Occupational neurotoxicity and movement disorders: a historical perspective.

It is shown that while metal toxicity has been known to be associated with risks to the health of miners and other workers for over a thousand years generally little was done before the 19th century to enquire into the relationship between lead, mercury, and manganese and neurological movement disorders. Reasons for this are suggested.

Correlation studies of individual variation in susceptibility to various components of HPNS in mice.

Individual convulsion threshold pressures were determined in mice exposed successively to type I and type II convulsions of the high-pressure neurological syndrome (HPNS), as well as in others exposed, in successive compressions, to type I convulsions under diverse conditions of replication of compression rate. Correlation analyses of the results showed the following degrees of correlation of individual convulsion-threshold pressures: type I with type II-negligible (r2 less than equal to 0.2); type I with type I at the same compression rate-closely correlated (r2 greater than or equal to 0.8); type I with type I at a different compression rate-negligible (r2 less than or equal to 0.2). Individual susceptibility to HPNS (type I) convulsions thus is a stable characteristic of individual seizures vary independently of one another. Likewise, the magnitude of the individual compression rate effect varies independently of intrinsic individual susceptibility to type I HPNS seizures. The results support the view that the HPNS is a composite entity, define constraints on personnel selection, and provide a basis for estimating the efficacy of various selection strategies.

Changes in CNS responses to high pressure during maturation of newborn mice.

From birth to maturity CD-2 mice were exposed to progressively increasing pressures of helium-oxygen. In all age groups a regular progression of changes in locomotor behavior was observed including, in sequence, increased locomotor activity and two types of convulsions designated as types I and II. The effects of altering compression rate and of reserpine pretreatment were recorded for all age groups. Maturation in these mice is associated with increased resistance to high-pressure neurological syndrome convulsions of either type, in contrast to what might have been expected from previous phylogenetic studies. The patterns in development of the two seizure types differ greatly in detail, further supporting the previously advanced inference that they represent neurological events that differ in kind rather than merely quantitatively. The effect of the results on theories that concern the mechanism of action of pressure on the vertebrate central nervous system is discussed.

Autosomal dominant "spheroid body myopathy".

A slowly progressive autosomal dominant neuromuscular disease--termed spheroid body myopathy--is described in four successive generations and documented by muscle biopsies in five patients of two generations. With an onset in adolescence, the disease proceeds to some motor incapacitation, but life span is apparently not shortened. The salient morphologic feature is the presence of spheroid bodies, chiefly occurring in type 1 myofibers. Ultrastructurally, these spheroid bodies are composed of tiny filaments but are devoid of organelles; in some cases they resemble cytoplasmic bodies. "Smearing in the 1-band" is a frequent and early finding. At a later age, signs of denervation are also present, both clinically and in muscle biopsies. The clinical and morphologic features justify the designation of this neuromuscular condition as a distinct entity.