Comparison of the Mechanical Properties and Push-out Bond Strength of Self-adhesive and Conventional Resin Cements on Fiber Post Cementation.

OBJECTIVES: The purpose of this study was to compare the mechanical properties and push-out bond strength of self-adhesive resin cements (SACs) and a conventional resin cement (CRC). METHODS AND MATERIALS: Eighty bovine incisors were divided into four groups for cementation of a fiberglass post (Whitepost - FGM Dental Group, Coral Springs, FL) with different resin cements: three SACs (Maxcem Elite, MAX - Kerr; Calibra Universal, CAL - Dentsply; and RelyX Unicem 2, RUN - 3M Oral Care) and one CRC (RelyX Ultimate, RXU - 3M Oral Care). The groups were subdivided into two groups each (n=10) for evaluation of the push-out bond strength test (POBS) after 24 hours of water storage or after thermal aging (5000 cycles), following 24 hours of storage. The failure modes were evaluated using a stereomicroscope. Flexural strength (FS) and modulus of elasticity (EM) were determined using a three-point bending. Also, pH of the cements was measured over 48 hours and filler morphology was observed by scanning electron microscopy. Appropriate statistical analyses were performed by SPSS 21.0 (SPSS Inc., Chicago, IL, USA), with a significance level set at 5%. Results: RXU presented the highest POBS at both evaluation times. Among the SACs, RUN and CAL presented significantly lower POBS than MAX in cervical and middle-thirds at the 24-hour evaluation, and in all root regions after thermocycling. Adhesive failure between the cement and dentin were the most prevalent fractures at both times evaluated. MAX presented the lowest FS and RUN showed the highest EM. The pH reached the minimal point at the 30-minute evaluation for RXU and MAX. For RUN and CAL, the minimal pH was observed at the 60-minute evaluation. RXU and RUN presented spherical and regular filler particles, while MAX and CAL presented irregularly shaped and sized filler particles. CONCLUSIONS: The mechanical behavior of SACs is not superior to CRC; however, among all the SACs evaluated, MAX presented the highest POBS and stability after thermocycling evaluation. MAX also reached the closest neutral pH after 48 hours. Therefore, SACs with low initial pH and strong neutralization reactions are recommended, because these characteristics may lead to better mechanical properties and stability.

Natural infection with Trypanosoma cruzi in three species of non-human primates in southeastern Mexico: A contribution to reservoir knowledge.

The mechanisms of infection and dispersion of Trypanosoma cruzi among animals, especially in the sylvatic environment, are still not entirely clear, and various aspects of the transmission dynamics of this parasite in the sylvatic environment are still unknown. T. cruzi is a parasite with a great biological and genetic diversity that infects a wide variety of hosts, therefore, transmission cycles of this parasite are complex. The objective of this study was to determine the prevalence of T. cruzi infection and analyze the genetic variability of the discrete typing units (DTUs) of the parasite in three non-human primate species (Alouatta palliata, Alouatta pigra, and Ateles geoffroyi) in southeastern Mexico. A total of one hundred sixty-four serum samples (42 samples of A. pigra, 41 samples of A. palliata (free-ranging) and 81 samples of A. geoffroyi (hosted in care centers)) were analyzed for the detection of anti-T. cruzi antibodies by ELISA assays. The seroprevalence of infection was 23.39% in A. palliata, 21.40% in A. pigra and 16.27% in A. geoffroyi. Additionally, presence of parasite DNA was assessed by PCR, and the identification of DTUs was performed by real-time PCR coupled to High Resolution Melting (qPCR-HRM). Different DTUs (TcI, TcII, TcIII, TcV and TcVI) were found in the analyzed monkeys. In addition, infection of monkeys was not associated with age or gender, but it was associated with the species. This study reveals the risk of infection in the study area and that the different DTUs of the parasite can coexist in the same habitat, indicating that T. cruzi transmission in the study area is very complex and involves many ecological factors. However, there is a need for long-term studies of host-parasite interactions to provide a solid understanding of the ecology of these species and to understand the dispersion strategies of T. cruzi.

Actualización y controversias en el tratamiento de las malformaciones congénitas de la vía aérea pulmonar / Update and disagreements in the treatment of congenital pulmonary airway malformations

Congenital pulmonary airway malformations (CPAM) are rare and occur due to a failure in lung embryological development. They are classified according to their pathological characteristics and their anatomical origin. They can occur from the antenatal period to adulthood, can be associated with hydrops fetalis, respiratory distress, recurrent infections, or in an otherwise asymptomatic patient. In this article we carry out a scope review of the literature to answer frequent questions of the clinical teams in charge of patients with CPAM, such as the antenatal approach, the different types of surgeries and the management of asymptomatic patients. Although the indication for surgery is clear in symptomatic patients, little is known about its natural history of this condition, including the possibility of spontaneous resolution and the development of complications or neoplasm. So, the treatment of asymptomatic patients continues to be controversial. Therapeutic decisions must be made by multidisciplinary teams with the informed participation of parents and patients. In our opinion, considering the excellent results of minimally invasive surgery, its low incidence of complications, and practically zero mortality when performed by experienced groups, it seems reasonable to consider elective resection of a MCVAP in asymptomatic patients.

Las malformaciones congénitas de la vía aérea pulmonar (MCVAP) son infrecuentes y ocurren debido a una falla en el desarrollo embriológico pulmonar. Se clasifican de acuerdo con sus características patológicas y a su origen anatómico. Se pueden presentar desde el periodo antenatal hasta la adultez, asociarse a cuadros de hidrops fetal, distrés respiratorio, infecciones recurrentes, o como un hallazgo en pacientes asintomáticos. En este artículo realizamos una revisión bibliográfica exploratoria para responder dudas frecuentes de los equipos clínicos a cargo de pacientes con MCVAP, como el enfrentamiento antenatal, los distintos tipos de cirugía y su abordaje, y el manejo de pacientes asintomáticos. Si bien la indicación de cirugía es clara en pacientes sintomáticos, poco se conoce acerca de su historia natural, incluyendo la posibilidad de resolverse de forma espontánea, de complicarse o de evolucionar hacia el desarrollo de una neoplasia, por lo que el tratamiento de pacientes asintomáticos continúa siendo controversial. Las decisiones terapéuticas deben ser tomadas por equipos multidisciplinarios con la participación informada de los padres y de los pacientes. En nuestra opinión, considerando los excelentes resultados de la cirugía mínimamente invasiva, su baja incidencia de complicaciones y prácticamente nula mortalidad, al ser realizada por grupos con experiencia, nos parece razonable plantear la resección electiva de una MCVAP en un paciente asintomático.

On the possibility of using temperature to aid in thyroid nodule investigation.

Thyroid nodules are common, and their investigation is very important to exclude the possibility of cancer. The increase in blood vessels of malignant tumours may be related to local temperature augmentation detectable on the skin surface. The objective of this paper is to evaluate the feasibility of Infrared Thermography for cancer identification. For this purpose, two studies were performed. One used numerical modelling to simulate regional metabolic temperature propagation to evaluate whether a nodule is perceptible on the skin surface. A second study considered thyroid nodule identification by using convolutional neural networks (CNNs). First, variations in nodular size and fat thickness were investigated, showing that the fat layer has an important role in regional heat transfer. In the second study, the training process achieved accuracy of 96% for in-sample and 95% for validation. In the testing phase, 92% accuracy, 100% precision and 80% recall were achieved. Thus, the presented studies suggest the feasibility of using Infrared Thermography with the CNN Artificial Intelligence technique as additional information in the investigation of thyroid nodules for patients without a very thick subcutaneous fat layer.

ECO-SEOM-SEEO safety recommendations guideline for cancer patients receiving intravenous therapy.

PURPOSE: Cancer patients require implantation of venous access devices to meet their personalized therapeutic needs, which are often complex due to the nature of the medication and the disease status. Therefore, it is essential to have standardized protocols that guarantee the best results in health and patient safety. METHODS: To learn about the availability of protocols and aspects related to safety in clinical practice and to detect possible opportunities for improvement, a survey has been conducted in various Spanish hospitals, in addition to a review of the evidence regarding the various devices available and complications associated with the administration of chemotherapy. RESULTS: As a result of both analyses, the Foundation for Excellence and Quality in Oncology (ECO), the Spanish Society of Medical Oncology (SEOM), and the Spanish Society of Oncology Nursing (SEEO) have developed a catheter selection algorithm based on patient characteristics and treatment to facilitate the clinical decision-making process, as well as some recommendations aimed at ensuring patient safety and rational use of available resources. CONCLUSIONS: In conclusion, both the venous access catheter selection algorithm and the proposed recommendations aim to respond to the needs revealed in clinical practice and to become an integrable tool in electronic prescription systems to offer homogeneous criteria for action in cancer patients that require venous access, optimizing the use of available health resources with the highest safety and quality of life for the patient.

Presence of Seropositive Patients to Trypanosoma cruzi in a Municipality of the Mixtec Sierra of the State of Puebla: A Preliminary Study.

PURPOSE: The state of Puebla has the social marginalization and ecological conditions for the transmission of infectious agents to be effective. Until a few years ago, the state of Puebla was considered non-endemic to the presence of Trypanosoma cruzi as there are no official reports of chronic cases. The objective of this work was to carry out a preliminary study on the prevalence of anti-T. cruzi antibodies in rural areas of the Huatlatlauca municipality in the Mixtec sierra of the state of Puebla. METHODS: A total of 196 serum samples from 12 rural localities were tested by using four tests: two enzyme-linked immunosorbent assays, an xenodiagnoses and PCR assay. RESULTS: Overall, 28 (14.2%) of 196 samples were positive for T. cruzi by ≥ 2 tests (95% CI 6.6-20.8%). Our results suggested that the municipality of Huatlatlauca in the Mixteca Sierra of the state of Puebla is an area with endemic potential for the disease with a high prevalence rate in the adult population and with cases in newborns, these high transmission rates are probably associated with problems of congenital and vector transmission. CONCLUSION: Additional studies should be conducted to generate adequate campaigns for the control of Chagas disease in this area.

[Primary tumours and pseudotumors of the hand in adults. Epidemiological analysis of cases, management and evolution]. / Tumores y seudotumores primarios de la mano en adultos. Análisis epidemiológico de casos, manejo y evolución.

INTRODUCTION: Tumors in the hand are rare, and malignant tumors in the hand are peculiar; However, primary pseudotumoral lesions of the hand, such as ganglion, are very frequent. Most of the tumors found in the bone and soft tissue can be presented in the same way in the hand but their frequency and distribution is different. Despite the low incidence of benign and malignant tumors in the hand, these can be locally invasive or compromise the hand function. The main objective of this study is to determine the epidemiology, types, location and management of tumors and pseudotumors of the hand in adults in the Mexican population. MATERIAL AND METHODS: We designed a retrospective study by review of clinical records of patients in our institution with diagnosis of tumors or pseudotumors in hand from January 2007 to December 2016 evaluating variables such as age, gender, laterality, Diagnosis, histological lineage, localization and treatment. RESULTS: Our study comprises 215 patients with an average age of 44.23 years, predominantly women. Pseudotumors are the most frequently encountered (synovial cyst), followed by benign soft tissue tumors, benign bone tumors, and, finally, malignant tumors. DISCUSSION: After all we suggests a possible new classification for the hand that is simple, reproducible and give guidance for treatment. The need for a classification system is imminent to standardize diagnostics, guide future research, focus treatments and preserve hand function.

INTRODUCCIÓN: Los tumores en la mano son poco frecuentes y los tumores malignos son particularmente raros; sin embargo, las lesiones seudotumorales primarias de la mano, como gangliones, son muy frecuentes. La mayoría de los tumores que se encontraron en el hueso y tejido blando pueden presentarse de igual manera en la mano, pero su frecuencia y distribución es distinta. A pesar de la baja incidencia de los tumores benignos y malignos en la mano, éstos pueden ser localmente invasivos o comprometer su función. El objetivo principal de este estudio es determinar la epidemiología, tipos, localización y manejo de los tumores y seudotumores de la mano en adultos en población mexicana. MATERIAL Y MÉTODOS: Se diseñó un estudio retrospectivo mediante revisión de expedientes clínicos de pacientes de nuestra institución con diagnóstico de tumores o seudotumores en la mano de Enero de 2007 a Diciembre de 2016 evaluando variables como edad, género, lateralidad, abordaje diagnóstico, estirpe histológica, localización y tratamiento. RESULTADOS: Nuestro estudio comprende 215 pacientes con una edad promedio de 44.23 años, predominantemente mujeres. Los seudotumores son los que con más frecuencia se detectan (quiste sinovial), seguidos de los tumores benignos de tejido blando, tumores óseos benignos y, por último, los tumores malignos. DISCUSIÓN: Después de todo, sólo sugerimos una clasificación para la mano que es sencilla y reproducible y dar orientación para el tratamiento. La necesidad de un sistema de clasificación es inminente para estandarizar los diagnósticos, guiar futuras investigaciones, enfocar tratamientos y preservar la función de la mano, independientemente de la epidemiología que se observe.

[Strength and function of hand before and after release of carpal tunnel in patients with type 2 diabetes mellitus by open and endoscopic approach. Case-control study]. / Fuerza y función de mano antes y después de liberación de túnel del carpo en pacientes con diabetes mellitus tipo 2 por abordaje abierto y endoscópico. Estudio de casos y controles.

BACKGROUND: Carpal tunnel syndrome (CTS) is the upper extremity neuropathy more frequent. Treatments led to the entrapment of the median nerve in the carpal tunnel are more complicated and the results less promising and unsatisfactory in diabetic patients. The objective of this study is to compare the results of strength and hand function in healthy patients against patients with diabetes mellitus type 2 (DM2) with a diagnosis of CTS before and after the open and endoscopic release of the carpal tunnel. MATERIAL AND METHODS: This is an observational, retrospective and descriptive study for a period of five years where we evaluated the results in healthy patients and with DM2, with diagnosis of CTS who underwent surgical treatment by open or endoscopic approach; we applied the DASH questionnaire, force grip and clamp fine measurements, presence of infection, pain and complications. RESULTS: The results of 86 patients evaluated, showed a statistical association in the decrease in scores on the functional scale DASH with both approaches, association between remission of hypoesthesias in healthy patients with either of the two approaches as opposed to diabetic patients and association between developing DM2 and complications in the short term. CONCLUSION: Both approaches improve symptoms and function of the hand in healthy and diabetic patients, but the fi rst group will present cases of complete remission in contrast to the group of diabetic patients.

ANTECEDENTES: El síndrome del túnel del carpo (STC) es la neuropatía más frecuente de la extremidad superior a nivel mundial. Los tratamientos dirigidos para el atrapamiento del nervio mediano en el túnel del carpo son más complicados y los resultados menos prometedores e insatisfactorios en pacientes diabéticos. El objetivo de este estudio es comparar los resultados de fuerza y función de la mano en pacientes sanos contra pacientes con diabetes mellitus tipo 2 (DM2) con diagnóstico de STC antes y después de la liberación abierta y endoscópica del túnel del carpo. MATERIAL Y MÉTODOS: Se diseñó un estudio observacional, retrospectivo y descriptivo durante un período de cinco años en el que se evaluaron pacientes sanos y con DM2 con diagnóstico de STC que fueron sometidos a tratamiento quirúrgico por abordaje abierto o endoscópico y a quienes se les aplicó el cuestionario DASH, mediciones de fuerza de prensión y pinza fi na, presencia de hipoestesias, dolor y complicaciones. RESULTADOS: Los resultados de los 86 pacientes evaluados mostraron una asociación estadística en la disminución de los puntajes de la escala funcional DASH con ambos abordajes, asociación entre la remisión de hipoestesias en pacientes sanos con cualquiera de los dos abordajes a diferencia de los pacientes diabéticos y asociación entre padecer DM2 y tener complicaciones a corto plazo. CONCLUSIÓN: Ambos abordajes mejoran los síntomas y función de la mano en pacientes sanos y diabéticos, pero el primer grupo presentará casos de remisión completa a diferencia del grupo de pacientes diabéticos.

Tspan33 is Expressed in Transitional and Memory B Cells, but is not Responsible for High ADAM10 Expression.

Tetraspanins are a family of transmembrane proteins that form membrane microdomains. They play important roles in migration, adhesion and other cellular processes. TspanC8, a subfamily of tetraspanins, was found to associate and promote ADAM10 trafficking and cell surface localization. One of its members, Tspan33, is expressed in activated B cells. Using RT-PCR and flow cytometry, we analysed the pattern of expression of Tspan33 in B cells from healthy donors. We found Tspan33 expression in early and late stages of B cell development. However, Tspan33 expression did not correlate with ADAM10 surface expression. We also found expression of Tspan33 early in the activation process. Given its predominant expression in activated B cells and in several lymphomas, but not in naive B cells, we hypothesize that Tspan33 could be a potential target for therapeutic purposes.

Persistent effects of pre-Columbian plant domestication on Amazonian forest composition.

The extent to which pre-Columbian societies altered Amazonian landscapes is hotly debated. We performed a basin-wide analysis of pre-Columbian impacts on Amazonian forests by overlaying known archaeological sites in Amazonia with the distributions and abundances of 85 woody species domesticated by pre-Columbian peoples. Domesticated species are five times more likely than nondomesticated species to be hyperdominant. Across the basin, the relative abundance and richness of domesticated species increase in forests on and around archaeological sites. In southwestern and eastern Amazonia, distance to archaeological sites strongly influences the relative abundance and richness of domesticated species. Our analyses indicate that modern tree communities in Amazonia are structured to an important extent by a long history of plant domestication by Amazonian peoples.

Prevalencia y trascendencia de los hallazgos extracardíacos encontrados en resonancia magnética de corazón / Prevalence and significance of extracardiac findings in cardiac magnetic resonance imaging

Objetivos: Valorar el número de lesiones incidentales detectadas por resonancia magnética (RM) cardíaca, establecer el porcentaje de hallazgos incluidos en el informe y definir el porcentaje de lesiones extracardíacas con implicancia en el manejo del paciente. Materiales y métodos: Se revisaron retrospectivamente 918 RM de corazón, realizadas desde mayo de 2006 hasta marzo de 2015, en busca de hallazgos extracardíacos. Estos fueron clasificados en nada/poco relevantes o relevantes, y en relación causa-efecto con la sintomatología cardíaca. Resultados: Se encontraron 271 hallazgos extracardíacos. El 35,7% resultó relevante y el 18,8% tenía una relación de causa-efecto con la sintomatología cardíaca. Los hallazgos extracardíacos relevantes fueron informados en el 58,4% de los casos y los poco/nada relevantes en el 26,6%. Discusión: Diferentes muestras poblacionales y protocolos de RM cardíaca pueden condicionar los porcentajes de los hallazgos extracardíacos detectados. Además, el análisis de estas imágenes tiene peculiaridades que requieren conocimiento y entrenamiento para una correcta valoración. Conclusión: Se detectaron hallazgos extracardíacos de diversa relevancia en un 26,4% de los pacientes. Analizar estos hallazgos y establecer su valoración es parte fundamental del informe radiológico de la RM cardíaca.

Objectives: To assess the number of incidental lesions detected on cardiac magnetic resonance imaging (MRI), in order to establish the percentage of findings included in the report and evaluate the percentage of extracardiac lesions that have implications on patient management. Materials and methods: A retrospective review was conducted on 918 cardiac MRI (performed from May 2006 to March 2015) to search for extracardiac findings. These were classified in not relevant or relevant, and in relation with cause-effect cardiac symptoms. Results: A total of 271 extracardiac findings were observed, of which 35.7% were relevant, and 18.8% had a cause-effect relationship with the cardiac symptoms. Relevant extracardiac findings were reported in 58.4% of cases, and not relevant findings in 26.6% of cases. Discussion: Different sample populations and protocols (performing cardiac MRI) can determine differences when establishing percentage of extracardiac findings. Furthermore, analysis of cardiac MR images has peculiarities that require knowledge and training for proper assessment. Conclusión: Extracardiac findings of distinct relevance were detected in 26.4% of patients. To analyse and to assess the importance of these findings is a fundamental part of the cardiac MRI report.

Lactam inhibiting Streptococcus mutans growth on titanium.

The aim of this work was to analyze the activity of novel synthetic lactams on preventing biofilm formation on titanium surfaces. Titanium (Ti6Al4V) samples were exposed to Streptococcus mutans cultures in the presence or absence of a synthetic lactam. After 48h incubation, planktonic growth was determined by spectrophotometry. Biofilm was evaluated by crystal violet staining and colony forming units (CFU·ml(-)(1)), followed by scanning electron microscopy (SEM). Results showed that the average of adhered viable cells was approximately 1.5×10(2)CFU/ml in the presence of lactam and 4×10(2)CFU/ml in its absence. This novel compound was considerable active in reducing biofilm formation over titanium surfaces, indicating its potential for the development of antimicrobial drugs targeting the inhibition of the initial stages of bacterial biofilms on dental implants abutments.

Spinocerebellar ataxia type 2: Measures of saccade changes improve power for clinical trials

BACKGROUND:Saccadic eye movement abnormalities are common in patients with spinocerebellar ataxia type 2, but it is unclear how these alterations progress over time. The aim of this study was to assess the progression of saccade involvement in spinocerebellar ataxia type 2 patients, identify its main determinants, and evaluate its usefulness as outcome measures in clinical trials.METHODS:A prospective 5-year follow-up study was performed with 30 spinocerebellar ataxia type 2 patients and their matched healthy controls, who were evaluated a total of four times by clinical and electrooculographical assessments of horizontal saccades and by the scoring of ataxia.RESULTS:Patients showed significant decreases in saccade peak velocity and saccade accuracy as well as increases of saccadic latency during the follow-up period. Annual progression rates were significantly higher in patients compared to controls. Faster progression rates of saccade slowing were associated with higher trinucleotide cytosine-adenine-guanine repeat expansions. Sample-size estimates for two-arm trials would require 19 patients per group to detect a 50 percent reduction in disease progression using saccade peak velocity as outcome variable, but 44 and 124 patients using saccade latency and accuracy, respectively (power, 80 percent; alpha = 0.05).CONCLUSIONS:Electrooculographical measures of saccade changes are useful for the objective quantification of disease course in spinocerebellar ataxia type 2. The progression rate of saccade slowing is influenced by the expansion size, providing novel insight into the cumulative polyglutamine neurotoxicity, and supporting the usefulness of saccade peak velocity as a sensitive biomarker during the natural history of the disease, and as suitable outcome measure for therapeutic trials (AU)

[Intercarpal fusion as a salvage procedure in Kienböck disease]. / Artrodesis intercarpiana como tratamiento de salvamento en pacientes con enfermedad de Kienböck.

INTRODUCTION: Functional results of four surgical techniques to resolve the IIIB-IV Litchman's stage of the Kienböck disease were analyzed. We observed the evolution from 2000 to 2015. MATERIAL AND METHODS: Transversal retrospective study of 33 patients treated with different surgical techniques and evaluated with Quick-DASH scale, dynamometer and EVA. RESULTS: Less functional limitation was found in the patients who underwent the intercarpal fusion with or without neurotomy of the posterior interosseous. DISCUSSION: It was shown that the fact of making a less aggressive surgery is enough to evolve into an increase in symptoms and a decrease in function and strength; therefore, the intercarpal fusion performed at the right time of the natural history of the disease can achieve better results than other methods used previously and endorsed by international associations. CONCLUSIONS: The surgical technique of choice in our series to prevent disease progression was the intercarpal fusion and neurotomy of the posterior interosseous nerve.

INTRODUCCIÓN: Se analizaron los resultados funcionales de cuatro técnicas quirúrgicas de salvamento para resolver la etapa IIIB-IV de Litchman de la enfermedad de Kienböck. Observamos la evolución de los procedimientos quirúrgicos de salvamento realizados del 2000 al 2015. MATERIAL Y MÉTODOS: Estudio retrospectivo transversal de 33 pacientes tratados con cuatro técnicas quirúrgicas distintas a quienes se les realizó la escala Quick-DASH, dinamometría y EVA. RESULTADOS: Se encontró menor limitación funcional al año postquirúrgico en los individuos a los cuales se les realizó la artrodesis intercarpiana con o sin neurotomía del nervio interóseo posterior, con una media de 16.4, una mediana de 16.35, una moda de 15.3 y una p 0.05. DISCUSIÓN: Se demostró que una cirugía poco agresiva es suficiente para evolucionar a un aumento sintomatológico y un descenso de la función y fuerza, por lo que la artrodesis intercarpiana logra mejores resultados que otros procedimientos usados con anterioridad y avalados por las grandes asociaciones internacionales. CONCLUSIONES: La técnica quirúrgica de salvamento de elección en nuestra serie, que sugiere evitar la progresión de la enfermedad de Kienböck, es la artrodesis intercarpiana más neurotomía del nervio interóseo posterior, ya que presenta menor número de complicaciones.

Endometrial effect of progesterone delivered by vaginal rings in estrogen-treated postmenopausal women.

AIM: The type of estrogen and progestin as well as their doses, route and regimens of administration may each affect the benefit-risk profile of postmenopausal hormone therapy. The aim of this study was to evaluate the endometrial effect of progesterone released continuously from a vaginal ring, combined with transdermal estradiol in postmenopausal women. METHOD: Forty-four postmenopausal women participated in a randomized, double-blind, dose-finding study evaluating two hormonal treatments, combining 50 microg/day of estradiol delivered by transdermal patches and either 0.5-g or 1-g progesterone vaginal rings (PVR) given for 12 weeks. The effect on the endometrium was assessed by histology and the detection of the proliferative marker Ki-67. We also measured the serum concentration of estradiol and progesterone, the tissue concentration of progesterone and the immunolocalization of estradiol and progesterone receptors in the endometrium. RESULTS: Endometrial thickness was increased after both treatments, although endometrial histology appeared atrophic in most biopsies. A circulating dose-response of serum progesterone levels was observed from the first to the 12th week of PVR use. In the high-progesterone-dose group, the scarce presence of Ki-67 and hormone receptors reflected the predominant action of progesterone in endometrial glands and stroma, in parallel with a lower tissue concentration of progesterone in this group. CONCLUSION: The PVR appears to be a promising method of administering natural progesterone to postmenopausal women treated with estrogen. Estradiol levels corrected the menopausal symptoms, as expected, and the presence of atrophic endometrium in the majority of women indicated that both doses of progesterone oppose the stimulatory estradiol effects, although the percentage of proliferative tissue was not negligible in both groups.