Differences In Fiber Diameter Research Articles

Effect of nozzle polarity and connection on electrospinning of polyacrylonitrile nanofibers

In this study, two power supplies having positive/ground and negative/ground electrode output ends were used separately for electrospinning of polyacrylonitrile nanofibers. Depending on type of power supply and electrode connection, electrospinning led to different fiber diameters and deposition areas. The nozzle was connected to a high voltage end while the collector was grounded. Regardless of power supply used, finer fibers with a larger deposition area were obtained, compared to that using the same setup but with a reverse electrode connection. With an increase in the applied voltage, fiber deposition area, and productivity increased for all electrode connections. Grounded nozzles provide much better control over fiber deposition than the reverse electrode connections. Finite element modeling was used to analyze the electric field profile in the electrospinning zone. It was revealed that high electric intensity was mainly located in the part that was charged with a high voltage electrode, which could explain the differences in fiber diameter and deposition area.

The stimulation of myoblast differentiation by electrically conductive sub-micron fibers

Myotubes assemble with bundles of myofibers to form the structural units in skeletal muscle. Therefore, myotube formation plays an important role in restoring muscular functions, and substrates to promote the differentiation of myoblasts to myotubes need to be developed for muscle tissue engineering. In this study, we developed electrically conductive composite fibers of poly( l-lactide-co-ɛ-caprolactone) (PLCL) blended with polyaniline (PANi) using an electrospinning method, and then investigated the effect of these composite fibers on the differentiation of myoblasts. The prepared PLCL/PANi fibers showed no significant difference in fiber diameter or contact angle, regardless of the incorporation of PANi. The fibers containing 30% PANi (PLCL/PANi-30) maintained elastic properties of maximum elongation at break (160 ± 14.4%). The composite fibers were cytocompatible, as the DNA content on each fiber was similar for up to 8 days of C2C12 myoblast culture. After 4 days of culture, the number of cells positive for sarcomeric myosin was 3.6-times greater on the electrically conductive fibers (21 ± 1 and 19 ± 2 for PLCL/PANi-15 and -30 fibers, respectively) than on the PLCL/PANi-0 fibers (6 ± 2). Furthermore, the level of myogenin expression detected on day 8 of culture on PLCL/PANi-15 was approximately 1.6-fold greater than the PLCL/PANi-0 fibers. Similar results were observed for the expression of other genes including troponin T (2-fold greater) and the myosin heavy chain gene (3-fold greater). These results indicate that electrically conductive substrates can modulate the induction of myoblasts into myotube formation without additional electrical stimulation, suggesting that these fibers may have potential as a temporary substrate for skeletal tissue engineering.

Comparison of the Effects of an Ionic Liquid and Triethylbenzylammonium Chloride on the Properties of Electrospun Fibers, 1 – Poly(lactic acid)

AbstractImproving the conductivity of electrospinning solutions is often achieved by adding small amounts of conductive additives. HMIMCl, a room temperature ionic liquid, and TEBAC, a quaternary ammonium salt, were added to polylactic acid in chloroform and their effects on solution properties, electrospinning, and fiber properties were investigated. Both additives increased the conductivity which decreased the fiber diameter, but differences were observed on the fiber dispersity and fiber morphology. The conductive solutions caused fiber backbuilding with aggregation and fiber fusion. Reasons for the differences in fiber diameter and fiber morphology are discussed.magnified image

Counterpoint: Spectral properties of the surface emg do not provide information about motor unit recruitment and muscle fiber type

The surface electromyogram (EMG) comprises the sum of the electrical contributions made by the active motor units to the interference signal detected by electrodes placed on the skin overlying the muscle. Because it provides a global measure of motor unit activity, this signal is a valuable tool for

Resistance to fracture and structural characteristics of different fiber reinforced post systems

Objectives The aim of this study was to investigate the ultrastructure and resistance to fracture of eight different types of fiber post, and to verify the existence of a correlation between structural characteristics and flexural strength. Methods Eight types of fiber post were selected for this study. Fiber Kor (Jeneric-Pentron), Para Post Fiber White (Colténe), Luscent Anchor (Dentatus), Twin-Luscent Anchor (Dentatus), Style Post (Metalor), DT White-Post (VDW), DT Light-Post (VDW) and ER Dentin Post (Brasseler). Ten posts of each experimental group were selected for a three-point bending test, and one was processed for SEM evaluation. A universal testing machine loading at an angle of 90° was employed for the three-point bending test. The test was carried out until fracturing of the post. After fracture testing, the posts with the highest and the lowest values of flexural strength of each system were additionally processed for SEM analysis. SEM evaluation was performed using a PC-measurement program to assess the fiber/matrix ratio and fiber dimensions. Results The fracture load of the tested systems ranged from 60 to 96 N and the flexural strength from 565 to 898 MPa. DT White-Post and DT Light-Post (898 and 842 MPa, respectively) had significantly higher flexural strengths than the other posts. Style Post (565 MPa) showed a significantly lower flexural strength than all other posts. The differences in fiber diameter ranged from 8.2 to 21 μm and for the fiber/matrix ratio from 41 to 76%. Of the various structural characteristics investigated, only the fiber/matrix ratio showed a significant correlation to the flexural strength ( r = 0.922, p = 0.003). Significance The FRC-posts investigated displayed significant differences with regard to fracture load and flexural strength. A strong and significant linear correlation between the fiber/matrix ratio and the flexural strength was found.

Effects of season on fleece traits of Angora does in the US

Twenty nonpregnant Angora does were used to determine seasonal effects on fleece traits, including fiber growth and follicle activity. Does grazed pastures and were supplemented with a 50% concentrate diet at a level near that required for BW maintenance. Clean fiber growth rate was greatest ( p<0.05) among seasons in summer and lowest ( p<0.05) in winter (1.13, 0.85, 0.98 and 1.20 mg/cm 2 per day for autumn, winter, spring and summer, respectively); seasonal differences in fiber diameter were similar (34.9, 31.7, 33.7 and 36.5 μm for autumn, winter, spring and summer, respectively). Fleece fiber medullation was greatest ( p<0.05) in summer (0.48, 0.32, 0.40 and 0.76%), and medullated fiber diameter was greater in spring and summer than winter (69, 65, 73 and 71 μm for autumn, winter, spring and summer, respectively). Primary follicle activity varied with season more than did activity of secondary follicles (primary: 74, 23, 79 and 99%; secondary: 97, 86, 94 and 99%; for autumn, winter, spring and summer, respectively). In summary, Angora goats in the US appear to exhibit seasonal follicle and fiber growth cycles, the knowledge of which may improve future nutritional management for efficient feed use in mohair production. The optimal time of shearing US Angoras for minimal contamination with medullated fibers may be just before spring and autumn equinoxes when it is likely that medullated fibers have been recently shed.

Improved wool production in transgenic sheep expressing insulin-like growth factor 1.

Transgenic sheep were produced by pronuclear microinjection with a mouse ultra-high-sulfur keratin promoter linked to an ovine insulin-like growth factor 1 (IGF1) cDNA. Five transgenic lambs resulted from the microinjection of 591 embryos; one male and one female showed IGF1 expression in the skin. A progeny test of the ram was carried out by matings to 43 non-transgenic ewes. Of 85 lambs born, 43 (50.6%) were transgenic. At yearling shearing (approximately 14 months of age), clean fleece weight was on average 6.2% greater in transgenic animals than in their non-transgenic half-sibs, with a greater effect in males (9.2%) than females (3.4%). Transgenics showed a small but significant increase in bulk, but male transgenics had a lower staple strength than female transgenics and non-transgenics which did not differ significantly. There were no significant differences in fiber diameter, medullation, and hogget body weight. To our knowledge this is the first reported improvement in a production trait by genetic engineering of a farm animal without adverse effects on health or reproduction.

MORPHOLOGIC OBSERVATIONS ON THE DERMAL NERVES IN VITILIGO: AN ULTRASTRUCTURAL STUDY

Vitiligo is a common idiopathic skin disorder. The etiology is unknown, although various hypotheses have been advanced. These include the neuronal hypothesis, where neuronal factors are thought to play a role in the pathogenesis of this disease. Skin biopsies were taken from marginal and central parts of four vitiligo patients. Biopsies were also taken from nonvitiliginous skin of each patient and from four normal control subjects. Sections were examined under the electron-microscope. Nerve fibers in the superficial dermis were examined. Subtle ultrastructural changes, including regeneration and degeneration, were consistently found in dermal nerves of vitiligo lesions. The most consistent feature, seen in all four vitiligo patients studied (in both lesional and marginal areas), was an increased thickness of the basement membrane of Schwann cells. This change was found in approximately three-quarters of all dermal nerves in vitiligo biopsies, but in only about one-quarter of dermal nerves in normal control skin. About half the abnormal dermal nerves in vitiligo skin showed minor axonal damage, although indicators of regeneration (increased mitochondria and rough endoplasmic reticulum) predominated. The dermal nerves in vitiligo showed no difference in fiber diameter or fiber density in comparison with controls. In vitiligo both axonal degeneration and nerve regeneration may occur, with the latter possibly being a reactive change to earlier axonal damage. These findings support the hypothesis that there is a neuronal component to this disease.

Bend properties of sapphire fibers at elevated temperatures I: Bend survivability

The effect of temperature on the bend radius that a c-axis-oriented sapphire fiber can withstand was determined for fibers of various diameter. Bend stress rupture tests were performed for times of 1–100 h and temperatures of 300–1700 °C. Fibers would survive the bend test undeformed, would fracture or would deform. The bend survival radius was determined to be the radius above which no fibers fractured or deformed for a given time-temperature treatment. It was found that the ability of fibers to withstand curvature decreases substantially with time and increasing temperature and that fibers of smaller diameter (40–83 μm) withstood smaller bend radii than would be expected from just a difference in fiber diameter when compared with the bend results of the fibers of large diameter (144 μm). This was probably due to different flaw populations, causing high temperature bend failure for the tested sapphire fibers of different diameters.

The diameters of guinea pig auditory nerve fibres: Distribution and correlation with spontaneous rate

In the mammalian auditory nerve physiological recordings revealed that the spontaneous discharge rate of single auditory fibres correlates with the diversity of input-output functions which may be important for intensity discrimination (e.g., Sachs and Abbas, 1974, Liberman, 1978; Winter et al., 1990). In this study we determined if the spontaneous discharge rate of auditory nerve fibres in the guinea pig is correlated with an anatomical feature, namely the diameter of the respective fibres. The diameter of myelinated (Type I) guinea pig auditory nerve fibres was measured after staining with different techniques. Measurements were made on semithin sections using a video image analysis system. The diameters of fibres stained with toluidine blue from the portion of the auditory nerve containing fibres from the basal turn of the cochlea were found to have a normal distribution. Fibres were also labelled with horseradish peroxidase by bulk injection into the spiral ganglion. It was found that the presence of horseradish peroxidase within the fibres reduced the measured diameter in comparison to adjacent unlabelled fibres. A number of fibres were physiologically characterized with respect to spontaneous discharge rate and subsequently intracellularly labelled with horseradish peroxidase. Fibre diameter of a selected sample of intracellularly labelled fibres was measured over a distance of 800 μm within the internal auditory meatus. At the positions nearest to the spiral ganglion fibres possessing low spontaneous rates were found to have smaller diameters than high spontaneous rate fibres. No difference in fibre diameter was found for the positions near the cochlear nucleus.

Endurance exercise alters the morphology of fast- and slow-twitch rat neuromuscular junctions.

The present investigation studied the effects of an endurance exercise program on the morphology of nerve terminals of phasic extensor digitorum longus (EDL) and tonic soleus (SOL) muscles from young mature female Sprague-Dawley rats. The animals were treadmill exercised for 30 consecutive days for 1 h/day at velocities up to 30 m/min. The area, perimeter, nerve longitudinal extent length, and fiber diameter of camera lucida drawings of zinc iodide osmium-stained nerve terminals were analyzed with a computerized morphometry system. Additionally, the number of nerve terminal branches and percentage of end-plates with sprouts were determined. Nerve terminals from exercised EDL and SOL had significantly greater areas than those from corresponding controls, with no changes in the perimeters. The magnitude of the changes were greater in the EDL. The exercised EDL nerve terminals were also significantly longer than controls and had more branches and sprouts. No training differences in fiber diameter were observed for either muscle. These data confirm previous suggestions that physical activity or exercise levels affect the morphology of the neuromuscular junction.

Chicken Breast Muscle Fiber Type and Diameter as Influenced by Age and Intramuscular Location

Six trials were conducted to determine the influence of muscle (pectoralis major and pectoralis minor) and location within the muscle on fiber type and diameter in four different age groups of chicken. Broilers obtained from a commercial processing plant, Athens Canadian Randombred chickens, roasters, and broiler breeder hens were killed via cervical dislocation. Muscle samples were removed from the anterior, middle, and posterior areas of the pectoralis major (p. major), and from the anterior and posterior areas of the pectoralis minor (p. minor). Frozen transverse muscle sections, 10 mm thick, were prepared at −20 C, stained for adenosine phosphatase activity, and photomicrographed for fiber typing and fiber diameter measurement.No differences were found in fiber types by age group, sex, or location within the muscle. The p. minor muscle had more intermediate fibers than the p. major muscle. Fiber diameters were significantly larger in the posterior portion of the p. major muscle than in the anterior or middle portions in two of the broiler trials, the female roasters, and the breeder hens. No significant differences in fiber diameter were noted for the p. minor muscle.

Regional differences in fiber size in the cochlear nerve.

The topographical variations in fiber size in the cochlear nerve of cat were quantitatively studied by electron microscopy. Measurements of fiber size as they appeared at the outlet of the spiral lamina show that fibers originating from the basal part of the cochlea are larger than those from the apex. When the diameter of apical fibers and their axoplasms at two different levels are compared, a significant variation in size is observed. As they appear in the internal acoustic meatus the apical fibers are larger at the level of the nerve trunk compared with the same fibers near the ganglion cell bodies. There are significant differences in fiber diameter with regard to their length for fibers derived from the apical turn. These results are compared with previous findings.

Special histochemical muscle-fibre characteristics of the human lateral pterygoid muscle

The histochemical fibre-type profile was analyzed in 10 human lateral pterygoid muscles from young adults with complete dentitions and normal intermaxillary relations. The distributions of various types of fibre in the lateral pterygoid differed from those of normal human limb and trunk muscles as well as from those of human masseter and temporal muscles. There was a marked predominance of type I fibres, a high frequency of adenosine triphosphatase (ATPase) intermediate fibres and type IIC fibres and lack of type IIA ones. The muscle fibres, especially the type II fibres, were smaller than those in limb and trunk muscles. There was marked intra-muscular variability in both the proportion and diameter of the types. Type I fibres were larger in diameter than the others and occupied, on average, 81 per cent of the overall fibre crass-sectional area. Type II and the ATPase intermediate fibres were larger in males than in females. There was no difference in type I fibre diameter or fibre-type proportion between females and males. No difference in fibre diameter was observed between the two heads of the muscle, but the proportions of fibre types differed significantly in four muscles. The fibre-type composition in the adult lateral pterygoid muscle indicates a capacity for endurance during continuous work at relatively low forces and accords with the stabilizing effect on the mandibular joint attributed to this muscle.

The measurement of, and factors affecting, the strength of attachment of wool to the skin of sheep

To measure wool loosening before and after treatment with defleecing agents a 2 kg spring balance was used to measure the force required to pluck wool staples from sheep. The results are expressed as g force per fibre or as g force per unit of staple linear density (kTex), where 1 kTex = area staple cross section (mm2) x wool specific gravity (1 -3). The linear density of each staple plucked can be determined by a gravimetric method or more simply and quickly by using a pair of hand calipers that have been previously calibrated. Where fibre diameter is known an estimate can be made of the number of fibres present. The average force required to pluck a fibre from the follicle (depilation force) is about 15 to 25% of that required to break the fibre. The optimum reduction in fibre strength for purposes of harvesting weakened wool lies somewhere between the depilation and breaking forces. There are breed differences in depilation force that cannot be entirely explained by differences in fibre diameter, SIP ratio, fibre density or follicle depth, although a high degree of follicle bending in fine-wool Merinos (mean score 5.6 vs 3.6 for other breeds) may cause the higher than expected values observed for depilation force in fine-wool Merinos. The depilation force was found to vary within animals from day to day as well as between animals. It increased (ca. 30%) following an increase in intake from 600 to 1200 g day-I and decreased rapidly (ca. 40%) for up to 3-5 hours after death. Oral dosing of four sheep with cyclophosphamide (CPA) at 12 mg kg-1 had no effect on the rate of wool loosening for the first four days, but there was an exponential reduction to 40% of the control values over the next six days. Injecting six sheep with a micronized preparation of dexamethasone-21 -isonicotinate (Voren �) caused an immediate loosening of the wool but at a slower rate, the maximum extent (25%of the control values) not being achieved until after 40 days, lnjecting 27 mg of L-thyroxine eight days after dosing had no effect on this response or the rate of wool regrowth. Voren and CPA given together to four sheep acted synergistically, resulting in depilation forces about 20% of the control values 30 days later.

Effect of zinc deficiency on the weight, cellularity and zinc concentration of different skeletal muscles in the post-weanling rat.

Zinc-deficient (ZD), weight-restricted (WR), pair-fed (PF) andad lib.-fed (AL) Sprague-Dawley male rats were killed after feeding the respective Zn-deficient and Zn-supplemented diets from 3 to 8 weeks of age. Animals killed at the start of the experiment served as a baseline control (BC).Four different skeletal muscles – biceps brachii, soleus, plantaris and extensor digitorum longus (EDL) – were studied for changes in weight, the number and diameter of muscle fibres and Zn concentration.The soleus muscle had the highest concentration of Zn. It was the only muscle to reduce its Zn concentration due to Zn deficiency.There was a loss of muscle fibres during normal growth (groups BCv.AL) in the soleus muscle (P&lt; 0.05). The estimated length of muscle and the diameter of the muscle fibres in all four muscles increased significantly (P&lt; 0.001). Therefore postweanling growth appears to occur as a result of longitudinal and transverse increases in the dimensions of these muscles.The reduction in muscle fibre number in ZD rats compared to BC animals may occur within the range of expected fibre loss during normal growth. Fibre loss in ZD rats may be more affected by feeding-pattern-dependent metabolic changes than by a deficiency of Zn per se (groups ZDv.WR). Soleus fibre loss in ZD rats may be related to the high Zn concentration in this muscle.The effect of Zn deficiency per se on muscle fibre diameter may be inaccurately interpreted by comparing the ZD animals with their PF and AL controls. There was no significant difference in fibre diameter in any of the four muscles when ZD and WF rats were compared.

The relative importance of sources of variation in fibre diameter for Australian Merino sheep

Variation in fibre diameter was estimated in five Merino strains under the headings: between sheep; between sites over the body of the sheep; between fibres within sites; and between points along the fibre. The variation between fibres constitutes some two-thirds of the total, and that between sheep, on which the classer can operate, is about one-fifth. By means of correlations between crimps per inch and fibre diameter together with selection differentials, the differences in fibre diameter which a classer is likely to achieve in making clips into two and three lines respectively were estimated. These were less than 1 µm in all cases. Between-line variances computed on the basis of these between-line ' differences in fibre diameter will reduce the total variance within a resulting line by fractions that are always less than 2%. It is concluded that the elimination of crimp-based classing should not produce bulk wools that are unacceptable on the basis of variation in fibre diameter.

The ultrastructure of the neuromuscular junctions of mammalian red, white, and intermediate skeletal muscle fibers.

Distinct ultrastructural differences exist at the neuromuscular junctions of red, white, and intermediate fibers of a mammalian twitch skeletal muscle (albino rat diaphragm). The primary criteria for recognizing the three fiber types are differences in fiber diameter, mitochondrial content, and width of the Z line. In the red fiber the neuromuscular relationship presents the least sarcoplasmic and axoplasmic surface at each contact. Points of contact are relatively discrete and separate, and axonal terminals are small and elliptical. The junctional folds are relatively shallow, sparse, and irregular in arrangement. Axoplasmic vesicles are moderate in number, and sarcoplasmic vesicles are sparse. In the white fiber long, flat axonal terminals present considerable axoplasmic surface. Vast sarcoplasmic surface area is created by long, branching, closely spaced junctional folds that may merge with folds at adjacent contacts to occupy a more continuous and widespread area. Axoplasmic and sarcoplasmic vesicles are numerous. Both axoplasmic and sarcoplasmic mitochondria of the white fiber usually contain intramitochondrial granules. The intermediate fiber has large axonal terminals that are associated with the most widely spaced and deepest junctional folds. In all three fiber types, the junctional sarcoplasm is rich in free ribosomes, cisternae of granular endoplasmic reticulum, and randomly distributed microtubules.

Studies of the optic nerve of the rhesus monkey: Nerve fiber spectrum and physiological properties

This report describes a combined study of the anatomy and physiology of the optic nerve of the rhesus monkey. An optic nerve was fixed in osmium tetroxide and embedded in epon for the histological study: 60,898 fibers were measured and tabulated according to outside diameter. The fiber spectrum was unimodal with a peak frequency at 1.2 μ and a range of 0.4–6 μ. The total number of fibers was 1,410,000. The compound action potentials of the entire optic nerve and of small fascicles of the optic nerve were recorded at the optic disk: conduction velocities, recovery cycles and afterpotentials were studied. These properties of the nerve fibers showed a continuous range of values which were associated with differences in fiber diameter. It is concluded that the fibers of the optic nerve form a homogeneous population; thus the anatomical and physiological findings are not in conflict. Differences between the properties of fibers in the optic nerve and in the retina are described and discussed in terms of the known ultrastructure of the retinal nerve fiber layer.

Further Studies on Bovine Muscle Tenderness as Influenced by Carcass Position, Sarcomere Length, and Fiber Diameter

SUMMARYInterrelationships of fiber diameter, sarcomere length, and tenderness were studied in 12 bovine muscles of horizontally placed and vertically suspended carcass sides. In comparison with the horizontally placed sides, the vertically suspended sides had greater sarcomere lengths in the psoas major, latissimus dorsi, and rectus femoris muscles. Conversely, vertical suspension permitted the longissimus dorsi, gluteus medius, adductor, biceps femoris, and semitendinosus muscles to shorten in sarcomere length. In general the differences in sareomere lengths of muscles (between sides) were associated (r=–.82 P &lt;.01) with differences in fiber diameter. Differences in fiber diameter (between sides) were highly related to differences in shear force (r= .73, P &lt;.01, as were differences in sarcomere length (T = ‐.80, P &lt;.01). When museles shortened, there were corresponding decreases in sarcomere length, increases in fiber diameter, and decreases in tenderness.