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At least 199 records · Page 11Linked to original sources
PubMed1989

Calcitonin gene-related peptide-like immunoreactivity in nerve fibers in the human skin. Relation to fibers containing substance P-, somatostatin- and vasocactive intestinalpolypeptide-like immunoreactivity.

Calcitonin gene-related peptide-like immunoreactivity was demonstrated in in sensory nerve fibers in the epidermis and dermis as free nerve endings and around blood vessels and hair follicles of the human finger pad and arm skin. The vast majority of the calcitonin gene-related immunoreactive fibers was shown to display also substance P-like immunoreactivity and a few fibers in the dermis were somatostatin positive. No fibers displaying both substance P and somatostatin-like immunoreactivity were found but a few substance P immunoreactive fibers in the dermis-epidermis region were found to contain also vasointestinal polypeptide-like immunoreactivity. In the sweat glands, abundant calcitonin gene-related peptide positive, but substance P negative, fibers were observed with a similar distribution pattern as the vasoactive intestinal polypeptide immunoreactive fibers and these fibers were suggested to be of sympathetic origin.

Adult↗
PubMed1981

Intracytoplasmic vacuoles in alpha W fibers of dystrophic chicken muscle--probable early pathologic event initiates massive fiber necrosis.

An electron-microscopic study on dystrophic chicken white muscle, posterior latissimus dorsi (PLD), was performed with histochemical identification of three fiber types of beta R (red), alpha R and alpha W (white) fibers to evaluate the pathophysiology in fiber necrosis. As seen in histochemically stained sections, vacuolar formation in the cytoplasm, an outstanding pathologic feature in chicken dystrophy, was recognized in the alpha W fibers by electron microscopy. The vacuole was membrane-bound and thought to originate from coalescence or dilatation of extensively proliferated sarcotubular system. There was evidence of a delay in fiber type transformation from alpha R to alpha W in dystrophic white muscle, while the initial pathologic event of sarcotubular system proliferation might be expressed only after muscle fibers had attained histochemical characteristics of alpha W fibers. Localized myofibrillar degeneration was encountered in the vicinity of the vacuole with focal membrane defect. An influx of extracellular fluid through the vacuolated sarcotubular system into the sarcoplasm may activate certain proteases, such as calcium-dependent protease because the extracellular fluid contains high concentration of calcium ion. The activated protease then degrades structural protein, especially Z-line protein, followed by fiber necrosis with phagocytosis.

Animals↗
PubMed1994

Acrylic resin-fiber composite--Part II: The effect of polymerization shrinkage of polymethyl methacrylate applied to fiber roving on transverse strength.

This study determined the effect of polymerization shrinkage of polymethyl methacrylate (PMMA) coating of fiber roving on the transverse strength of an acrylic resin-glass fiber composite. The test specimens were heat-cured acrylic resin reinforced with glass fibers. The glass fiber rovings were treated with four PMMA-MMA mixtures (30 specimens per group) of various ratios assumed to have different amounts of polymerization shrinkage. A transverse strength test was used to determine the fracture resistance of the test specimens and the polymerization shrinkage of the PMMA-MMA mixtures was measured. After the specimens were fractured, single glass fibers used to reinforce the test specimens were studied by SEM. The fracture resistance of the specimens was statistically different (p < 0.001) among treatments, and the polymerization shrinkage of the PMMA-MMA mixture also varied as the calculations predicted. The SEM micrographs showed differences in thickness of the acrylic resin layer on the surface of the fibers with PMMA-MMA mixtures of various ratios. According to the results, the ratio that caused only minor polymerization shrinkage of PMMA in the glass fiber roving improved the fracture resistance of the test specimens and seemed to increase the amount of PMMA inside the fiber roving.

Analysis of Variance↗
PubMed2000

Protein diffusion in living skeletal muscle fibers: dependence on protein size, fiber type, and contraction.

Sarcoplasmic protein diffusion was studied under different conditions, using microinjection in combination with microspectrophotometry. Six globular proteins with molecular masses between 12 and 3700 kDa, with diameters from 3 to 30 nm, were used for the experiments. Proteins were injected into single, intact skeletal muscle fibers taken from either soleus or extensor digitorum longus (edl) muscle of adult rats. No correlation was found between sarcomere spacing and the sarcoplasmic diffusion coefficient (D) for all proteins studied. D of the smaller proteins cytochrome c (diameter 3.1 nm), myoglobin (diameter 3.5 nm), and hemoglobin (diameter 5.5 nm) amounted to only approximately 1/10 of their value in water and was not increased by auxotonic fiber contractions. D for cytochrome c and myoglobin was significantly higher in fibers from edl (mainly type II fibers) compared to fibers from soleus (mainly type I fibers). Measurements of D for myoglobin at 37 degrees C in addition to 22 degrees C led to a Q(10) of 1.46 for this temperature range. For the larger proteins catalase (diameter 10.5 nm) and ferritin (diameter 12.2 nm), a decrease in D to approximately 1/20 and approximately 1/50 of that in water was observed, whereas no diffusive flux at all of earthworm hemoglobin (diameter 30 nm) along the fiber axis could be detected. We conclude that 1) sarcoplasmic protein diffusion is strongly impaired by the presence of the myofilamental lattice, which also gives rise to differences in diffusivity between different fiber types; 2) contractions do not cause significant convection in sarcoplasm and do not lead to increased diffusional transport; and 3) in addition to the steric hindrance that slows down the diffusion of smaller proteins, diffusion of large proteins is further hindered when their dimensions approach the interfilament distances. This molecular sieve property progressively reduces intracellular diffusion of proteins when the molecular diameter increases to more than approximately 10 nm.

Animals↗
PubMed1976

Sarcomere length dispersion in single skeletal muscle fibers and fiber bundles.

Light diffraction patterns produced by single skeletal muscle fibers and small fiber bundles of Rana pipiens semitendinosus have been examined at rest and during tetanic contraction. The muscle diffraction patterns were recorded with a vidicon camera interfaced to a minicomputer. Digitized video output was analyzed on-line to determine mean sarcomere length, line intensity, and the distribution of sarcomere lengths. The occurrence of first-order line intensity and peak amplitude maxima at approximately 3.0 mum is interpreted in terms of simple scattering theory. Measurements made along the length of a singel fiber reveal small variations in calculated mean sarcomere length (SD about 1.2%) and its percent dispersion (2.1% +/- 0.8%). Dispersion in small multifiber preparations increases approximately linearly with fiber number (about 0.2% per fiber) to a maximum of 8-10% in large bundles. Dispersion measurements based upon diffraction line analysis are comparable to SDs calculated from length distribution histograms obtained by light micrography of the fiber. First-order line intensity decreases by about 40% during tetanus; larger multifibered bundles exhibit substantial increases in sarcomere dispersion during contraction, but single fibers show no appreciable dispersion change. These results suggest the occurrence of asynchronous static or dynamic axial disordering of thick filaments, with a persistence in long range order of sarcomere spacing during contraction in single fibers.

Animals↗
PubMed1979

Summary of measurements of employee exposure to airborne dust and fiber in sixteen facilities producing man-made mineral fibers.

The results of an industry-wide study to determine the exposure of workers to man-made mineral fibers are summarized. The purpose of the study was to determine current employee exposures to airborne fibers and to utilize results to estimate past exposures. Measured exposures of workers to airborne total particulate matter and fibers are presented; samples were evaluated by phase contrast and electron microscopy. Results of the three year study, which encompassed 16 facilities and over 1500 eight hour samples, show that although there is a wide variation in concentrations of airborne fibers and particulate matter between and within the facilities surveyed, the concentrations of airborne particulate matter and fibers are generally less than 2.5 mg/m3 and 0.5 fibers/cm3, respectively. The norminal fiber size of the fibers manufactured and average airborne fiber concentration were highly correlated.

Air Pollutants↗
PubMed1992

DNA sequences of the tail fiber genes of bacteriophage P2: evidence for horizontal transfer of tail fiber genes among unrelated bacteriophages.

We have determined the DNA sequence of the bacteriophage P2 tail genes G and H, which code for polypeptides of 175 and 669 residues, respectively. Gene H probably codes for the distal part of the P2 tail fiber, since the deduced sequence of its product contains regions similar to tail fiber proteins from phages Mu, P1, lambda, K3, and T2. The similarities of the carboxy-terminal portions of the P2, Mu, ann P1 tail fiber proteins may explain the observation that these phages in general have the same host range. The P2 H gene product is similar to the products of both lambda open reading frame (ORF) 401 (stf, side tail fiber) and its downstream ORF, ORF 314. If 1 bp is inserted near the end of ORF 401, this reading frame becomes fused with ORF 314, creating an ORF that may represent the complete stf gene that encodes a 774-amino-acid-long side tail fiber protein. Thus, a frameshift mutation seems to be present in the common laboratory strain of lambda. Gene G of P2 probably codes for a protein required for assembly of the tail fibers of the virion. The entire G gene product is very similar to the products of genes U and U' of phage Mu; a region of these proteins is also found in the tail fiber assembly proteins of phages TuIa, TuIb, T4, and lambda. The similarities in the tail fiber genes of phages of different families provide evidence that illegitimate recombination occurs at previously unappreciated levels and that phages are taking advantage of the gene pool available to them to alter their host ranges under selective pressures.

Amino Acid Sequence↗
PubMed1987

Plasticity of skeletal muscle: regenerating fibers adapt more rapidly than surviving fibers.

The properties of mammalian skeletal muscle demonstrate a high degree of structural and functional plasticity as evidenced by their adaptability to an atypical site after cross-transplantation and to atypical innervation after cross-innervation. We tested the hypothesis that, regardless of fiber type, skeletal muscles composed of regenerating fibers adapt more readily than muscles composed of surviving fibers when placed in an atypical site with atypical innervation. Fast muscles of rats were autografted into the site of slow muscles or vice versa with the donor muscle innervated by the motor nerve to the recipient site. Surviving fibers in donor muscles were obtained by grafting with vasculature intact (vascularized muscle graft), and regenerating fibers were obtained by grafting with vasculature severed (free muscle graft). Our hypothesis was supported because 60 days after grafting, transposed muscles with surviving fibers demonstrated only a slight change from the contractile properties and fiber typing of donor muscles, whereas transplanted muscles with regenerating fibers demonstrated almost complete change to those of the muscle formerly in the atypical site.

Animals↗
PubMed1993

Muscle fiber type composition and fiber size in successfully and unsuccessfully endurance-raced horses.

Triplicate biopsies from three different depths of the gluteus medius muscle were obtained in 36 endurance-raced horses, aged 8.42 +/- 2.85 yr. Twenty of the horses were considered excellent endurance performers according to the mean speed of their three fastest records in endurance events for the past 2 or 3 years, whereas 16 were moderate performers, with a mean racing speed < 12.5 km/h (in 120- to 180-km endurance rides), < 14 km/h (in 80- to 120-km endurance rides), or < 13.5 km/h (in 40- to 60-km endurance rides). Significant differences in muscle fiber type composition and fiber size were recorded; excellent performers had a higher percentage and a larger size of type I and type IIa fibers (high and low myosin adenosinetriphosphatase activity at pH 4.5, respectively) and a lower percentage of type IIb fibers (moderate myosin adenosinetriphosphatase activity at pH 4.5), including both type IIb oxidative (moderate to high NADH-tetrazolium reductase activity) and IIb nonoxidative (low NADH-tetrazolium reductase activity). The differences in distribution of myofiber types and in fiber sizes were more marked in the deeper parts compared with the superficial regions of muscle. Our results also imply a greater homogeneity among the fiber type sizes across the muscle in horses with a superior endurance performance than in horses that had been poorly or moderately endurance raced. Thus the results show that fiber type proportions and fiber size in equine skeletal muscle are directly related to the athletic ability of the horse for endurance events.

Aging↗
PubMed1998

Two-channel polarization analyzer in the sustaining fiber-dimming fiber ensemble of crayfish visual system.

Polarization sensitivity (PS) was examined in two classes of neurons, sustaining fibers and dimming fibers, in the medulla externa (second optic neuropile) of the crayfish, Pacifasticus leniusculus. Visual responses were recorded intracellularly and extracellularly. The influence of e-vector orientation (theta) was probed in steady-state responses, with brief flashes and with a rotating polarizer. The results indicate that the entire sustaining fiber population appears to be maximally sensitive to vertically polarized light. Although the evidence is less complete for dimming fibers, they appear to be maximally inhibited by vertically polarized light and excited by horizontally polarized light. Thus the sustaining fibers and dimming fibers form a two-channel polarization analyzer that captures the main features of the polarization system established in photoreceptors and lamina monopolar cells. The available evidence suggests that this two-channel system has the same characteristics across most or all of the retinula. Lateral inhibition in sustaining fibers is differentially sensitive to theta. Inhibition is substantial at theta = 90 degrees (horizontal) and essentially absent at theta = 0 degrees. The details of the sustaining fiber polarization response closely follow features established in more peripheral neurons, including the magnitude of PS, enhanced responsiveness to a changing e-vector, and modest directionality to a changing e-vector in approximately 40% of the cells.

Animals↗
PubMed1990

Fusion between myoblasts and adult muscle fibers promotes remodeling of fibers into myotubes in vitro.

Muscle satellite cells are residual embryonic myoblast precursors responsible for muscle growth and regeneration. In order to examine the role of satellite cells in the initial events of muscle regeneration, we placed individual mature rat muscle fibers in vitro along with their satellite cells. When the satellite cells were allowed to proliferate, they produced populations of myoblasts that fused together to form myotubes on the laminin substrate. These myoblasts and myotubes also fused with the adult fibers. When they did so, the fibers lost their adult morphology, and by 8 days in vitro, essentially all of them were remodeled into structures resembling embryonic myotubes. However, when proliferating satellite cells were eliminated by exposure to cytosine arabinoside (araC), the vast majority of fibers retained their adult shape. Addition of C2C12 cells (a myoblast line derived from adult mouse satellite cells) to araC-treated fiber cultures resulted in their fusion with the rat muscle fibers and restored the ability of the fibers to remodel, whereas addition of either a fibroblast cell line or a transformed, non-fusing variant of C2C12 cells, or addition of conditioned medium from C2C12 cells, failed to do so. These results imply that myoblast fusion is responsible for triggering adult fiber remodeling in vitro.

Animals↗
PubMed1994

Dissolution of man-made vitreous fibers in rat alveolar macrophage culture and Gamble's saline solution: influence of different media and chemical composition of the fibers.

The effect of different chemical compositions of man-made vitreous fibers (MMVF) on their dissolution by alveolar macrophages (AM) in culture and in Gamble's solution was studied. The fibers were exposed to cultured rat AMs, culture medium alone; or Gamble's saline solution for 2, 4, or 8 days. The dissolution of the fibers was studied by measuring the amount of silicon (Si), iron (Fe), and aluminum (Al) in each medium. The AMs in culture dissolved Fe and Al from the fibers but the dissolution of Si was more marked in the cell culture medium without cells and in the Gamble's solution. The dissolution of Si, Fe, and Al was different for different fibers, and increased as a function of time. The Fe and Al content of the fibers correlated negatively with the dissolution of Si by AMs from the MMVF, i.e., when the content of Fe and Al of the fibers increased the dissolution of Si decreased. These results suggest that the chemical composition of MMVFs has a marked effect on their dissolution. AMs seem to affect the dissolution of Fe and Al from the fibers. This suggests that in vitro models with cells in the media rather than only culture media or saline solutions would be preferable in dissolution studies of MMVFs.

Animals↗
PubMed2003

Self-centering of a ball lens by laser trapping: fiber-ball-fiber coupling analysis.

Fiber-to-fiber coupling through use of a laser-trapped microball lens is examined. A model based on radiation pressure predicts that the ball lens will align axially between the fiber endfaces. Laser manipulation of the ball lens axial position results in a configuration in which the ball lens optically bridges the gap between the fibers. Experimental results are presented for several fiber endface separations, and it is found that the presence of the microball lens can increase the coupling by a factor of 2 above the level expected by direct fiber-to-fiber coupling for the same fiber endface separation.

Journal Article↗
PubMed2005

Fiber optic liquid leak detection technique with an ultrasonic actuator and a fiber Bragg grating.

We present a technique for liquid leak detection in which ultrasonic and optical waves are introduced into a fiber simultaneously. The system is based on an ultrasonic technique using an ultrasonic actuator and a fiber Bragg grating receiver. A fiber-guided ultrasonic wave is utilized to stress the fiber Bragg grating, which is remote from the ultrasonic transmitter. When the traveling ultrasonic wave encounters a liquid, part of the wave will leak out from the fiber, which results in an ultrasonic strain decrease in the fiber Bragg grating. The ultrasonic wave and its attenuation are detected by the light variation of a narrowband laser source reflected and transmitted from the fiber Bragg grating, and the amplitude variation of the ultrasound can eventually be correlated with the fiber area coupled with the liquid.

Journal Article↗
PubMed2004

Visualization and mechanical manipulations of individual fibrin fibers suggest that fiber cross section has fractal dimension 1.3.

We report protocols and techniques to image and mechanically manipulate individual fibrin fibers, which are key structural components of blood clots. Using atomic force microscopy-based lateral force manipulations we determined the rupture force, FR, f fibrin fibers as a function of their diameter, D, in ambient conditions. As expected, the rupture force increases with increasing diameter; however, somewhat unexpectedly, it increases as FR approximately D1.30+/-0.06. Moreover, using a combined atomic force microscopy-fluorescence microscopy instrument, we determined the light intensity, I, of single fibers, that were formed with fluorescently labeled fibrinogen, as a function of their diameter, D. Similar to the force data, we found that the light intensity, and thus the number of molecules per cross section, increases as I approximately D1.25+/-0.11. Based on these findings we propose that fibrin fibers are fractals for which the number of molecules per cross section increases as about D1.3. This implies that the molecule density varies as rhoD approximately D -0.7, i.e., thinner fibers are denser than thicker fibers. Such a model would be consistent with the observation that fibrin fibers consist of 70-80% water and only 20-30% protein, which also suggests that fibrin fibers are very porous.

Crystallography↗
PubMed1994

[Observations on gingival fibers of upper premolar region--structures and functions of dentogingival fibers].

It was the purpose of this paper to observe the structural features and discuss the functions of the dentogingival fibers in the human gingiva of the upper premolar region. They were observed by a light microscope. The results are as follows: 1. There is a large number of dentogingival fibers in the lingual gingiva of the upper premolar region. 2. Ten to fifteen dentogingival fibers form a bundle. And the bundle is twisted. 3. The dentogingival fibers increase in proportion to the thickening of the gingiva, and it seems that the dentogingival fibers is one of the main functional fibers. 4. Enlargement of the epithelial attachment and the increase of the fibers in the papillae accompany the cell differentiation of the epithelial basal cells. 5. It is observed that the tension of the dentogingival fibers extend widely to the epithelial cells of the stratum spinosum.

Bicuspid↗
PubMed1975

[Congenital desproportion of various types of muscle fiber, with relative small size of type I fibers. Morphological documents on muscle biopsies in 3 members of the same family].

In two sisters with a neo-natal hypotonia, muscle biopsies demonstrated as main pathological feature a disproportion in size between the two types of muscle fibers defined according to their myofibrillar ATPase activity. Type I fiber mean diameter was at the lower limit of the normal values, and type II fibers were larger than normal. Their father's biopsy also showed an abnormal smallness of the type I fibers, with a bimodal distribution. By electron microscopy, the small type I fibers did not reveal any significant abnormality in children's biopsies. In father's biopsy, there was an abnormal degree of filamentary interchange between contiguous myofibrils and a few stacks of rods in the type I fibers. These three cases demonstrate the familiar character of the disorder. The relationship of this new entity with the other congenital myopathies is controversial, as a similar congenital fiber type disproportion, has been found in association with different ultrastructural changes. Several data favour an insufficient development of the type I fibers rather than an atrophying process. The mechanism of this "hypotrophy" remains unknown.

Adenosine Triphosphatases↗
PubMed1987

Muscle fiber types in thoracic erector spinae muscles. Fiber types in idiopathic and other forms of scoliosis.

Histochemical studies of the thoracic part of the erector spinae muscles in scoliosis have shown a consistently higher proportion of Type 1 fibers on the convex side. The fiber distribution of the multifidus and semispinalis muscles was studied in adolescent idiopathic scoliosis (AIS). Compared with sex- and age-matched controls, a "normal" percentage of Type 1 fibers was found on the convex right side and significantly smaller percentage of Type 1 fibers on the concave side. Boys with AIS showed the same pattern as girls. In two patients with double major curves, the same pattern could be seen on the convexity of both curves. Patients with congenital scoliosis or scoliosis with early onset showed a different pattern with a "normal" percentage of Type 1 fibers on the concave side but a significantly greater percentage of Type 1 fibers on the convex side. In AIS, the deviation in the fiber distribution may constitute a primary factor in the pathogenesis of scoliosis. In congenital scoliosis the differences in fiber distribution between the convex and concave sides are considered secondary in the pathogenesis of the spinal curvature.

Adolescent↗