Stone ablation efficacy: a comparison of a thulium fibre laser and two pulse-modulated holmium:YAG lasers.

We present preliminary stone ablation rate results from an automated bench model using two pulse-modulated Ho:YAG lasers and a thulium fibre laser (TFL) in contact and non-contact modes. Ablation rate was assessed using automated apparatus that moved the laser fibre across flat BegoStone phantoms at a constant stone-to-fibre working distance (WD). Pre-soaked and unsoaked stones were used. A range of powers (20-60 W) was tested at WD of up to 3 mm. In pseudocontact, the prototype Ho:YAG laser produced higher ablation than the reference Ho:YAG laser at all powers tested (p < 0.002), and higher ablation than TFL at 20 W and 40 W (p < 0.001). At distance, ablation rates for the prototype were higher than the reference Ho:YAG laser using pre-soaked stones at WD up to 3 mm (p < 0.001). TFL required the laser fibre to be moved faster (5-12 mm/s) for optimal ablation, compared to 1-3 mm/s for the Ho:YAG lasers. TFL was unable to demonstrate ablation with unsoaked BegoStone. At any given power, similar ablation rates were achievable with all three lasers under optimised conditions. Novel pulse-modulation modes demonstrated higher ablation rates than the reference Ho:YAG laser's pulse-modulation at a range of powers and WDs. Ablation rate of Ho:YAG lasers decreased linearly with WD whereas the ablation rate of TFL decreased rapidly beyond 2 mm WD. TFL was more affected by scan speed and pre-soaking of stone than Ho:YAG lasers. Ho:YAG lasers may be more practical in clinical settings because they are less dependent on ablation technique.

Genetic and epigenetic basis of psoriasis pathogenesis.

Psoriasis is a chronic inflammatory skin disease whose prevalence varies among different populations worldwide. It is a complex multi-factorial disease and the exact etiology is largely unknown. Family based studies have indicated a genetic predisposition; however they cannot fully explain the disease pathogenesis. In addition to genetic susceptibility, environmental as well as gender and age related factors were also been found to be associated. Recently, imbalances in epigenetic networks are indicated to be causative elements in psoriasis. The present knowledge of epigenetic involvement, mainly the DNA methylation, chromatin modifications and miRNA deregulation is surveyed here. An integrated approach considering genetic and epigenetic anomalies in the light of immunological network may explore the pathogenesis of psoriasis.

Impedance as a method to sense proximity at the electrode-retina interface.

Precise positioning of a stimulating electrode in the eye is not possible by simple visualization. However, reliable measurement of responses to retinal stimulation requires consistent positioning. The present study focuses on impedance measurement techniques to sense the proximity of the electrode to the retina. A platinum-iridium stimulation electrode was placed inside the rat eye and impedance was recorded at different positions of the stimulating electrode relative to the retina. The presence of robust electrically evoked response in the superior colliculus indicates that the electrode may not have to be in absolute contact in order to elicit a neural response. Optical coherence tomography imaging confirmed the distance-impedance relationship.

Morphological alterations in retinal neurons in the S334ter-line3 transgenic rat.

The S334ter-line-3 rat is a transgenic model of retinal degeneration developed to express a rhodopsin mutation similar to that found in human retinitis pigmentosa (RP) patients. Previous studies have focused on physiological changes in retinal cells and higher centers of the visual system with this model of retinal degeneration. However, little is known about the morphological changes in retinal cells during the development of the S334ter-line-3 rat. In order to understand and aid vision-rescue strategies, our aim has been to describe the retinal degeneration pattern in this model. We focus on changes in the morphologies of horizontal, bipolar, and amacrine cells in developing S334ter-line-3 rat retinas. Degeneration of photoreceptors begins in the central retina and progresses toward the periphery. In retinas at post-natal day 15 (P15), horizontal and rod bipolar cells show normal morphology. However, at P21, horizontal and rod bipolar cells exhibit abnormal processes at the outer plexiform layer, whereas the outer nuclear layer is significantly thinner. A glial reaction occurs concomitantly. In contrast, modifications in cone-bipolar and amacrine cells are much slower and do not occur until P90 and P180, respectively. The density of horizontal and rod-bipolar cells significantly drops after P60. Overall, the S334ter-line-3 model exhibits the hallmarks of cellular remodeling caused by photoreceptor degeneration. Its moderately fast time course makes the S334ter-line-3 a good model for studying vision-rescue strategies.

Immunocytochemical analysis of retinal neurons under electrical stimulation.

To function successfully, a retinal prosthesis needs to provide effective stimulation in a safe manner. To date, most studies have been dedicated to assessing proper stimulation parameters, for example, determining stimulus threshold. Few studies have looked at the effects of prolonged stimulation on retinal morphology. One previous study did show gross morphological changes in the rat retina due to mechanical pressure, with and without electrical stimulation (Colodetti, L., Weiland, J.D., Colodetti, S., Ray, A., Seiler, M.J., Hinton, D.R., Humayun, M.S., 2007). Here, we used immunocytochemistry to investigate the effects of the same experimental conditions on neuronal structure in finer detail. For this purpose, we first defined four experimental groups. In Group 1, the stimulating electrode was near but did not contact the retina, and we did not apply current pulses. In Group 2, the electrode also did not contact the retina, but we applied current pulses of 0.09 microC/phase. In Group 3, the stimulating electrode directly contacted the retina, but we did not apply current pulses. In Group 4, the stimulating electrode directly contacted the retina, and we applied current pulses of 0.09 microC/phase. We found neural damage only in the outer retina, including a disturbance of synaptic vesicle proteins in the photoreceptor terminals and a remodeling of horizontal and rod bipolar cells' processes. These results show that, although gross morphological changes are mainly concentrated around the area of electrode contact, immunocytochemistry can reveal changes in adjacent areas as well.