Phytochrome activation of k channels and chloroplast rotation in mougeotia: action spectra.

The action spectra for K(+) channel activation and chloroplast rotation are shown to be similar. Both phenomena exhibit activation at 660 nanometers, inhibition at 740 nanometers, and partial activation at 460 to 500 nanometers. This confirms that K(+) channels in Mougeotia are regulated by phytochrome, and indicates that both phenomena share at least part of the same transduction pathway.

Fractal filtering of channel data.

The fractal dimension of subsets of time series data can be used to modulate the extent of filtering to which the data is subjected. In general, such fractal filtering makes it possible to retain large transient shifts in baseline with very little decrease in amplitude, while the baseline noise itself is markedly reduced (Strahle, W.C.

Calcium activation of mougeotia potassium channels.

Phytochrome mediates chloroplast movement in the alga Mougeotia, possibly via changes in cytosolic calcium. It is known to regulate a calcium-activated potassium channel in the algal plasma membrane. As part of a characterization of the potassium channel, we examined the properties of calcium activation.

Red light regulates calcium-activated potassium channels in mougeotia plasma membrane.

The alga Mougeotia has a large central chloroplast whose positioning is regulated by photoactivation of phytochrome, possibly via modulation of cytosolic calcium (Serlin B, Roux SJ [1984] Proc Natl Acad Sci USA 81: 6368-6372). We used the patch clamp technique to examine the effects of red and far-red light on ion channel activity in the plasma membrane of Mougeotia protoplasts to determine if ion channels play a role in chloroplast movement. Patch clamping in the cell-attached mode reveals two channels of about 2 and 4 picoamperes amplitude at 0 millivolt (inside pipette) and estimated conductances of 30 and 65 picosiemens.

Tetrahydroaminoacridine (THA) as a pharmacological probe in Alzheimer's disease (AD) and other neurodegenerative disorders.

Unlike other potent enhancers of cholinergic function in the central nervous system (CNS), THA appears to sustain improved function in many moderately impaired AD patients when the Summers procedure is followed. THA has a complex pharmacology. In addition to its enhancement of cholinergic transmission a hydroxylated metabolite might chelate aluminum (A1), thereby removing multiple toxicological constraints on CNS function.