lecture 2 Flashcards
1
Q
what has gastric juice in peptic ulcer disease caused?
A
- enhanced ability to degrade the mucosal barrier
2
Q
what pH is pepsinogen stable up to?
A
- 10 to 11
3
Q
what pH is pepsin stable to?
A
- around pH 7
4
Q
how is pepsin activation decided?
A
- pepsin taken and incubated overnight at different pHs
- return to pH 2 and see if any activity is found
5
Q
what causes the dip at pH 2?
A
- will digest itself as a protein so some activity is lost
6
Q
what pH is pepsin completely denatured?
A
- pH 7
(after pH7 its irreversibly denatured)
7
Q
what can extend the denaturation profile of pepsin?
A
- gastric juice
- extends to around pH 7.5 and 8
8
Q
what diseases are associated with reflux?
A
- GORD (gastro-oesophageal reflux disease)
- OME (otitis media with effusion, glue ear)
- LPR (laryngo pharyngeal reflux)
- Rhinitis and sinusitis
- VFL (vocal fold epithelial cell hyperplasia)
- larangomalacia (incomplete development of larynx in children, collapses)
9
Q
what occurs in glue ear?
A
- where middle part of ear canal fills up with fluid
- hole made so can suck out contents
- fit a grommet in ear
10
Q
how can we tell the diseases are linked with reflux?
A
- pepsin is measured on the tissue but pepsin shouldn’t be there
11
Q
what is the standard for diagnosis of reflux?
A
- 24 hour double probe pH monitoring
12
Q
where are the probes?
A
- oesophageal probe (5cm above lower oesophageal sphincter)
- pharyngeal probe (pH probe, 1cm above upper oesophageal sphincter)
13
Q
what is regarded as a positive pharyngeal reflux event?
A
- drop below pH 4.0 preceded by precipitous drop at distal probe
- tells us low pH gastric juice has come out stomach through oesophagus
14
Q
why is it damaging?
A
- a pH of 3.5 added on a tissue causes cell death
15
Q
what happened in pepsin detection with laryngo pharyngeal reflux?
A
- pepsin levels in sputum were measured
16
Q
what is a slot blot?
A
- nitrocellulose membrane and vacuum system
- can suck sample onto membrane
- to measure the pepsin levels
- can slot and measure area under curve for pepsin amount
17
Q
what is another method used to measure pepsin?
A
- activity assay
18
Q
what occurs in this method?
A
- 200ul of specimen + 1ml of acidified haemoglobin
- incubated at 37 degrees for 10 mins
- add 3ml of 6.2% TCA (trichloroacetic acid)
- incubate for 10 min at 37 degrees
- filter
- read at 280nm
19
Q
what does TCA do?
A
- precipitates the protein
- any undigested haemoglobin is precipitated
- leaves only digested protein (peptides and amino acids) in solution
20
Q
what were the results for LPR patients?
A
- no reflux event = still pepsin present
- 1 reflux event = pepsin present
- more than 1 reflux event = pepsin present
21
Q
what does this tell us?
A
- pH4 isn’t best to measure as shouldn’t be reflux event at that pH but pepsin is present meaning reflux event has taken place
- contradictory results
22
Q
what happens if stayed at pH 4?
A
- gives just over 1 reflux event
23
Q
what happens when shifting to pH 4.1?
A
- get 4 reflux events
24
Q
what happens at ph 4.5?
A
- 10 reflux events
25
what happens at pH 5?
- almost 30 reflux events
26
what is needed for a lower pH buffer?
- glycine HCl buffer system
27
what are the conclusions from this experiment?
- pepsin is present in sputum of patients with normal pharyngeal probe testing
- pepsin from human gastric juice is capable of enzymatic cavity at pH 5
28
what are the laryngeal damage models?
- watertight seal made between glass tube and larynx
- larynx suspended in krebs ringer solution
29
how is tissue damage measured?
- DNA release is measured at different pHs
30
what type of tissue is the sub glottic?
- columnar epithelium
31
what type of tissue is the supra glottic?
- squamous epithelium
32
what are the potential damage solutions?
- untreated
- ph7.4 krebs ringers
- ph4 krebs ringers
- ph2 krebs ringers
- ph4 krebs ringers + 1mg.ml porcine pepsin
- ph2 krebs ringers + 1mg/ml porcine pepsin
33
what is shown in sub glottic mucosa?
- damage with every reagent apart from untreated and ph7.4 krebs ringers
34
what is shown in vocal fold mucosa (squamous)?
- no real evidence of damage until ph2 krebs ringers + 1mg/ml porcine pepsin
35
what is shown in supra glottic mucosa?
- damage from ph2 krebs ringers onwards
36
what is shown at posterior commissure mucosa?
- no damage
- resistant to pepsin digestion
37
what is sown at ventricle mucosa?
- damage shown only with addition of 1mg/ml porcine pepsin
38
which tissue is damaged most based?
- sub glottic
39
what are the mechanisms of mucosal protection?
- stomach has mucus layer and bicarbonate secretion
- oesophagus has squamous. epithelium
- larynx has some squamous and some columnar, carbonic anhydrase
40
what is the laryngopharyngeal reflex?
- larynx more sensitive so less protected than oesophagus
- hoarseness, chronic cough, globus pharyngeus (lump in throat), heartburn
