Tuesday, September 4, 2012

High levels of DDT in breast milk in mothers living in malaria-stricken villages in South Africa

ScienceDaily (Sep. 3, 2012) ? The highest levels ever of DDT in breast milk have been measured in mothers living in malaria-stricken villages in South Africa. The values lie well over the limits set by the World Health Organization. DDT has been used for many years in South Africa, sprayed indoors to fight malaria. It works, but it exposes the inhabitants to other risks not yet fully known.

"To our ears, spraying DDT inside people's homes sounds absurd. But it is one of the most effective agents against malaria. And by only spraying adult mosquitoes in the vicinity of people, the risk of developing resistance in mosquitoes decreases, " says Henrik Kylin, environmental chemist and professor at Water and Environmental Studies, Link?ping. Together with South African researchers and doctors, he is collaborating on a project to map the effects of DDT on the population.

"We know a lot about how DDT affects nature and animals, but the effects on people's health are not as well studied, especially concerning long-term exposure."

"Based on the argument that "malaria is worse than DDT," people accept this spray treatment programme. The purpose of our project is to study the side effects, thereby creating a better basis for decisions."

In a newly published article, the researchers report on a study of DDT levels in breast milk from nursing mothers in four villages, of which three are afflicted by malaria. DDT has been used continuously in these three villages for more than 60 years. The spray treatment takes place a couple of times a year and is carried out by specially trained and equipped staff.

The levels proved to be unacceptably high in the villages sprayed. They were well over (100 times greater) the highest daily dosage recommended by WHO. In once case they measured the highest known level of DDT in breast milk ever, more than 300 times higher than the level allowed in cow's milk.

DDT has been associated with diagnoses such as breast cancer, diabetes, impaired sperm quality, spontaneous abortions, and neurological disorders in children. In the region where the measurements were carried out, malformed genitalia among boys was significantly more common in areas treated with DDT compared with untreated areas.

"DDT contains oestrogen-like substances; we know that the breakdown products from DDT counteract male sexual development," Kylin says. Based on breast milk samples, it was estimated that boys ingest somewhat more DDT than girls, with the exception of first-born children. This could depend on the fact that the fat content of breast milk is higher if a boy is nursing. First-born children, however, get the highest levels, depending -- as Kylin explains -- on the mother's higher stored levels of DDT at her first birth.

What surprised the researchers more was the large differences between the treated villages. Despite apparently similar conditions, the measured DDT levels were twice as high in one treated village compared with one of the others. A whole range of factors may come into play here, such as procedures in connection with treatment, the condition of the walls, ventilation, people's behaviour and cleaning habits. Identifying these factors, the researchers write, could contribute to decreasing exposure, thereby also the risk for both mothers and children.

"Unfortunately the smallest children are exposed to the highest DDT levels; they are also extra sensitive to chemical influence," Kylin says.

He also emphasizes the staff operating the spray treatments as an overlooked risk group requiring further study.

As things stand today, there is no real alternative to DDT in these malaria-stricken areas. "Mosquito-proof netting has successfully been tested in a few places, but doesn't work everywhere," Kylin says.

He is convinced that research could have come farther in finding alternatives for DDT if malaria were a widespread illness in rich countries.

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The above story is reprinted from materials provided by Link?ping Universitet.

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Journal Reference:

  1. Hindrik Bouwman, Henrik Kylin, Barbara Sereda, Riana Bornman. High levels of DDT in breast milk: Intake, risk, lactation duration, and involvement of gender. Environmental Pollution, 2012; 170: 63 DOI: 10.1016/j.envpol.2012.06.009

Note: If no author is given, the source is cited instead.

Disclaimer: This article is not intended to provide medical advice, diagnosis or treatment. Views expressed here do not necessarily reflect those of ScienceDaily or its staff.

Source: http://feeds.sciencedaily.com/~r/sciencedaily/top_news/top_environment/~3/-UmulA_Hi0o/120903142949.htm

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Daily Kos: Don't Buy It: A conversation with communications ...

Last Sunday, Daily Kos published a review of communications maven and newly annointed author Anat Shenker-Osorio's thought-provoking (and conversation-stimulating) book, Don't Buy It: The Trouble with Talking Nonsense about the Economy. During this past week, the author and I carried on a further email discussion about the issues raised in her work about communicating on the economy. That discussion is reproduced below, and she is also making herself available in comments for users to ask questions. Enjoy! And please join in!

Head shot of

Anat Shenker-Osorio

How do you view your book as differing from Drew Westen's or from George Lakoff's work? What does it bring to the table that they don't, in terms of focus, expansion of ideas or different views?

I owe a great intellectual debt to George and Drew?both for specific analytical approaches and more generally for introducing the application of what are academic modes of analysis to real, live, political debates. Although their insights come from different fields, one essential critique they both bring is a long overdue call to stop trying to appeal to Enlightenment era reason and persuade via facts, figures and logic.

I take up aspects of what they've offered, in terms of appealing to emotion and recognizing the power of words to evoke and convey unconscious notions at odds with our best intentions. Then, I push these insights into the very concrete realm of advice for advocates struggling with how to convince a confused, overwhelmed and dejected public that progressive economic policies are the only way to improve things for our nation.

So, one difference is topical?this book is about how to talk about the economy. And another is that the findings here emerge from over 3 years of in the field research into how people make sense of and come to judgements, based on analysis of reams of written data, expert interviews and focus groups.

How many people do we need to get to adopt consistent use of a metaphor before it goes mainstream? What seems to be the crucial mass?

That's a tough one! Short of massive, longitudinal, psycho-linguistic experimentation?I'm not sure we could ever say for sure. To my knowledge, this hasn't been measured.

This said, the well-proven idea behind conceptual metaphor is that we all have access to any one of the set of them that exist for a concept. As members of a shared language community, the simplifications we rely upon for a complex concept like the economy are the same. The differences lie in our defaults?whether I (for example) am more likely to think and talk about the economy in comparing it to an object in motion whereas you (again, for example) tend to call upon natural elements for your comparison.

In a sense, all of the accessible metaphors are "mainstream"?understandable to all of us. But, repetition is what makes one more top of mind and that's what we need to have happen. With the better metaphors, of course?we have way too much repetition of the unhelpful ones.

Obviously media and politicians are necessary to bring on board if you want to change the language and the metaphors. Anyone else? (And sometimes even media and politicians aren't enough, correct?)

Yes, economists. Because there's a well-established tendency for people to assume they can't understand economic concepts and our lack of education on these topics (as I note in the book) makes them seem even more mysterious, Americans are more likely to believe in and turn to minted experts. In this case, that means economists.

Further, because pocketbook issues are so much on all our minds and thus tongues, the more people we have taking conscious pains to get the words about them right the better. When advocates are arguing for whatever particular policy is up for discussion, wage hikes, tax levels, regulations, if they do so grounded in a better model for what the economy actually behaves like, not only would their immediate argument make more sense, they'd bolster other ones up in the process.

Obviously, I'd like to see Hollywood screenwriters, journalist and other makers of mainstream discourse brought up to speed as well.

(Continue reading below the fold.)

Can't adoption of new terms and modes of thinking take at least a generation? What if you don't have time, as in climate change, for example?

If they were truly "new" then, yes. But, as I mentioned above, they aren't. It isn't possible to invent a simplifying model for people from scratch. All you can do is activate and more readily bring to mind one that exists. In other words, we actually used to know a lot of the stuff this book asks us to make present and immediate for people.

But, this said, we've fallen so deeply into unhelpful rhetorical grooves it's not easy to start actively changing what we write and say. I compare this to writing with your non-dominant hand. When I grab a pen, I do it with my right hand and easily jot down what I need to do. This is akin to typing up that press release, or tweet or speech using the words and phrases you always have?the missive practically writes itself because we've all argued about whatever we're passionate about for so long, so many times. But, to actively go against what you're used to saying?that's like choosing to write with your left hand (in my case). It's awkward. It's slow. It's frustrating?especially with your right hand just sitting there!

You are right, we don't have time. One of my big laments in the book is the squandering of our opportunity to really have the biggest, most effective, conversation about what a just and sustainable economy can and should look like. I'd argue the biggest opening in that window was end of 2007/early 2008. It's not closed now, but people are no longer in the space of wondering what happened and what should be. We're now just hanging on trying to keep what little didn't go under.

What do you do when Republicans flat-out lie in an attack, in a manner that forces you to use their terms on a stance you don't believe in? Example: ?GOP attacks Obama as the biggest spender ever, as someone who's raised taxes.? This is utterly false. And the mode right now is to come back (with charts!) saying, "See! We DON'T spend! We freeze federal wages! We lower taxes!" This is fighting on their ground. Yes, it's correcting the facts, but raising taxes is what is needed, spending is what is NEEDED ? Yet their flat-out blatant lie forces us to end up defending a stance we don't believe in. How do we escape this linguistic thought trap? Do you correct that, even though it then means fighting on their turf? Or do you somehow try to shift it to: "And what's wrong with that? Government is good, etc."?

I recently got into a fierce debate with activists I admire who were intent upon broadcasting how Romney's tax plan was found to raise taxes on many groups. They found this "fact" (already of dubious use given how hard it is to break a frame using actual evidence) to be a real zinger. At first, I tried a simple one sentence rebuttal: ?I thought we were for taxes?? Sadly, things devolved from there.

I firmly believe that when we message from the other guy's values, we lose. This was true when we said abortion was about getting government out (thanks, Hyde Amendment!), claimed curbing energy consumption was about abating terrorism (let's drill in Alaska and build keystone!) and attempted to make our pro-immigrant case by saying we wanted them to "get right with the law." And it's equally true about economic issues.

The way I'd respond to this kind of flat out lie is to correct the facts without accepting the frame. So, to use your example, "It would be amazing if that were the case. I'd love to say we put even more teachers in your kids' classes, hired the best American workers to shore up our bridges and patch up our roads, and brought medical care within reach of your ailing grandparents. But we didn't?and it's high time we do." There's so much potential for humor in lieu of defensiveness (and charts).

By the end of the book, it seems we've almost moved from discussing language to undoing the holy belief in the Protestant work ethic (which, I agree, is disgraceful, dysfunctional prism through which to view the value of life as lived). Quite a different?and near impossible??undertaking, yes? Where do words leave off and ideas begin? Are they so entwined they're impossible to really completely separate, ever?

I'm not a fan of said ethic but I'd argue that's actually not the opponent I'm tackling here in the book. If people want to work crazy hours because they love their jobs, enjoy their colleagues, seek to avoid their spouse, are about to cure cancer, or whatever personal motivation propels this?more power to them. I personally love my work and do lots of it. I'm going to guess you and most of your readers are in this camp too.

But what I do want to see banished is the idea that we are supposed to work for the Economy. The idea that keeping It happy or growing, or healthy or what have you is our greatest responsibility, our moral duty?that's just sick. The economy is nothing outside of us so the notion that we owe it fealty is ridiculous; it's deeply damaging to all of us as workers and to our planet that must somehow endure a growth at all costs is good approach.

You urge the use of the metaphor of instability, an internal imbalance to describe income inequality instead of gaps, or vertical or scale metaphors. Yet isn't that so close to using the "body" metaphor you described earlier as NOT good to use? After all, dizziness, the feeling of unbalance or something feeling unstable is one that's experienced very physically, by the body.

Example: "Being off balance is a familiar and unpleasant experience that transcends demographic groups. No matter where you?re from or what you have, you?ve spun yourself into dizziness at one time or another. What this model refers to is an instability that can only be righted internally."

The critical thing in considering what a certain metaphor is likely to evoke is to ascertain what we'd call its entailments. More simply, the set of immediate associations we have with it. I would argue that the ability to feel off-balance or dizzy is not a salient feature of a human body. In other words, if people were asked to free associate about bodies, they'd talk about organs, feelings, health, perhaps bodily functions but dizziness wouldn't be top of mind.

Therefore, I'm not concerned that evoking internal imbalance necessarily brings with it the idea of a body. Many things depend upon balance to operate well?airplanes, cars, moving toys, other machines.

However, at the risk of compressing too much into one answer, it is actually important to have the conversation about inequality at both levels: how it affects the whole and how it affects specific individuals in known marginalized groups. We need the human element in the simplifying model because of all the economic issues I discuss in the book, inequality is the one most acutely relevant to the experience of people in our society. Humans experience the economy, so it's important for the model we use to talk about to allow for that.

Source: http://www.dailykos.com/story/2012/09/02/1125642/-Don-t-Buy-It-A-conversation-with-communications-consultant-and-author-Anat-Shenker-Osorio

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Monday, September 3, 2012

Wedding: Torgerson-Duncan

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Susan Emily Torgerson and Chase Douglas Duncan were married on May 27 in Harrisburg, Ore.

Submitted photo

Jim and Marna Duncan of Grass Valley are pleased to announce the wedding of their son, Chase Douglas Duncan, to Susan Emily Torgerson.
The couple ...

Source: http://www.theunion.com/ARTICLE/20120901/ANNOUNCEMENTS/120839941/1058/RSS

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Sunday, September 2, 2012

Learn How To Start Building More Muscle Today : Premier Diet and ...

Posted by haleyjonas on Saturday, September 1, 2012 ? Leave a Comment?

Are you prepared to take muscle building seriously? You may just need the right kind of information and the right kind of advice. This article contains useful information for getting the muscle definition you?ve always wanted. Take them into consideration so that you can obtain the sort of muscles you would like to have.

TIP! Watch what you eat when you?re working to build muscle. Staying hydrated is always important, but it is even more so in building muscle since up to 70% of muscle mass is water.

Include the ?big three? into your routine every time. This refers to bench presses, dead lifts and squats, all of which are common exercises for building bulk. These compound exercises can make you stronger and improve your muscle tone as well as increasing your muscle mass. Add variations of these exercises to your usual workouts.

TIP! You can get stronger with a strict and effective workout routine that focuses on muscle building. This means that you should gradually be able to lift heavier weights.

Aim to mix up your grips for working out the back. When doing deadlifts or rack pulls, use mixed or staged grips, if you want to attain more strength. The grip that is staggered gives a twist in one direction and the underhand grip gives a twist to the opposite direction. This will prevent the bar from moving all around in your hands.

TIP! When you are planning to build muscles on a certain day, eat good. Approximately 60 minutes prior to exercising, consume calories.

Compound exercises are an excellent way to build muscles to their fullest extent. Working out many muscles in one lift is more efficient. For example, bench presses exercise your triceps, chest and shoulders all at once.

TIP! To build larger muscles, eat lots of protein. Protein synthesis is the process your body uses to store protein.

Keep an eye on your body fat while you?re building up muscle. You do not want to monitor just your weight, as you could be gaining muscle, but losing fat. You can feel discouraged when watching your weight, but it?s not good for pegging your muscle growth in the beginning.

TIP! Warming up with some light exercises is essential before you do any heavy lifting. Including ten or fifteen minute warm-ups can increase your blood flow and prepare your muscles for intense workouts.

You must exercise great care when choosing how often to do your muscle building exercises. If you do too little in your workout, you won?t see much progress. However, it is important to not to push yourself too far either. For example, overworking your body can cause stretchmarks or permanent injury to your muscles and joints.

TIP! Train opposing muscles when you are in the midst of a workout; try doing the chest and back together, or the hamstrings with quads. This way, one muscle can get a rest while you are working out the other.

A great way to deal with muscles that limit your progress is to use the concept of pre-exhausting. When you do rows, for example, your biceps could give out before your lats do. You can rest your biceps and work on your lats with an exercise that provides the appropriate isolation, like the straight-arm pulldown. If you do so, this will make your lats very tired, and our biceps will work right.

TIP! Make sure that you are using your brain when performing squats. Lower the bar to near the middle of the traps.

When your exercise routine incorporates muscle building, you should remove alcohol from your life. A beer here and there, or a little bit of wine is okay, but alcohol should never be drank in excess. When you are trying to build muscles it is not a smart idea to intake alcohol.

TIP! An often overlooked part of a good exercise program is warming up. As muscles strengthen, they are under additional stress, which may make them more prone to injury.

TIP! It is imperative that you eat well while trying to build up your muscle. Rebuilding muscle fibers involves consuming the proper amounts of certain nutrients.

Keep doing cardio exercises even when focusing on strength training. Although cardio may seem unrelated to muscle building, it is important to burn fat so that your hard-earned muscles are visible and not hidden under a layer of fat. 3 moderate cardio exercises per week of 20 minutes per session will be enough to properly exercise the heart without negating your weight training progress.

TIP! When the lifting gets tough, the tough cheat a little. If you need to finish a few extra reps in order to get the most out of your workout, don?t use your entire body.

Too many people botch their muscle building efforts by rushing them. Performing an exercise with care and deliberation, will give you far better results than quickly churning out sets in bad form. Take your time, and make certain that you are performing the exercise correctly.

TIP! Cool down with a short stretching routine to ensure that your muscles start the repair process from a healthy point. Anyone that is under forty years old needs to make sure that each stretch is held for a minimum of thirty seconds.

When attempting to gain muscles, you should attempt to have a diet rich in fresh, whole foods. Avoid pre-packaged foods that come in boxes, which often contain chemicals, preservatives, and fillers that can hinder your body?s ability to heal itself. Eating a healthful diet has benefits beyond contributing to increasing your muscle mass.

TIP! Avoid relying on vitamin supplements. Protein supplements are potentially helpful when added to a regimen.

A muscle workout offers a number of benefits to your life in general, not just your health, and you don?t need to bulk up to get these benefits. It can raise your self-esteem, provide your body with greater strength, improve the functioning of your joints, plus strengthen your lungs if it is done in conjunction with some form of light to moderate cardio workout.

TIP! Meat is very helpful for building up your muscles. A good protein target is one gram of protein per pound of mass.

Focus on form when you are new to muscle building activities. You can add weight as time passes, but if you have bad form initially, things are unlikely to improve in the future. This can cause injuries, which is the opposite of what you are striving for.

TIP! Be sure that you limit yourself to working out at about three or possible four times in a week. This can give your body time to recover.

In order to achieve muscle building success, it is necessary to obtain the best information available. If you apply the tips you just read, you can successfully build muscles over time. Simply incorporate the tips into your daily routines. Just make sure you stick to your plan, and stay determined

TIP! Be sure that your training regimen coincides with your goals. Sticking with the same routine can help you make more rapid progress toward your goals.

Source: http://pdfbox.org/learn-how-to-start-building-more-muscle-today-2/

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Home State Jurisdiction - Updates in Michigan Family Law - Typepad

The Uniform Child Custody Jurisdiction and Enforcement Act ["UCCJEA"] was enacted to serve the following purposes: (1) to avoid interstate jurisdictional competition and conflict in child custody matters, (2) to promote cooperation between courts of other states so that a custody determination can be rendered in a state best suited to decide the case in the interest of the child, (3) to discourage the use of the interstate system for continuing custody controversies, (4) to deter child abductions, (5) to avoid relitigation of custody issues, and (6) to facilitate enforcement of custody orders. The UCCJEA treats a foreign country, such as Japan, as a state of the United States, unless the laws of the foreign country violate fundamental principles of human rights. [See section 207] Home state jurisdiction is prioritized to make this uniform law consistent with the Parental Kidnapping Preventation Act.

The UCCJEA contemplates jurisdiction in the state where the child and parents have actually lived for at least six months immediately prior to the commencement of a child custody action. Subjective intent of the parents is not important. This issue often arises with respect to deployed parents who have lived abroad with the child for an extended period of time. Servicemembers do not lose their legal residency ["home of record"] just because they are or have been deployed abroad. But that does not mean that the home of record is a state having home state jurisdiction to make an initial child custody determination.

Consider the following case, which illustrates the importance of the prioritizing of home state jurisdiction. The court held that the "state" (in this case, Japan) having home state jurisdiction was the state where the child had actually lived with a parent or parents immediately preceding the filing of the child custody proceeding.

Carter v Carter, 758 NW2d 1 (NB 2008) presented a dispute over whether Nebraska had jurisdiction over a child custody dispute under the UCCJEA. After living in Nebraska for about 3 years, Stuart Carter, his wife, Nahoko Hata Carter, and their 10-week-old son moved to Japan for approximately 2? years during Stuart's permanent military duty assignment. At the end of his assignment, without warning or Nahoko's consent, Stuart took Alex to Nebraska and immediately filed for legal separation and custody.

Nahoko, who was both a Japanese and an American citizen, filed a motion for summary disposition, arguing that Nebraska was not Alex's home state and, therefore, did not have jurisdiction over the parties and the subject matter.
??? ???
Under the facts of this case, for Nebraska to exercise initial jurisdiction over a child custody dispute, Nebraska must be the home state as defined by the UCCJEA. The UCCJEA provides that a state has jurisdiction to make an initial custody determination only if under section 201??????

(1) this state is the home state of the child on the date of the commencement of the proceeding or was the home state of the child within six months before the commencement of the proceeding and the child is absent from this state but a parent or person acting as a parent continues to live in this state.

Stuart Carter asserted that the Nebraska court properly exercised jurisdiction over Alex because, at the time of the filing, Nebraska was Alex's home state. Home state of the child is defined in the UCCJEA as

the state in which a child lived with a parent or a person acting as a parent for at least six consecutive months immediately before the commencement of a child custody proceeding. In the case of a child less than six months of age, the term means the state in which the child lived from birth with any of the persons mentioned. A period of temporary absence of any of the mentioned persons is part of the period.

The Carter panel emphasized that in an earlier decision, the Nebraska Court of Appeals had held that the plain and ordinary meaning of "home state" is the state where the child has "lived" with a parent or person acting as a parent for the 6 months immediately preceding the action. Stuart's? argument that the 2 years spent in Japan was only a "temporary absence" from Nebraska and that thus, Alex continued to live in Nebraska for well over the requisite 6-month period was rejected. Section 201 states that "[a] period of temporary absence of any of the mentioned persons is part of the period." Thus, under the UCCJEA, a "temporary absence" should be counted as part of the 6 months during which the child must live in a state for it to be the home state.?????

Stuart argued that the absence was temporary because it was due to a military assignment, but the Court disagreed, holding that time spent living in another state or country due to a permanent military duty assignment is not considered a "temporary absence" simply because it was motivated by such assignment. Stuart's subjective intent about residency did not carry the day. It is the state where the child was actually living for at least 6 months prior to the commencement of the action that had home state jurisdiction.

Since Alex had moved to Japan with both parents and had actually lived there for more than two years, Japan had become Alex's new home state. Therefore, custody jurisdiction was in Japan. [The UCCJEA considers a foreign country as a "state" with some exceptions, not raised in this case. See UCCJEA Section 105.] Alex's mother was awarded substantial attorney fees and costs since she had to come all the way from Japan to Nebraska to defend against Stuart's claim.

Download Carter_v_Carter

Once all parents and children have left a state, then a return to the former home state by one parent does not restore home state jurisdiction to that state. See UCCJEA ? 202 NCCUSL commentary number 2 (noting that all members of the family have left the state to reside elsewhere, a parent cannot reestablish "exclusive, continuing jurisdiction" in the first state by resuming residence in that state). See also Griffith v Tressell, 925 A.2d 702 (2007). Download Griffith v Tressel

Additional resources: Commentary of NCCUSL on sections 202 and 203 of the UCCJEA.

Download Comment to Section 202 and 203

See also the Commentary of the National Conference of Commissioners on Uniform State Laws for the UCCJEA. Download Commentary.UCCJEA

Full text of Michigan's UCCJEA: Download UCCJEA, Michigan

More about parental kidnapping may be found here.

Source: http://jeannehannah.typepad.com/blog_jeanne_hannah_traver/2012/09/home-state-jurisdiction-where-the-parents-and-child-actually-live.html

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Saturday, September 1, 2012

Illinois: Don?t Look Now, But. . . (Powerlineblog)

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Mystery of operon evolution probed

ScienceDaily (Aug. 30, 2012) ? The threads of an evolutionary mystery that dates to the birth of molecular biology are beginning to unravel, thanks to a new investigation by computational bioengineers at Rice University and the University of Texas MD Anderson Cancer Center.

In new research published online this week in PLoS Computational Biology, Rice's Oleg Igoshin and MD Anderson's Christian Ray offer a possible explanation for the existence of jointly controlled clusters of genes called operons, which are found in bacterial chromosomes but not in those of higher order organisms like humans.

The new study harkens to one of the earliest 20th-century discoveries in molecular biology, and it could help clear 21st-century hurdles for synthetic biologists.

In the early 1960s, just as scientists were discovering how cells transcribed information from DNA to create the necessary proteins for life, French scientists Jacques Monod and Fran?ois Jacob found that the bacterium Escherichia coli used three specialized genes to create the proteins it needed to break down and digest lactose. They also found that these three metabolic genes were switched on and off together from a single control point.

Monod and Jacob had discovered the first operon, a set of multiple genes that are controlled as one. It marked the first time that scientists had identified a gene regulatory network, and it earned them a share of the 1965 Nobel Prize in Physiology or Medicine. Monod and Jacob's lac operon turned out to be the first of many bacterial operons. But by the late 1960s, it was clear that operons weren't the biological norm. None have ever been found in humans, for instance, and very few have been identified in multicellular organisms.

"There's never been a definitive explanation for why nature would preferentially select for operons in prokaryotes but not in eukaryotes," said Igoshin, associate professor of bioengineering at Rice. "In addition, we do not know how genes get grouped into operons. Why, for example, are some interacting genes selected to be in one operon while others are not?"

Igoshin and Ray are computational bioengineers who apply mathematics and computational bioinformatics to study cell signaling and other biochemical processes. Ray, a former Rice postdoctoral research associate in Igoshin's research group, is now in the Department of Systems Biology at MD Anderson. Ray and Igoshin began investigating operons in late 2009 to determine whether their evolution might have been influenced by the "noisy" nature of biochemical signals that regulate bacterial gene transcription.

"When a cell is responding to its environment, it can use regulators to control gene expression, but the amount of control that the cell has is limited by the number of molecules like messenger RNAs, which mediate protein production," Ray said. "So, in bacteria, the number of copies of a protein expressed by a gene can vary widely, say from 50 one hour to 100 the next. And this happens even when conditions outside the cell have not changed."

Igoshin and Ray knew that these random fluctuations were less of an issue for eukaryotic cells, which have larger volumes and more copies of messenger RNA and proteins. So they hypothesized that operons play a role in helping bacteria deal with these "noisy" conditions.

To test their idea, they developed a series of mathematical models of gene networks that could be run on a computer rather than on cell cultures, as well as statistical tests that could be performed using the information accumulated in bioinformatic databases.

Their mathematical models of gene networks covered six different types of protein-protein interactions. For each interaction type, they compared how operons affected noise in networks encoded by the member genes. For three of the six networks, operons worked to suppress noise. For the other three, they worked to increase noise. The findings from the simulations therefore suggested that operons could reduce the detrimental effects of noisy signals in some gene regulatory networks, but not others.

To further test the idea, Igoshin and Ray examined the operon organization of the E. coli genome. They found operons were frequent when the type of interaction that they encoded worked to suppress noise. When the encoded interaction did not suppress noise, operons were infrequent.

"Operons that emerged in the course of evolution in E. coli are consistent with selection for noise suppression and selection against noise amplification," Igoshin said.

The study also suggested why specific genes might be found in a specific operon.

"Certain genes perform much better when they're controlled as a unit, particularly if they produce co-ingredients that are required in proportional amounts," Ray said. "In the simulations, when these were split up and put onto separate operons, the inherent noise in the control signals would create a situation where the cell had way too much or too little of one co-product. In some cases, this is just inefficient, but in others the buildups could be toxic."

Ray and Igoshin said the study has implications for synthetic biologists who are trying to imbue cells with new biological functions not found in nature.

"For example, if you need to take multiple enzymes from different species and put them into a bacterium -- something that was done recently to produce a low-cost anti-malaria drug -- it might be easier to take them separately and put them into different parts of the chromosome," Igoshin said. "What this new finding shows is that there may be a cost for that in terms of overall fitness of the organism. Nature sometimes groups things together, particularly in cases where one of the enzymes makes or consumes toxic intermediates, and synthetic biologists would do well to pay attention to these types of interactions as they prepare their designs."

The research was funded by a fellowship from the National Library of Medicine Computational Biology and Medicine Training Program of the Keck Center of the Gulf Coast Consortia and the National Institute of General Medical Sciences.

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The above story is reprinted from materials provided by Rice University. The original article was written by Jade Boyd.

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Journal Reference:

  1. J. Christian J Ray, Oleg A. Igoshin. Interplay of Gene Expression Noise and Ultrasensitive Dynamics Affects Bacterial Operon Organization. PLoS Computational Biology, 2012; 8 (8): e1002672 DOI: 10.1371/journal.pcbi.1002672

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Source: http://feeds.sciencedaily.com/~r/sciencedaily/most_popular/~3/HXDFb0H8mbQ/120830173502.htm

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