Eco Toxicology Lecture 1

8/3/2019 Eco Toxicology Lecture 1

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Ecotoxicology


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Ecotoxicology is derived from the words

ecology a study concerned with howorganisms interact in nature with each other

(the biotic environment) and the physical and

chemical aspects of the environment (abiotic

environment) and toxicology a study of

adverse effects of xenobiotics.


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It is an area of study concerned with the harmful

effects of chemicals within the context of ecology.

It requires an understanding of ecological principles

and theory as swell as a grasp of how chemicals can

affect individuals, populations, communities and

ecosystems.

It is a multidisciplinary subject applying basic

biochemical, chemical, pathological, physiological, and

epidemiological knowledge to gain an understandingof why certain substances cause an untoward

alteration in biological systems which ultimately have

an effect on populations, communities and

ecosystem.


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Ecotoxicology is thus defined as the study of

harmful effects of chemicals upon ecosystem.

These adverse effects occur at various levels

within the body, such as an organ, a type of

cell, or a specific biochemical.

These adverse effects may occur in many

forms, ranging from immediate death to subtle

changes not realized until months or years

later.


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Levels of Biological OrganizationTohelp protectyour privacy, PowerPointprevented thisexternalpicturefrom being automatically downloaded. Todownload and display thispicture, click Optionsin theMessageBar, and then click Enableexternalcontent.


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Macromolecules are substances contributing

to form and organization of cells and tissue.

They are constructed from organic buildingblocks (monomers) linked together by repetitive

formation of covalent bonds to form polymers.

There three main classes:

Sugar monomers made to polysaccharide

polymers (e.g. glucose converted to glycogen

for storage purposes).

Amino acids made into polypeptide chains,

called proteins (e.g. enzymes that catalyze

reactions in the body)


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Nucleotides are polymerized into chains tomake nucleic acids (e.g. deoxyribonucleic acid,DNA, which holds the genetic information in

living organisms and ribonucleic acid, RNA,which is a short lived copy of DNA that is usedfor protein synthesis).

Org

anelles

are structures th

at occur in ne

arly

allcell types and may be regarded as internal

organs.

i.e They are organised units of living substancewith specific functions in cell metabolism.

E.g. mitochondriaan organelle mainlyconcerned in production of energy for drivingcellularactivities.


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The cell is the structural unit of all living things

consisting of cytoplasm and nucleus.

The cell has many critical structures and

processes which are necessary for its normal

function and survival including cell division,DNA replication, energy generation.

Any compound that disrupts one or moreimportant cellular processes may cause cellular

dysfunction which may lead to cytotoxicity


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Tissues are cells serving the same general

function that are grouped together and united

by varying amounts of intercellular substances(e.g. muscle, bone, nerve tissue, etc)

Tissues have many critical structures and

processes which are necessary for the properfunction of the organs they comprise.

Any compound that disrupts the structuralorganization of tissues, or important tissue

functions may cause general organ dysfunction,

which may lead to organ toxicity.


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An organ is derived from a group of cells that

become specialized for a particular function (e.gkidney).

A population can be simply defined as a groupof potentially interbreeding individuals of a

single species.

Communities are collections of interacting

populations in a given place.


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An ecosystem is compose of groups of all

types ( communities) of organisms that function

together as well as interact with the physicalenvironment, including energy flow and cycling

of material between living and nonliving

components.

Biosphere is the whole earth ecosystem.


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Learn also

cytoplasm, nucleus, nucleoli, chromatin,

chromosomes, organelles, mitochondria,endoplamic reticulum, golgi apparatus,

lysosomes, microfilament, centrosome,

microtubules, all stages of mitosis and meiosis).


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Terminology in Toxicology

Bioaccumulate

The increased concentration of harmfulsubstances in tissues of organisms higher up

the food chain

Biotransformation

The sum of the processes by which a

xenobiotic is subjected to chemical change by

living organisms

Carcinogen

Any substance that causes cancer


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Mutagen

Any substance that causes DNA damage,

ranging from changes in one or a few basepairs to gross changes in chromosomestructure or number

Pollutant

A substance present in greater than naturalconcentration as a result of human activity andhaving a net detrimental effect on itsenvironment

Risk

Probability a substance will cause harm underspecific conditions of use, i.e., hazard


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Teratogen

Any substance that causes fetal malformations

(birth defects) Toxicologist

A toxicologist is a scientist that determines the

harmful effects of agents and the cellular,biochemical, and molecular mechanisms

responsible for the effects.

Toxicosis

A diseased condition resulting from poisoning

Toxigenic

An organism producing toxins or poisons


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Toxin, Toxicant, and poison are often used interchangeably in

the literature; however, there are subtle differences as indicated

below


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Toxoid

A toxin that has been treated to destroy its

toxicity.

Xenobiotic

Compounds exogenous (external) to normalmetabolism of the organism, i.e., foreign

compounds

Toxic substances may be organic or inorganic

in composition


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Toxic substances may be systemic toxins or

organ toxins.

Asystemic toxin is one that affects the entire

body or many organs rather than a specific site.

Eg, potassium cyanide is a systemic toxicant inthat it affects virtually every cell and organ in

the body by interfering with the cell's ability to

utilize oxygen.

Lead is a specific organ toxin; (central nervous

system and kidney)


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Germ cells are those cells that are involved in

the reproductive process and can give rise to a

new. Toxicity to germ cells can cause effects on the

developing fetus (such as birth defects,

abortions).

Somatic cells are all body cells except the

reproductive germ cells.

Toxicity to somatic cells causes a variety of

toxic effects to the exposed individual (such as

dermatitis, death, and cancer).

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Eco Toxicology Lecture 1