Can Animal Models Be Useful In Understanding Physiological Basis Of Anorexia

Employ of brute models in biomedical research

People frequently ask how the apply of animals in experiments can be justified when animals are clearly so different from humans. The reply is that animals are used in specific areas of research where they practise not differ from humans for the characteritics being studied, and where the differences are of no significance to the project. Animals are therefore used every bit highly specific 'models' of humans.

Models should resemble the thing being modelled, but must be unlike in other ways

The similarities and differences between models must be considered in every project. The of import features of a model can exist seen using an illustration: a doll is a model of a human used to entertain a child. To be a useful model for this purpose information technology needs to be like a human in some respects, such as having characteristics that a child recognises as a head, a body, eyes, nose, limbs etc. Nonetheless, it is dissimilar from a human in many other respects. If information technology were to exist more human, and have a nervous system and so that it feels pain, and blood so that it bleeds when damaged so information technology would be a worse model for its particular purpose. We would non desire blood on the carpet or the ethical dilema of causing pain.

A model must therefore be like the thing being modelled in some respects, and unlike information technology in another respects, with some characteristics beingness neutral. Models are also specific for a particular purpose. We cannot do medical reserch using dolls, and similarly a rat may be suitable for some inquiry projects and not for others.

Models can exist "better" than the thing existence modelled

Humans have certain cognative abilities such as addition, subtraction, multiplication and partitioning which can be modelled using an electronic calculator. This sort of model can be called a "super model" considering it performs a specific task better than the thing being modelled. Given the choice between using our brain to multiply a two three digit numbers or the calculator, well-nigh of us will choose the latter. The calculator is a highly abstract model of a very specific man role, and is only of value for i specific purpose.

In some cases animal models and in-vitro models are super-models of humans, because if humans were bachelor for the experiment we would cull not to use them. For instance, if we desire to study some aspects of genetics we may choose a computer model, a fruit fly or a mouse. We know plenty near genetics to be reasonably sure that the results tin be applied to humans, but our models are able to give results apace and cheaply.

The similarities and differences between animals and humans are taken into account when choosing a model

In trying to assess the validity of animal experiments it does not make sense to compile lists of differences between animals and humans, because we desire them to exist dissimilar in many ways. When studing obesity a mouse strain might exist a good model of humans considering it becomes obese, gets diabetes and dies young. The same strain may be useless in a long-term toxicity study for exactly the same reasons. Each inquiry project must give careful consideration to the choice of the specific model.

An example: a model for the treatment of colon cancer

Colon cancer can usually exist treated finer unless information technology has already spread to the liver. By the time it is diagnosed this may have already happened, and by this stage it could be inoperable. In this instance, however, a new microwave probe, about the size of a pencil, has been developed. This could exist inserted into tumours, allowing a dose of microwaves to be applied, cooking the tumour and killing information technology.

The problem was to decide the dose (volts) and time required to cook a liver tumor of a given size with this probe. The experiments also needed to decide whether several tumours could be treated in 1 patient, and what happened to an individual with some liver / tumor tissue killed in this way. Would it kill the patient? Conspicuously information technology would be both unethical and impractical to use a human for these studies, fifty-fifty when terminally sick patients are bachelor, so an creature model was needed.

As the probe could not be scaled down, the animal model needed to have a liver of about the aforementioned size equally a man. Rats were clearly unsuitable, but pigs were a more than appropriate option. The pigs were anaesthetised, and 1 or two areas of the liver treated with various doses of microwaves. After being allowed to recover the pigs were and so killed at different time-points.

This enquiry showed the dose of microwaves which is predicited to kill squealer liver tissue of various diameters. The pigs were found to tolerate several lesions, and after two months the lesions had shrunk, although the animals were not kept long enough to observe whether they disappeared.

Clinical trials ensure that the model has worked successfully

There is no absolute assurance that the animal tests accurately predict human being responses. As this was pig, not human, liver and information technology was normal tissue, not a tumour, it is notwithstanding necessary to do a small clinical trial earlier widespread use. If the prediction had been inaccurate, then the first human patients would suffer. Fortunately, the grunter data was highly predictive of the human results, and several terminally ill patients have now be successfully treated and take left hospital apparently fully recovered.

With the development of new drugs the clinical trial is time-consuming and expensive. With this unproblematic surgical model at that place were some terminal cancer patients who it was estimated simply had a few weeks to live, simply were able and willing to requite informed consent. In this example it did not matter that the pig differs from humans in many ways so long as the liver was most the same size as the man liver, and it responds in a similar style to microwaves.

Alternatives that supplant the use of animals are also used as models

Most of the replacement alternatives to the utilize of animals are models of the same sort. They resemble some very specific human features, but differ in many other ways. Every bit an example, in early on human pregnancy in that location is a surge of hormones affecting the uterus. Many years agone pregnancy was diagnosed using an creature model. A sample of urine was injected into some mice and the increase in uterus weight measured, or into frogs which and then ovulated if the woman was pregnant. Now this can be modelled in a abode pregnancy testing kit.