Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Toxicology > Nitrate and nitrite (FINAL) > Flashcards

Nitrate and nitrite (FINAL) Flashcards

1
Q

Explain accumulation of nitrate by plants

A
  • Nitrate (NO3) is absorbed from the soil by the plant, is converted to nitrite (NO2)
  • Nitrite is converted to ammonia (NH3)
  • Ammonia is converted to amino acids then to vegetable protein
  • Nitrase reductase converts nitrate to nitrite
  • When the rate of nitrate-to-nitrite is reduced, w/ continuation of nitrite uptake from the soil, this leads to nitrate accumulation in the plant
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What plant species favor nitrate accumulation?

A

Sweet clover, alfalfa, corn, wheat, etc.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What content/form of N in the soil favors nitrate accumulation in plants?

A

High nitrate or ammonia

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What are some soil conditions that enhance nitrate uptake?

A
  • Rains or moisture
  • Acidic soil (low pH)
  • Low soil molybdenum, sulfur, or phosphorus
  • Low soil temp (13 C)
  • Soil aeration or drought
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

T/F: Decreased light reduces activity of nitrate reductase

A

TRUE

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

T/F: The use of phenoxy acetic acid herbicides can increase nitrate accumulation in plants

A

TRUE

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Which plant parts contain the most nitrate?

A

The stalks contain the highest concentrations

Leaves contain less than stalks or stems

The seed (grain) and flower contain little or no nitrate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

T/F: Mature plants have higher nitrate than younger plants

A

FALSE–younger plants have higher nitrate than mature plants

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Name 10 nitrate-accumulating plants

A
  1. Pigweed (Amaranthus retroflexus)
  2. Oats (Avena sativa)
  3. Beets (Beta vulgaris)
  4. Johnson grass, sudan grass, milo (Sorghum spp)
  5. Corn, maize (Zea mays)
  6. Lamb’s quarters (Chenopodium album)
  7. Sweet clover (Melilotus spp)
  8. Alfalfa (Medicago sativa)
  9. Wheat (Triticum aestivum)
  10. Sunflower (Helianthus annuus)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is this?

A

Pigweed (Amaranthus spp)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Plant name?

A

Lamb’s quarters (Chenopodium album)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is this?

A

Alfalfa (Medicago sativa)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What’s this?

A

Sudan grass

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What plant is this?

A

Johnson grass

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What are nitrate/nitrite used for?

A
  • Fertilizers
  • Sodium nitrite IV is used as a vasodilator
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Sources of nitrate/nitrite poisoning?

A
  • Rapid ingestion of forages or hays containing high amounts of nitrate
  • Accidental ingestion of feeds or water contaminated w/ nitrate
  • Overdose w/ nitrite IV
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Are nitrates soluble in water?

A

yes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

T/F: Nitrate fertilizers are salty

A

TRUE–they’re palatable

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What are nitrates and nitrites sources of (in soil)?

A

Sources of nitrogen oxide gases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What converts nitrate to nitrite?

A

Nitrate reductase (microflora)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What is the LD50 for ruminants?

A

Approx. 0.5-1 g/kg

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What forage nitrate level can cause acute toxicosis?

A

Greater than 1%

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Can nitrate/nitrite tolerance develop over time?

A

Yes

24
Q

Which species is most susceptible to nitrate poisoning?

A

Ruminants (rumen microflora)

25
Q

Which species is resistant to nitrate poisoning?

A

Pigs

26
Q

Which species is very sensitive to IV nitrite?

A

Horses

27
Q

T/F: Nitrate is 10x more toxic than nitrite

A

FALSE–Nitrite is 10x more toxic than nitrate

28
Q

What are the types of nitrate poisoning?

A

Acute or chronic

(Chronic nitrate poisoning is not common)

29
Q

T/F: Factors that stimulate rumen microflora increase nitrate reductase activity, thus increasing toxicity

A

TRUE

30
Q

T/F: Young animals are more susceptible than adults

A

TRUE

(because that’s almost always the freakn case)

31
Q

What diseases increase toxicity?

A

Anemia and methemoglobinemia

32
Q

What is nitrate reduced by/to? What is that then converted to?

A

Nitrate is reduced by the rumen microflora to nitrite

Nitrite is then converted to ammonia

33
Q

What is ammonia converted to?

A

Amino acids and microbial proteins

34
Q

T/F: The rate of conversion of nitrite to ammonia is slower than the rate of conversion of nitrate to nitrite

A

TRUE

35
Q

What does the difference between conversion rates result in?

A

Accumulation of nitrite in the rumen which is rapidly absorbed

36
Q

What occurs in erythrocytes?

A

The nitrite ion enters the erythrocytes in exchange for chloride ion

37
Q

Can nitrite cross the placenta?

A

Yes–it crosses the placenta and enters fetal erythrocytes (fetal hemoglobin is more sensitive)

38
Q

What is the half-life of nitrite?

A

Nitrite = less than 1 hr in dogs, sheep and ponies

Nitrate = 4-48 hrs

39
Q

What is the mechanism of action in acute toxicosis?

A
  • 1 molecule of nitrite interacts with 2 molecules of hemoglobin –> oxidation of ferrous iron to ferric and conversion of hemoglobin to methemoglobin
  • Methemoglobin cannot carry oxygen
  • Direct vasodilation and hypotension
  • Abortion due to fetal methemoglobinemia
40
Q

What levels of methemoglobin show clinical signs? When will death occur?

A
  • Clinical signs of anoxia develop if methemoglobin is 20-40%
  • Death from anoxemia occurs when methemoglobin reaches 80-90%
41
Q

What is the mechanism of action of chronic toxicosis?

A

Abortion due to decreased progesterone

42
Q

Clinical signs of nitrate/nitrite poisoning?

A
  • Sudden death w/ no observed signs
  • Signs occur rapidly (w/in 30 min to 4 hr)
  • Rapid breathing
  • Restlessness
  • Apprehension
  • Dyspnea
  • Weakness
  • Ataxia
  • Sternal recumbency
  • Cyanosis
  • Terminal convulsions
  • Death w/in a day or a few hours
  • Abortion (due to fetal anoxia)
43
Q

Lesions?

A

Congestion in various organs

Brown-chocolate color of blood (methemoglobin)

44
Q

What is used for chemical analysis?

What about animals that have been dead several hours?

What is best to be used prior to death?

A
  • Forage, hay, and water for nitrate
  • Ocular fluid is specimen of choice for nitrate in animals dead for several hours (>30ppm indicates excessive exposure)
  • Serum, plasma, urine, and rumen contents can be used for nitrate, but they are unstable after death
45
Q

Methemoglobin concentration for preservation?

A

One part blood to 20 parts phosphate buffer (pH 6.6)

46
Q

Diagnosis?

A
  • History, clinical signs of resp signs w/o lung lesions, and methemoglobinemia usually allow presumptive diagnosis
  • Diphenylamine test
47
Q

What is the diphenylamine test? What do positive results indicate?

A

Qualitative test for nitrate in forages (hay, pasture, silage), rumen contents, and water

+ results indicate >5,000 ppm nitrate

48
Q

How do you perform the diphenylamine test?

A
  • Mix 0.5g diphenylamine w/ 20mL of distilled water, then bring the total to 100mL w/ concentrated sulfuric acid
  • Carefully put a drop of solution on inner tissue of the plant stem
  • Dark blue color indicates + result
  • Positive specimens have to be sent to the lab for quantitative analysis (false positives possible)
49
Q

DDx (general)?

A
  • Agents causing methemoglobinemia
  • Agents inhibiting oxygen utilization by tissues
  • Hemolytic agents
  • Carbon monoxide (bright red blood)
  • Cardiac toxicants
50
Q

DDx for agents causing methemoglobnemia?

A
  • Agents causing methemoglobinemia
    • Nitrate in ruminants
    • Nitrite
    • Copper
    • Acetaminophen in cats
51
Q

DDx for agents inhibiting oxygen utilization by tissues? How can you differentiate between them?

A
  • Cyanide (bright red blood)
  • Hydrogen sulfide (dark blood)
52
Q

What are some other hemolytic agents?

A
  • Copper
  • Zinc
  • Naphthalene
  • Bromate
  • Iodate
  • Arsine gas
  • Onion
  • Mustard
  • Red maple
  • Gossypol
  • Snake venoms
  • Others
53
Q

What are some cardiac toxicants?

A
  • Digitalis
  • Magnesium
  • Calcium
  • Potassium
  • Fluoroacetate in herbivores
  • Others
54
Q

What is the treatment for nitrate/nitrite poisoning?

A
  • Methylene blue 1% slowly IV for ruminants and monogastrics except cats as a reducing agent (4-30 mg/kg)
  • Activated charcoal
  • Ruminal lavage w/ cold water
  • Oral antibiotics may inhibit rumen microflora and nitrate reductase
55
Q

Prognosis?

A

Animals usually die before treatment because death is rapid

Toxicology (22 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions