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Showing posts with label News. Show all posts
Showing posts with label News. Show all posts

Friday, 19 July 2019

The genes for developing cephalopod eyes are the same as those forming our legs

The squid totam, the species involved in the study. | Laptew Productions

Scientists presented the results of evolutionary analysis of genes responsible for eye formation in cephalopods. They have shown that they are present in humans, but with a totally different role.

Cephalopods are a class of molluscs that includes marine animals with tentacles such as octopus, squid or cuttlefish. Compared to vertebrates, they have evolved closely. Some of their organs such as the brain or the eyes have developed with such complexity that many scientists are still trying to understand the mechanisms behind this unique evolutionary mystery in these invertebrates.

A team of biologists presented at a meeting, the results of their study on the eyes of cephalopods, which also have a lens whose role is to do the tuning (accommodation), as in humans. This allows them to benefit from excellent vision.

The researchers worked on totam ( Doryteuthis pealeii ) squid embryos and examined which genes are responsible for the first stages of eye formation, and when and under what circumstances they activate or deactivate. After comparing with vertebrate genes, biologists have found that the genes involved in the early stages of lower limb formation are the same as those related to cephalopod eye development.

And yet the formation of these two parts of the body is not identical, and these genes play no role for the eyes of vertebrates, whose development takes place differently.

During lens formation in cephalopods, long membranes emerge to allow overlapping of eye cells and form the typical sphere of the lens, while in vertebrates, degraded cells are kept compacted by a specific protein.

The astonishment of the researchers was considerable during this discovery. To confirm this, they administered small squids of WNT, a well-known protein in developmental biology. The latter naturally stops certain processes of organ formation, including those involved in the formation of the lower limbs, by inhibiting the expression of these genes. They then found that the lens was no longer formed, proving that the genes involved in its formation are the same as those involved in the development of lower limbs in humans.

The group is continuing its research to discover other possible similarities between cephalopods and vertebrates. The next step is to understand the role of each of these genes in the formation of cephalopod eyes.


Monday, 15 July 2019

Contact lenses in the shower: a Britisher becomes blind

The daily shower is usually a relaxing time without risk for most people. But for contact lens wearers, it may be different. This is particularly the case for a 29-year-old British girl who regularly showered while keeping his lenses, until this practice causes the infection of his right eye, leaving him one-eyed, despite the treatments and operations performed thereafter.

Nick Humphreys, 29, of Shropshire, England, usually keeps his contact lenses in the shower, unaware that this practice can increase the risk of eye infections. In 2018, he contracted keratitis in Acanthamoeba , a rare parasitic infection of the cornea. " If I had known how dangerous it was to wear contact lenses in the shower, I would never have asked my doctor, " says Humphreys.

Contact lenses and water: a higher risk of eye infection

The Acanthamoeba is a unicellular amoeba commonly found in water, soil and air, according to the Control Center for Disease Prevention (CDC). Lentil wearers are at risk of contracting this infection if they adopt certain practices, such as cleaning lenses with tap water, swimming or showering while keeping their lenses.

Acanthamoeba observed under a microscope. It exists in two forms: active (left) and dormant (right). Credits: Wikimedia

This amoeba has a particular affinity for contact lens surfaces, which means that lenses can be " a vehicle for hosting and transmitting microorganisms to the eye, " write the authors of a 2010 article. on the subject published in the journal Journal of Optometry .

But when Humphreys started wearing lenses in 2013 to be able to play sports without glasses, he was not aware of this risk in the shower. He often took a shower with his contact lenses after a morning workout. " I did not think about it at the time. I was never told not to wear contact lenses in the shower. There is no warning on the packaging, and my opticians have never mentioned a risk.

From infectious keratitis to blindness

After being diagnosed with Acanthamoeba keratitis in early 2018, eye drops were given to him for the infection, but a few months later, he suddenly became blind in the right eye. He was then prescribed a more powerful medicine, which had to be applied to his eyes every hour, even at night. Humphreys remained confined to his home and felt intense pain in his right eye.

"My eyes hurt too much and the only time I left was to go to the hospital ." He later underwent two operations of the right eye, the first to strengthen the tissues of the cornea and the second to protect the cornea with a tissue transplant from a fetal placenta. This procedure is known as amniotic membrane grafting. Although his infection is resolved, Humphreys remains blind in the right eye.

He should have a cornea transplant in August. This operation replaces damaged corneal tissue with healthy corneal tissue from a deceased donor. Humphreys is now working with the charity Fight for Sighth to raise awareness of the risks of showering or swimming with contact lenses. " It's crucial that people know that this is a reality and that it can happen because of something as simple as taking a shower, " concludes Humphreys.


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