Toxicology of Aquatic Contaminants

A potent toxin produced by phytoplankton (Gambierdiscus toxicus) that accumulates in large reef fish like barracuda, grouper, and snapper. It's not destroyed by cooking and causes ciguatera, a common fish-borne illness.

Ciguatoxin accumulates in the fat, head, viscera, and eggs of fish. It's not destroyed by cooking.

Ciguatoxin is first metabolized by enzymes in the liver (CYP3A4) within 24 hours of exposure. After 24 hours, other enzymes (CYP4 family members) are activated to help breakdown the toxin. Finally, glutathione conjugation further detoxifies the toxin.

Saxitoxin is a neurotoxin produced by certain phytoplankton (Alexandrium species). It gets into shellfish through filter feeding. This toxin is water-soluble and not destroyed by cooking.

Saxitoxin poisoning is caused by eating contaminated shellfish like mussels, clams, oysters, and scallops. This toxin can cause paralytic shellfish poisoning (PSP).

Saxitoxin is believed to be poorly metabolized by mammals. The intact toxin has been found in the liver, spleen, and brain of mammals exposed to it.

Tetrodotoxin, a very potent toxin, is found in pufferfish, blue-ringed octopus, and some newts and frogs. Its origin is unknown, but it might be produced by bacteria. It's water-soluble and heat stable.

Tetrodotoxin can cause death within 17 minutes of exposure. It primarily affects cardiovascular and respiratory systems. However, the exact metabolic pathway of Tetrodotoxin in humans is still unknown.

The movement of an electrical signal along a neuron, allowing communication between nerve cells.

A crucial protein embedded in the neuron's membrane that controls the flow of sodium ions (Na+) into the cell.

A type of seafood toxin that blocks the action of voltage-gated sodium channels, preventing nerve signals from being transmitted.

The state where the membrane potential of a neuron becomes more positive, allowing the action potential to propagate down the neuron.

The state where the membrane potential of a neuron returns to its resting state, becoming more negative.

The process of restoring the neuron to its original state after an action potential has passed.

The process of transmitting a nerve signal from one neuron to another.

The chemical messenger that travels between neurons across the synapse, transferring the signal.

Ciguatoxin is a potent toxin that disrupts the normal function of nerve cells, leading to a disruption in signal transmission.

Saxitoxin and Tetrodotoxin work by blocking the channels that nerve cells use to transmit signals, effectively silencing the communication pathways.

Saxitoxin is not effectively broken down by the body, and its intact form can be found in organs like the liver, spleen, and brain, indicating poor elimination.

Although Tetrodotoxin's metabolism in humans is not fully understood, existing research suggests that it might be broken down differently than in marine life, highlighting species-specific variations.

Xenobiotics are foreign compounds that are not naturally found in the environment. They can persist in the body due to their chemical stability and resistance to breakdown.

Fish toxins are often lipophilic, which means they readily dissolve in fats. This allows them to easily accumulate in the fatty tissues of fish, particularly as they age.

Older fish, because of their size and age, are more likely to have accumulated higher levels of toxins. Factors like proximity to pollution, diet, and body fat content also contribute to bioaccumulation.

The process by which toxins accumulate in organisms at higher trophic levels in a food chain.

A group of chemicals that persist in the environment for a long time and can accumulate in living organisms. They are often byproducts of industrial processes.

A highly toxic form of mercury that is readily absorbed by fish. It can have harmful effects on human health.

A group of chemicals that were widely used in electrical equipment and other products. They can have harmful effects on human health.

A type of toxin that can affect the immune system, reproductive system, and nervous system. They can cause various health problems.

A long-lasting insecticide that was banned in Canada and restricted in the United States.

A family of chemicals that are used to make products water, stain, and oil repellent. They are not easily broken down in the environment.

A metal that is found in fish tissue. It can be harmful in high concentrations.

Polychlorinated biphenyls (PCBs) are a group of 209 synthetic chemicals used in various industries, but now banned due to their persistence in the environment and harmful effects.

PCBs can cause a range of health problems, including cancer, immune suppression, and developmental issues. They interfere with the body's normal functions by disrupting hormone regulation and cellular processes.

Dioxins are a group of 75 toxic chemicals, often produced as byproducts of industrial processes. They are very long-lived and bioaccumulate in the food chain, mainly in fat-rich fish.

Dioxins are suspected carcinogens. They can also harm the immune system, disrupt hormone balance, and cause developmental problems, especially in fetuses.

Bioaccumulation refers to the process where toxins build up in living organisms as they consume contaminated food. The higher an organism is in the food chain, the more toxins it accumulates.

Lipophilic substances are attracted to fats and oils. Such substances readily dissolve in, and are stored in, fatty tissue and accumulate in the body.

The half-life of a substance is the time it takes for its concentration in the body to decrease by half. Substances with longer half-lives remain in the body for a longer time.

The CYP1A family are enzymes involved in the metabolism of various drugs and toxins. They are responsible for breaking down harmful substances, but some toxins can resist their action.

Mercury (Hg) in the environment can be transformed into a more toxic form called methyl-mercury (CH3-Hg) by bacteria.

Methyl-mercury (CH3-Hg) is a highly fat-soluble compound. This allows it to accumulate in the fatty tissues of fish, especially in species with high fat content. This process, called bioaccumulation, leads to higher concentrations of methyl-mercury in larger, older fish.

Methyl-mercury (CH3-Hg) can be absorbed by fish through their gills and through their diet. It can then be passed up the food chain, accumulating in larger and longer-lived fish.

The half-life of methyl-mercury in humans is estimated to be between 30 and 120 days, meaning it takes that long for half the amount present in the body to be eliminated.

Methyl-mercury (CH3-Hg) can disrupt protein function by binding to protein sulfhydryl or thiol (SH) groups, which are crucial for various cellular processes.

Exposure to high levels of methyl-mercury can lead to various health problems, including visual and hearing impairments, and cognitive development issues, especially in developing fetuses. The fetus is particularly vulnerable to the effects of methyl-mercury.

Methyl-mercury is highly stable and fat-soluble, allowing it to be stored in the mother's fat tissue. During pregnancy, these stored toxins can be released and transferred to the developing fetus through the placenta.

Dietary restrictions, such as limiting the size and frequency of fish consumption, especially for children and pregnant women, help minimize exposure to methyl-mercury and its associated health risks.