Histologic assessment of neurons in rat models of cerebral ischemia

We describe a method for typing neurons into four progressive stages of ischemic deterioration based on visual characterization of the nucleus in terms of its optical contrast, delineation along the nuclear-cytoplasmic interface, and its shape. Difficulty in assessing nuclear shape required the introduction of an angularity comparator chart to improve the investigator's accuracy. Three investigators typed neurons obtained from normal, ischemic, and ischemic-reperfused rat brains. Accuracy and reproducibility of the investigators' typing decisions with and without the angularity comparator charts were evaluated. The accuracy of subjective shape assessment was compared with objective digitizer measurements of the same. The angularity comparator charts reduced subjective shape classification error by two thirds, and group error (overall performance expressed by the coefficient of variance) decreased from 15.9% to 4.7% for Type I (normal cells), from 33.9% to 17.3% for Type II (cells with angular nuclei), from 15.5% to 14.1% for Type III (cells with smeared nuclei), and from 3.2% to 5.5% for Type IV (dead cells). Thus, Type I and IV neurons can be assessed at a higher reproducibility than the intermediate Types II and III. Our typing method can also be used to evaluate the effect of treatment regimes on ischemic neuronal damage.