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  • Polymer and Materials Science  (9)
  • Diterpene  (3)
  • Mechanoreceptors  (3)
  • 1
    ISSN: 1432-1106
    Keywords: Mechanoreceptors ; Cutaneous Afferents ; Afterpotentials ; Primary Afferent Depolarization ; Spinal Cord
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Mechanoreceptors of the hairy skin and the central pad of the cat's hind foot were activated using piezo-electric crystals as mechanical stimulators. Their afferent fibres were traced in the lumbar spinal cord by stimulating antidromically and by recording the collision of the antidromic and orthodromic action potentials. Low threshold mechanoreceptor units could be stimulated in isolation. It was possible, therefore, to follow the postspike excitability changes of their fibres in the spinal cord without interference from other spinal cord potentials. Primary afferent depolarization has been induced in cutaneous afferents by stimulating muscle and cutaneous nerves. It has been found that the a cutaneous fibres of mechanoreceptors were depolarized by volleys in a cutaneous fibres and to a lesser degree by volleys in Group I b, II and III muscle afferents but not by high threshold cutaneous afferents. The primary afferent depolarization of cutaneous fibres has been subjected to the action of an impulse propagating down that fibre to its central terminals. Excitability testing revealed that the amplitude and the time course of the primary afferent depolarization were only altered up to about 30 ms after the impulse indicating an active depolarization of the presynaptic terminals.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 31 (1978), S. 511-522 
    ISSN: 1432-1106
    Keywords: Muscle group IV afferent units ; Muscle pain ; Chemo-nociceptors ; Mechanoreceptors ; Contraction-sensitive receptors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In an attempt to differentiate between nociceptive group IV muscle receptors and “ergoceptive” ones, the discharges of single group IV fibres from skeletal muscle in response to local pressure, sustained stretch, repetitive contraction and intra-arterial injections of bradykinin, 5-hydroxytryptamine (5-HT), potassium, phosphate, and lactate were studied in anaesthetized cats. Of the 75 fibres of the study, 5 units were activated by sustained stretch, the responses occurring with a delay. These stretch-sensitive units could not be activated by local pressure or muscular contraction. Thirteen group IV afferents raised their discharge frequency during repetitive contractions. Some of the units responded immediately with the onset of the contractions, whereas the others showed a pronounced delay. Forty-six units were tested with all or most of the above mechanical and chemical stimuli. In 32 afferents a response to at least one of the stimuli was present. Taking only these units into account, several groups of receptors could be distinguished by their different response combinations. One group was activated by pain-producing substances, but not by muscular activity and thus showed nociceptive properties. Another group showed a raised activity during muscular contractions but did not respond to the algesic agents bradykinin and 5-HT. Units belonging to this group might serve as “ergoceptors”. The borderline between the two groups was not sharp, a considerable number of group IV afferents was found which had both nociceptive and “ergoceptive” properties.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 6 (1968), S. 100-115 
    ISSN: 1432-1106
    Keywords: Mechanoreceptors ; Pacinian corpuscles ; Cutaneous afferents ; Peripheral encoding ; Skin sensitivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The properties of mechanosensitive units with large myelinated afferents were determined in the hairless skin of the central pad of the cat's hind foot, and the total afferent outflow from this region after short skin indentations and during constant force stimuli was measured in the plantar nerves. Basically three types of mechanosensitive units with afferent conduction velocities above 40 m/s were found: (a) receptors with the properties of Pacinian corpuscles (PC-receptors); (b) receptors which showed burst discharges for up to 500 ms after the onset of a constant force stimulus (RA-receptors); and (c) receptors which discharged throughout a constant force stimulus (SA-receptors). The afferent conduction velocities of these units were in the same range as those of receptors from the surrounding hairy skin. A considerable proportion of receptors from both skin areas had no collaterals in the dorsal columns. The afferent outflow after short skin indentations of up to 5 μ displacement consisted of impulses from PC-receptors only. Stimuli of 20 μ recruited between 50 and 100 afferent units of which less than 10% were other than PC-units. During constant force stimuli the afferent outflow came from SA-receptors only. Ten seconds after stimulus onset a 500 g stimulus evoked an afferent discharge of about 1000 imp/s and a 1000 g stimulus of about 1700 imp/s. At all times a power function of the form F=K · (S−S0)n related the afferent discharge F to the stimulus intensity S. The exponents were around n=0.5 and tended to increase in the course of the stimulus.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-1335
    Keywords: Tumorpromoter ; Phorbol ; Diterpene ; Leukemogenesis cocarcinogens ; Tumorpromotor ; Cocarcinogene ; Phorbol ; Diterpen ; Leukämogenese
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Phorbol und sechs strukturverwandte Substanzen, die die polyfunktionellen Diterpene des Tiglian-, Ingenan- und Lathyrantyps repräsentieren, wurden an SWR-Mäusen auf systemische promovierende und leukämogene Wirkung geprüft. Zur systemischen Initiation wurde kurz nach Geburt 15 μg Dimethylnitrosamin (DMN) s.c. injiziert. Die Diterpene wurden i.p. entweder mit oder ohne vorhergehende Initiation mit DMN gegeben. Systemische Promotion für Leber zeigten alle geprüften Diterpene mit der Entstehung von Adenomen. Einige der Diterpene erwiesen sich wirksamer als Phorbol. Die relativ hohe Dosis von DMN, die als Initiator verwendet wurde, machte eine Auswertung bezüglich promovierender Wirkung auf die Lunge unmöglich. Die leukämogene Wirkung von Phorbol bei SWR Mäusen wurde für drei verschiedene Dosen bestätigt. Die übrigen Diterpene zeigten mit der jeweils geprüften Dosis keine signifikante leukämogene Wirkung. Die leukämogene Wirkung des Phorbols wurde durch vorausgehende DMN-Injektion vollständig verhindert. Die fehlende Korrelation zwischen promovierender Wirkung an Haut, systemischer promovierender Wirkung an Leber und leukämogener Wirkung der getesteten Diterpene wird diskutiert.
    Notes: Summary Phorbol and six structurally related compounds representing the polyfunctional diterpenes of the tigliane, ingenane, and lathyrane types were tested for systemic promoting and leukemogenic activity in SWR mice. For systemic initiation soon after birth, 15 μg dimethylnitrosamine (DMN) was injected s.c. The diterpenes were administered i.p. either with or without prior systemic initiation with DMN. Systemic promotion was expressed for liver by induction of adenomas with all the diterpenes tested, some of them being more potent than phorbol. The relatively high dose of DMN used as initiator prevented an evaluation of promoting action in relation to lung carcinogenesis. The leukemogenic effect of phorbol in SWR mice was confirmed at three different dose levels. The other diterpenes tested had no significant leukemogenic activity. The leukemogenic action of phorbol was totally inhibited by prior DMN injection. The lack of correlation between promoting action in skin, systemic promoting action in liver and leukemogenic action, among the diterpenes tested, is discussed.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1432-1335
    Keywords: Diterpene ; Tumorpromoter ; Plasminogen-Aktivator ; Blutplättchen-Aggregation ; Diterpene ; Tumor promoter ; Plasminogen activator ; Platelet aggregation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary Phorbol and eight of its derivatives were investigated for their ability to stimulate the synthesis of the enzyme plasminogen activator in cultured chick embryo fibroblasts and to aggregate human blood platelets and have been assayed for tumor, promoting and skin, irritant activities. Over a range of concentrations, elevation in the levels of plasminogen activator activity induced by phorbol derivatives correlates well with their promoting and irritant properties. In the platelet aggregation assay however, the parallelism between the activities measured in different biological assays was less complete. While strong promoters, such as TPA, are potent aggregating agents, and weak promoters, such as PDA, are poor or ineffective inducers of aggregation, two derivatives, PDD and PDB, deviate from this general result. Platelets must be exposed to PDD in relatively high concentrations before they will aggregate, and PDB was found to be the most potent aggregating agent of all the derivatives tested.
    Notes: Zusammenfassung Phorbol und acht seiner Derivate wurden auf ihre Fähigkeit untersucht, die Synthese von Plasminogen-Aktivator in Zellkulturen von Hühnerembryo-Fibroblasten zu stimulieren und die Aggregation von Blutplättchen zu induzieren und auf ihre tumorpromovierende und hautirritierende Wirkung getestet. Die Erhöhung der Plasminogen-Aktivator Aktivität durch Phorbolderivate korreliert gut mit ihren irritierenden und promovierenden Eigenschaften. Im Test auf Blutplättchen-Aggregation ist die Korrelation nicht eindeutig: Sie gilt für starke Promotoren (wie TPA), die auch hochwirksame Induktoren der Aggregation sind, sowie für schwache Promotoren (wie PDA), die nur gering oder nicht induzieren; Ausnahmen sind PDD und PDB: PDD, ein starker Promoter, ist nur schwach wirksam, PDB, ein schwacher Promotor, ist dagegen das am stärksten aggregationsstimulierende Derivat.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Journal of cancer research and clinical oncology 103 (1982), S. 17-29 
    ISSN: 1432-1335
    Keywords: Diterpene ; Tumor promoter ; Differentiation ; Leukemia cells
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary 12-O-Tetradecanoylphorbol-13-acetate (TPA), the prototype polyfunctional diterpene ester tumor promoter of two-step carcinogenesis in mouse skin, induced differentiation of human promyelocytic leukemia cells (HL-60) in culture. Differentiation of HL-60 cells was characterized by increased phagocytosis, increased lysozyme activity (EC 3.2.1.17) in the growth medium, and changes in morphology to those characteristics of more mature cells resembling macrophages. Many of the cells treated with TPA became aggregated, attaching firmly to culture flasks. The average intracellular myeloperoxidase activity (EC 1.11.1.7) per cell decreased during induction of differentiation by TPA. It was also found that TPA enhanced, rather than inhibited, differentiation of HL-60 cells induced by DMSO. In addition to TPA, several polyfunctional diterpene esters of the tigliane, ingenane, and daphnane type have been tested for their ability to induce morphological and functional changes of HL-60 cells. The activities of the compounds to induce these changes correlated well with their activities as tumor promoters in two-step carcinogenesis in mouse skin. In particular, half the concentrations required for induction of adhesion of the cells to flasks were roughly correlated to the potency of these compounds as tumor promoters. Among the compounds tested, phorbol-12,13-didecanoate (PDD), ingenol-3-hexadecanoate, Pimelea factor P1 and Pimelea factor P2 were as active as TPA, while 4-O-methyl-TPA and 4α-PDD were much less active. Phorbol and ingenol were totally inactive up to a concentrations 10,000-fold higher than that of TPA.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Weinheim [u.a.] : Wiley-Blackwell
    Materials and Corrosion/Werkstoffe und Korrosion 45 (1994), S. 21-28 
    ISSN: 0947-5117
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Microbial deterioration of materials - fundamentals: Mathematical modelling of destruction mechanismsModern trends in materials science require novel methods and strategies. The general aim is to describe by models the reactions occurring at the surface and within a solid. At the present time, however, it is only possible to derive, from the experimental work, mathematical relations, and this is not sufficient for a prediction of materials behaviour. On the basis of the three steps involved in the description of materials behaviour, i. e. rules of thumb, statistical evaluation of experimental data (including models developed for the presentation of reaction kinetics), and development of physical models (among others Monte Carlo simulations), these three steps and, in particular, the preliminary step of biocorrosion, i. e. biofilm formation, are discussed. Only physical models allow a prediction of reactions, although a prediction independent from experiment is not possible because of the unknown distributions of the acting energies and their possible fluctuations. Beyond that an outline is given of the description of corrosion reactions and crack propagation. A general problem, in particular in connection with biological reactions, is the lack of interdisciplinary education of scientists and engineers.
    Notes: Die moderne Entwicklung der Werkstoffwissenschaft bedingt einen Wandel in den Methoden und Strategien. Es wird angestrebt, die an und im Festkörper ablaufenden Reaktionen in Form von Modellen zu beschreiben. Gegenwärtig gelingt es aber nur, aus experimentellen Untersuchungen mathematische Zusammenhänge abzuleiten, womit eine Vorhersage des Werkstoffverhaltens mit theoretischen Mitteln nicht gelingt.Ausgehend von den drei Erkenntnisstufen zur Beschreibung des Werkstoffverhaltens, den Faustregeln, einer Auswertung von Experimenten mit statistischen Methoden, hierzu gehören auch reaktionskinetische Modellansätze, und der Entwicklung physikalischer Modelle, u.a. Monte-Carlo-Simulationen, werden diese insbesondere für die „Vorstufe“ der biokorrosiven Schädigung vorgestellt, der Biofilmbildng. Nur physikalische Modelle ermöglichen die „Voraussage“ von Reaktionsabläufen, wobei infolge der Unkenntnis der Verteilungen für die wirkenden Energien und deren möglichen Fluktuationen eine vom Experiment getrennte Voraussage nicht möglich ist.In einem Überblick wird darüber hinaus auch auf die Beschreibung von Korrosionsreaktionen und das Rißwachstum eingegangen. Ein generelles Problem, insbesondere im Zusammenhang mit biologischen Reaktionsabläufen, stellt die nicht fachgrenzenübergreifende Ausbildung von Naturwissenschaftlern and Ingenieuren dar.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Weinheim [u.a.] : Wiley-Blackwell
    Materials and Corrosion/Werkstoffe und Korrosion 47 (1996), S. 716-717 
    ISSN: 0947-5117
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 317-326 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Intensity-fluctuation laser-light-scattering spectroscopy has been used to characterize the temperature dependence of the translational diffusion coefficient through the helix-coil region for the DNA isolated from bacteriophage N1. The diffusion coefficient does not change smoothly, but exhibits fine structure detail similar to that seen in the uv absorption hyperchromicity. These changes are related to the heterogeneous distribution of bases along the N1-DNA chain.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 327-340 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Intensity-fluctuation laser-scattering spectroscopy measurements have been reported for the DNA isolated from bacteriophage φ29. The cumulant method of data analysis gives well-defined weighted average decay frequencies. Available theoretical models are shown to yield good values for the diffusion coefficient and longest intramolecular relaxation time for low-molecular-weight DNA's but not for higher molecular weight species. The temperature dependence of the apparent diffusion coefficient exhibits drastic oscillations in the helix-coil transition region. The number of these oscillations is consistent with independent measurements of uv hyperchromicity measurements and suggests that φ29-DNA is composed of at least three regions of differing G + C content.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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