Fiber Size Distribution Research Articles

Skeletal muscle fiber size and fiber type distribution in human cancer: Effects of weight loss and relationship to physical function

Cancer patients frequently experience weight loss, with negative consequences for functionality and prognosis. The extent to which muscle atrophy contributes to weight loss, however, is not clear, as few studies have directly measured muscle fiber morphology in cancer patients. Whole body and regional tissue composition were measured, along with the cross-sectional area (CSA) and fiber type of mechanically-isolated, single muscle fibers, in 19 cancer patients (8 with a history of weight loss, 11 weight-stable) and 15 non-diseased controls. Whole body fat mass was reduced in cancer patients with a history of weight loss, but no differences in whole body or leg fat-free mass were apparent. In contrast, reductions (∼20%) in single muscle fiber CSA were found in both slow-twitch, myosin heavy chain (MHC) I and fast-twitch, MHC IIA fibers in both weight-stable patients and those with a history of weight loss. Fiber type distribution showed a shift towards a fast-twitch phenotype compared to controls, which may preserve muscle function in cancer patients despite atrophy, as positive relationships were found between the fractions of hybrid MHC IIAX and I/IIA fibers and 6-min walk performance. Our results suggest that, although not apparent from whole body or regional measurements, cancer is associated with reduced skeletal muscle fiber size independent of weight loss history and a shift towards fast-twitch fibers, phenotypes that resemble adaptations to muscle disuse.

Evaluation of growth age for the diverse conversion of Ficus carica L. cut branches using steam explosion

Growth age determines the composition and structure of woody biomass and hence its conversion performance. Effects of growth age of seasonal Ficus carica L. cut branches (FCBs) on the diverse conversion efficiency by steam explosion (SE) were evaluated. Results showed that sugar contents increased with the growth age of FCBs (0.5-, 1- and 3-year-old). Sugar conversions increased dramatically after SE for all FCBs, and the highest sugar conversion was observed at 1-year-old FCB, reaching 48.4% for glucan. SE decreased number- and weight-average molecular weight and increased polydispersity of lignin. 1-year-old FCB obtained the highest specific surface area value (0.439m2/g) after SE, 64.0% and 28.8% higher than that of 0.5- and 3-year-old FCBs. Morphology observation of single fibers showed the homogeneous fiber size distribution for 1-year-old FCB after SE, which should be helpful to increase the adsorptivity of enzymes during hydrolysis. Through SE, 1-year-old FCB obtained higher sugar contents, bigger specific surface area, homogeneous fiber size distribution, and hence higher sugar conversion during enzymatic hydrolysis. Therefore, the analysis of physicochemical property and the hydrolysis performance suggested that 1-year-old FCB would be a desirable substrate for the conversion process using SE.

Heightened TWEAK-NF-κB signaling and inflammation-associated fibrosis in paralyzed muscles of men with chronic spinal cord injury.

Individuals with long-standing spinal cord injury (SCI) often present with extreme muscle atrophy and impaired glucose metabolism at both the skeletal muscle and whole body level. Persistent inflammation and increased levels of proinflammatory cytokines in the skeletal muscle are potential contributors to dysregulation of glucose metabolism and atrophy; however, to date no study has assessed the effects of long-standing SCI on their expression or intracellular signaling in the paralyzed muscle. In the present study, we assessed the expression of genes (TNFαR, TNFα, IL-6R, IL-6, TWEAK, TWEAK R, atrogin-1, and MuRF1) and abundance of intracellular signaling proteins (TWEAK, TWEAK R, NF-κB, and p-p65/p-50/105) that are known to mediate inflammation and atrophy in skeletal muscle. In addition, based on the effects of muscle inflammation on promotion of skeletal muscle fibrosis, we assessed the degree of fibrosis between myofibers and fascicles in both groups. For further insight into the distribution and variability of muscle fiber size, we also analyzed the frequency distribution of SCI fiber size. Resting vastus lateralis (VL) muscle biopsy samples were taken from 11 men with long-standing SCI (≈22 yr) and compared with VL samples from 11 able-bodied men of similar age. Our results demonstrated that chronic SCI muscle has heightened TNFαR and TWEAK R gene expression and NF-κB signaling (higher TWEAK R and phospho-NF-κB p65) and fibrosis, along with substantial myofiber size heterogeneity, compared with able-bodied individuals. Our data suggest that the TWEAK/TWEAK R/NF-κB signaling pathway may be an important mediator of chronic inflammation and fibrotic adaptation in SCI muscle.

Experimental study on the effect of dust deposition on solar photovoltaic panels in desert environment

The accumulation of dust particles deteriorates the performance of solar cells and results in appreciable losses in the generated power due to the sun irradiance scattering effects on the surface of the solar panel. This study investigates the impact of dust accumulation on photovoltaic solar modules in Baghdad city in Iraq. For this purpose an experiment has been conducted to quantify losses caused by the accumulation of dust on the surface of three identical photovoltaic solar modules. The modules have been installed with direct exposure to weather conditions, in a well controlled experimental setup. Subsequently, measurements of dust accumulation on modules have been taken on daily, weekly and monthly basis. The dust density and size distribution of aerosol particles and fibers have been also investigated and measured by a highly sensitive aerosols measuring system. The dusted module and another similar clean module have been then exposed to constant radiation and constant temperature using a solar simulator as light source. The deposition of the dust on the surface of the photovoltaic solar modules showed a reduction in both the short circuit current (Isc) and the output power compared to the same parameters of the clean module. The average degradation rate of the efficiencies of the solar modules exposed to dust are; 6.24%, 11.8% and 18.74% calculated for exposure periods of one day, one week and one month. The experimental results are well compared with the calculations obtained by a theoretical model recently developed by the authors.

Numerical prediction of the effect of uptake velocity on three-dimensional structure, porosity and permeability of meltblown nonwoven laydown

This work describes the first detailed model of meltblowing process which allows prediction of such integral laydown properties as thickness, porosity and permeability. Also, such laydown properties as the detailed three-dimensional micro-structure, fiber-size distribution and polymer mass distribution are predicted. The effects of the governing meltblowing parameters on the variation of all these laydown properties are accounted for, with the influence of the collector screen velocity being in focus. For this aim numerical solutions of the system of quasi-one-dimensional equations of the dynamics of free liquid polymer jets moving, cooling and solidifying when driven by surrounding air jet are constructed. Multiple polymer jets are considered simultaneously when they are deposited on a moving screen and forming a nonwoven laydown. The results reveal the three-dimensional configuration of the laydown and, in particular, its porosity and permeability, as well as elucidate the dependence of the laydown structure on the forming conditions, in particular, on the velocity of the screen motion. It is shown and explained how an increase in the velocity of the collector screen increases porosity and permeability of the meltblown nonwoven laydown.

Insight into interfacial effect on effective physical properties of fibrous materials. I. The volume fraction of soft interfaces around anisotropic fibers.

With advances in interfacial properties characterization technologies, the interfacial volume fraction is a feasible parameter for evaluating effective physical properties of materials. However, there is a need to determine the interfacial volume fraction around anisotropic fibers and a need to assess the influence of such the interfacial property on effective properties of fibrous materials. Either ways, the accurate prediction of interfacial volume fraction is required. Towards this end, we put forward both theoretical and numerical schemes to determine the interfacial volume fraction in fibrous materials, which are considered as a three-phase composite structure consisting of matrix, anisotropic hard spherocylinder fibers, and soft interfacial layers with a constant dimension coated on the surface of each fiber. The interfacial volume fraction actually represents the fraction of space not occupied by all hard fibers and matrix. The theoretical scheme that adopts statistical geometry and stereological theories is essentially an analytic continuation from spherical inclusions. By simulating such three-phase chopped fibrous materials, we numerically derive the interfacial volume fraction. The theoretical and numerical schemes provide a quantitative insight that the interfacial volume fraction depends strongly on the fiber geometries like fiber shape, geometric size factor, and fiber size distribution. As a critical interfacial property, the present contribution can be further drawn into assessing effective physical properties of fibrous materials, which will be demonstrated in another paper (Part II) of this series.

Quality factors of PVA nanofibrous filters for airborne particles in the size range of 10–125 nm

PVA nanofibrous filter samples were fabricated in a laboratory under eight different electrospinning conditions; they were first characterized in terms of fiber size distributions by automatic SEM analysis. The quality factors of these nanofibrous filters were then evaluated using sodium chloride nanoparticles in the size range of 10–125nm. Results showed that, as expected, single layer filters with smaller fiber diameters and greater solidity were efficient. However, these characteristics led to lower quality factors due to their greater pressure drops. Single layer filters made with higher applied voltage, longer tip to collector distance and shorter deposition time corresponded to greater filter quality factors. The quality factor of single layer filter was inversely related to filter thicknesses. Multilayer filters made by stacking thin nanofibrous filters greatly increased the filter quality factors.

Herbal Extract Incorporated Nanofiber Fabricated by an Electrospinning Technique and its Application to Antimicrobial Air Filtration

Recently, with the increased attention to indoor air quality, antimicrobial air filtration techniques have been studied widely to inactivate hazardous airborne microorganisms effectively. In this study, we demonstrate herbal extract incorporated (HEI) nanofibers synthesized by an electrospinning technique and their application to antimicrobial air filtration. As an antimicrobial herbal material, an ethanolic extract of Sophora flavescens, which exhibits great antibacterial activity against pathogens, was mixed with the polymer solution for the electrospinning process. We measured various characteristics of the synthesized HEI nanofibers, such as fiber morphology, fiber size distribution, and thermal stability. For application of the electrospun HEI nanofibers, we made highly effective air filters with 99.99% filtration efficiency and 99.98% antimicrobial activity against Staphylococcus epidermidis. The pressure drop across the HEI nanofiber air filter was 4.75 mmH2O at a face air velocity of 1.79 cm/s. These results will facilitate the implementation of electrospun HEI nanofiber techniques to control air quality and protect against hazardous airborne microorganisms.

Estimation of the thermal conductivity of hemp based insulation material from 3D tomographic images

In this work, we are interested in the structural and thermal characterization of natural fiber insulation materials. The thermal performance of these materials depends on the arrangement of fibers, which is the consequence of the manufacturing process. In order to optimize these materials, thermal conductivity models can be used to correlate some relevant structural parameters with the effective thermal conductivity. However, only a few models are able to take into account the anisotropy of such material related to the fibers orientation, and these models still need realistic input data (fiber orientation distribution, porosity, etc.). The structural characteristics are here directly measured on a 3D tomographic image using advanced image analysis techniques. Critical structural parameters like porosity, pore and fiber size distribution as well as local fiber orientation distribution are measured. The results of the tested conductivity models are then compared with the conductivity tensor obtained by numerical simulation on the discretized 3D microstructure, as well as available experimental measurements. We show that 1D analytical models are generally not suitable for assessing the thermal conductivity of such anisotropic media. Yet, a few anisotropic models can still be of interest to relate some structural parameters, like the fiber orientation distribution, to the thermal properties. Finally, our results emphasize that numerical simulations on 3D realistic microstructure is a very interesting alternative to experimental measurements.

A Perturbation Based Decomposition of Compound-Evoked Potentials for Characterization of Nerve Fiber Size Distributions.

The characterization of peripheral nerve fiber distributions, in terms of diameter or velocity, is of clinical significance because information associated with these distributions can be utilized in the differential diagnosis of peripheral neuropathies. Electro-diagnostic techniques can be applied to the investigation of peripheral neuropathies and can yield valuable diagnostic information while being minimally invasive. Nerve conduction velocity studies are single parameter tests that yield no detailed information regarding the characteristics of the population of nerve fibers that contribute to the compound-evoked potential. Decomposition of the compound-evoked potential, such that the velocity or diameter distribution of the contributing nerve fibers may be determined, is necessary if information regarding the population of contributing nerve fibers is to be ascertained from the electro-diagnostic study. In this work, a perturbation-based decomposition of compound-evoked potentials is proposed that facilitates determination of the fiber diameter distribution associated with the compound-evoked potential. The decomposition is based on representing the single fiber-evoked potential, associated with each diameter class, as being perturbed by contributions, of varying degree, from all the other diameter class single fiber-evoked potentials. The resultant estimator of the contributing nerve fiber diameter distribution is valid for relatively large separations in diameter classes. It is also useful in situations where the separation between diameter classes is small and the concomitant single fiber-evoked potentials are not orthogonal.

Muscle growth of triploid Atlantic cod juveniles (Gadus morhua)

This study has investigated the muscle growth of diploid and triploid Atlantic cod (Gadus morhua) juveniles raised in replicate tanks over a period of 29 weeks and analysed at three sampling points (February, June and September). Data for weight, length, condition factor (K), muscle fibre growth and myogenic progenitor cells (MPCs) number were collected and results were analysed in relation to body growth and ploidy status. Diploids were significantly heavier than triploids throughout the trial (~10–20%) and had K in June and September samplings. Over the whole period, the rate of muscle fibres' recruitment was 318 fibres per day and 252 fibres per day for diploid and triploid cod respectively. The larger body weight of diploids resulted in a total number of fast fibre number of 114 979 compared to 91 086 in triploids. The average diameter of the 2.5% of the smallest fibres (2.5th percentile) was higher in diploids than triploids at the start of the trial, with a reversed picture for the average of the upper 2.5% (97.5th percentile) at the end of the trial. The probability density function of the estimated muscle fibre diameters showed similar fibre size distribution between size-matched diploids and triploids at all sample points. The peak fibre diameter was approximately 25 μm in February and increased to approximately 50 μm in June and September, irrespectively of ploidy. Pax 7 were used as molecular markers for MPCs. A positive correlation between Pax 7+ cells and total body length was observed only among triploid fish at the onset of the experiment.

Low levels of Survival Motor Neuron protein are sufficient for normal muscle function in the SMNΔ7 mouse model of SMA.

Spinal Muscular Atrophy (SMA) is an autosomal recessive disorder characterized by loss of lower motor neurons. SMA is caused by deletion or mutation of the Survival Motor Neuron 1 (SMN1) gene and retention of the SMN2 gene. The loss of SMN1 results in reduced levels of the SMN protein. SMN levels appear to be particularly important in motor neurons; however SMN levels above that produced by two copies of SMN2 have been suggested to be important in muscle. Studying the spatial requirement of SMN is important in both understanding how SMN deficiency causes SMA and in the development of effective therapies. Using Myf5-Cre, a muscle-specific Cre driver, and the Cre-loxP recombination system, we deleted mouse Smn in the muscle of mice with SMN2 and SMNΔ7 transgenes in the background, thus providing low level of SMN in the muscle. As a reciprocal experiment, we restored normal levels of SMN in the muscle with low SMN levels in all other tissues. We observed that decreasing SMN in the muscle has no phenotypic effect. This was corroborated by muscle physiology studies with twitch force, tetanic and eccentric contraction all being normal. In addition, electrocardiogram and muscle fiber size distribution were also normal. Replacement of Smn in muscle did not rescue SMA mice. Thus the muscle does not appear to require high levels of SMN above what is produced by two copies of SMN2 (and SMNΔ7).

Preparation and Characterization of Polymer Blends from <i>Nang noi srisaket 1</i> Silk Fibroin, Gelatin and Chitosan Nanofiber Mats Using Formic Acid Solution

Silk fibroin, gelatin, and chitosan blended solution in formic acid with different composition ratios were electrospun. The fiber could be produced from SF:G : C blended solution at weight blending ratios (%wt: %wt: ml) of 10:20:0, 10:20:0.5, 10:20;1, 10:20:1.5, 10:20:2, and 20:10:1. When the chitosan content in blended solution increased, the average diameter decreased from 245 to 100 nm and fiber size distribution was narrow. The SF: G: C solution at ratio of 10:20:1 under high electric field and long spinning distance provided the continuous and uniform fibers. The formic acid as solvent did not affect to the electrospinnability and morphology of SF: G: C blended nanofiber. Tensile strength of SF: G: C (10:20:1) blended nanofiber was decreased with increasing of silk fibroin content, SF: G: C (20:10:1). The results indicated that SF: G: C electrospun nanofiber mats could be prepared and have a potential to be applied in membrane application.

Simulations of filter media performances from microtomography-based computational domain. Experimental and analytical comparison

In this work, synchrotron X-ray microtomography was used to produce high spatial resolution images of one fibrous filter, made of binderless monodispersed fiberglass. Based on these images, representative computational domains were created using the import interface of the GeoDict software. Both flow and collection efficiency simulations were then carried out using the CFD modules of GeoDict. In parallel, permeability and collection efficiency measurements were performed on the same media, to provide an experimental comparison. A very good agreement was found between the experimental and simulated permeability values. However, simulated efficiency values tend to underestimate the experimental ones. In the second part of the paper, an image analysis program based on Matlab® was used to determine the structural properties of the fibrous structures, namely the thickness, the solid volume fraction and the fiber size distribution. These data were introduced into analytical models that successfully predict the permeability and collection efficiency values.

Agent-based computational model investigates muscle-specific responses to disuse-induced atrophy.

Skeletal muscle is highly responsive to use. In particular, muscle atrophy attributable to decreased activity is a common problem among the elderly and injured/immobile. However, each muscle does not respond the same way. We developed an agent-based model that generates a tissue-level skeletal muscle response to disuse/immobilization. The model incorporates tissue-specific muscle fiber architecture parameters and simulates changes in muscle fiber size as a result of disuse-induced atrophy that are consistent with published experiments. We created simulations of 49 forelimb and hindlimb muscles of the rat by incorporating eight fiber-type and size parameters to explore how these parameters, which vary widely across muscles, influence sensitivity to disuse-induced atrophy. Of the 49 muscles modeled, the soleus exhibited the greatest atrophy after 14 days of simulated immobilization (51% decrease in fiber size), whereas the extensor digitorum communis atrophied the least (32%). Analysis of these simulations revealed that both fiber-type distribution and fiber-size distribution influence the sensitivity to disuse atrophy even though no single tissue architecture parameter correlated with atrophy rate. Additionally, software agents representing fibroblasts were incorporated into the model to investigate cellular interactions during atrophy. Sensitivity analyses revealed that fibroblast agents have the potential to affect disuse-induced atrophy, albeit with a lesser effect than fiber type and size. In particular, muscle atrophy elevated slightly with increased initial fibroblast population and increased production of TNF-α. Overall, the agent-based model provides a novel framework for investigating both tissue adaptations and cellular interactions in skeletal muscle during atrophy.

Human Adipocytes Induce Inflammation and Atrophy in Muscle Cells During Obesity.

Inflammation and lipid accumulation are hallmarks of muscular pathologies resulting from metabolic diseases such as obesity and type 2 diabetes. During obesity, the hypertrophy of visceral adipose tissue (VAT) contributes to muscle dysfunction, particularly through the dysregulated production of adipokines. We have investigated the cross talk between human adipocytes and skeletal muscle cells to identify mechanisms linking adiposity and muscular dysfunctions. First, we demonstrated that the secretome of obese adipocytes decreased the expression of contractile proteins in myotubes, consequently inducing atrophy. Using a three-dimensional coculture of human myotubes and VAT adipocytes, we showed the decreased expression of genes corresponding to skeletal muscle contractility complex and myogenesis. We demonstrated an increased secretion by cocultured cells of cytokines and chemokines with interleukin (IL)-6 and IL-1β as key contributors. Moreover, we gathered evidence showing that obese subcutaneous adipocytes were less potent than VAT adipocytes in inducing these myotube dysfunctions. Interestingly, the atrophy induced by visceral adipocytes was corrected by IGF-II/insulin growth factor binding protein-5. Finally, we observed that the skeletal muscle of obese mice displayed decreased expression of muscular markers in correlation with VAT hypertrophy and abnormal distribution of the muscle fiber size. In summary, we show the negative impact of obese adipocytes on muscle phenotype, which could contribute to muscle wasting associated with metabolic disorders.

Nanofiber protein adsorption affected by electrospinning physical processing parameters

Proteins as a mediator in the interfacial interactions between cell and substrates play an important role in the regulation of cell functions. In this study, polycaprolactone (PCL) nanofibers were prepared using electrospinning apparatus to obtain substrates with various physical characteristics and the same chemistry. Electrospin processing parameters were designed by Taguchi method and their effects on PCL fiber properties evaluated. Scanning electron microscopy was used for visual observation of fiber diameter, size distribution and bead formation. Mechanical properties of each specimen including tensile strength and elongation at break were assessed by means of standard mechanical test machine and correlated to the spinning parameters. In addition, adsorption of serum protein to each sample was quantified by Bradford method. SDS-PAGE analysis confirmed these results and revealed a significant difference between protein adsorption (up to 250 %) for the fibers with the same chemical composition. Additional experiments confirmed that the degree of protein adsorption is improved on increasing the quantity of beads in the structures. It was also verified that with increasing the time of exposure from 1 to 24 h, higher amount of proteins were adsorbed. The selected sample with the average diameter of 274 nm without any bead exhibited the highest tensile strength (7.6 MPa) and the lowest amount of adsorption. The results indicated that electrospinning processing parameters change the physical characteristics of the fibers (diameter and bead) and also their biological performance such as protein adsorption as well as cell attachment and cell spreading.

Effect of zno nanoparticles on diameter of bubbfil PVA/ZnO nanofibers

The PVA/ZnO nanofibers are obtained by the bubbfil spinning. Distribution of fiber size is tenable by nano-ZnO concentration. Experiment reveals fiber size distribution changes from Gaussian distribution to Poisson distribution when ZnO concentration varies gradually from 2 wt.% to 15 wt.%.

Effect of Refiner Plate Pattern Design on Refined Fibre Size Distribution – a Time Series Study

In a multi-step batch or continuous operating process, quantitative & qualitative optimization of every single step is always aimed at. Even the smallest aberration in processing parameters affects the quality of the fi nal product. Therefore, it is necessary to study time series quality of products delivered by every single step, so as to ensure product quality in a long run. Refi ning is one of the most crucial steps in fi breboard manufacturing, as it has a major impact on fi bre quality and energy consumption. Refi ning plate pattern is key to good results, which have to be optimized based on experience or onsite testing. We tested three different refi ning plate patterns: straight bar design pattern (TYPE 1), spiral bars design pattern (TYPE 2) and bar with groove pattern (TYPE 3), and their impact on fi bre size quality in a time series. Reported results include fi bre size distribution of three different types of plate patterns observed for 1500 hrs and relative quantity of fi ne fi bres observed in time series for three variants of disc type refi ners. Our research showed that fi bre quality within desired limits was best delivered by TYPE 2 plates; however, fi bre quality also varied with time series for three of them, so different time periods of desired fi bre quality were analysed.

A Phase 1/2a Follistatin Gene Therapy Trial for Becker Muscular Dystrophy

Becker muscular dystrophy (BMD) is a variant of dystrophin deficiency resulting from DMD gene mutations. Phenotype is variable with loss of ambulation in late teenage or late mid-life years. There is currently no treatment for this condition. In this BMD proof-of-principle clinical trial, a potent myostatin antagonist, follistatin (FS), was used to inhibit the myostatin pathway. Extensive preclinical studies, using adeno-associated virus (AAV) to deliver follistatin, demonstrated an increase in strength. For this trial, we used the alternatively spliced FS344 to avoid potential binding to off target sites. AAV1.CMV.FS344 was delivered to six BMD patients by direct bilateral intramuscular quadriceps injections. Cohort 1 included three subjects receiving 3 × 10(11) vg/kg/leg. The distance walked on the 6MWT was the primary outcome measure. Patients 01 and 02 improved 58 meters (m) and 125 m, respectively. Patient 03 showed no change. In Cohort 2, Patients 05 and 06 received 6 × 10(11) vg/kg/leg with improved 6MWT by 108 m and 29 m, whereas, Patient 04 showed no improvement. No adverse effects were encountered. Histological changes corroborated benefit showing reduced endomysial fibrosis, reduced central nucleation, more normal fiber size distribution with muscle hypertrophy, especially at high dose. The results are encouraging for treatment of dystrophin-deficient muscle diseases.