Branched-chain amino acids supplementation enhances exercise capacity and lipid oxidation during endurance exercise after muscle glycogen depletion.

AIM: It has been demonstrated that branched-chain amino acids (BCAA) transaminase activation occurs simultaneously with exercise-induced muscle glycogen reduction, suggesting that BCAA supplementation might play an energetic role in this condition. This study aimed to test whether BCAA supplementation enhances exercise capacity and lipid oxidation in glycogen-depleted subjects. METHODS: Using a double-blind cross-over design, volunteers (N.=7) were randomly assigned to either the BCAA (300 mg . kg . day -1) or the placebo (maltodextrine) for 3 days. On the second day, subjects were submitted to an exercise-induced glycogen depletion protocol. They then performed an exhaustive exercise test on the third day, after which time to exhaustion, respiratory exchange ratio (RER), plasma glucose, free fatty acids (FFA), blood ketones and lactate were determined. BCAA supplementation promoted a greater resistance to fatigue when compared to the placebo (+17.2%). Moreover, subjects supplemented with BCAA showed reduced RER and higher plasma glucose levels during the exhaustive exercise test. CONCLUSION: In conclusion, BCAA supplementation increases resistance to fatigue and enhances lipid oxidation during exercise in glycogen-depleted subjects.

Clinical analysis of the neodymium:YLF picosecond laser as a microkeratome for laser in situ keratomileusis. Partially Sighted Eye Study.

PURPOSE: To evaluate the use of a picosecond neodymium:YLF (Nd:YLF) laser as a nonmechanical intrastromal microkeratome. SETTING: Universita Cattolica del Sacro Cuore, Rome, Italy. METHODS: An intrastromal spiral disc pattern of picosecond laser pulses was used to create a corneal flap for laser in situ keratomileusis (LASIK) in 14 partially sighted eyes. RESULTS: Flaps with a 6.0 mm diameter and 180 to 200 microns depth were successfully created in most cases. The underlying stroma was treated with a Lambda Physik excimer laser using a 3.5 to 4.5 mm optical zone. Patients were divided into 3 groups for target corrections of 5.0, 10.0, and 15.0 diopters of myopia. Good corneal clarity and refractive undercorrection were recorded in each group 6 months postoperatively. The undercorrection was due in part to the limited optical zone of the laser's delivery system. Some flap decentration was noted. CONCLUSION: This pilot study indicates that the Nd:YLF picosecond laser may be clinically applied for creating corneal flaps for LASIK. Further refinements of the laser delivery system will include enlargement of the flap diameter and improvements in flap centration. The use of a femtosecond laser may expand the capabilities and precision of this technology.

The picosecond laser for nonmechanical laser in situ keratomileusis.

PURPOSE: To introduce the clinical use of the Nd:YLF picosecond laser as a nonmechanical microkeratome. METHODS: A commercially available Nd:YLF picosecond laser (25 microJ/pulse, 30 psec, 1053 nm) was used to deliver intrastromal pulses of focused high power laser light to generate a flap for laser in situ keratomileusis (LASIK) and perform picosecond laser keratomileusis (PLK) in two partially sighted patients with high myopia. RESULTS: Case #1: A 6 mm, 150 microns flap for LASIK was successfully created and the underlying stroma treated with an excimer laser for a target correction of -15.00 D of myopia. Good corneal clarity and a refractive change of -14.00 D was recorded 2 months postoperatively. Case #2: Both eyes of a high myope (-22.00 D right eye, -21.50 D left eye) underwent picosecond laser keratomileusis, removing a 3.2 mm diameter lenticule of 120 microns thickness under a 200 microns flap. Postoperative refraction was -2.00 D at 7 months in the right eye and -0.75 D at 2 months in the left eye with improvement of spectacle-corrected visual acuity from 20/200 to 20/70 in each eye. CONCLUSION: The Nd:YLF picosecond laser can be safely used in creating a corneal flap for LASIK and in performing picosecond laser keratomileusis for high myopia. Future refinements in the laser will include a larger flap diameter and femtosecond pulsing capability.

Intrastromal photorefractive keratectomy for myopia by Nd:YLF picosecond laser.

BACKGROUND: An intrastromal photorefractive keratectomy (ISPRK) by Nd:YLF Picoseconds Laser has been performed on 17 eyes with corrected visual acuity of 20/200 or worse. The purpose of this study was to study the safety and effectiveness of ISPRK using different laser parameters. METHODS: The Neodymiun Yttrium Lithium Fluoride laser system (Nd:YLF) was used to perform the myopic treatment. We studied the effect of pattern depth, the numbers of patterns, the thickness of a single spiral pattern, the distance between two patterns along Z axis, the pattern curvature perpendicular to the Z axis, the energy, the spatial density, and the repetition frequency of the laser pulse. RESULTS: The laser treatment was completed in 12 patients. In the first group at 180 days postoperatively we did not find corneal opacities, anterior chamber or lens opacities. Pupil diameter and reactivity, endothelial cell density, and IOP were normal. Pachymetry showed an average reduction of the central corneal thickness of 99 microns (+/- 14.7 SD). Topography showed an average reduction of the corneal dioptric power of 2 D (+/- 0.4 SD). In the second group at 120 days postoperatively findings were similar. Pachymetry showed an average reduction of the central corneal thickness of 118.5 mu (+/- 12.5 SD). Topography showed an average reduction of the corneal dioptric power of 2.4D (+/- 0.9 SD). CONCLUSIONS: It is possible to change the corneal power by reducing the corneal thickness with the Nd:YLF laser but the predictability of the result is unknown. Because Bowman's layer is intact, there is no scarring or haze.