Ultrastructural Characterization of Prolonged Normothermic and Cold Cerebral Ischemia in the Adult Rat

Abstract

The ultrastructural effects of prolonged normothermic and cold ischemia on the cerebral cortex of the adult rat were investigated. Complete cerebral ischemia was produced by cardiac arrest and the animals' temperature was maintained at 37°C for periods ranging from 0 to 81 hours before electron microscopy preparation. Electron micrographs of cold cerebral ischemia were generated after stabilizing the rat's temperature at 0°C after cardiac arrest for periods ranging from 0 hours to 6 months. A qualitative examination of the electron micrographs shows structural signatures of energy depletion such as vessel leaking and chromatin clumping after 1 hour at 37°C and after 24 hours at 0°C, followed by synapse degradation after 6 hours at 37°C and 1 week at 0°C. Evidence of advanced necrosis was observed after 36 hours at 37°C and 2 months at 0°C. A deep learning algorithm was introduced that demonstrates the temperature dependence of ischemia-induced ultrastructural changes and that can also successfully distinguish between early ischemic changes and advanced necrosis.

Onset and progression of postmortem histological changes in the central nervous system of RccHan™: WIST rats

“…Environmental conditions influence postmortem changes. In the present study, the onset and progression of these changes was notably slower in animals stored under refrigeration in contrast with animals stored at room temperature, corroborating the positive effect of refrigeration in delaying postmortem changes (46)(47)(48). Overall, severity of findings after 48 h at room temperature was higher than after seven days under refrigeration and similar to or slightly lower than after 14 days under refrigeration, confirming that higher environmental temperatures accelerate the progression of autolytic changes.…”

Postmortem changes in brain cell structure: a review

“…h, but the ability to visualize them was lost by a PMI of 24 h (de Wolf et al, 2020). When stored at 0 °C, this study found that synapses could be visualized at 48 h of PMI but were lost at the next time point studied of 168 h of PMI.…”

“…Hukkanen 1987 note the formation of network-like structures in myelin lamellae at 24 h (Hukkanen and Röyttä, 1987). de Wolf 2000 notes unravelling of myelin sheaths at 9 h PMI with storage at 37 °C (de Wolf et al, 2020). Ansari 1976b notes that myelin lamellae splitting can also occur in cerebral edema and that its occurrence may be associated with the postmortem increase in the water content of the brain (Ansari et al, 1976b).…”

“…Haines 1968 notes a slight swelling of myelin in some areas, first noticed at 18 h of PMI (Haines and Jenkins, 1968). On the other hand, de Wolf 2020 describes myelin thinning, first noticed at 3.86 h of PMI with storage at 37 °C (de Wolf et al, 2020). Aside from these artifacts, myelin is generally reported to be stable in the PMI.…”

Cryonics Takes Another Big Step Toward the Mainstream

“…This issue of RR contains a comprehensive study to understand the ultrastructural effects of circulatory arrest on the mammalian brain. 4 The authors of this article show that ischemia-induced damage to the brain is a time-and temperature-dependent process. It takes many hours of normothermic global ischemia, and several weeks of cold global ischemia, to damage the fine structure of the brain to a degree that the original structure of the brain cannot be recognized or inferred.…”