Characterization of salt interferences in second-harmonic generation detection of protein crystals.

Studies were undertaken to assess the merits and limitations of second-harmonic generation (SHG) for the selective detection of protein and polypeptide crystal formation, focusing on the potential for false positives from SHG-active salts present in crystallization media. The SHG activities of salts commonly used in protein crystallization were measured and quantitatively compared with reference samples. Out of 19 salts investigated, six produced significant background SHG and 15 of the 96 wells of a sparse-matrix screen produced SHG upon solvent evaporation. SHG-active salts include phosphates, hydrated sulfates, formates and tartrates, while chlorides, acetates and anhydrous sulfates resulted in no detectable SHG activity. The identified SHG-active salts produced a range of signal intensities spanning nearly three orders of magnitude. However, even the weakest SHG-active salt produced signals that were several orders of magnitude greater than those produced by typical protein crystals. In general, SHG-active salts were identifiable through characteristically strong SHG and negligible two-photon-excited ultraviolet fluorescence (TPE-UVF). Exceptions included trials containing either potassium dihydrogen phosphate or ammonium formate, which produced particularly strong SHG, but with residual weak TPE-UVF signals that could potentially complicate discrimination in crystallization experiments using these precipitants.

Role of roughness parameters on the tribology of randomly nano-textured silicon surface.

This experimental work is oriented to give a contribution to the knowledge of the relationship among surface roughness parameters and tribological properties of lubricated surfaces; it is well known that these surface properties are strictly related, but a complete comprehension of such correlations is still far to be reached. For this purpose, a mechanical polishing procedure was optimized in order to induce different, but well controlled, morphologies on Si(100) surfaces. The use of different abrasive papers and slurries enabled the formation of a wide spectrum of topographical irregularities (from the submicro- to the nano-scale) and a broad range of surface profiles. An AFM-based morphological and topographical campaign was carried out to characterize each silicon rough surface through a set of parameters. Samples were subsequently water lubricated and tribologically characterized through ball-on-disk tribometer measurements. Indeed, the wettability of each surface was investigated by measuring the water droplet contact angle, that revealed a hydrophilic character for all the surfaces, even if no clear correlation with roughness emerged. Nevertheless, this observation brings input to the purpose, as it allows to exclude that the differences in surface profile affect lubrication. So it is possible to link the dynamic friction coefficient of rough Si samples exclusively to the opportune set of surface roughness parameters that can exhaustively describe both height amplitude variations (Ra, Rdq) and profile periodicity (Rsk, Rku, Ic) that influence asperity-asperity interactions and hydrodynamic lift in different ways. For this main reason they cannot be treated separately, but with dependent approach through which it was possible to explain even counter intuitive results: the unexpected decreasing of friction coefficient with increasing Ra is justifiable by a more consistent increasing of kurtosis Rku.

Ag surface diffusion and out-of-bulk segregation in CrN-Ag nano-composite coatings.

CrN-Ag nanocomposite coatings are deposited on Si(100) wafers and 20MnCr5 steel disks in a mixed Ar+N2 atmosphere by reactive magnetron sputtering. Structure, composition and morphology were investigated by Scanning Electron Microscopy (SEM), Auger Electron Spectroscopy (AES), X-ray Photoemission Spectroscopy (XPS), X-ray Diffraction (XRD) and Focused Ion Beam (FIB) cross sectional analysis. The as deposited film matrix is mainly composed by CrN phase (78%), but a relevant part (28%) is composed by Cr2N. Ag agglomerates in the CrN matrix forming elongated grains 200-400 nm wide and 50-100 nm high, which extends on the top of CrN columns. At the surface Ag aggregates into two different structures: large tetrahedral crystalline clusters, with typical dimension ranging from 200 to 500 nm, and smaller Ag nanoparticles with diameter of 15-25 nm. The annealing in N2 atmosphere up to 500 degrees C does not affect size and distribution of the Ag grains in the sub-surface region, while it induces a size increase of the bigger Ag clusters on the surface, mainly related to Ag surface diffusion and clusters coalescence. Annealing at higher temperature leads to an evident Ag out-of-bulk segregation, generating Ag depleted voids in the near-surface region, and further increasing of the Ag clusters size at the surface. Tribological tests on as deposited CrN-Ag film reveal a coefficient of friction against a steel ball reduced with respect to CrN film, probably related to the presence of Ag which acts as solid lubricant, but the coating is removed after a very short sliding distance. The poor mechanical properties of the realized Ag-based coatings are confirmed by lower hardness and Young modulus values with respect to pure CrN.

Detection of membrane protein two-dimensional crystals in living cells.

It is notoriously difficult to grow membrane protein crystals and solve membrane protein structures. Improved detection and screening of membrane protein crystals are needed. We have shown here that second-order nonlinear optical imaging of chiral crystals based on second harmonic generation can provide sensitive and selective detection of two-dimensional protein crystalline arrays with sufficiently low background to enable crystal detection within the membranes of live cells. The method was validated using bacteriorhodopsin crystals generated in live Halobacterium halobium bacteria and confirmed by electron microscopy from the isolated crystals. Additional studies of alphavirus glycoproteins indicated the presence of localized crystalline domains associated with virus budding from mammalian cells. These results suggest that in vivo crystallization may provide a means for expediting membrane protein structure determination for proteins exhibiting propensities for two-dimensional crystal formation.

Analgesia in thoracic surgery: review.

Post-thoracotomy pain is one of the most severe types of postoperative pain. It can last up to 2 months and can become chronic in 30% of patients. Pain relief after thoracic surgery is of particular significance, not only for ethical considerations but also for reduction of postoperative pulmonary and cardiac complications. Because of the difficulty in pain control, many approaches have been suggested, but a multimodal therapeutic strategy that provides a central or peripheral block associated with nonsteroidal anti-inflammatory (NSAID) and adjuvant drugs is now the cornerstone of treatment, offering the possibility of reducing opioid requirements and side effects. Thoracic epidural analgesia with local anesthetics and opioids is regarded as the gold standard treatment for post-thoracotomy pain management because it results in early extubation, better ventilatory mechanisms and gas exchange, decreased incidence of atelectasis, pneumonia and chronic postoperative pain. When epidural analgesia is contraindicated or cannot be performed, other regional techniques of analgesia can be used. An alternative method of providing adequate pain relief is a thoracic paravertebral block: continuous paravertebral infusion of local anesthetic via a catheter placed percutaneously or under direct vision during thoracotomy. This is effective in controlling postoperative pain and in preserving pulmonary function. Other techniques, such as intercostal and interpleural blocks, are rarely utilized, whereas a single shot of intrathecal injection of a hydrophilic opioid, such as morphine, appears to be effective. Cryoanalgesia, which is successful in the immediate postoperative period, has been abandoned for its brief duration and increased incidence of chronic pain.

Haemodynamic and metabolic changes during major liver resection with use of hepatic total vascular exclusion.

We evaluated haemodynamic changes during major liver resection that involved total hepatic vascular exclusion (HVE) carried out through clamping hepatic pedicle and inferior caval vein upper and above the liver. Fourteen patients, undergoing different procedures of major liver resection, were enrolled in this study which used complete cardiovascular monitoring. Haemodynamic parameters were measured and calculated at five different times during the operation. Changes such as reduction in cardiac output and increase in systemic vascular resistance, though significant, were well tolerated in all patients, allowing the execution of major liver surgery. HVE offers a significant reduction in haemorrhagic and air embolus risk, but it requires the use of complete haemodynamic monitoring to evaluate tolerance to clamping and correction of unavoidable cardiovascular changes.

Subclavian venous catheterization: greater success rate for less experienced operators using ultrasound guidance.

OBJECTIVE: To determine if ultrasound guidance can be safely performed and improve success rates for subclavian venous catheterization performed by less experienced operators. DESIGN: Prospective, randomized study. SETTING: Twenty-bed trauma-surgical-medical intensive care unit in a 524-bed, community, tertiary care, teaching hospital. PATIENTS: After the decision for central venous cannulation was made, informed consent was obtained, and less experienced operators then attempted to insert subclavian catheters in 33 critical care patients. INTERVENTIONS: Catheter placements were attempted, either by landmark technique, ultrasound technique, or by landmark attempts with ultrasound salvage. Catheterization techniques to be used were randomized using a random number table. MEASUREMENTS AND MAIN RESULTS: Fifty-three placement procedures were attempted in 33 patients. One procedure was excluded from data analysis. Successful catheterizations, occurrence rates of complications, number of attempts, and number of catheter kits used were recorded. In the analysis, 52 catheterization procedures were studied. Twelve (44%) catheters were successfully placed from 27 attempts using the landmark technique vs. 23 (92%) successful catheterizations during 25 ultrasound procedures (p = .0003). Fifteen failed landmark technique attempts had ultrasound salvage attempted, with 12 (80%) catheters successfully inserted. Eleven complications (minor) occurred in 27 attempts of subclavian venous catheterization using conventional landmark technique vs. one complication (minor) in 25 attempts of subclavian venous catheterization with ultrasound guidance (p = .002). There were no major complications in either group. The landmark group required an average of 2.5 venipunctures and 1.4 catheter kits per attempted catheterization. The ultrasound group required an average of 1.4 venipuncture attempts and 1.0 insertion kit. The statistical significance in differences in groups for the average number of venipunctures was p = .0007 and average number of kits used was p = .0003. CONCLUSIONS: Ultrasound guidance improves the success rate of subclavian venous catheterization performed by less experienced operators. There were no major complications in either group. Ultrasound guidance is usually successful in allowing performance of subclavian venous catheterizations when landmark techniques fail.

Intra-hospital transport of the anaesthetized patient.

This study evaluated the anaesthetic management of 20 patients, undergoing intra-operative radiation therapy for pancreatic or rectal tumours. Patients with a re-approximated surgical incision were transferred from the operating room to the radiotherapy department while still under anaesthesia. The risks of such transport as well as guidelines for the patient's care during this phase are examined. The results of this study indicate that in order to transport anaesthetized patients safely it is necessary to ensure stable cardiovascular, respiratory and metabolic conditions prior to their transfer. It is also important to guarantee adequate analgesia and to establish appropriate monitoring during transport.

[Intraoperative radiotherapy: anesthesiologic problems during transport of patients]. / Radioterapia intraoperatoria: problemi anestesiologici durante il trasporto del paziente.

In this study the condition of anesthesia in 8 patients, undergoing intraoperative radiation therapy (IORT) for pancreatic or rectal tumors, is evaluated. Patients with reapproximated surgical incision were transferred from the operating room to the radiotherapy department while still under anesthesia. The risks of such transport as well as guidelines for the patient's care during this phase are examined. The results of this study indicate that in order to move anesthetized patients safely it is necessary to ensure stable cardiovascular, respiratory and metabolic conditions prior to their transfer. It is also important to guarantee adequate analgesia and to establish appropriate monitoring during transport.

[The effects of nitrous oxide on evoked potentials recorded during enflurane and isoflurane anesthesia]. / Effets du protoxyde d'azote sur les potentiels évoqués enregistrés pendant l'anesthésie à l'enflurane et à l'isoflurane.

The effects on median nerve somatosensory evoked potentials produced by nitrous-oxide (67%) were studied in 20 patients undergoing elective surgery under enflurane or isoflurane anaesthesia. This study demonstrates that nitrous-oxide does not significantly modify spinal (N13) and cortical (N20) component latencies nor central conduction time. The addition of nitrous-oxide to enflurane or isoflurane (up to 1 MAC) causes a significant reduction of N20 amplitude.