Biochemistry/ Microbiology Flashcards
what is the origin of the connective tissue of the PDL?
mesendermal
what cells are found in the connective tissues in the PDL?
- fibroblasts
- cementoblasts
- osteoblasts.
what is the extracellular matrix made up of in the connective tissue of the PDL?
- fibres
- ground substance
what do elastic fibres in the PDL mature from oxytalan to?
- elaunin.
why do elastin fibres in the PDL never mature to elastin?
so they are always embryonic.
what type of fibres make up the majority of the PDL?
Collagen Type 1.
what is the base structure of type 1 collagen?
- triple helical of 3 polypeptide alph chains.
what is the main amino acid in the polypeptide chain of type 1 collagen?
Glycine.
what are the 3 amino acids that make up type 1 collagen?
- Glycine
- Proline
- Hydroproline.
what amino acid in type 1 collagen forms hydrogen bonds between the 3 chains?
Glycine.
what type of bond is formed between the 3 polypeptide bonds in type 1 collagen to give it the helical structure?
hydrogen bonds.
what % of the collagen in the PDL is Type 1?
80%
what % of the collagen in the PDL is type 3?
20%
where in the body can type 1 collagen be found?
- Bone
- Dentine
- Tendon
what can cause % of type 3 collagen variations between people?
age.
what has to be expressed for type 3 collagen to be expressed?
Type 1 collagen.
why is hydroxyproline important in the structure of type 1 collagen?
for the stability of the collagen triple helix
what does hydroxyproline need to work in the body?
Vitamin C.
what are the effects of not having enough vitamin C?
Skirvy - without vit C hydroxyproline will not be stable causing a breakdown of collagen.
what is the enzyme that hydrolates proline?
prolyl hydroxylase.
what is prolyl hydroxylase dependent on?
vitamin C.
at what terminal is collagen assembled?
Carboxyl.
why once the helix of collagen is formed does the carboxyl terminal chains come together in globular form?
to prevent the 3 helix chain from unfolding.
what is Pro-collagen?
central helical domain with 2 non-helical globular extentions at the amino and carboxyl terminals.
how does pro-collagen become tropocollagen?
once pro-collagen is secreted into the extracellular matrix, propeptidase cleaves off the globular extensions becoming tropocollagen.
how are fibrils in the PDL stabilised?
via covalent cross links formed from modified lysine and hydroxylysine residues.
what does Lysyl oxidase convert R groups of lysine and hydroxysine to?
Allysine and Hydroxyallysine.
what is Lysyl oxidase dependent on?
copper.
what are non-reducible cross links? and are they found in the PDL?
they are stable non-reducible cross-links formed spontaneously with age. This doesn’t happen in the PDL.
what does it mean for the PDL when they do not form non-reducible cross-links? and why dont they have any?
forever young.
dont have any due to the fast turnover rate of protein within the PDL tissue.
Is procollage intracellular or extracellular?
intracellular
Is tropocollage intracellular or extracellular?
extracellular.
what is the function of collagenase?
break down collagen
what is collagenase produced by?
- fibroblasts
- polymorphonuclepcytes
- macrophages
what is collagenase inhibited by?
TIMP
How does collagenase break down collagen?
Cleaves collagen to 3/4 and 1/4 fragments.
what enzyme breaks down collagen further after collagenase?
gelatinase.
why does collagen have a very high turnover rate?
because it never matures.
what makes up ground substance?
- non-collagenous proteins (NCPs)
- Hyaluronic acid (GAG)
- Protoglycans (PGs)
what are glycoproteins?
- protein plus -O- and -N- linked sugars.
- protease resistant.
what is the basic structure of a protecglycans?
protein core and GAGs.
In the PDL what are the 2 small leucine-rick proteoglycans?
- Decorin
- Biglycan
what are the main functions of PGs and GAGs in connective tissue?
- collagen fibril orientation/ diameter.
- control of mineralisation
- generation of the eruptive force.
How do PGs and GAGs control collagen fibril orientation/ diameter?
- PGs bind to collagen fibrils enabling them to control fibrillogenesis.
If there is a higher GAG concentration in the PDL what can we assume about the collagen fibrils?
smaller.
If there is a higher decorin concentration in the PDL what can we assume about the collagen fibrils?
larger diameter fibrils.
If there is a higher CS rich PGs concentration in the PDL what can we assume about the collagen fibrils?
small fibres.
why with age does the diameter of fibrils in the PDL increase?
due to GAG% decreasing and the decorin sulphate % increasing with age.
How do PGs and GAGs control mineralisation in connective tissue?
- GAGS can inhibit deposition of hydroxyapatite crystals in soft connective tissue - this prevents the PDL mineralising and becoming hard like bone.
How do PGs and GAGs control the generation of the eruptive force?
GAGs attract water, swell up and push the tooth upwards.
during disease of the PDL does GAG content increase or decrease?
increases,
during disease of the PDL does dermatan sulphate content increase or decrease?
decreases
during disease of the PDL does chondroitin sulphate content increase or decrease? and why?
increases - promotes the decrease in collagen size.
what are the disease related changes in the PDL?
- total sulphate GAG content increase
- % decorin sulphate decreases and decorin decreases.
- % CS increases and versican increases.
- collagen content decreases
- Gelatinase activity increases.
what is a pathogen?
a microb capable of causing host damage/ disease
what is a opportunistic pathogen?
an organism that is a member of the resident microbiota or normally inhabiting the external environment that causes infection under certain circumstances.
what is a symbiont?
member of the resident microbiota that confers benefit to the host
what is a pathobiont?
member of the resident microbiota that causes disease when loss of the normal balance between the host and resident microbiota occurs.
what is pathognicity?
capacity of a microbe to cause damage in a host
what is virulence?
relative capacity of an organism to cause damage in a host ‘degree of pathogenicity’
what is a virulence determinant/factor?
component of pathogen that damages the host / allows pathogen to cause disease.
what type of microbes are found in a healthy PDL?
Gram +ve facultative anaerobes predominate
what type of microbes are found in gingivitis?
increase in obligately anaerobic population.
what type of microbes are found in periodontitis?
Gram -ve anaerobes and spirochaetes predominate.
what happens to the PDL during periodontal pocket formation?
- increase inflammation
- increase bleeding
- increase temp
- increase pH
- decrease in O2
what is the ecological plaque hypothesis?
- increase plaque causes increase inflammation.
- this then causes high GCF flow, bleeding, raises pH , raised temp and low O2.
- This them encourages disease associated communities.
why are their difficulties in defining aetiology for perio disease?
- differences in definition of disease.
- episodic / cyclic nature of the disease.
- sampling and detection techniques .
How much of the microbiota is non-culturable?
40%
what are the 3 bacteria found in the complex cluster?
- P. Gingivalis
- T. Forsythia
- T. Denticola.
what are 2 tests that can be used in clinic to test for microbes?
- parocheck
- my periopath.
what causes diavetes-mellitus associated gingivitis?
increase proportions of capnocytophage.
what innate defences are in GCF?
- IgG
- IgA
- IgM
- complement
- lymphocytes
- Polymorphes (neutrophils)
- Defensins.
how does epithelial defences produce an innate defence?
production of cylokine and chemokine following bacterial insult.
how do neutrophils produce an innate defence?
regulate proportion of bacteria present/
what is tissue damage in the PDL dependent on?
the survival of organisms via attachment to either other organisms or surfaces in the pocket/crevis.
what is meant by accessory pathogens?
cells that cannot cause damage themselves just aid pathogens that can.
what is the pathway for microbial pathogenesis?
- entry
- attachement
- multiplication + consolidation
- avoiding host defences.
- tissue damage
- release and spread.
How can indirect damage be done to the PDL from bacteria?
host responses causing damage to host tissue due to being triggered by bacteria.
what is the purpose of adhesin?
enable binding of bacteria
what is the purpose of invasin?
enable invasion of bacteria
what is the purpose of impedin?
enables avoidance of bacteria.
what is the purpose of aggressin?
enables bacteria to cause direct damage to host.
what is the purpose of modulin?
enalbles the bacteria to induce indirect damage by pertubing regulation of host defenses.
How does the capsule around bacteria benefit it?
- k-antigens
- adhesion
- resistance to phagocytosis and complement.
how does the pili/fibrils around bacterial benefit it?
- adhesion
- gene transfer
- receptors.
how do extra-cellular products in the bacteria benefit it?
- nutrition
- host damage
- interaction with host cells.
how does the flagellum benefit the bacteria?
- mobility
- H antigens
- inter-action with host cells.
how can the peptidoglycan cell wall around bacteria benfit it?
induction of cytokines.
what is part of the cell wall in bacteria that is only found in Gram +? and how does it help the bacteria in the host?
Lipoteichoic acids
- adhesion
- induction of cytokines
- resistance to host defences.
what is part of the cell wall in bacteria that is only found in Gram -? and how does it help the bacteria in the host?
Lipopolysaccharides.
- o- antigen
- induction of cytokines and inflammatory response
- resistance to host defences
- adhesion
- mediation of bone resorption
- killing of macrophages.
where are toll-like receptors found?
on immune cells.
what is the function of toll-like receptors?
detect microbial components and start cellular response.
what is the purpose of protease?
break down host proteins.
what are extracellular virulence factors?
- enzymes (proteases, collagenase, fibrinolysine, IgA/IgG protease)
- Leukotoxins
- Cytotoxins
what is the purpose of collagenase?
distruction og PDL
what is the purpose of fibrinolydin/ hyaluronidase/ heparinase?
breakdwon of host proteins.
what is the purpose of IgA and IgG protease?
breakdown of immunoglobulins.
what is the purpose of leukotoxins?
kill polymorphs
what is the purpose of cytotoxins?
specific toxins and metabolic products will cause host cell death.
what is the main idea of the keystone pathogen concept?
that some organisms may have a disproportionate influence on the pathogenicity of the community.
what are examples of keystone pathogens?
Porphyromonas gingivalis.
Aggregatibacter actinomycetemcomitans
why is Porphyromonas gingivalis a keystone pathogen?
- it manipulates host defences.
- produces extracellular vesicles.
- invasion of epithelial cells and local chemokine paralysis.
- inhibits e-selectin up-regulation - affecting neutrophil migration and adhesion.
- inhibition of complement activation
- direct cytotoxicity
what are the virulence factors for Porphyromonas gingivalis?
- gingipain
- PPAD
- LPS
- capsule
- haemagglutinin
- Fimbriae
- extracellular vesicles.
what type of pathogen is Porphyromonas gingivalis?
Gram - ve obligate anaerobe
what type of pathogen is Aggregatibacter actinomycetemcomitans?
Gram -ve coccobaculus anaerobic
what are the virulence factors for Aggregatibacter actinomycetemcomitans?
- produces potent leukotoxins for neutrophils and over produced by serotype B.
- cytolethal distending toxin - lymphocytes
- Adhesins - epithelial cells, biofilm formation, coaggnegation
- LPS - stimulates bone resorption
- cell-associated material - induces bone resorption
- collagenase
- invasive-gingival connective tissue
what are gingipains unique to?
p. gingivalis
what are leukotoxins unique to?
Aggregatibacter actinomycetemcomitans
what are the main function of gingipain?
- cleave host defence peptides, complement, Ig.
- cleave cell receptors eg CD14
- degrade cytokines, chemokines, plasma protease inhibitors
- Activation of protease activated receptors.
- Activation of matrix metallo-proteinsases (MMPs) and degradation of tissue inhibitors of MMPs (TIMPS)
- immune evasion
- nutrition
what is the function of stem cells in the PDL?
To differentiate into other cells - they aid in keeping the PDL young.
is procollagen a procollagen peptidase?
no.
what is ankylosis?
where the PDL is mineralised, meaning that the tooth is stuck in place and cannot be removed. XLa of a tooth like this could result in jaw fracture.
where is decorin found?
around collagen fibres in the PDL - it decorates it.
