Change in translucency of squid mantle muscle upon storage

ABSTRACT:   Change in the translucency of squid mantle muscle during itsstorage at 0°C was studied by monitoring L* valueand turbidity. Two indicators showed that squid mantle muscle lostits translucency and reached maximal turbidity within 24 hof storage. Thickness of mantle muscle also increased by 15% in12 h, earlier than the loss of translucency. ATP contentdecreased with storage time and was completely lost in almost 24 h,a similar period to translucency loss, but later than rigor contraction.Development of black color on skin surface by chromatophores wasfully achieved in 24 h. It was thus concluded that ATPcontent was well correlated with a loss of translucency or increasein the turbidity of mantle muscle and development of dark coloron the surface skin of mantle.     

TMAOase, trimethylamine-N-oxide demethylase, isa thermostable and active enzyme at 80°C

ABSTRACT:   Purified trimethylamine- N -oxide demethylase (TMAOase)from walleye pollack muscle is a thermostable protein that was notinactivated after heating at 80°C for 30 min.The heated enzyme was electrophoresed in the same manner as fornative enzyme. Circular dichroism (CD) spectra for purified enzymechanged reversibly in the temperature range of 10–80°C.As the enzyme was still active at 80°C, the CD spectralchange did not directly relate to enzyme activity. TMAOase activity inthe myofibrillar fraction decreased sharply above 30°C,but was extracted and recovered from the heated myofibrillar fraction,suggesting that the activity seemed to be interrupted and apparently inactivateddue to the thermal alteration of myofibrillar proteins or some unknownfactors. The complicated profile found in dimethylamine (DMA) formationfrom trimethylamine- N -oxide (TMAO) in walleye pollack muscleduring heating consisted of both enzymic and non-enzymic processes.Most DMA was produced enzymatically below 40°C and interruptedabove 40°C. Therefore, DMA and trimethylamine was formednon-enzymatically at high temperatures regardless of the presenceof native enzyme. A new, simple and easy purification method wasproposed based on the thermostable nature of the enzyme.     

DYNAMIC COMPUTED TOMOGRAPHY OF THE PANCREAS IN NORMAL DOGS AND IN A DOG WITH PANCREATIC INSULINOMA

To establish optimal imaging conditions for enhanced computed tomography (CT) for canine pancreatic tumors, 10 healthy beagles were subjected to dynamic CT. This technique was then applied to a dog with suspected insulinoma. The changes in mean peak enhancement and the delay time of the aorta and pancreas were determined. In normal beagles, maximal arterial and pancreatic CT enhancement was observed at 15 +/- 2 s (795 +/- 52 Housfield unit [HU]) and 28 +/- 9 s (118 +/- 16HU) after contrast medium injection, respectively. Multiphase enhanced CT was performed in a pug with suspected insulinoma using the CT protocol defined for the normal beagles with some parameters modified; the images were acquired at the arterial (14 s after contrast medium injection), pancreatic (after 28 s), and equilibrium (after 90 s) phases; scanning was followed by exploratory laparotomy. CT images were characterized by an enhanced mass in the left pancreatic lobe at the arterial phase, during which the difference between the CT values of the mass and normal pancreas was the highest. Histopathologic diagnosis of the pancreatic mass was insulinoma. Thus, it appears that enhanced CT imaging can be used to delineate the pancreas from a pancreatic mass, and it may be helpful in deciding the need for surgery.     

Thermal denaturation and autolysis profiles of myofibrillar proteins of mantle muscle of jumbo squid Docidicus gigas

ABSTRACT:    Jumbo squid was very similar to Japanese common squid in terms of myofibrillar Ca²⁺-, Mg²⁺- and K⁺(EDTA)-ATPase activities. Myofibrils of jumbo squid were significantly stabilized upon addition of Ca²⁺ and destabilized by increasing KCl concentration for heating. Incubation of muscle homogenate of jumbo squid induced a selective cleavage of myosin into two major fragments and the cleavage was inhibited by EDTA. Autolysis was prominent at and above 0.3 M NaCl where myosin filaments dissolve. The enzyme involved in the autolysis was proved to be unstable showing maximal autolysis rate at 25°C. Washing the homogenate partially reduced the autolysis activity.