Lead Toxicity in Animals

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Questions and Answers

What is the result of gamma-hexa chlorocyclohexane (γ-HCH) binding to GABA receptors?

Hyperpolarization of the neuron

Depolarization of the neuron

Stimulation of GABA-dependent Cl- flux into the neuron

Inhibition of GABA-dependent Cl- flux into the neuron (correct)

What is a characteristic of organochlorine insecticides that contributes to their persistence in the environment?

High volatility

High water solubility

High lipid solubility (correct)

Rapid rates of degradation

What is the consequence of slow biotransformation of organochlorine insecticides?

Environmental persistence and accumulation (correct)

Enhanced biodegradation

Rapid excretion from the body

Increased metabolism

What is the result of bioaccumulation and biomagnification in food chains?

An increase in the concentration of contaminants in higher trophic levels Signup and view all the answers

Why have organochlorine insecticides been banned in many countries?

Due to their toxicity and environmental persistence Signup and view all the answers

What is a common source of lead poisoning in cattle?

Grazing in contaminated areas Signup and view all the answers

What is the characteristic of organochlorine insecticides that contributes to their ability to accumulate in living tissue?

High lipid solubility Signup and view all the answers

What is the definition of a pesticide?

Any substance or mixture of substances used to prevent, destroy, repel, or mitigate any undesirable plant or animal pest Signup and view all the answers

What is the veterinary importance of pesticides?

To control vector-borne diseases, promote agricultural production, and control domestic pests Signup and view all the answers

What is the fate of most ingested lead?

It is eliminated in the faeces Signup and view all the answers

What is the effect of the complex aromatic ring structure of organochlorine insecticides on their biotransformation?

It slows down their biotransformation Signup and view all the answers

How can individuals be exposed to pesticides?

Occupationally, environmentally, and at their residence Signup and view all the answers

Which enzyme is inhibited by lead?

Haeme synthetase Signup and view all the answers

What is the consequence of the sequestration of organochlorine insecticides in body tissue having a high lipid content?

Accumulation of the insecticides in the body Signup and view all the answers

What is the primary route of elimination for mercury?

Urine Signup and view all the answers

How are pesticides grouped based on their target of action?

Based on their target of action Signup and view all the answers

What is the effect of selenium and vitamin E on mercury toxicity?

They protect against toxicity Signup and view all the answers

What is the mechanism of action of insecticides?

They target the nervous system of insects Signup and view all the answers

What determines the intensity of biological effect of insecticides?

The dosage and duration of exposure Signup and view all the answers

Which form of mercury is highly toxic when inhaled?

Elemental mercury Signup and view all the answers

What is a characteristic of chemical insecticides?

They are non-selective and can affect non-target species Signup and view all the answers

What is the primary organ where mercury is stored?

Liver and kidneys Signup and view all the answers

What is the mode of action of lead toxicity?

Inhibition of haeme synthetase Signup and view all the answers

What is an example of how pesticides can be used to control vector-borne diseases?

By controlling vectors that transmit diseases like malaria and Tryps Signup and view all the answers

Study Notes

Lead Toxicity

Lead is a ubiquitous environmental contaminant
Cattle, horses, and dogs are more susceptible to lead toxicity, while chickens, goats, pigs, and cats are more resistant
Only 1-2% of lead is absorbed from the gastrointestinal tract, and about 98% is eliminated in the feces
After absorption, lead is carried to erythrocyte membranes and then to the liver, where it is excreted in bile and reabsorbed through the enterohepatic biliary cycle
Lead toxicity arises from the inhibition of haeme synthetase, a thiol-containing enzyme required for incorporating iron into the haeme molecule

Mercury Toxicity

Mercury is a liquid at room temperature and exists in various organic and inorganic forms
Young ruminants are more susceptible to mercury toxicity than horses and pigs
Elemental mercury is non-toxic orally but highly toxic through inhalation, while inorganic mercury is less toxic and organic mercury is more toxic
Selenium and vitamin E can protect against mercury toxicity
Sources of mercury poisoning include organic and inorganic forms, such as fungicides, seed dressing agents, and mercuric salts

Toxico-kinetics of Mercury

Mercury is distributed throughout the body and stored mainly in the liver and kidneys after absorption
Mercury is eliminated slowly, primarily in the urine

Pesticides

Definition: any substance or mixture of substances used to prevent, destroy, repel, or mitigate any undesirable plant or animal pest
Veterinary importance: control of vector-borne diseases, promotion of agricultural production, and control of domestic pests
Individuals may be exposed to pesticides through occupational, environmental, or residential means

Classification of Pesticides

Insecticides: destroy, repel, or prevent harmful insects
Herbicides: control weeds
Rodenticides: control rodents
Fungicides: control fungi

Insecticides

All chemical insecticides poison the nervous systems of target organisms
Mechanism of action may be similar in all species, with only the dosage dictating the intensity of biological effect
Examples: γ-HCH (lindane) and DDT

Kinetics of Organochlorine Insecticides

Properties: persistence in the environment, accumulation in living tissue, bio-concentration, and bio-magnification in food chains
Biologically active body burdens at higher levels due to low volatility, chemical stability, high lipid solubility, and slow rates of degradation
Slow biotransformation due to complex aromatic ring structure and number of chlorine substituents
Environmental persistence and accumulation lead to sequestration in body tissue with high lipid content

Bioconcentration and Biomagnification

Bioaccumulation: intake of a long-lasting contaminant exceeds the ability to metabolize or excrete, leading to accumulation within the tissue of the organism
Biomagnification: concentration of a contaminant is magnified hundreds or thousands of times as it passes up the food chain

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Description

This quiz covers the sources of lead toxicity in animals, including vegetation grown in contaminated areas, grazing in contaminated areas, and use of certain drugs. It also discusses the susceptibility of different animal species to lead toxicity.