In previous papers we studied the rising phase of a miniature endplate current (MEPC) to derive diffusion and forward rate constants controlling acetylcholine (AcCho) in the intact neuromuscular junction. The present study derives similar values (but with smaller error ranges) for these constants by including experimental results from the fallins phase of the MEPC. We find diffusion to be 4 x 10-6 cm2 slightly slower than free diffusion, forward binding to be 3.3 x 107 M-s-, and the distance from an average release site to the nearest exit from the cleft to be 1.6 jtm. We also estimate the back reaction rates. Heidmann and Changeux (7).] In our approach we use the shape of the MEPC as a function of AcChoR concentration to derive forward binding rates as well as information on AcCho diffusion in the intact neuromuscular cleft. We thus complement the results obtained by chemical techniques and by single-channel recording. The derived parameters support our motivating assumptions of the "saturating disk model" used by Salpeter and colleagues (8-11) to explain the generation of the MEPC. METHODSWe recorded MEPCs by voltage clamp from the intercostal muscle of the lizard Anolis carolinensis, using experimental techniques as in the first two papers of this series (1, 2) with minor modifications.Three groups were used: (i) control muscle (esterases and receptor concentration unaltered); (ii) receptors intact and esterases fully inactivated [with 1 mM diisopropyl fluorophosphate (iPr2P-F) for 1 hr]; (iii) receptors partially inactivated [with 40 nM a-bungarotoxin (BTX) for 40 min] to -0.36 its normal value (papers 1 and 2) and esterases inactivated with iPr2P-F as in ii. The filtering conditions of the voltage clamp were modified from those used in papers 1 and 2 to improve the signal-to-noise ratio. Because the falling phase of MEPCs is slow relative to the rise time, the signals were low-pass-filtered at 1 kHz (two-pole Butterworth filter) and the digitizer sampling rate was reduced to 6.25 kHz. Even though the Nyquist frequency is only a factor of 3 above our filter cutoff, aliasing was judged to be less than 4% of peak current. All experiments were done at 22 ± 10C and -100 mV holding potential. Fall time (tf) values were obtained from the experimental MEPC as 1.23 x the 90-40% fall time. The factor 1.23 is the conversion from 90-40% to efolding time for a pure exponential. Fig. 1 shows six examples of measured MEPC traces, illustrating the three conditions used in the present study. Fig. 2 plots the relation between tf and MEPC amplitude Ac, and Table 1 gives the mean values of tf and Ac under these conditions. RESULTSWe confirm (12-15) that inactivation of esterases lengthens tf appreciably and that, when cr is reduced by BTX treatment, tf is somewhat shortened again (12, 15). Our additional observations are that, when esterases are intact, tf does not depend on Ac ( Fig. 2A), but after esterase inactivation tf increases with increasing Ac (Fig. 2B). Finally, decreasing a, with esterases inactivated, alm...

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The exposure of infants, very often but by no means always resulting in death, was widespread in many parts of the Roman Empire. This treatment was inflicted on large numbers of children whose physical viability and legitimacy were not in doubt. It was much the commonest, though not the only, way in which infants were killed, and in many, perhaps most, regions it was a familiar phenomenon. While there was some disapproval of child-exposure, it was widely accepted as unavoidable. Some, especially Stoics, disagreed, as did contemporary Judaism, insisting that all infants, or at least all viable and legitimate infants, should be kept alive. Exposure served to limit the size of families, but also to transfer potential labour from freedom to slavery (or at any rate tode factoslavery). Disapproval of exposure seems slowly to have gained ground. Then, after the sale of infants was authorized by Constantine in A.D. 313, the need for child-exposure somewhat diminished, and at last — probably in 374 — it was subjected to legal prohibition. But of course it did not cease.

We have extremely strong reasons for supposing that the exposure of infants, very often resulting in death, was common in many different parts of the Roman Empire, and that it had considerable demographic, economic and psychological effects. The evidence for the first of these propositions has been reviewed or alluded to in several recent publications.1 However, a thorough new study, covering the whole of Greek and Roman antiquity, would be worth while. In the meantime Donald Engels has declared that in the Greek and Roman worlds the exposure of children was ‘of negligible importance’ (‘The problem of female infanticide in the Greco-Roman World’, CPh 75 (1980), 112–20).