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  • 1
    ISSN: 1432-0568
    Keywords: Cementum ; Cementoblast ; Extrinsic fiber ; Intrinsic fiber ; Periodontal ligament
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract To elucidate how intrinsic and extrinsic fibers are arranged during cementogenesis, rat cellular cementum was observed in various developmental stages by light and electron microscopy. As cementogenesis progressed, the periodontal ligament cells showed characteristics of collagen-secreting cells, wing-like processes, and delimited extracellular compartments. The principal fibers were organized into substantial bundles in these compartments. The organization of extrinsic and intrinsic fibers progressed in parallel with the extracellular compartmentalization. The main results suggest the following. (1) The extracellular compartments formed by periodontal ligament cells regulate the three-dimensional architecture of the principal fibers. (2) The compartments formed by cementoblasts are essential for the formation of the typical intrinsic-extrinsic fiber structures. When the cementoblasts move away from the cementum surface or are embedded in the cementum, these cells retract the processes that have encircled the principal fibers. At the same time, these cells secrete intrinsic fibers around the principal fibers. This results in the typical intrinsic-extrinsic fiber structures. (3) In the early stage when the cellular compartmentalization is not established, both the intrinsic and extrinsic fibers are irregularly arranged.
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  • 2
    ISSN: 1432-0568
    Keywords: Cellular cementum ; Acellular cementum ; Cementoblast ; Rat molar
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The initial genesis of acellular and cellular cementum was examined in rat molars by light and electron microscopy. Before root dentinogenesis, flattened dental follicle cells formed compartments by regularly arranged cellular processes which demarcated collagen fibril bundles oriented in parallel with the root long axis in both of the two kinds of cementum. After this stage, compartments disappeared from the dental follicle cells, which became elongated and polarized, with the cytoplasmic side facing toward the root surface in the acellular cementogenesis. Fibril bundles, oriented in parallel with the root long axis, decreased in number, and principal fibers appeared. Some principal fibers were attached on the first acellular cementum. Observations suggested that the fibril bundles, which had been oriented in parallel with the root long axis, were reoriented to merge into the principal fibers. In cellular cementogenesis, the dental follicle cells continued to hold the fibril bundles in cellular compartments. The regular processes were transformed into randomly oriented, finger-like processes. At the same time, fibers, which may be secreted from the finger-like processes, appeared around the preformed fibril bundles oriented in parallel with the root long axis. The different cellular behavior may result in the different fiber arrangement of acellular and cellular cementum.
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  • 3
    ISSN: 1432-0568
    Keywords: Cementoblast ; Extrinsic fiber ; Intrinsic fiber ; Periodontal ligament ; Rat molar
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The formation of intrinsic fibers was examined in the advanced stage of rat cellular cementogenesis by light and electron microscopy. Using scanning electron microscopy, cementoblasts showed wing-like processes, partly encircling principal fibers. At the cementum-facing side of the cells these processes showed segmentation into finger-like processes, arranged in parallel with the cementum surface. Transmission electron microscopy showed many cytoplasmic fragments around intrinsic fibers at the cementum surface. These fragments contained microtubules and collagenous secretory granules that were arranged in parallel with the cementum surface and the intrinsic fibers. The wing-like processes contained microtubules and secretory granules that were arranged perpendicularly to the cementum surface and in parallel with the principal fibers. These observations suggest that: (1) the cytoplasmic fragments are cross-sectioned finger-like processes; (2) cementoblasts secrete intrinsic fibers from the finger-like processes and additional principal fibers from the wing-like processes; (3) cementoblasts constantly shorten their wing-like processes by forming finger-like processes. This development starts at the side facing the cementum and proceeds towards the periodontal ligament. With the segmentation, the cementoblasts change the arrangement of secretory granules to secrete intrinsic fibers around preformed principal fibers.
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  • 4
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: In this study, we examined the effects of a 105 amino acid carboxyl terminal fragment of β-amyloid precursor protein (CT105) and inflammatory cytokines on working memory in rats, by using a three-panel runway set-up. CT105 at 10 nmol/side significantly impaired working memory when it was administered bilaterally into the hippocampus. Furthermore, to elucidate the interaction of CT105 with inflammatory cytokines, we co-administered tumor necrosis factor-alpha (TNF-α) and interleukin-1β (IL-1β) in combination with CT105. Concurrent injections of CT105 (1.0 nmol/side) and TNF-α (100 ng/side) produced a synergistic deficit of working memory, whereas IL-1β (100 ng/side) combined with CT105 (1.0 nmol/side) did not affect the working memory performance. These results indicate that the CT105-induced impairment of working memory is strongly aggravated by an increase in the level of the inflammatory cytokine TNF-α, which may occur in the brains of patients with Alzheimer's disease.
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  • 5
    ISSN: 1573-904X
    Keywords: N-benzyloxycarbonyl-thioprolythioprolinal-dimethylacetal (ZTTA) ; prolyl endopeptidase (PEP) ; PEP inhibitor ; basal forebrain lesion ; choline acetyltransferase ; step-through type passive avoidance test
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
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  • 6
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    ISSN: 1600-0765
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The bundling of principal fibers was investigated in tangential sections through the tooth-related portion in developing rat molars by light and electron microscopy. When root dentin calcification began, cross sections of principal fibers emerged as fibril aggregates in the narrow intercellular spaces in a densely packed population of periodontal ligament cells. Subsequently, these cells changed shape and location to widen the intercellular spaces. The fibril aggregates became thicker in these spaces. With root development, the collagen fibrils formed loosely aggregated bundles and the periodontal ligament cells extended cell processes between the bundles. The cell processes usually contained microfilaments suggestive of actin filaments, and as the cell processes extended and came in close apposition, they formed delimited compartments. These compartments appeared to be a sheath-like structure, and the loose fibril bundles developed into tight fibril bundles in the compartments. Finally the principal fibers consisted of many tight fibril bundles, which were partially or entirely surrounded by cell processes and cell bodies. The findings suggest that the sheath-like, cellular compartments cause the tight bundling of the principal fibers.
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    ISSN: 1600-0765
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The principal fibers and cellular cementum were examined in various developmental stages in rat molars by light and electron microscopy, and their development and structure were studied. The principal fibers increased in thickness with root development. At any given stage, the principal fibers consisted of small fiber bundles on the cementum surface and showed a branching structure. Sharpey's fibers also showed a similar branching structure and increased in thickness, as traced superficially in the cementum. It was suggested that the principal fibers increased in thickness by means of the aggregation of fiber bundles. The development of cellular cementum was divided into two (early and late) phases on the basis of the fiber arrangement. The early cementum was believed to contain a few Sharpey's fibers and many randomly arranged intrinsic fibers. The late cementum contained thicker Sharpey's fibers with branches and the intrinsic fibers which appeared to encircle Sharpey's fibers and/or meander among them.
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  • 8
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    ISSN: 1600-0765
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The initial attachment of principal fibers to the root dentin surface was investigated in developing rat molars by light and electron microscopy. Ruthenium red was used to intensely stain the first deposited material on the root dentin surface. Observations suggested that when the principal fibers became embedded in the ruthenium red-positive material, there was no complicated interweaving between the principal fibers and the root dentinal matrix fibers. Therefore, it is likely that the initial principal fiber attachment to the root dentinal matrix fibers is mediated by the ruthenium red-positive material.
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  • 9
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: We have previously shown that behavioral changes induced by cannabinoid were due to an elevation of prostaglandin E2 (PGE2) via the arachidonic acid cascade in the brain. In the present study, we investigated the participation of the prostanoid EP3 receptor, the target of PGE2 in the brain, in behavioral suppression induced by Δ8-tetrahydrocannabinol (Δ8-THC), an isomer of the naturally occurring Δ9-THC, using a one-lever operant task in rats. Intraperitoneal administration of Δ8-THC inhibited the lever-pressing behavior, which was significantly antagonized by both the selective cannabinoid CB1 receptor antagonist SR141716A and the cyclooxygenase inhibitor diclofenac. Furthermore, intracerebroventricular (i.c.v.) administration of PGE2 significantly inhibited the lever-pressing performance similar to Δ8-THC. Prostanoid EP3 receptor antisense-oligodeoxynucleotide (AS-ODN; twice a day for 3 days, i.c.v.) significantly decreased prostanoid EP3 receptor mRNA levels as determined by the RT-PCR analysis in the cerebral cortex, hippocampus and midbrain. AS-ODN also antagonized the PGE2-induced suppression of the lever pressing. In the same way, the suppression of lever-pressing behavior by Δ8-THC was significantly improved by AS-ODN. It is concluded that the suppression of lever-pressing behavior by cannabinoid is due to activation of the prostanoid EP3 receptor through an elevation of PGE2 in the brain.
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  • 10
    ISSN: 1432-2072
    Keywords: AP159 ; Anxiolytic ; 5HT1A receptor ; Anti-amnesia ; Rat ; Mouse
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract AP159 ([N-cyclohexyl-1,2,3,4-tetrahydrobenzo(b)thieno(2,3c)pyridine]-3-carboamide,hydrochloride) showed clear anti-conflict activity in rats in the absence of effects on muscle relaxation, potentiation of anesthesia (in mice) or anticonvulsant activity (in mice). This anticonflict effect was antagonized by treatment with Ro15-1788. By contrast with the deficits produced by diazepam, AP159 did not impair passive avoidance. The latter drug also improved scopolamine-induced amnesia in the same task. AP159 did not inhibit3H-flunitrazepam binding, but potently inhibited3H-8OH-DPAT binding. This compound increased serotonin and 5HIAA content of the midbrain raphe nuclei and of the amygdala centralis. AP159 has been shown to be a novel non-BZP anxiolytic agent with no side effects in laboratory animals; it could be a clinically effective anxiolytic agent.
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