Alternatives to Laboratory Animals

In recent years, there has been a growing interest in alternatives to animal experimentation. Public attention was, and still is, focused on potential alternatives in toxicology in particular, probably because of the moral implications of testing some chemical products (e.g. cosmetics) by means of in vivo procedures such as the Draize eye test. In contrast, the use of laboratory animals for quality control of biological products such as vaccines is scarcely criticised. Nevertheless, the use of animals for that purpose is extensive and alternatives are urgently needed for several reasons. The development of models which can reduce the number of animals used or refine the experimental procedures used is receiving attention at several institutions. This paper outlines the activities of the Laboratory for the Control of Bacterial Vaccines of the National Institute of Public Health and Environmental Protection (RIVM) in the Netherlands, especially with regard to the testing of diphtheria and tetanus vaccines.

The addition of different concentrations (5–20mg/dish) of allyl isopropylacetamide (AIA) and veronal (VER) to mouse liver, skin and heart tissue explant cultures increased the biosynthesis of porphyrin from endogenous precursors several-fold as compared to controls.

Maximal effects were observed after a 12-hour incubation in liver culture for both AIA and VER (at 5mg drug/dish); after 2 and 6 hours in skin for AIA (10mg/dish) and VER (5mg/dish). In heart, with AIA (5mg/dish) and VER (20mg/dish), a peak was found after 2 hours, but a second increase was observed later after AIA induction.

Colchicine (O.1mg/dish) did not by itself alter porphyrin biosynthesis by any tissue However, when added before or after porphyrin induction by AIA, it was able to both prevent and reverse the effect of the inducer in liver explants only, having no action whatever on other tissues or when VER was used.

The usefulness of the non-animal experimental model of tissue explant cultures for investigating the porphyrinogenic properties and/or toxicity of drugs and their mechanism of action is emphasised.

Pain can either signal the threat of tissue-damage (nociception) or can result from tissue damage itself. The physiology and “pathology” of pain, in the second instance, suggest that it can be diagnosed (not “measured”, “assessed”, etc.) on the basis of its association, but not equality, with tissue damage and by its coincidence with changes in behaviour. Pain will be present as part of a syndrome and cannot occur without cause or association. Pain may occur in experiments:

a) coincidentally and unrelated to any experimental procedure,

b) accidentally, when a procedure goes amiss, and

c) as part of the experimental design.

Where pain is intrinsic to the aims of an experiment (for example in the testing of analgesics), “escape routes” and “limits” must be formulated for the benefit of experimental subjects. In addition, the empirical value of the experiment must be assessed.

There is insufficient information on the use and efficacy of analgesic drugs in animals. These drugs, however, are neither the only nor the most effective means of alleviating physical pain in animals. Other forms of treatment are considered. All depend on sound diagnosis and prognosis. Decisive action against the cause of pain is necessary.

An in vitro method for characterising the degradation of glass fibres in an intramacrophage-type environment is reported. Human blood monocytes provide the phagocytically active cultures and a “semi-dynamic cell replenishment method”, whereby cultures are replenished every three weeks with monocytes from the same donor, has enabled exposure times exceeding 26 weeks to be achieved. Tests indicated an affinity of monocytes for glass fibre, and superoxide activity in freshly isolated cells was measured and found to be comparable with that for alveolar macrophages.

Two interactive computer programs are described which illustrate different approaches to teaching the pharmacology of neuromuscular transmission. Both programs are based on a simulation of the in vivo sciatic nerve–tibialis anterior muscle preparation of the cat. Program 1 simulates the preparation and allows students to follow a schedule set by the teacher, or design experiments themselves using drugs (including unknowns) and procedures selected from an extensive menu. The sequence of events and the doses used are entirely in the hands of the user and students “learn by discovery”. Program 2 is an interactive, computer-assisted learning package based on a software simulation of experiments which can be performed on this preparation to illustrate the fundamental pharmacology. The program is menu-driven, contains extensive textual information, makes use of animated graphics, and is accompanied by educational support material and assessments. Details of each program are presented and their use as alternatives to animal experiments is discussed in relation to the primary teaching objectives of practical classes.