Acetylcholine Quanta

Canepa, F. G.

doi:10.1038/201184a0

Cited by 22 publications

(7 citation statements)

References 3 publications

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“…If as in the cat superior cervical ganglion, only 85 % of the total bound ACh is releasable (Birks & MacIntosh, 1961), a value of 57,000 molecules of ACh per quantum is obtained. These figures may be compared with the figure of 62,000 molecules which is the most that could be contained in a vesicle of 500 A diameter (Canepa, 1964).…”

Section: Discussionmentioning

confidence: 99%

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Presynaptic action of hemicholinium at the neuromuscular junction

Elmqvist¹,

Quastel²

1965

The Journal of Physiology

205

105

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Section: Discussionmentioning

confidence: 99%

“…These figures may be compared with the figure of 62,000 molecules which is the most that could be contained in a vesicle of 500 A diameter (Canepa, 1964).…”

Section: Discussionmentioning

confidence: 99%

Presynaptic action of hemicholinium at the neuromuscular junction

Elmqvist¹,

Quastel²

1965

The Journal of Physiology

205

105

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“…The maximum number of ACh molecules that can be accommodated inside a vesicle with a 400 A inside diameter, is 45,000 (Canepa, 1964;Hubbard, 1970). Estimates of the amount of ACh required to produce a one quantum response equivalent to a m.e.p.p.…”

Section: Discussionmentioning

confidence: 99%

Neuromuscular transmission in a mammalian preparation in the absence of blocking drugs and the effect of D‐tubocurarine

Hubbard¹,

Wilson²

1973

The Journal of Physiology

157

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SUMMARY1. Neuromuscular transmission in the presence and absence of D-tubocurarine was examined in cut muscle preparations of the rat diaphragm using intracellular recording techniques. The method of localizing the endplates is described and evidence is presented indicating that end-plate potential (e.p.p.) recordings were made close to the end-plate region and that reliable estimates of the quantum content of e.p.p.s could be made.2. During repetitive nerve stimulation at rates between 2 and 10 Hz, e.p.p. amplitudes declined in response to the first 6-8 stimuli to reach a plateau level which was maintained for 1500 stimuli. At higher rates of stimulation some 500-700 stimuli were needed before a plateau level of amplitude was reached. It was demonstrated that these amplitude changes reflected similar changes in the quantal release of ACh. 3. Tubocurarine in a concentration of 4 x 10-g/ml. had no effect on quantal release but did reduce quantal size. In the presence of tubocurarine, 8 x 10-g/ml., small reductions in the quantum content of the first e.p.p. in response to a train of stimuli and the maintained quantal release were observed. In the presence of tubocurarine 4 x 10-7 g/ml., the quantum content of the first e.p.p. and the maintained release were further reduced, to the level previously described for curarized preparations. At this concentration a significant effect of tubocurarine upon the presynaptic measurements could be detected (t test). Studies on single junctions revealed that the post-and presynaptic effects of tubocurarine developed with different time courses.4. Neuromuscular preparations in vivo have been reported to be much more resistant to maintained stimulation than curarized neuromuscular J.

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“…The structure was solved in space group P21 with two crystallographically different molecules in the asymmetric unit. From physiological considerations Canepa (1964) suggested that one of these molecular forms was incorrect, and Dunitz (1963), observing some unusual systematic absences, suggested that the crystal used was a twinned P2~/c rather than a single P2~ specimen. Taking this into account, the structure was refined from the previous photographic intensities corrected for twinning by Canepa, Pauling & Serum (1966), referred to hereafter as CPS, to a final R of 0.10.…”

Section: Introductionmentioning

confidence: 99%

A reinvestigation of the crystal structure of acetylcholine bromide

Svinning¹,

Sørum²

1975

Acta Crystallogr Sect B

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A reinvestigation of the structure of acetylcholine bromide, [CTHI602N]+Br -, with X-ray diffraction intensities collected from two untwinned crystals has been carried out. The crystals are monoclinic, space group P21/n, with a= 10.966 (4), b= 13.729 (7), c=7-159 (4)/l, fl= 108.18 (7) °, Z=4. The structure was refined by full-matrix least-squares calculations with 1730 observed reflexions, and anisotropic temperature factors for all non-hydrogen atoms. The final R was 0.041. Atomic coordinates, thermal parameters, bond lengths and angles are compared with those from previous work on acetylcholine derivatives.

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Acetylcholine Quanta

Cited by 22 publications

References 3 publications

Presynaptic action of hemicholinium at the neuromuscular junction

Presynaptic action of hemicholinium at the neuromuscular junction

Neuromuscular transmission in a mammalian preparation in the absence of blocking drugs and the effect of D‐tubocurarine

A reinvestigation of the crystal structure of acetylcholine bromide

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