Mathematical Modeling of Stress Fiber Reorganization Induced by Cyclic Stretch

Arterial endothelial cells (ECs) are subjected to pulsatile strain due to pressure changes in the cardiac cycle and this may play a significant role in vascular function in health and disease. Further, ECs differentially respond to different patterns of strain. There is much evidence that cyclic uniaxial strain results in a perpendicular orientation of ECs and their stress fibers, while no such alignment occurs in response to cyclic equaibiaxial stretch. It is unclear how cells and their stress fibers determine their specific response to particular spatiotemporal changes in the matrix, however. Given that ECs located at regions in the arterial tree prone to atherogenesis are non-aglined, while ECs in relatively healthy regions are oriented perpendicular to the principal direction of cyclic stretch, it is important to understand the mechanisms which regulate stretch-induced stress fiber alignment. The focus of this thesis was to develop realistic models to describe the dynamic changes in the organization of stress fibers in response to diverse spatiotemporal patterns of stretch. The model is based on the premise that stress fibers are pre-stressed at a ?homeostatic? level so that stress fibers are extended beyond their unloaded lengths, and that perturbation in stress fiber length from the homeostatic level destabilizes the stress fibers. A deterministic model described experimentally measured time courses of stress fiber reorientation perpendicular to the direction of cyclic uniaxial stretch, as well as the lack of alignment in response to equibiaxial stretch. In the case of cyclic simple elongation with transverse matrix contraction, stress fibers oriented in the direction of least perturbation in stretch. Model analysis indicated the need for a time-dependent stress fiber mechanical property, however. Thus, a stochastic model was developed that incorporated the concept that stress fibers tend to self-adjust to an equilibrium level of extension when they are perturbed from their unload lengths with the turnover of stress fibers. The stochastic model successfully described experimentally measured time courses of stress fiber reorganization over a range of frequencies. At a frequency of 1 Hz, stress fibers predominantly oriented perpendicular to stretch, while at 0.1 Hz the extent of stress fiber alignment was markedly reduced and at 0.01 Hz there was no alignment at all. Both the deterministic and stochastic models accurately described the relationship between stretch magnitude and the extent of stress fiber alignment in endothelial cells subjected to cyclic uniaxial stretch. Parameter sensitivity analyses for each model were used to demonstrate the effects of each parameter on the characteristics of the system response. In summary, the mathematical models were capable of describing stress fiber reorganization in response to diverse temporal and spatial patterns of stretch. These models provide a theoretical framework to elucidate the mechanisms by which adherent cells sense the characteristics of matrix deformation and describe a mechanism by which the cells can then adapt to such deformations to maintain mechanical homeostasis

Integrated Experimental and Theoretical Approaches toward Understanding Strain-Induced Cytoskeletal Remodeling and Mechanotransduction

Actin stress fibers (SFs) are mechanosensitive structural elements that respond to applied strain to regulate cell morphology, signal transduction, and cell function. The purpose of this dissertation is to elucidate the effects of mechanical stretch on cell mechanobiology via the following three aims. First, a sarcomeric model of SFs was developed to describe the role of actomyosin crossbridge cycling in SF tension regulation and reorientation in response to various modes of stretch. Using model parameters extracted from literature, this model described the dependence of cyclic stretch-induced SF alignment on a two-dimensional (2-D) surface on positive perturbations in SF tension caused by the rate of lengthening, which was consistent with experimental findings. Second, the sarcomeric model was used to predict how stretch-induced pro-inflammatory mechanotransduction depends on the mode of strain application. Together with experimental data, the results indicated that stretch-induced stress fiber alignment, MAPK activations and downstream pro-inflammatory gene expressions are dependent on SF strain rate (and related changes in SF tension) rather than SF turnover. Third, to produce biocompatible materials that are both mechanically resilient under (physiological) load and also mechanosensitive, a novel hybrid engineered tissue was developed that transmits strain stimuli to cells residing in three-dimensional (3-D) collagen microspheres. However, the macroscopic stress is largely borne by a more resilient acellular polyethylene glycol diacrylate (PEGDA) hydrogel supporting the microspheres. Careful analysis indicated that cell alignment occurs prior to significant collagen fibril alignment

Estudio de factibilidad para la apertura de un comercial dedicado a la venta de materiales de tapicería en el Cantón Milagro.

La falta de comercialización de materiales de tapicería genera que haya un mercado insatisfecho por parte de los tapiceros y consumidores, se sienten afectados con esta situación actual ya que los materiales son escasos, con precios demasiado elevados los cual no les dan muchas alternativas de variedad tanto en modelo como diseños de los mismos. La investigación se fundamenta en la aplicación de una muestra no probabilística y el uso de técnicas de investigación específicamente la encuesta. Luego de lo mencionado, el proyecto se basa en comercializar materiales de tapicería de manera que los consumidores obtengan mejores opciones de compra y paguen un precio justo por el mismo, permitiéndoles optimizar la rentabilidad y disponer de mejores ingresos para sus familias, proyectando así un cambio positivo y favorecedor para ambas partes; trabajando organizadamente para alcanzar un crecimiento armónico y fortaleciendo el sector artesanal. Finalmente el negocio va dirigido a una red de consumidores los cuales son las personas que se dedican a las labores de tapicería, productores de muebles y al público que tiene necesidad de comprar este producto, de esta manera ayudara al desarrollo productivo del Cantón Milagro

Electroencephalography and transcranial Doppler ultrasonography in neonatal citrullinemia

The authors present a case of citrullinemia with a genotype of argininosuccinate synthetase (ASS1), c.380 G>A (p.R127Q)/c.380 G>A (p.R127Q), in two alleles. A 3-day-old female infant presented with status epilepticus and coma. Laboratory data showed hyperammonemia and marked lactic acidosis in the blood and cerebrospinal fluid; electroencephalography showed severely suppressed cerebral activity and focal paroxysmal volleys of slow and sharp waves (< 1Hz) over the left hemisphere. Real-time transcranial Doppler ultrasonography showed a brain edema and high peaked systolic and low diastolic flows in basal, anterior, and middle cerebral arteries; however, immediately after a blood exchange transfusion, systolic flows were lower and diastolic flows were higher. The resistance indices were significantly different (means: 0.58 vs. 0.37; p=0.01). The patient was placed on diet therapy. After six blood exchange transfusions and peritoneal dialysis, her neurologic examination results and serum ammonia and lactate values were normal. The authors found that electroencephalography and transcranial Doppler ultrasonography were useful for the diagnosis and follow-up treatment of neonatal citrullinemia

Korean Red Ginseng Improves Blood Pressure Stability in Patients with Intradialytic Hypotension

Introduction. Intradialytic hypotension (IDH) is a common complication during hemodialysis which may increase mortality risks. Low dose of Korean red ginseng (KRG) has been reported to increase blood pressure. Whether KRG can improve hemodynamic stability during hemodialysis has not been examined. Methods. The 8-week study consisted of two phases: observation phase and active treatment phase. According to prehemodialysis blood pressure (BP), 38 patients with IDH were divided into group A (BP ≥ 140/90 mmHg, n = 18) and group B (BP < 140/90 mmHg, n = 20). Patients were instructed to chew 3.5 gm KRG slices at each hemodialysis session during the 4-week treatment phase. Blood pressure changes, number of sessions disturbed by symptomatic IDH, plasma levels of vasoconstrictors, blood biochemistry, and adverse effects were recorded. Results. KRG significantly reduced the degree of blood pressure drop during hemodialysis (P < 0.05) and the frequency of symptomatic IDH (P < 0.05). More activation of vasoconstrictors (endothelin-1 and angiotensin II) during hemodialysis was found. The postdialytic levels of endothelin-1 and angiotensin II increased significantly (P < 0.01). Conclusion. Chewing KRG renders IDH patients better resistance to acute BP reduction during hemodialysis via activation of vasoconstrictors. Our results suggest that KRG could be an adjuvant treatment for IDH

Bioequivalence Evaluation of Two Formulations of Celecoxib 200 mg Capsules in Healthy volunteers by using a validated LC/MS/MS method

The bioequivalence study to compare a new formulation of celecoxib to its reference formulation was designed as an open-label, randomized, single-dose, two-way crossover, comparative bioavailability study by using a validated LC/MS/MS method. In order to determine the plasma concentrations of celecoxib, a sensitive LC/MS/MS method was developed. The method was validated to possess adequate specificity, linearity, precision, accuracy and stability. The linearity of calibration curve was assessed between the concentration intervals (5–2000 ng/mL) with a correlation coefficient over 0.999. Regarding pharmacokinetic investigation, the mean celecoxib AUC0-t values from the test and reference drug formulations were 7360.44 ± 1714.14 h•ng/mL and 7267.48 ± 2077.68 h•ng/mL, respectively, and the corresponding AUC0-∞ values were 8197.45 ± 2040.31 h•ng/mL and 7905.54 ± 2286.12 h•ng/mL, respectively. The Cmax of the test and reference drugs was 705.30 ± 290.63 ng/mL and 703.86 ± 329.91 ng/mL, respectively, and the corresponding Tmax was 3.4 ± 1.6 h and 2.9 ± 1.4 h. Lastly, the T1/2 values of the test and reference drugs were 13.9 ± 7.9 h and 12.9 ± 7.7 h, respectively. The 90% confidence intervals for AUC0-t, AUC0-∞, and Cmax were 97.00-108.85, 98.01-112.09, and 93.20-116.13, respectively, satisfying the bioequivalence criteria of 80-125% range. In conclusion, these results demonstrated that the bioequivalence of two formulations of celecoxib was established successfully by utilizing present developed LC/MS/MS method

Effects of Water Quality on Dissolution of Yerba Mate Extract Powders

Yerba mate tea is known as one of the most popular nonalcoholic beverages favoured by South Americans due to its nutrition facts and medicinal properties. The processing of yerba mate tea is found to affect the properties of its final forms. This study presents an investigation into the effects of water sources on the dissolution of yerba mate extract powders. Comparisons were conducted between yerba mate teas prepared by dissolving yerba mate extract powders into tap water and deionized water. Topics to be explored in this work are the major compositions and antioxidant activities, including total phenol content, reducing power, DPPH scavenging activity, and ABTS+• scavenging capacity. It is indicated that there is little difference for antioxidant activities and major constituents of yerba mate teas between both water sources. However, a deeper color is seen in the tap water case, resulting from the reaction between tannic acid and ions. This research finding can be treated as a way to benefit the yerba mate tea processing for applications

Genetic Analysis of Floral Symmetry Transition in African Violet Suggests the Involvement of Trans-acting Factor for CYCLOIDEA Expression Shifts

With the growing demand for its ornamental uses, the African violet (Saintpaulia ionantha) has been popular owing to its variations in color, shape and its rapid responses to artificial selection. Wild type African violet (WT) is characterized by flowers with bilateral symmetry yet reversals showing radially symmetrical flowers such as dorsalized actinomorphic (DA) and ventralized actinomorphic (VA) peloria are common. Genetic crosses among WT, DA, and VA revealed that these floral symmetry transitions are likely to be controlled by three alleles at a single locus in which the levels of dominance are in a hierarchical fashion. To investigate whether the floral symmetry gene was responsible for these reversals, orthologs of CYCLOIDEA (CYC) were isolated and their expressions correlated to floral symmetry transitions. Quantitative RT-PCR and in situ results indicated that dorsal-specific SiCYC1s expression in WT S. ionantha (SCYC1A and SiCYC1B) shifted in DA with a heterotopically extended expression to all petals, but in VA, SiCYC1s' dorsally specific expressions were greatly reduced. Selection signature analysis revealed that the major high-expressed copy of SCYC1A had been constrained under purifying selection, whereas the low-expressed helper SiCYC1B appeared to be relaxed under purifying selection after the duplication into SCYC1A and SiCYC1B. Heterologous expression of SCYC1A in Arabdiopsis showed petal growth retardation which was attributed to limited cell proliferation. While expression shifts of SCYC1A and SiCYC1B correlate perfectly to the resulting symmetry phenotype transitions in F1s of WT and DA, there is no certain allelic combination of inherited SiCYC1s associated with specific symmetry phenotypes. This floral transition indicates that although the expression shifts of SCYC1A/1B are responsible for the two contrasting actinomorphic reversals in African violet, they are likely to be controlled by upstream trans-acting factors or epigenetic regulations

Exponential ATP amplification through simultaneous regeneration from AMP and pyrophosphate for luminescence detection of bacteria

a b s t r a c t Bacteria monitoring is essential for many industrial manufacturing processes, particularly those involving in food, biopharmaceuticals, and semiconductor production. Firefly luciferase ATP luminescence assay is a rapid and simple bacteria detection method. However, the detection limit of this assay for Escherichia coli is approximately 10 4 colony-forming units (CFU), which is insufficient for many applications. This study aims to improve the assay sensitivity by simultaneous conversion of PP i and AMP, two products of the luciferase reaction, back to ATP to form two chain-reaction loops. Because each consumed ATP continuously produces two new ATP molecules, this approach can achieve exponential amplification of ATP. Two consecutive enzyme reactions were employed to regenerate AMP into ATP: adenylate kinase converting AMP into ADP using UTP as the energy source, and acetate kinase catalyzing acetyl phosphate and ADP into ATP. The PP i -recycling loop was completed using ATP sulfurylase and adenosine 5 0 phosphosulfate. The modification maintains good quantification linearity in the ATP luminescence assay and greatly increases its bacteria detection sensitivity. This improved method can detect bacteria concentrations of fewer than 10 CFU. This exponential ATP amplification assay will benefit bacteria monitoring in public health and manufacturing processes that require high-quality water. Ó 2011 Elsevier Inc. All rights reserved. Bacteria monitoring is essential for many industrial manufacturing processes, and particularly those involving food, semiconductors, and biopharmaceuticals. The presence of bacteria reduces production yield and may cause serious health problems in humans. Researchers have developed several rapid assays for detecting bacteria in water. These methods include polymerase chain reactions, fluorescence in situ hybridization [1], b-D-glucuronidase activity measurement The ATP luminescence assay is a rapid, sensitive, and easy-toperform method based on the detection of ATP, a molecule ubiquitously present in all living cells. The enzyme luciferase catalyzes the oxidation of the substrate luciferin while transforming the energy derived from ATP into light, which can be quantified by a luminometer. This assay has been widely used in bacteria monitoring for food hygiene [4] and surface cleanliness The current detection limit of the ATP luminescence method for Escherichia coli is approximately 10 4 colony-forming units (CFU) 1 [12,13], which is not sensitive enough for many industrial and medical applications. Several approaches have been adopted to improve the assay sensitivity. The first strategy involves the identification of chemical extractants that can effectively disrupt bacterial cells while not interfering with the luminescence assay. Both dimethyl sulfoxide (DMSO) 0003-2697/$ -see front matter