Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Dimensionality Reduction”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,099 records · Page 61Linked to original sources
PubMed1998

Left ventricular remodelling and improved long-term outcomes in chronic heart failure.

Several targets for heart failure therapy may be met through different mechanisms which are not necessarily associated. In the Australia/New Zealand Heart Failure Research Collaborative Group Study, patients with chronic stable heart failure of ischaemic aetiology on treatment including ACE inhibitors were randomized to treatment with either the vasodilator beta-blocking drug carvedilol or placebo. At 12 months, symptoms and exercise performance were unchanged, but ejection fraction increased significantly with carvedilol treatment; at 20 months, the rate of death and hospitalization was also significantly reduced in the carvedilol-treated group. In a sub-study using two dimensional echocardiography, progressive left ventricular (LV) dilatation occurred in the placebo group, compared with significant reductions in LV volumes with the carvedilol treatment group. An overview of all available carvedilol trial data showed the odds of death reduced by one-half with treatment (OR 0.51, 95% CI 0.33-0.77, 2P = 0.0014). Thus, improved LV remodelling occurs with carvedilol treatment in heart failure and is associated with improved long-term outcomes including survival. Improved LV function may, in part, mediate the survival benefit of carvedilol and provide a reliable surrogate for long-term outcomes.

Adrenergic beta-Antagonists↗
PubMed2004

Improved pulse sequences for pure exchange solid-state NMR spectroscopy.

Spin-exchange experiments are useful for improving the resolution and establishment of sequential assignments in solid-state NMR spectra of uniformly (15)N-labeled proteins oriented macroscopically in phospholipid bilayers. To exploit this advantage fully, it is crucial that the diagonal peaks in the two-dimensional exchange spectra are suppressed. This may be accomplished using the recent pure-exchange (PUREX) experiments, which, however, suffer from up to a threefold reduction of the cross-peak intensity relative to experiments without diagonal-peak suppression. This loss in sensitivity may severely hamper the applicability for the study of membrane proteins. In this paper, we present a two-dimensional exchange experiment (iPUREX) which improves the PUREX sensitivity by 50%. The performance of iPUREX is demonstrated experimentally by proton-mediated (15)N-(15)N spin-exchange experiments for a (15)N-labeled N-acetyl-L-valyl-L-leucine dipeptide. The relevance of exchange experiments with diagonal-peak suppression for large, uniformly (15)N-labeled membrane proteins in oriented phospholipid bilayers is demonstrated numerically for the G-protein coupled receptor rhodopsin.

Kinetics↗
PubMed1991

The effects of blood pressure reduction on abnormal left ventricular diastolic function in hypertensive patients.

To investigate whether reduction in blood pressure has a beneficial effect on left ventricular diastolic function, we investigated 20 hypertensive patients with evidence of diastolic dysfunction at baseline and at 3 and 6 months after initiation of captopril therapy. Two-dimensional echocardiography was used to determine left ventricular mass index and Doppler ultrasound to assess diastolic function. Fifteen of the 20 patients had a significant reduction in blood pressure at 3 and 6 months and left ventricular mass index remained unchanged during the study period. Despite reduction in blood pressure, no difference in isovolumic relaxation time, early and atrial filling velocities or their ratio was observed. Our results suggest that a direct relationship between blood pressure and left ventricular diastolic function does not exist and that other factors such as alterations in muscle or collagen composition of the left ventricle may be more important in determining abnormal diastolic function in hypertension.

Adult↗
PubMed2006

Specific configuration of dendritic degeneration in pyramidal neurons of the medial prefrontal cortex induced by differing corticosteroid regimens.

We previously demonstrated that hypercorticalism induces pronounced volumetric reductions in the rat medial prefrontal cortex (mPFC) and that these structural changes correlate with deficits in executive function. By applying 3-dimensional analysis of Golgi-Cox-stained material, we now demonstrate that corticosteroids can exert differential effects on dendritic arborizations of pyramidal neurons in lamina II/III of the mPFC. Treatment with the glucocorticoid receptor-selective agonist dexamethasone and with the natural adrenosteroid, corticosterone (CORT), results in significant reductions in the total length of apical dendrites in the pyramidal neurons in lamina II/III of the anterior cingulate/prelimbic and infralimbic cortices. Interestingly, although these treatments do not affect the number of dendritic branches, they are associated with impoverished arborizations in their distal portions and, in CORT-treated animals, with increased branching in the middle portions of the apical dendritic tree. Deprivation of corticosteroids by adrenalectomy leads to decreases in total apical dendritic length and spine number, but in this case, dendritic impoverishment was restricted to the middle/proximal segments of the dendritic trees. None of the treatments influenced the architecture of the basal dendrites. These results add to our knowledge of the morphological substrates through which corticosteroids may disrupt mPFC-dependent behaviors.

Adrenal Cortex Hormones↗
PubMed2002

Detection of oxidant sensitive thiol proteins by fluorescence labeling and two-dimensional electrophoresis.

Oxidants can activate signaling pathways and modulate a variety of cellular activities. Their action at a molecular level involves the post-translational modification of protein thiols. We have developed a proteomic method to monitor the reduction and oxidation of protein thiols, and identify those thiol proteins most sensitive to oxidation. Cells were disrupted in the presence of N-ethylmaleimide to block the reduced thiol proteins and dithiothreitol was added to reduce the oxidized thiol proteins before labeling with 5-iodoacetamidofluorescein. Two-dimensional (2-D) electrophoresis was used to resolve the labeled samples. We applied the method to Jurkat T lymphocytes and examined the effect of diamide on the oxidized and reduced thiol protein profiles. A small percentage of protein thiols were already oxidized in untreated cells. Exposure of cells to 2 mM diamide for ten minutes led to a dramatic increase in thiol protein oxidation as seen in the oxidized thiol protein map. However, it was difficult to detect any change in the pattern of reduced thiol proteins. Separation of proteins by 2-D electrophoresis revealed approximately 200 thiol proteins that were oxidized by diamide treatment. This method will be valuable in elucidating redox signaling pathways.

Electrophoresis, Gel, Two-Dimensional↗
PubMed1997

Comparison of screening methods for detection of extended-spectrum beta-lactamases and their prevalence among blood isolates of Escherichia coli and Klebsiella spp. in a Belgian teaching hospital.

Using a set of 33 well-defined extended-spectrum beta-lactamase (ESBL)-producing strains of Escherichia coli and Klebsiella pneumoniae, we compared three screening methods for ESBL detection: (i) a double-disk synergy test, (ii) a three-dimensional test (both the double-disk synergy test and the three-dimensional test were performed with ceftriaxone, ceftazidime, aztreonam, and cefepime), and (iii) the Etest ESBL screen (AB Biodisk, Solna, Sweden), based on the recognition of a reduction in the ceftazidime MIC in the presence of clavulanic acid. In the double-disk test, all four indicator antibiotics scored equally and 31 of the 33 reference strains were recognized. In the three-dimensional test, ceftriaxone was the only satisfactory indicator and 30 ESBL-positive strains were detected by this antibiotic. Both systems produced two false-positive results with cefepime. With the Etest ESBL screen, 15 of 16 TEM-related and 11 of 16 SHV-related ESBL-producing strains scored positive. In 10 cases the clavulanic acid on one end of the strip interfered with the MIC determination for ceftazidime, which was read on the opposite end. This MIC had to be determined with an extra ceftazidime-only strip. No false-positive results were noted. Eighty-six blood isolates of E. coli and Klebsiella species were screened for ESBL expression by the double-disk and three-dimensional tests, both with ceftriaxone. Six strains with suspicious antibiogram phenotypes also gave positive results by the double-disk test. One E. coli strain remained undetected by the three-dimensional test. Identification of the enzymes suspected of being ESBLs by isoelectric focusing (all strains) and DNA sequencing (1 strain) confirmed the screening test results except for one Klebsiella oxytoca strain, which proved to be a hyperproducer of its chromosomal enzyme and which also had a negative Etest score. The five true ESBL producers were all confirmed by the Etest ESBL screen. Pulsed-field gel electrophoresis proved that the E. coli strains were unrelated, but that two of the three K. pneumoniae strains were closely related.

Aztreonam↗
PubMed1984

Selective saturation NMR imaging.

The application of selective saturation (or solvent suppression) techniques in nuclear magnetic resonance (NMR) imaging offers the opportunity to significantly expand the range of NMR studies. Data acquired at 1.44 T are presented using a two-dimensional spin-echo sequence preceded by a selective (saturating) radiofrequency pulse. Individual water or lipid proton resonances were eliminated (greater than 90% reduction in signal intensity) resulting in images of H2O or -CH2- distribution with resolution and imaging time equivalent to conventional proton images. Data are also presented demonstrating the feasibility of using selective saturation to image proton metabolites at low concentrations with a three-dimensional chemical shift imaging approach. Lactate was investigated because of its importance in the pathophysiology of ischemic insult. Phantom studies without solvent suppression failed to detect lactate at 80 mM; however, with solvent suppression, lactate at 40 mM was imaged in a reasonable time (approximately 50 min). With the favorable NMR characteristics of the methyl protons of lactate and with improvements in imaging systems, this technique may play an important role in the noninvasive evaluation of tissue ischemia using 1H NMR.

Arm↗
PubMed2004

Undersized mitral annuloplasty alters left ventricular shape during acute ischemic mitral regurgitation.

BACKGROUND: Underlying left ventricular (LV) dysfunction contributes to poor survival after operation to correct ischemic mitral regurgitation (IMR). Many surgeons do not appreciate that a key component of the Bolling undersized mitral ring annuloplasty concept is to decrease LV wall stress by altering LV shape, but precise 3-dimensional (3-D) geometric data do not exist substantiating this effect. We tested the hypothesis that annular reduction decreases regional circumferential LV radius of curvature (ROC) in a model of acute IMR. METHODS: Eight adult sheep underwent insertion of an adjustable Paneth-type annuloplasty suture and radiopaque markers on the LV and mitral annulus. The animals were studied with biplane videofluoroscopy during baseline conditions, then before and after tightening the annuloplasty suture during proximal left circumflex occlusion. End-systolic circumferential regional LV ROC and mitral annular area were computed. RESULTS: Acute IMR was eliminated (MR grade 2.1+/-0.4 to 0.4+/-0.4, mean+/-SD, P<0.05) by tightening the Paneth annuloplasty suture. Paneth suture tightening during circumflex occlusion also decreased end-systolic regional circumferential radii of curvature at the basal (anterior, 3.40+/-0.16 to 3.34+/-0.14 cm; posterior, 3.31+/-0.23 to 3.24+/-0.26 cm; P<0.05) and equatorial levels (anterior, 2.99+/-0.21 to 2.89+/-0.29 cm; posterior, 2.86+/-0.38 to 2.81+/-0.41 cm; P<0.05). CONCLUSIONS: Acute proximal circumflex occlusion caused IMR and increased end-systolic LV radii of curvature in this experimental preparation. Annular reduction sufficient to abolish IMR also decreased end-systolic anterior and posterior LV ROC, which would be expected to reduce LV wall stress and oxygen consumption in these regions, both potentially beneficial effects. The long-term effects of undersized annuloplasty on LV remodeling and function, however, will require further study in chronic animal preparations or patients with chronic IMR.

Acute Disease↗
PubMed1999

Dynamic outflow obstruction due to the transient extensive left ventricular wall motion abnormalities caused by acute myocarditis in a patient with hypertrophic cardiomyopathy: reduction in ventricular afterload by disopyramide.

A 65-year-old woman was admitted to the coronary care unit because of acute pulmonary edema. Immediate 2-dimensional and Doppler echocardiograms revealed extensive left ventricular wall motion abnormalities and left ventricular hypertrophy with extreme outflow obstruction. Although an ECG showed ST-segment elevation in the anterolateral leads, a coronary arteriogram revealed normal epicardial arteries. Heart failure was relieved after diminishing the dynamic outflow obstruction with disopyramide administration. An endomyocardial biopsy from the right ventricle on the 8th hospital day showed borderline myocarditis. Wall motion abnormalities gradually normalized within 2 weeks. It is speculated that her pulmonary edema would not have been relieved so readily without the immediate reduction in ventricular afterload by disopyramide. These clinical changes over time were observed with serial echo-Doppler examinations.

Acute Disease↗
PubMed2005

The three-dimensional structures of peptide methionine sulfoxide reductases: current knowledge and open questions.

Methionine sulfoxides are easily formed in proteins exposed to reactive oxidative species commonly present in cells. Their reduction back to methionine residues is catalyzed by peptide methionine sulfoxide reductases. Although grouped in a unique family with respect to their biological function, these enzymes are divided in two classes named MsrA and MsrB, depending on the sulfoxide enantiomer of the substrate they reduce. This specificity-based classification differentiates enzymes which display no sequence homology. Several three-dimensional structures of peptide methionine sulfoxide reductases have been determined, so that members of both classes are known to date. These crystal structures are reviewed in this paper. The folds and active sites of MsrAs and MsrBs are discussed in the light of the methionine sulfoxide reductase sequence diversity.

Amino Acid Sequence↗
PubMed2006

Detection of reversible protein thiol modifications in tissues.

Oxidation/reduction reactions of protein thiol groups (PSH) have been implicated in many physiological and pathological processes. Although many new techniques for separation and identification of modified cysteinyl residues in proteins have been developed, critical assessment of reagents and sample processing often are overlooked. We carefully compared the effectiveness of N-ethylmaleimide (NEM), iodoacetamide (IAM), and iodoacetic acid (IAA) in alkylating protein thiols and found that NEM required less reagent (125 vs. 1000 mol:mol excess), required less time (4 min vs. 4h), and was more effective at lower pHs (4.3 vs. 8.0) in comparison with IAM and IAA. The relative efficacy of dithiothreitol (DTT) and tris(2-carboxyethyl)phosphine (TCEP) for reducing protein disulfides suspended in NaPO(4) buffer or MeOH was assessed, and no differences in total normalized fluorescence were detected at the concentrations tested (10-100mM); however, individual band resolution appeared better in samples reduced with DTT in MeOH. In addition, we found that oxidation ex vivo was minimized in tissue samples that were homogenized in aqueous buffers containing excess molar quantities of NEM compared with samples homogenized in MeOH containing NEM. Using NEM for thiol alkylation, DTT for disulfide reduction, and mBBr for labeling the reduced disulfide and fluorimetric detection, we were able to generate an in-gel standard curve and quantitate total disulfide contents within biological samples as well as to identify changes in specific protein bands by scanning densitometry. We demonstrated that reagents and techniques we have identified for disulfide detection in complex samples are also applicable to two-dimensional electrophoresis separations.

Alkylation↗
PubMed2004

A pragmatic approach to metal artifact reduction in CT: merging of metal artifact reduced images.

The purpose of this study was to improve metal artifact reduction (MAR) in X-ray computed tomography (CT) by the combination of two artifact reduction methods. The presented method constitutes an image-based weighted superposition of images processed with two known methods for MAR: linear interpolation of reprojected metal traces (LI) and multi-dimensional adaptive filtering of the raw data (MAF). Two weighting concepts were realized that take into account mean distances of image points from metal objects or additional directional components. Artifact reduction on patient data from the jaw and the hip region shows that although the application of only one of the MAR algorithms can already improve image quality, these methods have specific drawbacks. While MAF does not correct corrupted CT values, LI often introduces secondary artifacts. The corrective impact of the merging algorithm is almost always superior to the application of only one of the methods. The results obtained with directional weighting are equal to or in many cases better than those of the distance weighting scheme. Merging combines the advantages of two fundamentally different approaches to artifact reduction and can improve the quality of images that are affected by metal artifacts.

Algorithms↗
PubMed2006

Effectiveness of iterative algorithms in recovering phase in the presence of noise.

Inversion of coherent X-ray diffraction patterns allows the imaging of three-dimensional density distributions. The recovery of such shapes often requires application of iterative algorithms, such as Fienup's error reduction or hybrid input/output. Since the measurement of such a pattern records the intensity in reciprocal space, any errors due to noise will probably not have a straightforward impact on the final real-space result. In this paper, the effect of the types of noise common in coherent X-ray diffraction (CXD) experiments, counting statistics, scatter from alien particles and detector noise, on the recovered real-space density projection is explored by simulating a two-dimensional CXD pattern and adding noise. It is found that an R factor measuring the reproducibility between the best and second-best real-space result is a leading indicator of performance.

Algorithms↗
PubMed1992

[Three-dimensional display of the prostate based on transrectal ultrasonogram].

A software for a lap top computer to display prostatic contour three-dimensionally based on transrectal ultrasonograms was developed, and its clinical usefulness was examined. The prostatic contour of a case with prostatic cancer showed a typical irregular surface, and that of a case with prostatic hypertrophy had a smooth spherical shape, while that of a normal case had a flat shape. Each showed its characteristic shape. Estimation of the prostatic weight by assuming that the prostatic contour has ellipsoidal contour is a simple method for prostatic weight measurement, but it has a tendency to underestimate the weights, especially in normal cases. Three-dimensional display of the contour of prostatic cancer, prostatic hypertrophy, and normal prostate revealed that it could be estimated as ellipsoid in prostatic cancer or hypertrophy, while the normal prostatic contour was too flat to be calculated as such. Among 52 patients with benign prostatic hypertrophy who underwent transrectal ultrasonotomography before and during the anti-androgen therapy more than three time, nine cases showed transient reduction of more than 30% in prostatic weight and then reenlargement of more than 30%. In these cases, three-dimensional display of prostatic contour was done. The display was useful to visualize clearly which part reenlarged. Therefore, usefulness of the three-dimensional display of the prostate was verified.

Aged↗
PubMed1994

Influence of positive end-expiratory pressure on right and left ventricular performance assessed by Doppler two-dimensional echocardiography.

The advent of modern Doppler two-dimensional ultrasound technology has overcome the need of invasive measurements of several important cardiac parameters. It allows estimation of preload, contractility, and afterload. Positive end-expiratory pressure (PEEP) is associated with a reduction in cardiac output. The responsible mechanisms are controversial. To evaluate the cardiovascular responses to PEEP, we employed different Doppler hemodynamic indices for the first time, combined with conventional two-dimensional echocardiography. Twenty-one healthy, young, and unsedated volunteers were admitted to the study. Under spontaneous respiration, PEEP level was increased stepwise (0, 5, 7.5, 10, 12.5 cm H2O). At each PEEP level, the following right and left ventricular parameters were assessed with Doppler two-dimensional echocardiography: two-dimensional variables: end-diastolic volume indices (EDVI), ejection fraction (EF), and left ventricular afterload-LaPlace relation (combined with cuff systolic pressure); Doppler variables: cardiac index (CI) (combined with two-dimensional measure of valve area), maximum velocity (Vmax), time velocity integral (TVI), acceleration time (AT), deceleration time (DT), deceleration rate (DR), ratio of early to atrial peak (E/A), ratio of isovolumic contraction time to ejection time (IVCT/ET), and maximum blood acceleration (dv/dt) in aorta and main pulmonary artery. Increasing PEEP resulted in a proportional decrease in biventricular EDVI. Moreover, PEEP application is also causing a drop of CI, which is determined from a decrease in Vmax and TVI, while EF, IVCT/ET, dv/dt, Doppler trans-atrioventricular parameters, and afterload stay in normal ranges. Employing Doppler hemodynamic indices for the first time in this study setting clearly supports data that the drop in EDVI and CI during PEEP is caused by reduction in ventricular filling due to decreased venous return. Using the Doppler parameters IVCT/ET and dv/dt, changes in myocardial contractility, as well as changes in afterload (LaPlace relation) can be ruled out.

Adult↗
PubMed1979

Visualization of multidimensional spectra in flow cytometry.

Flow data from a cell sorter have been processed by hardwired circuits which include amplification, discrimination, coincidence requirements, peak sensing and holding, A-D conversion, and a computerized pulse height analysis with storage of the spectra obtained. Two dimensional spectra can be stored directly in memory, on tape and disk. Three and four parametric cellular events can be recorded on line during the flow measurement in a sequential mode on tape for subsequent recall. Simple processing of these data can be performed for displaying of two dimensional projections from these multidimensional spaces based on threshold conditions for the remaining parameters. Interfaced transmission of the stored data to a large scale computer enables more sophisticated data analysis. Data reduction by means of a multidimensional probability analysis has been carried out in order to transfer the spectra to a computerized picture system for display. This system creates perspective two-dimensional images from a three-dimensional data space. Frequency can be converted into grey levels. Hard copy in color (color as the third dimension and color intensity as frequency) simplifies the visualization of multiparametric flow data sets.

Animals↗
PubMed2003

Accurate preoperative estimation of liver-graft volumetry using three-dimensional computed tomography.

BACKGROUND: The aim of this study was to clarify the value of three-dimensional computed-tomography (3D-CT) volumetry for size matching in living-donor liver transplantation (LDLT). METHODS: 3D-CT volumetry was applied to 25 donors who underwent hepatectomy for a living relative needing an orthotopic liver transplantation. Fifteen patients underwent extended left lobectomy, one patient an extended left lateral lobectomy, and nine patients right lobectomy. 3D-CT imaging was performed with the workstation ZIO M900 (Zio Software Inc., Tokyo, Japan). The estimated volume of the grafts in two-dimensional (2D) and 3D images were compared, and an error ratio was calculated. RESULTS: 3D-CT imaging revealed the anatomy of the hepatic vein bifurcation and the shape of the graft. The error ratio was 12.8+/-2.3% in 3D, compared with 19.4+/-2.5% in 2D. As such, 3D-CT volumetry appears to be more exact than conventional 2D-CT volumetry, but volumetry by 3D-CT still produces an error ratio of approximately 13%. The weight transition of the rats' livers under preservation in University of Wisconsin (UW) solution indicated that the graft volume seems to decrease during perfusion with UW solution. Mismatch of the cutting line and volume reduction by dehydration (approximately 5% reduction 1 hour after perfusion) seems to cause the error in 3D-CT volumetry. CONCLUSIONS: Three-dimensional CT volumetry is useful for size matching in cases of living-related orthotopic liver transplantation.

Adult↗
PubMed2005

A "de-streaking" method for two-dimensional electrophoresis using the reducing agent tris(2-carboxyethyl)-phosphine hydrochloride and alkylating agent vinylpyridine.

Optimal isoelectric focusing in the alkaline region remains a challenge in two-dimensional gel electrophoresis (2-DE), though various attempts had been made to reduce basic end streaking. The present study reports the application of a novel reduction and alkylation step prior to 2-DE analysis using tris(2-carboxyethyl)-phosphine hydrochloride as a reducing agent and vinylpyridine as an alkylating agent. This simple sample preparation approach effectively eliminates basic end streaks, thereby enabling the analysis and identification of more protein spots resolved by 2-DE.

Alkylating Agents↗