Constriction flows of monodisperse linear entangled polymers: Multiscale modeling and flow visualization

We explore both the rheology and complex flow behavior of monodisperse polymer melts. Adequate quantities of monodisperse polymer were synthesized in order that both the materials rheology and microprocessing behavior could be established. In parallel, we employ a molecular theory for the polymer rheology that is suitable for comparison with experimental rheometric data and numerical simulation for microprocessing flows. The model is capable of matching both shear and extensional data with minimal parameter fitting. Experimental data for the processing behavior of monodisperse polymers are presented for the first time as flow birefringence and pressure difference data obtained using a Multipass Rheometer with an 11:1 constriction entry and exit flow. Matching of experimental processing data was obtained using the constitutive equation with the Lagrangian numerical solver, FLOWSOLVE. The results show the direct coupling between molecular constitutive response and macroscopic processing behavior, and differentiate flow effects that arise separately from orientation and stretch. (c) 2005 The Society of Rheology.

Photoconductivity excitation spectrum for stretch-oriented PPV

We have obtained the photoconductivity (PC) excitation spectrum for a stretch-oriented poly(paraphenylene vinylene) film over a wide spectral range (up to 5 eV). The measurements were performed in the surface cell configuration with the electric field parallel or perpendicular to the stretch direction. Although the sample had a stretch ratio of similar to 4, the dark conductivity and the steady-state photoconductivity were both about 40 and 20 times higher with the electric field parallel to the average chain direction, respectively. However, the shape of the PC excitation spectrum was independent of field direction and did not show a significant rise in the ultraviolet, as is usually observed for measurements in the photodiode configuration. The implications of these results to the charge photogeneration mechanism in conjugated polymers are discussed.

Self-Assembly of Poly(4-vynil-N-alkylpyridinium) Bromide onto Silica: Effect of Side-Chain Length on Structural Aspects at a Molecular Level

Self-assembly of poly(4-vynil-N-alkyl)pyridinium bromide with alkyl side chains of 2, 5, 7, 10, or 16 carbons from ethanolic solutions onto flat silica surfaces was studied by means of ellipsometry, atomic force microscopy (AFM), contact angle measurements, and sum-frequency generation (SFG) vibrational spectroscopy in the CH3 and CH2 stretch region. Ab initio quantum-chemical calculations on the N-alkylpyridinium side-group with restricted Hartree-Fock (RHF) method and 6-311G (d,p) basis set were C one to estimate the charge distribution along the pyridinium ring and the alkyl side-chain. SFG results showed that longer side chains promote the disorientation of the alkyl groups at the surface, corroborating with the contact angle values. AFM images revealed film homogeneity, regardless the alkyl side group. However, after 24 h contact with water, ringlike structures appeared on the film surfaces, when the polycation alkyl side chain had 7 or less carbons, and as the alkyl chain increased to 10 or 16 carbons, the films dewetted because the hydrophobic interactions prevailed over the electrostatic interactions between the pyridinium charged groups and the negatively charged SiO2 surface. Under acid conditions (HCl 0.1 mol.L-1), the film mean thickness values decreased up to 50% of original values when the alkyl side chains were ethyl or pentyl groups due to ion-pair disruption, but for longer groups they remained unchanged. Quantum-chemical optimization and Mulliken electron population showed that (i) from C2 to C15 the positive charge at the headgroup (HG) decreased 0.025, while the charge at combined HG + alpha-CH2 increased 0.037; and (ii) for C6 or longer, the alkyl side group presents a tilt in the geometry, moving away from the plane. Such effects summed up over the whole polymer chain give support to suggest that when the side chains are longer than 7 carbons, the hydrophobic interaction decreases film stability and increases acid resistance.

Role of TRP Channels in Mediating the Calcium Signaling Response of Brain Endothelial Cells to Mechanical Stretch

Traumatic brain injury (TBI) often results in disruption of the blood brain barrier (BBB), which is an integral component to maintaining the central nervous system homeostasis. Recently cytosolic calcium levels ([Ca2+]i), observed to elevate following TBI, have been shown to influence endothelial barrier integrity. However, the mechanism by which TBI-induced calcium signaling alters the endothelial barrier remains unknown. In the present study, an in vitro BBB model was utilized to address this issue. Exposure of cells to biaxial mechanical stretch, in the range expected for TBI, resulted in a rapid cytosolic calcium increase. Modulation of intracellular and extracellular Ca2+ reservoirs indicated that Ca2+ influx is the major contributor for the [Ca2+]i elevation. Application of pharmacological inhibitors was used to identify the calcium-permeable channels involved in the stretch-induced Ca2+ influx. Antagonist of transient receptor potential (TRP) channel subfamilies, TRPC and TRPP, demonstrated a reduction of the stretch-induced Ca2+ influx. RNA silencing directed at individual TRP channel subtypes revealed that TRPC1 and TRPP2 largely mediate the stretch-induced Ca2+ response. In addition, we found that nitric oxide (NO) levels increased as a result of mechanical stretch, and that inhibition of TRPC1 and TRPP2 abolished the elevated NO synthesis. Further, as myosin light chain (MLC) phosphorylation and actin cytoskeleton rearrangement are correlated with endothelial barrier disruption, we investigated the effect mechanical stretch had on the myosin-actin cytoskeleton. We found that phosphorylated MLC was increased significantly by 10 minutes post-stretch, and that inhibition of TRP channel activity or NO synthesis both abolished this effect. In addition, actin stress fibers formation significantly increased 2 minutes post-stretch, and was abolished by treatment with TRP channel inhibitors. These results suggest that, in brain endothelial cells, TRPC1 and TRPP2 are activated by TBI-mechanical stress and initiate actin-myosin contraction, which may lead to disruption of the BBB.

Mutagenesis in the C-terminal region of human interleukin 5 reveals a central patch for receptor alpha chain recognition.

Cassette mutagenesis was used to identify side chains in human interleukin 5 (hIL-5) that mediate binding to hIL-5 receptor alpha chain (hIL-5R alpha). A series of single alanine substitutions was introduced into a stretch of residues in the C-terminal region, including helix D, which previously had been implicated in receptor alpha chain recognition and which is aligned on the IL-5 surface so as to allow the topography of receptor binding residues to be examined. hIL-5 and single site mutants were expressed in COS cells, their interactions with hIL-5R alpha were measured by a sandwich surface plasmon resonance biosensor method, and their biological activities were measured by an IL-5-dependent cell proliferation assay. A pattern of mutagenesis effects was observed, with greatest impact near the interface between the two four-helix bundles of IL-5, in particular at residues Glu-110 and Trp-111, and least at the distal ends of the D helices. This pattern suggests the possibility that residues near the interface of the two four-helix bundles in hIL-5 comprise a central patch or hot spot, which constitutes an energetically important alpha chain recognition site. This hypothesis suggests a structural explanation for the 1:1 stoichiometry observed for the complex of hIL-5 with hIL-5R alpha.

TRPV2 Channels Contribute to Stretch-Activated Cation Currents and Myogenic Constriction in Retinal Arterioles

Purpose: Activation of the transient receptor potential channels, TRPC6, TRPM4, and TRPP1 (PKD2), has been shown to contribute to the myogenic constriction of cerebral arteries. In the present study we sought to determine the potential role of various mechanosensitive TRP channels to myogenic signaling in arterioles of the rat retina.

Methods: Rat retinal arterioles were isolated for RT-PCR, Fura-2 Ca2+ microfluorimetry, patch-clamp electrophysiology, and pressure myography studies. In some experiments, confocal immunolabeling of wholemount preparations was used to examine the localization of specific mechanosensitive TRP channels in retinal vascular smooth muscle cells (VSMCs).

Results: Reverse transcription-polymerase chain reaction analysis demonstrated mRNA expression for TRPC1, M7, V1, V2, V4, and P1, but not TRPC6 or M4, in isolated retinal arterioles. Immunolabeling revealed plasma membrane, cytosolic and nuclear expression of TRPC1, M7, V1, V2, V4, and P1 in retinal VSMCs. Hypoosmotic stretch-induced Ca2+ influx in retinal VSMCs was reversed by the TRPV2 inhibitor tranilast and the nonselective TRPP1/V2 antagonist amiloride. Inhibitors of TRPC1, M7, V1, and V4 had no effect. Hypoosmotic stretch-activated cation currents were similar in Na+ and Cs+ containing solutions suggesting no contribution by TRPP1 channels. Direct plasma membrane stretch triggered cation current activity that was blocked by tranilast and specific TRPV2 pore-blocking antibodies and mimicked by the TRPV2 activator, Δ9-tetrahydrocannabinol. Preincubation of retinal arterioles with TRPV2 blocking antibodies prevented the development of myogenic tone.

Conclusions: Our results suggest that retinal VSMCs express a range of mechanosensitive TRP channels, but only TRPV2 appears to contribute to myogenic signaling in this vascular bed.

Quantitative Proteomic Analysis Reveals Metabolic Alterations, Calcium Dysregulation, And Increased Expression Of Extracellular Matrix Proteins In Laminin α2 Chain-deficient Muscle.

Congenital muscular dystrophy with laminin α2 chain deficiency (MDC1A) is one of the most severe forms of muscular disease and is characterized by severe muscle weakness and delayed motor milestones. The genetic basis of MDC1A is well known, yet the secondary mechanisms ultimately leading to muscle degeneration and subsequent connective tissue infiltration are not fully understood. In order to obtain new insights into the molecular mechanisms underlying MDC1A, we performed a comparative proteomic analysis of affected muscles (diaphragm and gastrocnemius) from laminin α2 chain-deficient dy(3K)/dy(3K) mice, using multidimensional protein identification technology combined with tandem mass tags. Out of the approximately 700 identified proteins, 113 and 101 proteins, respectively, were differentially expressed in the diseased gastrocnemius and diaphragm muscles compared with normal muscles. A large portion of these proteins are involved in different metabolic processes, bind calcium, or are expressed in the extracellular matrix. Our findings suggest that metabolic alterations and calcium dysregulation could be novel mechanisms that underlie MDC1A and might be targets that should be explored for therapy. Also, detailed knowledge of the composition of fibrotic tissue, rich in extracellular matrix proteins, in laminin α2 chain-deficient muscle might help in the design of future anti-fibrotic treatments. All MS data have been deposited in the ProteomeXchange with identifier PXD000978 (http://proteomecentral.proteomexchange.org/dataset/PXD000978).

Improvement Of The Physical Performance Is Associated With Activation Of No/pgc-1α/mttfa Signaling Pathway And Increased Protein Expressions Of Electron Transport Chain In Gastrocnemius Muscle From Rats Supplemented With L-arginine.

To examine the influence of l-arginine supplementation in combination with physical training on mitochondrial biomarkers from gastrocnemius muscle and its relationship with physical performance. Male Wistar rats were divided into four groups: control sedentary (SD), sedentary supplemented with l-arginine (SDLA), trained (TR) and trained supplemented with l-arginine (TRLA). Supplementation of l-arginine was administered by gavage (62.5mg/ml/day/rat). Physical training consisted of 60min/day, 5days/week, 0% grade, speed of 1.2km/h. The study lasted 8weeks. Skeletal muscle mitochondrial enriched fraction as well as cytoplasmic fractions were obtained for Western blotting and biochemical analyses. Protein expressions of transcriptor coactivator (PGC-1α), transcriptor factors (mtTFA), ATP synthase subunit c, cytochrome oxidase (COXIV), constitutive nitric oxide synthases (eNOS and nNOS), Cu/Zn-superoxide dismutase (SOD) and manganese-SOD (Mn-SOD) were evaluated. We also assessed in plasma: lipid profile, glycemia and malondialdehyde (MDA) levels. The nitrite/nitrate (NOx(-)) levels were measured in both plasma and cytosol fraction of the gastrocnemius muscle. 8-week l-arginine supplementation associated with physical training was effective in promoting greater tolerance to exercise that was accompanied by up-regulation of the protein expressions of mtTFA, PGC-1α, ATP synthase subunit c, COXIV, Cu/Zn-SOD and Mn-SOD. The upstream pathway was associated with improvement of NO bioavailability, but not in NO production since no changes in nNOS or eNOS protein expressions were observed. This combination would be an alternative approach for preventing cardiometabolic diseases given that in overt diseases a profound impairment in the physical performance of the patients is observed.

Fish Biodiversity Of The Vitória-trindade Seamount Chain, Southwestern Atlantic: An Updated Database.

Despite a strong increase in research on seamounts and oceanic islands ecology and biogeography, many basic aspects of their biodiversity are still unknown. In the southwestern Atlantic, the Vitória-Trindade Seamount Chain (VTC) extends ca. 1,200 km offshore the Brazilian continental shelf, from the Vitória seamount to the oceanic islands of Trindade and Martin Vaz. For a long time, most of the biological information available regarded its islands. Our study presents and analyzes an extensive database on the VTC fish biodiversity, built on data compiled from literature and recent scientific expeditions that assessed both shallow to mesophotic environments. A total of 273 species were recorded, 211 of which occur on seamounts and 173 at the islands. New records for seamounts or islands include 191 reef fish species and 64 depth range extensions. The structure of fish assemblages was similar between islands and seamounts, not differing in species geographic distribution, trophic composition, or spawning strategies. Main differences were related to endemism, higher at the islands, and to the number of endangered species, higher at the seamounts. Since unregulated fishing activities are common in the region, and mining activities are expected to drastically increase in the near future (carbonates on seamount summits and metals on slopes), this unique biodiversity needs urgent attention and management.

Mixed rain forest in southeastern Brazil: tree species regeneration and floristic relationships in a remaining stretch of forest near the city of Itaberá, Brazil

The aim of this work was to evaluate the floristic composition, richness, and diversity of the upper and lower strata of a stretch of mixed rain forest near the city of Itaberá, in southeastern Brazil. We also investigated the differences between this conservation area and other stretches of mixed rain forest in southern and southeastern Brazil, as well as other nearby forest formations, in terms of their floristic relationships. For our survey of the upper stratum (diameter at breast height [DBH] > 15 cm), we established 50 permanent plots of 10 × 20 m. Within each of those plots, we designated five, randomly located, 1 × 1 m subplots, in order to survey the lower stratum (total height > 30 cm and DBH < 15 cm). In the upper stratum, we sampled 1429 trees and shrubs, belonging to 134 species, 93 genera, and 47 families. In the lower stratum, we sampled 758 trees and shrubs, belonging to 93 species, 66 genera, and 39 families. In our floristic and phytosociological surveys, we recorded 177 species, belonging to 106 genera and 52 families. The Shannon Diversity Index was 4.12 and 3.5 for the upper and lower strata, respectively. Cluster analysis indicated that nearby forest formations had the strongest floristic influence on the study area, which was therefore distinct from other mixed rain forests in southern Brazil and in the Serra da Mantiqueira mountain range.

Comparison of direct immunofluorescence, conventional cell culture and polymerase chain reaction techniques for detecting respiratory syncytial virus in nasopharyngeal aspirates from infants

A total of 316 samples of nasopharyngeal aspirate from infants up to two years of age with acute respiratory-tract illnesses were processed for detection of respiratory syncytial virus (RSV) using three different techniques: viral isolation, direct immunofluorescence, and PCR. Of the samples, 36 (11.4%) were positive for RSV, considering the three techniques. PCR was the most sensitive technique, providing positive findings in 35/316 (11.1%) of the samples, followed by direct immunofluorescence (25/316, 7.9%) and viral isolation (20/315, 6.3%) (p < 0.001). A sample was positive by immunofluorescence and negative by PCR, and 11 (31.4%) were positive only by RT-PCR. We conclude that RT-PCR is more sensitive than IF and viral isolation to detect RSV in nasopharyngeal aspirate specimens in newborn and infants.

Survey of Leptospira spp in pampas deer (Ozotoceros bezoarticus) in the Pantanal wetlands of the state of Mato Grosso do Sul, Brazil by serology and polymerase chain reaction

This work reports a survey of Leptospira spp in pampas deer (Ozotoceros bezoarticus) in the Pantanal wetlands of the state of Mato Grosso do Sul, Brazil by serology and polymerase chain reaction (PCR). Seventy pampas deer were captured in the dry season and surveyed using PCR, microscopic agglutination test (MAT) (n = 51) and by both techniques (n = 47). PCR detected infections in two pampas deer and MAT detected infections in three. Through sequencing and phylogenetic analyses, the PCR-amplified fragment detected in deer was identified as Leptospira interrogans. Serovars Pomona and Butembo were detected using MAT and the highest titre was 200 for serovar Pomona. Epidemiological aspects of the findings are discussed.

Performance of transport and selective media for swine Bordetella bronchiseptica recovery and it comparison to polymerase chain reaction detection

Three comparative assays were performed seeking to improve the sensitivity of the diagnosis of Bordetella bronchiseptica infection analyzing swine nasal swabs. An initial assay compared the recovery of B. bronchiseptica from swabs simultaneously inoculated with B. bronchiseptica and some interfering bacteria, immersed into three transport formulations (Amies with charcoal, trypticase soy broth and phosphate buffer according to Soerensen supplemented with 5% of bovine fetal serum) and submitted to different temperatures (10ºC and 27ºC) and periods of incubation (24, 72 and 120 hours). A subsequent assay compared three selective media (MacConkey agar, modified selective medium G20G and a ceftiofur medium) for their recovery capabilities from clinical specimens. One last assay compared the polymerase chain reaction to the three selective media. In the first assay, the recovery of B. bronchiseptica from transport systems was better at 27ºC and the three formulations had good performances at this temperature, but the collection of qualitative and quantitative analysis indicated the advantage of Amies medium for nasal swabs transportation. The second assay indicated that MacConkey agar and modified G20G had similar results and were superior to the ceftiofur medium. In the final assay, polymerase chain reaction presented superior capability of B. bronchiseptica detection to culture procedures.

Coactivation of the shoulder and arm muscles during closed kinetic chain exercises on an unstable surface

Introduction: The purpose of this study was to compare the electromyography index of muscle coactivation of the following muscle pairs: posterior deltoid and pectoralis major (PD/PM); triceps brachii and biceps brachii (TB/BB); and serratus anterior and upper trapezius (SA/UT) during three different closed kinetic chain exercises (wall-press, bench-press and push-up) on an unstable surface at the maximal load. Methods: A total of 20 healthy sedentary men participated in the study. Integral linear values were obtained from three sustained contractions of six seconds each for the three proposed exercises. Mean coactivation index values were compared using the mixed-effects linear model, with a five percent significance level. Results: Electromyography indexes of muscle coactivation showed significant differences for the PD/PM and TB/BB muscle pairs. No differences were found between exercises for the SA/UT muscle pair. Conclusion: Our results seem to differ from those of previous studies, which reported that the similarity in exercises performed is responsible for the comparable muscle activation levels.

Evaluating Patellar Kinematics Through Magnetic Resonance Imaging During Open- and Closed-Kinetic-Chain Exercises

Purpose: To evaluate patellar kinematics of volunteers Without knee pain at rest and during isometric contraction in open- and closed-kinetic-chain exercises. Methods: Twenty individuals took part in this study. All were submitted to magnetic resonance imaging (MRI) during rest and voluntary isometric contraction (VIC) in the open anti closed kinetic chain at 15 degrees, 30 degrees, and 45 degrees of knee flexion. Through MRI and using medical e-film software, the following measurements were evaluated: sulcus angle, patellar-tilt angle, and bisect offset. The mixed-effects linear model was used for comparison between knee positions, between rest and isometric contractions, and between (he exercises. Results: Data analysis revealed that the sulcus angle decreased as knee flexion increased and revealed increases with isometric contractions in both the open and closed kinetic chain for all knee-flexion angles. The patellar-tilt angle decreased with isometric contractions in both the open and closed kinetic chain for every knee position. However, in the closed kinetic chain, patellar tilt increased significantly with the knee flexed at 15 degrees. The bisect offset increased with the knee flexed at 15 degrees during isometric contractions and decreased as knee flexion increased during both exercises. Conclusion: VIC in the last degrees of knee extension may compromise patellar dynamics. On the other hand, it is possible to favor patellar stability by performing muscle contractions with the knee flexed at 30 degrees and 45 degrees in either the open or closed kinetic chain.