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Trottier Symposium Fall 2013

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McGill University
CHEM 182
Joe Schwarcz

WOC Lecture 6: STOMACH CHEMISTRY ANTIBIOTICS Man on alka-seltzer ad=Sammy Davis Jr. was jewish, black and blind in one eye Gastrointestinal tract- role to digest food What is the chemical responsible for the breakdown of food in the stomach- hydrochloric acid- it equivalent to pH of undiluted lemon juice; the role of the acid in our stomach is to break down protein Stomach: breaks down large molecules (carbs, protein- done by acid); situated under the heart (many who are having a heart attack think they have a stomach problem) Small intestine, unlike stomach, works in an alkaline enviro (small in sense of diameter- 7-10 meter long vs 1ish meter of colon); metabolism of fats- presents a problem- food in stomach is highly acidic then in si need to neutralize acidity== =Pancreas- alkaline juice with enzymes that will break down fat Acid in stomach is HCl- if excess acid (eating too much, eating too fast, spicy food-depends on person, smoking, pain relievers (prostaglandin suppression that deals with stomach acid)), need to neutralize it- acid+base->salt +water ; hydrochloric acid +sodium bicarbonate-> water +sodium chloride Main antacids: 1. sodium bicarbonate (Alka-Seltzer: mixture of sodium bicarbonate and ASA)- fast, cheap, BUT acid rebound, short duration, high in sodium, systemic alkalosis *note: baking soda vs baking powder: powder has added acid. CO2 is produced to raise dough only if in acidic medium 2.TUMS- calcium carbonate (CaCO3produce CO2, calcium chloride CaCl3 and water)- found in chalk. Also calcium carbonate used for osteoporosis treatment Advantage: longer lasting than 1, fast, cheap Disadvantage: acid rebound, kidney stone, tetracycline absorption (calcium chelates/traps tetracycline) 3. Aluminum and magnesium hydroxide (both weak bases aka Philips Milk of Mg- diarrhea; aluminum-constipation therefore BOTH WORK IN OPPOSITE DIRECTION=> mix them): MAALOX (50-50 mixture) contains simethicone so no gas formed- good tasting. If don’t treat acid= ulcer in the stomach; If don’t treat ulcer= bleeding ulcer If don’t treat bleeding ulcer= perforate ulcer- leads to infection; leading cause of death (5 million people; 4000 deaths in US) [Actor that died of a perforate ulcer: Rudolf Valentino (died 1926)- silent movies, more than 100000 attended funeral proceeding, women committed suicide due to his death] 2 forms of ulcers: A. Gastic Ulcers: Older people; weakened stomach wall; often walk around with hand on stomach (Napolean died from this) B. Duodenal Ulcer: younger people: NOT caused by excess acid (though makes things worse)- affects duodenum (first part of small intestine and called this because in 12 fingers long) which is especially prone to ulcer since near the stomach and receives its acidic content therefore cause is not enough pancreatic juices. GERD- Gastro Esophageal Reflux Disorder- 20 million people; valve in esophagus before stomach- valve may be weakened, acid goes up esophagus= heartburn. Instead of just using antacids: Acid Secretion- acetylcholine, prostaglandins, gastrin, histamine (H2 receptors) and proton (acid) pump A. Histamine: goes to cells, fits into H2 receptors and release HCl- approach is to block receptor with Histamine H2 receptor antagonist- 1. first one devised 40 yrs ago called cimetidine (Tagemet 400mg) that heal stomach ulcers very quickly with side effects of mental changes, sexual dysfunction, gynecomastia (breast growing in men) therefore antagonist not specific enough (didn’t just fit into H2, also fit into receptors associated with androgen receptors) so created more specific ones: 2. Zantac (ranitidine 3. Glaxo 4. Pepcid 2-4 take long time to work B. Inhibit Proton Pump: 1. Losec: 6billion$- 20mg (used to be most prescribed pill in the world- omeprazole) Preloset in US H+, K+ ATPase inhibitor- less used today 2. Nexium (esomeprazole magnesium)- NOW more used- 1 patent expired; Omeprazole exists as 2 optical isomers (nonsuperimposable mirror images) – S omeprazole=esomeprazole ; Losec is R Both R and S isomers of emoprazole are partly metabolized in the liver. The S isomer esomeprazole (Nexium), is LESS metabolized than theR isomer- For equivalent amounts esomeprazole (Nexium) reduces stomach acidity somewhat more than omeprazole (Losec). There is no proven clinical benefits in using esomeprazone over omeprazone (Losec) Prilosec (30mg-20capsules)- 84$; nexium (30mg-20capsules)-184$ Cause of Ulcers: Former belief: stress->acid->ulcer (“once ulcer, always an ulcer; A peptic ulcer is a psychosomatic disorder”-Dr.Masterson 1988) Studyto prove stress caused ulcer- Executive monkey experiment (1950s)- NOT ethical 2 monkeys experienced Electricals shocks, every 20sec for 6hrs at a time, for 23 days; one can pull bar to stop shock (executive monkey) and only he developed ulcer vs monkey who had no control. Barry Marshall and Robin Warren in Perth Australia (1983) found that bacteria causes ulcers ; not well accepted; Robin Warren observed and isolated Hpylori from patient’s stomach and Barry Marshall infected himself and got ulcers; Hpylori feeds on urea (body waste) to form ammonia (a base that protects it) and CO2  ulcer should be threated with antibiotic (revolutionary idea) Antibiotics/Zantac(antacid)- 1/52 recurrence Zantac- 42/52 recurrence Triple Therapy- proton pump inhibitor, 2 antibiotics stomach protector, proton pump, inhibitor antibiotics test if infected with Hpylori- label carbon 13 urea; if labelled carbon 13 comes out as CO2, then infected by Hpylori Today estimated 90% duodenal ulcers and 70% of stomach ulcers caused by H pylori 10-20% population may be infected with Hpylori, 1-4% gastrointestinal disease, not sure about cancer and other disease Barry Marshall and Robin Warren won Nobel Prize in 2005 (won about 1.5million Ca$) **note that -is means inflammation There is no nobel prize for mathematics (nobel's wife or girlfriend left him for mathematician) nobel discovered dynamite- brother died but thought it was him and called him merchant of death therefore didn't want to be remembered as this so created nobel peace prize Leading cause of death in Canada is cancer (used to be heart disease- still is in US) Canada in 1900: pneumonia, tb and today: cancer(30%) and heart disease(22%)-since we live longer Worldwide leading cause of death is Infectious and parasitic diseases Bacteria Antibiotics only available on large scale in late 1940s-early 1950s th The 7 Seal (Ingmar Bergman 1956 movie on black plague) Middle ages: 25 million (1/4 pop of Europe);1800s: 30% of population;1935: 250000 deaths per year of pneumonia;Today: obesity and smoking History of antibiotics: William Henry Perkin (1865)- Discovery of synthetic dye called “mauve” H.C. Gram (1884)(Dannish)- Gentian violet dye had a certain effect on bacteria- gram positive picked up dye and gram negative didn’t. “Magic Bullet”- Paul Erlich (1907)- possible to make absorbed substance poison to harmful bacteria only – sleeping sickness tse-tse fly with dye called Trypan red, somewhat effect [dyes can fight bacteria];
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