Static SIMS studies of the oxides and hydroxides of aluminium.

The degree of hydroxylation or hydration of aluminium surfaces has been examined by static secondary ion mass spectroscopy (SSIMS). The SSIMS spectra of a series of aluminium oxide, oxyhydroxide and hydroxide surfaces have been obtained using instruments in three configurations. Similarities were observed in both negative and positive secondary ions spectra. Even though a direct comparison of the relative intensities cannot be made from one instrument to the other, a similar ranking of the various aluminium hydroxylation states was observed. Several ranking methods are discussed, as well as the similarities and differences observed while using the three instruments. Similar secondary ions were detected whatever the degree of hydroxylation of the aluminium oxide. This argues in favour of the formation of fragments by the combination of individually sputtered atoms or clusters to form the more stable secondaries, rather than the kick-off of 'structure-related' clusters originating directly from the upper surface layer.

Effect of food on porcine gut regulatory peptides in arterial and portal venous blood.

The concentrations of gut regulatory peptides were monitored simultaneously in the portal and arterial circulations of 8 healthy conscious swine in the fasted state and after a standard mixed meal. The sampling was achieved via chronic cannulations of these two vessels. Portal/arterial differences of insulin and glucagon were similar to those previously described, indicating the importance of hepatic extraction of these two hormones. Portal/arterial differences for the gastrointestinal regulatory peptides were relatively small, however, and the liver is unlikely to be of major importance in the metabolism of these peptides.

Lymph, pancreatic and gastrointestinal hormones in response to feeding in the conscious pig.

Concentrations of several gastrointestinal hormonal peptides were measured in lymph from the cisterna chyli and in arterial plasma; in healthy, conscious pigs during ingestion of a meal. Lymph concentrations of the pancreatic hormones insulin, glucagon and pancreatic polypeptide were small compared with plasma concentrations, although postprandial increments were significant. In contrast lymph concentrations of gastrin, cholecystokinin, motilin and gastric inhibitory peptide (GIP) from the foregut showed a more marked postprandial rise than the pancreatic hormones. Indeed the total integrated responses of these peptides in lymph reached about 50% of those seen in arterial plasma. It would appear unlikely that the lymphatics constitute an important transport mechanisms for these regulatory peptides. However, lymph concentrations of hormones may reflect levels in interstitial fluid better than plasma and may be of value in assessing putative physiological actions within a target tissue.