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Results for “functionality”

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PubMed1999

The flow-function relationship in patients with chronic coronary artery disease and reduced regional function: a Doppler transesophageal and bidimensional transthoracic echocardiography study.

BACKGROUND: Infra-low dose dipyridamole allows one to selectively explore myocardial viability. Transesophageal echocardiography Doppler measurement of left anterior descending coronary artery flow at baseline and following dipyridamole is an efficient tool to assess coronary flow response. Aim of this study was to determine the flow-function relationship during coronary vasodilatory stress in patients with coronary artery disease and baseline dysfunction. METHODS AND RESULTS: Twelve patients with resting dyssynergies and 6 controls underwent assessment of regional function and of left anterior descending blood flow velocity. Flow and function were evaluated at rest and following infra-low dose dipyridamole (0.28 mg/Kg over 4 min). Controls showed a normal function at rest and after dipyridamole. Six patients ('Responders') with resting dyssynergies showed an improvement in segments of left anterior descending artery territory, whereas the other six ones ('Non-responders') showed no functional change. Controls and 'Responders' had similar values of resting peak diastolic left anterior descending artery flow velocity both at rest and after dipyridamole, whereas 'Non-responders' showed a blunted flow response to dipyridamole. CONCLUSION: Myocardial segments with a resting dysfunction and a contractile reserve more often exhibit a residual flow response, whereas segments with fixed pattern show a flat flow response during coronary vasodilator stress.

Blood Flow Velocity↗

PubMed1997

Empirical scoring functions: I. The development of a fast empirical scoring function to estimate the binding affinity of ligands in receptor complexes.

This paper describes the development of a simple empirical scoring function designed to estimate the free energy of binding for a protein-ligand complex when the 3D structure of the complex is known or can be approximated. The function uses simple contact terms to estimate lipophilic and metal-ligand binding contributions, a simple explicit form for hydrogen bonds and a term which penalises flexibility. The coefficients of each term are obtained using a regression based on 82 ligand-receptor complexes for which the binding affinity is known. The function reproduces the binding affinity of the complexes with a cross-validated error of 8.68 kJ/mol. Tests on internal consistency indicate that the coefficients obtained are stable to changes in the composition of the training set. The function is also tested on two test sets containing a further 20 and 10 complexes, respectively. The deficiencies of this type of function are discussed and it is compared to approaches by other workers.

Binding Sites↗

PubMed2005

Hazard functions and expected spike density functions for neuron spike activity in the cochlear nucleus of the cat.

The goal of these experiments was to evaluate the effect of stimulus evoked input and post spike refractoriness on the shapes of post stimulus time histograms (PSTHs). The time courses of spontaneous and/or evoked activity were studied in 153 neurons located predominantly in the dorsal cochlear nucleus in cats anesthetized with Nembutal. Tone bursts were presented to the ipsilateral ear in a free sound field. About half the cells were characterized by the pauser/build-up type of PSTH. Marked refractoriness was evidenced by relatively long recovery times of the hazard functions of spontaneous and tone-evoked spike activity. On presentation of tonal bursts, the time dependence of the probability of the first spike in the absence of a preceding spike (expected spike density function) was greater than the PSTH (actual spike density function). The initial PSTH peak with pause was shaped primarily by stimulus evoked input, whereas refractoriness tended to diminish the build-up portion of the PSTH. In chopper cells, PSTH peaks were usually not reflected in expected spike density functions showing that post spike refractoriness plays a major role in shaping the PSTH. In primary-like cells, refractoriness was small and had little effect on the shape of the PSTH. Some presumptively inhibitory cells showed a tendency to burst discharges with non-monotonic hazard functions. A very small number of cells showed a tendency to internal tuning to a defined signal periodicity.

Acoustic Stimulation↗

PubMed1993

Assessing selfcare status in quadriplegia: comparison of the quadriplegia index of function (QIF) and the functional independence measure (FIM).

The purpose of this study was to compare the quadriplegia index of function (QIF) to the functional independence measure (FIM) in assessing the daily performance of selfcare activities by individuals with cervical spinal cord injury. This study evaluated feeding, grooming and bathing activities in 22 C4-C7, Frankel A-D spinal cord injury patients between 3 and 12 months postinjury. The manual muscle test (MMT) was performed on 17 of these subjects during the same window of time as the QIF and the FIM. An upper extremity motor score (UEMS) was derived from the MMT. In order to relate motor power to functional ability, the UEMS was used as a measure of neurological function to test the hypothesis that the QIF scores are more highly correlated to motor power than are the FIM scores for this population. Spearman coefficients were calculated to correlate the QIF, the FIM and the UEMS. For the bathing and grooming categories, both the QIF and the FIM showed significant and similar correlations to the UEMS. For the feeding category, however, the QIF had a significantly better correlation to the UEMS than did the FIM (Rho = 0.90 vs 0.53, p < 0.01). Use of the QIF feeding scale may allow the detection of changes in function as individuals recover that the FIM scale would miss. Further evaluation of the remaining selfcare and mobility scales is needed. Modification of the FIM with more sensitive portions of the QIF would improve the discriminative ability of outcome studies and program evaluations.

Adolescent↗

PubMed2003

Renal function may not be restored when using decreasing differential function as the criterion for surgery in unilateral hydronephrosis.

OBJECTIVE: To evaluate the use of decreasing differential function (DF) as an indication for surgery in children with congenital hydronephrosis followed according to a flow chart with repeated renography and ultrasonography. PATIENTS AND METHODS: The hospital records of consecutive children (0-12 years old) who underwent an Anderson-Hynes pyeloplasty between 1993 and 2000 were reviewed. Follow-up was recommended according to a flow chart, with isotope renography and ultrasonography at 1, 3 and 6 months, and at 1 (2), 3 and 5 years of age. The diagnosis and follow-up were often at the referring hospital. The criteria for surgery included a decrease in renographic DF of > 10% of DF, and a DF of < 42%, breakthrough pyelonephritis despite antibiotic prophylaxis, pain or an anterior-posterior pelvic diameter of > 50 mm. RESULTS: Fifty-two children with unilateral hydronephrosis were included; eight had surgery because of decreasing DF of the hydronephrotic kidney. Seven children had a prenatal diagnosis. Only one of these eight children was managed according to the recommended procedures for follow-up. In two and possibly three children there was significant irreversible kidney damage since the initial renography before surgery. In one child the initial renography was at 15 months and the DF was < 10%. There was a functional improvement after surgery in three children. CONCLUSION: Few children undergo surgery for decreasing DF of the hydronephrotic kidney in this study. Failure to adhere to the follow-up schedule was common; this may jeopardize kidney function when using decreasing DF as a criterion for surgery. Therefore, not complying (by medical staff or the patient) with the follow-up should be considered when using expectant management for asymptomatic hydronephrosis. The serious consequences for renal function of not complying with follow-up can be avoided by surgery if the patient risks renal functional deterioration, by close cooperation with medical staff at referring hospitals, and by close follow-up at an early age with renography and ultrasonography.

Child↗

PubMed2002

Peripheral blood markers of inflammation predict mortality and functional decline in high-functioning community-dwelling older persons.

OBJECTIVES: Several peripheral blood markers of inflammation have demonstrated prognostic ability, but the value of combining multiple markers as a measure of inflammatory burden remains unknown. The objective of this study was to determine the prognostic value of combining four peripheral blood measures of inflammation in healthy older persons. DESIGN: Inception cohort study with 7 years of follow-up. SETTING: Three communities. PARTICIPANTS: Eight hundred seventy high-functioning subjects aged 70 to 79 who had serum albumin, cholesterol, interleukin (IL)-6, and C-reactive protein (CRP) levels measured at baseline. MEASUREMENTS: Three- and 7-year mortality and Rosow- Breslau functional decline. RESULTS: A summary score was created that assigned one point each for the following blood levels: albumin <3.8 g/dL, cholesterol <170 mg/dL (bottom decile), IL-6>3.8 pg/mL (top tertile), and CRP>2.65 mg/L (top tertile). By 3 years, 6% of subjects had died, and, by 7 years, 23% had died. In subjects with three or four markers of inflammation, the adjusted odds ratios (AORs) for 3- and 7-year mortality were 6.6 and 3.2, respectively, compared with those who had no abnormal markers. Subjects with one or two markers were at more moderate and statistically insignificant increased risk of 3- and 7-year mortality with AORs of 1.5 and 1.3, respectively. The risks for functional decline at 3- and 7-years were generally small (AOR = 1.1-1.9) and not statistically significant. CONCLUSIONS: In high-functioning older persons, a measure of inflammation can identify those at a much higher risk of mortality and a possibly higher risk of functional decline. Whether therapies directed at reducing inflammation can attenuate such risk remains to be determined.

Aged↗

PubMed2001

Aesthetic and functional results of harvesting radial forearm flap, especially with regard to hand function.

There is controversy in the literature regarding donor site morbidity following radial forearm flap harvesting. The aim of this study was to verify possible functional and aesthetic impairments at the donor site. Thirty-five patients who underwent maxillofacial reconstruction using radial forearm flap were asked to give their subjective assessment of the aesthetic outcome at the donor site and of postoperative hand function. They were also examined for trophic status; cold intolerance and tactile sensitivity of split-thickness skin graft, palm and finger pads; grip strength and finger-to-thumb pinch strength; range of movement for the wrist and finger joints; as well as functional hand testing. Slight impairments regarding hand strength and mobility were observed. However, due to their small extent they were of no clinical relevance, as shown by 85.7% of our patients displaying optimal functional hand testing values (80-100%), and 88.6% giving a positive subjective assessment (80-100%) of postoperative vs preoperative hand function. The results show that donor site morbidity following radial forearm flap harvesting is low.

Cold Temperature↗

PubMed2004

Excitation energies for a benchmark set of molecules obtained within time-dependent current-density functional theory using the Vignale-Kohn functional.

In this article we explain how the existing linear response theory of time-dependent density-functional theory can be extended to obtain excitation energies in the framework of time-dependent current-density-functional theory. We use the Vignale-Kohn current-functional [G. Vignale and W. Kohn, Phys. Rev. Lett. 77, 2037 (1996)] which has proven to be successful for describing ultranonlocal exchange-correlation effects in the case of the axial polarizability of molecular chains [M. van Faassen, P. L. de Boeij, R. van Leeuwen, J. A. Berger, and J. G. Snijders, Phys. Rev. Lett. 88, 186401 (2002); J. Chem. Phys. 118, 1044 (2003)]. We study a variety of singlet excitations for a benchmark set of molecules. The pi(*)<--pi transitions obtained with the Vignale-Kohn functional are in good agreement with experiment and other theoretical results and they are in general an improvement upon the adiabatic local density approximation. In case of the pi(*)<--n transitions the Vignale-Kohn functional fails, giving results that strongly overestimate the experimental and other theoretical results. The benchmark set also contains some other types of excitations for which no clear failures or improvements are observed.

Journal Article↗

PubMed2004

On the importance of the "density per particle" (shape function) in the density functional theory.

The central role of the shape function sigma(r) from the density functional theory (DFT), the ratio of the electron density rho(r) and the number of electrons N of the system (density per particle), is investigated. Moreover, its relationship with DFT based reactivity indices is established. In the first part, it is shown that an estimate for the chemical hardness can be obtained from the long range behavior of the shape function and its derivative with respect to the number of electrons at a fixed external potential. Next, the energy of the system is minimized with the constraint that the shape function should integrate to unity; the associated Lagrange multiplier is shown to be related to the electronic chemical potential micro of the system. Finally, the importance of the shape function for both molecular structure, reactivity, and similarity is outlined.

Journal Article↗

PubMed2004

Structures and correlation functions of multicomponent and polydisperse hard-sphere mixtures from a density functional theory.

The structures of nonuniform binary hard-sphere mixtures and the correlation functions of uniform ternary hard-sphere mixtures were studied using a modified fundamental-measure theory based on the weight functions of Rosenfeld [Rosenfeld, Phys. Rev. Lett. 63, 980 (1989)] and Boublik-Mansoori-Carnahan-Starling-Leland equation of state [Boublik, J. Chem. Phys. 53, 471 (1970); Mansoori et al., J. Chem. Phys. 54, 1523 (1971)]. The theoretical predictions agreed very well with the molecular simulations for the overall density profiles, the local compositions, and the radial distribution functions of uniform as well as inhomogeneous hard-sphere mixtures. The density functional theory was further extended to represent the structure of a polydisperse hard-sphere fluid near a hard wall. Excellent agreement was also achieved between theory and Monte Carlo simulations. The density functional theory predicted oscillatory size segregations near a hard wall for a polydisperse hard-sphere fluid of a uniform size distribution.

Journal Article↗

PubMed2004

Norbornane: an investigation into its valence electronic structure using electron momentum spectroscopy, and density functional and Green's function theories.

We report on the results of an exhaustive study of the valence electronic structure of norbornane (C(7)H(12)), up to binding energies of 29 eV. Experimental electron momentum spectroscopy and theoretical Green's function and density functional theory approaches were all utilized in this investigation. A stringent comparison between the electron momentum spectroscopy and theoretical orbital momentum distributions found that, among all the tested models, the combination of the Becke-Perdew functional and a polarized valence basis set of triple-zeta quality provides the best representation of the electron momentum distributions for all of the 20 valence orbitals of norbornane. This experimentally validated quantum chemistry model was then used to extract some chemically important properties of norbornane. When these calculated properties are compared to corresponding results from other independent measurements, generally good agreement is found. Green's function calculations with the aid of the third-order algebraic diagrammatic construction scheme indicate that the orbital picture of ionization breaks down at binding energies larger than 22.5 eV. Despite this complication, they enable insights within 0.2 eV accuracy into the available ultraviolet photoemission and newly presented (e,2e) ionization spectra, except for the band associated with the 1a(2) (-1) one-hole state, which is probably subject to rather significant vibronic coupling effects, and a band at approximately 25 eV characterized by a momentum distribution of "s-type" symmetry, which Green's function calculations fail to reproduce. We note the vicinity of the vertical double ionization threshold at approximately 26 eV.

Journal Article↗

PubMed2004

The "JK-only" approximation in density matrix functional and wave function theory.

Various energy functionals applying the "JK-only" approximation which leads to two-index two-electron integrals instead of four-index two-electron integrals in the electron-electron interaction term of the electronic energy are presented. Numerical results of multiconfiguration self-consistent field calculations for the best possible "JK-only" wave function are compared to those obtained from the pair excitation multiconfiguration self-consistent (PEMCSCF) method and two versions of density matrix functional theory. One of these is derived making explicit use of some necessary conditions for N representability of the second-order density matrix. It is shown that this method models the energy functional based on the best possible "JK-only" wave function with good accuracy. The calculations also indicate that only a minor fraction of the total correlation energy is incorporated by "JK-only" approaches for larger molecules.

Journal Article↗

PubMed2007

Assessment of the exchange-correlation functionals for the physical description of spin transition phenomena by density functional theory methods: all the same?

This study aims to assess present day density functionals in the description of spin crossover iron(II) complexes. Two recently synthesized spin crossover complexes were considered. Theoretical calculations were made using 53 of the most popular exchange-correlation density functionals with triple zeta plus polarization quality basis sets. The present work shows that even though different density functionals can lead to different energy gaps between spin states, most of them are very similar for these two compounds when a comparison between energy gaps is sought. The present work shows that even though different exchange correlations can lead to different energy gaps between spin states, the difference between these gaps calculated at different geometries and that calculated at a given reference geometry is surprisingly independent of the choice of functional. The reasons for the similarities and the differences among exchange and correlation functional combinations are discussed.

Journal Article↗

PubMed1996

New infinite families of exact sums of squares formulas, Jacobi elliptic functions, and Ramanujan's tau function.

In this paper, we give two infinite families of explicit exact formulas that generalize Jacobi's (1829) 4 and 8 squares identities to 4n(2) or 4n(n + 1) squares, respectively, without using cusp forms. Our 24 squares identity leads to a different formula for Ramanujan's tau function tau(n), when n is odd. These results arise in the setting of Jacobi elliptic functions, Jacobi continued fractions, Hankel or Turánian determinants, Fourier series, Lambert series, inclusion/exclusion, Laplace expansion formula for determinants, and Schur functions. We have also obtained many additional infinite families of identities in this same setting that are analogous to the eta-function identities in appendix I of Macdonald's work [Macdonald, I. G. (1972) Invent. Math. 15, 91-143]. A special case of our methods yields a proof of the two conjectured [Kac, V. G. and Wakimoto, M. (1994) in Progress in Mathematics, eds. Brylinski, J.-L., Brylinski, R., Guillemin, V. & Kac, V. (Birkhäuser Boston, Boston, MA), Vol. 123, pp. 415-456] identities involving representing a positive integer by sums of 4n(2) or 4n(n + 1) triangular numbers, respectively. Our 16 and 24 squares identities were originally obtained via multiple basic hypergeometric series, Gustafson's C(l) nonterminating (6)phi(5) summation theorem, and Andrews' basic hypergeometric series proof of Jacobi's 4 and 8 squares identities. We have (elsewhere) applied symmetry and Schur function techniques to this original approach to prove the existence of similar infinite families of sums of squares identities for n(2) or n(n + 1) squares, respectively. Our sums of more than 8 squares identities are not the same as the formulas of Mathews (1895), Glaisher (1907), Ramanujan (1916), Mordell (1917, 1919), Hardy (1918, 1920), Kac and Wakimoto, and many others.

Journal Article↗

PubMed1996

Structure-function relationship of lipoprotein lipase-mediated enhancement of very low density lipoprotein binding and catabolism by the low density lipoprotein receptor. Functional importance of a properly folded surface loop covering the catalytic center.

We examined the structure-function relationship of human lipoprotein lipase (hLPL) in its ability to enhance the binding and catabolism of very low density lipoproteins (VLDL) in COS cells. Untransfected COS cells did not bind to or catabolize normal VLDL. Expression of wild-type hLPL by transient transfection enhanced binding, uptake, and degradation of the VLDL (a property of LPL that we call bridge function). Heparin pretreatment and a monoclonal antibody ID7 that blocks LDL receptor-binding domain of apoE both inhibited binding, and apoE2/E2 VLDL from a Type III hyperlipidemic subject did not bind. However, LDL did not reduce 125I-VLDL binding to the hLPL-expressing cells, whereas rabbit beta-VLDL was an effective competitor. By contrast, LDL reduced uptake and degradation of 125I-VLDL to the same extent as excess unlabeled VLDL or beta-VLDL. These data suggest that binding occurs by direct interaction of VLDL with LPL but the subsequent catabolism of the VLDL is mediated by the LDL receptor. Mutant hLPLs that were catalytically inactive, S132A, S132D, as well as the partially active mutant, S251T, and S172G, gave normal enhancement of VLDL binding and catabolism, whereas the partially active mutant S172D had markedly impaired capacity for the process; thus, there is no correlation between bridge function and lipolytic activity. A naturally occurring genetic variant hLPL, S447-->Ter, has normal bridge function. The catalytic center of LPL is covered by a 21-amino acid loop that must be repositioned before a lipid substrate can gain access to the active site for catalysis. We studied three hLPL loop mutants (LPL-cH, an enzymatically active mutant with the loop replaced by a hepatic lipase loop; LPL-cP, an enzymatically inactive mutant with the loop replaced by a pancreatic lipase loop; and C216S/C239S, an enzymatically inactive mutant with the pair of Cys residues delimiting the loop substituted by Ser residues) and a control double Cys mutant, C418S/C438S. Two of the loop mutants (LPL-cH and LPL-cP) and the control double Cys mutant C418S/C438S gave normal enhancement of VLDL binding and catabolism, whereas the third loop mutant, C216S/C239S, was completely inactive. We conclude that although catalytic activity and the actual primary sequence of the loop of LPL are relatively unimportant (wild-type LPL loop and pancreatic lipase loops have little sequence similarity), the intact folding of the loop, flanked by disulfide bonds, must be maintained for LPL to express its bridge function.

Animals↗

PubMed1998

Functional food science and gastrointestinal physiology and function.

The gut is an obvious target for the development of functional foods, acting as it does as the interface between diet and the metabolic events which sustain life. The key processes in digestive physiology which can be regulated by modifying diet are satiety, the rate and extent of macronutrient breakdown and absorption from the small bowel, sterol metabolism, the colonic microflora, fermentation, mucosal function and bowel habit, and the gut immune system. The intestinal microflora is the main focus of many current functional foods. Probiotics are foods which contain live bacteria which are beneficial to health whilst prebiotics, such as certain non-digestible oligosaccharides which selectively stimulate the growth of bifidobacteria in the colon, are already on the market. Their claimed benefits are to alleviate lactose maldigestion, increase resistance to invasion by pathogenic species of bacteria in the gut, stimulate the immune system and possibly protect against cancer. There are very few reports of well-designed human intervention studies with prebiotics as yet. Certain probiotic species have been shown to shorten the duration of rotavirus diarrhoea in children but much more work is needed on the mechanism of immunomodulation and of competitive exclusion and microflora modification. The development of functional foods for the gut is in its infancy and will be successful only if more fundamental research is done on digestive physiology, the gut microflora, immune system and mucosal function.

Bacteria↗

PubMed2005

Self-rated executive function: development of the executive function index.

There are several self-rating executive function (SREF) measures in existence that were developed solely in clinical populations or which sample a limited range of executive functions. The Executive Function Index (EFI) was developed here in a normal population with five subscales derived through factor analysis: Motivational Drive, Strategic Planning, Organization, Impulse Control, and Empathy. The content of three second order factors is consistent with the functions mediated by dorsolateral, orbitofrontal, and medial prefrontal circuits. Intrascale reliability and demographic relationships are reported as well as strong correlations with other SREF measures validated in clinical and neuroimaging studies. This brief measure provides a quick and efficient means of collecting data in large samples in order to test hypotheses regarding the role of prefrontal systems in various aspects of behavior and to corroborate findings of other methods, such as objective tests and functional neuroimaging.

Adolescent↗

PubMedDate not supplied

Lung function in an Australian population: contributions of polygenic factors and the Pi locus to individual differences in lung function in a sample of twins.

A study of lung function in 203 twin pairs aged 18-34 years living in Sydney detected significant genetic variation in females and males. There was no evidence of family environmental effects in either sex and most of the repeatable variation in females was heritable. However, there was evidence for systematic environmental differences between males affecting lung function so that the heritability was lower in males (about 0.6) than females (about 0.8). An effect of smoking on lung function was detected but accounted for less than 3% of the variance. Lung function in females was greater in the M subtype heterozygotes at the Pi locus than in the M subtype homozygotes or in other Pi phenotypes with low alpha 1-antitrypsin activity. The Pi polymorphism accounted for approximately 9% of the total variance in female lung function. No effect of the Pi locus was found in males.

Adolescent↗