Toxicity of Heavy Metals and Treatments

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Questions and Answers

Chronic lead poisoning is called ______.

plumbism

Lead inhibits the enzyme ______, which is needed to make haem.

ferrochelatase

Heavy metal poisoning primarily works by inhibiting enzymes that contain ______ groups.

Chronic exposure to cadmium can cause a bone disease called ______.

Itai-Itai Signup and view all the answers

Fluorine binds to enzymes that contain ______ groups.

SH Signup and view all the answers

Arsenic is absorbed through the descending ______ and then re-excreted into the gastrointestinal tract.

colon Signup and view all the answers

Symptoms of fluorine poisoning can include ______ of the teeth.

mottling Signup and view all the answers

Acute arsenic toxicity is characterized by ______-watery diarrhea and bloody dysentery.

rice Signup and view all the answers

Selenium poisoning can cause a variety of symptoms including localized ______ of the eye.

haemorrhage Signup and view all the answers

BAL is an oily solution used as a chelating agent to treat ______ poisoning.

arsenic Signup and view all the answers

Copper poisoning can cause ______ in fish.

kyphosis Signup and view all the answers

Mercury poisoning can cause ______ patches on the mucous membrane of the mouth.

aphthous Signup and view all the answers

Zinc can cause a fuzzy appearance of the ______.

gills Signup and view all the answers

Lead is not easily excreted in ______.

urine Signup and view all the answers

Freshly prepared ferric hydroxide solution is the classic antidote for ______ poisoning.

arsenic Signup and view all the answers

Antimony poisoning can cause loss of ______ in dogs.

smell Signup and view all the answers

Atropine blocks ______ receptors but not nicotinic receptors.

muscarinic Signup and view all the answers

Oximes, such as pralidoxime, are antidotes for ______ poisoning.

organophosphate Signup and view all the answers

Organochlorine insecticides, like DDT, are known for being ______, meaning they persist in the environment.

non-biodegradable Signup and view all the answers

In birds, organochlorines disrupt estrogen metabolism and calcium mobilization to ______ in eggshells.

eggs Signup and view all the answers

DDI and chlorinated cyclodienes inhibit calmodulin's ability to transport ______.

calcium Signup and view all the answers

Type I pyrethroids are known to induce the ______-syndrome, which includes tremors and hyperexcitability.

T Signup and view all the answers

Fluorocitrate, formed from fluoroacetate, inhibits the enzyme ______, preventing citrate conversion.

aconitase Signup and view all the answers

Zinc phosphide is an inorganic rodenticide that has a ______ fish odor.

rotten Signup and view all the answers

Study Notes

Heavy Metal Toxicity

Heavy metal poisoning inhibits enzymes containing SH groups.
Stomach tube washing is a treatment for most heavy metals except barium chloride and antimony trichloride.

Arsenic Toxicity

Absorption occurs in the descending colon, excretion through the gastrointestinal tract.
Arsenic is used in weed killers and wood preservatives.
Arsenic storage occurs in bone and keratinized tissues.
Arsenic can be detected even in decomposed remains.
Arsenic elimination from the body takes 2 weeks after treatment, 6 weeks after stopping arsenic-based drug administration.
Acute arsenic toxicity leads to rice-watery diarrhea and bloody dysentery.
Antidotes for arsenic poisoning include freshly prepared ferric hydroxide solution and British Anti-Lewisite (BAL).

Mercury Toxicity

Mercury is re-excreted through the cecum.
Mercury permanently inhibits selenoenzymes like thioredoxin reductase.
Symptoms of mercury poisoning include aphthous patches on the mouth's mucous membrane.
Antidotes for mercury poisoning include BAL (British Anti-Lewisite) and albumin. Leishica solution (500 ml skimmed milk, 50 g glucose, 20 g sodium bicarbonate, 3 egg whites, and barley water) is another treatment.

Antimony Toxicity

Antimony poisoning can cause loss of smell and aphthous patches in the mouth's mucous membrane.

Lead Toxicity

Lead is not easily excreted in urine.
Chronic lead poisoning is called plumbism.
Lead inhibits enzymes 8-ALAD and ferrochelatase, crucial for haem production.
Lead poisoning symptoms include microcytic hypochromic anemia, erythrocytic basophilic stippling, and acid-fast inclusion bodies in the renal cortex.
Lead poisoning treatment uses CaNa2EDTA and D-penicillamine.

Cadmium Toxicity

Cadmium interferes with zinc-related metabolic processes.
Chronic cadmium exposure causes Itai-Itai disease (osteomalacia and osteoporosis).

Fluorine Toxicity

Fluorine binds to enzymes like aconitase and AChE.
Fluorine poisoning causes hyperesthesia and tooth mottling.
Chronic exposure causes osteomalacia and osteoporosis.
Aluminium sulphate can precipitate leftover fluorine in the stomach.
Fluoride detection is not possible in decomposed remains.

Selenium Toxicity

Selenium poisoning in fish causes various symptoms like nephrocalcinosis, ascites, localized eye haemorrhage, cataracts, exophthalmia, lordosis, and kyphosis.
Tributyltin (TBT) can cause localised eye and base haemorrhage as well as cataracts in fish.
Copper poisoning causes kyphosis in fish.
Zinc poisoning causes a fuzzy appearance in fish gills.

Reproductive Toxicity (Female)

Follicle-stimulating hormone (FSH) and luteinizing hormone (LH) stimulate estrogen production in ovarian follicles.
Early pregnancy stages involve pre-implantation and organogenesis.
The fetal period begins with organ formation and extends to birth.
Exposure to toxins during pregnancy can lead to growth retardation and neonatal jaundice in offspring.
Exposure to toxins in females before puberty can cause irreversible infertility.

Reproductive Toxicity (Male)

Sertoli cells in the testes provide support to spermatogenic cells, forming a blood-testis barrier to help with sperm maturation.
Leydig cells produce testosterone.
Spermatogenic cells develop into sperm cells.
Spermatogenesis (sperm development) takes 50-54 days in rats.
Immature spermatozoa are released from Sertoli cells into the seminiferous tubules.

Genotoxicity

Genotoxicity is a substance's ability to damage DNA.
Types of mutations include reverse phenotype, transition, transversion, missense, and frameshift.
Monosomy involves a missing chromosome; trisomy involves an extra chromosome.
Examples are Turner syndrome (47, X), Down syndrome (trisomy 21), Klinefelter syndrome (47, XXY), and other sex chromosome trisomies (47, XXX).
Oncogenes are mutated proto-oncogenes causing uncontrolled cell growth.
Tumor suppressor genes prevent uncontrolled cell growth, mutations increase cancer risk.
Substances like aflatoxins, cosmetics, bromouracil, and mitomycin can generate reactive radicals that react with DNA forming adducts.

Neurotoxicity

Neurotoxicity damages the nervous system.
Oligodendrocytes and Schwann cells myelinate nerve fibers.
Astrocytes and endothelial cells form the blood-brain barrier.
Lipophilic toxins easily cross the blood-brain barrier.
Anterograde transport moves substances from the cell body to nerve terminals.
Retrograde transport moves substances in the opposite direction.
Substances like nitrogen trichloride, aluminium, organophosphates (causing neuropathy) and toxins affecting the synthesis of glutathione can cause neurotoxicity via dying-back processes and glial scar formation.

Insecticides

Type I pyrethroids inhibit Ca2+/Mg2+ ATPase.
Secondary messengers relay signals in cells.
Some neurotoxins interfere with secondary messenger systems and ion channels.
Anticholinesterase insecticides (organophosphates and carbamates) inhibit acetylcholinesterase (AChE), critical for nerve signal transmission.
Organophosphates bind to AChE, resulting in irreversible inhibition.
Atropine blocks muscarinic receptors, while oximes (pralidoxime, obidoxime) reactivate AChE.
Organochlorine insecticides, like DDT, are non-biodegradable.

Rodenticides

Zinc phosphide is a black, rotten fish-smelling rodenticide.
Sodium fluoroacetate and fluoroacetamide block the citric acid cycle by inhibiting aconitase.
ANTU reacts with sulfhydryl (SH) groups in the body.

Mycotoxins

Mycotoxins are toxins produced by fungi, characterized by low lipid/water solubility and large molecular weights.
Fusarium mycotoxins include aflatoxins (e.g., aflatoxin B1).
Aflatoxins (e.g., aflatoxin B1) are metabolized to reactive epoxides that bind to DNA, leading to liver damage.

Permissible Levels

Permissible levels for aflatoxin B1 are 20 ppb in food for humans and animals.

Other Toxic Substances

Carbon Monoxide (CO) binds to hemoglobin, inhibiting oxygen transport.
Other toxins include ochratoxin, citrinin, nitrous oxide, and chlorine and bromine compounds.

Poisonous Plants

Various plants and their parts (seeds, fruit, etc.) are toxic, containing proteins like ricin, atropine, solanine, and alkaloids like narcotine, morphine, and narceine.

Toxicodynamics

Toxicodynamics is the effect of toxins on the body, including enzyme inhibition (e.g., AChE) and receptor binding (mimicking or blocking endogenous substances).
Toxin damage to cell membranes leading to cell death is another mechanism.
Other routes of absorption and excretion include sweat, tears, breast milk, and exhalation.

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Description

This quiz explores the toxic effects of heavy metals such as arsenic and mercury, including their absorption, excretion, and treatment options. Learn about the symptoms of poisoning and the specific antidotes for chemical toxicity. Gain a better understanding of heavy metal toxicity to enhance your knowledge in toxicology.