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  • 1
    ISSN: 0886-1544
    Keywords: axonal transport ; ATP ; nucleotides ; saltatory movement ; dynein ; video microscopy ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: In a permeabilized axon model, exogenous ATP can reactivate intraaxonal saltatory organelle movements (microscopically visible manifestations of fast axonal transport). We have studied the dependence of the reactivated movements on the ATP concentration and have also examined the nucleotide specificity of the reactivation. Organelle transport was visualized in isolated lobster giant motor axons using Nomarski optics and video microscopy. The axons were permeabilized with saponin, and movement was reactivated with ATP or other nucleotides. Some slight movement was seen with ATP concentrations as low as 10 μM. The velocity and frequency of the reactivated transport increased with increasing ATP concentrations up to about 5 mM. Movement was also reactivated by deoxyadenosine triphosphate, but not by AMP-PNP (a nonhydrolyzable ATP analogue), ADP, or AMP. Although other nucleotides (CTP, GTP, UTP, ITP) could reactivate transport, movement equivalent to that produced by 0.1 mM ATP was only seen with tenfold or greater concentrations of the other nucleotides. This pattern of specificity is consistent with the hypothesis that a dynein-like ATPase, rather than a myosin, is involved in fast axonal transport.
    Additional Material: 1 Ill.
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  • 2
    ISSN: 0886-1544
    Keywords: tissue culture ; Swann cell ; pulsatile movement ; time-lapse cinemicrography ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Slow pulsatile movements of Schwann cells in vitro were studied quantitatively by using time-lapse cinemicrography. Schwann cells from peripheral nerves of 3-day-old rats were cultured in serum-free medium. Most Schwann cells showed intermittent episodes of pulsatile movement; each episode consisted of one or several contractile pulses. About half of the episodes consisted of a single pulse, and episodes with more than four pulses were rare. The average episode of activity lasted 2.6 min, while the average duration of a single pulse was 1.5 min. The mean quiescent interval between episodes of activity was 3.7 min. Some cells showed no pulsatile activity. Active cells averaged 6.6 episodes/h. The fraction of time which a Schwann cell spent in pulsatile activity varied widely, with an average of 28%. Behavior of Schwann cells in HEPES-buffered Hanks saline was generally similar to that in the complete medium. Raising K+ to 40 mM or Ca++ to 10 mM did not markedly affect the time course of the pulsatile motility, although the contractions were more vigorous in the high Ca++. Pulsatile movement was reversibly inhibited by cytochalasin B and appeared to be potentiated by drugs that disrupt microtubules.
    Additional Material: 5 Ill.
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  • 3
    ISSN: 1432-0878
    Keywords: Adrenergic nerves, arterioles ; Chemical sympathectomy ; 6-aminodopamine, 6-hydroxydopamine ; Fluorescence histochemistry ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary A 6-hydroxydopamine analogue, 6-aminodopamine (6-ADA), was compared with 6-hydroxydopamine (6-OHDA) as a potential agent for chemical sympathectomy. The adrenergic terminals innervating arterioles of the frog retrolingual membrane were used as a test system. Four days after two topical treatments with 0.25 mg/ml of either drug, most of the periarteriolar adrenergic nerves demonstrated swelling, fiber disruption, or a bright beaded appearance in the fluorescence microscope. Treatment with 0.5 mg/ml 6-OHDA abolished all fluorescence. After 0.5 mg/ml 6-ADA, no normal adrenergic fibers were seen, although a few fibers survived and exhibited a beaded appearance. In contrast to 6-OHDA, this higher dose of 6-ADA produced some signs of general tissue toxicity. After treatment with either drug, electron microscopy revealed adrenergic nerves with large electron-opaque structures containing the degenerated remains of large granular vesicles. Nerve areas which contained the degenerating structures occasionally alternated with swollen axonal regions containing many microtubules but no vesicles. Cholinergic nerves showed no evidence of damage. These results suggest that 6-ADA selectively destroys peripheral adrenergic nerves much like 6-OHDA, providing an additional marker for the ultrastructural identification of adrenergic nerves. Their analogous chemical suggest a similar metabolic mechanism for destruction of adrenergic nerves.
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