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PubMed1993

Fiber-type caffeine sensitivities in skinned muscle fibers from humans susceptible to malignant hyperthermia.

BACKGROUND: The response to contracture tests may depend upon the relative proportion of muscle fiber types within the muscle specimen. To determine whether a difference in fiber-type caffeine sensitivities exists between malignant hyperthermia susceptible (MHS) and malignant hyperthermia-nonsusceptible (MHN) skeletal muscle, we compared the fiber-type caffeine sensitivities in chemically skinned muscle fibers dissected from vastus lateralis muscle from 15 MHS and 16 MHN patients. METHODS: Muscle fiber type was determined in each fiber by the difference in strontium-induced tension measurements and in 36 fibers, after contracture testing, by ATPase enzyme histochemistry. Caffeine sensitivity was defined as the threshold concentration inducing more than 10% of the maximal tension obtained with a calcium 1.6 x 10(-2) mM solution. RESULTS: Significant difference in the mean (+/- SD) caffeine sensitivity was found between type I MHS fibers (2.63 +/- 0.85 mM) versus type II MHS fibers (3.47 +/- 1.2 mM) and between type I MHN fibers (5.89 +/- 1.8 mM) versus type II MHN fibers (10.46 +/- 2.6 mM). The mean (+/- SD) caffeine sensitivities for a given muscle fiber type (I or II) were different between groups of MHS and MHN patients. Both type I and II MHS fibers had significantly lower caffeine sensitivities, and this increase in caffeine sensitivity was significantly smaller in type I than in type II fiber. CONCLUSIONS: The current study indicates that a truly MHS patient cannot have a false-negative result solely related to abnormal type II fibers contained in a given muscle strip. Although the occurrence of a very high proportion of type I fibers in MHN human muscle could result in a false-positive contracture outcome, such an occurrence is expected to be rare.

Caffeine↗
PubMed2006

Comparison of germanium oxide fibers with silica and sapphire fiber tips for transmission of erbium: YAG laser radiation.

BACKGROUND AND OBJECTIVES: Endoscopic applications of the Erbium:YAG laser have been limited due to the lack of a suitable optical fiber delivery system. The purpose of this study was to compare the transmission of Er:YAG laser radiation through germanium oxide trunk fibers with silica and sapphire fiber tips for potential use in contact tissue ablation during endoscopy. STUDY DESIGN/MATERIALS AND METHODS: Er:YAG laser radiation with a wavelength of 2.94 microm, pulse length of 300 microseconds, pulse energies from 5 to 1,360 mJ, coupled into pulse repetition rates of 3-10 Hz, was through 1-m-long germanium oxide fibers with either 1-cm-long, 550-microm-diameter silica or sapphire tips. RESULTS: Transmission through the germanium oxide/sapphire fibers measured 65+/-5% compared with 55+/-4% for the germanium oxide/silica fibers (P<0.05). The damage threshold for the hybrid fibers averaged 309+/- 44 mJ and 126+/-43 mJ, respectively (n = 7 fibers each) (P<0.05). The highest pulse energies transmitted through the fibers were 700 mJ and 220 mJ, respectively. CONCLUSIONS: Improved index-matching of the trunk fiber and fiber tip at 2.94 microm resulted in higher transmission and damage thresholds for the germanium oxide/sapphire fibers. The germanium oxide/sapphire fiber may represent a promising mid-infrared optical fiber delivery system for use in endoscopic applications of the Er:YAG laser requiring a flexible, biocompatible, and robust fiber delivery system for contact tissue ablation.

Aluminum Oxide↗
PubMed1983

Attenuation of the negative chronotropic effect of myelinated fibers by nonmyelinated fibers in the vagus nerve of the rabbit.

In the adult rabbit, both myelinated and nonmyelinated efferent fibers travel from the cervical vagus nerve to the sinoauricular node. The myelinated fibers convey the negative chronotropic effect. The influence of the nonmyelinated fibers was studied. Stimulation (4/sec) of the myelinated fibers, while the compound action potential was monitored continuously, caused a slowing of the heart rate. Subsequent activation of the non-myelinated fibers attenuated this negative chronotropic effect. Stimulation of adrenergic fibers was excluded, based on data from histochemical studies and the effects of blockade of beta- and muscarinic receptors. The lengthening of the RR interval during activation of the myelinated fibers alone was about 3.5 times larger than during activation of all fiber groups. When the conduction of the myelinated fibers was blocked (anodal block), activation of the nonmyelinated fibers did not show any effect on heart rate. It was concluded that the negative chronotropic effect is conducted via small myelinated fibers and that the nonmyelinated fibers modulate the effect of these cardiomotor fibers, without having an effect on heart rate on their own. This modulation is effected either via a presynaptic mechanism on preganglionic fibers or via an interaction with postganglionic neurons. The nonmyelinated fibers constitute a novel peripheral system to modulate heart rate.

Adrenergic Fibers↗
PubMed2002

Baseline dietary fiber intake and colorectal adenoma recurrence in the wheat bran fiber randomized trial.

BACKGROUND: The Wheat Bran Fiber (WBF) trial was a double-blind, high-fiber versus low-fiber phase III intervention trial in which participants were randomly assigned to receive a cereal fiber supplement of either 2.0 g/day or 13.5 g/day to assess whether a high-fiber supplement could decrease risk of recurrent colorectal adenomas. Although no effect of the supplement on polyp recurrence was observed, participants consumed a baseline average of 17.5 grams of fiber per day, which may have been sufficient to protect against adenoma recurrence. Therefore, we examined whether baseline fiber intake affected colorectal adenoma recurrence or modified the effect of treatment group in the WBF trial participants. METHODS: Quartiles of baseline fiber intake were calculated on the basis of the distribution in the study population. Odds ratios (ORs) for adenoma recurrence were calculated using the lowest quartile of fiber intake as the reference. The effect of fiber from specific food sources on adenoma recurrence was also assessed. All statistical tests were two-sided. RESULTS: Adjusted ORs (95% confidence intervals) for adenoma recurrence were 0.79 (0.56 to 1.12), 0.76 (0.54 to 1.08), and 0.83 (0.57 to 1.19) for the second, third, and fourth quartiles, respectively. Fiber from the three primary food sources (fruits; breads, cereals and crackers; and vegetables) had no appreciable effect on adenoma recurrence. Baseline fiber intake also had little effect on adenoma recurrence when the population was stratified by treatment group. In addition, there was no interaction between treatment group and quartile of baseline fiber intake. CONCLUSIONS: No association was found between amount of fiber consumed at baseline and adenoma recurrence in the WBF trial participants. The baseline fiber intake, whether considered as a whole or from specific sources, did not modify the effect of treatment group.

Adenoma↗
PubMed2005

Effect of fiber volume fraction and length on the wear characteristics of glass fiber-reinforced dental composites.

OBJECTIVE: The main objective of this study was to evaluate the wear characteristics of fiber-reinforced dental composites. Variables under investigation include the fiber weight percent added to the matrix as well as fiber length. METHODS: Dental specimens with glass fiber content of 2, 5.1, 5.7, and 7.6 wt% with fiber length of either 1.5 or 3 mm, were prepared by mixing an activated dental resin with commercial glass fibers. The specimens were then tested on a pin on disc setup, where the antagonist disc was manufactured of a similar fiber-reinforced composite with 5.1 wt% fiber and fiber length of 3 mm. The volume loss and coefficient of friction of the specimens was monitored periodically throughout testing. In addition, the wear surfaces of all specimens were evaluated using a scanning electron microscope. RESULTS: The specimens with 5.7 wt% fibers and fiber length of 3 mm performed better in this study compared to all other fiber-reinforced specimens under all load conditions. In fact, this specimen had a comparable wear rate to a particle-filled dental composite. For the fiber lengths considered, increasing the length of the fibers increased the wear resistance of the specimen. The coefficient of friction showed a good correlation with the wear resistance of specimens. SIGNIFICANCE: Fiber-reinforced composites demonstrated a high resistance to wear and may therefore be advantageous for dental applications, where high wear resistance is essential to functionality.

Bisphenol A-Glycidyl Methacrylate↗
PubMed1993

The effects of soluble-fiber polysaccharides on the adsorption of a hydrophobic carcinogen to an insoluble dietary fiber.

Dietary fiber is believed to decrease the incidence of colorectal cancer, but not all types of fiber are equally protective. Dietary fibers may be divided broadly into insoluble and soluble fibers, and there is evidence from animal experiments that the latter not only fails to protect against colorectal cancer but may enhance its development. Adsorption of carcinogens to insoluble dietary fiber in the intestinal tract is one of the mechanisms by which dietary fiber is believed to protect against colorectal cancer. In previous in vitro experiments, we showed that the hydrophobic carcinogen 1,8-dinitropyrene (DNP) adsorbs to insoluble plant cell wall components (insoluble dietary fibers). Soluble polysaccharides (pectic polysaccharides) extracted from the walls of parenchyma cells of dicotyledonous plants were found to maintain DNP in aqueous solutions and decrease its adsorption to insoluble wall components. In the present study, we examined a commercial preparation of pectin and seven other soluble-fiber polysaccharides with diverse structures for their effects on the distribution of DNP. Many of these are used as emulsifiers and stabilizers in the food industry. They all maintained DNP in aqueous solution and decreased its adsorption to alpha-cellulose, which we used as an example of an insoluble dietary fiber. Gum arabic was the most effective and kappa-carrageenan the least. The capacity of the polysaccharides to act as emulsifiers and stabilizers may explain their effects on DNP distribution. The monosaccharide glucose and the disaccharide cellobiose had no effect on the distribution of DNP. These results indicate three possible mechanisms by which soluble-fiber polysaccharides may enhance the development of colorectal cancer. First, because they reduce the ability of insoluble dietary fibers to adsorb hydrophobic carcinogens, more carcinogens may enter the colon maintained in solution than adsorbed onto insoluble fibers. Second, if soluble-fiber polysaccharides are maintaining hydrophobic carcinogens in solution and these polysaccharides are degraded by bacterial enzymes in the colon, then the carcinogens may come out of solution and be deposited onto the mucosal surface of the colon. Third, soluble-fiber polysaccharides may cross the intestinal epithelium and carry with them carcinogens maintained in solution. These studies have important consequences for nutrition, because soluble-fiber polysaccharides represent a common component of foods.

Adsorption↗
PubMed1996

White matter of the cerebellum of the chicken (Gallus domesticus): a quantitative light and electron microscopic analysis of myelinated fibers and fiber compartments.

Low magnification light microscopic examination of the white matter in appropriately stained avian and mammalian cerebellum reveals a mediolateral succession in which areas of large, heavily myelinated fibers alternate with areas containing nearly exclusively small fibers. A large fiber accumulation (LFA) and its medially adjoining small fiber area (SFA) form a fiber compartment, which, with related parts of cortex and central nuclei, constitutes a so-called cerebellar module. The composition and the apparent mediolateral heterogeneity of cerebellar fiber compartments was quantified in the chicken by morphometrical analysis of myelinated fiber profiles in light (LM) and electron (EM) microscopic micrographs. In LM versus EM, approximately 37% of the myelinated fiber population is neglected. This deficit concerns profiles that are smaller than 1.2 micron2 (diameter < 1.2 microns). EM analysis is therefore considered a prerequisite and forms the main part of this study. The myelinated fiber population has a left-skewed log normal size distribution. Ninety-nine percent of the myelinated fibers fall within the range of 0.1 to 20 microns2 (diameter = 0.4-5.0 microns) and 90% are even smaller than 7 micron2 (diameter < 3.0 microns). Small fibers are abundant in both parts of the compartment. Statistical comparisons provide quantitative confirmation of the LM distinction of LFAs and SFAs. It appears, moreover, that, apart from typical LFAs and SFAs, transitional zones rather than sharp borders can be distinguished between the two. The medial border of the LFA appears to be more sharply defined than its lateral border. Distinct mediolateral fluctuations were found with respect to fiber density (166-243 fibers/1,000 microns2), mean profile area (2.4-4.0 microns2), and interspace (31-47%). These differences reflect the contrast between LFA (lower density, larger mean profile area) and SFA (higher density, smaller mean profile area). The interspace discriminates less well between LFA and SFA but is often smaller in the LFA and larger in the SFA. The presented quantitative characteristics of mediolateral heterogeneity in the cerebellar fiber layer can be used as reference for morphometric studies on the different fiber systems of the cerebellar white matter and the functional organization of the compartments.

Animals↗
PubMed1995

The effect of fiber length on the dissolution by macrophages of rockwool and glasswool fibers.

The effect of fiber length on the dissolution of experimental rockwool and commercial glasswood fibers in rat alveolar macrophage (AM) culture and in mere culture medium was studied. The ultrastructure of macrophages after their exposure to fibers and the suitability of macrophage-type cell line P388D1 culture in dissolution studies were also explored. The fiber samples included short (ground) and long (untreated) rockwool and glasswool fibers. The fibers were incubated in rat AM cultures, in P388D1 culture, or in mere culture medium for 4 or 8 days. The dissolution of the fibers was determined by measuring the amounts of silicon (Si), iron (Fe), and aluminum (Al) in the medium. There were no differences in the diameter of the fibers, but a clear difference existed in the length of the short and long fibers. The dissolution of Si, Fe, and Al was more pronounced from experimental rockwool than from commercial glasswool fibers. The dissolution of Si was always greater in mere culture medium than in rat AM culture. Moreover, the dissolution of Si was greater from the long fibers than from the short ones. On the contrary, the dissolution of Fe and Al in AM culture exceeded that in mere culture medium. The dissolution of Si, Fe, and Al from both fibers in P388D1 culture was similar to their dissolution in rat AM culture. The fibers were also effectively phagocytized by the macrophages. The present results together suggest that the intracellular and the extracellular dissolutions of man-made vitreous fibers differ from each other.

Aluminum↗
PubMed1997

Quantitative analyses of myosin heavy-chain mRNA and protein isoforms in single fibers reveal a pronounced fiber heterogeneity in normal rabbit muscles.

A highly sensitive method of reverse-transcriptase polymerase chain reaction (RT-PCR) was established to study myosin heavy-chain (MHC) mRNA isoform expression in single fibers of rabbit limb muscles. In combination with myofibrillar adenosine triphosphatase histochemistry and electrophoretic separation of MHC protein isoforms in fragments of the same fibers, the direct RT-PCR method identified the pMHC20-40 and pMHC24-79 cDNA sequences as being specific to MHCIIb and MHCIId/x isoforms, respectively. In addition, a direct RT-PCR was established for determining relative amounts of MHC mRNA isoforms by using a sequence specific to alpha-skeletal actin as an endogenous reference. Analyses of large amounts of single fibers revealed an unexpected heterogeneity of the fast fiber population with regard to numerous fibers coexpressing MHCIIb and MHCIId/x. Based on quantitative RT-PCR, the percentages of MHCIIb/MHCIId hybrid fibers amounted to approximately 55% in the deep portion of gastrocnemius, to 43% in the adductor magnus, and to 12% in psoas muscle. Moreover, the two MHC mRNA isoforms were nonuniformly distributed along the fiber length. Qualitative RT-PCR detected even higher amounts of hybrid fibers in the three muscles. The percentages of hybrid fibers identified at the protein level were smaller in adductor magnus muscle (25%) and psoas muscle (5%), but equaled that of the mRNA analysis in gastrocnemius muscle (61%). The detection of high amounts of IIBD and IIDB fibers suggested that hybrid fibers represent functional elements within the fiber spectrum of normal muscles. Our observations on hybrid fibers reveal a heterogeneity within the fiber population of normal muscles that has not been realized to date.

Animals↗
PubMed2005

Fiber-type composition of the human jaw muscles--(part 2) role of hybrid fibers and factors responsible for inter-individual variation.

This is the second of two articles about fiber-type composition of the human jaw muscles. It reviews the functional relationship of hybrid fibers and the adaptive properties of jaw-muscle fibers. In addition, to explain inter-individual variation in fiber-type composition, we discuss these adaptive properties in relation to environmental stimuli or perturbations. The fiber-type composition of the human jaw muscles is very different from that of limb and trunk muscles. Apart from the presence of the usual type I, IIA, and IIX myosin heavy-chains (MyHC), human jaw-muscle fibers contain MyHCs that are typical for developing or cardiac muscle. In addition, much more frequently than in limb and trunk muscles, jaw-muscle fibers are hybrid, i.e., they contain more than one type of MyHC isoform. Since these fibers have contractile properties that differ from those of pure fibers, this relatively large quantity of hybrid fibers provides a mechanism that produces a very fine gradation of force and movement. The presence of hybrid fibers might also reflect the adaptive capacity of jaw-muscle fibers. The capacity for adaptation also explains the observed large inter-individual variability in fiber-type composition. Besides local influences, like the amount of muscle activation and/or stretch, more general influences, like aging and gender, also play a role in the composition of fiber types.

Adaptation, Physiological↗
PubMed2000

[Ultrastructure differences of in vitro cotton fiber and native cotton fiber].

Native cotton fiber and in vitro cotton fiber that was induced from cotton ovule callus by suspension culture were observed using transmission electron microscope and scanning electron microscope. The ovule surface on the first day preanthesis was quite smooth. On the anthesis, it had a lot of protuberances. Two kinds of callus, smooth and rough were found. The microfibrils of callus was vertical to the cell long axis and they changed their orientations with the development of the in vitro cotton fiber: from the vertical to shallow spiral and then to parallel to the cell long axis. So was the native cotton fiber. It suggests that in vitro cotton fiber and native cotton fiber have similar development process. Compared with the ovule surface cell, most callus cells had smaller nuclear. During the development of the fiber, the plasm of native cotton fiber was denser than that of in vitro fiber, and it has more cellular organ than in vitro fiber. The cell wall of native cotton fiber was thicker and denser than that of the in vitro cotton fiber too. It suggests that the physiological activity of in vitro cotton fiber was less active than native cotton fiber.

Cotton Fiber↗
PubMedDate not supplied

Analysis of the intermolecular contacts within sickle hemoglobin fibers: effect of site-specific substitutions, fiber pitch, and double-strand disorder.

An atomic model of the sickle hemoglobin (HbS) fiber was synthesized by combining the molecular coordinates of the fiber (obtained from electron microscopy) with atomic coordinates of the sickle hemoglobin double strand (obtained from X-ray crystallography). The model is stereochemically acceptable. The majority of polymerization-sensitive HbS mutants are located at fiber contact sites and the majority of the mutants that do not affect polymerization are not located at contact sites. The residues at intermolecular contacts in the fiber model are reported. We have searched the coordinate space in the vicinity of the EM reconstructions to find models with alternative sets of coordinates that satisfy the mutant data, contain 5-A contacts between double strands, and are stereochemically acceptable. This involved a systematic examination over 297 different models. The alternative fiber models were generated with a range of fiber pitch, double-strand positions, and double-strand polarity. Models which had unacceptably close contacts between atoms, failed to satisfy the mutant data, or did not have 5-A contacts between double strands were considered unacceptable. None of the acceptable alternative fiber models improved the agreement between the polymerization behavior of HbS mutants and their contact site location. However, several models could account for the polymerization data equally well. Residue locations for single-site HbS mutations that could discriminate between alternative fiber models are proposed. The twist of HbS fibers varies in an apparent random manner with an average rotation of 7.8 +/- 2.5 degrees per molecule and a maximum rotation of 16 degrees per molecule. The number of interdouble-strand contacts as a function of fiber twist shows a broad maximum around 9 degrees and may account for the observed range of fiber pitch. This study shows that the upper limit on the fiber twist could result from a loss of axial contacts and repulsive van der Waals interactions between residues involved in interstrand contacts. The loss of axial contacts limits the radial growth of the fiber. In the appendix we analyze the methodology used by I. Cretegny and S. J. Edelstein [(1993) J. Mol. Biol. 230, 733-738] to build a model of the fiber. Our examination reveals shortcomings in the methodology of Cretegny and Edelstein. One result of these shortcomings is that the model synthesized by Cretegny and Edelstein is not stereochemically acceptable because it gives rise to a large number of excessively close (less than 1.4 A) atom-atom contacts, suggesting interpenetration of the molecular envelopes.

Amino Acid Sequence↗
PubMed2003

Implantation sites and fiber diameters affect the rate of degradation in absorbable polydioxanone fibers.

PURPOSE: The purpose of this study is to test the question of whether implantation sites and fiber diameters affect the rate of degradation in absorbable polydioxanone fibers. TYPE OF STUDY: Randomized trial. METHODS: Forty-eight mature rabbits were used. In the first study, using 24 rabbits, a 0.3-mm diameter polydioxanone fiber was implanted into the subcutaneous, intra-articular, and intramedullary sites. Six rabbits each were killed at 1, 2, 3, and 6 weeks after surgery. In the second study, the remaining 24 rabbits were divided into 2 groups of 12 animals each. In group I, a 0.3-mm diameter fiber was implanted into the intramedullary and subcutaneous sites. In group II, a 0.6-mm diameter fiber was implanted in the same manner. In each group, 6 rabbits were killed at 3 and 6 weeks. In each study, all fiber specimens underwent tensile testing to determine the material properties. We defined the percentage of the maximum load of each fiber specimen compared with the normal control value as the I/N ratio. RESULTS: In the first study, the maximum load and the stiffness of the fibers implanted into the intramedullary site were significantly lower than those of the fibers implanted into the other 2 sites at each period (P <.0001). In the second study, the I/N ratio of group I was significantly less than that of group II at each implanted site (P <.0001). CONCLUSIONS: Polydioxanone fiber implanted into the intramedullary site deteriorates more rapidly than that implanted into the subcutaneous and the intra-articular sites. Thin fibers deteriorate more rapidly than thick fibers. Therefore, the degradation of absorbable synthetic fibers intended for use in ligament reconstruction should be evaluated not only in the subcutaneous site but also in the intramedullary site using various diameter fibers.

Absorbable Implants↗
PubMed1998

Free radical activity of synthetic vitreous fibers: iron chelation inhibits hydroxyl radical generation by refractory ceramic fiber.

Synthetic vitreous fibers are in widespread use but the parameters that dictate their carcinogenicity are still a matter of scientific debate. The free radical activities of a panel comprising an asbestos sample and five different respirable synthetic vitreous fiber samples were determined, to address the hypothesis that carcinogenic fibers have greater free radical activity than noncarcinogenic fibers. On the basis of recent inhalation studies, the six samples were divided into three carcinogenic fibers-amphibole asbestos, silicon carbide, and refractory ceramic fiber 1 (designated with the abbreviation RCF 1)-and three noncarcinogenic fibers--man-made vitreous fiber 10 (a glass fiber sample designated with the abbreviation MMVF 10), Code 100/475 glass fiber, and RCF4. All experiments were carried out with equal fiber numbers. Of the two assays of free radical activity used, the plasmid assay of DNA scission showed only amosite asbestos to have free radical activity, while the salicylate assay of hydroxyl activity showed that both amosite asbestos and RCF1 release hydroxyl radicals; silicon carbide fibers had no free radical activity in either of the assays. None of the noncarcinogenic fibers demonstrated free radical activity in either of the assays. The differences in the two assays in demonstrating free radical activity with RCF1 may be due to increased release of Fe from RCF1 under the more acid conditions of the salicylate assay, which was confirmed by the fact that soluble iron caused hydroxylation of salicylate. Presence of an iron chelator inhibited the ability of the RCF1 fibers to cause hydroxylation of salicylate, demonstrating that RCF1 generates hydroxyl radical by Fenton chemical reaction in the same way as amphibole asbestos.

Animals↗
PubMed1976

Myosin-free ghosts of single fibers and an attempt to re-form myosin filaments in the ghost fibers.

With the final aim of replacing myosin in a single muscle fiber, a technique for removing myosin almost completely from single fibers was developed and an attempt to "re-form" thick filaments in the myosin-free ghosts of single fibers was made. Complete removal of myosin from single glycerol-treated rabbit psoas fibers with Hasselbach-Schneider solution was difficult. However, when skinned glycerol-treated fibers were used and 1% (v/v) Triton X-100 was added to the Hasselbach-Schneider solution, almost complete removal of myosin was possible. The myosin-free ghosts of skinned single fibers were very fragile but retained the overall structure. In the ghost fibers, Z-membranes and thin filaments remained. The ghost fibers, after irrigation with myosin, underwent contraction upon addition of Mg-ATP. In the myosin-irrigated fibers, thick filaments were re-formed in lengths from one Z-membrane to the other Z-membrane of a sarcomere, running parallel to the thin filaments. The packing of these two filaments was not good. The isometric tension developed by the irrigated fibers upon addition of mg-ATP was about 10% of the tension developed by untreated fibers. The weak tension developed by irrigated fibers is probably due to the irregular packing of the thick and thin filaments in the fibers. The ghost fibers also contracted, though only slightly, upon addition of Mg-ATP after irrigation with heavy meromyosin.

Adenosine Triphosphate↗
PubMed1998

Compositional and weave pattern analyses of glass fibers in dental polymer fiber composites.

PURPOSE: This study compared weave patterns and glass compositions of five glass fiber materials found in commercial fiber-reinforced dental composites. MATERIALS AND METHODS: A scanning electron microscope (SEM) was used to investigate the woven structure of five glass fiber products, and an energy-dispersive x-ray spectrometer (SEM/EDS) was used to determine the elemental composition of these glass fibers in the bulk and at the surface of the fiber. Five fibers of each product were analyzed. RESULTS: The fiber products were either unidirectional rovings or bidirectional weaves. More precisely, the woven structures were linen weave, twill weave, or twill weave ribbon. SEM/EDS analysis revealed that the composition of the glass fibers was typical for E (electrical)-glass fibers with one exception. One product intended for use in fixed prosthodontics included unidirectional fibers with a composition consistent with a modified high-tensile-strength R-glass. Boron oxide found on the surface of glass fibers would likely contribute to an increased potential for corrosion of fiber-reinforced composite. CONCLUSIONS: The predominant fiber composition in these products is E-glass. Because the degree of hydrolytic stability of polymer-fiber composites over time may lead to material failure in permanent restorations, this property should be investigated further.

Acrylic Resins↗
PubMed1996

Comparative analysis of adenovirus fiber-cell interaction: adenovirus type 2 (Ad2) and Ad9 utilize the same cellular fiber receptor but use different binding strategies for attachment.

We have analyzed the binding of adenovirus (Ad) serotypes from subgroups B, C, and D through fiber-virus and fiber-fiber cross-competition experiments. Since viruses in these distinct subgroups display markedly different tropisms, it was unexpected that the subgroup C viruses Ad2 and 5 and the subgroup D virus Ad9 cross-competed for the same cellular fiber receptor. The subgroup B serotype Ad3 recognized a receptor distinct from the Ad2, 5, and 9 fiber receptor. However, despite sharing the same fiber receptor, Ad2 and Ad9 displayed markedly different binding characteristics that appeared to result from direct Ad9 binding to cells via alpha(v)-integrins. Unlike Ad2, Ad9 binding to many cell lines was not abrogated by competition with the fiber 9 knob (F9K). Ad9 binding to fiber receptor-deficient cells was blocked by a monoclonal antibody to alpha(v)-integrins. In contrast, Ad9 binding to alpha(v)-deficient cells that express fiber receptor was blocked by F9K. Transfection of an alpha(v)-integrin-deficient cell line with a plasmid that expresses alpha(v)beta5 resulted in Ad9 binding that was not significantly blocked by F9K but was blocked with a combination of F9K and penton base. These results imply that the shorter length of fiber 9 (11 nm) relative to fiber 2 (37 nm) permits fiber-independent binding of Ad9 penton base to alpha(v)-integrins. The difference in fiber length may explain the different binding characteristics and tissue tropisms of each virus despite both utilizing the same fiber and penton base receptors.

Adenoviruses, Human↗
PubMed1987

Fiber types and fiber diameters in canine respiratory muscles.

In the present study, we measured fiber types and fiber diameters in canine respiratory muscles and examined regional variation within the diaphragm. Samples of eight diaphragm regions, internal intercostals, external intercostals, transversus abdominis, and triceps brachii were removed from eight adult mongrel dogs, frozen, and histochemically processed for standard fiber type and fiber diameter determinations. The respiratory muscles were composed of types I and IIa fibers; no IIb fibers were identified. Fiber composition differed between muscles (P less than 0.0001). Normal type I percent (+/- SE) were: diaphragm 46 +/- 2, external intercostal 85 +/- 6, internal intercostals 48 +/- 3, transversus abdominis 53 +/- 1, and triceps 33 +/- 7. The diaphragm also contained a type I subtype [6 +/- 1% (SE)] previously thought only to occur in developing muscle. Fiber composition varied between diaphragm regions (P less than 0.01). Most notably, left medial crus contained 64% type I fibers. Fiber size also varied systematically among muscles (P less than 0.025) and diaphragm regions (P less than 0.0005). External intercostal fiber diameter was largest (47-50 microns) and diaphragm was smallest (34 microns). Within diaphragm, crural fibers were larger than costal (P less than 0.05). We conclude that there are systematic differences in fiber composition and fiber diameter of the canine respiratory muscles.

Analysis of Variance↗