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Welcome to The Visible Embryo, a comprehensive educational resource on human development from conception to birth.

The Visible Embryo provides visual references for changes in fetal development throughout pregnancy and can be navigated via fetal development or maternal changes.

The National Institutes of Child Health and Human Development awarded Phase I and Phase II Small Business Innovative Research Grants to develop The Visible Embryo. Initally designed to evaluate the internet as a teaching tool for first year medical students, The Visible Embryo is linked to over 600 educational institutions and is viewed by more than one million visitors each month.

Today, The Visible Embryo is linked to over 600 educational institutions and is viewed by more than 1 million visitors each month. The field of early embryology has grown to include the identification of the stem cell as not only critical to organogenesis in the embryo, but equally critical to organ function and repair in the adult human. The identification and understanding of genetic malfunction, inflammatory responses, and the progression in chronic disease, begins with a grounding in primary cellular and systemic functions manifested in the study of the early embryo.

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Pregnancy Timeline by SemestersFetal liver is producing blood cellsHead may position into pelvisBrain convolutions beginFull TermWhite fat begins to be madeWhite fat begins to be madeHead may position into pelvisImmune system beginningImmune system beginningPeriod of rapid brain growthBrain convolutions beginLungs begin to produce surfactantSensory brain waves begin to activateSensory brain waves begin to activateInner Ear Bones HardenBone marrow starts making blood cellsBone marrow starts making blood cellsBrown fat surrounds lymphatic systemFetal sexual organs visibleFinger and toe prints appearFinger and toe prints appearHeartbeat can be detectedHeartbeat can be detectedBasic Brain Structure in PlaceThe Appearance of SomitesFirst Detectable Brain WavesA Four Chambered HeartBeginning Cerebral HemispheresFemale Reproductive SystemEnd of Embryonic PeriodEnd of Embryonic PeriodFirst Thin Layer of Skin AppearsThird TrimesterSecond TrimesterFirst TrimesterFertilizationDevelopmental Timeline
CLICK ON weeks 0 - 40 and follow along every 2 weeks of fetal development
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Home | Pregnancy Timeline | News Alerts |News Archive Aug 12, 2014

Artificially created sugar chains are inserted into mouse embryonic stem cells with the resulting
stem cells transforminng into neural rosettes — precursors to many types of mature neural cells


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Sugar chains guide stem cells to a neural fate

Embryonic stem cells can develop into a multitude of cells types. The key to this may be the long sugar chains dangling from proteins on the surfaces of cells.

Researchers would like to understand how to channel stem cell development into specific types of mature cells in order to make specific organ cells or other tissues needed in living organisms.

Kamil Godula's group at the University of California, San Diego, has now created synthetic sugar molecules to take the place of natural sugars found on the surface of cells. These sugar chains assist mature cells in attracting and then differentiating stem cells into their own mature cell type.

Synthetic sugar molecules can therefore be more easily manipulated to direct the process of stem cell differentiation.

Godula's report appears in the Journal of the American Chemical Society.

Natural sugar structures are difficult to manage, so Godula's group strung small sugar fragments together to create synthetic versions of natural sugar chains. They also used these 'glycopolymers' to determine how specific growth factors recognize cell membrane surface sugar chains and then go on to determine stem cell fate.

By tagging individual glycopolymers, Dr. Godula's team were able to identify sugar substructures that had the greatest affinity for fibroblast growth factor 2, a growth factor involved in neural development.

To test their synthetic sugar molecules in a living system, the scientists slipped the sugar molecules into the cell membranes of mouse embryonic stem cells (those that lacked natural sugar chains). Six days later, the manipulated cells transformed into 'neural rosettes' — precursors for many types of mature neural cells.

Untreated cells did not transform.

Godula's group is working on a number of similar 'hand made' molecular sugars to explore a variety of developmental pathways.

Growth factor (GF) signaling is a key determinant of stem cell fate. Interactions of GFs with their receptors are often mediated by heparan sulfate proteoglycans (HSPGs). Here, we report a cell surface engineering strategy that exploits the function of HSPGs to promote differentiation in embryonic stem cells (ESCs). We have generated synthetic neoproteoglycans (neoPGs) with affinity for the fibroblast growth factor 2 (FGF2) and introduced them into plasma membranes of ESCs deficient in HS biosynthesis. There, the neoPGs assumed the function of native HSPGs, rescued FGF2-mediated kinase activity, and promoted neural specification. This glycocalyx remodeling strategy is versatile and may be applicable to other types of differentiation.

Mia Huang, Alex Smith and Greg Trieger, all members of Godula's research group, co-authored the paper. UC San Diego and the National Institute of Biomedical Imaging and Bioengineering supported this work. The synthesis of glycopolymers was carried out, in part, at the Molecular Foundry, Lawrence Berkeley National Laboratory, supported by the Department of Energy's Office of Basic Energy Services.

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