Bending forces and nucleotide state jointly regulate F-actin structure.

ATP-hydrolysis-coupled actin polymerization is a fundamental mechanism of cellular force generation1-3. In turn, force4,5 and actin filament (F-actin) nucleotide state6 regulate actin dynamics by tuning F-actin's engagement of actin-binding proteins through mechanisms that are unclear. Here we show that the nucleotide state of actin modulates F-actin structural transitions evoked by bending forces. Cryo-electron microscopy structures of ADP-F-actin and ADP-Pi-F-actin with sufficient resolution to visualize bound solvent reveal intersubunit interfaces bridged by water molecules that could mediate filament lattice flexibility. Despite extensive ordered solvent differences in the nucleotide cleft, these structures feature nearly identical lattices and essentially indistinguishable protein backbone conformations that are unlikely to be discriminable by actin-binding proteins. We next introduce a machine-learning-enabled pipeline for reconstructing bent filaments, enabling us to visualize both continuous structural variability and side-chain-level detail. Bent F-actin structures reveal rearrangements at intersubunit interfaces characterized by substantial alterations of helical twist and deformations in individual protomers, transitions that are distinct in ADP-F-actin and ADP-Pi-F-actin. This suggests that phosphate rigidifies actin subunits to alter the bending structural landscape of F-actin. As bending forces evoke nucleotide-state dependent conformational transitions of sufficient magnitude to be detected by actin-binding proteins, we propose that actin nucleotide state can serve as a co-regulator of F-actin mechanical regulation.

Facilitators of peer leader retention within a Type 2 diabetes intervention trial for US Latinos/Hispanics of Mexican origin.

Peer support is effective in improving self-management behaviors and health outcomes among individuals with Type 2 diabetes. Volunteer peer support programs offer a cost-effective resource for diabetes self-management support; however, factors affecting the retention of volunteer peer leaders remain understudied. Herein, we examined factors associated with volunteer retention and satisfaction among 34 predominantly Mexican-origin peer leaders who assisted patients from a Federally Qualified Health Center located on the US/Mexico border with their diabetes management. Peer leaders completed surveys with open- and close-ended questions at baseline, 6 months and 12 months. Quantitative and qualitative data analyses were guided by the Volunteer Process Model. Using nonparametric Mann-Whitney U tests, self-efficacy as a peer leader at 6 months was most associated with interest to continue volunteering (P = 0.01), and satisfaction with support from the program at 12 months was most associated with interest to continue volunteering (P = 0.01). The qualitative data indicated that the relationship between the peer leaders and their patients was the primary factor for a satisfying volunteer experience. Future research should focus on increasing peer leaders' self-efficacy and satisfaction with program support and examine how organizations can support the development of the patient-peer relationship. Practitioners should consider appealing to volunteer peers' motivations to promote their retention.

Trace metals and metalloids in Andean flamingos (Phoenicoparrus andinus) and Puna flamingos (P. jamesi) at two wetlands with different risk of exposure in the Bolivian Altiplano.

Birds are widely used as bioindicators in monitoring programs in wetlands. We compare concentrations of seven trace metals and metalloids (TMM) As, Cd, Cu, Fe, Hg, Pb, Znin both feathers and blood in two flamingo species in two high-altitude wetlands in Bolivia, with different levels of anthropogenic point source pollution. Lake Uru Uru (LUU) receives discharges from mining operations, and also effluents from the nearby city of Oruro, while Laguna Colorada (LCo) does not receive contaminants from anthropogenic sources. We sampled water and sediments at each site, as well as flamingos in three age classes in an effort to establish a benchmark for long-term monitoring. Metal concentrations in water did not differ between sites, whereas Zn and Pb concentrations of TMM in sediments were higher at LUU, and Hg higher at LCo. TMM concentrations were highly specific for all separate elements, but results point to differences between Andean flamingo (Phoenicoparrus andinus) chicks and the rest of the classes considered. As flamingo chicks did not molt before sampling, we pose that TMM concentrations in their blood and feathers may respond mainly to local conditions. Eggshells provide additional information, since adults transfer some TMM during egg development. Long-term monitoring in these species should include different age classes and sample both feathers and eggshells to monitor the environmental conditions and bioaccumulation of TMM in these species. Future studies should include sites devoid of natural sources of TMM to help distinguish sources of contamination, since some TMM (As and Pb) may be naturally in high concentrations in remote areas, like Laguna Colorada.

Narrow-Spectrum Antibiotic Targeting of the Radical SAM Enzyme MqnE in Menaquinone Biosynthesis.

Antibiotic resistance continues to spread at an alarming rate, outpacing the introduction of new therapeutics and threatening to globally undermine health care. There is a crucial need for new strategies that selectively target specific pathogens while leaving the majority of the microbiome untouched, thus averting the debilitating and sometimes fatal occurrences of opportunistic infections. To address these challenges, we have adopted a unique strategy that focuses on oxygen-sensitive proteins, an untapped set of therapeutic targets. MqnE is a member of the radical S-adenosyl-l-methionine (RS) superfamily, all of which rely on an oxygen-sensitive [4Fe-4S] cluster for catalytic activity. MqnE catalyzes the conversion of didehydrochorismate to aminofutalosine in the essential menaquinone biosynthetic pathway present in a limited set of species, including the gut pathogen Helicobacter pylori (Hp), making it an attractive target for narrow-spectrum antibiotic development. Indeed, we show that MqnE is inhibited by the mechanism-derived 2-fluoro analogue of didehydrochorismate (2F-DHC) due to accumulation of a radical intermediate under turnover conditions. Structures of MqnE in the apo and product-bound states afford insight into its catalytic mechanism, and electron paramagnetic resonance approaches provide direct spectroscopic evidence consistent with the predicted structure of the radical intermediate. In addition, we demonstrate the essentiality of the menaquinone biosynthetic pathway and unambiguously validate 2F-DHC as a selective inhibitor of Hp growth that exclusively targets MqnE. These data provide the foundation for designing effective Hp therapies and demonstrate proof of principle that radical SAM proteins can be effectively leveraged as therapeutic targets.

Interactions between individual and perceived environmental factors on Latinas' physical activity.

Background: Latinas have disproportionately low levels of physical activity (PA) and the ecological correlates of their PA remain unclear. This study aims to test interactions between individual and environmental factors on Latinas' PA. Methods: We analyzed baseline data from 436 Latinas participating in a PA randomized controlled trial in San Diego, CA [Fe en Acción/Faith in Action]. Measures included demographics, perceived environment, PA and anthropometrics. Mixed effects models examined interactions between individual and environmental factors on self-reported leisure-time and transportation, and accelerometer-assessed PA. Results: Significant positive associations were found between neighborhood aesthetics and leisure-time moderate-to-vigorous PA (MVPA) and between having destinations within walking distance from home and transportation PA (P < 0.05). We found significant interactions of income with aesthetics and sidewalk maintenance as well as between weight status and safety from crime. Favorable aesthetics was related to more leisure-time MVPA only among lower income women (odds ratio (OR) = 1.57; 95% confidence interval (CI): 1.18, 2.08); however, higher income women reporting better sidewalk maintenance reported more leisure-time MVPA (OR = 1.51; 95% CI: 1.06, 2.15). Higher perceived safety from crime was positively related to transportation PA only among overweight/obese women. Conclusions: Subgroup differences should be considered when developing interventions targeting the neighborhood environment to promote Latinas' PA.

Circulating Adipokine Levels in Non-diabetic Subjects with High Normal Blood Pressure.

OBJECTIVE: This study aimed to evaluate the levels of the adipokines, resistin and adiponectin in normotensive and high normal blood pressure patients. METHODS: Circulating levels of the adipokines, resistin and adiponectin were measured by enzyme-linked immunosorbent assay (ELISA; R'D Systems, Minneapolis) in 20 high normal blood pressure patients and in 20 age-matched normotensive non-diabetic subjects. Statistical analysis was performed with analysis of variance (ANOVA). RESULTS: The control group showed non-significantly decreased levels of resistin when compared with patients with high normal blood pressure [systolic 130-139 mmHg; diastolic 85-89 mmHg] (12.25 vs 14.38 pg/mL, p = 0.40). There were significantly higher levels of adiponectin in the control group when compared with high normal blood pressure patients (11.3 vs 7.51 µg/mL, p = 0.028). CONCLUSIONS: High normal blood pressure patients have increased levels of resistin and lower values of adiponectin when compared with age-matched non-diabetic normotensive subjects. This may explain why those patients showed more progression to hypertension, atherosclerosis and cardiovascular risk than normotensive subjects.

Synthesis and characterization of modified chitosan as a promising material for enterosorption of heavy metal ions.

Currently, an important ecological problem is environmental pollution and its negative impact on living organisms, the consequences of which are deterioration in general health and the manifestation of various diseases, poisoning, endo- and exotoxicosis. Enterosorption method was proposed as a promising method for removing toxic substances from the living organisms using enterosorbents which can absorb various toxic substances of endogenous and exogenous nature in the lumen of the gastrointestinal tract. It has been proposed to use polymer-containing enterosorbents for eliminating of heavy metals from the organism. The purpose of this research was to synthesize a quaternized derivative of chitosan, specifically N-(2-hydroxybenzyl)-N-ethyl-N-methyl chitosan chloride (Q-CHS). The synthesis of Q-CHS involved the formation of a Schiff base, followed by the quaternization of the amino group of chitosan (CHS). The structures of both pure CHS and quaternized CHS were studied using various physico-chemical methods, including FTIR, NMR, XRD, SEM, DSC and TGA analyses in order to determine the structure and confirm the formation of the final product.

Myosin forces elicit an F-actin structural landscape that mediates mechanosensitive protein recognition.

Cells mechanically interface with their surroundings through cytoskeleton-linked adhesions, allowing them to sense physical cues that instruct development and drive diseases such as cancer. Contractile forces generated by myosin motor proteins mediate these mechanical signal transduction processes through unclear protein structural mechanisms. Here, we show that myosin forces elicit structural changes in actin filaments (F-actin) that modulate binding by the mechanosensitive adhesion protein α-catenin. Using correlative cryo-fluorescence microscopy and cryo-electron tomography, we identify F-actin featuring domains of nanoscale oscillating curvature at cytoskeleton-adhesion interfaces enriched in zyxin, a marker of actin-myosin generated traction forces. We next introduce a reconstitution system for visualizing F-actin in the presence of myosin forces with cryo-electron microscopy, which reveals morphologically similar superhelical F-actin spirals. In simulations, transient forces mimicking tugging and release of filaments by motors produce spirals, supporting a mechanistic link to myosin's ATPase mechanochemical cycle. Three-dimensional reconstruction of spirals uncovers extensive asymmetric remodeling of F-actin's helical lattice. This is recognized by α-catenin, which cooperatively binds along individual strands, preferentially engaging interfaces featuring extended inter-subunit distances while simultaneously suppressing rotational deviations to regularize the lattice. Collectively, we find that myosin forces can deform F-actin, generating a conformational landscape that is detected and reciprocally modulated by a mechanosensitive protein, providing a direct structural glimpse at active force transduction through the cytoskeleton.

Impact of Delivering a Healthy Lifestyle Intervention: Promotora Findings from Familias Sanas y Activas II.

Background: Community health workers, promotoras, have been identified as effective change agents of their community members' health behaviors and health status. However, few studies have examined the effects of delivering an intervention on the promotoras themselves. Objectives: This study assessed whether promotoras delivering a healthy lifestyle intervention for adults improved their health behaviors and health status from baseline to 6- and 12-months post-baseline. Methods: Volunteer promotoras were trained to promote healthy lifestyles including physical activity through workshops and free group exercise classes throughout their communities. Twenty completed all required trainings and delivered at least one class during the period between baseline and 12-month assessments. The promotoras were measured on the following variables: Systolic and diastolic blood pressure, waist circumference, weight, and height. Additionally, they reported their health behaviors and status including moderate-to-vigorous physical activity, beverage consumption, sleep duration, and depressive symptoms. Results: Repeated measures ANOVAs showed statistically significant decreases from baseline to 6 months for systolic blood pressure (p ≤ 0.05), diastolic blood pressure (p ≤ 0.001) and body mass index (p ≤ 0.05). Changes in self-reported measures were not statistically significant although trends were observed with increases in water consumption. Conclusions: Findings from this study suggest positive effects associated with delivery of a PA intervention. This is one of the first studies to focus on a cohort of promotoras to examine health outcomes from delivering a healthy lifestyle intervention. It is important to further explore these impacts on the community health workers as they have become increasingly essential to the health of some communities.

Green Synthesis for Carbon Quantum Dots via Opuntia ficus-indica and Agave maximiliana: Surface-Enhanced Raman Scattering Sensing Applications.

In this study, we present an alternative method for synthesizing carbon quantum dots (CQDs) using a green synthesis approach via extracts from Agave maximiliana and Opuntia ficus-indica(Ofi). The extracts from both plants were used as the carbon source for the CQDs. The synthesis method employs mesoporous zeolite 4A as a refractory for the thermal treatment of the samples. Transmission electron microscopy analysis established that the size of the CQDs shows a narrow distribution centered around 2 nm with a maximum size of less than 3 nm for both cases. The CQDs exhibit absorption bands associated with π-π* transitions located around 220 nm. In both cases, photoluminescence (PL) phenomenon was detected by irradiating the samples with a UV wavelength and detecting emissions close to the blue wavelength. Additionally, both kinds of CQDs were tested as surface-enhanced Raman scattering (SERS) substrates against methylene blue (MB), indicating an enhancement associated with ring deformation and stretching modes of the v(C-C) and v(C-N) bonds located around 1400 and 1620 cm-1, respectively. Complementarily, in the framework of density functional theory, H2nC2(2m+1) structures (with n = 3-5 and m = 1-3) were used as a theoretical representation of CQDs in interaction with the MB molecule. It is used for developing the analysis of charge transfer effects between both systems and for specifying elements that generate the SERS effect associated with the chemical enhancement mechanism.

Investigating prostate cancer tumour-stroma interactions: clinical and biological insights from an evolutionary game.

BACKGROUND: Tumours are made up of a mixed population of different types of cells that include normal structures as well as ones associated with the malignancy, and there are multiple interactions between the malignant cells and the local microenvironment. These intercellular interactions, modulated by the microenvironment, effect tumour progression and represent a largely under-appreciated therapeutic target. We use observations of primary tumour biology from prostate cancer to extrapolate a mathematical model. Specifically, it has been observed that in prostate cancer three disparate cellular outcomes predominate: (i) the tumour remains well differentiated and clinically indolent--in this case the local stromal cells may act to restrain the growth of the cancer; (ii) early in its genesis the tumour acquires a highly malignant phenotype, growing rapidly and displacing the original stromal population (often referred to as small cell prostate cancer)--these less common aggressive tumours are relatively independent of the local microenvironment and (iii) the tumour co-opts the local stroma--taking on a classic stromagenic phenotype where interactions with the local microenvironment are critical to the cancer growth. METHODS: We present an evolutionary game theoretical construct that models the influence of tumour-stroma interactions in driving these outcomes. We consider three characteristic and distinct cellular populations: stromal cells, tumour cells that are self-reliant in terms of microenvironmental factors and tumour cells that depend on the environment for resources, but can also co-opt stroma. RESULTS: Using evolutionary game theory we explore a number of different scenarios that elucidate the impact of tumour-stromal interactions on the dynamics of prostate cancer growth and progression, and how different treatments in the metastatic setting can affect different types of tumours. CONCLUSION: The tumour microenvironment has a crucial role in selecting the traits of the tumour cells that will determine prostate cancer progression. Equally important treatments like hormone therapy affect the selection of these cancer phenotypes making it very important to understand how they impact prostate cancer's somatic evolution.

PEG-crosslinked-chitosan hydrogel films for in situ delivery of Opuntia ficus-indica extract.

In the present study, chitosan-based wound dressings loaded with the extract of Opuntia ficus-indica (OPU) were prepared. OPU is known for its capability to accelerate skin injury repair. Chitosan (Ch) was crosslinked with a low molecular weight diepoxy-poly(ethylene glycol) (diePEG), and hydrogel films with different Ch/PEG composition and OPU content were prepared by casting. The occurrence of crosslinking reaction was confirmed by FTIR spectroscopy. FTIR and DSC analysis suggested that ionic interactions occur between chitosan and OPU. Tensile tests evidenced that the crosslinking caused a decrease of Young's modulus, which approaches the value of the human skin modulus. Swelling characteristics, water vapor transmission rate, and release kinetics demonstrated that these films are adequate for the proposed application. Finally, a scratch test on a keratinocytes monolayer showed that the rate of cell migration in the presence of OPU-loaded samples is about 3-fold higher compared to unloaded films, confirming the repairing activity of OPU.

EPDR1 up-regulation in human colorectal cancer is related to staging and favours cell proliferation and invasiveness.

The finding of novel molecular markers for prediction or prognosis of invasiveness in colorectal cancer (CRC) constitutes an appealing challenge. Here we show the up-regulation of EPDR1 in a prospective cohort of 101 CRC patients, in a cDNA array of 43 patients and in in silico analyses. EPDR1 encodes a protein related to ependymins, a family of glycoproteins involved in intercellular contacts. A thorough statistical model allowed us to conclude that the gene is significantly up-regulated in tumour tissues when compared with normal mucosa. These results agree with those obtained by the analysis of three publicly available databases. EPDR1 up-regulation correlates with the TNM staging parameters, especially T and M. Studies with CRC cell lines revealed that the methylation of a CpG island controls EPDR1 expression. siRNA knocking-down and overexpression of the gene following transient plasmid transfection, showed that EPDR1 favours cell proliferation, migration, invasiveness and adhesion to type I collagen fibres, suggesting a role in epithelial to mesenchymal transition. Both statistical and functional analysis correlated EPDR1 overexpression with invasiveness and dissemination of tumour cells, supporting the inclusion of EPDR1 in panels of genes used to improve molecular subtyping of CRC. Eventually, EPDR1 may be an actionable target.

Cellular mechanisms of epilepsy: a status report.

The cellular phenomena underlying focal epilepsy are currently understood in the context of contemporary concepts of cellular and synaptic function. Interictal discharges appear to be due to a combination of synaptic events and intrinsic currents, the exact proportion of which in any given neuron may vary according to the anatomic and functional substrate involved in the epileptic discharge and the epileptogenic agent used in a given model. The transition to seizure appears to be due to simultaneous increments in excitatory influences and decrements in inhibitory processes--both related to frequency-dependent neuronal events. A variety of specific hypotheses have been proposed to account for the increased excitability that occurs during epileptiform activity. Although each of the proposed mechanisms is likely to contribute significantly to the epileptic process, no single hypothesis provides an exclusive unifying framework within which all kinds of focal epilepsy can be understood. The spread of epileptic activity throughout the brain, the development of primary generalized epilepsy, the existence of "gating" mechanisms in specific anatomic locations, and the extrapolation of hypotheses derived from simple models of focal epilepsy to explain more complex forms of human epilepsy, all are not yet fully understood.

Penicillin as epileptogenic agent: its effect on an isolated neuron.

Penicillin induces partial depolarization and increased excitability of the neuronal membrane of crayfish stretch receptor. Such effects suggest that the epileptic focus created by the topical application of penicillin to the mammalian cerebral cortex may result from the lowering of the threshold for impluse initiation by excitatory synaptic action within the neuron population.

Penicillin as an epileptogenic agent: effect on an isolated synapse.

Penicillin enhances the excitatory postsynaptic potential of the squid stellate ganglion. This effect suggests the hypothesis that the epileptic focus created by the topical application of penicillin to the mammalian cerebral cortex is produced by the facilitation of excitatory synaptic coupling within the preexisting positive recurrent feedback system.

Inhibition of an in vivo antigen-specific IgE response by antibodies to CD23.

Immunoglobulin E (IgE) mediates many allergic responses. CD23 is a 45-kilodalton type II transmembrane glycoprotein expressed in many cell types. It is a low-affinity IgE receptor and interacts specifically with CD21, thereby modulating IgE production by B lymphocytes in vitro. In an in vivo model of an allergen-specific IgE response, administration of a rabbit polyclonal antibody to recombinant human truncated CD23 resulted in up to 90 percent inhibition of ovalbumin-specific IgE synthesis. Both Fabs and intact IgG inhibited IgE production in vitro and in vivo. Thus, CD23 participates in the regulation of IgE synthesis in vivo and so could be important in allergic disease.

A randomized controlled trial to prevent obesity among Latino paediatric patients.

BACKGROUND: Obesity disproportionately affects Latino youth. Community clinics are an important resource, yet there is little evidence for the efficacy of clinic-based approaches in this population. OBJECTIVE: The purpose of this study was to test the efficacy of a clinic-based intervention to lower body mass index (BMI) and improve body composition among overweight Latino children. METHODS: A randomized trial (2 group × 3 repeated measures) was conducted among 297 randomly sampled, overweight paediatric patients (5-10 years old) and their parents. The 12-month family-based culturally tailored behavioural intervention (Luces de Cambio) was based on the 'traffic light' concepts to address behaviour change and was delivered by clinic health educators and mid-level providers. The primary study outcome was child BMI (kg m-2 ) assessed at baseline, 6-month (n = 191) and 12-month (n = 201) post-baseline. A subsample of the children was examined for overall and site-specific adiposity using dual-energy X-ray absorptiometry (n = 79). RESULTS: There were no significant intervention effects on child BMI (p > 0.05); however, intervention children showed significantly (p < 0.05) lower total and trunk per cent fat compared with the usual care condition. CONCLUSIONS: The Luces intervention did not reduce child BMI, yet small but significant reductions were observed for child per cent body fat. Further research is needed to identify and reduce barriers to recruitment and participation among Latino families.

Granulometric analysis of corneal endothelium specular images by using a germ-grain model.

Specular microscopy is widely used to study the human corneal endothelium status in vivo. In this paper, the corneal endothelium is represented as a binary image composed of the cell inscribed circles. The granulometric distribution function of the complement of this image is used as a functional descriptor, which provides information about the shape, size and spatial arrangement of cells. Experimental evaluation using bootstrap techniques shows its ability to discriminate between controls and pathological cases. It represents a reliable and graphical alternative to the classical indices (cell density, hexagonality and coefficient of variation of cell areas), which behave poorly when detecting subtle abnormalities.

Normalizing temporal patterns to analyze sit-to-stand movements by using registration of functional data.

Functional data analysis techniques provide an alternative way of representing movement and movement variability as a function of time. In particular, the registration of functional data provides a local normalization of time functions. This normalization transforms a set of curves, records of repeated trials, yielding a new set of curves that only vary in terms of amplitude. Therefore, main events occur at the "same time" for all transformed curves and interesting features of individual recordings remain after averaging processes. This paper presents an application of the registration process to the analysis of the vertical forces exerted on the ground by both feet during the sit-to-stand movement. This movement is particularly interesting in functional evaluations related to balance control, lower extremity dysfunction or low-back pain.