Transgastric laparoscopic polypectomy in giant gastric polyps not susceptible of endoscopic management: novel surgical technique and case series.

BACKGROUND: The identification of gastric polyps incidentally in endoscopies of the upper digestive tract has increased its incidence, varying between 0.5% and 23%. 10% of these polyps have symptoms, 40% are hyperplastic. We allow ourselves to propose a laparoscopic technique for the management of giant hyperplastic polyps associated with a pyloric syndrome, not susceptible to endoscopic resection. METHOD: A series of patients approached by laparoscopic transgastric polypectomy due to the giant gastric polyps associated with pyloric syndrome, in Bogotá, Colombia, from January 2015 to December 2018. RESULTS: Seven patients, 85% female, with an average age of 51 years, who were admitted for pyloric syndrome and were taken to laparoscopic management, with an average surgical time of 42 min, intraoperative bleeding 7-8 cc, tolerance to the oral route 24 hours, no conversion, without mortality. CONCLUSIONS: Transgastric polypectomy for the management of benign giant gastric polyps that cannot be resected endoscopically turns out to be a feasible method, with a low rate of complications and without mortality.

ANTECEDENTES: La identificación de pólipos gástricos de manera incidental en endoscopias de vías digestivas altas ha aumentado su incidencia, que varía entre el 0.5% y el 23%. El 10% de estos pólipos presentan síntomas y el 40% son hiperplásicos. Nos permitimos proponer una técnica laparoscópica para el manejo de los pólipos hiperplásicos gigantes asociados a síndrome pilórico no susceptibles de resección endoscópica. MÉTODO: Serie de pacientes llevados a polipectomía transgástrica laparoscópica por hallazgo de pólipos gástricos gigantes asociados a síndrome pilórico, en Bogotá, Colombia, de enero de 2015 a diciembre de 2018. RESULTADOS: Un total de siete pacientes, el 85% de sexo femenino, con edad promedio de 51 años, ingresaron por síndrome pilórico y fueron llevados a manejo laparoscópico, con un tiempo quirúrgico promedio de 42 minutos, sangrado intraoperatorio de 7-8 cc, tolerancia a la vía oral a las 24 horas, no conversión, sin mortalidad. CONCLUSIONES: La polipectomía transgástrica para el manejo de pólipos gástricos gigantes benignos que no pueden ser resecados por vía endoscópica resulta ser un método factible, con una baja tasa de complicaciones y sin mortalidad.

Laparoendoscopic surgery for the treatment of gastrointestinal stromal tumors: A case series.

INTRODUCTION: Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal neoplasms of the gastrointestinal tract. The standard management for localized GIST is the complete surgical resection. For this procedure, laparoendoscopic cooperative surgery (LECS) has been proposed as a safe and effective alternative. We want to show our experience with LECS technique for the management of GIST and a literature review. MATERIALS AND METHODS: A retrospective, cross-sectional study was carried out, which included patients with a diagnosis of localized GIST treated with LECS technique between January 2011 and December 2018. RESULTS: During the period of the study, 21 patients were managed by LECS technique, with a male-female rate 3:1. Average surgical time was 98.5 min, 100% negative borders in all patients. Intraoperative bleeding was 30.7 cc and all patients had orally tolerance in the first 24 h. None of them required ICU management, no mortality was reported. CONCLUSIONS: The LECS technique has demonstrated to be a viable, safe, and effective technique for the management of gastric GIST's, showing superiority in organ function preservation and in the range of oncological margins. Prospective studies are necessary to obtain knowledge about the outcome of patients managed through LECS technique.

INTRODUCCIÓN: Los tumores del estroma gastrointestinal (GIST) son las neoplasias mesenquimales más comunes del tracto gastrointestinal. El tratamiento estándar para los GIST localizados es la resección quirúrgica completa. Para este procedimiento, el abordaje cooperativo laparo-endocopico (ACLE) se ha propuesto como una alternativa segura y eficaz. Queremos mostrar nuestra experiencia con la técnica ACLE para el manejo de GIST y unzaa revisión de la literatura. MATERIAL Y MÉTODOS: Se realizó un estudio retrospectivo, transversal, que incluyó pacientes con diagnóstico de GIST localizado tratados con la técnica ACLE entre enero de 2011 y diciembre de 2018. RESULTADOS: Durante el periodo de estudio se manejaron 21 pacientes con técnica de ACLE, con una tasa hombre-mujer de 3:1. El tiempo quirúrgico promedio fue de 98.5 min, con 100% de bordes negativos en todos los pacientes. El sangrado intraoperatorio fue de 30.7 cc y todos los pacientes tuvieron tolerancia oral en las primeras 24H. Ninguno de ellos requirió manejo en UCI, no se reportó mortalidad. CONCLUSIONES: La técnica ACLE ha demostrado ser una técnica viable, segura y eficaz para el manejo de los GIST gástricos. Mostrando superioridad en la preservación de la función orgánica y en los magines oncológicos. Son necesarios estudios prospectivos para conocer el resultado de los pacientes manejados mediante la técnica ACLE.

Suprahepatic Cava Thrombus Due to Wilms Tumor: Technique Without Cardiopulmonary Bypass.

Wilms tumor is a frequent malignant neoplasia in pediatric population. Extension to the inferior vena cava is a complication that occurs in approximately 4%-15% of cases. Surgical techniques derived from the field of adult transplant surgery allow the resection of the tumor with its thrombus extension. In the case of a 6-year-old male patient with a stage III Wilms tumor that originated from the left renal vein, thrombectomy and left radical nephroureterectomy were accomplished without extracorporeal circulation. Surgical technique applied in adult transplant surgery for removal of advanced renal tumors, could be a safe and feasible technique in pediatric population.

Timberlake's behavior systems: A paradigm shift toward an ecological approach.

Timberlake's Behavior Systems model constitutes a discontinuity in theoretical and empirical consequences of traditional approaches to the experimental study of behavior, such as operant as well as classical conditioning. Here we consider the synergy of an animal-centered approach and acknowledge that niche-related behaviors as functional activities create synergy with Gibson's ecological approach, in at least three terms. These are: an ecological stance for learning and behavior, hierarchical organization of behavior systems, and affordances implied in the process of tuning experimental procedures. The ideas expressed herein favor a paradigm shift toward an ecological approach to behavioral science.

The effect of lever height on the microstructure of operant behavior.

The effect of lever height on the temporal organization of reinforced lever pressing was examined. Lever pressing was reinforced on a variable-interval 30-s schedule in rats, with lever height manipulated across six successive conditions. Parameters of the organization of responses in bouts (bout length distribution, bout-initiation rate, within-bout rate, and sequential dependency) were estimated. These estimates revealed (1) a qualitative change in the distribution of IRTs and their sequential dependency when the lever was too high, (2) a mixture of geometrically-distributed bout lengths at all lever heights, and (3) longer bouts at lower and intermediate lever heights. In accordance with previous data, these findings suggest that lower and intermediate lever heights favored lever pressing with longer bout lengths, faster bout initiation, faster within-bout responding, and more sequentially dependent timing. These results underscore the disociability of motoric capacity in operant performance, and may reflect the influence of the body size on the temporal organization of the operant.

An affordance analysis of unconditioned lever pressing in rats and hamsters.

Two experiments were conducted to assess the effect of lever height on lever pressing that was not explicitly reinforced - i.e., operant-level responding. Two rodent species were used as subjects, rats (Experiment 1) and hamsters (Experiment 2), aiming to compare the behavioral support offered by one lever at various heights relative to the subjects' body size. Results showed that lever height had a substantial effect on response rate. The rate of lever pressing varied similarly for rats and hamsters as a function of lever height, when lever height was re-scaled relative to body size. The distribution of inter-response times showed that lever pressing was organized in bouts separated by pauses. This pattern of responding was accurately described in both experiments by a mixture of two exponential distributions. These findings support an analysis of affordances in non-human species.

Hamsters' (Mesocricetus auratus) memory in a radial maze analog: the role of spatial versus olfactory cues.

The golden hamster's (Mesocricetus auratus) performance on radial maze tasks has not been studied a lot. Here we report the results of a spatial memory task that involved eight food stations equidistant from the center of a circular platform. Each of six male hamsters depleted the food stations along successive choices. After each choice and a 5-s retention delay, the hamster was brought back to the center of the platform for the next choice opportunity. When only one baited station was left, the platform was rotated to evaluate whether olfactory traces guided hamsters' choices. Results showed that despite the retention delay hamsters performed above chance in searching for food. The choice distributions observed during the rotation probes were consistent with spatial memory and could be explained without assuming guidance by olfactory cues. The radial maze analog we devised could be useful in furthering the study of spatial memory in hamsters.

The "lunching" effect: pigeons track motion towards food more than motion away from it.

Four experiments measured pigeons' pecking at a small touch-screen image (the CS) that moved towards or away from a source of food (the US). The image's effectiveness as a CS was dependent on its motion, direction, and distance relative to the US. Pecking to the CS increased with proximity to the US when the CS moved towards the US (Experiment 1). This held true even when a departing CS signalled a US of greater magnitude (Experiment 2). Response rates to stationary stimuli were greater the closer they were to the hopper; but rate was less than when the same spot was part of a motion towards food, and greater than when it was part of a motion away (Experiment 3). The rate of responding in all three cases (motion towards, stationary, motion away) decreased exponentially with distance from the hopper. The distance and motion effects observed under these Pavlovian contingencies were different when pecking to the spot was required for reinforcement (Experiment 4).

Búsqueda de alimento en hámsteres dorados(Mesocricetus auratus): el efecto de la distancia entre múltiples fuentes de alimento / Foraging behavior in golden hamsters (Mesocricetus auratus): effect of the distance among multiple patches

Se evaluó el patrón de desplazamiento y la eficiencia en la búsqueda de alimento de cuatro hámsteres en un encierro con múltiples metas, variando la distancia entre ellas. La distancia entre las metas se manipuló en orden aleatorio, según dos condiciones: la de Metas Cercanas (10 cm entre ellas) y la condición de Metas Distantes (21.5 cm entre ellas). Los sujetos debían extraer el alimento colocado dentro de unos cilindros (estaciones) trepando a ellos en un encierro de 110 cm2. Los resultados mostraron, en ambas condiciones, que la distancia recorrida entre las subidas a las estaciones fue mayor en momentos más tardíos del ensayo. Por otro lado, aunque la proporción más alta de elecciones se centró en las estaciones adyacentes, éstas ocurrieron en mayor medida para la condición de Estaciones Distantes, y hubo un mayor número de elecciones a estaciones ubicadas diagonalmente o salteadas en la condición de Estaciones Cercanas.

The pattern of travel and the efficiency in foraging behavior was evaluated in four hamsters searching for food within an enclosure with multiple patches. Two different distances among patches were randomly arranged: Near-Patches (10 cm separation) and Distant-Patches (21.5 cm separation). Subjects obtained the food by mounting over the cylinders (stations) placed in the enclosure of 110 cm2. Results showed that in both, Near and Distant conditions, the distance between responses was longer in late stages of the trials then in early stages. Nonetheless, the most choices to adjacent stations were in Distant-Patches condition, while skips and diagonal-station choices were more frequently showed in the Near-Patches condition.

Measuring resistance to change at the within-session level.

Resistance to change is often studied by measuring response rate in various components of a multiple schedule. Response rate in each component is normalized (that is, divided by its baseline level) and then log-transformed. Differential resistance to change is demonstrated if the normalized, log-transformed response rate in one component decreases more slowly than in another component. A problem with normalization, however, is that it can produce artifactual results if the relation between baseline level and disruption is not multiplicative. One way to address this issue is to fit specific models of disruption to untransformed response rates and evaluate whether or not a multiplicative model accounts for the data. Here we present such a test of resistance to change, using within-session response patterns in rats as a data base for fitting models of disruption. By analyzing response rate at a within-session level, we were able to confirm a central prediction of the resistance-to-change framework while discarding normalization artifacts as a plausible explanation of our results.

Deslocamento, sensibilidade ao reforço e múltiplas alternativas / Travel, sensitivity to reinforcement, and multiple alternatives

Quando ratos procuram por alimento em oito alternativas disponíveis concorrentemente e saltam barreiras parase deslocar de um local para outro, as distribuições de tempo e respostas geralmente ficam aquém das distribuiçõesde reforços. Esse resultado pode refletir a maneira pela qual as barreiras são introduzidas na situação. O presente experimento explorou essa possibilidade com ratos. Esquemas concorrentes de reforço com components de intervalo randômico de diferentes durações forneceram alimento em oito barras instaladas em quatro câmaras experimentais conectadas a uma plataforma central. Primeiro, os ratos podiam entrar nas câmaras e mudar de uma barra para a outra sem restrições. Depois, o acesso às câmaras foi obstruído e as barras foram separadas uma da outra por barreiras de 300 mm de altura. Finalmente, as oito barreiras aumentaram de 300 para 700 mm. Os tempos de visita e de mudança e a quantidade de respostas de mudança foram menores quando os ratos visitavam as barras sem restrições.Com a introdução das barreiras, essas medidas aumentaram, atingindo os maiores valores quando a altura das barreiras aumentou. Para as respostas, a sensibilidade ao reforçamento, estimada pelo parâmetro s da lei generalizadada igualação, aumentou com aumentos no requisito para o deslocamento, indicando uma tendência à super igualação. No entanto, apenas um rato mostrou a mesma tendência para a alocação de tempo. (AU)

When rats search for food in eight alternatives concurrently available and climb barriers to travel from one siteto another, the distributions of times and responses often lag behind those of the reinforcers. This result may reflect the way in which the barriers are introduced into the situation. The present experiment explored this possibility with rats. Concurrent schedules of reinforcement with random interval components of different values provided food in eight levers mounted in four chambers connected to a central platform. First, the rats were allowed to enterthe chambers and switch from one lever to another with out restrictions. Then access to the chambers was obstructed and the levers separated from one another by 300-mm-high barriers. Finally, the height of the barriers was increased from 300 to 700 mm. The shortest visit times, giving-up times, and giving-up responses were produced when rats visited the levers without restrictions. With the barriers in place these measures increased, reachinghigher values when barrier height was increased. For responses, sensitivity to reinforcement, as estimated by theparameter s of the generalized matching law, increased with increasing travel requirement, indicating a tendency toward over matching. However, for time allocation only one rat showed the same tendency. (AU)