TeachableMedicalNews article 04052023

Teachable moment in classrooms:

  1. nervous system chapter – axons and synapses as structures of neurons
  2. nervous system chapter – transmission of a nerve impulse using a chemical synapse
  3. nervous system chapter – formation of myelin sheet along axons
  4. cellular basis of life chapter – zinc-finger proteins in gene regulation
  5. endocrine system chapter – protein kinases are important for cellular actions

The news item:  Recently this report appeared:

Freeze-dried blueberries recalled due to potential lead contamination

The voluntary recall covers packages of organic blueberries sold under the brand name Natierra, with expiration dates of December 2022 and January 2025.

The article states that long term exposure to lead in children may affect the central nervous system causing learning disabilities, developmental defects, and in adults causing damage to the nervous system and internal organs.

So, Why Do I Care??  Long term exposure to lead harms about 500,000 children in the USA alone. The consequences last for decades, and can not be undone. It is good to understand why the metal lead poses such severe consequences.

Plain English, Please!!!  First, let’s talk about how lead (Pb in the periodic table) gets into our bodies. Typically, lead comes into our bodies through eating lead-contaminated food or drinking water, because lead compounds are soluble in water. The heavy metal lead has similar chemical properties to the biologically important metal calcium. Because of that similarity the small intestine readily absorbs lead just as it absorbs calcium.

Second, let’s talk about what biological processes are harmed by lead. Once absorbed into the bloodstream the lead ions take the place of the calcium and zinc ions. Here are a few examples. A. Lead kills cells by starting a cell death (apoptosis) program. B. When neurons develop they grow, and build synapses, that building program is directed by zinc-finger proteins in the nucleus, and carried out by dozens of calcium-binding protein kinases in the cytoplasm. Lead slows down those processes. C. When neurons want to pass on a nerve impulse through a synapse, calcium-channels are part of that process. Lead moving through the calcium-channels alters the release of neurotransmitters from the synapse.

Third, let’s talk about why the nervous system of children is especially vulnerable to lead poisoning. During early childhood and even during fetal development billions of neurons build out the interconnected network of the nervous system. The proper working of those neurons depends on the ability to grow in length, to make synapses for communication, and to release neurotransmitters from the synapses. In addition, special cells form an insulating layer around the axons of neurons, and this insulation, the myelin, speeds up the flow of nerve impulses. Because the presence of lead impairs all those processes, the nervous system doesn’t develop properly, and doesn’t move nerve impulses fast enough for normal operation. The end result is lower reaction time, lower processing speed and cognitive functions. These harmful results happen after long-term (chronic) exposure to lead.  That is why decreasing or shortening exposure to lead (such as recalling lead-contaminated fruit) is a normal part of fighting against lead poisoning.

Go back

Your message has been sent