Transgenic (Tg) mouse lines that express chimeric mouse-human prion protein (PrP), designated MHu2M, are susceptible to prions from patients with sporadic Creutzfeldt-Jakob disease (sCJD). With the aim of decreasing the incubation time to fewer than 200 days, we constructed transgenes in which one or more of the nine human residues in MHu2M were changed to mouse. The construct with murine residues at positions 165 and 167 was expressed in Tg(MHu2M,M165V,E167Q) mice and resulted in shortening the incubation time to Ϸ110 days for prions from sCJD patients. The construct with a murine residue at position 96 resulted in lengthening the incubation time to more than 280 days for sCJD prions. When murine residues 96, 165, and 167 were expressed, the abbreviated incubation times for sCJD prions were abolished. Variant CJD prions showed prolonged incubation times between 300 and 700 days in Tg(MHu2M) mice on first passage and incubation times of Ϸ350 days in Tg(MHu2M,M165V,E167Q) mice. On second and third passages of variant CJD prions in Tg(MHu2M) mice, multiple strains of prions were detected based on incubation times and the sizes of the proteaseresistant, deglycosylated PrP Sc fragments. Our discovery of a previously undescribed chimeric transgene with abbreviated incubation times for sCJD prions should facilitate studies on the prion species barrier and human prion diversity.

The purpose of this open study was to find out whether botulinum toxin A (BTX-A) relieves the signs and symptoms of chronic limb spasticity. The study comprised 40 patients, aged 12-82 years, with moderate to severe spasticity of the upper (13) or lower limbs (27) refractory to conventional physical and medical treatments. Outcome measures were clinical and blinded videotape assessments of spasticity and motor function. Electromyography guided BTX-A injections were given in one or two sessions at total doses averaging 175 U in the upper limb (range 70-270 U) and 221 U in the lower limb (range 100-500 U). Thirty four patients (85%) derived worthwhile benefit, with improved limb posture and increased range of passive motion in 31, pain reduction in 28 of 31 with pain, and improved function in 16. Side effects were limited to local and usually mild discomfort from the injections (19), symptomatic local weakness (one), and local infection (one). Preliminary experience indicates that BTX-A is a promising adjunctive treatment for selected patients with spasticity. ( Neurol Neurosurg Psychiatry 1995:58;232-235)