The germ theory of disease
After giving birth, women are vulnerable to infections, but in the days when most women had their children at home attended by their female relatives, serious infections after delivery were relatively rare. But as society, moved into the late 18th and early 19th centuries medical intervention began to cost women their women lives. Semmelweis discovered that puerperal disease was caused by an infectious disease, which doctors were carrying on their hands. He discovered that if doctors washed their hands with chlorinated lime between patients, there was a smaller chance that the disease was spread. Semmelweis presented his findings to other doctors and met with strong opposition. It was hard for doctors to admit that they themselves had spread the disease, and hand washing probably seemed rather an odd practice in that time. There was no indoor plumbing and the chlorinated lime would eventually have damaged the hands. But germs also couldn’t be seen yet with a microscope, and people didn’t really believe what they couldn’t see.
Cholera in London
The people who suffered most from cholera were the poor in large towns, who lived in overcrowded homes with poor sanitation. Most doctors then thought that diseases such as cholera were spread either by touch or by ‘bad air’ (miasma). But John Snow discovered that the disease was spread through water infected with an infectious agent.
The work of Semmelweis and Snow led gradually to the acceptance of the idea that infectious diseases are brought about by an infectious agent (or ‘germ’) which is transferred from one individual to another and causes disease. But deep-rooted views of the causes of disease were hard to shift. It took many years of work by many people working in many countries before there was a widespread acceptance of the theory.
One of the persons helping with establishing the theory was Louis Pasteur. At the time there was a widespread belief that livings things could arise from dead things, this was the theory of spontaneous generation. But Pasteur discovered that the micro-organisms were already present in air. He had established the germ theory of disease but he did not know how to identify the different kinds of germs.
Another person who helped with establishing the theory was Robert Koch. Koch became interested in examining microbes with the more powerful microscopes which were becoming available. He observed the germs multiplying and investigated the conditions which would stop them reproducing.
By the end of the 19th century the idea that infectious diseases were caused by germs was almost universally accepted.
As result of the work of scientists such as Semmelweis, Snow, Pasteur and Koch, a picture of the nature of infectious diseases began to be developed, a model which has moved much further forward though the 20th century, aided by ever sophisticated technology.
People catch infectious diseases when an infectious agent (or germ) invades their bodies. Germs cause tissue damage as they reproduce themselves in or on the body, and it is this which gives the symptoms of disease
Bacteria & viruses
Bacteria are single-celled organisms. Most bacteria are either harmless or beneficial, but some invade human tissues and grow to form colonies in certain organs causing disease. In a disease caused by bacteria the symptoms tend to com on gradually, getting steadily worse.
In contrast, viruses are not really independent organisms, but ‘packets’ of DNA with some enzymes contained in an outer case of protein. Viruses cannot survive on their own and they can only multiply by invading a healthy cell. Once inside the host cell the virus takes over the cell’s biochemistry and uses it to produce new copies of itself. This process continues until the host cell structure completely breaks down, releasing the new viruses to infect other cells.
It’s this cell destruction and the body’s reaction to it which gives rise to the symptoms of viral diseases. In diseases caused by viruses the symptoms come and go – for example, the temperature goes right up, then falls a bit, then shoots up again
Infected people spread diseases by coughing, sneezing, talking and spitting. Infection doesn’t lead to sickness straight away. Your body is protected by the immune system. Immunisation helps to prevent sickness by using the body’s own immune system to fight infection.
First disease “cured” by this was smallpox. Made illegal in Britain in 1840 because some people were cured but others still died.
When farming girls suffered from cowpox they didn’t get smallpox.
In 1794 Jenner tested his theory (infecting people with cowpox which protected people from smallpox)
He took pus from cowpox and scratched it into a small boy’s arm. Then he did the same few months later with smallpox
Later Pasteur took microbes from infected chickens and inserted them in healthy chicken but they died. A student infected chickens with older microbes. They got ill but didn’t die. Then they infected them with healthy microbes. They were they immune to new injection.
The anthrax germ was very hard to grow in laboratory . But Koch developed a new way. Pasteur used this way. He heated it for a few days on 40C and this weakened the vaccination.
Pasteur “stole” this method from the younger Toussaint.
Pasteur was challenged if the vaccination worked at Pouilly-le-Fort and it worked.
When rabid dogs bite people those people will die.
A boy was bitten and his mother heard of Pasteur. She sended the boy to him and by using his method he cured the boy.
Vaccination gradually became more popular. Immunisation is not only a issue of a single person but also of preventing the disease to spread.
Some Ethical problems are:
1. Are vaccinations really effective in preventing disease?
2. What are the side-effects and what is the chance my child gets affected?
3. What do authorities do if my child suffers lasting damage from vaccination?
Medicines to treat disease
Plants are the main source of drugs. Medicines produced from plants are used by 80% of people in the world. But out of 250.000 flowering plants in the world only 5000 have been tested for useful drugs.
The modern pharmaceutical industry has developed very fast. Until the mid- 1930s the pharmaceutical industry was small, producing very simple chemicals. Most of these drugs didn’t even work. The doctors relied on the immune system to take care of the illness while the drugs were only used to relieve the symptoms. Only one or two of these drugs actually worked.
Since chemicals were used to treat diseases in 1935 the pharmaceutical industry has changed rapidly.
These days Paul Ehrlich is often seen as the father of modern chemotherapy. His idea was to make chemicals kill bacteria without harming the other parts of the body. Dyes were used to find the infected parts. As a result of the research into dyes another drug was discovered: Prontosil. The medicine was the first of sulphonamide drugs and it saved many lives. Three years later another successful sulphonamide drug was discovered.
Another important discovery was antibiotics. It was found in 1928 by Alexander Fleming and he called the antibiotic Penicillium notatum, better known as penicillin. This medicine cured many diseases but what the researchers did not anticipate was the problem of drug resistance. Because of this new drugs had to be developed and tested. To test drugs animals were used, but this caused a whole load of ethical problems to arise. Ethics is all about what is moral and what isn’t moral to do. Only when the results of animal tests have been approved by the Medicines Control Agency , can clinical trials of the drug on humans begin. The best form of these clinical trials is the ‘double blind study’ in which the drug is given to some patients, but not to others. The patients get divided into two groups: the control group and the group that actually receives the medicine. People in the control group get a placebo. The patients nor the doctors know which patients get the placebo and which get the drug.
Medical ethics committees decide if the potential benefit of a drug is worth the risk to the volunteers. Members of an ethical committee want to see that volunteers are being thoroughly screened so that unsuitable volunteers are not included. A trial, for example, should not involve people who are taking or have recently taken other drugs which might interact with the drug to be tested.
Since the discovery of penicillin, the search for other new other antibiotics has been stimulated. A new drug, streptomycin, but the new drug costs a lot of money. So first they had to find out just how effective the new drug could be. Clinical trials showed that the drug was very effective, but it had some harmful side effects so the search for new antibiotics is still going on.
TB is one of the diseases that doesn’t have an effective treatment yet. One of the factors speeding up the spread of TB is HIV. Another factor is that badly managed TB treatments are threatening to make TB incurable. The WHO has developed a treatment strategy for detecting and curing TB. Some elements of this strategy are: political commitment, drug supplies and a drug regime which has proved effective. Drug resistance develops rapidly in TB so single drug treatments only make it worse. That is why doctors use a combination of drugs, because it is very unlikely that TB will become immune to all the different drugs. The majority of people who died even though they had the multi-drug treatment were also infected with HIV. At present there is no drug treatment available for viral diseases as powerful in its effects as antibiotics are against bacterial diseases. But recent research has developed drugs for anti viral diseases such as influenza.
Alternatives in medicine
More and more people are realizing that there are limits to the technology nowadays. But what can people do, when all else fails? People turn to the old techniques, the traditional forms of medicines. Especially people who are suffering from a long term illness, where doctors said that there was no hope anymore turn to the Alternatives. Also people that have serious trouble with an allergy turn a lot of the time to Alternatives.
Of course doctors and scientist find it difficult to accept the Alternatives. This is because we still don’t know how they work, or if they even work at all. We cannot measure or check them, on a way Science accepts.
Most of the time health of different countries is compared with the life expectancy. The life expectancy of a country can increase and decrease, but when it increases the expectancy of a healthy life has stayed the same. Conclusion: people get disabled, or get (serious) diseases in ‘’extra’’ years of life.
Medicines you get from a doctor, care most of the time only about your body. Alternative medicines however care about body, mind and the environment of the patient. Doctors and scientist see patients as a biological machine, not as a real person.
Alternative medicines had many successes. But many of them are still untested, so no one knows if they are dangerous or not. This could cause all kinds of health problems, and even death.
Alternative medicines can be sorted out in 4 big groups.
1. Nutritional medicine; herbals, clinical ecology and homeopathy, which claim to help the whole body to work better.
2. Mind body therapies which relax and focus the mind. 3. Acupuncture and healing claim to free up the flow of energy in the body.
4. Osteopathy and chiropractic which make structural changes in the body.
Acupuncture is technique from China. You stick very thin needles into your body.
In Acupuncture you believe in chi and qi. These are two sorts of energy which change place in your body. If chi and qi aren’t in balance anymore you get ill. The needle-technique can prevent or restore this balance. cupuncture is most of the time used if people get back pain. It’s also (relatively) cheap. Still, Alternatives aren’t really accepted yet. People say it’s a suspicion and it’s like a placebo. But what does it really matter? Many people get cured from Alternatives, and that’s, what we think, really matters.
What are genetic diseases?
- They are not infectious
- They cannot be "caught" from another infected person
- They are being passed on trough the generations of a family
Sometimes genetic diseases occur because of problems with whole chromosomes. With Down's syndrome the person effected got an extra copy of chromosome 21. They suffer from hearth issues and physical problems. Often the disease is not passed on because the people don't live long enough to get children, or they are sterile. Cystic fibrosis is a disease which causes a sticky mucus to create problems with breathing and the digestive system. Sufferers need to have physiotherapy several times a day and many medicines to stay alive. A child can only get the disease when both, his father and his mother are carriers.
Huntington's disease is a different type of genetic disease. A child can be affected by the disease by one dominant gene of his/her parents. The disease slowly (between the age of 30-50) destroys the nerve cells in the central nervous system. This is why people, suffering from Huntington’s, sometimes have strange facial expressions and suffer from; memory loss, bizarre behavior, inappropriate anger and strange, unexpected movements of arms and legs. Dr. James Gusella discovered a "genetic marker" present in the DNA of people with Huntington’s disease. With this data he created a test which made it possible to know if you have Huntington’s, before the effects occur. This made it easier for people to decide whether they would get children or not. Also fetuses could be screened to see if they had Huntington’s, if they were infected the pregnancy could be ended.
"Is the baby all right?"
For ages the first information about the baby, came when the baby was born. Now we can get a lot of information before the baby is born by, Antenatal testing. It's used to detect genetic problems and problems in development in the fetus. Some of the simple tests for genetic diseases are blood tests and ultrasound scanning. But when there is a problem Amniocentesis or Chorionic sampling is done. Amniocentesis involves taking some of the amniotic fluid around the fetus, while chorionic sampling is taking a sample from the developing placenta.
"What about abortion?”
There are two types of abortion, natural and medical abortion. Natural abortion happens when the fetus dies (mostly because of some sort of genetic problem). This is also often called a miscarriage. Sometimes there is a risk to the health of the mother or the baby, then a medical abortion is used. Another reason for a medical abortion is that the baby is not wanted. Abortion causes many discussions. Some people think that a woman can chose if she wants to be pregnant, and that you can't take the life of any human being. While other people think that a baby can't get a happy life when he knows that he is not really wanted.
Difficult choices have to be made. A child that is sick and might be suffering, or no child at al? Parents have to decide about the life of their own child. Sometimes people with a disability have a happy life, while other's are suffering a lot. Also there are many people that have problems with the ethical side of abortion.
Genetic counseling is helping people to deal with the fact that they have a genetic disease and help them making difficult choices. Genetic counselors often use family pedigrees to show the statistic chances that their child will have their genetic disease. They help people finding a solution perfect for them taken account their religious and social believes.
"Are there any solutions?"
A couple can chose to get no children, or screen every fetus for genetic diseases. This last option is not for al people because of the ethical problems. Another option is fertilizing an ova, and then using only the embryo's free of problem genes. The embryo's are implanted in the mother's uterus to grow further to become a healthy child.
Genetic screening is used to reduce disease. There are positive things about it, but also negative things. Some people think, that when genetic screening is used more often, it could change our way of life. For example it might affect our choice in partner and, health insurance companies could use the information to sell people cheap life insurance. That's why people are thinking about
How far we should go.
You could say that people with a genetic disease are not aloud to reproduce. If you want this plan to succeed you have to screen everyone before they are aloud to have sex. This is simply not possible because it's to expensive.
The basic principle of genetic engineering
Genetic engineering rests on the principle that all organisms, however different they may appear to be, have in common certain fundamental similarities at the level of their genetic material. Genes are written in a chemical code along the length of DNA molecules. There are four molecular ‘letters’ in the code and they are the same in all organisms. Because of this, genes can be moved by scientists between completely unrelated species. Furthermore, the gene operates in its new host in much the same way that it did in its old.
The process of moving a gene
First, you need to identify the gene you want to move. Then you can use a special kind of enzyme to cut the gene out from where it normally is, the same enzyme can then be used to make a cut in part of the genetic material of the bacterium. Finally you use a different enzyme to insert the human gene into the bacterium’s DNA.
A different simple way is to fire the genes, using a tiny gun, at the organisms you want to genetically engineer. Another technique is to use a virus or bacterium to carry the gene from one species to another. A final way is to inject the DNA directly into the fertilised egg of an organism.
Traditional agricultural breeding programmes
Agriculture requires the following four stages: sowing of seeds, caring for the plants, harvesting and selecting & keeping back some of the seeds for the next generation.
Traditional agriculture uses some sophisticated breeding methods. One frequently used technique in traditional agricultural breeding programmes is to cross two different varieties (or sometimes two closely related species). Farmers then select among the offspring for the characteristics they want. Then they need several years ‘bulking up’ the plants to make sure there are enough of them not just for research but for large-scale farming. It typically takes about 6 to 10 years to come up with a new crop variety using traditional breeding programmes. Genetic engineering provides a faster way of developing new crop varieties.
Applications of genetic manipulation in agriculture
There are two main reasons why crops are genetically engineered: to make them herbicide-tolerant or to make them resistant to pests.
Genetic engineering holds out the hope that instead of researchers starting with desirable crops and then finding herbicides that kill the weeds without harming the crops, they could start with the most desirable herbicides and then genetically alter the crops so that they, unlike their weeds, are unaffected by the chemicals.
Benefits to the farmer: often cheaper and easier to apply, may mean an extra herbicide is available and particularly effective (greater range of weeds being controlled, resulting in higher crop yields). Benefits to consumer: decrease in food prices (due to increase in crop yields and lower costs farmers on herbicides) and lower rates of herbicide application, the use of less toxic chemicals & decreased risk to domestic water supplies.
Are genetically modified foods safe for humans?
Most experts agree that the various crops currently on the market are safe for animal and human consumption, being neither toxic nor allergenic. However, some transgenic maizes have an antibiotic-resistant marker gene. The possibility has been raised that when consuming large amounts of foods containing these marker genes begin to be consumed, the gene might move to disease-causing micro-organisms in the gut and so makes them resistant to antibiotics too. Most experts suggest that the chances of this happening are not great. Nevertheless, the existence of a finite risk has slowed down the regulatory approval of transgenic maize.
The most likely solution is for companies to use other, less controversial markers, but this is less easy.
Are genetically modified crops good or bad for the environment?
Genetically modified crops may turn out to be good for the environment. The benefits to the environment: the herbicides to which crop tolerance is being developed generally break down faster to non-toxic products in the soil and are less likely to leach into ground water, they are often active in smaller amounts meaning that the total mass of chemicals applied to a crop should be less; some herbicides reduce need for pre-emergence application. However, it is possible that these crops prove harmful for the environment. One possibility is that they may be more likely to invade and then damage natural habitats. Another problem is that the genes from them might escape, via pollen, to other plants. A third problem is that transgenic crops might lead to a reduction in biodiversity. Scientists have tried to develop various models to predict the ecological consequences of genetic engineering.
Other uses of genetically engineered plants and animals
- Genetically modified plants: used to reduce human diseases
- Genetically modified plants: to produce vaccines
- Genetically modified animals: as models of human diseases
- Genetically modified pigs: to serve as human transplant sources.
- Genetically modified fish: to grow faster