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Results for “feature stability”

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At least 127 records · Page 7Linked to original sources
PubMed1994

Prognostic implications of stable versus transient "borderline features" in bulimic patients.

BACKGROUND: This study examined the association between "borderline features" and treatment response in bulimic patients. METHOD: Treatment response was assessed in 69 bulimic patients over 6 months of treatment (and 1-year response in 44 of the patients). Patients were classified as a function of whether "borderline features" were (1) "stably" present (at pretreatment and after 3 months), (2) "transiently" present (at pretreatment only), or (3) "absent" (at both time points). RESULTS: The stably borderline profile coincided systematically with Axis II comorbidity (not with mood disorders) and was generally predictive of poorer 6- and 12-month response of eating and comorbid symptoms. Hierarchical regressions showed predictive effects to have a partial independence from effects caused by concurrent eating symptoms and depression. CONCLUSION: Results highlight the importance, with respect to prognosis in bulimia nervosa, of establishing the temporal stability of features that imply character disturbance.

Adult↗
PubMed1987

Calibration, quality control, and stability of a quantitative enzyme immunochromatographic method for therapeutic drug monitoring.

We describe a noninstrumented quantitative method for therapeutic drug monitoring (AccuLevel test) that uses a factory-calibrated unit test format and a novel single-level approach to quality control. The AccuLevel method is based on the principles of immunochromatography, which provides a number of convenient protocol advantages without sacrificing assay performance or quality assurance. Most of the benefits of the immunochromatographic method derive by virtue of the fact that quantification is dependent on enzyme migration rather than enzyme activity. Since migration height is almost solely a function of a highly stable, immobilized, dry antibody reagent, the AccuLevel test is extremely insensitive to environmental factors. The predictable and uniform dependence of quantification on antibody site concentration allows complete reliability with a single-level control. These features of stability, factory calibration, and unitized test components make the AccuLevel immunochromatography method amenable to new quality control schemes.

Antibodies, Monoclonal↗
PubMed2005

Divergent effects of matrix metalloproteinases 3, 7, 9, and 12 on atherosclerotic plaque stability in mouse brachiocephalic arteries.

Matrix metalloproteinases (MMPs) are thought to be involved in the growth, destabilization, and eventual rupture of atherosclerotic lesions. Using the mouse brachiocephalic artery model of plaque instability, we compared apolipoprotein E (apoE)/MMP-3, apoE/MMP-7, apoE/MMP-9, and apoE/MMP-12 double knockouts with their age-, strain-, and sex-matched apoE single knockout controls. Brachiocephalic artery plaques were significantly larger in apoE/MMP-3 and apoE/MMP-9 double knockouts than in controls. The number of buried fibrous layers was also significantly higher in the double knockouts, and both knockouts exhibited cellular compositional changes indicative of an unstable plaque phenotype. Conversely, lesion size and buried fibrous layers were reduced in apoE/MMP-12 double knockouts compared with controls, and double knockouts had increased smooth muscle cell and reduced macrophage content in the plaque, indicative of a stable plaque phenotype. ApoE/MMP-7 double knockout plaques contained significantly more smooth muscle cells than controls, but neither lesion size nor features of stability were altered in these animals. Hence, MMP-3 and MMP-9 appear normally to play protective roles, limiting plaque growth and promoting a stable plaque phenotype. MMP-12 supports lesion expansion and destabilization. MMP-7 has no effect on plaque growth or stability, although it is associated with reduced smooth muscle cell content in plaques. These data demonstrate that MMPs are directly involved in atherosclerotic plaque destabilization and clearly show that members of the MMP family have widely differing effects on atherogenesis.

Animals↗
PubMed1991

The assessment of schizotypal features over two points in time.

The expression of schizotypal personality traits was assessed in mid-adolescence and again in young adulthood for three groups of offspring defined by the psychiatric diagnosis of their parents. Parental diagnoses included schizophrenic disorder (47 offspring), affective disorder (39 offspring), and 'no psychiatric disorder', or normal controls (82 offspring). Initially, schizotypal traits were assessed from video-taped semi-structured psychiatric interviews, subsequently rated by trained psychiatrists blind to the parental psychiatric status of the subjects, and/or direct clinical interviews (Schedule for Affective Disorders-Lifetime Version (SADS-L)). The second assessment was conducted by trained social workers and psychologists by means of a semi-structured interview specifically for DSM-III-R personality disorders (Personality Disorder Examination) and sections of the SDS-L where indicated. These interviewers were blind to the parental status and to previous psychiatric assessments of the offspring. The rates of stability of features or the rates of progression to axis I psychotic disorders (Schizophrenia, Schizoaffective Disorder, and Unspecified Functional Psychosis) were evaluated. Concordance of assessments over time is reported as a function of threshold for expression of traits at initial evaluation, i.e., two or more, three or more, or four or more features present. Concordance increases as the threshold for expression increases, as expected. The effect of comorbid clinical status, e.g., the coexistence of schizotypal traits and anxiety and/or depressive features on the concordance pattern, is also examined by parental diagnostic group status. The offspring of affective disorder parents exhibited higher rates of anxiety and/or depressive features at both points in time, exhibited higher concordance for anxiety and/or depressive features, and exhibited higher rates of 'transformation' of initial schizotypal features to anxiety and/or depressive features at the second assessment.

Adolescent↗
PubMed1976

Predator prey interactions with time delays.

A general (Volterra-Lotka type) integrodifferential system which describes a predator-prey interaction subject to delay effects is considered. A rather complete picture is drawn of certain qualitative aspects of the solutions as they are functions of the parameters in the system. Namely, it is argued that such systems have, roughly speaking, the following features. If the carrying capacity of the prey is smaller than a critical value then the predator goes extinct while the prey tends to this carrying capacity; and if the carrying capacity is greater than, but close to this critical value then there is a (globally) asymptotically stable positive equilibrium. However, unlike the classical, non-delay Volterra-Lotka model, if the carrying capacity of the prey is too large then this equilibrium becomes unstable. In this event there are critical values of the birth and death rates of the prey and predator respectively (which hitherto have been fixed) at which "stable" periodic solutions bifurcate from the equilibrium and hence at which the system is stabilized. These features are illustrated by means of a numerically solved example.

Animals↗
PubMed2006

Patchy propagators, brain dynamics, and the generation of spatially structured gamma oscillations.

Propagator theory of brain dynamics is generalized to incorporate a new class of patchy propagators that enable treatment of approximately periodic structures such as are seen in the visual cortex. Complex response fields are also incorporated to allow for features such as orientation preference and wave-number selectivity. The results are applied to the corticothalamic system associated with the primary visual cortex. It is found that this system can generate gamma ( > or = 30 Hz) oscillations during stimulation, whose properties are consistent with experimental findings on gamma frequency and bandwidth, and existence of fine-scale spatial structure. It is found that a potential resonance is associated with each reciprocal lattice vector corresponding to periodic modulations of the propagators. It is found that the lowest resonances are the most likely to give rise to noticeable spectral peaks and increases of correlation amplitude, length, and time, and that these aspects are prominent only if the system is close to marginal stability, in accord with previous measurements and discussions of cortical stability. These features also enable gamma resonances to be stimulus-evoked, with substantial resonance sharpening for relatively small changes in mean neural firing rate. The results also imply dependence of gamma frequency on stimulus features.

Action Potentials↗
PubMedDate not supplied

Synthetic fragments and analogues of elastin. II. Conformational studies.

Conformational studies on synthetic repetitive sequences and analogues of elastin are described. CD and nmr measurements gave evidence of flexible beta-turns as the dominant structural feature whose stability was found to decrease by increasing the number of repetitive units. The sequences comprised the structural unit Gly-X-Gly (X = Val, Leu, Ala), with X-Gly or Gly-Gly located at the corners of the bend. Based on that, it is proposed that these regions of elastin, unlike the proline-containing sequences, contribute to the elasticity of the protein through a classical mechanism in terms of the rotational isomeric state theory.

Amino Acid Sequence↗
PubMed1992

Initial experience with a new compression device for hemostasis after femoral arterial puncture.

We evaluated a new hemostasis device to maintain focused pressure over the femoral artery puncture site for 2-6 hours in 330 cases after diagnostic catheterization or coronary angioplasty. No patient developed later hematoma or vascular complications. The initial favorable experience suggests that this hemostasis device has advantageous features of stability and site visualization and is a suitable adjunct to current methods of maintaining puncture site pressure after brief manual compression following arterial catheterization.

Cardiac Catheterization↗
PubMed1990

General features in the stoichiometry and stability of ionophore A23187-cation complexes in homogeneous solution.

Existing literature describing the stoichiometry and stability of complexes between A23187 and divalent cations in solution has been extended to include additional transition series cations, the heavy-metal cations Cd2+ and Pb2+, plus seven lanthanide series trivalent cations. Stability constants of 1:1 complexes between the ionophore and the divalent cations vary by 6.2 orders of magnitude between Cu2+ and Ba2+ which are the strongest and weakest complexes, respectively. Considering alkaline-earth and first-series transition cations together, the pattern of stability constants obeys the extended Irving-Williams series as is seen with many nonionophorous liganding agents. Cd2+ and Pb2+ are bound with an affinity similar to those of Mn2+ and Zn2+, whereas the lanthanides are bound with little selectivity and slightly higher stability. Titration of the ionophore in the 10(-5) M concentration range with di- and trivalent cations gives rise first to complexes of stoichiometry MA2 and subsequently to MA as the metal concentration is increased. The second stepwise stability constants for formation of the MA2 species exceeds the first constant by approximately 10-fold. With lanthanides, heavy metals, and transition-metal cations, OH-, at near physiological concentrations, competes significantly with free ionophore for binding to the 1:1 complexes. This competition is not apparent when Ca2+ or Mg2+ are the central cations. Possible implications of the 1:1 complex selectivity pattern, the ionophore-hydroxide competitive binding equilibria, and potential ternary complexes involving 1:1 ionophore:cation complexes and other anions present in biological systems are discussed with respect to the ionophore's transport selectivity and biological actions.

Biological Transport↗
PubMed1982

Comparative biochemical studies of the callus matrix in immobilized and non-immobilized fractures.

Fracture healing in both non-immobilized and immobilized rat fracture callus, though different radiographically and histologically; is characterized by similar biochemical changes in the ground substance. Although the callus formed in the immobilized model is appreciably smaller than that formed when the fracture is not immobilized, the chemical composition of the organic matrix of the existing callus undergoes similar modifications regardless of fixation and histological response. Previous studies of endochondral fracture repair have demonstrated an elevation in fracture callus hexosamine content during the early stages of healing of the non-immobilized fracture. This corresponded histologically to a predominance of cartilaginous tissue in the callus matrix. In the present study, the biochemistry, histology, and roentgenographic features of stabilized and non-stabilized rat fractures are compared. Similar elevations in hexosamine are noted at two weeks in both models. These elevations are attributed to changes in proteoglycan rather than glycoprotein concentration of the tissue.

Animals↗
PubMed2005

Effects of heat treatment on the aggregation and charging of Stöber-type silica.

Colloidal silica is known to be stable at high salt concentrations and low pH, where silica is basically uncharged. This observation is in qualitative disagreement with the theory of Derjaguin, Landau, Verwey, and Overbeek (DLVO), which predicts rapid aggregation (or coagulation) under these conditions. This study reports a very different behaviour for Stöber-type silica heated at 800 degrees C, as these particles follow DLVO theory quantitatively. Unheated samples behave approximatively according to DLVO theory, but they show systematic deviations, in particular, featuring higher stability at low pH. The heat treatment also substantially modifies the charging properties, as heated particles show titratable surface charge densities in the range expected for the water-silica interface, while much higher charge densities are observed for the unheated samples. The electrophoretic mobilities, on the other hand, are hardly influenced by the heat treatment. We suspect that the suspension stability of the unheated particles is influenced by the presence of a hairy-layer of polysilicilic acid chains on the surface.

Journal Article↗
PubMed2006

Pressure induced transition between superhydrophobic states: configuration diagrams and effect of surface feature size.

The stability of wetting states, namely the Cassie state (partial wetting) and the Wenzel state (complete wetting) of surfaces with protrusions, is determined by comparing the total free energy of a liquid drop in terms of their apparent contact angles for different protrusion features. It is found that when the area fraction of the topographical features and the intrinsic contact angle for a flat surface are large, the Cassie state is favored, but it can be either the metastable or stable state. It is shown that the transition from the Cassie state to the Wenzel state requires the application of a pressure to the meniscus between the surface protrusions. The critical transition pressure increases not only with increasing area fraction and intrinsic contact angle, but also with decreasing protrusion size. During the transition, a high-pressure gas can be trapped around the protrusions that can cause the Cassie state to be recovered after the release of the applied pressure. The analysis shows that a droplet can 'hang' upside-down when the protrusion size is very small; namely, the protrusions can pin the meniscus. These results are discussed relative to the advancing and receding contact angle.

Journal Article↗
PubMed2000

L-Glutamate dehydrogenase from the antarctic fish Chaenocephalus aceratus. Primary structure, function and thermodynamic characterisation: relationship with cold adaptation.

In order to study the molecular mechanisms of enzyme cold adaptation, direct amino acid sequence, catalytic features, thermal stability and thermodynamics of the reaction and of heat inactivation of L-glutamate dehydrogenase (GDH) from the liver of the Antarctic fish Chaenocephalus aceratus (suborder Notothenioidei, family Channichthyidae) were investigated. The enzyme shows dual coenzyme specificity, is inhibited by GTP and the forward reaction is activated by ADP and ATP. The complete primary structure of C. aceratus GDH has been established; it is the first amino acid sequence of a fish GDH to be described. In comparison with homologous mesophilic enzymes, the amino acid substitutions suggest a less compact molecular structure with a reduced number of salt bridges. Functional characterisation indicates efficient compensation of Q(10), achieved by increased k(cat) and modulation of S(0.5), which produce a catalytic efficiency at low temperature very similar to that of bovine GDH at its physiological temperature. The structural and functional characteristics are indicative of a high extent of protein flexibility. This property seems to find correspondence in the heat inactivation of Antarctic and bovine enzymes, which are inactivated at very similar temperature, but with different thermodynamics.

Acclimatization↗
PubMed1999

A method of finishing the occlusion.

The preadjusted orthodontic appliance has improved the efficiency and effectiveness of the orthodontist in achieving good final results for patients in general. However, the orthodontist is limited in achieving excellent final results because of individual patient variation from the prescription of the preadjusted appliance as well as the orthodontist's ability to precisely place the appliance. This article presents a comprehensive system of evaluation of the individual patient to be used during the finishing stage of treatment and a written system of notation that can guide the orthodontist in producing an excellent finished result for each patient. In this system the orthodontist considers multiple aspects of esthetics, occlusion and function, periodontal health and root alignment, and stability. Every feature of these characteristics is examined and desired changes are noted on the "detailing form" resulting in a written plan that guides the orthodontist to achieve excellence in finishing. This written form can also act as a final checklist of obtainment of the goals of orthodontic treatment. This system of finishing can improve the efficiency of the individual orthodontist and assist in communication in multidoctor practices.

Dental Occlusion↗
PubMed1998

GTPase-activating proteins: helping hands to complement an active site.

Stimulation of the intrinsic GTPase activity of GTP-binding proteins by GTPase-activating proteins (GAPs) is a basic principle of GTP-binding-protein downregulation. Recently, the molecular mechanism behind this reaction has been elucidated by studies on Ras and Rho, and their respective GAPs. The basic features involve stabilizing the existing catalytic machinery and supplementing it by an external arginine residue. This represents a novel mechanism for enzyme active-site formation.

Amino Acid Sequence↗
PubMed1993

Solution structure by 2D 1H-NMR of a chimeric peptide recognized by galanin and neuropeptide Y receptors.

The 25 amino acid residue chimeric peptide M32, galanin(1-13)-neuropeptide Y(25-36)-amide, was synthesized. The peptide was found to be recognized by both galanin and NPY receptors. The solution structure in 30% (v/v) 1,1,1,3,3,3-hexafluoro-2-propanol was examined by 2-D 1H-NMR and by CD. Proton resonance assignments were made, and structures were calculated using DIANA and refined by restrained energy minimization and molecular dynamics. The obtained structures contain an alpha-helical part in the NPY portion of the peptide including residues 13-20, and in some structures it continues to the C-terminal Tyr25. The more flexible N-terminal portion of the peptide has the freedom to approach the C-terminal alpha-helix, via a reverse turn or a nascent alpha-helix, which permits the N-terminus with Trp2 to come into close contact with the C-terminus with Tyr25. Among the ten NMR structures with lowest energy, there are structures reminiscent of the horseshoe shape of aPP, a close relative of NPY with known crystal structure. It appears that the strong alpha-helical character of the NPY (25-36) amide fragment of M32 helps to stabilize structural features in the galanin-derived part of the peptide. It is noteworthy that this rigid NPY portion of M32 does not prevent the recognition of the peptide by galanin receptors; rather, the peptide has unusually high affinity: IC50 = 0.1 nM at galanin receptors. The chimeric peptide M32 is also recognized by NPY receptors with submicromolar affinity (IC50 = 0.25 microM). The availability of a solution structure for peptide M32, which is recognized by two peptide receptors that are both members of the family of G-protein-coupled receptors, may be useful in understanding peptide receptor-ligand interactions and in designing new galanin and NPY receptor ligands.

Amino Acid Sequence↗
PubMed2005

Inactivation of horseradish peroxidase by phenoxyl radical attack.

To test the hypothesis that horseradish peroxidase (HRP) can be inactivated by phenoxyl radicals upon reaction with H(2)O(2)/phenol, we probed HRP-catalyzed phenol oxidation at various phenol/H(2)O(2) concentrations. To this end the total protein, phenolic product, active protein, and iron concentrations in the aqueous phase were determined by protein assay, phenol-(14)C isotopic labeling, resonance Raman and atomic absorption spectroscopy, respectively. Additionally, resonance Raman and FTIR measurements were carried out to probe possible structural changes of the enzyme during the reaction. The data obtained provide the first experimental support for the hypothesis that HRP can be inactivated by a phenoxyl radical attack. The heme macrocycle destruction involving deprivation of the heme iron occurs as a result of the reaction. An intermediate type of the active protein was observed by Raman difference spectra at low concentrations which features a stabilization of the quantum mixed state of the heme iron and a significant amount of phenoxylphenol-type oligomers in solution and probably also in the heme pocket. This work provides a basis for evaluating the relative contributions of different HRP inactivation mechanisms and is thus critical for optimizing engineering applications involving HRP reactions.

Enzyme Activation↗