Mean segmental transit time of radiopaque markers through the right colon, left colon and rectosigmoid areas of adults and children has been calculated form their distribution on consecutive plain films of the abdomen. Overall mean transit does not differ significantly in the large bowel between adults and children. However, there are regional differences within the colon in relation to age. Mean transit time in the right colon is 13.8 hours in adults and 7.7 in children (p less than 0.01). Corresponding values in the left colon are 14.1 and 8.7 hours (p less than 0.02) and, in the rectum, 11 and 12.4 hours (p = NS). The percentage of the mean total large bowel transit time spent in the right colon, left colon and rectosigmoid area are respectively for adults and children 33 +/- 4 and 28 +/- 3 per cent (p = NS); 39 +/- 4 and 32 +/- 4 per cent (p = NS); and 28 +/- 4 and 41 +/- 4 per cent (p less than 0.05), indicating a relative stagnation in the rectosigmoid area of children. These physiologic differences may have implications in diseased states.

This study was done to understand the different available methods used to calculate colorectal transit times. A single abdominal radiograph is taken following six successive daily ingestions of the same number of identical radiopaque markers. This method correlates well (P less than 0.001) with that using a single ingestion of markers with daily x-ray films until total expulsion. In techniques used to measure colorectal transit time with multiple ingestion of markers, the number of days of ingestion depends on the kinetics of marker defecation. This was found to differ markedly in various groups of control subjects and constipated patients (P less than 0.001) and can be used to obtain reliable data, even in subjects with severe constipation. When they ingest 20 markers, constipated patients are found to retain eight or more markers three days after ingestion, and taking a plain film of the abdomen on that day is sufficient to make a diagnosis of constipation. Transit time studies are reproducible from month to month in patients with an irritable bowel syndrome. Control subjects who claim that their bowel habits are not modified by stress have shorter transit times, similar in both sexes, than those who say they are (P less than 0.001). This may explain why a large percentage of constipated patients have been found by most authors to have "normal" colorectal transit times. The choice of control subjects is thus a key element in studies of functional bowel motor disorders. Stool frequency and consistency, in health, correlate only to rectosigmoid transit time.

The influence of the origin and kind of caseinophosphopeptide (CPP) on iron absorption was assessed by comparing a commercially available CPP mixture (CPPs) and derived chromatographic fractions with the purified, chemically phosphopeptide of beta-casein [beta-CN(1-25)] using a perfused rat duodenal loop system; gluconate iron was used as control. Only iron complexed to beta-CN(1-25) displayed a better bioavailability than gluconate iron. The results obtained with various chromatographic fractions indicated that phosphopeptides of different origins (alpha(s)- versus beta-caseins) display specific effects. These findings contribute to the explanation of the discrepancy about the role of caseinophosphopeptides on mineral bioavailability in vivo.