Malignant peripheral nerve sheath tumor mimicking carotid body tumor--case report and review.

Malignant peripheral nerve sheath tumor is a rare neurogenic tumor that usually presents in geriatic patients. Typically, it is found in the trunk and extremities and rarely presents in the head and neck region. It may mimic a carotid body tumor when it presents in the neck. We report the first case of malignant peripheral nerve sheath tumor of the vagus nerve in an adolescent boy. He presented with an asymptomatic lateral neck lump that was thought to be a benign schwannoma on preoperative imaging. We describe the diagnostic dilemma and management difficulties in this patient and review the literature.

Antibiotics and postoperative abscesses in complicated appendicitis: is there any association?

INTRODUCTION: Complicated appendicitis has significant infective postoperative morbidity. There is no universally-accepted antibiotic regime, although traditionally, triple antibiotics are recommended. Our complicated appendicitis clinical pathway recommends ceftriaxone and metronidazole. The study aimed to determine if choice of antibiotics influenced the risk of infective complications. METHODS: We reviewed all paediatric appendicectomy patients between January 1, 2005 and December 31, 2005. All patients with intraoperative diagnosis of perforated appendicitis were recruited, excluding infants, immunocompromised patients, and patients allergic to the guideline antibiotics. All operations were performed by registrar/consultant surgeons and were laparoscopic, unless technically not feasible. RESULTS: There were 82 patients with perforated appendicitis. 62 patients (76 percent) followed pathway antibiotics, and 20 patients (24 percent) deviated from the pathway by receiving additional empiric gentamycin. We compared the pathway compliant and deviation groups, and found no significant differences in patient characteristics, clinical presentation, operation, length of stay and infective complications. Overall there was one wound infection and five (six percent) postoperative abscesses. Initial peritoneal cultures and subsequent drainage cultures of patients who developed abscesses were sensitive to treatment antibiotics. CONCLUSION: In complicated appendicitis, empirical perioperative addition of gentamycin to ceftriaxone and metronidazole did not reduce the risk of developing intra-abdominal abscess, compared to changing antibiotics on clinical grounds. Patients developed postoperative abscesses despite initial peritoneal cultures growing organisms sensitive to treatment antibiotics.

Determination of pharmaceuticals and related impurities by capillary electrophoresis.

In the first part of this work, the use of capillary electrophoresis (CE) for the separation of two groups of pharmaceuticals, namely a metabolite of tamoxifen and a basic drug substance, DS1 was investigated. The effects of pH and types of modifiers, e.g. surfactant, bile salt, gamma-cyclodextrin and hydroxypropyl-beta-cyclodextrin on selectivity, separation and peak shape were studied. Besides achieving complete separation of the compounds, the CE system was capable of providing separation with significant improvements in overall peak shape of the compounds compared with HPLC. In the case of the basic drug substance DS1, validation of the CE system developed in terms of linearity, selectivity, sensitivity and reproducibility was satisfactorily performed. At the same time, a study of the sample solvent matrix effects on the separation of this group of compounds was examined. The system was successfully applied to the analysis of laboratory-synthesized samples. Good correlation was observed between CE and HPLC, although higher efficiency and faster speed of separation were obtained using the CE system developed. For the tamoxifen metabolite, special emphasis was placed on the use of CE for the separation of the pair of isomers. This was readily achieved through the introduction of gamma-cyclodextrin in the electrolyte. Resolution of at least 1.5 was obtained for the isomers using the CE method.

The use of mixed surfactants in micellar electrokinetic chromatography.

The use of mixed surfactants for the separation of nine phenylthiohydantoin amino acids (PTH amino acids) by micellar electrokinetic chromatography (MEKC) was examined. The potential of a mixed surfactant system, consisting of cationic and anionic surfactants, for enhancing the selectivity of MEKC separations was explored. Both sodium dodecyl sulfate (SDS) and cetyltrime-thylammonium bromide (CTAB) in the electrophoretic medium were found to improve the separation of the PTH-amino acids compared to the use of CTAB or SDS alone. Complete separation of the PTH amino acids was achieved using a buffer containing 2.5 mM CTAB and 40 mM SDS. The analysis was performed without the need to reverse the polarity of the electrodes, typically required if oppositely charged micelles are used. The migration behavior of the nine PTH amino acids using the mixed surfactant system was compared with MEKC in presence of SDS alone.

High density cultivation of hybridoma in charged porous carriers.

A porous carrier whose surface is charged with polyethyleneimine (PEI) was evaluated for high-density cultivation of immobilized hybridoma cells. The carrier was used either in suspension or in fixed bed. For suspended carriers, the effect of carrier pore size, ion-exchange capacity (IEC), mixing intensity and inoculum concentration on the attachment and growth of HBs MAb-producing hybridoma cells in carrier CELLSNOW EX were studied. The carrier with 100 microns pore size was more efficient than that with 500 microns in supporting cell attachment. In addition, the amount of antibody which was detected by PHA (passive hemagglutination assay) was 4-times higher in 100 microns compared with 500 microns pore size. At low initial cell concentration, 2.8 x 10(5) ml-1, the attached cells did not grow in the first 7 d as indicated by a negligible glucose consumption. However, cell proliferation was observed at high inoculum, 9 x 10(5) ml-1. Hybridoma cells were expected to attach faster to EX with high IEC than with low IEC but results showed no significant difference. A different hybridoma cell line producing monoclonal antibody (MAb) against penicillin-G-amidase was successfully cultivated in an axial-flow fixed bed containing CELLSNOW carriers. The specific glucose uptake rate as an indicator for cell activity was 24-times higher compared with conventional chemostat cultures. The CELLSNOW carriers offers many advantages over other carriers.

Determination of antihistamines in pharmaceuticals by capillary electrophoresis.

Capillary electrophoresis with on-column UV detection at 214 nm was used to separate a group of nine antihistamines. All these compounds were satisfactorily separated within ca. 6 min using a mixed carrier system containing sodium dodecyl sulphate with beta-cyclodextrin and tetrabutylammonium hydrogensulphate as modifiers. The application of the method to the determination of the amount of antihistamines present in commercial pharmaceutical samples was demonstrated. In addition, the migration behaviour of the antihistamines in the mixed carrier system was examined.

An optimization procedure for the isocratic high-performance liquid chromatographic separations of environmental pollutants.

This paper describes the use of the overlapping resolution mapping procedure to optimize the separation of priority pollutants by isocratic, reversed-phase high-performance liquid chromatography. Three classes of pollutants are considered: polycyclic aromatic hydrocarbons, substituted phenols and phthalate esters. The procedure requires only seven chromatographic runs for each set of pollutants before an optimized mobile phase composition is derived which can satisfactorily resolve all the components in the respective mixtures of pollutants. The main advantage of such a systematic scheme to optimize mobile phase compositions is an improvement in method development times compared to conventional techniques. Another benefit is that expenditures on solvents are reduced.

Some applications of Freon-22 in supercritical fluid chromatographic analysis of environmental pollutants.

The applications of Freon-22 (R22) as a mobile phase and as a modifier in supercritical fluid chromatography were investigated. For the purpose of this investigation, the separation of eleven phenols listed by the United States Environmental Protection Agency as priority pollutants was studied. It was found that the use of neat R22 greatly reduced the retention times of the phenols compared with the use of neat carbon dioxide as mobile phase. Satisfactory separation of all the eleven phenols could be achieved using 5% R22 as modifier in carbon dioxide. The promising results obtained in this preliminary investigation indicate the potential for the use of R22 in supercritical fluid separation processes.

Direct coupling of supercritical fluid extraction-supercritical fluid chromatography for the determination of selected polycyclic aromatic hydrocarbons in aqueous environmental samples.

A rapid and simple method is described for the quantitative determination of polycyclic aromatic hydrocarbons in aqueous environmental samples. A microscale on-line supercritical fluid extraction-supercritical fluid chromatography system using carbon dioxide is employed. The extract is analysed using capillary supercritical fluid chromatography with UV detection. Detection was carried out at 254 nm. An extraction efficiency of as high as 91% was obtained for the PAHs.

Separation of selected PAHs by using high performance capillary electrophoresis with modifiers.

The effect of varying SDS concentration in a micellar electrokinetic capillary chromatographic system (MECC) is investigated. In addition, the introduction of γ-cyclodextrin as modifier to the electrophoretic medium, containing SDS and a phosphate-borate buffer, is shown to give satisfactory separation of the seven selected PAHs. The separation efficiency is increased with the addition of γ-cyclodextrin.

Optimization of the gradient HPLC separation of selected phthalates using the overlapping resolution mapping technique.

Optimization procedures for the reversed-phase separations of six phthalates using the isoselective multisolvent gradient elution (IMGE) system are described. A systematic experimental design has been employed to gather retention data on the compounds in a mixture. The data were then fitted into a second-order polynomial equation and an overlapping resolution mapping (ORM) technique of data analysis was subsequently used to establish the optimum solvent mixture for the highest resolution of all adjacent peaks in the chromatogram.

Analysis of priority substituted phenols by micellar electrokinetic chromatography.

The use of micellar electrokinetic capillary chromatography (MECC) for the separation of eleven substituted phenols listed by the United States Environmental Protection Agency as priority pollutants was demonstrated. The effects of the pH and ionic strength of the buffer, and the length of the separation column on resolution were investigated. The retention characteristics of the eleven phenols in MECC are discussed.

Retention of eleven priority phenols using micellar electrokinetic chromatography.

The use of micellar electrokinetic chromatography (MECC) for the separation of eleven substituted phenols listed by the United States Environmental Protection Agency as priority pollutants was investigated. Solutions of potassium and sodium dodecyl sulphate in phosphate-borate buffer of pH 6.6, 7.0 and 7.5 were used as the electrophoretic media. Satisfactory separation of the eleven phenols was obtained using a 180-microns capillary at 10 kV and pH 6.6 with a solution containing both sodium and potassium dodecyl sulphate. Observations on the retention behaviour of the phenols in MECC were related to their physico-chemical properties.

Supercritical fluid extraction and chromatography of cholesterol in food samples.

A method based on supercritical fluid chromatography is presented which can be used for the determination of cholesterol in certain foods. The method involves the extraction with supercritical carbon dioxide and analysis of the extracts using a capillary column with supercritical carbon dioxide as mobile phase and flame ionization detection. Quantification is achieved using cholesteryl chloroacetate as an internal standard.