Table 1.

Hcys treatment at time 0, stage 14 (53 h)

	Control	Hcys, 0.5–2.5 μmol	Hcys, 5–7.5 μmol	Hcys, 10 μmol	Hcys, 15 μmol	Hcys, 20 μmol
Survival	≥85%	≥85%	≥85%	≥85%	≤25%	0.0%
NTD	0%	0–5%	≤18%	≥30%	≥75%	—

Embryos were treated with d,l-Hcys in the amounts indicated, at incubation time 0, 24, and 48 h. They were harvested at 53 h (stage 14) and evaluated for the occurrence of grossly or histologically visible defects in neural tube closure. d,l-Hcys (10 μmol) gave the best rate of (survival) × (% defects). NTD, neural tube defects; control, pooled embryos with no treatment, saline treatment, and treatment with amino acids other than Hcys.