Anatomical and histological characteristics of the lungs in the ground squirrel (Spermophilus citellus).

The aim of this work was to study the topography, morphology, vascularisation, histology and innervation of the lungs in the ground squirrel (Spermophilus citellus) and compare these data with those concerning the rat, mole rat, rabbit and mouse. The research was carried out on 15 animals. It was revealed that the right lung has four lobes (cranial, middle, caudal and accessory lobes), while the left lung is not divided into segments. The functional vessels are a. pulmonalis dextra et sinistra and vv. pulmonales (5-6), while the nutritive vessels of the lungs are a. bronchoesophagea dextra and v. bronchoesophagea dextra. Histological tissue sections of the lungs revealed that the wall of terminal bronchioles contains no cartilage and the mucosal epithelium is pseudostratified, cubic and ciliated. Clara cells (club cells, bronchiolar exocrine cells) are present but have no cilia. The lung alveolar diameter is 37 µm on average, and the thickness of the alveolar wall and the interalveolar septa is 1.38 µm. Destruction of the alveolar walls, accumulation of erythrocytes in the capillaries of alveolar septa and destruction of the cytolemma of the capillary endothelium were detected. In addition, connective tissue fibres and peripheral nerves were detected by silver impregnation.

Lack of clastogenic effects of L-thyroxine in whole-blood cultured human lymphocytes

Thyroid hormones stimulate aerobic metabolism which may lead to oxidative stress accompanied by damage to various cellular macromolecules, including DNA. Previous comet assay studies have shown that thyroid hormones cause DNA damage due to the creation of reactive oxygen species (ROS). However, cytogenetic studies have been equivocal because although an increase in the sister-chromatid exchange frequency per cell has been reported increased micronuclei frequency has not. We used cytogenetic examination of chromosome breakage and aberrations in whole-blood cultures of human peripheral blood lymphocytes to investigate possible clastogenic effects when lymphocytes were exposed to 0.002 µM to 50 µM of L-thyroxine for 24 h and 48 h, these concentrations being chosen because they had been used in previous studies of sister-chromatid exchange and micronuclei frequency. Under our experimental conditions thyroxine did not induced any statistically significant increase in chromosome breakage or aberrations. This lack of clastogenic effects is in contrast to the reported comet assay results obtained using purified lymphocytes, possibly because whole-blood cultures contain catalase and glutathione peroxidase capable of reducing the effects of reactive oxygen species.