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ANSC 464
Exam 2
| Question | Answer |
|---|---|
| What is the difference between the terms "gut microbiota-brain axis" and "microbial endocrinology"? | Gut microbiota-brain axis refers to bidirectional signaling between the brain to the gut (via multiple signaling pathways), while microbial endocrinology refers to the study of this bidirectional communication (via neuroendocrine signals) |
| List the three main types of signaling utilized by gastrointestinal microbes and the brain that enables communication: | immune, chemical, neuronal |
| True/False: Microbes are capable of producing and responding to the same neurochemicals produced by the brain. | True |
| True/False: The gastrointestinal microbiome is composed of only bacteria and no other microbes. | False |
| Animal models have been invaluable for investigating gut microbiota-brain axis because: Some central nervous system features are what across species? | evolutionary conserved |
| Animal models have been invaluable for investigating gut microbiota-brain axis because: Some animals can be what for transplanting what type of microbes? | "humanized", human |
| Animal models have been invaluable for investigating gut microbiota-brain axis because: Animal models can be used as tools for studying what? | selective phenotypes |
| Animal models have been invaluable for investigating gut microbiota-brain axis because: Animal modeling enables research strategies that are what to perform in clinical trials? | unethical or impossible |
| What is a microbiome? | a small community of living organisms occupying a habitat |
| What are microbial communities comprised of? | bacteria, archaea, fungi, viruses |
| What are archaea? | single celled organism without a nucleus |
| What does endogenous mean? | growing or originating from within the host |
| What does exogenous mean? | originating from the external environment |
| What is a long-term biological interaction in which members of one species gain benefits while those of the other species neither benefit nor are harmed? | commensalism |
| What is a mutually beneficial relationship between different organisms? | symbiotic |
| What is an organism living in symbiosis with another? | symbiont |
| What are opportunistic microbes that emerge as a result of perturbations in the healthy microbiome? | pathobiont |
| True/False: Microbes colonize “nearly every environmentally exposed body surface” of the host. | true |
| What does the gut microbiome process and break down? | nutrients (especially dietary components that host digestive system cannot process on its own) |
| What does the gut microbiome improve the function of? | intestinal barrier |
| What does the gut microbiome educate? | mucosal immune system |
| What does the gut microbiome process and produce? | bioactive compounds |
| What is layer of connective tissue that forms part of the moist linings known as mucous membranes; located just below the epithelium? | lamina propria |
| What is the inside space of a tubular structure, such as the intestine.? | lumen |
| The first thing that intestinal dendritic cells will do is sample what? | intestinal lumen |
| Where does the intestinal dendritic cells migrate to after sampling the intestinal lumen? | mesenteric lymph nodes |
| After the intestinal dendritic cells migrate to the lymph nodes, then they present the antigen to what (initiation of tolerogenic or protective immune responses)? | T cells |
| What produce immunoglobulin A (IgA), which, along with antimicrobial peptides: Neutralize bacterial toxins, shape the microflora content and prevent breach of the epithelial layer? | B cells |
| What could be located at the tips of villi or within lymphoid follicles located along the length of the intestine? | DCs |
| Which microbe communicating pathway involves ENS? | neuronal |
| What is one of the main divisions of the autonomic nervous system and consists of a mesh-like system of neurons that governs the function of the gastrointestinal tract? | ENS |
| What does ENS stand for? | enteric nervous system |
| What is the longest nerve of the autonomic nervous system and comprises both sensory and motor fibers; It comprises two nerves—but they are typically referred to collectively as a single subsystem? | vagus |
| Which microbe communicating pathway involves neurotransmitters, metabolites, and neuroendocrine hormones (e.g. HPA axis)? | chemical signaling |
| Which microbe communicating pathway involves cytokine signaling and metabolites? | immune system |
| Various factors can influence the composition and diversity of the gut microbiome, such as what? | Birthing process, age, diet, stress, medications (antibiotics), environmental factors, pathogen exposure |
| What is a drug that inhibits the growth of or destroys microorganisms? | antibiotic |
| What term describes specialized plant fibers; that act like fertilizers to stimulate the growth of healthy bacteria? | prebiotic |
| What term describes microorganism(s) introduced into the body for its beneficial qualities? | probiotic |
| What is a coined term for probiotics that confer mental health benefits to the host? | psychobiotics |
| What are examples of medical advances aimed at intervening or modifying some of the factors that influence the gut microbiome in order to optimize health? | fecal transplant, dietary modifications, probiotics, phage therapy, postbiotics |
| What are the consequences of microbial alterations? | modified microbial components & metabolites, dysregulate enteric & systemic immunity, impaired blood-brain barrier, altered meningeal immune functions, and dysregulated CNS immune functions |
| What is the movement of genetic material between unicellular and/or multicellular organisms not by inheritance? | horizontal/lateral gene transfer |
| What is a primary means of spread of mobile genetic elements (plasmids and transposons) between bacteria? | conjugative transfer |
| What is the circulation of nutrient-rich blood between the intestine and liver? | portal circulation |
| What is a sensory receptor that responds to mechanical pressure or distortion? | mechanoreceptors |
| What is a sensory receptor which transduces a chemical substance to generate a biological signal? | chemoreceptor |
| What is a surgical procedure that involves cutting/removing sections of the vagus nerve (e.g., vagotomized mice have had their vagus nerve severed/removed)? | vagotomy |
| What is a model organism (host) that is colonized with a specific community of known microbes? | gnotobiotic |
| What is status of a laboratory animal (host) that is routinely tested to guarantee the absence of particular pathogens? | specific pathogen free (SPF) |
| What is an abbreviation for species, indicating several species of a particular genus? | spp. |
| What is a study that looks at a single time point? | cross-sectional |
| What is a study that looks at multiple time points; follows the same individuals across time? | longitudinal |
| What is the elevated plus maze test? | a common test for rodent anxiety |
| What is the definition of the term “microbial endocrinology”? | The study of bidirectional neurochemical interaction between the host and the microbiome. |
| Are microbiome-host interactions unidirectional or bidirectional? | Bidirectional |
| What are some of the methodological issues encountered when studying microbial endocrinology? | Innervation and microbial communities are not homogeneous throughout the length of the intestine; The capacity for microbes to produce neuroactive components is dependent on the availability of suitable substrates |
| Provide a basic definition of the “gut microbiota-brain axis”. | The network of connections involving multiple biological systems that allow bidirectional communication between gut bacteria and the brain. |
| Give a brief description of chemical signaling between gut microbes and the brain. | direct and indirect signaling via neuroactive chemicals (e.g., short chain fatty acids [SCFAs], neurotransmitters, endocrine hormones) |
| Give a brief description of neuronal signaling between gut microbes and the brain. | physical afferent and efferent nerve pathways (enteric nervous system & vagus nerve) linking the brain and the gastrointestinal tract |
| Give a brief description of immune signaling between gut microbes and the brain. | bidirectional interaction between the brain, intestinal microbes, and the immune system (central, peripheral, systemic). |
| Identify pitfalls of animal models: | not designed to fully recapitulate the human experience and gut microbiomes are substantially different across species. |
| Did Dr. Lyte receive the grant for NIH Director's Pioneer Award? | no |
| What are some possible overlaps between this and the material covered in Module 1? | The HPA axis (& neuroendocrine hormone signaling pathways) affects neuroimmune communication; peripheral immune signaling can change behavior; psychological stress impacts physiological functioning in the periphery (top-down signaling) |
| What are specialized intestinal cells that respond to chemical and mechanical stimuli and produce neuroendocrine molecules (hormones) and neurotransmitters (e.g., serotonin) involved in digestion, absorption, and appetite? | enteroendocrine cells |
| What are the criteria of validity for animal models of psychiatric disorders? | face validity, predictive validity, construct validity |
| What validity critiques whether a model recapitulates what it is meant to. The aim is to “mimic diagnostic criteria of the psychiatric conditions”? | face |
| What validity is about the ability to predict the efficacy of treatments (often pharmacological)? | predictive |
| What validity deals with the accuracy with which the model measures what it is intended to measure? | construct |
| What term describes an imbalance of microbial species ...and sometimes a reduction in microbial diversity (but not always).? | dysbiosis |
| Was Dr. Hsiao’s career path always straightforward (i.e., did she always know what she wanted to do)? | No, her path was not always straightforward; she even considered dropping out of grad school within her first couple years! |
| What did you learn about the etymology (i.e., origin) of the word “bug”? | It likely derives from words for "ghost" or "goblin" |
| Is the majority of serotonin made in the intestines or in the brain? | intestines |
| What fad diet does Dr. Hsiao talk about as a treatment for epilepsy? | Ketogenic |
| What was the proposed alternative intervention for epilepsy treatment (especially for kids, who find it hard to stick to a strict ketogenic diet)? | deliver just the metabolites or chemicals |
| What was one big caveat Dr. Hsiao mentioned regarding this alternative intervention for epilepsy? | Results from mouse studies cannot be directly translated to humans |
| Provide a basic definition of the term “allostasis”. | The active process of the body to maintain homeostasis in the face of stress |
| Fill in the blank: Mood disorders are often classified as a ________ in allostasis. | failure |
| What do experiments in germ free (GF) mice and in animal models of chronic stress indicate about gut microbial involvement in allostasis? | Gut microbiota are involved in maintaining allostasis via affecting the stress response pathways in the brain. This communication is bidirectional, as chronic stress can also lead to lasting alterations in the composition & function of the gut microbiota. |
| List one major benefit of human clinical studies investigating the role of the gut microbiome in stress/disease. | We can study patients that are experiencing a real disease (e.g., depression) |
| List one major caveat of human clinical studies investigating the role of the gut microbiome in stress/disease. | There is a LOT of inter-individual microbiome variability in the human population |
| List one major benefit of animal models investigating the role of the gut microbiome in stress/disease. | We can transplant microbiota from humans or other animals |
| List one major caveat of animal models investigating the role of the gut microbiome in stress/disease. | We cannot say for certain whether the anxiety-like or depressive-like behaviors that we measure in animals are an accurate reflection of the human condition |
| Authors describe a human study testing the impacts of 30 days of probiotic treatment. If both the treatment and the placebo group report the same results, what conclusions can be drawn about the study? | Cannot say whether these probiotics are effective at treating stress-, anxiety-, or depression-related symptoms. There was a placebo effect . Also, no difference in physiological biomarkers (glucocorticoid levels). |
| Is microbial distribution homogenous throughout the intestine? | No, gut microbiota show high inter-subject variation |
| What part of the gut is where the mucus is not attached to the epithelium and forms a diffusion barrier containing antibacterial products that limit penetration by bacteria.? | small intestine |
| What part of the gut is where the bacteria are compartmentalized to the outer loose mucus layer; the inner mucus layer, which is attached to the epithelium, is almost free of bacteria and protects the epithelium. | colon |
| What are caveats of using the term dysbiosis? | There is too much individual variation to what "healthy" is, what healthy is for one isn't equal to another (preexisting conditions), and where do we draw the line between healthy & unhealthy |
| One benefit of using animal modeling when studying the gut-brain-axis is we can test specific pre-, pro- or postbiotics in animal disease models to determine if they are what kind of treatment option in humans? | may be viable |
| One benefit of using animal modeling when studying the gut-brain-axis is that animals can be used in experimental manipulations that would be what in humans (e.g., enteric pathogen infection, chronic stress) ? | unethical |
| One benefit of using animal modeling when studying the gut-brain-axis is that we can control almost all of what in animal experiments, removing possible confounds that often make clinical studies difficult? | variables |
| One benefit of using animal modeling when studying the gut-brain-axis is we can derive what kind of animals? | germ free & gnotobiotic |
| One limitation of human clinical trials in gut microbiome-brain axis research is correlation does not equal what? | causation |
| One limitation of human clinical trials in gut microbiome-brain axis research is human psychiatric disorders are complex, with what across subjects? | wide variation |
| One limitation of human clinical trials in gut microbiome-brain axis research is that what is not always a reliable way of measuring psychological symptoms? | self reporting |
| One limitation of human clinical trials in gut microbiome-brain axis research is that what may confound results? | placebo effect |
| Studies in germ-free animals indicate that microbes are involved in regulating the stress response (i.e., allostasis). What do studies of chronic or early life stress tell us? | Microbes are also responsive to stress signals (e.g., chronic or early life stress can lead to long term alterations in microbial composition) |
| [T/F]: Animal models are considered valid if they meet at least 3 principles of validity: face, predictive, & construct. Models of human diseases that have unknown etiology (depression) are still able to meet these validity criteria if designed correctly. | false |
| Last week, you read about a probiotic study that had a clear placebo effect. What is the definition of "placebo effect" and what does it indicate? | The placebo effect is a beneficial effect produced by a non-therapeutic drug or treatment (e.g., sugar pill), which cannot be attributed to the properties of the placebo itself, and must therefore be due to the patient's belief in the treatment. |
Created by:
Hoofin'it