A computational framework for testing hypotheses of the minimal mechanical requirements for cell aggregation using early annual killifish embryogenesis as a model.

Introduction: Deciphering the biological and physical requirements for the outset of multicellularity is limited to few experimental models. The early embryonic development of annual killifish represents an almost unique opportunity to investigate de novo cellular aggregation in a vertebrate model. As an adaptation to seasonal drought, annual killifish employs a unique developmental pattern in which embryogenesis occurs only after undifferentiated embryonic cells have completed epiboly and dispersed in low density on the egg surface. Therefore, the first stage of embryogenesis requires the congregation of embryonic cells at one pole of the egg to form a single aggregate that later gives rise to the embryo proper. This unique process presents an opportunity to dissect the self-organizing principles involved in early organization of embryonic stem cells. Indeed, the physical and biological processes required to form the aggregate of embryonic cells are currently unknown. Methods: Here, we developed an in silico, agent-based biophysical model that allows testing how cell-specific and environmental properties could determine the aggregation dynamics of early Killifish embryogenesis. In a forward engineering approach, we then proceeded to test two hypotheses for cell aggregation (cell-autonomous and a simple taxis model) as a proof of concept of modeling feasibility. In a first approach (cell autonomous system), we considered how intrinsic biophysical properties of the cells such as motility, polarity, density, and the interplay between cell adhesion and contact inhibition of locomotion drive cell aggregation into self-organized clusters. Second, we included guidance of cell migration through a simple taxis mechanism to resemble the activity of an organizing center found in several developmental models. Results: Our numerical simulations showed that random migration combined with low cell-cell adhesion is sufficient to maintain cells in dispersion and that aggregation can indeed arise spontaneously under a limited set of conditions, but, without environmental guidance, the dynamics and resulting structures do not recapitulate in vivo observations. Discussion: Thus, an environmental guidance cue seems to be required for correct execution of early aggregation in early killifish development. However, the nature of this cue (e.g., chemical or mechanical) can only be determined experimentally. Our model provides a predictive tool that could be used to better characterize the process and, importantly, to design informed experimental strategies.

On the quantification of the dosimetric accuracy of collapsed cone convolution superposition (CCCS) algorithm for small lung volumes using IMRT.

Specialized techniques that make use of small field dosimetry are common practice in today's clinics. These new techniques represent a big challenge to the treatment planning systems due to the lack of lateral electronic equilibrium. Because of this, the necessity of planning systems to overcome such difficulties and provide an accurate representation of the true value is of significant importance. Pinnacle3 is one such planning system. During the IMRT optimization process, Pinnacle3 treatment planning system allows the user to specify a minimum segment size which results in multiple beams composed of several subsets of different widths. In this study, the accuracy of the engine dose calculation, collapsed cone convolution superposition algorithm (CCCS) used by Pinnacle3, was quantified by Monte Carlo simulations, ionization chamber, and Kodak extended dose range film (EDR2) measurements for 11 SBRT lung patients. Lesions were < 3.0 cm in maximal diameter and <27.0cm3 in volume. The Monte Carlo EGSnrc\BEAMnrc and EGS4\MCSIM were used in the comparison. The minimum segment size allowable during optimization had a direct impact on the number of monitor units calculated for each beam. Plans with the smallest minimum segment size (0.1 cm2 to 2.0 cm2) had the largest number of MUs. Although PTV coverage remained unaffected, the segment size did have an effect on the dose to the organs at risk. Pinnacle3-calculated PTV mean doses were in agreement with Monte Carlo-calculated mean doses to within 5.6% for all plans. On average, the mean dose difference between Monte Carlo and Pinnacle3 for all 88 plans was 1.38%. The largest discrepancy in maximum dose was 5.8%, and was noted for one of the plans using a minimum segment size of 1.0 cm2. For minimum dose to the PTV, a maximum discrepancy between Monte Carlo and Pinnacle3 was noted of 12.5% for a plan using a 6.0 cm2 minimum segment size. Agreement between point dose measurements and Pinnacle3-calculated doses were on average within 0.7% in both phantoms. The profiles show a good agreement between Pinnacle3, Monte Carlo, and EDR2 film. The gamma index and the isodose lines support the result.

Adaptación cultural del formulario EORTC QLQ CR-29 para su aplicación en pacientes con cáncer de recto en el Instituto Nacional de Cancerología de Colombia / Cross-cultural Adaptation of the EORTC QLQ CR-29 Questionnaire for Use in Colorectal Cancer Patients at the National Cancer Institute of Colombia

Objetivo: efectuar la adaptación cultural de la versión 2.0 en Español neutro del cuestionario EORTC QLQ CR-29. Método: se siguió el algoritmo propuesto por el grupo de calidad de vida del EORTC efectuando traducción, comparación de traducciones, traducción inversa y prueba piloto. Resultados: se efectuaron cambios en los términos usados para calificar las opciones de respuesta de los ítems. En cuatro de los ítems se realizaron modificaciones en algunas palabras del instrumento. En la prueba piloto se constató que los cambios realizados permitían más facilidad en la comprensión del instrumento. Conclusión: se cuenta con una versión adaptada del cuestionario EORTC QLQ CR-29 para ser usada en Colombia, que puede ser sometida a los procesos de validación para establecer sus características psicométricas al ser usada en la valoración de calidad de vida relacionada con la salud de los pacientes con cáncer de recto.

Objective: To validate a cross-cultural version of the EORTC QLQ CR-29 questionnaire version 2.0 (neutral Spanish) for use in Colombian patients. Methods: The EORTC quality of life group algorithm was applied including translation, translation comparison, reverse translation, and pilot application of the questionnaire. Results: The terms used to define the answers across items were modified. In four items the instrument was also modified using different words. The pilot verified a better understanding after the changes. Conclusions: An adapted version of the EORTC QLQ CR-29 is available for Colombia. Thus, validation of psychometric properties through its application in colorectal cancer patients is currently suitable.

Predict-prevent control method for perturbed excitable systems.

We present a control method based on two steps: prediction and prevention. For prediction we use the anticipated synchronization scheme, considering unidirectional coupling between excitable systems in a master-slave configuration. The master is the perturbed system to be controlled, meanwhile the slave is an auxiliary system which is used to predict the master's behavior. The prevention is obtained by sending a control signal to the master system, which temporarily lowers its excitability threshold and prevents its future reaction to the external perturbation. We demonstrate theoretically and experimentally that an efficient control may be achieved.

Experiencia en el manejo endovascular para el tratamiento de la aorta torácica / Experience in endovascular management for thoracic aorta treatment

Antecedentes: el tratamiento endovascular ofrece la posibilidad de cubrir el origen de la disección y evitar que progrese hasta aneurisma de la aorta, y con ello demuestra una reducción en la mortalidad hasta del 16 porciento.Objetivo: evaluar los resultados quirúrgicos en términos de morbi-mortalidad de los pacientes sometidos a manejo endovascular de las lesiones de la aorta torácica en la Fundación Cardiovascular de Colombia desde 2003 hasta 2005. Diseño–método: estudio longitudinal tipo descriptivo retrospectivo, en el que se evaluaron las historias clínicas de todos los pacientes sometidos a manejo endovascular de patología toracoabdominal; en éste sólo se incluyeron los pacientes con procedimientos de la aorta torácica, desde 2003 hasta 2005. El análisis de los datos se realizó en Stata/SE 8,0...

Endarterectomía carotídea en pacientes sintomáticos y asintomáticos: resultados de morbi-mortalidad desde 1998 hasta 2005 / Carotid endarterectomy in symptomatic and asymptomatic patients: morbid-mortality results from 1998 to 2005

Antecedentes: el accidente cerebrovascular es la tercera causa de muerte y probablemente la causa más importante de discapacidad a largo plazo. La tasa de mortalidad está entre 15% y 35% con el primer ataque y se eleva a 65% para los accidentes cerebrovasculares subsiguientes. Los resultados a largo y mediano plazo avalan esta técnica quirúrgica para el tratamiento de la enfermedad carotídea, al demostrar altos perfiles de seguridad. Objetivo: determinar los resultados de morbilidad y mortalidad quirúrgica y a 3, 6 y 12 meses de seguimiento, en los pacientes sometidos a endarterectomía carotídea desde 1998 hasta septiembre de 2005. Diseño-método: se evaluaron las historias clínicas de los pacientes sometidos a endarterectomía carotídea, desde 1998 hasta septiembre de 2005. Resultados: se realizaron 42 procedimientos desde 1998 hasta septiembre de 2005; el 57% de los pacientes eran hombres, con edad promedio de 68,8 ± 9,9 años. Los antecedentes de importancia fueron: hipertensión arterial (82%), tabaquismo (61%) y dislipidemia (50%). El 82% de los pacientes mostraban síntomas de enfermedad carotídea. Once pacientes tuvieron lesión de carótida derecha, 16 de carótida izquierda y 15 lesión bilateral, con un promedio de obstrucción de 85 ± 11,4%. La mortalidad fue de 4,7% y no estaba relacionada con el procedimiento quirúrgico. A septiembre de 2005 el 57% de los pacientes egresados estaban libres de síntomas. Conclusiones: la mortalidad para este grupo de pacientes es comparable con los resultados publicados en todo el mundo. La seguridad del procedimiento avala esta técnica quirúrgica como la primera opción en el manejo de la patología carotídea.

Antecedents: cerebrovascular disease is the third cause of death and probably the most common cause of significant long term disability. Mortality rate with first stroke is between 15% and 35% and goes up to 65% with subsequent strokes. Results at long and middle term endorse carotid endarterectomy for carotid artery disease treatment by demonstrating high safety profiles. Objective: to determine the surgical morbidity and mortality results at 3, 6 and 12 months of follow-up in patients submitted to carotid endarterectomy from 1998 to 2005. Design-Method: clinical histories of patients submitted to carotid endarterectomy from 1998 to September 2005 were evaluated. Results: 42 procedures were realized since 1998 until September 2005. 57% of the patients were men with mean age 68.8 ± 9.9 years. Important antecedents were arterial hypertension (82%), cigarette smoking (61) and dyslipidemia (50%). 82% showed symptoms of carotid disease. 11 patients had right carotid lesion and in 15 the lesion was bilateral, with mean obstruction of 85 ± 11.4%. Mortality was 4.7% and was not related to the surgical procedure. At September 2005, 57% of the discharged patients were asymptomatic. Conclusions: mortality for this group of patients is comparable to the worldwide published results. Procedure safety guarantees this surgical technique as the first option in this carotid pathology management.

Tratamiento de aorta abdominal e ilíacas con técnica endovascular / Treatment of abdominal aorta and iliac arteries with endovascular technique

Antecedentes: desde 1991 la técnica endovascular se ha aplicado con éxito en el manejo de los aneurismas de aorta infrarrenal, y se ha perfeccionado de manera tal que rápidamente se ha convertido en una alternativa para pacientes de alto riesgo para la cirugía convencional. Objetivo: describir los resultados institucionales en el manejo de las patologías de aorta abdominal e ilíacas mediante técnica endovascular desde 2003 a 2005.Diseño-Método: estudio descriptivo, longitudinal, retrospectivo, en el que se analizaron las historias clínicas de los pacientes sometidos a procedimiento endovascular de aorta abdominal e ilíacas. El análisis se realizó en Stata 8,0 S/E...

Antecedents: since 1991 endovascular technique has been successfully used in the management of infra-renal aortic aneurysms and it has been improved in such a way that it has quickly turned into an alternative for patients considered having high risk for conventional surgery. Objective: describe the institutional results in the management of abdominal aortic pathologies through endovascular technique from 2003 to 2005. Design-Method: descriptive, longitudinal, retrospective study in which clinical histories of patients that underwent an endovascular procedure of abdominal aorta and iliac arteries were analyzed. The analysis was performed in Stata 8,0 S/E. Results: 9 patients received exclusively treatment for abdominal aortic and iliac lesions. All were male individuals with mean age 68.9 ± 8.1 years. 6 patients had diagnosis of infra-renal aortic aneurysm and the other 3 had anastomotic aneurysms. Requirement of endoprosthesis was evidenced in an average of 1.9 ± 0.8. Femoro-femoral bypass surgery was performed as simultaneous procedure in 4 of the 9 patients. 77.8% of patients had no complications. Mortality due to the procedure was 22% (2 patients) and it is important to notice that only these 2 patients had complications. Conclusions: exclusion of aortic and iliac aneurysms with modular endoprosthesis is being widely implemented as a valid treatment option, with excellent results that avoid the risks of conventional surgery and its associated morbidity.

Polarization model for poorly-organized interfacial water: hydration forces between silica surfaces.

The main goal of this paper is to review the theoretical models which can be used to describe the interactions between silica surfaces and to show that a model proposed earlier by the authors (the polarization model), which accounts concomitantly for double layer and hydration forces, can be adapted to explain recent experiments in this direction. When the water molecules near the interface were considered to have an ice-like structure, a strong coupling between the double layer and hydration forces (described by the correlation length between neighboring dipoles, lambda(m)) generates long range interactions, larger than the experimentally determined interactions between silica surfaces. Arguments are brought that a gel layer is likely to be formed on the surface of silica, which, by generating disorder in the interfacial water layers, can decrease strongly the value of lambda(m). Since the prediction of lambda(m) involves a choice for the microscopic structure of water, which is often unknown, the polarization model is also presented here as a phenomenological theory, in which lambda(m) is used as a fitting parameter. Two extreme cases are considered. In one of them, the water molecules near the interface are considered to have an ice-like structure, whereas in the other they are considered randomly distributed. In the first case, the dipole correlation length lambda(m)=14.9 Angstrom. In the second limiting case, lambda(m) can be of the order of 1 Angstrom. It is shown that, for lambda(m)=4 Angstrom, a more than qualitative agreement with the experiment could be obtained, for reasonable values of the parameters involved (e.g. surface dipole strength and density, dipole location, surface charge).

Manejo endovascular de la aorta torácica / Endovascular treatment of thoracic aorta

En comparación con el tratamiento convencional, la terapia endovascular en aneurisma de aorta torácica, presenta los mejores resultados, por lo que se convierte en el tratamiento de elección para la patología de aorta torácica descendente endovascular, por su baja morbimortalidad perioperatoria. El tratamiento quirúrgico por vía retroperitoneal y/o endovascular para aneurisma de aorta abdominal infrarrenal, resulta ser especialmente seguro en pacientes octogenarios o con alta morbilidad. Esta cohorte institucional presenta resultados perioperatorios y en el seguimiento, similares a los reportados en la literatura mundial.

Compared with the conventional treatment, endovascular therapy in thoracic aortic aneurysm shows the best results, being the election treatment for the pathology of the descending thoracic aorta, due to its low peri-operative morbid-mortality. Surgical treatment by retro-peritoneal route and/or endovascular for infra-renal abdominal aortic aneurysm is especially safe in octogenarian patients or in those with a high mortality rate. This institutional cohort show peri-operative and follow-up results similar to those reported in the world literature.

Arteria carótida y placa carótida un órgano / Carotid artery and plaque. Carotid: an organ

En estos momentos es posible hacer recomendaciones sobre las indicaciones de la endarterectomía carotídea, basadas en los ensayos clínicos publicados y en la revisión de grandes series quirúrgicas. Las indicaciones para la cirugía dependerán del grado de estenosis y de la morfología de la placa, así como del estado clínico del paciente y de la morbi-mortalidad del equipo quirúrgico. Este al igual que otros estudios con grandes series de casos, evidencia que la endarterectomía carotídea y/o el manejo endovascular, realizado por equipos expertos, es un procedimiento seguro en pacientes con indicación quirúrgica.

It is now possible to recommend indications for aortic endarterectomy, based on published clinical essays and revision of large surgical series. Surgery indications will depend on the stenosis degree and the plaque morphology, as well as on the patient's clinical state and the morbid-mortality in this surgical team. As other studies with large case series, evidences that carotid endarterectomy and/or endovascular management, when realized by expert teams, is a safe procedure in patients with surgical indication.

Spared nerve injury rats exhibit thermal hyperalgesia on an automated operant dynamic thermal escape task.

Well-established methods are available to measure thermal and mechanical sensitivity in awake behaving rats. However, they require experimenter manipulations and tend to emphasize reflexive behaviors. Here we introduce a new behavioral test, with which we examine thermal sensitivity of rats with neuropathic injury. We contrast thermal hyperalgesia between spared nerve injury and chronic constriction injury rats. This device is a fully automated thermal sensitivity assessment tool designed to emphasize integrated learned responses to thermal painful and non-painful stimuli that are applied dynamically to a surface on which the animal is standing. It documents escape behavior in awake, unrestrained animals to innocuous and noxious heating of the floor where the animal is located. Animals learn to minimize pain by escaping to the opposite non-heated side; escape latency is recorded. On this device, thermal stimulus-response curves showed > 6 degrees C leftward shift in both groups of neuropathic rats. In contrast, when these animals were tested on hotplate the stimulus-response shift was < 2 degrees C. Spared nerve injury rats showed even less evidence for thermal hyperalgesia when thermal sensitivity was tested by measuring paw withdrawal to infrared heating, plantar test. The implications of test dependent magnitude of thermal hyperalgesia are discussed from the viewpoint of the tests used, as well as the animal models studied. It is argued that the dynamic thermal operant task reveals the relevance of the neuropathic injury associated pain-like behavior in relation to the whole organism.

Anticipated synchronization: a metaphorical linear view.

We study the regime of anticipated synchronization recently described on a number of dynamical systems including chaotic ones. We use simple linear caricatures to show the minimal setups able to reproduce the basic facts described.

Subharmonic stochastic synchronization and resonance in neuronal systems.

We study the response of a model neuron, driven simultaneously by noise and at least two weak periodic signals. We focus on signals with frequencies components kf(0),(k+1)f(0),...(k+n)f(0) with k>1. The neuron's output is a sequence of pulses spaced at random interpulse intervals. We find an optimum input noise intensity for which the output pulses are spaced approximately 1/f(0), i.e., there is a stochastic resonance (SR) at a frequency missing in the input. Even higher noise intensities uncover additional, but weaker, resonances at frequencies present in the input. This is a different form of SR whereby the most robust resonance is the one enhancing a frequency, which is absent in the input, and which is not possible to recover via any linear processing. This can be important in understanding sensory systems including the neuronal mechanism for perception of complex tones.

Herpes gestationis / Herpes gestationis

Herpes gestationis es una rara enfermedad autoinmune que se presenta en mujeres embarazadas, compromete principalmente la piel y puede manifestarse como lesiones bulosas intensamente pruriginosas que, en ocasiones, son de difícil diagnóstico. Nosotros reportamos 2 casos clínicos simultáneos que se presentaron en nuestro servicio en marzo del año 2002, hecho que no deja de sorprender dado lo infrecuente y poco común de esta patología

Síndrome antifosfolípidos y embarazo / Antiphospholipid syndrome and pregnancy

El SAF es una enfermedad del sistema inmune (trombofilia), en la cual existen anticuerpos con aparente especificidad por fosfolípidos con carga eléctrica negativa. Se define como la ocurrencia de trombosis, aborto recurrente o ambos junto con la presencia de anticuerpos antifosfolípidos circulantes (anticoagulante lúpico, anticardiolipinas y ß2-glicoproteina I). Su incidencia de todas las trombofílias es de un 3.5 por ciento a 6 por ciento. Existen hipótesis actuales que explicarían su patogenia basados en la activación de células endoteliales; el daño oxidativo del endotelio vascular y en la modulación de la coagulación. La forma de presentación esta dada por criterios clínicos mayores y menores, donde el sustrato de los sucesos trombóticos y una mala historia obstétrica. Estos fenómenos son la base para indicar su estudio. El diagnóstico se confirma con exámenes de laboratorio, con medición de anticuerpos, (serología). El tratamiento durante el embarazo, los resultados perinatales mejoran con el uso (ideal) de heparina de bajo peso molecular, (alternativa: heparina estándar sc + neosyntron, vo.), ácido acetilsalicílico y calcio diario, durante todo el embarazo y en el puerperio. El control tiene que ser frecuente, por un equipo médico multidisciplinario, con apoyo de laboratorio y de evaluación ecográfica Doppler seriados. Se presentan 2 casos clínicos de embarazo y SAF, manejo, tratamiento y resultado neonatal

Estudio prospectivo, randomizado, comparativo de la eficacia, seguridad y costos de cefuroxima vs cefradina en la pielonefritis aguda del embarazo / Efficacy, safety and cost of cefuroxime compared with cephradine in the treatment of acute pyelonephritis during pregnancy

Background: Second generation cephalosporins (CFPs) are more active in the treatment of acute pyelonephritis during pregnancy but their cost is considerably higher than their predecessors. Cefuroxime, a second generation CFP with oral and parenteral presentations, might offer significant advantages and become a first choice antimicrobial in this setting. Aim: To compare the efficacy, safety and cost of cefuroxime and cephradine in the treatment of acute pyelonephritis in pregnancy. Patients and methods: Hospitalized women with 12 to 34 weeks of pregnancy, with clinical and bacteriological diagnosis of acute pyelonephritis, were randomly assigned to receive cefuroxime (Curocef (r), GlaxoWellcome) 750 mg t.i.d, i.v or cephradine 1 g q.i.d., i.v. If the isolated organism was resistant to the assigned drug the patient was excluded. Once patients were afebrile, they were switched to an oral form of the same antimicrobial. They were discharged according to the clinical status and treated for a total of 14 days. Laboratory tests, including urine culture were requested during controls and at the end of follow-up at 28 days. Results: One hundred and one patients were randomized: 49 to receive cephradine and 52 to receive cefuroxime. Patients in the cefuroxime group had fewer febrile days (mean 1.7 vs 2.2, p<0.05), faster clinical recovery (mean 2.7 vs 3.1 days, p<0.05), a higher rate of bacteriological cure at 28 days (78.8 percent and 59.2 percent, p<0.05) and lower rate of failure (21.2 percent vs 40.8 percent p<0.05). The rate of resistance of isolated uropathogens was l4 percent to cephradine and 1 percent to cefuroxime. Conclusions: Cefuroxime can be considered as a first choice option in the treatment of acute pyelonephritis during pregnancy due to its tolerance, microbiological activity and efficacy

Ataxia de Friedreich y embarazo / Friedreich's ataxia and pregnancy

Se presenta un caso clínico exitoso de embarazo y parto en un paciente portadora de una ataxia de Friedrich

Microbiología aislada en la rotura prematura de membranas de término y factores de riesgo de infección en la madre y recién nacido / Isolated microbiology in the premature rupture of membranes of term and risk factors of maternal infection and newborn

El manejo óptimo de la rotura prematura de membranas a término, tendiente a reducir la morbilidad infecciosa materna y neonatal, sigue siendo motivo de controversia. Los objetivos de este estudio fueron: conocer la prevalencia y microbiología de la invasión microbiana de la cavidad amniótica e infección cervicovaginal y determinar los factores de riesgo de infección en la madre y recién nacido en la rotura prematura de membranas a término. Entre agosto de 1990 y diciembre de 1993, pacientes con rotura prematura de membranas a término fueron invitadas a participar en este trabajo. Se efectuó amniocentesis transabdominal y se tomó muestra del flujo cervicovaginal, para investigar el estado microbiológico de la cavidad amniótica y del cérvix. Se analizaron factores de riesgo de infección. Ciento cinco mujeres fueron enroladas. La prevalencia de invasión microbiana de la cavidad amniótica fue 41,0 por ciento (43/105) y de infección cervicovaginal 61,0 por ciento (64/105). La tasa de infección materna (infección ovular clínica y/o endometritis) fue 8,6 por ciento (9/105); apareció sólo en mujeres con invasión microbiana de la cavidad amniótica y/o infección cérvicovaginal (14,1 por ciento (9/64 comparada con 0 por ciento (0/41) p<0,01) en pacientes sin infección en ambos compartimentos. Las bacterias más comúnmente aisladas de la cavidad amniótica fueron ureaplasma urealyticum, gardnerella vaginalis y peptostreptococcus sp. Los microorganismos más frecuentes en el cérvix fueron ureaplasma urealyticum, gardnerella vaginalis, mycoplasma hominis y streptococcus agalactiae. No se relacionaron con morbilidad infecciosa materna las variables: intervalo rotura de membranas-parto, duración parto, número de exámenes vaginales, score cervical, manejo activo o expectante, ruta del parto y paridad. La morbilidad infecciosa materna en la rotura prematura de membranas a término se relaciona con la presencia infección cervicovaginal e invasión microbiana de la cavidad amniótica, independdientemente de otros factores de riesgo tradicionales

Experiencia en el uso de misoprostol vaginal como inductor de trabajo de parto en pacientes en un servicio de alto riesgo obstetrico / Experience in the use of vaginal misoprostol as inductor of labor in patients in an obstetric high risk service

Se presentan 90 pacientes de alto riesgo obstétrico inducidas por Misoprostol intravaginal 50 µg en dosis únicas; con un éxito de 93 por ciento y escasas complicaciones