After last week’s post about pus in semen, I thought that it might be helpful to describe another important sperm test, one that shows whether or not they’re alive.
Good sperm are alive. Not only do they swim, they live and breathe just as all living cells do. Some are dead, meaning that the ship is no longer sailing, and its motor and crew are gone.
One way of figuring out whether or not sperm are alive is to dip them in colored dye. A dead sperm can’t push the dye out of its body, but a live sperm can. In the picture, the sperm are stained with a pink dye called Eosin. The dead sperm are the ones that become pink, and the live sperm are the ones that push the dye outside and stay clear (a light bluish green in the photograph.)
The result of the test is typically described in the percentage of sperm that are alive, and of course, the more living sperm the better. But even when all of the sperm are dead, a condition called “necrospermia”, couples can still conceive using in-vitro fertilization with intra-cytoplasmic sperm injection.
That doctors can successfully use dead sperm with in-vitro fertilization illustrates a conundrum in reproductive medicine today. The ultimate barrier to fertilization is no longer the entire sperm’s health, but the quality of its DNA cargo. Unfortunately, we don’t yet have a way of knowing the condition of a single sperm’s DNA before inserting that sperm into an egg.
So if a man’s sperm don’t wiggle, the first thing to know is whether they’re alive and sluggish or whether they’re dead. A vital stain makes that distinction. But if they’re dead, a man shouldn’t despair. Dead sperm can still be used in intra-cytoplasmic sperm injection as long as their DNA is good. Unfortunately, the only way to know that right now is to inject the sperm and to see what happens.
The horrific earthquake and tsunami in northern Japan remind us that no matter how powerful we become or careful we are, nature asserts itself in ways that we can’t imagine. The nuclear engineers and technicians working to contain the radiation leaking from the damaged power plant in Fukushima are nothing short of heroic. Radiation can cause all sorts of ills, from acute sickness to cancer and infertility.
In the testis, developing sperm cells are exquisitely sensitive to radiation. Kyodo News reported that after an explosion at the Fukushima No. 2 reactor on March 15, radiation levels measured as high as 8,217 micro sievert or 0.8217 rem per hour. (Micro sievert and rem are units of radiation dosage.)
Does that amount of radiation harm developing sperm cells? I asked Marvin Meistrich, Ph.D., Professor of Experimental Radiation Oncology and the Florence M. Thomas Professor of Cancer Research at the University of Texas M. D. Anderson Cancer Center, a world’s expert in radiation and sperm. Dr. Meistrich explained that sustained exposure to 20 rem of radiation over 4 weeks caused sperm counts to drop to 1/10th of their original amount. At doses of 40-80 rem, sperm counts fell to about 1/100th of the starting number, and in some cases were wiped out entirely. At 200 rem, that drop to zero sperm became permanent. For one-time doses, Dr. Meistrich explained that 15-20 rem caused a short-term fall in sperm count, and 400 rem or more resulted in permanent loss of sperm.
We know that radiation changes DNA, the sperm’s precious genetic cargo. What we don’t know is what dose causes a harmful DNA change that damages a developing embryo or causes disease later in life.
The radiation leakage in Fukushima seems to be in the range at which damage to sperm occurs. I can only hope that the workers at Fukushima and the people near the plants are aware of the dangers and take action to protect themselves.
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