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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
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Home | Pregnancy Timeline | News Alerts |News Archive Oct 28, 2014

Potassium channels are tiny pores that stud the surface of almost all cell types in the body.
The channels aid transmission of signals between brain cells as well as
help control the frequency of our heartbeats.

 







CDC Growth Standards 0 to 2 Years of Age


 

 

'Paradigm shift' explains potassium channels

A new discovery is being described as a 'paradigm shift' in understanding how ions pass through cell walls.

Researchers at the University of Dundee, the Max Planck Institute for Biophysical Chemistry, the University of Göttingen and the University of Oxford have observed how ion permeate through potassium channels and the process does not follow previous predictions.

They have published their research in the journal Science.


Potassium channels are tiny pores that stud the surface of almost all cell types in the human body. The channels aid transmission of signals between brain cells as well as help control the frequency of our heartbeats.

When these channels are not working properly, they are implicated in a range of diseases of the heart and of the neurodegenerative system.

These pores allow potassium ions to pass through the cell wall using extremely rapid-fire 'open and close gates', acting as a highly efficient filtration system.


A previous theory in ion trasmission led to American biochemist Roderick MacKinnon receiving the 2003 Nobel Prize in Chemistry. MacKinnon proposed that ions were separated by water as they passed through these channels and that ion-to-ion contact was unlikely due to high electrostatic repulsion.

MacKinnon's previous research was limited to examining the potassium channels by looking at static or `closed-state' crystal structures. Advances in computing now allow researchers to now look at these channels 'in action' and with much more detail. Therefore, the new research has found a completely different scenario, using advances in technology that reveal fundamental physical principles in potassium channels' operation which here to fore could not be seen.

Computer simulations at the atomic level — including transmembrane voltage — found that water is not transported through potassium channels along with ions, nor is needed to separate potassium ions. Instead, pairs of potassium ions are stably formed and pass through potassium channels with startling efficiency, driven by electrostatic repulsion.


"Our findings explain how potassium flux is able to happen at the maximum physically attainable speed, vital to the fast response of neurons.

"This is a paradigm shift in the field. It changes our understanding of how these hugely important channels work. These channels are tremendously important as they are active in all cells — so it is vital that we understand how they work."

Dr Ulrich Zachariae, Reader in Computational Biophysics and Drug Discovery, the University of Dundee.


Abstract
Potassium channels selectively conduct K+ ions across cellular membranes with extraordinary efficiency. Their selectivity filter exhibits four binding sites with approximately equal electron density in crystal structures with high K+ concentrations, previously thought to reflect a superposition of alternating ion- and water-occupied states. Consequently, cotranslocation of ions with water has become a widely accepted ion conduction mechanism for potassium channels. By analyzing more than 1300 permeation events from molecular dynamics simulations at physiological voltages, we observed instead that permeation occurs via ion-ion contacts between neighboring K+ ions. Coulomb repulsion between adjacent ions is found to be the key to high-efficiency K+ conduction. Crystallographic data are consistent with directly neighboring K+ ions in the selectivity filter, and our model offers an intuitive explanation for the high throughput rates of K+ channels.

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