Anatomy and physiology of human body are essential and fundamental subjects for medical or nutritional sciences. In medical and nutrition training organizations, dissection of small animals such as rats and mice are often carried out for the purpose of learning the structure and function of the human body. This is a very useful or effective methods to understand the three-dimensional (3D) structures of anatomy. However, in most cases, the anatomical practices for students will not gain the sufficient educational effects comparable to the cost of sacrificing animals due to the shortage of training time. We have previously reported an animal fixation method that can be carried out conveniently, safely, and repeatedly in rats by using of Farmer’s fixative. This liquid consists of mixture with acetic acid and ethanol (acetic acid:ethanol; 1:3, v:v). Although this method made it possible to dissect, anatomize, and observe various tissues and organs, there are several weaknesses such as insufficiency of fixation in deep organs. In order to solve or alleviate these defects, the authors changed the fixing method and the composition of the fixing solution and evaluated the qualities of specimens fixed with our present method. In this experiments, it was found that performing immersion fixation in addition to perfusion fixation and using a concentration of acetic acid: ethanol at 1:7 as the perfusion fixative are most appropriate condition for anatomical practices. Through these improvements, we were able to make specimens of rat more suitable for dissection training and detailed observations. Furthermore, since this method can be used repeatedly without scarifying new experimental living animals, it is possible to realize “Reduction” in 3R. In this paper, we mainly discuss on improvements and qualities by comparing our previous method with present procedure.
Eye damage is defined as the production of reversible changes in the eye, following the application of a test chemical to the ocular surface. Chemicals causing such changes are classified as category 2 by the United Nations Globally Harmonized System of Classification and Labeling of Chemicals (UN GHS). In 2015, an eye irritation test (EIT) method developed to identify category 2 chemicals was scientifically validated and approved by the OECD as the test guideline 492 (OECD TG 492). A new EIT using LabCyte CORNEA-MODEL24, a commercially available recombinant human corneal epithelial (RhCE) tissue model developed by Japan Tissue Engineering Co., Ltd. (J-TEC), has been established as a similar method to the OECD TG 492. Here we report the results of a validation study conducted according to the performance standard for the OECD TG 492 to evaluate the accuracy and performance reliability of LabCyte CORNEA-MODEL24 EIT at three independent laboratories. LabCyte CORNEA-MODEL24 EIT was highly predictive and reliable, showing sensitivity of 97%, specificity of 68.9%, and overall accuracy of 83.5%. These results satisfy the acceptance criteria of the performance standard for the OECD TG 492 (90% for sensitivity, 60% for specificity and 75% for accuracy). The reproducibility of results within- and between the three participating laboratories was also within acceptable ranges. Altogether, the results from this validation study confirm that LabCyte CORNEA-MODEL24 EIT is a robust method to identify chemicals with the potential to trigger eye irritation events.