Evaluation of SARS-CoV-2 Rapid Antigen Tests in Use on the Isle of Youth, Cuba.

INTRODUCTION: The use of various diagnostic techniques is increasingly common in pandemic scenarios. It is important to update evaluations of their metric properties in different times and settings. OBJECTIVE: Evaluate metric properties of a SARS-CoV-2 rapid antigen test relative to a reference standard. METHODS: We carried out a prospective evaluation study of the SARS-CoV-2 rapid antigen test as compared to the RT-PCR test, which is considered the reference standard. Our sample was comprised of 778 individuals, and we calculated sensitiv- ity, specificity, predictive values, prevalence and validity indices. RESULTS: Of the total 778 samples, 70 were true positives, 658 were true negatives, and 27 were false negatives when compared to RT-PCR test results. We obtained a sensitivity of 75.3% (95% CI = 65.96-84.50); a specificity of 96.1% (95% CI = 94.53-97.59); 72.2% for positive predictive value, and 96.6% for negative predictive value. The estimated preva- lence was 11.9% and the validity index was 93.6%. CONCLUSIONS: The index values validate use of the SARS- CoV-2 rapid antigen test until prevalence falls below 2.5%, since as SARS-CoV-2 infection prevalence decreases, so does the predictive value of the PCR result. The use of the SARS-CoV-2 rapid antigen test on the Isle of Youth, Cuba, was decisive in the pandemic's clinical- epidemiological management.

Diversity, properties and functions of bacterial arginases.

The metalloenzyme arginase hydrolyzes l-arginine to produce l-ornithine and urea. In bacteria, arginase has important functions in basic nitrogen metabolism and redistribution, production of the key metabolic precursor l-ornithine, stress resistance and pathogenesis. We describe the regulation and specific functions of the arginase pathway as well as summarize key characteristics of related arginine catabolic pathways. The use of arginase-derived ornithine as a precursor molecule is reviewed. We discuss the biochemical and transcriptional regulation of arginine metabolism, including arginase, with the latter topic focusing on the RocR and AhrC transcriptional regulators in the model organism Bacillus subtilis. Finally, we consider similarities and contrasts in the structure and catalytic mechanism of the arginases from Bacillus caldovelox and Helicobacter pylori. The overall aim of this review is to provide a panorama of the diversity of physiological functions, regulation and biochemical features of arginases in a variety of bacterial species.

Monitoreo hemodinámico en el paciente crítico

RESUMEN La atención al paciente crítico requiere del manejo del sistema cardiovascular y del equilibrio del medio interno, por lo cual es necesario el monitoreo hemodinámico. Con el objetivo de describir el sustento fisiológico del monitoreo hemodinámico y los medios para su determinación se realizó una búsqueda de información en las bases de dato Scopus, SciELO, PubMed, LILACS, AmeliCA y Redib. El monitoreo hemodinámico permite determinar la necesidad de administrar fluidos y su respuesta terapéutica; al analizar la curva de Frank-Starling. Además, necesita la determinación de parámetros estáticos y dinámicos, que analizan el gasto cardíaco, la presión de pulso, medidos mediante métodos invasivos, mínimamente invasivos y no invasivos. La variabilidad de la presión de pulso y del volumen sistólico constituyen nuevas variables útiles en el proceso. El estudio mediante ecocardiografía de la vena cava inferior juega un importante papel en el monitoreo hemodinámico.

ABSTRACT Caring for the critically ill patient requires management of the cardiovascular system and balance of the internal environment. Hemodynamic monitoring is therefore necessary. With the objective of describing the physiological basis of hemodynamic follow-up and means for its determination, a search for information was carried out in the -Scopus, SciELO, PubMed, LILACS, AmeliCA, and Redib- databases. Hemodynamic monitoring allows determining when fluid administration is required and its therapeutic response by analyzing the Frank Starling curve. It requires the determination of static and dynamic parameters that analyze cardiac output and pulse pressure. These parameters are measured by invasive, minimally invasive and noninvasive methods. Pulse pressure and stroke volume variability are useful new variables in the process. Echocardiographic study of the inferior vena cava plays an important role in the hemodynamic follow-up.

Parameterizing a tumor humeral prosthesis and development of a set.

BACKGROUND: The reconstruction of the proximal humerus is possible from the resection of the tumor and the placement of a prosthesis. In some cases, they do not meet the anthropometric aspects of the patients. OBJECTIVE: To determine the parameters to size the components of a humeral prosthesis and the development of a set, using design software. METHOD: Forty patients were selected for prostheses, radiographs and CT scans were analyzed and statistical tests were applied to the measurements. RESULTS: The length of the tumors was 8-20 cm. The minimum length of the humerus was 28 cm and 33 cm the maximum. Correlation was observed between the humerus and the tumor and the height of the patient with p = 0.93088 and p = 0.904564, respectively; humerus diameter, p = 0.2345. The set will include three components, diameter 6-10 mm, and length of 24, 26 and 28 cm. Three modular spacers with lengths of 6, 8.5 and 13 cm. Crowns 6.5 and 8.5 cm long, 1.3 cm in diameter and 5 mm nut. CONCLUSION: With the development of the set, poorly calculated resections and adaptation to any humerus size can be resolved.

ANTECEDENTES: La reconstrucción del húmero proximal es posible a partir de la resección del tumor y la colocación de una prótesis. En algunos casos, las prótesis no cumplen con los aspectos antropométricos de los pacientes. OBJETIVO: Determinar los parámetros para dimensionar los componentes de una prótesis de húmero y el desarrollo de un set, mediante software de diseño. MÉTODO: Se seleccionaron 40 pacientes para prótesis, se analizaron radiografías y tomografías computarizadas, y se aplicaron pruebas estadísticas a las mediciones. RESULTADOS: La longitud de los tumores fue de 8-20 cm. La longitud mínima del húmero fue de 28 cm y la máxima fue de 33 cm. Se observó correlación entre el húmero y el tumor y la altura del paciente, con p = 0.93088 y p = 0.904564, respectivamente; para el diámetro del húmero, p = 0.2345. El set incluye tres componentes, con diámetro de 6-10 mm y longitud de 24, 26 y 28 cm; tres espaciadores modulares con longitudes de 6, 8,5 y 13 cm; coronas de 6,5 y 8,5 cm de largo, 1,3 cm de diámetro y tuerca de 5 mm. CONCLUSIÓN: Con el desarrollo del set se pueden resolver resecciones mal calculadas y la adaptación a cualquier tamaño de húmero.

Placental pathology and perinatal risk during the COVID-19 pandemic.

BACKGROUND: Respiratory and immune changes during pregnancy can lead to viral infections. In coronavirus disease 2019 (COVID-19), clinical characteristics and perinatal risks are difficult to assess and are relatively unknown. OBJECTIVE: To review placental pathology in asymptomatic women with COVID-19, and to evaluate effects on perinatal outcomes. MATERIAL AND METHOD: Retrospective, observational, cross-sectional study that included 29 pregnant women in 2020. The women underwent COVID-19 tests and were divided in two groups: 1) control, COVID-19-negative patients, and 2) asymptomatic COVID-19-positive patients; the placentas were studied at the pathology department, and clinical data were retrieved from the electronic medical record; in addition, a literature review was carried out. RESULTS: When the groups were compared, no differences were observed in general data and clinical characteristics. On the day of delivery, patients 2, 4, 5, 6, 8 and 9 of the COVID-19 group were between day 0 and 10.5 after having tested positive; only patients 1, 3 and 7 had overcome the infection. There was a decrease in weeks of gestation in the COVID-19 group (37.8 ± 1.8 vs. 39 ± 0.8; p ≤ 0.05). COVID-19-positive patients' placental histopathology showed a higher prevalence of thrombotic alterations in placental villi (55.5 vs. 0%). CONCLUSIONS: COVID-19 asymptomatic infection potentiates preexisting prothrombotic profile, thus increasing the risk of placental thrombosis and, potentially, of thrombosis in pregnant women.

ANTECEDENTES: Los cambios respiratorios e inmunitarios en el embarazo pueden conducir a infecciones virales. En la enfermedad por coronavirus 2019 (COVID-19) las características clínicas y riesgos perinatales son difíciles de evaluar y son relativamente desconocidos. OBJETIVO: Revisar patología placentaria en mujeres asintomáticas con COVID-19 y evaluar efectos en datos perinatales. MATERIAL Y MÉTODO: Estudio retrospectivo, observacional y transversal, incluye 29 mujeres embarazadas en 2020. Se realizaron prueba COVID-19 y dividieron en dos grupos: 1) control, pacientes COVID-19 negativas y 2) COVID-19 asintomáticas con COVID-19 positivo; las placentas se estudiaron en patología y los datos clínicos se tomaron del expediente electrónico; asimismo, se realizó revisión de literatura. RESULTADOS: Al comparar grupos no se observó diferencia en datos generales y características clínicas. El día del parto, las pacientes 2, 4, 5, 6, 8 y 9 del grupo COVID-19 se encontraban entre día 0 y 10.5 después de positividad; únicamente las pacientes 1, 3 y 7 habían superado la infección. Se presentó disminución de semanas de gestación en el grupo COVID-19 (37.8 ± 1.8 vs. 39 ± 0.8; p ≤ 0.05). La histopatología placentaria en COVID-19 mostró mayor prevalencia de alteraciones trombóticas en vellosidades placentarias (55.5 vs. 0%). CONCLUSIONES: La infección asintomática por COVID-19, potencializa perfil protrombótico preexistente, incrementando riesgo de trombosis placentaria y trombosis en mujeres embarazadas.

Genetic regulation, biochemical properties and physiological importance of arginase from Sinorhizobium meliloti.

In bacteria, l-arginine is a precursor of various metabolites and can serve as a source of carbon and/or nitrogen. Arginine catabolism by arginase, which hydrolyzes arginine to l-ornithine and urea, is common in nature but has not been studied in symbiotic nitrogen-fixing rhizobia. The genome of the alfalfa microsymbiont Sinorhizobium meliloti 1021 has two genes annotated as arginases, argI1 (smc03091) and argI2 (sma1711). Biochemical assays with purified ArgI1 and ArgI2 (as 6His-Sumo-tagged proteins) showed that only ArgI1 had detectable arginase activity. A 1021 argI1 null mutant lacked arginase activity and grew at a drastically reduced rate with arginine as sole nitrogen source. Wild-type growth and arginase activity were restored in the argI1 mutant genetically complemented with a genomically integrated argI1 gene. In the wild-type, arginase activity and argI1 transcription were induced several fold by exogenous arginine. ArgI1 purified as a 6His-Sumo-tagged protein had its highest in vitro enzymatic activity at pH 7.5 with Ni2+ as cofactor. The enzyme was also active with Mn2+ and Co2+, both of which gave the enzyme the highest activities at a more alkaline pH. The 6His-Sumo-ArgI1 comprised three identical subunits based on the migration of the urea-dissociated protein in a native polyacrylamide gel. A Lrp-like regulator (smc03092) divergently transcribed from argI1 was required for arginase induction by arginine or ornithine. This regulator was designated ArgIR. Electrophoretic mobility shift assays showed that purified ArgIR bound to the argI1 promoter in a region preceding the predicted argI1 transcriptional start. Our results indicate that ArgI1 is the sole arginase in S. meliloti, that it contributes substantially to arginine catabolism in vivo and that argI1 induction by arginine is dependent on ArgIR.

The International Society for the Study of Vulvovaginal Disease Surgical Oncological Procedure Definitions Committee "Surgical Terminology for Vulvar Cancer Treatment".

OBJECTIVES: The International Society for the Study of Vulvovaginal Disease (ISSVD) Surgical Oncological Procedure Definitions Committee propose a consistent terminology based on well-defined and reproducible anatomic landmarks that can be used by all who are involved in care of patients with vulvar conditions. MATERIALS AND METHODS: The fundamental principles behind the new terminology contained descriptions of the area extension and depth of the surgical procedure. RESULTS: Vulvar Surgical Topographic Anatomy LandmarksExtension. The internal border of the vulva is the hymenal ring. The genitocrural folds are the external lateral borders.The vertical line through the clitoris and the anus defines lateral portions of the vulva.The horizontal line from the upper border of the hymenal ring defines anterior and posterior portion of the vulva.Depth. The floor of the vulva is represented by the median perineal fascia or perineal membrane of the urogenital diaphragm.A. Vulvectomy1. Extension: partial/total vulvectomy. Removal of part/entire vulvar/perineal integument independent of the depth.2. Depth: superficial/deep. Removal of the most superficial layer/removal of the vulvar tissue to the superficial aponeurosis of the urogenital diaphragm and/or pubic periosteum.B. Inguinofemoral lymphadenectomy1. Superficial inguinofemoral lymphadenectomy. Removal of the nodes located beside the inguinal ligament and along the great saphenous vein.2. Deep femoral lymphadenectomy. Removal of the nodes below the cribriform lamina and medial to the femoral vein. CONCLUSIONS: This terminology helps avoid confusion and promote better understanding and exchange of experiences among gynecologic oncologists involved in vulvar carcinoma care.

Volumetric measurement of the acetabular cavity in patients with unilateral neglected developmental dysplasia of the dislocated hip operated in a single time.

BACKGROUND: Plain radiography is the most often imaging method used for postoperative assessment of inveterate developmental dysplasia of the hip. This technique does not permit to achieve an accurate diagnose of intra-articular changes, specifically articular congruity. OBJECTIVE: analyze the morphological changes of the acetabular volume by computed tomography, in patients operated by medium adductor myotomy, psoas tenotomy, open hip reduction, diaphysectomy, varus osteotomy and derotating and Dega-type acetabuloplasty. METHOD: A pilot clinical trial was conducted including six patients with unilateral inveterate dysplasia admitted to the Rehabilitation National Institute. Computed tomography were analyzed using an engineering design software. RESULTS: It was found that in all cases analyzed, operated acetabular volume was greater than the contralateral (8 to 48%), however, no significant difference between the volumes was found (p = 2.46). Significant difference between the volume and the age of patients, in multifactorial ANOVA tests (p = 0.006), Cochran's (p = 0.00019) and Kruskal-Wallis (p = 2.925 × 10-8) was found. CONCLUSION: It is clear that the proposed measurement technique is able to identify differences between volumes (operated and contralateral). The clinical monitoring of these patients can validate the results obtained by this measurement technique, and it will serve to estimate the effectiveness of the surgical technique applied in patients.

ANTECEDENTES: El método más utilizado para la evaluación posquirúrgica de la displasia del desarrollo de la cadera inveterada es la radiografía convencional, lo que impide medir con precisión cambios intraarticulares. OBJETIVO: Analizar los cambios morfológicos del volumen acetabular mediante tomografía computarizada en pacientes operados con miotomía de aductor mediano, tenotomía de psoas, reducción abierta de cadera, diafisectomía, osteotomía varizante y desrotadora, y acetabuloplastia tipo Dega. MÉTODO: Se realizó un estudio piloto en el que se analizaron tomografías de seis pacientes del Instituto Nacional de Rehabilitación con displasia inveterada unilateral, por medio de software de diseño para determinar el volumen acetabular. RESULTADOS: Se encontró que el volumen acetabular operado fue mayor que el contralateral (8 vs. 48%), pero no se halló diferencia significativa entre los volúmenes (p = 2.46). Se encontraron diferencias significativas entre los volúmenes y la edad de los pacientes, evaluadas mediante ANOVA multifactorial (p = 0.006), Cochran (p = 2.925 × 10−8) y Kruskal-Wallis (p = 0.00019). CONCLUSIÓN: Es claro que la técnica de medición propuesta permite identificar diferencias entre volúmenes (operado y contralateral). El seguimiento clínico de estos pacientes podrá validar los resultados obtenidos por este método y servirá para poder estimar la eficacia de la técnica quirúrgica aplicada en los pacientes.

Effect of insertion angle on the stability of orthodontic mini-implants in a rabbit tibia model: A finite element analysis.

INTRODUCTION: Mini-implants are an alternative to traditional methods of anchorage in orthodontic treatment. However, there are still questions concerning their application, in particular, with the insertion angle. OBJECTIVE: To determine whether the angle of insertion of the mini-implant is a determining factor in their primary stability when they support orthodontic loads. MATERIALS AND METHODS: A finite element model (FEM) of tibia bone, spring and mini-implant was developed. The three-dimensional model of the rabbit tibia was constructed based on tomographic slices. The angles that were analyzed were 90°, 80°, 70°, 60°, 50°, 45°, 40°, and 30°. A horizontal force of 2 N applied to the head of the mini-implants was simulated. The von Mises stresses and displacements were determined using FEM. RESULTS: Von Mises stresses were lower for an insertion angle of 40° followed by 90° and 70°; likewise, the displacements of the mini-implants with respect to the spring were lower for the 40° angle followed by 90° and 70°, we found a statistically significant association between the insertion angle and displacement. CONCLUSION: All mini-implants underwent a degree of angulation and displacement; however, mini-implants inserted to the bone surface at 40° tend to have better primary stability, and they can withstand loads immediately.

INTRODUCCIÓN: Los miniimplantes son una alternativa para los métodos de anclaje tradicionales en el tratamiento de ortodoncia. Sin embargo, existen interrogantes referentes a su uso, en particular en cuanto al ángulo de inserción. OBJETIVO: ­Determinar si el ángulo de inserción es un factor determinante en la estabilidad primaria de los miniimplantes cuando soportan cargas. MÉTODO: Se desarrolló un modelo tridimensional de elementos finitos del conjunto tibia, miniimplante y resorte a partir de cortes tomográficos; finalmente, el resorte fue modelado empleando elementos de contacto. Las angulaciones analizadas fueron 90°, 80°, 70°, 60°, 50°, 45°, 40° y 30°. Una fuerza de 2 N fue aplicada a los implantes. Se determinaron los esfuerzos de von Mises y los desplazamientos empleando elementos finitos. RESULTADOS: Los esfuerzos de von Mises fueron menores para un ángulo de inserción de 40°, seguido por los de 90° y 70°; de igual forma, los desplazamientos en los miniimplantes con respecto al resorte fueron menores para un ángulo de 40°, seguido por los de 90° y 70°. CONCLUSIÓN: Todos los miniimplantes presentaron un cierto grado de angulación y desplazamiento, pero los ­insertados en la superficie ósea a 40° tienden a presentar mejor estabilidad primaria y pueden ser inmediatamente sometidos a carga.

[Effect of BioOsteo® in combination with epidermal growth factor and ascorbic acid in a rat tibia defect]. / Efecto de BioOsteo® en combinación con el factor de crecimiento epidérmico y el ácido ascórbico en un defecto de la tibia de la rata.

BACKGROUND: Treatment of bone defects derived from trauma or from removal of tumors or osteosynthesis materials can cause socioeconomic problems as a result of treatment length. OBJECTIVE: The purpose of this study was to determine the effect of the implant material BioOsteo® in combinations with epidermal growth factor (EGF) and ascorbic acid (AA) on the consolidation of a non-critical size bone defect. MATERIALS AND METHODS: A unicortical non-critical bone defect was practiced in the right tibia of Wistar rats and 3 weeks later, a biomechanical property analysis was performed through a three-point bending test. RESULTS: We found that a 1 time single-dose local application of AA + EGF + BioOsteo, directly over the non-critical bone defect microenvironment improves its repair. ANTECEDENTES:: El tratamiento de los defectos óseos originados por traumatismos o por retiro de materiales de osteosíntesis o de tumores puede ocasionar problemas socioeconómicos derivados del tiempo de tratamiento. OBJETIVO:: Determinar el efecto del material de implante BioOsteo en combinación con factor de crecimiento epidérmico (EGF) y ácido ascórbico (AA) sobre la consolidación de un defecto óseo de tamaño no crítico. MATERIAL Y MÉTODOS:: Se practicó un defecto óseo unicortical no critico en la tibia derecha de ratas Wistar y 3 semanas después se realizó el análisis de las propiedades biomecánicas por medio del ensayo de flexión en tres puntos. RESULTADOS:: Encontramos que la aplicación local de una dosis única de AA + EGF + BioOsteo directamente sobre el microambiente del defecto óseo no crítico favorece su reparación.

Racekiela andina sp. nov. (Spongillida: Spongillidae): first report of a freshwater sponge from the Venezuelan Andes.

The genus Racekiela Bass & Volkmer-Ribeiro, 1998 comprises six species of freshwater sponges distributed along the Palaearctic, Nearctic and Neotropical regions (Van Soest et al. 2017). They are characterized by an isodictyal skeleton solely of acanthoxeas, sparse spongin fibers, and tri-layered gemmules with radially embedded gemmoscleres of two types, short birotules and long pseudobirotules (Manconi & Pronzato 2002; Volkmer-Ribeiro & Machado 2007). Four species occur in the Northern Hemisphere: R. biceps (Lindenschmidt, 1950) from Michigan (Lindenschmidt 1950), R. pictouensis (Potts, 1885) from eastern Canada to New York (Penney & Racek 1968), R. ryderii (Potts, 1882) which ranges from eastern North America to the British Isles, Faroes and Norway (Manconi & Pronzato 2002), and the recently described R. montemflumina Carballo, Cruz-Barraza, Yáñez & Gómez, 2017 from Northwestern Mexico (Carballo et al. 2017). It is worthy to note that R. pictouensis is considered to be an ecomorph of R. ryderii by several authors (Porrier 1977; Ricciardi & Reiswig 1993). The other two species, R. cavernicola (Volkmer-Ribeiro, Bichuette & Machado, 2010) and R. sheilae (Volkmer-Ribeiro, De Rosa-Barbosa & Tavares, 1988), are both known only from Brazil (Volkmer-Ribeiro & Machado 2007; Volkmer-Ribeiro et al. 2010). Here we describe a new member of the genus, found in lakes of high-mountain ecosystems, or páramos, in the Cordillera de Mérida. This constitutes the first record of specimens belonging to Racekiela for the Andes and Venezuela.

Análisis del comportamiento mecánico del tejido subyacente a las tuberosidades isquiáticas por medio del método del elemento finito / Analysis of mechanical behavior of the underlying tissue to the ischial tuberosities using finite element method

Las úlceras por presión son las complicaciones secundarias más comunes a una lesión medular, las cuales ponen en riesgo tanto la salud como la vida de quienes las padecen. Las úlceras por presión más comunes en lesionados medulares aparecen en la región pélvica, principalmente en las tuberosidades isquiáticas (TI's). Una estrategia usada en la clínica es medir la presión generada entre el paciente y la superficie donde se encuentra para evaluar el riesgo que representa dicha superficie para el desarrollo de úlceras por presión sin embargo, este tipo de mediciones superficiales no garantizan que la presión en los tejidos internos subyacentes a prominencias óseas sea inocua. Con el fin de estudiar los mecanismos de formación de úlceras por presión, se realizó el análisis de un modelo de pelvis y tejido subyacente por medio del Método de los Elementos Finitos (MEF). De esta manera se puede estudiar el comportamiento de las TI's sobre su tejido circundante, así como analizar los efectos biomecánicos que provocan las úlceras. Se construyó el modelo computacional por medio de un software de CAD (Computing Aided Design) de la pelvis a partir de cortes tomográficos. El modelo fue exportado al software COMSOL y se analizaron seis casos de estudio: un análisis de la pelvis sobre bloques de tejido sano y cinco casos más, los cuales simulan lesiones en el tejido con distintas profundidades, representando úlceras superficiales e internas. Los resultados mostraron que los puntos de máximo esfuerzo, en todas las pruebas, se localizan justo debajo de la TIs además se encontró que las lesiones internas presentan mayores esfuerzos y deformaciones, los cuales pueden ser precursores de daño en el tejido.

Pressure ulcers are the most common secondary complication to a spinal cord injury, which endanger both health and life of the patients who suffer them. The most common pressure ulcers in spinal cord injuries occur in the pelvic region, mainly in the ischial tuberosities (ITs). A strategy used in clinic is to quantify the pressure generated between the patient and the surface, in order to assess the risk posed by that surface for developing pressure ulcers. Despite this, this type of surface measurements does not guarantee that pressure in the internal tissues underlying to bony prominences, to be safe. In order to study the mechanisms of formation of pressure ulcers, an analysis of a model of the pelvis and its underlying tissue was performed using the Finite Element Method (FEM). By this means we can study the behavior of ITs on its surrounding tissue, and at the same time, we analyze the biomechanical effects those cause ulcers. The computational model of the pelvis was built from tomographic slices using CAD software (Computing Aided Design). The model was exported to the finite element software COMSOL and six study cases were analyzed: an analysis of the pelvis on healthy tissue blocks and five more cases, which simulate tissue injury with different depths, representing surface and internal ulcers. The results showed that the maximum stress points in all tests are located just below the ITs it was also found that internal injuries present higher stresses and strains, which can be precursors of tissue damage.

Quantification of the ciliary muscle and crystalline lens interaction during accommodation with synchronous OCT imaging.

Two SD-OCT systems and a dual channel accommodation target were combined and precisely synchronized to simultaneously image the anterior segment and the ciliary muscle during dynamic accommodation. The imaging system simultaneously generates two synchronized OCT image sequences of the anterior segment and ciliary muscle with an imaging speed of 13 frames per second. The system was used to acquire OCT image sequences of a non-presbyopic and a pre-presbyopic subject accommodating in response to step changes in vergence. The image sequences were processed to extract dynamic morphological data from the crystalline lens and the ciliary muscle. The synchronization between the OCT systems allowed the precise correlation of anatomical changes occurring in the crystalline lens and ciliary muscle at identical time points during accommodation. To describe the dynamic interaction between the crystalline lens and ciliary muscle, we introduce accommodation state diagrams that display the relation between anatomical changes occurring in the accommodating crystalline lens and ciliary muscle.

Calculation of crystalline lens power using a modification of the Bennett method.

We present a method for measuring lens power from extended depth OCT biometry, corneal topography, and refraction using an improvement on the Bennett method. A reduced eye model was used to derive a formula for lens power in terms of ocular distances, corneal power, and objective spherical equivalent refraction. An error analysis shows that the formula predicts relaxed lens power with a theoretical accuracy of ± 0.5 D for refractive error ranging from -10 D to + 10 D. The formula was used to calculate lens power in 16 eyes of 8 human subjects. Mean lens power was 24.3 D ± 1.7 D.

Genetic and biochemical characterization of arginine biosynthesis in Sinorhizobium meliloti 1021.

L-Ornithine production in the alfalfa microsymbiont Sinorhizobium meliloti occurs as an intermediate step in arginine biosynthesis. Ornithine is required for effective symbiosis but its synthesis in S. meliloti has been little studied. Unlike most bacteria, S. meliloti 1021 is annotated as encoding two enzymes producing ornithine: N-acetylornithine (NAO) deacetylase (ArgE) hydrolyses NAO to acetate and ornithine, and glutamate N-acetyltransferase (ArgJ) transacetylates l-glutamate with the acetyl group from NAO, forming ornithine and N-acetylglutamate (NAG). NAG is the substrate for the second step of arginine biosynthesis catalysed by NAG kinase (ArgB). Inactivation of argB in strain 1021 resulted in arginine auxotrophy. The activity of purified ArgB was significantly inhibited by arginine but not by ornithine. The purified ArgJ was highly active in NAO deacetylation/glutamate transacetylation and was significantly inhibited by ornithine but not by arginine. The purified ArgE protein (with a 6His-Sumo affinity tag) was also active in deacetylating NAO. argE and argJ single mutants, and an argEJ double mutant, are arginine prototrophs. Extracts of the double mutant contained aminoacylase (Ama) activity that deacetylated NAO to form ornithine. The purified products of three candidate ama genes (smc00682 (hipO1), smc02256 (hipO2) and smb21279) all possessed NAO deacetylase activity. hipO1 and hipO2, but not smb21279, expressed in trans functionally complemented an Escherichia coli ΔargE : : Km mutant. We conclude that Ama activity accounts for the arginine prototrophy of the argEJ mutant. Transcriptional assays of argB, argE and argJ, fused to a promoterless gusA gene, showed that their expression was not significantly affected by exogenous arginine or ornithine.

Estudio mecánico del fijador interno de columna INO: primera parte: comportamiento bajo en carga cuasi-estática de flexo-compresión / A mechanical study of the spine internal fixator INO: first part: behavior under quasi-static flexoid compression load

Se estudió mecánicamente in vitro el fijador interno de columna INO (Instituto Nacional de Ortopedia) de placas longitudinales y tornillos pediculares, bajo carga cuasi-estática (n = 5) de flexocompresión anterior, para determinar su resistencia a la flexión (N.m), rigidez (N.m/mm) y flexibilidad (mm/N.m). El modelo experimental representó una corpectomía total, utilizándose discos de plástico como cuerpos vertebrales; los tornillos pediculares se fijaron pivotantes (apoyo esférico de las tuercas hacia la placa) a las placas longitudinales. Los ensayos se realizaron en una máquina Instron 4502, aplicando la carga con un brazo de palanca de 39 mm. Los valores medios de resistencia a la flexión, rigidez y flexibilidad obtenidos fueron de 31.184 N.m [de (desviación estándar) = 2.73], 1.205 N.m/mm (de = 0.225) y 0.852 mm/N.m (de = 0.152) respectivamente; la falla observada fue alargamiento y flexión plástica de los cuatro tornillos pediculares. La resistencia a la flexión obtenida para el fijador INO representa el 309.3 por ciento y 53.7 por ciento de la resistencia de los fijadores Rogozinski e Isola, los de menor y mayor resistencia respectivamente, de los doce fijadores estudiados por Cunningham; su rigidez, el 42 por ciento y 17.5 por ciento de la rigidez correspondiente a los fijadores Kirschner e Isola, los de menor y mayor rigidez, y su flexibilidad, el 238.5 por ciento y 572.4 por ciento de la flexibilidad de estos últimos fijadores. Por tanto, el fijador interno INO tiene resistencia a la flexión aceptable pero es más flexible que todos los fijadores estudiados por Cunningham.

Análogos de la hormona hipotalámica liberadora de gonadotropinas (GnRH) y cáncer mamario / Analogues of hypothalamic, gonadotropins releasing hormone (GnRH) and breast cancer

La hormonas esteroides, hormonas peptídicas, factores de crecimiento y otros factores tróficos, están involucrados en la regulación del crecimiento tumoral. La terapia hormonal del cáncer mamario consiste en una variedad de medidas médicas y quirúrgicas como la ooforectomía e hipofisectomía. El tratamiento de tumores hormonodependientes como el cáncer mamario, generalmente emplean antiestrógenos, pero con el advenimiento de análogos de la hormona liberadora de gonadotropinas (a-GnRH); estos neuropéptidos podrían jugar un importante papel en el tratamiento del cáncer mamario, por sus escasos efectos colaterales