Quantitative distribution of tetanus toxin in peripheral nerves and central nervous system

Tetanus toxin reduces local and descending regulation of the H-reflex

INTRODUCTION

Skeletal muscles that are under the influence of tetanus toxin show an exaggerated reflex response to stretch. We examined which changes in the stretch reflex may underlie the exaggerated response.

METHODS

H-reflexes were obtained from the tibialis anterior (TA) and flexor digitorum brevis (FDB) muscles in rats 7 days after intramuscular injection of tetanus toxin into the TA.

RESULTS

We found effects of the toxin on the threshold, amplitude, and duration of H-waves from the TA. The toxin inhibited rate-dependent depression in the FDB between the stimulation frequencies of 0.5–50 HZ and when a conditioning magnetic stimulus applied to the brain preceded a test electrical stimulus delivered to the plantar nerve.

CONCLUSIONS

Tetanus toxin increased the amplitude of the Hwave and reduced the normal depression of H-wave amplitude that is associated with closely timed stimuli, two phenomena that could contribute to hyperactivity of the stretch reflex.

Tetanus toxin-[2,3-3H]propionamid. Synthesis, specific activity, immunoreactivity, toxicity and ascent into the spinal cord

Tetanus toxin was tritiated with various amounts of N-succinimidyl-[2,3-3H]propionate. A tenfold molar excess of reagent over toxin was used for the introduction of about 5 nmol of [2,3-3H]propionate into 1 nmol of toxin, corresponding to a specific activity of about 48 MBq/mg protein. The labelling procedure did not change significantly the immunoreactivity of tetanus toxin, but reduced the toxicity in mice from 12 ng/kg to 16 ng/kg. Tetanus toxin-[2,3-3H]propionamid was carried through the peripheral nerves into the spinal cord. It could be used instead of 125I-labelled toxin for the detection of anti-tetanus toxin antibodies with a detection limit of 0.25 mU/ml of serum.

Serum protein binding of lead in vitro in amyotrophic lateral sclerosis patients and controls

The binding of lead to serum proteins was studied in vitro in ALS-patients and controls. Serum was incubated with 210Pb, the proteins were separated by isoelectric focusing and the radioactivity in the different protein fractions was determined by liquid scintillation counting. The activity was concentrated in the orosomucoid (acid alpha1-glycoprotein) fraction both in ALS-patients and controls under the present experimental conditions and the capacity of this protein to bind lead was demonstrated in a control experiment. The findings are discussed in relation to our earlier observations on increased concentrations of lead in cerebrospinal fluid and plasma in ALS-patients and the hypothetical role of the retrograde axonal transport in motoneurons in the pathogenesis of ALS. The present observations do not lend support to the idea that the increased plasma concentrations of lead in the disease would be related to qualitative differences in serum protein binding.

Capillary permeability in ALS, determined through transcapillary escape rate of 125I-albumin

Since various macromolecules have experimentally been demonstrated to be taken up by the motor end-plates and subsequently transported through retrograde axoplasmic flow, noxious substances may gain entrance to the lower motorneurons through the same route. Consequently, the function of the capillary barrier in skeletal muscle is of interest in diseases of the lower motorneurons. The transcapillary escape of 125I-albumin was determined in six ALS patients. The values fell within the range earlier reported for normals.

Intraaxonal and extraaxonal transport of 125I-tetanus toxin in early local tetanus

The distribution of radioactivity in the sciatic nerve, the spinal ganglia, the ventral roots and the spinal cord was studied by means of histoautoradiography after injection of 125I-labelled tetanus toxin into gastrocnemius muscles of cats. In the sciatic nerve the major part of the radioactivity was found in the epineurium, but some axons also contained radioactivity. In the ventral root the radioactivity was strictly confined to a few axons; no radioactivity was found in other parts of the ventral root. In the spinal cord the radioactivity was confined to a few motoneurones where it was found in the soma as well as in the dendrites. Transient cooling of the ventral roots prevented the ascent of radioactivity into the spinal cord. Colchicine and vinblastine, after local application to the sciatic nerve, reduced the amount of radioactivity found in the ventral roots and in the spinal cord. However, the same effect was also obtained but to a lesser degree with lumicolchicine. It is concluded that the intraaxonal compartment is involved in the neural ascent of tetanus toxin into the spinal cord.