Sweat and Cystic Fibrosis

Bert Bert
Wed Apr 13 10:11:38 EST 1994

Hello Netters!

This is the text of a letter I sent to Lap-Chee Tsui a couple of
months ago.

Although he hasn't responded, I still think my hypothesis is
plausable and even think that Neel's new book (Physician to the Gene
Pool, John Wiley and Sons, 1994) in his chapters on the Yanomama 
Indians, which he describes as a "no salt" culture (Circulation, 52,
146-151 (1975), may lend some creedence to my wild speculation.

                             October 26, 1993

Dr. Lap-Chee Tsui
Hospital for Sick Children
Department of Genetics
555 University Avenue
Toronto, Ontario CANADA M5G 1X9

Dear Lap-Chee:

     You and I met during the Molecular Genetics Gordon Conference
this summer at Newport.

     Ever since your talk, I have been thinking subliminally about
the color slide you presented from your 1992 TIGS article showing
the frequency of different CFTR mutations in different ethnic groups.
That slide reminded me very much of Doug Wallace's fascinating work
on tracing the evolution of the Amerinidians as they formed
different linguistic groups and mated, allowing for diagnostic
mutations within rapidly diverging (maternally derived) mitochondrial
DNA. I know that you know Doug and this work, but I'm reminding you
of it because I want to set the stage for what I think is my novel
thought and my request of you.

     This weekend I was reading a book, by a scientist who has 
been studying herbal remedies among Amazonian tribes of Amerinidians.
In one of his descriptions, the Harvard trained ethnobiologist
describes his increasing fatigue while hiking through the rainforest
and savannah in the following way:

     "I later learned that physiology was on Kamainja's side.
      Caucasians tend to have a higher basic metabolic rate than
      South American Indians and therefore have more body heat to
      dissipate -- an adaptation to a colder European climate.
      Because the rain forest is such a humid environment, sweating
      is an ineffective way to cool the body -- the sweat never
      evaporates.  As a result the Indians sweat very little".

It occurred to me that this comment might be used to answer a
question which has plagued me since the cloning of the CFTR locus: 
What are the heterozygote advantages of the mutant alleles?

Since sweat secretion in response to beta-adrenergic stimulation is
completely lacking in CF homozygotes and is reduced to 1/2 normal in
heterozygotes, I am thinking that diminished sweat capacity may be 
among the heterozygote advantages conferred by CFTR protein mutations.
Therefore,  a study of the ethno-geographic distribution of the
mutant alleles should show more heterozygosity in populations where 
such 'sweat supression' has a selective advantage, such as the
Amazonian indians.  Is there any data from the consortium to
support or refute this hypothesis?

In either case, I am writing you in the hope of establishing that I 
have done enough thinking about this issue that I would be honored 
to collaborate with you in suggesting these ideas to the scientific
community in the form of a publication.  Would you be willing to
co-author something with me that stated something of this hypothesis?


                               Bert Gold, Ph.D.
                               Assistant Professor of Pathology

Netters interested in this idea or collaboration are welcome to
contact me.

Bert Gold   Temple Path, Jefferson Path, Fels Inst.   PHILADELPHIA
(215) 707-8024 VOICE
(215) 707-2781 FAX
bert at sgi1.fels.temple.edu
gold at astro.ocis.temple.edu

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