Bulletin Autumn‧Winter 1995

r e l e v a nt i n t r a c e l l u l ar s i g n al t r a n s d u c t i on p a t hwa y s. Base d o n these data t h ey have hypothesized tha t the macrophage utilizes only a limited number of second messengers whose capabilities are magnified t h r ough their ability to interact and cooperate w i t h one another. The emphasis is n ow o n studying the spatial and t emp o r al relationship s that exist amo ng the various intracellula r transduction pathways. The Messenge r Molecule — Calciu m Ion One o f the second messenger molecules the investigators ar e particularly interested i n is c a l c i um i o n, Ca2+. Ca2+ has t w o i mp o r t a nt characteristics. Not o n l y is it an i mp o r t a nt i n t e rmed i a ry agent but, u n l i ke other second messengers tha t are 'killed' b y the cell after they have carried out their special function, Ca2+ remains intact. So, whe re does it go thereafter? What happen s to it? Prof. Lee and Dr. Kong are seeking an answer to these questions. Ca2+ is k n o w n t o b e r e l e a s ed f r o m intracellular stores during macrophage activation to stimulate many enzymes and cellular processes elsewhere i n the cell. To trace the intracellular journey of the researchers have to use some very sophisticated techniques and equipment. For e x amp l e , t h ey n e ed t o f i n d w a y s o f visualizing Ca2+, and this is done by c omp l e x i ng it w i t h a fluorescent dye w h i ch gives a green fluorescence under laser light. The cell under i n v e s t i g a t i on is p l a c ed u n d e r a c o n f o c al microscope wh i ch is different f r om an ordinary microscope i n that it can v i ew the cell at various focal depths. The data are stored i n a computer i n digital form, and can be recalled later and comb i ned to construct a 3D picture of the cell. By noting the time at wh i ch the pictures we re taken, it is possible to get a g o od idea of wh e re Ca2+ was released, whe re it went, w h e n it began the trip and at what speed. The data p r esen t ed i n Fig. 3 s h ow t he changes i n internal Ca2+ concentration w h e n the macrophage cell encounters a bacterium. As is apparent i n all three cell studies, there are significant increases i n Ca2+ level. Fig. 3 Before Activation After Activation Research 22