Ultrafast Third-Order Nonlinear Optical Response Excited by fs Laser Pulses at 1550 nm in GaN Crystals

The ultrafast third-order optical nonlinearity of c-plane GaN crystal, excited by ultrashort (fs) high-repetition-rate laser pulses at 1550 nm, wavelength important for optical communications, is investigated for the first time by optical third-harmonic generation in non-phase-matching conditions. As the thermo-optic effect that can arise in the sample by cumulative thermal effects induced by high-repetition-rate laser pulses cannot be responsible for the third-harmonic generation, the ultrafast nonlinear optical effect of solely electronic origin is the only one involved in this process. The third-order nonlinear optical susceptibility of GaN crystal responsible for the third-harmonic generation process, an important indicative parameter for the potential use of this material in ultrafast photonic functionalities, is determined.     

Diagnosing anal sphincter injury with transanal ultrasound and manometry

PURPOSE: This study was undertaken to evaluate how well anorectal manometry and transanal ultrasonography diagnose anal sphincter injury. METHODS: Anorectal manometry and transanal ultrasonography were performed in 20 asymptomatic nulliparous women and 20 asymptomatic parous women, and the results were compared with those obtained in 31 incontinent women who subsequently underwent sphincteroplasty and, thus, had operatively verified anal sphincter injury. By using computerized manometry analysis, mean maximum resting and squeeze pressures, sphincter length, and vector symmetry were determined in all women. All transanal ultrasounds were interpreted blinded as to the patient's history, physical examination, and manometry results. RESULTS: Manometric resting and squeeze pressures were significantly higher in the asymptomatic nulliparous women than in the asymptomatic parous women, and both groups had significantly higher pressures than the incontinent women ( P <0.001). Anal sphincter length and vector symmetry index were significantly decreased in incontinent women compared with asymptomatic women ( P <0.01). Decreased resting and squeeze pressures suggestive of possible sphincter injury were found in 90 percent of incontinent women with known anal sphincter injury. Decreased anal sphincter length and vector symmetry were found in only 42 percent of women with known anal sphincter injury. Transanal ultrasound was able to identify 100 percent of the known sphincter injuries but also falsely diagnosed injury in 10 percent of the asymptomatic nulliparous women with intact anal sphincters. False identification of sphincter injury increased when transanal ultrasound scanning was performed proximal to the distal 1.5 cm of the anal canal. CONCLUSION: Although nonspecific, decreased resting and squeeze pressures were found in 90 percent of patients with anal sphincter injury. Decreased anal sphincter length or vector symmetry index were present in only 42 percent of patients with known sphincter injury. When limited to the distal 1.5 cm of the anal canal, transanal ultrasound identified all known sphincter injuries but falsely identified injury in 10 percent of women with intact anal sphincters. Transanal ultrasound in combination with decreased anal pressures correctly identified all intact sphincters and 90 percent of known anal sphincter injuries.Read at the meeting of The American Society of Colon and Rectal Surgeons, Orlando, Florida, May 8 to 13, 1994. Winner of the New England Society of Colon and Rectal Surgeons Award.     

Do laparoscopic skills transfer to robotic surgery?

Background

Identifying the set of skills that can transfer from laparoscopic to robotic surgery is an important consideration in designing optimal training curricula. We tested the degree to which laparoscopic skills transfer to a robotic platform.

Methods

Fourteen medical students and 14 surgery residents with no previous robotic but varying degrees of laparoscopic experience were studied. Three fundamentals of laparoscopic surgery tasks were used on the laparoscopic box trainer and then the da Vinci robot: peg transfer (PT), circle cutting (CC), and intracorporeal suturing (IS). A questionnaire was administered for assessing subjects' comfort level with each task.

Results

Standard fundamentals of laparoscopic surgery scoring metric were used and higher scores indicate a superior performance. For the group, PT and CC scores were similar between robotic and laparoscopic modalities (90 versus 90 and 52 versus 47; P > 0.05). However, for the advanced IS task, robotic-IS scores were significantly higher than laparoscopic-IS (80 versus 53; P < 0.001). Subgroup analysis of senior residents revealed a lower robotic-PT score when compared with laparoscopic-PT (92 versus 105; P < 0.05). Scores for CC and IS were similar in this subgroup (64 ± 9 versus 69 ± 15 and 95 ± 3 versus 92 ± 10; P > 0.05). The robot was favored over laparoscopy for all drills (PT, 66.7%; CC, 88.9%; IS, 94.4%).

Conclusions

For simple tasks, participants with preexisting skills perform worse with the robot. However, with increasing task difficulty, robotic performance is equal or better than laparoscopy. Laparoscopic skills appear to readily transfer to a robotic platform, and difficult tasks such as IS are actually enhanced, even in subjects naive to the technology.     

Immunohistochemical study of tubular epithelial cells and vascular endothelial cells in glomerulonephritis

Background and aims: In order to assess the role played by tubular epithelial cells (TEC) and interstitial vascular endothelial cells (VEC) in interstitial fibrogenesis in human glomerulonephritis, we studied the expression of markers of activated fibroblasts (α-smooth muscle actin (αSMA) and vimentin (Vim)) and of the transforming growth factor β (TGFβ), at the level of these cells. Methods: We studied retrospectively 41 renal biopsies from patients with primary and secondary glomerulonephritis [24 males, 17 females, mean age 45.5?±?12.9?years]. Immunohistochemistry using monoclonal antibodies (SMA, Vim, TGFβ) was assessed using a semiquantitative score, that was correlated with biological and histological data (quantified using a scoring system in order to assess active-inflammatory and chronic–sclerotic/fibrotic lesions). Results: The presence of SMA and Vim as markers of myofibroblasts was found in TECs and VECs. TEC Vim expression correlated with interstitial Vim expression (r?=?0.38; p?=?0.008), interstitial infiltrate (r?=?0.31; p?=?0.027), interstitial fibrosis (R?=?0.25; p?=?0.042), GFR (r?=??0.35; p?=?0.016), SMA (r?=??0.42; p?=?0.015), TGFβ (r?=?0.25; p?=?0.046), and hemoglobin (r?=??0.55; p?r?=??0.32; p?=?0.023) and interstitial fibrosis (r?=??0.34; p?=?0.017). Conclusion: Our study reflects the complexity of the involvement of VEC and mainly of TEC in fibrosis. The expression of mesenchymal markers at the tubular cell level (especially Vim) correlates with histological interstitial changes, with the decrease of renal function and more strongly with anemia.     

Quiescent satellite glial cells of the adult trigeminal ganglion

Sensory ganglia comprise functional units built up by neurons and satellite glial cells (SGCs). In animal species there was proven the presence of neuronoglial progenitor cells in adult samples. Such neural crest-derived progenitors were found in immunohistochemistry (IHC). These findings were not previously documented in transmission electron microscopy (TEM). It was thus aimed to assess in TEM if cells of the human adult trigeminal ganglion indeed have ultrastructural features to qualify for a progenitor, or quiescent phenotype. Trigeminal ganglia were obtained from fifteen adult donor cadavers. In TEM, cells with heterochromatic nuclei, a pancytoplasmic content of free ribosomes, few perinuclear mitochondria, poor developed endoplasmic reticulum, lack of Golgi complexes and membrane trafficking specializations, were found included in the neuronal envelopes built-up by SGCs. The ultrastructural pattern was strongly suggestive for these cells being quiescent progenitors. However, further experiments should correlate the morphologic and immune phenotypes of such cells.