YJBM Podcast Clocks and Cycles: Episode I

Transcript

00:00 --> 00:03Yale podcast network.
00:05 --> 00:17Hello and Welcome to another episode of the Yale Journal of biology and Medicine podcast. YJBM is a pubMed index quarterly Journal edited by Yale medical graduate and professional students and peer reviewed by experts in the fields of biology and medicine.
00:18 --> 00:25Each issue of the Journal is devoted to a focus topic and in this series. We're taking you through the past, present, and future of the clocks and cycles.
00:25 --> 00:44Or July episode is devoted to YJBM's issues on Clocks and Cycles, which was just published last June and you can find this issue on why YJBM's website or and pub med. I'm Amelia Hallworth a second year graduate student in Microbiology and I'm Lisa Ogawa McLean and I am a fifth year student in molecular biophysics and biochemistry.
00:45 --> 00:57Today we're interviewing doctor Adam Silver, an associate professor of biology at the University of Hartford. In addition to his work on the immune system and the circadian Clock that we will talk about today? He also works on the gut microbiome.
00:58 --> 01:15So doctor Silver can you please give a brief introduction of the circadian Clock and the immune system as they pertain to your research? I'd be happy to. Thank you for having me today. Thank you for coming so the master circadian Clock is located in the Super chiasmatic nucleus of the hypothalamus in the brain.
01:16 --> 01:26Regulates nearly all aspects of our Physiology, and behavior, which oscillate over the course of a 24 hour period. Now the Clock regulates activities that the Organism.
01:27 --> 01:35So, like the sleep wake cycle this cellular so for example, the recruitment of cells in at the molecular levels like gene expression.
01:35 --> 01:47So since we're more likely to encounter pathogens during the day when we are active. We initially were interested in determining if certain aspects of our immune system fluctuated over the daily cycle.
01:47 --> 02:14So is our immune system at its peak. When were active and potentially more likely to encounter pathogens so in theory, we don't need our immune response at its peak. When were sleeping. So this would be kind of a waste of energy and could potentially inhibit tissue repair so currently I've been interested in the other end of the spectrum so how do pathogens or even microbes in general alter our Clock so This is why we feel tired? When were sick?
02:14 --> 02:20So just the recognition of pathogens impact the Clock, which is closely tide to the sleep Wake Cycle.
02:21 --> 02:54So Is it true then that the light is the main driver of the circadian Clock. That's what regulates the circadian rhythm. The Clock cycle. So it is so the master Clock isn't trained by exogenous cues and like you said light is the biggest one. However, other environmental stimuli can align the Clock such as temperature food, even exercise so the master Clock, then regulates peripheral oscillators throughout the body, so that can be found in various organs tissues as well as cells.
02:54 --> 03:03And then this synchronization or you could think of it like talk to the periphery is mediated through various neural and hormonal signals.
03:05 --> 03:32So if if those external signals like light and temperature aren't changing but then, when you get sick. The pathogens are altering the Clock. Even though those signals aren't changing I guess possibly the pathogens may be acting further downstream is that what you're finding that's a great question and I would say right now, we don't know so that would be something that I'd be interested in would be to determine those molecular mechanisms of how that is actually happening.
03:33 --> 03:55So other than that? What are currently some of the bigger intriguing questions in your field kind of like I mentioned just now would be looking at some of those molecular mechanisms. So we know that various immune parameters fluctuate over the 24 hour period, however, really more work needs to be done to determine those molecular mechanisms.
03:55 --> 04:02I think it would be very important to determine the clocks influence on the adaptive immune response as well.
04:03 --> 04:15And then if you take kind of both of these points and put them together. I think they'll enhance the field of Chrono Therapeutics. So time delivery of drugs and vaccines in order to develop maximum efficacy.
04:16 --> 04:48And I think ultimately that's why I would like to see the research field. Go to kind of personalized. Medison, which takes into account and individuals circadian rhythm so really briefly on the topic of drugs targeting the circadian rhythm are there known diseases that are associated with I guess the Clock gene so interesting Lee in 2014. There was a paper that revealed that oscillating jeans or associated with nearly every major disease that was funded by the NIH.
04:49 --> 05:11So diseases like cancer Alzheimer's disease, Schizophrenia Down syndrome, obesity, where most strongly associated with circadian jeans and they go on to reveal that 56 of the Top 100 best selling drugs in the US target the product of a circadian gene.
05:12 --> 05:25Yeah, that's really interesting are there any drugs that currently target the Clock jeans specifically if it Clock chain not just once that oscillate that I'm not sure.
05:26 --> 05:44OK, so how did you get to where you are and how did your research interests develop into studying the immune system in the circadian rhythm a long story. I'll try to keep it short, but I kind of consider myself a Jack of all trades master of nothing.
05:45 --> 06:13So as a graduate student or I could say I consider myself a microbiologist at heart. Even though right now. I study circadian rhythms and the immune response so as a graduate student. I studied the beneficial symbiosis between Aeromonas Verrone and the medicinal. Leech so really bacteria host interactions in the laboratory of doctor your graph the University of Connecticut.
06:14 --> 06:24And after my PhD work I wanted to continue bacteria host interactions. But I thought it would be really cool living in Connecticut. I'm from Connecticut.
06:24 --> 06:32To study tick bacteria interactions and then, who better to work with and Yale Zone Doctor Errol Vic rig.
06:33 --> 06:49So actually started on a project in his lab for the first six months of my tenure, there looking at tix salivary gland proteins. That could help facilitate Borrelia. The causative agent of Lyme disease getting into the mammalian host.
06:50 --> 06:56An and then during that time, another post doc in the lab who actually did his PhD work on circadian rhythms.
06:57 --> 07:14He got some really cool. Preliminary data and then he actually took a job in Spain. He was from Spain. So he left an aerial approached me and said Hey. Adam do you do you want to take over this project and even though it was totally out of my comfort zone?
07:15 --> 07:20I thought it was too great of an opportunity and just too cool of research to pass up.
07:21 --> 07:41And for a while. I really struggled. Because imagine I was kind of on my own in the lab because I was surrounded by microbiologists or immunologists and no one really knew anything about circadian rhythms, so for awhile. I really felt like I was on an island on my my lab mates were great and trying to help me as most they couldn't help me with the immunology peace.
07:42 --> 07:47But it wasn't until I found some collaborators and other labs here at Yale that were really able to.
07:48 --> 07:49To help me?
07:52 --> 07:59You know where I am now, I'm in a small really undergraduate institution that focuses on teaching.
07:59 --> 08:10Anne I kind of took that route because as a graduate student. I really enjoyed my interactions with the undergraduates. When I was teaching labs and I was kind of kept in the back of my head and.
08:12 --> 08:14I've been there 6 years now.
08:17 --> 08:20How many students do you have in your lab currently?
08:21 --> 08:27So because their undergraduates and I have quite a bit of turnover, it fluctuates.
08:28 --> 08:37Anywhere from 2 to 5, so and I try to stagger them. So I can have more senior students training newer students on various projects.
08:39 --> 08:58So I guess we're on the topic of your post doc while you're at your post. Doc you published a couple of very cool papers that came out in 2012, so in the first one, you showed that there were Clock jeans that were being expressed in a rhythmic way in various immune cells so which immune cells were you studying where there are reasons. You picked those and what do they do?
08:58 --> 09:07So we looked at splenic macrophages, dendritic cells and B cells and these have various roles.
09:08 --> 09:21For example, a macrophages are best known for regulating inflammation and whose defense dendritic cells for their work as integer presenting cells and B cells for antibody secretion.
09:21 --> 09:27So really kind of cells that were involved in both the innate and adaptive immune responses.
09:27 --> 09:29And you know why.
09:30 --> 09:33Just some of the major major cell types that are found in the spleen.
09:35 --> 09:54And I guess sort of looking back at this, it seems like you would expect every cell in your body would know what time it is, but at the time that seems like it was kind of a surprising result. So why was that so surprising and has something changed since then to make this seamless less surprising overtime.
09:54 --> 10:01Yeah, I think that's you're exactly right the way you ask that question.
10:01 --> 10:10Because I think 10 years ago, it was kind of surprising as we knew that some immune parameters fluctuated over the 24 hour period.
10:10 --> 10:20And then at that point right about 10 years ago. We were uncovering more and more mean parameters fluctuating over over the daily cycle.
10:21 --> 10:26But even look, but like you said. Looking back on that now I still think it's interesting that.
10:27 --> 10:34We have those 3 different cell types. We looked at and if you look there on slightly different time so to speak.
10:35 --> 10:46And what I think is so cool, you have different cell types in the spleen on slightly different time and also they?
10:47 --> 10:54Their absolute numbers in relative cell numbers can also fluctuate throughout the day.
10:55 --> 11:01And then so you have individual cells in the spleen on their own time and then the spleen as a whole site tissue.
11:02 --> 11:14All those individual cells make up the timing of the spleen and do you know if that pertains to their functional role in the immune response?
11:16 --> 11:22I think it. It definitely contributes but to what extent it's not quite known just yet.
11:23 --> 11:56OK, well in in another paper, you showed that um toll like Receptor 9 expression is controlled by their circadian Clock. So you look specifically you found that this toll like Receptor had this circadian rhythm so first? What are the toll like receptors and what role do they play in our immune response so to like receptors are a class of pattern recognition receptor located in or on the surface is of certain immune cells that identify pathogen associated molecular patterns.
11:56 --> 12:04Also refer to his pants and some researchers in the field refer to those as Maps microbial associated molecular patterns.
12:05 --> 12:16So these are conserved microbial components that are exclusive to micro organisms, so as an example things like bacterial DNA or viral DNA.
12:16 --> 12:44Bacterial LPS or flagella and so things that are unique to micro organisms and to date, 10 human TL. Rs have been identified 12 mouse. TL Rs have been identified and imagine each of these TL Rs recognizes and binds to a specific microbial login and then there's some binding. We usually induce proinflammatory cytokines. Some kind of a stab Lish in Anti Microbial State.
12:44 --> 12:49In addition to this, it'll initiate.
12:49 --> 12:53Or help direct the adaptive immune response as well.
12:53 --> 13:25So what is recognized by toll like receptor 9? What is the leg in DNA so specifically materialen viral or do what are called. CPG DNA motives so to stimulate synthetic to stimulate TLR 9. Muse they think like a synthetic nucleotide. So what would I guess. We talked about this a little bit earlier, but what is the functional relevance for the circadian rhythm and TLR receptor expression you mentioned you probably wouldn't want to have your immune response activated too much at night.
13:25 --> 13:27How much of a role with this business play?
13:28 --> 13:30So we're looking at.
13:30 --> 13:34Like TLR expression itself.
13:35 --> 13:36Uh.
13:38 --> 14:08So imagine if MRNA levels fluctuate over the 24 hour period. It would write suggests that save responsiveness of these toll like receptors also fluctuates over a 24 hour period, making them more likely to pick up those microbes have heightened responsiveness at certain times of day compared to others when we are more likely to encounter those pathogens and.
14:08 --> 14:15Just sort of give People a sense of the scale. How much is this punctuating is it like nothing to 100 or somewhere in the middle of that.
14:15 --> 14:18Oh, that's a That's a great question.
14:20 --> 14:29So a friend of mine who helped develop a statistical program that detects the cycling of jeans.
14:30 --> 14:48You know, Essentia Lee told me one time over coffee that you can set this so low that you can detect cycling and very minimal amounts of gene expression very small differences and you could almost argue that maybe every gene is cycling if.
14:49 --> 14:52If looking at right those small differences.
14:53 --> 15:00But honestly it's going to depend on say which TLR which team we're looking at.
15:01 --> 15:03There will be.
15:03 --> 15:08Larger differences in amplitude during the cycling we could say.
15:09 --> 15:20So then do all the toll like receptors cycle or are there. Some that aren't oscillating at all, even when you're looking at small changes so?
15:21 --> 15:25It's going to depend in this cell type or looking at.
15:25 --> 15:30And then so a lot of the work I've done recently so again I work at A.
15:30 --> 16:01Smaller predominantly undergraduate institution and I don't have a tremendous amount of funding funding. So the questions. I can ask are going to be smaller scale, so recently. I've looked at M. RNA expression levels. But in an ideal scenario. I look at M. RNA expression followed up by protein levels to see if protein levels also oscillate in circadian fashion and then follow that up with looking at responsiveness.
16:01 --> 16:09Over the course of a 24 even 48 hour period and then do we see cycling because imagine?
16:09 --> 16:30Just because we don't see circadian variations at the M, RNA level doesn't mean we won't see them at the protein level or responsiveness because sometimes your post transcriptional regulation could be done in a Sir Cadian fashion, so there are multiple levels of complexity at play here.
16:30 --> 16:36And so there are known proteins that have sort of that post transcriptional regulation.
16:36 --> 16:38But so the big thing is.
16:38 --> 16:52At least you know what I can show is do we see at least daily variations in responsiveness. So we see daily variations in M RNA expression and then couple that with.
16:53 --> 17:08Daily changes or variations and responsiveness, then we can say OK. This gene is most likely under controlled by the circadian Clock and then you could really dive into the molecular mechanisms. There, like we did in the TLR 9 paper.
17:08 --> 17:41So I guess if you're looking at the TLR is that seemed to be like the most circuiting controlled in the ones that seem to be the least circadian controlled are there any functional differences that jump out at you in terms of I guess what? They're doing in the immune system and what they might be recognizing like you said. We had the paper on TLR 9:00. We went into a good amount of detail on that some of my recent work is looking at the TL Rs as a whole, but kind of dialing it back several years now. Some of the preliminary data that my colleague came up with.
17:41 --> 17:44Was actually dealing with TLR 3?
17:45 --> 17:48And its role in West Nile virus.
17:48 --> 18:08And he actually had some really cool data that shows that in mice. Mice are more susceptible to West Nile virus infection at certain times of day compared to another an really had some initial data. That kind of link that with TLR 3's TLR 3 does play a role in West Nile recognition.
18:09 --> 18:14So, like big picture big scale TLR work I think that would be.
18:15 --> 18:18Kind of the next cool thing that's out there.
18:19 --> 18:37And so I guess then even bigger picture are any of these receptors potential drug targets for sort of stimulating the immune response. So are there any drugs that currently target them or is there any like the field sort of looking at that at this point?
18:38 --> 18:58He is so researchers are always trying to find new adjutants out there, so things that are going to boost vaccine efficacy. Ann I know. Some studies out there that have used TLR agonists to try to enhance vaccine efficacy for example.
18:59 --> 19:01I know.
19:01 --> 19:32They've used TLR 9 logins in an anti tumor vaccine and a vaccine against Melanoma actually so are any of these in clinical trapped in the clinical trial stage or is I believe I believe so cool. That's very cool like this has potential to do all kinds of stuff just as you mentioned the circadian Clock is impacting basically all the diseases. So as we mentioned earlier. We talked about the pathogen molecules feeding back in regulating the circadian Clock.
19:33 --> 20:03So just sort of evolutionarily big picture why might it be important for the circadian Clock to be affected by the presence or absence of microbes so really to be quite honest that I think this is just right speculation almost anecdotal. But, perhaps from the pathogen's point of view. If you disturb the Clock. It will essentially weak in the host, which might confirm survival advantage for the Organism or flipping that.
20:03 --> 20:11It could be our body's way of forcing us to rest repair tissue damage. When we're sick right. Maybe This is why we feel tired? When were sick.
20:12 --> 20:27Our body recognizes a pathogen that triggers are molecular Clock is kind of telling us to slow down so like I said kind of repair that tissue damage. But to really understand this and to get it. This I think we really need to workout those molecular mechanisms.
20:28 --> 20:59OK so this has been nagging at me a little bit so if the immune system is controlled by the circadian rhythm. We know that there are some areas that see more or less light during a 24 hour period so like in Alaska in Canada. They have some really long days during part of the air and then in other parts of the year. They're really short do. We know and can you speculate maybe on how this effects the immune system or is because the?
20:59 --> 21:10Circadian rhythm is regulated by the light, maybe they see no ill effects from having the shorter or longer days.
21:11 --> 21:16So right circadian rhythms influence nearly all aspects of Physiology and behavior.
21:17 --> 21:34So did it so to disrupt those rhythms or alter those rhythms can lead to serious short-term and long-term pathologies, such as depression or impaired immune function both of those have been shown but with That being said.
21:34 --> 21:52Circadian rhythms will still exist in the absence of an external Q. However, the rhythms will slowly start to get out of sync. So we really rely on sunlight to kind of reset our Clock everyday thing to keep a sometime so to speak.
21:53 --> 22:11So there are measures actually they can be taken by individuals, living in Alaska or say Canada like you mentioned by using artificial light like lightboxes early in the morning can help kind of reset your Clock and keep it on time.
22:12 --> 22:25I always think it's I think back to this, but I was studying this when both my kids were born and you know imagine. I'm in the hospital with my wife and we're like OK. We need to get at least 1 decent night sleep when we're here.
22:25 --> 22:28And we send the kids off to the nursery.
22:28 --> 22:43In the nurseries in constant light so we're kind of getting their circadian rhythms off to a terrible start. You know, and I could even think native New Englander you know in late January, February.
22:43 --> 22:46It feels like weeks where you just don't see the sun.
22:47 --> 23:14An it starts to be a drag you know, so seasonal depression is a thing and it's Tide into the sun. It's tight into our circadian rhythms also I notice then like phones now have sort of the blue light filter. So I think that's wonderful so that helps us. Maybe not trigger the wake period. When were maybe like scrolling through our phones at night. It's it's so funny but that's what they say is that?
23:15 --> 23:32How we live nowadays with TV and working late and constant light in your computer being on it really screws up our rhythms. You know in me like all even think if I go into the refrigerator in the middle of the night like Oh my goodness? What did I just do but our body has mechanisms in place to.
23:32 --> 23:44Make it so we're not that sensitive but I always laugh how when I was studying these things I would perform 24 hours straight experiments or 36 hours.
23:44 --> 23:51An thinking Oh wow. I'm showing how important our circadian rhythms are and I'm destroying my own.
23:52 --> 24:00Yeah, exactly I feel like we've also been seeing in the news. A lot more about how night shift work and have a negative effect on our health and so, yeah, so it's really.
24:01 --> 24:31That's funny but you are noticing it as you were working through the night and there are measured with night shift work. There are measures. You can do, but it's very challenging. You essentially have to train your body like it's a complete flip cycle like draw your shades and pretend like it's it's Day when it's really night so today. We've mostly been talking about human and mouse circadian clocks, So what other organisms have circadian clocks and what differences are there.
24:32 --> 24:39Between these kind of clocks do ticks have a circadian Clock that might affect whether or not you get Lyme disease.
24:40 --> 25:10So I'll answer the first part of the question to start so virtually all forms of life, including bacteria. Fungi plants drosophila. The fruit flies. Fish mice and obviously humans exhibit circadian rhythms. I think it's pretty wild that even single. Celled organisms right like bacteria, which reproduce many times over the course of a 24 hour period experience circadian rhythms for example, sign on.
25:10 --> 25:23Bacteria express' daily rhythms and photosynthesis, but imagine like their entire life span is like 20 minutes right. So why would they experience circadian rhythms.
25:24 --> 25:36So I think it fits into the notion of bacteria being treated like a multi cellular Organism? Do the quorum sensing so cell communication. That's probably a topic for another podcast.
25:37 --> 25:44Invite you back if we ever get around to talking about that, but but actually that's so that's actually one of the things I'm interested in in.
25:45 --> 25:49You know now that I have tenure at a smaller institution. I feel like I can.
25:50 --> 26:18Tackle some of the questions that I'm interested in and can wander off a little bit so like I said my PhD work was looking at the beneficial symbiosis between microorganism in the medicinal each and I'd love to take that system and bring in my circadian rhythm work. So how does the Leech undergoes circadian rhythms I have some?
26:19 --> 26:25Anecdotal evidence that it does from some of my former labmates that notice things.
26:25 --> 26:32Like higher bacterial numbers present in the digestive tract of the Leech at one time of day compared to another.
26:34 --> 26:47But then going back and seeing how bacteria could impact the leeches circadian rhythms how the leeches circadian rhythms impact the bacteria and the digestive tract. A Leech and then we could apply that to our own gut microbes.
26:48 --> 26:49That would be very cool.
26:49 --> 27:04And I know it's it's been a couple years since I've been following the circadian Clock literature. Other than cyanobacteria do you know if they found circadian clocks and other bacteria, particularly pathogens. It would make a lot of sense for them to be able to tell the immune system going to be ready for me or not.
27:05 --> 27:17So that was something that really was our initial hypothesis was especially being an arrow's lab in all the vector borne diseases that we worked with.
27:20 --> 27:40You know was there a manipulation between the microorganism in the vector where it would manipulate the vector to bite us at the time when our immune system was at its lowest in order to enhance infection or Conversely did our immune system evolved to peak when those the counters might occur.
27:42 --> 27:56I'm trying to think of I feel like that. I know of some pro does Ella that experience. Some type SUV of rhythms, but examples of bacteria off the Top of my head. I can't think of any.
27:57 --> 28:18Well, one of the arguably maybe one of the most important bacteria to humans and other animals is the mitochondria and our endosymbiotic relationship with our mitochondria has anyone looked at whether the mitochondria show or mitochondrial gene expression shows any sort of circadian rhythm.
28:19 --> 28:24Or in immune cells or other cells of the body. I don't know off hand.
28:26 --> 28:30I would I would think someone has in A.
28:31 --> 28:38And it would be a friend of mine who is actually was a postdoc here who did transcriptome analysis.
28:38 --> 28:39Of.
28:40 --> 28:42Many different tissue types.
28:43 --> 28:46I don't know I don't think they looked at mitochondria sorry China.
28:47 --> 29:01Go through the rolodex in my head. I don't know, but yeah, that's really interesting. This push it right. Then you could write tight and I don't know if you flick chloroplasts in sino bacteria right exactly if listeners wanted to learn more about this topic. What resources might you recommend.
29:02 --> 29:33So I don't know if it's OK to plug my own work, here, but they can start by reading the short review article. Let's set to be published in the June issue of the Yale Journal of biology and Medison so in that review was actually 3 undergraduates and I reviewed the field of the circadian immune connection really from the past 5 years, so really just a little snapshot, but really in that article. We cite some really excellent reviews from some huge names in the field.
29:33 --> 29:47In biology in the immune response so they could start with our review and then look at some of those. I think more comprehensive kind of bigger picture reviews that we site. I think would be a great place to start.
29:47 --> 29:54And we are Open Access, so anyone is free to access this review article.
29:54 --> 30:03And then finally do you have any practical advice for listeners, especially potentially young aspiring researchers maybe are starting to think about joining a lab?
30:04 --> 30:08I think in terms of joining a lab.
30:09 --> 30:13I think try to get a few rotations under your Belt to see what you really like.
30:13 --> 30:16And I think looking back on my time.
30:17 --> 30:21When it came time to make a career decision I think.
30:23 --> 30:42Or how should I say think about where you want to end up an if it's an industry. I would really try to learn as many techniques as possible so I did apply just some industry jobs and I feel like having experience doing many different types of techniques really got me those interviews.
30:43 --> 30:56At the end of the day I wanted to work at a smaller research institution, where teaching was also a focus and in hindsight. I wish I had more real teaching experience.
30:57 --> 31:18So I know potentially go out to even a Community College and see if you can add junked at night to really see what it's like to be a professor and have your own class an that will help you tremendously in your first year as well as getting an interview because I've been on a few search committees and that really makes a difference.
31:19 --> 31:20Thank you for that great advice.
31:21 --> 31:51And thank you for being on our podcast today. You're very welcome. Thank you for having me it's been great listeners. Thank you for tuning into this episode of the Yale Journal of biology and medicine podcast join us next month for a second podcast on clocks and cycles, where we will be interviewing Doctor Shah Yang, who works on the interaction between the circuit in Clock in the metabolism and thank you to the school of Medicine for being a home for YJBM the podcast. Thank you to the Yale Broadcast Center for help with recording editing and publishing our podcast.
31:51 --> 32:23Thank you to the YJBM editorial board, especially the deputy editors for this issue, Ian and Devon. and For more information on YJBM podcast please medicine.yale.edu/YJBM be sure to check out our Journal by searching Yale Journal of biology and medicine at pubmed.com. We'd love your feedback and questions so feel free to tell us your thoughts by emailing us at YJBM at yale.edu if you enjoyed our podcast. Please share the podcast on SoundCloud and Apple podcasts.
32:23 --> 32:27And Spotify see you next month for the next installment of the YJBM podcast.

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Do you feel like you get sick more often when you aren't getting enough sleep or when you travel overseas? There might be a reason for that! For the first episode based on YJBM's Clocks and Cycles issue, join the Yale Journal of Biology and Medicine hosts, Amelia and Lisa, as they interview Dr. Silver about his work on how the circadian clock impacts your immune system. For more information about YJBM or to read the Clocks and Cycles issue, visit medicine.yale.edu/yjbm.

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