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Biomedical subjects

Hans Agren

Publications and source records attributed to Hans Agren.

At least 37 records · Page 2Linked to original sources
PubMed2006

Efficacy and tolerability of reboxetine compared with citalopram: a double-blind study in patients with major depressive disorder.

The objective of this study was to compare efficacy and tolerability of the selective noradrenaline reuptake inhibitor reboxetine with the selective serotonin reuptake inhibitor citalopram, in the treatment of major depressive disorder (MDD). In total, 357 outpatients with MDD were randomized to treatment with reboxetine 8-10 mg or citalopram 20-40 mg per day during 24 weeks. Primary end-point was change from baseline in the Hamilton Depression Rating Scale (HAM-D, 21 items). Sexual function/dysfunction was measured by the Sexual Function scale (SF). Observed case analysis showed that both treatments yielded a gradual reduction of HAM-D scores: reboxetine with -21.4 and citalopram with -22.1 points (NS). LOCF analysis showed a greater reduction of the HAM-D scores with citalopram compared with reboxetine (-19.6 vs. -17.8; P = 0.034). The response rate was 90.3% for reboxetine and 92.7% for citalopram (NS). The most common side effect in the reboxetine group was dry mouth, and in the citalopram group sexual dysfunction. At week 24, anorgasmia was reported by 5.9% of the sexually active women in the reboxetine group vs 39% in the citalopram group. The dropout number was 91 in the reboxetine group, and 54 in the citalopram group. To summarize, both treatments gave a satisfactory antidepressant effect. The side effect profile differed between the groups, with a notably high prevalence of sexual dysfunctions in the citalopram group. The high number of dropouts in the reboxetine group, is considered as a result of the non-titration starting dose of 8 mg reboxetine per day, which gave a high incidence of early side-effects.

Adolescent↗
PubMed2005

Quantum chemical studies of three-photon absorption of some stilbenoid chromophores.

Three-photon absorption of a series of donor-acceptor trans-stilbene derivatives is studied by means of density functional theory applied to the third-order response function and its residues. The results obtained by using different functionals are compared with experimental data for similar systems obtained from the literature. With a Coulomb attenuated, asymptotically corrected functional, the excitation energy to the first resonance state is much improved. Comparison with experiment indicates that this is the case for the three-photon cross section as well. In particular, the overestimation of the cross sections and underestimation of excitation energies offered by the density functional theory using common density functionals is corrected for. It is argued that a reliable theory for three-photon absorption in charge transfer and other chromophore systems thereby has been obtained. Further elaboration of the theory and its experimental comparison call for explicit inclusion of solvent polarization and pulse propagation effects.

Journal Article↗
PubMed2005

Calculations of two-photon charge-transfer excitations using Coulomb-attenuated density-functional theory.

In this work, we show that an implementation of Coulomb-attenuated density-functional theory leads to considerably better prospects than hitherto for modeling two-photon absorption cross sections for charge-transfer species. This functional, which corrects for the effect of poor asymptotic dependence of commonly used functionals, essentially brings down the widely different results for larger charge-transfer species between Hartree-Fock and density-functional theory (DFT)-B3LYP into a closer range. The Coulomb-attenuated functional, which retains the best aspects of the Hartree-Fock and DFT-B3LYP methods, proves to be very promising for further modeling design of multiphoton materials with technical applications.

Journal Article↗
PubMed2005

Second-harmonic generation of solvated molecules using multiconfigurational self-consistent-field quadratic response theory and the polarizable continuum model.

We present the first implementation of the quadratic response function for multiconfigurational self-consistent-field wave functions of solvated molecules described by a polarizable continuum model employing a molecule-shaped cavity. We apply the methodology to the first hyperpolarizability beta and, in particular, the second-harmonic generation process for a series of conjugated push-pull oligomers, as well as for para-nitroaniline. The effect of solvation on the dispersion of the hyperpolarizability and the change in the hyperpolarizability for increasing chain length of the oligomers in vacuum and in solution is considered. The effect of a correlated description is analyzed by comparing the Hartree-Fock hyperpolarizabilities to the multiconfigurational self-consistent-field hyperpolarizabilities. The effect of geometry relaxation in the solvent on the properties of the solvated molecules are also investigated.

Journal Article↗
PubMed2005

Long-term citalopram administration reduces responsiveness of HPA axis in patients with major depression: relationship with S-citalopram concentrations in plasma and cerebrospinal fluid (CSF) and clinical response.

RATIONALE: A dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis is a well-documented neurobiological finding in major depression. Moreover, clinically effective therapy with antidepressant drugs may normalize the HPA axis activity. OBJECTIVE: The aim of this study was to test whether citalopram (R/S-CIT) affects the function of the HPA axis in patients with major depression (DSM IV). METHODS: Twenty depressed patients (11 women and 9 men) were challenged with a combined dexamethasone (DEX) suppression and corticotropin-releasing hormone (CRH) stimulation test (DEX/CRH test) following a placebo week and after 2, 4, and 16 weeks of 40 mg/day R/S-CIT treatment. RESULTS: The results show a time-dependent reduction of adrenocorticotrophic hormone (ACTH) and cortisol response during the DEX/CRH test both in treatment responders and nonresponders within 16 weeks. There was a significant relationship between post-DEX baseline cortisol levels (measured before administration of CRH) and severity of depression at pretreatment baseline. Multiple linear regression analyses were performed to identify the impact of psychopathology and hormonal stress responsiveness and R/S-CIT concentrations in plasma and cerebrospinal fluid (CSF). The magnitude of decrease in cortisol responsivity from pretreatment baseline to week 4 on drug [delta-area under the curve (AUC) cortisol] was a significant predictor (p<0.0001) of the degree of symptom improvement following 16 weeks on drug (i.e., decrease in HAM-D21 total score). The model demonstrated that the interaction of CSF S-CIT concentrations and clinical improvement was the most powerful predictor of AUC cortisol responsiveness. CONCLUSION: The present study shows that decreased AUC cortisol was highly associated with S-CIT concentrations in plasma and CSF. Therefore, our data suggest that the CSF or plasma S-CIT concentrations rather than the R/S-CIT dose should be considered as an indicator of the selective serotonergic reuptake inhibitors (SSRIs) effect on HPA axis responsiveness as measured by AUC cortisol response.

Adrenocorticotropic Hormone↗
PubMed2005

Can octupolar molecules be poled by an external electric field?

Octupolar molecules are generally believed to be of potential use in developing nonlinear optical materials owing to the fact that they do not easily form molecular aggregates. This is often put against the conjectured drawback that electric fields have no poling, or ordering, effect for this class of molecules because of the lack of a permanent ground state dipole moment. In this paper, we analyze this notion in some detail and present results from molecular dynamics computer simulations of an ensemble of a prototypical octupolar molecule, the 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) molecule, dissolved in chloroform. It is found that TATB molecules indeed show rather significant dipole moments in solutions because of the dual action of the thermal motions of the atoms and the strong intermolecular interactions. Applied electric fields accordingly show significant effects on the orientations of the molecular dipole moments. We also find that TATB molecules can aggregate because of the strong hydrogen-bonding interactions between the molecules, though they lack a static permanent dipole moment. Thus, the simulation results for TATB molecules in solution present us with a totally different notion about the collective properties of octupolar molecules. Taking account of quantum chemistry results, we found that the collective molecular nonlinear optical (NLO) properties are enhanced after the onset of the electric field, showing significant anisotropic characteristics.

Journal Article↗
PubMed2005

Density functional theory study of indirect nuclear spin-spin coupling constants with spin-orbit corrections.

This work outlines the calculation of indirect nuclear spin-spin coupling constants with spin-orbit corrections using density functional response theory. The nonrelativistic indirect nuclear spin-spin couplings are evaluated using the linear response method, whereas the relativistic spin-orbit corrections are computed using quadratic response theory. The formalism is applied to the homologous systems H2X (X=O,S,Se,Te) and XH4 (X=C,Si,Ge,Sn,Pb) to calculate the indirect nuclear spin-spin coupling constants between the protons. The results confirm that spin-orbit corrections are important for compounds of the H2X series, for which the electronic structure allows for an efficient coupling between the nuclei mediated by the spin-orbit interaction, whereas in the case of the XH4 series the opposite situation is encountered and the spin-orbit corrections are negligible for all compounds of this series. In addition we analyze the performance of the density functional theory in the calculations of nonrelativistic indirect nuclear spin-spin coupling constants.

Journal Article↗
PubMed2005

Two-photon absorption in solution by means of time-dependent density-functional theory and the polarizable continuum model.

We present the first study of two-photon absorption (TPA) of solvated molecules based on direct evaluation of TPA cross sections from the quadratic response of time-dependent perturbations. A set of prototypical two-photon (TP) chromophores has been selected and analyzed: a pure pi system (t-stilbene) and its substituted homologs obtained employing a donor (D) and an acceptor (A) group to probe the solvent effects along the series pi, D-pi-D, A-pi-D, and A-pi-A. For the selected systems we have calculated the TPA cross sections in different environments by means of the polarizable continuum model. The data have been analyzed to evaluate how the structural and environmental parameters contribute to the final two-photon absorption cross section. These include molecular structure, geometry relaxation in solution, polarity, and refractive index of the solvent. The performances of the three common functionals SVWN, BLYP, and B3LYP have been compared. The results show a significant solvent dependence of the TPA cross section and an unusual trend when passing from cyclohexane to water. The data have also been rationalized in terms of the main orbital excitations leading to the transitions. Finally, trends along the series have been described and comparison with experiments and previous calculations has been drawn.

Absorption↗
PubMed2005

Density-functional theory study of electric and magnetic properties of hexafluorobenzene in the vapor phase.

A series of electric and magnetic properties of hexafluorobenzene have been calculated, including the electric dipole polarizability, magnetizability, electric quadrupole moment, and nonlinear mixed electric dipole-magnetic dipole-electric quadrupole hyperpolarizabilities needed to obtain estimates of the Kerr, Cotton-Mouton, Buckingham, Jones, and magnetoelectric birefringences in the vapor phase. Time-dependent density-functional theory was employed for the calculation of linear-, quadratic, and cubic response functions. A number of density functionals have been considered, along with Sadlej's triple-zeta basis set and the augmented correlation-consistent polarized valence double zeta and augmented correlation-consistent polarized valence triple zeta basis sets. Comparisons have been made with experiment where possible. The analysis of results allows for an assessment of the capability of time-dependent density-functional theory for high-order electromagnetic properties of an electron-rich system such as hexafluorobenzene.

Journal Article↗
PubMed2005

Time-dependent density-functional theory calculations of triplet-triplet absorption.

We present density-functional theory calculations of triplet-triplet absorption by three different approaches based on time-dependent density-functional theory (DFT): unrestricted DFT linear response, open-shell restricted DFT linear response applied to the triplet state, and quadratic response with triplet excitations applied to the ground state. Comparison is also made with corresponding results obtained by Hartree-Fock and multiconfiguration self-consistent-field response theory. Two main conclusions concerning triplet-triplet transitions are drawn in this study: First, the very good agreement between unrestricted and restricted DFT results indicates that spin contamination of the triplet state is not a serious problem when computing triplet-triplet spectra of common organic molecules. Second, DFT response calculations of triplet-triplet transitions can be affected by triplet instability problems, especially for the combination of DFT quadratic response with functionals containing fractional exact Hartree-Fock exchange.

Journal Article↗
PubMed2005

Neuropeptide Y and corticotropin-releasing hormone in CSF mark response to antidepressive treatment with citalopram.

Neuropeptides appear to play a role in the pathophysiology of depression and electroconvulsive treatment and lithium affect these compounds in human cerebrospinal fluid (CSF) and rodent brain. Consequently, we investigated whether long-term treatment with the selective serotonin reuptake inhibitor (SSRI) citalopram (Cit) would also affect neuropeptides in CSF of depressed patients. Changes in CSF monoamine metabolites were also explored. CSF concentrations of corticotropin-releasing hormone (CRH)-like immunoreactivity (-LI), neuropeptide Y (NPY)-LI, and Cit were determined in 21 patients with major depression. Lumbar puncture was performed in the morning at baseline and was repeated after at least 4 wk of Cit treatment (40 mg/d). The severity of depression was assessed by the Hamilton Rating Scale for Depression (HAMD). Cit treatment was associated with a significant increase in NPY-LI and decrease in CRH-LI. An evaluation of the relationship between changes in concentrations of NPY-LI, CRH-LI, and the clinical response showed significant correlations between these parameters. Significant NPY and CRH changes in CSF following treatment as well as correlations to changes in HAMD support the hypothesis that these two peptides play a role in affective disorders and are markers of therapeutic response.

Adult↗
PubMed2005

Charge-transfer Zn-porphyrin derivatives with very large two-photon absorption cross sections at 1.3-1.5 microm fundamental wavelengths.

A series of charge-transfer Zn-porphyrin derivatives with large two-photon absorption cross sections at 1.3-1.5 microm fundamental wavelengths are designed using time-dependent hybrid density functional theory. The fluorescence of these chromospheres is expected to be in the region of 700-900 nm. These unique features make them suitable for a variety of biophotonic and telecommunication applications.

Absorption↗
PubMed2005

Cubic response functions in time-dependent density functional theory.

We present density-functional theory for time-dependent response functions up to and including cubic response. The working expressions are derived from an explicit exponential parametrization of the density operator and the Ehrenfest principle, alternatively, the quasienergy ansatz. While the theory retains the adiabatic approximation, implying that the time-dependency of the functional is obtained only implicitly-through the time dependence of the density itself rather than through the form of the exchange-correlation functionals-it generalizes previous time-dependent implementations in that arbitrary functionals can be chosen for the perturbed densities (energy derivatives or response functions). In particular, general density functionals beyond the local density approximation can be applied, such as hybrid functionals with exchange correlation at the generalized-gradient approximation level and fractional exact Hartree-Fock exchange. With our implementation the response of the density can always be obtained using the stated density functional, or optionally different functionals can be applied for the unperturbed and perturbed densities, even different functionals for different response order. As illustration we explore the use of various combinations of functionals for applications of nonlinear optical hyperpolarizabilities of a few centrosymmetric systems; molecular nitrogen, benzene, and the C(60) fullerene. Considering that vibrational, solvent, and local field factors effects are left out, we find in general that very good experimental agreement can be obtained for the second dynamic hyperpolarizability of these systems. It is shown that a treatment of the response of the density beyond the local density approximation gives a significant effect. The use of different functional combinations are motivated and discussed, and it is concluded that the choice of higher order kernels can be of similar importance as the choice of the potential which governs the Kohn-Sham orbitals.

Journal Article↗
PubMed2005

Sense of coherence and social support in relation to recovery in first-episode patients with major depression: a one-year prospective study.

Major depression is a common illness, with a lifetime prevalence rate of 10-13% for men and 21-24% for women. The experience of having a serious illness such as major depression affects the individual's quality of life and requires significant adaptation in order to cope. The aim of this study was to explore sense of coherence and social support in patients treated for a first episode of major depression in a 1-year follow up. The study design was prospective and longitudinal. A total of 24 patients, aged 18 years or over, with a first episode of major depression were included. Semi-structured interviews and self-assessment questionnaires were used at baseline as well as in a 1-year follow up in order to measure the level of severity of the depression, social support, and sense of coherence. The result showed that 71% of the patients had recovered at follow up. The sense of coherence scores were low at baseline, although the patients who recovered increased their sense of coherence scores significantly. Another factor of importance for recovery was a significant increase in social support. Social support is an important cornerstone in the restoration of a person's sense of coherence. It can be used in interventions that include the patient's family or close social network in combination with support to assist the patient to view his/her situation as comprehensible, manageable, and meaningful, thereby promoting or improving health. Mental health nurses are in a key position to identify patients' strengths and weaknesses so that the support and interventions provided can be tailored to meet the needs of each patient.

Adaptation, Psychological↗
PubMed2004

Density functional response theory calculations of three-photon absorption.

Three-photon absorption probabilities delta(3PA) have been calculated through application of a recently derived method for cubic response functions within density functional theory (DFT). Calculations are compared with Hartree-Fock (HF) and with a coupled cluster hierarchy of models in a benchmarking procedure. Except for cases having intermediate states near resonance, density functional theory is demonstrated to be in sufficient agreement with the highly correlated methods in order to qualify for predictions of delta(3PA). For the larger systems addressed, a set of acceptor A and donor D substituted pi-conjugated systems formed by trans-stilbene and dithienothiophene (DTT), we find noticeable differences in the magnitude of delta(3PA) between HF and DFT, although similar trends are followed. It is shown that the dipolar structures, TS-AD and DTT-AD, have substantially larger delta(3PA) than other types of modifications which is in accordance with observations for two-photon absorption. This is the first application of density functional theory to three-photon absorption beyond the use of few-state models.

Journal Article↗
PubMed2004

HPA axis activation determined by the CRH challenge test in patients with few versus multiple episodes of treatment-refractory depression.

OBJECTIVE: In clinical guidelines, risk factors for a malignant illness course include 3 or more lifetime episodes of depression. Our aim was to investigate the activation of the hypothalamic-pituitary-adrenal hormonal axis in treatment-refractory affective disorder in pauciepisodic (one or two episodes) versus multiepisodic (three or more episodes) patients. METHODS: We evaluated the HPA axis in 37 patients with treatment-refractory affective disorder and in 27 healthy volunteers by measuring adrenocorticotropin hormone (ACTH) and cortisol responses following administration of corticotropin-releasing hormone (CRH). In retrospective life charts was recorded every previous illness episode for each patient. RESULTS: Seven of the patients were pauciepisodic and 30 were multiepisodic. The pauciepisodic patients had significantly larger peak and total ACTH responses to CRH compared to the multiepisodic patients as well as to the control group. Multiepisodic patients showed no difference compared to controls in ACTH secretion pre- and post-CRH. Cortisol secretion was the same in all three groups. CONCLUSIONS: The pituitary adrenocortical responses were stronger in pauciepisodic patients than in multiepisodic patients and in volunteers. This cross-sectional study suggests that the HPA axis, in refractory multiepisodic affective disorders, might weaken its original activity as the illness recurs with more episodes.

Adrenocorticotropic Hormone↗
PubMed2004

Density-functional and electron correlated study of five linear birefringences--Kerr, Cotton-Mouton, Buckingham, Jones, and magnetoelectric--in gaseous benzene.

We present the results of an extended study of five birefringences--Kerr, Cotton-Mouton, Buckingham, Jones, and Magnetoelectric--on benzene in the gas phase. The relevant molecular quantities--first-order properties, linear, quadratic, and cubic response functions--are computed employing the density-functional theory (DFT) response theory, with a choice of functionals. In some cases, different functionals are employed for the wave-function computational step and for the subsequent analytical response calculation to determine the combination yielding at the same time the optimal energy and energy derivative results. Augmented correlation consistent basis sets of double and triple zeta quality are used. The DFT results are compared to those obtained at the Hartree-Fock level and in some cases within a coupled cluster singles and doubles electronic structure model. The study tries to assess the ability of the DFT response theory to describe a wide range of properties in a system of rather large size and high complexity. The relative strength of the five birefringences for plausible experimental conditions is determined and, when possible, comparison is made with the results of the measurements.

Journal Article↗