho foi estudar, em modelo experimental de obstrução biliar, as alterações histológicas hepáticas em ratos jovens e compará-las com o animal adulto. Avaliou-se a semiquantificação da proliferação ductular e inflamação pelo HE; quantificação da fibrose portal e periportal pelo picrosírius; semiquantificação da expressão de desmina e a-actina de músculo liso pelas células estreladas e miofibroblastos. Apesar das respostas de proliferação ductular e inflamação mais lentas no rato jovem, a fibrose e a expressão de desmina foram mais intensas neste grupo / Biliary atresia is an hepatic disease of infancy. Etiology is unknown, and diagnosis is made by liver biopsy, with ductular proliferation being the main histological feature. Bile duct ligation in rats is an useful experimental model of biliary obstruction. The aim of this study of extra-hepatic cholestasis was analyse hepatic histological alterations in young rats compared to adult animals. The responses were studied by semiquantification of ductular proliferation and inflammatory infiltrated by HE stain; quantification of portal and periportal fibrosis with the sirius-red stain; semiquantification of the expression of desmin and a-smooth muscle actin by the hepatic stellated cells and myofibroblasts. In young animals, despite the very slow response of ductular proliferation and inflammation observed with HE, there were significantly more fibrosis and expression of desmin than in adult group