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Zebrafish share skin-deep similarities with people, making them helpful models to study skin conditions like vitiligo and melanoma

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Zebrafish share skin-deep similarities with people, making them helpful models to study skin conditions like vitiligo and melanoma

The melanocytes in zebrafish stripes share many similarities to those in people.
Dan Olsen/iStock via Getty Images Plus

Craig Ceol, UMass Chan Medical School

Melanocytes are a small subset of epidermal cells that play an outsize role in protecting your skin from the damaging effects of sun exposure. They do this by synthesizing melanins, which are pigments sent to other skin cells to shield them from harmful ultraviolet light. A lack of functioning melanocytes causes a wide range of skin conditions, including skin cancer and vitiligo, an autoimmune condition in which the body attacks melanocytes and causes patches of depigmented skin.

For nearly 20 years, I have been studying melanocytes and the role they play in disease. Difficulties growing human melanocytes in cell cultures have led researchers like me to use alternative models to study them.

My lab and others have pioneered the use of zebrafish to study melanocytes. Using this small freshwater fish as a model organism, my team and I recently discovered a new way in which melanocytes regenerate. This process enables flexibility for these cells to recover from injuries and may be applicable to other types of tissues.

What zebrafish and people have in common

New students and nonscientists often ask me, “Why zebrafish?” There are several reasons why zebrafish are good models to study melanocytes.

Melanocytes in zebrafish are similar in many ways to those in people. These cells develop in embryos in the same way those in humans do, use the same genetic programs and make the same melanins. Melanocyte dysfunction in zebrafish also leads to the same diseases and cancers found in people.

Unlike melanocytes in mouse or human skin, zebrafish melanocytes are externally visible in their dark stripes and spotted scales. Researchers can place the whole fish directly under a microscope and see the cells without the need for a biopsy.

Zebrafish against white background
Zebrafish melanocytes can be found in their dark stripes and spotted scales.
Craig Ceol, CC BY-ND

Importantly, researchers can manipulate and perform experiments on zebrafish melanocytes in ways that are unethical or not feasible to do with people. Unlike studies that use isolated melanocytes in a petri dish, these experiments can take place in the context of a whole animal, where we can monitor the surrounding skin and other biological factors for their influence on how melanocytes behave and function.

Diversity of melanocyte stem cells

In work spearheaded by Tyler Frantz, a graduate student in my lab, our team has focused our attention on the process by which new melanocytes regenerate after injury.

Melanocyte regeneration is important for recovering from skin disorders such as vitiligo. It’s also relevant to age-related conditions like hair graying, in which melanocyte stem cells either die or become dormant and no longer produce the mature melanocytes that give hair its color.

Close-up of zebrafish melanocytes -- small dark circles clustered in a band
The small dark circles clustered in a band across this photo are zebrafish melanocytes, magnified 100 times.
Craig Ceol, CC BY-ND

To study melanocyte regeneration, we removed these cells from zebrafish and followed their process of regrowth. Since melanocyte stem cells in zebrafish are externally visible, we tracked these cells in real time to see how they divided and matured. Additionally, we measured which genes were expressed in individual melanocyte stem cells and their descendants during regeneration.

We found that dying melanocytes trigger this regenerative process by sending the signal for melanocyte stem cells – cells that can give rise to new melanocytes – to activate. Surprisingly, we identified two types of stem cells that each took a different route to make new melanocytes. One type of stem cell directly converted into melanin-producing melanocytes. The other type of stem cell divided to create two types of daughter cells. One type was new melanocytes, and the other was new stem cells ready to respond to future injury.

Researchers have known that a single stem cell is capable of making the multiple types of cells needed to regenerate tissue. Our zebrafish studies indicate that multiple different stem cells in skin, and potentially other tissues, can together reconstruct one particular cell type after injury. The involvement of multiple stem cells likely enables regeneration to nimbly adjust to different types of injuries.

From fish to people

Our findings from zebrafish are likely relevant to human skin. When we examined cells taken from the fluid within a blister in human skin, we found cells that look remarkably similar to zebrafish melanocyte stem cells. We are planning to see whether these human cells are activated in skin regeneration to make new melanocytes, which would confirm their identity as melanocyte stem cells.

Ultimately, we envision using these findings to develop treatments that reinvigorate melanocyte stem cells, which could help reverse skin color loss in vitiligo and other diseases. Such treatments may also help counteract age-related pigment loss in hair and skin.

The unique features of zebrafish have allowed us to uncover a new mode of cellular regeneration. Because of cross-species similarities, we expect that these and many other findings from research using zebrafish may be applied to human biology.The Conversation

Craig Ceol, Assistant Professor of Molecular Medicine, UMass Chan Medical School

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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Why the Justice Department is suing a software company to stop landlords colluding on rents

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theconversation.com – Roger Alford, Professor of Law, University of Notre Dame – 2024-11-18 07:27:00

Landlords don’t have to communicate directly to collude on rental prices.
AP Photo/Gene J. Puskar

Roger Alford, University of Notre Dame

Of all the reasons it could be hard to pay rent each month, did you have an algorithm-powered illegal cartel on your list?

Millions of people across the United States are paying far more rent than they can reasonably afford, with rental housing prices rising far quicker than household income. In 2022, 22.4 million U.S. households were spending more than 30% of their income on rent and utilities, up from 20.4 million in 2019.

Many of these households faced severe cost burdens, with an all-time high of 11.6 million struggling with housing costs that consume more than half of their income. In Chicago, Cincinnati, Minneapolis, Virginia Beach and Washington, year-over-year rental prices are climbing at double-digit rates.

Several factors drive the high cost of rentals, including increasing demand, a dwindling supply of low-rent units, the rising cost of capital to build new rentals, and regulatory barriers restricting the construction of multifamily units.

But there’s another surprising factor driving up rental prices: landlords colluding with the help of technology. The U.S. Justice Department is suing the company RealPage, Inc., accusing it of selling software to landlords that allows them to collectively set prices – the illegal practice of price-fixing. As a former official in the Justice Department’s Antitrust Division and a law professor, I’ve been following the case closely.

The perils of price-fixing

The Federal Trade Commission defines price-fixing as an agreement, conspiracy or combination among competitors to raise, fix or otherwise maintain the price at which their goods or services are sold.

Any agreement that restricts price competition violates the antitrust laws. Examples of price-fixing agreements include commitments among competitors to hold prices firm, adopt a standard formula for computing prices, or adhere to a minimum fee or price schedule.

So when competitors share proprietary, confidential current price information – directly or indirectly through an intermediary – to stabilize or control industry pricing, they have crossed the line into illegal collusion, according to the FTC. That is the case in major portions of the U.S. rental market, the Justice Department argues.

One algorithm for all

In August 2024, the Justice Department and eight states filed a lawsuit in a federal court in North Carolina against RealPage. The Justice Department accused the company of selling software to landlords that collects nonpublic information from competing landlords and uses that combined information to make pricing recommendations.

two men and a woman in business attire stand behind a lectern and in front of flags and a logo
Attorney General Merrick Garland, Deputy Attorney General Lisa Monaco and Acting Associate Attorney General Benjamin Mizer at a news conference about the Justice Department suing RealPage on Aug. 23, 2024.
AP Photo/Mark Schiefelbein

Landlords who use the software input the rental prices they charge, and the software aggregates all the data from the company’s customers. The software’s algorithm then makes recommendations for what to charge. The recommendations are generally higher than the current market rate, and most customers take the recommendations, which push prices in a market higher.

Even if landlords retain some authority to deviate from the algorithm’s recommendations, it is illegal for competing landlords to jointly delegate key aspects of their pricing to a common algorithm, according to the Justice Department suit. The Justice Department declared that “RealPage replaces competition with coordination. It substitutes unity for rivalry. It subverts competition and the competitive process. It does so openly and directly – and American renters are left paying the price.”

The case is unusual in that, unlike a typical price-fixing cartel, the landlords used RealPage’s algorithms to dramatically improve their ability to engage in price-fixing. Algorithmic price-fixing is typically easier and more effective than other types of cartel behavior. The software can easily aggregate massive amounts of proprietary data, optimize cartel gains, monitor real-time deviations from cartel pricing and minimize incentives to cheat.

“It’s much easier to price-fix when you’re outsourcing it to an algorithm versus when you’re sharing manila envelopes in a smoke-filled room,” Justice Department antitrust chief Jonathan Kanter told The New York Times.

Since 2022, RealPage and various property managers have been named as defendants in more than 30 class action lawsuits alleging the RealPage software is used to unlawfully fix rental prices. Federal courts tend to be sympathetic to such arguments, as shown in the denial of a motion to dismiss the case in one of the private lawsuits filed against RealPage.

In that case, the court held that a price-fixing agreement could exist as a matter of law. Landlords provided RealPage’s algorithmic system with their proprietary commercial data, knowing that RealPage would require the same from their competitors and would use all of that data to recommend rental prices to all of the company’s clients.

A news report summarizes the government’s case against RealPage.

Classic price-fixing or data-driven decisions?

Some landlords seem to be aware that in sharing confidential price information to RealPage’s software, they were facilitating the unlawful monitoring and raising of rental prices. The Justice Department complaint quoted a landlord commenting on RealPage’s software, “I always liked this product because your algorithm uses proprietary data from other subscribers to suggest rents and term. That’s classic price-fixing.”

Even RealPage’s own executives have boasted that when landlords collectively use their software, they can use “every possible opportunity to increase price,” according to the complaint.

RealPage argued that its software “simply helps landlords make data-driven decisions” in a competitive market. The company claims its tools are designed to reflect market conditions and optimize occupancy rates, not to engage in price-fixing.

The company describes the impact of its alleged collusion with landlords as “a rising tide [that] raises all ships.” Perhaps a better description for their service is a rising tide that raises all ships for those who have one.

The Justice Department’s case and the private cases are in the early stages of litigation. If the department is successful, RealPage will be barred from engaging in the anticompetitive practices related to helping landlords share proprietary pricing information.The Conversation

Roger Alford, Professor of Law, University of Notre Dame

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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Why do I feel better when I wake myself up instead of relying on an alarm? A neurologist explains the science of a restful night’s sleep

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theconversation.com – Beth Ann Malow, Professor of Neurology and Pediatrics, Vanderbilt University – 2024-11-18 07:25:00

Your internal body clock can help wake you up without an alarm.

Riska/E+ via Getty Images

Beth Ann Malow, Vanderbilt University

Curious Kids is a series for children of all ages. If you have a question you’d like an expert to answer, send it to curiouskidsus@theconversation.com.


Why do I feel better rested when I wake myself up than I do if my alarm or another person wakes me up? – Calleigh H., age 11, Oklahoma


We’ve all experienced this: You’re in the middle of a lovely dream. Perhaps you’re flying. As you’re soaring through the air, you meet an eagle. The eagle looks at you, opens its beak and – BEEP! BEEP! BEEP!

Your alarm goes off. Dream over, time to get up.

Many people – kids and adults alike – notice that when they wake up naturally from sleep, they feel more alert than if an alarm or another person, like a parent, wakes them up. Why is that?

I’m a neurologist who studies the brain, specifically what happens in the brain when you’re asleep. I also take care of children and adults who don’t sleep well and want to sleep better. My research involves working with parents to help them teach their children good sleep habits.

To understand how to sleep better, and why waking up naturally from sleep helps you feel more alert, you need to start by understanding sleep cycles.

The sleep cycle

The sleep cycle consists of four stages. One of these is REM, which stands for rapid eye movements. The other three are non-REM stages. When you fall asleep, you first go into a state of drowsiness called non-REM Stage 1.

This is followed by deeper stages of sleep, called non-REM stages 2 and 3. Each stage of non-REM is deeper than the one before. Then, about 90 minutes after you first fall asleep, you enter the fourth stage, which is REM sleep. This is a stage of lighter sleep where you do much of your dreaming. After a few minutes, you return to non-REM sleep again.

Segments of a circle indicate the four stages of the sleep cycle: Non-REM 1, Non-REM 2, Non-REM 3, and REM.

The four stages of the sleep cycle.

The Conversation, CC BY

These cycles repeat themselves throughout the night, with most people having four to six cycles of non-REM sleep alternating with REM sleep each night. As the night goes on, the cycles contain less non-REM sleep and more REM sleep. This is why it’s important to get enough sleep, so that the body can get enough of both REM sleep and non-REM sleep.

REM vs. non-REM sleep

How do researchers like me know that a person is in non-REM vs. REM sleep? In the sleep lab, we can tell from their brain waves, eye movements and the tension in their muscles, like in the chin. These are measured by putting sensors called electrodes on the scalp, around the eyes and on the chin.

These electrodes pick up brain activity, which varies from waves that are low in amplitude (the height of the wave) and relatively fast to waves that are high in amplitude (a taller wave) and relatively slow. When we are awake, the height of the waves is low and the waves are relatively fast. In contrast, during sleep, the waves get higher and slower.

Non-REM Stage 3 has the tallest and slowest waves of all the sleep stages. In REM sleep, brain waves are low in amplitude and relatively fast, and the eye movements are rapid, too. People need both non-REM and REM stages for a healthy brain, so they can learn and remember.

Waking up naturally

When you wake up in the morning on your own, it’s usually as you come to the end of whatever stage of sleep you were in. Think of it like getting off the train when it comes to a stop at the station. But when an alarm or someone else wakes you up, it’s like jumping off the train between stops, which can feel jolting. That’s why it’s good to wake up naturally whenever possible.

People can actually train their brains to wake up at a consistent time each day that is a natural stopping point. Brains have an internal 24-hour clock that dictates when you first start to feel sleepy and when you wake up. This is related to our circadian rhythms.

You can adjust your circadian rhythm so that you wake naturally each morning.

Training the brain to wake up at a consistent time

First, it’s important to go to bed at a consistent time that allows you to get enough sleep. If you stay up too late doing homework or looking at your phone, that can interfere with getting enough sleep and make you dependent on an alarm – or your parents – to wake you up.

Other things that can help you fall asleep at a healthy time include getting physical activity during the day and avoiding coffee, soda or other drinks or foods that contain caffeine. Physical activity increases brain chemicals that make it easier to fall asleep, while caffeine does the opposite and keeps you awake.

Second, you need to be aware of light in your environment. Light too late in the evening, including from screens, can interfere with your brain’s production of a chemical called melatonin that promotes sleep. But in the morning when you wake up, you need to be exposed to light.

Morning light helps you synchronize, or align, your circadian rhythms with the outside world and makes it easier to fall asleep at night. The easiest way to do this is to open up your shades or curtains in your room. In the winter, some people use light boxes to simulate sunlight, which helps them align their rhythms.

Benefits of a good night’s sleep

A good sleep routine entails both a consistent bedtime and wake time and regularly getting enough sleep. That usually means 9-11 hours for school-age kids who are not yet teens, and 8-10 hours for teens.

This will help you be at your best to learn at school, boost your mood, help you maintain a healthy weight and promote many other aspects of health.


Hello, curious kids! Do you have a question you’d like an expert to answer? Ask an adult to send your question to CuriousKidsUS@theconversation.com. Please tell us your name, age and the city where you live.

And since curiosity has no age limit – adults, let us know what you’re wondering, too. We won’t be able to answer every question, but we will do our best.The Conversation

Beth Ann Malow, Professor of Neurology and Pediatrics, Vanderbilt University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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As the Taurid meteor shower passes by Earth, pseudoscience rains down – and obscures a potential real threat from space

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theconversation.com – Mark Boslough, Research Associate Professor of Earth and Planetary Sciences, University of New Mexico – 2024-11-15 07:31:00

This image of a Taurid fireball was taken in 2014 by NASA’s All Sky Fireball Network in Tullahoma, Tenn.

NASA

Mark Boslough, University of New Mexico

With the Taurid meteor shower now hitting the night skies worldwide, look for what could be a celestial treat – you might see shooting stars, and maybe even fireballs, the biggest and brightest meteors.

As the full moon begins to wane after Nov. 15, the sky will be darker, due to diminishing moonlight, so finding the meteors will get easier. That said, the best visibility for the meteors through the rest of the month will come just before moonrise each night.

Beyond the light show, there is something else that scientists as well as onlookers have long wondered about: the possibility that bigger chunks are in the Taurid meteor streams, chunks the size of boulders, buildings or even mountains.

And if that’s true, could one of those monster-sized Taurid objects collide with Earth? Could they wipe out a city, or worse? Is it possible that’s already happened, sometime in our planet’s past?

This animation simulates the motion of the hypothetical Taurid meteor swarm through space.

As a physicist who researches the risk that comets and asteroids pose to the Earth, I’m aware that this is a subject where pseudoscience often competes with actual science. So let’s try to find the line between fact and fiction.

Pig Pen, glowing tails and shooting stars

Comet Encke is the so-called parent comet of the Taurid meteors. It’s relatively small, just over 3 miles (almost 5 kilometers) in diameter, and crosses inside Earth’s orbit and back out every 3.3 years.

As Encke moves, it sheds dust wherever it goes, like the Peanuts character Pig Pen. A meteor shower occurs when that dust and debris light up while entering Earth’s atmosphere at high speeds. Ultimately, they vanish into an incandescent puff of vapor with a glowing tail, creating the illusion of a “shooting star.”

But dust isn’t all that breaks off the comet. So do bigger chunks, the size of pebbles and stones. When they collide with the air, they create the much brighter fireballs, which sometimes explode.

Against a black and white starscape, a bright spot appears in the center of the photo.

An image of comet Encke, taken by NASA’s MESSENGER spacecraft in November 2013.

NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington/Southwest Research Institute

Doomsday showers

The “coherent catastrophism” hypothesis suggests that comet Encke was created when an even larger comet broke up into pieces; Encke survived as the largest piece. The hypothesis also suggests that other mountain-sized chunks broke off and coalesced into a large swarm of fragments too. If such a swarm exists, there is a possibility that those large chunks could one day hit Earth as it passes through the swarm.

But just because something might be physically possible doesn’t mean that it exists. Mainstream astronomers have rejected this theory’s most catastrophic predictions. Among other reasons, scientists have never observed high concentrations of these mountain-sized objects.

Despite the lack of evidence, researchers on the fringes of science have embraced the idea. They claim the Earth experienced a global catastrophic swarm 12,900 years ago; the impact, they say, caused continent-wide firestorms, floods and abrupt climate change that led to the mass extinction of large mammals, such as woolly mammoths, and the disappearance of early Americans known as the Clovis people.

The evidence for a catastrophic cause of these events, most of which did not happen, is lacking. Nevertheless, the idea has gained a large following and formed the basis for British author Graham Hancock’s popular TV series, “Ancient Apocalypse.”

A black and white photo of a forest of flattened trees.

This photo shows the flattened trees resulting from the Tunguska event.

Universal History Archives/Universal Images Group via Getty Images

The Tunguska event

But even outlandish ideas can have elements of truth, and there are hints that some objects – more than just dust and debris, but less than doomsday size – indeed exist in the Taurid meteor stream, and that the Earth has already encountered them.

One clue comes from an event on June 30, 1908, when an enormous explosion in the sky blew down millions of trees in Siberia. This was the Tunguska event – an airburst from an object that may have been up to 160 feet (about 50 meters) in diameter.

The collision unleashed several megatons of energy, which is roughly the equivalent of a large thermonuclear bomb. What happens is this: The incoming object penetrates deep into Earth’s atmosphere, and the dense air slows it down and heats it up until it vaporizes and explodes.

Could this object have been a Taurid? After all, the Taurids cross Earth’s orbit twice a year – not just in autumn, but also in June.

A fireball appears in the night sky.

In a 2015 photo, a glowing Taurid fireball descends over Lake Simcoe in Ontario, Canada.

Orchidpost/iStock via Getty Images Plus

Here’s the evidence: First, the descriptions of the trajectory of the Tunguska airburst, as reported by eyewitness observers, is consistent with that of an object coming from the Taurid stream.

What’s more, the pattern of blast damage on the ground beneath an airburst depends on the trajectory of the exploding object. Supercomputer simulations show that the shape of the surface blast that would be caused by an exploding Taurid object matches the pattern of fallen trees at Tunguska.

Finally, during the Taurid meteor shower in 1975, people observed large fireballs – and seismometers, previously placed on the Moon by Apollo astronauts, detected seismic events on the lunar surface. Scientists interpreted those events as impacts, presumably made by the Taurid meteors.

In 2032 and 2036, the Taurid swarm – assuming it exists – is predicted to be closer to the Earth than any time since 1975. That might mean the Moon, and perhaps the Earth, could be pelted again in those years.

There is time to figure this out. Scientists can expand their astronomical surveys to look for Tunguska-sized objects at the locations where they are predicted to be the next time they are in our vicinity.

Most scientists remain skeptical that such a swarm exists, but it’s the job of planetary defenders to investigate possible threats, even if the risk is small. After all, a Tunguska-sized object could conceivably demolish a major city and kill millions; an accurate count of objects on a potential collision course is essential.

Put doomsday scenarios and ancient apocalypses aside. The real question, and still an open one, is whether a Taurid swarm could deliver more Tunguska-sized objects than would otherwise be expected. This would mean we have underestimated the risk from future airbursts.The Conversation

Mark Boslough, Research Associate Professor of Earth and Planetary Sciences, University of New Mexico

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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