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Results for “feature stability”

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PubMed1992

Symmetry breaking dynamics of human multilimb coordination.

The dynamics of pattern formation and change are studied in a complex multicomponent system, specifically the arms and legs of human Ss. Among the novel features observed are differential stability of coordinative modes produced by limbs moving in the same versus different directions (Experiment 1); transitions between coordinative modes preceded by a slow drift in relative phase (Experiments 1 and 2); bifurcations or phase transitions from 1 four-limb pattern to another (Experiment 2); and spontaneous emergence of non-1:1-frequency- and phase-locked patterns, in addition to periods of relative coordination (Experiment 3). All observed relative phasing patterns and their dynamics (stability, loss of stability, intermittency) are shown to arise from the same underlying nonlinear dynamical structure, an important feature of which is broken symmetry.

Acceleration↗

PubMed2002

Features associated with the delayed initiation of mood stabilizers at illness onset in bipolar disorder.

BACKGROUND: Whether delays in the initiation of appropriate pharmacotherapy for bipolar illness negatively affect course, outcome, or lifetime suicide risk remains at issue. METHOD: Lifetime affective syndromes and the initial emergence of affective symptoms were assessed by lifecharting in 56 DSM-IV bipolar patients. Lifetime treatment interventions were recorded by clinical interview with corroboration via record reviews. Lag times to the initiation of a mood stabilizer (after initial symptom onset and/or first lifetime affective episode) were assessed relative to functional outcome and lifetime suicide attempts. RESULTS: Mean +/- SD lag time from initial affective symptoms until first mood stabilizer treatment was 9.8 +/- 9.4 years. A greater number of years from symptom onset to first mood stabilizer was associated with poorer past year social functioning (r = -0.35, p =.008), more annual hospitalizations (r = 0.38, p =.004), and a greater likelihood for making a lifetime suicide attempt (odds ratio = 7.26, 95% confidence interval = 1.62 to 32.59; Wald chi2 = 6.69, df = 1, p =.010). Delayed mood stabilizer initiation was linked with poorer outcomes in these domains regardless of initial index episode polarities of mania versus depression. Prolonged delays to bipolar diagnoses and mood stabilizer initiation were associated with earlier ages at affective symptom onset (p <.03) and milder severity of initial symptoms (p =.003). Psychotherapy initiation often preceded mood stabilizer introduction by >/= 8 years. CONCLUSION: Delays in the initiation of mood stabilizer pharmacotherapy at illness onset, even for relatively mild symptoms at illness onset and regardless of index episode polarity, may confer an elevated risk for suicidal behavior, poorer social adjustment, and more hospitalizations in bipolar disorder. Greater surveillance screening for bipolar illness in patients who first present for psychotherapy may help to diminish these adverse outcomes.

Adolescent↗

PubMed2001

Empirical and ab initio energy/architectural patterns for 73 nido-6 -carborane isomers, from B(6)H(9)(-) to C(4)B(2)H(6).

Qualitative rules governing carbon and bridge-hydrogen placement permit the prediction of the most stable isomeric structures for the various carboranes. Seventy-three isomeric boron hydride and carborane structures, from B(6)H(9)(-) to C(4)B(2)H(6), were computed at the ab initio MP2(fc)/6-31G level to determine their relative stabilities quantitatively. Specific architectural features, recognized to be unfavorable, were assigned "energy penalty" values that allow the projection of comprehensive thermodynamic stability values via a simple additivity procedure. These values match the ab initio results with surprising precision. Our study includes Siebert's nido-2,3,5-C(3)B(3)H(7) and Wrackmeyer's nido-2,4-C(2)B(4)H(8) nido-6 carboranes, which contain "unusual" CH-B-bridge hydrogens.

Journal Article↗

PubMed1995

Human fatty acid synthase mRNA: tissue distribution, genetic mapping, and kinetics of decay after glucose deprivation.

To better understand the accelerated decay of fatty acid synthase (FAS) message that occurs after glucose deprivation (J. Biol. Chem. 1993. 268: 6961-6970), we characterized the 3' terminus of the human message and the kinetics of FAS mRNA decay in HepG2 cells. The FAS gene was localized to human chromosome 17q24-25 and to syntenic distal mouse chromosome 11. Expression of the FAS message in human tissues was ubiquitous with high levels in liver, lung, and intra-abdominal adipose tissue. The 806 nucleotide 3' untranslated region of the human mRNA contained two regions with the instability pentamer AUUUA. Unlike short-lived messages containing AUUUA motifs, FAS mRNA decay after glucose deprivation was not first order, and there were no detectable changes in the poly(A) tail. Glucose deprivation transiently caused FAS message to sediment more rapidly than control message in density gradients. In vivo treatment with different translational inhibitors showed that translation per se was not necessary for FAS mRNA decay; association of polysomes with FAS message protected it from decay. In cell-free decay experiments, FAS mRNA decay was more rapid using components from glucose-deprived than glucose-treated cells. These data suggest that glucose regulates cytoplasmic HepG2 FAS mRNA stability by partitioning the message between a translated pool not subject to degradation and a decay compartment, features reminiscent of regulated stability for other diet-responsive messages.

Amino Acid Sequence↗

PubMed2003

On the formation of persistent states in neuronal network models of feature selectivity.

We study the existence and stability of localized activity states in neuronal network models of feature selectivity with either a ring or spherical topology. We find that the neural field has mono-stable, bi-stable, and tri-stable regimes depending on the parameters of the weighting function. In the case of homogeneous inputs, these localized activity states are marginally stable with respect to rotations. The response of a stable equilibrium to an inhomogeneous input is also determined.

Animals↗

PubMed1998

Identification of a human VPF/VEGF 3' untranslated region mediating hypoxia-induced mRNA stability.

Hypoxia is a prominent feature of malignant tumors that are characterized by angiogenesis and vascular hyperpermeability. Vascular permeability factor/vascular endothelial growth factor (VPF/VEGF) has been shown to be up-regulated in the vicinity of necrotic tumor areas, and hypoxia potently induces VPF/VEGF expression in several tumor cell lines in vitro. Here we report that hypoxia-induced VPF/VEGF expression is mediated by increased transcription and mRNA stability in human M21 melanoma cells. RNA-binding/electrophoretic mobility shift assays identified a single 125-bp AU-rich element in the 3' untranslated region that formed hypoxia-inducible RNA-protein complexes. Hypoxia-induced expression of chimeric luciferase reporter constructs containing this 125-bp AU-rich hypoxia stability region were significantly higher than constructs containing an adjacent 3' untranslated region element without RNA-binding activity. Using UV-cross-linking studies, we have identified a series of hypoxia-induced proteins of 90/88 kDa, 72 kDa, 60 kDa, 56 kDa, and 46 kDa that bound to the hypoxia stability region element. The 90/88-kDa and 60-kDa species were specifically competed by excess hypoxia stability region RNA. Thus, increased VPF/VEGF mRNA stability induced by hypoxia is mediated, at least in part, by specific interactions between a defined mRNA stability sequence in the 3' untranslated region and distinct mRNA-binding proteins in human tumor cells.

Base Sequence↗

PubMed2002

Vertebral injuries: detection and implications.

Vertebral injuries occur in a predictable and reproducible manner that is dependent upon the mechanism of injury. Each mechanism of injury leaves distinct imaging 'fingerprints' regardless of the location in the spine. This chapter will discuss four areas: the mechanisms of injury and their imaging 'fingerprints'; abnormalities of alignment and anatomy, bony integrity, cartilage or joint space, and soft tissues-the ABCS of injury; the imaging features that will indicate stability of the spine following injury; and the classification of spine injuries into two categories-'major' or 'minor'. The imaging features described in this chapter apply to both radiography as well as to computed tomography (CT). Although helical CT is being used more commonly for the evaluation of suspected cervical injuries, radiography of the entire spine remains the standard.

Cartilage, Articular↗

PubMedDate not supplied

Stability and change of DSM-III-R personality disorder dimensions in adolescents followed up 2 years after psychiatric hospitalization.

We examined the stability of DSM-III-R personality disorder dimensions in a clinical sample of adolescents. Sixty adolescent inpatients were reliably assessed with the Personality Disorder Examination (PDE) soon after admission to the Yale Psychiatric Institute, and were independently reassessed with the same instrument 2 years following discharge. PDE symptom ratings were summed to create dimensional scores for each personality disorder. To assess the dimensional stability of personality disorders, intraclass correlation coefficients (ICCs) were computed. To assess the magnitude of the difference between baseline and follow-up scores, paired t tests were used. Significant ICCs were observed for histrionic, narcissistic, dependent, obsessive-compulsive, and passive-aggressive personality disorders. Compared to baseline, dimensional scores for most personality disorders were significantly lower at follow-up-and none was significantly higher. Diagnostic stability is a key defining feature of personality disorders. We observed low-to-moderate stability for dimensional measures of personality dysfunction in adolescents-suggesting that previous reports of modest personality disorder stability in this age group cannot be attributed solely to limitations of the categorical approach to such pathology. Alternatively, our findings may be viewed as consistent with reports in the adult literature that personality disorders may improve over time, and can potentially benefit from treatment.

Adolescent↗

PubMed1982

A perspective on mechanisms of chromosomal mutations in relation to chromosome-stability-deficient mutants of Drosophila.

A working hypothesis that eukaryote chromosomal mutations result from specific misrecombination is proposed in relation to X-ray-induced mutations in the mouse. Unique features of chromosome-stability-deficient mutations and of tumor mutations in Drosophila are reviewed; these mutations could serve as very good models for elucidating the mechanisms of chromosome-aberration-related diseases in humans.

Animals↗

PubMed1981

Binocular pattern stabilization by afterimage technique: reliability of children's time-dependent judgments of chromatic features.

To investigate visual afterimage technique as a means of producing retinally stabilized pattern, children's judgments of time-dependent shifts in chromatic appearance of random-dot configurations were twice examined within a 3-wk. interval. 13 subjects, aged 7 to 12 yr., were very consistent (r = .93) in their test-retest response times. This supports the belief that after image procedures can be developed as a reliable means of studying developmental aspects of stabilized pattern perception.

Child↗

PubMed2000

Biomechanical stability of five stand-alone anterior lumbar interbody fusion constructs.

Anterior lumbar interbody fusion (ALIF) cages are expected to reduce segmental mobility. Current ALIF cages have different designs, suggesting differences in initial stability. The objective of this study was to compare the effect of different stand-alone ALIF cage constructs and cage-related features on initial segmental stability. Human multisegmental specimens were tested intact and with an instrumented L3/4 disc level. Five different ALIF cages (I/F, BAK, TIS, SynCage, and ScrewCage) were tested non-destructively in axial rotation, flexion/extension and lateral bending. A cage 'pull-out' concluded testing. Changes in neutral zone (NZ) and range of motion (ROM) were analyzed. Cage-related measurements normalized to vertebral dimensions were used to predict NZ and ROM. No cage construct managed to reduce NZ. The BAK and TIS cages had the largest NZ increase in flexion/extension and lateral bending, respectively. Cages did reduce ROM in all loading directions. The TIS cage was the least effective in reducing the ROM in lateral bending. Cages with sharp teeth had higher 'pull-out' forces. Antero-posterior and mediolateral cage dimensions, cage height and wedge angle were found to influence initial stability. The performance of stand-alone ALIF cage constructs generally increased the NZ in any loading direction, suggesting potential directions of initial segmental instability that may lead to permanent deformity. Differences between cages in flexion/extension and lateral bending NZ are attributed to the severity of geometrical cage-endplate surface mismatch. Stand-alone cage constructs reduced ROM effectively, but the residual ROM present indicates the presence of micromotion at the cage-endplate interface.

Adult↗

PubMed2006

Rationale for the posterior-stabilized rotating-platform knee.

The nonposterior-stabilized mobile-bearing knee and the posterior-stabilized fixed-bearing design have been successfully used for the past three decades. Lessons learned from their use have culminated in the design of a posteior-stabilized mobile-bearing knee that incorporates beneficial features of both. The posterior-stabilized mobile-bearing knee is aimed at addressing polyethylene wear issues related to the fixed-bearing design, and improve upon stability and range of motion typical of nonposterior-stabilized mobile-bearing knee designs.

Biomechanical Phenomena↗

PubMed2025

G4STAB: a multi-input deep learning model to predict G-quadruplex thermodynamic stability based on sequence and salt concentration.

MOTIVATION: G-quadruplexes (G4s) are non-canonical nucleic acid structures formed in guanine-rich regions that modulate gene regulation and genomic stability. The thermodynamic stability of G4s directly influences their biological functions and potential as therapeutic targets. However, current quantitative frameworks for predicting G4 stability rely on predetermined structural features, limiting their effectiveness for diverse G4 topologies, and fail to account for environmental factors such as ion concentration and pH that significantly modulate G4 stability in cellular contexts. RESULTS: We present G4STAB, a multi-input deep learning neural network that accurately predicts DNA G4 melting temperatures based on sequence features, salt concentration, and pH. Trained on 2382 diverse DNA G4 sequences, our model achieves high accuracy (R 2=0.8) without relying on predetermined G4 structural features. G4STAB successfully captures established G4 stability determinants and proposes previously unobserved sequence-stability relationships. Analysis of 391 502 experimentally validated G4s reveals that cancer-like ionic environments alter G4 stability profiles, with a 13.5-fold increase in the number of structures exhibiting physiological melting temperatures (36-42°C). These findings suggest systematic genomic patterns in G4 stability responses across chromosomes and gene types. AVAILABILITY AND IMPLEMENTATION: G4STAB is available at https://github.com/donn-liew/G4STAB; G4STAB web database interface is available at https://donn-liew.github.io/g4stab-web-database/.

G-Quadruplexes↗

PubMed1993

Stability, structure and complexity of yeast chromosome III.

The complete sequence of yeast chromosome III provides a model for studies relating DNA sequence and structure at different levels of organisation in eukaryotic chromosomes. DNA helical stability, intrinsic curvature and sequence complexity have been calculated for the complete chromosome. These features are compartmentalised at different levels of organisation. Compartmentalisation of thermal stability is observed from the level delineating coding/non-coding sequences, to higher levels of organisation which correspond to regions varying in G + C content. The three-dimensional path reveals a symmetrical structure for the chromosome, with a densely packed central region and more diffuse and linear subtelomeric regions. This interspersion of regions of high and low curvature is reflected at lower levels of organisation. Complexity of n-tuplets (n = 1 to 6) also reveals compartmentalisation of the chromosome at different levels of organisation, in many cases corresponding to the structural features. DNA stability, conformation and complexity delineate telomeres, centromere, autonomous replication sequences (ARS), transposition hotspots, recombination hotspots and the mating-type loci.

Amino Acid Sequence↗

PubMed1988

Structural studies of analgesics and their interactions. XII. Structure and interactions of anti-inflammatory fenamates. A concerted crystallographic and theoretical conformational study.

A theoretical conformational analysis of fenamates, which are N-arylated derivatives of anthranilic acid or 2-aminonicotinic acid with different substituents on the aryl (phenyl) group, is reported. The analysis of these analgesics, which are believed to act through the inhibition of prostaglandin biosynthesis, was carried out using semi-empirical potential functions. The results and available crystallographic observations have been critically examined in terms of their relevance to drug action. Crystallographic studies of these drugs and their complexes have revealed that the fenamate molecules share a striking invariant feature, namely, the six-membered ring bearing the carboxyl group is coplanar with the carboxyl group and the bridging imino group, the coplanarity being stabilized by resonance interactions and an internal hydrogen bond between the imino and carboxyl groups. The results of the theoretical analysis provide a conformational rationale for the observed invariant coplanarity. The second six-membered ring, which provides hydrophobicity in a substantial part of the molecule, has limited conformational flexibility in meclofenamic, mefenamic and flufenamic acids. Comparison of the conformational energy maps of these acids shows that they could all assume the same conformation when bound to the relevant enzyme. The present study provides a structural explanation for the difference in the activity of niflumic acid, which can assume a conformation in which the whole molecule is nearly planar. The main role of the carboxyl group appears to be to provide a site for intermolecular interactions in addition to helping in stabilizing the invariant coplanar feature and providing hydrophilicity at one end of the molecule. The fenamates thus provide a good example of conformation-dependent molecular asymmetry.

Analgesics↗

PubMed2005

Histomorphology and microradiography of quadriceps tendon-patellar bone grafts in press-fit anterior cruciate ligament reconstruction.

The press-fit fixation technique has become an alternative fixation method in anterior cruciate ligament (ACL) reconstruction. While the stability of press-fit fixated grafts reported in the literature predominantly had been analysed by biomechanical testing, this study investigated the specific histomorphologic and microradiographic features important for graft stability, using human quadriceps tendon-patellar bone (QTPB) grafts. Six QTPB grafts with cylindrical bone plugs were obtained from frozen fresh human cadaver knees and fixed to porcine, bovine, or human femora in a press-fit technique. The specimens were plastinated, dissected into 1.5 mm slices, studied microradiographically and stained for histologic evaluation. The specimens showed an osseous inclusion of the graft within the femoral tunnel, which was most evident on the cancellous side. Histologic analysis revealed a trabecular interdigitation with a penetration of patellar and femoral trabecular structures, contributing to primary stability of the press-fit fixation. Graft inclusion was most obvious in bovine and least in human femora, assumably because of varying bone quality. The circular bone-to-bone contact in press-fit fixation technique should contribute to both rapid and stable graft healing.

Animals↗

PubMed1990

Correlation between stability of a protein and its dipeptide composition: a novel approach for predicting in vivo stability of a protein from its primary sequence.

Statistical analysis of 12 unstable and 32 stable proteins revealed that there are certain dipeptides, the occurrence of which is significantly different in the unstable proteins compared with those in the stable ones. Based on the impact of these dipeptides on the unstable proteins over the stable ones, a weight value of instability is assigned to each of the dipeptides. For a given protein the summation of these weight values normalized to the length of its sequence helps to distinguish between unstable and stable proteins. Results suggest that the in vivo instability of proteins is possibly determined by the order of certain amino acids in its sequence. An attempt is made to correlate metabolic stability of proteins with features of their primary sequence where weight values of instability for a protein of known sequence could thus be used as an index for predicting its stability characteristics.

Amino Acid Sequence↗

PubMed1977

Differential stabilities of soil enzymes. Assay and properties of phosphatase and arylsulphatase.

Methods have been refined for the assay of phosphatase and arylsulphatase activities in soil, based on the chromogenic p-nitrophenyl ester substrates. Basic assay conditions have been defined, and pH optima and kinetic parameters have been determined. The enzymes follow Michaelis-Menten kinetics; this conclusion is based on three methods of analysis of data determined over a wide range of substrate concentrations. The enzyme activities are very stable to storage of wet soil for up to 4 weeks at soil temperatures and above. For example, phosphatase had a half-life of approximately 2 weeks at 50 degrees C; arylsulphatase was rather less stable. Both enzymes retained 80% of activity after incubation with pronase for 1 week at 25 degrees C. On the basis of this work and studies on other soil enzymes, it is concluded that remarkable stability is a general feature of soil enzymes.

Arylsulfatases↗