Multiple Choice Questions Test - VIII (Basic Periodontology).
Properties of Junctional epithelium:
- Thickness varies from 15-18 cells at the base of gingival sulcus to 1-2 cells at its most apical portion.
- JE cells have numerous golgi apparatus, abundant rough endoplasmic reticulum with cisternae and polyribosomes.
- JE cells exhibit a unique set of cytokeratins including cytokeratin 5, 13, 14 and 19. Occasionally weak activity of cytokeratins 8, 16 and 18 is also seen. Compared to other epithelia, JE cells are interconnected by a few desmosomes and occasionally by gap junctions .These features account for the remarkable permeability of JE.
In absence of clinical signs of inflammation, approximately 30,000 PMN’s migrate per minute FROM JE of all teeth into the oral cavity.
Basic Biofilm Properties:
• Cooperating community of various types of microorganisms.
• Microorganisms are arranged in micro-colonies.
• Microcolonies are surrounded by protective matrix.
• Within the micro-colonies are differing environments.
• Microorganisms have primitive communication system.
• Microorganisms in biofilm are resistant to antibiotics, antimicrobials, and host response.
Reference: Marsh and Bradshaw. Physiological approaches to the control of oral biofilms. Adv Dent Res 1997;11: 176-185.
MMP1 matrix metallopeptidase 1 is also known as interstitial collagenase.
Re-classification of Actinobacillus actinomycetemcomitans as Aggregatibacter actinomycetemcomitans has been done due to Phylogenetic similarity of Actinobacillus actinomycetemcomitans and Haemophilus aphrophilus, Haemophilus paraphrophilus, and Haemophilus segnis.
Reference: Niels Nørskov-Lauritsen and Mogens Kilian.Reclassification of Actinobacillus actinomycetemcomitans, Haemophilus aphrophilus, Haemophilus paraphrophilus and Haemophilus segnisas Aggregatibacter actinomycetemcomitans gen. nov., comb. nov., Aggregatibacter aphrophilus comb. nov. and Aggregatibacter segnis comb. nov., and emended description ofAggregatibacter aphrophilus to include V factor-dependent and V factor-independent isolates. IJSEM September 2006 vol. 56 no. 9. 2135-2146.
The immunofluorescence and immunohistochemical staining revealed the presence of Porphyromonas gingivalis, Prevotella intermedia, Actinobacillus actinomycetemcomitans and Actinomyces naeslundii within gingival tissues
Reference: Saglie FR, Smith CT, Newman MG, Carranza FA, Pertuiset JH, Cheng L, Auil E, Nisengard RJ. The presence of bacteria in oral epithelium in periodontal disease. II. Immunohistochemical identification of bacteria. J Periodontol 1986: 57: 492–500.
Lipoxins were the first eicosanoids to be discovered with a role in the resolution of inflammation, i.e. they are anti-inflammatory mediators during arachidonic acid metabolism. They are trihydroxy-eicosatetraenoic acids, derived from arachidonic acid with the four double bonds in conjugation. They are formed by platelets but their synthesis depends upon neutrophils. Platelets depend upon neutrophils for LTA4, which is converted to LXA4 and LXB4 by the action of platelet 12-lipoxygenase. LTC4, LTD4, and LTE4 are also synthesized in platelets from LTA4.
The complement system is part of innate and adaptive immunity. It guards the host’s intravascular space by opsonizing and lysing bacteria. In addition, it promotes the local acute inflammatory response, which in turn, instructs and influences the adaptive immune response. The complement system consists of plasma proteins of the activating cascades and membrane regulators and receptors. Complement system consists of 3 pathways: the classical complement pathway, the lectin pathway, and the alternative complement pathway. The pathways differ in the manner in which they are activated and ultimately produce a key enzyme called C3 convertase.
Several proinflammatory cytokines act as key molecules contributing to the destruction of periodontal tissue in periodontal inflammation, including interleukin-1 (IL-1), tumor necrosis factor-alpha (TNF-α), interferon-gamma (IFN-γ), interleukin-6 (IL-6) and, very importantly, RANKL. Most studies indicate that INF-γ does not promote osteoclastogenesis.
Reference: Takayanagi, H., et al. 2000. T-cell-mediated regulation of osteoclastogenesis by signalling cross-talk between RANKL and IFN-gamma. Nature.408:600-605.
Human immunoglobulins are made up of LIGHT and HEAVY chains. Genetically these are encoded by a total of 14 constant region genes which are organized into three gene families, namely
- 1 KAPPA gene
- 4 LAMBDA genes
- 9 HEAVY CHAIN genes.
Allelic variation is present only for kappa locus and six of the nine heavy chain loci.
The nine heavy chains of the antibodies form CLASSES and SUBCLASSES of human immunoglobulin. Together with the five different light chains, these genes represent 14 distinct ISOTYPES which can be identified in all normal human sera. ALLOTYPES are the allelic variations within the constant regions that exist for some of these isotypes, and are inherited in a Mendelian co-dominant fashion. IDIOTYPES consist of the unique combination of VH and VL which characterize a particular immunoglobulin`s combining sites.
So, in summary we can infer that
- Constant region on heavy chain determines the Immunoglobulin class.
- Constant region on heavy and light chains determine the allotypes.
- Variable region of light and heavy chains determine idiotypes.
Bacteriophages (bacterial viruses, also called phages) are viruses that infect bacteria. Bacterial cells can undergo one of two types of infections by viruses termed lytic infections and lysogenic (temperate) infections. They contribute to horizontal gene transfer by both transduction and lysogenic conversion.