Effect of postnatal exposure to cigarette smoke on the tracheal epithelium of albino rat

Environmental tobacco smoke [ETS] is one of the most common indoor pollutants to which many children are exposed. The present work was carried out to investigate the his-ological changes of rat tracheal epithelium after postnatal exposure to cigarette smoke. Fifteen newborn albino rats were daily exposed to side-stream cigarette smoke [10 cigarettes a day, 6 days a week] for 12 weeks. From the trachea, paraffin sections were prepared and stained with Haematoxylin and eosin [H and E] stain and alcian blue-periodic acid-Schiff's stain [AB/PAS]. Toluidine blue stained semithin sections were also prepared and examined by light microscope. Ultrathin sections were processed for electron microscopic [EM] examination. In H and E stained sections the tracheal mucosa of the experimental animals showed erosion in the epithilium, oedema, and heavy mono-nuclear cellular infiltrate in the corium which resulted in polyp formation and decreased number of ciliated cells. Preneoplastic variants in the form of squamous metaplasia and dysplasia were also seen. AB/PAS stained sections revealed progressive increase in the number of goblet cells. Semithin sections showed increased number of globule leucocytes, basal cell hyperplasia and dysplasia. Electron microscope revealed swollen cilia, intracytoplasrmic cilia and loss of some basal bodies. Goblet cells were packed with numerous confluent mucus granules. Moreover, degenerated and apoptotic cells were also observed Therefore, it is strongly recommended to protect children from exposure to ETS and to warn parents about the hazards of continuous exposure of their children to cigarette smoke

Morphometric and ultrastructural changes in the sciatic nerve of the albino rat after a long period of immobilization of the knee and ankle joints

The sciatic nerve was used as a model to study the effect of a long period of immobilization on the peripheral nerves. Ten young adult male albino rats were used in this investigation. The left knee and ankle joints were immobilized for 12 weeks using a plaster cast. The contralateral right side was used as control. After removal of the cast, segments from the sciatic nerves of the immobilized and control sides were excised and processed for ultrastructural and morphometric studies. Morphometric study revealed that immobilization of the rat hind limb resulted in a highly significant reduction [43%] in the cross-sectional area of the sciatic nerve, a highly significant reduction [33%] in the total number of the myelinated fibers, a highly significant reduction [21%] in the mean diameter of the myelinated fibers and a highly significant increase [19%] in the myelinated fiber density/mm[2]. The size distribution of the myelinated fibers showed marked changes after immobilization. The statistical data showed a shift toward, the small size distribution and the small diameter myelinated fibers outnumbered the medium-sized and the large diameter fibers. Moreover, myelinated fibers with a diameter >15 micro were observed only in the experimental sciatic nerve. These results indicate that the small myelinated fibers were the least affected and may confirm the assumption that the motor fibers are those who are usually affected by immobilization. Ultrastructural observations revealed splitting of the myelin lamellae, presence of marked intramyelinic edematous clefts between the split myelin lamellae, infolded myelin loops and myelin degeneration. Changes in the axons included formation of myelin rings and figures in some of the larger axons, degeneration, compression, irregularity and shrinkage of axons. Degradation of myelin lipids was reflected by formation of large vacuoles and layered structures inside Schwann cells. These ultrastructural and morphometric changes may shed some light on a definite structural neural involvement in the mechanism underlying the immobilization-associated polyneuropathy

Light and electron microscopic study of the thyroid gland of female albino rats after collagen-induced arthritis

Adult female albino rats were subjected to experimental arthritis by the injection of arthritic material formed of bovine collagen II dissolved in acetic acid and mixed with Incomplete Freund's Adjuvant [IFA]. Thyroid glands were processed for light and electron microscopic examination. Two groups of control rats were used. The first control group comprised healthy non-treated rats. The second control group comprised IFA -treated rats. Compared with the control rats, light microscopic examination of the thyroid gland of the arthritic rats revealed a marked distortion of the thyroid architecture. The thyroid follicles appeared either degenerated, homogenized or lost. The follicular cells appeared low cubical or flattened with scanty cytoplasm and darkly stained nuclei. The parafollicular C-cells were ill-defined. The colloidal material was either highly vacuolated or depleted. Intraluminal and interfollicular mononuclear cell infiltration was observed. Compared with the control rats, electron microscopic examination of the thyroid gland of the arthritic rats revealed a distorted ultrastructure of the follicular cells. The rough endoplasmic reticulum appeared dilated, distorted, vesiculated and partially degranulated. Secretory granules were rarely seen. Lysosomes and apical cytoplasmic granules were absent. Large cytoplasmic vacuoles and secretory crystalline deposits were seen in some follicular cells. The luminal border lost its apical microvilli and the follicular lumen of some cells contained crystalline colloidal deposits. The nucleus appeared folded and contained more electron-dense clumped chromatin. Pyknotic and karyolytic nuclei were observed. The C-cells showed irregular plasma membrane, disintegrated nucleus and grouping of the secretory granules at one pole of the cell. The present observations may reflect a reduction in the functional activity of the thyroid gland [hypothyroidism] in the female rats subjected to collagen-induced arthritis. Therefore, it is recommended to monitor the thyroid hormones in patients with rheumatoid arthritis and to check the presence of thyroid auto-antibodies in these patients

histological and biochemical study of the protective effect of melatonin on acute paraquat toxicity in albino rats

The acute toxic effect of the herbicide paraquat [PQ] and the protective effect of the antioxidant melatonin against its toxicity were experimentally investigated both biochemically and histologically. Sixty rats were divided into six equal groups. Melatonin [Mgroup] and saline [Control group] were given once i.p. [10 mg /kg] to rats of both groups. PQ in high dose [50 mg /kg] and low dose [15mg /kg] was given i.p. to rats of high and low PQ groups i.p. [HPQ and LPQ]. A single dose of melatonin was injected i.p. 30 minutes prior to high and low PQ doses in rats of MHPQ and MLPQ groups. All rats were sacrificed after 24 hours and blood samples were collected for the biochemical analysis. Lung, liver and kidney specimens were processed for staining with haematoxylin and eosin, and P.A.S. reaction for light microscopic examination. Liver frozen sections were prepared and stained by Sudan black for lipid demonstration. The results revealed that both doses of PQ significantly increased serum malondialdehyde level and decreased serum concentration of glutathione and glutathione reductase activity compared to control values. These changes improved significantly in groups received melatonin prior to PQ i.e. MHPQ and MLPQ groups. Histologically, extensive damage to lung, liver and kidney was observed in rats of HPQ group. In the lung, marked congestion and bleeding were observed and the alveoli appeared filled with coagulated material, collapsed or manifested a compensatory emphysema. The bronchiolar wall showed sloughing of the epithelial lining and peribronchiolar lymphocytic infiltration. In the liver, blood sinusoids were markedly congested, the normal lobular pattern was lost and the hepatocytes exhibited vacoulation, fatty degeneration and necrosis. In the kidney, glomerular alterations and renal tubular necrosis were observed. Melatonin did not improve the toxic effect of PQ on the three organs in rats of MHPQ group. The low dose of PQ induced minimal tissue damage compared to HPQ group and the kidney was the most affected organ. Melatonin prior to low PQ dose improved the histological picture of the three organs which appeared almost similar to the controls, except the kidney which showed some degenerative changes. In conclusion, melatonin affords protection for the biochemical parameters affected by both doses of PQ while histologically, the single dose of melatonin can protect the organs only in animals exposed to low dose of PQ