Natriuretic peptides mainly consist of atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), and C-type natriuretic peptide (CNP), and they belong to the family of endogenous polypeptide mediators of cardiac origin. The term natriuresis means discharge of sodium through urine and is known to have vasodilatory effects. All the three peptides are circulatory hormones of cardiac origin secreted by plasma, with half-lives of around 1 minute and 30 seconds. ANP and BNP hormones act at the site of their synthesis and also circulate in the body. Out of these three hormones, CNP is least secreted with low circulating levels. Increase in sodium loads, extracellular volumes and distension of auricles and ventricles increases the secretion of ANP and BNP.1
ANP, BNP, and CNP are closely related and have a characteristic 17 amino acid residue ring structure formed by an intramolecular disulfide bridge between two cysteine residues. The amino- and carboxyl terminal tails vary between the different peptides, leading to polypeptides of 28 amino acids (ANP), 32 amino acids (BNP), and 53 amino acids (CNP). They also exist as a pro-hormone with a relatively high molecular weight that is cleaved before release into the circulation.2 Both ANP and BNP function through a natriuretic receptor, which generates cyclic-GMP (guanosine mono phosphate) to produce vasodilation and natriuresis.
ANPClick Image To Enlarge +Structure of atrial natriuretic peptide (ANP) (1-28) alpha (human, ovine, canine).
ANP is a cardiac hormone involved in the physiological maintenance of blood volume and arterial blood pressure.3In lab experiments, introduction of the ANP gene to increase the endogenous plasma levels has been used to treat experimental forms of hypertension. Other peptides in the natriuretic peptide family, BNP and CNP, have hypotensive actions similar to ANP although CNP lacks significant natriuretic activity.
ANP release increases in patients with ischemic left ventricular dysfunction. ANP, atrial natriuretic factor, atrial natriuretic hormone, cardionatrin, cardiodilatin, or atriopeptin are polypeptide hormones secreted by heart muscle cells. These hormones are powerful vasodilators and are known to play important role in balancing the levels of body water, sodium, potassium, and adipose tissue. These hormones are released by heart muscle cells in the upper chamber of the heart in response to high blood pressure. The loads of water, sodium, and adipose levels into the circulatory system are reduced by ANP, which functions exactly the opposite of aldosterone, secreted by the zona glomerulosa.
Inside of the heart, cardiac myocytes are responsible for production, storage, and release of ANP. Kim et al., demonstrated that GLP-1R activation promotes the secretion of ANP and a reduction of blood pressure.4
Patients with pulmonary hypertension have elevated concentration of ANP. Reports have also shown a positive correlation between plasma ANP and PAP (pulmonary artery pressure) in patients with different types of congenital heart disease.5
A clinical study in Finland concluded that low levels of mid-regional ANP and N-terminal pro-BNP predicted development of type 2 diabetes. Decreased levels of natriuretic peptides are signs of insulin resistance such as in obesity. Low natriuretic peptide levels lead to faster blood glucose progression over time and predict the development of diabetes in healthy subjects.6 Though it is well known that there is a reduced level of natriuretic peptides in individuals with obesity and diabetes, recently published data7 also shows low levels of natriuretic peptides in people with polycystic ovary syndrome.
BNPClick Image To Enlarge +Structure of the 32 residue peptide nesiritide, a recombinant human protein.
Brain natriuretic peptide, also known as B-type natriuretic peptide (also BNP), is a 32-amino acid polypeptide secreted by the ventricles of the heart in response to excessive stretching of heart muscle cells (cardiomyocytes). Circulating levels of BNP-proBNP are normally very low in healthy individuals. In response to increased myocardial wall stress due to volume- or pressure-overload states (such as in heart failure), the BNP gene is activated in cardiomyocytes. The release of BNP is modulated by calcium ions. It has been demonstrated that this peptide has a great pathophysiological importance in diagnosing heart failure8 as well as in risk stratification and guiding heart failure therapy.
BNP has known effects on kidneys, vascular vessels, the endocrine system, and the heart. The earliest findings on BNP were in its effects on the increase on glomerular filtration rate, renal plasma flow, and urine flow rate with inhibition of distal sodium reabsorption. Another important function is BNP may relax myocardium and vascular smooth muscle, causing arterial and venous dilation, which in turn leads to blood pressure reduction and ventricular preload release9. BNP is not only taken as a cardiac biomarker but also a surrogate marker of heart failure, acute coronary syndrome, and myocardial infarction.
Multiple studies have documented the clinical usefulness of BNP and proBNP for diagnosis, prognosis, and treatment of congestive heart failure and for risk stratification in patients with acute coronary syndrome.
Natrecor (nesiritide), from Johnson & Johnson’s subsidiary Scios, was approved in 2001 for treatment of acutely decompensated congestive heart failure. It is a recombinant form of human BNP.
CNPClick Image To Enlarge +C-type natriuretic peptide (CNP) is a 22 amino acid peptide distributed primarily in the central nervous system.
CNP is a 22 amino acid peptide, but unlike ANP and BNP, CNP does not have direct natriuretic activity as CNP is a selective agonist for the B-type natriuretic receptor, whereas ANP and BNP are selective for the A-type natriuretic receptor.
CNP, the third of the natriuretic peptide family, is known to be distributed primarily in the central nervous system and is believed to act as a neuropeptide in contrast to ANP and BNP, which act as cardiac hormones. It has been demonstrated that ANP-B receptor is activated by CNP, which is present not only in the CNS but also in peripheral tissues including blood vessels. The evidence presented in one paper by S. Suga et al.,10demonstrates the endothelial production of CNP, and the presence of natriuretic receptors in vascular SMC (smooth muscle cells) and EC (endothelial cells) suggest the possible existence of vascular natriuretic peptides.
Research has also shown the presence of CNP receptors in the retinal pigment epithelium (RPE) of the eye, and CNP protects the RPE against advanced glycation end product-induced barrier dysfunction.11A new report suggests CNP possesses renoprotective properties and is present in kidneys, but its modulation during aging is not known. CNP levels decline with aging and urinary CNP levels increase with aging. This urinary-to-plasma levels CNP ratio can be a novel biomarker for renal fibrosis.
The natriuretic peptide family plays a distinct physiological and pathophysiological role in cardiovascular control. It consists of at least four ligands—ANP, BNP, CNP, and DNP (dendroaspis natriuretic peptide)—and three types of receptors expressed in target tissues with tissue specificity. The prognostic use, as well as the therapeutic monitoring value, of BNP measurements is instrumental in preventing incidence of heart failure and other heart diseases.
Renewable tidal energy sufficient to power about half of Scotland could be harnessed from a single stretch of water off the north coast of the country, engineers say.
Researchers have completed the most detailed study yet of how much tidal power could be generated by turbines placed in the Pentland Firth, between mainland Scotland and Orkney, and estimate 1.9 gigawatts (GW) could be available.
The in-depth assessment by engineers at the Universities of Oxford and Edinburgh offers valuable insights into how to develop and regulate this clean energy resource effectively.
The Pentland Firth is a prime candidate to house marine power projects because of its tidal currents, which are among the fastest in the British Isles.
Engineers say that their study improves on previous estimates of the generating capacity of turbines embedded in the Firth – ranging from 1 to 18 GW – which were too simplistic or based on inappropriate models. Researchers calculated that as much as 4.2 GW could be captured, but because tidal turbines are not 100 per cent efficient, they say that 1.9 GW is a more realistic target.
To exploit the Firth’s full potential, turbines would need to be located across the entire width of the channel. In order to minimise the impacts on sea life and shipping trade, a number of individual sites have been identified for development by the UK Crown Estate, which will lease these sites to tidal energy firms.
Researchers have pinpointed locations where turbines would need to be positioned for the Firth to meet its full energy production potential.
The research was commissioned and funded as part of the Energy Technologies Institute’s Performance Assessment of Wave and Tidal Array Systems project (PerAWAT).
Professor Alistair Borthwick, of the School of Engineering at the University of Edinburgh, who worked on the research, said: “Our research builds on earlier studies by analysing the interactions between turbines and the tides more closely. This is a more accurate approach than was used in the early days of tidal stream power assessment, and should be useful in calculating how much power might realistically be recoverable from the Pentland Firth.”
Teaching science through art, literature, or music is the new approach to making the subject fun for kids, says science educator Arthur Eisenkraft
The nemesis of most kids in school is the dreaded subject of science. Just when you begin to start liking the subjects, they decide to stop liking you and hit you over the head with a range of incomprehensible theories and chemical periodicals, species, trigonometry and taxonomy. So how does one make science interesting? According to Arthur Eisenkraft, one of America’s leading science educators, any subject can be made fascinating by engaging the students with whatever they love to do, and using that to teach science to them.
This was the crux of the lecture “Engaging Students in Science with Art, Physics, and Literature” Arthur delivered recently at the Azim Premji University as part of the Public Lecture Series. The director of the Centre of Science and Math in Context (COSMIC) in the University of Massachusetts, Boston, the award-winning teacher, apart from being a part of many science education projects, has been engaging students with various arts, to teach sciences.
Science is philosophy“Science is nothing but a philosophy. It’s all about asking the question why. It’s relatively easier to connect to a student with arts than science. So I project how one can use literature, art, sports, music, theatre, and technology, among others, to teach science to students,” says Arthur.
The professor, who was in the city last year as well to help out with the University’s work, says, “The science education system needs to rework its approach to students. It is easy to teach science without any interest. But if the student needs to learn, it is through their own interests that a real connection can take place and a passion ignited for science in them.”
Arthur sums up his talk in a nutshell: “My focus is to get students to enjoy every subject they study by pulling out all the stops. If teachers can get them to be interested, engaged and excited any way possible, they will do better. If it’s through art, I’ll give them some art. If it’s literature, I’ll give them some. Not all the time. But just enough so they will be engaged and find something that has meaning for them.”
He further explains that this will help them learn things which at first might not interest them. “This applies not just to science. Our job as teachers is to motivate and encourage students. Once we do that, it’s easy to learn.”
On asking how he would teach science to a musician, Arthur reveals that there is a lot of science involved in music. “For my physics students, one of their month-long projects is a light and sound show with instruments they build. Now for this, they have to understand how string and tube instruments work. They need to figure out why the shortest string or the shortest tube make the highest notes which helps them learn the physics principles on waves. There are some students who just want to make the light and sound show and don’t care about the physics part, but they still have to learn it since it’s a requirement. On the other hand, I don’t really care a lot about their show. I want them to learn physics. But if I can teach them using the show, then I will let them do it,” he reveals.
“It’s a win-win bargain, says Arthur. “They can have a good time making their music and I’ll let them do that as long as they learn physics. So we’re both happy.”
The 63-year-old professor also talked about ‘Quantoons’, a form of quantum cartoons he uses to illustrate science through comic formats. The cartoons depict scientific principles and theories in simple cartoon graphics. “It started with a column for students to get interested in science, which my colleague was willing to illustrate. So over the years we had over 50 of them done and decided to put them in a book. A lot of people enjoy cartoons, so it’s easy to reach science to them through cartoons,” he grins.
His advice to teachers is that they first enjoy the opportunity to be with students. “Let the students know how much you respect their thinking and enjoy the subject matter.” Arthur’s plans says: “I will continue to try and change one teacher at a time and one school at a time.”
Houston … we have ants in space! Colony of 800 arrives on International Space Station http://www.independent.co.uk/news/science/houston–we-have-ants-in-space-colony-of-800-arrives-on-international-space-station-9070339.html
New Year weight-loss regime won’t work
From the 4:3 (son of 5:2) to the Overnight diet, the rash of new, fad weight-loss regimes have one thing in common: they don’t work
The point of this diet is to make eating difficult. This – and here’s the genius – is the point of all the diets that are currently flooding the airwaves, magazines and newspapers. There has been a tsunami of them this year – the 4:3 (son of 5:2), the DODO (day on, day off), the Juicing, the Overnight, the Sugar Free, the Monomeals (one food only at each meal) – variously endorsed by celebrities including Gwyneth Paltrow, Cameron Diaz and Victoria Beckham.
And these are just the new ones. Still around and popular are the Paleo (caveman diet), the Alkaline (avoid acid foods), the Ornish (low fat), the TLC (“Therapeutic Lifestyle Changes”, aka low fat). Millions of people are following these diets – or trying to – and buying the books and programmes that help them do so. It is a multi-billion pound industry, grown fat on our collective anxiety about our expanding waistlines.
Yet we know there is only one way to lose weight. Eat less and do more. The task that the diet gurus face is how to help us achieve this simple but extraordinarily challenging goal. The answer – common to all – is to make eating difficult, so that we consume fewer calories, partly because obtaining them is so damned complicated, involving minute inspection of food labels, careful weighing of ingredients, deep alterations to shopping lists, and unfamiliar food-preparation tasks.
You might just as well tell people to stand on their heads while eating. It would achieve the same end. But it wouldn’t sell many books.
Last year, an estimated four in 10 British slimmers tried the 5:2 intermittent fasting diet and it looks like its successor, the 4:3 or Every Other Day Diet – where dieters fast on alternate days and eat normally the rest of the time – will prove just as popular. Fasting is, by definition, the most radical way of cutting calories.
But the 5:2 was not radical enough for some. It allowed consumption of a limited number of calories on a fasting day (500 for women, 600 for men). Hence the 4:3, to step up the pressure, and now the DODO, or Day On/Day Off diet, which requires complete fasting during the Day On, avoiding tedious calorie-counting.
A more timid version is the Overnight diet, the invention of weight-loss expert Dr Caroline Apovian, which starts each week with a “one-day power up”, during which only smoothies may be consumed – a fast of a (limited) kind. This is followed by a “six-day fuel up”, based on low-fat dairy, lean protein, whole grains and as many fruits and vegetables as you like. You may recognise this. It has been standard NHS dietary advice for at least the past 20 years – and available for free.
For sheer gall, however, the Joe Juice Diet takes some beating. Joe Cross used to be 100lbs overweight, stoked up on steroids and suffering from an autoimmune disease. Now, the American is set to be one of many faces of the juice diet in the UK this year, after he swapped fast food for fresh fruit and vegetable juices. He consumed nothing else for 60 days, made a film about it called Fat, Sick and nearly Dead, and has now released a book, The Reboot with Joe Juice Diet. Joe’s juice diet is simple: after the initial fast, which may last anything from a few days to a few months, it encourages people to increase their consumption of vegetables and fruit. Sound familiar? It has only been conventional medical wisdom for at least the past three decades.
The sugar-free diet, in its most extreme version, cuts out all foods that contain added sugars, in addition to fruit and any vegetables that contain natural sugars, such as parsnips, carrots and peas. Tricky stuff identifying which veg do and don’t contain natural sugars.
Simpler to follow, but less radical, is a version of this diet that involves eating fruit (but not juices) and vegetables and living without all added sugars, honey and processed foods that contain sugars. That rules out everything from packaged soups to sauces.
But simpler is also more difficult. It means meals must be prepared from scratch, using natural ingredients. Which spells success for the diet. Instead of having a ready-cooked microwave dish, dieters must peel onions and chop sprouts. It’s labour-intensive and time-consuming – and they end up eating less.
The Monomeals diet involves eating one type of food per meal, normally a particular fruit or vegetable. It could be a bowl of grapes, bunch of bananas or a plate of broccoli. Variations of this diet have emerged over the years – the Cabbage Soup Diet was an early example. If you are eating mainly cabbage, or mainly any one type of food, you will get bored and will eat less. Simple. Job done.
There is a danger, with all these diets, of taking them to extremes. The consequences are unpredictable, but mostly not good. A surgeon once told me of his alarm, when opening up the abdomen of a patient, to discover all his internal organs stained a deep orange. He had been living on carrots.
Obesity experts learnt years ago that searching for the most effective diet was like looking for El Dorado – it was doomed to failure. It was not the diet that determined how much weight you lost, but the rigour with which you followed it. The new challenge was how to match individuals to the diets that best suited them. A new term was coined: nutrigenomics – the science of increasing adherence rates to promote weight loss. If success in dieting depends on the individual’s psychological determination to change, then it is up to dieters to select the diet that works best for them. That means finding the diet that most effectively eases the demands on willpower.
The need to do so is more urgent than ever. The National Obesity Forum warned earlier this month forecasts that half the population could be obese by 2050 if sufficient action is not taken may have understated the true scale of the crisis. Public Health England recently predicted that 60 per cent of men, 50 per cent of women and 25 per cent of children could be obese by that date. It is easy to say that something must be done, but harder to decide what, at least where dieting is concerned. Official advice is to avoid “fad diets” which promise rapid weight loss – because of the difficulty of keeping the pounds off when the diet ends.
The NHS Choices Live Well website advises: “It can be tempting to put your faith in one of the countless schemes that promise rapid, easy weight loss. Unfortunately, even if these fad diets do help you to lose weight you are unlikely to maintain a healthy weight in the months and years afterwards.”
The grim fact is that most people who start a New Year diet and begin shedding pounds will ultimately put them back on again, and frequently end up heavier than they started.
One in four people in Britain are said to be dieting to lose weight at any one time. They expend large amounts of effort and huge amounts of money buying special foods, joining diet clubs and counting calories. They will suffer from the constant hunger and the loss of one of life’s great pleasures – eating – and when they fail, as most ultimately will, they will feel guilt and self-hatred. Only a small minority will successfully lose weight and keep it off for more than five years, research suggests.
For the rest, whose weight bounces back up again, there is an additional caution. Repeated on a regular basis, yo-yo dieting may be damaging to health. Research has shown that repeated rapid weight gain and loss may increase the risk of heart disease, heart attacks and premature death. Some diets claim to alter metabolism so that calories are burnt faster or absorbed more slowly. But if there is any effect on metabolism – and this is disputed – the effect is minimal. The reason for the obesity explosion in Britain – where an estimated 27 million adults are obese or overweight – and across the Western world, is that an energy imbalance has built up as we consume more and do less.
The most successful diet of all time is the Atkins diet – but only if you are counting £s rather than lbs. More than 45 million copies of the Atkins diet books have been sold since the 1970s. It recommends unlimited consumption of butter, fatty meat and high-fat dairy products, while carbohydrate intake is restricted to 30 grams a day, equivalent to a small potato.
Research suggests that it is safe and effective at promoting weight loss in the short term – calorie for calorie, protein appears to be more satisfying and thus better at curbing appetite than fat or carbohydrate. But, in the long term this is a diet practically guaranteed to induce heart disease. People who stuck with it for more than a year suffered headaches, muscle cramps and diarrhoea caused by carbohydrate deficiency. The minimum requirement of carbohydrate for an adult is 150 grams a day, but on the Atkins diet it is cut to one-fifth of that.
Is dieting worth it? It depends why you are doing it. To get into that size 10 dress for a wedding? Certainly. To improve your health? It depends how overweight you are to start with.
For the severely obese, losing weight may be life-saving. But for the merely overweight, the benefits – if any – are less certain. There is no guarantee that shedding pounds will improve their health.
What we do know is that the obese – those with a body mass index score of 30 or over – are at greater risk of ill health from heart disease, diabetes, some types of cancer and joint problems. Obesity is estimated to cause at least 30,000 excess deaths a year in the UK.
But there is scant evidence to show that losing weight will cut the risk. Does a person who loses 20 pounds acquire the reduced risk of a person who started out 20 pounds lighter? We do not know.
The moral is do not waste time deciding which diet to follow. Low-carb or no-carb, high or low fat, protein rich or poor – it makes no difference. It is not the diet that determines how much weight you lose but the determination with which you follow it. Not just this week or next, but over months and years.
Better still, of course, to avoid putting the weight on in the first place. But if you have read this far, it is likely too late for that.
Alarm to sound for comet mission http://www.bbc.co.uk/news/science-environment-25782249
A Mars mystery rock is puzzling scientists who cannot explain how a mysterious rock suddenly appeared in front of the Mars Opportunity rover. “It was a total surprise, we were like ‘wait a second, that wasn’t there before, it can’t be right. Oh my god! It wasn’t there before!’ We were absolutely startled,” said NASA Mars Exploration Rover lead scientist Steve Squyres according to a Jan. 17, 2014, Fox News report.
“After a decade of exploring the Martian surface, the scientists overseeing veteran rover Opportunity thought they’d seen it all. That was until a rock mysteriously ‘appeared’ a few feet in front of the six-wheeled rover a few days ago.”
The Mars mystery rock was made public by Steve Squyres of Cornell University during Thursday night’s special NASA Jet Propulsion Laboratory “10 years of roving Mars” event at the California Institute of Technology in Pasadena. The event celebrated the 10 years that twin rovers Spirit and Opportunity have spent on Mars.
The Opportunity rover has not moved in more than a month on Mars but photos taken within a few days shows the sudden appearance of a rock that was not there before. The “Before” picture, taken on Sol 3528, shows only bare bedrock. The “After” picture, taken on Sol 3540, shows a fist-sized rock that scientists cannot explain. One sol is a Mars day which is slightly longer than an Earth day.
So far, scientists have two major explanations for the Mars mystery rock. First, the rock landed there after a nearby meteorite event. Or second, the rover somehow moved the rock and flipped it while it tried to make a turn. Opportunity’s front right steering actuator has stopped working which would cause the wheel to be unable to fully turn left or right.
“So if you do a turn in place on bedrock, as you turn that wheel across the rock, it’s gonna kinda ‘chatter.’ This jittery motion across the bedrock may have propelled the rock out of place, ‘tiddlywinking’ the object from its location and flipping it a few feet away from the rover,” says Steve Squyres who emphasizes that this might be “the possible culprit behind the whole mystery.”
“I must stress that I’m guessing now.”
Steve Squyres’ theory about the Mars mystery rock is the leading theory behind the case of the random bright rock that scientists have nicknamed “Pinnacle Island” – but nobody knows for sure where Pinnacle Island came from.
In particular, the rock has twice as much manganese as anything previously analyzed on Mars.
“Mars keeps throwing new stuff at us,” said Mars Exploration rover lead scientist Steve Squyres.
The rock suddenly appeared on photographs taken by the Opportunity rover on Sol (Martian day) 3540 or January 8 Earth time, according to NASA’s website.
Photographs previously taken on Sol 3536 showed no trace of the rock. The body was named ‘Pinnacle Island’.
“It was a total surprise, we were like, ‘Wait a second, that wasn’t there before, it can’t be right. Oh my God! It wasn’t there before!’ We were absolutely startled,” Squyres told Discovery News.
So far, there are two theories about the rock’s origin.
The first is that the Opportunity rover itself flipped the rock over as it rolled forward, while the second is that the mysterious rock just landed there after a meteorite impact nearby. However, the latter is highly unlikely, the researchers say.
The Opportunity rover is about to celebrate its 10th anniversary on the Red Planet, with its stay originally scheduled to last just three months.
The rover is equipped with a powerful set of tools to study Martian soils that may hold clues to past water activity on the planet.
A decade ago Opportunity discovered hematite on the planet in the form of small concretions nicknamed ‘blueberries’, thus providing the first evidence of liquid water on the red planet.
Meanwhile, other rovers on Mars’s surface are also contributing new findings.
In December, the Curiosity rover discovered signs of an ancient freshwater lake on the planet that existed 3.5 billion years ago and may have supported small organisms for tens of millions of years.
Back in September, Curiosity found traces of water in the Martian soil, too. The report suggested that each cubic foot of Martian soil contains about two pints of liquid water, though the molecules are bound to other minerals in the soil.