According to Hammadeh, past attempts to clarify the relationship between cigarette smoking and male infertility have had trouble identifying a molecular mechanism underlying any such link. So he believes the new finding should help convince male smokers struggling with infertility to kick the habit.
"Because of the fact that cigarette smoke contains mutagens and carcinogens, there have been concerns that smoking may have adverse effects on male reproduction," Hammadeh noted. The new findings help bear that out, he said.
The second study was led by Dr. Claus Yding Andersen, a professor of human reproductive physiology at the University Hospital of Copenhagen in Denmark. It focused on the impact of maternal smoking during the first trimester of pregnancy upon the development of the male fetus.
In this case, the authors analyzed tissue from the testes of 24 embryos that had been aborted between 37 and 68 days following conception.
After classifying the prospective mothers according to smoking habits, the research team found that the number of so-called "germ cells" -- cells that develop into sperm in males and eggs in females -- were 55 percent lower in the testes of embryos obtained from women who smoked. This observation held regardless of the mother's alcohol and coffee consumption habits.
As well, embryonic levels of so-called "somatic cells" (those that go on to form other types of tissue) were 37 percent lower among those women who smoked.
In both the case of germ and somatic cells, drop-offs in levels appeared to be "dose-dependent," meaning that the more the prospective mother smoked, the lower the number of cells grown by the embryo.
Based on these findings early in fetal growth, Anderson and his colleagues conclude that the apparent impact of smoking on cellular production might continue in male offspring
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