short-chain peptides (K"^ channel blockers) from 
the venom of the scorpion Centruroides limpidus 
limpidus; 3) the cloning of four genes that code for 
scorpion toxins of C. noxius; and 4) an analysis 
of the pancreatic secretagogue effect of scorpion 
toxins. 
The research in the laboratory of Randy J. Read, 
Ph.D. (University of Alberta, Edmonton) is aimed at 
advancing the understanding of infectious diseases 
at the molecular level, using information from the 
three-dimensional structures of key proteins. There 
are two major aspects to this w^ork. First, x-ray crys- 
tallography is employed to determine the structures 
of a number of proteins involved in the process of 
infection. Second, computational techniques are 
being developed to exploit such structural informa- 
tion in the rational design of new drugs for the treat- 
ment of infectious disease. 
Over the past year, the laboratory of Ranulfo 
Romo, M.D., Ph.D. (National Autonomous Univer- 
sity of Mexico, Mexico City) has investigated the 
representation of tactile signals in the cerebral cor- 
tex of awake monkeys. A first objective of this re- 
search was to define quantitatively the neural 
representation of moving tactile signals in the so- 
matosensory cortex. It was found that neurons of the 
somatosensory cortex respond to tactile stimuli 
moving at speeds from 20 to 100 mm/s. Also, the 
direction of the moving tactile stimulus appears to 
be coded by a neuronal population distributed in 
the somatosensory cortex. These cortical neural sig- 
nals should account for tactile performance. 
The research of Janet Rossant, Ph.D. (Mount Sinai 
Hospital, Toronto) and her colleagues focuses on 
the early development of the mouse embryo. Studies 
at the time of gastrulation have indicated that one 
cell type, mesoderm, instructs the overlying ecto- 
derm cells to make the tissue that will later form the 
brain. Retinoic acid, a vitamin A derivative, may be 
involved in anterior-posterior patterning of the 
brain at this time, as indicated through studies of 
transgenic mice designed to provide a readout of 
retinoic acid action in the embryo. Finally, new 
genes expressed at these early stages are being iso- 
lated by a "gene-trap" approach. 
In one area of the cerebral cortex, visual informa- 
tion is transformed into information about the spa- 
tial distribution of objects in the environment. To 
understand this transformation, Jean-Pierre Roy, 
M.D. (McGill University, Montreal) and his col- 
leagues study cells that respond when the subject 
moves in its environment. The laboratory examines 
how, in those cells, the response to certain charac- 
teristics of the visual input (for example, differen- 
tial speed of motion of points in a visual display) 
could signal the relative depth of objects in the envi- 
ronment. The group's hypothesis stems from the ob- 
servation that when one moves while examining an 
object, objects that are at different depths will ap- 
pear to move at different speeds. 
The entry of calcium into cells through voltage- 
gated calcium ion channels is responsible for a num- 
ber of important physiological properties of differ- 
ent cell types. Much research has been directed 
toward understanding the diversity of calcium ion 
channels, and it has been proposed that distinct 
channels are selectively localized in nerve cells and 
that each type contributes uniquely to neuronal 
physiology. Utilizing molecular genetic techniques, 
the laboratory of Terry P. Snutch, Ph.D. (University 
of British Columbia, Vancouver) has determined the 
molecular basis for a large portion of the calcium 
ion channel heterogeneity that has been previously 
described. An unexpected finding is that a much 
larger number of channel isoforms can be defined at 
the molecular level than previously anticipated. 
The distinct isoforms are unequally distributed in 
the nervous system, and this suggests that they play 
different roles in the functioning of nerve cells. 
The research interest of the laboratory of Lap- 
Chee Tsui, Ph.D. (Hospital for Sick Children, To- 
ronto) concerns several general topics within the 
scope of the molecular biology of mammalian gene 
regulation and function. A major research activity 
centers around cystic fibrosis (CF). The identifica- 
tion of the gene and, subsequently, the different 
mutations causing the disease have provided the mo- 
lecular basis for understanding the missing function 
in patients with CF, for DNA testing of individuals 
for carrier status, and for developing improved 
means of therapy. More recent work also shows that 
it is possible to correlate certain symptoms of the 
disease with the mutations carried by a patient. In 
another study the mutation causing a small and de- 
fective eye lens in a mutant mouse strain has been 
identified and serves as an excellent model for the 
study of human eye diseases. Yet another set of ex- 
periments has led to a new technique that prom- 
ises to revolutionize the gene mapping field. The 
laboratory also has begun a significant effort on the 
characterization of the entire chromosome 7 as part 
of the international genome study, in order to fa- 
cilitate the cloning of any disease genes that are lo- 
cated on it. 
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