Cryopreservation of Winter-dormant Apple Buds IV: Critical Temperature Variation that Can Compromise Survival.

BACKGROUND: Precise temperature control in several key areas during cryopreservation of dormant, winter apple buds is critical for maximal survival. OBJECTIVE: To consider the effects of pre-harvest temperature, the duration of incubation at -30°C and variation in rewarming rate on survival. MATERIALS AND METHODS: Dormant winter buds of Malus x domestica cultivars were harvested with two different acclimation histories and cryopreserved with variation in incubation time at -30°C. Recovery from LN using slow, intermediate and rapid rewarming was investigated as well as preservation after prolonged storage at -4°C. RESULTS: The effects on survival of preharvest temperature regime and an altered -30°C incubation regime are cultivar dependent and an increase in rewarming rate has a strong negative effect on recovery. CONCLUSION: Post-thaw survival of the winter-dormant buds can be compromised by increased temperature over a period as short as 5 days prior to bud harvest. Varying incubation times at -30°C produce variable, cultivar dependent, survival and moderate increases in rewarming rates can also radically reduce survival.

Studies of the interaction of troponin I with proteins of the I-filament and calmodulin.

1. All lysine residues in native troponin I from rabbit fast-twitch skeletal muscle reacted with methyl acetimidate and ethyl acetimidate. 2. The reactivity of lysine-18 of troponin I to acetimidate was much diminished when the troponin I was complexed in the presence of Ca2+ with troponin C alone or in the whole troponin complex. 3. In the presence of EGTA, lysine-18 of troponin I in the troponin I-troponin C complex was more reactive to acetimidate than it was in the presence of Ca2+. 4. No masking of lysine residues could be detected when troponin I interacted with calmodulin or actin. 5. Sedimentation-equilibrium studies indicated that the complex of troponin I with calmodulin was more readily dissociated in the absence of Ca2+ than was its complex with troponin C under otherwise identical conditions. 6. These studies suggest that the nature of the involvement of the N-terminal region of troponin I is a major difference between its modes of interaction with calmodulin and with troponin C.