Chick embryos, incubated at 38-39°C to stages 8-11 (HamburgerHamilton staging), were injected (under the vitelline membrane) with ten MLD (mice) per 0.05 ml of tetanus toxin or with avian physiological saline solution.Seventeen hours after the injection the embryos were harvested and fixed in Bouin's solution. Selected control and experimental specimens were sectioned for histological study.Observations of gross specimens show that open neural folds of younger embryos are more susceptible than are the more extensively closed tubes of older embryos. The progressively more caudal restriction of toxin-susceptible sites with increasing age is a manifestation of this correlation with the degree of closure at injection time.Study of serial sections establishes the concentration of lesions almost exclusively in neural tissue, especially in the alar region of the neuraxis. Tetanus-induced lesions include encephaloschisis, myeloschisis and platyneury at various levels of the neural tube. These basic defects are comparable to those reported after treatment with many CNS teratogens.Suggestions are made concerning the possible effect of tetanus toxin on biochemical interactions that might lead to aberrations from the normal morphogenesis of the central nervous system.The current need for intensive investigation into the problem of congenital anomalies of the central nervous system is well recognized. There is also a need for increased research activity in the field of infectious diseases of the nervous system. One of the most neglected of these is bacterial infection with Clostridium tetani. Although considerable clinical literature exists on the effects of tetanus infection, little work is available concerning the effect of tetanus toxin on embryonic tissue. Gray and Worthing ('41) used the toxin in their studies of chemical interference with early morphogenesis and found it produced a variety of neural lesions in chick embryos. Since then, considerable new knowledge has developed both in the methods of treating experimental embryos and in the interpretation of tetanus toxin chemistry. The present investigation is therefore justified, and extends our knowledge of the toxin's effect on embryonic neural tissue.
MATERIALS AND METHODSThe materials for this study consisted of 124 White Leghorn embryos ranging in development from stage 8 to 11. All embryos were staged according to the morphological criteria of Hamburger and Hamilton ('51). Eggs were incubated in a n Oakes incubator (without forced draft) for 26-45 hours at 38-39°C to bring the embryos to stages 8-11. Embryos were exposed through a window cut over the blastoderm after it had been brought into position by the manipulation proposed by Harkmark and Graham ('51). Suitable embryos, staged under the dissecting microscope, were injected either with tetanus toxin or avian physiological saline. The tetanus toxin used had a potency of Lf 50, Kf 210 and 1,380,000 LDso (mice) per ml. Prior E. CORLISS, A. A. FEDINEC AND G . G. ROBERTSON to injection the toxin was ster...
