[Method of measurement of cadmium influx by fura-2 titration in MDCK cell evidenced. Fluorescence video-microscopy study].

Cadmium influx rate in mammal kidney cells (MDCK) is analyzed using an original method based on fura-2 titration. The method relies on the high affinity of the fluorophore for the metal. It follows that the excitation spectrum shift of fura-2 can be linearly correlated to the influx rate of cadmium.

Herbicide isoproturon-specific binding in the freshwater macrophyte Elodea densa--a single-cell fluorescence study.

The experimental approach to the effects of the phenylurea herbicide Isoproturon (IPU), on the photosynthesis activity of leaf cells of the freshwater macrophyte Elodea densa was based on the fast induction kinetics of the PSII chlorophyll a in vivo fluorescence. FI/FP ratios determined on the induction curves exhibited a noticeable effect at 5 micrograms IPU.liter-1.

Multidrug resistance bypass in cells exposed to doxorubicin-loaded nanospheres. Absence of endocytosis.

Multidrug resistance bypass has been achieved in vitro with polyalkylcyanoacrylate nanospheres loaded with doxorubicin as previously shown by Cuvier et al. Fluorescence-imaging experiments were performed to determine if the endocytosis of the particles by the cells could be responsible for this activity. The results obtained with three lines of sensitive and resistant cells (K562, MCF7, and C6) demonstrate that the particles were not internalized by the cells, nor were they adsorbed onto the cell surface.

Spatial and temporal distribution of [Ca2+]i in normal human myotubes. A fura-2 imaging study.

The spatio-temporal distribution of intracellular, free calcium ions, [Ca2+]i, induced in human myotubes by electrical stimulation typically showed a relatively large increase of [Ca2+]i in the vicinity of the plasmalemma. The similarity of this distribution, with that observed after the application of caffeine, and the lack of any effect of lanthanum, strongly suggest that the main source of Ca2+ participating in the electrically induced transient is the sarcoplasmic reticulum. Aneurally cultured human myotubes therefore display a 'skeletal muscle type' coupling between membrane depolarization and calcium release.

Fura-2 imaging of spontaneous and electrically induced oscillations of intracellular free Ca2+ in rat myotubes.

Rat myotubes have a resting [Ca2+]i of about 82 nM. Myotubes 3-5 days old (quiescent myotubes) display electrically induced and spontaneous transients in the intracellular concentration of free Ca2+ ions ([Ca2+]i) uncoupled to any detectable contraction. By contrast, 1- to 2-day-old myotubes are insensitive to electrical stimuli and, after 6 days in culture, stimulated myotubes always show [Ca2+]i transients and twitch contractions.

Digital-imaging microscopy analysis of calcium release from sarcoplasmic reticulum in single rat cardiac myocytes.

Digital imaging microscopy of fura-2 fluorescence has allowed us to assess the dynamic patterns of local Ca increase in newly isolated rat myocardial cells. Of the myocytes bathed in a saline solution (1.8 mM Ca2+, 37 degrees C, pH 7.

Effect of local anaesthetics on mitochondrial membrane potential in living cells.

Using the laser dye rhodamine 123, we demonstrated that local anaesthetics can reach mitochondria in cell culture and reversibly decrease, or even collapse, their transmembrane potential. This effect is highly dependent on the lipid-solubility of the local anaesthetic and can be facilitated by the presence of a lipophilic anion.

[Is muscular acetylcholinesterase activity correlated with the intracellular concentration of free calcium?].

The role of the calcium ion Ca2+ as an agent of intracellular control in a variety of physiological processes is well established. In vertebrate skeletal muscle fibers, Ca2+ is involved in muscle contraction, modulation of membrane permeability and regulation of metabolic activity. Recently it was suggested that ion fluxes through membranes regulate the level of two cholinergic macromolecules, the acetylcholine receptor and the A12 form of acetylcholinesterase (AChE), the presumed synaptic form of the enzyme.

Reduction of membrane-bound dopamine beta-hydroxylase from the cytoplasmic surface of the chromaffin-granule membrane.

Resealed bovine chromaffin-granule 'ghosts' were used for assaying the membrane-bound form of dopamine beta-hydroxylase. Hydroxylation of the substrate tyramine is dependent on its accumulation within the 'ghosts', where the active site of the enzyme is located. Free tyramine in the medium is at a low concentration, low ionic strength and a relatively high pH (7.

Chemical studies on yeast hexokinase. Specific modification of a single tyrosyl residue with 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide.

1. Of the 15 tyrosyl residues/subunit of yeast hexokinase A (ATP:D-hexose 6-phosphotransferase) only one residue is specifically modified at pH 8.0 with 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide hydrochloride.