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Molecular Basis Of Disease > Non-essential Trace Elements (Lead, Mercury and Arsenic) > Flashcards

Non-essential Trace Elements (Lead, Mercury and Arsenic) Flashcards

1
Q

What items were lead commonly found in? Why has lead been taken out of many of these items?

A

petrol
paint
pipes
car batteries

lead is an industrial pollutant

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2
Q

How many mg’s of lead is found in the body and where is most of this located

A

2 mg
90% in skeleton

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3
Q

How much lead in micrograms/L is the maximum limit which can be contained in blood

A

250
50 in children

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4
Q

In 1918 which occupation showed 40% of employes had lead toxicity

A

painters and lead acid battery reconditioners

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5
Q

Lead toxicity leads to neurological disorders, erythrocyte damage and anaemia. What are the molecular changes in lead toxicity which causes these symptoms?

A

neurological disorders:
- Pb disrupts synapse formation and neurochemical development
erythrocyte defects/anaemia:
- Pb inhibits delta-aminolevulinic acid dehydratase which interferes with heme synthesis

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6
Q

Pb toxicity inhibits enzymes like ATPase by….

A

binding to functional groups of enzymes

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7
Q

Pb can block functions of which other elements?

A

Calcium
Iron
Zinc

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8
Q

Where does lead accumulate in the human body when at toxic levels

A

mammary gland (can be dangerous when breast feeding)
bones

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9
Q

Pb toxicity creates….. by…..

A

reactive free radicals by the Fenton reaction (can bind instead of iron) and by inhibiting antioxidant enzymes

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10
Q

What is the treatment of Lead toxicity

A

chelating agents (e.g. EDTA)
- excretion in urine

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11
Q

Where is mercury found in high concentrations

A

industrial pollutants
- coal burning
- fumigants and fungicides
amalgams (alloys)
- mixture of mercury and other metals (e.g. dental fillings)
Fish
- whale meat in Japan
present in sewage
- due to industrial waste

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12
Q

Why is mercury found in all human tissue even with no known exposure to mercury?

A

Bioaccumulation: the absorption rate of mercury in the human body is faster than excretion rates as the body doesn’t not have good methods to remove mercury

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13
Q

Mercury comes in a few forms. What is the toxicity of each of these forms?

A

element/ metallic (quicksilver) = low toxicity
organic (mercury and carbon) = highly toxic
inorganic = low toxicity

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14
Q

Liquid mercury is poorly absorbed by the gut. What are the ways it is absorbed?

A

skin
inhalation

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15
Q

What is the most dangerous mercury compound? What did the compound used to be commonly used in?

A

dimethylmercury

thermometers

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16
Q

Why is dimethylmercury so dangerous?

A

metabolised to methylmercury
- this can be absorbed by the gut and can form a complex with cysteine
- cross the blood brain barrier easily and bioaccumulates
- irreversibly inhibits selenium-dependant enzymes (e.g. thioredoxin reductase which reduces antioxidants) leading to increased ROS in the brain

17
Q

Methylmercury causes an increase in antibodies against myelin basic protein (MBP) and glial fibrillary acidic protein (GFAB) what does this cause?

A

these are essential proteins for myelination of neurons and CNS function.
- leading to nervous system dysfunction

18
Q

Symptoms of organic mercury toxicity

A

tremors
irritability
numbness
deafness
blurred vision
lack of co-ordination
kidney necrosis
difficulty swallowing

19
Q

How is mercury toxicity diagnosed

A

whole blood or hair analysis

20
Q

What is the treatment for mercury poisoning

A

chelation therapy

21
Q

inorganic mercury (e.g. mercuric nitrate) was used to treat small animals fur for making felt hats. These hats would slowly release mercury over time. What are the symptoms people exposed to inorganic mercury over a long period of time experienced?

A

red fingers, toes and cheeks
sweating, loss of hearing, bleeding from ears and mouth
loss of appendages such as teeth, hair and nails
lack of coordination, poor memory, shyness, insomnia, nervousness, tremors and dizziness

22
Q

Minamata disease results from the methylmercury toxicity. In 1918 there was an outbreak in Japan. Where and why did this occur?

A

methylmercury was released into waste water by a chemical factor causing it to accumulate in the soil and water-ways

23
Q

Minamata disease results from the methylmercury toxicity. In 1918 there was an outbreak in Japan. How did the people of the area end up with minamata disease?

A

they consumes contaminated seafood (whale meat contained 20x acceptable levels)

24
Q

What are the symptoms of Minamata disease?

A

ataxia
numbness in hands and feet
general muscle weakness
impaired eyesight and hearing

in serious cases:
- insanity
- paralysis
- coma
- death within weeks of symptom onset

25
Q

Where is Arsenic naturally found?

A

in rock near gold deposits

26
Q

What locations in the world contain high concentrations of arsenic?

A
  1. mine trailings
  2. ground water in India and Bangladesh
27
Q

What are the common uses of arsenic

A

pesticides to kill insects attacking crops
timber preservation
batteries
electronic devices

28
Q

There are inorganic and organic forms of arsenic. Where is inorganic (metallic form) arsenic found?

A

rocks, minerals and mine tailings

29
Q

There are inorganic and organic forms of arsenic. re is organic arsenic ( usually arsenic oxides) found?

A

found in shellfish and some fish
some bacteria
- able to utilise organic arsenic for photosynthesis if there is no oxygen

30
Q

Arsenic oxide can attack thiol groups like cysteine. What does this cause?

A

thiol groups are important for many enzymes to function

31
Q

What is the toxicity levels of organic and inorganic arsenic

A

organic = less toxic form
inorganic = toxic form

32
Q

How does arsenic enter the body? does it accumulate like mercury?

A

arsenic enters through oral route

does no accumulate excreted through faeces
- cleared from the blood within a few hours

therefore there is no effect from small amounts of arsenic (toxicity occurs over long term ingestion)

33
Q

long term ingestion of arsenic causes what symptoms?

A

skin discolouration and thickening of skin
damage to:
- heart
- liver
- kidney
- nerves
- blood vessels
cancers of:
- skin
- bladder
- lung
- liver
- kidney
- prostate

34
Q

What is dimethylarsinic acid?

A

methylated arsenic

35
Q

dimethylarsinic acid is intracellular arsenic. This binds to thiol groups of metalloproteins (e.g. cysteine) what does this cause in cells?

A
  1. forms ROS which induces DNA double strand breaks by inhibiting DNA repair enzymes
  2. reduced cellular energy by inhibiting pyruvate dehydrogenase complex (PDH)
    - disrupting pyruvate to acetyl-CoA
  3. causes cell death by necrosis (no ATP for apop)
36
Q

What are the treatments for arsenic

A

chelation therapy (EDTA)
hemodialysis

Molecular Basis Of Disease (17 decks)

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