ABSTRACT
We used an in vitro model for glioma cell invasion (transwell migration assay) and patch-clamp techniques to investigate the role of volume-activated Cl(-) currents (I(Cl,Vol)) in glioma cell invasion. Hypotonic solutions ( approximately 230 mOsm) activated outwardly rectifying currents that reversed near the equilibrium potential for Cl(-) ions (E(Cl)). These currents (I(Cl,Vol)) were sensitive to several known Cl(-) channel inhibitors, including DIDS, tamoxifen, and 5-nitro-2-(3-phenylpropylamino)-benzoate (NPPB). The IC(50) for NPPB inhibition of I(Cl,Vol) was 21 microm. Under isotonic conditions, NPPB (165 microm) blocked inward currents (at -40 mV) and increased input resistance in both standard whole-cell recordings and amphotericin perforated-patch recordings. Reducing [Cl(-)](o) under isotonic conditions positively shifted the reversal potential of whole-cell currents. These findings suggest a significant resting Cl(-) conductance in glioma cells. Under isotonic and hypotonic conditions, Cl(-) channels displayed voltage- and time-dependent inactivation and had an I(-) > Cl(-) permeability. To assess the potential role of these channels in cell migration, we studied the chemotactic migration of glioma cells toward laminin or vitronectin in a Boyden chamber containing transwell filters with 8 microm pores. Inhibition of I(Cl,Vol) with NPPB reduced chemotactic migration in a dose-dependent fashion with an IC(50) of 27 microm. Time-lapse video microscopy during patch-clamp recordings revealed visible changes in cell shape and/or movement that accompanied spontaneous activation of I(Cl,Vol), suggesting that I(Cl,Vol) is activated during cell movement, consistent with the effects of NPPB in migration assays. We propose that I(Cl,Vol) contributes to cell shape and volume changes required for glioma cell migration through brain tissue.
Subject(s)
Cell Movement , Chloride Channels/metabolism , Glioma/metabolism , Glioma/pathology , Neoplasm Invasiveness/physiopathology , 4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid/pharmacology , Cell Membrane Permeability/drug effects , Cell Movement/drug effects , Cell Size/drug effects , Chemotaxis/drug effects , Chloride Channels/antagonists & inhibitors , Diffusion Chambers, Culture , Dose-Response Relationship, Drug , Electrophysiology , Humans , Laminin/pharmacology , Microscopy, Video/methods , Nitrobenzoates/pharmacology , Patch-Clamp Techniques , Tamoxifen/pharmacology , Tumor Cells, Cultured , Vitronectin/pharmacologySubject(s)
Dentists , Professional Impairment , Substance-Related Disorders , Ethics, Dental , Humans , MissouriABSTRACT
The effect of bilateral cingulumotomy on sequential tapping behavior was investigated in 6 patients, Contrary to previous clinical studies and predictions derived from data on cingulate lesions in the rat, a consistent decrement in postoperative performance was not found. Temporal integration of behavior in man, as measured in terms of accuracy of sequential motor performance, does not appear to be critically dependent upon the integrity of the cingulum bundle at the level of interruption investigated in the present study.
