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R Astier

Publications and source records attributed to R Astier.

6 recordsLinked to original sources
PubMed1989

[Pulsed lasers in the treatment of urinary calculi].

Intracorporeal lithotripsy of urinary calculi by pulsed dye laser recently enriched the urologist's therapeutic arsenal. We recall the in vitro studies and animal experimentations which demonstrated the feasibility of laser lithotripsy and the absence of harmful tissue damage. The ideal indications for intracorporeal lithotripsy are ureteral stones accessible by rigid and, more especially, flexible ureteroscopy. The results of the first published series using this technique are very encouraging.

Animals↗
PubMed1989

[Endocorporeal lithotripsy using a pulsed laser].

Intracorporeal lithotripsy of urinary calculi by pulsed dye laser has recently enriched the urologist's therapeutic arsenal. We recall the in vitro studies and animal experimentations which demonstrated the feasibility of laser lithotripsy and the absence of harmful tissue damage. The ideal indications for intracorporeal lithotripsy are ureteral stones accessible by rigid and, more especially, flexible ureteroscopy. The results of the first published series using this technique are very encouraging.

Humans↗
PubMed1985

[In vitro opening of human atheromatous coronary arteries using a pulsed laser].

This study was undertaken to assess the respective values of pulsed and continuous laser emission for in vitro recanalisation of very stenosed atheromatous human coronary arteries. The Nd-YAG laser used emitted a 10 Hz 10 ns burst in the infrared band (1 064 microns). Previous spectroscopic studies had shown no specific band of absorption in the spectral field of emission of the usual lasers. The laser beam was focused in the axis of the segment of coronary artery irradiated. The crater or neo lumen obtained usually had irregular walls. No perforation of the arterial wall or macroscopic debris were observed. Histological studies showed minimal burn lesions with sparse coagulation necrosis limited to a few tens of micron thickness. The percentage recanalisation obtained with pulses of 200 mJ attained 50% for a total energy of 450 J delivered in 2 mn. This study confirmed the feasibility of disobliteration of atheromatous coronary arteries by pulsed laser. Our results suggest that ultra short pulsed laser acts more by a mechanical than by a thermal mechanism which may lead to less side effects than observed in vivo with continuous laser emission.

Coronary Disease↗
PubMed1983

Spectral evidence for sub-picosecond iron displacement after ligand detachment from hemoproteins by femtosecond light pulses.

We have measured spectral and kinetic differences in protoheme, sperm whale or horse heart myoglobin and human hemoglobin following photodissociation induced by optical pulses of 80 fs duration. Full ligation was performed with oxygen or carbon monoxide. Femtosecond kinetics and transient difference spectra revealed the appearance of a deoxy species with tau approximately equal to 250-300 fs. The transient deoxy species in myoglobin and hemoglobin evidenced a 3-4 nm red shift of their delta A spectra compared with the equilibrium delta A spectrum. This shift was not observed after photodissociation of the carbon monoxide liganded protoheme. We proposed that the 250 fs time constant corresponding to the appearance of the deoxy-like species is related to the displacement of the ferrous iron out of the heme plane. Consequently, the small red shift of the delta A spectra observed in photodissociated hemoproteins may be tentatively attributed to changes in the vibrational modes of either the proximal histidine-Fe2+ bond and/or of the N4 porph-Fe-N epsilon His (F8) bent.

Animals↗
PubMed1983

Femtosecond photolysis of CO-ligated protoheme and hemoproteins: appearance of deoxy species with a 350-fsec time constant.

Photolysis of HbCO, MbCO, and CO-protoheme has been investigated by measuring transient differential spectra and kinetics of induced absorption after excitation with a 250-fsec laser pulse at 307 nm. Probing was performed by a part of a continuum pulse between 395 and 445 nm. Photodissociation of the three liganded species occurred within the pulse duration. By contrast, the formation of deoxy species appeared with a mean (+/- SD) response time of 350 +/- 50 fsec. This time constant was identical for the three species and independent of the presence or absence of the protein structure. Our results suggest the formation of a transient high-spin in plane iron (II) species which relaxes in 350 fsec to a high-spin stable state with concerted kinetics of CO departure and iron displacement. The spin transition is suspected to occur via liganded excited states which relax in part to non-reactive states with a 3.2-psec time constant.

Carbon Monoxide↗