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.

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.

Hippopotamidae family is nowadays represented by two species within two different genera: pygmy hippopotamus (Choeropsis liberiensis) and common hippopotamus (Hippopotamus amphibius). The common hippopotamus has a very unique anatomy, and the shape of the body, especially the head is adapted for a semi-aquatic life style. The morphological examination and description of the gross anatomical features of the hippopotamus skull is described in this paper. The shape of the skull is adapted for the amphibian way of life. Their eyes, ears and nostrils are placed high on the roof of the skull which allows these organs to remain above the surface of the water while the animal is being submerged underwater. The skull is massive, but the brain case (neurocranium) is extremely small compared with the splanchnocranium and complete head. The dental formula of the common hippopotamus is: incisors (I) 2/2, canines (C) 1/1, premolars (P) 3-4/3-4 and molars (M) 3/3. Incisors and canine teeth are formed in the shape of tusks and are used for threat or “demonstration of power” among animals when vigorously fi ghting. Incisor teeth grow continuously and are twice bigger in males than in females.

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Morphometric parameters of the lateral ventricle choroid plexus epithelial cells (average area, perimeter, bounding rectangle area, average nuclear area, nuclear perimeter, nuclear circularity and average nucleocytoplasmic ratio) were studied in postnatal and juvenile (10 th , 16 th and 38 th postnatal days) 15 male and 15 female rats. The results were statistically analyzed by factorial ANOVA.Mean values of epithelial cells area, bounding rectangle area and perimeter were signifi cantly higher in 16 days old, than in 10 and 38 days old rats. Opposite to this, the nucleocytoplasmic ratio was lower in the 16 days old, than in 10 and 38 days old rats. Average nuclear area and perimeter showed similar trends, while nuclear circularity increased from the 10 th to the 38 th day. Signifi cant sex differences were in the epithelial cells area, bounding rectangle area and perimeter, being higher in males than in females in both 16 and 38 days groups. Nucleocytoplasmic ratio was higher in 10 days old male rats, but lower in 16 and 38 days old male rats. Generally, choroid epithelial cells size increased on the 16 th and then decreased on the 38 th day, but still remained higher compared to the 10 th day. Nuclear size after increasing on day 16, also decreased on day 38, but to values lower than on day 10. The general decrease of nucleocytoplasmic ratio which accompanied these changes indirectly suggests a functional decrease. In the investigated period the male rat choroid epithelial cells were larger, but their nucleocytoplasmic ratio, which suggests the functional status, was lower than in females, indicating sex differences in the growth dynamics of the rat choroid plexus.