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Phases of insulin release were studied in the perfused pancreas with glucose or calcium used as stimulators. Stimulation patterns included constant prolonged single steps, restimulations and staircase stimulations. Except at low concentrations, glucose elicited early spikes of insulin and the slowly rising second phase. In single-step experiments, total insulin in the spikes increased with higher glucose concentration. However, time patterns were the same; ratios of initial secretion rate to total insulin secreted were constant. Total insulin in the spikes was a skewed sigmoidal function of glucose concentration; mathematical differentiation of this function approximated a bell-shaped distribution curve. Staircase experiments showed that insulin released as a spike at each step did not correlate with the increment of glucose but rather with the available insulin for a given glucose concentration, minus that released in previous steps. A two-compartmental model for insulin storage has been expanded by the hypothesis that labile insulin exists as a bell-shaped distribution of packets that rapidly release insulin when their sensitivity or threshold to glucose has been reached. Glucose was maintained at permissive concentrations and calcium was perfused as continuous single steps with restimulation and as staircases. Results were qualitatively like those with glucose. Spike responses, in terms of time, were similar to each other; total insulin released as spikes depended on that insulin releasable by an absolute calcium concentration minus that released in any previous step. It was concluded that glucose and calcium act together or sequentially on the insulin packets whose threshold to stimulator varies according to a bell-shaped distribution density.

Shallow subembayments respond differently than deep channels to physical forces acting in estuaries. The U.S. Geological Survey measured suspended-sediment concentrations at five locations in Honker Bay, a shallow subembayment of San Francisco Bay, and the adjacent channel to investigate the spatial and temporal differences between deep and shallow estuarine environments. During the first freshwater pulse of the wet season, the channel tended to transport suspended sediments through the system, whereas the shallow area acted as off-channel storage where deposition would likely occur. Following the freshwater pulse, suspended-sediment concentrations were greater in Honker Bay than in the adjacent deep channel, due to the larger supply of erodible sediment on the bed. However, the tidal variability of suspended-sediment concentrations in both Honker Bay and in the adjacent channel was greater after the freshwater pulse than before. During wind events, suspended-sediment concentrations in the channel were not affected; however, wind played a crucial role in the resuspension of sediments in the shallows. Despite wind-wave sediment resuspension in Honker Bay, tidally averaged suspended-sediment flux was controlled by the flooddominated currents.