Inhibition of Embryo Formation in Certain Nematodes by Roentgen Radiation. ∗

Abstract

Although it is generally recognized that embryonic tissue is more radiosensitive than that of adults, 1 it was thought of interest to determine the effects of roentgen radiation on certain nematodes in which the young develop inside the body of the mother. Such experiments were undertaken in the hope that (a) they might yield information concerning differential susceptibility of cells, and (b) roentgen radiation might prove to be a useful tool in the study of trichinosis. Results of preliminary experiments 2 have been confirmed and extended in this report.

Experiments with Trichinella spiralis. Larvae, removed from infected rat muscle by pepsin digestion, were irradiated with dosages of radiation ranging from 400 r to 6,400 r (H.V.L. ca. 1.5 mm al., 427 r/m). The larvae were then fed to healthy rats and recovered from the intestine 5 days later. Microscopic study of 33 unirradiated female trichinae indicated a mean number of 59.4 worm-shaped embryos (with a standard error of the mean of 4.4) per female. Seventeen females irradiated with only 400 r contained 27.4 ± 5.5 worm-shaped embryos per animal. An irradiation of 1600 r reduced the number of worm-shaped embryos per female (25 examined) to 16.15 ± −3.25. Irradiations of 2000 r (39 examined) and 2,500 r (14 examined) completely inhibited the formation of worm-shaped embryos, but many late cleavage stages were present. Following irradiations of 3,000 r (23 examined), 3,500 r (23 examined) and 3,750 r (20 examined), embryonic development was stopped in early cleavage stages, although the adults themselves were apparently not injured. A dose of 5,000 r (6 examined) inhibited further development of the irradiated larvae.

Inasmuch as the control as well as the irradiated worms at this time contained some undeveloped embryos, the question arose as to their possible development, in time.