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 1,045 records · Page 58Linked to original sources

Simultaneous classification and feature clustering using discriminant vector quantization with applications to microarray data analysis.

In many applications of supervised learning, automatic feature clustering is often desirable for a better understanding of the interaction among the various features as well as the interplay between the features and the class labels. In addition, for high dimensional data sets, feature clustering has the potential for improvement in classification accuracy and reduction in computational complexity. In this paper, a method is developed for simultaneous classification and feature clustering by extending discriminant vector quantization (DVQ), a prototype classification method derived from the principle of minimum description length using source coding techniques. The method incorporates feature clustering with classification performed by fusing features in the same clusters. To illustrate its effectiveness, the method has been applied to microarray gene expression data for human lymphoma classification. It is demonstrated that incorporating feature clustering improves classification accuracy, and the clusters generated match well with biological meaningful gene expression signature groups.

Algorithms↗

[Echocardiographic determination of morphologic and functional indicators in competitive runners with mild hypertension].

The authors examined four groups of 30-60-year-old men who different by the blood pressure at rest and the amount of physical activity: a control group of healthy inactive subjects (n = 10), healthy contesting endurance runners (n = 10), inactive men with mild essential hypertension (n = 10) and contesting endurance runners with mild essential hypertension who had been active for at least 8 years and had dispensary care (n = 10). Indicators of left ventricular hypertrophy were evaluated by one-dimensional echocardiography and also some functional indicators (pulse volume, systemic vascular resistance and fractionated reduction), using the method of pulsed Doppler echocardiography. The hypertonic runners had in all investigated indicators of left ventricular hypertrophy the highest values but differed significantly only from the control group (p less than 0.01). Individual prevalence of values which are beyond the accepted physiological range are however surprisingly low (10-20%). From the functional aspect they are characterized by a significantly higher pulse volume as compared with controls, in the remaining indicators they do not differ significantly. Echocardiographic examination of runners with mild hypertension can help to detect subjects with left ventricular hypertrophy which may already be a complication of the basic disease. Contest activities should not be permitted, unless it is possible to test left ventricular function by a haemodynamic loading test.

Adult↗

Role of a disulfide bond in the thermal stability of the LamB protein trimer in Escherichia coli outer membrane.

In order to understand the unusual heat resistance of LamB protein (the outer membrane component of the maltose transport system in Escherichia coli and its receptor for bacteriophage lambda), we investigated the role of its 2 cysteinyl residues. Our studies show that Cys22 and Cys38 form an intrasubunit disulfide bond which contributes to the heat stability of the LamB protein trimer. Physical evidence for the disulfide was obtained by using site-directed mutagenesis to convert Asn36 to Met, which allowed cyanogen bromide cleavage between the 2 cysteines. Upon reduction one of the N36M fragments migrated as two pieces, resolved by two-dimensional polyacrylamide gel electrophoresis. Other mutagenized LamB proteins, in which 1 or both Cys residues were converted to Ser, exhibited a sharp loss of thermal stability. In contrast to wild-type LamB protein trimer, which does not dissociate to monomers even after 60 min at 100 degrees C, only 10-15% of the mutant LamB proteins remain trimeric after boiling 10 min. The disulfide bond in LamB protein is not required for its transport function, since both mutagenized LamB protein and N-ethylmaleimide-labeled LamB protein exhibit normal uptake of sugars in proteoliposomes. Finally, the disulfide bond must not be between subunits of the LamB trimer since reversible dissociation of trimer is achieved by low pH or denaturants in the absence of reducing agent.

Amino Acid Sequence↗

Characterization of the somatogenic receptor in rat liver. Hydrodynamic properties and affinity cross-linking.

Rat liver somatogenic receptors have been characterized by gel permeation chromatography, sucrose density gradients in H2O and D2O, and affinity cross-linking using 125I-bovine growth hormone (bGH) as a specific somatogenic receptor ligand. Cross-linking of 125I-bovine growth hormone to a Triton X-100-treated low density fraction isolated from livers of late pregnant rats followed by sodium dodecylsulfate-polyacrylamide gel electrophoresis under reducing conditions showed three major binders with Mr 95,000, 86,000, and 43,000 and a minor binder of Mr 55,000, after correction for bound ligand assuming a 1:1 binding ratio of ligand-receptor. The Mr 86,000, 55,000, and 43,000 species were recovered in the detergent-soluble supernatant after high-speed centrifugation, whereas the Mr 95,000 species remained Triton X-100 insoluble. Detergent-soluble 125I-bGH-receptor complexes were further analyzed by sedimentation into sucrose density gradients. The sedimentation coefficient was S20,w = 5.2 S and the partial specific volume v = 0.72 ml/g. Gel permeation chromatography on a Sepharose S-400 column indicated a Stokes radius of 61 A for the 125I-bGH-receptor-Triton X-100 complex. Based on these figures, the molecular weight of the complex was calculated as 131,100. The molecular weight of the ligand-free receptor-Triton X-100 complex was calculated as Mr 109,100. Affinity cross-linking and sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the 61 A peak from Sephacryl S-400 chromatography (cf. above) showed two binding entities, one major and one minor with Mr values 86,000 and 43,000, respectively, in the absence of reductant. When electrophoresis was run in the presence of reductant the Mr 43,000 species was the major binding entity. Furthermore, two-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis (first dimension, nonreducing and second dimension, reducing) showed that a disulfide-linked binder at Mr 43,000 is contained within the Mr 86,000 species. As with pregnant rats, female and male rats both showed 125I-bovine growth hormone binders of Mr 95,000, 84,000, 55,000, 43,000, and additionally an Mr 35,000 binder.

Animals↗

Myocardial ischemia. Relationship between local flow, function and ST-segment elevation.

The significance of reductions in local myocardial flow on mechanical function and intramural electrocardiograms (ECG) was studied in anesthetized open-chest dogs. Local dimensional changes in the anterior wall of the left ventricle were recorded by ultrasonic technique. By platinum electrodes in the same region, both intramural ECG and hydrogen tension were recorded. Local flow was calculated from hydrogen desaturation curves. At approx. 25% flow reduction (constriction of the left anterior descending coronary artery (LAD)) local enddiastolic dilation and reduced systolic shortening appeared. Significant ST-segment elevation first appeared with flow reduction of 50%. After complete LAD-occlusions, enddiastolic dilation appeared within 20 sec, ST-segment elevation 40 sec later. It is concluded that mechanical and electrical events can be dissociated during acute myocardial ischemia: enddiastolic dilation and reduced systolic shortening are more sensitive indicators of moderate reductions in myocardial tissue flow than ST-segment elevation.

Animals↗

[Breath-holding three-dimensional MR imaging: evaluation of phase reordering for motion artifact suppression].

To suppress image degradation due to respiratory corruption during breath holding, a method of reordering of phase encoding was introduced in three-dimensional MR imaging. Without trade-offs in SNR, CNR, and examination time, the method provided a significant reduction of respiratory motion-induced artifacts both in phantom and in vivo experiments. More than twenty seconds of breath holding ensured acceptable image quality regardless of respiratory motion thereafter. Signal intensity change during data acquisition altered the obtained image contrast compared with that of standard sequential linear phase encoding. This technique can be readily implemented on standard two-and three-dimensional pulse sequences and will improve image quality when a patient cannot hold his/her breath during the whole imaging period.

Artifacts↗

Botulinum toxin A compared with stretching casts in the treatment of spastic equinus: a randomised prospective trial.

Conservative therapies for equinus in cerebral palsy may help to postpone calf surgery in younger children. This study reports a prospective randomised trial of intramuscular botulinum toxin A (BtA) as an alternative to serial casting in 20 children with a dynamic component to calf equinus. Outcome was assessed in the short term to show the effect of one treatment cycle. Assessments were by clinical examination, video gait analysis, and three-dimensional gait analysis. BtA was of efficacy similar to that of serial casting. Tone reduction in the BtA group allowed a more prolonged improvement in passive dorsiflexion, which may allow more opportunity for increase in muscle length. Gait analysis showed an improved mean ankle kinematic pattern in a subsection of both groups, which was maintained at 12 weeks in the BtA group, whereas the cast group relapsed. There were fewer side effects in the BtA group. Median time to reintervention was similar.

Botulinum Toxins, Type A↗

Reduction of actin-related protein complex 2/3 in fetal Down syndrome brain.

Down syndrome (DS) patients present with morphological abnormalities in brain development, leading to mental retardation. Given the importance of actin cytoskeleton to form the basis of various cell functions, the regulation of actin system is crucial during brain development. We therefore aimed to study the expression levels of actin binding proteins in fetal DS and control cortex. We evaluated the levels of eight actin binding proteins using the proteomic approach of two-dimensional gel electrophoresis with subsequent mass spectroscopical identification of protein spots. In fetal DS brain we found a significant reduction of the actin-related protein complex 2/3 (Arp2/3) 20 kDa subunit and the coronin-like protein p57, which are involved in actin filament cross-linking and nucleation and capping of actin filaments. We conclude that deficient levels of these proteins may, at least partially, be involved in the dysgenesis of the brain in DS.

Actin Cytoskeleton↗

Spatial patterns of increased spinal cord membrane-bound protein kinase C and their relation to increases in 14C-2-deoxyglucose metabolic activity in rats with painful peripheral mononeuropathy.

1. Three-dimensional spatial patterns of changes in membrane-bound protein kinase C (PKC) were examined in the lumbar spinal cords (L1-L5) of rats with an experimental painful peripheral mononeuropathy. Painful peripheral mononeuropathy was produced by loosely ligating the rat's common sciatic nerve, resulting in chronic constrictive nerve injury (CCI). Changes in spinal cord membrane-bound PKC distribution were assayed by employing an established quantitative [3H]-phorbol-12,13-dibutyrate ([3H]PDBu) autoradiographic assay, which includes spinal cord sectioning, incubation of spinal cord sections with [3H]PDBu, production of autoradiographs, and computer-assisted image processing. 2. Sciatic nerve ligation induced demonstrable thermal hyperalgesia in response to radiant heat stimulation and spontaneous pain-related behaviors (such as lifting of the nerve-ligated hind paw) in CCI rats 3, 7, and 10 days after unilateral sciatic nerve ligation. 3. Consistent with behavioral changes, CCI rats examined 3 or 10 days after sciatic nerve ligation displayed a three-dimensional pattern of increased membrane-bound PKC in the lumbar spinal cord (L1-L5) strikingly different from that of sham-operated rats: in the dorsoventral dimension, reliable increases in membrane-bound PKC occurred mainly within spinal cord laminae I-IV and V-VI in CCI rats; in the ipsilateral-contralateral dimension, changes in membrane-bound PKC were seen on both sides of the spinal cord in CCI rats with reliably higher levels of membrane-bound PKC on the side ipsilateral than on the side contralateral to sciatic nerve ligation; in the rostrocaudal dimension, increases in membrane-bound PKC in the spinal cord dorsal horns of CCI rats extended from spinal segments L2-L5. 4. Both three-dimensional increases in spinal cord membrane-bound PKC and nociceptive behaviors (thermal hyperalgesia and spontaneous pain behaviors) in CCI rats were reliably reduced after three daily intrathecal treatments with 80 nmol GM1 ganglioside (a glycosphingolipid shown to prevent PKC translocation/activation), the first of which was given 1 h after sciatic nerve ligation. This reduction was seen 24 h but not 7 days after the last GM1 ganglioside treatment. 5. This three-dimensional increase in membrane-bound PKC in the spinal cord dorsal horn of CCI rats displayed high correlations with thermal hyperalgesia and with spontaneous pain-related behaviors in CCI rats observed both 3 and 10 days after sciatic nerve ligation. Similar correlations were observed between decreases in levels of membrane-bound PKC in the spinal cord dorsal horn and the attenuation of nociceptive behaviors in CCI rats after three daily intrathecal treatments with GM1 ganglioside.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

Resolution dependency of microstructural properties of cancellous bone based on three-dimensional mu-tomography.

Micro-computed tomography (microCT) is an emerging technique for the non-destructive assessment and analysis of the three-dimensional cancellous bone architecture. However, the procedures the procedures and applications used to quantify bone structures are not yet standardized. The aim of this study was to provide more insight in the resolution-dependency of microstructural properties of three-dimensional trabecular bone. Ten iliac crest bone biopsies were measured using a newly devised microCT system providing a nominal isotropic resolution of 14 microns. To study the resolution dependency the measured data were reconstructed on reduced image arrays with reduction factors ranging from 2 to 20. To assess the structural properties, morphometric parameters were computed based on a truly three-dimensional approach. The results showed a strong resolution dependency of the structural properties and that, if very precise results are needed, only the highest resolution will predict the correct values. Nevertheless, since the properties either decrease or increase monotonously up to a nominal resolution of about 175 microns, the values appear to be restorable using a suitable calibration procedure.

Bone Matrix↗

Intraoperative transesophageal ultrasonography can measure renal blood flow.

OBJECTIVE: To determine the feasibility of acquiring Doppler-derived indices of renal blood flow by transesophageal ultrasonography in the perioperative period. DESIGN: Prospective, sequential, institutional review board-approved study. SETTING: University teaching hospital. PARTICIPANTS: Nine patients with normal renal function, scheduled for elective primary coronary artery bypass graft surgery. INTERVENTIONS: Two-dimensional images of renal parenchyma and Doppler measurement of intrarenal arterial blood flow during internal mammary dissection were acquired. To effect renal blood flow changes, the renal vasodilator dopamine, 2 microg/kg/min, was infused for 20 minutes after baseline measurements were made. Renal Doppler measurements were repeated to determine whether transesophageal ultrasonography can follow these changes. MEASUREMENTS AND MAIN RESULTS: Hemodynamic measurements (heart rate, mean arterial blood pressure, cardiac output, and cardiac index) and Doppler velocity measurements of intrarenal arterial blood flow (peak systolic, end-diastolic, and mean velocity) were made at time 1 (T1 = baseline) and at time 2 (T2 = after 20 minutes of dopamine infusion). The derived Doppler indices, pulsatility index and resistive index, were calculated according to standard formulae. Measurements were compared by paired Student's t-test (two-tailed, p < 0.05, significant). There were no statistical differences between cardiac index (2.10 +/- 0.93 L/min/m2 v 2.21 +/- 0.92 L/min/m2, p = 0.254) and mean arterial pressure (82.3 +/- 11.2 mmHg v 83.3 +/- 14.5 mmHg, p = 0.872) between T1 and T2. Systolic renal velocity increased from 44.7 +/- 13.0 cm/s to 63.0 +/- 20.4 cm/s (p = 0.005), diastolic velocity increased from 12.7 +/- 4.0 cm/s to 22.4 +/- 7.8 cm/s (p = 0.0003), and mean velocity increased from 22.5 +/- 6.6 cm/s to 34.1 +/- 11.7 cm/s (p = 0.003) after infusion of dopamine. These results indicate an increase in renal blood flow from baseline values. The pulsatility index decreased from 1.44 +/- 0.29 to 1.21 +/- 0.24 (p = 0.0005), whereas the resistive index decreased from 0.71 +/- 0.06 to 0.64 +/- 0.06 (p = 0.0004) after dopamine. Reductions in pulsatility and resistive indices indicate a reduction in renal vascular resistance. CONCLUSION: This study demonstrates the ability to acquire two-dimensional images of kidney and renal arterial Doppler velocities using transesophageal ultrasonography during cardiac surgery. Transesophageal renal arterial Doppler waveform analysis can follow changes in renal blood flow patterns secondary to interventional therapy.

Adult↗

Dimensional complexity of neuromagnetic activity reduced during finger movement of greater difficulty.

OBJECTIVE: We investigated the variation in dimensionality (D2) of neuromagnetic activity over the primary sensorimotor cortex (SM1) in healthy adults performing motor tasks of different difficulty. METHODS: Magnetoencephalography (MEG) was used to record neuromagnetic activity during self-paced, brisk unimanual finger extension at a rate of 1 and 2 Hz using the index finger of the dominant and non-dominant hands in 16 healthy subjects. Motor task difficulty was rated by the relative difference in time measurement between 1 and 2 Hz finger movements of both hands. The relative difference in dimensionality of SM1 activity was calculated by subtracting the D2 value in 2 Hz movement from that in 1 Hz one within subjects. RESULTS: Simple regression analyses show a significantly negative relationship between the relative dimensional complexity and the relative motor task difficulty in the contralateral SM1 for the left- (p<0.05), but not the right- (p=0.447) hand movement. CONCLUSIONS: The present data suggest that a motor task of greater difficulty may engender a reduction of simultaneously active quasi-independent neuronal generators in the contralateral SM1 underpinned by stronger neuronal connectivity of a relatively low dimensionality. SIGNIFICANCE: The decrease in dimensional complexity of MEG activity associated with a motor task of greater difficulty gives new insights to motor control strategy.

Adult↗

Formation of three-dimensional structure in protein fragments. Reactivation of reduced hen egg lysozyme fragment 1-127.

Regeneration of enzymic activity from reduced hen egg lysozyme peptide 1-127 was effected with a glutathione oxidation-reduction buffer. The rate of regeneration was nearly as great for peptide 1-127 as for reduced lysozyme itself, and the yields were the same (greater than 80%). The regenerated fragment 1-127 was shown to be indistinguishable from fragment 1-127 before reduction by ion exchange chromatography, amino acid analysis, polyacrylamide gel electrophoresis, and disulfide analysis. These results show that the COOH-terminal dipeptide Arg-Leu is not essential for the acquisition of the native three-dimensional structure of lysozyme.

Amino Acids↗

Effects of left ventricular pressure reductions on right ventricular systolic performance.

Reductions in left ventricular pressure (LVP) have been shown to produce a leftward shift of the interventricular septum and to reduce left ventricular contribution to right ventricular performance. To evaluate the magnitude of this contribution in the intact heart, five anesthetized pigs were implanted with a left prosthetic ventricle to gradually decrease LVP while maintaining arterial systemic pressure. Three descriptors of RV global and regional systolic function were studied in the septum to free wall (RVSFW) and anterior to posterior (RVAP) dimensions and in an outflow tract segment length (RVSL), during both steady state and transient inferior vena cava occlusion. LVP gradual reduction from 102 +/- 4 to 11 +/- 3 mmHg (90% decrease in peak systolic pressure) produced no changes in the RV global stroke work curve or in the RVAP and RVSL pressure-dimension relationships. However, the reduction in LVP resulted in parallel shifts in the RVSFW dimension, with 16.6 +/- 6.7% increase in the intercept D(o) of the end-systolic relationship and 16.5 +/- 2.5% increase in D(o) of the dimensional stroke work relationship, with no significant changes in their respective slopes as calculated by linear regression. Therefore, in the normal intact heart, large reductions in left ventricular pressure affect the geometry of the right ventricle because of septal shifting, but there is a negligible net effect of this anatomic ventricular interaction on overall right ventricular performance.

Animals↗

Production of systolic anterior motion of the mitral valve in dogs.

Production of an experimental preparation of systolic anterior motion (SAM) of the mitral valve was attempted for the purpose of clarifying its causal factors. Fourteen thoracotomized dogs under pentobarbital anesthesia were administered dobutamine, and the echocardiogram, left ventricular pressure, and aortic pressure of each were simultaneously recorded. In two of the dogs in which SAM was produced, two-dimensional echocardiograms were also obtained. Although SAM was absent in all 14 dogs before the administration of dobutamine, it appeared in nine of them after the drug was given. In seven of these dogs, the magnitude of SAM and outflow pressure gradient varied in a dose-dependent manner. No signs of asymmetric septal hypertrophy were observed in any of these dogs. SAM tended to occur even when there was no reduction in preejection period when narrowing of the left ventricular outflow tract was observed. On the two-dimensional echocardiograms, the position of coaptation of the mitral valve was shifted closer to the base of the anterior leaflet in the presence of dobutamine-induced SAM than before the drug was administered. Although the left ventricular cavity became narrow, it was not completely obliterated. This study demonstrates that experimental preparations of SAM can be produced by the administration of dobutamine with a relatively high success rate in normal dogs, and that experimental SAM is accompanied by an outflow tract pressure gradient.

Animals↗

Forces and torques during fracture reduction: Intraoperative measurements in the femur.

Reduction is a crucial step in fracture treatment. We determined intraoperative peak forces and torques during fracture reduction in seven patients with eight fractures of the femoral shaft. All fractures were temporarily stabilized by external fixation. Force and torque measurements were performed during the subsequent intramedullary nailing procedure. A three-dimensional load cell was attached to the distal femur fragment using two Schanz screws. All forces and torques were registered on-line during the reduction process. The maximum resulting force was 411 N, the maximum resulting torque 74 N x m. The highest force was observed along the shaft axis with 396 N for distraction. The maximum torque value was measured around the frontal axis, being 74 N x m for antecurvature. These results may assist the development of new reduction techniques and devices.

Adult↗

New bis-catechols 5-lipoxygenase inhibitors.

Three polyhydroxy-2-phenylnaphthalenes (1-3) and the oxy analogue of tetrahydroxypavinan (4) were prepared and evaluated for their antioxidant properties (inhibition of diphenylpycrylhydrazyl radical (DPPH), reduction of iron (III) ion) and inhibition of 5-lipoxygenase (5-LO) activity. Their three-dimensional structures were established on the basis of spectroscopic data and semiempirical calculations. Compounds 1 and 2 were found as potent 5-LO inhibitors as nordihydroguaiaretic acid (NDGA), whereas 4 is 2.5 times less potent than NDGA. The reliability of the 3-D structures with the 5-LO inhibition properties is discussed. Their antioxidant properties show that tested compounds are expected to act as redox inhibitors.

Animals↗

H2-forming N5, N10-methylenetetrahydromethanopterin dehydrogenase from Methanobacterium thermoautotrophicum catalyzes a stereoselective hydride transfer as determined by two-dimensional NMR spectroscopy.

5,6,7,8-Tetrahydromethanopterin is a coenzyme playing a key role in the energy metabolism of methanogenic archaea. In Methanobacterium thermoautotrophicum, the reduction of N5, N10-methenyl-5,6,7,8-tetrahydromethanopterin at C(14a) with H2 to N5, N10-methylene-5,6,7,8-tetrahydromethanopterin can be catalyzed by H2-forming methylenetetrahydromethanopterin dehydrogenase, a new hydrogenase present in most methanogenic archaea, which is unique because it does not contain nickel or iron/sulfur clusters. In this work, the stereochemistry of this enzymatic hydride-transfer reaction is elucidated by means of a series of heteronuclear two-dimensional NMR experiments. It is found that the hydride from H2 is transferred by the enzyme into the rel-(pro-R) position of the C(14a) methylene group of the reaction product N5, N10-methylene-5,6,7,8-tetrahydromethanopterin. NMR experiments are described that show that the hydrogen nucleus of the hydride transferred to the oxidized coenzyme partially originates from water. The stereochemical course of this reaction is the same as that for direct hydride transfer. It is demonstrated that the diastereotopic atoms at C(14a) of the reaction product epimerize in an uncatalyzed reaction under the conditions of operation of the enzyme (k = 0.01 s-1 at 58 degree C and pH 6.5).(ABSTRACT TRUNCATED AT 250 WORDS)

Circular Dichroism↗