Calcium influx factor directly activates store-operated cation channels in vascular smooth muscle cells.

Recently, we described a novel 3-pS Ca(2+)-conducting channel that is activated by BAPTA and thapsigargin-induced passive depletion of intracellular Ca(2+) stores and likely to be a native store-operated channel in vascular smooth muscle cells (SMC). Neither Ca(2+) nor inositol 1,4,5-trisphosphate or other second messengers tested activated this channel in membrane patches excised from resting SMC. Here we report that these 3-pS channels are activated in inside-out membrane patches from SMC immediately upon application of Ca(2+) influx factor (CIF) extracted from mutant yeast, which has been previously shown to activate Ca(2+) influx in Xenopus oocytes and Ca(2+) release-activated Ca(2+) current in Jurkat cells. In bioassay experiments depletion of Ca(2+) stores in permeabilized human platelets resulted in the release of endogenous factor, which activated 3-pS channels in isolated inside-out membrane patches excised from SMC and exposed to permeabilized platelets. The same 3-pS channels in excised membrane patches were also activated by acid extracts of CIF derived from human platelets with depleted Ca(2+) stores, which also stimulated Ca(2+) influx upon injection into Xenopus oocytes. Specific high pressure liquid chromatography fractions of platelet extracts were found to have CIF activity when injected into oocytes and activate 3-pS channels in excised membrane patches. These data show for the first time that CIF produced by mammalian cells and yeast with depleted Ca(2+) stores directly activates native 3-pS cation channels, which in intact SMC are activated by Ca(2+) store depletion.

An assessment of functional-anatomical variability in neuroimaging studies.

A key issue in functional neuroimaging is the amount of variability produced by individual differences in anatomical and functional patterns of activation. This variability affects summed images created when responses are averaged across subjects as well as comparisons between groups of subjects.In this report, functional-anatomical variability was explored at two different levels. The first level addressed whether responses defined in one group of subjects would replicate in a second subject group performing the same tasks. The likelihood that significant changes would be found in the second subject group was well-predicted by magnitudes and t-values of the responses in the first group.The second level of analysis addressed how closely the peak locations of changes in blood flow clustered together across subjects. The variability (mean vector distance) of peak locations among individual difference images was approximately 11.5 mm from the averaged peak location found across subjects. This value probably represents an upper bound for functional-anatomical variability using current PET data analysis techniques. Moreover, the variability was similar for responses distributed across different cortical areas and the cerebellum. This result is inconsistent with the hypothesis that some areas of the brain may have particularly high anatomical variability in normal right-handed subjects, thus precluding the use of averaging techniques for these areas.