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ABSTRACT
Crowding generally refers to people’s psychological response to density, that is, to their feelings of being crowded, having a lack of privacy or an increase in unwanted interactions or psychological distress. Population density may be raised either by increasing the number of species living in the same area and/or by reducing their living space. The lungs are a pair of primary organs of respiration, present in the thoracic cavity beside the mediastinum. They are covered by a thin double-layered serous membrane called the pleura. The respiratory system consists of two components, the conducting portion, and the respiratory portion. The conducting portion brings the air from outside to the site of the respiration. The respiratory portion helps in the exchange of gases and oxygenation of the blood. The aim of this study was to investigate the effects of crowding (space limitation) on the airways and lung histology in Wistar rats. Twentyfive (25) male wistar rats of comparable age weighing between 160g-190g were used for this experiment. The rats were divided into five (5) groups (A, B, C, D and E) with five (5) animals in each group. Group A served as Control, while Group B to E served as the Test Groups. Crowding stress was induced by reducing the size of the cages for the cages for the different test groups. Group A animals which were the control were placed in a cage with the dimension 42cmX30cmX24cm. Group B animals were placed in a cage having the same size and dimension as that of the control, that is 42cmX30cmX24cm. Group C animals were placed in a cage that was three-quarter (¾) the size of the control, that is 31.5cmX22.5cmX24cm. Group D animals were placed in a cage that is half (½) the size of the control, that is 30cmX21cmX24cm. Group E animals were placed in a cage that is one-quarter (¼) the size of the control, that is 21cmX15cmX24cm. The animals in all the groups were allowed to live in their various cage dimensions for a duration of seven (7) weeks. At the end of the experiment the animals were sacrificed under chloroform anesthesia and thereafter samples of trachea and lung tissue was also harvested for histological evaluation. The harvested trachea and lung tissue samples were placed in universal bottles containing 10% formal saline. At the end of the experiment, sections of the trachea and lungs were collected and fixed immediately into 10% formal saline for routine histopathological examination. They were later dehydrated by passing through varying and increasing concentration of alcohol, that is 70-100% and thereafter cleared in xylene and then the tissue were embedded in molten paraffin and then sectioned and stained with hematoxylin and eosin dye as described by Lillie in 1965. The sections were examined under light microscope at a high power magnification and photomicrograph were taken. The histopathological evaluation were performed by a pathologist. The results showed the trachea and lungs responded to increased crowding by mobilizing inflammatory cells and cells of the mononuclear phagocyte system. This phenomenon challenges the immune system, leading to increase in white blood cell secretion for defense. Consequently, as crowding intensifies, immune cell activation also increases.
