Activation and inactivation of bovine caudate acetylcholinesterase by trivalent cations.

Kinetic analysis of the interaction of trivalent cations with mammalian brain acetylcholinesterase revealed at least three distinct concentration-dependent effects on enzyme activity. Acetylcholinesterase was purified from bovine caudate nucleus by affinity chromatography to a specific activity of 1.1 mmoles acetylthiocholine X hr-1 X (mg protein)-1. The cations studied included the chloride salts of lanthanum, terbium, yttrium and scandium in low and high ionic strength buffers (2 mM Pipes +/- 0.1 M NaCl). At low ionic strength, high affinity noncompetitive or allosteric activation was observed at very low cation concentrations (1-10 microM); at higher concentrations (50-200 microM) these cations were noncompetitive inhibitors; and at 200-500 microM they exerted a mixed competitive-noncompetitive inhibition. Activation by low cation concentrations was not evident in high ionic strength buffers, while enzyme inhibition by all the trivalent cations was similar at low and high ionic strength. Inhibition by all of the multivalent cations was fully reversed by a 10-fold excess of EDTA or by a 100-fold dilution of the inhibited enzyme. The water-soluble carboxyl group affinity reagent, 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide, was shown to specifically block the activating effect of the multivalent cations supporting the suggestion that the beta- or "activator" peripheral anionic sites (P1) involve a carboxyl group outside the enzyme active site.

Monoamines in the caudal neurosecretory complex: biochemistry and immunohistochemistry.

Monoaminergic inputs to the caudal neurosecretory complex (CNc) of Poecilia latipinna have been identified using histofluorescence and immunohistochemical techniques. The present study was undertaken to identify specific monoamines and determine the relative contribution of indolamines and catecholamines in supraspinal and intrinsic innervation of the nucleus. The CNc was deafferented by transecting the spinal cord rostral to the CNc. Ten days subsequently, CNc of spinal-transected and control fish were processed for either biochemical or immunohistochemical analysis. Norepinephrine and serotonin were detected in pooled samples of control CNc. Following deafferentation, the content of both monoamines was diminished. Using immunohistochemical labeling for serotonin or for the catecholamine-synthesizing enzymes, tyrosine hydroxylase (TH) or dopamine-beta-hydroxylase (DBH), the number of monoamine fibers was decreased in deafferented CNc compared to control. A substantial serotonergic innervation remains after deafferentation, as evidenced by serotonin-positive neurons and heavy, varicose fibers. Occasional TH/DBH-positive cells and fibers remain after deafferentation. These data suggest that both norepinephrine and serotonin are associated with descending supraspinal projections, while serotonin predominates as the intrinsic monoamine.

Violent emergence from anesthesia: is it a pharmacological or psychological reaction?

A violent emergence from deep sedation is an uncommon reaction in the daily practice of anesthesia in the oral and maxillofacial surgery office. We present a case of a 22-yr-old male with a severe violent emergence from deep sedation that we attribute to a psychological rather than a pharmacological cause. A differential diagnosis is discussed, as are methods of treatment.

Dermoid cyst of the floor of the mouth.

Sublingual dermoid cysts are uncommon in the head and neck region. They are most often seen in young adults and can become unusually large with few symptoms. A case is presented to demonstrate the slow, expansive growth pattern and relatively painless swelling in the floor of the mouth that occurred over a 9-year period.