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56 Cards in this Set
- Front
- Back
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True or False. Australian doctors Marshall and Warren isolated H. pylori in 1982.
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True
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What is the comparative genome of H. pylori?
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The complete DNA genomic sequence for 2 separate H. pylori strains: each has a single small chromosome of approximately 1.7 million nucleotides, comprising about 1550 individual genes.
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E. coli has about 5 milion nucleotides and humans habe about 3 billio. What is the cagA gene?
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It encodes for the CagA protein. Some reserach indicates that people infected with H. pylori strains bearing this cagA gene have higher risk of azquiring peptic ulcer disease or stomach cancer.
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What is typ IV secretion system?
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cagA is part of a region in the H. pylori chromosome thatalso has genes encoding proteins that form a type IV secretion system. Bacterial cells assemble these systems to export large, complex molecules into host cells, for example B. pertussis (whooping cough) uses this system to introduce its toxin into human respiratory cells.
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True or False. Strains of H.pylori bearing the cagA gene cause more severe inflammation and tissue injury in the stomach lining than do strains without the gene.
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True
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What is VacA?
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It is a toxin, encoded by a gene. It forms vacuoles in host cells. It also turns off the infection fighting WbCs in the stomach, diminishing the immune response to H. pylori. This is present in every H. pylori strain.
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True or False. It has 4 variations, depending on where in the gene it is found. m1 and m2, s1 and s2. H. pylori strains with both the m1 and s1 variations produce more damaging frm of the VacA toxin.
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True
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True or False. The stomach produces 2 hormones that affect eating behavior: leptin, which signals the brain to stop eating and ghrelin, which stimulates appetite.
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True
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What does substantial variation of H. pylori suggests?
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Either bacteria have existed fr a ery long time as a species or that any particular variant is not so much better adapted to the human stomach as to outcompete all the others.
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What protein does cagA gene encode?
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CagA protein
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H. pylori genes near cagA encode TFSS proteins assembe into a structure analogus to a miniature hypodermic needle, what does this structure injects?
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It injects the CagA protein into the epithelial cells that line the human stomach.
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What happen when CagA proteins enters the epithelial cells?
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After CagA enters the epithelial cell, enzymes in the host chemically transform the protein, allowing it to interact with several human proteins. These interactions ultimately affect the cell's shape, secretions and signals to other cells.
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What gene causes severe inflammation and tissue injury in the stomach lining?
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cagA gene
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What is the active agent or toxin that causes large holes or vacuoles?
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VacA protein
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What is VacA protein?
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VacA protein is encoded by vacA gene. It forms vacuoles and turns off the infection-fighting WBC in the stomach, diminishing the immune response to H. pylori.
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What is present in every H. pylori strain?
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vacA gene
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Why does VacA diminishes the immune response to H. pylori?
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It turns off the infection-fighting WBC in the stomach.
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Who discovered the four variations of vacA gene?
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John C. Atheton from England
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What are the four variations of vacA gene?
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m1 and m2 in the middle region of the gene
s1 and s2 in the region that encodes the protein's signal sequence, which enables the protein to move through the cell membrane |
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What enable the VacA protein to move through the cell membrane?
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s1 and s2
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Where can we find m1 and m2?
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in the middle region of cagA gene
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Where can we find s1 and s2?
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in the region that encodes the protein's signal sequence.
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What does s1 and s2 do?
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It enable CagA protein to move through the cell membrane.
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What are the three subtypes of s1?
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s1a, s1b, s1c
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Why are some people more susceptible to stomach cancer?
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When it carries pro-inflammatory variations and i colonized with H. pylori strains containing the cagA gene andthe s1/m1 vacA genotype.
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What geographic regions can you find vacA gene s1?
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s1c is predomiated in East Asia, s1b is Mediterranean area and s1a is in Northern Europe
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What was initially found out when H. pylori strains was studie in Latin America?
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Initially found out that s1b - Mediterranean was the most common, suggesting tha H. pylori was brought by Spanish and Portuguese settler or African slaves
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Why do they have to study H. pylori strains in Latin America?
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Because the results could indicate when and how the bacteria arrive in the New World
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What was the flaw about their initial finding of H. pylori strain in Latin America?
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The study was conducted in Latin America's coastal cities, where people have mixed European, African and Amerindian ancestries.
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Where do they get their sample from their second study of H. pylori strains in Latin America?
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Stomach samples from Amazonian population - people in Puerto Ayacucho, a market town on the Orinoco River in Venezuela
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What do they find out in the H. pylori strains taken from the Amazonian population? And what's the relevance of this result?
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Found out that s1c - East Asia strain is prevalent. Ths work provided evidene that H. pyolori had been transported across the Bering Strait by the ancestors of the present-day Amerindians and thus has been present in humans for at least 11,000 years.
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What are the five ancient populations that modern H. pylori can be traced from?
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Two arising in Africa, Two in western or central Eurasia and One in East Asia
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True or False. Genetic variations of H. pylori can be used to trace human settlemnt and migration patterns over the past 60,000 years because H. pylori is so much genetically diverse than Homo sapiens?
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True
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What are the hosts for H. pylori?
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Humans
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How does H. pylori get transmitted?
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mouth-to-mouth or feces-to-mouth transmission
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How can we determine the presence of H. pylori?
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Determined by tests of blood, stool, breath or stomach tissue
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True or False. H. pylori is the only bacterium that can persist in the acidic environment of the human stomach.
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True
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What causes peptic ulcer and stomach cancer, except H. pylori?
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Aspirin and nonsteriodal inflammatory agents such as ibuprofen
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True or False. In 1900, stomach cancer is the leading cause of cancer death in the U.S.
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True
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How many % did the mortality rates of stomach cancer decline?
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80% putting it below the rates for colon, prostrate, breast and lung cancer
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What is esophageal adenocarcinoma?
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An aggresive cancer that develops in the inner lining of the esophagus just above the stomach.
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What is the fastest-increasing major cancer in the country?
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Esophageal adenocarcinoma climbing by 7 to 9 % each year
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What is the survival rate when one is diagnosed with esophageal adenocarcinoma?
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Five-year survival rate is less than 10%
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What is the primary risk factor of esopharengeal adinocarcinoma?
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Gastoresophageal reflux disease (GERD) - commonly called as acid reflux
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What is gastroesopharengeal reflux disease (GERD)?
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A chronic disorder involving regurgitation of acidic stomach contents into the esophagus.
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What is a Barett esophagus?
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premalignant lesion
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What do GERD progess into?
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GERD may initiatie a 20-to-50 year process: in some cases, the disorder slowly progresses to Barrett's esophagus andthen to adenocarcinoma, paralleling the gradual changes that lead to cancers in other epithelial tissues
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What is the theory of interaction between H. pylori and human host?
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Negative feedback loop. To minimize damage from infection of H. pylori, humans have developed ways to signal to bacteria, through immune responses and changs in the pressure and acidity in the stomach. And H. pylori in turn, can signal the host cells to alleviate the stresses on the bacteria.
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How do H. pylori regulate the acidity of its environment?
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Strains bearing the cagA gene can ue the CagA protein as signaling molecule. when acidity is high, the cagA gene produces relatively large amount of f the protein, which triggers an inflammatory response from the host that lowers acidity by affecting the hormonal regulation of the acid-producing cells in the stomach lining. Low acidity, in contrast, curtails the production of CagA and hence reduces the inflammation.
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How does cagA strain increase the risk of stomach cancer?
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The cagA strains substantially increase the risk of stomach cancer because they inject the CagA protein into the stomach's epithelial cells for decades, affectng the longevity of the host cells and thier propensity to induce inflammation that promotes cancer.
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How do cagA strains decreases the risks of esopharengeal cancer?
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CagA strains effectively modulate acid production in the stomach, preventing acidity levels from rising too high.
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What are the other physiological effects of the absence of H. pylori?
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It affects eating behavior because of the interruption in the stomach hormones - leptin and ghrelin.
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What is leptin?
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Hormone that signals the brain to stop eating.
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What is ghrelin?
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Hormone that stimulates appetitie.
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What does eradication of H. pylori with antibiotics do with regads to leptin and ghrelin?
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Eradication of H. pylori with antibiotics tend to lower leptin and increase ghrelin
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Why do researchers failed to find effective probiotics?
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Complexity and coevolutionof the human microbiota, the organism that share our bodies. Our microbiota are highly evolved for living within us and within each other - "home court advantage"
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