Multiple Choice Question Test - XII (Basic Periodontology).
Aggregatibacter actinomycetemcomitans has six recognized serotypes a-f, which are classified into 3 major phylogenetic lineages: (i) serotype b, (ii) serotype c, and (iii) serotype a, d, e and f. Serotype b is found to contain the highly leukotoxic strains and is most commonly seen in patients with localized juvenile periodontitis. Recently serotype g has been identified.
Reference: Brian Henderson, John M. Ward, and Derren Ready; Aggregatibacter (Actinobacillus) actinomycetemcomitans: a triple A* periodontopathogen?; Periodontology 2000; 54(1): 78-105; 2010.
Decay-accelerating factor recognizes C4b and C3b fragments that condense with cell-surface hydroxyl or amino groups when nascent C4b and C3b are locally generated during C4 and c3 activation. Interaction of daf with cell-associated C4b and C3b polypeptides interferes with their ability to catalyze the conversion of C2 and factor B to enzymatically active C2a and Bb and thereby prevents the formation of C4b2a and C3bBb, the amplification convertases of the complement cascade. It is present on all leukocytes, erythrocytes and platelets.
Reference: Medof ME, Walter EI, Rutgers JL, Knowles DM, Nussenzweig V: Identification of the complement decay-accelerating factor (DAF) on epithelium and glandular cells and in body fluids. J Exp Med 1987, 165:848 – 864.
In humans, the MHC complex consists of more than 200 genes located close together on chromosome 6. Genes in this complex are categorized into three basic groups: class I, class II, and class III. Class II MHC molecules are composed of two polypeptide chains an α and a β chain of approximately equal length and both chains have four regions:
- First is the cytoplasmic region which contains sites for phosphoylation and binding to cytoskeletal elements
- The transmembrane region contains hydrophic amino acids by which the molecule is anchored in the cell membrane
- A highly conserved α2 domain and a highly conserved β2 domain to which CD4 binds
- A highly polymorphic peptide binding region formed from the α1 and β1 domains
C reactive protein (CRP) is termed `acute-phase` because the time-course of the rise above normal levels is rapid within 6 hours, peaking at about 48 hours. The half-life of CRP is about 19 hours and relatively constant, so that levels fall sharply after initiation unless the plasma level is maintained high by continued CRP production in response to continued antigen exposure and inflammation. It therefore represents a good marker for disease activity, and to some degree, severity. However, although it is not specific for a single disease process, CRP can be utilised as a tool for monitoring immune activity in patients with a particular disease. In most situations, the factors controlling CRP release and regulation are essentially those controlling inflammation or tissue injury. It is therefore relatively tightly regulated depending on the presence and degree of inflammation, with typical rises and falls in plasma CRP levels, forming a characteristic homeostatic, oscillatory cycle when inflammation occurs.
Reference: Brendon J Coventry et al. CRP identifies homeostatic immune oscillations in cancer patients: a potential treatment targeting tool? Journal of Translational Medicine 2009, 7:102
The difference between controlled release and sustained release is that controlled release is a perfectly zero order release; that is, the drug releases over time irrespective of concentration. Sustained release implies slow release of the drug over a time period. It may or may not be controlled release.
Epstein-Barr virus (EBV) causes in humans infectious mononucleosis as a "primary" disease. Burkitt`s Lymphoma and Nasopharyngeal Carcinoma may be considered as "secondary" diseases developing only in persons with long preceeding EBV infection. Following the primary infection with EBV, virus can be isolated from the salivary duct and from throat swabs for months or years, and B-Iymphocytes are lifelong carriers of EBV genomes and can be used to establish lymphoblastoid cell lines.
Reference: H. Wolf, E. Wilmes and G. J. Bayliss. Epstein-Barr Virus: Its Site of Persistence and Its Role in the Development of Carcinomas. Haematology and Blood Transfusion Vol. 26, 191-196.
Cathepsin G is a neutral serine protease that is expressed and synthesized at the promyelocyte stage of development and is packaged in the azurophil (primary) granules. It has important role at the site of inflammation.
Fimbriae (the oligomeric form of fimbrillin) are considered important in the adherence and colonization of Porphyromonas gingivalis in the oral cavity. Fimbrillin is the major subunit protein of fimbriae from this human periodontal pathogen. The fimbrillin is encoded by fimA gene.
Reference: Hua Xie et al. Regulation of the Porphyromonas gingivalis fimA (Fimbrillin) Gene. Infect Immun. 2000 December; 68(12): 6574–6579.
Osteopontin and bone sialoprotein, originally characterized as bone sialoproteins I and II. Both proteins also have an RGD sequence that recognizes the vitronectin receptor αvβ3 through which these proteins can mediate cell attachment and activate cell signaling pathways.
Reference: Jaro Sodek & Marc D.Mckee.Molecular and cellular biology of alveolar bone. Periodontology 2000, Vol. 24, 2000, 99–126.
Tetracyclines, particularly doxycycline , tend to be highly concentrated in the gingival crevicular fluid at levels 5–10 times greater than those found in serum and these antibiotics show substantivity because they bind to the tooth structure and are slowly released as still-active agents.
Reference: Pascale D, Gordon J, Lamster I, Mann P, Seiger M, Arndt W. Concentration of doxycycline in human gingival fluid. J Clin Periodontol 1986: 13: 841–844.