Dr. Raabe's Work

["Mercado, Don" <don.mercado@lmco.com>]

Interesting.....

Radiation Effects May Be
                    Inherited 

                    November 10, 1997

                    NEW YORK (Reuters) - Defects in cell reproduction
and growth resulting
                    from exposure to radiation may be passed along to
future generations,
                    according to a study in laboratory mice. 

                    The defects occurred in about 20% of the children
and grandchildren of male
                    mice whose gonads were exposed to extremely high
radiation levels prior to
                    mating. 

                    Scientists at the University of California-Davis, in
Davis, California, observed
                    the defects in embryos, called "chimera," which were
created when embryo
                    cells taken from the female mates of irradiated mice
were combined with
                    embryo cells taken from mice that had not been
exposed to radiation. 

                    "We allowed that (chimera) to go through two or
three cycles of cell division
                    and looked at the relative number of cells from the
two partners," says study
                    co-author Dr. Otto Raabe, professor emeritus of
radiation biophysics at the
                    University. "We have a way of labeling the cells so
we can tell which were
                    from the radiation-exposed versus the 'control'
cells." 

                    The researchers then measured the "proliferation
ratio" of the cells. "Basically,
                    if nothing unusual happens, you'd expect to have
about equal numbers in cells
                    from both halves of the chimera," Raabe explains.
"But cells from the
                    irradiated parent do not proliferate, or divide, as
fast. They have what we call
                    a 'proliferation disadvantage.'" 

                    The researcher says these decreases in proliferation
were tied to paternal
                    irradiation "with doses of gamma radiation to the
backsides of the male mice."

                    "The key here is that the radiation effect is on the
developing sperm and it
                    occurs at a specific point in the developing sperm,
not on the mature sperm,"
                    explains Raabe. During successive matings, at about
six to seven weeks after
                    radiation, "the embryos produced by conceptions at
that time are the ones
                    that have this effect (proliferation decrease). The
ones produced earlier or
                    later don't have this effect." 

                    The researcher says the effect has been observed
with radiation doses varying
                    from 1 rem to 100 rem. And at 100 rem, the
researchers found that the effect
                    can be inherited by the offspring of the irradiated
males. 

                    The researcher says radiation exposure of 100 rem
may apply to survivors of
                    an atomic bomb blast. He notes that radiation
therapy for cancer patients
                    "could be much higher but is focused on certain
areas of the body, not
                    whole-body radiation at this level." He says 1 rem
exposure is "within
                    radiation worker acceptable levels." The one-year
limit for radiation workers,
                    such as workers in nuclear power plants and hospital
workers involved with
                    radioactive materials, is 5 rems. 

                    "We haven't done any heritability studies at 1 rem,"
Raabe says. "That's the
                    next part of the study. But we've had the
proliferation effect down to 1 rem." 

                    "If this (the new study) is confirmed, then
germ-cell irradiation during critical
                    periods prior to conception may require special
radiation safety
                    considerations for radiation workers in their
reproductive years," the
                    researcher states. 

                    SOURCE: Radiation Research (1997;148)