Development and optimization of a gas chromatography/mass spectrometry method for the analysis of thermochemolytic degradation products of phthiocerol dimycocerosate waxes found in Mycobacterium tuberculosis.

RATIONALE: The phthiocerol dimycocerosates (PDIMs) are certain stable and hydrophobic waxes found in the cell membrane of Mycobacterium tuberculosis, bacteria that cause an infectious disease of growing concern worldwide. Previous studies report the analysis of derivatives of the hydrolysed PDIMs from biological samples, following complex extraction and offline derivatization of PDIMs biomarkers, prior to their analysis by gas chromatography/mass spectrometry (GC/MS). METHODS: We developed and optimized a GC/MS method based on selected ion monitoring (SIM) to detect the derivatives produced via the thermally assisted hydrolysis and methylation (THM) of the PDIMs from the cell membrane of M. tuberculosis. The extraction of PDIMs from culture is simple, and their thermochemolysis is carried out automatically online, thus avoiding the time-consuming derivatization steps of hydrolysis and esterification, usually performed offline. RESULTS: For standard PDIMs in petroleum ether, our optimized method gave an excellent linearity (R(2) = 0.99) at concentrations between 0.172 and 27.5 ng/mL, a good precision (RSD = 11.42%), and a limit of detection (LOD) of 100 pg/mL. For the PDIMs extracted from dilutions of M. tuberculosis culture, the method gave good linearity (R(2) = 0.9685) and an estimated LOD of 400 CFU/mL (CFU = colony forming units) in sterile distilled water. CONCLUSIONS: A GC/MS(SIM) method is presented for the rapid and quantitative detection of M. tuberculosis, based on the online thermochemolysis of lipidic biomarkers extracted from the bacterial culture. The method has the potential to be applied in human and veterinary clinical laboratories for the rapid diagnosis of tuberculosis in infected biological samples.

Ion trap mass spectrometry on a comet nucleus: the Ptolemy instrument and the Rosetta space mission.

In May 2014, the Rosetta spacecraft is scheduled to rendezvous with the comet Churyumov-Gerasimenko ('67P'). One of the instruments on board the 'Lander' which will descend on to the surface of the comet is a miniaturised GC/MS system that incorporates an ion trap mass spectrometer, specially developed for isotope ratio analysis. This article describes the development and optimisation of the ion trap for this unique application, and presents a summary of the range of pre-programmed experiments that will contribute to the characterisation of the solid and volatile cometary materials.

Anterior cervical discectomy and fusion without instrumentation.

STUDY DESIGN: Review of clinical file information and postoperative imaging, collected prospectively over a period of 14 years, in anticipation of study. OBJECTIVES: 1) Assessment of technical success in achieving anterior cervical fusion without internal fixation; 2) assessment of postoperative neck pain relevant to technical success or failure of fusion; and 3) assessment of morbidity arising from iliac crest bone graft donor site. SUMMARY OF BACKGROUND DATA: After anterior cervical discectomy and bone grafting for cervical radiculopathy or the intractable pain of cervical spondylosis, common clinical practice varies widely between the extremes of internal fixation in all cases, and never applying fixation. The clinical information and relevant imaging of 97 consecutive patients, 46 male, was reviewed at 12 months after surgery. METHODS: All surgery was performed at no more than 2 contiguous levels, by one surgeon (S.M.E.). After anterior discectomy alone, or combined with posterior vertebral body margin osteophytectomy, anterior bone grafting (Smith-Robinson) was performed at each level using a tricortical autogenous iliac crest bone block inserted under compression. In the interests of maximizing resource allocation and minimizing potential complications, all surgery was completed without internal fixation. A postoperative semirigid cervical collar was prescribed for 2 months. RESULTS: In 54 patients having 1-level fusion, there were 6 pseudarthroses (11%). In 43 patients having 2-level fusion, 12 patients demonstrated pseudarthroses (28% of patients) at a total of 18 levels (21% of levels). Only 2 of the 97 patients had pain related to the donor site. CONCLUSIONS: These results tend to confirm published reports of high pseudarthrosis rates in anterior cervical fusions carried out at 2 or more levels without fixation, as against improved fusion rates when internal fixation is applied. The authors are inclined to change their practice to include internal fixation in the form of anterior plating for fusions carried out at more than one level. Patients with technically successful fusions were less likely to have postoperative neck pain. Donor site pain was not a significant postoperative complication.

Who was Meyerding?

Henry William Meyerding is best known for his spondylolisthesis classification system, but he achieved much more while working at the Mayo Clinic, Minnesota, during the first half of the 20th century. A brief biography is presented, as well as some personal insights into the character of H. W. Meyerding.