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Absorción de nitrógeno y rendimiento de arroz con diferentes formas de nitrógeno aplicado previo al riego Nitrogen uptake and rice yield with different forms of nitrogen applied before irrigation
César Eugenio Quintero,Fabio Prats,María de los ángeles Zamero,Edgardo Santiago Arévalo
Ciencia del Suelo , 2011,
Abstract: En la Argentina el arroz se siembra sobre suelo seco con maquinaria y luego se lo riega por inundación desde inicios del macollaje hasta la madurez. Esto determina condiciones especiales donde el nitrógeno puede perderse tanto por volatilización como por desnitrificación. Las fuentes de N más recomendadas en arroz son las amoniacales o amídicas; sin embargo, las fuentes nítricas podrían presentar ventajas importantes. Se realizó un ensayo a campo con el objetivo de evaluar la respuesta y eficiencia de absorción de distintas fuentes y formas de nitrógeno. Se utilizó: urea, sulfato de amonio (SA), nitrato de calcio (CN), solución de urea-nitrato de amonio-tiosulfato (UAN+ATS) y nitrato de amonio calcáreo (CAN). Se aplicó una dosis de N 60 kg/ha previo al riego para todas las fuentes, incluyendo un tratamiento testigo. Se evaluó la absorción de N y el rendimiento. El rendimiento en grano del tratamiento control fue de 9.756 kg/ha y su absorción total de N fue de 137 kg/ha; mientras que los fertilizados absorbieron de 164 a 185 kg/ ha. Las fuentes puras (urea, SA y CN) mostraron una alta tasa de absorción del N inicial, con una recuperación aparente del N del fertilizante de 80 al 100% en diferenciación de panícula. La mayor respuesta se observó con el CN, con una alta eficiencia de uso del fertilizante. Las fuentes mixtas (UAN+ATS y CAN) mostraron menor absorción y recuperación del N proveniente del fertilizante. Los resultados de este ensayo indican que las pérdidas por desnitrificación no fueron importantes y que las fuentes nítricas podrían ser utilizadas en fertilización de arroz. In Argentina, rice is mechanically sowed on dry soil and is then flooded from early tillering to maturity. This practice gives rise to conditions that promote nitrogen losses by volatilization and denitrification. The most recommended N fertilizers for rice have N in the form of ammonium or amides; however, nitric sources have shown advantages. A field trial was conducted to evaluate the responsiveness and absorption efficiency of different sources and forms of nitrogen. Urea, ammonium sulfate (AS), calcium nitrate (CN), solution of urea-ammonium nitrate-thiosulfate (UAN + ATS) and calcium ammonium nitrate (CAN) were tested. A fertilizer rate of 60 kg N/ha was applied before irrigation and a control treatment with no N was included. Rice N uptake and yield was measured. The control treatment yielded 9756 kg/ha and total N uptake was 137 kg/ha, while the fertilized treatments absorbed from 164 to 185 kg N/ha. Pure fertilizer sources (urea, SA, CN) showed a high rate of initial
Absorción de nitrógeno y rendimiento de arroz con diferentes formas de nitrógeno aplicado previo al riego
Quintero,César Eugenio; Prats,Fabio; Zamero,María de los ángeles; Arévalo,Edgardo Santiago; Spinelli,Nicolás Blas; Boschetti,Graciela Norma;
Ciencia del suelo , 2011,
Abstract: in argentina, rice is mechanically sowed on dry soil and is then flooded from early tillering to maturity. this practice gives rise to conditions that promote nitrogen losses by volatilization and denitrification. the most recommended n fertilizers for rice have n in the form of ammonium or amides; however, nitric sources have shown advantages. a field trial was conducted to evaluate the responsiveness and absorption efficiency of different sources and forms of nitrogen. urea, ammonium sulfate (as), calcium nitrate (cn), solution of urea-ammonium nitrate-thiosulfate (uan + ats) and calcium ammonium nitrate (can) were tested. a fertilizer rate of 60 kg n/ha was applied before irrigation and a control treatment with no n was included. rice n uptake and yield was measured. the control treatment yielded 9756 kg/ha and total n uptake was 137 kg/ha, while the fertilized treatments absorbed from 164 to 185 kg n/ha. pure fertilizer sources (urea, sa, cn) showed a high rate of initial n uptake, with an 80 to 100% apparent recovery of n fertilizer at the panicle differentiation stage. surprisingly, the greatest response was observed in the treatment with cn, presenting a high fertilizer use efficiency. the mixed sources (uan+ats, can) showed a lower n uptake and fertilizer recovery. the results of this field trial indicate that denitrification losses were not significant and nitric sources could be used in rice fertilization.
Traffic noise affects forest bird species in a protected tropical forest
Arévalo,J. Edgardo; Newhard,Kimberly;
Revista de Biología Tropical , 2011,
Abstract: the construction of roads near protected forest areas alters ecosystem function by creating habitat fragmentation and through several direct and indirect negative effects such as increased pollution, animal mortality through collisions, disturbance caused by excessive noise and wind turbulence. noise in particular may have strong negative effects on animal groups such as frogs and birds, that rely on sound for communication as it can negatively interfere with vocalizations used for territorial defense or courtship. thus, birds are expected to be less abundant close to the road where noise levels are high. in this study, we examined the effects of road traffic noise levels on forest bird species in a protected tropical forest in costa rica. data collection was conducted in a forest segment of the carara national park adjacent to the coastal highway. we carried out 120 ten minute bird surveys and measured road noise levels 192 times from the 19th to the 23rd of april and from the 21st to the 28th of november, 2008. to maximize bird detection for the species richness estimates we operated six 12m standard mist nets simultaneously with the surveys. the overall mist-netting effort was 240net/h. in addition, we estimated traffic volumes by tallying the number of vehicles passing by the edge of the park using 24 one hour counts throughout the study. we found that the relative abundance of birds and bird species richness decreased significantly with the increasing traffic noise in the dry and wet season. noise decreased significantly and in a logarithmic way with distance from the road in both seasons. however, noise levels at any given distance were significantly higher in the dry compared to the wet season. our results suggest that noise might be an important factor influencing road bird avoidance as measured by species richness and relative abundance. since the protected forest in question is located in a national park subjected to tourist visitation, these results have
Traffic noise affects forest bird species in a protected tropical forest
J. Edgardo Arévalo,Kimberly Newhard
Revista de Biología Tropical , 2011,
Abstract: The construction of roads near protected forest areas alters ecosystem function by creating habitat fragmentation and through several direct and indirect negative effects such as increased pollution, animal mortality through collisions, disturbance caused by excessive noise and wind turbulence. Noise in particular may have strong negative effects on animal groups such as frogs and birds, that rely on sound for communication as it can negatively interfere with vocalizations used for territorial defense or courtship. Thus, birds are expected to be less abundant close to the road where noise levels are high. In this study, we examined the effects of road traffic noise levels on forest bird species in a protected tropical forest in Costa Rica. Data collection was conducted in a forest segment of the Carara National Park adjacent to the Coastal Highway. We carried out 120 ten minute bird surveys and measured road noise levels 192 times from the 19th to the 23rd of April and from the 21st to the 28th of November, 2008. To maximize bird detection for the species richness estimates we operated six 12m standard mist nets simultaneously with the surveys. The overall mist-netting effort was 240net/h. In addition, we estimated traffic volumes by tallying the number of vehicles passing by the edge of the park using 24 one hour counts throughout the study. We found that the relative abundance of birds and bird species richness decreased significantly with the increasing traffic noise in the dry and wet season. Noise decreased significantly and in a logarithmic way with distance from the road in both seasons. However, noise levels at any given distance were significantly higher in the dry compared to the wet season. Our results suggest that noise might be an important factor influencing road bird avoidance as measured by species richness and relative abundance. Since the protected forest in question is located in a national park subjected to tourist visitation, these results have conservation as well as management implications. A decrease in bird species richness and bird abundance due to intrusive road noise could negatively affect the use of trails by visitors. Alternatives for noise attenuation in the affected forest area include the enforcement of speed limits and the planting of live barriers. Rev. Biol. Trop. 59 (2): 969-980. Epub 2011 June 01. Las carreteras cerca de bosques alteran la función del ecosistema por fragmentación del hábitat y tienen otros efectos negativos como contaminación, mortalidad de animales y ruido excesivo; sobre todo en animales como rana
Comportamiento de la infección experimental por aislamientos colombianos de Giardia duodenalis en el modelo animal del gerbo ( Meriones unguiculatus)
Arévalo,Adriana; Duque,Sofía; Nicholls,Rubén Santiago;
Biomédica , 2005,
Abstract: introduction. natural and experimental giardia infections have been reported from bovines, equines, goats, canines, felines and rodents such as mice, rats and gerbils. the latter have provided successful animal models for giardia duodenalis and giardia muris experimental infections. objective. the gerbil model was used to establish the pattern of infection of colombian giardia human isolates. materials and methods. giardia cysts were obtained from stool specimens of symptomatic giardiasis patients by means of sucrose-percoll gradients. animal inoculation was performed by gastric intubation and injection with 5x103 giardia cysts. the course of infection was established by counting cysts every day and trophozoites weekly throughout a period of 30 days. results. the pattern of cyst excretion was found to be intermittent. cysts were released during the second and third weeks of infection but not during the first or fourth weeks. the mean minimal number of cysts released per 2-hr collection period was 79 and the mean maximum number was 17,943. colonization of the small intestine by trophozoites was observed with a mean number ranging from 15,000 to 6,577,778 trophozoites/ml. discussion and conclusions. gerbils inoculated with g. duodenalis isolates obtained from geographical areas outside colombia resolved the infection between 86 and 114 days after infection, whereas gerbils infected with colombian g. duodenalis isolates resolved the infection at 30 days. the gerbil proved to be a good animal model for experimental infection with colombian isolates of g. duodenalis. experimental giardia infection of gerbils permit a sufficient yield of cysts and trophozoites to be used as antigens for the immunization of other animals and to obtain giardia antibodies that could be used for giardia antigen detection assays in stool specimens.
Estudio de niveles de Immunoglobulina A secretora en secreción salival de ni os sanos
Edgardo Tomasello H,Luz Arévalo F,María E Fuenzalida C,Emilio Torres Kameid
Revista chilena de pediatría , 1981,
Abstract:
Genetic diversity of Giardia intestinalis populations in Colombia
Ravid,Zaava; Duque,Sofía; Arévalo,Adriana; Nicholls,Rubén Santiago; Wasserman,Moisés;
Biomédica , 2007,
Abstract: introduction. giardia intestinalis is a protozoan parasite that causes a gastrointestinal infection known as giardiosis, which is transmitted primarily through fecal-oral contamination. genetic studies of axenically cultivated giardia isolates have identified two major genetic groups distributed throughout the world. in the present study 24 native strains of the parasite were analyzed by the rapd technique (random amplified polymorphic dna). objective. to determine the level of polymorphism and the complexity of giardia intestinalis circulating strains in specific areas of colombia. materials and methods. the rapd method was used, as it allows for a quick, simple and reliable analysis that requires no prior knowledge of the genetics of the parasite. a rapd analysis was conducted on native isolates collected in colombia between 1997 and 2001, established in continuous cultures. several primers were tested separately, in order to enhance the capacity for discrimination of the method. results. of the 24 strains that were included in the study, 22 were arranged in independent clusters. the strains that were from the same geographic area and collected at about the same time, generally displayed highly similar but distinguishable rapd patterns. clones isolated from a strain were analyzed as well, and it was possible to differentiate them molecularly. conclusion. the studied strains showed to belong to genotype a .the results suggest that the colombian strains studied consist of a heterogeneous mixture of closely related populations.
Obtención, purificación y caracterización de anticuerpos policlonales IgY desarrollados en gallina, dirigidos contra aislamientos colombianos de Giardia duodenalis
García,Dabeiba Adriana; Nicholls,Rubén Santiago; Arévalo,Adriana; Torres,Orlando; Duque,Sofía;
Biomédica , 2005,
Abstract: introduction. the development of polyclonal antibodies requires laboratory animals, as the usually rabbits, which are bled for obtaining the immunoglobulins.hens are an alternative to developing igy polyclonal antibodies. objective. in the current study, hens were used to develop igy anti- giardia duodenalis antibodies and to evaluate five protocols for its purification. materials and methods. three hens were immunized intramuscularly immunized with colombian giardia duodenalis isolates trophozoites on day 0, 15, 30, 45, 60, 90 and 120. the hen eggs were collected before each immunization, and igy purified from yolk by delipidation (d) and precipitation (p) using five different protocols: m1: (p: ammonium sulfate/d:dextran sulfate-calcium chloride), m2: (d: dextran sulfate-calcium chloride/p: ammonium sulfate), m3: (d: chloroform/p: ammonium sulfate 50%), m4: (d: solution a/p: solution b) and m5: (d: chloroform/p: ammonium sulfate 30%). the immunochemistry evaluation of igy anti- giardia duodenalis was assayed by immunodiffusion, counterimmunoelectrophoresis (cie) and western blot. the purity of igy was assayed by sds-page under reducing and nonreducing conditions. immunoglobulin concentration (mg/ml) was estimated by spectrophotometry and densitometry. results. igy anti- giardia duodenalis by cie had titres up to 1:32. sds-page, without 2- mercaptoethanol showed a 180 kd band characteristic of the whole to igy and, with 2- mercaptoethanol, two bands of 68 and 30 kd, characteristic of its light and heavy chains, respectively. the greatest concentrations of immunoglobulin were recovered by method two (m2), producing 4.6 mg of igy per ml of initial egg yolk. conclusions. the easy and inexpensive production of igy anti- giardia duodenalis in hens is an advantage for using it to develop immunoassays that detect the parasite in fecal eluates.
Diversidad genética de poblaciones de Giardia intestinalis en Colombia Genetic diversity of Giardia intestinalis populations in Colombia
Zaava Ravid,Sofía Duque,Adriana Arévalo,Rubén Santiago Nicholls
Biomédica , 2010,
Abstract: Introducción. Giardia intestinalis es un parásito protozoario que causa la infección gastrointestinal conocida como giardiosis, la cual se transmite principalmente a través de la contaminación fecal-oral. Estudios genéticos de aislamientos de Giardia cultivados axénicamente han identificado dos grupos genéticos principales distribuidos en el mundo. En el presente estudio se analizaron 24 cepas nativas del parásito por medio de la técnica RAPD (ADN polimórfico amplificado aleatoriamente). Objetivo. Determinar el nivel de polimorfismo y la complejidad de las cepas circulantes en áreas específicas de Colombia. Materiales y métodos. Se utilizó el método RAPD debido a que permite obtener un análisis rápido, sencillo y confiable, que no requiere conocimiento previo de la genética del parásito. El análisis RAPD se realizó en cultivos continuos de aislamientos nativos recolectados en Colombia entre 1997 y 2001. Se evaluaron separadamente diversos iniciadores con el objeto de incrementar la capacidad de discriminación del método. Resultados. De las 24 cepas incluidas en el estudio, 22 se agruparon en clusters independientes. Las cepas que provenían de la misma zona geográfica, y que fueron recolectadas aproximadamente al mismo tiempo, generalmente presentaron patrones RAPD sumamente similares pero distinguibles entre sí. Se analizaron así mismo los clones aislados de una misma cepa y fue posible diferenciarlos molecularmente. Conclusión. Los resultados de las cepas estudiadas indicaron que éstas corresponden al genotipo A, y sugieren que consisten en una mezcla heterogénea de poblaciones strechamente relacionadas. Introduction. Giardia intestinalis is a protozoan parasite that causes a gastrointestinal infection known as giardiosis, which is transmitted primarily through fecal-oral contamination. Genetic studies of axenically cultivated Giardia isolates have identified two major genetic groups distributed throughout the world. In the present study 24 native strains of the parasite were analyzed by the RAPD technique (Random Amplified Polymorphic DNA). Objective. To determine the level of polymorphism and the complexity of Giardia intestinalis circulating strains in specific areas of Colombia. Materials and methods. The RAPD method was used, as it allows for a quick, simple and reliable analysis that requires no prior knowledge of the genetics of the parasite. A RAPD analysis was conducted on native isolates collected in Colombia between 1997 and 2001, established in continuous cultures. Several primers were tested separately, in order to enhance the capacity for
？Cuántos somos? ？Dónde estamos? ？Dónde debemos estar? El papel del psiquiatra en México: Análisis preliminar
Lara Mu？oz, María del Carmen;Fouilloux, Claudia;Arévalo Ramírez, Minou del Carmen;Santiago Ventura, Yuridia;
Salud mental , 2011,
Abstract: the recently modified general law on health (ley general de salud) establishes in article 74b, section vii, that any individual with mental or behavioral disorders will have <>; this leads us to the questions titling this article. in mexico, according to the national psychiatric epidemiology survey, 28.6% of the population has presented one of the 23 idc disorders at some point in their lives. only one out of 10 patients with a mental disorder had access to specialized care. one of the most important limiting factors explaining the difference between subjects requiring services and those being provided for is the insufficient number of available psychiatrists. the worldwide mean number of psychiatrists per 100000 individuals is 3.96 (sd 5.94) and their distribution varies from one region to another; they average 0.06 in low-income countries and 9.0 in those with high incomes. as a medical specialty, psychiatry is relatively new. not until the xixth century did the treatment of mental disorder become part of the medical realm. in mexico, the teaching of psychiatry as a specialty begins in 1950. in 2010, 137 positions for psychiatry residency were made available throughout the country: campeche, coahuila, jalisco, mexico city, nuevo león, puebla, sonora, san luis potosí, tabasco, tamaulipas and yucatán. most openings (and educational venues) providing specialization in psychiatry are in mexico city. regardless, the number of psychiatrists remains scarce and the scope of their activity does not fulfill the world health organization's recommendations. the purpose of this paper was to determine the number and distribution of psychiatrists in mexico and propose new fields for their activities. methods a descriptive, cross-sectional, heterodemic study was conducted. the following data sources were reviewed: the 2008 directory of the mexican p
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