Effect Of Postmortem Storage Research Articles

Effect of postmortem storage on activity of μ- and m-calpain in five bovine muscles1

An in situ system involving incubation of 60- to 80-g pieces of muscle at 4 degrees C under different conditions was used to determine the effects of time of postmortem storage, of pH, and of temperature on activities of mu- and m-calpain activity in bovine skeletal muscle. Casein zymograms were used to allow measurement of calpain activity with a minimum of sample preparation and to ensure that the calpains were not exposed to ionic strengths of 100 or greater before assay of their activities. In 4 of the 5 muscles (longissimus dorsi, lumbar; longissimus dorsi, thoracic; psoas major; semimembranosus; and triceps brachii) studied, mu-calpain activity decreased nearly to zero within 48 h postmortem. Activity of m-calpain also decreased in the in situ system used but at a much slower rate. Activities of both mu- and m-calpain decreased more slowly in the triceps brachii muscle than in the other 4 muscles during postmortem storage. Although previous studies have indicated that mu-calpain but not m-calpain is proteolytically active at pH 5.8, these studies have used calpains obtained from muscle at death. Both mu- and m-calpain are proteolytically inactive if their activities are measured at pH 5.8 and after incubating the muscle pieces for 24 h at pH 5.8. Western analysis suggested that neither the large 80-kDa subunit nor the small 28-kDa subunit of m-calpain was autolyzed during postmortem storage of the muscle pieces. As has been reported previously, the 80-kDa subunit of mu-calpain was autolyzed to 78- and then to a 76-kDa polypeptide after 7 d postmortem, but the 28-kDa small subunit was not autolyzed; hence, the autolyzed mu-calpain molecule in postmortem muscle is a 76-/28-kDa molecule and not a 76-/18-kDa molecule as previously assumed. Because both subunits were present in the postmortem calpains, loss of mu-calpain activity during postmortem storage is not due to dissociation of the 2 subunits and inactivation. Although previous studies have shown that the 76-/18-kDa mu-calpain molecule is completely active proteolytically, it is possible that the 76-/28-kDa mu-calpain molecule in postmortem muscle is proteolytically inactive and that this accounts for the loss of mu-calpain activity during postmortem storage. Because neither mu- nor m-calpain is proteolytically active at pH 5.8 after being incubated at pH 5.8 for 24 h, other proteolytic systems such as the caspases may contribute to postmortem proteolysis in addition to the calpains.

Effect of postmortem storage on the [ 3H]hemicholinium-3 binding site in the rat brain. Preliminary study for investigations of human patients with Alzheimer's disease

The effect of postmortem storage at room temperature (24–26°C, 0–4 h) and cold-room temperature (4°C, (0–24 h) on the [ 3H]hemicholinium-3 binding sites in the brain hippocampus, cortex and cerebellum of 3-month-old Wistar rats was studied. A slow decrease in the density of the binding sites was observed at both temperatures, which was best fit by a linear model common for all three brain regions. No systematic alterations of the affinity of the binding sites for hemicholinium-3 were found. The values obtained from experiments with animals were compared with the values measured in the frontal cortex of old men. Approaches to the evaluation of data obtained from postmortem samples of human brain tissue of patients with Alzheimer's disease are proposed.

Effect of post-mortem storage on Ca ++-dependent proteases, their inhibitor and myofibril fragmentation

Post-mortem changes in two calcium-dependent proteases, their inhibitor, myofibril fragmentation index (MFI) and collagen (amount and solubility) were studied. Whereas the activity of high Ca ++-requiring calcium-dependent protease (CDP-II) remained nearly constant throughout post-mortem storage, there was a progressive decrease in the activities of low Ca ++-requiring calcium-dependent protease (CDP-I) and their specific inhibitor, with the inhibitor being the most susceptible to post-mortem storage. Results indicated that the greatest changes in MFI occur within the first 24 h of post-mortem storage. There were no detectable changes in either total or soluble collagen content with post-mortem storage. Hence, it was concluded that improvement in tenderness resulting from post-mortem storage must be derived from changes in the myofibrils and since CDP-I activities paralleled the myofibrillar changes, it seems reasonable to suggest that CDP-I, not CDP-II, plays an important role in the fragmentation of myofibrils and consequently in improvement of meat tenderness resulting from post-mortem storage.

Effects of postmortem storage by freezing on ligament tensile behavior

The purpose of this study is to examine the effect of prolonged postmortem freezing storage (between 1 1 2 and 3 months at −20°C) on the structural properties of the medial collateral ligament (MCL)-bone complex as well as the mechanical properties of the MCL substance from the rabbit knee. Tensile testing of the femur-MCL-tibia specimen was performed and no statistically significant changes were noted between the fresh and stored samples in terms of the cyclic stress relaxation, the load-deformation characteristics, as well as the load, deformation and energy absorbing capability at failure. The area of hysteresis of the stored samples was significantly reduced in the first few cycles, however. The mechanical properties of the MCL substance, as represented by the stress-strain curves, tensile strength and ultimate strain also did not change following storage. We conclude, therefore, proper and careful storage by freezing would have little or no effect on the biomechanical properties of the ligaments.

Effect of Postmortem Storage on Cold-Shortened Bovine Muscle: Analysis by SDS-Polyacrylamide Gel Electrophoresis

Myofibrils were isolated from the longissimus (L) muscle of control (CON) and cold-shortened (CS) muscles after 0, 1, 3, 7, and 10 days of postmortem storage at 2°C. Isolated myofibrils were then examined by SDS-polyacrylamide gel electrophoresis to monitor the changes in the myofibrillar proteins during postmortem storage. The main changes in CS muscles were the gradual appearance of 110,000-, 95,000-, and 30,000d-dalton components and the disappearance of desmin and troponin-T components of myofibrils. In addition, there was a gradual increase in the intensity of a protein around 55,000-daltons. CON samples showed similar changes to those of CS samples. It appears that myofibrillar proteins of cold-shortened muscles are affected by postmortem aging in a manner similar to that of the normally chilled muscles.

Effects of Postmortem Storage on Muscle Protein Degradation: Analysis by SDS-Polyacrylamide Gel Electrophoresis

Changes in myofibrillar proteins of bovine longissimus and semitendinosus muscles were examined during 14 days of postmortem storage at 2°C by SDS-Polyacrylamide gel electrophoresis. Major changes in both muscles were: (1) appearance of a 95,000-dalton component; (2) gradual disappearance of troponin-T and gradual appearance of a 30,000-dalton component; (3) gradual increase in intensity of a protein around 55,000-daltons; and (4) gradual appearance of a 110,000-dalton component. With the exception of the 95,000-dalton component, the other changes have been reported previously by other authors. At the present time we have no knowledge of the origin of the 95,000-dalton component, but it is known that calcium-activated factor (CAF) is responsible for degradation of troponin-T. Appearance of the 95,000-dalton component during postmortem storage suggests involvement of CAF for increasing tenderness during postmortem storage.

Effects of Postmortem Storage and Temperature on Muscle Protein Degradation: Analysis by SDS Gel Electrophoresis

ABSTRACTThe proteolytic breakdown of the major contractile proteins of bovine longissimus muscle was examined during postmortem storage by sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis. Samples of muscle stored at 4°C for 14 days exhibited little proteolysis of the major contractile proteins; however, samples stored at 37°C for 1 day showed significant degradation of myosin heavy chains and almost complete proteolysis of this protein by day 14. Major degradation products of the myosin heavy chains included a series of polypeptides having molecular weights between 145,000 and 125,000. These experiments demonstrate that substantial degradation of the myosin heavy chain and other muscle proteins can occur during the storage of meat, and this phenomenon was highly temperature dependent.

Effects of post-mortem storage on synaptic 5-HT binding and uptake in mammalian brain.

Synaptosomes and synaptic membranes were isolated from rat brain after various storage times and temperatures of the tissue. Synaptosomal 5-HT uptake was diminished by about 20% within the first hour after decapitation. No significant change in the incorporation rate was observed for the seven proceeding hours if the brains were stored at room temperature. After an initial decrease of about 15%, 5-HT incorporation remained constant for at least 24 hours if the tissue was stored at 4 degrees C. Electron micrographs showed that nerve endings were highly disrupted by freezing and thawing of the brains.--The capacity of high affinity 5-HT binding to the microsomal synaptic membrane fraction decreased with the first hour by about 13% to 120--130 fmoles 5-HT/mg protein and remained almost constant for the next eight hours. Freezing at --80 degrees C of whole brain or of isolated membranes did not affect 5-HT receptor interaction.--The capacity of specific 5-HT binding to membranes isolated from human post-mortem brain was comparable to that found with synaptic membranes from rat brain. In contrast to the control values, a significant decrease in 5-HT binding was observed in membrane fractions isolated from brain after cerebral insult.