Stories tagged Cells

Nov
29
2006

I'm new here and want to ask a question - not write a short story. If this is the wrong place for a question, please help me out.

Is the human egg really the largest cell in the body? That's what the human body movie said. But isn't a neuron a cell, and isn't the axon a part of it, so that a single neuron can be a yard long - as in the sciatic nerve? Wouldn't that be larger than an egg cell?

And while i'm at it, here's a comment: The movie said that the brain controls the GI tract, but my understanding is that although the brain can influence your stomach and bowels, through emotions for example, the GI tract operates pretty much on its own. In fact, Dr. Michael Gershon calls the GI tract "The Second Brain" in his wonderful book by that title.

All in all, i thought the movie was fantastic, and wish there had been much, much more of it!

Nov
15
2006

New cure: Could a new paint made with a spikey-shaped polymer be a new way to fight the flu? Scientists think they've found a paint that can kill flu bugs on contact.
New cure: Could a new paint made with a spikey-shaped polymer be a new way to fight the flu? Scientists think they've found a paint that can kill flu bugs on contact.
Can you add a paintbrush as a method of fighting the flu along with chicken soup and antibiotics?

Scientists are debating that topic this week after researchers contend they’ve found a polymer-based paint that can kill flu-bearing viruses on touch. The new findings were reported on Scientific American’s website.

The researchers from the Massachusetts Institute of Technology say that the paint can be applied to surfaces in public places such as hospitals, schools or airplanes, where people congregate and can possibly pass along flu germs.

Through the tests, researchers have found that the spiky-shaped polymers when painted on surfaces can kill bacteria, including esherichia coli and Staphylococcus aureus -- bugs that are waiting to jump on to people’s unsuspecting hands, get into bodies and become full-born flu.

These pokey-polymers work by punching holes into the cell wall of a flu bug microbe, letting its contents spill out. The polymer molecules are positively charged, keeping them standing rigid and in position to burst more microbes. That ongoing battle neutralizes flu because those microbes have a wall around them that is susceptible to being speared.

The paint coatings were found non-toxic to monkey cells through tests, but they will need further study before getting government approval to be made commercially available.

Skeptics, however, think that the new information is just another piece in the puzzle of people looking to profit from the latest flu hysteria. They point to new efforts by people pointing to “improved” handwashes and new devices that remind you to wash your hands regularly.

Sep
15
2006

Black cottonwood: Courtesy Oak Point Nursery
Black cottonwood: Courtesy Oak Point Nursery

Ever heard of Populus trichocarpa? It sure is shaking up what researchers understand about plant biology and evolution. That’s right, Populus trichocarpa is a tree, more specifically a black cottonwood.

The black cottonwood is the first tree to have its full DNA code sequenced. Reports state the poplar tree has far less DNA in its cells than humans or other mammals, but twice the number of genes. The poplar has 485 million basepairs! Basepairs are the letters orchestrating a genetic code (A=adenine, T=thymine, C=cytosine, G=guanine). Researchers have found more than 45,000 possible genes (units of hereditary information). To put this number in perspective, humans and other mammals have a little over 20-25,000 genes.

Why is this cool?

Besides figuring out specific questions about botany, having the full DNA sequence of the black cottonwood will also have industrial implications.

The research team discovered 93 genes of the poplar where involved in making cellulose. Cellulose is an organic material found in large quantities on Earth. Cellulose is the primary structural component of green plants. It can be broken down into sugar, fermented into alcohol and distilled to produce fuel-quality ethanol.

Dr. Gerald Tuskan, the lead author of the report in Science, stated, “Biofuels are not only attractive for their potential to cut reliance on oil imports but also their reduced environmental impact.”

Populus trichocarpa identification:

Leaf structure: Alternate, simple, deciduous, ovate-laneolate to deltoid, dark green and silvery white underneath, wavy margins.

Fruit: Releases cottony-tufted seeds
Bark: When young, it is smooth and yellowish tan to gray; later on it turns gray to gray-brown and has deep furrows and flattened ridges.

Form: Tallest broad-leaved tree in the West. Able to grow up to 200 feet tall and 6 feet in diameter.

Found: Flood plains and along river and stream banks. Prefers moist/wet sites.

Keep your eyes open for a black cottonwood tree near you!

Sep
08
2006

Ouch, she should have used more sunscreen: Courtesy  Wikipedia
Ouch, she should have used more sunscreen: Courtesy Wikipedia

Have you ever been sunburned? Did you wear sunscreen? A recent study published in New Scientist might change your mind on how frequently an individual should reapply sunscreen.

Researchers at the University of California Riverside stated, “if you apply sunscreen anything less than once every two hours, you might be better off not using any in the first place.”

Kerry Hanson and colleagues exposed human skin samples grown in a lab to UV radiation. The samples were covered with three common UV filters found in many sunscreens (benzophenone-3, octocrylene and octylmethoxycinnamate). Findings suggested the protective compounds sunk into the skin resulting in its protective capability being greatly reduced.

Researchers also found the skin samples tested contained more reactive oxygen species (ROS) when compared to skin exposed to UV without sunscreen application. ROS are free radicals that damage skin cells and increase the odds of skin cancer. At low levels, ROS are able to assist in cell signaling processes. However, at higher levels ROS damage cellular macromolecules and could lead to apoptosis (programmed cell death).

For now the researchers advise to use sunscreens and reapply them often. The Skin Cancer Foundation recommends reapplying sunscreen every two hours. Active individuals are advised to reapply even more frequently due to sweat washing away sunscreen.

Aug
27
2006

Embryo, 8 cells: Courtesy of Wikimedia Commons.
Embryo, 8 cells: Courtesy of Wikimedia Commons.

Stem cell research is a hot topic in our country these days. Much of the controversy surrounds embryonic stem cell research and the issue of extracting cells from, and in turn destroying, developing embryos.

If only there was a way to obtain stem cells without killing the developing embryo…

Well, it looks like there is.

Researchers have found a way to extract a single cell from an embryo to be used for stem cells, while keeping the embryo intact.

Usually, stem cells are removed from an embryo when they are about 4 or 5 days old and the embryo has developed into a microscopic hollow ball structure known as a blastocyst. Extracting cells from the blastocyst causes it to fall apart and destroys the embryo. The new research findings show that stem cells can be harvested from less developed embryos, those with only 8 to 10 cells, and can leave the embryos unharmed.

Sounds like a solution to the stem cell debate, doesn’t it?

However, there are still ethical concerns with the new stem cell research technique. Critics fear that an embryo that had a cell extracted from it will be less likely to be able to implant in the womb or will not develop properly, leading to health problems in the resulting child. Others are opposed because the extracted cell potentially could have developed into a new embryo itself.

It seems that the stem cell controversy will never end. But this discovery may be a step towards a solution.

What do you think? Is the new stem cell extraction technique ethical?

Jul
28
2006

Youth Potion: anti-aging potion    photo from wikimedia
Youth Potion: anti-aging potion photo from wikimedia

Want to live 200 years?

Scientists have found a small molecule that can be used to extend the lifespan of mammalian cells. The research reported in the July issue of Nature Chemical Biology showed that the synthetic organic molecule CGK733 blocks the machinery that senses DNA damage. They found that CGK733 could extend the lifetime of cultured cells by about 20 doublings and could actually rescue cells that were already senescent. Senescent cells are cells that can stay alive but have stopped dividing.

Magnetic nano probe used to see drug interactions inside living cells

Prof. Kim Tae-kook at the Korea Advanced Institute of Science and Technology and his associates developed a technology dubbed MAGIC, short for magnetism-based interactive capture. This state-of-the-art magnetic nano-probe technology uses fluorescent materials to check whether any drug can mix with targeted proteins inside the cell.
Read more in The Korea Times or in Nature Chemical Biology press release and abstract.

Jul
26
2006

Maria McNamara of University College Dublin, and colleagues in the UK, Spain, and US, have recovered bone marrow from 10-million-year-old fossilized bones of frogs and salamanders found in Spain.

The marrow was preserved in 3D, and still has its original texture and color. Scientists think they may be able to extract traces of protein and DNA.

Even more interestingly, the fossils prove that ancient salamanders produced blood cells in their bone marrow. Modern salamanders, on the other hand, produce blood cells in their spleens.

Last year, US scientists recovered some tissue resembling blood vessels from a 65-million-year-old Tyrannosaurus rex fossil. They also found traces of what appeared to be red blood cells. (More on the T. rex find.)

And now that they're looking, scientists think they may find examples of preserved bone marrow in many fossils, raising the possibility of analyzing the proteins and DNA of lots of long-extinct organisms.

Jul
19
2006

On Tuesday, the US Senate passed three bills regarding stem cell research.

Two were pretty uncontroversial: one encouraged stem-cell research using cells from sources other than embryos—adult bone marrow or hair follicles, or umbilical cord/placental blood. (The National Institutes of Health is already spending $571 million this fiscal year on this kind of stem cell research.) And one prohibited “fetal farming”—gestating fetuses for the purpose of providing tissue and other material for research.

The House of Representatives passed the bill about fetal farming, but voted down the bill promoting alternative stem cell sources. President Bush signed the ban on the commercial production of human fetal tissue into law today.

The third bill—which President Bush has just vetoed—would have expanded federal support of medical research using embryonic stem cells. Right now, researchers using federal funds can only study a handful of embryonic stem cell lines that existed before August 2001. The failed bill would have allowed federal funding for research on stem cells from thousands of unneeded embryos created in fertility clinics. (Couples with extra embryos resulting from fertility treatments would have had the option of donating them to research instead of having them destroyed by the clinic.) An override of the veto is unlikely.

What ARE stem cells?
Stem cells are simply cells that can develop into other types of cells. They can make copies of themselves indefinitely, and can become specialized for various body tissues. They are produced by embryos and also found in limited numbers in adults, but embryonic stem cells are pluripotent--they can become almost any kind of cell in the body--while adult stem cells are more limited. Scientists think they might be able to grow replacements for damaged tissues if they can coax stem cells to become the specific types of cells needed. Stem cells could someday provide treatments or cures for cancer, spinal cord injuries, burns, strokes, heart disease, Alzheimer’s and Parkinson’s, diabetes, and other ailments.

Mouse stem cells: (Courtesy NSF)
Mouse stem cells: (Courtesy NSF)

Why not use the pre-2001 stem cell lines?

In August 2001, the Bush administration and National Institutes of Health said that 60 stem cell lines had already been developed. Federal funds would be limited to research on those lines, and could not be used to create any more. But further investigation showed that less than 22 lines were actually available, and all of them had been maintained in culture dishes with blood products from rodents--scientists say the cells can’t ethically be used to treat people because of the danger of animal viruses and other contamination. Many of the lines aren’t aging well; if they don’t keep growing and dividing, they die, and some lines are accumulating mutations and other defects. Most research is limited to six of the stem cell lines. And they aren’t a very genetically diverse lot.

But the White House says,

"The use of mouse cells is standard scientific practice. ... As the Food and Drug Administration has indicated, the resulting stem cell lines can be carefully screened to ensure they are safe for use in any future clinical trials. Drug and biological products are routinely co-cultured with animal cells with no adverse consequences for the millions of people who have benefited from them."

Why not use private money?
Some labs have produced additional stem cell lines using private money, but researchers have to be scrupulous about segregating work on the newer cells from work done with federal money. The University of California, San Francisco, for example, is spending $5 million to set up a separate stem cell research lab where scientists can work without the federal restrictions. All the lab equipment they need already exists elsewhere on campus, but it can't be used for new stem cell work.

Some states see an opportunity in the federal restrictions. California announced that state money--$3 billion over 10 years--would be available for research into embryonic stem cells and therapeutic cloning. But the initiative is being fought in court. Connecticut has an 10-year, $100 million initiative. Illinois spent $10 million last year. New Jersey spent about $25 million in the last two years. And Maryland has approved a $15 million budget. But scientists in other countries are doing far more work with embryonic stem cells than scientists in the US. And losing out now means that the US could lose the eventual commercial applications developed through such research to the countries with looser regulations.

What's the issue with using embryonic stem cells?
Harvesting stem cells destroys a developing embryo. That's the crux of the whole issue. Those who oppose embryonic stem cell research say that the potential cures promised by stem cell research supporters offer false hope to some suffering Americans while encouraging the destruction of embryos to provide the cells. Members of the US Senate, debating earlier this week, expressed the gamut of opinions:

Senator Orrin Hatch (R-Utah) said,

"I do not question that an embryo is a living cell. But I do not believe that a frozen embryo in a fertility clinic freezer constitutes human life."

Senator Bill Frist (R-Tenn.), the Senate majority leader and a transplant surgeon, said,

"I believe that the progress of science and a pro-life position demand that Congress can send a message. I hope that we can redeem this loss of life in part by using these embryos to seed research that will save lives in the future."

Senator David Vitter (R-Louisiana) said,

"...I firmly believe that [neither] Congress, independent researchers nor any human being should be allowed, in effect, to play God by determining that one life is more valuable than another."

Senator Tom Coburn (R-Oklahoma), who is also a physician, said,

"The fact is, there is not one cure in this country today from embryonic stem cells."

Senator Tom Harkin (D-Iowa) said,

"So the choice is this ... throw [the embryos] away or use them to ease suffering and, hopefully, cure diseases."

Senator Sam Brownback (R-Kansas) said,

"We do not need to treat humans as raw material."

and

"It is immoral to destroy the youngest of human lives for research purposes. We don't need to do it."

Public opinion polls show that 70% of Americans support embryonic stem cell research. What do YOU think? Should the US government help fund it?

Jun
25
2006

Sunbathers: Soaking up the sun in the California desert. Courtesy Mark Ryan.
Sunbathers: Soaking up the sun in the California desert. Courtesy Mark Ryan.

Here’s a question for the start of summer: why does exposure to the sun darken our skin but lighten our hair?

First let’s take a look at our skin. Human skin is the body’s largest organ, and acts as a barrier between our inner organs and the outside world. It’s made up of essentially two parts the epidermis and the dermis. The epidermis is the outer section and is comprised of a layer of living cells, topped by a layer of dead cells. The dead cells are the skin we see.

Even though the upper epidermis is just a lot of dead cells, it contains keratin, a tough protein that also makes up our hair and fingernails, Keratin is thicker on the bottoms of our feet and the palms of our hands for added protection against abrasions and other intrusions from the outside world.

Inside the dermis is where all the skin’s functioning equipment is located, These include nerves, sweat glands, hair follicles, blood vessels and special cells called melanocytes, which produce melanin, the material responsible for skin pigmentation, hair and eye color. Most humans have about the same amount of melanocytes, some just produce more melanin than others. Albinos, however, produce no melanin at all.

When our skin gets exposed to sunlight (particularly ultraviolet rays) melanocytes begin producing melanin to help protect the dermis, and keep the skin cells from getting fried. The melanin acts as an absorbing agent. So over time, as exposure to the sun continues, more melanin is produced and subsequently the skin becomes darker.

The hair is a different story. Hair color is also determined by melanin, but hair cells are dead, so sunlight doesn’t initiate melanin production but rather begins to break down the melanin already in the hair, and the hair’s color begins to fade or lighten.

Sunglasses may not be so cool: Courtesy Mark Ryan
Sunglasses may not be so cool: Courtesy Mark Ryan

I thought this last part was strange. The pituitary gland is tied to your optic nerve and is sensitive to sunlight. When light enters your eyes, it triggers your pituitary gland to produce a melanocyte-stimulating hormone (MSH) that activates your melanocytes to produce melanin. This means that wearing sunglasses can actually cause sunburn.

Jun
04
2006

A severed spinal cord or damage to the the optic nerve used to be considered irrepairable. Recent developments by researchers from Massachusetts Institute of Technology, University of Hong Kong, and the Fourth Military Medical University,, Xian, China have used a self-assembling peptide scaffold to repair severed brain structures in blind rodents and restore their sight[Ellis-Behnke et al., Proc. Natl. Acad. Sci. USA (2006) 103, 5054].

Injecting a 1% peptide scaffold solution into the gap between severed brain tissue promoted axon regrowth and a closing up of the gap. The self-assembling material biodegrades and does not appear to provoke a significant immune response. A second series of experiments will look at repairing damage due to strokes.

Source: nanotoday