June 29, 2018 | David F. Coppedge

What Your Cells Do For You

Until recently, we humans had no idea the complexity of the systems that keep us alive.

Nature creates its own plaster to protect wounds from infection (Medical Xpress). A cut in the skin can start a deadly infection if not closed quickly. This article explains how the body makes a temporary plaster cast of fibrin molecules that coil around red blood cells to seal off a wound quickly before reconstruction of the tissue begins.

Scientists have found that a protein film forms rapidly over a wound as part of the natural clotting process, and it provides protection for at least 12 hours.

They believe this bio-film gives the immune system time to marshal its defences to deal with any infection.

‘Walking molecules” haul away damaged DNA to the cell’s emergency room (Phys.org). Emergency room? Walking molecules? Yes; the emergency room for damaged DNA is right at the nuclear pore, a very complex gateway to the nucleus (see it described on Evolution News). Myosin motors are the walking molecules that carry broken DNA to these locations for repair. The language of the article is intelligently designed to help readers relate to other things they know are intelligently designed: emergency health systems.

The scientists found that after the DNA strands are broken, the cell prompts a series of threads— nuclear actin filaments— to assemble and create a temporary highway to the edge of the nucleus. Then come the paramedics—proteins known as myosins.

“Myosins are conveyed as a walking molecule because they have two legs. One is attached and the other moves. It’s like a molecular machine that walks along the filaments.”

The myosins pick up the injured DNA, walk along the filament road and then reach the emergency room, a pore at the periphery of the nucleus.

“We knew, based on our prior study, that there was an emergency room—the nuclear pore where the cell fixes its broken DNA strands. Now, we have discovered how the damaged DNA travels there” Chiolo said. “What we think is happening here is that the damage triggers a defense mechanism that quickly builds the road, the actin filament, while also turning on an ambulance, the myosin.”

Developmental Biology: Neurons That Divide Together Wire Together (Current Biology). Are home theater systems intelligently designed? If so, you can understand the analogy made by two writers for this dispatch about biological networks of neurons.

If you have ever assembled an elaborate home entertainment system, you are likely familiar with how challenging it can be not only to plug all of the wiring into the correct ports, but also to make sure that the setup is space-efficient, modular, and reproducible. Yet this task is analogous to a problem all developing nervous systems must solve on a much larger scale: the adult human central nervous system, for example, is estimated to have hundreds of trillions of synapses. What developmental strategies do nervous systems use to wire complex circuits? A recent study by Pinto-Teixeira et al., along with two related studies, illustrates how simple developmental processes can be combined to produce, differentiate, and wire a large population of neurons with complex synaptic connections ….

The word “simple” must be taken in context. No neuron is simple! Neurons are loaded with complex specified information, molecular machines and hierarchical networks. Neurons are made in such a way, though, where they can connect to other neurons quickly and easily. That may sound “simple,” but how do neurons know where to connect? In your home entertainment system, you can’t just connect wires at random! Examining the process in a human eye or brain would be too challenging, so these scientists looked to the humble fruit fly to attempt to get their minds around neural network construction.

How do T4 and T5 neurons find their targets within the retinotopic map? On the basis of both clonal analysis and live imaging of developing neurons, Pinto-Teixeira et al. suggest that birth location and timing are critical for targeting T4 and T5 dendrites and axons to the appropriate retinotopic map positions. The relative birth positions of T4 and T5 correlate with the dorsoventral organization of their projections, whereas birth timing correlates with anteroposterior organization. Posterior visual fields map onto earlier-born T4 and T5 neurons, while anterior visual fields map onto later-born T4 and T5 neurons. Critically, the columnar neurons in the medulla that define the retinotopic array display the same correlation between birth timing and anteroposterior organization. These observations suggest that, as T4 and T5 neurons are born, they target the most recently-born upstream columns. Taken together, this combination of birth location and timing, as well as the shared lineage of T4 and T5 subtypes receiving signals from the same point in visual space, form a complement of simple developmental strategies that solve a complex wiring problem.

Got that? Don’t worry; it won’t be on the test. There will just be one question: “True or false: fruit fly retinotopic map networks illustrate intelligent design.”

Have you thanked your Maker yet today? Now you have some specific things you can praise Him for.



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