Una propuesta de evaluación formativa en ciencias morfológicas / A proposal of formative assessment in morphology sciences

La carrera de Medicina Veterinaria de la Universidad Nacional del Centro de la Provincia de Buenos Aires (UNCPBA) presenta un sistema de correlatividades estricto que conlleva a frecuentes retrasos académicos. El porcentaje de alumnos que aprobó la cursada 2009 (considerando la prueba parcial y sus instancias de recuperación) del curso Histología Embriología y Teratología fue menor al 80% con una tendencia descendente considerando el periodo 2006­2009. El objetivo del trabajo fue analizar si la implementación de cambios metodológicos que incluyeran actividades con principios de evaluación formativa, lograba mejorar la calidad del proceso enseñanza-aprendizaje. La propuesta incluyó: dictado de temas evaluados en los trabajos prácticos (TP) con la antelación suficiente para permitir su lectura y comprensión; archivos power point con imágenes de las preparaciones histológicas en cada TP; evaluación de TP con devolución escrita de las correcciones; posibilidad de recuperación de los TP correspondientes a tejidos básicos contra entrega de la evaluación corregida; seminarios obligatorios y consultas concebidas como encuentros de aprendizaje previo a las mesas de exámenes finales. Como indicadores de impacto de la propuesta, se utilizaron el porcentaje de alumnos que aprobó la cursada (%AAC) y el número de veces que rindieron el examen final hasta aprobarlo. Se compararon los periodos 2010-2012 (nueva propuesta) y 2006-2009 (cursadas tradicionales) mediante Chi2. El %AAC fue mayor para el periodo 2010­2012 (93,1%) comparado con el periodo 2006­2009 (82,4%; p<0,05). Sin embargo, no hubo diferencias significativas en el porcentaje de alumnos que rindió entre 1 y 4 veces el examen final (50,2%, 27,6%, 15,6% y 6,6% respectivamente; p>0,05). Las modificaciones propuestas resultarían una estrategia que mejora el rendimiento académico evidenciado por un aumento en el porcentaje de aprobación de cursada, sin embargo no incidió positivamente en el desempeño académico en instancias de examen final sugiriendo la necesidad de buscar estrategias para hacer más eficiente la acreditación final del curso.

The program of the UNCPBA Veterinary Medicine degree has a strict subject correlative order system leading to frequent academic delays. The percentage of students who completed the Histology Embryology and Teratology 2009 course (considering the partial tests and two resist examinations) was below 80% with a downward trend for the period 2006­2009. The objective of this work was to examine whether the implementation of methodological changes that include activities with principles of formative assessment could improve the quality of the teaching-learning process. The proposal included: to teach the topics evaluated in practical works (PW) allowing enough time for reading and comprehension; to present the students with power point files with images of histological preparations in each PW; to give them the PW assessment in writing; to allow resist of PWs corresponding to basic tissues after delivery of the corrected assessment; mandatory seminars and consultation meetings designed as learning instances prior to final exams. As indicators of the impact of the proposal the percentage of students who completed the course (PSC) and the number of times students sat for the final exam to pass it were taken into account. Periods 2010­2012 (new proposal) and 2006-2009 (traditional course) were compared by Chi2. The PSC was higher for the period 2010­2012 (93.1%) compared to the 2006­2009 period (82.4%; p<0.05). However, there were no significant differences in the percentage of students who sat between 1 and 4 times the final examination (50.2%, 27.6%, 15.6% and 6.6% respectively, p>0.05). The changes proposed would become a strategy to improve the academic performance as evidenced by an increase in the percentage of students completing the course; however, they had no positive impact on the academic performance at the final examinations instances suggesting the need to find strategies to make more efficient the final accreditation of the course.

In vitro development of murine embryos in presence of campylobacter fetus / Desarrollo de embriones murinos in vitro en presencia de campylobacter fetus

Bovine campylobacteriosis caused by Campylobacter fetus is associated with reproductive losses. The knowledge about the mechanisms of bacterial pathogenesis is limited, then a murine experimental model is proposed. BALB/c females and males were used. Two-cell embryos were cultured in Ham-F10 as control group (CG). Treatment groups were constituted by the addition of Cfv 1 and 3, or Cff 2 and 5. Morulae were placed in Ham-F10 (CG); treatment groups were constituted by the addition of Cfv27, CFF (cell-free filtrate) and Brucella broth (BB). Blastocysts were cultured in MEM (CG); challenge group were constituted by the addition of Cfv 27. Differentiation, hatching, hatched, adhesion and expansion were evaluated. Results were analyzed by Chi2 test. In two-cell embryo, the differentiation rate was not modified when the study strains were added (p > 0.05). The differentiation rate at 24 h for embryos at the morula stage was lower for BB, Cfv, and CFF, compared with CG (p < 0.05). After 48 h culture, no differences were observed in blastocyst formation for Cfv and BB, compared to CG (p > 0.05). However, the differentiation rate for the CFF group was lower than for CG (p < 0.05). At 48 and 72 h, the hatching rate was higher in CFF and Cfv groups than in CG (p < 0.05). Differences were not detected in blastocyst cultures. In conclusion, under these experimental conditions, Cf was not detrimental to the development of murine embryos. Efforts will be intensified to establish in vitro infection models that reproduce their pathogenicity.

La campilobacteriosis bovina caudada por Campylobacter fetus produce pérdidas reproductivas existiendo poca información de los mecanismos de patogenicidad de dicha bacteria, por lo cual se propone un modelo utilizando ratones BALC/c. Embriones de dos células fueron cultivados en Ham-F10: grupo control (GC), los grupos experimentales fueron adicionados con las cepas Cfv 1, Cfv 3, Cff 2 y Cff 5. Mórulas fueron cultivadas en Ham-F10 (GC); los grupos tratados recibieron Cfv27, CFF (filtrado libre de células) y caldo Brucella (BB). Blastocistos fueron cultivados en MEM (GC) y MEM más Cfv 27 (grupo desafiado). Se evaluó: diferenciación, "hatching", "hatched", adhesión y expansión. Los resultados fueron analizados por Chi2. En embriones de dos células, la diferenciación no fue modificada por acción de las cepas evaluadas (p > 0,05). Para embriones en estadío de mórula, la diferenciación a las 24 h de cultivo fue menor para BB, Cfv, y CFF, comparado con el GC (p < 0,05). Luego de 48 h de cultivo, no hubo diferencias entre Cfv, BB, y CG (p > 0,05), no obstante para el grupo CFF la diferenciación fue menor al CG (p < 0,05). El porcentaje de "hatching" (48 y 72 h de cultivo), fue mayor en los grupos CFF y Cfv comparado con el GC (p < 0,05). La adición de Cfv 27 no modificó el desarrollo de blastocistos. En el modelo propuesto, Cf no afectó negativamente el desarrollo embrionario. Futuros trabajos serán necesarios para establecer un modelo de infección in vitro en pos de reproducir su patogenicidad.

Albendazole sulphoxide administered prior to mating andits relation with fertilization and mouse embryo development / Albendazol sulfóxido administrado previo al apareamiento y su relación con la fertilización y el desarrollo embrionario de ratón

The aim of this work was to evaluate the effect of albendazole sulphoxide (ABZSO) administered to Balb C mice prior to mating on fertilization rate and preimplantational embryo development. Twenty four female mice 5-8 weeks of age were superovulated by intraperitoneal injection of 7.5 UI of equine chorionic gonadotropin (eCG, Novormon®, Laboratorios Syntex S.A., Argentina); 48 h later they received 10 IU of human chorionic gonadotropin (hCG, Profasi®, Laboratorios Serono, Méjico) and were paired with males of proven fertility. Females received 100 mg/kg or 200 mg/kg of ABZSO orally at the time of hCG administration, prior to mating. The control group received carboxymethylcellulose, vehicle used to prepare the drug suspension. Pregnant females were killed by cervical dislocation at day 4 of pregnancy and non fertilized oocyte and embryos were flushed from uteri. The possible effects of ABZSO were evaluated considering the fertilization rate, the total number of collected embryos per female; the percentage of embryos morphologically normal; the differentiation rate (determined by the relation between the number of blastocyst and the total of morphologically normal embryos) and the cleavage rate determined by counting the nuclei. The variables were analyzed on a per litter basis using the Kruskal-Wallis test. The fertilization rate was lower in females administered ABZSO at a dose of 200 mg/kg (P<0.05). However, no statistically significant differences were found in the embryonic parameters after the administration of 100 mg/kg or 200 mg/kg of ABZSO compared to the untreated control group (P>0.05). In conclusion, a single acute exposure to ABZSO prior to mating at around the time of fertilization at a dose higher than the one usually administered in human and veterinary medicine affects the fertilization rate but it has no adverse effects on early embryo development.

El objetivo de este trabajo fue evaluar el efecto de albendazol sulfóxido (ABZSO) administrado a ratonas Balb C previo al apareamiento, sobre la tasa de fertilización y el desarrollo embrionario preimplantacional. Se utilizaron 24 hembras de 5 a 8 semanas de edad las que fueron inducidas a superovular por inyección intraperitoneal de 7,5 UI de gonadotrofina coriónica equina (eCG, Novormon®, Laboratorios Syntex S.A. Argentina) seguidas, 48 h más tarde por 10 UI de gonadotrofina coriónica humana (hCG, Profasi®, Laboratorios Serono, México). Al momento de recibir la dosis de hCG, fueron apareadas con machos de fertilidad probada. Las hembras fueron dosificadas oralmente con ABZSO disuelto en carboximetilcelulosa en dosis de 100 mg/kg (Grupo 100) y 200 mg/kg (Grupo 200) previo al apareamiento. El grupo control recibió carboximetilcelulosa. Las hembras preñadas fueron sacrificadas por dislocación cervical en el día 4 de preñez y se recolectaron ovocitos sin fertilizar y embriones preimplantacionales mediante el lavado de cuernos uterinos. Se determinó la tasa de fertilización, el número promedio de embriones recolectados por hembra, el porcentaje de embriones morfológicamente normales, el porcentaje de diferenciación y la velocidad de clivaje estimada por recuento de núcleos. Las variables fueron analizadas sobre la base de la camada utilizando el test de Kruskal-Wallis. La tasa de fertilización resultó menor para hembras que recibieron albendazol sulfóxido a razón de 200 mg/kg de peso (P<0,05); no obstante, no se observaron diferencias significativas en los parámetros embrionarios luego de la administración de 100 mg/kg ó 200 mg/kg de ABZSO comparado con el grupo control (P>0,05). En conclusión, la exposición aguda de ABZSO realizada previo al apareamiento a una dosis mayor de aquella utilizada en medicina humana y veterinaria afecta la tasa de fertilización pero no muestra efectos adversos sobre el desarrollo embrionario temprano.

Effects of albendazole sulphoxide on embryonic, foetal and placental parameters in Wistar rats / Efectos de albendazol sulfóxido sobre parámetros embrionarios, fetales y placentarios en ratas Wistar

The aim of this work was to evaluate the effect of albendazole sulphoxide (ABZSO), administered to Wistar rats during pregnancy on embryonic, foetal and placental parameters. A colpocytological control was performed daily and detection of spermatozoa in the vaginal smear was considered as day 0 of pregnancy. For the preimplantational study, ABZSO (10 mg/kg) was orally administered at day 2 of pregnancy; at day 4 the embryos were collected. For the postimplantational study, ABZSO (10 mg/kg) was orally administered by gavages at day 2, 6 or 10 of pregnancy (G2, G6 and G10 Groups respectively); the control group was administered the same volume of carboxymethylcellulose vehicle used to prepare the drug suspension. Fetuses were obtained from pregnant rats sacrificed on day 20 of gestation. Maternal body weight gains were analyzed using the one-way ANOVA test. Embryonic and foetal variables were analized on a per litter basis by the Kruskal-Wallis test. Skeletal anomalies were analyzed using an X² test. The significance level accepted was established at P<0.05. In the preimplantational analysis, the cleavage rate was lower in the experimental group (P<0.05). In the postimplantational analysis there were no differences in the net weight increase among females of the different groups (P>0.05). The number of fetuses and the foetal vesicles weight were lower in the G10 group (P<0.05). This group showed the highest percentage of resorptions (P<0.05) and fetuses morphologically abnormal. An increase in the number of bones affected in fetuses of G6 and G10 groups was observed. The most common malformations were at vertebral, costal and head level. Weights and placental diameters were lower in the G10 group (P<0.05). We conclude that ABZSO at the dose used in this study affects the cleavage rate in preimplantational embryo development, without interrupting pregnancy. Furthermore; the developmental toxicity is related to day of administration.

El objetivo de este trabajo fue caracterizar los efectos de albendazol sulfóxido (ABZSO) durante la gestación de ratas Wistar, sobre parámetros embrionarios, fetales y placentarios. Se efectuó colpocitología diaria de las hembras considerándose día 0 de gestación el día de aparición de espermatozoides en vagina. Estudio preimplantacional: ABZSO (10 mg/kg) fue dosificado oralmente el día 2 de gestación; el día 4 de gestación se realizó la recolección de embriones. Estudio post-implantacional: ABZSO (10 mg/kg) fue dosificado oralmente los días 2, 6 ó 10 de gestación (Grupos G2, G6 y G10, respectivamente). Hembras controles recibieron carboximetilcelulosa, vehículo usado para solubilizar la droga. Las hembras fueron sacrificadas al día 20 de gestación. Variables embrionarias y fetales fueron analizadas sobre la base de las camadas mediante test de Kruskal-Wallis; ganancia de peso de las madres por ANOVA y porcentaje de fetos con alteraciones esqueléticas mediante X2. Estudio preimplantacional: la tasa de recolección embrionaria, el número de embriones recolectados y el porcentaje de diferenciación fueron similares entre grupos (P>0,05). La velocidad de clivaje fue menor en el grupo experimental (P<0,05). Estudio post-implantacional: la ganancia de peso de las madres no difirió entre grupos (P>0,05), el número de fetos y el peso de las vesículas fetales fueron menores en el grupo G10 (P<0,05). Los porcentajes de reabsorciones y de fetos con características morfológicas anormales fueron mayores en el grupo G10 (P<0,05). Las alteraciones esqueléticas fueron mayores en los grupos G6 y G10 (P<0,05) observándose con mayor frecuencia en vértebras, costillas y cabeza. Pesos y diámetros placentarios fueron menores en el grupo G10 (P<0,05). Se concluye que, bajo las condiciones del presente estudio, el ABZSO administrado en la etapa preimplantacional afecta la velocidad de clivaje sin detener la gestación mientras que su efecto en el desarrollo post-implantacional...

Regulation of mouse embryo development by autocrine throphic factors

Embryo development depends on maternal and embryonic factors. When occurs in vitro, embryos secrete factors that stimulate their development. The purpose of this study was to investigate the possible effects of embryos at morula stage on mouse embryo development in vitro. To obtain conditioned media (CM), morulas were cultured in groups of 5 (CM5) or 10 (CM10) in microdrops of Ham-Fl0 culture medium during 24h and later they were removed. Subsequently, 365 morulas were cultured in CM5 and CM10 or in Ham-F10 media (as control group). No differences in blastocyst formation could be found between embryos cultured for 24h in Ham-F1O, CM5 or CM10 (49.66, 53.04, 60.00% respectively). However, CM5 significantly increased differentiation in embryos cultured for 48h as compared to Ham-FlO medium (80.00% and 64.14 respectively). The CM5 caused a significant increase in the hatching rate compared to Ham-F10 evaluated at 78 and 96h of culture (66.96 vs. 52.41% and 70.43 vs. 55.17%, respectively). After 72, 78 and 96h of culture the hatching rate for embryos cultured in CM10 was significantly higher than that in Ham-F10 (64.76 vs. 47.59%, 67.62 vs. 52.41% and 73.33 vs. 55.17%, respectively). At 48h of culture, differences between CM5, CMl0 and Ham-F10 were not observed. These results suggest that preimplantational mouse embryos produce trophic factor/factors that enhance the differentiation and hatching process

Typological series for ovarian follicles of sexually mature Myocastor coypus (coypu)

We are herein putting forward the results derived from the careful examination of the ovary of a sexually mature Myocastor coypus which was carried out to establish a follicular typological series. Sexually mature virgin females from breeding farms were used and their ovaries were processed by routinely histological techniques. The following analysis criteria were considered for the follicular classification: size of the oocyte in follicles at different stages of development, size of the follicle regarding the number of follicular cells, and follicular morphology. Complementary characteristics were also analyzed: mean follicular diameter, presence and thickness of the pellucid zone, mean size of follicular cells, their shape in all follicular types, presence and extent of the antrum, and presence of thecas. By combining these different criteria, a follicular typological series was obtained according to Pedersen and Peters (1968) nomenclature together with a qualitative and quantitative characterization of the follicular types.

The anthelmintic albendazole affects in vivo the dynamics and the detyrosination-tyrosination cycle of rat brain microtubules

Albendazole (ABZ) is an anthelmintic benzimidazole drug widely used in human and veterinary medicine. ABZ has binding affinity to both mammalian and helminth parasite tubulin. In the current work, we have performed in vitro assays and in vivo experiments in which rats were given ABZ orally to better characterize the action of the drug on the polymerization of rat brain microtubules and on the detyrosination/tyrosination cycle that occurs on the COOH-terminal end of alpha-tubulin. The results showed that ABZ inhibits brain microtubule polymerization in vitro, and significantly delayed microtubule assembly in vivo. The tyrosination reaction cycle was not affected in vitro; however, in rats to which the drug was administered orally, the levels of in vitro tyrosination were reduced when compared to the controls with mock treatment. These results suggest that this apparent inhibition would be due to a decrease in the amount of substrate caused by the depolymerizing effect of ABZ and the subsequent tyrosination in the intact brain with endogenous tyrosine. In conclusion, ABZ strongly affects tubulin dynamics both in vivo and in vitro. The outcome of these experiments is a contribution to the understanding of the molecular mechanisms involved in the antimicrotubular action of benzimidazole compounds.