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Meningiomas are tumors of the cerebral meninges, with slow growth and usually benign, whose treatment is essentially surgery. They have progesterone receptors, and to a lesser extent estrogen, which sometimes causes them to have growth or involution linked to hormonal treatment. Its spontaneous involution is extremely rare. We present the case of a male with a meningioma of the sphenoid planum. He had a history of diabetes mellitus, myasthenia gravis and prostate cancer. He was in treatment with analogs of GnRH (leuprorelin), antiandrogen (bicalutamide), β3 agonists and α1 blockers. 15 months after the hormonal blockade, a reduction of the tumor of approximately 90% of its volume was detected. Previous reports show that treatment with gonadotropin analogues produces growth in some meningiomas. Other reports of spontaneous involution affect diabetic patients and patients in treatment with α1 blockers. Literature focus on meningiomas with spontaneous involution is reviewed.

The ability to accurately and precisely measure the thickness of biomaterial constructs is critical for characterizing both specific dimensional features and related mechanical properties. However, in the absence of a standardized approach for thickness measurements, a variety of imaging modalities have been employed, which have been associated with varying limits of accuracy, particularly for ultrathin hydrated structures. Electron microscopy (EM), a commonly used modality, yields thickness values for extensively processed and nonhydrated constructs, potentially resulting in overestimated mechanical properties, including elastic modulus and ultimate tensile strength. Confocal laser scanning microscopy (CLSM) has often been used as a nondestructive imaging alternative. However, published CLSM-derived image analysis protocols use arbitrary signal intensity cutoffs and provide minimal information regarding thickness variability across imaged surfaces. To address the aforementioned limitations, we present a standardized, user-independent CLSM image acquisition and analysis approach developed as a custom ImageJ macro and validated with collagen-based scaffolds. In the process, we also quantify thickness discrepancies in collagen-based scaffolds between CLSM and EM techniques, further illustrating the need for improved strategies. Employing the same image acquisition protocol, we also demonstrate that this approach can be used to estimate the surface roughness of the same scaffolds without the use of specialized instrumentation.

Resumen Los pseudoquistes abdominales son una complicacion infrecuente de las derivaciones ventriculo-peritoneales de liquido cefalorraquideo (LCR), por lo que su etiologia, diagnostico y manejo terapeutico son muy controvertidos. Nuestro objetivo es ofrecer una revision sistematica, critica y actualizada, de la complicacion, valiendonos de una busqueda y revision de la literatura mas relevante existente a proposito de dicho tema. La forma de aparicion de los pseudoquistes es generalmente mediante clinica abdominal muy inespecifica. La etiologia mas validada es la existencia de una infeccion concomitante del sistema de derivacion del LCR, y como tal el tratamiento precisa antibioterapia y sustitucion de todo o parte del sistema. Sin embargo, el pseudoquiste no necesita de un tratamiento activo, salvo casos concretos. Este manejo, presentado algoritmicamente en el presente trabajo, logra una tasa de recurrencia menor que otras opciones que, no obstante, sigue siendo importante, y se asocia ademas a otras complicaciones de las derivaciones relacionadas con varios factores.

RESUMEN Objetivo: Describir la seguridad del alta en las primeras 12 horas del posoperatorio en mujeres cometidas histerectomía por laparoscopia por patología benigna de útero. Materiales y métodos: Estudio de cohorte histórica descriptiva. Se incluyeron todas las mujeres llevadas a histerectomía laparoscópica por patología benigna, quienes fueron dadas de alta después de 12 horas del procedimiento en un hospital de alta complejidad en Bogotá, Colombia, entre enero del 2013 y abril del 2019. Se excluyeron pacientes con comorbilidades (diabetes, enfermedad cardiovascular y pulmonar obstructiva crónica), limitaciones para la movilización y aquellas que presentaron complicaciones intraoperatorias. Se realizó un muestreo consecutivo. Se evaluaron variables demográficas, y como variables de seguridad, el reingreso por urgencias y complicaciones clasificadas según la escala de Dindo a los 15 días del postoperatorio. Se hace análisis descriptivo. Resultados: Durante el período de estudio se realizaron 860 histerectomías por laparoscopia, de estas, 67 (7,8%) cumplieron con los criterios de selección. Once pacientes (16,4%) reingresaron por el servicio de urgencias, de las cuales, siete (63,6%) acudieron por dolor, una (9%) por sangrado activo, una (9%) por fiebre, y dos (18%) por síntomas urinarios. Se presentaron seis (8,9%) complicaciones postoperatorias de las cuales dos pacientes (2,9%) tuvieron hematoma de cúpula vaginal, dos (2,9%) hemoperitoneo, una (1,4%) infección urinaria y una (1,4%) lesión ureteral; cuatro pacientes (5,9%) requirieron hospitalización, estas últimas se clasificaron en el estadio IIIb de Dindo. Conclusiones: El alta temprana surge como alternativa al cuidado hospitalario para este tipo de población. Se requieren estudios con grupo control y asignación aleatoria para aportar mejor evidencia respecto a este manejo. ABSTRACT Objective: To describe the safety of early discharge in the first 12 hours of the postoperative period in women undergoing laparoscopic hysterectomy for benign uterine disease. Materials and methods: Descriptive historical cohort study. The study included all women undergoing laparoscopic hysterectomy due to benign disease and discharged after 12 hours of the procedure in a high complexity hospital in Bogota Colombia, between January 2013 and April 2019. Patients with comorbidities (diabetes, cardiovascular disease and chronic obstructive pulmonary disease) mobility limitations and intraoperative complications were excluded. Consecutive sampling was used. The variables assessed included demographics and safety variables such as readmission through the emergency service and complications classified according to the Dindo scale on the fifteenth postoperative day. A descriptive analysis is made. Results: Of 860 laparoscopic hysterectomies performed during the study period, 67 (7.8%) met the selection criteria. Eleven patients (16.4%) were readmitted through the emergency service, one (9%) due to active bleeding, and two (18%) because of urinary symptoms. There were six (8.9%) postoperative complications, including vaginal vault hematoma in two patients (2.9%), hemoperitoneum in two cases (2,9%), one (1.4%) urinary infection and one (1.4%) ureteral injury; four patients (5.9%) required hospitalization and were classified as stage IIIb on the Dindo scale. Conclusions: Early discharge emerges as an alternative to in-hospital care for this type of population. Randomized controlled studies are needed to produce additional evidence regarding this management approach

Collagen and elastin represent the two most predominant proteins in the body and are responsible for modulating important biological and mechanical properties. Thus, the focus of this review is the use of collagen and elastin as biomaterials for the fabrication of living tissues. Considering the importance of both biomaterials, we first propose the notion that many tissues in the human body represent a reinforced composite of collagen and elastin. In the rest of the review, collagen and elastin biosynthesis and biophysics, as well as molecular sources and biomaterial fabrication methodologies, including casting, fiber spinning, and bioprinting, are discussed. Finally, we summarize the current attempts to fabricate a subset of living tissues and, based on biochemical and biomechanical considerations, suggest that future tissue-engineering efforts consider direct incorporation of collagen and elastin biomaterials.

Background Cognitive impairment is common in older patients with heart failure (HF), leading to higher 30-day readmission rates than those without cognitive impairment. Objectives The aim of this study was to determine whether increased readmissions in older adults with cognitive impairment are related to HF severity and whether readmissions can be modified by caregiver inclusion in nursing discharge education. Methods This study used prospective quality improvement program of cognitive testing and inclusion of caregivers in discharge education with chart review. Two hundred thirty-two patients older than 70 years admitted with HF were screened for cognitive impairment using the Mini-Cog; if score was less than 4, nurses were asked to include caregivers in education on 2 cardiovascular units with an enhanced discharge program. Individuals with ventricular assist device, transplant, or hospice were excluded. Measurements include Mini-Cog score, 30-day readmissions, readmission risk score, ejection fraction, brain natriuretic peptide, and medical comorbidities. Results Readmission Risk Scores for HF did not correlate with Mini-Cog scores, but admission brain natriuretic peptide levels were less abnormal in those with better Mini-Cog scores. Only for patients with cognitive impairment, involving caregivers in discharge teaching given by registered and advanced practice nurses was associated with decreased 30-day readmissions from 35% to 16% (P = .01). Readmission rates without/with cognitive impairment were 14.1% and 23.8%, respectively (P = .09). Abnormal Mini-Cog screen was associated with a significantly increased risk of 30-day readmission (odds ratio, 2.23; 95% confidence interval, 1.06-4.68; P = .03), whereas nurse documentation of education with family was associated with a significantly decreased risk of 30-day readmission (odds ratio, 0.46; 95% confidence interval, 0.24-0.90; P = .02). Conclusions Involving caregivers in discharge education significantly reduced 30-day readmission rates for patients with HF and cognitive impairment. The Readmission Risk Score was similar between patients older than 70 years with and without cognitive impairment. We have hypothesis-generating evidence that identification of cognitive impairment and targeted caregiver engagement by nurses may be critical in the reduction of readmission rates for older patients with HF.

Background: Group A streptococcal infections are a major cause of benign and deadly human infections with their most destructive manifestation taking the form of necrotizing soft tissue in...

Resumen: Objetivo: Determinar las características epidemiológicas, el tratamiento, las estrategias de reperfusión y los eventos adversos intrahospitalarios de pacientes con infarto de miocardio con elevación del segmento ST en Perú. Métodos: Estudio observacional, prospectivo, multicéntrico a nivel nacional, en pacientes mayores de 18 años hospitalizados con diagnóstico de infarto de miocardio con elevación del segmento ST. Resultados: Desde febrero de 2016 a febrero de 2017, 396 pacientes fueron enrolados; la edad promedio fue de 64.9 ± 12 años y el 21% eran mujeres. En las primeras 12 h de evolución un 38% fueron fibrinolisados, en un 29% se realizó PCI primaria y un 33% no recibieron reperfusión. En el 12.9% se usó estrategia farmacoinvasiva. La tasa de éxito de la fibrinólisis fue de un 65% y la de la PCI primaria fue de un 82%. La estancia hospitalaria fue de 6 días (RIQ 5-10). La mortalidad intrahospitalaria llegó a un 10.1%, siendo la principal causa de muerte el choque cardiogénico. La tasa de reinfarto intrahospitalario fue de 2.2% y de falla cardiaca postinfarto, de 25%. La edad > 75 años, grandes tamaños de infarto, la fracción de eyección de ventrículo izquierdo 75 years, large infarct size, left ventricular ejection fraction

Resumen Objetivo Evaluar si las tasas de recurrencia y las supervivencias libres de recurrencia/progresion (RFS) son diferentes en meningiomas de grado I de la Organizacion Mundial de la Salud (OMS) sometidos a resecciones grado I, II, III y IV de la escala de Simpson. Materiales y metodos Revisamos de manera retrospectiva los datos de los pacientes que se sometieron a tratamiento quirurgico de meningiomas de grado I de la OMS localizados en la convexidad, hoz/parasagital y base de craneo entre junio de 1991 y diciembre de 2011. En el caso de las resecciones grado IV de Simpson la cirugia se complemento con radiocirugia o radioterapia sobre el resto tumoral. Comparamos las tasas de recurrencia y las RFS de los diferentes grados de Simpson tanto de manera global como por localizacion. Resultados En el estudio se incluyeron 208 meningiomas. No existieron diferencias significativas en las tasas de recurrencia y en las RFS entre los diferentes grados de Simpson. Por localizacion, tampoco detectamos diferencias entre los grados de reseccion. En meningiomas de convexidad, las tasas de recurrencia en los grados I y III fueron del 7 y del 33%, respectivamente (p = 0,131). Conclusiones Este estudio sugiere que las tasas de control tumoral son independientes de los grados de Simpson. En meningiomas de hoz/parasagital y de base de craneo debe valorarse la agresividad quirurgica frente a los riesgos de lesionar estructuras neurovasculares. En meningiomas de convexidad, el objetivo inicial deberia ser una reseccion grado I.

Obesity-induced insulin resistance and metabolic syndrome continue to pose an important public health challenge worldwide as they significantly increase the risk of type 2 diabetes and atherosclerotic cardiovascular disease. Advances in the pathophysiologic understanding of this process has identified that chronic inflammation plays a pivotal role. In this regard, given that both animal models and human studies have demonstrated that the interaction of P-selectin glycoprotein ligand-1 (PSGL-1) with P-selectin is not only critical for normal immune response but also is upregulated in the setting of metabolic syndrome, PSGL-1/P-selectin interactions provide a novel target for preventing and treating resultant disease. Current approaches of interfering with PSGL-1/P-selectin interactions include targeted antibodies, recombinant immunoglobulins that competitively bind P-selectin, and synthetic molecular therapies. Experimental models as well as clinical trials assessing the role of these modalities in a variety of diseases have continued to contribute to the understanding of PSGL-1/P-selectin interactions and have demonstrated the difficulty in creating clinically relevant therapeutics. Most recently, however, computational simulations have further enhanced our understanding of the structural features of PSGL-1 and related glycomimetics, which are responsible for high-affinity selectin interactions. Leveraging these insights for the design of next generation agents has thus led to development of a promising synthetic method for generating PSGL-1 glycosulfopeptide mimetics for the treatment of metabolic syndrome.

Leaf pathogens are limiting factors in banana (Musa spp.) production, with Pseudocercospora spp. responsible for the important Sigatoka disease complex. In order to investigate cellular processes and genes involved in host defence responses, quantitative real-time PCR (RT-qPCR) is an analytical technique for gene expression quantification. Reliable RT-qPCR data, however, requires that reference genes for normalization of mRNA levels in samples are validated under the conditions employed for expression analysis of target genes. We evaluated the stability of potential reference genes ACT1, α-TUB, UBQ1, UBQ2, GAPDH, EF1α, APT and RAN. Total RNA was extracted from leaf tissues of Musa acuminata genotypes Calcutta 4 (resistant) and Cavendish Grande Naine (susceptible), both subjected to P. musae infection. Expression stability was determined with NormFinder, BestKeeper, geNorm and RefFinder algorithms. UBQ2 and RAN were the most stable across all M. acuminata samples, whereas when considering inoculated and non-inoculated leaf samples, APT and UBQ2 were appropriate for normalization in Calcutta 4, with RAN and α-TUB most stable in Cavendish Grande Naine. This first study of reference genes for relative quantification of target gene expression in the M. acuminata-P. musae interaction will enable reliable analysis of gene expression in this pathosystem, benefiting elucidation of disease resistance mechanisms.

Resumen: Introducción: La cirugía laparoscópica ginecológica demanda un entrenamiento en simuladores para desarrollar habilidades diferentes a la cirugía convencional. No hay un acuerdo sobre las competencias estándar que debe obtener un aprendiz en un simulador de laparoscopia. Objetivo: Identificar las competencias en cirugía laparoscópica ginecológica que se pueden adquirir con entrenamientos simulados y los tipos de simuladores que permiten hacerlo. Métodos: Se realizó una revisión de revisiones en MEDLINE, EMBASE, ERIC y publicaciones oficiales de instituciones en cirugía endoscópica. Los criterios de inclusión fueron artículos relacionados con habilidades y simulación en laparoscopia realizada por ginecólogos graduados o en formación. Resultados: Se seleccionaron 12 revisiones sistemáticas, donde se evidenciaron 11 tareas, 7 habilidades y 5 procedimientos que se pueden practicar en los simuladores. Los simuladores encontrados se dividieron en simuladores de realidad virtual, videosimuladores y cajas de entrenamiento. La heterogeneidad de los estudios no permitió agrupar estos hallazgos en un metaanálisis. Se listan los métodos para evaluar la transferencia de las habilidades adquiridas. Conclusiones: El entrenamiento simulado en laparoscopia permite desarrollar varias competencias quirúrgicas. Su práctica en los simuladores es medible con parámetros objetivos para evaluar la transferencia de las competencias a la cirugía real, con posibles beneficios para el paciente. Abstract: Introduction: Gynaecological laparoscopic surgery demands training in simulators to develop skills different from conventional surgery. There is no agreement on proficiency standards that a trainee must obtain in a laparoscopy simulator. Objective: To identify the competences in gynaecological laparoscopic surgery that can be acquired with simulated training and the types of simulators that allow this to be done. Methods: A review of reviews was carried out in MEDLINE, EMBASE, ERIC and official publications of institutions in endoscopic surgery. Inclusion criteria were articles related to laparoscopic skills and simulation made by graduate gynaecologists or in training. Results: A total of 12 systematic reviews were selected in which there was evidence of 11 tasks, 7 skills, and 5 procedures that could be practiced on the simulators. The simulators found were divided in virtual reality simulators, video simulators, and box trainers. The heterogeneity of the studies did not allow these findings to be grouped in a meta-analysis. The methods for evaluating the transfer of acquired skills are listed. Conclusions: Simulated training in laparoscopy allows several surgical skills to be developed. Their practice in simulators is measurable with objective parameters to evaluate transfer of skills to real surgery, with possible benefits for the patient. Palabras clave: Simulación, Entrenamiento, Competencias, Habilidades, Laparoscopia, Ginecología, Keywords: Simulation, Training, Competence, Skills, Laparoscopy, Gynaecology

Since the first report in 1954, abdominal pseudocysts have been recognized as a particularly uncommon complication of ventriculoperitoneal shunts of CSF, so their etiology, diagnosis, and therapeutic management remain very controversial. Our objective is to offer a critical and updated systematic review of those controversial points, using a thorough search and review of the most relevant literature available. The clinical presentation of pseudocysts is normally through non-specific abdominal symptoms. The most validated etiology consists on the existence of a concomitant infection of the CSF shunt system, and so, treatment needs of antibiotherapy and total or partial substitution of the system. However, the pseudocyst itself doesn't need an active treatment, except for some specific cases. This management, algorithmically presented in the present work, achieves a lower recurrence rate than other options, but this one is still important, and is also associated with other complications of those shunts related with several other factors which need to be taken in account.

ObjectivesChronic critical illness (CCI) is a phenotype that occurs frequently in patients with severe injury. Previous work has suggested that inflammatory changes leading to CCI occur early following injury. However, the modifiable factors associated with CCI are unknown. We hypothesized that hypothermia, an early modifiable factor, is associated with CCI.MethodsTo determine the association of hypothermia and CCI, a secondary analysis of the Inflammation and Host Response to Injury database was performed, and subsequently validated on a similar cohort of patients from a single level 1 trauma center from January 2015 to December 2019. Hypothermia was defined as initial body temperature ≤34.5°C. CCI was defined as death or sustained multiorgan failure ≥14 days after injury. Data were analyzed using univariable analyses with Student’s t-test and Pearson’s χ2test, and logistic regression. An arrayed genomic analysis of the transcriptome of circulating immune cells was performed in these patients.ResultsOf the initial 1675 patients, 254 had hypothermia and 1421 did not. On univariable analysis, 120/254 (47.2%) of patients with hypothermia had CCI, compared with 520/1421 (36.6%) without hypothermia who had CCI, pConclusionsHypothermia is associated with the development of CCI in severely injured patients. There are transcriptomic changes which indicate that the changes induced by hypothermia may be associated with persistent CCI. Thus, early reversal of hypothermia following injury may prevent the CCI.Level of evidenceIII.

Background The Short Form Health Survey (SF-36) and the Centers for Disease Control and Prevention (CDC) Healthy Days items are well known measures of health-related quality of life. The validity of the SF-36 for older adults and those with disabilities has been questioned. Objective Assess the extent to which the SF-36 and the Centers for Disease Control and Prevention (CDC) Healthy Days items measure the same aspects of health; whether the SF-36 and the CDC unhealthy days items are invariant across gender, functional status, or the presence of chronic health conditions of older adults; and whether each of the SF-36's eight subscales is independently associated with the CDC Healthy Days items. Methods We analyzed data from 66,269 adult Medicare advantage members age 65 and older. We used confirmatory factor analyses and regression modeling to test associations between the CDC Healthy Days items and subscales of the SF-36. Results The CDC Healthy Days items were associated with the SF-36 global measures of physical and mental health. The CDC physically unhealthy days item was associated with the SF-36 subscales for bodily pain, physical role limitations, and general health, while the CDC mentally unhealthy days item was associated with the SF-36 subscales for mental health, emotional role limitations, vitality and social functioning. The SF-36 physical functioning subscale was not independently associated with either of the CDC Healthy Days items. Conclusions The CDC Healthy Days items measure similar domains as the SF-36 but appear to assess HRQOL without regard to limitations in functioning.

Object The aim of this study is to assess if the recurrence rates and recurrence/progression-free survivals (RFS) are different after Simpson's grades I, II, III and IV resections in World Health Organisation (WHO) grade I meningiomas. Material and methods A retrospective review was conducted on the data of patients who underwent surgical treatment of WHO grade I meningiomas located in convexity, falx/parasagittal, and skull base (anterior/media/posterior) between June 1991 and December 2011. In Simpson's grade IV resections, surgical treatment was supplemented with radiotherapy/radiosurgery on the tumour remains. A comparison was made on the recurrence rates and RFSs between Simpson's grades I, II, III, and IV resections, both overall and in tumour subsets according to their location. Results A total of 208 meningiomas were included in this study. There were no significant differences in recurrence rates and RFSs between Simpson's grades I, II, III, and IV. No significant differences were noted between the different degrees of Simpson in any of the location groups. In convexity meningiomas, the recurrence rates were 7% and 33% in Simpson's grades I and III resections, respectively (p = .131). Conclusions It has been shown that the rates of tumour control in meningiomas are not related to Simpson grades. In falx/parasagittal and skull base meningiomas, more aggressive attempts of tumour resection must be balanced against the risks of damaging critical neurovascular structures. In convexity meningiomas, a Simpson's grade I resection should be attempted first.

Background Ventricular assist devices (VADs) have improved survival among end-stage heart disease patients. Since 2002, heart transplant candidates with VADs have been afforded 30 days of elective time at the highest urgency category (Status 1A) under Organ Procurement and Transplantation Network (OPTN) policy. We aimed to determine the effect of increasing elective time at the highest urgency category for heart transplant candidates with VADs. This analysis was requested by OPTN during its evaluation of heart allocation policy. Methods We simulated several allocation schemes wherein elective Status 1A time was increased to 45, 60, and 90 days; results were compared with a baseline simulation of 30 days and with the actual observed heart transplant waiting list cohort. Results The simulations showed that increasing elective Status 1A time for candidates with VADs did not substantially change waiting list mortality overall or for sub-groups of concern, which were candidates with VADs listed at a lower-urgency category (Status 1B), those with with VAD complications, total artificial heart, or intraaortic balloon pump support; or those with extracorporeal membrane oxygenation. Across the different time allowances, the average post-transplant death rate remained stable. It also remained stable for recipients previously listed as Status 1A or 1B categories for VAD and for recipients with VAD complications or an intraaortic balloon pump at transplant, on extracorporeal membrane oxygenation, and those without devices. Conclusions Our results suggest that increasing time in the highest urgency category for candidates with VADs would not improve waiting list mortality or post-transplant outcomes for heart transplant candidates overall.

Most β-lactam antibiotics are ineffective against Mycobacterium tuberculosis due to the microbe’s innate resistance. The emergence of multidrug-resistant (MDR) and extensively drug-resistant (XDR) strains has prompted interest to repurpose this class of drugs. To identify the genetic determinants of innate β-lactam resistance, we carried out a synthetic lethality screen on a transposon mutant library for susceptibility to imipenem, a carbapenem β-lactam antibiotic. Mutations in 74 unique genes demonstrated synthetic lethality. The majority of mutations were in genes associated with cell wall biosynthesis. A second quantitative real-time PCR (qPCR)-based synthetic lethality screen of randomly selected mutants confirmed the role of cell wall biosynthesis in β-lactam resistance. The global transcriptional response of the bacterium to β-lactams was investigated, and changes in levels of expression of cell wall biosynthetic genes were identified. Finally, we validated these screens in vivo using the MT1616 transposon mutant, which lacks a functional acyl-transferase gene. Mice infected with the mutant responded to β-lactam treatment with a 100-fold decrease in bacillary lung burden over 4 weeks, while the numbers of organisms in the lungs of mice infected with wild-type bacilli proliferated. These findings reveal a road map of genes required for β-lactam resistance and validate synthetic lethality screening as a promising tool for repurposing existing classes of licensed, safe, well-characterized antimicrobials against tuberculosis., IMPORTANCE The global emergence of multidrug-resistant and extensively drug-resistant M. tuberculosis strains has threatened public health worldwide, yet the pipeline of new tuberculosis drugs under development remains limited. One strategy to cope with the urgent need for new antituberculosis agents is to repurpose existing, approved antibiotics. The carbapenem class of β-lactam antibiotics has been proposed as one such class of drugs. Our study identifies molecular determinants of innate resistance to β-lactam drugs in M. tuberculosis, and we demonstrate that functional loss of one of these genes enables successful treatment of M. tuberculosis with β-lactams in the mouse model.

Flow-based microfluidic systems have been widely utilized for cell migration studies given their ability to generate versatile and precisely defined chemical gradients and to permit direct visualization of migrating cells. Nonetheless, the general need for bulky peripherals such as mechanical pumps and tubing and the complicated setup procedures significantly limit the widespread use of these microfluidic systems for cell migration studies. Here we present a simple method to power microfluidic devices for chemotaxis assays using the commercially available ALZET® osmotic pumps. Specifically, we developed a standalone chemotaxis platform that has the same footprint as a multiwell plate and can generate well-defined, stable chemical gradients continuously for up to 7 days. Using this platform, we validated the short-term (24 hours) and long-term (72 hours) concentration dependent PDGF-BB chemotaxis response of human bone marrow derived mesenchymal stem cells., Harvard Stem Cell Institute, National Institutes of Health (U.S.) (grant HL095722), National Institutes of Health (U.S.) (grant HL097172), Massachusetts Institute of Technology (MIT-UROP program), Massachusetts Institute of Technology (John Reed Fund), National Institute of Biomedical Imaging and Bioengineering (U.S.) (BioMEMS Resource Center (P41 EB 002503))