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Qualitative Detection (qualitative + detection)
Selected AbstractsMethionine sulphoxide reductase is an important antioxidant enzyme in the gastric pathogen Helicobacter pyloriMOLECULAR MICROBIOLOGY, Issue 5 2004Praveen Alamuri Summary The ability of Helicobacter pylori to colonize the stomach requires that it combat oxidative stress responses imposed by the host. The role of methionine sulfoxide reductase (Msr), a methionine repair enzyme, in H. pylori stress resistance was evaluated by a mutant analysis approach. An msr mutant strain lacked immunologically detectable sulphoxide reductase protein and also showed no enzyme activity when provided with oxidized methionines as substrates. The mutant strain showed diminished growth compared to the parent strain in the presence of chemical oxidants, and showed rapid viability loss when exposed to oxidizing conditions. The stress resistance and enzyme activity could be recovered by complementing the mutant with a functional copy of the msr gene. Upon fractionation of parent strain and the complemented mutant cells into membranes and cytoplasmic proteins, most of the immunologically detectable Msr was localized to the membrane, and this fraction contained all of the Msr activity. Qualitative detection of the whole cell protein pattern using 2,4-dinitro phenyl hydrazine (DNPH) showed a far greater number of oxidized protein species in the mutant than in the parent strain when the cells were subjected to oxygen, peroxide or s-nitrosoglutathione (GSNO) induced stress. Importantly, no oxidized proteins were discerned in either strain upon incubation in anaerobic conditions. A mutant strain that synthesized a truncated Msr (corresponding to the MsrA domain) was slightly more resistant to oxidative stress than the msr strain. Mouse colonization studies showed Msr is an important colonization factor, especially for effective longer-term (14 and 21 days) colonization. Complementation of the mutant msr strain by chromosomal insertion of a functional gene restored mouse colonization ability. [source] In vivo detection of hemorrhage in human atherosclerotic plaques with magnetic resonance imaging,JOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 1 2004Vincent C. Cappendijk MD Abstract Purpose To investigate the performance of high-resolution T1-weighted (T1w) turbo field echo (TFE) magnetic resonance imaging (MRI) for the identification of the high-risk component intraplaque hemorrhage, which is described in the literature as a troublesome component to detect. Materials and Methods An MRI scan was performed preoperatively on 11 patients who underwent carotid endarterectomy because of symptomatic carotid disease with a stenosis larger than 70%. A commonly used double inversion recovery (DIR) T1w turbo spin echo (TSE) served as the T1w control for the T1w TFE pulse sequence. The MR images were matched slice by slice with histology, and the signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) of the MR images were calculated. Additionally, two readers, who were blinded for the histological results, independently assessed the MR slices concerning the presence of intraplaque hemorrhage. Results More than 80% of the histological proven intraplaque hemorrhage could be detected using the TFE sequence with a high interobserver agreement (Kappa = 0.73). The TFE sequence proved to be superior to the TSE sequence concerning SNR and CNR, but also in the qualitative detection of intraplaque hemorrhage. The false positive TFE results contained fibrous tissue and were all located outside the main plaque area. Conclusion The present study shows that in vivo high-resolution T1w TFE MRI can identify the high-risk component intraplaque hemorrhage with a high detection rate in patients with symptomatic carotid disease. Larger clinical trials are warranted to investigate whether this technique can identify patients at risk for an ischemic attack. J. Magn. Reson. Imaging 2004;20:105,110. © 2004 Wiley-Liss, Inc. [source] Assessment of hepatitis C virus-RNA clearance under combination therapy for hepatitis C virus genotype 1: performance of the transcription-mediated amplification assayJOURNAL OF VIRAL HEPATITIS, Issue 1 2008D. Ferraro Summary., Monitoring of HCV-RNA in blood during antiviral therapy is performed mostly by commercially available reverse transcription polymerase chain reaction-based (RT-PCR) assays, with a lower detection limit of 30,50 IU/mL of HCV-RNA. Use of different tests in the pivotal trials of combination therapy has generated some discordance, in terms of predictive value of the early virological response (EVR). To evaluate whether the use of a more sensitive test, as a qualitative assay based on transcription mediated amplification (TMA) with a lower detection limit of 5,10 IU/mL of HCV-RNA, may obtain a better prediction of EVR and of the ultimate virological outcome, we retrospectively evaluated serial samples from 108 naïve patients with HCV genotype 1 chronic hepatitis, treated with pegylated ,2b interferon plus ribavirin for 48 weeks and with a 24 weeks stopping rule. Serum samples of patients, obtained during treatment at weeks 4, 12, 24 and 48 and after treatment at week 24, were evaluated by TMA. Comparison of the RT-PCR and TMA assays for the qualitative detection of HCV-RNA showed no significant differences in performance when these tests were used at the end of the treatment period for assessing patients without an on-treatment virological response and those who eventually obtain a sustained virological response. Our results show instead that the use of TMA assay to detect HCV-RNA at 12 and 24 weeks of the combination therapy is more effective than RT-PCR in identifying patients with the highest probability of sustained HCV-RNA clearance. [source] High-frequency mode conversion technique for stiff lesion detection with magnetic resonance elastography (MRE)MAGNETIC RESONANCE IN MEDICINE, Issue 6 2009Yogesh K. Mariappan Abstract A novel imaging technique is described in which the mode conversion of longitudinal waves is used for the qualitative detection of stiff lesions within soft tissue using magnetic resonance elastography (MRE) methods. Due to the viscoelastic nature of tissue, high-frequency shear waves attenuate rapidly in soft tissues but much less in stiff tissues. By introducing minimally-attenuating longitudinal waves at a significantly high frequency into tissue, shear waves produced at interfaces by mode conversion will be detectable in stiff regions, but will be significantly attenuated and thus not detectable in the surrounding soft tissue. This contrast can be used to detect the presence of stiff tissue. The proposed technique is shown to readily depict hard regions (mimicking tumors) present in tissue-simulating phantoms and ex vivo breast tissue. In vivo feasibility is demonstrated on a patient with liver metastases in whom the tumors are readily distinguished. Preliminary evidence also suggests that quantitative stiffness measurements of stiff regions obtained with this technique are more accurate than those from conventional MRE because of the short shear wavelengths. This rapid, qualitative technique may lend itself to applications in which the localization of stiff, suspicious neoplasms is coupled with more sensitive techniques for thorough characterization. Magn Reson Med, 2009. © 2009 Wiley-Liss, Inc. [source] | ||||||||||