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Histone deacetylases (HDACs) are components of nuclear multiprotein complexes that deacetylate histones and perform important roles in repression of transcription. Using specific rabbit mAbs, we analyzed by immunohistochemistry and confocal immunofluorescence analysis the expression and subcellular localization of HDAC1–4 and HDAC9 in sections of adult human third molars. HDAC2 and HDAC9 were expressed in some pulpal cells and strongly expressed in the majority of mature odontoblasts. In contrast, only weak expression of HDAC1, HDAC3 and HDAC4 was observed. Confocal immunofluorescence analysis together with the DNA stain DRAQ5 revealed that HDAC2 and HDAC9 were coexpressed within the odontoblast nucleus, but localized to distinct subnuclear structures. In contrast to the current point of view, HDAC2 is strongly expressed in a terminally differentiated cell type. Our results imply that class I and II HDACs are involved in the transcriptional regulation of human odontoblasts in vivo.

The aim of this study was to evaluate the role of host periosteum and recipient bed perforation on the healing of an onlay graft to the mandible based on histologic and immunohistochemical analysis. Each of the 12 adult sheep used in the study received four iliac corticocancellous onlay bone grafts on the lateral surface of the mandible. In experiment 1, the block graft was placed in direct contact with the recipient bed and fixed with micro-screws, and in experiment 2, the recipient cortical bed was perforated before graft placement. The host periosteum around the graft was excised before flap replacement in experiment 3, and in experiment 4, a sheet of silicone membrane was placed between the graft and the recipient bed. The animals were euthanised at 4, 8, 12 and 16 weeks after surgery and the findings were analysed by routine microscopy (haematoxylin and eosin and tartrate-resistant acid phosphatase [TRAP] stains) and immunohistochemistry for proliferation and apoptotic markers (Ki67, caspase-3 and TUNEL stains). After 8 weeks, full graft–host integration was seen in all the experimental groups except experiment 4. After 16 weeks, pronounced graft resorption and volume reduction was observed in experiments 1 and 2, whilst experiment 3 was characterised with extensive connective tissue infiltration and severe resorption of the graft. The number of osteoclasts expressed peaked at 4 weeks in experiments 1 and 2 and at 16 weeks in experiment 3. Immunoreactivity for Ki67 by osteoblasts lining the trabecular bone of the graft’s spongiosa expressed moderate level of Ki67 at 8 weeks, and thereafter declined markedly. The strongest expression of caspase-3 on the bone surface was observed after 16 weeks. Recipient cortical bed perforation offered no advantage over non-perforated bed regarding healing and integration of a bone graft. Excision of the host overlying the periosteum was accompanied with rapid absorption of the grafts and partial or complete replacement with fibrous connective tissue. This study also demonstrated that cell death by apoptosis is a fundamental component of osteoblastic phenotypic differentiation during healing of corticocancellous bone graft.

Özet Türbin kanatlarının soğutulması farklı bölgelerinde farklı soğutma teknikleri kullanarak yapılmaktadır. Kompresörde üretilen havanın yaklaşık %20’si soğutma sistemlerinde kullanılmaktadır. Kanat içine gönderilen bu hava önce iç kanallardan daha sonrada kanat dış profili üzerinden ve kanat uç kısmından dışarıya atılarak soğutma gerçekleştirilir. Bu soğutma tekniklerinin iç soğutma ve yüzeyde hava filmi meydana getirme ve çarpmalı jetle soğutma teknikleri uygulanmaktadır. Kanatta iç soğutma yapılması için bazen U şeklinde soğutma kanalları kullanılmaktadır. Bu kanallarda çeşitli açılarda kanatçıklar (ripler) kullanılarak soğutma performansları arttırılmaya çalışılmaktadır. Bu çalışmada U şeklindeki 180° dönüşlü düz bir kanalın ve alt ve üst yüzeylerine 90° ve 45° yerleştirilen kanatçıkların yerleştirildiği kanallardaki soğutma performansına etkisi 3 farklı Reynolds sayısı (22000, 27500 ve 33000) için deneysel olarak sıvı kristal termografisi metoduyla kanal yüzeyindeki ısı geçiş katsayısı ve Nu sayısının değişimi araştırılmıştır. Elde edilen sonuçlar jet geometrisinin etkisi, Reynolds sayısının etkisi, kanal içindeki hız dağılımı ve ısı geçiş katsayısı dağılımları gösterilmiştir.