Is postural tremor size controlled by interstitial potassium concentration in muscle?

OBJECTIVES: To determine whether factors associated with postural tremor operate by altering muscle interstitial K(+). METHODS: An experimental approach was used to investigate the effects of procedures designed to increase or decrease interstitial K(+). Postural physiological tremor was measured by conventional means. Brief periods of ischaemic muscle activity were used to increase muscle interstitial K(+). Infusion of the beta(2) agonist terbutaline was used to decrease plasma (and interstitial) K(+). Blood samples were taken for the determination of plasma K(+). RESULTS: Ischaemia rapidly reduced tremor size, but only when the muscle was active. The beta(2) agonist produced a slow and progressive rise in tremor size that was almost exactly mirrored by a slow and progressive decrease in plasma K(+). CONCLUSIONS: Ischaemic reduction of postural tremor has been attributed to effects on muscle spindles or an unexplained effect on muscle. This study showed that ischaemia did not reduce tremor size unless there was accompanying muscular activity. An accumulation of K(+) in the interstitium of the ischaemic active muscle may blunt the response of the muscle and reduce its fusion frequency, so that the force output becomes less pulsatile and tremor size decreases. When a beta(2) agonist is infused, the rise in tremor mirrors the resultant decrease in plasma K(+). Decreased plasma K(+) reduces interstitial K(+) concentration and may produce greater muscular force fluctuation (more tremor). Many other factors that affect postural tremor size may exert their effect by altering plasma K(+) concentration, thereby changing the concentration of K(+) in the interstitial fluid.

Massive sequestration of human sickle cells after transfusion to a baboon.

A baboon was exchange-transfused with sickle cell anemia patients' blood. The animal died suddenly, and postmortem examination showed widespread red cell sequestration, particularly in the spleen and liver. The clinical and pathological findings were similar to those in children with sickle cell anemia who die of acute splenic sequestration syndrome. A control animal, exchange-transfused with normal human blood, tolerated the procedure without difficulties for a period of 4 days, when a delayed transfusion reaction occurred. Thus the baboon can be used as a model for the abnormal circulatory behavior of sickle cells and for the sickle cell sequestration syndrome.

Elimination of bacteria from dogs with antibiotics.

The effect of oral administration of neomycin cephalothin or kanamycin cephalothin on the aerobic intestinal bacterial flora, was studied in dogs maintained under isolation conditions in a conventional animal room. The dogs were successfully freed of aerobic bacteria with both combinations within two to seven days after the start of antibiotic treatment, and were maintained bacteria free for up to 21 days. Decontamination was attained more rapidly in dogs that were bathed in hexachlorophene surgical soap before and during the first and third days of antibiotic treatment. There was no evidence of toxicity from either of the antibiotic combinations. These results indicate that, as with mice and monkeys, decontamination of dogs with oral antibiotics is feasible. The technique is of potential value in preventing endogenous bacterial infections in canine experimental studies involving use of immunosuppressive agents.