More Wonders to Be Thankful For

Deer Ears

Read and be awestruck

by David F. Coppedge

If you can hear, praise God and don’t take it for granted. This quote is hard to understand, but we give you just a small taste of what is involved in hearing to arouse awe. Read the rest of the open-access paper if you dare.

Cochlear outer hair cell horizontal top connectors mediate mature stereocilia bundle mechanics (Science Advances).

Sensory hair cells of the inner ear are active mechanosensitive machines that transform sound-induced mechanical vibrations into electrical signals. The sensory epithelium of the cochlea, the organ of Corti, has two types of sensory hair cells, the inner and outer hair cells (IHCs and OHCs, respectively). IHCs are genuine sensory cells that transmit information via the cochlear nerve fibers to the brainstem auditory nuclei. In contrast, OHCs, which are endowed with electromotility, constitute the cochlear amplifiers that contribute to the detection of weak sound-induced vibrations. The organ of Corti sensory epithelium is positionedbetween a sheet of paucicellular connective tissue, the basilar membrane, and an acellular gel, the tectorial membrane (TM). Sound-induced vibrations of the basilar and tectorial membranes stimulate the mechanosensitive sensory cells’ stereocilia bundles. The mammalian stereocilia hair bundles of OHCs are arranged in three rows of graded height and are tightly interconnected….

Tissue self-organization based on collective cell migration by contact activation of locomotion and chemotaxis (PNAS). Do you take tissues for granted? We have skin, muscle, bone, and numerous other cell types that bind together into coherent organs with vital functions. But how do they come together in the embryo? How does an individual cell know where to go? These scientists had trouble figuring that out in an amoeba! How much more difficult would it be to explain in the human body? It must be much more complex than simple cell-cell contact. How do cells form tubes, as in the blood vessels and digestive tract? How do particular organs within tissues form, like hair follicles?

Migration of cells as a group is pivotal to the making of various tissues in developing embryos; however, their complexity hinders one from identifying the exact rules. We exploited relatively simple and conditional multicellularity of the social amoeba Dictyostelium to analyze tissue patterning from bottom up by identifying the navigation rules at the individual cell level.We uncovered a guidance mechanism directed by cell–cell contact which gives rise to collective migration and competes with diffusive attractant molecules. Competition of the two directional cues forms the basis of how cells position themselves in the multicellular aggregate according to cell type.

Once seen as nerve cells’ foot soldier, the axon emerges as decision-maker (Science Daily). Even cells that didn’t seem that important are turning out, under more investigation, to be “smarter” than scientists thought. “As far as cells go, neurons are pretty weird,” Harvard neurologists remarked. Here’s why they were surprised at what they found. Think of a complex military system…

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image credit: Magda Ehlers