class 7

Question 1

What historical figure is associated with symptoms caused by mercury exposure in the hat-making industry?

Answer 1

The “Mad Hatter” character from Lewis Carroll’s “Alice’s Adventures in Wonderland” is associated with symptoms such as tremors and hallucinations, known as “Mad Hatter’s disease,” caused by mercury nitrate used in the felting process.

Question 2

What are the primary forms of mercury in the environment, and how is methylmercury formed?

Answer 2

Mercury exists in several forms: elemental (Hg⁰), inorganic (Hg²⁺ and Hg⁺), and organic (methylmercury, MeHg). Methylmercury is formed when mercury is converted by microorganisms in water bodies.

Question 3

How does methylmercury enter and biomagnify in the food chain?

Answer 3

Methylmercury enters the aquatic food chain, starting with phytoplankton, and biomagnifies at each trophic level, leading to the highest concentrations in top predators like large fish.

Question 4

What is the mechanism by which methylmercury is absorbed and distributed in the human body?

Answer 4

Methylmercury is well absorbed from the gastrointestinal tract (estimated at 95% from fish), distributed to all tissues, including the brain, and accumulates in hair. It’s primarily excreted through feces.

Question 5

Explain how methylmercury uses cysteine to cross the blood-brain barrier.

Answer 5

Methylmercury binds to the amino acid cysteine, forming a complex that mimics methionine. This allows it to trick transport systems, like the LAT1 transporter, to cross the blood-brain barrier and enter the brain.
methylmercury has a clever trick. It puts on a disguise by grabbing onto a helper named cysteine, which normally gets a free pass into the brain because it’s good for you. When methylmercury holds onto cysteine, it looks just like another good guy the brain needs, so the guard lets it through the gate.

Question 6

Describe the role of oxidative stress in methylmercury-induced neurotoxicity.

Answer 6

Methylmercury induces oxidative stress by binding to glutathione (GSH), impairing its antioxidant function, and interfering with the mitochondrial respiratory chain, leading to increased production of reactive oxygen species (ROS) and cellular damage.

Question 7

How does methylmercury exposure affect motor performance and oxidative stress in the brain?

Answer 7

Methylmercury preferentially targets the cerebellum, leading to motor performance deficits and increased oxidative stress, which may explain the observed impairments in individuals with methylmercury poisoning.

Question 8

What effects does methylmercury have on brain development, particularly in fetal exposure?

Answer 8

Methylmercury crosses the placental barrier, affecting fetal brain development even at low levels, leading to decreased IQ, impaired movements, visuospatial perception deficits, and speech impairments, known as Fetal Minamata disease.

Question 9

How does methylmercury disrupt neuronal migration during brain development?

Answer 9

Methylmercury may bind to proteins crucial for neuronal structure and movement, such as actin and cell adhesion molecules (CAMs), disrupting the neuronal migration process essential for proper circuit formation and leading to cognitive and movement impairments.

Question 10

What strategies have shown potential in counteracting the negative effects of methylmercury exposure?

Answer 10

Consumption of fruits rich in antioxidants, such as acai, has shown potential in counteracting the negative effects of methylmercury exposure by reducing oxidative stress and improving motor performance.

Question 11

What caused “Mad Hatter’s disease” in the hat-making industry?

Answer 11

Hat makers were exposed to mercury, which caused symptoms like shaking and hallucinations.

Question 12

What happens to mercury when it gets into water bodies?

Answer 12

Tiny organisms in water turn mercury into methylmercury, a toxic form that builds up in fish.

Question 13

How does methylmercury move up the food chain?

Answer 13

It starts in small water plants and moves up to big fish and animals, getting more concentrated at each step.

Question 14

How does our body deal with methylmercury from fish?

Answer 14

Our stomach absorbs almost all of it, it spreads through our body, and can even get into our brain. It mostly leaves our body through poop.

Question 15

How does methylmercury trick its way into the brain?

Answer 15

It attaches to a protein called cysteine, disguising itself as something the brain needs, so it gets let in.

Question 16

What does methylmercury do to the brain’s defense system?

Answer 16

It grabs onto the brain’s cleanup crew, glutathione, stopping it from getting rid of harmful substances.

Question 17

Why is methylmercury bad for our brain cells?

Answer 17

It creates too many harmful oxygen particles that damage cells, a bit like rusting metal.

Question 18

How does methylmercury exposure affect movement?

Answer 18

It damages the part of the brain that helps control movement, leading to problems like clumsiness.

Question 19

What’s so bad about babies being exposed to methylmercury?

Answer 19

It can harm the developing brain, leading to problems with IQ, movement, seeing shapes, and talking.

Question 20

Can eating certain foods help against mercury damage?

Answer 20

Yes, foods high in antioxidants, like acai berries, can fight the damage mercury causes in the brain.

Question 21

Why is mercury used in gold mining, and what environmental problem does this cause?

Answer 21

Mercury is used to extract gold from ore because it binds to gold, forming an amalgam. This causes environmental problems when mercury vapor is released into the air or when liquid mercury enters waterways, leading to contamination and toxic exposure for wildlife and humans.

Question 22

How does methylmercury affect pregnant individuals and their unborn children differently from others?

Answer 22

Methylmercury crosses the placenta and can harm the developing brain of the fetus, leading to more severe and lasting impacts than in adults, including lower IQ and developmental delays, even at lower exposure levels.

Question 23

What is “Minamata disease,” and how did it reveal the dangers of methylmercury?

Answer 23

Minamata disease is a neurological syndrome caused by severe mercury poisoning, identified in Minamata, Japan, where industrial wastewater contaminated local seafood. It highlighted the toxic effects of methylmercury on humans, especially the devastating impact on fetal brain development.

Question 24

Explain the global mercury cycle and why mercury pollution is a worldwide concern.

Answer 24

The global mercury cycle describes how mercury moves through the environment, from air to water to living organisms. It’s a concern because mercury released in one place can travel long distances through the atmosphere, contaminating areas far from the original source and affecting global health and ecosystems.

Question 25

How does methylmercury’s mimicry of the amino acid methionine allow it to enter the brain, and what are the consequences?

Answer 25

Methylmercury binds to cysteine, mimicking methionine, which tricks transporters into allowing it into the brain. This leads to neurological damage by disrupting protein function, increasing oxidative stress, and impairing neurodevelopment.

Question 26

bioaccumulation &
biomagnification

Answer 26

Bioaccumulation
Imagine you have a piggy bank, and every day you add one coin to it. Over time, those coins start to add up, right? Bioaccumulation is similar but with chemicals in living things. For example, a fish in a polluted lake might absorb harmful chemicals from the water. Every day, it takes in a little more, and since it can’t get rid of these chemicals very well, they start to build up in its body over time. Just like the coins in the piggy bank, these chemicals accumulate, which can be harmful to the fish.

Biomagnification
Now, let’s say you have several piggy banks, each one inside a larger one. You start by putting coins in the smallest piggy bank. Then, when it’s full, you put it into a slightly larger piggy bank, and start filling that one. Each level represents a step up the food chain. Biomagnification happens when the chemicals that have bioaccumulated in the smaller creatures become even more concentrated as bigger creatures eat them. So, if a small fish has a lot of a chemical in its body, and a bigger fish eats lots of small fish, that bigger fish will end up with even more of the chemical in its body. This process continues up the food chain, so the top predators end up with the highest concentration of harmful chemicals.

Question 27

how is mercury excreted from the body

Answer 27

just feces

Question 28

how does methylmercury get into the brain

Answer 28

Transporter = large neutral amino
acid transporter 1 (LAT1) - transports
essential amino acids across cell
membranes, including BBB
Also found on placental barrier

Question 29

cysteine

Answer 29

plays a key
role in maintaining a protein’s
shape & function

Question 30

GSH =

Answer 30

One of the most important antioxidants in
our cells. very good at finding free radicals &
neutralizing them, protecting the cells from damage

Question 31

oxidative stress

Answer 31

Oxidative stress happens when there are too many free radicals and not enough antioxidants to neutralize them. Just like too much garbage in the streets can cause problems in a city, too many free radicals in your body can damage cells, proteins, and even your DNA. This can lead to health issues over time, like aging faster or being more prone to diseases.

Question 32

Free Radicals =

Answer 32

unstable molecules that can
damage cell parts, much like rust can damage
metal

Question 33

One of the most important antioxidants in our cells is
called:

Answer 33

GSH

Question 34

So MeHg can increase oxidative stress by (i)
forming the :

Answer 34

GSH-MeHg complex

Question 35

MeHg can also (ii) increase the production of ROS
by interfering with the….

Answer 35

mitochondria respiratory
chain

Question 36

It appears that one area of the brain
the MeHg seems to preferentially
target is the…

Answer 36

cerebellum

Question 37

how is MeHg disrupting migration

Answer 37

unclear but it appears that it might bind to
proteins in
(1) The cytoskeleton (i.e., Actin)
Protein crucial for the structure & movement of
neurons
MeHg disrupts structural framework (i.e.,
actin) necessary for neuronal movement
(2) Cell Adhesion Molecules (CAMS)
Ex. N-cadherin important for cell-cell adhesion
MeHg exposure can alter expression or
function of N-cadherin, leading to
inadequate adhesion & impaired migration