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At least 271 records · Page 15Linked to original sources
PubMed2006

Wavelength-spacing tunable multiwavelength erbium-doped fiber laser based on four-wave mixing of dispersion-shifted fiber.

We experimentally demonstrate a wavelength-spacing tunable multiwavelength erbium-doped fiber laser based on degenerate four-wave mixing in a dispersion-shifted fiber incorporating multiple-fiber Bragg gratings. We have achieved stable operation of the multiwavelength erbium-doped fiber laser, which has 0.8 nm spacing ten-channel lasing wavelengths and a high extinction ratio of more than approximately 45 dB, at room temperature. The output power of the multiwavelength erbium-doped fiber laser is stable, so the peak fluctuation is less than approximately 0.2 dB. By changing the properties such as loss and polarization state of multiple fiber Bragg grating cavities, we can exercise flexible control of the wavelength spacing of the multiwavelength output. We can also obtain switchable multiwavelength lasing operation by elimination of the effects of alternate single-fiber Bragg gratings.

Journal Article↗
PubMed1983

[Biological effects of mineral fibers on lymphocytes in vitro. Comparative studies of asbestos and glass fibers].

The biological effects of asbestos and glass fibers on lymphocytes in vitro were investigated. Blastoid transformation and beta 2 microglobulin production of human peripheral blood lymphocytes (PBL) induced by phytohemagglutinin were inhibited by Canadian chrysotile B (Standard sample of the Union Internationale Contre le Cancer; UICC standard sample) but it was not the case for crocidolite (UICC standard sample) and small and large glass fibers (John Manville, Canada). Cytotoxic activities of natural killer and killer cells of PBL were investigated using K562 cells and Chang liver cells as target cells respectively. Chrysotile inhibited the both activities but crocidolite and two kind of glass fibers not. In regard to release of lactic dehydrogenase and beta-glucuronidase from mouse peritoneal macrophages exposed to mineral fibers, chrysotile showed more effective reaction compared to crocidolite and amosite (UICC standard sample), on the other hand large glass fiber showed the similar reaction to chrysotile but small glass fiber and milled amosite did not induce any more enzymatic release than the control. In addition to chemical compositions of mineral fibers, the morphological characteristics were also discussed in relation to their biological effects.

Animals↗
PubMed2000

Effects of mimosine on fiber shedding, follicle activity, and fiber regrowth in Spanish goats.

Ten 2-yr-old Spanish wethers (58.2 +/- 7.21 kg BW) were used to determine effects of 2-d intravenous infusion of mimosine (beginning on January 8) on fiber shedding, follicle activity, and fiber regrowth. Primary and secondary follicle activity on d 0 were 43 +/- 6.2% and 96 +/- 1.7%, respectively. Five wethers were infused with mimosine at 120 mg/(kg BW x d) and the other five received saline. At 7 to 10 d after the start of infusion, all five goats infused with mimosine exhibited shedding, whereas shedding by controls was not observed. Cashmere fiber shedding score (5-point scale: 1 = no shedding, 5 = excessive shedding) on d 4 was greater for mimosine goats than for controls (1.2 vs 2.0; P < .001), and shedding score for wethers receiving mimosine was greater (P < .05) on d 12, 16, and 20 than on d 0 and 4 (4.1 to 4.6 vs 1.4 and 2.0). Guard hair shedding score for goats receiving mimosine was greatest (P < .01) among the days after infusion for d 12 and greater (P < .01) on d 16 than on d 0 and 4. Nonetheless, cashmere fiber yield from combed fleece of mimosine goats (average of 73%) was much greater than for a clipping of the uncombed side (average of 28%) when the cashmere fiber shedding score exceeded 4.0. Secondary follicle activity on d 12 was lower (P < .01) for mimosine than for control wethers (6.8 vs 67.7%), and secondary follicle activity for mimosine-infused goats on d 12 was lower (P < .01) than on d 0 (98.9%), 4 (98.3%), and 20 (99.5%). Mimosine infusion resulted in no detectable fiber regrowth in wk 4 to 7 after the start of infusion, but regrowth rate in the following two 4-wk periods was similar for mimosine and control wethers. In conclusion, 2-d intravenous infusion of mimosine at 120 mg/(kg BW x d) in the winter induced cashmere shedding but had less effect on guard hairs, suggesting future potential use of chemicals such as mimosine to remove cashmere fiber.

Animals↗
PubMed1976

[Quantitative studies on the regeneration of myelinated nerve fibers. II. Variations of the number and size of regenerating nerve fibers after localized crushing or total section].

1. The number and size of myelinated nerve fibers have been determined at standard levels, in the nerve to medial head of right and left gastrocnemius muscles of 112 rats in which the left sciatic nerve had suffered an experimental lesion according one of the following four modalities: localized crushing, total section followed or not by suture and resection of a nervous segment of about 1 cm. 2. In the nerve to medial head of right gastrocnemius muscle (contralateral nerve used as control), the number of myelinated fibers decreased in average to 10% after crushing, 5% or 4% after section followed or not by suture. However, an increase of 6% was observed after resection. The mean values of the mean diameters showed a decrease of 8% after crushing and 5% after section without suture. This value did not seem to be affected by section followed by immediate suture and after resection, it increased of 11%. On the whole, male rats appeared to be more sensitive than female to the effects of the operation. 3. The nerves of 12 rats have been observed from 15 to 334 days after resection of about 1 cm of sciatic nerve. The 20% of the regenerating myelinated nerve fibers which have succeeded to cross over such a distance had a distribution which remained unimodal; the diameter of the large fibres did not exceed 8 micronm. 4. 34 rats have been sacrificed from 15 to 715 days after sciatic nerve section which was not followed by suture. The number of myelinated nerve fibers became normal again during the 4th month and reached afterwards a mean value of 130%, with very marked variations. The nerve fibre distribution was most frequently unimodal, but may came bimodal one year after the operation in certain nerves. Their mean diameter never exceeded 60% of the normal. 5. The nerves of 34 rats have been examined from 15 to 720 days after section and immediate suture. The number of myelinated nerve fibers returned to normal during the second month and increased afterwards to an average of 150% with very important variations. The nerve fiber distribution was generally unimodal, but may become bimodal 7 months after the operation. Their mean diameter reached only 50 to 55% of the normal. 6. 32 rats have been sacrificed from 10 to 720 rats after a localized crushing. The number of myelinated nerve fibers come back to normal during the 4th week and later increased up to a mean of 115%. Their distribution became early bimodal from the 97th day onwards. Although, their mean diameter nerver exceeded 80% of the normal, the histograms of the regenerating nerve and of the control nerve could be almost superposed during the second year.

Animals↗
PubMed2004

The effect of fiber position and polymerization condition on the flexural properties of fiber-reinforced composite.

The aim of this study was to investigate the influence of the position of the fiber rich layer on the flexural properties of fiber-reinforced composite (FRC) construction. In addition, the total residual monomer content of FRC was quantitatively determined to find out the difference of the effectiveness of two types of light-curing units using liquid chromatography (HPLC). Unidirectional continuous E-glass FRC and hybrid particulate filler composite resins were used in the fabrication of test specimens. Four different positions of the FRC layer were used: compression, neutral, tension, and vertical side position. A three-point bending test (ISO 10477) was performed to measure the flexural properties of the specimens. Position of the FRC layer had a significant effect on the flexural strength (p<0.001, ANOVA). Also, the type of light-curing device had an effect on flexural strength (p<0.001). Specimens with FRC positioned on the compression side showed flexural strength of approximately 250 MPa, whereas FRC positioned on the tension side showed strength ranging from 500 to 600 MPa. Mean flexural modulus with FRC placed horizontally ranged between 9-12 GPa; no significant difference was found between these groups. However when fiber reinforcement was positioned vertically, the flexural modulus raised up to 16 GPa. Specimens with 24 vol% glass fibers contained 52% less residual monomer than specimens without glass fibers. The monomer content was lower in specimens polymerized with the curing device with higher polymerization temperature. In order to optimize flexural strength of low fiber volume fraction, the fibers should be placed at the tension side of the specimen.

Analysis of Variance↗
PubMed1980

Elastic system fibers (oxytalan, elaunin and elastic fibers) in the skin of a freshwater teleost : optical and electron microscopy study.

The oxytalan, elaunin and elastic fibers which represent a system of connective tissue fibers -- the elastic system (ESP) -- were studied in the dermis of a teleost by optical and electron microscopy. The oxytalan fibers were identified at the dermo-epidermal junction. They are bound, by one of their extremities to the basal lamina, and by the other are in continuity with elaunin fibers. The elaunin fibers cross the entire stratum compactum perpendicularly and in the deeper zone are interconnected to other elaunin fibers. Thick elastic fibers, forming an apparent continuous layer were observed between the stratum compactum and the stratum spongiosum. The ultrastructural characteristics and functional properties of the ESF are discussed.

Animals↗
PubMed1994

Mechanisms of fiber-induced diseases: implications for the safety evaluation of synthetic vitreous fibers.

Inhalation of certain natural mineral fibers, such as amphibole asbestos, is associated with the development of inflammatory, fibroproliferative, and neoplastic diseases in the lung and pleura of man and experimental animals. The mechanisms by which fibers induce fibrosis and cancer are largely unknown, but are thought to be modulated by reactive oxygen species and altered growth factor pathways. Studies in rats using intracavitary implantation and instillation of fiber preparations led to the belief that all fibers with certain dimensional characteristics had similar toxic potential. It is now known that different fiber types of similar dimension can vary substantially in biological activity. A variety of physicochemical properties govern fiber toxicity and carcinogenicity, including: size and shape; surface chemistry; solubility and biopersistence; and chemical composition. Although the molecular event(s) that translate fiber-induced cellular injury into a pathologic state are unknown, there is strong evidence in man and laboratory animals to suggest both dose dependency and thresholds for effects.

Air Pollutants, Occupational↗
PubMed1977

Extraocular muscle fibers: ultrastructural identification of iontophoretically labeled fibers contracting in response to succinylcholine.

Cat extraocular muscle fibers (from the superior rectus or inferior oblique) were penetrated in vivo with Procion red-filled glass microelectrodes. When stable penetrations were obtained, succinylcholine (Sch), 8 to 20 microng, was injected into the femoral vein. In some fibers, a depolarization-repolarization response was obtained with the same time course (2 min.) as the total muscle contraction. The depolarizing fibers were labeled iontophoretically. The ultrastructural characteristics of five depolarizing fibers and three control (nondepolarizing) fibers were then studied. The fibers that did not depolarize to Sch had the characteristics of singly innervated cells, whereas those sensitive to Sch had morphological characteristics of multi-innervated fibers.

Animals↗
PubMed1978

Fiber in the gastrointestinal tract.

It has long been recognized that fruit, vegetables, and cereal fiber alter bowel function. The right colon can be regarded as a fermenter and an absorbing organ, and the left colon is for continence. A rationale for the use of fiber based on physical chemical properties is discussed. On this basis, the use of coarse wheat bran, apples, oranges, and carrots is recommended to treat diverticular disease, spastic colon, and constipation.

Cellulose↗
PubMed2001

Relationship between capillary angiogenesis, fiber type, and fiber size in chronic systemic hypoxia.

Whether chronic hypoxia causes angiogenesis in skeletal muscle is controversial. Male Wistar rats, 5--6 wk of age, were kept at constant 12% O(2) for 3 wk, and frozen sections of their postural soleus (SOL), phasic extensor digitorum longus (EDL), and tibialis anterior (TA) muscles were compared with those of normoxic controls. Capillary supply increased in SOL muscles [capillary-to-fiber ratio (C/F) = 2.55 +/- 0.09 hypoxia vs. 2.17 +/- 0.06 normoxia; capillary density (CD) = 942 +/- 14 hypoxia vs. 832 +/- 20 mm(-2) normoxia, P < 0.01] but not in EDL muscles (C/F = 1.44 +/- 0.04 hypoxia vs. 1.42 +/- 0.04 normoxia; CD = 876 +/- 52 hypoxia vs. 896 +/- 24 mm(-2) normoxia). The predominantly glycolytic cortex of TA muscles showed higher C/F after hypoxia (1.79 +/- 0.09 vs. 1.53 +/- 0.05 normoxia, P < 0.05), whereas the mainly oxidative TA core with smaller fibers showed no change in capillarity. The region of the SOL muscle with large-sized (mean fiber area 2,843 +/- 128 microm(2)) oxidative fibers (90% type I) had a higher C/F (by 30%) and CD (by 25%), whereas there was no angiogenesis in the region with sparse (76%) and smaller-sized (2,200 +/- 85 microm(2)) type I fibers. Thus systemic hypoxia differentially induces angiogenesis between and within hindlimb skeletal muscles, with fiber size contributing either directly (via a metabolic stimulus) or indirectly (via a mechanical stimulus) to the process.

Animals↗
PubMed2004

Noxious stimuli evoke a biphasic flexor reflex composed of A delta-fiber-mediated short-latency and C-fiber-mediated long-latency withdrawal movements in mice.

The nociceptive flexor reflex was studied in mice, focusing in particular on movement. Electrical stimuli delivered to the ventral aspect of the toe through a pair of needle electrodes inserted subcutaneously elicited a biphasic withdrawal reflex that was composed of short- and long-latency movements of the ipsilateral hind paw. The first response had a lower activation threshold compared with the second movement. Similar biphasic responses were observed in the afferent volley recorded from the sciatic nerve as well as in the electromyographic activity recorded from the femoris biceps muscle. Tetrodotoxin, applied over the sciatic nerve, abolished the first movement, but the second response was preserved, revealing that the first movement was elicited by the activation of myelinated Adelta-fibers, whereas the second movement was mediated by unmyelinated C-fibers. Thus, simultaneous activation of Adelta- and C-fibers leads to separate, but sequentially occurring withdrawal movements of the hind paw in mice. Systemic administration of morphine suppressed the withdrawal reflex, which was attributable to a preferential reduction of the Adelta-fiber-mediated short-latency component. This method will be useful for understanding how Adelta-fiber- and C-fiber-mediated nociceptive reflexes are affected by drugs in the whole animal system.

Animals↗
PubMed1996

Sprouting of crossed entorhinodentate fibers after a unilateral entorhinal lesion: anterograde tracing of fiber reorganization with Phaseolus vulgaris-leucoagglutinin (PHAL).

Fibers from the contralateral entorhinal cortex (EC) to the dentate gyrus partially replace the input lost after an ipsilateral EC lesion. To study the morphology and course of single sprouted crossed entorhinodentate fibers, the anterograde tracer Phaseolus vulgaris-leucoagglutinin (PHAL) was used. Rats that survived for 4 to 8 weeks after a unilateral entorhinal lesion received PHAL deposits into the entorhinal cortex contralateral to the lesion. Control animals received a similar PHAL deposit. Single PHAL-labeled fibers in the molecular layer of the contralateral (EC lesion) fascia dentata were drawn with a camera lucida, and an axon-branching index (branch points/100 microns axon length) was calculated for these crossed entorhinodentate fibers in controls and operated animals. In animals with EC lesions, the density of PHAL-labeled crossed entorhinodentate fibers had increased remarkably. Single crossed entorhinodentate axons showed significantly more axon branch points in experimental than in control animals. In addition, some axon segments displayed high densities of small axonal extensions. Frequently, tanglelike structures were observed in the denervated outer molecular layer. These tangles consisted of one or more PHAL-labeled axons that intertwined and formed an axon tangle filled completely with branches, extensions, and boutons. Our data indicate that crossed EC fibers sprout by forming additional collaterals, axonal extensions, and tangles. Abnormal neurite formations are a characteristic feature of plaques in Alzheimer's disease. Future studies must be done to show whether or not there is a close relationship between axonal tangles and plaques in Alzheimer's disease, which, like the present lesion paradigm, severely affects entorhinal projection neurons.

Acetylcholinesterase↗
PubMed2004

Use of total dietary fiber across four lemur species (Propithecus verreauxi coquereli, Hapalemur griseus griseus, Varecia variegata, and Eulemur fulvus): does fiber type affect digestive efficiency?

In vivo digestibility and transit of two experimental diets were compared across four lemur species for which gastrointestinal morphology and preliminary data on physiology differ:Varecia variegata (VV), Eulemur fulvus (EF), Propithecus verreauxi (PV), and Hapalemur griseus (HG). Since free-ranging groups consume varied amounts of slowly fermentable insoluble fiber (IF) and rapidly fermentable soluble fiber (SF), differences in digestibility may be related to variation in the fiber types consumed. To investigate this, two diets were designed to provide 28% of dry matter (DM) as total dietary fiber (TDF). The ratio of IF/SF (g/g) differed across the diets (12.15:1 for the IF diet, and 3.76:1 for the IF/SF diet). The DM digestibility (DMD) of both diets differed across species: DMD was lower for EF and VV (approximately 56-58%), and higher for PV (72%) and HG (76%). The fiber digestibility results were as follows: TDF digestibility was similar for VV and EF (23% and 28%), higher for PV (56%), and highest for HG (66%). IF digestibility was lower for VV and EF (20% and 28%), and higher for PV and HG (53% and 62%). The transit times (TTs) of the two markers Cr and Co were similar (approximately 3.5 hr for VV and EF, 25 hr for PV, and 30 hr for HG). The mean retention times (MRTs) showed the same trend. The results from these captive groups suggest there are large differences in digestive efficiency that are likely related to the varied fiber composition of the free-ranging diet, and the amount of time the digesta are retained in the gut.

Animals↗
PubMed1985

Causes of the increased fiber density in muscular dystrophies studied with single fiber EMG during electrical stimulation.

The impulse transmission in motor end-plates and along muscle fibers was studied with single fiber EMG in 13 patients with muscular dystrophy during intramuscular nerve stimulation and direct muscle fiber stimulation. For comparison, three patients with spinal muscular atrophy (SMA) and five normal subjects were studied. At nerve stimulation, 25% of the recordings in the patients with muscular dystrophy showed "increased" jitter (> 55 microsec), 48% "normal" (10-55 microsec), and 27% "abnormally low" jitter (< 5 microsec). At direct muscle fiber stimulation, the jitter was "abnormally low" in 91% of the recordings; 9% of the recordings had normal jitter. In SMA, no abnormally low jitter values were found. Increased jitter is a sign of impaired impulse transmission in immature intramuscular nerves and motor end-plates. "Abnormally low jitter" suggests the presence of branched muscle fibers and ephaptic transmission between hyperexcitable fibers.

Action Potentials↗
PubMed1993

Regenerating retinal fibers display error-free homing along undamaged normal fibers.

After crushing one optic nerve in a bony fish, retinal fibers regenerate to both tecta. Anterograde labelling indicates that the ipsilaterally regenerating fibers have a rather straight growth, apparently along the undamaged fibers of the contralateral retina. In contrast, the contralaterally regenerating fibers deviate widely from a straight course. Retrograde labelling shows a mirror-symmetric distribution of regenerated ipsilateral and resident contralateral ganglion cells in a comparable annulus. In contrast, ganglion cells in the regenerated contralateral retina show no topological order after comparable small Dil applications to the ventrolateral tectum. These data suggest that regenerating fibers can orient on the undisturbed, contralateral fibers.

Animals↗
PubMed2000

Contraction-induced muscle fiber damage is increased in soleus muscle of streptozotocin-diabetic rats and is associated with elevated expression of brain-derived neurotrophic factor mRNA in muscle fibers and activated satellite cells.

The expression of brain-derived neurotrophic factor (BDNF) is elevated in the soleus muscle of streptozotocin-diabetic rats. To determine whether this diabetes-induced elevation was associated with or enhanced by muscle activity we have induced high-intensity muscle contraction by electrically stimulating the sciatic nerve. In 6-week diabetic rats, intense contraction of the soleus muscle resulted in a two- to four-fold elevation of BDNF mRNA and increased plasma levels of creatine kinase that were associated with severe focal muscle fiber damage and concomitant satellite cell activation. Focal muscle fiber damage and concomitant satellite cell activation were also observed in the soleus muscle of nonstimulated diabetic rats, but to a much lesser extent. No effects of muscle contraction, i.e., experimentally induced or during normal daily activity, on muscle fiber structure or BDNF mRNA expression were seen in diabetic extensor digitorum longus (EDL) muscle. Using a nonradioactive in situ hybridization technique for electron microscopy, the elevated expression of BDNF mRNA in the diabetic soleus muscle was localized within muscle fibers as well as activated satellite cells. This study shows that diabetic soleus muscle, in contrast to diabetic EDL and to soleus and EDL muscle of normal animals, is highly susceptible to contraction-induced damage. Intense contraction and the associated muscle fiber damage in the diabetic soleus muscle result in an upregulation of BDNF mRNA in muscle fibers and activated satellite cells, which may be involved in the restoration and/or maintenance of nerve/muscle integrity.

Animals↗
PubMed1986

Wheat germ agglutinin inhibits nerve fiber growth and concanavalin A stimulates nerve fiber initiation in cultures of dorsal root ganglia neurons.

Treatment of dorsal root ganglion (DRG) neurons with the lectin wheat germ agglutinin (WGA; 25 micrograms/ml), which binds to N-acetylglucosamine containing glycoconjugates, inhibits nerve fiber growth in culture. DRG neurons treated with WGA have significantly reduced total output in nerve fiber length per neuron as well as reductions in the average length of the individual nerve fibers extended. The inhibition of nerve fiber growth by WGA is concentration-dependent, specific, reversible and not mimicked by treatment with several metabolic poisons. In contrast, treatment with the lectin concanavalin A (25 micrograms/ml), which binds to mannose-containing glycoconjugates, increases the number of nerve fibers produced per neuron. These results suggest that lectins which bind to distinct carbohydrate moieties can differentially regulate nerve fiber growth.

Animals↗
PubMed1990

Coding of stimulus location and intensity in populations of mechanosensitive nerve fibers of the raccoon: II. Across-fiber response patterns.

The major aim of this study was to determine whether information about stimulus location and intensity can be precisely encoded in the population response profiles of mechanosensitive nerve fibers. Across-fiber patterns (AFPs) were reconstructed using data obtained previously (58) from 129 single median nerve fibers and 61 posterior tibial nerve fibers of the raccoon. Punctate mechanical stimuli of varying intensities were presented to six standard test sites on the glabrous skin of the forepaw and hindpaw, and the AFP produced by each unique stimulus was determined. Innervation density (ID) at each of the test sites was estimated from the integrated voltage of compound action potentials evoked by constant current stimulation of the skin at each site. Differences in ID between corresponding regions of the forepaw and hindpaw were estimated by counts of myelinated fibers and measurements of skin areas supplied by the median and tibial nerves, respectively. All AFPs were adjusted to take into account the differences in ID among the various skin sites on the two paws. The data indicated that different stimulus locations and intensities on each paw could be precisely and unambiguously encoded by AFPs; location was represented primarily by the shape of the AFP, whereas intensity was represented by the height of the AFP. The discriminability of location and intensity was shown to be directly related to the magnitude of the difference between the AFPs elicited by any two stimuli. Consistent with expectations, AFPs for stimuli delivered distally on each paw showed greater differences as a function of stimulus location and intensity than AFPs for stimuli applied proximally. Furthermore, AFPs produced by stimuli to the forepaw showed greater changes than AFPs for stimuli to comparable sites on the hindpaw. It was concluded that systematic differences in the population response profiles of median and tibial nerve fibers could account for regional variations in tactile acuity across each paw and differences between the two paws.

Afferent Pathways↗