Posts Tagged ‘embryo’

The electric, flashy development of tadpoles

// July 22nd, 2011 // 1 Comment » // Recent Research

Tufts researcher Dany Adams was filming the development of tadpole embryos, when she decided to leave the camera hooked up to a microscope going overnight. She was hoping to get some good time-lapse footage. What she got was bioelectric patterns which flashed across the developing tadpole face, outlining the future positions of eyes, nose and mouth.

“I was completely blown away.” said Dany, Ph.D, according to the Tufts press release. “I think I thought something like, ‘OK, I know what I’ll be studying for the next 20 years.” It had never been seen before, and was published in the August issue of Developmental Dynamics. Watch the video below.

“When a frog embryo is just developing, before it gets a face, a pattern for that face lights up on the surface of the embryo,” said Dany. “We believe this is the first time such patterning has been reported for an entire structure, not just for a single organ. I would never have predicted anything like it. It’s a jaw dropper.”

Bioelectric signals cause cells to form patterns marked by differences in pH levels and membrane voltage, according to the researchers. The tadpoles were stained with a reporter dye that caused negatively charged areas to shine brightly while other areas look dark.

There were three bioelectric waves they saw in the footage.

xenopus

It's Xenopus! Image by Luis Beltran

First, a wave of negative ions flashed across the whole embryo at about the same time as cilia formed, tiny hairs which allow the embryo to move.

The second flash was a patterning that matched shape changes that were soon to occur in the face region. Bright areas, negative ions, show places where the surface will fold in.

Thirdly, localised regions of bright, negative areas formed, grew and disappeared without disturbing the existing pattern. At this point, the embryo began to elongate.

If bioelectric signalling is important to embryo development, you would expect development to be altered by screwing around with the signal process – and that’s exactly what happened. The researchers disrupted signalling by inhibiting a protein involved called ductin, which transports hydrogen ions. Some embryos grew two brains, others had unusual nasal or jaw development, and so on.

Interesting, I guess, but a bit sad for the baby tadpoles imho. Plus, I feel like it doesn’t take much to disrupt embryo development. Take away any protein that’s switched on at that sensitive time and development takes a detour…

All the same, bioelectricity may play a crucial role in embryo growth. Laura Vandenberg, another author on the paper, said “developmental biologists are used to thinking of sequences in which a gene produces a protein product that in turn ultimately leads to development of an eye or a mouth. But our work suggests that something else – a bioelectrical signal – is required before that can happen.”

ResearchBlogging.org

Vandenberg, L., Morrie, R., & Adams, D. (2011). V-ATPase-dependent ectodermal voltage and ph regionalization are required for craniofacial morphogenesis Developmental Dynamics, 240 (8), 1889-1904 DOI: 10.1002/dvdy.22685

Super cute kittens conceived by science

// March 18th, 2011 // 2 Comments » // Recent Research, Sex and Reproduction

african black-footed kitten

African black-footed kitten conceived by IVF

This little kitty is a rare African black-footed cat conceived through IVF in an attempt to keep the species alive.

About 40 of these cats live in zoos worldwide, while a few wild cats live in South Africa where they are protected, but sometimes poisoned and killed by farmers.

How could you poison these little kittens, they’re so CUTE!!! Ahem. So, I have been visiting Zooborns again, it’s a serious habit.

Let’s pretend this post is about something more than just cute pictures of cats, and talk about the science that conceived them.

Audubon Center for Research of Endangered Species aim to protect seriously endangered species by creating a “frozen zoo”, banking genetic material such as eggs, sperm, embryos and tissue samples. Frozen, thawed sperm and IVF technology sparked the life of these kittens, which were really conceived six years ago and frozen as embryos.

The embryos were thawed and implanted into the surrogate mother Bijou in December last year.

african black-footed cat

Man, what did I DO last night?

It must be a bizarre experience for the mother, although I’ve heard tomcats have a barbed penis so perhaps she’s lucky to have skipped the usual event.

The frozen zoo contains frozen semen from the gorilla, Sumatran tiger, jaguar, Jabiru stork, and caracal. Other cell samples cover the African and Asian elephants, Baird’s tapir, colobus monkey, roan antelope, and black bear.

“The next step for us will be to clone the black-footed cat and transfer the embryo to a domestic cat surrogate,” said Audubon Center for Research of Endangered Species Senior Scientist Dr. C. Earle Pope in the media release.

Cloning endangered species, is that a good idea or not? I can’t tell.

Science that’s only skin deep

// December 3rd, 2010 // 2 Comments » // How Things Work, Recent Research, Science Communication, Sex and Reproduction

I’m a guest blogger for the RiAus, and this post also appeared on their fancy website. To tell the truth, I really wanted to call this post “Hormonally Yours” in homage to the Shakespeare Sisters (anyone?) but I’ll save it for another post.

Recently I was in Arnhem Land, visiting some Indigenous communities with a couple of friends. While I was there, I got pretty jealous of everybody’s darker skin. “It’s so well suited for Australia,” one of my friends lamented. “I should be in Norway or something.”

Pale skin like mine is not great for Australia. I tan pretty easily, but only after being burned bright red. While I was in the NT I slathered sunscreen religiously, but still managed to get a highly embarrassing burn on my lower back when I was building a sandcastle (an epic sand turtle, actually. Totally worth it.)

Anyway, enough about me and my weirdly tanned lower back (it’s been months! Why won’t it go away?) Let’s talk about Nina Jablonski, an anthropologist. In 2000 she suggested a new reason why skin colour varies so much. It’s not an adaptation to protect against skin cancer and sunburn, like I always thought it was.

It’s real job is to keep us highly fertile by maintaining a delicate balance between two key vitamins: Vitamin D and Folic acid.

Pica's skin tone matched her UVB exposure like her scarf matched her dress. Image by Monja Con Patines

Vitamin D is obtained through some foods, but mostly from drinking in sunshine. UV light turns cholesterol into Vitamin D, which then goes to either your liver or kidneys to be converted to an active form.

Once active it helps white blood cells like macrophages kill bacteria, and helps control levels of calcium and phosphate – important for building healthy bones.

Deficiency in Vitamin D causes rickets, a disease resulting in soft, easily broken bones and deformity which can lead to early death.

So getting enough UV (specifically UVB light) is important to not dying, and therefore having reproductive success later in life. It’s been backed up by Yuen, A. (Vitamin D: In the evolution of human skin colour DOI: 10.1016/j.mehy.2009.08.007)

Natural selection favours soaking up UV.

Penny stayed under foliage at noon to protect her folic acid. Image by Monja Con Patines

Folic acid is obtained in leafy vegetables and fortified cereals. Rather than being made by UV, the light can destroy folic acid by literally breaking it apart. (Jablonski, N. The evolution of human skin coloration DOI: 10.1006/jhev.2000.0403)

Critical for DNA synthesis, folic acid is essential during pregnancy when a lot of new cells are being made.

Folic acid prevents against 70% of neural tube defects in embryos. Its destruction by UV is bad news.

Natural selection favours avoiding UV.

So there’s an ideal amount of UV light that needs to get through the skin – enough to produce Vitamin D, but not too much to destroy all the folic acid. Getting the balance right for the environment you’re in means higher fertility, which drives natural selection

This is what Nina Jablonski thinks caused the evolution of skin colour through the sepia spectrum we see today. Dark skin, with high melanin, stops more UV light. That’s exactly what you want if you live in a place with a lot of sun, like places near the equator. Light skin lets more UV in, which is great if you live somewhere overcast and not very high on UV.

Understanding how your skin colour (NOT your race) influences these two vitamins is important in being healthy. It’s more important now than ever, because we humans travel a LOT.

Sadly, Australia is pretty high in UV and I am pretty white. Thank god for sunscreen.

Things are rarely that simple though, and I imagine there’s a few different things going on that connect UV light to skin colour.

On Tuesday the RiAus is holding an event called Skin Deep: Exploring human ancestry. They’ll be showing a preview of a new SBS documentary about skin colour scientific research, as well as results from the Genographic Project. Basically they took DNA samples from a lot of volunteers and some national identities, and now they’re giving us the goss on who’s related to who’s secret love child.

I’ll be there, I’d love to see you (though seats are limited.) I’ll be the one tweeting in the corner. Follow me @CaptainSkellett

Would love to hear from anyone who took part in the Genographic Project, and anyone who didn’t. Who would you most like to be related to? For me it’s David Attenborough, then I can dream of inheriting his voice.






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