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Sensitive Methods (sensitive + methods)
Selected AbstractsOn-line sample preconcentration with chemical derivatization of bacterial biomarkers by capillary electrophoresis: A dual strategy for integrating sample pretreatment with chemical analysisELECTROPHORESIS, Issue 21 2005Adam S. Ptolemy Abstract Simple, selective yet sensitive methods to quantify low-abundance bacterial biomarkers derived from complex samples are required in clinical, biological, and environmental applications. In this report, a new strategy to integrate sample pretreatment with chemical analysis is investigated using on-line preconcentration with chemical derivatization by CE and UV detection. Single-step enantioselective analysis of muramic acid (MA) and diaminopimelic acid (DAP) was achieved by CE via sample enrichment by dynamic pH junction with ortho -phthalaldehyde/N -acetyl- L -cysteine labeling directly in-capillary. The optimized method resulted in up to a 100-fold enhancement in concentration sensitivity compared to conventional off-line derivatization procedures. The method was also applied toward the detection of micromolar levels of MA and DAP excreted in the extracellular medium of Escherichia coli bacterial cell cultures. On-line preconcentration with chemical derivatization by CE represents a unique approach for conducting rapid, sensitive, and high-throughput analyses of other classes of amino acid and amino sugar metabolites with reduced sample handling, where the capillary functions simultaneously as a concentrator, microreactor, and chiral selector. [source] Lie detection by functional magnetic resonance imagingHUMAN BRAIN MAPPING, Issue 3 2002Tatia M.C. Lee Abstract The accurate detection of deception or lying is a challenge to experts in many scientific disciplines. To investigate if specific cerebral activation characterized feigned memory impairment, six healthy male volunteers underwent functional magnetic resonance imaging with a block-design paradigm while they performed forced-choice memory tasks involving both simulated malingering and under normal control conditions. Malingering that demonstrated the existence and involvement of a prefrontal-parietal-sub-cortical circuit with feigned memory impairment produced distinct patterns of neural activation. Because astute liars feign memory impairment successfully in testing once they understand the design of the measure being employed, our study represents an extremely significant preliminary step towards the development of valid and sensitive methods for the detection of deception. Hum. Brain Mapping 15:157,164, 2002. © 2002 Wiley-Liss, Inc. [source] Investigations into Salmonella contamination in poultry feedmills in the United KingdomJOURNAL OF APPLIED MICROBIOLOGY, Issue 4 2010R.H. Davies Abstract Aims:, To investigate and compare commercial and farm-level milling operations in respect of the monitoring and control of Salmonella contamination. Methods and Results:, Four commercial feedmills and four on-farm poultry feed mixers were intensively sampled. Samples included dust and spillages and were cultured for Salmonella. Serovars in ingredients on farms were associated with wildlife and/or livestock, whereas those in commercial mill ingredients were associated with domestically produced cereals and imported vegetable protein. Endemic contamination of two commercial feedmills was reflected in isolates obtained from finished products and destination flocks. Renovation of equipment and chemical treatment of equipment and feed had not removed endemic strains, and previous routine monitoring in the commercial mills had not revealed the degree of contamination found in the present investigations. Conclusions:, Ingredient contamination was diverse and reflected the sources and storage environments used by mills and farms, respectively. The use of dust and spillage samples showed a clear sensitivity advantage over the previously used monitoring methods in the feedmills. Significance and Impact of the Study:, Monitoring for Salmonella contamination of commercial feedmills requires sensitive methods, such as those employed in this study. This is particularly important for endemic contamination. [source] Chemical characterization of Azadirachta indica grafted on Melia azedarach and analyses of azadirachtin by HPLC-MS-MS (SRM) and meliatoxins by MALDI-MSPHYTOCHEMICAL ANALYSIS, Issue 4 2010Moacir Rossi Forim Abstract Introduction , Melia azedarach adapted to cool climates was selected as rootstocks for vegetative propagation of Azadirachta indica. Cleft grafting of A. indica on M. azedarach rootstock showed excellent survival. Little is known about the chemistry of grafting. Objective , The roots, stems, leaves and seeds of this graft were examined in order to verify if grafted A. indica would produce limonoids different from those found in non-grafted plants. Intact matured fruits were also studied to verify if they were free of meliatoxins. Methodology , After successive chromatographic separations the extracts afforded several limonoids. HPLC-MS/MS and MALDI-MS were used to develop sensitive methods for detecting azadirachtin on all aerial parts of this graft and meliatoxins in fruits, respectively. Results , The stem afforded the limonoid salannin, which was previously found in the oil seeds of A. indica. Salannin is also found in the root bark of M. azedarach. Thus, the finding of salannin in this study suggests that it could have been translocated from the M. azedarach rootstock to the A. indica graft. HPLC-MS/MS analyses showed that azadirachtin was present in all parts of the fruits, stem, flowers and root, but absent in the leaves. The results of MALDI-MS analyses confirmed the absence of meliatoxins in graft fruits. Conclusion , This study showed that A. indica grafted onto M. azedarach rootstock produces azadirachtin, and also that its fruits are free of meliatoxins from rootstocks, confirming that this graft forms an excellent basis for breeding vigorous Neem trees in cooler regions. Copyright © 2010 John Wiley & Sons, Ltd. [source] Use of activated graphitized carbon chips for liquid chromatography/mass spectrometric and tandem mass spectrometric analysis of tryptic glycopeptidesRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 4 2009William R. Alley Jr. Protein glycosylation has a significant medical importance as changes in glycosylation patterns have been associated with a number of diseases. Therefore, monitoring potential changes in glycan profiles, and the microheterogeneities associated with glycosylation sites, are becoming increasingly important in the search for disease biomarkers. Highly efficient separations and sensitive methods must be developed to effectively monitor changes in the glycoproteome. These methods must not discriminate against hydrophobic or hydrophilic analytes. The use of activated graphitized carbon as a desalting media and a stationary phase for the purification and the separation of glycans, and as a stationary phase for the separation of small glycopeptides, has previously been reported. Here, we describe the use of activated graphitized carbon as a stationary phase for the separation of hydrophilic tryptic glycopeptides, employing a chip-based liquid chromatographic (LC) system. The capabilities of both activated graphitized carbon and C18 LC chips for the characterization of the glycopeptides appeared to be comparable. Adequate retention time reproducibility was achieved for both packing types in the chip format. However, hydrophilic glycopeptides were preferentially retained on the activated graphitized carbon chip, thus allowing the identification of hydrophilic glycopeptides which were not effectively retained on C18 chips. On the other hand, hydrophobic glycopeptides were better retained on C18 chips. Characterization of the glycosylation sites of glycoproteins possessing both hydrophilic and hydrophobic glycopeptides is comprehensively achieved using both media. This is feasible considering the limited amount of sample required per analysis (<1,pmol). The performance of both media also appeared comparable when analyzing a four-protein mixture. Similar sequence coverage and MASCOT ion scores were observed for all proteins when using either stationary phase. Copyright © 2009 John Wiley & Sons, Ltd. [source] Natural intramolecular isotope measurements in physiology: elements of the case for an effort toward high-precision position-specific isotope analysis,RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 15 2001J. T. Brenna Chemical information available in organisms can be categorized into three major domains, macromolecular, small molecules, and isotope ratios. Information about physiological state is commonly obtained by qualitative and quantitative analysis in the macromolecular and small molecule domains. Genomics and proteomics are emerging approaches to analysis of macromolecules, and both areas yield definitive information on present physiological state. There is relatively little record of past physiological states of the individual available in these domains. Natural isotopic variability, particularly on an intramolecular level, is likely to retain more physiological history. Because of ubiquitous isotopic fractionation, every stereochemically unique position in every molecule has an isotope ratio that reflects the processes of synthesis and degradation. This fact highlights a vast amount of organismal chemical information that is essentially unstudied. Isotope measurements can be classified according to the chemical complexity of the analyte into bulk, compound-specific, and position-specific or intramolecular levels. Recent advances in analysis of isotope ratios are transforming natural science, and particularly answering questions about ecosystems using bulk methods; however, they have had relatively little impact on physiology. This may be because the vast complexities of physiological questions demand very selective information available in position-specific isotope analysis (PSIA). The relatively few high-precision PSIA studies, based on isotope ratio mass spectrometry (IRMS), have revealed intramolecular isotope ratio differences in pivotal physiological compounds including amino acids, glucose, glycerol, acetate, fatty acids, and purines. The majority of these analyses have been accomplished by laborious offline methods; however, recent advances in instrumentation presage rapid PSIA that will be necessary to attack real physiological problems. Gas-phase pyrolysis has been shown to be an effective method to determine 13C/12C at high precision for molecular fragments, and technologies to extend C-based PSIA to N and other organic elements are emerging. Two related efforts are warranted, (a) development of rapid, convenient, and sensitive methods for high-precision PSIA, a necessary precursor to (b) a concerted investigation into the relationship of metabolic state to intramolecular isotope ratio. Inherent in this latter goal is the need to identify long-lived molecules in long-lived cells that retain a record of early isotopic conditions, as has been shown for post-mortem human neuronal DNA. Using known metabolic precursor-product relationships between intramolecular positions, future studies of physiological isotope fractionation should reveal the relationship of diet and environment to observed isotope ratio. This science of isotope physiology, or simply isotopics, should add an important tool for elucidation of early factors that effect later health, probably the most difficult class of biomedical issues. Copyright © 2001 John Wiley & Sons, Ltd. [source] Optimization of Volumetric Computed Tomography for Skeletal Analysis of Model Genetic OrganismsTHE ANATOMICAL RECORD : ADVANCES IN INTEGRATIVE ANATOMY AND EVOLUTIONARY BIOLOGY, Issue 5 2008Sergio X. Vasquez Abstract Forward and reverse genetics now allow researchers to understand embryonic and postnatal gene function in a broad range of species. Although some genetic mutations cause obvious morphological change, other mutations can be more subtle and, without adequate observation and quantification, might be overlooked. For the increasing number of genetic model organisms examined by the growing field of phenomics, standardized but sensitive methods for quantitative analysis need to be incorporated into routine practice to effectively acquire and analyze ever-increasing quantities of phenotypic data. In this study, we present platform-independent parameters for the use of microscopic x-ray computed tomography (microCT) for phenotyping species-specific skeletal morphology of a variety of different genetic model organisms. We show that microCT is suitable for phenotypic characterization for prenatal and postnatal specimens across multiple species. Anat Rec, 291:475,487, 2008. © 2008 Wiley-Liss, Inc. [source] Pharmacokinetics of intravenous and oral midazolam in plasma and saliva in humans: usefulness of saliva as matrix for CYP3A phenotypingBRITISH JOURNAL OF CLINICAL PHARMACOLOGY, Issue 4 2008Bettina Link WHAT IS ALREADY KNOWN ABOUT THE SUBJECT , Midazolam is a frequently used probe drug for CYP3A phenotyping in plasma. Midazolam and its hydroxy-metabolites can be detected in saliva. WHAT THIS STUDY ADDS , The concentrations of midazolam and its hydroxy-metabolites are much lower in saliva than in plasma, but the midazolam concentrations in both matrices show a significant linear correlation. , Saliva appears to be a suitable matrix for CYP3A phenotyping with midazolam, but very sensitive methods are required due to the low concentrations of midazolam and its hydroxy-metabolites. AIMS To compare midazolam kinetics between plasma and saliva and to find out whether saliva is suitable for CYP3A phenotyping. METHODS This was a two way cross-over study in eight subjects treated with 2 mg midazolam IV or 7.5 mg orally under basal conditions and after CYP3A induction with rifampicin. RESULTS Under basal conditions and IV administration, midazolam and 1,-hydroxymidazolam (plasma, saliva), 4-hydroxymidazolam and 1,-hydroxymidazolam-glucuronide (plasma) were detectable. After rifampicin, the AUC of midazolam [mean differences plasma 53.7 (95% CI 4.6, 102.9) and saliva 0.83 (95% CI 0.52, 1.14) ng ml,1 h] and 1,-hydroxymidazolam [mean difference plasma 11.8 (95% CI 7.9 , 15.7) ng ml,1 h] had decreased significantly. There was a significant correlation between the midazolam concentrations in plasma and saliva (basal conditions: r = 0.864, P < 0.0001; after rifampicin: r = 0.842, P < 0.0001). After oral administration and basal conditions, midazolam, 1,-hydroxymidazolam and 4-hydroxymidazolam were detectable in plasma and saliva. After treatment with rifampicin, the AUC of midazolam [mean difference plasma 104.5 (95% CI 74.1, 134.9) ng ml,1 h] and 1,-hydroxymidazolam [mean differences plasma 51.9 (95% CI 34.8, 69.1) and saliva 2.3 (95% CI 1.9, 2.7) ng ml,1 h] had decreased significantly. The parameters separating best between basal conditions and post-rifampicin were: (1,-hydroxymidazolam + 1,-hydroxymidazolam-glucuronide)/midazolam at 20,30 min (plasma) and the AUC of midazolam (saliva) after IV, and the AUC of midazolam (plasma) and of 1,-hydroxymidazolam (plasma and saliva) after oral administration. CONCLUSIONS Saliva appears to be a suitable matrix for non-invasive CYP3A phenotyping using midazolam as a probe drug, but sensitive analytical methods are required. [source] Case-orientated approach to the management of hepatocellular adenoma,BRITISH JOURNAL OF SURGERY (NOW INCLUDES EUROPEAN JOURNAL OF SURGERY), Issue 12 2006D. J. van der Windt Background: Treatment of suspected hepatocellular adenoma (HA) remains controversial. The aim of this study was to evaluate the management of HA at a time when magnetic resonance imaging (MRI) and computed tomography (CT) are highly sensitive methods for diagnosing HA. Methods: Between January 2000 and January 2005, data from 48 consecutive women with HA (median age 36 years) were prospectively collected. The protocol for diagnostic work-up consisted of multiphasic MRI or CT. Management was observation if the tumour was smaller than 5 cm and surgical intervention if it was 5 cm or larger. Results: The median follow-up was 24 (range 3,73) months. Sixteen (33 per cent) patients had invasive procedures because of tumour size 5 cm or larger, malignant characteristics or haemorrhage. The remaining 32 patients (67 per cent) were observed; haemorrhage and malignant degeneration did not occur and none of the lesions showed enlargement after withdrawal of oral contraceptives. Multiple HAs were found in 32 (67 per cent) patients; liver steatosis was significantly more common in these patients than in those with a solitary lesion (59 versus 19 per cent; P = 0·008). Conclusion: Observation of adenomas smaller than 5 cm is justified because of improved radiological reliability. Resection should be reserved for patients with malignant tumour characteristics or with single lesions 5 cm or larger. Copyright © 2006 British Journal of Surgery Society Ltd. Published by John Wiley & Sons, Ltd. [source] Value of preoperative diagnostic modalities in patients with recurrent thyroid carcinomaBRITISH JOURNAL OF SURGERY (NOW INCLUDES EUROPEAN JOURNAL OF SURGERY), Issue 9 2000A. Frilling Background The prognosis of differentiated thyroid carcinoma is usually excellent, but the majority of patients who develop a recurrence have a higher risk of death from the disease. Beside clinical examination, several diagnostic tools, such as ultrasonography, 131I scanning, [18F]fluorodeoxyglucose positron emission tomography (FDG-PET) and thyroglobulin (TG) measurement under raised thyroid-stimulating hormone in serum can detect tumour recurrences. This prospective study compared the value of different diagnostic modalities in the detection of recurrent differentiated thyroid cancer. Methods From April 1992 to October 1999, 181 patients with thyroid carcinoma, of whom 150 had a well differentiated tumour, subjected to surgical treatment were identified prospectively. Some 107 patients (71 per cent) presented with primary tumour and 43 patients (29 per cent) with recurrent disease. The patients with tumour recurrence were evaluated regarding the mode of detection of recurrent disease, including clinical examination, ultrasonography, fine-needle biopsy (FNB), TG measurement and FDG-PET, the surgical treatment and outcome. Results Some 63 per cent of patients presented with regional lymph node metastases and 37 per cent with local recurrence. None of the patients with local recurrence was operated on for primary tumour in this department. In 87 per cent the recurrence was detected by clinical examination. Ultrasonography and 131I scan revealed suspicious findings in 97 and 69 per cent respectively. FNB disclosed abnormal cytological findings in 95 per cent. There were pathological TG levels in 86 per cent of patients. Among patients with a raised level of TG and negative scan results, 13 underwent FDG-PET, with pathological findings in 82 per cent. Conclusion In patients with well differentiated thyroid carcinoma, ultrasonography and FNB are the most sensitive methods for the detection of local recurrence or regional lymph node metastases. FDG-PET is a useful diagnostic tool in patients with a negative 131I scan and a raised level of TG. © 2000 British Journal of Surgery Society Ltd [source] Characterization of mediators of microbial virulence and innate immunity using the Caenorhabditis elegans host,pathogen modelCELLULAR MICROBIOLOGY, Issue 7 2003Rosanna A. Alegado Summary The soil-borne nematode, Caenorhabditis elegans, is emerging as a versatile model in which to study host,pathogen interactions. The worm model has shown to be particularly effective in elucidating both microbial and animal genes involved in toxin-mediated killing. In addition, recent work on worm infection by a variety of bacterial pathogens has shown that a number of virulence regulatory genes mediate worm susceptibility. Many of these regulatory genes, including the PhoP/Q two-component regulators in Salmonella and LasR in Pseudomonas aeruginosa, have also been implicated in mammalian models suggesting that findings in the worm model will be relevant to other systems. In keeping with this concept, experiments aimed at identifying host innate immunity genes have also implicated pathways that have been suggested to play a role in plants and animals, such as the p38 MAP kinase pathway. Despite rapid forward progress using this model, much work remains to be done including the design of more sensitive methods to find effector molecules and further characterization of the exact interaction between invading pathogens and C. elegans' cellular components. [source] | ||||||||||||||||