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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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patients obtain reliable information on high-quality clinical trials. Now you can go to one website and search all registers to identify clinical trial research underway around the world!




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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 Feb 24, 2014


Progesterone and other fatty signaling molecules are critical for sperm fertility.

Image Credit: C. Cain


WHO Child Growth Charts




The secret life of fertile sperm

Just announced findings could lead to new diagnostic tests and treatments for male infertility.

To better understand the causes of male infertility, researchers at the University of California at San Francisco (UCSF) are exploring both physiologic and biochemical factors that differentiate fertile sperm from infertile sperm.

At the 58th Annual Biophysical Society Meeting, held Feb. 15-19, 2014, in San Francisco, Calif., the team presented its work to identify and characterize proteins — known as ion channels — which are crucial for sperm fertility and are expressed in a sperm cell's outer membrane.

"Any knowledge gained in this area may help create much-needed diagnostic testing and treatments for male infertility, which is in essence an idiopathic (of unknown cause and appearing spontaneously) disease. At this time 80 percent of male infertility cases can't be diagnosed or treated," said Melissa Miller, a postdoctoral fellow who presented the team's findings. Miller works in the labs of both of her co-authors, Polina Lishko of the University of California, Berkeley (UCB), and Yuriy Kirichok at the University of California, San Francisco (UCSF).

To study ion channels, researchers are recording the electrical activity of sperm ions.

"Our labs have characterized three ion channels responsible for sperm regulation (1) calcium (CatSper), (2) potassium (Slo1), and (3) protons (Hv1) within sperm cells.

So far, the most studied is the CatSper channel, which is exclusively expressed within sperm cells and may represent an ideal target for a unisex contraceptive; no other cell in the body is known to express this protein."

"We recently reported that the female hormone progesterone activates CatSper via a non-gene pathway. In normal fertile sperm, CatSper activity was greatly increased by adding progesterone. Patch clamp recording of patient-derived sperm cells — with CatSper deleted — showed no response to progesterone nor did they produce a basal CatSper current.

"This shows that there is direct regulation of the CatSper channel in human sperm by steroid hormones."

Melissa Miller, postdoctoral fellow, University of California, San Francisco (UCSF).

Steroid hormones can control fundamental physiologic functions through both traditional gene pathways, as well as through nongenomic pathways.

Previous research established that nongene signals plays a vital role in both activating human sperm cells and pain perception within neurons of the spinal cord.

Because the molecular determinantion of this pathway is poorly understood, Miller's team is working to uncover the precise molecular signals that occur between sperm cells and neurons under the influence of progesterone.

"The lack of CatSper activity is strongly related to male infertility, so identification of this self-generated molecular signal would give us a new marker for male infertility. Then we could immediately use this information in the clinic to quickly assess the potential for fertilization by this individual."

Melissa Miller, postdoctoral fellow, University of California, San Francisco (UCSF).

The knowledge gained from the team's work may be used in the future development of new pain management therapies, in addition to being used in diagnostic tests and treatments for male infertility.

The presentation "Regulation of CatSper Channel through Non-conventional Lipid Signaling" by Melissa R. Miller, Yuriy Kirichok and Polina Lishko was presented on February 18, 2014 in San Francisco's Moscone Convention Center.

The sperm-specific cation channel, CatSper, regulates intracellular calcium levels and is crucial for male fertility, both in mice and humans. CatSper triggers hyperactivation, a type of inducible motility that enables sperm to penetrate the egg's protective vestments. For this motility change, human CatSper requires elevation of intracellular pH with simultaneous extracellular stimulation by progesterone which sperm encounter during their journey to the oocyte. In the absence of these stimuli, CatSper retains some basal activity which can be reversibly inhibited by mild lipid extraction. Here we report that basal CatSper activity, as recorded using whole-cell patch clamp technique from mature human spermatozoa, requires a lipid signaling molecule produced within the sperm plasma membrane. Furthermore, treatment with the female hormone progesterone up-regulates the production of this lipophilic signal. Development of a novel lipid extraction technique has provided a method for concentration, isolation, and identification of this lipid signaling molecule providing a better understanding of the lipidic pathways regulating male fertility in humans.

Each year, the Biophysical Society Annual Meeting brings together more than 7,000 researchers working in the multidisciplinary fields representing biophysics. With more than 4,200 poster presentations, over 200 exhibits, and more than 20 symposia, the BPS Annual Meeting is the largest meeting of biophysicists in the world. Despite its size, the meeting retains its small-meeting flavor through its subgroup symposia, platform sessions, social activities, and committee programs.

The 58th Annual Meeting will be held at the Moscone Convention Center, 747 Howard Street, San Francisco, California.

The Biophysical Society invites professional journalists, freelance science writers and public information officers to attend its Annual Meeting free of charge. For press registration, contact Alisha Yocum at ayocum@biophysics.org or Jason Bardi at 240-535-4954.