Experimental models Flashcards
What is an experimental model?
Model requires:
Accuracy in reflecting what you want to study
Ethics
Necessity - does the experiment need doing, and in a particular way?
Cost
Numbers
What are the regulations in experimenting?
All drugs must be tested on animals before humans.
Use of human tissue is tightly regulated.
You can’t test on animals if there is an alternative.
If animals are used, the smallest one possible is used.
Genetically modified organisms is also regulated.
What are the types of cell culture?
Traditional cell culture - cells stick to plastic well or don’t.
3-D culturing
Organoids
Down this list there is: improved modelling of living tissue.
Increased complexity.
Increased technical difficulty.
What are cell cultures useful for?
Understanding cellular structures and processes.
Knowing what proteins do - genetic alteration e.g. to mimic patient genotypes.
What are the similarities of 2D and 3D cell cultures?
Experiments require appropriate cell lines.
Primary cell lines are grown directly from a patient sample.
Immortalised cell lines - grown from patients but grow forever.
They require the correct cell culture media.
How are 3D cell cultures grown?
3D cell culture grows cells in a collagen matrix, which is more like a tissue environment.
The matrix can be changed to be stiffer or looser, so changes the environment.
What are organoids?
Stem cells taken from an organ, grown in a 3D matrix, with growth factors and appropriate conditions.
What are the benefits of organoids?
Creates more than one cell type.
Replicates organs and interactions more accurately.
Allows genetic experiments without using an organism.
What are the limitations of organoids?
Not a complete replica.
Limited growth.
Complex.
Time consuming.
What are single cell organisms?
Yeast and bacteria.
They are easy to genetically modify, by plasmids and artificial chromosomes.
They are easy to grow and use, and are cheap.
What are single cell organisms useful for?
Producing proteins for your experiments
Simple molecular interactions
Can understand the organism.
What are whole organism models?
Can understand how things work in a complete system.
Have lots of control - genetically identical, age, diet, sex, environment.
This reduces the numbers needed for meaningful data.
What is the order of whole organism models?
The smallest model possible is always used.
Invertebrates
Vertebrates that aren’t mammals - zebrafish.
Mammals - mice, then rats, guinea pigs, farm animals, primates.
What are important considerations of whole organism models?
Despite being genetically similar, and similar on a tissue level, the differences are real and cannot be assumed to be the same.
What are clinical trials?
Test new drugs or inventions.
This is very expensive.
Follows on from animal experiments and safety experiments.
Stages are safety work, then small sample size then large patient group effects.
What are human studies?
Uses human volunteers - tissues e.g. blood, biopsy, whole organs.
Good as they can report their own feelings and outcomes.
What are the issues with researching on humans?
Ethically protected
Genetically variable
Expensive
Genetic modification almost impossible
Once stratified very few patients available - specific variations of disease
However it is accurate, and variability is realistic.
What are the requirements of an experiment?
Work in a relevant model.
Practical - cheapest accurate thing used.
Enough samples
Positive and negative controls
Repeated experiments.
How many repeats are done?
Normally at least 3 times.
High enough to obtain statistical significance, but not using resources unnecessarily.
