ABSTRACT
The involvement of ceramide in death receptor-mediated apoptosis has been widely examined with most studies focusing on the role of ceramide generated from sphingomyelin hydrolysis. We now analyze the effect of the ceramide acyl chain length by studying tumor necrosis factor α receptor-1 (TNFR1)-mediated apoptosis in a ceramide synthase 2 (CerS2) null mouse, which cannot synthesize very-long acyl chain ceramides. CerS2 null mice were resistant to lipopolysaccharide/galactosamine-mediated fulminant hepatic failure even though TNFα secretion from macrophages was unaffected. Cultured hepatocytes were also insensitive to TNFα-mediated apoptosis. In addition, in both liver and in hepatocytes, caspase activities were not elevated, consistent with inhibition of TNFR1 pro-apoptotic signaling. In contrast, Fas receptor activation resulted in the death of CerS2 null mice. Caspase activation was blocked because of the inability of CerS2 null mice to internalize the TNFR1; whereas Fc-TNFα was internalized to a perinuclear region in hepatocytes from wild-type mice, no internalization was detected in CerS2 null mice. Our results indicate that altering the acyl chain composition of sphingolipids inhibits TNFR1 internalization and inhibits selective pro-apoptotic downstream signaling for apoptosis.
Subject(s)
Galactosamine/pharmacology , Lipopolysaccharides/pharmacology , Liver/drug effects , Liver/metabolism , Receptors, Tumor Necrosis Factor, Type I/metabolism , Sphingolipids/chemistry , Animals , Apoptosis/drug effects , Apoptosis/genetics , Blotting, Western , Hepatocytes/drug effects , Hepatocytes/metabolism , Mice , Mice, Knockout , Microscopy, Confocal , Sphingosine N-Acyltransferase/genetics , Sphingosine N-Acyltransferase/metabolism , Tumor Necrosis Factor-alpha/metabolismABSTRACT
Alveolar bone resorption following tooth extraction is not uncommon. The dimensions of the alveolar bone are of great importance from both esthetic and implant planning reasons. This paper reviews the rational of ridge preservation following tooth extraction in order to minimize bone loss. The different treatment modalities for that purpose will also be discussed. When extracting a tooth, the dental professional should consider performing a ridge preservation procedure according to the accepted indications. The knowledge of the various options as well as their pros and cones will help the clinician in providing this kind of treatment.
Subject(s)
Alveolar Bone Loss/etiology , Alveolar Bone Loss/prevention & control , Tooth Extraction/adverse effects , Bone Regeneration , Bone Substitutes , Bone Transplantation , Guided Tissue Regeneration, Periodontal , Humans , Membranes, Artificial , Tooth Socket/surgeryABSTRACT
The acellular dermal matrix (ADM) allograft is widely used in periodontal surgery. A MEDLINE search was performed for retrieving related articles. This article reviews ADM processing and mode of use, indications and contraindications, surgical techniques and clinical results for the treatment of localized and generalized gingival recessions with ADM and comparisons with other methods of treatment for root recessions. Two case reports are presented, illustrating the use of ADM and connective tissue grafts for root coverage.
