Simultaneous determination of eight metabolites of organophosphate and pyrethroid pesticides in urine.

A simultaneous method for quantifying eight metabolites of organophosphate pesticides and pyrethroid pesticides in urine samples has been established. The analytes were extracted using liquid-liquid extraction coupled with WCX solid phase extraction (SPE) cartridges. Eight metabolites were chemically derivatized before analysis using gas chromatography-tandem mass spectrometry (GC-MS-MS). The separation was performed on a HP-5MS capillary column (30 m × 0.25 mm × 0.25 µm) with temperature programming. The detection was performed under electro-spray ionization (ESI) in multiple reaction monitoring (MRM) mode. An internal standard method was used. The extraction solvent, types of SPE cartridges and eluents were optimized by comparing the sample recoveries under different conditions. The results showed that the calibration curves of the five organophosphorus pesticides metabolites were linear in the range of 0.2-200 µg/L (r2 ≥ 0.992) and that of the three pyrethroid pesticides metabolites were linear in the range of 0.025-250 µg/L (r2 ≥ 0.991). The limits of detection (LODs, S/N ≥ 3) and the limits of quantification (LOQs, S/N ≥ 10) of the eight metabolites were 0.008-0.833 µg/L and 0.25-2.5 µg/L, respectively. The recoveries of the eight metabolites ranged from 54.08% to 82.49%. This efficient, stable, and cost-effective method is adequate to handle the large number of samples required for surveying the exposure level of organophosphorus and pyrethroid pesticides in the general population.

Characterization of molecular interactions of an immobilized biotinylated monolayer and streptavidin-coated microspheres by bond-rupture scanning.

Bond-rupture approach has been used in the understanding of biomolecular interactions of highly specific recognition, e.g., an antibody and its antigen, by a functionalized and self-assembled monolayer (SAM). One of the most challenging issues of diagnostics is to distinguish between true binding and the ever-present non-specific binding in which a species gives false results in conventional affinity methods. In this study, bond-rupture scanning was proposed to characterize bindings by introducing energy mechanically through displacement of a resonant quartz crystal. This system was able to measure the resonant frequency difference, due to mass changes and bond breakages between supramolecular interaction of biotinylated SAM and streptavidin-coated polystyrene microsphere (SCPM). Both 2-µm and 4-µm of SCPMs revealed two recognized desorption patterns at 4 V and 2 V amplitudes respectively. It rapidly provided confirmation of the presence of a target analyte. From this study, it can be shown that an established approach of dynamic bond-rupture scanning can be adopted as a promising diagnostic tool for investigating various interactions of bacteria or virus on an immobilized biomolecular surface by measuring the characteristic level of mechanical energy required to break bonds.

Laparoscopic splenectomy and periesophagogastric devascularization with endoligature for portal hypertension in children.

BACKGROUND: Bleeding from esophagogastric varices is an importment complication of portal hypertension. Recently, significant progress in laparoscopic technology has enabled the devascularization of the lower esophagus and upper stomach in a less invasive way. In this article, we report our preliminary experience with laparoscopic splenectomy and periesophagogastric devascularization by endoligature and its effectiveness for bleeding varices with hypersplenism in children. PATIENTS AND METHODS: Six children with bleeding portal hypertension and developed severe thrombocytopenia and/or leukopenia underwent laparoscopic splenectomy and selective pericardial devascularization by using silk endoligature combined with a Harmonic Scalpel (Ethicon Endosurgery, Cincinnati, OH). The patients included 5 males and 1 female, who ranged in age from 8 to 17 years. After a massive splenectomy was performed, we devascularized the periesophagogastric collateral vessels and perforating veins of the upper stomach to the level of the incisura angularis and the lower esophagus 5 or 6 cm away from the esophagocardia junction. The stem of the gastric coronary vein and paraesophageal collateral veins were not dissected in order to reserve portal blood flow toward the azygous shunt. RESULTS: All the procedures were completed successfully under a whole laparoscope. The operative time ranged from 180 to 270 minutes. Intraoperative blood loss was estimated to be from 80 to 200 mL. None of the patients required a blood transfusion. There were no significant complications either intra- operatively or postoperatively, and all patients had returned to usual activity by 5 days. Postoperative platelet count and white blood cell count increased in individual patients. The data were statistically significant (p = 0.006 and 0.002, respectively). During a postoperative follow-up period of 8-40 months, all children were asymptomatic, with improved growth and hematology and no rebleeding, sepsis, or encephalopathy. CONCLUSIONS: Laparoscopic massive splenectomy with selective periesophagogastric devascularization is a feasible, effective, and safe surgical procedure and has all the benefits of minimally invasive surgery. It offers a new alternative modality for children with bleeding portal hypertension and hypersplenism.

Bone-muscle interaction of the fractured femur.

The interaction forces of a fractured femur among the bone, muscle, and other soft tissues are not well understood. Only a small number of in vivo measurements have been made and with many limitations. Mathematical modeling is a useful alternative, overcoming limitations and allowing investigation of hypothetical simulated reductions. We aimed to develop a model to help understand best practices in fracture reduction and to form a base to develop new technologies and procedures. The simulation environment allows muscle forces and moments to deform a fractured femur, and the behavior of forces during reduction can be found. Visual and numerical output of forces and moments during simulated reduction procedures are provided. The output can be probed throughout the reduction procedure down to the individual muscle's contribution. This is achieved by construction of an anatomically correct three-dimensional mathematical model of the lower extremity and muscles. Parameters are fully customizable and can be used to investigate simple, oblique, and some comminuted fractures. Results were compared with published in vivo measurements and were of the same magnitude. A simple midshaft fracture had a maximum resulting force of 428 N, whereas traction from the hip reached a maximum value of 893 N at 60 mm of displacement. Monte Carlo analysis revealed that the deforming force was most sensitive to the muscles' rest lengths. The developed model provides greater understanding and detail than in vivo measurements have to date. It allows new treatment procedures to be developed and importantly to assess the outcome.

Bond rupture of biomolecular interactions by resonant quartz crystal.

Significant progress has been achieved in understanding affinity-based diagnostics, which use the highly specific "lock and key" recognition and binding between biomolecules, for example, an antibody and its antigen. These are the most specific of analytical tests. One of the most challenging issues is to distinguish between true binding and ever-present nonspecific binding in which more loosely bound proteinaceous material gives false results in conventional affinity methods. We have used bond-rupture scanning to eliminate nonspecific binding by introducing energy mechanically through displacement of a resonant quartz crystal. The removal of the analyte was recorded with a simple all-electronic detection system quickly providing confirmation of the presence of the target molecule. The system can measure the resonant frequency difference and detect noise signals, respectively, due to mass changes and bond breaks between biotinylated self-assembled monolayer (SAM) and streptavidin-coated polystyrene microspheres (SCPM). Both static and dynamic scanning modes can reveal previously unrecognized desorption of streptavidin-coated polystyrene microspheres. An established framework of bond-rupture scanning is a promising diagnostic tool for investigating the specific and nonspecific interactions by measuring the characteristic level of mechanical energy required to break the bond.