Returned Traveller Lab

Question 1

When would be the right time to do a blood film?

Answer 1

Generally done when there is an abnormality the full blood count.
They are also very useful in identifying cell abnormalities such as shape and size.

Question 2

Briefly describe the procedure of carrying out a blood film?

Answer 2

Take 2 microscope slides and clean them with ethanol on a tissue.
Place a small drop of blood on one end of a microscope slide.
Hold other slide on drop and allow capillary action to spread blood across slide then pull back in a quick motion to create a thin monolayer.

Question 3

What should be done to a blood film sample before staining can take place?

Answer 3

The sample should be fixed

Question 4

What is a differential stain?

Answer 4

A stain that uses more than 1 stain, allowing it to differentiate between cell types and intracellular cell structures.

Question 5

What is a giemsa stain?

Answer 5

Is a differential stain used to stain blood cells, can be used to identify malaria and other parasitic diseases.

Question 6

What is the procedure of carrying out a giemsa stain?

Answer 6

1. To fix the sample onto the slide, place on a staining rack over the sink, using a pastette flood the slide with methanol and leave for 1 minute.
2. Pour off the methanol. Leave to dry.
3. Flood the slide with the giemsa stain and leave on for 30mins.
4. Rinse slide with gentle stream of water and cell-side up on the bench to dry.

Question 7

What are some of the pippete volumes available?

Answer 7

P20=2-20microlitres
P200=20-200microlitres
P1000=200microlitres-1ml

Question 8

What type of nucleus do neutrophils have?

Answer 8

Multilobed (2-5)

Question 9

What type of nucleus do monocytes have?

Answer 9

Large kidney shaped

Question 10

What type of nucleus do eosinophils?

Answer 10

Bi-lobed

Question 11

What type of nucleus do basophils have?

Answer 11

Bi-lobed (colourised by granules)

Question 12

What type of nucleus do lymphocytes have?

Answer 12

large, round

Question 13

When would be appropriate to carry out a gram stain?

Answer 13

It is used as the 1st step when trying to identify species of bacteria.

Question 14

What is the 4 steps of gram stains?

Answer 14

1. Initial stain
2. Complex formation
3. Decoularise
4. Counterstain

Question 15

What happens during the initial stain phase of gram stains?

Answer 15

Crystal violet is applied to the smear slide.
The dye will disscosiate into crystal violet ions (CV+) and chloride ions (Cl-) in aqueos solution.
The CV+ ions bind and stain the negatively charged components of the bacterial cell wall.
Wash with water after 1 min incubation.
Gram positive and negative both appear purple at this stage.

Question 16

What happens during the complex formation phase of gram stains?

Answer 16

Gram’s iodine is applied to fix the dye within the cells.
It forms complexes with the CV+ ions, these complexes are insoluble so become trapped in the cell.
1 min incubation, then wash to remove excess. Both bacterial types still appear purple.

Question 17

What happens during the decolourise phase of gram stains?

Answer 17

Decoularise with alcohol/acetone then rinse with water, this will remove colour from gram- but not gram+.
If you apply too much the colour will be taken from both. You should apply dropwise until it runs off clear.
It dissolves the lipids that make up the outer membrane of gram- and dehydrates the peptidoglycan layer in both cells.
Gram - now colourless while gram+ is still purple.

Question 18

What happens during the counterstain phase of gram stains?

Answer 18

Apply safranin, taken up by both cells types and binds to lipid cell membrane. 45 secs incubation then wash to remove excess.
Gram - now appear pink.
Gram+ now appear purple.

Question 19

If a blood sample is collected into a tube containing citrate, then centrifuged, its components will separate into three layers (based on density). What are the layers from most superficial to deepest/densest?

Answer 19

Plasma
WBC’s/Platelets
Red blood cells