Pathophysiology of ischemic cell death: III. Role of extracellular factors.

The purpose of this study was to determine the effect on cell survival of extracellular changes that occur during ischemia, over and above the depletion of O2 and substrate. Rabbit retinas were deprived in vitro of both O2 and substrate, and then returned to control medium for 4 h before recovery was assessed by measuring protein synthesis, glucose utilization, and tissue water. Experimental conditions were altered in various ways during the period of O2 and substrate deprivation in order to modify the changes taking place in the interstitial fluid as a result of the failure of energy metabolism.

Pathophysiology of ischemic cell death: II. Changes in plasma membrane permeability and cell volume.

Isolated rabbit retinas were subjected for various durations to several types of ischemic insult, and then returned to control medium for periods of up to 4 3/4 h before measurements were made of total water, inulin-free water, and plasma membrane permeability as assessed by mannitol penetration into the inulin-free water. Neither anoxia nor substrate deprivation alone, for as long as 50 min, caused significant irreversible swelling, but they were synergistic in combination. Restricting the volume of extracellular fluid during the combined deprivation caused the changes responsible for swelling to occur much sooner.

Pathophysiology of ischemic cell death: I. Time of onset of irreversible damage; importance of the different components of the ischemic insult.

Rabbit retina was used as an example of organized central nervous tissue in in vitro experiments designed to characterize the onset of cell death from ischemia. Retinas were subjected to progressively longer periods of different types of ischemic insult and then given an opportunity to recover before being tested for irreversible damage, using failure to reinstitute protein synthesis as the principal criterion. Anoxia was more damaging than substrate deprivation, but they were synergistic in combination.

In vitro retina as an experimental model of the central nervous system.

Methods are described for isolating adult rabbit retinal and maintaining it in a medium designed to resemble CSF. Morphologic, metabolic, nd electrophysiologic measurements obtained on the in vitro retinas showed that they remained in a nearly physiological state for at least 8 h, and even after 2 days in vitro they still exhibited a high level of metabolic activity and electrical responsiveness to light. Physiological activity was modified by photic stimulation, and data are presented to document changes in metabolism in response to the changes in function.

Synthesis and degradation of retinal proteins in darkness and during photic stimulation.

Rabbit retinas were maintained in a physiological state in vitro and exposed to 0.5-h pulses of labeled leucine. Protein synthesis was determined from incorporation of the label, and degradation from its subsequent release.