Renal dysplasia is a developmental disorder of the renal parenchyma involving anomalous differentiation. It is characterized by persistent metanephric ducts surrounded by primitive mesenchyme, fetal or immature glomeruli, fetal or immature tubules, interstitial fibrosis, and dysontogenic metaplasia involving tissues such as cartilage. Renal dysplasia has been rarely reported in rats. Here, we observed a small left kidney in a rat used in a short-term repeat toxicity study. The rat showed no clinical signs throughout the study. All parameters, including those reflecting kidney functions, were normal upon hematological examination and urinalysis. Grossly, the kidney was small (5 × 8 mm) and its surface appeared normal. Histological examination revealed that the cortex and medulla were poorly demarcated and contained immature/atrophic glomeruli, immature renal tubules, and mesenchymal cells. The cortex contained immature glomeruli, atrophic glomeruli with cystic dilatation of Bowman’s capsular space, and some atypical tubules. Primitive metanephric tubules in the medulla were larger in diameter than normal collecting ducts, lined by a tall columnar epithelium with pale cytoplasm and basal nucleus, and surrounded by loose mesenchymal cells. Occasional tubules contained pale eosinophilic homogenous material in the lumen. Thus, this was diagnosed as a case of renal dysplasia on the basis of histologic features and is the first reported case of renal dysplasia in Sprague Dawley rats.

Two unrecorded alien plants, Melilotus officinalis (L.) Lam. and M. indicus (L.) All. (Leguminosae) were found in Korea. M. officinalis is native to Eurasia and widely distributed in agricultural regions throughout the world. M. indicus is native to Mediterranean and Southwestern Europe, and naturalized in temperate regions all over the world. These species are morphologically similar to M. suaveolens (Jeon-dong-ssa-ri). However, M. officinalis is distinguished from M. suaveolens by transverse nerved legumes, definite ovary stalks, and five to eight number of ovules in ovary. M. indicus is also distinguished from M. suaveolens by smaller size of flowers, broadly triangular calyx teeth, globose legumes, and minutely papillose seeds. The local name of M. officinalis and M. indicus were given as “Ju-reumjeon- dong-ssa-ri” and “Jom-jeon-dong-ssa-ri” based on transverse nerved legumes and overall smaller size than M. suaveolens, respectively. The descriptions on morphological characters and photographs at the habitat of M. officinalis and M. indicus are provided.