The effect of optic nerve section on blood glucose levels in Paranephrops zealandicus (Crustacea: Macrura)

Role of methionine-enkephalin on the regulation of carbohydrate metabolism in the rice field crab Oziotelphusa senex senex

In the present study, the role of eyestalks and involvement of methionine-enkephalin in the regulation of haemolymph sugar level was studied. Bilateral eyestalk ablation significantly decreased the haemolymph sugar levels, whereas injection of eyestalk extract into ablated crabs significantly increased the haemolymph sugar levels. Total carbohydrate (TCHO) and glycogen levels were significantly increased in hepatopancreas and muscle of eyestalk-ablated crabs, with a decrease in phosphorylase activity. Injection of eyestalk extract into ablated crabs resulted in partial/complete reversal of these changes. Injection of methionine-enkephalin into intact crabs significantly increased the haemolymph sugar level in a dose-dependent manner. Total tissue carbohydrate and glycogen levels were significantly decreased, with an increase in phosphorylase activity in hepatopancreas and muscle tissues of intact crabs after methionine-enkephalin injection. Methionine-enkephalin injection did not cause any changes in haemolymph sugar, tissue total carbohydrate and glycogen levels and activity levels of phosphorylase in eyestalk-ablated crabs. These results suggest that the eyestalks are the main source of hyperglycaemic hormone and methionine-enkephalin induces hyperglycaemia through eyestalks.

Fluorescence studies of the calcium binding to whiting (Gadus merlangus) parvalbumin

The calcium binding by parvalbumin of whiting (Gadus merlangus) has been studied using tryptophanyl fluorescence characteristics. Titration of Ca2+-free parvalbumin with Ca2+ leads to a very pronounced blue shift, narrowing and intensification of the fluorescence spectrum. These spectral changs proceed in two stages reflecting the existence of at least three forms which can be interpreted as (a) the protein without Ca2+, (b) with one Ca2+ and (c) with two bound Ca2+ ions/molecule. The fluorescence of these forms has been identified and the fluorescence spectra measured at varied Ca2+ concentrations were resolved into three components corresponding to these spectral forms. The dependence of the relative concentration of the three fomrs on Ca2+ concentrations agree well with the two-step binding of Ca2+ to parvalbumin: Protein + Ca in equilibrium K1 protein x Ca; Protein x Ca + Ca in equilibrium K2 Ca x protein x Ca. The equilibrium binding constants K1 and K2 obtained by the computer fit are approximately 5 X 10(8) M-1 and 6 X 10(6) M-1. This scheme and the K1 and K2 value are in a good agreement with the independent experimental data resulting from EGTA titration of Ca2+-saturated parvalbumin and pH titratin of parvalbumin in the presence of EGTA and CA2+.