Regulatory mechanisms associated with egg production and egg activation in Oreochromis niloticus.

This study investigated several important aspects of reproductive physiology in the Nile tilapia (Oreochromis niloticus). Although tilapias have been cultured for several decades, there has been a rapid increase in production by aquaculture over recent years. Tilapia have thus become one of the main teleosts contributing significantly to world aquaculture. However, significant problems exist that constrain the efficient management of reproduction in these fish. These include low fecundity, and the asynchronous, and hence unpredictable, nature of spawning cycles. Manipulation of photoperiod has proved to be a powerful tool in the control of reproductive cycles in various other fish species, and has become an established aspect of the culture of certain species. We know very little about the ways in which photoperiod might be involved in the control of reproduction in tilapiine species, especially the hormonal rhythms associated with this regulatory mechanism. In addition, manipulation of environmental parameters such as photoperiod has often been reported to influence fertilization rates in some teleosts. Spawning induction using the application of exogenous hormones, a technique often used in aquaculture to produce predictable spawning patterns, is also associated with problems concerning fertilization. It is clear from the literature that there is very little information available concerning the precise mechanisms involved with fertilization and egg activation in fish. Thus, the research described in this Thesis falls into two main sections. The first section investigates how photoperiod may impart a regulatory role over reproduction in O. niloticus broodstock, how circulating levels of the hormone melatonin vary in this species, and describes the isolation and partial characterization of a melatonin receptor from this species. In the second part of this Thesis, I have made a preliminary investigation of the precise mechanisms that might be involved at egg activation in fish using tilapia as a research model; these studies were then extended to three other commercially-important fish. Tilapia are now a major aquaculture species with production levels of over a million tonnes annually. The hatchery production of fry however, remains very inefficient due to relatively low fecundity and lack of spawning synchrony. Any methodology that enables farmers to synchronise the reproductive cycles of their broodstock would have immense practical advantages. Light is already known to play an important role in the initiation of gonad maturation in other fish species. In this investigation the reproductive performance of 32 sibling Nile tilapia was evaluated under four different photoperiods: short daylength (6L:18D), normal daylength (12L:12D), long daylength (18L:6D), and continuous illumination (24L:0D). Significantly larger eggs (P < 0.05) were produced under normal daylength (12L:12D) compared to other treatment groups. Fish reared under long daylength (18L:6D) exhibited significantly higher (P < 0.05) total fecundity (2408 ± 70 eggs spawn-1) and relative fecundity (7.2 ± 0.2 eggs g-1 body weight) concomitant with a significant reduction in inter-spawn-interval (ISI, 15 ± 1 days) in comparison with the rest of the trials. This investigation shows that long daylength (18L:6D) helps improve some important reproductive traits in Nile tilapia, and suggests that such methodology may be used to alleviate the production problems caused by low fecundity and poor spawning synchrony, and thus play a valuable future role in tilapia culture. Plasma melatonin levels were determined by radioimmunoassay (RIA) in fish kept under controlled photo-thermal conditions to investigate how the hormone melatonin varies with environmental change. Six melatonin profiles were described, the first over a 24 hour period (diel cycle), the second describing only changes in melatonin during the night-time, and four further profiles describing the melatonin levels of fish under four different experimental light regimes: short daylength (6L:18D), normal daylength (12L:12D), long daylength (18L:6D), and continuous illumination (24L:0D). Results showed that in tilapia, melatonin is produced in a rhythmic way; melatonin profiles showed that maximal levels of melatonin were reached as soon as the light went off, then these levels remain high throughout the dark phase and just after the onset of the light phase, melatonin levels were suppressed to base levels. Studies also demonstrated that melatonin levels were very low in O. niloticus (50 - 100 pg/ml) compared with salmonids and other species, in which much higher production of melatonin (600 - 1000 pg/ml) has been reported. Experiments showed that a negative correlation exists between melatonin levels and reproduction in tilapia. Those fish exposed to long daylength (18L:6D) exhibited the lowest melatonin levels but highest fecundity, and lowest ISI; fish reared under short daylength (6L:18D) exhibited the highest melatonin levels but much reduced fecundity and longer ISI. Although, it appears that photoperiod thus seems to play an important role in the reproduction of O. niloticus, and is certainly known to impart a strong regulatory effect upon reproduction in other fish, the present investigation also shows that those fish reared under continuous illumination produced the second highest fecundity and exhibited reduced Inter-Spawning-Interval (ISI). However, melatonin levels in these fish were kept constant at very low levels (20 - 30 pg/ml). Interestingly, these observations might suggest that melatonin may not be exerting a strong effect upon reproduction in O. niloticus. Results also showed that the role of melatonin in the reproduction of O. niloticus is not as well-defined as in other species of fish. There was clearly a negative relationship between melatonin level and reproductive activity in our experiments; although the results of the continuous illumination treatment produced data that suggested that melatonin might not play a major role in the regulation of reproduction in this species. It was clearly important therefore, to further elucidate the role and function of melatonin in this species. In a further series of experiments, the melatonin receptor from O. niloticus was successfully cloned (Mella), and a partial sequence of this receptor was obtained. This partial sequence was generated using primers based upon known sequence information for the melatonin receptor in rainbow trout. The tilapia melatonin receptor was highly expressed in the brain. However, no expression was found in either gonadal or somatic tissues other than brain after 25 cycles of PCR amplification. In the present study, photoperiod was shown to enhance various reproductive parameters in tilapia, melatonin profiles were defined throughout known periods of light:dark, and a melatonin receptor isolated and partially characterised. However, further research is required to fully characterise the precise function of melatonin in the regulation of tilapia reproduction, especially in terms of its interaction with other endogenous factors, and its relationship with exogenous factors other than photoperiod. Studies in a variety of organisms including amphibians, fish, ascidians, nemerteans, echinoderms, mammals, and even a species of flowering plant, clearly demonstrate that an increase in intracellular egg calcium is crucial to the process of egg activation at fertilization. Mammalian studies suggest that calcium is released from internal egg stores at fertilization by a sperm-derived cytosolic protein factor. Recent studies in the mouse have identified this sperm-derived factor as being a novel sperm-specific phospholipase C (PLC) isoform (PLCQ. Homologues of PLCζ have since been isolated from human and monkey sperm. In addition, sperm factor activity has been detected in non-mammalian species including chicken, Xenopus, and a flowering plant. In this thesis, I report novel evidence for the existence of a similar sperm-derived factor in a commercially important species of teleost fish, the Nile tilapia. Using an established bioassay for calcium release, the sea urchin egg homogenate, it was clearly demonstrated that protein extracts obtained from O. niloticus spermatozoa exhibited PLC activity similar to that seen in mammalian sperm extracts, and also induce calcium release when added directly to the homogenate. Further, sperm extracts prepared from O. niloticus induced calcium oscillations when injected into mouse oocytes, suggesting that O. niloticus sperm contained a similar calcium-mobilizing molecule to that found in mammalian sperm. The same bioassay was used to assay the calcium-releasing properties of sperm extracts prepared from three further commercially important aquaculture species: Atlantic halibut (Hippoglossus hippoglossus), African catfish (Clarias gariepinus), and rainbow trout (Onchorhynchus mykiss). All three of these species exhibited the ability to release calcium in the bioassay, suggesting that the four species of teleost tested in this Thesis appear to use a similar mechanism of egg activation as that reported for mammalian species. However, it was not possible to identify the specific sperm-specific molecule involved, nor the precise cell signalling system used, although present data would support the involvement of a PLC molecule. Several attempts were undertaken to isolate a possible PLC£ homologue from O. niloticus, using molecular techniques such as the Polymerase Chain Reaction (PCR) and screening of a tilapia bacteria artificial chromosome (BAC) library. However, within the time frame imposed by this Thesis, I was unable to successfully isolate a PLC£ homologue from O. niloticus, although research effort in this area is gathering pace and now involves cDNA library screening, and genomic technology. Nevertheless, the results presented herein have provided a valuable insight into the process of egg activation in fish and should provide a stable foundation for future research. Further elucidation of this crucial biological process in fish may help in the reduction of commercial loss post-fertilization, and during early embryonic development

La inteligencia emocional y su impacto para optimizar el desempeño del personal de la mediana empresa y sucursales dedicada a la pastelería y cafetería, ubicada en la ciudad de San Salvador.

La inteligencia emocional en las empresas es un término que poco a poco toma gran importancia en las organizaciones, demandan profesionales capaces de identificar y gestionar sus propias emociones y ajenas, así como también las habilidades sociales y con capacidad de adaptarse a las distintas situaciones, estimando por medio de diferentes métodos la evaluación del desempeño del personal, como lo es en la mediana empresa dedicada a la pastelería y cafetería. El presente trabajo se realizó con el fin de proporcionar instrumentos de evaluación de desempeño referente a la inteligencia emocional, para optimizar el desempeño laboral que se requiere de acuerdo a sus necesidades. Es por ello, que la investigación se llevó a cabo en el municipio de San Salvador, en una empresa donde se realizó un censo, ya que contaba con cuarenta y uno empleados, se utilizó instrumentos como la entrevista y cuestionario para adquirir la información necesaria de la situación actual de la empresa, además en la investigación se utilizó el método analítico ya que se explica la relación entre las variables, además el tipo investigación se realizó explicativo, detallando el impacto de inteligencia emocional y el desempeño laboral. En el diseño de la investigación es no experimental debido a que se observó la problemática por parte del equipo investigador. En el instrumento proporcionado se efectúa de acuerdo a la problemática de la empresa. Se presenta formularios, de acuerdo a la información obtenida de los resultados. Se concluye: 1. La falta de conocimiento de filosofía institucional y la necesidad de compartir los valores a los empleados. 2. Dificultad de comunicación en la minoría de los empleados. 3. La importancia de incluir la inteligencia emocional en las evaluaciones de desempeño. 4. La falta de conocimiento de nombre y métodos utilizados para la evaluación de desempeñoii 5. No poseen un plan de capacitación para mejorar y reforzar habilidades que aporten beneficio a la empresa. Se recomienda: 1. Incluir dentro del plan de capacitación la identidad corporativa y buscar la retroalimentación, así también crear fuentes visibles a través de canales de comunicación. 2. Mejorar la comunicación de los empleados y las diferentes áreas implementando actividades y creando un buen ambiente de trabajo. 3. La elaboración de un instrumento de evaluación de desempeño tomando como enfoque la inteligencia emocional de acuerdo a las necesidades vigentes de la organización. 4. Capacitar a la encargada de recursos humanos para que obtenga conocimientos e instrumentos para un mejor proceso de gestión y control de desempeño. 5. Crear un plan de capacitación para los empleados con el fin de mejorar habilidades y actitudes y dar un enfoque sobre la inteligencia emocional que ayudará en la capacidad interpersonal del empleado. Además, aportando el desempeño del personal se tomó como relevancia la inteligencia emocional en diferentes áreas como el conocimiento y desempeño del cargo, característica del individuo evaluado y cantidad de trabajo/Calidad de trabajo, ofreciendo al trabajador beneficios basado en las competencias o habilidades emocionales, asimismo informando al empleado cuál es su posición actual en lo que respecta a su desempeño y aportando para optimizar, y finalmente para determinar el plan de capacitación

Death receptor 5 expression is inversely correlated with prostate cancer progression.

Prostate carcinoma (PCa) is one of the most common cancers in men. Prostate-specific antigen (PSA) has been widely used to predict the outcome of PCa and screening with PSA has resulted in a decline in mortality. However, PSA is not an optimal prognostic tool as its sensitivity may be too low to reduce morbidity and mortality. Consequently, there is a demand for additional robust biomarkers for prostate cancer. Death receptor 5 (DR5) has been implicated in the prognosis of several cancers and it has been previously shown that it is negatively regulated by Yin Yang 1 (YY1) in prostate cancer cell lines. The present study investigated the clinical significance of DR5 expression in a prostate cancer patient cohort and its correlation with YY1 expression. Immunohistochemical analysis of protein expression distribution was performed using tissue microarray constructs from 54 primary PCa and 39 prostatic intraepithelial neoplasia (PIN) specimens. DR5 expression was dramatically reduced as a function of higher tumor grade. By contrast, YY1 expression was elevated in PCa tumors as compared with that in PIN, and was increased with higher tumor grade. DR5 had an inverse correlation with YY1 expression. Bioinformatic analyses corroborated these data. The present findings suggested that DR5 and YY1 expression levels may serve as progression biomarkers for prostate cancer

Valoración de la escorrentía de las colinas de la ciudad de Portoviejo

Portoviejo, capital of the province of Manabí, founded on March 12, 1535, is one of the oldest cities on the Ecuadorian coast. It is characterized by a stable temperate climate with an annual average temperature of around 24⁰C. The average rainfall for the years 2000 to 2009 is 596.20 mm per year, the wettest years are 2000 with 733 mm and 2008 with 823 mm; while the driest are 2001, 2003, and 2009 with rainfall below 500 mm. Maximum precipitation values ​​in 1997 and 1998 for the El Niño phenomenon. The city is located in a valley, whose average elevation has been estimated at 40.00 meters above sea level, and in the northeast and southwest areas it is limited by hills whose maximum levels oscillate between 250 ~ 300 meters above sea level. The parishes of Progreso, Pacheco, San Pablo and Briones are located in the lower part of the hills of the northeast sector. During the rainy season they experience landslide problems, with consequent flooding due to surface runoff and water erosion. zone. For the control of runoff there is a sewer system, which is insufficient, since the lower area is flooded, causing year-to-year urban problems of vehicular and human traffic, in addition to material losses. With the purpose of contributing with design elements that allow to diagnose the current situation of the runoff and its control works, in the present work, based on the methodology proposed by the Soil Conservation Service of the United States (Soil Conservation Service - SCS), complemented with the techniques of Geographic Information Systems (GIS), runoff was estimated by sector for return periods 2, 3, 5, 10, 20, 50 and 100 years. Index Terms — Hydrology, rainfall, return periods, climate change, runoff contro

Aprovechamiento energético de residuos sólidos

En muchos países de la región iberoamericana, la biomasa supone más del 30 % del consumo energético nacional. En los países industrializados, el consumo de biomasa energética suele ser muy inferior, por la contribución predominante de los “combustibles fósiles”. Tal situación tuvo un punto de inflexión en la década de los 70, con la primera crisis del petróleo, que permitió dejar en evidencia la insostenibilidad de un modelo basado en el uso casi exclusivo de los combustibles fósiles. Actualmente, la amenaza más significativa es el incremento en las emisiones de gases de efecto de invernadero y el calentamiento global. En la mayoría de los países y en los eventos internacionales existe un interés creciente por la utilización energética de los residuos, el ahorro y la eficiencia energética con el doble objetivo de reducir la dependencia energética y reducir los impactos ambientales. En esta publicación se presentan varios proyectos de investigación desarrollados y aplicados a nivel real de valorización de la biomasa residual. El retorno al uso de la biomasa con fines energéticos no presupone una vuelta atrás en el desarrollo tecnológico; al contrario, el uso de este recurso biológico se encuentra directamente relacionado con nuevas formas de uso de los residuos y el desarrollo de nuevos procesos y tecnologías que permitan la producción de combustibles más avanzados con elevadas prestaciones, altas eficiencias energéticas, bajas emisiones y costos inferiores a los combustibles fósiles. Algunos de estos procesos están en fase comercial y otros en pleno desarrollo, como ocurre con otras fuentes de energías renovables

Influence of the El Niño phenomena on the climate change of the Ecuadorian coast

The climate on the Ecuadorian coast depends mainly on the marine currents of Humboldt and El Niño, which appear in the dry and rainy seasons, respectively. The Humboldt current is distinguished by being cold, while that of El Niño is hot. The presence of the El Niño current causes an increase in the evaporation of ocean waters with the consequent appearance of the rainy season. There are anomalous seasons of the El Niño stream, when the water temperature rises above the norm, higher than 25.5 °C, which has been called El Niño phenomena. The appearance of this natural phenomena has proven to be decisive in the climate change of the coast of Ecuador. In order to have technical information, important for the planning, control and development of the water resources of the DHM, in this research a temporal analysis of the monthly rainfall during 55 years, 1963-2017 period, is carried out. The National Institute of Hydrology and Meteorology of Ecuador (Instituto National de Meteorología e Hidrología - INAMHI) at station M005, located in the Botanical Garden of the Technical University of Manabí in Portoviejo, obtained these records. An analysis of the monthly and annual patterns is made, establishing that the El Niño events occurred in 1983, 1997 and 1998, have established guidelines for the change in the production of rainwater in the levels of intensity and temporal distribution, increasing the months of drought, while precipitation levels increase, concentrating in fewer months, basically in February and March. This is a situation that increases the water deficit, especially when there is not enough infrastructure of hydraulic works for the storage and regulation of runoff

Nonlinear Controller for the Set-Point Regulation of a Buck Converter System

In this paper, we present a nonlinear PID controller based on saturation functions with variable parameters in order to regulate the output voltage of a buck converter in the presence of changes in the input voltage. The main feature of the proposed controller is to bound the control input with a variable parameter to avoid the windup effect generated by the combination of the integral control action and some operation conditions. The main advantages of the proposed nonlinear PID controller are its low computing cost and the simple tuning task to implement the control strategy in an embedded system. The acceptable behavior of the closed-loop system is presented through the simulation and experimental results

Local ancestry inference provides insight into Tilapia breeding programmes

Tilapia is one of the most commercially valuable species in aquaculture with over 5 million tonnes of Nile tilapia, Oreochromis niloticus, produced worldwide every year. It has become increasingly important to keep track of the inheritance of the selected traits under continuous improvement (e.g. growth rate, size at maturity or genetic gender), as selective breeding has also resulted in genes that can hitchhike as part of the process. The goal of this study was to generate a Local Ancestry Interence workflow that harnessed existing tilapia genotyping-by-sequencing studies, such as Double Digest RAD-seq derived Single-Nucleotide Polymorphism markers. We developed a workflow and implemented a suite of tools to resolve the local ancestry of each chromosomal locus based on reference panels of tilapia species of known origin. We used tilapia species, wild populations and breeding programmes to validate our methods. The precision of the pipeline was evaluated on the basis of its ability to identify the genetic makeup of samples of known ancestry. The easy and inexpensive application of local ancestry inference in breeding programmes will facilitate the monitoring of the genetic profile of individuals of interest, the tracking of the movement of genes from parents to offspring and the detection of hybrids and their origin

Diseño y desarrollo de un sistema informático de evaluación de proyectos de rentabilidad social para Alcaldías Municipales de El Salvador

En el presente documento se plantea el diseño y desarrollo de un sistema de evaluación de proyectos con enfoque social para las instituciones municipales, con el fin de dar una referencia acertada a la toma de decisión que en la actualidad le compete al consejo municipal para ayudar a utilizar de una manera más eficiente los fondos que el estado distribuye a las alcaldía, las cuales, tienen un gran reto al saber que la población tiene muchas demandas y necesidades que deben ser satisfecha

Improving Sustainability through Corrosion Resistance of Reinforced Concrete by Using a Manufactured Blended Cement and Fly Ash

The objective of this paper is to report the improvement of sustainability through the increase of reinforced concrete corrosion resistance by using a blended cement and fly ash. Different reinforced concrete mixtures were prepared with partial substitution of a manufactured blended cement with fly ash from a thermal power plant in Andorra (Teruel, Spain). These mixtures were manufactured using three different water/cement ratios (0.46, 0.59, and 0.70) and three substitution percentages of cement by fly ash (0%, 25%, and 50%). The test cylinders underwent an accelerated carbonation process and exposure to different chloride levels, with the aim of characterizing the corrosion level of the different mixtures. The addition of local FA matched or even improved the resistance of the control mixture against carbonation and chlorides.This work was economically supported by Conacyt: National Scholarship Call: 290604 (No. 309129), mixed scholarship: Scholarship 2012–2013 for foreign mobility (290674), Basic Science Project 155363, Universidad Autónoma de Nuevo León and Universidad de Alicante