Development of intracellular calcium measurement by time-resolved photon-counting fluorescence.

Calcium green I, a ratiometric probe based on fluorescence lifetime measurements, was used to monitor intracellular calcium activity ([Ca2+]i) in RINm5F cells using a time-resolved fluorescence confocal microscope. The probe affinity constant has been recalibrated in single cells using ionomycin as a calcium ionophore and ethylenebis(oxyethylenenitrilo)tetraacetic acid as a calcium buffer; Kd was found to equal 150 nmol/L. The kinetics of ionomycin equilibration showed that the calcium release from calcium stores occurs before equilibration with extracellular calcium. The response to the muscarinic agonist carbachol, measured on 17 cells receiving three consecutive applications was characterized both by a [Ca2+]i peak lasting 50 s without any trailing plateau and by desensitization with a 30% decrease in the response. The dose-dependent response was obtained for a carbachol concentration from 5 mumol/L to 0.5 mmol/L. The ability of our set-up to obtain a value every 10 ms enabled us to record asynchronous spikes of [Ca2+]i in the RINm5F cells. The spikes, lasting less than 1 s, are significantly bigger than the noise, and they are not observed in the colonic HT29 cells.

[New aspects of drug hepatotoxicity]. / Nouveautés en hépatotoxicité médicamenteuse.

This article sets out to report the new hepatotoxic drugs identified during the course of 1989 and to describe the state of the art about drugs suspected of hepatotoxicity, such as amoxicillin-a clavulinic or, to a lesser extent, octreotide. In contrast, Exifone, a recently introduced drug, was withdrawn from the market within a year. One is surprised to find drugs such as Buprenorphine and Trimebutine listed, which have never induced clinical cases of hepatitis despite widespread use. The article also reviews the drugs with recognized hepatotoxicity and tries to present the most up-to-date information about them.

Unusual presentation of a case of brain abscess after endoscopic injection sclerotherapy of esophageal varices.

Although an increasing number and variety of complications of endoscopic injection sclerotherapy (EIS) of bleeding esophageal varices have been reported, infectious complications are rare. A case of brain abscess following EIS is reported which was characterised by an unusual clinical presentation in that there was no fever or leucocytosis. This presentation could have led to the abscesses being mistaken for brain metastases. The outcome of antimicrobial therapy was favorable which provided further evidence in support of the diagnosis.

Restrained torsional dynamics of nuclear DNA in living proliferative mammalian cells.

Physical parameters, describing the state of chromatinized DNA in living mammalian cells, were revealed by in situ fluorescence dynamic properties of ethidium in its free and intercalated states. The lifetimes and anisotropy decays of this cationic chromophore were measured within the nuclear domain, by using the ultra-sensitive time-correlated single-photon counting technique, confocal microscopy, and ultra-low probe concentrations. We found that, in living cells: 1) free ethidium molecules equilibrate between extracellular milieu and nucleus, demonstrating that the cation is naturally transported into the nucleus; 2) the intercalation of ethidium into chromatinized DNA is strongly inhibited, with relaxation of the inhibition after mild (digitonin) cell treatment; 3) intercalation sites are likely to be located in chromatin DNA; and 4) the fluorescence anisotropy relaxation of intercalated molecules is very slow. The combination of fluorescence kinetic and fluorescence anisotropy dynamics indicates that the torsional dynamics of nuclear DNA is highly restrained in living cells.