Intermediates in the constitutive and regulated secretory pathways released in vitro from semi-intact cells

To quantify synaptophysin in the same gel (see Figs. 3 and 4), the bottom part was cut, transferred to nitrocellulose, and probed with SY38 antibody as described above . In two experiments, quantitation of fluorograms was done with a densitometer (Bio-Rad Laboratories, Cambridge, MA) (Figs . 5A and 6B) . A PhosphorImager (Molecular Dynamics, Sunnyvale, CA) was used for the remainder. For densitometric quantitation, an adjacent scan below the chromogranin B and secretogranin II bands was subtracted as background . For PhosphorImager quantitation, pixel volume from the broad region of top of the gel well above the chromogranin B band, where proteoglycans were most concentrated, was quantified as proteoglycans . Chromogranin B and secretogranin II were quantified by subtracting as background the average pixel volume from equal areas above and below each band, to subtract contributions from rapidly migrating proteoglycans.