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PubMed1995

[Morphometric study of chorda tympani-derived fibers along their course in the lingual nerve].

The topographical organization of chorda tympani-derived fibers (Ch-fibers) was investigated macroscopically and histologically along their entire course through the lingual nerve in 81 adult Japanese cadavers (113 sides), in order to obtain basic data to explain the taste disturbance occurring after oral anesthesia. Ch-fibers frequently (approx. 80%) merged and intermingled with nerve bundles composed of fibers of the lingual nerve proper (L-fibers) above the level of the mandibular foramen (intermingled type). However, on 23 sides (20.4%) the Ch-fibers could be separated under a stereomicroscope from the L-fiber bundles during their course behind the oral cavity (separated type). Moreover, on 12 of the 23 sides, the Ch-fibers were clearly separated from the L-fibers, since the Ch-fibers formed an independent nerve bundle attached to the surface of the L-fiber bundles throughout almost their entire course to the tongue. Irrespective of whether they were intermingled or separated, however, the Ch-fibers traveled downward, maintaining their superficial and posterolateral topographical organization in the lingual nerve. In 8 of the 12 clearly separated cases, the perimeter of the myelinated fibers was analyzed at three levels: the hard palate, the mandibular foramen and immediately above the angle of the mandible. At each level, the perimeter spectrum of Ch-fibers was significantly smaller (mean: 16.6 +/- 5.4 microns, e.q. at the level of the mandibular foramen) than that of the L-fibers (mean: 20.2 +/- 6.2 microns, at the same level) (p < 0.01). Moreover, the lingual nerve consistently had 2-3 buccal branches supplying the lining of the oral cavity posterior to the internal oblique line of the mandibular ramus. These buccal branches did not contain Ch-fibers, but were composed of only L-fibers, possibly including pain fibers. These observations suggest that physicians performing nerve block to and around the mandibular foramen tend to regard the inferior alveolar nerve and the lingual nerve as targets of the block, irrespective of whether or not this is intended, since the buccal branch of the lingual nerve should also be anesthetized in such cases. Moreover, local anesthetics seem to have a rapid effect on Ch-fibers, because of their superficial position in the lingual nerve and their smaller diameter than L-fibers. Consequently, Ch-fibers along the lingual nerve seem to be easily damaged by local anesthesia of the oral region. Greater care should therefore be exercised to avoid producing a taste disturbance when performing oral anesthesia in clinical practice.

Adult↗
PubMed1996

Ubiquitous fiber exposure in selected sampling sites in Europe.

OBJECTIVES: This study evaluates personal exposure to respirable inorganic and organic fibers during normal human lifetimes and assesses the order of magnitude of the contribution of inorganic fibers other than asbestos to total fiber exposure from man-made and natural sources. METHODS: Four groups (suburban schoolchildren, rural retired persons, office workers, and taxi drivers), with five persons per group, were monitored for 24 h four times during one year. Personal sampling pumps collected airborne dust on gold-precoated Nuclepore filters. The fibers were analyzed for fiber sizes specified by the World Health Organization. RESULTS: The geometric mean concentrations ranged from 9000 fibers.m-3 (office workers) to 20000 fibers.m-3 (schoolchildren) for organic fibers, and from 600 fibers.m-3 (taxi drivers) to 4000 fibers.m-3 (schoolchildren) for gypsum fibers. For other inorganic fibers the concentrations were around 5000 fibers.m-3. The contribution of fibers with an elemental composition similar to that of man-made vitreous fibers (MMVF) was less than about one-quarter of the content of other inorganic fibers. The fiber size distributions were uniform across the groups, and the organic fibers were the longest and thinnest nonasbestos fibers. CONCLUSIONS: Lifetime exposure to fibers can be ranked as organic fibers > other inorganic fibers > fibers with an elemental composition similar to MMVF > MMVF. Information on the biological effects of fibers is difficult to interpret for use in assessing the health risk from exposure to low levels of ubiquitous fibers, and there is a lack of knowledge on the effects of organic fibers.

Adolescent↗
PubMed1993

Growth cone choices of Drosophila motoneurons in response to muscle fiber mismatch.

In Drosophila embryos, each motoneuron is accurately matched to one or more singly identifiable muscle fibers. In this article we altered the number and pattern of the embryonic muscle fibers using genetic, heat shock, and laser ablation methods to test whether motoneuron growth cones are able to recognize specific targets. The choices made by two motoneurons were assayed using both intracellular dye fills and immunocytochemistry. The motoneurons RP1 and RP3 have nearly identical central and peripheral axonal trajectories. However, RP3 innervates the two most ventral longitudinal muscle fibers, 7 and 6, while RP1 grows past these fibers to innervate only muscle fiber 13. In rhomboid mutants muscle fiber 7 does not develop. Despite the loss of one of its targets, RP3 faithfully innervated the remaining muscle fiber 6 in over 80% of the observed cases. Furthermore, neuron RP1 accurately innervated muscle fiber 13, although it traversed one fiber fewer to reach it. Laser ablation of muscle fiber 7 confirmed the target choices shown by the motoneurons. In numb mutants, multiple muscle fibers, including 7, 13, and 12, fail to develop. This allowed us to test whether fibers distal to the target are involved in muscle fiber recognition, possibly by halting the growth cone advance. In mutant embryos, RP3 innervated muscle fiber 6 at the same frequency regardless of the absence of the distal muscle fiber 13. By contrast, RP1, which had lost its target entirely, frequently failed to innervate any muscle fiber during the period examined. Finally, muscle fiber 13 can be duplicated in wild-type embryos by means of a brief heat pulse during myogenesis. Presented with two targets, RP1 innervated both fibers in each case examined, while RP3 synapsed with muscle fibers 7 and 6 normally. Neuron-specific antibodies revealed that the embryonic growth cone choices were not transient, but persisted into the larval neuromuscular projections. These results indicate that each motoneuron growth cone has a primary target preference, which is retained even when the numbers of the muscle fibers, and therefore their relative positions, are altered. We therefore suggest that synaptic recognition by Drosophila motoneuron growth cones relies on unique features of the individual muscle fibers.

Animals↗
PubMed1997

Capsaicin-sensitive A delta fibers in cat tooth pulp.

How close a correlation there is between the conduction velocity and receptive properties of pulpal nerve fibers is still unclear. Our specific aims were to confirm whether: (1) capsaicin affects not only polymodal C fibers but A delta fibers as well, and (2) A alpha polymodal nociceptors exist in the tooth pulp. A total of 139 functional single cat tooth pulp nerve fibers was isolated for analysis, of which 21 were A beta, 37 C, and 81 A delta fibers. The A delta fibers were divided into two groups: One (n = 38) consisted of those fibers whose conduction velocities were more than 2.0 m/s both inside and outside the tooth pulp, and the other (n = 43) consisted of those fibers whose intrapulpal conduction velocities were less than 2.0 m/s, with extrapulpal conduction velocities greater than 2.0 m/s. We used 82 fibers to record the neural response following the topical application of capsaicin for 60 min at increasing concentrations (1 nM, 100 nM, 10 muM) through thin dentin. Six of 25 slow A delta, 10/20 C, and no A beta (0/11) or fast A delta (0/26) fibers responded to 1 nM or 100 nM of capsaicin. When the three concentrations of capsaicin solution were applied in turn, the electrical threshold and latency of A beta and fast A delta fibers did not change, whereas those of slow A delta and C fibers gradually increased. In 0/11 A beta, 0/26 fast A delta, 13/25 slow A delta, and 18/20 C fibers, the conduction was blocked reversibly or irreversibly following the application of 10 muM of capsaicin. The amplitude of the late component of antidromic action potential of fast A delta fibers decreased after the capsaicin application. No neural discharge could be recorded from 19 (3 A beta, 5 fast A delta, 6 slow A delta, and 5C) fibers following the application of a single high concentration of capsaicin (10 muM). A single low concentration of capsaicin (100 nM) activated only some slow-conducting fibers (0/4 A beta, 0/4 FA delta, 3/6 SA delta and 4/6 C). Response properties recorded from the remaining 18 fibers (3 A beta, 3 fast A delta, 6 slow A delta, and 6 C) were not changed following the application of the control vehicle. These results confirm that a low concentration of capsaicin has an excitatory effect on the response of slow pulpal A delta as well as C fibers, and that a high concentration of capsaicin blocks the conduction of slow A delta and C fibers as well as the terminals of fast A delta fibers in the pulp.

Animals↗
PubMed2002

Distribution of myelinated and unmyelinated nerve fibers and their possible role in blood flow control in crotaline snake infrared receptor organs.

We used transmission electron microscopic montages to examine the composition of nerve bundles serving the infrared pit organs of two species of crotaline snakes, Agkistrodon blomhoffii and A. brevicaudus. In the three main bundles, the myelinated fibers totaled 2,200-3,700, and unmyelinated fibers 2,400. We also discovered for the first time two accessory bundles composed almost entirely of unmyelinated fibers running alongside the main bundles, containing an average total of 3,300 unmyelinated fibers vs. an average of 10 myelinated fibers. Thus, the average total of unmyelinated fibers was nearly twice that of myelinated fibers. To study the nature of the unmyelinated fibers, we did double staining immunohistochemistry with antibodies for substance P (SP) and vasoactive intestinal polypeptide (VIP) in combination with and without capsaicin pretreatment. SP and VIP immunoreactive varicose fibers ran straight toward the center of the pit membrane in parallel with arterioles and venules, and also formed a dense network around the periphery of the membrane. There were three types of fibers: fibers containing only SP, fibers containing only VIP, and fibers containing both peptides. SP-only fibers were distributed singly throughout the pit membrane and in small bundles around the periphery. SP+VIP fibers were distributed sparsely in the pit membrane and around its periphery. VIP-only fibers were distributed throughout the pit membrane and were of smaller diameter than SP and SP+VIP fibers. After treatment with capsaicin, most of the three types of varicose fibers disappeared from the central part of the pit membrane, but those around the periphery remained unaffected. The capsaicin-sensitive fibers may be unmyelinated sensory types, and the unaffected ones may be autonomic nerve fibers.

Agkistrodon↗
PubMed2004

Two fast-type fibers in claw closer and abdominal deep muscles of the Australian freshwater crustacean, Cherax destructor, differ in Ca2+ sensitivity and troponin-I isoforms.

One type of fast fiber and two types of slow (slow-twitch, S1 and slow-tonic, S2) fibers are found in decapod crustacean skeletal muscles that differ in contractile properties and myofibrillar protein isoform compositions. In this study the structural characteristics, protein isoform compositions, and Ca2+-activation properties of fast fibers in the claw closer (F1) and abdominal deep flexor (F2) muscles of Cherax destructor were analyzed. For comparison, myofibrillar protein isoform compositions of slow (long-sarcomere) fibers from claw and abdomen were also determined; our results indicate that the slow fibers in the claw closer were the slow-twitch (S1) type and those in the abdominal superficial flexor were primarily slow-tonic (S2) type. F1 fibers had shorter resting sarcomere lengths (2.93 microm in unstretched fibers and 3.06 microm in stretched fibers) and smaller fiber diameter (256 microm) than F2 fibers (sarcomere lengths 3.48 microm in unstretched and 3.46 microm in stretched; 747 microm diameter). Moreover, F1 fibers showed a narrower range in sarcomere lengths than F2 fibers (2.81 to 3.28 microm vs. 2.47 to 4.05 micro m in unstretched fibers). Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblotting showed that the fast fibers from claw and abdomen differed in troponin-I composition; F1 fibers expressed two isoforms of troponin-I (TnI1 and TnI2) in approximately equal amounts, whereas F2 fibers expressed primarily TnI3 and lower levels of TnI1. F1 fibers were more sensitive to Ca2+, as shown by higher pCa values at threshold activation (pCa(10)=6.50+/-0.07) and at 50% maximum force (pCa(50)=6.43+/-0.07) than F2 fibers (pCa(10)=6.12+/-0.04 and pCa(50)=5.88+/-0.03, respectively). F1 fibers also had a greater degree of co-operativity in Ca2+ activation, as shown by a higher maximum slope of the force-pCa curve (n(Ca)=12.98+/-2.27 vs. 4.34+/-0.64). These data indicate that there is a greater fast fiber-type diversity in crustacean muscles than was previously supposed. Moreover, the differences in activation properties suggest that the TnI isoform composition influences the Ca2+ sensitivity of the contractile mechanism.

Animals↗
PubMed1996

Responses of auditory nerve fibers of the unanesthetized decerebrate cat to click pairs as simulated echoes.

1. To elucidate the peripheral contribution to "echo" processing in the auditory system, we examined the characteristics of auditory nerve responses to click-pair stimuli in unanesthetized, decerebrate cats. We used equilevel click pairs at peak levels of 45, 65, and 85 dB SPL re 20 microPa. The interclick intervals ranged from 1 to 32 ms. This study reports results from 78 auditory nerve fibers in 7 cats. The fibers were divided into 2 groups: 33 low- and 45 high-spontaneous rate (SR), with SRs less than and > or = 20 spikes/s, respectively. A method was introduced to quantify the second-click response, and its recovery was examined as a function of the interclick interval. 2. In general, auditory nerve fibers showed a gradual recovery of the second-click response as interclick interval was increased. Noticeable differences in the second-click response recovery functions emerged among fiber populations that were related to the SR. Low-SR fibers showed little change in the recovery functions of the second-click response as the click level was increased from 45 to 85 dB SPL. In contrast, high-SR fibers showed slower recoveries with increasing click level from 45 to 85 dB SPL. At 45 and 65 dB SPL, the recovery functions of the two SR groups were similar. At 85 dB SPL, high-SR fibers exhibited slower recovery than low-SR fibers, regardless of fiber characteristic frequency. The interclick intervals at 50% second-click response ranged from 1 to 6 ms (mean, 1.4 ms) among low-SR fibers. The interclick intervals at 50% second-click response for high-SR fibers, whereas similar to those for the low-SR fibers at 45 and 65 dB SPL, ranged from 2 to 16 ms (mean, 3 ms) for high-SR fibers, at 85 dB SPL. 3. We also examined auditory nerve compound action potentials (CAPs) evoked by click-pair stimuli for various interclick intervals and click levels. With increasing interclick interval, the amplitude of the second-click CAP increased, and with increasing level, the second-click CAP showed slower recovery. At 45 dB SPL, the recovery functions of the second-click CAP were similar to those of the high- and low-SR fibers. At higher levels, the CAP exhibited lower second-click response values than both high- and low-SR fiber populations for interclick intervals < 4-8 ms. At 85 dB SPL, as interclick interval increased, between 8 and 16 ms, the CAP second-click response converged with that of the high-SR fibers, and by 32 ms, the second-click response values were similar for the CAP, high- and low-SR fibers. 4. The present results are consistent with those of forward masking studies at the level of the auditory nerve in that both demonstrate a short-term reduction of the neural responses. However, the two results differ in that we observed that high-SR fibers exhibited slower recovery than low-SR fibers in response to click-pair stimuli, opposite of the trend observed in the forward masking studies of responses to pure-tone bursts. 5. The present results on auditory nerve fiber responses to click-pair stimuli provide a reference for comparison with responses of central auditory neurons to similar stimuli. This information should serve to elucidate the peripheral contribution to the processing of echoes in the auditory system.

Acoustic Stimulation↗
PubMed1985

Peptide-containing nerve fibers in the stomach wall of rat and mouse.

Peptide-containing nerve fibers were found to be numerous in the glandular stomach of the rat and mouse. The immunoreactive neuropeptides demonstrated included vasoactive intestinal polypeptide (VIP), peptide histidine isoleucine (PHI), gastrin-releasing peptide (GRP), substance P (SP), enkephalin, somatostatin, cholecystokinin, and neuropeptide Y (NPY). The density and distribution of the various peptide-containing fibers did not differ overtly between the pyloric and oxyntic gland areas except for the GRP fibers, which were fewer in the pyloric than in the oxyntic mucosa. The entire VIP nerve fiber population was found to also contain PHI. Immunoreactive NPY was found to occur in the VIP/PHI fibers (VIP/PHI/NPY fibers) in the smooth muscle and intramural ganglia of both rat and mouse and in the mucosa of the mouse. Mucosal VIP/PHI fibers in the rat did not contain any NPY-like material. Perivascular NPY fibers in both species and mucosal NPY fibers in the rat did not contain VIP or PHI. The mucosa harbored numerous GRP fibers and VIP/PHI (rat) or VIP/PHI/NPY (mouse) fibers, and a modest number of NPY (rat) and SP fibers. In the submucosa the peptide-containing nerve fibers were found mainly in the ganglia and around blood vessels. Blood vessels received a rich supply of NPY fibers; the number of perivascular VIP/PHI, GRP, and SP fibers was much lower by comparison. The smooth muscle and myenteric ganglia harbored not only VIP/PHI/NPY, GRP, and SP fibers but also enkephalin, somatostatin, and cholecystokinin fibers. Gastrin-releasing peptide, VIP/PHI/NPY, SP, and enkephalin nerve cell bodies occurred in the myenteric ganglia. As studied in the rat, vagal denervation did not affect the density and distribution of the various peptide-containing nerve fibers. After sympathectomy, mucosal and perivascular NPY fibers disappeared. The other types of peptide-containing nerve fibers were not affected.

Animals↗
PubMed1994

Human adenovirus type 41 contains two fibers.

DNA sequencing of the subgroup F human adenovirus serotype 41 (TAK, Ad41) fiber gene revealed the presence of two adjacent open reading frames encoding information for proteins with molecular weights of 60.6 kDa and 41.4 kDa (Pieniazek, et al; Nucleic Acids Res. 18: p. 1901, 1990). In this paper, various approaches were used to characterize the two proteins and determine whether both fibers were expressed in infected cells as well as on viral particles. We initially used a reverse transcriptase-polymerase chain reaction with primers for the short and long fiber genes to amplify mRNA from Ad41 infected HEp-2 cells at 48 h post-infection. Two distinct DNA bands; one slightly larger than 1.1 kbp and the other at about 1.7 kbp were identified. Second, we used polyclonal anti-Ad41 virion and monoclonal anti-Ad5 fiber antibodies to demonstrate that at both 24 and 36 h post-infection, Ad41 expressed two fiber proteins of the expected size. Specifically, by SDS-PAGE, one fiber (short) had a molecular weight of 40 kDa, while the other (long) had a molecular weight of 60 kDa. Third, by electron microscopy, two sizes of fibers were released from CsCl purified virions, both having a characteristic adenovirus morphology, with a knob at one end. The long fiber measured 315A in length and the short fiber was 250A long. These measurements are consistent with the two Ad41 fibers being encoded by the above open reading frames. We also performed a computer search to compare fiber sequences from other human adenovirus serotypes with that of the Ad41 short and long fiber proteins. The primary structure of both Ad41 fibers were found to be similar in that they contained tail, shaft and knob regions. Further, the tail region of both fibers (amino acids 1-42) showed a 74% overall homology to each other and contained the Ad conserved sequence NH2-F-N-P-V-Y-P-Y-COOH. An interesting difference, however, was observed in the shaft region where the long fiber (amino acids 43-389) had twenty-two 16-amino acid repeat motifs, while the short fiber (amino acids 43-233) had only twelve. Finally, we noted that the long fiber knob region was about 15% longer than that of the short fiber, and showed little overall homology. In conclusion, human adenovirus subgroup F (type 41) virions appear to differ from those of all other human adenoviruses (subgenera A-E) in that they contain two fiber genes and correspondingly, two different sized fibers.(ABSTRACT TRUNCATED AT 400 WORDS)

Adenoviruses, Human↗
PubMed1995

Human adenovirus serotypes 3 and 5 bind to two different cellular receptors via the fiber head domain.

The adenovirus fiber protein is responsible for attachment of the virion to cell surface receptors. The identity of the cellular receptor which mediates binding is unknown, although there is evidence suggesting that two distinct adenovirus receptors interact with the group C (adenovirus type 5 [Ad5]) and the group B (Ad3) adenoviruses. In order to define the determinants of adenovirus receptor specificity, we have carried out a series of competition binding experiments using recombinant native fiber polypeptides from Ad5 and Ad3 and chimeric fiber proteins in which the head domains of Ad5 and Ad3 were exchanged. Specific binding of fiber to HeLa cell receptors was assessed with radiolabeled protein synthesized in vitro, and by competition analysis with baculovirus-expressed fiber protein. Fiber produced in vitro was found as both monomer and trimer, but only the assembled trimers had receptor binding activity. Competition data support the conclusion that Ad5 and Ad3 interact with different cellular receptors. The Ad5 receptor distribution on several cell lines was assessed with a fiber binding flow cytometric assay. HeLa cells were found to express high levels of receptor, while CHO and human diploid fibroblasts did not. A chimeric fiber containing the Ad5 fiber head domain blocked the binding of Ad5 fiber but not Ad3 fiber. Similarly, a chimeric fiber containing the Ad3 fiber head blocked the binding of labeled Ad3 fiber but not Ad5 fiber. In addition, the isolated Ad3 fiber head domain competed effectively with labeled Ad3 fiber for binding to HeLa cell receptors. These results demonstrate that the determinants of receptor binding are located in the head domain of the fiber and that the isolated head domain is capable of trimerization and binding to cellular receptors. Our results also show that it is possible to change the receptor specificity of the fiber protein by manipulation of sequences contained in the head domain. Modification or replacement of the fiber head domain with novel ligands may permit adenovirus vectors with new receptor specificities which could be useful for targeted gene delivery in vivo to be engineered.

Adenoviruses, Human↗
PubMed2005

Performance and safety of holmium: YAG laser optical fibers.

BACKGROUND AND PURPOSE: Lower-pole ureteronephroscopy requires transmission of holmium:YAG energy along a deflected fiber. Current ureteroscopes are capable of high degrees of deflection, which may stress laser fibers beyond safe limits during lower-pole use. We hypothesized that optical fiber and safety measures differ among manufacturers. MATERIALS AND METHODS: Small (200-273-microm) and medium-diameter (300-400-microm) Ho:YAG fibers were tested in a straight and 180 degrees bent configuration. Energy transmission was measured by an energy detector. Fiber durability was assessed by firing the laser in sequentially tighter bending diameters. The fibers were bent to 180 degrees with a diameter of 6 cm and run at 200- to 4000-mJ pulse energy to determine the minimum energy required to fracture the fiber. The bending diameter was decreased by 1-cm increments and testing repeated until a bending diameter of 1 cm was reached. The maximum deflection of the ACMI DUR-8E ureteroscope with each fiber in the working channel was recorded. The flow rate through the working channel of the DUR-8E was measured for each fiber. RESULTS: The mean energy transmission differed among fibers (P < 0.001). The Lumenis SL 200 and the InnovaQuartz 400 were the best small and medium-diameter fibers, respectively, in resisting thermal breakdown (P < 0.01). The Dornier Lightguide Super 200 fractured repeatedly at a bend diameter of 2 cm and with the lowest energy (200 mJ). The other small fibers fractured only at a bend diameter of 1 cm. The Sharplan 200 and InnovaQuartz Sureflex 273T were the most flexible fibers, the Lumenis SL 365 the least. The flow rate was inversely proportional to four times the power of the diameter of the fiber. CONCLUSIONS: Optical performance and safety differ among fibers. Fibers transmit various amounts of energy to their cladding when bent. During lower-pole nephroscopy with the fiber deflected, there is a risk of fiber fracture from thermal breakdown and laser-energy transmission to the endoscope. Some available laser fibers carry a risk of ureteroscope damage.

Aluminum↗
PubMed1998

Velocity, force, power, and Ca2+ sensitivity of fast and slow monkey skeletal muscle fibers.

In this study, we determined the contractile properties of single chemically skinned fibers prepared from the medial gastrocnemius (MG) and soleus (Sol) muscles of adult male rhesus monkeys and assessed the effects of the spaceflight living facility known as the experiment support primate facility (ESOP). Muscle biopsies were obtained 4 wk before and immediately after an 18-day ESOP sit, and fiber type was determined by immunohistochemical techniques. The MG slow type I fiber was significantly smaller than the MG type II, Sol type I, and Sol type II fibers. The ESOP sit caused a significant reduction in the diameter of type I and type I/II (hybrid) fibers of Sol and MG type II and hybrid fibers but no shift in fiber type distribution. Single-fiber peak force (mN and kN/m2) was similar between fiber types and was not significantly different from values previously reported for other species. The ESOP sit significantly reduced the force (mN) of Sol type I and MG type II fibers. This decline was entirely explained by the atrophy of these fiber types because the force per cross-sectional area (kN/m2) was not altered. Peak power of Sol and MG fast type II fiber was 5 and 8.5 times that of slow type I fiber, respectively. The ESOP sit reduced peak power by 25 and 18% in Sol type I and MG type II fibers, respectively, and, for the former fiber type, shifted the force-pCa relationship to the right, increasing the Ca2+ activation threshold and the free Ca2+ concentration, eliciting half-maximal activation. The ESOP sit had no effect on the maximal shortening velocity (Vo) of any fiber type. Vo of the hybrid fibers was only slightly higher than that of slow type I fibers. This result supports the hypothesis that in hybrid fibers the slow myosin heavy chain would be expected to have a disproportionately greater influence on Vo.

Animals↗
PubMed1975

Retrograde changes in the nerve fibers of the dorsal spinocerebellar and spinocervical tracts in the cat.

The potential retrograde changes that occur in the proximal segment of transected nerve fibers found in the region of the spinocervical tract (SCT) and in the region of the dorsal spinocerebellar tract (DSCT) after unilateral dorsolateral column (DLC) lesions were studied in kittens and adult cats. Nerve fibers in the region of the SCT and DSCT in the spinal segments caudal to the lesion were studied in transverse sections of Epon embedded material that had been fixed by vascular perfusion with a 4% buffered paraformaldehyde solution, post-fixed in osmium tetroxide, and stained with Azur II-methylene blue. T8 level DLC lesions in the 10-week old kitten resulted in a 14 to 25% decrease in mean fiber diameter in the SCT fibers (larger than or equal to 5 mu) of the T13 level. Retrograde fiber degeneration occurred in the small and large caliber fibers of the DSCT. A 15 to 30% decrease in mean fiber diameter occurred in the DSCT fibers (greater than or equal to 5 mu). The fiber density of the DSCT decreased by 20 to 30% and this could be correlated with a 20% loss of class C neurons (Loewy, '70) and a severe atrophy affecting the remaining 80% of the surviving class C neurons in the L3 segment. Mid-cervical DLC lesions in the 10-week old kitten resulted in a 10% decrease in mean fiber diameter in the SCT fibers (less than or equal to 5 mu), a 15% decrease in mean fiber diameter in the DSCT fibers (less than or equal to 5 mu), and no change in fiber density could be determined despite the finding that these lesions produced about a 10% loss of class C neurons. A T1 level lesion in a 20-week old kitten produced no change in the SCT fibers suggesting that the changes seen in the 10-week old kitten after midcervical lesions were probably age-dependent changes. A 20% decrease in mean fiber diameter (less than 5 mu) and a 6% decrease in fiber density was detected in the DSCT. T13-L1 level DLC lesions in the adult cats resulted in degeneration of some of the large and medium size fibers in the DSCT which was most noticeable at 20 to 25 days after surgery. DLC lesions did not cause degenerative changes in the SCT fibers 5 to 25 days after surgery.

Animals↗
PubMed1992

Design and control of the head retractor muscle in a turtle, Pseudemys (Trachemys) scripta: I. Architecture and histochemistry of single muscle fibers.

We are using the head retractor muscle (RCCQ) of a turtle, Pseudemys scripta, to analyze the neuromuscular mechanisms by which organisms vary the force and timing of muscle contraction. Previously we demonstrated that RCCQ comprises three histochemically defined fiber types: fast glycolytic (Fg), fast oxidative glycolytic (FOG), and slow oxidative (SO). In the present paper we report the 1) architectural features of single muscle fibers in RCCQ, including their lengths, diameters, and taper characteristics, 2) histochemical profiles of single muscle fibers, and 3) quantitative relations between our architectural and histochemical variables. Single fibers in RCCQ exhibit an order of magnitude variation in length (4-60 mm). Approximately 40% span the full muscle. The remaining fibers generally attach to bone or tendon at one end, and the other end tapers intramuscularly; rarely a fiber may taper at both ends. The maximum (untapering) diameters of single fibers are bimodally distributed, forming two diameter classes. Fibers also vary in the percentage of their total length that tapers and in the shape of the tapering region. Large diameter muscle fibers generally are longer and have shorter, more blunted tapers than small diameter fibers. The large diameter fibers are almost all Fg types; these fibers have a median diameter of 59.3 microns, and they account for approximately 60% of total fibers in RCCQ. FOG and SO fibers generally have small diameters (median: 32.5 microns and 35.8 microns), and they typically account for 30% and 10% of total fibers. We use these relations to draw inferences about the attachments and architecture of glycolytic (Fg) and oxidative (FOG, SO) fiber types. Taken together, our data suggest that single muscle fibers in RCCQ may be architecturally as well as histochemically specialized to perform different roles in head retraction. In the accompanying paper we report the efferent innervation of these fibers and consider some of the neural control problems posed by these diverse fiber types.

Animals↗
PubMed2000

Growth- and breed-related changes of muscle fiber characteristics in cattle.

The objective of this study was to investigate the growth- and breed-related changes of muscle fiber characteristics in cattle and their importance to meat quality. Four cattle breeds with different growth impetus and muscularity were reared and slaughtered under experimental conditions. German Angus as a beef type, Galloway as a hardy type, Holstein Friesian as a dairy type, and double-muscled Belgian Blue as an extreme type for muscle growth were used. Between 5 and 17 bulls of each breed were slaughtered at 0, 2, 4, 6, 12, 18, and 24 mo of age. Muscle fiber traits were determined and classified by computerized image analysis, and several measures of meat quality were also determined, including shear force value, meat color, and i.m. fat content. The postnatal growth of semitendinosus muscle in cattle was characterized by a nearly 10-fold increase of muscle fiber area from birth to 24 mo of age. In the first few months after birth, a transformation of type IIA fibers into IIB fibers was found, whereas type I fibers were nearly unaffected by age. The apparent total muscle fiber number of semitendinosus muscle did not increase during postnatal life. These results confirm that the fiber number is determined in embryonic development. Throughout the study, the double-muscled Belgian Blue (BBDM) bulls had almost twice the fiber number of the other breeds, emphasizing a more extensive hyperplasia of muscle fibers during embryonic development in BBDM compared with the other three breeds. The apparent number of type I fibers was, however, not affected by breed, which suggests that the additional fibers found in BBDM postnatally were type IIB and IIA fibers. We did not find significant differences in muscle fiber total number, muscle fiber type frequencies, or meat quality characteristics among breeds, with the exception of BBDM. Having pooled the four breeds, paler meat was related to a higher frequency of type IIB fibers, a lower area of type IIA and type I fiber, and a higher total muscle fiber number. These findings based on data of double muscling give us some hints for biological causes for the variation of meat quality. Further investigation, in particular within each breed, is necessary to identify the superior fiber traits for bovine meat production.

Animal Husbandry↗
PubMed1992

Content and composition of dietary fiber in 117 frequently consumed foods.

Twenty-three fruits, 33 vegetables, 41 grain products, 7 legumes, 4 nuts, and 9 miscellaneous foods were analyzed by an accurate chemical method to determine their dietary fiber content and composition. The mean (+/- standard deviation) dietary fiber content of fruits was 1.4 +/- 0.7 g/100 g (fresh weight); of vegetables, 2.0 +/- 0.8 g; of 32 refined grains (less than 5% fiber), 2.3 +/- 1.0 g; of legumes, 4.0 +/- 0.7 g; and of nuts, 6.4 +/- 2.1 g; the dietary fiber content of nine higher-fiber grains (greater than 5%) was variable. The soluble fiber fraction averaged 23% of the total fiber in refined grains, 3% in nuts, and 13% to 20% in the other food groups. Dietary fiber composition of every food group was heterogenous. Pectin, which was negligible in grains, constituted approximately 15% to 30% of the fiber in fruits, vegetables, legumes, and nuts. Hemicelluloses composed about half of the total fiber in grains, and approximately 25% to 35% of total fiber in other foods. Cellulose was one third or less of the total fiber in most foods, except for legumes, in which it was about one half. Values for total dietary fiber content generally agree with those reported previously. The soluble fiber fraction was lower than what has been reported because the distribution of total fiber between the soluble and insoluble fractions is determined by the method of analysis. The analyses used in this study demonstrated that the concentration of dietary fiber in many frequently consumed foods is 1% to 3%. The generally similar fiber concentrations of food within a group--fruits, vegetables, refined grains, and legumes--suggest that an average value for the fiber concentration in that group can be used to rank food intakes and histories into low, medium, or high dietary fiber contents.

Dietary Fiber↗
PubMed1984

Structure and distribution of neuromuscular junctions on slow muscle fibers in the frog.

Neuromuscular junctions on slow fibers in frog cruralis muscle have been examined with light and electron microscopy. The slow fiber bundle of this muscle is approximately half slow fibers and half fast twitch fibers. Each slow fiber has two-five clusters of nerve terminals in its central region. In contrast, fast fibers in the same bundle have single anastomosing neuromuscular junctions. The average length of terminal clusters on slow fibers is half that of the terminals on fast fibers. Less cholinesterase activity is associated with nerve terminals on slow muscle fibers. The two types of muscle fiber were identified in freeze-fracture replicas by characteristic patterns of the sarcolemmal caveolae and square arrays. Presynaptic membranes of terminals on fast fibers have long, paired double rows of intramembrane particles which lie along the sides of ridges aligned above each fold in the muscle. Ridges are less prominent or absent in terminals on slow fibers and the associated membrane particles are more often in single rows. The lengths of the particle rows also tend to be shorter and rows tend to branch and to lie at various orientations with respect to the longitudinal axis of the terminal. The average length of the particle rows per unit length of nerve terminal on slow fiber terminals is half that of particle rows on fast fiber terminals. It is concluded that the total length as well as the concentration of these active zone specializations is less at terminals on slow fibers. The lack of parallel orientation of the presynaptic active zones at slow fiber terminals corresponds to a lack of postsynaptic folds. Postsynaptic specializations seen in thin sections through slow fibers are either on flat expanses of sarcolemma or on low sarcolemmal bulges. Patches of large intramembrane particles, similar to those on fast fibers, mark regions of postsynaptic specialization in freeze-fracture replicas of slow fibers.

Animals↗
PubMed1987

Identification of sarcolemma-associated antigens with differential distributions on fast and slow skeletal muscle fibers.

We have identified three sarcolemma-associated antigens, including two antigens that are differentially distributed on skeletal muscle fibers of the fast, fast/slow, and slow types. Monoclonal antibodies were prepared using partially purified membranes of adult chicken skeletal muscles as immunogens and were used to characterize three antigens associated with the sarcolemma of muscle fibers. Immunofluorescence staining of cryosections of adult and embryonic chicken muscles showed that two of the three antigens differed in expression by fibers depending on developmental age and whether the fibers were of the fast, fast/slow, or slow type. Fiber type was assigned by determining the content of fast and slow myosin heavy chain. MSA-55 was expressed equally by fibers of all types. In contrast, MSA-slow and MSA-140 differed in their expression by muscle fibers depending on fiber type. MSA-slow was detected exclusively at the periphery of fast/slow and slow fibers, but was not detected on fast fibers. MSA-140 was detected on all fibers but fast/slow and slow fibers stained more intensely suggesting that these fiber types contain more MSA-140 than fast fibers. These sarcolemma-associated antigens were developmentally regulated in ovo and in vitro. MSA-55 and MSA-140 were detected on all primary muscle fibers by day 8 in ovo of embryonic development, whereas MSA-slow was first detected on muscle fibers just before hatching. Those antigens expressed by fast fibers (MSA-55 and MSA-140) were expressed only after myoblasts differentiated into myotubes, but were not expressed by fibroblasts in cell culture. Each antigen was also detected in one or more nonskeletal muscle cell types: MSA-55 and MSA-slow in cardiac myocytes and smooth muscle of gizzard (but not vascular structures) and MSA-140 in cardiac myocytes and smooth muscle of vascular structures. MSA-55 was identified as an Mr 55,000, nonglycosylated, detergent-soluble protein, and MSA-140 was an Mr 140,000, cell surface protein. The Mr of MSA-slow could not be determined by immunoblotting or immunoprecipitation techniques. These findings indicate that muscle fibers of different physiological function differ in the components associated with the sarcolemma. While the function of these sarcolemma-associated antigens is unknown, their regulated appearance during development in ovo and as myoblasts differentiate in culture suggests that they may be important in the formation, maturation, and function of fast, fast/slow, and slow muscle fibers.

Animals↗