|Year : 2015 | Volume
| Issue : 1 | Page : 7-10
Animal experimentations: Part I: General considerations
Department of Periodontics, Guru Nanak Institute of Dental Sciences and Research, Kolkata, West Bengal, India
|Date of Web Publication||18-Mar-2015|
Prof. T K Pal
Professor and Head of Department, Department of Periodontics, Guru Nanak Institute of Dental Sciences and Research, Kolkata - 700 114, West Bengal
Source of Support: None, Conflict of Interest: None
| Abstract|| |
All materials, in the form of drugs or devices, which are intended for human use are required to be tested first in suitable animals. Many biological understandings are established on various modes of cruelties on animals. This observational notes guide us to accept or modify or even reject materials for ultimate human use. The science of experiments on animals gives us the remedial solutions to many of our human sufferings. This unique and important discipline is in need of proper understanding for selection of suitable number of animals and its proper care in captivity, and further refinements of code of conducts and ethical issues.
Keywords: Animal experimentations, biomedical research, ethical issues
|How to cite this article:|
Pal T K. Animal experimentations: Part I: General considerations. J Int Clin Dent Res Organ 2015;7:7-10
| Introduction|| |
Experimentation on animals is the basis of the biomedical sciences, not only for the advancement of man's understanding of the nature of life and the mechanisms of specific vital processes, but also for improvement of method of prevention, diagnosis, and treatment of man and animals.
Animals have been used in research and experimentation since medical research began. It was animal experimentation that revealed the most elementary knowledge of the physiological functions of man and animal. Galen (AD 130-200) had proved the fact that arteries contained blood by exposing a length of artery in live animals.  In 1798, Edward Jenner developed a vaccine from the cowpox agent that protected people against small pox. The understanding of infectious diseases was furthered by Robert Koch's study of anthrax in 1876. Barting and Best discovered, in the early 1920s, that pancreatic extracts would reverse diabetic coma in dogs is a classic example of the contributions of animal research to human health. 
It was only by early 19 th century that there was widespread use of animals for experimentation purpose, with the aim of advancing medical science. Following World War II biomedical research developed at an unprecedented rate. In early periods, experiments were mainly regarding physiological research with no immediate therapeutic objective. Early experiments were carried out without use of anesthesia and would be regarded cruel in the present times,  inviting wrath of animal welfare groups. In the present time, numerous animal experiments are being carried out under ethical codes, and are published in various reputed journals and texts. Animal model are not only used to study human diseases, but also to increase our knowledge of basic biological responses and to evaluate the safety and efficacy of various artificial and biological compounds and devices. It is estimated that the number of animals used annually for biomedical purpose range from 1 million for India to 2 million for Canada and 6 million for Japan. 
Experiments being carried out on live animals may sound inhuman, but they can be justified. It is inevitable to conduct these experiments. They are used for proper understanding and pathogenesis of different diseases, to undertake drug trial, to generate a variety of biomedical products like vaccines, in immunological studies, etc. Animals are also indispensable for in vivo and ex vivo testing to evaluate biomedical devices and for testing biocompatibility of materials. 
Apart from experiments, proper animals are very useful for testing potency and safety of many biological substances used in field of human and veterinary medicine. There are numerous manmade substances that never existed before in nature, for example, synthetic pharmaceuticals, food additives, agrochemicals; and it is essential to test biological activity of these substances. It is obvious that such test first be carried out on animal subjects before trial on humans. 
The advances observed in most medical therapies of recent years stem from studies performed on animals. Such studies are directly applicable to human beings because there is basically no difference between functioning of human tissue and that of animals. It seems likely that the phenomenon of life-sustaining processes and the adjustments to diseases are similar, if not identical certainly throughout the class of mammalia, if not others. Some differences obviously exist among species, but most biological events, wound healing in particular, seen comparable, only the magnitude and timing of specific features may differ. The problem is anatomical, more than physiological or cellular. 
| Selection of Experimental Animals|| |
It is essential for any experiment that care should be given to choice of the species employed. Success or failure in any series of animal experiments depends on the choice of a suitable subject. Lack of attention to this point will lead to waste of many animal lives, as well as time and trouble on the part of the experimenter. Obviously the best experimental animal to use to investigate a problem involving any species is that species itself but for reasons of economy, speed, sentiment, or law; this is not always possible.
It has been estimated that more than 1,200,000 species of animals have been described, but 97% of the animals used for biomedical purpose belong to only 10 of them. They are rat, mouse, rabbit, chicken, dog, guinea pig, pig, hamster, monkey, and cat. Only occasionally are animals of less common species are used, for example, armadillo is suitable for leprosy research.
The animals used in research must be easy to obtain and suitable for the experiment at hand. The handling of the animal should be easy. They should be easy to feed and their diet also should be cheap and easily obtainable. The experimental animal should have a psychological makeup such that it is tolerant of captivity and is able to breed freely in captivity. The living condition of the animal should be readily reproducible; this includes adequate temperature, humidity, light, etc. Finally, the animal should be healthy and be resistant to infections, an unhealthy or diseased animal is not suitable for research work.
For selection of suitable animal; specific anatomical, physiological, pathological, and/or psychological characteristics need to be considered based on current scientific literature as under: 
- Factors related to the species
- Size, body conformation, and anatomic characteristics
- Age and life expectancy
- Feeding habits
- Genetic characteristics
- Health status
- Indigenous factors
- Space and caging
- Factors related to the research project
- Type of agent being investigated
- Dosage of the drug and route schedule of administration
- Factors related to the investigator(s)
- Past experience and existing knowledge
- Field of interest
On practical basis, the size and configuration of the animal may be an important parameter. Small animals afford several advantages; they generally cost less, are easy to handle, breed faster, and have higher metabolic rate. On the other hand, in large animals, surgical procedures and intravenous injections are more easily carried out, and larger amounts of tissue and body fluids can be obtained. Body formation is especially important where long-term restraint is required.
Besides, the age of animal, their sex, and reproductive status should also be considered. Depending on length of study, the life span of the animal model and growth rate may be important factors. Is the study going to be acute or chronic? If acute, what phase of life does it involve: Fetal development, the new born period, maturity, or old age? Different animals have varying responses at each of these stages. Newborn and aged animals are often more susceptible to certain disease processes, while hormonal effects are usually most prominent in the prime of life.
Other factors to be considered in selecting a species for a particular experiment are the reproductive characteristics, gestation period, litter size, and fetal growth rate. The sexual dimorphism of mice may be useful for a study analyzing the hormonal effects of drugs. Rabbits have a relatively short gestation period and their in utero growth rate and organogenesis are known. Therefore, this species are useful in rapid screening of compounds in studies on teratogenesis. 
The choice of animal is also influenced by the kind of study/experiment to be carried out, for example, 'acute' experiments, that is, those in which animal is either rendered de-cerebrate or maintained under anesthesia throughout the experiment and not allowed to recover. Many important discoveries concerning reflex action; synaptic transmission; perception of light and sound; secretion of digestive glands; and behavior of cardiovascular, respiratory, and excretory systems towards natural and synthetic drugs have been made by means of this experiment.  For these experiments, the animal must be large enough to enable the investigator to carry out dissection. Rabbits, cats, and dogs are suitable, but mice and rats are too small. Secondly, anesthetizing de-cerebration must be easily accomplished and a good blood pressure maintained. This criterion is fulfilled by cats and dogs, but not by rabbits. Thirdly, in those instances in which the results are likely to be of medical significance, the behavior of the system under investigation should correspond as closely as possible to that of man. In this respect, the circulatory and neuromuscular system of the cat and dog appear to be more satisfactory than rodents. Sometime cadaveric animal is sufficient to test the dimensional and biomechanical testing of some medical and dental devices, for example, implants. ,,
In studies which require long-term restraint, body conformation of animal is important. Pigs and non-human primates both have cardiovascular system similar to that of man; but for study requiring long-term monitoring, the primate may be the animal of choice because of the comparative simplicity of confining it in a restrained apparatus.
Genetic background, microbial status, and environmental factors will influence the characteristics of the animal model. Modern technology has increased our ability to manipulate and understand the genetic basis for many species. Whether or not these advances will become important for in vivo biocompatibility evaluation is not yet clear.
An investigator should consider the influence of genetics, which surely have on the interpretation of biocompatibility research data. It is equally important, however, to consider other significant factors that can have dramatic effects on the quality and consistency of the animal model, such as the microbial flora.
An entire scientific discipline, known as gnotobiology, is devoted to establishing and controlling the microbial status of laboratory animals. A gnotobiotic animal is one which carries one or more known forms of living organisms and no demonstrable organisms that are not known to the investigator. An axenic animal, often referred to as germfree, is free of all detectable microorganisms. These animals require highly sophisticated management techniques and housing, and are normally used for specialized studies. It is unlikely that efficacy testing of biomaterials would require the utilization of either gnotobiotic or axenic animals.
Many laboratory animals, commonly used in biomaterial research evaluation, are defined as specific pathogen-free (SPF). These animals are derived by cesarean section and housed in a well-controlled environment, known as a barrier facility, to prevent exposure to pathogenic organisms. An animal that is designated as SPF will have an undefined microflora, except that it is known to be free of specifically named pathogens. For example, a SPF rabbit designated as Pasteurella-free, could carry other pathogens, such as Eimeria species or Encephalitozoon cuniculi.
A conventional animal is one that has uncontrolled microflora and is reared and maintained under conditions where limited effort is made to control exposure to pathogens. It is possible that such animals are free of selected pathogens, but no assumptions should be made unless diagnostic evidence supports a disease-free state.
The selection of an animal model is, then, a complex challenge. Old habits die hard and the past experiences of the investigator are often the most important factor in his/her choice of a species. Another important factor is the body of knowledge available to members about a particular species and strain of the laboratory animal. Veterinary staff of an institution should provide a valuable resource to investigator as they begin to identify the most scientifically appropriate model for biomaterial evaluation. Veterinarians who have specialized training or experience in laboratory animal medicine will be able to recommend specific animal models, give advice concerning the biology, genetics, microbial status, source, and environmental and health factors that will facilitate the investigators in decision making. The choice of species must be within the limits of the law and should be based on moral and ethical imperatives. The veterinarian can also provide guidelines on the appropriate methods of restraint, use of anesthetics and pain-relieving agents, postoperative care, and method of euthanasia. 
| Conclusion|| |
Public attitudes towards the use of animal will continue to influence legislation and funding resources for scientific research. Selection of appropriate models and judicious utilization of animals will help to allay the concerns of the public and facilitate the ultimate goal of providing products that benefit mankind.
| References|| |
Howard-Jones N. A CIOMS ethical codes for animal experimentations. WHO Chron 1985;39:51-6.
Orlans F, Barbara. Review of experimental protocols. Laboratory animal science (special issue); 1997.
Arthur G, Vijayan L. Rationale for animal experimentation and animal ethics. Trends in Biomaterials and Artificial Organs; 1995. p. 9.
Pal AK, Pal TK, Mukherjee K, Pal S. An experimental study for evaluation of biological compatibility of calcium hydroxyapatite chitosan composites. J Indian Soc Periodontol 2003;6.
Kohad RM, Yeltiwar RK. Experimental animals in medical and dental research. Bull Indian Soc Periodontol 1992;16.
Chakraborty A, Kundu B, Basu D, Pal TK, Nandi SK. In-vivo
bone response and interfacial properties of Titanium alloy implant with different designs in rabbit model with time. Indian J Dent Res 2011;22:277-84.
Banerjee S, Chakraborty A, Pal TK. Bone density and dental implants. J Indian Dent Assoc 2014;30.
Pal TK, Chakraborty A, Banerjee S. A microanatomical comparision of goat jaw cancallousbone with human mandible: Histomorphometric study for implant dentistry. J Int Clin Dent Res Organ 2014;6.
Pal S, Pal TK. Clinical trial of HA-coated titanium dental implants: Ethical issues-Critical Reviews. In: Bourne JR, editor. Biomedical Engineering Vol 25. Nashville: Vanderbitt University; 1997. p. 120-5.
| Authors|| |
About the author
Dr. T. K. Pal, a 1977 graduate from Dr. R. Ahmed Dental College, completed his M.D.S. in Periodontics (1980) from King George's Medical College, Lucknow, and further did his Ph.D. in Dental Implantology from Jadavpur University, Kolkata. He had a post-doctoral training in Dental Implantology at New York University. He worked at Dr. R. Ahmed Dental College (1981-2002) and now heads Periodontics at Guru Nanak Institute of Dental Sciences and Research, Kolkata. He has 77 publications and delivered about 100 Memorial Orations, Keynote Addresses, Guest Lectures and also conducted Implant courses across the country. He was the President of Indian Society of Periodontology in 1994 and also served as President of West Bengal State Dental Association as well as West Bengal Dental Services Association. He was the Founder-Editor of West Bengal State Dental Journal in 1985 and member of Editorial Board in many National Journals including co-authorship of 3 textbooks. He holds the patent-right for his innovation on Titanium Dental Implant and was honored with National Republic Day Scientist Award on 26th January, 1998, by Govt. of India. He is the recipient of Dr. Y. P. Guglani Prize for 4 times and received Rotary Young Dentist Award (1997), Millennium Award (1998) and National Bite-in Award (2011) for his continued scientific endeavors. He has been cited in the Who's Who in the World (1998).