Transmittance histograms

Fig. 56. A comparison of local and average measurements during hydrogen loading, (i) Height histogram. Changes in the (ii) topographical and (iii) transmittance histograms. The peak values and FWHM values of both the topography (A in ii) and transmittance (A in iii) are used to compare the local dynamic behavior in terms of phase coexistence (B in ii) and optical transmittance (B in iii) (Kerssemakers et al., 2002b).

Obtain isodensity histogram showing cell wall areas of identical UV absorbance or transmittance. 

As the vesicular concentration is equivalent to tnoles/volume and V = 4/3nr, so r is proportional to the cubed root of the vesicle content [8,20], Thus, the data for each release event can be replotted as the frequency of release events versus the cubed root of vesicular amount (in moles). A second explanation suggests that a lognormal distribution of vesicular amount will result if multiplicative deviations from the mean occur such as if integral differences in the number of uptake transporters per vesicle result in multiplicative transmitter accumulation rates [21], Thus, release event data can also be plotted as the frequency of release events vs. the log transform of quantal size. When the amperometricaUy recorded data are plotted after either of the aforementioned transformations, a dramatically different histogram with a nearly gaussian distribution results that is said to reflect the vesicular size distribution. Small deviations in the gaussian shape are possibly due to variations in the vesicular concentration, which is assumed to be constant. 

Histograms of frequency versus apparent concentration that have been prepared for voltanunograms collected from cells with and without l-DOPA exposure provide similar distributions for both types of cells [13]. These histograms are presented in Figure 9. The apparent average vesicle concentration measured in this experiment is 3.47 0.17 XM for events from L-DOPA-exposed cells, as compared to 3.35 0.24 pM for control cells. These data have led to the conclusion that loading vesicles by increased transmitter synthesis does not lead to elevated concentrations at individual release sites. It is proposed instead that vesicles increase in size as catecholamine content increases [13]. 

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