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At least 379 records · Page 21Linked to original sources
PubMed2000

Fiber arrangement of the rat splenic capsule with special reference to elastic fibers.

The fiber arrangement of the rat splenic capsule was examined under scanning electron microscope (SEM) after selective removal by chemical maceration of capsule components, in conjunction with examination of thin sections using a transmission electron microscope (TEM). TEM findings were compared to those of the guinea-pig, mouse and dog. Serosal cells of the rat splenic capsule showed labyrinthic channels that consisted of expanded intercellular spaces and tunnel-like spaces or slits in the basal cytoplasm. The channels contained fascicles of collagenous fibrils, forming a loose net on an underlying elastic lamina of densely aggregated elastic fibers. The fibrous tunica was an intermingled layer of elastic and collagenous fibers and sparse interstitial cells. The fibrous components were arranged more densely in the external layer than in the internal layer of the capsule. The elastic lamina comprised the outermost layer of the fibrous tunica in the intertrabecular region, but was situated deep in the trabecular region. Outward branches of the lamina in the trabecular region were arranged in a spiral. Intrachannel fibrillar fascicles were continuous, via fenestrations in the elastic lamina, with thick fascicles of collagenous fibers. The elastic lamina may play a role in effective contraction of whole spleen. In the guinea-pig, mouse and dog, elastic fibers were fragmented and not arranged in laminae. Typical smooth muscle cells were abundant in the dog. The channel spaces in the serosal tunica are discussed from the viewpoint of extravascular lymphatic flow for circulation of the peritoneal serous fluid.

Animals↗
PubMed2006

Comparison of clinical characteristics between congenital fiber type disproportion myopathy and congenital myopathy with type 1 fiber predominance.

Congenital myopathies are clinical and genetic heterogeneous disorders characterized by skeletal muscle weakness and specific structural changes in muscle fiber. Congenital myopathy with fiber type disproportion (CFTD) is an established disorder of congenital myopathy. CFTD is characterized by non-progressive childhood neuromuscular disorders with a relatively good prognosis and type 1 fiber predominance and smallness. Congenital myopathy with type 1 fiber predominance (CMT1P) is also a distinct entity of congenital myopathy characterized by non-progressive childhood neuromuscular disorders and type 1 fiber predominance without smallness. Little is known about CMT1P. Clinical characteristics, including dysmorphic features such as hip dislocation, kyphoscoliosis, contracture, and high arch palate, were analyzed along with laboratory and muscle pathologies in six patients with CMT1P and three patients with CFTD. The clinical manifestations of CFTD and CMT1P were similar. However, the frequency of dysmorphic features is less in CMT1P than in CFTD. Long term observational studies of CMT1P are needed to determine if it will change to another form of congenital myopathy or if CMT1P is a distinct clinical entity.

Adult↗
PubMedDate not supplied

Asbestos fibers: 1. A modified preparation of tissue samples for analysis by electron microscopy. 2. Presence of fibers in tissues of baboon fed chrysotile asbestos.

A specimen preparation technique is described which yields uniformly dispersed particles on transmission electron microscope (TEM) grids. It is relatively rapid and probably incurs no fiber loss. This technique was used to test the hypothesis that orally administered chrysotile asbestos may pass through the wall of the gastrointestinal tract (GI) of the neonate baboon. A test neonate baboon was bottle-fed chrysotile asbestos which was suspended in a milk formula. Control and test baboons were sacrificed at the end of a 9-day feeding period, and several tissues were removed and preserved. Kidney, liver, and spleen tissues were prepared for TEM analysis. Tissues from the control animal showed no fibers. The number of chrysotile fibers recovered from the test kidney cortex was significantly higher than the level found in the control kidney cortex (p less than 0.005). The frequency distribution of fibers lengths in the kidney cortex was very similar to that of the feeding suspension. This study suggests that a wide range of fiber sizes can penetrate the GI tract and migrate.

Animals↗
PubMed2004

Fermentation of "Quick Fiber" produced from a modified corn-milling process into ethanol and recovery of corn fiber.

Approximately 9% of the 9.7 billion bushels of corn harvested in the United States was used for fuel ethanol production in 2002, half of which was prepared for fermentation by dry grinding. The University of Illinois has developed a modified dry grind process that allows recovery of the fiber fractions prior to fermentation. We report here on conversion of this fiber (Quick Fiber [QF]) to ethanol. QF was analyzed and found to contain 32%wt glucans and 65%wt total carbohydrates. QF was pretreated with dilute acid and converted into ethanol using either ethanologenic Escherichia coli strain FBR5 or Saccharomyces cerevisiae. For the bacterial fermentation the liquid fraction was fermented, and for the yeast fermentation both liquid and solids were fermented. For the bacterial fermentation, the final ethanol concentration was 30 g/L, a yield of 0.44 g ethanol/g of sugar(s) initially present in the hydrolysate, which is 85% of the theoretical yield. The ethanol yield with yeast was 0.096 gal/bu of processed corn assuming a QF yield of 3.04 lb/bu. The residuals from the fermentations were also evaluated as a source of corn fiber oil, which has value as a nutraceutical. Corn fiber oil yields were 8.28%wt for solids recovered following pretreatment.

Biomass↗
PubMed1991

Biomechanical properties and collagen fiber orientation of TMJ discs in dogs: Part 1. Gross anatomy and collagen fiber orientation of the discs.

The present study investigated the gross anatomy and collagen fiber orientation of TMJ discs in dogs using macroscopic, stereomicroscopic, light microscopic, and scanning electron microscopic techniques. Results showed that (1) the surface of the disc has an undulated configuration (a "fingerprint pattern" under stereomicroscope), which appears to aid in storing synovial fluid and providing lubrication to the joint; (2) the fine fibrils in the middle part are twisted together tightly, presenting a wavy, winding, lamina layer structure anteroposteriorly that works to absorb shock; (3) the mediolateral fibers are composed of loose and less wavy bundles, and they are crossed perpendicularly by anteroposterior fibers in anterior and posterior bands. In fact, a fibrous anulus in the periphery of the disc is composed of the mediolateral fibers of anterior and posterior bands and the anteroposterior fibers of the medial and lateral portions of the middle band, which suggests a stabilizing function.

Animals↗
PubMed1993

[A comparative study of the structural state of skeletal muscle and smooth muscle fiber tropomyosin in ghost skeletal muscle fibers by a fluorescent probe method].

The structural state of skeletal muscle and smooth muscle fiber tropomyosins in ghost fibers of skeletal muscles has been studied by means of polarization microfluorimetry. Tropomyosins and F-actin of ghost fibers were labelled with N-(iodoacetyl)-N-(1-naphthyl-5-sulfo)-ethylenediamine (1,5-IA-EDANS) or the phalloidin-rhodamine complex, respectively. It has been found that skeletal tropomyosin bound to ghost muscle fibers is more flexible in comparison with smooth muscle tropomyosin. The flexibility of the thin filaments of the ghost fibers labelled in F-actin by the phalloidin-rhodamine complex and containing smooth muscle tropomyosin is higher than that of the thin filaments containing the bound skeletal muscle protein.

Animals↗
PubMed1997

Growth-associated protein 43 immunoreactivity in the superficial dorsal horn of the rat spinal cord is localized in atrophic C-fiber, and not in sprouted A-fiber, central terminals after peripheral nerve injury.

Peripheral nerve injury induces the up-regulation in dorsal root ganglion cells of growth-associated protein 43 (GAP-43) and its transport to the superficial laminae of the dorsal horn of the spinal cord, where it is located primarily in unmyelinated axons and growth-cone like structures. Peripheral nerve injury also induces the central terminals of axotomized myelinated axons to sprout and form novel synaptic contacts in lamina II of the dorsal horn. To investigate whether the sprouting of A-fiber central terminals into lamina II is the consequence of GAP-43 incorporation into their terminal membranes, we have used an ultrastructural analysis with double labelling to identify the localization of GAP-43 immunoreactivity. Transganglionic transport of wheat germ agglutinin conjugated to horseradish peroxidase (WGA-HRP) was used to identify C-fiber terminals. Transganglionic transport of the B fragment of cholera toxin conjugated to horseradish peroxidase (B-HRP) was used to label A-fiber sciatic nerve central terminals in combination with GAP-43 immunocytochemistry. GAP-43 was found to colocalize only with WGA-HRP- and not with B-HRP-labelled synapses or axons. In addition, many single-labelled GAP-43 synapses were observed. Many of the WGA-HRP-labelled terminals that were characterized by degenerative changes were GAP-43 immunoreactive. Our results indicate that peripheral nerve injury induces novel synapse formation of A fibers in lamina II but that up-regulated levels of GAP-43 are present mainly in other axon projections to the superficial dorsal horn.

Animals↗
PubMed2004

Refractoriness cannot explain why C-fiber laser-evoked brain potentials are recorded only if concomitant Adelta-fiber activation is avoided.

Co-activation of Adelta- and C-fiber nociceptors by brief cutaneous laser heat stimuli may induce a dual sensation composed of first and second pain but evokes only a single, Adelta-fiber related, late laser-evoked potential (LEP). Yet, when concomitant activation of Adelta-nociceptors is avoided, C-nociceptor activation evokes an ultra-late LEP. As cumulating evidence indicates that late and ultra-late LEPs may share common generators, investigators have hypothesized that when Adelta-fibers trigger a late LEP, the later arriving C-fiber afferent volley cannot trigger an ultra-late LEP because underlying generators are in a 'refractory state'. Better understanding of these interactions could have important consequences regarding the functional significance of LEPs. Therefore, this hypothesis was tested by applying two consecutive laser stimuli to the hand dorsum such as to produce a second Adelta-nociceptor afferent volley arriving at generators during their expected 'refractory period'. Results showed that late LEPs evoked by the second stimulus were not altered and consequently that this hypothesis does not hold. In addition, when stimuli ended the sensory detection task, an ample P600 component was recorded. Studies have shown that this component is probably related to the P3b component described in other sensory modalities. This result provides support to the 'context closure' model hypothesizing that this component reflects the closure of information processing occurring when expectations are terminated. Altogether, these results suggest that late and ultra-late LEPs reflect very general processes, which are mainly related to detection and orientation and constitute only a fraction of the central processing of both nociceptive inputs.

Adult↗
PubMed1976

Impulse conduction in the myelinated giant fibers of the earthworm. Structure and function of the dorsal nodes in the median giant fiber.

The dorsal openings in the myelin sheath of the median giant fiber (MGF) of the earthworm (Lumbricus terrestris L.) have been studied with electronmicroscopical and electrophysiological methods. The fine structure of the dorsal nodes (DN) resembles in many aspects the Ranvier nodes in vertebrate and crustacean nerve fibers. The nodal membrane directly faces the extracellular collagenous capsule of the ventral cord and displays a conspicuous electrondense undercoat. The myelin sheath of the paranode shows a characteristic differentiation into large desmosomal contracts. Recordings of the transmembrane and longitudinal surface currents along the dorsal side of the MGF during spike propagation support the view that an active inward current is restricted there to the DN. The inward current density in the DN reaches outstandingly high values similar to those measured in vertebrate nodes of Ranvier. The nodal activity can be blocked by application of tetrodotoxin and local anaesthetics. Local electrical stimulation of only one DN may suffice to elicit propagated actions potentials up and down the MGF. It is concluded that the dorsal nodes of the median giant fiber of the earthworm are highly specialized excitable structures mediating saltatory impulse conduction in these fibers.

Animals↗
PubMed2002

Increased incidence rate of colorectal tumors due to the intake of a soluble dietary fiber in rat chemical carcinogenesis can be suppressed by substituting partially an insoluble dietary fiber for the soluble one.

In epidemiologic studies on human colorectal tumors, results on the relative protective effect of soluble and insoluble fibers are not consistent. We studied in this work the effect in rats of feeding guar gum or guar gum together with cellulose on the incidence of colorectal tumors induced by 1,2-dimethylhydrazine. The results were as follows: (i) The enhancement of tumor formation by feeding solely guar gum (guar gum group) was suppressed completely when two-thirds of the guar gum was replaced with cellulose (cellulose-guar gum group). The odds ratio for tumor formation was 0.075 (95% CI 0.006-0.936, p = 0.044) for guar gum group vs. no fiber control and 0.833 (0.134-5.167, p = 0.83) for cellulose-guar gum group vs. the control. (ii) In both groups, serum cholesterol and triglyceride levels decreased significantly compared to the no fiber control group, and fecal excretion of total bile acids almost doubled. (iii) In guar gum group rats, the deconjugation activity (beta-glucuronidase, beta-glucosidase) was higher than the control or cellulose-guar gum group rats. (iv) The amount of cecal short-chain fatty acids was almost double in guar gum group rats compared to the cellulose-guar gum group or the control rats, and pH of the cecal content of the guar gum group rats had a tendency to be lower. (v) The concentration of fecal secondary bile acids was extremely low in the younger rats of the guar gum group. From these results, it seemed significant to study the cancer preventive effect of the mixed feeding to experimental animals of water-soluble and insoluble fibers instead of the singular feeding.

Animals↗
PubMed1980

Dietary fibers: V. Binding of bile salts, phospholipids and cholesterol from mixed micelles by bile acid sequestrants and dietary fibers.

Mixed micelles were prepared containing combinations of either taurocholate or taurochenodeoxycholate, monoolein, oleic acid, dioleylphosphatidylcholine (lecithin) and cholesterol. These were incubated with commercial bile-acid-sequestering resins, cholestyramine and DEAE-Sephadex, or various dietary fibers and fiber components including wheat bran, cellulose, alfalfa, lignin and 2 viscosity grades of guar gum. Binding was determined as the difference between the radioactivity of each micellar component added and that recovered in the centrifugal supernatant after incubation. In general, the extent of bile salt sequestration was characteristic and reproducible for each bile salt, and was largely unaffected by the presence of one or more additional components of the micellar mixture, including the other bile salt. Cholestyramine bound 81-92% of the bile salts and 86-99% of the phospholipid and cholesterol present in micelles. DEAE-Sephadex sequestered only 49% of the taurocholate and 84% of the taurochenodeoxycholate, but completely removed all of the phospholipid and cholesterol from micelles containing either bile salt. Among the dietary fibers, guar gum of either viscosity bound between 20-38% of each micellar component, whereas lignin, alfalfa, wheat bran and cellulose were progressively less effective in sequestration of individual components of mixed micelles. The extent of sequestration of micellar components by these resins and fibers is reasonably correlated with the effects of these same materials on lymphatic absorption of lipids and to their suggested hypocholesteremic properties.

Bile Acids and Salts↗
PubMed2000

Scanning laser polarimetry, retinal nerve fiber layer photography, and perimetry in the diagnosis of glaucomatous nerve fiber defects.

BACKGROUND: Retinal nerve fiber layer defects are part of early glaucomatous damage. In the present study, we compared the ability of retinal nerve fiber layer photography (NFP) and scanning laser polarimetry (SLP) to detect nerve fiber layer defects in glaucoma patients. METHODS: Besides ophthalmological standard examinations, we performed NFP (Zeiss Ikon fundus camera 30 degrees, green filter), SLP (GDx, 1.0.14 and 2.0.09, LDT) and automated perimetry (Oculus, Twinfield, 30 degrees) in 150 glaucoma patients [74 with primary open-angle glaucoma (POAG) and 76 with normal-tension glaucoma (NTG)]. The perimetric results were evaluated according to a modified Aulhorn classification. NFP and SLP were graded according to Quigley. RESULTS: In POAG, 42% of NFP and 5% of SLP were not evaluable. In NTG, 24% of NFP and 4% of SLP were not evaluable. In POAG, NFP and SLP revealed a direct agreement in 54.5%, and in NTG, 55%; there was a small difference of one stage in 39.5% (POAG) and 41% (NTG). In POAG, NFP/SLP showed agreement with perimetric results in 35%/30% of cases and differences of one stage in 56%/58%. In NTG, NFP/SLP agreed with perimetry in 52%/48% of cases and differed by only one stage in 32%/39%. Larger deviations were found in less than 13% of the cases. CONCLUSIONS: NFP and SLP mostly showed good agreement or little deviation as to grading of nerve fiber layer damage. In clinical use, SLP has advantages over NFP because a higher rate of good-quality images can be obtained and pupils do not have to be dilated. Additionally, SLP measurements provide quantitative data and a large normative data base exists.

Adult↗
PubMed1990

A-fibers mediate mechanical hyperesthesia and allodynia and C-fibers mediate thermal hyperalgesia in a new model of causalgiform pain disorders in rats.

Unilateral tight ligation of about half of the sciatic nerve in rats rapidly produces sympathetically dependent neuropathic pain which lasts many months and resembles causalgia in humans. The sensory abnormalities detected at the plantar side of the hindpaws include: (1) nocifensive responses to repetitive light touch (allodynia); (2) bilateral reduction in withdrawal thresholds to repetitive von-Frey hair stimulation (mechanical hyperesthesia); (3) bilateral reduction in withdrawal thresholds to CO2 laser heat pulses; and (4) unilateral increase in response duration to an intense laser heat pulse (thermal hyperalgesia). Using neonatal capsaicin treatment, we determined the type of afferent fiber remaining in the partially injured nerve, which mediates these disorders. Capsaicin, which destroys most C- and some A delta-fibers in peripheral nerves, had no effect on the touch-evoked allodynia and mechanical hyperesthesia that are produced by partial sciatic nerve injury. These disorders were, therefore, mediated by myelinated fibers. In contrast, thermal hyperalgesia failed to develop in capsaicin-treated rats following partial nerve injury. Thus, thermal hyperalgesia produced by partial nerve injury appears to be mediated by heat-nociceptive C-fibers.

Afferent Pathways↗
PubMed1993

Serotonin (5-HT) fibers of the rat dura mater: 5-HT-positive, but not authentic serotoninergic, tryptophan hydroxylase-like fibers.

Serotonin (5-HT)-positive, but not tryptophan-5-hydroxylase (TPOH)-positive, authentic serotoninergic fibers were shown in the rat dura mater. 5-HT immunoreactive fibers in the dura are postulated to result from 5-HT uptake from circulating blood elements (e.g. platelets, mast cells) by perivascular sympathetic nerve fibers. A robust TPOH-immunoreactive mast cell population was identified in the dura; this result confirms the TPOH antibody specificity to cells known to synthesize 5-HT. While these results indicate that there are no authentic serotoninergic fibers in the dura mater, the mast cells, platelets and cerebrospinal fluid can serve as a source of 5-HT activating 5-HT receptors known to be present in this tissue.

Animals↗
PubMed1983

Experimental and immunohistochemical studies concerning the major origins of the substance P-containing fibers in the lateral lemniscus and lateral parabrachial area of the rat, including the fiber pathways.

The origins and pathways of substance P-containing fibers in the lateral lemniscus and lateral parabrachial area of the rat were investigated by means of the indirect immunofluorescence technique. Following the placement of various knife cuts or lesions, the following could be concluded: (1) The cells of origin of substance P-containing fibers in the lateral lemniscus and lateral parabrachial area are localized in the ventral reticular formation of the rhombencephalon from the level of P2.8 to P7.0 in the atlas of Palkovits and Jacobowitz; (2) The fibers from these origins pass the ventral reticular formation of the rhombencephalon to form a dense bundle; (3) the fibers turn dorsally at the mid-rhombencephalon junction to reach the lateral lemniscus and lateral parabrachial area. The present study demonstrates the linking of the functions of the parabrachial area and lateral lemniscus via substance P innervation.

Animals↗
PubMed2006

The role of fiber durability/biopersistence of silica-based synthetic vitreous fibers and their influence on toxicology.

This work summarizes what is known about the role of fiber durability/biopersistence of silica-based synthetic vitreous fibers (SVFs) and their influence on toxicology. The article describes the key processes leading from exposure to biological effect, including exposure, pulmonary deposition, clearance by various mechanisms, accumulation in the lung, and finally possible biological effects. The dose-dimension-durability paradigm is used to explain the key determinants of SVF toxicology. In particular, the key role played by the durability/biopersistence of long (>20microm) fibers is highlighted. Relevant literature on the prediction of in-vitro dissolution rates from chemical composition is summarized. Data from in-vitro and in-vivo durability/biopersistence tests show that these measures are highly correlated for long fibers. Both durability and biopersistence are correlated with the outcome of chronic inhalation bioassays. A schematic approach is presented for the design and testing of new SVFs with lower biopersistence.

Animals↗
PubMed1997

Congenital familial myopathy with type 2 fiber hypoplasia and type 1 fiber predominance.

A 12-month-old girl with delayed developmental milestones, due to muscle hypotonia and weakness from early infancy, exhibited type 2 fiber hypoplasia. A muscle biopsy specimen disclosed type 1 fiber predominance and type 2B fiber deficiency compatible with congenital myopathy. During the following 4 years, she continued to have mild muscle weakness, but no mental retardation. Her mother had similar symptoms from early infancy with minimal progression. Although type 2 fiber hypoplasia is a non-specific finding in various diseases, it may be a specific finding in a limited number of patients with hereditary congenital non-progressive myopathy.

Adult↗
PubMed1988

Effects of pH on mineral-phytate, protein-mineral-phytate, and mineral-fiber interactions. Possible consequences of atrophic gastritis on mineral bioavailability from high-fiber foods.

A common gastrointestinal tract problem afflicting the elderly is that of reduced hydrochloric acid secretion by the stomach mucosa. This results in raised stomach pH values and in reduced activity of the digestive enzyme pepsin, which is responsible for the hydrolysis of dietary proteins to polypeptides. The effects of these alterations of the stomach on the digestion of high-fiber foods and resultant mineral bioavailability have not been defined. This paper reviews the effects of pH on the mineral-phytate, protein-mineral-phytate, and mineral-fiber interactions that would be present in high-fiber foods. Possible consequences of raised stomach pH values on mineral bioavailability from high-fiber foods are discussed.

Biological Availability↗