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Posts tagged "developmental biology"


Top 5 misconceptions about evolution: A guide to demystify the foundation of modern biology.

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Human embryo at 7 weeks gestation, measuring approximately 14 mm (crown to rump). the fingers and face are developing and growing rapidly but are still forming their shape. It is possible to clearly see the formation of the skull, which begins to close, which will form the fontanelle (“soft spots”) that subsequently shut as children grow, creating a suture in the skull. This openness facilitates at birth in normal delivery, and allows the growth of the child’s brain.

Photo: Ralph Hutchings/Getty images 


(via afro-dominicano)

The concept of an embryo is a staggering one, and forming an embryo is the hardest thing you will ever do. To become an Embryo, you had to build yourself from a single cell. You had to respire before you had lungs, digest before you had a gut, build bones when you were pulpy, and form orderly arrays of neurons before you knew how to think. One of the critical differences between you and a machine is that a machine is never required to function until after it is built. Every animal has to function even as it builds itself.
 Gilbert, Principles of developmental biology 8th edition (2006)

So remember.. don’t do it! 
(via ikenbot)

(via afro-dominicano)

Men who lose the ability to produce sperm after chemotherapy might one day be able to regain their fertility. That’s because, for the first time, infertility has been reversed in a male primate using an injection of stem cells.

Cancer drugs often work by destroying rapidly dividing cells, as these are a typical feature of cancer. Unfortunately, the drugs can also kill other rapidly dividing cells, including those that produce sperm. Some men choose to freeze sperm samples before therapy so they can use them for artificial insemination at a later date, but this is not an option for boys who have not yet reached puberty.

Kyle Orwig at the University of Pittsburgh School of Medicine in Pennsylvania may have a solution. He says that while boys don’t make sperm cells, they do possess “spermatogonial” stem cells that will eventually produce them.

To see if these stem cells could be used to restore fertility, Orwig and his team took samples of the cells from the testes of prepubescent and adult male rhesus macaques, and froze them. The monkeys were then given chemotherapy agents known to shut down sperm production. A few months later, the researchers injected each monkey’s own spermatogonial stem cells back into its testes.

Sperm production was re-established in nine of the 12 adult animals and started normally in three out of five prepubescent animals once they reached maturity. The resulting sperm were used to fertilise eggs and produce healthy embryos.

“I think this is the best option we have ever had,” says Renee Reijo Pera, director of Stanford University’s Center for Human Embryonic Stem Cell Research and Education, who wasn’t involved in the study. “I know a lot of people have thought about doing this before but no has ever been able to successfully demonstrate this in a clinical setting with a species genetically very similar to us.”

Orwig says there are some concerns that implanting stem cells could reintroduce cancer cells that may have been present in the original tissue. However, centres in the US and Europe are already banking testicular tissue for boys in the hope that new stem cell-based therapies will become available.

“In the most optimistic scenario our research suggests a man could have his own stem cells transplanted, giving him the opportunity to have children via natural intercourse,” Orwig says. It’s not yet ready for clinical translation, he says, “but it’s an important step forward”.

Journal reference: Cell Stem Cell, DOI: 10.1016/j.stem.2012.07.017

(via ohyeahdevelopmentalbiology)

The Cell’s Muscles and Bones

By Torsten Wittmann, UCSF

Cell movement begins with lamellipodia. A thin sheet of actin filaments (light purple) that stretches out to the cell’s periphery, lamellipodia generate pushing forces that drive the cell forward. Microtubules (cyan) can barely penetrate this actin network, but they direct cell motility in other ways, such as controlling cell adhesion and acting as the cell’s internal compass.

Image: A human HaCat keratinocyte responds to epidermal growth factor by rapidly forming a lamellipod around most of its perimeter. The cell was fixed and processed within minutes after EGF addition. F-actin is stained with fluorescently labeled phalloidin (light purple), and microtubules are labeled with an antibody (cyan). DNA dye stains the nucleus dark purple.

(via ohyeahdevelopmentalbiology)

Remember in Jurassic Park when they got dinosaur DNA from an ancient mosquito’s stomach? Well, if they had been interested in dinosaur proteins, they only had to look at a dinosaur bone. 

Dinosaur bones are at least 65 million years old. And all of the meat has turned to stone. Over this amount of time and with this much abuse, scientists thought no DNA or proteins could survive. They were wrong. 

Recently, scientists were able to pull proteins out of a T. rex bone. Now they have done some additional work that suggests dinosaurs are closely related to birds. It is amazing that our technology has become so sensitive that we can examine dinosaur proteins.

Illustration comparing various species’  embryo development.

Illustration comparing various species’  embryo development.

BONE marrow transplants may beat stem-cell injections as a way of increasing the production of blood cells when tissue is from an unrelated donor.

A potential problem of either treatment - used for diseases like sickle cellanaemia - is graft-versus-host disease. This potentially fatal condition occurs when donated blood cells launch an immune attack on the host.

Members of the US Blood and Marrow Transplant Clinical Trials Networkmonitored 273 people receiving donated stem cells and 278 recipients of bone marrow over two years. They found no difference in survival rates. But while those given stem cells produced blood cells more quickly, they also had graft-versus-host disease more often. The findings were presented at the American Society of Haematology Annual Meeting in San Diego this week.

“People tend to favour stem cells because of not having to harvest bone marrow, and quicker engrafting,” says David Marks at the University of Bristol, UK. “We will need to reconsider that choice.”

Alcian blue staining of a whiptail lizard. 

Image(s) by Andrea Wills (2007 Woods Hole Embryology Course) 

About whiptail lizards

(via ohyeahdevelopmentalbiology)