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At least 397 records · Page 22Linked to original sources
PubMed1997

Venous microembolic signals detected in patients with cerebral sinus thrombosis.

BACKGROUND AND PURPOSE: We sought to assess the usefulness of the Doppler technique in the monitoring of microembolic signals in the main venous outflow pathways in superior sagittal sinus thrombosis. METHODS: Transcranial Doppler ultrasound was performed with a range-gated 2-MHz transducer in 6 patients with superior sagittal sinus thrombosis, in 5 subjects with platelet hyperaggregability, and in 20 healthy volunteers. Emboli monitoring was performed mainly in one distal internal jugular vein for 10 to 15 minutes. RESULTS: Three of the six patients (50%) with superior sagittal sinus thrombosis had microemboli. None of the patients with platelet hyperaggregation or healthy volunteers revealed microemboli. CONCLUSIONS: Microemboli can be found in superior sagittal sinus thrombosis by Doppler ultrasound. Their prognostic significance remains to be determined.

Adult↗
PubMed2004

Microembolic signals detected by transcranial Doppler sonography during carotid endarterectomy and correlation with serial diffusion-weighted imaging.

BACKGROUND AND PURPOSE: Embolic events are a major cause for procedure-related strokes after carotid endarterectomy (CEA). Transcranial Doppler sonography can reveal embolic events as microembolic signals (MES) during CEA. MES during declamping and shunting are frequently detected. MES during shunting are rare and known to be correlated with the neurological outcome of the patient. In the present study, we analyzed the occurrence of MES within different stages of CEA and whether MES within those stages were correlated with cerebral ischemia, as detected by diffusion-weighted imaging (DWI), and brain infarction, as detected by contrast-enhanced MRI. METHODS: Thirty-three patients were monitored intraoperatively for MES using transcranial Doppler sonography. DWI was performed within 24 hours before and after surgery. Positive postoperative DWI led to reexamination with contrast-enhanced T1-MRI 7 to 10 days after CEA for detection of cerebral infarction. RESULTS: MES were detected in 32 of 33 patients. The highest number of MES was found during shunting and declamping. A significant correlation was found between MES and DWI-lesions during dissection. A significant correlation was found between MES during dissection and shunting, and nonsignificant correlation was found between MES and the occurrence of cerebral infarction. CONCLUSIONS: MES could be regularly detected during CEA. Dissection and shunting seem to be the most vulnerable stages of the procedure.

Aged↗
PubMed2001

Detecting, signalling and repairing DNA double-strand breaks.

DNA double-strand breaks (DSBs) can be generated by a variety of genotoxic agents, including ionizing radiation and radiomimetic chemicals. They can also occur when DNA replication complexes encounter other forms of DNA damage, and are produced as intermediates during certain site-specific recombination processes. It is crucial that cells recognize DSBs and bring about their efficient repair, because a single unrepaired cellular DSB can induce cell death, and defective DSB repair can lead to mutations or the loss of significant segments of chromosomal material. Eukaryotic cells have evolved a variety of systems to detect DNA DSBs, repair them, and signal their presence to the transcription, cell cycle and apoptotic machineries. In this review, I describe how work on mammalian cells and also on model organisms such as yeasts has revealed that such systems are highly conserved throughout evolution, and has provided insights into the molecular mechanisms by which DNA DSBs are recognized, signalled and repaired. I also explain how defects in the proteins that function in these pathways are associated with a variety of human pathological states.

Animals↗
PubMed1989

Construction of a calorimeter prototype with a high sensitivity pulsed signal detection circuit.

A calorimeter based on a Wheatstone bridge detector is considered to be an ideal absolute absorbed dose measuring device. One drawback of the calorimeter is that its output signals are extremely small. The signal size can be increased by increasing the bridge excitation voltage, which, however, may lead to excess self-heating of a temperature-sensing thermistor in the calorimeter detector and may require corrections. The use of pulsed excitation was investigated in this study in place of a conventional DC excitation to induce higher bridge output voltage while keeping the average self-heating of a thermistor to a reasonably low value. Performance evaluations of our prototype pulsed calorimeter are presented.

Calorimetry↗
PubMed2002

Early fluorescence signals detect transitions at mammalian serotonin transporters.

The mammalian serotonin transporters rSERT or hSERT were expressed in oocytes and labeled with sulforhodamine-MTS. The endogenous Cys-109 residue contributes most of the signal, and the labeled transporter shows normal function. The SERT fluorescence decreases in the presence of 5-HT and also depends on the inorganic substrates of SERT. The fluorescence also increases with membrane depolarization. During voltage-jump experiments, fluorescence relaxations show little inactivation or history dependence. The fluorescence signal has a voltage dependence similar to that of the prepriming step of the previously described voltage-dependent transient current. However, the fluorescence relaxations are the fastest voltage-dependent events yet studied at SERT; their time constants of approximately 8-30 ms are severalfold faster than the prepriming or inactivation phases of the transient currents. These fluorescence signals are interpreted within the framework of the gate-lumen-gate model. The signals may monitor initial events at the outer gate.

Animals↗
PubMed2003

Signal detection via residence-time asymmetry in noisy bistable devices.

We introduce a dynamical readout description for a wide class of nonlinear dynamic sensors operating in a noisy environment. The presence of weak unknown signals is assessed via the monitoring of the residence time in the metastable attractors of the system, in the presence of a known, usually time-periodic, bias signal. This operational scenario can mitigate the effects of sensor noise, providing a greatly simplified readout scheme, as well as significantly reduced processing procedures. Such devices can also show a wide variety of interesting dynamical features. This scheme for quantifying the response of a nonlinear dynamic device has been implemented in experiments involving a simple laboratory version of a fluxgate magnetometer. We present the results of the experiments and demonstrate that they match the theoretical predictions reasonably well.

Journal Article↗
PubMed1994

Signal detection in complex comodulated backgrounds by normal-hearing and cochlear-impaired listeners.

Comodulation masking release (CMR) was investigated in normal-hearing and cochlear-impaired listeners. The narrow-band masker centered on the tonal signal was flanked by a series of other narrow noise bands, some of which had temporal envelopes that were the same as that of the on-signal band (comodulated bands) and some of which had different temporal envelopes (codeviant bands). Previous research using such stimuli with normal-hearing listeners indicated that CMR was often substantially reduced when two codeviant bands were present at spectral locations close to the signal frequency, but that CMR recovered to some extent when more codeviant bands were added. In the present study, cochlear-impaired listeners showed an abnormally large reduction in CMR when codeviant bands were present, and poorer recovery of CMR with increasing number of codeviant bands. Supplementary experiments suggested that the poor recovery of CMR with increasing number of codeviant bands may have been due to the small range (in dB) over which CMR could occur in cochlear-impaired listeners. It is possible that abnormal reduction in CMR with codeviant bands present was due to poor peripheral analysis in hearing-impaired listeners.

Acoustic Stimulation↗
PubMed2000

Signal detection of endothelin receptor subtypes in human cirrhotic liver by a new in situ hybridization method.

Endothelin (ET) has been implicated in the regulation of hepatic microcirculation and development of portal hypertension, but the role of ET in cirrhosis of the liver has not yet been elucidated. We present here the application of peptide nucleic acid (PNA) probes in a fast and sensitive in situ hybridization (ISH) method for localizing the mRNA of endothelin receptor subtypes in formalin-fixed, paraffin-embedded sections of normal and cirrhotic human liver. The results of ISH using synthetic FITC-labeled PNA probes combined with the catalyzed signal amplification (CSA) system were compared with those using the standard detection system. It was indicated that the CSA-ISH protocol is more sensitive for the detection of mRNA target than the standard ISH protocol. Our results with CSA-ISH showed that the expression of mRNA for the endothelin B receptor was significantly upregulated in hepatic sinusoidal lining cells in cirrhotic human liver tissues compared to control normal liver tissue. Therefore, the CSA detection system may facilitate and enhance the use of in situ hybridization protocols, and CSA-ISH will be used as an important diagnostic technique in the future.

Humans↗
PubMed2005

Highly sensitive signal detection of duplex dye-labelled DNA oligonucleotides in a PDMS microfluidic chip: confocal surface-enhanced Raman spectroscopic study.

Rapid and highly sensitive detection of duplex dye-labelled DNA sequences in a PDMS microfluidic channel was investigated using confocal surface enhanced Raman spectroscopy (SERS). This method does not need either an immobilization procedure or a PCR amplification procedure, which are essential for a DNA microarray chip. Furthermore, Raman peaks of each dye-labelled DNA can be easily resolved since they are much narrower than the corresponding broad fluorescence bands. To find the potential applicability of confocal SERS for sensitive bio-detection in a microfluidic channel, the mixture of two different dye-labelled (TAMRA and Cy3) sex determining Y genes, SRY and SPGY1, was adsorbed on silver colloids in the alligator teeth-shaped PDMS microfluidic channel and its SERS signals were measured under flowing conditions. Its major SERS peaks were observable down to the concentration of 10(-11) M. In the present study, we explore the feasibility of confocal SERS for the highly sensitive detection of duplex dye-labelled DNA oligonucleotides in a PDMS microfluidic chip.

Colloids↗
PubMed2002

A molecular sensor detects signal transduction from caveolae in living cells.

Biochemical and cell fractionation studies suggest caveolae contain functionally organized sets of signaling molecules that are capable of transmitting specific signals to the cell. It is not known, however, whether any signals actually originate from caveolae in living cells. To address this question, we have engineered the calcium sensor yellow cameleon so that it is targeted either to the plasma membrane, caveolae, or the cytoplasm of endothelial cells. Quantitative measurements of the three Ca2+ pools detected by these probes indicate that caveolae are preferred sites of Ca2+ entry when Ca2+ stores in the endoplasmic reticulum are depleted. These results suggest that the signaling machinery in control of Ca2+ entry is functionally organized in the caveolae of living cells.

Animals↗
PubMed1998

Variability of velocity and duration of microembolic signals detected by bigated transcranial Doppler sonography in carotid endarterectomy.

OBJECTIVE: To differentiate between gaseous and particular microemboli in carotid surgery one clinical approach is the interpretation of the effective sample volume length (SVL). We investigated whether such a clinical interpretation is based on reproducible measurements. METHODS: Microembolic signals (MES) recorded during carotid endarterectomy by a bigated transcranial Doppler device were analyzed off-line. In the two sample volumes, the duration and the velocity of the MES were measured by two observers independently from each other twice within 2 weeks. The SVL of the MES were calculated by multiplying duration with velocity. RESULTS: In the anatomical proximal sample volume 215 MES were recorded of which 203 (94.5%) were also present in the distal. The SVL medians of the MES were 2.2-4.1 mm lower in the distal than in the proximal sample volume as a result of lower velocity and shorter duration of the MES in the distal sample volume. The median of the paired differences of the SVL was 0.2 mm (interquartile range: 0.0-1.2) in the proximal sample volume and 0.8 mm (0.2-1.8) in the distal sample volume for observer 1, and 0.6 mm (0.4-2.2) and 0.9 mm (0.5-1.6) for observer 2. The median of the paired differences of the SVL between the observers was 1.4 mm (1.2-2.9) in the proximal sample volume and 1.6 mm (1.3-3.0) in the distal. CONCLUSION: The intra- and interobserver agreement on calculating SVL is good. However, the depth of insonation influences some features of embolic signals.

Aged↗
PubMed2006

Cross-polarisation method for improvement of 14N NQR signal detectability.

This is a study of the cross-polarization effects in the case of 14N quadrupolar spin-system with a long spin-lattice relaxation time. Two important benefits of the cross-polarization technique were demonstrated for PETN: (i) a polarization transfer resulting in increased NQR single shot signal response and (ii) a dynamic reduction in recovery time of the NQR system allowing scan repetition on a much shorter timescale. It was proved that this technique can reduce the optimal waiting time between pulse sequences up to 60 times through a significant reduction of the relaxation time of the quadrupolar spin-system. All experiments were carried out at room temperature using spin-locking multi-pulse sequences and small external magnetic field.

Algorithms↗
PubMedDate not supplied

A tiered approach is more cost effective than traditional pharmacist-based review for classifying computer-detected signals as adverse drug events.

OBJECTIVE: To develop a cost-efficient method for identifying adverse drug events (ADEs) and medication errors (MEs) identified using outpatient electronic medical records within ambulatory settings. DESIGN: Comparison of sensitivity and cost of "traditional" pharmacist based approach to identifying ADEs and MEs during a 4 month period with a tiered approach. RESULTS: The proportion of computer generated signals analyzed identified as ADEs were similar using the two approaches while the number of MEs was nearly double with tiered reviews suggesting the same or better sensitivity. Traditional pharmacist review cost $68.70 US dollars to detect an ADE and tiered approach cost only $42.40. CONCLUSION: Tiered review of ADEs and MEs by personnel with increasing clinical capability is more cost-efficient than pharmacist review.

Adolescent↗
PubMed1982

Role of the frontal lobes on an attention task: a signal detection analysis.

Sensitivity and criterion were studied on an attention task requiring detection of new stimuli for a group of 20 patients with unilateral hemispheric damage restricted to the anterior or posterior areas. Patients performed a simple attention task, in which the presence of a novel stimulus had to be detected against the repetition of the same stimulus repeated. Only the site of the lesion (anterior vs posterior damage) influenced the performance of the task. In fact, frontal patients had both lower capacity to discriminate between signals and nonsignals and lower confidence in their responses.

Attention↗
PubMed2006

Contribution of reduced and oxidized glutathione to signals detected by magnetic resonance spectroscopy as indicators of local brain redox state.

The reduced form of glutathione (GSH; gamma-glutamyl cysteinyl glycine) is supposedly the most powerful reducing battery in the central nervous system against oxidative stress. We evaluated the contribution of GSH and GSSG to MEGA-PRESS (a frequency-selective refocusing technique) signals assessed by magnetic resonance spectroscopy (MRS). GSH gave a single positive signal (2.95 ppm) by the MEGA-PRESS. In contrast, GSSG gave a multiplet of reversed signals (3.03, 3.23, and 3.34 ppm). A phantom solution mimicking the normal in vivo condition (GSH:GSSG=100:1) gave a single positive peak. Even when the ratio was changed to 10:1, corresponding to toxic oxidative stress, GSH was prominent and GSSG signals were minimal. Thus, GSSG signals could be negligible. In the phantom solution (creatine:GSH:aspartate:gamma-aminobutyric acid=7:3:1:1), the creatine signal overshadowed the other signals. Through the MEGA-PRESS, a single peak of GSH stood out over other signals. In vivo, the brains of healthy volunteers gave similar signals as the in vitro phantom solution, indicating that the signal originated from GSH. The estimated concentration of GSH in the human brain was 1.9+/-0.37 mM (mean+/-S.D., n=4). In conclusion, MEGA-PRESS allowed us to assess GSH levels in vivo non-invasively.

Brain↗