Abstract
AbstractVirgin females of Melanoplus sanguinipes were starved for three days from emergence and then provided with food for various periods of time, ranging from five minutes to 72 hours. The temporal sequence of changes in neurosecretory activity, blood protein level and gut protease activity was investigated.The starved insect has a neurosecretory system loaded with stainable product. Feeding, however, promotes a massive release of this material within 20 to 40 minutes. A significant increase in the synthetic activity of the neurosecretory cells (measured as 3H‐L‐cystine incorporation) does not begin until about two hours after food intake. Five or six blood protein bands can be separated electrophoretically, of which 2 and 3 are always present in relatively high concentrations. They are also the most variable, the changes in total blood protein level being almost entirely a reflection of the changes in these two. the blood protein level being almost entirely a reflection of the changes in these two. The blood protein level decreases during the first 12 hours of feeding (from 1.94 to 1.07 g/100 ml) but increases rapidly over the next 60 hours to reach a value of almost 4 g/100 ml. Total protease activity (crop + midgut lumen + caeca) increases shortly after feeding has begun and after four hours is significantly greater than in the three‐day starved female. The activity continues to rise until it is about 2.5 × the starvation level after 72 hours.It is suggested that feeding stimulates the synthesis and release of neurosecretory material. The correlation between the rapid release of neurosecretion and early increase in protease activity is consistent with the hypothesis that the hormone acts directly upon the midgut epithelium stimulating protease synthesis. Furthermore the decrease in the level of blood protein for the first 12 hours after feeding could mean that it is being utilised in the production of digestive enzyme.
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