Effects of a non-steroidal aromatase inhibitor on ovarian function in cattle

Two studies were designed to characterize the effects of a non-steroidal aromatase inhibitor, letrozole, on ovarian function in cattle. The specific objective was to test the hypothesis that letrozole will arrest dominant follicle growth resulting in emergence of a new follicular wave at a predictable interval post-treatment. In a first experiment, postpubertal beef heifers were assigned randomly to four treatment groups and given phosphate-buffered saline (controls; n=10), or letrozole at a dose of 500 (n=9), 250 (n=10), or 125 (n=10) µg/kg intravenously 4 days after follicular ablation (~2.5 days after wave emergence). In a second study, postpubertal beef heifers were assigned randomly to four treatment groups. One group received no treatment (control; n=17) and the other groups (n=9-10) were given 85 µg/kg of letrozole per day (250 µg/kg total dose), from Days 1 to 3, Days 3 to 5, or Days 5 to 7 (Day 0 = pre-treatment ovulation,) corresponding to the periods before, during and after selection of the dominant follicle, respectively. Follicular dynamics were monitored ultrasonically and blood samples were collected for endocrine assays. Follicle diameter profiles and plasma LH, FSH, and estradiol concentrations were analyzed. Additionally, during the second trial, CL diameter profiles and plasma progesterone concentrations were measured. In both studies, the diameter profile of the dominant follicle was larger in heifers treated with letrozole than in control heifers (

Development of a non-steroidal aromatase inhibitor-based protocol for the control of ovarian function using a bovine model

Five studies were designed to characterize the effects of a non-steroidal aromatase inhibitor, letrozole, on ovarian function in cattle. The general hypothesis was that non-steroidal aromatase inhibitors have potential as a steroid-free option for the control of ovarian function for the purposes of fixed-time artificial insemination and embryo production. The specific objectives were to determine the effect of route and vehicle, type of aromatase inhibitor, and duration of aromatase inhibitor treatment (short vs prolonged) on ovarian follicles in cattle, and to test the efficacy of an aromatase inhibitor-based protocol to synchronize ovulation in cattle. In the first experiment, heifers were treated with letrozole intravenously (n=10) or intramuscularly (n=10) or allocated in iv and im control groups (n=5/group). During the second experiment, heifers were divided randomly into two groups (n=15/group) and an intravaginal device containing 1 g of letrozole or a blank device (control) was inserted. The third experiment was designed with the goal of formulating and testing an intravaginal device that provides biologically active circulating concentrations of an aromatase inhibitor for a minimum of 4 days. The biological significance of the pharmacokinetic differences between the letrozole intravaginal devices resulting from the third study was evaluated during the fourth study. A final study was designed to determine the effect of stage of the estrous cycle on the proportion of animals that ovulated and the synchrony of ovulation of heifers treated with an aromatase inhibitor-based ovulation-synchronization protocol and to determine subsequent pregnancy outcomes. In all the studies, the effects of aromatase inhibitor on ovarian function were assessed by transrectal ultrasound examination of the ovaries, and blood samples were collected for hormone concentration determination. Results demonstrated that route of administration, or more precisely, the nature of iii the vehicle used for the administration of letrozole (intravenous, intramuscular depot, short release intravaginal or prolonged release intravaginal) has an impact on the effects of letrozole on hormonal profiles and ovarian dynamics. The intramuscular route appeared to provide a prolonged release of letrozole from the injection site which had a marked effect on estradiol production, dominant follicle lifespan, and CL form and function. Letrozole treatment during the ovulatory follicle wave by means of a gel-based intravaginal releasing device during the second study resulted in more rapidly growing dominant follicles and larger ovulatory follicles, delayed ovulation (by 24 h) of a single follicle and formation of a CL that secreted higher levels of progesterone. A wax-based vehicle allowed for a steady and continuous delivery of the active compound over the treatment period. During the third study, the addition of a letrozole-containing gel coating increased the rate of initial absorption and hastened the increase on plasma concentrations of the active ingredient, while the letrozole-containing wax-based vehicle prolonged drug-delivery from the intravaginal device. When tested in vivo during the fourth study, we confirmed that letrozole-impregnated intravaginal devices formulated with a wax base plus a gel coat vehicle was most suitable for the application of a letrozole-based protocol for the synchronization of ovulation in cattle, since it effectively delivered elevated concentrations of letrozole, and reduced estradiol production resulting in increased follicular growth and lifespan, without adversely affecting progesterone production. The application of a letrozole-impregnated intravaginal device for 4 days, combined with PGF treatment at device removal and GnRH 24 h post-device removal increased the percentage of ovulations and synchrony of ovulation in cattle, regardless the stage of the estrous cycle at initiation of treatment. As observed in previous studies, the effects observed could be associated with an increase in circulating LH iv concentrations. However, the effects of treatment on gonadotropin concentrations are inconclusive, possibly due to inadequate sampling frequency. The impact of letrozole treatment of oocyte fertility remains unknown. The results of the five experiments support our general hypothesis that non-steroidal aromatase inhibitors have potential as a steroid-free option for the control of ovarian function in cattle. However, further research is needed in order to elucidate the effects of letrozole treatment during the proestrous on oocyte competence and fertility of the resulting ovulations in cattle

La experiencia escolar en las políticas de inclusión

El presente trabajo expone los resultados de una investigación en curso sobre los modos de apropiación de las políticas destinadas a promover la “inclusión escolar” en el marco de las transformaciones de la escuela secundaria y la experiencia escolar de los estudiantes bajo estas nuevas condiciones.El foco es la experiencia escolar de los estudiantes, entendida como la manera en que estos actores, individuales y colectivos, socializan y se constituyen como sujetos, cómo dotan de sentido su paso por la escuela. Para poder captar la experiencia escolar se adopta un abordaje metodológico cualitativo a través del cual se pretende reconstruir el conjunto de condiciones objetivas del campo para luego comprender las representaciones y percepciones de los sujetos desde su posición en el espacio social (Bourdieu, 1998).Partimos de la hipótesis de que la experiencia escolar de los jóvenes de las escuelas analizadas, está atravesada por una tensión caracterizada por la presencia espacios de trabajo pedagógico, donde se sienten reconocidos como sujetos, escuchados y considerados en sus condiciones vitales, pero cuyo aporte al desarrollo del conocimiento se les revela como de menor valor comparativo respecto de otros espacios en la misma escuela y de otras instituciones.Asimismo, estas instancias y profesores reconocidos por su aporte a la continuidad en los estudios y a la apropiación del los conocimientos que transmiten, se diferencian de aquellos otros en los que contrariamente perciben una ausencia de involucramiento con su proceso de aprendizaje. Por último se desarrollará una reflexión sobre la exclusión educativa

Funciones de índice de sitio para Austrocedrus chilensis en el sudoeste de Río Negro (Argentina)

No obstante los avances en el conocimiento del manejo de los bosques de Austrocedrus chilensis (D. Don) Florin et Boutleje (ciprés de la cordillera), aún se carecen de modelos de producción y para desarrollarlos es esencial la correcta evaluación de la calidad de sitio. En este trabajo se presenta el desarrollo y ajuste de tres variantes de un modelo predictivo del crecimiento en altura dominante que permiten generar funciones de índice de sitio para esta especie. Empleando el método de la ecuación de la diferencia se desarrollaron tres expresiones diferentes del modelo de Chapman-Richards que resultaron invariantes a la edad de referencia. Dos expresiones resultaron polimórficas con asíntota común, mientras que la restante fue anamórfica con asíntota variable. Para generar los datos altura-edad, un total de 23 árboles de sitio, tomados de 10 parcelas, fueron apeados para realizarles el análisis de fuste y reconstruir su crecimiento pasado en altura. En las pruebas convencionales de bondad de ajuste los tres modelos presentaron resultados satisfactorios y ninguno se demostró superior. Considerando criterios e indicadores específicos para las funciones de sitio, el comportamiento predictivo de los tres modelos resultó aceptable, aunque todos mostraron sesgo e imprecisión para edades juveniles. En el rango de edades de mayor importancia práctica la precisión es razonable y el sesgo desaparece, siendo la formulación anamórfica la de mejor desempeño. Para mejorar el comportamiento predictivo, los resultados obtenidos sugieren el uso de la edad a la altura del pecho y el desarrollo de una variante polimórfica con asíntota variable de ese modelo.In spite of increased knowledge about Austrocedrus chilensis (D. Don) Florin et Boutleje (ciprés de la cordillera) forest management, there is a lack of yield models, and to develop them a sound evaluation of site quality is critical. This paper is aimed at presenting the development and fitting of three formulations of a predictive model for dominant height useful in generating site index curves for this species. Using the difference-equation approach, three different base-age invariant equations based on the Chapman-Richards model were produced. Two models showed a polymorphic pattern with common asymptote while the remainder was anamorphic with varying asymptote. To acquire height-age data, a total number of 23 site trees from 10 sample plots were destructively sampled to recover their past height growth through stem analysis techniques. In conventional goodness of fit test, all models showed satisfactory results and no one appeared to be superior. According to specific criteria and indicators set for site index curves, the predictive behaviour of the three models was acceptable, though they all showed bias and lack of precision for young ages. In the range of ages with more practical importance the precision is reasonable and bias vanishes, being the anamorphic formulation the one with best performance. In order to improve the predictive behaviour, results suggest that breast-height age should be used and that a polymorphic formulation with varying asymptote should be developed for this model.Laboratorio de Investigación de Sistemas Ecológicos y Ambientale

Exportación de monitores de concentración de O2 ambiental a Venezuela

Fil: Yapura, Paola. Universidad de Buenos Aires. Facultad de Ciencias Económicas. Buenos Aires, Argentina

Liderazgo transformacional en la felicidad en el trabajo del personal de salud en un hospital nacional del Cusco, 2022

El presente trabajo de investigación tiene como objetivo determinar cuál es la influencia del liderazgo en la felicidad en el trabajo del personal de salud de un hospital nacional del Cusco en el 2022. La metodología de estudio fue de alcance cuantitativo con diseño no experimental y transversal teniendo como resultados: que el liderazgo transformacional influye en 10.2% en la felicidad en el trabajo del personal de salud, así como en sus dimensiones de compromiso individual en un 9.7%, en satisfacción laboral en un 16.5% y en el compromiso organizativo afectivo en un 5.4% del personal de salud de un hospital nacional del Cusco, lo que indica que el liderazgo transformacional aunque parezca el porcentaje bajo si ejerce influencia en la felicidad del trabajo así como en sus dimensiones

Stand dynamics, spatial pattern and site quality in Austrocedrus chilensis forests in Patagonia, Argentina

Aim of study: The objective of this study was to analyze the stand structure and spatial pattern of two A. chilensis stands with contrasting soil conditions and different site qualities in order to explore if these differences lead to patterns similar to the ones observed under different precipitation conditions.Area of study: The study was carried out in two stands located near the city of El Bolsón (41° 56’S - 71° 33’ W), Rio Negro, Argentina.Material and Methods: We evaluated age difference between canopy strata (upper and lower) in two stands with different site qualities by means of a Mann-Whitney test. Dead individuals by diameter class were compared by means of a chi square test. Spatial distribution pattern was analyzed using the pair-correlation function and the mark-correlation function.Main results: Both sites exhibited a random spatial distribution of A. chilensis but different processes seem to underlie the patterns. In the low-quality site facilitation and continuous establishment led to a transient clumped spatial pattern. Mortality mediated by competition occurred mainly on small trees resulting in the current random pattern. On the other hand, spatial pattern in the high-quality site does not reflect a facilitation mediated recruitment. The upper strata established synchronously and subsequent regeneration was episodic.Research highlights: The results show that the differences in site quality may lead to different establishment spatial patterns, showing the importance of facilitation processes in sites with drier soil conditions and lower quality, although results may be site specific, due to the lack of replications.Keywords: Spatial analysis; regeneration; mortality; competition; facilitation.Abbreviations used:  LQ: low-quality site; HQ: high-quality site

Cambio en el paisaje cultural de la montaña del salkantay y su impacto en las ideologías locales. el caso de soraypampa (prov. de Anta, región Cusco)

El motivo para la realización del presente trabajo de investigación, se centra en la perspectiva de la gestión del patrimonio cultural, ligada con el manejo del paisaje cultural, dentro de un contexto ideológico, republicano y contemporáneo del mundo andino. Además, esta la idea de cómo perciben los habitantes de la circunscripción el cambio del paisaje a través de la introducción de infraestructura turística y cuál es la concepción de la sacralidad y paisaje cultural intangible que ellos tienen, luego cómo perciben los habitantes del área de estudio la actitud de la montaña del Salkantay frente a la introducción de infraestructura turística, de cómo se degrada el paisaje cultural con el uso inadecuado de su espacio circundante. Por otro lado, como la construcción de la infraestructura turística (hoteles), trae como consecuencia una alteración drástica del carácter sagrado de la montaña en estudio y finalmente sugerir un manejo multidisciplinario de acuerdo a los estándares internacionales ofrecidos a través de la experiencia y de entidades como la UNESCO. PALABRAS CLAVE: Paisaje cultural, ideológico, montaña, sacralidad, geografía sagrada, multidisciplinario.--- The reason for the realization of this research focuses on the perspective of cultural heritage management, linked to the management of the cultural landscape, within an ideological, context, prehispanic, colonial, republican and contemporary of the Andean world. Besides this the idea of how they perceive the inhabitants of the district landscape change through the introduction of tourism infrastructure and what is the concept of intangible cultural landscape sacred and they have, then how they perceive the inhabitants of the study area attitude Salkantay mountain against the introduction of tourism infrastructure, how the cultural landscape degrades the inappropriate use of the surrounding space. On the other hand, the construction of tourist infrastructure (hotels), results in a drastic alteration of the sacredness of the mountain in study and finally suggest a multidisciplinary management according to international standards offered through experience and entities such as UNESCO. KEYWORDS: Cultural landscape, Ideological, Mountain, Sacrelity, Sacred Geography, Multidisciplinary.Tesi

Simultaneous Inversion of Six Parameters for Three-Layered Metal Specimens

Layered media is used extensively in the aerospace and automotive industries from paint on metal surfaces to actuators with piezoelectric layers. NDE of such materials is used for manufacturing quality control or damage inspection. A method of inversion for thickness and wavespeeds from ultrasonic data using the minimization of the difference between measured and constructed transfer function magnitudes in transmission has been developed [1,2]. Using this method, for a three-layer metal/liquid/metal specimen immersed in water it is possible to invert accurately for up to four parameters, for example, three thicknesses and one wavespeed. Kinra, Wang, Zhu, and Rawal [3] reported thickness measurements on three-layer metal-clad specimens