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At least 163 records · Page 9Linked to original sources
PubMed1990

Effects of a 2.15-micron laser on human atherosclerotic xenografts in vivo.

The thulium-holmium-chromium:yttrium-aluminum-garnet (THC:YAG) laser has a tissue effect similar to that of the CO2 laser, with the advantage of transmissibility through flexible fibers. The authors used a human-rabbit xenograft model to evaluate the thrombotic and healing responses of atherosclerotic vessels subjected to laser energy. Occluded atherosclerotic human coronary artery segments were recanalized in vitro by use of the THC:YAG laser. Destruction of plaque by the laser was achieved with minimal collateral thermal damage. These vascular segments were then transplanted into the rabbit abdominal aorta. The authors observed that the luminal surface of the lased vessels was more thrombogenic than that of the nonlased control vessels. However, occlusion of the lased vessels did not occur. Repair of laser-treated tissue progressed until a mature, nonthrombogenic fibrin-platelet aggregate was adherent to the luminal wall. Overall, the lased vessels behaved in a fashion similar to the nonlased control vessels. On the basis of these results, the authors believe that the THC:YAG laser may have use in human angioplasty.

Angioplasty, Laser↗
PubMed1990

Subconjunctival THC: YAG laser limbal sclerostomy Ab externo in the rabbit.

A chromium-sensitized, and thulium and holmium-doped YAG laser (THC:YAG laser) was used to create bilateral limbal sclerostomies in six Dutch pigmented rabbits. The laser is a long-pulsed (300 microseconds) [corrected], compact, self-contained, solid-state laser operating in the near infrared (2.1 microns). A 1-mm conjunctival stab incision was made 12 mm away from the sclerostomy site to allow entry of a specially designed 26-gauge (480 microns) optic probe that delivers energy at right angles to the long axis of the fiber. Probe insertion minimally disturbed the conjunctiva. Pulse energies of 60 to 150 mJ were used with a repetition rate of 5 pulses/s. Energy levels ranging from 1.35 to 6.6 J produced full-thickness sclerostomies. Histopathology showed a sharply defined perforating limbal wound at all energy levels. The overlying conjunctiva was intact, with swelling of the adjacent cornea. A peripheral iridectomy was intentionally created with the laser through the peripheral limbus, resulting in a sharply defined perforating tract through the iris/ciliary body. This technique may simplify filtering sclerostomy surgery, without anterior chamber instrumentation and with minimal conjunctival trauma.

Animals↗
PubMed1994

Update of the subconjunctival THC:YAG (holmium) laser sclerostomy ab externo clinical trial: 30-month report.

A THC:YAG laser (thulium, holmium, chromium-doped YAG crystal) was used to create 93 thermal sclerostomies ab externo in 81 glaucomatous eyes of 76 patients. Pulse energies of 80 to 120 mJ were used, with a repetition rate of 5 pulses per second. Total energy levels to produce full-thickness sclerostomies ranged from 1.4 to 7.2 J. Estimated probability of success was 0.66 at 12 months and 0.57 up to 30 months. The mean intraocular pressure in the successful cases was 12.8 +/- 4.0 mm Hg.

Adolescent↗
PubMed1993

THC:YAG nasolacrimal duct recanalization.

In an early exploration of a new technique for creating a patent nasolacrimal duct system, a chromium-sensitized and thulium- and holmium-doped YAG laser was used to canalize the nasolacrimal duct of a fresh-frozen bisected human cadaver head. The laser--long-pulsed (300 milliseconds), compact, self-contained, and solid-state--operates in the near infrared range (2.1 microns). The technique involved passing a 550-micrometer quartz fiberoptic through the dilated superior punctum and canalicular system, down through the nasolacrimal duct. The quartz fiberoptic was then withdrawn into the area of the lacrimal sac. Pulse energies of 500 mJ were used at a repetition rate of five pulses per second to ablate the duct lining. The nasolacrimal duct was then unroofed and the epithelial lining of the duct histopathologically evaluated.

Dacryocystorhinostomy↗
PubMed1993

Subconjunctival THC:YAG ("holmium") laser thermal sclerostomy ab externo. A one-year report.

BACKGROUND: Laser sclerostomy can be performed in a less-invasive manner than standard filtering surgery. Longer wavelengths in the infrared range have water-absorptive characteristics that facilitate perforation of the sclera. The goal was to perform laser sclerostomy ab externo to avoid intraocular instrumentation and minimize conjunctival trauma. METHODS: A thulium, holmium, chromium-doped:YAG (THC:YAG) crystal laser was used to create thermal sclerostomies in 49 glaucomatous eyes of 46 patients. The laser is a long-pulsed (300-microsecond), compact, self-contained, solid-state laser operating in the near infrared (2.1 microns). Energy was delivered via a specially designed 22-gauge (712-microns) optic probe that emits energy at a right angle to the long axis of the fiber. Pulse energies of 80 to 120 mJ were used. Total energy levels to produce full-thickness sclerostomies ranged from 1.4 to 7.2 J. Subconjunctival 5-fluorouracil (5-FU) injections were administered in 46 eyes. Success was defined as an intraocular pressure (IOP) of less than or equal to 22 mmHg with or without medications. For eyes in which preoperative IOP was less than or equal to 22 mmHg, success was defined as a decrease in IOP of greater than or equal to 30%. RESULTS: Estimated probability of success allowing for one retreatment was 0.75 at 6 months and 0.68 at 12 months. Mean IOP of successful cases was 13.3 mmHg at both 6 and 12 months. Twelve cases failed within the initial 6 months, and two additional cases failed by 12 months. CONCLUSION: THC:YAG ("holmium") laser thermal sclerostomy is an alternative to other full-thickness filtration procedures. Further evaluation and understanding will define its ultimate role in glaucoma management.

Adolescent↗
PubMed1993

Q-switched CTE:YAG laser sclerostomies on human autopsy eyes.

Experimental laser sclerostomies were performed on human eye-bank eyes with a new mid-infrared solid-state laser that is characterized by adequate optic-fiber transmission and low-thermal tissue interaction. The laser presented herein works with a chromium thulium erbium-doped (CTE): YAG crystal as the active medium, emitting radiation at a wavelength of 2.69 microns. In the Q-switch mode, the pulse duration is tunable from 0.5 to 2.5 microseconds. The maximal energy is 50 mJ/pulse (1-10 Hz). Attenuation of energy transmission in quartz (0.3 ppm) optic fibers is < 8 dB/m (diameter, 200 microns). Absorption depths of 2.69 microns radiation in water is 12.5 microns. In vitro procedures performed were ab-interno and ab-externo full-thickness sclerostomies. Histological and micro-morphological examination was performed by light microscopy and scanning electron microscopy. Collateral tissue damage in processed sclerostomies did not exceed 50(+/- 10) microns at typical fluences (10 J/cm2). In contact guidance, 10-15 laser pulses were required in the full-thickness ab-externo procedure, whereas up to 50 pulses were required in the ab-interno procedure. The number of laser pulses applied corresponded to the length of the filtration canals created. The canal was significantly longer (2.5 +/- 1 mm) in the ab-interno approach than in the ab-externo approach (1 +/- 0.2 mm). The intraocular ostium of the filtration canal in the ab-externo procedure showed enhanced signs of mechanical deterioration. It is concluded that both the wavelength (2.69 microns) and the pulse duration (0.5-2.5 microseconds) of the CTE: YAG laser are appropriate for laser sclerostomy.(ABSTRACT TRUNCATED AT 250 WORDS)

Eye↗
PubMed1996

The role of lysosomes in the selective concentration of mineral elements. A microanalytical study.

The role of the lysosome during the intracellular concentration of diverse mineral elements has been evidenced by the electron probe X-ray microanalysis (EPMA). This highly sensitive technique allows an in situ chemical analysis of any chemical element with an atomic number greater than 11, present in ultra-thin tissue sections. Therefore, it has been demonstrated by using this EPMA that 21 out of the 92 elements of the periodic table, once injected in a soluble form, were selectively concentrated within lysosomes of several types of mammalian cells. Amongst these 21 elements, 15 are concentrated and precipitated in an insoluble from in association with phosphorus whereas the other 6 are precipitated in association with sulphur. Amongst the 15 elements which precipitate with phosphorus in lysosomes, there are: 3 group IIIB elements of the periodic system, (aluminium, gallium and indium); the rare-earth elements (cerium, gadolinium, lanthanum, thulium and samarium); 2 group IVA elements (hafnium and zirconium), two actinides (uranium and thorium) and elements such as chromium and niobium. The 6 elements which precipitate with sulphur comprise the 3 group VIII elements of the classification (nickel, palladium, platinum) and the 3 group IB elements (copper, silver and gold). The mechanisms responsible for this selective concentration involve enzymatic processes and predominantly acid phosphatases for elements precipitating as phosphates and arylsulfatases for elements precipitating with sulphur.

Cell Compartmentation↗
PubMed1995

Acetylacetonato-lanthanide complexes as eminent catalytic sites for artificial ribonucleases.

Acetylacetonato complexes of lutetium, ytterbium, thulium, and europium ions efficiently hydrolyze the phosphodiester linkage in adenylyl(3'-5')adenosine. The pseudo first-order rate constant (3.2 x 10(-2) h-1) at pH 7.2 and 30 degrees C for the 1:1 lutetium-acetylacetonato complex (0.5 mmol dm-3) is close to the value (3.5 x 10(-2) h-1) for free lutetium ion of the same concentration. Potentialities of these complexes as the catalytic sites of artificial ribonucleases are indicated.

Binding Sites↗