Foreword 
HE Howard Hughes Medical Institute (HHMI) is pleased to present the sixth volume in the 
series Research in Progress. From its origin in 1986 as a means of providing a brief but 
informative overview of the research being carried out by the Institute's investigators, this 
publication has become a valuable source of information for not only the entire HHMI commu- 
nity but also many scientists and nonscientists who are interested in current progress in biomed- 
ical research in general. One measure of the usefulness of these reports is that last year approxi- 
mately 2,000 copies were distributed, many to individuals requesting it for the first time. 
New readers may be interested in other HHMI publications, some of which describe the pro- 
grams of the Institute or deal with general topics in scientific research and education. The Annual 
Scientific Report is the official archival record of the Institute as a Medical Research Organization 
(MRO). It contains a description of the research by each HHMI investigator, including a bibliogra- 
phy, and highlights other activities of the Institute. A general Annual Report of the Howard 
Hughes Medical Institute describes for a lay audience the various HHMI programs and gives a 
summary of Institute financial data. 
A series of reports for a general audience on subjects of current scientific interest is also published. 
The first report, produced last year and entitled Finding the Critical Shapes, describes exciting 
advances in structural biology and how the determination of the structure of biologically important 
molecules and the correlation of structure with function are leading to understanding of life processes 
and new approaches to the prevention and treatment of diseases. This report was widely acclaimed by 
a broad spectrum of readers, especially teachers who found it useful in their classrooms. Over 33,000 
copies have been distributed. A second report, on genetics and human diseases, entitled Blazing a 
Genetic Trail, has recently been released; it is clear that it also will be highly successful and in great 
demand, as the first printing of 45,000 copies has almost been exhausted in a few weeks in response to 
many requests, including again teachers all across the country. 
HHMI has a large grants program that complements its research activities as an MRO. It is antici- 
pated that this year grant awards will total approximately $47 million. The grants program supports 
education in the biomedical and related sciences at the precollege, college undergraduate, graduate, 
and postdoctoral levels. These initiatives are described in detail in an annual publication entitled 
Grants for Science Education. In 1990 a report on Support for Science Education and Research, 
summarizing the level of funding by foundations and voluntary health associations, was also 
published. 
In addition to providing an up-to-date report on the rapid progress in biomedical research as 
illustrated by the work being done in HHMI laboratories, this issue of Research in Progress reflects 
the continued expansion of the Institute's activities. As of July 1 , 1 99 1 , there were 223 HHMI investi- 
gators based at 52 institutions across the nation. Their research is the core of the Institute's activities, 
and we invite you to share, in these pages, in the excitement of discovery and the advances in the 
knowledge of biological processes and disease mechanisms that hold great promise for the betterment 
of the human condition. 
Purnell W. Choppin, M.D. 
President 
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