Kobaylarda timus' un postnatal gelişimi üzerinde makroskobik ve ışık mikroskobik incelemeler

Bu araştırmada, postnatal dönemde kobay timus'larında (thymus) meydana gelen makroskobik ve ışık mikroskobik değişimler incelendi. Bu amaçla çalışmada, l günlük, 1,2,4, 6, 8, 12, 16, 20 ve 24 haftalık olmak üzere on grup oluşturuldu. Her gruptan altı adet olmak üzere toplam altmış adet kobay kullanıldı. Bir günlük kobaylar, tam gelişmiş bir timus'a sahipti. Korteks (cortex) ve medulla kolaylıkla ayırt edildi. Korteks'te; çok sayıda küçük lenfosit, lenfoblast, makrofaj ve epiteliyal retikulum hücreleri, medulla'da ise; lenfositler, epiteliyal retikulum hücreleri ve Hassal cisimcikleri (Corpusculum thymicum) görüldü. Doğumdan sonra, vücut ağırlığı artışına paralel olarak timus ağırlığı da artarak, 6. haftada maksimum düzeye ulaştı. Altıncı haftadan sonra timus ağırlığında azalma tespit edildi. İnvolüsyon belirtilerinden biri olan yağ hücreleri, ilk olarak altıncı haftada gözlendi. Artan yaşla birlikte, yağ doku miktarının artarak korteks içine girdiği ve yağ infıltrasyonu sonucu korteks parenşiminde azalma olduğu saptandı. Hassal cisimcikleri hem yoğunluk bakımından azaldı, hem de hacim bakımından küçüldü. Medulla'da bağdokunun belirginleştiği dikkati çekti. Sonuç olarak, timus'un doğumla birlikte gelişimini tamamladığı, puberteden sonra invole olduğu ve hayat boyunca fonksiyonel aktivitesini sürdürdüğü tespit edildi.

Macroscopic and light microscopic investigations on the postnatal development of thymus in the guinea pig

In this investigation, the morphological and ultra-structural variations occurred in thymuses of guinea pigs in postnatal period were examined. In the study, 10 groups, 1 day and 1, 2, 4, 6, 8, 12, 16, 20 and 24 weeks of groups consisting of 6 guinea pigs in each group (a total of 60 guinea pigs) were used. One day old guinea pigs had a completely developed thymus. Cortex and medulla were easily distinguished. In cortex, a number of small lymphocytes, lymphoblasts, epithelial reticulum cells were seen whereas in medulla, epithelial reticulum cells and Hassall's corpuscles were observed. After birth, thymus weight increased parallel to body weight and reached to the maximum level in the sixth week. After the sixth week, a decrease in thymus weight was determined. The lipid cells, one of the involution signs, were first seen in the sixth week. Together with the increasing age, increased amount of lipid tissue caused a decrease in cortex parenchyma as a result from entering the cortex and lipid infiltration. Hassall's corpuscles decreased both in view of number and in view of volume. In medulla, a marked connective tissue was observed. In conclusion, it was determined that thymus was completed its development at birth. It was also involuted after puberty and continued its functional activity during all life.

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