Teen use of any illicit drug other than marijuana at new low, same true for alcohol

Teenagers' use of drugs, alcohol and tobacco declined significantly in 2016 at rates that are at their lowest since the 1990s, a new national study showed.

But University of Michigan researchers cautioned that while these developments are "trending in the right direction," marijuana use still remains high for 12th-graders.

The results derive from the annual Monitoring the Future study, now in its 42nd year. About 45,000 students in some 380 public and private secondary schools have been surveyed each year in this national study, designed and conducted by research scientists at U-M's Institute for Social Research and funded by the National Institute on Drug Abuse. Students in grades 8, 10 and 12 are surveyed.

Overall, the proportion of secondary school students in the country who used any illicit drug in the prior year fell significantly between 2015 and 2016. The decline in narcotic drugs is of particular importance, the researchers say. This year's improvements were particularly concentrated among 8th- and 10th-graders.

Considerably fewer teens reported using any illicit drug other than marijuana in the prior 12 months -- 5 percent, 10 percent and 14 percent in grades 8, 10 and 12, respectively -- than at any time since 1991. These rates reflect a decline of about one percentage point in each grade in 2016, but a much larger decline over the longer term.

In fact, the overall percentage of teens using any of the illicit drugs other than marijuana has been in a gradual, long-term decline since the last half of the 1990s, when their peak rates reached 13 percent, 18 percent and 21 percent, respectively.

Marijuana, the most widely used of the illicit drugs, dropped sharply in 2016 in use among 8th-graders to 9.4 percent, or about one in every 11 indicating any use in the prior 12 months. Use also declined among 10th-graders as well, though not by a statistically significant amount, to 24 percent or about one in every four 10th-graders.

The annual prevalence of marijuana use (referring to the percentage using any marijuana in the prior 12 months) has been declining gradually among 8th-graders since 2010, and more sharply among 10th-graders since 2013. Among 12th-graders, however, the prevalence of marijuana use is higher (36 percent) and has held steady since 2011. These periods of declining use (or in the case of 12th-graders, stabilization) followed several years of increasing use by each of these age groups.

Daily or near-daily use of marijuana -- defined as use on 20 or more occasions in the previous 30 days -- also declined this year among the younger teens (significantly so in 8th grade to 0.7 percent and to 2.5 percent among 10th-graders). However, there was no change among 12th-graders in daily use, which remains quite high at 6 percent or roughly one in every 17 12th-graders -- about where it has been since 2010.

Prescription amphetamines and other stimulants used without medical direction have constituted the second-most widely used class of illicit drugs used by teens. Their use has fallen considerably, however. In 2016, 3.5 percent, 6.1 percent and 6.7 percent of 8th-, 10th- and 12th-graders, respectively, say they have used any in the prior 12 months -- down from recent peak levels of 9 percent, 12 percent and 11 percent, respectively, reached during the last half of the 1990s.

Prescription narcotic drugs have presented a serious problem for the country in recent years, with increasing numbers of overdose deaths and emergencies resulting from their use. Fortunately, the use of these drugs outside of medical supervision has been in decline, at least among high school seniors -- the only ones for whom narcotics use is reported. In 2004, a high proportion of 12th-graders -- 9.5 percent, or nearly one in 10 -- indicated using a prescription narcotic in the prior 12 months, but today that percentage is down by half to 4.8 percent.

"That's still a lot of young people using these dangerous drugs without medical supervision, but the trending is in the right direction," said Lloyd Johnston, the study's principal investigator. "Fewer are risking overdosing as teenagers, and hopefully more will remain abstainers as they pass into their twenties, thereby reducing the number who become casualties in those high-risk years."

Users of narcotic drugs without medical supervision were asked where they get the drugs they use. About four in every 10 of the past-year users indicated that they got them "from a prescription I had."

"That suggests that physicians and dentists may want to consider reducing the number of doses they routinely prescribe when giving these drugs to their patients, and in particular to teenagers," Johnston said.

Heroin is another narcotic drug of obvious importance. There is no evidence in the study that the use of heroin has risen as the use of prescription narcotics has fallen -- at least not in this population of adolescents still in school, who represent over 90 percent of their respective age groups.

In fact, heroin use among secondary school students also has declined substantially since recent peak levels reached in the late 1990s. Among 8th-graders, the annual prevalence of heroin use declined from 1.6 percent in 1996 to 0.3 percent in 2016. And among 12th-graders, the decline was from 1.5 percent in 2000 to 0.3 percent in 2016.

"So, among secondary school students, at least, there is no evidence of heroin coming to substitute for prescription narcotic drugs -- a dynamic that apparently has occurred in other populations," Johnston said. "Certainly there will be individual cases where that happens, but overall the use of heroin and prescription narcotics both have declined appreciably and largely in parallel among secondary school students."

The ecstasy epidemic, which peaked at about 2001, was a substantial one for teens and young adults, Johnston said. Ecstasy is a form of MDMA (methylenedioxy-methamphetamine) as is the much newer form on the scene, "Molly."

"The use of MDMA has generally been declining among teens since about 2010 or 2011, and it continued to decrease significantly in 2016 in all three grades even with the inclusion of Molly in the question in more recent years," Johnston said.

MDMA's annual prevalence now stands at about 1 percent, 2 percent and 3 percent in grades 8, 10 and 12, respectively.

Synthetic marijuana (often sold over the counter as "K-2" or "Spice") continued its rapid decline in use among teens since its use was first measured in 2011. Among 12th-graders, for example, annual prevalence has fallen by more than two-thirds, from 11.4 percent in 2011 to 3.5 percent in 2016. Twelfth-graders have been showing an increased appreciation of the dangers associated with these drugs. It also seems likely that fewer students have access to these synthetic drugs, as many states and communities have outlawed their sale by retail outlets.

Bath salts constitute another class of synthetic drugs sold over the counter. Their annual prevalence has remained quite low -- at 1.3 percent or less in all grades -- since they were first included in the study in 2012. One of the very few statistically significant increases in use of a drug this year was for 8th-graders' use of bath salts (which are synthetic stimulants), but their annual prevalence is still only 0.9 percent with no evidence of a progressive increase.

A number of other illicit drugs have shown declining use, as well. Among them are cocaine, crack, sedatives and inhalants (the declining prevalence rates for these drugs may be seen in the tables and figures associated with this release.)

Alcohol

The use of alcohol by adolescents is even more prevalent than the use of marijuana, but it, too, is trending downward in 2016, continuing a longer-term decline. For all three grades, both annual and monthly prevalence of alcohol use are at historic lows over the life of the study. Both measures continued to decline in all three grades in 2016.

Of even greater importance, measures of heavy alcohol use are also down considerably, including self-reports of having been drunk in the previous 30 days and of binge drinking in the prior two weeks (defined as having five or more drinks in a row on at least one occasion).

Binge drinking has fallen by half or more at each grade level since peak rates were reached at the end of the 1990s. Today, the proportions who binge drink are 3 percent, 10 percent and 16 percent in grades 8, 10 and 12, respectively.

"Since 2005, 12th-graders have also been asked about what we call 'extreme binge drinking,' defined as having 10 or more drinks in a row or even 15 or more, on at least one occasion in the prior two weeks," Johnston said. "Fortunately, the prevalence of this particularly dangerous behavior has been declining as well."

In 2016, 4.4 percent of 12th-graders reported drinking at the level of 10 or more drinks in a row, down by about two-thirds from 13 percent in 2006.

Rates of daily drinking among teens has also fallen considerably over the same intervals. Flavored alcoholic beverages and alcoholic beverages containing caffeine have both declined appreciably in use since each was first measured -- again, particularly among the younger teens, where significant declines in annual prevalence continued into 2016.

Tobacco

Declines in cigarette smoking and certain other forms of tobacco use also occurred among teens in 2016, continuing an important and now long-term trend in the use of cigarettes.

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New robot has a human touch

Most robots achieve grasping and tactile sensing through motorized means, which can be excessively bulky and rigid. Scientists have now devised a way for a soft robot to feel its surroundings internally, in much the same way humans do. Stretchable optical waveguides act as curvature, elongation and force sensors in a soft robotic hand.

A group led by Robert Shepherd, assistant professor of mechanical and aerospace engineering and principal investigator of Organic Robotics Lab, has published a paper describing how stretchable optical waveguides act as curvature, elongation and force sensors in a soft robotic hand.

Doctoral student Huichan Zhao is lead author of "Optoelectronically Innervated Soft Prosthetic Hand via Stretchable Optical Waveguides," which is featured in the debut edition of Science Robotics.

"Most robots today have sensors on the outside of the body that detect things from the surface," Zhao said. "Our sensors are integrated within the body, so they can actually detect forces being transmitted through the thickness of the robot, a lot like we and all organisms do when we feel pain, for example."

Optical waveguides have been in use since the early 1970s for numerous sensing functions, including tactile, position and acoustic. Fabrication was originally a complicated process, but the advent over the last 20 years of soft lithography and 3-D printing has led to development of elastomeric sensors that are easily produced and incorporated into a soft robotic application.

Shepherd's group employed a four-step soft lithography process to produce the core (through which light propagates), and the cladding (outer surface of the waveguide), which also houses the LED (light-emitting diode) and the photodiode.

The more the prosthetic hand deforms, the more light is lost through the core. That variable loss of light, as detected by the photodiode, is what allows the prosthesis to "sense" its surroundings.

"If no light was lost when we bend the prosthesis, we wouldn't get any information about the state of the sensor," Shepherd said. "The amount of loss is dependent on how it's bent."

The group used its optoelectronic prosthesis to perform a variety of tasks, including grasping and probing for both shape and texture. Most notably, the hand was able to scan three tomatoes and determine, by softness, which was the ripest.

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Why we walk on our heels instead of our toes: Longer virtual limbs

Walking heel-to-toe gives humans the mechanical advantage of longer 'virtual limbs'

James Webber took up barefoot running 12 years ago. He needed to find a new passion after deciding his planned career in computer-aided drafting wasn't a good fit. Eventually, his shoeless feet led him to the University of Arizona, where he enrolled as a doctoral student in the School of Anthropology.

Webber was interested in studying the mechanics of running, but as the saying goes, one must learn to walk before they can run, and that -- so to speak -- is what Webber has been doing in his research.

His most recent study on walking, published in the Journal of Experimental Biology, specifically explores why humans walk with a heel-to-toe stride, while many other animals -- such as dogs and cats -- get around on the balls of their feet.

It was an especially interesting question from Webber's perspective, because those who do barefoot running, or "natural running," land on the middle or balls of their feet instead of the heels when they run -- a stride that would feel unnatural when walking.

Indeed, humans are pretty set in our ways with how we walk, but our heel-first style could be considered somewhat curious.

"Humans are very efficient walkers, and a key component of being an efficient walker in all kind of mammals is having long legs," Webber said. "Cats and dogs are up on the balls of their feet, with their heel elevated up in the air, so they've adapted to have a longer leg, but humans have done something different. We've dropped our heels down on the ground, which physically makes our legs shorter than they could be if were up on our toes, and this was a conundrum to us (scientists)."

Webber's study, however, offers an explanation for why our heel-strike stride works so well, and it still comes down to limb length: Heel-first walking creates longer "virtual legs," he says.

We Move Like a Human Pendulum

When humans walk, Webber says, they move like an inverted swinging pendulum, with the body essentially pivoting above the point where the foot meets the ground below. As we take a step, the center of pressure slides across the length of the foot, from heel to toe, with the true pivot point for the inverted pendulum occurring midfoot and effectively several centimeters below the ground. This, in essence, extends the length of our "virtual legs" below the ground, making them longer than our true physical legs.

As Webber explains: "Humans land on their heel and push off on their toes. You land at one point, and then you push off from another point eight to 10 inches away from where you started. If you connect those points to make a pivot point, it happens underneath the ground, basically, and you end up with a new kind of limb length that you can understand. Mechanically, it's like we have a much longer leg than you would expect."

Webber and his adviser and co-author, UA anthropologist David Raichlen, came to the conclusion after monitoring study participants on a treadmill in the University's Evolutionary Biomechanics Lab. They looked at the differences between those asked to walk normally and those asked to walk toe-first. They found that toe-first walkers moved slower and had to work 10 percent harder than those walking with a conventional stride, and that conventional walkers' limbs were, in essence, 15 centimeters longer than toe-first walkers.

"The extra 'virtual limb' length is longer than if we had just had them stand on their toes, so it seems humans have found a novel way of increasing our limb length and becoming more efficient walkers than just standing on our toes," Webber said. "It still all comes down to limb length, but there's more to it than how far our hip is from the ground. Our feet play an important role, and that's often something that's been overlooked."

When the researchers sped up the treadmill to look at the transition from walking to running, they also found that toe-first walkers switched to running at lower speeds than regular walkers, further showing that toe-first walking is less efficient for humans.

Ancient Human Ancestors Had Extra-Long Feet

It's no wonder humans are so set in our ways when it comes to walking heel-first -- we've been doing it for a long time. Scientists know from footprints found preserved in volcanic ash in Latoli, Tanzania, that ancient hominins practiced heel-to-toe walking as early as 3.6 million years ago.

Our feet have changed over the years, however. Early bipeds (animals that walk on two feet) appear to have had rigid feet that were proportionally much longer than ours today -- about 70 percent the length of their femur, compared to 54 percent in modern humans. This likely helped them to be very fast and efficient walkers. While modern humans held on to the heel-first style of walking, Webber suggests our toes and feet may have gotten shorter, proportionally, as we became better runners in order to pursue prey.

"When you're running, if you have a really long foot and you need to push off really hard way out at the end of your foot, that adds a lot of torque and bending," Webber said. "So the idea is that as we shifted into running activities, our feet started to shrink because it maybe it wasn't as important to be super-fast walkers. Maybe it became important to be really good runners."

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Brain blocks new memory formation on waking to safeguard consolidation of existing memories

During consolidation, the brain produces new proteins that strengthen fragile memory traces. However, if a new experience occurs while an existing memory trace is being consolidated, the new stimuli could disrupt the consolidation process. Some memory consolidation occurs while we are asleep. But what happens if we wake up during consolidation? How does the brain prevent events that occur just after awakening from interrupting the consolidation process? Researchers have the answer

Throughout our waking lives we are exposed to a continuous stream of stimuli and experiences. Some of these experiences trigger the strengthening of connections between neurons in the brain, and begin the process of forming memories. However, these initial memory traces are fragile and only a small number will become long-term memories with the potential to last a lifetime. For this transition to occur, the brain must stabilize the memory traces through a process called consolidation.

Let's sleep on it

During consolidation, the brain produces new proteins that strengthen the fragile memory traces. However, if a new experience occurs while an existing memory trace is being consolidated, the new stimuli could disrupt or even hijack the consolidation process.

The brain partially solves this problem by postponing some of the memory consolidation to a period in which new experiences are minimalized, that is, while we are asleep. But what happens if we wake up while consolidation is taking place? How does the brain prevent events that occur just after awakening from interrupting the consolidation process?

A new study by Prof. Abraham Susswein of the Mina and Everard Goodman Faculty of Life Sciences and The Leslie and Susan Gonda (Goldschmied) Multidisciplinary Brain Research Center at Bar-Ilan University, has now answered this question. Published ineLife, the article's first author is Roi Levy, whose doctoral research -- conducted in Prof. Susswein's lab -- is described in the present study, which also includes part of the doctoral research of David Levitan.

Susswein and his colleagues have used a seemingly unlikely subject for their study, namely the sea hare Aplysia. These marine slugs are convenient for neuroscientific investigation because of their simple nervous systems and large neurons, and because they have been shown to be capable of basic forms of learning.

Just after training during waking hours, proteins are synthesized to initiate the consolidation of new memory. Consolidation proteins are produced again in greater quantities during sleep for subsequent processes on the memory trace. The researchers found that blocking the production of consolidation proteins in sleeping sea slugs prevents these creatures from forming long-term memories, confirming that, like us, they do consolidate memories during sleep.

Overcoming Memory Block

Susswein, Levy and Levitan now show that exposing sea slugs to new stimuli immediately after they wake up does not trigger the formation of new memories. In a learning paradigm affecting sea slugs' feeding activity, the animals were trained after being awakened from sleep. On awakening, interactions between new experiences and consolidation are prevented because the brain blocks long-term memory arising from the new stimuli. However, when the researchers treated the slugs just prior to the training with a drug that inhibits protein production, they found that the new stimuli could generate long-term memory. These findings show that proteins blocking the formation of new memories prevent an experience upon waking from being effective in producing memory. Removing this block -- by inhibiting protein production -- allows experiences just after waking to be encoded in memory. This even applies to experiences that are too brief to trigger memory formation in fully awake sea slugs.

Susswein says, "The major insight from this research is that there is an active process in the brain which inhibits the ability to learn new things and protects the consolidation of memories."

Two Heads are Better than One

The researchers also compared learning by fully awake sea slugs trained in isolation and those trained with companions. They discovered that training in social isolation appears to inhibit new learning, and identified similar molecular processes common to both training in isolation and to training on waking from sleep.

For the Future

"Our next step following on from this work," says Susswein, "is to identify these memory blocking proteins and to fathom how they prevent the formation of new memories." He adds: "We may also find that the blocking process accounts for why we cannot remember our dreams when we wake up."

An important future challenge is to investigate whether the same proteins could ultimately be used to block unwanted memories, for example, in cases of Post-Traumatic Stress Disorder.

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Cancer spread is increased by a high fat diet, ground-breaking evidence shows

Researchers discover new cancer spreading protein

New research shows that the metastatic process (cancer spread) is enhanced by fat intake. Mice given a high fat diet, including palmitic acid (a major component of palm oil which is found in lots of household products) developed the most aggressive cancer spread. The study identifies for the first time a protein called CD36 which has an essential role in cancer spreading.

Cancer is most deadly when it has begun to spread as successful treatment is much more difficult. Scientists around the globe are therefore trying to understand how the process occurs and develop new ways to stop it.

Professor Benitah's team found CD36 was present on metastatic cancer cells from patients with a range of different tumours including oral tumours, melanoma skin cancer, ovarian, bladder, lung and breast cancer. To confirm its essential role in cancer spread, they added CD36 to non-metastatic cancer cells which then caused the cells to become metastatic.

"Although we have not yet tested this in all tumour types, we can state that CD36 is a general marker of metastatic cells, the first I know of that is generally specific to metastasis," says Professor Benitah, Head of the Stem Cell and Cancer Lab at IRB Barcelona.

"We expect this study to have a big impact on the scientific community and to further advances in metastasis research, and we hope to be able to validate the potential of CD36 as an anti-metastasis treatment. Things like this don't happen every day."

The researchers next looked at the role of fat intake on cancer spread. They provided mice with a high fat diet then injected them with a type of human oral cancer. The high fat diet caused 50% more mice to have larger and more frequent metastases.

They went on to test a specific saturated fatty acid called palmitic acid -- a major component of animal and vegetable fats and present at high levels in palm oil which is used in many house hold products from peanut butter and processed food to toothpaste. The researchers treated human oral tumours with palmitic acid for two days then injected them into mice fed a standard diet. The team observed that all the mice with CD36 developed cancer spread compared to only half when not treated with palmitic acid.

"In mice inoculated with human tumour cells, there appears to be a direct link between fat intake and an increase in metastatic potential through CD36. More studies are needed to unravel this intriguing relationship, above all because industrialised countries are registering an alarming increase in the consumption of saturated fats and sugar," warns Professor Benitah. "Fat is necessary for the function of the body, but uncontrolled intake can have an effect on health, as already shown for some tumours such as colon cancer, and in metastasis, as we demonstrate here."

Using mice with human oral cancer, the researchers were next able to show that blocking CD36 completely prevented metastasis. In mice with cancer cells that had already metastasised, CD36 blocking antibodies led to the complete removal of metastases in 20% of the mice, whilst in the others it caused a dramatic reduction of 80-90% of metastases and reduced the size. Importantly, this was all achieved with no serious side effects.

The researchers are now developing new antibody-based therapeutics against CD36 that could potentially be suitable to treat a range of cancers in patients in the future.

Dr Lara Bennett, Science Communications Manager at Worldwide Cancer Research said: "We have been supporting Professor Benitah's work for a number of years and it is fantastic to now see these truly game-changing results. If the team are able to go on to develop this antibody into a treatment for humans it could save thousands of lives every year."

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Learning makes animals intelligent

The fact that animals can use tools, have self-control and certain expectations of life can be explained with the help of a new learning model for animal behavior. Researchers have combined knowledge from the fields of artificial intelligence, ethology and the psychology of learning to solve several problems concerning the behavior and intelligence of animals

Animals are often very effective; an oystercatcher opens mussels quickly, a baboon takes every opportunity to steal food from tourists or a rat navigates with ease between the bins in a park. Previously these behaviours have been considered to be inherited instincts, even though it is well known that animals have great learning abilities. Researchers from Stockholm University and Brooklyn College have now created an associative learning model that explains how effective behaviours can arise. This means that an animal does not only learn that the last step of a behaviour chain, the one that is rewarding, is valuable. An animal can learn that all steps towards the reward are valuable.

"Our learning model may also explain how advanced behaviours are created at an individual level. Behaviours like self-control, chimpanzee tool use as well as other phenomena like animals having certain expectations of live," says Magnus Enquist, professor of ethology at Stockholm University. "Similar models are used in the field of artificial intelligence, but they have been ignored in animal studies."

Since the 1970s it has been known that animals weigh the cost of a certain behaviour against the profit and that they, to a high degree, make optimal decisions, which is assumed to be genetically determined. The research group's new model deals not only with learning, it also takes into account the idea that what animals are able to learn can be genetically regulated.

"Young animals are often a bit clumsy, while adult animals are extremely skilled. A small cub does not even consider a vole as food, while an adult fox is an expert vole catcher," says Johan Lind associate professor of ethology at Stockholm University. "Our model shows how genetic regulation of learning can influence the development of species-specific behaviour and intelligence since evolution can affect curiosity and the speed of learning among other things."

The researchers' new model could also explain counterproductive behaviour in artificial environments.

"Many learning models can explain optimal behaviour, but to explain counterproductive behaviour an understanding of the mechanisms of the behaviour is needed. Using our model, we manage to explain why animals get stuck in suboptimal behaviour. Like a hamster running in its hamster wheel despite having food next to it. Our model has captured fundamental aspects of learning," says Stefano Ghirlanda, professor of psychology at Brooklyn College in New York.

The learning model and the research results were recently published in the journal Royal Society Open Science.

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New insights into skin cells could explain why our skin doesn't leak

The discovery of the shape and binding capability of epidermal cells could explain how skin maintains a barrier even when it is shedding. New research into how epidermal cells form a barrier may explain the paradox of how we can shed them without compromising our skin's integrity. It could also help us to understand what happens when it forms incorrectly, which could lead to conditions like psoriasis and eczema.

The authors of the study say their new understanding of how epidermal cells form a barrier may explain the paradox of how we can shed them without compromising our skin's integrity. It could also help us to understand what happens when it forms incorrectly, which could lead to conditions like psoriasis and eczema.

Humans lose 200,000,000 skin cells every hour. During a 24-hour period, a person loses almost five thousand million skin cells. It has been a challenge for scientists to explain how this colossal shedding process can occur without there being a break in the skin barrier.

Scientists have previously known the epidermis consists of a thick outer barrier of dead epidermal cells, which are constantly shedding. What they've known less about is a secondary barrier deeper below the surface in the epidermis that is made up of only a single layer of cells, which forms a much thinner, though no less important, protective barrier.

Now, a team from Keio University in Japan, working with a researcher at Imperial College London, have discovered that the shape of the epidermal cells combined with their ability to temporarily glue together, may explain how they form this strong barrier.

The researchers suggest that a shape of an epidermal cell is actually a flattened version of a tetrakaidecahedron -- a 14-sided 3D solid made out of six rectangular and eight hexagonal sides. The authors came to their conclusion after studying skin cells in mouse models using a confocal and two-photon microscopes, and developing mathematical models.

The tetrakaidecahedron shape was first proposed in 1887 by William Thomson (Lord Kelvin), a Scotch-Irish mathematical physicist and engineer. He claimed that the tetrakaidecahedron was the best shape for packing equal-sized objects together to fill space with minimal surface area.

The team in today's study say the epidermal cells' unique tetrakaidecahedron-like geometry means that it can always form a very tight, cohesive bond with the epidermal cells surrounding it. This is because the mix of rectangular and hexagonal sides enables the cell to always be tightly connected to the cells surrounding it.

The team also discovered that these cells manufacture proteins, which act as a temporary glue that binds the cells together in what are called 'tight junctions'. The combination of the cells' geometry and tight junction formation means that the skin barrier can maintain its integrity even though it is very thin.

When new cells underneath form the new tight junctions, this pushes the older cells upwards towards the surface of the skin, and the older cells lose their tight junctions. In this way, the tight junction barrier in the cell sheet is always maintained.

The team suggest that 'malfunctions' in the production of the tight junctions may be a contributing factor that explains why some people have conditions such as eczema, where the skin barrier is weakened, which leads to bacterial infiltration, inflammation, scratching and further infection. In other cases, fails in the interlocking barrier between cells -- the tight junctions -- may partly explain why in psoriasis there is an overproduction of epidermal cells, causing thick patches of skin on the surface.

Dr Reiko Tanaka, one of the study's authors from the Department of Bioengineering at Imperial College London, said: "It is amazing to think that an abstract concept for a shape devised by the mathematician Lord Kelvin over a century ago may be an important shape in nature, helping our skin to maintain its effectiveness as barrier.

"Our study is also helping us to see how the cells that make up our skin can switch on a mechanism to make a kind of glue, which binds the cells together, ensuring that our skin maintains its integrity.

"Our skin is the largest organ in our body and it is vital that we completely understand how it works, so when it doesn't work as it should, such as in eczema or psoriasis, we can understand the mechanisms that might be causing the problems."

The study is published in the journal eLIFE.

The next steps will see the team analysing how skin thickness is determined and how the balance between cell growth and cell shedding is maintained. Faults in this process can lead to a thickening of the skin, leading to conditions like psoriasis. The team will also determine why skin thins as we get older, providing new insights into aging, or when it thins because special treatments like steroids are administered to treat eczema.

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