Force measurements with optical tweezers inside living cells

The force exerted by optical tweezers can be measured by tracking the momentum changes of the trapping beam, a method which is more general and powerful than traditional calibration techniques as it is based on first principles, but which has not been brought to its full potential yet, probably due to practical difficulties when combined with high-NA optical traps, such as the necessity to capture a large fraction of the scattered light. We show that it is possible to measure forces on arbitrary biological objects inside cells without an in situ calibration, using this approach. The instrument can be calibrated by measuring three scaling parameters that are exclusively determined by the design of the system, thus obtaining a conversion factor from volts to piconewtons that is theoretically independent of the physical properties of the sample and its environment. We prove that this factor keeps valid inside cells as it shows good agreement with other calibration methods developed in recent years for viscoelastic media. Finally, we apply the method to measuring the stall forces of kinesin and dynein in living A549 cells.Publisher PD

HoloTrap: Interactive hologram design for multiple dynamic optical trapping

This work presents an application that generates real-time holograms to be displayed on a holographic optical tweezers setup; a technique that allows the manipulation of particles in the range from micrometres to nanometres. The software is written in Java, and uses random binary masks to generate the holograms. It allows customization of several parameters that are dependent on the experimental setup, such as the specific characteristics of the device displaying the hologram, or the presence of aberrations. We evaluate the software's performance and conclude that real-time interaction is achieved. We give our experimental results from manipulating 5 micron-diametre microspheres using the program.Comment: 17 pages, 6 figure

Design strategies for optimizing holographic optical tweezers setups

We provide a detailed account of the construction of a system of holographic optical tweezers. While much information is available on the design, alignment and calibration of other optical trapping configurations, those based on holography are relatively poorly described. Inclusion of a spatial light modulator in the setup gives rise to particular design trade-offs and constraints, and the system benefits from specific optimization strategies, which we discuss.Comment: 16 pages, 15 figure

Plant-microbe interactions and the new biotechnological methods of plant disease control

Plants constitute an excellent ecosystem for microorganisms. The environmental conditions offered differ considerably between the highly variable aerial plant part and the more stable root system. Microbes interact with plant tissues and cells with different degrees of dependence. The most interesting from the microbial ecology point of view, however, are specific interactions developed by plant-beneficial (either non-symbiotic or symbiotic) and pathogenic microorganisms. Plants, like humans and other animals, also become sick, but they have evolved a sophisticated defense response against microbes, based on a combination of constitutive and inducible responses which can be localized or spread throughout plant organs and tissues. The response is mediated by several messenger molecules that activate pathogen-responsive genes coding for enzymes or antimicrobial compounds, and produces less sophisticated and specific compounds than immunoglobulins in animals. However, the response specifically detects intracellularly a type of protein of the pathogen based on a gene-for-gene interaction recognition system, triggering a biochemical attack and programmed cell death. Several implications for the management of plant diseases are derived from knowledge of the basis of the specificity of plant-bacteria interactions. New biotechnological products are currently being developed based on stimulation of the plant defense response, and on the use of plant-beneficial bacteria for biological control of plant diseases (biopesticides) and for plant growth promotion (biofertilizers)

Plankton Taxonomic and Size Diversity of Mediterranean Brackish Ponds in Spring: Influence of Abiotic and Biotic Factors

In this study, performed in Mediterranean brackish ponds during spring season, we assessed the effects of biotic interactions and abiotic factors on the size and taxonomic structure of the phytoplankton and zooplankton. We used a taxonomic and a size diversity index as a descriptor of the community structure. We predicted that the size diversity of each trophic level would be mainly related to biotic interactions, such as size-based fish predation (in the case of zooplankton) and food resource availability (in the case of phytoplankton), whereas taxonomic diversity would be more affected by abiotic variables (e.g., conductivity, pond morphology). Our results showed a negative relationship between phytoplankton size diversity and food resource availability leading to low size diversities under food scarcity due to dominance of small species. Conductivity also negatively affected the phytoplankton size diversity, although slightly. Regarding zooplankton size diversity, none of predictors tested seemed to influence this index. Similar fish size diversities among ponds may prevent a significant effect of fish predation on size diversity of zooplankton. As expected, taxonomic diversity of phytoplankton and zooplankton was related to abiotic variables (specifically pond morphometry) rather than biotic interactions, which are usually body size dependent, especially in these species-poor brackish environments

La evaluación del estrés y del trauma: presentación de la versión española de la escala de trauma acumulativo (cts)

This paper reviews some of the most usual definitions of stress and trauma including the notion of accumulative trauma. Then, the Spanish version of the Cumulative Trauma Scale by Kira et al (2008) is presented. It has been developed by following a process of translation and by applying it to two small groups of subjects to test it for comprehension (pilot test).En este artículo se revisan las definiciones al uso de estrés y trauma, incluyendo la noción de trauma acumulativo. Seguidamente, se presenta la versión española de la primera escala existente que lo mide: la Escala de Trauma Acumulativo (CTS) de Kira et al (2008). Para obtener esta versión se ha seguido un proceso de traducción-retraducción y también se ha aplicado a dos grupos reducidos de sujetos a modo de prueba piloto

Catch-up growth in juvenile rats, fat expansion, and dysregulation of visceral adipose tissue

BACKGROUND: Accelerated catch-up growth following intrauterine restriction increases the risk of developing visceral adiposity and metabolic abnormalities. However, the underlying molecular mechanisms of such metabolic programming are still poorly understood. METHODS: A Wistar rat model of catch-up growth following intrauterine restriction was used. A gene expression array was performed in the retroperitoneal adipose tissue sampled at postnatal day (PD) 42. RESULTS: Five hundred and forty-six differentially expressed genes (DEGs) were identified (adjusted p value < 0.05). Gene ontology enrichment analysis identified pathways related to immune and lipid metabolic processes, brown fat cell differentiation, and regulation of PI3K. Ccl21, Npr3, Serpina3n, Pnpla3, Slc2a4, and Serpina12 were validated to be upregulated in catch-up pups (all p < 0.01) and related to several fat expansion and metabolic parameters, including body weight at PD42, postnatal body weight gain, white and brown adipose tissue mass, plasma triglycerides, and insulin resistance index (all p < 0.05). CONCLUSIONS: Genes related to immune and metabolic processes were upregulated in retroperitoneal adipose tissue following catch-up growth in juvenile rats and were found to be associated with fat expansion and metabolic parameters. Our results provide evidence for several dysregulated genes in white adipose tissue that could help develop novel strategies to prevent the metabolic abnormalities associated with catch-up growth

Prevalencia de la obesidad en la población atendida en asistencia primaria de Girona, 1995–1999

ResumenObjetivosEstimar y comparar la prevalencia de la obesidad y el sobrepeso en la población de Girona, entre 1995 y 1999, estratificando geográficamente por sexo y edad.MétodosMedidas directas de talla y peso correspondientes a 24.554 usuarios mayores de 14 años (10.595 varones y 13.959 mujeres) atendidos en cuatro áreas básicas de salud (ABS): Girona 1, Girona 4, Salt y Camprodon, así como en un centro de atención primaria (CAP) de la provincia de Girona. Se calculó el índice de masa corporal (IMC) como el cociente entre el peso y la talla al cuadrado. La obesidad se define como los grados II y III del índice de Garrow (IMC ≥ 30 kg/m2) y el sobrepeso como el grado I (25 kg/m2 ≤ IMC < 30 kg/m2). Al no utilizarse una muestra aleatoria de sujetos, el cálculo de prevalencias y de sus errores estándar se corrigió mediante el uso de ponderaciones adecuadas. La comparación de las prevalencias entre dos ABS distintas para cada sexo se realizó utilizando un contraste paramétrico de diferencia de proporciones. La comparación entre las prevalencias de un determinado grado del índice de Garrow, controlando por sexo y edad, se llevó a cabo utilizando una regresión logística jerárquica.ResultadosLa prevalencia de la obesidad se estimó en 15,6% entre los varones de 20 a 74 años (desde el 14,0% en Girona 1 hasta el 22,4% en Camprodon) y en un 17,5% entre las mujeres (un 15,6% en Girona 1 y un 22,7% en Camprodon), un 16,7% de promedio ponderado. La prevalencia del sobrepeso se sitúa en el 44% en varones y en un 33% en mujeres, un 37,8% de promedio ponderado. Existe una gradación en las prevalencias de la obesidad, con diferencias estadísticamente significativas: Girona 1, Salt, Girona 4, Camprodon y Sils.ConclusionesLas estimaciones de la prevalencia de la obesidad y sobrepeso obtenidas en este trabajo no están tan alejadas como se creía de las estimadas en poblaciones de nuestro entorno. De hecho, podrían ser muy similares a las estimadas en la Unión Europea y, para algunos grupos de edad, incluso a las de Estados Unidos.AbstractObjectivesTo estimate the prevalence of obesity and overweight in the population of Girona (Spain) between 1995 and 1999 and to divide the prevalences in geographical areas according to age and sex.MethodsHeight and weight were directly measures in 24,554 health care consumers older than 14 years (10,595 men and 13,959 women) treated in four primary health care areas: Girona 1, Girona 4, Salt and Camprodon and in one primary health care center in the province of Girona. Body mas index (BMI) was calcuted by dividing weight in kilograms bye height in meters squared. Obesity was defined as grades II and III of Garrow's index (BMI ≥ 30 kg/m2) and overweight as degree I (25 kg/m2 ≥ BMI < 30 kg/m2). Because the sample was not randomized, the prevalences were adequately weighted. The comparison between prevalences in two different primary health care areas for each sex (in the same Garrow's index and age group) was carried out using a parametric test of differences in proportions (Student's t-test). A hierarchical logistic regression was used to compare prevalences in the same grade Garrow's index, controlling for age and sex.ResultsThe prevalence of obesity was estimated as 15.6% in men aged from 20-74 years (from 14.0% in Girona 1 to 22.4% in Camprodon) and 17.5% for women (15.6% in Girona 1, 22.7% in Camprodon). The weighted mean was 16.7%. The prevalence of overweight was 44% in men and 33% in women and the weighted mean was 37.8%. The prevalence of obesity was graduated with statistically significant differences between Girona 1, Salt, Girona 4, Camprodon and Sils.ConclusionsThe estimates of the prevalences of obesity and overweight obtained in this study were closer to those of other studies in similar populations than previously believed. Inde-ed, the prevalences may be similar to those of the European Union and, in some age groups, to those of the United States

Growth Differentiation Factor 15 is a potential biomarker of therapeutic response for TK2 deficient myopathy

GDF-15 is a biomarker for mitochondrial diseases. We investigated the application of GDF-15 as biomarker of disease severity and response to deoxynucleoside treatment in patients with thymidine kinase 2 (TK2) deficiency and compared it to FGF-21. GDF-15 and FGF-21 were measured in serum from 24 patients with TK2 deficiency treated 1–49 months with oral deoxynucleosides. Patients were grouped according to age at treatment and biomarkers were analyzed at baseline and various time points after treatment initiation. GDF-15 was elevated on average 30-fold in children and 6-fold in adults before the start of treatment. There was a significant correlation between basal GDF-15 and severity based on pretreatment distance walked (6MWT) and weight (BMI). During treatment, GDF-15 significantly declined, and the decrease was accompanied by relevant clinical improvements. The decline was greater in the paediatric group, which included the most severe patients and showed the greatest clinical benefit, than in the adult patients. The decline of FGF-21 was less prominent and consistent. GDF-15 is a potential biomarker of severity and of therapeutic response for patients with TK2 deficiency. In addition, we show evidence of clinical benefit of deoxynucleoside treatment, especially when treatment is initiated at an early age