Cooperative density wave and giant spin gap in the quarter-filled zigzag electron ladder

Strong cooperative interactions occur between four different broken symmetries involving charge ordering and bond distortions in the quarter-filled correlated zigzag electron ladder. The ground state is singlet, with spin gap several times larger than in the spin-Peierls state of the one-dimensional quarter-filled chain with the same parameters. We propose the quarter-filled zigzag electron ladder model for several different organic charge transfer solids with coupled pairs of quasi-one-dimensional stacks, in which the spin-gap transition temperatures are unusually high.

The utility of structure-activity relationship (SAR) models for prediction and covariate selection in developmental toxicity: comparative analysis of logistic regression and decision tree models

Structure-activity relationship (SAR) models can be used to predict the biological activity of potential developmental toxicants whose adverse effects include death, structural abnormalities, altered growth and functional deficiencies in the developing organism. Physico-chemical descriptors of spatial, electronic and lipophilic properties were used to derive SAR models by two modeling approaches, logistic regression and Classification and Regression Tree (CART), using a new developmental database of 293 chemicals (FDA/TERIS). Both single models and ensembles of models (termed bagging) were derived to predict toxicity. Assessment of the empirical distributions of the prediction measures was performed by repeated random partitioning of the data set. Results showed that both the decision tree and logistic regression derived developmental SAR models exhibited modest prediction accuracy. Bagging tended to enhance the prediction accuracy and reduced the variability of prediction measures compared to the single model for CART-based models but not consistently for logistic-based models. Prediction accuracy of single logistic-based models was higher than single CART-based models but bagged CART-based models were more predictive. Descriptor selection in SAR for the understanding of the developmental mechanism was highly dependent on the modeling approach. Although prediction accuracy was similar in the two modeling approaches, there was inconsistency in the model descriptors.

Decision tree SAR models for developmental toxicity based on an FDA/TERIS database

Humans are exposed to thousands of environmental chemicals for which no developmental toxicity information is available. Structure-activity relationships (SARs) are models that could be used to efficiently predict the biological activity of potential developmental toxicants. However, at this time, no adequate SAR models of developmental toxicity are available for risk assessment. In the present study, a new developmental database was compiled by combining toxicity information from the Teratogen Information System (TERIS) and the Food and Drug Administration (FDA) guidelines. We implemented a decision tree modeling procedure, using Classification and Regression Tree software and a model ensemble approach termed bagging. We then assessed the empirical distributions of the prediction accuracy measures of the single and ensemble-based models, achieved by repeating our modeling experiment many times by repeated random partitioning of the working database. The decision tree developmental SAR models exhibited modest prediction accuracy. Bagging tended to enhance the accuracy of prediction. Also, the model ensemble approach reduced the variability of prediction measures compared to the single model approach. Further research with data derived from animal species- and endpoint-specific components of an extended and refined FDA/TERIS database has the potential to derive SAR models that would be useful in the developmental risk assessment of the thousands of untested chemicals.

A twelve-week, double-blind, randomized comparison of nortriptyline and paroxetine in older depressed inpatients and outpatients

Selective serotonin reuptake inhibitors may be less efficacious than tricyclic antidepressants in the treatment of severe depression in older patients. The authors compared the 12-week clinical outcome of older depressed patients treated with nortriptyline or paroxetine in a double-blind randomized comparison in 116 psychiatric inpatients and outpatients (mean age: 72+/-8 years) who presented with a major depressive episode or melancholic depression. Discontinuation and response rates were compared in patients who began or who completed treatment. The discontinuation rate due to side effects was significantly higher with nortriptyline than with paroxetine (33% vs. 16%). There were no significant differences between the rates of response in the Intent-to-Treat analysis (nortriptyline: 57% vs. paroxetine: 55% ), or the Completer analysis (nortriptyline: 78% vs. paroxetine: 84%). Although paroxetine appears to be better tolerated than nortriptyline, the efficacy of these two drugs does not appear to differ in the acute treatment of older depressed patients, including hospitalized patients and those with melancholic features.

Progression to insulin-requiring diabetes in seronegative prediabetic subjects: the role of two HLA-DQ high-risk haplotypes

AIMS/HYPOTHESIS

Most Caucasians with Type I (insulin-dependent) diabetes mellitus develop an autoimmune form of diabetes known as Type IA diabetes, based on the presence of humoral responses to islet autoantigens. Alleles at the HLA locus account for the strongest susceptibility to this form of diabetes, which requires insulin therapy. Because a number of patients who develop insulin-requiring diabetes are islet autoantibody negative, the HLA class II haplotypes, DQA1*0501-DQB1*0201 and DQA1*0301-DQB1*0302, were evaluated to assess whether they are an independent risk factor for progression to insulin requirement in first-degree relatives of Type I diabetic patients.

METHODS

Both HLA-DQ genotyping and islet cell autoantibody assessment (insulin, GAD65, IA-2 autoantibodies and cytoplasmic islet cell antibodies) were evaluated prospectively in 74 relatives of Type I diabetic patients who developed diabetes treated with insulin (prediabetics) and in 426 control subjects who did not develop insulin-requiring diabetes. Based on the presence of DQA1*0501-DQB1*0201 and/or DQA1*0301-DQB1*0302, the number of HLA-DQ high-risk haplotypes was assigned as 0, 1 or 2.

RESULTS

A higher prevalence of 2 HLA-DQ high-risk haplotypes was present in seronegative prediabetic subjects as compared to non-diabetic autoantibody negative first-degree relatives (33.3 % vs 10.1 % respectively; p < 0.05). Moreover, in seronegative relatives who developed insulin-requiring diabetes, the presence of 2 HLA-DQ high-risk haplotypes conferred an increased cumulative risk of developing insulin requirement of 27 % at 12.5 years of follow-up, compared to a risk of 6 % for non-diabetic relatives who were antibody-negative and had 0 or 1 HLA-DQ high-risk haplotypes (Log rank p = 0.01).

CONCLUSION/INTERPRETATION

These data provide evidence for a phenotype, which is associated with the absence of conventional islet autoantibodies at initial screening, while usually remaining seronegative, and the presence of 2 HLA-DQ high-risk haplotypes with progression to clinical Type I diabetes after a prolonged follow-up. Given the fact that in humans the highest risk-conferring locus associated and linked to the disease is the HLA cluster, and that HLA-DQ molecules play a key role in the development of autoimmune diabetes, our observations imply that as yet unidentified immunologic abnormalities could well exist in seronegative relatives at risk of developing clinical diabetes and carrying 2 HLA-DQ high-risk haplotypes.

Influence of serotonin-transporter-linked promoter region polymorphism on platelet activation in geriatric depression

OBJECTIVE

Depression has been associated with increased platelet activation. Variations in the serotonin-transporter-linked promoter region (5-HTTLPR) polymorphism may influence the degree of activation. The authors examined the association among depression, platelet activation, and 5-HTTLPR genotype.

METHOD

Elderly subjects with (N=61) and without (N=12) major depression were assessed for cognitive impairment, cardiovascular disease, and two indices of platelet activation. The depressed subjects were genotyped for the 5-HTTLPR polymorphism.

RESULTS

The depressed subjects were older, were more cognitively impaired, and had higher platelet factor 4 and beta-thromboglobulin levels; cardiovascular disease was minimal in both groups. In the depressed group, subjects with the 5-HTTLPR l/l genotype had significantly higher platelet factor 4 and beta-thromboglobulin levels.

CONCLUSIONS

Platelet activation is increased in elderly depressed patients, especially those with the 5-HTTLPR l/l genotype. This finding suggests how genetic differences may influence cardiovascular mortality in depressed patients with ischemic heart disease.

Treatment outcome in suicidal vs. non-suicidal elderly patients

The authors investigated treatment outcome in elderly suicidal and non-suicidal patients with recurrent major depression. Patients without suicidal ideation in the current episode (Non-Ideators; n=150) were compared with 30 patients who expressed suicidal ideation (Ideators). Patients received combined pharmacotherapy and psychotherapy during acute and continuation treatment. Ideators had higher numbers of lifetime suicide attempts and reported significantly higher levels of depression, anxiety, and hopelessness before starting treatment. Ideators and Non-Ideators had almost identical remission rates (77% vs. 78%), but Ideators had higher relapse rates during continuation treatment (26% vs. 13%) and were more likely to receive augmentation pharmacotherapy. Anxiety and use of adjunctive medication, but not suicidal ideation, were negatively related to both remission and relapse. Our data suggest that elderly suicidal patients have an overall favorable treatment outcome. However, treatment response may be more brittle and may require the continuing use of adjunctive medications to prevent early relapse.

Steady-state and time-resolved fluorescence studies on wild type and mutant chromatium vinosum high potential iron proteins: holo- and apo-forms

Detailed circular dichroism (CD), steady-state and time-resolved tryptophan fluorescence studies on the holo- and apo- forms of high potential iron protein (HiPIP) from Chromatium vinosum and its mutant protein have been carried out to investigate conformational properties of the protein. CD studies showed that the protein does not have any significant secondary structure elements in the holo- or apo- HiPIP, indicating that the metal cluster does not have any effect on formation of secondary structure in the protein. Steady-state fluorescence quenching studies however, suggested that removal of the iron-sulfur ([Fe(4)S(4)](3+)) cluster from the protein leads to an increase in the solvent accessibility of tryptophans, indicating change in the tertiary structure of the protein. CD studies on the holo- and apo- HiPIP also showed that removal of the metal prosthetic group drastically affects the tertiary structure of the protein. Time-resolved fluorescence decay of the wild type protein was fitted to a four-exponentials model and that of the W80N mutant was fitted to a three-exponentials model. The time-resolved fluorescence decay was also analyzed by maximum entropy method (MEM). The results of the MEM analysis agreed with those obtained from discrete exponentials model analysis. Studies on the wild type and mutants helped to assign the fast picosecond lifetime component to the W80 residue, which exhibits fast fluorescence energy transfer to the [Fe(4)S(4)](3+) cluster of the protein. Decay-associated fluorescence spectra of each tryptophan residues were calculated from the time-resolved fluorescence results at different emission wavelengths. The results suggested that W80 is in the hydrophobic core of the protein, but W60 and W76 are partially or completely exposed to the solvent.

Direct observation of release of cytochrome c from lipid-encapsulated protein by peroxide and superoxide: a possible mechanism for drug-induced apoptosis

Release of cytochrome c from inside lipid vesicles and from inside proteoliposomes formed by cytochrome c oxidase has been studied by spectrophotometric methods. The protein encapsulated inside vesicles did not form complex with sodium azide solution added externally. Both hydrogen peroxide and superoxide were found to cause release of cytochrome c from the lipid encapsulated protein, which was detected from the distinct spectral changes due to the formation of the azide complex of cytochrome c in the solution. Cytochrome c encapsulated inside proteoliposomes containing cytochrome c oxidase (CcO) did not release the cytochrome c during enzymatic turnover of CcO. The anticancer drug, doxorubicin, was found to inhibit the biochemical function of cytochrome c oxidase and release of cytochrome c was observed from the proteoliposome encapsulating the protein during the enzymatic turnover in the presence of doxorubicin. The results indicated that the inhibition of enzymatic activity by doxorubicin possibly leads to the formation of reactive oxygen species, which induce the release of cytochrome c from inside to outside of the membrane.

pH-induced conformational transition in the soluble CuA domain of Paracoccus denitrificans cytochrome oxidase

The pH-induced conformational transition in the CuA domain of subunit II of cytochrome oxidase of Paracoccus denitrificans (PdII) has been investigated using various spectroscopic and stopped-flow kinetic methods. UV-visible absorption and circular dichroism studies showed that an increase in pH from 6 to 10 leads to a conformation change with pK(a) = 8.2 associated with the CuA site of the protein. The secondary structure of the protein was, however, shown to remain unchanged in these two conformational states. Thermal and urea-induced unfolding studies showed that the "low-pH" conformation is more stable compared to the "high-pH" conformation of the protein. Moreover, the overall stability of the protein was found to decrease on reduction of the metal centers in the low-pH form, while the oxidation state of the metal centers did not have any significant effect on the overall stability of the protein in the high-pH form. Stopped-flow pH-jump kinetic studies suggested that the conformational transition is associated with a slow deprotonation step followed by fast conformational equilibrium. The results are discussed in the light of understanding the pH-induced conformational change in the beta-barrel structure of the protein and its effect on the coordination geometry of the metal site.

A double-blind randomized comparison of nortriptyline plus perphenazine versus nortriptyline plus placebo in the treatment of psychotic depression in late life

OBJECTIVE

To conduct the first randomized study comparing the efficacy of an antidepressant alone versus an antidepressant plus a neuroleptic in the treatment of late-life psychotic depression.

METHOD

The efficacy of nortriptyline plus placebo versus nortriptyline plus perphenazine was compared in 36 patients aged 50 years or older presenting with a major depressive episode with psychotic features (DSM-III-R criteria). Patients were started openly on nortriptyline treatment titrated to therapeutic levels. They were then randomly assigned under double-blind conditions to addition of perphenazine or placebo. Outcomes were compared in the 2 treatment groups using measures including the Hamilton Rating Scale for Depression (HAM-D) and the Brief Psychiatric Rating Scale (BPRS); side effects were assessed with the Geriatric Movement Disorder Assessment.

RESULTS

Both treatments were well tolerated. Of the 36 randomly assigned patients, 2 (1 in each group) dropped out due to treatment-related adverse effects. Four additional patients dropped out for administrative reasons. Thirty patients received nortriptyline for at least 4 weeks combined with either perphenazine (N = 14) or placebo (N = 16) for at least 2 weeks (median = 9 weeks). There was no significant difference between the completers in the 2 treatment groups when comparing their scores on the HAM-D, the BPRS, its psychoticism subscale, or any side effects measure. Rates of response (defined as resolution of both depression and psychosis) did not differ significantly in the 2 groups (nortriptyline-plus-perphenazine group, 50% vs. nortriptyline-plus-placebo group, 44%).

CONCLUSION

When treating older patients with psychotic depression, the addition of a moderate dose of a traditional neuroleptic to a tricyclic antidepressant was well tolerated but did not improve efficacy. This finding supports existing data suggesting that the pathophysiology (and thus the required treatment) of psychotic depression may be different early and late in life.

Paroxetine versus nortriptyline in the continuation and maintenance treatment of depression in the elderly

Elderly depressed patients are vulnerable to recurrence of depression and benefit from long-term antidepressant therapy. Physicians increasingly use selective serotonin re-uptake inhibitors (SSRIs) as maintenance therapy, although in the absence of data showing that SSRIs are as efficacious as tricyclic antidepressants (TCAs) in the prevention of depression relapse and recurrence. Our objective was to evaluate, in an open trial, the efficacy of paroxetine versus nortriptyline for preventing recurrence of depression in the elderly. Elderly patients with major depression were randomly assigned in a double-blinded fashion to receive either paroxetine or nortriptyline for the acute treatment of depression. Patients who did not respond or tolerate their assigned medications were crossed over openly to the comparator agent. Patients whose depression remitted continued antidepressant medication (paroxetine n = 38; nortriptyline n = 21) during an open 18-month follow-up study. We examined the rates of and times to relapse and to termination of treatment for any reason. Paroxetine (PX) and nortriptyline (NT) patients had similar rates of relapse (16% vs. 10%, respectively) and time to relapse (60.3 weeks vs. 58.8 weeks, respectively) over 18 months. A lower burden of residual depressive symptoms and side effects during continuation and maintenance treatment was evident in nortriptyline-treated patients. Paroxetine and nortriptyline demonstrated similar efficacy in relapse and recurrence prevention in elderly depressed patients over an 18-month period.

Initial recovery patterns may predict which maintenance therapies for depression will keep older adults well

BACKGROUND

Although active maintenance treatments appear superior to placebo in preventing depression recurrence in older adults, few data are available to guide maintenance modality selection to maximize the probability of continued wellness for a given patient. Patients' temporal patterns of acute treatment response may predict who requires which maintenance therapy to remain well.

METHODS

Depression levels were observed over 16 weeks of combined nortriptyline (NT) and interpersonal psychotherapy (IPT) in 140 persons aged >or=60 years with recurrent major depression. Subjects were empirically classified into four groups: rapid, sustained responders; delayed, sustained responders; mixed responders without sustained improvement; prolonged nonresponders. Groups were compared on subsequent recovery rates and on time to depression recurrence after randomization to 3 years of combined maintenance therapy (monthly IPT with NT), monotherapy (either IPT or NT alone), or medication clinic with placebo. Pretreatment psychosocial and clinical variables were controlled.

RESULTS

Initial response profile predicted ultimate recovery rates, as well as who remained well, given the maintenance treatment received. Rapid initial responders showed lower recurrence risk with either combined or monotherapy, relative to placebo. Specific types of monotherapy appeared equally effective in rapid responders. In initially mixed responders, only combined therapy was superior to placebo. It was marginally superior to monotherapy. For delayed responders, combined therapy was superior to placebo; monotherapy did not differ from the other maintenance conditions. Prolonged nonresponders did not benefit from maintenance treatment.

LIMITATIONS

Subjects had only recurrent, unipolar depression. Initial response profile groups were established empirically and require replication. Sample sizes in initial response profile by maintenance treatment cells were small.

CONCLUSION

The ability to match patients to maintenance treatments more likely to prevent recurrence may be enhanced by considering the temporal profile of initial response to acute treatment.

Accounting for covariate measurement error in a Cox model analysis of recurrence of depression

When a covariate measured with error is used as a predictor in a survival analysis using the Cox model, the parameter estimate is usually biased. In clinical research, covariates measured without error such as treatment procedure or sex are often used in conjunction with a covariate measured with error. In a randomized clinical trial of two types of treatments, we account for the measurement error in the covariate, log-transformed total rapid eye movement (REM) activity counts, in a Cox model analysis of the time to recurrence of major depression in an elderly population. Regression calibration and two variants of a likelihood-based approach are used to account for measurement error. The likelihood-based approach is extended to account for the correlation between replicate measures of the covariate. Using the replicate data decreases the standard error of the parameter estimate for log(total REM) counts while maintaining the bias reduction of the estimate. We conclude that covariate measurement error and the correlation between replicates can affect results in a Cox model analysis and should be accounted for. In the depression data, these methods render comparable results that have less bias than the results when measurement error is ignored.

Re-integerization of fractional charges in the correlated quarter-filled band

Previous work has demonstrated the existence of soliton defect states with charges +/-e/2 in the limits of zero and infinite on-site Coulomb interactions in the one-dimensional (1D) quarter-filled band. For large but finite on-site Coulomb interaction, the low temperature 2kF bond distortion that occurs within the 4kF bond-distorted phase is accompanied by charge ordering on the sites. We show that a "re-integerization" of the defect charge occurs in this bond-charge-density-wave state due to a "binding" of the fractional charges. We indicate briefly possible implications of this result for mechanisms of organic superconductivity.

The posttreatment illness course of depression in bereaved elders. High relapse/recurrence rates

Losing close attachments through death in late life is common and can lead to depression. Previous work has shown the clinical benefits of treating these depressions. This article describes the 2-year course of 53 elderly subjects with bereavement-related depression after responding to various treatments. Forty-six patients experienced a full response to acute treatment, but 36% experienced relapse or recurrence. This finding suggests that the treatment response in depressed bereaved older patients is more brittle than expected.

A double-blind randomized comparison of nortriptyline and paroxetine in the treatment of late-life depression: 6-week outcome

BACKGROUND

Some studies have suggested that selective serotonin reuptake inhibitors may be less efficacious than tricyclic antidepressants in the treatment of severe depression in older patients. The objective of this study was to compare the 6-week outcome of treatment with nortriptyline and paroxetine in older patients with a major depressive episode.

METHOD

A double-blind randomized comparison of nortriptyline and paroxetine was conducted in 80 elderly (mean +/- SD age = 75.0 +/- 7.4 years) psychiatric inpatients and outpatients who presented with a major depressive episode. Dropout and response rates were compared in patients who began or completed treatment. Rates of response of inpatients and patients with melancholic depression were also compared.

RESULTS

Over 6 weeks, there were no significant differences in dropout rates due to side effects (nortriptyline, 14% vs. paroxetine, 19%) or for any reason (27% vs. 33%). Similarly, there were no significant differences between the rates of favorable response to nortriptyline or paroxetine (intent-to-treat analysis, 57% vs. 44%; completer analysis, 78% vs. 66%). Analyses restricted to inpatients or to patients with melancholic depression yielded similar results.

CONCLUSION

Nortriptyline and paroxetine appear to have similar efficacy and tolerability in the acute (6-week) treatment of older depressed patients, including hospitalized patients and those with melancholic features.

Effect of continuation treatment on residual symptoms in late-life depression: how well is "well"?

The objectives of this report were (1) to describe residual depressive symptoms in elderly patients during continuation therapy with combined nortriptyline and interpersonal psychotherapy; (2) to determine which symptoms were persistent; (3) to determine the clinical correlates of residual depressive symptoms; and (4) to document distinct response pattern clusters during combined continuation therapy.

METHOD

Box plot analyses of Hamilton depression scores and Global Assessment Scale scores, repeated twice monthly over 4 months, were conducted using data from 105 elderly depressives. Temporal trends in the data were examined via random regression analysis. Individual trajectories for each of the 105 patients were examined for patterns of response during continuation therapy.

RESULTS

We observed a low mean Hamilton rating of 7 (SD = 2.3) at the start of continuation therapy and 5 (SD = 3.0) at the end. Both Hamilton and GAS scores showed modest but significant improvement over time. Hamilton variability was most apparent in symptoms of mood lowering, apathy, anxiety (psychological and somatic), feelings of guilt, anergia, insomnia, and loss of libido; other symptoms (retardation, agitation, hypochondriasis, loss of appetite, loss of weight, suicidal ideation, and loss of insight) showed clear resolution. A diagnosis of RDC situational depression was associated with higher levels of residual symptoms, while level of chronic medical burden, personality dysfunction, and social support were not. Examination of response patterns showed that a quarter of patients experienced one or more brief symptomatic exacerbations.

CONCLUSION

On average, an excellent level of symptom resolution was achieved for most patients with Hamilton scores comparable to those seen in healthy elderly controls. These data support a position of therapeutic optimism in late-life depression and underscore full remission as an achievable therapeutic goal.

EEG sleep measures in later-life bereavement depression. A randomized, double-blind, placebo-controlled evaluation of nortriptyline

The authors examined 1) effects of nortriptyline (NT) on electroencephalographic (EEG) sleep measures in elderly patients with bereavement-related depression in remission under randomized, double-blind, placebo-controlled conditions, and 2) the effects of clinical remission on sleep after discontinuation of medication. Subjects were classified as responders to placebo (n = 9) or NT (n = 18) and had EEG sleep studies at three time-points: before treatment (T1), remitted on medication or placebo (T2), and remitted off medication or placebo (T3). As compared with placebo, NT was differentially associated with decreases in REM sleep time and percent and increases in REM sleep density (T2). No changes in EEG sleep measures occurred in placebo responders. REM sleep measures in NT responders reverted to T1 levels after T3, with persistence of robust clinical remission and normal subjective sleep quality. These data suggest that NT alters REM sleep, but that EEG sleep characteristics in bereavement-related depression persist into remission.