Toxicological and pharmacological effects arise when chemicals interact with biophysical functions in discrete cell types. Researchers have a continuing need to screen novel compounds for their potential therapeutic needs and, once these have been discovered, to understand their molecular actions. Histochemistry can be used to facilitate the development of the knowledge on the distribution of a compound, the receptors to which it binds and the modulation of the physiological functions that are being investigated.

Toxicological and pharmacological effects arise when chemicals interact with biophysiological functions in discrete cell types. There is a continuing need to screen novel compounds for their potential therapeutic effects, and once these have been "discovered" to understand their molecular actions, as the basis of using such compounds safely and for rational drug design. Pharmacology now uses all of the sophisticated molecular research techniques that are available for the development of safer and more efficacious drugs. Histochemistry has been usefully applied to developing new drugs (and assessing chemical safley) and is potentially cost effective. The need to test novel substances for their potential adverse effects has raised many questions. Toxicological pathology has moved away from the cataloging of lesions towards understanding the basis of the events that underly cell injury, especially for those secondary consequences of chemical injury that lead to malignancy and chronic disease. The focal nature of toxicologic lesions de mands the use of microtechniques to provide data to help understand these questions. Histochemistry is under-utilized, but offers one of the key ap proaches necessary to address the problem of understanding interactions between a cell population and a chemical, the modulation of cellular biochem istryor the presence of a lesion in a test animal can be rationalised in terms of species differences that have no relevance to man as opposed to those that are of clinical significance or represent a warning of dire consequences to man.

Individual cells behave in surpnsmg ways that cannot be deduced from the averaged results of an organ as assessed by the use of conventional biochemical methods. Thus multicellular plant and animals systems are being investigated by an increasing array of histochemical and cytochemical techniques based on general chemical or specific immunological interactions to identify structural materials and to assess biological activities. In recent years there has been an increasing range of fluorescent probes, along with advanced computerised imaging and analysis techniques, which allows the behaviour of individual living cells to be followed in considerable detail. The parallel use of microinjection, microelectrodes and patch-clamping provides additional information about cells and their responses. Recombinant DNA technology has highlighted the desirability and the power of microinjecting defined materials into specific cells and so manipulating their fundamental biochemistry. New hypotheses are being tested which will form the cornerstone of future developments across the whole spectrum of biotechnology. The First European Workshop on Biotechnology Applications of Microinjection, Microscopic Imaging and Fluorescence was run at the University of East London, U.K, 21st-24th April, 1992 with the objective of bringing together a diverse group of individuals who were using these state-of-the-art applications for biotechnological exploration. A novel feature of the meeting was paiticipation by instrument manufacturers in the programme: there were hands-on workshops (where living cells could be examined), combined with the poster sessions.