Health and disease III
Drug development
Possible drugs are synthesised (made) in a lab
In Vitro Screening - potential medicines are tested on cell cultures, tissue cultures and isolated organs.
Animal testing - Chemical are then tested on animals, to find out how they work in a living organism as well as what dose is needed and any side effects
Clinical testing - Healthy volunteers are given a very low dose, which is gradually increased. If the results are good, it can be tested on people suffering from the illness. The optimum dose is found.
Placebos - Some patients are given a placebo, a substance that looks like the drug, but doesn't do anything, e.g. a sugar pill. It allows the doctors to see the actual difference the drug makes
Blind and double blind trials - The patient doesn't know whether they are getting the placebo or the drug. Double blind are when the doctor doesn't know either
Once the drug has passed all the test, it will be granted a licence and can be prescribed to patients
Antibiotics
Either kill bacteria (bactericidal) or prevent them from reproducing (bacteriostatic)
No effect on viruses
No effect on human cells
Some bacteria develop resistance due to mutations or over-prescribing
Bacteria never become immune to an antibiotic
Investigating antibiotics and Antiseptics
In a lab
Cultured in a growth medium containing : carbohydrates, minerals, proteins and vitamins
Growth medium can either be agar jelly or a nutrient broth solution
Incubate the bacteria at 25 degrees to prevent the growth of harmful pathogens
Make sure enough oxygen is available to prevent the growth of anaerobic bacteria
The effect of substances of bacteria growth
Place paper discs soaked in different types antibiotics on a sterilised agar plate with an even covering of bacteria. Makes sure to leave space between the disk
Antibiotics should diffuse into the agar jelly.
Antibiotic resistant bacteria will continue to grow on the area around the paper disks
A clear area will be left where the bacteria have died as they are non-resistance to the antibiotic
Make sure to use a control, a paper disk with no antibiotic so you can be sure the paper has no effect
Leave the petri dish for 48 hours at 25 degrees
Calculate the area of the inhibition zone
The more effective the antibiotic, the larger the inhibition zone
Preparing an uncontaminated culture
Petri dishes and growth mediums must be sterilised before use. This can be done by placing them in an autoclave which uses high temperatures to kill any pathogens
If an inoculating loop is used, it must be sterilised by passing it through a flame and then cooled
Working next to a Bunsen burner will kill airborne microbes due to convection currents
The lid of the petri dish should be lightly taped on to allow oxygen to enter the dish to prevent the growth of anaerobic bacteria
The dish should be stores upside down to prevent drops of condensation falling on the agar
Risk factors for non-communicable diseases
What are risk factors?
Things linked to an increases in the likelihood that a person will develop a disease
Some risk factors are unavoidable like age or gender
Some risk factors are lifestyle based ad can be changed
Many diseases are cause by several risk factors
The more risk factors you have for one disease the more likely you are to get it
Smoking
Major risk factor for Cardiovascular disease, associated with the heart and blood vessels
Nicotine increases heart rate, which increases blood pressure
High blood pressure can damage artery walls which can lead to the build up of fatty deposits
This can cause a heart attack or stroke
Smoking is also a risk factor for cancer, cigarette smoke contains chemicals called carcinogens which can cause mutations in the genes that control cell division
Alcohol
Drinking too much alcohol is a major risk factor for liver disease
Ethanol is broken down in the liver and the toxic products can damage live cells
Toxic chemicals from the intestines can also cause liver damage
Drinking too much over a long period of time can lead to permanent liver damage
Diet
Diets with too few nutrients can lead to malnutrition, and is a risk factor for scurvy
Too many nutrients can lead to obesity, which is a risk factor for diabetes and CVD
Exercise
Too little exercise can lead to obesity
Inactive people are more likely to develop high blood pressure and CVD
Measuring obesity
Obesity - being very overweight and having too much body fat
Body mass Index (BMI)
BMI = mass(kg) / height squared (m)
Below 18.5 = underweight
18.5 - 24.9 = normal
25 - 29.9 = overweight
30 - 39.9 = moderately obese
above 40 = severely obese
BMI isn't always reliable as it doesn't take account for muscle mass
Treating CVD
What is CVD?
disease of the heart and blood vessels
Arteries narrow when fatty deposits build up inside them
Deposits can also trigger blood clots to form
Lifestyle changes
Balanced diet
Withdrawal from alcohol and smoking
Exercise regularly
Disadvantages
Long term
Sudden change in lifestyle may not be safe
Medication
Statins
Reduces the amount of LDL-Cholesterol in bloodstream
Statins slow down the rate of fatty deposits forming
Reduces risk of strokes and heart attacks
Disadvantages
Muscle pain
Weakness
Bad reactions can make people reluctant to take them
Antihypertensives
Reduce blood pressure
Helps prevent damage to blood vessels, reduces risk of fatty deposits forming
Types
Diuretics - flush out excess water
ACE inhibitors - relax blood vessels
Beta Blockers - cause the heart to beat slower
Disadvantages
Side effects like headaches and dizziness
Anticoagulants
Make blood clots less likely to form, less chance of heart attacks
Warfarin reduces fibrin production
Disadvantages
Slow to take action
Patients can suffer excessive bleeding
Risk of internal bleeding
Surgical procedures
Stents
Wire mesh tubes can be inserted into arteries to widen them and keep them open
Keep coronary arteries open, making sure blood can pass through
Surgery is simple and relatively quick
Disadvantages
Risk of complications
May need to be replaced
Risk of blood clot developing
Patient needs to take anticoagulants
Coronary bypass surgery
A piece of healthy vessel taken from elsewhere in the body is used the bypass a blocked section of the coronary arteries
Disadvantages
Coronary bypass surgery is longer and more invasive that stent surgery
long recovery time
Donor hearts
If heart disease is severe, the whole heart can be replaced
Disadvantages
Severe shortage of suitable donor hearts
Potentially dangerous operation
Risk of rejection by the immune system
Specific bacteria are only killed by a specific antibiotic
Genes
Differnet alleles of a gene may be more prone to mutation or how well you absorb nutrients
These factors could be more common in particular ethnic groups
Environmental
Air pollution can cause lung disease
Posions in food and drink can damage the body
Malnutrition - when a person eats to much or too little of a nutrient, this could lead to deficiency diseases or obesity
Used to treat bacterial infections