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Under ideal conditions, Escherichia coli cells divide after adding a fixed cell size, a strategy known as the adder. This concept applies to various microbes and is often explained as the division that occurs after a certain number of stages, associated with the accumulation of precursor proteins at a rate proportional to cell size. However, under poor media conditions, E. coli cells exhibit a different size regulation. They are smaller and follow a sizer-like division strategy where the added size is inversely proportional to the size at birth. We explore three potential causes for this deviation: degradation of the precursor protein and two models where the propensity for accumulation depends on the cell size: a nonlinear accumulation rate, and accumulation starting at a threshold size termed the commitment size. These models fit the mean trends but predict different distributions given the birth size. To quantify the precision of the models to explain the data, we used the Akaike information criterion and compared them to open datasets of slow-growing E. coli cells in different media. We found that none of the models alone can consistently explain the data. However, the degradation model better explains the division strategy when cells are larger, whereas size-related models (power-law and commitment size) account for smaller cells. Our methodology proposes a data-based method in which different mechanisms can be tested systematically.

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Introduction: We introduce the third case reported in the literature of an atypical presentation of pleomorphic adenoma located in the nasal vestibule of a young patient who assisted at our clinic. Case Report: A young man with no important medical history consulted due to a painless mass-type slow-growth lesion associated with right nasal obstruction. He underwent surgical management and complete resection of the mass. The pathological study revealed a pleomorphic adenoma, confirmed by immunohistochemistry. Conclusion: This case confirms that pleomorphic adenomas can occur anywhere in the head and neck, even in areas without upper air-digestive tract mucosa.

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Introducción: se presenta el caso de un tonsilolito gigante periamigdalino como hallazgo en una radiografía panorámica de rutina en odontología. Caso clínico: se presenta el caso de un paciente masculino de 26 años a quien le realizaron radiografía panorámica de control, en la que se evidenció una gran imagen radiopaca a nivel periamigdalino derecho de aproximadamente 2 cm de diámetro; el paciente fue asintomático al momento de la consulta y al recibir tratamiento quirúrgico se evidenció un tonsilolito gigante que fue retirado en bloque sin complicaciones. Discusión: se presentan diagnósticos diferenciales de imágenes radiopacas encontradas en radiografías de cabeza y cuello compatibles con tonsilolitos. Conclusiones: se recuerda esta entidad diagnóstica que, aunque rara, se debe tener presente como posible hallazgo en estudios de imagen cabeza y cuello o síntomas a nivel amigdalino.

Introduction: We present the case of a giant tonsil stone as a finding in routine pano-ramic radiography in dentistry. Clinical case: we present the case of a 26 years-old male patient who underwent a control panoramic radiography where a large radiopa-que image of approximately 2 cm in diameter was evidenced at the right peritonsillar level; the patient was asymptomatic at the time of the consultation, when recei-ving surgical treatment, a giant tonsillolith was evidenced which was removed en bloc without complications. Discussion: differential diagnosis of radiopaque ima-ges found in head and neck radiographs compatible with tonsilloliths are presented. Conclusions: Although rare, this entity should be kept in mind as a possible finding in head and neck imaging studies or symptoms at tonsillar space.

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INTRODUCTION: Myotonic dystrophy type 1 is a rare genetic disorder that mainly affects the musculoskeletal system; However, it may cause several complications in other body systems representing challenges for health care providers. PATIENT CONCERNS: We present the case of a patient with a history of previously diagnosed type 1 myotonic dystrophy who presented to the emergency department with cough dyspnea, and thoracic pain. DIAGNOSIS: Differential diagnoses included pulmonary embolism with a moderate probability according to the Wells score, acute coronary syndrome, acute heart failure, and pneumonia. Diagnostic workup involved chest radiography, EKG, and a CTPA which revealed pneumonia, posteriorly the patient presented de novo atrial fibrillation. INTERVENTIONS: The patient was successfully treated with empiric antibiotic therapy and amiodarone, respiratory and physical therapy. OUTCOMES: The patient was discharged on day 34, however oxygen weaning was not possible. CONCLUSION: Treatment of MD1 patients is challenging due to the various mechanisms of the disease; patients with new-onset deterioration should be screened for the most common complications such as cardio-respiratory events.The authors suggest pneumonia as a risk factor for basal respiratory function deterioration and a contributing factor for triggering cardiac events for further research in prospective studies.

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RESUMEN El lupus eritematoso sistémico ampolloso (LESA) es una enfermedad vesículo-ampollosa mediada por autoanticuerpos en pacientes con lupus eritematoso sistémico (LES). Se observan vesículas y ampollas tensas sobre una piel edematosa, eritematosa y, en ocasiones, normal en cualquier región del cuerpo, incluyendo áreas mucosas y que no han sido fotoexpuestas. Se presenta el caso de un paciente varón de 16 años de edad con nefritis lúpica, que al séptimo día de hospitalización presenta múltiples ampollas serosas y hemorrágicas sobre el rostro, el tronco, el abdomen y las extremidades superiores. El estudio histológico mostró una dermatosis ampollar subepidérmica con numerosos neutrófilos.

ABSTRACT Bullous systemic lupus erythematosus (BSLE) is a vesiculobullous disease mediated by autoantibodies in patients with systemic lupus erythematosus (SLE). Tense vesicles and bullae are seen on an edematous, erythematous and sometimes normal skin in any body region, including mucous membranes and non-photoexposed areas. This is the case of a 16-year-old male patient with lupus nephritis who, on the seventh day of hospitalization, presented multiple serous and hemorrhagic blisters on the face, trunk, abdomen and upper extremities. The histological study showed a subepidermal bullous dermatosis with numerous neutrophils.

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La dilatación gástrica aguda se fundamenta por dos teorías, la mecánica que es explicada por el síndrome de arteria mesentérica superior, y la atónica que es producto de una condición médica en la que el estómago progresivamente se vuelve hipotónico y se sobredistiende aún en ausencia de una causa mecánica obstructiva; con mayor frecuencia la dilatación gástrica aguda se presenta en pacientes con trastornos de la alimentación y puede conllevar a una complicación rara pero letal como la perforación gástrica. Presentamos el caso de una paciente de 18 años, quien acude al servicio de emergencia con dolor abdominal agudo, es intervenida quirúrgicamente, donde se encontró perforación de la pared gástrica anterior. Se le realizó una gastrectomía parcial proximal, y se envió el espécimen para estudio patológico. La histopatología mostró necrosis transmural predominantemente en fondo gástrico.

Acute gastric dilation is based on two theories, the mechanical one that is explained by the superior mesenteric artery syndrome and the atonic one, the latter is the product of a medical condition in which the stomach progressively becomes hypotonic and over-distended even in the absence of an obstructive mechanical cause; it most often occurs in patients with eating disorders; which can lead to a rare but fatal complication such as gastric perforation. We present the case of an 18 year old patient who comes to the emergency service of our hospital with acute abdominal pain, undergoes surgery, where there is perforation of the anterior gastric wall, and a proximal. Partial gastrectomy is performed, and a sends the specimen for pathology study. Histopathology shows transmural necrosis predominantly in the gastric fundus.

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BACKGROUND: How small, fast-growing bacteria ensure tight cell-size distributions remains elusive. High-throughput measurement techniques have propelled efforts to build modeling tools that help to shed light on the relationships between cell size, growth and cycle progression. Most proposed models describe cell division as a discrete map between size at birth and size at division with stochastic fluctuations assumed. However, such models underestimate the role of cell size transient dynamics by excluding them. RESULTS: We propose an efficient approach for estimation of cell size transient dynamics. Our technique approximates the transient size distribution and statistical moment dynamics of exponential growing cells following an adder strategy with arbitrary precision. CONCLUSIONS: We approximate, up to arbitrary precision, the distribution of division times and size across time for the adder strategy in rod-shaped bacteria cells. Our approach is able to compute statistical moments like mean size and its variance from such distributions efficiently, showing close match with numerical simulations. Additionally, we observed that these distributions have periodic properties. Our approach further might shed light on the mechanisms behind gene product homeostasis.

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Una de las técnicas más utilizadas para la predicción de producción de bioproductos y distribución intracelular de flujos de microorganismos es el Análisis de Balance de Flujos - FBA por sus siglas en inglés. El FBA requiere de una función objetivo que represente el objetivo biológico del microorganismo estudiado. En este trabajo se propone un nuevo tipo de funciones objetivo basada en la combinación de objetivos de compartimentos físicos presentes en el microorganismo estudiado. Este tipo de funciones objetivo son examinadas junto con un modelo estequiométrico extraído de la reconstrucción iMM904 del microorganismo S. cerevisiae. Su desempeño se compara con la función objetivo más usada en la literatura, la maximización de biomasa, en condiciones experimentales anaeróbicas en cultivos continuos y aeróbicas en cultivos tipo lote. La función objetivo propuesta en este trabajo mejora las predicciones de crecimiento en un 10% y las predicciones de producción de etanol en un 75% respecto a las obtenidas por la función objetivo de maximización de biomasa, en condiciones anaeróbicas. En condiciones aeróbicas tipo lote la función objetivo propuesta mejora en un 98% las predicciones de crecimiento y en un 70% las predicciones de etanol con respecto a la función objetivo de biomasa.

Flux Balance Analysis - FBA - is one of the most used techniques in prediction of microorganism bioproducts. It requires an objective function that represents biological objective of the studied microorganism. This paper presents a new kind of objective functions based on individual physical compartment objetives in the studied microorganism. These kind of functions was tested with a stoichiometric model extracted from iMM904 reconstruction of S. cerevisiae and its performance is compared with the most used objective function in literature, growth maximization, in anaerobic and aerobic batch conditions. The presented objective function outperform growth predictions in 10% and ethanol predictions in 75% compared with obtained by maximization of growth objective function, in anaerobic conditions. In aerobic batch conditions the presented objective function outperforms in 98% growth preditions and 70% ethanol predictions compared with growth maximization.

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BACKGROUND: The main objective of flux balance analysis (FBA) is to obtain quantitative predictions of metabolic fluxes of an organism, and it is necessary to use an appropriate objective function to guarantee a good estimation of those fluxes. METHODOLOGY: In this study, the predictive performance of FBA was evaluated, using objective functions arising from the linear combination of different cellular objectives. This approach is most suitable for eukaryotic cells, owing to their multiplicity of cellular compartments. For this reason, Saccharomyces cerevisiae was used as model organism, and its metabolic network was represented using the genome-scale metabolic model iMM904. As the objective was to evaluate the predictive performance from the FBA using the kind of objective function previously described, substrate uptake and oxygen consumption were the only input data used for the FBA. Experimental information about microbial growth and exchange of metabolites with the environment was used to assess the quality of the predictions. CONCLUSIONS: The quality of the predictions obtained with the FBA depends greatly on the knowledge of the oxygen uptake rate. For the most of studied classifications, the best predictions were obtained with "maximization of growth", and with some combinations that include this objective. However, in the case of exponential growth with unknown oxygen exchange flux, the objective function "maximization of growth, plus minimization of NADH production in cytosol, plus minimization of NAD(P)H consumption in mitochondrion" gave much more accurate estimations of fluxes than the obtained with any other objective function explored in this study.

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El microorganismo Saccharomyces cerevisiae cuenta con gran número de modelos biológicos conocidos como reconstrucciones, las cuales pueden ser a escala genómica. De estas reconstrucciones a escala genómica provienen los modelos matemáticos, también llamados modelos estequiométricos. Una de las técnicas más usadas para estudiar estos modelos es el Análisis de Balance de Flujos (FBA). El proposito del FBA es predecir el crecimiento del microorganismo bajo estudio, y la producción y consumo de componentes como el etanol, CO2 glicerol, sucinato, acetato y piruvato. Para determinar si las predicciones obtenidas mediante FBA son únicas se utiliza la técnica de Análisis de Variabilidad Flujos (FVA). El presente trabajo muestra los resultados de aplicar el FBA a la reconstrucción reciente del microorganismo S. cerevisiae, la denominada iMM904 y los compara con un conjunto de datos experimentales presente en la literatura. Este trabajo también estudia la existencia de múltiples predicciones FBA utilizando la técnica FVA. Los resultados ilustran que es posible predecir el crecimiento del microorganimo S. cerevisiae, con errores entre el 11% y 28%; la producción de CO2, con errores entre el 0.3% y 4.5% y la producción de etanol, con errores entre el 11% y 13%.

Several biological models, named reconstructions, are used for the study of the S. cerevisiae microorganism. The reconstructions can be genomic scaled. Mathematical models are generated from the reconstructions and they are called stoichiometric models. The flux balance analysis (FBA) is one of the tools used for the analysis of these models. The FBA attempts to predict the evolution of the microorganism and the consumption and production of components like glucose, ethanol, glycerol, succinate, acetate and pyruvate. A Flux variability analysis (FVA) is used to determine the uniqueness of the FBA predictions. This paper shows the results of applying FBA to the iMM904 reconstruction of S. cerevisiae and compares them with experimental data from literature. The results in this paper show that it is possible to predict the evolution with errors between 11% and 28% ; the production of CO2 with errors between 0.3% and 4.5%; and the production of ethanol with errors between 11% and 13%, using FBA for the iMM904 model.

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